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Review
Photodynamic therapy as a new treatment modality for inflammatory and infectious conditions Expert Rev. Clin. Immunol. Early online, 1–21 (2015)
Aurelie Reinhard1–3, William J Sandborn4, Hassan Melhem5, Lina Bolotine1,2, Mathias Chamaillard6 and Laurent Peyrin-Biroulet*3,7 1 Universite de Lorraine, Centre de recherche en automatique de Nancy, 54506 Vandoeuvre-le`s-Nancy, France 2 Centre national de la recherche scientifique, Centre de recherche en automatique de Nancy, UMR 7039, 54506 Vandœuvre-le`s-Nancy, France 3 Institut National de la Sante et de la Recherche Medicale, U954, 54500 Vandoeuvre-le`s-Nancy, France 4 Division of Gastroenterology, University of California San Diego, La Jolla, CA, USA 5 Laboratoire NGERE, Faculte de Medecine, 9, Av de la Foreˆt de Haye, Vandoeuvre-le`s-Nancy, 54505 France 6 Institut Pasteur de Lille, Centre d’Infection et d’Immunite de Lille, 59019 Lille, France 7 Department of Hepatogastroenterology, University Hospital of NancyBrabois, University of Lorraine Allee du Morvan, 54511 Vandoeuvre-le`s-Nancy, France *Author for correspondence: Tel.: +33 383 153 631 Fax: +33 383 153 633 [email protected]
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Photodynamic therapy (PDT) is currently used as a minimally invasive therapeutic modality for cancer. Whereas antitumor treatment regimens require lethal doses of photosensitizer and light, sublethal doses may have immunomodulatory effects, antibacterial action and/or regenerative properties. A growing body of evidence now indicates that non-lethal PDT doses can alleviate inflammation or treat established soft-tissue infections in various murine models of arthritis, experimental encephalomyelitis, inflammatory bowel disease and chronic skin ulcers. Furthermore, PDT is already used in clinical application and clinical trial for the treatment of psoriasis, chronic wounds and periodontitis in humans. Sublethal PDT should be regarded as a new viable option for the treatment of inflammatory conditions. KEYWORDS: antimicrobial . immune modulation . inflammation . photodynamic therapy . wound healing
Photodynamic therapy (PDT) is a minimally invasive therapeutic modality that is currently used for the treatment of cancer [1]. The procedure involves administration of a photosensitizer (PS) and subsequent local illumination of the disease site at an appropriate wavelength [1]. The PS is preferentially taken up by rapidly dividing cells (such as tumor cells, microbial cells and activated immune cells) [2,3]. Once activated by light, the PS interacts with molecular oxygen to produce a variety of short-lived reactive oxygen species [1]. The oxidative stress induced by PDT results in necrotic or apoptotic cell death and can produce a variety of effects in immune cells [1,4]. The PS’s type, intracellular site and concentration, and the dose of light applied all influence the exact effects of PDT [2]. High-dose PDT results in direct cytotoxicity within the tumor cells (via oxidative damage to membranes and organelles) and an antivascular action (with impairment of the blood supply to the area via platelet aggregation and, thus, vascular occlusion) [1]. Furthermore, antitumor PDT regimens may also lead to antitumor immunity. Tumor antigens released due to direct cytotoxic effect increase the host immune response
10.1586/1744666X.2015.1032256
against cancer. In contrast, a growing body of evidence now indicates sublethal PDT may suppress the immune response while keeping the cell viability intact [2,5]. The immunosuppressive effect of PDT was first observed in 1986, with the suppression of a contact hypersensitivity reaction in mice previously exposed to a hapten [6]. In some circumstances, inflammatory conditions are also characterized by the uncontrolled proliferation of invading microbes [3], which perturbs the wound-healing process [7,8]. In this context, PDT may change cytokine release or surface receptor expression by the immune cells, promote wound healing by stimulating growth factor synthesis [9,10] and kill or at least inactivate several microbial strains [11–14]. PDT (whether transcutaneous, intra-articular or intraluminal) with sublethal PS and/or light (also called low-dose PDT [LDPDT]) can alleviate inflammation in various murine models of arthritis [15–17], encephalomyelitis [18,19] and inflammatory bowel disease [20,21], or treat established soft-tissue infections in animals model of burn or skin ulcers [9,22,23]. Accordingly, PDT is already used in clinical application and clinical trial for the treatment of psoriasis [24–26], chronic
2015 Informa UK Ltd
ISSN 1744-666X
1
Review
Reinhard, Sandborn, Melhem, Bolotine, Chamaillard & Peyrin-Biroulet
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wounds [27,28], acne vulgaris [29–31] and periodontitis [32–35] in humans. The present article reviews research on the mechanisms underlying anti-inflammatory, antibacterial and healing properties of PDT. The authors also review the research data on the use of PDT to treat certain inflammatory conditions. Mechanisms of action of PDT in infectious & inflammatory conditions
PDT is known to have immunomodulatory, antimicrobial and wound-healing properties (FIGURE 1) [10,36,37]. Immunomodulatory action of PDT
The influence of PDT on the immune response is highly complex and depend on many factors, such as the PS’s formulation, pharmacokinetics and location within cells (especially immune cells), the duration between PS administration and irradiation, the fluence (in J/cm2, i.e., the delivery rate), the fluence rate (in mW/ cm2, i.e., the power of irradiation) and the wavelength (i.e., the extent of tissue penetration) [5]. In some circumstances, PDT has the capacity to increase the host immune response against cancer [38,39]. Indeed, the photo-induced direct damage of neoplastic cells, creating and releasing a mixture of tumor antigens and cellular danger signals, triggers an acute inflammatory response which activates and matures dendritic cells and other cellular components of both the innate and adaptive immune systems [39]. In contrast, LDPDT (i.e., with low levels of PS and/or light) can have immunomodulatory effects able to treat different models of autoimmune disease or inflammatory disorders [37] (FIGURE 1). Sublethal PDT can directly alter the immune cell function (cell signaling events, cytokine production and surface receptor expression) and, thus, alleviate immune-mediated disease [2,37]. Apoptosis of immune cells
Induction of apoptosis by PDT is a well-documented phenomenon that is directly linked to the PS’s localization within the mitochondria [1,40]. Mitochondrial damage has been widely described in PDT-treated tumor cells [41–44]. However, there is relatively little detailed information on PDT’s capacity to induce apoptosis in non-transformed cells in general and immune cells in particular. Very few studies have demonstrated apoptosis in PDT-treated leukocytes [45–47]. One of the key events in PDT-induced apoptosis in immune cells is the accumulation of PS in activated immune cells [46,47]. Hydrophobic PSs bind to plasma lipoproteins, especially low-density lipoproteins. Activated T- and B-cells take up more PS than resting (naı¨ve) cells [46,47]. This greater uptake may be due to the upregulation and increased turnover of low-density lipoprotein receptors [45]. Thus, activated T- and B-lymphocytes may be more vulnerable to the cytotoxic effects of PDT, even with sublethal PDT regimens [48]. Modulation of the expression of immune cell surface molecules
Sublethal PDT may alter cell–cell interactions by modifying the immune cells’ surface receptor expression [2,37,48]. Following LDPDT, APCs may not be able to effectively activate T-cells doi: 10.1586/1744666X.2015.1032256
because of the downregulation of a number of cell surface receptors required for T-cell–APC communication [49]. Dendritic cells (DCs) are potent APCs that act as sentinel cells. They abundantly express MHC antigens, adhesion and co-stimulation molecules, and thus activate naı¨ve T-lymphocytes. Moreover, dendritic cells are an important source of the pro-inflammatory cytokine IL-12 that promotes T-cell–mediated immunity [48]. In vitro treatment of mouse splenic dendritic cells with sublethal levels of verteporfin and light induces a dramatic fall in surface expression of MHC class I and II antigens, CD80 and CD86 co-stimulatory molecules, and CD54 (an adhesion molecule involved in cell–cell interactions) [49]. Furthermore, a study by Obochi et al. demonstrated that pre-treatment of murine skin grafts with benzoporphyrin derivative (BPD)-PDT prolongs their survival in immunocompetent allogeneic recipients [50]. LDPDT decreases the expression of MHC and co-stimulatory molecules expressed by graft Langerhans cells, which, in turn, limits the cells’ capacity to stimulate T-lymphocytes [50]. Studies have shown contradictory effects of PDT on Langerhans cells. Some studies in humans showed an immunosuppressive effect of PDT on the skin via a reduction of Langerhans cells [51,52], whereas others reported no difference in Langerhans cell number [50,53]. Immune response of skin to PDT appears complex; PDT seems to have, in some circumstances, a direct cytotoxic effect or probably induces an adaptive response against oxidative stress which serves to lower the immunostimulatory properties of these cells [37]. Another interesting point is that topical PDT has been shown to decrease the Mantoux response in healthy Mantouxpositive volunteers, confirming that PDT induces immunosuppression probably by altering the expression of and cellular responsiveness to various inflammatory cytokines [54]. Modulation of the type & level of cytokine release
PDT can decrease or increase cytokine expression levels [55]. Larisch et al. have demonstrated that sublethal PS and light level (610 nm, 1.8 mW/cm2, 0–1080 mJ/cm2) significantly reduced the secretion of IL-6 (an important pro-inflammatory cytokine) and increase the expression of the anti-inflammatory cytokine IL-10 in various cell lines [56]. An in vivo study in mouse has also shown that PDT of tumor tissue or healthy tissue leads to a change in the cytokine expression profile [57]. Antitumor PDT (hematoporphyrin derivative 5 mg/kg, 75 mW/cm2, 100 J/cm2) induced a strong increase in IL-6 production and a decrease in the production of IL-10 [57]. In the same study, low-intensity PDT on healthy tissue (1.3 J/cm2, 0.745 mW/cm2) led to a significant increase in the production of IL-10 in mice [57]. The immunosuppressive effect of PDT was convincingly demonstrated by Elmet and Bowen, who reported for the first time that pre-treatment with hematoporphyrin derivative-PDT reduced the contact hypersensitivity response by 50% in mice whose skin had been previously sensitized with a hapten 2,4-dinitrofluorobenzene [6]. The same results were obtained following BPDPDT [58]. Other researchers have observed an increase in Expert Rev. Clin. Immunol.
PDT as a new treatment modality for inflammatory & infectious conditions
→ Antimicrobial properties: – Kill pathogens
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– Bactericidal effects of host immune cells
PDT for non-oncological disorders (Low dose PDT)
→ Healing properties: – Kill invading microbes
→ Inflammatory bowel disease → Arthritis → Experimental allergic encephalomelitis → Psoriasis → Chronic wounds → Acne vulgaris → Periodontitis
er Photosensitizer injection
Review
– Stimulate growth factors synthesis and modify cytokines release
→ Immunomodulatory properties: – Apoptosis of immune cells Irradiation
– Cytokines modification – Alteration of surface receptors expression
1112 1 10 2 9 3 4 8 7 6 5
Drug light interval
Figure 1. Mechanisms of action of PDT for non-oncological disorders. PDT: Photodynamic therapy.
IL-10 production in mice with a decrease in contact hypersensitivity [58]. The immunosuppressive effects of PDT are reversed by the administration of recombinant IL-12 or antiIL-10 antibody and absent in IL-10 knock-out mice [58]. The latter researchers concluded that IL-10 has a key role in the immunosuppression effect induced by BPD-PDT [58]. IL-10 is produced by a wide variety of cell types (including Th2-type T-cells) and inhibits the cell-mediated immune response by decreasing MHC class II expression, APCs’ co-stimulatory functions and the latter’s ability to secrete IL-12 [59–61]. Simkin et al. postulated that PDT might promote Th2-like immune responses by lowering the availability of IL-12 – possibly by increasing IL-10 concentrations [58]. A year later, however, Gollnick et al. reported that IL-10 is not involved in suppression of the contact hypersensitivity response following hematoporphyrin derivativePDT [62]. The PS’s formulation and pharmacokinetics, the drug–light interval and the body surface area irradiated are parameters that govern PDT’s immunomodulatory effect and can sometimes lead to contrasting immunological effects [5]. Wound healing & tissue regeneration
Another property of PDT is its potential for accelerating the regeneration of injured tissues (FIGURE 1). Wound healing is a highly dynamic process and involves complex interactions between extracellular matrix molecules, soluble mediators, various resident cells and infiltrating leukocyte subtypes [8]. In repair, the immediate goal is to achieve tissue integrity and homeostasis. To achieve this goal, the healing process involves informahealthcare.com
three phases that overlap in time and space: inflammation, tissue formation and tissue remodeling [8]. The wound-healing process requires the release of several cytokines, especially IL-10, that stimulate resorption of tissue inflammation and growth factors (VEGF, FGF, PDGF and TGF-b) that promote the cell proliferation and extracellular matrix synthesis in order to repair the damaged tissue [8]. A number of studies have revealed the key role of pro-inflammatory cytokines (IL-1a, IL-1b, IL-6, TNF-a) in prolonging the inflammatory phase [63,64] and the beneficial role of anti-inflammatory cytokines (IL-10, TGF-b) in the wound-healing process [8,65]. Several studies using LDPDT (with low doses of light and/or PS) have clearly demonstrated the beneficial effect of PDT in wound healing [9,10,66,67]. LDPDT appears to hasten the process of wound healing as judged by different studies reporting more rapid re-epithelialization and remodeling [9,10,66,67]. Other studies have reported that sublethal PS and light levels are associated with the upregulation of IL-10 and downregulation of pro-inflammatory cytokines [56–58]. A more recent study evaluating in vitro the release of cytokines by keratocyte postPDT demonstrated a decrease in IL-6 and IL-8 concentrations within 5 h of PDT application [68]. The latter researchers had previously studied the impact of PDT on the in vitro release of growth factors in cultures of keratocytes and had observed elevated concentrations of FGF within 5 h of PDT; in contrast, VEGF and TGF concentrations were unchanged [69]. Tissue and mucosal healing implies the cessation of the initial inflammatory phase [8]. Chronic wounds are frequently doi: 10.1586/1744666X.2015.1032256
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Review
Reinhard, Sandborn, Melhem, Bolotine, Chamaillard & Peyrin-Biroulet
contaminated by bacteria, which cause persistent inflammation and delayed healing [8]. The mechanism underlying tissue regeneration by PDT remains poorly understood, but may result from the impact of PDT on immune response (with stimulation of growth factor synthesis and modulation of cytokine release within the damaged tissue) and the antimicrobial action involved in stopping inflammation [70]. Antimicrobial properties
Growing interest in the antimicrobial effects of PDT over the last decade has prompted use of this technique in a broad range of localized infections (FIGURE 1). This revival of interest has largely been driven by the increasing incidence of infections by antibiotic-resistant bacteria. Antimicrobial PDT has multiple applications, as it can be used to kill or inactivate various pathogens in ex vivo tissues or biological materials (such as blood) and in vivo [3]. PDT has been successfully used to kill pathogens and even to save lives in several animal models of localized infections, such as surface wounds, burns, infections in oral sites, abscesses and infections in the middle ear [9,71]. Thus, the use of PDT as an antimicrobial therapy has been rapidly developed for clinical applications in dermatology and dentistry [3]. In the near future, antimicrobial PDT applications are likely to become more widespread, since the technique presents several advantages over conventional techniques. In particular, use of PDT is without risk to the surrounding tissue and does not appear to induce pathogen resistance. Furthermore, PDT can be used in non-perfused tissue (burns, bone or cartilage) and is less toxic than antibiotics [3]. Recent data demonstrated that the therapeutic beneficial effect of PDT for localized microbial infections results from both direct bacterial killing and also indirect PDT-driven bactericidal effects of host neutrophils [36,72]. On the molecular level, the reactive oxygen species produced by PDT can induce direct microbial photo-inactivation or photo-destruction [73]. Once the PS penetrates into the bacterial cell, it binds to DNA and provokes strand breaks [73,74], or oxidative damage may also occur within the cell’s plasma membrane, leading to the leakage of cellular constituents or inactivation of membrane transporters [73,74]. However, the antibacterial effect could also be achieved by the induction of an immune response against bacteria, but the exact mechanism remains unknown. PDTmediated enhancement of antibacterial immunity can be achieved with modest dose of PDT that allows bacterial reduction without killing the host neutrophils [36]. PDT in animal models of infectious & inflammatory conditions
Several studies have demonstrated the positive impact of sublethal PDT in various murine models of soft-tissue infections or inflammatory and autoimmune disorders, and PDT has been used in several dermatological conditions (SUPPLEMENTARY TABLE 1) (supplementary material can be found online at www.informahealthcare.com/suppl/10.1586/1744666X.2015.1032256/Suppl. doi: 10.1586/1744666X.2015.1032256
doc) [75,76]. The PS can be applied topically or systemically (via oral or intravenous route) [77]. A large range of light sources can be used, including incoherent polychromatic sources (gas discharge lamps and light-emitting diodes) and coherent monochromatic sources (intense pulsed light [78], potassium titanyl phosphate laser, pulsed dye laser and infrared laser) [77]. The light can be administered via different routes – intraluminal (the oral cavity, intranasal or gastric), intra-articular, cutaneous (to a small area of the skin or a large part of the body), transcutaneous or to blood cells during apheresis (using phototherapy UV-A [PUVA], which is not the same as PDT) (FIGURE 2) [77]. The potential advantages of sublethal PDT include the ability to treat large areas of diseased tissue and areas not reachable by surgery, and apply retreatment [1]. Moreover, sublethal PDT is a safe, effective procedure that produces excellent cosmetic results in dermatological applications [1,77]. Localized infections
Infections are widely known to perturb the wound-healing process by delaying the re-epithelialization due to bacterial proliferation. In the recent past, PDT has been successfully used to kill pathogens and even to save life in several animal models of localized infections such as surface wounds, ulcers, burns, infections in oral sites and abscesses [9,11–14,23,71,79,80]. Hamblin et al. were the first group to report the use of mouse wound infection models to investigate the effects of PDT in treating excisional wound infected with Escherichia coli and Pseudomonas aeruginosa [11,12]. The experiment consisted in a single wound (100 mm2) realized on the backs of healthy mice and infected with a suspension of bioluminescent bacteria transduced with a plasmid containing a lux gene operon, which permitted to monitor the infection in real time by a sensitive charge-coupled camera. The wound was treated 1 h later by a topical polycationic PS conjugated at a total fluence of 160 J/cm2 in four 40 J/cm2 aliquots, with imaging taking place after each aliquot of light (TABLE 1). In PDT-treated mice, the authors observed a light dose dependent loss of luminescence with a 99% reduction after the four light aliquots, which was not seen in the untreated wound (TABLE 1) [11]. Moreover, PDT of infected wound did not lead to any damage in host tissue or inhibition of wound healing at these doses, which can be explained by the combination of the topical delivery method together with the large conjugate charge size and the relatively short incubation time (30 min) [11]. In order to test PDT on a more clinically relevant model, the authors performed the same experiment, but using a strain of invasive bacteria P. aeruginosa which led to a fatal sepsis after intraperitoneal injection in animals [12]. During P. aeruginosa infection, all non-treated animals died within 5 days contrary to the PDT-treated group where 90% of mice survived (TABLE 1) [12]. Using similar mouse models, Wong et al. [13] and Zolfaghari et al. [14] studied the effects of methylene blue and toluidine blue O mediated PDT on Vibrio vulnificus and methicillin-resistant Staphylococcus aureus wound infections. A significant reduction of bacterial number was observed in both the studies and PDT could cure mice with Expert Rev. Clin. Immunol.
PDT as a new treatment modality for inflammatory & infectious conditions
Review
Intra-articular PDT
Cutaneous PDT
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Application for: psoriasis or melanomas Intra-articular photosensitizer injection with trancutaneous or intra articular PDT illumination Potential indication for arthritis Topical application of photosensitizer and absorption by cells
Light illumination destruction of targeted cells
Intraluminal PDT
Intraluminal illumination after i.v. photosensitizer injection Application for Barrett’s Esophagus Potential indication for colitis
Laser fiber
Figure 2. Schematic description of PDT administration in vivo and application in inflammatory conditions. iv.: Intravenous; PDT: Photodynamic therapy.
otherwise fatal V. vulnificus wound infections (TABLE 1) [13,14]. However, the relevance of all these results is questionable because PDT treatment was applied rapidly after the wound bacterial inoculation (30 min–1 h). A recent study using more realistic animal infection models including full-thickness burns [9], established infections in which the bacteria have penetrated tissue [22,23], showed the same antibacterial PDT efficacy associated with a fast wound-healing process (TABLE 1) [9,22,23]. Morimoto et al. reported the efficacy of 5-aminolevulinic acid (ALA)-PDT in methicillin-resistant S. aureus–infected ulcers (TABLE 1) [22]. PDT was applied 2 days after the wound infection. The authors reported decrease in bacterial count on surface ulcer and accelerated wound healing, whereas vancomycin therapy was not effective (TABLE 1) [22]. However, it is not clear whether the cause for eradication of the local tissue infection is a direct killing of the pathogens or PDT-induced indirect action on the immune system to prevent infection or healing of the tissue due to the PDT-triggered immune response or a combination of these factors. Arthritis
PDT has been used in two models of arthritis (TABLE 1). In a murine model of methicillin-resistant S. aureus arthritis, PDT’s positive impact was directly related to direct bacterial killing by PDT and indirect PDT-induced bactericidal effects of host neutrophils (TABLE 1) [72,81–84]. In an animal model of adjuvantinformahealthcare.com
enhanced arthritis, PDT’s beneficial effect resulted in the modulation of joint tissue inflammation (TABLE 1) [15,17,85,86]. Ratkay et al. have demonstrated the efficacy of transcutaneous PDT (whole-body irradiation, BPD 0.5 mg/kg, 80 J/cm2) on an adjuvant-enhanced arthritis model in MLR/1pr mice [86]. Animals that underwent three PDT sessions at 10-day intervals had fewer histopathological and clinical signs of disease [86]. Compared with other immunomodulatory agents tested (indomethacin, cyclosporine A and 3 Gy sublethal whole-body irradiation), PDT has proven to be equally effective and lacks the other treatments’ adverse effects (TABLE 1) [86]. Ratkay et al. suggested that PDT’s efficacy resulted from the selective destruction of circulating adjuvant-activated T-cells and/or the localized destruction of joint-infiltrating macrophages [86]. A more recent study in a murine model of antigen-induced arthritis has demonstrated the efficacy and feasibility of local treatment with LDPDT using liposomal temoporfin (metatetra[hydroxyphenyl]chlorin) (0.05–0.01 or 0.005 mg/kg, 5 J/cm2) (TABLE 1) [15]. The intravenously injected PS accumulated rapidly and substantially in the inflamed joints [15]. A histological evaluation revealed a reduction in the severity of arthritis for all groups that received PDT, relative to untreated animals (TABLE 1). This reduction occurred in a dose-dependent manner with a significant decrease in the severity of inflammation for groups treated with 0.05 and 0.01 mg/kg of liposomal meta-tetra(hydroxyphenyl)chlorin [15]. PDT application in these doi: 10.1586/1744666X.2015.1032256
doi: 10.1586/1744666X.2015.1032256
In vitro and in vivo evaluation of PDT to treat potentially lethal wound infections
In vitro and in vivo study evaluating the effect of TBO-PDT against Vibrio vulnificus
In vivo evaluation of PDT to kill MRSA strain
In vitro and in vivo study evaluating the antibacterial activity of free hypericin and nanoencapsulated forms on biofilm and planktonic cells and infected wounds in rats
Hamblin et al. (2003)
Wong et al. (2005)
Zolfaghari et al. (2009)
Nafee et al. (2013)
5-ALA 0, 50 or 200 mg/kg
Hypericin 0.24 M
Excisional skin wounds infected by S. aureus in rat
Established infections, MRSAinfected ulcers
Methylene blue at 100 mg/ml
TBO at various concentrations (0, 1, 10 or 100 mg/ml)
Poly-lysine chlorine e6 (Ce6) conjugate 200 M
Poly-lysine chlorine e6 (Ce6) conjugate 100 M
Photosensitizer and concentration
Excisional and superficial wound models infected with MRSA
Excisional wounds infected with V. vulnificus
Invasive- bacteria (potentially lethal) infecting excisional wounds (Pseudomonas aeruginosa)
Bacteria infecting excisional wounds (Escherichia coli)
Animal model
Intraperitoneally
Topically
Topically
Topically
Topically
Topically
Mode of delivery
One day after injection
–
Immediately after application
2 min after application
30 min after application
30 min after application
Pretreatment with drug/ incubation time
–
Daily for 5 days
–
–
4 aliquots illumination
4 aliquots illumination
No. of sessions
405
–
670
PDT-1200 lamp emits from 560 to 780
665
665
Wavelength (nm)
PDT is effective at reducing the total number of viable MRSA in a wound In vivo study revealed faster healing in rats with better epithelialization, keratinization and development of collagen fibers when nanoencapsulated hypericin was used
360 J/cm2
23.5 J/cm2
ALA-PDT accelerated wound healing and decreased bacterial counts on MRSAinfected skin ulcers
TBO-PDT protects mice from V. vulnificus lethal wound infections. Ten of 19 (53%) mice exposed to TBO at 100 mg/ml and treated with light survived
150 J/cm2 at 80 mW/cm2
0, 10, 50 J/cm2
Control mice died in 5 days; in contrast, rapid light dosedependent eradication of bacteria in PDTtreated mice with 90% survival
Rapid eradication of bacteria infecting the wound demonstrated the possible use of PDT for localized infections and the safety of this method
Results
Total fluence 240 J/cm2 in four aliquots
Total fluence 160 J/cm2 in four 40J/cm2 aliquots
Light treatment parameters
[22]
[23]
[14]
[13]
[12]
[11]
Ref.
8-MOP: 8-methoxypsoralen; AOM: Azoxymethane; ALA: Aminolevulinic acid; BPD: Benzoporphyrin derivative monoacid ring A; DSS: Dextran sodium sulfate; LZD: Linezolid; MB: Methyl Blue; MRSA: Methicillin-resistant Staphylococcus aureus; mTHPC: Meta-tetra(hydroxyphenyl)chlorin; NS: Non-specified; PDT: Photodynamic therapy; TBO: Toluidine blue O; VCM: Vancomycin.
Evaluation of ALAPDT efficacy in MRSA-infected ulcers in mice
In vitro and in vivo study evaluating the use of PDT to treat wound infections
Hamblin et al. (2002)
Morimoto et al. (2014)
Study design
Study (year)
Table 1. Summary of representative articles published in literature, demonstrating a promising application of photodynamic therapy in some inflammatory and infectious conditions.
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Review Reinhard, Sandborn, Melhem, Bolotine, Chamaillard & Peyrin-Biroulet
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In vivo evaluation of therapeutic effect of MB-PDT combined with antibiotics: LZD or VCM
In vivo optimization of Photofrin-PDT light dosimetry in order to maximize bacterial killing in murine MRSA arthritis
In vivo study evaluating the therapeutic effect of mTHPC-PDT in a murine model of antigen-induced arthritis. Comparative study with different formulations
In vivo comparative study of PDT and other immunomodulatory treatments in murine arthritis model
Tanaka et al. (2013)
Tanaka et al. (2011)
Hansch et al. (2008)
Ratkay et al. (1994)
Murine adjuvantenhanced arthritis
Liposomal BPD 0.5 mg/kg
Free mTHPC, liposomal mTHPC and pegylated liposomal mTHPC. 0.1, 0.05, 0.01 or 0.005 mg/kg
Murine adjuvantenhanced arthritis
1
Photofrin 100 mg/ml
MB 100 M
Photosensitizer and concentration
Murine MRSA arthritis
Murine MRSA arthritis
Animal model
Intravenous injection
Intravenous injection
Intra-articular
Intra-articular
Mode of delivery
NS
12 h after injection
Drug–light interval
Review
Photodynamic therapy as a new treatment modality for inflammatory and infectious conditions Expert Rev. Clin. Immunol. Early online, 1–21 (2015)
Aurelie Reinhard1–3, William J Sandborn4, Hassan Melhem5, Lina Bolotine1,2, Mathias Chamaillard6 and Laurent Peyrin-Biroulet*3,7 1 Universite de Lorraine, Centre de recherche en automatique de Nancy, 54506 Vandoeuvre-le`s-Nancy, France 2 Centre national de la recherche scientifique, Centre de recherche en automatique de Nancy, UMR 7039, 54506 Vandœuvre-le`s-Nancy, France 3 Institut National de la Sante et de la Recherche Medicale, U954, 54500 Vandoeuvre-le`s-Nancy, France 4 Division of Gastroenterology, University of California San Diego, La Jolla, CA, USA 5 Laboratoire NGERE, Faculte de Medecine, 9, Av de la Foreˆt de Haye, Vandoeuvre-le`s-Nancy, 54505 France 6 Institut Pasteur de Lille, Centre d’Infection et d’Immunite de Lille, 59019 Lille, France 7 Department of Hepatogastroenterology, University Hospital of NancyBrabois, University of Lorraine Allee du Morvan, 54511 Vandoeuvre-le`s-Nancy, France *Author for correspondence: Tel.: +33 383 153 631 Fax: +33 383 153 633 [email protected]
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Photodynamic therapy (PDT) is currently used as a minimally invasive therapeutic modality for cancer. Whereas antitumor treatment regimens require lethal doses of photosensitizer and light, sublethal doses may have immunomodulatory effects, antibacterial action and/or regenerative properties. A growing body of evidence now indicates that non-lethal PDT doses can alleviate inflammation or treat established soft-tissue infections in various murine models of arthritis, experimental encephalomyelitis, inflammatory bowel disease and chronic skin ulcers. Furthermore, PDT is already used in clinical application and clinical trial for the treatment of psoriasis, chronic wounds and periodontitis in humans. Sublethal PDT should be regarded as a new viable option for the treatment of inflammatory conditions. KEYWORDS: antimicrobial . immune modulation . inflammation . photodynamic therapy . wound healing
Photodynamic therapy (PDT) is a minimally invasive therapeutic modality that is currently used for the treatment of cancer [1]. The procedure involves administration of a photosensitizer (PS) and subsequent local illumination of the disease site at an appropriate wavelength [1]. The PS is preferentially taken up by rapidly dividing cells (such as tumor cells, microbial cells and activated immune cells) [2,3]. Once activated by light, the PS interacts with molecular oxygen to produce a variety of short-lived reactive oxygen species [1]. The oxidative stress induced by PDT results in necrotic or apoptotic cell death and can produce a variety of effects in immune cells [1,4]. The PS’s type, intracellular site and concentration, and the dose of light applied all influence the exact effects of PDT [2]. High-dose PDT results in direct cytotoxicity within the tumor cells (via oxidative damage to membranes and organelles) and an antivascular action (with impairment of the blood supply to the area via platelet aggregation and, thus, vascular occlusion) [1]. Furthermore, antitumor PDT regimens may also lead to antitumor immunity. Tumor antigens released due to direct cytotoxic effect increase the host immune response
10.1586/1744666X.2015.1032256
against cancer. In contrast, a growing body of evidence now indicates sublethal PDT may suppress the immune response while keeping the cell viability intact [2,5]. The immunosuppressive effect of PDT was first observed in 1986, with the suppression of a contact hypersensitivity reaction in mice previously exposed to a hapten [6]. In some circumstances, inflammatory conditions are also characterized by the uncontrolled proliferation of invading microbes [3], which perturbs the wound-healing process [7,8]. In this context, PDT may change cytokine release or surface receptor expression by the immune cells, promote wound healing by stimulating growth factor synthesis [9,10] and kill or at least inactivate several microbial strains [11–14]. PDT (whether transcutaneous, intra-articular or intraluminal) with sublethal PS and/or light (also called low-dose PDT [LDPDT]) can alleviate inflammation in various murine models of arthritis [15–17], encephalomyelitis [18,19] and inflammatory bowel disease [20,21], or treat established soft-tissue infections in animals model of burn or skin ulcers [9,22,23]. Accordingly, PDT is already used in clinical application and clinical trial for the treatment of psoriasis [24–26], chronic
2015 Informa UK Ltd
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Reinhard, Sandborn, Melhem, Bolotine, Chamaillard & Peyrin-Biroulet
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wounds [27,28], acne vulgaris [29–31] and periodontitis [32–35] in humans. The present article reviews research on the mechanisms underlying anti-inflammatory, antibacterial and healing properties of PDT. The authors also review the research data on the use of PDT to treat certain inflammatory conditions. Mechanisms of action of PDT in infectious & inflammatory conditions
PDT is known to have immunomodulatory, antimicrobial and wound-healing properties (FIGURE 1) [10,36,37]. Immunomodulatory action of PDT
The influence of PDT on the immune response is highly complex and depend on many factors, such as the PS’s formulation, pharmacokinetics and location within cells (especially immune cells), the duration between PS administration and irradiation, the fluence (in J/cm2, i.e., the delivery rate), the fluence rate (in mW/ cm2, i.e., the power of irradiation) and the wavelength (i.e., the extent of tissue penetration) [5]. In some circumstances, PDT has the capacity to increase the host immune response against cancer [38,39]. Indeed, the photo-induced direct damage of neoplastic cells, creating and releasing a mixture of tumor antigens and cellular danger signals, triggers an acute inflammatory response which activates and matures dendritic cells and other cellular components of both the innate and adaptive immune systems [39]. In contrast, LDPDT (i.e., with low levels of PS and/or light) can have immunomodulatory effects able to treat different models of autoimmune disease or inflammatory disorders [37] (FIGURE 1). Sublethal PDT can directly alter the immune cell function (cell signaling events, cytokine production and surface receptor expression) and, thus, alleviate immune-mediated disease [2,37]. Apoptosis of immune cells
Induction of apoptosis by PDT is a well-documented phenomenon that is directly linked to the PS’s localization within the mitochondria [1,40]. Mitochondrial damage has been widely described in PDT-treated tumor cells [41–44]. However, there is relatively little detailed information on PDT’s capacity to induce apoptosis in non-transformed cells in general and immune cells in particular. Very few studies have demonstrated apoptosis in PDT-treated leukocytes [45–47]. One of the key events in PDT-induced apoptosis in immune cells is the accumulation of PS in activated immune cells [46,47]. Hydrophobic PSs bind to plasma lipoproteins, especially low-density lipoproteins. Activated T- and B-cells take up more PS than resting (naı¨ve) cells [46,47]. This greater uptake may be due to the upregulation and increased turnover of low-density lipoprotein receptors [45]. Thus, activated T- and B-lymphocytes may be more vulnerable to the cytotoxic effects of PDT, even with sublethal PDT regimens [48]. Modulation of the expression of immune cell surface molecules
Sublethal PDT may alter cell–cell interactions by modifying the immune cells’ surface receptor expression [2,37,48]. Following LDPDT, APCs may not be able to effectively activate T-cells doi: 10.1586/1744666X.2015.1032256
because of the downregulation of a number of cell surface receptors required for T-cell–APC communication [49]. Dendritic cells (DCs) are potent APCs that act as sentinel cells. They abundantly express MHC antigens, adhesion and co-stimulation molecules, and thus activate naı¨ve T-lymphocytes. Moreover, dendritic cells are an important source of the pro-inflammatory cytokine IL-12 that promotes T-cell–mediated immunity [48]. In vitro treatment of mouse splenic dendritic cells with sublethal levels of verteporfin and light induces a dramatic fall in surface expression of MHC class I and II antigens, CD80 and CD86 co-stimulatory molecules, and CD54 (an adhesion molecule involved in cell–cell interactions) [49]. Furthermore, a study by Obochi et al. demonstrated that pre-treatment of murine skin grafts with benzoporphyrin derivative (BPD)-PDT prolongs their survival in immunocompetent allogeneic recipients [50]. LDPDT decreases the expression of MHC and co-stimulatory molecules expressed by graft Langerhans cells, which, in turn, limits the cells’ capacity to stimulate T-lymphocytes [50]. Studies have shown contradictory effects of PDT on Langerhans cells. Some studies in humans showed an immunosuppressive effect of PDT on the skin via a reduction of Langerhans cells [51,52], whereas others reported no difference in Langerhans cell number [50,53]. Immune response of skin to PDT appears complex; PDT seems to have, in some circumstances, a direct cytotoxic effect or probably induces an adaptive response against oxidative stress which serves to lower the immunostimulatory properties of these cells [37]. Another interesting point is that topical PDT has been shown to decrease the Mantoux response in healthy Mantouxpositive volunteers, confirming that PDT induces immunosuppression probably by altering the expression of and cellular responsiveness to various inflammatory cytokines [54]. Modulation of the type & level of cytokine release
PDT can decrease or increase cytokine expression levels [55]. Larisch et al. have demonstrated that sublethal PS and light level (610 nm, 1.8 mW/cm2, 0–1080 mJ/cm2) significantly reduced the secretion of IL-6 (an important pro-inflammatory cytokine) and increase the expression of the anti-inflammatory cytokine IL-10 in various cell lines [56]. An in vivo study in mouse has also shown that PDT of tumor tissue or healthy tissue leads to a change in the cytokine expression profile [57]. Antitumor PDT (hematoporphyrin derivative 5 mg/kg, 75 mW/cm2, 100 J/cm2) induced a strong increase in IL-6 production and a decrease in the production of IL-10 [57]. In the same study, low-intensity PDT on healthy tissue (1.3 J/cm2, 0.745 mW/cm2) led to a significant increase in the production of IL-10 in mice [57]. The immunosuppressive effect of PDT was convincingly demonstrated by Elmet and Bowen, who reported for the first time that pre-treatment with hematoporphyrin derivative-PDT reduced the contact hypersensitivity response by 50% in mice whose skin had been previously sensitized with a hapten 2,4-dinitrofluorobenzene [6]. The same results were obtained following BPDPDT [58]. Other researchers have observed an increase in Expert Rev. Clin. Immunol.
PDT as a new treatment modality for inflammatory & infectious conditions
→ Antimicrobial properties: – Kill pathogens
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– Bactericidal effects of host immune cells
PDT for non-oncological disorders (Low dose PDT)
→ Healing properties: – Kill invading microbes
→ Inflammatory bowel disease → Arthritis → Experimental allergic encephalomelitis → Psoriasis → Chronic wounds → Acne vulgaris → Periodontitis
er Photosensitizer injection
Review
– Stimulate growth factors synthesis and modify cytokines release
→ Immunomodulatory properties: – Apoptosis of immune cells Irradiation
– Cytokines modification – Alteration of surface receptors expression
1112 1 10 2 9 3 4 8 7 6 5
Drug light interval
Figure 1. Mechanisms of action of PDT for non-oncological disorders. PDT: Photodynamic therapy.
IL-10 production in mice with a decrease in contact hypersensitivity [58]. The immunosuppressive effects of PDT are reversed by the administration of recombinant IL-12 or antiIL-10 antibody and absent in IL-10 knock-out mice [58]. The latter researchers concluded that IL-10 has a key role in the immunosuppression effect induced by BPD-PDT [58]. IL-10 is produced by a wide variety of cell types (including Th2-type T-cells) and inhibits the cell-mediated immune response by decreasing MHC class II expression, APCs’ co-stimulatory functions and the latter’s ability to secrete IL-12 [59–61]. Simkin et al. postulated that PDT might promote Th2-like immune responses by lowering the availability of IL-12 – possibly by increasing IL-10 concentrations [58]. A year later, however, Gollnick et al. reported that IL-10 is not involved in suppression of the contact hypersensitivity response following hematoporphyrin derivativePDT [62]. The PS’s formulation and pharmacokinetics, the drug–light interval and the body surface area irradiated are parameters that govern PDT’s immunomodulatory effect and can sometimes lead to contrasting immunological effects [5]. Wound healing & tissue regeneration
Another property of PDT is its potential for accelerating the regeneration of injured tissues (FIGURE 1). Wound healing is a highly dynamic process and involves complex interactions between extracellular matrix molecules, soluble mediators, various resident cells and infiltrating leukocyte subtypes [8]. In repair, the immediate goal is to achieve tissue integrity and homeostasis. To achieve this goal, the healing process involves informahealthcare.com
three phases that overlap in time and space: inflammation, tissue formation and tissue remodeling [8]. The wound-healing process requires the release of several cytokines, especially IL-10, that stimulate resorption of tissue inflammation and growth factors (VEGF, FGF, PDGF and TGF-b) that promote the cell proliferation and extracellular matrix synthesis in order to repair the damaged tissue [8]. A number of studies have revealed the key role of pro-inflammatory cytokines (IL-1a, IL-1b, IL-6, TNF-a) in prolonging the inflammatory phase [63,64] and the beneficial role of anti-inflammatory cytokines (IL-10, TGF-b) in the wound-healing process [8,65]. Several studies using LDPDT (with low doses of light and/or PS) have clearly demonstrated the beneficial effect of PDT in wound healing [9,10,66,67]. LDPDT appears to hasten the process of wound healing as judged by different studies reporting more rapid re-epithelialization and remodeling [9,10,66,67]. Other studies have reported that sublethal PS and light levels are associated with the upregulation of IL-10 and downregulation of pro-inflammatory cytokines [56–58]. A more recent study evaluating in vitro the release of cytokines by keratocyte postPDT demonstrated a decrease in IL-6 and IL-8 concentrations within 5 h of PDT application [68]. The latter researchers had previously studied the impact of PDT on the in vitro release of growth factors in cultures of keratocytes and had observed elevated concentrations of FGF within 5 h of PDT; in contrast, VEGF and TGF concentrations were unchanged [69]. Tissue and mucosal healing implies the cessation of the initial inflammatory phase [8]. Chronic wounds are frequently doi: 10.1586/1744666X.2015.1032256
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Reinhard, Sandborn, Melhem, Bolotine, Chamaillard & Peyrin-Biroulet
contaminated by bacteria, which cause persistent inflammation and delayed healing [8]. The mechanism underlying tissue regeneration by PDT remains poorly understood, but may result from the impact of PDT on immune response (with stimulation of growth factor synthesis and modulation of cytokine release within the damaged tissue) and the antimicrobial action involved in stopping inflammation [70]. Antimicrobial properties
Growing interest in the antimicrobial effects of PDT over the last decade has prompted use of this technique in a broad range of localized infections (FIGURE 1). This revival of interest has largely been driven by the increasing incidence of infections by antibiotic-resistant bacteria. Antimicrobial PDT has multiple applications, as it can be used to kill or inactivate various pathogens in ex vivo tissues or biological materials (such as blood) and in vivo [3]. PDT has been successfully used to kill pathogens and even to save lives in several animal models of localized infections, such as surface wounds, burns, infections in oral sites, abscesses and infections in the middle ear [9,71]. Thus, the use of PDT as an antimicrobial therapy has been rapidly developed for clinical applications in dermatology and dentistry [3]. In the near future, antimicrobial PDT applications are likely to become more widespread, since the technique presents several advantages over conventional techniques. In particular, use of PDT is without risk to the surrounding tissue and does not appear to induce pathogen resistance. Furthermore, PDT can be used in non-perfused tissue (burns, bone or cartilage) and is less toxic than antibiotics [3]. Recent data demonstrated that the therapeutic beneficial effect of PDT for localized microbial infections results from both direct bacterial killing and also indirect PDT-driven bactericidal effects of host neutrophils [36,72]. On the molecular level, the reactive oxygen species produced by PDT can induce direct microbial photo-inactivation or photo-destruction [73]. Once the PS penetrates into the bacterial cell, it binds to DNA and provokes strand breaks [73,74], or oxidative damage may also occur within the cell’s plasma membrane, leading to the leakage of cellular constituents or inactivation of membrane transporters [73,74]. However, the antibacterial effect could also be achieved by the induction of an immune response against bacteria, but the exact mechanism remains unknown. PDTmediated enhancement of antibacterial immunity can be achieved with modest dose of PDT that allows bacterial reduction without killing the host neutrophils [36]. PDT in animal models of infectious & inflammatory conditions
Several studies have demonstrated the positive impact of sublethal PDT in various murine models of soft-tissue infections or inflammatory and autoimmune disorders, and PDT has been used in several dermatological conditions (SUPPLEMENTARY TABLE 1) (supplementary material can be found online at www.informahealthcare.com/suppl/10.1586/1744666X.2015.1032256/Suppl. doi: 10.1586/1744666X.2015.1032256
doc) [75,76]. The PS can be applied topically or systemically (via oral or intravenous route) [77]. A large range of light sources can be used, including incoherent polychromatic sources (gas discharge lamps and light-emitting diodes) and coherent monochromatic sources (intense pulsed light [78], potassium titanyl phosphate laser, pulsed dye laser and infrared laser) [77]. The light can be administered via different routes – intraluminal (the oral cavity, intranasal or gastric), intra-articular, cutaneous (to a small area of the skin or a large part of the body), transcutaneous or to blood cells during apheresis (using phototherapy UV-A [PUVA], which is not the same as PDT) (FIGURE 2) [77]. The potential advantages of sublethal PDT include the ability to treat large areas of diseased tissue and areas not reachable by surgery, and apply retreatment [1]. Moreover, sublethal PDT is a safe, effective procedure that produces excellent cosmetic results in dermatological applications [1,77]. Localized infections
Infections are widely known to perturb the wound-healing process by delaying the re-epithelialization due to bacterial proliferation. In the recent past, PDT has been successfully used to kill pathogens and even to save life in several animal models of localized infections such as surface wounds, ulcers, burns, infections in oral sites and abscesses [9,11–14,23,71,79,80]. Hamblin et al. were the first group to report the use of mouse wound infection models to investigate the effects of PDT in treating excisional wound infected with Escherichia coli and Pseudomonas aeruginosa [11,12]. The experiment consisted in a single wound (100 mm2) realized on the backs of healthy mice and infected with a suspension of bioluminescent bacteria transduced with a plasmid containing a lux gene operon, which permitted to monitor the infection in real time by a sensitive charge-coupled camera. The wound was treated 1 h later by a topical polycationic PS conjugated at a total fluence of 160 J/cm2 in four 40 J/cm2 aliquots, with imaging taking place after each aliquot of light (TABLE 1). In PDT-treated mice, the authors observed a light dose dependent loss of luminescence with a 99% reduction after the four light aliquots, which was not seen in the untreated wound (TABLE 1) [11]. Moreover, PDT of infected wound did not lead to any damage in host tissue or inhibition of wound healing at these doses, which can be explained by the combination of the topical delivery method together with the large conjugate charge size and the relatively short incubation time (30 min) [11]. In order to test PDT on a more clinically relevant model, the authors performed the same experiment, but using a strain of invasive bacteria P. aeruginosa which led to a fatal sepsis after intraperitoneal injection in animals [12]. During P. aeruginosa infection, all non-treated animals died within 5 days contrary to the PDT-treated group where 90% of mice survived (TABLE 1) [12]. Using similar mouse models, Wong et al. [13] and Zolfaghari et al. [14] studied the effects of methylene blue and toluidine blue O mediated PDT on Vibrio vulnificus and methicillin-resistant Staphylococcus aureus wound infections. A significant reduction of bacterial number was observed in both the studies and PDT could cure mice with Expert Rev. Clin. Immunol.
PDT as a new treatment modality for inflammatory & infectious conditions
Review
Intra-articular PDT
Cutaneous PDT
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Application for: psoriasis or melanomas Intra-articular photosensitizer injection with trancutaneous or intra articular PDT illumination Potential indication for arthritis Topical application of photosensitizer and absorption by cells
Light illumination destruction of targeted cells
Intraluminal PDT
Intraluminal illumination after i.v. photosensitizer injection Application for Barrett’s Esophagus Potential indication for colitis
Laser fiber
Figure 2. Schematic description of PDT administration in vivo and application in inflammatory conditions. iv.: Intravenous; PDT: Photodynamic therapy.
otherwise fatal V. vulnificus wound infections (TABLE 1) [13,14]. However, the relevance of all these results is questionable because PDT treatment was applied rapidly after the wound bacterial inoculation (30 min–1 h). A recent study using more realistic animal infection models including full-thickness burns [9], established infections in which the bacteria have penetrated tissue [22,23], showed the same antibacterial PDT efficacy associated with a fast wound-healing process (TABLE 1) [9,22,23]. Morimoto et al. reported the efficacy of 5-aminolevulinic acid (ALA)-PDT in methicillin-resistant S. aureus–infected ulcers (TABLE 1) [22]. PDT was applied 2 days after the wound infection. The authors reported decrease in bacterial count on surface ulcer and accelerated wound healing, whereas vancomycin therapy was not effective (TABLE 1) [22]. However, it is not clear whether the cause for eradication of the local tissue infection is a direct killing of the pathogens or PDT-induced indirect action on the immune system to prevent infection or healing of the tissue due to the PDT-triggered immune response or a combination of these factors. Arthritis
PDT has been used in two models of arthritis (TABLE 1). In a murine model of methicillin-resistant S. aureus arthritis, PDT’s positive impact was directly related to direct bacterial killing by PDT and indirect PDT-induced bactericidal effects of host neutrophils (TABLE 1) [72,81–84]. In an animal model of adjuvantinformahealthcare.com
enhanced arthritis, PDT’s beneficial effect resulted in the modulation of joint tissue inflammation (TABLE 1) [15,17,85,86]. Ratkay et al. have demonstrated the efficacy of transcutaneous PDT (whole-body irradiation, BPD 0.5 mg/kg, 80 J/cm2) on an adjuvant-enhanced arthritis model in MLR/1pr mice [86]. Animals that underwent three PDT sessions at 10-day intervals had fewer histopathological and clinical signs of disease [86]. Compared with other immunomodulatory agents tested (indomethacin, cyclosporine A and 3 Gy sublethal whole-body irradiation), PDT has proven to be equally effective and lacks the other treatments’ adverse effects (TABLE 1) [86]. Ratkay et al. suggested that PDT’s efficacy resulted from the selective destruction of circulating adjuvant-activated T-cells and/or the localized destruction of joint-infiltrating macrophages [86]. A more recent study in a murine model of antigen-induced arthritis has demonstrated the efficacy and feasibility of local treatment with LDPDT using liposomal temoporfin (metatetra[hydroxyphenyl]chlorin) (0.05–0.01 or 0.005 mg/kg, 5 J/cm2) (TABLE 1) [15]. The intravenously injected PS accumulated rapidly and substantially in the inflamed joints [15]. A histological evaluation revealed a reduction in the severity of arthritis for all groups that received PDT, relative to untreated animals (TABLE 1). This reduction occurred in a dose-dependent manner with a significant decrease in the severity of inflammation for groups treated with 0.05 and 0.01 mg/kg of liposomal meta-tetra(hydroxyphenyl)chlorin [15]. PDT application in these doi: 10.1586/1744666X.2015.1032256
doi: 10.1586/1744666X.2015.1032256
In vitro and in vivo evaluation of PDT to treat potentially lethal wound infections
In vitro and in vivo study evaluating the effect of TBO-PDT against Vibrio vulnificus
In vivo evaluation of PDT to kill MRSA strain
In vitro and in vivo study evaluating the antibacterial activity of free hypericin and nanoencapsulated forms on biofilm and planktonic cells and infected wounds in rats
Hamblin et al. (2003)
Wong et al. (2005)
Zolfaghari et al. (2009)
Nafee et al. (2013)
5-ALA 0, 50 or 200 mg/kg
Hypericin 0.24 M
Excisional skin wounds infected by S. aureus in rat
Established infections, MRSAinfected ulcers
Methylene blue at 100 mg/ml
TBO at various concentrations (0, 1, 10 or 100 mg/ml)
Poly-lysine chlorine e6 (Ce6) conjugate 200 M
Poly-lysine chlorine e6 (Ce6) conjugate 100 M
Photosensitizer and concentration
Excisional and superficial wound models infected with MRSA
Excisional wounds infected with V. vulnificus
Invasive- bacteria (potentially lethal) infecting excisional wounds (Pseudomonas aeruginosa)
Bacteria infecting excisional wounds (Escherichia coli)
Animal model
Intraperitoneally
Topically
Topically
Topically
Topically
Topically
Mode of delivery
One day after injection
–
Immediately after application
2 min after application
30 min after application
30 min after application
Pretreatment with drug/ incubation time
–
Daily for 5 days
–
–
4 aliquots illumination
4 aliquots illumination
No. of sessions
405
–
670
PDT-1200 lamp emits from 560 to 780
665
665
Wavelength (nm)
PDT is effective at reducing the total number of viable MRSA in a wound In vivo study revealed faster healing in rats with better epithelialization, keratinization and development of collagen fibers when nanoencapsulated hypericin was used
360 J/cm2
23.5 J/cm2
ALA-PDT accelerated wound healing and decreased bacterial counts on MRSAinfected skin ulcers
TBO-PDT protects mice from V. vulnificus lethal wound infections. Ten of 19 (53%) mice exposed to TBO at 100 mg/ml and treated with light survived
150 J/cm2 at 80 mW/cm2
0, 10, 50 J/cm2
Control mice died in 5 days; in contrast, rapid light dosedependent eradication of bacteria in PDTtreated mice with 90% survival
Rapid eradication of bacteria infecting the wound demonstrated the possible use of PDT for localized infections and the safety of this method
Results
Total fluence 240 J/cm2 in four aliquots
Total fluence 160 J/cm2 in four 40J/cm2 aliquots
Light treatment parameters
[22]
[23]
[14]
[13]
[12]
[11]
Ref.
8-MOP: 8-methoxypsoralen; AOM: Azoxymethane; ALA: Aminolevulinic acid; BPD: Benzoporphyrin derivative monoacid ring A; DSS: Dextran sodium sulfate; LZD: Linezolid; MB: Methyl Blue; MRSA: Methicillin-resistant Staphylococcus aureus; mTHPC: Meta-tetra(hydroxyphenyl)chlorin; NS: Non-specified; PDT: Photodynamic therapy; TBO: Toluidine blue O; VCM: Vancomycin.
Evaluation of ALAPDT efficacy in MRSA-infected ulcers in mice
In vitro and in vivo study evaluating the use of PDT to treat wound infections
Hamblin et al. (2002)
Morimoto et al. (2014)
Study design
Study (year)
Table 1. Summary of representative articles published in literature, demonstrating a promising application of photodynamic therapy in some inflammatory and infectious conditions.
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In vivo evaluation of therapeutic effect of MB-PDT combined with antibiotics: LZD or VCM
In vivo optimization of Photofrin-PDT light dosimetry in order to maximize bacterial killing in murine MRSA arthritis
In vivo study evaluating the therapeutic effect of mTHPC-PDT in a murine model of antigen-induced arthritis. Comparative study with different formulations
In vivo comparative study of PDT and other immunomodulatory treatments in murine arthritis model
Tanaka et al. (2013)
Tanaka et al. (2011)
Hansch et al. (2008)
Ratkay et al. (1994)
Murine adjuvantenhanced arthritis
Liposomal BPD 0.5 mg/kg
Free mTHPC, liposomal mTHPC and pegylated liposomal mTHPC. 0.1, 0.05, 0.01 or 0.005 mg/kg
Murine adjuvantenhanced arthritis
1
Photofrin 100 mg/ml
MB 100 M
Photosensitizer and concentration
Murine MRSA arthritis
Murine MRSA arthritis
Animal model
Intravenous injection
Intravenous injection
Intra-articular
Intra-articular
Mode of delivery
NS
12 h after injection
Drug–light interval
