bs_bs_banner

International Journal of Urology (2014) 21, 856–864

doi: 10.1111/iju.12501

Review Article

Lower urinary tract symptoms, benign prostatic hyperplasia/benign prostatic enlargement and erectile dysfunction: Are these conditions related to vascular dysfunction? Shogo Shimizu,1 Panagiota Tsounapi,2 Takahiro Shimizu,1 Masashi Honda,2 Keiji Inoue,3 Fotios Dimitriadis4 and Motoaki Saito1 1

Department of Pharmacology, Kochi Medical School, Kochi University, Nankoku, 2Division of Urology, Tottori University School of Medicine, Yonago, 3Department of Urology, Kochi Medical School, Kochi University, Nankoku, Japan; and 4B’ Urologic Department, Papageorgiou General Hospital, School of Medicine, Aristotle University, Thessaloniki, Greece

Abbreviation & Acronyms α-SMA = alpha smooth muscle actin ARB = angiotensin II type 1 receptor blocker BBF = bladder blood flow bFGF = basic fibroblast growth factor BOO = bladder outlet obstruction BP = blood pressure BPE = benign prostatic enlargement BPH = benign prostatic hyperplasia BPO = benign prostatic obstruction DHIC = detrusor hyperactivity with impaired contractility DM = diabetes mellitus DO = detrusor overactivity DU = detrusor underactivity ED = erectile dysfunction HIF-1α = hypoxia-inducible factor 1α HT = hypertension IPSS = International Prostate Symptom Score KATP = adenosine triphosphate-sensitive potassium LUTS = lower urinary tract symptoms MDA = malondialdehyde MetS = metabolic syndrome NGF = nerve growth factor NO = nitric oxide NOS = nitric oxide synthase Nrf2 = nuclear factor erythroid 2-related factor 2 OAB = overactive bladder PDE5i = phosphodiesterase 5 inhibitor ROS = reactive oxygen species SHR = spontaneously hypertensive rats TGB-β1 = transforming growth factor beta 1 WKY = Wistar-Kyoto Correspondence: Motoaki Saito M.D., Ph.D., Department of Pharmacology, Kochi Medical School, Kochi University, Nankoku 783-8505, Japan. Email: [email protected] Received 11 March 2014; accepted 16 April 2014. Online publication 15 June 2014

856

Abstract: Although the pathogenesis of lower urinary tract symptoms, benign prostatic hyperplasia/benign prostatic enlargement and erectile dysfunction is poorly understood and thought to be multifactorial, it has been traditionally recognized that these conditions increase with age. There is increasing evidence that there is an association between cardiovascular disease and lower urinary tract symptoms as well as benign prostatic hyperplasia/ benign prostatic enlargement and erectile dysfunction in elderly patients. Age might activate systemic vascular risk factors, resulting in disturbed blood flow. Hypertension, diabetes, hyperlipidemia and atherosclerosis are also linked to the etiology of lower urinary tract symptoms, benign prostatic hyperplasia/benign prostatic enlargement and erectile dysfunction. In the present review, we discuss the relationship between decreased pelvic blood flow and lower urinary tract symptoms, benign prostatic hyperplasia/benign prostatic enlargement and erectile dysfunction. Furthermore, we suggest possible common mechanisms underlining these urological conditions. Key words: benign prostatic enlargement, benign prostatic hyperplasia, erectile dysfunction, lower urinary tract symptoms, pelvic blood flow, urinary bladder.

Introduction LUTS, BPH/BPE and ED are common conditions in elderly men, and the prevalence of these disorders increases with aging in men.1 In a clinical study by Ponholzer et al., the LUTS score was higher in individuals with more vascular risk factors (HT, DM and hyperlipidemia).2 ED is also up to threefold more prevalent in individuals with vascular risk factors (obesity, HT, type 2 DM and hypertriglyceridemia).3 Specifically, recent attention has been focused on pelvic arterial atherosclerosis as one of the important risk factors for OAB, BPH/BPE and ED. The associations between LUTS, BPH/BPE and ED have a link with the progressive development of vascular occlusive disease in elderly people.4–6 The vascular risk factors; that is, aging and HT, might decrease the pelvic arterial blood flow, and result in dysfunction of the bladder, prostate and penis.7–9 Impairment of blood supply to the lower urinary tract, prostate and penis leads to tissue hypoxia, which can induce structural damage and functional alterations.7,10,11 In a clinical study, transrectal color Doppler ultrasonography of elderly men has shown a significant decrease in bladder and prostatic blood flow in comparison with asymptomatic younger controls.12,13 BPE secondary to BPH could result in LUTS, including storage symptoms, such as increased frequency/urgency and incontinence, and also voiding symptoms, such as slow/intermittent urine stream or straining.14,15 Moderate-to-severe LUTS secondary to BPH is estimated to affect 10–25% of the current worldwide population, approximately 900 million men.16–19 Furthermore, it is estimated that by the year 2018, approximately 1.1 billion men will have BPH-LUTS in the worldwide population.16 SHR is characterized by excessive neuroendocrine activity and sympathetic overactivity, and is a commonly used animal model used to study DO/OAB, BPH and ED.20–22 Furthermore, blood flow in the urinary bladder, dorsolateral and ventral prostate, and penis in SHR proved to be significantly decreased compared with that in the WKY rat.9 We have reported that SHR is a useful model that shows various kinds of disorders including DO, BPH/BPE and ED with a decrease in pelvic blood © 2014 The Japanese Urological Association

LUTS, BPH/BPE, ED and pelvic blood flow

flow.10,23,24 In the present review article, we discuss the relationship between pelvic blood flow and development of LUTS, BPH/BPE and ED, and suggest one possible mechanism of development of LUTS, BPH/BPE and ED.

Pathogenesis of LUTS and BBF Several studies have reported that a decrease in BBF resulting in bladder ischemia induces LUTS, including OAB, DO and DU, in human and animal models.2,25–28 It has been reported that chronic bladder ischemia is caused by BOO in males or by atherosclerosis in both males and females. In males, BOO as a result of BPH has been recognized with common symptoms for LUTS. During the obstruction of the bladder, the resulting increased intravesical pressure causes occlusion of detrusor blood vessels and reduction of BBF (ischemic phase) and oxygen tension (hypoxia), which is followed by increased blood flow and oxygen tension after micturition (reperfusion phase), resulting in ischemia-reperfusion injury in the bladder.29,30 Prolonged chronic ischemia and repeated ischemia-reperfusion injury in the bladder leads to generation of oxidative stress, resulting in injury to neural pathways responsible for micturition, changing the biochemical, histological and neuronal factors of the bladder, and subsequently causing micturition problems.27,31,32 In a study by Masuda et al. to investigate the involvement of oxidative stress against bladder dysfunction, hydrogen peroxide was intravesically injected in rats. The afferent C-fiber pathway was upregulated by the stimulation of oxidative stress, and afterwards it induced DO and urination frequency.33

Chronic bladder ischemia in humans In men, LUTS are traditionally associated with BOO as a result of BPH, but not all cases of LUTS are linked to BOO.34,35 In a clinical study, elderly women suffered from age-associated bladder dysfunction with the same frequency as the elderly men, as shown after urodynamic assessment.36 These data suggest that there might be common reasons, such as aging-associated sexindependent factors.37 Pinggera et al., by applying transrectal color Doppler ultrasonography, reported that elderly patients with LUTS had a significant decrease in bladder or prostate blood flow compared with asymptomatic young patients.13 Chronic ischemia of the bladder and prostate might be responsible for the development of LUTS. Pathophysiological conditions of MetS might be associated with the development of LUTS as a result of the risk of atherosclerotic disease.38,39 A clinical study by Ponholzer showed that there is a relationship between LUTS and vascular risk factors; that is, HT, DM, hyperlipidemia and nicotine use for atherosclerosis. The IPSS was significantly increased in both men and women with two or more risk factors. The authors suggest that atherosclerosis could result in the development of LUTS in both sexes.2 Vascular risk factors impact pelvic arterial blood flow and cause a disturbance in the blood flow through lower urinary tracts. In men, atherosclerosis also induces BPH/BOO and leads to chronic ischemia.40 Thus, LUTS in men might be developed by both atherosclerosis and BOO, which could synergistically act to reduce the BBF.40 The major source artery of the human bladder is the superior and inferior vesical arteries, which are branches of the internal iliac artery. It is known that pelvic artery insuffi© 2014 The Japanese Urological Association

ciency might result in reduced BBF with the generation of ROS and, subsequently, in the upregulation of oxidative stresssensitive genes, stimulatory molecules, muscarinic receptor activity, utrastructural damage and neurodegeneration.27,31,32,41,42 These processes induce marked bladder wall fibrosis and loss of bladder compliance.7,11,13 In addition, in a clinical study, patients with LUTS treated with an α1A-blocker, tamsulosin, were shown to increase BBF and cystometric vesical capacity.25

Chronic bladder ischemia in animal models In a number of studies using a rabbit model, with iliac atherosclerosis in the pelvic arteries, mild or moderate bladder ischemia proved to result in the development of fibrosis, partial denervation of the detrusor muscle and finally it caused DO, which led to the appearance of storage symptoms as represented by OAB.27,31,32,41–43 In contrast, severe bladder ischemia induces the development of denervation and, subsequently, it reduces the bladder smooth muscle contraction resulting in DU and voiding symptoms. It appears to reduce the amplitude of intravesical pressure and decreases the responses to some stimuli with severe fibrosis.27,31,42 It is speculated that the development of bladder dysfunction in chronic bladder ischemia could be associated with the degree and duration of ischemia. However, the timecourse of the effects is not completely understood. There is an increasing number of reports about other animal models of chronic bladder ischemia excluding BOO. These models should be useful tools for understanding the impact of atherosclerosisinduced LUTS. The Watanabe heritable hyperlipidemic rabbit has been shown as a good model of DHIC due to chronic decreased BBF by hyperlipidemia, which is accompanied by progressive atherosclerosis.44 This model is useful for elucidating the mechanism of bladder dysfunction, especially DHIC. In another study, arterial balloon endothelial injury of the iliac artery combined with a 2% cholesterol diet for 8 weeks induced chronic bladder ischemia and caused bladder hyperactivity in the rat.28 SHR is also known to be a valuable animal model used to study HT and urinary frequency/DO. Improvement of the BBF followed by reducing oxidative stress and inflammation could be an important treatment for urinary bladder dysfunction. A decrease in BBF is linked to the development of vascular remodeling stimulated by oxidative stress and inflammation.28 A non-selective α1-blocker, doxazosin, reportedly increases BBF in rats with BOO, accompanied by suppression of the reduction in bladder smooth muscle contractility.45 Treatment with a relative α1A-blocker, tamsulosin, resulted in an increase in BBF, and improved DO in a rat model of bladder overdistention.46 A number of studies published by our group showed that chronic daily treatment with vasodilators, such as nicorandil (KATP channel opener and NO donor), hydroxyfasudil (Rho kinase inhibitor) and silodosin or naftopidil (selective α1A- and relative selective α1D-blockers, respectively) improved the BBF and urodynamic parameter in SHR.24,47–49 Chronic treatment with a PDE5i, tadalafil or a β3-adrenergic receptor agonist, mirabegron, protect bladder function and morphology in chronic bladder ischemia.50,51 Treatment with silodosin and eviprostat, a phototherapeutic agent for the treatment of LUTS in BPH, improved bladder 857

S SHIMIZU ET AL.

hyperactivity with chronic bladder ischemia through an antioxidant and anti-inflammatory effect.52,53

Possible pathogenesis of BPH/BPE In 1999, Abrams in an attempt to distinguish the differences among the pathophysiologies of the prostate.54 For BPE, he described the condition of increased size of the prostate gland usually secondary to BPH. Approximately 50% of men with histological BPH develop BPE. BPO is used to describe BOO secondary to BPE, and therefore is as a result of BPH; whereas just 50% of men with BPE have associated BOO.54 BPH, the actual hyperplasia of the prostate gland, commonly evolves as an age-related phenomenon in almost all men, initiating at approximately 40 years-of-age.55 The disease might affect up to 50% of men aged 60–69 years, and the prevalence increases with age. Although BPH is not a life threatening condition, it affects patients’ quality of life significantly and should not be underestimated.56 BPH/BPE arises from the transition zone of the prostate, and consists of a nodular overgrowth of the epithelium and fibromuscular tissue within the transitional zone and periurethral areas.57,58 Even though the pathogenesis of BPH/ BPE is not yet well clarified and considered to be multifactorial, the remodeling of the prostatic tissue in the transition zone is mainly characterized by: (i) hypertrophia of the basal cells; (ii) alterations in the secretions of the luminal cells, which lead to calcification, clogged ducts and inflammation; (iii) infiltration of lymphocytes with production of pro-inflammatory cytokines; (iv) an increase in the production of ROS, which damages the epithelial and stromal cells; (v) upregulated production of TGF-β1 and bFGF, which induces stromal proliferation, transdifferentiation and extracellular matrix production; (vi) alterations of autonomous innervation, which decreases relaxation and further results in high adrenergic tonus; and (vii) modifications in the neuroendocrine cell function and release of neuroendocrine peptides.59,60

Comorbidities in the aging male HT and BPH/BPE There are a number of studies proposing a role of the vascular system in the development of BPH. Essential HT is an important modifiable risk factor for cardiovascular and renal diseases. The incidence of HT increases in the same manner as BPH with older age. A retrospective analysis by Michel et al. of 9857 patients with diagnosed BPH was carried out in order to study the safety and efficacy of tamsulosin.61 In that study, BPH patients were separated from normotensive (men with diastolic BP of 90 mmHg or less), those with measured HT (men with diastolic BP greater than 90 mmHg), those with diagnosed HT (according to the case record, irrespective of present BP or medication) and those with measured HT who were receiving antihypertensive medication (i.e. diuretic, β-adrenoceptor antagonist, calcium channel blocker, angiotensin-converting enzyme inhibitor). The outcomes of that study showed a significantly greater extent of BPH symptoms as defined by the IPSS or Qmax in patients with measured HT than in normotensive patients. Additionally, BPH symptom severity increased with the number of prescribed antihypertensive drugs. Overall, 858

the data from that study suggest that an association between BPH and HT is more likely to be pathophysiologically relevant.61 Additionally, another study adding supportive evidence to the aforementioned data, showed a prevalence of HT in men undergoing BPH-related surgery compared with a series of control patients.62

Metabolic syndrome and BPH/BPE MetS is a pathological condition characterized by the simultaneous presence of a number of risk factors for heart disease. In a study by Kwon et al., the authors investigated the association between MetS and the predictors of the progression of BPH.63 The findings of that study showed that MetS is correlated with the predictors of the risk of BPH progression in men aged in their 50s with moderate-to-severe LUTS. Furthermore, in another study by De Nunzio et al., the authors investigated the correlation between MetS and prostatic diseases.64 They suggested that MetS induces BPH-LUTS by multiple pathophysiologies, including: (i) chronic inflammation that further leads to the development of BPH nodules; (ii) the insulin growth factor pathway, leading to prostate cell growth; and (iii) pelvic atherosclerosis, leading to chronic ischemia of the bladder and prostate, which can eventually impair the function of the organs. These aforementioned referred mechanisms might still exist after BPH-LUTS development, and in a continuous manner affect the clinical progression of BPH.

Prostatic blood flow and BPH/BPE in humans Ghafar et al. suggested previously that the prostatic vascular system probably plays a role in the development of BPH.65 Furthermore, Berger et al. reported that atherosclerosis is a risk factor for BPH.66 Additionally, another study by Berger et al. showed that an age-related impairment in the blood supply of the lower urinary tract plays a role in the development of BPH, and also that this vascular damage probably causes chronic ischemia and therefore is a contributing factor in the pathogenesis of BPH.66,67

Possible pathogenesis of ED ED is defined as the persistent inability to attain and/or maintain penile erection in order to permit satisfactory sexual intercourse.68 It is estimated that more than 150 million men worldwide have some degree of ED. In the Massachusetts Male Aging Study in 1994, the prevalence of ED was reported to be 52% among men aged 40–70 years.69 Arterial HT affects more than 20% of the general population, with its incidence rising with age. Arterial HT and aging are considered as major risk factors for ED.70 The International Index of Erectile Function has proven to be a cross-cultural and psychometrically valid measure of male ED.71 According to the underlying causes, ED can be classified as psychogenic, endocrinological, neurogenic and vasculogenic. ED frequently coexists with HT, DM, hyperlipidemia and cardiovascular disease.72 It has been proven that ED and coronary artery disease share common pathways. One of the basic mechanisms that contributes to the pathophysiology of organic ED is endothelial dysfunction, which develops as a result of decreased synthesis and bioavailability of NO, and © 2014 The Japanese Urological Association

LUTS, BPH/BPE, ED and pelvic blood flow

∗

200

∗

∗

200

∗

∗

W

SH R+ Si l

SH

W

W

BBF (mL/min/100g tissue) #

200

∗

∗

100

HT impairs pelvic arterial blood flow resulting in reduced BBF and loss of bladder compliance. The SHR is a rat strain widely used model of genetic HT. The SHR develops bladder hyperactivity, and is considered a valuable tool for exploring the pathogenesis of DO.8,75 The SHR was originally established from normotensive Wistar and WKY rats. However, recent studies showed that WKY rats have bladder hyperactivity of a frequency and amplitude similar to the SHR.76,77 The SHR shows a significant decrease in BBF and bladder capacity.9 In contrast, the SHR shows an increase in the voiding frequency compared with normotensive Wistar rats.24,47,48,75 NGF is one of the neurotrophins families involved in C-fiber afferent nerve excitability and reflex bladder activity, and thought to be a biomarker of DO. The hypercontractivity in the SHR is related to the enhanced NGF secretion and related neuroplasticity.75,76 First, our hypothesis was that vasodilating drugs in the bladder could improve HT-related bladder dysfunction through improvement of BBF and three drugs; that is, nicorandil, silodosin and hydroxyfasudil were found to increase the BBF

R+ SH

SH

R+

Si

l

R SH

ar ist W

SH

R+

Ni

c

SH R

ar ist

Bladder dysfunction in the SHR

Fa s

0

0

SHR as a chronic ischemia model in the pelvic organs and penis

∗

100

R

0

#

SH

100

200

ar

200

ist

#

W

(b)

ist ar

0

SH R

0

ist ar

0

R SH R+ Ni c

100

ist ar

100

subsequent atherosclerosis. Atherosclerosis leads to an impairment of the blood flow required for erection.73 The impairment of erectile function in men with essential HT arises not from the increased BP, but by the associated stenotic lesions.74 Atherosclerosis seems to be the primary pathogenetic mechanism compromising penile arterial flow, whereas the reduction of BP by antihypertensive drugs might worsen the situation. The atherosclerotic process in penile arteries might result in decreased blood flow, whereas endothelial dysfunction secondary to HT and other related diseases could lead to neurovegetative changes and contribute to ED.70

© 2014 The Japanese Urological Association

200

100

W

Fig. 1 General characteristics of the experimental animals. (a) Mean blood pressure in the experimental rat. (b) BBF in the experimental rat. Wistar: 18-week-old Wistar rat, control group; SHR: 18-week-old SHR group; SHR+Nic: 18-week-old SHR treated with nicorandil at a daily dose of 10 mg/kg i.p.; SHR+Sil: 18-week-old SHR treated with silodosin at a daily dose of 100 μg/kg p.o.; SHR+Fas: 18-weekold SHR treated with hydroxyfasudil at a daily dose of 1 mg/kg i.p. Data are expressed as means ± SEM of eight separate determinations in each group. *Significantly different from Wistar group (P < 0.05); #Significantly different from SHR group (P < 0.05). Reproduced by Saito et al.,21 Inoue et al.44 and Inoue et al.45

∗

SH R+ Fa s

Mean blood pressure (mmHg)

SH R

(a)

without significant effects on BP (Fig. 1).24,47,48 In the SHR, BP, micturition frequency and NGF (a biomarker of DO) concentrations in the bladder were significantly higher than those in the age-matched Wistar rat. In contrast, single voided volume in the metabolic cage or cystometrogram, and BBF in the SHR were significantly lower than those in the Wistar rat. Six-week daily treatment with nicorandil, silodosin and hydroxyfasudil significantly ameliorated bladder dysfunction in the SHR (Figs 2,3).24,47,48 As silodosin and naftopidil are used worldwide against BPH-LUTS, we characterized these two drugs with this model. We found that both silodosin and naftopidil improved HT-related bladder dysfunction in the SHR, and naftopidil but not silodosin improved urinary frequency in the light-cycle as a result of inhibition of urine production (Fig. 3).49 Antihypertensive therapies could improve HT-associated bladder dysfunction. However, some of these therapies failed to improve the symptoms of male LUTS. For example, angiotensin-converting enzyme inhibitors and calcium channel blockers did not improve the IPSS. In contrast, ARBs have a favorable effect against male LUTS.78 Recently, our study showed that ARBs might have additional benefits on bladder function beyond BP reduction.79 Our study reported that treatment with an ARB olmesartan for six-week daily ameliorated urodynamic parameter, BBF and the oxidative stress in the SHR. An L-type calcium channel blocker, nifedipine, is widely used as an important drug in the treatment of HT and coronary heart disease.80 Nifedipine had a strong hypotensive effect, but did not significantly recover BBF and urodynamic parameter in the SHR. These findings suggest that recovery of BBF is more marked, and has an important target on LUTS compared with reduction of BP. The strong positive immunoreactivities of 4-hydroxynonenal (an oxidative stress marker), Nrf2 (a master regulator of the endogenous antioxidant responses) and NGF were observed mainly in the urothelium in the SHR compared with those in the Wistar rat. Olmesartan, but not nifedipine, 859

S SHIMIZU ET AL.

Single voided volume in the metabolic cage (mL)

∗#

1.0

∗# 1.0

∗

∗

0

(b)

ist ar W

Single voided volume in cystometrogram (mL)

0.5

0.5

∗#

∗

5

5

0

0

0

l

s Fa

ist

Si SH

W

R+

ar W

R+

ist

Ni

SH R

SH

Micturition frequency/12 h (light cycle)

20 15

∗

10

∗

#

#

5

0 SH

R+

Na

f1 Na R+ SH

f3

0

l Si

SH R

R+ SH

W

ist

ar

0

significantly reduced these markers in the SHR bladder. Thus, we suggest one possible mechanism of the bladder dysfunction in the SHR; mild or moderate oxidative stress stimulates the urothelium and upregulates Nrf2, with subsequent upregulation of NGF and induces DO (Fig. 4).

BPH/BPE in the SHR Yamashita et al. previously showed that the hyperplastic changes in the ventral prostate in the SHR are developed with advancing age, and usually these changes are observed in

s

5

Fa

10

∗#

R+

10

ar

10

SH R

15

c

15

ar

15

(b)

∗

20

SH

∗#

SH R

∗

20

#

ist

R+ SH

SH

W

R+

ist

SH R

ar

l Si

SH R

ist W 20

W

Fig. 2 Voiding behavior studies in the experimental animals. (a) Single voided volume measured by metabolic cages in the experimental rat. (b) Single voided volume measured cystometrography in the experimental rat. Wistar: 18-week-old Wistar rat, control group; SHR: 18-week-old SHR group; SHR+Nic: 18-week-old SHR treated with nicorandil at a daily dose of 10 mg/kg i.p.; SHR+Sil: 18-week-old SHR treated with silodosin at a daily dose of 100 μg/kg p.o.; SHR+Fas: 18-week-old SHR treated with hydroxyfasudil at a daily dose of 1 mg/kg i.p. Data are expressed as means ± SEM of eight separate determinations in each group. *Significantly different from Wistar group (P < 0.05); #Significantly different from SHR group (P < 0.05). Reproduced from Saito et al.,21 Inoue et al.44 and Inoue et al.45

Micturition frequency/24 h

∗

860

∗#

∗

0

ar

0

(a)

SH R+ Si l

SH R

W

ist ar

SH R+ Ni c

SH R

W

ist ar

0

SH R

0

∗

as

∗#

1.0

SH R+ F

(a)

Fig. 3 Micturition frequency of the experimental animals. (a) Micturition frequency within 24 h (12 h light and 12 h dark) in the experimental rats. (b) Micturition frequency in the light cycle (12 h) in the experimental rat. Wistar: 18-week-old Wistar rat, control group; SHR: 18-week-old SHR group; SHR+Nic: 18-week-old SHR treated with nicorandil at a daily dose of 10 mg/kg i.p.; SHR+Sil: 18-week-old SHR treated with silodosin at a daily dose of 100 μg/kg p.o.; SHR+Fas: 18-week-old SHR treated with hydroxyfasudil at a daily dose of 1 mg/kg i.p.; SHR+Naf10: 18-week-old SHR treated with naftopidil at a daily dose of 10 mg/kg p.o.; SHR+Naf30: 18-week-old SHR treated with naftopidil at a daily dose of 30 mg/kg p.o. Data are expressed as means ± SEM of eight separate determinations in each group. *Significantly different from Wistar group (P < 0.05); #Significantly different from SHR group (P < 0.05). Reproduced from Saito et al.,21 Inoue et al.,44 Inoue et al.45 and Saito et al.46

15-week-old SHR.81 This genetically selected rat strain is characterized by a reduced blood flow in the dorsolateral and ventral prostate when compared with its normotensive control WKY rat.9 Yono et al. have treated the SHR with doxazosin, an α1-blocker, and observed the normalization of the decreased blood flow in the prostate.9 Another study that adds strong evidence to the high importance of the blood flow in normal prostatic function is from Nakamura and Itakura, whereby chronic administration of another α1-blocker, terazosin, showed inhibition of hyperplastic changes in the SHR prostate.82 A © 2014 The Japanese Urological Association

LUTS, BPH/BPE, ED and pelvic blood flow

androgen-dependent organ and androgens are established risk factors for the development of BPH/BPE, we did not find any differences in the dihydrotestosterone levels between the SHR and the WKY rat. This means that the BPH development in our SHR model was mainly derived from decreased prostatic blood flow and subsequently from mild hypoxia, and is not controlled by androgen levels (Fig. 7).10

BBF ↓

Release of oxidative stress ↑ inflammation ↑ ?

Transcription factor Nrf2 ↑

Bladder urothelial damage

C fiber activation

Bladder NGF ↑

DO Fig. 4

Possible mechanism for the development of DO in the SHR.

study by Morelli et al. demonstrated that the SHR showed significant immunopositivity for hypoxyprobe staining, for hypoxia detection, with hypoxic cells being predominantly distributed in the epithelial layers of the prostatic ducts compared with the WKY rat, where the hypoxyprobe staining was almost undetectable.83 This reveals a lower oxygenation of the SHR prostate. In the same study, the authors also observed that the SHR prostate was characterized by morphological alterations, such as dilation of the hypoxic glandular alveolas, and reduction of interstitial and stromal spaces compared with WKY prostate samples.83 In a very recent study from our laboratory, we investigated the relationship between prostatic blood flow and prostatic hyperplasia in the SHR.10 We hypothesized that chronic ischemia in the prostate causes a mild hypoxia, which further induces an upregulation in HIF-1α, which is the master regulator of oxygen homeostasis, and also in the ROS, which subsequently activate TGF-β1 and bFGF in the prostate, leading further to stromal proliferation, transdifferentiation and extracellular matrix production. For our study, we used chronic administration of nicorandil to investigate the prostate blood flow and hyperplasia in the SHR. Nicorandil is known to have dual actions, a nitrate-like action and a KATP channel opener action.84 Additionally, we have previously shown the effect of nicorandil to increase the BBF in the SHR and also to ameliorate the HT-related bladder dysfunction in the SHR.24 Our data showed a hyperplastic ventral prostate in the SHR compared with the WKY rat. Also, prostatic blood flow was significantly decreased in the SHR (Fig. 5). The SHR also showed increased levels of MDA (an oxidative stress marker), HIF-1α, TGF-β1, bFGF and α-SMA compared with the WKY rat (Figs 5,6). Examination of the histology revealed epithelial cells being longer in shape with irregularities in the nuclear arrangement in the ventral prostate, whereas the WKY group showed normal, unfolded, closely packed, acini tapered by low cuboidal cells demonstrating a uniform monolayer arrangement. Chronic nicorandil treatment significantly normalized all the aforementioned parameters (Figs 5,6). Although the prostate is an © 2014 The Japanese Urological Association

ED in the SHR The SHR is known to show various kinds of disorders, including ED.9 In the study by Yono et al., untreated SHRs demonstrated lower blood flow to the penis than normotensive WKY rats. Chronic ischemia/hypoxia, which is a result of decreased blood flow, induces fibrosis and reduces NOS expressions in the SHR genitourinary tract.7 These changes that influence smooth muscle relaxation in the penis might contribute to the induction of ED in the SHR.9 In a study by Zhang et al., the authors developed an atherosclerosis-induced ED rabbit model by balloon de-endothelialization of the iliac artery.82 The arterial ballooning produced diffused atherosclerotic occlusive disease and caused a significant decrease in intracavernosal blood flow compared with the age-matched control group.85 In that study, the authors suggested that oxidative stress accumulates in the ischemic penis in arteriogenic ED. The oxidative burden of the ischemic erectile tissue could exceed its anti-oxidant capacity and lead to oxidative injury. This might contribute to impairment of NO-mediated endothelium-dependent smooth muscle relaxation, and structural damage in the ischemic penis.85 Furthermore, the authors showed that arterial occlusive disease of major penile arteries decreased the erectile tissue blood flow, reduced the intracavernosal perfusion pressure and impaired the metabolic waste clearance from the erectile tissue. These changes were associated with cellular and subcellular reactions evidenced by accumulation of oxidatively modified products, upregulation of oxidation-sensitive genes encoding super oxide dismutase, adrenergic receptor and ultrastructural alterations.82 During penile ischemia, nutrient deficiency, inadequate antioxidant enzymatic activity, hypoxia and lack of perfusion to clear waste products constitute an environment conductive to the formation and accumulation of oxidative radicals.85 Furthermore, in a study by Vignozzi et al., the authors created an in vivo experimental model of penile prolonged hypoxia in the rat by bilateral cavernous neurotomy, which completely prevented spontaneous or apomorphine-induced erections and, therefore, physiological penile reoxygenations.86 In a previous study from our laboratory, we investigated the Rho–Rho kinase pathway in the erectile function in the SHR.23 For this purpose, we have treated the SHR with hydroxyfasudil. By using in vitro organ bath studies, we found a significant lower ability of the non-treated SHR to relax and a hypercontractility compared with the normotensive control. Hydroxyfasudil treatment significantly recovered these abnormalities in the penile function.23 Furthermore, the SHR showed significantly lower cyclic guanosine monophosphate concentrations, endothelial NOS mRNA levels and phosphorylated endothelial NOS. Treatment with hydroxyfasudil significantly normalized the cyclic guanosine monophosphate content, the endothelial NOS mRNA expression and endothelial NOS phosphorylation.23 861

S SHIMIZU ET AL.

Prostatic blood flow (mL/min/100 g)

SH R+ Ni c1 0

W (b)

SH R

Ventral prostate in HE staining

KY

(a)

(c)

MDA (nmol/mg protein)

#

3.0

∗

100

∗

4.0

#

200

2.0 1.0

(b)

TGF-b1 (pg/mg protein) ∗

0.6

c1

R

SH

Ni SH

R+

R+

Ni

W

SH

KY

0 c1

R SH

W KY (a)

0

0

0

Fig. 5 Histological, functional and oxidative stress changes in the prostate of the SHR. (a) Hematoxylin– eosin staining images showing typical alterations in the histology in the ventral prostate in the SHR (magnification: ×200). (b) Blood flow and (c) MDA levels in the prostate of the experimental animals. WKY: 18-week-old Wistar-Kyoto rats, control group; SHR: 18-week-old SHR group; SHR+Nic10: 18-week-old SHRs treated with nicorandil at a daily dose of 10 mg/kg, i.p. Data are expressed as means ± SEM. *Significantly different from WKY group (P < 0.05); #Significantly different from SHR group (P < 0.05). Reproduced from Saito et al.10

bFGF (pg/mg protein) ∗

1.6

c1 SH

R+

R+

Ni

W

Ni

R

0 c1

R SH SH

α-SMA ∗

(c) 2

1

c1 0

R SH

R+

Ni

SH

W KY

0

α-SMA

42 kDa

β-actin

40 kDa

Conclusion All these clinical and translational studies add supportive evidence in our findings showing that impairment in the blood flow 862

SH

0

KY

0

W KY

0.8

0

# 0.3

Fig. 6 TGF-β1, bFGF and α-SMA levels in the prostatic tissue. (a) Levels of TGF-β1 and (b) bFGF in the prostate of the experimental animals. (c) α-SMA protein expression levels in the prostate of the experimental animals. WKY: 18-week-old WistarKyoto rats, control group; SHR: 18-week-old SHR group; SHR+Nic10: 18-week-old SHRs treated with nicorandil at a daily dose of 10 mg/kg, i.p. Data are expressed as means ± SEM. *Significantly different from WKY group (P < 0.05); #Significantly different from SHR group (P < 0.05). Reproduced from Saito et al.10

in the pelvic organs and penis induces mild hypoxia, which further possibly induces development of DO, BPH/BPE and ED. We suggest that chronic ischemia in the pelvic organs and penis induces, not all but in some part, LUTS, BPH/BPE and ED. © 2014 The Japanese Urological Association

LUTS, BPH/BPE, ED and pelvic blood flow

Chronic ischemia in prostate Prostatic blood flow ↓

Release of Release oxidativeofstress ↑ oxidative stress inflammation ↑

HIF-1 a ↑

14

15

16

TGF-b1, bFGF ↑ 17

Stromal proliferation transdifferentiation and extracellar matrix production

18

19

BPH/BPE Fig. 7

Possible mechanisms mediating the development of BPH in the SHR.

Acknowledgments

20

21

This study was supported by a grant in aid from the Japan Society for the Promotion of Science (#24592431 and 20591880). 22

Conflict of interest None declared.

References 1 Lowe FC. Treatment of lower urinary tract symptoms suggestive of benign prostatic hyperplasia: sexual function. BJU Int. 2005; 95 (Suppl 4): 12–18. 2 Ponholzer A, Temml C, Wehrberger C et al. The association between vascular risk factors and lower urinary tract symptoms in both sexes. Eur. Urol. 2006; 50: 581–6. 3 Gorbachinsky I, Akpinar H, Assimos DG. Metabolic syndrome and urologic diseases. Rev. Urol. 2010; 12: e157–80. 4 Kohler TS, McVary KT. The relationship between erectile dysfunction and lower urinary tract symptoms and the role of phosphodiesterase type 5 inhibitors. Eur. Urol. 2009; 55: 38–48. 5 Berger AP, Deibl M, Leonhartsberger N et al. Vascular damage as a risk factor for benign prostatic hyperplasia and erectile dysfunction. BJU Int. 2005; 96: 1073–8. 6 Braun MH, Sommer F, Haupt G et al. Lower urinary tract symptoms and erectile dysfunction: co-morbidity or typical “Aging Male” symptoms? Results of the “Cologne Male Survey”. Eur. Urol. 2003; 44: 588–94. 7 Tarcan T, Azadzoi KM, Siroky MB et al. Age-related erectile and voiding dysfunction: the role of arterial insufficiency. Br. J. Urol. 1998; 82 (Suppl 1): 26–33. 8 Yono M, Tanaka T, Tsuji S et al. Effects of age and hypertension on alpha1-adrenoceptors in the major source arteries of the rat bladder and penis. Eur. J. Pharmacol. 2011; 670: 260–5. 9 Yono M, Yamamoto Y, Yoshida M et al. Effects of doxazosin on blood flow and mRNA expression of nitric oxide synthase in the spontaneously hypertensive rat genitourinary tract. Life Sci. 2007; 81: 218–22. 10 Saito M, Tsounapi P, Oikawa R et al. Prostatic ischemia induces ventral prostatic hyperplasia in the SHR; possible mechanism of development of BPH. Sci. Rep. 2014; 4. doi: 10.1038/srep03822. 11 Siroky MB. The aging bladder. Rev. Urol. 2004; 6 (Suppl 1): S3–7. 12 De EJ, Hou P, Estrera AL et al. Pelvic ischemia is measurable and symptomatic in patients with coronary artery disease: a novel application of dynamic contrast-enhanced magnetic resonance imaging. J. Sex. Med. 2008; 5: 2635–45. 13 Pinggera GM, Mitterberger M, Steiner E et al. Association of lower urinary tract symptoms and chronic ischaemia of the lower urinary tract in elderly

© 2014 The Japanese Urological Association

23

24

25

26

27 28

29

30 31

32 33

34 35

36

women and men: assessment using colour Doppler ultrasonography. BJU Int. 2008; 102: 470–4. AUA guideline on management of benign prostatic hyperplasia (2003). Chapter 1: diagnosis and treatment recommendations. J. Urol. 2003; 170: 530–47. Abrams P, Cardozo L, Fall M et al. The standardisation of terminology of lower urinary tract function: report from the Standardisation Sub-committee of the International Continence Society. Neurourol. Urodyn. 2002; 21: 167–78. Casabe A, Roehrborn CG, Da Pozzo LF et al. Efficacy and safety of the coadministration of tadalafil once daily with finasteride for 6 months in men with lower urinary tract symptoms and prostatic enlargement secondary to benign prostatic hyperplasia. J. Urol. 2014; 191: 727–33. Verhamme KM, Dieleman JP, Bleumink GS et al. Incidence and prevalence of lower urinary tract symptoms suggestive of benign prostatic hyperplasia in primary care-the Triumph project. Eur. Urol. 2002; 42: 323–8. Coyne KS, Sexton CC, Thompson CL et al. The prevalence of lower urinary tract symptoms (LUTS) in the USA, the UK and Sweden: results from the Epidemiology of LUTS (EpiLUTS) study. BJU Int. 2009; 104: 352–60. Irwin DE, Milsom I, Hunskaar S et al. Population-based survey of urinary incontinence, overactive bladder, and other lower urinary tract symptoms in five countries: results of the EPIC study. Eur. Urol. 2006; 50: 1306–14; discussion 1314–15. Fibbi B, Morelli A, Vignozzi L et al. Characterization of phosphodiesterase type 5 expression and functional activity in the human male lower urinary tract. J. Sex. Med. 2010; 7: 59–69. Filippi S, Morelli A, Sandner P et al. Characterization and functional role of androgen-dependent PDE5 activity in the bladder. Endocrinology 2007; 148: 1019–29. Kedia GT, Uckert S, Jonas U et al. The nitric oxide pathway in the human prostate: clinical implications in men with lower urinary tract symptoms. World J. Urol. 2008; 26: 603–9. Saito M, Ohmasa F, Dimitriadis F et al. Hydroxyfasudil ameliorates penile dysfunction in the male spontaneously hypertensive rat. Pharmacol. Res. 2012; 66: 325–31. Saito M, Ohmasa F, Tsounapi P et al. Nicorandil ameliorates hypertension-related bladder dysfunction in the rat. Neurourol. Urodyn. 2012; 31: 695–701. Pinggera GM, Mitterberger M, Pallwein L et al. alpha-Blockers improve chronic ischaemia of the lower urinary tract in patients with lower urinary tract symptoms. BJU Int. 2008; 101: 319–24. Wada N, Watanabe M, Kita M et al. Analysis of bladder vascular resistance before and after prostatic surgery in patients with lower urinary tract symptoms suggestive of benign prostatic obstruction. Neurourol. Urodyn. 2012; 31: 659–63. Azadzoi KM, Tarcan T, Kozlowski R et al. Overactivity and structural changes in the chronically ischemic bladder. J. Urol. 1999; 162: 1768–78. Nomiya M, Sagawa K, Yazaki J et al. Increased bladder activity is associated with elevated oxidative stress markers and proinflammatory cytokines in a rat model of atherosclerosis-induced chronic bladder ischemia. Neurourol. Urodyn. 2012; 31: 185–9. Lin AT, Chen MT, Yang CH et al. Blood flow of the urinary bladder: effects of outlet obstruction and correlation with bioenergetic metabolism. Neurourol. Urodyn. 1995; 14: 285–92. Matsumoto S, Kakizaki H. Causative significance of bladder blood flow in lower urinary tract symptoms. Int. J. Urol. 2012; 19: 20–5. Azadzoi KM, Shinde VM, Tarcan T et al. Increased leukotriene and prostaglandin release, and overactivity in the chronically ischemic bladder. J. Urol. 2003; 169: 1885–91. Azadzoi KM, Yalla SV, Siroky MB. Oxidative stress and neurodegeneration in the ischemic overactive bladder. J. Urol. 2007; 178: 710–15. Masuda H, Kihara K, Saito K et al. Reactive oxygen species mediate detrusor overactivity via sensitization of afferent pathway in the bladder of anaesthetized rats. BJU Int. 2008; 101: 775–80. Andersson KE. Storage and voiding symptoms: pathophysiologic aspects. Urology 2003; 62: 3–10. Hyman MJ, Groutz A, Blaivas JG. Detrusor instability in men: correlation of lower urinary tract symptoms with urodynamic findings. J. Urol. 2001; 166: 550–2; discussion 553. Chancellor MB, Rivas DA. American Urological Association symptom index for women with voiding symptoms: lack of index specificity for benign

863

S SHIMIZU ET AL.

37 38 39

40 41

42

43 44

45

46

47

48

49

50 51

52

53

54 55 56

57 58 59

60 61

prostate hyperplasia. J. Urol. 1993; 150: 1706–8; discussion 1708–9. Chapple CR, Wein AJ, Abrams P et al. Lower urinary tract symptoms revisited: a broader clinical perspective. Eur. Urol. 2008; 54: 563–9. Kaplan SA. Male pelvic health: a urological call to arms. J. Urol. 2006; 176: 2351–2. Mariappan P, Chong WL. Prevalence and correlations of lower urinary tract symptoms, erectile dysfunction and incontinence in men from a multiethnic Asian population: results of a regional population-based survey and comparison with industrialized nations. BJU Int. 2006; 98: 1264–8. Yamaguchi O, Nomiya M, Andersson KE. Functional consequences of chronic bladder ischemia. Neurourol. Urodyn. 2014; 33: 54–8. Azadzoi KM, Chen BG, Radisavljevic ZM et al. Molecular reactions and ultrastructural damage in the chronically ischemic bladder. J. Urol. 2011; 186: 2115–22. Azadzoi KM, Tarcan T, Siroky MB et al. Atherosclerosis-induced chronic ischemia causes bladder fibrosis and non-compliance in the rabbit. J. Urol. 1999; 161: 1626–35. Brading AF, Turner WH. The unstable bladder: towards a common mechanism. Br. J. Urol. 1994; 73: 3–8. Yoshida M, Masunaga K, Nagata T et al. The effects of chronic hyperlipidemia on bladder function in myocardial infarction-prone Watanabe heritable hyperlipidemic (WHHLMI) rabbits. Neurourol. Urodyn. 2010; 29: 1350–4. Das AK, Leggett RE, Whitbeck C et al. Effect of doxazosin on rat urinary bladder function after partial outlet obstruction. Neurourol. Urodyn. 2002; 21: 160–6. Okutsu H, Matsumoto S, Ohtake A et al. Effect of tamsulosin on bladder blood flow and bladder function in a rat model of bladder over distention/emptying induced bladder overactivity. J. Urol. 2011; 186: 2470–7. Inoue S, Saito M, Takenaka A. Hydroxyfasudil ameliorates bladder dysfunction in male spontaneously hypertensive rats. Urology 2012; 79: 1186 e9–14. Inoue S, Saito M, Tsounapi P et al. Effect of silodosin on detrusor overactivity in the male spontaneously hypertensive rat. BJU Int. 2012; 110: E118–24. Saito M, Shimizu S, Ohmasa F et al. Characterization of silodosin and naftopidil in the treatment of bladder dysfunction in the spontaneously hypertensive rat. Neurourol. Urodyn. 2013; 32: 393–8. Nomiya M, Yamaguchi O, Akaihata H et al. Progressive vascular damage may lead to bladder underactivity in rats. J. Urol. 2014; 191: 1462–9. Sawada N, Nomiya M, Hood B et al. Protective effect of a beta3-adrenoceptor agonist on bladder function in a rat model of chronic bladder ischemia. Eur. Urol. 2013; 64: 664–71. Goi Y, Tomiyama Y, Nomiya M et al. Effects of silodosin, a selective alpha1A-adrenoceptor antagonist, on bladder blood flow and bladder function in a rat model of atherosclerosis induced chronic bladder ischemia without bladder outlet obstruction. J. Urol. 2013; 190: 1116–22. Matsui T, Oka M, Fukui T et al. Suppression of bladder overactivity and oxidative stress by the phytotherapeutic agent, Eviprostat, in a rat model of atherosclerosis-induced chronic bladder ischemia. Int. J. Urol. 2012; 19: 669–75. Abrams P. LUTS, BPH, BPE, BPO: a plea for the logical use of correct terms. Rev. Urol. 1999; 1: 65. Roehrborn CG. Benign prostatic hyperplasia: an overview. Rev. Urol. 2005; 7 (Suppl 9): S3–S14. Calais Da Silva F, Marquis P, Deschaseaux P et al. Relative importance of sexuality and quality of life in patients with prostatic symptoms. Results of an international study. Eur. Urol. 1997; 31: 272–80. Sarma AV, Wei JT. Clinical practice. Benign prostatic hyperplasia and lower urinary tract symptoms. N. Engl. J. Med. 2012; 367: 248–57. Untergasser G, Madersbacher S, Berger P. Benign prostatic hyperplasia: age-related tissue-remodeling. Exp. Gerontol. 2005; 40: 121–8. De Marzo AM, Coffey DS, Nelson WG. New concepts in tissue specificity for prostate cancer and benign prostatic hyperplasia. Urology 1999; 53: 29–39; discussion 39–42. Steiner MS, Couch RC, Raghow S et al. The chimpanzee as a model of human benign prostatic hyperplasia. J. Urol. 1999; 162: 1454–61. Michel MC, Heemann U, Schumacher H et al. Association of hypertension with symptoms of benign prostatic hyperplasia. J. Urol. 2004; 172: 1390–3.

864

62 Bourke JB, Griffin JP. Hypertension, diabetes mellitus, and blood groups in benign prostatic hypertrophy. Br. J. Urol. 1966; 38: 18–23. 63 Kwon H, Kang HC, Lee JH. Relationship between predictors of the risk of clinical progression of benign prostatic hyperplasia and metabolic syndrome in men with moderate to severe lower urinary tract symptoms. Urology 2013; 81: 1325–9. 64 De Nunzio C, Aronson W, Freedland SJ et al. The correlation between metabolic syndrome and prostatic diseases. Eur. Urol. 2012; 61: 560–70. 65 Ghafar MA, Puchner PJ, Anastasiadis AG et al. Does the prostatic vascular system contribute to the development of benign prostatic hyperplasia? Curr. Urol. Rep. 2002; 3: 292–6. 66 Berger AP, Bartsch G, Deibl M et al. Atherosclerosis as a risk factor for benign prostatic hyperplasia. BJU Int. 2006; 98: 1038–42. 67 Berger AP, Horninger W, Bektic J et al. Vascular resistance in the prostate evaluated by colour Doppler ultrasonography: is benign prostatic hyperplasia a vascular disease? BJU Int. 2006; 98: 587–90. 68 Lue TF, Giuliano F, Montorsi F et al. Summary of the recommendations on sexual dysfunctions in men. J. Sex. Med. 2004; 1: 6–23. 69 Feldman HA, Goldstein I, Hatzichristou DG et al. Impotence and its medical and psychosocial correlates: results of the Massachusetts Male Aging Study. J. Urol. 1994; 151: 54–61. 70 Doumas M, Tsakiris A, Douma S et al. Factors affecting the increased prevalence of erectile dysfunction in Greek hypertensive compared with normotensive subjects. J. Androl. 2006; 27: 469–77. 71 Rosen RC, Riley A, Wagner G et al. The international index of erectile function (IIEF): a multidimensional scale for assessment of erectile dysfunction. Urology 1997; 49: 822–30. 72 Lue TF. Erectile dysfunction. N. Engl. J. Med. 2000; 342: 1802–13. 73 Kefi A, Demir Ö, Seçil M et al. Doppler ultrasonography in erectile dysfunction patients with risk factors. Turk. J. Urol. 2005; 31: 202–6. 74 Hsieh JT, Lue TF, Muller SC. The influence of blood flow and blood pressure on penile erection. Int. J. Impot. Res. 1989; 1: 35–42. 75 Steers WD, Clemow DB, Persson K et al. The spontaneously hypertensive rat: insight into the pathogenesis of irritative symptoms in benign prostatic hyperplasia and young anxious males. Exp. Physiol. 1999; 84: 137–47. 76 Jin LH, Lee HJ, Shin HY et al. Development and changes with age of detrusor overactivity in spontaneous hypertensive rats as observed by simultaneous registrations of intravesical and intraabdominal pressures. Int. Neurourol. J. 2011; 15: 192–8. 77 Jin LH, Andersson KE, Kwon YH et al. Selection of a control rat for conscious spontaneous hypertensive rats in studies of detrusor overactivity on the basis of measurement of intra-abdominal pressures. Neurourol. Urodyn. 2010; 29: 1338–43. 78 Ito H, Taga M, Tsuchiyama K et al. IPSS is lower in hypertensive patients treated with angiotensin-II receptor blocker: posthoc analyses of a lower urinary tract symptoms population. Neurourol. Urodyn. 2013; 32: 70–4. 79 Shimizu S, Saito M, Oiwa H et al. Olmesartan ameliorates urinary dysfunction in the spontaneously hypertensive rat via recovering bladder blood flow and decreasing oxidative stress. Neurourol. Urodyn. 2014; 33: 350–7. 80 Lundy A, Lutfi N, Beckey C. Review of nifedipine GITS in the treatment of high risk patients with coronary artery disease and hypertension. Vasc. Health Risk Manag. 2009; 5: 429–40. 81 Yamashita M, Zhang X, Shiraishi T et al. Determination of percent area density of epithelial and stromal components in development of prostatic hyperplasia in spontaneously hypertensive rats. Urology 2003; 61: 484–9. 82 Nakamura H, Itakura C. Influence of terazosin on the epithelium in the prostate gland of spontaneously hypertensive rats. J. Toxicol. Pathol. 1992; 5: 101–4. 83 Morelli A, Filippi S, Comeglio P et al. Acute vardenafil administration improves bladder oxygenation in spontaneously hypertensive rats. J. Sex. Med. 2010; 7: 107–20. 84 Markham A, Plosker GL, Goa KL. Nicorandil. An updated review of its use in ischaemic heart disease with emphasis on its cardioprotective effects. Drugs 2000; 60: 955–74. 85 Zhang Q, Radisavljevic ZM, Siroky MB et al. Dietary antioxidants improve arteriogenic erectile dysfunction. Int. J. Androl. 2011; 34: 225–35. 86 Vignozzi L, Morelli A, Filippi S et al. Effect of sildenafil administration on penile hypoxia induced by cavernous neurotomy in the rat. Int. J. Impot. Res. 2008; 20: 60–7.

© 2014 The Japanese Urological Association