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PAIN 155 (2014) 723–732
www.elsevier.com/locate/pain
Differential regulation of peripheral IL-1b-induced mechanical allodynia and thermal hyperalgesia in rats Min J. Kim a,1, Sang Y. Lee b,1, Kui Y. Yang a, Soon H. Nam b, Hyun J. Kim b, Young J. Kim b, Yong C. Bae c, Dong K. Ahn a,⇑ a b c
Department of Oral Physiology, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea Department of Pediatric Dentistry, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea Department of Oral Anatomy, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea
Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article.
a r t i c l e
i n f o
Article history: Received 22 August 2013 Received in revised form 18 December 2013 Accepted 30 December 2013
Keywords: Air puff IL-1b Mechanical allodynia NMDA Thermal hyperalgesia TRPV1
a b s t r a c t This study examined the differential mechanisms of mechanical allodynia and thermal hyperalgesia after injection of interleukin (IL) 1b into the orofacial area of male Sprague-Dawley rats. The subcutaneous administration of IL-1b produced both mechanical allodynia and thermal hyperalgesia. Although a pretreatment with iodoresiniferatoxin (IRTX), a transient receptor potential vanilloid 1 (TRPV1) antagonist, did not affect IL-1b-induced mechanical allodynia, it significantly abolished IL-1b-induced thermal hyperalgesia. On the other hand, a pretreatment with D-AP5, an N-methyl-D-aspartate (NMDA) receptor antagonist, and NBQX, an a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist, blocked IL-1b-induced mechanical allodynia. Pretreatment with H89, a protein kinase A (PKA) inhibitor, blocked IL-1b-induced mechanical allodynia but not thermal hyperalgesia. In contrast, pretreatment with chelerythrine, a protein kinase C (PKC) inhibitor, inhibited IL-1b-induced thermal hyperalgesia. Subcutaneous injections of 2% lidocaine, a local anesthetic agent, blocked IL-1b-induced thermal hyperalgesia but not IL-1b-induced mechanical allodynia. In the resiniferatoxin (RTX)-pretreated rats, a subcutaneous injection of IL-1b did not produce thermal hyperalgesia due to the depletion of TRPV1 in the primary afferent fibers. Double immunofluorescence revealed the colocalization of PKA with neurofilament 200 (NF200) and of PKC with the calcitonin gene-related peptide (CGRP) in the trigeminal ganglion. Furthermore, NMDA receptor 1 (NR1) and TRPV1 predominantly colocalize with PKA and PKC, respectively, in the trigeminal ganglion. These results suggest that IL-1b-induced mechanical allodynia is mediated by sensitized peripheral NMDA/AMPA receptors through PKA-mediated signaling in the largediameter primary afferent nerve fibers, whereas IL-1b-induced thermal hyperalgesia is mediated by sensitized peripheral TRPV1 receptors through PKC-mediated signaling in the small-diameter primary afferent nerve fibers. Ó 2014 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.
1. Introduction Inflammation is associated with a complex pattern of local and systemic changes, including inflammatory cell migration, cytokine release, edema, erythema, release of acute-phase proteins, fever, pain, and hyperalgesia. Many inflammatory mediators are believed to play an essential role in inflammatory hypernociception at the sites of inflamed tissue. Although the precise molecular events
⇑ Corresponding author. Address: Department of Oral Physiology, School of Dentistry, Kyungpook National University, 188-1 Sam Deok 2ga, Chung-gu, Daegu 700-412, Republic of Korea. Tel.: +82 53 660 6840; fax: +82 53 421 4077. E-mail address: [email protected] (D.K. Ahn). 1 Drs. Kim and Lee contributed equally to this study.
responsible for the sensory changes at the site of inflammation and surrounding tissues are not completely understood, it is likely that inflammatory mediators regulate the changes in transduction sensitivity and the activation of chemosensitive nociceptors [43]. Interleukin 1b (IL-1b) is released from activated macrophages and monocytes during infection or inflammation and plays an important role in acute inflammatory responses [16]. Since the first report showed that cytokines play a role in mediating inflammatory hyperalgesia [17,37], several studies have demonstrated the participation of cytokines in pain modulation. The intrathecal administration of IL-1b produces mechanical and thermal hyperalgesia in rats [34,40] suggesting that central IL-1b, a proinflammatory cytokine, has a potent hyperalgesic role [17]. In addition to the role of central IL-1b, local injections of IL-1b also have been found to produce
0304-3959/$36.00 Ó 2014 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.pain.2013.12.030
724
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M.J. Kim et al. / PAIN 155 (2014) 723–732
mechanical and thermal hyperalgesia in rats [1,2,17,35]. These results suggest that IL-1b also participates in pain processes as a potent hyperalgesic agent at the peripheral sites. Recent reverse-transcriptase polymerase chain reaction and in situ hybridization data have demonstrated that the IL-1 receptor is expressed in the sensory neurons [9,31] and that IL-1b excites nociceptive fibers in vivo within 1 minute of the application of IL-1b [19]. The evidence indicates that peripheral IL-1b produces hyperalgesic effects through the modification of ion channels in nociceptors, leading to changes in neuronal excitability and pain behavior. Although the peripheral pronociceptive action of IL-1b has been evaluated, the underlying cellular mechanisms of IL-1binduced mechanical allodynia and thermal hyperalgesia in the orofacial area, which are mediated by a complex signaling cascade and intracellular kinases, are not completely understood. In the present study, a rat model was used to examine the role of peripheral ionotropic receptors, such as a transient receptor potential vanilloid 1 (TRPV1), N-methyl-D-aspartate (NMDA), and aamino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, in the mechanical allodynia and thermal hyperalgesia produced by a subcutaneous injection of IL-1b in the orofacial area. Moreover, the cellular mechanisms of protein kinases that participate in the IL-1b-induced mechanical allodynia and thermal hyperalgesia were evaluated further. Finally, this study confirmed the differential regulation of peripheral 1b-induced mechanical allodynia and thermal hyperalgesia after the application of lidocaine or resiniferatoxin (RTX), which depleted TRPV1 in the primary afferent fiber.
2.2.1. Evaluation of mechanical allodynia The withdrawal behavioral responses produced by 10 successive trials of a ramp of air-puff pressure (4 seconds of duration, 10 seconds of intervals) were examined and the air-puff threshold was then assessed, as described previously [1–4]. The intensity of the air-puff pressure was controlled using a pneumatic pump module (BH2 system, Harvard Apparatus, Holliston, MA). Air puffs were applied through a 26-gauge metal tube (length, 10 cm) located 1 cm from the skin at a 90° angle. Application of air puffs can stimulate only the IL-1b injection sites because a 26-gauge metal tube was used for air-puff application. The air-puff threshold was determined to be the air-puff pressure at which each rat responded in 50% of the trials. The cut-off pressure for the air puff was 40 psi, as described previously [1–4]. The naïve rats did not respond to a pressure of
PAIN 155 (2014) 723–732
www.elsevier.com/locate/pain
Differential regulation of peripheral IL-1b-induced mechanical allodynia and thermal hyperalgesia in rats Min J. Kim a,1, Sang Y. Lee b,1, Kui Y. Yang a, Soon H. Nam b, Hyun J. Kim b, Young J. Kim b, Yong C. Bae c, Dong K. Ahn a,⇑ a b c
Department of Oral Physiology, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea Department of Pediatric Dentistry, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea Department of Oral Anatomy, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea
Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article.
a r t i c l e
i n f o
Article history: Received 22 August 2013 Received in revised form 18 December 2013 Accepted 30 December 2013
Keywords: Air puff IL-1b Mechanical allodynia NMDA Thermal hyperalgesia TRPV1
a b s t r a c t This study examined the differential mechanisms of mechanical allodynia and thermal hyperalgesia after injection of interleukin (IL) 1b into the orofacial area of male Sprague-Dawley rats. The subcutaneous administration of IL-1b produced both mechanical allodynia and thermal hyperalgesia. Although a pretreatment with iodoresiniferatoxin (IRTX), a transient receptor potential vanilloid 1 (TRPV1) antagonist, did not affect IL-1b-induced mechanical allodynia, it significantly abolished IL-1b-induced thermal hyperalgesia. On the other hand, a pretreatment with D-AP5, an N-methyl-D-aspartate (NMDA) receptor antagonist, and NBQX, an a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist, blocked IL-1b-induced mechanical allodynia. Pretreatment with H89, a protein kinase A (PKA) inhibitor, blocked IL-1b-induced mechanical allodynia but not thermal hyperalgesia. In contrast, pretreatment with chelerythrine, a protein kinase C (PKC) inhibitor, inhibited IL-1b-induced thermal hyperalgesia. Subcutaneous injections of 2% lidocaine, a local anesthetic agent, blocked IL-1b-induced thermal hyperalgesia but not IL-1b-induced mechanical allodynia. In the resiniferatoxin (RTX)-pretreated rats, a subcutaneous injection of IL-1b did not produce thermal hyperalgesia due to the depletion of TRPV1 in the primary afferent fibers. Double immunofluorescence revealed the colocalization of PKA with neurofilament 200 (NF200) and of PKC with the calcitonin gene-related peptide (CGRP) in the trigeminal ganglion. Furthermore, NMDA receptor 1 (NR1) and TRPV1 predominantly colocalize with PKA and PKC, respectively, in the trigeminal ganglion. These results suggest that IL-1b-induced mechanical allodynia is mediated by sensitized peripheral NMDA/AMPA receptors through PKA-mediated signaling in the largediameter primary afferent nerve fibers, whereas IL-1b-induced thermal hyperalgesia is mediated by sensitized peripheral TRPV1 receptors through PKC-mediated signaling in the small-diameter primary afferent nerve fibers. Ó 2014 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.
1. Introduction Inflammation is associated with a complex pattern of local and systemic changes, including inflammatory cell migration, cytokine release, edema, erythema, release of acute-phase proteins, fever, pain, and hyperalgesia. Many inflammatory mediators are believed to play an essential role in inflammatory hypernociception at the sites of inflamed tissue. Although the precise molecular events
⇑ Corresponding author. Address: Department of Oral Physiology, School of Dentistry, Kyungpook National University, 188-1 Sam Deok 2ga, Chung-gu, Daegu 700-412, Republic of Korea. Tel.: +82 53 660 6840; fax: +82 53 421 4077. E-mail address: [email protected] (D.K. Ahn). 1 Drs. Kim and Lee contributed equally to this study.
responsible for the sensory changes at the site of inflammation and surrounding tissues are not completely understood, it is likely that inflammatory mediators regulate the changes in transduction sensitivity and the activation of chemosensitive nociceptors [43]. Interleukin 1b (IL-1b) is released from activated macrophages and monocytes during infection or inflammation and plays an important role in acute inflammatory responses [16]. Since the first report showed that cytokines play a role in mediating inflammatory hyperalgesia [17,37], several studies have demonstrated the participation of cytokines in pain modulation. The intrathecal administration of IL-1b produces mechanical and thermal hyperalgesia in rats [34,40] suggesting that central IL-1b, a proinflammatory cytokine, has a potent hyperalgesic role [17]. In addition to the role of central IL-1b, local injections of IL-1b also have been found to produce
0304-3959/$36.00 Ó 2014 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.pain.2013.12.030
724
Ò
M.J. Kim et al. / PAIN 155 (2014) 723–732
mechanical and thermal hyperalgesia in rats [1,2,17,35]. These results suggest that IL-1b also participates in pain processes as a potent hyperalgesic agent at the peripheral sites. Recent reverse-transcriptase polymerase chain reaction and in situ hybridization data have demonstrated that the IL-1 receptor is expressed in the sensory neurons [9,31] and that IL-1b excites nociceptive fibers in vivo within 1 minute of the application of IL-1b [19]. The evidence indicates that peripheral IL-1b produces hyperalgesic effects through the modification of ion channels in nociceptors, leading to changes in neuronal excitability and pain behavior. Although the peripheral pronociceptive action of IL-1b has been evaluated, the underlying cellular mechanisms of IL-1binduced mechanical allodynia and thermal hyperalgesia in the orofacial area, which are mediated by a complex signaling cascade and intracellular kinases, are not completely understood. In the present study, a rat model was used to examine the role of peripheral ionotropic receptors, such as a transient receptor potential vanilloid 1 (TRPV1), N-methyl-D-aspartate (NMDA), and aamino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, in the mechanical allodynia and thermal hyperalgesia produced by a subcutaneous injection of IL-1b in the orofacial area. Moreover, the cellular mechanisms of protein kinases that participate in the IL-1b-induced mechanical allodynia and thermal hyperalgesia were evaluated further. Finally, this study confirmed the differential regulation of peripheral 1b-induced mechanical allodynia and thermal hyperalgesia after the application of lidocaine or resiniferatoxin (RTX), which depleted TRPV1 in the primary afferent fiber.
2.2.1. Evaluation of mechanical allodynia The withdrawal behavioral responses produced by 10 successive trials of a ramp of air-puff pressure (4 seconds of duration, 10 seconds of intervals) were examined and the air-puff threshold was then assessed, as described previously [1–4]. The intensity of the air-puff pressure was controlled using a pneumatic pump module (BH2 system, Harvard Apparatus, Holliston, MA). Air puffs were applied through a 26-gauge metal tube (length, 10 cm) located 1 cm from the skin at a 90° angle. Application of air puffs can stimulate only the IL-1b injection sites because a 26-gauge metal tube was used for air-puff application. The air-puff threshold was determined to be the air-puff pressure at which each rat responded in 50% of the trials. The cut-off pressure for the air puff was 40 psi, as described previously [1–4]. The naïve rats did not respond to a pressure of
