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P38 mediates mechanical allodynia in a mouse model of type 2 diabetes
Abstracts (196) Activation of mast cell tryptase and protease-activated receptor 2 mediate neuropathic pain induced by paclitaxel Y Chen, C Yang, and Z Wang; University of Illinois at Chicago, Chicago, IL
S25
D07 Signal Transduction (198) P38 mediates mechanical allodynia in a mouse model of type 2 diabetes
Paclitaxel chemotherapy is often limited by long-lasting painful neuropathy. Mast cell activation and evoked protease-activated receptor 2 (PAR2) activity have been implicated in inflammatory pain and migraine. In this study, we tested the hypothesis that mast cell tryptase may be released by paclitaxel, thereby activating PAR2 and resulting in mechanical and thermal hypersensitivity. Correlating with the development of thermal hyperalgesia and tactile allodynia after repeated administration of paclitaxel, mast cell tryptase activity was increased in peripheral tissues and primary afferent neurons in mice. FSLLRY-NH2, a PAR2 antagonist, was able to block paclitaxel-induced neuropathic pain behaviors in a dose- and time-dependent manner. Furthermore, blocking PAR2 downstream signaling pathways such as PLCb, PKCe, and PKA effectively attenuated paclitaxel-induced thermal and tactile hypersensitivity. Taken together, these data implicated PAR2 as a cellular mechanism critical for paclitaxel-induced pain.
H Cheng, J Dauch, J Hayes, Y Hong, and E Feldman; University of Michigan, Ann Arbor, MI
D06 Regulation of Gene Expressions
(199) Paclitaxel, at ultra low sub-apoptotic doses, induces substance P release via synchronized activation of PKA and PKC
(197) NGF and IL-6 rapidly control gene expression in DRG neurons via signaling to translation initiation factors T Price, O Melemedjian, K Peebles, M Asiedu, and N Ertz; University of Arizona, Tucson, AZ Alterations in gene expression downstream of cytokine or neurotrophin signaling are widely accepted as a contributing factor to chronic pain but the role of protein synthesis control in this process is not well understood. Interleukin (IL)6 is a pleiotropic cytokine that modulates a variety of physiological events such as cell proliferation, differentiation, survival, and apoptosis. IL-6 levels are elevated after nerve injury and mechanical allodynia is profoundly attenuated in IL-6 knockout mice. Nerve growth factor (NGF) levels are elevated in chronic pain states and blocking NGF function attenuates pain in various pre-clinical models. Moreover, injection of NGF produces long lasting nociceptive sensitization in humans. We hypothesized that NGF and IL-6 may exert control over gene expression in sensory neurons via signaling to translation initiation factors, pathways that are critical for synaptic plasticity in the CNS. Treatment of primary sensory neurons in culture with IL-6 results in dose-dependent phosphorylation of ERK and eIF4E. These IL-6 effects are dependent on ERK signaling to Mnk and eIF4E because it is attenuated by the Mnk inhibitor CGP-57380. Treatment with NGF activates the mammalian target of rapamycin (mTOR) pathway resulting in the phosphorylation of 4EBP and eIF4G. Co-treatment with both NGF and IL-6 results in the activation of the ERK and mTOR pathways, converging on the eIF4F complex, stabilizing it and inducing a rapid increase in nascent protein synthesis. These results demonstrate that IL-6 and NGF have the capacity to fundamentally alter the protein synthesis capacity of primary sensory neurons leading to changes in gene expression that may be linked to the development and maintenance of chronic pain states. This abstract will also be presented as an Oral Paper Presentation on May 8. Refer to the daily Schedule-At-A-Glance for presentation time and location.
Previously, we reported that db/db mouse, a leptin receptor null mutant, develops mechanical allodynia at early stage of diabetes from 8 to 12 wk of age. Using this window of pain behaviors, we detected increased phosphorylation of mitogen activated protein kinases (MAPK) in the dorsal root ganglion (DRG) of db/db mice. In the DRG, members of MAPK, including ERK1/2, p38, are phosphorylated prior and during the period of pain behaviors as demonstrated by the immunoblots for the phosphorylated protein. The phosphoERK1/2 and p38 were both detected in small to medium-sized DRG neurons using immunohistochemsitry. In contrast, phospho-c-jun N-termonal kinase (JNK) was not activated in DRG of diabetic mice. Using intrathecal administration of specific kinase inhibitors, we determined that p38, but not ERK1/2, mediates the mechanical allodynia in this animal model. The p38 activation also contributes to the upregulation of cyclooxygenase 2 and nitric oxide synthase 2 expression in DRG of db/db mice. The current findings provide evidence that inhibition of p38 actions is a potential strategy for treating painful neuropathy of type 2 diabetes.
Y He and Z Wang; University of Illinois, Chicago, IL As one of the most effective and frequently used antineoplastic agents, paclitaxel produces neuropathic pain during and often persists after chemotherapy. Previous studies have developed various rodent models of paclitaxel-induced pain syndrome; however, a clear cellular mechanism has yet to emerge. The aim of this study was to identify the molecular mechanisms underlying this dose-limiting side effect of paclitaxel in cellular models. We treated isolated dorsal root ganglion sensory neurons and DRG-like F11 cells with paclitaxel in a sub-apoptotic dose range (0.1-50 nM) which was verified not to induce apoptosis. Paclitaxel increased [Ca21]i and enhanced the release of substance P in a dose-dependent manner. Substance P release was attenuated when extracellular and/or intracellular Ca21 was removed or chelated. Moreover, PKC or PKA inhibitors significantly blocked paclitaxel-evoked release of substance P. During paclitaxel treatment, PKA and PKC (e & d isoforms) were simultaneously activated and actions of these kinases appeared to be synchronized by a common mechanism. In conclusion, these results suggested the presence of a non-apoptotic form of neuropathic pain induced by paclitaxel, which may be mediated by synchronized activation of PKA and PKC.
S25
D07 Signal Transduction (198) P38 mediates mechanical allodynia in a mouse model of type 2 diabetes
Paclitaxel chemotherapy is often limited by long-lasting painful neuropathy. Mast cell activation and evoked protease-activated receptor 2 (PAR2) activity have been implicated in inflammatory pain and migraine. In this study, we tested the hypothesis that mast cell tryptase may be released by paclitaxel, thereby activating PAR2 and resulting in mechanical and thermal hypersensitivity. Correlating with the development of thermal hyperalgesia and tactile allodynia after repeated administration of paclitaxel, mast cell tryptase activity was increased in peripheral tissues and primary afferent neurons in mice. FSLLRY-NH2, a PAR2 antagonist, was able to block paclitaxel-induced neuropathic pain behaviors in a dose- and time-dependent manner. Furthermore, blocking PAR2 downstream signaling pathways such as PLCb, PKCe, and PKA effectively attenuated paclitaxel-induced thermal and tactile hypersensitivity. Taken together, these data implicated PAR2 as a cellular mechanism critical for paclitaxel-induced pain.
H Cheng, J Dauch, J Hayes, Y Hong, and E Feldman; University of Michigan, Ann Arbor, MI
D06 Regulation of Gene Expressions
(199) Paclitaxel, at ultra low sub-apoptotic doses, induces substance P release via synchronized activation of PKA and PKC
(197) NGF and IL-6 rapidly control gene expression in DRG neurons via signaling to translation initiation factors T Price, O Melemedjian, K Peebles, M Asiedu, and N Ertz; University of Arizona, Tucson, AZ Alterations in gene expression downstream of cytokine or neurotrophin signaling are widely accepted as a contributing factor to chronic pain but the role of protein synthesis control in this process is not well understood. Interleukin (IL)6 is a pleiotropic cytokine that modulates a variety of physiological events such as cell proliferation, differentiation, survival, and apoptosis. IL-6 levels are elevated after nerve injury and mechanical allodynia is profoundly attenuated in IL-6 knockout mice. Nerve growth factor (NGF) levels are elevated in chronic pain states and blocking NGF function attenuates pain in various pre-clinical models. Moreover, injection of NGF produces long lasting nociceptive sensitization in humans. We hypothesized that NGF and IL-6 may exert control over gene expression in sensory neurons via signaling to translation initiation factors, pathways that are critical for synaptic plasticity in the CNS. Treatment of primary sensory neurons in culture with IL-6 results in dose-dependent phosphorylation of ERK and eIF4E. These IL-6 effects are dependent on ERK signaling to Mnk and eIF4E because it is attenuated by the Mnk inhibitor CGP-57380. Treatment with NGF activates the mammalian target of rapamycin (mTOR) pathway resulting in the phosphorylation of 4EBP and eIF4G. Co-treatment with both NGF and IL-6 results in the activation of the ERK and mTOR pathways, converging on the eIF4F complex, stabilizing it and inducing a rapid increase in nascent protein synthesis. These results demonstrate that IL-6 and NGF have the capacity to fundamentally alter the protein synthesis capacity of primary sensory neurons leading to changes in gene expression that may be linked to the development and maintenance of chronic pain states. This abstract will also be presented as an Oral Paper Presentation on May 8. Refer to the daily Schedule-At-A-Glance for presentation time and location.
Previously, we reported that db/db mouse, a leptin receptor null mutant, develops mechanical allodynia at early stage of diabetes from 8 to 12 wk of age. Using this window of pain behaviors, we detected increased phosphorylation of mitogen activated protein kinases (MAPK) in the dorsal root ganglion (DRG) of db/db mice. In the DRG, members of MAPK, including ERK1/2, p38, are phosphorylated prior and during the period of pain behaviors as demonstrated by the immunoblots for the phosphorylated protein. The phosphoERK1/2 and p38 were both detected in small to medium-sized DRG neurons using immunohistochemsitry. In contrast, phospho-c-jun N-termonal kinase (JNK) was not activated in DRG of diabetic mice. Using intrathecal administration of specific kinase inhibitors, we determined that p38, but not ERK1/2, mediates the mechanical allodynia in this animal model. The p38 activation also contributes to the upregulation of cyclooxygenase 2 and nitric oxide synthase 2 expression in DRG of db/db mice. The current findings provide evidence that inhibition of p38 actions is a potential strategy for treating painful neuropathy of type 2 diabetes.
Y He and Z Wang; University of Illinois, Chicago, IL As one of the most effective and frequently used antineoplastic agents, paclitaxel produces neuropathic pain during and often persists after chemotherapy. Previous studies have developed various rodent models of paclitaxel-induced pain syndrome; however, a clear cellular mechanism has yet to emerge. The aim of this study was to identify the molecular mechanisms underlying this dose-limiting side effect of paclitaxel in cellular models. We treated isolated dorsal root ganglion sensory neurons and DRG-like F11 cells with paclitaxel in a sub-apoptotic dose range (0.1-50 nM) which was verified not to induce apoptosis. Paclitaxel increased [Ca21]i and enhanced the release of substance P in a dose-dependent manner. Substance P release was attenuated when extracellular and/or intracellular Ca21 was removed or chelated. Moreover, PKC or PKA inhibitors significantly blocked paclitaxel-evoked release of substance P. During paclitaxel treatment, PKA and PKC (e & d isoforms) were simultaneously activated and actions of these kinases appeared to be synchronized by a common mechanism. In conclusion, these results suggested the presence of a non-apoptotic form of neuropathic pain induced by paclitaxel, which may be mediated by synchronized activation of PKA and PKC.