Sensitization of sodium channels by cystathionine ¦Â-synthetase activation in colon sensory neurons in adult rats with neonatal maternal deprivation

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• 作者：Shufen Hu ; Weiyuan Xu ; Xiuhua Miao ; Yanping Gao ; Liyan Zhu ; Youlang Zhou ; Ying Xiao ; Guang-Yin Xu
• 关键词：Neonatal maternal deprivation ; Dorsal root ganglion ; Visceral pain ; Voltage-gated sodium channels ; Hydrogen sulfide
• 刊名：Experimental Neurology
• 出版年：2013
• 出版时间：October, 2013
• 年：2013
• 卷：248
• 期：Complete
• 页码：275-285
• 全文大小：1308 K

文摘

class=""h4"">Background

The pathogenesis of pain in irritable bowel syndrome (IBS) is poorly understood and treatment remains difficult. We have previously reported that TTX-resistant (TTX-R) sodium channels in colon-specific dorsal root ganglion (DRG) neurons were sensitized and the expression of the endogenous hydrogen sulfide producing enzyme cystathionine ¦Â-synthetase (CBS) was upregulated in a rat model of visceral hypersensitivity induced by neonatal maternal deprivation (NMD). However, the detailed molecular mechanism for activation of sodium channels remains unknown. This study was designed to examine roles for CBS-H₂S signaling in sensitization of sodium channels in a previously validated rat model of IBS.

class=""h4"">Methods

Neonatal male rats (postnatal days 2-15) were exposed to a 3 hour period of daily maternal separation with temperature maintained at ~ 33 ¡ãC. Colon-specific dorsal root ganglion (DRG) neurons were labeled with DiI and acutely dissociated for measuring excitability and sodium channel current under whole-cell patch clamp configurations. The expression of Na_V1.8 was analyzed by Western blot and Immunofluorescence study. The endogenous H₂S producing enzyme CBS antagonist was injected intraperitoneally.

class=""h4"">Results

We showed that CBS was colocalized with Na_V1.8 in colon-specific DRG neurons pre-labeled with DiI. Pretreatment of O-(Carboxymethyl) hydroxylamine hemihydrochloride (AOAA), an inhibitor of CBS, significantly reduced expression of Na_V1.8 in NMD rats. AOAA treatment also inhibited the TTX-R sodium current density, right-shifted the V_1/2 of activation curve, and reversed hyperexcitability of colon-specific DRG neurons in NMD rats. Conversely, addition of NaHS, a donor of H₂S, greatly enhanced TTX-R sodium current density, left shifted the activation curve and enhanced excitability of colon DRG neurons in age-matched healthy rats. Furthermore, application of H-89, an inhibitor of protein kinase A, markedly attenuated the potentiation of TTX-R sodium current density by NaHS.

class=""h4"">Conclusion

These data suggest that sensitization of sodium channels of colon DRG neurons in NMD rats is most likely mediated by CBS-H₂S signaling, thus identifying a potential target for treatment for chronic visceral pain in patients with IBS.