CaSR在DON诱导拒食中的作用及饱感激素负反馈调节机制研究

Deoxynivalenol (DON) is one of the most serious mycotoxin which severely contaminates grains and feeds in the world. Exposure to DON causes anorexia in animal. Calcium-sensing receptor (CaSR) is believed to function as a toxin sensor on enteroendocrine cell and a mediator of satiety hormone release through CaSR-TRPM5 signaling pathway. Satiety hormone will activate anorexigenic neurons via negative-feedback regulation of appetite center and eventually cause anorexia. Our preliminary experiments indicated that exposure to DON induced satiety hormones cholecystokinin (CCK) and peptide YY (PYY) release, which were correlative to DON-induced anorexia. While, blocking CaSR could down-regulate DON-induced satiety hormone release and anorexia. Based on our findings, our lab proposed a hypothesis, "Upstream mechanism of DON-induced anorexia is that DON will activate CaSR and induce satiety hormone release; Downstream mechanism of DON-induced anorexia is that negative-feedback regulation of appetite center by satiety hormone induces anorexia". In order to verify this hypothesis, our lab will elucidate mechanisms of DON-induced anorexia by using respective receptor blocking and gene silencing or gene knockout as parallel techniques. We will investigate CaSR-TRPM5 signaling pathway for DON-induced satiety hormones CCK and PYY release using primary murine enteroendocrine cell, based on our findings in STC-1 cell. Then we will explore whether CaSR plays a role in regulating satiety signal transduction and activation of anorexigenic neurons. The ultimate goal of these studies is to further reveal mechanisms of DON-induced anorexia from negative-feedback regulation perspective. These findings are expected to offer significant ideas that will discover efficacious interventions to food poisoning of DON over what we have known up to date.

脱氧雪腐镰刀菌烯醇(DON)是污染谷物和饲料最严重的霉菌毒素之一，可导致动物拒食。肠道内分泌细胞表面的钙敏感受体(CaSR)可识别毒物，经CaSR-TRPM5信号通路诱导饱感激素分泌，负反馈调节食欲中枢，导致拒食。我们研究发现，DON能诱导饱感激素CCK和PYY分泌，与拒食呈正相关；阻断CaSR下调DON诱导的饱感激素分泌和拒食。在此基础上，我们提出“DON诱导拒食的上游机制是DON激活CaSR，诱导饱感激素分泌；下游机制是饱感激素负反馈调节食欲中枢，诱导拒食”。为证实这一假说，本课题以药理阻断和基因沉默或敲除为平行观察手段，在前期STC-1细胞的研究基础上，从原代肠道内分泌细胞层面阐释DON诱导饱感激素分泌的CaSR-TRPM5信号通路；揭示CaSR对DON诱导的饱感信号传导和拒食神经元激活的调控作用。从饱感激素负反馈调节的视角，揭示DON诱导拒食的机制，为有效防治DON中毒提供新思路。

脱氧雪腐镰刀菌烯醇(DON)是污染谷物和饲料最严重的霉菌毒素之一，可导致动物拒食。肠道内分泌细胞表面的钙敏感受体(CaSR)可识别毒物，经CaSR-TRPM5信号通路诱导饱感激素分泌，负反馈调节食欲中枢，导致拒食。我们提出“DON诱导拒食的上游机制是DON激活CaSR，诱导饱感激素分泌；下游机制是饱感激素负反馈调节食欲中枢，诱导拒食”。为证实这一假说，本课题以药理阻断和基因沉默为平行观察手段，从原代肠道内分泌细胞层面阐释DON诱导饱感激素分泌的CaSR-TRPM5信号通路；揭示CaSR对DON诱导的饱感信号传导和拒食神经元激活的调控作用。研究发现，DON能够诱导原代肠道内分泌细胞[Ca2+]i升高，这说明Ca2+可能作为第二信使，参与信号转导。DON还能够诱导原代肠道内分泌细胞分泌饱感激素CCK、PYY、GLP-1和GIP。选用特异性拮抗剂阻断CaSR-TRPM5信号通路，能够降低细胞[Ca2+]i和饱感激素CCK、PYY、GLP-1和GIP的分泌，说明CaSR-TRPM5信号通路可能参与了DON诱导的细胞内钙离子动员和饱感激素分泌。首次证明，DON诱导的拒食反应与肠道饱感激素CCK、PYY、GLP-1和GIP的分泌呈正相关。阻断CaSR-TRPM5信号通路中，能够减弱DON诱导的饱感激素(CCK、PYY、GLP-1、GIP)分泌、拒食反应、下丘脑中即刻早期基因C-Fos和拒食基因(MC4R、POMC和CART)的表达，说明CaSR-TRPM5信号通路可能通过调控饱感激素分泌，进而参与拒食神经元激活，最终调控DON诱导的拒食反应。试验发现，趋炎性细胞因子白介素1β(IL-1β)和肿瘤坏死因子α(TNF-α)也参与介导了DON诱导的拒食反应，而神经递质5-羟色胺(5-HT)和瞬时受体电位通道(TRP)参与调控DON诱导的呕吐反应。本研究为有效防治DON中毒提供了新思路。