Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Barcelona, Spain.
Neurogastroenterol Motil. 2012 Dec;24(12):e580-90. doi: 10.1111/nmo.12027. Epub 2012 Oct 17.
Nerve growth factor (NGF)-mucosal mast cell (MMC) interaction has been implicated in the remodeling of enteric circuitries and associated functional changes. We investigated the involvement of NGF and its receptor TrkA in the altered colonic contractile activity observed in the model of oral ovalbumin (OVA)-induced MMC hyperactivity in rats. We also studied the role of colonic MMCs as a source of NGF.
Rats received oral OVA, alone or with the TrkA antagonist K252a. Colonic co-expression of NGF/TrkA and rat mast cell protease II (RMCPII) (double immunofluorescence), RMCPII content (ELISA) and expression of NGF, Brain-derived neurotrophic factor (BDNF) and TrkA/B (QT-PCR) were assessed. Colonic contractile activity was determined in vivo and in vitro.
TrkA, but not NGF, was localized in colonic MMCs (RMCPII-positive). Oral ovalbumin exposure increased colonic RMCPII levels but did not change the percentage of TrkA-positive MMCs. Neither OVA nor K252a, alone or combined, altered NGF, BDNF or TrkA/B expression. Spontaneous colonic activity in vivo and in vitro was altered by OVA, an effect prevented by K252a. Electrical stimulation-induced contractile responses in vivo and carbachol responses in vitro were increased by OVA in a K252a-independent manner. In OVA-treated animals, inhibition of NO synthesis with l-NNA significantly enhanced spontaneous colonic activity in vitro, a response completely prevented by K252a.
CONCLUSIONS & INFERENCES: These results suggest that NGF-TrkA-dependent pathways are implicated in colonic contractile alterations observed during OVA exposure in rats. NGF-TrkA system might represent a potential target for treatment of gastrointestinal disorders characterized by colonic motor alterations.
神经生长因子（NGF）-黏膜肥大细胞（MMC）相互作用与肠回路的重塑及其相关的功能变化有关。我们研究了 NGF 及其受体 TrkA 在口服卵清蛋白（OVA）诱导的大鼠 MMC 活性亢进模型中观察到的结肠收缩活动改变中的作用。我们还研究了结肠 MMC 作为 NGF 来源的作用。
大鼠接受口服 OVA，单独或与 TrkA 拮抗剂 K252a 一起。通过双免疫荧光评估 NGF/TrkA 和大鼠肥大细胞蛋白酶 II（RMCPII）的结肠共表达（RMCPII 含量（ELISA）和 NGF、脑源性神经营养因子（BDNF）和 TrkA/B 的表达（QT-PCR）。体内和体外评估结肠收缩活性。
TrkA，但不是 NGF，定位于结肠 MMC（RMCPII 阳性）。口服 OVA 暴露增加了结肠 RMCPII 水平，但没有改变 TrkA 阳性 MMC 的百分比。OVA 或 K252a 单独或联合使用均未改变 NGF、BDNF 或 TrkA/B 的表达。体内和体外的自发性结肠活动均被 OVA 改变，K252a 可预防这种作用。体内电刺激诱导的收缩反应和体外 carbachol 反应在 OVA 处理的动物中以 K252a 不依赖的方式增加。在 OVA 处理的动物中，用 l-NNA 抑制 NO 合成可显著增强体外自发性结肠活动，这种反应被 K252a 完全阻止。
这些结果表明，NGF-TrkA 依赖性途径参与了大鼠暴露于 OVA 期间观察到的结肠收缩改变。NGF-TrkA 系统可能是治疗以结肠运动改变为特征的胃肠道疾病的潜在靶点。
