Department of Physiology and Biophysics, VCU Program in Enteric Neuromuscular Sciences, Virginia Commonwealth University, Richmond, Virginia.
Department of Physiology and Biophysics, VCU Program in Enteric Neuromuscular Sciences, Virginia Commonwealth University, Richmond, Virginia
Am J Physiol Cell Physiol. 2014 Jun 15;306(12):C1129-41. doi: 10.1152/ajpcell.00021.2014. Epub 2014 Apr 16.
The signaling pathways mediating sustained contraction of mouse colonic longitudinal smooth muscle and the mechanisms involved in hypercontractility of this muscle layer in response to cytokines and TNBS-induced colitis have not been fully explored. In control longitudinal smooth muscle cells, ACh acting via m3 receptors activated sequentially Gα12, RhoGEF (LARG), and the RhoA/Rho kinase pathway. There was abundant expression of MYPT1, minimal expression of CPI-17, and a notable absence of a PKC/CPI-17 pathway. LARG expression was increased in longitudinal muscle cells isolated from muscle strips cultured for 24 h with IL-1β or TNF-α or obtained from the colon of TNBS-treated mice. The increase in LARG expression was accompanied by a significant increase in ACh-stimulated Rho kinase and ZIP kinase activities, and sustained muscle contraction. The increase in LARG expression, Rho kinase and ZIP kinase activities, and sustained muscle contraction was abolished in cells pretreated with the Jun kinase inhibitor, SP600125. Expression of the MLCP activator, telokin, and MLCP activity were also decreased in longitudinal muscle cells from TNBS-treated mice or from strips treated with IL-1β or TNF-α. In contrast, previous studies had shown that sustained contraction in circular smooth muscle is mediated by sequential activation of Gα13, p115RhoGEF, and dual RhoA-dependent pathways involving phosphorylation of MYPT1 and CPI-17. In colonic circular smooth muscle cells isolated from TNBS-treated mice or from strips treated with IL-1β or TNF-α, CPI-17 expression and sustained muscle contraction were decreased. The disparate changes in the two muscle layers contribute to intestinal dysmotility during inflammation.
介导小鼠结肠纵行平滑肌持续收缩的信号通路以及细胞因子和 TNBS 诱导的结肠炎引起该肌层过度收缩的机制尚未完全阐明。在对照的纵行平滑肌细胞中，ACh 通过 m3 受体作用，依次激活 Gα12、RhoGEF（LARG）和 RhoA/Rho 激酶通路。MYPT1 表达丰富，CPI-17 表达很少，PKC/CPI-17 通路明显不存在。在培养 24 小时的 IL-1β 或 TNF-α的肌条或从 TNBS 处理的小鼠结肠分离的纵行肌细胞中，LARG 表达增加。LARG 表达的增加伴随着 ACh 刺激的 Rho 激酶和 ZIP 激酶活性以及持续的肌肉收缩的显著增加。用 Jun 激酶抑制剂 SP600125 预处理细胞可消除 LARG 表达、Rho 激酶和 ZIP 激酶活性以及持续的肌肉收缩的增加。来自 TNBS 处理的小鼠或用 IL-1β 或 TNF-α处理的肌条的纵行肌细胞中的 MLCP 激活剂 telokin 的表达和 MLCP 活性也降低。相比之下，先前的研究表明，环形平滑肌的持续收缩是通过 Gα13、p115RhoGEF 的顺序激活以及涉及 MYPT1 和 CPI-17 磷酸化的双 RhoA 依赖性途径介导的。在来自 TNBS 处理的小鼠或用 IL-1β 或 TNF-α处理的肌条分离的结肠环形平滑肌细胞中，CPI-17 表达和持续的肌肉收缩减少。这两个肌层的不同变化导致炎症期间肠道运动障碍。
