Chitapanarux Taned, Chen Stephen L, Lee Helen, Melton Andrew C, Yee Hal F
Department of Medicine, CURE Digestive Diseases Research, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, CA 90095, USA.
Am J Physiol Gastrointest Liver Physiol. 2004 Jan;286(1):G31-6. doi: 10.1152/ajpgi.00325.2003. Epub 2003 Sep 4.
Intestinal response to injury requires coordinated regulation of the tension exerted by subepithelial myofibroblasts (SEM). However, the signals governing relaxation of intestinal SEM have not been investigated. Our aim was to test the hypothesis that signal transduction pathways initiated by C-type natriuretic peptide (CNP) induce intestinal SEM relaxation. We directly quantified the effects of CNP on isometric tension exerted by cultured human colonic SEM. We also measured the effects of CNP on cGMP content, myosin regulatory light chain (MLC) phosphorylation, and cytosolic Ca2+ concentration. CNP induced relaxation of SEM within 10 s. By 10 min, relaxation reached a plateau that was sustained for 2 h. CNP-induced relaxation was saturable, with a maximal decrease in tension (51.7 +/- 3.8 dyn) observed at 250 nM. SEM relaxation in response to CNP constituted approximately 23% of total basal tension. CNP increased intracellular cGMP content and reduced MLC phosphorylation. Effects of CNP on cGMP and MLC exhibited the same dose dependence as CNP-induced relaxation. MLC phosphorylation decreased within 2 min of CNP exposure and was sustained for at least 45 min. CNP also stimulated a large transient increase in cytosolic Ca2+ concentration that occurred within 30 s and was nearly complete by 1 min. We also observed that calyculin-A, a potent inhibitor of MLC phosphatase, completely abolished the reduction in MLC phosphorylation induced by CNP. These results suggest that CNP induces intestinal SEM relaxation through cGMP-associated reductions in MLC phosphorylation. Moreover, these findings raise the possibility that CNP plays a role in intestinal wound healing.
肠道对损伤的反应需要对上皮下肌成纤维细胞（SEM）施加的张力进行协调调节。然而，尚未研究控制肠道SEM舒张的信号。我们的目的是检验以下假设：由C型利钠肽（CNP）启动的信号转导途径诱导肠道SEM舒张。我们直接量化了CNP对培养的人结肠SEM施加的等长张力的影响。我们还测量了CNP对环磷酸鸟苷（cGMP）含量、肌球蛋白调节轻链（MLC）磷酸化和细胞质钙离子（Ca2+）浓度的影响。CNP在10秒内诱导SEM舒张。到10分钟时，舒张达到平台期并持续2小时。CNP诱导的舒张具有饱和性，在250 nM时观察到张力最大降低（51.7±3.8达因）。对CNP反应的SEM舒张约占总基础张力的23%。CNP增加细胞内cGMP含量并降低MLC磷酸化。CNP对cGMP和MLC的影响与CNP诱导的舒张表现出相同的剂量依赖性。CNP暴露后2分钟内MLC磷酸化降低，并持续至少45分钟。CNP还刺激细胞质Ca2+浓度在30秒内大幅短暂升高，并在1分钟时几乎完全升高。我们还观察到，强效MLC磷酸酶抑制剂煅房蛤毒素A完全消除了CNP诱导的MLC磷酸化降低。这些结果表明，CNP通过与cGMP相关的MLC磷酸化降低诱导肠道SEM舒张。此外，这些发现增加了CNP在肠道伤口愈合中起作用的可能性。
