Retracted: PKC‐delta and PKD activate MAPK signal pathway in mechano‐transcription of colonic smooth muscle cells

Abstract

BackgroundMechanical dilation‐induced expression of cyclooxygenase‐2 (COX‐2) in colonic smooth muscle cells (SMCs) plays a critical role in motility dysfunction in obstructive bowel disorders. The aims of the present study were to investigate whether PKCs and PKD are involved in stretch‐induced expression of COX‐2 in colonic SMC, and to determine whether inhibition of PKCs and PKD has beneficial effects on motility dysfunction in bowel obstruction.MethodsStatic mechanical stretch was mimicked in vitro in primary culture of rat colonic circular SMCs (RCCSMCs) and in colonic circular muscle stripes. A Flexercell FX‐4000 TensionPlus System was used to stretch the cultured SMCs. Partial colon obstruction in rats was surgically induced with a silicon band placed in the distal colon.Results(1) Time‐dependent static stretch activated PKCs in RCCSMCs. Pan‐PKC, classical PKC‐beta, new PKC‐delta, atypical PKC‐zeta, and PKD phosphorylation levels rose in 15‐min‐stretched cells. (2) Stretch‐induced COX‐2 mRNA and protein expression were inhibited by PKC‐delta inhibitor rottlerin, general PKC inhibitor chelerythrine, and PKD inhibitor CID755673. PKC‐beta and PKC‐zeta inhibition did not block stretch‐induced COX‐2 expression. (3) Stretch‐induced expression of COX‐2 depends on activation of mitogen‐activated protein kinase (MAPK) ERKs, p38, and JNKs. We found that PKC‐delta inhibitor treatment significantly inhibited stretch‐induced activation of all MAPK ERKs, p38, and JNKs. However, PKD inhibitor blocked activation of p38, but not ERKs and JNKs. Stretch‐induced MAPK activation was unaffected by PKC‐beta or PKC‐zeta inhibition. (4) Treatments with ERK inhibitor PD98059, p38 inhibitor SB203580, or JNK inhibitor SP600125 did not prevent stretch‐induced PKC activation. PKD inhibitor treatment hampered stretch‐induced expression of COX‐2 and improved smooth muscle contractility in the stretched muscle stripes Furthermore, in vivo inhibition of mechano‐transcription by daily administration of general PKC inhibitor chelerythrine or p38 inhibitor SB203580 significantly improved smooth muscle contractility and lumen distension in colon obstruction.Conclusions & InferencesMechanical stretch induces phosphorylation of PKCs and PKD in the colonic SMCs. PKC‐delta and PKD are involved in the activation of MAPKs and induction of COX‐2 in response to mechanical stretch. Inhibition of mechano‐transcription has beneficial effects on motility dysfunction in bowel obstruction.