Role of protein kinase C in intestinal ischemic preconditioning

Introduction. Tissue protection by ischemic preconditioning (IPC) has been previously characterized in organs such as the heart and involves at least in part PKC activation. It is not yet clear whether such preconditioning against ischemia/reperfusion (I/R) injury operates in the intestine, and, if so, whether IPC involves protein kinase C (PKC). Materials and methods. IPC of the small intestine in male Sprague Dawley rats was induced by 10-min superior mesenteric artery (SMA) clamp followed by 120-min reperfusion. Sham-operated control or IPC rats were then rechallenged with 20-min SMA clamp. Histological injury to jejunal mucosa was assessed by microscopic examination and Parks' injury score (Grade 0-4; 0 = no damage). PKC activity was determined by immunoprecipitation of specific isoforms followed by in vitro kinase assay using mucosal scrapings of the harvested jejunum. Data were expressed as mean ± SEM and analyzed by one-way ANOVA with multiple comparison tests. Results. Ten-minute SMA clamp led to epithelial damage that was fully reversed by 120-min reperfusion. Activity of several PKC isoforms (PKCα, -δ, -ε) increased after 10-min ischemia. Epithelial injury associated with 20-min SMA clamp was attenuated by prior IPC. The protective effect of IPC on intestinal mucosa was prevented when animals were pretreated with the conventional (c) and novel (n) PKC inhibitor Gö6850, but not with Gö6976 (selective cPKC inhibitor), rottlerin (selective PKCδ inhibitor), or saline control. Conclusions. Brief mesenteric ischemia induces a reversible epithelial injury in rats associated with activation of several PKC isoforms. Injury induced by mesenteric ischemia is reduced by brief ischemic preconditioning, an effect that is abolished by nonselective PKC inhibition but not by a selective inhibitor of cPKC or PKCδ. The results suggest that activation of nPKC isoform(s), especially PKCε during and following ischemic insults (IPC), may play an important role in protection against I/R injury in the intestine.