Protein kinase epsilon dampens the secretory response of model intestinal epithelia during ischemia.

BACKGROUND

Luminal fluid sequestration and diarrhea are early manifestations of mesenteric ischemia. This can be modeled in vitro with the use of T84 intestinal epithelia, where ischemia induces Cl(-) secretion with adenosine-mediated autocrine feedback. Protein kinase C (PKC) regulates epithelial transport and, in some organ systems, is involved in the response to ischemic stress. The purpose of this study was to define the role of PKC on epithelial transport during ischemia.

METHODS

By voltage-current clamp, short-circuit current (Isc) equals Cl(-) secretion. Ischemic conditions were simulated with the use of a well-established chemical hypoxia protocol.

RESULTS

Chemical hypoxia briskly activated Isc. Gö6850, an antagonist of novel and conventional PKC isoforms, markedly enhanced the ischemia-induced Isc response, although Gö6976 (which inhibits only conventional isoforms) had no effect. Rottlerin, a specific inhibitor of PKC delta, did not attenuate ischemic Isc. Both phorbol 12-myristate, 13-acetate and bryostatin-1, which selectively activate PKC epsilon in T84 cells, markedly attenuated the Isc response to ischemia. Both agents also inhibited the Isc response to exogenous adenosine.

CONCLUSIONS

PKC (likely the novel epsilon isoform) in intestinal epithelia modulates ischemia-induced alterations in ion transport. Inhibition of PKC epsilon exaggerates the secretory response that is induced by ischemia and by authentic adenosine; conversely, augmented activation of PKC epsilon inhibits secretion. Manipulation of PKC epsilon could limit luminal fluid sequestration during mesenteric ischemia.