Proceedings of The Physiological Society
University College London (2011) Proc Physiol Soc 24, C01 and PC01
Protective role of calmodulin in alcohol-induced trypsinogen activation
J. V. Gerasimenko1, P. Ferdek1, O. V. Gerasimenko1, O. H. Petersen1
1. School of Biosciences, Cardiff University, Cardiff, United Kingdom.
MRC Group, School of Biosciences, Cardiff University, Museum Avenue Cardiff CF10 3AX, Wales, UK. Acute pancreatitis is generally initiated by premature trypsinogen activation in pancreatic acinar cells mediated by excessive intracellular calcium release from internal stores. One of the major causes of acute pancreatitis is excessive alcohol intake, but the molecular mechanism of this severe inflammatory disease is not completely understood. We now show that in two-photon permeabilized mouse pancreatic acinar cells even a relatively low ethanol concentration as well as its non-oxidative metabolite palmitoleic acid ethyl ester (POAEE) elicit calcium release from intracellular stores and also induce intracellular trypsinogen activation (1, 2). Reintroducing the calcium sensor calmodulin (at a normal intracellular concentration found in intact cells) to the permeabilized cells dramatically reduced ethanol-induced calcium release and trypsinogen activation. Pre-incubation of cells with a calmodulin activator CALP-3 (100 mkM) abolished the ethanol and POAEE effects in intact and permeabilized cells (1). Both ethanol-elicited and POAEE-induced calcium liberation and trypsin activity were significantly reduced in acinar cells from mice in which type 2 inositol trisphosphate receptors had been knocked out. Double knock out of inositol trisphosphate receptors of both types 2 and 3 further reduced ethanol-induced or POAEE-induced calcium release and trypsinogen activation to very low levels (1, 2). Thus, the calmodulin-sensitive inositol trisphosphate receptor calcium release channels, that are responsible for normal pancreatic stimulus-secretion coupling, also play a major role in the toxic action of ethanol. Calmodulin provides a protective mechanism, regulating the sensitivity of the calcium release process (1). The marked inhibition of ethanol-induced (or POAEE-induced) Ca2+ release and trypsin activation by a calmodulin activator suggests potential therapeutic benefits for treatment of pancreatitis.
Where applicable, experiments conform with Society ethical requirements