Abstract
Bile acids are known to induce Ca2+ signals in pancreatic acinar cells. We have recently shown that phosphatidylinositol 3-kinase (PI3K) regulates changes in free cytosolic Ca2+ concentration ([Ca2+]i) elicited by CCK by inhibiting sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA). The present study sought to determine whether PI3K regulates bile acid-induced [Ca2+]i responses. In pancreatic acinar cells, pharmacological inhibition of PI3K with LY-294002 or wortmannin inhibited [Ca2+]i responses to taurolithocholic acid 3-sulfate (TLC-S) and taurochenodeoxycholate (TCDC). Furthermore, genetic deletion of the PI3K γ-isoform also decreased [Ca22+]i responses to bile acids. Depletion of CCK-sensitive intracellular Ca2+ pools or application of caffeine inhibited bile acid-induced [Ca2+]i signals, indicating that bile acids release Ca2+ from agonist-sensitive endoplasmic reticulum (ER) stores via an inositol (1,4,5)-trisphosphate-dependent mechanism. PI3K inhibitors increased the amount of Ca2+ in intracellular stores during the exposure of acinar cells to bile acids, suggesting that PI3K negatively regulates SERCA-dependent Ca2+ reloading into the ER. Bile acids inhibited Ca2+ reloading into ER in permeabilized acinar cells. This effect was augmented by phosphatidylinositol (3,4,5)-trisphosphate (PIP3), suggesting that both bile acids and PI3K act synergistically to inhibit SERCA. Furthermore, inhibition of PI3K by LY-294002 completely inhibited trypsinogen activation caused by the bile acid TLC-S. Our results indicate that PI3K and its product, PIP3, facilitate bile acid-induced [Ca2+]i responses in pancreatic acinar cells through inhibition of SERCA-dependent Ca2+ reloading into the ER and that bile acid-induced trypsinogen activation is mediated by PI3K. The findings have important implications for the mechanism of acute pancreatitis since [Ca2+]i increases and trypsinogen activation mediate key pathological processes in this disorder.
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© 2008 Springer Medizin Verlag Heidelberg
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Fischer, L., Gukovskaya, A.S., Gukovsky, I., Büchler, M.W., Pandol, S.J. (2008). Phosphatidylinositol 3-kinase reguliert Gallensalz-induzierte Kalziumsignale der pankreatischen Azinuszelle. In: Arbogast, R., Schackert, H.K., Bauer, H. (eds) Chirurgisches Forum 2008. Deutsche Gesellschaft für Chirurgie, vol 37. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-78833-1_59
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DOI: https://doi.org/10.1007/978-3-540-78833-1_59
Publisher Name: Springer, Berlin, Heidelberg
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