Pancreatic protease activation by alcohol metabolite depends on Ca²⁺ release via acid store IP₃ receptors

• Published in: Proceedings of the National Academy of Sciences - PNAS 2009-06, Vol.106 (26), p.10758-10763
• Main Authors: Gerasimenko, Julia V, Lur, György, Sherwood, Mark W, Ebisui, Etsuko, Tepikin, Alexei V, Mikoshiba, Katsuhiko, Gerasimenko, Oleg V, Petersen, Ole H
• Format: Article
• Language: English
• Subjects: Acinar cells; Alcoholic pancreatitis; Alcohols; Animals; Antibodies; Biological Sciences; Calcium; Calcium - metabolism; Cells, Cultured; Dose-Response Relationship, Drug; Endoplasmic reticulum; Endoplasmic Reticulum - drug effects; Endoplasmic Reticulum - metabolism; Enzyme Activation - drug effects; Esters; Ether - chemistry; Ether - pharmacology; Fatty acids; Fatty Acids, Monounsaturated - chemistry; Fatty Acids, Monounsaturated - pharmacology; Female; Genotype; Inositol 1,4,5-Trisphosphate Receptors - genetics; Inositol 1,4,5-Trisphosphate Receptors - metabolism; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Pancreas - cytology; Pancreas - drug effects; Pancreas - metabolism; Receptors; Ryanodine Receptor Calcium Release Channel - genetics; Ryanodine Receptor Calcium Release Channel - metabolism; Trypsin - metabolism; Type C Phospholipases - metabolism; Vacuoles
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0904818106

Toxic alcohol effects on pancreatic acinar cells, causing the often fatal human disease acute pancreatitis, are principally mediated by fatty acid ethyl esters (non-oxidative products of alcohol and fatty acids), emptying internal stores of Ca²⁺. This excessive Ca²⁺ liberation induces Ca²⁺-dependent necrosis due to intracellular trypsin activation. Our aim was to identify the specific source of the Ca²⁺ release linked to the fatal intracellular protease activation. In 2-photon permeabilized mouse pancreatic acinar cells, we monitored changes in the Ca²⁺ concentration in the thapsigargin-sensitive endoplasmic reticulum (ER) as well as in a bafilomycin-sensitive acid compartment, localized exclusively in the apical granular pole. We also assessed trypsin activity in the apical granular region. Palmitoleic acid ethyl ester (POAEE) elicited Ca²⁺ release from both the ER as well as the acid pool, but trypsin activation depended predominantly on Ca²⁺ release from the acid pool, that was mainly mediated by functional inositol 1,4,5- trisphosphate receptors (IP₃Rs) of types 2 and 3. POAEE evoked very little Ca²⁺ release and trypsin activation when IP₃Rs of both types 2 and 3 were knocked out. Antibodies against IP₃Rs of types 2 and 3, but not type 1, markedly inhibited POAEE-elicited Ca²⁺ release and trypsin activation. We conclude that Ca²⁺ release through IP₃Rs of types 2 and 3 in the acid granular Ca²⁺ store induces intracellular protease activation, and propose that this is a critical process in the initiation of alcohol-related acute pancreatitis.