Bile acids activate ryanodine receptors in pancreatic acinar cells via a direct allosteric mechanism.
The earliest critical event of pancreatitis is a long lasting high amplitude rise of intracellular Ca(2+) concentration of the acinar cell, which can be triggered by high concentration of bile acids. Although, Ca(2+)-release through ryanodine receptors (RyR) is involved in the process, the significance and the exact mechanism of bile acid's action on RyR has not been fully elucidated yet. Therefore, we aimed to test with various techniques and aspects whether bile acids exert a direct effect on RyR and SERCA pump. Our data show that taurocholic acid (TCA)-induced Ca(2+) release in pancreatic acinar cells was significantly reduced by the RyR antagonist dantrolene. Further, we show that TCA enhanced RyR's (3)H-ryanodine binding and triggered robust Ca(2+)-release from RyR-enriched vesicles in the pathologically relevant concentration range. RyR single channel current analysis demonstrated that 200μM TCA induced a 5-fold increase in the channel's open probability and caused a significant lengthening of the mean open time. TCA also suppressed Ca(2+)-uptake rate and ATP-ase activity of SERCA-enriched vesicles, but interestingly, failed to decrease Ca(2+) elimination rate in intact cells. Overall, our results strongly suggest that TCA opens RyR by an allosteric mechanism, which contribute significantly to bile acid-induced pathologic Ca(2+)-leak from the endoplasmic reticulum in pancreatic acinar cells.
Department of Physiology, University of Debrecen, Faculty of Medicine, 98. Nagyerdei krt. PO Box: 22, Debrecen 4012, Hungary. Electronic address: geyer.nikoletta@med.unideb.hu.
Nikolett
N
Geyer
Department of Physiology, University of Debrecen, Faculty of Medicine, 98. Nagyerdei krt. PO Box: 22, Debrecen 4012, Hungary. Electronic address: diszigyuszi@gmail.com.
Gyula
G
Diszházi
Department of Physiology, University of Debrecen, Faculty of Medicine, 98. Nagyerdei krt. PO Box: 22, Debrecen 4012, Hungary. Electronic address: csl@edu.unideb.hu.
László
L
Csernoch
Department of Physiology, University of Debrecen, Faculty of Medicine, 98. Nagyerdei krt. PO Box: 22, Debrecen 4012, Hungary; Research Center for Molecular Medicine, University of Debrecen, Faculty of Medicine, 98. Nagyerdei krt. PO Box: 72, Debrecen 4012, Hungary. Electronic address: jona.istvan@med.unideb.hu.
István
I
Jóna
Department of Physiology, University of Debrecen, Faculty of Medicine, 98. Nagyerdei krt. PO Box: 22, Debrecen 4012, Hungary; Research Center for Molecular Medicine, University of Debrecen, Faculty of Medicine, 98. Nagyerdei krt. PO Box: 72, Debrecen 4012, Hungary. Electronic address: almassy.janos@med.unideb.hu.
János
J
Almássy
D061354:Acinar Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D001647:Bile Acids and Salts / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002756:Cholagogues and Choleretics / Q000494:pharmacology; D003620:Dantrolene / Q000494:pharmacology; D051379:Mice; D008861:Microsomes / Q000378:metabolism; D046790:Pancreas, Exocrine / Q000166:cytology*; D051381:Rats; D012433:Ryanodine / Q000737:chemistry / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism; D013656:Taurocholic Acid / Q000494:pharmacology
D001647:Bile Acids and Salts; D002756:Cholagogues and Choleretics; D019837:Ryanodine Receptor Calcium Release Channel; D012433:Ryanodine; D013656:Taurocholic Acid; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D003620:Dantrolene; D002118:Calcium
Bile acid; Calcium release; Pancreas; Pancreatitis; Ryanodine receptor; SERCA