Oxidant-impaired intracellular Ca2+ signaling in pancreatic acinar cells: role of the plasma membrane Ca2+-ATPase.
Pancreatitis is an inflammatory disease of pancreatic acinar cells whereby intracellular calcium concentration ([Ca(2+)](i)) signaling and enzyme secretion are impaired. Increased oxidative stress has been suggested to mediate the associated cell injury. The present study tested the effects of the oxidant, hydrogen peroxide, on [Ca(2+)](i) signaling in rat pancreatic acinar cells by simultaneously imaging fura-2, to measure [Ca(2+)](i), and dichlorofluorescein, to measure oxidative stress. Millimolar concentrations of hydrogen peroxide increased cellular oxidative stress and irreversibly increased [Ca(2+)](i), which was sensitive to antioxidants and removal of external Ca(2+), and ultimately led to cell lysis. Responses were also abolished by pretreatment with (sarco)endoplasmic reticulum Ca(2+)-ATPase inhibitors, unless cells were prestimulated with cholecystokinin to promote mitochondrial Ca(2+) uptake. This suggests that hydrogen peroxide promotes Ca(2+) release from the endoplasmic reticulum and the mitochondria and that it promotes Ca(2+) influx. Lower concentrations of hydrogen peroxide (10-100 muM) increased [Ca(2+)](i) and altered cholecystokinin-evoked [Ca(2+)](i) oscillations with marked heterogeneity, the severity of which was directly related to oxidative stress, suggesting differences in cellular antioxidant capacity. These changes in [Ca(2+)](i) also upregulated the activity of the plasma membrane Ca(2+)-ATPase in a Ca(2+)-dependent manner, whereas higher concentrations (0.1-1 mM) inactivated the plasma membrane Ca(2+)-ATPase. This may be important in facilitating "Ca(2+) overload," resulting in cell injury associated with pancreatitis.
Bruce
Jason I E
JI
Faculty of Life Sciences, 2nd Floor Core Technology Facility, 46 Grafton St., The Univ. of Manchester, Manchester M13 9NT, UK. jason.bruce@manchester.ac.uk
Elliott
Austin C
AC
D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002462:Cell Membrane / Q000201:enzymology; D002756:Cholagogues and Choleretics / Q000494:pharmacology; D002766:Cholecystokinin / Q000494:pharmacology; D005452:Fluoresceins; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D066298:In Vitro Techniques; D016877:Oxidants / Q000494:pharmacology*; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D046790:Pancreas, Exocrine / Q000166:cytology / Q000201:enzymology*; D010195:Pancreatitis / Q000378:metabolism; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000378:metabolism*; D051381:Rats
D002756:Cholagogues and Choleretics; D005452:Fluoresceins; D016877:Oxidants; C037631:2',7'-dichlorofluorescein; D002766:Cholecystokinin; D006861:Hydrogen Peroxide; D053499:Plasma Membrane Calcium-Transporting ATPases; D002118:Calcium