Hydroperoxide-induced increases in intracellular calcium due to annexin VI translocation and inactivation of plasma membrane Ca2+-ATPase.
Oxidative stress can cause changes in intracellular free calcium concentration ([Ca2+]i) that resemble those occurring under normal cell signaling. In the alveolar macrophage, hydroperoxide-induced elevation of [Ca2+]i modulates the respiratory burst and other important physiologic functions. The source of Ca2+ released by hydroperoxide is intracellular but separate from the endoplasmic reticulum pool released by receptor-mediated stimuli (Hoyal, C. R., Gozal, E., Zhou, H., Foldenauer, K., and Forman, H. J. (1996) Arch. Biochem. Biophys. 326, 166-171). Previous studies in other cells have suggested that mitochondria are a potential source of oxidant-induced [Ca2+]i elevation. In this study we have identified another potential source of hydroperoxide-releasable intracellular calcium, that bound to annexin VI on the inner surface of the plasma membrane. Translocation of annexin VI from the membrane during exposure to t-butyl hydroperoxide matched elevation of [Ca2+]i as a function of time and t-butyl hydroperoxide concentration. The translocation was possibly due to a combination of ATP depletion and oxidative modification of membrane lipids and proteins. A sustained increase in [Ca2+]i occurring > 50 pmol/10(6) cells (50 microM under these conditions) appeared to be a consequence of membrane Ca2+-ATPase dysfunction. These results suggest that exposure to oxidative stress results in early alterations to the plasma membrane and concomitant release of Ca2+ into the cytosol. In addition it suggests a mechanism for participation of annexin VI translocation that may underlie the alterations in macrophage function by oxidative stress.
Hoyal
C R
CR
Department of Molecular Pharmacology, University of Southern California, Los Angeles, California 90033, USA.
Thomas
A P
AP
Forman
H J
HJ
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D017317:Annexin A6 / Q000378:metabolism*; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors*; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D008297:Male; D018384:Oxidative Stress; D010545:Peroxides / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D020122:tert-Butylhydroperoxide
D017317:Annexin A6; D010545:Peroxides; D000244:Adenosine Diphosphate; D020122:tert-Butylhydroperoxide; D000252:Calcium-Transporting ATPases; D002118:Calcium