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.
Department of Molecular Pharmacology, University of Southern California, Los Angeles, California 90033, USA.
C R
CR
Hoyal
A P
AP
Thomas
H J
HJ
Forman
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