Inhibition of Na+/Ca2+ exchanger by peroxynitrite in microsomes of pulmonary smooth muscle:: role of matrix metalloproteinase-2

Treatment of bovine pulmonary artery smooth muscle microsomes with peroxynitrite (ONOO-) (100 muM) markedly stimulated matrix metalloproteinase-2 (MMP-2) activity and also enhanced Ca(2+)ATPase activity and ATP-dependent Ca2+ uptake. Pretreatment of the microsomes with vitamin E (1 mM) and TIMP-2 (50 mug/ml) preserved the increase in MMP-2 activity, Ca(2+)ATPase activity and also ATP-dependent Ca2+ uptake in the microsomes. In contrast, Na+-dependent Ca2+ uptake in the microsomes was inhibited by ONOO- and this was found to be reversed by vitamin E (1 mM) and TIMP-2 (50 mug/ml). However, changes caused by ONOO- in MMP-2 activity, ATPdependent Ca2+ uptake and Na+-dependent Ca2+ uptake were not reversed upon pretreatment of the microsomes with a low concentration of 5 mug/ml of TIMP-2 which, on the contrary, reversed MMP-2 (1 mug/ml)-mediated alteration on these parameters. The inhibition of Na+-dependent Ca2+ uptake by ONOO- and MMP-2 overpowered the stimulation of ATP-dependent Ca2+ uptake in the microsomes. Treatment with ONOO- abolished the inhibitory effect of TIMP-2 (5 mug/mI) on MMP-2 (1 mug/ml) causing C-14-gelatin degradation. Overall, the present study suggests that ONOO- inactivated TIMP-2, the ambient inhibitor of MMP-2, leading to activation of the ambient proteinase, MMP-2, and subsequently stimulated Ca2+ ATPase activity and ATP-dependent Ca2+ uptake, but inhibited Na+-dependent Ca2+ uptake, resulting in a marked decrease in Ca2+ uptake in microsomes of bovine pulmonary artery smooth muscle. (C) 2004 Elsevier B.V. All rights reserved.