ENHANCED RATE OF H2O2 RELEASE FROM BOVINE PULMONARY-ARTERY ENDOTHELIAL-CELLS INDUCED BY TGF-BETA-1

We have previously reported that transforming growth factor-beta1 (TGF -beta1) produces a ''prooxidant'' effect on cultured bovine pulmonary artery endothelial cells (BPAEC) [S. K. Das and B. L. Fanburg. Am. J. Physiol. 261 (Lung Cell. Mol. Physiol. 5): L249-L254, 1991]. This effe ct was found to be associated with a lowering of total cellular GSH (A . C. White, S. K. Das, and B. L. Fanburg. Am. J. Respir. Cell Mol. Bio l. 6: 364-368, 1992). In this study, we demonstrate a twofold increase in the rate of extracellular H2O2 release from BPAEC after a 72-h exp osure to TGF-beta1 (2 ng/ml, added at times 0 and 48 h). Increasing an d decreasing the levels of cellular GSH with diethylmaleate (DEM, 0.05 mM) and buthionine sulfoximine (BSO, 0.01 mM), respectively, did not affect the rate of TGF-beta1-induced increase in H2O2 release when com pared with the individual effects of these reagents on control cells. The addition of BSO (0.01 mM) to control cells failed to demonstrate a n increase in the rate of H2O2 release, despite a more profound decrea se in cellular GSH by these cells than detected in cells treated with TGF-beta1 alone. Moreover, a single dose of TGF-beta1 (2 ng/ml) induce d a 63-85% increase in the rate of H2O2 release within 16 h of exposur e, well before the previously demonstrated lowering of cellular GSH. T hese results indicate that the increase in H2O2 production by TGF-beta 1-stimulated BPAEC is associated with, but does not appear to be the r esult of, a lowering of cellular GSH. This study further suggests that the TGF-beta1-induced H2O2 production occurs at a site inaccessible t o detoxification by GSH.