OXIDANT/ANTIOXIDANT EFFECTS OF TGF BETA1 ON LUNG CELLS

Tufts Medical Center, Boston MA

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Abstract

TGFbetas, a family of multifunctional polypeptides, have been strongly implicated in pulmonary remodeling processes and lung disease. We have found that TGFbeta1 produces a "pro-oxidant" effect on endothelial cells and fibroblasts in culture as manifested by a reduction in cellular glutathione, a major determinant of cellular redox status, and stimulation of extracellular H2O2 release that is associated with an elevation in NADH: flavin oxidoreductase activity at the cell surface. Anti-oxidants prevent TGFbeta1-induced growth inhibition of endothelial cells, while reactive oxygen species, lowering of cellular glutathione and Fe3+ potentiate it. In contrast, while growth-arrested fibroblasts show no proliferative response to TGFbeta1 alone, the growth stimulatory effect of certain growth factors is enhanced by TGFbeta1. From these studies, we hypothesize that the action of TGFbeta1 on cellular redox status may be an important and previously unrecognized regulator of growth processes of both endothelial cells and fibroblasts. In the present proposal we plan to further test this hypothesis and specifically will: 1) Further characterize the cell surface-associated NADH oxidase activated by TGFbeta1 and determine its relationship to intracellular H2O2 and redox status; 2) Examine the influence of the redox status of the cell on autocrine production of TGFbeta1, a likely perpetuator of TGFbeta1 action, as measured by a quantitative PCR for TGFbeta1 mRNA, ELISA for TGFbeta1 protein and analysis of the human TGFbeta1 gene promoter using transiently transfected cells; 3) Determine intermediary processes resulting from stimulation of cellular H2O2 production by assessing the influence of TGFbeta1 and cellular redox status on the transcription factor AP-1 and cellular kinases; and 4) Evaluate the possible role of H2O2 production and cellular redox status in the augmentation of fibroblast proliferation produced by fibroblast growth factor in the presence on TGFbeta1. We anticipate that the composite studies will help to establish cellular redox status as an important intermediary in the actions of TGFbeta1 that may contribute to remodeling of the lung in disease states.