Role of TGF-β1 in vascular smooth muscle cell apoptosis induced by Angiotensin II

Both Angiotensin II and transforming growth factor beta-1 JGF-beta 1) are important mediators of vascular smooth muscle cell function and have been reported to mediate the balance between proliferation and apoptosis. Some crosstalk between Angiotensin II and TGF beta 1 in end-organ hypertension has been established. However, whether TGF-beta 1 is able to mediate Angiotensin II-induced vascular cell damage remains unknown. Vascular smooth muscle cells were obtained from rat thoracic aorta and cultured in 10% foetal calf serum. In all experiments, medium was changed to a low-serum (0.4% foetal calf serum) or serum-free one with or without Angiotensin H. Apoptosis was assessed by DNA fragmentation, DNA synthesis was measured as bromo-deoxyuridine uptake. TGF-beta 1 production was determined by Enzyme-linked Immunosorbent Assay (ELISA) from cell conditioned media, RT-PCR from cell lysates and confocal immunostaining of fixed cells. Angiotensin II induced apoptosis in the absence of DNA synthesis when coincubated at 1 mu M. Neither the specific anti-TGF-beta 1 monoclonal antibody (50 mu g/ ml) nor the novel activin-like kinase (ALK)-4/5/7 synthetic inhibitor SB-431542 (4-(5-benzo(1,3)dioxol-5-yl-4-pyridin-2-y1-1H-imidazol-2-y1) benzamide) at 10 liM were able to inhibit this effect. Angiotensin II induced expression of TGF-beta 1 without further secretion of this cytokine. This effect was not affected by incubation with the ATI inhibitor irbesartan (10 mu M). A pharmacological approach to TGF-beta 1 inhibition would be unable to reverse the apoptotic effect of Angiotensin II on vascular smooth muscle cells. (c) 2006 Elsevier B.V, All rights reserved.