Sustained contraction and loss of NO production in TGF β 1 ‐treated endothelial cells

Background and purpose: Transforming growth factor β 1 (TGFβ 1 ) is generated in atherosclerotic and injured vessel walls. We examined whether the endothelial‐to‐mesenchymal transdifferentiation induced by TGFβ 1 affects endothelial functions. Experimental approach: Bovine aortic endothelial cells (BAECs) were treated with 3 ng ml −1 TGFβ 1 for 7 days. Contraction of TGFβ 1 ‐treated BAECs was assessed by collagen gel contraction assay. Protein expression and phosphorylation were assessed by Western blotting. Intracellular Ca 2+ concentration and NO production were measured using fura2 and DAF‐2, respectively. Key results: TGFβ 1 ‐treated BAECs showed dense actin fibers and expressed smooth muscle marker proteins; they also changed into smooth muscle‐like, spindle‐shaped cells in collagen gel cultures. ATP (10 μM) induced a gradual contraction of collagen gels containing TGFβ 1 ‐treated BAECs but not of gels containing control BAECs. ATP‐induced contraction of TGFβ 1 ‐treated BAECs was not reversed by the removal of ATP but was partially suppressed by a high concentration of sodium nitroprusside (1 μM). TGFβ 1 ‐treated BAECs showed sustained phosphorylation of myosin light chain in response to ATP and low levels of basal MYPT1 expression. ATP‐induced Ca 2+ transients as well as eNOS protein expression were not affected by TGFβ 1 in BAECs. However, ATP‐induced NO production was significantly reduced in TGFβ 1 ‐treated BAECs. Anti‐TGFβ 1 antibody abolished all of these TGFβ 1 ‐induced changes in BAECs. Conclusions and Implications: Mesenchymal transdifferentiation induced by TGFβ 1 leads to sustained contraction and reduced NO production in endothelial cells. Such effects, therefore, would not be beneficial for vascular integrity. British Journal of Pharmacology (2006) 149 , 355–364. doi: 10.1038/sj.bjp.0706883