Sustained contraction and loss of NO production in TGFβ1‐treated endothelial cells

Background and purpose: Transforming growth factor β1 (TGFβ1) is generated in atherosclerotic and injured vessel walls. We examined whether the endothelial-to-mesenchymal transdifferentiation induced by TGFβ1 affects endothelial functions. Experimental approach: Bovine aortic endothelial cells (BAECs) were treated with 3 ng ml−1 TGFβ1 for 7 days. Contraction of TGFβ1-treated BAECs was assessed by collagen gel contraction assay. Protein expression and phosphorylation were assessed by Western blotting. Intracellular Ca2+ concentration and NO production were measured using fura2 and DAF-2, respectively. Key results: TGFβ1-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 TGFβ1-treated BAECs but not of gels containing control BAECs. ATP-induced contraction of TGFβ1-treated BAECs was not reversed by the removal of ATP but was partially suppressed by a high concentration of sodium nitroprusside (1 μM). TGFβ1-treated BAECs showed sustained phosphorylation of myosin light chain in response to ATP and low levels of basal MYPT1 expression. ATP-induced Ca2+ transients as well as eNOS protein expression were not affected by TGFβ1 in BAECs. However, ATP-induced NO production was significantly reduced in TGFβ1-treated BAECs. Anti-TGFβ1 antibody abolished all of these TGFβ1-induced changes in BAECs. Conclusions and Implications: Mesenchymal transdifferentiation induced by TGFβ1 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