Sustained contraction and loss of NO production in TGFβ 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 (1μM). 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.