Smad2 Mediates Transforming Growth Factor-β Induction of Endothelial Nitric Oxide Synthase Expression

Abstract

Abstract-Transforming growth factor-␤ (TGF-␤) increases expression of endothelial nitric oxide synthase (eNOS), although the precise mechanism by which it does so is unclear. We report that Smad2, a transcription factor activated by TGF-␤, mediates TGF-␤ induction of eNOS in endothelial cells. TGF-␤ induces Smad2 translocation from cytoplasm to nucleus, where it directly interacts with a specific region of the eNOS promoter. Overexpression of Smad2 increases basal levels of eNOS, and further increases TGF-␤ stimulation of eNOS expression. Key Words: endothelial cell Ⅲ hypoxia Ⅲ atherosclerosis A lthough endothelial nitric oxide synthase (eNOS or NOS3) was originally described as a constitutive NOS, subsequent work showed that eNOS expression is regulated by a variety of physiological and pathophysiological factors. 1-6 Expression of eNOS is increased by exercise, shear stress, hypoxia, hyperthyroidism, cirrhosis, and endothelial cell proliferation. [7][8][9][10] Various mediators can also increase eNOS expression, including estrogens, angiotensin II, glucose, oxidized linoleic acid, lysophosphatidylcholine, hydrogen peroxide, and transforming growth factor-␤. 1-6 Expression of eNOS is decreased by hypoxia, inflammation, and pulmonary hypertension. [11][12][13][14] Mediators that decrease eNOS expression include oxidized LDL, lipopolysaccharide, and tumor necrosis factor-␣. Regulation of eNOS ExpressionThe level of eNOS expression is determined by multiple mechanisms, including posttranscriptional regulation 15-18 and posttranslational regulation. 19 -36 Expression of eNOS is also regulated at the transcriptional level. The 5Ј-flanking region of the eNOS gene lacks a TATA box, but contains elements that mediate constitutive expression of genes in endothelial cells, including Sp1 sites and GATA. [37][38][39][40][41][42] The 5Ј-flanking region also contains many putative sites for further transcriptional regulation of eNOS. However, only a few of these sites have been formally shown to regulate eNOS transcription, including PEA3 and AP-1 binding sites. 43,44 Finally, a region of the eNOS promoter extending from Ϫ1269 and Ϫ935 mediates TGF-␤ induction of eNOS transcription. 45 TGF-␤ and Vascular PathophysiologyTGF-␤ belongs to a superfamily of dimeric growth factors, including bone morphogenetic proteins and activins. 46 -48 TGF-␤ regulates diverse biological processes, including cell proliferation, differentiation, and migration. TGF-␤ also regulates cellular functions within the cardiovascular system, including angiogenesis, fibrosis, and production of extracellular matrix. TGF-␤ Signal Transduction and SmadsAfter its secretion and activation, TGF-␤ forms a complex with type I and type II TGF-␤ receptors on target cells. Once bound to TGF-␤, the type II TGF-␤ receptor phosphorylates the type I receptor, and the type I receptor in turn phosphorylates transcription factors known as Smads. Smad family members mediate TGF-␤ signal transduction, and include receptor Smads (Smad2 and Smad3) that associate with and are ...

The physiological role of endoglin in the cardiovascular system

“…Moreover, S-Eng TGF-␤1 administration (14). This observation is in agreement with the finding that TGF-␤1 regulates eNOS expression (148) and induces vasodilatation in wild-type mice, this vasodilatation being severely impaired in Eng ϩ/Ϫ mice (147). Thus an in vivo overexpression of S-endoglin appears to result in the same phenotype as L-endoglin deficiency, suggesting opposing functional effects of both isoforms on the NO and COX-2 systems.…”

Nitric Oxide Formation Is Inversely Related to Serum Levels of Antiangiogenic Factors Soluble Fms-Like Tyrosine Kinase-1 and Soluble Endogline in Preeclampsia

“…This soluble form of endoglin, in turn, decreases the arterial vasodilatation induced by TGF-␤1 and -␤3, which is mediated by NO. Indeed, TGF-␤ receptor activation increases NO formation through increased eNOS expression and activation, 53,54 and sEng attenuates eNOS activation by TGF-␤ by interfering with the Thr495 dephosphorylation of eNOS, thus contributing to decreased NO synthesis. 34 The negative correlations that we found between plasma or whole blood nitrite concentrations and sEng support the suggestion that sEng plays a role in the pathogenesis of preeclampsia by decreasing NO formation.…”

Atorvastatin Increases Endoglin, SMAD2, Phosphorylated SMAD2/3 and eNOS Expression in ApoE/LDLR Double Knockout Mice

“…We therefore focused on the endoglin relationship with SMAD proteins in our experiment. It was demonstrated that SMAD2 inhibits proinflammatory adhesion molecules, such as E-selectin, and at the same time induces eNOS expression 24,28,29) . To the best of our knowledge, there are no in Fig.…”