MEK1,2 response element mediates angiotensin II—stimulated plasminogen activator inhibitor-1 promoter activation

Abstract

IntroductionPlasminogen activator inhibitor-1 (PAI-1) is the major regulator of both tissue and urokinase plasminogen activators. 1,2 Inhibition of plasminogen activation by PAI-1 reduces the generation of plasmin and thereby impairs fibrinolysis. In addition, PAI-1 has also been suggested to reduce plasmin-mediated activation of matrix metalloproteases 3 and compete with cellular ␣v␤3 integrin matrix interactions, which contribute to cellular migration. 4 Overexpression of PAI-1 in transgenic mice or by adenovirus-mediated gene transfer increases thrombosis, 5,6 and PAI-1 deficiency enhances fibrinolysis and neointimal remodeling. 7,8 Increased levels of PAI-1 have been demonstrated in vascular lesions induced by balloon catheter injury and atherosclerosis. [9][10][11][12] Within these vascular lesions, PAI-1 expression is prominently increased in neointimal smooth muscle cells. 9,13 In previous animal studies using angiotensin-converting enzyme inhibition, angiotensin type 1 receptor antagonism and systemic angiotensin II (Ang II) infusion, our group and others have demonstrated that the Ang II/AT 1 pathway plays an important role in regulating vascular PAI-1 gene expression in vivo. 9,[14][15][16] A host of agonists, including Ang II, transforming growth factor-␤ (TGF-␤), very low density lipoprotein (VLDL), and phorbol ester, require the activity of MAPK/ERK kinase1 and 2 (MEK1,2) to induce PAI-1 mRNA expression. [17][18][19][20] Although the MEK/ERK pathway plays a key role in controlling PAI-1 mRNA levels, the mechanism(s) that mediates the effects of MEK1,2 on PAI-1 transcription have not been identified. Previous reports have demonstrated that the MEK/ERK pathway can affect phosphorylation, nuclear transport, and transactivation of a number of transcription factors, including Elk-1, Sma-and Mad-related protein (SMAD), c-Jun, Sp1, and signal transducer and activator of transcription 3 (STAT3). [21][22][23][24][25] In addition, Ras/MEK/ERK activation can lead to increased expression of intermediate-early response genes, such as c-fos, egr-1, and junB. 26 Although the promoter of the PAI-1 gene contains an array of potential response elements for these transcription factors, 27-29 the contributions of these transcriptional elements to the effects of MEK1,2 on the PAI-1 promoter activity have not yet been elucidated.Given the importance of PAI-1 in vascular physiology and its possible contribution to vasculopathies, further understanding of how the MAP kinase pathways affect PAI-1 expression in vascular smooth muscle cells (VSMCs) is of considerable importance. In this study, we identified and characterized the MEK1,2 response element in the 5Ј flanking region of PAI-1 gene in VSMCs. These studies identified 2 adjacent cis-acting AP-1-like and Sp1-like sequences that functionally cooperate in MEK-induced PAI-1 promoter activation. These results establish a mechanistic link between the MEK/ERK pathway and the activation of the PAI-1 promoter. Materials and methods MaterialsDominant-negative AP-1 (A-Fos), and ...

Genes overexpressed in cerebral arteries following salt-induced hypertensive disease are regulated by angiotensin II, JunB, and CREB

“…The delayed stable induction of OPN and PAI-1 transcript by ANG II also agrees with previous findings that prolonged ERK leads to their induction (8,15). Persistent upregulation of junB in malignant hypertension may thus indicate a defect in the regulation of junB that contributes to remodeling and involves OPN and PAI-1 expression.…”

“…injury in Dahl S rats (18). In cultured VSMCs, ERK phosphorylation induced by mechanical injury leads to the overexpression of OPN protein, and ANG II induces PAI-1 expression in a ERK-dependent manner (8,31). Furthermore, OPN and PAI-1 were identified in a matricellular gene cluster as highly ANG II responsive (7).…”

Proteomic Patterns and Prediction of Glomerulosclerosis and Its Mechanisms

“…In contrast, knockdown of endogenous thymosin ␤4 prevented Ang II-induced PAI-1 expression. Previous data have shown that Ang induces PAI-1 upregulation via c-Fos/c-Jun binding to Sp1 and activated protein-1 sequences in the PAI-1 promoter (35). Of note, thymosin ␤4 enhances c-Fos/c-Jun DNA-binding activity to the activated protein 1 element (26).…”

Induction of plasminogen activator inhibitor I gene expression by intracellular calcium via hypoxia-inducible factor-1

“…45 Additionally, the participation of the ERK pathway in the A23187-dependent PAI-1 induction in this study is in line with a recent report on the Ang-II-mediated PAI-1 expression in VSMCs. 61 Although the latter study did not investigate the direct involvement of Ca 2ϩ in Ang-II-dependent PAI-1 expression, it was shown that the Ang-II-dependent PAI-1 promoter activation requires the coactivation of specific ␤-1 glycoprotein (SP-1) and AP-1. 61 Thus, it appears that, depending on the stimulus and the cell type downstream from ERK, different transcription factors may activate PAI-1 expression.…”