Endothelin-1, via ET A Receptor and Independently of Transforming Growth Factor-β, Increases the Connective Tissue Growth Factor in Vascular Smooth Muscle Cells

Endothelin (ET)-1 is a potent vasoconstrictor that participates in cardiovascular diseases. Connective tissue growth factor (CTGF) is a novel fibrotic mediator that is overexpressed in human atherosclerotic lesions, myocardial infarction, and experimental models of hypertension. In vascular smooth muscle cells (VSMCs), CTGF regulates cell proliferation/apoptosis, migration, and extracellular matrix (ECM) accumulation. Our aim was to investigate whether ET-1 could regulate CTGF and to investigate the potential role of ET-1 in vascular fibrosis. In growth-arrested rat VSMCs, ET-1 upregulated CTGF mRNA expression, promoter activity, and protein production. The blockade of CTGF by a CTGF antisense oligonucleotide decreased FN and type I collagen expression in ET-1–treated cells, showing that CTGF participates in ET-1–induced ECM accumulation. The ET A , but not ET B , antagonist diminished ET-1–induced CTGF expression gene and production. Several intracellular signals elicited by ET-1, via ET A receptors, are involved in CTGF synthesis, including activation of RhoA/Rho-kinase and mitogen-activated protein kinase and production of reactive oxygen species. CTGF is a mediator of TGF-β– and angiotensin (Ang) II–induced fibrosis. In VSMCs, ET-1 did not upregulate TGF-β gene or protein. The presence of neutralizing transforming growth factor (TGF)-β antibody did not modify ET-1–induced CTGF production, showing a TGF-β–independent regulation. We have also found an interrelationship between Ang II and ET-1 because the ET A antagonist diminished CTGF upregulation caused by Ang II. Collectively, our results show that, in cultured VSMCs, ET-1, independently of TGF-β and through the activation of several intracellular signals via ET A receptors, regulates CTGF. This novel finding suggests that CTGF could be a mediator of the profibrotic effects of ET-1 in vascular diseases.