TGF-beta signaling in vascular fibrosis

Transforming growth factor-beta (TGF-beta) participates in the pathogenesis of multiple cardiovascular diseases, including hypertension, restenosis, atherosclerosis, cardiac hypertrophy and heart failure. TGF-beta exerts pleiotropic effects on cardiovascular cells, regulating cell growth, fibrosis and inflammation. TGF-beta has long been believed to be the most important extracellular matrix regulator. We review the complex mechanisms involved in TGF-beta-mediated vascular fibrosis that includes the Smad signaling pathway, activation of protein kinases and crosstalk between these pathways. TGF-beta blockade diminishes fibrosis in experimental models, however better antifibrotic targets are needed for an effective therapy in human fibrotic diseases. A good candidate is connective tissue growth factor (CTGF), a downstream mediator of TGF-beta-induced fibrosis. Among the different factors involved in vascular fibrosis, Angiotensin II (AngII) has special interest. AngII can activate the Smad pathway independent of TGF-beta and shares with TGF-beta many intracellular signals implicated in fibrosis. Blockers of AngII have demonstrated beneficial effects on many cardiovascular diseases and are now one of the best options to block TGF-beta fibrotic responses. A better knowledge of the intracellular signals of TGF-beta can provide novel therapeutic approaches for fibrotic diseases.