RhoA/Rho-kinase signaling: a therapeutic target in pulmonary hypertension

Abstract

Pulmonary arterial hypertension (PAH) is a devastating disease characterized by progressive elevation of pulmonary arterial pressure and vascular resistance due to pulmonary vasoconstriction and vessel remodeling as well as inflammation. Rho-kinases (ROCKs) are one of the best-described effectors of the small G-protein RhoA, and ROCKs are involved in a variety of cellular functions including muscle cell contraction, proliferation and vascular inflammation through inhibition of myosin light chain phosphatase and activation of downstream mediators. A plethora of evidence in animal models suggests that heightened RhoA/ROCK signaling is important in the pathogenesis of pulmonary hypertension by causing enhanced constriction and remodeling of the pulmonary vasculature. Both animal and clinical studies suggest that ROCK inhibitors are effective for treatment of severe PAH with minimal risk, which supports the premise that ROCKs are important therapeutic targets in pulmonary hypertension and that ROCK inhibitors are a promising new class of drugs for this devastating disease.

Keywords: Rho-kinase; fasudil; pulmonary arterial hypertension; vasoconstriction.

Figure 1

Mechanisms through which current drugs elicit pulmonary vasodilatation to treat pulmonary hypertension. Abbreviations: ET-1, endothelin-1; CCBs, calcium channel blockers; PGI₂, prostacyclin; NO, nitric oxide; CaM, calmodulin; SR, sarcoplasmic reticulum; AC, adenylate cyclase; MLCK, myosin light chain kinase; MLCPh, myosin light chain phosphatase, PDE5, phosphodiesterase 5; PLC, phospholipase C; sGC, soluble guanylate cyclase.

Figure 2

Schematic illustration of possible Rho-kinase mediated pathophysiological mechanisms that may contribute to the development of pulmonary hypertension. Abbreviation: VSMC, vascular smooth muscle cells.