Background: Pulmonary artery vasoconstriction and vascular remodeling contribute to a sustained elevation of pulmonary vascular resistance and pressure in patients with pulmonary arterial hypertension (PH), an often fatal hemodynamic disease. The effect of docosahexaenoic acid monoacylglyceride (MAG-DHA) and the role of the 17 kDa protein kinase C-potentiated inhibitor protein (CPI-17) were determined on vasoconstriction and smooth muscle cell proliferation of human pulmonary arteries (HPA).
Methods: HPA were obtained from 16 patients undergoing lung resection for carcinoma. The mechanical tension and Ca(2+) sensitivity were measured on arterial rings treated with endothelin-1 (ET-1) in the absence or presence of MAG-DHA. The effect of MAG-DHA on the level of proliferation of smooth muscle cells isolated from HPA was evaluated in order to determine the role of CPI-17 protein.
Results: MAG-DHA treatment decreased the reactivity and Ca(2+) sensitivity induced by ET-1 in HPA. MAG-DHA treatment also decreased the expression of vascular endothelial growth factor (VEGF) induced by ET-1. Moreover, both VEGF inhibitor and MAG-DHA treatments reduced Ca(2+) hypersensitivity induced by ET-1, which was associated to a reduction in CPI-17 and myosin-binding subunit of the myosin light chain phosphatase (MYPT-1) phosphorylation levels. Proliferation of ET-1-stimulated HPA smooth muscle cells (PASMc) was also decreased following CPI-17 small interfering RNA transfection and MAG-DHA treatments. Western blot analyses revealed that MAG-DHA treatment resulted in decreased phosphorylation levels of CPI-17 and extracellular signal-regulated kinases (ERK) in PASMc treated with ET-1.
Conclusions: We have demonstrated that VEGF interacts with CPI-17 signaling pathway resulting in an increase in Ca(2+) sensitivity and proliferation of PASMc, whereas MAG-DHA treatment reversed these effects.