Abstract 230: Protein Farnesylation Inhibitor Tipifarnib Prevents Development of Chronic Hypoxia-induced Pulmonary Hypertension

Abstract

Study objectives: Small GTPase RhoB contributes to pulmonary vascular remodelling in pulmonary hypertension. Farnesylation of RhoB augments cell proliferation while geranylgeranylation of RhoB is believed to be pro-apoptotic. We hypothesized that farnesyltransferase inhibitors may prevent vascular pathology in pulmonary hypertension. We studied the effects of farnesyltransferase inhibitor Tipifarnib on pulmonary vascular remodelling and vasoreactivity in chronically hypoxic pulmonary hypertensive mice and cultured human pulmonary artery endothelial cells (HPAECs). Chemical proteomics was used to characterise Tipifarnib-induced changes in protein prenylation while label- free quantitative proteomics was used to characterise changes induced by overexpression of RhoB prenylation mutants: farnesylated-only or geranlygeranylated-only RhoB in HPAECs. The effects of Tipifarnib on Ras and Rho GTPases expression and activity, filamentous and globular actin levels and eNOS pathway, were also studied. Results: Oral administration of Tipifarnib significantly attenuated chronic hypoxia-induced pulmonary hypertension in mice. This protective effect was associated with a marked improvement of endothelium-dependent vasodilatation, reduction in pulmonary vascular muscularization and a decrease in the right ventricular systolic pressure. Tipifarnib reduced farnesylation and increased geranyl-geranylation of several proteins, including Rho GTPases and Ras and reduced their activity in vitro and in vivo. Tipifarnib-induced changes in cultured cells were associated with a decrease in cell proliferation, decreased polymerization of actin and increased eNOS mRNA and protein levels. Proteomic analysis of HPAECs overexpressing prenylation mutants of RhoB suggests that protective effects of Tipifarnib may result, at least in part, from inhibition of RhoB farnesylation. Conclusions: We demonstrate protective effects of farnesyltransferase inhibitor Tipifarnib in chronic hypoxia-induced pulmonary hypertension. The effects of Tipifarnib may result from inhibition of small GTPases activity and increase in NO signalling.