Tipifarnib prevents development of hypoxia-induced pulmonary hypertension

Aims. RhoB plays a key role in the pathogenesis of hypoxia - induced pulmonary hypertension. Farne sylated RhoB promotes growth responses in cancer cells and we investigated whether inhibition of protein farnesylation will have a protective effect. Methods and Results. The analysis of l ung tissues from rodent models and pulmonary hypertensive patients showed increased levels of protein farnesylation. Oral farnesyltransferase inhibitor tipifarnib prevented development of hypoxia - induced pulmonary hypertension in mice. Tipifarnib reduced hypoxia - induced vascular cell proliferation, increased endothelium - dependent vasodilatation and reduced vasoconstriction of intrapulmonary arteries without affecting cell viability. Protective effects of tipifarnib were associated with inhibition of Ras and RhoB, actin depolymerisation and increased eNOS expression in vi tro and in vivo . Farnesylated - only RhoB (F - RhoB) increased proliferative responses in cultured pulmonary vascular cells, mimicking the effects of hypoxia, while both geranylgeranylated - only RhoB (GG - RhoB) and tipifarnib had an inhibitory effect. Label - fre e proteomics linked F - RhoB with cell survival, activation of cell cycle and mitochondrial biogenesis. Hypoxia increased and tipifarnib reduced the levels of F - RhoB - regulated proteins in the lung, reinforcing the importance of RhoB as a signalling mediator. Unlike simvastatin, tipifarnib did not increase the expression levels of Rho proteins. Conclusions. Our study demonstrates the importance of protein farnesylation in pulmonary vascular remodeling and provides a rationale for selective targeting of this pa thway in pulmonary hypertension

The role of neutrophil extracellular traps (NETs) in the pathogenesis of pulmonary hypertension (PH).

Rationale: Inflammation contributes to vasoconstriction and vascular remodelling in pulmonary hypertension (PH), but the mechanisms contributing to the disease are not fully understood. Recent data link neutrophil extracellular traps (NETs) and NET components with endothelial dysfunction, thrombosis, and lung injury. NETs, produced as a result of neutrophil cell death induced by inflammation or cytotoxic stress, comprise chromatin fibers associated with a number of proteins, including myeloperoxidase and neutrophil elastase. Hypothesis and Aims: I hypothesized that NETs may contribute to pulmonary vascular remodelling in PH. The aim of the present study was to measure the levels of NET markers in plasma of PH patients and to analyse the effects of NETs on human pulmonary artery endothelial cell (HPAEC) function in vitro. Methods and Results: Chronic thromboembolic pulmonary hypertension (CTEPH), patients and idiopathic pulmonary arterial hypertension (IPAH) patients showed increased plasma levels of NET components including myeloperoxidase, neutrophil elastase and circulating DNA, compared with healthy volunteers. Endarterectomy specimens from CTEPH patients and plexiform lesions in IPAH lungs showed accumulation of NET-forming peptidylarginine deiminase 4+ (PAD4) neutrophils and co-localization of NET markers, DNA, myeloperoxidase and citrullinated histone 3. Incubation of NETs with HPAECs in vitro activated transcription factor nuclear factor kappa B (NFκB), increased expression of pro-inflammatory and pro-angiogenic factors, compromised endothelial barrier function and induced endothelial angiogenesis. These effects depended on direct contact of NETs with the endothelial cell surface. NETs also increased Matrigel plug vascularization in mice, increased endothelin 1 (ET-1) release by endothelial cells and increased proliferation of pulmonary artery smooth muscle cells in vitro. Levels of ET-1 in plasma of CTEPH patients significantly correlated with the levels of NET markers in patient plasma. NETs-induced pro-angiogenic responses depended on myeloperoxidase/H2O2-induced activation of Toll-like receptor 4 (TLR4)/NFκB signalling. Conclusion: NETs- induced endothelial dysfunction is likely to play a contributory role in the pulmonary vascular remodelling in PH. Inhibition of NET components or NET formation in vivo may represent a new therapeutic approach in the treatment of PH.Open Acces