Pulmonary arterial hypertension (PAH) is a chronic and progressive disease characterized by a persistent elevation of pulmonary artery pressure accompanied by right ventricular hypertrophy (RVH). The current treatment for pulmonary hypertension is limited and only provides symptomatic relief due to unknown etiology and pathogenesis of the disease. Both vasoconstriction and structural remodeling (enhanced proliferation of VSMC) of the pulmonary arteries contribute to the progressive course of PAH, irrespective of different underlying causes. The exact molecular mechanism of PAH, however, is not fully understood. The purpose of this review is to provide recent advances in the mechanistic investigation of PAH. Specifically, this review focuses on nitric oxide (NO), oxidative stress and inflammation and how these factors contribute to the development and progression of PAH. This review also discusses recent and potential therapeutic advancements for the treatment of PAH.

Pulmonary arterial hypertension (PAH) is characterized by a persistent elevation of pulmonary arterial pressure and pulmonary arterial remodeling with unknown etiology. Current therapeutics available for PAH are primarily directed at reducing the pulmonary blood pressure through their effects on the endothelium. It is well accepted that pulmonary arterial remodeling is primarily due to excessive pulmonary arterial smooth muscle cell (PASMC) proliferation that leads to narrowing or occlusion of the pulmonary vessels. Future effective therapeutics will be successful in reversing the vascular remodeling in the pulmonary arteries and arterioles. The purpose of this review is to provide updated information on molecular mechanisms involved in pulmonary arterial remodeling with a focus on growth factors, transcription factors, and epigenetic pathways in PASMC proliferation. In addition, this review will highlight novel therapeutic strategies for potentially reversing PASMC proliferation.

Abstract-The purpose of this study was to determine the role of the proinflammatory cytokine interleukin (IL) 6 in cold-induced hypertension. Four groups of male Sprague-Dawley rats were used (6 rats per group). After blood pressure was stabilized, 3 groups received intravenous delivery of adenoassociated virus carrying IL-6 small hairpin RNA (shRNA), adenoassociated virus carrying scrambled shRNA, and PBS, respectively, before exposure to a cold environment (5°C). The last group received PBS and was kept at room temperature (25°C, warm) as a control. Adenoassociated virus delivery of IL-6 shRNA significantly attenuated cold-induced elevation of systolic blood pressure and kept it at the control level for Յ7 weeks (length of the study). Chronic exposure to cold upregulated IL-6 expression in aorta, heart, and kidneys and increased macrophage and T-cell infiltration in kidneys, suggesting that cold exposure increases inflammation. IL-6 shRNA delivery abolished the cold-induced upregulation of IL-6, indicating effective silence of IL-6. Interestingly, RNA interference knockdown of IL-6 prevented cold-induced inflammation, as evidenced by a complete inhibition of tumor necrosis factor-␣ expression and leukocyte infiltration by IL-6 shRNA. RNA interference knockdown of IL-6 significantly decreased the cold-induced increase in vascular superoxide production. It is noted that IL-6 shRNA abolished the cold-induced increase in collagen deposition in the heart, suggesting that inflammation is involved in cold-induced cardiac remodeling. Cold exposure caused glomerular collapses, which could be prevented by knockdown of IL-6, suggesting an important role of inflammation in cold-induced renal damage. In conclusion, cold exposure increased IL-6 expression and inflammation, which play critical roles in the pathogenesis of cold-induced hypertension and cardiac and renal damage. (Hypertension. 2010;55:1484-1491.)