Tsantan Sumtang Alleviates Chronic Hypoxia-Induced Pulmonary Hypertension by Inhibiting Proliferation of Pulmonary Vascular Cells

Hypoxia-induced pulmonary hypertension (HPH) is a severe condition associated with significant morbidity and mortality in people living at high altitude. Tsantan Sumtang, a traditional Tibetan medicine, has been routinely used for the treatment of cardiopyretic disease, as well as stenocardia. Interestingly, our previous research found that Tsantan Sumtang improved HPH in rats maintaining in a hypobaric chamber. We performed a series of experiments to test the indexes of vasoconstriction and vascular remodeling, the key pathophysiological characteristics of HPH. Our results showed that Tsantan Sumtang relaxed noradrenaline (NE)-precontracted rat pulmonary artery rings in a concentration-dependent manner in vitro. The PGI2-cAMP (prostaglandin I2-cyclic adenosine monophosphate) pathway, NO-cGMP (nitric oxide-cyclic guanosine monophosphate) pathway, and the opening of K(+) channels (inward rectifier K(+) channels, large conductance Ca(2+)-activated K(+) channels, and voltage-dependent K(+) channels) might play major roles in the vasorelaxation effect. In vivo, the administration of Tsantan Sumtang resulted in a substantial decrease in the rat mean pulmonary artery pressure (mPAP) and the right ventricular hypertrophy index (RVHI). The reduction of thickness of small pulmonary arterial wall and the WT% (the ratio of the vascular wall thickness to the vascular diameter) were observed. The smooth muscle muscularization of the arterials was alleviated by Tsantan Sumtang treatment at the same time. Tsantan Sumtang also reduced remodeling of pulmonary arterioles by suppressing the expression of proliferating cell nuclear antigen (PCNA), α-smooth muscle actin (α-SMA), cyclin D1, and cyclin-dependent kinase 4 (CDK4) through inhibition of p27Kip1 degradation. Therefore, Tsantan Sumtang could be applied as a preventative medication for HPH, which would be a new use for this traditional medicine.