Abstract: Objective To explore the therapeutic mechanism of tanshinone IIA in the treatment of pulmonary arterial hypertension (PAH) in rats. Methods A total of 100 male SD rats were randomized into 5 groups (n=20), and except for those in the control group with saline injection, all the rats were injected with monocrotaline (MCT) on the back of the neck to establish models of pulmonary hypertension. Two weeks after the injection, the rat models received intraperitoneal injections of tanshinone IIA (10 mg/kg), phosphatidylinositol 3 kinase (PI3K) inhibitor (1 mg/kg), both tanshinone IIA and PI3K inhibitor, or saline (model group) on a daily basis. After 2 weeks of treatment, HE staining and α-SMA immunofluorescence staining were used to evaluate the morphology of the pulmonary vessels of the rats. The phosphorylation levels of PI3K, protein kinase B (PKB/Akt) and endothelial nitric oxide synthase (eNOS) in the lung tissue were determined with Western blotting; the levels ofeNOS and NO were measured using enzyme-linked immunosorbent assay (ELISA). Results The results of HE staining and α-SMA immunofluorescence staining showed that tanshinone IIA effectively inhibited MCT-induced pulmonary artery intima-media thickening and muscularization of the pulmonary arterioles (P<0.01). The results of Western blotting showed that treatment with tanshinone IIA significantly increased the phosphorylation levels of PI3K, Akt and eNOS proteins in the lung tissue of PAH rats; ELISA results showed that the levels of eNOS and NO were significantly decreased in the rat models after tanshinone IIA treatment (P<0.01). Conclusion Treatment with tanshinone IIA can improve MCT-induced pulmonary hypertension in rats through the PI3K/Akt-eNOS signaling pathway.

Key words: pulmonary hypertension; PI3K/Akt-eNOS; tanshinone IIA; monocrotaline; signaling pathway