Senescence Marker Protein 30 Deficiency Exacerbates Pulmonary Hypertension in Hypoxia-Exposed Mice

Pulmonary arterial hypertension is a fatal disease caused by pulmonary arterial vasoconstriction and organic stenosis due to the proliferation of pulmonary smooth muscle cells and endothelial cells. Endothelial dysfunction, including impaired nitric oxide (NO) bioavailability, plays a crucial role in the pathogenesis of pulmonary hypertension, and endothelial nitric oxide synthase (eNOS) is an important modulator of pulmonary vasodilatation. Although senescence marker protein (SMP) 30 is known as an anti-aging protein, the role of SMP30 in pulmonary vessels is still unclear. In this study, we examined the role of SMP30 in pulmonary vasculature using SMP30-deficient mice.We used female SMP30-deficient mice and wild-type littermate (WT) mice at the age of 12 to 18 weeks. The WT and SMP30-deficient mice were exposed to normoxia or hypoxia (10% oxygen for 4 weeks). In normoxia, the right ventricular systolic pressure (RVSP) was not different between the WT and SMP30-deficient mice, but in hypoxia, the RVSP was significantly higher in the SMP30-deficient mice compared to the WT mice (P < 0.05). The hypoxia-induced increases in right ventricular hypertrophy and medial smooth muscle area of the pulmonary artery were comparable between the WT and the SMP30-deficient mice. Western blotting showed that eNOS phosphorylation in lung tissue was reduced in the SMP30-deficient mice compared to the WT mice in normoxia. However, in hypoxic conditions, eNOS phosphorylation was reduced in both the WT and SMP30-deficient mice with no differences in Akt phosphorylation.Our study demonstrated that SMP30 is involved in the development of hypoxia-induced pulmonary hypertension by impairment of eNOS activity.