Abstract
Background: Pulmonary artery hypertension is often associated with connective tissue disease and major determinant of prognosis. MRL/lpr mouse, which has hypergammaglobulinemia and products various autoimmuno antibody, develops vasculitis and nephritis spontaneously and is widely used as the model of lupus nephritis or Sjogren syndrome. In this study, we examined the right ventricular pressure overload, pathological features and the signaling molecules in the lung tissues of MRL/lpr mice. Methods: We used the female MRL/lpr mice at the age of 12 to 18 weeks. We measured right ventricular systolic pressure (RVSP) by a micro-manometer catheter and the ratio of right ventricular weight to left ventricular weight including ventricular septum (RV/LV). Lung sections were stained with α-smooth muscle actin, and the medial smooth muscle area was expressed as a percentage of the external area of the vessel. Levels of endothelial nitric oxide synthase (eNOS), survivin, endothelin-1 (ET-1), and activin receptor-like kinase-1 (ALK-1) were analyzed by Western blotting. Results: RVSP in the MRL/lpr mice was significantly higher (29.8 ± 7.2 vs. 19.2 ± 1.9 mmHg, P < 0.05) than that in WT C57/Bl6 mice. RV/LV was increased in the MRL/lpr mice compared to the WT C57/Bl6 mice (0.33 ± 0.58 vs. 0.20 ± 0.67, P < 0.05). The medial smooth muscle area of MRL/lpr mice were larger than that of WT C57/bl6 (56.3 ± 4.0 vs. 39.5 ± 6.1%, P < 0.05). Western blot analysis revealed the markedly elevated levels of ET-1 and survivin as well as decreased ALK-1 expression and eNOS phosphorylation in the lung tissue of MRL/lpr mice. Conclusion: We demonstrated that MRL/lpr mice were complicated with pulmonary hypertension. The possible mechanisms include the vasoconstriction enhanced by increased ET-1 level and impaired vasodilatation caused by decreased eNOS phosphorylation and ALK-1 expression. In addition, upregulation of survivin promoted the medial wall thickening of pulmonary vessels. MRL/lpr mice appeared to be a useful model in considering the mechanism of pulmonary hypertension associated with connective tissue diseases.
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