Statin ameliorates hypoxia-induced pulmonary hypertension associated with down-regulated stromal cell-derived factor-1

Mobilization of stem cells/progenitors is regulated by the interaction between stromal cell-derived factor-1 (SDF-1) and its ligand, CXC chemokine receptor 4 (CXCR4). Statins have been suggested to ameliorate pulmonary arterial hypertension (PAH); however, the mechanisms involved, especially their effects on progenitors, are largely unknown. Therefore, we examined whether pravastatin ameliorates hypoxia-induced PAH in mice, and if so, which type of progenitors and what mechanism(s) are involved. Chronic hypoxia (10% O-2 for 5 weeks) increased the plasma levels of SDF-1 and mobilization of CXCR4(+)/vascular endothelial growth factor receptor (VEGFR)2(+)/c-kit(+) cells from bone marrow (BM) to pulmonary artery adventitia in Balb/c mice in vivo, both of which were significantly suppressed by simultaneous oral treatment with pravastatin (2 mg/kg/day). Furthermore, in vitro experiments demonstrated that hypoxia enhances differentiation of VEGFR2(+)/c-kit(+) cells into alpha-smooth muscle actin(+) cells. Importantly, pravastatin ameliorated hypoxia-induced PAH associated with a decrease in the number of BM-derived progenitors accumulating in the pulmonary artery adventitia. The expression of intercellular adhesion molecule-1 (ICAM-1) and its ligand, CD18 (beta 2-integrin), were enhanced by hypoxia and were again suppressed by pravastatin. These results suggest that pravastatin ameliorates hypoxia-induced PAH through suppression of SDF-1/CXCR4 and ICAM-1/CD18 pathways with a resultant reduction in the mobilization and homing of BM-derived progenitor cells.