Inhibition of HIF/Ob/ObR-b axis reverses experimental pulmonary hypertension

Abstract

Introduction Excessive pulmonary smooth muscle cell (P-SMC) proliferation and perivascular infiltration lead to irreversible remodeling in pulmonary arterial hypertension (PAH), contributing to the disease severity. However, these mechanisms are not specifically targeted by the current PAH therapies. Since leptin (Ob), a HIF-dependent gene, and its receptor ObR-b contribute to systemic vascular remodeling, we questioned whether targeting HIF/Ob/ObR-b axis would be an effective anti-proliferative and anti-inflammatory strategy against PAH. Methods We used control and PAH human lung tissues and human primary cultures (early passages ≤ 5) of pulmonary endothelial cells (P-ECs) and P-SMCs. Experimental pulmonary hypertension (PH) was induced in rodents by exposing them to chronic hypoxia (3 weeks, FiO 2 = 10%). We used respectively ObR-deficient rats ( ObR -/− ) and their wild type littermates, an inductive treatment with recombinant Ob (3 μg/g by daily IP injections) and 2 different curative strategies, a soluble Ob neutralizer (ObR: Fc, 100 μg/day by IP injections) and an indirect HIF/Ob inhibitor, dichloroacetate (DCA, 1 g/L in drinking water). Results By using control and human lung tissues and human primary cultures, we demonstrate that in idiopathic PAH: – P-ECs overproduce Ob, in a HIF-dependent manner, and P-SMCs overexpress ObR-b, as compared to controls; – P-SMCs proliferate more in response to exogenous Ob than controls; – increased P-EC-derived Ob leads to an excessive P-SMC proliferation; – Ob drives perivascular inflammation by activating monocytes and macrophages and by inducing cell adhesion molecule expression in P-ECs. Consistently, we show that Ob administration can worsen PH severity in mice. We also demonstrate that Ob/ObR-b axis contributes to PH susceptibility, using ObR -/− rats, which displayed less severe hypoxia-induced PH, as assessed by pulmonary hemodynamics, arterial muscularization, P-SMC proliferation and perivascular inflammation. Importantly, we demonstrate the efficacy of 2 curative strategies targeting Ob/ObR-b axis in experimental PH: ObR:Fc and DCA. Conclusion We demonstrate here, for the first time, that targeting HIF/Ob/ObR-b axis represents an important therapeutical tool to develop anti-proliferative and anti-inflammatory strategies in experimental PH development and progression.