Abstract P083: Gender Specific Effects in Nox4-/- Mice in Hypoxia Induced Pulmonary Hypertension and Pulmonary Vascular Resistance

Abstract

Oxidative stress and Noxs have been implicated in the pathogenesis of experimental and human pulmonary arterial hypertension (PH). Gender differences in PH may be, in part, due to increased formation of NADPH oxidase (Nox) derived reactive oxygen species (ROS). A large body of evidence implicates E2 in the pathogenesis of PAH and an interaction between E2 and Noxs has been suggested. We hypothesised that i) Estrogen (E2) leads to Nox-induced oxidative stress, which promotes PASMC damage, ii) E2-induced Nox activation may account for gender differences in PH. Cultured human PASMC were stimulated with E2 (1nM). ROS production was assessed by chemiluminescence (O2-) and proliferation by BrdU assay. E2 increased superoxide (219%; p<0.05) and proliferation in PASMC, effects blocked by GKT137831 (Nox4/1 inhibitor). In vivo studies were conducted to assess the role of Nox4 in hypoxia-induced pulmonary hypertension in male and female mice. Hypobaric hypoxia was used to induce PH in mice, which were divided into 8 groups: normoxic WT (NWT), hypoxic WT (HWT), normoxic Nox4-/- (NKO) and hypoxic Nox4-/- (HKO) for both male and female mice. In male HWT mice, RVSP (20.5 NWT vs. 45.2mmHg HWT, p<0.001) and RVH by Fulton Index (0.20 NWT vs. 0.395 HWT, p<0.01) were increased, an effect that was significantly reduced in male Nox4-/- mice (RVSP: 36.4mmHg HKO; RVH: 0.030 HKO; p<0.05). In female HWT mice, RVSP (21.4 NWT vs. 39.8mmHg HWT, p<0.05) and RVH (0.20 NWT vs. 0.31 HWT, p<0.01) were elevated in hypoxia, yet female Nox4-/- mice were not protected against hypoxia-induced PAH (RVSP: 34.2mmHg HKO; RVH: 0.33 HKO). Hypoxia-induced endothelial dysfunction in both male and female WT pulmonary arteries was improved in male HKO, however, endothelial dysfunction remained in HKO females. In female Nox4-/- mice, increased spleen and uterine weight (which has been associated with altered ovarian hormone biogenesis) suggests a role for inflammatory and fibrotic processes. In conclusion, genetic ablation of Nox4 in males, but not females, protects against the development of hypoxic PH. The effects of E2 on oxidative stress is present in PASMCs where Nox4-derived ROS may be an important regulator of, and impact on, molecular processes contributing to vascular remodelling in PAH.