Y-Chromosome Gene, Uty, Confers Male Protection Against Pulmonary Hypertension By Mediating Pro-Inflammatory Chemokine Effects

Background: Idiopathic pulmonary arterial hypertension (PAH) is a terminal vascular lung disease characterized by increased PA pressure resulting in right ventricular (RV) failure and death. For reasons largely unknown, PAH is up to 4x more prevalent in females. We published that the Y-Chromosome (Chrm) is protective against hypoxia (Hx)-induced pulmonary hypertension (PH) in mice and identified four Y-Chrm genes expressed in the lung. Here, we identify the protective Y-Chrm gene, investigate its mechanism and demonstrate a novel therapeutic approach. Methods and Results: To test the effect of Y-Chrm candidate genes on PH development, we knocked down (KD) each Y-Chrm gene via sequential intratracheal instillation of siRNA in the lungs of male mice exposed to Hx. KD of Y-Chrm gene Uty, but none of the other genes, resulted in more severe PH measured by increased RV systolic pressure (RVSP) and decreased pulmonary arterial acceleration time (PAAT) compared to control (n=4/group; RVSP: Uty-KD= 48.93mmHg, Control= 37.33mmHg, p=0.04; PAAT: Uty-KD= 11.88ms, Control= 14.43ms, p=0.01). RNAseq analysis (Uty-KD vs Control) revealed an increase in pro-inflammatory cytokines Cxcl9 (Log2FC: 1.3, p-adjusted=0.05) and Cxcl10 (Log2FC: 0.9, p-adjusted=0.002). We found Cxcl9/10 significantly upregulated in human PAH lungs vs healthy and female PAH lungs vs male (RT-qPCR). Fluorescent in-situ hybridization revealed Uty and Cxcl9/10 expression co-localized in CD68 + macrophages within the lung. Treatment of human pulmonary artery endothelial cells (PAEC) with Cxcl9/10 resulted in significantly increased apoptosis. We inhibited Cxcl9/10 activity in female rats 14 days post monocrotaline (MCT) injection by treating them with a small molecular inhibitor. Treated rats (n=6) had less severe PH than vehicle-treated controls (n=5) when measured 28-days post MCT (RVSP: Treated= 36.75mmHg, Vehicle=43.62 mmHg, p=0.03; PAAT: Treated= 26.7ms, Vehicle=20 ms, p=0.01; RV hypertrophy index (RV/(LV+IVS)): Treated= 0.48, Vehicle= 0.35, p=0.01). Conclusion: Y-Chrm gene, Uty, is protective against PH. Uty inhibition increases pro-inflammatory cytokines Cxcl9/10 which contribute to PAEC death. Inhibition of Cxcl9/10 activity may provide a novel therapy for the treatment of PH.