Y‐Chromosome Gene, Uty, Protects Against Pulmonary Hypertension by Reducing Lung Pro‐Inflammatory Cytokines

RATIONALE Idiopathic pulmonary arterial hypertension (PAH) is a terminal vascular lung disease up to 4x more common 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 Uty as the protective Y‐Chrm gene and investigate its mechanism of protection against PH to illuminate novel therapeutic targets. METHODS AND RESULTS To test the effect of Y‐Chrm candidate genes on PH development, each of the four candidate YChrm genes were independently knocked‐down in the lungs of male mice exposed to Hxinduced PH via sequential intratracheal instillation of siRNA. Knockdown of Y‐Chrm gene Uty, but none of the other genes, resulted in more severe PH measured by increased right ventricular systolic pressure (RVSP) and decreased pulmonary arterial acceleration time (PAAT) when compared to experimental controls (n=4/group; RVSP: Uty‐KD= 48.93 mmHg, Control= 37.33 mmHg, p=0.04; PAAT: Uty‐KD= 11.88 ms, Control= 14.43 ms, p= 0.01). Pathway enrichment analysis of RNAseq data (Uty‐Knockdown vs Control) revealed an induction of proinflammatory cytokines including Cxcl9 (Log2FC: 1.3, p‐adjusted= 0.05) and Cxcl10 (Log2FC: 0.9, p‐adjusted=0.002). We found Cxcl9 and Cxcl10 were also significantly up‐regulated in human PAH lungs vs healthy (RT‐qPCR) and female PAH lungs vs male (GSE15197). Fluorescent in‐situ hybridization revealed Uty expression co‐localized with CD68+ macrophages, Cxcl9 and Cxcl10 in the lung. Upon stimulation, macrophages derived from bone marrow of male Uty‐knockout mice displayed increased expression of Cxcl9 and Cxcl10 compared to wildtype mice. Human pulmonary artery endothelial cells treated with Cxcl9 and Cxcl10 in‐vitro exhibited significantly increased cell death compared to those treated with vehicle. CONCLUSION Y‐Chrm gene, Uty, is protective against PH development and may explain Y‐Chrm protection in PH. Since Uty inhibition (both in‐vitro and in‐vivo) results in an increase in pro‐inflammatory cytokines, we hypothesize that a reduction or absence of Uty in the lungs of PAH patients or females results in an increase in lung pro‐inflammatory cytokines which contributes to vascular endothelial dysfunction and more severe PH. Support or Funding Information American Heart Association grant 17PRE33420159 (C.M.C.), Iris Cantor‐UCLA Women’s Health Center Executive Advisory Board NCATS UCLA CTSI Grant Number UL1TR001881 (C.M.C.), and NIH grants R01HL129051 (M.E.), R01HL131182 (M.E. and A.P.A.).