Abstract Background Pulmonary arterial hypertension (PAH) is a sex-biased disease characterized by pulmonary artery remodeling, increase resistance, hypoxemia, and right ventricle failure. Pulmonary hemodynamics and long-term prognosis of patients with PAH are adversely affected by common comorbidities such as obstructive sleep apnea. However, the impact of intermittent hypoxia (IHx), the hallmark of obstructive sleep apnea, on endothelial dysfunction, hyperproliferation and apoptosis-resistance, remains poorly understood. Thus, we sought to investigate the contribution of IHx to the severity of pulmonary artery endothelial cells phenotype in PAH. Methods Pulmonary artery endothelial cells of pulmonary arterial hypertension patients (ECPAH), both sexes, isolated from the lung explants of patients with PAH were subjected to IHx for 7 consecutive days in Biospherix chambers. IHx paradigm consisted of exposing the cells 8 continuous hours to 30 cycles/h of IHx (1 minute of 3% O2 followed by 1 minute of 7% O2) and 16h of 7% O2. We selected 7% O2 because it corresponds to the level of oxygen at the pulmonary artery circulation. Molecular, cell biology approaches and bioinformatics (RNASeq, ChIP, quantitative RT-PCR, site-directed mutagenesis, siRNA, DNA methylation analysis, Western blotting, EdU cell proliferation and Tunel cell death) were used to analyze the effects of IHx on ECPAH phenotype. Results The studies indicate that IHx exerts sex-specific effects on the ECPAH phenotype compared to the normoxic one. Specifically, the expression of the long-noncoding RNA XIST and of X-linked epigenetic regulator O-linked N-acetyl-glucosamine transferase (OGT), and its pair enzyme glycoside hydrolase O-GlcNAcase (OGA) were altered. As result, an abnormal OGT/OGA cycling led to sex-specific increase of global O-glycosylation of endothelial proteins, including the JunD transcription factor. O-glycosylation of JunD at Ser27 and Thr117, two amino acid residues well-conserved in mammals, and the only ones that can be not only phosphorylated but also O-glycosylated, became transcriptionally impaired causing downregulation of pro-survival/anti-apoptotic proteins Bcl2, IAP1/2, and XIAP and decreased apoptosis-resistance of ECPAH. Moreover, the suppressor of cytokine signaling 1 (Socs1), a negative regulator of immune responses, was significantly downregulated via either the transcriptional inactivation of JunD, a Socs1 regulator, or via epigenetic methylation of the Socs1 promoter involving XIST signaling network. Conclusions Our studies demonstrate that on a PAH background, IHx modulates in a sex-specific manner the transcriptional profile of endothelial cells via XIST signaling network and the dynamic interplay O-glycosylation/phosphorylation of JunD transcription factor and suggest potential therapeutic strategies to overcome apoptosis-resistance of ECPAH and mitigate ECPAH dysfunction and inflammation. This abstract is funded by: RO1HL127022
Qin et al. (2026) studied this question.