Red blood cell proteomic profiling in mild and severe obstructive sleep apnea patients before and after positive airway pressure treatment.

Obstructive Sleep Apnea (OSA) is characterized by recurrent-episodes of apneas/hypopneas during sleep, leading to recurrent intermittent-hypoxia and sleep fragmentation. Non-treated OSA can result in cardiometabolic diseases. In this study, we applied a shotgun-proteomics strategy to deeper investigate the red blood cell-(RBC) homeostasis regulation in the context of OSA-severity and their response to six months of positive airway pressure (PAP)-treatment. RBC-samples from patients with Mild/Severe-OSA before/after-PAP treatment and patients as simple-snoring controls were selected. The mass-spectrometry raw-data was analysed by MaxQuant for protein identification/quantification followed by statistical Linear Models-(LM) and Linear Mixed Models-(LMM) to investigate OSA-severity effect and interaction with PAP, respectively. The functional/biological network analysis were performed by DAVID-platform. The results indicated that key-enzymes of the Embden-Meyerhof-Parnas (EMP)-glycolysis and pentose phosphate pathway-(PPP) were differentially changed in Severe-OSA, suggesting that the O2-dependent metabolic flux through EMP and PPP maybe compromised in these cells due to severe intermittent hypoxia/reoxygenation-induced oxidative-stress events in these patients. The Rapoport-Luebering-glycolytic shunt showed a significant downregulation across OSA-severity maybe to increase hemoglobin-O2 affinity to adapt to O2 low availability in the lung, although EMP-glycolysis showed decreased only in Severe-OSA. Proteins of the immunoproteasome were upregulated in Severe-OSA maybe to respond to severe oxidative-stress. In Mild-OSA, proteins related to the ubiquitination/neddylation-(Ub/Ned)-dependent proteasome system were upregulated. After PAP, proteins of Glycolysis and Ub/Ned-dependent proteasome system showed reactivated in Severe-OSA. In Mild-OSA, PAP induced upregulation of immunoproteasome proteins, suggesting that this treatment may increase oxidative-stress in these patients. Once validated these proteins maybe candidate biomarkers for OSA or OSA-therapy response.