Altitude acclimatization via hypoxia-mediated oxidative eustress involves interplay of protein nitrosylation and carbonylation: A redoxomics perspective

Aim: Hypoxia is an important feature of multiple diseases like cancer and obesity and also an environmental stressor to high altitude travelers. Emerging research suggests the importance of redox signaling in physiological responses transforming the notion of oxidative stress into eustress and distress. However, the behavior of redox protein post-translational modifications (PTMs), and their correlation with stress acclimatization in humans remains sketchy. Scant information exists about modifications in redoxome during physiological exposure to environmental hypoxia. In this study, we investigated redox PTMs, nitrosylation and carbonylation, in context of extended environmental hypoxia exposure. Methods: The volunteers were confirmed to be free of any medical conditions and matched for age and weight. The human global redoxome and the affected networks were investigated using TMT-labeled quantitative proteo-bioinformatics and biochemical assays. The percolator PSM algorithm was used for peptide-spectrum match (PSM) validation in database searches. The FDR for peptide matches was set to 0.01. 1-way ANOVA and Tukey's Multiple Comparison test were used for biochemical assays. p-value<0.05 was considered statistically significant. Three independent experiments (biological replicates) were performed. Results were presented as Mean +/- standard error of mean (SEM). Key findings: This investigation revealed direct and indirect interplay between nitrosylation and carbonylation especially within coagulation and inflammation networks; interlinked redox signaling (via nitrosylation-carbonylation); and novel nitrosylation and carbonylation sites in individual proteins. Significance: This study elucidates the role of redox PTMs in hypoxia signaling favoring tolerance and survival. Also, we demonstrated direct and indirect interplay between nitrosylation and carbonylation is crucial to extended hypoxia tolerance.