Acclimatization to oxidative stress at high altitude

Hypoxia-mediated oxidative stress has been implicated in the pathophysiology of high altitude maladaptations. To explore whether prolonged exposure to high altitude can trigger an adaptive response to oxidative stress and restore redox homeostasis in the body, the study was conducted to evaluate biochemical variables related to oxidative stress and antioxidant status in humans at sea level (190 m) and following 3- and 13- month sojourns at altitude (4,500 m). After 3 months at altitude, whole-blood thiobarbituric acid reactive substances (TBARS) were significantly higher (65.6%), nonenzymatic antioxidants like ascorbic acid and caeruloplasmin were significantly lower (41% and 22%, respectively) and plasma total antioxidant status (TAS), glutathione levels, and superoxide dismutase activity were marginally altered as compared to their basal values. After 13 months at altitude, TBARS levels regressed back to preexposure levels. Plasma total antioxidant status (TAS) improved by 21%, glutathione levels by 32.8%, and plasma bilirubin by 35.8% as compared to sea level. Average concentrations of ascorbic acid and caeruloplasmin were 18% and 37% higher as compared to the subjects studied after a 3-month stay at high altitude. In addition, there was a progressive rise in erythrocytic superoxide dismutase activity and persistent hyperurecemia. The study observed that on prolonged exposure to high altitude humans could mount an effective adaptive response to oxidative stress by activating the antioxidant defense. Hence, strengthening the antioxidant defense could be an effective strategy to prevent free-radical-mediated pathophysiological alterations and quicken acclimatization to oxidative stress.