Leukocyte Responses To Short-term Normobaric Hypoxia

Abstract

PURPOSE Severe hypoxia has been shown to exert immunosuppressive effects which must be considered when exposing athletes to hypoxia to enhance endurance capacity. We studied the effect of moderate normobaric hypoxia (HYP) on parameters of immune function and cellular protection in peripheral human leukocytes such as oxidative burst (burst), phagocytosis (phago), expression of heat shock proteins (HSP HO-1). The contribution of oxidative stress was tested by application of antioxidants (a-tocopherol and a-lipoic acid (AO)). METHODS Twelve non-altitude acclimated male subjects (27.1±7.0 yrs, 79.6±8 kg, 184±5 cm) were exposed to 4 h of HYP (FiO2 12.5%, corresponding to an altitude of 4100 m above SL). Blood samples were drawn before (0 h), during (2 h) at the end (+4h), 1 h (+5h), 4 h (+8h) and 20 h (+24h) after the end of HYP. To exclude diurnal changes same procedure was performed in normoxia. AO or placebo were given randomly in a double-blind crossover design. Phago (opsonized FITC-conjugated E. coli), burst (stimulation with opsonized E. coli) and expression of HSP and HO-1 (flow cytometry and RT-PCR, respectively) were quantified in leukocytes. RESULTS Oxygen saturation averaged 87.1±4.3% during HYP. Percentage of phagocytosing granulocytes was reduced after HYP (+5h). Burst was increased during the reoxygenation phase (+5–24h). Nevertheless, these changes remained within the reference range. Protein and mRNA expression of HSP and HO-1 were not significantly changed by HYP. AO did not influence this expression either. CONCLUSIONS Protective HSPs do not seem to be essential after moderate hypoxia as performed in the present study. Also, the cellular redox state appears to be of minor importance. Although phago and burst are slightly influenced by HYP, immune function is likely not impaired. Nevertheless, immunosuppressive effects of HYP may become relevant in context with additional physical stress.