Hypoxic exercise training reduces senescent T-lymphocyte subsets in blood

The integration and control of systemic immune responses depends on the regulated trafficking of T-lymphocytes. This study elucidates how various exercises regimens with/without hypoxia affect phenotypic characteristics of T-lymphocyte subsets in blood. Fifty sedentary males were randomly divided into five groups. Each group (n = 10) received one of five interventions: normoxic (21%O2) resting (N-C), hypoxic (15%O2) resting (H-C), normoxic exercise (50%Wmax under 21%O2, N-T), hypoxic-relative exercise (50% maximal heart rate reserve under 15%O2, H-RT), or hypoxic-absolute exercise (50%Wmax under 15%O2, H-AT) for 30 min/day, 5 days/week for 4 weeks. Before the intervention, strenuous exercise up to exhaustion increased the mobilization of CD3, CD4, CD8, or CD8bright lymphocytes expressing activated (CD11a) or senescent (KLRG1) molecules into the peripheral blood compartment. The H-AT for 4 weeks up-regulated co-stimulatory molecule CD28 expression and was accompanied by depressed KLRG1 level on CD3, CD4, CD8, or CD8bright lymphocytes at rest or following exercise. Simultaneously, this intervention increased interferon-γ (IFN-γ) level and unchanged interleukin-4 level, as well as, decreased myeloperoxidase (MPO) and interleukin-6 levels in plasma. However, no significant changes in resting and exercise-induced mobilizations of various T-lymphocyte subsets and productions of cytokines and MPO occurred following the N-C, H-C, N-T, and H-RT interventions. Therefore, we conclude that 4-week H-AT intervention reduced senescent T-lymphocyte subsets with increasing IFN-γ level in blood, which responses are accompanied by depressed oxidative stress and pro-inflammatory cytokine production. These findings can help to determine an effective hypoxic exercise regimen to minimize immune dysfunction by retarding T-lymphocyte senescence.