Systemic hypoxia appears to attenuate autophagy in human peripheral blood mononuclear cells during repeated sprint exercises

This research investigated the modulation of autophagy and protein synthesis markers in human peripheral blood mononuclear cells (PBMCs) of moderately trained men following repeated sprint exercises (RSE) performed under hypoxia (HYP, 13% FIO₂), with bilateral blood flow restriction (BFR, 45% of resting arterial occlusive pressure), or normoxia. Using a crossover design, participants completed three sets of five 10-s sprints under each condition. mRNA and protein levels were assessed using qPCR and Western immunoblotting. Exercise significantly increased the microtubule-associated light chain 3B (LC3B)-II/I ratio (p < 0.001, dz = 0.58), with the effect being more pronounced in NOR (p = 0.011, dz = 0.81). Conversely, p62 protein levels were unchanged (p > 0.05). However, a tendency towards a reduced LC3B-II/I ratio was observed in HYP (p = 0.056, dz = 0.34) but not in BFR. No significant effects of exercise or conditions were found for mRNA expression of Atg4B, Beclin, and HIF1-α. Exercise increased the phosphorylation of rpS6 (p < 0.001, dz = 0.96), while the phosphorylation of p70S6K and 4E-BP1 remained unchanged (p > 0.05). These findings demonstrate, for the first time, that a 5 × 10-s RSE protocol induces the early stages of autophagy in PBMCs, whereas hypoxia tended to attenuate this effect. However, the effects on protein synthesis markers were heterogeneous, without influence of HYP and BFR.