NOX2-Driven Oxidative Stress and Endothelial Dysfunction in Male Elite Adolescent Soccer Players

Background: Intense physical exercise induces oxidative stress and inflammation in adult professional athletes, but data on adolescent elite athletes remain limited. Methods: Twentyfour elite adolescent soccer players were recruited and evaluated three times: pre-season baseline (T0), after one month of pre-season training (T1), and at the end of the first half of the competitive season (T2, approximately 4 months after T0). Saliva samples were collected as non-invasive surrogate indicators reflecting oxidative stress- and endothelialrelated signaling. In vitro studies were performed on endothelial cells exposed to H2O2 concentrations observed in athletes. Results: Athletes showed a significant increase in salivary oxidative stress markers (NOX2 levels and H2O2) at T1 and T2 versus T0. Endothelial impairment was evidenced by reduced salivary NOx concentration and elevated endothelin (ET-1) levels. In vitro, endothelial cells exposed to H2O2 (8 μM) showed increased sNOX2-dp and ET-1 levels, reduced eNOS phosphorylation, and impaired tube formation (mesh number and area) compared with untreated cells. NOX2ds-tat treatment reduced cell damage and restored angiogenic capacity. Conclusions: Our findings indicate that adolescent elite athletes experience significant salivary oxidative stress- and endothelialrelated alterations, potentially reflecting cardiovascular stress. These results underscore the importance of cardiovascular monitoring and the potential benefits of antioxidant strategies, even in young athletes participating in high-intensity sports.