Author(s): GARCÍA GONZÁLEZ, E., GARCIA-PEREZ, G.1, DE NIGRIS, E.1, GALVAN ALVAREZ, V.1,3, MARTINEZ-CANTON, M.1, ALMEIDA-RAMOS, F.1, MORALES-ALAMO, D.1, SANTANA, A.1,4, MARTIN-RINCON, M.1, GALLEGO-SELLES, A.1, CALBET, J.A.L.1,2, Institution: PHYSICAL EDUCATION DEPARTMENT, Country: SPAIN, Abstract-ID: 2645

INTRODUCTION:
Angiotensin-Converting Enzyme 2 (ACE2) drives the protective ACE2/Ang-(1-7)/MasR axis, balancing tissue homeostasis against RAS-mediated stress. Simultaneously, ACE2 acts as a critical molecular gateway for viral entry, yet the mechanisms governing its acute regulation in skeletal muscle remain undefined. We hypothesised that exercise upregulates this gateway via redox-sensitive signalling mediated by NADPH oxidase 2 (NOX2) and Xanthine Oxidase (XO). To test this, we utilised post-exercise ischaemia (Isch) to amplify metabolic stress and polyphenol blockade to demonstrate causality.
METHODS:
Thirty-six men participated in two independent experiments involving incremental cycling to exhaustion (Exh) immediately followed by unilateral Isch (300 mmHg). Study I (n=11; crossover) examined severe hypoxia (PIO2:73mmHg) vs. normoxia. Study II (n=25; parallel design) investigated mechanistic blockade using Zynamite®-PX (140mg mangiferin/quercetin) vs Placebo administered every 8h for 48h prior to exercise. Vastus lateralis biopsies were collected at Rest (Pre), Exh (unilateral), and 60s post-exercise (Isch vs. perfused leg (Perf); Study I). Western blotting assessed RAS (ACE2/ACE1/AT1R/AT2R), TMPRSS2 and redox markers (NOX2/XO). Stats: RM/Mixed ANOVA, t-tests and Linear Mixed Models (LMM).
RESULTS:
Exh triggered a rapid upregulation of ACE2 (2.8-fold; p=0.01) and TMPRSS2 (1.6-fold; p<0.001) concurrent with NOX2 activation (p-p47phox: 2.9-fold; p=0.003) and XO increase (3.9-fold). Classical RAS components (ACE1, AT1R) remained unaltered, while AT2R decreased (-13%; p=0.03). In Study I, Isch maintained elevated ACE2/TMPRSS2 and increased further XO/NOX2, whereas Perf allowed rapid recovery (ACE2: -67% vs Isch; p=0.01). Crucially (Study II), Zynamite®-PX blunted the Exh-induced NOX2/XO response and abolished ACE2 upregulation (Time×Treat: p=0.02). ACE2 abundance strongly correlated with TMPRSS2 (R²c=0.71) and NOX2 activation (R²c=0.96) in mixed models.
CONCLUSION:
These novel data demonstrate, for the first time in humans, that the viral entry protein ACE2 is dynamically regulated by acute exercise via a redox-sensitive mechanism (NOX2/XO). The finding that polyphenol blockade abolishes this response identifies cellular redox state as a primary "switch" for ACE2 expression. Consequently, while exercise promotes metabolic health, the acute oxidative stress of exhaustive effort may transiently open molecular windows for viral susceptibility, a process modifiable via specific antioxidant strategies.

PID2021-125354OB-C21/AEI/10.13039/501100011033/FEDER, EU; CSD (EXP_75097); (SD-24/03, ID 877) CUCIC. AGS: Catalina Ruiz postdoctoral (CUCIC-GOBCAN and ESF)