Renin–angiotensin system activation and oxidative stress in hospitalized COVID-19 patients: a single-centre prospective observational study

BACKGROUND: The renin-angiotensin system (RAS) plays a critical role in vascular homeostasis and inflammation, and its dysregulation has been implicated in the pathophysiology of COVID-19. We investigated the dynamics of RAS peptides and markers of endothelial dysfunction in relation to respiratory disease progression in hospitalized COVID-19 patients. METHODS: In this single-centre prospective observational study, 155 adult patients with confirmed SARS-CoV-2 infection were enrolled at hospital admission. Plasma levels of renin, angiotensin I (Ang I), angiotensin II (Ang II), angiotensin 1-7 (Ang 1-7), the Ang II/Ang I ratio (as a surrogate of ACE activity), and asymmetric dimethylarginine (ADMA)-a marker of endothelial dysfunction -were measured at baseline (D0) and day 3 (D3). Endothelial injury was further assessed using the Endothelial Activation and Stress Index (EASIX). Patients were stratified by respiratory trajectory using the WHO ordinal scale. Biomarker kinetics were analysed with baseline-adjusted regression models, and 28-day clinical status was evaluated using partial proportional-odds regression. RESULTS: Of 155 patients, 89 (57%) experienced worsening respiratory status. These patients exhibited progressive RAS activation with higher renin and Ang I at D3 (p < 0.001), a decline in the Ang II/Ang I ratio (p < 0.001), and a rise in Ang 1-7 (p < 0.001). ADMA and EASIX levels increased in parallel, with significantly higher ADMA in worsening vs. non-worsening patients at D3 (0.72 [0.62-0.87] vs. 0.61 [0.50-0.70] µM/L; p < 0.001). Biomarker trajectories differed according to disease course, with significant interaction terms between baseline values and respiratory deterioration. At 28 days, outcomes were associated with renin, Ang I, Ang 1-7, and the Ang II/Ang I ratio, but not with Ang II. Elevated baseline ADMA also independently predicted worse prognosis. CONCLUSIONS: Worsening respiratory status in COVID-19 is associated with delayed activation of the RAS, a shift toward the alternative Ang 1-7 pathway, and parallel increases in endothelial dysfunction markers. These findings suggest that serial measurements of RAS peptides and ADMA may aid in identifying high-risk phenotypes and inform personalized therapeutic strategies in COVID-19.