Effects of post-acute sequelae of COVID-19 on circulating milieu-mediated endothelial function

Introduction: Patients with post-acute sequelae of COVID-19 (PASC) are at increased risk of cardiovascular disease (CVD). Vascular endothelial dysfunction is a key mechanism of increased CVD risk. Acute infection with COVID-19 changes the circulating milieu to induce endothelial dysfunction characterized by reduced endothelial cell nitric oxide (NO) production and increased reactive oxygen species (ROS)-related oxidative stress. Whether circulating milieu-mediated impairments in endothelial function change over time in those with vs. without PASC is currently unknown. Hypothesis: We tested the hypothesis that patients who develop PASC (PASC+) would exhibit a greater reduction in circulating milieu-related endothelial cell function after 6 months in comparison with those who do not develop PASC (PASC-). Methods and Results: This was a retrospective cohort study as part of the NIH RECOVER (Researching COVID to Enhance Recovery) Initiative. Serum samples were obtained from n=64 participants (39 women/25 men, 22-79 years of age) at the University of Texas Health Science Center, San Antonio within 1 month of infection with COVID-19 and then again 5-6 months after infection. At the 6-month time point, n=39 patients were clinically diagnosed as PASC+ based on the presence of symptoms, including fatigue, malaise, musculoskeletal symptoms, cardiopulmonary symptoms, dizziness and/or dysautonomia for at least 3 months and a self-reported PASC score ≥12 on a validated PASC symptom scale of 0-25 (PASC+: 15.6±3.4, PASC-: 0.0±0.0, p<0.0001). Circulating milieu-induced endothelial dysfunction was assessed by exposing human aortic endothelial cells (HAECs) in culture to 10% serum (in media) for 2 hours. Fluorescent probes were used to detect acetylcholine (ACh)-stimulated NO production (DAR-4M) and whole cell ROS bioactivity (CellROX). At baseline, there was no difference in ACh-stimulated NO production between the PASC+ and PASC- group (PASC+: 1.48±0.14 AU vs. PASC-: 1.43±0.14 AU, p>0.05). In the PASC+ group, ACh-stimulated NO production was significantly lower (1.43±0.12 AU, P=0.01) at 6 months vs baseline, whereas no changes were observed in the PASC- group (1.44±0.09AU, p>0.05). No difference in ROS bioactivity was observed between groups at baseline (PASC+: 1620±666 AU, PASC-: 1630±847 AU, p>0.05). ROS bioactivity did not change in either group at 6 months vs baseline (PASC+: 1558±625AU, p>0.05; PASC-: 1589±806AU, p>0.05). Neither age, sex, PASC score nor PASC symptoms influenced the change in NO production or ROS bioactivity. Conclusions: Circulating milieu-induced endothelial NO production is reduced 6 months after infection in patients with COVID-19 who develop PASC. Funding. OT2HL161847 This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.