The Role of Angiotensin 1‐7 in Isolated Human Arterioles with SARS‐CoV‐2

Introduction The vascular endothelium plays a crucial role to regulate vascular tone. Recently, our laboratory reported severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2) infection significantly reduced endothelial‐dependent vasodilation months after exposed to SARS‐CoV‐2 in human microvessels. SARS‐CoV‐2 enters host cells through angiotensin‐converting enzyme (ACE)2 as a cell surface receptor. Downregulation of ACE2 protein expression by the virus leads to imbalance between angiotensin (ANG) II and ANG 1‐7, causing vasoconstriction, inflammation and increase oxidative stress. With this background, we intend to test our new hypothesis that administration of ANG 1‐7 will improve vasodilation in human arterioles from previously SARS‐CoV‐2 positive subjects. Methods Fresh human tissues were obtained as de‐identified surgical discarded specimens. Control subjects (n=9) were SARS‐CoV‐2 negative and without known virus exposure. We had 11 previously SARS‐CoV‐2 positive subjects or post‐COVID. For all post‐COVID patients, a negative COVID test was obtained prior to collection of surgical specimens. We isolated arterioles (100‐200 µm) and cannulated onto glass micropipettes under 60 mmHg and examined for diameter changes to the endothelial‐dependent vasodilator acetylcholine (ACh;10−9 to 10−5 M) using videomicroscopy. Flow‐mediated dilation (FMD) was recorded at steady‐state during varying intraluminal pressure gradients (5‐100 cm H2O). All post‐COVID vessels were incubated in a culture media at 37°C for 12–15 hours with or without 1 nM of ANG 1‐7. Results Dilation to ACh and FMD in arterioles from post‐COVID was significantly reduced (ACh max. dilation at 10−5 M: 74±6% vs. 93±4% in control, n=7‐9, P<0.001;FMD max. dilation at 100 cm H2O: 49±3% vs. 86±2% in control, n=6‐11, P<0.001) while overnight incubation of 1 nM ANG 1‐7 significantly improved the dilation (ACh max. dilation at 10−5 M: 74±6% in post‐COVID vs. 88±5% in post‐COVID + AND 1‐7, n=11, P<0.001;FMD max. dilation at 100 cm H2O: 49±3% in post‐COVID vs. 76±3% in post‐COVID + ANG 1‐7, n=11, P<0.001). Conclusion Administration of ANG 1‐7 significantly improved vasodilation in isolated arterioles from post‐COVID subjects.

Prolonged Endothelial Dysfunction in Human Arterioles with SARS-CoV-2

The vascular endothelium plays a crucial role to regulate vascular tone. Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection is known to cause vascular endothelial dysfunction. However, the long-term effects of SARS-CoV-2 in resistance vessels remains unknown. This study is designed to test whether endothelium-dependent vasodilation in human arterioles remains impaired after clearance of SARS-CoV-2 virus. Fresh human adipose tissues were obtained as discarded surgical specimens from control subjects (n=15, no SARS-CoV-2 exposure, 46.7±4 years) and previously SARS-CoV-2 positive subjects (PSPSs: n=8, 35.8±3.8 years). Among PSPSs, the time between positive and negative SARS-CoV-2 test results was ≤3 months (n=6) or 8 months (n=2). Isolated arterioles (100-200 µm) were cannulated under 60 mmHg and examined for diameter changes to acetylcholine (ACh;10?9 to 10?5 M) and sodium nitroprusside (SNP: 10?9 to 10?4 M) using videomicroscopy. Flow-mediated dilation (FMD) was recorded at steady-state during graded increases in intraluminal pressure gradients (5-100 cm H2O). Dilation to ACh and FMD in arterioles from PSPSs was significantly reduced (ACh max. dilation at 10?5 M: 60±6% vs. 92.8±3.9% in control, n=7-8, P<0.001;FMD max. dilation at 100 cm H2O: 39.9±5.7% vs. 85.8±1.8% in control, n=6-8, P<0.001, Fig.1) while endothelial-independent dilation in response to SNP was not different between groups (max. dilation at 10-4 M: 86.6±2.7% vs. 92.3±2.1% in control, n=5). To compare time-dependent effects of previous SARS-CoV-2 infection, we compared max. dilator capacity vs. time after exposure (Fig. 2). At ≤3 months post exposure, FMD was significantly impaired (% max. dilation: 26.7±7.4, n=5) whereas at 8 months endothelial function began to normalize (% max. dilation: 41.8±17.6, n=2). In conclusion, we observed significantly reduced endothelial-dependent dilation months after exposed to SARS-CoV-2. Our data suggests SARS-CoV-2 may cause long-term endothelial dysfunction in human arterioles.