In Vitro Screening Identifies TRPV4 and PAR1 as Targets for Endothelial Barrier Stabilization in COVID‐19

ABSTRACT

Study objective Endothelial dysfunction and increased microvascular permeability are hallmarks of severe COVID‐19. At present, the underlying mechanisms of endothelial barrier failure in COVID‑19 remain elusive. Here, we show that increased thrombin activity in plasma from severe COVID‐19 patients activates endothelial protease‐activated receptor (PAR1), which mediates barrier failure by triggering TRPV4‐mediated Ca2+ influx in lung microvascular endothelial cells. Methods Citrate plasma was sampled as part of the Pa‐COVID‐19 cohort study (ethics approval EA2/066/20) from patients with severe COVID‐19 (high flow O2 or mechanically ventilated;WHO severity score 5‐7) COVID‑19. Plasma samples were diluted to 10% (v/v) in cell culture medium without FCS and tested for their ability to disrupt barrier integrity of primary human pulmonary microvascular endothelial cells (HPMEC) monolayers by electrical cell‐substrate impedance sensing (ECIS), immunofluorescence for endothelial VE‐cadherin and F‐actin, western blot analyses of PAR‐1 cleavage, and real‐time Ca2+ imaging. Plasma from healthy donors served as control. Results COVID‐19 plasma had elevated thrombin activity while levels of antithrombin III, a key anti‐coagulant with thromboprotective function were decreased. COVID‐19 plasma caused endothelial barrier dysfunction as measured by ECIS and gap formation in HPMEC monolayers. Endothelial barrier disruption and endothelial Ca2+ influx in response to COVID‐19 plasma could be blocked by selective antagonists targeting thrombin (Argatroban), its receptor PAR1 (SCH79797), or TRPV4 (HC‐067047). Conclusion Here, we identify a novel signaling axis involving thrombin, its receptor PAR1, and TRPV4 as mechanism for increased microvascular permeability in COVID‑19. Targeting this signaling axis in endothelial barrier failure may provide a promising adjunctive therapy in COVID‐19.