COVID-19: a disease of the endothelium?

The recent emergence of coronavirus disease 2019 (COVID-19) and the subsequent pandemic has resulted in a healthcare emergency of unparalleled magnitude. Recent evidence suggests that COVID-19 is associated with a significant risk of thrombotic sequelae. The evidence to date suggests that the underlying mechanism is due to the ability of COVID-19 to downregulate angiotensin-converting enzyme 2 (ACE2) on endothelial cells, resulting in oxidative damage and subsequent thrombosis. As such, individuals with higher baseline levels of oxidative stress are at greater risk of complications. Both D-dimer and thrombomodulin have emerged as prognostic markers for COVID-19. Given that the thrombotic consequences of COVID-19 have led to high mortality rates, multiple strategies to prevent thrombosis have been proposed and trialled, including heparin, anti-platelet therapy, and other unconventional therapies such as ivermectin. The striking overlap between risk factors for severe COVID-19 and vitamin D deficiency, including obesity, older age, and African or Asian ethnic origin, has led some researchers to hypothesise that vitamin D supplementation could hold promise as a prophylactic or therapeutic agent for COVID-19. There are myriad clinical trials currently underway with the aim of becoming approved efficacious treatments for the thrombotic sequelae of COVID-19