ACE2 and COVID-19: First, whether the expressions of innate immune regulators in EC are differentially modulated in response to stimulations of PAMPs and DAMPs; second, whether EC are equipped with ACE2 to serve as cellular targets for infections by SARS-CoV-2 and other viruses; third, whether EC have trained immunity function which amplifies cytokine responses into cytokine storms; and fourth, EC undergo various types of cell death in response to virus infections and DAMP stimuli, which trigger thromboembolism and cardiovascular complications of COVID-19.