GPX4 and COVID-19: Then, to mechanistically prove that TNFα was involved in the COVID-19 induced ferroptotic response, we measured by immunoblot GPX4, SLC7A11, FTH1, and SAT1 after having treated HUVECs with a siRNA for TNFR1 or scramble (the efficiency of TNFR1 silencing is shown in Supplementary Figure S1).