Fig. 1.
Inhibition activity of bardoxolone methyl and bardoxolone. a SARS-CoV-2 3CLpro inhibition activity of bardoxolone methyl and bardoxolone. Various concentrations of bardoxolone methyl and bardoxolone were pre-incubated with SARS-CoV-2 3CLpro for 30 min at room temperature before the addition of pNA-substrate. b Anti-SARS-CoV-2 activity and cytotoxicity of bardoxolone methyl and bardoxolone in Vero cells or Calu-3 cells. Cells were infected with SARS-CoV-2 at MOI of 0.01 (Vero cell line) and 1 (Calu-3 cell line) in the treatment of different doses of bardoxolone methyl and bardoxolone for 48 h. The viral yield in the cell supernatant was then quantified by qRT-PCR. The cytotoxicity of the compounds at different concentrations was measured by CCK-8 assays. The EC50 and CC50 were calculated by nonlinear regression analysis using Origin 2018 software. The selective indexes (SI) were calculated as the ratio of CC50 to EC50. c Immunofluorescence microscopy of virus infection upon treatment of bardoxolone methyl. Virus infection and drug treatment were performed as mentioned above. At 48 h post infection, the infected Vero cells were fixed, and then probed with mouse sera against the SARS-CoV-2 nucleoprotein as the primary antibody and Alexa 488-labeled goat anti-mouse IgG as the secondary antibody, respectively. The nuclei were stained with DAPI dye. Bars, 500 μm