Fig. 7

Recombinant ACE2 protein reshaped the profile of the RAS system in ALI induced by coexposed to SARS-CoV-2 spike RBD and LPS. A The study design for the ACE2 rescue study. Male C57BL/6 J mice were intratracheally administrated with LPS (0.5 mg/kg). SARS-CoV-2 spike RBD-Fc (5.5 nmol/kg) was intraperitoneally injected three times (at 30 min before and at 1 and 2 h after) during LPS treatment. Recombinant human ACE2 protein (1 mg/kg) or equivalent control BSA was intraperitoneally injected 30 min prior to the administration of LPS. The lung tissues were obtained 3 days after LPS treatment for further assessment of the severity of acute lung injury. B Ang I and C Ang II concentrations in the BALF were determined by ELISA analysis (n = 5–6 per group). D The mRNA expression levels of AT1R and AT2R in the lung tissues of mice with indicated treatment were determined by qPCR analysis (n = 5 per group). E–F The protein expression levels of IκB, p-IκB NOX1 and NOX2 in the lung tissues were determined by western blot analysis, and the representative results were shown. Data are shown as mean ± S.D., **P < 0.01, and N.S. indicates not significant