Fig. 8

Spike protein induces IL-18 expression via impairment of mitophagy resulting in EC permeability. Representative immunofluorescence images (a) and summary data (b) showing stained TOM20 and LAMP1 in HPAEC in the presence of CCCP (10 μM) and RBD protein (2.5 μg/mL) (1-way ANOVA test, N = 4–6). Nuclei counterstained with DAPI. Scale bar, 20 μm. c Protein extracts were subjected to western blot analysis for IL-18 after CCCP and RBD/S1 (2.5 μg/mL) protein treatment in HPAEC and HCMEC (1-way ANOVA test, N = 4). d Representative images of MitoROX staining and quantitative analysis of fluorescence intensity in IgG- and S1 protein-treated HCMEC. Scale bar, 20 μm (Student’s t-test, N = 6). e Representative immunoblots and quantitative analysis of IL-18 in HCMEC with or without IgG (2.5 μg/mL) or S1 (2.5 μg/mL) protein and MitoQ (1 μM) stimulation (1-way ANOVA test, N = 4). f Measurement of endothelial cell permeability in HCMEC or mice primary PAEC (MPAEC) treated with Spike protein (Student’s t-test, N = 3–4). g Measurement of permeability in HPAEC treated with S1 protein (5 μg/mL) and IL-18BP (2 μg/mL) (1-way ANOVA test, N = 4). Results represent means ± SE. *p < 0.05, **p < 0.01, ***p < 0.001. ns no significant differences