Fig. 1.

Combination of Dex and ALN is able to treat SARS-CoV-2 Delta variant infection. a AMs isolated from ICR mice were treated with Dex, ALN or combination for 24 h or 48 h. The Ctsl mRNA was analyzed by qPCR. D, Dex; A, ALN. “#” and “*” are compared with “24 h-Ctrl” and “48 h-Ctrl” group, respectively. b AMs isolated from ICR mice were treated with Dex, ALN or combination for 24 h, stained with pHrodo™ Red dextran (red), and observed under confocal microscope. Scale bar, 10 μm. c AMs isolated from ICR mice were infected with SARS-CoV-2 Delta variant (2.5 × 10⁴ TCID50) for 2 h, then virus was removed and cells were re-cultured with dexamethasone, alendronate or combination for another 22 h or 46 h. The level of virus load was analyzed by qPCR. d ACE2-overexpression A549 cells were incubated with Delta for 4 h, then virus was removed and cells were re-cultured with dexamethasone (1 μM), alendronate (50 μM) or combination for another 20 h. Cells were stained with anti-NP antibodies. Scale bar, 20 μm. e, f Dex, ALN or both were delivered to ICR mice by intranasal administration. Twenty-four hours later, AMs were collected to validate Ctsl expression (e) or endosomal pH analysis (f). g–i ICR mice were treated with LPS (100 μg/per mouse) by intranasal administration. Four hours later, dexamethasone (1 μg/per mouse) or alendronate (150 μg/per mouse) or both were given. At 24 h, the level of TNF-α (g), IL-1β (h) or IL-6 (i) in bronchoalveolar lavage fluid (BALF) were analyzed by ELISA. j–n hACE2-transgenic mice were infected with 1 × 10⁵ TCID₅₀ Delta. At 2 h post infection, administered with Dex (i.n., 50 μl, 1 μg), ALN (i.n., 50 μl, 150 μg) or both once per day for 5 days. The lung tissues were fixed for NP (j) and CTSL immunostaining (k) or H&E staining (l). The mRNA of IL-6 (m) and TNF-α (n) were detected by qPCR. k scale bar, 10 μm. l scale bar, 100 μm. Rab7, endosomal marker; CD11c, a marker of AMs. o–q AMs isolated from ICR mice were infected with SARS-CoV-2 Omicron variant (2.5 × 10⁴ TCID50) for 2 h, then virus was removed and cells were re-cultured with dexamethasone, alendronate or combination for another 22 h or 46 h. The level of virus load (o), TNF-α (p) and IL-6 (q) was analyzed by qPCR. The data represent mean ± SD. * p < 0.05, ** p < 0.01, *** p < 0.001, by one-way ANOVA (a, c, e–i, l–q)