Fig. 1

Corticosteroids abrogate cytotoxicity in Mycobacterium tuberculosis (Mtb)-infected cells. a Protective effect of dexamethasone and other corticosteroids (10 µM) in Mtb-infected MRC-5 lung fibroblasts (multiplicity of infection (MOI) 10). Host cell viability was quantified using PrestoBlue. Data derived from high-throughput screen with measurements of duplicate assay plates. b Dose–response curve of dexamethasone in Mtb-infected MRC-5 lung fibroblasts analyzed using the fibroblast survival assay (FSA). c Representative fluorescent microscopy images of Mtb-infected primary human macrophages (Mφ; MOI 1), J774.2 Mφ (MOI 5), and BV-2 microglia (MOI 5) treated with dexamethasone (5 µM), rifampicin (5 µM), or DMSO (0.05%). Nuclei were stained with 4′,6-diamidino-2-phenylindole (DAPI; scale bar: 100 µm). Images are representative of two to three individual experiments with multiple replicates. d–g Dexamethasone (5 µM)-treated J774.2 mouse Mφ (d), primary human Mφ from healthy donors (e) and TB patients (f), and BV-2 mouse microglia (g) were infected with the wild-type Mtb strain Erdman at varying MOI and surviving cells were stained with DAPI to determine the number of living cells 48 h post infection. Data from one experiment with duplicates are shown in b; data were pooled from two (d, f, g) or three (e) independent experiments with multiple replicates. Results are expressed as the mean ± SEM. Statistical analysis were performed by unpaired t-test (**p ≤ 0.01; ***p ≤ 0.001)