Figure 1. TNT-induced reactive oxygen species mediate macrophage cell death.

THP-1 macrophages were infected with Mtb strains at an MOI of 10:1 and treated with N-acetylcysteine (NAC, 100 μM) when indicated. ROS levels were measured with the fluorescent probe H₂DCFDA at (A) 4, 24 and 48 h or (B) 48 h post-infection. (C) Cell viability of infected macrophages was measured 48 h after infection as the total ATP content with a luminescent ATP detection assay kit. (D) The Mtb intracellular growth in infected macrophages was measured at 4 h and 48 h post-infection and expressed as CFU per ml. (E) Wt Mtb H37Rv was grown in Middlebrook 7H9 medium with 0.5% glycerol, 0.02% Tyloxapol and 10% OADC and supplemented with N-acetyl-cysteine (NAC, 100 μM). The OD₆₀₀ was measured at the indicated time points. Asterisks indicate significant differences (p-value<0.01, calculated using the Two-way ANOVA with Bonferroni’s correction) compared with the indicated conditions. Data are represented as mean ± SEM.