Low-Dose Oxygen Enhances Macrophage-Derived Bacterial Clearance following Cigarette Smoke Exposure

Figure 3

40% oxygen promotes bacterial clearance by CS-exposed macrophages. MH-S macrophages in cell culture were exposed to cigarette smoke (CS) or air (control) and 21% or 40% oxygen exposure for a total of 24 hours. (a) We quantified cytokines IL-6 and TNF-α in the cell-free media following the specified CS and oxygen exposure (, mean ± SEM, by one-way ANOVA). (b) Using FACS, we measured CD86 and MMR MFI on CD11b⁺ cells prior to PAO1-GFP exposure (MFI ± SEM, , compared to the control + 21% O₂ group by one-way ANOVA with Bonferroni correction). (c) Following 24 hours of CS and oxygen exposure (or controls), we incubated cells with PAO1-GFP for 3 hours. Intracellular CFUs were expressed as a fold change compared to the control + 21% O₂ group (mean ± SEM, , compared to control + 21% O₂ and CS + 21% O₂ groups by one-way ANOVA with Bonferroni correction). (d) Using FACS following PAO1-GFP exposure, we quantified the MFI of GFP expression among MH-S cells (left) as well as the phagocytosis index (GFP MFI ×  %  MH-S cells with GFP signal). (e) Following PAO1-GFP exposure, we performed nonlinear regression of best fit across all data points to demonstrate the relationship of intracellular and extracellular CFU counts (each dot represents a single well, -9 for each group).

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