Figure 2

Cigarette smoke extract causes minimal airway epithelial cell cytotoxicity. A: Mitochondrial activity was quantified using an MTS-based assay with hTBE cells that were first treated with media without or with CSE at the indicated concentration for 4 hours, followed by incubation for 20 hours in media containing the same CSE concentration without or with IFN-γ. B: Mitochondrial activity was quantified using an MTS-based assay with hTBE cells that were first treated with media without or with CSE at the indicated concentration for 48 hours, followed by incubation for 24 hours in media containing the same CSE concentration without or with IFN-γ. In A and B, values are expressed as mean ± S.D. (n = 3 replicates). C: Dead and live hTBE cell numbers were quantified by detection of plasma membrane permeability to ethidium homodimers in dead cells and intracellular esterase activity in live cells. Cell monolayers were first treated with media without or with CSE at the indicated concentration for 48 hours, followed by incubation for 24 hours in media containing the same CSE concentration without or with IFN-γ. Values were calculated as dead cells/total cells and each condition represents the mean ± S.D. for 4 random low power fields (500-750 cells/field) from duplicate samples. In A-C, a significant difference (p < 0.05) in uninduced or IFN-γ-induced levels between cells treated versus not treated with CSE is indicated by an asterisk.