Effect of pro-inflammatory cytokines on the toxicity of the arylhydroxylamine metabolites of sulphamethoxazole and dapsone in normal human keratinocytes

Sulphonamides, such as sulphamethoxazole (SMX) and the related sulphone dapsone (DDS), show a higher incidence of cutaneous drug reactions (CDRs) in patients with the acquired immunodeficiency syndrome (AIDS) compared with human immunodeficiency virus (HIV) negative patients. During HIV infection, pro-inflammatory cytokines such as interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) are increased. We hypothesized that this increase in pro-inflammatory cytokines may increase the toxicity of the arylhydroxylamine metabolites of SMX (S-NOH) and DDS (D-NOH) in keratinocytes through a reduction in glutathione (GSH) content. We evaluated the effect of TNF-α on GSH levels in normal human epidermal keratinocytes (NHEK) and found a significant decrease in GSH after 24 h. Pre-treatment with TNF-α also resulted in an increase in the recovery of D-NOH, but failed to alter drug–protein covalent adduct formation in NHEK. We also evaluated the effect of TNF-α, IL-1β, interferon-γ (IFN-γ), lipopolysaccharide (LPS) and conditioned media (obtained from monocytes stimulated with LPS) on the cytotoxicity of pre-formed arylhydroxylamine metabolites in NHEK. Priming cells with cytokines did not significantly alter the cytotoxicity of the metabolites. The effect of pre-treatment with TNF-α on reactive oxygen species (ROS) generation in NHEK was also determined. While ROS formation in NHEK was increased in the presence of D-NOH, TNF-α did not alter the level of ROS generation. Our data suggest that the level of GSH reduction induced by pro-inflammatory cytokines does not predispose NHEK to cellular toxicity from either S-NOH or D-NOH.