Evaluation of selective and non-selective cyclooxygenase inhibitors on sulfur mustard-induced pro-inflammatory cytokine formation in normal human epidermal keratinocytes

Abstract Sulfur mustard (SM) is a highly toxic chemical warfare agent, which produces blisters after skin contact. Treatment of SM-induced adverse health effects, such as cutaneous blistering, ulceration, and inflammation remains a challenging task. Antidotes or specific therapeutic measures are lacking. Some drugs ( e.g. cyclooxygenase (COX) inhibitors) exhibited beneficial effects after SM poisoning in vivo . However, in vitro studies that evaluate and compare the potency of COX inhibitors are missing. In the presented study, non-specific (acetylsalicylic acid, ibuprofen, diclofenac, indomethacin, and piroxicam), COX-2-specific (celecoxib and parecoxib) inhibitors and COX-independent drugs (paracetamol and tofacitinib) were compared regarding anti-inflammatory and cytoprotective effects after SM exposure in post-exposure treatment settings. Normal human epidermal keratinocytes (NHEK) were used as a surrogate model. Prostaglandin E 2 (PGE 2 ) formation, a direct indicator for COX activity, was determined by ELISA. Changes in pro-inflammatory cytokine levels after SM exposures were assessed by quantitative determination of 27 inflammatory cytokines using a multiplex method. Cytotoxicity was determined using an XTT viability assay. The results demonstrated that SM highly increased PGE 2 production and release of pro-inflammatory cytokines, predominantly IL-6, IL-8 and TNF-α. In general, all COX inhibitors and paracetamol were able to reduce the PGE 2 formation, while tofacitinib, an inhibitor of Janus kinase, had no influence on PGE 2 levels. In addition, IL-6, IL-8, and TNF-α formation were also inhibited, but sometimes independently of PGE 2 . The COX-2 specific celecoxib was identified as the most potent drug to reduce IL-6, IL-8 and TNF-α formation after SM exposures in vitro . However, cell viability was not improved significantly by any of the investigated drugs in our experiments.