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 E2 (PGE2) 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 PGE2 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 PGE2 formation, while tofacitinib, an inhibitor of Janus kinase, had no influence on PGE2 levels. In addition, IL-6, IL-8, and TNF-α formation were also inhibited, but sometimes independently of PGE2. 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.