Mitigation of nitrogen mustard-induced skin injury by the β-blocker carvedilol and its enantiomers

The chemical warfare agent sulfur mustard and its structural analog nitrogen mustard (NM) cause severe vesicating skin injuries. The pathologic mechanisms for the skin injury following mustard exposure are poorly understood, therefore, no effective countermeasure is available. Previous reports demonstrated the protective activity of carvedilol, an FDA-approved β-blocker, against ultraviolet radiation-induced skin damage. Thus, the current study evaluated the effects of carvedilol on NM-induced skin injuries in vitro and in vivo. In the murine epidermal cell line JB6 Cl 41-5a, β-blockers with different receptor subtype selectivity were examined. Carvedilol and both of its enantiomers R- and S-carvedilol were the only tested ligands statistically reducing NM-induced cytotoxicity. Carvedilol also reduced NM-induced apoptosis and p53 expression. In SKH-1 mice, NM increased epidermal thickness, damaged skin architecture, and induced NF-kB related pro-inflammatory genes as assessed by RT² Profiler{trade mark, serif} PCR Arrays. To model chemical warfare scenario, 30 minutes after exposure to NM, 10 µM carvedilol was applied topically. Twenty-four hours after NM exposure, carvedilol attenuated NM-induced epidermal thickening, which in such a short time is due to an anti-inflammatory activity; Ki-67 expression, a marker of cellular proliferation, and multiple pro-inflammatory genes. Supporting the in vitro data, the non-β-blocking R-enantiomer of carvedilol had similar effects as racemic carvedilol, and there was no difference between carvedilol and R-carvedilol in the RT² Profiler{trade mark, serif} PCR Array data suggesting that the skin protective effects are independent of the β-adrenergic receptors. These data suggest that the β-blocker carvedilol and its enantiomers can be repurposed as countermeasures against mustard-induced skin injuries. Significance Statement The chemical warfare agent sulfur mustard and its structural analog nitrogen mustard cause severe vesicating skin injuries for which no effective countermeasure is available. This study evaluated the effects of an FDA-approved b-blocker carvedilol on nitrogen mustard-induced skin injuries, to repurpose this cardiovascular drug as a medical countermeasure.