Pharmacologic inhibition of TRPA1 counteract tear gas induced cutaneous injuries.

Deployment of the tear gas agent 2-chlorobenzalmalononitrile (CS) for riot control has significantly increased in recent years. The effects of CS have been believed to be transient and benign. However, CS induces severe pain, blepharospasm, lachrymation, airway obstruction, and skin blisters, and with frequent injuries and hospitalizations have been reported following exposure. We have identified the sensory neuronal ion channel, transient receptor potential ankyrin 1 (TRPA1), as a key CS target resulting in acute irritation and pain, and also as a mediator of neurogenic inflammation. Here, we examined the effects of pharmacologic TRPA1 inhibition on CS-induced cutaneous injury. We modeled CS-induced cutaneous injury by applying 10 µL CS agent (200 mM in dimethyl sulfoxide, DMSO) to each side of the right ears of 8-9 week-old C57BL/6 male mice, whereas left ears were treated with solvent only (DMSO). The TRPA1 inhibitor HC-030031 or A-967079 was administered post-CS exposure. CS induced strong tissue swelling, plasma extravasation, and a dramatic increase in inflammatory cytokine levels in the mouse ear skin. We also showed that the effects of CS were not transient, but caused persistent skin injuries. These injury parameters were reduced with TRPA1 inhibitor treatment. Further, we tested the pharmacologic activity of advanced TRPA1 antagonists in vitro Our findings showed that TRPA1 is a crucial mediator of CS-induced nociception and tissue injury, and that TRPA1 inhibitors are effective countermeasures that reduce key injury parameters when administered post-exposure. Additional therapeutic efficacy studies with advanced TRPA1 antagonists and decontamination strategies are warranted. Significance Statement CS tear gas agent has been deployed as a crowd dispersion chemical agent in recent times. Exposure to CS tear gas agents has been believed to cause transient acute toxic effects that are minimal at most. Here, we found that CS tear gas exposure causes both acute and persistent skin injuries, and that treatment with transient receptor potential ion channel ankyrin 1 (TRPA1) antagonists ameliorated skin injuries.