Contact sensitizer 2,4‐dinitrochlorobenzene is a highly potent human TRPA1 agonist

Abstract 2,4‐Dinitrochlorobenzene ( DNCB ) is widely used in human clinical studies and in experimental animal studies to evoke allergic contact dermatitis. 2,4‐Dinitrochlorobenzene is a potent immunogen capable of inducing contact sensitization in all humans exposed. However, the mechanism by which DNCB evokes such symptoms is presently unknown. TRPA 1 is a nonselective cation channel that is expressed in peptidergic sensory neurons and fibroblasts. TRPA 1 activation was recently implicated in the pathophysiology of atopic dermatitis especially in transducing cutaneous itch signals. Here, we test the hypothesis that DNCB acts as a TRPA 1 agonist and thereby evokes allergic symptoms. We found that DNCB activates human TRPA 1 dose dependently in FLIPR experiments with an EC 50 of 167 nM, an effect that was fully blocked by selective TRPA 1 antagonists C hembridge‐5861528 and A‐967079. Similarly, DNCB activated nonselective TRPA 1 current in patch clamp studies. Neutralization of 3 critical cysteines in TRPA1 resulted in a loss of DNCB agonism.