The antagonism of histamine H1 and H4 receptors ameliorates chronic allergic dermatitis via anti-pruritic and anti-inflammatory effects in NC/Nga mice.

BACKGROUND Although histamine H1 receptor (H1R) antagonists are commonly used to treat atopic dermatitis, the treatment is not always effective. The histamine H4 receptor (H4R) was recently described as important to the pruritus in dermatitis. Here, we investigated whether the combination of a H1R antagonist plus a H4R antagonist attenuates chronic dermatitis in NC/Nga mice. METHODS Chronic dermatitis was developed by repeated challenges with picryl chloride on the dorsal back and ear lobes. The therapeutic effects of the H1R antagonist olopatadine and H4R antagonist JNJ7777120 on scratching and the severity of dermatitis were evaluated. In addition, the mechanisms responsible for the anti-allergic effects of H1R and/or H4R antagonism were examined using bone marrow-derived mast cells (BMMC) and keratinocytes. RESULTS JNJ7777120 attenuated scratching behavior after a single administration and improved dermatitis, as assessed with clinical scores, pathology, and cytokine levels in skin lesions when administered repeatedly. These effects were augmented by combined treatment with olopatadine, having a similar therapeutic efficacy to prednisolone. JNJ7777120 inhibited dose-dependently the production of thymus and activation-regulated chemokine/CCL17 and macrophage-derived chemokine/CCL22 from antigen-stimulated BMMC. In addition, olopatadine reversed the histamine-induced reduction of semaphorin 3A mRNA in keratinocytes. CONCLUSION Combined treatment with H1R and H4R antagonists may have a significant therapeutic effect on chronic dermatitis through the synergistic inhibition of pruritus and skin inflammation.