Inhibitory effect of a histamine 4 receptor antagonist on CCL17 and CCL22 production by monocyte-derived Langerhans cells in patients with atopic dermatitis

We examined the inhibitory effect of a histamine 4 receptor (H4R) antagonist (JNJ7777120) on CCL17 and CCL22 chemokine production by human monocyte‐derived Langerhans cells (MoLC) in patients with atopic dermatitis (AD) and healthy controls (HC). We confirmed the significantly higher production of both CCL17 and CCL22 in the MoLC of AD patients compared with HC. The H4R antagonist significantly inhibited the production of both CCL17 and CCL22 in the MoLC of AD patients. With regard to TLR2‐signaled enhancement, peptidoglycan (PGN)‐enhanced production of CCL17 and CCL22 by MoLC was inhibited by the H4R. Immunoblotting analysis demonstrated that phosphorylated p38 mitogen‐activated protein kinase was induced by PGN and that this enhancement was attenuated by the application of the H4R antagonist. These data indicate that H4 signaling modulates the production of T‐helper 2 chemokine in MoLC and contributes to chronic inflammation in AD patients. Our data suggest a possible novel therapeutic approach using a H4R antagonist in the treatment of patients with AD.