Histamine H1-receptor antagonistic drug olopatadine suppresses TSLP in atopic dermatitis model mice

Expression and function of histamine and its receptors in atopic dermatitis

Background

Atopic dermatitis constitutes a most burdensome chronic inflammatory skin disease. Standard treatment is cumbersome and often targets its main symptom, pruritus, only insufficiently.

Findings

Recent advances in our understanding of the role of histamine and its four receptors suggest new approaches which target the histamine receptors alone or as combination therapies to more efficiently combat pruritus and inflammation in atopic dermatitis.

Conclusions

With this review, we provide an overview on histamine and the expression of its four receptors on skin resident and nonresident cells. Furthermore, we summarize recent studies which suggest anti-histamine therapy to efficiently combat pruritus and inflammation in atopic dermatitis and discuss possible approaches to incorporate these findings into more effective treatment strategies for atopic dermatitis in childhood.

Histamine and Skin Barrier: Are Histamine Antagonists Useful for the Prevention or Treatment of Atopic Dermatitis?

Atopic Dermatitis (AD), the most common chronic inflammatory skin disease, is characterized by an overactive immune response to a host of environmental allergens and dry, itchy skin. Over the past decade important discoveries have demonstrated that AD develops in part from genetic and/or acquired defects in the skin barrier. Histamine is an aminergic neurotransmitter involved in physiologic and pathologic processes such as pruritus, inflammation, and vascular leak. Enhanced histamine release has been observed in the skin of patients with AD and antihistamines are often prescribed for their sedating and anti-itch properties. Recent evidence suggests that histamine also inhibits the terminal differentiation of keratinocytes and impairs the skin barrier, raising the question whether histamine might play a role in AD barrier impairment. This, coupled with the notion that histamine’s effects mediated through the recently identified histamine receptor H4R, may be important in allergic inflammation, has renewed interest in this mediator in allergic diseases. In this paper we summarize the current knowledge on histamine and histamine receptor antagonists in AD and skin barrier function.

The role of histamine H1 and H4 receptors in atopic dermatitis: from basic research to clinical study

Histamine plays important roles in inflammation and nervous irritability in allergic disorders, including atopic dermatitis (AD). It has been shown to regulate the expression of pruritic factors, such as nerve growth factor and semaphorin 3A, in skin keratinocytes via histamine H1 receptor (H1R). Furthermore, H1R antagonist reduced the level of IL-31, a cytokine involving the skin barrier and pruritus, in chronic dermatitis lesions in NC/Nga mice and patients with AD. Histamine plays roles in the induction of allergic inflammation by activating eosinophils, mast cells, basophils, and Th2 cells via histamine H4 receptor (H4R). H4R, in addition to H1R, is expressed on sensory neurons, and a decrease in scratching behaviors was observed in H4R-deficient mice and mice treated with a H4R antagonist. We found that the combined administration of H1R and H4R antagonists inhibited the itch response and chronic allergic inflammation, and had a pharmacological effect similar to that of prednisolone. Although the oral administration of H1R antagonists is widely used to treat AD, it is not very effective. In contrast, JNJ39758979, a novel H4R antagonist, had marked effects against pruritus in Japanese patients with AD in a phase II clinical trial. Next generation antihistaminic agents possessing H1R and H4R antagonistic actions may be a potent therapeutic drug for AD.