Increased expression of the histamine H4 receptor following differentiation and mediation of the H4 receptor on interleukin-8 mRNA expression in HaCaT keratinocytes.

Recent in vivo studies have demonstrated involvement of the histamine H4 receptor in pruritus and skin inflammation. We previously reported that an H4 receptor antagonist attenuated scratching behaviour and improved skin lesions in an experimental model of atopic dermatitis. We also reported the expression of the H4 receptor in human epidermal tissues. In this study, we investigated the expression of H4 receptor mRNA and the function of the receptor in a culture system that mimics in vivo inflammation on the HaCaT human keratinocyte cell line. Increased expression of the H4 receptor was observed in HaCaT cells following differentiation. Treatment of HaCaT cells with histamine and TNFα enhanced the mRNA expression of interleukin (IL)-8. These increases in expression were significantly inhibited by the H4 receptor antagonist JNJ7777120. Our results indicate that IL-8 mRNA expression might be enhanced by histamine and TNFα via H4 receptor stimulation in keratinocytes.