The role of miRNA in the pathogenesis of atopic dermatitis

Allergic diseases including asthma, atopic dermatitis and allergic rhinitis are the most common chronic diseases during the childhood period. Atopic dermatitis is a chronically relapsing inflammatory condition of the skin, characterized by intense pruritus. The mechanism might be that the gene dysregulation of both the innate and the adaptive immune systems cause persisting inflammation. MicroRNAs (miRNAs) first described in 1993 downregulate gene expression and effect cell function by binding to messenger RNA. The regulation by miRNAs might be quite common in human diseases. More than 1/3 of human genes are regulated by miRNAs. So far, some studies revealed that five miRNAs (miR-146a, miR-148a, miR148b, miR-152, and miR-155) are possibly associated with allergic diseases or the regulation of Th1/Th2 pathway .This purpose of our study is to evaluate whether there is any special mMiRNA expression in the peripheral blood of children with atopic dermatitis in Taiwan. ESULT: 7 Taiwanese children are evaluated including 24 healthy children, 33 patients with atopic dermatitis and 30 only airway allergic children (Asthma and/or allergic rhinitis). Children with atopic dermatitis or only airway allergic disease have significantly lower miR-146a expression compared with healthy children (P = 0.003, P = 0.001). The expression level of miR-146a has a significantly negative correlation with total IgE (r = -0.220, P = 0.044, two-tailed). Children with atopic dermatitis has significantly lower miR-155 expression compared with healthy children (P = 0.043). The expression level of miR-155 has a significantly negative correlation with total IgE (r = -0.255, P = 0.020, two-tailed). The expression level of miR-148a, miR-148b or miR-152 has no significant correlation with atopic dermatitis.ONCLUSION: he discovery of miRNAs as regulators of the immune system was almost in mouse model or human cell culture. Our study is first report about that miRNAs may be involved in atopic dermatitis by studying leukocytes in human blood. Taiwanese children with atopic dermatitis have significantly lower miR-146a and miR-155 expression compared with healthy children. Although the mechanism of this interaction is still unknown, the result of this study suggests that miR-146a and miR-155 maybe negatively regulate gene expression to suppress atopic dermatitis. The miRNA based gene therapy such as miR-146a or miR-155 RNAi could be a potential therapy for allergic diseases especially in atopic dermatitis. Before these two miRNAs can be used as a therapeutic tool, these data should be verified in a larger study.