Mechanisms of IFN-γ-induced apoptosis of human skin keratinocytes in patients with atopic dermatitis

Background: Enhanced apoptosis of keratinocytes is the main cause of eczema and spongiosis in patients with the common inflammatory skin disease atopic dermatitis (AD). Objective: The aim of the study was to investigate molecular mechanisms of AD-related apoptosis of keratinocytes. Methods: Primary keratinocytes isolated from patients with AD and healthy donors were used to study apoptosis by using annexin V/7-aminoactinomycin D staining. Illumina mRNA Expression BeadChips, quantitative RT-PCR, and immunofluorescence were used to study gene expression. In silico analysis of candidate genes was performed on genome-wide single nucleotide polymorphism data. Results: We demonstrate that keratinocytes of patients with AD exhibit increased IFN-gamma-induced apoptosis compared with keratinocytes from healthy subjects. Further mRNA expression analyses revealed differential expression of apoptosis-related genes in AD keratinocytes and skin and the upregulation of immune system-related genes in skin biopsy specimens of chronic AD lesions. Three apoptosis-related genes (NOD2, DUSP1, and ADM) and 8 genes overexpressed in AD skin lesions (CCDC109B, CCL5, CCL8, IFI35, LYN, RAB31, IFITM1, and IFITM2) were induced by IFN-gamma in primary keratinocytes. The protein expression of IFITM1, CCL5, and CCL8 was verified in AD skin. In line with the functional studies and AD-related mRNA expression changes, in silico analysis of genome-wide single nucleotide polymorphism data revealed evidence of an association between AD and genetic markers close to or within the IFITM cluster or RAB31, DUSP1, and ADM genes. Conclusion: Our results demonstrate increased IFN-g responses in skin of patients with AD and suggest involvement of multiple new apoptosis-and inflammation-related factors in the development of AD. (J Allergy Clin Immunol 2012;129:1297-306.)