Deficiency of Autophagy-Related Gene 5 in Keratinocytes Leads to Aggravation of Epidermal Damage in 2,4-Dinitrochlorobenzene-Induced Allergic Contact Dermatitis

Abstract

Objective: The interrelationship between apoptosis and autophagy plays an important role in many pathophysiological processes, however, whether their interplay is involved in allergic contact dermatitis (ACD) has not yet been elucidated. So, we conducted this study to determine whether keratinocyte-specific autophagy-related gene 5 (ATG5) deficiency can regulate apoptosis to inhibit skin damage in mice with 2,4-dinitrochlorobenzene (DNCB)-induced ACD. Methods: This study involved keratinocyte-specific Atg5 conditional knockout (cKO) mice (Krt14cre/+-Atg5 flox/flox) and control mice (Krt14+/+-Atg5 flox/flox). We painted DNCB on the right ear of each mouse to induce ACD. Dermatitis scoring and measurements of ear weight and thickness were performed to evaluate inflammation levels. An immunohistochemical assay was performed to analyze immune cell infiltration. Histological study and TUNEL staining were performed to compare the differences in skin lesions between Atg5 cKO mice and control mice. Immunofluorescence and western blotting were used to examine the levels of ATG5 and apoptosis-related protein. The results were statistically analyzed by t test. Results: After DNCB stimulation of mice ears, we observed a more severe phenotype in Atg5 cKO mice than in control mice (dermatitis score: 7.500 ± 2.588 vs. 3.250 ± 0.822, P = 0.003). Further analysis of ATG5 protein confirmed keratinocyte-specific ablation of Atg5 in cKO mice and showed that DNCB did not influence ATG5 expression. Immunohistochemistry assay revealed that the infiltrated immune cells were not involved in aggravation of the phenotype of DNCB-stimulated Atg5 cKO mice. However, the histological study (P = 0.024), TUNEL staining (P = 0.024), immunofluorescence (P = 0.036), and western blotting showed that the increase in keratinocyte death, especially apoptosis, contributed to aggravation of the phenotype of DNCB-stimulated Atg5 cKO mice. Conclusion: Deficiency of Atg5 in keratinocytes increases apoptosis, aggravating skin damage in DNCB-induced ACD mice. This has no relationship with the involvement of immune cells.