Role Of Autophagy In Cutaneous Lichen Planus

Background Lichen planus(LP)is a chronic inflammatory,T lymphocytes mediated autoimmune skin disease and the exact mechanism is still unclarified.Histologically,LP shows mainly a wedge-shaped thickening of the granular layer and liquefactive degeneration of the basal layer of the epidermis,and subepithelial band-like dense inflammatory infiltrate of T lymphocytes in the dermis.Autophagy can maintain cellular homeostasis through the lysosomal degradation pathway.Abnormal autophagy levels have been proved to be associated with a variety of autoimmune skin diseases,such as systemic lupus erythematosus,psoriasis,vitiligo and so on.Autophagy not only regulates the homeostasis of immune system,but also participates in physiological and pathological processes of keratinocytes.Previous studies have confirmed that the autophagy of T lymphocytes is involved in the pathogenesis of oral lichen planus,therefore it can be suspected that autophagy of keratinocytes may be involved in the pathogenesis of cutaneous lichen planus(CLP).Objective To observe the expressions of autophagy associated protein LC3 B,mTOR and Rab11 a in the epidermis of lichen planus and to explore the significance of autophagy of keratinocytes in the pathogenesis of cutaneous lichen planus.Methods Biopsy specimens from 12 patients with CLP and 6 healthy controls were studied using immunohistochemical staining method.The samples were divided into 3categories: lesional,peri-lesional and non-lesional specimens.The lesional,and peri-lesional specimens were from patients with CLP.The non-lesional specimens were from healthy individuals.LC3 B positive cells were counted and the expressions of mTOR and Rab11 a were evaluated using an immunostaining-intensity-distribution(IID)index.Results LC3B-positive cells expressed mainly at the superficial layer,and the number in lesional specimens was greater than in peri-lesional and non-lesional specimens.The mTOR expressed mainly in the basal layer of epidermis in the control specimens,but were observed at all epidermal layers in CLP specimens.The IID index scores for mTOR showed significant differences in each layer of the epidermis among the three groups.The IID index scores for mTOR expression in the suprabasal and superficial layers were highest in the lesional and lowest in the non-lesional groups.For the basal layer,the IID index scores for mTOR expression of lesional group were higher than that of the peri-lesional group and the normal control group.The expression of Rab11 a was significantly higher in lesional specimens of CLP than in control specimens,especially in the superbasal layer,but there was no significance between lesional and peri-lesional specimens.The IID index scores for Rab11 a among the three groups in each layer showed significant differences in the basal layer(p = 0.022 < 0.05)and in the suprabasal layer(p = 0.000 < 0.05).The IID index scores for Rab11 a expression of the lesional group in basal layer were significantly higher than the scores of the normal control group,and the IID index scores for Rab11 a expression of the CLP groups in the suprabasal layer were significantly higher than that of the normal control group.No significant differences were found among the three groups in the superficial layerConclusion This work shows significant increases of LC3 B,mTOR and Rab11 a expressions in the epidermis of CLP compared with those of non-lesional skin,which suggests that autophagy may be related to the pathogenesis of CLP.