Neutrophil extracellular traps contribute to the occurrence and development of psoriasis via activating AIM2 inflammasomes in keratinocytes / 中华皮肤科杂志

ABSTRACT

Objective:To investigate the role of neutrophil extracellular traps (NETs) in psoriatic lesions in activation of absent in melanoma 2 (AIM2) inflammasomes in keratinocytes.Methods:Four skin specimens and 4 peripheral blood specimens were collected from patients with advanced psoriasis vulgaris, who were treated at Department of Dermatology, Xijing Hospital, the Fourth Military Medical University from January to December in 2018. In addition, 4 skin specimens were collected from healthy human controls, and 3 foreskin specimens from children aged under 15 years after circumcision. Tissue immunofluorescence study was performed to determine the expression of NETs and AIM2 inflammasomes in normal skin tissues and psoriatic lesions. Neutrophils were separated from peripheral blood of patients with psoriasis vulgaris by using magnetic beads, and NETs were extracted. Primary keratinocytes were isolated from foreskin tissues, and divided into 4 groups to be stimulated with phosphate-buffered saline (PBS) (control group) , NET extracts (NET group) , DNase Ⅰ-treated NET extracts (NET degradation group) or DNase Ⅰ (degrader control group) respectively for 48 hours. Western blot analysis was performed to determine the expression of AIM2 inflammasomes and its downstream molecules, and enzyme-linked immunosorbent assay (ELISA) to detect the level of IL-1β in the cell culture supernatant in the NET group and control group. Statistical analysis was carried out by using one-way analysis of variance and Dunnett- t test for multiple comparisons. Results:NET structures were observed in the epidermis of psoriatic lesions, but not in that of the healthy controls. Besides, the expression of AIM2 inflammasomes was higher in the epidermis of psoriatic lesions than in the healthy controls. Western blot analysis showed that there were significant differences in the protein expression of AIM2 and its downstream molecules pro-IL-1β and IL-1β among groups ( F = 23.80, 5.82, 15.64 respectively, all P < 0.001) . The NET group showed significantly higher protein expression of AIM2 (1.42 ± 0.03) , pro-IL-1β (1.32 ± 0.08) and IL-1β (1.40 ± 0.05) compared with the control group ( t = 15.14, 4.26, 8.71, respectively, all P < 0.05) , while no significant difference in the expression of AIM2, pro-IL-1β and IL-1β was observed between the NET degradation group (1.15 ± 0.07, 0.93 ± 0.03, 1.07 ± 0.05, respectively) and control group ( t = 2.10, 2.18, 1.40 respectively, all P > 0.05) . In addition, the IL-1β level in the cell culture supernatant was significantly higher in the NET group (13.15 ± 3.77 pg/ml) than in the control group (3.61 ± 0.20 pg/ml, t = 2.53, P < 0.05) . Conclusion:NETs exist in the epidermis of psoriatic lesions, can aggravate the inflammatory process in psoriasis, and contribute to the occurrence and development of psoriasis, likely by activating AIM2 and promoting the cleavage and secretion of IL-1β in keratinocytes.