IL-37 Is Protective In Allergic Contact Dermatitis Through Mast Cell Inhibition

Objiective Allergic contact dermatitis is a common inflammatory skin disease,caused by the skin or mucous membrance repeated exposure to allergens.IL-33 actives mast cells to degranulate and release histamine,protease,inflammatory cytokines and chemokines involved in pathological process.IL-37 has immunosuppressive and anti-inflammatory effects.To explore the effect of IL-37 on rat ACD model、IL-33 induces mast cells activation and its underlying mechanism,provide a theoretical foundation and guidance for clinical treatment.Methods There were six-week-old healthy females Spargue-Dawley rats in specific pathogen-free grade adaptively fed for one week.The rats were randomly divided into 5 groups,Control group,ACD group,IL-37+ACD group,SIS3+ACD group,SIS3+IL-37+ACD group.Control group was left untreated,ACD group was induced with DNFB,IL-37+ACD group was intraperitoneally injected with IL-37 b solution and create the ACD model,SIS3+ACD group was intraperitoneally injected with SIS3 solution and create the ACD model,SIS3+IL-37+ACD group was intraperitoneally injected with IL-37 and SIS3 and create the ACD model.Experiment 1: Explore the effect of IL-37 on ACD rats1.Symptom observation: Measure the swelling thickness of rat ears;2.Pathological observation: HE staining of rat swollen ears,observation of dermal layer changes,inflammatory cell infiltration,and toluidine blue staining to observe the activation of mast cells;3.Detection of inflammatory factors: To detect the levels of inflammatory factors TNF-α,IL-1β,IFN-γ,IL-13 and IL-33 in the tissues of the ear;4.Detection of mast cell related indicators: detection of IgE level in ear.Experiment 2: Explore the effects of IL-37 on ACD rats in the MAPK and NF-KB signaling pathways1.Inflammatory factor detection: IL-33 stimulates each group of RPMCs,and detects the level of IL-6,TNF-α,IL-13 and MCP-1;2.Mast cell degranulation detection: β-hexosaminidase release and histamine release of RPMCs in each group;3.Detection of MAPK family proteins and NF-κB related proteins: Western Blot was used to detect the protein expression of JNK,ERK,P38 and NF-κB in each group of RPMCs;4.Receptor detection: use qRT-PCR to detect the levels of ST2 and Smad3 in RPMCs.Experiment 3: Explore the combination of IL-37 and Smad3 effect on the ACD rats1.Detection of inflammatory factors: IL-33 stimulated each group of RPMCs,and detected the content of IL-6 and TNF-α in the supernatant;2.Mast cell degranulation test: β-hexosaminidase release test and histamine release test of RPMCs in each group.Results Experiment 1: IL-37 can significantly ameliorate the swelling of the ear in ACD rats.The thickness of the ear is reduced.Histopathology found that the dermal edema of the ears is reduced,the inflammatory cell infiltration is reduced,the thickness of the dermis is reduced,and the number of mast cells The number is reduced.ELISA was used to detect the levels of inflammatory factors,TNF-α,IL-1β,IFN-γ and IL-13 were significantly reduced;IL-33 and IgE levels were reduced,and the expression was proportional to the number of mast cells.Experiment 2: IL-37 can inhibit IL-33-induced RPMCs to secrete IL-6,TNF-α,IL-13,and MCP-1,possibly by inhibiting P38 MAPK and NF-κB signaling pathways to exert anti-inflammatory effects.Experiment 3: IL-37 inhibits the activation of mast cells induced by IL-33 by binding to Smad3,and exerts an anti-inflammatory effect.Conclusion1.IL-37 can ameliorate the inflammatory symptoms of allergic contact dermatitis.2.IL-37 binds to Smad3 to restrain the P38 MAPK and NF-κB signaling pathways to inhibit the inflammation caused by the degranulation of MCs induced by IL-33.