The Role And Mechanism Of LIGHT In IMQ-induced Mouse Psoriasiform Skin Inflammation

Background Psoriasis is identified as an autoimmune disease which affecting about 2% of world population.The main clinical features include erythema,pruritus and desquamation.There is no an effective therapy for psoriasis.The major treatment of this disease is to neutralize IL-17(Interleukin 17),which is known as the main target of psoriasis.The underlying pathogenesis of psoriasis is still largely unclear.TNF superfamily member 14(TNFSF14),also known as LIGHT(lymphotoxin-like inducible protein that competes with glycoprotein D for herpesvirus entry on T cells).LIGHT has two receptors in mice,HVEM and LTβR(lymphotoxin β-receptor),and in human,there is another receptor Dc R3.As a costimulatory molecule,LIGHT plays important roles in T cell activation,immune inflammation and fibrosis.However,the role of LIGHT in the development of psoriasis keeps unclear.Dendritic cells(DCs)is an immune cell type of innate immune system.DCs’ s function is absorbing,processing and presenting antigens.DCs also has ability of secreting cytokines.In pathological conditions,when DCs mistakenly regarded “self” as “non-self”,auto-immune disease will occur.In recent year studies,psoriasis has been reported to be related with IL-23(Interleukin 23),a cytokine secreted primarily by DCs.Complement system,an important component of innate immune system,can react to antigen stimulation rapidly.In recent studies,when complement fragment C5 a combined with its receptor C5 a R1,DCs’ s function can be influenced in allostimulation.In the present study,by using imiquimod(IMQ)-induced mouse psoriasiform dermatitis models,we mainly focus on the role of LIGHT and the relationship of LIGHT with DCs function and C5a/C5 a R1 pathway during the development of psoriasis.Objective 1.To elucidate the relationship between psoriasis and the expression of LIGHT and LTβR/HVEM.2.To confirm the essential role of LIGHT in IMQ-induced psoriasiform skin inflammation in mice.3.To explore the mechanisms of LIGHT promoting psoriatic skin inflammation.4.To explore the role of C5a/C5 a R1 pathway in IMQ-induced psoriasiform skin inflammation and its relationship with LIGHT.Method 1.The expression of LIGHT and its receptor LTβR/HVEM in IMQ-induced psoriatic skin inflammation in mice.1)Skin samples of psoriasis from IMQ-treated mice was collected,and the expression of LIGHT and LTβR/HVEM was assayed by Immunohistochemistry(IHC)and Western Blot(WB);2)Draining lymph node from IMQ-treated LIGHT+/+ mice at day 0,3,6 were collected and lymphocytes were isolated.The expression of LTβR/HVEM on lymphocytes was examined by Flow cytometry(FCM).2.The role of LIGHT in the development of psoriasiform skin inflammation in mice.1)Skin inflammation was evaluated by PASI(psoriasis area and severity index)in IMQ-treated LIGHT+/+ and LIGHT-/-mice;2)Skin samples of LIGHT+/+ and LIGHT-/-mice were stained by hematoxylin-eosin(H&E)to evaluate proliferation degree;3)Immune cells infiltration in skin and draining lymph nodes of IMQ-treated LIGHT+/+ and LIGHT-/-mice were measured by FCM,and the expression of cytokines was examined by Immunofluorescence(IF);3.The mechanisms of LIGHT in promting IMQ-induced mouse psoriatic skin inflammation.1)The percentage and function of DCs from draining lymph node of IMQ-treated LIGHT+/+ and LIGHT-/-mice were examined by FCM;DCs inflitration in skin samples of LIGHT+/+ and LIGHT-/-mice was assayed by IF using anti-CD11 c antibody;2)BMDCs of LIGHT+/+ and LIGHT-/-mice were stimulated by IMQ and cells were tested by FCM.4.The role of C5a/C5 a R1 pathway in IMQ-induced mouse psoriasiform skin inflammation.1)Skin samples were collected from IMQ-treated mice,and C5 a R expression was measured by IHC;2)Skin inflammation in C5 a R1+/+ and C5 a R1-/-mice was evaluated by PASI;proliferation degree was assayed by H&E staining;3)To explore the relationship of LIGHT with C5a/C5 a R1,psoriatic skin samples collected from IMQ-treated LIGHT+/+ and LIGHT-/-mice were measured by IHC using the anti-C5 a R1 antibody.Results 1.Increased expression of LIGHT and its receptor HVEM in IMQ-induced psoriasiform skin in mice.Compared with that in skin sample from Vaseline-treated mice,the expression of LIGHT and its receptor HVEM was significantly increased in skin samples from IMQ-treated mice.2.LIGHT deficiency decreased the IMQ-induced psoriatic skin inflammation.1)Compared with LIGHT+/+ mice,skin proliferation degree and PASI scores were significantly decreased in LIGHT-/-mice;2)Compared with LIGHT+/+ mice,the expression of IL-17 and TNF-α,the percenatge of IFN-γ secreting CD3+ T cells and IL-17 secreting γδT cells were decreased,while the Tregs percentage was increased in LIGHT-/-mice;3.LIGHT deficiency impaired DCs functions in IMQ-induced psoriatic mice.1)LIGHT deficiency significantly attenuated DCs infiltration;2)LIGHT deficiency remarkably reduced the expression of CD80,CD86 and MHC-Ⅱ on DCs in psoriatic mice and on IMQ-treated BMDCs;3)LIGHT deficiency impaired IL-23 secretion of IMQ-stimulated.BMDCs.4.C5 a R1 deficiency decreased the skin inflammation and was influenced by LIGHT during IMQ-induced mouse psoriasis development.1)Compared with skin sample from Vaseline-treated mice,the expression of C5 a R1 in skin samples from IMQ-treated mice was significantly increased;2)Compared to C5 a R1+/+ mice,skin proliferation,the percentage of p DCs and PASI scores were significantly decreased in IMQ-treated C5 a R1-/-mice;3)LIGHT deficiency significantly attenuated C5 a R1 expression in skin sample of IMQ-treated mice.Conclusion 1.LIGHT-HVEM interaction plays a critical role in the development of IMQ-induced mouse psoriasiform skin inflammation;2.LIGHT mediates IMQ-induced mouse psoriasiform skin inflammation by promoting DCs functions;3.LIGHT is involved in C5a/C5 a R1-mediated mouse psoriasiform skin inflammation.