The Protective Effect And Immunosuppressive Mechanism Of Fingomolid(FTY720) In Light-induced Retinal Degeneration(LIRD) In Rats

Background: Recently,with the wide application of various electronic optical equipments and microscopes,light-induced retinal damage(LIRD)has been a threat to visual function of people.If the retina is stimulated by extense or long time of light exposure,it may cause irreversible vision damage,or even blindness.However,the mechanism and treatment of LIRD are still unclear.And,the latest findings indicated that immune reaction is involved in the process of LIRD.Fingomolid(FTY720),a wellknown immunosuppressive agent,derived from Cordyceps sinensis,was found to be able to treat relapsing multiple sclerosis and prevent organ rejection.FTY720 can avoid lymphocytes emigrate from secondary lymphoid organs,reduce the immune cells in peripheral blood and the potential tissue damage.Objectives: Based on the study on the mechanism of LIRD and protective effect of FTY720,the objectives of the experiment include: 1.estabilishment of an experimental model of LIRD in rats;2.investigation of the CD3~+,CD4~+ and CD8~+ T cells on retina in LIRD;3.observing the protective effect of FTY720 on retinal structure and function in LIRD;4.if immune response is involved in the LIRD,exploring whether FTY720 can block the apoptosis of retinal cells and protect the retina by immunosuppressive mechanism.Materials and methods: Sprague-Dawley(SD)rats were classified into four groups: non-light damaged group(NLD),the light damaged group(LD),FTY720 group and the vehicle group.All rats were raised in dim cycle light after birth.The LD rats were subjected to intensive light(2700Lux)damage for 6 hours.The FTY720 rats were injected with 10mg/kg of FTY720 before light damage.At 1,3,5,7 days after light exposure,the eyes were harvested for immunohistochemistry to observe the CD3~+CD4~+ and CD3~+CD8~+ T cells on retina.Western Blotting was used to test the expression of CD3~+,CD4~+ and CD8~+ protein on retina.TUNEL staining was applied to detect the apoptosis cells in the outer nuclear layer(ONL)of retina.On the seventh day after light exposure,flash-electroretinograms(F-ERG)were performed to examine the function of retina,the retina was sliced for HE staining and pathology examination,and the number of the layers of ONL were counted.Results: 1.In the LD group,there was significant damage of retina with the reduction of the number of the layers of ONL.The amplitude of a-wave,b-wave and Ops-wave of F-ERGs were decreased(P<0.001).2.In the LD group,CD3~+CD4~+ and CD3~+CD8~+ T cells on retina were found with the increased expression of CD3~+ and CD4~+ protein.The apoptosis cells were also detected on ONL.3.In the FTY720 group,the number of the layers of ONL,the amplitude of a-wave,b-wave and Ops-wave of FERGs were higher than LD group significantly(P<0.001),and no CD3~+CD4~+ and CD3~+CD8~+ T cells were found in the retina.And compared with the LD group,the expression of CD3~+ and CD4~+ on retina was decreased.No apoptosis cells were observed in ONL.Conclusion: 1.In the light induced retina damage model,light stimulation can activate the immune response in retina,causes the infiltration of CD3~+CD4~+ and CD3~+CD8~+ T cells in retina,the apoptosis and reduction of retinal photoreceptor cells(RPC),leading to the retinal structure damage and function damage or loss.2.FTY720 can effective protect the retinal structure and function from light damage.3.The immune reposne in the retina and the apotpsis of RPC are inhibited by FTY720 in the retina of LIRD.