Changes In Antigen Presenting Function Of Microglial Cell Influence Cell Apoptosis In Cultured Rat Retinal Tissue

Microglial Cell,which has been demonstrated to play essential roles in the initiation and development of neural degeneration and apoptosis in many neuronal disorders,is one member of several neuroglial cells in central nervous system(CNS).Besides the common features shared by neuroglial cells,microglial cell is the first protection for CNS against the invasion of pathogens and is also regarded as the most representative immunological cell in CNS.Antigen presenting function is one of microlial cell's immune functions. CNS extends into the eyeball and differentiates into retina which also contains microglial cells.It has been demonstrated that microglial cell is closely related with the initiation and development of various retinal diseases,in which diabetic retinopathy(DR) is one of the commonest diseases that may ultimately lead to world wide legal blindness. According to the present evidences,the major mechanisms of microglial cells causing DR lie in the injury of retinal ganglion cells(RGCs) and of blood-retinal barrier(BRB). Given the immunologic features and intimate link with DR,it is postulated that changes of the immunological function of microglial cells is one of the possible mechanisms that result in RGCs injury in DR.In this study,we investigate how the change in antigen presenting function of microglial cell influences cell apoptosis in cultured retinal tissue in microglia-retina co-culture system.Objectives:To investigate the expresstion of major histocompability complexâ…¡(MHC-â…¡) and co-stimulatory molecule B7.1/CD80 on microglial cell after being stimulated by T cell factor interleukin(IL) 4 or by advanced glycation end products(AGEs).To further discuss the relationship between the change in antigen presenting function of microglial cells and cell apoptosis in cultured rat retinal tissue.Methods:Microglial cells were acquired from the mixed culture system of the newborn SD rat pups retinas,and were seeded into sterilized Petri dishes in certain densities according to various molecular biological methods.Diluted with culture medium,IL-4 or AGEs of different concentrations were added in to the Petri dishes as treating sample,with pure culture medium in the dishes as control counterparts.After 24 hours incubation,the media were removed. Some dishes of treated microglial cells were harvested for MHC-â…¡and CD80 analysis by means of immunocytochemistry or Western Blot,while others were filled with some culture medium and were placed in the incubator for followed co-culture use.Adult male SD rats weighed 200g to 250g were anesthetized and eye enucleated.Each retina was carefully isolated from other parts of the eyeball and was co-cultured for hours in Petri dishes containing microglial cells that had been treated with IL-4 or AGEs.24 hours later the retinas were fixated and dehydrated,and then were made into frozen sections for TUNEL analysis.Results:Compared with control group,IL-4 up-regulated the expression MHC-â…¡and CD80,while AGEs down regulated both.On protein level,Western Blot analysis demonstrated that IL-4 increased MHC-â…¡protein quantity,contrast to AGEs group.However,the expression of CD80 protein quantity-which markedly decreased in AGEs group-in IL-4 group has no significant difference with that in control group.IL-4 stimulation made microglial cells decrease the quantity of apoptotic cells in retinal tissue,indicating protective merit,while AGEs stimulation just did the opposite.Conclusion:The property of microglial behaviors depend on the local microenvironment. Appropriate regulation by T cell factor IL-4 may up-regulate the antigen presenting function of microglial cells,which is furtherly induced to be protective.One the other hand,the classic pathogenic factors of diabetes-AGEs-inhibits antigen presenting function of microglial cells and renders them harmful features.