The Effect Of A_2A Rantagonist On Microglial Activation In Experimental Glaucoma

Background:Glaucoma i s t he f irst l eading cause of ir reversible vi sion l oss in t he world.Glaucoma-related visual function damage has a negative impact on the quality of patients'life and contributes to significant costs both for individual and society.It is generally agreed that intolerant elevated intraocular pressure is t he main risk factor for glaucomatous optic neuropathy.Elevated intraocular pressure leads to the obstruction o f a xoplasmic flow o f the retinal ganglion cells?RGCs?and/or the ischemia of optic nerve,both of which subsequently causing the apoptosis or the death o f R GCs.However,it is a ccepted by s ome r esearchers t hat glaucoma is a neurodegerative disease in which neuroinflammation is involved.Microglia and it's inflammatory mediators are important component of neuroinflammation.Recent studies r evealed that p harmacological b lockade o r genetic inactivation o f adenosine A_2A receptor(A_2AR)affords a robust neuroprotection in central nervous system.It is unknown w hether A_2AR a ntagonist w ould exert neuroprotection o n RGCs in glaucoma by the control of microglia-driven neuroinlammation.Projection:This project plans to find out the effect of A_2AR antagonist on microglia and RGCs under chronic ocular hypertension and explore the relationship between microglia and RGCs by means of in vitro and in vivo experiments.Methods:Chronic ocular hypertension model was induced in one eye of Male Sprague Dawley rats by ligation of three episcleral veins.The survival of retinal RGCs and the activiation o f microglia under chronic oc ular hypertension w ithout or with the int ravitreous inj ection of A_2AR a ntagonist--zm241385 were assessed by fluorescent labeling,Realtime-PCR and Western blot.ELISA was e mployed t o measure the secretion of inflammatory m ediators by mic roglia when glutamate and/or zm241385 was added into the culture system.Results:The density of RGCs decreased and the microglia changed their rafiemidmorphology to an spheroidal/amoeboid form w ith retraction of t heir processes under chronic oc ular hypertension during w hich t he expression o f t umor necrosis factor-??TNF-??and interleukin-1??IL-1??in whole retina also increased.The decrease of RGCs density in central retina and the increase of TNF-?and IL-1?expression w ere ameliorated with i njection of z m241385 i nto t he vi treous.T he up-regulated secretion o f t heses pr o-inflammatory cytokines by microglia in vitro under high c oncentration o f glutamate was do wn-regulated when zm241385 was added into the culture system.Conclusions:A_2AR antagonist--zm241385 is protective for RGCs located in the central area of retina and has a negative effct on retinal neuroinflammation under chronic ocular hy pertension;z m241385 alleviated the activiation of microglia stimulated by high concentration of glutamate.The downregulation of microglia-driven neuroinlammation in r etina by zm241385 under high concentration of gl utamate may be one of the mechanisms that protected RGCs in experimental glaucoma.