Study On The Role Of Adrenergic Receptors In Photoreceptor Death After Experimental Retinal Detachment

Purpose: Photoreceptor death is the major cause of visual loss after retinal detachment(RD).Previous study indicated photoreceptor microenvironmental impairment may be the initiating phase happened after RD and lead to photoreceptor death.Adrenergic receptors have been implicated in neuronal cell survival,and have been considered as the upstream targets for microenvironment recovery and photoreceptor protection against RD.Our study primarily focused on the pathological pattern of photoreceptor microenvironmental impairment within human eyes with RD.Based on the findings from RD patient,we then investigated the protective effects of antagonist of α1-AR and agonist of α2-AR receptors,as well as the signaling events.Methods: 1.Subretinal fluid samples were collected from nine patients with primary rhegmatogenous RD,while the vitreous samples were collected from nine patients with primary RD.The control vitreous samples were collected from patients with idiopathic macular hole or epiretinal membrane.The levels of protein carbonyl content were detected by Elisa.The relative levels of multiple cytokines and chemokines in the vitreous samples and subretinal fluid samples were analyzed using a human cytokine array.2.(1)Experimental RD was created in Brown Norway rats and evaluated.The levels of protein carbonyl content,IL-1β,MCP-1 were detected by Elisa.DHE probe was introduced for in vivo detection of reactive oxygen species(ROS).(2)Elisa detection,TUNEL staining and DHE probe were used to investigate the role of NADPH oxidase-mediated ROS overproduction in inducing photoreceptor death after creation of RD.(3)The anti-oxidative stress and anti-inflammatory effects of α1-AR antagonist doxazosin,and α2-AR agonist guanabenz were tested by Elisa and DHE probe.The neuronal protective effects of doxazosin and guanabenz were evaluated by TUNEL staining,HE staining and electroreinogram.Statistical analyses were performed using One-Way ANOVA or Kruskal Wallis test.P<0.05 was considered to be significantly different.Results: 1.Levels of protein carbonyl content(PCC)in the vitreous and subretinal fluid of RD patients were elevated(P<0.05),accompanied by elevation of IL-18,MCP-1,TNF-α(P<0.01).In addition,cytokines as IL-1β,IL-6,IL-33,VEGF were found to be increased in the subretinal fluid(P<0.01).2.(1)Levels of PCC were elevated in BN rat retina with experimental RD,and peaked at 6 h after creation of RD.The creation of RD also leads to increasing number of DHE positive cells in outer nuclear layer(ONL),and elevation of IL-1β 、 MCP-1(P<0.01).(2)Inhibition of NADPH oxidase by apocynin significantly decreased the level of PCC(P<0.01),attenuated photoreceptor death(P<0.01)and reserved retinal structures(P<0.001).(3)Intraperitoneal injection of doxazosin or guanabenz significantly decreased the level of PCC(P<0.01)and the concentration of IL-1β 、 MCP-1(P<0.05),resulting in attenuation of photoreceptor apoptosis(P<0.01),reservation of retinal structure and retinal function(P<0.05).Conclusion: 1.Activation of oxidative stress and release of various cytokines were the pathological patterns in human eyes with RD.2.(1)Overproduction of ROS and cytokines as IL-1β,MCP-1 were the early-stage events after creation of experimental RD in BN rats.(2)NADPH-mediated overproduction of ROS was involved in photoreceptor apoptosis after creation of experimental RD.(3)Functional alterations of α1-AR or α2-AR were implicated in photoreceptor survival through down regulation of NADPH-mediated overproduction of ROS and less release of pro-inflammatory cytokines.