The protactive effects and mechanisms of cx3cr1 antibody on retinal neuron in rats with ischemia reperfusion injury by intravitreal injection

Abstract

Background Study confirmed that the active microglia may injure retinal ganglion cells (RGCs) in retinal ischemia reperfusion injury (IRI), and increased cx3cr1 expression is an important factor in microglial activation, and thus blocking the expression of cx3cr1 can inhibit microglial activation, which may be useful in neuronal protection. Objective This study was to analyze the protective effects of cx3cr1 antibody on retinal neuron in rat eyes with IRI. Methods Ninety SD rats were divided into 4 groups according to random number table.IRI models were established by perfusing normal saline solution into the anterior chamber.The cx3cr1 antibody of 1 μl (0.2 μg/μl) was intravitreally injected in the right eyes in the normal rats or model rats as the only cx3cr1 antibody injected group and the model cx3cr1 antibody injected group, respectively, and no any drug was injected in the rats of the normal control group and model control group.Retinal sections were prepared 48 hours after modeling, and apoptosis of retinal neutron was observed under the transmission electron microscope; the morphology of retinas was exmined and the number of survival RGCs was calculated by histopathologic method.The expression of CD68 in activated retinal microglial cells was detected by immunochemistry, and the relative expression levels of cx3cr1 mRNA, tumor necrosis factor-α (TNF-α) mRNA and interleukin-1β (IL-1β) mRNA in the retinas were assayed by real time quantitative PCR. Results The cell nucleus of RGCs showed the round and ellipse in shape and there were abundant organelles in the cells.The mophology of photoreceptors was normal with abundant mitochondrions.Irregular cell shape, disrupture of outer segment membranous disc, proliferative microglial cells in RGC layer were seen in the model group.However, these findings were mild in the model cx3cr1 antibody group.The mean number of survival RGCs was (38.100±3.929), (37.200±5.266), (26.700±2.584) and (31.700±2.946)/field in the normal control group, only cx3cr1 antibody injected group, model control group and model cx3cr1 antibody injected group, showing significant differences between the model group and the normal control group, only cx3cr1 antibody injected group or model cx3cr1 antibody injected group (t=7.492, 6.125, -4.607, all at P<0.01). The expression levels (absorbance) of CD68 in rat retinas were significantly higher in the model group than those in the normal control group, only cx3cr1 antibody injected group and model cx3cr1 antibody injected group (t=-3.397, P=0.008; t=-6.207, P=0.000; t=3.494, P=0.007). The relative expression levels of cx3cr1 mRNA, TNF-α mRNA and IL-1β mRNA in rat retinas were raised in the model group compared with the only cx3cr1 antibody injected group and model cx3cr1 antibody injected group (all at P<0.01). No significant differences were observed in these indicators between the normal control group and the only cx3cr1 antibody injected group (all at P<0.05). Conclusions Intravitreal injection of cx3cr1 antibody to neutralize cx3cr1 levels in retinas can effectively inhibit the activation of retinal microglia, decrease the release of inflammatory factors, reduce the apoptosis of RGCs and thereby protect the retinal neutrons against IRI in SD rats.Intravitreal injection of cx3cr1 is safe and feasible. Key words: Receptors, CXCR3; Microglia/cytology; Neutralization; Retina/pathology; Reperfusion injury; Tumor necrosis factor-α; Interleukin-1β; Apoptosis; Rats, Sprague-Dawley