Retinal ischemia-reperfusion injury and pretreatment with Lycium barbarum glycopeptide

AIM:To investigate the antioxidant protective effect of Lycium barbarum glycopeptide(LbGP)pretreatment on retinal ischemia-reperfusion(I/R)injury(RIRI)in rats.METHODS:RIRI was induced in Sprague Dawley rats through anterior chamber perfusion,and pretreatment involved administering LbGP via gavage for 7d.After 24h of reperfusion,serum alanine aminotransferase(ALT),aspartate aminotransferase(AST),and creatinine(CREA)levels,retinal structure,expression of Caspase-3 and Caspase-8,superoxide dismutase(SOD)activity,and malondialdehyde(MDA)in the retina were measured.RESULTS:The pretreatment with LbGP effectively protected the retina and retinal tissue from edema and inflammation in the ganglion cell layer(GCL)and nerve fiber layer(NFL)of rats subjected to RIRI,as shown by light microscopy and optical coherence tomography(OCT).Serum AST was higher in the model group than in the blank group(P=0.042),but no difference was found in ALT,AST,and CREA across the LbGP groups and model group.Caspase-3 expression was higher in the model group than in the blank group(P=0.006),but no difference was found among LbGP groups and the model group.Caspase-8 expression was higher in the model group than in the blank group(P=0.000),and lower in the 400 mg/kg LbGP group than in the model group(P=0.016).SOD activity was lower in the model group than in the blank group(P=0.001),and the decrease was slower in the 400 mg/kg LbGP group than in the model group(P=0.003).MDA content was higher in the model group than in the blank group(P=0.001),and lower in the 400 mg/kg LbGP group than in the model group(P=0.016).The pretreatment with LbGP did not result in any observed liver or renal toxicity in the model.CONCLUSION:LbGP pretreatment exhibits dosedependent anti-inflammatory,and antioxidative effects by reducing Caspase-8 expression,preventing declines of SOD activity,and decreasing MDA content in the RIRI rat model.

Network pharmacology investigation of the mechanism underlying the therapeutic action of Shikang granules in retinal ischemia-reperfusion injuries

Background:Retinal ischemia/reperfusion(I/R)injury often results in vision loss,and effective clinical management options are currently lacking.Shikang granules(SKG)are traditional Chinese medicine-based preparations commonly used in clinical practice for treating optic atrophy.Methods:Despite decades of clinical use,the precise mechanism of action(MoA)of SKG remains elusive.Here,we employ a network pharmacological approach to elucidate its MoA by identifying active ingredients and relevant targets using the Traditional Chinese Medicine System Pharmacology Database and Analytical Platform.Targets associated with retinal I/R injury were sourced from GeneCards,Online Mendelian Inheritance in Man,and DisGeNET.Venny software facilitated the identification of intersecting targets,which were then subjected to gene ontology functional analysis and Kyoto Encyclopedia of Genes and Genomes pathway analysis.To validate the protective effect and explore the MoA of SKG in retinal I/R injuries,we conducted experiments using rat models.Results:Our animal experiments demonstrated that SKG mitigated apoptosis following retinal I/R injury by upregulating the expression of the anti-apoptotic protein Bcl-2 and downregulating the expression of BAX,Caspase-9,Caspase-3,PARP,and cytochrome C.Additionally,SKG was found to increase the expression of PI3K and AKT.Conclusions:SKG may exert its protective effects by inhibiting apoptosis through modulation of pro-apoptotic and anti-apoptotic protein expression,as well as activation of the PI3K/AKT pathway.

Houttuynia cordata Thunb rescues retinal ganglion cells through inhibiting microglia activation in a rat model of retinal ischemia-reperfusion

AIM:To determine whether Houttuynia cordata Thunb(HCT)can increase the survival of the retinal ganglion cells(RGCs)and inhibit microglia activation following retinal ischemia-reperfusion(RIR)injury.METHODS:Rat model of RIR was induced by transient elevation of the intraocular pressure(IOP).HCT was orally administered for 2 d before the performance of retinal RIR model and once a day for the next 14 d.After 14 d of RIR injury,the rats were sacrificed for further analysis.Survival RGCs were stained with haematoxylin and eosin(H&E).Apoptosis of RGCs was detected by TUNEL staining.Retinal function was examined by flash-electroretinography(F-ERG).Retinal microglia were labeled using Iba-1,one specific marker for microglia.The m RNA expression levels of inducible nitric oxide synthase(i NOS),tumor necrosis factor alpha(TNF-α),and interleukin 1 beta(IL-1β)were assessed by quantitative real time reverse transcription polymerase chain reaction(q RT-PCR).RESULTS:Systemic HCT treatment significantly reduced RGCs death by H&E staining and exhibited an anti-apoptotic effect as assessed by TUNEL staining at day 14 after RIR injury.HCT greatly improved the retinal function as examined by F-ERG.The number of activated microglia significantly increased after RIR injury,which was significantly attenuated by HCT treatment.Besides,RIR injury induced a strong upregulation of pro-inflammatory genes TNF-α,i NOS and IL-1βm RNAs at day 14 post injury,which was suppressed by HCT.CONCLUSION:Neuroprotective effects of HCT encourage the survival of RGCs through inhibiting microglia activation due to RIR injury.Together these results support the use of HCT as promising therapy for the ischemic events of the retina diseases.

Interleukin-4 promotes microglial polarization toward a neuroprotective phenotype after retinal ischemia/reperfusion injury

Glaucoma results from irreversible loss of retinal ganglion cells(RGCs)through an unclear mechanism.Microglial polarization and neuroinflammation play an important role in retinal degeneration.Our study aimed to explore the function of microglial polarization during glaucoma progression and identify a strategy to alleviate retinal neuroinflammation.Retinal ischemia/reperfusion injury was induced in C57BL/6 mice.In a separate cohort of animals,interleukin(IL)-4(50 ng/mL,2μL per injection)or vehicle was intravitreally injected after retinal ischemia/reperfusion injury.RGC loss was assessed by counting cells that were positive for the RGC marker RNA binding protein,mRNA processing factor in retinal flat mounts.The expression of classically activated(M1)and alternatively activated(M2)microglial markers were assessed by quantitative reverse transcription-polymerase chain reaction,immunofluorescence,and western blotting.The results showed that progressive RGC loss was accompanied by a continuous decrease in M2 microglia during the late phase of the 28-day period after retinal ischemia/reperfusion injury.IL-4 was undetectable in the retina at all time points,and intravitreal IL-4 administration markedly improved M2 microglial marker expression and ameliorated RGC loss in the late phase post-retinal ischemia/reperfusion injury.In summary,we observed that IL-4 treatment maintained a high number of M2 microglia after RIR and promoted RGC survival.

Involvement of moesin phosphorylation in ischemia/reperfusion induced inner blood-retinal barrier dysfunction

AIM: To investigate the role of moesin and its underlying signal transduction in retinal vascular damage induced by retinal ischemia-reperfusion(RIR) insult.METHODS: C57 BL/6 mice were subjected to continued ischemia for 45 min, followed by blood reperfusion. The expression and phosphorylation of moesin in retinal vessels were detected by immunohistochemistry and Western blotting. The inner blood-retinal barrier was evaluated using FITCdextran leakage assay on whole-mount retina. Further studies were conducted to explore the effects of p38 mitogen-activated protein kinase(MAPK) pathway on the involvement of moesin in RIR-evoked retinal vascular hyperpermeability response. RESULTS: It revealed that RIR induced moesin phosphorylation in a time-dependent manner after reperfusion. The phosphorylation of moesin was alleviated by inhibitions of p38 MAPK, while this treatment also ameliorated the dysfunction of inner blood-retinal barrier. CONCLUSION: The results suggest that moesin is involved in RIR-evoked retinal vascular endothelial dysfunction and the phosphorylation of moesin is triggered via p38 MAPK activation.

MSC移植对视网膜缺血—再灌注损伤后神经节细胞中HIF-1α及Caspase-3表达的影响

目的探讨间充质干细胞(mesenchymal stem cells,MSC)移植对视网膜缺血-再灌注损伤低氧诱导因子-1α(hypoxia inducible factor-1α,HIF-1α)及Caspase-3表达及神经节细胞凋亡的影响,为MSC移植治疗视网膜缺血-再灌注损伤提供实验依据。方法将65只健康SD大鼠随机分为3组:正常组5只、模型组30只、MSC移植组30只,各组均将左眼作为实验眼制作视网膜缺血-再灌注损伤模型。贴壁筛选法体外培养SD大鼠MSC,模型组于缺血-再灌注1h予以玻璃体内注射PBS缓冲液,MSC移植组于缺血-再灌注后1h予以玻璃体腔注射MSC。各组SD大鼠分别于缺血-再灌注损伤后1h、6h、12h、24h、48h及72h处死,并立即摘除左眼眼球,固定包埋并切片,免疫组织化学法检测各组SD大鼠视网膜缺血-再灌注后HIF-1α及Caspase-3的表达情况。结果正常组未检测到HIF-1α及Caspase-3有表达,在视网膜缺血-再灌注后1h、6h、12h、24h、48h及72h模型组HIF-1α的表达分别为0.620±0.025、1.889±0.099、7.591±0.359、4.756±0.156、2.564±0.164、1.023±0.144;MSC移植组分别为0.222±0.058、0.774±0.162、1.831±0.124、1.567±0.059、0.930±0.010、0.583±0.065。模型组Caspase-3表达分别为0.106±0.093、0.593±0.083、1.760±0.087、3.855±0.142、2.429±0.070、1.329±0.080;MSC移植组分别为0.028±0.004、0.180±0.032、0.887±0.0075、1.857±0.050、1.554±0.079、0.957±0.087。与模型组相比,MSC移植组HIF-1α及Caspase-3的表达明显减少,差异均有统计学意义(均为P<0.05)。结论视网膜缺血-再灌注损伤后行MSC玻璃体内注射可抑制神经节细胞HIF-1α及Caspase-3的表达,减少神经节细胞的凋亡,对视网膜缺血-再灌注损伤有一定的保护作用。