Protective effects of antithrombin III on retinal ischemia/reperfusion injury in rats: a histopathologic study

PURPOSE: To investigate the effect of antithrombin III (AT III) on retinal ischemia/reperfusion (I/R) injury in rats. METHODS: The study was carried out on 10 Wistar albino rats (20 eyes) and four-vessel occlusion method was employed to induce retinal ischemia in this study. Rats were divided into two groups: Group I (control group, 10 eyes) and Group II (AT III, 10 eyes). In both groups, vertebral arteries were occluded bilaterally an electric needle coagulator under an operating microscope. A total of 48 hours after the initial procedure, the rats were re-anesthetized and both common carotid arteries were clamped to interrupt blood flow. In Group II, rats were injected intravenously with 250 U/kg of AT III 5 minutes before the induction of ischemia. Duration of ischemia was 30 minutes. At the end of this period, clamp was removed for the reperfusion of the eye for 4 hours. Following the reperfusion period, the animals were killed by decapitation. Retinal sections were evaluated under light and electron microscope. The signs of I/R injury at the microscopic level, i.e., cellular degeneration, vacuolization between retinal layers, increase in the retinal thickness due to edema, mononuclear cell infiltration, and apoptotic cells, were recorded for each group. RESULTS: Retinal sections obtained from the rats in the AT III group revealed a well preserved retinal structure. When average thickness values of the two groups were compared to each other, the difference was significant with respect to inner nuclear and inner plexiform layers indicating increased retinal thickness values in Group I due to tissue edema resulting from I/R injury. Similarly, mononuclear cell infiltration and apoptotic cell counts were found to be significantly higher in control group compared to AT III group showing the inhibitory effect of AT III on leukocyte infiltration and apoptotic cell death in rat retina. CONCLUSIONS: Antithrombin III attenuated I/R injury in rat retina.     

Diosmin protects rat retina from ischemia/reperfusion injury

Abstract Objective: Diosmin, a natural flavone glycoside, possesses antioxidant activity and has been used to alleviate ischemia/reperfusion (I/R) injury. The aim of this study was to clarify whether the administration of diosmin has a protective effect against I/R injury induced using the high intraocular pressure (IOP) model in rat retina, and to determine the possible antioxidant mechanisms involved. Methods: Retinal I/R injury was induced in the rats by elevating the IOP to 110?mmHg for 60?min. Diosmin (100?mg/kg) or vehicle solution was administered intragastrically 30?min before the onset of ischemia and then daily after I/R injury until the animals were sacrificed. The levels of malondialdehyde (MDA) and the activities of total-superoxide dismutase (T-SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) in the retinal tissues were determined 24?h after I/R injury. At 7 days post-I/R injury, electroretinograms (ERGs) were recorded, and the density of surviving retinal ganglion cells (RGCs) was estimated by counting retrograde tracer-labeled cells in whole-mounted retinas. Retinal histological changes were also examined and quantified using light microscopy. Results: Diosmin significantly decreased the MDA levels and increased the activities of T-SOD, GSH-Px, and CAT in the retina of rats compared with the ischemia group (P<0.05), and suppressed the I/R-induced reduction in the a- and b-wave amplitudes of the ERG (P<0.05). The thickness of the entire retina, inner nuclear layer, inner plexiform layer, and outer retinal layer and the number of cells in the ganglion cell layer were significantly less after I/R injury (P<0.05), and diosmin remarkably ameliorated these changes on retinal morphology. Diosmin also attenuated the I/R-induced loss of RGCs of the rat retina (P<0.05). Conclusion: Diosmin protected the retina from I/R injury, possibly via a mechanism involving the regulation of oxidative parameters.     

Aprotinin reduces ischemia-reperfusion injury in the retina of guinea pigs

PURPOSE: The aim of this study was investigate the role of aprotinin on retinal lipid peroxidation and histopathological changes during ischemia/reperfusion (I/R) of guinea pigs. METHODS: Three groups of seven pigmented guinea pigs each were formed: a control (group 1), ischemia/saline (group 2) and ischemia/aprotinin (group 3). One eye of each animal was selected for histopathological evaluation and the other for biochemical assay. Bilateral pressure-induced retinal ischemia was instigated for 90 min and was followed by 24 hours of reperfusion. Animals in the ischemia/aprotinin and ischemia/saline groups received either 20,000 KIU/kg of aprotinin or saline, repeated four times at 6-hour intervals, with the first dose administered 5 min prior to the ischemic insult. The animals were killed at 24 hours of reperfusion. Retinal malondialdehyde (MDA) levels and the thickness of the inner plexiform layers were measured. RESULTS: The level of MDA in group 1 was significantly (p<0.001) lower than the other groups. The mean MDA level in group 2 was significantly (p<0.01) higher than in group 3. The inner plexiform layer in group 1 was significantly (p<0.001) thinner than in the other groups. The mean thickness of the inner plexiform layer in group 2 was significantly (p<0.01) higher than in group 3. CONCLUSIONS: These data indicate that intraperitoneally administrated aprotinin has a protective effect against I/R injury in the retina of guinea pig as evidenced by reduced retinal MDA level and retinal thickness.     

Effects of melatonin,vitamin E and octreotide on lipid peroxidation during ischemia-reperfusion in the guinea pig retina

PURPOSE: The purpose of this study is to provide evidence that free radical damage is a component of retinal ischemia-reperfusion (I/R) injury, and to determine whether melatonin, vitamin E and octreotide can protect the retina from this injury. METHODS: The right eyes of 50 male guinea pigs weighing 500-600 g were used. The animals were randomly assigned to group 1 (control), group 2 (I/R), group 3 (melatonin + I/R), group 4 (vitamin E + I/R) and group 5 (octreotide + I/R). Groups 3, 4 and 5 received four subcutaneous injections with a 6-h interval for a total daily dose of 10 mg/kg melatonin, 150 mg/kg vitamin E and 22 microg/kg octreotide. The first dose of each substance was administered 5 minutes before retinal ischemia, which was induced for 1.5 hours, followed by reperfusion for 24 hours. All three substances were repeated for 6, 12 and 18 hours during reperfusion. The animals were killed at 24 hours of reperfusion. Retinas were isolated and processed for the quantification of malondialdehyde (MDA). RESULTS: The compounds had the following relationships: melatonin more than vitamin E more than octreotide in preventing retinal damage by ischemia-reperfusion. All three gave significantprotection against the formation of MDA (10.4+/-2.3, 12.4+/-2.4, 13.9+/-1.5 nmol/100 mg tissue wet weight, respectively) compared to the control (3.7+/-1.3 nmol/100 mg tissue wet weight) and I/R groups (22.7+/-6.2 nmol/100 mg tissue wet weight). CONCLUSIONS: This study demonstrates the inhibitory effect of melatonin, vitamin E and octreotide on MDA levels during retinal ischemia-reperfusion injury.     

大鼠视网膜缺血再灌注损伤后脑源性神经生长因子对细胞凋亡及caspase-2和caspase-3表达的影响

目的:探讨caspase-2和caspase-3在大鼠视网膜缺血再灌注损伤中的表达与细胞凋亡的关系及脑源性神经生长因子对其的影响及对视网膜的保护作用。方法:实验于2007-02/2007-07在青岛大学医学院附属医院中心实验室完成。前房加压法制作大鼠视网膜缺血再灌注损伤模型,28只大鼠随机分为正常组和手术组,其中手术组大鼠左眼为缺血再灌注组,右眼为治疗组(BDNF玻璃体腔注射),手术组又按照再灌注后不同时间段分为1,6,12,24,48,72h组。光学显微镜观察并计数视网膜神经节细胞的数量。应用末端脱氧核苷酸转移酶介导的脱氧尿苷三磷酸缺口末端标记法(TUNEL)检测视网膜神经节细胞凋亡、免疫组织化学法(SABC)和酶联免疫吸附实验(ELISA)检测视网膜组织中caspase-2和caspase-3的表达情况。结果:正常视网膜未见凋亡细胞表达,缺血后6～24h可见大量凋亡细胞表达,48h开始下降。凋亡细胞在缺血后24h达到高峰,caspase-2缺血6h后逐渐增加,24h达高峰,然后在48至72h下降。caspase-3表达改变与caspase-2改变基本一致。BDNF治疗组各观察指标表达变化规律与缺血组基本一致,但能明显抑制凋亡细胞的表达,同时使caspase-2和caspase-3的表达降低。结论:视网膜缺血再灌注损伤诱导了神经节细胞的凋亡;BDNF可抑制caspase-2和caspase-3的表达,减少神经节细胞凋亡,对视网膜缺血再灌注损伤有治疗作用。     

The protective effects of melatonin,vitamin E and octreotide on retinal edema during ischemia-reperfusion in the guinea pig retina

PURPOSE: The purpose of this study is to provide evidence that free radical damage is a component of retinal ischemia-reperfusion (I/R) injury, and to determine whether melatonin, vitamin E and octreotide can protect retina from this injury. METHODS: The right eyes of 50 male guinea pigs weighing 500-600 g were used. The animals were randomly assigned to group 1 (control), group 2 (I/R), group 3 (melatonin + I/R), group 4 (vitamin E + I/R) and group 5 (octreotide + I/R). Groups 3, 4 and 5 received four subcutaneous injections at six-hour intervals for total dosage of 10 mg/kg melatonin, 150 mg/kg vitamin E and 22 microg/kg octreotide respectively. The first dose of each substance was administered 5 minutes before retinal ischemia. Retinal ischemia was induced for 1.5 hours, then followed by reperfusion for 24 hours. Infections of all three substances were repeated at 6, 12 and 18 hours during reperfusion. The animals were killed at 24 hours of reperfusion. Sagittal sections of 4 microm were cut and stained with hematoxylin and eosin for light microscopic evaluation. The average thickness (edema) of the inner plexiform layer for each eye was measured in sagittal sections near the optic nerve and expressed in microns. RESULTS: The efficacy of each compound had the following relationships: melatonin>vitamin E>octreotide in preventing retinal damage by ischemia-reperfusion. The mean thickness of the inner plexiform layer was 13.3 +/- 0.8 microm, 25.9 +/- 2. 0 microm, 20.0 +/- 0. 7 microm, 21.6 +/- 0.7 microm, 23.9 +/- 0.8 microm respectively in the control, I/R, I/R plus melatonin, I/R plus vitamin E and I/R plus octreotide groups. The thickness of the inner plexiform layer in group 1 (control) was significantly less than the other groups (p<0.001). The inner plexiform layer was thicker in the I/R group than with I/R plus melatonin, I/R plus vitamin E and I/R plus octreotide (all p < 0.01). The inner plexiform layer was thicker in the I/R plus octreotide group than the I/R plus vitamin E and I.R plus melatonin groups both (p < 0.05). Compared to the I/R plus melatonin group, the inner plexiform layer was significantly thicker in the I/R plus vitamin E group (p < 0. 05). CONCLUSIONS: This study demonstrates a protective effect of melatonin, vitamin E and octreotide on the retina during retinal ischemia-reperfusion injury.     

Fas/FasL系统在大鼠视网膜缺血再灌注凋亡损伤中的作用及bFGF的影响

目的：探讨Fas／FasL在大鼠视网膜缺血再灌注损伤中的表达与细胞凋亡的关系及碱性成纤维细胞生长因子(basic fibroblast growth Factor,bFGF)的影响。方法：前房加压法制作大鼠视网膜缺血再灌注损伤模型，28只大鼠随机分为正常组和手术组，其中手术组大鼠左眼为缺血再灌注组，右眼为治疗组，手术组又按照再灌注后不同时间段分为1，6，12，24，48，72h组。应用末端脱氧核酸转移酶介导的脱氧三磷酸尿苷缺口末端标记法检测视网膜神经细胞凋亡指数(apoptosis index，AI)，免疫组织化学法检测视网膜组织中Fas，FasL的表达。结果：视网膜神经细胞的凋亡出现于再灌注后6h，并逐渐递增，24h达到高峰，48h开始下降，72h组不明显。Fas，FasL表达改变与凋亡的神经细胞改变基本一致。bFGF治疗组各观察指标表达变化规律与缺血组基本一致，但AI值在12，24，48h组明显低于缺血组(P＜0．05)；Fas表达在6，12，24h组较缺血组显下降(P＜0．05)；FasL表达在12，24，48h组较缺血组明显下降(P＜0．05)。结论：Fas／FasL死亡诱导系统参与视网膜缺血再灌注损伤，导致神经节细胞的凋亡；bFGF可抑制Fas、FasL的表达，减少神经节细胞凋亡，对视网膜缺血再灌注损伤有治疗作用。     

The effect of thalidomide on vascular endothelial growth factor and tumor necrosis factor-α levels in retinal ischemia/reperfusion injury

Background To evaluate the effects of thalidomide treatment on the temporal course of TNF-α, VEGF production and the histopathological changes in ischemia/reperfusion (I/R) injured guinea pigs retina. Methods Control, ischemia, and thalidomide/ischemia groups including seven animals each were formed. Retinal ischemia was induced in male guinea pigs by cannulating anterior chambers and lifting the bottle to a height of 205 cm for 90 min in the ischemia and thalidomide/ischemia groups. The thalidomide/ischemia group received thalidomide (300 mg/kg/day) via nasogastric tube 24 h before ischemia and during 7 days of reperfusion. Guinea pigs were sacrificed for histopathological examination to evaluate the mean thickness of the inner plexiform layer (IPL), polymorphonuclear leukocyte (PMNL) infiltration, and biochemical analysis of retinal VEGF and TNF-α levels by ELISA. Results The mean retinal VEGF and TNF-α levels of the control, ischemia, and thalidomide/ischemia groups were 10.22 ± 2.58 and 270.41 ± 69.77 pg/ml; 35.80 ± 5.97 and 629.93 ± 146.41 pg/ml; 19.01 ± 3.01 and 340.93 ± 158.26 pg/ml, respectively. The retinal VEGF levels were significantly higher in I/R injured groups. The thalidomide/ischemia group retinal VEGF level was significantly lower versus the ischemia group. The retinal TNF-α levels were significantly elevated in the ischemia group, but no difference was observed between the thalidomide/ischemia and control groups. Also, the retinal TNF-α level was significantly lower in the thalidomide/ischemia group versus the ischemia group. The mean thickness of IPL and PMNL infiltration showed no difference between the control and thalidomide/ischemia groups. However, there was a significant difference between the control and ischemia groups. Conclusion Thalidomide treatment decreases PMNL infiltration, retinal edema, VEGF, and TNF-α synthesis following I/R injury to the guinea pig retina. This study supported by Firot University Research Fund.     

Protective Effects of Vitamin E Forms (Alpha-tocopherol, Gamma-tocopherol and d-alpha-tocopherol Polyethylene Glycol 1000 Succinate) on Retinal Edema During Ischemia–reperfusion Injury in the Guinea Pig Retina

Purpose: The purpose of this study is to provide evidence that free radical damage is a component of retinal ischemia–reperfusion (I/R) injury, and to determine whether alpha-tocopherol, gamma-tocopherol and d-alpha-tocopherol polyethylene glycol 1000 succinate (TPGS) can protect the retina from this injury. Methods: The right eyes of 40 male guinea pigs weighing 500–600 g were used. The animals were randomly assigned to group 1 (control), group 2 (I/R), group 3 (I/R plus alpha-tocopherol), group 4 (I/R plus gamma-tocopherol) and group 5 (I/R plus TPGS). Groups 3, 4 and 5 received four subcutaneous injections at six-hour intervals for total dosage of 800 IU/kg alpha-tocopherol, 1000 IU/kg gamma-tocopherol and 750 IU/kg TPGS, respectively. The first dose of each substance was administered 5 minutes before retinal ischemia. Retinal ischemia was induced for 90 minutes, then followed by reperfusion for 24 hours. Injections of three substances were repeated at 6, 12 and 18 hours during reperfusion. The animals were killed at 24 hours of reperfusion. Sagittal sections of 4 μm were cut and stained with hematoxylin and eosin for light microscopic evaluation. The average thickness (edema) of the inner plexiform layer for each eye was measured in sagittal sections near the optic nerve and expressed in microns. Results: All the three substances showed statistically significant protection against the formation of retinal edema during ischemia–reperfusion injury. The mean thickness of the inner plexiform layer were 15.0, 25.44, 19.81, 21.38 and 20.88 μm in control, I/R, I/R plus alpha-tocopherol, I/R plus gamma-tocopherol and I/R plus TPGS groups, respectively. The results showed that the thickness of the inner plexiform layer in group 1 (control) was significantly lower than the other groups (p<0.001). The inner plexiform layer was thicker in the I/R group than with I/R plus alpha-tocopherol (p<0.001), I/R plus gamma-tocopherol (p<0.001) and I/R plus TPGS (p<0.01). The inner plexiform layer was not thicker in the I/R plus TPGS group than in the I/R plus alpha-tocopherol and I/R plus gamma-tocopherol groups. Compared to the I/R plus alpha-tocopherol group, the inner plexiform layer was significantly thicker in the I/R plus gamma-tocopherol group (p<0.01). Conclusions: The results from these experiments indicate that vitamin E forms have protective effects on the retina during retinal ischemia–reperfusion injury, but, the effects of alpha-tocopherol and TPGS appear to be much greater than that of gamma-tocopherol.     

GM-1对大鼠视网膜缺血再灌注损伤的保护作用

目的 探讨单唾液酸神经节苷脂（monosialoganglioside,GM-1）对大鼠视网膜缺血冉灌注损伤后视网膜组织及超微结构的保护作用.方法 健康成年Wistar大鼠75只,随机分为3组：正常组5只、NS组35只,GM-1组35只.正常对照组不加任何处理因素,NS组和GM-1组通过升高眼压造成视网膜缺血60 min,分别于缺血前12 h、1 h及缺血结束时3次腹腔注射NS 3mL/kg或GM-1 3mL/kg（10 mg/mL）,并于再灌注0 h（单纯缺血后）、1 h、6 h、12 h、24 h、3 d和7 d共7个时间点取双眼眼球,每时间点5只,HE染色观察视网膜组织结构并测量视网膜内层平均厚度（mean thickhess of the inner retinal layers,MTIRL）,透射电镜观察视网膜超微结构变化.结果 缺血再灌注后,内层视网膜依次表现出水肿、凋亡、萎缩的损伤过程.GM-1可明显减轻其水肿和萎缩的程度,并减少凋亡的发生.结论 GM-1对视网膜缺血再灌注损伤具有明确的保护作用,可能是其有效治疗药物.     

Protective effects of catalase on retinal ischemia/reperfusion injury in rats

Retinal ischemia/reperfusion (I/R) injury causes profound tissue damage, especially retinal ganglion cell (RGC) death. The aims of the study were to investigate whether catalase (CAT) has a neuroprotective effect on RGC after I/R injury in rats, and to determine the possible antioxidant mechanism. Wistar female rats were randonmized into four groups: normal control group (Control group), retinal I/R with vehicle group (I/R with vehicle group), retinal I/R with AAV-CAT group (I/R with AAV-CAT group), and normal retina with AAV-CAT group (normal with AAV-CAT group). One eye of each rat was pretreated with recombinant adeno-associated virus containing catalase gene (I/R with AAV-CAT group or normal with AAV-CAT group) and recombinant adeno-associated virus containing GFP gene (I/R with vehicle group) by intravitreal injection 21 days before initiation of I/R injury. Retinal I/R injury was induced by elevating intraocular pressure to 100 mmHg for 1 h. The number of RGC and inner plexiform layer (IPL) thickness were measured by fluorogold retrograde labeling and hematoxylin and eosin staining at 6 h, 24 h, 72 h and 5d after injury. Hydrogen peroxide (H₂O₂), the number of RGC, IPL thickness, malondialdehyde(MDA), 8-hydroxy-2-deoxyguanosine (8-OHdG), CAT activity and nitrotyrosine were measured by fluorescence staining, immunohistochemistry and enzyme-linked immunosorbent assay analysis at 5 days after injury. Electroretinographic (ERG) evaluation was also used. Pretreatment of AAV-CAT significantly decreased the levels of H₂O₂, MDA, 8-OHdG and nitrotyrosine, increased the catalase activity, and prevented the reduction of a- and b- waves in the I/R with AAV-CAT group compare with the I/R with vehicle group (p < 0.01). Catalase attenuated the I/R-induced damage of RGC and IPL and retinal function. Therefore, catalase can protect the rat retina from I/R-induced injury by enhancing the antioxidative ability and reducing oxidative stress, which suggests that catalase may be relevant for the neuroprotection of inner retina from I/R-related diseases.     

川芎嗪对大鼠缺血再灌注视网膜SOD,MD和NO水平及细胞凋亡的影响

目的 :观察川芎嗪对大鼠视网膜缺血再灌注后视网膜超氧化物歧化酶 (superoxidedismutase ,SOD)、丙二醛 (malondialdehyde ,MDA)、一氧化氮 (nitricoxide ,NO)水平及视网膜细胞凋亡的影响。方法 :采用大鼠视网膜压力缺血再灌注模型 ,分光光度法测定SOD、MDA和NO ,琼脂糖凝胶电泳分析DNA断裂。结果 :视网膜缺血 6 0min再灌注后SOD水平下降 ,而MDA和NO水平则升高 ;视网膜缺血 6 0min再灌注 12h ,提取DNA进行琼脂糖凝胶电泳可见凋亡样DNA断裂 (ApoptoticDNAfragmentation)。川芎嗪能显著对抗视网膜缺血再灌注时视网膜SOD水平的下降、MDA和NO水平的升高 ;同时能阻断大鼠视网膜缺血再灌注 12h后视网膜细胞DNA凋亡样断裂。结论 :川芎嗪可能通过抑制自由基的产生和提高抗氧化能力来对抗大鼠视网膜缺血再灌注诱导的细胞凋亡     

盐酸氟桂嗪对家兔视网膜缺血—再灌注损伤保护作用的ERG观察

目的 动态观察盐酸氟桂嗪对家兔视网膜缺血－再灌注损伤的保护作用。方法 应用前房灌注加压法使前房内压力升高至16kPa。维持１h后再灌注,再灌注后第2、7、14天分别记录其ERG,与缺血前ERG相比,观察b波的变化。药物治疗组在造成缺血前12h,缺血－再灌注即刻及再灌注后12h静脉给予药物治疗。结果 药物治疗组ERG的b波与正常眼相比无明显差异。结论 盐酸氟桂嗪对视网膜缺血－再灌注损伤有保护作用。     

Retinal ischemia and reperfusion causes capillary degeneration: similarities to diabetes

PURPOSE: Retinal neurons and vasculature interact with each other under normal conditions, and occlusion of the retinal vasculature can result in damage to retinal neurons. Whether damage to the neural retina will damage the vasculature, however, is less clear. This study was conducted to explore the relationship between vascular and nonvascular cells of the retina. The response of the retinal vasculature to an injury (ischemia and reperfusion; I/R) that is known to cause neuronal degeneration was studied. METHODS: I/R injury to the retinas was induced in Lewis rats and C57BL/6J mice by elevating intraocular pressure (IOP), and reperfusion was established immediately afterward. Some rats were pretreated with aminoguanidine (AMG, 50 mg/Kg BW in drinking water) before the procedure. Poly(ADP-ribose) polymerase (PARP) activity and expression of inducible nitric oxide synthase (iNOS), and cycloxygenase-2 (COX-2) were measured by Western blot analysis, and levels of TNF-alpha and intercellular adhesion molecule (ICAM)-1 mRNA were measured by qPCR at 2 and 7 days after the procedure. Also at 2 and 7 days after the I/R injury, apoptosis of retinal neural cells (demonstrated by TUNEL assay), density of cells in the ganglion cell layer, and thickness of retinas were quantitated, and the number of TUNEL-positive capillary cells and degenerated capillaries were assessed. Retinal neurodegeneration and capillary degeneration were also examined in C57BL/6J mice 2, 5, 8, and 14 days after I/R injury. RESULTS: As expected, loss of cells in the retinal ganglion cell layer was apparent 2 days after I/R injury in the rat and mouse models. In contrast, the retinal vasculature had essentially no pathology at this time in either model. Surprisingly, the number of degenerated capillaries increased greatly by 7 to 8 days after the injury. Administration of aminoguanidine significantly inhibited the I/R-induced capillary degeneration as well as neurodegeneration in the rat model. Retinal I/R caused increased PARP activity (detected by poly(ADP-ribosy)lated proteins), as well as upregulation of iNOS, COX-2, TNF-alpha, and ICAM-1 levels in rats, consistent with an inflammatory process. CONCLUSIONS: Capillary degeneration is an unrecognized component of acutely elevated IOP and develops only after neurodegeneration is severe. Thus, this finding raises the possibility that damage to the neural retina contributes to capillary degeneration. Aminoguanidine, a nonspecific inhibitor of iNOS, inhibited I/R-induced degeneration of both neuronal and vascular cells of the retina. The model of retinal ischemia and reperfusion will be a useful tool for investigating the relationship between neuronal damage and vascular damage in glaucoma and other diseases such as diabetic retinopathy.     

Interleukin-6 in retinal ischemia reperfusion injury in rats

PURPOSE: To study the role of interleukin (IL)-6 after retinal ischemia-reperfusion (I/R) injury in rats. METHODS: Intraocular pressure of adult male Lewis albino rats was raised to create retinal ischemia for 1 hour. Retinal reperfusion was reestablished, and the animals were killed at various time points after the injury. Their eyes were enucleated and processed for immunohistochemistry to detect IL-6 and ED-1 (a marker of microglial/phagocytic cells), enzyme-linked immunosorbent assay (ELISA) of IL-6 protein, and semiquantitative real-time RT-PCR for IL-6 mRNA. The neuroprotective effect of IL-6 was evaluated by giving intravitreal injections of 150 or 300 ng rat recombinant IL-6 to eyes immediately after I/R injury and counting cresyl violet-stained retinal ganglion cell layer cells (RGCLCs) and fluorochrome-labeled retinal ganglion cells (RGCs) on flat preparations of retinas at 7 days. RESULTS: IL-6-positive cells appeared after I/R injury in the inner plexiform layer (IPL) and the inner nuclear layer (INL). Their numbers were significantly higher 18 hours after the injury, and most of these cells were also ED-1 positive. ELISA showed noticeable increases in endogenous retinal IL-6 protein levels 8 hours after I/R injury. Semiquantitative real-time RT-PCR showed significant increases in endogenous retinal IL-6 mRNA levels between 2 and 18 hours. Exogenously added IL-6 prevented between 50% and 70% of RGC loss after I/R injury. CONCLUSIONS: IL-6 is upregulated after retinal I/R injury, and its expression by microglia/phagocytic cells may protect RGC layer neurons from I/R injury. Exogenously added IL-6 protects the inner retina after I/R injury.     

Neuroprotective effect of small interfering RNA targeted to caspase-3 on rat retinal ganglion cell loss induced by ischemia and reperfusion injury

Purpose: To investigate neuroprotective effects of siRNA targeted to caspase-3 against ischemia and reperfusion (I/R) injury in rat eyes. Methods: Retinal ischemia was induced in Wistar rats by increasing the intraocular pressure (IOP) to 110 mmHg for 120 min. To examine the effect of siRNA on rat caspase-3, siRNA was injected into the vitreous cavity 24 h prior to induction of retinal ischemia. Eyes were removed at 2, 7 or 14 days later, and then analyzed for the number of retinal ganglion cells (RGCs), the retinal thickness and the amount of apoptosis of the retinal neural cells (as demonstrated by the TUNEL assay). The amount of caspase-3 mRNA was analyzed by rt-PCR. Differences between groups were evaluated by an unpaired t test. Results: The numbers of RGCs in the saline and non-silencing siRNA controls were reduced significantly at 2 and 7 days after the I/R injury. RGCs were significantly retained in eyes pretreated with siRNA targeted to caspase-3 as compared to the control eyes at 2 days after the I/R injury. Inner retinal thickness in the control eyes was significantly thinner as compared to the treated eyes at 2 and 7 days after the I/R injury. After siRNA treatment, the amount of caspase-3 mRNA was significantly lower when compared to the saline control group. Conclusions: The injection of siRNA targeted to caspase-3 into the vitreous cavity of rat eyes may block caspase-3, and may thus be able to prevent retinal cell death associated with ischemic injury. As inhibition of the apoptosis pathway may provide a neuroprotective effect, examination of new strategies for treating these disorders needs to be undertaken.     

Neuroprotective Effects of Granulocyte Colony-Stimulating Factor on Ischemia-Reperfusion Injury of the Retina

Purpose: It has been reported that granulocyte colony-stimulating factor (G-CSF) provides neuroprotection in models in which neuronal cell death is induced. This research was designed to investigate the effects of G-CSF on neurodegeneration of the inner retinal layer in a rat model of ischemic reperfusion (I/R) injury. Materials and Methods: Retinal ischemia was induced by increasing the intraocular pressure to 110 mm Hg for 45 min in the left eyes of the rats. A sham operation was carried out on the right eyes. G-CSF (100 μg/kg/day in 0.3 ml saline) or the same volume of saline was intraperitoneally injected just before the operation and continued for 4 consecutive days (a total of 5 consecutive days). Morphological examinations, including the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, were performed 7 days after I/R induction. The expression of phosphorylated AKT in the retina was examined by Western blot analysis and immunohistochemistry. Results: Cell loss in the ganglion cell layer was more significantly reduced in the I/R-induced eyes of the G-CSF-injected rats than in the I/R-induced eyes of the saline-injected rats (20.3 vs. 6.6%). The inner retinal thickness ratios, such as the inner plexiform layer to the inner limiting membrane/outer nuclear layer and the inner nuclear layer/outer nuclear layer, were significantly better preserved in the I/R-induced eyes of the G-CSF-injected rats than in the I/R-induced eyes of the saline-injected rats. TUNEL assays showed fewer apoptotic cells in the retinal sections of the I/R-induced eyes of the G-CSF-injected rats. The phosphorylation of AKT (p-AKT/AKT) was upregulated in the retinas of the I/R-induced eyes of the G-CSF-injected rats. Conclusion: Our results demonstrated that systemic injection of G-CSF can protect retinal ganglion cells and inner retinal layers from I/R injury. The effects could be associated with the activation of AKT.     

Protective effects of pentoxifylline in retinal ischemia/reperfusion injury

We studied the effect of pentoxifylline on retinal lipid peroxidation and histopathologic changes due to ischemia/reperfusion (I/R). A total of 15 pigmented male guinea pigs were divided into 3 equal groups as control, sham and treatment groups. After application of high intraocular pressure for 90 min for the induction of retinal ischemia, 24-hour reperfusion was established in the sham and treatment groups. In the treatment and sham groups, either 45 mg/kg of pentoxifylline or saline was given 3 times at 8-hour intervals. Biochemical assay and histopathologic evaluation were performed on one randomly selected eye of each animal which was enucleated at the end of the reperfusion period, and retinal malondialdehyde (MDA) levels and thickness of the retinal tissue were determined for each group. The mean MDA level of the sham group was significantly higher versus the control and treatment groups (p < 0.001). When compared with the control group, the mean MDA level of the treatment group was slightly higher, but the difference was not statistically significant (p > 0.05). In comparison with the control group there was a significant increase in the thickness of the retina in the sham group (p < 0.0001), and no significant difference was found in the retinal thickness of the treatment group (p > 0.05). Pentoxifylline might have a preventive effect on the I/R injury of the retina.     

视网膜缺血再灌注损伤的机制及bFGF对其干预作用

目的探讨碱性成纤维细胞生长因子(basic fibric growth factor;bFGF)在大鼠视网膜缺血再灌注损伤(retina ischemi—a/reperfusion injury;RIRI)中治疗作用及机制。方法采用升高眼内压的方法建立大鼠视网膜缺血-再灌注模型,并将48只大鼠随机分为正常组、缺血组、治疗组。在再灌注后1、6、12、24、72h时段分别应用末端脱氧核酸转移酶介导的脱氧三磷酸尿苷缺口末端标记法(TUNEL)检测视网膜组织中凋亡细胞的表达,采用过氧化物酶标记的链酶卵白素(streptavidin perox—idase,SP)免疫组化方法检测caspase-3的表达,使用原子吸收光度计测定细胞内钙离子的变化。结果在大鼠RIRI中,缺血组凋亡细胞在再灌注6h组开始出现,以后时段依次递增,至24h达到高峰,于72h已无明显表达。Caspase-3表达改变与凋亡细胞表达相似。钙离子于再灌注后1h开始升高,至24h达到高峰,72h出现下降。而在bFGF治疗组各观察指标变化规律基本同上,但各指标与缺血组相比较均下降,于再灌注6、12、24h时段两者差别具有统计学意义。结论细胞凋亡可能在视网膜缺血再灌注损伤中起到重要作用,bFGF可通过对细胞内钙离子、自由基以及凋亡蛋白表达的调控而达到对细胞凋亡的抑制,并进而达到对视网膜缺血再灌注损伤的治疗作用。     

碱性成纤维细胞生长因子对鼠视网膜缺血再灌注损伤的治疗作用

目的探讨玻璃体腔注射碱性成纤维细胞生长因子(basic fibroblast growth factor, bFGF)对实验性视网膜缺血再灌注损伤的治疗作用.方法采用升高眼内压的方法,制作实验性视网膜缺血再灌注损伤大鼠模型.将Wistar大鼠随机分为正常组、缺血组及治疗组.再灌注开始时,缺血组大鼠玻璃体腔内注入平衡盐溶液,治疗组注入bFGF 2 μg.观察再灌注后不同时间段各组鼠视网膜组织学及超微结构变化,光镜下计数视网膜神经节细胞(retinal ganglion cells, RGCs),应用图像分析系统测量视网膜内层厚度.结果视网膜缺血再灌注早期,治疗组大鼠视网膜水肿较缺血组轻,各时间段治疗组大鼠视网膜内层厚度均较缺血组厚,治疗组大鼠RGCs数目多于缺血组.再灌注后168 h,缺血组大鼠神经纤维层厚度及RGCs数目明显低于正常组,而治疗组大鼠神经纤维层厚度及RGCs数目与正常组比较,差异无显著意义(P<0.05).再灌注后24 h,缺血组大鼠RGCs核膜肿胀,线粒体嵴模糊不清,可见凋亡小体,神经纤维中微管模糊、减少甚至消失;而治疗组仅部分核膜轻度肿胀,胞浆内细胞器丰富,线粒体及微管结构较清楚.结论大鼠玻璃体腔注射bFGF对实验性视网膜缺血再灌注损伤具有治疗作用.