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.     

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.     

Anti-inflammatory effects of vitamin E on experimental lens-induced uveitis

The anti-phlogistic effect of dietary vitamin E supplementation on the acute inflammation observed in experimental lens-induced uveitis in Brown Norway rats was studied. The effects of vitamin E were examined using histopathologic parameters as well as by measuring the levels of arachidonic acid metabolites. Histologic examination of the eyes revealed that the vitamin E-deficient animals had the most severe destruction of the retina, while those animals receiving the vitamin E-supplemented diet exhibited the best preservation of the retinal architecture. Levels of arachidonic acid metabolites, as determined by radioimmunoassay, were significantly higher in vitamin E deficient rats as compared with rats on a normal diet.Abbreviations AA arachidonic acid - leukotriene B₄ LTB₄ - prostaglandin E₂ PGE₂ - thromboxane B₂ TxB₂     

Effects of vitamin e, pentoxifylline and aprotinin on light-induced retinal injury

PURPOSE: A considerable amount of clinical and experimental evidence exists suggesting the involvement of reactive oxygen species (ROS) in the etiology of light-induced retinal injury. The aim of this study was to investigate the protective role of vitamin E, pentoxifylline (PTX) and aprotinin against light-induced retinal injury in guinea pigs. METHODS: Thirty adult male guinea pigs were divided into 5 groups of 6 animals each. The first group was used as control. The guinea pigs were kept in cyclic light for 2 weeks before the experiments. The animals were maintained in 12-hour light-dark cycles, before and after exposure to intense white fluorescent light, for as long as 12 h and then returned to cyclic light. Groups 3-5 received intraperitoneal injections of vitamin E, PTX and aprotinin, respectively. One eye of each animal was selected for histopathological evaluation and the other for biochemical assay. Retinal malondialdehyde (MDA) levels and the thickness of the outer nuclear layers were measured. RESULTS: The compounds had the following relationships: vitamin E more than PTX more than aprotinin in preventing light-induced retinal damage. All 3 gave significant protection against the formation of MDA. Retinas of all 3 treatment groups had been protected from light-induced injury. CONCLUSION: The intraperitoneal vitamin E, PTX and aprotinin supplementations may strengthen the antioxidant defense system because of decreased ROS, and these agents may play a role in treating light-induced retinal injury.     

Expression of B7 molecules in the eye during experimental autoimmune anterior uveitis (EAAU)

PURPOSE: We have reported that CTLA4-Fc, a fusion protein that binds B7, prevents the induction of EAAU and reduces the severity of disease in Lewis rats. Since B7.1 and B7.2 have distinctive roles in other autoimmune diseases, we investigated their roles in the development of EAAU. METHODS: Lewis rats were immunized with melanin associated antigen (MAA). Eyes were collected at different stages of EAAU and the expression of B7 on iris and ciliary body (ICB) cell suspensions determined by flow cytometry analysis. The incidence of EAAU after treatment with anti B7, and the requirement of B7.1 and B7.2 for proliferation and cytokine production of lymphoid cells to MAA were also studied. RESULTS: B7.2 is up-regulated in resident ICB cells or bone-marrow derived cells which have infiltrated the ICB by day 10 and remains elevated during the acute phase of disease. B7.1 is expressed later during the acute phase. Both B7.1 and B7.2 are down-regulated during remission, with low levels of B7.2 and no detectable B7.1. The incidence of EAAU was reduced by anti-B7.2 treatment and completely inhibited by a combination of both B7.1 and B7.2 antibodies. Neither anti-B7.1 nor anti-B7.2 alone affected proliferation or cytokine production. However, administration of both anti-B7.1 and B7.2 completely inhibited proliferation as well as IL-2 and TNF-alpha production. CONCLUSIONS: B7.1 and B7.2 are expressed in the eye at different times during EAAU. Both B7 molecules are required for the induction of EAAU, although they probably have different roles.     

The development of eye shape and the origin of lower field myopia in the guinea pig eye

In a variety of species, the refractive state of the eye differs in different parts of the visual field (VF) with greater myopia in the region that views the ground (“lower field myopia”). We studied the refraction and eye shape of the normal guinea pig eye to determine what feature(s) underlie this visual adaptation. Guinea pigs (n = 67) were either newborn or raised under incandescent light until 14, 37 or 45 days of age (20, 44, 20 and 11 eyes respectively). Refractive error was measured on-axis and 30° off-axis in the superior (SVF), inferior (IVF), temporal (TVF) and nasal (NVF) visual fields. Eye shape was analyzed from images of frozen hemisections in both the horizontal and vertical mid plane in 14 day animals, and in the vertical plane at 0, 14 and 45 days of age. Axial distances in vitro were correlated with in vivo high frequency ultrasound (r² = 0.90). In the horizontal plane, asymmetry was caused by a ±6° conical zone surrounding the optic nerve (12° off-axis in NVF), suggesting significant myopia in this zone. At 30°, there was no asymmetry in eye length, but the NVF was +1.7 D more myopic due to asymmetry in corneal power. In the vertical plane at 30°, the IVF was more myopic than the SVF by −3.8 D at 0 days, −5.9 D at 14 days and −6.0 D at 37 days. It resulted from vertical asymmetry in the distance of the retina from the lens center, which was longest in the mid IVF. This non-linear ramp retina was present at birth. In older animals, the peak of the ramp shifted more centrally, and the eye developed longer lengths in the extreme upper periphery (SVF) which may have been caused by the low position of the room ceiling. The vertical asymmetry in eye shape was mirrored by changes in choroid thickness, suggesting a mechanism by which eye shape was refined by vision during development. In early life, ocular growth in the vertical plane was 1.7 times higher in the center relative to the periphery, a pattern that reversed in the following month. Since emmetropization was achieved over this period, local visual cues related to clear vision may provide a switch to change ocular growth from a central to a peripheral emphasis.     

豚鼠近视眼视网膜Müller细胞近视因子基因的表达

目的 研究视网膜近视因子基因在原代培养的豚鼠近视眼视网膜Müller细胞中的表达变化.方法 3～4周龄断乳三色豚鼠40只,取20只建立近视眼模型(以右眼作为实验眼,以对侧未遮盖眼作自身对照),剩余的20只豚鼠作正常对照.用眼罩遮盖法建立豚鼠近视眼模型,用酶消化法原代培养其视网膜Müller细胞.RT-PCR检测酪氧酸羟化酶(tyrosine hydroxylase,TH)、诱导型一氧化氙合成酶(inducible nitric oxide synthase,iNOS)、神经型一氧化氮合成酶(neu-ronal nitric oxide synthase,nNOS)、内皮型一氧化氮合成酶(endothelial nitric oxide synthase,eNOS)、视黄醛脱氢酶(retinaldehyde dehydrogenase,RALDH)、醛脱氢酶(aldehyde dehydrogenase,ALDH)、碱性成纤维细胞生长因子(basic fi-broblast growth factor,bFGF)、转化生长因子β(transforming growth factor-β,TGF-β)的mRNA在正常对照眼、自身对照眼和近视眼视网膜Müller细胞中的表达情况.数据分析采用One-way ANOVA检验.结果 眼罩遮盖10 d后,遮盖眼眼轴延长,近视形成.酶消化法成功培养出视网膜Müller细胞.正常对照眼、自身对照眼和遮盖眼视网膜Müller细胞均阳性表达nNOS、bFGF、TH、TGF-B mRNA,且遮盖眼表达nNOS、bFGF和TGF-B mRNA上调(P<0.05),TH mRNA下调(P<0.05).iNOS mRNA仅在遮盖眼视网膜Müller细胞阳性表达.三组视网膜Müller细胞均不表达eNOS、RALDH和ALDH mRNA.结论 豚鼠近视眼视网膜Müller细胞表达nNOS、iNOS、bFGF和TGF-B mRNA上调,TH mRNA下调.Müller细胞是近视眼视网膜信号因子一氧化氮(nitric oxide,NO)、多巴胺(dopamine,DA)、bFGF和TGF-β的一个重要来源.     

外源性褪黑素对豚鼠形觉剥夺性近视褪黑素受体、iNOS、c-fos表达的影响

目的探讨外源性褪黑素(melatonin,MLT)在豚鼠形觉剥夺性近视(form deprived myopia,FDM)形成中的作用。方法将40只7d龄豚鼠,随机分为4组,每组10只,右眼建立FDM模型,左眼为自身对照眼。A组为对照组,腹腔注射5mL.kg-1生理盐水,B、C、D组为MLT干预组,腹腔注射不同剂量MLT(5mg.kg-1、10mg.kg-1、20mg.kg-1)。8周后A超测量双眼眼轴长度,行检影验光检测双眼屈光度,免疫组织化学法分析MLT受体MT1、诱导型一氧化氮合酶(inducible nitric oxide synthase,iNOS)及c-fos的表达。结果 A组遮盖眼屈光度数、眼轴长度,视网膜中iNOS、MT1、c-fos表达分别为(-7.86±0.26)D、(8.51±0.16)mm、0.4836±0.0247、0.3179±0.0344、0.2282±0.0246。不同剂量MLT作用于FDM眼后,随外源性MLT剂量的增加,以上指标变化被明显抑制甚至逆转。C组FDM眼的屈光度数、眼轴长度,视网膜中iNOS、MT1、c-fos平均光密度值表达分别为(-4.30±0.59)D、(8.04±0.24)mm、0.3733±0.0427、0.3743±0.0447、0.3713±0.0786;D组分别为(-3.41±0.88)D、(7.43±0.39)mm、0.3079±0.1261、0.4055±0.0919、0.4458±0.0974。C组、D组各指标分别与A组比较差异均有统计学意义(均为P<0.05);但B组与A组之间的差异均无统计学意义(均为P>0.05)。结论外源性MLT能抑制甚至逆转FDM鼠屈光度、眼轴长度及视网膜iNOS、MT1、c-fos的免疫活性,同时发现高剂量组较低剂量组结果明显。据此可推断,外源性MLT对FDM的形成有抑制作用。     

Effect of vitamin E in the treatment of bovine-albumin-induced uveitis in rabbits.

In order to assess the role of vitamin E, an antioxidant, in the treatment of uveitis, a controlled experimental study was carried out on 20 New Zealand albino rabbits with bovine-albumin-induced uveitis. In all vitamin-E-treated animals, clinical and histopathological study of the retina and uvea revealed no significant changes in comparison with those in untreated rabbits.     

Effects of pyrrolidine dithiocarbamate, an NF-kappaB inhibitor, on cytokine expression and ocular inflammation in experimental autoimmune anterior uveitis.

AIMS: The aim of this study was to investigate the effects of pyrrolidine dithiocarbamate (PDTC), a nuclear factor (NF)-kappaB inhibitor, on cytokine expression and suppression of anterior chamber inflammation in experimental autoimmune anterior uveitis. Uveitis was induced in the Lewis rats with the injection of a melanin-associated antigen into the peritoneum and footpad. At defined time points, cytokine mRNA expressions in the iris and ciliary body were measured by using a semiquantitative polymerase chain-reaction method. RESULTS: We found that interferon-gamma (IFN-gamma) and tumor necrosis factor (TNF)-alpha mRNA expression peaked during the active phase of uveitis, whereas interleukin (IL)-10 mRNA increased during the disease resolution. In a separate experiment, PDTC (100 and 200 mg/kg/day) was administrated intraperitoneally daily after immunization. We found that PDTC (100 and 200 mg/kg/day) effectively suppressed ocular inflammation, as indicated by reduced clinical scores and inflammatory cells infiltration in aqueous humor and the iris and ciliary body. CONCLUSIONS: The inhibitory effects of PDTC are mainly resulted from inhibiting the expression of proinflammatory cytokines, TNF-alpha and IFN-gamma but augmenting anti-inflammatory cytokines, IL-10 expression. These findings suggest that the application of NF-kappaB inhibitors may be a potential therapeutic method for the treatment of acute anterior uveitis.     

转化生长因子-β（TGF-β）影响豚鼠巩膜成纤维细胞增殖和α-平滑肌肌动蛋白（α-SMA）表达的研究

目的　本研究探讨转化生长因子-β（ｔｒａｎｓｆｏｒｍｉｎｇｇｒｏｗｔｈｆａｃｔｏｒ,ＴＧＦ-β）体外刺激豚鼠巩膜成纤维细胞,观察豚鼠巩膜成纤维细胞增殖和α-平滑肌肌动蛋白（α-ｓｍｏｏｔｈｍｕｓ-ｃｌｅａｃｔｉｎ,α-ＳＭＡ）的表达。方法　原代培养豚鼠巩膜成纤维细胞并鉴定,ＭＴＴ法检测豚鼠巩膜成纤维细胞的增殖,培养液分别加入２０ｎｇ·ｍＬ－１ ＴＧＦ-β１、ＴＧＦ-β２、ＴＧＦ-β３,分别于１２ｈ、２４ｈ、４８ｈ、７２ｈ,Ｒｅａｌ-ｔｉｍｅＰＣＲ检测α-ＳＭＡｍＲＮＡ,Ｗｅｓｔｅｒｎ-ｂｌｏｔｔｉｎｇ和免疫荧光化学法检测其蛋白表达。结果　与对照组相比,ＴＧＦ-β１、ＴＧＦ-β２和ＴＧＦ-β３促进豚鼠巩膜成纤维细胞增殖,呈剂量依赖性（Ｐ＜０．０５）,其中ＴＧＦ-β１促进豚鼠巩膜成纤维细胞增殖作用最强（Ｐ＜０．０５）;ＴＧＦ-β１、ＴＧＦ-β２和ＴＧＦ-β３均增加α-ＳＭＡ的表达（均为Ｐ＜０．００１）,ＴＧＦ-β３促进α-ＳＭＡ表达作用最强（Ｐ＜０．００１）。结论　ＴＧＦ-β通过调控细胞外基质合成参与调控巩膜组织重塑。     

Retinoic acid signals the direction of ocular elongation in the guinea pig eye

A growing eye becomes myopic after form deprivation (FD) or compensates for the power and sign of imposed spectacle lenses. A possible mediator of the underlying growth changes is all-trans retinoic acid (RA). Eye elongation and refractive error (RE) was manipulated by raising guinea pigs with FD, or a spectacle lens worn on one eye. We found retinal-RA increased in myopic eyes with accelerated elongation and was lower in eyes with inhibited elongation. RA levels in the choroid/sclera combined mirrored these directional changes. Feeding RA (25 mg/kg) repeatedly to guinea pigs, also resulted in rapid eye elongation (up to 5 times normal), and yet the RE was not effected. In conclusion, RA may act as a signal for the direction of ocular growth.     

单眼形觉剥夺对豚鼠后极部巩膜整合素β1表达的影响

目的探讨豚鼠形觉剥夺性近视模型中巩膜整合素β1的表达及其与形觉剥夺的关系。方法40只出生后1周花色豚鼠,右眼遮盖作为形觉剥夺组,左眼不作处理作为对照组。遮盖2、4、8周和遮盖8周去遮盖1周后测量屈光度,眼科A超测定眼轴长度;对两组4个时间点眼球后壁行SP法免疫组织化学染色和RT-PCR检测巩膜整合素β1蛋白和mRNA水平的动态变化。结果与对照组相比,形觉剥夺组4个时间点眼球后壁巩膜整合素β1表达明显减少,差异有统计学意义（P〈0.05）,去遮盖1周后,表达上调,但仍低于对照组（P〈0.05）;而对照组间相比较,差异无统计学意义（P〉0.05）;形觉剥夺组和对照组屈光度、眼轴长度比较,差异有显著的统计学意义（P〈0.05）。结论豚鼠形觉剥夺时,后极部巩膜整合素β1表达减少,去遮盖后表达上调,提示整合素β1可能参与了形觉剥夺性近视的发生,其影响巩膜重塑的机制有待进一步研究。     

Effects of cyclosporine on T-cell subsets in experimental autoimmune uveitis

The effective inhibition of S-antigen (S-Ag) induced experimental autoimmune uveitis (EAU) by Cyclosporine (CsA) suggests strongly the important role of T-cells in the modulation of this disease. The authors evaluated the changes in T-cell subsets induced by this agent in S-Ag immunized Lewis rats. Using the fluorescence-activated cell sorter and monoclonal antibody preparations directed against rat T-cell subsets, a comparison was made between lymphocyte populations obtained from CsA or olive oil treated S-Ag immunized rats taken 5, 10, 12, and 14 days after antigenic challenge. The T-cell subpopulations of lymphocyte preparations from the spleen and peripheral blood of CsA-treated and control animals appeared to parallel each other, with both groups showing an increase in the suppressor/cytotoxic fraction beginning on day 12 and approaching the percentage of inducer cells by day 14. Lymphocyte preparations from lymph nodes draining the site of S-Ag immunization from CsA-treated animals demonstrated a different T-cell subset profile than did controls. Beginning on day 10, the control group was noted to have an increased inducer cell fraction as compared with the CsA group. This increase in the inducer fraction paralleled an increase in the in vitro proliferative responses to the S-Ag. These data suggest that CsA appears to prevent the development of inducer cells in the lymph nodes draining the S-Ag immunization site, the T-cell subgroup the authors have seen capable of inducing EAU.     

Phospholipase A2, leukotriene C4 and prostaglandin E2 levels in aqueous humour of guinea pigs with experimental S-antigen induced autoimmune uveitis

Purified S-antigen was used to induce experimental autoimmune uveitis in 42 guinea pigs. 16 animals were used as controls. Footpad immunization with fresh bovine S-antigen in physiologic saline mixed with complete Freunds's adjuvant induced a clinical disease in 95% of the eyes in test animals. In aqueous humour the increase in phospholipase-A2 and proteins as well as myeloperoxidase measured from iris-ciliary blocks correlated well with the severity of uveitis evaluated by clinical grading. Leukotriene C4 and prostaglandin E2 were only elevated in aqueous humour drawn from eyes showing a mild form of uveitis. Neither leukotriene C4 nor prostaglandin E2 were detected in eyes graded as clinically moderate or severe. In serum samples phospholipase A2, leukotriene C4, prostaglandin E2 and gamma glutamyl transpeptidase were measured. Of these biochemical parameters, only gamma glutamyl transpeptidase was significantly elevated in test animals with experimental autoimmune uveitis. Histological analysis revealed focal mononuclear cell infiltrations in the choroid. Mononuclear as well as polymorphonuclear cell infiltration was seen predominantly in the pars plana region of the ciliary body of test animals with uveitis. Simultaneous destruction of the outer segments of the photoreceptor layer was seen.     

Effects of experimental hyperlipoproteinemia on the canine eye

Hyperlipoproteinemia was induced in dogs of different ages. No effects were observed in the fundus. Lipid was deposited in peripheral cornea in proportion to the level of plasma cholesterol in three of 12 eyes. Extensive lipid deposition was observed in the anterior peripheral corneal stroma. In electron micrographs, intracytoplasmic membrane-bound vacuoles were seen in keratocytes and crystalline spaces were present in corneal stroma.