Preventional and therapeutic effects of aldose reductase inhibitor FR74366 on rat galactose cataract

Preventional and reversal effects of a new aldose reductase inhibitor FR74366 on the rat galactose cataract were examined biochemically and light microscopically. A high concentration (0.075%) FR74366 showed sufficient effects both to prevent and reverse cataract, but low concentrations (0.025%) FR74366 was not effective as 0.075% FR74366. These results indicate that FR74366 can be useful drug for cataract.     

醛糖还原酶抑制剂AL-1576对大鼠半乳糖性白内障的防治研究

背景 糖性白内障是糖尿病的主要眼部并发症之一,研究表明醛糖还原酶(AR)活性的升高与糖尿病的慢性并发症密切相关,是抗糖性白内障药物研究的重要靶点,其研究对糖性白内障的防治具有重要意义. 目的 探讨AR抑制剂AL-1576对半乳糖性白内障的防治效果和作用机制. 方法 4～5周龄SD大鼠42只,通过喂养质量分数50％半乳糖饲料制作半乳糖性白内障模型.大鼠按照随机数字表法平均分为7个组,AL-1576预防组,早、中、晚期治疗组在喂食50％半乳糖饲料的当天及5、10、15d后开始添加质量分数0.0125％ AL-1576,另设空白对照组、模型对照组和AL-1576干预10d后撤除的早期撤药组.在裂隙灯显微镜下动态观察各组大鼠晶状体的混浊程度并进行分级,造模35 d时摘出晶状体,分别测量其干质量、湿质量,计算并比较各组晶状体含水量的变化;检测造模35 d时各组大鼠晶状体内AR活性、超氧化物歧化酶(SOD)活性以及谷胱甘肽( GSH)的含量.结果 模型对照组大鼠12只眼晶状体均为Ⅳ级混浊,AL-1576预防组12只眼晶状体均透明,早期撤药组为Ⅱ～Ⅲ级混浊,早期治疗组为Ⅱ级混浊,而中期治疗组、晚期治疗组均为Ⅲ～Ⅳ级混浊,7个组晶状体混浊的程度差异均有统计学意义(H=17.760,P=0.009).各AL-1576治疗组大鼠晶状体含水量、AR活性均比模型对照组明显降低,差异均有统计学意义(P＜0.05),但给药的时间越晚,晶状体含水量、AR活性降低的程度越小;各AL-1576治疗组大鼠晶状体SOD活性和GSH的含量明显高于模型对照组,差异均有统计学意义( P＜0.05),AL-1576预防组的升高幅度最大. 结论 在半乳糖性白内障形成的不同阶段给予AR抑制剂AL-1576可明显抑制AR的活性.AL-1576通过阻断和减轻晶状体水肿,提高晶状体的抗氧化能力,预防和延缓晶状体混浊的发生.     

醛糖还原酶抑制剂和肌醇对糖尿病视网膜毛细血管周细胞的保护作用

目的观察醛糖还原酶抑制剂和肌醇对实验性糖尿病大鼠视网膜病变毛细血管周细胞的保护作用。方法给链脲佐菌素诱发的糖尿病大鼠分别管饲醛糖还原酶抑制剂或肌醇，于实验6个月末进行视网膜毛细血管消化铺片及透射电镜观察。结果糖尿病组的视网膜可见毛细血管内皮细胞／周细胞比值升高、无细胞毛细血管形成、周细胞线粒体肿胀、内皮细胞增生和毛细血管基底膜增厚；管饲醛糖还原酶抑制剂组的视网膜血管形态无明显改变；但管饲肌醇组的视网膜血管改变较管饲醛糖还原酶抑制剂组明显。结论醛糖还原酶抑制剂可有效预防实验性糖尿病性视网膜病变的形态学改变，肌醇能部分阻止视网膜形态学异常的发生。     

Relative importance of aldose reductase versus nonenzymatic glycosylation on sugar cataract formation in diabetic rats.

The relative importance of sorbitol formation versus nonenzymatic glycosylation and advanced glycosylation end products (AGEs) on sugar cataract formation was examined in diabetic rats. Diabetes was experimentally induced in young, 50 g rats with streptozotocin, and aldose reductase inhibitors were administered in the diet for up to 8 weeks at concentrations of 0.06% for tolrestat or ponalrestat and 0.0125% for AL-1576. Cataract formation was monitored by hand-held slit lamp for up to 11 weeks. Lens polyol levels were monitored by GLC, glycosylated protein levels were spectrophotometrically determined, and AGE products were estimated by fluorescence measurements and ELISA. Sugar cataract formation was observed in all untreated diabetic rats while cataract formation was inhibited in all diabetic rats treated with the AR inhibitors. Lens sorbitol levels were reduced in all ARI-treated rats. Glycosylated lens protein levels were elevated in the diabetic rats, and these levels were not significantly lower in the non-cataractous lenses from ARI-treated diabetic rats. Fluorescence measurements of the lens proteins revealed increased lens AGE levels in all diabetic rats, and these were slightly reduced in the aldose reductase inhibitor treated diabetics. With ELISA, immunoreactive AGEs were only detected in cataractous lenses from the untreated diabetic rats. Immunoreactive AGEs were not detected in the clear lenses of the aldose reductase inhibitor treated diabetics or in the non-diabetic controls. These results support the concept that sugar cataract formation is initiated by the aldose reductase catalyzed intracellular accumulation of polyols and that these sugar cataracts can be prevented through inhibition of aldose reductase.     

Topical aldose reductase inhibitor for correcting corneal endothelial changes in diabetic patients.

BACKGROUND--Marked variations in cell size (polymegethism) and shape (pleomorphism) are characteristic of the corneal endothelium in diabetic patients and animals. METHOD--Wide field specular microscopy was used to evaluate the clinical efficacy of treating the diabetic corneal endothelium with topical instillation of 0.5% aldose reductase inhibitor, CT-112. RESULTS--Morphological variations (polymegethism and pleomorphism) of the endothelium in eight eyes from eight patients receiving CT-112 resolved within 3 months after initiation of treatment. In contrast, no change in endothelial morphology was noted in five eyes from five patients who received placebo. CONCLUSION--These observations suggest that aldose reductase may be involved in the aetiology of corneal endothelial variations in diabetic patients.     

Effect of an aldose reductase inhibitor,AL-1576, on the development of UV-B and X-ray cataract

The effect of an aldose reductase inhibitor, AL-1576, on the development of UV-B and X-ray-induced cataract was studied with 100 female Brown-Norway rats. Histological studies were made with 32 eyes. A new histological procedure enabled detailed information on UV or X-ray-induced impairment on the lens, as well as on the potential efficiency of anticatarct drugs. No definite effect of the aldose reductase inhibitor, AL-1576, on the development of UV or X-ray-induced cataract could be found. It may be concluded that AL-1576 cannot prevent damage caused by irradiation, like that of other oxidative influences. Disadvantageous effects of AL-1576 on the lens could be excluded.     

Morphological classification of the prevention by aldose reductase inhibitor of rat galactosemic cataract

A morphological classification indicating the stage of the prevention of aldose reductase inhibitor (ARI) on the rat galactosemic cataract was investigated. Three week old rats (body weight 50 g) were fed with a 25% galactose diet. Two kinds of ARIs (ADN-138, FR-74366) were used with a different dose 25% galactose fed each drug. The rats on the 25% galactose diet rapidly developed cataracts in the equatorial region of the lens followed by total cataracts. The morphological processes of the galactose cataracts receiving preventive treatment of ARI were divided into 5 types according to their intensity.     

The effects of an aldose reductase inhibitor on the progression of diabetic retinopathy

The polyol pathway has long been associated with diabetic retinopathy. Glucose is converted to sorbitol with the aid of the enzyme aldose reductase. Aldose reductase inhibitors can prevent changes induced by diabetes. A total of 30 patients with minimal background retinopathy were randomly divided into a ponalrestat-taking group and a placebo-taking group. All were followed for 6 months and twenty-three were followed for 12 months. The baseline microaneurysm count was 2.6 ± 1.9 (mean ± SD) for the ponalrestat group and 3.5 ± 2.9 for the placebo group. At 6 months the counts were 3.1 ± 3.5 and 2.9 ± 3.6 and after 12 months 3.0 ± 4.1 and 2.9 ± 3.4. There is no statistically significant difference between the groups at 0, 6 or 12 months of study. The change in retinopathy severity level did not significantly differ between the two groups at either 6 or 12 months. Ponalrestat adminstration at a dosage of 600 mg daily for 12 months has no significant effect on the course of minimal retinopathy in diabetic patients.     

Effect of aldose reductase inhibitors on naphthalene cataract formation in the rat

Naphthalene feeding can result in cataract formation in rats and rabbits due to specific metabolites of naphthalene. The concomitant administration of the aldose reductase inhibitor Al1576 to naphthalene-fed rats was proven to prevent cataract formation. To determine whether this effect was directly linked to the ability of Al1576 to inhibit enzyme aldose reductase, a variety of structurally diverse aldose reductase inhibitors, including the carboxylic acids tolrestat, Ponalrestat, and FK366, and the spirohydantoins, sorbinil and Al1576, were investigated for their ability to inhibit naphthalene-induced cataracts. Brown Norway rats, administered naphthalene by gavage, were fed normal rat chow containing these aldose reductase inhibitors at levels known to inhibit sugar cataract formation. The lens changes in these rats were monitored over a 90-day period by portable slit-lamp microscopy and histologic study. Al1576 showed a dose-dependent reduction in naphthalene-induced cataract formation, with no naphthalene-associated deposits seen in toluidine blue-stained lens sections. Sorbinil also reduced lens changes, whereas tolrestat, Ponalrestat, and FK366 had no effect. These results suggest that inhibition of naphthalene-induced cataract formation by structurally diverse aldose reductase inhibitors was not linked to the inhibition of aldose reductase.     

The effects of aldose reductase inhibitor on the corneal endothelial morphology in diabetic rats

Diabetic rats were produced by intravenous injection of streptozotocin. Of these, eleven rats were treated with topical instillation of 0.5% aldose reductase inhibitor (ARI), while ten received vehicle alone. The corneal endothelium of these diabetic rats was examined by specular microscopy and compared to age-matched nondiabetic rats (ten rats). Computerized morphometric analysis of individual cells demonstrated that the endothelium of the untreated diabetic rats had marked polymegathism (increased coefficient of variation in cell area) and pleomorphism (decreased percentage of hexagonal cells), as previously observed in diabetic patients. Similar endothelial changes were also noted in the ARI-treated diabetic rats, but to a significantly lesser extent. These results suggest that topically applied ARI can be effective in reducing morphologic changes of the diabetic endothelium, and that activation of the sorbitol pathway may be implicated in the etiology of such endothelial changes.     

Improvement of corneal fluorescein staining in post cataract surgery of diabetic patients by an oral aldose reductase inhibitor,ONO-2235

AIM: While the mechanism in the pathogenesis of diabetic corneal disease is unclear, aldose reductase has been implicated in corneal disease. The effects of an oral aldose reductase inhibitor (ARI) on the ocular surface of diabetic patients after cataract surgery were studied. METHODS: This clinical trial was designed to be randomised, double blinded, and placebo controlled. Pseudophakic patients with diabetes were randomly assigned to treatment with either oral ARI (ONO-2235) (n=12) or placebo (n=9) for 12 weeks. The vital staining of the ocular surface, tear production and clearance, break up time in tears (BUT), corneal and conjunctival sensation, and symptom score before treatments were examined as well as 4, 8, 12 weeks after the administration. Specular microscopic evaluation was also performed. RESULTS: After a 12 week period of oral ARI administration, fluorescein staining scores (from 2.04 (SD 1.12) to 1.46 (1.18); p=0.016), conjunctival sensation (from 1.15 (0.37) to 1.36 (0.31); p=0.0006), and symptom scores (from 5.38 (1.932) to 4.00 (2.07); p=0.0002) recovered significantly. Fluorescein staining of oral ARI administration also decreased compared with placebo (p=0.017). Rose bengal staining, tear clearance, and corneal sensation were improved although this increase was minor. Tear production, BUT, and specular microscopic evaluation of the corneal epithelium and endothelium did not demonstrate a significant change. CONCLUSION: Oral ARI opposes the ocular surface changes caused by diabetes, by recovery of ocular surface sensitivity as demonstrated through an improvement in vital staining.     

Efficacy of Alrestatin, an aldose reductase inhibitor, in human diabetic and nondiabetic lenses.

Immediately after cataract extraction, lenses from diabetic and nondiabetic patients were collected, classified, and assayed or incubated in high-glucose medium. The distribution of cataract types within the diabetic and nondiabetic groups was almost identical. The aldose reductase (AR) inhibitor AY22,284 (Alrestatin) was as effective in blocking sorbitol formation in diabetic as in nondiabetic lenses. While there was no difference in the level of intralenticular glucose, the diabetic lens produced significantly more sorbitol than did the nondiabetic lens. Also, the activity of polyol dehydrogenase (PD) was much lower in the diabetic population. The diabetic lenses swelled slightly more (P <.2) than nondiabetic lenses in high glucose media, and AY22,284 was effective in reducing the swelling of diabetic lenses in 35.5 mM glucose medium. While these results are preliminary, they suggest that diabetes, in some way, may confer on the human lens an increased susceptibility to osmotic stress via the sorbitol pathway. It is also reassuring to note that an AR inhibitor is no less effective in blocking the more active AR in the diabetic than in the nondiabetic lens. The therapeutic implications of this are discussed.     

A new approach against sugar cataract through aldose reductase inhibitors.

Aldose reductase inhibition is one of the therapeutic strategies that has been proposed to prevent or ameliorate long term diabetic complications including retinopathy and sugar cataract. Rats were fed with a galactose rich diet and the aldose reductase inhibitor Tolrestat was topically delivered by ocular instillation. The levels of lens aldose reductase activity, galactitol and the onset of cataract were evaluated during and after treatment with the inhibitor.Topical application of 1-3% Tolrestat (10 microl) four times daily resulted, after 9 days, in a significant decrease in the enzyme activity. Well after interrupting treatment with the drug, the enzyme activity remained impaired and galactose induced cataract was prevented. Our findings may represent the basis for therapeutic plans to prevent sugar cataract by long term cyclic treatments with aldose reductase inhibitors, with reduction in drug doses and side effects.