Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0086543 (cataract)
 29,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Studies have been made of the effects of X-ray on various lens reducing systems, including the levels of NADPH and glutathione (GSH), the activity of the hexose monophosphate shunt (HMS) and of certain enzymes, including GSH reductase, GSH peroxidase, and glucose-6-phosphate dehydrogenase (G-6-PG). It was found that during several weeks following X-irradiation but prior to cataract formation, there was very little change in the number of reduced -SH groups per unit weight of lens protein but that, with the appearance of cataract, there was a sudden loss of protein -SH groups. In contrast, the concentration of GSH in the X-rayed lens decreased throughout the experimental period. Similarly, the concentration of NADPH in the X-rayed lens was found to decrease significantly relative to controls 1 week prior to cataract formation, and the ratio of NADPH to NADP+ in the lens shifted at this time period from a value greater than 1.0 in the control lens to less than 1.0 in the X-rayed lens. A corresponding decrease occurred in the activity of the HMS in X-rayed lenses as measured by culture in the presence of 1-14C-labeled glucose, G-6-PD was partially inactivated in the X-rayed lens. Of the eight enzymes studied, G-6-PD appeared to be the most sensitive to X-irradiation. The data indicate that X-irradiation results in a steady decrease in the effectiveness of lens reducing systems and that when these systems reach a critically low point, sudden oxidation of protein -SH groups and formation of high-molecular-weight protein aggregates may be initiated.
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PMID:The effects of X-irradiation on lens reducing systems. 3 84

zeta-Crystallin is a major protein in the lens of certain mammals. In guinea pigs it comprises 10% of the total lens protein, and it has been shown that a mutation in the zeta-crystallin gene is associated with autosomal dominant congenital cataract. As with several other lens crystallins of limited phylogenetic distribution, zeta-crystallin has been characterized as an "enzyme/crystallin" based on its ability to reduce catalytically the electron acceptor 2,6-dichlorophenolindophenol. We report here that certain naturally occurring quinones are good substrates for the enzymatic activity of zeta-crystallin. Among the various quinones tested, the orthoquinones 1,2-naphthoquinone and 9,10-phenanthrenequinone were the best substrates whereas menadione, ubiquinone, 9,10-anthraquinone, vitamins K1 and K2 were inactive as substrates. This quinone reductase activity was NADPH specific and exhibited typical Michaelis-Menten kinetics. Activity was sensitive to heat and sulfhydryl reagents but was very stable on freezing. Dicumarol (Ki = 1.3 x 10(-5) M) and nitrofurantoin (Ki = 1.4 x 10(-5) M) inhibited the activity competitively with respect to the electron acceptor, quinone. NADPH protected the enzyme against inactivation caused by heat, N-ethylmaleimide, or H2O2. Electron paramagnetic resonance spectroscopy of the reaction products showed formation of a semiquinone radical. The enzyme activity was associated with O2 consumption, generation of O2- and H2O2, and reduction of ferricytochrome c. These properties indicate that the enzyme acts through a one-electron transfer process. The substrate specificity, reaction characteristics, and physicochemical properties of zeta-crystallin demonstrate that it is an active NADPH:quinone oxidoreductase distinct from quinone reductases described previously.
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PMID:Identification and characterization of the enzymatic activity of zeta-crystallin from guinea pig lens. A novel NADPH:quinone oxidoreductase. 137 Apr 56

Tocopherols and tocotrienols (vitamin E) and ascorbic acid (vitamin C) as well as the carotenoids react with free radicals, notably peroxyl radicals, and with singlet molecular oxygen (1O2), this being the basis of their function as antioxidants. RRR-alpha-tocopherol is the major peroxyl radical scavenger in biological lipid phases such as membranes or low-density lipoproteins (LDL). L-Ascorbate is present in aqueous compartments (e.g. cytosol, plasma, and other body fluids) and can reduce the tocopheroxyl radical; it also has a number of metabolically important cofactor functions in enzyme reactions, notably hydroxylations. Upon oxidation, these micronutrients need to be regenerated in the biological setting, hence the need for further coupling to nonradical reducing systems such as glutathione/glutathione disulfide, dihydrolipoate/lipoate, or NADPH/NADP+ and NADH/NAD+. Carotenoids, notably beta-carotene and lycopene as well as oxycarotenoids (e.g. zeaxanthin and lutein), exert antioxidant functions in lipid phases by free-radical or 1O2 quenching. There are pronounced differences in tissue carotenoid patterns, extending also to the distribution between the all-trans and various cis isomers of the respective carotenoids. Antioxidant functions are associated with lowering DNA damage, malignant transformation, and other parameters of cell damage in vitro as well as epidemiologically with lowered incidence of certain types of cancer and degenerative diseases, such as ischemic heart disease and cataract. They are of importance in the process of aging. Reactive oxygen species occur in tissues and cells and can damage DNA, proteins, carbohydrates, and lipids. These potentially deleterious reactions are controlled in part by antioxidants that eliminate prooxidants and scavenge free radicals. Their ability as antioxidants to quench radicals and 1O2 may explain some anticancer properties of the carotenoids independent of their provitamin A activity, but other functions may play a role as well. Tocopherols are the most abundant and efficient scavengers of peroxyl radicals in biological membranes. The water-soluble antioxidant vitamin C can reduce tocopheroxyl radicals directly or indirectly and thus support the antioxidant activity of vitamin E; such functions can be performed also by other appropriate reducing compounds such as glutathione (GSH) or dihydrolipoate. The biological efficacy of the antioxidants is also determined by their biokinetics.
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PMID:Antioxidant functions of vitamins. Vitamins E and C, beta-carotene, and other carotenoids. 144 60

Since most of the known factors that are associated with cataract formation are oxidative in nature, one would expect that a highly reductive environment might arrest or retard the progress of cataract formation. Reduced nucleotides, both NADH and NADPH, are potent reductants with a large negative redox potential of -320 mV. Lenses of certain species contain high levels of these nucleotides, presumably due to the presence of taxon specific crystallins. We have utilized this situation to investigate whether the levels of reduced pyridine nucleotides modulate photo-oxidative damage to the lens. We have monitored the time dependent loss of tryptophan fluorescence upon photodamage for lenses from guinea pig, rabbit and frog (Rana) that contain high levels of pyridine nucleotides and compared with the lenses from rat, Xenopus and a mutant strain of guinea pig that contain significantly lower amounts of these nucleotides. About 75% and 90% of the initial fluorescence intensity is lost in the case of rat and Xenopus lenses, respectively, after a total of 35 min exposure. Rabbit, guinea pig and frog lenses, under identical conditions, show only about 35-40% loss of the initial fluorescence. It appears that the lenses that contain high levels of reduced nucleotides are less susceptible to photodamage. The observed anti-oxidative role of reduced nucleotides in the lenses indicates the possibility of testing reductants (NADPH, NADH and their functional analogues) as potential candidates to therapeutically intervene in the process of cataractogenesis.
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PMID:Levels of reduced pyridine nucleotides and lens photodamage. 145 82

Human lens was found to contain aldehyde dehydrogenase at a level of activity similar to that of bovine lens, namely 1.76 +/- 0.51 IU/g. The enzyme, which appears to be a tetramer of 229 kD, was less susceptible to inhibition by cataractogenic agents than the bovine enzyme. The lipid peroxidation product malondialdehyde was a good substrate of the human lens enzyme. The in vitro aldose reductase reaction, which we have shown is caused by glyceraldehyde-stimulated free-radical NADPH oxidation, is inhibited by the potential anti-cataract agents, bendazac acid and bendazac lysine; these compounds also inhibit ferricytochrome c reduction in the presence of DL-glyceraldehyde and scavenge superoxide radicals. These results are consistent with the hypotheses that aldehyde dehydrogenase is a protective enzyme in the human lens, and that the peroxy radical scavenging effects of bendazac acid and bendazac lysine contribute to their anti-cataract activity.
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PMID:Aldehyde dehydrogenase, aldose reductase, and free radical scavengers in cataract. 182 64

Aldose reductase activity can be measured in the neutrophil and it has been proposed that this may be a marker for risk of complications in diabetes. We have studied aldose reductase activity in neutrophil, nerve, and lens in diabetic patients undergoing sural nerve biopsy or cataract extraction. A correlation was demonstrated between lens and neutrophil aldose reductase activity (r = 0.53, p = 0.01) but no correlations were demonstrated between nerve aldose reductase activities and nerve morphometry, nerve function or neutrophil aldose reductase activity. No significant difference was found between neutrophil aldose reductase activities in groups of patients with severe neuropathy, or cataract, or no complications (24 (interquartile range 16-32) vs 24 (16-40) vs 24 (16-40) nmol NADPH min-1 10(8)-cells-1). In a group of 56 Type 1 diabetic patients screened within 6 years of diagnosis, multiple regression analysis failed to show any relationship between neutrophil aldose reductase activity and abnormalities of neurophysiological function. These results suggest that neutrophil aldose reductase activity cannot be used as a marker for the development of cataract or neuropathy in diabetes.
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PMID:Neutrophil aldose reductase activity as a potential marker for neuropathy and cataract in diabetes. 183 41

Effects of novel aldose reductase inhibitors, M16209 (1-(3-bromobenzo[b]furan-2-ylsulfonyl)hydantoin) and M16287 (1-(3-chlorobenzo[b]furan-2-ylsulfonyl)hydantoin), on galactose-induced cataract formation in rats were investigated. Rats fed a 30% galactose diet developed lenticular opacity in the peripheral region by the 6th day of galactose feeding and showed gradual progression of opacity from the equator to the center of lenses. Histological study on the 15th day showed apparent lens fiber swelling and vacuolation predominantly in the equatorial and anterior cortical regions. Biochemical changes such as accumulation of galactitol, depletion of myo-inositol and decrease in glutathione (GSH) content in lenses preceded the appearance of opacity. Remarkable increase in NADPH content and decrease in NADP+ content, in addition to elevation of the ratio of Na+/K+, in lenses were also observed on the 15th day. Both M16209 and M16287 (10, 30 and 100 mg/kg/day, p.o.) dose-dependently ameliorated these morphological and biochemical changes except that restoration of myo-inositol content was incomplete. These results indicate that M16209 and M16287 can prevent galactose-induced cataract formation through amelioration of metabolic disorders and thus have high potential for clinical use in the treatment of some diabetic complications.
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PMID:Effects of novel hydantoin derivatives with aldose reductase inhibiting activity on galactose-induced cataract in rats. 212 52

Dimeric and monomeric proteins containing dihydrodiol dehydrogenase and aldehyde reductase activities were purified from pig lens. The dimeric enzyme of Mr 65,000 specifically oxidized the trans-dihydrodiols of naphthalene and benzene with NADP+ as a strict cofactor, and reduced alpha-diketones, aromatic aldehydes and glyceraldehyde with NADPH as a cofactor. The monomeric enzyme of Mr 35,000, although identical with aldose reductase, oxidized the trans-dihydrodiol of naphthalene at a pH optimum of 7.6. These results suggest that the two enzymes are involved in the pathogenesis of naphthalene cataract.
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PMID:Isolation from pig lens of two proteins with dihydrodiol dehydrogenase and aldehyde reductase activities. 269 Aug 27

The disposition and disposal of the -SH groups of the lens during aging and cataractogenesis have been investigated by laser Raman spectroscopy as a noninvasive microprobe in the intact living lens. In this procedure -SH and -S-S- give unique discrete Raman signals (at 2580 and 508 cm-1) that may be used to calculate relative concentrations in a very small volume of the lens. We present evidence showing an unexpected and remarkable difference with respect to these groups between the mouse lens and the lenses of guinea pig and man. The mouse lens nucleus exhibits a precipitous fall in the -SH concentration on aging from 1 to 6 months; concomitantly, there is a rise in -S-S- of comparable magnitude, indicating a direct conversion. The guinea pig lens, however, is quite different with respect to the age-dependent change in nuclear -S-S-: there is none between 6 months and 5 years. In the human lens -S-S- behaves exactly as in the guinea pig lens: the level is low and does not change with age between 9 and 65 years. With respect to nuclear -SH, these two latter species of lenses show some decrease with age but nothing like the approach to zero found in the aging mouse lens nucleus. These differences involving lenticular -SH and -S-S- appear to be correlated with the hard nucleus in the mouse lens and the softer nuclei of lenses in guinea pigs and humans. The relatively high level of -S-S- in the old but clear mouse lens does not support the idea that protein aggregation involving formation of intermolecular -S-S- bonds is necessarily an important cause of nuclear cataract. The small but significant age-related depression of -SH in guinea pig lens nuclei without any accumulation of -S-S- may be explained as a result of glutathione (GSH) oxidation and subsequent extrusion of glutathione disulfide (GSSG) by the lens. We propose that the oxidation of glutathione proceeds by reaction with protein disulfide groups to yield protein sulfhydryl (PSH) and a mixed disulfide of glutathione and protein; the mixed disulfide is capable of being reduced by glutathione reductase and NADPH, yielding the original PSH and GSSG, which is extruded from the lens. It remains to be determined if this mechanism is more active in guinea pig and human lenses than in the mouse lens.
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PMID:Disulfide bond formation in the eye lens. 386 9

The protein aldose reductase has been implicated in cataract in diabetes and galactosaemia. Recently it has been suggested that a number of non-steroidal anti-inflammatory agents have inhibitory activity against aldose reductase activity, and therefore might be used to prevent diabetic complications including cataract. Steady state kinetic experiments show that Clinoril (Sulindac sulphoxide) acts as a non-competitive inhibitor of NADPH oxidation with purified bovine lens aldose reductase, with an action that may involve binding to more than one site on the protein. As a preliminary to studying the effect on human lens and cataract, a double-masked, placebo-controlled study using random allocation into parallel groups was conducted on 20 volunteers to determine the penetration of Clinoril (Sulindac) and its metabolites into normal human red cells, and the effect of the drug on red cell NADPH-oxidising activity. It was found that while Clinoril, the sulphoxide form of the drug, and its metabolites the sulphone and the sulphide could be detected in the appropriate plasma samples (up to 36 micrograms of the sulphone/ml of plasma), very little could be detected in the red cells. There was no significant effect on red cell NADPH-oxidising activity.
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PMID:The inhibition of bovine lens aldose reductase by Clinoril, its absorption into the human red cell and its effect on human red cell aldose reductase activity. 392 May 99


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