naphthoquinones and Cataract

Topics: Amino Acids; Animals; Biological Transport, Active; Cataract; Cell Membrane Permeability; Chemical Phenomena; Chemistry; Chemistry Techniques, Analytical; Cholinesterase Inhibitors; Chondroitin; Collagen; Cornea; Crystallins; Epithelium; Galactose; Galactosemias; Glucose; Humans; Lens, Crystalline; Naphthoquinones; Ocular Physiological Phenomena; Protein Biosynthesis; Rabbits; Sulfhydryl Compounds; Wound Healing

Cataract induced by exposure to naphthalene is thought to mainly involve its metabolic activation, forming 1,2-naphthoquinone (1,2-NQ), which can modify proteins through chemical modifications. In the present study, we examined the effect of 1,2-NQ on aggregation of crystallins (cry) associated with cataract. Incubation of bovine β-cry with 1,2-NQ caused covalent modification of β-cry at Cys117 and Lys125 accompanied by reduction in its thiol content, resulting in a concentration- and temperature-dependent aggregation of β-cry, whereas only little aggregation of α-cry induced by 1,2-NQ was seen. Interestingly, addition of α-cry to the reaction mixture of β-cry and 1,2-NQ markedly blocked β-cry aggregation induced by 1,2-NQ in a concentration-dependent manner. These results suggest that β-cry predominantly undergoes chemical modification by 1,2-NQ, causing its aggregation, which is suppressed by the chaperone-like protein, α-cry. This β-cry aggregation may be, at least in part, involved in the induction of cataract caused by 1,2-NQ.

Topics: alpha-Crystallins; beta-Crystallins; Cataract; Humans; Molecular Chaperones; Naphthoquinones; Protein Aggregation, Pathological; Protein Binding

Naphthalene induces cataract formation through the accumulation of its reactive metabolite, 1,2-naphthoquinone (1,2-NQ), in the ocular lens. 1,2-NQ increases lens protein oxidation and disrupts fiber cell membrane function; however, the association of these effects with changes in membrane structure is not understood. The goal of this study was to determine the direct effects of 1,2-NQ on membrane lipid oxidation and structural organization.. Iodometric approaches were used to measure the effects of naphthalene and 1,2-NQ on lipid hydroperoxide (LOOH) formation in model membranes composed of cholesterol and dilinoleoylphosphatidylcholine. Membrane samples were prepared at various cholesterol-to-phospholipid mole ratios and subjected to autoxidation at 37°C for 48 hours in the absence or presence of either agent alone (0.1-5.0 μM) or in combination with vitamin E. Small-angle x-ray diffraction was used to measure the effects of naphthalene and 1,2-NQ on membrane structure before and after exposure to oxidative stress.. 1,2-NQ increased LOOH formation by 250% (P < 0.001) and 350% (P < 0.001) at 1.0 and 5.0 μM, respectively, whereas naphthalene decreased LOOH levels by 25% (P < 0.01) and 10% (NS). The pro-oxidant effect of 1,2-NQ was inversely affected by membrane cholesterol enrichment and completely blocked by vitamin E. 1,2-NQ also increased cholesterol domain formation by 360% in membranes exposed to oxidative stress; however, no significant changes in membrane lipid organization were observed with naphthalene under the same conditions.. These data suggest a novel mechanism for naphthalene-induced cataract, facilitated by the direct effects of 1,2-NQ on lipid peroxidation and cholesterol domain formation.

Topics: Analysis of Variance; Cataract; Cholesterol; Humans; Lipid Peroxidation; Lipid Peroxides; Membrane Lipids; Models, Biological; Naphthalenes; Naphthoquinones

An injection of 1,2-naphthoquinone (NQ) into the anterior chamber of mouse eye produces anterior cortical cataract. It was previously shown by histology that mitochondria in lens epithelial cells are the target of ocular drug toxicity. In this work we investigated NQ-induced cataract by closely examining morphological changes of mitochondria and other cellular organelles in the lens epithelium. Mitochondria exhibited marked swelling in 2 hrs after NQ injection but restored the normal condensed configuration at 4.5 hrs. The nuclear chromatin showed condensation at 2 hrs and returned to the normal appearance at 4.5 hrs. This was unexpected because the lens at 4.5 hrs was cataractous due to vacuole formation in fiber cell layers. The result indicates that, although lens epithelial mitochondria are the target of NQ toxicity, cataract begins to develop before mitochondria and other subcellular organelles become totally dysfunctional. At 1 week after NQ injection, most mitochondria disintegrated and the fragmented chromatin appeared to leak out through the ruptured nuclear membrane. SOD injected with NQ significantly delayed the onset of cataract and protected lens epithelial cells. A second SOD injection further delayed cataract development.

Topics: Animals; Cataract; Lens, Crystalline; Male; Mice; Mice, Inbred C57BL; Microscopy, Electron; Mitochondria; Naphthoquinones; Superoxide Dismutase

N-acetyl-p-benzoquinone imine (NAPQI), a semiquinone metabolite of acetaminophen, produces cataract in mice. Naphthalene is biotransformed to the cataractogenic metabolite 1,2-naphthoquinone (NQ). Intracameral injection of NAPQI elicits a rapid increase in free intracellular Ca2+ in the lens epithelium and calpain activation before lens opacification begins. In order to test whether the cellular response is a common feature of quinone-induced cataracts, we injected in this work 1,2-naphthoquinone (NA) in the anterior chamber of mouse eye and followed cellular responses in the lens prior to opacity development. A marked rise in free intracellular Ca2+ in the lens epithelium and concurrent activation of calpain were observed within 1 hr after NQ injection preceding lens opacity development. These results support the suggestion that Ca2+ release and calpain activation are involved in the mechanism of quinone-induced cataractogenesis.

Topics: Animals; Anterior Chamber; Calcium; Calpain; Cataract; Epithelial Cells; Glycoproteins; Lens, Crystalline; Male; Mice; Mice, Inbred C57BL; Microscopy, Confocal; Naphthoquinones; Oligopeptides

The oxidation of naphthalene-1,2-dihydrodiol (ND) to o-naphthoquinone (NQ) in the lens is believed to be responsible for the formation of cataracts in naphthalene-fed rats. Studies using either recombinant rat lens (RLAR) or human muscle aldose reductase (HMAR) incubated in vitro with ND in the presence of NAD(P) verified that aldose reductase (EC 1.1.1.21) is the dihydrodiol dehydrogenase that catalyzes the oxidation of ND to NQ. Kinetic studies of Vmax/Km indicated that RLAR catalyzes the NAD-dependent oxidation of ND with an optimal pH of 9.0. The corresponding activity of HMAR was lower than that of rat enzyme. The metabolite produced by the incubation of RLAR with ND in the presence of 2-mercaptoethanol and NAD in 20 mM phosphate buffer, pH 7.5, was isolated by C18 reversed-phase high-performance liquid chromatography. The elution profile showed the formation of a new peak that was identical with a peak generated when NQ was incubated under the same condition. The metabolite in both peaks was identified as 4-(2-hydroxyethylsulfanyl)-1, 2-dihydro-1,2-naphthalenedione (HNQ) by 1H and 13C NMR analyses using homonuclear correlation spectroscopy, heteronuclear multiple quantum coherence, and heteronuclear shift correlations via multiple bond connectivities as well as infrared analysis. HNQ is readily autoxidized to 2,3-dihydro-1-oxa-4-thia-9,10-phenanthrenedione. The stoichiometry of 1:1 between the consumption of ND and the formation of NADH for the formation of HNQ implies that rat lens aldose reductase catalyzes a 2e- oxidation of ND to yield the corresponding ketol, which is autoxidized to NQ.

Topics: Aldehyde Reductase; Animals; Cataract; Cells, Cultured; Disease Models, Animal; Humans; Lens, Crystalline; Naphthols; Naphthoquinones; Oxidation-Reduction; Rats

The effects of aldose reductase inhibitors on lens protein modifications induced by naphthalene-1,2-dihydrodiol were investigated in vitro to confirm the role of aldose reductase on naphthalene cataract formation. HPLC analysis of naphthalene-1, 2-dihydrodiol incubated with aldose reductase and NAD+indicated the formation of a metabolite peak corresponding to 1,2-naphthoquinone. Soluble proteins from rat lenses prepared by gel filtration of crude lens extracts through Sephadex PD-10, incubated with naphthalene-1, 2-dihydrodiol in the presence of NAD+displayed an absorbance ca 450 nm and their spectra were essentially identical to those of 1, 2-naphthoquinone-protein adducts. Similar spectra were also obtained from proteins isolated from the intact rat lens after in vitro incubation in medium containing naphthalene-1,2-dihydrodiol. The spectra obtained from lens proteins incubated with 1, 2-dihydroxynaphthalene were distinct from those of either naphthalene-1,2-dihydrodiol or 1,2-naphthoquinone. Aldose reductase inhibitors possessing either hydantoin or carboxylic acid groups prevented protein modification induced by naphthalene-1, 2-dihydrodiol but not protein modification induced by 1, 2-dihydroxynaphthalene or 1,2-naphthoquinone. Therefore, the metabolite formed from naphthalene-1,2-dihydrodiol by aldose reductase is 1,2-naphthoquinone. Lens proteins modified by naphthalene-1,2-dihydrodiol appear essentially identical to protein adducts formed with 1,2-naphthoquinone and their formation can be prevented by both hydantoin and carboxylic acid containing aldose reductase inhibitors.

Topics: Aldehyde Reductase; Animals; Cataract; Chromatography, High Pressure Liquid; Crystallins; Enzyme Inhibitors; Fluorenes; Hydantoins; Imidazoles; Imidazolidines; Lens, Crystalline; Naphthalenes; Naphthols; Naphthoquinones; Phthalazines; Rats; Spectrophotometry

Porcine and bovine lens GSTs were compared in the stability against various oxidative stress which is a major factor of cataract formation in order to clarify the role of lens glutathione S-transferase (GST) and its relation to cataractogenesis. Class pi porcine lens GST was inactivated reversibly by biological disulfides, cystine and cystamine, and also inactivated by active oxygen species such as O2- generated through xanthine-xanthine oxidase system and H2O2. On the other hand, class mu bovine lens GST was insensitive to such applied oxidative stress. Furthermore, 1,2-naphthoquinone, which is a metabolite of naphthalene and an actual inducer of naphthalene cataract, strongly inactivated porcine lens GST though it did not affect bovine enzyme. Thus, porcine and bovine lens GSTs had different sensitivity to various oxidative stress which could induce cataract formation. The results suggest that the differential expression of GST isozymes among animals may explain the variation in the cataract formation caused by oxidative stress.

Topics: Animals; Cataract; Cattle; Cystamine; Cystine; Glutathione Transferase; Lens, Crystalline; Naphthoquinones; Reactive Oxygen Species; Swine

The polycyclic aromatic hydrocarbon naphthalene is bioactivated by cytochromes P450 to an electrophilic epoxide intermediate, which subsequently is metabolized to naphthoquinones (NQ) and possibly to a free radical intermediate. These reactive intermediates may bind covalently to lenticular tissues, cause oxidant stress and/or lipid peroxidation, thereby initiating cataracts. To evaluate this hypothesis, male C57BL/6 or DBA/2 mice were treated with naphthalene or one of several naphthoquinone and naphthol metabolites, in the presence or absence of modulators of chemical bioactivation and detoxification. In C57BL/6 mice, cataracts were caused by naphthalene (500-2000 mg/kg ip) in a dose-dependent fashion. The incidence of naphthalene-induced cataracts was decreased by pretreatment with the P450 inhibitors SKF 525A and metyrapone, the antioxidants caffeic acid and vitamin E, the glutathione (GSH) precursor N-acetylcysteine, and the free radical spin trapping agent alpha-phenyl-N-t-butylnitrone (p less than 0.05). Naphthalene cataractogenicity was enhanced by pretreatment with the cytochrome P450 inducer phenobarbital and the GSH depletor diethyl maleate (DEM) (p less than 0.05), and was unaffected by pretreatment with the prostaglandin synthetase inhibitors aspirin or naproxen, or the epoxide hydrolase inhibitor trichloropropene oxide. Cataracts were initiated by 1,2-NQ and 1,4-NQ (5-250 mg/kg ip) in a dose-dependent fashion, with a molar potency about 10-fold higher than that for naphthalene. NQ cataractogenicity was enhanced by pretreatment with DEM (p less than 0.05). 1-Naphthol (56 to 562 mg/kg ip) demonstrated a cataractogenic potency intermediary to that for naphthalene and NQ. DBA/2 mice treated with naphthalene (2000 mg/kg ip), 1,4-NQ (65-250 mg/kg ip), 1,2-NQ (30-250 mg/kg ip), or DEM followed by 1,4-NQ (125 mg/kg ip) did not develop cataracts. These results suggest that naphthalene cataractogenesis in C57BL/6 mice requires P450-catalyzed bioactivation to a reactive intermediate, which may be the NQ and/or a free radical derivative, either of which is dependent upon GSH for detoxification.

Topics: Animals; Cataract; Cytochrome P-450 Enzyme System; Glutathione; Male; Mice; Mice, Inbred C57BL; Mice, Inbred DBA; Naphthalenes; Naphthoquinones; Trichloroepoxypropane

We have examined the mercapturic acid pathway of the cataractous rabbit lens following induction by naphthalene as an oxidative foreign substance. 1,2-Naphthoquinone, which is formed in the eye from naphthalene diol and other naphthalene derivatives by a combination of enzymic and non-enzymic reactions, readily oxidizes GSH and GSH S-transferase [EC 2.5.1.18] in the lens scavenging system. 1,2-Naphthoquinone appeared in the rabbit aqueous humor after 8 h, and showed a maximum level in the lens 24 h after naphthalene administration, with marked accumulation in the lens nucleus. At the same time, the GSH level and GSH S-transferase activity in the lens decreased after 4 h, and lens opacification appeared 7 days after naphthalene administration. Furthermore, we identified the naphthalene metabolite, N-acetyl-S-(1,2-dihydro-2-hydroxynaphthyl) cysteine, in the lens of rabbit after naphthalene administration and in an in vitro experiment on lens homogenate using gas chromatography-mass spectrometry (GC-MS). This compound is an intermediate of the mercapturic acid pathway, and indicates that naphthalene derivatives are metabolized through the mercapturic acid pathway which acts as a scavenging system in the lens.

Topics: Acetylcysteine; Animals; Aqueous Humor; Cataract; Female; Gas Chromatography-Mass Spectrometry; Glutathione; Glutathione Transferase; Lens, Crystalline; Naphthalenes; Naphthoquinones; Rabbits

Topics: Animals; Cataract; Lens, Crystalline; Naphthalenes; Naphthoquinones; Pigmentation; Rabbits; Rats

Topics: Cataract; Cortisone; Glucose; Humans; Iris; Lens, Crystalline; Naphthoquinones; Pilocarpine

I have discussed five aspects of lens metabolism and their possible relationship to cataract in man, and this has left me with five fundamental questions to be answered. 1. Are the fluorescent tryptophan derivatives, found only in the lens of man and higher primates, involved in the development of brown nuclear cataract? 2. Is naphthalene cataract in rabbits a model for any type of cataract in man--i.e., are quinones ever formed in the human eye? 3. Is diabetes the only cataract in which osmotic swelling is important? 4. Does self-digestion of protein in the human lens contribute to cataract development? 5. Are the consequences of the abnormal maturation of lens fibers, which occurs in tryptophan deficiency cataract in rats, ever seen in man?

Topics: Aging; Animals; Ascorbic Acid; Cataract; Crystallins; Diabetic Retinopathy; Humans; Lens, Crystalline; Naphthalenes; Naphthoquinones; Peptide Hydrolases; Sorbitol; Tryptophan

Topics: Animals; Cataract; Chick Embryo; Chloroquine; Culture Media; Culture Techniques; Hydroquinones; Lens, Crystalline; Naphthols; Naphthoquinones; Ouabain; Phenacetin; Phenobarbital; Phenylbutazone; Phenylhydrazines; Photomicrography; Prednisolone; Primaquine; Pyrogallol; Sulfanilamides; Vitamin K

Topics: Animals; Aqueous Humor; Ascorbic Acid; Cataract; Diet; Glutathione; In Vitro Techniques; Lens, Crystalline; Naphthalenes; Naphthoquinones; Rabbits; Vitreous Body

Topics: Acids; Animals; Benzene Derivatives; Cataract; Chick Embryo; Culture Techniques; Erythrocytes; Hydrogen-Ion Concentration; Lens, Crystalline; Naphthoquinones; Phenylhydrazines; Primaquine; Toxicology

Oxidation of tyrosine in the presence of bovine lens proteins leads to the formation of brown or black melanoproteins. Both tyrosinase and the oxidizing system of ferrous sulphate-ascorbic acid-EDTA are effective. The fluorescence of the lens proteins is both altered and enhanced by the tyrosine-oxidizing systems. Their fluorescence spectra resemble those of urea-insoluble proteins of human cataractous lens and of 1,2-naphthaquinone-proteins of naphthalene cataract. The lens proteins lose their thiol groups and, in acid hydrolysates of treated beta-and gamma-crystallins, a substance has been detected chromatographically that behaves similarly to a compound formed when 3,4-dihydroxyphenylalanine (dopa) is oxidized by tyrosinase in the presence of cysteine. Analysis and behaviour of this substance from hydrolysates of lens proteins suggest that it is a compound of cysteine and dopa.

Topics: Animals; Ascorbic Acid; Cataract; Catechol Oxidase; Cattle; Chemical Phenomena; Chemistry; Chromatography, Paper; Crystallins; Cysteine; Dihydroxyphenylalanine; Edetic Acid; Fluorescence; Iron; Naphthoquinones; Oxidation-Reduction; Proteins; Sulfates; Sulfur; Tyrosine

Topics: Animals; Cataract; Cattle; Chemistry Techniques, Analytical; Color; Crystallins; Fluorescence; Humans; Lens, Crystalline; Naphthalenes; Naphthoquinones; Rabbits; Solubility; Sulfhydryl Compounds; Urea; Vitreous Body; Water

Topics: Animals; Cataract; Cattle; Humans; In Vitro Techniques; Infant, Newborn; Lens, Crystalline; Naphthoquinones