3-Hydroxykynurenine and 3-Hydroxyanthranilic acid may act as endogenous antioxidants in the eye lens

Luthra, Manni; Balasubramanian, D.

doi:10.1016/s0014-4835(05)80177-0

Cited by 24 publications

(15 citation statements)

References 10 publications

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“…Among the tryptophan metabolites present in the lens, Ky, 3HK and 3HKG (and some β‐carbolines) have been shown to be photodynamically inert (11–13). They may, therefore, act as UVA filters to the posterior regions of the eye, and some of them may even act as endogenous antioxidants (11,29). Bova et al (8) have suggested that AHBG, which is formed from 3HKG by the loss of ammonia and subsequent hydrogenation, is a UVA protectant filter.…”

Section: Discussionmentioning

confidence: 99%

Role of Xanthurenic Acid 8-O-β-d-Glucoside, a Novel Fluorophore that Accumulates in the Brunescent Human Eye Lens¶

Thiagarajan

Shirao

Ando

et al. 2007

Photochemistry and Photobiology

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We have been able to identify a blue fluorophore from the low‐molecular weight soluble fraction of human adult nondiabetic brunescent cataract lenses as xanthurenic acid 8‐O‐β‐d‐glucoside (XA8OG) (excitation = 338 nm and emission = 440 nm). To determine the role of this fluorophore in the lens, we have examined its photophysical and photodynamic properties. We found XA8OG to have a fluorescence quantum yield (ϕ) of 0.22 and a major emission lifetime of 12 ns. We found it to be a UVA‐region sensitizer, capable of efficiently generating singlet oxygen species but little of superoxide. We also demonstrated that XA8OG oxidizes proteins when irradiated with UVA light, causing photodynamic covalent chemical damage to proteins. Its accumulation in the aging human lens (and the attendant decrease of its precursor O‐β‐d‐glucoside of 3‐hydroxykynurenine) can, thus, add to the oxidative burden on the system. XA8OG, thus, appears to be an endogenous chromophore in the lens, which can act as a cataractogenic agent.

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Section: Discussionmentioning

confidence: 99%

Role of Xanthurenic Acid 8-O-β-d-Glucoside, a Novel Fluorophore that Accumulates in the Brunescent Human Eye Lens¶

Thiagarajan

Shirao

Ando

et al. 2007

Photochemistry and Photobiology

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“…It has been described that aerobic irradiation of KYN produces superoxide radicals and leads to reduction of cytochrome c [62, 63]. Additionally, in vitro studies show that KYN is able to photooxidize cysteine, NADH, and ascorbic acid and this capacity may be directly relevant to photobiological processes occurring in the lens in vivo .…”

Section: Metabolites With Redox and Neuroactive Propertiesmentioning

confidence: 99%

Kynurenines with Neuroactive and Redox Properties: Relevance to Aging and Brain Diseases

Ocampo

Huitrón

González-Esquivel

et al. 2014

Oxidative Medicine and Cellular Longevity

105

119

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The kynurenine pathway (KP) is the main route of tryptophan degradation whose final product is NAD+. The metabolism of tryptophan can be altered in ageing and with neurodegenerative process, leading to decreased biosynthesis of nicotinamide. This fact is very relevant considering that tryptophan is the major source of body stores of the nicotinamide-containing NAD+ coenzymes, which is involved in almost all the bioenergetic and biosynthetic metabolism. Recently, it has been proposed that endogenous tryptophan and its metabolites can interact and/or produce reactive oxygen species in tissues and cells. This subject is of great importance due to the fact that oxidative stress, alterations in KP metabolites, energetic deficit, cell death, and inflammatory events may converge each other to enter into a feedback cycle where each one depends on the other to exert synergistic actions among them. It is worth mentioning that all these factors have been described in aging and in neurodegenerative processes; however, has so far no one established any direct link between alterations in KP and these factors. In this review, we describe each kynurenine remarking their redox properties, their effects in experimental models, their alterations in the aging process.

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“…Apart from the color bias that they introduce to the transmission of light, some of them can also act as photodynamic agents which, upon absorption of UVA and visible light, cause sensitized covalent chemical changes in the substrate molecules through the generation of reactive oxygen species (ROS) such as singlet oxygen ('0,) superoxide anion radical (O;-), hydroxyl radical ('OH) or peroxide (H,O,). We have shown earlier that, among the Trp oxidation products, NFK and KUA are particularly active photodynamic agents, while Ky and 3HK are benign [36]; indeed, 3HK might even be an endogenous antioxidant [37]. In this connection, it is of interest to investigate whether compound A can act as a photodynamic agent and cause further damage to the lens.…”

Section: -Hydroxyquinolinementioning

confidence: 99%

Protein‐associated pigments that accumulate in the brunescent eye lens

Luthra

Ranganathan

et al. 1994

FEBS Letters

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Brunescent (dark brown) cataract is particularly prevalent in the tropics. Enzymatic digestion of the insoluble protein fraction of brunescent cataractous eye lenses from India, followed by high performance liquid chromatographic separation of the pigments and spectroscopic investigations, have led to the identification of one of the pigments as 4-hydroxyquinoline-3-[a-aminoacetic acid] (compound A). The 4-hydroxyquinoline moiety is shown to be a photodynamic agent that generates O;-and leads to protein crosslinking. This suggests that the compound A may play a long-term deleterious role in situ in the lens.

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3-Hydroxykynurenine and 3-Hydroxyanthranilic acid may act as endogenous antioxidants in the eye lens

Cited by 24 publications

References 10 publications

Role of Xanthurenic Acid 8-O-β-d-Glucoside, a Novel Fluorophore that Accumulates in the Brunescent Human Eye Lens¶

Role of Xanthurenic Acid 8-O-β-d-Glucoside, a Novel Fluorophore that Accumulates in the Brunescent Human Eye Lens¶

Kynurenines with Neuroactive and Redox Properties: Relevance to Aging and Brain Diseases

Protein‐associated pigments that accumulate in the brunescent eye lens

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