Two-Photon Excited Fluorescence Lifetime Imaging of Tetracycline-Labeled Retinal Calcification.

Deposition of calcium-containing minerals such as hydroxyapatite and whitlockite in the subretinal pigment epithelial (sub-RPE) space of the retina is linked to the development of and progression to the end-stage of age-related macular degeneration (AMD). AMD is the most common eye disease causing blindness amongst the elderly in developed countries; early diagnosis is desirable, particularly to begin treatment where available. Calcification in the sub-RPE space is also directly linked to other diseases such as Pseudoxanthoma elasticum (PXE).

Fluorescence Lifetime Imaging of Human Sub-RPE Calcification In Vitro Following Chlortetracycline Infusion.

We have shown that all sub-retinal pigment epithelial (sub-RPE) deposits examined contain calcium phosphate minerals: hydroxyapatite (HAP), whitlockite (Wht), or both. These typically take the form of ca. 1 μm diameter spherules or >10 μm nodules and appear to be involved in the development and progression of age-related macular degeneration (AMD).

Imaging hydroxyapatite in sub-retinal pigment epithelial deposits by fluorescence lifetime imaging microscopy with tetracycline staining.

Significance: Recent evidence suggests that hydroxyapatite (HAP) in sub-retinal pigment epithelial (sub-RPE) deposits in aged human eyes may act to nucleate and contribute to their growth to clinically detectable size. Sub-RPE deposits such as drusen are clinical hallmarks of age-related macular degeneration (AMD), therefore enhanced and earlier detection is a clinical need. We found that tetracycline-family antibiotics, long known to stain HAP in teeth and bones, can also label the HAP in sub-RPE deposits.

Effect of high sugar levels on miRNA expression. Studies with galactosemic mice lenses.

Purpose: Development of cataract is associated with apoptotic death of the lens epithelial cells. The purpose of this investigation was to examine whether this could be explained by enhancement in the expression of certain pro-apoptotic microRNAs (miRs), known to induce apoptosis by hybridizing with target mRNAs, with the consequence of gene silencing. In addition, it was intended to investigate if such expression could be antagonized by reactive oxygen species (ROS) scavengers.

Role of ultraviolet irradiation and oxidative stress in cataract formation-medical prevention by nutritional antioxidants and metabolic agonists.

Purpose: Cataract is a significant cause of visual disability with relatively high incidence. It has been proposed that such high incidence is related to oxidative stress induced by continued intraocular penetration of light and consequent photochemical generation of reactive oxygen species, such as superoxide and singlet oxygen and their derivatization to other oxidants, such as hydrogen peroxide and hydroxyl radical. The latter two can also interact to generate singlet oxygen by Haber-Weiss reaction.

Effectiveness of topical caffeine in cataract prevention: studies with galactose cataract.

Purpose: The primary objective of the study was to investigate the possible inhibition of cataract formation by topical administration of caffeine using the galactosemic rat model. It was hypothesized that caffeine will do so by acting as scavenger of reactive oxygen species known to be generated under hyperglycemic conditions.

Methods: Cataract was induced by feeding young rats a diet containing 24% galactose for a period of 25 days.

Inhibition of selenite-induced cataract by caffeine.

Purpose: The objective of the investigation was to study possible inhibition of oxidative stress and cataract formation by caffeine in vivo.

Methods: Oxidative stress and consequent cataract formation was induced by intraperitoneal administration of a single dose of sodium selenite (1.16 μmol) to Sprague-Dawley rat pups on day 9 postnatally.

Kynurenine-induced photo oxidative damage to lens in vitro: protective effect of caffeine.

Photochemical generation of reactive species of oxygen in the lens and aqueous and consequent physiological damage to the tissue has been implicated in the genesis of human cataracts. The present studies were undertaken to examine the feasibility of possible prevention of such damage to the lens initiated by UV activation of kynurenine, a well-known photosensitizer in the human lens. The studies were done by organ culturing intact mouse lenses in medium containing kynurenine and exposed to UVA.

Prevention of oxidative damage to lens by caffeine.

Purpose: The primary objective of this study was to examine the possibility of inhibiting oxidative damage to the lens in vitro by caffeine.

Methods: Oxidative damage was inflicted by incubating mouse lenses in Tyrode medium containing 0.1 mM Fe(8)Br(8), an iron complex soluble in aqueous medium.

UV-B-induced damage to the lens in vitro: prevention by caffeine.

Ultraviolet (UV) irradiation is one of the significant risk factors in the genesis of cataracts. Pathogenetically, the process can be triggered by the intraocular generation of various reactive species of oxygen that are well known to be initiated by the penetration of light, especially of the UV frequencies. The contribution of UV exposure in the etiology of this disease is likely to increase further due to ozone depletion in the upper atmosphere.

Prevention of oxidative stress to the retina by pyruvate. A preliminary report.

Aim: Oxidative stress is considered to be a significant risk factor in the pathogenesis of many eye diseases associated with aging. The purpose of this study was to investigate the susceptibility of retinal tissue to reactive oxygen species (ROS)-induced damage, and to examine if this can be prevented by compounds having the ability to scavenge ROS as well as support the tissue bioenergetically via normal as well as anaplerotic metabolic pathways.

Methods: Experiments were conducted on retinas isolated from CD-1 mice.

Induction of ultraviolet cataracts in vitro: prevention by pyruvate.

Ultraviolet (UV) radiation is one of the important cataract risk factors. The present studies examined the hypothesis that this effect is due to the UV penetration through the cornea and subsequent induction of a photochemical generation of reactive species of oxygen (ROS) in the aqueous and lens. The hypothesis was ascertained by rat lens organ culture studies conducted under UV (365 nm), with media containing micromolar levels of riboflavin, with and without pyruvate, the latter acting as an ROS scavenger.

Susceptibility of the ocular lens to nitric oxide: implications in cataractogenesis.

Oxides of nitrogen, such as nitric oxide (NO), are now biologically referred to as reactive nitrogen species. The generation of NO gives rise to several other reactive species, such as NO+, NO-, NO2, N2O3, and ONOO- and so forth, which are all capable of inflicting tissue damage. Indeed, NO generation is known to be associated with retinal degeneration and glaucoma.

Lens thiol depletion by peroxynitrite. Protective effect of pyruvate.

Pyruvate (PY) is known to be a potent scavenger of H(2)O(2 )by undergoing its peroxidative decarboxylation. While doing so, it also inhibits .OH generation, in addition to its direct .