Are retrotransposons long-term hitchhikers

Photochemistry and Photobiology, 2012

All-trans-retinal (AtRal) can accumulate in the retina as a result of excessive exposure to light. The purpose of this study was to compare cytotoxicity of AtRal and photodegraded AtRal (dA-tRal) on cultured human retinal pigment epithelial cells in dark and upon exposure to visible light. AtRal was degraded by exposure to visible light. Cytotoxicity was monitored by imaging of cell morphology, propidium iodide staining of cells with permeable plasma membrane and measurements of reductive activity of cells. Generation of singlet oxygen photosensitized by AtRal and dAtRal was monitored by time-resolved measurements of characteristic singlet oxygen phosphorescence. Photodegradation of AtRal resulted in a decrease in absorption of visible light and accumulation of the degradation products with absorption maximum at $330 nm. Toxicity of dAtRal was concentrationdependent and was greater during irradiation with visible light than in dark. DAtRal was more cytotoxic than AtRal both in dark and during exposure to visible light. Photochemical properties of dAtRal indicate that it may be responsible for the maximum in the action spectra of retinal photodamage recorded in animals. In conclusion, photodegradation products of AtRal may impose a significant threat to the retina and therefore their roles in retinal pathology need to be explored.

Photochemistry and Photobiology, 2010

All-trans-retinal is the precursor of A2E, a fluorophore within lipofuscin, which accumulates in human retinal pigment epithelial (hRPE) cells and contributes to age-related macular degeneration. Here we have compared the in vitro dark cytotoxicity and visible-light-mediated photoreactivity of all-trans-retinal and A2E in hRPE cells. All-trans-retinal caused distinct cytotoxicity in hRPE cells measured with MTS and LDH assays. Significant increases in intracellular oxidized glutathione (GSSG), extracellular GSH and GSSG levels and lipid hydroperoxide production were observed in cells incubated in the dark with 25 and 50 μM all-trans-retinal. Light modified all-trans-retinal's harmful action and decreased extracellular glutathione and hydroperoxide levels. A2E (<25 μM) did not affect cell metabolism or cytoplasmic membrane integrity in the dark or when irradiated. 25 μM A2E raised the intracellular GSSG level in hRPE cells to a much smaller extent than 25 μM all-trans-retinal. A2E did not induce glutathione efflux or hydroperoxide generation in the dark or after irradiation. These studies support our previous conclusions that although A2E may be harmful at high concentrations or when oxidized, its phototoxic properties are insignificant compared to those of all-trans-retinal. The endogenous production of A2E may serve as a protective mechanism to prevent damage to the retina by free all-trans-retinal.

Photochemistry and Photobiology, 1981

The incorporation of 1 1,12-[15-3H]-dihydroretinal, a retinal in which the crucial 1 I-ene is saturated, into the retinae of vitamin A deficient rats as a result of intraperitoneal injection of the corresponding alcohol was shown by the presence of the tritium label in the rod outer segments and by identification of the extracted retinals using high pressure liquid chromatography. The amplitude of the electroretinogram (ERG) b-wave, diminished as the result of vitamin A deprivation, was not affected by administration of the analogue, although similar treatment of deprived litter mates with trans retinal restored the ERG b-wave amplitude to a normal level. The evidence that the analogue is bound to opsin forming 11,12-dihydrorhodopsin is as follows: (I) when incubated with 1 I-cis retinal, extracts from vitamin A deficient rats regenerate 1.4 nmol rhodopsin while extracts from rats deficient in vitamin A and supplemented with I 1,12-dihydroretinal regenerate 0.6 nmol rhodopsin indicating binding of the dihydroretinal blocks rhodopsin regeneration. (2) 1 1,12dihydroretinal is shown to remain unchanged in hexane-washed retinae after extraction with methylene chloride and (3) injection of retinal into animals previously injected with 1 1.12-dihydroretinal also fails to restore visual sensitivity as measured by the ERG b-wave. Our results indicate that the dihydrochromophore occupies the same binding site as the natural 1 I-cis retinal and that occupation of the chromophore binding site of opsin is not sufficient to restore the visual sensitivity in a vitamin-Adeprived animal.

Toxicologic Pathology, 2016

Retinal degeneration due to chronic ambient light exposure is a common spontaneous age-related finding in albino rats, but it can also be related to exposures associated with environmental chemicals and drugs. Typically, light-induced retinal degeneration has a central/hemispherical localization whereas chemical-induced retinal degeneration has a diffuse localization. This study was conducted to identify and characterize treatment-related retinal degeneration in National Toxicology Program rodent bioassays. A total of 3 chronic bioassays in F344/N rats (but not in B6C3F1/N mice) were identified that had treatment-related increases in retinal degeneration (kava kava extract, acrylamide, and leucomalachite green). A retrospective light microscopic evaluation of the retinas from rats in these 3 studies showed a dose-related increase in the frequencies of retinal degeneration, beginning with the loss of photoreceptor cells, followed by the inner nuclear layer cells. These dose-related i...

Acta Ophthalmologica, 2011

To investigate the effect of octreotide acetate on neovascularization, retinal structures, and apoptotic cell death in an oxygen-induced retinopathy (OIR) mouse model. Materials and methods: A total of 26 C57BL/6J mice were exposed to 75 ± 2% oxygen from postnatal day 7 to 12. On day 12, 12 mice (group C) were injected with 0.1 µg intravitreal octreotide acetate (IVOA) and 14 mice (group D) were injected with 0.05 µg IVOA, in the right eye. The contralateral eyes were injected with 1 µL isotonic saline (control group, group B). Four mice were used as negative controls (group A). Neovascularization was quantified by counting the number of retinal vascular endothelial cell nuclei anterior to the inner limiting membrane. Structural changes were examined by light and electron microscopy. Apoptosis was investigated using the TUNEL technique. Results: The retinal vascular endothelial cell nuclei count was lower in groups C (P < 0.0001) and D (P < 0.0001) compared with group B. Light microscopy showed no retinal toxicity. Electron microscopy showed mitochondrial damage in the inner segment of the photoreceptors in the OIR mouse model without increasing in the IVOA-injected groups. There was no significant difference in the apoptotic cell death in any of the groups. Conclusion: There was mitochondrial damage in the inner segment of the photoreceptors in the OIR mouse model without increasing the apoptotic cell death.

Toxicologic pathology, 2007

Many medications that are administered systemically for nonocular conditions may evoke ocular toxicological complications. Therefore, the eye is routinely investigated histopathologically in preclinical in vivo toxicity studies. The retinal pigment epithelium is a likely target for systemically administered compounds, since the underlying choroid is highly vascularized. The specialized pigment epithelium has numerous functions that all maintain the integrity and function of photoreceptors. Consequently, toxic effects on the pigment epithelium will eventually affect the neural retina. The potential of pigment epithelial cells to respond to toxic injury is limited, but a standardized terminology to describe its morphological changes does not exist in the scientific literature. Detailed morphologic analysis, however, might allow early detection of retinotoxicity and may provide evidence on the underlying pathomechanism. We here review toxic effects on the pigment epithelium focusing in...

Neurochemistry International, 1997

We have examined whether in vivo exposure to the glutamate analogue\ kainic acid\ induces cell loss through apoptosis and:or through necrosis[ The vulnerability of rabbit retinal cells was evaluated by routine histopathology[ The DNA fragmentation was examined using an in situ method "TUNEL] TdT! mediated biotin!dUTP nick!end labelling# and agarose gel electrophoresis of extracted retinal DNA[ Retinas were examined at 29 min\ and 3\ 05\ 13 and 25 h\ and 1Ð4 days following the intraocular admin! istration of 039 nmol kainic acid[ Although pyknotic cells could be seen already at 29 min post!injection\ TUNEL!labelled nuclei were _rst observed 3 h after the injection[ A relatively large number of pyknotic cells and of TUNEL!labelled nuclei were still seen at 4 days post!injection[ Pyknotic cells were seen throughout the inner nuclear layer "mostly in the proximal half of the layer# and in the ganglion cell layer[ The TUNEL!labelled nuclei were almost only seen in the proximal inner nuclear layer[ Analysis of DNA by electrophoresis revealed the presence of large molecular weight fragments 3 h after the injection\ and of oligonucleosome!size fragments between 05 h and 1 days after the injection[ The present study thus presents evidence that\ in our model\ the retinal cell loss induced by kainic acid is preceded\ probably in most cells\ by a fragmentation of DNA characteristic of apoptotic cell death[ The process of cell loss following kainic acid administration was found to be relatively slow\ further suggesting that a programmed type of cell death\ which eventually induces apoptosis\ is involved[ No indication that cells were lost also through necrosis was obtained[ Þ 0886

Journal of Ophthalmic and Vision Research, 2016

Purpose: To characterize histopathologic and electroretinographic (ERG) changes in the retina of pigmented rats injected with sodium iodate in order to establish a model of retinal degeneration for future cell therapy studies. Methods: In 50 male pigmented rats weighing 250-300 grams, NaIO 3 was injected into the left orbital venous plexus at 40 and 60 mg/kg doses (25 eyes in each group). Fourteen rats received phosphate buffered saline (PBS) injection in their left orbital plexus and were considered as the sham-control group. Histopathologic and ERG studies were performed at baseline and on days 1, 7, 14 and 28 after the injections. Results: Progressive retinal pigment epithelial (RPE) changes were observed from the first day of injection in both the 40 and 60 mg/kg study groups in a dose dependent manner. These changes manifested as loss of melanin pigment and accumulation of lipofuscin in RPE cells with subsequent cell death and patchy loss of RPE cells (in flat mounts), as well as thinning of the outer nuclear layer and later the inner nuclear layer in the succeeding days. ERG showed a progressive and significant decrease in a-and b-wave amplitudes in both case groups relative to baseline values and the controls (P < 0.05). Conclusion: NaIO 3 injection into the retrobulbar venous plexus of pigmented rats can result in significant and progressive damage to the RPE and subsequently to the neuroretina of the injected eye, and may serve as a model of retinal degeneration.

Vision Research, 1980

Male weanling Long-Evans and Sprague-Dawley rats were administered a vitamin A deficient diet and the electroretinogram (ERG) and/or visual evoked response (VER) were recorded weekly. After 6-10 weeks, when the animal showed a greatly decreased VER and ERG, the animal was injected intraperitoneally with a retinal isomer. Following dark adaptation for I8 hr. the ERG and VER were recorded. The rat was then sacrificed and the retina dissected The retina was used for either solubilizing the visual pigment in 2% Ammonyx LO or extracting the retinals in methylene chloride. The visual pigments were characterized by the absorbance spectra and the retinal isomers were identified by high pressure liquid chromatography (HPLC). The physiologically occurring isomers of retinal (I I-cis and all-trans) are incorporated in the retina of deprived animals and the VER and ERG amplitudes for a given light intensity, diminished as a result of vitamin A deprivation, are restored to their normal values. 9-cis retinal is also incorporated into the retina, as shown by extraction of the retina with organic solvent and identification of the isomers by HPLC; a pigment is formed which has a &, blue-shifted from that of rhodopsin. The ERG and VER amplitudes of deprived rats injected with 94s retinal are restored to normal. No incorporation of 13-cis retinal into the retina is observed and the ERG and VER amplitudes are not significantly affected.

Toxicologic Pathology, 2011

Seven-week-old female BALB/c mice received a single intraperitoneal injection of N-ethyl-N-nitrosourea (ENU) (50, 100, 200, 400, or 600 mg/kg), and retinal damage was evaluated after 7 days. Sequential morphological features of the retina and retinal apoptosis, as determined by the TUNEL assay, were analyzed 6, 12, 24, and 72 hr and 7 days after treatment with 600 mg/kg of ENU. Moreover, older mice (25 to 34 weeks of age) received an intraperitoneal injection of 600 mg/kg ENU and were sacrificed 7 days later. All animals were necropsied, and both eyes were examined histopathologically. Two of the 5 mice that received 600 mg/kg ENU died during the experimental period. Histopathologically, all mice that received 600 mg/kg of ENU experienced retinal degeneration characterized by the loss of photoreceptor cells (disappearance of the outer nuclear layer and photoreceptor layer) in both the central and peripheral retina within 7 days. One of 5 mice treated with 400 mg/kg ENU exhibited retinal damage that was restricted to the central retina. Older mice treated with 600 mg/kg ENU exhibited retinal damage that was similar to the retinal damage in younger mice. In the 600 mg/kg ENU-treated mice, TUNEL-positive photoreceptor cells peaked 72 hr after ENU treatment. Retinal thickness and the photoreceptor cell ratio in the central and peripheral retina were significantly decreased, and the retinal damage ratio was significantly increased 7 days after treatment. In conclusion, ENU induces retinal degeneration in adult mice that is characterized by photoreceptor cell apoptosis.