Light-induced Retinal Damage In Rats Research Articles

Effect of hydrogen-rich saline on melanopsin after acute blue light-induced retinal damage in rats.

Excessive exposure to blue light can cause retinal damage. Hydrogen-rich saline (HRS), one of the hydrogen therapies, has been demonstrated to be effective in eye photodamage, but the effect on the expression of melanopsin in intrinsically photosensitive retinal ganglion cells (ipRGCs) is unknown. In this study, we used a rat model of light-induced retinal injury to observe the expression of melanopsin after HRS treatment and to determine the effect of HRS on retinal ganglion cell protection. Adult SD rats were exposed to blue light (48 h) and treated with HRS for 0, 3, 7, and 14 days. Real-time polymerase chain reaction (qRT-PCR) and Western blotting (WB) were performed to find the expression of genes and proteins, respectively. The function of retinal ipRGCs was measured by pattern-evoked electroretinography (pERG). The number and morphological changes of melanopsin-positive ganglion cells in the retina were observed by immunofluorescence (IF). Acute blue light exposure caused a decrease in ipRGC function, decreased expression of melanopsin protein and the melanopsin-positive RGCs, and diminished immunoreactivity in dendrites. However, over time, melanopsin showed a tendency to self-recovery, with an increase in melanopsin protein expression and the number of melanopsin-positive RGCs, with incomplete recovery of function within two weeks. HRS treatment accelerated the recovery process, with a significant increase in melanopsin expression and the number of melanopsin-positive RGCs, and an improvement in the pERG waveform within two weeks.

Allyl isothiocyanate attenuates LED light-induced retinal damage in rats: exploration for the potential molecular mechanisms

Purpose Environmental light pollution due to artificial light may increase the rate and severity of retinal diseases, and plant-based nutritional interventions with antioxidant properties have the potential to reverse this phenomenon. We aimed to investigate the potential effects of allyl isothiocyanate (AITC) against white light-emitting diode (LED)-induced retinal degeneration (RD) in the rats. Methods Twenty-eight male rats were allocated as: (i) Control, (ii) LED, (iii) LED + AITC (10 mg/kg BW), (iv) LED + AITC (20 mg/kg BW). Rats were administered with AITC for 28 days, followed by two days of intense environmental LED light (750 Lux) exposure to the eyes. Animals were sacrificed immediately at the end of the study, then the blood and eyeballs were taken for the biochemical, western blotting, and histopathology examinations. Results AITC lowered the serum and retina malondialdehyde (MDA) levels while significantly (p < 0.05) improving the retinal antioxidant enzyme activities in a dose-dependent manner. AITC improved retinal and outer nuclear layer (ONL) thickness as compared to the LED group (p < 0.05). AITC increased the levels of Bax, caspase-3, HO-1, GAP43, and VEGF, while decreasing IL-1β, IL-6, NF-κB, Bcl-2, GFAP, Grp78, activating ATF4 and ATF6 as compared to the LED group (p < 0.05). Conclusion In conclusion, four weeks of AITC administration to the rats showed specific protective effects against two days of intense LED light-induced retinal damage; through antiinflammatory, antioxidant, anti-apoptotic, and modulating mitochondrial metabolic pathways.

Assessment of Visual and Chromatic Functions in a Rodent Model of Retinal Degeneration

We evaluated the photoreceptor response of pigmented P23H and normal pigmented Long Evans (LE) rats over time using functional tests in variable lighting conditions. Pigmented P23H rats were studied by optomotor testing and electroretinogram (ERG) recordings at P30, P150, and P240. Pigmented LE rats were used as a normal wild-type control. Stimuli were modified with colored filters. Neutral density filters were used to reduce luminance. Age-related decreases in visual acuity (VA) and contrast sensitivity (CS) were observed in P23H rats. Good correlations in measurements without filter and with green filter were observed between LE and P23H P30 rat values. Differences between groups were smaller with red and purple filters. A strong relationship with luminance was observed in LE rats (VA and CS) and with P23H P30 rats (CS). A decline in the ERG responses of P23H rats was consistent with the gradual loss of photoreceptors. Differences in a- and b-wave amplitudes with different colored filters were negligible with the exception of the red filter, which resulted in smaller responses. Visual function parameters decreased with age in pigmented P23H rats. Irrespective of luminance, color filter, and retinal degeneration, minimum thresholds of VA and CS were found. Smaller differences than expected were found using color filters. Responses to functional tests at long wavelengths were observed, where there is very low photoreceptor spectral sensitivity. The use of filters with functional testing could minimize light-induced retinal damage in rats.

Application of clotrimazole via a novel controlled release device provides potent retinal protection.

Age-related macular degeneration is the leading cause of legal blindness among older individuals. Therefore, the development of new therapeutic agents and optimum drug delivery systems for its treatment are crucial. In this study, we investigate whether clotrimazole (CLT) is capable of protecting retinal cells against oxidative-induced injury and the possible inhibitory effect of a sustained CLT-release device against light-induced retinal damage in rats. In vitro results indicated pretreatment of immortalized retinal pigment epithelium cells (RPE-J cells) with 10–50 µM CLT before exposure to oxygen/glucose deprivation conditions for 48 h decreased the extent of cell death, attenuated the percentage of reactive oxygen species-positive cells, and decreased the levels of cleaved caspase-3. The device consists of a separately fabricated reservoir, a CLT formulation, and a controlled release cover, which are made of poly(ethyleneglycol) dimethacrylate (PEGDM) and tri(ethyleneglycol) dimethacrylate (TEGDM). The release rate of CLT was successfully tuned by changing the ratio of PEGDM/TEGDM in the cover. In vivo results showed that use of a CLT-loaded device lessened the reduction of electroretinographic amplitudes after light exposure. These findings indicate that the application of a polymeric CLT-loaded device may be a promising method for the treatment of some retinal disorders.

Protective effect of saturated hydrogen saline against blue light-induced retinal damage in rats.

To explore the effect of saturated hydrogen saline on blue light-induced retinal damage in rats. The retinal damage of rats was induced by blue light exposure for 6 hours and examined 8 hours, 16 hours and 24 hours after the exposure. One hundred female Sprague-Dawley rats were randomly divided into four groups. Group 1 included 30 rats received light exposure without any other treatment. Group 2 included 30 rats received light exposure with intraperitoneal injection of normal saline. Group 3 included 30 rats received light exposure with intraperitoneal injection of saturated hydrogen saline. And Group 4 included the other 10 rats which did not receive any treatment. The amount of intraperitoneal injection of saturated hydrogen saline and normal saline was calculated in the ratio of 1ml/100g of rat weight. Specimens were collected and processed by H-E staining, ultrastructure observation, biochemical measurement. Morphological changes were observed by light microscope and transmission electron microscope (TEM) and the retinal outer nuclear layer (ONL) thickness was measured by IPP 6.0, while the malondialdehyde (MDA) was measured by colorimetric determination at 532 nm. Although the structure of retina in Group 1 and Group 2 was injured heavily, the injury in Group 3 was mild. The differences between Group 1 and Group 2 were not significant. Compared with the rats in Group 1 and Group 2, the ones in Group 3 had more clearly demarcated retina structure and more ordered cells by light microscope and TEM observation. The ONL thicknesses (400 times) of four groups at each time point except between Group 1 and Group 2 were significantly different (P<0.05). The thicknesses of the ONL in Group 1 at three time points were 30.41±4.04µm, 26.11±2.82µm and 20.63±1.06µm, in Group 2 were 31.62±4.54µm, 25.08±3.63µm and 19.07±3.86µm, in Group 3 were 29.75±3.62µm, 28.83±1.97µm and 27.61±1.83µm. In Group 4 the mean of the thickness was 37.35±1.37µm. As time went by, the damage grew more severely. At 24h point, the differences were most significant. Compared with Group 4, the thickness was 46.23% thinner in Group 1, 50.29% thinner in Group 2 and 28.04% thinner in Group 3. The stack structures of membranous disc in Group 3 were injured slightly, but in Group 1 and Group 2 the damage was more obvious by TEM. Compared with Group 4 at each time point, the content of MDA in Group 1 was higher (P<0.05). The content of MDA in Group 3 was significantly lower than those of Group 1 (P<0.05) and Group 2 (P<0.05). Between the Group 1 and Group 2, the MDA concentration at each time point was no significant difference (P>0.05). Saturated hydrogen saline could protect the retina from light-induced damage by attenuating oxidative stress.

Effects of Single Intravitreal rhEPO Injection on Light-Induced Retinal Injury in Rats

Purpose: To observe the effects of a single intravitreal rhEPO injection on light-induced retinal damage in rats and to explore the possible mechanisms.Methods: Male Sprague-Dawley rats were randomly divided into a normal group, a control group (PBS intravitreal injection), and a number of treatment groups (intravitreal rhEPO injection at 0.625, 1.25, 2.5, 5, 10, or 20 U). After dark adaptation for 24 h, rats were exposed to white light (2800 lx) for 5 h. Based on the effects of rhEPO on the ERG-b wave, an optimal dose (5U) was chosen for further experiments that included histopathological examination and outer nuclear layer (ONL) counting at 5 and 10 days after light exposure. Cell apoptosis and proteins (caspase-3, bcl-xL) were also examined at 3 days. Some cell signaling related proteins (AKT, ERK1/2 and STAT5) were also analyzed. In another experiment, rats received intravitreal injection of rhEPO (5U) at 30 min after light exposure. ERG and morphological changes were examined at 3 days after light exposure.Results: ERG-b wave amplitudes are well preserved in rats receiving 2.5, 5, or 10 U rhEPO, in comparison with the PBS control. The dose-effect relationship was bell-shaped, with the maximum effect at 5 U. Less apoptotic cells were in the ONL in the 5U group. The rats receiving 5 U rhEPO at 30 min after light exposure also had higher b-wave amplitude. Caspase-3 expression was down-regulated and Bcl-xL was up-regulated in the rhEPO group. Phosphorylated ERK(1,2) was reduced in the rhEPO group.Conclusion: A single intravitreal injection of rhEPO can postpone photoreceptor light damage in rats. The optimal dose was 5 U in this study. The effective time window was from 24 h prior to light exposure to 5 h after. RhEPO may be involved in the regulation of the expression of Caspase-3 and Bcl-xL. The possible cell signal transduction maybe through the ERK1/2 pathway.

Effects of Chaihu Shugan San on behavior and plasma levels of corticotropin releasing hormone and adrenocorticotropic hormone of rats with chronic mild unpredicted stress depression

To investigate the effects of Chaihu Shugan San (CHSGS), a compound traditional Chinese herbal medicine, on behavior and plasma levels of corticotropin releasing hormone (CRH) and adrenocorticotropic hormone (ACTH) of rats with chronic mild unpredicted stress depression. Forty male Sprague-Dawley rats were randomly divided into 4 groups: normal control group, untreated group, fluoxetine group and CHSGS group. Except the normal control group, rats were singly housed and exposed to an unpredicted sequence of mild stressor for continuous 4 weeks to induce depression. Since the fifteenth day, rats were intragastrically administered with equal volume agents respectively for 2 weeks [normal saline for the normal control group and the untreated group, fluoxetine (1.8 mg/kg) for the fluoxetine group and CHSGS (5.9 g/kg) for the CHSGS group]. Behavioral scores of rats were detected by open-field test and sucrose preference test, and the plasma levels of CRH and ACTH in different groups were detected by radioimmunoassay. Compared with the normal control group, body weights of the rats in the untreated group were significantly decreased. Scores of crossing, rears and grooming in open-field test were reduced significantly. Pure water consumption in sucrose preference test was increased significantly. The levels of plasma CRH and ACTH were significantly increased. The depressive behaviors of the rats were improved significantly and the levels of plasma CRH and ACTH were obviously reduced in the CHSGS group. Chronic mild unpredicted mild stress can affect the neuroendocrine and behavior and cause depression in rats. CHSGS can regulate HPA hyperactivity of rats caused by chronic stress and has antidepressive effects.

Protective effect of Huangban Granule against light-induced retinal damage in rats

Protective effect of Huangban Granule against light-induced retinal damage in rats

Protective Effect of TEMPOL Derivatives against Light-Induced Retinal Damage in Rats

OT-551 (1-hydroxy-4-cyclopropanecarbonyloxy-2,2,6,6-tetramethylpiperidine hydrochloride), a TEMPOL-H (OT-674) derivative, is a new catalytic antioxidant. In the present study, the efficacy of OT-551 and OT-674 in retinal neuroprotection was tested in a model of light-induced photoreceptor degeneration. Albino rats were intraperitoneally injected with OT-551, OT-674, or water, approximately 30 minutes before a 6-hour exposure to 2700-lux white fluorescent light. Retinal protection was evaluated histologically by measuring the thickness of the outer nuclear layer (ONL) and functionally by electroretinogram (ERG) analysis, 5 to 7 days after exposure to light. Levels of protein modification by 4-hydroxynonenal (4-HNE) and 4-hydroxyhexenal (4-HHE), which are end products of the nonenzymatic oxidation of n-6 and n-3 polyunsaturated fatty acids, respectively, were measured by Western dot blot analysis immediately after exposure to light. After exposure to light, water-treated animals had a 77% loss of ERG b-wave amplitudes and a 26% and 56% loss of mean ONL thickness in the inferior and superior hemispheres, respectively. Compared with water-treated rats, ERG b-wave amplitudes in light-exposed eyes were significantly higher in 25 (P < 0.05)-, 50 (P < 0.05)-, and 100 (P < 0.001)-mg/kg OT-551-treated rats. Mean ONL thickness in the superior hemisphere was significantly higher in 25 (P < 0.01)-, 50 (P < 0.01)-, and 100 (P < 0.001)-mg/kg OT-551-treated, light-exposed eyes and in 100 mg/kg (P < 0.05) OT-674-treated eyes. No decrease of ONL thickness was observed in the light-protected covered fellow eyes in any animal. Increased levels of 4-HNE- and 4-HHE-protein modifications after exposure to light in water-treated eyes were completely counteracted by 100 mg/kg OT-551. Systemic administration of OT-551 and OT-674 provides both functional and morphologic photoreceptor cell protection against acute light-induced damage, most likely by inhibiting lipid peroxidation. The protection by OT-551 was greater than OT-674.

Intraperitoneal Injection of Ginkgo biloba Extract Enhances Antioxidation Ability of Retina and Protects Photoreceptors After Light-Induced Retinal Damage in Rats

Purpose: To investigate the effect of Ginkgo biloba extract EGb 761, a free-radical scavenger, on the antioxidation capability of retina after light-induced retinal damage in rats in an attempt to understand the mechanism by which EGb 761 protects the photoreceptors after light-induced retinal damage. Methods: Seventy-two female Sprague-Dawley (SD) rats were evenly randomized into normal control group (NC group), light-induced retinal damage model group (M group), model + normal saline group (MN group), and model + EGb 761 group (ME group). Light-induced retinal damage model was induced via exposure to white light at 2740 ± 120 lux for 6 hr. Rats in MN group and ME group were intraperitoneally injected daily with normal saline and 0.35% EGb 761 (100 mg/kg), respectively, 1 week before and 2 weeks after light exposure. The levels of malondialdehyde (MDA), total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) in the retinal tissues were determined 24 hrs after light exposure; photoreceptor apoptosis was detected 4 days after light exposure. One and 2 weeks after light exposure, histopathologic examination was carried out, and the outer nuclear layer (ONL) thickness (number of nuclei) in the superior and inferior retina was counted. Results: Twenty-four hours after exposure, the MDA levels in the other three groups were significantly higher than that in the NC group (p < 0.05); those in the M and MN groups were similar to each other (p > 0.05); and that of the ME group was significantly lower than those in the M and MN group (p < 0.05). The activities of T-SOD, GSH-Px, and CAT were similar in the M and MN groups (p > 0.05); the activities in the M and MN groups were significantly lower than those in the NC and ME groups (p < 0.05); and the activities in the ME group were significantly higher than those in the M and MN groups (p < 0.05). Four days after exposure, the apoptotic photoreceptors within the ONL in the ME group were obviously fewer than those in the M and MN groups. One week and 2 weeks after exposure, the ONL thickness (number of nuclei) in the ME group was more than that in the M and MN groups but less than that in the NC group. Conclusions: Intraperitoneal injection of EGb 761 can enhance the antioxidation ability of retina and partially inhibit the apoptosis of photoreceptors, thus exert a protective effect on photoreceptors.

Protective effects of soft acrylic yellow filter against blue light-induced retinal damage in rats

Recently, a yellow intraocular lens (IOL) was developed for the purpose of reducing potential blue light-induced retinal damage after cataract surgery. However, the effect of yellow filters on retinal protection remains to be clarified. To test the protective effects of yellow filters on blue light-induced retinal damage, a yellow and a clear soft acrylic filter were attached to the right and left eyes, respectively, of albino rats and exposed to 4.5 k lux blue fluorescent lights with peak wavelength at 420 nm (ranging 380–500 nm; short blue) or 446 nm (ranging 400–540 nm; long blue) for 6 h. To assess retinal damage, the electroretinogram (ERG) was recorded at 7 days, outer nuclear layer (ONL) thickness and area were measured at 7 days, apoptosis was analyzed by TUNEL staining at 24 h, and the level of lipid peroxidation in retinas was assessed by Western dot blots using specific antibodies against 4-hydroxynonenal (4-HNE)- and carboxyethylpyrrole (CEP)-modified proteins immediately after light exposure. After short blue light exposure, a- and b-wave ERG amplitudes and the ONL thickness at 1–2.5 mm inferior and 0.5–2.5 mm superior to optic nerve head (ONH) were significantly reduced. TUNEL staining in the ONL at 0–2 mm inferior and 1–2 mm superior to the ONH, and retinal levels of 4-HNE- and CEP-modified proteins were significantly increased in the clear filter-covered eyes compared to yellow filter-covered eyes. After long blue light exposure, the only difference seen was a greater ONL thickness at 1.5 mm superior to the ONH in yellow filter-covered eye. Transmission of light through the yellow filter was 58% for short blue and 89% for long blue compared to the clear filter. The ONL area was not different between clear filter-covered and -uncovered eyes after exposure to short or long blue light. Given the results, yellow IOL material protects the retina against acute shorter wavelength blue light exposure more effectively than the clear IOL material.

Expression of multiple forms of clusterin during light-induced retinal degeneration

Purpose. Clusterin has been associated with active cell death in several different model systems, including animal models of retinal degeneration. Clusterin is also expressed in normal tissues, a finding that leads to the question of how it could then play a cell death-specific role during tissue regression. To address this paradox, we have examined clusterin expression during light-induced retinal damage in rats. Methods. Normal albino rats were reared in darkness and then exposed to intense visible light to induce retinal degeneration. Clusterin expression was then examined at various times after light treatment. Standard molecular techniques including Northern analysis, immunohistochemistry, and Western analysis were employed. Results. Northern analysis established that the largest increase in clusterin expression occurs after a decrease in interphotoreceptor retinoid binding protein, IRBP, expression (an indication of a photoreceptor cell dysfunction) and after an increase in heme oxygenase 1, HO-1, expression (an oxidative stress inducible gene), suggesting that induction of clusterin expression is an oxidative stress response. Immunohistochemical analysis with two different clusterin-specific antibodies, anti(SGP-2) and anti(301), localized distinct forms of clusterin to Müller cells and degenerating photo-receptor cells. Western analysis demonstrated degeneration associated isoforms of clusterin in light treated retina that are not present in normal retina. Conclusion. Clusterin over-expression is characteristic of a retinal degeneration phenotype and we propose that clusterin action may be defined by the nature in which it is modified. We hypothesize that alternate processing leads to retinal degeneration-specific forms of the protein (65, 61, and 50 kDa) that are not present in normal retina.

Short Wavelength Light-Induced Retinal Damage in Rats

Purpose: To evaluate short wavelength light-induced retinal damage in rats. Methods: Pigmented rats were exposed to 300–500 nm wavelength light for 30 seconds, 1, 3, 10, 20, 60, or 90 minutes. Electroretinogram a-, b-, and c-waves were recorded 48 hours after the exposure. Results: While the a- and b-wave amplitudes were reduced significantly after exposures of 60 minutes and longer, the c-wave amplitude was reduced after only 3 minutes of exposure. Conclusions: Rat retinal pigment epithelium is more sensitive to damage by exposure to 300–500 nm wavelength light than the neural retina.

Changes in clusterin expression associated with light-induced retinal damage in rats.

Prolonged periods of high-intensity visible light exposure lead to photoreceptor cell degeneration, but the mechanism of damage is not understood. Increased clusterin mRNA levels have been found in several models of apoptosis, as well as in neurodegeneration. We report here that changes in clusterin mRNA levels are also associated with light-induced retinal damage in adult male albino rats. Animals previously maintained in darkness or a weak cyclic light environment were exposed to intense visible green light for up to 24 h. Some rats were pretreated with a synthetic antioxidant, dimethylthiourea (DMTU), which reduces photoreceptor cell degeneration. Clusterin mRNA steady-state levels increased with the duration of light exposure in both cyclic light and dark reared animals, suggesting that an apoptotic mechanism may be involved. Animals pretreated with DMTU showed a delay in the initial increase in clusterin mRNA levels, suggesting that oxidative damage is involved in the damage mechanism. However, the incomplete suppression of increasing steady-state clusterin mRNA levels by DMTU suggests that either oxidative damage triggers a second pathway or multiple damage mechanisms are induced in the retina by light exposure.

Differences in Sensitivity of Various Ophthalmological Methods of detecting Light-induced Retinal Damage in Rats

Differences in Sensitivity of Various Ophthalmological Methods of detecting Light-induced Retinal Damage in Rats

Pretreatment with bendazac attenuates retinal damage induced by intense light in rats

Bendazac is a drug which protects proteins from denaturation induced by different agents. It is also effective in protecting rabbits from X-ray-induced cataract. This study deals with the effects of bendazac on the intense light-induced retinal damage in rats. Four groups of animals received orally 0, 50, 100 or 200 mg/kg of bendazac l-lysine salt three times a day for 3 days and once the fourth day, before 1 h exposure to intense-green filtered light. Fourteen days after housing in a dark room, the rats were sacrificed and the retinae were examined by light microscopy. Retinal damage was graded according to a score severity from 0 to 5. The mean score for control animals was 2.23, whereas a dose-related and statistically significant reduction of retinal damage was detected in bendazac treated rats, i.e. 1.72, 1.54 and 1.40. A protective activity in the distribution of the severity score, i.e. a higher incidence of no damaged retinae and a lower frequency in the most severely affected ones, was also observed in treated versus control rats. These results suggest a potential therapeutic value of bendazac in the treatment of those conditions, such as retinitis pigmentosa and senile macular degeneration, in which the light exposure plays a role as a co-factor.