Rats have been extensively used in light damage studies. Retinal damage threshold for white light were found at 1-10 J/cm2, and the action spectrum resembled the absorption spectrum of visual pigment. We wished to answer the question whether a different class of light damage, the "blue light hazard", with white light damage thresholds at about 300 J/cm2, and an action spectrum peaking in the ultra-violet, could also be demonstrated in rat. To that purpose 5 deg patches of retina were exposed to white xenon light with exposure times between 10 sec and 1 hr. We found that for funduscopic threshold damage the product of irradiance and exposure time was constant at a level of 315 J/cm2. Thereafter, the action spectrum was measured by exposing rat eyes to narrow band spectral lights. Threshold irradiant dose ranged from 4 J/cm2 at 379 nm to 2000 J/cm2 at 559 nm. Thus, susceptibility for damage sharply increased towards the ultra-violet, just like in earlier monkey studies. We conclude that in similar experimental conditions susceptibility to photic injury in rat is comparable to that in primates. Rat is the first species for which two different action spectra of photochemical damage have been established.
"Blue light (from 450 to 495 nm) is high-energy visible light and is related to the pathogenesis of age-related macular degeneration and retinitis pigmentosa [1,2]. A previous report suggested that retinal damage is inversely proportional to wavelength (from 379 to 559 nm) of light in a rat in vivo model . In another previous study using rhesus macaque, retinal dysfunction and damage induced by blue LED light were observed as residual infiltration in retinal pigment endothelial (RPE) cells and the photoreceptor outer segment . "
[Show abstract][Hide abstract] ABSTRACT: Bilberry extract (B-ext) and lingonberry extract (L-ext) are currently used as health supplements. We investigated the protective mechanisms of the B-ext and L-ext against ultraviolet A (UVA)-induced retinal photoreceptor cell damage. Cultured murine photoreceptor (661W) cells were exposed to UVA following treatment with B-ext and L-ext and their main constituents (cyanidin, delphinidin, malvidin, trans-resveratrol, and procyanidin). B-ext, L-ext, and constituents improved cell viability and suppressed ROS generation. Phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK), c-Jun N-terminal kinase (JNK), and protein kinase B (Akt) were analyzed by Western blotting. B-ext and cyanidin inhibited phosphorylation of p38 MAPK, and B-ext also inhibited phosphorylation of JNK by UVA. L-ext, trans-resveratrol, and procyanidin alleviated the reduction of phosphorylated Akt levels by UVA. Finally, a cotreatment with B-ext and L-ext showed an additive effect on cell viability. Our findings suggest that both B-ext and L-ext endow protective effects against UVA-induced retinal damage.
BMC Complementary and Alternative Medicine 04/2014; 14(1):120. DOI:10.1186/1472-6882-14-120 · 2.02 Impact Factor
"Molecular changes in opsin genes can allow for previously unseen cues to become visible, as occurs with the shift to UV vision from a SWS gene. What is remarkable about this evolutionary change is that it occurs in so many taxa, despite the dire potential for retinal damage due to UV light absorption . When UVS cones (λ max ≈ 360 nm ) evolve, UV cues provide stark, visual contrast, which is frequently used during mate choice by many species  . "
[Show abstract][Hide abstract] ABSTRACT: Fascinating new data, revealed through gene sequencing, comparative genomics, and genetic engineering, precisely establish which genes are involved in mate choice and mating activity--behaviors that are surprisingly understudied from a genetic perspective. Discussed here are some of the recently identified visual and chemosensory genes that are involved in mate choice and mating behavior. These genes' products are involved in the production, transmission, and receipt of crucial sensory mate-choice cues that affect fitness. This review exposes newfound evidence that alternative splicing, gene-expression pattern changes, and molecular genetic variation in sensory genes are crucial for both intra- and interspecific mate choice and mating success. Many sensory genes have arisen through gene duplications, and data amassed from studies conducted at scales ranging from individual genes to genomic comparisons show that strong, positive Darwinian selection acts on several mating-related genes and that these genes evolve rapidly.
"It is generally accepted that the shorter wavelengths of light pose the greatest potential hazard to biologic systems because they contain the most energy . Indeed, blue light, which is the component of visible light reaching the retina with the lowest wavelength and hence greatest energy , has been shown to induce retinal damage, particularly to the retinal pigmented epithelium [23,32,40-43] and to photoreceptors [44-47], by a process involving the production of reactive oxygen intermediates. It is of interest to note in the present study that there was an intensity peak in the filtered light impinging on the cells which corresponded to the blue part of the electromagnetic spectrum, but no attempt was made to ascribe any of the effects to this component of white light; the suggestion that the blue component of light may be the destructive one may, perhaps, be inferred from other studies [23,32,40-47]. "
[Show abstract][Hide abstract] ABSTRACT: To determine the effects of visible light on normal or metabolically compromised cultured rat RGC-5 cells.
Cultured RGC-5 cells were exposed to different durations as well as intensities of optical radiation, filtered to exclude wavelengths below 400 nm. Some cells were also subjected to metabolic compromise by depriving them of serum (serum deprivation; SD). Treated cells were assayed for cell viability using the 3,(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay, for DNA breakdown by terminal deoxynucleotidyl transferase (TdT)-mediated d-UTP-linked nick end labeling (TUNEL), apoptotic protein activation by immunoblotting, and the production of reactive oxygen species (ROS) with dihydroethidium. A subset of cells was treated with 100 pM rotenone as an alternative means to induce metabolic stress; this was to determine that the influence of light on compromised cells was not specific to serum-deprivation alone.
Exposure to the light for 48 h activated both caspase-3 and Bcl-associated X-protein (Bax) in cultured RGC-5 cells. Furthermore, light (1000 or 4000 lux), SD, and rotenone caused minor but significant decreases in cellular MTT reduction. SD and light also led to cellular DNA breakdown, although only light caused ROS production. Light (48 h) significantly exacerbated the effect of SD on MTT reduction and DNA cleavage. Furthermore, the antioxidant, trolox, significantly blunted the detrimental influence of light on cell viability, increase in TUNEL-positive cells, and the generation of ROS.
Exposure to light was slightly, but significantly, harmful to healthy RGC-5 cells alone, but was much more toxic to those cells that were energetically compromised. Continuous light exposure can therefore detrimentally affect metabolically stressed RGC-5 cells. This may have implications for some ocular retinopathies such as glaucoma.
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