Three Major Causes of Metabolic Retinal Degenerations and Three Ways to Avoid Them.

An imbalance of homeostasis in the retina leads to neuron loss and this eventually results in a deterioration of vision. If the stress threshold is exceeded, different protective/survival mechanisms are activated. Numerous key molecular actors contribute to prevalent metabolically induced retinal diseases-the three major challenges are age-related alterations, diabetic retinopathy and glaucoma. These diseases have complex dysregulation of glucose-, lipid-, amino acid or purine metabolism. In this review, we summarize current knowledge on possible ways of preventing or circumventing retinal degeneration by available methods. We intend to provide a unified background, common prevention and treatment rationale for these disorders and identify the mechanisms through which these actions protect the retina. We suggest a role for herbal medicines, internal neuroprotective substances and synthetic drugs targeting four processes: parainflammation and/or glial cell activation, ischemia and related reactive oxygen species and vascular endothelial growth factor accumulation, apoptosis and/or autophagy of nerve cells and an elevation of ocular perfusion pressure and/or intraocular pressure. We conclude that in order to achieve substantial preventive or therapeutic effects, at least two of the mentioned pathways should be targeted synergistically. A repositioning of some drugs is considered to use them for the cure of the other related conditions.

The possible alleviating effect of garlic supplement on the neural retina in a rat model of hypercholesterolemia: a histological and immunohistochemical study.

The purpose of this work was to prove that oxidative stress is the main mechanism responsible for retinal neurodegenerative changes, subsequent apoptosis, and inflammatory cytokine release in rats fed with a high cholesterol diet (HCD) and determine the role of garlic in alleviating these changes. Forty rats were equally divided into four groups: control, garlic-treated (positive control), HCD, and HCD + garlic-treated (HCD + G). By the end of the experiment (24 weeks) blood samples were collected for assessment of serum lipid profile, oxidative stress parameters, and plasma levels of IL-6 and TNF-α. Both eyes of the rats were enucleated; one was used for light microscopic examination and the other for electron microscopic examination. There was a significant increase in the levels of serum lipids, oxidative stress parameters, IL-6 and TNF-α, and area of expression of caspase-3 in the HCD group compared to both the control and HCD + G groups. Histological examination revealed degenerative changes in all layers of the neural retina in the HCD group. Garlic administration resulted in a significant improvement in the biochemical, immunohistochemical, and histological characteristics of hypercholesterolemic rats. These findings support the hypotheses that garlic has strong antioxidant, anti-apoptotic, and anti-inflammatory properties. Garlic ameliorates the neurodegenerative changes in the neural retina of hypercholesteremic rats.

Cynaroside protects the blue light-induced retinal degeneration through alleviating apoptosis and inducing autophagy in vitro and in vivo.

BACKGROUND: Blue light can directly penetrate the lens and reach the retina to induce retinal damage, causing dry age-related macular degeneration (dAMD). Cynaroside (Cyn), a flavonoid glycoside, was proved to alleviate the oxidative damage of retinal cells in vitro. However, whether or not Cyn also exerts protective effect on blue light-induced retinal degeneration and its mechanisms of action are unclear. PURPOSE: This study aims to evaluate the protective effects of Cyn against blue-light induced retinal degeneration and its underlying mechanisms in vitro and in vivo. STUDY DESIGN/METHODS: Blue light-induced N-retinylidene-N-retinylethanolamine (A2E)-laden adult retinal pigment epithelial-19 (ARPE-19) cell damage and retinal damage in SD rats were respectively used to evaluate the protective effects of Cyn on retinal degeneration in vitro and in vivo. MTT assay and AnnexinV-PI double staining assay were used to evaluate the in vitro efficacy. Histological analysis, TUNEL assay, and fundus imaging were conducted to evaluate the in vivo efficacy. ELISA assay, western blot, and immunostaining were performed to investigate the mechanisms of action of Cyn. RESULTS: Cyn decreased the blue light-induced A2E-laden ARPE-19 cell damage and oxidative stress. Intravitreal injection of Cyn (2, 4 µg/eye) reversed the retinal degeneration induced by blue light in SD rats. Furthermore, Cyn inhibited the nuclear translocation of NF-κB and induced autophagy, which led to the clearance of overactivated pyrin domain containing 3 (NLRP3) inflammasome in vitro and in vivo. CONCLUSION: Cyn protects against blue light-induced retinal degeneration by modulating autophagy and decreasing the NLRP3 inflammasome.

Vitamin A and Daucus carota root extract mitigate STZ-induced diabetic retinal degeneration in Wistar albino rats by modulating neurotransmission and downregulation of apoptotic pathways.

The objective of our study was to explore the deleterious effects of diabetes on the visual functions of the retina and to address whether the administration of vitamin A and carrot root extract (CE) confer retinal protection in hyperglycemic rats via modulation of oxidative stress, biochemical alternations, and retinal neurotransmission. Fifty male Wistar albino rats weighing 180 ± 12.41 g were randomized into five groups (n = 10): controls, diabetic group (injected with 40 mg/kg dissolved in 0.1 sodium citrate buffer), diabetic group treated with vitamin A (2,500 IU/kg, low dose), diabetic group treated with vitamin (5,000 IU/kg, high dose), and diabetic groups administered CE (200 mg/kg/every other day). Our findings showed that, compared to controls, diabetic rats showed a significant decrease in their retinal thickness, increased apoptotic ganglion cells, and a noticeable degeneration of their synaptic layers. The inner retina displayed increased activity of neovascularization; however, the outer retina exhibited vacuolar degeneration of the photoreceptor cell layer. Our biochemical assessments showed reduced levels of CAT, SOD, and GST along with increased lipid peroxidation. Concurrently, cellular angiogenic and stress markers were significantly elevated associated with increased apoptotic activities as evidenced by increased expressions of annexin-V and PARP. Furthermore, the neurotransmitter content of the retina was altered in diabetic rats compared to controls and diabetic-treated groups. Paradoxically, vitamin A and CE supplementation attenuate these retinal insults in diabetic animals and normalized aforementioned assayed parameters; evidencing that both treatments exerted ameliorative impacts and restored visual functions by diminishing oxidative stress and neuronal degeneration. PRACTICAL APPLICATIONS: Diabetes is a complex disease that involves various physiological perturbations especially visual functions. In our study, we showed that vitamin A and carrot root extract (CE) confer remarkable protection against retinal degeneration in STZ-induced diabetic rats. Our findings showed that the chemical and phytochemical ingredients of the vitamin A and CE substantially attenuated the histopathological changes, oxidative stress, inflammatory reactions, and cellular death in diabetic rats. These favorable changes are attributable to the high content of retinoic acid, carotenoids, and phenolic compounds that effectively regulates the production of visual pigments, increases the antioxidant defense system, and diminishes the pro-inflammatory and apoptotic pathways. Thus, the nutritional values of vitamin A and CE represent promising therapeutic choices to mitigate the retinal-induced diabetic insults.

Saffron: Chemical Composition and Neuroprotective Activity.

Crocus sativus L. belongs to the Iridaceae family and it is commonly known as saffron. The different cultures together with the geoclimatic characteristics of the territory determine a different chemical composition that characterizes the final product. This is why a complete knowledge of this product is fundamental, from which more than 150 chemical compounds have been extracted from, but only about one third of them have been identified. The chemical composition of saffron has been studied in relation to its efficacy in coping with neurodegenerative retinal diseases. Accordingly, experimental results provide evidence of a strict correlation between chemical composition and neuroprotective capacity. We found that saffron's ability to cope with retinal neurodegeneration is related to: (1) the presence of specific crocins and (2) the contribution of other saffron components. We summarize previous evidence and provide original data showing that results obtained both "in vivo" and "in vitro" lead to the same conclusion.

Shihu Yeguang Pill protects against bright light-induced photoreceptor degeneration in part through suppressing photoreceptor apoptosis.

Photoreceptor cells are first-order retinal neurons that directly contribute to the formation of vision. Photoreceptor degeneration is the primary cause of vision impairment during the course of retinopathies such as retinitis pigmentosa and age-related macular degeneration, for which photoreceptor-targeted therapies are currently unavailable. Shihu Yeguang Pill (SYP), a classic formula in traditional Chinese medicine, has a long histology of clinical application for the treatment of a wide range of retinopathies in China. However, whether SYP is pharmacological effective at protecting photoreceptor cells is unclear. The current study thus directly addressed the pharmacological implications of SYP in photoreceptor degeneration in a mouse model characterized by bright light-induced retinal degeneration. Non-invasive full-retinal assessment was carried out to evaluate the effect of SYP on the retinal structure and function through optical coherence tomography and electroretinography, respectively. In addition, photoreceptor apoptosis, second-order neuron impairment and reactive changes in retinal microglial and müller cells, hallmark pathologies associated with photoreceptor degeneration, were assessed using immunohistochemistry and real-time PCR analyses. The results showed that SYP treatment attenuated bright light-induced impairment of the retinal structure and function. Moreover, SYP treatment suppressed photoreceptor apoptosis, alleviated the impairment of bipolar and horizontal cells and mitigated the reactive changes of müller and microglial cells in the bright light-exposed retinas. Real-time PCR analyses showed that dysregulated expression of pro-apoptotic c-fos and c-jun and anti-apoptotic bcl-2 as well as proinflammatory TNF-α in the bright light-exposed retinas was partially normalized as a result of SYP treatment. In summary, the work here demonstrates for the first time that SYP treatment protects the retinas from developing bright light-induced photoreceptor degeneration and associated alterations in second-order neurons and glial cells. The findings here thus provide experimental evidence to better support the mechanism-guided clinical application of SYP in the treatment of related retinal degenerative diseases.

Metabolite therapy guided by liquid biopsy proteomics delays retinal neurodegeneration.

BACKGROUND: Neurodegenerative diseases are incurable disorders caused by progressive neuronal cell death. Retinitis pigmentosa (RP) is a blinding neurodegenerative disease that results in photoreceptor death and progresses to the loss of the entire retinal network. We previously found that proteomic analysis of the adjacent vitreous served as way to indirectly biopsy the retina and identify changes in the retinal proteome. METHODS: We analyzed protein expression in liquid vitreous biopsies from autosomal recessive (ar)RP patients with PDE6A mutations and arRP mice with Pde6ɑ mutations. Proteomic analysis of retina and vitreous samples identified molecular pathways affected at the onset of photoreceptor death. Based on affected molecular pathways, arRP mice were treated with a ketogenic diet or metabolites involved in fatty-acid synthesis, oxidative phosphorylation, and the tricarboxylic acid (TCA) cycle. FINDINGS: Dietary supplementation of a single metabolite, ɑ-ketoglutarate, increased docosahexaeonic acid levels, provided neuroprotection, and enhanced visual function in arRP mice. A ketogenic diet delayed photoreceptor cell loss, while vitamin B supplementation had a limited effect. Finally, desorption electrospray ionization mass spectrometry imaging (DESI-MSI) on ɑ-ketoglutarate-treated mice revealed restoration of metabolites that correlated with our proteomic findings: uridine, dihydrouridine, and thymidine (pyrimidine and purine metabolism), glutamine and glutamate (glutamine/glutamate conversion), and succinic and aconitic acid (TCA cycle). INTERPRETATION: This study demonstrates that replenishing TCA cycle metabolites via oral supplementation prolongs retinal function and provides a neuroprotective effect on the photoreceptor cells and inner retinal network. FUNDING: NIH grants [R01EY026682, R01EY024665, R01EY025225, R01EY024698, R21AG050437, P30EY026877, 5P30EY019007, R01EY018213, F30EYE027986, T32GM007337, 5P30CA013696], NSF grant CHE-1734082.

ß-alanine supplementation induces taurine depletion and causes alterations of the retinal nerve fiber layer and axonal transport by retinal ganglion cells.

To study the effect of taurine depletion induced by ß-alanine supplementation in the retinal nerve fiber layer (RNFL), and retinal ganglion cell (RGC) survival and axonal transport. Albino Sprague-Dawley rats were divided into two groups: one group received ß-alanine supplementation (3%) in the drinking water during 2 months to induce taurine depletion, and the other group received regular water. After one month, half of the rats from each group were exposed to light. Retinas were analyzed in-vivo using Spectral-Domain Optical Coherence Tomography (SD-OCT). Prior to processing, RGCs were retrogradely traced with fluorogold (FG) applied to both superior colliculi, to assess the state of their retrograde axonal transport. Retinas were dissected as wholemounts, surviving RGCs were immunoidentified with Brn3a, and the RNFL with phosphorylated high-molecular-weight subunit of the neurofilament triplet (pNFH) antibodies. ß-alanine supplementation decreases significantly taurine plasma levels and causes a significant reduction of the RNFL thickness that is increased after light exposure. An abnormal pNFH immunoreactivity in some RGC bodies, their proximal dendrites and axons, and a further diminution of the mean number of FG-traced RGCs compared with Brn3a+RGCs, indicate that their retrograde axonal transport is affected. In conclusion, taurine depletion causes RGC loss and axonal transport impairment. Finally, our results suggest that care should be taken when ingesting ß-alanine supplements due to the limited understanding of their potential adverse effects.

Green Tea Extract Ameliorates Ischemia-Induced Retinal Ganglion Cell Degeneration in Rats.

PURPOSE: Oxidative stress induced by reduced blood circulation is a critical pathological damage to retinal ganglion cells (RGCs) in glaucoma. We previously showed that green tea extract (GTE) and its catechin constituents alleviate sodium iodate-induced retinal degeneration in rats. Here, we investigated the therapeutic effect of GTE on ischemia-induced RGC degeneration in rats. METHODS: RGC degeneration was induced by ischemic reperfusion in adult Fischer F344 rats. Green tea extract (Theaphenon E) was intragastrically administered 4 times within 48 hours after ischemia. RGC survival, pupillary light reflex, expressions of cell apoptosis, oxidative stress, and inflammation-related proteins were studied. RESULTS: Ischemic reperfusion significantly induced apoptotic RGCs, RGC loss, and larger constricted pupil area compared to the untreated normal rats. Expressions of activated caspase-3 and caspase-8, Sod2, and inflammation-related proteins as well as p38 phosphorylation were significantly upregulated in the ischemia-injured rats. Compared to the saline-fed ischemic rats, significantly higher number of surviving RGCs, less apoptotic RGCs, and smaller constricted pupil area were observed in the GTE-fed ischemic rats. GTE also reduced the increased protein expressions caused by ischemic injury but enhanced the Jak phosphorylation in the retina. Notably, green tea extract did not affect the survival of RGCs in the uninjured normal rats. CONCLUSIONS: In summary, GTE offers neuroprotection to RGCs under ischemic challenge, suggesting a potential therapeutic strategy for glaucoma and optic neuropathies.

Liver-Specific, but Not Retina-Specific, Hepcidin Knockout Causes Retinal Iron Accumulation and Degeneration.

The liver secretes hepcidin (Hepc) into the bloodstream to reduce blood iron levels. Hepc accomplishes this by triggering degradation of the only known cellular iron exporter ferroportin in the gut, macrophages, and liver. We previously demonstrated that systemic Hepc knockout (HepcKO) mice, which have high serum iron, develop retinal iron overload and degeneration. However, it was unclear whether this is caused by high blood iron levels or, alternatively, retinal iron influx that would normally be regulated by retina-produced Hepc. To address this question, retinas of liver-specific and retina-specific HepcKO mice were studied. Liver-specific HepcKO mice had elevated blood and retinal pigment epithelium (RPE) iron levels and increased free (labile) iron levels in the retina, despite an intact blood-retinal barrier. This led to RPE hypertrophy associated with lipofuscin-laden lysosome accumulation. Photoreceptors also degenerated focally. In contrast, there was no change in retinal or RPE iron levels or degeneration in the retina-specific HepcKO mice. These data indicate that high blood iron levels can lead to retinal iron accumulation and degeneration. High blood iron levels can occur in patients with hereditary hemochromatosis or result from use of iron supplements or multiple blood transfusions. Our results suggest that high blood iron levels may cause or exacerbate retinal disease.

Bilberry extract and anthocyanins suppress unfolded protein response induced by exposure to blue LED light of cells in photoreceptor cell line.

Purpose: The purpose of this study was to investigate the effects of bilberry extract with its anthocyanins on retinal photoreceptor cell damage and on the endoplasmic reticulum (ER) stress induced by exposure to blue light-emitting diode (LED) light. Methods: Cultured murine photoreceptor cells (661W) were exposed to blue LED light with or without bilberry extract or its anthocyanins in the culture media. Aggregated short-wavelength opsin (S-opsin) in murine photoreceptor cells was observed with immunostaining. The expression of factors involved in the unfolded protein response was examined with immunoblot analysis and quantitative real-time reverse transcription (RT)-PCR. Furthermore, cell death was observed with double staining with Hoechst 33342 and propidium iodide after dithiothreitol (DTT) treatment. Results: Bilberry extract and anthocyanins suppressed the aggregation of S-opsin, activation of ATF4, and expression of the mRNA of the factors associated with the unfolded protein response (UPR). In addition, bilberry extract and the anthocyanins inhibited the death of photoreceptor cells induced by DTT, an ER stress inducer. Conclusions: These findings suggest that bilberry extract containing anthocyanins can alter the effects of blue LED light and DTT-induced retinal photoreceptor cell damage. These effects were achieved by modulating the activation of ATF4 and through the suppression of the abnormal aggregation of S-opsin.

Antioxidant effects of Lycium barbarum polysaccharides on photoreceptor degeneration in the light-exposed mouse retina.

We assessed the neuroprotective effects of Lycium barbarum Polysaccharides (LBP) on photoreceptor degeneration and the mechanisms involved in oxidative stress in light-exposed mouse retinas. Mice were given a gavage of LBP (150 mg/kg or 300 mg/kg) or phosphate buffered saline (PBS) for 7 days before exposure to light (5000 lx for 24 h). We found that LBP significantly improved the electroretinography (ERG) amplitudes of the a- and b-waves that had been attenuated by light exposure. In addition, changes caused by light exposure including photoreceptor cell loss, nuclear condensation, an increased number of mitochondria vacuoles, outer membrane disc swelling and cristae fractures were distinctly ameliorated by LBP. LBP treatment also significantly prevented the generation of reactive oxygen species (ROS) compared with PBS treatment. The levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and thioredoxin reductase (TrxR1) mRNA were decreased in PBS-treated mice compared with controls but increased remarkably in LBP-treated mice. The mRNA levels of the DNA repair gene Poly (ADP-ribose) polymerase (PARP14) was increased in PBS-treated mice but decreased significantly in the LBP-treated mice. Our findings indicate that pretreatment with LBP effectively protected photoreceptor cells against light-induced retinal damage probably through the up-regulation of the antioxidative genes Nrf2 and TrxR1, the elimination of oxygen free radicals, and the subsequent reduction in the mitochondrial reaction to oxidative stress and enhancement in antioxidant capacity. In addition, the decreased level of PARP14 mRNA in LBP-treated mice also indicated a protective effect of LBP on delaying photoreceptor in the light-damaged retina.

Taurine Depletion Causes ipRGC Loss and Increases Light-Induced Photoreceptor Degeneration.

Purpose: To examine if light exposure exacerbates retinal neuronal loss induced by taurine depletion. Methods: Albino rats received ß-alanine in the drinking water to induce taurine depletion. One month later, half of the animals were exposed to white light (3000 lux) continuously for 48 hours and the rest remained in normal environmental conditions. A control group of animals nontreated with ß-alanine also was prepared, and half of them were exposed to light using the same protocol. All the animals were processed 2 months after the beginning of the experiment. Retinas were dissected as wholemounts and immunodetected with antibodies against Brn3a, melanopsin, S-opsin, and L-opsin to label different retinal populations: Brn3a+ retinal ganglion cells (RGCs) (image-forming RGCs), m+RGCs (non-image-forming RGCs), and S- and L/M-cones, respectively. Results: Light exposure did not affect the numbers of Brn3a+RGCs or m+RGCs but diminished the numbers of S- and L/M-cones and caused the appearance of rings devoid of cones, mainly in an "arciform" area in the superotemporal retina. Taurine depletion caused a diminution of all the studied populations, with m+RGCs the most affected, followed by S-cones. Light exposure under taurine depletion increased photoreceptor degeneration but did not seem to increase Brn3a+RGCs or m+RGCs loss. Conclusions: Our results document that taurine is necessary for cell survival in the rat retina and even more under light-induced photoreceptor degeneration. Thus, taurine supplementation may help to prevent retinal degenerations, especially those that commence with S-cone degeneration or in which light may be an etiologic factor, such as inherited retinal degenerations, AMD, or glaucoma.

670nm light treatment following retinal injury modulates Müller cell gliosis: Evidence from in vivo and in vitro stress models.

Photobiomodulation (PBM) with 670 nm light has been shown to accelerate wound healing in soft tissue injuries, and also to protect neuronal tissues. However, little data exist on its effects on the non-neuronal components of the retina, such as Müller cells (MCs), which are the principal macroglia of the retina that play a role in maintaining retinal homeostasis. The aim of this study was to explore the effects of 670 nm light on activated MCs using in vivo and in vitro stress models. Adult Sprague-Dawley rats were exposed to photo-oxidative damage (PD) for 24 h and treated with 670 nm light at 0, 3 and 14 days after PD. Tissue was collected at 30 days post-PD for analysis. Using the in vitro scratch model with a human MC line (MIO-M1), area coverage and cellular stress were analysed following treatment with 670 nm light. We showed that early treatment with 670 nm light after PD reduced MC activation, lowering the retinal expression of GFAP and FGF-2. 670 nm light treatment mitigated the production of MC-related pro-inflammatory cytokines (including IL-1ß), and reduced microglia/macrophage (MG/MΦ) recruitment into the outer retina following PD. This subsequently decreased photoreceptor loss, slowing the progression of retinal degeneration. In vitro, we showed that 670 nm light directly modulated MC activation, reducing rates of area coverage by suppressing cellular proliferation and spreading. This study indicates that 670 nm light treatment post-injury may have therapeutic benefit when administered shortly after retinal damage, and could be useful for retinal degenerations where MC gliosis is a feature of disease progression.

Enhancing the efficacy of AREDS antioxidants in light-induced retinal degeneration.

PURPOSE: Light-induced photoreceptor cell degeneration and disease progression in age-related macular degeneration (AMD) involve oxidative stress and visual cell loss, which can be prevented, or slowed, by antioxidants. Our goal was to test the protective efficacy of a traditional Age-related Eye Disease Study antioxidant formulation (AREDS) and AREDS combined with non-traditional antioxidants in a preclinical animal model of photooxidative retinal damage. METHODS: Male Sprague-Dawley rats were reared in a low-intensity (20 lux) or high-intensity (200 lux) cyclic light environment for 6 weeks. Some animals received a daily dietary supplement consisting of a small cracker infused with an AREDS antioxidant mineral mixture, AREDS antioxidants minus zinc, or zinc oxide alone. Other rats received AREDS combined with a detergent extract of the common herb rosemary, AREDS plus carnosic acid, zinc oxide plus rosemary, or rosemary alone. Antioxidant efficacy was determined by measuring retinal DNA levels 2 weeks after 6 h of intense exposure to white light (9,000 lux). Western blotting was used to determine visual cell opsin and arrestin levels following intense light treatment. Rhodopsin regeneration was determined after 1 h of exposure to light. Gene array analysis was used to determine changes in the expression of retinal genes resulting from light rearing environment or from antioxidant supplementation. RESULTS: Chronic high-intensity cyclic light rearing resulted in lower levels of rod and cone opsins, retinal S-antigen (S-ag), and medium wavelength cone arrestin (mCAR) than found for rats maintained in low cyclic light. However, as determined by retinal DNA, and by residual opsin and arrestin levels, 2 weeks after acute photooxidative damage, visual cell loss was greater in rats reared in low cyclic light. Retinal damage decreased with AREDS plus rosemary, or with zinc oxide plus rosemary whereas AREDS alone and zinc oxide alone (at their daily recommended levels) were both ineffective. One week of supplemental AREDS plus carnosic acid resulted in higher levels of rod and cone cell proteins, and higher levels of retinal DNA than for AREDS alone. Rhodopsin regeneration was unaffected by the rosemary treatment. Retinal gene array analysis showed reduced expression of medium- wavelength opsin 1 and arrestin C in the high-light reared rats versus the low-light rats. The transition of rats from low cyclic light to a high cyclic light environment resulted in the differential expression of 280 gene markers, enriched for genes related to inflammation, apoptosis, cytokine, innate immune response, and receptors. Rosemary, zinc oxide plus rosemary, and AREDS plus rosemary suppressed 131, 241, and 266 of these genes (respectively) in high-light versus low-light animals and induced a small subset of changes in gene expression that were independent of light rearing conditions. CONCLUSIONS: Long-term environmental light intensity is a major determinant of retinal gene and protein expression, and of visual cell survival following acute photooxidative insult. Rats preconditioned by high-light rearing exhibit lower levels of cone opsin mRNA and protein, and lower mCAR protein, than low-light reared animals, but greater retention of retinal DNA and proteins following photooxidative damage. Rosemary enhanced the protective efficacy of AREDS and led to the greatest effect on the retinal genome in animals reared in high environmental light. Chronic administration of rosemary antioxidants may be a useful adjunct to the therapeutic benefit of AREDS in slowing disease progression in AMD.

Effects of the Tangningtongluo formula as an alternative strategy for diabetics via upregulation of insulin receptor substrate-1.

Tangningtongluo (TNTL), a traditional Chinese medicine, has been widely used in clinics for decades in southwest China. Its pharmacological properties and underlying molecular mechanisms remain unclear. The main goal of ethnopharmacology is to identify novel bioactive compounds derived from plants for use in indigenous medical practice. This knowledge can be used to develop novel pharmaceuticals. In the present study, hyperglycemic C57BL/KsJ­db/db (db/db) mice were used to test the effect of TNTL on microvasculature of the retina and hypoglycemia. Metformin (Met) was selected as a positive control. 26­week­old mice were randomly assigned to receive either the anti­diabetic agent Met [140 mg/kg body weight (BW)], 1.8, 0.9 or 0.45 g/kg BW TNTL, or a placebo. The fasting blood glucose, serum insulin and glycated hemoglobin levels were measured. Histopathologic examination of the pancreas was performed to confirm the hypoglycemic effect. Fluorescein angiography was applied to detect diabetes­induced retinal angioma in the db/db mice. TNTL intake significantly decreased the fasting blood glucose level in a dose­dependent manner. Additionally, TNTL intervention resulted in a significant decrease in the insulin resistance index. Notably, TNTL treatment markedly reduced the speed of retinal degeneration and mildly reversed microvascular caliber degeneration. Western blot analysis indicated that upregulation of phosphorylated insulin receptor substrate­1 (p­IRS­1) by the administration of TNTL may be strongly involved in the improvement of insulin resistance. In conclusion, TNTL exerted a strong hypoglycemic effect and reversed retinal degeneration via upregulation of ISR­1. The present findings provide important scientific evidence supporting TNTL as an effective alternative approach for the management of Type 2 diabetes mellitus.

Intraperitoneal injection of (-)-Epigallocatechin-3-gallate protects against light-induced photoreceptor degeneration in the mouse retina.

PURPOSE: (-)-epigallocatechin-3-gallate (EGCG), a major catechin component of green tea, is reported to delay or prevent certain forms of cancer, arthritis, cardiovascular disease, and neurodegenerative disorders. In this study, we determined if systemically administered EGCG could protect the retina against light damage (LD) in mice. METHODS: BALB/cJ mice were treated with either EGCG or saline via intraperitoneal (IP) injection, and then placed under constant cool white light-emitting diode (LED) light (10,000 lux) for 5 h. Retinal structure and function were evaluated using optical coherence tomography (OCT), histology, and electroretinography (ERG) 7 days after LD. In addition, the mRNAs of several oxidative stress genes were quantified by qPCR before LD and 24 h after LD. RESULTS: OCT and photomicrographs of mouse retinas showed morphologic protection of photoreceptors. Mice in the EGCG group had significantly higher ERG amplitudes for all three wave types compared with mice in the saline control group, which indicated that EGCG protected retinal function. Furthermore, qPCR results showed that EGCG administration can increase the mRNA level of the antioxidant gene Sod2 before LD and 24 h after LD. CONCLUSIONS: The IP injection of EGCG attenuated the detrimental effects of bright light on the retinas of BALB/cJ mice by protecting the structure and function of the retina.

Persimmon Leaves (Diospyros kaki) Extract Protects Optic Nerve Crush-Induced Retinal Degeneration.

Retinal ganglion cell (RGC) death is part of many retinal diseases. Here, we report that the ethanol extract of Diospyros kaki (EEDK) exhibits protective properties against retinal degeneration, both in vitro and in vivo. Upon exposure to cytotoxic compounds, RGC-5 cells showed approximately 40% cell viability versus the control, while pre-treatment with EEDK markedly increased cell viability in a concentration-dependent manner. Further studies revealed that cell survival induced by EEDK was associated with decreased levels of apoptotic proteins, such as poly (ADP-ribose) polymerase, p53, and cleaved caspase-3. In addition to apoptotic pathways, we demonstrated that expression levels of antioxidant-associated proteins, such as superoxide dismutase-1, glutathione S-transferase, and glutathione peroxidase-1, were positively modulated by EEDK. In a partial optic nerve crush mouse model, EEDK had similar ameliorating effects on retinal degeneration resulting from mechanical damages. Therefore, our results suggest that EEDK may have therapeutic potential against retinal degenerative disorders, such as glaucoma.

Chemical Exacerbation of Light-induced Retinal Degeneration in F344/N Rats in National Toxicology Program Rodent Bioassays.

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 increased frequencies of degenerative retinal lesions localized within the central/hemispherical region are suggestive of exacerbation of light-induced retinal degeneration.

Cyanidin-3-glucoside and its phenolic acid metabolites attenuate visible light-induced retinal degeneration in vivo via activation of Nrf2/HO-1 pathway and NF-κB suppression.

SCOPE: Cyanidin-3-glucoside (C3G) is a major anthocyanin in berries and a potential nutritional supplement for preventing retinal degeneration. However, the protective mechanism of C3G and its metabolites, protocatechuic acid (PCA) and ferulic acid (FA), remain unclear. The molecular mechanisms of C3G and its metabolites against retinal photooxidative damage in vivo are investigated. METHODS AND RESULTS: Pigmented rabbits were orally administered C3G, PCA, and FA (0.11 mmol/kg/day) for 3 weeks. Electroretinography, histological analysis, and TUNEL assay showed that C3G and its metabolites attenuated retinal cell apoptosis. The expression of oxidative stress markers were upregulated after light exposure but attenuated by C3G and FA, which may be attributed to the elevated secretion and expression of heme oxygenase (HO-1) and nuclear factor erythroid-2 related factor 2 (Nrf2). C3G, PCA, and FA attenuated the secretion or expression of inflammation-related genes; FA suppressed nuclear factor kappa B (NF-κB) activation. The treatments attenuated the light-induced changes on certain apoptotic proteins and angiogenesis-related cytokines. CONCLUSION: C3G and FA reduced light-induced retinal oxidative stress by activating the Nrf2/HO-1 antioxidant pathway. FA attenuated the light-induced retinal inflammation by suppressing NF-κB activation. C3G and its metabolites attenuated the photooxidation-induced apoptosis and angiogenesis in the retina.