Madecassoside protects retinal pigment epithelial cells against hydrogen peroxide-induced oxidative stress and apoptosis through the activation of Nrf2/HO-1 pathway

Identification of components that increase NAD+ levels in oxygen-glucose deprived HUVEC s from Schisandra chinensis (Turcz.) Baill. Based on spectrum-effect correlation analysis and target cell extraction

Schisandra chinensis (Turcz.) Baill, a traditional Chinese medicine with significant nourishing functions, has a regulatory effect on the cardiovascular system, digestive system, central nervous system, and endocrine and immune systems. It can protect the cardiovascular system, improve immunity, and has anti-oxidant and anti-aging properties. This study aimed to identify the chisandra chinensis components that increased NAD+ levels, by using spectrum-effect analysis and experimental validations. First, the quality of the S. chinensis extract was analyzed by HPLC-MS. The extract of S. chinensis increased the NAD+ levels of HUVECs during oxygen and glucose deprivation injury, and protected HUVEC s from injury from superoxide dismutase (SOD) and aging. The relationships of spectral effects were studied by partial least square regression. Coupled with target cell extraction, the material basis for increasing NAD+ levels in S. chinensis was obtained. The pharmacological activity of S. chinensis was verified at the cellular level. The related enzymes of the NAD+ synthesis and decomposition pathways were identified, showing that S. chinensis increased the level of NAD+ by increasing the activity of related enzymes in the synthesis pathways of NMNAT1, NMNAT2, NMNAT3, and NAMPT, but had no effect on the decomposition pathway. Finally, four constituents were confirmed, in vitro, to be the basis of S. chinensis-induced increases in the levels of NAD+. The EC50 values of the four constituents were also determined.

Madecassoside mitigates acute myocardial infarction injury by activating the PKCB/SPARC signaling pathway

The current treatments and drugs of myocardial infarction (MI) remain insufficient. In recent years, natural products have garnered significant attention for their potential in treating cardiovascular diseases due to their availability and lower toxicity. Saponins, in particular, showed promising effects for cardiac protection. In this study, we investigated the therapeutic effects of the saponin compound madecassoside in the treatment of MI, and underlying molecular mechanisms. The acute MI model was established in male mice by ligation of the left anterior descending coronary artery. The mice were treated with madecassoside (20 mg· kg-1 ·d-1, i.g.) for 14 days. After sacrificing the mice, hearts were harvested for analysis. We showed that madecassoside administration significantly mitigated cardiac function decline in MI mice by promoting angiogenesis and inhibiting myocardial cell apoptosis and fibrosis. By conducting systems pharmacology and RNA sequencing, we demonstrated that madecassoside upregulated SPARC gene expression by activating protein kinase C-β (PKCB) that had a strong promoting effect on endothelial cell angiogenesis, thus playing a crucial protective role against MI. We showed that inhibition of SPARC gene significantly reduced madecassoside-stimulated migration and tube formation of endothelial cells in vitro; co-administration of the PKCB-specific inhibitor ruboxistaurin (10 mg· kg-1 ·d-1, i.g.) abolished the cardioprotective effect of madecassoside in MI mice, validating the critical role of the PKCB/SPARC signaling pathway. This study demonstrates that madecassoside regulates the PKCB/SPARC pathway, promotes the proliferation and regeneration of vascular endothelial cells, and effectively alleviates the symptoms of MI.

The novel secretome ST266 activates Akt and protects against oxidative stress-mediated injury in human RPE and Müller cells

Oxidative stress-mediated retinal pigment epithelial (RPE) cell damage is associated with age-related macular degeneration (AMD). ST266 is the biological secretome produced by a novel population of amnion-derived multipotent progenitor cells. Herein, we investigated the effect of ST266 on RPE cell injury induced by hydroquinone (HQ), a cigarette smoke related oxidant, hydrogen peroxide (H2O2) and all-trans retinal (atRal), a pro-oxidant component of the retinoid cycle. We additionally investigated its effect on Müller cell injury induced by H2O2. Cultured human RPE cells were pre-treated for 1 h in the presence or absence of MK-2206, a protein kinase B (Akt) inhibitor, then treated with varying concentrations of HQ, H2O2, or atRal for 1.5 h. Cultured human Müller cells (MIO-M1) were pre-treated for 1 h in the presence or absence of MK-2206, then treated with varying concentrations of H2O2 for 1.5 h. Media were then replaced with STM100 (control media into which the ST266 secretome proteins were collected) or ST266 at various times. Cell viability was determined with WST-1 reagent. Mitochondrial membrane potential (Δψm) was quantified by a fluorescence plate reader. The protein phosphorylation levels of Akt, glycogen synthase kinase 3 beta (GSK-3β), and p70 ribosomal S6 kinase (p70S6K) were measured by Western blot. ST266 significantly improved RPE and MIO-M1 cell viability that was reduced by oxidant exposure and improved oxidant-disrupted Δψm. In both cell types, ST266 induced phosphorylation of Akt, GSK-3β, and p70S6K. MK-2206 significantly eliminated ST266-mediated protein phosphorylation of Akt, GSK-3β, and p70S6K and abolished the ST266-protective effect on cell viability. In conclusion, ST266 activates Akt, protects against oxidative stress-mediated cell injury in an Akt-dependent manner, and improves Δψm, suggesting a potential role for ST266 therapy in treating retinal diseases such as AMD.

Natural plant medications for the treatment of retinal diseases: The blood-retinal barrier as a clue

BACKGROUND

Retinal diseases significantly contribute to the global burden of visual impairment and blindness. The occurrence of retinal diseases is often accompanied by destruction of the blood‒retinal barrier, a vital physiological structure responsible for maintaining the stability of the retinal microenvironment. However, detailed summaries of the factors damage the blood‒retinal barrier and treatment methods involving natural plant medications are lacking.

PURPOSE

To comprehensively summarize and analyze the protective effects of active substances in natural plant medications on damage to the blood-retina barrier that occurs when retinal illnesses, particularly diabetic retinopathy, and examine their medicinal value and future development prospects.

METHODS

In this study, we searched for studies published in the ScienceDirect, PubMed, and Web of Science databases. The keywords used included natural plant medications, plants, natural herbs, blood retinal barrier, retinal diseases, diabetic retinopathy, age-related macular degeneration, and uveitis. Chinese herbal compound articles, non-English articles, warning journals, and duplicates were excluded from the analysis.

RESULTS

The blood‒retinal barrier is susceptible to high glucose, aging, immune responses, and other factors that destroy retinal homeostasis, resulting in pathological changes such as apoptosis and increased vascular permeability. Existing studies have shown that the active compounds or extracts of many natural plants have the effect of repairing blood-retinal barrier dysfunction. Notably, berberine, puerarin, and Lycium barbarum polysaccharides exhibited remarkable therapeutic effects. Additionally, curcumin, astragaloside IV, hesperidin, resveratrol, ginsenoside Rb1, luteolin, and Panax notoginseng saponins can effectively protect the blood‒retinal barrier by interfering with distinct pathways. The active ingredients found in natural plant medications primarily repair the blood‒retinal barrier by modulating pathological factors such as oxidative stress, inflammation, pyroptosis, and autophagy, thereby alleviating retinal diseases.

CONCLUSION

This review summarizes a series of plant extracts and plant active compounds that can treat retinal diseases by preventing and treating blood‒retinal barrier damage and provides reference for the research of new drugs for treating retinal diseases.

Regulatory factors of Nrf2 in age-related macular degeneration pathogenesis

Age-related macular degeneration (AMD) is a complicated disease that causes irreversible visual impairment. Increasing evidences pointed retinal pigment epithelia (RPE) cells as the decisive cell involved in the progress of AMD, and the function of anti-oxidant capacity of PRE plays a fundamental physiological role. Nuclear factor erythroid 2 related factor 2 (Nrf2) is a significant transcription factor in the cellular anti-oxidant system as it regulates the expression of multiple anti-oxidative genes. Its functions of protecting RPE cells against oxidative stress (OS) and ensuing physiological changes, including inflammation, mitochondrial damage and autophagy dysregulation, have already been elucidated. Understanding the roles of upstream regulators of Nrf2 could provide further insight to the OS-mediated AMD pathogenesis. For the first time, this review summarized the reported upstream regulators of Nrf2 in AMD pathogenesis, including proteins and miRNAs, and their underlying molecular mechanisms, which may help to find potential targets via regulating the Nrf2 pathway in the future research and further discuss the existing Nrf2 regulators proved to be beneficial in preventing AMD.

Lutein Modulates Cellular Functionalities and Regulates NLRP3 Inflammasome in a H2O2-Challenged Three-Dimensional Retinal Pigment Epithelium Model

Excessive hydrogen peroxide (H2O2) generated during retinal cell metabolic activity could lead to oxidative degeneration of retinal pigment epithelium (RPE) tissue, a specific pathological process implicated in various retinal diseases resulting in blindness, which can be mitigated by taking dietary antioxidants to prevent inflammation and impaired cellular dysfunction. This study tested the hypothesis that damages induced by oxidative stresses can be mitigated by lutein in a H2O2-challenged model, which was based on an ARPE-19 cell monolayer cultured on three-dimensional (3D)-printed fibrous scaffolds. Pretreating these models with lutein (0.5 μM) for 24 h can significantly lower the oxidative stress and maintain phagocytosis and barrier function. Moreover, lutein can modulate the NLRP3 inflammasome, leading to a ∼40% decrease in the pro-inflammatory cytokine (IL-1β and IL-18) levels. Collectively, this study suggests that the 3D RPE model is an effective tool to examine the capability of lutein to modulate cellular functionalities and regulate NLRP3 inflammation.

The Role of Glutathione in Age-Related Macular Degeneration (AMD)

Age-related macular degeneration (AMD) is a chronic disease that usually develops in older people. Pathogenetic changes in this disease include anatomical and functional complexes. Harmful factors damage the retina and macula. These changes may lead to partial or total loss of vision. The disease can occur in two clinical forms: dry (the progression is slow and gentle) and exudative (wet-progression is acute and severe), which usually starts in the dry form; however, the coexistence of both forms is possible. The etiology of AMD is not fully understood, and the precise mechanisms of the development of this illness are still unknown. Extensive genetic studies have shown that AMD is a multi-factorial disease and that genetic determinants, along with external and internal environmental and metabolic-functional factors, are important risk factors. This article reviews the role of glutathione (GSH) enzymes engaged in maintaining the reduced form and polymorphism in glutathione S-transferase theta-1 (GSTT1) and glutathione S-transferase mu-1 (GSTM1) in the development of AMD. We only chose papers that confirmed the influence of the parameters on the development of AMD. Because GSH is the most important antioxidant in the eye, it is important to know the influence of the enzymes and genetic background to ensure an optimal level of glutathione concentration. Numerous studies have been conducted on how the glutathione system works till today. This paper presents the current state of knowledge about the changes in GSH, GST, GR, and GPx in AMD. GST studies clearly show increased activity in ill people, but for GPx, the results relating to activity are not so clear. Depending on the research, the results also suggest higher and lower GPx activity in patients with AMD. The analysis of polymorphisms in GST genes confirmed that mutations lead to weaker antioxidant barriers and may contribute to the development of AMD; unfortunately, a meta-analysis and some research did not confirm that connection. Unspecific results of many of the parameters that make up the glutathione system show many unknowns. It is so important to conduct further research to understand the exact mechanism of defense functions of glutathione against oxidative stress in the human eye.

Natural compounds efficacy in Ophthalmic Diseases: A new twist impacting ferroptosis

Ferroptosis, a distinct form of cell death, is characterized by the iron-mediated oxidation of lipids and is finely controlled by multiple cellular metabolic pathways. These pathways encompass redox balance, iron regulation, mitochondrial function, as well as amino acid, lipid, and sugar metabolism. Additionally, various disease-related signaling pathways also play a role in the regulation of ferroptosis. In recent years, with the introduction of the concept of ferroptosis and the deepening of research on its mechanism, ferroptosis is closely related to various biological conditions of eye diseases, including eye organ development, aging, immunity, and cancer. This article reviews the development of the concept of ferroptosis, the mechanism of ferroptosis, and its latest research progress in ophthalmic diseases and reviews the research on ferroptosis in ocular diseases within the framework of metabolism, active oxygen biology, and iron biology. Key regulators and mechanisms of ferroptosis in ocular diseases introduce important concepts and major open questions in the field of ferroptosis and related natural compounds. It is hoped that in future research, further breakthroughs will be made in the regulation mechanism of ferroptosis and the use of ferroptosis to promote the treatment of eye diseases. At the same time, natural compounds may be the direction of new drug development for the potential treatment of ferroptosis in the future. Open up a new way for clinical ophthalmologists to research and prevent diseases.

Chlorophytum borivilianum aqueous root extract prevents deterioration of testicular function in mice and preserves human sperm function in hydrogen peroxide (H2O2)-induced oxidative stress

ETHNOPHARMACOLOGICAL RELEVANCE

Chlorophytum borivilianum (C. borivilianum) (CB) has traditionally been used to treat male sexual dysfunctions and has been claimed to possess aphrodisiac properties.

AIM OF THE STUDY

To investigate the ability of CB to ameliorate H2O2-induced oxidative stress in testes and sperm in mice and prevent H2O2-induced oxidative in human sperm.

MATERIALS AND METHODS

Oxidative stress was induced in male mice by pre-exposure to 2% H2O2 orally for seven consecutive days, followed by 100 and 200 mg/kg b. w. administration. CB for another seven days. At the end of treatment, mice were sacrificed and testes and epididymal sperm were harvested. Serum FSH, LH and testosterone levels were measured and sperm parameters were obtained. Meanwhile, oxidative stress levels in mice testes and sperm, steroidogenesis and spermatogenesis markers in mice testes were assessed by molecular biological techniques. In another experiment, sperm from thirty-two healthy fertile men were incubated with 200 μM H2O2 and CB (100 and 200 μg/ml) simultaneously and were then evaluated for sperm parameter changes.

RESULTS

In mice, CB administration ameliorates persistent increases in oxidative stress and decreases in anti-oxidative enzyme levels in testes and sperm following H2O2 pre-exposure. Additionally, CB also helps to ameliorate deterioration in sperm parameters and testicular steroidogenesis and spermatogenesis and restores the serum FSH, LH and testosterone levels near normal in mice. In humans, CB helps to prevent deterioration in sperm parameters following H2O2 exposure.

CONCLUSION

CB is potentially useful to preserve the male reproductive capability and subsequently male fertility in high oxidative stress conditions.

Neuroprotective Nanoparticles Targeting the Retina: A Polymeric Platform for Ocular Drug Delivery Applications

Neuroprotective drug delivery to the posterior segment of the eye represents a major challenge to counteract vision loss. This work focuses on the development of a polymer-based nanocarrier, specifically designed for targeting the posterior eye. Polyacrylamide nanoparticles (ANPs) were synthesised and characterised, and their high binding efficiency was exploited to gain both ocular targeting and neuroprotective capabilities, through conjugation with peanut agglutinin (ANP:PNA) and neurotrophin nerve growth factor (ANP:PNA:NGF). The neuroprotective activity of ANP:PNA:NGF was assessed in an oxidative stress-induced retinal degeneration model using the teleost zebrafish. Upon nanoformulation, NGF improved the visual function of zebrafish larvae after the intravitreal injection of hydrogen peroxide, accompanied by a reduction in the number of apoptotic cells in the retina. Additionally, ANP:PNA:NGF counteracted the impairment of visual behaviour in zebrafish larvae exposed to cigarette smoke extract (CSE). Collectively, these data suggest that our polymeric drug delivery system represents a promising strategy for implementing targeted treatment against retinal degeneration.

FOXO4 mediates resistance to oxidative stress in lens epithelial cells by modulating the TRIM25/Nrf2 signaling

Oxidative stress damage to the lens is a key factor in most cataracts. Forkhead box O 4 (FOXO4), a member of the forkhead box O family, plays a pivotal role in oxidative stress. FOXO4 is upregulated in lens of age-related cataract patients, but its role in cataract has not been elucidated. Herein, we investigated the role and mechanism of FOXO4 during oxidative stress damage in lens epithelial cells. H₂O₂ treatment enhanced FOXO4 expression in HLEpiC cells. Short hairpin RNAs mediated FOXO4 silence aggravated H₂O₂-induced cell apoptosis. In addition, upon H₂O₂ exposure, silencing of FOXO4 reduced SOD and CAT activities, as well as increased intracellular MDA and ROS levels. FOXO4 silencing also inhibited Nrf2 nuclear translocation, followed by reducing the expressions of Nrf2-governed antioxidant genes HO-1 and NOQ-1. Exogenous overexpression of FOXO4 was also involved in this study and exhibited opposite effects of FOXO4-silencing. Mechanistically, FOXO4 directly bound the promoter of TRIM25 and regulated its transcription, thereby activating the Nrf2 signaling. Taken together, in the condition of oxidative stress, the expression of FOXO4 showed a compensatory upregulation and it exhibited an anti-oxidative effect by modulating the transcription of TRIM25, thus activating the Nrf2 signaling. The FOXO4/TRIM25/Nrf2 axis may be associated with the pathological mechanisms of cataract.

Fisetin Attenuated Oxidative Stress-Induced Cellular Damage in ARPE-19 Human Retinal Pigment Epithelial Cells Through Nrf2-Mediated Activation of Heme Oxygenase-1

Fisetin is a kind of bioactive flavonol, widely present in various fruits such as strawberries and apples, and is known to act as a potent free radical scavenger. However, the mechanism of action related to the antioxidant activity of this compound in human retinal pigment epithelial (RPE) cells is not precisely known. In this study, we aimed to investigate whether fisetin could attenuate oxidative stress-induced cytotoxicity on human RPE ARPE-19 cells. To mimic oxidative stress, ARPE-19 cells were treated with hydrogen peroxide (H₂O₂), and fisetin significantly inhibited H₂O₂-induced loss of cell viability and increase of intracellular reactive oxygen species (ROS) production. Fisetin also markedly attenuated DNA damage and apoptosis in H₂O₂-treated ARPE-19 cells. Moreover, mitochondrial dysfunction in H₂O₂-treated cells was alleviated in the presence of fisetin as indicated by preservation of mitochondrial membrane potential, increase of Bcl-2/Bax expression ratio, and suppression of cytochrome c release into the cytoplasm. In addition, fisetin enhanced phosphorylation and nuclear translocation of nuclear factor erythroid 2 related factor 2 (Nrf2), which was associated with increased expression and activity of heme oxygenase-1 (HO-1). However, the HO-1 inhibitor, zinc protoporphyrin, significantly reversed the protective effect of fisetin against H₂O₂-mediated ARPE-19 cell injury. Therefore, our results suggest that Nrf2-mediated activation of antioxidant enzyme HO-1 may play an important role in the ROS scavenging activity of fisetin in RPE cells, contributing to the amelioration of oxidative stress-induced ocular disorders.

Fucoxanthin Pretreatment Ameliorates Visible Light-Induced Phagocytosis Disruption of RPE Cells under a Lipid-Rich Environment via the Nrf2 Pathway

Fucoxanthin, a special xanthophyll derived from marine algae, has increasingly attracted attention due to its diverse biological functions. However, reports on its ocular benefits are still limited. In this work, the ameliorative effect of fucoxanthin on visible light and lipid peroxidation-induced phagocytosis disruption in retinal pigment epithelium (RPE) cells was investigated in vitro. Marked oxidative stress, inflammation, and phagocytosis disruption were evident in differentiated RPE cells following their exposure to visible light under a docosahexaenoic acid (DHA)-rich environment. Following pretreatment with fucoxanthin, however, the activated nuclear factor erythroid-derived-2-like 2 (Nrf2) signaling pathway was observed and, furthermore, when the fucoxanthin -pretreated RPE cells were irradiated with visible light, intracellular reactive oxygen species (ROS), malondialdehyde (MDA) levels and inflammation were obviously suppressed, while phagocytosis was significantly improved. However, following the addition of Nrf2 inhibitor ML385, the fucoxanthin exhibited no ameliorative effects on the oxidative stress, inflammation, and phagocytosis disruption in the RPE cells, thus indicating that the ameliorative effect of fucoxanthin on the phagocytosis of RPE cells is closely related to the Nrf2 signaling pathway. In conclusion, these results suggest that fucoxanthin supplementation might be beneficial to the prevention of visible light-induced retinal injury.

Plant-Derived Compounds as Promising Therapeutics for Vitiligo

Vitiligo is the most common depigmenting disorder characterized by white patches in the skin. The pathogenetic origin of vitiligo revolves around autoimmune destruction of melanocytes in which, for instance, oxidative stress is responsible for melanocyte molecular, organelle dysfunction and melanocyte specific antigen exposure as well as melanocyte cell death and thus serves as an important contributor for vitiligo progression. In recent years, natural products have shown a wide range of pharmacological bioactivities against many skin diseases, and this review focuses on the effects and mechanisms of natural compounds against vitiligo models. It is showed that some natural compounds such as flavonoids, phenols, glycosides and coumarins have a protective role in melanocytes and thereby arrest the depigmentation, and, additionally, Nrf2/HO-1, MAPK, JAK/STAT, cAMP/PKA, and Wnt/β-catenin signaling pathways were reported to be implicated in these protective effects. This review discusses the great potential of plant derived natural products as anti-vitiligo agents, as well as the future directions to explore.

Honokiol alleviates LPS-induced acute lung injury by inhibiting NLRP3 inflammasome-mediated pyroptosis via Nrf2 activation in vitro and in vivo

Background

Honokiol (HKL) has been reported to ameliorate lipopolysaccharide (LPS)-induced acute lung injury (ALI). However, its potential mechanism of its protective effects remains unclear. In this study, the protective mechanism of HKL on LPS-induced ALI was explored in vivo and in vitro.

Methods

In vivo, the SD rats were intratracheally instilled with LPS (5 mg/kg) to establish an acute lung injury model and then treated with HKL (1.25/2.5/5 mg/kg) or ML385 (30 mg/kg) intraperitoneally. In vitro, the human bronchial epithelial cell line (BEAS-2B) was stimulated with LPS and ATP to induce pyroptosis and treated with HKL (12.5/25/50 μM). Small interfering RNA (siRNA) technique was used to knockdown Nrf2 in BEAS-2B cells. The protein and mRNA expression levels of Nrf2, HO-1, NLRP3, ASC, CASP1, and GSDMD in cells and lung tissues were detected by western blot and real time-PCR. The expression levels of interleukin (IL)-1β, IL-18, MPO, MDA, and SOD in bronchoalveolar lavage fluid (BALF) and supernatant were determined by ELISA. The degree of pathological injury of lung tissue was evaluated by H&E staining.

Results

The results showed that HKL could alleviate oxidative stress and inflammatory responses by regulating the levels of MPO, MDA, SOD, IL-1β, IL-18 in supernatant. And it could also inhibit the expression levels of NLRP3, ASC, CASP1, GSDMD via activation of Nrf2 in BEAS-2B cells. Further studies revealed that HKL could attenuate the pathological injury in LPS-induced ALI rats, and the molecular mechanism was consistent with the results in vitro.

Conclusions

Our study demonstrated that HKL could alleviate LPS-induced ALI by reducing the oxidative stress and inhibiting NLRP3 inflammasome-mediated pyroptosis, which was partly dependent on the Nrf2 activation.

Graphical Abstract

Lycium barbarum polysaccharide protects ARPE‑19 cells against H2O2‑induced oxidative stress via the Nrf2/HO‑1 pathway

Age-related macular degeneration (AMD) is a global health problem. Lycium barbarum polysaccharide (LBP), a traditional Chinese herbal medicine, has been proven to be effective against several eye diseases. However, only a few studies have investigated the effectiveness of LBP for AMD. In the present study, the human retinal epithelial cell line, ARPE-19, was pretreated with LBP for 24 h before exposure to H₂O₂ (500 µM). Cell viability was assessed, and a series of oxidative and antioxidant indicators were evaluated to determine the influence of LBP on H₂O₂-triggered oxidative stress. The present study also determined the apoptosis status, as well as the expression levels of apoptotic proteins and nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway proteins. The present study aimed to determine the protective role for LBP pretreatment and its underlying molecular mechanism. The results of the present study suggest that pretreatment of ARPE-19 cells with LBP exhibit high efficacy at reducing oxidative damage and inhibiting cell apoptosis. Furthermore, LBP may modulate the expression of proteins involved in the apoptotic pathway and activate the Nrf2 signaling pathway.

Glutathione Metabolism and the Novel Role of Mitochondrial GSH in Retinal Degeneration

Glutathione (GSH) is present ubiquitously, and its role as a crucial cellular antioxidant in tissues, including the retina, is well established. GSH's antioxidant function arises from its ability to scavenge reactive oxygen species or to serve as an essential cofactor for GSH S-transferases and peroxidases. This review summarizes the general functions, retinal distribution, disorders linked to GSH deficiency, and the emerging role for mitochondrial GSH (mGSH) in retinal function. Though synthesized only in the cytosol, the presence of GSH in multiple cell organelles suggests the requirement for its active transport across organellar membranes. The localization and distribution of 2-oxoglutarate carrier (OGC) and dicarboxylate carrier (DIC), two recently characterized mitochondrial carrier proteins in RPE and retina, show that these transporters are highly expressed in human retinal pigment epithelium (RPE) cells and retinal layers, and their expression increases with RPE polarity in cultured cells. Depletion of mGSH levels via inhibition of the two transporters resulted in reduced mitochondrial bioenergetic parameters (basal respiration, ATP production, maximal respiration, and spare respiratory capacity) and increased RPE cell death. These results begin to reveal a critical role for mGSH in maintaining RPE bioenergetics and cell health. Thus, augmentation of mGSH pool under GSH-deficient conditions may be a valuable tool in treating retinal disorders, such as age-related macular degeneration and optic neuropathies, whose pathologies have been associated with mitochondrial dysfunction.