D609 protects retinal pigmented epithelium as a potential therapy for age-related macular degeneration

D609 Suppresses Antituberculosis Response by Regulating Dendritic Cells Antigen Presentation

OBJECTIVE

To elucidate the role of phosphatidylcholine-specific phospholipase C (PC-PLC) in the antituberculosis (anti-TB) immune response mediated by dendritic cells (DCs).

METHODS

In vivo, C57BL/6J mice infected with the Mycobacterium tuberculosis strain H37Rv. Before infection, the mice were pretreated with the PC-PLC inhibitor D609. Bacillary loads in lung and spleen tissues were quantified through colony-forming unit (CFU) assays. Hematoxylin and eosin (H&E) staining was performed to assess inflammatory infiltration and tissue damage. Levels of inflammatory mediators in peripheral venous blood were quantified using enzyme-linked immunosorbent assays (ELISAs). Flow cytometry was employed to determine the proportions of conventional DCs (cDCs) and their subsets, cDC1 and cDC2, within lung, spleen, and lymph node tissues. In vitro, mouse bone marrow-derived dendritic cells (BMDCs) pretreated with D609. The expression levels of chemokines and pro-inflammatory cytokines were assessed via quantitative polymerase chain reaction (qPCR) and ELISA. BMDCs were loaded with H37Rv expressing red fluorescent protein (RFP-H37Rv) or DQ-OVA, and flow cytometry was utilized to analyze the impact of D609 on antigen phagocytosis and processing. Furthermore, flow cytometry was employed to evaluate the effect of D609 pretreatment on the expression levels of costimulatory molecules on BMDCs. The capacity of D609-treated BMDCs to activate and proliferate T cells, as well as to induce interferon-gamma (IFN-γ) secretion, was assessed through a DC-T cell coculture system.

RESULTS

In vivo analysis revealed that mice pretreated with D609 exhibited a marked increase in tissue bacterial load, enhanced inflammatory infiltration, and a reduction in pro-inflammatory mediator expression in peripheral venous blood. There was a notable decrease in the number of cDCs in lung and lymph node tissues, with a pronounced reduction in cDC1 in the lungs and cDC2 in the lymph nodes. In vitro studies demonstrated that D609 pretreated BMDCs displayed a significant decline in inflammatory mediator production, antigen phagocytosis, and antigen processing capabilities, potentially due to altered expression of costimulatory molecules. Coculture experiments indicated that D609 pretreated BMDCs showed a substantial reduction in their ability to stimulate T cell activation, proliferation, and IFN-γ secretion.

CONCLUSION

Our findings suggest that PC-PLC plays a critical role in the functionality of DCs, including the production of chemokines and pro-inflammatory cytokines, migration to lymph nodes, and antigen presentation to T cells, which collectively contribute to T cell activation and effective clearance of Mycobacterium tuberculosis. Further investigation into the regulatory mechanisms of PC-PLC in DCs may uncover novel therapeutic targets for the development of advanced anti-TB treatments.

Screening and evaluation of antioxidants for retinal pigment epithelial cell protection: L-ergothioneine as a novel therapeutic candidate through NRF2 activation

The continual exposure of retinal tissues to oxidative stress leads to discernible anatomical and physiological alterations. Specifically, the onslaught of oxidative damage escalates the irreversible death of retinal pigmented epithelium (RPE) cells, pinpointed as the fundamental pathological event in dry age-related macular degeneration (AMD). There is a conspicuous lack of effective therapeutic strategies to counteract this degenerative process. This study screened a library of antioxidants for their ability to protect RPE cells against oxidative stress and identified L-ergothioneine (EGT) as a potent cytoprotective agent. L-ergothioneine provided efficient protection against oxidative stress-damaged RPE and maintained cell redox homeostasis and normal physiological functions. It maintained the normal structure of the retina in mice under oxidative stress conditions. Transcriptomic analysis revealed that EGT counteracted major gene expression changes induced by oxidative stress. It upregulated antioxidant gene expression and inhibited NRF2 translocation. The inhibition of NRF2 abolished EGT's protective effects, suggesting that NRF2 activation contributes to its mechanism of action. In conclusion, we identified EGT as a safe and effective small-molecule compound that is expected to be a novel antioxidative agent for treating AMD.

Phenotypic high-throughput screening identifies aryl hydrocarbon receptor agonism as common inhibitor of toxin-induced retinal pigment epithelium cell death

The retinal pigment epithelium (RPE) is essential to maintain retinal function, and RPE cell death represents a key pathogenic stage in the progression of several blinding ocular diseases, including age-related macular degeneration (AMD). To identify pathways and compounds able to prevent RPE cell death, we developed a phenotypic screening pipeline utilizing a compound library and high-throughput screening compatible assays on the human RPE cell line, ARPE-19, in response to different disease relevant cytotoxic stimuli. We show that the metabolic by-product of the visual cycle all-trans-retinal (atRAL) induces RPE apoptosis, while the lipid peroxidation by-product 4-hydroxynonenal (4-HNE) promotes necrotic cell death. Using these distinct stimuli for screening, we identified agonists of the aryl hydrocarbon receptor (AhR) as a consensus target able to prevent both atRAL mediated apoptosis and 4-HNE-induced necrotic cell death. This works serves as a framework for future studies dedicated to screening for inhibitors of cell death, as well as support for the discussion of AhR agonism in RPE pathology.

PEDF protects retinal pigment epithelium from ferroptosis and ameliorates dry AMD-like pathology in a murine model

Age-related macular degeneration (AMD) is the leading cause of irreversible vision damage among elderly individuals. There is still no efficient treatment for dry AMD. Retinal pigment epithelial (RPE) degeneration has been confirmed to play an important role in dry AMD. Recent studies have reported that ferroptosis caused by iron overload and lipid peroxidation may be the primary causes of RPE degeneration. However, the upstream regulatory molecules of RPE ferroptosis remain largely unknown. Pigment epithelium-derived factor (PEDF) is an important endogenic protective factor for the RPE. Our results showed that in the murine dry AMD model induced by sodium iodate (SI), PEDF expression was downregulated. Moreover, dry AMD-like pathology was observed in PEDF-knockout mice. Therefore, the aim of this study was to reveal the effects and mechanism of PEDF on RPE ferroptosis and investigate potential therapeutic targets for dry AMD. The results of lipid peroxidation and transmission electron microscope showed that retinal ferroptosis was significantly activated in SI-treated mice and PEDF-knockout mice. Restoration of PEDF expression ameliorated SI-induced retinal dysfunction in mice, as assessed by electroretinography and optical coherence tomography. Mechanistically, western blotting and immunofluorescence analysis demonstrated that the overexpression of PEDF could upregulate the expression of glutathione peroxidase 4 (GPX4) and ferritin heavy chain-1 (FTH1), which proved to inhibit lipid peroxidation and RPE ferroptosis induced by SI. This study revealed the novel role of PEDF in ferroptosis inhibition and indicated that PEDF might be a potential therapeutic target for dry AMD.

Eyedrop delivery of therapeutic proteins with zwitterionic polymers to treat dry age-related macular degeneration

In clinics, therapeutic proteins are commonly used to treat retinal diseases through intraocular injection, the treatment which suffers from rather low patient compliance. Topical administration (e.g. eye-drops) of large molecule drugs remains a major challenge due to the presence of various barriers in the eye. In this study, zwitterion-grafted chitosan (CS-ZW) was developed and then self-assembled with protein therapeutics including adalimumab (ADA) or catalase (CAT) for the treatment of dry age-related macular degeneration (dAMD) via topical eyedrops. Since CS-ZW can cross the mucus layer and open the tight junctions between epithelial cells, their delivered therapeutic proteins can be shuttled across the ocular barriers to reach the diseased site in the fundus. CS-ZW/ADA eyedrops delivering ADA to bind TNF-α in the fundus achieved a similar therapeutic effect to intravitreal ADA injection in a mouse dAMD model. In addition, the therapeutic effect was further improved by combining eyedrop formulations of CS-ZW/ADA and CS-ZW/CAT, the latter of which can clear reactive oxygen species (ROS) in the lesion to further assist dAMD treatment. Our work provides a simple and effective delivery vehicle that can non-invasively treat fundus diseases such as dAMD, showing potential advantages in reducing side effects associated with intraocular injection and improving patient compliance.

Cellular zinc metabolism and zinc signaling: from biological functions to diseases and therapeutic targets

Zinc metabolism at the cellular level is critical for many biological processes in the body. A key observation is the disruption of cellular homeostasis, often coinciding with disease progression. As an essential factor in maintaining cellular equilibrium, cellular zinc has been increasingly spotlighted in the context of disease development. Extensive research suggests zinc's involvement in promoting malignancy and invasion in cancer cells, despite its low tissue concentration. This has led to a growing body of literature investigating zinc's cellular metabolism, particularly the functions of zinc transporters and storage mechanisms during cancer progression. Zinc transportation is under the control of two major transporter families: SLC30 (ZnT) for the excretion of zinc and SLC39 (ZIP) for the zinc intake. Additionally, the storage of this essential element is predominantly mediated by metallothioneins (MTs). This review consolidates knowledge on the critical functions of cellular zinc signaling and underscores potential molecular pathways linking zinc metabolism to disease progression, with a special focus on cancer. We also compile a summary of clinical trials involving zinc ions. Given the main localization of zinc transporters at the cell membrane, the potential for targeted therapies, including small molecules and monoclonal antibodies, offers promising avenues for future exploration.

A systematic study on the treatment of hepatitis B-related hepatocellular carcinoma with drugs based on bioinformatics and key target reverse network pharmacology and experimental verification

BACKGROUND

Chronic hepatitis B virus (HBV) infection is the major etiology of hepatocellular carcinoma (HCC). However, the mechanism of hepatitis B-related hepatocellular carcinoma (HBV-related HCC) is still unclear. Therefore, understanding the pathogenesis and searching for drugs to treat HBV-related HCC was an effective strategy to treat this disease.

PURPOSE

Bioinformatics was used to predict the potential targets of HBV-related HCC. The reverse network pharmacology of key targets was used to analyze the clinical drugs, traditional Chinese medicine (TCM) and small molecules of TCM in the treatment of HBV-related HCC.

METHODS

In this study, three microarray datasets totally containing 330 tumoral samples and 297 normal samples were selected from the GEO database. These microarray datasets were used to screen DEGs. And the expression profile and survival of 6 key genes were analyzed. In addition, Comparative Toxicogenomics Database and Coremine Medical database were used to enrich clinical drugs and TCM of HBV-related HCC by the 6 key targets. Then the obtained TCM were classified based on the Chinese Pharmacopoeia. Among these top 6 key genes, CDK1 and CCNB1 had the most connection nodes and the highest degree and were the most significantly expressed. In general, CDK1 and CCNB1 tend to form a complex, which is conducive to cell mitosis. Hence, this study mainly studied CDK1 and CCNB1. HERB database was used to predict small molecules TCM. The inhibition effect of quercetin, celastrol and cantharidin on HepG2.2.15 cells and Hep3B cells was verified by CCK8 experiment. The effects of quercetin, celastrol and cantharidin on CDK1 and CCNB1 of HepG2.2.15 cells and Hep3B cells were determined by Western Blot.

RESULTS

In short, 272 DEGs (53 upregulated and 219 downregulated) were identified. Among these DEGs, 6 key genes with high degree were identified, which were AURKA, BIRC5, CCNB1, CDK1, CDKN3 and TYMS. Kaplan-Meier plotter analysis showed that higher expression levels of AURKA, BIRC5, CCNB1, CDK1, CDKN3 and TYMS were associated with poor OS. According to the first 6 key targets, a variety of drugs and TCM were identified. These results showed that clinical drugs included targeted drugs, such as sorafenib, palbociclib and Dasatinib. and chemotherapy drugs, such as cisplatin and doxorubicin. TCM, such as the TCM flavor was mainly warm and bitter, and the main meridians were liver and lung. Small molecules of TCM included flavonoids, terpenoids, alkaloids and glycosides, such as quercetin, celastrol, cantharidin, hesperidin, silymarin, casticin, berberine and ursolic acid, which have great potential in anti-HBV-related HCC. For molecular docking of chemical components, the molecules with higher scores were flavonoids, alkaloids, etc. Three representative types of TCM small molecules were verified respectively, and it was found that quercetin, celastrol and cantharidin inhibited the proliferation of HepG2.2.15 cells and Hep3B cells along concentration gradient. Quercetin, celastrol and cantharidin decreased CDK1 expression in HepG2.2.15 and Hep3B cells, but for CCNB1, only cantharidin decreased CCNB1 expression in the two strains of cells.

CONCLUSION

In conclusion, AURKA, BIRC5, CCNB1, CDK1, CDKN3 and TYMS could be potential targets for the diagnosis and prognosis of HBV-related HCC. Clinical drugs include chemotherapeutic and targeted drug, traditional Chinese medicine is mainly bitter and warm TCM. Small molecular of TCM including flavonoids, terpenoids and glycosides and alkaloids, which have great potential in anti-HBV-related HCC. This study provides potential therapeutic targets and novel strategies for the treatment of HBV-related HCC.

Metallothioneins, a Part of the Retinal Endogenous Protective System in Various Ocular Diseases

Metallothioneins are the metal-rich proteins that play important roles in metal homeostasis and detoxification. Moreover, these proteins protect cells against oxidative stress, inhibit proapoptotic mechanisms and enhance cell differentiation and survival. Furthermore, MTs, mainly MT-1/2 and MT-3, play a vital role in protecting the neuronal retinal cells in the eye. Expression disorders of these proteins may be responsible for the development of various age-related eye diseases, including glaucoma, age-related macular degeneration, diabetic retinopathy and retinitis pigmentosa. In this review, we focused on the literature reports suggesting that these proteins may be a key component of the endogenous protection system of the retinal neurons, and, when the expression of MTs is disrupted, this system becomes inefficient. Moreover, we described the location of different MT isoforms in ocular tissues. Then we discussed the changes in MT subtypes' expression in the context of the common eye diseases. Finally, we highlighted the possibility of the use of MTs as biomarkers for cancer diagnosis.

MD2 Inhibits Choroidal Neovascularization via Antagonizing TLR4/MD2 Mediated Signaling Pathway

PURPOSE

To explore the pathological mechanism of Toll-like receptor 4 (TLR4) mediating neovascular age-related macular degeneration (nAMD) and the potential role of the TLR4 coreceptor myeloid differentiation protein 2 (MD2).

METHODS

In the study, we inhibited MD2 with the chalcone derivative L2H17 and we utilized a laser-induced choroidal neovascularization (CNV) mouse model and Tert-butyl hydroperoxide (TBHP)-challenged rhesus choroid-retinal endothelial (RF/6A) cells to assess the effect of MD2 blockade on CNV.

RESULTS

Inhibiting MD2 with L2H17 reduced angiogenesis in CNV mice, and significantly protected against retinal dysfunction. In retina and choroid/retinal pigment epithelium (RPE) tissues, L2H17 reduced phospho-ERK, phospho-P65 but not phospho-P38, phospho-JNK, and reduced the transcriptional levels of IL-6, TNF-α, ICAM-1 but not VCAM-1. L2H17 could protect RF/6A against TBHP-induced inflammation, oxidative stress, and apoptosis, via inhibiting the TLR4/MD2 signaling pathway and the following downstream mitogen-activated protein kinase (MAPK) and nuclear transcription factor-κB (NF-κB) activation.

CONCLUSIONS

Inhibiting MD2 with L2H17 significantly reduced CNV, suppressed inflammation, and oxidative stress by antagonizing TLR4/MD2 pathway in an MD2-dependent manner. MD2 may be a potential therapeutic target and L2H17 may offer an alternative treatment strategy for nAMD.

Inhibition of cGAS-STING by JQ1 alleviates oxidative stress-induced retina inflammation and degeneration

Atrophic (“dry”) form of age-related macular degeneration (AMD) is a leading cause of vision loss characterized by macular retinal pigment epithelium (RPE) and the ensuing photoreceptor degeneration. cGAS-STING signaling is a key cytosolic DNA sensor system in innate immunity and have recently been shown promotes RPE degeneration. However, expression regulation and therapeutic potential of cGAS and STING are not explored in retina under dry AMD pathogenic conditions. Our analysis shows upregulated STING RNA and increased chromatin accessibility around cGAS and STING promoters in macular retinas from dry AMD patients. cGAS-STING activation was detected in oxidative stress-induced mouse retina degeneration, accompanied with cytosolic leakage of damaged DNA in photoreceptors. Pharmaceutical or genetic approaches indicates STING promotes retina inflammation and degeneration upon oxidative damage. Drug screening reveals that BRD4 inhibitor JQ1 reduces cGAS-STING activation, inflammation and photoreceptor degeneration in the injured retina. BRD4 inhibition epigenetically suppresses STING transcription, and promotes autophagy-dependent cytosolic DNA clearance. Together, our results show that activation of cGAS-STING in retina may present pivotal innate immunity response in GA pathogenesis, whereas inhibition of cGAS-STING signaling by JQ1 could serve as a potential therapeutic strategy.

Schematic summary of the mechanism underlying BRD4 inhibition on cGAS-STING signaling during retina degeneration. Cytosolic DNA accumulation and activation of cGAS-STING pathway were detected in retina photoreceptors after oxidative injury. BRD4 inhibition alleviates retinal inflammation and degeneration by epigenetically silencing STING transcription and by promoting autophagy-dependent cytosolic DNA clearance.

Reprogramming of fibroblasts into expandable cardiovascular progenitor cells via small molecules in xeno-free conditions

A major hurdle in cardiac cell therapy is the lack of a bona fide autologous stem-cell type that can be expanded long-term and has authentic cardiovascular differentiation potential. Here we report that a proliferative cell population with robust cardiovascular differentiation potential can be generated from mouse or human fibroblasts via a combination of six small molecules. These chemically induced cardiovascular progenitor cells (ciCPCs) self-renew long-term in fully chemically defined and xeno-free conditions, with faithful preservation of the CPC phenotype and of cardiovascular differentiation capacity in vitro and in vivo. Transplantation of ciCPCs into infarcted mouse hearts improved animal survival and cardiac function up to 13 weeks post-infarction. Mechanistically, activated fibroblasts revert to a plastic state permissive to cardiogenic signals, enabling their reprogramming into ciCPCs. Expanded autologous cardiovascular cells may find uses in drug discovery, disease modelling and cardiac cell therapy.

Tricyclodecan-9-yl-Xanthogenate (D609): Mechanism of Action and Pharmacological Applications

Tricyclodecan-9-yl xanthogenate (D609) is a synthetic tricyclic compound possessing a xanthate group. This xanthogenate compound is known for its diverse pharmacological properties. Over the last three decades, many studies have reported the biological activities of D609, including antioxidant, antiapoptotic, anticholinergic, anti-tumor, anti-inflammatory, anti-viral, anti-proliferative, and neuroprotective activities. Its mechanism of action is extensively attributed to its ability to cause the competitive inhibition of phosphatidylcholine (PC)-specific phospholipase C (PC-PLC) and sphingomyelin synthase (SMS). The inhibition of PCPLC or SMS affects secondary messengers with a lipidic nature, i.e., 1,2-diacylglycerol (DAG) and ceramide. Various in vitro/in vivo studies suggest that PCPLC and SMS inhibition regulate the cell cycle, block cellular proliferation, and induce differentiation. D609 acts as a pro-inflammatory cytokine antagonist and diminishes Aβ-stimulated toxicity. PCPLC enzymatic activity essentially requires Zn2+, and D609 might act as a potential chelator of Zn2+, thereby blocking PCPLC enzymatic activity. D609 also demonstrates promising results in reducing atherosclerotic plaque formation, post-stroke cerebral infarction, and cancer progression. The present compilation provides a comprehensive mechanistic insight into D609, including its chemistry, mechanism of action, and regulation of various pharmacological activities.

TLR4-Dependent DUOX2 Activation Triggered Oxidative Stress and Promoted HMGB1 Release in Dry Eye

Dry eye disease (DED) is one of the most common ocular surface diseases worldwide. DED has been characterized by excessive accumulation of reactive oxygen species (ROS), following significant corneal epithelial cell death and ocular surface inflammation. However, the key regulatory factor remains unclear. In this study, we tended to explore whether DUOX2 contributed to DED development and the underlying mechanism. Human corneal epithelial (HCE) cells were treated with hyperosmolarity, C57BL/6 mice were injected of subcutaneous scopolamine to imitate DED. Expression of mRNA was investigated by RNA sequencing (RNA-seq) and quantitative real-time PCR (qPCR). Protein changes and distribution of DUOX2, high mobility group box 1 (HMGB1), Toll-like receptor 4 (TLR4), and 4-hydroxynonenal (4-HNE) were evaluated by western blot assays and immunofluorescence. Cell death was assessed by Cell Counting Kit-8 (CCK8), lactate dehydrogenase (LDH) release, and propidium iodide (PI) staining. Cellular ROS levels and mitochondrial membrane potential (MMP) were analyzed by flow cytometry. RNA-seq and western blot assay indicated a significant increase of DUOX2 dependent of TLR4 activation in DED both in vitro and in vivo. Immunofluorescence revealed significant translocation of HMGB1 within corneal epithelial cells under hyperosmolar stress. Interestingly, after ablated DUOX2 expression by siRNA, we found a remarkable decrease of ROS level and recovered MMP in HCE cells. Moreover, knockdown of DUOX2 greatly inhibited HMGB1 release, protected cell viability and abolished inflammatory activation. Taken together, our data here suggest that upregulation of DUOX2 plays a crucial role in ROS production, thereafter, induce HMGB1 release and cell death, which triggers ocular surface inflammation in DED.

D609 inhibition of phosphatidylcholine-specific phospholipase C attenuates prolonged insulin stimulation-mediated GLUT4 downregulation in 3T3-L1 adipocytes

Glucose uptake is stimulated by insulin via stimulation of glucose transporter 4 (GLUT4) translocation to the plasma membrane from intracellular compartments in adipose tissue and muscles. Insulin stimulation for prolonged periods depletes GLUT4 protein, particularly in highly insulin-responsive GLUT4 storage vesicles. This depletion mainly occurs via H₂O₂-mediated retromer inhibition. However, the post-receptor mechanism of insulin activation of oxidative stress remains unknown. Here, we show that phosphatidylcholine-specific phospholipase C (PC-PLC) plays an important role in insulin-mediated downregulation of GLUT4. In the study, 3T3-L1 adipocytes were exposed to a PC-PLC inhibitor, tricyclodecan-9-yl-xanthogenate (D609), for 30 min prior to the stimulation with 500 nM insulin for 4 h, weakening the depletion of GLUT4. D609 also prevents insulin-driven H₂O₂ generation in 3T3-L1 adipocytes. Exogenous PC-PLC and its product, phosphocholine (PCho), also caused GLUT4 depletion and promoted H₂O₂ generation in 3T3-L1 adipocytes. Furthermore, insulin-mediated the increase in the cellular membrane PC-PLC activity was observed in Amplex Red assays. These results suggested that PC-PLC plays an important role in insulin-mediated downregulation of GLUT4 and that PCho may serve as a signaling molecule.

Umbilical cord blood plasma-derived exosomes as a novel therapy to reverse liver fibrosis

Background

Cirrhosis is a chronic liver disease whereby scar tissue replaces healthy liver parenchyma, leading to disruption of the liver architecture and hepatic dysfunction. Currently, there is no effective disease-modifying therapy for liver fibrosis. Recently, our group demonstrated that human umbilical cord blood (UCB) plasma possesses therapeutic effects in a rat model of acute liver failure.

Methods

In the current study, we tested whether exosomes (Exo) existed in UCB plasma and if they produced any antifibrotic benefits in a liver fibrosis model.

Results

Our results showed that UCB-Exo improved liver function and increased matrix metalloproteinase/tissue inhibitor of metalloproteinase degradation to reduce the degree of fibrosis. Moreover, UCB-Exo were found to suppress hepatic stellate cell (HSC) activity in vitro. These effects were associated with suppression of transforming growth factor-β/inhibitor of DNA binding 1 signaling.

Conclusions

These results further support that UCB-Exo have antifibrotic effects in mice with liver fibrosis and activated HSCs and may herald a new cell-free antifibrotic therapy.

New insights into oxidative stress and immune mechanisms involved in age-related macular degeneration tackled by novel therapies

The prevalence of age-related macular degeneration (AMD) has increased in the last years. Although anti-VEGF agents have improved the prognosis of exudative AMD, dry AMD has still devastating effects on elderly people vision. Oxidative stress and inflammation are mechanisms involved in AMD pathogenesis and its progression. Molecular pathways involving epidermal growth factor receptor (EGFR), bone morphogenetic protein (BMP4) and the nuclear erythroid related factor 2 (Nrf2) are behind oxidative stress in AMD due to their participation in antioxidant cellular pathways. As a consequence of the disbalance produced in the antioxidant mechanisms, there is an activation of innate and adaptative immune response with cell recruitment, changes in complement factors expression, and modification of cellular milieu. Different therapies are being studied to treat dry AMD based on the possible effects on antioxidant molecular pathways or their action on the immune response. There is a wide range of treatments presented in this review, from natural antioxidant compounds to cell and gene therapy, based on their mechanisms. Finally, we hypothesize that alpha-1-antitrypsin (AAT), an anti-inflammatory and immunomodulatory molecule that can also modulate antioxidant cellular defenses, could be a good candidate for testing in AMD. This article is part of the special ssue on 'The Quest for Disease-Modifying Therapies for Neurodegenerative Disorders'.

Melatonin ameliorates oxidative stress-mediated injuries through induction of HO-1 and restores autophagic flux in dry eye

This study aimed to investigate the protective effect of melatonin on the corneal epithelium in dry eye disease(DED) and explore its underlying mechanism. Human corneal epithelial(HCE) cells was exposure to t-butylhydroperoxide(tBH), C57BL/6 mice were injected of subcutaneous scopolamine to imitate DED. Melatonin was used both in vivo and in vitro. Cell viability was detected by Cell Counting Kit-8 assay and Lactate Dehydrogenase Leakage. The change of cellular reactive oxygen species (ROS) levels, mitochondrial membrane potential (MMP), and apoptosis was analyzed by flow cytometry. Western blot assays and immunofluorescence were carried out to measure protein changes. mRNA expression was investigated by RNA sequencing (RNA-Seq) and quantitative real-time PCR. The change of autophagic flux were observed through mCherry-GFP-LC3 transfection and electron microscopy(TEM). Clinical parameters of corneal epithelium defects, conjunctival goblet cells, tear volume, and level of ocular surface inflammation was recorded. Melatonin was able to reduce excessive ROS production and maintain mitochondrial function. TEM assay found melatonin rescued impaired autophagic flux under tBH. Moreover, melatonin significantly preserved cell viability, abolished LDH release, and decreased apoptosis. RNA-Seq indicated that melatonin greatly activating hemeoxygenase-1 (HO-1) expression. Interestingly, HO-1 ablation largely attenuated its protective effects. Besides, in dry eye mouse model, intraperitoneal injection of melatonin showed greatly improved clinical parameters, inhibited activated NLRP3 inflammation cascade, and increased density of goblet cells and tear volume. Thus, melatonin protects corneal epithelial cells from oxidative damage, maintain normal level of autophagy, and reduce inflammation via trigging HO-1 expression in DED.

Antioxidant Defenses in the Human Eye: A Focus on Metallothioneins

The human eye, the highly specialized organ of vision, is greatly influenced by oxidants of endogenous and exogenous origin. Oxidative stress affects all structures of the human eye with special emphasis on the ocular surface, the lens, the retina and its retinal pigment epithelium, which are considered natural barriers of antioxidant protection, contributing to the onset and/or progression of eye diseases. These ocular structures contain a complex antioxidant defense system slightly different along the eye depending on cell tissue. In addition to widely studied enzymatic antioxidants, including superoxide dismutase, glutathione peroxidase, catalase, peroxiredoxins and selenoproteins, inter alia, metallothioneins (MTs) are considered antioxidant proteins of growing interest with further cell-mediated functions. This family of cysteine rich and low molecular mass proteins captures and neutralizes free radicals in a redox-dependent mechanism involving zinc binding and release. The state of the art of MTs, including the isoforms classification, the main functions described to date, the Zn-MT redox cycle as antioxidant defense system, and the antioxidant activity of Zn-MTs in the ocular surface, lens, retina and its retinal pigment epithelium, dependent on the number of occupied zinc-binding sites, will be comprehensively reviewed.