Effects of Resvega on Inflammasome Activation in Conjunction with Dysfunctional Intracellular Clearance in Retinal Pigment Epithelial (RPE) Cells

Inhibition of oxidative stress-induced epithelial-mesenchymal transition in retinal pigment epithelial cells of age-related macular degeneration model by suppressing ERK activation

INTRODUCTION

Epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells is related to the pathogenesis of various retinopathies including age-related macular degeneration (AMD). Oxidative stress is the major factor that induces degeneration of RPE cells associated with the etiology of AMD.

OBJECTIVES

Sodium iodate (NaIO3) generates intracellular reactive oxygen species (ROS) and is widely used to establish a model of AMD due to the selective induction of retinal degeneration. This study was performed to clarify the effects of multiple NaIO3-stimulated signaling pathways on EMT in RPE cells.

METHODS

The EMT characteristics in NaIO3-treated human ARPE-19 cells and RPE cells of the mouse eyes were analyzed. Multiple oxidative stress-induced modulators were investigated and the effects of pre-treatment with Ca2+ chelator, extracellular signal-related kinase (ERK) inhibitor, or epidermal growth factor receptor (EGFR) inhibitor on NaIO3-induced EMT were determined. The efficacy of post-treatment with ERK inhibitor on the regulation of NaIO3-induced signaling pathways was dissected and its role in retinal thickness and morphology was evaluated by using histological cross-sections and spectral domain optical coherence tomography.

RESULTS

We found that NaIO3 induced EMT in ARPE-19 cells and in RPE cells of the mouse eyes. The intracellular ROS, Ca2+, endoplasmic reticulum (ER) stress marker, phospho-ERK, and phospho-EGFR were increased in NaIO3-stimulated cells. Our results showed that pre-treatment with Ca2+ chelator, ERK inhibitor, or EGFR inhibitor decreased NaIO3-induced EMT, interestingly, the inhibition of ERK displayed the most prominent effect. Furthermore, post-treatment with FR180204, a specific ERK inhibitor, reduced intracellular ROS and Ca2+ levels, downregulated phospho-EGFR and ER stress marker, attenuated EMT of RPE cells, and prevented structural disorder of the retina induced by NaIO3.

CONCLUSIONS

ERK is a crucial regulator of multiple NaIO3-induced signaling pathways that coordinate EMT program in RPE cells. Inhibition of ERK may be a potential therapeutic strategy for the treatment of AMD.

Non-Neovascular Age-Related Macular Degeneration Assessment: Focus on Optical Coherence Tomography Biomarkers

The imagistic evaluation of non-neovascular age-related macular degeneration (AMD) is crucial for diagnosis, monitoring progression, and guiding management of the disease. Dry AMD, characterized primarily by the presence of drusen and retinal pigment epithelium atrophy, requires detailed visualization of the retinal structure to assess its severity and progression. Several imaging modalities are pivotal in the evaluation of non-neovascular AMD, including optical coherence tomography, fundus autofluorescence, or color fundus photography. In the context of emerging therapies for geographic atrophy, like pegcetacoplan, it is critical to establish the baseline status of the disease, monitor the development and expansion of geographic atrophy, and to evaluate the retina's response to potential treatments in clinical trials. The present review, while initially providing a comprehensive description of the pathophysiology involved in AMD, aims to offer an overview of the imaging modalities employed in the evaluation of non-neovascular AMD. Special emphasis is placed on the assessment of progression biomarkers as discerned through optical coherence tomography. As the landscape of AMD treatment continues to evolve, advanced imaging techniques will remain at the forefront, enabling clinicians to offer the most effective and tailored treatments to their patients.

Resveratrol Alleviates Retinal Ischemia-Reperfusion Injury by Inhibiting the NLRP3/Gasdermin D/Caspase-1/Interleukin-1β Pyroptosis Pathway

Purpose

The purpose of this study is to investigate the anti-pyroptotic effect of resveratrol in the context of ischemia-reperfusion (I/R)-induced retinal injury, with a particular focus on Müller glial cells (MGCs) and to elucidate the underlying molecular mechanisms.

Methods

The retinal I/R model was constructed in mice and pyroptotic markers were measured at six, 12, 24, 48, and 72 hours after I/R injury to determine the peak of pyroptotic activity. The effects of resveratrol on pyroptosis, inflammasomes, and the activation of MGCs after I/R injury were observed on the retina of mice. Moreover, induction of pyroptosis in rat Müller glial cells (r-MC) via lipopolysaccharide was used to explore the effects of resveratrol on pyroptosis of r-MC in vitro.

Results

After the induction of retinal I/R injury in mice, the intricate involvement of pyroptosis in the progressive degeneration of the retina was observed, reaching its zenith at the onset of 24 hours after I/R injury. Resveratrol treatment alleviated I/R injury on the retina, relieved retinal ganglion cells death. In addition, resveratrol inhibited Caspase-1 activation, gasdermin D (GSDMD-N) cleavage, the inflammasome assembly, and the release of inflammatory cytokines, simultaneously relieving the MGCs activation. Furthermore, resveratrol inhibited the pyroptosis-related NLRP3/GSDMD-N/TMS1/ASC/Caspase-1/IL-1β pathway in r-MC cells, and mitigated cells death in vitro.

Conclusions

Pyroptosis plays an important role in the pathogenesis of retinal I/R injury. Resveratrol can attenuate pyroptotic-driven damage in the retina and MGC by inhibiting the NLRP3/GSDMD-N/TMS1/ASC/Caspase-1/IL-1β pyroptosis pathway.

Plumbagin rescues the granulosa cell's pyroptosis by reducing WTAP-mediated N6-methylation in polycystic ovary syndrome

The survival of ovary granulosa cells (GC) is critical in the initiation and progression of polycystic ovary syndrome (PCOS) in females. Here, we found that the PCOS process is accompanied by massive GC pyroptosis resulting from Caspase-1 inflammasome activation. Administration of plumbagin, an effective compound isolated from plant medicine, can prevent the pyroptosis of GC and the onset of PCOS. Mechanistic study indicates the over-activation of the inflammasome in GC is due to the upregulation of WTAP, a key regulator of the RNA N6-methylase complex. WTAP mediates the mRNA N6-methylation of NLRP3 inflammasome component ASC and enhances ASC RNA stability, which results in the overactivation of the inflammasome in GCs from the PCOS model. Plumbagin treatment suppresses the WTAP-mediated N6-methylation of ASC mRNA and reduces the pyroptosis of GCs. This study supports the profound potential of plumbagin in PCOS treatment.

Resvega, a Nutraceutical Preparation, Affects NFκB Pathway and Prolongs the Anti-VEGF Effect of Bevacizumab in Undifferentiated ARPE-19 Retina Cells

Age-related macular degeneration (AMD) is an irreversible chronic degenerative pathology that affects the retina. Despite therapeutic advances thanks to the use of anti-vascular endothelial growth factor (VEGF) agents, resistance mechanisms have been found to accentuate the visual deficit. In the present study, we explored whether a nutraceutical formulation composed of omega-3 fatty acids and resveratrol, called Resvega®, was able to disrupt VEGF-A secretion in human ARPE-19 retina cells. We found that Resvega® inhibits VEGF-A secretion through decreases in both the PI3K-AKT-mTOR and NFκB signaling pathways. In NFκB signaling pathways, Resvega® inhibits the phosphorylation of the inhibitor of NFκB, IκB, which can bind NFκB dimers and sequester them in the cytoplasm. Thus, the NFκB subunits cannot migrate to the nucleus where they normally bind and stimulate the transcription of target genes such as VEGF-A. The IκB kinase complex (IKK) is also affected by Resvega® since the nutraceutical formulation decreases both IKKα and IKKβ subunits and the IKKγ subunit which is required for the stimulation of IKK. Very interestingly, we highlight that Resvega® could prolong the anti-angiogenic effect of Avastin®, which is an anti-VEGF agent typically used in clinical practice. Our results suggest that Resvega® may have potential interest as nutritional supplementation against AMD.

Hydroquinone predisposes for retinal pigment epithelial (RPE) cell degeneration in inflammatory conditions

In addition to hypoxia, inflammation is capable of inducing vascular endothelial growth factor (VEGF) expression in human retinal pigment epithelial (RPE) cells. Excessive levels of VEGF promote choroidal neovascularization and thereby contribute to the pathogenesis of wet age-related macular degeneration (AMD). Intravitreal anti-VEGF injections ameliorate pathological vessel neoformation in wet AMD but excessive dampening of VEGF can result in a degeneration of the RPE. In the present study, we induced VEGF production by exposing human ARPE-19 cells to the pro-inflammatory IL-1α and subsequently to hydroquinone, a component of tobacco smoke that is a major environmental risk factor for AMD. Effects were monitored by measuring the levels of VEGF and anti-angiogenic pigment epithelium-derived factor (PEDF) using an enzyme-linked immunosorbent assay (ELISA) technique. In addition, we measured the production of reactive oxygen species (ROS) using the 2′,7′-dichlorofluorescin diacetate (H2DCFDA) probe and studied the effects of two anti-oxidants, ammonium pyrrolidinedithiocarbamate (APDC) and N-acetyl-cysteine (NAC), on VEGF production. Cellular and secreted VEGF as well as secreted PEDF levels were reduced at all tested hydroquinone concentrations (10, 50, or 200 µM); these effects were evident prior to any reduction of cell viability evoked by hydroquinone. Cell viability was carefully explored in our previous study and verified by microscoping in the present study. APDC further reduced the VEGF levels, whereas NAC increased them. The 50 μM concentration of hydroquinone increased ROS production in ARPE-19 cells primed with IL-1α. Hydroquinone disturbs the regulatory balance of VEGF and PEDF in inflammatory conditions. These data support the idea that hydroquinone mediates RPE degeneration by reducing VEGF levels and may predispose to dry AMD since VEGF is as well important for retinal integrity.

Effective inhibition of adipogenesis-mediated inflammation by a macular carotenoid, lutein in vitro

An absolute interlinks between inflammation and obesity with scarce investigations on the role of lutein in inflammation-induced obesity motivated us to explore the protective mechanism of lutein on adipogenesis-mediated inflammation in vitro by culturing RAW264.7 macrophages in adipocyte conditioned medium. The RAW264 macrophage cells were cultured with adipocyte-conditioned media, and the potency of lutein on the expression of adipocyte inflammation-associated protein markers (IL-1β, MCP-1, TNF-α, IL-6, NF-κB, and IKKα/β) were analyzed by western blotting. The data revealed that lutein effectively reduces the protein levels of major inflammatory markers such as NF-κB, IL-1β, MCP-1, and TNF-α in differentiated adipocytes. Interestingly, lutein hampered inflammation in the RAW264 cells that were cultured in adipocyte-conditioned media by lowering the protein expression of IL-1β, MCP-1, and TNF-α. The blockage of inflammation by lutein in both differentiated adipocytes, and adipogenesis-induced macrophages is associated with suppression of IKK α/β phosphorylation. These data suggest that lutein potentially alters adipocyte differentiation-mediated inflammation by regulating the NF-κB signaling pathway. Thus, lutein could be utilized as a potent nutraceutical agent in the management of obesity and associated inflammation. PRACTICAL APPLICATIONS: Lutein isolated from a dietary source exhibited an inhibitory effect in adipogenesis-induced inflammations. The findings of this study authenticate the diversified prospective of lutein in regulating obesity and other inflammation-related diseases. Thus, it is understood that continuous intake of lutein-rich food or dietary intervention of lutein may reduce the risk of developing obesity.

Therapeutic potential of PGC-1α in age-related macular degeneration (AMD) - the involvement of mitochondrial quality control, autophagy, and antioxidant response

INTRODUCTION

Age-related macular degeneration (AMD) is the leading, cause of sight loss in the elderly in the Western world. Most patients remain still without any treatment options. The targeting of Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), a transcription co-factor, is a putative therapy against AMD.

AREAS COVERED

The characteristics of AMD and their possible connection with PGC-1α as well as the transcriptional and post-transcriptional control of PGC-1α are discussed. The PGC-1α-driven control of mitochondrial functions, and its involvement in autophagy and antioxidant responses are also examined. Therapeutic possibilities via drugs and epigenetic approaches to enhance PGC-1α expression are discussed. Authors conducted a search of literature mainly from the recent decade from the PubMed database.

EXPERT OPINION

Therapy options in AMD could include PGC-1α activation or stabilization. This could be achieved by a direct elevation of PGC-1α activity, a stabilization or modification of its upstream activators and inhibitors by chemical compounds, like 5-Aminoimidazole-4-carboxamide riboside, metformin, and resveratrol. Furthermore, manipulations with epigenetic modifiers of PGC-1α expression, including miRNAs, e.g. miR-204, are considered. A therapy aimed at PGC-1α up-regulation may be possible in other disorders besides AMD, if they are associated with disturbances in the mitochondria-antioxidant response-autophagy axis.

RESVEGA, a Nutraceutical Omega-3/Resveratrol Supplementation, Reduces Angiogenesis in a Preclinical Mouse Model of Choroidal Neovascularization

Age-related macular degeneration (AMD) is an eye disease that is characterized by damage to the central part of the retina, the macula, and that affects millions of people worldwide. At an advanced stage, a blind spot grows in the center of vision, severely handicapping patients with this degenerative condition. Despite therapeutic advances thanks to the use of anti-VEGF, many resistance mechanisms have been found to accentuate the visual deficit. In the present study, we explored whether supplementation with Resvega^®, a nutraceutical formulation composed of omega-3 fatty acids and resveratrol, a well-known polyphenol in grapes, was able to counteract laser-induced choroidal neovascularization (CNV) in mice. We highlight that Resvega^® significantly reduced CNV in mice compared with supplementations containing omega-3 or resveratrol alone. Moreover, a proteomic approach confirmed that Resvega^® could counteract the progression of AMD through a pleiotropic effect targeting key regulators of neoangiogenesis in retina cells in vivo. These events were associated with an accumulation of resveratrol metabolites within the retina. Therefore, a supplementation of omega-3/resveratrol could improve the management or slow the progression of AMD in patients with this condition.

VEGF-R2/Caveolin-1 Pathway of Undifferentiated ARPE-19 Retina Cells: A Potential Target as Anti-VEGF-A Therapy in Wet AMD by Resvega, an Omega-3/Polyphenol Combination

Age-related macular degeneration (AMD) is one of the main causes of deterioration in vision in adults aged 55 and older. In spite of therapies, the progression of the disease is often observed without reverse vision quality. In the present study, we explored whether, in undifferentiated ARPE-19 retinal cells, a disruption of the VEGF receptors (VEGF-R)/caveolin-1 (Cav-1)/protein kinases pathway could be a target for counteracting VEGF secretion. We highlight that Resvega^®, a combination of omega-3 fatty acids with an antioxidant, resveratrol, inhibits VEGF-A secretion in vitro by disrupting the dissociation of the VEGF-R2/Cav-1 complex into rafts and subsequently preventing MAPK activation. Moreover, DNA ChIP analysis reveals that this combination prevents the interaction between AP-1 and vegf-a and vegf-r2 gene promoters. By these pathways, Resvega could present a potential interest as nutritional complementation against AMD.

Hydroquinone Induces NLRP3-Independent IL-18 Release from ARPE-19 Cells

Age-related macular degeneration (AMD) is a retinal disease leading to impaired vision. Cigarette smoke increases the risk for developing AMD by causing increased reactive oxygen species (ROS) production and damage in the retinal pigment epithelium (RPE). We have previously shown that the cigarette tar component hydroquinone causes oxidative stress in human RPE cells. In the present study, we investigated the propensity of hydroquinone to induce the secretion of interleukin (IL)-1β and IL-18. The activation of these cytokines is usually regulated by the Nucleotide-binding domain, Leucine-rich repeat, and Pyrin domain 3 (NLRP3) inflammasome. ARPE-19 cells were exposed to hydroquinone, and cell viability was monitored using the lactate dehydrogenase (LDH) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide salt (MTT) assays. Enzyme-linked immunosorbent assays (ELISAs) were used to measure the levels of proinflammatory cytokines IL-1β and IL-18 as well as NLRP3, caspase-1, and poly (ADP-ribose) polymerase (PARP). Hydroquinone did not change IL-1β release but significantly increased the secretion of IL-18. Cytoplasmic NLRP3 levels increased after the hydroquinone treatment of IL-1α-primed RPE cells, but IL-18 was equally released from primed and nonprimed cells. Hydroquinone reduced the intracellular levels of PARP, which were restored by treatment with the ROS scavenger N-acetyl-cysteine (NAC). NAC concurrently reduced the NLRP3 levels but had no effect on IL-18 release. In contrast, the NADPH oxidase inhibitor ammonium pyrrolidinedithiocarbamate (APDC) reduced the release of IL-18 but had no effect on the NLRP3 levels. Collectively, hydroquinone caused DNA damage seen as reduced intracellular PARP levels and induced NLRP3-independent IL-18 secretion in human RPE cells.