The Nrf2 activator MIND4-17 protects retinal ganglion cells from high glucose-induced oxidative injury

Expression and functional significance of phosphoenolpyruvate carboxykinase 1 in uveal melanoma

Uveal melanoma (UVM), an uncommon yet potentially life-threatening ocular cancer, arises from melanocytes in the uveal tract of the eye. The exploration of novel oncotargets for UVM is of paramount importance. In this study, we show that PCK1 (phosphoenolpyruvate carboxykinase 1) expression is upregulated in various UVM tissues as well as in primary UVM cells and immortalized lines. Furthermore, bioinformatics studies reveal that PCK1 overexpression in UVM correlates with advanced disease stages and poor patient survival. Genetic silencing (utilizing viral shRNA) or knockout (via CRISPR/Cas9) of PCK1 significantly curtailed cell viability, proliferation, cell cycle progression, and motility, while provoking apoptosis in primary and immortalized UVM cells. Conversely, ectopic overexpression of PCK1, achieved through a viral construct, bolstered UVM cell proliferation and migration. Gαi3 expression and Akt phosphorylation were reduced following PCK1 silencing or knockout, but increased after PCK1 overexpression in UVM cells. Restoring Akt phosphorylation through a constitutively active mutant Akt1 (S473D) ameliorated the growth inhibition, migration suppression, and apoptosis induced by PCK1 silencing in UVM cells. Additionally, ectopic expression of Gαi3 restored Akt activation and counteracted the anti-UVM cell effects by PCK1 silencing. In vivo, the growth of subcutaneous xenografts of primary human UVM cells was significantly inhibited following intratumoral injection of adeno-associated virus (aav) expressing PCK1 shRNA. PCK1 depletion, Gαi3 downregulation, Akt inhibition, proliferation arrest, and apoptosis were detected in PCK1-silenced UVM xenografts. Collectively, our findings demonstrate that PCK1 promotes UVM cell growth possibly by modulating the Gαi3-Akt signaling pathway.

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.

Ferroptosis: mechanisms and advances in ocular diseases

As an essential trace element in the body, iron is critical for the maintenance of organismal metabolism. Excessive iron facilitates reactive oxygen species generation and inflicts damage on cells and tissues. Ferroptosis, a newly identified iron-dependent type of programmed cell death, has been implicated in a broad set of metabolic disorders. Ferroptosis is mainly characterized by excess iron accumulation, elevated lipid peroxides and reactive oxygen species, and reduced levels of glutathione and glutathione peroxidase 4. The vast emerging literature on ferroptosis has shown that numerous diseases, such as cancers, neurodegeneration, and autoimmune diseases, are associated with ferroptosis. Meanwhile, recent studies have confirmed the relationship between ferroptosis and eye diseases including keratopathy, cataract, glaucoma, retinal ischemia-reperfusion injury, age-related macular degeneration, retinitis pigmentosa, diabetic retinopathy, and retinoblastoma, indicating the critical role of ferroptosis in ocular diseases. In this article, we introduce the primary signaling pathways of ferroptosis and review current advances in research on ocular diseases involving iron overload and ferroptosis. Furthermore, several unanswered questions in the area are raised. Addressing these unanswered questions promises to provide new insights into preventing, controlling, and treating not only ocular diseases but also a variety of other diseases in the near future.

HDAC3 Inhibition Alleviates High-Glucose-Induced Retinal Ganglion Cell Death through Inhibiting Inflammasome Activation

Purpose

The exact effects of histone deacetylase 3 (HDAC3) inhibition in DR related retinal ganglion cells (RGCs) death remained unclear. This study is aimed at detecting the influence of HDAC3 on the high-glucose-induced retinal ganglion cell death.

Methods

The retinal HDAC3 expression in DR of different time points was analyzed by immunohistochemical assay and western blot. Besides, the expression of HDAC3 and both retinal thickness and RGC loss were analyzed. The effects of HDAC3 inhibitor on cell viability, oxidative stress, and apoptosis in high-glucose- (HG-) treated RGCs were analyzed. Both inflammatory and antioxidative factors were detected by ELISA.

Results

Advanced effects of HDAC3 inhibition on the expression of NLRP3 inflammasome were detected using western blots. High HDAC3 expression was detected only in the late DR mice (4 months of diabetes duration) but not early DR mice (2 months of diabetes duration). The immunohistochemical assay showed that HDAC3 expression was correlated with both retinal thickness and RCG contents. HDAC3 inhibitor significantly protected the HG-treated RGCs from damaged cell viability, severe apoptosis, and oxidative stress. Advanced pathway analyses showed that HDAC3 inhibition inactivated NLRP3 inflammasome and thus alleviated retinal inflammation. Conclusion. In conclusion, HDAC3 was involved in RGC loss and thus promoted the progression of neurodegeneration of DR. Besides, HDAC3 inhibitor demonstrated protective effects in neurodegeneration in DR through downregulation of NLRP3 activity. The effects of HDAC3 inhibitor in DR management should be confirmed in clinical trials.

Retina regeneration: lessons from vertebrates

Unlike mammals, vertebrates such as fishes and frogs exhibit remarkable tissue regeneration including the central nervous system. Retina being part of the central nervous system has attracted the interest of several research groups to explore its regenerative ability in different vertebrate models including mice. Fishes and frogs completely restore the size, shape and tissue structure of an injured retina. Several studies have unraveled molecular mechanisms underlying retina regeneration. In teleosts, soon after injury, the Müller glial cells of the retina reprogram to form a proliferating population of Müller glia-derived progenitor cells capable of differentiating into various neural cell types and Müller glia. In amphibians, the transdifferentiation of retinal pigment epithelium and differentiation of ciliary marginal zone cells contribute to retina regeneration. In chicks and mice, supplementation with external growth factors or genetic modifications cause a partial regenerative response in the damaged retina. The initiation of retina regeneration is achieved through sequential orchestration of gene expression through controlled modulations in the genetic and epigenetic landscape of the progenitor cells. Several developmental biology pathways are turned on during the Müller glia reprogramming, retinal pigment epithelium transdifferentiation and ciliary marginal zone differentiation. Further, several tumorigenic pathways and gene expression events also contribute to the complete regeneration cascade of events. In this review, we address the various retinal injury paradigms and subsequent gene expression events governed in different vertebrate species. Further, we compared how vertebrates such as teleost fishes and amphibians can achieve excellent regenerative responses in the retina compared with their mammalian counterparts.

Contribution of Müller Cells in the Diabetic Retinopathy Development: Focus on Oxidative Stress and Inflammation

Diabetic retinopathy is a neurovascular complication of diabetes and the main cause of vision loss in adults. Glial cells have a key role in maintenance of central nervous system homeostasis. In the retina, the predominant element is the Müller cell, a specialized cell with radial morphology that spans all retinal layers and influences the function of the entire retinal circuitry. Müller cells provide metabolic support, regulation of extracellular composition, synaptic activity control, structural organization of the blood–retina barrier, antioxidant activity, and trophic support, among other roles. Therefore, impairments of Müller actions lead to retinal malfunctions. Accordingly, increasing evidence indicates that Müller cells are affected in diabetic retinopathy and may contribute to the severity of the disease. Here, we will survey recently described alterations in Müller cell functions and cellular events that contribute to diabetic retinopathy, especially related to oxidative stress and inflammation. This review sheds light on Müller cells as potential therapeutic targets of this disease.

Senescence marker protein 30 (SMP30) protects against high glucose-induced apoptosis, oxidative stress and inflammatory response in retinal ganglion cells by enhancing Nrf2 activation via regulation of Akt/GSK-3β pathway

Senescence marker protein 30 (SMP30) is an aging-related protein that participates in the regulation of tissue damage under various pathological conditions. However, the role of SMP30 in mediating high glucose (HG)-induced injury of retinal ganglion cells (RGCs) has not been fully determined. We found that SMP30 expression declined during HG stimulation in RGCs. Cellular functional studies showed that the up-regulation of SMP30 dramatically prohibited HG-evoked apoptosis, oxidative stress and inflammatory response in RGCs. Mechanism research reported that SMP30 overexpression led to the enhancement of nuclear factor erythroid 2-related factor (Nrf2) activation in HG-stimulated RGCs. Moreover, SMP30 overexpression enhanced the phosphorylation of Akt and glucogen synthase kinase-3β (GSK-3β), and the suppression of Akt markedly abolished SMP30-mediated Nrf2 activation in HG-stimulated RGCs. Additionally, the suppression of Nrf2 substantially reversed SMP30-overexpression-induced anti-HG injury effects in RGCs. Overall, these findings suggest that SMP30 protects against HG injury of RGCs by potentiating Nrf2 through regulation of the Akt/GSK-3β pathway. Our work underscores that SMP30/Akt/GSK-3β/Nrf2 may exert a vital role in mediating the injury of RGCs during diabetic retinopathy.

iKeap1 activates Nrf2 signaling to protect myocardial cells from oxygen glucose deprivation/re-oxygenation-induced oxidative injury

Nuclear factor E2-related factor 2 (Nrf2) activation could efficiently protect myocardial cells from oxygen glucose deprivation/re-oxygenation (OGDR). An ultra-large structure-based virtual screening has discovered iKeap1 as a novel, direct and potent Keap1 inhibitor. Here we found that iKeap1 efficiently activated Nrf2 signaling in H9c2 myocardial cells and primary murine myocardiocytes. iKeap1 induced Keap1-Nrf2 disassociation, cytosol Nrf2 protein stabilization and nuclear translocation. The antioxidant response element (ARE) activity and expression of Nrf2 cascade genes (HO1, NQO1 and GCLC) were increased in iKeap1-treated myocardial cells. In H9c2 cells and murine myocardiocytes, iKeap1 potently inhibited OGDR-induced oxidative injury by inhibiting reactive oxygen species (ROS) production, mitochondrial depolarization, lipid peroxidation and DNA damage. In addition, OGDR-induced myocardial cell death and apoptosis were largely ameliorated after pretreatment with the novel Keap1 inhibitor. Significantly, in H9c2 cells iKeap1-induced myocardial cytoprotection against OGDR was abolished with Nrf2 silencing or knockout (using CRISPR/Cas9 method). Moreover, CRISPR/Cas9-induced Keap1 knockout led to constitutive activation of Nrf2 cascade and inhibited OGDR-induced oxidative injury. Importantly, iKeap1 was unable to further protect Keap1-knockout H9c2 cells from OGDR. Together, iKeap1 activated Nrf2 signaling to protect myocardial cells from OGDR-induced oxidative injury and cell death.

Regulatory Role of Nrf2 Signaling Pathway in Wound Healing Process

Wound healing involves a series of cellular events in damaged cells and tissues initiated with hemostasis and finally culminating with the formation of a fibrin clot. However, delay in the normal wound healing process during pathological conditions due to reactive oxygen species, inflammation and immune suppression at the wound site represents a medical challenge. So far, many therapeutic strategies have been developed to improve cellular homeostasis and chronic wounds in order to accelerate wound repair. In this context, the role of Nuclear factor erythroid 2-related factor 2 (Nrf2) during the wound healing process has been a stimulating research topic for therapeutic perspectives. Nrf2 is the main regulator of intracellular redox homeostasis. It increases cytoprotective gene expression and the antioxidant capacity of mammalian cells. It has been reported that some bioactive compounds attenuate cellular stress and thus accelerate cell proliferation, neovascularization and repair of damaged tissues by promoting Nrf2 activation. This review highlights the importance of the Nrf2 signaling pathway in wound healing strategies and the role of bioactive compounds that support wound repair through the modulation of this crucial transcription factor.

Obacunone protects retinal pigment epithelium cells from ultra-violet radiation-induced oxidative injury

Ultra-violet (UV) radiation (UVR) causes significant oxidative injury to retinal pigment epithelium (RPE) cells. Obacunone is a highly oxygenated triterpenoid limonoid compound with various pharmacological properties. Its potential effect in RPE cells has not been studied thus far. Here in ARPE-19 cells and primary murine RPE cells, obacunone potently inhibited UVR-induced reactive oxygen species accumulation, mitochondrial depolarization, lipid peroxidation and single strand DNA accumulation. UVR-induced RPE cell death and apoptosis were largely alleviated by obacunone. Obacunone activated Nrf2 signaling cascade in RPE cells, causing Keap1-Nrf2 disassociation, Nrf2 protein stabilization and nuclear translocation. It promoted transcription and expression of antioxidant responsive element-dependent genes. Nrf2 silencing or CRISPR/Cas9-induced Nrf2 knockout almost reversed obacunone-induced RPE cytoprotection against UVR. Forced activation of Nrf2 cascade, by Keap1 knockout, similarly protected RPE cells from UVR. Importantly, obacunone failed to offer further RPE cytoprotection against UVR in Keap1-knockout cells. In vivo, intravitreal injection of obacunone largely inhibited light-induced retinal damage. Collectively, obacunone protects RPE cells from UVR-induced oxidative injury through activation of Nrf2 signaling cascade.

PGK1 inhibitor CBR-470-1 protects neuronal cells from MPP+

The neurotoxin MPP⁺ (1-methyl-4-phenylpyridinium ion) disrupts mitochondrial function leading to oxidative stress and neuronal death. Here we examine whether activation of the Keap1-Nrf2 cascade can protect SH-SY5Y neuroblastoma cells from MPP⁺-induced cytotoxicity. Treatment of SH-SY5Y cells with CBR-470-1, an inhibitor of the glycolytic enzyme phosphoglycerate kinase 1 (PGK1), leads to methylglyoxal modification of Keap1, Keap1-Nrf2 disassociation, and increased expression of Nrf2 responsive genes. Pretreatment with CBR-470-1 potently attenuated MPP⁺-induced oxidative injury and SH-SY5Y cell apoptosis. CBR-470-1 neuroprotection is dependent upon Nrf2, as Nrf2 shRNA or CRISPR/Cas9-mediated Nrf2 knockout, abolished CBR-470-1-induced SH-SY5Y cytoprotection against MPP⁺. Consistent with these findings, PGK1 depletion or knockout mimicked CBR-470-1-induced actions and rendered SH-SY5Y cells resistant to MPP⁺-induced cytotoxicity. Furthermore, activation of the Nrf2 cascade by CRISPR/Cas9-induced Keap1 knockout protected SH-SY5Y cells from MPP⁺. In Keap1 or PGK1 knockout SH-SY5Y cells,CBR-470-1 failed to offer further cytoprotection against MPP⁺. Collectively PGK1 inhibition by CBR-470-1 protects SH-SY5Y cells from MPP⁺ via activation of the Keap1-Nrf2 cascade.