A novel miR-338-3p/SLC1A5 axis reprograms retinal pigment epithelium to increases its resistance to high glucose-induced cell ferroptosis

U2AF65 mediated circPVT1 promotes NSCLC cell proliferation and inhibits ferroptosis through the miR-338-3p/GPX4 axis

BACKGROUND

Dysregulation of circRNA expression is associated with increased metastasis and an adverse prognosis in non-small cell lung cancer (NSCLC). Herein, this study assessed the role and regulatory mechanism of circPVT1 in NSCLC development.

METHODS

CircPVT1 expression was determined using qPCR. Functional assays, including cell proliferation, colony formation, and ferroptosis-related measurements (ROS, MDA, SOD, GSH and Fe2+ levels), were conducted following circPVT1 knockdown. The interactions between RNA and protein were determined through RIP, dual-luciferase reporter and fluorescence in situ hybridization. Actinomycin D assay was employed to test circPVT1 stability. Additionally, tumor progression in vivo was evaluated in xenograft models with U2AF65 knockdown.

RESULTS

CircPVT1 was significantly elevated in NSCLC samples, correlating with worse clinical outcomes. Its knockdown resulted in diminished cell proliferation and increased ferroptosis. Mechanically, circPVT1 sponges miR-338-3p, facilitating GPX4 expression, which enhanced cell proliferation. U2AF65 bound to and stabilized circPVT1, promoting cell proliferation. In animal models, U2AF65 knockdown suppressed tumor progression by regulating the circPVT1/miR-338-3p/GPX4 signaling pathway.

CONCLUSIONS

U2AF65 stabilizes circPVT1 to promote NSCLC advancement through miR-338-3p suppression and GPX4 upregulation. Thus, circPVT1 and U2AF65 may be potential therapeutic targets in NSCLC.

Circular RNA NXN (circNXN) promotes diabetic retinopathy by regulating the miR-338-3p/FGFR1 axis

Diabetic retinopathy (DR) is the leading manifestation of diabetic microangiopathy. However, effective biomarkers and therapies are lacking. Circular RNAs (circRNAs) have been implicated in various diseases including DR. However, the role of circRNAs in DR remains elusive. In the present study, circNXN was upregulated in high glucose (HG)-treated human retinal microvascular endothelial cells (hRMECs). circNXN knockdown inhibited the proliferation, migration, and angiogenesis of hRMECs and promoted apoptosis. In addition, circNXN acted as a sponge for miR-338-3p to facilitate the FGFR1 (fibroblast growth factor receptor 1) expression. Furthermore, rescue assays revealed that the reduced promoting effect on hRMECs induced by the knockdown of circNXN could be reversed by a miR-338-3p inhibitor in HG-treated hRMECs. Additionally, in a DR rat model, circNXN downregulation ameliorated retinal vasculature changes. Our findings reveal a new therapeutic strategy for DR that may provide a new approach to clinical DR therapy.

miRNAs, piRNAs, and lncRNAs: A triad of non-coding RNAs regulating the neurovascular unit in diabetic retinopathy and their therapeutic potentials

Diabetic Retinopathy (DR), a leading complication of diabetes mellitus, has long been considered as a microvascular disease of the retina. However, recent evidence suggests that DR is a neurovascular disease, characterized by the degeneration of retinal neural tissue and microvascular abnormalities encompassing ischemia, neovascularization, and blood-retinal barrier breakdown, ultimately leading to blindness. The intricate relationship between the retina and vascular cells constitutes a neurovascular unit, a multi-cellular framework of retinal neurons, glial cells, immune cells, and vascular cells, which facilitates neurovascular coupling, linking neuronal activity to blood flow. These interconnections between the neurovascular components get compromised due to hyperglycemia and are further associated with the progression of DR early on in the disease. As a result, therapeutic approaches are needed to avert the advancement of DR by acting at its initial stage to delay or prevent the pathogenesis. Non-coding RNAs (ncRNAs) such as microRNAs, piwi-interacting RNAs, and long non-coding RNAs regulate various cellular components in the neurovascular unit. These ncRNAs are key regulators of neurodegeneration, apoptosis, inflammation, and oxidative stress in DR. In this review, research related to alterations in the expression of ncRNAs and, correspondingly, their effect on the disintegration of the neurovascular coupling will be discussed briefly to understand the potential of ncRNAs as therapeutic targets for treating this debilitating disease.

Advanced glycation end products and reactive oxygen species: uncovering the potential role of ferroptosis in diabetic complications

Advanced glycation end products (AGEs) are a diverse range of compounds that are formed when free amino groups of proteins, lipids, and nucleic acids are carbonylated by reactive carbonyl species or glycosylated by reducing sugars. Hyperglycemia in patients with diabetes can cause an overabundance of AGEs. Excess AGEs are generally acknowledged as major contributing factors to the development of diabetic complications because of their ability to break down the extracellular matrix directly and initiate intracellular signaling pathways by binding to the receptor for advanced glycation end products (RAGE). Inflammation and oxidative stress are the two most well-defined pathophysiological states induced by the AGE-RAGE interaction. In addition to oxidative stress, AGEs can also inhibit antioxidative systems and disturb iron homeostasis, all of which may induce ferroptosis. Ferroptosis is a newly identified contributor to diabetic complications. This review outlines the formation of AGEs in individuals with diabetes, explores the oxidative damage resulting from downstream reactions of the AGE-RAGE axis, and proposes a novel connection between AGEs and the ferroptosis pathway. This study introduces the concept of a vicious cycle involving AGEs, oxidative stress, and ferroptosis in the development of diabetic complications.

Role of MicroRNA in linking diabetic retinal neurodegeneration and vascular degeneration

Diabetic retinopathy is the major cause of blindness in diabetic patients, with limited treatment options that do not always restore optimal vision. Retinal nerve degeneration and vascular degeneration are two primary pathological processes of diabetic retinopathy. The retinal nervous system and vascular cells have a close coupling relationship. The connection between neurodegeneration and vascular degeneration is not yet fully understood. Recent studies have found that microRNA plays a role in regulating diabetic retinal neurovascular degeneration and can help delay the progression of the disease. This article will review how microRNA acts as a bridge connecting diabetic retinal neurodegeneration and vascular degeneration, focusing on the mechanisms of apoptosis, oxidative stress, inflammation, and endothelial factors. The aim is to identify valuable targets for new research and clinical treatment of diabetic retinopathy.

Ferroptosis: a novel mechanism of cell death in ophthalmic conditions

Ferroptosis, a new type of programmed cell death proposed in recent years, is characterized mainly by reactive oxygen species and iron-mediated lipid peroxidation and differs from programmed cell death, such as apoptosis, necrosis, and autophagy. Ferroptosis is associated with a variety of physiological and pathophysiological processes. Recent studies have shown that ferroptosis can aggravate or reduce the occurrence and development of diseases by targeting metabolic pathways and signaling pathways in tumors, ischemic organ damage, and other degenerative diseases related to lipid peroxidation. Increasing evidence suggests that ferroptosis is closely linked to the onset and progression of various ophthalmic conditions, including corneal injury, glaucoma, age-related macular degeneration, diabetic retinopathy, retinal detachment, and retinoblastoma. Our review of the current research on ferroptosis in ophthalmic diseases reveals significant advancements in our understanding of the pathogenesis, aetiology, and treatment of these conditions.

Non-Apoptotic Programmed Cell Death as Targets for Diabetic Retinal Neurodegeneration

Diabetic retinopathy (DR) remains the leading cause of blindness among the global working-age population. Emerging evidence underscores the significance of diabetic retinal neurodegeneration (DRN) as a pivotal biomarker in the progression of vasculopathy. Inflammation, oxidative stress, neural cell death, and the reduction in neurotrophic factors are the key determinants in the pathophysiology of DRN. Non-apoptotic programmed cell death (PCD) plays a crucial role in regulating stress response, inflammation, and disease management. Therapeutic modalities targeting PCD have shown promising potential for mitigating DRN. In this review, we highlight recent advances in identifying the role of various PCD types in DRN, with specific emphasis on necroptosis, pyroptosis, ferroptosis, parthanatos, and the more recently characterized PANoptosis. In addition, the therapeutic agents aimed at the regulation of PCD for addressing DRN are discussed.

USP48 deubiquitination stabilizes SLC1A5 to inhibit retinal pigment epithelium cell inflammation, oxidative stress and ferroptosis in the progression of diabetic retinopathy

BACKGROUND

Diabetic retinopathy is one of the complications of diabetes mellitus. The aim of this study was to explore the effects of ubiquitin-specific protease 48 (USP48) and its underlying mechanisms in the development of diabetic retinopathy.

METHODS

CCK-8 assay, EdU assay, and flow cytometry were used to measure the proliferative ability and the apoptotic rate of ARPE-19 cells, respectively. ELISA kits were utilized to assess the levels of inflammatory cytokines. The levels of Fe2+, ROS and MDA were detected using the corresponding biochemical kits. The protein expression of USP48 and SLC1A5 was examined through western blot. The mRNA level of SLC1A5 was determined using RT-qPCR. The interaction relationship between USP48 and SLC1A5 was evaluated using Co-IP assay.

RESULTS

High glucose (HG) treatment significantly inhibited cell proliferation and elevated cell apoptosis, inflammation, ferroptosis and oxidative stress in ARPE-19 cells. HG treatment-caused cell damage was hindered by USP48 or SLC1A5 overexpression in ARPE-19 cells. Fer-1 treatment improved HG-caused cell damage in ARPE-19 cells, which was blocked by USP48 knockdown. Moreover, USP48 knockdown decreased SLC1A5 expression. SLC1A5 downregulation reversed the improvement effects of USP48 upregulation on cell damage in HG-treated ARPE-19 cells.

CONCLUSION

USP48 overexpression deubiquitinated SLC1A5 to elevate cell proliferation and suppress cell apoptosis, inflammation, ferroptosis and oxidative stress in HG-triggered ARPE-19 cells, thereby inhibiting the progression of diabetic retinopathy.

Identification of biomarkers associated with ferroptosis in diabetic retinopathy based on WGCNA and machine learning

Objective: Diabetic retinopathy (DR) is a chronic progressive eye disease that affects millions of diabetic patients worldwide, and ferroptosis may contribute to the underlying mechanisms of DR. The main objective of this work is to explore key genes associated with ferroptosis in DR and to determine their feasibility as diagnostic markers. Methods: WGCNA identify the most relevant signature modules in DR. Machine learning methods were used to de-screen the feature genes. ssGSEA calculated the scoring of immune cells in the DR versus control samples and compared the associations with the core genes by Spearman correlation. Results: We identified 2,897 differential genes in DR versus normal samples. WGCNA found tan module to have the highest correlation with DR patients. Finally, 20 intersecting genes were obtained from differential genes, tan module and iron death genes, which were screened by LASSO and SVM-RFE method, and together identified 6 genes as potential diagnostic markers. qPCR verified the expression and ROC curves confirmed the diagnostic accuracy of the 6 genes. In addition, our ssGSEA scoring identified these 6 core genes as closely associated with immune infiltrating cells. Conclusion: In conclusion, we analyzed for the first time the potential link of iron death in the pathogenesis of DR. This has important implications for future studies of iron death-mediated pro-inflammatory immune mechanisms.

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.

Relationship between Biochemical Pathways and Non-Coding RNAs Involved in the Progression of Diabetic Retinopathy

Diabetic retinopathy (DR) is a progressive blinding disease, which affects the vision and quality of life of patients, and it severely impacts the society. This complication, caused by abnormal glucose metabolism, leads to structural, functional, molecular, and biochemical abnormalities in the retina. Oxidative stress and inflammation also play pivotal roles in the pathogenic process of DR, leading to mitochondrial damage and a decrease in mitochondrial function. DR causes retinal degeneration in glial and neural cells, while the disappearance of pericytes in retinal blood vessels leads to alterations in vascular regulation and stability. Clinical changes include dilatation and blood flow changes in response to the decrease in retinal perfusion in retinal blood vessels, leading to vascular leakage, neovascularization, and neurodegeneration. The loss of vascular cells in the retina results in capillary occlusion and ischemia. Thus, DR is a highly complex disease with various biological factors, which contribute to its pathogenesis. The interplay between biochemical pathways and non-coding RNAs (ncRNAs) is essential for understanding the development and progression of DR. Abnormal expression of ncRNAs has been confirmed to promote the development of DR, suggesting that ncRNAs such as miRNAs, lncRNAs, and circRNAs have potential as diagnostic biomarkers and theranostic targets in DR. This review provides an overview of the interactions between abnormal biochemical pathways and dysregulated expression of ncRNAs under the influence of hyperglycemic environment in DR.

Ferroptosis in the ageing retina: A malevolent fire of diabetic retinopathy

Ageing retina is prone to ferroptosis due to the iron accumulation and impaired efficiency of intracellular antioxidant defense system. Ferroptosis acts as a cell death modality that is characterized by the iron-dependent accumulation of lipid peroxidation. Ferroptosis is distinctively different from other types of regulated cell death (RCD) at the morphological, biochemical, and genetic levels. Diabetic retinopathy (DR) is a common microvascular complication of diabetes. Its prevalence and severity increase progressively with age. Recent reports have shown that ferroptosis is implicated in the pathophysiology of DR. Under hyperglycemia condition, the endothelial cell and retinal pigment epithelium (RPE) cell will undergo ferroptosis, which contributes to the increased vascular permeability and the disrupted blood retinal barrier (BRB). The underlying etiology of DR can be attributed to the impaired BRB integrity and subsequent damages of the neurovascular units. In the absence of timely intervention, the compromised BRB can ultimately cause profound visual impairments. In particular, the ageing retina is vulnerable to ferroptosis, and hyperglycemia will accelerate the progression of this pathological process. In this article, we discuss the contributory role of ferroptosis in DR pathogenesis, and summarize recent therapeutic trials that targeting the ferroptosis. Further study on the ferroptosis mediated damage would enrich our knowledge of DR pathology, and promote the development of clinical treatment for this degenerative retinopathy.

Exosomes derived from BMSCs alleviates high glucose-induced diabetic retinopathy via carrying miR-483-5p

Diabetic retinopathy (DR) is a progressive disease which can cause health problem. It has been reported that bone marrow mesenchymal stem cells (BMSCs)-secreted exosomes could regulate the progression of DR via carrying microRNAs. Meanwhile, miR-483-5p was downregulated in DR; however, whether BMSCs-secreted exosomes can modulate DR progression via carrying miR-483-5p remains unclear. To mimic DR in vitro, ARPE-19 cells were exposed to 30 mM high glucose (HG). Exosomes were isolated from BMSCs and identified by transmission electron microscopy, nanoparticle tracking analysis, and western blot. Cell counting kit-8 assay was applied for assessing the cell viability. Flow cytometry was applied to test the cell apoptosis. Meanwhile, dual luciferase assay was used to evaluate the association among miR-483-5p and downstream target insulin-like growth factor 1 receptor (IGF-1R). In addition, quantitative reverse-transcription polymerase chain reaction and western blot were used for exploring the level of miR-483-5p and IGF-1R. HG significantly induced apoptosis in ARPE-19 cells, while BMSCs-derived exosomes reversed this phenomenon. In addition, inhibition of miR-483-5p expression of exosomes further aggravated HG-induced ARPE-19 cell apoptosis. Meanwhile, IGF-1R was the downstream messenger RNA of miR-483-5p, and IGF-1R silencing could reverse the effect of exosomes with downregulated miR-483-5p on HG-induced cell injury. Exosomes derived from BMSCs inhibit the progression of DR via carrying miR-483-5p. Thus, our study might provide a theoretical basis for discovering new strategies against DR.

Targeting ferroptosis: New perspectives of Chinese herbal medicine in the treatment of diabetes and its complications

Ferroptosis is a non-apoptotic mode of cell death. A large number of studies have confirmed that ferroptosis plays a vital role in the occurrence and development of diabetes and diabetic complications. Previous studies have found that Chinese herbal medicines have very promising results in the prevention and treatment of diabetes and diabetic complications, and some of these herbs or herbal natural compounds may act via the inhibition of ferroptosis. In this review, we summarized the relationship between ferroptosis and diabetes and diabetic complications, and discussed its molecular mechanisms. We also reviewed the published studies of herbal medicines or herbal natural compounds that improved diabetes or diabetic complications via the ferroptosis pathway. In addition, we are trying to provide new insights for better treatment of diabetes and diabetic complications with Chinese herbal medicine and its herbal compounds.

Epigenetic modulation of ferroptosis in cancer: Identifying epigenetic targets for novel anticancer therapy

Ferroptosis is a newly recognized form of oxidative-regulated cell death resulting from iron-mediated lipid peroxidation accumulation. Radical-trapping antioxidant systems can eliminate these oxidized lipids and prevent disrupting the integrity of cell membranes. Epigenetic modifications can regulate ferroptosis by altering gene expression or cell phenotype without permanent sequence changes. These mechanisms include DNA methylation, histone modifications, RNA modifications, and noncoding RNAs. Epigenetic alterations in cancer can control the expression of ferroptosis regulators or related pathways, leading to changes in cell sensitivity to ferroptosis inducers or cancer progression. Epigenetic alterations in cancer are influenced by a wide range of cancer hallmarks, contributing to therapeutic resistance. Targeting epigenetic alterations is a promising approach to overcoming cancer resilience. However, the exact mechanisms involved in different types of cancer remain unresolved. Discovering more ferroptosis-associated epigenetic targets and interventions can help overcome current barriers in anticancer therapy. Many papers on epigenetic modifications of ferroptosis have been continuously published, making it essential to summarize the current state-of-the-art in the epigenetic regulation of ferroptosis in human cancer.

Spotlight on iron and ferroptosis: research progress in diabetic retinopathy

Iron, as the most abundant metallic element within the human organism, is an indispensable ion for sustaining life and assumes a pivotal role in governing glucose and lipid metabolism, along with orchestrating inflammatory responses. The presence of diabetes mellitus (DM) can induce aberrant iron accumulation within the corporeal system. Consequentially, iron overload precipitates a sequence of important adversities, subsequently setting in motion a domino effect wherein ferroptosis emerges as the utmost pernicious outcome. Ferroptosis, an emerging variant of non-apoptotic regulated cell death, operates independently of caspases and GSDMD. It distinguishes itself from alternative forms of controlled cell death through distinctive morphological and biochemical attributes. Its principal hallmark resides in the pathological accrual of intracellular iron and the concomitant generation of iron-driven lipid peroxides. Diabetic retinopathy (DR), established as the predominant cause of adult blindness, wields profound influence over the well-being and psychosocial strain experienced by afflicted individuals. Presently, an abundance of research endeavors has ascertained the pervasive engagement of iron and ferroptosis in the microangiopathy inherent to DR. Evidently, judicious management of iron overload and ferroptosis in the early stages of DR bears the potential to considerably decelerate disease progression. Within this discourse, we undertake a comprehensive exploration of the regulatory mechanisms governing iron homeostasis and ferroptosis. Furthermore, we expound upon the subsequent detriments induced by their dysregulation. Concurrently, we elucidate the intricate interplay linking iron overload, ferroptosis, and DR. Delving deeper, we engage in a comprehensive deliberation regarding strategies to modulate their influence, thereby effecting prospective interventions in the trajectory of DR's advancement or employing them as therapeutic modalities.

The Regulation of Ferroptosis by Noncoding RNAs

As a novel form of regulated cell death, ferroptosis is characterized by intracellular iron and lipid peroxide accumulation, which is different from other regulated cell death forms morphologically, biochemically, and immunologically. Ferroptosis is regulated by iron metabolism, lipid metabolism, and antioxidant defense systems as well as various transcription factors and related signal pathways. Emerging evidence has highlighted that ferroptosis is associated with many physiological and pathological processes, including cancer, neurodegeneration diseases, cardiovascular diseases, and ischemia/reperfusion injury. Noncoding RNAs are a group of functional RNA molecules that are not translated into proteins, which can regulate gene expression in various manners. An increasing number of studies have shown that noncoding RNAs, especially miRNAs, lncRNAs, and circRNAs, can interfere with the progression of ferroptosis by modulating ferroptosis-related genes or proteins directly or indirectly. In this review, we summarize the basic mechanisms and regulations of ferroptosis and focus on the recent studies on the mechanism for different types of ncRNAs to regulate ferroptosis in different physiological and pathological conditions, which will deepen our understanding of ferroptosis regulation by noncoding RNAs and provide new insights into employing noncoding RNAs in ferroptosis-associated therapeutic strategies.

Oxidative Stress and Its Regulation in Diabetic Retinopathy

Diabetic retinopathy is the retinal disease associated with hyperglycemia in patients who suffer from type 1 or type 2 diabetes. It includes maculopathy, involving the central retina and characterized by ischemia and/or edema, and peripheral retinopathy that progresses to a proliferative stage with neovascularization. Approximately 10% of the global population is estimated to suffer from diabetes, and around one in 5 of these individuals have diabetic retinopathy. One of the major effects of hyperglycemia is oxidative stress, the pathological state in which elevated production of reactive oxygen species damages tissues, cells, and macromolecules. The retina is relatively prone to oxidative stress due to its high metabolic activity. This review provides a summary of the role of oxidative stress in diabetic retinopathy, including a description of the retinal cell players and the molecular mechanisms. It discusses pathological processes, including the formation and effects of advanced glycation end-products, the impact of metabolic memory, and involvements of non-coding RNA. The opportunities for the therapeutic blockade of oxidative stress in diabetic retinopathy are also considered.

Ferroptosis: new insight into the mechanisms of diabetic nephropathy and retinopathy

Diabetic nephropathy (DN) and diabetic retinopathy (DR) are the most serious and common diabetes-associated complications. DN and DR are all highly prevalent and dangerous global diseases, but the underlying mechanism remains to be elucidated. Ferroptosis, a relatively recently described type of cell death, has been confirmed to be involved in the occurrence and development of various diabetic complications. The disturbance of cellular iron metabolism directly triggers ferroptosis, and abnormal iron metabolism is closely related to diabetes. However, the molecular mechanism underlying the role of ferroptosis in DN and DR is still unclear, and needs further study. In this review article, we summarize and evaluate the mechanism of ferroptosis and its role and progress in DN and DR, it provides new ideas for the diagnosis and treatment of DN and DR.

Research progress on the mechanism of ferroptosis and its role in diabetic retinopathy

Ferroptosis is iron-dependent regulatory cell death (RCD). Morphologically, ferroptosis is manifested as mitochondrial atrophy and increased mitochondrial membrane density. Biochemically, ferroptosis is characterized by the depletion of glutathione (GSH), the inactivation of glutathione peroxidase 4 (GPX4), and an increase in lipid peroxides (LPO)and divalent iron ions. Ferroptosis is associated with various diseases, but the relationship with diabetic retinopathy(DR) is less studied. DR is one of the complications of diabetes mellitus and has a severe impact on visual function. The pathology of DR is complex, and the current treatment is unsatisfactory. Therefore, exploring pathogenesis is helpful for the clinical treatment of DR. This paper reviews the pathological mechanism of ferroptosis and DR in recent years and the involvement of ferroptosis in the pathology of DR. In addition, we propose problems that need to be addressed in this research field. It is expected to provide new ideas for treating DR by analyzing the role of ferroptosis in DR.

Autophagy Activation Promoted by Pulses of Light and Phytochemicals Counteracting Oxidative Stress during Age-Related Macular Degeneration

The seminal role of autophagy during age-related macular degeneration (AMD) lies in the clearance of a number of reactive oxidative species that generate dysfunctional mitochondria. In fact, reactive oxygen species (ROS) in the retina generate misfolded proteins, alter lipids and sugars composition, disrupt DNA integrity, damage cell organelles and produce retinal inclusions while causing AMD. This explains why autophagy in the retinal pigment epithelium (RPE), mostly at the macular level, is essential in AMD and even in baseline conditions to provide a powerful and fast replacement of oxidized molecules and ROS-damaged mitochondria. When autophagy is impaired within RPE, the deleterious effects of ROS, which are produced in excess also during baseline conditions, are no longer counteracted, and retinal degeneration may occur. Within RPE, autophagy can be induced by various stimuli, such as light and naturally occurring phytochemicals. Light and phytochemicals, in turn, may synergize to enhance autophagy. This may explain the beneficial effects of light pulses combined with phytochemicals both in improving retinal structure and visual acuity. The ability of light to activate some phytochemicals may further extend such a synergism during retinal degeneration. In this way, photosensitive natural compounds may produce light-dependent beneficial antioxidant effects in AMD.

Identification of key ferroptosis genes in diabetic retinopathy based on bioinformatics analysis

OBJECTIVES

Diabetic retinopathy (DR) is a retinal microvascular disease associated with diabetes. Ferroptosis is a new type of programmed cell death that may participate in the occurrence and development of DR. Therefore, this study aimed to identify the DR ferroptosis-related genes by bioinformatics methods.

METHODS

The RNAseq data of DR and healthy control retinas were downloaded from the gene expression synthesis (GEO) database and analyzed using the R package DESeq2. The key modules were obtained using the WGCNA algorithm, and their genes were intersected with ferroptosis-related genes in the FerrDb database to obtain differentially expressed ferroptosis-related genes (DE-FRGs). Enrichment analysis was conducted to understand the function and enrichment pathways of ferroptosis genes in DR, and hub genes were identified by protein-protein interaction (PPI) analysis. The diagnostic accuracy of hub genes for DR was evaluated according to the area under the ROC curve. The TRRUST database was then used to predict the regulatory relationship between transcription factors and target genes, with the mirDIP, ENCORI, RNAnter, RNA22, miRWalk and miRDB databases used to predict the regulatory relationship between miRNAs and target genes. Finally, another data set was used to verify the hub genes.

RESULTS

In total, 52 ferroptosis-related DEGs (43 up-regulated and 9 down-regulated) were identified using 15 DR samples and 3 control samples and were shown to be significantly enriched in the intrinsic apoptotic signaling pathway, autophagosome, iron ion binding and p53 signaling pathway. Seven hub genes of DR ferroptosis were identified through PPI network analysis, but only HMOX1 and PTGS2 were differentially expressed in another data set. The miRNAs prediction showed that hsa-miR-873-5p was the key miRNA regulating HMOX1, while hsa-miR-624-5p and hsa-miR-542-3p were the key miRNAs regulating PTGS2. Furthermore, HMOX1 and PTGS2 were regulated by 13 and 20 transcription factors, respectively.

CONCLUSION

The hub genes HMOX1 and PTGS2, and their associated transcription factors and miRNAs, may be involved in ferroptosis in diabetic retinopathy. Therefore, the specific mechanism is worthy of further investigation.

Longitudinal Association of DNA Methylation With Type 2 Diabetes and Glycemic Traits: A 5-Year Cross-Lagged Twin Study

Investigators of previous cross-sectional epigenome-wide association studies (EWAS) in adults have reported hundreds of 5'-cytosine-phosphate-guanine-3' (CpG) sites associated with type 2 diabetes mellitus (T2DM) and glycemic traits. However, the results from EWAS have been inconsistent, and longitudinal observations of these associations are scarce. Furthermore, few studies have investigated whether DNA methylation (DNAm) could be modified by smoking, drinking, and glycemic traits, which have broad impacts on genome-wide DNAm and result in altering the risk of T2DM. Twin studies provide a valuable tool for epigenetic studies, as twins are naturally matched for genetic information. In this study, we conducted a systematic literature search in PubMed and Embase for EWAS, and 214, 33, and 117 candidate CpG sites were selected for T2DM, HbA1c, and fasting blood glucose (FBG). Based on 1,070 twins from the Chinese National Twin Registry, 67, 17, and 16 CpG sites from previous studies were validated for T2DM, HbA1c, and FBG. Longitudinal review and blood sampling for phenotypic information and DNAm were conducted twice in 2013 and 2018 for 308 twins. A cross-lagged analysis was performed to examine the temporal relationship between DNAm and T2DM or glycemic traits in the longitudinal data. A total of 11 significant paths from T2DM to subsequent DNAm and 15 paths from DNAm to subsequent T2DM were detected, suggesting both directions of associations. For glycemic traits, we detected 17 cross-lagged associations from baseline glycemic traits to subsequent DNAm, and none were from the other cross-lagged direction, indicating that CpG sites may be the consequences, not the causes, of glycemic traits. Finally, a longitudinal mediation analysis was performed to explore the mediation effects of DNAm on the associations of smoking, drinking, and glycemic traits with T2DM. No significant mediations of DNAm in the associations linking smoking and drinking with T2DM were found. In contrast, our study suggested a potential role of DNAm of cg19693031, cg00574958, and cg04816311 in mediating the effect of altered glycemic traits on T2DM.

Targeting Novel Regulated Cell Death: Pyroptosis, Necroptosis, and Ferroptosis in Diabetic Retinopathy

Diabetic retinopathy (DR) is one of the primary causes of visual impairment in the working-age population. Retinal cell death is recognized as a prominent feature in the pathological changes of DR. Several types of cell death occurrence have been confirmed in DR, which might be the underlying mechanisms of retinal cell loss. Regulated cell death (RCD) originates from too intense or prolonged perturbations of the intracellular or extracellular microenvironment for adaptative responses to cope with stress and restore cellular homeostasis. Pyroptosis, necroptosis, and ferroptosis represent the novel discovered RCD forms, which contribute to retinal cell death in the pathogenesis of DR. This evidence provides new therapeutic targets for DR. In this review, we summarize the mechanisms of three types of RCD and analyse recent advances on the association between novel RCD and DR, aiming to provide new insights into the underlying pathogenic mechanisms and propose a potential new strategy for DR therapy.