Effects of amygdalin on ferroptosis and oxidative stress in diabetic retinopathy progression via the NRF2/ARE signaling pathway

Clinical observations and mechanistic insights of traditional Chinese medicine in the management of diabetic retinopathy

CONTEXT

Diabetic retinopathy (DR) is one of the leading causes of vision impairment and blindness among diabetic patients globally. Despite advancements in conventional treatments, the quest for more holistic approaches and fewer side effects persists. Traditional Chinese medicine (TCM) has been used for centuries in managing various diseases, including diabetes and its complications.

OBJECTIVE

This review evaluated the efficacy and underlying mechanisms of TCM in the management of DR, providing information on its potential integration with conventional treatment methods.

METHODS

A comprehensive literature review was conducted using PubMed, Web of Science, and the China National Knowledge Infrastructure (CNKI) with the search terms 'traditional Chinese medicine', 'diabetic retinopathy', 'clinical efficacies' and their combinations. Studies published before 2023 without language restriction were included, focusing on clinical trials and observational studies that assessed the effectiveness of TCM in DR treatment.

RESULTS

The review synthesized evidence of empirical traditional Chinese formulas, traditional Chinese patent medicines, and isolated phytochemicals on DR treatment. The key mechanisms identified included the reduction of oxidative stress, inflammation, and neovascularization, as well as the improvement in neurovascular functionality and integrity of the retinal blood barrier.

CONCLUSIONS

TCM shows promising potential to manage DR. More large-scale, randomized controlled trials are recommended to validate these findings and facilitate the integration of TCM into mainstream DR treatment protocols.

CircZNF609 inhibits miR-150-5p to promote high glucose-induced damage to retinal microvascular endothelial cells

Hyperglycemia is a key contributor to diabetic macrovascular and ocular complications. It triggers a cascade of cellular damage, particularly in the retinal microvascular endothelial cells (RMECs). However, the underlying molecular mechanisms remain only partially understood. This study hypothesizes that CircZNF609 plays a pivotal role in mediating high glucose-induced damage in RMECs by modulating miR-150-5p and its downstream target genes, thereby affecting cellular survival, apoptosis, and oxidative stress. Gene expression datasets (GSE193974 and GSE160308) and clinical samples were used to investigate the expression levels of CircZNF609 and its interaction with miR-150-5p in the context of diabetic retinopathy (DR). Our results demonstrate that CircZNF609 is upregulated in both peripheral blood stem cells from DR patients and high glucose-stimulated hRMECs. Functional experiments reveal that silencing CircZNF609 improves cell viability, reduces apoptosis, inhibits tube formation, and modulates oxidative stress markers, whereas CircZNF609 overexpression exacerbates these effects. Moreover, miR-150-5p, a microRNA, was found to be negatively regulated by CircZNF609 and downregulated in DR. Its overexpression mitigates high glucose-induced cell injury. Our findings suggest a novel mechanism whereby CircZNF609 exacerbates high glucose-induced endothelial cell damage by sponging miR-150-5p, implicating the CircZNF609/miR-150-5p axis as a potential therapeutic target in diabetic retinopathy.

MSC-derived small extracellular vesicles mitigate diabetic retinopathy by stabilizing Nrf2 through miR-143-3p-mediated inhibition of neddylation

Diabetic retinopathy (DR) is a highly hazardous and widespread complication of diabetes mellitus (DM). The accumulated reactive oxygen species (ROS) play a central role in DR development. The aim of this research was to examine the impact and mechanisms of mesenchymal stem cell (MSC)-derived small extracellular vesicles (sEV) on regulating ROS and retinal damage in DR. Intravitreal injection of sEV inhibited Cullin3 neddylation, stabilized Nrf2, decreased ROS, reduced retinal inflammation, suppressed Müller gliosis, and mitigated DR. Based on MSC-sEV miRNA sequencing, bioinformatics software, and dual-luciferase reporter assay, miR-143-3p was identified to be the key effector for MSC-sEV's role in regulating neural precursor cell expressed developmentally down-regulated 8 (NEDD8)-mediated neddylation. sEV were able to be internalized by Müller cells. Compared to advanced glycation end-products (AGEs)-induced Müller cells, sEV coculture decreased Cullin3 neddylation, activated Nrf2 signal pathway to combat ROS-induced inflammation. The barrier function of endothelial cells was impaired when endothelial cells were treated with the supernatant of AGEs-induced Müller cells, but was restored when treated with supernatant of AGEs-induced Müller cells cocultured with sEV. The protective effect of sEV was, however, compromised when miR-143-3p was inhibited in sEV. Moreover, the protective efficacy of sEV was diminished when NEDD8 was overexpressed in Müller cells. These findings showed MSC-sEV delivered miR-143-3p to inhibit Cullin3 neddylation, stabilizing Nrf2 to counteract ROS-induced inflammation and reducing vascular leakage. Our findings suggest that MSC-sEV may be a potential nanotherapeutic agent for DR, and that Cullin3 neddylation could be a new target for DR therapy.

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.

Upregulation of HMOX1 associated with M2 macrophage infiltration and ferroptosis in proliferative diabetic retinopathy

The roles of immune cell infiltration and ferroptosis in the progression of proliferative diabetic retinopathy (PDR) remain unclear. To identify upregulated molecules associated with immune infiltration and ferroptosis in PDR, GSE60436 and GSE102485 datasets were downloaded from the Gene Expression Omnibus (GEO). Genes associated with immune cell infiltration were examined through Weighted Gene Co-expression Network Analysis (WGCNA) and CIBERSORT algorithm. Common differentially expressed genes (DEGs) were intersected with ferroptosis-associated and immune cell infiltration-related genes. Localization of cellular expression was confirmed by single-cell analysis of GSE165784 dataset. Findings were validated by qRT-PCR, ELISA, Western blotting, and immunofluorescence staining. As a result, the infiltration of M2 macrophages was significantly elevated in fibrovascular membrane samples from PDR patients than the retinas of control subjects. Analysis of DEGs, M2 macrophage-related genes and ferroptosis-related genes identified three hub intersecting genes, TP53, HMOX1 and PPARA. qRT-PCR showed that HMOX1 was significantly higher in the oxygen-induced retinopathy (OIR) mouse model retinas than in controls. Single-cell analysis confirmed that HMOX1 was located in M2 macrophages. ELISA and western blotting revealed elevated levels of HMOX1 in the vitreous humor of PDR patients and OIR retinas, and immunofluorescence staining showed that HMOX1 co-localized with M2 macrophages in the retinas of OIR mice. This study offers novel insights into the mechanisms associated with immune cell infiltration and ferroptosis in PDR. HMOX1 expression correlated with M2 macrophage infiltration and ferroptosis, which may play a crucial role in PDR pathogenesis.

Gualou-Xiebai herb pair ameliorate atherosclerosis in HFD-induced ApoE-/- mice and inhibit the ox-LDL-induced injury of HUVECs by regulating the Nrf2-mediated ferroptosis

ETHNOPHARMACOLOGICAL RELEVANCE

Atherosclerosis (AS) is a chronic vascular ailment characterized by inflammatory and lipid deposition in the arterial wall caused by endothelial injury. Ferroptosis is a novel type of cell death, and endothelial ferroptosis is a significant contributor to the progression of AS. Gualou-Xiebai (GLXB) is a renowned Chinese herb pair that serves a crucial function in treating AS. However, whether the underlying mechanism of GLXB plays a role in anti-atherosclerotic effects by inhibiting ferroptosis in endothelial cells has not been determined.

AIM OF THE STUDY

To explore the influence of GLXB on endothelial ferroptosis and determine its underlying mechanism of action in AS.

MATERIALS AND METHODS

In ApoE-/- mice, ultrasound was performed in mice fed a high-fat diet (HFD) for 12 weeks to assess the success of AS establishment. Then, ApoE-/- mice were treated with GLXB and Simvastatin (positive control) for 4 weeks. The effects of GLXB on AS pathology were assessed through aorta imaging and hematoxylin-eosin (HE) staining. To confirm the presence of ferroptosis, mitochondrial damage was observed using transmission electron microscope (TEM), along with analysis of free iron and lipid peroxidation levels. In vitro: ox-LDL-induced human vascular endothelial cells (HUVECs) injury and treated with GLXB, the ferroptosis inducer Erastin and an Nrf2 inhibitor ML385. Cell viability was evaluated using the CCK-8 assay in all groups. Flow cytometry was employed to detect lipid peroxidation and intracellular ferrous iron levels. Immunofluorescence staining microscopy verified Nrf2 nuclear translocation. Protein expression were measured by Western blot analysis.

RESULTS

GLXB improved atherosclerotic aortic lesions and vascular plaques. GLXB inhibited endothelial injury in the aorta by decreasing the levels of inflammatory factors and adhesion factors, and by decreasing the shedding of endothelial cells. GLXB suppressed ferroptosis in ApoE-/- mice by attenuating mitochondrial damage in ECs, increasing the levels of glutathione (GSH) and superoxide dismutase (SOD) in aortic tissues and down-regulating the levels of levels of lipid peroxide (LPO) and malondialdehyde (MDA). Interestingly, Erastin was used to demonstrate in vitro that GLXB inhibition of ferroptosis attenuated ox-LDL-induced injuring effects on HUVECs that were reversed by Erastin. Mechanistically, GLXB activates the Nrf2 signaling pathway to inhibit ferroptosis by increasing downstream anti-ferroptosis target proteins and promoting the interaction between Nrf2 and SLC7A11. More convincingly, ML385 (Nrf2 inhibitor) reversed the anti-ferroptosis effect of GLXB.

CONCLUSION

GLXB inhibits ferroptosis-mediated endothelial cell injury via activating the Nrf2 signaling pathway and further alleviates AS pathological damage.

Emerging role of ferroptosis in diabetic retinopathy: a review

BACKGROUND

Diabetic retinopathy (DR) is a significant complication of diabetes and the primary cause of blindness among working age adults globally. The development of DR is accompanied by oxidative stress, characterised by an overproduction of reactive oxygen species (ROS) and a compromised antioxidant system. Clinical interventions aimed at mitigating oxidative stress through ROS scavenging or elimination are currently available. Nevertheless, these treatments merely provide limited management over the advanced stage of the illness. Ferroptosis is a distinctive form of cell death induced by oxidative stress, which is characterised by irondependent phospholipid peroxidation.

PURPOSE

This review aims to synthesise recent experimental evidence to examine the involvement of ferroptosis in the pathological processes of DR, as well as to explicate the regulatory pathways governing oxidative stress and ferroptosis in retina.

METHODS

We systematically reviewed literature available up to 2023.

RESULTS

This review included 12 studies investigating the involvement of ferroptosis in DR.

Autophagy, Pyroptosis and Ferroptosis are Rising Stars in the Pathogenesis of Diabetic Nephropathy

Diabetic nephropathy (DN) is one of the most common microvascular complications in diabetes and can potentially develop into end-stage renal disease. Its pathogenesis is complex and not fully understood. Podocytes, glomerular endothelial cells (GECs), glomerular mesangial cells (GMCs) and renal tubular epithelial cells (TECs) play important roles in the normal function of glomerulus and renal tubules, and their injury is involved in the progression of DN. Although our understanding of the mechanisms leading to DN has substantially improved, we still need to find more effective therapeutic targets. Autophagy, pyroptosis and ferroptosis are programmed cell death processes that are associated with inflammation and are closely related to a variety of diseases. Recently, a growing number of studies have reported that autophagy, pyroptosis and ferroptosis regulate the function of podocytes, GECs, GMCs and TECs. This review highlights the contributions of autophagy, pyroptosis, and ferroptosis to DN injury in these cells, offering potential therapeutic targets for DN treatment.

Armeniacae semen amarum: a review on its botany, phytochemistry, pharmacology, clinical application, toxicology and pharmacokinetics

Armeniacae semen amarum-seeds of Prunus armeniaca L. (Rosaceae) (ASA), also known as Kuxingren in Chinese, is a traditional Chinese herbal drug commonly used for lung disease and intestinal disorders. It has long been used to treat coughs and asthma, as well as to lubricate the colon and reduce constipation. ASA refers to the dried ripe seed of diverse species of Rosaceae and contains a variety of phytochemical components, including glycosides, organic acids, amino acids, flavonoids, terpenes, phytosterols, phenylpropanoids, and other components. Extensive data shows that ASA exhibits various pharmacological activities, such as anticancer activity, anti-oxidation, antimicrobial activity, anti-inflammation, protection of cardiovascular, neural, respiratory and digestive systems, antidiabetic effects, and protection of the liver and kidney, and other activities. In clinical practice, ASA can be used as a single drug or in combination with other traditional Chinese medicines, forming ASA-containing formulas, to treat various afflictions. However, it is important to consider the potential adverse reactions and pharmacokinetic properties of ASA during its clinical use. Overall, with various bioactive components, diversified pharmacological actions and potent efficacies, ASA is a promising drug that merits in-depth study on its functional mechanisms to facilitate its clinical application.

Silva H, P. de Carvalho R, Ventura ALM, Calaza KC, Silveira MS, Kubrusly RCC, de Melo Reis RA. The Healthy and Diseased Retina Seen through Neuron-Glia Interactions

The retina is the sensory tissue responsible for the first stages of visual processing, with a conserved anatomy and functional architecture among vertebrates. To date, retinal eye diseases, such as diabetic retinopathy, age-related macular degeneration, retinitis pigmentosa, glaucoma, and others, affect nearly 170 million people worldwide, resulting in vision loss and blindness. To tackle retinal disorders, the developing retina has been explored as a versatile model to study intercellular signaling, as it presents a broad neurochemical repertoire that has been approached in the last decades in terms of signaling and diseases. Retina, dissociated and arranged as typical cultures, as mixed or neuron- and glia-enriched, and/or organized as neurospheres and/or as organoids, are valuable to understand both neuronal and glial compartments, which have contributed to revealing roles and mechanisms between transmitter systems as well as antioxidants, trophic factors, and extracellular matrix proteins. Overall, contributions in understanding neurogenesis, tissue development, differentiation, connectivity, plasticity, and cell death are widely described. A complete access to the genome of several vertebrates, as well as the recent transcriptome at the single cell level at different stages of development, also anticipates future advances in providing cues to target blinding diseases or retinal dysfunctions.

Neurovascular Cell Death and Therapeutic Strategies for Diabetic Retinopathy

Diabetic retinopathy (DR) is a major complication of diabetes and a leading cause of blindness worldwide. DR was recently defined as a neurovascular disease associated with tissue-specific neurovascular impairment of the retina in patients with diabetes. Neurovascular cell death is the main cause of neurovascular impairment in DR. Thus, neurovascular cell protection is a potential therapy for preventing the progression of DR. Growing evidence indicates that a variety of cell death pathways, such as apoptosis, necroptosis, ferroptosis, and pyroptosis, are associated with neurovascular cell death in DR. These forms of regulated cell death may serve as therapeutic targets for ameliorating the pathogenesis of DR. This review focuses on these cell death mechanisms and describes potential therapies for the treatment of DR that protect against neurovascular cell death.