Pathological Role of Unsaturated Aldehyde Acrolein in Diabetic Retinopathy

Visualization of Acrolein Upregulation during Ferroptosis by a Ratiometric Fluorescent Probe

Ferroptosis is a pattern of cell death caused by iron-dependent accumulation of lipid peroxides and is closely associated with the occurrence and development of multiple diseases. Acrolein (ACR), one of the final metabolites of lipid peroxidation, is a reactive carbonyl species with strong biotoxicity. Effective detection of ACR is important for understanding its role in the progression of ferroptosis and studying the specific mechanisms of ferroptosis-mediated diseases. However, visualization detection of ACR during ferroptosis has not yet been reported. In this work, the first ratiometric fluorescent probe (HBT-SH) based on 2-(2'-hydroxyphenyl) benzothiazole (HBT) was designed for tracing endogenous ACR with an unprecedented regiospecific ACR-induced intramolecular cyclization strategy, which employs 2-aminoethanethiol as an ACR-selective recognition receptor. The experimental results showed that HBT-SH has excellent selectivity, high sensitivity (LOD = 0.26 μM) and good biocompatibility. More importantly, the upregulation of ACR levels was observed during ferroptosis in HeLa cells and zebrafish, indicating that ACR may be a specific active molecule that plays an essential biological role during ferroptosis or may serve as a potential marker of ferroptosis, which has great significance for studying the pathological process and treatment options of ferroptosis-related diseases.

GRg1 inhibits the TLR4/NF-kB signaling pathway by upregulating miR-216a-5p to reduce growth factors and inflammatory cytokines in DR

BACKGROUND

Diabetic retinopathy (DR) is a common diabetic neurodegenerative disease that affects vision in severe cases. Current therapeutic drugs are ineffective for some patients with severe side effects, and ginsenoside-Rg1 (GRg1) has been shown to protect against DR and may serve as a new potential drug for DR. This study aimed to confirm the protective effect of GRg1 against DR and its molecular mechanism.

METHODS

Human retinal microvascular endothelial cells (hRMECs) and rats were used to construct DR models in vitro and in vivo. Cell proliferation was detected by BrdU assays, the cell cycle was detected by flow cytometry, and TNF-α, IL-6 and IL-1β levels were detected by ELISA. qRT‒PCR, Western blotting and immunohistochemistry were used to detect the expression of related genes and proteins, and angiogenesis assays were used to assess angiogenesis. RIP and RNA pull down assays were used to determine the relationship between miR-216a-5p and TLR4; retinal structure and changes were observed by HE staining and retinal digestive spread assays.

RESULTS

GRg1 effectively inhibited HG-induced hRMEC proliferation, cell cycle progression and angiogenesis and reduced the levels of intracellular inflammatory cytokines and growth factors. HG downregulated the expression of miR-216a-5p and upregulated the expression of TLR4/NF-kB signaling pathway-related proteins. Importantly, GRg1 inhibited TLR4/NF-kB signaling pathway activation by upregulating miR-216a-5p, thereby inhibiting HG-induced cell proliferation, cell cycle progression, angiogenesis, and the production of inflammatory cytokines and growth factors. In addition, animal experiments confirmed the results of the cell experiments.

CONCLUSIONS

GRg1 inhibits TLR4/NF-kB signaling by upregulating miR-216a-5p to reduce growth factors and inflammatory cytokines in DR, providing a potential therapeutic strategy for DR.

Fresh Washed Microbiota Transplantation Alters Gut Microbiota Metabolites to Ameliorate Sleeping Disorder Symptom of Autistic Children

Accumulating studies have raised concerns about gut dysbiosis associating autism spectrum disorder (ASD) and its related symptoms. However, the effect of gut microbiota modification on the Chinese ASD population and its underlying mechanism were still elusive. Herein, we enrolled 24 ASD children to perform the first course of fresh washed microbiota transplantation (WMT), 18 patients decided to participate the second course, 13 of which stayed to participate the third course, and there were 8 patients at the fourth course. Then we evaluated the effects of fresh WMT on these patients and their related symptoms. Our results found that the sleeping disorder symptom was positively interrelated to ASD, fresh WMT significantly alleviated ASD and its sleeping disorder and constipation symptoms. In addition, WMT stably and continuously downregulated Bacteroides/Flavonifractor/Parasutterella while upregulated Prevotella_9 to decrease toxic metabolic production and improve detoxification by regulating glycolysis/myo-inositol/D-glucuronide/D-glucarate degradation, L-1,2-propanediol degradation, fatty acid β-oxidation. Thus, our results suggested that fresh WMT moderated gut microbiome to improve the behavioral and sleeping disorder symptoms of ASD via decrease toxic metabolic production and improve detoxification. Which thus provides a promising gut ecological strategy for ASD children and its related symptoms treatments.

Diet as a Source of Acrolein: Molecular Basis of Aldehyde Biological Activity in Diabetes and Digestive System Diseases

Acrolein, a highly reactive α,β-unsaturated aldehyde, is a compound involved in the pathogenesis of many diseases, including neurodegenerative diseases, cardiovascular and respiratory diseases, diabetes mellitus, and the development of cancers of various origins. In addition to environmental pollution (e.g., from car exhaust fumes) and tobacco smoke, a serious source of acrolein is our daily diet and improper thermal processing of animal and vegetable fats, carbohydrates, and amino acids. Dietary intake is one of the main routes of human exposure to acrolein, which is a major public health concern. This review focuses on the molecular mechanisms of acrolein activity in the context of its involvement in the pathogenesis of diseases related to the digestive system, including diabetes, alcoholic liver disease, and intestinal cancer.

Acrolein-inducing ferroptosis contributes to impaired peripheral neurogenesis in zebrafish

Introduction

Diabetes mellitus (DM) is associated with physiological disorders such as delayed wound healing, diabetic retinopathy, diabetic nephropathy, and diabetic peripheral neuropathy (DPN). Over 50% of diabetic patients will develop DPN, characterized by motor dysfunction and impaired sensory nerve function. In a previous study, we have uncovered acrolein (ACR) as an upstream initiator which induced impaired glucose homeostasis and microvascular alterations in zebrafish. Whether ACR has specific effects on peripheral neurogenesis and mediates DPN, is still waiting for clarification.

Methods

To evaluate the function of ACR in peripheral nerve development, in vivo experiments were performed in Tg(hb9:GFP) zebrafish. In addition, a series of rescue experiments, metabolomics assessment, and bioinformatics analysis was performed aimed at identifying the molecular mechanisms behind ACR's function and impaired neurogenesis.

Results

Impaired motor neuron development was confirmed in wild-type embryos treated with external ACR. ACR treated embryos displayed ferroptosis and reduction of several amino acids and increased glutathione (GSH). Furthermore, ferroptosis inducer caused similarly suppressed neurogenesis in zebrafish embryos, while anti-ACR treatment or ferroptosis inhibitor could successfully reverse the detrimental phenotypes of ACR on neurogenesis in zebrafish.

Discussion

Our data indicate that ACR could directly activate ferroptosis and impairs peripheral neurogenesis. The data strongly suggest ACR and activated ferroptosis as inducers and promising therapeutic targets for future DPN studies.

Reduced Acrolein Detoxification in akr1a1a Zebrafish Mutants Causes Impaired Insulin Receptor Signaling and Microvascular Alterations

Increased acrolein (ACR), a toxic metabolite derived from energy consumption, is associated with diabetes and its complications. However, the molecular mechanisms are mostly unknown, and a suitable animal model with internal increased ACR does not exist for in vivo studying so far. Several enzyme systems are responsible for acrolein detoxification, such as Aldehyde Dehydrogenase (ALDH), Aldo-Keto Reductase (AKR), and Glutathione S-Transferase (GST). To evaluate the function of ACR in glucose homeostasis and diabetes, akr1a1a-/- zebrafish mutants are generated using CRISPR/Cas9 technology. Accumulated endogenous acrolein is confirmed in akr1a1a-/- larvae and livers of adults. Moreover, a series of experiments are performed regarding organic alterations, the glucose homeostasis, transcriptome, and metabolomics in Tg(fli1:EGFP) zebrafish. Akr1a1a-/- larvae display impaired glucose homeostasis and angiogenic retina hyaloid vasculature, which are caused by reduced acrolein detoxification ability and increased internal ACR concentration. The effects of acrolein on hyaloid vasculature can be reversed by acrolein-scavenger l-carnosine treatment. In adult akr1a1a-/- mutants, impaired glucose tolerance accompanied by angiogenic retina vessels and glomerular basement membrane thickening, consistent with an early pathological appearance in diabetic retinopathy and nephropathy, are observed. Thus, the data strongly suggest impaired ACR detoxification and elevated ACR concentration as biomarkers and inducers for diabetes and diabetic complications.

An Update on Connexin Gap Junction and Hemichannels in Diabetic Retinopathy

Diabetic retinopathy (DR) is one of the main causes of vision loss in the working age population. It is characterized by a progressive deterioration of the retinal microvasculature, caused by long-term metabolic alterations inherent to diabetes, leading to a progressive loss of retinal integrity and function. The mammalian retina presents an orderly layered structure that executes initial but complex visual processing and analysis. Gap junction channels (GJC) forming electrical synapses are present in each retinal layer and contribute to the communication between different cell types. In addition, connexin hemichannels (HCs) have emerged as relevant players that influence diverse physiological and pathological processes in the retina. This article highlights the impact of diabetic conditions on GJC and HCs physiology and their involvement in DR pathogenesis. Microvascular damage and concomitant loss of endothelial cells and pericytes are related to alterations in gap junction intercellular communication (GJIC) and decreased connexin 43 (Cx43) expression. On the other hand, it has been shown that the expression and activity of HCs are upregulated in DR, becoming a key element in the establishment of proinflammatory conditions that emerge during hyperglycemia. Hence, novel connexin HCs blockers or drugs to enhance GJIC are promising tools for the development of pharmacological interventions for diabetic retinopathy, and initial in vitro and in vivo studies have shown favorable results in this regard.