ALDH2 attenuates early-stage STZ-induced aged diabetic rats retinas damage via Sirt1/Nrf2 pathway

Neurotrophins of the retina and their involvement in early-stage diabetic retinopathy in an animal model of type 1 diabetes mellitus

IntroductionDiabetic retinopathy (DR) is a blindness-causing disease which belongs to the group of neurodegenerative diseases. Neurodegeneration of the retina is a process, in which retinal neurons suffer irreversible damage. This study aimed to assess the involvement of neurotrophins (brain-derived neurotrophic factor [BDNF] and nerve growth factor [NGF]) in the pathogenesis of DR.MethodsThe study was performed using male Lewis rats with type 1 diabetes mellitus induced by streptozotocin, and the control group included rats without drug administration. In vivo examinations performed over four weeks included eye fundus imaging, measurement of intraocular pressure, and glycemia. After sacrifice, serum and eyeballs were harvested. Post-mortem analyses included a histopathological analysis of the retina and the measurement of BDNF and NGF levels in the serum and eyeball homogenate.ResultsIn the experimental group, early-stage DR was confirmed, and changes in the retina were observed: diabetic rats had relatively thicker outer nuclear layers and relatively thinner inner plexiform layers. A lower level of BDNF was observed in the serum of rats with DR, while the level of NGF in the eyeball homogenate positively correlated with vascular changes.ConclusionsThe observed changes in the levels of neurotrophins in early-stage DR may indicate their involvement in the disease pathogenesis.

From aldehyde metabolism to delay aging: targeting ALDH2 as a novel strategy

Aldehydes are molecules that are commonly found in both human physiology and the environment. The accumulation of these substances can lead to the cross-linking of intracellular DNA and proteins, thereby disrupting cellular function and contributing to the processes of premature aging and age-related diseases. Aldehyde dehydrogenase 2 (ALDH2), the key member of ALDH family, is an enzyme responsible for aldehyde metabolism, composed of four identical subunits located within the mitochondrial matrix. Its primary role is to catalyze the oxidation of aldehydes, resulting in the formation of their corresponding acid metabolites. This paper presents a succinct overview of the sources and metabolic pathways of key aldehydes within the human body, compares the various primary enzymes involved in aldehyde metabolism, and explores the structural and functional characteristics of ALDH2. Furthermore, ALDH2 is proposed as a potential therapeutic target for addressing aging and associated diseases. The discussion also includes prospective research avenues, particularly focusing on ALDH2 agonists and aldehyde scavengers designed to enhance the clearance of reactive aldehydes and safeguard cellular functions, thereby mitigating aldehyde-induced cellular damage and potentially delaying the aging process.

ALDH2 Overexpression Improves the Blood-brain Barrier and Represses Mitochondrial Dysfunction in Chronic Cerebral Hypoperfusion Through the SIRT1/ROS Axis

The study investigated the mechanism of ALDH2 in mitochondrial dysfunction and blood-brain barrier (BBB) damage arising from chronic cerebral hypoperfusion (CCH). A rat model of bilateral common carotid artery occlusion (BCCAO) was established and treated with AAV-ALDH2. ALDH2 expression, cognitive function, and levels of inflammation- and oxidative stress-related factors, were examined, followed by observing changes in BBB and mitochondrial functions. A rat neuron model of oxygen glucose deprivation/re-oxygenation (OGD/R) was constructed and treated with AAV-ALDH2 and the SIRT1 inhibitor Sirtinol. 4-HNE, SIRT1, ROS levels, mitochondrial membrane potential (MMP), and ATP production were detected, followed by oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) assays. ALDH2 was down-regulated in BCCAO-modeled rats. In BCCAO-modeled rats, ALDH2 overexpression repressed learning/memory deficits and BBB leakage, elevated SOD and GSH levels, decreased the levels of inflammation-related factors, ROS, 4-HNE, and MDA, and improved mitochondrial morphology. In OGD/R-stimulated neurons, ALDH2 overexpression diminished ROS and 4-HNE levels and ECAR and increased MMP, OCR, and ATP production, which was abrogated by Sirtinol. Overall, ALDH2 up-regulation exerts suppressive effects on BBB damage and mitochondrial dysfunction in CCH via the SIRT1/ROS axis.

Protective Role and Enhanced Intracellular Uptake of Curcumin in Retinal Cells Using Self-Emulsifying Drug Delivery Systems (SNEDDS)

Background: Sirtuin-1 (SIRT1), a histone deacetylase enzyme expressed in ocular tissues with intracellular localization, plays a critical protective role against various degenerative ocular diseases. The link between reduced SIRT1 levels and diabetic retinopathy (DR) has prompted the exploration of natural therapeutic compounds that act as SIRT1 agonists. Curcumin (CUR), which has been shown to upregulate SIRT1 expression, is one such promising compound. However, effective delivery of CUR to the deeper ocular tissues, particularly the retina, remains a challenge due to its poor solubility and limited ocular penetration following topical administration. Within this context, the development of self-nanoemulsifying drug delivery systems (SNEDDS) for CUR topical ocular delivery represents a novel approach. Methods: In accordance with our prior research, optimized SNEDDS loaded with CUR were developed and characterized post-reconstitution with simulated tear fluid (STF) at a 1:10 ratio, showing suitable physicochemical and technological parameters for ocular delivery. Results: An entrapment efficiency (EE%) of approximately 99% and an absence of drug precipitation were noticed upon resuspension with STF. CUR-SNEDDS resulted in a better stability and release profile than free CUR under simulated ocular conditions. In vitro analysis of mucoadhesive properties revealed that CUR-SNEDDS, modified with a cationic lipid, demonstrated enhanced interactions with mucin, indicating the potential for improved ocular retention. Cytotoxicity tests demonstrated that CUR-SNEDDS did not affect the viability of human corneal epithelial (HCE) cells up to concentrations of 3 μM and displayed superior antioxidant activity compared to free CUR in an oxidative stress model using retinal pigment epithelial (ARPE-19) cells exposed to hydroquinone (HQ). Cell uptake studies confirmed an enhanced accumulation of CUR within the retinal cells following exposure to CUR-SNEDDS compared to neat CUR. CUR-SNEDDS, at lower concentrations, were found to effectively induce SIRT1 expression. Conclusions: The cytocompatibility, antioxidant properties, and enhanced cellular uptake suggest that these developed systems hold promise as formulations for the delivery of CUR to the retina.

Therapeutic effects of Mudan granules on diabetic retinopathy: Mitigating fibrogenesis caused by FBN2 deficiency and inflammation associated with TNF-α elevation

ETHNOPHARMACOLOGICAL RELEVANCE

Mudan granules (MuD), a time-honored traditional Chinese patent medicine (TCPM), are widely utilized in the clinical treatment of diabetic peripheral neuropathy (DPN). In the field of biomedical diagnostics, both diabetic retinopathy (DR) and DPN are recognized as critical microvascular complications associated with diabetes. According to the principles of traditional Chinese medicine (TCM), these conditions are primarily attributed to a deficiency in Qi and the obstruction of collaterals. Despite this, the protective effects of MuD on DR and the underlying mechanisms remain to be comprehensively elucidated.

AIMS OF THE STUDY

The purpose of this study was to investigate the effect of MuD on DR and to further explore the promising therapeutic targets.

METHODS

A diabetic mouse model was established by administering 60 mg/kg of streptozotocin (STZ) via intraperitoneal injection for five consecutive days. The therapeutic efficacy of MuD was evaluated using a comprehensive approach, which included electroretinogram (ERG) analysis, histopathological examination, and assessment of serum biochemical markers. Then, the pharmacodynamic mechanisms of MuD were systematically analyzed using Tandem Mass Tags-based proteomics. Meanwhile, the candidate compounds of MuD were analyzed by ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) and molecular docking was applied to estimate the affinity of the active ingredient to their potential key targets. In addition, the functional mechanisms identified through bioinformatics analysis were confirmed by molecular biological methods.

RESULTS

We demonstrated that MuD provided significant protection to retinal function and effectively mitigated the reduction in retinal thickness observed in the animal model. Through proteomic analysis, we identified a substantial regulation by MuD of 70 biomarkers associated with diabetic retinal damage. These proteins were notably enriched in the tumor necrosis factor (TNF) signaling pathway, a critical mediator in inflammatory processes. A particularly intriguing finding was the significant downregulation of fibrillin-2 (FBN2) in the diabetic retina compared to the control group (0.36 times the level), and its most pronounced upregulation (3.26 times) in the MuD treatment group. This suggests that FBN2 may play a pivotal role in the protective effects of MuD. Molecular docking analyses have unveiled a robust interplay between the components of MuD and TNF-α. Further corroboration was provided by molecular biological methods, which confirmed that MuD could suppress TNF-mediated inflammation and prevent retinal neovascularization and fibrogenesis.

CONCLUSION

MuD have the potential to alleviate diabetic retinal dysfunction by effectively curbing the fibrogenesis-associated neoangiogenesis and mitigating the inflammatory response, thereby restoring retinal health and function.

ALDH2 alleviates inflammation and facilitates osteogenic differentiation of periodontal ligament stem cells in periodontitis by blocking ferroptosis via activating Nrf2

This paper elucidated the effects and mechanisms of aldehyde dehydrogenase 2 (ALDH2) on periodontitis. Rat model of periodontitis and periodontal ligament stem cell (PDLSC) model of periodontitis were constructed. PDLSC were transfected by ALDH2 overexpression vectors, and then treated by ML385 (Nrf2 inhibitor), ferrostatin-1 (ferroptosis inhibitor) and FIN56 (ferroptosis inducer), respectively. ALDH2, nuclear factor erythroid 2-related factor 2 (Nrf2) and glutathione peroxidase 4 (GPX4) proteins was evaluated by immunohistochemistry and Western blot. Ferroptosis-related factors, including Fe2+ and glutathione (GSH), were assessed by commercial kits. Pro-inflammatory factors (interleukin-6 [IL-6] and tumor necrosis factor-α [TNF-α]) and osteogenic differentiation-related proteins (osteocalcin [OCN] and runt-related transcription factor 2 [RUNX2]) were scrutinized by commercial kits and Western blot. In both periodontal tissues of periodontitis rats and PDLSC model of periodontitis, down-regulated ALDH2, Nrf2, GPX4 and GSH, but elevated Fe2+ level was discovered. ALDH2 overexpression in PDLSC resulted in an increase in Nrf2 expression. In PDLSC model of periodontitis, ALDH2 increased GPX4 and GSH levels, decreased Fe2+, IL-6 and TNF-α levels, and elevated OCN and RUNX2 expression. However, these effects of ALDH2 were counteracted by ML385. Additionally, the suppression of ALDH2 on IL-6 and TNF-α levels and promotion of it on OCN and RUNX2 expression in PDLSC model of periodontitis was further intensified by ferrostatin-1, but reversed by FIN56. ALDH2 may alleviate inflammation and facilitate osteogenic differentiation of PDLSC in periodontitis by hindering ferroptosis via activating Nrf2, suggesting it to be a promising candidate for treating periodontitis.

Preclinical study of diabetic foot ulcers: From pathogenesis to vivo/vitro models and clinical therapeutic transformation

Diabetic foot ulcer (DFU), a common intractable chronic complication of diabetes mellitus (DM), has a prevalence of up to 25%, with more than 17% of the affected patients at risk of amputation or even death. Vascular risk factors, including vascular stenosis or occlusion, dyslipidemia, impaired neurosensory and motor function, and skin infection caused by trauma, all increase the risk of DFU in patients with diabetes. Therefore, diabetic foot is not a single pathogenesis. Preclinical studies have contributed greatly to the pathogenesis determination and efficacy evaluation of DFU. Many therapeutic tools are currently being investigated using DFU animal models for effective clinical translation. However, preclinical animal models that completely mimic the pathogenesis of DFU remain unexplored. Therefore, in this review, the preparation methods and evaluation criteria of DFU animal models with three major pathological mechanisms: neuropathy, angiopathy and DFU infection were discussed in detail. And the advantages and disadvantages of various DFU animal models for clinical sign simulation. Furthermore, the current status of vitro models of DFU and some preclinical studies have been transformed into clinical treatment programs, such as medical dressings, growth factor therapy, 3D bioprinting and pre-vascularization, Traditional Chinese Medicine treatment. However, because of the complexity of the pathological mechanism of DFU, the clinical transformation of DFU model still faces many challenges. We need to further optimize the existing preclinical studies of DFU to provide an effective animal platform for the future study of pathophysiology and clinical treatment of DFU.

Aldehyde Dehydrogenase and Aldo-Keto Reductase Enzymes: Basic Concepts and Emerging Roles in Diabetic Retinopathy

Diabetic retinopathy (DR) is a complication of diabetes mellitus that can lead to vision loss and blindness. It is driven by various biochemical processes and molecular mechanisms, including lipid peroxidation and disrupted aldehyde metabolism, which contributes to retinal tissue damage and the progression of the disease. The elimination and processing of aldehydes in the retina rely on the crucial role played by aldehyde dehydrogenase (ALDH) and aldo-keto reductase (AKR) enzymes. This review article investigates the impact of oxidative stress, lipid-derived aldehydes, and advanced lipoxidation end products (ALEs) on the advancement of DR. It also provides an overview of the ALDH and AKR enzymes expressed in the retina, emphasizing their growing importance in DR. Understanding the relationship between aldehyde metabolism and DR could guide innovative therapeutic strategies to protect the retina and preserve vision in diabetic patients. This review, therefore, also explores various approaches, such as gene therapy and pharmacological compounds that have the potential to augment the expression and activity of ALDH and AKR enzymes, underscoring their potential as effective treatment options for DR.

Ketorolac and (-)-Epicatechin change retinal GFAP and NRF2 expression on hyperglycemic CD1 mice

Our objective was to determine whether (-)-Epicatechin administered alone or simultaneously with topical Ketorolac decreased the relative expression of GFAP and modulated the response of Nrf2 in a mouse model with induced hyperglycemia. We found that GFAP and Nrf2 decreased in the groups that received treatments alone or simultaneous during 8 weeks; even when the effect on the Nrf2 was not pronounced, it showed a higher concentration when GFAP decreased. Our results suggest a protective effect of Ketorolac and (-) - Epicatechin, which seem to limit the preclinical retinal damage caused by inflammation in hyperglycemia.

Aldehyde dehydrogenase 2 and NOD-like receptor thermal protein domain associated protein 3 inflammasome in atherosclerotic cardiovascular diseases: A systematic review of the current evidence

Inflammation and dyslipidemia underlie the pathological basis of atherosclerosis (AS). Clinical studies have confirmed that there is still residual risk of atherosclerotic cardiovascular diseases (ASCVD) even after intense reduction of LDL. Some of this residual risk can be explained by inflammation as anti-inflammatory therapy is effective in improving outcomes in subjects treated with LDL-lowering agents. NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome activation is closely related to early-stage inflammation in AS. Aldehyde dehydrogenase 2 (ALDH2) is an important enzyme of toxic aldehyde metabolism located in mitochondria and works in the metabolism of toxic aldehydes such as 4-HNE and MDA. Despite studies confirming that ALDH2 can negatively regulate NLRP3 inflammasome and delay the development of atherosclerosis, the mechanisms involved are still poorly understood. Reactive Oxygen Species (ROS) is a common downstream pathway activated for NLRP3 inflammasome. ALDH2 can reduce the multiple sources of ROS, such as oxidative stress, inflammation, and mitochondrial damage, thereby reducing the activation of NLRP3 inflammasome. Further, according to the downstream of ALDH2 and the upstream of NLRP3, the molecules and related mechanisms of ALDH2 on NLRP3 inflammasome are comprehensively expounded as possible. The potential mechanism may provide potential inroads for treating ASCVD.

Kruppel-Like Factor (KLF6) Regulates Oxidative Stress and Apoptosis of Human Retinal Pigment Epithelial Cells Induced by High Glucose Through Transcriptional Regulation of USP22 and the Downstream SIRT1/Nrf2 Pathway

Oxidative stress and apoptosis play an important role in diabetic retinopathy (DR). KLF6 and its transcriptional regulator USP22 are abnormally expressed in DR, but the specific role and mechanism have not been reported. In this paper, we will discuss the specific roles and mechanisms of KLF6 and USP22 on oxidative stress and apoptosis in DR. In this study, RT-qPCR and western blot were used to detect the expression of KLF6 and USP22 in ARPE-19 cells. Subsequently, after KLF6 was overexpressed and USP22 expression was inhibited by cell transfection, the oxidative stress and apoptosis related indexes were detected by CCK-8, ELISA, TUNEL and other techniques to explore the mechanism. In addition, we used luciferase and ChIP to detect the association between KLF6 and USP22. Finally, the expression of proteins related to the SIRT1/Nrf2 pathway was detected by western blot. The results showed that silencing USP22 increased the activity, and inhibited apoptosis and oxidative stress of ARPE-19 cells induced by high glucose (HG). KLF6 transcriptionally activates USP22. Overexpression of KLF6 reversed the protective effects of silencing USP22 on HG-induced ARPE-19 cells against apoptosis and antioxidant stress, which may be achieved by regulating the SIRT1/Nrf2 pathway. In conclusion, KLF6 regulated oxidative stress and apoptosis of ARPE-19 cells induced by high glucose through transcriptional regulation of USP22 and the downstream SIRT1/Nrf2 pathway.

Silibinin Ameliorates Formaldehyde-Induced Cognitive Impairment by Inhibiting Oxidative Stress

Silibinin is a flavonoid extracted from the medicinal plant Silybum marianum (milk thistle), traditionally used to treat liver disease. Recent studies have shown that the antioxidative stress and anti-inflammatory effects of milk thistle are used in the treatment of neurological diseases. Silibinin has antioxidative stress and antiapoptotic effects and reduces cognitive impairment in models of Alzheimer's disease (AD). However, the underlying mechanism of silibinin related to improvement of cognition remains poorly understood. In this study, we used the model of lateral ventricle injection of formaldehyde to examine the related mechanism of silibinin in improving cognitive impairment disorders. Oral administration of silibinin for three weeks significantly attenuated the cognitive deficits of formaldehyde-induced mice in a Y-maze test and Morris water maze test. Y-maze results show that silibinin increases the rate of spontaneous response alternation in FA-induced mice. Silibinin increases the target quadrant spending time and decreases escape latency in the Morris water maze test. We examined the effect of silibinin on the NRF2 signaling pathway, and silibinin promoted the nuclear transfer of NRF2 and increased the expression of HO-1 but did not significantly increase the protein expression of NRF2 in the hippocampus. Well, silibinin reduces the content of DHE and decreases the levels of apoptosis of mature neuron cells. We investigated the effect of silibinin on the content of formaldehyde degrading enzymes; biochemical analyses revealed that silibinin increased GSH and ALDH2 in formaldehyde-induced mice. In addition, as one of the pathological changes of AD, TAU protein is also hyperphosphorylated in FA model mice. Silibinin inhibits the expression of GSK-3β in model mice, thereby reducing the phosphorylation of TAU proteins ser396 and ser404 mediated by GSK3β. Based on our findings, we verified that the mechanism of silibinin improving cognitive impairment may be antioxidative stress, and silibinin is one of the potentially promising drugs to prevent formaldehyde-induced cognitive impairment.

Proteomic and Morphological Profiling of Mice Ocular Tissue During High-altitude Acclimatization Process: An Animal Study at Lhasa

PURPOSE

High-altitude environment mainly with hypobaric hypoxia could induce pathological alterations in ocular tissue. Previous studies have mostly focused on sporadic case reports and simulated high-altitude hypoxia experiments. This aim of this study was to explore the proteomic and morphological changes of ocular tissue in mice at real altitude environment.

METHODS

In this study, mice were flown from Chengdu (elevation: 500 m) to Lhasa (elevation: 3600 m). After exposure for 1day, 3, 6, 10, 20, 30, and 40days, the mice were euthanatized to obtain blood and ocular tissue. Serological tests, ocular pathological examinations, integral ocular proteomics analysis, and Western blot were conducted.

RESULTS

We focused on acute phase (1-3 days) and chronic phase (>30 days) during high-altitude acclimatization. Serum interleukin-1 was increased at 3 days, while superoxide dismutase, interleukin-6, and tumor necrosis factor-α showed no statistical changes. H&E staining demonstrated that the cornea was edematous at 3 days and exhibited slower proliferation at 30 days. The choroid showed a consistently significant thickening, while there existed no noticeable changes in retinal thickness. Overall, 4073 proteins were identified, among which 71 and 119 proteins were detected to have significant difference at 3 days and 40 days when compared with the control group. Functional enrichment analysis found the differentiated proteins at 3 days exposure functionally related with response to radiation, dephosphorylation, negative regulation of cell adhesion, and erythrocyte homeostasis. Moreover, the differential profiles of the proteins at 40 days exposure exhibited changes of regulation of complement activation, regulation of protein activation cascade, regulation of humoral immune response, second-messenger-mediated signaling, regulation of leukocyte activation, and cellular iron homeostasis. Interestingly, we found the ocular proteins with lactylation modification were increased along high-altitude adaptation.

CONCLUSION

This is the first work reporting the ocular proteomic and morphological changes at real high-altitude environment. We expect it would deep the understanding of ocular response during altitude acclimatization.

Structure-Function Relationships in the Rodent Streptozotocin-Induced Model for Diabetic Retinopathy: A Systematic Review

The streptozotocin (STZ)-induced rodent model is one of the most commonly employed models in preclinical drug discovery for diabetic retinopathy (DR). However, standardization and validation of experimental readouts are largely lacking. The aim of this systematic review was to identify and compare the most useful readouts of STZ-induced DR and provide recommendations for future study design based on our findings. We performed a systematic search using 2 major databases, PubMed and EMBASE. Only articles describing STZ-induced DR describing both functional and structural readouts were selected. We also assessed the risk of bias and analyzed qualitative data in the selected studies. We identified 21 studies that met our inclusion/exclusion criteria, using either rats or mice and study periods of 2 to 24 weeks. Glucose level thresholds used to define hyperglycemia were inconsistent between studies, however, most studies used either 250 or 300.6 mg/dL as a defining criterion for hyperglycemia. All included studies performed electroretinography (ERG) and reported a reduction in a-, b-, or c-wave and/or oscillatory potential amplitudes. Spectral-domain optical coherence tomography and fluorescein angiography, as well as immunohistochemical and histopathological analyses showed reductions in retinal thickness, vascular changes, and presence of inflammation. Risk of bias assessment showed that all studies had a high risk of bias due to lack of reporting or correctly following procedures. Our systematic review highlights that ERG represents the most consistent functional readout in the STZ model. However, due to the high risk of bias, caution must be used when interpreting these studies.

Aldehyde Dehydrogenase 2 as a Therapeutic Target in Oxidative Stress-Related Diseases: Post-Translational Modifications Deserve More Attention

Aldehyde dehydrogenase 2 (ALDH2) has both dehydrogenase and esterase activity; its dehydrogenase activity is closely related to the metabolism of aldehydes produced under oxidative stress (OS). In this review, we recapitulate the enzyme activity of ALDH2 in combination with its protein structure, summarize and show the main mechanisms of ALDH2 participating in metabolism of aldehydes in vivo as comprehensively as possible; we also integrate the key regulatory mechanisms of ALDH2 participating in a variety of physiological and pathological processes related to OS, including tissue and organ fibrosis, apoptosis, aging, and nerve injury-related diseases. On this basis, the regulatory effects and application prospects of activators, inhibitors, and protein post-translational modifications (PTMs, such as phosphorylation, acetylation, S-nitrosylation, nitration, ubiquitination, and glycosylation) on ALDH2 are discussed and prospected. Herein, we aimed to lay a foundation for further research into the mechanism of ALDH2 in oxidative stress-related disease and provide a basis for better use of the ALDH2 function in research and the clinic.

Neuroprotective effects of Alda-1 mitigate spinal cord injury in mice: involvement of Alda-1-induced ALDH2 activation-mediated suppression of reactive aldehyde mechanisms

Spinal cord injury (SCI) is associated with high production and excessive accumulation of pathological 4-hydroxy-trans-2-nonenal (4-HNE), a reactive aldehyde, formed by SCI-induced metabolic dysregulation of membrane lipids. Reactive aldehyde load causes redox alteration, neuroinflammation, neurodegeneration, pain-like behaviors, and locomotion deficits. Pharmacological scavenging of reactive aldehydes results in limited improved motor and sensory functions. In this study, we targeted the activity of mitochondrial enzyme aldehyde dehydrogenase 2 (ALDH2) to detoxify 4-HNE for accelerated functional recovery and improved pain-like behavior in a male mouse model of contusion SCI. N-(1,3-benzodioxol-5-ylmethyl)-2,6-dichlorobenzamide (Alda-1), a selective activator of ALDH2, was used as a therapeutic tool to suppress the 4-HNE load. SCI was induced by an impactor at the T9–10 vertebral level. Injured animals were initially treated with Alda-1 at 2 hours after injury, followed by once-daily treatment with Alda-1 for 30 consecutive days. Locomotor function was evaluated by the Basso Mouse Scale, and pain-like behaviors were assessed by mechanical allodynia and thermal algesia. ALDH2 activity was measured by enzymatic assay. 4-HNE protein adducts and enzyme/protein expression levels were determined by western blot analysis and histology/immunohistochemistry. SCI resulted in a sustained and prolonged overload of 4-HNE, which parallels with the decreased activity of ALDH2 and low functional recovery. Alda-1 treatment of SCI decreased 4-HNE load and enhanced the activity of ALDH2 in both the acute and the chronic phases of SCI. Furthermore, the treatment with Alda-1 reduced neuroinflammation, oxidative stress, and neuronal loss and increased adenosine 5′-triphosphate levels stimulated the neurorepair process and improved locomotor and sensory functions. Conclusively, the results provide evidence that enhancing the ALDH2 activity by Alda-1 treatment of SCI mice suppresses the 4-HNE load that attenuates neuroinflammation and neurodegeneration, promotes the neurorepair process, and improves functional outcomes. Consequently, we suggest that Alda-1 may have therapeutic potential for the treatment of human SCI. Animal procedures were approved by the Institutional Animal Care and Use Committee (IACUC) of MUSC (IACUC-2019-00864) on December 21, 2019.

ALDH2/SIRT1 Contributes to Type 1 and Type 2 Diabetes-Induced Retinopathy through Depressing Oxidative Stress

Clinical observations found vision-threatening diabetic retinopathy (DR) occurs in both type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) patients, but T1DM may perform more progressive retinal abnormalities at the same diabetic duration with or without clinical retinopathy. In the present study, T1DM and T2DM patients without manifestations of DR were included in our preliminary clinical retrospective observation study to investigate the differentiated retinal function at the preclinical stage. Then, T1DM and T2DM rat models with 12-week diabetic duration were constructed to explore the potential mechanism of the discrepancy in retinal disorders. Our data demonstrated T1DM patients presented a poor retinal function, a higher allele frequency for ALDH2GA/AA, and a depressed aldehyde dehydrogenase 2 (ALDH2) activity and silent information regulator 1 (SIRT1) level, compared to T2DM individuals. In line with this, higher amplitudes of neurovascular function-related waves of electroretinograms were found in T2DM rats. Furthermore, the retinal outer nuclear layers were reduced in T1DM rats. The levels of retinal oxidative stress biomarkers including total reactive oxygen species, NADPH oxidase 4 and mitochondrial DNA damage, and inflammatory indicators covering inducible/endothelial nitric acid synthase ratio, interleukin-1, and interleukin-6 were obviously elevated. Notably, the level of retinal ALDH2 and SIRT1 in T1DM rats was significantly diminished, while the expression of neovascularization factors was dramatically enhanced compared to T2DM. Together, our data indicated that the ALDH2/SIRT1 deficiency resulted in prominent oxidative stress and was in association with DR progression. Moreover, a differentiating ALDH2/SIRT1 expression may be responsible for the dissimilar severity of DR pathological processes in chronic inflammatory-related T1DM and T2DM.

Protective effect of aldehyde dehydrogenase 2 against rat corneal dysfunction caused by streptozotocin-induced type I diabetes

Aldehyde dehydrogenase 2 plays a pivotal role in detoxifying aldehydes, and our previous study revealed that aldehyde dehydrogenase 2 could alleviate diabetic retinopathy-associated damage. We aimed to characterize the potential role of aldehyde dehydrogenase 2 in diabetic keratopathy. Twenty-four rats with streptozotocin-induced (60 mg/kg, single intraperitoneal injection) type 1 diabetes mellitus (T1DM) were divided the T1DM group and the T1DM + Alda1 (an activator of aldehyde dehydrogenase 2) group (5 mg/kg/d, intraperitoneal injection, 1/2/3 months), while an additional 12 healthy rats served as the control group. Corneal morphology was examined in vivo and in vitro at one, two, and three months after T1DM induction. Additionally, serum inflammatory factors were measured by ELISA, and the expression of corneal vascular endothelial growth factor A (VEGF-A) and aldehyde dehydrogenase 2 was measured by immunofluorescence staining. Corneal cell death was evaluated by terminal-deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) staining. Slit lamp analysis showed that the area of corneal epithelial cell injury in the T1DM + Alda1 group was significantly smaller than that in the T1DM group at one and two months after T1DM induction (all P < 0.05). OCT analysis and HE staining showed that the central corneal thickness (indication of corneal edema) and the epithelial keratinization level in the T1DM + Alda1 group was evidently decreased compared with those in the T1DM group (all P < 0.05). The serum inflammatory factors interleukin-1 and interleukin-6 were significantly upregulated in the T1DM group compared with the T1DM + Alda1 group at three months after T1DM induction (all P < 0.05), while there were no differences in SOD or TNF-α levels among all groups. Furthermore, corneal VEGF-A expression and corneal cell death in the T1DM + Alda1 group were dramatically reduced compared to those in the T1DM group (all P < 0.05). In conclusion, the aldehyde dehydrogenase 2 agonist Alda1 attenuated rat corneal dysfunction induced by T1DM by alleviating corneal edema, decreasing corneal cell death, and downregulating corneal VEGF-A expression.

MicroRNA-93-5p participates in type 2 diabetic retinopathy through targeting Sirt1

OBJECTIVE

To investigate the role of miR-93-5p in rats with type 2 diabetic retinopathy (DR) through targeting Sirt1.

METHODS

The targeting correlation between miR-93-5p and Sirt1 was validated by dual-luciferase reporter gene assay. Type 2 diabetes mellitus (T2DM) rat models were received intravitreal injection of antagomir NC (negative control), miR-93-5p antagomir, miR-93-5p agomir and/or recombinant Sirt1, followed by observation of pathological changes in retina via HE staining. Besides, retinal vascular permeability was determined by fluorescein isothiocyanate-bovine serum albumin (FITC-BSA), while the retinal vasculature was observed through retinal trypsin digestion. Expression of miR-93-5p and Sirt1 was measured by qRT-PCR and Western blotting, while the levels of VEGF, proinflammatory cytokines and anti-oxidative indicators were determined using corresponding kits.

RESULTS

MiR-93-5p could target Sirt1 as analyzed by the luciferase reporter gene assay. Rats in the T2DM group presented the up-regulation of miR-93-5p and down-regulation of Sirt1 in the retina, and miR-93-5p inhibition could up-regulate Sirt1 expression in the T2DM rats. Recombinant Sirt1 decreased retinal vascular permeability and acellular capillaries with improved pathological changes in retina from T2DM rats, which was abolished by miR-93-5p agomir. Moreover, miR-93-5p inhibition or Sirt1 overexpression decreased the levels of VEGF and proinflammatory cytokines while enhancing the activity of anti-oxidative indicators. However, indicators above had no significant differences between T2DM group and T2DM + agomir + Sirt1 group.

CONCLUSION

MiR-93-5p, via targeting Sirt1, could affect the vascular permeability and acellular capillaries and mitigate the inflammation and oxidative stress in the retinas, which may play a critical role in DR.

Evaluation of the neuronal and microvascular components of the macula in patients with diabetic retinopathy

PURPOSE

To investigate whether abnormal retinal microcirculation correlates with retinal neuronal changes in untreated diabetic eyes without macular edema.

METHODS

This study enrolled 29 diabetic patients without diabetic retinopathy (DR), 18 patients with mild non-proliferative diabetic retinopathy (NPDR), 15 patients with moderate NPDR, 14 patients with severe NPDR, 27 patients with proliferative diabetic retinopathy (PDR), and 25 healthy control subjects. Pattern electroretinography (PERG) and optical coherence tomography angiography (OCT-A) tests were performed.

RESULTS

Differences in the mean values for the area, acircularity index, and perimeter of foveal avascular zone were statistically significant between the healthy control group and the diabetic patients (P  < 0.05 for all). P50 and N95 amplitudes were statistically significantly lower in the PDR group compared to diabetic patients without DR, control, and moderate NPDR groups (P  < 0.05 for all). The whole retina vessel densities in superficial and deep capillary plexus were lower in the PDR group compared to the diabetic patients without DR and control group (P < 0.05 for all). There were statistically significant positive correlations between the amplitudes of the P50 and N95 waves with the vessel densities.

CONCLUSION

The existence of significant correlations between PERG and OCT-A parameters in diabetic patients has shown that vascular and neuronal changes in the macula affect each other in diabetic patients.

GSNOR and ALDH2 alleviate traumatic spinal cord injury

Traumatic spinal cord injury (SCI) enhances the activity of S-nitrosoglutathione reductase (GSNOR) and inhibits the mitochondrial aldehyde dehydrogenase 2 (ALDH2) activity, resulting in prolonged and sustained pain and functional deficits. This study's objective was to test the hypotheses that GSNOR's specific inhibitor N6022 mitigates pain and improves functional recovery in a mouse model of SCI. Furthermore, the degree of recovery is enhanced and the rate of recovery is accelerated by an ALDH2 activator Alda-1. Using both wild-type and GSNOR^-/^- mice, the SCI model deployed for groups was contusion at the T9-T10 vertebral level. The enzymatic activity of GSNOR and ALDH2 was measured, and the expression of GSNOR and ALDH2 was determined by western blot analysis. Functional improvements in experimental animals were assessed with locomotor, sensorimotor, and pain-like behavior tests. Wild-type SCI animals had enhanced GSNOR activity and decreased ALDH2 activity, leading to neurovascular dysfunction, edema, and worsened functional outcomes, including locomotor deficits and pain. Compared to wild-type SCI mice, GSNOR^-/^- mice had better functional outcomes. Monotherapy with either GSNOR inhibition by N6022 or enhanced ALDH2 activity by Alda-1 correlated well with functional recovery and lessened pain. However, combination therapy provided synergistic pain-relieving effects and more significant functional recovery compared with monotherapy. Conclusively, dysregulations in GSNOR and ALDH2 are among the causative mechanisms of SCI injury. Either inhibiting GSNOR or activating ALDH2 ameliorates SCI. Combining the specific inhibitor of GSNOR (N6022) with the selective activator of ALDH2 (Alda-1) provides greater protection to the neurovascular unit and confers greater functional recovery. The study is novel, and the combination therapy (N6022 + Alda-1) possesses translational potential.

Silencing of miR-20b-5p Exerts Inhibitory Effect on Diabetic Retinopathy via Inactivation of THBS1 Gene Induced VEGF/Akt/PI3K Pathway

INTRODUCTION

Diabetic retinopathy (DR) is a damaging complication of the eye. Studies investigating molecular mechanisms of DR are lacking, leading to poor clinical outcomes. miR-20b-5p is up-regulated in DR. The present study aimed to confirm the involvement of miR-20b-5p in DR and the mechanism involved.

METHODS

Microarray analysis was done to study the differentially expressed miRs. DR model was established using Sprague-Dawley rats, the expression of miR-20b-5p was altered using inhibitor or mimic as treatment. THBS1 was one of the potential genes identified by microarray bioinformatics analysis associated with DR. The expression of THBS1 was suppressed by siRNA to study the mechanism behind involvement of miR-20b-5p in DR. In addition, the levels of miR-20b-5p VEGF/PI3K/Akt pathway associated genes were studied. Correlation between THBS1 and miR-20b-5p was evaluated. Cell apoptosis, growth and tube formation assay was performed.

RESULTS

The retinal tissues of DR rats showed over-expressed miR-20b-5p and decreased THBS1 via VEGF/PI3K/Akt cascade. THBS1 was confirmed as the target gene of miR-20b-5p by dual-luciferase reporter gene assay. Upregulation of miR-20b-5p or knockdown of THBS1 caused increased tube formation and cell proliferation, whereas it blocked the cell apoptosis of endothelial cells in rats.

CONCLUSION

The outcomes suggested that silencing of miR-20b-5p resulted in inhibition of tube formation and cell growth in vascular endothelial cells of rats subjected to DR altering the VEGF/PI3K/Akt cascade by up-regulation of THBS1.

ALDH2 protects naturally aged mouse retina via inhibiting oxidative stress-related apoptosis and enhancing unfolded protein response in endoplasmic reticulum

During the process of aging, the retina exhibits chronic oxidative stress (OS) damage. Our preliminary experiment showed that acetaldehyde dehydrogenase 2 (ALDH2) could alleviate retinal damage caused by OS. This study aimed to explore whether ALDH2 could inhibit mice retinal cell apoptosis and enhance the function of unfolded protein response in endoplasmic reticulum (UPRER) through reducing OS in aging process. Retinal function and structure in vivo and in vitro were examined in aged ALDH2+ overexpression mice and ALDH2 agonist Alda1-treated aged mice. Levels of ALDH2, endoplasmic reticulum stress (ERS), apoptosis and inflammatory cytokines were evaluated. Higher expression of ALDH2 was observed at the outer nuclear layer (ONL) and the inner nuclear layer (INL) in aged ALDH2+ overexpression and aged Alda1-treated mice. Moreover, aged ALDH2+ overexpression mice and aged Alda1-treated mice exhibited better retinal function and structure. Increased expression of glucose-regulated protein 78 (GRP78) and ERS-related protein phosphorylated eukaryotic initiation factor 2 (peIF2α) and decreased expression of apoptosis-related protein, including C/EBP homologous protein (CHOP), caspase12 and caspase9, and retinal inflammatory cytokines were detected in the retina of aged ALDH2+ overexpression mice and aged Alda1-treated mice. The expression of ALDH2 in the retina was decreased in aging process. ALDH2 could reduce retinal oxidative stress and apoptosis, strengthen UPRER during the aging process to improve retinal function and structure.

Inflammatory cells proliferate in the choroid and retina without choroidal thickness change in early Type 1 diabetes

Increasing evidence points to inflammation as a key factor in the pathogenesis of diabetic retinopathy (DR). Choroidal inflammatory changes in diabetes have been reported and in vivo choroidal thickness (CT) has been searched as a marker of retinopathy with contradictory results. We aimed to investigate the early stages in the retina and choroid in an animal model of Type 1 diabetes. Type 1 diabetes was induced in male Wistar rats via a single i.p. streptozotocin injection. At 8 weeks after disease onset, CT, choroidal vascular density, VEGF and VEGFR2 expression, microglial cell and pericyte distribution were evaluated. Diabetic rats showed no significant change in CT and choroidal vascular density. A widened pericyte-free gap between the retinal pigment epithelium and the choroid was observed in diabetic rats. The immunoreactivity of VEGFR2 was decreased in the retina of diabetic rats, despite no statistically significant difference in the immunoreactivity of VEGF. The density of microglial cells significantly increased in the choroid and retina of diabetic rats. Reactive microglial cells were found to be more abundant in the choroid of diabetic rats. Evidences of the interconnection between the superficial, intermediate, and deep plexuses of the retina were also observed. At early stages, Type 1 diabetes does not affect choroidal thickness and choroidal vascular density. Proliferation and reactivity of microglial cells occurs in the choroidal stroma and the retina. The expression of VEGFR2 decreases in the retina.

MiR-221/SIRT1/Nrf2 signal axis regulates high glucose induced apoptosis in human retinal microvascular endothelial cells

Background

Diabetic retinopathy (DR) is a serious symptom associated with diabetes and could cause much suffer to patients. MiR-221, SIRT1 and Nrf2 were associated with apoptosis and proliferation and their expression were altered in DR patients. However, their roles and regulatory mechanisms in human retinal microvascular endothelial cells (hRMEC) were not clear.

Methods

Expression of mRNA was detected by qRT-PCR. Protein expression was detected by Western blot. Interaction between miR-221 and SIRT1 was predicted by bioinformatics analysis and validated by dual-luciferase reporter assay. We analyzed the viability and apoptosis of hRMEC by MTT assay and FACS assay, respectively.

Results

High glucose (HG) treatment enhanced expression of miR-221 and inhibited expression of SIRT1 and Nrf2. MiR-221 overexpression promoted apoptosis under HG condition. Moreover, miR-221 directly interacted with mRNA of SIRT1 and inhibited SIRT1 expression in hRMEC, through which miR-221 inhibited Nrf2 pathway and induced apoptosis of hRMEC.

Conclusion

Our data demonstrated that miR-221/SIRT1/Nrf2 signal axis could promote apoptosis in hRMEC under HG conditions. This finding could provide theoretical support for future studies and may contribute to development of new treatment options to retard the process of DR development.

Potential Protective and Therapeutic Roles of the Nrf2 Pathway in Ocular Diseases: An Update

Nuclear factor- (erythroid-derived 2-) like 2 (Nrf2) is a regulator of many processes of life, and it plays an important role in antioxidant, anti-inflammatory, and antifibrotic responses and in cancer. This review is focused on the potential mechanism of Nrf2 in the occurrence and development of ocular diseases. Also, several Nrf2 inducers, including noncoding RNAs and exogenous compounds, which control the expression of Nrf2 through different pathways, are discussed in ocular disease models and ocular cells, protecting them from dysfunctional changes. Therefore, Nrf2 might be a potential target of protecting ocular cells from various stresses and preventing ocular diseases.

Protection of retinal function and morphology in MNU-induced retinitis pigmentosa rats by ALDH2: an in-vivo study

BACKGROUND

Retinitis pigmentosa (RP) is a kind of inherited retinal degenerative diseases characterized by the progressive loss of photoreceptors. RP has been a conundrum without satisfactory countermeasures in clinic until now. Acetaldehyde dehydrogenase 2 (ALDH2), a major enzyme involved in aldehyde detoxification, has been demonstrated to be beneficial for a growing number of human diseases, such as cardiovascular dysfunction, diabetes mellitus and neurodegeneration. However, its protective effect against RP remains unknown. Our study explored the impact of ALDH2 on retinal function and structure in N-methyl-N-nitrosourea (MNU)-induced RP rats.

METHODS

Rats were gavaged with 5 mg/kg Alda-1, an ALDH2 agonist, 5 days before and 3 days after MNU administration. Assessments of retinal function and morphology as well as measurement of specific proteins expression level were conducted.

RESULTS

Electroretinogram recordings showed that Alda-1 administration alleviated the decrease in amplitude caused by MNU, rendering protection of retinal function. Mitigation of photoreceptor degeneration in MNU-treated retinas was observed by optical coherence tomography and retinal histological examination. In addition, Western blotting results revealed that ALDH2 protein expression level was upregulatedwith increased expression of SIRT1 protein after the Alda-1 intervention. Besides, endoplasmic reticulum stress (ERS) was reduced according to the significant downregulation of GRP78 protein, while apoptosis was ameliorated as shown by the decreased expression of PARP1 protein.

CONCLUSIONS

Together, our data demonstrated that ALDH2 could provide preservation of retinal function and morphology against MNU-induced RP, with the underlying mechanism at least partly related to the modulation of SIRT1, ERS and apoptosis.

The Role of Lipoxidation in the Pathogenesis of Diabetic Retinopathy

Lipids can undergo modification as a result of interaction with reactive oxygen species (ROS). For example, lipid peroxidation results in the production of a wide variety of highly reactive aldehyde species which can drive a range of disease-relevant responses in cells and tissues. Such lipid aldehydes react with nucleophilic groups on macromolecules including phospholipids, nucleic acids, and proteins which, in turn, leads to the formation of reversible or irreversible adducts known as advanced lipoxidation end products (ALEs). In the setting of diabetes, lipid peroxidation and ALE formation has been implicated in the pathogenesis of macro- and microvascular complications. As the most common diabetic complication, retinopathy is one of the leading causes of vision loss and blindness worldwide. Herein, we discuss diabetic retinopathy (DR) as a disease entity and review the current knowledge and experimental data supporting a role for lipid peroxidation and ALE formation in the onset and development of this condition. Potential therapeutic approaches to prevent lipid peroxidation and lipoxidation reactions in the diabetic retina are also considered, including the use of antioxidants, lipid aldehyde scavenging agents and pharmacological and gene therapy approaches for boosting endogenous aldehyde detoxification systems. It is concluded that further research in this area could lead to new strategies to halt the progression of DR before irreversible retinal damage and sight-threatening complications occur.

Epigenetic Regulation Associated With Sirtuin 1 in Complications of Diabetes Mellitus

Diabetes mellitus (DM) has been one of the largest health concerns of the 21st century due to the serious complications associated with the disease. Therefore, it is essential to investigate the pathogenesis of DM and develop novel strategies to reduce the burden of diabetic complications. Sirtuin 1 (SIRT1), a nicotinamide adenosine dinucleotide (NAD⁺)-dependent deacetylase, has been reported to not only deacetylate histones to modulate chromatin function but also deacetylate numerous transcription factors to regulate the expression of target genes, both positively and negatively. SIRT1 also plays a crucial role in regulating histone and DNA methylation through the recruitment of other nuclear enzymes to the chromatin. Furthermore, SIRT1 has been verified as a direct target of many microRNAs (miRNAs). Recently, numerous studies have explored the key roles of SIRT1 and other related epigenetic mechanisms in diabetic complications. Thus, this review aims to present a summary of the rapidly growing field of epigenetic regulatory mechanisms, as well as the epigenetic influence of SIRT1 on the development and progression of diabetic complications, including cardiomyopathy, nephropathy, and retinopathy.

Relationships Between Neurodegeneration and Vascular Damage in Diabetic Retinopathy

Diabetic retinopathy (DR) is a common complication of diabetes and constitutes a major cause of vision impairment and blindness in the world. DR has long been described exclusively as a microvascular disease of the eye. However, in recent years, a growing interest has been focused on the contribution of neuroretinal degeneration to the pathogenesis of the disease, and there are observations suggesting that neuronal death in the early phases of DR may favor the development of microvascular abnormalities, followed by the full manifestation of the disease. However, the mediators that are involved in the crosslink between neurodegeneration and vascular changes have not yet been identified. According to our hypothesis, vascular endothelial growth factor (VEGF) could probably be the most important connecting link between the death of retinal neurons and the occurrence of microvascular lesions. Indeed, VEGF is known to play important neuroprotective actions; therefore, in the early phases of DR, it may be released in response to neuronal suffering, and it would act as a double-edged weapon inducing both neuroprotective and vasoactive effects. If this hypothesis is correct, then any retinal stress causing neuronal damage should be accompanied by VEGF upregulation and by vascular changes. Similarly, any compound with neuroprotective properties should also induce VEGF downregulation and amelioration of the vascular lesions. In this review, we searched for a correlation between neurodegeneration and vasculopathy in animal models of retinal diseases, examining the effects of different neuroprotective substances, ranging from nutraceuticals to antioxidants to neuropeptides and others and showing that reducing neuronal suffering also prevents overexpression of VEGF and vascular complications. Taken together, the reviewed evidence highlights the crucial role played by mediators such as VEGF in the relationship between retinal neuronal damage and vascular alterations and suggests that the use of neuroprotective substances could be an efficient strategy to prevent the onset or to retard the development of DR.

Fushiming Capsule Attenuates Diabetic Rat Retina Damage via Antioxidation and Anti-Inflammation

AIMS

Diabetic retinopathy (DR) remains one of the leading causes of acquired blindness. Fushiming capsule (FSM), a compound traditional Chinese medicine, is clinically used for DR treatment in China. The present study was to investigate the effect of FSM on retinal alterations, inflammatory response, and oxidative stress triggered by diabetes.

MAIN METHODS

Diabetic rat model was induced by 6-week high-fat and high-sugar diet combined with 35 mg/kg streptozotocin (STZ). 30 days after successful establishment of diabetic rat model, full field electroretinography (ffERG) and optical coherence tomography (OCT) were performed to detect retinal pathological alterations. Then, FSM was administered to diabetic rats at different dosages for 42-day treatment and diabetic rats treated with Calcium dobesilate (CaD) capsule served as the positive group. Retinal function and structure were observed, and retinal vascular endothelial growth factor-α (VEGF-α), glial fibrillary acidic (GFAP), and vascular cell adhesion protein-1 (VCAM-1) expressions were measured both on mRNA and protein levels, and a series of blood metabolic indicators were also assessed.

KEY FINDINGS

In DR rats, FSM (1.0 g/kg and 0.5 g/kg) treatment significantly restored retinal function (a higher amplitude of b-wave in dark-adaptation 3.0 and OPs2 wave) and prevented the decrease of retinal thickness including inner nuclear layer (INL), outer nuclear layer (ONL), and entire retina. Additionally, FSM dramatically decreased VEGF-α, GFAP, and VCAM-1 expressions in retinal tissues. Moreover, FSM notably improved serum antioxidative enzymes glutathione peroxidase, superoxide dismutase, and catalase activities, whereas it reduced serum advanced glycation end products, methane dicarboxylic aldehyde, nitric oxide, and total cholesterol and triglycerides levels.

SIGNIFICANCE

FSM could ameliorate diabetic rat retina damage possibly via inhibiting inflammation and improving antioxidation.

Colonic electrical stimulation improves colonic transit in rotenone-induced Parkinson's disease model through affecting enteric neurons

AIMS

The aims of this study were to investigate the effect of colonic electrical stimulation (CES) on delayed colonic transit in Parkinson's disease (PD) model induced by rotenone and its possible mechanisms.

MAIN METHODS

Sprague-Dawley male rats were implanted with a pair of electrodes on the serosa at the proximal colon and rotenone was subcutaneously injected for 6 weeks to induce the PD model. Behavior activity, stool volume and open-field test were recorded during the injection. Colonic propulsion rate was measured 6 weeks after rotenone injection. Colon samples of all rats were collected for the measurement of phosphorylated alpha-synuclein, choline acetyltransferase (CHAT), neuronal nitric oxide synthase (nNOS), and tyrosine hydroxylase (TH). The protocols of control rats were the same as the PD rats except that no electrodes were implanted and no rotenone was injected.

KEY FINDINGS

(1) Rotenone-induced PD rats demonstrated weight loss, significant decrease of the dopaminergic neurons in substantia nigra, and impairment of colon movement. (2) CES significantly accelerated the delayed colonic transmit (91.67 ± 5.58% vs 51.33 ± 4.18%), superior to Macrogol-4000. (3) CES significantly upregulated the expression of CHAT, nNOS and TH protein in colon of PD rats. (4) In colon of PD rats, the phosphorylated alpha-synuclein was significantly upregulated, but CES had no significant effect on phosphorylated alpha-synuclein.

SIGNIFICANCE

Our data show that CES can normalize the delayed colonic transit and this normalization may attribute to affecting enteric excitatory and inhibitory neurons.

MicroRNA-183 inhibition exerts suppressive effects on diabetic retinopathy by inactivating BTG1-mediated PI3K/Akt/VEGF signaling pathway

Diabetic retinopathy (DR) is a serious diabetic complication caused by both environmental and genetic factors. Molecular mechanisms of DR may lead to the discovery of reliable prognostic indicators. The current study aimed to clarify the mechanism of microRNA-183 (miR-183) in DR in relation to the PI3K/Akt/VEGF signaling pathway. Microarray-based gene expression profiling of DR was used to identify the differentially expressed genes. Sprague-Dawley rats were used for the establishment of DR models, and then miR-183 was altered by mimic or inhibitor or BTG1 was downregulated by siRNA to explore the regulatory mechanism of miR-183 in DR. Furthermore, the expression of miR-183, CD34, endothelial nitric oxide synthase (eNOS), BTG1 and the PI3K/Akt/VEGF signaling pathway-related genes as well as reactive oxygen species (ROS) level was determined, and the relationship between miR-183 and BTG1 was also verified. Cell growth, cell apoptosis, and angiogenesis were determined. Microarray analysis revealed the involvement of miR-183 in DR via the PI3K/Akt/VEGF signaling pathway by targeting BTG1. Upregulated miR-183 and downregulated BTG1 were observed in retinal tissues of DR rats. miR-183 overexpression activated the PI3K/Akt/VEGF signaling pathway, upregulated CD34, eNOS, and ROS, and inhibited BTG1. BTG1 was confirmed as a target gene of miR-183. miR-183 overexpression or BTG1 knockdown promoted cell growth and tube formation while it suppressed cell apoptosis of vascular endothelial cells in DR rats. In this study, we demonstrated that miR-183 silencing inhibiting cell growth and tube formation in vascular endothelial cells of DR rats via the PI3K/Akt/VEGF signaling pathway by upregulating BTG1.

Protective effects of hydrogen gas in a rat model of branch retinal vein occlusion via decreasing VEGF-α expression

BACKGROUND

Oxidative stress (OS) is an essential factor in the pathogenesis of branch retinal vein occlusion (BRVO). Studies have demonstrated the role of hydrogen gas in the regulation of OS. This study was designed to evaluate the efficacy of hydrogen gas on the BRVO rat model.

METHODS

Twenty-four BRVO rats were randomly divided into two groups: the hydrogen gas (H) group (42% H2, 21% O2, 37% N2) and the model (M) group (21% O2, 79% N2). Rats in the H group inhaled hydrogen gas for 8 h every day up to 30 d post-occlusion. Twelve age-matched healthy rats served as the control (C) group. Retinal function and morphology were detected at 1, 7, 14 and 30 d post-occlusion. Furthermore, the expression of vascular endothelial growth factor (VEGF-α) was detected by immunofluorescent staining.

RESULTS

Full-field electroretinography (ffERG) revealed that the amplitude of the b-wave (dark-adaptation 3.0 response), the amplitude of the OPs2 wave and the light-adapted flicker response in the H group were all higher than those in the M group at 7 d post-occlusion (all p < 0.05). The reopen time of occlusive retinal vessels in the H group was 2.235 ± 1.128 d, which was shorter than that in the M group (4.234 ± 2.236 d, p < 0.05). The rats in the H group had a thinner IPL + GCL + NFL and an increased total retina compared with those in the M group at 3 d post-occlusion (p < 0.05), while the rats in the H group had a thicker INL, IPL + GCL + NFL and total retina compared with those at 7, 14 and 30 d post-occlusion (p < 0.05). Moreover, the flow velocity of ear vein blood was increased in the H group compared with that in the M group (p < 0.05). The expression of VEGF-α in the H group was dramatically decreased compared with that in the M group at 1, 7 and 14 d post-occlusion (p < 0.05), while the expression kept in similar level at 30 d post-occlusion (p > 0.05).

CONCLUSIONS

Our findings demonstrate that inhalation of hydrogen gas could alleviate retinal oedema, shorten reopen time and improve retinal function, and the potential mechanism might be related to a decrease in VEGF-α expression.