Scutellarin alleviates blood-retina-barrier oxidative stress injury initiated by activated microglia cells during the development of diabetic retinopathy

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.

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.

Food therapy of scutellarein ameliorates pirarubicin‑induced cardiotoxicity in rats by inhibiting apoptosis and ferroptosis through regulation of NOX2‑induced oxidative stress

Pirarubicin (THP) is one of the most commonly used antineoplastic drugs in clinical practice. However, its clinical application is limited due to its toxic and heart‑related side effects. It has been reported that oxidative stress, inflammation and apoptosis are closely associated with cardiotoxicity caused by pirarubicin (CTP). Additionally, it has also been reported that scutellarein (Sc) exerts anti‑inflammatory, antioxidant, cardio‑cerebral vascular protective and anti‑apoptotic properties. Therefore, the present study aimed to investigate the effect of food therapy with Sc on CTP and its underlying molecular mechanism using echocardiography, immunofluorescence, western blot, ROS staining, and TUNEL staining. The in vivo results demonstrated that THP was associated with cardiotoxicity. Additionally, abnormal changes in the expression of indicators associated with oxidative stress, ferroptosis and apoptosis were observed, which were restored by Sc. Therefore, it was hypothesized that CTP could be associated with oxidative stress, ferroptosis and apoptosis. Furthermore, the in vitro experiments showed that Sc and the NADPH oxidase 2 (NOX2) inhibitor, GSK2795039 (GSK), upregulated glutathione peroxidase 4 (GPX4) and inhibited THP‑induced oxidative stress, apoptosis and ferroptosis. However, cell treatment with the ferroptosis inhibitor, ferrostatin‑1, or inducer, erastin, could not significantly reduce or promote, respectively, the expression of NOX2. However, GSK significantly affected ferroptosis and GPX4 expression. Overall, the results of the present study indicated that food therapy with Sc ameliorated CTP via inhibition of apoptosis and ferroptosis through regulation of NOX2‑induced oxidative stress, thus suggesting that Sc may be a potential therapeutic drug against CTP.

Redox Regulation of Immunometabolism in Microglia Underpinning Diabetic Retinopathy

Diabetic retinopathy (DR) is the leading cause of visual impairment and blindness among the working-age population. Microglia, resident immune cells in the retina, are recognized as crucial drivers in the DR process. Microglia activation is a tightly regulated immunometabolic process. In the early stages of DR, the M1 phenotype commonly shifts from oxidative phosphorylation to aerobic glycolysis for energy production. Emerging evidence suggests that microglia in DR not only engage specific metabolic pathways but also rearrange their oxidation-reduction (redox) system. This redox adaptation supports metabolic reprogramming and offers potential therapeutic strategies using antioxidants. Here, we provide an overview of recent insights into the involvement of reactive oxygen species and the distinct roles played by key cellular antioxidant pathways, including the NADPH oxidase 2 system, which promotes glycolysis via enhanced glucose transporter 4 translocation to the cell membrane through the AKT/mTOR pathway, as well as the involvement of the thioredoxin and nuclear factor E2-related factor 2 antioxidant systems, which maintain microglia in an anti-inflammatory state. Therefore, we highlight the potential for targeting the modulation of microglial redox metabolism to offer new concepts for DR treatment.

Scutellarin Alleviates Diabetic Retinopathy via the Suppression of Nucleotide-Binding Oligomerization Domain (NOD)-Like Receptor Pyrin Domain Containing Protein 3 Inflammasome Activation

PURPOSE

Diabetic retinopathy, a prevalent complication of diabetes, represents the leading cause of vision loss and blindness among middle-aged and elderly populations. Recent research has demonstrated the ameliorating effects of scutellarin on diabetes-associated complications such as diabetic retinopathy and type 2 diabetic cardiomyopathy. However, investigations into its protective impact and underlying mechanisms on diabetic retinopathy are scant. This study aims to explore the therapeutic potential of scutellarin in diabetic retinopathy treatment.

METHODS

Diabetic retinopathy was induced in rats through intraperitoneal injections of streptozotocin (STZ, 60 mg/kg) administered daily for three consecutive days. Following this, diabetic retinopathy rats received daily intragastric administration of scutellarin (40 mg/kg) for 42 days.

RESULTS

Our findings suggest that scutellarin alleviates histological damage in the retinal tissues of streptozotocin-challenged rats. Furthermore, scutellarin effectively enhances total retinal thickness and increases the number of ganglion cell layer (GCL) cells in the retinal tissues of streptozotocin-treated rats. Scutellarin also demonstrated anti-inflammatory and antioxidant effects in the retinal tissues of STZ-induced rats, as indicated by reduced levels of tumor necrosis factor-α, interleukin-1β, and interleukin-6, and elevated levels of glutathione peroxidase, superoxide dismutase, and catalase. Additionally, scutellarin effectively inhibited the expression of NOD-like receptor pyrin domain containing protein 3 inflammasome-related markers in the retinal tissues of streptozotocin-administered rats.

CONCLUSIONS

Collectively, our results indicate that scutellarin significantly reduces streptozotocin-induced retinal inflammation, an effect that may be partially attributed to the suppression of NLRP3 inflammasome activation.

Quercetin protects against hyperglycemia-induced retinopathy in Sprague Dawley rats by regulating the gut-retina axis and nuclear factor erythroid-2-related factor 2 pathway

Hyperglycemia-related retinopathy is a disease with a high blindness rate. Recent reports indicate that many flavonol compounds have the potential to prevent the occurrence of disease in the retina by regulating the gut-retina axis. Here, we hypothesized that quercetin could alleviate the symptoms of retinopathy. To clarify the mechanism, Sprague Dawley rats were fed a high-fat diet containing quercetin for 12 weeks and injected with streptozotocin in the ninth week. Additionally, neomycin and ampicillin were used to establish a pseudo-sterile rat model. Afterward, changes in the retina were investigated by using electroretinogram and optical coherence tomography. Blood and tissue samples were collected and biochemical components were analyzed. The extent of intestinal injury was determined via hematoxylin-eosin staining. Microbial community structure was analyzed by using 16S ribosomal RNA sequencing. Finally, the expression of genes was analyzed using real-time polymerase chain reaction. The results showed that quercetin reduced the decline in electroretinography amplitude and outer nuclear layer thickness, increased the activities of antioxidant enzymes, decreased the contents of proinflammatory factors and blood glucose, enhanced the concentration of insulin, and inhibited intestinal dysbiosis and improved gut morphology. Importantly, the underexpression of nuclear factor erythroid-2 related factor 2 in the retina was reversed by quercetin. However, trend changes were no longer significant in most of the indicators after antibiotic treatment. In summary, quercetin has therapeutic effects on retinopathy by regulating the gut-retina axis and nuclear factor erythroid-2 related factor 2 pathway, and the presence of gut microbiota helps quercetin exert its effects on the retina.

Therapeutic potential of elema-1,3,7(11),8-tetraen-8,12-lactam from Curcuma wenyujin on diabetic retinopathy via anti-inflammatory and anti-angiogenic pathways

ETHNOPHARMACOLOGICAL RELEVANCE

In traditional Chinese medicine, the causes of diabetic retinopathy (DR) are blood stasis and heat. Curcuma wenyujin Y. H. Chen & C. Ling and its extracts have the effects of promoting blood circulation to remove blood stasis, clearing the heart, and cooling the blood, and have been used in the treatment of DR. Elema-1,3,7 (11),8-tetraen-8,12-lactam (Ele), an N-containing sesquiterpene isolated from this plant. However, the anti-inflammatory and anti-angiogenic effects of Ele and its therapeutic potential in DR are still unknown.

AIM OF THE STUDY

To evaluate the anti-inflammatory and anti-angiogenic effects of Ele and its therapeutic potential in DR.

MATERIALS AND METHODS

In vitro, anti-inflammatory and anti-angiogenic effects were assessed using TNF-α or VEGF-stimulated HUVECs. Protein expression was analyzed using Western blotting. ICAM-1 and TNF-α mRNA expressions were analyzed using real-time quantitative RT-PCR. The therapeutic potential in DR was assessed using both animal models of STZ-induced diabetes and oxygen-induced retinopathy. The retinal vascular permeability was measured using Evans blue, and the quantitation of retinal leukostasis using FITC-coupled Con A. The retinal neovascular tufts were analyzed using fluorescein angiography and counting pre-retinal vascular lumens.

RESULTS

Ele inhibited NF-κB pathway, and ICAM-1, TNF-α mRNA expression in TNF-α- stimulated HUVECs. It also inhibits the multistep process of angiogenesis by inhibiting the phosphorylation of VEGFR2 and its downstream signaling kinases Src, Erk1/2, Akt, and mTOR in VEGF-stimulated HUVECs. Intravitreal injection of Ele can significantly reduce retinal microvascular leakage, leukostasis, and expression of ICAM-1, TNF-α in diabetic rats and inhibits oxygen-induced retinal neovascularization and VEGFR2 phosphorylation in OIR mice.

CONCLUSIONS

Ele has anti-inflammatory and anti-angiogenic effects through inhibiting NF-κB and VEGFR2 signaling pathways, and it may be a potential drug candidate for DR.

Alleviate oxidative stress in diabetic retinopathy: antioxidant therapeutic strategies

OBJECTIVES

This review outlines the function of oxidative stress in DR and discusses therapeutic strategies to treat DR with antioxidants.

METHODS

Published papers on oxidative stress in DR and therapeutic strategies to treat DR with antioxidants were collected and reviewed via database searching on PubMed.

RESULTS

The abnormal development of DR is a complicated process. The pathogenesis of DR has been reported to involve oxidative stress, despite the fact that the mechanisms underlying this are still not fully understood. Excessive reactive oxygen species (ROS) accumulation can damage retina, eventually leading to DR. Increasing evidence have demonstrated that antioxidant therapy can alleviate the degeneration of retinal capillaries in DR.

CONCLUSION

Oxidative stress can play an important contributor in the pathogenesis of DR. Furthermore, animal experiments have shown that antioxidants are a beneficial therapy for treating DR, but more clinical trial data is needed.

Flavonoids improve type 2 diabetes mellitus and its complications: a review

The prevalence of type 2 diabetes mellitus (T2DM) is increasing every year. Medications are currently the most common therapy for T2DM. However, these medications have certain adverse effects. In order to find safe and effective ways to improve this disease, researchers have discovered that some natural products can decrease blood sugar. Flavonoids are one of the most essential low molecular weight phenolic chemicals in the plant world, which widely exist in plant roots, stems, leaves, flowers, and fruits. They possess a variety of biological activities, including organ protection, hypoglycemic, lipid-lowering, anti-oxidative and anti-inflammatory effects. Some natural flavonoids ameliorate T2DM and its complications through anti-oxidation, anti-inflammatory action, glucose and lipid metabolism regulation, insulin resistance management, etc. Hence, this review aims at demonstrating the potential benefits of flavonoids in T2DM and its complications. This laid the foundation for the development of novel hypoglycemic medications from flavonoids.

Network pharmacology mechanism of Scutellarin to inhibit RGC pyroptosis in diabetic retinopathy

To investigate the effect of scutellarin (SCU) in diabetic retinopathy (DR) and explore the associated molecular network mechanism. The animal model of DR was established from diabetic mellitus (DM) rats by intraperitoneally injected streptozotocin (STZ) at dosage 55 mg/kg. Meanwhile, SCU was intraperitoneally administrated to protect retina from cell pyroptosis induced by DM, and cell pyroptosis was detected by using HE, Nissl staining, and immunofluorescence recognition. Moreover, the hub gene involving in pyroptosis in DR was screened by bioinformatics and network pharmacology, designated as Venny intersection screen, GO and KEGG analysis, PPI protein interaction, and molecular docking. Lastly, the expressional change of hub genes were validated with experimental detection. Cell pyroptosis of the DR, specifically in retina ganglion cells (RGC), was induced in DM rats; SCU administration results in significant inhibition in the cell pyroptosis in DR. Mechanically, 4084 genes related to DR were screened from GeneCards and OMIM databases, and 120 SCU therapeutic targets were obtained, by using GeneCards, TCMSP with Swiss Target Prediction databases. Moreover, 357 targets related to pyroptosis were found using GenenCards database, and Drug, disease and phenotypic targets were analyzed online using the Draw Venn Diagram website, and 12 cross targets were obtained. Through GO function and KEGG pathway enrichment analysis, 659 BP related items, 7 CC related items, 30 MF related items, and 70 signal pathways were screened out; Of these, eleven proteins screened from cross-target PPI network were subsequently docked with the SCU, and their expressions including caspase-1, IL-1β, IL-18, GSDMD and NLRP3 in RGC indicated by immunofluorescence, and the mRNA expression for caspase-1 in DR indicated by quantitative PCR, were successfully validated. SCU can effectively protect RGC pyroptosis in DR, and underlying mechanisms are involved in the inhibition of caspase-1, GSDMD, NLRP3, IL-1β and IL-18. Our findings therefore provide crucial evidence to support the clinic practice of SCU for the treatment of DR, and explained the underlying molecular network mechanism.

Effects of diabetes on microglial physiology: a systematic review of in vitro, preclinical and clinical studies

Diabetes mellitus is a heterogeneous chronic metabolic disorder characterized by the presence of hyperglycemia, commonly preceded by a prediabetic state. The excess of blood glucose can damage multiple organs, including the brain. In fact, cognitive decline and dementia are increasingly being recognized as important comorbidities of diabetes. Despite the largely consistent link between diabetes and dementia, the underlying causes of neurodegeneration in diabetic patients remain to be elucidated. A common factor for almost all neurological disorders is neuroinflammation, a complex inflammatory process in the central nervous system for the most part orchestrated by microglial cells, the main representatives of the immune system in the brain. In this context, our research question aimed to understand how diabetes affects brain and/or retinal microglia physiology. We conducted a systematic search in PubMed and Web of Science to identify research items addressing the effects of diabetes on microglial phenotypic modulation, including critical neuroinflammatory mediators and their pathways. The literature search yielded 1327 records, including 18 patents. Based on the title and abstracts, 830 papers were screened from which 250 primary research papers met the eligibility criteria (original research articles with patients or with a strict diabetes model without comorbidities, that included direct data about microglia in the brain or retina), and 17 additional research papers were included through forward and backward citations, resulting in a total of 267 primary research articles included in the scoping systematic review. We reviewed all primary publications investigating the effects of diabetes and/or its main pathophysiological traits on microglia, including in vitro studies, preclinical models of diabetes and clinical studies on diabetic patients. Although a strict classification of microglia remains elusive given their capacity to adapt to the environment and their morphological, ultrastructural and molecular dynamism, diabetes modulates microglial phenotypic states, triggering specific responses that include upregulation of activity markers (such as Iba1, CD11b, CD68, MHC-II and F4/80), morphological shift to amoeboid shape, secretion of a wide variety of cytokines and chemokines, metabolic reprogramming and generalized increase of oxidative stress. Pathways commonly activated by diabetes-related conditions include NF-κB, NLRP3 inflammasome, fractalkine/CX3CR1, MAPKs, AGEs/RAGE and Akt/mTOR. Altogether, the detailed portrait of complex interactions between diabetes and microglia physiology presented here can be regarded as an important starting point for future research focused on the microglia-metabolism interface.

The role of the mTOR pathway in diabetic retinopathy

The retina, the part of the eye, translates the light signal into an electric current that can be sent to the brain as visual information. To achieve this, the retina requires fine-tuned vascularization for its energy supply. Diabetic retinopathy (DR) causes alterations in the eye vascularization that reduce the oxygen supply with consequent retinal neurodegeneration. During DR, the mammalian target of rapamycin (mTOR) pathway seems to coordinate retinal neurodegeneration with multiple anabolic and catabolic processes, such as autophagy, oxidative stress, cell death, and the release of pro-inflammatory cytokines, which are closely related to chronic hyperglycemia. This review outlines the normal anatomy of the retina and how hyperglycemia can be involved in the neurodegeneration underlying this disease through over activation or inhibition of the mTOR pathway.

Scutellarin suppresses triple-negative breast cancer metastasis by inhibiting TNFα-induced vascular endothelial barrier breakdown

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer with high vascularity and frequent metastasis. Tumor-associated abnormal vasculature was reported to accelerate TNBC metastasis. Scutellarin (SC) is a natural flavonoid with a cardiovascular protective function. In this study, SC reduced TNBC metastasis and alleviated tumor-associated vascular endothelial barrier injury in vivo. SC rescued the tumor necrosis factor-α (TNFα)-induced diminishment of endothelial junctional proteins and dysfunction of the endothelial barrier in vitro. SC reduced the increased transendothelial migration of TNBC cells through a monolayer composed of TNFα-stimulated human mammary microvascular endothelial cells (HMMECs) or human umbilical vein endothelial cells (HUVECs). TNFα induced the nuclear translocation of enhancer of zeste homolog-2 (EZH2), and its chemical inhibitor GSK126 blocked TNFα-induced endothelial barrier disruption and subsequent TNBC transendothelial migration. TNF receptor 2 (TNFR2) is the main receptor by which TNFα regulates endothelial barrier breakdown. Extracellular signal-regulated protein kinase (ERK)1/2 was found to be downstream of TNFα/TNFR2 and upstream of EZH2. Additionally, SC abrogated the TNFR2-ERK1/2-EZH2 signaling axis both in vivo and in vitro. Our results suggest that SC reduced TNBC metastasis by suppressing TNFα-initiated vascular endothelial barrier breakdown through rescuing the reduced expression of junctional proteins by regulating the TNFR2-ERK1/2-EZH2 signaling pathway.

Sesamin protects against neurotoxicity via inhibition of microglial activation under high glucose circumstances through modulating p38 and JNK signaling pathways

Diabetes mellitus (DM), one of the principal causes of morbidity and mortality worldwide, is implicated in the progression of age-related neurodegenerative diseases (NDDs), in which microglial activation is a crucial mediator. Sesamin, a kind of phytochemical, shows inhibitory effects on microglial activation. The present study studied whether sesamin protects against neurotoxicity triggered by high glucose-induced microglial activation. We firstly demonstrated that high doses of glucose, which mimics hyperglycemia in DM, did induce the activation of murine BV2 microglial cells, increasing inflammatory responses such as the production of ROS or inflammatory mediators like IL-1β, TNF-⍺, and nitric oxide, through activation of p38 and JNK signaling pathways. Next, conditioned medium (CM) collected from high glucose-activated BV2 cell culture was used to show aggravated neurotoxicity in differentiated PC12 cells, indicating that high glucose-activated microglia could induce neurotoxicity. Interestingly, pretreatment of BV2 cells with sesamin diminished high glucose-induced microglia activation and inflammatory responses. Moreover, neurotoxicity in PC12 cells was found to be decreased in the group treated with CM from the sesamin-pretreated BV2 cell culture, suggesting sesamin inhibited microglial activation, thereby protecting neurons from activated microglia-mediated neurotoxicity. Thus, sesamin might be a potential compound to use in the prevention of diabetic-induced NDDs.

Scutellarin protects the kidney from ischemia/reperfusion injury by targeting Nrf2

BACKGROUND

Acute kidney injury (AKI) results in high morbidity and mortality among inpatients, while effective treatment and intervention are still absent. Therefore, this study aims to explore the effects of Scutellarin (Scu) in experimental models in vivo and in vitro.

METHODS

In vivo experiment, we employed a total of 30 Wistar rats, which further were modelled by a bilateral renal pedicle clip for 45 min, then received 50 mg/kg/day Scu. In vitro, HK-2 cells were administered with 20μΜ Scu and then incubated in hypoxia/reoxygenation (H/R) conditions for 24 h. The knockdown of Nrf2 expression was conducted by small interfering RNA (siRNA) transfection.

RESULTS

As a result, the AKI model was well established with an increased SCr, BUN, KIM-1 level, and histological injury score, while Scu treatment reduced the levels above and increased the antioxidative enzyme HO-1. H/R induced an increase of ROS in HK-2 cells, while Scu decreased the ROS level. Bioinformatics results showed the transcription factor Nrf2 was a hub protein during the AKI, which also bound to Scu with low binding energy, indicating that the downstream effect of Scu might be mediated by Nrf2. To verify the suppose above, we employed siRNA against Nrf2, which shows a significant increase in ROS after Nrf2 was blocked. Meanwhile, the HO-1 showed similar expression compared with the 'H/R + Nrf2 siRNA' and 'H/R + Nrf2 siRNA + Scu' group, implying the protective effect of Scu was mediated by the Nrf2/HO-1 pathway.

CONCLUSION

Scu led to up-regulation of HO-1 through activating the Nrf2 signalling pathway, protecting the kidneys from ischemia/reperfusion (I/R)-induced oxidative damage.

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

BACKGROUND

Oxidative stress-induced cell ferroptosis occurs during the pathogenesis of diabetic retinopathy (DR), but the detailed molecular mechanisms are still unclear. The present study aimed to investigate this issue.

MATERIALS AND METHODS

The retinal pigment epithelium (RPE) was treated with high glucose (30 mM) in vitro to mimic the realistic conditions of DR progression in vivo. Cell viability was determined by MTT assay and trypan blue staining assay. Gene expressions were examined by Real-Time qPCR and Western Blot analysis. FCM was used to detect cell apoptosis and ROS generation. Dual-luciferase reporter gene system assay was used to verify the targeting sites.

RESULTS

High glucose increased reactive oxygen species (ROS) levels, promoted cell ferroptosis, and suppressed cell proliferation and viability in RPE, which were reversed by co-treating cells with both a ferroptosis inhibitor ferrostatin-1 and an ROS scavenger, N-acetyl-L-Cysteine (NAC). In addition, we screened out a miR-338-3p/ASCT2 (SLC1A5) axis that played an important role in this process. Mechanistically, miR-338-3p targeted the 3' untranslated regions (3'UTR) of SLC1A5 for its inhibition and degradation, and high glucose downregulated SLC1A5 by upregulating miR-338-3p in RPE cells. Next, the miR-338-3p inhibitor and SLC1A5 overexpression vectors were delivered into the RPE cells, and the following gain- and loss-of-function experiments validated that both miR-338-3p ablation and SLC1A5 upregulation abrogated the regulating effects of high glucose on cell proliferation, viability, ferroptosis and ROS production in RPE cells.

CONCLUSIONS

Collectively, data in the present study indicated that targeting the miR-338-3p/SLC1A5 axis could block high glucose-induced ferroptosis in RPE cells.

Serum Iba-1, GLUT5, and TSPO in Patients With Diabetic Retinopathy: New Biomarkers for Early Retinal Neurovascular Alterations? A Pilot Study

Purpose

This study explored the possibility of highlighting early retinal neurovascular alterations of diabetic retinopathy (DR) by monitoring in DR patients the serum levels of microglial biomarkers ionized calcium-binding adapter molecule 1 (Iba-1), glucose transporter 5 (GLUT5), and translocator protein (TSPO), along with serum changes of the endothelial dysfunction marker arginase-1.

Methods

Serum markers were determined by enzyme-linked immunosorbent assay in 50 patients: 12 non-diabetic subjects, 14 diabetic patients without DR, 13 patients with non-proliferative DR (NPDR), and 11 patients with proliferative DR (PDR). The results were correlated with hyperreflective retinal spots (HRS), observed with optical coherence tomography (OCT).

Results

Although HRS were absent in diabetic patients without DR, NPDR patients showed an average of 4 ± 1 HRS, whereas the highest presence was detected in PDR patients, with 8 ± 1 HRS (P < 0.01 vs. NPDR). HRS were positively correlated (P < 0.01) with serum levels of arginase-1 (r = 0.91), Iba-1 (r = 0.96), GLUT5 (r = 0.94), and TSPO (r = 0.88). Moreover, serum proinflammatory cytokines and chemokines showed a positive correlation (P < 0.01) with HRS number and the serum markers analyzed.

Conclusions

Serum markers of microglial activation positively correlate with retinal HRS in NPDR and PDR patients.

Translational Relevance

These data corroborate the possibility of highlighting early retinal neurovascular changes due to diabetes by monitoring circulating microglial markers.

Si-Miao-Yong-An Decoction for Diabetic Retinopathy: A Combined Network Pharmacological and In Vivo Approach

Si-Miao-Yong-An decoction (SMYAD), a traditional Chinese medicine formula, is mainly used to clear away heat and detoxify and to promote blood circulation and relieve pain. Diabetic retinopathy (DR) is the most common type of microvascular complication caused by diabetes. This study is designed to examine the protective effect of SMYAD against DR and further to reveal the engaged mechanism via integrating network pharmacology and in vivo experimental evidence. Streptozotocin (STZ) was intraperitoneally injected into mice to induce diabetes. The dysfunction of the blood retina barrier (BRB) was observed by conducting Evan's blue leakage assay, detecting tight junction (TJ) protein expression and counting the number of acellular capillaries in retinas. Our results showed that SMYAD alleviated BRB breakdown in vivo. Network pharmacology results demonstrated that regulating inflammation, immune responses, and angiogenesis might be associated with the efficacy of SMYAD in alleviating DR, in which the tumor necrosis factor (TNF) and hypoxia inducible factor 1 (HIF1) signal pathways were involved. Next, immunofluorescence staining results showed that SMYAD decreased microglia activation in retinas and reduced the enhanced adhesion of leukocytes into retinal vessels. SMYAD reduced the elevated serum TNFα content and retinal TNFα expression. SMYAD abrogated the activation of nuclear factor κB (NFκB) and HIF1α and consequently decreased the enhanced expression of some pro-inflammatory molecules and vascular endothelial growth factor (VEGF) in retinas. These results indicate that SMYAD attenuated DR development through suppressing retinal inflammation and angiogenesis via abrogating NFκB-TNFα and HIF1α-VEGF signal pathways.

Early Microglial Changes Associated with Diabetic Retinopathy in Rats with Streptozotocin-Induced Diabetes

Although morphological changes in microglia have been reported to be associated with diabetic retinopathy, little is known about the early changes in the microglia and macrophages during the progression of this condition. The present study was aimed at characterizing retinal microglial activation in the early stages of experimental diabetic retinopathy. Toward this end, a model of diabetic retinopathy was generated by intraperitoneally injecting male Sprague-Dawley rats with streptozotocin. No apparent histological changes were observed during the early stages of experimental diabetic retinopathy. However, at 4 to 16 weeks after the onset of diabetes, the retinas from diabetic rats exhibited higher density of microglia than those from age-matched normal controls, with microglial density peaking at 12 weeks. In particular, the proportion of the activated microglia increased significantly in the diabetic rats, specifically in the nerve fiber and ganglion cell layers, whereas it decreased in the inner plexiform layer within 12 weeks. Furthermore, the resident retinal microglial cells were activated immediately after diabetes induction, peaked at 12 weeks, and remained for up to 16 weeks after disease onset. Thus, experimental diabetic retinopathy causes gradual hypoxia and neuroinflammation, followed by the activation of microglia and the migration of macrophages. The distribution and density of retinal microglial activation changed typically with the progression of the disease in early-stage diabetic rats.

Scutellarin alleviates type 2 diabetes (HFD/low dose STZ)-induced cardiac injury through modulation of oxidative stress, inflammation, apoptosis and fibrosis in mice

BACKGROUND

Diabetes is a serious global health concern which severely affected public health as well as socio-economic growth worldwide. Scutellarin (SCU), a bioactive flavonoid, is known for its efficacious action against a range of ailments including cardiovascular problems. The present study was conducted to find out possible protective effect and its associated mechanisms of SCU on experimental type 2 diabetes-induced cardiac injury.

METHODS

Type 2 diabetes was induced by treating animals with high fat diet for 4 weeks and a single intraperitoneal dose (35 mg/kg body weight) of streptozotocin and diabetic animals received SCU (10 or 20 mg/kg/day) for 6 weeks.

RESULTS

Scutellarin attenuated type 2 diabetes-induced hyperglycemia, bodyweight loss, hyperlipidaemia, cardiac functional damage with histopathological alterations and fibrosis. Scutellarin treatment to type 2 diabetic mice ameliorated oxidative stress, inflammatory status and apoptosis in heart. Furthermore, the underlying mechanisms for such mitigation of oxidative stress, inflammation and apoptosis in heart involved modulation of Nrf2/Keap1 pathway, TLR4/MyD88/NF-κB mediated inflammatory pathway and intrinsic (mitochondrial) apoptosis pathway, respectively.

CONCLUSIONS

The current findings suggest that SCU is effective in protecting type 2 diabetes-induced cardiac injury by attenuating oxidative stress and inflammatory responses and apoptosis, and it is also worth considering the efficacious potential of SCU to treat diabetic cardiomyopathy patients.

Advances in Chemical Constituents, Clinical Applications, Pharmacology, Pharmacokinetics and Toxicology of Erigeron breviscapus

Dengzhanxixin (DZXX), the dried whole plant of Erigeron breviscapus (Vaniot) Hand.-Mazz., belonging to Compositae and first published in Materia Medica of South Yunnan by Lan Mao in the Ming Dynasty (1368 AD–1644 AD), is included in Medicinal Materials and Decoction Pieces of the 2020 edition of the Pharmacopeia of the People’s Republic of China. Its main chemical components are flavonoids that mainly include flavonoid, flavonols, dihydroflavones, flavonol glycosides, flavonoid glycosides, coffee acyl compounds, and other substances, such as volatile oil compounds, coumarins, aromatic acids, pentacyclic terpenoids, phytosterols, and xanthones. Among them, scutellarin and 1,5-dicoffeoylquininic acid are the main active components of DZXX. DZXX has pharmacological effects, such as improving cerebral and cerebrovascular ischemia, increasing blood flow, inhibiting platelet aggregation, promoting antithrombotic formation, improving microcirculation, reducing blood viscosity, protecting optic nerves, exhibiting anti-inflammatory properties, scavenging free radicals, and eliciting antioxidant activities. It is widely used in the treatment of cardiovascular and cerebrovascular ischemic diseases, kidney diseases, liver diseases, diabetic complications, and glaucoma. Pharmacokinetic studies have shown that the active components of DZXX have a low bioavailability and a high elimination rate in vivo. Nevertheless, its utilization can be improved through liposome preparation and combination with other drugs. Acute and subacute toxicity studies have shown that DZXX is a safe medicinal material widely used in clinical settings. However, its target and drug action mechanism are unclear because of the complexity of its composition. In this paper, the clinical application and pharmacological toxicology of DZXX are reviewed to provide a reference for further studying its active components and action mechanism.

Oral Scutellarin Treatment Ameliorates Retinal Thinning and Visual Deficits in Experimental Glaucoma

Purpose: Intraocular pressure (IOP) is currently the only modifiable risk factor for glaucoma, yet glaucoma can continue to progress despite controlled IOP. Thus, development of glaucoma neurotherapeutics remains an unmet need. Scutellarin is a flavonoid that can exert neuroprotective effects in the eye and brain. Here, we investigated the neurobehavioral effects of scutellarin treatment in a chronic IOP elevation model. Methods: Ten adult C57BL/6J mice were unilaterally injected with an optically clear hydrogel into the anterior chamber to obstruct aqueous outflow and induce chronic IOP elevation. Eight other mice received unilateral intracameral injection of phosphate-buffered saline only. Another eight mice with hydrogel-induced unilateral chronic IOP elevation also received daily oral gavage of 300 mg/kg scutellarin. Tonometry, optical coherence tomography, and optokinetics were performed longitudinally for 4 weeks to monitor the IOP, retinal nerve fiber layer thickness, total retinal thickness, visual acuity, and contrast sensitivity of both eyes in all three groups. Results: Intracameral hydrogel injection resulted in unilateral chronic IOP elevation with no significant inter-eye IOP difference between scutellarin treatment and untreated groups. Upon scutellarin treatment, the hydrogel-injected eyes showed less retinal thinning and reduced visual behavioral deficits when compared to the untreated, hydrogel-injected eyes. No significant difference in retinal thickness or optokinetic measures was found in the contralateral, non-treated eyes over time or between all groups. Conclusion: Using the non-invasive measuring platform, oral scutellarin treatment appeared to preserve retinal structure and visual function upon chronic IOP elevation in mice. Scutellarin may be a novel neurotherapeutic agent for glaucoma treatment.

The Metaflammatory and Immunometabolic Role of Macrophages and Microglia in Diabetic Retinopathy

Emergent studies reveal the roles of inflammatory cells and cytokines in the development of diabetic retinopathy (DR), which is gradually portrayed as a chronic inflammatory disease accompanied by metabolic disorder. Through the pathogenesis of DR, macrophages or microglia play a critical role in the inflammation, neovascularization, and neurodegeneration of the retina. Conventionally, macrophages are generally divided into M1 and M2 phenotypes which mainly rely on glycolysis and oxidative phosphorylation, respectively. Recently, studies have found that nutrients (including glucose and lipids) and metabolites (such as lactate), can not only provide energy for cells, but also act as signaling molecules to regulate the function and fate of cells. In this review, we discussed the intrinsic correlations among the metabolic status, polarization, and function of macrophage/microglia in DR. Hyperglycemia and hyperlipidemia could induce M1-like and M2-like macrophages polarization in different phases of DR. Targeting the regulation of microglial metabolic profile might be a promising therapeutic strategy to modulate the polarization and function of macrophages/microglia, thus attenuating the progression of DR.

Asiatic acid attenuates diabetic retinopathy through TLR4/MyD88/NF-κB p65 mediated modulation of microglia polarization

AIM

This study aimed to evaluate the effects of Asiatic acid (AA), a naturally occurring compound of pentacyclic triterpenoid, on the pathological processes of diabetic retinopathy (DR).

METHODS

SD rats were induced to develop early DR by intraperitoneal injection of STZ (60 mg/kg). Four weeks after injection, the diabetic rats were orally administrated with 37.5 mg/kg or 75 mg/kg AA every day for four weeks. The integrity of blood-retinal barrier (BRB) was measured by Evans blue staining. The polarization of microglia was determined by real-time PCR, western blot, and ELISA assays. The inner BRB (iBRB) or outer BRB (oBRB) breakdown was induced in human retinal endothelial cells or APRE19 cells through co-culture with high glucose and LPS-stimulated microglia BV2 cells. The damage to the iBRB and oBRB was measured using transendothelial/transepithelial electrical resistance (TEER/TER) and FITC-conjugated dextran cell permeability assays.

KEY FINDINGS

Results demonstrated that AA alleviated BRB breakdown, as evidenced by decreased protein expression of occludin, claudin-5, and ZO-1. Furthermore, AA treatment suppressed inflammation and M1 polarization, while it increased M2 polarization in the retina of DR rats. In vitro, the iBRB or oBRB breakdown was alleviated by AA. LPS-induced M1-polarization of BV2 cells under high glucose condition was also repressed through AA administration. Finally, we demonstrated that AA weakened the TLR4/MyD88/NF-κB p65 signaling pathway both in vivo and in vitro.

SIGNIFICANCE

AA ameliorated early DR by regulating microglia polarization via the TLR4/MyD88/NF-κB p65 pathway. These data indicate that AA is a potential candidate for DR treatment.

Is Iba-1 protein expression a sensitive marker for microglia activation in experimental diabetic retinopathy?

AIM

To investigate the changes of Iba-1 and other potential markers for microglia activation in experimental diabetic retinopathy (DR).

METHODS

Male Sprague-Dawley rats were rendered diabetes via intraperitoneal injection of streptozotocin. The retinas were harvested at 1 to 24wk after diabetes onset. Hypoxia-treated mouse microglial cell line (BV2 cells) was employed as the in vitro model to mimic diabetic condition. The expressions of Iba-1, CD11b, ICAM-1 as well as the inflammatory factors were examined with real-time polymerase chain reaction, Western blot and immunofluorescence both in vivo and in vitro.

RESULTS

Compared with age-matched normal control, the number of microglia (Iba-1 positive immunostaining) in diabetic rat retinas was increased from 1 to 24wk of diabetes, which was most obvious at 12wk of diabetes. Iba-1 protein expression detected by Western blot was increased slightly in diabetic rat retinas compared with that in age-matched normal control; however, there was statistically significant between two groups only at 2wk after diabetes onset. The mRNA expression of Iba-1 was decreased significantly at 2 and 4wk of diabetic rat retinas, and remained unchanged at 8 and 12wk of diabetes. In BV2 cells, there was no significant change for the Iba-1 protein expression between normoxia and hypoxia groups; however, its mRNA level was decreased significantly under hypoxia. To further characterize microglial activation, F4/80, CD11b and inflammatory factors were detected both in vivo and in vitro. Compared with normal control, the expressions of F4/80 and CD11b as well as the inflammatory factors, such as ICAM-1, iNOS, COX2, IL-1β and IL-6, were increased significantly both in vivo and in vitro.

CONCLUSION

Iba-1 protein expression might not be a sensitive marker to evaluate the activation of microglia in experimental DR. However, Iba-1 immunostaining, in combination with other markers like CD11b and ICAM-1, could be well reflect the activation of microglia. Thus, it is of great importance to explore other potential marker to evaluate the activation of microglia.

Casein Kinase 2-Interacting Protein-1 Alleviates High Glucose-Reduced Autophagy, Oxidative Stress, and Apoptosis in Retinal Pigment Epithelial Cells via Activating the p62/KEAP1/NRF2 Signaling Pathway

Background

Casein kinase 2-interacting protein-1 (CKIP-1) has been proved to be associated with complications of diabetes. Diabetic retinopathy is a main diabetic complication which usually leads to blindness. The current study aims to investigate the role of CKIP-1 in high glucose-treated retinal pigment epithelial (RPE) cells which is a component of blood-retinal barriers.

Methods

The RPE cells, ARPE-19, are treated with high glucose to mimic the diabetic stimulation. CKIP-1 was overexpressed in ARPE-19 cells to evaluate its effects on autophagy, oxidative stress, and apoptosis induced by high glucose treatment, using Western blot, immunofluorescence, and flow cytometry assays, respectively.

Results

CKIP-1 was expressed at a lower level in high glucose-treated cells than in normal glucose cells. Overexpression of CKIP-1 enhanced the Nrf2 translocation to the nucleus. Furthermore, high glucose-induced autophagy, oxidative stress, and apoptosis were inhibited after overexpression of CKIP-1. Also, CKIP-1 regulates the p62/Keap1/Nrf2 signaling, which might be the potential mechanism in this model.

Conclusion

In conclusion, CKIP-1 may be a potential therapeutic target that protects RPE cells from injury and subsequent diabetic retinopathy induced by high glucose.

Tectorigenin protect HUVECs from H2O2-induced oxidative stress injury by regulating PI3K/Akt pathway

Oxidative stress injury (OSI) occurs in many cardiovascular diseases, and the OSI of endothelial cells is the main pathological basis of these diseases. Tectorigenin has an effect on oxidative stress in fibroblasts, keratinocytes, and neuroblastoma. This study attempted to reveal the effect of Tectorigenin on OSI in endothelial cells. An OSI cell model was firstly established by treating human umbilical vein endothelial cells (HUVECs) with H₂O₂. The H₂O₂-induced HUVECs were further pre-treated with Tectorigenin or PI3K inhibitor. Then the viability and apoptosis of HUVECs were evaluated using MTT, Hochest 33258 staining and TUNEL staining. Lactate dehydrogenase (LDH) leakage, enzyme activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and malondialdehyde (MDA) level were measured through colorimetric assays. The expressions of apoptosis-related factors and the activation of the PI3K/Akt pathway in HUVECs were detected by RT-qPCR or Western blot. Tectorigenin had no inhibiting effect on the viability of HUVECs at the concentrations of 0.1, 0.5, 0.5, 1, and 10 μmol/L. Tectorigenin reversed the H₂O₂ induced-destruction of HUVECs morphology. Tectorigenin increased the viability and decreased the apoptosis of H₂O₂-induced HUVECs. Tectorigenin increased Bcl-2 expression and the enzyme activities of SOD and GSH-Px, but decreased LDH leakage, MDA level, and the expressions of Bax and Cleaved Caspase-3 in H₂O₂-induced HUVECs. Furthermore, Tectorigenin increased the ratios of p-PI3K to PI3K and p-Akt to Akt in H₂O₂-induced HUVECs. PI3K inhibitor had an opposite effect of Tectorigenin on the OSI in H₂O₂-induced HUVECs and its effect was further reversed by Tectorigenin. Tectorigenin protected HUVECs against H₂O₂-induced OSI via PI3K/Akt pathway.

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.

Scutellarein alleviates the dysfunction of inner blood-retinal-barrier initiated by hyperglycemia-stimulated microglia cells

AIM

To investigate the alleviation of scutellarein (SN) against inner blood-retinal-barrier (iBRB) dysfunction in microglia cells stimulated by hyperglycemia and to elucidate the engaged mechanism.

METHODS

Microglia BV2 cells were stimulated by using 25 mmol/L D-glucose. The same concentration of mannitol (25 mmol/L) was applied as an isotonic contrast. Real-time PCR, Western-blot assay and immunofluorescence staining assay was performed. The dysfunction of iBRB in vitro was detected by using transendothelial electrical resistance (TEER) assay. Additionally, the leakage of fluorescein isothiocyanate (FITC)-conjugated dextran (70 kDa) was detected.

RESULTS

SN abrogated microglia BV2 cells activation and reduced the phosphorylated activation of extracellular signal-regulated protein kinase (ERK)1/2. SN also decreased the transcriptional activation of nuclear factor κB (NFκB) and the elevated expression of tumor necrosis factor α (TNFα), interleukin (IL)-6 and IL-1β in BV2 cells treated with D-glucose (25 mmol/L). SN attenuated iBRB dysfunction in human retinal endothelial cells (HRECs) or choroid-retinal endothelial RF/6A cells when those cells were treated with TNFα, IL-1β or IL-6, or co-cultured with microglia cells stimulated by D-glucose. Moreover, SN restored the decreased protein expression of tight junctions (TJs) in TNFα-treated HRECs and RF/6A cells.

CONCLUSION

SN not only alleviate iBRB dysfunction via directly inhibiting retinal endothelial injury caused by TNFα, IL-1β or IL-6, but also reduce the release of TNFα, IL-1β and IL-6 from microglia cells by abrogating hyperglycemia-mediated the activation of microglia cells.

The Benefits of Flavonoids in Diabetic Retinopathy

Diabetic retinopathy (DR), one of the most common complications of diabetes, is the leading cause of legal blindness among adults of working age in developed countries. After 20 years of diabetes, almost all patients suffering from type I diabetes mellitus and about 60% of type II diabetics have DR. Several studies have tried to identify drugs and therapies to treat DR though little attention has been given to flavonoids, one type of polyphenols, which can be found in high levels mainly in fruits and vegetables, but also in other foods such as grains, cocoa, green tea or even in red wine. Flavonoids have anti-inflammatory, antioxidant and antiviral effects. Since it is known that diabetes induces oxidative stress and inflammation in the retina leading to neuronal death in the early stages of the disease, the use of these compounds can prove to be beneficial in the prevention or treatment of DR. In this review, we summarize the molecular and cellular effects of flavonoids in the diabetic retina.

Scutellarin attenuates hypoxia/reoxygenation injury in hepatocytes by inhibiting apoptosis and oxidative stress through regulating Keap1/Nrf2/ARE signaling

Scutellarin is a natural flavonoid that has been found to exhibit anti-ischemic effect. However, the effect of scutellarin on hepatic hypoxia/reoxygenation (ischemia-reperfusion (I/R)) injury remains unknown. The aim of the present study was to explore the protective effect of scutellarin on I/R-induced injury in hepatocytes. Our results showed that scutellarin improved cell viability in hepatocytes exposed to hypoxia/reoxygenation (H/R). Scutellarin treatment resulted in decreased levels of reactive oxygen species (ROS) and malondialdehyde (MDA), and increased superoxide dismutase (SOD) activity in H/R-induced hepatocytes. In addition, scutellarin reduced cell apoptosis in H/R-stimulated hepatocytes, as proved by the decreased apoptotic rate. Moreover, scutellarin significantly up-regulated bcl-2 expression and down-regulated bax expression in hepatocytes exposed to H/R. Furthermore, scutellarin treatment caused significant decrease in Keap1 expression and increase in nuclear Nrf2 expression. Besides, scutellarin induced the mRNA expressions of heme oxygenase-1 (HO-1) and NAD(P)H:quinone oxidoreductase 1 (NQO1). Inhibition of Nrf2 significantly reversed the protective effects of scutellarin on H/R-stimulated hepatocytes. In conclusion, these findings demonstrated that scutellarin protected hepatocytes from H/R-induced oxidative injury through regulating the Keap1/Nrf2/ARE signaling pathway, indicating a potential relevance of scutellarin in attenuating hepatic I/R injury.

Microglia mediated neuroinflammation - signaling regulation and therapeutic considerations with special reference to some natural compounds

Neuroinflammation plays a central role in multiple neurodegenerative diseases and neurological disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), cerebral ischemic injury etc. In this connection, microglia, the key players in the central nervous system, mediate the inflammatory response process. In brain injuries, activated microglia can clear the cellular debris and invading pathogens and release neurotrophic factors; however, prolonged microglia activation may cause neuronal death through excessive release of inflammatory mediators. Therefore, it is of paramount importance to understand the underlying molecular mechanisms of microglia activation to design an effective therapeutic strategy to alleviate neuronal injury. Recent studies have shown that some natural compounds and herbal extracts possess anti-inflammatory properties that may suppress microglial activation and ameliorate neuroinflammation and hence are neuroprotective. In this review, we will update some of the common signaling pathways that regulate microglia activation. Among the various signaling pathways, the Notch-1, mitogen-activated protein kinases (MAPKs), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) have been reported to exacerbate microglia mediated neuroinflammation that is implicated in different neuropathological diseases. The search for natural compounds or agents, specifically those derived from natural herbal extracts such as Gastrodin, scutellarin, RG1 etc. has been the focus of many of our recent studies because they have been found to regulate microglia activation. The pharmacological effects of these agents and their potential mechanisms for regulating microglia activation are systematically reviewed here for a fuller understanding of their biochemical action and therapeutic potential for treatment of microglia mediated neuropathological diseases.

Preventing diabetic retinopathy by mitigating subretinal space oxidative stress in vivo

Patients with diabetes continue to suffer from impaired visual performance before the appearance of overt damage to the retinal microvasculature and later sight-threatening complications. This diabetic retinopathy (DR) has long been thought to start with endothelial cell oxidative stress. Yet newer data surprisingly finds that the avascular outer retina is the primary site of oxidative stress before microvascular histopathology in experimental DR. Importantly, correcting this early oxidative stress is sufficient to restore vision and mitigate the histopathology in diabetic models. However, translating these promising results into the clinic has been stymied by an absence of methods that can measure and optimize anti-oxidant treatment efficacy in vivo. Here, we review imaging approaches that address this problem. In particular, diabetes-induced oxidative stress impairs dark-light regulation of subretinal space hydration, which regulates the distribution of interphotoreceptor binding protein (IRBP). IRBP is a vision-critical, anti-oxidant, lipid transporter, and pro-survival factor. We show how optical coherence tomography can measure subretinal space oxidative stress thus setting the stage for personalizing anti-oxidant treatment and prevention of impactful declines and loss of vision in patients with diabetes.

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.

Ginsenoside Rg1 prevents early diabetic retinopathy via reducing retinal ganglion cell layer and inner nuclear layer cell apoptosis in db/db mice

Background

Diabetic retinopathy (DR), a diabetic vascular complication, is prone to developing into blindness. Ginsenoside Rg1 (GRg1), a major saponin in ginseng, exerts high anti-apoptotic activity.

Methods

This study aimed to explore the protective effects of GRg1 against diabetes-induced retinal damage. Measurements of blood glucose, blood lipids and vascular permeability were performed, as well as assessments of pathological changes, and the retinal thickness of each layer. Retinal cell apoptosis related protein expression levels were measured by immunofluorescence and western blot assays.

Results

Our data demonstrated that GRg1 effectively reduced blood glucose and triglyceride levels and maintained normal retinal permeability and physiological structure. GRg1 maintained the thickness of the ganglion cell layer (GCL) and the inner nuclear layer (INL) by reducing cell apoptosis.

Conclusions

These data strongly indicate that GRg1 prevents diabetic retinal changes by decreasing GCL and INL cell apoptosis. GRg1 may be a promising drug for early DR treatment.

Endothelial tight junctions and their regulatory signaling pathways in vascular homeostasis and disease

Endothelial tight junctions (TJs) regulate the transport of water, ions, and molecules through the paracellular pathway, serving as an important barrier in blood vessels and maintaining vascular homeostasis. In endothelial cells (ECs), TJs are highly dynamic structures that respond to multiple external stimuli and pathological conditions. Alterations in the expression, distribution, and structure of endothelial TJs may lead to many related vascular diseases and pathologies. In this review, we provide an overview of the assessment methods used to evaluate endothelial TJ barrier function both in vitro and in vivo and describe the composition of endothelial TJs in diverse vascular systems and ECs. More importantly, the direct phosphorylation and dephosphorylation of TJ proteins by intracellular kinases and phosphatases, as well as the signaling pathways involved in the regulation of TJs, including and the protein kinase C (PKC), PKA, PKG, Ras homolog gene family member A (RhoA), mitogen-activated protein kinase (MAPK), phosphatidylinositol 3-kinase (PI3K)/Akt, and Wnt/β-catenin pathways, are discussed. With great advances in this area, targeting endothelial TJs may provide novel treatment for TJ-related vascular pathologies.

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.