Resveratrol blocks diabetes-induced early vascular lesions and vascular endothelial growth factor induction in mouse retinas

Diabetic Müller-Glial-Cell-Specific Il6ra Knockout Mice Exhibit Accelerated Retinal Functional Decline and Thinning of the Inner Nuclear Layer

Purpose

Interleukin-6 (IL-6) is implicated in the pathology of diabetic retinopathy (DR). IL-6 trans-signaling via soluble IL-6 receptor (IL-6R) is primarily responsible for its pro-inflammatory functions, whereas cis-signaling via membrane-bound IL-6R is anti-inflammatory. Using a Müller-glial-cell-specific Il6ra-/- mouse, we examined how loss of IL-6 cis-signaling in Müller glial cells (MGCs) affected retinal thinning and electroretinography (ERG) response over 9 months of diabetes.

Methods

Diabetes was induced in wildtype and knockout mice with streptozotocin (40 mg/kg, daily for 5 days). Spectral domain optical coherence tomography (SD-OCT), ERG, and fundoscopy/fluorescein angiography (FA) were assessed at 2, 6, and 9 months of diabetes. MGCs and bipolar neurons were examined in retinal tissue sections by immunofluorescence.

Results

Diabetic MGC Il6ra-/- mice had significantly thinner retinas than diabetic wildtype mice at 2 (-7.6 µm), 6 (-12.0 µm), and 9 months (-5.0 µm) of diabetes, as well as significant thinning of the inner nuclear layer (INL). Diabetic MGC Il6ra-/- mice also showed a reduction in scotopic B-wave amplitude and B-wave/A-wave ratio earlier than wildtype diabetic mice. In retinal sections, we found a decrease in bipolar neuronal marker PKCα only in diabetic MGC Il6ra-/- mice, which was significantly lower than both controls and diabetic wildtype mice. Glutamine synthetase, a Müller cell marker, was reduced in both wildtype and MGC Il6ra-/- diabetic mice compared to their respective controls.

Conclusions

IL-6 cis-signaling in MGCs contributes to maintenance of the INL in diabetes, and loss of the IL-6 receptor reduces MGC-mediated neuroprotection of bipolar neurons in the diabetic retina.

A Mediterranean Diet May Be Protective in the Development of Diabetic Retinopathy

The Mediterranean diet is recognized as one of the healthiest available dietary patterns. This perception results from its beneficial effects on the cardiovascular system and, also, on hypertension, diabetes, and cancer compared with other diets. Its impact on the course of diabetes is assessed in the available scientific literature; however, little information is available about its impact on diabetic retinopathy. The MD is characterized mainly by the consumption of fish, seafood, foods of plant origin, and fresh fruit and vegetables. It is also recommended to consume legumes, which are a source of folic acid, magnesium, iron, and dietary fiber. High consumption of nuts and unrefined grains is also recommended in the MD. Marine fish provide polyunsaturated acids from the omega-3 group. Olive oil plays a very important role, especially olive oil obtained from mechanical pressing. Additionally, olive oil contains vitamins E, K, and polyphenols. Polyphenols, which are present in a diverse range of vegetables, fruits, and seeds, have the ability to decrease oxidative stress, inflammation, and insulin resistance. Resveratrol is naturally found in grape skins and seeds, as well as in peanuts and berries, and is a constituent of red wine. Resveratrol can inhibit increased vascular leakage and loss of pericytes and regulate the level of VEGF protein in the retina, thus inhibiting the development of DR. Consumption of fruits, vegetables, fish, and olive oil may be correlated with a lower risk of diabetic retinopathy. This paper presents the definition of the Mediterranean diet and its influence on the course of diabetes and diabetic retinopathy.

Antioxidant Nutraceutical Strategies in the Prevention of Oxidative Stress Related Eye Diseases

This review aims to discuss the delicate balance between the physiological production of reactive oxygen species and the role of antioxidant nutraceutical molecules in managing radicals in the complex anatomical structure of the eye. Many molecules and enzymes with reducing and antioxidant potential are present in different parts of the eye. Some of these, such as glutathione, N-acetylcysteine, α-lipoic acid, coenzyme Q10, and enzymatic antioxidants, are endogenously produced by the body. Others, such as plant-derived polyphenols and carotenoids, vitamins B2, C, and E, zinc and selenium, and omega-3 polyunsaturated fatty acids, must be obtained through the diet and are considered essential nutrients. When the equilibrium between the production of reactive oxygen species and their scavenging is disrupted, radical generation overwhelms the endogenous antioxidant arsenal, leading to oxidative stress-related eye disorders and aging. Therefore, the roles of antioxidants contained in dietary supplements in preventing oxidative stress-based ocular dysfunctions are also discussed. However, the results of studies investigating the efficacy of antioxidant supplementation have been mixed or inconclusive, indicating a need for future research to highlight the potential of antioxidant molecules and to develop new preventive nutritional strategies.

Nutritional Factors: Benefits in Glaucoma and Ophthalmologic Pathologies

Glaucoma is a chronic optic neuropathy that can lead to irreversible functional and morphological damage if left untreated. The gold standard therapeutic approaches in managing patients with glaucoma and limiting progression include local drops, laser, and/or surgery, which are all geared at reducing intraocular pressure (IOP). Nutrients, antioxidants, vitamins, organic compounds, and micronutrients have been gaining increasing interest in the past decade as integrative IOP-independent strategies to delay or halt glaucomatous retinal ganglion cell degeneration. In our minireview, we examine the various nutrients and compounds proposed in the current literature for the management of ophthalmology diseases, especially for glaucoma. With respect to each substance considered, this minireview reports the molecular and biological characteristics, neuroprotective activities, antioxidant properties, beneficial mechanisms, and clinical studies published in the past decade in the field of general medicine. This study highlights the potential benefits of these substances in glaucoma and other ophthalmologic pathologies. Nutritional supplementation can thus be useful as integrative IOP-independent strategies in the management of glaucoma and in other ophthalmologic pathologies. Large multicenter clinical trials based on functional and morphologic data collected over long follow-up periods in patients with IOP-independent treatments can pave the way for alternative and/or coadjutant therapeutic options in the management of glaucoma and other ocular pathologies.

Resveratrol: Its Path from Isolation to Therapeutic Action in Eye Diseases

Due to the confirmed therapeutic potential of resveratrol (Rv) for eye diseases, namely its powerful anti-angiogenic and antioxidant effects, this molecule must be studied more deeply. Nowadays, the pharmaceutic and pharmacokinetic available studies offer a troubling picture because of its low stability and bioavailability. To overcome this problem, researchers started to design and create different delivery systems that could improve the delivery amount of Rv. Therefore, this review aims to shed light on the proper and efficient techniques to isolate, purify and quantify the Rv molecule, and how this therapeutic molecule can be a part of a delivery system. The Rv great impact on aspects regarding its stability, bioavailability and absorption are also debated here, based on the existent literature on in vitro and in vivo human and animal studies. Moreover, after its absorption the Rv influence at the molecular level in ocular pathologies is described. In addition, the present review summarizes the available literature about Rv, hoping that Rv will gain more attention to investigate its unexplored side.

The Protective Role of Apelin in the Early Stages of Diabetic Retinopathy

Diabetic retinopathy (DR) is one of the most common and serious microvascular complications of diabetes. Although current treatments can control the progression of DR to a certain extent, there is no effective treatment for early DR. Apart from vascular endothelial growth factor, it has been noted that the apelin/APJ system contributes to the pathogenesis of DR. We used a high-fat diet/streptozotocin-induced type 2 diabetic mouse model. The mice were divided into a lentivirus control group (LV-EGFP), an apelin-overexpression group (LV-Apelin+), and an apelin-knockdown group (LV-Apelin-), all of which were administrated intravitreal injections. LV-Apelin+ ameliorated the loss of pericytes in DR mice, whereas LV-Apelin- aggravated the loss of pericytes. Similarly, LV-Apelin+ reduced the leakage of retinal vessels, whereas LV-Apelin- exacerbated it. The genes and signaling pathway related to cell adhesion molecules were downregulated, whereas the cell-cell tight junctions and anti-apoptotic genes were upregulated in response to apelin overexpression. However, the alterations of these same genes and signaling pathways were reversed in the case of apelin knockdown. Additionally, LV-Apelin+ increased ZO-1 and occludin levels, whereas LV-Apelin- decreased them. Our results suggest that apelin can reduce vascular leakage by protecting pericytes, which offers a promising new direction for the early treatment of DR.

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.

Potential Roles of Anti-Inflammatory Plant-Derived Bioactive Compounds Targeting Inflammation in Microvascular Complications of Diabetes

Diabetes mellitus (DM) is a group of metabolic disorders, the characteristics of which include chronic hyperglycemia owing to defects in insulin function, insulin secretion, or both. Inflammation plays a crucial role in DM pathogenesis and innate immunity in the development of microvascular complications of diabetes. In addition, hyperglycemia and DM mediate a proinflammatory microenvironment that can result in various microvascular complications, including diabetic nephropathy (DNP), diabetic neuropathy (DN), and diabetic retinopathy (DR). DNP is a major cause of end-stage renal disease. DNP can lead to albuminuria, decreased filtration, mesangium expansion, thickening of the basement membrane, and eventually renal failure. Furthermore, inflammatory cells can accumulate in the interstitium and glomeruli to deteriorate DNP. DN is another most prevalent microvascular complication of DM and the main cause of high mortality, disability, and a poor quality of life. DNs have a wide range of clinical manifestations because of the types of fiber dysfunctions and complex structures of the peripheral nervous system. DR is also a microvascular and multifactorial disease, as well as a major cause of visual impairment globally. Pathogenesis of DR is yet to be fully revealed, however, numerous studies have already confirmed the role of inflammation in the onset and advancement of DR. Despite evidence, and better knowledge regarding the pathogenesis of these microvascular complications of diabetes, there is still a deficiency of effective therapies. Bioactive compounds are mainly derived from plants, and these molecules have promising therapeutic potential. In this review, evidence and molecular mechanisms regarding the role of inflammation in various microvascular complications of diabetes including DNP, DN, and DR, have been summarized. The therapeutic potential of several bioactive compounds derived from plants in the treatment of these microvascular complications of diabetes has also been discussed.

The Role of Resveratrol in Eye Diseases—A Review of the Literature

Resveratrol (3,5,4′-trans-trihydroxystilbene) is a polyphenolic phytoalexin belonging to the stilbene family. It is commonly found in grape skins and seeds, as well as other plant-based foods. Oxidative stress and inflammation play a key role in the initiation and progression of age-related eye disorders (glaucoma, cataracts, diabetic retinopathy, and macular degeneration) that lead to a progressive loss of vision and blindness. Even though the way resveratrol affects the human body and the course of many diseases is still the subject of ongoing scientific research, it has been shown that the broad spectrum of anti-inflammatory and neuroprotective properties of resveratrol has a beneficial effect on eye tissues. In our research, we decided to analyze the current scientific literature on resveratrol, its possible mechanisms of action, and its therapeutic application in order to assess its effectiveness in eye diseases.

Unconventional avenues to decelerated diabetic retinopathy

Diabetic retinopathy (DR) is an important microvascular complication of diabetes mellitus (DM), causing significant visual impairment worldwide. Current gold standards for retarding the progress of DR include blood sugar control and regular fundus screening. Despite these measures, the incidence and prevalence of DR and vision-threatening DR remain high. Given its slowly progressive course and long latent period, opportunities to contain or slow DR before it threatens vision must be explored. This narrative review assesses the recently described unconventional strategies to retard DR progression. These include gut-ocular flow, gene therapy, mitochondrial dysfunction-oxidative stress, stem cell therapeutics, neurodegeneration, anti-inflammatory treatments, lifestyle modification, and usage of phytochemicals. These therapies impact DR directly, while some of them also influence DM control. Most of these strategies are currently in the preclinical stage, and clinical evidence remains low. Nevertheless, our review suggests that these approaches have the potential for human use to prevent the progression of DR.

Diabetic macular ischaemia- a new therapeutic target?

Diabetic macular ischaemia (DMI) is traditionally defined and graded based on the angiographic evidence of an enlarged and irregular foveal avascular zone. However, these anatomical changes are not surrogate markers for visual impairment. We postulate that there are vascular phenotypes of DMI based on the relative perfusion deficits of various retinal capillary plexuses and choriocapillaris. This review highlights several mechanistic pathways, including the role of hypoxia and the complex relation between neurons, glia, and microvasculature. The current animal models are reviewed, with shortcomings noted. Therefore, utilising the advancing technology of optical coherence tomography angiography (OCTA) to identify the reversible DMI phenotypes may be the key to successful therapeutic interventions for DMI. However, there is a need to standardise the nomenclature of OCTA perfusion status. Visual acuity is not an ideal endpoint for DMI clinical trials. New trial endpoints that represent disease progression need to be developed before irreversible vision loss in patients with DMI. Natural history studies are required to determine the course of each vascular and neuronal parameter to define the DMI phenotypes. These DMI phenotypes may also partly explain the development and recurrence of diabetic macular oedema. It is also currently unclear where and how DMI fits into the diabetic retinopathy severity scales, further highlighting the need to better define the progression of diabetic retinopathy and DMI based on both multimodal imaging and visual function. Finally, we discuss a complete set of proposed therapeutic pathways for DMI, including cell-based therapies that may provide restorative potential.

Inherited Retinal Dystrophies: Role of Oxidative Stress and Inflammation in Their Physiopathology and Therapeutic Implications

Inherited retinal dystrophies (IRDs) are a large group of genetically and clinically heterogeneous diseases characterized by the progressive degeneration of the retina, ultimately leading to loss of visual function. Oxidative stress and inflammation play fundamental roles in the physiopathology of these diseases. Photoreceptor cell death induces an inflammatory state in the retina. The activation of several molecular pathways triggers different cellular responses to injury, including the activation of microglia to eliminate debris and recruit inflammatory cells from circulation. Therapeutical options for IRDs are currently limited, although a small number of patients have been successfully treated by gene therapy. Many other therapeutic strategies are being pursued to mitigate the deleterious effects of IRDs associated with oxidative metabolism and/or inflammation, including inhibiting reactive oxygen species’ accumulation and inflammatory responses, and blocking autophagy. Several compounds are being tested in clinical trials, generating great expectations for their implementation. The present review discusses the main death mechanisms that occur in IRDs and the latest therapies that are under investigation.

Antioxidant and Anti-inflammatory Properties of Resveratrol in Diabetic Nephropathy: A Systematic Review and Meta-analysis of Animal Studies

Background: Accumulated experimental evidence suggests that resveratrol may have an effect on diabetic nephropathy by inhibiting inflammation and decreasing oxidative stress. However, the credibility of the evidence for this practice is unclear. Thus, we aimed to perform a systematic review and meta-analysis of animal studies to evaluate the antioxidant and anti-inflammatory properties of resveratrol when used in the treatment of diabetic nephropathy.

Methods: Electronic bibliographic databases including PubMed, EMBASE, and Web of Science were searched for relevant studies. The methodological quality of animal studies was assessed based on the SYstematic Review Center for Laboratory animal Experimentation Risk of Bias (SYRCLE’s RoB) tool. A meta-analysis was performed based on the Cochrane Handbook for Systematic Reviews of Interventions by using RevMan 5.4 software. This study was registered within International Prospective Register of Systematic Reviews (PROSPERO) as number CRD42021293784.

Results: Thirty-six qualified studies involving 726 animals were included. There was a significant association of resveratrol with the levels of blood glucose (BG), serum creatinine (Scr), blood urea nitrogen (BUN), catalase (CAT), superoxide dismutase (SOD), malondialdehyde (MDA), glutathione (GSH), glutathione peroxidase (GPx), and interleukin-1β (IL-1β). Nevertheless, resveratrol treatment did not effectively decrease the levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). In addition, more remarkable antioxidant and hypoglycemic effects were observed in type 2 diabetic nephropathy rather than in type 1 diabetic nephropathy based on subgroup analysis.

Conclusion: In this meta-analysis, resveratrol can exert its antioxidant activities by reducing the levels of MDA and recovering the activities of SOD, CAT, GSH, and GPx. With regard to pro-inflammatory cytokines, resveratrol had a positive effect on the reduction of IL-1β. However, the analysis indicated that resveratrol had no effect on IL-6 and TNF-α levels, probably because of the methodological quality of the studies and their heterogeneity. Current evidence supports the antioxidant and anti-inflammatory properties of resveratrol, but its relationship with the levels of some inflammatory cytokines such as IL-6 and TNF-α in animals with diabetic nephropathy needs further elucidation.

Adiponectin accumulation in the retinal vascular endothelium and its possible role in preventing early diabetic microvascular damage

Adiponectin (APN), a protein abundantly secreted from adipocytes, has been reported to possess beneficial effects on cardiovascular diseases in association with its accumulation on target organs and cells by binding to T-cadherin. However, little is known about the role of APN in the development of diabetic microvascular complications, such as diabetic retinopathy (DR). Here we investigated the impact of APN on the progression of early retinal vascular damage using a streptozotocin (STZ)-induced diabetic mouse model. Our immunofluorescence results clearly showed T-cadherin-dependent localization of APN in the vascular endothelium of retinal arterioles, which was progressively decreased during the course of diabetes. Such reduction of retinal APN accompanied the early features of DR, represented by increased vascular permeability, and was prevented by glucose-lowering therapy with dapagliflozin, a selective sodium-glucose co-transporter 2 inhibitor. In addition, APN deficiency resulted in severe vascular permeability under relatively short-term hyperglycemia, together with a significant increase in vascular cellular adhesion molecule-1 (VCAM-1) and a reduction in claudin-5 in the retinal endothelium. The present study demonstrated a possible protective role of APN against the development of DR.

Resveratrol and endoplasmic reticulum stress: A review of the potential protective mechanisms of the polyphenol

The endoplasmic reticulum (ER) is an organelle that performs a set of essential functions in cellular biology. These include synthesis of lipids, homeostasis of calcium, and controlling the folding of proteins. Inflammation and oxidative stress are two important reasons behind the accumulation of misfolded or unfolded proteins in the ER. In such circumstances, a series of measures are undertaken in the cell which are collectively called unfolded protein response (UPR). The aim of UPR is to reduce the burden of protein aggregates and promote survival. However, extended and unrestricted ER stress (ERS) can induce further inflammation and apoptosis. ERS and the UPR are involved in different diseases such as neurodegenerative and cardiovascular diseases. Resveratrol (RSV), a natural polyphenol, has well-documented evidence supporting its numerous biological properties including antioxidant, antiinflammatory, antiobesity, antidiabetic, and antiischemic activities. The compound is also known for its potential beneficial effects on cognitive function and liver, kidney, and lung health. In this review, the role of ERS in several pathological conditions and the potential protective effects of RSV are discussed. However, the scarcity of clinical data means that more research needs to be conducted to gain a lucid understanding of RSV's effects on endoplasmic reticulum stress (ERS) in humans.

Antioxidants for the Treatment of Retinal Disease: Summary of Recent Evidence

Retinal tissue is prone to oxidant burden and oxidative stress secondary to the generation of reactive oxygen species from high metabolic demand. The formation of reactive oxygen species occurs primarily from the mitochondrial respiratory chain as well as several enzymatic and oxidation reactions that occur in the neurosensory retina and retinal pigment epithelium. This oxidative stress has been implicated in the pathogenesis of several retinal diseases and the role of antioxidants as a therapeutic treatment shows promise in slowing the progression of certain diseases. The aim of this narrative review is to describe the mechanisms of retinal oxidative stress and summarize the current available evidence for antioxidants as a treatment for vitreoretinal disorders.

The neurovascular extracellular matrix in health and disease

The blood-brain barrier (BBB) is a vital interface that supports normal brain functions. Endothelial cells (ECs) are the main component of the BBB and are highly specialized to govern the transfer of substances into brain. The EC lumen is enmeshed with an extracellular matrix (ECM), known as the endothelial glycocalyx layer (EGL). The lumen-facing EGL is primarily comprised of proteoglycans (PGs) and glycosaminoglycans (GAGs), which function as the first line of defense for blood-to-brain transfer of substances. Circulating factors must first penetrate the EGL before interacting with the EC. The abundance and composition of the PG and GAGs can dictate EGL function, and determine which circulating substances communicate with the ECs. The EGL can interact with circulating factors through physio-chemical interactions with the EC. Some disease states reveal a "thinning" of the EGL that may increase EC interactions with components of the systemic circulation and alter BBB function. EGL changes may also contribute to the cognitive complications of systemic diseases, such as sepsis and diabetes. For decades, researchers have measured how genetic and environmental factors influence the peripheral EGL constituents; however, much less is known about the neurovascular EGL. In this mini-review, we introduce components of the EGL and innovative ways to measure their abundance and composition that may contribute to BBB dysfunction.

Resveratrol-Elicited PKC Inhibition Counteracts NOX-Mediated Endothelial to Mesenchymal Transition in Human Retinal Endothelial Cells Exposed to High Glucose

Diabetes-associated long-term hyperglycaemia leads to oxidative stress-mediated fibrosis in different tissues and organs. Endothelial-to-mesenchymal-transition (EndMT) appears to play a role in diabetes-associated fibrotic conditions. Here, we investigate whether EndMT is implicated in the diabetic retinopathy fibrotic process and evaluate the possibility that resveratrol could counteract EndMT by inhibiting high glucose (HG)-induced increases in ROS. Primary Human Retinal Endothelial Cells (HRECs) were either pre-treated for 24 h with 1 µM resveratrol or left untreated, then glucose (30 mM) was applied at 3-day intervals for 10 days. qRT-PCR and ELISA were used to detect mRNA or protein expression of endothelial markers (CD31, CDH5, vWF) or mesenchymal markers (VIM, αSMA and collagen I), respectively. Intracellular ROS levels were measured with carboxy-DCFDA, while NOX-associated ROS levels were evaluated using the NADPH-specific redox biosensor p47-roGFP. Treatment of HRECs with HG increased intracellular ROS levels and promoted phenotype shifting towards EndMT, evidenced by decreased expression of endothelial markers concomitant with increased expression of mesenchymal ones. HG-induced EndMT appears to be mediated by NADPH-associated ROS generation as pre-treatment of HRECs with resveratrol or the NADPH inhibitor, diphenyleneiodonium chloride (DPI), attenuated ROS production and EndMT transition, suggesting that the effect of resveratrol on HG-induced ROS occurs via down-regulation of NADPH oxidase. It is worth noting that resveratrol or Chelerythrine, a Protein kinase C (PKC) inhibitor, reduce ROS and EndMT in HG-exposed cells, suggesting that NADPH activation occurs via a PKC-dependent mechanism. Taken together, our results provide the basis for a resveratrol-based potential protective therapy to prevent diabetic-associated complications.

New Highlights of Resveratrol: A Review of Properties against Ocular Diseases

Eye diseases are currently a major public health concern due to the growing number of cases resulting from both an aging of populations and exogenous factors linked to our lifestyles. Thus, many treatments including surgical pharmacological approaches have emerged, and special attention has been paid to prevention, where diet plays a preponderant role. Recently, potential antioxidants such as resveratrol have received much attention as potential tools against various ocular diseases. In this review, we focus on the mechanisms of resveratrol against ocular diseases, in particular age-related macular degeneration, glaucoma, cataract, diabetic retinopathy, and vitreoretinopathy. We analyze, in relation to the different steps of each disease, the resveratrol properties at multiple levels, such as cellular and molecular signaling as well as physiological effects. We show and discuss the relationship to reactive oxygen species, the regulation of inflammatory process, and how resveratrol can prevent ocular diseases through a potential epigenetic action by the activation of sirtuin-1. Lastly, various new forms of resveratrol delivery are emerging at the same time as some clinical trials are raising more questions about the future of resveratrol as a potential tool for prevention or in therapeutic strategies against ocular diseases. More preclinical studies are required to provide further insights into RSV's potential adjuvant activity.

Oral administration of resveratrol or lactic acid bacterium improves lens elasticity

A decrease in the elasticity of the ocular lens during aging is associated with loss of the accommodative ability of the eye, leading to presbyopia. Although near vision impairment is a social issue affecting the length of healthy life expectancy and productivity of elderly people, an effective treatment to improve near vision has not yet become available. Here we examined the effect of Enterococcus faecium WB2000, Lactobacillus pentosus TJ515, and resveratrol on lens elasticity in rats, where the stiffness of the ocular lens increases exponentially during the aging process. A combination of WB2000 and resveratrol improved lens elasticity not only in the long term but also with just short-term treatment. In addition, TJ515 decreased stiffness in the eye lens with long-term treatment. Therefore, the oral administration of WB2000 and resveratrol or TJ515 may be a potential approach for managing the progression of near vision impairment.

Noninvasive temporal detection of early retinal vascular changes during diabetes

Diabetes associated complications, including diabetic retinopathy and loss of vision, are major health concerns. Detecting early retinal vascular changes during diabetes is not well documented, and only few studies have addressed this domain. The purpose of this study was to noninvasively evaluate temporal changes in retinal vasculature at very early stages of diabetes using fundus images from preclinical models of diabetes. Non-diabetic and Akita/+ male mice with different duration of diabetes were subjected to fundus imaging using a Micron III imaging system. The images were obtained from 4 weeks- (onset of diabetes), 8 weeks-, 16 weeks-, and 24 weeks-old male Akita/+ and non-diabetic mice. In total 104 fundus images were subjected to analysis for various feature extractions. A combination of Canny Edge Detector and Angiogenesis Analyzer plug-ins in ImageJ were utilized to quantify various retinal vascular changes in fundus images. Statistical analyses were conducted to determine significant differences in the various extracted features from fundus images of diabetic and non-diabetic animals. Our novel image analysis method led to extraction of over 20 features. These results indicated that some of these features were significantly changed with a short duration of diabetes, and others remained the same but changed after longer duration of diabetes. These patterns likely distinguish acute (protective) and chronic (damaging) associated changes with diabetes. We show that with a combination of various plugging one can extract over 20 features from retinal vasculature fundus images. These features change during diabetes, thus allowing the quantification of quality of retinal vascular architecture as biomarkers for disease progression. In addition, our method was able to identify unique differences among diabetic mice with different duration of diabetes. The ability to noninvasively detect temporal retinal vascular changes during diabetes could lead to identification of specific markers important in the development and progression of diabetes mediated-microvascular changes, evaluation of therapeutic interventions, and eventual reversal of these changes in order to stop or delay disease progression.

The potential health benefits of dietary natural plant products in age related eye diseases

In the past decade, there has been a tremendous increase in the number of cases of age-related eye diseases such as age-related macular degeneration (AMD), cataract, diabetic retinopathy and glaucoma. These diseases are the leading causes of visual impairment and blindness all over the world and are associated with many pathological risk factors such as aging, pollution, high levels of glucose (hyperglycaemia), high metabolic rates, and light exposure. These risk factors lead to the generation of uncontrollable reactive oxygen species (ROS), which causes oxidative stress. Oxidative stress plays a crucial role in the pathogenesis of age-related eye diseases through the activation of nuclear factor kappa B (NF-κB), vascular endothelial growth factor (VEGF), and lipid peroxidation, which leads to the production of inflammatory cytokines, angiogenesis, protein and DNA damages, apoptosis that causes macular degeneration (AMD), cataract, diabetic retinopathy and glaucoma. This review provides updated information on the beneficial effects of dietary natural plant products (DPNPs) against age-related eye diseases. In this review, supplementation of DPNPs demonstrated preventive and therapeutic effects on people at risk of or with age-related eye diseases due to their capacity to scavenge free radicals, ameliorate inflammatory molecules, neutralize the oxidation reaction that occurs in photoreceptor cells, decrease vascular endothelial growth factor and the blood-retinal barrier and increase the antioxidant defence system. However, further experiments and clinical trials are required to establish the daily doses of DPNPs that will safely and effectively prevent age-related eye diseases.

Mitochondrial Dysfunction as a Novel Target for Neuroprotective Nutraceuticals in Ocular Diseases

The eyes require a rich oxygen and nutrient supply; hence, the high-energy demand of the visual system makes it sensitive to oxidative stress. Excessive free radicals result in mitochondrial dysfunction and lead to retinal neurodegeneration, as an early stage of retinal metabolic disorders. Retinal cells are vulnerable because of their coordinated interaction and intricate neural networks. Nutraceuticals are believed to target multiple pathways and have shown neuroprotective benefits by scavenging free radicals and promoting mitochondrial gene expression. Furthermore, encouraging results demonstrate that nutraceuticals improve the organization of retinal cells and visual functions. This review discusses the mitochondrial impairments of retinal cells and the mechanisms underlying the neuroprotective effects of nutraceuticals. However, some unsolved problems still exist between laboratory study and clinical therapy. Poor bioavailability and bioaccessibility strongly limit their development. A new delivery system and improved formulation may offer promise for health care applications.

Intravitreal injection of resveratrol inhibits laser-induced murine choroidal neovascularization

AIM

To determine the effects of intravitreal resveratrol (RSV) on murine laser-induced choroidal neovascularization (CNV).

METHODS

The toxicity of RSV to choroidal endothelial cell (CEC) was measured using thiazolyl blue tetrazolium bromide (MTT) assay. Effects of RSV on choroidal endothelial cell (CEC) migration were evaluated with a modified Boyden chamber assay, while tube formation was evaluated in a 2-D gel assay. CNV was induced by laser photocoagulation in mice. The effects of intravitreal injection of RSV on CNV development were evaluated by fluorescein angiography (FA), confocal analysis of isolectin B4 labeled choroidal flat mounts, and histologic examination of CNV membranes. Immunostaining was used to analyze the expression and phosphorylation of vascular endothelial growth factor receptor 2 (VEGFR2).

RESULTS

No significant cell toxicity was observed in CEC if the concentration of RSV was less than 200 µmol/L (P>0.05). RSV inhibited vascular endothelial growth factor (VEGF)-induced CEC migration (P<0.05) and tube formation (P<0.05) in vitro. Furthermore, intravitreal injection of RSV significantly inhibited laser induced CNV formation in mice. The FA leakage, CNV volume and CNV area analysis revealed that there were 41%, 45%, and 58% reduction in RSV-treated eyes (1.691±0.1032, 178 163±78 623 µm³ and 6508±619.0 µm², respectively) compared with those in control (2.724±0.08447, 379 676±98 382 µm³ and 16 576±2646 µm², respectively; P<0.05). Phospho-VEGFR2 expression was much weaker in the sections of CNV lesions in RSV injected mice compared with that in control (P<0.05).

CONCLUSION

Intravitreal injection of RSV exerts an inhibitory effect on CNV, which may through suppressing endothelial cell migration, tube formation and VEGFR2 phosphorylation.

A review on the potential of Resveratrol in prevention and therapy of diabetes and diabetic complications

Diabetes mellitus (DM) is a major world health problem and one of the most studied diseases, which are highly prevalent in the whole world, it is frequently associated with severe clinical complications, such as diabetic cardiomyopathy, nephropathy, retinopathy, neuropathy etc. Scientific research is continuously casting about for new monomer molecules from Chinese herbal medicine that could be invoked as candidate drugs for fighting against diabetes and its complications. Resveratrol (RES), a polyphenol phytoalexin, possesses diverse biochemical and physiological actions, including antiplatelet, estrogenic, and anti-inflammatory properties. It is recently gaining scientific interest for RES in controlling blood sugar and fighting against diabetes and its complications properties in various types of diabetic models. These beneficial effects seem to be due to the multiple actions of RES on cellular functions, which make RES become a promising molecule for the treatment of diabetes and diabetic complications. Here, we review the mechanism of action and potential therapeutic use of RES in prevention and mitigation of these diseases in recent ten years to provide a reference for further research and development of RES.

Attenuation of diabetic retinopathy and neuropathy by resveratrol: Review on its molecular mechanisms of action

Resveratrol is an important phenolic phytochemical from the therapeutic perspective. It has therapeutic impacts over wide range of diseases, especially the ones related to oxidative stress. Resveratrol, being primarily a potent anti-oxidant phytochemical, has significant impact against major diseases as inflammatory disorders, diabetes, and cancer. In the current review article, we intend to highlight the molecular aspects of the mechanism of action of resveratrol against major diabetic implications, namely, retinopathy and neuropathy. Both these diabetic implications are among the first fallouts of chronic hyperglycaemia. Resveratrol, via multiple molecular pathways, tend to attenuate and reverse these deformity and other disease-causing implications.

Histone acetyltransferase and Polo-like kinase 3 inhibitors prevent rat galactose-induced cataract

Diabetic cataracts can occur at an early age, causing visual impairment or blindness. The detailed molecular mechanisms of diabetic cataract formation remain incompletely understood, and there is no well-documented prophylactic agent. Galactose-fed rats and ex vivo treatment of lenses with galactose are used as models of diabetic cataract. To assess the role of histone acetyltransferases, we conducted cataract prevention screening with known histone acetyltransferase (HAT) inhibitors. Ex vivo treatment with a HAT inhibitor strongly inhibited the formation of lens turbidity in high-galactose conditions, while addition of a histone deacetylase (HDAC) inhibitor aggravated turbidity. We conducted a microarray to identify genes differentially regulated by HATs and HDACs, leading to discovery of a novel cataract causative factor, Plk3. Plk3 mRNA levels correlated with the degree of turbidity, and Plk3 inhibition alleviated galactose-induced cataract formation. These findings indicate that epigenetically controlled Plk3 influences cataract formation. Our results demonstrate a novel approach for prevention of diabetic cataract using HAT and Plk3 inhibitors.

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.

Resveratrol inhibits high-glucose-induced inflammatory "metabolic memory" in human retinal vascular endothelial cells through SIRT1-dependent signaling

Diabetes induces vascular endothelial damage and this study investigated high-glucose-induced inflammation "metabolic memory" of human retinal vascular endothelial cells (HRVECs), the effects of resveratrol on HRVECs, and the underlying signaling. HRVECs were grown under various conditions and assayed for levels of sirtuin 1 (SIRT1); acetylated nuclear factor κB (Ac-NF-κB); NOD-like receptor family, pyrin domain containing 3 (NLRP3); and other inflammatory cytokines; and cell viability. A high glucose concentration induced HRVEC inflammation metabolic memory by decreasing SIRT1 and increasing Ac-NF-κB, NLRP3, caspase 1, interleukin-1β, inducible nitric oxide synthase, and tumor necrosis factor α, whereas exposure of HRVECs to a high glucose medium for 4 days, followed by a normal glucose concentration for an additional 4 days, failed to reverse these changes. A high glucose concentration also significantly reduced HRVEC viability. In contrast, resveratrol, a selective SIRT1 activator, markedly enhanced HRVEC viability and reduced the inflammatory cytokines expressions. In addition, high glucose reduced AMP-activated protein kinase (AMPK) phosphorylation and retained during the 4 days of the reversal period of culture. The effects of resveratrol were abrogated after co-treatment with the SIRT1 inhibitor nicotinamide and the AMPK inhibitor compound C. In conclusion, resveratrol was able to reverse high-glucose-induced inflammation "metabolic memory" of HRVECs by activation of the SIRT1/AMPK/NF-κB pathway.

Oxidative Stress as the Main Target in Diabetic Retinopathy Pathophysiology

Diabetic retinopathy (DR) is one of the most common complications of diabetes mellitus (DM) causing vision impairment even at young ages. There are numerous mechanisms involved in its development such as inflammation and cellular degeneration leading to endothelial and neural damage. These mechanisms are interlinked thus worsening the diabetic retinopathy outcome. In this review, we propose oxidative stress as the focus point of this complication onset.

Longitudinal In Vivo Characterization of the Streptozotocin-Induced Diabetic Mouse Model: Focus on Early Inner Retinal Responses

Purpose

The goal of this study was to perform an extensive temporal characterization of the early pathologic processes in the streptozotocin (STZ)-induced diabetic retinopathy (DR) mouse model, beyond the vascular phenotype, and to investigate the potential of clinically relevant compounds in attenuating these processes.

Methods

Visual acuity and contrast sensitivity (CS) were studied in the mouse STZ model until 24 weeks postdiabetes onset. ERG, spectral domain optical coherence tomography (SD-OCT), leukostasis, and immunohistochemistry were applied to investigate neurodegeneration, inflammation, and gliosis during early-, mid- and late-phase diabetes. Aflibercept or triamcinolone acetonide (TAAC) was administered to investigate their efficacy on the aforementioned processes.

Results

Visual acuity and CS loss started at 4 and 18 weeks postdiabetes onset, respectively, and progressively declined over time. ERG amplitudes were diminished and OP latencies increased after 6 weeks, whereas SD-OCT revealed retinal thinning from 4 weeks postdiabetes. Immunohistochemical analyses linked these findings to retinal ganglion and cholinergic amacrine cell loss at 4 and 8 weeks postdiabetes onset, respectively, which was further decreased after aflibercept administration. The number of adherent leukocytes was augmented after 2 weeks, whereas increased micro- and macroglia reactivity was present from 4 weeks postdiabetes. Aflibercept or TAAC showed improved efficacy on inflammation and gliosis.

Conclusions

STZ-induced diabetic mice developed early pathologic DR hallmarks, from which inflammation seemed the initial trigger, leading to further development of functional and morphologic retinal changes. These findings indicate that the mouse STZ model is suitable to study novel integrative non-vascular therapies to treat early DR.

Effect of Resveratrol on In Vitro and In Vivo Models of Diabetic Retinophathy: A Systematic Review

A large number of preclinical studies suggest the involvement of resveratrol in the prevention and treatment of eye diseases induced by oxidative stress and inflammation. We tested the hypothesis that resveratrol influences many pathways of in vitro and in vivo models of diabetic retinopathy through a systematic literature review of original articles. The review was conducted in accordance with the PRISMA guidelines. A literature search of all original articles published until April 2019 was performed. The terms “resveratrol” in combination with “retina”, “retinal pathology”, “diabetic retinopathy” and “eye” were searched. Possible biases were identified with the adopted SYRCLE’s tool. Eighteen articles met inclusion/exclusion criteria for full-text review. Eleven of them included in vitro experiments, 11 studies reported in vivo data and 3 studies described both in vitro and in vivo experiments. Most of the in vivo studies did not include data that would allow exclusion of bias risks, according to SYRCLE’s risk of bias tool. Both in vitro and in vivo data suggest anti-apoptotic, anti-inflammatory and anti-oxidative actions of resveratrol in models of diabetic retinopathy. However, results on its anti-angiogenic effects are contradictory and need more rigorous studies.

Resveratrol-delivery vehicle with anti-VEGF activity carried to human retinal pigmented epithelial cells exposed to high-glucose induced conditions

As an integrated approach to defeat diabetic retinopathy, a common complication of diabetes leading to vision loss, a delivery vehicle able to transport resveratrol (Rv) directly into retina pigmented epithelial D407 cells was designed. Rv, a molecule with known therapeutic potential, was successfully inserted into a microcapsule based on porous CaCO₃ templates revealing an encapsulation efficiency of 96.8 ± 4.0%. Four alternative layers of polyelectrolytes were deposited via electrostatic-driven layer-by-layer assembly approach on the template and covered by rhodamine 6G (Rh6G). The as-designed PMs-Rv-Rh6G microcapsules were internalized into D407 cells grown in normal and high glucose-induced inflammation conditions, being able to cross the cellular membrane and localize near the nucleus after 24 h treatment. The metabolic activity of D407 cells was not diminished by PMs-Rv-Rh6G even after 24 h treatment, meaning that the microcapsules do not exert any toxicity toward the cells, based on WST-1 and lactate dehydrogenase assays. Notably, the PMs-Rv-Rh6G treatment is able to inhibit the vascular endothelial growth factor (VEGF) protein, as was proved by the ELISA assay. Therefore, the proposed PMs-Rv-Rh6G microcapsules could be implemented as a potential self-reporting intraocular Rv-delivery vehicle with anti-VEGF activity in the management of diabetic retinopathy.

Nutraceuticals for the Treatment of Diabetic Retinopathy

Diabetic retinopathy (DR) is one of the most common complications of diabetes mellitus and is characterized by degeneration of retinal neurons and neoangiogenesis, causing a severe threat to vision. Nowadays, the principal treatment options for DR are laser photocoagulation, vitreoretinal surgery, or intravitreal injection of drugs targeting vascular endothelial growth factor. However, these treatments only act at advanced stages of DR, have short term efficacy, and cause side effects. Treatment with nutraceuticals (foods providing medical or health benefits) at early stages of DR may represent a reasonable alternative to act upstream of the disease, preventing its progression. In particular, in vitro and in vivo studies have revealed that a variety of nutraceuticals have significant antioxidant and anti-inflammatory properties that may inhibit the early diabetes-driven molecular mechanisms that induce DR, reducing both the neural and vascular damage typical of DR. Although most studies are limited to animal models and there is the problem of low bioavailability for many nutraceuticals, the use of these compounds may represent a natural alternative method to standard DR treatments.

Novel function of VEGF-B as an antioxidant and therapeutic implications

Oxidative stress, due to insufficiency of antioxidants or over-production of oxidants, can lead to severe cell and tissue damage. Oxidative stress occurs constantly and has been shown to be involved in innumerable diseases, such as degenerative, cardiovascular, neurological, and metabolic disorders, cancer, and aging, thus highlighting the vital need of antioxidant defense mechanisms. Vascular endothelial growth factor B (VEGF-B) was discovered a long time ago, and is abundantly expressed in most types of cells and tissues. VEGF-B remained functionally mysterious for many years and later on has been shown to be minimally angiogenic. Recently, VEGF-B is reported to be a potent antioxidant by boosting the expression of key antioxidant enzymes. Thus, one major role of VEGF-B lies in safeguarding tissues and cells from oxidative stress-induced damage. VEGF-B may therefore have promising therapeutic utilities in treating oxidative stress-related diseases. In this review, we discuss the current knowledge on the newly discovered antioxidant function of VEGF-B and the related molecular mechanisms, particularly, in relationship to some oxidative stress-related diseases, such as retinitis pigmentosa, age-related macular degeneration, diabetic retinopathy, glaucoma, amyotrophic lateral sclerosis, Alzheimer's disease, and Parkinson's disease.

Health Benefits of Polyphenols and Carotenoids in Age-Related Eye Diseases

Oxidative stress and inflammation play a critical role in the initiation and progression of age-related ocular abnormalities as cataract, glaucoma, diabetic retinopathy, and macular degeneration. Therefore, phytochemicals with proven antioxidant and anti-inflammatory activities, such as carotenoids and polyphenols, could be of benefit in these diseases. We searched PubMed and Web of Science databases for original studies investigating the benefits of different carotenoids and polyphenols in age-related ophthalmic diseases. Our results showed that several polyphenols (such as anthocyanins, Ginkgo biloba, quercetin, and resveratrol) and carotenoids (such as lutein, zeaxanthin, and mezoxanthin) have shown significant preventive and therapeutic benefits against the aforementioned conditions. The involved mechanisms in these findings include mitigating the production of reactive oxygen species, inhibiting the tumor necrosis factor-α and vascular endothelial growth factor pathways, suppressing p53-dependent apoptosis, and suppressing the production of inflammatory markers, such as interleukin- (IL-) 8, IL-6, IL-1a, and endothelial leucocyte adhesion molecule-1. Consumption of products containing these phytochemicals may be protective against these diseases; however, adequate human data are lacking. This review discusses the role and mechanisms of polyphenols and carotenoids and their possible synergistic effects on the prevention and treatment of age-related eye diseases that are induced or augmented by oxidative stress and inflammation.

Resveratrol: A miraculous natural compound for diseases treatment

Resveratrol (3, 5, 4'-trihydroxystilbene) is a nonflavonoid polyphenol that naturally occurs as phytoalexin. It is produced by plant sources such as grapes, apples, blueberries, plums, and peanut. This compound has critical roles in human health and is well known for its diverse biological activities such as antioxidant and anti-inflammatory properties. Nowadays, due to rising incidence of different diseases such as cancer and diabetes, efforts to find novel and effective disease-protective agents have led to the identification of plant-derived compounds such as resveratrol. Furthermore, several in vitro and in vivo studies have revealed the effectiveness of resveratrol in various diseases such as diabetes mellitus, cardiovascular disease, metabolic syndrome, obesity, inflammatory, neurodegenerative, and age-related diseases. This review presents an overview of currently available studies on preventive properties and essential molecular mechanisms involved in various diseases.

Endothelial Glycocalyx as a Shield Against Diabetic Vascular Complications: Involvement of Hyaluronan and Hyaluronidases

The endothelial glycocalyx (EG), which covers the apical surface of the endothelial cells and floats into the lumen of the vessels, is a key player in vascular integrity and cardiovascular homeostasis. The EG is composed of PGs (proteoglycans), glycoproteins, glycolipids, and glycosaminoglycans, in particular hyaluronan (HA). HA seems to be implicated in most of the functions described for EG such as creating a space between blood and the endothelium, controlling vessel permeability, restricting leukocyte and platelet adhesion, and allowing an appropriate endothelial response to flow variation through mechanosensing. The amount of HA in the EG may be regulated by HYAL (hyaluronidase) 1, the most active somatic hyaluronidase. HYAL1 seems enriched in endothelial cells through endocytosis from the bloodstream. The role of the other main somatic hyaluronidase, HYAL2, in the EG is uncertain. Damage to the EG, accompanied by shedding of one or more of its components, is an early sign of various pathologies including diabetes mellitus. Shedding increases the blood or plasma concentration of several EG components, such as HA, heparan sulfate, and syndecan. The plasma levels of these molecules can then be used as sensitive markers of EG degradation. This has been shown in type 1 and type 2 diabetic patients. Recent experimental studies suggest that preserving the size and amount of EG HA in the face of diabetic insults could be a useful novel therapeutic strategy to slow diabetic complications. One way to achieve this goal, as suggested by a murine model of HYAL1 deficiency, may be to inhibit the function of HYAL1. The same approach may succeed in other pathological situations involving endothelial dysfunction and EG damage.

Antidiabetic properties of Capparis spinosa L. and its components

An increasing line of evidence confirmed that apart from conventional hypoglycemic drugs, diet and medicinal plants have beneficial effects on diabetes. Capparis spinosa L. (Caper) is a perennial shrub in the Capparidaceae family. It grows in different regions of the world, particularly in Asian and African countries. A wide range of biological activities such as antioxidant, anti-inflammatory, anticancer, antimicrobial, and antidiabetic effects have been reported for this plant. In this review, it is focused on beneficial effects of C. spinosa on diabetes. Several studies have showed the antihyperglycemic and hypolipidemic activities of C. spinosa. The putative mechanisms involved in the antihyperglycemic effects of C. spinosa include reducing carbohydrate absorption from the small intestine, inhibiting gluconeogenesis in the liver, enhancing glucose uptake by tissues, and beta cell protection/regeneration. This plant also ameliorates cardiovascular disorders, liver damage, and nephropathy in animal models of diabetes, which are attributed to its antioxidant phytochemicals such as phenolic compounds, flavonoids, carotenoids, tocopherols, and terpenes. Antihyperglycemic and hypolipidemic activities of C. spinose, along with its beneficial effects on diabetic complications, make it a good candidate for the management of diabetes. Well-designed clinical trials are necessary to define the advantages and disadvantages of C. spinose for diabetic patients.

miRNA15a regulates insulin signal transduction in the retinal vasculature

We previously reported that tumor necrosis factor alpha (TNFα) could inhibit insulin signal transduction in retinal cells. We recently found that miR15a/16 also reduced TNFα in retinal endothelial cells (REC) and in vascular specific miR15a/16 knockout mice. Since in silico programs suggested that miR15a could directly bind the insulin receptor, we wanted to determine whether miR15a altered insulin signal transduction. We used a luciferase-based binding assay to determine whether miR15a directly bound the insulin receptor. We then used Western blotting, ELISA, and qPCR to investigate whether miR15a altered insulin signaling proteins in REC and in both miR15a/16 endothelial cell knockout and overexpressing mice. We also treated some REC with resveratrol to determine if resveratrol could increase miR15a expression, since resveratrol is protective to the diabetic retina. We found that miR15a directly bound the 3'UTR of the insulin receptor. Treatment with resveratrol increased miR15a expression in REC grown in high glucose. While total insulin receptor levels were not altered, insulin signal transduction was reduced in REC grown in high glucose and was restored with treatment with resveratrol. miR15a knockout mice had reduced insulin receptor phosphorylation and Akt2 levels, with increased insulin receptor substrate 1 (IRS-1) phosphorylation on serine 307, a site known to inhibit insulin signaling. In contrast, overexpression of miR15a increased insulin signal transduction. Taken together, these data suggest that miR15a binds the insulin receptor and indirectly regulates insulin receptor actions. It also offers an additional mechanism by which resveratrol is protective to the diabetic retina.

Neutralization of placental growth factor as a novel treatment option in diabetic retinopathy

The current standard of care in clinical practice for diabetic retinopathy (DR), anti-vascular endothelial growth factor (VEGF) therapy, has shown a significant improvement in visual acuity. However, treatment response can be variable and might be associated with potential side effects. This study was designed to investigate inhibition of placental growth factor (PlGF) as a possible alternative therapy for DR. The effect of the anti-PlGF antibody (PL5D11D4) was preclinically evaluated in various animal models by investigating different DR hallmarks, including inflammation, neurodegeneration, vascular leakage and fibrosis. The in vivo efficacy was tested in diabetic streptozotocin (STZ) and Akimba models and in the laser induced choroidal neovascularization (CNV) mouse model. Intravitreal (IVT) administration of the anti-PlGF antibody was compared to anti-VEGFR-2 antibody (DC101), anti-VEGF antibody (B20), VEGF-Trap (aflibercept) and triamcinolone acetonide (TAAC). Vascular leakage was investigated in the mouse STZ model by fluorescein isothiocyanate labeled bovine serum albumin (FITC-BSA) perfusion and in the Akimba model by fluorescein angiography (FA). Repeated IVT administration of the anti-PlGF antibody reduced vascular leakage, which was comparable to a single administration of VEGFR-2 inhibition in the mouse STZ model. PL5D11D4 treatment did not alter retinal ganglion cell (RGC) density, as demonstrated by Brn3a staining, whereas DC101 significantly reduced RGC number with 20%. Immunohistological stainings were performed to investigate inflammation (CD45, F4/80) and fibrosis (collagen type 1a). In the CNV model, IVT injection(s) of PL5D11D4 dose-dependently reduced inflammation and fibrosis, as compared to PBS treatment. Equimolar single administration of the anti-PlGF antibody and aflibercept (21 nM) and TAAC decreased leukocyte and macrophage infiltration with 50%, whereas DC101 and B20 (21 nM) had no effect on the inflammatory response. Similar results were observed in the mouse STZ model on the number of microglia and macrophages in the retina. Repeated administration of PL5D11D4 (21 nM) and TAAC similarly reduced fibrosis, while no effect was observed after equimolar DC101, B20 nor aflibercept administration (21 nM). In summary, the anti-PlGF antibody showed comparable efficacy as well-characterized VEGF-inhibitor on the process of vascular leakage, but differentiates itself by also reducing inflammation and fibrosis, without triggering a neurodegenerative response.

Aralia elata inhibits neurodegeneration by downregulating O-GlcNAcylation of NF-κB in diabetic mice

AIM

To investigate the role of O-GlcNAcylation of nuclear factor-kappa B (NF-κB) in retinal ganglion cell (RGC) death and analysedthe effect of Aralia elata (AE) on neurodegeneration in diabetic mice.

METHODS

C57BL/6mice with streptozotocin-induced diabetes were fed daily with AE extract or control (CTL) diet at the onset of diabetes mellitus (DM). Two months after injection of streptozotocin or saline, the degree of cell death and the expression of O-GlcNAc transferase (OGT), N-acetyl-b-D-glucosaminidase (OGA), O-GlcNAcylated proteins, and O-GlcNAcylation of NF-κB were examined.

RESULTS

AE did not affect the metabolic status of diabetic mice. The decrease in the inner retinal thickness (P<0.001 vs CTL, P<0.01 vs DM) and increases in RGCs with terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (P<0.001 vs CTL, P<0.0001 vs DM), glial activation, and active caspase-3 (P<0.0001 vs CTL, P<0.0001 vs DM) were blocked in diabetic retinas of AE extract-fed mice. Expression levels of protein O-GlcNAcylation and OGT were increased in diabetic retinas (P<0.0001 vs CTL), and the level of O-GlcNAcylation of the NF-κB p65 subunit was higher in diabetic retinas than in controls (P<0.0001 vs CTL). AE extract downregulated O-GlcNAcylation of NF-κB and prevented neurodegeneration induced by hyperglycemia (P<0.0001 vs DM).

CONCLUSION

O-GlcNAcylation of NF-κB is concerned in neuronal degeneration and that AE prevents diabetes-induced RGC apoptosis via downregulation of NF-κB O-GlcNAcylation. Hence, O-GlcNAcylation may be a new object for the treatment of DR, and AE may have therapeutic possibility to prevent diabetes-induced neurodegeneration.

The anti-ALS drug riluzole attenuates pericyte loss in the diabetic retinopathy of streptozotocin-treated mice

Loss of pericytes, considered an early hallmark of diabetic retinopathy, is thought to involve abnormal activation of protein kinase C (PKC). We previously showed that the anti-amyotrophic lateral sclerosis (ALS) drug riluzole functions as a PKC inhibitor. Here, we examined the effects of riluzole on pathological changes in diabetic retinopathy. Pathological endpoints examined in vivo included the number of pericytes and integrity of retinal vessels in streptozotocin (STZ)-induced diabetic mice. In addition, PKC activation and the induction of monocyte chemotactic protein (MCP1) were assessed in diabetic mice and in human retinal pericytes exposed to advanced glycation end product (AGE) or modified low-density lipoprotein (mLDL). The diameter of retinal vessels and the number of pericytes were severely reduced, and the levels of MCP1 and PKC were increased in STZ-induced diabetic mice. Administration of riluzole reversed all of these changes. Furthermore, the increased expression of MCP1 in AGE- or mLDL-treated cultured retinal pericytes was inhibited by treatment with riluzole or the PKC inhibitor GF109203X. In silico modeling showed that riluzole fits well within the catalytic pocket of PKC. Taken together, our results demonstrate that riluzole attenuates both MCP1 induction and pericyte loss in diabetic retinopathy, likely through its direct inhibitory effect on PKC.

p53 coordinates decidual sestrin 2/AMPK/mTORC1 signaling to govern parturition timing

Inflammation and oxidative stress are known risk factors for preterm birth (PTB); however, the mechanisms and pathways that influence this condition are not fully described. Previously, we showed that mTORC1 signaling is increased in mice harboring a uterine-specific deletion of transformation-related protein 53 (p53d/d mice), which exhibit premature decidual senescence that triggers spontaneous and inflammation-induced PTB. Treatment with the mTORC1 inhibitor rapamycin reduced the incidence of PTB in the p53d/d mice. Decidual senescence with heightened mTORC1 signaling is also a signature of human PTB. Here, we have identified an underlying mechanism for PTB and a potential therapeutic strategy for treating the condition. Treatment of pregnant p53d/d mice with either the antidiabetic drug metformin or the antioxidant resveratrol activated AMPK signaling and inhibited mTORC1 signaling in decidual cells. Both metformin and resveratrol protected against spontaneous and inflammation-induced PTB in p53d/d females. Using multiple approaches, we determined that p53 interacts with sestrins to coordinate an inverse relationship between AMPK and mTORC1 signaling that determines parturition timing. This signature was also observed in human decidual cells. Together, these results reveal that p53-dependent coordination of AMPK and mTORC1 signaling controls parturition timing and suggest that metformin and resveratrol have therapeutic potential to prevent PTB.

Neurovascular dysfunction and neurodegeneration in dementia and Alzheimer's disease

Vascular insults can initiate a cascade of molecular events leading to neurodegeneration, cognitive impairment, and dementia. Here, we review the cellular and molecular mechanisms in cerebral blood vessels and the pathophysiological events leading to cerebral blood flow dysregulation and disruption of the neurovascular unit and the blood-brain barrier, which all may contribute to the onset and progression of dementia and Alzheimer's disease (AD). Particularly, we examine the link between neurovascular dysfunction and neurodegeneration including the effects of AD genetic risk factors on cerebrovascular functions and clearance of Alzheimer's amyloid-β peptide toxin, and the impact of vascular risk factors, environment, and lifestyle on cerebral blood vessels, which in turn may affect synaptic, neuronal, and cognitive functions. Finally, we examine potential experimental treatments for dementia and AD based on the neurovascular model, and discuss some critical questions to be addressed by future studies. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock.

Resveratrol and Ophthalmic Diseases

Resveratrol, a naturally occurring plant polyphenol found in grapes, is the principal biologically active component in red wine. Clinical studies have shown that resveratrol due to its potent anti-oxidant and anti-inflammatory properties are cardio-protective, chemotherapeutic, neuroprotective, and display anti-aging effects. Oxidative stress and inflammation play a critical role in the initiation and progression of age-related ocular diseases (glaucoma, cataract, diabetic retinopathy and macular degeneration) that lead to progressive loss of vision and blindness. In vitro and in vivo (animal model) experimental studies performed so far have provided evidence for the biological effects of resveratrol on numerous pathways including oxidative stress, inflammation, mitochondrial dysfunction, apoptosis, pro-survival or angiogenesis that are implicated in the pathogenesis of these age-related ocular disorders. In this review, we provide a brief overview of current scientific literature on resveratrol, its plausible mechanism(s) of action, its potential use and current limitations as a nutritional therapeutic intervention in the eye and its related disorders.