Resveratrol and the eye: activity and molecular mechanisms

Risk factors for diabetic retinopathy, diabetic macular edema, and sight-threatening diabetic retinopathy

OBJECTIVE

To identify the risk factors for the development of diabetic retinopathy (DR), diabetic macular edema (DME), and sight-threatening DR (STDR) based on a city-wide diabetes screening program.

RESEARCH DESIGN AND METHODS

Diabetic patients were prospectively recruited between June 2016 and December 2022. All patients underwent dilated fundus photography centered on the disc and macula or macular spectral domain optical coherence tomography (SD-OCT) scan. Complete medical history was documented. Systematic examination, blood analysis, and urinalysis were performed. Multivariate logistic regression analysis adjusting for age and sex was conducted.

RESULTS

Out of 7274 diabetic patients, 6840 had gradable images, among which 3054 (42.0%) were graded as DR, 1153 (15.9%) as DME, and 1500 (20.6%) as STDR. The factors associated with DR, DME, and STDR included younger age (odds ratio [OR]: 0.96, 0.97, and 0.96 respectively), lower BMI (OR: 0.97, 0.95, and 0.95 respectively), longer duration of diabetes (OR: 1.07, 1.03, and 1.05 respectively) and positive of urinary albumin (OR: 2.22, 2.56, and 2.88 respectively). Other associated factors included elevated blood urea nitrogen (OR: 1.22, 1.28, and 1.27 respectively), higher LDL-cholesterol, lower blood hemoglobin (OR: 0.98, 0.98, and 0.98), insulin intake, presence of diabetic foot pathologies and diabetic peripheral neuropathy. We also identified novel risk factors, including high serum potassium (OR: 1.37, 1.46, and 1.55 respectively), high-serum sodium (OR: 1.02, 1.02, and 1.04 respectively). Better family income was a protective factor for DR, DME, and STDR. Alcohol consumption once a week was also identified as a protective factor for DR.

CONCLUSIONS

Similar risk factors for DR, DME, and STDR were found in this study. Our data also indicates high serum sodium, high serum potassium, low blood hemoglobin, and level of family income as novel associated factors for DR, DME, and STDR, which can help with DR monitoring and management.

The potential benefits of polyphenols for corneal diseases

The cornea functions as the primary barrier of the ocular surface, regulating temperature and humidity while providing protection against oxidative stress, harmful stimuli and pathogenic microorganisms. Corneal diseases can affect the biomechanical and optical properties of the eye, resulting in visual impairment or even blindness. Due to their diverse origins and potent biological activities, plant secondary metabolites known as polyphenols offer potential advantages for treating corneal diseases owing to their anti-inflammatory, antioxidant, and antibacterial properties. Various polyphenols and their derivatives have demonstrated diverse mechanisms of action in vitro and in vivo, exhibiting efficacy against a range of corneal diseases including repair of tissue damage, treatment of keratitis, inhibition of neovascularization, alleviation of dry eye syndrome, among others. Therefore, this article presents a concise overview of corneal and related diseases, along with an update on the research progress of natural polyphenols in safeguarding corneal health. A more comprehensive understanding of natural polyphenols provides a novel perspective for secure treatment of corneal diseases.

Pharmacotherapy and Nutritional Supplements for Neovascular Eye Diseases

In this review, we aim to provide an overview of the recent findings about the treatment of neovascular retinal diseases. The use of conventional drugs and nutraceuticals endowed with antioxidant and anti-inflammatory properties that may support conventional therapies will be considered, with the final aim of achieving risk reduction (prevention) and outcome improvement (cooperation between treatments) of such sight-threatening proliferative retinopathies. For this purpose, we consider a medicinal product one that contains well-defined compound(s) with proven pharmacological and therapeutic effects, usually given for the treatment of full-blown diseases. Rarely are prescription drugs given for preventive purposes. A dietary supplement refers to a compound (often an extract or a mixture) used in the prevention or co-adjuvant treatment of a given pathology. However, it must be kept in mind that drug-supplement interactions may exist and might affect the efficacy of certain drug treatments. Moreover, the distinction between medicinal products and dietary supplements is not always straightforward. For instance, melatonin is formulated as a medicinal product for the treatment of sleep and behavioral problems; at low doses (usually below 1 mg), it is considered a nutraceutical, while at higher doses, it is sold as a psychotropic drug. Despite their lower status with respect to drugs, increasing evidence supports the notion of the beneficial effects of dietary supplements on proliferative retinopathies, a major cause of vision loss in the elderly. Therefore, we believe that, on a patient-by-patient basis, the administration of nutraceuticals, either alone or in association, could benefit many patients, delaying the progression of their disease and likely improving the efficacy of pharmaceutical drugs.

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.

Nano-Formulation of Antioxidants as Effective Inhibitors of γD-Crystallin Aggregation

The aggregation of crystallin proteins is related to cataracts and age-related macular degeneration. Apart from surgical replacement of the cataract lens, no other alternative treatment is available till date for this ailment. In the current work, we carried out an in-depth investigation of the effect of polyphenol-loaded nano-formulations on the aggregation of γD-crystallin. At first, the protein was allowed to form amorphous aggregates under denaturing conditions. Several polyphenols were then tried to inhibit the aggregation of the protein. Among the polyphenols tested, resveratrol and quercetin were found to be the most effective. Since polyphenols are prone to degradation, they were encapsulated in chitosan nanoparticles in order to provide ambient conditions for them to function effectively. The loading efficiency and polyphenol release kinetics were subsequently tested. Finally, the efficacy of resveratrol/quercetin-loaded chitosan nano-particles as inhibitors of γD-crystallin aggregation was confirmed in a series of experiments demonstrating the potency of the system in the prospective therapeutic intervention of eye ailments concerning self-assembly of γD-crystallin proteins.

Dietary Intake and Diabetic Retinopathy: A Systematic Review of the Literature

Diabetic retinopathy (DR) is a common microvascular complication of diabetes mellitus. The evidence connecting dietary intake and DR is emerging, but uncertain. We conducted a systematic review to comprehensively summarize the current understanding of the associations between dietary consumption, DR and diabetic macular edema (DME). We systematically searched PubMed, Embase, Medline, and the Cochrane Central Register of Controlled Trials between January 1967 to May 2022 for all studies investigating the effect of diet on DR and DME. Of the 4962 articles initially identified, 54 relevant articles were retained. Our review found that higher intakes of fruits, vegetables, dietary fibers, fish, a Mediterranean diet, oleic acid, and tea were found to have a protective effect against DR. Conversely, high intakes of diet soda, caloric intake, rice, and choline were associated with a higher risk of DR. No association was seen between vitamin C, riboflavin, vitamin D, and milk and DR. Only one study in our review assessed dietary intake and DME and found a risk of high sodium intake for DME progression. Therefore, the general recommendation for nutritional counseling to manage diabetes may be beneficial to prevent DR risk, but prospective studies in diverse diabetic populations are needed to confirm our findings and expand clinical guidelines for DR management.

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.

Recent Developments of Nanostructures for the Ocular Delivery of Natural Compounds

Ocular disorders comprising various diseases of the anterior and posterior segments are considered as the main reasons for blindness. Natural products have been identified as potential treatments for ocular diseases due to their anti-oxidative, antiangiogenic, and anti-inflammatory effects. Unfortunately, most of these beneficial compounds are characterised by low solubility which results in low bioavailability and rapid systemic clearance thus requiring frequent administration or requiring high doses, which hinders their therapeutic applications. Additionally, the therapeutic efficiency of ocular drug delivery as a popular route of drug administration for the treatment of ocular diseases is restricted by various anatomical and physiological barriers. Recently, nanotechnology-based strategies including polymeric nanoparticles, micelles, nanofibers, dendrimers, lipid nanoparticles, liposomes, and niosomes have emerged as promising approaches to overcome limitations and enhance ocular drug bioavailability by effective delivery to the target sites. This review provides an overview of nano-drug delivery systems of natural compounds such as thymoquinone, catechin, epigallocatechin gallate, curcumin, berberine, pilocarpine, genistein, resveratrol, quercetin, naringenin, lutein, kaempferol, baicalin, and tetrandrine for ocular applications. This approach involves increasing drug concentration in the carriers to enhance drug movement into and through the ocular barriers.

Normal-tension glaucoma: Current concepts and approaches-A review

Normal tension glaucoma (NTG) has remained a challenging disease. We review, from an epidemiological perspective, why we should redefine normality, act earlier at lower pre-treatment intraocular pressure (IOP) level, and the role of ocular perfusion pressures, noting that perfusion is affected by defective vascular bed autoregulation and endothelial dysfunction. The correlation of silent cerebral infarcts (SCI) and NTG may indicate that NTG belongs to a wider spectrum of small vessel diseases (SVD), with its main pathology being also on vascular endothelium. Epidemiological studies also suggested that vascular geometry, such as fractal dimension, may affect perfusion efficiency, occurrence of SCI, SVD and glaucoma. Artificial intelligence with deep learning, may help predicting NTG progression from vascular geometry. Finally, we review latest evidence on the role of minimally-invasive glaucoma surgery, lasers, and newer drugs. We conclude that IOP is not the only modifiable risk factors as, many vascular risk factors are readily modifiable.

Synthetic Biology-Driven Microbial Production of Resveratrol: Advances and Perspectives

Resveratrol, a bioactive natural product found in many plants, is a secondary metabolite and has attracted much attention in the medicine and health care products fields due to its remarkable biological activities including anti-cancer, anti-oxidation, anti-aging, anti-inflammation, neuroprotection and anti-glycation. However, traditional chemical synthesis and plant extraction methods are impractical for industrial resveratrol production because of low yield, toxic chemical solvents and environmental pollution during the production process. Recently, the biosynthesis of resveratrol by constructing microbial cell factories has attracted much attention, because it provides a safe and efficient route for the resveratrol production. This review discusses the physiological functions and market applications of resveratrol. In addition, recent significant biotechnology advances in resveratrol biosynthesis are systematically summarized. Furthermore, we discuss the current challenges and future prospects for strain development for large-scale resveratrol production at an industrial level.

Dexmedetomidine inhibits endoplasmic reticulum stress to suppress pyroptosis of hypoxia/reoxygenation-induced intestinal epithelial cells via activating the SIRT1 expression

Dexmedetomidine (Dex) can protect the intestine against ischemia/reperfusion (I/R)-induced injury. Sirtuin 1 (SIRT1) pathway, which could be activated by Dex, was reported to inhibit I/R injury. Pyroptosis plays an important role in intestinal diseases. We aimed to investigate whether Dex could attenuate pyroptosis of hypoxia/reoxygenation (H/R)-induced intestinal epithelial cells via activating SIRT1. The intestinal epithelial cell line IEC-6 with or without SIRT1 knockdown after H/R treatment was exposed to Dex, then cell viability, endoplasmic reticulum stress (ERS), apoptosis, pyroptosis, inflammatory cytokines production and SIRT1 expression were detected. Results showed that Dex treatment had no significant effect on IEC-6 cell viability but rescued the H/R-reduced cell viability. The expression of proteins involved in ERS including Grp78, Gadd153 and caspase 12 was enhanced upon H/R stimulation, but was reversely reduced by Dex. The cell apoptosis increased by H/R was also decreased by Dex. Additionally, Dex inhibited pyroptosis and inflammation, which were markedly promoted upon H/R stimulation. The expression of SIRT1, which was reduced after H/R treatment was also partially rescued by Dex. Finally, the above effects of Dex were all blocked by SIRT1 knockdown. In conclusion, Dex could inhibit H/R-induced intestinal epithelial cells ERS, apoptosis and pyroptosis via activating SIRT1 expression.

Resveratrol attenuates retinal ganglion cell loss in a mouse model of retinal ischemia reperfusion injury via multiple pathways

BACKGROUND

Resveratrol (RES) is a natural polyphenol that has been shown to protect retinal ganglion cells (RGCs) following retinal ischemia reperfusion (I/R) injury. However, the molecular mechanisms of resveratrol function are yet to be fully elucidated. Thus, this study explored the potential mechanisms of resveratrol in vivo.

METHODS

A retinal ischemia reperfusion injury model was established in adult male C57BL/6 J mice. Intraperitoneal injection of resveratrol was administered continuously for 5 days. RGC survival was determined by immunofluorescence staining with Brn3a. Flash electroretinography (ERG) was conducted to assess visual function. Proteins of HIF-1a, VEGF, p38, p53, PI3K, Akt, Bax, Bcl2, and Cleaved Caspase3 were detected using Western blot.

RESULTS

RES administration significantly ameliorated retinal thickness damage and increased Brn3a stained RGCs 7 days after I/R injury. We also found that administration of RES remarkably inhibited the upregulation of mitochondrial apoptosis-related protein Bax and Cleaved Caspase3, as well as increased the expression of Bcl2. Furthermore, RES administration significantly suppressed the I/R injury-induced upregulation of the HIF-1a/VEGF and p38/p53 pathways, while activating the I/R injury-induced downregulation of the PI3K/Akt pathway. Moreover, RES administration remarkably improved retinal function after I/R injury-induced functional impairment.

CONCLUSIONS

Our data demonstrated that resveratrol can mitigate retinal ischemic injury induced RGC loss and retinal function impairment by inhibiting the HIF-1a/VEGF and p38/p53 pathways while activating the PI3K/Akt pathway. Therefore, our results further reinforce that resveratrol has potential for treating glaucoma.

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.

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.

The Protective Effects of Flavonoids in Cataract Formation through the Activation of Nrf2 and the Inhibition of MMP-9

Cataracts account for over half of global blindness. Cataracts formations occur mainly due to aging and to the direct insults of oxidative stress and inflammation to the eye lens. The nuclear factor-erythroid-2-related factor 2 (Nrf2), a transcriptional factor for cell cytoprotection, is known as the master regulator of redox homeostasis. Nrf2 regulates nearly 600 genes involved in cellular protection against contributing factors of oxidative stress, including aging, disease, and inflammation. Nrf2 was reported to disrupt the oxidative stress that activates Nuclear factor-κB (NFκB) and proinflammatory cytokines. One of these cytokines is matrix metalloproteinase 9 (MMP-9), which participates in the decomposition of lens epithelial cells (LECs) extracellular matrix and has been correlated with cataract development. Thus, during inflammatory processes, MMP production may be attenuated by the Nrf2 pathway or by the Nrf2 inhibition of NFκB pathway activation. Moreover, plant-based polyphenols have garnered attention due to their presumed safety and efficacy, nutritional, and antioxidant effects. Polyphenol compounds can activate Nrf2 and inhibit MMP-9. Therefore, this review focuses on discussing Nrf2's role in oxidative stress and cataract formation, epigenetic effect in Nrf2 activity, and the association between Nrf2 and MMP-9 in cataract development. Moreover, we describe the protective role of flavonoids in cataract formation, targeting Nrf2 activation and MMP-9 synthesis inhibition as potential molecular targets in preventing cataracts.

New resveratrol micelle formulation for ocular delivery: characterization and in vitro/in vivo evaluation

Many eye diseases, such as corneal wound healing after injury, involve oxidative stress and inflammatory responses; however, many efficient natural antioxidants (e.g. resveratrol) have limited application in ophthalmology due to their poor solubility, low stability and poor ocular bioavailability. In this work, the aim was to formulate resveratrol into a micelle ophthalmic solution for efficient delivery to the eye. A Soluplus micelle ophthalmic solution containing resveratrol (Sol-Res) was formulated and optimized with a small and uniform dispersion in an ophthalmic solution. Sol-Res did not show any cell toxicity but promoted cell proliferation in both the short- and long-term cytotoxicity tests. The in vivo eye irritation test also verified the well ocular tolerance of the Sol-Res ophthalmic solution. The chemical stability of resveratrol in micelles in an aqueous solution was greatly improved over the free resveratrol solution, and Sol-Res also showed a good storage stability in the short-term storage stability test. Sol-Res showed improved in vitro passive permeation, in vitro cellular uptake, and in vivo corneal permeation over the free Res suspension solution. Furthermore, Sol-Res favored in vivo corneal wound healing, and the inhibition of key anti-inflammation mediators and the production of antioxidant factors in mRNA expression was observed in the Sol-Res treated wound healing corneas, suggesting that the mechanisms that regulate proinflammatory cytokines and oxidative stress might be involved in its therapeutic effect. Therefore, Sol-Res might be a promising candidate for further clinical application.

Matrix Metalloproteinases in Age-Related Macular Degeneration (AMD)

Age-related macular degeneration (AMD) is a complex, multifactorial and progressive retinal disease affecting millions of people worldwide. In developed countries, it is the leading cause of vision loss and legal blindness among the elderly. Although the pathogenesis of AMD is still barely understood, recent studies have reported that disorders in the regulation of the extracellular matrix (ECM) play an important role in its etiopathogenesis. The dynamic metabolism of the ECM is closely regulated by matrix metalloproteinases (MMPs) and the tissue inhibitors of metalloproteinases (TIMPs). The present review focuses on the crucial processes that occur at the level of the Bruch’s membrane, with special emphasis on MMPs, TIMPs, and the polymorphisms associated with increased susceptibility to AMD development. A systematic literature search was performed, covering the years 1990–2020, using the following keywords: AMD, extracellular matrix, Bruch’s membrane, MMPs, TIMPs, and MMPs polymorphisms in AMD. In both early and advanced AMD, the pathological dynamic changes of ECM structural components are caused by the dysfunction of specific regulators and by the influence of other regulatory systems connected with both genetic and environmental factors. Better insight into the pathological role of MMP/TIMP complexes may lead to the development of new strategies for AMD treatment and prevention.

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.

Association of alcohol intake with incidence and progression of diabetic retinopathy

PURPOSE

We examined the longitudinal association of baseline alcohol intake and frequency with the 6-year incidence and progression of diabetic retinopathy (DR) in a population-based cohort of Singaporean Indians.

METHODS

We included 656 participants with diabetes mellitus, gradable retinal photographs from baseline (2007-2009) and follow-up (2013-2015) examinations, information on alcohol intake and other relevant data from the Singapore Indian Eye Study were included. Incident DR was defined using the Modified Airlie House Classification as no DR at baseline and at least minimal non-proliferative DR at follow-up; and DR progression as at least a one-step worsening in DR at follow-up from minimal or worse status at baseline, excluding those with proliferative DR.

RESULTS

The mean age (SD) of our participants (n=656) was 58.8 (9.2) years, and 54.4% were male. At follow-up, 82 of 510 (16%) participants developed DR, and 45 of 146 (30.8%) had DR progression. 65 (12.7%) and 28 (19.1%) participants consumed alcohol in incident DR and progression categories, respectively. In multivariable analyses, those who consumed alcohol had nearly two-thirds reduced odds of incident DR (OR (95% CI): 0.36 (0.13 to 0.98)) compared with those who did not. Participants with infrequent consumption of alcohol also had a reduction in odds of incident DR (0.17 (0.04 to 0.69)), compared with non-drinkers. No association was found between alcohol consumption and DR progression.

CONCLUSIONS AND RELEVANCE

In our longitudinal population of Singapore Indians, baseline alcohol intake, particularly infrequent consumption, was associated with lower risk of developing DR, compared with non-drinkers, in line with previous cross-sectional findings.

Resveratrol as Inducer of Autophagy, Pro-Survival, and Anti-Inflammatory Stimuli in Cultured Human RPE Cells

Purpose: To investigate the mechanism by which resveratrol acts upon retinal pigment epithelial (RPE) cells and to characterize its effect upon autophagy, survival, and inflammation, with consequent implications to treatment for age-related macular degeneration (AMD). Methods: Cultured ARPE-19 cells were exposed to 10 and 50 μM resveratrol. Cell survival/death was determined by annexin-FITC/propidium iodide using flow cytometry, while autophagy was studied by detecting autophagic vacuoles formation (acridine orange and transmission electron microscopy), as well as LC3II/I ratio and p62 expression by Western blot. In addition, time-lapse confocal microscopy of a pDENDRA-LC3 expression vector was performed to detect autophagy in transfected ARPE-19 cells under the different treatment conditions. Inhibition of proteasomal and autophagy-lysosomal fusion was carried out by MG-132 and chloroquine, respectively, while induction of autophagy was achieved by rapamycin treatment. Detection of secreted cytokines by ARPE-19 cells using Human XL Cytokine Array was performed under oxidative stress (H₂O₂) and resveratrol treatments, respectively. Results: Resveratrol induced autophagy in ARPE-19 cells as determined by augmented presence of autophagic vacuoles, increased LC3II/I ratio and decreased p62 expression, as well as time-lapse confocal microscopy using pDENDRA-LC3 expression vector. Resveratrol acted similarly to proteasomal inhibition and downstream of mammalian target of rapamycin (mTOR), since upstream inhibition of autophagy by 3-methyladenine could not inhibit autophagy in ARPE-19 cells. Co-treatmeant by rapamycin and/or proteasome inhibition showed no additive effect upon autophagy induction. ARPE-19 cells treated by resveratrol showed lower cell death rate compared to untreated controls. Resveratrol induced a specific anti-inflammatory response in ARPE-19 cells. Conclusions: Resveratrol can induce autophagy, pro-survival, and anti-inflammatory stimuli in ARPE-19 cells, properties which could be plausible to formulate future treatment modalities for AMD.

Toxic effects of A2E in human ARPE-19 cells were prevented by resveratrol: a potential nutritional bioactive for age-related macular degeneration treatment

Age-related macular degeneration (AMD) is a late-onset retinal disease and the leading cause of central vision loss in the elderly. Degeneration of retinal pigment epithelial cells (RPE) is a crucial contributing factor responsible for the onset and progression of AMD. The toxic fluorophore N-retinyl-N-retinylidene ethanolamine (A2E), a major lipofuscin component, accumulates in RPE cells with age. Phytochemicals with antioxidant properties may have a potential role in both the prevention and treatment of this age-related ocular disease. Particularly, there is an increased interest in the therapeutic effects of resveratrol (RSV), a naturally occurring polyphenol (3,4',5-trihydroxystilbene). However, the underlying mechanism of the RSV antioxidative effect in ocular diseases has not been well explored. We hypothesized that this bioactive compound may have beneficial effects for AMD. To this end, to investigate the potential profits of RSV against A2E-provoked oxidative damage, we used human RPE cell line (ARPE-19). RSV (25 µM) attenuates the cytotoxicity and the typical morphological characteristics of apoptosis observed in 25 µM A2E-laden cells. RSV pretreatment strengthened cell monolayer integrity through the preservation of the transepithelial electrical resistance and reduced the fluorescein isothiocyanate (FITC)-dextran diffusion rate as well as cytoskeleton architecture. In addition, RSV exhorts protective effects against A2E-induced modifications in the intracellular redox balance. Finally, RSV also prevented A2E-induced mitochondrial network fragmentation. These findings reinforce the idea that RSV represents an attractive bioactive for therapeutic intervention against ocular diseases associated with oxidative stress such as AMD.

PFN1 and integrin-β1/mTOR axis involvement in cornea differentiation of fibroblast limbal stem cells

Ex vivo limbal stem cell transplantation is the main therapeutic approach to address a complete and functional re-epithelialization in corneal blindness, the second most common eye disorder. Although important key points were defined, the molecular mechanisms involved in the epithelial phenotype determination are unclear. Our previous studies have demonstrated the pluripotency and immune-modulatory of fibroblast limbal stem cells (f-LSCs), isolated from the corneal limbus. We defined a proteomic profile especially enriched in wound healing and cytoskeleton-remodelling proteins, including Profilin-1 (PFN1). In this study we postulate that pfn-1 knock down promotes epithelial lineage by inhibiting the integrin-β1(CD29)/mTOR pathway and subsequent NANOG down-expression. We showed that it is possible modulate pfn1 expression levels by treating f-LSCs with Resveratrol (RSV), a natural compound: pfn1 decline is accompanied with up-regulation of the specific differentiation epithelial genes pax6 (paired-box 6), sox17 (sex determining region Y-box 17) and ΔNp63-α (p63 splice variant), consistent with drop-down of the principle stem gene levels. These results contribute to understand the molecular biology of corneal epithelium development and suggest that pfn1 is a potential molecular target for the treatment of corneal blindness based on epithelial cell dysfunction.

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.

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.

Effects of Resveratrol on Inflammatory Biomarkers in Glaucomatous Human Trabecular Meshwork Cells

Purpose: Resveratrol (RSV), an antioxidant polyphenol, has demonstrated beneficial effects in various ocular diseases including glaucoma. Our study was designed to evaluate the effects of RSV on nitric oxide synthase (NOS) enzymes, nitric oxide (NO) and interleukin-1 alpha (IL-1 α), in human glaucomatous trabecular meshwork (TM) cells. Methods: Western blot was utilized to determine endothelial and inducible NOS (eNOS, iNOS) expression. The concentration-related effects of RSV on IL-1 α and NO levels were assessed using the respective ELISA kits. Results: Densitometry data showed concentration-related increases in eNOS, and reduction in iNOS expression at high RSV concentrations. RSV treatment (0.1, 1, 10 and 100 µM) resulted in increased NO levels (6 ± 0.7, 7 ± 0.8, 7.3 ± 0.7 and 9.5 ± 1 nM/mg protein, respectively). The average value obtained for control was 4.8 ± 0.6 nM/mg protein. Significant increases in IL-1α levels were observed with lower concentrations of RSV. However, at higher RSV concentrations (10–100 μM), IL-1 levels decreased. Conclusions: Resveratrol increased NO in glaucomatous TM cells, possibly by increasing eNOS expression. Thus, RSV-induced NO production supports the beneficial effects of this antioxidant in glaucoma. Furthermore, our results showing a reduction in iNOS, a contributor to oxidative stress expression, further support RSV’s antioxidant capabilities in vision.

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.

The Effects of Resveratrol in Patients with Cardiovascular Disease and Heart Failure: A Narrative Review

Cardiovascular disease (CVD) is the main cause of death globally and responsible for the second highest number of deaths in Canada. Medical advancements in the treatment of CVD have led to patients living longer with CVD but often progressing to another condition called heart failure (HF). As a result, HF has emerged in the last decade as a major medical concern. Fortunately, various “traditional” pharmacotherapies for HF exist and have shown success in reducing HF-associated mortality. However, to augment the treatment of patients with CVD and/or HF, alternative pharmacotherapies using nutraceuticals have also shown promise in the prevention and treatment of these two conditions. One of these natural compounds considered to potentially help treat HF and CVD and prevent their development is resveratrol. Herein, we review the clinical findings of resveratrol’s ability to be used as an effective treatment to potentially help treat HF and CVD. This will allow us to gain a more fulsome appreciation for the effects of resveratrol in the health outcomes of specific patient populations who have various disorders that constitute CVD.

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.

Role of Sirtuin 1 in the pathogenesis of ocular disease (Review)

Sirtuin (SIRT)1, a member of the SIRT family, is a highly conserved NAD+‑dependent histone deacetylase, which has a regulatory role in numerous physiological and pathological processes by removing acetyl groups from various proteins. SIRT1 controls the activity of numerous transcription factors and cofactors, which impacts the downstream gene expression, and eventually alleviates oxidative stress and associated damage. Numerous studies have revealed that dysfunction of SIRT1 is linked with ocular diseases, including cataract, age‑associated macular degeneration, diabetic retinopathy and glaucoma, while ectopic upregulation of SIRT1 protects against various ocular diseases. In the present review, the significant role of SIRT1 and the potential therapeutic value of modulating SIRT1 expression in ocular development and eye diseases is summarized.

Age-Related Macular Degeneration: New Paradigms for Treatment and Management of AMD

Age-related macular degeneration (AMD) is a well-characterized and extensively studied disease. It is currently considered the leading cause of visual disability among patients over 60 years. The hallmark of early AMD is the formation of drusen, pigmentary changes at the macula, and mild to moderate vision loss. There are two forms of AMD: the “dry” and the “wet” form that is less frequent but is responsible for 90% of acute blindness due to AMD. Risk factors have been associated with AMD progression, and they are taking relevance to understand how AMD develops: (1) advanced age and the exposition to environmental factors inducing high levels of oxidative stress damaging the macula and (2) this damage, which causes inflammation inducing a vicious cycle, altogether causing central vision loss. There is neither a cure nor treatment to prevent AMD. However, there are some treatments available for the wet form of AMD. This article will review some molecular and cellular mechanisms associated with the onset of AMD focusing on feasible treatments for each related factor in the development of this pathology such as vascular endothelial growth factor, oxidative stress, failure of the clearance of proteins and organelles, and glial cell dysfunction in AMD.

Oxidative stress and reactive oxygen species: a review of their role in ocular disease

For many years, oxidative stress arising from the ubiquitous production of reactive oxygen species (ROS) has been implicated in the pathogenesis of various eye diseases. While emerging research has provided some evidence of the important physiological role of ROS in normal cell function, disease may arise where the concentration of ROS exceeds and overwhelms the body’s natural defence against them. Additionally, ROS may induce genomic aberrations which affect cellular homoeostasis and may result in disease. This literature review examines the current evidence for the role of oxidative stress in important ocular diseases with a view to identifying potential therapeutic targets for future study. The need is particularly pressing in developing treatments for conditions which remain notoriously difficult to treat, including glaucoma, diabetic retinopathy and age-related macular degeneration.

Resveratrol reverses the adverse effects of bevacizumab on cultured ARPE-19 cells

Age-related macular degeneration (AMD) and proliferative diabetic retinopathy (PDR) are one of the major causes of blindness caused by neo-vascular changes in the retina. Intravitreal anti-VEGF injections are widely used in the treatment of wet-AMD and PDR. A significant percentage of treated patients have complications of repeated injections. Resveratrol (RES) is a polyphenol phytoalexin with anti-oxidative, anti-inflammatory and anti-proliferative properties. Hence, we hypothesized that if RES is used in combination with bevacizumab (BEV, anti-VEGF), it could reverse the adverse effects that precipitate fibrotic changes, drusen formation, tractional retinal detachment and so on. Human retinal pigment epithelial cells were treated with various combinations of BEV and RES. There was partial reduction in secreted VEGF levels compared to untreated controls. Epithelial-mesenchymal transition was lower in BEV + RES treated cultures compared to BEV treated cultures. The proliferation status was similar in BEV + RES as well as BEV treated cultures both groups. Phagocytosis was enhanced in the presence of BEV + RES compared to BEV. Furthermore, we observed that notch signaling was involved in reversing the adverse effects of BEV. This study paves way for a combinatorial strategy to treat as well as prevent adverse effects of therapy in patients with wet AMD and PDR.

RES-loaded pegylated CS NPs: for efficient ocular delivery

The objective of this study is to develop resveratrol (RES) loaded polyethylene glycols (PEGs) modified chitosan (CS) nanoparticles (NPs) by ionic gelation method for the treatment of glaucoma. While increasing the concentration of PEG, the particle size and polydispersity index of the formulations increased. Entrapment efficiency and RES loading (RL) of NPs decreased while increasing PEG concentration. The in vitro release of NPs showed an initial burst release of RES (45%) followed by controlled release. Osmolality of formulations revealed that the prepared NPs were iso-osmolar with the tear. Ocular tolerance of the NPs was evaluated using hen's egg test on the chorioallantoic membrane and it showed that the NPs were non-irritant. RES-loaded PEG-modified CS NPs shows an improved corneal permeation compared with RES dispersion. Fluorescein isothiocyanate loaded CS NPs accumulated on the surface of the cornea but the PEG-modified CS NPs crossed the cornea and reached retinal choroid. RES-loaded PEG-modified CS NPs reduced the intra-ocular pressure (IOP) by 4.3 ± 0.5 mmHg up to 8 h in normotensive rabbits. These results indicate that the developed NPs have efficient delivery of RES to the ocular tissues and reduce the IOP for the treatment of glaucoma.

Co-encapsulated resveratrol and quercetin in chitosan and peg modified chitosan nanoparticles: For efficient intra ocular pressure reduction

Natural anti-oxidants resveratrol (RES) and quercetin (QUR) posses the ability to reduce intra ocular pressure efficiently. Concurrent administration of RES and QUR was able to enhance the bioavailability of RES. Present research work describes upsurge of QUR in RES loaded chitosan (CS) nanoparticles (NPs) and polyethylene glycol (PEG) modified CS NPs for improved delivery and synergic effects on reducing intra ocular pressure for the treatment of glaucoma. CS NPs and PEG modified CS NPs were prepared by ionic gelation of tripolyphosphate and CS. The synthesised NPs were spherical in shape and RES entrapment and loading efficiency in the formulation decreased with increasing PEG concentration. Particle size of the formulation increased while incorporating PEG and drugs. The crystalline nature of RES and QUR changed in the NPs and that was confirmed by XRD study. Free radical neutralising efficiency improved while incorporating QUR in the formulation. Ex-vivo corneal permeation of RES was higher from RES and QUR loaded formulation than RES alone containing NPs and free RES dispersion. RES and QUR loaded PEG modified CS NPs showed sustained and enhanced reduction of intra ocular pressure (5.5±0.5mmHg) in normotensive rabbits.

Tissue Distribution of trans-Resveratrol and Its Metabolites after Oral Administration in Human Eyes

Purpose. This study was performed to measure the concentration of trans-resveratrol and its three metabolites in human eyes. Methods. The patients who underwent pars plana vitrectomy for rhegmatogenous retinal detachment were included. The participants were orally given trans-resveratrol-based supplement (Longevinex®). A suitable amount of conjunctiva, aqueous humor, and vitreous humor were obtained during the operation. High-performance liquid chromatography (HPLC) with mass spectrometry (LC/MS/MS) was used to detect the concentration of trans-resveratrol and its three metabolites in the various samples. Results. The average concentration of resveratrol in the conjunctiva was 17.19 ± 15.32 nmol/g (mean ± SD). The concentration of resveratrol in the aqueous humor was close to the limit of detection, but its metabolites could be quantified. The concentrations of resveratrol metabolites in the aqueous humor can be detected. In the vitreous humor, the average concentration of resveratrol-3-O-sulfate was 62.95 ± 41.97 nmol/L. The sulfate conjugations of resveratrol were recovered in the conjunctiva, aqueous humor, and vitreous humor. Conclusions. Resveratrol and its three metabolites can be detected in the ocular tissues after oral administration. Although the concentration of parent resveratrol was low in the eyes, its metabolites could be detected and may have a role in the treatment of ocular diseases.

Dietary Compound Chrysin Inhibits Retinal Neovascularization with Abnormal Capillaries in db/db Mice

Diabetic retinopathy (DR) develops in a significant proportion of patients with chronic diabetes, characterized by retinal macular edema and abnormal retinal vessel outgrowth leading to vision loss. Chrysin, a naturally-occurring flavonoid found in herb and honeycomb, has anti-inflammatory, antioxidant, and anti-cancer properties. This study sought to determine the protective effects of chrysin on retinal neovascularization with abnormal vessels and blood-retinal barrier (BRB) breakdown in 33 mM glucose-exposed human retinal endothelial cells and in db/db mouse eyes. High glucose caused retinal endothelial apoptotic injury, which was inhibited by submicromolar chrysin. This compound diminished the enhanced induction of HIF-1α, vascular endothelial growth factor (VEGF), and VEGF receptor-2 (VEGFR2) in high glucose-exposed retinal endothelial cells. Consistently, oral administration of 10 mg/kg chrysin reduced the induction of these proteins in db/db mouse eye tissues. In addition, chrysin restored the decrement of VE-cadherin and ZO-1 junction proteins and PECAM-1 in hyperglycemia-stimulated retinal endothelial cells and diabetic mouse retina, possibly maintaining tight cell-cell interactions of endothelial cells and pericytes. Anti-apoptotic chrysin reduced the up-regulation of Ang-1, Ang-2, and Tie-2 crucial to retinal capillary occlusion and BRB permeability. Furthermore, orally treating chrysin inhibited acellular capillary formation, neovascularization, and vascular leakage observed in diabetic retinas. These observations demonstrate, for the first time, that chrysin had a capability to encumber diabetes-associated retinal neovascularization with microvascular abnormalities and BRB breakdown.

Retinal microcirculation in association with caffeinated and alcoholic drinks in subjects at increased cardiovascular risk

OBJECTIVES

The association of caffeinated and alcoholic drinks with microcirculation is poorly investigated. The aim of the study was to investigate the associations of daily consumption of caffeinated and alcoholic drinks with retinal vessel calibers.

METHODS

In consecutive adults at increased risk but free of CVD and diabetes mellitus, (n=181, age: 51.32±12.42 y, 51.4% women), we determined CRAE, CRVE and AVR, respectively. Daily consumption of caffeinated and alcoholic drinks was assessed through 24 h recalls.

RESULTS

After adjustment for potential confounders: (i) caffeine was positively associated with CRVE (b=0.177, P=.006 for left, b=0.208, P=.002 for right eye, respectively) (ii) decaffeinated coffee was positively associated with CRAE (b=0.141, P=.035 for left eye) and negatively associated with CRVE (b=-0.234, P<.001 for left, b=-0.189, P=.006 for right eye, respectively). Regular coffee, tea, alcohol, and any type of alcoholic drink did not associate with retinal vessel calibers.

CONCLUSIONS

Alcohol and alcoholic drinks' consumption were not associated, while decaffeinated coffee and caffeine consumption were associated in an opposing pattern with retinal vessel calibers. The reason of this controversy merits further investigation.

Angiogenesis and Inflammation Crosstalk in Diabetic Retinopathy

Diabetic retinopathy (DR) is one of the most prevalent microvascular complications of diabetes and one of the most frequent causes of blindness in active age. Etiopathogenesis behind this important complication is related to several biochemical, hemodynamic and endocrine mechanisms with a preponderant initial role assumed by polyol pathways, increment of growth factors, accumulation of advanced glycation end products (AGE), activation of protein kinase C (PKC), activation of the renin-angiotensin-aldosterone system (RAAS), and leukostasis. Chronic and sustained hyperglycemia works as a trigger to the early alterations that culminate in vascular dysfunction. Hypoxia also plays an essential role in disease progression with promotion of neovascularization and vascular dystrophies with vitreous hemorrhages induction. Thus, the accumulation of fluids and protein exudates in ocular cavities leads to an opacity augmentation of the cornea that associated to neurodegeneration results in vision loss, being this a devastating characteristic of the disease final stage. During disease progression, inflammatory molecules are produced and angiogenesis occur. Furthermore, VEGF is overexpressed by the maintained hyperglycemic environment and up-regulated by tissue hypoxia. Also pro-inflammatory mediators regulated by cytokines, such as tumor necrosis factor (TNF-α) and interleukin-1 beta (IL-1β), and growth factors leads to the progression of these processes, culminating in vasopermeability (diabetes macular edema) and/or pathological angiogenesis (proliferative diabetic retinopathy). It was found a mutual contribution between inflammation and angiogenesis along the process. J. Cell. Biochem. 117: 2443-2453, 2016. © 2016 Wiley Periodicals, Inc.