Resveratrol and the eye:activity and molecular mechanisms

Purpose: Alcohol consumption is inversely correlated with the incidence of cardiovascular disease. It is thought that red wine is specifically responsible for these cardiovascular benefits, due to its ability to reduce vascular inflammation, facilitate vasorelaxation, and inhibit angiogenesis. This is because of its high polyphenolic content. Resveratrol is the main biologically active polyphenol within red wine. Owing to its vascular-enhancing properties, resveratrol may be effective in the microcirculation of the eye, thereby helping prevent ocular diseases such as age-related macular degeneration, diabetic retinopathy, and glaucoma. Such conditions are accountable for worldwide prevalence of visual loss. Method: A review of the relevant literature was conducted on the ScienceDirect, Web of Science, and PubMed databases. Key words used to carry out the searches included 'red wine', 'polyphenols', 'resveratrol', 'eye' and 'ocular'. Articles relating to the effects of resveratrol on the eye were reviewed. Results: The protective effects of resveratrol within the eye are extensive. It has been demonstrated to have anti-oxidant, anti-apoptotic, anti-tumourogenic, anti-inflammatory, anti-angiogenic and vasorelaxant properties. There are potential benefits of resveratrol supplementation across a wide range of ocular diseases. The molecular mechanisms underlying these protective actions are diverse. Conclusion: Evidence suggests that resveratrol may have potential in the treatment of several ocular diseases. However, while there are many studies indicating plausible biological mechanisms using animal models and in-vitro retinal cells there is a paucity of human research. The evidence base for the use of resveratrol in the management of ocular diseases needs to be increased before recommendations can be made for the use of resveratrol as an ocular supplement. © 2014 Springer-Verlag.

Resveratrol inhibits the release of soluble fms-like tyrosine kinase (sFlt-1) from human placenta

Objective - Soluble vascular endothelial growth factor receptor–1 (also know as soluble fms-like tyrosine kinase [sFlt]-1) is a key causative factor of preeclampsia. Resveratrol, a plant phytoalexin, has antiinflammatory and cardioprotective properties. We sought to determine the effect of resveratrol on sFlt-1 release. Study Design - Human umbilical vein endothelial cells, transformed human trophoblast-8 (HTR/SVneo)-8/SVneo trophoblast cells, or placental explants were incubated with cytokines and/or resveratrol. Conditioned media were assayed for sFlt-1 by enzyme-linked immunosorbent assay and cell proteins used for Western blotting. Results - Resveratrol inhibited cytokine-induced release of sFlt-1 from normal placental explants and from preeclamptic placental explants. Preincubation of human umbilical vein endothelial cells or HTR-8/SVneo cells with resveratrol abrogated sFlt-1 release. Resveratrol prevented the up-regulation of early growth response protein-1 (Egr-1), a transcription factor necessary for induction of the vascular endothelial growth factor receptor–1 gene and caused up-regulation of heme oxygenase–1, a cytoprotective enzyme found to be dysfunctional in preeclampsia. Conclusion - In summary, resveratrol can inhibit sFlt-1 release and up-regulate heme oxygenase–1; thus, may offer therapeutic potential in preeclampsia.

Retinal effects of resveratrol

Resveratrol is a plant polyphenol that has potent anti-inflammatory and anti-oxidant properties. age-related macular degeneration is a degenerative condition characterized by elevated levels of oxidation triggered cell damage and a subsequent inflammatory cascade. Resveratrol prevents activation of inflammatory pathways and is also a potent scavenger of reactive oxygen species and free radicals. Experiments using the mouse model have demonstrated that resveratrol reduces angiogenesis. The evidence suggests that resveratrol would be a useful inclusion in ocular nutritional supplements.

In vitro protective effect and antioxidant mechanism of Resveratrol induced by Dapsone Hydroxylamine in human cells

Dapsone (DDS) hydroxylamine metabolites cause oxidative stress- linked adverse effects in patients, such as methemoglobin formation and DNA damage. This study evaluated the ameliorating effect of the antioxidant resveratrol (RSV) on DDS hydroxylamine (DDSNHOH) mediated toxicity in vitro using human erythrocytes and lymphocytes. The antioxidant mechanism was also studied using in-silico methods. In addition, RSV provided intracellular protection by inhibiting DNA damage in human lymphocytes induced by DDS-NHOH. However, whilst pretreatment with RSV (10-1000 μM significantly attenuated DDS-NHOH-induced methemoglobinemia, but it was not only significantly less effective than methylene blue (MET), but also post-treatment with RSV did not reverse methemoglobin formation, contrarily to that observed with MET. DDS-NHOH inhibited catalase (CAT) activity and reactive oxygen species (ROS) generation, but did not alter superoxide dismutase (SOD) activity in erythrocytes. Pretreatment with RSV did not alter these antioxidant enzymes activities in erythrocytes treated with DDS-NHOH. Theoretical calculations using density functional theory methods showed that DDS-NHOH has a pro-oxidant effect, whereas RSV and MET have antioxidant effect on ROS. The effect on methemoglobinemia reversion for MET was significantly higher than that of RSV. These data suggest that the pretreatment with resveratrol may decrease heme-iron oxidation and DNA damage through reduction of ROS generated in cells during DDS therapy.

Resveratrol stimulates hydrogen sulfide (H2S) formation to relax murine corpus cavernosum

Introduction: Resveratrol (RVT) found in red wine protects against erectile dysfunction and relaxes penile tissue (corpus cavernosum) via a nitric oxide (NO) independent pathway. However, the mechanism remains to be elucidated. Hydrogen sulfide (H2S) is a potent vasodilator and neuromodulator generated in corpus cavernosum. Aims: We investigated whether RVT caused the relaxation of mice corpus cavernosum (MCC) through H2S. Methods: H2S formation is measured by methylene blue assay and vascular reactivity experiments have been performed by DMT strip myograph in CD1 MCC strips. Main Outcome Measures: Endothelial NO synthase (eNOS) inhibitor Nω-Nitro-L-arginine (L-NNA, 0.1mM) or H2S inhibitor aminooxyacetic acid (AOAA, 2mM) which inhibits both cystathionine-β-synthase (CBS) and cystathionine-gamma-lyase (CSE) enzyme or combination of AOAA with PAG (CSE inhibitor) has been used in the presence/absence of RVT (0.1mM, 30min) to elucidate the role of NO or H2S pathways on the effects of RVT in MCC. Concentration-dependent relaxations to RVT, L-cysteine, sodium hydrogen sulfide (NaHS) and acetylcholine (ACh) were studied. Results: Exposure of murine corpus cavernosum to RVT increased both basal and L-cysteine-stimulated H2S formation. Both of these effects were reversed by AOAA but not by L-NNA. RVT caused concentration-dependent relaxation of MCC and that RVT-induced relaxation was significantly inhibited by AOAA or AOAA+PAG but not by L-NNA. L-cysteine caused concentration-dependent relaxations, which are inhibited by AOAA or AOAA+PAG significantly. Incubation of MCC with RVT significantly increased L-cysteine-induced relaxation, and this effect was inhibited by AOAA+PAG. However, RVT did not alter the effect of exogenous H2S (NaHS) or ACh-induced relaxations. Conclusions: These results demonstrate that RVT-induced relaxation is at least partly dependent on H2S formation and acts independent of eNOS pathway. In phosphodiesterase 5 inhibitor (PDE-5i) nonresponder population, combination therapy with RVT may reverse erectile dysfunction via stimulating endogenous H2S formation. Yetik-Anacak G, Dereli MV, Sevin G, Ozzayim O, Erac Y, and Ahmed A. Resveratrol stimulates hydrogen sulfide (H2S) formation to relax murine corpus cavernosum.

Hydrogen sulfide:a novel mechanism for the vascular protection by resveratrol under oxidative stress in mouse aorta

Reactive oxygen species (ROS) decreases bioavailability of nitric oxide (NO) and impairs NO-dependent relaxations. Like NO, hydrogen sulfide (H2S) is an antioxidant and vasodilator; however, the effect of ROS on H2S-induced relaxations is unknown. Here we investigated whether ROS altered the effect of H2S on vascular tone in mouse aorta and determined whether resveratrol (RVT) protects it via H2S. Pyrogallol induced ROS formation. It also decreased H2S formation and relaxation induced by l-cysteine and in mouse aorta. Pyrogallol did not alter sodium hydrogensulfide (NaHS)-induced relaxation suggesting that the pyrogallol effect on l-cysteine relaxations was due to endogenous H2S formation. RVT inhibited ROS formation, enhanced l-cysteine-induced relaxations and increased H2S level in aortas exposed to pyrogallol suggesting that RVT protects against "H2S-dysfunctions" by inducing H2S formation. Indeed, H2S synthesis inhibitor AOAA inhibited the protective effects of RVT. RVT had no effect on Ach-induced relaxation that is NO dependent and the stimulatory effect of RVT on H2S-dependent relaxation was also independent of NO. These results demonstrate that oxidative stress impairs endogenous H2S-induced relaxations and RVT offers protection by inducing H2S suggesting that targeting endogenous H2S pathway may prevent vascular dysfunctions associated by oxidative stress.

Cellular signalling pathways involved in muscle atrophy in cancer cachexia

Cancer cachexia encompases severe weight loss, characterised by the debilitating atrophy of adipose and skeletal muscle mass. Skeletal muscle proteolysis in cancer cachexia is mediated by a sulphated glycoprotein with a relative molecular mass of 24kDa, termed Proteolysis-Inducing Factor (PIF). PIF induced a significant increase in protein degradation, peaking at 4.2nM PIF (p<0.001), ‘chymotrypsin-like’ activity of the proteasome (p<0.001) and increased expression of components of the ATP-ubiquitin dependent proteolytic pathway. This was attenuated in vitro by pre-incubation with the PKC inhibitor calphostin C (100µM) and NF-kB the inhibitors SN50 (18µM), curcumin (50µM) and resveratrol (30µM), 2 hours prior to the addition of PIF. In vivo studies found the IKK inhibitor resveratrol (1mg/kg) to be successful in attenuating protein degradation (p<0.001) and upregulation of ubiquitin-dependent proteolysis in MAC16 tumour bearing mice. C2C12 myoblasts transfected with mutant IkBα and PKCα inserts did not elicit a PIF-induced response, suggesting the importance of the transcription factor NF-kB and PKC  involvement in PIF signal transduction. 15(S)-HETE acts as an intracellular mediator of PIF and exerts an effect through the activation of PKC and subsequently IKK, which phosphorylates IkBα and allows NF-kB to migrate to the nucleus. This effect was negated with the PKC inhibitor calphostin C (300nM). A commercially produced PIF receptor antibody was raised in rabbits immunised with a peptide containing the partial N-terminal sequence of the PIF receptor. The PIF receptor antibody was successful in attenuating the PIF-induced increase in skeletal muscle catabolism and protein degradation in vitro at 10µg/ml (p<0.001) and 3.47mg/kg in vivo (p<0.001). The data suggest great potential in the development of this antibody as a therapy against cancer cachexia.

Mechanism of induction of muscle protein degradation by angiotensin II

Angiotensin I and II have been shown to directly induce protein degradation in skeletal muscle through an increased activity and expression of the ubiquitin-proteasome proteolytic pathway. This investigation determines the role of the nuclear transcription factor nuclear factor-κB (NF-κB) in this process. Using murine myotubes as a surrogate model system both angiotensin I and II were found to induce activation of protein kinase C (PKC), with a parabolic dose-response curve similar to the induction of total protein degradation. Activation of PKC was required for the induction of proteasome expression, since calphostin C, a highly specific inhibitor of PKC, attenuated both the increase in total protein degradation and in proteasome expression and functional activity increased by angiotensin II. PKC is known to activate I-κB kinase (IKK), which is responsible for the phosphorylation and subsequent degradation of I-κB. Both angiotensin I and II induced an early decrease in cytoplasmic I-κB levels followed by nuclear accumulation of NF-κB. Using an NF-κB luciferase construct this was shown to increase transcriptional activation of NF-κB regulated genes. Maximal luciferase expression was seen at the same concentrations of angiotensin I/II as those inducing protein degradation. Total protein degradation induced by both angiotensin I and II was attenuated by resveratrol, which prevented nuclear accumulation of NF-κB, confirming that activation of NF-κB was responsible for the increased protein degradation. These results suggest that induction of proteasome expression by angiotensin I/II involves a signalling pathway involving PKC and NF-κB. © 2005 Elsevier Inc. All rights reserved.

Induction of protein degradation in skeletal muscle by a phorbol ester involves upregulation of the ubiquitin-proteasome proteolytic pathway

Although muscle atrophy is common to a number of disease states there is incomplete knowledge of the cellular mechanisms involved. In this study murine myotubes were treated with the phorbol ester 12-0-tetradecanoylphorbol-13-acetate (TPA) to evaluate the role of protein kinase C (PKC) as an upstream intermediate in protein degradation. TPA showed a parabolic dose-response curve for the induction of total protein degradation, with an optimal effect at a concentration of 25 nM, and an optimal incubation time of 3 h. Protein degradation was attenuated by co-incubation with the proteasome inhibitor lactacystin (5 μM), suggesting that it was mediated through the ubiquitin-proteasome proteolytic pathway. TPA induced an increased expression and activity of the ubiquitin-proteasome pathway, as evidenced by an increased functional activity, and increased expression of the 20S proteasome α-subunits, the 19S subunits MSS1 and p42, as well as the ubiquitin conjugating enzyme E214k, also with a maximal effect at a concentration of 25 nM and with a 3 h incubation time. There was also a reciprocal decrease in the cellular content of the myofibrillar protein myosin. TPA induced activation of PKC maximally at a concentration of 25 nM and this effect was attenuated by the PKC inhibitor calphostin C (300 nM), as was also total protein degradation. These results suggest that stimulation of PKC in muscle cells initiates protein degradation through the ubiquitin-proteasome pathway. TPA also induced degradation of the inhibitory protein, I-κBα, and increased nuclear accumulation of nuclear factor-κB (NF-κB) at the same time and concentrations as those inducing proteasome expression. In addition inhibition of NF-κB activation by resveratrol (30 μM) attenuated protein degradation induced by TPA. These results suggest that the induction of proteasome expression by TPA may involve the transcription factor NF-κB. © 2005 Elsevier Inc. All rights reserved.

Induction of proteasome expression in skeletal muscle is attenuated by inhibitors of NF-κB activation

The potential for inhibitors of nuclear factor-κB (NF-κB) activation to act as inhibitors of muscle protein degradation in cancer cachexia has been evaluated both in vitro and in vivo. Activation of NF-κB is important in the induction of proteasome expression and protein degradation by the tumour factor, proteolysis-inducing factor (PIF), since the cell permeable NF-κB inhibitor SN50 (18 μM) attenuated the expression of 205 proteasome α-subunits, two subunits of the 195 regulator MSSI and p42, and the ubiquitin-conjugating enzyme, E214k, as well as the decrease in myosin expression in murine myotubes. To assess the potential therapeutic benefit of NF-κB inhibitors on muscle atrophy in cancer cachexia, two potential inhibitors were employed; curcumin (50 μM) and resveratrol (30 μM). Both agents completely attenuated total protein degradation in murine myotubes at all concentrations of PIF, and attenuated the PIF-induced increase in expression of the ubiquitin-proteasome proteolytic pathway, as determined by the 'chymotrypsin-like' enzyme activity, proteasome subunits and E2 14k. However, curcumin (150 and 300 mg kg-1) was ineffective in preventing weight loss and muscle protein degradation in mice bearing the MAC16 tumour, whereas resveratrol (1 mg kg-1) significantly attenuated weight loss and protein degradation in skeletal muscle, and produced a significant reduction in NF-κB DNA-binding activity. The inactivity of curcumin was probably due to a low bioavailability. These results suggest that agents which inhibit nuclear translocation of NF-κB may prove useful for the treatment of muscle wasting in cancer cachexia.