Pharmacological preconditioning with resveratrol: role of CREB-dependent Bcl-2 signaling via adenosine A3 receptor activation

Resveratrol in cardiovascular health and disease

Resveratrol, initially used for cancer therapy, has shown beneficial effects against most degenerative and cardiovascular diseases from atherosclerosis, hypertension, ischemia/reperfusion, and heart failure to diabetes, obesity, and aging. The cardioprotective effects of resveratrol are associated with its preconditioning-like action potentiated by its adaptive response. During preconditioning, small doses of resveratrol can exert an adaptive stress response, forcing the expression of cardioprotective genes and proteins such as heat shock and antioxidant proteins. Similarly, resveratrol can induce autophagy, another form of stress adaptation for degrading damaged or long-lived proteins, as a first line of protection against oxidative stress. Resveratrol's interaction with multiple molecular targets of diverse intracellular pathways (e.g., action on sirtuins and FoxOs through multiple transcription factors and protein targets) intertwines with those of the autophagic pathway to give support in the modified redox environment after stem cell therapy, which leads to prolonged survival of cells. The successful application of resveratrol in therapy is based upon its hormetic action similar to any toxin: exerting beneficial effects at lower doses and cytotoxic effects at higher doses.

MicroRNA signatures of resveratrol in the ischemic heart

Until the middle of the last decade, few people had heard of microRNAs (miRNAs), 21- to 23-nucleotide conserved RNAs. MicroRNAs represent a new paradigm because they regulate most physiological processes and thus have immense potential for medical advancement. Resveratrol, a red wine-derived polyphenolic compound, has been shown to have significant effects in various disease models, such as cardioprotection in ischemic heart, diabetes, and chemoprevention of cancers. The targets of resveratrol include various pathways and molecules, such as sirtuins, FOXOs, and autophagy. The successful application of resveratrol lies in understanding its mechanisms of action through direct and indirect interactions with pathways, including miRNAs. For example, a unique miRNA footprint is present in the heart treated with resveratrol. Targets of those miRNAs have potential implications for physiological and pathophysiological processes in health and disease.

Multifaceted approach to resveratrol bioactivity: Focus on antioxidant action, cell signaling and safety

Resveratrol (RVT) is a naturally occurring trihydroxy stilbene that displays a wide spectrum of physiological activity. Its ability to behave therapeutically as a component of red wine has attracted wide attention. The phenol acts as a protective agent involving various body constituents. Most attention has been given to beneficial effects in insults involving cancer, aging, cardiovascular system, inflammation and the central nervous system. One of the principal modes of action appears to be as antioxidant. Other mechanistic pathways entail cell signaling, apoptosis and gene expression. There is an intriguing dichotomy in relation to pro-oxidant property. Also discussed are metabolism, receptor binding, rationale for safety and suggestions for future work. This is the first comprehensive review of RVT based on a broad, unifying mechanism.

Resveratrol and cardiovascular health

Resveratrol (3,4',5-trihydroxystilbene) is a member of natural, plant-derived chemicals known as polyphenols and is attracting increased attention due to its diverse health benefits especially in case of cardiovascular disease, cancer, diabetes and neurological problems. Despite impressive gains in diagnosis and treatment, cardiovascular disease (CVD) remains a serious clinical problem and threat to public health. Resveratrol possesses potent antioxidant properties and has been shown to decrease low-density lipoprotein-cholesterol oxidation and platelet aggregation. This compound also possesses a range of additional cardioprotective and vasoprotective properties including antiatherosclerotic and vasorelaxation action. Resveratrol also has the capacity to interact with multiple molecular targets, which involve diverse intracellular pathways. Most well-known is the ability of resveratrol to activate sirtuins, a class of NAD(+)-dependent deacetylase that affect multiple transcription factors and other protein targets. Recently, resveratrol was found to induce autophagy and regenerate myocardial ischemic tissue treated with stem cells. Overall observation indicates that resveratrol has a high therapeutic potentials for the treatment of cardiovascular diseases.

Neuregulin signaling and heart failure

Neuregulin-1 (NRG-1), a ligand of receptor tyrosine kinases of the ErbB family, plays a critical role in cardiovascular development and maintenance of adult heart function. Results from cellular, animal, and clinical experiments have shown NRG-1 to be a promising drug candidate for restoring cardiac function after cardiac injury. Various mechanisms have been suggested to be involved in this process, such as improving sarcomeric structure or cell-cell adhesion, promoting proliferation and survival of cardiac myocytes, balancing Ca(2+) homeostasis, modulating inotropic effects, promoting angiogenesis, and preventing atherosclerosis. However, the contribution of these effects to the restoration of cardiac function remains to be estimated, and it may depend on the specific events that led to heart failure. Meanwhile, distinct and crossed signaling pathways downstream of NRG-1 may play a role in these underlying mechanisms, resulting in a complicated network of signaling mediating the function of NRG-1.

Dose-dependency of resveratrol in providing health benefits

This review describes the dose-dependent health benefits of resveratrol, a polyphenolic antioxidant that is found in a variety of foods, especially grape skin and red wine. Resveratrol provides diverse health benefits including cardioprotection, inhibition of low-density lipoprotein, activation of nitric oxide (NO) production, hindering of platelet aggregation [32] A.A.E. Bertelli, D.E. Giovannini, R.L. Caterina, W. Bernini, M. Migliori and M. Fregoni et al., Antiplatelet activity of cis-resveratrol, Drugs Exp Clin Res 22 (1996), pp. 61-63. View Record in Scopus | Cited By in Scopus (111) and promotion of anti-inflammatory effects. Studies have shown that at a lower dose, resveratrol acts as an anti-apoptotic agent, providing cardioprotection as evidenced by increased expression in cell survival proteins, improved postischemic ventricular recovery and reduction of myocardial infarct size and cardiomyocyte apoptosis and maintains a stable redox environment compared to control. At higher dose, resveratrol acts as a pro-apoptotic compound, inducing apoptosis in cancer cells by exerting a death signal. At higher doses, resveratrol depresses cardiac function, elevates levels of apoptotic protein expressions, results in an unstable redox environment, increases myocardial infarct size and number of apoptotic cells. At high dose, resveratrol not only hinders tumor growth but also inhibits the synthesis of RNA, DNA and protein, causes structural chromosome aberrations, chromatin breaks, chromatin exchanges, weak aneuploidy, higher S-phase arrest, blocks cell proliferation, decreases wound healing, endothelial cell growth by fibroblast growth factor-2 (FGF-2) and vascular endothelial growth factor, and angiogenesis in healthy tissue cells leading to cell death. Thus, at lower dose, resveratrol can be very useful in maintaining the human health whereas at higher dose, resveratrol has pro-apoptotic actions on healthy cells, but can kill tumor cells.

The myocardial infarct size-limiting effect of sitagliptin is PKA-dependent, whereas the protective effect of pioglitazone is partially dependent on PKA

Pioglitazone (PIO) and glucagon-like peptide-1 (GLP-1) analogs limit infarct size (IS) in experimental models. The effects of the dipeptidyl-peptidase-IV inhibitors, which increase the endogenous levels of GLP-1, on myocardial protection, are unknown. We studied whether sitagliptin (SIT) and PIO have additive effects on IS limitation in the mouse. Mice received 3-day or 14-day oral SIT (300 mg.kg(-1).day(-1)), PIO (5 mg.kg(-1).day(-1)), SIT + PIO, or vehicle. In addition, mice received intravenous H-89 [20 mg/kg, a protein kinase A (PKA) inhibitor] or vehicle 1 h before ischemia. Rats underwent 30 min myocardial ischemia and 4 h reperfusion. SIT, PIO, and SIT + PIO for 3 days significantly reduced IS (24.3 +/- 2.7, 23.0 +/- 0.8, and 14.7 +/- 0.9%) compared with controls (46.2 +/- 2.8%). H-89 completely blocked the effect of SIT and partially blocked the PIO effect. SIT, but not PIO, increased cAMP levels. PKA activity was increased by PIO and to a greater extent by SIT. PIO, but not SIT, increased cytosolic phospholipase A(2) and cyclooxygenase-2 activity. Accordingly, 6-keto-PGF(1alpha) and 15-deoxy-PGJ(2) increased by PIO but not SIT. In contrast, SIT, and to a lesser extent PIO, increased 15-epi-lipoxin A(4) levels. H-89 completely blocked the effect of SIT and PIO on 15-epi-lipoxin A(4) levels. PIO, and to a greater extent SIT, increased endothelial nitric oxide synthase and cAMP response element-binding protein phosphorylation, an effect that was blocked by H-89. With a 14-day pretreatment experiment, IS was 46.4 +/- 1.0% in the control group, 16.9 +/- 0.6% in SIT (P < 0.001), 19.1 +/- 1.1% in PIO (P = 0.014), and 12.9 +/- 0.7% in SIT + PIO (P < 0.001). We found that SIT and PIO limit IS using different pathways. The protective effect of SIT is via cAMP-dependent PKA activation, whereas PIO mediates its effects via both PKA-dependent and -independent pathways.

Resveratrol increases iodide trapping in the rat thyroid cell line FRTL-5

BACKGROUND

Resveratrol, a polyphenol found in grapes, exhibits several beneficial health effects by its antioxidant, antiinflammatory, and chemopreventive properties. The aim of the present study was to determine the effect of resveratrol on iodide trapping and efflux as well as its mode of action using FRTL-5 cells, having in mind the pivotal role of the natrium iodide symporter (NIS) in the treatment of differentiated thyroid cancers.

METHODS

Cells were treated with resveratrol for various times and doses, in the presence or absence of thyrotropin (TSH). Iodide trapping, iodide efflux, rat NIS (rNIS) protein expression, and cyclic AMP (cAMP) production were evaluated.

RESULTS

Resveratrol increased iodide trapping in a time-dependent (optimal 6 hours) and dose-dependent (100 microM) way in the presence of TSH. It showed an additive effect when concomitantly added with an optimal dose of TSH. Resveratrol (50 microM) increased (threefold) rNIS protein expression. In TSH-deprived cells, resveratrol also provoked an increase in rNIS protein (>3-fold in 6 hours) with an optimum at 40 microM. Resveratrol did not inhibit iodide efflux from FRTL-5 cells. It neither increased intracellular cAMP nor induced the arborization of living cells, two TSH-induced effects. A non-cAMP mode of action is highly suspected.

CONCLUSIONS

Resveratrol increases iodide trapping in FRTL-5 cells, increasing iodide influx and rNIS protein level even in the absence of TSH. It has an additive effect with TSH. Consequently, resveratrol could be a promising molecule for radioiodide therapy in follicular and papillary differentiated thyroid carcinoma in association with recombinant human TSH.

Neuregulin-1/ErbB signaling and chronic heart failure

Neuregulin-1 (NRG-1), a cardioactive growth factor released from endothelial cells, is indispensable for cardiac development, structural maintenance, and functional integrity of the heart. In recent years, a growing number of studies have focused on NRG-1 and members of the ErbB family that serve as receptors for NRG-1 in order to better understand the role of this signaling pathway in physiology and pathophysiology of the heart. An essential role for NRG-1 and ErbB in heart development and functionality has been suggested by studies in conditional NRG-1/ErbB-deficient mice and by the cardiac-related side effects of anti-ErbB2 antibody therapies used for treatment of breast cancer. In vitro and in vivo studies using recombinant human neuregulin-1 (rhNRG-1), which contains the epidermal growth factor (EGF)-like domain (necessary for ErbB2/ErbB4 activation), have further supported the hypothesis that NRG-1 plays an important role in heart function. Consistent with other studies, expression of rhNRG-1 not only restored normal cardiomyocytic structure altered by nutritional deficiency in cell cultures, but also improved the pumping function of the heart in several animal models of chronic heart failure (CHF). As a result of these findings, proteins involved in the NRG-1/ErbB-signaling pathway have been explored as potential drug targets for treatment of heart failure. Clinical trials to evaluate the safety and efficacy of rhNRG-1 have been conducted in both China and Australia. As predicted, rhNRG-1 treatment improved both cardiac function and reversed remodeling of the heart. Therefore, rhNRG-1 may represent a new drug for treatment of CHF with a novel therapeutic mechanism.

Cardioprotection by resveratrol: a novel mechanism via autophagy involving the mTORC2 pathway

AIMS

On the basis of our previous reports that cardioprotection induced by ischaemic preconditioning induces autophagy and that resveratrol, a polyphenolic antioxidant present in grapes and red wine induces preconditioning-like effects, we sought to determine if resveratrol could induce autophagy.

METHODS AND RESULTS

Resveratrol at lower doses (0.1 and 1 microM in H9c2 cardiac myoblast cells and 2.5 mg/kg/day in rats) induced cardiac autophagy shown by enhanced formation of autophagosomes and its component LC3-II after hypoxia-reoxygenation or ischaemia-reperfusion. The autophagy was attenuated with the higher dose of resveratrol. The induction of autophagy was correlated with enhanced cell survival and decreased apoptosis. Treatment with rapamycin (100 nM), a known inducer of autophagy, did not further increase autophagy compared with resveratrol alone. Autophagic inhibitors, wortmannin (2 microM) and 3-methyladenine (10 mM), significantly attenuated the resveratrol-induced autophagy and induced cell death. The activation of mammalian target of rapamycin (mTOR) was differentially regulated by low-dose resveratrol, i.e. the phosphorylation of mTOR at serine 2448 was inhibited, whereas the phosphorylation of mTOR at serine 2481 was increased, which was attenuated with a higher dose of resveratrol. Although resveratrol attenuated the activation of mTOR complex 1, low-dose resveratrol significantly induced the expression of Rictor, a component of mTOR complex 2, and activated its downstream survival kinase Akt (Ser 473). Resveratrol-induced Rictor was found to bind with mTOR. Furthermore, treatment with Rictor siRNA attenuated the resveratrol-induced autophagy.

CONCLUSION

Our results indicate that at lower dose, resveratrol-mediated cell survival is, in part, mediated through the induction of autophagy involving the mTOR-Rictor survival pathway.

Resveratrol: its biologic targets and functional activity

The polyphenolic phytoalexin resveratrol (RSV) and its analogues have received tremendous attention over the past couple of decades because of a number of reports highlighting their benefits in vitro and in vivo in a variety of human disease models, including cardio- and neuroprotection, immune regulation, and cancer chemoprevention. These studies have underscored the high degree of diversity in terms of the signaling networks and cellular effector mechanisms that are affected by RSV. The activity of RSV has been linked to cell-surface receptors, membrane signaling pathways, intracellular signal-transduction machinery, nuclear receptors, gene transcription, and metabolic pathways. The promise shown by RSV has prompted heightened interest in studies aimed at translating these observations to clinical settings. In this review, we present a comprehensive account of the basic chemistry of RSV, its bioavailability, and its multiple intracellular target proteins and signaling pathways.

Resveratrol prevents doxorubicin cardiotoxicity through mitochondrial stabilization and the Sirt1 pathway

Doxorubicin (DOX) is one of the most effective chemotherapeutic drugs; however, its incidence of cardiotoxicity compromises its therapeutic index. DOX-induced heart failure is thought to be caused by reduction/oxidation cycling of DOX to generate oxidative stress and cardiomyocyte cell death. Resveratrol (RV), a stilbene found in red wine, has been reported to play a cardioprotective role in diseases associated with oxidative stress. The objective of this study was to test the ability of RV to protect against DOX-induced cardiomyocyte death. We hypothesized that RV protects cardiomyocytes from DOX-induced oxidative stress and subsequent cell death through changes in mitochondrial function. DOX induced a rapid increase in reactive oxygen species (ROS) production in cardiac cell mitochondria, which was inhibited by pretreatment with RV, most likely owing to an increase in MnSOD activity. This effect of RV caused additional polarization of the mitochondria in the absence and presence of DOX to increase mitochondrial function. RV pretreatment also prevented DOX-induced cardiomyocyte death. The protective ability of RV against DOX was abolished when Sirt1 was inhibited by nicotinamide. Our data suggest that RV protects against DOX-induced oxidative stress through changes in mitochondrial function, specifically the Sirt1 pathway leading to cardiac cell survival.

The biological responses to resveratrol and other polyphenols from alcoholic beverages

Although excessive consumption of ethanol in alcoholic beverages causes multi-organ damage, moderate consumption, particularly of red wine, is protective against all-cause mortality. These protective effects could be due to one or many components of the complex mixture of bioactive compounds present in red wine including flavonols, monomeric and polymeric flavan-3-ols, highly colored anthocyanins as well as phenolic acids and the stilbene polyphenol, resveratrol. The therapeutic potential of resveratrol, firstly in cancer chemoprevention and then later for cardioprotection, has stimulated many studies on the possible mechanisms of action. Further indications for resveratrol have been developed, including the prevention of age-related disorders such as neurodegenerative diseases, inflammation, diabetes, and cardiovascular disease. These improvements are remarkably similar yet there is an important dichotomy: low doses improve cell survival as in cardio- and neuro-protection yet high doses increase cell death as in cancer treatment. Fewer studies have examined the responses to other components of red wine, but the results have, in general, been similar to resveratrol. If the nonalcoholic constitutents of red wine are to become therapeutic agents, their ability to get to the sites of action needs to be understood. This mini-review summarizes recent studies on the possible mechanisms of action, potential therapeutic uses, and bioavailability of the nonalcoholic constituents of alcoholic beverages, in particular resveratrol and other polyphenols.

Mechanism for resveratrol-induced cardioprotection against reperfusion injury involves glycogen synthase kinase 3beta and mitochondrial permeability transition pore

Resveratrol pretreatment can protect the heart by inducing pharmacological preconditioning. Whether resveratrol protects the heart when applied at reperfusion remains unknown. We examined the effect of resveratrol on myocardial infarct size when given at reperfusion and investigated the mechanism underlying the effect. Isolated rat hearts were subjected to 30 min ischemia followed by 2 h of reperfusion, and myocardial samples were collected from the risk zone for Western blot analysis. Mitochondrial swelling was spectrophotometrically measured as a decrease in absorbance at 520 nm (A(520)). Resveratrol reduced infarct size and prevented cardiac mitochondrial swelling. Resveratrol enhanced GSK-3beta phosphorylation upon reperfusion, an effect that was mediated by the cyclic guanosine monophosphate (cGMP)/protein kinase G (PKG) pathway. Resveratrol translocated GSK-3beta from cytosol to mitochondria via the cGMP/PKG pathway. Further studies showed that mitochondrial GSK-3beta was co-immunoprecipitated with cyclophilin D but not with VDAC (voltage dependent anion channel) or ANT (adenine nucleotide translocator). These data suggest that resveratrol prevents myocardial reperfusion injury presumably by targeting the mPTP through translocation of GSK-3beta from cytosol to mitochondria. Translocated GSK-3beta may ultimately interact with cyclophilin D to modulate the mPTP opening.

Cardioprotection by HO-4038, a novel verapamil derivative, targeted against ischemia and reperfusion-mediated acute myocardial infarction

Many cardiac interventional procedures, such as coronary angioplasty, stenting, and thrombolysis, attempt to reintroduce blood flow (reperfusion) to an ischemic region of myocardium. However, the reperfusion is accompanied by a complex cascade of cellular and molecular events resulting in oxidative damage, termed myocardial ischemia-reperfusion (I/R) injury. In this study, we evaluated the ability of HO-4038, an N-hydroxypiperidine derivative of verapamil, on the modulation of myocardial tissue oxygenation (Po(2)), I/R injury, and key signaling molecules involved in cardioprotection in an in vivo rat model of acute myocardial infarction (MI). MI was created in rats by ligating the left anterior descending coronary artery (LAD) for 30 min followed by 24 h of reperfusion. Verapamil or HO-4038 was infused through the jugular vein 10 min before the induction of ischemia. Myocardial Po(2) and the free-radical scavenging ability of HO-4038 were measured using electron paramagnetic resonance spectroscopy. HO-4038 showed a significantly better scavenging ability of reactive oxygen radicals compared with verapamil. The cardiac contractile functions in the I/R hearts were significantly higher recovery in HO-4038 compared with the verapamil group. A significant decrease in the plasma levels of creatine kinase and lactate dehydrogenase was observed in the HO-4038 group compared with the verapamil or untreated I/R groups. The left ventricular infarct size was significantly less in the HO-4038 (23 +/- 2%) compared with the untreated I/R (36 +/- 4%) group. HO-4038 significantly attenuated the hyperoxygenation (36 +/- 1 mmHg) during reperfusion compared with the untreated I/R group (44 +/- 2 mmHg). The HO-4038-treated group also markedly attenuated superoxide production, increased nitric oxide generation, and enhanced Akt and Bcl-2 levels in the reperfused myocardium. Overall, the results demonstrated that HO-4038 significantly protected hearts against I/R-induced cardiac dysfunction and damage through the combined beneficial actions of calcium-channel blocking, antioxidant, and prosurvival signaling activities.

Resveratrol disrupts peroxynitrite-triggered mitochondrial apoptotic pathway: a role for Bcl-2

Resveratrol (3,4',5-trihydroxystilbene) is a phytochemical believed to be partly responsible for the cardioprotective effects of red wine due to its numerous biological activities. Here, we studied biochemical pathways underlying peroxynitrite-mediated apoptosis in endothelial cells and potential mechanisms responsible for resveratrol cytoprotective action. Peroxynitrite triggered endothelial cell apoptosis through caspases-8, -9 and -3 activation implying both mitochondrial and death receptor apoptotic pathways. Resveratrol was able to prevent peroxynitrite-induced caspases-3 and -9 activation, but not caspase-8 activation. Additionally, peroxynitrite increased intracellular levels of Bax without affecting those of Bcl-2, increasing consequently the Bax/Bcl-2 ratio. This ratio decreased when cells where pre-incubated with 10 and 50 muM resveratrol, mainly due to resveratrol ability per se to increase Bcl-2 intracellular levels without affecting Bax intracellular levels. These results propose an additional mechanism whereby resveratrol may exert its cardioprotective effects and suggest a key role for Bcl-2 in the resveratrol anti-apoptotic action, especially in disrupting peroxynitrite-triggered mitochondrial pathway.

The role of Neuregulin-1beta/ErbB signaling in the heart

Products of the Neuregulin-1 (Nrg-1) gene, along with the ErbB family of receptor tyrosine kinases through which Nrg-1 ligands signal, play a critical role during cardiovascular development. Through studies of genetically manipulated mice, as well as studies in cells isolated from adult hearts, it appears that Nrg-1/ErbB signaling is an essential paracrine mediator of cell-cell interactions that not only regulates tissue organization during development, but also helps to maintain cardiac function throughout an organism's life. Studies in cells isolated from the heart demonstrate that Nrg-1 can activate a number of signaling pathways, which mediate cellular adaptations to stress in the myocardium. These observations provide insight as to why ErbB2-targeted cancer treatments have deleterious effects on cardiac function in some cancer patients. Moreover emerging data suggest that Nrg-1 ligands might be useful clinically to restore cardiac function after cardiac injury. In this review we will attempt to synthesize the literature behind this rapidly growing and exciting area of research.

Cardioprotection with alpha-tocopheryl phosphate: amelioration of myocardial ischemia reperfusion injury is linked with its ability to generate a survival signal through Akt activation

The emerging potential of alpha-tocopheryl phosphate, a phosphoric acid ester of alpha-tocopherol, in health benefits was tested gavaging this compound (5 mg/kg body wt) to a group of rats for a period of thirty days while the control rats were given water only. After thirty days, the rats were sacrificed, the hearts excised, and the isolated hearts were perfused by working mode. Both control and experimental hearts were subjected to 30-min global ischemia followed by 2 h of reperfusion. The tocopheryl phosphate fed rats exhibited significant cardioprotection as evidenced by improved ventricular performance and reduced myocardial infarct size and cardiomyocyte apoptosis. Supplementation with alpha-tocopheryl phosphate converted MAP kinase-induced death signal into a survival signal by enhancing anti-apoptotic p42/44 ERK kinase and p38 MAPKbeta and reducing pro-apoptotic proteins p38 MAPKalpha and JNK. In concert, the phosphorylation of pro-apoptotic c-Src was also reduced. Tocopheryl phosphate increased the DNA binding of the redox-sensitive transcription factor NFkappaB and potentiated the activation of anti-death protein Bcl-2 and survival signaling protein Akt. The results of this study demonstrated for the first time that tocopheryl phosphate could ameliorate myocardial ischemic reperfusion injury by converting ischemia/reperfusion-mediated death signal into a survival signal by modulating MAP kinase signaling.

Redox regulation of resveratrol-mediated switching of death signal into survival signal

In this study, we determined the changes in the intracellular redox environment of the heart during ischemia and reperfusion and the effects of resveratrol on such changes. Because redox regulation by thioredoxin (Trx) plays a crucial role in signal transduction and cytoprotection against ROS, the effects of resveratrol on the changes in the amounts of thioredoxin were monitored in an attempt to determine the role of intracellular thioredoxin in resveratrol-mediated changes in intracellular redox environment and its role in resveratrol-mediated cardioprotection. Rats were randomly divided into four groups: group I, control (rats were gavaged with vehicle only); group II, rats were gavaged with 2.5 mg/kg body wt resveratrol per day for 10 days; group III, rats were given resveratrol for 10 days, but on the 7th day, they were treated with shRNA against Trx-1; group IV, rats were given resveratrol for 10 days, but were injected (iv) with cisplatin (1 mg/kg body wt) on days 1, 3, 5, 7, and 9. In concert, two groups of mice (Dn-Trx-1) and a corresponding wild-type group were also gavaged with 2.5 mg/kg body wt resveratrol for 10 days. After 10 days, isolated rat and mouse hearts perfused via working mode were made globally ischemic for 30 min followed by 2 h of reperfusion. Ischemia/reperfusion developed an infarct size of about 40% and resulted in about 25% apoptotic cardiomyocytes, which were reduced by resveratrol. Cisplatin, but not shRNA-Trx-1, abolished the cardioprotective abilities of resveratrol. In the experiments with mouse hearts, similar to rat hearts, resveratrol significantly reduced the ischemia/reperfusion-mediated increase in infarct size and apoptosis in both groups. MDA formation, a presumptive marker for lipid peroxidation, was increased in the I/R group and reduced in the resveratrol group, and resveratrol-mediated reduction in MDA formation was abolished with cisplatin, but not with shRNA-Trx-1. I/R-induced reduction in GSH/GSSH ratio was prevented by resveratrol, and resveratrol-mediated preservation of GSH/GSSG ratio was reduced by cisplatin, but not by sh-RNA-Trx-1. RT-PCR revealed an increase in both Trx-1 and Trx-2 transcripts; but only Trx-2 protein, not Trx-1 protein, was enhanced with resveratrol by Western blot analysis. Electron paramagnetic resonance spectroscopic study revealed that resveratrol treatment significantly increased the decay rates of nitroxide radicals compared to control hearts, suggesting that resveratrol can switch into the reduction state more compared to control heart. Finally, resveratrol generated a survival signal by phosphorylation of Akt and increase in induction of Bcl-2 expression, which was inhibited by cisplatin, but not by shRNA-Trx-1. Taken together, the results of this study indicate that resveratrol provides cardioprotection by maintaining intracellular redox environments, and Trx-2 is likely to play a role in switching I/R-induced death signal into survival signal.

The A3 adenosine receptor: an enigmatic player in cell biology

Adenosine is a primordial signaling molecule present in every cell of the human body that mediates its physiological functions by interacting with 4 subtypes of G-protein-coupled receptors, termed A1, A2A, A2B and A3. The A3 subtype is perhaps the most enigmatic among adenosine receptors since, although several studies have been performed in the years to elucidate its physiological function, it still presents in several cases a double nature in different pathophysiological conditions. The 2 personalities of A3 often come into direct conflict, e.g., in ischemia, inflammation and cancer, rendering this receptor as a single entity behaving in 2 different ways. This review focuses on the most relevant aspects of A3 adenosine subtype activation and summarizes the pharmacological evidence as the basis of the dichotomy of this receptor in different therapeutic fields. Although much is still to be learned about the function of the A3 receptor and in spite of its duality, at the present time it can be speculated that A3 receptor selective ligands might show utility in the treatment of ischemic conditions, glaucoma, asthma, arthritis, cancer and other disorders in which inflammation is a feature. The biggest and most intriguing challenge for the future is therefore to understand whether and where selective A3 agonists or antagonists are the best choice.

Alterations in both death and survival signals for apoptosis in heart failure due to volume overload

Heart failure is known to be associated with an increase in cardiomyocyte apoptosis; however, neither its occurrence nor the mechanisms involved in hearts failing due to volume overload are completely understood. This study examined some of the signal pathways, which are known to regulate pro- or anti-apoptotic proteins, in heart failure due to volume overload induced by arteriovenous (AV) shunt in male Sprague-Dawley rats. Animals were assessed for cardiac function at 16 weeks of the operation and the left ventricle was used for studying apoptosis and associated signal transduction mechanisms. Hemodynamic and echocardiographic data indicated the presence of severe heart failure in AV shunt rats. A marked elevation in the amount of tumor necrosis factor-alpha and increased occurrence of apoptosis were detected in the volume overloaded myocardium. Western blot analysis revealed a significant increase in BAX and caspases 3/9 proteins in the failing hearts whereas the levels of phosphorylated Akt and Bcl-2 proteins were decreased. These data suggest that there is a downregulation in the Akt-dependent survival signal involving anti-apoptotic protein, Bcl-2, whereas the signals for the pro-apoptotic protein, BAX, are upregulated and these alterations may play a role in cardiomyocyte apoptosis in heart failure due to volume overload.

Adenosinergic cardioprotection: Multiple receptors, multiple pathways

Adenosine, formed primarily via hydrolysis of 5'-AMP, has been historically dubbed a "retaliatory" metabolite due to enhanced local release and beneficial actions during cellular/metabolic stress. From a cardiovascular perspective, evidence indicates the adenosinergic system is essential in mediation of intrinsic protection (e.g., pre- and postconditioning) and determining myocardial resistance to insult. Modulation of adenosine and its receptors thus remains a promising, though as yet not well-realized, approach to amelioration of injury in ischemic-reperfused myocardium. Adenosine exerts effects through A(1), A(2A), A(2B), and A(3) adenosine receptor subtypes (A(1)AR, A(2A)AR, A(2B)AR, and A(3)AR), which are all expressed in myocardial and vascular cells, and couple to G proteins to trigger a range of responses (generally, but not always, beneficial). Adenosine can also enhance tolerance to injurious stimuli via receptor-independent metabolic effects. Given adenosines contribution to preconditioning, it is no surprise that postreceptor signaling typically mimics that associated with preconditioning. This involves activation/translocation of PKC, PI3 kinase, and MAPKs, with ultimate effects at the level of mitochondrial targets-the mitochondrial K(ATP) channel and/or the mitochondrial permeability transition pore (mPTP). Nonetheless, differences in cytoprotective signaling and actions of the different adenosine receptor subtypes have been recently revealed. Our understanding of adenosinergic cytoprotection continues to evolve, with roles for the A(2) subtypes emerging, together with evidence of essential receptor "cross-talk" in mediation of protection. This review focuses on current research into adenosine-mediated cardioprotection, highlighting recent findings which, together with a wealth of prior knowledge, may ultimately facilitate adenosinergic approaches to clinical cardiac protection.

Lithium increases PGC-1alpha expression and mitochondrial biogenesis in primary bovine aortic endothelial cells

Lithium is a therapeutic agent commonly used to treat bipolar disorder and its beneficial effects are thought to be due to a combination of activation of the Wnt/beta-catenin pathway via inhibition of glycogen synthase kinase-3beta and depletion of the inositol pool via inhibition of the inositol monophosphatase-1. We demonstrated that lithium in primary endothelial cells induced an increase in mitochondrial mass leading to an increase in ATP production without any significant change in mitochondrial efficiency. This increase in mitochondrial mass was associated with an increase in the mRNA levels of mitochondrial biogenesis transcription factors: nuclear respiratory factor-1 and -2beta, as well as mitochondrial transcription factors A and B2, which lead to the coordinated upregulation of oxidative phosphorylation components encoded by either the nuclear or mitochondrial genome. These effects of lithium on mitochondrial biogenesis were independent of the inhibition of glycogen synthase kinase-3beta and independent of inositol depletion. Also, expression of the coactivator PGC-1alpha was increased, whereas expression of the coactivator PRC was not affected. Lithium treatment rapidly induced a decrease in activating Akt-Ser473 phosphorylation and inhibitory Forkhead box class O (FOXO1)-Thr24 phosphorylation, as well as an increase in activating c-AMP responsive element binding (CREB)-Ser133 phosphorylation, two mechanisms known to control PGC-1alpha expression. Together, our results show that lithium induces mitochondrial biogenesis via CREB/PGC-1alpha and FOXO1/PGC-1alpha cascades, which highlight the pleiotropic effects of lithium and reveal also novel beneficial effects via preservation of mitochondrial functions.

Differential proteomic profiling to study the mechanism of cardiac pharmacological preconditioning by resveratrol

Recent studies demonstrated that resveratrol, a grape-derived polyphenolic phytoalexin, provides pharmacological preconditioning of the heart through a NO-dependent mechanism. To further explore the molecular mechanisms involved in resveratrol-mediated cardioprotection, we monitored the effects of resveratrol treatment after ischemia-reperfusion on the protein profile by implementation of proteomic analysis. Two groups of rats were studied; one group of animals was fed resveratrol for 7 days, while the other group was given vehicle only. The rats were sacrificed for the isolated working heart preparation and for isolation of cytoplasmic fraction from left ventricle homogenates to carry out the proteomic as well as immunoblot at baseline and at the end of 30 min ischemia/2-h perfusion. The results demonstrate significant cardioprotection with resveratrol evidenced by improved ventricular recovery and reduced infarct size and cardiomyocyte apoptosis. The left ventricular cytoplasmic fractions were separated by two-dimensional electrophoresis (2-DE). Differentially regulated proteins were detected with quantitative computer analysis of the Coomassie blue stained 2-DE images and identified by MALDI-TOF (MS) and nanoLC-ESI-Q-TOF mass spectrometry (MS/MS). Five redox-regulated and preconditioning- related proteins were identified that were all upregulated by resveratrol: MAPKK, two different alphaB-crystallin species, HSP 27 and PE binding protein. Another HSP27 species and aldose reductase were downregulated and peroxiredoxin- 2 remained constant. The results of the immunoblot analysis of phosphorylated MAPKK, -HSP27 and -alphaB-crystallin and PE binding protein were consistent with the proteomic findings, but not with peroxiredoxin-2. The proteomic analysis showed also downregulation of some proteins in the mitochondrial respiratory chain and matrix and the myofilament regulating protein MLC kinase-2. The results of the present study demonstrate that proteomic profiling enables the identification of resveratrol induced preconditioning-associated proteins which reflects not only changes in their expression level but also isoforms, post-translational modifications and regulating binding or activating partner proteins.

Infection of human immunodeficiency virus and intracellular viral Tat protein exert a pro-survival effect in a human microglial cell line

The interaction of human immunodeficiency virus type 1 (HIV-1) with CD4+ T lymphocytes is well studied and typically results in virally induced cytolysis. In contrast, relatively little is known concerning the interplay between HIV-1 and microglia. Recent findings suggest that, counter-intuitively, HIV-1 infection may extend the lifespan of microglia. We developed a novel cell line model system to confirm and mechanistically study this phenomenon. We found that transduction of a human microglial cell line with an HIV-1 vector results in a powerful cytoprotective effect following apoptotic challenge. This effect was reproduced by ectopic expression of a single virus-encoded protein, Tat. Subsequent studies showed that the pro-survival effects of intracellular Tat could be attributed to activation of the PI-3-kinase (PI3K)/Akt pathway in the microglial cell line. Furthermore, we found that expression of Tat led to decreased expression of PTEN, a negative regulator of the PI-3-K pathway. Consistent with this, decreased p53 activity and increased E2F activity were observed. Based on these findings, a model of possible regulatory circuits that intracellular Tat and HIV-1 infection engage during the cytoprotective event in microglia has been suggested. We propose that the expression of Tat may enable HIV-1 infected microglia to survive throughout the course of infection, leading to persistent HIV-1 production and infection in the central nervous system.

Modulation of the Akt/Ras/Raf/MEK/ERK pathway by A₃ adenosine receptor

Downstream A₃ receptor signalling plays an important role in the regulation of cell death and proliferation. Therefore, it is important to determine the molecular pathways involved through A₃ receptor stimulation. The phosphatidylinositide-3-OH kinase (PI3K)/Akt and the Raf/mitogen-activated protein kinase (MAPK/ERK) kinase (MEK)/mitogen-activated protein kinase (MAPK) pathways have central roles in the regulation of cell survival and proliferation. The crosstalk between these two pathways has also been investigated. The focus of this review centres on downstream mediators of A₃ adenosine receptor signalling.

Generation of survival signal by differential interaction of p38MAPKalpha and p38MAPKbeta with caveolin-1 and caveolin-3 in the adapted heart

Sphingomyelin breakdown product ceramide has recently been found to induce an adaptive response and reduce myocardial ischemia/reperfusion injury. Since activation of MAP kinases plays an essential role in myocardial adaptation to ischemic stress and since ceramide is involved in lipid raft formation where MAP kinases can be translocated in response to stress, we reasoned that preconditioning may potentiate the translocation of MAP kinases into the lipid raft. To test the hypothesis, rats were divided into five groups: (i) control, (ii) ischemia/reperfusion (I/R), (iii) I/R+C-2 ceramide, (iv) adapted and (v) adapted+desipramine, an inhibitor of ceramide formation. Isolated hearts were preperfused for 15 min with Krebs Henseleit bicarbonate (KHB) buffer in the absence or presence of 10 microM desipramine followed by adaptation induced by four cyclic episodes of 5 min ischemia and 10 min reperfusion. For myocardial adaptation to ischemia with ceramide, the hearts were perfused with 1 microM C-2 ceramide. All hearts were then subjected to 30 min ischemia and 2 h of reperfusion. As expected, both ischemic adaptation and ceramide adaptation made the heart resistant to I/R injury as evidenced by improved ventricular performance and reduced myocardial infarct size and cardiomyocyte apoptosis, which were significantly blocked with desipramine indicating the involvement of ceramide in ischemic adaptation. Ceramide also participated in the formation of lipid raft, and desipramine disrupted the raft formation. In the adapted hearts, there was an increased association of the proapoptotic p38MAPKalpha with caveolin-1 while there was a reduced association of anti-apoptotic p38MAPKbeta with caveolin-3 indicating reduced amount of p38MAPKalpha and increased amount of p38MAPKbeta were available to the adapted hearts thereby generating a survival signal. Desipramine decreased the association of P38MAPKalpha and C-2 ceramide increased the association of P38MAPKalpha with the lipid raft. The survival signal was further confirmed by increased phosphorylation of AKT and enhanced induction of expression of Bcl-2 during adaptation and its reversal with desipramine. The results indicated a unique ceramide signaling the ischemic and PC hearts involving lipid rafts, which generated a survival signal by differentially associating the p38MAPKalpha and p38MAPKbeta with the caveolin-1 and caveoli-3, respectively.

Functional and cytoarchitectural spinal cord protection by ATL-146e after ischemia/reperfusion is mediated by adenosine receptor agonism

BACKGROUND

ATL-146e protects the spinal cord from ischemia/reperfusion injury, presumably via adenosine A(2A) receptor activation, but this relationship remains unproven. We hypothesized that spinal cord functional and cytoarchitectural preservation from ATL-146e would be lost with simultaneous administration of the specific adenosine A(2A) antagonist ZM241385 (ZM), thus proving that adenosine A(2A) receptor activation is responsible for the protective effects of this compound.

METHODS

New Zealand White rabbits underwent 45 minutes of infrarenal aortic cross-clamping. Groups (n = 10) included sham, ischemia, ischemia plus ATL-146e (ATL-146E), ischemia plus ZM, or ischemia with both compounds (agonist-antagonist). Tarlov scores were recorded every 12 hours. After 48 hours, the spinal cord was fixed for histology and microtubule-associated protein 2 immunohistochemistry.

RESULTS

Tarlov scores at 48 hours were significantly better in the sham and ATL-146E groups (5.0 and 3.9, respectively) compared with the other three groups (all < or =1.3; P < .001). On hematoxylin and eosin, neuronal viability was higher in the sham, ATL-146E, and agonist-antagonist groups compared with the control and ZM groups (P < .05). Microtubule-associated protein 2 expression was preserved in the sham and ATL-146E groups but was lost in the ATL + ZM, ZM241385, and control groups.

CONCLUSIONS

ATL-146e preserves the spinal cord in terms of both cytoarchitecture and function after reperfusion of the ischemic spinal cord, but this preservation is not completely blocked by competitive adenosine A(2A) receptor antagonism. Although ATL-146e does seem to partially function through activation of the adenosine A(2A) receptor, the neuroprotective mechanism may not be limited to this particular receptor.

Balance of purines may determine life or death of retinal ganglion cells as A3 adenosine receptors prevent loss following P2X7 receptor stimulation

The purines ATP and adenosine can act as a coordinated team of transmitters. As extracellular adenosine is frequently derived from the enzymatic dephosphorylation of released ATP, the distinct actions of the two purines can be synchronized. In retinal ganglion cells (RGCs), stimulation of the P2X7 receptor for ATP leads to increased intracellular Ca2+ and death. Here we define the contrasting effects of adenosine and identify protective actions mediated by the A3 receptor. Adenosine attenuated the rise in Ca2+ produced by the P2X7 agonist 3'-O-(4-benzoylbenzoyl)ATP (BzATP). Adenosine was also neuroprotective, increasing the survival of ganglion cells exposed to BzATP. The A3 adenosine receptor agonist 2-chloro-N6-(3-iodobenzyl)-adenosine-5'-N-methyluronimide (Cl-IB-MECA) mimicked the inhibition of the Ca2+ rise, whereas the A3 antagonist 3-Ethyl-5-benzyl-2-methyl-4-phenylethynyl-6-phenyl-1,4-(+/-)-dihydropyridine-3,5-dicarboxylate (MRS-1191) reduced the protective effects of adenosine. Both Cl-IB-MECA and a second A3 receptor agonist IB-MECA reduced the cell loss triggered by BzATP. The actions of BzATP were mimicked by ATPgammaS, but not by ATP. In summary, adenosine can stop the rise in Ca2+ and cell death resulting from stimulation of the P2X7 receptor on RGCs, with the A3 adenosine receptor contributing to this protection. Hydrolysis of ATP into adenosine and perhaps inosine shifts the balance of purinergic action from that of death to the preservation of life.

Amelioration of Ischemia/Reperfusion-Induced Myocardial Infarction by the 2-Alkynyladenosine Derivative 2-Octynyladenosine (YT-146)

The present study was aimed at determining whether the novel adenosine A2-agonist YT-146 may have cardioprotective effects against ischemia-reperfusion injury. Anesthetized open-chest dogs underwent 90-min occlusion of the left anterior descending artery and subsequent 300-min reperfusion. The animals were randomly assigned to receive vehicle, 3, or 10 microg/kg YT-146 or ischemic preconditioning (4 episodes of 5 min occlusion followed by 5 min of reperfusion). Blood pressure, heart rate, and regional myocardial blood flow throughout the experiment were measured, as was the myocardial infarct size after reperfusion. The infarct size of the vehicle-treated dog was 56.2% +/- 2.7% (n = 5), whereas that of 3 or 10 microg/kg YT-146-treated dog was smaller (ie, 29.5% +/- 8.7% or 20.2% +/- 7.0%, respectively; n = 5). The infarct size of the dog treated with 10 microg/kg YT-146 was reduced to a degree similar to that of the ischemic preconditioning (19.2% +/- 6.3%, n = 5). YT-146 at both doses elicited a dose-dependent increase in acute hyperemic coronary flow immediately after reperfusion. The cardioprotective effect may be attributed to the limitation of the infarct size, probably via A2-receptor-mediated coronary artery dilatation during the early period of reperfusion.

Sinus arrest during adenosine stress testing in liver transplant recipients with graft failure: three case reports and a review of the literature

BACKGROUND

Nuclear stress imaging is used frequently to evaluate patients with end-stage liver disease who are being considered for orthotopic liver transplantation.

METHODS AND RESULTS

We present three patients who, following graft failure, developed sinus arrest during adenosine stress testing performed in anticipation of repeat liver transplantation. All had undergone uneventful adenosine stress imaging prior to initial transplantation. The mechanisms of action, pharmacokinetics, and pharmacodynamics of adenosine are reviewed, and possible reasons for this phenomenon are discussed. Finally, cautions regarding the use of adenosine and treatment of adenosine-induced sinoatrial and atrioventricular block are reviewed.

CONCLUSION

Adenosine should be used with caution in patients following orthotopic liver transplantation due to an increased risk of sinus arrest. Should sinus arrest or atrioventricular block occur, it appears to respond readily to cessation of adenosine infusion and intravenous aminophylline with no significant sequelae.

The introduction of the stilbene synthase gene enhances the natural antiradical activity of Lycopersicon esculentum mill

Tomato (Lycopersicon esculentum) is a vegetable rich in antioxidants, such as lycopene, lutein, and zeaxanthin. Their presence is responsible for the characteristic ability of this product to inhibit the formation of reactive oxygen species, including singlet oxygen. The grapes and wines derived from grapes also contain powerful antioxidants. The antioxidant effect is derived from the polyphenols such as resveratrol and proanthocyanidin. Resveratrol is phytoalexin that is synthesized via the activation of the gene, stilbene synthase (STS). We decided to determine if the introduction of this gene into Lycopersicon esculentum Mill could modify its antioxidant activity. Using Electronic Paramagnetic Resonance (EPR) spectroscopy, which permits the detection of antiradical activity, especially *OH (hydroxyl radical), we showed that the antioxidant activity of the products, into which the gene STS had been introduced, was almost double than that of natural products and that their activity was especially pronounced due to ripening. Moreover, resveratrol concentrations in modified tomatoes were much higher than that found in the individual fruit. In the isolated hearts subjected to ischemia/reperfusion, the rats fed with modified tomato exhibited better cardiac performance, reduced myocardial infarct size and decreased number of apoptotic cardiomyocytes, and reduced oxidative stress compared to unmodified tomato or resveratrol alone indicating superior cardioprotective abilities of modified tomatoes.

A3 adenosine receptor-mediated protection of the ischemic heart

The A3 adenosine receptor (A3AR) is attributed with multiple beneficial actions in ischemic-reperfused myocardium, including modulation of oncotic and apoptotic cell death and enhancement of contractile function. Additionally, the A3AR may attenuate vascular dysfunction and improve long-term outcome from myocardial insult (modulating hypertrophy and angiogenesis). Available evidence indicates that this receptor sub-type is minimally activated by endogenous adenosine during ischemia (A3AR antagonists exerting no effects on ischemic outcome), and is thus amenable to activation with exogenous agonists. Protected phenotypes arise with both pre- and post-ischemic treatment with A3AR agonists, and transient A3AR agonism also triggers early and delayed preconditioned states. The molecular basis for the varied protective actions of the A3AR remains poorly defined, and may well vary between species (e.g. rodent vs. human) and protective responses (e.g. acute vs. delayed protection). Nonetheless, A3ARs may be more promising as therapeutic "anti-ischemic" targets compared with other adenosine receptor subtypes, since A3AR agonists elicit fewer and less significant side-effects. This review addresses current knowledge and controversy regarding the protective actions (and associated signaling) of A3ARs in ischemic-reperfused heart.