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

Muscle Atrophy Induced by Mechanical Unloading: Mechanisms and Potential Countermeasures

Prolonged periods of skeletal muscle inactivity or mechanical unloading (bed rest, hindlimb unloading, immobilization, spaceflight and reduced step) can result in a significant loss of musculoskeletal mass, size and strength which ultimately lead to muscle atrophy. With advancement in understanding of the molecular and cellular mechanisms involved in disuse skeletal muscle atrophy, several different signaling pathways have been studied to understand their regulatory role in this process. However, substantial gaps exist in our understanding of the regulatory mechanisms involved, as well as their functional significance. This review aims to update the current state of knowledge and the underlying cellular mechanisms related to skeletal muscle loss during a variety of unloading conditions, both in humans and animals. Recent advancements in understanding of cellular and molecular mechanisms, including IGF1-Akt-mTOR, MuRF1/MAFbx, FOXO, and potential triggers of disuse atrophy, such as calcium overload and ROS overproduction, as well as their role in skeletal muscle protein adaptation to disuse is emphasized. We have also elaborated potential therapeutic countermeasures that have shown promising results in preventing and restoring disuse-induced muscle loss. Finally, identified are the key challenges in this field as well as some future prospectives.

Neurotrophic function of phytochemicals for neuroprotection in aging and neurodegenerative disorders: modulation of intracellular signaling and gene expression

Bioactive compounds in food and beverages have been reported to promote health and prevent age-associated decline in cognitive, motor and sensory activities, and emotional function. Phytochemicals, a ubiquitous class of plant secondary metabolites, protect neuronal cells by interaction with cellular activities, in addition to the antioxidant and anti-inflammatory function. In aging and age-associated neurodegenerative disorders, phytochemicals protect neuronal cells by neurotrophic factor-mimic activity, in addition to suppression of apoptosis signaling in mitochondria. This review presents the cellular mechanisms underlying anti-apoptotic function and neurotrophic function of phytochemicals in the brain. Phytochemicals bind to receptors of neurotrophic factors, and also receptors for γ-aminobutyric acid, acetylcholine, serotonin, and glutamate and estrogen, and activate downstream signal pathways. Phytochemicals also directly intervene intracellular signaling molecules to modify the brain function. Finally, phytochemicals enhance the endogenous biosynthesis of genes coding anti-apoptotic Bcl-2 and neurotrophic factors, such as brain-derived and glial cell line-derived neurotrophic factor. The gene induction may play a major role in the neuroprotective function of dietary compounds shown by epidemiological studies. Quantitative measurement of neurotrophic factors induced by phytochemicals in the serum, cerebrospinal fluid, and other clinical samples is proposed as a surrogate assay method to evaluate the neuroprotective potency. Development of novel neuroprotective compounds is expected among compounds chemically synthesized from the brain-permeable basic structure of phytochemicals.

Resveratrol induces mitochondria-mediated, caspase-independent apoptosis in murine prostate cancer cells

Found in the skins of red fruits, including grapes, resveratrol (RES) is a polyphenolic compound with cancer chemopreventive activity. Because of this activity, it has gained interest for scientific investigations. RES inhibits tumor growth and progression by targeting mitochondria-dependent or -independent pathways. However, further investigations are needed to explore the underlying mechanisms.

The present study is focused on examining the role of RES-induced, mitochondria-mediated, caspase-independent apoptosis of prostate cancer cells, namely transgenic adenocarcinoma of mouse prostate (TRAMP) cells. These cells were exposed to RES for various times, and cell killing, cell morphology, mitochondrial membrane potential (Δψm), expression of Bax and Bcl2 proteins, the role of caspase-3, and DNA fragmentation were analyzed.

TRAMP cells exposed to RES showed decreased cell viability, altered cell morphology, and disrupted Δψm, which led to aberrant expression of Bax and Bcl2 proteins. Furthermore, since the caspase-3 inhibitor, z-VAD-fmk (benzyloxycarbonyl-valine-alanine-aspartic acid-fluoromethyl ketone), had no appreciable impact on RES-induced cell killing, the killing was evidently caspase-independent. In addition, RES treatment of TRAMP-C1, TRAMP-C2, and TRAMP-C3 cells caused an appreciable breakage of genomic DNA into low-molecular-weight fragments.

These findings show that, in inhibition of proliferation of TRAMP cells, RES induces mitochondria-mediated, caspase-independent apoptosis. Therefore, RES may be utilized as a therapeutic agent to control the proliferation and growth of cancer cells.

Nutritional strategies to counteract muscle atrophy caused by disuse and to improve recovery

Periods of immobilisation are often associated with pathologies and/or ageing. These periods of muscle disuse induce muscle atrophy which could worsen the pathology or elderly frailty. If muscle mass loss has positive effects in the short term, a sustained/uncontrolled muscle mass loss is deleterious for health. Muscle mass recovery following immobilisation-induced atrophy could be critical, particularly when it is uncompleted as observed during ageing. Exercise, the best way to recover muscle mass, is not always applicable. So, other approaches such as nutritional strategies are needed to limit muscle wasting and to improve muscle mass recovery in such situations. The present review discusses mechanisms involved in muscle atrophy following disuse and during recovery and emphasises the effect of age in these mechanisms. In addition, the efficiency of nutritional strategies proposed to limit muscle mass loss during disuse and to improve protein gain during recovery (leucine supplementation, whey proteins, antioxidants and anti-inflammatory compounds, energy intake) is also discussed.

Mitochondria and endothelial function

In contrast to their role in cell types with higher energy demands, mitochondria in endothelial cells primarily function in signaling cellular responses to environmental cues. This article provides an overview of key aspects of mitochondrial biology in endothelial cells, including subcellular location, biogenesis, dynamics, autophagy, reactive oxygen species production and signaling, calcium homeostasis, regulated cell death, and heme biosynthesis. In each section, we introduce key concepts and then review studies showing the importance of that mechanism to endothelial control of vasomotor tone, angiogenesis, and/or inflammatory activation. We particularly highlight the small number of clinical and translational studies that have investigated each mechanism in human subjects. Finally, we review interventions that target different aspects of mitochondrial function and their effects on endothelial function. The ultimate goal of such research is the identification of new approaches for therapy. The reviewed studies make it clear that mitochondria are important in endothelial physiology and pathophysiology. A great deal of work will be needed, however, before mitochondria-directed therapies are available for the prevention and treatment of cardiovascular disease.

Short-term caloric restriction, resveratrol, or combined treatment regimens initiated in late-life alter mitochondrial protein expression profiles in a fiber-type specific manner in aged animals

Aging is associated with a loss in muscle known as sarcopenia that is partially attributed to apoptosis. In aging rodents, caloric restriction (CR) increases health and longevity by improving mitochondrial function and the polyphenol resveratrol (RSV) has been reported to have similar benefits. In the present study, we investigated the potential efficacy of using short-term (6 weeks) CR (20%), RSV (50 mg/kg/day), or combined CR+ RSV (20% CR and 50 mg/kg/day RSV), initiated at late-life (27 months) to protect muscle against sarcopenia by altering mitochondrial function, biogenesis, content, and apoptotic signaling in both glycolytic white and oxidative red gastrocnemius muscle (WG and RG, respectively) of male Fischer 344 × Brown Norway rats. CR but not RSV attenuated the age-associated loss of muscle mass in both mixed gastrocnemius and soleus muscle, while combined treatment (CR + RSV) paradigms showed a protective effect in the soleus and plantaris muscle (P < 0.05). Sirt1 protein content was increased by 2.6-fold (P < 0.05) in WG but not RG muscle with RSV treatment, while CR or CR + RSV had no effect. PGC-1α levels were higher (2-fold) in the WG from CR-treated animals (P < 0.05) when compared to ad-libitum (AL) animals but no differences were observed in the RG with any treatment. Levels of the anti-apoptotic protein Bcl-2 were significantly higher (1.6-fold) in the WG muscle of RSV and CR + RSV groups compared to AL (P < 0.05) but tended to occur coincident with elevations in the pro-apoptotic protein Bax so that the apoptotic susceptibility as indicated by the Bax to Bcl-2 ratio was unchanged. There were no alterations in DNA fragmentation with any treatment in muscle from older animals. Additionally, mitochondrial respiration measured in permeabilized muscle fibers was unchanged in any treatment group and this paralleled the lack of change in cytochrome c oxidase (COX) activity. These data suggest that short-term moderate CR, RSV, or CR + RSV tended to modestly alter key mitochondrial regulatory and apoptotic signaling pathways in glycolytic muscle and this might contribute to the moderate protective effects against aging-induced muscle loss observed in this study.

Proteomic profiling reveals that resveratrol inhibits HSP27 expression and sensitizes breast cancer cells to doxorubicin therapy

The use of chemopreventive natural compounds represents a promising strategy in the search for novel therapeutic agents in cancer. Resveratrol (3,4′,5-trans-trihydroxystilbilene) is a dietary polyphenol found in fruits, vegetables and medicinal plants that exhibits chemopreventive and antitumor effects. In this study, we searched for modulated proteins with preventive or therapeutic potential in MCF-7 breast cancer cells exposed to resveratrol. Using two-dimensional electrophoresis we found significant changes (FC >2.0; p≤0.05) in the expression of 16 proteins in resveratrol-treated MCF-7 cells. Six down-regulated proteins were identified by tandem mass spectrometry (ESI-MS/MS) as heat shock protein 27 (HSP27), translationally-controlled tumor protein, peroxiredoxin-6, stress-induced-phosphoprotein-1, pyridoxine-5′-phosphate oxidase-1 and hypoxanthine-guanine phosphoribosyl transferase; whereas one up-regulated protein was identified as triosephosphate isomerase. Particularly, HSP27 overexpression has been associated to apoptosis inhibition and resistance of human cancer cells to therapy. Consistently, we demonstrated that resveratrol induces apoptosis in MCF-7 cells. Apoptosis was associated with a significant increase in mitochondrial permeability transition, cytochrome c release in cytoplasm, and caspases -3 and -9 independent cell death. Then, we evaluated the chemosensitization effect of increasing concentrations of resveratrol in combination with doxorubicin anti-neoplastic agent in vitro. We found that resveratrol effectively sensitize MCF-7 cells to cytotoxic therapy. Next, we evaluated the relevance of HSP27 targeted inhibition in therapy effectiveness. Results evidenced that HSP27 inhibition using RNA interference enhances the cytotoxicity of doxorubicin. In conclusion, our data indicate that resveratrol may improve the therapeutic effects of doxorubicin in part by cell death induction. We propose that potential modulation of HSP27 levels using natural alternative agents, as resveratrol, may be an effective adjuvant in breast cancer therapy.

Protective Effects of Resveratrol on TNF-α-Induced Endothelial Cytotoxicity in Baboon Femoral Arterial Endothelial Cells

Endothelial injury induced by inflammatory factors plays a critical role in the pathogenesis of cardiovascular disease. Endothelial cell (EC) apoptosis, proliferation, migration, and cellular adhesion molecule (CAM) expression contribute to the development of atherosclerosis. We investigated the effects of resveratrol (0.1-100  μ M) on the proliferation, migration, and CAM expression of primary cultures of baboon arterial endothelial cells (BAECs). In addition, we tested its effects under normal conditions as well as under inflammatory conditions induced by tumour necrosis factor-α (TNF-α) administered either by cotreatment, pretreatment, or posttreatment. Immunocytochemistry, MTT, wound-healing, and flow cytometry assays were performed. The resveratrol treatment significantly enhanced BAEC proliferation and attenuated TNF-α-induced impairment of proliferation at the optimal doses of 1-50 µM. Resveratrol at a high dose (100  μ M) and TNF-α impaired BAEC migration, while low doses of resveratrol (1-50  μ M) attenuated TNF-α-induced impairment of BAEC migration. Moreover, resveratrol inhibited TNF-α-induced ICAM-1 and VCAM-1 expression. Taken together, our results suggest that the resveratrol protects BAECs after inflammatory stimulation as well as ameliorates inflammatory effects at low concentrations. Consequently, resveratrol should be considered as a candidate drug for the prevention and treatment of inflammatory vascular diseases.

The β6-integrin-ERK/MAP kinase pathway contributes to chemo resistance in colon cancer

5-Fluorouracil (5-FU) is the most widely used chemo drug for the treatment of colon cancer. However, a sub-population of colon cancer patients do not respond to 5-FU and this treatment does not provide survival benefit due to chemo resistance. The mechanisms involved in 5-FU resistance are not fully understood and multiple factors have been involved in the sensitivity of cancer cells to 5-FU. We previously reported that β6-integrin plays an important role in invasion, metastasis and degradation of extracellular matrix of colon cancer. In this study, we investigated whether β6-integrin is associated with chemo resistance in colon cancer. We found that over-expression of β6-integrin protected SW480 and HT-29 colon cancer cells from 5-FU-induced growth inhibition and apoptosis, which were accompanied by changes in cytochrome C released from the mitochondria and activity of caspase-3 and caspase-9. Moreover, β6-integrin resulted in up-regulation of Bcl-2 and down-regulation of Bax. We also found that β6-integrin induced 5-FU resistance through the ERK/MAP kinase pathway and the β6-ERK2 direct binding. The results indicate β6-integrin might be a novel therapeutic target in colon cancer therapy.

Malvidin-3-glucoside protects endothelial cells up-regulating endothelial NO synthase and inhibiting peroxynitrite-induced NF-kB activation

Anthocyanins are the most abundant flavonoid constituents of fruits and vegetables and several epidemiological studies suggest that the consumption of these compounds protect against several diseases, including vascular disorders. Previously, we have reported that anthocyanins are able to counteract peroxynitrite-induced apoptotic effects in endothelial cells through inhibition of several crucial signaling cascades, upstream and downstream of mitochondria. Following these studies, here we investigated possible effects of malvidin-3-glucoside, one of the main dietary anthocyanins, on NO bioavailability and on peroxynitrite-induced NF-kB activation in the same cell model. Our results show that treatment of bovine arterial endothelial cells with malvidin-3-glucoside up-regulated eNOS mRNA, leading to the enhancement of eNOS activity and NO production, an effect even greater when cells were further stimulated with peroxynitrite. On the other hand, in these activated endothelial cells, malvidin-3-glucoside suppressed pro-inflammatory mediators, namely iNOS expression/NO biosynthesis, COX-2 expression and IL-6 production, through inhibition of NF-kB activation. These findings suggest a potential role of malvidin-3-glucoside in NO balance and in inhibition of pro-inflammatory signaling pathways, supporting its benefits in cardiovascular health and pointing to anthocyanins as a promising tool for development of functional foods and nutraceuticals to improve endothelial function.

Potential roles of longan flower and seed extracts for anti-cancer

Polyphenol-rich plants are known to possess benefits to human health. Recent studies have revealed that many Traditional Chinese Medicines (TCMs) are rich sources of polyphenols and exhibit antioxidant and anti-inflammatory activities, and these TCMs have been shown experimentally to overcome some chronic diseases, including cancer. Longan flowers and seeds, two TCMs traditionally used for relieving pain and urinary diseases, have been revealed in our recent reports and other studies to possess rich amounts of polyphenolic species and exhibit strong anti-oxidant activity, and these could be applied for the treatment of diabetes and cancer. Herein, we review the recent findings regarding the benefits of these two TCMs in the treatment of human cancer and the possible cellular and molecular mechanisms of both substances.

Protective role of malvidin-3-glucoside on peroxynitrite-induced damage in endothelial cells by counteracting reactive species formation and apoptotic mitochondrial pathway

The health-promoted benefits of anthocyanins, including vascular protective effects and antiatherogenic properties, have now been recognized, but the involved molecular mechanisms have not been well elucidated. Following our previous work on cytoprotective mechanisms of some anthocyanins against apoptosis triggered by peroxynitrite in endothelial cells, here we investigated the protective role of malvidin-3-glucoside, a major dietary anthocyanin, on such deleterious process, by exploring the interference on cellular reactive species formation and on apoptotic mitochondrial pathway. Preincubation of cells with 25 μM malvidin-3-glucoside protected efficiently endothelial cells from peroxynitrite-promoted apoptotic death, an effect which may be partially mediated by its ability to decrease the formation of reactive species after cell aggression, as assessed by the dichlorodihydrofluorescein diacetate assay and by carbonyl groups formation. Moreover, malvidin-3-glucoside inhibited mitochondrial apoptotic signaling pathways induced by peroxynitrite, by counteracting mitochondrial membrane depolarization, the activation of caspase-3 and -9, and the increase in the expression of the proapoptotic Bax protein. Altogether, our data expands our knowledge about the molecular mechanisms underlying the vascular protection afforded by malvidin-3-glucoside, and anthocyanins in general, in the context of prevention of endothelial dysfunction and atherosclerosis.

Grape antioxidant dietary fibre prevents mitochondrial apoptotic pathways by enhancing Bcl-2 and Bcl-xL expression and minimising oxidative stress in rat distal colonic mucosa

Grape antioxidant dietary fibre (GADF) is a grape product rich in dietary fibre and natural antioxidants. We reported previously that GADF intake reduced apoptosis and induced a pro-reducing shift in the glutathione (GSH) redox status of the rat proximal colonic mucosa. The aim of the study was to elucidate the molecular mechanisms responsible for the anti-apoptotic effect of GADF and their association with the oxidative environment of the distal colonic mucosa. The ability of GADF to modify colonic crypt cell proliferation was also investigated. Male Wistar rats (n 20) were fed with diets containing either cellulose (control group) or GADF (GADF group) as fibre for 4 weeks. GADF did not modify cell proliferation but induced a significant reduction of colonic apoptosis. The anti-apoptotic proteins Bcl-2 (B-cell lymphoma-2) and Bcl-xL (B-cell lymphoma extra large) were up-regulated in the mitochondria and down-regulated in the cytosol of the GADF mucosa, whereas the opposite was found for the pro-apoptotic protein Bax (Bcl-2-associated X protein), leading to an anti-apoptotic shift in the pattern of expression of the Bcl-2 family. Cytosolic cytochrome c and cleaved caspase-3 levels and caspase-3 activity were reduced by GADF. The modulation of the antioxidant enzyme system and the increase of the cytosolic GSH:glutathione disulfide (GSSG) ratio elicited by GADF helped to reduce oxidative damage. The cytosolic GSH:GSSG ratio was negatively related to apoptosis. These results indicate that GADF acts on the expression of the pro- and anti- apoptotic Bcl-2 proteins, attenuating the mitochondrial apoptotic pathway in the distal colonic mucosa. This effect appears to be associated with the antioxidant properties of GADF.

Resveratrol, a polyphenol phytoalexin, protects cardiomyocytes against anoxia/reoxygenation injury via the TLR4/NF-κB signaling pathway

Previous studies indicate resveratrol pretreatment can protect cardiomyocytes. However, it is largely unknown whether resveratrol protects cardiomyocytes when applied at reperfusion. The purpose of this study was to investigate whether resveratrol given at reoxygenation could protect cardiomyocytes under the anoxia/reoxygenation (A/R) condition and to examine the underlying mechanism. In this study, primary cultures of neonatal rat cardiomyocytes were randomly distributed into three groups: control group, A/R group (cultured cardiomyocytes were subjected to 3 h anoxia followed by 2 h reoxygenation), and the resveratrol group (cardiomyocytes were subjected to 3 h anoxia/2 h reoxygenation, and 5, 10 or 20 μM resveratrol was applied 5 min after reoxygenation). In order to evaluate cardiomyocyte damage, cell viability, lactate dehydrogenase (LDH) release, caspase-3 activity, and apoptosis were analyzed by the cell counting kit (CCK)-8 assay, colorimetric method and flow cytometry, respectively. The mRNA and protein expression of Toll-like receptor 4 (TLR4) were detected by quantitative real-time PCR and western blot analysis. Nuclear factor-κB (NF-κB) p65 protein and I-κBα protein levels were also examined by western blot analysis. The levels of proinflammatory cytokines in the culture medium were assessed by enzyme-linked immunosorbent assay. We found that resveratrol prevented a reduction in cell viability, decreased the amount of LDH release, attenuated apoptotic cells and decreased caspase-3 activity induced by A/R in cardiomyocytes. Furthermore, resveratrol treatment significantly attenuated the TLR4 expression, inhibited NF-κB activation and reduced the levels of tumor necrosis factor (TNF)-α and interleukin (IL)-1β caused by A/R injury in the culture medium. Treatment with resveratrol shortly after the onset of reoxygenation improves cell survival and attenuates A/R-induced inflammatory response. This protection mechanism is possibly related to the TLR4/NF-κB signaling pathway.

Upregulation of PTEN by peroxynitrite contributes to cytokine-induced apoptosis in pancreatic beta-cells

Phosphatase and tensin homolog (PTEN), a tumor suppressor gene, by negatively regulating the PI3K-Akt signaling pathway, participates in multiple biological processes such as cell proliferation, apoptosis, differentiation, and migration. Recent studies show that selective deletion of PTEN in pancreatic beta-cells leads to resistance to streptozotocin (STZ)-induced diabetes, but the mechanism is unclear. One major mechanism underlying STZ toxicity is cytokine-mediated beta-cell destruction in which oxidative stress plays a key role. The present study investigated the role of PTEN in cytokine-induced beta-cell apoptosis, and further explored whether oxidative stress, particularly peroxynitrite formation, could regulate PTEN-Akt pathway. Incubation of betaTC-6 cells with cytokine mixture (IL-1beta, TNF-alpha, and IFN-gamma) or exogenous peroxynitrite significantly increased apoptotic cell percentage, elevated PTEN and p-PTEN levels, and inhibited Akt activation. Transfection with PTEN-specific siRNA protected betaTC-6 cells from cytokine or peroxynitrite-mediated cell apoptosis and partially reversed Akt inhibition. Furthermore, nitrotyrosine formation, an indicator of peroxynitrite production, was significantly elevated after cytokine treatment. Preventing peroxynitrite formation by administrating NAC/L: -NMMA, or scavenging peroxynitrite directly by UA, attenuated cytokine-induced PTEN upregulation, Akt inhibition, and beta-cell apoptosis. These findings suggest that peroxynitrite-mediated PTEN upregulation plays an important role in cytokine-induced pancreatic beta-cell apoptosis.

Mediation of endogenous antioxidant enzymes and apoptotic signaling by resveratrol following muscle disuse in the gastrocnemius muscles of young and old rats

Hindlimb suspension (HLS) elicits muscle atrophy, oxidative stress, and apoptosis in skeletal muscle. Increases in oxidative stress can have detrimental effects on muscle mass and function, and it can potentially lead to myonuclear apoptosis. Resveratrol is a naturally occurring polyphenol possessing both antioxidant and antiaging properties. To analyze the capacity of resveratrol to attenuate oxidative stress, apoptosis and muscle force loss were measured following 14 days of HLS. Young (6 mo) and old (34 mo) rats were administered either 12.5 mg·kg(-1)·day(-1) of trans-resveratrol, or 0.1% carboxymethylcellulose for 21 days, including 14 days of HLS. HLS induced a significant decrease in plantarflexor isometric force, but resveratrol blunted this loss in old animals. Resveratrol increased gastrocnemius catalase activity, MnSOD activity, and MnSOD protein content following HLS. Resveratrol reduced hydrogen peroxide and lipid peroxidation levels in muscles from old animals after HLS. Caspase 9 abundance was reduced and Bcl-2 was increased, but other apoptotic markers were not affected by resveratrol in the gastrocnemius muscle after HLS. The data indicate that resveratrol has a protective effect against oxidative stress and muscle force loss in old HLS animals; however, resveratrol was unable to attenuate apoptosis following HLS. These results suggest that resveratrol has the potential to be an effective therapeutic agent to treat muscle functional decrements via improving the redox status associated with disuse.

Effects of resveratrol and flavonols on cardiovascular function: Physiological mechanisms

Resveratrol and flavonols are commonly found together in fruits and vegetables and, therefore, consumed in the diet. These two polyphenols share both vasorelaxant and antioxidant activity and may act together to improve cardiovascular function. This review examines the mechanisms by which resveratrol and flavonols influence cardiovascular function and perhaps offer a new approach for the development of therapeutic agents for the prevention and/or treatment of coronary artery disease.

Effect of resveratrol on endothelial cell function: Molecular mechanisms

The polyphenolic natural product resveratrol (RV), best known for its occurrence in grape skin and red wine, is considered a candidate drug for prevention and treatment of cardiovascular diseases. This review aims to summarize the molecular effects of RV on endothelial cells, which line the inner walls of blood vessels and play a key role in the development of those diseases. We describe how RV enhances endothelial nitric oxide production, improves endothelial redox balance and inhibits endothelial activation in response to pro-inflammatory and metabolic insults. Furthermore, we summarize effects of RV on endothelial senescence, apoptosis, endothelin-1 release, and endothelial progenitor cell function. As many of RV's actions seem to be mediated by SIRT₁, different mechanistic possibilities how RV may lead to SIRT₁ activation are discussed.

Resveratrol promotes osteogenic differentiation and protects against dexamethasone damage in murine induced pluripotent stem cells

Resveratrol is a natural polyphenol antioxidant that has been shown to facilitate osteogenic differentiation. A recent breakthrough has demonstrated that ectopic expression of four genes is sufficient to reprogram murine and human fibroblasts into induced pluripotent stem (iPS) cells. However, the roles of resveratrol in the differentiation and cytoprotection of iPS cells have never been studied. In this study, we showed that, in addition to cardiac cells, neuron-like cells, and adipocytes, mouse iPS cells could differentiate into osteocyte-like cells. Using atomic force microscopy that provided nanoscale resolution, we monitored mechanical properties of living iPS cells during osteogenic differentiation. The intensity of mineralization and stiffness in differentiating iPS significantly increased after 14 days of osteogenic induction. Furthermore, resveratrol was found to facilitate osteogenic differentiation in both iPS and embryonic stem cells, as shown by increased mineralization, up-regulation of osteogenic markers, and decreased elastic modulus. Dexamethasone-induced apoptosis in iPS cell-derived osteocyte-like cells was effectively prevented by pretreatment with resveratrol. Furthermore, resveratrol significantly increased manganese superoxide dismutase expression and intracellular glutathione level, thereby efficiently decreasing dexamethasone-induced reactive oxygen species (ROS) production and cytotoxicity. Transplantation experiments using iPS cell-derived osteocyte-like cells further demonstrated that oral intake of resveratrol could up-regulate osteopontin expression and inhibit teratoma formation in vivo. In sum, resveratrol can facilitate differentiation of iPS cells into osteocyte-like cells, protect these iPS cell-derived osteocyte-like cells from glucocorticoid-induced oxidative damage, and decrease tumorigenicity of iPS cells. These findings implicate roles of resveratrol and iPS cells in the stem cell therapy of orthopedic diseases.

Silymarin modulates doxorubicin-induced oxidative stress, Bcl-xL and p53 expression while preventing apoptotic and necrotic cell death in the liver

The emergence of silymarin (SMN) as a natural remedy for liver diseases, coupled with its entry into NIH clinical trial, signifies its hepatoprotective potential. SMN is noted for its ability to interfere with apoptotic signaling while acting as an antioxidant. This in vivo study was designed to explore the hepatotoxic potential of Doxorubicin (Dox), the well-known cardiotoxin, and in particular whether pre-exposures to SMN can prevent hepatotoxicity by reducing Dox-induced free radical mediated oxidative stress, by modulating expression of apoptotic signaling proteins like Bcl-xL, and by minimizing liver cell death occurring by apoptosis or necrosis. Groups of male ICR mice included Control, Dox alone, SMN alone, and Dox with SMN pre/co-treatment. Control and Dox groups received saline i.p. for 14 days. SMN was administered p.o. for 14 days at 16 mg/kg/day. An approximate LD(50) dose of Dox, 60 mg/kg, was administered i.p. on day 12 to animals receiving saline or SMN. Animals were euthanized 48 h later. Dox alone induced frank liver injury (>50-fold increase in serum ALT) and oxidative stress (>20-fold increase in malondialdehyde [MDA]), as well as direct damage to DNA (>15-fold increase in DNA fragmentation). Coincident genomic damage and oxidative stress influenced genomic stability, reflected in increased PARP activity and p53 expression. Decreases in Bcl-xL protein coupled with enhanced accumulation of cytochrome c in the cytosol accompanied elevated indexes of apoptotic and necrotic cell death. Significantly, SMN exposure reduced Dox hepatotoxicity and associated apoptotic and necrotic cell death. The effects of SMN on Dox were broad, including the ability to modulate changes in both Bcl-xL and p53 expression. In animals treated with SMN, tissue Bcl-xL expression exceeded control values after Dox treatment. Taken together, these results demonstrated that SMN (i) reduced, delayed onset, or prevented toxic effects of Dox which are typically associated with hydroxyl radical production, (ii) performed as an antioxidant limiting oxidative stress, (iii) protected the integrity of the genome, and (iv) antagonized apoptotic and necrotic cell death while increasing antiapoptotic Bcl-xL protein levels and minimizing the leakage of proapoptotic cytochrome c from liver mitochondria. These observations demonstrate the protective actions of SMN in liver, and raise the possibility that such protection may extend to other organs during Dox treatment including the heart.

The mitochondrial death pathway: a promising therapeutic target in diseases

The mitochondrial pathway to apoptosis is a major pathway of physiological cell death in vertebrates. The mitochondrial cell death pathway commences when apoptogenic molecules present between the outer and inner mitochondrial membranes are released into the cytosol by mitochondrial outer membrane permeabilization (MOMP). BCL-2 family members are the sentinels of MOMP in the mitochondrial apoptotic pathway; the pro-apoptotic B cell lymphoma (BCL)-2 proteins, BCL-2 associated x protein and BCL-2 antagonist killer 1 induce MOMP whereas the anti-apoptotic BCL-2 proteins, BCL-2, BCL-x_l and myeloid cell leukaemia 1 prevent MOMP from occurring. The release of pro-apoptotic factors such as cytochrome c from mitochondria leads to formation of a multimeric complex known as the apoptosome and initiates caspase activation cascades. These pathways are important for normal cellular homeostasis and play key roles in the pathogenesis of many diseases. In this review, we will provide a brief overview of the mitochondrial death pathway and focus on a selection of diseases whose pathogenesis involves the mitochondrial death pathway and we will examine the various pharmacological approaches that target this pathway.