Antioxidant properties of EPC-K1: a study on mechanisms

Water-Soluble Vitamin E-Tocopheryl Phosphate

The hydrophobicity of vitamin E poses transport and metabolic challenges to regulate its bioavailability and to prevent its accumulation in lipid-rich tissues such as adipose tissue, brain, and liver. Water-soluble precursors of vitamin E (α-tocopherol, αT), such as its esters with acetate (αTA), succinate (αTS), or phosphate (αTP), have increased solubility in water and stability against reaction with free radicals, but they are rapidly converted during their uptake into the lipid-soluble vitamin E. Therefore, the bioavailability of these precursors as intact molecules is low; nevertheless, at least for αTS and αTP, the recent research has revealed unique regulatory effects on signal transduction and gene expression and the modulation of cellular events ranging from proliferation, survival/apoptosis, lipid uptake and metabolism, phagocytosis, long term potentiation, cell migration, telomere maintenance, and angiogenesis. Moreover, water-soluble derivatives of vitamin E including some based on αTP are increasingly used as components of nanocarriers for enhanced and targeted delivery of drugs and other molecules (vitamins, including αT and αTP itself, vitamin D3, carnosine, caffeine, docosahexaenoic acid (DHA), insulin) and cofactors such as coenzyme Q10. In this review, the chemical characteristics, transport, metabolic pathways, and molecular mechanisms of action of αTP in cells and tissues are summarized and put into perspective with its possible role in the prevention of a number of diseases.

The α-tocopherol derivative ESeroS-GS induces cell death and inhibits cell motility of breast cancer cells through the regulation of energy metabolism

Cancer cells are known to exhibit different hallmarks compared with normal cells. Therefore, targeting these features may improve the response to cancer therapy. In this study, we provided direct evidence that the α-tocopherol derivative ESeroS-GS inhibited the viability, migration, and invasion of breast cancer cells. ESeroS-GS induced cell death in different cancer cells in a dose-dependent manner but showed no significant effects on MCF-10A mammary epithelial cells. Although the ESeroS-GS-induced cell death in MDA-MB-231 breast cancer cells was accompanied with the generation of reactive oxygen species and the down regulation of mitochondrial membrane potential (MMP), no such effect on reactive oxygen species and MMP was seen in MCF-10A cells. Further studies indicated that ESeroS-GS down-regulated the expression of hexokinase II, SDH B, UQCRC2 and COX II in MDA-MB-231 cells but not in MCF-10A cells. The down-regulation of these enzymes accounts for the decreased oxidative phosphorylation (OXPHOS) and glycolysis in MDA-MB-231 cells upon ESeroS-GS treatment. We also found that sub-toxic concentration of ESeroS-GS treatment resulted in the impairment of F-actin cytoskeleton assembly and the consequently decreased migratory and invasive ability of MDA-MB-231 cells, which might be due to the inhibition of cellular energy metabolism. These results indicate that ESeroS-GS shows potential to become a novel anti-cancer agent by targeting the energy metabolism of cancer cells.

Mitochondrial therapeutics for cardioprotection

Mitochondria represent approximately one-third of the mass of the heart and play a critical role in maintaining cellular function-however, they are also a potent source of free radicals and pro-apoptotic factors. As such, maintaining mitochondrial homeostasis is essential to cell survival. As the dominant source of ATP, continuous quality control is mandatory to ensure their ongoing optimal function. Mitochondrial quality control is accomplished by the dynamic interplay of fusion, fission, autophagy, and mitochondrial biogenesis. This review examines these processes in the heart and considers their role in the context of ischemia-reperfusion injury. Interventions that modulate mitochondrial turnover, including pharmacologic agents, exercise, and caloric restriction are discussed as a means to improve mitochondrial quality control, ameliorate cardiovascular dysfunction, and enhance longevity.

alpha-Tocopheryl phosphate--an active lipid mediator?

The vitamin E (alpha-tocopherol, alphaT) derivative, alpha-tocopheryl phosphate (alphaTP), is detectable in small amounts in plasma, tissues, and cultured cells. Studies done in vitro and in vivo suggest that alphaT can become phosphorylated and alphaTP dephosphorylated, suggesting the existence of enzyme(s) with alphaT kinase or alphaTP phosphatase activity, respectively. As a supplement in animal studies, alphaTP can reach plasma concentrations similar to alphaT and only a part is dephosphorylated; thus, alphaTP may act both as pro-vitamin E, but also as phosphorylated form of vitamin E with possibly novel regulatory activities. Many effects of alphaTP have been described: in the test tube alphaTP modulates the activity of several enzymes; in cell culture alphaTP affects proliferation, apoptosis, signal transduction, and gene expression; in animal studies alphaTP prevents atherosclerosis, ischemia/reperfusion injury, and induces hippocampal long-term potentiation. At the molecular level, alphaTP may act as a cofactor for enzymes, as an active lipid mediator similar to other phosphorylated lipids, or indirectly by altering membrane characteristics such as lipid rafts, fluidity, and curvature. In this review, the molecular and cellular activities of alphaTP are examined and the possible functions of alphaTP as a natural compound, cofactor and active lipid mediator involved in signal transduction and gene expression discussed.

Grape extract protects mitochondria from oxidative damage and improves locomotor dysfunction and extends lifespan in a Drosophila Parkinson's disease model

A botanical extract (Regrapex-R) prepared from whole grape (Vitis vinifera) and Polygonum cuspidatum, which contains polyphenols, including flavans, anthocyanins, emodin, and resveratrol, exhibited dose-dependent scavenging effects on reactive oxygen species (ROS). The extract inhibited increases of ROS and protein carbonyl in isolated rat liver mitochondria following exposure to 2,2'-azobis (2-amidino propane) dihydrocholoride (AAPH), a potent lipid oxidant generator. The antioxidant effects of this extract were further demonstrated by protecting enzyme activities of the mitochondrial respiratory electron transport chain (complexes I and II) and pyruvate dehydrogenase in isolated liver mitochondria with AAPH insult. In human neuroblastoma cells (SKN-MC), pretreatment of extract protected cells against AAPH induced oxidation in maintaining cell viability and inhibiting excessive ROS generation. Extract was fed to transgenic Drosophila expressing human alpha-synuclein. This model for Parkinson disease recapitulates essential features of the disorder, including loss of dopaminergic neurons in the substantia nigra and a locomotor dysfunction that is displayed by a progressive loss of climbing ability measured using a geotaxis assay. Male transgenic flies fed the extract (0.16-0.64 mg/100 g of culture medium) showed a significant improvement in climbing ability compared to controls. Female transgenic flies showed a significant extension in average lifespan. These results suggest that Regrapex-R is a potent free radical scavenger, a mitochondrial protector, and a candidate for further studies to assess its ability to protect against neurodegenerative disease and potentially extend lifespan.

Melatonin impairs NADPH oxidase assembly and decreases superoxide anion production in microglia exposed to amyloid-beta1-42

Melatonin shows significant protective effects in Alzheimer's disease (AD) models in vitro and in vivo; these effects are related to its function as an antioxidant. The source of reactive oxygen species (ROS) generation in the AD brain is primarily the amyloid-beta (Abeta)- activated microglial nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. However, the effects of melatonin on the activation of NADPH oxidase remain unclear. In the present study, the cultures of microglia were incubated in the presence of fibrillar Abeta(1-42), which induces the assembly and the activation of NADPH oxidase, and triggers the production of superoxide anion-derived ROS. Pretreatment of microglia with melatonin dose-dependently prevents the activation of NADPH oxidase and decreases the production of ROS. Melatonin inhibits the phosphorylation of the p47(phox) subunit of NADPH oxidase via a PI3K/Akt-dependent signalling pathway, blocks the translocation of p47(phox) and p67(phox) subunit to the membrane, down-regulates the binding of p47(phox) to gp91(phox), and impairs the assembly of NADPH oxidase. Our data offer new insights into the mechanism of inhibiting ROS generation by melatonin in Abeta-activated microglia. Inhibition of ROS production indirectly might be the underlying mechanism for the neuroprotection by melatonin in the AD brain.

Endothelin stimulates vascular hydroxyl radical formation: effect of obesity

Reactive oxygen species (ROS) and endothelin-1 (ET-1) contribute to vascular pathophysiology in obesity. In this context, whether ET-1 modulates hydroxyl radical (•OH) formation and the function of ROS/•OH in obesity is not known. In the present study, formation and function of ROS, including •OH, were investigated in the aorta of lean and leptin-deficient obese ob/ob mice. Hydroxyl radical formation was detected ex vivo using terephthalic acid in intact aortic rings and the involvement of ROS in ET-1-mediated vasoreactivity was analyzed using the antioxidant EPC-K1, a combination of α-tocopherol and ascorbic acid. Generation of either •OH, •O2−, and H2O2was strongly inhibited by EPC-K1 (all P < 0.05). In obese mice, basal vascular •OH formation and ROS activity were reduced by 3-fold and 5-fold, respectively ( P < 0.05 vs. lean). ET-1 markedly enhanced •OH formation in lean (6-fold, P < 0.05 vs. untreated) but not in obese mice. Obesity increased ET-1-induced contractions ( P < 0.05 vs. lean), and ROS scavenging further enhanced the response ( P < 0.05 vs. untreated). Exogenous ROS, including •OH caused stronger vasodilation in obese animals ( P < 0.05 vs. lean), whereas endothelium-dependent relaxation was similar between lean and obese animals. In conclusion, we present a sensitive method allowing ex vivo measurement of vascular •OH generation and provide evidence that ET-1 regulates vascular •OH formation. The data indicate that in obesity, vascular formation of ROS, including •OH is lower, whereas the sensitivity to ROS is increased, suggesting a novel and important role of ROS, including •OH in the regulation of vascular tone in disease status associated with increased body weight.

Antioxidants and Cardioprotection

Limiting myocardial ischemia-reperfusion (IR) injury is essential for preventing contractile dysfunction and limiting morbidity and mortality associated with ischemic heart disease. Over the last few decades, it has become clear that during IR insults, myocardial oxygen radical formation is accelerated and plays a critical role in mediating cellular damage and dysfunction. This review provides a brief summary of a variety of approaches that have been undertaken to alleviate the oxidant stress associated with myocardial IR, and a summary of the data demonstrating the potential therapeutic value of oxidant scavenging in limiting IR-induced myocardial damage. Included is a review of investigations using novel free radical scavengers, antioxidant extracts from a variety of plants, polyphenolic compounds from foods such as cocoa, soy, grapes, and wine, as well as vitamin E, vitamin C, and beta-carotene. Also reviewed is the evidence that exercise-induced increases in endogenous antioxidants may be an important change contributing to cardioprotection. One must conclude from this brief review that current evidence suggests that enhancing oxidant-scavenging capacity protects against some of the cardiomyocyte disturbances during IR and helps salvage myocardial tissue. Data in cultured cell and animal models are convincing; trials in humans are significantly more conflicting, but still promising.

Cellular, molecular and clinical aspects of vitamin E on atherosclerosis prevention

Randomised clinical trials and epidemiologic studies addressing the preventive effects of vitamin E supplementation against cardiovascular disease reported both positive and negative effects, and recent meta-analyses of the clinical studies were rather disappointing. In contrast to that, many animal studies clearly show a preventive action of vitamin E in several experimental settings, which can be explained by the molecular and cellular effects of vitamin E observed in cell cultures. This review is focusing on the molecular effects of vitamin E on the cells playing a role during atherosclerosis, in particular on the endothelial cells, vascular smooth muscle cells, monocytes/macrophages, T cells, and mast cells. Vitamin E may act by normalizing aberrant signal transduction and gene expression in antioxidant and non-antioxidant manners; in particular, over-expression of scavenger receptors and consequent foam cell formation can be prevented by vitamin E. In addition to that, the cellular effects of alpha-tocopheryl phosphate and of EPC-K1, a composite molecule between alpha-tocopheryl phosphate and l-ascorbic acid, are summarized.

Imbalance between production and scavenging of hydroxyl radicals in patients maintained on hemodialysis

BACKGROUND

Reactive oxygen species are as being related to the pathophysiology of endstage renal disease (ESRD). We measured the plasma hydroxyl radical (.OH)-producing ability and .OH-scavenging activity in patients with ESRD to clarify the pathophysiological states involved.

METHODS

We used electron spin resonance to measure plasma N-t-butyl-alpha-phenylnitron radical spin adduct (pPBN rsa) as .OH-producing ability and plasma 3,3,5,5-tetramethyl-1-pyrroline-N-oxide radical spin adduct (pM4PO rsa) as .OH-scavenging activity. Oxidative injuries were evaluated by determining oxidised low-density lipoprotein (Ox-LDL).

RESULTS

The pPBN rsa of the ESRD patients was lower than that of the controls (1.83 vs 2.94 micromol/g protein). The pM4PO rsa of the ESRD patients was higher than that of the controls (3.85 vs 3.15 mmol L: -ascorbic acid 2-[3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-1-benzopyran-6-yl hydrogen phosphate] potassium salt (EPC-K1)/g protein). The pPBN rsa and pM4PO rsa were correlated, both in the ESRD patients and in the controls (r = 0.47 and r = 0.53). Ox-LDL was correlated with hemodialysis (HD) duration (r = 0.49) and was negatively correlated with pPBN rsa (r = -0.54), which indicates that oxidative stress was increased as HD therapy was prolonged and suppressed pPBN rsa.

CONCLUSIONS

There was an imbalance between .OH-producing ability and .OH-scavenging activity, in the ESRD patients, and this may be responsible for compromising the health of ESRD patients.

Scavenging of reactive oxygen species and prevention of oxidative neuronal cell damage by a novel gallotannin, pistafolia A

Pistafolia A is a novel gallotannin isolated from the leaf extract of Pistacia weinmannifolia. In the present investigation, the ability of Pistafolia A to scavenge reactive oxygen species including hydroxyl radicals and superoxide anion was measured by ESR spin trapping technique. The inhibition effect on iron-induced lipid peroxidaiton in liposomes was studied. The protective effects of Pistafolia A against oxidative neuronal cell damage and apoptosis induced by peroxynitrite were also assessed. The results showed that Pistafolia A could scavenge both hydroxyl radicals and superoxide anion dose-dependently and inhibit lipid peroxidation effectively. In cerebellar granule cells pretreated with Pistafolia A, peroxynitrite-induced oxidative neuronal damage and apoptosis were prevented markedly. The antioxidant capacity of Pistafolia A was much more potent then that of the water-soluble analog of vitamin E, Trolox. The results suggested that Pistafolia A might be used as an effective natural antioxidant for the prevention and cure of neuronal diseases associated with the production of peroxynitrite and related reactive oxygen species.

Combination of a free radical scavenger and heparin reduces cerebral hemorrhage after heparin treatment in a rabbit middle cerebral artery occlusion model

BACKGROUND AND PURPOSE

We sought to investigate the effects of EPC-K1, a free radical scavenger, on reducing heparin-produced cerebral hemorrhage in a rabbit model of middle cerebral artery (MCA) photothrombosis and to investigate whether the combination of EPC-K1 and heparin enhances neuroprotection from cerebral ischemic damage.

METHODS

In the heparin-alone group (n=8), heparin was administered intravenously for 24 hours, starting from 3 hours after MCA occlusion. In the EPC-K1-alone group (n=8), EPC-K1 was administered as a bolus injection (10 mg/kg) twice at 3 and 6 hours after MCA occlusion. In the combination group (n=8), EPC-K1 and heparin both were administered as in the single-drug procedures. In the vehicle group (n=10), saline were infused for 24 hours.

RESULTS

Heparin prolonged activated partial thromboplastin time by approximately 3 times that of control animals. In the heparin-treated animals, the hemorrhage size was significantly increased (P<0.0001) and neurological symptoms were significantly worse (P<0.01) than in control animals at 48 hours. The combination of EPC-K1 and heparin dramatically reduced heparin-produced cerebral hemorrhage (P<0.0001), with a significant reduction in infarct volume (reduction by 63.2% and 57.2% of heparin-alone and control animals, respectively, P<0.0001) and a significant improvement in neurological symptoms (P<0.01 versus heparin-alone and control animals, respectively).

CONCLUSIONS

These data indicate that free radical formation may play a key role in intracerebral hemorrhage exacerbated by heparin treatment and that the combination of a free radical scavenger and heparin augmented neuroprotection from acute brain ischemia. The results of the present study may suggest a potential clinical approach for the treatment of acute stroke.

Nitric oxide induces oxidative stress and apoptosis in neuronal cells

Within the central nervous system and under normal conditions, nitric oxide (NO) is an important physiological signaling molecule. When produced in large excess, NO also displays neurotoxicity. In our previous report, we have demonstrated that the exposure of neuronal cells to NO donors induced apoptotic cell death, while pretreatment with free radical scavengers L-ascorbic acid 2-[3, 4-dihydro-2,5,7,8-tetramethyl-2-(4,8, 12-trimethyltridecyl)-2H-1-benzopyran-6-yl-hydrogen phosphate] potassium salt (EPC-K1) or superoxide dismutase attenuated apoptosis effectively, suggesting that reactive oxygen species (ROS) may be involved in the cascade of events leading to apoptosis. In the present investigation, we directly studied the kinetic generation of ROS in NO-treated neuronal cells by flow cytometry using 2', 7'-dichloro-fluorescein diacetate and dihydrorhodamine 123 as redox-sensitive fluorescence probes. The results indicated that exposure of cerebellar granule cells to the NO donor S-nitroso-N-acetylpenicillamine (SNAP) induced oxidative stress, which was characterized by the accumulation of cytosolic and mitochondrial ROS, the increase in the extracellular hydrogen peroxide level, and the formation of lipid peroxidation products. SNAP treatment also induced apoptotic cell death as confirmed by the formation of cytosolic mono- and oligonucleosomes. Pretreating cells with the novel antioxidant EPC-K1 effectively prevented oxidative stress induced by SNAP, and attenuated cells from apoptosis.