The multiple functions of coenzyme Q

Oxidative Stress and Natural Antioxidants: Back and Forth in the Neurological Mechanisms of Alzheimer's Disease

Alzheimer's disease (AD) is characterized by the progressive degeneration of neuronal cells. With the increase in aged population, there is a prevalence of irreversible neurodegenerative changes, causing a significant mental, social, and economic burden globally. The factors contributing to AD are multidimensional, highly complex, and not completely understood. However, it is widely known that aging, neuroinflammation, and excessive production of reactive oxygen species (ROS), along with other free radicals, substantially contribute to oxidative stress and cell death, which are inextricably linked. While oxidative stress is undeniably important in AD, limiting free radicals and ROS levels is an intriguing and potential strategy for deferring the process of neurodegeneration and alleviating associated symptoms. Therapeutic compounds from natural sources have recently become increasingly accepted and have been effectively studied for AD treatment. These phytocompounds are widely available and a multitude of holistic therapeutic efficiencies for treating AD owing to their antioxidant, anti-inflammatory, and biological activities. Some of these compounds also function by stimulating cholinergic neurotransmission, facilitating the suppression of beta-site amyloid precursor protein-cleaving enzyme 1, α-synuclein, and monoamine oxidase proteins, and deterring the occurrence of AD. Additionally, various phenolic, flavonoid, and terpenoid phytocompounds have been extensively described as potential palliative agents for AD progression. Preclinical studies have shown their involvement in modulating the cellular redox balance and minimizing ROS formation, displaying them as antioxidant agents with neuroprotective abilities. This review emphasizes the mechanistic role of natural products in the treatment of AD and discusses the various pathological hypotheses proposed for AD.

Protection of coenzyme Q10 against contrast-induced acute kidney injury in male diabetic rats

BACKGROUND

Diabetes mellitus (DM) is a major risk factor for contrast-induced acute kidney injury (CI-AKI). DM and CI-AKI result in oxidative damage and inflammation that can be reduced when treated with the coenzyme Q-10 (CoQ10). The aim of this study was to investigate the therapeutic potential of CoQ10 in renal function, renal hemodynamics, oxidative profile and renal histology in diabetic rats subjected to CI-AKI.

METHODS

Wistar rats, male, randomized into five groups: citrate: control animals received citrate buffer (streptozotocin vehicle, 0.4 mL); Tween: control animals of CoQ10 treatment received 1% Tween 80 (CoQ10 vehicle, 0.5 mL); DM: animals that received streptozotocin (60 mg/kg); DM + IC: DM animals treated with iodinated contrast (IC, 6 mL/kg); DM + IC + CoQ10: DM animals treated with CoQ10 (10 mg/kg) and that received IC (6 mL/kg). The protocols lasted 4 weeks. An evaluation was made to measure renal function, inulin clearance and serum creatinine, renal hemodynamics by renal blood flow (RBF) and renal vascular resistance (RVR), markers of oxidative stress such as urinary peroxides and nitrate, lipid peroxidation, thiols in renal tissue and renal histological analysis.

RESULTS

DM animals showed reduced renal function, which was followed by an increase inserum creatinine and significant reduction of inulin clearance and RBF. It was noticed an increase in RVR and redox imbalance with higher urinary peroxides and nitrate lipid peroxidation levels with depletion of thiols in renal tissue. IC treatment exacerbated these changes in DM + IC. CoQ10 administration ameliorated renal function, prevented hemodynamic changes and neutralized oxidative damage and progression of the histologic damage in the DM + IC + CoQ10 group.

CONCLUSION

This study demonstrated the renoprotection properties of CoQ10 in an experimental model of risk factor of DM for CI-AKI. CoQ10 presented an antioxidant effect on the CI-AKI in male diabetic rats by improving renal function and renal hemodynamics, preserving morphology and reducing oxidative stress.

Targeted Antioxidants in Exercise-Induced Mitochondrial Oxidative Stress: Emphasis on DNA Damage

Exercise simultaneously incites beneficial (e.g., signal) and harming (e.g., damage to macromolecules) effects, likely through the generation of reactive oxygen and nitrogen species (RONS) and downstream changes to redox homeostasis. Given the link between nuclear DNA damage and human longevity/pathology, research attempting to modulate DNA damage and restore redox homeostasis through non-selective pleiotropic antioxidants has yielded mixed results. Furthermore, until recently the role of oxidative modifications to mitochondrial DNA (mtDNA) in the context of exercising humans has largely been ignored. The development of antioxidant compounds which specifically target the mitochondria has unveiled a number of exciting avenues of exploration which allow for more precise discernment of the pathways involved with the generation of RONS and mitochondrial oxidative stress. Thus, the primary function of this review, and indeed its novel feature, is to highlight the potential roles of mitochondria-targeted antioxidants on perturbations to mitochondrial oxidative stress and the implications for exercise, with special focus on mtDNA damage. A brief synopsis of the current literature addressing the sources of mitochondrial superoxide and hydrogen peroxide, and available mitochondria-targeted antioxidants is also discussed.

Neuroprotective Effect of Antioxidants in the Brain

The brain is vulnerable to excessive oxidative insults because of its abundant lipid content, high energy requirements, and weak antioxidant capacity. Reactive oxygen species (ROS) increase susceptibility to neuronal damage and functional deficits, via oxidative changes in the brain in neurodegenerative diseases. Overabundance and abnormal levels of ROS and/or overload of metals are regulated by cellular defense mechanisms, intracellular signaling, and physiological functions of antioxidants in the brain. Single and/or complex antioxidant compounds targeting oxidative stress, redox metals, and neuronal cell death have been evaluated in multiple preclinical and clinical trials as a complementary therapeutic strategy for combating oxidative stress associated with neurodegenerative diseases. Herein, we present a general analysis and overview of various antioxidants and suggest potential courses of antioxidant treatments for the neuroprotection of the brain from oxidative injury. This review focuses on enzymatic and non-enzymatic antioxidant mechanisms in the brain and examines the relative advantages and methodological concerns when assessing antioxidant compounds for the treatment of neurodegenerative disorders.

An optimized pyrimidinol multifunctional radical quencher

A series of aza analogues (4-9) of the experimental neuroprotective drug idebenone (1) have been prepared and evaluated for their ability to attenuate oxidative stress induced by glutathione depletion and to compensate for the decrease in oxidative phosphorylation efficiency in cultured Friedreich's ataxia (FRDA) fibroblasts and lymphocytes and also coenzyme Q10-deficient lymphocytes. Modification of the redox core of the previously reported 3 improved its antioxidant and cytoprotective properties. Compounds 4-9, having the same redox core, exhibited a range of antioxidant activities, reflecting side chain differences. Compounds having side chains extending 14-16 atoms from the pyrimidinol ring (6, 7, and 9) were potent antioxidants. They were superior to idebenone and more active than 3, 4, 5, and 8. Optimized analogue 7 and its acetate (7a) are of interest in defining potential therapeutic agents capable of blocking oxidative stress, maintaining mitochondrial membrane integrity, and augmenting ATP levels. Compounds with such properties may find utility in treating mitochondrial and neurodegenerative diseases such as FRDA and Alzheimer's disease.

Brain regional heterogeneity and toxicological mechanisms of organophosphates and carbamates

The brain is a well-organized, yet highly complex, organ in the mammalian system. Most investigators use the whole brain, instead of a selected brain region(s), for biochemical analytes as toxicological endpoints. As a result, the obtained data is often of limited value, since their significance is compromised due to a reduced effect, and the investigators often arrive at an erroneous conclusion(s). By now, a plethora of knowledge reveals the brain regional variability for various biochemical/neurochemical determinants. This review describes the importance of brain regional heterogeneity in relation to cholinergic and noncholinergic determinants with particular reference to organophosphate (OP) and carbamate pesticides and OP nerve agents.

Pulse Q-band EPR and ENDOR spectroscopies of the photochemically generated monoprotonated benzosemiquinone radical in frozen alcoholic solution

Quinones are essential cofactors in many physiological processes, among them proton-coupled electron transfer (PCET) in photosynthesis and respiration. A key intermediate in PCET is the monoprotonated semiquinone radical. In this work we produced the monoprotonated benzosemiquinone (BQH(•)) by UV illumination of BQ dissolved in 2-propanol at cryogenic temperatures and investigated the electronic and geometric structures of BQH(•) in the solid state (80 K) using EPR and ENDOR techniques at 34 GHz. The g-tensor of BQH(•) was found to be similar to that of the anionic semiquinone species (BQ(•-)) in frozen solution. The peaks present in the ENDOR spectrum of BQH(•) were identified and assigned by (1)H/(2)H substitutions. The experiments reconfirmed that the hydroxyl proton (O-H) on BQH(•), which is abstracted from a solvent molecule, mainly originates from the central CH group of 2-propanol. They also showed that the protonation has a strong impact on the electron spin distribution over the quinone. This is reflected in the hyperfine couplings (hfc's) of the ring protons, which dramatically changed with respect to those typically observed for BQ(•-). The hfc tensor of the O-H proton was determined by a detailed orientation-selection ENDOR study and found to be rhombic, resembling those of protons covalently bound to carbon atoms in a π-system (i.e., α-protons). It was found that the O-H bond lies in the quinone plane and is oriented along the direction of the quinone oxygen lone pair orbital. DFT calculations were performed on different structures of BQH(•) coordinated by four, three, or zero 2-propanol molecules. The O-H bond length was found to be around 1.0 Å, typical for a single covalent O-H bond. Good agreement between experimental and DFT results were found. This study provides a detailed picture of the electronic and geometric structures of BQH(•) and should be applicable to other naturally occurring quinones.

The Redox System in C. elegans, a Phylogenetic Approach

Oxidative stress is a toxic state caused by an imbalance between the production and elimination of reactive oxygen species (ROS). ROS cause oxidative damage to cellular components such as proteins, lipids, and nucleic acids. While the role of ROS in cellular damage is frequently all that is noted, ROS are also important in redox signalling. The "Redox Hypothesis" has been proposed to emphasize a dual role of ROS. This hypothesis suggests that the primary effect of changes to the redox state is modified cellular signalling rather than simply oxidative damage. In extreme cases, alteration of redox signalling can contribute to the toxicity of ROS, as well as to ageing and age-related diseases. The nematode species Caenorhabditis elegans provides an excellent model for the study of oxidative stress and redox signalling in animals. We use protein sequences from central redox systems in Homo sapiens, Drosophila melanogaster, and Saccharomyces cerevisiae to query Genbank for homologous proteins in C. elegans. We then use maximum likelihood phylogenetic analysis to compare protein families between C. elegans and the other organisms to facilitate future research into the genetics of redox biology.

Oxidative stress and epilepsy: literature review

Backgrounds. The production of free radicals has a role in the regulation of biological function, cellular damage, and the pathogenesis of central nervous system conditions. Epilepsy is a highly prevalent serious brain disorder, and oxidative stress is regarded as a possible mechanism involved in epileptogenesis. Experimental studies suggest that oxidative stress is a contributing factor to the onset and evolution of epilepsy. Objective. A review was conducted to investigate the link between oxidative stress and seizures, and oxidative stress and age as risk factors for epilepsy. The role of oxidative stress in seizure induction and propagation is also discussed. Results/Conclusions. Oxidative stress and mitochondrial dysfunction are involved in neuronal death and seizures. There is evidence that suggests that antioxidant therapy may reduce lesions induced by oxidative free radicals in some animal seizure models. Studies have demonstrated that mitochondrial dysfunction is associated with chronic oxidative stress and may have an essential role in the epileptogenesis process; however, few studies have shown an established link between oxidative stress, seizures, and age.

The measured and calculated affinity of methyl- and methoxy-substituted benzoquinones for the Q(A) site of bacterial reaction centers

Quinones play important roles in mitochondrial and photosynthetic energy conversion acting as intramembrane, mobile electron, and proton carriers between catalytic sites in various electron transfer proteins. They display different affinity, selectivity, functionality, and exchange dynamics in different binding sites. The computational analysis of quinone binding sheds light on the requirements for quinone affinity and specificity. The affinities of 10 oxidized, neutral benzoquinones were measured for the high affinity Q(A) site in the detergent-solubilized Rhodobacter sphaeroides bacterial photosynthetic reaction center. Multiconformation Continuum Electrostatics was then used to calculate their relative binding free energies by grand canonical Monte Carlo sampling with a rigid protein backbone, flexible ligand, and side chain positions and protonation states. Van der Waals and torsion energies, Poisson-Boltzmann continuum electrostatics, and accessible surface area-dependent ligand-solvent interactions are considered. An initial, single cycle of GROMACS backbone optimization improves the match with experiment as do coupled-ligand and side-chain motions. The calculations match experiment with an root mean square deviation (RMSD) of 2.29 and a slope of 1.28. The affinities are dominated by favorable protein-ligand van der Waals rather than electrostatic interactions. Each quinone appears in a closely clustered set of positions. Methyl and methoxy groups move into the same positions as found for the native quinone. Difficulties putting methyls into methoxy sites are observed. Calculations using a solvent-accessible surface area-dependent implicit van der Waals interaction smoothed out small clashes, providing a better match to experiment with a RMSD of 0.77 and a slope of 0.97.

arNOX: generator of reactive oxygen species in the skin and sera of aging individuals subject to external modulation

An aging-related cell-surface oxidase (aging-related NADH oxidase, arNOX) generating superoxide and other reactive oxygen species is shed from the cell surface and is found in saliva, urine, perspiration, and interstitial fluids that surround the collagen and elastin matrix underlying dermis. arNOX activity correlates with age and reaches a maximum at about age 65 in males and 55 in females. arNOX activities are highly correlated with values of human skin where a causal relationship is indicated. Ongoing efforts focus on cloning arNOX proteins and development of antiaging formulas based on arNOX inhibition (intervention).

Coenzyme Q10 and its effects in the treatment of neurodegenerative diseases

According to clinical and pre-clinical studies, oxidative stress and its consequences may be the cause or, at least, a contributing factor, to a large number of neurodegenerative diseases. These diseases include common and debilitating disorders, characterized by progressive and irreversible loss of neurons in specific regions of the brain. The most common neurodegenerative diseases are Parkinson's disease, Huntington's disease, Alzheimer's disease and amyotrophic lateral sclerosis. Coenzyme Q10 (CoQ10) has been extensively studied since its discovery in 1957. It is a component of the electron transportation chain and participates in aerobic cellular respiration, generating energy in the form of adenosine triphosphate (ATP). The property of CoQ10 to act as an antioxidant or a pro-oxidant, suggests that it also plays an important role in the modulation of redox cellular status under physiological and pathological conditions, also performing a role in the ageing process. In several animal models of neurodegenerative diseases, CoQ10 has shown beneficial effects in reducing disease progression. However, further studies are needed to assess the outcome and effectiveness of CoQ10 before exposing patients to unnecessary health risks at significant costs.

Biological consequences of statins in Candida species and possible implications for human health

The statins, simvastatin and atorvastatin are the most widely prescribed drugs. Statins lower cholesterol levels through their action on HMG-CoA (3-hydroxy-3-methylglutaryl-CoA) reductase, an essential enzyme for the biosynthesis of cholesterol. Fungal HMG-CoA reductases are also inhibited by statins, resulting in reduced levels of ergosterol (the fungal equivalent of cholesterol) and concomitant growth inhibition. This effect occurs in a range of fungal species and possibly affects fungal colonization of people on statin therapy. Furthermore, it may suggest that statins could have a role in new antifungal therapies. Possibly associated with the reduction in ergosterol levels, statins also inhibit respiratory growth. In the yeast, Candida glabrata, passage with statins dramatically increased the frequencies of petite mutants that were devoid of mitochondrial DNA, suggesting that statins caused a defect in the maintenance of mitochondrial DNA. These observations in C. glabrata may provide further insights into side effects of statins in humans undergoing treatment for hypercholesterolaemia. In addition, C. glabrata may be highly useful for the preliminary screening of agents to reduce statin side effects.

Evaluation of the mutagenic and genotoxic potential of ubiquinol

Ubiquinol (the reduced form of coenzyme Q(10)) is the two-electron reduction product of ubiquinone (the oxidized form of coenzyme Q(10)), and has been shown to be an integral part of living cells, where it functions as an antioxidant in both mitochondria and lipid membranes. To provide information to enable a Generally Regarded as Safe (GRAS) evaluation for the use of ubiquinol in selected foods, a series of Organisation of Economic Cooperation and Development (OECD) and good laboratory practice (GLP) toxicological studies was conducted to evaluate the mutagenic and genotoxic potential of Kaneka QH brand of ubiquinol. Ubiquinol did not induce reverse mutations in Salmonella typhimurium strains TA100, TA1535, TA98, and TA1537 and Escherichia coli WP2uvrA at concentrations up to 5000 mu g/plate, in either the absence and presence of exogenous metabolic activation by rat liver S9. Likewise, ubiquinol did not induce chromosome aberrations in Chinese hamster lung fibroblast (CHL/IU) cells in short-term (6-h) tests with or without rat liver S9 at concentrations up to 5000 mu g/ml or in a continuous (24-h) treatment test at concentrations up to 1201 mu g/ml. Finally, no mortalities, no abnormal clinical signs, and no significant increase in chromosome damage were observed in an in vivo micronucleus test when administered orally at doses up to 2000 mg/kg/day. Thus, ubiquinol was evaluated as negative in the bacterial reverse mutation, chromosomal aberration, and rat bone marrow micronucleus tests under the conditions of these assays.

Subchronic Oral Toxicity of Ubiquinol in Rats and Dogs

Ubiquinol is the two-electron reduction product of ubiquinone (coenzyme Q10or CoQ10) and functions as an antioxidant in both mitochondria and lipid membranes. In humans and most mammals, including dogs, the predominant form of coenzyme Q is coenzyme Q10, whereas the primary form in rodents is coenzyme Q9(CoQ9). Therefore, the subchronic toxicity of ubiquinol was evaluated and compared in Sprague-Dawley rats and beagle dogs. In the initial rat study, males and females were given ubiquinol at doses of 0, 300, 600, or 1200 mg/kg or ubiquinone at 1200 mg/kg by gavage for 13 weeks. This was followed by the second study, where females were given with doses of 75, 150, 200, or 300 mg/kg/day in order to determine a no observed adverse effect level (NOAEL). In the dog study, the test material was administered to males and females at dose levels of 150, 300, and 600 mg/kg, and ubiquinone was included at 600 mg/kg. Clinical observations, mortality, body weights, food and water consumption, ophthalmoscopy, urinalysis, hematology, blood biochemistry, gross findings, organ weights, and histopathological findings were examined. In both species, determination of plasma and liver ubiquinol concentrations, measured as total coenzyme Q10, were performed. There were no deaths or test article–related effects in body weight, food consumption, ophthalmology, urinalysis, or hematology in rats. Histopathological examinations revealed test article–related effects on the liver, spleen, and mesenteric lymph node in female rats but not in male rats. In the liver, fine vacuolation of hepatocytes was observed in the ubiquinol groups at 200 mg/kg and above. These changes were judged to be of no toxicological significance because they were not considered to induce cytotoxic changes. Microgranuloma and focal necrosis with accumulation of macrophages were observed in the ubiquinol groups at 300 mg/kg and above. These findings were accompanied by slight increases in blood chemistry enzymes (aspartate aminotransferase [AST], alanine aminotransferase [ALT], and lactate dehydrogenase [LDH]), which was suggestive of either potential hepatotoxicity or a normal physiological response to ubiguinol loading. Microgranuloma, and focal necrosis were judged to be only adverse effects induced by test article based on their incidence and pathological characteristics. These changes observed in liver were thought due to uptake of the administered ubiquinol by the liver as an adaptive response to xenobiotics, and the microgranulomas and focal necrosis were considered the results of excessive uptake of ubiquinol, which exceeded the capacity for adaptive response. Based on these findings the NOAEL in rats was conservatively estimated to be 600 mg/kg/day for males and 200 mg/kg/day for females. In dogs, there were no deaths or ubiquinol-related toxicity findings during the administration period. No test article–related effects were observed in body weight, food consumption, ophthalmology, electrocardiogram, urinalysis, hematology, or blood chemistry. Histopathological examination revealed no effects attributable to administration of ubiquinol or ubiquinone in any organs examined. Based on these findings, a NOAEL for ubiquinol in male and female dogs was estimated to be more than 600 mg/kg/day under the conditions of this study.

Nitrite-driven anaerobic ATP synthesis in barley and rice root mitochondria

Mitochondria isolated from the roots of barley (Hordeum vulgare L.) and rice (Oryza sativa L.) seedlings were capable of oxidizing external NADH and NADPH anaerobically in the presence of nitrite. The reaction was linked to ATP synthesis and nitric oxide (NO) was a measurable product. The rates of NADH and NADPH oxidation were in the range of 12-16 nmol min(-1) mg(-1) protein for both species. The anaerobic ATP synthesis rate was 7-9 nmol min(-1) mg(-1) protein for barley and 15-17 nmol min(-1) mg(-1) protein for rice. The rates are of the same order of magnitude as glycolytic ATP production during anoxia and about 3-5% of the aerobic mitochondrial ATP synthesis rate. NADH/NADPH oxidation and ATP synthesis were sensitive to the mitochondrial inhibitors myxothiazol, oligomycin, diphenyleneiodonium and insensitive to rotenone and antimycin A. The uncoupler FCCP completely eliminated ATP production. Succinate was also capable of driving ATP synthesis. We conclude that plant mitochondria, under anaerobic conditions, have a capacity to use nitrite as an electron acceptor to oxidize cytosolic NADH/NADPH and generate ATP.

Healthy aging: regulation of the metabolome by cellular redox modulation and prooxidant signaling systems: the essential roles of superoxide anion and hydrogen peroxide

The production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) has long been proposed as leading to random deleterious modification of macromolecules with an associated progressive development of age associated systemic disease. ROS and RNS formation has been posited as a major contributor to the aging process. On the contrary, this review presents evidence that superoxide anion (and hydrogen peroxide) and nitric oxide (and peroxynitrite) constitute regulated prooxidant second messenger systems, with specific sub-cellular locales of production and are essential for normal metabolome and physiological function. The role of these second messengers in the regulation of the metabolome is discussed in terms of radical formation as an essential contributor to the physiologically normal regulation of sub-cellular bioenergy systems; proteolysis regulation; transcription activation; enzyme activation; mitochondrial DNA changes; redox regulation of metabolism and cell differentiation; the concept that orally administered small molecule antioxidant therapy is a chimera. The formation of superoxide anion/hydrogen peroxide and nitric oxide do not conditionally lead to random macromolecular damage; under normal physiological conditions their production is actually regulated consistent with their second messenger roles.

Coenzyme Q(10)--its role as a prooxidant in the formation of superoxide anion/hydrogen peroxide and the regulation of the metabolome

Coenzyme Q10 plays a central role in cellular bioenergy generation and its regulation. Closed membrane systems generate a proton motive force to create transient localized bio-capacitors; the captured energy is used for the synthesis of mitochondrial ATP but also for many other processes, such as metabolite translocations, nerve conduction and a host of other bioenergy requiring processes. Coenzyme Q10 plays a key role in many of these sub-cellular membrane energy generating systems. Integral to this phenomenon is the prooxidant role of coenzyme Q10 in generating the major superoxide anion/hydrogen peroxide second messenger system. This messenger system, largely but not exclusively, arises from coenzyme Q10 semiquinone function; it contributes to the regulation of sub-cellular redox potential levels; transcription/gene expression control; is essential for modulated protein turnover and activation; mediates hormone and growth factor extracellular signaling. The regulated prooxidant formation of the superoxide anion/H2O2 second messenger system is essential for the normal physiological function of the metabolome. The normally functioning metabolome is the expression of a finely tuned dynamic equilibrium comprised of thousands of anabolic and catabolic reactions and all cellular signaling systems must be finely regulated. There is still much to be learnt about the up/down regulation of the H2O2 messenger system. The concept that superoxide anion/H2O2 cause random macromolecular damage is rebutted. The administration of antioxidants to quench the inferred toxicity of these compounds as a therapy for age associated diseases is unsupported by extant mammalian clinical trials and should be subject to serious re-evaluation. The role of ascorbic acid as a beneficial hydrogen peroxide prodrug is discussed.

Study on safety and bioavailability of ubiquinol (Kaneka QH™) after single and 4-week multiple oral administration to healthy volunteers

The safety and bioavailability of ubiquinol (the reduced form of coenzyme Q(10)), a naturally occurring lipid-soluble nutrient, were evaluated for the first time in single-blind, placebo-controlled studies with healthy subjects after administration of a single oral dose of 150 or 300 mg and after oral administration of 90, 150, or 300 mg for 4 weeks. No clinically relevant changes in results of standard laboratory tests, physical examination, vital signs, or ECG induced by ubiquinol were observed in any dosage groups. The C(max) and AUC(0-48 h) derived from the mean plasma ubiquinol concentration-time curves increased non-linearly with dose from 1.88 to 3.19 micro g/ml and from 74.61 to 91.76 micro g h/ml, respectively, after single administration. Trough concentrations had nearly plateaued at levels of 2.61 micro g/ml for 90 mg, 3.66 micro g/ml for 150 mg, and 6.53 micro g/ml for 300 mg at day 14, and increased non-linearly with dose in the 4-week study. In conclusion, following single or multiple-doses of ubiquinol in healthy volunteers, significant absorption of ubiquinol from the gastrointestinal tract was observed, and no safety concerns were noted on standard laboratory tests for safety or on assessment of adverse events for doses of up to 300 mg for up to 2 weeks after treatment completion.

Nitrite in nitric oxide biology: cause or consequence? A systems-based review

All life requires nitrogen compounds. Nitrite is such a compound that is naturally occurring in nature and biology. Over the years, the pharmacological stance on nitrite has undergone a surprising metamorphosis, from a vilified substance that generates carcinogenic nitrosamines in the stomach to a life-saving drug that liberates a protective agent (nitric oxide or NO) during hypoxic events. Nitrite has been investigated as a vasodilator in mammals for over 125 years and is a known by-product of organic nitrate metabolism. There has been a recent rediscovery of some of the vasodilator actions of nitrite in physiology along with novel discoveries which render nitrite a fundamental molecule in biology. Until recently nitrite was thought to be an inert oxidative breakdown product of endogenous NO synthesis but the past few years have focused on the reduction of nitrite back to NO in the circulation as a possible mechanism for hypoxic vasodilatation. Nitrite has evolved into an endogenous signaling molecule and regulator of gene expression that may not only serve as a diagnostic marker but also find its role as a potential therapeutic agent of cardiovascular disease. These data therefore warrant a reevaluation on the fate and metabolism of nitrite in biological systems. This review serves to encompass the history and recent evolution of nitrite, the compartment-specific metabolism of nitrite and its role in plasma as a biomarker for disease, the role of nitrite as a potential regulator of NO homeostasis, and the future of nitrite-based research.

Endocrine disrupting contaminants--beyond the dogma

Descriptions of endocrine disruption have largely been associated with wildlife and driven by observations documenting estrogenic, androgenic, antiandrogenic, and antithyroid actions. These actions, in response to exposure to ecologically relevant concentrations of various environmental contaminants, have now been established in numerous vertebrate species. However, many potential mechanisms and endocrine actions have not been studied. For example, the DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane] metabolite, p,p -DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene] is known to disrupt prostaglandin synthesis in the uterus of birds, providing part of the explanation for DDT-induced egg shell thinning. Few studies have examined prostaglandin synthesis as a target for endocrine disruption, yet these hormones are active in reproduction, immune responses, and cardiovascular physiology. Future studies must broaden the basic science approach to endocrine disruption, thereby expanding the mechanisms and endocrine end points examined. This goal should be accomplished even if the primary influence and funding continue to emphasize a narrower approach based on regulatory needs. Without this broader approach, research into endocrine disruption will become dominated by a narrow dogma, focusing on a few end points and mechanisms.

Evaluation of the mutagenic potential of ubidecarenone using three short-term assays

Addition of ubidecarenone, coenzyme Q(10) (CoQ(10)), to foods has been proposed for its nutritive value. Ubidecarenone is present naturally in a number of foods, including meats (e.g., beef, chicken) and fish (e.g., herring, rainbow trout), and on average, people are estimated to consume 2-20 mg/day of this metabolically important substance. Currently, relatively little formal evidence regarding the safety of ubidecarenone has been identified in the toxicology literature, despite its consumption by humans for centuries without reported notable adverse effects. As such, a series of toxicological studies, including mouse bone marrow micronucleus, chromosomal aberration, and bacterial reverse mutation tests, were conducted to evaluate the in vivo and in vitro mutagenic potential of CoQ(10). The test article, ubidecarenone, was devoid of clastogenic activity when administered orally to mice at doses up to 2000 mg/kg/day. In addition, the test article did not induce chromosomal aberration in CHL/IU cells exposed to concentrations as great as 5.0 mg/ml, nor did it induce reverse mutations in Salmonella typhimurium and Escherichia coli at concentrations as great as 5000 microg/plate.

High-sensitive determination of coenzyme Q10 in iodinate–β-cyclodextrin medium by inclusion reaction and catalytic polarography

A novel polarographic method for the determination of coenzyme Q(10) in beta-cyclodextrin (beta-CD) and iodinate system is proposed. The stability of coenzyme Q(10) to light was improved by the formation of coenzyme Q(10)-beta-CD inclusion complex. In addition, the sensitivity for the determination of coenzyme Q(10) was enhanced by both the formation and the polarographic catalytic wave of the inclusion complex in the presence of iodinate. In 0.1 mol/L HAc-NaAc (pH 4.7)-5.0 x 10(-5) mol/L beta-CD-1.2 x 10(-3) mol/L potassium iodinate-ethanol/water (60:40, v/v) medium, coenzyme Q(10)-beta-CD inclusion complex yielded a sensitive association/parallel catalytic wave. The second-order derivative peak current of the catalytic wave was proportional to coenzyme Q(10) concentration in the range of 6.0 x 10(-8)-2.5 x 10(-7) mol/L, and the detection limit was 1.0 x 10(-8) mol/L. The proposed method has high analytical sensitivity and is allowed to determine coenzyme Q(10) under light.

Ubiquinone synthesis in mitochondrial and microsomal subcellular fractions of Pneumocystis spp.: differential sensitivities to atovaquone

The lung pathogen Pneumocystis spp. is the causative agent of a type of pneumonia that can be fatal in people with defective immune systems, such as AIDS patients. Atovaquone, an analog of ubiquinone (coenzyme Q [CoQ]), inhibits mitochondrial electron transport and is effective in clearing mild to moderate cases of the infection. Purified rat-derived intact Pneumocystis carinii cells synthesize de novo four CoQ homologs, CoQ7, CoQ8, CoQ9, and CoQ10, as demonstrated by the incorporation of radiolabeled precursors of both the benzoquinone ring and the polyprenyl chain. A central step in CoQ biosynthesis is the condensation of p-hydroxybenzoic acid (PHBA) with a long-chain polyprenyl diphosphate molecule. In the present study, CoQ biosynthesis was evaluated by the incorporation of PHBA into completed CoQ molecules using P. carinii cell-free preparations. CoQ synthesis in whole-cell homogenates was not affected by the respiratory inhibitors antimycin A and dicyclohexylcarbodiimide but was diminished by atovaquone. Thus, atovaquone has inhibitory activity on both electron transport and CoQ synthesis in this pathogen. Furthermore, both the mitochondrial and microsomal fractions were shown to synthesize de novo all four P. carinii CoQ homologs. Interestingly, atovaquone inhibited microsomal CoQ synthesis, whereas it had no effect on mitochondrial CoQ synthesis. This is the first pathogenic eukaryotic microorganism in which biosynthesis of CoQ molecules from the initial PHBA:polyprenyl transferase reaction has been unambiguously shown to occur in two distinct compartments of the same cell.

Potential role of ubiquinone (coenzyme Q10) in pediatric cardiomyopathy

Pediatric cardiomyopathy (PCM) represents a group of rare and heterogeneous disorders that often results in death. While there is a large body of literature on adult cardiomyopathy, all of the information is not necessarily relevant to children with PCM. About 40% of children who present with symptomatic cardiomyopathy are reported to receive a heart transplant or die within the first two years of life. In spite of some of the advances in the management of PCM, the data shows that the time to transplantation or death has not improved during the past 35 years. Coenzyme Q10 is a vitamin-like nutrient that has a fundamental role in mitochondrial function, especially as it relates to the production of energy (ATP) and also as an antioxidant. Based upon the biochemical rationale and a large body of data on patients with adult cardiomyopathy, heart failure, and mitochondrial diseases with heart involvement, a role for coenzyme Q10 therapy in PCM patients is indicated, and preliminary results are promising. Additional studies on the potential usefulness of coenzyme Q10 supplementation as an adjunct to conventional therapy in PCM, particularly in children with dilated cardiomyopathy, are therefore warranted.

Coenzyme Q2 induced p53-dependent apoptosis

Coenzyme Q functions as an electron carrier and reversibly changes to either an oxidized (CoQ), intermediate (CoQ.-), or reduced (CoQH2) form within a biomembrane. The CoQH2 form also acts as an antioxidant and prevents cell death, and thus has been successfully used as a supplement. On the other hand, the value of the CoQ/CoQH2 ratio has been shown to increase in a number of diseases, presumably due to an anti-proliferative effect involving CoQ. In the present study, we examined the effect of CoQ and its isoprenoid side chain length variants on the growth of cells having different p53 statuses. Treatment with CoQs having shorter isoprenoid chains, especially CoQ2, induced apoptosis in p53-point mutated BALL-1 cells, whereas treatment with longer isoprenoid chains did not. However, CoQ2 did not induce apoptosis in either a p53 wild-type cell line or a p53 null mutant cell line. These results indicated that the induction of apoptosis by CoQ2 was dependent on p53 protein levels. Moreover, CoQ2 induced reactive oxygen species (ROS) and the phosphorylation of p53. An antioxidant, l-ascorbic acid, inhibited CoQ2-induced p53 phosphorylation and further apoptotic stimuli. Overall, these results suggested that short tail CoQ induces ROS generation and further p53-dependent apoptosis.

Skeletal muscles, heart, and lung are the main sources of oxygen radicals in old rats

The aim of this study was to compare rat tissues with respect to their reactive oxygen and nitrogen species (RONS) generating activities as a function of age. We quantified the RONS generation in vivo in young (6 months) and in old (30 months) male Sprague-Dawley rats using the recently developed spin trap 1-hydroxy-3-carboxy-pyrrolidine, applied intravenously. This spin trap reacts with superoxide radical and peroxynitrite yielding a stable spin adduct which is detectable by means of electron paramagnetic resonance (EPR) spectroscopy in frozen tissues. In old rats RONS generation was significantly increased compared to their young counterparts in the following order: blood<skeletal muscle<lung<heart, but did not change in intestine, brain, liver, and kidney. Experiments with isolated heart mitochondria showed a significant rate of RONS generation in succinate-supplemented mitochondria from old rats while no RONS were detected in mitochondria from young rats. This study identifies heart, lung, and skeletal muscle as the tissues with increased RONS formation as a function of age.

28-Day repeated dose toxicity study of dried microorganism in rats

Ubidecarenone, also known as CoQ(10), is currently sold as a dietary supplement in the United States, with a majority of these products derived from the fermentation of carbohydrates or tobacco leaf extracts. In addition to its availability in dietary supplements, CoQ(10) is now being considered for use in foods. Accordingly, as part of the process for attaining "Generally Recognized as Safe" status, and to supplement information already available regarding the safety of CoQ(10) per se, a 28-day oral toxicity study in rats was conducted to evaluate the subacute safety of a microorganism biomass used as a new source in CoQ(10) production. Groups of Crj:CD(SD) rats (SPF) (6 males or females per group, 4 groups per sex) received dried microorganism at doses of 0, 500, 1000 or 2000 mg/kg/day via intragastric intubation. Clinical observations were recorded, and body weight, and food and water consumptions measured throughout the study. At the end of the study, aortic blood samples were collected from all animals for analysis of hematological and clinical chemistry parameters, and gross pathologic examination was performed. Histopathologic examination was performed on select tissues from the control and high-dose groups. There were no treatment-related changes that were considered to be of toxicological significance. Since rats treated with 2000 mg/kg of dried microorganism did not demonstrate any treatment-related changes, the no-observable-adverse-effect level (NOAEL) for dried microorganism was estimated to be greater than 2000 mg/kg/day under the present study conditions.

Antioxidant and prooxidant properties of mitochondrial Coenzyme Q

Coenzyme Q is both an essential electron carrier and an important antioxidant in the mitochondrial inner membrane. The reduced form, ubiquinol, decreases lipid peroxidation directly by acting as a chain breaking antioxidant and indirectly by recycling Vitamin E. The ubiquinone formed in preventing oxidative damage is reduced back to ubiquinol by the respiratory chain. As well as preventing lipid peroxidation, Coenzyme Q reacts with other reactive oxygen species, contributing to its effectiveness as an antioxidant. There is growing interest in using Coenzyme Q and related compounds therapeutically because mitochondrial oxidative damage contributes to degenerative diseases. Paradoxically, Coenzyme Q is also involved in superoxide production by the respiratory chain. To help understand how Coenzyme Q contributes to both mitochondrial oxidative damage and antioxidant defences, we have reviewed its antioxidant and prooxidant properties.

Endosymbiosis and the design of eukaryotic electron transport

The bioenergetic organelles of eukaryotic cells, mitochondria and chloroplasts, are derived from endosymbiotic bacteria. Their electron transport chains (ETCs) resemble those of free-living bacteria, but were tailored for energy transformation within the host cell. Parallel evolutionary processes in mitochondria and chloroplasts include reductive as well as expansive events: On one hand, bacterial complexes were lost in eukaryotes with a concomitant loss of metabolic flexibility. On the other hand, new subunits have been added to the remaining bacterial complexes, new complexes have been introduced, and elaborate folding patterns of the thylakoid and mitochondrial inner membranes have emerged. Some bacterial pathways were reinvented independently by eukaryotes, such as parallel routes for quinol oxidation or the use of various anaerobic electron acceptors. Multicellular organization and ontogenetic cycles in eukaryotes gave rise to further modifications of the bioenergetic organelles. Besides mitochondria and chloroplasts, eukaryotes have ETCs in other membranes, such as the plasma membrane (PM) redox system, or the cytochrome P450 (CYP) system. These systems have fewer complexes and simpler branching patterns than those in energy-transforming organelles, and they are often adapted to non-bioenergetic functions such as detoxification or cellular defense.

Fasting, lipid metabolism, and triiodothyronine in rat gastrocnemius muscle: interrelated roles of uncoupling protein 3, mitochondrial thioesterase, and coenzyme Q

We investigated the role of uncoupling protein 3 (UCP3) during fasting and examined the effect of triiodothyronine (T3) administration in such a condition. The possible involvement of mitochondrial thioesterase (MTE I) and the role of putative cofactors, such as coenzyme Q (CoQ), was also examined. Here, we report that fasting induced a more than twofold elevation in the expression and activity of MTE I, and an increase in UCP3 expression, without any associated uncoupling activity. Administration of T3 to fasting rats further up-regulated UCP3 as well as MTE I expression, markedly enhanced MTE I enzyme activity and prevented the impairment of the uncoupling activity of UCP3 normally seen during fasting. Indeed, T3-treatment induced an UCP3-dependent decrease in mitochondrial membrane potential, which was abolished by the addition of either GDP or superoxide dismutase (SOD). T3 administration also prevented the marked decrease of CoQ levels observed in fasting rats and this provides evidence that also, in vivo, CoQ represents an essential cofactor for the UCP3-mediated uncoupling. The data also show that MTE I and UCP3 are likely involved in the same biochemical mechanism and that UCP3 postulated functions, such as lipid handling and uncoupling, are not mutually exclusive but may coexist in vivo.

Phylloquinone, what can we learn from plants?

The plant plasma membrane contains redox proteins able to mediate a trans-membrane electron flow. This electron flow might be responsible for the generation of the active oxygen species observed as a reaction to pathogen attack or stress. Vitamin K1 could be identified as a possible lipid soluble electron carrier in plant plasma membrane preparations. Such a function would be analogous to coenzyme Q in animal plasma membranes. What we are going to outline in this contribution is a concept of how the electron transport system of the plant plasma membrane could interact with quinones, thus contributing to the metabolism of free radicals in plants.

Distribution of coenzyme Q homologues in brain

Ubiquinone (coenzyme Q10), in addition to its function as an electron and proton carrier in mitochondrial electron transport coupled to ATP synthesis, acts in its reduced form (ubiquinol) as an antioxidant, inhibiting lipid peroxidation in biological membranes and protecting mitochondrial inner-membrane proteins and DNA against oxidative damage accompanying lipid peroxidation. Tissue ubiquinone levels are subject to regulation by physiological factors that are related to the oxidative activity of the organism: they increase under the influence of oxidative stress, e.g. physical exercise, cold adaptation, thyroid hormone treatment, and decrease during aging. In the present study, coenzyme Q homologues were separated and quantified in the brains of mice, rats, rabbits, and chickens using high-performance liquid chromatography. In addition, the coenzyme Q homologues were measured in cells such as NG-108, PC-12, rat fetal brain cells and human SHSY-5Y and monocytes. In general, Q1 content was the lowest among the coenzyme homologues quantified in the brain. Q9 was not detectable in the brains of chickens and rabbits, but was present in the brains of rats and mice. Q9 was also not detected in human cell lines SHSY-5Y and monocytes. Q10 was detected in the brains of mice, rats, rabbits, and chickens and in cell lines. Since both coenzyme Q and vitamin E are antioxidants, and coenzyme Q recycles vitamins E and C, vitamin E was also quantified in mice brain using HPLC-electrochemical detector (ECD). The quantity of vitamin E was lowest in the substantia nigra compared with the other brain regions. This finding is crucial in elucidating ubiquinone function in bioenergetics; in preventing free radical generation, lipid peroxidation, and apoptosis in the brain; and as a potential compound in treating various neurodegenerative disorders.