Curcumin prevents mitochondrial dysfunction in the brain of the senescence-accelerated mouse-prone 8

The aging brain suffers mitochondrial dysfunction and a reduced availability of energy in the form of ATP, which in turn may cause or promote the decline in cognitive, sensory, and motor function observed with advancing age. There is a need for animal models that display some of the pathological features of human brain aging in order to study their prevention by e.g. dietary factors. We thus investigated the suitability of the fast-aging senescence-accelerated mouse-prone 8 (SAMP8) strain and its normally aging control senescence-accelerated mouse-resistant 1 (SAMR1) as a model for the age-dependent changes in mitochondrial function in the brain. To this end, 2-months old male SAMR1 (n = 10) and SAMP8 mice (n = 7) were fed a Western type diet (control groups) for 5 months and one group of SAMP8 mice (n = 6) was fed an identical diet fortified with 500 mg curcumin per kg. Dissociated brain cells and brain tissue homogenates were analyzed for malondialdehyde, heme oxygenase-1 mRNA, mitochondrial membrane potential (MMP), ATP concentrations, protein levels of mitochondrial marker proteins for mitochondrial membranes (TIMM, TOMM), the mitochondrial permeability transition pore (ANT1, VDAC1, TSPO), respiration complexes, and fission and fusion (Fis, Opa1, Mfn1, Drp1). Dissociated brain cells isolated from SAMP8 mice showed significantly reduced MMP and ATP levels, probably due to significantly diminished complex V protein expression, and increased expression of TSPO. Fission and fusion marker proteins indicate enhanced mitochondrial fission in brains of SAMP8 mice. Treatment of SAMP8 mice with curcumin improved MMP and ATP and restored mitochondrial fusion, probably by up-regulating nuclear factor PGC1α protein expression. In conclusion, SAMP8 compared to SAMR1 mice are a suitable model to study age-dependent changes in mitochondrial function and curcumin emerges as a promising nutraceutical for the prevention of neurodegenerative diseases that are accompanied or caused by mitochondrial dysfunction.     

Corrections by melatonin of liver mitochondrial disorders under diabetes and acute intoxication in rats

The aim of the present work was to investigate the mechanisms of oxidative damage of the liver mitochondria under diabetes and intoxication in rats as well as to evaluate the possibility of corrections of mitochondrial disorders by pharmacological doses of melatonin. The experimental (30 days) streptozotocin‐induced diabetes mellitus caused a significant damage of the respiratory activity in rat liver mitochondria. In the case of succinate as a respiratory substrate, the ADP‐stimulated respiration rate V₃ considerably decreased (by 25%, p < 0·05) as well as the acceptor control ratio (ACR) V₃/V₂ markedly diminished (by 25%, p < 0·01). We observed a decrease of the ADP‐stimulated respiration rate V₃ by 35% (p < 0·05), with glutamate as substrate. In this case, ACR also decreased (by 20%, p < 0·05). Surprisingly, the phosphorylation coefficient ADP/O did not change under diabetic liver damage. Acute rat carbon tetrachloride‐induced intoxication resulted in considerable decrease of the phosphorylation coefficient because of uncoupling of the oxidation and phosphorylation processes in the liver mitochondria. The melatonin administration during diabetes (10 mg·kg^‐1 body weight, 30 days, daily) showed a considerable protective effect on the liver mitochondrial function, reversing the decreased respiration rate V₃ and the diminished ACR to the control values both for succinate‐dependent respiration and for glutamate‐dependent respiration. The melatonin administration to intoxicated animals (10 mg·kg⁻¹ body weight, three times) partially increased the rate of succinate‐dependent respiration coupled with phosphorylation. The impairment of mitochondrial respiratory plays a key role in the development of liver injury under diabetes and intoxication. Melatonin might be considered as an effector that regulates the mitochondrial function under diabetes. Copyright © 2011 John Wiley & Sons, Ltd.     

Progesterone prevents mitochondrial dysfunction in the spinal cord of wobbler mice

In the Wobbler mouse, a mutation of the Vps54 protein increases oxidative stress in spinal motoneurons, associated to toxic levels of nitric oxide and hyperactivity of nitric oxide synthase (NOS). Progesterone neuroprotection has been reported for several CNS diseases, including the Wobbler mouse neurodegeneration. In the present study, we analyzed progesterone effects on mitochondrial-associated parameters of symptomatic Wobbler mice. The activities of mitochondrial respiratory chain complexes I, II-III and IV and protein levels of mitochondrial and cytosolic NOS were determined in cervical and lumbar cords from control, Wobbler and Wobbler mice receiving a progesterone implant for 18 days. We found a significant reduction of complex I and II-III activities in mitochondria and increased protein levels of mitochondrial, but not cytosolic nNOS, in the cervical cord of Wobbler mice. Progesterone treatment prevented the reduction of complex I in the cervical region and the increased level of mitochondrial nNOS. Wobbler motoneurons also showed accumulation of amyloid precursor protein immunoreactivity and decreased activity and immunostaining of MnSOD. Progesterone treatment avoided these abnormalities. Therefore, administration of progesterone to clinically afflicted Wobblers (i) prevented the abnormal increase of mitochondrial nNOS and normalized respiratory complex I; (ii) decreased amyloid precursor protein accumulation, a sign of axonal degeneration, and (iii) increased superoxide dismutation. Thus, progesterone neuroprotection decreases mitochondriopathy of Wobbler mouse cervical spinal cord.     

Attenuation of cardiac mitochondrial dysfunction by melatonin in septic mice

The existence of an inducible mitochondrial nitric oxide synthase has been recently related to the nitrosative/oxidative damage and mitochondrial dysfunction that occurs during endotoxemia. Melatonin inhibits both inducible nitric oxide synthase and inducible mitochondrial nitric oxide synthase activities, a finding related to the antiseptic properties of the indoleamine. Hence, we examined the changes in inducible nitric oxide synthase/inducible mitochondrial nitric oxide synthase expression and activity, bioenergetics and oxidative stress in heart mitochondria following cecal ligation and puncture-induced sepsis in wild-type (iNOS(+/+)) and inducible nitric oxide synthase-deficient (iNOS(-/-)) mice. We also evaluated whether melatonin reduces the expression of inducible nitric oxide synthase/inducible mitochondrial nitric oxide synthase, and whether this inhibition improves mitochondrial function in this experimental paradigm. The results show that cecal ligation and puncture induced an increase of inducible mitochondrial nitric oxide synthase in iNOS(+/+) mice that was accompanied by oxidative stress, respiratory chain impairment, and reduced ATP production, although the ATPase activity remained unchanged. Real-time PCR analysis showed that induction of inducible nitric oxide synthase during sepsis was related to the increase of inducible mitochondrial nitric oxide synthase activity, as both inducible nitric oxide synthase and inducible mitochondrial nitric oxide synthase were absent in iNOS(-/-) mice. The induction of inducible mitochondrial nitric oxide synthase was associated with mitochondrial dysfunction, because heart mitochondria from iNOS(-/-) mice were unaffected during sepsis. Melatonin treatment blunted sepsis-induced inducible nitric oxide synthase/inducible mitochondrial nitric oxide synthase isoforms, prevented the impairment of mitochondrial homeostasis under sepsis, and restored ATP production. These properties of melatonin should be considered in clinical sepsis.     

Comparison of the effects of melatonin and pentoxifylline on carbon tetrachloride-induced liver toxicity in mice

The purpose of the study was to determine whether along and in combination melatonin (MLT) and pentoxlfylline (PTX) exerted beneficial effects on histopathological changes and changes in oxidant and antioxidant systems in liver caused by CCl₄-induced liver toxicity in mice. Mice were randomly divided into six groups: control, olive oil, toxicity, MLT, PTX, PTX+MLT. MLT 10 mg/kg/day, PTX 50 mg/kg/day, and the same individual doses in MLT+PTX combination were given intraperitoneally to mice for 7 day. CCl₄ 0.8 mg/kg/day was administered on the 4th, 5th, and 6th days of therapy in all groups except the control and olive oil groups. In the toxicity group, increased concentrations of malondialdehyde (MDA) and lipid hydroperoxides (LOOH) and decreased glutathione peroxidase (GSH-Px) and catalase (CAT) activities were found compared to the control and olive oil groups (p < 0.05). Compared to the toxicity group, both the PTX group and the PTX+MLT group had decreased MDA and LOOH levels, whereas MLT reduced only LOOH levels (p < 0.01). MLT, PTX and MLT+PTX increased the GSH-Px and CAT activities compared to the toxicity group (p < 0.05). MLT increased CAT activity compared to PTX and MLT+PTX (p < 0.05). Superoxide dismutase enzyme activity did not change in any group (p < 0.05). Histopatholically, ballooning, degeneration, apoptosis, and bridging necrosis were seen in the toxicity group. MLT, PTX and MLT+PTX decreased the apoptosis and bridging necrosis (p < 0.01), and PTX and MLT+PTX decreased balloon degeneration compared to the toxicity group (p < 0.01). These results indicate that administration of PTX and MLT alone and in combination before onset of liver toxicity might prevent the oxidative damage by reducing oxidative stress and increasing antioxidant enzyme levels.     

Doxorubicin-induced thiol-dependent alteration of cardiac mitochondrial permeability transition and respiration

Doxorubicin (DOX) is a highly effective treatment for several forms of cancer. However, clinical experience shows that DOX induces a cumulative and dose-dependent cardiomyopathy that has been ascribed to redox-cycling of the drug on the mitochondrial respiratory chain generating free radicals and oxidative stress in the process. Mitochondrial dysfunction including induction of the mitochondrial permeability transition (MPT) and inhibition of mitochondrial respiration have been implicated as major determinants in the pathogenesis of DOX cardiotoxicity. The present work was aimed at investigating whether the inhibition of mitochondrial respiration occurs secondarily to MPT induction in heart mitochondria isolated from DOX-treated rats and whether one or both consequences of DOX treatment are related with oxidation of protein thiol residues. DOX-induced oxidative stress was associated with the accumulation of products of lipid peroxidation and the depletion of alpha-tocopherol in cardiac mitochondrial membranes. No changes in mitochondrial coenzyme Q9 and Q10 concentrations were detected in hearts of DOX-treated rats. Cardiac mitochondria from DOX-treated rats were more susceptible to diamide-dependent induction of the MPT. Although DOX treatment did not affect state 4 respiration, state 3 respiration was decreased in heart mitochondria isolated from DOX-treated rats, which was reversed in part by adding either cyclosporin A or dithiothreitol, but not Trolox. The results suggest that in DOX-treated rats, (i) induction of the MPT is at least in part responsible for decreased mitochondrial respiration, (ii) heart mitochondria are more susceptible to diamide induced-MPT, (iii) thiol-dependent alteration of mitochondrial respiration is partially reversible ex vivo with dithiothreitol. Collectively, these data are consistent with the thesis that thiol-dependent alteration of MPT and respiration is an important factor in DOX-induced mitochondrial dysfunction.     

Curcuminoids modulates oxidative damage and mitochondrial dysfunction in diabetic rat brain

Diabetes exacerbates neuronal injury induced by hyperglycemia mediated oxidative damage and mitochondrial dysfunction. The aim of the present study is to investigate the effects of curcuminoids, polyphenols of Curcuma longa (L.) on oxidative stress and mitochondrial impairment in the brain of streptozotocin (STZ)-induced diabetic rats. A marked increase in lipid peroxidation and nitrite levels with simultaneous decrease in endogenous antioxidant marker enzymes was observed in the diabetic rat brain, which was restored to normal levels on curcuminoids treatment. Down-regulation of mitochondrial complex I and IV activity caused by STZ induction was also up-regulated on oral administration of curcuminoids. Moreover, curcuminoids administration profoundly elevated the ATP level, which was earlier reduced in the diabetic brain. These results suggest that curcuminoids exhibit a protective effect by accelerating antioxidant defense mechanisms and attenuating mitochondrial dysfunction in the brain of diabetic rats. Curcuminoids thus may be used as a promising therapeutic agent in preventing and/or delaying the progression of diabetic complications in the brain.     

Mitochondrial dysfunction in platelets and hippocampi of senescence-accelerated mice

Senescence-accelerated mice (SAM) strains are useful models to understand the mechanisms of age-dependent degeneration. In this study, measurements of the mitochondrial membrane potential (Δψ_m) of platelets and the Adenosine 5^′-triphosphate (ATP) content of hippocampi and platelets were made, and platelet mitochondria were observed in SAMP8 (faster aging mice) and SAMR1 (aging resistant control mice) at 2, 6 and 9 months of age. In addition, an Aβ-induced (Amyloid beta-protein) damage model of platelets was established. After the addition of Aβ, the Δψ_m of platelets of SAMP8 at 1and 6 months of age were measured. We found that platelet Δψ_m, and hippocampal and platelet ATP content of SAMP8 mice decreased at a relatively early age compared with SAMR1. The platelets of 6 month-old SAMP8 showed a tolerance to Aβ-induced damages. These results suggest that mitochondrial dysfunction might be one of the mechanisms leading to age-associated degeneration in SAMP mice at an early age and the platelets could serve as a biomarker for detection of mitochondrial function and age related disease.     

Protective role of PARK2/Parkin in sepsis-induced cardiac contractile and mitochondrial dysfunction

Mitochondrial quality control plays a vital role in the maintenance of optimal mitochondrial function. However, its roles and regulation remain ill-defined in cardiac pathophysiology. Here, we tested the hypothesis that PARK2/Parkin, an E3-ligase recently described as being involved in the regulation of cardiac mitophagy, is important for (1) the maintenance of normal cardiac mitochondrial function; and (2) adequate recovery from sepsis, a condition known to induce reversible mitochondrial injury through poorly understood mechanisms. Investigations of mitochondrial and cardiac function were thus performed in wild-type and Park2-deficient mice at baseline and at 2 different times following administration of a sublethal dose of E. coli lipopolysaccharide (LPS). LPS injection induced cardiac and mitochondrial dysfunctions that were followed by complete recovery in wild-type mice. Recovery was associated with morphological and biochemical evidence of mitophagy, suggesting that this process is implicated in cardiac recovery from sepsis. Under baseline conditions, multiple cardiac mitochondrial dysfunctions were observed in Park2-deficient mice. These mild dysfunctions did not result in a visibly distinct cardiac phenotype. Importantly, Park2-deficient mice exhibited impaired recovery of cardiac contractility and constant degradation of mitochondrial metabolic functions. Interestingly, autophagic clearance of damaged mitochondria was still possible in the absence of PARK2 likely through compensatory mechanisms implicating PARK2-independent mitophagy and upregulation of macroautophagy. Together, these results thus provide evidence that in vivo, mitochondrial autophagy is activated during sepsis, and that compensation for a lack of PARK2 is only partial and/or that PARK2 exerts additional protective roles in mitochondria.     

Melatonin prevents glutamate-induced oxytosis in the HT22 mouse hippocampal cell line through an antioxidant effect specifically targeting mitochondria

The pineal hormone melatonin has neuroprotective effects in a large number of models of neurodegeneration. Melatonin crosses the blood-brain barrier, shows a decrease in its nocturnal peaks in blood with age that has been associated with the development of neurodegenerative disorders, and has been shown to be harmless at high concentrations. These properties make melatonin a potential therapeutic agent against neurodegenerative disorders but the pathways involved in such neuroprotective effects remain unknown. In the present report we study the intracellular pathways implicated in the complete neuroprotection provided by melatonin against glutamate-induced oxytosis in the HT22 mouse hippocampal cell line. Our results strongly suggest that melatonin prevents oxytosis through a direct antioxidant effect specifically targeted at the mitochondria. Firstly, none of the described transducers of melatonin signalling seems to be implicated in the neuroprotection provided by this indole. Secondly, melatonin does not prevent cytosolic GSH depletion-dependent increase in reactive oxygen species (ROS), but it totally prevents mitochondrial ROS production despite the fact that the latter is much higher than the former. And finally, there is a high correlation between the concentration at which melatonin and closely related indoles exert a direct antioxidant effect in vitro and a neuroprotective effect against glutamate-induced oxytosis.     

Hemin prevents cardiac and diaphragm mitochondrial dysfunction in sepsis

Free radical-mediated mitochondrial dysfunction may play a role in the genesis of sepsis-induced multiorgan failure. Several cellular defenses protect against free radicals, including heme oxygenase. No previous study has determined if measures that increase heme oxygenase levels reduce mitochondrial dysfunction following endotoxin. The purpose of the present study was to determine if mitochondrial dysfunction following endotoxin (LPS) administration can be attenuated by administration of hemin, a pharmacological inducer of heme oxygenase. Blood pressure, heart rate, cardiac and diaphragm mitochondrial function, plasma nitrite/nitrate levels, and tissue markers of free radical generation were compared among rats given saline, LPS, hemin, or a combination of hemin and LPS. Endotoxin (LPS) administration produced large reductions in mitochondrial function (e.g., ATP production rate decreased in both tissues, P < 0.001). Administration of hemin increased tissue heme oxygenase levels, ablated LPS-induced alterations in mitochondrial function, attenuated LPS-induced increases in plasma nitrite/nitrate levels, and prevented LPS-mediated increases in tissue markers of free radical generation. These data indicate that tissue heme oxygenase levels modulate the degree of LPS-induced mitochondrial dysfunction. Measures that increase heme oxygenase levels may provide a means of reducing sepsis-induced mitochondrial dysfunction and tissue injury.     

Lactosylceramide contributes to mitochondrial dysfunction in diabetes

Sphingolipids have been implicated as key mediators of cell-stress responses and effectors of mitochondrial function. To investigate potential mechanisms underlying mitochondrial dysfunction, an important contributor to diabetic cardiomyopathy, we examined alterations of cardiac sphingolipid metabolism in a mouse with streptozotocin-induced type 1 diabetes. Diabetes increased expression of desaturase 1, (dihydro)ceramide synthase (CerS)2, serine palmitoyl transferase 1, and the rate of ceramide formation by mitochondria-resident CerSs, indicating an activation of ceramide biosynthesis. However, the lack of an increase in mitochondrial ceramide suggests concomitant upregulation of ceramide-metabolizing pathways. Elevated levels of lactosylceramide, one of the initial products in the formation of glycosphingolipids were accompanied with decreased respiration and calcium retention capacity (CRC) in mitochondria from diabetic heart tissue. In baseline mitochondria, lactosylceramide potently suppressed state 3 respiration and decreased CRC, suggesting lactosylceramide as the primary sphingolipid responsible for mitochondrial defects in diabetic hearts. Moreover, knocking down the neutral ceramidase (NCDase) resulted in an increase in lactosylceramide level, suggesting a crosstalk between glucosylceramide synthase- and NCDase-mediated ceramide utilization pathways. These data suggest the glycosphingolipid pathway of ceramide metabolism as a promising target to correct mitochondrial abnormalities associated with type 1 diabetes.     

The daily rhythms of mitochondrial gene expression and oxidative stress regulation are altered by aging in the mouse liver

The circadian clock regulates many cellular processes, notably including the cell cycle, metabolism and aging. Mitochondria play essential roles in metabolism and are the major sites of reactive oxygen species (ROS) production in the cell. The clock regulates mitochondrial functions by driving daily changes in NAD⁺ levels and Sirt3 activity. In addition to this central route, in the present study, we find that the expression of some mitochondrial genes is also rhythmic in the liver, and that there rhythms are disrupted by the Clock^Δ19 mutation in young mice, suggesting that they are regulated by the core circadian oscillator. Related to this observation, we also find that the regulation of oxidative stress is rhythmic in the liver. Since mitochondria and ROS play important roles in aging, and mitochondrial functions are also disturbed by aging, these related observations prompt the compelling hypothesis that circadian oscillators influence aging by regulating ROS in mitochondria. During aging, the expression rhythms of some mitochondrial genes were altered in the liver and the temporal regulation over the dynamics of mitochondrial oxidative stress was disrupted. However, the expression of clock genes was not affected. Our results suggested that mitochondrial functions are combinatorially regulated by the clock and other age-dependent mechanism(s), and that aging disrupts mitochondrial rhythms through mechanisms downstream of the clock.     

The effects of melatonin on neurohormonal regulation in cardiac cachexia: A mechanistic review

Heart failure (HF) is one of the prominent health concerns and its morbidity is comparable to many malignancies. Cardiac cachexia (CC), characterized by significant weight loss and muscle wasting, frequently occurs in progressive stage of HF. The pathophysiology of CC is multifactorial including nutritional and gastrointestinal alterations, immunological and neurohormonal activation, and anabolic/catabolic imbalance. Neurohormones are critically involved in the development of both HF and CC. Melatonin is known as an anti-inflammatory and antioxidant hormone. It seems that melatonin possibly regulates the neurohormonal signaling pathway related to muscle wasting in CC, but limited comprehensive data is available on the mechanistic aspects of its activity. In this, we reviewed the reports regarding the role of neurohormones in CC occurrence and possible activity of melatonin in modulation of HF and subsequently CC via neurohormonal regulation. In addition, we have discussed proposed mechanisms of action for melatonin considering its possible interactions with neurohormones. In conclusion, melatonin likely regulates the signaling pathways related to muscle wasting in CC by reducing tumor necrosis factor α levels and activating the gene expression of insulin-like growth factor-1. Also, this hormone inhibits the proteolytic pathway by inhibiting nuclear factor-κB (NF-κB), renin-angiotensin system and forkhead box protein O1 pathways and could increase protein synthesis by activating Akt and mammalian target of rapamycin. To elucidate the positive role of melatonin in CC and exact mechanisms related to muscle wasting more cellular and clinical trial studies are needed.     

Proteomic analysis of mitochondrial dysfunction in neurodegenerative diseases

Alzheimer’s, Parkinson’s and Huntington’s disease, and amyotrophic lateral sclerosis are the most relevant neurodegenerative syndromes worldwide. The identification of the etiology and additional factors contributing to the onset and progression of these diseases is of great importance in order to develop both preventive and therapeutic intervention. A common feature of these pathologies is the formation of aggregates, containing mutated and/or misfolded proteins, in specific subsets of neurons, which progressively undergo functional impairment and die. The relationship between protein aggregation and the molecular events leading to neurodegeneration has not yet been clarified. In the last decade, several lines of evidence pointed to a major role for mitochondrial dysfunction in the onset of these pathologies. Here, we review how proteomics has been applied to neurodegenerative diseases in order to characterize the relationship existing between protein aggregation and mitochondrial alterations. Moreover, we highlight recent advances in the use of proteomics to identify protein modifications caused by oxidative stress. Future developments in this field are expected to significantly contribute to the full comprehension of the molecular mechanisms at the heart of neurodegeneration.     

Myocardial ischemia and in vitro mitochondrial metabolic efficiency

The purpose of this study was to evaluate the oxidative capacities and the rate of energy synthesis in isolated mitochondria extracted from normal and post-ischemic myocardium. Isolated rat hearts were perfused according to the working mode with a Krebs Heinseleit buffer containing glucose (11 mM), insulin (10 IU/1) and caprylic acid (25 M). After a 15 min perfusion in normoxic conditions, the hearts were subjected to a 20 min local zero-flow ischemia followed by a 20 min reperfusion. During the perfusion, the aortic and coronary flows, the aortic pressure and the electrocardiogram were monitored. At the end of the reperfusion period, the non-ischemic and ischemic zones (NIZ and IZ, respectively) were separated and the mitochondria were harvested from each zone. The oxygen uptake and the rate of energy production of the NIZ and IZ mitochondria were then assessed with palmitoylcarnitine as substrate in 2 buffers differing in their free calcium concentration (0.041 and 0.150 M). Ischemia provoked a 50% reduction of coronary and aortic flows. The reperfusion of the IZ allowed the partial recovery of coronary flow, but the aortic flow decreased beneath its ischemic value because of the occurrence of severe arrhythmias, stunning and probably hibernation. The IZ mitochondria displayed a lower rate of oxygen consumption, whatever the buffer free calcium concentration. Conversely, their rate of energy production was increased, indicating that their metabolic efficiency was improved as compared to NIZ mitochondria. This might be due to the mitochondrial calcium overload persisting during reperfusion, to the activation of the inner membrane Na⁺/Ca²⁺ exchange and to a significant mitochondrial swelling. On the other hand, the presence of an elevated free calcium concentration in the respiration buffer provoked some energy wasting characterized by a constant AMP production. This was attributed to some accumulation of acetate and the activation of the energy-consuming acetylCoA synthetase. In conclusion, ischemia and reperfusion did not alter the membrane integrity of the mitochondria but improved their metabolic efficiency. Nevertheless, these in vitro results can not reflect the mitochondrial function in the reperfused myocardium. The mitochondrial calcium overload reported to last during reperfusion in the cardiomyocytes might mimic the free calcium-induced reduction of metabolic efficiency observed in vitro in the present study. The resulting energy wasting might be responsible for the contractile abnormalities noticed in the reperfused myocardium.     

High doses of sodium tungstate can promote mitochondrial dysfunction and oxidative stress in isolated mitochondria

Tungstate (W) is recognized as an agent of environmental pollution and a substitute to depleted uranium. According to some preliminary studies, tungstate toxicity is related to the formation of reactive oxygen species (ROS) under abnormal pathological conditions. The kidneys and liver are the main tungstate accumulation sites and important targets of tungstate toxicity. Since the mitochondrion is the main ROS production site, we evaluated the mechanistic toxicity of tungstate in isolated mitochondria for the first time, following a two‐step ultracentrifugation method. Our findings demonstrated that tungstate‐induced mitochondrial dysfunction is related to the increased formation of ROS, lipid peroxidation, and potential membrane collapse, correlated with the amelioration of adenosine triphosphate and glutathione contents. The present study indicated that mitochondrial dysfunction was associated with disruptive effects on the mitochondrial respiratory chain and opening of mitochondrial permeability transition (MPT) pores, which is correlated with cytochrome c release. Our findings suggest that high concentrations of tungstate (2 mM)‐favored MPT pore opening in the inner membranes of liver and kidney mitochondria of rats. Besides, the results indicated higher tungstate susceptibility in the kidneys, compared with the liver.     

Hydrogen sulfide attenuates homocysteine-induced osteoblast dysfunction by inhibiting mitochondrial toxicity

Homocysteine (Hcy) is detrimental to bone health in a mouse model of diet-induced hyperhomocysteinemia (HHcy). However, little is known about Hcy-mediated osteoblast dysfunction via mitochondrial oxidative damage. Hydrogen sulfide (H₂S) has potent antioxidant, anti-inflammatory, and antiapoptotic effects. In this study, we hypothesized that the H₂S mediated recovery of osteoblast dysfunction by maintaining mitochondrial biogenesis in Hcy-treated osteoblast cultures in vitro. MC3T3-E1 osteoblastic cells were exposed to Hcy treatment in the presence or absence of an H₂S donor (NaHS). Cell viability, osteogenic differentiation, reactive oxygen species (ROS) production were determined. Mitochondrial DNA copy number, adenosine triphosphate (ATP) production, and oxygen consumption were also measured. Our results demonstrated that administration of Hcy increases the intracellular Hcy level and decreases intracellular H₂S level and expression of the cystathionine β-synthase/Cystathionine γ-lyase system, thereby inhibiting osteogenic differentiation. Pretreatment with NaHS attenuated Hcy-induced mitochondrial toxicity (production of total ROS and mito-ROS, ratio of mitochondrial fission (DRP-1)/fusion (Mfn-2)) and restored ATP production and mitochondrial DNA copy numbers as well as oxygen consumption in the osteoblast as compared with the control, indicating its protective effects against Hcy-induced mitochondrial toxicity. In addition, NaHS also decreased the release of cytochrome c from the mitochondria to the cytosol, which induces cell apoptosis. Finally, flow cytometry confirmed that NaHS can rescue cells from apoptosis induced by Hcy. Our studies strongly suggest that NaHS has beneficial effects on mitochondrial toxicity, and could be developed as a potential therapeutic agent against HHcy-induced mitochondrial dysfunction in cultured osteoblasts in vitro.     

Role of melatonin on electromagnetic radiation-induced oxidative stress and Ca2+ signaling molecular pathways in breast cancer

Aims: Exposure to electromagnetic radiation (EMR) may increase breast cancer risk by inducing oxidative stress and suppressing the production of melatonin. Aim of the present review is to discuss the mechanisms and risk factors of EMR and oxidative stress-induced breast cancer, to summarize the controlled studies evaluating measures for prevention, and to conclude with evidence-based strategies for prevention.

Materials: Review of the relevant literature and results from our recent basic studies, as well as critical analyses of published systematic reviews were obtained from the Pubmed and the Science Citation Index.

Results: It has been proposed that chronic exposure to EMR may increase the risk of breast cancer by suppressing the production of melatonin; this suppression may affect the development of breast cancer either by increasing levels of circulation of estrogen or through over production of free oxygen radicals. Most epidemiological studies have also indicated overall effect of EMR exposure in premenopausal women, particularly for estrogen receptor positive breast tumors. Enhanced voltage-dependent Ca²⁺ current and impaired inhibitory G-protein function, and derangement of intracellular organelles with a Ca²⁺ buffering effect, such as endoplasmic reticulum and mitochondria have been also shown to contribute to disturbed Ca²⁺ signaling in breast cancer.

Conclusion: Melatonin may modulate breast cancer through modulation of enhanced oxidative stress and Ca²⁺ influx in cell lines. However, there is not enough evidence on increased risk of breast cancer related to EMR exposure.     

Amelioration of age-dependent increase in protein carbonyls of cerebral hemispheres of mice by melatonin and ascorbic acid

Melatonin secreted by the pineal gland acts as a free radical scavenger besides its role as a hormonal signaling agent. It detoxifies a variety of free radicals and reactive oxygen intermediates including hydroxyl radical, peroxynitrite anion and singlet oxygen. Ascorbic acid (Vitamin C), a water soluble vitamin, is a naturally occurring antioxidant and cofactor in various enzymes. Protein carbonyls are formed as a consequence of the oxidative modification of proteins by reactive oxygen species. Oxidative modification alters the function of protein and is thought to play an important role in the decline of cellular functions during aging. In the present study, the effect of melatonin and ascorbic acid on age-related carbonyl content of cerebral hemispheres in mice was investigated. Protein carbonyls of cerebral hemispheres have been found to be significantly higher in 18-month-old mice as compared to 1-month old mice. Administration of a single dose of melatonin (10 mg/kg body weight) and ascorbic acid (10 mg/kg body weight) intraperitoneally for three consecutive days decreases the carbonyl content in 1- and 18-month-old mice significantly. The present study thus suggests that the formation of protein carbonyls in the cerebral hemispheres of the aging mice can be prevented by the antioxidative effects of melatonin and ascorbic acid that could in turn be beneficial in having health benefits from age-related neurodegenerative diseases.