Modulatory role of glutathione monoester in augmenting age-associated neuronal antioxidant system.

An ever-increasing number of reports show the involvement of free radicals in the functional and structural changes occurring in the brain as a part of the normal aging process. This study aimed to assess the potential efficacy of glutathione monoester (GME) when administered intraperitoneally (12 mg/kg body weight) for 20 days on memory and the antioxidant defense system and lipid peroxidation in discrete brain regions such as cortex, striatum, and hippocampus of young and aged rats. Age-associated decline in memory and activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione, vitamin E, and vitamin C, and elevated levels of lipid peroxidation and oxidized glutathione, were observed in all the brain regions studied (p < .001). GME administration was effective in restoring the antioxidant status and in decreasing lipid peroxidation level in aged rat brain regions.

Age-associated alterations of lipofuscin, membrane-bound ATPases and intracellular calcium in cortex, striatum and hippocampus of rat brain: protective role of glutathione monoester.

Brain aging has become an area of intense research and a subject of much speculation fueled largely from the widely recognized fact that age is the biggest risk factor in most neurodegenerative diseases and age-related increase of reactive oxygen species is particularly detrimental to postmitotic tissues. In the present study, we have evaluated the possible role of glutathione monoester (GME), when administered intraperitoneally (12mg/kg body weight) for 20 days on age-associated changes in the levels of lipofuscin, Na+K+, Mg2+, Ca2+ ATPase activities and intracellular calcium levels in discrete brain regions of young and aged male albino Wistar rats. An age-associated increase in lipofuscin, intracellular calcium in cortex, striatum and hippocampus was observed and contradictorily, a decrease in the activities of membrane-bound enzyme activities was also observed. Supplementation of GME brought these changes to near normalcy. Thus, GME improves neuronal antioxidant status, thereby effectively attenuating any putative increase in oxidative stress with age.

Age-dependent upregulation of p53 and cytochrome c release and susceptibility to apoptosis in skeletal muscle fiber of aged rats: role of carnitine and lipoic acid.

Mitochondrial dysfunction has been implicated in the regulation of myofiber loss during aging, possibly by apoptotic pathways. However, the mitochondrial-mediated pathway of apoptosis by cytochrome c in skeletal muscle remains ambiguous. To understand this, we have studied the upstream and downstream events of cytochrome c release, and assessed the efficacy of carnitine and lipoic acid cosupplementation. The results show that elevated levels of cytosolic cytochrome c activate apoptosis in aged rats, and was confirmed further by in vitro caspase-3 assay. Interestingly, the exogenous addition of cytochrome c results in a much higher increase of caspase-3 activity in aged treated rats than age-matched control rats, strongly suggesting that cytochrome c is a limiting factor for caspase-3 activation in the cytosol. Carnitine and lipoic acid supplement decreased apoptosis in aged rats by maintaining mitochondrial membrane integrity and thereby preventing further loss of cytochrome c in vivo. Furthermore, the upregulation of p53 observed in aged rats is attributed to the loss of outer mitochondrial membrane integrity and subsequent release of cytochrome c through BH3-only proteins. In conclusion, the p53-dependent activation of the mitochondrial-cytochrome c pathway of apoptosis in the present study suggests the existence of cross talk between mitochondria and nucleus. However, the exact molecular mechanism remains to be explored. Oral supplements of carnitine and lipoic acid play an antiapoptotic role in aged rat skeletal muscle by protecting mitochondrial membrane integrity.

Age-associated oxidative macromolecular damages in rat brain regions: role of glutathione monoester.

The generation of reactive oxygen species (ROS) and resultant oxidative stress has been implicated in the mechanism of brain dysfunction due to age-related neurodegenerative diseases. We have evaluated the efficacy of glutathione monoester (GME) when administered intraperitoneally (12 mg/kg body weight) for 20 days on glutathione, ROS, superoxide anion production, lipid peroxidation (LPO), protein carbonyls, thiol status, oxidative DNA damage products such as 8-hydroxy deoxy guanosine and DNA protein cross-links in discrete brain regions of young and aged rats. An age associated increase in ROS, superoxide anion production, LPO, protein oxidation, and DNA damage products in cortex, striatum, and hippocampus was observed which was reversed by GME. Contradictorily, a decline in the levels of glutathione, total thiol, and nonprotein and protein thiols was observed which was also reversed upon GME administration. These findings suggest that GME administration inhibits free radical-induced oxidative macromolecular damage in aged rats and thereby protects the brain from ROS.

Cytochrome c oxidase rather than cytochrome c is a major determinant of mitochondrial respiratory capacity in skeletal muscle of aged rats: role of carnitine and lipoic acid.

The release of mitochondrial cytochrome c followed by activation of caspase cascade has been reported with aging in various tissues, whereas little is known about the caspase-independent pathway involved in mitochondrial dysfunction. To determine the functional impact of cytochrome c loss on mitochondrial respiratory capacity, we monitored NADH redox transitions and oxygen consumption in isolated skeletal muscle mitochondria of 4- and 24-month-old rats in the presence and absence of exogenous cytochrome c; and assessed the efficacy of cosupplementation of carnitine and lipoic acid on age-related alteration in mitochondrial respiration. The loss of mitochondrial cytochrome c with age was accompanied with alteration in respiratory transition, which in turn was not rescued by exogenous addition of cytochrome c to isolated mitochondria. The analysis of mitochondrial and nuclear-encoded cytochrome c oxidase subunits suggests that the decreased levels of cytochrome c oxidase may be attributed for the irresponsiveness to exogenously added cytochrome c on mitochondrial respiratory transitions, possibly through reduction of upstream electron carriers. Oral supplementation of carnitine and lipoic acid to aged rats help to maintaining the mitochondrial oxidative capacity by regulating the release of cytochrome c and improves cytochrome c oxidase transcript levels. Thus, carnitine and lipoic acid supplementation prevents the loss of cytochrome c and their associated decline in cytochrome c oxidase activity; thereby, effectively attenuating any putative decrease in cellular energy and redox status with age.

Protective efficacy of alpha-lipoic acid on acetylcholinesterase activity in aged rat brain regions.

The purpose of the present investigation was to measure the activity of acetylcholinesterase in discrete regions of young and aged rat brain before and after DL-alpha-lipoic acid supplementation. Two groups of male albino rats were used in this study (4 and 24 months of age). DL-alpha-lipoic acid was administered intraperitoneally with a regimen of 100 mg/kg body weight per day using alkaline saline as a vehicle for 7 and 14 days. The activity was measured in the cerebral cortex, cerebellum, striatum, hippocampus and hypothalamus, and found to be significantly decreased in some of the brain regions in aged rats. Administration of lipoic acid into aged rats reversed the decrease in the activity in the discrete brain regions. These results suggest that lipoic acid is effective in restoration of the activity of acetylcholinesterase in aged rats.

Combined efficacies of DL-alpha-lipoic acid and meso 2,3 dimercaptosuccinic acid against arsenic induced toxicity in antioxidant systems of rats.

Health hazards caused by heavy metals have become a great concern to the population. Arsenic as an environmental agent is considered to be a toxic substance due to its carcinogenic potential in humans. Since arsenic compounds might exert their toxicity by the generation of reactive oxygen species, we have evaluated the effect of both DL-alpha-lipoic acid (LA) and meso 2,3 dimercapto succinic acid (DMSA) on the antioxidants and lipid peroxidation in arsenic treated rats. The objective of the study was to determine whether DL-alpha-lipoic acid and meso 2,3 dimercapto succinic acid could rehabitate antioxidant depletion and damage to biomolecules in protection against oxidative insults. A significant increase in the levels of reactive oxygen species formation and lipid peroxidation and decrease in the activities of antioxidant enzymes were observed in arsenic exposed rats. Supplementation of DL-alpha-lipoic acid and meso 2,3 dimercapto succinic acid to arsenic fed rats significantly increased the activities of superoxide dismutase, catalase, glutathione peroxidase with elevation in the levels of reduced glutathione, total sulfhydryl, ascorbic acid and alpha-tocopherol. In addition, significant decrease in the levels of reactive oxygen species formation and lipid peroxidation was also observed in our study. From our results, we conclude that DL-alpha-lipoic acid and meso 2,3 dimercapto succinic acid play a synergistic role in decreasing arsenic induced oxidative damage by elevating the antioxidant status in liver and kidney.

Emerging role of Centella asiatica in improving age-related neurological antioxidant status.

Free radicals have been hypothesized to play an important role in ageing process. There exists an imbalance between free radical production and antioxidant defense mechanism, which may lead to cell death during ageing. Our study was designed to determine whether extract of Centella asiatica, an antioxidant, when administered orally (300 mg/kg body weight/day) for 60 days would prevent age-related changes in antioxidant defense system, lipid peroxidation (LPO) and protein carbonyl (PCO) content in rat brain regions such as cortex, hypothalamus, striatum, cerebellum and hippocampus. Aged rats elicited a significant decline in the antioxidant status and increased the LPO and PCO as compared to control rats in all five regions studied. The increase in LPO and PCO contents were (64%, 34%) in cortex, (86%, 30%) in cerebellum, (51%, 47%) in striatum, (77%, 27%) in hypothalamus and (58%, 45%) in hippocampus, respectively, in aged rats as compared to young rats. Supplementation of C. asiatica was effective in reducing brain regional LPO and PCO levels and in increasing the antioxidant status. Thus, C. asiatica by acting as a potent antioxidant exerted significant neuroprotective effect and proved efficacious in protecting rat brain against age related oxidative damage.

Arsenic intoxication-induced reduction of glutathione level and of the activity of related enzymes in rat brain regions: reversal by DL-alpha-lipoic acid.

The purpose of this study was to examine the effects of DL: -alpha-lipoic acid (LA) on arsenic (As) induced alteration of glutathione (GSH) level and of the activity of glutathione-related enzymes-glutathione peroxidase (GSH-Px), glutathione reductase (GR), and glucose-6-phosphate dehydrogenase (G6PDH)-in rat brain regions (cortex, hypothalamus, striatum, cerebellum and hippocampus). Male Wistar rats of 150+/-10 g weight were divided into four groups: control and three experimental groups supplemented with arsenic (sodium arsenite) alone (100 ppm mixed in drinking water), lipoic acid alone (70 mg kg(-1) body weight), arsenic plus lipoic acid (100 ppm arsenic in drinking water plus 70 mg lipoic acid kg(-1) body weight). The arsenic content of brain regions was found to increase with the administration of sodium arsenite. Arsenic exposure elicited a significant decline in glutathione content and in the activity of related enzymes, with the greatest decreases seen in the cortex, striatum, and hippocampus, whereas there were no significant differences between control rats and the group treated with lipoic acid alone. Highly elevated content of the thiobarbituric acid-reactive substance malondialdehyde (MDA) in the brain regions of arsenic-exposed rats reflected extensive lipid peroxidation (LPO) processes. Simultaneous lipoic acid treatment was effective in reducing brain regional arsenic levels and lipid peroxidation and in increasing the glutathione content and the activity of its related enzymes. Lipoic acid, by acting as an alternative sulfhydryl nucleophile to glutathione, prevents its oxidation to glutathione disulfide in detoxifying reactions against reactive oxygen species and consequently increases the activity of glutathione-related enzymes.

Age-associated decreased activities of mitochondrial electron transport chain complexes in heart and skeletal muscle: role of L-carnitine.

The mitochondrial respiratory chain is a powerful source of reactive oxygen species (ROS), considered as the pathogenic agent of many diseases and aging. L-Carnitine (4-N-trimethylammonium-3-hydroxybutric acid) plays an important role in transport of fatty acid from cytoplasm to mitochondria for energy production. Previous studies in our laboratory reported L-carnitine as a free radical scavenger in aged rats. In the present study we focused the effect of L-carnitine on the activities of electron transport chain in young and aged rats. The activities of electron transport chain complexes were found to be significantly decreased in aged rats when compared to young control rats. Supplementation of carnitine to young and aged rats for 14 and 21 days improved the electron transport chain complexes levels in aged rats when compared with young rats in duration dependent manner. No significant changes were observed in young rats. Our result suggested that L-carnitine improved the activities of electron transport chain enzymes there by improving the energy status in aged rats.

Ascorbic acid and alpha-tocopherol as potent modulators on arsenic induced toxicity in mitochondria.

Arsenic exists ubiquitously in our environment and various forms of arsenic circulate in air, water, soil and living organisms. Since arsenic compounds have shown to exert their toxicity chiefly by generating reactive oxygen species, we have evaluated the effect of antioxidants ascorbic acid and alpha-tocopherol on lipid peroxidation, antioxidants and mitochondrial enzymes in liver and kidney of arsenic exposed rats. A significant increase in the level of lipid peroxidation and decrease in the levels of antioxidants and in the activities of mitochondrial enzymes were observed in arsenic intoxicated rats. Co-administration of arsenic treated rats with ascorbic acid and alpha-tocopherol showed significant reduction in the level of lipid peroxidation and elevation in the levels of ascorbic acid, alpha-tocopherol, glutathione and total sulfhydryls and in the activities of isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, succinate dehydrogenase, NADH-dehydrogenase and cytochrome c oxidase. From our results, we conclude that ascorbic acid and alpha-tocopherol alleviate arsenic- induced alterations in mitochondria.

Effects of levocarnitine on mitochondrial antioxidant systems and oxidative stress in aged rats.

OBJECTIVE: Levocarnitine is important in beta-oxidation of fatty acids. We evaluated the role of levocarnitine in the skeletal muscle mitochondrial antioxidant system of aged rats. METHODS: Male albino Wistar rats were used in this study. The animals were divided into two groups: young rats (group I) and aged rats (group II). These rats were further subdivided into three groups: one control group (groups Ia and IIa) and two experimental groups (groups Ib, IIb and Ic, IIc) for supplementation with levocarnitine for 14 and 21 days, respectively. After the experimental period, the animals were killed by cervical decapitation; blood and skeletal muscle were isolated for further analysis. RESULTS: Levels of antioxidant enzymes such as superoxide dismutase, catalase and glutathione peroxidase, and non-enzymatic antioxidants such as reduced glutathione, ascorbic acid (vitamin C) and tocopherol (vitamin E) were found to be decreased in the blood and skeletal muscle mitochondria of aged rats. Supplementation with levocarnitine in aged rats improved the antioxidant status in a dose-dependent manner. CONCLUSIONS: These findings demonstrated that levocarnitine enhances the activity of the mitochondrial antioxidant system and decreases the incidence of free radical-induced lipid peroxidation in aged rats.

Effect of DL-alpha-lipoic acid on the status of lipid peroxidation and protein oxidation in various brain regions of aged rats.

Free radicals have been implicated in the development of many acute and chronic diseases and in conditions involving brain or neurological tissue. The primary genetic material is subjected to damage by endogenous and exogenous agents, which may lead to instability and transcriptional infidelity. In the present study, we evaluated the protective effect of DL-alpha-lipoic acid, a metabolic antioxidant on lipid peroxidation, protein carbonyl content in various brain regions of aged rats when compared to brain regions of young rats. DL-alpha-lipoic acid was administered intraperitoneally (100mg/kg body weight/day) to experimental rats. Nucleic acid and protein content were low whereas thiobarbituric acid reactive substances and protein carbonyl content (markers of free radical damage) were high in cortex, striatum, hippocampus and hypothalamus followed by cerebellum of aged rat brain. Lipoate administration for 14 days in aged rats increased the levels of nucleic acid and protein and reduced lipid peroxidation and protein oxidation. These results demonstrate that lipoic acid is a potent antioxidant for neuronal cells against age associated oxidative damage.