Increased levels of lipid peroxides in aged rat brain as revealed by direct assay of peroxide values

Specific microglial phagocytic phenotype and decrease of lipid oxidation in white matter areas during aging: Implications of different microenvironments

Physiological aging is characterized by an imbalance of pro-inflammatory and anti-inflammatory mediators leading to neuroinflammation. Microglial cells, which are highly regulated by the local microenvironment, undergo specific changes depending upon the brain area during aging. The aim of this study was to evaluate the influence of age over microglial cells along different brain areas and microenvironments. For this purpose, transgenic mice with overproduction of either the anti-inflammatory IL-10 cytokine or the pro-inflammatory IL-6 cytokine were used. Our results show that, during aging, microglial cells located in white matter (WM) areas maintain their phagocytic capacity but present a specific phagocytic phenotype with receptors involved in myelin recognition, arguing for aging-derived myelin damage. Whereas IL-10 overproduction anticipates the age-related microglial phagocytic phenotype, maintaining it over time, IL-6 overproduction exacerbates this phenotype in aging. These modifications were linked with a higher efficiency of myelin engulfment by microglia in aged transgenic animals. Moreover, we show, in a novel way, lower lipid oxidation during aging in WM areas, regardless of the genotype. The novelty of the insights presented in this study open a window to deeply investigate myelin lipid oxidation and the role of microglial cells in its regulation during physiological aging.

Antioxidative effects of the spice cardamom against non-melanoma skin cancer by modulating nuclear factor erythroid-2-related factor 2 and NF-κB signalling pathways

The role of dietary factors in inhibiting or delaying the development of non-melanoma skin cancer (NMSC) has been investigated for many years. Cardamom, which is a dietary phytoproduct, has been commonly used in cuisines for flavour and has numerous health benefits, such as improving digestion and stimulating metabolism and having antitumorigenic effects. We have investigated the efficacy of dietary cardamom against 7,12-dimethylbenz[a]anthracene (DMBA)-induced skin papillomatogenesis in Swiss albino mice that closely resembles human NMSC. Mice were grouped into normal wild type (untreated), vehicle-treated (acetone), carcinogen-treated (DMBA), and DMBA and cardamom-treated (DMBA+CARD) to delineate the role of cardamom against DMBA-induced papillomatogenesis. Oral administration of cardamom to DMBA-treated mice up-regulated the phase II detoxification enzymes, such as glutathione-S-transferase and glutathione peroxidase, probably via activation of nuclear factor erythroid-2-related factor 2 transcription factor in 'DMBA+CARD' mice. Furthermore, reduced glutathione, glutathione reductase, superoxide dismutase and catalase were also up-regulated by cardamom in the same 'DMBA+CARD' group of mice compared with DMBA-treated mice. Cardamom ingestion in DMBA-treated mice blocked NF-κB activation and down-regulated cyclo-oxygenase-2 expression. As a consequence, both the size and the number of skin papillomas generated on the skin due to the DMBA treatment were reduced in the 'DMBA+CARD' group. Thus, the results from the present study suggest that cardamom has a potential to become a pivotal chemopreventive agent to prevent papillomagenesis on the skin.

Saffron suppresses oxidative stress in DMBA-induced skin carcinoma: A histopathological study

Cancer chemoprevention is the use of natural, synthetic or biological substances to reverse or prevent the development of cancer. Saffron is a naturally derived plant product that acts as an antispasmodic, diaphoretic, carminative, emmenagogic and sedative. Our aim in this study was to investigate the chemopreventive effect of aqueous saffron on chemically induced skin carcinogenesis using a histopathological approach. Mice were divided into five groups: carcinogen control (CC), normal control (NC) and saffron-treated Groups A, B and C. Groups A, B, C and CC mice received three topical applications of 7,12 dimethylbenz[a]anthracene (DMBA) followed by croton oil on shaven dorsal skin for 8 weeks. NC mice received topical skin applications of the vehicle, acetone, only. Saffron infusion was fed orally to three groups of mice either before (Group A) or after (Group C) or both before and after (Group B) DMBA applications. The activities of antioxidant enzymes glutathione-S transferase (GST), glutathione peroxidase (GPx), catalase (CAT) and superoxide dismutase (SOD) in liver tissue samples taken at 0, 6, 10 and 12 weeks from all groups were assessed. Standard histological examination of skin demonstrated a beneficial action of saffron in mice where saffron treatments were given both before and after the induction of skin carcinogenesis. Saffron ingestion inhibited the formation of skin papillomas in animals and simultaneously reduced their size. In conclusion, saffron inhibits DMBA-induced skin carcinoma in mice when treated early. This may be due, at least in part, to the induction of cellular defense systems.

Effect of garlic on lipid peroxidation and antioxidation enzymes in DMBA-induced skin carcinoma

OBJECTIVE

Naturally occurring phytochemicals display an active cancer preventive strategy to inhibit, delay, or reverse human carcinogenesis. Studies have indicated that certain daily-consumed dietary phytochemicals have cancer protective effects mediated by carcinogens. Lipid peroxide plays a detrimental role in all cancers including skin carcinogenesis. Garlic, a phytochemical, has acquired a special position in the folklore of many cultures as a formidable prophylactic and therapeutic medicinal agent. In this report, we pursue the chemopreventive effect of aqueous garlic on skin carcinogenesis.

METHODS

"Swiss albino mice" were divided into five groups depending on the combination of skin cancer-inducing 7,12-dimethylbenz[a]anthracene and garlic treatments. Histology of the affected skin and biochemical assays for lipid peroxide, catalase, superoxide dismutase, glutathione-S-transferase, and glutathione peroxidase were performed to demonstrate the effect of garlic in mice. Immunoblotting was performed with cyclo-oxygenase-2, p53, and caspase-3 to demonstrate expressions of the respective proteins in skin lysates.

RESULTS

Garlic extracts inhibited the oxidative modification of lipids, thus protecting cells from injury by the oxidized molecules. The best chemopreventive action of garlic was observed in mice in which garlic treatment was performed before and after the induction of skin carcinogenesis. Garlic ingestion delayed formation of skin papillomas in animals and simultaneously decreased the size and number of papillomas, which was also reflected in the skin histology of the mice treated.

CONCLUSION

The protective effects against skin cancer elicited by garlic in mice are believed to be due at least in part to the induction cellular defense systems.

Regional responses in antioxidant system to exercise training and dietary Vitamin E in aging rat brain

We have evaluated the effect of exercise, Vitamin E and a combination of both on the antioxidant enzymes (AOEs)-superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) along with the products of lipid peroxidation (LP)-malondialdehyde (MDA) and lipofuscin-like auto fluorescent substances (LF-like AFS) in discrete brain regions of rats of 4 (young adults), 8 (old adults), 12 (middle-age) and 22 months (mos) old of age. Hippocampus (HC) showed greater increase in GSH-Px activity than cerebral cortex (CC) to exercise and Vitamin E and was irrespective of the age. A combination of both was effective in the CC of all age groups but not in the supplemented sedentary of 12- and 22-mo-olds. CAT activity increased significantly in the HC of supplemented and trained rats but not in the combination group of any age. SOD increased in both the regions of supplemented trainees. However, old were more benefited in terms of maximal elevation in the HC. Vitamin E reduced MDA content in both regions of adult. LF-like AFS decreased significantly in supplemented sedentary and trainees of all ages. Our results demonstrate that an age-related deficit in AOEs in the CC and HC can be overcome through Vitamin E plus exercise, and further suggests the rationale for looking at these markers of oxidative stress in several age-related neuronal diseases.

Sex-dependent antioxidant enzyme activities and lipid peroxidation in ageing mouse brain

We investigated whether oxidant status and antioxidant enzyme activities during ageing of mouse brain are regulated in sex-dependent manner. In the homogenate from the brain of 1, 4, 10 and 18 months old male and female CBA mice, lipid peroxidation (LPO), total superoxide dismutase (tSOD), catalase (CAT) and glutathione peroxidase (Gpx) were determined. LPO was age- and sex-related, favoring males over females throughout the lifespan with the peak in both sexes at 10 months of age. Throughout ageing, no difference in tSOD activity between male and female brains was observed, except in immature 1 month old mice. Gender-related difference in Gpx activity was observed, with higher level in females comparing to males, reaching statistical significance in senescent (18 months old) animals. CAT activity was drastically changed with ageing in both the male and female brain. We found different age associated trends in CAT activity in males and females: decreased with age in males and increased with age in females. Taken together, the present findings indicate that brains of female mice have lower oxidant and higher antioxidant capacity mostly related to CAT and to a lesser extent to Gpx activity.

Lipid peroxidation and the aging process

Consistent evidence supports the hypothesis that a progressive accumulation of oxidative damage to important cellular molecules is a fundamental mechanism involved in most senescence-associated alterations. Oxidative damage occurs when free radicals produced within an organism are not completely destroyed by the appropriate endogenous defense systems. Because lipids are a major component of living organisms and probably the first easy target of free radicals once they are produced, lipid peroxidation might play an important role in initiating and/or mediating some aspects of the aging process. It has been widely demonstrated that there is an age-associated increase in the steady-state concentrations of lipid peroxidation products. However, establishing the involvement of this phenomenon in the pathogenesis of the aging process has not been an easy task. The recent development of more reliable techniques to measure lipid peroxidation, together with more well-defined animal models of aging, should be of great help in future studies in this field. The current evidence for the presence and importance of lipid peroxidation in the aging process is discussed in this review.

Docosahexaenoic acid abundance in the brain: a biodevice to combat oxidative stress

Docosahexaenoic acid (DHA) (22:6) is a polyunsaturated fatty acid of the n - 3 series which is believed to be a molecular target for lipid peroxides (LPO) formation. Its ubiquitous nature in the nervous tissue renders it particularly vulnerable to oxidative stress, which is high in brain during normal activity because of high oxygen consumption and generation of reactive oxygen species (ROS). Under steady state conditions potentially harmful ROS and LPO are maintained at low levels due to a strong antioxidant defense mechanism, which involves several enzymes and low molecular weight reducing compounds. The present review emphasizes a paradox: a discrepancy between the expected high oxidability of the DHA molecule due to its high degree of unsaturation and certain experimental results which would indicate no change or even decreased lipid peroxidation when brain tissue is supplied or enriched with DHA. The following is a critical review of the experimental data relating DHA levels in the brain to lipid peroxidation and oxidative damage there. A neuroprotective role for DHA, possibly in association with the vinyl ether (VE) linkage of plasmalogens (pPLs) in combating free radicals is proposed.

Antioxidative effects of docosahexaenoic acid in the cerebrum versus cerebellum and brainstem of aged hypercholesterolemic rats

Female Wistar rats (100 weeks old) were divided into two groups; one group was fed a high-cholesterol diet (HC) and the other a high-cholesterol diet plus docosahexaenoic acid (HC-fed DHA rats). Fatty acid concentrations in brain tissues were analyzed by gas chromatography. In the HC-fed DHA rats, brain catalase (CAT), GSH, and glutathione peroxidase (GPx) increased in the cerebrum but not in the brainstem or cerebellum. The rate of increase was 23.0% for CAT, 24.5% for GSH, and 26.3% for GPx compared with that in the HC animals (p < 0.05). In the cerebrum of the HC-fed DHA rats, CAT and GPx increased, with an increase in the ratio of DHA to arachidonic acid. The cerebrum, unlike the other areas of the brain, seems to be more sensitive to DHA in stimulating CAT and GPx. We suggest that DHA plays an important role in inducing an antioxidative defense against active oxygen by enhancing the cerebral activities of CAT, GPx, and GSH.

Influence of docosahexaenoic acid on cerebral lipid peroxide level in aged rats with and without hypercholesterolemia

Female Wistar rats, 100 weeks old, were divided into four groups: one group was fed a high-cholesterol diet, one received a non-cholesterol diet, and the others were fed either a non- or a high-cholesterol diet plus docosahexaenoic acid. The level of lipid peroxide (LPO) in brain tissue was measured with a LPO assay kit. Fatty acid concentrations were analyzed by gas chromatography. Brain LPO in the aged and hypercholesterolemic rats fed docosahexaenoic acid decreased in the cerebrum but not in the brain stem or cerebellum. In the cerebrum, LPO showed a decrease, with an increase in the ratio of docosahexaenoic acid to arachidonic acid. The cerebrum, unlike the other areas of the brain, was more sensitive to docosahexaenoic acid as the concentrations of LPO decreased.

Effect of the long-term feeding of dietary lipids on the learning ability, fatty acid composition of brain stem phospholipids and synaptic membrane fluidity in adult mice: a comparison of sardine oil diet with palm oil diet

The effect of 12 month feeding of 5% palm oil or sardine oil diet on the maze-learning ability, fatty acid composition of brain stem phospholipids and synaptic membrane fluidity in mice was studied. The time required to reach the maze exit and the number of times that a mouse strayed into blind alleys in the maze were measured three times every 4 days. The time and number of mice fed on the sardine oil diet were less than those of animals fed on the palm oil diet in the first and second trials. The results of fatty acid composition analysis of brain stem phosphatidylethanolamine showed that the percentage of docosahexaenoic acid (22:6, n-3; DHA) was higher, but the arachidonic acid (20:4, n-6; AA) and docosatetraenoic acid (22:4, n-6; DTA) were lower in the sardine oil diet fed-mice than in the palm oil diet fed-animals. Moreover, the microviscosity of the synaptic plasma membrane in the sardine oil diet group was lower than that in the palm oil diet group. These results suggest that the adult mice fed on the sardine oil diet for a long period maintain higher levels of docosahe xaenoic acid in brain phospholipids, synaptic membrane fluidity and maze-learning ability than animals fed on the palm oil diet.

Mitochondrial membrane fluidity and oxidative damage to mitochondrial DNA in aged and AD human brain

Oxidative damage on biological molecules has been proposed as a major cause of alterations observed in aging brain as well as in neurodegenerative diseases. In this study, we measured membrane fluidity in mitochondria extracted from three cerebral regions and cerebellum of Alzheimer disease (AD) patients and age-matched controls by means of fluorescence polarization technique. A significant reduction of mitochondrial membrane fluidity was found in AD, except in cerebellum. In controls, a decrease of membrane fluidity was observed along with age, and it was also related to the content of the oxidized nucleoside 8-hydroxy-2'-deoxyguanosine (OH8dG) in mitochondrial DNA (mtDNA). Alteration in membrane fluidity seems to be a result of lipid peroxidation, since it dramatically decreased when mitochondria were exposed to FeCl2 and H2O2. The parallel increase of viscosity in mitochondrial membrane and the amount of OH8dG in mtDNA is suggestive of a relationship between these biological markers of oxidative stress. These results provide further evidence that oxidative stress may play a role in the pathogenesis of AD.

Age effect on brain pH during ischemia/reperfusion and pH influence on peroxidation

Older gerbils are more sensitive to ischemia/reperfusion injury (IRI) than younger ones. Utilizing 31P-NMR to monitor in vivo pH and high energy phosphates of brain cortex undergoing an IRI showed that cortical intracellular pH decreased to 6.35 after ischemia and then increased with reperfusion, but older gerbils required significantly more time to recover than younger animals. Brain high energy phosphates dropped during ischemia but rebounded within 20 min reperfusion in younger gerbil brain but remained significantly lower in older gerbil brain for 50 min. These data suggest that IRI-induced brain acidification may enhance oxidative damage. In an in vitro system it was shown in both young and old brain homogenate that peroxidation rate increased when the pH of the incubation medium was decreased from 7.4 to 6.4. This was true in the presence or absence of an ADP/Fe/Ascorbate system in both young and old brain homogenate. Enhancement of peroxidation rate by ADP/Fe/Ascorbate addition was much more pronounced at pH 7.4 (30- to 40-fold increase) as compared to pH 6.4 (7.8- to 9.5-fold increase). This data can be interpreted to indicate that the lower pH makes endogenous Fe more available to catalyze oxidative damage. The fact that brain pH and high energy phosphates remain lower in older gerbil brains during IRI suggests that brain mitochondria from older animals are less capable of responding to a large oxidative stress brought on by an IRI.(ABSTRACT TRUNCATED AT 250 WORDS)

The potent free radical scavenger alpha-lipoic acid improves memory in aged mice: putative relationship to NMDA receptor deficits

alpha-Lipoic acid (alpha-LA) improved longer-term memory of aged female NMRI mice in the habituation in the open field test at a dose of 100 mg/kg body weight for 15 days. In a separate experiment, no such effect could be found for young mice. alpha-LA alleviated age-related NMDA receptor deficits (Bmax) without changing muscarinic, benzodiazepine, and alpha 2-adrenergic receptor deficits in aged mice. The carbachol-stimulated accumulation of inositol monophosphates was not changed by the treatment with alpha-LA. These results give tentative support to the hypothesis that alpha-LA improves memory in aged mice, probably by a partial compensation of NMDA receptor deficits. Possible modes of action of alpha-LA based on its free radical scavenger properties are discussed in relation to the membrane hypothesis of aging.

Lipid peroxidation inhibits oleoyl-CoA: 1-acyl-sn-glycero-3-phosphocholine O-acyltransferase in rat CNS axolemma-enriched fractions

The effect of phospholipid peroxidation on the acylation of lysoPtdCho (lysophosphatidylcholine) by axolemma-enriched fraction prepared from rat brain stem was investigated. After two types of peroxidative treatments, the in vitro induction of malondialdehyde and conjugated dienes formation in axolemmal membranes correlated to a shift in the ratio of saturated/unsaturated fatty acids. By using an Fe2+ (20 microM)-ascorbate (0.25 mM) peroxidation system, the residual acyltransferase activity was 55% of the initial one. No change in Km value for either oleoyl-CoA or lysoPtdCho was found, whereas a loss of 24% in Vmax was observed. After 5 min preincubation with 150 mM t-BuOOH, 70% inactivation of the acylation reaction was observed. A near suppression of enzyme activity was reached with 400 mM. The apparent Km for oleoyl-CoA decreased sharply (from 6.6 microM in control preparations to 4.1 microM in t-BuOOH-treated membranes), indicating a 2-fold increase in the enzymatic affinity for this substrate. The apparent Km for lysoPtdCho increased markedly (from 1.56 microM in the control preparations to 5.88 microM in t-BuOOH-treated membranes) whereas a decrease of Vmax (from 1.65 to 0.80 nmol/min/mg protein) for the same substrate was observed. Significant enzyme inactivation (loss of 60% of initial activity) was seen when 10 mumol of photooxidized phospholipids were preincubated with axolemmal membranes. Significant dose-dependent enzyme inactivation was brought about by addition of 10-60 mumol of peroxidized PtdEtn/100 micrograms axolemmal protein. The percent enzyme inhibition by peroxidized PtdCho at equivalent amounts was lower than that by PtdEtn.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging does not affect the susceptibility to lipid peroxidation and lysosomal enzyme release of rat visual system structures and sciatic nerve

The aim of the present study was to clarify the issue of lipid peroxidation operating in visual system structures and sciatic nerve of the rat as a contributing factor to senescence. In 4-, 14- and 28-month-old male rats, the amount of endogenous malondialdehyde, conjugated dienes and extractable phospholipids were all taken as indices of lipid peroxidation. In addition, the total free and released enzyme activities of four lysosomal hydrolases were evaluated. The susceptibility of all these parameters to in vitro iron-induced peroxidation was also taken as an age-related indicator of the endogenous peroxidative potential of the nervous tissues examined. Our data show that the content of malondialdehyde and phospholipids did not change in an age-related fashion. Furthermore, the susceptibility of rat visual system structures to lipid peroxidation, together with the release of lysosomal enzymes were unchanged as a function of aging. The results do not lend support to the hypothesis that an increase in overall lipid peroxidation is peculiar to the aging phenomenon of the central nervous system areas which delimit the rat visual pathway.