Iron-dependent peroxidation of rat brain: a regional study

The effect of stocking rate and supplementary selenium on the fatty acid composition and subsequent peroxidisability of poultry muscle tissues

Selenium (Se) plays a crucial role in protecting biological materials from oxidative damage through the action of the selenoprotein glutathione peroxidase (GSH-Px), and the effectiveness of this protection is often dependent upon Se supply. Recent evidence has indicated that GSH-Px mRNA expression can be upregulated in response to potential oxidative damage risk, and that this upregulation is independent of Se supply. The current study aimed to determine the effect of Se supplementation, stocking rate and tissue fatty acid profile on GSH-Px activity in breast and thigh tissue of commercial broilers. A total of 168 Ross 308 broiler chicks were enrolled onto the study. Prior to enrolment, birds were brooded as a single group and received a starter diet containing no additional Se. The study was a 2 × 2 factorial design comprising of two levels of dietary Se (high Se, 0.5 mg/kg total Se, low Se background Se only), and two stocking rates (high, 30 kg/m², and low, 15 kg/m²). At 15 days of age, birds were blocked by live weight and randomly allocated to one of the four treatments, with six pen replicates per treatment. At 42 days of age, one bird was randomly selected from each pen replicate, euthanased and breast and thigh tissue harvested. GSH-Px activity, thiobarbituric acid reactive substances (TBARS), and fatty acid (FA) content of these tissues were determined. There was no effect (P > 0.05) of stocking rate on GSH-Px activity or TBARS. GSH-Px activity did not differ between tissue types but was greater in high Se birds (P < 0.001) compared to low Se. TBARS concentrations were greater in thigh tissue (P < 0.001), and these thigh concentrations were greater in high Se birds (P < 0.05). There were marked differences between breast and thigh tissue in most FAs (P < 0.001), with breast generally containing greater proportions of polyunsaturated FA, so that breast tissue had a higher (P < 0.001) peroxidisability index (PI) than thigh. A positive correlation between GSH-Px activity and PI in the thigh tissue of high Se birds (Pearson Correlation 0.668; P = 0.025) may indicate that increasing susceptibility to peroxidisation in lipid-rich tissues may also upregulate GSH-Px activity in Se-replete birds. This study suggests that ensuring adequate dietary selenium could be a useful tool to mitigate adverse effects on meat quality caused by oxidation, particularly in lipid-rich meat.

Pleurotus ostreatus, an edible mushroom, enhances glucose 6-phosphate dehydrogenase, ascorbate peroxidase and reduces xanthine dehydrogenase in major organs of aged rats

CONTEXT

Aging is now considered to be associated with an elevation in oxidative damage to macromolecules and enhanced levels of inflammation. Therefore, inhibition of age-related oxidative stress by natural supplement is an important study.

OBJECTIVES

To investigate whether the treatment with Pleurotus ostreatus (Jacq.: Fr) Kumm, (Pleurotaceae) can ameliorate oxidative damage in aged rats.

MATERIALS AND METHODS

Male Wistar rats were divided into three groups of six each: group 1, normal young rats; group 2, normal aged untreated rats; group 3, normal aged rats treated with P. ostreatus (200 mg/kg body wt administered intraperitoneally for 21 days). On the 22nd day, rats were sacrificed by decapitation; the liver, kidneys, heart and brain were removed from each rat for the biochemical and isozyme analyses of the antioxidant enzymes glucose 6-phosphate dehydrogenase (G6PDH), ascorbate peroxidase (Apx) and xanthine dehydrogenase (XDH).

RESULTS

An elevated activity of XDH was observed in the liver (G2:13.72 ± 4.1 versus G1: 7.57 ± 1.15; p < 0.05), kidneys (G2:101.48 ± 12.3 versus G1: 31.15 ± 1.71; p < 0.01), heart (G2: 63.21 ± 3.96 versus G1: 37.3 ± 2.70; p < 0.01) and brain (G2: 39.02 ± 3.96 versus G1: 19.84 ± 1.22; p < 0.001). The activities of G6PDH and Apx were lowered in major organs of aged untreated rats. However, treatment of P. ostreatus to aged rats resulted in decreased XDH and increased G6PDH and Apx activities in liver, kidneys, heart and brain. Interestingly, analyses of isozyme pattern of these enzymes are support the results obtained from the spectrophotometric determinations.

CONCLUSION

These results suggest that an extract of P. ostreatus can protect the age-related oxidative damage in major organs of Wistar rats by enhancing the antioxidant enzymes G6PDH and Apx and by reducing XDH.

Neurotoxicity of Nigerian bonny light crude oil in rats

Biometal accumulation may contribute to organ toxicity in individuals using the Nigerian bonny light crude oil (BLCO) for ailment management. We assessed the levels of biometals, antioxidant status, along with histomorphometric analysis to investigate the effect of BLCO, commonly use in folklore medicine, on the brain. Adult male Wistar rats were dosed by gavage with BLCO at 0, 200, and 800 mg/kg(-1) of BLCO for 7 days. Results showed the accumulation of iron, zinc, nickel and lead, in contrast to copper, in BLCO-treated rats. Administration of BLCO disrupted the brain's antioxidant system and significantly increased levels of hydrogen peroxide and lipid peroxidation. Although the Purkinje layer and maximum width of Purkinje cells were not affected, BLCO treatment significantly decreased molecular layer, granular layer, and density of Purkinje cells of the cerebellum. The neurotoxicity of BLCO may be the result of oxidative stress resulting from loss of biometal homeostasis as well as toxicant injury from other constituents of BLCO.

Neuroprotection against oxidative injury by a nucleic acid-based health product (Squina DNA) through enhancing mitochondrial antioxidant status and functional capacity

High levels of reactive oxygen species inflict oxidative damage on various cellular components that eventually culminate in a variety of diseases. This study investigated the cytoprotective effects of a nucleic acid-based health product (Squina [Hong Kong, China] DNA) against oxidative stress, particularly in neuronal cells. Adult female Sprague-Dawley rats were treated with Squina DNA, and changes in mitochondrial antioxidant status and functional capacity were assessed by the activities of antioxidant enzymes and ATP generation capacity in brain, heart ventricular, kidney, skeletal muscle, and liver tissues of control and Squina DNA-treated rats. The effects of Squina DNA pretreatment on brain/neuronal cell injury were investigated in a rat model of cerebral ischemia/reperfusion (I/R) injury and a neuroblastoma SH-SY5Y cell model of β-amyloid (Aβ) protein fragment 25-35-induced toxicity. Long-term Squina DNA treatment caused dose-dependent increases in mitochondrial antioxidant status and functional capacity in rat brain, heart ventricular, kidney, skeletal muscle, and liver tissues. Squina DNA pretreatment significantly prevented I/R injury in brain tissue. The cerebroprotection was associated with a reversal of I/R-induced impairment in mitochondrial antioxidant status and disruption in membrane integrity. Squina DNA ethanol extract also significantly inhibited the Aβ-induced apoptosis in SH-SY5Y neuronal cells, as evidenced by less caspase 3 and caspase 9 activation as well as mitochondrial cytochrome c release in Aβ-challenged cells. Squina DNA may enhance the resistance of tissues and cells to oxidative stress, particularly in pathological conditions such as stroke and aging-related neurodegenerative diseases.

Recovery of motor deficit, cerebellar serotonin and lipid peroxidation levels in the cortex of injured rats

The sensorimotor cortex and the cerebellum are interconnected by the corticopontocerebellar (CPC) pathway and by neuronal groups such as the serotonergic system. Our aims were to determine the levels of cerebellar serotonin (5-HT) and lipid peroxidation (LP) after cortical iron injection and to analyze the motor function produced by the injury. Rats were divided into the following three groups: control, injured and recovering. Motor function was evaluated using the beam-walking test as an assessment of overall locomotor function and the footprint test as an assessment of gait. We also determined the levels of 5-HT and LP two and twenty days post-lesion. We found an increase in cerebellar 5-HT and a concomitant increase in LP in the pons and cerebellum of injured rats, which correlated with their motor deficits. Recovering rats showed normal 5-HT and LP levels. The increase of 5-HT in injured rats could be a result of serotonergic axonal injury after cortical iron injection. The LP and motor deficits could be due to impairments in neuronal connectivity affecting the corticospinal and CPC tracts and dysmetric stride could be indicative of an ataxic gait that involves the cerebellum.

Iron-dextran injection into the substantia nigra in rats decreases striatal dopamine content ipsilateral to the injury site and impairs motor function

Iron chloride injections into the rat SNc can cause chronic decreases in striatal dopamine (DA) levels. However, changes in striatal DA content after iron-dextran injection into rat SNc have not been completely elucidated. The aim of this work was to measure striatal DA concentrations after iron-dextran injection into the SNc. We divided 40 male Wistar rats into five groups, including control, saline injected then sacrificed 7 days or 30 days later, and iron-dextran injected then sacrificed 7 days or 30 days later. Striatal DA content was measured in control animals and in all animals sacrificed 7 days or 30 days after injection, and motor performance was assessed in iron-dextran and saline injected groups 30 days after injection. The striatal DA levels were determined using HPLC. There were significant (P < 0.05) decreases in DA concentrations in the striatum ipsilateral to the injection site in the iron-dextran treated rats compared to control and saline-injected rats. There were no significant differences in DA concentration between the sham-operated (i.e., saline-injected) and control rats. We also observed motor deficits in the iron-dextran injected rats. The striatal DA reduction observed after iron-dextran injection may be attributable to iron-induced oxidative injury in the SNc. Motor deficits, in turn, may be explained by subsequent disturbances in striatal and cortical dopaminergic neuromodulation.

Oxidative stress-mediated macromolecular damage and dwindle in antioxidant status in aged rat brain regions: Role of l-carnitine and dl-α-lipoic acid

BACKGROUND

The free radical theory of aging has significant relevance in a number of age-related neurological disorders. Too many free radicals create cellular pollution that shuts down energy levels. They have also been implicated in the loss of physiological functioning associated with the aging of post mitotic cells such as the brain. The activities of enzymatic antioxidative defenses decrease in rat brain may be possible causes of age-associated increase in oxidative damage to macromolecules.

METHODS

We determined whether DL-alpha-lipoic acid (100 mg/kg body weight/day), and L-carnitine (300 mg/kg body weight/day) together when administered for 30 days declines the rate of oxidative stress-mediated macromolecular damages such as lipid peroxidation (LPO), protein carbonyl (PCO) and DNA protein cross-links in different anatomic regions (cortex, striatum and hippocampus). The activities of antioxidant enzymes in programmed aging were evaluated in the cortex, striatum and hippocampus of young and aged rat brain regions.

RESULTS

Aged rats elicited a significant decline in the antioxidant status and increase in LPO, PCO and DNA protein cross-links as compared to young rats in all the 3 brain regions. The increase in LPO, PCO and DNA protein cross-links were (35.8%, 35.6%, 43.5%) in cortex, (32.5%, 40.3%, 29.8%) in striatum and (62.7%, 42.4%, 34.9%) in hippocampus, respectively, in aged rats as compared to young rats. Co-supplementation of carnitine and lipoic acid was found to be effective in reducing brain regional LPO, PCO and DNA protein cross-links and in increasing the activities of enzymatic antioxidants in aged rats to near normalcy.

CONCLUSION

The combination of l-carnitine and lipoic acid overcame the oxidative stress induced rate of lipid peroxidation, protein carbonyl formation, accumulation of DNA protein cross-links and deficits in antioxidant enzyme activities in various brain regions of aged rats.

Brain thiobarbituric acid-reactive substances in rats after short periods of ozone exposure

It has been proposed that molecules derived from reactions that occur between the ozone and the lung tissue mediate nonpulmonary effects caused by ozone exposure. Free radicals are among those proposed molecules that flow throughout the bloodstream to other organs producing lipid peroxidation. In order to elucidate on aspect of ozone toxicity mechanisms, we measured the thiobarbituric acid-reactive products (TBARS), as an index of lipid peroxidation, in a variety of brain regions in rats exposed to 1 ppm of ozone for 1, 3, 6, and 9h. Another group exposed to 9h of O(3) plus 3h of clean-air exposure was also included. The results showed an important increase in TBARS content in all the studied structures. Such effect seems to be transient. These findings indicates that acute ozone exposure can produce cerebral peroxidation as it has been found in rats exposed chronically, suggesting an involvement of free radicals in brain effects of ozone exposure.

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.

Lipid peroxidation measurement by thiobarbituric acid assay in rat cerebellar slices

Lipid peroxidation by reactive oxygen species (ROS) is known to be involved in the damaging mechanism of several acute and chronic brain disorders. The most prominent and currently used assay as an index for lipid peroxidation products is the thiobarbituric acid assay (TBA test). It is based on the reactivity of an end product of lipid peroxidation, malondialdehyde (MDA) with TBA to produce a red adduct. However, it is known that the MDA levels are frequently overestimated, that the reaction lacks specificity and mainly reflects the susceptibility of brain tissue to the generation and degradation of newly formed lipid hydroperoxides under the TBA test conditions. The present paper shows that artifactual lipid peroxidation by TBA test conditions can be prevented and that the MDA level overestimation can be minimized in cerebellar slices. This can be done by incubating the slices in a continuous tissue perfusion system, by adding butylated hydroxytoluene (BHT) to the homogenization solutions and by carrying out the assay anaerobically on deproteinizated supernatants of cerebellar slice homogenates. The present research also showed that lipid peroxidation products generated during incubation of the slices by hydrogen peroxide (H2O2) could be measured without artifactual interference by the TBA test conditions.

Oxidative stress in organ preservation: a multifaceted approach to cardioplegia

Every transplant is a reperfused organ and, therefore, undergoes some degree of oxidative damage. Postischemic reperfusion injury results in non-specific free radical-mediated acute endothelial damage, cell death and organ failure. The endothelium is a key site of injury from reactive oxygen species (ROS), and the endothelial cell dysfunction is central to the pathogenesis of arteriosclerosis. Accelerated arteriosclerosis, secondary to chronic allograft rejection, is a major long-term complication of heart transplantation. Therefore, preservation methods that would decrease injury during reperfusion are very important. We have developed a unique preservation solution, with a multifaceted approach, which best preserves the organ from ROS for an extended period of time before transplantation. The advantages of extending this period of preservation include an expansion of the donor pool, by permitting more distant procurement, the ability to perform detailed tissue typing, therefore, improves histocompatibility match and a reduction in emergency surgery as a result of graft rejection.

Mechanisms of hypoxic-ischemic injury in the term infant

The pathogenesis of hypoxic-ischemic brain injury in the term infant is multifactorial and complex. Over the past decade the investigative emphasis has turned to cellular and molecular mechanisms of injury, and it has been increasingly recognized that the neonatal brain differs vastly from the adult brain in terms of response to hypoxia-ischemia. This review will discuss the initiation and evolution of brain injury in the term neonate, and the inherent biochemical and physiologic qualities of the neonatal brain that make its response to hypoxia-ischemia unique. Attention will be given to specific areas of investigation including excitotoxicity, oxidative stress, and inflammation. The coalescence of these entities to a final common pathway of hypoxic-ischemic brain injury will be emphasized.

The Time Course of Hydroxyl Radical Formation following Spinal Cord Injury: The Possible Role of the Iron-Catalyzed Haber-Weiss Reaction

This study explores whether the hydroxyl radical (*OH)-one of the most destructive reactive oxygen species-plays a role in secondary spinal cord injury (SCI). First, we measured the time course of *OH formation in rat spinal tissue after impact SCI by administering salicylate as a trapping agent into the intrathecal space of the cord and measuring the hydroxylation products of salicylate, 2,3- and 2,5-dihydroxybenzoic acid (2,3- and 2,5-DHBA) by HPLC. The 2,3-DHBA concentration was significantly higher in injured spinal tissue than in sham controls at 5 min, 1 and 3 h, but not at 5 h post-injury. Second, we generated *OH by administering H(2)O(2) and FeCl(2)/EDTA (Fenton's reagents) at the concentrations produced by SCI into the gray matter of the cord for 4 h and found that it induced significant cell loss at 24 h post-*OH exposure. Mn (III) tetrakis (4-benzoic acid) porphyrin(MnTBAP)-a broad spectrum reactive species scavenger-significantly reduced *OH-induced cell death. Finally, we generated superoxide and administered FeCl(3)/EDTA in the intrathecal space of the cord at the concentration produced by SCI and measured extracellular *OH formation in the gray matter of the cord by microdialysis sampling. We found that the levels of *OH significantly increased compared to the pre-administration level, indicating that *OH can be produced in vivo by the iron-catalyzed Haber-Weiss reaction. All together, we demonstrated that *OH is an endogenous secondary damaging agent following SCI and the metal-catalyzed Haber-Weiss reaction may contribute to early *OH formation after SCI.

Alpha lipoic acid for dementia

BACKGROUND

Oxidative processes have been implicated in the pathogenesis of neurodegenerative dementias including Alzheimer's disease. Protecting the central nervous system against these damaging mechanisms may be a useful therapeutic approach. Alpha lipoic acid (ALA) is an endogenous antioxidant that interrupts cellular oxidative processes in both its oxidized and reduced forms. These properties might qualify ALA for a modulatory role in the treatment of people with dementia.

OBJECTIVES

To assess the role and clinical efficacy of alpha lipoic acid in the treatment of dementia.

SEARCH STRATEGY

A search of the Specialized Register of the Cochrane Dementia and Cognitive Improvement Group (CDCIG) on 3 February 2003 using the terms 'alpha lipoic acid' and 'thioctic'. The CDCIG Specialized register is updated regularly and contains records from all major health care databases (MEDLINE, EMBASE, PsycInfo, CINAHL) as well as from many trials databases.

SELECTION CRITERIA

All double-blind randomized placebo-controlled trials examining the efficacy of alpha lipoic acid in dementia

DATA COLLECTION AND ANALYSIS

No trials were found that met the selection criteria

MAIN RESULTS

No meta-analysis could be performed. A systematic search of the Specialized Register of the Cochrane Dementia and Cognitive Improvement Group, as well as registers of ongoing and unpublished trials could not identify any studies investigating the use of ALA for dementia.

REVIEWER'S CONCLUSIONS

In the absence of randomized double-blind placebo-controlled trials investigating ALA for dementia, no evidence exists to explore any potential effects. Until data from trials become available for analysis, ALA cannot be recommended for people with dementia.

Fe2+ decreases the taurine-induced Cl- current in acutely dissociated rat hippocampal neurons

The effects of ferrous ions (Fe(2+)) on taurine-induced Cl(-) current (I(tau)) recorded from single neurons, which was freshly isolated from the rat hippocampal CA1 area, were studied with conventional whole-cell recording under voltage-clamp conditions. Using standard pharmacological approaches, we found that the currents gated by concentrations of taurine (<or=10 mM), which existed in about 90% of the hippocampal neurons tested, were predominantly mediated by strychnine-sensitive glycine receptors. When co-applied with taurine, Fe(2+) effectively depressed I(tau) in a concentration-dependent manner, with an IC(50) of 3.76 mM and Hill coefficient of 1.01, while preincubation with 1 mM Fe(2+) alone did not affect the following membrane currents elicited by taurine. The result suggests that resting taurine-gated channels are insensitive to Fe(2+). Since internal cell dialysis with 3 mM Fe(2+) failed to modify I(tau), it was deduced that the site of action of Fe(2+) is extracellular. Furthermore, the Lineweaver-Burke double reciprocal plot of normalized response to taurine against the concentration of taurine illustrated that the depression of I(tau) was noncompetitive, therefore Fe(2+) may act on the glycine receptor-chloride ionophore complex at a site distinct from where taurine binds. Various concentrations of Fe(2+) ranging from 0.1 to 20 mM depressed I(tau) and this extracellular depression was independent of membrane voltage. These results indicate that Fe(2+) decreases I(tau) in acutely dissociated rat hippocampal neurons and the inhibition of glycine receptors by Fe(2+) might be one possible approach through which Fe(2+) induces seizures.

Spinal cord injury increases iron levels: catalytic production of hydroxyl radicals

This study used a weight drop impact injury model to explore the role of iron and the reality of iron-catalyzed hydroxyl radical ((*)OH) formation in secondary spinal cord injury (SCI). The time course of total extracellular iron was measured following SCI by microcannula sampling and atomic absorption spectrophotometry analysis. Immediately following SCI, the total iron concentration increased from an undetectable level to an average of 1.32 microM. The time course of SCI-induced (*)OH-generating catalytic activity in the cord was obtained by determining the ability of tissue homogenate to convert hydrogen peroxide to (*)OH and then measuring 2,3-dihydroxybenzoic acid, a hydroxylation product of salicylate. The concentration of 2,3-DHBA quickly and significantly increased (p <.001) and returned to sham level (p = 1) by 30 min post-SCI. Desferrioxamine (80 and 800 mg/kg body weight) significantly (p <.001) reduced the catalytic activity, suggesting that iron is the major contributor of the activity. Administering FeCl(3) (100 microM)/EDTA (0.5 mM) in ACSF into the cord through a dialysis fiber significantly increased SCI-induced (*)OH production in the extracellular space, demonstrating that Fe(3+) can catalyze (*)OH production in vivo. Our results support that iron-catalyzed (*)OH formation plays a role in the early stage of secondary SCI.

Effect of DL-alpha-lipoic acid on the status of lipid peroxidation and antioxidant enzymes in various brain regions of aged rats

The effect of DL-alpha-lipoic acid on lipid peroxidation and antioxidant enzymes were evaluated in various brain regions of young and aged rats. Lipoate contents of discrete brain regions were also measured. In aged rats, the activities of superoxide dismutase, glutathione peroxidase, glutathione reductase and glucose-6-phosphate dehydrogenase were low whereas thiobarbituric acid reactive substances were found to be high. Catalase activity in various brain regions was little altered in aged rats. Lipoic acid an antioxidant was administered intraperitoneally (100mg/kg body weight per day) for 7 and 14 days. Lipoate administered aged rats showed a duration dependent reduction in the level of lipid peroxidation and elevation in the activities of antioxidant enzymes. There was a rise in the level of lipoate in aged rats after supplementation of lipoate in all the brain regions examined. From our results we conclude that lipoate supplementation had a beneficial effect in both preventing and reversing abnormalities in ageing brain. This beneficial effect was associated with normalization of lipid peroxidation and partial restoration in the activities of various enzymatic antioxidants suggesting that lipoate supplementation could improve brain antioxidant functions in the elderly.

Effects of Fe(2+) on ion channels: Na(+) channel, delayed rectified and transient outward K(+) channels

The effects of Fe(2+) on the properties of three types of ion channels were studied in acutely dissociated rat hippocampal pyramidal neurons from area CA1 at postnatal ages of 7-14 days using the whole cell patch clamp technique. The results indicated that: (1) in the existence of Fe(2+), the activation voltage threshold of transient outward K(+) currents (I(A)) was decreased. The normalized current-voltage curves of activation were well fitted with a single Boltzmann function, and the V(1/2) was 2.44+/-1.14 mV (n=15) in control, whereas 1.79+/-1.53 (n=15), -2.96+/-0.92 (n=14), -5.11+/-1.31 (n=13), -9.05+/-1.64 mV (n=12) in 1, 10, 100 and 1000 microM Fe(2+), respectively. Differences between two groups were significant (P<0.05, n=12-15), except for that between the control and 1 microM (P>0.05, n=15). (2) Fe(2+) caused a left shift of the current-voltage curves of steady-state inactivation of I(A) in a concentration-dependent manner. The curves were well fitted with a single Boltzmann function with similar slope (P>0.05, n=10-13). The V(1/2) were -70.71+/-1.23 (n=13), -71.14+/-1.37 (n=13), -78.21+/-1.17 (n=11), -84.61+/-1.34 (n=12), and -89.68+/-2.59 mV (n=10) in control, 1, 10, 100 and 1000 microM Fe(2+), respectively. Fe(2+) also shifted the current-voltage curves of Na(+) channel steady-state inactivation to more negative depolarization potentials in parallel, with V(1/2), -67.37+/-1.33 mV (n=12) in control, and -67.52+/-1.28 mV (n=12), -68.24+/-1.61 mV (n=10), -71.58+/-1.45 mV (n=10), -76.65+/-1.76 mV (n=9) in 1, 10, 100 and 1000 microM Fe(2+) solutions, respectively. (3) In Fe(2+) solutions, the recovery from inactivation of I(A) was slowed. (4) With application of different concentrations of Fe(2+), the voltage threshold of activation of delayed rectified outward K(+) currents (I(K)) was decreased, while Fe(2+) showed a little inhibition at more positive depolarization. Briefly, the results demonstrated that Fe(2+) is a dose- and voltage-dependent, reversible modulator of I(A), I(K) and Na(+) channels. The results will be helpful to explain the mechanism of Fe(2+) physiological function and Fe(2+) intoxication in the central nervous system.

Low concentrations of estradiol reduce beta-amyloid (25-35)-induced toxicity, lipid peroxidation and glucose utilization in human SK-N-SH neuroblastoma cells

The present studies were undertaken to determine the role of physiologically relevant concentrations of estrogens on amyloid-induced changes in cell viability, metabolic demands, and lipid peroxidation in response to the toxic fragment of beta-amyloid (betaAP 25-35). To this end, SK-N-SH human neuroblastoma cells were exposed to betaAP 25-35 or betaAP 25-35 plus 17beta-estradiol, and cell viability, media glucose use and lactate production were measured at time points ranging from 3 to 15 h for examination of acute effects, or at 48 and 72 h time points for chronic effects. Addition of betaAP 25-35 to SK-N-SH cells decreased the number of viable cells from 5% at 3 h to 35% at 15 h when compared to vehicle controls. Chronic treatment for 48 and 72 h caused decreases in viable cell number of 70% and 65%, respectively. Paradoxically, both glucose utilization and lactate production were found to be increased for the betaAP-treated cells. Concomitant estrogen treatment was found to be neuroprotective, as the severity of the insult on cell viability was decreased by 40% at 15 h and up to 71% at 72 h. Likewise, the addition of 17beta-estradiol decreased both the glucose use and lactate production of the cells. Chronic treatment with betaAP caused increases in lipid peroxidation over vehicle treated controls of 82% and 78% at 48 and 72 h, respectively, while decreases in peroxidation of 48% were seen with simultaneous estrogen treatment. These results indicate that the neuroprotective effects of estrogens against betaAP-induced toxicity are due in part to their capability to decrease lipid peroxidation and may additionally be attributable to decreasing the metabolic load of the cell.

Intranigral iron infusion in the rat. Acute elevations in nigral lipid peroxidation and striatal dopaminergic markers with ensuing nigral degeneration

Iron is known to induce lipid peroxidation and recent evidence indicates that both iron and lipid peroxidation are elevated in the substantia nigra in Parkinson's disease (PD). To test whether excess intranigral iron induces lipid peroxidation, we infused an iron citrate solution (0.63 nmol in 0.25 microL) into the rat substantia nigra and measured nigral thiobarbituric acid reactive products at 1-h, 1-d, 1-wk, and 1-mo postinfusion. In a separate group of iron-infused animals, histologic analysis within the substantia nigra through 1-mo postinfusion was accomplished by thionine- and iron-staining, with concurrent assessment of striatal neurochemical markers. Concentrations of nigral thiobarbituric acid reactive products were significantly elevated at 1 h and 1 d in iron-infused animals compared to vehicle-infused and unoperated animals, with a return to control values by 1 wk. Similarly, striatal dopamine turnover was acutely elevated, suggesting damage to dopaminergic neurons, which was confirmed histologically. Although iron-staining within the iron diffusionary area was increased through the postinfusion month, there was an apparent progression of the cellular character of staining from predominantly neuronal to reactive glial and finally to oligodendroglial by 1 mo postinfusion. This progression of cellular iron-staining may indicate a shifting of infused iron to a more bound unreactive form, thus explaining only an acute elevation in lipid peroxidation through 1 d following intranigral iron infusion. The data indicate that damage to nigral neurons induced by iron infusion is transciently associated with a marker of oxidative damage and supports the possibility that iron-induced oxidative stress contributes to the pathogenesis of PD.

Regional distribution of iron, transferrin, ferritin, and oxidatively-modified proteins in young and aged Fischer 344 rat brains

Iron dysregulation in the brain is thought to contribute to the oxidative damage seen in neurodegenerative diseases including Alzheimer's disease and Parkinson's disease. A role for iron in the oxidative stress thought to contribute to normal ageing is less certain. To better characterize the role of iron in normal ageing, the concentrations of iron, transferrin, ferritin, and protein carbonyl groups are measured in nine separate regions of Fischer 344 rats. The largest (approximately 30%) age-related increases in brain iron concentration are seen in the temporal cortex, medial septum, and cerebellum. Ferritin concentration in these same brain regions increases 50 to 250% with age, while protein carbonyl concentration is only -27 to +4%, of young rats. These results indicate that an increase in the major iron-binding protein ferritin compensates for any age-related increase in iron concentration, and suggest that the increased ferritin is cytoprotective, serving to prevent the accumulation of protein carbonyl groups (a principal product of metal-catalysed oxidation of proteins).

Neurochemical mechanisms in brain injury and treatment: a review

This article reviews cellular energy transformation processes and neurochemical events that take place at the time of brain injury and shortly thereafter emphasizing hypoxia-ischemia, cerebrovascular accident, and traumatic brain injury. New interpretations of established concepts, such as diffuse axonal injury, are discussed; specific events, such as free radical production, excess production of excitatory amino acids, and disruption of calcium homeostasis, are reviewed. Neurochemically-based interventions are also presented: calcium channel blockers, excitatory amino acid antagonists, free radical scavengers, and hypothermia treatment. Concluding remarks focus on the role of clinical neuropsychologists in validation of treatment interventions.

Modulations in antioxidant enzymes in different tissues of marine bivalve Perna viridis during heavy metal exposure

Lipid peroxidation induced by metals at sub-lethal levels, alter physiological and biochemical characteristics of biological systems. To counter the detrimental effects of the prooxidant activity of metals, a group of antioxidant enzyme systems function in the organisms. The present study was performed to investigate into the lipid peroxidation product formation due to the exposure to effects of the metals namely aluminium, lead and cadmium at sub-lethal concentrations and the biological response through protective antioxidant enzyme activity in the marine mussels, Perna viridis Lin.. This organism is a known bioindicator and bioconcentrator of metals in the environment. The results of the present study were: (a) accumulation of lead showed a definite linear increase during the period of exposure whereas aluminium and cadmium showed fluctuations. Mantle and gill tissues showed greater accumulation of metals when compared to digestive gland; (b) lead and aluminium induced lipid peroxidation was greater in tissues than the peroxidation induced by cadmium. Cadmium induced peroxidation was observed only after the day 7 of the exposure; (c) anti-oxidant enzymes activity levels were significantly higher in digestive gland and mantle than gills; (d) mantle was observed to significantly contribute to the organismal response to lipid peroxidation as indicated by high activity levels of anti-oxidant enzymes.

Free radicals enhance basal release of D-[3H]aspartate from cerebral cortical synaptosomes

Excessive generation of free radicals has been implicated in several pathological conditions. We demonstrated previously that peroxide-generated free radicals decrease calcium-dependent high K(+)-evoked L[3H]-glutamate release from synaptosomes while increasing calcium-independent basal release. The present study evaluates the nonvesicular release of excitatory amino acid neurotransmitters, using D-[3H]aspartate as an exogenous label of the cytoplasmic pool of L-glutamate and L-aspartate. Isolated presynaptic nerve terminals from the guinea pig cerebral cortex were used to examine the actions and interactions of peroxide, iron, and desferrioxamine. Pretreatment with peroxide, iron alone, or peroxide with iron significantly increased the calcium-independent basal release of D-[3H]aspartate. Pretreatment with desferrioxamine had little effect on its own but significantly limited the enhancement by peroxide. High K(+)-evoked release in the presence of Ca2+ was enhanced by peroxide but not by iron. These data suggest that peroxide increases nonvesicular basal release of excitatory amino acids through Fenton-generated hydroxyl radicals. This release could cause accumulation of extracellular excitatory amino acids and contribute to the excitotoxicity associated with some pathologies.

Mitochondria from Alzheimer's fibroblasts show decreased uptake of calcium and increased sensitivity to free radicals

Many of the biological abnormalities seen in samples of the brain and other tissues from patients with Alzheimer's disease, are consistent with an excessive action of oxygenic free radicals. Mitochondria from fibroblasts grown in tissue culture from skin samples taken at autopsy from patients with histologically confirmed Alzheimer's disease, take up significantly less calcium than do fibroblast mitochondria from age matched non-demented controls. Following exposure to oxygenic free radicals generated by adding ferrous ions to the incubation mixture, calcium uptake is increased to a greater extent in Alzheimer's mitochondria than in controls. At the doses used, pretreatment with the lazaroid antioxidant drug U-74500A, or with the iron chelator deferoxamine, prevents the free radical induced increase in calcium uptake by control mitochondria, but provides only partial protection for Alzheimer's mitochondria. These observations suggest that Alzheimer's fibroblast mitochondria have impaired calcium transport processes and show increased sensitivity to oxygenic free radicals.

Role of nerve growth factor in oxidant homeostasis: glutathione metabolism

Free radicals are generated in the CNS by ongoing oxygen metabolism and biological events associated with injury and inflammation. Increased free radical levels may also persist in some chronic neurological diseases and in the aged. Nerve growth factor (NGF) is a member of the neurotrophin family of proteins that can regulate neuronal development, maintenance, and recovery from injury. NGF protected rat pheochromocytoma PC12 cells, an adrenal chromaffin-like NGF-responsive cell line, from the oxidant stress accompanying hydrogen peroxide treatment by stimulating GSH levels and enzymes in the GSH metabolism cycle and in the GSH/GSH peroxidase antioxidant redox system, a ubiquitous cellular antioxidant system. Specifically, NGF increased gamma-glutamylcysteine synthetase (GCS) activity, the rate-limiting enzyme for GSH synthesis, by 50% after 9 h and GSH levels by 100% after 24 h of treatment. NGF stimulated GSH peroxidase by 30% after 3 days and glucose 6-phosphate dehydrogenase by 50% after 2 days. Treatment with NGF and cycloheximide, or actinomycin D, which inhibit protein and RNA synthesis, respectively, blocked the NGF stimulation of GCS and glucose 6-phosphate dehydrogenase. Increased GSH levels due to NGF treatment were responsible for the significant protection of PC12 cells from hydrogen peroxide-induced stress. Pretreatment of PC12 cells with NGF for 24 h rescued cells from the toxic effects of the extracellular hydrogen peroxide generated by the glucose/glucose oxidase system but did not rescue cells that were subjected to GSH deprivation due to treatment with 10 microM L-buthionine-(S,R)-sulfoximine, an inhibitor of GCS.(ABSTRACT TRUNCATED AT 250 WORDS)

Quinolinic acid is a potent lipid peroxidant in rat brain homogenates

In this study, we describe the lipoperoxidative effect of quinolinic acid (QUIN) in vitro. The formation of thiobarbituric acid reactive products (TBA-RP), an index of lipid peroxidation, was measured in rat brain homogenates after incubation at 37 degrees C for 30 min in the presence of QUIN and some structurally and metabolically related compounds such as Kynurenine, Kynurenic acid, Glutamate, Aspartate and Kainate. Concentrations of QUIN in the range of 20 to 80 microM increased lipid peroxidation in a concentration-dependent manner from about 15% to about 50%. Kynurenic acid, a compound metabollically related to QUIN that can block its neurotoxic actions in vivo, also inhibited completely the QUIN-induced TBA-RP formation in our system. Lipid fluorescent material, another index of lipid peroxidation was also found increased by 49% after incubation with 40 microM QUIN. It is concluded that lipid peroxidation may be a damaging process involved in the neurotoxicity of QUIN.

Oxygen free radicals and brain dysfunction

Oxygen free radicals, any chemical moiety containing an oxygen atom with an unpaired electron in the outer orbital shell, are generated during many normal biochemical reactions in living tissue. The unpaired electron makes these compounds highly reactive and they can initiate disruptive peroxidation reactions with various substrates important to the survival of cells such as proteins, lipids and nucleic acids. A fairly complex defense system has evolved to protect living tissue from free radicals and to minimize the damage they might cause. Neurons are especially vulnerable to free radical attack and impaired defenses or exposure to excess free radicals can lead to neuronal death. Free radicals contribute to neuronal loss in cerebral ischemia and hemorrhage and may be involved in the degeneration of neurons in epilepsy, schizophrenia, tardive dyskinesia, normal aging, Parkinson's Disease and Alzheimer's Disease. The development of drugs that limit or prevent the attack of free radicals on neurons would be an important advance in the treatment of these conditions.

Autopsy samples of Alzheimer's cortex show increased peroxidation in vitro

The formation of thiobarbituric acid-reactive products was measured as an index of peroxidation by oxygen free radicals in homogenates of frontal cortex and cerebellum from brains taken at autopsy and verified histologically as being Alzheimer's (n = 6) or normal (n = 6). Compared with controls, basal peroxidation is significantly higher in Alzheimer's cortex, and this difference is also evident in the presence of exogenous iron. Peroxidation in cerebellum and levels of total glutathione, RNA, and DNA in cortex and cerebellum do not differ significantly between Alzheimer's brain and controls. Iron-induced peroxidation in cortex is reduced by the lazaroid U-74500A, with calculated IC50 values that are significantly higher in Alzheimer's samples (10 microM) than in controls (2.5 microM). These observations suggest that cerebral cortex from Alzheimer's patients differs from controls with respect to in vitro peroxidation.