Magnesium deprivation decreases cellular reduced glutathione and causes oxidative neuronal death in murine cortical cultures

The Role of Magnesium in Parkinson's Disease: Status Quo and Implications for Future Research

Neurodegenerative diseases represent an increasing economic, social, and, above all, medical burden worldwide. The second most prevalent disease in this category is Parkinson's disease, surpassed only by Alzheimer's. It is a treatable but still incurable systemic disease with a pathogenesis that has not yet been elucidated. Several theories are currently being developed to explain the causes and progression of Parkinson's disease. Magnesium is one of the essential macronutrients and is absolutely necessary for life as we know it. The magnesium cation performs several important functions in the cell in the context of energetic metabolism, substrate metabolism, cell signalling, and the regulation of the homeostasis of other ions. Several of these cellular processes have been simultaneously described as being disrupted in the development and progression of Parkinson's disease. The relationship between magnesium homeostasis and the pathogenesis of Parkinson's disease has received little scientific attention to date. The aim of this review is to summarise and critically evaluate the current state of knowledge on the possible role of magnesium in the pathogenesis of Parkinson's disease and to outline possible future directions for research in this area.

Protein Carbonyl, Lipid Peroxidation, Glutathione and Enzymatic Antioxidant Status in Male Wistar Brain Sub-regions After Dietary Copper Deficiency

Copper a quintessential transitional metal is required for development and function of normal brain and its deficiency has been associated with impairments in brain function. The present study investigates the effects of dietary copper deficiency on brain sub-regions of male Wistar rats for 2-, 4- and 6-week. Pre-pubertal rats were divided into four groups: negative control (NC), copper control (CC), pairfed (PF) and copper deficient (CD). In brain sub regions total protein concentration, glutathione concentration and Cu-Zn SOD activity were down regulated after 2-, 4- and 6 weeks compared to controls and PF groups. Significant increase in brain sub regions was observed in protein carbonyl and lipid peroxidation concentration as well as total SOD, Mn SOD and catalase activities after 2-, 4- and 6 weeks of dietary copper deficiency. Experimental evidences indicate that impaired copper homeostasis has the potential to generate reactive oxygen species enhancing the susceptibility to oxidative stress by inducing up- and down-regulation of non-enzymatic and enzymatic profile studied in brain sub regions causing loss of their normal function which can consequently lead to deterioration of cell structure and death if copper deficiency is prolonged.

Magnesium Sulfate Attenuates Lethality and Oxidative Damage Induced by Different Models of Hypoxia in Mice

Mg²⁺ is an important cation in our body. It is an essential cofactor for many enzymes. Despite many works, nothing is known about the protective effects of MgSO₄ against hypoxia-induced lethality and oxidative damage in brain mitochondria. In this study, antihypoxic and antioxidative activities of MgSO₄ were evaluated by three experimental models of induced hypoxia (asphyctic, haemic, and circulatory) in mice. Mitochondria protective effects of MgSO₄ were evaluated in mouse brain after induction of different models of hypoxia. Antihypoxic activity was especially pronounced in asphyctic hypoxia, where MgSO₄ at dose 600 mg/kg showed the same activity as phenytoin, which used as a positive control (P < 0.001). In the haemic model, MgSO₄ at all used doses significantly prolonged latency of death. In circulatory hypoxia, MgSO₄ (600 mg/kg) doubles the survival time. MgSO₄ significantly decreased lipid peroxidation and protein carbonyl and improved mitochondrial function and glutathione content in brain mitochondria compared to the control groups. The results obtained in this study showed that MgSO₄ administration has protective effects against lethality induced by different models of hypoxia and improves brain mitochondria oxidative damage.

Effects of dietary sodium selenite and organic selenium sources on immune and inflammatory responses and selenium deposition in growing pigs

The study was conducted to compare effects of different dietary Se sources (sodium selenite [NaSe], Se-enriched yeast [Se yeast] or L-selenomethionine [SeMet]) and one Se-deficient control diet on the expression of selected genes, hematological and clinical biochemical parameters, and muscle morphology in two parallel trials with finisher pigs. Se concentrations in blood plasma and tissues were also monitored. From the pigs in one of the parallel groups, muscle samples obtained from Musculus longissimus dorsi (LD) before and during the trial were examined. The pigs in the other parallel group were challenged once with lipopolysaccharide (LPS) intravenously. Transcriptional analyses of LD showed that selenogenes SelenoW and H were higher expressed in pigs fed Se-supplemented diets compared with control. Furthermore, the expression of interferon gamma and cyclooxygenase 2 was lower in the Se-supplemented pigs versus control. In whole blood samples prior to LPS, SelenoN, SelenoS and thioredoxin reductase 1 were higher expressed in pigs fed NaSe supplemented feed compared with the other groups, possibly indicating a higher level of oxidative stress. After LPS exposure glutathione peroxidase 1 and SelenoN were more reduced in pigs fed NaSe compared with pigs fed organic Se. Products of most above-mentioned genes are intertwined with the oxidant-antioxidant system. No significant effects of Se-source were found on hematologic parameters or microscopic anatomy. The Se-concentrations in various skeletal muscles and heart muscle were significantly different between the groups, with highest concentrations in pigs fed SeMet, followed by those fed Se yeast, NaSe, and control diet. Consistent with previous reports our results indicate that dietary Se at adequate levels can support the body's antioxidant system. Our results indicate that muscle fibers of pigs fed organic Se are less vulnerable to oxidative stress compared with the other groups.

Low levels of serum magnesium are associated with poststroke cognitive impairment in ischemic stroke patients

PURPOSE

Population-based studies have revealed a high prevalence of cognitive impairment after stroke. We aimed to determine the impact of serum magnesium (Mg²⁺) levels on the occurrence of poststroke cognitive impairment (PSCI).

PATIENTS AND METHODS

Acute ischemic stroke patients (n = 327) were enrolled in our study and serum Mg²⁺ levels were assessed on admission. The cognitive performance of each patient was evaluated using the Mini-Mental State Examination (MMSE) at a 1-month follow-up visit.

RESULTS

One hundred five (32.1%) patients were diagnosed with PSCI at 1-month poststroke. The serum Mg²⁺ levels in both the PSCI group and the non-PSCI group were significantly lower than those in normal control group (P<0.001). In addition, the PSCI group had lower levels of serum Mg²⁺ compared to the non-PSCI group (P=0.003). In the binary logistic regression analysis, a serum Mg²⁺ level of ≤0.82 mmol/L was significantly associated with an increased risk of developing PSCI by the 1-month follow-up (OR 2.236, 95% CI 1.232-4.058, P=0.008), as was age (OR 1.043, 95% CI 1.014-1.073, P=0.003).

CONCLUSION

Our results demonstrate the existence of a significant association between low levels of serum Mg²⁺ and the occurrence of PSCI 1-month poststroke, and these results suggest that low levels of serum Mg²⁺ on admission may serve as a risk factor for developing PSCI by 1-month poststroke.

Influence of magnesium supplementation on movement side effects related to typical antipsychotic treatment in rats

Chronic use of typical antipsychotic haloperidolis related to movement disturbances such as parkinsonism, akathisia and tardive dyskinesia which have been related to excitotoxicity in extrapyramidal brain areas, requiring their prevention and treatment. In the current study we evaluated the influence of the magnesium on prevention (for 28days before-), reversion (for 12days after-) and concomitant supplementation on haloperidol-induced movement disorders in rats. Sub-chronic haloperidol was related to orofacial dyskinesia (OD) and catalepsy development, increased generation of reactive species (RS) and levels of protein carbonyl (PC) in cortex, striatum and substantia nigra (SN) in all experimental protocols. When provided preventatively, Mg reduced the increase of OD and catalepsy time 14 and 7days after haloperidol administration, respectively. When supplemented after haloperidol-induced OD establishment, Mg reversed this behavior after 12days, while catalepsy was reversed after 6days of Mg supplementation.When Mg was concomitantly supplemented with haloperidol administration, OD and catalepsy were prevented. Moreover, Mg supplementation was able to prevent the RS generation in both cortex and SN, reducing PC levels in all brain areas evaluated. When supplemented after haloperidol, Mg reversed RS generation in cortex and striatum, decreasing PC levels in SN and striatum.The co-administration of haloperidol and Mg supplementation prevented RS generation in cortex, striatum and SN, and PC levels in the SN.These outcomes indicate that Mg supplementation may be a useful alternative to prevent movement disturbances resulting of classic antipsychotic pharmacotherapy as haloperidol.

Effects of cell phone radiation on lipid peroxidation, glutathione and nitric oxide levels in mouse brain during epileptic seizure

The objective of the this study was to evaluate the effects of cellular phone radiation on oxidative stress parameters and oxide levels in mouse brain during pentylenetetrazole (PTZ) induced epileptic seizure. Eight weeks old mice were used in the study. Animals were distributed in the following groups: Group I: Control group treated with PTZ, Group II: 15min cellular phone radiation+PTZ treatment+30min cellular phone radiation, Group III: 30min cellular phone radiation+PTZ treatment+30min cellular phone radiation. The RF radiation was produced by a 900MHz cellular phone. Lipid peroxidation, which is the indicator of oxidative stress was quantified by measuring the formation of thiobarbituric acid reactive substances (TBARS). The glutathione (GSH) levels were determined by the Ellman method. Tissue total nitric oxide (NOx) levels were obtained using the Griess assay. Lipid peroxidation and NOx levels of brain tissue increased significantly in group II and III compared to group I. On the contrary, GSH levels were significantly lower in group II and III than group I. However, no statistically significant alterations in any of the endpoints were noted between group II and Group III. Overall, the experimental findings demonstrated that cellular phone radiation may increase the oxidative damage and NOx level during epileptic activity in mouse brain.

Magnesium Supplementation Prevents and Reverses Experimentally Induced Movement Disturbances in Rats: Biochemical and Behavioral Parameters

Reserpine administration results in a predictable animal model of orofacial dyskinesia (OD) that has been largely used to access movement disturbances related to extrapyramidal oxidative damage. Here, OD was acutely induced by reserpine (two doses of 0.7 mg/kg subcutaneous (s.c.)), every other day for 3 days), which was administered after (experiment 1) and before (experiment 2) magnesium (Mg) supplementation (40 mg/kg/mL, peroral (p.o.)). In experiment 1, Mg was administered for 28 days before reserpine treatment, while in experiment 2, it was initiated 24 h after the last reserpine administration and was maintained for 10 consecutive days. Experiment 1 (prevention) showed that Mg supplementation was able to prevent reserpine-induced OD and catalepsy development. Mg was also able to prevent reactive species (RS) generation, thus preventing increase of protein carbonyl (PC) levels in both cortex and substantia nigra, but not in striatum. Experiment 2 (reversion) showed that Mg was able to decrease OD and catalepsy at all times assessed. In addition, Mg was able to decrease RS generation, with lower levels of PC in both cortex and striatum, but not in substantia nigra. These outcomes indicate that Mg is an important metal that should be present in the diet, since its intake is able to prevent and minimize the development of movement disorders closely related to oxidative damage in the extrapyramidal brain areas, such as OD.

Pretreatment with magnesium ameliorates lipopolysaccharide-induced liver injury in mice

BACKGROUND

Lipopolysaccharide (LPS), a component of the outer membrane of Gram-negative bacteria, is involved in the pathogenesis of sepsis. LPS administration induces systemic inflammation that mimics many of the initial clinical features of sepsis and has deleterious effects on several organs including the liver and eventually leading to septic shock and death. The present study aimed to investigate the protective effect of magnesium (Mg), a well known cofactor in many enzymatic reactions and a critical component of the antioxidant system, on hepatic damage associated with LPS-induced endotoxima in mice.

METHODS

Mg (20 and 40mg/kg, po) was administered for 7 consecutive days. Systemic inflammation was induced 1h after the last dose of Mg by a single dose of LPS (2mg/kg, ip) and 3h thereafter plasma was separated, animals were sacrificed and their livers were isolated.

RESULTS

LPS-treated mice suffered from hepatic dysfunction revealed by histological observation, elevation in plasma transaminases activities, C-reactive protein content and caspase-3, a critical marker of apoptosis. Liver inflammation was evident by elevation in liver cytokines contents (TNF-α and IL-10) and MPO activity. Additionally, oxidative stress was manifested by increased liver lipoperoxidation, glutathione depletion, elevated total nitrate/nitrite (NOx) content and glutathione peroxidase (GPx) activity. Pretreatment with Mg largely mitigated these alternations.

CONCLUSION

Pretreatment with Mg protects the liver from the acute injury which occurs shortly after septicemia.

Bradykinin B₁ antagonism inhibits oxidative stress and restores Na+K+ ATPase activity in diabetic rat peripheral nervous system

Diabetic peripheral neuropathy is one the most common complications of diabetes mellitus and frequently results in clinically significant morbidities such as pain, foot ulcers and amputations. The diabetic condition progresses from early functional changes to late, poorly reversible structural changes. The chronic hyperglycemia measured alongside diabetes development is associated with significant damage and failure of various organs. In the present study diabetes was induced in male Wistar rats by a single dose of streptozotocin (STZ) and the association between the BKB1-R and the oxidative stress and Na+-K+ ATPase activity in nervous tissues was analysed. The results showed that the resulting hyperglycemia induced a reduction of the neuronal electrical function integrity and increased oxidative stress in the sciatic nerve homogenates of 30 days diabetic rats. Malondialdehyde (MDA) used as a marker of oxidative stress was elevated whereas Biological Antioxidant Potential (BAP), glutathion (GSH) levels and superoxide dismutase (SOD) activity were decreased. Treatment of the rats 3 days before the end of the 4 week period with the BKB1 antagonist R-954 restored the neuronal activity and significantly attenuated the oxidative stress as shown by the level of the various markers returning close to levels found in control rats. Our results suggest that the BKB1-R subtype is overexpressed in sciatic nerve during the STZ-induced diabetes development as evidenced by inhibitory effects of the BKB1-R antagonist R-954. The beneficial role of BKB1-R antagonist R-954 for the treatment of diabetic neuropathy is also suggested.

Brain protection by rapeseed oil in magnesium-deficient mice

Diets given for 30 days with various mono-(MUFA) and poly-(PUFA) unsaturated fatty acid contents were evaluated for brain protection in magnesium-deficient mice: a commercial and three synthetic diets (n-6PUFA, n-3PUFA and MUFA-based chows enriched with 5% corn/sunflower oils 1:3, with 5% rapeseed oil and with 5% high oleic acid sunflower oil/sunflower oil 7:3, respectively). Unlike magnesium deprivation, they induced significant differences in brain and erythrocyte membrane phospholipid fatty acid compositions. n-3PUFA but not other diets protected magnesium-deficient mice against hyperactivity and moderately towards maximal electroshock- and NMDA-induced seizures. This diet also inhibited audiogenic seizures by 50%, preventing animal deaths. Because, like n-6PUFA diet, matched control MUFA diet failed to induce brain protections, alpha-linolenate (ALA) rather than reduced n-6 PUFA diet content is concluded to cause n-3PUFA neuroprotection. Present in vivo data also corroborate literature in vitro inhibition of T type calcium channels by n-3 PUFA, adding basis to ALA supplementation in human anti-epileptic/neuroprotective strategies.

A potential protective effect of alpha-tocopherol on vascular complication in spinal cord reperfusion injury in rats

Background

Paraplegia remains a potential complication of spinal cord ischemic reperfusion injury (IRI) in which oxidative stress induced cyclooxygenase activities may contribute to ischemic neuronal damage. Prolonged administration of vitamin E (α-TOL), as a potent biological antioxidant, may have a protective role in this oxidative inflammatory ischemic cascade to reduce the incidence of paraplegia. The present study was designed to evaluate the preventive value of α-TOL in IRI of spinal cord.

Methods

For this study, 50 male Sprague-Dawley rats were used and divided into five experimental groups (n = 10): Control group (C); α-TOL control group (CE) which received intramuscular (i.m.) α-TOL injections (600 mg/kg); Sham operated group (S), IRI rats were subjected to laparotomy and clamping of the aorta just above the bifurcation for 45 min, then the clamp was released for 48 hrs for reperfusion; and IRIE rats group, received 600 mg/kg of α-TOL i.m. twice weekly for 6 weeks, followed by induction of IRI similar to the IRI group. At the end of the experimental protocol; motor, sensory and placing/stepping reflex evaluation was done. Plasma nitrite/nitrate (NOx) was measured. Then animals' spinal cord lumbar segments were harvested and homogenized for measurement of the levels of prostaglandin E₂ (PGE₂), malondialdehyde (MDA) and advanced oxidation products (AOPP), while superoxide dismutase (SOD) and catalase (CAT) activity were evaluated.

Results

Induction of IRI in rats resulted in significant increases in plasma levels of nitrite/nitrate (p < 0.001) and spinal cord homogenate levels of PGE₂, MDA, advanced oxidation protein products AOPP and SOD with significant reduction (p < 0.001) in CAT homogenate levels. Significant impairment of motor, sensory functions and placing/stepping reflex was observed with IRI induction in the spinal cord (p < 0.001). α-TOL administration in IRIE group significantly improved all the previously measured parameters compared with IRI group.

Conclusions

α-TOL administration significantly prevents the damage caused by spinal cord IRI in rats with subsequent recovery of both motor and sensory functions. Alpha-tocopherol improves the oxidative stress level with subsequent reduction of the incidence of neurological deficits due to spinal cord IRI conditions.

Alterations in trace elements and oxidative stress in uremic patients with dementia

The present study was conducted to compare the trace elements and oxidative status between uremic patients with and without dementia. Chronic hemodialysis patients with dementia (n = 20) and without dementia (n = 25), and age-matched healthy volunteers (n = 20) were enrolled. The nutritional status, blood levels of trace elements aluminum (Al), zinc (Zn), copper (Cu), magnesium (Mg) and iron (Fe), malondialdehyde (MDA), and protein carbonyl production, antioxidant enzymes glutathione peroxidase (GPx), and glutathione reductase (GR) activities were measured. No significant difference in nutritional status or clinical characteristics was observed between nondementia and dementia patients. However, uremic patients with dementia have significantly higher Al, Cu, and Mg and lower Zn concentrations, as well as increased Cu/Zn ratio in comparison to nondementia patients. There were statistically significant increased MDA and carbonyl production and decreased GPx and GR activities in dementia patients. Furthermore, the significant associations of Al, Mg, and Cu/Zn ratio with oxidative status in patients with dementia were noted. The dementia may initially worsen with abnormal metabolism of trace elements and oxidative stress occurrence. Our results suggest that abnormalities in trace element levels are associated with oxidative stress and may be a major risk factor in the dementia development of uremic patients.

Threshold to N-methyl-D-aspartate-induced seizures in mice undergoing chronic nutritional magnesium deprivation is lowered in a way partly responsive to acute magnesium and antioxidant administrations

Magnesium deficiency may be induced by a diet impoverished in magnesium. This nutritional deficit promotes chronic inflammatory and oxidative stresses, hyperexcitability and, in mice, susceptibility to audiogenic seizures. Potentiation by low-magnesium concentrations of the opening of N-methyl-d-aspartate (NMDA) receptor/calcium channel in in vitro and ex vivo studies, and responsiveness to magnesium of in vivo brain injury states are now well established. By contrast, little or no specific attention has been, however, paid to the in vivo NMDA receptor function/excitability in magnesium deficiency. The present work reports for the first time that, in mice undergoing chronic nutritional deprivation in magnesium (35 v. 930 parts per million for 27 d in OF1 mice), NMDA-induced seizure threshold is significantly decreased (38 % of normal values). The attenuation in the drop of NMDA seizure threshold (percentage of reversal) was 58 and 20 % upon acute intraperitoneal administrations of magnesium chloride hexahydrate (28 mg magnesium/kg) and the antioxidant ebselen (20 mg/kg), respectively. In nutritionally magnesium-deprived animals, audiogenic seizures are completely prevented by these compound doses. Taken as a whole, our data emphasise that chronic magnesium deprivation in mice is a nutritional in vivo model for a lowered NMDA receptor activation threshold. This nutritional model responds remarkably to acute magnesium supply and moderately to acute antioxidant administration.

Pilot study to determine the hemodynamic safety and feasibility of magnesium sulfate infusion in children with severe traumatic brain injury

OBJECTIVE

Magnesium sulfate is neuroprotective in preclinical models, but there are limited safety data regarding its clinical use for pediatric traumatic brain injury. We conducted a pilot study in children with severe traumatic brain injury to a) examine if magnesium sulfate decreases mean arterial pressure, decreases cerebral perfusion pressure, increases intracranial pressure, or adversely effects cardiac conduction; and b) determine the feasibility of a multiple-center trial of magnesium sulfate.

DESIGN

Double-blinded, placebo-controlled, randomized pilot trial with repeated measurement of hemodynamic variables.

SETTING

Two pediatric trauma centers.

PATIENTS

Six children (3 months to 18 yrs) with severe traumatic brain injury.

INTERVENTIONS

: Magnesium sulfate (50 mg/kg) bolus followed by (8.3 mg/kg/hr) infusion for 24 hr vs. equivolume placebo.

MEASUREMENTS AND MAIN RESULTS

We screened 96 patients with severe traumatic brain injury during 24 months; 20 were eligible for enrollment, six provided informed consent, four received magnesium sulfate, and two received placebo. Before and after study drug infusion, we repeatedly measured blood ionized magnesium concentration, mean arterial pressure, cerebral perfusion pressure, intracranial pressure, heart rate, and corrected QT interval. Mean age (7.9 yrs), mean highest Glasgow Coma Scale score (6), gender (33% boys), inflicted injury rate (17%), and case mortality rate (17%) did not differ between those enrolled and those not enrolled. Compared with baseline, magnesium sulfate did not change cerebral perfusion pressure, intracranial pressure, heart rate, or corrected QT interval. Mean arterial pressure was unchanged until the late phase of magnesium sulfate infusion, when mean arterial pressure rose (82 +/- 5 vs. 93 +/- 6 mm Hg, p < .05). Sixty-four percent of corrected QT interval determinations obtained in the first 6 days after injury exceeded 440 msecs; 12% were >600 msecs.

CONCLUSIONS

In children with severe traumatic brain injury, magnesium sulfate administration did not decrease mean arterial pressure or cerebral perfusion pressure or adversely effect cardiac conduction. Our data suggest that enrollment of brain-injured children in a therapeutic trial remains challenging. These results provide information important for clinical trials of magnesium sulfate in children with severe traumatic brain injury.

Sensitivity of cerebellar glutathione system to neonatal ionizing radiation exposure

Reactive oxygen species (ROS) are relevant components of living organisms that, besides their role in the regulation of different important physiological functions, when present in excess are capable to affect cell oxidative status, leading to damage of cellular molecules and disturbance of normal cell function. ROS accumulation has been associated with a variety of conditions such as neurodegenerative diseases and ionizing radiation exposure. Cell ability to counteract ROS overproduction depends on the capacity of the endogenous antioxidant defenses--which includes the glutathione (GSH) system--to cope with. Since developing central nervous system (CNS) is especially sensitive to ROS-induced damage, the aim of the present work was to evaluate ROS, reduced GSH and oxidized glutathione (GSSG) levels in the cerebellum at different developmental ages after irradiation, in order to test if any changes were induced on these key oxidative stress-related cellular markers that might explain the high cerebellar vulnerability to radiation-induced injury. Since intracellular levels of GSH are maintained by glutathione reductase (GSHr), this enzymatic activity was also evaluated. Newborn Wistar rats were irradiated in their cephalic ends and the different parameters were measured, from 1h to 90 days post-irradiation. Results showed that an early transient increase in ROS levels followed by a decrease in cerebellar weight at 3-5 days post-irradiation were induced. An increase in cerebellar GSH levels was induced at 30 days after irradiation, together with a decrease in GSHr activity. These results support the hypothesis that ROS may represent a marker of damage prior to radiation-induced cell death. In contrast, it would be suggested that GSH system might play a role in the compensatory mechanisms triggered to counteract radiation-induced cerebellar damage.

N-Acetylcysteine Partially Reverses Oxidative Stress and Apoptosis Exacerbated by Mg-Deficiency Culturing Conditions in Primary Cultures of Rat and Human Hepatocytes

OBJECTIVE

The effects of magnesium (Mg) deficiency on the rate of oxidative stress and apoptosis in primary cultures of human hepatocytes were compared to cultured rat hepatocytes. The possible reversion by N-acetylcysteine (NAC) in Mg-deficient culturing conditions was evaluated.

METHODS

Incubations were conducted for up to 72 h in media containing a deficient (0-0.4 mM) or a physiological (0.8 mM) Mg concentration, and in the presence or absence of NAC after 24 h of culture in these Mg concentration conditions.

RESULTS

We obtained similar profiles in terms of apoptosis and oxidative stress in primary cultures of human hepatocytes, as compared to rat hepatocytes, i.e. a Mg concentration-dependent effect on the caspase-3 activity and GSH levels after 72 h of culture, caspase-3 activity being highest and GSH levels being lowest in Mg-free cultures. The addition of NAC to culture media after the first 24 h of culture increased GSH concentrations. This was accompanied in Mg-deficient cultures by a decrease in both the caspase-3 activity and the lipid peroxidation. However, when culturing hepatocytes with physiological Mg concentrations, an increase in both caspase-3 activity and lipid peroxidation was observed.

CONCLUSIONS

Our results indicate that Mg deficiency exacerbates the rate of apoptosis in cultured hepatocytes, associated with an increase in oxidative stress, the sensitivity of human hepatocytes being equivalent to that of rat hepatocytes. They also indicate a dual role of NAC and/or GSH, i.e. protective for hepatocytes placed in a Mg-deficient environment, while deleterious for hepatocytes placed in a Mg-physiological environment.

Magnesium deficiency impairs fear conditioning in mice

Magnesium (Mg2+) is one of the most abundant cations found in the body. In the central nervous system, Mg2+ plays an important role in the function of N-methyl-D-aspartate (NMDA)-type glutamate receptors, which are centrally involved in memory processing. Despite the relatively large concentration of Mg2+ in the CNS, little is known about the behavioral consequences of Mg2+ deficiency. The purpose of this study was to address this issue by assessing fear conditioning and related behaviors in mice maintained on normal or Mg(2+)-deficient diets. Young adult male C57Bl/6J mice were placed on a control or Mg(2+)-deficient diet, and testing was conducted between 10 and 21 days later. Magnesium-deficient mice exhibited impairments in contextual and cued fear conditioning. These impairments could not be attributed to changes in locomotor activity, exploration, or pain sensitivity. Furthermore, Mg(2+)-deficient mice were more sensitive to the convulsant effects of a peripheral injection of NMDA (100 mg/kg, IP). The results suggest that magnesium deficiency can lead to specific impairments in emotional memory. Such impairments may be related to hypersensitivity of NMDA-type glutamate receptors in Mg(2+)-deficient mice.

Magnesium depletion enhances cisplatin-induced nephrotoxicity

PURPOSE

Nephrotoxicity and magnesium (Mg)-depletion are well-known side effects to cisplatin (CP) treatment. The purpose of this present study was to investigate the role of Mg on CP induced changes in renal function. CP induced renal dysfunction was achieved by treatment with CP or vehicle (2.5 mg/kg) once weekly for 3 weeks. Since the CP-induced renal damage, including tubular reabsorption defects, is most prominent within the outer medulla (OM), changes in the expression pattern of OM aquaporins and sodium transporters including the Na,K-ATPase (alpha-subunit), type III Na,H-exchanger (NHE3), aquaporin 1 (AQP1) and 2 (AQP2) and the Na,K,2Cl-cotransporter (NKCC2) were investigated by semi-quantitative Western blotting.

EXPERIMENTAL DESIGN

Rats had access to either a diet with standard Mg or to a Mg-depleted diet. Cisplatin was administered to female Wistar rats once a week for 3 weeks according to four regimens: (1) Cisplatin 2.5 mg/kg body weight i.p., to rats on a diet with standard Mg, (2) Cisplatin 2.5 mg/kg body weight i.p., to rats on a diet with low Mg, (3) Isotonic NaCl 2.5 ml/kg body weight i.p., to rats on a diet with standard Mg, (4) Isotonic NaCl 2.5 ml/kg body weight i.p., to rats on a diet with low Mg.

RESULTS

CP had no effect on plasma creatinine or urea in rats with standard Mg intake, but the expression of all five transporters was significantly reduced when compared to vehicle treated rats on standard Mg-intake. Vehicle treated rats on low Mg-intake had a significant reduction in the expression of Na,K-ATPase, NHE3 and NKCC2, but unchanged expression levels of AQP1 or AQP2 when compared to standard treated controls. Forty percent of the CP-treated rats on low Mg-intake died during the experiment and the remaining animals had marked increased plasma creatinine and urea. Furthermore, the Western blot analysis revealed an almost complete disappearance of all four transporters, suggesting a dramatic synergistic effect of CP and Mg-depletion on renal function including the expression pattern of outer medullary sodium transporters and aquaporins.

CONCLUSIONS

This study indicates a substantial additive effect of Mg-depletion on cisplatin induced renal toxicity as evidenced by significant changes in plasma creatinine and urea, renal failure induced mortality and loss of renal transporters. This should give cause for concern since the nephrotoxicity observed during cisplatin treatment might be substantiated by the known Mg-loss associated with cisplatin treatment especially in patients suffering from intense gastro-intestinal side effects.

The protective effect of L-cysteine and glutathione on the adult and aged rat brain (Na+,K+)-ATPase and Mg2+-ATPase activities in galactosemia in vitro

The aim of this study was to evaluate whether the addition of the antioxidants L-cysteine (Cys) or the reduced glutathione (GSH) could reverse the alterations of brain total antioxidant status (TAS) and the modulated activities of the enzymes (Na+,K+)-ATPase, and Mg2+-ATPase in adult or aged rat brain homogenates induced by galactosemia in vitro. Mixture A [mix. A: galactose-1-phosphate (Gal-1-P, 2 mM) plus galactitol (Galtol, 2 mM) plus galactose (Gal, 4 mM) = classical galactosemia] or mixture B [mix. B: Galtol (2 mM) plus Gal (1 mM) = galactokinase deficiency galactosemia] were preincubated in the presence or absence of Cys (0.83 mM) or GSH (0.83 mM) with adult or aged brain homogenates at 37 degrees C for 1 h. TAS and the enzyme activities were determined spectrophotometrically. Mix. A or mix. B preincubation with the adult brain resulted in a significant (Na+,K+)-ATPase inhibition (-30%) and a Mg2+-ATPase stimulation (+300% and +33%, respectively), whereas lower modifications of the enzyme activities (p < 0.001) were found in the aged brain. Gal mixtures decreased TAS by 40% (p < 0.001) and by 20% (p < 0.01) in adult and aged samples, respectively. The antioxidants significantly increased TAS resulting in the reversion of (Na+,K+)-ATPase inhibition and Mg2+-ATPase stimulation by mix. B only. The inhibitory effect of Gal and its derivatives on brain (Na+,K+)-ATPase and their stimulatory effect on Mg2+-ATPase are being decreased with age, probably due to the producion of free radicals. Cys and GSH increased TAS resulting in a reversion of the inhibited (Na+,K+)-ATPase in both models of the in vitro galactosemia and the stimulated Mg2+-ATPase in galactokinase deficiency galactosemia only.

Mg2+-ATPase activity in suckling rat brain regions in galactosaemia in vitro. l-Cysteine and glutathione effects

Mg2+-ATPase activity is implicated with Mg2+ homeostasis, maintaining high brain intracellular Mg2+ content. We determined the in vitro effects of galactose-1-phosphate (Gal-1-P), galactitol (Galtol) and galactose (Gal) {mix A=Gal-1-P(2 mM)+Galtol(2 mM)+Gal(4 mM) concentrations commonly found in patients with classical galactosaemia} or Galtol and Gal {mix B=Galtol(2 mM)+Gal(1 mM) concentrations usually measured in patients with galactokinase deficiency galactosaemia} on Mg2+-ATPase activity in suckling rat brain frontal cortex, hippocampus or hypothalamus homogenates. Gal-1-P significantly (p<0.001) enhanced enzyme activity in all the brain areas measured, whereas Galtol and Gal failed to cause any effect in the same regions. Mix A remarkably (p<0.001) stimulated Mg2+-ATPase in the studied areas. On the contrary, mix B had no effect. The supplementation of antioxidant l-cysteine (Cys) or reduced Glutathione (GSH) in mix A failed to reverse to normal the activated enzyme in frontal cortex and hypothalamus, while they significantly reduced Mg2+-ATPase activation in hippocampus.

CONCLUSIONS

(a) Gal-1-P enormously activated Mg2+-ATPase in all the studied brain regions, (b) Mix A, also, excessively activated the enzyme in the same areas, (c) the production of free radicals may be implicated with the enzyme activation and (d) Cys or GSH significantly decreased the activated hippocampal Mg2+-ATPase.

Dietary magnesium depletion does not promote oxidative stress but targets apical cells within the mouse caput epididymidis

It is well documented that a dietary deficiency in magnesium can induce oxidative stress and an inflammatory response in animal models. In our study, we have investigated these responses in the mouse epididymis after mice had been fed a magnesium-deficient diet for a 2-week duration. The extracellular and intracellular concentrations of magnesium where shown to be depleted on this diet. This was followed, however, only in the liver of the Mg-deficient animals, by an increase in both alpha 2-macroglobulin (alpha-2m), an acute phase marker, and interleukin-6 transcripts suggesting that an inflammatory response had been initiated. These changes were correlated with a decrease in circulating neutrophils. To address the question of whether or not peroxidation was induced in mouse epididymis following hypomagnesia, we have monitored the level of endogenous peroxidation, their ability to respond to induced peroxidation as well as the expression and activity of the enzymatic glutathione peroxidase (GPX) antioxidant family. To evaluate if the epididymis had evolved specific protections against peroxidation, other organs such as the liver and the kidney were monitored in parallel. We detected no evidence for increased peroxidation in any of the mouse organs tested. However, GPX activity was found to be significantly lower in the liver and the kidney of Mg-deficient animals while it was unchanged in the epididymides of the same animals during the deficiency. Histological analysis of the epididymis showed no major difference in the overall cytological aspect of the organ. Segment 2 of the caput, however presented a significant increase in the number of apically located cells or blebbing cells. Immunohistochemical analysis proved that these cells were epididymal apical cells and not infiltrated leukocytes. These observations suggested that the mouse caput epididymidis segment 2 specifically responded to Mg deficiency via the apical cells. Finally, a comparative analysis of stress response genes was conducted in control and magnesium-deficient caput epididymidis samples. It brought forward some genes that might be involved in the peculiar response of the caput epithelium following hypomagnesia.

Potent mammalian cerebroprotection and neuronal cell death inhibition are afforded by a synthetic antioxidant analogue of marine invertebrate cell protectant ovothiols

Implicit strategies for neuroprotection in the adult brain include GABAA receptor activation, N-methyl-d-aspartate receptor and sodium voltage-gated channel inhibition. Ironically, these same targets may be harmful to the immature or developing brain. Protection has been demonstrated for both immature and mature brain with the use of a synthetic ovothiol analogue. The following beneficial effects have been demonstrated in mice: protection against audiogenic seizures, brain structures with clear-cut delineation of ibotenate-challenged white and grey matter lesions along with exceptional early and delayed protections, and potent cerebral cell death inhibition. The compound lacks both GABAergic activity and sodium channel blocker properties, which may help explain the lack of toxicity normally expressed in an immature brain utilizing these agents [J.W. Olney (2002) Neurotoxicology, 93, 1-10]. The oxidized form of the compound is virtually devoid of antioxidant activity. In vivo it exhibits cerebroprotective properties similar to those of reduced compounds endowed with antioxidant properties. This unexpected finding has prompted an extensive in vitro exploration of underlying molecular mechanisms that have led to the identification of several recycling mechanisms consistent with non rate-limiting conversion of oxidized to reduced compound forms. Taken as a whole, this work offers an unique combined in vitro and in vivo support that: (i). antioxidant therapy, here engineered from marine invertebrate egg protectants, may be a valuable strategy in protecting both mammalian adult and developing brain; and (ii). recycling (thiol-disulphide exchange) properties of the oxidized form of an antioxidant compound are as important as the antioxidant potential exhibited by a bioactive reduced antioxidant in certain neuroprotective processes.

Magnesium deficiency induces apoptosis in primary cultures of rat hepatocytes

The effects of extracellular magnesium (Mg) concentration on the rate of apoptosis in rat hepatocytes in primary culture were examined. After overnight attachment, incubations were conducted for up to 72 h in serum-free media containing low (0-0.4 mmol/L), physiological (0.8 mmol/L) or high (2 and 5.6 mmol/L) Mg concentrations. At 72 h, we observed numerous rounded hepatocytes on top of a shrunken cell monolayer at extracellular Mg concentrations < 0.8 mmol/L. These morphological features were associated with Mg-dependent differences in the total protein levels. The various Mg concentrations did not affect DNA synthesis; however, at a concentration < 0.8 mmol/L, the susceptibility of cultured rat hepatocytes to oxidative stress was increased as shown by the reduced glutathione concentration (10.6 +/- 2.8 vs. 37.3 +/- 4.1 nmol/mg protein with 0 and 0.8 mmol/L, respectively; P < 0.05) and increased lipid peroxidation (0.36 +/- 0.03 vs. 0.21 +/- 0.01 nmol malondialdehyde/mg protein with 0 and 0.8 mmol/L, respectively; P < 0.05). Fluorescence microscopy after Hoechst dye staining revealed numerous apoptotic figures in Mg-free monolayers compared with 0.8 and 5.6 mmol/L Mg conditions. These observations were confirmed quantitatively by flow-cytometric analysis after propidium iodide staining. The proportion of subdiploid cells decreased with increasing Mg concentration; for example, it was greater at 72 h in Mg-free cultures (76%) than in cultures containing 0.8 mmol/L or 5.6 mmol/L Mg (28%; P < 0.05). Caspase-3 was highly activated in Mg-free cultures after 48 h of treatment compared with 0.8 and 5.6 mmol/L conditions (P < 0.05). Overall, these results show that extracellular Mg deficiency has a negative effect on the survival of cultured rat hepatocytes by inducing apoptosis; however, supplementation of extracellular Mg did not reduce the spontaneous apoptosis that occurred over time in rat hepatocyte cultures.

Some magnesium status indicators and oxidative metabolism responses to low-dietary magnesium are affected by dietary copper in postmenopausal women

OBJECTIVE

A study with human volunteers was conducted to ascertain whether a low intake of copper (Cu) would exacerbate the response to a deficient intake of magnesium (Mg).

METHODS

Nineteen postmenopausal women, age 47 to 78 y, completed a metabolic unit study as designed. For 162 d, nine women were fed a diet containing 1.0 mg of Cu/2000 kcal and 10 women were fed 3.0 mg of Cu/2000 kcal. Diets contained 99 or 399 mg of Mg/2000 kcal for 81 d in a randomized, double-blind, crossover design. Differences were considered significant when statistical analysis yielded P </= 0.05.

RESULTS

Magnesium balance was highly positive when the dietary magnesium was high but non-positive when dietary magnesium was low. Copper balance was more positive when dietary copper was high than when it was low. Plasma ionized magnesium was decreased by magnesium deprivation. Several variables measured indicated that low dietary copper affected the response to magnesium deprivation or vice-versa. Red blood cell magnesium was lower when dietary copper was low than when it was high. When dietary magnesium was low, serum copper was lower in the women fed marginal copper than in those fed luxuriant copper. When dietary magnesium was high, low dietary copper did not affect serum copper. Magnesium deprivation decreased red blood cell superoxide dismutase when dietary copper was luxuriant; when dietary copper was low, magnesium deprivation did not have much of an effect. Apolipoprotein A1 was lowest when dietary magnesium and copper were low. The order in which the magnesium restriction occurred affected the response of a number of variables to this treatment including concentrations of serum magnesium and total and low-density lipoprotein cholesterol.

CONCLUSIONS

The findings indicated that, in short-term magnesium depletion experiments, the response to depletion can be influenced by other dietary factors including copper intake and a high magnesium intake before depletion, and that 100 mg of Mg/d is inadequate for postmenopausal women.

Magnesium reduces free radical concentration and preserves left ventricular function after direct current shocks

OBJECTIVE

Our objective was to determine if magnesium reduces free radicals generated by direct current countershock and preserves left ventricular contractile function.

BACKGROUND

We have previously shown that magnesium reduces free radicals in a coronary occlusion-reperfusion model, and therefore also might reduce free radical generation by direct current shocks.

METHODS

In eight swine weighing 18-27 kg (mean: 22 kg), using electron paramagnetic resonance, we monitored continuously the coronary sinus concentration of ascorbate free radical, a measure of free radical generation (total oxidative flux). Epicardial shocks (30 J) using a truncated exponential biphasic waveform (5/5 ms) were administered. Each animal received two shocks, one without and one with magnesium, 80 mg/min IV, beginning 10 min before the shock and continuing to 15 min after the shock. Percent fractional area shortening of the left ventricular cavity was determined by 2-dimensional echocardiography.

RESULTS

Magnesium shocks resulted in a significantly lower increase in the ascorbate free radical concentration (0.6+/-4.6%) than no-magnesium shocks (16+/-3.3%, P<0.05) at 12 min after the shock. Total radical flux was reduced 72% (P<0.05), and left ventricular fractional area shortening was preserved: baseline: 69+/-2.6%, no-magnesium shocks: 41+/-2.8% (P<0.05, versus baseline) and magnesium shocks 61+/-3.7%.

CONCLUSIONS

Magnesium pre-treatment reduced oxygen free radicals generated by direct current shocks; post-shock left ventricular contractile function was not impaired. Magnesium may be cardioprotective during epicardial ('surgical') defibrillation.