Biomedical subjects

C M Wannmacher

Publications and source records attributed to C M Wannmacher.

At least 19 recordsLinked to original sources

PubMed2001

In vitro stimulation of oxidative stress in cerebral cortex of rats by the guanidino compounds accumulating in hyperargininemia.

Hyperargininemia is a metabolic disorder biochemically characterized by tissue accumulation of arginine and other guanidino compounds. Convulsions, lethargy and psychomotor delay or cognitive deterioration are predominant clinical features of this disease. Although neurologic symptoms predominate in this disorder, their pathophysiology is still unknown. In the present study we investigated the in vitro effects of arginine, N-acetylarginine, argininic acid and homoarginine on some oxidative stress parameters in rat brain in the hope to identify a possible mechanism for the brain damage in hyperargininemia. Chemiluminescence, total radical-trapping antioxidant potential (TRAP), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) activities were measured in the cerebral cortex of rats in the presence of various concentrations of these compounds. The results showed that all guanidino compounds tested significantly increased chemiluminescence and decreased TRAP at concentrations similar to those observed in the tissue of hyperargininemic patients. Furthermore, these compounds inhibited CAT and GSH-Px activities to varying extents, with GSH-Px activity being more susceptible to their action. In turn, argininic acid inhibited all enzyme activities, and its main action was also directed towards GSH-Px. The results suggest that oxidative stress caused by guanidino compounds may be involved in the brain dysfunction amongst other potential pathophysiological mechanisms observed in hyperargininemia.

Age Factors↗

PubMed2001

Reduction of large neutral amino acid levels in plasma and brain of hyperleucinemic rats.

Neurological dysfunction is common in patients with maple syrup urine disease (MSUD). However, the mechanisms underlying the neuropathology of this disorder are poorly known. In the present study we investigated the effect of acute hyperleucinemia on plasma and brain concentrations of amino acids. Fifteen-day-old rats were injected subcutaneously with 6 micromol L-leucine per gram body weight. Controls received saline in the same volumes. The animals were sacrificed 30--120 min after injection, blood was collected and their brain rapidly removed and homogenized. The amino acid concentrations were determined by HPLC using orthophtaldialdehyde for derivatization and fluorescence for detection. The results showed significant reductions of the large neutral amino acids (LNAA) L-phenylalanine, L-tyrosine, L-isoleucine, L-valine and L-methionine, as well as L-alanine, L-serine and L-histidine in plasma and of L-phenylalanine, L-isoleucine, L-valine and L-methionine in brain, as compared to controls. In vitro experiments using brain slices to study the influence of leucine on amino acid transport and protein synthesis were also carried out. L-Leucine strongly inhibited [14C]-L-phenylalanine transport into brain, as well as the incorporation of the [14C]-amino acid mixture, [14C]-L-phenylalanine and [14C]-L-lysine into the brain proteins. Although additional studies are necessary to evaluate the importance of these effects for MSUD, considering previous findings of reduced levels of LNAA in plasma and CSF of MSUD patients during crises, it may be speculated that a decrease of essential amino acids in brain may lead to reduction of protein and neurotransmiter synthesis in this disorder.

Amino Acids↗

PubMed2001

Phenylalanine and phenylpyruvate inhibit ATP diphosphohydrolase from rat brain cortex.

The main objective of the present study was to characterize the inhibition by phenylalanine and phenylpyruvate of ATP diphosphohydrolase activity in synaptosomes from the brain cortex of rats. This enzyme participates together with a 5'-nucleotidase in adenosine formation from the neurotransmitter, ATP, in the synaptic cleft. The inhibition of ATP diphosphohydrolase was competitive for nucleotide hydrolysis but 5'-nucleotidase was not affected by these metabolites. Furthermore, the two substances inhibited enzyme activity by acting at the same binding site. If the enzyme inhibition observed in vitro also occurs in the brain of PKU patients, it may promote an increase in ATP levels in the synaptic cleft. In this case, the neurotoxicity of ATP could possibly be one of the mechanisms leading to the characteristic brain damage of phenylketonuria.

5'-Nucleotidase↗

PubMed2001

Inhibition of rat brain Na+, K+-ATPase activity induced by homocysteine is probably mediated by oxidative stress.

The objective of the present study was to investigate the effects of preincubation of hippocampus homogenates in the presence of homocysteine or methionine on Na+, K+-ATPase and Mg2+-ATPase activities in synaptic membranes of rats. Homocysteine significantly inhibited Na+, K+-ATPase activity, whereas methionine had no effect. Mg2+-ATPase activity was not altered by the metabolites. We also evaluated the effect of incubating glutathione, cysteine, dithiothreitol, trolox, superoxide dismutase and GM1 ganglioside alone or incubation with homocysteine on Na+, K+-ATPase activity. Tested compounds did not alter Na+, K+-ATPase and Mg2+-ATPase activities, but except for trolox, prevented the inhibitory effect of homocysteine on Na+, K+-ATPase activity. These results suggest that inhibition of this enzyme activity by homocysteine is possibly mediated by free radicals and may contribute to the neurological dysfunction found in homocystinuric patients.

Animals↗

PubMed2001

Inhibition of Na+,K+-ATPase activity from rat hippocampus by proline.

Na+,K+-ATPase and Mg2+-ATPase activities were determined in the synaptic plasma membranes from hippocampus of rats subjected to chronic and acute proline administration. Na+,K+-ATPase activity was significantly reduced in chronic and acute treatment by 33% and 40%, respectively. Mg2+-ATPase activity was not altered by any treatment. In another set of experiments, synaptic plasma membranes were prepared from hippocampus and incubated with proline or glutamate at final concentrations ranging from 0.2 to 2.0 mM. Na+,K+-ATPase, but not Mg2+-ATPase was inhibited (30%) by the two amino acids. In addition, competition between proline and glutamate for the enzyme activity was observed, suggesting a common binding site for these amino acids. Considering that Na+,K+-ATPase activity is critical for normal brain function, the results of the present study showing a marked inhibition of this enzyme by proline may be associated with the neurological dysfunction found in patients affected by type II hyperprolinemia.

Animals↗

PubMed2001

L-pyroglutamic acid inhibits energy production and lipid synthesis in cerebral cortex of young rats in vitro.

In the present study we investigated the effects of L-pyroglutamic acid (PGA), which predominantly accumulates in the inherited metabolic diseases glutathione synthetase deficiency (GSD) and gamma-glutamylcysteine synthetase deficiency (GCSD), on some in vitro parameters of energy metabolism and lipid biosynthesis. We evaluated the rates of CO2 production and lipid synthesis from [U-14C]acetate, as well as ATP levels and the activities of creatine kinase and of the respiratory chain complexes I-IV in cerebral cortex of young rats in the presence of PGA at final concentrations ranging from 0.5 to 3 mM. PGA significantly reduced brain CO2 production by 50% at the concentrations of 0.5 to 3 mM, lipid biosynthesis by 20% at concentrations of 0.5 to 3 mM and ATP levels by 52% at the concentration of 3 mM. Regarding the enzyme activities, PGA significantly decreased NADH:cytochrome c oxireductase (complex I plus CoQ plus complex III) by 40% at concentrations of 0.5-3.0 mM and cytochrome c oxidase activity by 22-30% at the concentration of 3.0 mM, without affecting the activities of succinate dehydrogenase, succinate:DCPIP oxireductase (complex II), succinate:cytochrome c oxireductase (complex II plus CoQ plus complex III) or creatine kinase. The results strongly indicate that PGA impairs brain energy production. If these effects also occur in humans, it is possible that they may contribute to the neuropathology of patients affected by these diseases.

Animals↗

PubMed2001

Reduced Na(+), K(+)-ATPase activity in erythrocyte membranes from patients with phenylketonuria.

Na(+), K(+)-ATPase activity was determined in erythrocyte membranes from 12 phenylketonuric patients of both sexes, aged 8.8 +/- 5.0 y, with plasma phenylalanine levels of 0.64 +/- 0.31 mM. The in vitro effects of phenylalanine and alanine on the enzyme activity in erythrocyte membranes from healthy individuals were also investigated. We observed that Na(+), K(+)-ATPase activity was decreased by 31% in erythrocytes from phenylketonuric patients compared with normal age-matched individuals (p < 0.01). We also observed a significant negative correlation between erythrocyte Na(+), K(+)-ATPase activity and plasma phenylalanine levels (r = -0.65; p < 0.05). All PKU patients with plasma phenylalanine levels higher than 0.3 mM had erythrocyte Na(+), K(+)-ATPase activity below the normal range. Phenylalanine inhibited in vitro erythrocyte Na(+), K(+)-ATPase activity by 22 to 34%, whereas alanine had no effect on this activity. However, when combined with phenylalanine, alanine prevented Na(+) K(+)-ATPase inhibition. Considering that reduction of Na(+), K(+)-ATPase activity occurs in various neurodegenerative disorders leading to neuronal loss, our previous observations showing a significant reduction of Na(+), K(+)-ATPase activity in brain cortex of rats subjected to experimental phenylketonuria and the present results, it is proposed that determination of Na(+), K(+)-ATPase activity in erythrocytes may be a useful peripheral marker for the neurotoxic effect of phenylalanine in phenylketonuria.

Adolescent↗

PubMed2001

Chronic postnatal administration of methylmalonic acid provokes a decrease of myelin content and ganglioside N-acetylneuraminic acid concentration in cerebrum of young rats.

Levels of methylmalonic acid (MMA) comparable to those of human methylmalonic acidemia were achieved in blood (2-2.5 mmol/l) and brain (1.35 umol/g) of rats by administering buffered MMA, pH 7.4, subcutaneously twice a day from the 5th to the 28th day of life. MMA doses ranged from 0.76 to 1.67 umol/g as a function of animal age. Control rats were treated with saline in the same volumes. The animals were sacrificed by decapitation on the 28th day of age. Blood was taken and the brain was rapidly removed. Medulla, pons, the olfactory lobes and cerebellum were discarded and the rest of the brain ("cerebrum") was isolated. Body and "cerebrum" weight were measured, as well as the cholesterol and triglyceride concentrations in blood and the content of myelin, total lipids, and the concentrations of the lipid fractions (cholesterol, glycerolipids, phospholipids and ganglioside N-acetylneuraminic acid (ganglioside-NANA)) in the "cerebrum". Chronic MMA administration had no effect on body or "cerebrum" weight, suggesting that the metabolites per se neither affect the appetite of the rats nor cause malnutrition. In contrast, MMA caused a significant reduction of plasma triglycerides, but not of plasma cholesterol levels. A significant diminution of myelin content and of ganglioside-NANA concentration was also observed in the "cerebrum". We propose that the reduction of myelin content and ganglioside-NANA caused by MMA may be related to the delayed myelination/cerebral atrophy and neurological dysfunction found in methylmalonic acidemic children.

Animals↗

PubMed2001

Inhibition of in vitro CO2 production and lipid synthesis by 2-hydroxybutyric acid in rat brain.

2-Hydroxybutyric acid appears at high concentrations in situations related to deficient energy metabolism (e.g., birth asphyxia) and also in inherited metabolic diseases affecting the central nervous system during neonatal development, such as "cerebral" lactic acidosis, glutaric aciduria type II, dihydrolipoyl dehydrogenase (E3) deficiency, and propionic acidemia. The present study was carried out to determine the effect of 2-hydroxybutyric acid at various concentrations (1-10 mM) on CO2 production and lipid synthesis from labeled substrates in cerebral cortex of 30-day-old Wistar rats in vitro. CO2 production was significantly inhibited (30-70%) by 2-hydroxybutyric acid in cerebral cortex prisms, in total homogenates and in the mitochondrial fraction. We also demonstrated a significant inhibition of lipid synthesis (20-45%) in cerebral cortex prisms and total homogenates in the presence of 2-hydroxybutyric acid. However, no inhibition of lipid synthesis occurred in homogenates free of nuclei and mitochondria. The results indicate an impairment of mitochondrial energy metabolism caused by 2-hydroxybutyric acid, a fact that may secondarily lead to reduction of lipid synthesis. It is possible that these findings may be associated with the neuropathophysiology of the situations where 2-hydroxybutyric acid is accumulated.

Analysis of Variance↗

PubMed2000

Propionic and L-methylmalonic acids induce oxidative stress in brain of young rats.

The in vitro effects of propionic and L-methylmalonic acids on some parameters of oxidative stress were investigated in the cerebral cortex of 21-day-old rats. Chemiluminescence, thiobarbituric acid-reactive substances (TBA-RS) and total radical-trapping antioxidant capacity (TRAP) were measured in brain tissue homogenates in the presence of propionic or L-methylmalonic acids at concentrations ranging from 1 to 10mM. Both acids significantly increased chemiluminescence and TBA-RS and decreased TRAP, indicating a simulation of lipid peroxidation and a reduction of tissue antioxidant potential. Other organic acids tested which accumulate in some organic acidemias (suberic, sebacic, adipic, 3-methylglutaric and 4-hydroxybutyric acids) did not affect these parameters. This study provides evidence that free radical generation may participate in the neurological dysfunction of propionic and methylmalonic acidemias.

Animals↗

PubMed2000

Effect of phenylalanine and p-chlorophenylalanine on Na+, K+-ATPase activity in the synaptic plasma membrane from the cerebral cortex of rats.

Na+, K+-ATPase activity was measured in synaptic plasma membrane from cerebral cortex of Wistar rats subjected to experimental phenylketonuria, i.e., chemical hyperphenylalaninemia induced by subcutaneous administration of 5.2 micromol phenylalanine / g body weight (twice a day) plus 0.9 micromol p-chlorophenylalanine / g body weight (once a day). The treatment was performed from the 6th to the 14th postpartum day and rats were killed 12 h after the last injection. Synaptic plasma membrane from cerebral cortex was prepared by a discontinuous density sucrose gradient for Na+, K+-ATPase activity determination. The results showed that the enzyme activity was decreased by 30% in animals subjected to experimental phenylketonuria when compared to control. The in vitro effects of the drugs on Na+, K+-ATPase activity were also investigated. Phenylalanine and p-chlorophenylalanine inhibited the enzyme activity and this inhibition was reversed by alanine. In addition, competition between phenylalanine and p-chlorophenylalanine for binding to the enzyme was observed, suggesting a common binding site for these substances. Our results suggest that reduction of Na+, K+-ATPase activity may be one of the mechanisms related to the brain dysfunction observed in human PKU.

Animals↗

PubMed2000

Platelet Na+, K+-ATPase activity as a possible peripheral marker for the neurotoxic effects of phenylalanine in phenylketonuria.

The in vitro effects of phenylalanine or alanine alone or combined on Na+, K+-ATPase activity in membranes from human platelets were investigated. The enzyme activity was assayed in membranes prepared from platelet-rich plasma of healthy donors. Phenylalanine or alanine were added to the assay to final concentrations of 0.3 to 1.2 mM, similar to those found in plasma of phenylketonuric patients. Phenylalanine inhibited Na+, K+-ATPase activity by 20-50% [F(4,25)=11.47 ; p<0.001]. Alanine had no effect on Na+, K+-ATPase activity but when combined with phenylalanine prevented the enzyme inhibition. These results, allied to others previously reported on brain Na+, K+-ATPase activity, may reflect a general inhibitory effect of phenylalanine on this important enzyme activity. Therefore, it is possible that measurement of Na+, K+-ATPase activity in platelets from PKU patients may be a useful peripheral marker for the neurotoxic effects of phenylalanine.

Alanine↗

PubMed2000

Inhibition of energy production in vitro by glutaric acid in cerebral cortex of young rats.

The present study investigated the effects of glutaric acid (GA), which predominantly accumulates in glutaric acidemia type I (GA-I), on some in vitro parameters of energy metabolism in cerebral cortex of rats. We first evaluated CO2 production from [U-14C] acetate, as well as ATP levels in brain of young Wistar rats. The effect of the acid on the activities of the respiratory chain complexes were also investigated. GA was tested at final concentrations ranging from 0.5 to 5.0 mM. GA significantly reduced brain CO2 production by 50% at the concentrations of 0.5 to 3.0 mM, ATP levels by 25% at the concentration of 3.0 mM, succinate:cytochrome C oxireductase (complex II plus CoQ plus complex III) by 25% at 5 mM concentration, and NADH:cytochrome C oxireductase (complex I plus CoQ plus complex Ill) by 25% at 2.5 and 5 mM concentrations. The results strongly indicate that GA impairs brain energy production. If these effects also occur in humans, it is possible that they may contribute to the neuropathology of patients affected by GA-I.

Acetates↗

PubMed2000

Phenylalanine inhibition of the phosphorylation of cytoskeletal proteins from cerebral cortex of young rats is prevented by alanine.

BACKGROUND: Phenylalanine has been considered the main responsible agent for the brain damage that occurs in phenylketonuria. METHODS AND RESULTS: In this work we studied the effect of this amino acid on the in vitro phosphorylation of cytoskeletal proteins of the cerebral cortex of rats. We observed that 2 mM phenylalanine, a concentration usually found in the plasma of phenylketonuric patients, decreased the in vitro 32P incorporation into these proteins. In addition, we investigated the effect of alanine on the inhibition of 32P incorporation into cytoskeletal proteins caused by phenylalanine. We observed that 0.5 mM alanine did not alter 32P incorporation but prevented the inhibition provoked by phenylalanine. CONCLUSION: In case the inhibition of cytoskeletal protein phosphorylation by phenylalanine also occurs in human phenylketonuria, it is possible that alanine supplementation to the phenylalanine-restricted diet may be beneficial to these patients.

Age Factors↗

PubMed1999

In vitro inhibition of Na+,K(+)-ATPase activity from rat cerebral cortex by guanidino compounds accumulating in hyperargininemia.

Hyperargininemia is a metabolic disorder biochemically characterized by tissue accumulation of arginine (Arg) and other guanidino compounds (GC). Convulsions, lethargy and psychomotor delay are predominant clinical features of this disease. Considering that some GC are epileptogenic and cause a decrease in membrane fluidity and that Na+,K(+)-ATPase, a membrane-bound enzyme, is essential for cellular excitability and is decreased in experimental and human epilepsy, in the present study we determined the in vitro effects of Arg, N-acetylarginine (NAA), argininic acid (AA) and homoarginine (HA) on the activity of Na+,K(+)-ATPase in the synaptic plasma membrane from cerebral cortex of young rats in the hope to identify a possible mechanism for the brain damage in hyperargininemia. The results showed that all GC tested, except Arg, significantly inhibited Na+,K(+)-ATPase activity at concentrations similar to those observed in plasma and CSF of patients with hyperargininemia. In addition, competition between NAA, AA and HA for the binding to the enzyme was observed, suggesting a common binding site for the GC. It is therefore possible that the inhibitory effect of GC on Na+,K(+)-ATPase may be related to the brain dysfunction observed in hyperargininemia.

Animals↗

PubMed1999

Chronic early leucine administration induces behavioral deficits in rats.

Sustained levels of leucine comparable to those of human Maple Syrup Urine Disease (MSUD) were achieved in blood and brain of rats by subcutaneous leucine administration twice a day from the 6th to the 28th day of life. Control rats were treated with saline in the same volumes. Behavioral studies using aversive and nonaversive tasks were performed during adult age. Chronic early leucine treatment impaired acquisition of a two-way shuttle avoidance task and altered habituation to an open field. Our results suggest that early postnatal leucine administration induces long-lasting behavioral deficits.

Animals↗

PubMed1999

Effect of chemically induced propionic acidemia on neurobehavioral development of rats.

High levels of propionic acid (PPA) comparable to those of human propionic acidemia were achieved in blood (1-5 mmol/l) and brain (1 micromol/g) of rats by administering saline-buffered propionate (pH 7.4) subcutaneously twice a day from the 6th to the 28th day of life. PPA doses ranged from 1.44 to 1.92 micromol/g body weight as a function of animal age. Control rats were treated with saline in the same volumes. Growth and development of physical landmarks were assessed by monitoring the following parameters daily: body weight, upper incisor eruption, eye opening, and hair coat. Development of some reflexes was also monitored, and a specific subset of motor skills was evaluated at days 14 and 21 of life by the free-fall righting test and the spontaneous alternation test. Chronic PPA administration had no effect on body weight, cerebral cortex weight, or cerebellum weight, but caused slight but significant delays in the day of appearance of hair coat and eye opening, indicating an effect of PPA on the development of physical parameters. Free-fall righting was impaired in PPA-treated animals. On the other hand, PPA administration had no effect on the performance of the animals in the spontaneous alternation tests. Long-term effects of early PPA administration were investigated by assessing animal performance in an aversive task (two-way shuttle avoidance task) and in a nonaversive (open-field task) behavioral task at 60 days of age. PPA-treated rats did not habituate to the open field, and presented a lack of retention of the shuttle-avoidance task. Our results suggest that early postnatal PPA administration to rats alters normal development and induces long-term behavioral deficits in aversive and nonaversive tasks.

Acidosis↗

PubMed1999

Inhibition of rat brain lipid synthesis in vitro by 4-hydroxybutyric acid.

4-Hydroxybutyric acid (4HB) is accumulated in succinic semialdehyde dehydrogenase deficiency, an inherited metabolic disease severely affecting the CNS during postnatal development. Thus, the present study was designed to evaluate the in vitro influence of 4HB on lipid synthesis and CO2 production from [U-14C] acetate in cerebral cortex of 30-day-old Wistar rats. In the presence of 4HB, there was an inhibition of lipid synthesis in cerebral cortex prisms and homogenates. However, no inhibition of lipid synthesis occurred in the homogenates free of nuclei and mitochondria. In addition, CO2 production was inhibited by 4HB in cerebral cortex prisms, and homogenates and in the mitochondrial fraction. These results might possibly be explained by an impairment of mitochondrial metabolism by 4HB which may secondarily inhibit lipid synthesis. The results reported here may help to better understand the neuropathophysiology of 4-hydroxybutyric aciduria.

Acetates↗