RESUMEN
The polyamines spermidine (SPD) and spermine (SPM) are implicated in nerve cell degeneration and regeneration. Over 70% of circulating polyamines are associated with red blood cells (RBC). Against this background we have analysed RBC polyamines in two neurodegenerative disorders, amyotrophic lateral sclerosis (ALS) and Parkinson's disease (PD). Twenty patients with the sporadic form of ALS, 20 patients with PD, and 20 healthy controls were studied. The highest levels of SPD and SPM were found in the PD group where the mean values were 134 and 115%, respectively, above those of the controls. The patients with PD also presented the lowest levels of the SPD precursor, putrescine (PUTR). In the patients suffering from ALS the SPD and SPM mean levels were increased by 46 and 112%, respectively. The RBC SPD/SPM ratio in the patients suffering from PD was significantly elevated in comparison with that of ALS patient group, suggesting a different involvement of the polyamine system in these disorders. It is at present unknown if raised polyamine levels may contribute to induce the degeneration of susceptible neurons or if the increase represents a compensatory protective reaction, or simply an unspecific epiphenomenon.
Asunto(s)
Esclerosis Amiotrófica Lateral/metabolismo , Poliaminas Biogénicas/metabolismo , Eritrocitos/metabolismo , Enfermedad de Parkinson/metabolismo , Poliaminas Biogénicas/análisis , Eritrocitos/química , Femenino , Humanos , Levodopa/uso terapéutico , Masculino , Persona de Mediana Edad , Enfermedad de Parkinson/tratamiento farmacológico , Putrescina/análisis , Putrescina/metabolismo , Espermidina/análisis , Espermidina/metabolismo , Espermina/análisis , Espermina/metabolismo , Factores de TiempoRESUMEN
To provide a background for future studies on neurodegenerative changes in the spinal cord, the present study analysed the distribution of the activity of methionine adenosyltransferase (ATP:L-methionine S-adenosyltransferase, EC 2.5.1.6, MAT), an enzyme that catalyses the synthesis of the biological methyl group donor S-adenosylmethionine (AdoMet), in spinal cords from bovine and pig, and compared the results with those from human spinal cord. The enzyme activity was estimated by a radiochemical method measuring the rate of formation of [(3)H]AdoMet from L-[methyl-(3)H]methionine and ATP. The MAT activity (V(max)) was quite homogeneously distributed between spinal regions and species investigated (19-50 pmol [(3)H]AdoMet/mg protein/minute), with the highest level found in the male bovine group. The bovine group (both males and females) also presented a 20% higher enzymatic activity in the dorsal horn as compared to the ventral horn and white matter areas. In the pig spinal cord, the highest level of activity was found in the white matter. The lowest affinity for methionine (highest K(m)) was found in the human spinal cord. Whole spinal cords of one cat and one rhesus monkey were also analysed and the levels of MAT activity were similar to that of humans and bovine females, respectively. Studies of MAT stability in the rat spinal cord (post-mortem time 0-72 hr) showed a significant decrease in enzyme activity during the interval of 0-8 hr (23 degrees ). From this time point on and up to 72 hr (4 degrees ), the significant decrease in the activity remained at 60% of the initial value.
Asunto(s)
Metionina Adenosiltransferasa/metabolismo , Médula Espinal/enzimología , Animales , Gatos , Bovinos , Estabilidad de Enzimas , Femenino , Humanos , Macaca mulatta , Masculino , Ratas , Ratas Sprague-Dawley , Especificidad de la Especie , Médula Espinal/metabolismo , Porcinos , Distribución TisularRESUMEN
The role of transmethylation mechanisms in the etiology of amyotrophic lateral sclerosis (ALS) is hitherto unexplored. The activity of L-methionine S-adenosyltransferase (MAT), a regulatory enzyme of S-adenosylmethionine biosynthesis, was investigated in erythrocytes of 21 patients with ALS, spinal cord specimens of 7 ALS patients, and matched controls. In ALS patients the activity of MAT in erythrocytes was sex-dependent. In comparison with controls, the male group presented a 33% higher V(max) (P < 0.05) and a 41% decrease in the affinity of MAT for methionine (K(m), P < 0.05). The type of ALS onset (limb or bulbar), age, or duration of the disease did not influence erythrocyte MAT activity. In the spinal cord, the activity of MAT was homogeneously distributed through dorsal horn, ventral horn, and white matter. Comparisons between data from controls and ALS patients and analysis of sex effect showed no significant differences. The kinetic difference of erythrocyte MAT in the male group of ALS patients might be interesting to explore since it is well known that there is a male predominance of 1.5 to 2. 5:1 in ALS.
Asunto(s)
Esclerosis Amiotrófica Lateral/enzimología , Eritrocitos/enzimología , Metionina Adenosiltransferasa/metabolismo , Médula Espinal/enzimología , Anciano , Esclerosis Amiotrófica Lateral/sangre , Esclerosis Amiotrófica Lateral/fisiopatología , Femenino , Humanos , Cinética , Masculino , Metionina Adenosiltransferasa/sangre , Persona de Mediana Edad , Valores de Referencia , Factores SexualesRESUMEN
The human neuroblastoma cell line SH-SY5Y was used to study the regulation of methionine adenosyltransferase (MAT II; E.C.2.5.1.6.) catalytic activity and transcript levels in cells of neuronal origin. The cells were exposed for 24 hr to a medium containing different concentrations of methionine (MAT substrate) as well as medium deficient of methionine. Furthermore, cells were treated with hydroxycobalamin, SAM, and the competitive MAT inhibitor cycloleucine. The MAT catalytic activity was inversely correlated to methionine concentrations, e.g. MAT Vmax increased 2-fold in cells grown in methionine-deficient medium as compared with cells cultured under standard conditions. Interestingly, MAT Km also increased from 9.04 +/- 0.44 to 12.08 +/- 0.83 in the methionine-deficient medium. Hydroxycobalamin caused an increase in activity at 40 microM while a decrease was observed at higher concentrations (100, 200, and 400 microM). Cycloleucine caused a significant inhibition of MAT catalytic activity, i.e. the inhibition was approximately 50% in the presence of 4 mM cycloleucine. The relevance of these results for the understanding of observations on MAT catalytic activity in brains of patients with Alzheimer's disease is discussed.
Asunto(s)
Regulación Enzimológica de la Expresión Génica/efectos de los fármacos , Metionina Adenosiltransferasa/metabolismo , Enfermedad de Alzheimer/enzimología , Northern Blotting , Catálisis , Cicloleucina/farmacología , Inhibidores Enzimáticos/farmacología , Humanos , Hidroxocobalamina/farmacología , Metionina Adenosiltransferasa/genética , ARN Mensajero/genética , ARN Mensajero/metabolismo , S-Adenosilmetionina/farmacología , Células Tumorales CultivadasRESUMEN
The activity of methionine adenosyltransferase (MAT) was investigated in erythrocytes and postmortem brain specimens (cortex gyrus frontalis, hippocampus and thalamus) of patients with schizophrenia treated with neuroleptics. In comparison with the control group, abnormally low values of MAT Vmax and an increased MAT affinity towards methionine (lower Km values) were found in erythrocytes. In the brain, a regionally selective decrease of MAT Km was found in cortex gyrus frontalis but the Vmax values were however, unchanged. In the regions of cortex gyrus frontalis and hippocampus, but not in thalamus, the values of Vmax and Km were inversely correlated with the duration of schizophrenia. In rats treated for 28 days with the typical neuroleptic haloperidol and the atypical clozapine, a significant increase of MAT activity was found in the corpus striatum. There is the possibility that the changes observed in MAT activity in patients with schizophrenia are attributed to the neuroleptic medication.
Asunto(s)
Antipsicóticos/uso terapéutico , Encéfalo/efectos de los fármacos , Eritrocitos/efectos de los fármacos , Metionina Adenosiltransferasa/metabolismo , Esquizofrenia/tratamiento farmacológico , Adulto , Anciano , Anciano de 80 o más Años , Envejecimiento/metabolismo , Análisis de Varianza , Animales , Encéfalo/enzimología , Eritrocitos/enzimología , Femenino , Humanos , Masculino , Metionina Adenosiltransferasa/sangre , Persona de Mediana Edad , Cambios Post Mortem , Ratas , Ratas Sprague-Dawley , Esquizofrenia/sangre , Esquizofrenia/enzimologíaRESUMEN
In the present study, levels of S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) in whole blood as well as L-methionine S-adenosyltransferase (MAT) activity in erythrocytes were assayed in a series of 20 patients with Parkinson's disease and 12 healthy control subjects. A significant difference was found with regard to SAM levels between patients and controls, with the detected levels being 383.1 +/- 41.5 nM for the parkinsonian patients and 680.6 +/- 30.9 nM for the controls. With regard to SAH, we found no difference between the groups. The catalytic activity of MAT was increased by 30% in patients compared to controls, with the Vmax for methionine being 17.9 +/- 3.7 and 13.9 +/- 2.2 pmol/mg/h, respectively.
Asunto(s)
Eritrocitos/enzimología , Metionina Adenosiltransferasa/metabolismo , Enfermedad de Parkinson/metabolismo , S-Adenosilhomocisteína/metabolismo , S-Adenosilmetionina/metabolismo , Antiparkinsonianos/administración & dosificación , Cromatografía Líquida de Alta Presión , Eritrocitos/química , Femenino , Humanos , Levodopa/administración & dosificación , Masculino , Persona de Mediana Edad , Enfermedad de Parkinson/tratamiento farmacológicoRESUMEN
The influence of vitamin B12 on the activity of methionine adenosyltransferase (MAT) in postmortem brains of patients with senile dementia of the Alzheimer's type (SDAT) was investigated. In samples of cortex gyrus frontalis from SDAT patients with normal and low levels of serum B12, MAT Vmax was significantly increased by 25% and 19%, respectively. MAT Vmax from a SDAT group chronically treated with B12 was similar to controls. In contrast to cortex gyrus frontalis, no significant alterations were seen in MAT activity in nucleus caudatus. This study provides evidence that SDAT is associated with significant alterations in transmethylation mechanisms in specific regions of the brain. The relationship between blood levels of B12 and the actual status of this vitamin in the brain influencing the rates of synthesis of both methionine and SAM may, however, be far more complex and cannot be directly clarified on the basis of the present human brain results.
Asunto(s)
Enfermedad de Alzheimer/tratamiento farmacológico , Núcleo Caudado/efectos de los fármacos , Giro del Cíngulo/efectos de los fármacos , Metionina Adenosiltransferasa/metabolismo , Vitamina B 12/farmacología , Edad de Inicio , Anciano , Anciano de 80 o más Años , Enfermedad de Alzheimer/sangre , Enfermedad de Alzheimer/enzimología , Análisis de Varianza , Estudios de Casos y Controles , Núcleo Caudado/enzimología , Femenino , Ácido Fólico/metabolismo , Giro del Cíngulo/enzimología , Humanos , Masculino , Vitamina B 12/sangreRESUMEN
ATP:1-methionine S-adenosyltransferase (EC 2.5.1.6, MAT) activity was analyzed in erythrocytes from nine patients with a clinical diagnosis of probable Alzheimer's disease (Pro.AD), four with possible Alzheimer's disease (Pos.AD), three with mild cognitive dysfunction (MCD) and two with dementia of vascular origin (VD), and 10 age-matched control subjects. Significantly lower kinetic parameters (Vmax and Km towards methionine) for MAT were observed in all the dementia cases. In the subgroup of Pro.AD patients who also had low plasma levels of vitamin B12 (B12), the reduction in MAT Km was significantly correlated with an increase in the serum levels of homocysteine, while no such correlation was observed in all the other dementia groups. Treatment for 6 months of this subgroup of Pro.AD patients with B12 (1 mg x 7 days + 1 mg/week, i.m.), S-adenosylmethionine (SAM, 200 mg twice daily, p.o.) and folate (2.5 mg every 2 days, p.o.) caused a significant decrease in homocysteine in parallel with a significant increase in Km for MAT. These findings support the hypothesis that aberrations in the B12 dependent transmethylation reactions might be involved in the pathogenesis of dementia, and suggest that the evaluation of erythrocyte MAT activity may be a useful marker for the detection of such an aberration.