The natural polyamines and the immune system.
Explore the source record for details and available documents.
Animals↗
Biomedical subjects
N Seiler
Publications and source records attributed to N Seiler.
Decreased hyperammonaemia and orotic aciduria due to inactivation of ornithine aminotransferase in mice with a hereditary abnormal ornithine carbamoyltransferase.
Mice with the X-chromosomal sparse-fur (spf) mutation are an animal model of some hereditary deficiencies of ornithine carbamoyltransferase (OCT) in man. Orotic aciduria and hyperammonaemia are the most conspicuous metabolic changes in these diseases. Selective inactivation of ornithine aminotransferase (OAT) by 5-fluoromethylornithine raises endogenous ornithine concentrations so that citrulline formation is effectively catalysed by the aberrant OCT, in spite of its low affinity for ornithine. As a consequence, blood and tissue ammonia concentrations and orotic acid excretion are reduced near to normal values, and the abnormal amino acid patterns in blood, brain and liver are normalized. Selective inactivation of OAT seems a promising therapeutic approach in some hereditary OCT deficiencies, and a total that may allow us to clarify the role of ammonia and orotic acid in the development of nanism and abnormal behaviour in spf mutant mice.
Amino Acids↗
Effects of ornithine aminotransferase inactivation by 5-fluoromethylornithine in rats following portacaval anastomosis.
5-Fluoromethylornithine (5FMOrn) is a selective inactivator of ornithine aminotransferase. Administration of this compound to rodents causes a prominent increase of tissue ornithine concentrations, and prevents the neurological consequences of acute ammonia intoxication. However, long-term treatment with 5FMOrn of rats with portacaval shunts did not result in decreased circulating ammonia concentrations, nor did it prevent other pathologic manifestations of shunting. The sensitivity to ammonia intoxication of rats with portacaval shunts was also unaffected by pretreatment with 5FMOrn, although liver ornithine concentrations were significantly elevated; specific activities of urea cycle enzymes were slightly higher in portacaval shunted compared to sham-operated controls following 5-FMOrn treatment. Administration of 5FMOrn dramatically elevated urinary excretion of several amino acids in rats with portacaval shunts, but not in sham-operated animals, suggesting that the reabsorption of amino acids from the glomerular filtrate may be impaired in shunted rats. These results suggest that, in contrast to acute hyperammonemic syndromes, 5-FMOrn may be of limited therapeutic value in chronic hyperammonemia syndromes in which there is significant portal-systemic shunting.
Amino Acids↗
Protection against lethal ammonia intoxication: synergism between endogenous ornithine and L-carnitine.
The protective effects of combinations of 5-fluoromethylornithine (5FMOrn), a selective inhibitor of ornithine aminotransferase, and of compounds known to antagonize ammonia toxicity, were studied in acute, lethal ammonia intoxication in mice. Two test conditions were used: (a) Mice were pretreated with 5FMOrn at a dose (5 mumol.kg-1) which partially protects against 13 mmol.kg-1 ammonium acetate. (b) Mice were pretreated with a maximally protective dose of 5FMOrn (0.1 mmol.kg-1), however, 15 mmol.kg-1 ammonium acetate was used for intoxication. Under these conditions treatment with 5FMOrn alone protected only marginally. Under condition (a), administration of L-citrulline, L-carnitine, and L-acetylcarnitine improved the protective effect of 5FMOrn significantly, in an additive manner. N-acetyl-L-glutamate administration was ineffective. Under condition (b), ornithine, arginine and citrulline did not improve the protective effect of 5FMOrn, even when these amino acids were given at doses, which were effective in preventing ammonia toxicity induced with 13 mmol.kg-1 ammonium acetate. The inability to improve the effect of 5FMOrn by these compounds is most probably due to the fact that 5FMOrn and these amino acids enhance urea formation by the same mechanism, namely by increasing the concentration of substrates of the urea cycle. In contrast, L-carnitine and L-acetylcarnitine, which are assumed to stimulate urea production by different mechanisms, or compounds which antagonize ammonia toxicity by a urea cycle-independent mechanism, such as antagonists of the NMDA-type glutamate receptor (MK-801; MDL 100,453), potentiated the effects of 5FMOrn. The principle reason for the observed protective effects of the treatments described in this work seems to be the prevention of accumulation of lethal concentrations of ammonia in the brain. But other effects may also contribute.
Acetates↗
Effect of ammonia on endocytosis, cytokine production and lysosomal enzyme activity of a microglial cell line.
Ammonia is a natural lysosomotropic compound. Concentrations of ammonium acetate > 2 mM impaired the phagocytic activity of BV-2 cells, an immortalized microglial cell line, as was determined by the uptake of fluorescent latex microspheres of different sizes. In contrast, an increase in the uptake of fluorescent dextran was observed with the elevation in ammonium acetate concentrations. This indicates that ammonia affects phagocytotic and pinocytotic activities of BV-2 cells differently. Interferon-gamma- and polyinosinic-polycytidylic acid-stimulated secretion of IL1 alpha as well as LPS-stimulated secretion of IL6 decreased with an elevation in ammonium acetate concentrations. The constitutive secretion of IL1 alpha was not significantly affected by ammonium acetate. However, an increase in LPS-stimulated IL1 alpha secretion was observed at 10 mM and 20 mM ammonium acetate. High concentrations of ammonia affected the activity of lysosomal enzymes of the BV-2 cells. Acid phosphatase and alpha-glucosidase activities increased with the increase in ammonium acetate up to 20 mM. The activity of cathepsin D was increased at 5 mM, but decreased at higher ammonia concentrations. The effects of ammonia on microglial functions are discussed with respect to pathogenetic mechanisms of dementia of the Alzheimer type.
Acetates↗
Polyamines and the recovery of intestinal morphology and function after ischemic damage in rats.
We have followed the time-course of the morphological and functional recovery of intestinal mucosa after 90 min of mesenteric vascular occlusion. At the end of the ischemic period the villi were smashed, but crypts were preserved. Microvillous hydrolase activities showed a dramatic drop when compared with sham-operated controls. Reperfusion was followed by an immediate upsurge of ornithine decarboxylase activity and a significant (p < 0.01) enhancement of putrescine and N1-acetyl-spermidine concentrations, while spermidine and spermine concentrations in mucosal cells decreased. This indicated that, both, de novo synthesis and degradation rates of the polyamines were increased. Treatment with alpha-difluoromethyl-ornithine, a selective inactivator of ornithine decarboxylase prevented the accumulation of active enzyme, but did not prevent morphological healing. It delayed however the recovery of sucrase and aminopeptidase-specific activities. Our results suggest that in addition to de novo synthesis, other sources of polyamines are mobilized to an extent that growth at a normal rate is supported. This indicates that the presence of active ornithine decarboxylase enzyme is not a prerequisite for the restitution of intestinal integrity after ischemia. We suggest that in a situation of inadequate polyamine supply the restoration of vital processes (mucosal regeneration) has priority over the restoration of specific functions.
Animals↗
Antileukemic effects of non-metabolizable derivatives of spermidine and spermine.
To determine whether non-metabolizable derivatives of spermidine and spermine exert anticancer effects, L1210 leukemic mice were treated with 5,8-dimethylspermidine and 5,8-dimethylspermine. Both derivatives cured 5% of the leukemic mice. The increase in median survival time, however, was slight. In combination with alpha-difluoromethylornithine (DFMO), an ornithine decarboxylase inhibitor, only 5,8-dimethylspermine had a favorable effect. Treatment with DFMO is known to increase the uptake of extracellular polyamines and presumably their derivatives, by depleting the intracellular putrescine and spermidine content. However, treatment of L1210 leukemia cells in vitro with DFMO did not affect the uptake of the methyl-substituted polyamines added to the growth medium. 5,8-Dimethylspermidine and 5,8-dimethylspermine repressed the ornithine decarboxylase activity when added to cultures of L1210 leukemia cells. S-Adenosylmethionine decarboxylase activity was only repressed by 5,8-dimethylspermine. This finding may explain the potentiation by this derivative and not by 5,8-dimethylspermidine, of the antileukemic effect of DFMO.
Adenosylmethionine Decarboxylase↗
Effects of inhibition of ornithine aminotransferase on thioacetamide-induced hepatogenic encephalopathy.
Repeated administration of thioacetamide (TAA) to CD1 mice produced hepatic failure and biochemical and behavioral effects characteristic of hepatogenic encephalopathy (HE). The symptoms in mice resembled those previously observed in rats after similar treatments. It is, however, obvious that both in rats and mice the severity of symptoms depends not only on dose and dosing schedule of TAA, but also on strain and body weight (age). Administration of 5-fluoromethylornithine (5FMOrn), a selective inactivator of ornithine aminotransferase (OAT), significantly reduced mortality, and it ameliorated most of the TAA-induced pathologic symptoms, such as hypothermia, decreased locomotor and exploratory behavior, pathologic liver function and amino acid patterns. The most prominent biochemical consequence of 5FMOrn administration is the elevation of ornithine concentrations in tissues, including the brain, and in body fluids. Elevated ornithine concentrations are, therefore, the most likely basis for the therapeutic effects of 5FMOrn. In agreement with this notion is the enhancement of citrulline and urea formation. These findings and the observation that administration of ornithine in combination with a branched-chain 2-oxoacid ameliorated the pathologic symptoms of portal-systemic encephalopathy suggest inhibition of OAT in the treatment of this disease. The liver protective effect of 5FMOrn is not yet understood; the enhancement of regenerative processes is a likely explanation.
Amino Acids↗
Is ammonia a pathogenetic factor in Alzheimer's disease?
An attempt was made to review experimental evidence in favor of the idea that ammonia plays a role in dementia of the Alzheimer type (DAT). Hyperammonemia causes biochemical and cellular dysfunctions in the brain, which can be found in brains of DAT patients. The most conspicuous among these findings are astrocytosis, impairment of glucose utilization, and a decreased rate of energy metabolism, and the impairment of neurotransmission, with a net increase in excitability and glutamate release. The derangement of lysosomal processing of proteins is another potential site of ammonia action. This aspect is especially important in view of the growing evidence for the role of the endosomal-lysosomal system in the formation of amyloidogenic fragments from beta-amyloid precursor protein. Ammonia is not considered a primary factor of the disease. However, since hyperammonemia and release of ammonia from the brains of DAT patients is well supported by published observations, ammonia should be taken into account as a factor that contributes to manifestations and the progression of DAT. If elevated ammonia concentrations turn out to be indeed as important in DAT, as is suggested in this review, rational therapeutic avenues can be envisaged that lead to the amelioration of symptoms and progression of the disease.
Alzheimer Disease↗
Endogenous ornithine in search for CNS functions and therapeutic applications.
The vertebrate brain has the machinery to transport arginine and ornithine, and to form within nerve endings from these amino acids glutamate and GABA, the major excitatory and inhibitory neurotransmitters. Ornithine aminotransferase is a key enzyme of the Arg-->Orn-->Glu-->GABA pathway; the physiological significance of this pathway is still unclear. With 5-fluoromethylornithine, a selective inactivator of ornithine aminotransferase, a tool is in our hands that allows us to study biochemical and behavioral consequences of elevated tissue ornithine concentrations. Increase of the rate of hepatic urea formation, and of ornithine decarboxylation are the most important changes in vertebrates following inactivation of ornithine aminotransferase. Administration of 5-fluoromethylornithine prevented the accumulation of lethal concentrations of ammonia in brain, and ameliorated pathological consequences of thioacetamide intoxication. Inhibition of ornithine catabolism has, therefore, potentials in the therapy of those hyperammonemic states which are characterized by a conditional deficiency of ornithine. The enhancement of polyamine formation due to elevated ornithine concentrations may allow us to favorably affect tissue regeneration following injury.
Ammonia↗
Depletion of polyamines prevents the neurotrophic activity of the GABA-agonist THIP in cultured rat cerebellar granule cells.
Effects of polyamine depletion by alpha-difluoromethylornithine (DFMO) were studied on the GABA-agonist mediated enhancement of the morphological development of cultured rat cerebellar granule cells. An increase in the number of neurite extending cells and in the cytoplasmic density of organelles relevant for protein synthesis was observed upon culturing in the presence of 4,5,6,7-tetrahydro-isoxazole[5,4-c]pyridin-3-ol (THIP) for 4 days. The intracellular concentrations of putrescine, spermidine, and spermine in these cultures were similar to the concentrations of the polyamines observed in cultures grown in a plain culture medium for 1, 2, 3 or 4 days, respectively. Upon culturing in the simultaneous presence of THIP and DFMO, the concentrations of putrescine and spermadine were reduced to less than 20% of the levels in the controls. This depletion was associated with a severely impaired morphological development of the granule cell cultures. Thus, the number of neurite extending cells was reduced to 50% of the number in the control cultures upon culturing in the presence of DFMO alone or in combination with THIP. Moreover, the THIP mediated increase in the cytoplasmic density of rough endoplasmic reticulum, Golgi apparatus and different types of vesicles was prevented by the exposure to DFMO.
Animals↗
The effects of structural analogs of putrescine on proliferation, morphology and karyotype of glioblastoma cells in culture.
In a previous study, we identified regions on the surface of tumor cells which act as acceptor sites for putrescine (Put) and studied the competition between structural analogs of Put (N,N'-tetramethyl-alpha,omega-diaminoalkanes) and Put bound to latex microspheres. A chain of four to seven carbons was necessary for inhibition of Put-latex binding to the cell surface of human glioblastoma (U251) cells. We show here that under the experimental conditions, N,N'-tetramethyl-1,4-butanediamine and N,N'-tetramethyl-1,7-heptanediamine exhibit an antitumor effect. In a first step (1-48 h after treatment), cells exposed to these compounds show large intracellular vacuoles. We failed to detect any acid phosphatase activity in these intracellular structures revealing that they were not lysosomes. Electron microscopy observations argue for the conclusion that these vacuoles are an hypertrophy of the endoplasmic reticulum (ER) and/or of the Golgi vesicles. Our hypothesis is that this typical effect of the analogs reveals that ER could be a physiological target of endogenous polyamines. At a later stage (6 days after treatment), the cells undergo morphological and biochemical changes: thin and long expansions characterize the cells and the GFA protein is overexpressed. Correlated to both these effects, karyotypic modifications are found in chromosomes 3 and 6. These changes evoke a differentiation of the treated cells. The work provides evidence that N-methylated polyamine analogs taking the place of endogenous putrescine demonstrate a hopeful antitumor effect.
Cell Differentiation↗
Enhanced endogenous ornithine concentrations protect against tonic seizures and coma in acute ammonia intoxication.
Pretreatment of mice with 5-fluoromethylornithine (5FMOrn), a selective inactivator of ornithine aminotransferase, diminishes the accumulation of ammonia in the brain after administration of ammonium acetate, and antagonizes ammonia-induced fatal tonic extensor convulsions. In about 50% of the treated animals the loss of the righting reflex and coma is prevented. Presumably these effects are based on the enhancement of urea formation by the increased liver ornithine concentrations. However, since brain ornithine concentrations are greatly enhanced by 5FMOrn, it is not excluded that ornithine has direct effects on cellular events involved in ammonia-induced seizure generation, even though 5FMOrn had no anticonvulsant properties in a series of established animal seizure models, including N-methyl-D,L-aspartate-induced convulsions. NMDA receptor antagonists are capable of preventing death, but do not protect against the generation of coma and tonic extensor convulsions in ammonium acetate intoxicated mice. Since no evidence was found for ammonia-induced glutamate release from rat hippocampus, there is no convincing evidence for the idea that the tonic convulsions are mediated by NMDA receptors. L-Methionine-D, L-sulfoximine (MSO)-induced seizures can be partially antagonized by pretreatment with 5FMOrn. However, the effect is considerably smaller than against ammonia-induced convulsions, although at the time of seizure onset brain ammonia levels of MSO-intoxicated mice were lower than in the animals receiving ammonium acetate. This suggests that MSO-convulsions are not entirely due to the elevation of brain ammonia concentrations, even though MSO administration mimics effects of ammonia on cortical inhibitory neuronal interactions.(ABSTRACT TRUNCATED AT 250 WORDS)
3-Mercaptopropionic Acid↗
Some biochemical and pathophysiological aspects of long-term elevation of brain ornithine concentrations.
Mice and chicken were given 5-fluoromethylornithine (5FMOrn), a selective inactivator of ornithine aminotransferase (OAT) over extended periods of time. This treatment allowed us to maintain elevated concentrations of ornithine in all tissues. Since gyrate atrophy, an autosomal recessive human disease, is characterized by the absence of OAT, special emphasis was put on the study of the visual system. Ophthalmoscopic and histologic examinations of the eye as well as electroretinograms and locomotor behaviour demonstrated an unimpaired visual system and brain. No toxic effects were observable in the treated mice. Likewise, chick embryo development was normal in spite of highly elevated brain and tissue ornithine concentrations. A likely explanation for the absence of toxic effects of 5FMOrn treatment, disregarding the non-toxicity of ornithine, is the fact that 10-20% of tissue OAT is refractory to inactivation by 5FMOrn. This residual activity may be sufficient to maintain vital functions.
Animals↗
[Preventing unemployment of staff, counseling unemployed patients. Looking for the first job].
Explore the source record for details and available documents.
Counseling↗
[Preventing unemployment of nurses, counsel the jobless patient: looking for the 1. job].
Explore the source record for details and available documents.
Humans↗
Antagonism of phencyclidine-induced hyperactivity in mice by elevated brain GABA concentrations.
Vigabatrin and (S)-4-allenylGABA (MDL 72483), two anticonvulsant GABA-T inhibitors, partially antagonize phencyclidine (PCP)-induced hyperactivity in mice at doses that do not affect spontaneous motor activity. The PCP antagonism is related to whole-brain GABA concentrations. The results indicate the potential use of GABA-T inhibitors in the therapy of PCP intoxications and perhaps also in the treatment of certain forms of endogenous psychoses.
Aminocaproates↗
Inhibition of ornithine aminotransferase by 5-fluoromethylornithine: protection against acute thioacetamide intoxication by elevated tissue ornithine levels.
5-Fluoromethylornithine (5FMOrn) is a selective inactivator of ornithine aminotransferase. Its administration causes a dramatic increase of ornithine concentrations in all tissues. Treatment of mice with 20 mg.kg-1 5FMOrn shortly before or after a lethal dose (600 mg.kg-1, intraperitoneally) of thioacetamide (TAA), followed by a second dose 24 hr later, prevented death of 60% of the mice. Pathologic symptoms of TAA intoxication (liver haemorrhage, elevation of amino acids in blood and tissues, diminution of liver spermidine and spermine concentrations, elevation of the activity of liver enzymes in the plasma) were significantly ameliorated by the treatment. The liver protective action of 5FMOrn is related to the elevation of ornithine concentration, as appears from the fact that other, less selective inactivators of ornithine aminotransferase, also produced some protection against acute intoxication with TAA, but not a structurally related compound with no effect on this enzyme.
Amino Acids↗