Plasma amine oxidase activities in Norrie disease patients with an X-chromosomal deletion affecting monoamine oxidase

Monoaminergic and Histaminergic Strategies and Treatments in Brain Diseases

The monoaminergic systems are the target of several drugs for the treatment of mood, motor and cognitive disorders as well as neurological conditions. In most cases, advances have occurred through serendipity, except for Parkinson's disease where the pathophysiology led almost immediately to the introduction of dopamine restoring agents. Extensive neuropharmacological studies first showed that the primary target of antipsychotics, antidepressants, and anxiolytic drugs were specific components of the monoaminergic systems. Later, some dramatic side effects associated with older medicines were shown to disappear with new chemical compounds targeting the origin of the therapeutic benefit more specifically. The increased knowledge regarding the function and interaction of the monoaminergic systems in the brain resulting from in vivo neurochemical and neurophysiological studies indicated new monoaminergic targets that could achieve the efficacy of the older medicines with fewer side-effects. Yet, this accumulated knowledge regarding monoamines did not produce valuable strategies for diseases where no monoaminergic drug has been shown to be effective. Here, we emphasize the new therapeutic and monoaminergic-based strategies for the treatment of psychiatric diseases. We will consider three main groups of diseases, based on the evidence of monoamines involvement (schizophrenia, depression, obesity), the identification of monoamines in the diseases processes (Parkinson's disease, addiction) and the prospect of the involvement of monoaminergic mechanisms (epilepsy, Alzheimer's disease, stroke). In most cases, the clinically available monoaminergic drugs induce widespread modifications of amine tone or excitability through neurobiological networks and exemplify the overlap between therapeutic approaches to psychiatric and neurological conditions. More recent developments that have resulted in improved drug specificity and responses will be discussed in this review.

Cerebrospinal fluid monoamine metabolite levels in human newborn infants born in winter differ from those born in summer

An earlier study has shown significant differences in the CSF monoamine metabolite levels in adults born during different seasons of the year. We study here the relationship between season of birth and CSF monoamine metabolite levels in 283 newborn febrile infants without neurological abnormalities, with an age distribution ranging from birth to about 3 months, adjusting for the confounding variables age and time at lumbar puncture, weight at birth, estimated gestational age at birth, gender, race, and medicaid status. Each of the three metabolite levels as well as their ratios HVA/5-HIAA and 5-HIAA/MHPG showed significant month-of-birth variations, but not the ratio HVA/MHPG. For HVA and MHPG levels, the maximum was obtained around the winter birth months November-December, whereas for 5-HIAA level, the maximum was obtained around the summer birth months June-July. The correlations between HVA and 5-HIAA were, in general, significantly positive within the different birth seasons and races. Among summer-born Caucasian infants, MHPG was significantly positively correlated with HVA and with 5-HIAA, whereas among winter-born Black infants, MHPG was significantly positively correlated with HVA. Season of birth is an unspecific environmental factor that may be proxy for several possible seasonally varying environmental circumstances such as the length of photoperiod, temperature, infections, nutrition, stress and lifestyle. Studies relating season of birth to monoaminergic turnover at different stages of life may yield important clues about the gestational and perinatal origins of neurodevelopment.

Association analysis of the functional monoamine oxidase A gene promoter polymorphism in psychiatric disorders

Functional characterization studies revealed that transcriptional activity of the human monoamine oxidase A (MAOA) gene is modulated by a polymorphic repetitive sequence located approximately 1.2 kb upstream of the ATG codon. To investigate the possible influence of the allelic variants of the MAOA gene-linked polymorphic region (MAOA-LPR) on the genetic predisposition to psychiatric disorders, we have performed a case-control association study. 174 patients with affective disorders and 258 patients with schizophrenia according to DSM-IV, as well as 229 population controls were tested. Statistical analysis showed no significant differences in allele or genotype frequencies between control and patient groups. Our results suggest that there is no association between MAOA-LPR genotype and susceptibility to recurrent major depression, bipolar disorder, and schizophrenia in our population.

Genetic factors in human sleep disorders with special reference to Norrie disease, Prader-Willi syndrome and Moebius syndrome

Sleep-wake problems are common in specific inborn errors of metabolism and structure of the central nervous system. Psychological factors, behavioural difficulties, metabolic disturbances, and widespread rather than focal damage to the nervous system are present in many of these diseases and all influence the sleep-wake cycle. However, a number of conditions cause relatively focal damage to the neuroanatomical substrate of sleeping and waking. These include fatal familial insomnia, with involvement of the prion protein gene on chromosome 20, Norrie disease, the Prader-Willi syndrome and the Moebius syndrome. The last three important conditions, although rare, are considered in detail in this review. They result in sensory deprivation, hypothalamic and mid-brain damage, and involve the X-chromosome, chromosome 15, and chromosome 13, respectively. These conditions cause a wide variety of sleep disturbance, including parasomnias, daytime sleepiness, and a condition like cataplexy. The place of the relevant gene products in normal sleep regulation needs further exploration.

Serotonin and externalizing behavior in young children

Considerable evidence suggests that there is a relationship between pathologic aggressive behavior and low cerebrospinal fluid (CSF) concentrations of the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) in both humans and non-human primates. The purpose of this investigation is to examine the relationship between CSF concentrations of human newborn 5-HIAA and subsequent aggressive behavior observed at 30 months of age. Leftover portions of culture negative CSF drawn from febrile infants (age, birth to 3 months) were assayed for 5-HIAA. Family environment and child behavior were assessed at 30 months by parent report. Subjects with 5-HIAA levels below the median of the distribution had higher externalizing behavior scores at 30 months than did subjects whose 5-HIAA levels fell above the median (P = 0.02). While it is likely that serotonin mediates one component of genetic liability to antisocial outcome, the magnitude of that component may be less than what has been inferred from previously published reports.

Family psychiatric history, cerebrospinal fluid monoamine metabolites, and temperament in infants

BACKGROUND

Variations in cerebrospinal fluid (CSF) levels of the monoamine metabolites 5-hydroxyindoleacetic acid, 3-methoxy-4-hydroxyphenylglycol, and homovanillic acid have been associated with behavioral abnormalities in nonhuman primates, and with psychopathology in studies of children and adults.

METHODS

We assayed monoamine metabolites in "left-over" spinal fluid from 167 neurologically normal newborn infants (0-3 months of age), and later (at age 18-21 months of age) obtained their family psychiatric histories and assessed their temperament using the Colorado Childhood Temperament Inventory (CCTI).

RESULTS

Family history of antisocial personality disorder predicted significantly lower scores for soothability (p = .003) at 18-21 months. There were no statistically significant associations between newborn monoamine metabolite levels and any aspect of temperament on the CCTI.

CONCLUSIONS

These findings suggest complex relationships between genetic liability for psychiatric disorders and CSF monoamine metabolite levels; those relationships do not seem to be mediated by infant temperament. It appears likely that interindividual differences in monoamine metabolite levels change over the course of development in humans.

Are MAO-A deficiency states in the general population and in putative high-risk populations highly uncommon?

Lack of monoamine oxidase A (MAO-A) due to either Xp chromosomal deletions or alterations in the coding sequence of the gene for this enzyme are associated with marked changes in monoamine metabolism and appear to be associated with variable cognitive deficits and behavioral changes in humans and in transgenic mice. In mice, some of the most marked behavioral changes are ameliorated by pharmacologically-induced reductions in serotonin synthesis during early development, raising the question of possible therapeutic interventions in humans with MAO deficiency states. At the present time, only one multi-generational family and a few other individuals with marked MAO-A deficiency states have been identified and studied in detail. Although MAO deficiency states associated with Xp chromosomal deletions were identified by distinct symptoms (including blindness in infancy) produced by the contiguous Norrie disease gene, the primarily behavioral phenotype of individuals with the MAO mutation is less obvious. This paper reports a sequential research design and preliminary results from screening several hundred volunteers in the general population and from putative high-risk groups for possible MAO deficiency states. These preliminary results suggest that marked MAO deficiency states are very rare.

Differential trace amine alterations in individuals receiving acetylenic inhibitors of MAO-A (clorgyline) or MAO-B (selegiline and pargyline)

Marked, dose-dependent elevations in the urinary excretion of phenylethylamine, para-tyramine, and meta-tyramine were observed in depressed patients treated for three or more weeks with 10, 30, or 60 mg/day of the partially-selective inhibitor of MAO-B, selegiline (l-deprenyl). In comparative studies with other, structurally similar acetylenic inhibitors of MAO, pargyline, an MAO-B > MAO-A inhibitor used in doses of 90 mg/day for three or more weeks, produced elevations in these trace amines which were similar to those found with the highest dose of selegiline studied. Clorgyline, a selective inhibitor of MAO-A used in doses of 30 mg/day for three or more weeks (a dose/time regimen previously reported to reduce urinary, plasma, and cerebrospinal fluid 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) > 80%, indicating a marked inhibitory effect on MAO-A in humans in vivo) produced negligible changes in trace amine excretion. In comparison to recent studies of individuals lacking the genes for MAO-A, MAO-B, or both MAO-A and MAO-B, the lack of change in trace amine excretion in individuals with a mutation affecting only MAO-A is in agreement with the observed lack of effect of clorgyline in the present study. Selegiline produced larger changes in trace amines--at least at the higher doses studied--than found in individuals lacking the gene for MAO-B, in agreement with other data suggesting a lesser selectivity for MAO-B inhibition when selegiline was given in doses higher than 10 mg/day. Overall, trace amine elevations in individuals receiving the highest dose of deprenyl or receiving pargyline were approximately three to five-fold lower than the elevations observed in individuals lacking the genes for both MAO-A and MAO-B, suggesting that these drug doses yield incomplete inhibition of MAO-A and MAO-B.

Monoamine metabolites in 'leftover' newborn human cerebrospinal fluid--a potential resource for biobehavioral research

Although variations in monoamine neurotransmission have been implicated in a variety of psychopathologic outcomes in man, little is known about how monoamines influence or are affected by developmental processes early in childhood. In this study, assays for 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), and 3-methoxy-4-hydroxyphenylglycol (MHPG) were obtained from leftover cerebrospinal fluid (CSF) of 119 human newborns. The levels of these monoamine metabolites were in keeping with pre-existing 'normative' data from two small previously published studies. The levels were largely unaffected by variations in the infants' physiologic condition at the time of lumbar puncture, and exhibited evidence for circadian rhythms. Among 32 infants (8 neurologically normal, 24 neurologically compromised) for whom more than one CSF sample was obtained during the first year of life, the correlations between baseline and follow-up measurements for 5-HIAA and HVA were on the order of 0.75. Correlations between twins (four sets) were significantly higher than those between unrelated individuals for 5-HIAA and HVA. At 9-month follow-up, neurologically normal infants in the lower extreme 15% of the distribution for 5-HIAA exhibited a trend toward lower scores for sociability on the Colorado Childhood Temperament Inventory (maternal report) than their counterparts at the upper extreme of the 5-HIAA distribution. Leftover CSF is a readily available resource for measurements of monoamine metabolites (and possibly other CSF constituents) in population-based samples of human newborns.

On the physiology of metazoa

The problem on integration and control of the various processes of the metazoan organism is a major challenge to the physiologist. The traditional research strategy in dealing with the problem is neuron-oriented and its roots extend back into the last century when knowledge of hormones was lacking. In the present article, the traditional strategy is analyzed in the light of available data and its logical basis is questioned. Different levels of communication are supposed to occur in the animal or human body. Circulating hormones are responsible for the highest level of communication that occurs between organs or tissues. The central concept in the article is that regulation of circulating hormones constitutes a higher level of control relative to regulation of intercellular hormones. This is regardless of whether the latter occurs in the nervous system or elsewhere. The approach is utilized in defining the mechanism that integrates and controls the part processes of the body. The mechanism is defined as endothelial; the vascular endothelial system is the controlling part and the nervous system is one of the subordinate parts. Thanks to the new approach, meaningful biological explanations of major psychiatric disorders are now possible.

Mammalian plasma and tissue-bound semicarbazide-sensitive amine oxidases: biochemical, pharmacological and toxicological aspects

Mammalian plasma and tissues contain various soluble and membrane-bound enzymes which metabolize the synthetic amine benzylamine particularly well. The sensitivity of these enzymes to inhibition by semicarbazide and related compounds suggests that they contain a cofactor with a reactive carbonyl group, which has been proposed to be either pyridoxal phosphate, pyrroloquinoline quinone or (more recently) 6-hydroxydopa. It is not yet clear if all of these semicarbazide-sensitive amine oxidases (SSAOs) are copper-dependent enzymes. A variety of compounds have now been identified as relatively selective inhibitors to distinguish the SSAOs from other amine oxidases, in order to investigate the properties of SSAOs and their potential role in biogenic and xenobiotic amine metabolism in vivo. While plasma SSAO is soluble, most tissue SSAOs appear to be membrane-bound, probably plasmalemmal enzymes, which may be capable of metabolizing extracellular amines. Vascular (and non-vascular) smooth muscle cells have particularly high SSAO activity, although recently the enzyme has been found in other cell types (e.g. adipocytes, chondrocytes, odontoblasts) implying a functional importance not restricted solely to smooth muscle. The substrate specificity of plasma and tissue SSAOs shows considerable species-related variations. For example, while some endogenously-occurring aromatic amines such as tyramine and tryptamine are metabolized well by SSAO in homogenates of rat blood vessels, and also in vitro inhibition of SSAO can potentiate vasoconstrictor actions of these amines in rat vascular preparations, these amines are poor substrates for human SSAO, thus complicating attempts to generalize possible physiological roles for these enzymes. Vascular SSAO can metabolize the xenobiotic aliphatic amine, allylamine, to the cytotoxic aldehyde acrolein and this has been linked to the ability of allylamine administration to produce cardiovascular lesions in experimental animals, sometimes mimicking features of atherosclerotic disease. Recent studies showing that the endogenously-occurring aliphatic amines methylamine and aminoacetone are metabolized in vitro to formaldehyde and methylglyoxal, respectively, by SSAO in some animal (including human) tissues, suggest the possibility that toxicological consequences upon cellular function could result if such conversions occur in vivo.

Specific genetic deficiencies of the A and B isoenzymes of monoamine oxidase are characterized by distinct neurochemical and clinical phenotypes

Monoamine oxidase (MAO) exists as two isoenzymes and plays a central role in the metabolism of monoamine neurotransmitters. In this study we compared the neurochemical phenotypes of previously described subjects with genetically determined selective lack of MAO-A or a lack of both MAO-A and MAO-B with those of two subjects with a previously described X chromosome microdeletion in whom we now demonstrate selective MAO-B deficiency. Mapping of the distal deletion breakpoint demonstrates its location in intron 5 of the MAO-B gene, with the deletion extending proximally into the Norrie disease gene. In contrast to the borderline mental retardation and abnormal behavioral phenotype in subjects with selective MAO-A deficiency and the severe mental retardation in patients with combined MAO-A/MAO-B deficiency and Norrie disease, the MAO-B-deficient subjects exhibit neither abnormal behavior nor mental retardation. Distinct neurochemical profiles characterize the three groups of MAO-deficient patients. In MAO-A-deficient subjects, there is a marked decrease in deaminated catecholamine metabolites and a concomitant marked elevation of O-methylated amine metabolites. These neurochemical changes are only slightly exaggerated in patients with combined lack of MAO-A and MAO-B. In contrast, the only biochemical abnormalities detected in subjects with the MAO-B gene deletion are a complete absence of platelet MAO-B activity and an increased urinary excretion of phenylethylamine. The differences in neurochemical profiles indicate that, under normal conditions, MAO-A is considerably more important than MAO-B in the metabolism of biogenic amines, a factor likely to contribute to the different clinical phenotypes.

Substrate-specificity of mammalian tissue-bound semicarbazide-sensitive amine oxidase

Although the existence of a membrane-bound (probably plasmalemmal) semicarbazide-sensitive amine oxidase (SSAO) is well established in various mammalian tissues, and especially within vascular smooth muscle, its importance and the possible consequences of its metabolism of certain physiological and xenobiotic amines in vivo are under continuing investigation. In this respect, there are major species-related differences in substrate specificity determined in vitro, not only towards the synthetic amine benzylamine, but also towards some other aromatic amines (e.g. tyramine, tryptamine, 2-phenylethylamine, dopamine, histamine) which are possible endogenous substrates. Inhibition of SSAO can potentiate the pharmacological activity of some amines in isolated tissue (e.g. blood vessel) preparations from some species. Recent evidence has accumulated that SSAO may also be involved in metabolizing endogenous aliphatic amines such as methylamine and aminoacetone, focussing attention on the fact that the aldehyde products (formaldehyde and methylglyoxal, respectively) are potentially cytotoxic agents. Indeed, SSAO has been implicated in experimental models of cardiovascular toxicity involving conversion of the industrial aliphatic amine allylamine to acrolein. In summary, metabolism by SSAO may reduce the physiological/pharmacological effects of some amines, but the resulting metabolites (aldehydes, H2O2) may also have important actions.

Pharmacological and clinical implications of MAO-B inhibitors

Although the involvement of monoamine oxidase B (MAO-B) in physiological function is not yet well understood, its inhibitors have been shown to be quite useful in the treatment of various neuropsychiatric disorders. Platelet MAO-B activity has been found to be reduced in several psychiatric disorders, related to substance abuse and associated with different personalities. 1-Deprenyl (selegiline), an archetypical MAO-B inhibitor, alone does not seem to exert an antidepressive effect, however, it may become useful when administered in combination with amine neurotransmitter precursors. MAO-B inhibitors are useful adjunct drugs to 1-DOPA in the symptomatic treatment of Parkinson's disease. Interestingly, 1-deprenyl alone can slow down the progress of otherwise disabled syndromes of Parkinson's disease. It has been proposed that 1-deprenyl may play a role in neuroprotection and neurorescue. MAO-B inhibitors can selectively and dramatically increase the level of beta-phenylethylamine, which has been shown to potentiate dopamine and noradrenaline function in the central nervous system. Several new types of highly selective, reversible and irreversible MAO-B inhibitors have recently been developed. The mechanism(s) of neuroprotective and rescue actions of 1-deprenyl and other MAO-B inhibitors will help to shed some light on our understanding of the neurodegenerative process.

Monoamine oxidase-A: pharmacodynamics in humans of moclobemide, a reversible and selective inhibitor

1. Single oral doses of 300, 450 and 600 mg moclobemide, a monoamine oxidase type A inhibitor, were administered in a cross-over design to eight healthy male volunteers. Plasma concentrations of the parent drug and of two monoamine metabolites (3,4-dihydroxyphenylglycol DHPG from noradrenaline; 5-hydroxy-indoleacetic acid 5HIAA from serotonin) were measured over time. 2. A physiological pharmacokinetic-pharmacodynamic model was used to describe MAO-A inhibition as reflected in the alterations of monoamine metabolites. Population values for the model parameters were obtained by a two-stage method allowing for repeated dosing per subject. 3. Even at the lowest dose an effect of moclobemide on plasma DHPG and 5HIAA concentrations was detectable in most subjects for up to 24 h. In contrast to DHPG, 5HIAA formation was only partially suppressed by moclobemide (maximum fractional extent of enzyme inhibition Imax: 0.57, CV 26%) suggesting the existence of 5HIAA formation pathways independent of those inhibitable by moclobemide. 4. Plasma moclobemide concentrations associated with 50% of maximum enzyme inhibition (IC50) were in the range of 100 (IC50,5HIAA at 300 mg) to 400 micrograms l-1 (IC50,DHPG at 600 mg).

Inversion (X)(p11.4q22) associated with Norrie disease in a four generation family

We report on a 4-generation family in which Norrie disease occurs together with a pericentric inversion of the X chromosome in all affected males and carrier females. The breakpoint in the short arm of the X chromosome appears to be at the purported location of the Norrie disease gene. This is the second report of an association between Norrie disease and a chromosome aberration involving Xp11, and the first report of a specific gene disruption, thus physical gene location, due to a pericentric chromosome inversion.

The new generation of monoamine oxidase inhibitors

Irreversible and unspecific inhibitors of MAO were the first modern antidepressants, but after an initial success they fell into discredit due to adverse side effects. In the past two decades interest in MAO inhibitors has been renewed because of progress in basic research, a milestone being the finding that there are two subtypes of MAO, MAO-A and MAO-B. These are distinct proteins with high amino acid homology, coded by separate genes both located on the short arm of the human chromosome X. The enzyme subforms show different substrate specificities in vitro and different distributions within the central nervous system and in peripheral organs. In the central nervous system of man MAO-A seems to be mainly involved in the metabolism of 5 HT and noradrenaline, whereas 2-phenylethylamine and probably dopamine are predominantly deaminated by MAO-B. In the intestinal tract tyramine is mainly metabolized by MAO-A. These characteristics indicate distinct physiological functions of the two MAO-subforms. Several irreversible and reversible non-hydrazine inhibitors with relative selectivities for one of the MAO-subforms have been developed. They belong to various chemical classes with different modes of enzyme inhibition. These range from covalent mechanism based interaction (e.g. by propargyl- and allylamine derivatives) to pseudosubstrate inhibition (e.g. by 2-aminoethyl-carboxamides) and non-covalent interaction (e.g. by brofaromine, toloxatone and possibly moclobemide). The most important pharmacological effects of the new types of MAO inhibitors are those observed in neuropsychiatric disorders. The inhibitors of MAO-A show a favorable action in various forms of mental depression. The drugs seem to have about the same activity as other types of antidepressants, including tricyclic and related compounds as well as classical MAO inhibitors. The onset of action of the MAO-A inhibitors is claimed to be relatively fast. Other possible indications of these drugs include disorders with cognitive impairment, e.g. dementia of the Alzheimer type. In subjects with Parkinson's disease the MAO-B inhibitor L-deprenyl exerts a L-dopa-sparing effect, prolongs L-dopa action and seems to have a favorable influence regarding on-off disabilities. The action is in general transitory (months to several years). In addition L-deprenyl has been shown to delay the necessity for L-dopa treatment in patients with early parkinsonism. Whether the drug influence the progression of the disease is still a matter of debate. L-deprenyl also appears to have some antidepressant effect (especially in higher doses) and to exert a beneficial influence in other disorders, e.g. dementia of the Alzheimer type.(ABSTRACT TRUNCATED AT 400 WORDS)

Clinical, biochemical, and neuropsychiatric evaluation of a patient with a contiguous gene syndrome due to a microdeletion Xp11.3 including the Norrie disease locus and monoamine oxidase (MAOA and MAOB) genes

Norrie disease is a rare X-linked recessive disorder characterized by blindness from infancy. The gene for Norrie disease has been localized to Xp11.3. More recently, the genes for monoamine oxidase (MAOA, MAOB) have been mapped to the same region. This study evaluates the clinical, biochemical, and neuropsychiatric data in an affected male and 2 obligate heterozygote females from a single family with a submicroscopic deletion involving Norrie disease and MAO genes. The propositus was a profoundly retarded, blind male; he also had neurologic abnormalities including myoclonus and stereotopy-habit disorder. Both obligate carrier females had a normal IQ. The propositus' mother met diagnostic criteria for "chronic hypomania and schizotypal features." The propositus' MAO activity was undetectable and the female heterozygotes had reduced levels comparable to patients receiving MAO inhibiting antidepressants. MAO substrate and metabolite abnormalities were found in the propositus' plasma and CSF. This study indicates that subtle biochemical and possibly neuropsychiatric abnormalities may be detected in some heterozygotes with the microdeletion in Xp11.3 due to loss of the gene product for the MAO genes; this deletion can also explain some of the complex phenotype of this contiguous gene syndrome in the propositus.