Bruce A. Davis

Transfection‐enforced Bcl‐2 overexpression and an anti‐Parkinson drug, rasagiline, prevent nuclear accumulation of glyceraldehyde‐3‐phosphate dehydrogenase induced by an endogenous dopaminergic neurotoxin, N‐methyl(R)salsolinol

An endogenous dopaminergic neurotoxin, N‐methyl(R)salsolinol, was found to induce apoptosis in human dopaminergic SH‐SY5Y cells by step‐wise activation of apoptotic cascade; collapse in mitochondrial membrane potential, ΔΨm, activation of caspases, and fragmentation of DNA. Recently, accumulation of gylceraldehyde‐3‐phosphate dehydrogenase (GAPDH) in nuclei was proposed to play an important role in apoptosis. In this paper, involvement of GAPDH in apoptosis induced by N‐methyl(R)salsolinol was studied. The isoquinoline reduced ΔΨm within 3 h, as detected by a fluorescence indicator, JC‐1, then after 16 h incubation, GAPDH accumulated in nuclei by detection with immunostaining. To clarify the role of GAPDH in apoptotic process, a stable cell line of Bcl‐2 overexpressed SH‐SY5Y cells was established. Overexpression of Bcl‐2 prevented the decline in ΔΨm and also apoptotic DNA damage induced by N‐methyl(R)salsolinol. In Bcl‐2 transfected cells, nuclear translocation of GAPDH was also completely suppressed. In addition, a novel antiparkinsonian drug, rasagiline, prevented nuclear accumulation of GAPDH induced by N‐methyl(R)salsolinol in control cells. These results suggest that GAPDH may accumulate in nuclei as a consequence of signal transduction, which is antagonized by anti‐apoptotic Bcl‐2 protein family and rasagiline. The results are discussed in concern to intracellular mechanism underlying anti‐apoptotic function of rasagiline analogues.

Aliphatic propargylamines: New antiapoptotic drugs

Two series of drugs, the aliphatic‐N‐methyl propargylamines and the aliphatic propargylamines, have been synthesised and shown to be specific, irreversible, and potent monoamine oxidase B inhibitors and neural rescue agents. In the latter case, an absolute stereochemical requirement for the R isomer exists. Both series of compounds have been shown, in numerous in vitro and in vivo experimental paradigms, to be effective neuronal rescue agents. Candidates from both series exhibit excellent bioavailability and pharmacokinetics and offer opportunities for treating neurodegenerative disorders and stroke and cognitive decline in companion animals. Drug Dev. Res. 42:150–156, 1997.

The trace amines and their acidic metabolites in depression — an overview

1. Investigations of the role of the trace amines (phenylethylamine, tryptamine, m- and p-tyramine) and their acidic metabolites (phenylacetic, indoleacetic, m- and p-hydroxyphenylacetic acids) in depression are reviewed. 2. The evidence for the phenylethylamine hypothesis of depression is mixed. 3. Reduced phenylacetic acid levels in urine, plasma and CSF and changes in those levels during treatment with antidepressants show potential as state markers for depression. 4. Impaired p-tyramine conjugation following a tyramine challenge may be a good trait marker for depression.

Neuroprotective effects of some monoamine oxidase-B inhibitors against DSP-4-induced noradrenaline depletion in the mouse hippocampus.

Abstract: DSP‐4 [N‐(2‐chloroethyl)‐N‐ethyl‐2‐bromobenzylamine], a selective noradrenaline (NA) uptake blocker, is capable of inducing long‐lasting depletion of NA in some noradrenergic axon terminals and of subsequently causing cell death to NA neuronal cell bodies in rodents. R(−)‐Deprenyl, a selective monoamine oxidase (MAO)‐B inhibitor, has been shown to be capable of protecting animals against this DSP‐4‐induced neuronal degeneration. Its action, however, has been claimed to be unrelated to the inhibition of MAO‐B activity but rather due to competition for the NA uptake sites. The effects of several types of MAO inhibitors against DSP‐4 toxicity, MAO‐B activity both in vivo and in vitro, and NA uptake into the hippocampus have been assessed. N‐(2‐Hexyl)‐N‐methylpropargylamine (2‐HxMP), a potent MAO‐B inhibitor, for example, exerts no appreciable effect on NA uptake but is quite potent in counteracting the NA‐depleting effect of DSP‐4. Such results rule out the possibility that the neuroprotective effect of the MAO‐B inhibitors is due mainly to their effect on NA uptake. The in vitro inhibition of MAO‐B activity seems to correlate positively with their neuroprotective effects against DSP‐4. In comparison to the MAO‐B inhibitors, NA uptake blockers, such as desipramine and S(+)‐deprenyl, exhibit relatively low efficacy in protecting the NA axon terminals from the effects of DSP‐4‐induced damage. The restoration of hippocampal NA levels is significantly enhanced with repeated treatments of R(−)‐deprenyl or 2‐HxMP even at very low doses following the DSP‐4 insult. This suggests that in addition to neuroprotection, these MAO‐B inhibitors may rescue some of the noradrenergic axon terminals damaged by DSP‐4.

Enantio-specific induction of apoptosis by an endogenous neurotoxin, N-methyl(R)salsolinol, in dopaminergic SH-SY5Y cells: suppression of apoptosis by N-(2-heptyl)-N-methylpropargylamine

Summary. Endogenous N-methyl(R)salsolinol, which caused parkinsonism in rats by injection in the striatum, was found to induce apoptosis in dopaminergic neuroblastoma SH-SY5Y cells. After 12-h incubation with 500 μM N-methyl(R)salsolinol, almost all the cells died with apoptosis and necrotic cell death was negligible. N-Methyl(R)salsolinol was much more potent to induce apoptosis than the (S)-enantiomer. The mechanism of apoptosis was studied in relation to changes in mitochondrial membrane potential, ΔΨm, using a fluorescent indicator, JC-1. Red fluorescence of J-aggregates representing hyperpolarized ΔΨm was found to decrease significantly within 60 min after incubation with N-methyl(R)salsolinol, but not by the (S)-enantiomer at the same concentration. It suggests that mitochondria may recognize the stereo-chemical structure of N-methyl(R)salsolinol. Aliphatic propargylamines, (R)-N-(2-heptyl)-N-methylpropargyl-amine and (R)-N-(2-heptyl)propargylamine, were found to prevent ΔΨm loss and subsequent apoptosis induced by N-methyl(R)salsolinol. These results suggest that mitochondria play a key role in the induction of apoptosis by the neurotoxin and the prevention by aliphatic propargylamines.

Biogenic amines and their metabolites in body fluids of normal, psychiatric and neurological subjects☆

The biogenic monoamines and their metabolites have been isolated, identified and quantified in human body fluids over the past forty years using a wide variety of chromatographic separation and detection techniques. This review summarizes the results of those studies on normal, psychiatric and neurological subjects. Tables of normal values and the methods used to obtain them should prove to be useful as a reference source for benchmark amine and metabolite concentrations and for successful analytical procedures for their chromatographic separation, detection and quantification. Summaries of the often contradictory results of the application of these methods to psychiatric and neurological problems are presented and may assist in the assessment of the validity of the results of experiments in this field. Finally, the individual, environmental and the methodological factors affecting the concentrations of the amines and their metabolites are discussed.

The effect of L-deprenyl on behavior, cognitive function, and biogenic amines in the dog

Behavioral and pharmacological effects of oral administration ofl-deprenyl in the dog are described. Spontaneous behavior is unaffected at doses below 3 mg/kg while at higher doses there was stereotypical responding. There was evidence of improved cognitive function in animals chronically treated with a 1 mg/kg dose but the effectiveness varied considerably between subjects. Chronic administration produced a dose dependent inhibition in brain, kidney and liver monoamine oxidase B, and had no effect on monoamine oxidase A. There were also dose dependent increases in brain phenylethylamine and in plasma levels of amphetamine. Dog platelets did not have significant levels of MAO-B. Brain dopamine and serotonin metabolism were unaffected byl-deprenyl at doses up to 1 mg/kg. It appears that for the dog, deamination of catecholamines is controlled by MAO-A. Nevertheless, it is suggested thatl-deprenyl serves as a dopaminergic agonist, and there is also evidence that it affects adrenergic transmission. These catecholaminergic actions may account for the effects ofl-deprenyl on behavior and cognitive function.

Characterization of human serum and umbilical artery semicarbazide-sensitive amine oxidase (SSAO): Species heterogeneity and stereoisomeric specificity

Semicarbazide-sensitive amine oxidases (SSAOs) are located in cardiovascular smooth muscle, cartilage and brown adipose tissues of different species, including human. The enzyme is also present in blood, and its activity appears to be altered under certain pathological conditions. SSAOs from both human umbilical arteries and serum were partially purified, and some of their biochemical properties were investigated. Both human artery and blood SSAO exhibited very similar substrate preference, lack of stereospecificity catalyzing the deamination of pro-R and pro-S benzylamine-deuterated enantiomers, and were very sensitive towards (E)-2-(4-fluorophenethyl)-3-fluoroallylamine (MDL-72974A). It was concluded that circulating serum SSAO is identical to the SSAO from vascular tissues. Human SSAO exhibited distinctly different properties in comparison to bovine and rat SSAOs.

Phenylethylamine and schizophrenia

1. The evidence that phenylethylamine (PEA) plays a role in the etiology of schizophrenia is reviewed. 2. PEA shares structural and physiological similarities with the amphetamines, the administration of which can induce a schizophrenia-like psychosis. 3. While there are a number of reports of high urinary PEA excretion in schizophrenic patients, the measurement of PEA in other body fluids and the measurement of phenylacetic acid (the major metabolite of PEA) has resulted in inconsistent findings. 4. The use of neuroleptic medication is a major confounding variable in most of the clinical studies. If PEA does have a role in the etiology of schizophrenia, the mechanism may involve PEAs ability to amplify dopamine responses.

Simultaneous analysis of twelve biogenic amine metabolites in plasma, cerebrospinal fluid and urine by capillary column gas chromatography-high-resolution mass spectrometry with selected-ion monitoring.

A procedure is described for the simultaneous determination of twelve acidic and alcoholic metabolites of trace and catecholic biogenic amines in plasma, cerebrospinal fluid and urine by capillary column gas chromatography--high-resolution mass spectrometry. Protein precipitation with sulphosalicylic acid, derivatization with two different reagent systems, final sample clean-up with a buffer wash and a program for automatically changing the reference mass of the mass spectrometer to suit each group of compounds as they are eluted from the column, are the main novel features of the procedure. A brief description of the synthesis of the deuterium-labelled internal standards is provided. The procedure is applied to biological samples and a comparison to reported values is given.