Detention in Juvenile Correctional Facilities Is Associated with Higher Platelet Monoamine Oxidase B Activity in Males

Juvenile delinquency is related to several biological factors, yet very few vulnerability biomarkers have been identified. Previous data suggest that the enzyme monoamine oxidase B (MAO-B) influences several personality traits linked to the propensity to engage in delinquent behavior. Building on this evidence, we assessed whether conduct disorder (CD), juvenile delinquency adjudications, or detention in a correctional facility were associated with either platelet MAO-B activity or the MAOB rs1799836 polymorphism. The study enrolled 289 medication-free male youths, including 182 individuals detained in a correctional facility (with or without a diagnosis of CD). Of the remaining 107 participants, 26 subjects had a diagnosis of CD, and 81 were mentally healthy controls. Platelet MAO-B activity was determined by spectrophotofluorometry, while MAOB rs1799836 was genotyped using qPCR. Platelet MAO-B activity, corrected for age and smoking, was significantly higher in juvenile detainees (p < 0.001), irrespective of CD diagnosis. MAOB rs1799836 was not associated with platelet MAO-B activity or with detention in a correctional facility, CD diagnosis, or delinquent behavior. These data suggest that detention in a juvenile correctional facility increases platelet MAO-B activity in male adolescents. Future studies are needed to determine the mechanisms and functional significance of MAO-B peripheral elevation in juvenile male detainees.

Monoamine oxidase-A targeting probe for prostate cancer imaging and inhibition of metastasis

Mitochondrial enzyme monoamine oxidase (MAO-A) is known to be overexpressed in prostate cancer (PCa) cells.

Enzymatic oxidation of substituted tryptamines catalysed by monoamine oxidase

The enzymatic deamination of 5-fl uorotryptamine and 5-hydroxytryptamine, 5-HT, catalysed by enzyme monoamine oxidase A (MAO-A, EC 1.4.3.4) was investigated using the kinetic (KIE) and solvent (SIE) isotope effects methods. The numerical values of deuterium isotope effects in the (1R) positions of 5-F-tryptamine were determined using non-competitive spectrophotomeric method. Isotopologue 5-F-[(1R)- -2H]-tryptamine, needed for kinetic studies was obtained by enzymatic decarboxylation of 5´-fl uoro-L-tryptophan, 5´-F-L-Trp, in fully deuteriated medium.

Substrate-dependent regulation of MAO-A in rat mesangial cells: involvement of dopamine D2-like receptors

In the present study, we investigated the existence of a back-regulation of the catecholamine-degrading enzyme monoamine oxidase (MAO)-A by dopamine in rat renal cells. In proximal tubule cells, MAO-A expression was not modified after dopamine receptor stimulation. In contrast, in mesangial cells, enzyme assay and Western blots showed that MAO activity and protein increased by ∼80% after 48-h incubation with the D2-like receptor agonist bromocriptine and quinpirole but not with the D1-like receptor agonist SKF-38393. This effect was prevented by the D2-receptor antagonist sulpiride and domperidone. The increase in MAO-A protein was preceded by an augmentation of MAO-A mRNA that was prevented by the transcriptional inhibitor actinomycin D. Bromocriptine effect was mimicked by the PKA inhibitor H89 and inhibited by the PKA activator 8-bromo-cAMP. These results show for the first time the existence of a dopamine-dependent MAO-A regulation involving D2-like receptors, inhibition of the cAMP-PKA pathway, and an ex novo enzyme synthesis.

Selective Decreases in MAO-B Activity in Post-Mortem Brains from Schizophrenic Patients with Type II Syndrome

The activities of the A and B forms of the enzyme monoamine oxidase (MAO, E.C. 1.4.3.4) have been assessed with the substrates 5-hydroxytryptamine and benzylamine respectively in seven areas of the brains of 39 patients with schizophrenia and 44 control subjects. Whereas previous studies have found the enzyme unchanged in brain in schizophrenia, in this study there was a modest but significant decrease in the activity of MAO-B in frontal and temporal cortices and in amygdala. This decrease could not be accounted for by neuroleptic medication, age, sex or post-mortem variables. In a series of 22 patients who had been assessed in life, the reduction in MAO-B activity was found to be associated specifically with the presence of negative symptoms (flattening of affect and paucity of speech). The findings are therefore consistent with other evidence for structural and neurochemical change in the temporal lobe that have been associated with the type II (defect state) syndrome of schizophrenia. The change in enzyme activity is unlikely to be related to a change in monoamine metabolism but may reflect a disturbance in glial function. The change in MAO-B activity in brain in this study is confined to particular areas of brain and a subgroup of patients; it is thought to be entirely unrelated to earlier reports of reductions of enzyme activity in platelets, which are probably attributable to prolonged neuroleptic medication.