Evidence for existence of immobilization stress-inducible semicarbazide-sensitive amine oxidase inhibitor in rat brain cytosol

Formaldehyde in brain: an overlooked player in neurodegeneration?

Formaldehyde is an environmental pollutant that is also generated in substantial amounts in the human body during normal metabolism. This aldehyde is a well-established neurotoxin that affects memory, learning, and behavior. In addition, in several pathological conditions, including Alzheimer's disease, an increase in the expression of formaldehyde-generating enzymes and elevated levels of formaldehyde in brain have been reported. This article gives an overview on the current knowledge on the generation and metabolism of formaldehyde in brain cells as well as on formaldehyde-induced alterations in metabolic processes. Brain cells have the potential to generate and to dispose formaldehyde. In culture, both astrocytes and neurons efficiently oxidize formaldehyde to formate which can be exported or further oxidized. Although moderate concentrations of formaldehyde are not acutely toxic for brain cells, exposure to formaldehyde severely affects their metabolism as demonstrated by the formaldehyde-induced acceleration of glycolytic flux and by the rapid multidrug resistance protein 1-mediated export of glutathione from both astrocytes and neurons. These formaldehyde-induced alterations in the metabolism of brain cells may contribute to the impaired cognitive performance observed after formaldehyde exposure and to the neurodegeneration in diseases that are associated with increased formaldehyde levels in brain.

Soluble vascular adhesion protein-1: decreased activity in the plasma of trauma victims and predictive marker for severity of traumatic brain injury

BACKGROUND

This study done was to investigate the clinical significance of soluble vascular adhesion protein-1 (sVAP-1) activity in trauma patients with different patterns.

METHODS

96 patients with consecutive trauma ≥15 years who were admitted to emergency department of the Second Affiliated Hospital, Shantou University Medical College, China, between January 2007 and December 2009 were enrolled in this study. Plasma was collected at admission. Injury-severity score (ISS) and Glasgow Coma Scale (GCS) were used to determine the patient conditions. sVAP-1 activity was determined by using the high performance liquid chromatographic (HPLC) system.

RESULTS

Mean sVAP-1 activity in trauma patients was significantly lower than that of controls (P<0.0001), and the level was negatively correlated with circulating leucocytes and neutrophils (P<0.0001). There was a significant correlation between lower sVAP-1 activity and injury patterns. However, plasma sVAP-1 activity increased significantly in accordance with the severity of traumatic brain injury (TBI), and the patients with sVAP-1 value above 8.61 nmol/ml/h have much higher mortality rate (25.0%) than patients with sVAP-1 value lower than 8.61 nmol/ml/h (0.0%) (P=0.011).

CONCLUSIONS

Trauma patients had a decreased sVAP-1 activity. However, isolated TBI patients with higher activity of sVAP-1 at admission were more likely to have a poor outcome.

Decreased serum semicarbazide sensitive aminooxidase (SSAO) activity in patients with major depression

Semicarbazide sensitive aminooxidase (SSAO) is known to interplay with monoamine oxidases (MAO) and several antidepressants. Taking into account the monoamine hypothesis concerning the pathophysiology of depression, the aim of the present pilot study was to evaluate serum SSAO activity in depressed patients. A total of 21 inpatients with major depression and 41 healthy controls were studied. Serum SSAO activity was determined by HPLC on days 1, 5 and 10 of inpatient treatment. At baseline without medication including antidepressants, highly depressed patients (MADRS score>or=30) had significantly decreased serum SSAO activity (mean 385+/-161 mU/l) when compared to healthy controls (mean 526+/-141 mU/l; p=0.003). This SSAO decrease was less pronounced at day 5 and day 10 under an antidepressive drug regime. Decreased serum SSAO activity was observed in patients with major depression, especially in those with high MADRS scores. The present results support the hypothesis of dysfunctional monoaminergic metabolism in the pathogenesis of depressive disorders. The disputable association between depression and monoamine metabolism requires further investigation, particularly with regard to SSAO activity and medication status.

Endogenous semicarbazide-sensitive amine oxidase (SSAO) inhibitor increases 1-methyl-4-phenylpyridinium ion (MPP+)-induced dopamine efflux by immobilization stress in rat striatum

The present study examined whether or not immobilization stress (IMMO)-inducible semicarbazide-sensitive amine oxidase (SSAO) inhibitor by separated gel filtration from 105,000 g supernate in rat brain cytosol contribute to the dopamine (DA) efflux by 1-methyl-4-phenylpyridinium ion (MPP(+)) in the rat striatum. The isoelectric point (pI) value of this inhibitor was determined by isoelectric focusing (IEF)-gel electrophoresis to about 3.8. The application of IMMO-induced SSAO inhibitor (3 microg) by IEF-gel electrophoresis increased DA efflux by MPP(+) in rat striatum. These results suggest that IMMO-inducible endogenous SSAO inhibitor enhances DA efflux by MPP(+).

Semicarbazide-sensitive amine oxidase (SSAO) in the brain

Semicarbazide-sensitive amine oxidase (SSAO) is widely distributed in almost tissues. However, its presence in brain microvessels is still controversial. The affinity of SSAO towards benzylamine (Bz) is considerably higher than that of monoamine oxidase (MAO). SSAO plays a role in the toxicity of several environmental and endogenous amines. SSAO-mediated production of toxic aldehydes has been proposed to be related to pathophysiological conditions. The most potent of inhibition of SSAO in monkey brain was observed by tricyclic antidepressant drug imipramine, as compared to tetracyclic drug maprotiline or non-cyclic drug nomifensine. An endogenous SSAO modulator in rat brain cytosol after immobilization stress (IMMO) was found and that this inhibitor could be induced by IMMO. SSAO activity in rat brain might be regulated by the level of this inhibitor. Semicarbazide, a SSAO inhibitor, enhances the formation of .OH products of efflux/oxidation due to 1-methyl-4-phenylpyridinium ion (MPP+). The precise physiological functions of SSAO could play an important role in the control of energy balance in adipose tissue. SSAO could play an important role in the regulation of adipocyte homeostasis.