Platelet monoamine oxidase activity in epilepsy

Evidence in support of using a neurochemistry approach to identify therapy for both epilepsy and associated depression

The present study aimed to develop a neurochemistry-based single or adjuvant therapy approach for comprehensive management of epilepsy and associated depression employing pentylenetetrazole-kindled animals. Kindling was induced in two-month-old male Swiss albino mice by administering a subconvulsant pentylenetetrazole dose (35mg/kg, i.p.) at an interval of 48±2h. These kindled animals were treated with saline and sodium valproate (300mg/kg/day, i.p.) for 15days. Except for the naïve group, all other groups were challenged with pentylenetetrazole (35mg/kg, i.p.) on days 5, 10, and 15 to evaluate the seizure severity. Depression was evaluated in all experimental groups after normalization of locomotor activity, using tail suspension and forced swim test on days 1, 5, 10, and 15. Four hours after behavioral evaluations on day 15, all animals were euthanized to collect their serum and discrete brain parts. Corticosterone levels were estimated in all the experimental groups as a marker of a dysregulated hypothalamus pituitary adrenal axis. Neurochemical alterations (norepinephrine, dopamine, tryptophan, kynurenine, serotonin, glutamate, GABA, and total nitrate levels) were also estimated in the cortical and hippocampal areas of the mouse brain. Results revealed that saline-treated kindled animals were associated with significant depression and altered neurochemical milieu in comparison with naïve animals. Chronic valproate treatment in kindled animals significantly reduced seizure severity score bud did not ameliorate associated depression or completely restore altered biochemical and neurochemical milieu. Based on the observation of neurochemical changes in all the groups, we propose that restoration of altered neurochemical milieu, elevated indoleamine 2,3-dioxygenase enzyme activity, and corticosterone levels using pharmacological tools with/out valproic acid may be explored for management of both epilepsy and comorbid depression.

Adjuvant indoleamine 2,3-dioxygenase enzyme inhibition for comprehensive management of epilepsy and comorbid depression

Epilepsy is one of the major neurological disorders frequently associated with psychiatric disorders such as depression. Alteration of tryptophan metabolism towards kynurenine pathway may be one of the plausible reasons for association of depression in epilepsy. Hence, this study was envisaged to evaluate the dose dependent inhibition of indoleamine 2,3-dioxygenase (IDO) enzyme (responsible for shifting tryptophan metabolism) employing minocycline with valproic acid for comprehensive management of epilepsy and comorbid depression. Kindling was induced in male swiss albino mice by administration of pentylenetetrazole subconvulsive dose (35mg/kg, i.p.) at an interval of 48±2h. Kindled animals were treated with saline, valproate (300mg/kg/day i.p.), valproate in combination with different doses of minocycline (10mg/kg; 20mg/kg; 40mg/kg)/day i.p. and minocycline per se (40mg/kg/day i.p.) for 15 days. Except naïve, all the groups were challenged with pentylenetetrazole (35mg/kg i.p.) on day 5, 10, and 15 to evaluate the seizure severity score. Depression was evaluated in all experimental groups using tail suspension and forced swim test on days 1, 5, 10 and 15, 2h after pentylenetetrazole challenge. Results suggested that saline treated kindled animals were significantly associated with depression. Chronic valproate treatment significantly reduced seizure severity score but unable to ameliorate the associated depression. Minocycline supplementation with valproic acid dose dependently ameliorated depression associated with epilepsy. Neurochemical and biochemical findings also supported the behavioural findings of the study. Thus, our results suggested that supplementation of IDO enzyme inhibitors with valproic acid could be explored further for comprehensive management of epilepsy and associated depression.

Human recombinant monoamine oxidase B as reliable and efficient enzyme source for inhibitor screening

Interest in inhibitors of monoamine oxidase type B (MAO B) has grown in recent years, due to their therapeutic potential in aging-related neurodegenerative diseases, such as Parkinson's disease and Alzheimer's disease. This study is devoted to the use of human recombinant MAO B obtained from a Baculovirus expression system (Supersomes MAO B, BD Gentest, MA, USA) as reliable and efficient enzyme source for MAO B inhibitor screening. Comparison of inhibition potencies (pIC50 values) determined with human cloned and human platelet MAO B for the two series of MAO B inhibitors, coumarin and 5H-indeno[1,2-c]pyridazin-5-one derivatives, showed that the difference between pIC50 values obtained with the two enzyme sources was not significant (P>0.05, Student's t-test). Hence, recombinant enzyme is validated as convenient enzyme source for MAO B inhibitor screening.

Genetics of platelet MAO activity in discordant schizophrenic and normal twins

Platelet monoamine oxidase (MAO) activity was compared in four age and sex-matched groups: monozygotic (MZ) twins discordant for schizophrenia, normal MZ twins, normal dizygotic (DZ) twins and unrelated individuals. Among the twin groups, schizophrenic and normal there was a remarkably consistent degree of genetic control amounting to 70-80 per cent of the variation in activity. The mean platelet MAO activity of the schizophrenic twins was significantly lower than that of controls, but not than that of their psychiatrically well, neuroleptic-free cotwins; indeed the correlation for the MZ twins discordant for schizophrenia was almost exactly the same as that for the normal MZs. Thus, lower platelet MAO activity in schizophrenia, where it is found, is genetically modulated and not the result of the illness or its treatment.

Human platelet monoamine oxidase activity in health and disease: a review

The most readily available source of monoamine oxidase in man is the platelet, although only the B form of the enzyme is represented in this site. Platelet activity is higher in women than in men. The enzyme activity is generally stable and is partly under genetic control. There is some evidence that individuals with low activity have a higher psychiatric morbidity than those with high activity. Despite some negative studies, the consensus of publication dealing with schizophrenia, migraine, and alcoholism find that mean platelet monoamine oxidase activity in the patient group is lower than in the controls. Values are raised in unipolar depression. Technical differences, or patient or control group heterogeneity, might well account for the absence of unanimity in the literature. A considerable degree of overlap between patient and control values, whatever the clinical diagnosis, appears to be the standard finding. Apart from these neuropsychiatric disturbances, platelet monoamine oxidase activity is raised in megaloblastic anaemia and reduced in iron deficiency anaemia. Although altered enzyme activity values may be linked to abnormal platelet populations in some of the haematological disorders discussed, in general the causes of abnormal platelet monoamine oxidase activity are unknown.