Brain-Derived Neurotrophic Factor (BDNF) and Serotonin Transporter (SERT) in Platelets of Patients with Mild Huntington's Disease: Relationships with Social Cognition Symptoms.

Deficits in social-cognition processing have been identified during early stages of Huntington Disease (HD), attracting interest on their relevance as possible predictors of  neurodegenerative progression. Since the neurotrophin Brain-Derived Neurotrophic Factor (BDNF) and the serotonin (5-HT) transporter (SERT) are known to modulate human adaptive behavior, we appraised these two proteins in mild-HD using blood platelets, with the aim at finding relationships with cognitive/psychosocial skills. Thirteen gene positive and symptomatic patients (9M/4W, HD-stage II, age> 40y) together 11 gender/age matched controls without a concurrent diagnosis of psychiatric disorders, underwent a blood test to determine BDNF storage and membrane-bound SERT in platelets by an ELISA immune-enzyme dosage and [3H]-paroxetine ([3H]-PAR) binding, respectively. Enrolled subjects were concurrently evaluated through a battery of socio-cognitive tests and emotion recognition questionnaires.Results showed greater intra-platelet BDNF (~ +20-22%) in patients versus controls, whereas equilibrium [3H]-PAR binding parameters, maximum density (Bmax) and dissociation constant (KD), did not appreciably vary in the two comparison groups. Cognitive/emotion abilities were found significantly reduced in patients. Additionally, platelet BDNF was unrelated to psycho-cognitive scores, but positively correlated with the illness duration. As well, SERT Bmax was unconnected to HD signs or socio-cognitive scores, whilst KDs negatively correlated with scores for angry voice recognition in both controls and patients. This pilot study suggests that platelet BDNF and SERT do not specifically underlie psychosocial deficits in stage II-HD, while higher BDNF storage in delayed mild symptoms, would derive from compensatory mechanisms. Supplementary investigations are warranted, by also comparing patients in other illness's phases.

Adenylate-cyclase activity in platelets of patients with obsessive-compulsive disorder.

Although the main biological hypothesis on the pathophysiology of obsessive-compulsive disorder (OCD) is centered on the serotonin system, indications are available that other neurotransmitters, and even second messengers, particularly the cyclic adenosine monophosphate (cAMP) signaling, may be involved, though effective data are few. Therefore, the aim of the present study was to evaluate and compare the basal and isoprenaline (ISO)-stimulated velocity of adenylate-cyclase (AC) in human platelet membranes of patients with OCD and healthy control subjects. The results showed that the basal and ISO-stimulated AC activity, as well as the dose-response curves of ISO by using agonist concentrations ranging between 0.1 nM and 10 muM, were not different in the two groups. However, OCD patients showed lower EC(50) and higher E(max) values than healthy subjects. These findings suggest the presence of supersensitive beta-adrenergic receptors in platelets of OCD patients.

In vitro effects of lead ions on peripheral benzodiazepine receptors and adenylyl cyclase activity in the mantle of Mytilus galloprovincialis.

As an extension of our previous work, where the density of peripheral benzodiazepine receptors (PBR) increased in mantle mitochondria of the marine mollusk Mytilus galloprovincialis Lmk. under chronic exposure to lead, the present study investigates the in vitro effects of an exogenous source of lead ions on PBR and on adenylyl cyclase (AC) complex in mantle membranes of mussels collected from a non-polluted coastal area. PBR binding experiments used the specific isoquinoline carboxamide derivative [3H]PK 11195, and AC activity was measured using a modified procedure adapted to M. galloprovincialis. Lead ions (Pb2+) dose-dependently decreased either the [3H]PK 11195 specific binding in mitochondria or basal AC velocity in plasma membranes of mussel mantle. The IC50 values for lead ions were 10 microM with [3H]PK 11195 binding and 25 microM with AC activity, with maximal inhibition values of 60% and 70%, respectively. Moreover, lead behaved as a non-competitive inhibitor on [3H]PK 11195 binding and as a 'mixed' inhibitor on AC activity. The present results suggest that some of the early effects induced by lead in mussel cell metabolism consist in significant changes of the PBR density and cyclic AMP production in the mantle of M. galloprovincialis.

Simultaneous analysis of clozapine, clomipramine and their metabolites by reversed-phase liquid chromatography.

1. The authors present here a sensitive and rapid reversed-phase liquid chromatographic method which enables the simultaneous analysis in plasma of two different drugs and their metabolites: the atypical neuroleptic clozapine and the tricyclic antidepressant clomipramine. 2. Samples and the internal standard (dibenzepine) were extracted through automated solid-phase procedure, evaporated dryness and injected into the chromatograph. Mobile phase was a mixture of water and acetonitrile (63:37, v:v) containing TEMED and triethylamine. The total chromatographic time was of 14 min and analyte peaks were detected by means of an ultraviolet spectrophotometer preset at 254 nm. 3. Results revealed an assay sensitivity of 5 microg/L for clozapine or norclozapine and of 10 microg/L for clomipramine and desmethylclomipramine. Recoveries for these drugs and their metabolites were more than 60% and their coefficient of variation (within day and day-to-day) ranged from 1.3 % to 2.5 %. In spiked plasma, within day and day-to-day coefficients of variability (CV) were less than 5%. The simultaneous evaluation of these two drugs with adequate sensitivity and precision makes it particularly useful for therapeutic drug monitoring during mono- or polypharmacotherapy.

Simultaneous plasma level analysis of clomipramine, N-desmethylclomipramine, and fluvoxamine by reversed-phase liquid chromatography.

A simple reversed-phase liquid chromatographic method enabling the simultaneous analysis in plasma of the tricyclic antidepressant clomipramine, its demethylated metabolite, and the selective serotonin reuptake inhibitor fluvoxamine, was developed. The drugs and dibenzepine, the internal standard, were extracted from 1 mL plasma through an automated solid-phase procedure, eluted in a total chromatographic time of approximately 14 min and detected by means of an ultraviolet spectrophotometer preset at 254 nm. An assay sensitivity of 10 microg/L was observed for all analytes. Recoveries for these drugs and their metabolites ranged between 65% and 98% and their coefficient of variation (within-day and day-to-day) between 1.9% and 2.9%. In spiked plasma, within-day and day-to-day imprecision data were less than 5%. The simultaneous determination of clomipramine, N-desmethylclomipramine, and fluvoxamine with adequate sensitivity and accuracy may be useful for the monitoring of drug treatment in depression and obsessive-compulsive disorder, where combinations of such drugs are employed.

Lack of stereoselectivity of 8-hydroxy-2(di-N-propylamino)tetralin-mediated inhibition of forskolin-stimulated adenylyl cyclase activity in human pre- and post-synaptic brain regions.

The stereoselectivity of the serotonin1A (5-HT1A) receptor compound 8-hydroxy-2(di-N-propylamino)tetralin (8-OH-DPAT) on forskolin-stimulated adenylyl cyclase activity was investigated in membranes from human 5-HT pre-synaptic (raphe nuclei) and post-synaptic (hippocampus and prefrontal cortex) regions of autopsy brains. After sample incubation with agonists and antagonists, results showed that both the racemic mixture of 8-OH-DPAT or its (+) and (-) enantiomers behaved as full agonists in the tested brain regions. Enantiomer potency (EC50, nM) and efficacy (percentage of maximal inhibition, %) values were similar in all regions under investigation. However, some inter and intra-region variations in racemic 8-OH-DPAT potency and efficacy have been observed. In particular, the potency of racemic 8-OH-DPAT was higher in the prefrontal cortex and raphe nuclei than in the hippocampus, where it was in fact lower than either single enantiomers. Agonist effects were competitively reversed by 5-HT1A antagonists, although once again a different profile was revealed in the hippocampus. The data underscores the lack of stereospecificity of 8-OH-DPAT-mediated inhibition of adenylyl cyclase activity in either pre- or post-synaptic human brain regions. Moreover, such results have significant implication, as they support the notion that human 5-HT1A receptors might vary from one brain region to the other.

Gender and age-related variation in adenylyl cyclase activity in the human prefrontal cortex, hippocampus and dorsal raphe nuclei.

The influence of gender and age on adenylyl cyclase activity was investigated, through a Dowex-alumina double step chromatographic procedure, in the prefrontal cortex, hippocampus and dorsal raphe nuclei obtained from autopsy cadavers. Results showed that forskolin-stimulated enzyme activity in raphe nuclei was greater in men than in women; a region-dependent rank order of basal, forskolin-induced adenylyl cyclase activity and percentage forskolin-stimulation was observed in women only. Lastly, basal values correlated positively with forskolin-stimulated adenylyl cyclase activity in all areas except the prefrontal cortex of the male subjects. Positive significant correlations were also found between both forskolin-stimulated enzyme activity and percentage forskolin stimulation and aging in the prefrontal cortex. Overall, the findings suggest that sex and/or age-related differences in brain adenylyl cyclase vary from one cerebral region to the other.

Regulation of the platelet serotonin transporter by protein kinase C in the young and elderly.

BACKGROUND: Some data show that different factors may influence the serotonin (5-HT) uptake rate. Our study aimed at evaluating the possible role of a protein kinase C (PKC) activator, i.e., 4-beta-12-tetradecanoylphorbol-13-acetate (beta-TPA) on the platelet 5-HT uptake of young and elderly subjects, through the measurement of the 5-HT uptake itself and 3H-paroxetine ([3H]PAR) binding sites, which correspond to the transporter protein. METHODS: Human platelets and 5-HT uptake were evaluated according to the method of Arora and Meltzer, while [3H]PAR binding was performed following the Marazziti et al method. RESULTS: The results showed that beta-TPA reduced significantly the maximal velocity (Vmax) of 5-HT uptake, with no change in the Michaelis constant or in [3H]PAR binding parameters, in platelets of both young and elderly subjects. Although this last group of subjects had a significantly lower Vmax than the other, the degree of inhibition was almost the same (75%) in both. CONCLUSIONS: These findings indicate that PKC decreases the 5-HT uptake rate by modifying the phosphorylation state of the transporter and with no change in the number of [3H]PAR binding sites. The responsiveness of this pathway is identical in both young and elderly subjects.

Effects of postmortem delay on serotonin and (+)8-OH-DPAT-mediated inhibition of adenylyl cyclase activity in rat and human brain tissues.

The reproducibility of serotonin (5-HT) and (+)8-OH-DPAT-mediated inhibition of adenylyl cyclase activity was assessed in membranes, stimulated by forskolin, of rat frontal cortex postmortem as well as of human fronto-cortical, hippocampal and dorsal raphe tissues obtained from autopsy brains. The results revealed that differences between basal and forskolin-stimulated enzyme activities were still significant after 48 h postmortem in rat cortex and in all human brain regions up to 46 h after death. However, a decrease of about 17 and 26% in forskolin-stimulated adenylyl cyclase activity was observed at 24 and 48 h, respectively, in rat cortex. 5-HT and the 5-HT1A receptor agonist, (+)8-hydroxy-2(di-N-propylamino)tetraline (8-OH-DPAT), were able to inhibit forskolin-stimulated adenylyl cyclase activity in a dose-dependent manner for 48 h after death in rat and human brain. In rat cortex, both 5-HT and (+)8-OH-DPAT potencies (EC50, nM) and efficacies (percent of maximum inhibition capacity, %) varied significantly with postmortem delay. Conversely, in human tissues, postmortem delay and subject age did not modify agonist potencies and efficacies. Furthermore, a regionality of 5-HT potency and efficacy was revealed in the human brain. 5-HT was equally potent in cortex and raphe nuclei, while being more potent but less effective in hippocampus. (+)8-OH-DPAT was more active in hippocampus and raphe nuclei than in cortex. (+)8-OH-DPAT behaved as an agonist in all areas, as its efficacy was similar or greater than those obtained with 5-HT. The (+)8-OH-DPAT dose-response curve was completely reversed by 5-HT1A receptor antagonists in rat cortex and all human brain areas. In conclusion, we suggest here that differences between rat and human brain might exist at the level of postmortem degradation of 5-HT-sensitive adenylyl cyclase activity. In human brain, 5-HT1A receptor-mediated inhibition of adenylyl cyclase seems to be reproducible, suggesting that reliable experiments can be carried out on postmortem specimens from patients with neuropsychiatric disorders.

Decreased platelet 3H-paroxetine binding in untreated panic disorder patients.

Different findings support the involvement of the serotonin (5-HT) system in panic disorder. The presence of the 5-HT transporter in blood platelets similar to that in presynaptic serotonergic neurons, permits the investigation of this structure in periphery. We therefore evaluated the binding of 3H-paroxetine, a selective 5-HT reuptake inhibitor which is considered the ligand of choice for labelling the 5-HT transporter, in platelets of 20 drug-free patients with panic disorder. The same measurement was repeated after one year's treatment with different drugs. The results showed patients to have a lower number of 3H-paroxetine sites than a group of age- and sex-matched controls, thus suggesting the involvement of the 5-HT transporter in panic disorder. This abnormality reverted after one year of treatment with specific drugs that provoked the symptom remission in all cases, which would suggest a link with the clinical improvement.

Gender-related seasonality of human platelet phenolsulfotransferase activity.

This study focused on the investigation of the possible effect of gender and season on the activity of the thermolabile and thermostable forms of platelet phenolsulfotransferase (PST) in a group of 23 healthy, drug-free volunteers of both sexes. The results showed a different seasonal profile of PST activity in men and women: in men, PST seasonal rhythms revealed a shallow profile with higher values in both the spring and summer than in the autumn. Conversely, in women, the PST seasonality showed a profile consisting overall of a main peak in the summer. Also, significant gender-dependent correlations were found between the photoperiod length and PST values. Our findings should stimulate further investigation into gender-dependent molecular mechanisms underlying the regulation of the metabolism of endogenous and xenobiotic agents, such as monoamines and phenols, which are the substrates of PST.

Effect of aging and sex on the [3H]-paroxetine binding to human platelets.

Since there exist conflicting results with regard to the possible effect of aging on platelet [3H]-imipramine binding, taken as a peripheral marker of the serotonin (5-HT) transporter, we reinvestigated this matter by comparing the binding of the more selective ligand [3H]-paroxetine in 20 aged and 23 young subjects. The results showed that neither the maximum binding capacity nor the dissociation constant (Kd) were significantly different in the two groups. When the subjects were compared according to sex, the young females revealed a statistically significant lower Kd than the males, while the contrary was true for the aged females. The Kd was significantly and negatively correlated to age in males. In addition, a significant age x gender interaction was also observed. Therefore, the sex of a subject would seem to provoke significant age-related changes in the Kd of [3H]-paroxetine binding to platelet membranes. This might indicate modifications in the 5-HT transporter that could form the basis of a sex-related difference in vulnerability to disorders, such as depression, where a dysfunction at this level is hypothesized.

[3H]ketanserin binding in human brain postmortem.

This study aimed at comparing the binding characteristics of [3H]ketanserin, a high-affinity serotonin 2A (5-HT2A) receptor antagonist, in the prefrontal cortex, hippocampus and striatum of human brain post-mortem. The results indicated the presence of a single population of binding sites in all the regions investigated, with no statistical difference in maximum binding capacity (B(max)) or dissociation constant (K(d)) values. The pharmacological profile of [3H]ketanserin binding was consistent with the labeling of the 5-HT2A receptor, since it revealed a competing drug potency ranking of ketanserin = spiperone > clozapine = haloperidol > methysergide > mesulergine > 5-HT. In conclusion, the 5-HT2A receptor, as labeled by [3H]ketanserin, would seem to consist of a homogenous population of binding sites and to be equally distributed in human prefronto-cortical, limbic and extrapyramidal structures.

Apparent absence of aging and gender effects on serotonin 1A receptors in human neocortex and hippocampus.

The effects of gender, aging and gender x age on the binding of the 5-HT1A receptor high-affinity agonist [3H]8-hydroxy-2(di-N-propylamino)tetralin ([3H]8-OH-DPAT), were evaluated and compared in tissues of human prefrontal, temporal, parietal, occipital cortex and hippocampus obtained from 21 autopsy subjects. The results revealed no variation with age or gender in either the [3H]8-OH-DPAT maximum binding capacity (Bmax) or dissociation constant (Kd) values. On the other hand, when separate correlations to subject ages were performed for men and women, aging effects on [3H]8-OH-DPAT Bmax and Kd were detected: in men, a significant age-dependent decrease in Kd values was observed in the occipital cortex; in women, the Bmax significantly decreased with aging in the parietal cortex and hippocampus, while increasing in occipito-cortical membranes. Overall, the present study reveals that, although neither gender nor aging 'per se' seem to modify the 5-HT1A receptor binding, gender may reveal region-specific aging effects, i.e. on receptor affinity in men and receptor density in women. Such findings should stimulate further investigation on the hypothesized existence of gender x age-related cross-connections between serotonergic system and hypothalamus-pituitary-gonadal circuits.

Further characterisation of [3H]8-hydroxy-2-(di-N-propylamino)tetralin binding sites in human brain postmortem.

The saturation parameters and the pharmacological characteristics of the binding of the serotonin 1A (5-HT1A) receptor agonist [3H]8-hydroxy-2-(di-N-propylamino)tetralin ([3H]8-OH-DPAT), as well as the effects of nucleotides and divalent cations (Mg2+, Mn2+) on it, were compared in some human postmortem brain regions: the main cortical areas, hippocampus and striatum. [3H]8-OH-DPAT labelled a single population of recognition sites with the highest maximal capacity (Bmax) in the hippocampus and the lowest affinity in the striatum. Among the various cortical areas, the frontal cortex exhibited the highest Bmax. The pharmacological profile of the [3H]8-OH-DPAT binding sites was consistent with the labelling of the 5-HT1A receptor in the hippocampus and cortex, whereas the striatal site shared strong similarity to the presynaptic serotonin transporter. Modulation of [3H]8-OH-DPAT binding by divalent cations and nucleotides was detectable and stable in autopsy brains. In particular, nucleotide effects were area-dependent: guanosine thiotriphosphate (GTP gamma S) reduced [3H]8-OH-DPAT binding to the same extent in the hippocampus and frontal cortex, while having no effect in the striatum. Divalent cation effects depended also upon the brain area: in the striatum, they inhibited [3H]8-OH-DPAT binding, while stimulating it in the hippocampus and, with less extent, in the frontal cortex. In summary, these findings suggest that the [3H]8-OH-DPAT binding and its modulatory parameters in human brain tissues seem to show similarities but also some differences with respect to those determined in the rat brain. Furthermore, postmortem stability of GTP and divalent cation sensitive 5-HT1A receptors underlines the need for further studies on the regulatory and functional properties of this receptor in the human brain.

Changes in platelet markers of obsessive-compulsive patients during a double-blind trial of fluvoxamine versus clomipramine.

Abnormalities of platelet serotonin (5-HT) transporter, which are supposed to reflect similar dysfunctions in the central nervous system (CNS), have been reported in obsessive-compulsive disorder (OCD). Other platelet parameters altered in OCD are represented by phenolsulfotransferase (PST) activity, an enzyme involved in the catabolism of catecholic neuro-transmitters, and peripheral benzodiazepine receptors. Since no information is available on the behavior of these putative markers during antiobsessive treatments, the aim of the present study was to measure and compare 3H-imipramine (3H-IMI) binding, which labels the 5-HT transporter, PST activity, and 3H-PK 11,195 binding, which labels peripheral benzodiazepine receptors, in a group of 18 patients with obsessive-compulsive disorder (OCD) before and after a treatment with fluvoxamine versus clomipramine. The results showed that at baseline the patients had a decreased number of 3H-IMI binding sites, which correlated negatively with the Y-BOCS total score, an increased PST activity and no difference in 3H-PK 11,195 binding, as compared with healthy volunteers. After eight weeks of treatment with either clomipramine or fluvoxamine, which was effective in all patients, the number of 3H-IMI binding sites increased significantly toward normal values, while the PST showed no change. These findings suggest that the reduction in 3H-IMI binding sites in OCD may be related to the severity of the illness and possibly to a positive response to serotonin re-uptake inhibitors, and might be considered as a state-dependent marker, whereas the PST activity would seem to be a trait of the illness.

Platelet sulfotransferase in different psychiatric disorders.

The aim of our study was to measure and compare platelet phenolsulfotransferase (PST) activity in patients affected by different psychiatric disorders and in healthy volunteers. The results showed that the activity of both of the two forms of PST was significantly higher in 30 patients with obsessive-compulsive disorder and in 25 manic patients than in 20 healthy volunteers. On the contrary, normal values were found in 11 dysthymic patients, 12 bipolar depressives, and 14 patients with panic disorder, whereas lower values were found in 12 unipolar depressives and 30 patients with migraine. It would therefore seem that different neuropsychiatric disorders are associated with different levels of PST activity.

Platelet abnormalities in aggressive subjects with mental deficiency.

Platelet 3H-imipramine (3H-IMI) binding and platelet sulfotransferase (ST) activity, taken as markers of the serotonin (5-HT) and sulfated neurotransmitters (tyramine, dopamine, serotonin, noradrenaline), respectively, were evaluated in 14 severely aggressive subjects institutionalized since childhood for mental retardation and in an equal number of healthy controls. The results showed the presence of a lower number of 3H-IMI binding sites and a higher ST activity in the patients as compared with controls. These data provide supporting evidence for the hypothesis of an abnormality of the 5-HT system and suggest possible dysfunctions of dopamine and sulfated amines in aggressive behavior, at least as reflected by platelet markers.

Platelet markers in suicide attempters.

1. The authors measured 3H-imipramine (3H-IMI) binding and serotonin (5HT) uptake parameters as well as sulphotransferase activity in platelets of suicide attempters. 2. Platelet 3H-IMI binding sites and 5HT uptake are related to similar sites and processes present in the brain, and sulphotransferase (ST) is an enzyme involved in the catabolism of cathecholamines. 3. The results showed the presence of a decreased density of both 3H-IMI binding and of 5HT uptake sites, with no change in ST activity in suicide attempters, as compared with healthy controls. 4. The reduced 3H-IMI binding and 5HT uptake may be related to a hypofunction of presynaptic serotonergic mechanisms which might be altered in suicidal behavior.