Dopamine receptors in human platelets

Risperidone Decreases Expression of Serotonin Receptor-2A (5-HT2A) and Serotonin Transporter (SERT) but Not Dopamine Receptors and Dopamine Transporter (DAT) in PBMCs from Patients with Schizophrenia

Dopamine and serotonin receptors and transporters play an essential role in the pathophysiology of schizophrenia; changes in their expression have been reported in neurons and leukocytes. Each antipsychotic induces a unique pattern in leukocyte function and phenotype. However, the use of polytherapy to treat schizophrenia makes it challenging to determine the specific effects of risperidone on peripheral blood mononuclear cells (PBMCs). The aim of this study was to evaluate the changes in the expression of D3, D5, DAT, 5-HT2A, and SERT in PBMCs from healthy volunteers (HV), drug-naive patients with schizophrenia (PWS), drug-free PWS, and PWS treated with risperidone for up to 40 weeks using quantitative PCR. Our study revealed elevated mRNA levels of D3, DAT, 5-HT2A, and SERT in unmedicated PWS. Treatment with risperidone led to a reduction only in the expression of 5-HT2A and SERT. Furthermore, we observed a moderate correlation between 5-HT2A expression and the positive and negative syndrome scale (PANSS), as well as SERT expression and PANSS scale. We also found a moderate correlation between 5-HT2A and SERT expression and the positive subscale. The duration of risperidone consumption had a significant negative correlation with the expression of 5-HT2A and SERT. Our study introduces the measurement of 5-HT2A and SERT expression in PBMCs as a useful parameter for assessing the response to risperidone in PWS.

Pheochromocytoma/paraganglioma-associated cardiomyopathy

Pheochromocytoma/paraganglioma (PPGL) are neuroendocrine tumors that frequently produce and release catecholamines. Catecholamine excess can manifest in several cardiovascular syndromes, including cardiomyopathy. PPGL-induced cardiomyopathies occur in up to 11% of cases and are most often associated with an adrenal pheochromocytoma (90%) and rarely with a paraganglioma derived from the sympathetic ganglia (10%). PPGL-associated cardiomyopathies can be chronic or acute, with takotsubo cardiomyopathy being the most often reported. These two types of PPGL-induced cardiomyopathy seem to have different pathophysiological backgrounds. Acute catecholaminergic stress inundates myocardial β-adrenoceptors and leads to left ventricle stunning and slight histological apoptosis. In chronic cardiomyopathy, prolonged catecholamine exposure leads to extended myocardial fibrosis, inflammation, and necrosis, and ultimately it causes dilated cardiomyopathy with a low ejection fraction. Sometimes, especially in cases associated with hypertension, hypertrophic cardiomyopathy can develop. The prognosis appears to be worse in chronic cases with a higher hospital mortality rate, higher cardiogenic shock rate at initial presentation, and lower left ventricular recovery rate after surgery. Therefore, establishing the correct diagnosis at an early stage of a PPGL is essential. This mini-review summarizes current data on pathophysiological pathways of cardiac damage caused by catecholamines, the clinical presentation of PPGL-induced cardiomyopathies, and discusses treatment options.

D1- and D2-type dopamine receptors are immunolocalized in pial and layer I astrocytes in the rat cerebral cortex

Pial astrocytes, a cellular component of the cerebral cortex surface structure, are observed in a wide range of mammalian species. Despite being recognized as such, the functional potential of pial astrocytes has long been overlooked. Our previous research demonstrated that pial astrocytes exhibit stronger immunoreactivity for muscarinic acetylcholine receptor M1 than protoplasmic astrocytes, indicating sensitivity to neuromodulators. Here, we examined whether pial astrocytes express receptors for dopamine, another crucial neuromodulator of cortical activity. We investigated the immunolocalization of each dopamine receptor subtype (D1R, D2R, D4R, D5R) in the rat cerebral cortex, and compared the intensity of immunoreactivity between pial astrocytes, protoplasmic astrocytes, and pyramidal cells. Our findings revealed that pial astrocytes and layer I astrocytes exhibit stronger D1R- and D4R-immunoreactivity than D2R and D5R. These immunoreactivities were primarily localized in the somata and thick processes of pial and layer I astrocytes. In contrast, protoplasmic astrocytes located in cortical layers II-VI displayed low or negligible immunoreactivities for dopamine receptors. D4R- and D5R-immunopositivity was distributed throughout pyramidal cells including somata and apical dendrites. These findings suggest that the dopaminergic system may regulate the activity of pial and layer I astrocytes via D1R and D4R.

Platelet Activation Favours NOX2-Mediated Muscle Damage in Elite Athletes: The Role of Cocoa-Derived Polyphenols

Mechanisms of exercise-induced muscle injury with etiopathogenesis and its consequences have been described; however, the impact of different intensities of exercise on the mechanisms of muscular injury development is not well understood. The aim of this study was to exploit the relationship between platelet activation, oxidative stress and muscular injuries induced by physical exercise in elite football players compared to amateur athletes. Oxidant/antioxidant status, platelet activation and markers of muscle damage were evaluated in 23 elite football players and 23 amateur athletes. Compared to amateurs, elite football players showed lower antioxidant capacity and higher oxidative stress paralleled by increased platelet activation and muscle damage markers. Simple linear regression analysis showed that sNOX2-dp and H₂O₂, sCD40L and PDGF-bb were associated with a significant increase in muscle damage biomarkers. In vitro studies also showed that plasma obtained from elite athletes increased oxidative stress and muscle damage in human skeletal muscle myoblasts cell line compared to amateurs’ plasma, an effect blunted by the NOX2 inhibitor or by the cell treatment with cocoa-derived polyphenols. These results indicate that platelet activation increased muscular injuries induced by oxidative stress. Moreover, NOX2 inhibition and polyphenol extracts treatment positively modulates redox status and reduce exercise-induced muscular injury.

Risk Factors for Cardiac Complications in Patients With Pheochromocytoma and Paraganglioma: A Retrospective Single-Center Study

BACKGROUND

Catecholamine excess arising from pheochromocytomas and paragangliomas (PPGLs) can cause a wide spectrum of cardiac manifestations. Although there are reviews of reported cases, these reviews lack detailed data, which makes it impossible to perform an accurate analysis. In this study, we conducted a comprehensive analysis of cardiovascular complications (CCs), including PPGL-related myocardial injury, cardiogenic shock, and arrhythmias requiring antiarrhythmic therapy, in a large cohort of patients with PPGL.

METHODS

We retrospectively analyzed the clinical data of consecutive patients with PPGL admitted between January 2018 and June 2020. The prevalence and the characteristics of patients with CCs were investigated. Moreover, comparisons were made between patients with and without CCs.

RESULTS

Compared with the non-CC group, the percentage of men was significantly lower (14/41 vs.92/175, 34.1% vs. 52.6%, p = 0.034) and the proportion of patients with paroxysmal hypertension was significantly higher (13/41 vs.29/173, 31.7% vs.16.8%, p = 0.03) in the CC group. More patients showed excessive sweating (19/41 vs 64/175, 46.3% vs. 24.0%, p = 0.004) and PPGL crisis (7/41 vs. 10/175, 17.1% vs.5.7%, p=0.035) in the CC group. In terms of laboratory findings, higher white blood cell [7.36 (6.49, 20.23) vs. 5.95 (5.1, 6.97)×10⁹/L, p<0.001] and platelet [339.28 ± 108.54 vs. 250.66 ± 70.83(×10⁹/L), p = 0.021] counts were more common in the CC group. There was also a higher prevalence of combination-producing PPGL in the CC group (13/24 vs.20/149, 54.2% vs.13.4%, p<0.001). However, the tumor size, invasive behavior on histology, and hemorrhage or necrosis on histology did not differ between the two groups. Platelet count [odds ratio (OR): 1.009; 95% confidence interval (CI) 1.001-1.016; p=0.023] and combination-secreting PPGL (OR: 5.009; 95% CI 1.365-18.38; p=0.015) are independent risk factors for CCs in patients with PPGL.

CONCLUSIONS

In patients with PPGL, even in the absence of signs and symptoms of CCs, a work up of cardiology should be strongly considered. Importantly, if patients with PPGLs have higher platelet counts and the combination-secreting pattern, they are more likely to have CCs. Thus, a careful cardiac evaluation should be performed.

Role of Neurons and Glia Cells in Wound Healing as a Novel Perspective Considering Platelet as a Conventional Player

Wound healing is a complex physiological process in which the damaged or injured tissue is replaced or regenerated by new cells or existing cells respectively in their synthesized and secreted matrices. Several cells modulate the process of wound healing including macrophages, fibroblasts, and keratinocytes. Apart from these cells, platelet has been considered as a major cellular fragment to be involved in wound healing at several stages by secreting its granular contents including growth factors, thus resulting in coagulation, inflammation, and angiogenesis. A distant cell, which is gaining significant attention nowadays due to its resemblance with platelet in several aspects, is the neuron. Not only neurons but also glia cells are also confirmed to regulate wound healing at different stages in an orchestrated manner. Furthermore, these neurons and glia cells mediate wound healing inducing tissue repair and regeneration apart from hemostasis, angiogenesis, and inflammation by secreting various growth factors, coagulation molecules, immunomodulatory molecules as well as neurohormones, neuropeptides, and neurotrophins. Therefore, in wound healing platelets, neurons and glia cells not only contribute to tissue repair but are also responsible for establishing the wound microenvironment, thus affecting the proliferation of immune cells, fibroblast, and keratinocytes. Here in this review, we will enlighten the physiological roles of neurons and glia cells in coordination with platelets to understand various cellular and molecular mechanism in brain injury and associated neurocognitive impairments.

Depression and Cardiovascular Disease: The Viewpoint of Platelets

Depression is a major cause of morbidity and low quality of life among patients with cardiovascular disease (CVD), and it is now considered as an independent risk factor for major adverse cardiovascular events. Increasing evidence indicates not only that depression worsens the prognosis of cardiac events, but also that a cross-vulnerability between the two conditions occurs. Among the several mechanisms proposed to explain this interplay, platelet activation is the more attractive, seeing platelets as potential mirror of the brain function. In this review, we dissected the mechanisms linking depression and CVD highlighting the critical role of platelet behavior during depression as trigger of cardiovascular complication. In particular, we will discuss the relationship between depression and molecules involved in the CVD (e.g., catecholamines, adipokines, lipids, reactive oxygen species, and chemokines), emphasizing their impact on platelet activation and related mechanisms.

Effect of Venlafaxine, Pramipexole, and Valsartan on Spermatogenesis in Male Rats

The study's aim was to explore the effect of venlafaxine, valsartan, and pramipexole on spermatogenesis. It was hypothesized that these drugs may affect the male fertility because of their long-term use in treatment of depression, hypertension, and Parkinson's diseases. Male rats were given venlafaxine, valsartan, and pramipexole at low- and high-dose levels orally once daily for 10 weeks. Testosterone (25 mg/kg) was given as a standard via an intramuscular route once weekly. Rats were sacrificed after blood collection by cardiac puncture, and testes were removed. Sperm parameters were examined from spermatozoa of the cauda epididymis, and testes were treated for histopathological analysis. Results showed nonsignificant effect of venlafaxine on the sperm count, whereas a decreased sperm count was noted in all the treatment groups as compared to that of the control except valsartan at a low dose, which significantly (p < 0.001) raised the sperm count (96.26 ± 2.4) in reference with the control value (49.13 ± 2.3). Treatments had variable effects on total sperm motility and morphological parameters, but valsartan at a low dose showed maximum sperm motility (71.55 ± 0.7) among all. DNA integrity of spermatozoa remained intact in all groups. Luteinizing hormone and follicle-stimulating hormone levels decreased, and testosterone levels increased in all treatment groups as compared to control values, which indicate fertility. Histopathology revealed normal texture of testes with venlafaxine and valsartan, but testicular damage occurred with high-dose pramipexole. It is concluded that the use of venlafaxine, valsartan, and pramipexole at a low dose is devoid of any harmful effect on spermatogenesis, whereas pramipexole at a high dose adversely affect it.

Parylene-C coated microporous PDMS structure protecting from functional deconditioning of platelets exposed to cardiostimulants

Most elderly patients after orthopedic and dental implant surgeries are exposed to cardiostimulants to reduce potential blood pressure-related risks of cardiovascular diseases. Such treatments lead to deconditioning of platelet function, which is an important factor in wound healing treatments. We introduced an innovative parylene-C coated microporous PDMS structure that can prevent the functional deconditioning of platelets caused by certain cardiostimulants. At different concentrations of cardiostimulants (IPR; isoprenaline and DA; dopamine), pre-activation, activation, and post-activation of platelets were intensively examined under mechanical and chemical stimulation mimicking the physiological environment on four different surfaces (glass, flat parylene-C coated glass (F-PPXC), microporous PDMS structure (P-PDMS), and parylene-C-coated microporous PDMS structure (S-PPXC)). The 3D microporous structure with parylene-C (S-PPXC) surface could attenuate the deconditioning of platelet function caused by IPR. Moreover, the S-PPXC surface further enhanced the DA-dependent stimulation of platelet function. The reason for this is that the 3D microporous structure with parylene-C S-PPXC induced stable and fast adhesion of platelets through increased surface roughness and softness, resulting in a significant enhancement of platelet activity. Therefore, we propose the use of functional S-PPXC surfaces as a novel strategy in the development of biomedical products.

Alterations of the Brain Proteome and Gut Microbiota in d-Galactose-Induced Brain-Aging Mice with Krill Oil Supplementation

Brain aging is commonly associated with neurodegenerative disorders, but the ameliorative effect of krill oil and the underlying mechanism remain unclear. In this study, the components of krill oil were measured, and the antiaging effects of krill oil were investigated in mice with d-galactose (d-gal)-induced brain aging via proteomics and gut microbiota analysis. Krill oil treatment decreased the expression of truncated dopamine- and cAMP-regulated phosphoproteins and proteins involved in the calcium signaling pathway. In addition, the concentrations of dopamine were increased in the serum (p < 0.05) and brain (p > 0.05) due to the enhanced expressions of tyrosine-3-monooxygenase and aromatic l-amino acid decarboxylase. Moreover, krill oil alleviated gut microbiota dysbiosis, decreased the abundance of bacteria that consume the precursor tyrosine, and increased the abundance of Lactobacillus spp. and short-chain fatty acid producers. This study revealed the beneficial effect of krill oil against d-gal-induced brain aging and clarified the underlying mechanism through proteomics and gut microbiota analysis.

Neuroleptic malignant-like syndrome causing thrombocytopaenia: a rare association

Neuroleptic malignant-like syndrome is a rare but potentially fatal complication of sudden withdrawal of dopaminergic drugs. Clinical features are similar to that of neuroleptic malignant syndrome (NMS) like hyperthermia, autonomic dysfunction, altered sensorium, muscle rigidity; but instead of history of neuroleptic use, there is history of withdrawal of dopaminergic drugs. Laboratory examination generally show elevated creatine phosphokinase levels and may show elevated total leucocyte count. Thrombocytopaenia has been very rarely reported with NMS but it has not been reported with NM-like syndrome. Here, we discuss a case of Parkinson's disease which presented with typical clinical features and risk factors of NM-like syndrome associated with thrombocytopaenia and type 1 respiratory failure. He was treated with bromocriptine and supportive care. Thrombocytopaenia and respiratory failure resolved with above treatment. The patient improved clinically and was successfully discharged on day 12 of admission.

Targeting GSK3 signaling as a potential therapy of neurodegenerative diseases and aging

INTRODUCTION

Glycogen synthase kinase 3 (GSK3) is at the center of cellular signaling and controls various aspects of brain functions, including development of the nervous system, neuronal plasticity and onset of neurodegenerative disorders. Areas covered: In this review, recent efforts in elucidating the roles of GSK3 in neuronal plasticity and development of brain pathologies; Alzheimer's and Parkinson's disease, schizophrenia, and age-related neurodegeneration are described. The effect of microglia and astrocytes on development of the pathological states is also discussed. Expert opinion: GSK3β and its signaling pathway partners hold great promise as therapeutic target(s) for a multitude of neurological disorders. Activity of the kinase is often elevated in brain disorders. However, due to the wide range of GSK3 cellular targets, global inhibition of the kinase leads to severe side-effects and GSK3 inhibitors rarely reach Phase-2 clinical trials. Thus, a selective modulation of a specific cellular pool of GSK3 or specific down- or upstream partners of the kinase might provide more efficient anti-neurodegenerative therapies.

Myocardial infarction risk and antipsychotics use revisited: a meta-analysis of 10 observational studies

OBJECTIVE

Associations between antipsychotic agent (AP) use and myocardial infarction (MI) risk have been inconsistent and remain controversial. We therefore conducted a meta-analysis of observational studies to address this knowledge gap.

METHOD

Detailed electronic database searches were performed to identify reports of observational studies that evaluated the association between AP use and the risk of MI. Pooled odds ratios (ORs) were calculated using random or fixed-effects models.

RESULTS

In total, four case-control studies, two case-crossover studies, one case-case time control study, three cohort studies, and one self-controlled case series were included. The pooled OR (95% confidence interval (CI)) between any AP use and MI risk was 1.55 (1.33-1.79) compared with non-use: 1.39 (1.06-1.82) for atypical AP use and 1.57 (1.29-1.91) for typical AP use. Subgroup analyses indicated that male gender, schizophrenia diagnosis, and AP exposure periods ≤60 days were associated with higher risk of MI.

CONCLUSION

Current evidence, based on 10 observational studies, suggested that AP use might be a potential risk factor of MI. However, we cannot conclude at this time due to significant heterogeneity among studies. We suggest that, instead of not using APs in fear of MI risk, careful cardiovascular monitoring before and during AP treatment in high-risk patients is needed. Additional high-quality prospective studies are required to evaluate the association between APs and the risk of MI.

Use of antipsychotics and risk of myocardial infarction: a systematic review and meta-analysis

AIM

There is emerging concern that antipsychotics may be associated with an increased risk of myocardial infarction (MI). A previous review identified five observational studies that did not provide an accurate estimate of the association between antipsychotic drug use and MI risk. More recent studies have produced variable results.

METHODS

We performed a systematic review and meta-analysis of observational studies to determine whether antipsychotic use affects the risk for MI. Our analysis included all observational studies that compared MI incidence among patients receiving antipsychotics vs. no treatment.

RESULTS

Nine observational studies were included in the analysis. The odds for developing MI were 1.88-fold higher (odds ratio (OR) 1.88, 95% confidence interval (CI) 1.39, 2.54) in antipsychotic users compared with individuals who had not taken antipsychotics. Subgroup analyses found an OR of 2.48 (95% CI 1.66, 3.69) among patients with schizophrenia and an OR of 2.64 (95% CI 2.48, 2.81) among short term (<30 days) antipsychotic users.

CONCLUSION

The findings of this meta-analysis support an increased risk of MI in antipsychotic drug users. The present systematic review expands previous knowledge by demonstrating an increased and more pronounced risk in short term users.

Platelet Activation in Human Immunodeficiency Virus Type-1 Patients Is Not Altered with Cocaine Abuse

Recent work has indicated that platelets, which are anucleate blood cells, significantly contribute to inflammatory disorders. Importantly, platelets also likely contribute to various inflammatory secondary disorders that are increasingly associated with Human Immunodeficiency Virus Type-1 (HIV) infection including neurological impairments and cardiovascular complications. Indeed, HIV infection is often associated with increased levels of platelet activators. Additionally, cocaine, a drug commonly abused by HIV-infected individuals, leads to increased platelet activation in humans. Considering that orchestrated signaling mechanisms are essential for platelet activation, and that nuclear factor-kappa B (NF-κB) inhibitors can alter platelet function, the role of NF-κB signaling in platelet activation during HIV infection warrants further investigation. Here we tested the hypothesis that inhibitory kappa B kinase complex (IKK) activation would be central for platelet activation induced by HIV and cocaine. Whole blood from HIV-positive and HIV-negative individuals, with or without cocaine abuse was used to assess platelet activation via flow cytometry whereas IKK activation was analyzed by performing immunoblotting and in vitro kinase assays. We demonstrate that increased platelet activation in HIV patients, as measured by CD62P expression, is not altered with reported cocaine use. Furthermore, cocaine and HIV do not activate platelets in whole blood when treated ex vivo. Finally, HIV-induced platelet activation does not involve the NF-κB signaling intermediate, IKKβ. Platelet activation in HIV patients is not altered with cocaine abuse. These results support the notion that non-IKK targeting approaches will be better suited for the treatment of HIV-associated inflammatory disorders.

Association Between Antipsychotic Use and Risk of Acute Myocardial Infarction

Background—

Antipsychotic medications have been increasingly and more widely prescribed despite continued uncertainty about their association with the incidence of acute myocardial infarction (AMI).

Methods and Results—

We investigated the risk of AMI associated with antipsychotic treatment in 56 910 patients with schizophrenia, mood disorders, or dementia first hospitalized or visiting an emergency room for AMI in 1999 to 2009. A case-crossover design was used to compare the distributions of antipsychotic exposure for the same patient across 1 to 30 and 91 to 120 days just before the AMI event. Adjustments were made for comedications and outpatient visits. The adjusted odds ratio of AMI risk was 2.52 (95% confidence interval, 2.37–2.68) for any antipsychotics, 2.32 (95% confidence interval, 2.17–2.47) for first-generation antipsychotics, and 2.74 (95% confidence interval, 2.49–3.02) for second-generation antipsychotics. The risk significantly increased ( P <0.001) with elevations in dosage and in short-term use (≤30 days). Male patients, elderly patients, and patients with dementia were at significantly increased risk (all P <0.001). Physically healthier patients with no preexisting diabetes mellitus, hypertension, or dyslipidemia were at significantly greater risk ( P <0.001), largely because they had been exposed to higher doses of antipsychotics ( P <0.001). A study of the selected binding of antipsychotics to 14 neurotransmitter receptors revealed only dopamine type 3 receptor antagonism to be significantly associated with AMI risk (adjusted odds ratio, 2.59; 95% confidence interval, 2.43–2.75; P <0.0001).

Conclusions—

Antipsychotic use may be associated with a transient increase in risk for AMI, possibly mediated by dopamine type 3 receptor blockades. Further education on drug safety and research into the underlying biological mechanisms are needed.

Dopamine D1 receptor gene polymorphism is associated with myocardial infarction

Dopamine D1 receptor (DRD1) gene is associated with the pathogenesis of myocardial infarction (MI) in aspects of plaque rupture, platelet aggregation, and neutrophil-mediated injury of cardiac myocytes. Thus, the study was designed to explore whether the A-48G polymorphism of the DRD1 gene was associated with MI. The genotype of the DRD1A-48G polymorphism was determined by polymerase chain reaction in the 602 Han Chinese participants, 255 MI patients and 347 controls without MI. A significant association was found between the A-48G polymorphism of DRD1 and MI (genotype model: χ(2)=13.2, unadjusted p=0.001; χ(2)=13.9, adjusted p=0.0002; dominant model: adjusted OR 2.05, 95%CI 1.40-3.00, p=0.0002; recessive model: adjusted OR 2.34, 95%CI 1.01-5.39, p=0.047). The G allele was a risk-increased allele for MI (unadjusted OR 1.83, 95%CI 1.34-2.50, p=0.0001; adjusted OR 1.94, 95%CI 1.40-2.68, p=0.00007). Thus, the study demonstrated the significant association between A-48G polymorphism of the DRD1 gene and MI.

The Effect of Psychoactive Drugs on in vitro Platelet Function

BACKGROUND: Neuro-hormonal and hemostatic mechanisms are important in a wide range of psychological and cardiovascular diseases. The use of psychoactive drugs in mental illnesses is often involved with hematologic side effects including impaired platelet function. Subsequently, the risk for the development of cardiovascular diseases may be higher in these patients. Interestingly, platelets that play a key role in cardiovascular complications contain quite a number of neuronal receptors which are involved in psychotic disorders. It has been widely discussed whether psychoactive drugs used in the therapy of psychotic disorders have a direct effect on platelet function and whether the effects are transmitted through the corresponding receptors on the platelet surface. MATERIAL AND METHODS: In this study, we tested several psychoactive drugs regarding their impact on whole blood platelet aggregation. RESULTS: Antidopaminergics preferentially inhibited ADP-induced aggregation whereas anticholinergics mainly inhibited U46619-induced aggregation. Because platelets respond selectively to different psychoactive drugs we assume that corresponding receptors have a functional aspect on platelets and that receptor blockade affects platelet aggregation through different mechanisms. CONCLUSION: The knowledge about the effects of psychoactive drugs on platelet function may help to characterize neuronal receptors on platelets and may contribute to a better understanding of altered platelet function during therapy with psychoactive drugs.

An intercalation mechanism as a mode of action exerted by psychotropic drugs: results of altered phospholipid substrate availabilities in membranes?

Patients respond differently to psychotropic drugs, and this is currently a controversial theme among psychiatrists. The effects of 16 psychotropics on cell membrane parameters have been reported. These drugs belong to three major groups used in therapeutic psychiatry: antipsychotics, antidepressants, and anxiolytic/hypnotics. Human platelets, lacking dopamine (D(2)) receptors (proposed targets of most psychotropics), have been used as a cell model. Here we discuss the effects of these drugs on three metabolic phenomena and also results from Langmuir experiments. Diazepam, in contrast to the remaining drugs, had negligible effects on metabolic phenomena and had no effects in Langmuir experiments. Psychotropic drugs may work through intercalation in membrane phospholipids. It is possible that the fluidity of membranes, rich in essential fatty acids, the content being influenced by diet, could be a contributing factor to the action of psychotropics. This might in turn explain the observed major differences in therapeutic response among patients.

The changes of aggregability of blood platelets in schizophrenia

OBJECTIVE

Oxidative stress in schizophrenia may be responsible for the changes of platelet function and reactivity. Therefore, the aim of our present study was to evaluate the response of platelets from patients with schizophrenia to platelet agonists such as ADP and collagen.

RESULTS

Platelet aggregation of schizophrenic patients and healthy subjects stimulated by collagen or ADP showed significant differences. Aggregation of platelets stimulated by collagen was significantly lower in schizophrenic patients (about 86%) than in healthy subjects (P=0.022), but when this process was induced by ADP, aggregation of platelets was significantly higher in schizophrenic patients (increase to about 112%) than in healthy subjects (P=0.018). We also observed that antipsychotic drugs (clozapine, risperidone, olanzapine, haloperidol) reduce aggregation of platelets of schizophrenic patients and healthy group in vitro.

CONCLUSION

The obtained results indicate that the response of platelets from schizophrenic patients to ADP and collagen is different than in healthy subjects.

Glycerophospholipid molecular species in platelets and brain tissues – are platelets a good model for neurons?

The molecular classes of phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylserine (PS) from the basal ganglia, cerebellum, cortex, erythrocytes and blood platelets of female rats were separated by an isocratic HPLC method using a silica column and ultraviolet detection. Each glycerophospholipid class were thereafter derivatized to dimethylphosphatidic acid (PA) molecular species, separated by reverse phase HPLC and detected by an evaporative laser scatter to quantify the different glycerophospholipid species. The distribution of molecular species in each class of the glycerophospholipids in the three brain areas was very similar with a predominance of the 18:0/22:6 species and very little of the 18:0/20:4 species. In contrast, the 18:0/20:4 species predominated in the blood cells which had a very low proportion of 18:0/22:6. These results are discussed on the background that platelets have been extensively used as a model for neurons and our previous physicochemical observation that phenothiazines appear to interact specifically with the 18:0/22:6 species of PS.

Clinically relevant concentrations of dopamine do not amplify agonist-induced human platelet Ca2+ mobilization or GP IIb IIIa activation and do not accelerate acute coronary thrombosis in dogs

BACKGROUND

Dopamine is an inotrope effective in the short term treatment of acute heart failure - including that caused by coronary artery disease. Catecholamines however can potentiate platelet activation and pre-dispose to coronary thrombosis.

AIMS

Dopamine was studied for effect on agonist induced human platelet Ca mobilization, human platelet GP iib iiia receptor activation and acute coronary thrombosis in dogs. Calcium sensitive indo-1, fluorescent immunostaining and flow cytometry were used for platelet studies while coronary thrombosis was induced in anesthetized dogs via endothelial damage, arterial wall injury and critical stenosis.

RESULTS

Dopamine 10 and 10 M had no effect on the amplitude of the platelet Ca signal evoked by thrombin 0.1 U/mL. Likewise, dopamine 10 M had no effect on GP IIb IIIa activation evoked by ADP 10 M and by thrombin 0.1 U/mL. In dogs, intravenous dopamine 8 ug/Kg/min had no effect on repetitive cycles of acute coronary thrombus formation. In positive control studies, epinephrine increased platelet responsiveness and accelerated canine coronary thrombosis.

CONCLUSION

Clinically relevant concentrations of dopamine did not amplify agonist induced human platelet Ca activation, GPiib iiia expression or experimental canine coronary thrombosis--providing a degree of reassurance concerning this versatile inotrope.

Platelet Dopamine: D2 Receptor Binding in Patients with Migraine

Clinical, genetic and pharmacological evidences suggest an abnormality of the dopaminergic system in the pathogenesis of migraine. Direct evidence of an abnormal metabolism of dopamine in migraine, however, is lacking. Platelets are a useful model to understand brain dopaminergic mechanisms. The present study has been undertaken to study the status of platelet dopamine receptor binding by carrying out radioligand receptor binding assay. Binding of3H-spiperone to platelet membranes, known to label dopamine (DA)—D2 receptors, was conducted in 20 patients with migraine and an equal number of healthy controls. The equilibrium dissociation constant (Kd) in patients with migraine (1.71 ± 0.19 nM) was found to be significantly lower ( P < 0.001) as compared with controls (3.14 ± 0.33 nM). However, no significant change was observed in the maximal number of binding sites (Bmax) in patients with migraine. No relationship of Kd with type of migraine, presence of vomiting, family history, frequency of attack, duration of illness and menstrual migraine was observed. The findings of the present study provide support for the involvement of the dopaminergic system in migraine.

In thrombin stimulated human platelets Citalopram, Promethazine, Risperidone, and Ziprasidone, but not Diazepam, may exert their pharmacological effects also through intercalation in membrane phospholipids in a receptor-independent manner

Intercalation of drugs in the platelet membrane affects phospholipid-requiring enzymatic processes according to the drugs' intercalation capability. We investigated effects of Promethazine, Citalopram, Ziprasidone, Risperidone, and Diazepam on phospholipase A(2) (PLA(2)) and polyphosphoinositide (PPI) metabolism in thrombin-stimulated human platelets. We also examined effects of the drugs on monolayers of glycerophospholipids using the Langmuir technique. Diazepam did not influence PLA( 2 ) activity, had no effects on PPI cycle, and caused no change in mean molecular area of phospholipid monolayers. The remaining psychotropic drugs affected these parameters in different ways and levels of potency suggesting that they act by being intercalated between the molecules of adjacent membrane phospholipids, thus causing changes in substrate availability for phospholipid-hydrolyzing enzymes (PLA(2) and Phospholipase C). We show that several psychotropic drugs can also have other cellular effects than receptor antagonism. These effects may be implicated in the psychotropic effects of the drugs and/or their side effects.

The dopamine agonism on ADP-stimulated platelets is mediated through D2-like but not D1-like dopamine receptors

Monoamines such as serotonin and epinephrine are known to be involved in platelet activation and aggregation. Dopamine is another monoamine identified in platelets, but published data about its effect on platelets and the receptors involved are controversial. In the present study, we investigated the dopamine agonism in platelets and the receptors involved in these pathways. Platelet-rich plasma (PRP) of healthy individuals was treated with agonists (ADP, epinephrine, dopamine) and various dopamine receptor and transporter antagonists such as SCH-23390, raclopride, clozapine, methylphenidate, and cocaine. Platelet activation was investigated by flow cytometry (CD62P and CD63 surface expression), optical aggregometry, and microaggregate adhesion to collagen IV in a flow chamber system. In our study, dopamine on its own had no effect on platelet activation in the different assays. However, when used in combination with ADP (10 muM), dopamine in a range of 1 to 100 muM significantly potentiated platelet microaggregate formation and adhesion to collagen under low shear flow conditions. Specific antagonists for D2-like receptors (L-741,626, raclopride, and clozapine) completely diminished the dopamine effect at selective concentrations, but not the effect of epinephrine. Neither the D1-like receptor antagonist SCH-23390 nor dopamine transporter antagonists (methylphenidate, cocaine) showed inhibitory effects on the dopamine agonism. Thus, dopamine is an ADP-dependent platelet agonist which acts via D2-like but not D1-like receptors or adrenergic receptors. Because many psychopharmacological drugs are directed to D2-like receptors, platelet dysfunction in patients being treated with such drugs may be linked to these mechanisms.

The psychotropic drug olanzapine (Zyprexa) increases the area of acid glycerophospholipid monolayers

The typical antipsychotics chlorpromazine (CPZ) and trifluoperazine (TFP) increase the mean molecular area (mma) of acidic, but not neutral, glycerophospholipids in monolayers at pH 7.36 measured by the Langmuir technique. The atypical antipsychotic olanzapine (OLP(1)) is structurally similar to TFP. We have therefore studied the effects of OLP on glycerophospholipid monolayers and in comparison with CPZ. Olanzapine (10 microM, in subphase, pH 7.36) influenced the isotherms (surface pressure versus mma) in monolayers of the neutral dipalmitoyl phosphatidylcholine (DPPC) and the acidic dipalmitoyl phosphatidylserine (DPPS) or 1-palmitoyl-2-oleoylphosphatidylserine (POPS) in the increasing order of mma: DPPS<DPPC<POPS at both lower and higher temperature. Thus, presence of an unsaturated acyl in PS increased the drug-induced effect on mma. The mma in the absence of drugs was lower at lower temperatures than at higher temperatures. OLP affected mma to a greater extent than CPZ, and caused the greatest interaction at surface pressure of 30 mN/m at higher temperatures. In contrast, CPZ gave the largest effect in the monolayers at surface pressure 30 mN/m at lower temperatures. CPZ did not alter the isotherms of DPPC, at lower or higher temperature, and only affected the packing of the DPPS and POPS monolayers. In contrast, OLP altered the isotherms of DPPC. It is suggested that the drugs affect the monolayer packing by intercalating between the glycerophospholipid molecules. Since CPZ has major side effects, while OLP has few, this may indicate that there is poor correlation between side effects and effects of the drugs on phospholipid monolayers.

Trifluoperazine causes a disturbance in glycerophospholipid monolayers containing phosphatidylserine (PS): effects of pH, acyl unsaturation, and proportion of PS

We have studied the interaction of trifluoperazine (TFP) with monolayers of various glycerophospholipids at 37 degrees C. TFP (1-10 microM) had little effect on surface pressure/molecular area isotherms in monolayers (on pure water) of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylethanolamine but greatly increased the mean molecular area (mma) of dipalmitoylphosphatidylserine; the increment was greatest between 0 and 1 microM, and a further increase to 10 microM TFP gave only a slight increase in mma. With phosphatidylserine (PS)-containing stearoyl and varying acyls in the sn-1 and -2 positions, respectively, TFP increased the mma in a manner that depended on the number of double bonds and chain length. In mixtures of DPPC with two of these PS species the TFP-induced mma of the monolayers (on buffer, pH 7.4) increased linearly with the proportion of PS. Both PS and TFP have ionizable groups, and the TFP-induced mma increase had optima at pH 5.0 and 7.0. We conclude that the TFP-PS interaction is mainly, but not entirely, driven by electrostatic interactions between the TFP cation and PS headgroup anion, with an insertion of the phenothiazine moiety among the acyls in the monolayer that depends on the packing of the acyls.

Upregulation of A2A adenosine receptors in platelets from patients affected by bipolar disorders under treatment with typical antipsychotics

Antipsychotic drugs, potent dopamine receptor antagonists, are commonly used in the treatment of psychotic and affective illness. The discovery of antagonistic interactions between A2A adenosine receptors (ARs) and D2 dopamine receptors (DRs) in the central nervous system suggests that the adenosine system may be involved in the pathogenesis of psychiatric and neurological disorders. In the present study, we demonstrated for the first time that human platelets co-express A2A ARs and D2 DRs assembled into an heteromeric complexes. We also investigated the effects of chronic treatment with either typical or atypical antipsychotics on A2A AR binding parameters and receptors responsiveness in human platelets from patients affected by bipolar disorder. Chronic administration of typical antipsychotics induced a significant upregulation of A2A AR binding sites. Since no effects on A2A AR were obtained following "in vitro" platelet treatment with a typical antipsychotic (haloperidol), we could exclude a direct effect of the drug on A2A AR at the peripheral level. Moreover, typical antipsychotics induced a significant increase in the agonist potency to mediate A2A AR-G protein coupling. On the contrary, chronic treatment with atypical antipsychotics did not induce any significant alterations in A2A AR equilibrium binding parameters and receptor responsiveness suggesting that typical but not atypical antipsychotic drugs induced a selective modification of A2A AR binding parameters in human platelets. These results are in accordance with the literature data describing the selective A2A AR upregulation induced by typical antipsychotics in human striatum suggesting platelets as a peripheral model of the interactions between adenosine and dopamine system occurring in the central nervous system.

Dopamine D5 receptor localization on cholinergic neurons of the rat forebrain and diencephalon: a potential neuroanatomical substrate involved in mediating dopaminergic influences on acetylcholine release

The study of dopaminergic influences on acetylcholine release is especially useful for the understanding of a wide range of brain functions and neurological disorders, including schizophrenia, Parkinson's disease, Alzheimer's disease, and drug addiction. These disorders are characterized by a neurochemical imbalance of a variety of neurotransmitter systems, including the dopamine and acetylcholine systems. Dopamine modulates acetylcholine levels in the brain by binding to dopamine receptors located directly on cholinergic cells. The dopamine D5 receptor, a D1-class receptor subtype, potentiates acetylcholine release and has been investigated as a possible substrate underlying a variety of brain functions and clinical disorders. This receptor subtype, therefore, may prove to be a putative target for pharmacotherapeutic strategies and cognitive-behavioral treatments aimed at treating a variety of neurological disorders. The present study investigated whether cholinergic cells in the dopamine targeted areas of the cerebral cortex, striatum, basal forebrain, and diencephalon express the dopamine D5 receptor. These receptors were localized on cholinergic neurons with dual labeling immunoperoxidase or immunofluorescence procedures using antibodies directed against choline acetyltransferase (ChAT) and the dopamine D5 receptor. Results from this study support previous findings indicating that striatal cholinergic interneurons express the dopamine D5 receptor. In addition, cholinergic neurons in other critical brain areas also show dopamine D5 receptor expression. Dopamine D5 receptors were localized on the somata, dendrites, and axons of cholinergic cells in each of the brain areas examined. These findings support the functional importance of the dopamine D5 receptor in the modulation of acetylcholine release throughout the brain.

Circulating neurotransmitters during the different wake-sleep stages in normal subjects

We investigated the changes of circulating neurotransmitters during the wake-sleep cycle in order to find possible correlations with the activity of central neurocircuitry functioning. Noradrenaline (NA), adrenaline (Ad), dopamine (DA), platelet serotonin (p-5HT), plasma serotonin (f-5HT) and plasma tryptophan (TRP) were assessed during the morning (supine resting + 1-min orthostasis + 5-min exercise) and at night (supine resting + slow wave sleep (SWS) + REM sleep). Only NA increased in the plasma during short-lasting (1-min) orthostasis morning waking period. Both NA and Ad rose during moderate exercise. The nocturnal results demonstrated that whereas Ad dropped during the supine resting, NA did not fall until SWS period. Although DA did not show significant changes during the nocturnal test, the NA/DA ratio showed significant reduction. The analysis of correlations supports the postulation that this finding reflects the DA modulatory role on neural sympathetic activity. Both f-5HT and p-5HT values were lower during sleep cycle than wake periods. However, they showed progressive rises during sleep stages. Conversely, the f-5HT/p-5HT ratio showed significantly greater values during the SWS period than during supine resting and REM periods. These findings are consistent with the postulation that f-5HT/p-5HT ratio is positively associated with parasympathetic activity during the sleep-cycle. We concluded that the profile of sleep-cycle circulating neurotransmitters differs from that obtained during waking periods. According to the above, we attempted to correlate the profile of circulating neurotransmitters with the very well-known central neurocircuitry functioning during wake-sleep cycle, in experimental mammals.

The vesicular monoamine content regulates VMAT2 activity through Galphaq in mouse platelets. Evidence for autoregulation of vesicular transmitter uptake

Variations in the neurotransmitter content of secretory vesicles enable neurons to adapt to network changes. Vesicular content may be modulated by vesicle-associated Go(2), which down-regulates the activity of the vesicular monoamine transmitter transporters VMAT1 in neuroendocrine cells and VMAT2 in neurons. Blood platelets resemble serotonergic neurons with respect to transmitter storage and release. In streptolysin O-permeabilized platelets, VMAT2 activity is also down-regulated by the G protein activator guanosine 5'-(beta(i)gamma-imido)triphosphate (GMppNp). Using serotonin-depleted platelets from peripheral tryptophan hydroxylase knockout (Tph1-/-) mice, we show here that the vesicular filling initiates the G protein-mediated down-regulation of VMAT2 activity. GMppNp did not influence VMAT2 activity in naive platelets from Tph1-/- mice. GMppNp-mediated inhibition could be reconstituted, however, when preloading Tph1-/- platelets with serotonin or noradrenaline. Galpha(q) mediates the down-regulation of VMAT2 activity as revealed from uptake studies performed with platelets from Galpha(q) deletion mutants. Serotonergic, noradrenergic, as well as thromboxane A(2) receptors are not directly involved in the down-regulation of VMAT2 activity. It is concluded that in platelets the vesicle itself regulates transmitter transporter activity via its content and vesicle-associated Galpha(q).