MK-801 alters Na+, K+-ATPase activity and oxidative status in zebrafish brain: reversal by antipsychotic drugs

Evaluation of antioxidant response and Na+-K+-ATPase activity in zebrafish exposed to polyethylene microplastics: Shedding light on a physiological adaptation

Although the toxicity of microplastics has already been demonstrated in different animal models, our knowledge about the response of freshwater fish to this pollutant is still limited. Thus, we aimed to evaluate the impact of exposure of zebrafish adults (Danio rerio) to environmentally relevant concentrations of polyethylene microplastics (PE-MPs) (5 and 50 µg/L) and at different times of exposure (10 and 20 days). Initially, scanning electron microscope image illustrated size and format of the particle and FTIR analysis confirmed the presence of PE-MPs in the gastrointestinal tract of fish (at both concentrations tested). Subsequently, an alteration of oxidative and antioxidant responses was evaluated in the liver and brain. The results showed that catalase (CAT) activity, in liver, was significantly decreased, as was glutathione S-transferases (GSTs) activity (on the 10th experimental day). However, after 20 days of exposure, we observed a concentration-dependent increase in GST activity in liver of the animals exposed to PE-MPs. Furthermore, the lipid peroxidation (LPO) level was significantly increased by exposure to MPs, especially in the brain, after 20 days of exposure. The increase in Na⁺-K⁺-ATPase activity in the animals' gills was correlated with the increased production of malondialdehyde (MDA), which suggests the existence of a compensatory mechanism in which the high activity of this enzyme would be necessary to regulate the loss of ions caused by the increase in the processes of LPO, which has never been previously demonstrated. Thus, our study sheds light on a new physiological adaptation to deal with the oxidative effects of PE-MPs, in addition to supporting the future use of the assessment of Na⁺/K⁺-ATPase activity as a biomarker of the toxicity of these pollutants.

Activation of D1/D5 Receptors Ameliorates Decreased Intrinsic Excitability of Hippocampal Neurons Induced by Neonatal Blockade of NMDA Receptors

BACKGROUND AND PURPOSE

Dysregulation of dopaminergic transmission combined with transient hypofunction of N-methyl-D-aspartate receptors (NMDARs) is a key mechanism that may underlie cognitive symptoms of schizophrenia.

EXPERIMENTAL APPROACH

Therefore, we aimed to identify electrophysiologic alterations in animals neonatally treated with the NMDA receptor antagonist, MK-801 or with saline solution.

KEY RESULTS

Patch-clamp whole-cell recordings from MK-801-treated animals revealed altered passive and active electrophysiologic properties compared with CA1 pyramidal cells from saline-treated animals, including upregulation of the K⁺ inward-rectifier conductance and fast-inactivating and slow/non-inactivating K⁺ currents. Upregulation of these membrane ionic currents reduced the overall excitability and altered the firing properties of CA1 pyramidal cells. We also explored the capability of cells treated with MK-801 to express intrinsic excitability potentiation, a non-synaptic form of hippocampal plasticity associated with cognition and memory formation. CA1 pyramidal cells from animals treated with MK-801 were unable to convey intrinsic excitability potentiation and had blunted synaptic potentiation. Furthermore, MK-801-treated animals also exhibited reduced cognitive performance in the Barnes maze task. Notably, activation of D1/D5 receptors with SKF-38, 393 partially restored electrophysiologic alterations caused by neonatal treatment with MK-801.

CONCLUSION AND IMPLICATIONS

Our results offer a molecular and mechanistic explanation based on dysregulation of glutamatergic in addition to dopaminergic transmission that may contribute to the understanding of the cognitive deterioration associated with schizophrenia.

Effect of liraglutide on neural and peripheral markers of metabolic function during antipsychotic treatment in rats

BACKGROUND

Liraglutide is a glucagon-like peptide-1 (GLP-1) receptor agonist that prevents metabolic side effects of the antipsychotic drugs (APDs) olanzapine and clozapine through unknown mechanisms.

AIM

This study aimed to investigate the effect of chronic APD and liraglutide co-treatment on key neural and peripheral metabolic signals, and acute liraglutide co-treatment on clozapine-induced hyperglycaemia.

METHODS

In study 1, rats were administered olanzapine (2 mg/kg), clozapine (12 mg/kg), liraglutide (0.2 mg/kg), olanzapine + liraglutide co-treatment, clozapine + liraglutide co-treatment or vehicle for six weeks. Feeding efficiency was examined weekly. Examination of brain tissue (dorsal vagal complex (DVC) and mediobasal hypothalamus (MBH)), plasma metabolic hormones and peripheral (liver and kidney) cellular metabolism and oxidative stress was conducted. In study 2, rats were administered a single dose of clozapine (12 mg/kg), liraglutide (0.4 mg/kg), clozapine + liraglutide co-treatment or vehicle. Glucose tolerance and plasma hormone levels were assessed.

RESULTS

Liraglutide co-treatment prevented the time-dependent increase in feeding efficiency caused by olanzapine, which plateaued by six weeks. There was no effect of chronic treatment on melanocortinergic, GABAergic, glutamatergic or endocannabionoid markers in the MBH or DVC. Peripheral hormones and cellular metabolic markers were unaltered by chronic APD treatment. Acute liraglutide co-treatment was unable to prevent clozapine-induced hyperglycaemia, but it did alter catecholamine levels.

CONCLUSION

The unexpected lack of change to central and peripheral markers following chronic treatment, despite the presence of weight gain, may reflect adaptive mechanisms. Further studies examining alterations across different time points are required to continue to elucidate the mechanisms underlying the benefits of liraglutide on APD-induced metabolic side effects.

Modulations in the ATPases during ketamine-induced schizophrenia and regulatory effect of "3-(3, 4-dimethoxy phenyl) -1- (4-methoxyphenyl) prop-2-en-1-one": an in vivo and in silico studies

Schizophrenia is a devastating illness and displays a wide range of psychotic symptoms. Accumulating evidence indicate impairment of bioenergetic pathways including energy storage and usage in the pathogenesis of schizophrenia. Although well-established synthetic drugs are being used for the management of schizophrenia, most of them have several adverse effects. Hence, natural products derived from medicinal plants represent a continuous major source for ethnomedicine-derived pharmaceuticals for different neurological disorders including schizophrenia. In the present study, we have investigated the neuroprotective effect of the novel bioactive compound i.e. "3-(3,4-dimethoxy phenyl) -1- (4-methoxyphenyl) prop-2-en-1-one" of Celastrus paniculata against ketamine-induced schizophrenia with particular reference to the activities of ATPase using in vivo and in silico methods. Ketamine-induced schizophrenia caused significant reduction in the activities of all three ATPases (Na⁺/K⁺, Ca²⁺ and Mg²⁺) in different regions of brain which reflects the decreased turnover of ATP, presumably due to the inhibition of oxidoreductase system and uncoupling of the same from the electron transport system. On par with the reference compound, clozapine, the activity levels of all three ATPases were restored to normal after pretreatment with the compound suggesting recovery of energy loss that was occurred during ketamine-induced schizophrenia. Besides, the compound has shown strong interaction and exhibited highest binding energies against all the three ATPases with a lowest inhibition constant value than the clozapine. The results of the present study clearly imply that the compound exhibit significant neuroprotective and antischizophrenic effect by modulating bioenergietic pathways that were altered during induced schizophrenia.

Lower vertebrate and invertebrate models of Alzheimer's disease - A review

Alzheimer's disease is a common neurodegenerative disorder which is characterized by the presence of beta- amyloid protein and neurofibrillary tangles (NFTs) in the brain. Till now, various higher vertebrate models have been in use to study the pathophysiology of this disease. But, these models possess some limitations like ethical restrictions, high cost, difficult maintenance of large quantity and lesser reproducibility. Besides, various lower chordate animals like Danio rerio, Drosophila melanogaster, Caenorhabditis elegans and Ciona intestinalis have been proved to be an important model for the in vivo determination of targets of drugs with least limitations. In this article, we reviewed different studies conducted on theses models for the better understanding of the pathophysiology of AD and their subsequent application as a potential tool in the preclinical evaluation of new drugs.

Understanding taurine CNS activity using alternative zebrafish models

Taurine is a highly abundant "amino acid" in the brain. Despite the potential neuroactive role of taurine in vertebrates has long been recognized, the underlying molecular mechanisms related to its pleiotropic effects in the brain remain poorly understood. Due to the genetic tractability, rich behavioral repertoire, neurochemical conservation, and small size, the zebrafish (Danio rerio) has emerged as a powerful candidate for neuropsychopharmacology investigation and in vivo drug screening. Here, we summarize the main physiological roles of taurine in mammals, including neuromodulation, osmoregulation, membrane stabilization, and antioxidant action. In this context, we also highlight how zebrafish models of brain disorders may present interesting approaches to assess molecular mechanisms underlying positive effects of taurine in the brain. Finally, we outline recent advances in zebrafish drug screening that significantly improve neuropsychiatric translational researches and small molecule screens.

Role of membrane cholesterol and lipid peroxidation in regulating the Na+/K+-ATPase activity in schizophrenia

BACKGROUND

Na⁺/K⁺-ATPase (NKA) activity is compromised in several neuropsychiatric disorders. Oxidative stress and membrane lipid composition play important roles in regulating NKA activity.

AIMS

The present study was undertaken to evaluate the effects of oxidative stress-induced membrane lipid damage and membrane cholesterol composition on NKA pump activity in schizophrenia.

SETTINGS AND DESIGN

It was a hospital-based, cross-sectional, observational study in 49 cases and 51 controls for 1 year.

MATERIALS AND METHODS

NKA pump activity in red blood cell membrane, serum levels of thiobarbituric acid reactive substances (TBARS), protein carbonyl (PC) adducts, and cholesterol were measured by standard spectrophotometric techniques in newly diagnosed schizophrenia patients by Diagnostic and Statistical Manual of Mental Disorders, 4^th Edition, Text Revision criteria. Membrane cholesterol was analyzed by chloroform and isopropanol extraction followed by measuring the cholesterol concentration by spectrophotometric technique.

STATISTICAL ANALYSIS AND RESULTS

Mean values for NKA pump activity, membrane cholesterol level, and serum cholesterol levels were significantly lower in the case group (P < 0.001). The activity of NKA pump was found to be directly correlated to membrane cholesterol level rather than with the serum cholesterol values. Although the NKA pump activity showed inverse relationship with the serum values of TBARS and PC products both, on multiple linear regression analysis, it was found to be significantly positively dependent on the membrane cholesterol (β = 0.268, P = 0.01) and negatively dependent on the serum TBARS (β = -0.63, P < 0.001) levels only.

CONCLUSION

Reduced membrane cholesterol and oxidative stress-induced damage to membrane lipids play crucial roles in decreasing the NKA activity in schizophrenia. Hence, for a better prognosis and treatment, measures are required to maintain optimum levels of cholesterol in neuronal tissues along with a proper control on oxidative stress.

Exploring Hallucinogen Pharmacology and Psychedelic Medicine with Zebrafish Models

After decades of sociopolitical obstacles, the field of psychiatry is experiencing a revived interest in the use of hallucinogenic agents to treat brain disorders. Along with the use of ketamine for depression, recent pilot studies have highlighted the efficacy of classic serotonergic hallucinogens, such as lysergic acid diethylamide and psilocybin, in treating addiction, post-traumatic stress disorder, and anxiety. However, many basic pharmacological and toxicological questions remain unanswered with regard to these compounds. In this study, we discuss psychedelic medicine as well as the behavioral and toxicological effects of hallucinogenic drugs in zebrafish. We emphasize this aquatic organism as a model ideally suited to assess both the potential toxic and therapeutic effects of major known classes of hallucinogenic compounds. In addition, novel drugs with hallucinogenic properties can be efficiently screened using zebrafish models. Well-designed preclinical studies utilizing zebrafish can contribute to the reemerging treatment paradigm of psychedelic medicine, leading to new avenues of clinical exploration for psychiatric disorders.

Zebrafish Whole-Mount In Situ Hybridization Followed by Sectioning

In situ hybridization is a powerful technique used for locating specific nucleic acid targets within morphologically preserved tissues and cell preparations. A labeled RNA or DNA probe hybridizes to its complementary mRNA or DNA sequence within a sample. Here, we describe RNA in situ hybridization protocol for whole-mount zebrafish embryos.

Zebrafish as a novel model to assess Na+/K(+)-ATPase-related neurological disorders

Modeling neurological disorders using zebrafish increases rapidly as this model system allows easy access to all developmental stages and imaging of pathological processes. A surprising degree of functional conservation has been demonstrated between human genes implicated in neurodegenerative diseases and their zebrafish orthologues. Zebrafish offers rapid high throughput screening of therapeutic compounds and live imaging of pathogenic mechanisms in vivo. Several recent zebrafish studies functionally assessed the role of the sodium-potassium pump (Na(+)/K(+)-ATPase). The Na(+)/K(+)-ATPase maintains the electrochemical gradients across the plasma membrane, essential for e.g. signaling, secondary active transport, glutamate re-uptake and neuron excitability in animal cells. Na(+)/K(+)-ATPase mutations are associated with neurological disorders, where mutations in the Na(+)/K(+)-ATPase α2 and α3 isoforms cause Familial hemiplegic migraine type 2 (FHM2) and Rapid-onset dystonia-parkinsonism (RDP)/Alternating hemiplegic childhood (AHC), respectively. In zebrafish, knock-down of Na(+)/K(+)-ATPase isoforms included skeletal and heart muscle defects, impaired embryonic motility, depolarized Rohon-beard neurons and abrupt brain ventricle development. In this review, we discuss zebrafish as a model to assess Na(+)/K(+)-ATPase isoform functions. Furthermore, studies investigating proteomic changes in both α2- and α3-isoform deficient embryos and their potential connections to the Na(+)/K(+)-ATPase functions will be discussed.

Effects of the putative antipsychotic alstonine on glutamate uptake in acute hippocampal slices

A dysfunctional glutamatergic system is thought to be central to the negative symptoms and cognitive deficits recognized as determinant to the poor quality of life of people with schizophrenia. Modulating glutamate uptake has, thus, been suggested as a novel target for antipsychotics. Alstonine is an indole alkaloid sharing with atypical antipsychotics the profile in animal models relevant to schizophrenia, though divergent in its mechanism of action. The aim of this study was to evaluate the effects of alstonine on glutamate uptake. Additionally, the effects on glutathione content and extracellular S100B levels were assessed. Acute hippocampal slices were incubated with haloperidol (10μM), clozapine (10 and 100μM) or alstonine (1-100μM), alone or in combination with apomorphine (100μM), and 5-HT(2) receptor antagonists (0.01μM altanserin and 0.1μM SB 242084). A reduction in glutamate uptake was observed with alstonine and clozapine, but not haloperidol. Apomorphine abolished the effect of clozapine, whereas 5-HT(2A) and 5-HT(2C) antagonists abolished the effects of alstonine. Increased levels of glutathione were observed only with alstonine, also the only compound that failed to decrease the release of S100B. This study shows that alstonine decreases glutamate uptake, which may be beneficial to the glutamatergic deficit observed in schizophrenia. Noteworthily, the decrease in glutamate uptake is compatible with the reversal of MK-801-induced social interaction and working memory deficits. An additional potential benefit of alstonine as an antipsychotic is its ability to increase glutathione, a key cellular antioxidant reported to be decreased in the brain of patients with schizophrenia. Adding to the characterization of the novel mechanism of action of alstonine, the lack of effect of apomorphine in alstonine-induced changes in glutamate uptake reinforces that D(2) receptors are not primarily implicated. Though clearly mediated by 5-HT(2A) and 5-HT(2C) serotonin receptors, the precise mechanisms that result in the effects of alstonine on glutamate uptake warrant elucidation.