Indoleamine-2,3-dioxygenase-1 is a molecular target for the protective activity of mood stabilizers against mania-like behavior induced by d-amphetamine

The dopamine transporter inhibition using GBR 12909 as a novel pharmacological tool to assess bipolar disorder-like neurobehavioral phenotypes in zebrafish

Dopamine (DA) is a neurotransmitter that plays an important role in brain physiology. Changes in DA-mediated signaling have been implicated with the pathophysiology of various neuropsychiatric conditions. Bipolar disorder (BD) is a mental disorder, characterized by alterning between manic/hypomanic and depressive mood. In experimental research, the pharmacological inhibition of DA reuptake using GBR 12909 serves as a tool to elicit BD-like phenotypes. Alternative model organisms, such as the zebrafish (Danio rerio), have been considered important systems for investigating the neurobehavioral changes involved in different neuropsychiatric conditions, including BD. Here, we discuss the use of GBR 12909 as a novel pharmacological strategy to mimic BD-like phenotypes in zebrafish models. We also emphasize the well-conserved DA-mediated signaling in zebrafish and the early expression of dopaminergic biomarkers in the brain, especially focusing on dopamine transporter (DAT), the main target of GBR 12909. Finally, we discuss potential advantages and limitations in the field, the perspectives of using GBR 12909 in BD research, and how distinct validation criteria (i.e., face, predictive, and construct validity) can be assessed in translational approaches using zebrafish-based models.

Ginsenoside Rb3 Promotes Opa1-Mediated Regenerative Neurogenesis via Activating the Ido1 Pathway in Ischemic Stroke

The activation of neural stem cells (NSCs) residing in the subventricular zone (SVZ) and dentate gyrus (DG) has been shown to promote the restoration of damaged brain tissues. Ginsenoside Rb3 (Rb3) is a bioactive substance known for its pharmacological properties in treating neurological disorders. This study investigated the effects of Rb3 on neural regeneration following ischaemic stroke (IS) and the underlying mechanisms involved. Male C57BL/6 mice were utilized and were subjected to middle cerebral artery occlusion/reperfusion (MCAO/R). Post-ischemia, Rb3 was administered through intraperitoneal (i.p.) injection for either 7 or 28 days. The promotion of Rb3 on regenerative neurogenesis was detected by immunofluorescence staining. NSCs were pretreated with different concentrations of Rb3 for 24 h before oxygen-glucose deprivation/reoxygenation (OGD/R) exposure. Afterward, immunofluorescence staining and flow cytometry were used to detect the migration and proliferation of Rb3 in OGD/R-induced NSCs. Furthermore, Adeno-associated virus (AAV) transduction experiments, siRNA transfection experiments, gene knockout experiments, targeted metabolomics analysis, molecular dynamics simulation, cellular thermal shift assay (CETSA), and drug affinity responsive target stability (DARTS) assays were used to explore the promotion and mechanism of Rb3 on regenerative neurogenesis following IS. Rb3 promoted Opa1-mediated NSCs migration and proliferation. Knockdown of Opa1 blunted the above-promoting effects of Rb3 in both the brains of ischemia-reperfusion (I/R)-treated mice and OGD/R-treated NSCs. Mechanistically, targeted metabolomics, molecular dynamics, molecular docking, CETAS, and DARTS experiments showed that Rb3 promoted Opa1-mediated neural regeneration required the activation of Ido1 and that Ido1 served as a direct target of Rb3 to repair I/R injury. Moreover, studies in siRNA-mediated knockdown and KO mice revealed that inhibition of Ido1 attenuated the enhancing effect of Rb3 on mitochondrial fusion. Our study provides novel evidence that Rb3 promotes neurogenesis through an Ido1/Opa1-mediated pathway involving the interaction between Rb3 and Ido1, leading to improved long-term neurological function. These results indicate that Rb3 or other mitochondrial fusion promoters could be a potential neurorestorative strategy for regenerative neurogenesis following IS.

The influence of acute dopamine transporter inhibition on manic-, depressive-like phenotypes, and brain oxidative status in adult zebrafish

Functional changes in dopamine transporter (DAT) are related to various psychiatric conditions, including bipolar disorder (BD) symptoms. In experimental research, the inhibition of DAT induces behavioral alterations that recapitulate symptoms found in BD patients, including mania and depressive mood. Thus, developing novel animal models that mimic BD-related conditions by pharmacologically modulating the dopaminergic signaling is relevant. The zebrafish (Danio rerio) has been considered a suitable vertebrate system for modeling BD-like responses, due to the well-characterized behavioral responses and evolutionarily conservation of the dopaminergic system of this species. Here, we investigate whether GBR 12909, a selective inhibitor of DAT, causes neurobehavioral alterations in zebrafish similar to those observed in BD patients. Behaviors were recorded after a single intraperitoneal (i.p.) administration of GBR 12909 at different doses (3.75, 7.5, 15 and 30 mg/kg). To observe temporal effects on behavior, swim path parameters were measured immediately after the administration period during 30 min. Locomotion, anxiety-like behavior, social preference, aggression, despair-like behavior, and oxidative stress-related biomarkers in the brain were measured 30 min post administration. GBR 12909 induced prominent effects on locomotor activity and vertical exploration during the 30-min period. Hyperactivity was observed in GBR 30 group after 25 min, while all doses markedly reduced vertical drifts. GBR 12909 elicited hyperlocomotion, anxiety-like behavior, decreased social preference, aggression, and induced depressive-like behavior in a behavioral despair task. Depending on the dose, GBR 12909 also decreased SOD activity and TBARS levels, as well as increased GR activity and NPSH content. Collectively, our novel findings show that a single GBR 12909 administration evokes neurobehavioral changes that recapitulate manic- and depressive-like states observed in rodents, fostering the use of zebrafish models to explore BD-like responses in translational neuroscience research.

A novel murine model of mania

Neuropathological mechanisms of manic syndrome or manic episodes in bipolar disorder remain poorly characterised, as the research progress is severely limited by the paucity of appropriate animal models. Here we developed a novel mania mice model by combining a series of chronic unpredictable rhythm disturbances (CURD), which include disruption of circadian rhythm, sleep deprivation, exposure to cone light, with subsequent interference of followed spotlight, stroboscopic illumination, high-temperature stress, noise disturbance and foot shock. Multiple behavioural and cell biology tests comparing the CURD-model with healthy controls and depressed mice were deployed to validate the model. The manic mice were also tested for the pharmacological effects of various medicinal agents used for treating mania. Finally, we compared plasma indicators of the CURD-model mice and the patients with the manic syndrome. The CURD protocol produced a phenotype replicating manic syndrome. Mice exposed to CURD presented manic behaviours similar to that observed in the amphetamine manic model. These behaviours were distinct from depressive-like behaviours recorded in mice treated with a depression-inducing protocol of chronic unpredictable mild restraint (CUMR). Functional and molecular indicators in the CURD mania model showed multiple similarities with patients with manic syndrome. Treatment with LiCl and valproic acid resulted in behavioural improvements and recovery of molecular indicators. A novel manic mice model induced by environmental stressors and free from genetic or pharmacological interventions is a valuable tool for research into pathological mechanisms of mania.

Is Poor Lithium Response in Individuals with Bipolar Disorder Associated with Increased Degradation of Tryptophan along the Kynurenine Pathway? Results of an Exploratory Study

Bipolar disorder is associated with an inflammation-triggered elevated catabolism of tryptophan to the kynurenine pathway, which impacts psychiatric symptoms and outcomes. The data indicate that lithium exerts anti-inflammatory effects by inhibiting indoleamine-2,3-dioxygenase (IDO)-1 activity. This exploratory study aimed to investigate the tryptophan catabolism in individuals with bipolar disorder (n = 48) compared to healthy controls (n = 48), and the associations with the response to mood stabilizers such as lithium, valproate, or lamotrigine rated with the Retrospective Assessment of the Lithium Response Phenotype Scale (or the Alda scale). The results demonstrate an association of a poorer response to lithium with higher levels of kynurenine, kynurenine/tryptophan ratio as a proxy for IDO-1 activity, as well as quinolinic acid, which, overall, indicates a pro-inflammatory state with a higher degradation of tryptophan towards the neurotoxic branch. The treatment response to valproate and lamotrigine was not associated with the levels of the tryptophan metabolites. These findings support the anti-inflammatory properties of lithium. Furthermore, since quinolinic acid has neurotoxic features via the glutamatergic pathway, they also strengthen the assumption that the clinical drug response might be associated with biochemical processes. The relationship between the lithium response and the measurements of the tryptophan to the kynurenine pathway is of clinical relevance and may potentially bring advantages towards a personalized medicine approach to bipolar disorder that allows for the selection of the most effective mood-stabilizing drug.

Ouabain inhibitor rostafuroxin attenuates dextromethorphan-induced manic potential

Dextromethorphan (DM) abuse produces mania-like symptoms in humans. ERK/Akt signaling activation involved in manic potential can be attenuated by the inhibition of ouabain-like cardiac steroids. In this study, increased phosphorylations of ERK/Akt and hyperlocomotion induced by DM (30 mg/kg, i.p./day × 7) were significantly protected by the ouabain inhibitor rostafuroxin (ROSTA), suggesting that DM induces the manic potential. ROSTA significantly attenuated DM-induced protein kinase C δ (PKCδ) phosphorylation, GluN2B (i.e., MDA receptor subunit) expression, and phospho-PKCδ/GluN2B interaction. DM instantly upregulated the nuclear factor erythroid-2-related factor 2 (Nrf2)-dependent system. However, DM reduced Nrf2 nuclear translocation, Nrf2 DNA binding activity, γ-glutamylcysteine mRNA expression, and subsequent GSH/GSSG level and enhanced oxidative parameters following 1-h of administration. ROSTA, PKCδ inhibitor rottlerin, and GluN2B inhibitor traxoprodil significantly attenuated DM-induced alterations in Nrf2-related redox parameters and locomotor activity induced by DM in wild-type mice. Importantly, in PKCδ knockout mice, DM failed to alter the above parameters. Further, ROSTA and traxoprodil also failed to enhance PKCδ depletion effect, suggesting that PKCδ is a critical target for the anti-manic potential of ROSTA or GluN2B antagonism. Our results suggest that ROSTA inhibits DM-induced manic potential by attenuating ERK/Akt activation, GluN2B/PKCδ signalings, and Nrf2-dependent system.

Ginsenoside Re Protects against Serotonergic Behaviors Evoked by 2,5-Dimethoxy-4-iodo-amphetamine in Mice via Inhibition of PKCδ-Mediated Mitochondrial Dysfunction

It has been recognized that serotonin 2A receptor (5-HT_2A) agonist 2,5-dimethoxy-4-iodo-amphetamine (DOI) impairs serotonergic homeostasis. However, the mechanism of DOI-induced serotonergic behaviors remains to be explored. Moreover, little is known about therapeutic interventions against serotonin syndrome, although evidence suggests that ginseng might possess modulating effects on the serotonin system. As ginsenoside Re (GRe) is well-known as a novel antioxidant in the nervous system, we investigated whether GRe modulates 5-HT_2A receptor agonist DOI-induced serotonin impairments. We proposed that protein kinase Cδ (PKCδ) mediates serotonergic impairments. Treatment with GRe or 5-HT_2A receptor antagonist MDL11939 significantly attenuated DOI-induced serotonergic behaviors (i.e., overall serotonergic syndrome behaviors, head twitch response, hyperthermia) by inhibiting mitochondrial translocation of PKCδ, reducing mitochondrial glutathione peroxidase activity, mitochondrial dysfunction, and mitochondrial oxidative stress in wild-type mice. These attenuations were in line with those observed upon PKCδ inhibition (i.e., pharmacologic inhibitor rottlerin or PKCδ knockout mice). Furthermore, GRe was not further implicated in attenuation mediated by PKCδ knockout in mice. Our results suggest that PKCδ is a therapeutic target for GRe against serotonergic behaviors induced by DOI.

Glutathione peroxidase-1 and neuromodulation: Novel potentials of an old enzyme

Glutathione peroxidase (GPx) acts in co-ordination with other signaling molecules to exert its own antioxidant role. We have demonstrated the protective effects of GPx,/GPx-1, a selenium-dependent enzyme, on various neurodegenerative disorders (i.e., Parkinson's disease, Alzheimer's disease, cerebral ischemia, and convulsive disorders). In addition, we summarized the recent findings indicating that GPx-1 might play a role as a neuromodulator in neuropsychiatric conditions, such as, stress, bipolar disorder, schizophrenia, and drug intoxication. In this review, we attempted to highlight the mechanistic scenarios mediated by the GPx/GPx-1 gene in impacting these neurodegenerative and neuropsychiatric disorders, and hope to provide new insights on the therapeutic interventions against these disorders.