Chronic haloperidol increases voltage-gated Na+ currents in mouse cortical neurons

Molecular and Functional Characterization of Different BrainSphere Models for Use in Neurotoxicity Testing on Microelectrode Arrays

The currently accepted methods for neurotoxicity (NT) testing rely on animal studies. However, high costs and low testing throughput hinder their application for large numbers of chemicals. To overcome these limitations, in vitro methods are currently being developed based on human-induced pluripotent stem cells (hiPSC) that allow higher testing throughput at lower costs. We applied six different protocols to generate 3D BrainSphere models for acute NT evaluation. These include three different media for 2D neural induction and two media for subsequent 3D differentiation resulting in self-organized, organotypic neuron/astrocyte microtissues. All induction protocols yielded nearly 100% NESTIN-positive hiPSC-derived neural progenitor cells (hiNPCs), though with different gene expression profiles concerning regional patterning. Moreover, gene expression and immunocytochemistry analyses revealed that the choice of media determines neural differentiation patterns. On the functional level, BrainSpheres exhibited different levels of electrical activity on microelectrode arrays (MEA). Spike sorting allowed BrainSphere functional characterization with the mixed cultures consisting of GABAergic, glutamatergic, dopaminergic, serotonergic, and cholinergic neurons. A test method for acute NT testing, the human multi-neurotransmitter receptor (hMNR) assay, was proposed to apply such MEA-based spike sorting. These models are promising tools not only in toxicology but also for drug development and disease modeling.

Canonical and Non-Canonical Antipsychotics' Dopamine-Related Mechanisms of Present and Next Generation Molecules: A Systematic Review on Translational Highlights for Treatment Response and Treatment-Resistant Schizophrenia

Schizophrenia is a severe psychiatric illness affecting almost 25 million people worldwide and is conceptualized as a disorder of synaptic plasticity and brain connectivity. Antipsychotics are the primary pharmacological treatment after more than sixty years after their introduction in therapy. Two findings hold true for all presently available antipsychotics. First, all antipsychotics occupy the dopamine D2 receptor (D2R) as an antagonist or partial agonist, even if with different affinity; second, D2R occupancy is the necessary and probably the sufficient mechanism for antipsychotic effect despite the complexity of antipsychotics' receptor profile. D2R occupancy is followed by coincident or divergent intracellular mechanisms, implying the contribution of cAMP regulation, β-arrestin recruitment, and phospholipase A activation, to quote some of the mechanisms considered canonical. However, in recent years, novel mechanisms related to dopamine function beyond or together with D2R occupancy have emerged. Among these potentially non-canonical mechanisms, the role of Na²⁺ channels at the dopamine at the presynaptic site, dopamine transporter (DAT) involvement as the main regulator of dopamine concentration at synaptic clefts, and the putative role of antipsychotics as chaperones for intracellular D2R sequestration, should be included. These mechanisms expand the fundamental role of dopamine in schizophrenia therapy and may have relevance to considering putatively new strategies for treatment-resistant schizophrenia (TRS), an extremely severe condition epidemiologically relevant and affecting almost 30% of schizophrenia patients. Here, we performed a critical evaluation of the role of antipsychotics in synaptic plasticity, focusing on their canonical and non-canonical mechanisms of action relevant to the treatment of schizophrenia and their subsequent implication for the pathophysiology and potential therapy of TRS.

Linked biaromatic compounds as cardioprotective agents

Cardiovascular diseases (CVDs) are widespread in the modern world, and their number is constantly growing. For a long time, CVDs have been the leading cause of morbidity and mortality worldwide. Drugs for the treatment of CVD have been developed almost since the beginning of the 20th century, and a large number of effective cardioprotective agents of various classes have been created. Nevertheless, the need for the design and development of new safe drugs for the treatment of CVD remains. Literature data indicate that a huge number of cardioprotective agents of various generations and mechanisms correspond to a single generalized pharmacophore model containing two aromatic nuclei linked by a linear linker. In this regard, we put forward a concept for the design of a new generation of cardioprotective agents with a multitarget mechanism of action within the indicated pharmacophore model. This review is devoted to a generalization of the currently known compounds with cardioprotective properties and corresponding to the pharmacophore model of biaromatic compounds linked by a linear linker. Particular attention is paid to the history of the creation of these drugs, approaches to their design, and analysis of the structure-action relationship within each class.

Cytokine cascades induced by mechanical trauma injury alter voltage-gated sodium channel activity in intact cortical neurons

BACKGROUND

Traumatic brain injury (TBI) triggers both immediate (primary) and long-term (secondary) tissue damages. Secondary damages can last from hours to days or even a lifetime. Secondary damages implicate several mechanisms, including influence of inflammatory mediators, mainly cytokines, on excitability of ion channels. However, studies should further explore the effects of inflammatory cytokines on voltage-gated sodium channels (VGSCs) and excitability in distal intact neurons.

METHODS

Mixed cultures of mouse cortical astrocytes and neurons were subjected to mechanical injury (trauma) to mimic TBI in vitro. Expression of various cytokines in these cultures were measured by real-time polymerase chain reaction and enzyme-linked immunosorbent assay. A trauma-conditioned medium with or without brain-derived neurotrophic factor (BDNF) was added to mouse primary cortical neurons for 6 and 24 h to mimic combined effects of multiple inflammatory cytokines on VGSCs. Spike behaviors of distal intact neurons were examined by whole-cell patch-clamp recordings.

RESULTS

Mechanical injury in mixed cortical neuron-astrocyte cultures significantly increased expression levels of multiple cytokines, including interleukin (IL)-1β, IL-6, tumor necrosis factor-α, monocyte chemoattractant protein-1, chemokine (C-C motif) ligand-5, IL-10, and transforming growth factor-β1, at 6 and 24 h after injury. Incubation in trauma-conditioned medium increased functional VGSCs in neuronal membranes and Na⁺ currents. Enhanced VGSCs were almost completely abolished by BDNF, and reinforcement of Na⁺ currents was also reduced in a dose-dependent manner. BDNF (30 ng/mL) also significantly reversed reduced neuronal cell viability, which was induced by medium conditioned at 6 h. At 6 and 24 h, trauma-conditioned medium significantly increased spike frequency but not spike threshold.

CONCLUSIONS

In TBI, the combined effect of inflammatory cytokines is directly involved in VGSC, Na⁺ current, and excitability dysfunction in distal intact neurons. BDNF may partly exert neuroprotective effects by maintaining balance of VGSC function in distal intact neurons.

Tumor necrosis factor-α enhances voltage-gated Na⁺ currents in primary culture of mouse cortical neurons

BACKGROUND

Previous studies showed that TNF-α could activate voltage-gated Na(+) channels (VGSCs) in the peripheral nervous system (PNS). Since TNF-α is implicated in many central nervous system (CNS) diseases, we examined potential effects of TNF-α on VGSCs in the CNS.

METHODS

Effects of TNF-α (1-1000 pg/mL, for 4-48 h) on VGSC currents were examined using whole-cell voltage clamp and current clamp techniques in primary culture of mouse cortical neurons. Expression of Nav1.1, Nav1.2, Nav1.3, and Nav1.6 were examined at both the mRNA and protein levels, prior to and after TNF-α exposure.

RESULTS

TNF-α increased Na(+) currents by accelerating the activation of VGSCs. The threshold for action potential (AP) was decreased and firing rate were increased. VGSCs were up-regulated at both the mRNA and protein levels. The observed effects of TNF-α on Na(+) currents were inhibited by pre-incubation with the NF-κB inhibitor BAY 11-7082 (1 μM) or the p38 mitogen-activated protein kinases (MAPK) inhibitor SB203580 (1 μM).

CONCLUSIONS

TNF-α increases Na(+) currents by accelerating the channel activation as well as increasing the expression of VGSCs in a mechanism dependent upon NF-κB and p38 MAPK signal pathways in CNS neurons.

Neuroprotective effect of interleukin-6 regulation of voltage-gated Na(+) channels of cortical neurons is time- and dose-dependent

Interleukin-6 has been shown to be involved in nerve injury and nerve regeneration, but the effects of long-term administration of high concentrations of interleukin-6 on neurons in the central nervous system is poorly understood. This study investigated the effects of 24 hour exposure of interleukin-6 on cortical neurons at various concentrations (0.1, 1, 5 and 10 ng/mL) and the effects of 10 ng/mL interleukin-6 exposure to cortical neurons for various durations (2, 4, 8, 24 and 48 hours) by studying voltage-gated Na(+) channels using a patch-clamp technique. Voltage-clamp recording results demonstrated that interleukin-6 suppressed Na(+) currents through its receptor in a time- and dose-dependent manner, but did not alter voltage-dependent activation and inactivation. Current-clamp recording results were consistent with voltage-clamp recording results. Interleukin-6 reduced the action potential amplitude of cortical neurons, but did not change the action potential threshold. The regulation of voltage-gated Na(+) channels in rat cortical neurons by interleukin-6 is time- and dose-dependent.