Mitochondrial complex I activity in microglia sustains neuroinflammation.

Sustained smouldering, or low-grade activation, of myeloid cells is a common hallmark of several chronic neurological diseases, including multiple sclerosis1. Distinct metabolic and mitochondrial features guide the activation and the diverse functional states of myeloid cells2. However, how these metabolic features act to perpetuate inflammation of the central nervous system is unclear. Here, using a multiomics approach, we identify a molecular signature that sustains the activation of microglia through mitochondrial complex I activity driving reverse electron transport and the production of reactive oxygen species. Mechanistically, blocking complex I in pro-inflammatory microglia protects the central nervous system against neurotoxic damage and improves functional outcomes in an animal disease model in vivo. Complex I activity in microglia is a potential therapeutic target to foster neuroprotection in chronic inflammatory disorders of the central nervous system3.

Environmental concentrations of tire rubber-derived 6PPD-quinone alter CNS function in zebrafish larvae.

N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6PPD-quinone) is a degradation product of 6PPD, an antioxidant widely used in rubber tires. 6PPD-quinone enters aquatic ecosystems through urban stormwater runoff and has been identified as the chemical behind the urban runoff mortality syndrome in coho salmon. However, the available data suggest that the acute effects of 6PPD-quinone are restricted to a few salmonid species and that the environmental levels of this chemical should be safe for most fish. In this study, larvae of a "tolerant" fish species, Danio rerio, were exposed to three environmental concentrations of 6PPD-quinone for only 24 h, and the effects on exploratory behavior, escape response, nonassociative learning (habituation), neurotransmitter profile, wake/sleep cycle, circadian rhythm, heart rate and oxygen consumption rate were analyzed. Exposure to the two lowest concentrations of 6PPD-quinone resulted in altered exploratory behavior and habituation, an effect consistent with some of the observed changes in the neurotransmitter profile, including increased levels of acetylcholine, norepinephrine, epinephrine and serotonin. Moreover, exposure to the highest concentration tested altered the wake/sleep cycle and the expression of per1a, per3 and cry3a, circadian clock genes involved in the negative feedback loop. Finally, a positive chronotropic effect of 6PPD-quinone was observed in the hearts of the exposed fish. The results of this study emphasize the need for further studies analyzing the effects of 6PPD-quinone in "tolerant" fish species.

Translatability of preclinical to early clinical tolerable and pharmacologically active dose ranges for central nervous system active drugs.

The primary purpose of this study was to assess the translatability of preclinical to early clinical tolerable and pharmacologically active dose ranges for central nervous system (CNS) active drugs. As a part of this, IBs were reviewed on reporting quality. Investigator's Brochures (IBs) of studies performed at the Centre for Human Drug Research (CHDR) reporting statistically significant results of CNS activity related to the drug's mechanism of action were included. The quality of IBs was assessed based on the presence of a rationale for the chosen animal model, completeness of pharmacokinetic (PK) results in reporting and internal validity information of the preclinical evidence. The IB-derisk tool was used to generate preclinical and early clinical data overviews data. For each compound, the overlap between pharmacologically active dose ranges and well-tolerated levels was calculated for three pharmacokinetic (PK) parameters: human equivalent dose (HED), maximum plasma concentration (Cmax) and area under the curve (AUC). Twenty-five IBs were included. In general, the quality of reporting in IBs was assessed as poor. About a third of studies did not explore the entire concentration-effect curve (pre)clinically. Single dose tolerability ranges were most accurately predicted by Cmax. Human equivalent dose and AUC were the best predictors of pharmacologically active ranges. Tolerable and pharmacologically active dose ranges in healthy volunteers can be reasonably well predicted from preclinical data with the IB-derisk tool. The translatability of preclinical studies can be improved by applying a higher reporting standard in IBs including comparable PK measurements across all preclinical and clinical studies.

Molecular and Genetic Mechanisms of Neurotoxicity During Anti-seizure Medications Use.

Abstract: Epilepsy is a multifactorial pathology that has allowed the development of various drugs aiming to combat it. This effort was formally initiated in the 1940s when phenytoin began to be used. It eventually turned out to be a drug with great anticonvulsant efficacy. At present, several potentially good new generation anti-seizure medications (ASMs) have been developed. Most of them present more tolerability and less toxic effects. However, they continue to have adverse effects at different levels. In addition, some seizures are difficult to treat with ASMs, representing 30% of the total cases of people who suffer from epilepsy. This review aims to explore the genetic and molecular mechanisms of ASMs neurotoxicity, proposing the study of damage caused by epileptic seizures, in addition to the deterioration generated by anti-seizure drug administration within the central nervous system. It is beyond question that there is a need to develop drugs that lower the lower the risk of secondary and toxic effects of ASMs. Simultaneously, we must find strategies that produce fewer harmful interactions and more health benefits when taking anti-seizure drugs.

Immunosuppression by opioids: Mechanisms of action on innate and adaptive immunity.

Opioids are excellent analgesics for the clinical treatment of various types of acute and chronic pain, particularly cancer-related pain. Nevertheless, it is well known that opioids have some nasty side effects, including immunosuppression, which is commonly overlooked. As a result, the incidence of opportunistic bacterial and viral infections increases in patients with long-term opioid use. Nowadays, there are no effective medications to alleviate opioid-induced immunosuppression. Understanding the underlying molecular mechanism of opioids in immunosuppression can enable researchers to devise effective therapeutic interventions. This review comprehensively summarized the exogenous opioids-induced immunosuppressive effects and their underlying mechanisms, the regulatory roles of endogenous opioids on the immune system, the potential link between opioid immunosuppressive effect and the function of the central nervous system (CNS), and the future perspectives in this field.

Plantas com ação no sistema nervoso central que constam na relação nacional de plantas medicinais de interesse ao sus (RENISUS) / Plants acting on the central nervous system: review plantas com ação no sistema nervoso central que constam na relação nacional de plantas medicinais de interesse ao sus (RENISUS) / Plantas con acción sobre el sistema nervioso central incluidas en la lista nacional de plantas medicinales de interés para sus (RENISUS)

A depressão é uma doença grave que atinge a população em geral, estudos epidemiológicos estimam que a prevalência da depressão ao longo da vida no Brasil está em torno de 15,5%. Os fatores que desencadeiam o aparecimento da depressão incluem fatores sociais, psicológicos, biológicos e também fatores externos específicos como eventos estressantes, solidão, consumo de álcool e drogas, doenças crônicas e dar á luz (depressão pós-parto). O objetivo da presente pesquisa consistiu em realizar uma revisão bibliográfica sobre as principais plantas medicinais com ação antidepressiva. A ansiedade vem se tornando um dos principais problemas da atualidade, sendo intensificada pela pandemia causada pelo coronavírus, onde constatou-se que durante o pico da pandemia onde os casos confirmados de COVID-19 no Brasil ascenderam de 45.757 para 330.890, e as mortes, de 2.906 para 21.048, o sentimento de tristeza/depressão atingiu 40% dos adultos brasileiros. Os sintomas de depressão podem ser amenizados quando a disponibilidade sináptica de monoaminas são aumentadas, e esse aumento pode ocorrer através da diminuição da metabolização desses neurotransmissores. Neste sentido, busca-se através da farmacoterapia a utilização de antidepressivos que disponibilizem as monoaminas na fenda sináptica. A escolha do fármaco é feita com base nos sintomas da depressão e na boa resposta a uma determinada classe de antidepressivos. Em fevereiro de 2009 o Ministério da saúde lançou a Relação Nacional de Plantas Medicinais de Interesse ao SUS (RENISUS), contendo 71 espécies vegetais que são distribuídas de forma in natura nas unidades básicas de saúde (UBS). Destas, somente três espécies apresentam efeito antidepressivo e ansiolítico comprovados na literatura sendo Matricharia chamomilla, Erytrinum mulungu e a Passiflora incarnata que também fazem parte da RENISUS. Além destas, outras espécies como a Melissa officinalis, Lippia alba, Valeriana officinalis e Piper methysticum são utilizadas pela população para tratar ansiedade, insônia e depressão, sugerindo desta forma que estas espécies sejam incluídas na RENISUS.

Depression is a serious disease that affects the general population, epidemiological studies estimate that the prevalence of depression throughout life in Brazil is around 15.5%. The factors that trigger the onset of depression include social, psychological, biological and also specific external factors such as stressful events, loneliness, alcohol and drug consumption, chronic diseases and giving birth (postpartum depression). The objective of the present research was to carry out a literature review on the main medicinal plants with antidepressant action. Anxiety has become one of the main problems of today, being intensified by the pandemic caused by the coronavirus, where it was found that during the peak of the pandemic where confirmed cases of COVID-19 in Brazil rose from 45,757 to 330,890, and deaths, from 2,906 to 21,048, the feeling of sadness/depression reached 40% of Brazilian adults. Symptoms of depression can be alleviated when synaptic availability of monoamines is increased, and this increase can occur through decreased metabolization of these neurotransmitters. In this sense, the use of antidepressants that make monoamines available in the synaptic cleft is sought through pharmacotherapy. The choice of drug is based on symptoms of depression and good response to a particular class of antidepressants. In February 2009, the Ministry of Health launched the National List of Medicinal Plants of Interest to the SUS (RENISUS), containing 71 plant species that are distributed in natura form in basic health units (UBS). Of these, only three species have antidepressant and anxiolytic effects proven in the literature, being Matricharia chamomilla, Erytrinum mulungu and Passiflora incarnata, which are also part of RENISUS. In addition to these, other species such as Melissa officinalis, Lippia alba, Valeriana officinalis and Piper methysticum are used by the population to treat anxiety, insomnia and depression, thus suggesting that these species are included in RENISUS.

Los estudios epidemiológicos estiman que la prevalencia de la depresión a lo largo de la vida en Brasil es de alrededor del 15,5%. Los factores que desencadenan la aparición de la depresión son sociales, psicológicos, biológicos y también factores externos específicos, como los acontecimientos estresantes, la soledad, el consumo de alcohol y drogas, las enfermedades crónicas y el parto (depresión posparto). El objetivo de esta investigación fue realizar una revisión bibliográfica sobre las principales plantas medicinales con acción antidepresiva. La ansiedad se ha convertido en uno de los principales problemas de la actualidad, intensificándose por la pandemia causada por el coronavirus, donde se encontró que durante el pico de la pandemia donde los casos confirmados de COVID-19 en Brasil aumentaron de 45.757 a 330.890, y las muertes, de 2.906 a 21.048, el sentimiento de tristeza/depresión alcanzó el 40% de los adultos brasileños. Los síntomas de la depresión pueden aliviarse cuando se aumenta la disponibilidad sináptica de las monoaminas, y este aumento puede producirse mediante una disminución de la metabolización de estos neurotransmisores. En este sentido, se busca a través de la farmacoterapia el uso de antidepresivos que hagan disponibles las monoaminas en la hendidura sináptica. La elección del fármaco se hace en función de los síntomas de la depresión y de la buena respuesta a una clase concreta de antidepresivos. En febrero de 2009, el Ministerio de Salud lanzó la Lista Nacional de Plantas Medicinales de Interés para el SUS (RENISUS), que contiene 71 especies de plantas que se distribuyen in natura en unidades básicas de salud (UBS). De ellas, sólo tres especies tienen efectos antidepresivos y ansiolíticos probados en la literatura: Matricharia chamomilla, Erytrinum mulungu y Passiflora incarnata, que también forman parte del RENISUS. Además de éstas, otras especies como Melissa officinalis, Lippia alba, Valeriana officinalis y Piper methysticum son utilizadas por la población para tratar la ansiedad, el insomnio y la depresión, lo que sugiere que estas especies se incluyan en el RENISUS.

Aminophylline in combination with caffeine citrate in neurodevelopmental treatment and follow-up of high-risk preterm infants using GMs assessment.

To explore the application effect of aminophylline combined with caffeine citrate and GMs in the evaluation of neurodevelopmental treatment and follow-up in high-risk preterm infants. A retrospective analysis of 66 high-risk preterm infants admitted to Hengshui People's Hospital from January 2020 to June 2021 was conducted. The children who received only conventional treatment were set as the control group, while those who received aminophylline and caffeine citrate on the basis of conventional treatment were set as the experimental group, 33 cases each group; GMs were used to evaluate the neurodevelopmental function of the children, and the treatment effect was analyzed. The normal proportion of GMs assessment results in the twisting phase and restless movement phase of the experimental group was superior to the control group (P<0.05); The proportion of children with normal neurodevelopment in the experimental group was significantly higher than that in the control group (P<0.05). Aminophylline in combination with caffeine citrate can help promote the neurodevelopment of children and improve their physical health using GMs assessment in the treatment and follow-up of high-risk preterm infants.

Bacopa monnieri: historical aspects to promising pharmacological actions for the treatment on central nervous system diseases / Bacopa monnieri: aspectos históricos de las acciones farmacológicas prometedoras para el tratamiento de enfermedades del sistema nervioso central

Bacopa monnieri(L.) Wettst. (Plantaginaceae), also known as Brahmi, has been used to improve cognitive processes and intellectual functions that are related to the preservation of memory. The objective of this research is to review the ethnobotanical applications, phytochemical composition, toxicity and activity of B. monnieri in the central nervous system. It reviewed articles on B. monnieri using Google Scholar, SciELO, Science Direct, Lilacs, Medline, and PubMed. Saponins are the main compounds in extracts of B. monnieri. Pharmacological studies showed that B. monnieri improves learning and memory and presents biological effects against Alzheimer's disease, Parkinson's disease, epilepsy, and schizophrenia. No preclinical acute toxicity was reported. However, gastrointestinal side effects were reported in some healthy elderly individuals. Most studies with B. monnieri have been preclinical evaluations of cellular mechanisms in the central nervous system and further translational clinical research needs to be performed to evaluate the safety and efficacy of the plant.

Bacopa monnieri (L.) Wettst. (Plantaginaceae), también conocida como Brahmi, se ha utilizado para mejorar los procesos cognitivos y las funciones intelectuales que están relacionadas con la preservación de la memoria. El objetivo de esta investigación es revisar las aplicaciones etnobotánicas, composición fitoquímica, toxicidad y actividad de B. monnieri en el sistema nervioso central. Se revisaron artículos sobre B. monnieri utilizando Google Scholar, SciELO, Science Direct, Lilacs, Medline y PubMed. Las saponinas son los principales compuestos de los extractos de B. monnieri. Los estudios farmacológicos mostraron que B. monnieri mejora el aprendizaje y la memoria y presenta efectos biológicos contra la enfermedad de Alzheimer, la enfermedad de Parkinson, la epilepsia y la esquizofrenia. No se informó toxicidad aguda preclínica. Sin embargo, se informaron efectos secundarios gastrointestinales en algunos ancianos sanos. La mayoría de los estudios con B. monnieri han sido evaluaciones preclínicas de los mecanismos celulares en el sistema nervioso central y es necesario realizar más investigaciones clínicas traslacionales para evaluar la seguridad y eficacia de la planta.

Ionic mitigation of CD4+ T cell metabolic fitness, Th1 central nervous system autoimmunity and Th2 asthmatic airway inflammation by therapeutic zinc.

T helper (Th) cells provide immunity to pathogens but also contribute to detrimental immune responses during allergy and autoimmunity. Th2 cells mediate asthmatic airway inflammation and Th1 cells are involved in the pathogenesis of multiple sclerosis. T cell activation involves complex transcriptional networks and metabolic reprogramming, which enable proliferation and differentiation into Th1 and Th2 cells. The essential trace element zinc has reported immunomodulatory capacity and high zinc concentrations interfere with T cell function. However, how high doses of zinc affect T cell gene networks and metabolism remained so far elusive. Herein, we demonstrate by means of transcriptomic analysis that zinc aspartate (UNIZINK), a registered pharmaceutical infusion solution with high bioavailability, negatively regulates gene networks controlling DNA replication and the energy metabolism of murine CD3/CD28-activated CD4+ T cells. Specifically, in the presence of zinc, CD4+ T cells show impaired expression of cell cycle, glycolytic and tricarboxylic acid cycle genes, which functionally cumulates in reduced glycolysis, oxidative phosphorylation, metabolic fitness and viability. Moreover, high zinc concentrations impaired nuclear expression of the metabolic transcription factor MYC, prevented Th1 and Th2 differentiation in vitro and reduced Th1 autoimmune central nervous system (CNS) inflammation and Th2 asthmatic airway inflammation induced by house dust mites in vivo. Together, we find that higher zinc doses impair the metabolic fitness of CD4+ T cells and prevent Th1 CNS autoimmunity and Th2 allergy.

Carotenoids from Marine Sources as a New Approach in Neuroplasticity Enhancement.

An increasing number of people experience disorders related to the central nervous system (CNS). Thus, new forms of therapy, which may be helpful in repairing processes' enhancement and restoring declined brain functions, are constantly being sought. One of the most relevant physiological processes occurring in the brain for its entire life is neuroplasticity. It has tremendous significance concerning CNS disorders since neurological recovery mainly depends on restoring its structural and functional organization. The main factors contributing to nerve tissue damage are oxidative stress and inflammation. Hence, marine carotenoids, abundantly occurring in the aquatic environment, being potent antioxidant compounds, may play a pivotal role in nerve cell protection. Furthermore, recent results revealed another valuable characteristic of these compounds in CNS therapy. By inhibiting oxidative stress and neuroinflammation, carotenoids promote synaptogenesis and neurogenesis, consequently presenting neuroprotective activity. Therefore, this paper focuses on the carotenoids obtained from marine sources and their impact on neuroplasticity enhancement.

The roles of Eph receptors, neuropilin-1, P2X7, and CD147 in COVID-19-associated neurodegenerative diseases: inflammasome and JaK inhibitors as potential promising therapies.

The novel coronavirus disease 2019 (COVID-19) pandemic has spread worldwide, and finding a safe therapeutic strategy and effective vaccine is critical to overcoming severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Therefore, elucidation of pathogenesis mechanisms, especially entry routes of SARS-CoV-2 may help propose antiviral drugs and novel vaccines. Several receptors have been demonstrated for the interaction of spike (S) protein of SARS-CoV-2 with host cells, including angiotensin-converting enzyme (ACE2), ephrin ligands and Eph receptors, neuropilin 1 (NRP-1), P2X7, and CD147. The expression of these entry receptors in the central nervous system (CNS) may make the CNS prone to SARS-CoV-2 invasion, leading to neurodegenerative diseases. The present review provides potential pathological mechanisms of SARS-CoV-2 infection in the CNS, including entry receptors and cytokines involved in neuroinflammatory conditions. Moreover, it explains several neurodegenerative disorders associated with COVID-19. Finally, we suggest inflammasome and JaK inhibitors as potential therapeutic strategies for neurodegenerative diseases.

Low doses of the organic insecticide spinosad trigger lysosomal defects, elevated ROS, lipid dysregulation, and neurodegeneration in flies.

Large-scale insecticide application is a primary weapon in the control of insect pests in agriculture. However, a growing body of evidence indicates that it is contributing to the global decline in population sizes of many beneficial insect species. Spinosad emerged as an organic alternative to synthetic insecticides and is considered less harmful to beneficial insects, yet its mode of action remains unclear. Using Drosophila, we show that low doses of spinosad antagonize its neuronal target, the nicotinic acetylcholine receptor subunit alpha 6 (nAChRα6), reducing the cholinergic response. We show that the nAChRα6 receptors are transported to lysosomes that become enlarged and increase in number upon low doses of spinosad treatment. Lysosomal dysfunction is associated with mitochondrial stress and elevated levels of reactive oxygen species (ROS) in the central nervous system where nAChRα6 is broadly expressed. ROS disturb lipid storage in metabolic tissues in an nAChRα6-dependent manner. Spinosad toxicity is ameliorated with the antioxidant N-acetylcysteine amide. Chronic exposure of adult virgin females to low doses of spinosad leads to mitochondrial defects, severe neurodegeneration, and blindness. These deleterious effects of low-dose exposures warrant rigorous investigation of its impacts on beneficial insects.

Ponesimod inhibits astrocyte-mediated neuroinflammation and protects against cingulum demyelination via S1P1 -selective modulation.

Ponesimod is a sphingosine 1-phosphate (S1P) receptor (S1PR) modulator that was recently approved for treating relapsing forms of multiple sclerosis (MS). Three other FDA-approved S1PR modulators for MS-fingolimod, siponimod, and ozanimod-share peripheral immunological effects via common S1P1 interactions, yet ponesimod may access distinct central nervous system (CNS) mechanisms through its selectivity for the S1P1 receptor. Here, ponesimod was examined for S1PR internalization and binding, human astrocyte signaling and single-cell RNA-seq (scRNA-seq) gene expression, and in vivo using murine cuprizone-mediated demyelination. Studies confirmed ponesimod's selectivity for S1P1 without comparable engagement to the other S1PR subtypes (S1P2,3,4,5 ). Ponesimod showed pharmacological properties of acute agonism followed by chronic functional antagonism of S1P1 . A major locus of S1P1 expression in the CNS is on astrocytes, and scRNA-seq of primary human astrocytes exposed to ponesimod identified a gene ontology relationship of reduced neuroinflammation and reduction in known astrocyte disease-related genes including those of immediate early astrocytes that have been strongly associated with disease progression in MS animal models. Remarkably, ponesimod prevented cuprizone-induced demyelination selectively in the cingulum, but not in the corpus callosum. These data support the CNS activities of ponesimod through S1P1 , including protective, and likely selective, effects against demyelination in a major connection pathway of the brain, the limbic fibers of the cingulum, lesions of which have been associated with several neurologic impairments including MS fatigue.

Oral treatment of 4-methylumbelliferone reduced perineuronal nets and improved recognition memory in mice.

Hyaluronan (HA) is a core constituent of perineuronal nets (PNNs) that surround subpopulations of neurones. The PNNs control synaptic stabilization in both the developing and adult central nervous system, and disruption of PNNs has shown to reactivate neuroplasticity. We investigated the possibility of memory prolongation by attenuating PNN formation using 4-methylumbelliferone (4-MU), an inhibitor of HA synthesis. Adult C57BL/6 mice were fed with chow containing 5% (w/w) 4-MU for 6 months, at a dose ~6.7 mg/g/day. The oral administration of 4-MU reduced the glycosaminoglycan level in the brain to 72% and the spinal cord to 50% when compared to the controls. Spontaneous object recognition test (SOR) performed at 2, 3, 6 and 7 months showed a significant increase in SOR score in the 6-months treatment group 24 h after object presentation. The effect however did not persist in the washout group (1-month post treatment). Immunohistochemistry confirmed a reduction of PNNs, with shorter and less arborization of aggrecan staining around dendrites in hippocampus after 6 months of 4-MU treatment. Histopathological examination revealed mild atrophy in articular cartilage but it did not affect the motor performance as demonstrated in rotarod test. In conclusion, systemic oral administration of 4-MU for 6 months reduced PNN formation around neurons and enhanced memory retention in mice. However, the memory enhancement was not sustained despite the reduction of PNNs, possibly due to the lack of memory enhancement training during the washout period. Our results suggest that 4-MU treatment might offer a strategy for PNN modulation in memory enhancement.

Novel Molecular Targets of Antidepressants.

Antidepressants target a variety of proteins in the central nervous system (CNS), the most important belonging to the family of G-protein coupled receptors and the family of neurotransmitter transporters. The increasing number of crystallographic structures of these proteins have significantly contributed to the knowledge of their mechanism of action, as well as to the design of new drugs. Several computational approaches such as molecular docking, molecular dynamics, and virtual screening are useful for elucidating the mechanism of drug action and are important for drug design. This review is a survey of molecular targets for antidepressants in the CNS and computer based strategies to discover novel compounds with antidepressant activity.

Nanocarriers for Delivery of Oligonucleotides to the CNS.

Nanoparticles with oligonucleotides bound to the outside or incorporated into the matrix can be used for gene editing or to modulate gene expression in the CNS. These nanocarriers are usually optimised for transfection of neurons or glia. They can also facilitate transcytosis across the brain endothelium to circumvent the blood-brain barrier. This review examines the different formulations of nanocarriers and their oligonucleotide cargoes, in relation to their ability to enter the brain and modulate gene expression or disease. The size of the nanocarrier is critical in determining the rate of clearance from the plasma as well as the intracellular routes of endothelial transcytosis. The surface charge is important in determining how it interacts with the endothelium and the target cell. The structure of the oligonucleotide affects its stability and rate of degradation, while the chemical formulation of the nanocarrier primarily controls the location and rate of cargo release. Due to the major anatomical differences between humans and animal models of disease, successful gene therapy with oligonucleotides in humans has required intrathecal injection. In animal models, some progress has been made with intraventricular or intravenous injection of oligonucleotides on nanocarriers. However, getting significant amounts of nanocarriers across the blood-brain barrier in humans will likely require targeting endothelial solute carriers or vesicular transport systems.

De-risking in Tier I CNS safety assessments is the primary function of study design and technical training of laboratory staff observers.

Derisking is not a pharmaceutical industry strategy to reduce time, effort, or costs in drug development. Derisking strategies originated within the National Institutes of Health as a predicate to good science. There is a growing sentiment within drug development programs to diminish the importance of behavioral measures in toxicological studies and in the Tiered Safety assessment plans of the U.S. Regulatory Agencies and the International Commission on Harmonization. The validity and reliability of the Functional Observational Batter (FOB) is critically dependent on consistency and technical quality in each risk assessment plan. US Federal and International drug approval organizations have universally adopted the concept of principles of test construction rather than delineating specific behavioral assay endpoints for inclusion of the FOB in nonclinical safety protocols. The validity and reliability of behavioral observations in standardized neurotoxicity screening is critically dependent on the FOB developed by the Study Director with the Sponsor throughout all stages of testing.. The individual risk factors selected for observation to be included in the early Tier 1 safety program should be determined by the mechanism and mode of action of the test article. The results of Tier I testing are the basis for Tier II testing designs. Critical to the compliance with Good Laboratory Practices is the documentation of training of the operational staff scheduled to conduct all aspects of the established protocol.

CNS pharmacology of NKCC1 inhibitors.

The Na-K-2Cl cotransporter NKCC1 and the neuron-specific K-Cl cotransporter KCC2 are considered attractive CNS drug targets because altered neuronal chloride regulation and consequent effects on GABAergic signaling have been implicated in numerous CNS disorders. While KCC2 modulators are not yet clinically available, the loop diuretic bumetanide has been used in clinical studies to treat brain disorders and as a tool for NKCC1 inhibition in preclinical models. Bumetanide is known to have anticonvulsant and neuroprotective effects under some pathophysiological conditions. However, as shown in several species from neonates to adults (mice, rats, dogs, and by extrapolation in humans), at the low clinical doses of bumetanide approved for diuresis, this drug has negligible access into the CNS, reaching levels that are much lower than what is needed to inhibit NKCC1 in cells within the brain parenchyma. Several drug discovery strategies have been used over the last ∼15 years to develop brain-permeant compounds that, ideally, should be selective for NKCC1 to eliminate the diuresis mediated by inhibition of renal NKCC2. The strategies employed to improve the pharmacokinetic and pharmacodynamic properties of NKCC1 blockers include evaluation of other clinically approved loop diuretics; development of lipophilic prodrugs of bumetanide; development of side-chain derivatives of bumetanide; and unbiased high-throughput screening approaches of drug discovery based on large chemical compound libraries. The main outcomes are that (1), non-acidic loop diuretics such as azosemide and torasemide may have advantages as NKCC1 inhibitors vs. bumetanide; (2), bumetanide prodrugs achieve significantly higher brain levels of the parent drug and have lower diuretic activity; (3), the novel bumetanide side-chain derivatives do not exhibit any functionally relevant improvement of CNS accessibility or NKCC1 selectivity vs. bumetanide; (4) novel compounds discovered by high-throughput screening may resolve some of the inherent problems of bumetanide, but as yet this has not been achieved. Thus, further research is needed to optimize the design of brain-permeant NKCC1 inhibitors. Another major challenge is to identify the mechanisms whereby various NKCC1-expressing cellular targets of these drug within (e.g., neurons, oligodendrocytes or astrocytes) and outside the brain parenchyma (e.g., blood-brain barrier, choroid plexus, endocrine and immune system), as well as molecular off-target effects, might contribute to their reported therapeutic and adverse effects.