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Attaining sufficient tissue exposure at the site of action to achieve the desired pharmacodynamic effect on a target is an important determinant for any drug discovery program, and this can be particularly challenging for oligonucleotides in deep tissues of the CNS. Herein, we report the synthesis and impact of stereopure phosphoryl guanidine-containing backbone linkages (PN linkages) to oligonucleotides acting through an RNase H-mediated mechanism, using Malat1 and C9orf72 as benchmarks. We found that the incorporation of various types of PN linkages to a stereopure oligonucleotide backbone can increase potency of silencing in cultured neurons under free-uptake conditions 10-fold compared with similarly modified stereopure phosphorothioate (PS) and phosphodiester (PO)-based molecules. One of these backbone types, called PN-1, also yielded profound silencing benefits throughout the mouse brain and spinal cord at low doses, improving both the potency and durability of response, especially in difficult to reach brain tissues. Given these benefits in preclinical models, the incorporation of PN linkages into stereopure oligonucleotides with chimeric backbone modifications has the potential to render regions of the brain beyond the spinal cord more accessible to oligonucleotides and, consequently, may also expand the scope of neurological indications amenable to oligonucleotide therapeutics.
In this study, the authors explore the impact of nitrogen-containing (PN) backbones on oligonucleotides that promote RNase H-mediated degradation of a transcript in the central nervous system (CNS). Using Malat1, a ubiquitously expressed non-coding RNA that is predominately localized in the nucleus, and C9orf72, a challenging RNA target requiring a more nuanced targeting strategy, as benchmarks, they show that chimeric oligonucleotides containing stereopure PS and one of the more promising PN backbones (PN-1) have more potent and durable activity throughout the CNS compared with more traditional PS-modified molecules in mouse models. They demonstrate that potency and durability benefits in vivo derive at least in part from increased tissue exposure, especially in more difficult to reach regions of the brain. Ultimately, these benefits enabled the authors to demonstrate pharmacodynamic effects on Malat1 and C9orf72 RNAs in multiple brain regions with relatively low doses.
Assuntos
Oligonucleotídeos Antissenso , Animais , Células Cultivadas , Sistema Nervoso Central , Guanidina/química , Camundongos , Neurônios/efeitos dos fármacos , Oligonucleotídeos Antissenso/química , Oligonucleotídeos Antissenso/farmacologia , Oligonucleotídeos Fosforotioatos , Ribonuclease H/metabolismoRESUMO
Over the past decade, glial cells have attracted attention for harboring unexploited targets for drug discovery. Several glial targets have attracted de novo drug discovery programs, as highlighted in this GLIA Special Issue. Drug repurposing, which has the objective of utilizing existing drugs as well as abandoned, failed, or not yet pursued clinical development candidates for new indications, might provide a faster opportunity to bring drugs for glial targets to patients with unmet needs. Here, we review the potential of the intermediate-conductance calcium-activated potassium channels KCa 3.1 as the target for such a repurposing effort. We discuss the data on KCa 3.1 expression on microglia in vitro and in vivo and review the relevant literature on the two KCa 3.1 inhibitors TRAM-34 and Senicapoc. Finally, we provide an outlook of what it might take to harness the potential of KCa 3.1 as a bona fide microglial drug target. GLIA 2016;64:1733-1741.
Assuntos
Reposicionamento de Medicamentos , Canais de Potássio Ativados por Cálcio de Condutância Intermediária/metabolismo , Microglia/metabolismo , Acetamidas/química , Acetamidas/farmacologia , Acetamidas/uso terapêutico , Animais , Humanos , Canais de Potássio Ativados por Cálcio de Condutância Intermediária/antagonistas & inibidores , Microglia/efeitos dos fármacos , Pirazóis/química , Pirazóis/farmacologia , Pirazóis/uso terapêutico , Compostos de Tritil/química , Compostos de Tritil/farmacologia , Compostos de Tritil/uso terapêuticoRESUMO
Minocycline, a second generation broad-spectrum antibiotic, has been frequently postulated to be a "microglia inhibitor." A considerable number of publications have used minocycline as a tool and concluded, after achieving a pharmacological effect, that the effect must be due to "inhibition" of microglia. It is, however, unclear how this "inhibition" is achieved at the molecular and cellular levels. Here, we weigh the evidence whether minocycline is indeed a bona fide microglia inhibitor and discuss how data generated with minocycline should be interpreted. GLIA 2016;64:1788-1794.
Assuntos
Antibacterianos/farmacologia , Microglia/efeitos dos fármacos , Minociclina/farmacologia , Animais , Antibacterianos/uso terapêutico , Bases de Dados Factuais/estatística & dados numéricos , Humanos , Microglia/fisiologia , Minociclina/uso terapêuticoRESUMO
The hippocampus plays an important role in emotional and cognitive processing, and both of these domains are affected in patients with major depressive disorder (MDD). Extensive preclinical research and the notion that modulation of serotonin (5-HT) neurotransmission plays a key role in the therapeutic efficacy of selective serotonin reuptake inhibitors (SSRIs) support the view that 5-HT is important for hippocampal function in normal and disease-like conditions. The hippocampus is densely innervated by serotonergic fibers, and the majority of 5-HT receptor subtypes are expressed there. Furthermore, hippocampal cells often co-express multiple 5-HT receptor subtypes that can have either complementary or opposing effects on cell function, adding to the complexity of 5-HT neurotransmission. Here we review the current knowledge of how 5-HT, through its various receptor subtypes, modulates hippocampal output and the activity of hippocampal pyramidal cells in rodents. In addition, we discuss the relevance of 5-HT modulation for cognitive processing in rodents and possible clinical implications of these results in patients with MDD. Finally, we review the data on how SSRIs and vortioxetine, an antidepressant with multimodal activity, affect hippocampal function, including cognitive processing, from both a preclinical and clinical perspective.
Assuntos
Antidepressivos/farmacologia , Transtorno Depressivo Maior/metabolismo , Hipocampo/efeitos dos fármacos , Células Piramidais/efeitos dos fármacos , Receptores de Serotonina/efeitos dos fármacos , Inibidores Seletivos de Recaptação de Serotonina/farmacologia , Serotonina/metabolismo , Antidepressivos/uso terapêutico , Transtorno Depressivo Maior/tratamento farmacológico , Hipocampo/metabolismo , Humanos , Células Piramidais/metabolismo , Receptores de Serotonina/metabolismo , Inibidores Seletivos de Recaptação de Serotonina/uso terapêutico , Transmissão SinápticaRESUMO
Huntington's disease (HD) is an autosomal dominant disease caused by the expansion of cytosine-adenine-guanine (CAG) repeats in one copy of the HTT gene (mutant HTT, mHTT). The unaffected HTT gene encodes wild-type HTT (wtHTT) protein, which supports processes important for the health and function of the central nervous system. Selective lowering of mHTT for the treatment of HD may provide a benefit over nonselective HTT-lowering approaches, as it aims to preserve the beneficial activities of wtHTT. Targeting a heterozygous single-nucleotide polymorphism (SNP) where the targeted variant is on the mHTT gene is one strategy for achieving allele-selective activity. Herein, we investigated whether stereopure phosphorothioate (PS)- and phosphoryl guanidine (PN)-containing oligonucleotides can direct allele-selective mHTT lowering by targeting rs362273 (SNP3). We demonstrate that our SNP3-targeting molecules are potent, durable, and selective for mHTT in vitro and in vivo in mouse models. Through comparisons with a surrogate for the nonselective investigational compound tominersen, we also demonstrate that allele-selective molecules display equivalent potency toward mHTT with improved durability while sparing wtHTT. Our preclinical findings support the advancement of WVE-003, an investigational allele-selective compound currently in clinical testing (NCT05032196) for the treatment of patients with HD.
RESUMO
We have developed a chiral route toward the synthesis of muscarinic M4 agonists that was enabled by the biocatalytic synthesis of the key spirocyclic diamine building blocks 10 and 12. Using these bifunctional compounds we were able to optimize a synthetic sequence toward a collection of advanced intermediates for further elaboration. These advanced intermediates were then used as starting points for early medicinal chemistry and the identification of selective M1/M4 agonists.
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A large hexanucleotide (G4C2) repeat expansion in the first intronic region of C9orf72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Several mechanisms have been proposed to explain how the repeat expansion drives disease, and we hypothesize that a variant-selective approach, in which transcripts affected by the repeat expansion are preferentially decreased, has the potential to address most of them. We report a stereopure antisense oligonucleotide, WVE-004, that executes this variant-selective mechanism of action. WVE-004 dose-dependently and selectively reduces repeat-containing transcripts in patient-derived motor neurons carrying a C9orf72-repeat expansion, as well as in the spinal cord and cortex of C9 BAC transgenic mice. In mice, selective transcript knockdown was accompanied by substantial decreases in dipeptide-repeat proteins, which are pathological biomarkers associated with the repeat expansion, and by preservation of healthy C9orf72 protein expression. These in vivo effects were durable, persisting for at least 6 months. These data support the advancement of WVE-004 as an investigational stereopure antisense oligonucleotide targeting C9orf72 for the treatment of C9orf72-associated ALS or FTD.
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There remains an insufficient number of P2X7 receptor antagonists with adequate rodent potency, CNS permeability, and pharmacokinetic properties from which to evaluate CNS disease hypotheses preclinically. Herein, we describe the molecular pharmacology, safety, pharmacokinetics, and functional CNS target engagement of Lu AF27139, a novel rodent-active and CNS-penetrant P2X7 receptor antagonist. Lu AF27139 is highly selective and potent against rat, mouse, and human forms of the receptors. The rat pharmacokinetic profile is favorable with high oral bioavailability, modest clearance (0.79 L/(h kg)), and good CNS permeability. In vivo mouse CNS microdialysis studies of lipopolysaccharide (LPS)-primed and 2'(3')-O-(benzoylbenzoyl)adenosine-5'-triphosphate (BzATP)-induced IL-1ß release demonstrate functional CNS target engagement. Importantly, Lu AF27139 was without effect in standard in vitro and in vivo toxicity studies. Based on these properties, we believe Lu AF27139 will be a valuable tool for probing the role of the P2X7 receptor in rodent models of CNS diseases.
Assuntos
Sistema Nervoso Central/metabolismo , Antagonistas do Receptor Purinérgico P2X/síntese química , Receptores Purinérgicos P2X7/metabolismo , Trifosfato de Adenosina/análogos & derivados , Trifosfato de Adenosina/farmacologia , Animais , Linhagem Celular , Sistema Nervoso Central/efeitos dos fármacos , Cães , Feminino , Meia-Vida , Humanos , Interleucina-1beta/metabolismo , Lipopolissacarídeos/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Microglia/citologia , Microglia/efeitos dos fármacos , Microglia/metabolismo , Microssomos Hepáticos/metabolismo , Monócitos/citologia , Monócitos/efeitos dos fármacos , Monócitos/metabolismo , Antagonistas do Receptor Purinérgico P2X/metabolismo , Antagonistas do Receptor Purinérgico P2X/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores Purinérgicos P2X7/químicaRESUMO
The multimodal antidepressant vortioxetine is thought to mediate its pharmacological effects via 5-HT1A receptor agonism, 5-HT1B receptor partial agonism, 5-HT1D, 5-HT3, 5-HT7 receptor antagonism and 5-HT transporter inhibition. Here we studied vortioxetine's functional effects across species (canine, mouse, rat, guinea pig and human) in cellular assays with heterologous expression of 5-HT3A receptors (in Xenopus oocytes and HEK-293 cells) and in mouse neuroblastoma N1E-115 cells with endogenous expression of 5-HT3A receptors. Furthermore, we studied the effects of vortioxetine on activity of CA1 Stratum Radiatum interneurons in rat hippocampus slices using current- and voltage-clamping methods. The patched neurons were subsequently filled with biocytin for confirmation of 5-HT3 receptor mRNA expression by in situ hybridization. Whereas, both vortioxetine and the 5-HT3 receptor antagonist ondansetron potently antagonized 5-HT-induced currents in the cellular assays, vortioxetine had a slower off-rate than ondansetron in oocytes expressing 5-HT3A receptors. Furthermore, vortioxetine's but not ondansetron's 5-HT3 receptor antagonistic potency varied considerably across species. Vortioxetine had the highest potency at rat and the lowest potency at guinea pig 5-HT3A receptors. Finally, in 5-HT3 receptor-expressing GABAergic interneurons from the CA1 stratum radiatum, vortioxetine and ondansetron blocked depolarizations induced by superfusion of either 5-HT or the 5-HT3 receptor agonist mCPBG. Taken together, these data add to a growing literature supporting the idea that vortioxetine may inhibit GABAergic neurotransmission in some brain regions via a 5-HT3 receptor antagonism-dependent mechanism and thereby disinhibit pyramidal neurons and enhance glutamatergic signaling.
Assuntos
Potenciais de Ação/efeitos dos fármacos , Antidepressivos/farmacologia , Interneurônios/efeitos dos fármacos , Células Piramidais/efeitos dos fármacos , Antagonistas do Receptor 5-HT3 de Serotonina/farmacologia , Vortioxetina/farmacologia , Potenciais de Ação/fisiologia , Animais , Região CA1 Hipocampal/efeitos dos fármacos , Região CA1 Hipocampal/metabolismo , Cães , Ácido Glutâmico/metabolismo , Cobaias , Células HEK293 , Humanos , Interneurônios/metabolismo , Camundongos , Ondansetron/farmacologia , Oócitos , Células Piramidais/metabolismo , Ratos , Receptores 5-HT3 de Serotonina/metabolismo , Serotonina/metabolismo , Técnicas de Cultura de Tecidos , Xenopus laevis , Ácido gama-Aminobutírico/metabolismoRESUMO
Prefrontal-subcortical circuits support executive functions which often become dysfunctional in psychiatric disorders. Vortioxetine is a multimodal antidepressant that is currently used in the clinic to treat major depressive disorder. Mechanisms of action of vortioxetine include serotonin (5-HT) transporter blockade, 5-HT1A receptor agonism, 5-HT1B receptor partial agonism, and 5-HT1D, 5-HT3, and 5-HT7 receptor antagonism. Vortioxetine facilitates 5-HT transmission in the medial prefrontal cortex (mPFC), however, the impact of this compound on related prefrontal-subcortical circuits is less clear. Thus, the current study examined the impact of systemic vortioxetine administration (0.8 mg/kg, i.v.) on spontaneous spiking and spikes evoked by electrical stimulation of the mPFC in the anterior cingulate cortex (ACC), medial shell of the nucleus accumbens (msNAc), and lateral septal nucleus (LSN) in urethane-anesthetized rats. We also examined whether vortioxetine modulated afferent drive in the msNAc from hippocampal fimbria (HF) inputs. Similar studies were performed using the selective 5-HT reuptake inhibitor [selective serotonin reuptake inhibitors (SSRI)] escitalopram (1.6 mg/kg, i.v.) to enable comparisons between the multimodal actions of vortioxetine and SSRI-mediated effects. No significant differences in spontaneous activity were observed in the ACC, msNAc, and LSN across treatment groups. No significant impact of treatment on mPFC-evoked responses was observed in the ACC. In contrast, vortioxetine decreased mPFC-evoked activity recorded in the msNAc as compared to parallel studies in control and escitalopram treated groups. Thus, vortioxetine may reduce mPFC-msNAc afferent drive via a mechanism that, in addition to an SSRI-like effect, requires 5-HT receptor modulation. Recordings in the LSN revealed a significant increase in mPFC-evoked activity following escitalopram administration as compared to control and vortioxetine treated groups, indicating that complex modulation of 5-HT receptors by vortioxetine may offset SSRI-like effects in this region. Lastly, neurons in the msNAc were more responsive to stimulation of the HF following both vortioxetine and escitalopram administration, indicating that elevation of 5-HT tone and 5-HT receptor modulation may facilitate excitatory hippocampal synaptic drive in this region. The above findings point to complex 5-HT receptor-dependent effects of vortioxetine which may contribute to its unique impact on the function of prefrontal-subcortical circuits and the development of novel strategies for treating mood disorders.
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Neuroplasticity is fundamental for brain functions, abnormal changes of which are associated with mood disorders and cognitive impairment. Neuroplasticity can be affected by neuroactive medications and by aging. Vortioxetine, a multimodal antidepressant, has shown positive effects on cognitive functions in both pre-clinical and clinical studies. In rodent studies, vortioxetine increases glutamate neurotransmission, promotes dendritic branching and spine maturation, and elevates hippocampal expression of the activity-regulated cytoskeleton-associated protein (Arc/Arg3.1) at the transcript level. The present study aims to assess the effects of vortioxetine on several neuroplasticity-related molecules in different experimental systems. Chronic (1 month) vortioxetine increased Arc/Arg3.1 protein levels in the cortical synaptosomes of young and middle-aged mice. In young mice, this was accompanied by an increase in actin-depolymerizing factor (ADF)/cofilin serine 3 phosphorylation without altering the total ADF/cofilin protein level, and an increase in the GluA1 subunit of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor phosphorylation at serine 845 (S845) without altering serine 831 (S831) GluA1 phosphorylation nor the total GluA1 protein level. Similar effects were detected in cultured rat hippocampal neurons: Acute vortioxetine increased S845 GluA1 phosphorylation without changing S831 GluA1 phosphorylation or the total GluA1 protein level. These changes were accompanied by an increase in α subunit of Ca2+/calmodulin-dependent kinase (CaMKIIα) phosphorylation (at threonine 286) without changing the total CaMKIIα protein level in cultured neurons. In addition, chronic (1 month) vortioxetine, but not fluoxetine, restored the age-associated reduction in Arc/Arg3.1 and c-Fos transcripts in the frontal cortex of middle-aged mice. Taken together, these results demonstrated that vortioxetine modulates molecular targets that are related to neuroplasticity.
Assuntos
Plasticidade Neuronal/efeitos dos fármacos , Piperazinas/farmacologia , Sulfetos/farmacologia , Animais , Antidepressivos/farmacologia , Proteínas do Citoesqueleto/metabolismo , Feminino , Lobo Frontal/efeitos dos fármacos , Lobo Frontal/metabolismo , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Fosforilação/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Receptores de AMPA/metabolismo , Serina/metabolismo , VortioxetinaRESUMO
Neuropathic pain is a debilitating, chronic condition with a significant unmet need for effective treatment options. Recent studies have demonstrated that in addition to neurons, non-neuronal cells such as microglia contribute to the initiation and maintenance of allodynia in rodent models of neuropathic pain. The Ca2+- activated K+ channel, KCa3.1 is critical for the activation of immune cells, including the CNS-resident microglia. In order to evaluate the role of KCa3.1 in the maintenance of mechanical allodynia following peripheral nerve injury, we used senicapoc, a stable and highly potent KCa3.1 inhibitor. In primary cultured microglia, senicapoc inhibited microglial nitric oxide and IL-1ß release. In vivo, senicapoc showed high CNS penetrance and when administered to rats with peripheral nerve injury, it significantly reversed tactile allodynia similar to the standard of care, gabapentin. In contrast to gabapentin, senicapoc achieved efficacy without any overt impact on locomotor activity. Together, the data demonstrate that the KCa3.1 inhibitor senicapoc is effective at reducing mechanical hypersensitivity in a rodent model of peripheral nerve injury.
Assuntos
Acetamidas/farmacologia , Hiperalgesia/complicações , Hiperalgesia/tratamento farmacológico , Canais de Potássio Ativados por Cálcio de Condutância Intermediária/antagonistas & inibidores , Traumatismos dos Nervos Periféricos/complicações , Bloqueadores dos Canais de Potássio/farmacologia , Compostos de Tritil/farmacologia , Acetamidas/efeitos adversos , Acetamidas/farmacocinética , Acetamidas/uso terapêutico , Animais , Células CHO , Cricetinae , Cricetulus , Relação Dose-Resposta a Droga , Estabilidade de Medicamentos , Humanos , Hiperalgesia/metabolismo , Hiperalgesia/fisiopatologia , Locomoção/efeitos dos fármacos , Microglia/efeitos dos fármacos , Microglia/metabolismo , Potássio/metabolismo , Bloqueadores dos Canais de Potássio/efeitos adversos , Bloqueadores dos Canais de Potássio/farmacocinética , Bloqueadores dos Canais de Potássio/uso terapêutico , Ratos , Compostos de Tritil/efeitos adversos , Compostos de Tritil/farmacocinética , Compostos de Tritil/uso terapêuticoRESUMO
A single i.v. infusion of ketamine, classified as an N-methyl-d-aspartate (NMDA) receptor antagonist, may alleviate depressive symptoms within hours of administration in treatment resistant depressed patients, and the antidepressant effect may last for several weeks. These unique therapeutic properties have prompted researchers to explore the mechanisms mediating the antidepressant effects of ketamine, but despite many efforts, no consensus on its antidepressant mechanism of action has been reached. Recent preclinical reports have associated the neurotransmitter serotonin (5-hydroxytryptamine; 5-HT) with the antidepressant-like action of ketamine. Here, we review the current evidence for a serotonergic role in ketamine's antidepressant effects. The pharmacological profile of ketamine may include equipotent activity on several non-NMDA targets, and the current hypotheses for the mechanisms responsible for ketamine's antidepressant activity do not appear to preclude the possibility that non-glutamate neurotransmitters are involved in the antidepressant effects. At multiple levels, the serotonergic and glutamatergic systems interact, and such crosstalk could support the notion that changes in serotonergic neurotransmission may impact ketamine's antidepressant potential. In line with these prospects, ketamine may increase 5-HT levels in the prefrontal cortex of rats, plausibly via hippocampal NMDA receptor inhibition and activation of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors. In addition, a number of preclinical studies suggest that the antidepressant-like effects of ketamine may depend on endogenous activation of 5-HT receptors. Recent imaging and behavioral data predominantly support a role for 5-HT1A or 5-HT1B receptors, but the full range of 5-HT receptors has currently not been systematically investigated in this context. Furthermore, the nature of any 5-HT dependent mechanism in ketamine's antidepressant effect is currently not understood, and therefore, more studies are warranted to confirm this hypothesis and explore the specific pathways that might implicate 5-HT.
Assuntos
Antidepressivos/uso terapêutico , Depressão/tratamento farmacológico , Ketamina/uso terapêutico , Serotonina/metabolismo , Transdução de Sinais/efeitos dos fármacos , Animais , Depressão/metabolismo , HumanosRESUMO
The oligomeric amyloid-ß (Aß) peptide is thought to contribute to the subtle amnesic changes in Alzheimer's disease (AD) by causing synaptic dysfunction. Here, we examined the time course of synaptic changes in mouse hippocampal neurons following exposure to Aß42 at picomolar concentrations, mimicking its physiological levels in the brain. We found opposite effects of the peptide with short exposures in the range of minutes enhancing synaptic plasticity, and longer exposures lasting several hours reducing it. The plasticity reduction was concomitant with an increase in the basal frequency of spontaneous neurotransmitter release, a higher basal number of functional presynaptic release sites, and a redistribution of synaptic proteins including the vesicle-associated proteins synapsin I, synaptophysin, and the post-synaptic glutamate receptor I. These synaptic alterations were mediated by cytoskeletal changes involving actin polymerization and p38 mitogen-activated protein kinase. These in vitro findings were confirmed in vivo with short hippocampal infusions of picomolar Aß enhancing contextual memory and prolonged infusions impairing it. Our findings provide a model for initiation of synaptic dysfunction whereby exposure to physiologic levels of Aß for a prolonged period of time causes microstructural changes at the synapse which result in increased transmitter release, failure of synaptic plasticity, and memory loss.
Assuntos
Doença de Alzheimer/diagnóstico , Peptídeos beta-Amiloides/farmacologia , Transtornos da Memória/diagnóstico , Plasticidade Neuronal/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Fragmentos de Peptídeos/farmacologia , Transmissão Sináptica/efeitos dos fármacos , Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Doença de Alzheimer/fisiopatologia , Animais , Animais Recém-Nascidos , Modelos Animais de Doenças , Regulação da Expressão Gênica , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Hipocampo/patologia , Humanos , Transtornos da Memória/genética , Transtornos da Memória/metabolismo , Transtornos da Memória/fisiopatologia , Camundongos , Camundongos Endogâmicos C57BL , Neurônios/metabolismo , Neurônios/patologia , Técnicas de Patch-Clamp , Terminações Pré-Sinápticas/efeitos dos fármacos , Cultura Primária de Células , Multimerização Proteica , Receptores de Glutamato/genética , Receptores de Glutamato/metabolismo , Sinapses/efeitos dos fármacos , Sinapsinas/genética , Sinapsinas/metabolismo , Sinaptofisina/genética , Sinaptofisina/metabolismo , Fatores de Tempo , Proteínas Quinases p38 Ativadas por Mitógeno/genética , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
The monoamine hypothesis has been the prevailing hypothesis of depression over the last several decades. It states that depression is associated with reduced monoamine function. Hence efforts to increase monoamine transmission by inhibiting serotonin (5-HT) and norepinephrine (NE) transporters has been a central theme in depression research since the 1960s. The selective 5-HT reuptake inhibitors (SSRIs) and 5-HT and NE reuptake inhibitors (SNRIs) that have emerged from this line of research are currently first line treatment options for major depressive disorder (MDD). One of the recent trends in antidepressant research has been to refine monoaminergic mechanisms by targeting monoaminergic receptors and additional transporters (e.g. with multimodal drugs and triple re-uptake inhibitors) or by adding atypical antipsychotics to SSRI or SNRI treatment. In addition, several other hypotheses of depression have been brought forward in pre-clinical and clinical research based on biological hallmarks of the disease and efficacy of pharmacological interventions. A central strategy has been to target glutamate receptors (for example, with intravenous infusions of the N-methyl-d-aspartate (NMDA) receptor antagonist ketamine). Other strategies have been based on modulation of cholinergic and γ-aminobutyric acid (GABA)ergic transmission, neuronal plasticity, stress/hypothalamic pituitary adrenal(HPA)-axis, the reward system and neuroinflammation. Here we review the pharmacological profiles of compounds that derived from these strategies and have been recently tested in clinical trials with published results. In addition, we discuss putative treatments for depression that are being investigated at the preclinical level and outline future directions for antidepressant research.
Assuntos
Antidepressivos/uso terapêutico , Transtorno Depressivo Maior/tratamento farmacológico , Quimioterapia Combinada , Humanos , Norepinefrina/metabolismo , Inibidores Seletivos de Recaptação de Serotonina/uso terapêuticoRESUMO
It has been known for several decades that serotonergic neurotransmission is a key regulator of cognitive function, mood, and sleep. Yet with the relatively recent discoveries of novel serotonin (5-HT) receptor subtypes, as well as an expanding knowledge of their expression level in certain brain regions and localization on certain cell types, their involvement in cognitive processes is still emerging. Of particular interest are cognitive processes impacted in neuropsychiatric and neurodegenerative disorders. The prefrontal cortex (PFC) is critical to normal cognitive processes, including attention, impulsivity, planning, decision-making, working memory, and learning or recall of learned memories. Furthermore, serotonergic dysregulation within the PFC is implicated in many neuropsychiatric disorders associated with prominent symptoms of cognitive dysfunction. Thus, it is important to better understand the overall makeup of serotonergic receptors in the PFC and on which cell types these receptors mediate their actions. In this Review, we focus on 5-HT receptor expression patterns within the PFC and how they influence cognitive behavior and neurotransmission. We further discuss the net effects of vortioxetine, an antidepressant acting through multiple serotonergic targets given the recent findings that vortioxetine improves cognition by modulating multiple neurotransmitter systems.
Assuntos
Cognição/fisiologia , Córtex Pré-Frontal/metabolismo , Receptores de Serotonina/metabolismo , Animais , Antidepressivos/farmacologia , Cognição/efeitos dos fármacos , Humanos , Vias Neurais/efeitos dos fármacos , Vias Neurais/metabolismo , Piperazinas/farmacologia , Córtex Pré-Frontal/efeitos dos fármacos , Inibidores Seletivos de Recaptação de Serotonina/farmacologia , Sulfetos/farmacologia , VortioxetinaRESUMO
Major depressive disorder (MDD) is primarily conceptualized as a mood disorder but cognitive dysfunction is also prevalent, and may limit the daily function of MDD patients. Current theories on MDD highlight disturbances in dendritic plasticity in its pathophysiology, which could conceivably play a role in the production of both MDD-related mood and cognitive symptoms. This paper attempts to review the accumulated knowledge on the basic biology of the activity-regulated cytoskeleton-associated protein (Arc or Arg3.1), its effects on neural plasticity, and how these may be related to mood or cognitive dysfunction in animal models of MDD. On a cellular level, Arc plays an important role in modulating dendritic spine density and remodeling. Arc also has a close, bidirectional relationship with postsynaptic glutamate neurotransmission, since it is stimulated by multiple glutamatergic receptor mechanisms but also modulates α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor internalization. The effects on AMPA receptor trafficking are likely related to Arc's ability to modulate phenomena such as long-term potentiation, long-term depression, and synaptic scaling, each of which are important for maintaining proper cognitive function. Chronic stress models of MDD in animals show suppressed Arc expression in the frontal cortex but elevation in the amygdala. Interestingly, cognitive tasks depending on the frontal cortex are generally impaired by chronic stress, while those depending on the amygdala are enhanced, and antidepressant treatments stimulate cortical Arc expression with a timeline that is reminiscent of the treatment efficacy lag observed in the clinic or in preclinical models. However, pharmacological treatments that stimulate regional Arc expression do not universally improve relevant cognitive functions, and this highlights a need to further refine our understanding of Arc on a subcellular and network level.
RESUMO
Although major depressive disorder is primarily considered a mood disorder, depressed patients commonly present with clinically significant cognitive dysfunction that may add to their functional disability. This review paper summarizes the available preclinical data on the effects of antidepressants, including monoamine reuptake inhibitors and the multimodal antidepressant vortioxetine, in behavioral tests of cognition such as cognitive flexibility, attention, and memory, or in potentially cognition-relevant mechanistic assays such as electroencephalography, in vivo microdialysis, in vivo or in vitro electrophysiology, and molecular assays related to neurogenesis or synaptic sprouting. The available data are discussed in context with clinically relevant doses and their relationship to target occupancy levels, in order to evaluate the translational relevance of preclinical doses used during testing. We conclude that there is preclinical evidence suggesting that traditional treatment with monoamine reuptake inhibitors can induce improved cognitive function, for example in cognitive flexibility and memory, and that the multimodal-acting antidepressant vortioxetine may have some advantages by comparison to these treatments. However, the translational value of the reviewed preclinical data can be questioned at times, due to the use of doses outside the therapeutically-relevant range, the lack of data on target engagement or exposure, the tendency to investigate acute rather than long term antidepressant administration, and the trend towards using normal rodents rather than models with translational relevance for depression. Finally, several suggestions are made for advancing this field, including expanded use of target occupancy assessments in preclinical and clinical experiments, and the use of translationally valuable techniques such as electroencephalography.
Assuntos
Antidepressivos/farmacologia , Cognição/efeitos dos fármacos , Piperazinas/farmacologia , Inibidores Seletivos de Recaptação de Serotonina/farmacologia , Inibidores da Recaptação de Serotonina e Norepinefrina/farmacologia , Sulfetos/farmacologia , Animais , VortioxetinaRESUMO
Drug design necessitates a clear understanding of the phenotypic response to be elicited by a given ligandtarget interaction. This relationship is relatively well understood for classical biological targets of drug action, but for some novel targets, notably those amenable to allosteric modulation, developing such understanding may represent a more challenging task. In order to gain knowledge on the nature of the functional response derived from mGlu4 receptor activation, its molecular and cell biology are reviewed, including signalling pathways involved, receptor localization in central nervous system and beyond, and potential genetic links to disease. Broadly held views for both, orthosteric agonists as well as allosteric modulators, are compared with specific observations for the case of mGlu4 receptor activation via orthosteric and allosteric mechanisms. First, sub-type selectivity and brain penetration of amino acid mGlu4 receptor agonists are discussed, followed by the quantification of functional allosteric effects, the potential role of heterodimers in the functional response, and the observation of supra-physiological efficacy of mGlu4 receptor PAMs. We show that, in our analysis, these attributes differ from those that may be expected by extrapolating from broad knowledge. In addition, recent progress with mGlu4 receptor radioligands and PET ligands is summarized.
Assuntos
Sistema Nervoso Central/metabolismo , Doenças Neurodegenerativas/metabolismo , Receptores de Glutamato Metabotrópico/metabolismo , Bibliotecas de Moléculas Pequenas/química , Regulação Alostérica , Sítio Alostérico , Transporte Biológico , Sistema Nervoso Central/patologia , Desenho de Fármacos , Regulação da Expressão Gênica , Humanos , Canais Iônicos/genética , Canais Iônicos/metabolismo , Ligantes , Proteínas Quinases Ativadas por Mitógeno/genética , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Doenças Neurodegenerativas/genética , Doenças Neurodegenerativas/patologia , Multimerização Proteica , Compostos Radiofarmacêuticos/química , Compostos Radiofarmacêuticos/metabolismo , Receptores de Glutamato Metabotrópico/agonistas , Receptores de Glutamato Metabotrópico/química , Receptores de Glutamato Metabotrópico/genética , Transdução de Sinais , Bibliotecas de Moléculas Pequenas/síntese química , Bibliotecas de Moléculas Pequenas/farmacologia , Relação Estrutura-AtividadeRESUMO
Metabotropic glutamate 4 (mGlu4) receptor is a promising target for the treatment of motor deficits in Parkinson's disease (PD). This is due in part to its localization at key basal ganglia (BG) synapses that become hyperactive in this pathology, particularly striatopallidal synapses. In this context, mGlu4 receptor activation using either orthosteric agonists or positive allosteric modulators (PAMs) improves motor symptoms in rodent PD models in certain conditions. However, literature data show that mGlu4 receptor PAMs have no effect at striatopallidal GABAergic synapses (unless combined with an orthosteric agonist) and on the firing activity of pallidal neurons, and fail to provide significant motor improvement in relevant PD models. This questions the mechanistic hypothesis that mGlu4 receptor PAMs should act at striatopallidal synapses to alleviate PD motor symptoms. To shed light on this issue, we performed brain slice electrophysiology experiments. We show that Lu AF21934, an mGlu4 PAM small-molecule probe-compound, was ineffective at striatopallidal synapses at all concentrations tested, while it significantly inhibited corticostriatal synaptic transmission. Similarly, Lu AF21934 did not affect electrophysiology readouts at striatopallidal synapses in the presence of haloperidol or in 6-hydroxydopamine-lesioned rats. Interestingly, co-application of Lu AF21934 with a glutamate transporter inhibitor revealed a significant inhibitory action at striatopallidal synapses. Possibly, this effect could rely on increased level/permanence of glutamate in the synaptic cleft. Such differential efficacy of mGlu4 receptor PAMs at corticostriatal vs. striatopallidal synapses raises several issues regarding the synaptic target(s) of these drugs in the BG, and challenges the mechanisms by which they alleviate motor deficits in experimental PD models.