RESUMEN
One hundred years of study have identified beta-Amyloid (A beta) as the most interesting feature of Alzheimer's disease (AD). Since the discovery of A beta as the principal component of amyloid plaques, the central challenge in AD research has been the understanding of A beta involvement in the neurodegenerative process of the disease. The ability of A beta to undergo conformational changes and subsequent aggregation has always been a limiting factor in finding out the activities of the peptide. Extensive research has been carried out to study the molecular mechanisms of amyloid self-assembly. The finding that soluble Abeta concentrations in the brain are correlated with the severity of AD, whereas fibrillar density is not /40,42/, has pointed attention toward the oligomeric forms of Abeta, which are generally considered the most toxic and, therefore, the most important species to be addressed. Despite great efforts in basic AD research, none of the currently available treatments is able to treat the devastating effects of the disease, leading to the consideration that there is more to reason than just A beta production and aggregation. Here we summarize the emerging evidence for the physiological functions of A beta, including our recent demonstration that A beta monomers are endowed with neuroprotective activity, and propose that A beta aggregation might contribute to AD pathology through a "loss-of-function" process. Finally, we discuss the current therapeutics targeting the cerebral load of A beta and possible new ones aimed at preserving the biological functions of A beta.
Asunto(s)
Enfermedad de Alzheimer/metabolismo , Péptidos beta-Amiloides/química , Péptidos beta-Amiloides/metabolismo , Enfermedad de Alzheimer/genética , Péptidos beta-Amiloides/genética , Animales , Humanos , Modelos Biológicos , Estructura Molecular , Fragmentos de Péptidos/química , Fragmentos de Péptidos/genética , Fragmentos de Péptidos/metabolismoRESUMEN
Knowing that expression of metabotropic glutamate 2 (mGlu2) receptors in the dorsal root ganglia is regulated by acetylation mechanisms, we examined the effect of two selective and chemically unrelated histone deacetylase (HDAC) inhibitors, N-(2-aminophenyl)-4-[N-(pyridine-3-ylmethoxy-carbonyl)aminomethyl]benzamide (MS-275) and suberoylanilide hydroamic acid (SAHA), in a mouse model of persistent inflammatory pain. Although a single subcutaneous injection of MS-275 (3 mg/kg) or SAHA (5-50 mg/kg) was ineffective, a 5-day treatment with either of the two HDAC inhibitors substantially reduced the nociceptive response in the second phase of the formalin test, which reflects the development of central sensitization in the dorsal horn of the spinal cord. Analgesia was abrogated by a single injection of the mGlu2/3 receptor antagonist (alphaS)-alpha-amino-alpha-[(1S,2S)-2-carboxycyclopropyl]-9H-xantine-9-propanoic acid (LY341495; 1 mg/kg, i.p.), which was inactive per se. Both MS-275 and SAHA up-regulated the expression of mGlu2 receptors in the dorsal root ganglion (DRG) and spinal cord under conditions in which they caused analgesia, without changing the expression of mGlu1a, mGlu4, or mGlu5 receptors. Induction of DRG mGlu2 receptors in response to SAHA was associated with increased acetylation of p65/RelA on lysine 310, a process that enhances the transcriptional activity of p65/RelA at nuclear factor-kappaB-regulated genes. Transcription of the mGlu2 receptor gene is known to be activated by p65/RelA in DRG neurons. We conclude that HDAC inhibition produces analgesia by up-regulating mGlu2 receptor expression in the DRG, an effect that results from the amplification of NF-kappaB transcriptional activity. These data provide the first evidence that HDAC inhibitors cause analgesia and suggest that HDACs are potential targets for the epigenetic treatment of pain.
Asunto(s)
Inhibidores Enzimáticos/farmacología , Epigénesis Genética , Inhibidores de Histona Desacetilasas , Inflamación/fisiopatología , Dolor/tratamiento farmacológico , Receptores de Glutamato Metabotrópico/genética , Aminoácidos/farmacología , Animales , Benzamidas/farmacología , Compuestos Bicíclicos Heterocíclicos con Puentes/farmacología , Inhibidores Enzimáticos/uso terapéutico , Ácidos Hidroxámicos/farmacología , Masculino , Ratones , Piridinas/farmacología , Receptores de Glutamato Metabotrópico/fisiología , Vorinostat , Xantenos/farmacologíaRESUMEN
Chronic 'pathological' pain is sustained by mechanisms of peripheral and central sensitization, which are being increasingly investigated at the molecular and cellular levels. The molecular determinants of nociceptive sensitization are natural targets for potential analgesic drugs used in the treatment of different forms of pain. Most of these determinants are common to all forms of chronic pain, and it is therefore not surprising that drugs specifically targeted for the treatment of neuropathic pain are effective in relieving nociceptive inflammatory pain and vice versa. The molecular mechanisms of sensitization that occur in peripheral nociceptors and the dorsal horns of the spinal cord are putative targets for context-dependent drugs, i.e. drugs that are able to discriminate between 'normal' and 'pathological' pain transmission. Among these, pregabalin and gabapentin bind to the alpha(2)delta subunit of voltage-sensitive Ca2+ channels, which sustain the enhanced release of pain transmitters at the synapses between primary afferent fibres and second-order sensory neurons under conditions of chronic pain. Pregabalin in particular represents a remarkable example of a context-dependent analgesic drug that acts at a critical step of nociceptive sensitization. Preclinical and clinical data suggest that pregabalin is more than a structural and functional analogue of gabapentin and may be effective in the treatment of nociceptive inflammatory pain that is resistant to gabapentin.
Asunto(s)
Analgésicos no Narcóticos/uso terapéutico , Dolor/tratamiento farmacológico , Ácido gamma-Aminobutírico/análogos & derivados , Aminas/uso terapéutico , Animales , Canales de Calcio/efectos de los fármacos , Enfermedad Crónica , Ácidos Ciclohexanocarboxílicos/uso terapéutico , Gabapentina , Guías como Asunto , Humanos , Dolor/etiología , Enfermedades del Sistema Nervioso Periférico/complicaciones , Pregabalina , Ácido gamma-Aminobutírico/uso terapéuticoRESUMEN
Alzheimer's disease (AD), the leading cause of senile dementia, has become a considerable social and economical problem. Current AD therapeutics provide mainly symptomatic short-term benefit, rather than targeting disease mechanisms. The hallmarks for AD are beta-amyloid plaques, neurofibrillary tangles, and regionalized neuronal loss. Additional neuropathological features have been described that may provide some clues to the mechanism by which neurons die in AD. Specifically, the aberrant expression of cell cycle proteins and the presence of de novo-replicated DNA in neurons have been described both in AD brain and in culture models of the disease. The unscheduled cell cycle events are deleterious to neurons, which undergo death rather than complete the cell cycle. Although our understanding of the neuronal cell cycle is not complete, experimental evidence suggests that compounds able of arresting the aberrant cell cycle will yield neuroprotection. This review focuses on drug development centered on the cell cycle hypothesis of AD.
Asunto(s)
Enfermedad de Alzheimer/tratamiento farmacológico , Enfermedad de Alzheimer/patología , Ciclo Celular/efectos de los fármacos , Degeneración Nerviosa/tratamiento farmacológico , Degeneración Nerviosa/metabolismo , Enfermedad de Alzheimer/metabolismo , Animales , Evaluación Preclínica de Medicamentos , Humanos , Modelos Neurológicos , Degeneración Nerviosa/patología , Fármacos Neuroprotectores/uso terapéuticoRESUMEN
During the past two decades, many pharmacological strategies have been investigated for the management of painful neuropathies. However, neuropathic pain still remains a clinical challenge. A combination of therapies is often required, but unfortunately in most cases adequate pain relief is not achieved. Recently, attention has been focused on the physiological and pharmacological effects of L-acetylcarnitine in neurological disorders. There are a number of reports indicating that L-acetylcarnitine can be considered as a therapeutic agent in neuropathic disorders including painful peripheral neuropathies. In this review article, we will examine the antinociceptive and the neuroprotective effects of Lacetylcarnitine as tested in clinical studies and in animal models of nerve injury.
RESUMEN
Neurospheres from adult mouse subventricular zone (SVZ) were grown in suspension cultures for 12-15 days. Neurospheres consisted mainly of neural precursor cells (NPCs) immunoreactive for nestin and also contained nestin-negative precursors. We used these neurospheres to determine the effects of synthetic beta-amyloid fragments (both betaAP(1-42) and betaAP(25-35)) on NPC proliferation, differentiation and survival. We show that neurospheres exposed to 25 microM betaAP(25-35) or betaAP(1-42) for 24 h (a toxic condition for mature neurons) did not undergo apoptosis. Instead, betaAP(25-35) orientated nestin-negative precursors towards nestin-positive NPCs and turned nestin-positive NPCs into neuroblasts. Intracerebroventricular infusion of full-length betaAP(1-42) increased the population of PSA-NCAM-positive cells in the SVZ, without affecting proliferation. We conclude that betaAP influences the fate of progenitor cells, driving their differentiation towards a neuronal lineage.
Asunto(s)
Péptidos beta-Amiloides/farmacología , Encéfalo/citología , Neuronas/efectos de los fármacos , Fragmentos de Péptidos/farmacología , Fenotipo , Células Madre , Animales , Antígenos de Superficie/metabolismo , Western Blotting/métodos , Bromodesoxiuridina/metabolismo , Antígeno CD24/metabolismo , Recuento de Células/métodos , Diferenciación Celular , Células Cultivadas , Proteína Ácida Fibrilar de la Glía/metabolismo , Inmunohistoquímica/métodos , Proteínas de Filamentos Intermediarios/metabolismo , Masculino , Ratones , Proteínas del Tejido Nervioso/metabolismo , Nestina , Molécula L1 de Adhesión de Célula Nerviosa/metabolismo , Neuronas/clasificación , Ácidos Siálicos/metabolismoRESUMEN
Wnts function through the activation of at least three intracellular signal transduction pathways, of which the canonical beta-catenin mediated pathway is the best understood. Aberrant canonical Wnt signaling has been involved in both neurodegeneration and cancer. An impairment of Wnt signals appears to be associated with aspects of neurodegenerative pathologies while overactivation of Wnt signaling is a common theme in several types of human tumors. Therefore, although therapeutic approaches aimed at modulating Wnt signaling in neurodegenerative and hyperproliferative diseases might impinge on the same molecular mechanisms, different pharmacological outcomes are required. Here we review recent developments on the understanding of the role of Wnt signaling in Alzheimer's disease and CNS tumors, and identify possible avenues for therapeutic intervention within a complex and multi-faceted signaling pathway.
Asunto(s)
Neoplasias del Sistema Nervioso Central/genética , Enfermedades Neurodegenerativas/genética , Transducción de Señal , Proteínas Wnt/metabolismo , Enfermedad de Alzheimer/metabolismo , Animales , Encéfalo/metabolismo , Neoplasias Encefálicas/metabolismo , Adhesión Celular , Movimiento Celular , Proliferación Celular , Neoplasias del Sistema Nervioso Central/metabolismo , Citoesqueleto/metabolismo , Humanos , Modelos Biológicos , Modelos Químicos , Neoplasias/metabolismo , Enfermedades Neurodegenerativas/metabolismo , Fenotipo , beta Catenina/metabolismoRESUMEN
The ability of activated glia to affect cerebral vascular tone has been evaluated using an in vitro experimental system in which basilar arteries were incubated with glial cultures activated by treatment with lipopolysaccharide (LPS). Vascular tone was measured with an isometric myograph. Contraction in response to high KCl and serotonin was reduced in arteries co-incubated for 24 h with LPS-activated glia, whereas the response to acetylcholine was not modified. The reduced contraction was prevented when the nitric oxide synthase (NOS) inhibitor L-N-nitro-arginine (L-NNA) was added throughout the whole incubation time (activation of glial cells with LPS + co-incubation of glial cells with cerebral arteries). Under these conditions, nitrite levels were drastically reduced. A reduced contraction to KCl was also observed after treatment of the cerebral vessel with sodium nitroprusside. In contrast, L-NNA added to the vessel did not modify the response to contracting stimuli and the expression of endothelial NOS was not modified in cerebral arteries pre-incubated with activated glia. These results suggest that activated glia, which finds an in vivo correlate in several neuropathological conditions, can contribute to changes of vascular tone by modifying the levels of nitric oxide (NO) to which the vessel is exposed.
Asunto(s)
Astrocitos/fisiología , Arteria Basilar/fisiología , Corteza Cerebral/irrigación sanguínea , Contracción Isométrica/fisiología , Neuroglía/fisiología , Óxido Nítrico/fisiología , Acetilcolina/farmacología , Análisis de Varianza , Animales , Animales Recién Nacidos , Astrocitos/efectos de los fármacos , Arteria Basilar/efectos de los fármacos , Western Blotting/métodos , Brefeldino A/farmacología , Células Cultivadas , Corteza Cerebral/citología , Técnicas de Cocultivo/métodos , Medio de Cultivo Libre de Suero/farmacología , Citocinas/farmacología , Relación Dosis-Respuesta a Droga , Interacciones Farmacológicas , Inhibidores Enzimáticos/farmacología , Inmunohistoquímica/métodos , Contracción Isométrica/efectos de los fármacos , Lipopolisacáridos/farmacología , Masculino , Miografía/métodos , Nitratos/metabolismo , Nitritos/metabolismo , Nitroarginina/farmacología , Cloruro de Potasio/farmacología , Ratas , Ratas Sprague-Dawley , Serotonina/farmacología , Factores de TiempoRESUMEN
The effects of the acetylcholinesterase inhibitor donepezil on cell viability and proliferation events have been analysed in SH-SY5Y human neuroblastoma cells. Short- (48 h) or long-term (7 days) exposure of SH-SY5Y cells to donepezil (100 nM-10 microM) induced a concentration-dependent inhibition of cell proliferation that was not modified by muscarinic and nicotinic receptor antagonists, or mimicked by galantamine, and was not related to induction of apoptosis. By analysing the distribution profile of cell populations within the cell cycle following treatment with 10 microM donepezil, a reduction of cells in the S-G2/M phases of the cycle and a parallel increase of the G0/G1 population were observed. In addition, the expression of two cyclins of the G1/S and G2/M transitions, cyclin E and cyclin B, was significantly reduced in donepezil-treated cells. In contrast, the expression of the cell cycle inhibitor p21 rapidly (6 h) increased following exposure to the drug. Finally, donepezil increased the expression of the neuronal marker MAP-2 in selected subpopulations of SH-SY5Y cells, suggesting that the effect on cell proliferation by donepezil may correlate to a trend to neuronal differentiation.
Asunto(s)
Inhibidores de la Colinesterasa/administración & dosificación , Sistemas de Liberación de Medicamentos/métodos , Indanos/administración & dosificación , Neuronas/efectos de los fármacos , Piperidinas/administración & dosificación , Ciclo Celular/efectos de los fármacos , Ciclo Celular/fisiología , Línea Celular Tumoral , Supervivencia Celular/efectos de los fármacos , Supervivencia Celular/fisiología , Donepezilo , Relación Dosis-Respuesta a Droga , Humanos , Neuronas/citología , Neuronas/enzimologíaRESUMEN
Glutamate is the major neurotransmitter in the mammalian central nervous system and plays a pivotal role in both acute and chronic pain. The actions of glutamate are mediated by two receptor families: ionotropic glutamate receptors (iGluRs), and metabotropic glutamate receptors (mGluRs). Activation of glutamate receptor can elicit both hyperalgesic and analgesic effects. Eight mGluRs subtypes (mGluR1-mGluR8) have been identified and classified into three groups. Among these, group I mGluRs (mGlu1 and -5) have been implicated in the processes of central sensitization and persistent nociception, whereas activation of group II mGluRs (mGlu2/3) is effective against neuropathic or inflammatory pain. In this review we focus on the role of mGlu2/3 in the modulation of persistent pain, and on their potential use as drug targets in pain management.
Asunto(s)
Dolor/tratamiento farmacológico , Enfermedades del Sistema Nervioso Periférico/tratamiento farmacológico , Receptores de Glutamato Metabotrópico/efectos de los fármacos , Acetilcarnitina/uso terapéutico , Analgésicos/uso terapéutico , Animales , Humanos , Nootrópicos/uso terapéutico , Dolor/etiología , Dolor/fisiopatología , Enfermedades del Sistema Nervioso Periférico/complicaciones , Enfermedades del Sistema Nervioso Periférico/fisiopatología , Receptores de Glutamato Metabotrópico/fisiologíaRESUMEN
17beta-Estradiol (17beta-E(2)) is known to exert neuroprotective activity against beta-amyloid, but its exact target and mechanism of action in this effect have not been elucidated. The involvement of astroglia in neuroprotection of 17beta-E(2) against the beta-amyloid fragment [betaAP((25-35))] has been evaluated using an experimental paradigm in which medium conditioned from rat astroglia pretreated with 17beta-E2 was transferred to pure rat cortical neurons challenged with 25 microm betaAP((25-35)) for 24 h. The toxicity of betaAP((25-35)) was assessed by flow cytometry, evaluating the ability of the peptide to induce an aberrant mitotic cell cycle in neurons. The results obtained indicate that conditioned medium from astrocytes preexposed to 17beta-E(2) for 4 h increased the viability of cortical neurons treated with betaAP((25-35)). This effect was not modified by treatment with the estrogen receptor antagonist ICI 182,780, added directly to neurons, nor was it mimicked by direct addition of 17beta-E(2) to neuronal cultures during exposure to betaAP((25-35)). A soluble factor stimulated by 17beta-E(2) seemed to be involved, and accordingly, the intracellular and released levels of TGF-beta1 were increased by 17beta-E(2) treatment, as established by Western blot analysis. In addition, the intracellular content of TGF-beta1 in immunopositive cells, as detected by flow cytometry, was reduced, suggesting that 17beta-E(2) stimulated mainly the release of the cytokine. In support of a role for TGF-beta1 in astrocyte-mediated 17beta-E(2) neuroprotective activity, incubation with a neutralizing anti-TGF-beta1 antibody significantly modified the reduction of neuronal death induced by 17beta-E(2)-treated astrocyte-conditioned medium.
Asunto(s)
Apoptosis/fisiología , Astrocitos/metabolismo , Estradiol/farmacología , Neuronas/citología , Fármacos Neuroprotectores/farmacología , Péptidos beta-Amiloides/farmacología , Animales , Apoptosis/efectos de los fármacos , Astrocitos/citología , Comunicación Celular/fisiología , Células Cultivadas , Medios de Cultivo Condicionados/farmacología , Fragmentos de Péptidos/farmacología , RatasRESUMEN
Recent evidence suggests a link between the aberrant re-expression of cell cycle proteins in adult neurons of the Alzheimer's disease brain and the process of apoptotic degeneration. Here we will discuss this unexpected phenomenon as related to the mechanisms of beta-amyloid toxicity, and its significance for therapeutic possibilities.
Asunto(s)
Enfermedad de Alzheimer/fisiopatología , Apoptosis/fisiología , Encéfalo/metabolismo , Proteínas de Ciclo Celular/metabolismo , Neuroquímica/tendencias , Neuronas/metabolismo , Péptidos beta-Amiloides/metabolismo , Animales , Humanos , Mitógenos/metabolismo , InvestigaciónRESUMEN
L-Acetylcarnitine (LAC, 100 mg/kg, s.c.), a drug commonly used for the treatment of painful neuropathies, substantially reduced mechanical allodynia in rats subjected to monolateral chronic constriction injury (CCI) of the sciatic nerve and also attenuated acute thermal pain in intact rats. In both cases, induction of analgesia required repeated injections of LAC, suggesting that the drug induces plastic changes within the nociceptive pathway. In both CCI- and sham-operated rats, a 24-day treatment with LAC increased the expression of metabotropic glutamate (mGlu) receptors 2 and 3 in the lumbar segment of the spinal cord, without changing the expression of mGlu1a or -5 receptors. A similar up-regulation of mGlu2/3 receptors was detected in the dorsal horns and dorsal root ganglia of intact rats treated with LAC for 5-7 days, a time sufficient for the induction of thermal analgesia. Immunohistochemical analysis showed that LAC treatment enhanced mGlu2/3 immunoreactivity in the inner part of lamina II and in laminae III and IV of the spinal cord. An increased mGlu2/3 receptor expression was also observed in the cerebral cortex but not in the hippocampus or cerebellum of LAC-treated animals. Reverse transcription-polymerase chain reaction combined with Northern blot analysis showed that repeated LAC injections selectively induced mGlu2 mRNA in the dorsal horns and cerebral cortex (but not in the hippocampus). mGlu3 mRNA levels did not change in any brain region of LAC-treated animals. To examine whether the selective up-regulation of mGlu2 receptors had any role in LAC-induced analgesia, we have used the novel compound LY 341495, which is a potent and systemically active mGlu2/3 receptor antagonist. LAC-induced analgesia was largely reduced 45 to 75 min after a single injection of LY 341495 (1 mg/kg, i.p.) in both CCI rats tested for mechanical allodynia and intact rats tested for thermal pain. We conclude that LAC produces analgesia against chronic pain produced not only by peripheral nerve injury but also by acute pain in intact animals and that LAC-induced analgesia is associated with and causally related to a selective up-regulation of mGlu2 receptors. This offers the first example of a selective induction of mGlu2 receptors and discloses a novel mechanism for drug-induced analgesia.
Asunto(s)
Acetilcarnitina/farmacología , Analgesia , Nootrópicos/farmacología , Receptores de Glutamato Metabotrópico/metabolismo , Nervio Ciático/efectos de los fármacos , Animales , Masculino , Ratas , Ratas Sprague-Dawley , Nervio Ciático/metabolismo , Nervio Ciático/patología , Temperatura , Regulación hacia ArribaRESUMEN
Metabotropic glutamate (mGlu) receptors have been considered as potential targets for neuroprotective drugs, but the lack of specific drugs has limited the development of neuroprotective strategies in experimental models of acute or chronic central nervous system (CNS) disorders. The advent of potent and centrally available subtype-selective ligands has overcome this limitation, leading to an extensive investigation of the role of mGlu receptor subtypes in neurodegeneration during the last 2 years. Examples of these drugs are the noncompetitive mGlu1 receptor antagonists, CPCCOEt and BAY-36-7620; the noncompetitive mGlu5 receptor antagonists, 2-methyl-6-(phenylethynyl)pyridine, SIB-1893, and SIB-1757; and the potent mGlu2/3 receptor agonists, LY354740 and LY379268. Pharmacologic blockade of mGlu1 or mGlu5 receptors or pharmacologic activation of mGlu2/3 or mGlu4/7/8 receptors produces neuroprotection in a variety of in vitro or in vivo models. MGlu1 receptor antagonists are promising drugs for the treatment of brain ischemia or for the prophylaxis of neuronal damage induced by synaptic hyperactivity. MGlu5 receptor antagonists may limit neuronal damage induced by a hyperactivity of N-methyl-d-aspartate (NMDA) receptors, because mGlu5 and NMDA receptors are physically and functionally connected in neuronal membranes. A series of observations suggest a potential application of mGlu5 receptor antagonists in chronic neurodegenerative disorders, such as amyotrophic lateral sclerosis and Alzheimer disease. MGlu2/3 receptor agonists inhibit glutamate release, but also promote the synthesis and release of neurotrophic factors in astrocytes. These drugs may therefore have a broad application as neuroprotective agents in a variety of CNS disorders. Finally, mGlu4/7/8 receptor agonists potently inhibit glutamate release and have a potential application in seizure disorders. The advantage of all these drugs with respect to NMDA or AMPA receptor agonists derives from the evidence that mGlu receptors do not "mediate," but rather "modulate" excitatory synaptic transmission. Therefore, it can be expected that mGlu receptor ligands are devoid of the undesirable effects resulting from the inhibition of excitatory synaptic transmission, such as sedation or an impairment of learning and memory.
Asunto(s)
Encefalopatías/tratamiento farmacológico , Fármacos Neuroprotectores/farmacología , Receptores de Glutamato Metabotrópico/agonistas , Receptores de Glutamato Metabotrópico/antagonistas & inhibidores , Animales , HumanosRESUMEN
Previous studies have identified the mammalian homologue of Bv8 (mBv8), a small protein originally isolated from skin secretions of the frog, Bombina variegata. In situ hybridization showed that mBv8 RNA was widely expressed in the rodent CNS, with high levels being detected in layer II of the cerebral cortex, limbic regions, cerebellar Purkinje cells, and dorsal and ventral horns of the spinal cord. A similar pattern of distribution was found by examining the presence of mBv8 protein by immunocytochemistry. Addition of frog Bv8 to cultured cerebellar granule cells reduced the extent of apoptotic death induced by switching the growing medium from 25 to 5 mM K+. Bv8 could also protect cultured cortical neurons against excitotoxic death. Both effects were prevented by PD98059 and LY294002, which inhibit the mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3-kinase (PI-3-K) pathways, respectively. In cultured cerebellar granule cells, Bv8 stimulated both the MAPK and the PI-3-K pathways, as revealed by Western blot analysis of phosphorylated p44/p42 MAPKs and phosphorylated Akt, respectively. We conclude that mBv8 acts as an endogenous neurotrophic factor and supports neuronal survival through the activation of the MAPK/PI-3-K pathways.
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Proteínas Anfibias , Apoptosis/fisiología , Supervivencia Celular/fisiología , Sistema Nervioso Central/metabolismo , Sistema de Señalización de MAP Quinasas/fisiología , Neuronas/metabolismo , Neuropéptidos , Fosfatidilinositol 3-Quinasas/metabolismo , Proteínas/metabolismo , Animales , Animales Recién Nacidos , Apoptosis/efectos de los fármacos , Astrocitos/citología , Astrocitos/efectos de los fármacos , Astrocitos/metabolismo , Supervivencia Celular/efectos de los fármacos , Células Cultivadas/citología , Células Cultivadas/efectos de los fármacos , Células Cultivadas/metabolismo , Sistema Nervioso Central/citología , Sistema Nervioso Central/crecimiento & desarrollo , Corteza Cerebelosa/citología , Corteza Cerebelosa/crecimiento & desarrollo , Corteza Cerebelosa/metabolismo , Corteza Cerebral/citología , Corteza Cerebral/crecimiento & desarrollo , Corteza Cerebral/metabolismo , Técnicas de Cocultivo , Relación Dosis-Respuesta a Droga , Agonistas de Aminoácidos Excitadores/farmacología , Inmunohistoquímica , Sistema de Señalización de MAP Quinasas/efectos de los fármacos , N-Metilaspartato/farmacología , Neuronas/citología , Neuronas/efectos de los fármacos , Fármacos Neuroprotectores/farmacología , Fosfatidilinositol 3-Quinasas/efectos de los fármacos , Proteínas/genética , Proteínas/farmacología , ARN Mensajero/metabolismo , RatasRESUMEN
Activation of group I metabotropic glutamate receptors (mGlu1 or -5 receptors) is known to either enhance or attenuate excitotoxic neuronal death depending on the experimental conditions. We have examined the possibility that these receptors may switch between two different functional modes in regulating excitotoxicity. In mixed cultures of cortical cells, the selective mGlu1/5 agonist, 3,5-dihydroxyphenylglycine (DHPG), amplified neurodegeneration induced by a toxic pulse of NMDA. This effect was observed when DHPG was either combined with NMDA or transiently applied to the cultures prior to the NMDA pulse. However, two consecutive applications of DHPG consistently produced neuroprotection. Similar effects were observed with DHPG or quisqualate (a potent agonist of mGlu1/5 receptors) in pure cultures of cortical neurons virtually devoid of astrocytes. In cultures of hippocampal pyramidal neurons, however, only protective effects of DHPG were seen suggesting that, in these particular cultures, group I mGlu receptors were endogenously switched into a "neuroprotective mode". The characteristics of the activity-dependent switch from facilitation to inhibition were examined in mixed cultures of cortical cells. The switch in the response to DHPG was observed when the two applications of the drug were separated by an interval ranging from 1-45 min, but was lost when the interval was extended to 90 min. In addition, this phenomenon required the initial activation of mGlu5 receptors (as indicated by the use of subtype-selective antagonists) and was mediated by the activation of protein kinase C. We conclude that group I mGlu receptors are subjected to an activity-dependent switch in regulating excitotoxic neuronal death and, therefore, the recent "history" of these receptors is critical for the response to agonists or antagonists.
Asunto(s)
Inhibición Neural/fisiología , Neurotoxinas/metabolismo , Receptores de Glutamato Metabotrópico/fisiología , Animales , Células Cultivadas , Corteza Cerebral/citología , Corteza Cerebral/efectos de los fármacos , Corteza Cerebral/fisiología , Activación Enzimática/fisiología , Agonistas de Aminoácidos Excitadores/envenenamiento , Antagonistas de Aminoácidos Excitadores/farmacología , Glicina/análogos & derivados , Glicina/farmacología , Ratones , N-Metilaspartato/envenenamiento , Degeneración Nerviosa/inducido químicamente , Degeneración Nerviosa/patología , Fármacos Neuroprotectores/farmacología , Proteína Quinasa C/metabolismo , Ácido Quiscuálico/farmacología , Receptor del Glutamato Metabotropico 5 , Resorcinoles/farmacología , Factores de TiempoRESUMEN
Cell-cycle-related proteins, such as cyclins or cyclin-dependent kinases, are re-expressed in neurons committed to death in response to a variety of insults, including excitotoxins, hypoxia and ischemia, loss of trophic support, or beta-amyloid peptide. In some of these conditions events that are typical of the mid-G1 phase, such as cyclin-dependent kinase 4/6 activation, are required for the induction of neuronal death. In other cases, the cycle must proceed further and recruit steps that are typical of the G1/S transition for death to occur. Finally, there are conditions in which cell-cycle proteins might be re-expressed, but do not contribute to neuronal death. We hypothesize that cell-cycle signaling becomes a mandatory component of neuronal demise when other mechanisms are not enough for neurons to reach the threshold for death. Under this scheme, the death threshold is set by the extent of DNA damage. Whenever the extent of DNA damage is below this threshold, a cell-cycle signaling becomes crucial for the induction of neuronal death through p53-dependent or -independent pathways.
Asunto(s)
Péptidos beta-Amiloides/metabolismo , Apoptosis/fisiología , Proteínas de Ciclo Celular/metabolismo , Daño del ADN/fisiología , Neuronas/metabolismo , Proteína p53 Supresora de Tumor/metabolismo , Péptidos beta-Amiloides/farmacología , Animales , Apoptosis/efectos de los fármacos , Proteínas de Ciclo Celular/efectos de los fármacos , Muerte Celular/efectos de los fármacos , Muerte Celular/fisiología , Daño del ADN/efectos de los fármacos , Humanos , Degeneración Nerviosa/metabolismo , Neuronas/efectos de los fármacos , Neurotoxinas/farmacología , Oligonucleótidos Antisentido/farmacología , Proteína p53 Supresora de Tumor/farmacologíaRESUMEN
We have examined the effect of various chemokines on neuronal toxicity in culture. In mixed cortical cultures, challenged with a brief pulse of N-methyl-D-aspartate (NMDA, 60 microM, 10 min), chemokines were either present for 2 h preceding the pulse or they were co-applied with NMDA and then kept in the medium for the following 20-24 h. Interleukin-8 (IL-8), regulated on activation of normal T cells expressed and secreted (RANTES) and macrophage/monocyte chemoattractant protein-1 (MCP-1), were neuroprotective under both conditions, whereas stromal cell-derived factor 1alpha (SDF-1alpha) was protective only when applied during and after the NMDA pulse. Mixed or pure neuronal cultures were also exposed for 48 h to a toxic fragment of the beta-amyloid peptide (beta-amyloid peptide-(25-35), 12.5 or 25 microM) in the absence or presence of chemokines. Among a number of chemokines, only RANTES was neuroprotective against beta-amyloid peptide-(25-35)-induced neurotoxicity in both cultures. We conclude that activation of chemokine receptors differentially affects neuronal degeneration induced by excitotoxins or beta-amyloid peptide in cortical cultures.
Asunto(s)
Péptidos beta-Amiloides/toxicidad , Quimiocinas/farmacología , N-Metilaspartato/toxicidad , Fármacos Neuroprotectores/farmacología , Animales , Astrocitos/citología , Astrocitos/efectos de los fármacos , Células Cultivadas , Quimiocina CCL5/farmacología , Relación Dosis-Respuesta a Droga , Feto , Interleucina-8/farmacología , Ratones , Neuronas/citología , Neuronas/efectos de los fármacosRESUMEN
We have examined the influence of reducing conditions on the activity of group-I or -II metabotropic glutamate receptors. In cultured cerebellar granule cells or in hippocampal slices, the reducing agent dithiothreitol (DTT) inhibited the stimulation of polyphosphoinositide (PPI) hydrolysis elicited by group-I mGlu receptor agonists without affecting responses to norepinephrine or carbamylcholine. Similarly, DTT reduced the increase in intracellular free Ca(2+) induced by glutamate in HEK-293 cells expressing mGlu5 receptors. In adult hippocampal slices, the selective group-II mGlu receptor agonist, (2S,1'R,2'R,3'R)-2-(2, 3-dicarboxycyclopropyl)glycine (DCG-IV) had no effect per se on PPI hydrolysis, but potentiated the response to quisqualate. Although DTT substantially attenuated the action of quisqualate, it did not affect the potentiation by DCG-IV, suggesting that group-II mGlu receptors are resistant to extracellular reduction. Accordingly, DTT did not affect the inhibition of forskolin-stimulated cAMP formation induced by maximally effective concentrations of group-II mGlu receptor agonists in hippocampal slices or in CHO cells expressing mGlu2 receptors. At structural level, DTT differentially affected the aggregation state of mGlu1a, -2/3 or -5 receptors. In immunoblots performed under non-reducing conditions, mGlu1a, -2/3 or -5 antibodies labeled exclusively a high-molecular weight band, corresponding to receptor dimers. Under reducing conditions, mGlu1a or -5 receptors were detected as monomers, whereas a large proportion of mGlu2/3 receptors was still present in a dimeric form. We conclude that reducing conditions differentially influence the aggregation state of group-I and -II mGlu receptors and suggest that dimerization affects the functional activity of native mGlu receptors.