RESUMEN
The letters, numbers, and objects subtests of the Rapid Automatized Naming Tests (RAN) were given to 50 first- and second-grade students. Student performance on the three RAN subtests were audiotaped and subjected to postacquisition processing to distinguish articulation and interarticulation pause times. This study investigated (1) the relations between the articulation and pause durations associated with the 50 stimuli of each RAN subtest and (2) the relations between the pause and articulation latencies of the three RAN subtests and reading. For both first- and second-grade students, pause and articulation times for RAN letters and objects were not found to be reliably related, in contrast to RAN numbers articulation and pause durations. RAN subtest pause durations were differentially related to reading; however, articulation was rarely related to reading. The RAN letters pause time was the most robust predictor of decoding and reading comprehension, consistently predicting all first- and second-grade measures. Analysis supported the view that reading is predicted by speed of processing associated with letters, not general processing speed.
Asunto(s)
Automatismo , Cognición , Pruebas Psicológicas , Lectura , Vocabulario , Adolescente , Femenino , Humanos , MasculinoRESUMEN
Amyloid precursor protein (APP) is cleaved to neurotoxic/proinflammatory amyloid beta protein (Abeta) or to the neuroprotective secreted alpha-APPs. A balance in APP metabolism may influence the outcome between toxicity and protection to central nervous system (CNS) neurons in Alzheimer's disease. Treatment of U-373 MG astrocytoma cells with aggregated Abeta (1-40) decreases APP secretion into the medium to 10-30% of control values. This decreased secretion appears to be specific for APP since Abeta treatment causes an approximately 2-fold increase in interleukin-8 (IL-8) secretion. Abeta treatment also causes a 4- to 9-fold increase in total cell-associated APP. This increase is due to cellular retention of alpha secretase-cleaved APP and a 2-fold increase in mature full-length APP. These data suggest that deposition of aggregated Abeta may contribute to Alzheimer's-associated neurotoxicity by altering the metabolism of the APP protein. Abeta may exert harmful effects by decreasing the secretion of neuroprotective or neurotrophic APP and, in addition, by increasing intracellular full-length APP; thereby providing increased substrate for generation of amyloidogenic peptide within astrocytes.
Asunto(s)
Péptidos beta-Amiloides/farmacocinética , Precursor de Proteína beta-Amiloide/metabolismo , Astrocitoma , Fragmentos de Péptidos/farmacocinética , Péptidos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/genética , Astrocitos/citología , Astrocitos/efectos de los fármacos , Astrocitos/metabolismo , Relación Dosis-Respuesta a Droga , Expresión Génica , Humanos , Fragmentos de Péptidos/metabolismo , ARN Mensajero/análisis , Células Tumorales Cultivadas/efectos de los fármacos , Células Tumorales Cultivadas/metabolismoRESUMEN
Chronic neurodegeneration in the brains of Alzheimer's disease (AD) patients may be mediated, at least in part, by the ability of amyloid beta (Abeta) to exacerbate inflammatory pathways in a conformation-dependent manner. In this regard, we previously reported that the Abeta-peptide-mediated potentiation of inflammatory cytokine secretion from interleukin-1beta (IL-1beta)-stimulated human astrocytoma cells was conformation dependent. Other amyloidogenic peptides, such as human amylin, which display similar conformation-dependent neurotoxic effects, may also elicit inflammatory cytokine secretion from glial cells. To test this hypothesis, we compared human and rat amylin for the effects on cytokine production in U-373 MG human astrocytoma cells. Human amylin alone stimulated U-373 MG cells to secrete IL-6 and IL-8 in a concentration-dependent manner with maximum effects seen at 10-25 microM peptide. In addition, human amylin markedly potentiated IL-1beta-stimulated cytokine production with a similar concentration dependence. In contrast, nonamyloidogenic rat amylin modestly stimulated cytokine secretion, either alone or combined with IL-1beta. Aging human amylin resulted in diminished cytokine secretion, probably due to the formation of large, less active aggregates. In agreement with our previous studies using Abeta, extracellular Ca(2+) was necessary for human amylin stimulation of cytokine secretion. Our data suggest that amyloidogenic peptides promote cytokine secretion through similar beta-sheeted secondary-structure- and extracellular-Ca(2+)-dependent mechanisms.
Asunto(s)
Enfermedad de Alzheimer/metabolismo , Amiloide/farmacología , Astrocitoma/metabolismo , Neoplasias Encefálicas/metabolismo , Citocinas/metabolismo , Proteínas de Neoplasias/metabolismo , Envejecimiento/metabolismo , Amiloide/química , Péptidos beta-Amiloides/química , Animales , Astrocitoma/patología , Neoplasias Encefálicas/patología , Calcio/farmacología , Relación Dosis-Respuesta a Droga , Sinergismo Farmacológico , Ácido Egtácico/farmacología , Humanos , Interleucina-1/farmacología , Polipéptido Amiloide de los Islotes Pancreáticos , Degeneración Nerviosa , Estructura Secundaria de Proteína , Ratas , Proteínas Recombinantes/farmacología , Homología de Secuencia de Aminoácido , Especificidad de la Especie , Células Tumorales Cultivadas/efectos de los fármacosRESUMEN
Neurodegenerative processes in Alzheimer's disease (AD) are thought to be driven, in part, by the deposition of amyloid beta (A beta), a 39-43-aminoacid peptide product resulting from an alternative cleavage of amyloid precursor protein (APP). In addition to its neurotoxic properties, A beta may influence neuropathology by stimulating glial cell cytokine and acute phase protein secretion in affected areas of the brain (e.g., cortex, hippocampus). Using an in vitro human astrocyte model (U-373 MG astrocytoma cells), the effects of A beta treatment on acute phase protein (APP and alpha-1-antichymotrypsin [alpha 1-ACT]) and interleukin-8 (IL-8) were examined. U-373 MG cells secreted increased levels of alpha 1-ACT and neurotrophic/neuroprotective alpha-cleaved APP (alpha APP) after exposure to interleukin-1 beta (IL-1 beta) for 24 hours. A beta treatment resulted in a similar, but modest increase in alpha 1-ACT secretion, a two- to threefold stimulation of IL-8 production, and, conversely, a profound reduction in the levels of secreted alpha APPs. A beta inhibited alpha APP secretion by U-373 MG cells in a concentration- and conformation-dependent manner. Moreover, the reduction in alpha APP secretion was accompanied by an increase in cell-associated APP. Another proinflammatory amyloidogenic peptide, human amylin, similarly affected APP processing in U-373 astrocytoma cells. These data suggest that A beta may contribute to Alzheimer's-associated neuropathology by lowering the production of neuroprotective/neurotrophic alpha APPs. Moreover, the concomitant increase in cell-associated APP may provide increased substrate for the generation of amyloidogenic peptides within astrocytes.
Asunto(s)
Enfermedad de Alzheimer/inmunología , Péptidos beta-Amiloides/inmunología , Precursor de Proteína beta-Amiloide/inmunología , Citocinas/inmunología , Enfermedad de Alzheimer/metabolismo , Línea Celular , Citocinas/metabolismo , Humanos , Inflamación , Procesamiento Proteico-Postraduccional/inmunologíaRESUMEN
Axotomy of superior cervical (sympathetic) ganglia (SCG) results in increased neuropeptide gene expression. In vitro, neuropeptide gene expression is similarly increased by exposure to the inflammatory cytokine interleukin-1 (IL-1). The effect of IL-1 in-vitro has been shown to be mediated by leukemia inhibitory factor (LIF). Since IL-1 regulates neuropeptide expression via LIF in vitro, we asked whether axotomy in vivo produces an increase in LIF mRNA, and whether that increase is regulated by IL-1 activity. Within 6 h following axotomy, ganglionic LIF mRNA is substantially elevated. Moreover, axotomy produces a rapid and transient increase in intraganglionic IL-1 beta mRNA, followed rapidly by an increase in ICAM-1 mRNA, thereby suggesting a local source of IL-1 activity. Pretreatment with the anti-inflammatory agent dexamethasone (DEX) reduces the increases of both IL-1 beta and LIF mRNAs following axotomy. mRNA encoding the specific signal-transducing Type I IL-1 receptor is present in unlesioned SCG in vivo, and increases following axotomy. Local application of IL-1 beta in vivo induces LIF mRNA even in uninjured ganglia, though not to the extent seen with axotomy. DEX treatment blocks this IL-1 beta-mediated increase in LIF mRNA. Therefore, DEX blocks the induction of LIF mRNA by inhibiting both the production of IL-1 and its action on LIF gene expression. Axotomy of a homozygous IL-1 receptor type I gene knockout mouse leads to a delayed and/or diminished induction of LIF mRNA in SCG, but does not prevent LIF mRNA expression. We conclude that while IL-1 is likely to be involved in the cascade of gene expression that follows axotomy, it alone is not sufficient to mediate the full induction of LIF mRNA by axotomy.
Asunto(s)
Ganglios Simpáticos/metabolismo , Inhibidores de Crecimiento/genética , Interleucina-1/fisiología , Interleucina-6 , Linfocinas/genética , Animales , Secuencia de Bases , Desnervación , Dexametasona/farmacología , Ganglios Simpáticos/patología , Regulación de la Expresión Génica , Inflamación/fisiopatología , Factor Inhibidor de Leucemia , Ratones , Ratones Noqueados , Datos de Secuencia Molecular , Plasticidad Neuronal , ARN Mensajero/genética , Ratas , Ratas Sprague-DawleyRESUMEN
Interleukin-1 beta (IL-1 beta) induces leukemia inhibitor factor (LIF) expression in a number of cell types including non-neuronal cells of the sympathetic superior cervical ganglion (SCG). Upregulation of LIF by inflammatory cytokines is usually associated with injury response. We characterized the molecular mechanism of LIF mRNA regulation by IL-1 beta in explanted neonatal rat SCG and a Schwann cell line. IL-1 beta increases LIF mRNA levels by interacting with IL-1 receptors in SCG, since this induction could be diminished by inclusion of either soluble IL-1 receptors or IL-1 receptor antagonist. The antiinflammatory glucocorticoid dexamethasone also inhibits LIF mRNA induction by IL-1 beta. LIF mRNA encodes a 3' AU-rich mRNA stability control sequence, but IL-1 beta does not appear to regulate the decay of LIF mRNA by this mechanism. IL-1 beta does not raise LIF gene transcription rate in cultured SCG 6 or 24 h after addition of IL-1 beta as measured by nuclear run-on assays. LIF gene transcription is induced repidly and transiently in an immortalized Schwann cell line, returning to uninduced rates by 1 h after induction. These results suggest that the IL-1 beta induction of LIF gene expression is at least partially transcriptional, but that LIF mRNA increases to a greater extent than LIF transcription, suggesting the possibility of posttranscriptional regulation as well.
Asunto(s)
Inhibidores de Crecimiento/biosíntesis , Interleucina-1/farmacología , Interleucina-6 , Linfocinas/biosíntesis , ARN Mensajero/biosíntesis , Transcripción Genética/efectos de los fármacos , Animales , Antiinflamatorios/farmacología , Sondas de ADN , Dexametasona/farmacología , Regulación de la Expresión Génica/efectos de los fármacos , Genoma , Inhibidores de Crecimiento/genética , Factor Inhibidor de Leucemia , Linfocinas/genética , Reacción en Cadena de la Polimerasa , Procesamiento Proteico-Postraduccional/fisiología , ARN Mensajero/genética , Ratas , Células de Schwann/metabolismo , Estimulación Química , Ganglio Cervical Superior/citología , Ganglio Cervical Superior/efectos de los fármacos , Ganglio Cervical Superior/metabolismo , Regulación hacia Arriba/efectos de los fármacosRESUMEN
Axotomy of sympathetic superior cervical ganglia (SCG) causes Schwann cells to induce mRNA encoding leukemia inhibitory factor (LIF), a neuropoietic cytokine that has been shown to promote sympathetic neuron survival and peptide gene regulation. LIF mRNA is virtually undetectable in uninjured SCG, but is induced by the inflammatory cytokine interleukin-1 (IL-1). The SC1 Schwann cell line was used to study this regulatory mechanism. LIF mRNA increased five-to-tenfold in SC1 cells when IL-1 receptors were stimulated with IL-1. The action of IL-1 is thought to be mediated by the type I IL-1 receptor (IL-1RI), which has been suggested to stimulate a ceramide-dependent protein kinase pathway, much like tumor necrosis factor-alpha. However, stimulation of the ceramide-dependent protein kinase pathways in SC1 cells with either 2-acetylceramide or sphingomyelinase treatment does not induce LIF mRNA accumulation, but 2-acetylceramide addition induces cyclooxygenase-2 mRNA in parallel experiments. Inhibition of phosphotidylcholine-phospholipase C activity, endosomal acidification, or activity of atypical protein kinase C reduce LIF induction by IL-1. These results are consistent with IL-1 regulation of LIF mRNA through stimulation of the endosomal, acidic sphingomyelinase pathway, leading to ceramide activation of protein kinase C zeta. Utilization of this branch of the ceramide signaling pathway may be cell type specific or may be specific for the LIF mRNA response.
Asunto(s)
Inhibidores de Crecimiento/biosíntesis , Interleucina-1/farmacología , Interleucina-6 , Isoenzimas/metabolismo , Linfocinas/biosíntesis , Proteína Quinasa C/metabolismo , ARN Mensajero/biosíntesis , Células de Schwann/metabolismo , Esfingomielina Fosfodiesterasa/metabolismo , Animales , Línea Celular , Endosomas/efectos de los fármacos , Endosomas/enzimología , Activación Enzimática/efectos de los fármacos , Factor Inhibidor de Leucemia , Sondas de Oligonucleótidos , Reacción en Cadena de la Polimerasa , Ratas , Células de Schwann/efectos de los fármacos , Células de Schwann/enzimologíaRESUMEN
Cell aggregation is one of several environmental cues that influence the expression of neurotransmitter phenotype during development. The expression of the catecholaminergic phenotype is increased in rat pheochromocytoma cells cultured at high density. In the present study we have investigated whether this cell density-mediated effect on the catecholaminergic phenotype is due to the stimulation of the tyrosine hydroxylase gene. When rat pheochromocytoma PC18 cells are cultured at high density (2 x 10(5) cells/cm2), tyrosine hydroxylase enzymatic activity and tyrosine hydroxylase protein increase two- to threefold over that observed in cells cultured at low density (1 x 10(4) cells/cm2). This increase in tyrosine hydroxylase protein observed in high-density cultures is fully accounted for by a preceding increase in tyrosine hydroxylase mRNA levels. The relative transcription rate of the tyrosine hydroxylase gene, measured using a nuclear run on assay, is two- to threefold greater in PC18 cells cultured at high density than in cells cultured at low density. Using flow cytometry, we have determined that in high-density cultures, there are approximately twice as many cells in the G0-G1 phases of the cell cycle compared with the number of G0-G1 cells observed in low-density cultures. However, when G0-G1 cells are isolated by cellular elutriation, tyrosine hydroxylase gene transcription rate remains two- to threefold greater in G0-G1 cells from high-density cultures than in G0-G1 cells from low-density cultures. These results indicate that increased cell-cell contact stimulates the transcription rate of the tyrosine hydroxylase gene, resulting in the subsequent increased expression of tyrosine hydroxylase mRNA and protein.
Asunto(s)
Comunicación Celular/fisiología , Feocromocitoma , Transcripción Genética/fisiología , Tirosina 3-Monooxigenasa/genética , Animales , Recuento de Células , Ciclo Celular , AMP Cíclico/análogos & derivados , AMP Cíclico/farmacología , Técnicas Citológicas , Dexametasona/farmacología , ARN Mensajero/metabolismo , Ratas , Tionucleótidos/farmacología , Factores de Tiempo , Células Tumorales CultivadasRESUMEN
The immune cytokine interleukin-1 (IL-1) causes a pronounced elevation in substance P (SP) immunoreactivity and the mRNA coding for its preprotachykinin precursor in cultured superior cervical (sympathetic) ganglia (SCG; Jonakait and Schotland, 1990; Freidin and Kessler, 1991; Hart et al., 1991). In this study we have investigated the possibility that the SCG can respond to other immune stimulators, notably lipopolysaccharide (LPS), a product of bacterial cell walls. LPS treatment of cultured SCG resulted in a dose-dependent increase in SP. However, LPS did not induce SP in the absence of non-neuronal cells, suggesting the necessity of a non-neuronal cell-derived intermediate. Since the LPS induction of SP was partially blocked by a specific IL-1 receptor antagonist (IL-1ra) and since LPS induced approximately an 8-fold increase in mRNA coding for IL-1 itself, we concluded that IL-1 is at least one of these LPS-induced intermediates. TNF-alpha, which also raises SP levels, may be another. IL-6, which may also be increased by LPS, does not increase levels of SP. The synthetic glucocorticoid hormone dexamethasone (DEX) blocks the LPS induction of SP with a Ki approximating 8 x 10(-11) M. The inhibition is due in part to the blockade of the LPS induction of ganglionic IL-1 mRNA. Moreover, inhibition of the LPS induction of SP by indomethacin implies mediation of the effect through prostaglandins. The inhibition by indomethacin suggests a non-monocytic cell source since prostaglandins are thought to restrict the LPS induction of monocytic IL-1.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Interleucina-1/biosíntesis , Lipopolisacáridos/farmacología , Sustancia P/biosíntesis , Ganglio Cervical Superior/metabolismo , Animales , Células Cultivadas , Dexametasona/farmacología , Interleucina-1/genética , Interleucina-4/biosíntesis , ARN Mensajero/análisis , Ratas , Ratas Sprague-DawleyRESUMEN
It has become increasingly clear that immune cytokines perform growth and differentiation functions in the nervous system similar to those performed in the immune system. In previous studies we have shown that interleukin-1 beta (IL-1 beta) raises substance P (SP) and the mRNA coding for its preprotachykinin precursor in cultured sympathetic superior cervical ganglia (SCG) (Jonakait and Schotland, 1990; Hart et al., 1991a). The action of IL-1 is blocked both by depolarization of the ganglia and by glucocorticoid hormones (Hart et al., 1991a). In the present report, we have found that IL-1 does not act directly upon neurons to raise SP, but rather induces the production of a soluble intermediate molecule that raises both SP and the cholinergic-specific enzyme ChAT. Its induction by IL-1 is blocked by the synthetic glucocorticoid hormone dexamethasone; its action is compromised under depolarizing conditions. Because medium conditioned by IL-1 (IL-1CM) is functionally similar to leukemia inhibitory factor (LIF), we sought to determine whether this molecule might be an active constituent of IL-1CM. Immunoprecipitation with an antiserum directed against LIF eliminated large proportions of SP-inducing activity from IL-1CM. In addition, steady-state levels of mRNA coding for LIF are increased by IL-1 treatment of SCG. These data suggest that LIF, induced by IL-1, may ultimately be responsible for the IL-1 induction of SP.
Asunto(s)
Ganglios Simpáticos/metabolismo , Inhibidores de Crecimiento/metabolismo , Interleucina-1/farmacología , Interleucina-6 , Linfocinas/metabolismo , Sustancia P/metabolismo , Animales , Animales Recién Nacidos , Secuencia de Bases , Colina O-Acetiltransferasa/metabolismo , Medios de Cultivo Condicionados , Dexametasona/farmacología , Ganglios Simpáticos/citología , Inhibidores de Crecimiento/genética , Factor Inhibidor de Leucemia , Linfocinas/genética , Sondas Moleculares/genética , Datos de Secuencia Molecular , Neuronas/metabolismo , Reacción en Cadena de la Polimerasa , Pruebas de Precipitina , ARN Mensajero/metabolismo , Ratas , Veratrina/farmacologíaRESUMEN
The administration of nicotine stimulates the transcription rate of the tyrosine hydroxylase gene in rat adrenal medulla. This stimulation occurs very rapidly (within 10 min) after the subcutaneous injection of nicotine and persists for at least 1 hr after a single injection of the drug. Repeated injections of the drug (seven injections once every 30 min) are associated with a more persistent activation of the gene (for at least 3 hr) and elicit the induction of tyrosine hydroxylase mRNA and tyrosine hydroxylase protein. Quantitatively, the increases in tyrosine hydroxylase gene transcription rate, mRNA, and protein are approximately equivalent. The effect of nicotine is dose dependent; a significant increase in tyrosine hydroxylase gene transcription rate is observed using 1.0 mg/kg nicotine, whereas 0.33 mg/kg nicotine produces no effect. The nicotinic receptor antagonists hexamethonium and mecamylamine partially inhibit the nicotine-mediated stimulation of the tyrosine hydroxylase gene. The lack of total blockade of the nicotine-mediated effect suggests that nicotine acting centrally may elicit the release of substances from the splanchnic nerve, that interact with receptors (other than the nicotinic receptor) that play a role in regulating the tyrosine hydroxylase gene. The administration of carbachol also stimulates rat adrenomedullary tyrosine hydroxylase gene transcription rate. The effect of carbachol is not inhibited by hexamethonium but is completely blocked by the muscarinic antagonist atropine. The muscarinic agonist bethanechol also stimulates this gene in rat adrenal medulla. Our results suggest that multiple receptors and signal transduction pathways are involved in the regulation of the tyrosine hydroxylase gene in the rat adrenal medulla.