RESUMEN
Hypersynchronous neuronal excitation manifests clinically as seizure (ictogenesis), and may recur spontaneously and repetitively after a variable latency period (epileptogenesis). Despite tremendous research efforts to describe molecular pathways and signatures of epileptogenesis, molecular pathomechanisms leading to chronic epilepsy remain to be clarified. We hypothesized that epigenetic modifications may form the basis for a cellular memory of epileptogenesis, and used a primary neuronal cell culture model of the rat hippocampus to study the translation of massive neuronal excitation into persisting changes of epigenetic signatures and pro-epileptogenic target gene expression. Increased spontaneous activation of cultured neurons was detected 3 and 7 days after stimulation with 10 µM glutamate when compared to sham-treated time-matched controls using calcium-imaging in vitro. Chromatin-immunoprecipitation experiments revealed short-term (3 h, 7 h, and 24 h) and long-term (3 d and 2 weeks) changes in histone modifications, which were directly linked to decreased expression of two selected epilepsy target genes, e.g. excitatory glutamate receptor genes Gria2 and Grin2a. Increased promoter methylation observed 4 weeks after glutamate stimulation at respective genes suggested long-term repression of Gria2 and Grin2a genes. Inhibition of glutamatergic activation or blocking the propagation of action potentials in cultured neurons rescued altered gene expression and regulatory epigenetic modifications. Our data support the concept of a cellular memory of epileptogenesis and persisting epigenetic modifications of epilepsy target genes, which are able to turn normal into pro-epileptic neurons and circuits.
Asunto(s)
Epigénesis Genética , Epilepsia/genética , Expresión Génica/fisiología , Hipocampo/citología , Neuronas/fisiología , Potenciales de Acción/efectos de los fármacos , Animales , Animales Recién Nacidos , Células Cultivadas , Metilación de ADN/efectos de los fármacos , Metilación de ADN/genética , Epigénesis Genética/efectos de los fármacos , Epigénesis Genética/fisiología , Fármacos actuantes sobre Aminoácidos Excitadores/farmacología , Expresión Génica/efectos de los fármacos , Ácido Glutámico/farmacología , Proteínas Asociadas a Microtúbulos/metabolismo , Modelos Biológicos , Neuronas/efectos de los fármacos , Quinoxalinas/farmacología , Ratas , Ratas Wistar , Receptores AMPA/genética , Receptores AMPA/metabolismo , Receptores de N-Metil-D-Aspartato/genética , Receptores de N-Metil-D-Aspartato/metabolismo , Bloqueadores de los Canales de Sodio/farmacología , Tetrodotoxina/farmacología , Valina/análogos & derivados , Valina/farmacologíaRESUMEN
Several multiple regression models have been developed to predict the first-year growth response to human growth hormone (hGH) in children with growth hormone deficiency (GHD). It was the aim of this study to analyse the significance of various growth parameters for a height prediction model. Data from 148 prepubertal children with idiopathic GHD were evaluated. The prediction model was developed by means of univariate and stepwise linear regression analysis and an "all possible" regression approach using Mallow's C(p) statistics. Six out of eight selected variables had a significant influence on the first-year growth rate. The most important parameter was the difference between target height SDS and height SDS at the start of therapy (THSDS-HSDSCO), accounting for 23.95% and 25.74% of the variability. No other single variable or combination of variables was more informative than the variable THSDS-HSDSCO alone. From these data, growth velocity for the first year of hGH treatment was estimated as 1.106 (THSDS-HSDSCO) + 6.8 cm/y +/- 2.2 cm (SE), allowing a prediction for different intervals between THSDS and HSDSCO. This equation was validated in a small group of 18 GHD patients demonstrating a predicted vs. observed first-year growth rate of 9.4 +/- 1.1 vs. 9.5 +/- 2.6 cm/y. We conclude that the difference between THSDS and height SDS at the start of therapy is an important predictor of the first-year growth response in children treated with hGH for idiopathic GHD. Unlike in previous studies, additional parameters did not increase predictability.
Asunto(s)
Trastornos del Crecimiento/tratamiento farmacológico , Crecimiento/efectos de los fármacos , Hormona de Crecimiento Humana/deficiencia , Hormona de Crecimiento Humana/uso terapéutico , Factores de Edad , Peso al Nacer , Niño , Preescolar , Interpretación Estadística de Datos , Femenino , Hormona de Crecimiento Humana/farmacología , Humanos , Modelos Lineales , Masculino , Modelos Teóricos , Factores Sexuales , Factores de TiempoRESUMEN
Forty-six patients (28 boys, 18 girls) were treated with growth hormone (GH) for short stature. Twenty-eight patients had total growth hormone deficiency (GHD), 12 partial GHD and 6 patients had short stature without GHD. Brain tumours were the cause of GHD in 8 patients and multiple pituitary hormone deficiency was present in 9 children. All patients received GH with subcutaneous injections only, 6-7 times/week. Mean final height for all patients was -1.11 SDS and was similar in boys (-1.09 SDS) and girls (-1.13 SDS). Target height SDS was -0.80 SDS in 42 patients, comparing favourably with a final height SDS of -1.05. Similar results were obtained in all patient sub-groups. Height velocity during the last year of therapy was between 2.1 and 9.9 cm/year in 34 patients and below 2 cm in 12 patients. As further growth is to be expected, target height will probably be reached by most patients.
