RESUMEN
BACKGROUND: Serum deoxyribonuclease I (DNase I) activity was reported to increase in the early phase after onset of acute myocardial infarction (AMI). Up to now, DNase I activity has been quantified by the single radial enzyme diffusion (SRED) method, which unfortunately requires a long incubation time. Therefore it is necessary to develop another assay suitable for measurement of serum DNase I concentrations in a clinical setting. METHODS: A sandwich ELISA was established for measurement of DNase I protein using a polyclonal antibody directed against DNase I protein and a biotinylated monoclonal for subsequent detection. Concentrations of serum DNase I protein were measured in healthy individuals and patients with AMI. RESULTS: This method was as precise as SRED, and took less time than SRED. A significant correlation was observed between DNase I concentration and enzyme activity (r=0.839; P<0.001). The average of serum DNase I in AMI patients within 0-12 h of chest pain was significantly higher than that in healthy individuals (P<0.001), and decreased with time. CONCLUSIONS: We have developed a sensitive ELISA capable of measuring DNase I protein concentrations. This method may be a useful alternative to SRED as an aid to diagnosis of AMI based on the serum DNase I level.
Asunto(s)
Desoxirribonucleasa I/sangre , Ensayo de Inmunoadsorción Enzimática/métodos , Adulto , Anticuerpos/inmunología , Especificidad de Anticuerpos , Desoxirribonucleasa I/inmunología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Infarto del Miocardio/sangre , Infarto del Miocardio/enzimología , Sensibilidad y Especificidad , Factores de TiempoRESUMEN
We have previously demonstrated that ischemia caused by acute myocardial infarction induces an abrupt increase of serum deoxyribonuclease I (DNase I) activity. In this study, we examined whether hypoxia can affect the levels of DNase I activity and/or its transcripts in vitro. We first exposed the human pancreatic cancer cell line QGP-1, which is the first documented DNase-I-producing cell line, to hypoxia (2% O2), and found that this induced a significant increase in both the activity and transcripts of DNase I. This response was mediated by increased transcription only from exon 1a of the two alternative transcription-initiating exons utilized simultaneously in the human DNase I gene (DNASE1); exposure of QGP-1 cells to hypoxia for 24 h resulted in a 15-fold increase of DNASE1 transcripts starting from exon 1a compared with the expression level under normoxic conditions. Promoter, electrophoretic mobility shift, and chromatin immunoprecipitation assays with QGP-1 cells exposed to hypoxia or normoxia showed that the region just upstream from exon 1a was involved in this response in a hypoxia-induced factor-1-independent, but at least in a Sp1 transcription factor-dependent manner possibly through enhanced binding of Sp1 protein to the promoter. These results indicate that DNASE1 expression is upregulated by hypoxia in the cells.
Asunto(s)
Desoxirribonucleasa I/biosíntesis , Desoxirribonucleasa I/genética , Regulación Enzimológica de la Expresión Génica , Regulación Neoplásica de la Expresión Génica , Hipoxia/genética , Neoplasias Pancreáticas/genética , Regulación hacia Arriba/genética , Línea Celular Tumoral , Humanos , Hipoxia/enzimología , Hipoxia/metabolismo , Neoplasias Pancreáticas/enzimología , Neoplasias Pancreáticas/metabolismo , Regiones Promotoras Genéticas , Factor de Transcripción Sp1/fisiologíaRESUMEN
Levels of deoxyribonuclease I (DNase I) activity in vivo have been shown to be altered by physiological and/or pathological processes. However, no information is available on the regulation of DNase I gene (DNASE1) expression in vivo or in vitro. We first mapped the transcription start sites of DNASE1 in human pancreas and in the DNase I-producing human pancreatic cancer cell line QGP-1, and revealed a novel site approximately 12 kb upstream of exon 1, which was previously believed to be the single transcription-starting exon. This initiation site marks an alternative starting exon, designated 1a. Exons 1 and 1a were used simultaneously as transcription-starting exons in pancreas and QGP-1 cells. Promoter assay, EMSA and chromatin immunoprecipitation analysis with QGP-1 cells showed the promoter region of exon 1a in which the Sp1 transcription factor is specifically involved in promoter activity. This is the first to be identified as a transcription factor responsible for gene expression of vertebrate DNase I genes. Furthermore, RT-PCR analysis indicated alternative splicing of human DNASE1 pre-mRNA in pancreas and QGP-1 cells. Only two transcripts among eight alternative splicing products identified can be translated to produce intact DNase I protein. These results suggest that human DNASE1 expression is regulated through the use of alternative promoter and alternative splicing.