RESUMO
BACKGROUND: Kidney injury, including chronic kidney disease and acute kidney injury, is a worldwide health problem. Hypoxia and transforming growth factor-ß (TGF-ß) are well-known factors that promote kidney injury. Hypoxia-inducible factor (HIF) and SMAD3 are their main downstream transcriptional factors. Hypoxia-HIF pathway and TGF-ß/SMAD3 pathway play a crucial role in the progression of kidney injury. However, reports on their interactions are limited, and the global transcriptional regulation under their control is almost unknown. METHODS: Kidney tubular epithelial cells were cultured and stimulated by hypoxia and TGF-ß. We detected global binding sites of HIF-1α and SMAD3 in cells using chromatin immunoprecipitation-sequencing (ChIP-Seq), and measured the gene expression using RNA-sequencing (RNA-Seq). ChIP-quantitative PCR (qPCR) was used to quantitatively evaluate bindings of SMAD3. RESULTS: ChIP-Seq revealed that 2,065 and 5,003 sites were bound by HIF-1α and SMAD3, respectively, with 614 sites co-occupied by both factors. RNA-Seq showed that hypoxia and TGF-ß stimulation causes synergistic upregulation of 249 genes, including collagen type I alpha 1 (COL1A1) and serpin peptidase inhibitor, clade E, member 1, which are well-known to be involved in fibrosis. Ontology of the 249 genes implied that the interaction of HIF-1α and SMAD3 is related to biological processes such as fibrosis. ChIP-qPCR of SMAD3 at HIF-1α binding sites near COL1A1 and SERPINE1 indicated that HIF-1α promotes the bindings of SMAD3, which is induced by TGF-ß. CONCLUSIONS: These findings suggest that HIF-1α induced by hypoxia activates the TGF-ß/SMAD3 pathway. This mechanism may promote kidney injury, especially by upregulating genes related to fibrosis.
Assuntos
Hipóxia Celular , Células Epiteliais/metabolismo , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Proteína Smad3/metabolismo , Fator de Crescimento Transformador beta/farmacologia , Linhagem Celular , Colágeno Tipo I/genética , Cadeia alfa 1 do Colágeno Tipo I , Expressão Gênica/efeitos dos fármacos , Humanos , Subunidade alfa do Fator 1 Induzível por Hipóxia/genética , Túbulos Renais Proximais/citologia , Inibidor 1 de Ativador de Plasminogênio/genética , RNA Mensageiro/análise , Análise de Sequência de RNA , Transdução de Sinais/efeitos dos fármacos , Proteína Smad3/genética , Transcriptoma , Regulação para Cima/efeitos dos fármacosRESUMO
Chronic tubulointerstitial hypoxia plays an important role as the final common pathway to end-stage renal disease. HIF-1 (hypoxia-inducible factor-1) is a master transcriptional factor under hypoxia, regulating downstream target genes. Genome-wide analysis of HIF-1 binding sites using high-throughput sequencers has clarified various kinds of downstream targets and made it possible to demonstrate the novel roles of HIF-1. Our aim of this study is to identify novel HIF-1 downstream epigenetic targets which may play important roles in the kidney. Immortalized tubular cell lines (HK2; human kidney-2) and primary cultured cells (RPTEC; renal proximal tubular cell lines) were exposed to 1% hypoxia for 24-72 h. We performed RNA-seq to clarify the expression of mRNA and long non-coding RNA (lncRNA). We also examined ChIP-seq to identify HIF-1 binding sites under hypoxia. RNA-seq identified 44 lncRNAs which are up-regulated under hypoxic condition in both cells. ChIP-seq analysis demonstrated that HIF-1 also binds to the lncRNAs under hypoxia. The expression of novel lncRNA, DARS-AS1 (aspartyl-tRNA synthetase anti-sense 1), is up-regulated only under hypoxia and HIF-1 binds to its promoter region, which includes two hypoxia-responsive elements. Its expression is also up-regulated with cobalt chloride exposure, while it is not under hypoxia when HIF-1 is knocked down by siRNA To clarify the biological roles of DARS-AS1, we measured the activity of caspase 3/7 using anti-sense oligo of DARS-AS1. Knockdown of DARS-AS1 deteriorated apoptotic cell death. In conclusion, we identified the novel lncRNAs regulated by HIF-1 under hypoxia and clarified that DARS-AS1 plays an important role in inhibiting apoptotic cell death in renal tubular cells.
Assuntos
Apoptose , Células Epiteliais/metabolismo , Fator 1 Induzível por Hipóxia/metabolismo , RNA Longo não Codificante/genética , Hipóxia Celular , Linhagem Celular , Epigênese Genética , Humanos , Túbulos Renais/citologia , Ligação Proteica , RNA Longo não Codificante/metabolismo , Elementos de Resposta , Regulação para CimaRESUMO
The acute onset of idiopathic nephrotic syndrome (NS) is often accompanied by acute kidney injury, which can lead to congestive heart failure and lung edema. In this report, we present two cases of NS-induced acute kidney injury successfully treated with a low dose of carperitide, a human atrial natriuretic peptide. In combination with standard diuretic therapy and immunotherapy, carperitide retained the renal function and spared the need for renal replacement therapy, including hemodialysis. Although further investigation in clinical trials is required to validate these findings, carperitide may be useful for maintaining the renal function in cases of NS-induced acute kidney injury.