The role of HIF-1 alpha in transcriptional regulation of the proximal tubular epithelial cell response to hypoxia.
Epithelial cells of the kidney represent a primary target for hypoxic injury in ischemic acute renal failure (ARF); however, the underlying transcriptional mechanism(s) remain undefined. In this study, human proximal tubular epithelial cells (HK-2) exposed to hypoxia in vitro demonstrated a non-lethal but dysfunctional phenotype, closely reflective of the epithelial pathobiology of ARF. HK-2 cells exposed to hypoxia demonstrated increased paracellular permeability, decreased proliferation, loss of tight junctional integrity, and significant actin disassembly in the absence of cell death. Microarray analysis of transcriptomic changes underlying this response identified a distinct cohort of 48 genes with a closely shared hypoxia-dependent expression profile. Within this hypoxia-sensitive cluster were genes identified previously as hypoxia-inducible factor-1 (HIF-1)-dependent (e.g. vascular endothelial growth factor and adrenomedullin) as well as genes not previously known to be hypoxia-responsive (e.g. stanniocalcin 2). In hypoxia, HIF-1 bound to evolutionarily conserved hypoxia-response elements (HRE) in the promoters of these genes as well as to the HRE consensus motif. A further subset of these genes, not associated with transcriptional regulation by HIF-1, was also present, suggesting alternative HIF-1-independent pathways. Overexpression of HIF-1 alpha in normoxia induced the expression of a significant number of the hypoxia-dependent genes; however, it did not induce the pathophysiologic epithelial response. In summary, hypoxia-elicited alterations in renal proximal tubular epithelial cells in vitro closely resemble the epithelial pathophysiology of ARF. Our data indicate that although this event may rely heavily on HIF-1-dependent gene transcription, it is likely that separate hypoxia-dependent transcriptional regulators also play a role.
Leonard
Martin O
MO
Conway Institute of Biomolecular and Biomedical Research and the Dublin Molecular Medicine Centre, University College Dublin, Belfield, Dublin 4, Ireland.
Cottell
David C
DC
Godson
Catherine
C
Brady
Hugh R
HR
Taylor
Cormac T
CT
D058186:Acute Kidney Injury / Q000235:genetics / Q000503:physiopathology; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002455:Cell Division; D015687:Cell Hypoxia / Q000235:genetics* / Q000502:physiology*; D002460:Cell Line; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D005809:Genes, Regulator; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000502:physiology*; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*
D018076:DNA, Complementary; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D014157:Transcription Factors