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Functional activation of heat shock factor and hypoxia-inducible factor in the kidney. J Am Soc Nephrol 2002 Aug;13(8):2094-101

Date

07/26/2002

Pubmed ID

12138141

DOI

10.1097/01.asn.0000022008.30175.5b

Scopus ID

2-s2.0-0036070078   55 Citations

Abstract

Renal ischemia is the result of a complex series of events, including decreases in oxygen supply (hypoxia) and the availability of cellular energy (ATP depletion). In this study, the functional activation of two stress-responsive transcription factors, i.e., heat shock factor-1 (HSF-1) and hypoxia-inducible factor-1 (HIF-1), in the kidney was assessed. When rats were subjected to 45 min of renal ischemia, electrophoretic mobility shift assays of kidney nuclear extracts revealed rapid activation of both HIF-1 and HSF. Western blot analyses further demonstrated that this activation resulted in increased expression of the HSF and HIF-1 target genes heat shock protein-72 and heme oxygenase-1, respectively. Whether hypoxia or ATP depletion alone could produce similar activation patterns in vitro was then investigated. Renal epithelial LLC-PK(1) cells were subjected to either ATP depletion (0.1 microM antimycin A and glucose deprivation) or hypoxia (1% O(2)). After ATP depletion, HSF was rapidly activated (within 30 min), whereas HIF-1 was unaffected. In contrast, hypoxia led to the activation of HIF-1 but not HSF. Hypoxic activation of HIF-1 was observed within 30 min and persisted for 4 h, whereas no HSF activation was detected even with prolonged periods of hypoxia. HIF-1 was transcriptionally active in LLC-PK(1) cells, as demonstrated by luciferase reporter gene assays using the vascular endothelial growth factor promoter or a synthetic promoter construct containing three hypoxia-inducible elements. Interestingly, intracellular ATP levels were not affected by hypoxia but were significantly reduced by ATP depletion. These findings suggest that HIF-1 is activated specifically by decreased O(2) concentrations and not by reduced ATP levels alone. In contrast, HSF is activated primarily by metabolic stresses associated with ATP depletion and not by isolated O(2) deprivation. In vivo, the two transcription factors are simultaneously activated during renal ischemia, which might account for observed differences between in vivo and in vitro epithelial cell injury and repair. Selective modulation of either pathway might therefore be of potential interest for modification of the response of the kidney to ischemia, as well as the processes involved in recovery from ischemia.

Author List

Eickelberg O, Seebach F, Riordan M, Thulin G, Mann A, Reidy KH, Van Why SK, Kashgarian M, Siegel N

Author

Scott K. Van Why MD Professor in the Pediatrics department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Adenosine Triphosphate
Animals
Cell Hypoxia
DNA-Binding Proteins
Gene Expression
Heat Shock Transcription Factors
Hypoxia-Inducible Factor 1
Hypoxia-Inducible Factor 1, alpha Subunit
Ischemia
Kidney
LLC-PK1 Cells
Male
Nuclear Proteins
Rats
Rats, Sprague-Dawley
Renal Circulation
Swine
Transcription Factors
Transcriptional Activation