title: Hypoxia induces apoptosis in SV40-immortalized rat proximal tubular cells through the mitochondrial pathways, devoid of HIF1-mediated upregulation of Bax.
abstract: Chronic hypoxia is a major contributor to tubulointerstitial injury in various renal diseases and apoptosis is apparently involved. Although many studies report hypoxia-induced apoptosis in cultured tubular cells, information has been limited in proximal tubular cells, those from the most susceptible portion of renal tubules against hypoxia. This study was to confirm a role for apoptosis in hypoxic proximal tubular cells and to investigate its association with HIF-1. Temperature-sensitive SV40-immortalized rat proximal tubular cells (IRPTCs) showed apoptosis in 21.9+/-2.9% by hypoxia (0.2% O(2), 48h), with alterations in mitochondrial signaling such as Bcl2 and caspase-9. Bax mRNA was unaffected during the process. However, treating IRPTCs at the nonpermissive temperature showed an upregulation of Bax by hypoxia, which was abrogated by overexpressing dominant-negative HIF-1alpha. These findings extend previous reports on hypoxia-mediated tubular cell apoptosis and demonstrate the possible involvement of HIF-1 as an upstream molecule of Bax.
authors.affiliation: Division of Nephrology and Endocrinology, University of Tokyo School of Medicine, 7-3-1, Hongo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Tetsuhiro
authors.initials: T
authors.lastname: Tanaka
authors.forename: Norio
authors.initials: N
authors.lastname: Hanafusa
authors.forename: Julie R
authors.initials: JR
authors.lastname: Ingelfinger
authors.forename: Takamoto
authors.initials: T
authors.lastname: Ohse
authors.forename: Toshiro
authors.initials: T
authors.lastname: Fujita
authors.forename: Masaomi
authors.initials: M
authors.lastname: Nangaku
mesh_terms: D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005799:Genes, Dominant; D000860:Hypoxia; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D015151:Immunoblotting; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D007687:Kidney Tubules, Proximal / Q000166:cytology* / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials; D008928:Mitochondria / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D016376:Oligonucleotides, Antisense / Q000737:chemistry; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013539:Simian virus 40 / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors; D014157:Transcription Factors; D014162:Transfection; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D015854:Up-Regulation; D051028:bcl-2-Associated X Protein
chemical_list: C494828:Bax protein, rat; D004268:DNA-Binding Proteins; C497444:Hif1a protein, rat; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins; D016376:Oligonucleotides, Antisense; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; C506435:Casp9 protein, rat; D053453:Caspase 9; D020169:Caspases