Hypoxia and expression of hypoxia-inducible factor in the aging kidney.
Renal senescence is characterized by interstitial fibrosis and loss of peritubular capillaries. In this study, we provided evidence of tubulointerstitial hypoxia and the operation of hypoxia-inducible factor (HIF) in the aging kidney. Using two distinct methods, pimonidazole immunostaining and the expression of the "hypoxia-responsive" reporter of the transgenic rats, we identified the age-related expansion of hypoxia in all areas of the kidney. Expansion was most prominent in the cortex. Clusters of hypoxic tubules were observed in the superficial cortical zones, areas adjacent to the outer nephrons and expanded in the medullary rays. The degree of hypoxia was positively correlated with the age-related tubulointerstitial injury (R(2) = 0.88, p <.01), which was associated with the upregulation of HIF-regulated genes, such as vascular endothelial growth factor (VEGF) and glucose transporter-1 (GLUT1) (real-time polymerase chain reaction). These findings point to the involvement of hypoxia and highlight the pathological relevance of HIF and its target genes in the aging kidney.
Tanaka
Tetsuhiro
T
Division of Nephrology and Endocrinology, University of Tokyo School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan.
Kato
Hideki
H
Kojima
Ichiro
I
Ohse
Takamoto
T
Son
Daisuke
D
Tawakami
Takahisa
T
Yatagawa
Toshiya
T
Inagi
Reiko
R
Fujita
Toshiro
T
Nangaku
Masaomi
M
D000375:Aging / Q000502:physiology*; D000818:Animals; D030801:Animals, Genetically Modified; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D015687:Cell Hypoxia / Q000502:physiology; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism* / Q000473:pathology; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D000099162:Endothelial PAS Domain-Containing Protein 1
D051792:Basic Helix-Loop-Helix Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012333:RNA, Messenger; D000099162:Endothelial PAS Domain-Containing Protein 1