Increased prolyl 4-hydroxylase expression and differential regulation of hypoxia-inducible factors in the aged rat brain.
Hypoxia-inducible factors (HIFs) are heterodimeric transcription factors that mediate the adaptive response of mammalian cells and tissues to changes in tissue oxygenation. In the present study, we show an age-dependent decline in cortical HIF-1alpha accumulation and activation of HIF target genes in response to hypoxia. This inducible response is significantly attenuated in the cerebral cortex of 18-mo-old Fischer 344 rat yet virtually absent in the cerebral cortex of 24-mo-old Fischer 344 rat. This attenuated HIF-1alpha response had no effect on mRNA upregulation of HIF-independent genes in the aged cortex. We have provided evidence that this absent HIF-1alpha response is directly correlated with an increase in the expression of the HIF regulatory enzyme, prolyl 4-hydroxylase (PHD). In addition, our study shows that cortical HIF-2alpha expression in senescent normoxic controls is also significantly greater than that of younger normoxic controls, despite no difference in HIF-2alpha mRNA levels. The posttranslational regulation of HIF-2alpha under normoxic conditions seems to be attenuated in the aged rat brain, which is an in vivo demonstration of differential regulation of HIF-1alpha and HIF-2alpha.
Ndubuizu
Obinna I
OI
Department of Physiology & Biophysics, Case Western Reserve University, Cleveland, Ohio 44106-4938, USA.
Chavez
Juan C
JC
LaManna
Joseph C
JC
D000367:Age Factors; D000375:Aging / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases / Q000378:metabolism; D002540:Cerebral Cortex / Q000201:enzymology*; D004268:DNA-Binding Proteins / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D051272:Glucose Transporter Type 1 / Q000378:metabolism; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D017874:Immediate-Early Proteins / Q000378:metabolism; D008297:Male; D011393:Procollagen-Proline Dioxygenase / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D000099162:Endothelial PAS Domain-Containing Protein 1
D051792:Basic Helix-Loop-Helix Proteins; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases; D004268:DNA-Binding Proteins; D051272:Glucose Transporter Type 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D017874:Immediate-Early Proteins; D011393:Procollagen-Proline Dioxygenase; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D000099162:Endothelial PAS Domain-Containing Protein 1; C497444:Hif1a protein, rat; C495679:Slc2a1 protein, rat; C467498:vascular endothelial growth factor A, rat; C580731:Egln1 protein, rat; C087100:Egln3 protein, rat; C526285:Ca9 protein, rat