Expression and actions of HIF prolyl-4-hydroxylase in the rat kidneys.

Abstract

Hypoxia inducible factor (HIF) prolyl-4-hydroxylase domain-containing proteins (PHDs) promote the degradation of HIF-1alpha. Because HIF-1alpha is highly expressed in the renal medulla and HIF-1alpha-targeted genes such as nitric oxide synthase, cyclooxygenase, and heme oxygenase are important in the regulation of renal medullary function, we hypothesized that PHD regulates HIF-1alpha levels in the renal medulla and, thereby, participates in the control of renal Na(+) excretion. Using real-time RT-PCR, Western blot, and immunohistochemical analyses, we have demonstrated that all three isoforms of PHD, PHD1, PHD2, and PHD3, are expressed in the kidneys and that PHD2 is the most abundant isoform. Regionally, all PHDs exhibited much higher levels in renal medulla than cortex. A furosemide-induced increase in renal medullary tissue Po(2) significantly decreased PHD levels in renal medulla, whereas hypoxia significantly increased mRNA levels of PHDs in cultured renal medullary interstitial cells, indicating that O(2) regulates PHDs. Functionally, the PHD inhibitor l-mimosine (l-Mim, 50 mg x kg(-1) x day(-1) i.p. for 2 wk) substantially upregulated HIF-1alpha expression in the kidneys, especially in the renal medulla, and remarkably enhanced (by >80%) the natriuretic response to renal perfusion pressure in Sprague-Dawley rats. Inhibition of HIF transcriptional activity by renal medullary transfection of HIF-1alpha decoy oligodeoxynucleotides attenuated l-Mim-induced enhancement of pressure natriuresis, which confirmed that HIF-1alpha mediated the effect of l-Mim. These results indicate that highly expressed PHDs in the renal medulla make an important contribution to the control of renal Na(+) excretion through regulation of HIF-1alpha and its targeted genes.

• Authors: Ningjun Li, Fan Yi, Christina M Sundy, Li Chen, Molly L Hilliker, Dustin K Donley, Daniel B Muldoon, Pin-Lan Li
• Journal: American journal of physiology. Renal physiology (Am J Physiol Renal Physiol) Vol. 292 Issue 1 Pg. F207-16 (Jan 2007) ISSN: 1931-857X [Print] United States
• PMID: 16885149 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• DNA-Binding Proteins
• Enzyme Inhibitors
• Immediate-Early Proteins
• RNA, Messenger
• Mimosine
• Furosemide
• Egln3 protein, rat
• Hypoxia-Inducible Factor-Proline Dioxygenases
• Heme Oxygenase-1

Topics

• Animals
• Blotting, Western
• Cell Separation
• Cells, Cultured
• DNA-Binding Proteins (biosynthesis, genetics, physiology)
• Enzyme Inhibitors (pharmacology)
• Furosemide (pharmacology)
• Heme Oxygenase-1 (biosynthesis)
• Hypoxia (metabolism)
• Hypoxia-Inducible Factor-Proline Dioxygenases
• Immediate-Early Proteins (biosynthesis, genetics, physiology)
• Immunohistochemistry
• Kidney (enzymology, physiology)
• Kidney Medulla (enzymology, physiology)
• Male
• Mimosine (pharmacology)
• Natriuresis (physiology)
• Osmotic Pressure
• RNA, Messenger (biosynthesis)
• Rats
• Rats, Sprague-Dawley
• Reverse Transcriptase Polymerase Chain Reaction
• Transfection