Effects of hypoxia and intracellular iron chelation on hypoxia-inducible factor-1alpha and -1beta in the rat carotid body and glomus cells.
The present investigation provides for the first time, unambiguous information on the occurrence of hypoxia-inducible factors (HIF-1alpha and HIF-1beta proteins) in normoxia (Nx) and their interaction with hypoxia (Hx) and intracellular Fe(2+) chelation in the rat carotid body (CB) glomus cells. HIF-1alpha bound to HIF-1beta translocated into the nucleus is identified on the basis of immunohistochemistry and immunofluorescence. In Nx, a weak expression of HIF-1alpha was observed in CB glomus cells. However, exposure of CB and glomus cells to Hx (Po(2) approximately 7 Torr) and Nx with ciclopirox olamine (CPX, 5 microM) for 1 h showed a significant ( P<0.001) increase in HIF-1alpha protein. The CBs and glomus cells exposed to Nx, Hx, and Nx with CPX showed a constant level of HIF-1beta protein expression. HIF-1alpha subunit is continuously synthesized and degraded under normoxic conditions, while it accumulates rapidly following exposure to low oxygen tensions. Hydroxylation of HIF-1alpha by prolyl hydroxylase for proteasomal degradation was dependent on iron, 2-oxoglutarate, and oxygen concentration. The intracellular iron that acts as a cofactor for prolyl hydroxylase activity belongs to the labile iron pool and can be easily chelated. Thus, chelation of intracellular labile iron by CPX in Nx significantly increased HIF-1alpha in CB glomus cells. Thus, the results are consistent with the hypothesis that HIF-1alpha which is present in the glomus cells translocates to the nucleus during exposure to Hx and to CPX in Nx.
Department of Physiology, B-400 Richards Building, University of Pennsylvania School of Medicine, 3700 Hamilton Walk, Philadelphia, PA 19104-6085, USA.
Santhosh M
SM
Baby
Arijit
A
Roy
Anil M
AM
Mokashi
Sukhamay
S
Lahiri
D000818:Animals; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D002344:Carotid Body / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D000077768:Ciclopirox; D004268:DNA-Binding Proteins; D005455:Fluorescent Antibody Technique; D000860:Hypoxia / Q000378:metabolism*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007502:Iron Chelating Agents / Q000494:pharmacology*; D008297:Male; D010100:Oxygen / Q000494:pharmacology; D011728:Pyridones / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018336:Receptors, Aryl Hydrocarbon / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*
C497398:ARNT protein, rat; D004268:DNA-Binding Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007502:Iron Chelating Agents; D011728:Pyridones; D018336:Receptors, Aryl Hydrocarbon; D014157:Transcription Factors; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D000077768:Ciclopirox; D010100:Oxygen