Although the main events occurring during hemolysis are knowing to include elevated plasma levels of heme, the mechanisms of its clearance from the plasma and its detoxification are largely unknown. Elevated plasma heme levels cause depletion of circulating hemopexin (Hx), the protein which binds heme specifically. Hx conserves iron, and we have recently shown that it completely prevents the heme-mediated formation of oxygen radicals that lead to peroxidation of lipids and proteins. Heme not complexed to Hx may initiate and/or sustain oxidative tissue (membrane) damage in acute and chronic hemolysis or during muscle injury, e.g. in myocardial infarctions. The objectives of the proposed work are 1) to characterize the structure/function relationships of Hx employing polyclonal antibodies directed against peptides synthetized according to Hx sequences and, by site-specific mutagenesis, to localize amino acids that are axial ligands for heme in the heme-Hx complex; 2) to delineate the mechanisms but which Hx is induce the mRNA level and to identify those regions on the rat Hx gene which regulate its synthesis, in particular during the acute phase reaction and during heme injections; 3) to express in an eukaryotic system a Hx possessing those characteristics of the native molecule which prevent the heme-canalized oxidations of lipids and proteins. The information obtained should provide a basis for additional therapeutic approaches for preventing tissue damage in states in which heme is released intravasculary.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK030203-10
Application #
3229339
Study Section
Hematology Subcommittee 2 (HEM)
Project Start
1981-04-01
Project End
1994-03-31
Budget Start
1991-04-01
Budget End
1992-03-31
Support Year
10
Fiscal Year
1991
Total Cost
Indirect Cost
Name
Weill Medical College of Cornell University
Department
Type
Schools of Medicine
DUNS #
201373169
City
New York
State
NY
Country
United States
Zip Code
10065
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Noyer, C M; Immenschuh, S; Liem, H H et al. (1998) Initial heme uptake from albumin by short-term cultured rat hepatocytes is mediated by a transport mechanism differing from that of other organic anions. Hepatology 28:150-5
Immenschuh, S; Nell, C; Iwahara, S et al. (1997) Gene regulation of HBP 23 by metalloporphyrins and protoporphyrin IX in liver and hepatocyte cultures. Biochem Biophys Res Commun 231:667-70
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Kietzmann, T; Immenschuh, S; Katz, N et al. (1995) Modulation of hemopexin gene expression by physiological oxygen tensions in primary rat hepatocyte cultures. Biochem Biophys Res Commun 213:397-403
Immenschuh, S; Iwahara, S; Satoh, H et al. (1995) Expression of the mRNA of heme-binding protein 23 is coordinated with that of heme oxygenase-1 by heme and heavy metals in primary rat hepatocytes and hepatoma cells. Biochemistry 34:13407-11
Iwahara, S; Satoh, H; Song, D X et al. (1995) Purification, characterization, and cloning of a heme-binding protein (23 kDa) in rat liver cytosol. Biochemistry 34:13398-406
Cope, L D; Yogev, R; Muller-Eberhard, U et al. (1995) A gene cluster involved in the utilization of both free heme and heme:hemopexin by Haemophilus influenzae type b. J Bacteriol 177:2644-53
van Dijk, H P; Kroos, M J; Starreveld, J S et al. (1995) Expression of haemopexin receptors by cultured human cytotrophoblast. Biochem J 307 ( Pt 3):669-72

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