title: Hemin causes mitochondrial dysfunction in endothelial cells through promoting lipid peroxidation: the protective role of autophagy.
abstract: The hemolysis of red blood cells and muscle damage results in the release of the heme proteins myoglobin, hemoglobin, and free heme into the vasculature. The mechanisms of heme toxicity are not clear but may involve lipid peroxidation, which we hypothesized would result in mitochondrial damage in endothelial cells. To test this, we used bovine aortic endothelial cells (BAEC) in culture and exposed them to hemin. Hemin led to mitochondrial dysfunction, activation of autophagy, mitophagy, and, at high concentrations, apoptosis. To detect whether hemin induced lipid peroxidation and damaged proteins, we used derivatives of arachidonic acid tagged with biotin or Bodipy (Bt-AA, BD-AA). We found that in cells treated with hemin, Bt-AA was oxidized and formed adducts with proteins, which were inhibited by α-tocopherol. Hemin-dependent mitochondrial dysfunction was also attenuated by α-tocopherol. Protein thiol modification and carbonyl formation occurred on exposure and was not inhibited by α-tocopherol. Supporting a protective role of autophagy, the inhibitor 3-methyladenine potentiated cell death. These data demonstrate that hemin mediates cytotoxicity through a mechanism which involves protein modification by oxidized lipids and other oxidants, decreased respiratory capacity, and a protective role for the autophagic process. Attenuation of lipid peroxidation may be able to preserve mitochondrial function in the endothelium and protect cells from heme-dependent toxicity.
authors.affiliation: Department of Pathology, Center For Free Radical Biology, University of Alabama at Birmingham, USA.
authors.forename: Ashlee N
authors.initials: AN
authors.lastname: Higdon
authors.forename: Gloria A
authors.initials: GA
authors.lastname: Benavides
authors.forename: Balu K
authors.initials: BK
authors.lastname: Chacko
authors.forename: Xiaosen
authors.initials: X
authors.lastname: Ouyang
authors.forename: Michelle S
authors.initials: MS
authors.lastname: Johnson
authors.forename: Aimee
authors.initials: A
authors.lastname: Landar
authors.forename: Jianhua
authors.initials: J
authors.lastname: Zhang
authors.forename: Victor M
authors.initials: VM
authors.lastname: Darley-Usmar
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001343:Autophagy / Q000502:physiology*; D015153:Blotting, Western; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D004285:Dogs; D042783:Endothelial Cells / Q000187:drug effects*; D004734:Energy Metabolism / Q000187:drug effects; D045604:Extracellular Fluid / Q000378:metabolism; D005456:Fluorescent Dyes; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006427:Hemin / Q000494:pharmacology*; D007202:Indicators and Reagents; D015227:Lipid Peroxidation / Q000187:drug effects*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects / Q000502:physiology; D017240:Mitochondrial Myopathies / Q000139:chemically induced* / Q000473:pathology; D011499:Protein Processing, Post-Translational / Q000502:physiology
chemical_list: D000975:Antioxidants; D005456:Fluorescent Dyes; D007202:Indicators and Reagents; D049452:Green Fluorescent Proteins; D006427:Hemin; D000255:Adenosine Triphosphate