Hemin causes mitochondrial dysfunction in endothelial cells through promoting lipid peroxidation: the protective role of autophagy

AN Higdon, GA Benavides… - American Journal …, 2012 - journals.physiology.org
AN Higdon, GA Benavides, BK Chacko, X Ouyang, MS Johnson, A Landar, J Zhang
American Journal of Physiology-Heart and Circulatory Physiology, 2012journals.physiology.org
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 …
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.
American Physiological Society