The permissive role of mitochondria in the induction of haem oxygenase-1 in endothelial cells.

TitleThe permissive role of mitochondria in the induction of haem oxygenase-1 in endothelial cells.
Publication TypeJournal Article
Year of Publication2009
AuthorsRicart, KC, Bolisetty, S, Johnson, MS, Perez, J, Agarwal, A, Murphy, MP, Landar, A
JournalBiochem J
Date Published2009 Apr 15
KeywordsAnimals, Biotinylation, Blotting, Western, Cattle, Cell Survival, Cells, Cultured, Endothelial Cells, Enzyme Activation, Heme Oxygenase-1, Iodoacetamide, Microscopy, Confocal, Microscopy, Fluorescence, Mitochondria, Organophosphorus Compounds, Polymerase Chain Reaction, Prostaglandin D2, Reactive Oxygen Species

HO-1 (haem oxygenase 1) is an essential antioxidant enzyme in the cell that exerts its effects through removal of pro-oxidant haem groups and the formation of antioxidant molecules and carbon monoxide. The electrophilic cyclopentenone 15d-PGJ2 (15-deoxy-Delta(12,14)-prostaglandin J2) induces the expression of HO-1 protein through the covalent modification of protein thiols. It has been shown that specific thiol residues of the redox-sensor Keap1 (Kelch-like ECH-associated protein 1) are modified by 15d-PGJ2, leading to activation of the transcription factor Nrf-2 (nuclear factor-erythroid 2 p45 subunit-related factor 2) and up-regulation of genes under control of the electrophile-response element, including HO-1. However, 15d-PGJ2 has also been shown to modify other proteins which comprise the electrophile-responsive proteome. Since 15d-PGJ2 has been shown to localize to the mitochondria in endothelial cells, we hypothesized that mitochondrial protein modification may also be important in Keap1/Nrf-2 signal transduction, leading to HO-1 up-regulation. In order to determine the role of mitochondrial protein thiol modification in HO-1 induction, we used the mitochondrial-targeted thiol-reactive compound IBTP [(4-iodobutyl)triphenylphosphonium]. IBTP had no effect on basal HO-1 levels, but effectively blocked HO-1 induction by a variety of reagents including haemin, iodoacetamide and 15d-PGJ2. Mechanistically, IBTP did not prevent the covalent modification of Keap1 by 15d-PGJ2. However, IBTP prevented the 15d-PGJ2-dependent increases in HO-1 mRNA and protein. Furthermore, IBTP prevented the nuclear accumulation of Nrf-2, suggesting cross-talk between mitochondria and antioxidant-response signal transduction. This effect was independent of reactive oxygen species formation or mitochondrial membrane potential. In addition, IBTP significantly enhanced the toxicity of high concentrations of 15d-PGJ2, suggesting that loss of mitochondrial control of HO-1 leads to increased susceptibility to electrophilic stress in endothelial cells. The implications for these studies in understanding the balance between cytoprotection and cytotoxicity in the context of diseases such as atherosclerosis is discussed.

Alternate JournalBiochem. J.
Citation Key10.1042/BJ20081350
PubMed ID19161347
PubMed Central IDPMC2737281
Grant ListR01 DK059600 / DK / NIDDK NIH HHS / United States
R01 DK071875-03 / DK / NIDDK NIH HHS / United States
R01 DK071875 / DK / NIDDK NIH HHS / United States
MC_U105663142 / / Medical Research Council / United Kingdom
R01 DK075532-04 / DK / NIDDK NIH HHS / United States
R01 DK075532 / DK / NIDDK NIH HHS / United States
R01 DK059600-07A2 / DK / NIDDK NIH HHS / United States