Interaction of heme with nitroxyl or nitric oxide amplifies heme oxygenase-1 induction: involvement of the transcription factor Nrf2.
Heme oxygenase-1 (HO-1) is a cytoprotective enzyme, the expression of which is highly sensitive to induction by pro-oxidant stimuli including the substrate heme and reactive oxygen species. Conceptually, the perception that HO-1 plays a key role in response to oxidative damage is paralleled by evidence showing high expression of HO-1 in a variety of cell systems challenged with nitric oxide (NO) or NO-derivatives, thus revealing a potential biological function for HO-1 against nitrosative stress. In this study, we report that exposure of cardiac cells to hemin (5-20 microM) in combination with compounds that liberate nitroxyl (HNO/NO-) or release NO significantly potentiates HO-1 mRNA and protein expression leading to a remarkable increase in heme oxygenase activity under both normoxic and hypoxic conditions. The amplification of the heme oxygenase pathway appears to involve a direct interaction between heme and the NO groups, as the ability of both NO(-)- and NO-releasing agents to induce HO-1 is totally lost by their pre-incubation for 1 hr in complete medium prior to cell treatment but is highly preserved by addition of hemin during the preincubation step. In addition, we show that the redox-sensitive transcription factor Nrf2 is highly expressed in the nuclear fraction of cells exposed to the NO- generator and that this effect is totally abolished by the presence of N-acetyl-L-cysteine. Interestingly, the expression of Nrf2 is gradually intensified by treating cells with a combination of the NO- releaser and increasing concentrations of hemin. Thus, a strict parallelism exists between the extent of HO-1 induction and expression of Nrf2 elicited by the heme-NO interaction. We propose that modification of the iron protoporphyrin centers by NO groups to modulate HO-1 expression might be regarded as a molecular switch to maximize heme oxygenase enzymatic activity and consequently mitigate the redox imbalance imposed by oxidative and nitrosative stress.
Naughton
P
P
Vascular Biology Unit, Department of Surgical Research, Northwick Park Institute for Medical Research, Harrow, Middlesex, HA1 3UJ, United Kingdom.
Hoque
M
M
Green
C J
CJ
Foresti
R
R
Motterlini
R
R
D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D000838:Anions; D015153:Blotting, Western; D002460:Cell Line; D002470:Cell Survival; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006418:Heme / Q000737:chemistry / Q000378:metabolism*; D006419:Heme Oxygenase (Decyclizing) / Q000378:metabolism*; D051547:Heme Oxygenase-1; D006427:Hemin / Q000737:chemistry; D009206:Myocardium / Q000166:cytology; D051267:NF-E2-Related Factor 2; D009569:Nitric Oxide / Q000737:chemistry / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism; D016877:Oxidants / Q000494:pharmacology; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010100:Oxygen / Q000378:metabolism; D011485:Protein Binding; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013438:Sulfhydryl Compounds / Q000378:metabolism; D013696:Temperature; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism*
D000838:Anions; D004268:DNA-Binding Proteins; D051267:NF-E2-Related Factor 2; C495637:Nfe2l2 protein, rat; D016877:Oxidants; D012333:RNA, Messenger; D013438:Sulfhydryl Compounds; D015534:Trans-Activators; D009569:Nitric Oxide; D006418:Heme; D012313:RNA; D006427:Hemin; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; D009584:Nitrogen; D010100:Oxygen; D000111:Acetylcysteine