Heme oxygenase-mediated resistance to oxygen toxicity in hamster fibroblasts.
The role of heme oxygenase (HO)-1 was evaluated in the oxygen-resistant hamster fibroblast cell line, O2R95, which moderately overexpress HO when compared with the parental cell line, HA-1. To suppress HO-1 expression, O2R95 were transfected with HO-1 antisense oligonucleotide or treated with tin-mesoporphyrin (SnMP). To increase HO-1 expression, cells were transfected with HO-1 cDNA in a pRC/cytomegalovirus (CMV) vector. All cells were challenged with a 48-h exposure to 95% O2 (hyperoxia). When HO activity was suppressed, O2R95 cells had significantly decreased cell viability, increased susceptibility to lipid peroxidation, and increased protein oxidation in hyperoxia. In contrast, further overexpression of HO-1 did not improve resistance to oxygen toxicity. Antisense-transfected cells and SnMP-treated cells with lowered HO activity showed increased levels of cellular heme compared with controls. In the HO-1 cDNA-transfected O2R95 cells, cellular heme was lowered compared with controls; however, cellular redox active iron levels were increased. We conclude that HO mediates cytoprotection to oxygen toxicity within a narrow range of expression. We speculate that this protective effect may be mediated in part through increased metabolism of the pro-oxidant heme but that higher levels of HO activity obviate protection by increased redox active iron release.
Dennery
P A
PA
Department of Pediatrics, Stanford University School of Medicine, Stanford, California 94305, USA. mn.phd@forsythe.stanford.edu
Sridhar
K J
KJ
Lee
C S
CS
Wong
H E
HE
Shokoohi
V
V
Rodgers
P A
PA
Spitz
D R
DR
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D006224:Cricetinae; D003587:Cytomegalovirus; D004351:Drug Resistance; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts; D005822:Genetic Vectors; D006419:Heme Oxygenase (Decyclizing) / Q000096:biosynthesis / Q000378:metabolism*; D051547:Heme Oxygenase-1; D007700:Kinetics; D015227:Lipid Peroxidation / Q000187:drug effects; D008665:Metalloporphyrins / Q000494:pharmacology; D016376:Oligonucleotides, Antisense / Q000494:pharmacology*; D018384:Oxidative Stress; D010100:Oxygen / Q000633:toxicity*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D014162:Transfection
D000975:Antioxidants; D004791:Enzyme Inhibitors; D008665:Metalloporphyrins; D016376:Oligonucleotides, Antisense; D011994:Recombinant Proteins; C055421:tin mesoporphyrin; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; D010100:Oxygen