Induction of the heme oxygenase-1 gene by metalloporphyrins.
Induction of expression of heme oxygenase-1 (HO-1) has been studied in primary cultures of chick embryo liver cells and in the LMH line of avian hepatoma cells. Cells were transiently transfected with selected constructs containing portions of the 5'-untranslated (promoter) region of the HO-1 gene linked to luciferase as reporter gene. LMH cells that had been stably transfected with selected wild type or mutant constructs were also studied. Metalloporphyrins, especially Fe protoporphyrin (heme) and Co protoporphyrin strongly induced luciferase expression in both types of transfected cells. Low concentrations of Zn mesoporphyrin, an inhibitor of HO activity, exerted a synergistic effect on heme-, but not Co protoporphyrin-dependent induction. The antioxidant and &bond;SH donor N-acetyl cysteine had little effect on the metalloporphyrin-dependent inductions of HO-1, in contrast to its marked inhibitory effect on the sodium arsenite-dependent induction of the HO-1 gene. Deletional analysis showed that the key element(s) required for the metalloporphyrin-dependent induction of HO-1 is located between -3.6 and -5.6 kb upstream of the transcription starting point. Data from electrophoretic mobility shift and site-directed mutagenesis experiments excluded a role for consensus AP-1 binding elements at -1576, -3647, or -4578 in the inductions produced by heme or Co protoporphyrin.
Shan
Y
Y
Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA.
Pepe
J
J
Lu
T H
TH
Elbirt
K K
KK
Lambrecht
R W
RW
Bonkovsky
H L
HL
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002478:Cells, Cultured; D002642:Chick Embryo; D017931:DNA Primers / Q000235:genetics; D004742:Enhancer Elements, Genetic; D015870:Gene Expression / Q000187:drug effects; D017930:Genes, Reporter; D006418:Heme / Q000494:pharmacology; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics*; D051547:Heme Oxygenase-1; D008156:Luciferases / Q000235:genetics; D008665:Metalloporphyrins / Q000494:pharmacology*; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic; D011524:Protoporphyrins / Q000494:pharmacology; D014162:Transfection
D017931:DNA Primers; D008665:Metalloporphyrins; D011524:Protoporphyrins; D006418:Heme; C007095:cobaltiprotoporphyrin; C058069:zinc mesoporphyrin; D008156:Luciferases; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1