The rat heme oxygenase-1 gene is transcriptionally induced via the protein kinase A signaling pathway in rat hepatocyte cultures.
Heme oxygenase-1 (HO-1) is the inducible form of the rate-limiting enzyme of heme degradation; it regulates the cellular content of heme. To investigate the role of the cAMP-dependent protein kinase (PKA) signaling pathway on hepatic HO-1 gene expression, primary rat hepatocyte cultures were treated with the PKA-stimulating agents dibutyryl-cAMP (Bt2cAMP), forskolin, and glucagon. HO-1 mRNA levels were induced by these agents in a time-dependent manner with a transient maximum after 6 hr of treatment. The induction of HO-1 was dose dependent, reaching a maximum at concentrations of 250 muM Bt2cAMP and 50 nM glucagon, respectively. The accumulation of HO-1 mRNA correlated with increased levels of HO-1 protein as determined by Western blot analysis. The Bt2cAMP-dependent induction of HO-1 mRNA expression was prevented by pretreatment with the PKA inhibitor KT5720 but not with the protein kinase G inhibitor KT5823. HO-1 mRNA induction by CdCl2 and heme was differentially affected by Bt2cAMP. Up-regulation of the HO-1 gene by Bt2cAMP occurred on the transcriptional level as determined by nuclear run-off assay and blocking of the Bt2cAMP-dependent induction of HO-1 mRNA by actinomycin D. Treatment with Bt2cAMP increased the half-life of HO-1 mRNA from 4.7 to 5.5 hr. Taken together, the results of the current study demonstrate that HO-1 gene expression is induced by activation of the cAMP signal transduction pathway via a transcriptional mechanism in primary rat hepatocyte cultures.
Immenschuh
S
S
Department of Pediatrics, Biochemistry, and Pharmacology, Cornell University Medical College, New York, New York 10021, USA. simmens@gwdg.de
Kietzmann
T
T
Hinke
V
V
Wiederhold
M
M
Katz
N
N
Muller-Eberhard
U
U
D000818:Animals; D019256:Cadmium Chloride / Q000494:pharmacology; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology*; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D004790:Enzyme Induction; D015971:Gene Expression Regulation, Enzymologic; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics*; D051547:Heme Oxygenase-1; D008099:Liver / Q000166:cytology / Q000201:enzymology*; D008297:Male; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar
D012333:RNA, Messenger; D003609:Dactinomycin; D003513:Cycloheximide; D000242:Cyclic AMP; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; D017868:Cyclic AMP-Dependent Protein Kinases; D019256:Cadmium Chloride