Protein kinase C pathway is involved in transcriptional regulation of C-reactive protein synthesis in human hepatocytes.
OBJECTIVE
C-reactive protein (CRP) is the prototype acute phase protein and a cardiovascular risk factor. Interleukin-1beta (IL-1beta) and IL-6 stimulate CRP synthesis in hepatocytes. We searched for additional pathways regulating CRP expression.


RESULTS
Primary human hepatocytes (PHHs) were treated with IL-1beta, IL-6, and protein kinase C (PKC) activator phorbol 12,13-dibutyrate (PDBu). CRP was analyzed by quantitative RT-PCR and ELISA. PDBu significantly induced CRP transcription by 21.0+/-9.24-fold and protein release by 2.9+/-0.5-fold. Transcriptional regulation was studied in detail in hepatoma G2 (HepG2) cells stably transfected with the 1-kb CRP promoter (HepG2-ABEK14 cells). In these cells, PDBu significantly induced CRP transcription by 5.39+/-0.66-fold. Competitive inhibition with bisindolylmaleimide derivative LY333531 abolished PDBu-mediated promoter activation. Competitive inhibition with IkappaB kinase inhibitor I229 also inhibited PDBu effects. Importantly, IL-8 significantly induced CRP release in PHHs by 58.675+/-19.1-fold, which was blockable by LY333531.


CONCLUSIONS
This study describes a novel PKC-dependent transcriptional regulation of CRP gene expression, which, in analogy to the classical IL-1beta and IL-6 pathways, is operational in hepatocytes only. It also identifies IL-8 as a potential physiological PKC activator. HepG2-ABEK14 cells may be useful for high throughput screening to identify inhibitors of CRP synthesis for the prevention of cardiovascular disease.
Ivashchenko
Yuri
Y
Aventis Pharma Deutschland GmbH, DG Cardiovascular Research, Frankfurt am, Germany.
Kramer
Frank
F
Schäfer
Stefan
S
Bucher
Andrea
A
Veit
Kerstin
K
Hombach
Vinzenz
V
Busch
Andreas
A
Ritzeler
Olaf
O
Dedio
Jürgen
J
Torzewski
Jan
J
D001011:Aorta / Q000166:cytology; D002097:C-Reactive Protein / Q000235:genetics*; D006528:Carcinoma, Hepatocellular / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D002460:Cell Line; D045744:Cell Line, Tumor; D042783:Endothelial Cells / Q000737:chemistry / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology; D004789:Enzyme Activation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D022781:Hepatocytes / Q000737:chemistry* / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology; D016209:Interleukin-8 / Q000378:metabolism; D008113:Liver Neoplasms / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D009131:Muscle, Smooth, Vascular / Q000166:cytology; D032389:Myocytes, Smooth Muscle / Q000737:chemistry / Q000378:metabolism; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D011493:Protein Kinase C / Q000378:metabolism*; D064546:Protein Kinase C beta; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*; D014471:Umbilical Veins / Q000166:cytology
D007375:Interleukin-1; D015850:Interleukin-6; D016209:Interleukin-8; D015240:Phorbol 12,13-Dibutyrate; D002097:C-Reactive Protein; D011493:Protein Kinase C; D064546:Protein Kinase C beta