Guanosine 3',5'-cyclic monophosphate (cGMP)/cGMP-dependent protein kinase induce interleukin-6 transcription in osteoblasts.
Natriuretic peptides and nitric oxide (NO) activate the cGMP/cGMP-dependent protein kinase (PKG) signaling pathway and play an important role in bone development and adult bone homeostasis. The cytokine IL-6 regulates bone turnover and osteoclast and osteoblast differentiation. We found that C-type natriuretic peptide and the NO donor Deta-NONOate induced IL-6 mRNA expression in primary human osteoblasts, an effect mimicked by the membrane-permeable cGMP analog 8-chlorophenylthio-cGMP (8-CPT-cGMP). Similar results were obtained in rat UMR106 osteosarcoma cells, where C-type natriuretic peptide and 8-CPT-cGMP stimulated transcription of the human IL-6 promoter and increased IL-6 secretion into the medium. Cotransfection of type I PKG enhanced the cGMP effect on the IL-6 promoter, whereas small interfering RNA-mediated silencing of PKG I expression prevented the cGMP effect on IL-6 mRNA expression. Step-wise deletion of the IL-6 promoter demonstrated a cAMP response element to be critical for transcriptional effects of cGMP, and experiments with dominant interfering proteins showed that cGMP activation of the promoter required cAMP response element binding-related proteins, and, to a lesser extent, proteins of the CAAT enhancer-binding protein and activator protein-1 (Fos/Jun) families. 8-CPT-cGMP induced nuclear translocation of type I PKG and increased cAMP response element binding-related protein phosphorylation on Ser(133). PKG regulation of the IL-6 promoter appeared to be of physiological significance, because inhibitors of the NO/cGMP/PKG signaling pathway largely prevented fluid shear stress-induced increases of IL-6 mRNA in UMR106 cells.
Broderick
Kate E
KE
Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0652, USA.
Zhang
Tong
T
Rangaswami
Hema
H
Zeng
Ying
Y
Zhao
Xin
X
Boss
Gerry R
GR
Pilz
Renate B
RB
D000818:Animals; D001859:Bone Neoplasms; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D006152:Cyclic GMP / Q000378:metabolism*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D017930:Genes, Reporter; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics*; D009569:Nitric Oxide / Q000494:pharmacology; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D012516:Osteosarcoma; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic; D014162:Transfection
D015850:Interleukin-6; D012333:RNA, Messenger; D009569:Nitric Oxide; D017869:Cyclic GMP-Dependent Protein Kinases; D006152:Cyclic GMP