title: Transcriptomic analysis of the effects of Toll-like receptor 4 and its ligands on the gene expression network of hepatic stellate cells.
abstract: BACKGROUND
  Intact Toll-like receptor 4 (TLR4) has been identified in hepatic stellate cells (HSCs), the primary fibrogenic cell type in liver. Here, we investigated the impact of TLR4 signaling on the gene expression network of HSCs by comparing the transcriptomic changes between wild-type (JS1) and TLR4 knockout (JS2) murine HSCs in response to two TLR4 ligands, lipopolysacchride (LPS), or high-mobility group box 1 (HMGB1).
  
  
  RESULTS
  Whole mouse genome microarray was performed for gene expression analysis. Gene interaction and co-expression networks were built on the basis of ontology and pathway analysis by Kyoto Encyclopedia of Genes and Genomes (KEGG). Gene expression profiles are markedly different between Wild type (JS1) and TLR4 knockout (JS2) HSCs under basal conditions or following stimulation with LPS or HMGB1. The differentially expressed genes between TLR4 intact and null HSCs were enriched in signaling pathways including p53, mTOR, NOD-like receptor, Jak-STAT, chemokine, focal adhesion with some shared downstream kinases, and transcriptional factors. Venn analysis revealed that TLR4-dependent, LPS-responsive genes were clustered into pathways including Toll-like receptor and PI3K-Akt, whereas TLR4-dependent, HMGB1-responsive genes were clustered into pathways including metabolism and phagosome signaling. Genes differentially expressed that were categorized to be TLR4-dependent and both LPS- and HMGB1-responsive were enriched in cell cycle, ubiquitin mediated proteolysis, and mitogen-activated protein kinase (MAPK) signaling pathways.
  
  
  CONCLUSIONS
  TLR4 mediates complex gene expression alterations in HSCs. The affected pathways regulate a wide spectrum of HSC functions, including inflammation, fibrogenesis, and chemotaxis, as well as cell growth and metabolism. There are common and divergent regulatory signaling downstream of LPS and HMGB1 stimulation via TLR4 on HSCs. These findings emphasize the complex cascades downstream of TLR4 in HSCs that could influence their cellular biology and function.
authors.affiliation: Division of Digestive Diseases, Department of Internal Medicine, Zhong Shan Hospital, Shanghai Medical College, Fu Dan University, 180 Feng Lin Road, Shanghai, 200032 China.
authors.forename: Yangyang
authors.initials: Y
authors.lastname: Ouyang
authors.affiliation: Division of Digestive Diseases, Department of Internal Medicine, Zhong Shan Hospital, Shanghai Medical College, Fu Dan University, 180 Feng Lin Road, Shanghai, 200032 China.
authors.forename: Jinsheng
authors.initials: J
authors.lastname: Guo
authors.affiliation: Institutes of Biomedical Sciences, Fu Dan University, Shanghai, 200032 China.
authors.forename: Chenzhao
authors.initials: C
authors.lastname: Lin
authors.affiliation: Key Laboratory of Systems Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032 China.
authors.forename: Jie
authors.initials: J
authors.lastname: Lin
authors.affiliation: Division of Digestive Diseases, Department of Internal Medicine, Zhong Shan Hospital, Shanghai Medical College, Fu Dan University, 180 Feng Lin Road, Shanghai, 200032 China.
authors.forename: Yirong
authors.initials: Y
authors.lastname: Cao
authors.affiliation: Division of Digestive Diseases, Department of Internal Medicine, Zhong Shan Hospital, Shanghai Medical College, Fu Dan University, 180 Feng Lin Road, Shanghai, 200032 China.
authors.forename: Yuanqin
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Division of Digestive Diseases, Department of Internal Medicine, Zhong Shan Hospital, Shanghai Medical College, Fu Dan University, 180 Feng Lin Road, Shanghai, 200032 China.
authors.forename: Yujin
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Division of Digestive Diseases, Department of Internal Medicine, Zhong Shan Hospital, Shanghai Medical College, Fu Dan University, 180 Feng Lin Road, Shanghai, 200032 China.
authors.forename: Shiyao
authors.initials: S
authors.lastname: Chen
authors.affiliation: Division of Digestive Diseases, Department of Internal Medicine, Zhong Shan Hospital, Shanghai Medical College, Fu Dan University, 180 Feng Lin Road, Shanghai, 200032 China.
authors.forename: Jiyao
authors.initials: J
authors.lastname: Wang
authors.affiliation: Key Laboratory of Systems Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032 China.
authors.forename: Luonan
authors.initials: L
authors.lastname: Chen
authors.affiliation: Division of Liver Diseases, Icahn School of Medicine at Mount Sinai, 1425 Madison Ave., Room 11-70C, New York, 10029-6574 NY USA.
authors.forename: Scott L
authors.initials: SL
authors.lastname: Friedman
keywords: Gene expression network; Hepatic stellate cells; High-mobility group box 1; Lipopolysaccharide; Toll-like receptor 4