title: Mitogen-activated protein kinase (MAPK) signalling pathways in HepG2 cells infected with a virulent strain of Klebsiella pneumoniae.
abstract: Klebsiella pneumoniae (KP), an enterobacterium, usually causes urinary tract infection or pneumonia; however, it has caused severe liver abscess in diabetic patients in recent years. How this emerging virulent KP strain causes liver abscess is not known. This study investigates signalling pathways in HepG2 cells infected by virulent KP. Cells were infected with bacteria for various durations and harvested to screen for signalling molecules by Western blotting. Our results showed that phosphorylated mitogen-activated protein kinase (MAPK) kinase (MEK) 1/2, p44/p42 MAPK and p90 ribosomal S6 kinase (p90RSK) were observed and this pathway was inhibited by MEK1/2 inhibitors U0126 and PD98059. Phosphorylation of MEK3/6, p38 kinase and ATF-2 was also observed and this pathway was inhibited by p38 kinase inhibitors SB203850 and SB202190. Toll-like receptor (TLR) 2 and 4 expressions were increased and maximized 2-4 h post infection. The JNK pathway, Elk, MAPKAPK-2 and HSP27 were not activated. These results suggest that KP infections induce signal transduction through TLR2 and TLR4 and activate two downstream MAP kinase pathways, MEK1/2-p44/p42 MAPK-p90RSK and MEK3/6-p38 kinase-ATF-2, but not the JNK pathway in HepG2 cells. The infected HepG2 eventually showed apoptosis and died.
authors.affiliation: Department of Microbiology and Immunology, Graduate Institute of Basic Medical Science, College of Medicine, Chang Gung University, Kwei San, Tao Yuan 333, Taiwan. jhwu@mail.cgu.edu.tw
authors.forename: June H
authors.initials: JH
authors.lastname: Wu
authors.forename: Li-Chun
authors.initials: LC
authors.lastname: Hong
authors.forename: Yi-Ying
authors.initials: YY
authors.lastname: Tsai
authors.forename: Hui-Wen
authors.initials: HW
authors.lastname: Chen
authors.forename: Wen-Xin
authors.initials: WX
authors.lastname: Chen
authors.forename: Ting Shu
authors.initials: TS
authors.lastname: Wu
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D015153:Blotting, Western / Q000379:methods; D002070:Butadienes / Q000494:pharmacology; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D007711:Klebsiella pneumoniae / Q000472:pathogenicity*; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048370:MAP Kinase Kinase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008954:Models, Biological; D009570:Nitriles / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D051195:Toll-Like Receptor 2 / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000378:metabolism; D014774:Virulence; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D002070:Butadienes; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007093:Imidazoles; D009570:Nitriles; D011725:Pyridines; C495342:TLR2 protein, human; C495345:TLR4 protein, human; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; C113580:U 0126; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one