Pneumococci induced TLR- and Rac1-dependent NF-kappaB-recruitment to the IL-8 promoter in lung epithelial cells.
Streptococcus pneumoniae is the major pathogen of community-acquired pneumonia. The respiratory epithelium constitutes the first line of defense against invading lung pathogens, including pneumococci. We analyzed the involvement of Toll-like receptors (TLR) and Rho-GTPase signaling in the activation of human lung epithelial cells by pneumococci. S. pneumoniae induced release of interleukin-8 (IL-8) by human bronchial epithelial cell line BEAS-2B. Specific inhibition of Rac1 by Nsc23766 or a dominant-negative mutant of Rac1 strongly reduced cytokine release. In addition, pneumococci-related cell activation (IL-8 release, NF-kappaB-activation) depended on MyD88, phosphatidylinositol 3-kinase, and Cdc42 but not on RhoA. Pneumococci enhanced TLR1 and TLR2 mRNA expression in BEAS-2B cells, whereas TLR4 and TLR6 expression was constitutively high. TLR1 and 2 synergistically recognized pneumococci in cotransfection experiments. TLR4, TLR6, LPS-binding protein, and CD14 seem not to be involved in pneumococci-dependent cell activation. At the IL-8 gene promoter, recruitment of phosphorylated NF-kappaB subunit p65 was blocked by inhibition of Rac1, whereas binding of the phosphorylated activator protein-1 subunit c-Jun to the promoter was not diminished. In summary, these results suggest that S. pneumoniae activate human epithelial cells by TLR1/2 and a phosphatidylinositol 3-kinase- and Rac1-dependent NF-kappaB-recruitment to the IL-8 promoter.
Schmeck
Bernd
B
Department of Internal Medicine/Infectious Diseases, Charité-Universitätsmedizin Berlin, Berlin, Germany.
Huber
Sylvia
S
Moog
Kerstin
K
Zahlten
Janine
J
Hocke
Andreas C
AC
Opitz
Bastian
B
Hammerschmidt
Sven
S
Mitchell
Tim J
TJ
Kracht
Michael
M
Rosseau
Simone
S
Suttorp
Norbert
N
Hippenstiel
Stefan
S
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism; D001980:Bronchi / Q000166:cytology / Q000378:metabolism*; D002460:Cell Line; D004847:Epithelial Cells / Q000378:metabolism; D006801:Humans; D016209:Interleukin-8 / Q000235:genetics* / Q000378:metabolism; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D015398:Signal Transduction; D013296:Streptococcus pneumoniae / Q000502:physiology*; D013301:Streptolysins / Q000378:metabolism; D051194:Toll-Like Receptor 1 / Q000378:metabolism; D051195:Toll-Like Receptor 2 / Q000235:genetics; D051197:Toll-Like Receptor 4 / Q000378:metabolism; D051996:Transcription Factor RelA / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D016209:Interleukin-8; C507779:MYD88 protein, human; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; D013301:Streptolysins; C419843:TLR protein, bacteria; C495342:TLR2 protein, human; C495345:TLR4 protein, human; D051194:Toll-Like Receptor 1; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051996:Transcription Factor RelA; C032290:plY protein, Streptococcus pneumoniae; D019869:Phosphatidylinositol 3-Kinases; D020830:rac1 GTP-Binding Protein; D020741:rho GTP-Binding Proteins