Involvement of Salmonella pathogenicity island 2 in the up-regulation of interleukin-10 expression in macrophages: role of protein kinase A signal pathway.
Salmonellae are facultative intracellular bacteria capable of surviving within macrophages. Salmonella pathogenicity island 2 (SPI-2) is required for growth within macrophages and for virulence in mice. In this study, we show the involvement of SPI-2 in a signal transduction pathway that induces cytokine expression in Salmonella-infected macrophages. High levels of interleukin-10 (IL-10) mRNA were induced in macrophages by infection with wild-type salmonellae compared to a strain carrying a mutation in the spiC gene, which is encoded within SPI-2. The two strains had the same effect on the expression of proinflammatory cytokines such as IL-1 alpha, IL-6, and tumor necrosis factor alpha. IL-10 expression was dose dependently blocked by treatment of infected macrophages with the protein kinase A (PKA) inhibitor H-89, while IL-10 expression was increased by the PKA activator dibutyryl cyclic AMP. Cyclic AMP-dependent PKA activity was higher in macrophages infected with wild-type salmonellae compared to the spiC mutant, and Ser(132) phosphorylation of cyclic AMP response element-binding protein (CREB), which is an important mediator of PKA activation, correlated with the levels of PKA activity. Taken together, these results indicate that salmonellae cause an SPI-2-dependent increase in PKA activity that leads to CREB phosphorylation, resulting in up-regulation of IL-10 expression in Salmonella-infected macrophages. Suppression of IL-10 expression by an antisense oligonucleotide did not affect the growth of wild-type salmonellae within macrophages, whereas growth was dose dependently inhibited by H-89, suggesting that the PKA signaling pathway plays a significant role in intramacrophage Salmonella survival.
Uchiya
Kei-ichi
K
Department of Microbiology, Faculty of Pharmacy, Meijo University, Yagotoyama 150, Tenpaku-ku, Nagoya 468-8503, Japan. kuchiya@ccmfs.meijo-u.ac.jp
Groisman
Eduardo A
EA
Nikai
Toshiaki
T
D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism*; D002460:Cell Line; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004789:Enzyme Activation; D016753:Interleukin-10 / Q000378:metabolism*; D008264:Macrophages / Q000276:immunology / Q000378:metabolism / Q000382:microbiology*; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D010766:Phosphorylation; D012481:Salmonella Infections, Animal / Q000382:microbiology; D012486:Salmonella typhimurium / Q000254:growth & development / Q000472:pathogenicity*; D015398:Signal Transduction; D015854:Up-Regulation
D001426:Bacterial Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D008565:Membrane Proteins; C440638:SPI-2 protein, Salmonella; D016753:Interleukin-10; D017868:Cyclic AMP-Dependent Protein Kinases