Bacterial cell wall component-induced tolerance represents an important protective mechanism during microbial infection.Tolerance induced by the TLR2 agonist bacterial lipoprotein(BLP)has been shown to attenuate the inflammatory response,and simultaneously to augment antimicrobial function,thereby conferring its protection against microbial sepsis.However,the underlying mechanism by which BLP tolerance augments bactericidal activity has not been fully elucidated.Here,we reported that the induction of BLP tolerance in murine macrophages upregulated the expression of Rab20,a membrane trafficking regulator,at both the mRNA and protein levels upon bacterial infection.The knockdown of Rab20 with Rab20 specific siRNA(siRab20)did not affect the phagocytosis of Escherichia coli(E.coli),but substantially impaired the intracellular killing of the ingested E.coli in BLP-tolerized macrophages.Furthermore,Rab20 was associated with GFP-E.coli containing phagosomes,and BLP tolerization resulted in the enhanced maturation of GFP-E.coli-containing phagosomes associated with Rab20 and strong lysosomal acidification.The knockdown of Rab20 substantially diminished lysosome acidification and disturbed the fusion of GFP-E.coli containing phagosomes with lysosomes in BLP-tolerized macrophages.These results demonstrate that Rab20 plays a critical role in BLP tolerization-induced augmentation of bactericidal activity via promoting phagosome maturation and the fusion of bacteria containing phagosomes with lysosomes.
Studying the cytokine profiles in animal models or patients with sepsis provides an experimental basis for the identification of diagnostic biomarkers and therapeutic targets. In this study, we used a liquid protein chip(LiquiChip), also known as flexible multi-analyte profiling technology, to perform quantitative analyses of several cytokines and chemokines(e.g., IL-1β,IL-2,IL-4, IL-5, IL-6, IL-10, IL-12, TNF-α, IFN-γ, granulocyte-macrophage colony-stimulating factor, keratinocyte chemoattractant,monocyte chemoattractant protein, monokine induced by gamma interferon, IFN-y-inducible protein 10, and macrophage inflammatory protein 1 alpha). The levels of these cytokines and chemokines were determined both in the blood and in tissues,including the lung, liver, heart, kidney, spleen, brain, stomach, intestine and muscle, of mice challenged with LPS. Our data showed variable production levels of LPS-induced cytokines in different mouse organs, and the cytokine in the blood did not correlate with those in the organs. We also showed that the levels of most cytokines peaked within 1 to 6 h and decreased rapidly afterward. A variety of inflammatory cytokines might be related to the damage in different organs during septic shock. Our data also suggest that the spleen might be an important target organ in the development of systemic inflammatory response syndrome and sepsis.
