title: Leptospiral hemolysins induce proinflammatory cytokines through Toll-like receptor 2-and 4-mediated JNK and NF-κB signaling pathways.
abstract: BACKGROUND
  Infection with pathogenic Leptospira species causes serious systemic inflammation in patients. Although a few leptospiral proinflammatory molecules have been identified, Leptospira likely encodes other unidentified strong inflammation stimulators. The pathogenic L. interrogans genome encodes numerous putative hemolysin genes. Since hemolysins from other bacteria can cause inflammatory reactions, we hypothesized that leptospiral hemolysins may function as proinflammatory stimulators that contribute to the strong inflammation associated with Leptospira infection.
  
  
  RESULTS
  We first used cytokine protein microarrays for systematic analysis of serum cytokine profiles in leptospirosis patients and leptospire-infected mice. We found that IL-1β, IL-6 and TNF-α were the main proinflammatory cytokines in the sera of both the patients and the mice. We then analyzed eight putative hemolysins in L. interrogans strain Lai. The results showed that five of them, Sph1, Sph2, Sph3, HlpA and TlyA were secreted and had hemolytic activity. More importantly, these five hemolysins induced the strong production of IL-1β, IL-6 and TNF-α in human and mouse macrophages (although a bit lower in the latter). Furthermore, blockade of TLR2 or TLR4 with either antibodies or inhibitors of the NF-κB or JNK signaling pathways significantly reduced the production of hemolysin-induced IL-1β, IL-6 and TNF-α. Macrophages isolated from TLR2-, TLR4-or double TLR2-and 4-deficient mice also confirmed that the leptospiral hemolysins that induce proinflammatory cytokines are both TLR2-and TLR4-dependent.
  
  
  CONCLUSIONS
  Our findings demonstrate that L. interrogans secretes many hemolysins that function as powerful inducers of proinflammatory cytokines through both TLR2-and TLR4-dependent JNK and NF-κB pathways.
authors.affiliation: Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.
authors.forename: Huan
authors.initials: H
authors.lastname: Wang
authors.forename: Yifei
authors.initials: Y
authors.lastname: Wu
authors.forename: David M
authors.initials: DM
authors.lastname: Ojcius
authors.forename: X Frank
authors.initials: XF
authors.lastname: Yang
authors.forename: Chenglin
authors.initials: C
authors.lastname: Zhang
authors.forename: Shibiao
authors.initials: S
authors.lastname: Ding
authors.forename: Xu'ai
authors.initials: X
authors.lastname: Lin
authors.forename: Jie
authors.initials: J
authors.lastname: Yan
mesh_terms: D000328:Adult; D000818:Animals; D002460:Cell Line; D016207:Cytokines / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D005260:Female; D006460:Hemolysin Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D018836:Inflammation Mediators / Q000276:immunology* / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D007921:Leptospira interrogans / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D007922:Leptospirosis / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000235:genetics / Q000276:immunology*; D008264:Macrophages / Q000276:immunology / Q000378:metabolism; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D016328:NF-kappa B / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000276:immunology* / Q000378:metabolism
chemical_list: D016207:Cytokines; D006460:Hemolysin Proteins; D018836:Inflammation Mediators; D016328:NF-kappa B; C495342:TLR2 protein, human; C495345:TLR4 protein, human; C493486:Tlr2 protein, mouse; C493487:Tlr4 protein, mouse; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D048031:JNK Mitogen-Activated Protein Kinases