Leptospiral hemolysins induce proinflammatory cytokines through toll-like receptor 2-and 4-mediated JNK and NF-κB signaling pathways

Huan Wang, Yifei Wu, David M. Ojcius, X. Frank Yang, Chenglin Zhang, Shibiao Ding, Xu'ai Lin, Jie Yan

Research output: Contribution to journalArticle

76 Scopus citations

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. Methodology/Principal Findings: 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/Significance: 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.

Original languageEnglish (US)
Article numbere42266
JournalPloS one
Volume7
Issue number8
DOIs
StatePublished - Aug 1 2012

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)
  • General

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