Mucosal Lipocalin 2 Has Pro-Inflammatory and Iron-Sequestering Effects in Response to Bacterial Enterobactin

PLoS Pathogens

Jeffrey N. Weiser¹  Michael A. Bachman²  Virginia L. Miller³ 

[1] Department of Genetics, The University of North Carolina, Chapel Hill, North Carolina, United States of America;Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America;Department of Pathology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America

关键词: Klebsiella pneumoniae;    Neutrophils;    Mouse models;    Bacterial pathogens;    Inflammation;    Pneumonia;    Nasopharynx;    Flow cytometry;   

DOI  :  10.1371/journal.ppat.1000622

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Nasal colonization by both gram-positive and gram-negative pathogens induces expression of the innate immune protein lipocalin 2 (Lcn2). Lcn2 binds and sequesters the iron-scavenging siderophore enterobactin (Ent), preventing bacterial iron acquisition. In addition, Lcn2 bound to Ent induces release of IL-8 from cultured respiratory cells. As a countermeasure, pathogens of the Enterobacteriaceae family such as Klebsiella pneumoniae produce additional siderophores such as yersiniabactin (Ybt) and contain the iroA locus encoding an Ent glycosylase that prevents Lcn2 binding. Whereas the ability of Lcn2 to sequester iron is well described, the ability of Lcn2 to induce inflammation during infection is unknown. To study each potential effect of Lcn2 on colonization, we exploited K. pneumoniae mutants that are predicted to be susceptible to Lcn2-mediated iron sequestration (iroA ybtS mutant) or inflammation (iroA mutant), or to not interact with Lcn2 (entB mutant). During murine nasal colonization, the iroA ybtS double mutant was inhibited in an Lcn2-dependent manner, indicating that the iroA locus protects against Lcn2-mediated growth inhibition. Since the iroA single mutant was not inhibited, production of Ybt circumvents the iron sequestration effect of Lcn2 binding to Ent. However, colonization with the iroA mutant induced an increased influx of neutrophils compared to the entB mutant. This enhanced neutrophil response to Ent-producing K. pneumoniae was Lcn2-dependent. These findings suggest that Lcn2 has both pro-inflammatory and iron-sequestering effects along the respiratory mucosa in response to bacterial Ent. Therefore, Lcn2 may represent a novel mechanism of sensing microbial metabolism to modulate the host response appropriately.

【 授权许可】

CC BY