Michigan, USAa; Division of Pathology, University of Michigan, Ann Arbor, Michigan, USAb; Department of Biostatistics, School of Public Overall health, University of Michigan, Ann Arbor, Michigan, USAc; Department of Molecular Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USAd; Department of Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, Michigan, USAeIron is crucial for a lot of cellular processes and is necessary by bacteria for replication. To obtain iron from the host, pathogenic Gram-negative bacteria secrete siderophores, including enterobactin (Ent). Even so, Ent is bound by the host protein lipocalin 2 (Lcn2), stopping bacterial reuptake of aferric or ferric Ent. Furthermore, the mixture of Ent and Lcn2 (Ent Lcn2) results in enhanced secretion of interleukin-8 (IL-8) compared to that induced by either stimulus alone. Modified or structurally distinct siderophores, like yersiniabactin (Ybt) and glycosylated Ent (GlyEnt, or salmochelin), provide iron to bacteria in spite of the presence of Lcn2. We hypothesized that the robust immune response to Ent and Lcn2 calls for iron chelation instead of the Ent Lcn2 complex itself as well as is often stimulated by Lcn2-evasive siderophores.25952-53-8 web To test this hypothesis, cultured respiratory epithelial cells were stimulated with combinations of purified siderophores and Lcn2 and analyzed by gene expression microarrays, quantitative PCR, and cytokine immunoassays. Ent triggered HIF-1 protein stabilization, induced the expression of genes regulated by hypoxia-inducible factor 1 (HIF-1 ), and repressed genes involved in cell cycle and DNA replication, whereas Lcn2 induced expression of proinflammatory cytokines. Iron chelation by excess Ent or Ybt substantially increased Lcn2-induced secretion of IL-8, IL-6, and CCL20. Stabilization of HIF-1 was sufficient to enhance Lcn2-induced IL-6 secretion. These data indicate that respiratory epithelial cells can respond to bacterial siderophores that evade or overwhelm Lcn2 binding by growing proinflammatory cytokine production.ue to its capability to assume a number of oxidative states, iron is definitely an necessary element in many human cellular processes, including DNA replication, oxygen metabolism, and electron transfer (1, two). Iron homeostasis represents a special challenge, because cost-free ferric iron (Fe3 ) is insoluble and ferrous iron (Fe2 ) might be toxic to cells.Buy1309982-17-9 As a result, ferric iron is transported while complexed to transferrin, keeping serum iron concentrations at 10 24 M (3?).PMID:23819239 Bacteria require ten 6 M iron in their cytosol for cellular processes, a a lot greater concentration of iron than is readily available (3). To obtain the iron required for growth in the ironlimiting circumstances from the human physique, Gram-negative pathogens for example Escherichia coli and Klebsiella pneumoniae secrete the siderophore enterobactin (Ent). Ent is usually a prototypical catecholate siderophore with the highest recognized affinity for iron (three, four, 6). To counter the iron-scavenging effects of Ent, neutrophils and host mucosal cells secrete lipocalin 2 (Lcn2; neutrophil gelatinaseassociated lipocalin [NGAL]; also known as siderocalin or 24p3) (7). Lcn2 binds Ent in its binding pocket, either in its ferric (FeEnt) or aferric type, thereby disrupting bacterial iron acquisition and inhibiting bacterial replication (7?0). Lcn2 is crucial for host defense, as Lcn2-deficient mice rapidly succumb to infection with E. coli and K. pneumoniae isolates that.