Macrophages and is upregulated during infection and inflammation (43). IL-6 is also a differentiation factor for Th17 lymphocytes that mediate protective immunity against siderophore-producing pathogens, for instance K. pneumoniae (44). In turn, CCL20 is usually a lymphocyte chemoattractant whose expression is amplified by IL-6 production, recruiting Th17 cells to web pages of inflammation by binding to its cognate receptor, CCR6. As a result, it is actually achievable that expression of CCL20 initiates an adaptive immune response (45?7). Lcn2-induced cytokines also are induced in response to disruptions in iron homeostasis. Iron chelation by DFO induces IL-iai.asm.orgInfection and ImmunitySiderophores with Lcn2 Induce Cytokine SecretionFIG six Ent stabilizes HIF-1 in A549 respiratory epithelial cells, that is sufficient to improve Lcn2-dependent IL-6 secretion. Cells had been stimulated for 16 h with p38α supplier combinations of 50 M Ent, three mM DMOG, or 25 M Lcn2, and Western blotting or ELISA was made use of to measure HIF-1 stabilization (A, B, and C), IL-8 secretion (D), or IL-6 secretion (E). Western blot information are representative of two independent experiments. ELISA values shown are indicates SEM from three replicate samples and are representative of a minimum of 2 independent experiments. Statistics have been calculated working with unpaired two-tailed t tests (, P 0.01; ns, P 0.05).and CCL20 production in intestinal epithelial cells (17, 48). In respiratory epithelial cells, the combination of siderophores and Lcn2 induces robust expression of IL-6 and CCL20. Thus, the cytokine response to bacterial siderophores and Lcn2 could serve as a multifaceted failsafe mechanism. Initially, IL-8 can recruit neutrophils to the site of infection. Second, IL-6 can upregulate hepcidin to limit additional iron availability for invading bacteria. Ultimately, IL-6 and CCL20 can act in concert to attract mature Th17 to web sites of infection and commit naive T cells towards the Th17 pathway. The presence or absence of siderophores probably is crucial towards the impact of Lcn2 on inflammation. In recent operate, stimulation of macrophages with Streptococcus pneumoniae induced IL-10 production in an Lcn2-dependent manner, which skewed macrophages toward a deactivated phenotype (49). In human and animal models, elevated Lcn2 correlated with worsening of pneumococcal pneumonia. These findings contrast with all the results of this perform, which demonstrate proinflammatory effects ofLcn2, and preceding operate by our group and others, TLR3 site demonstrating that Lcn2 is often a essential antimicrobial peptide that enhances survival through infection, particularly with K. pneumoniae (7, 8, 11, 13). In addition, our microarray analysis didn’t indicate any change in the gene expression of IL-10 in response to Lcn2. We hypothesize that the difference in outcome is since Streptococcus pneumoniae will not demand siderophores for its pathogenesis, and Lcn2 cannot correctly modulate inflammation through infection without siderophore-mediated iron chelation. In reality, patient survival from Gram-negative pneumonia correlated with improved Lcn2 within the bronchoalveolar lavage fluid (49). Iron homeostasis and metabolism are tightly regulated systems that require the expression and function of lots of proteins, like transferrin, transferrin receptor, and ferritin. Disruption of those systems as a consequence of iron chelation exerts a wide array of pathological effects on cells, like disruption of DNA replication, apoptosis, and cell cycle arrest (33, 50, 51). While these properties of iron chelators s.
