Summary
Granules are essential for the ability of neutrophils to fulfill their role in innate immunity. Granule membranes contain proteins that react to environmental cues directing neutrophils to ...sites of infection and initiate generation of bactericidal oxygen species. Granules are densely packed with proteins that contribute to microbial killing when liberated to the phagosome or extracellularly. Granules are, however, highly heterogeneous and are traditionally subdivided into azurophil granules, specific granules, and gelatinase granules in addition to secretory vesicles. This review will address issues pertinent to formation of granules, which is a process intimately connected to maturation of neutrophils from their precursors in the bone marrow. We further discuss possible mechanisms by which decisions are made regarding sorting of proteins to constitutive secretion or storage in granules and how degranulation of granule subsets is regulated.
Full text
Available for:
BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
Lipocalin‐2 (LCN2) was originally isolated from human neutrophils and termed neutrophil gelatinase‐associated lipocalin (NGAL). However, the functions of LCN2 and the cell types that are primarily ...responsible for LCN2 production remain unclear. To address these issues, hepatocyte‐specific Lcn2 knockout (Lcn2Hep–/–) mice were generated and subjected to bacterial infection (with Klesbsiella pneumoniae or Escherichia coli) or partial hepatectomy (PHx). Studies of Lcn2Hep–/– mice revealed that hepatocytes contributed to 25% of the low basal serum level of LCN2 protein (∼62 ng/mL) but were responsible for more than 90% of the highly elevated serum LCN2 protein level (∼6,000 ng/mL) postinfection and more than 60% post‐PHx (∼700 ng/mL). Interestingly, both Lcn2Hep–/– and global Lcn2 knockout (Lcn2–/–) mice demonstrated comparable increases in susceptibility to infection with K. pneumoniae or E. coli. These mice also had increased enteric bacterial translocation from the gut to the mesenteric lymph nodes and exhibited reduced liver regeneration after PHx. Treatment with interleukin (IL)‐6 stimulated hepatocytes to produce LCN2 in vitro and in vivo. Hepatocyte‐specific ablation of the IL‐6 receptor or Stat3, a major downstream effector of IL‐6, markedly abrogated LCN2 elevation in vivo. Furthermore, chromatin immunoprecipitation (ChIP) assay revealed that STAT3 was recruited to the promoter region of the Lcn2 gene upon STAT3 activation by IL‐6. Conclusion: Hepatocytes are the major cell type responsible for LCN2 production after bacterial infection or PHx, and this response is dependent on IL‐6 activation of the STAT3 signaling pathway. Thus, hepatocyte‐derived LCN2 plays an important role in inhibiting bacterial infection and promoting liver regeneration. (Hepatology 2015;61:692‐702)
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Neutrophil gelatinase-associated lipocalin (NGAL) is a siderophore-binding antimicrobial protein that is up-regulated in epithelial tissues during inflammation. We demonstrated previously that the ...gene encoding NGAL (LCN2) is strongly up-regulated by interleukin (IL)-1β in an NF-κB-dependent manner but not by tumor necrosis factor (TNF)-α, another potent activator of NF-κB. This is due to an IL-1β-specific synthesis of the NF-κB-binding co-factor IκB-ζ, which is essential for NGAL induction. We demonstrate here that NGAL is strongly induced by stimulation with TNF-α in the presence of IL-17, a pro-inflammatory cytokine produced by the newly discovered subset of CD4+ T helper cells, TH-17. In contrast to the murine NGAL orthologue, 24p3/lipocalin 2, we found no requirement for C/EBP-β or C/EBP-δ for NGAL induction by IL-17 and TNF-α as neither small interfering RNAs against the two C/EBP mRNAs nor mutation of the C/EBP sites in the LCN2 promoter abolished IL-17- and TNF-α-induced up-regulation of NGAL. NGAL induction is governed solely by NF-κB and its co-factor IκB-ζ. This was demonstrated by a pronounced reduction in the amount of NGAL mRNA and NGAL protein synthesized in cells treated with small interfering RNA against IκB-ζ and a total lack of activation of an LCN2 promoter construct with a mutated NF-κB site. As IL-17 stimulation stabilizes the IκB-ζ transcript, we propose a model where TNF-α induces activation and binding of NF-κB to the promoters of both NFKBIZ and LCN2 genes but induce only transcription of IκB-ζ. Co-stimulation with IL-17 leads to accumulation of IκB-ζ mRNA and IκB-ζ protein, which can bind to NF-κB on the LCN2 promoter and thus induce NGAL expression.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In addition to acting as a physical barrier against microorganisms, the skin produces antimicrobial peptides and proteins. After wounding, growth factors are produced to stimulate the regeneration of ...tissue. The growth factor response ceases after regeneration of the tissue, when the physical barrier protecting against microbial infections is re-established. We found that the growth factors important in wound healing, insulin-like growth factor I and TGF-alpha, induce the expression of the antimicrobial peptides/polypeptides human cationic antimicrobial protein hCAP-18/LL-37, human beta-defensin 3, neutrophil gelatinase-associated lipocalin, and secretory leukocyte protease inhibitor in human keratinocytes. Both an individual and a synergistic effect of these growth factors were observed. These findings offer an explanation for the expression of these peptides/polypeptides in the skin disease psoriasis and in wound healing and define a host defense role for growth factors in wound healing.
NGAL (neutrophil gelatinase-associated lipocalin) also known as lcn2 or siderochalin is constitutively expressed in myelocytes and stored in specific granules of neutrophils. It is highly induced in ...a variety of epithelial cells during inflammation. Analysis of the crystal structure of NGAL expressed in E.coli showed that NGAL has the ability to bind catecholate type siderophores and in this way prevent bacteria from acquisition of siderophore-bound iron. NGAL (or 24p3 as the highly homologous murine orthologue is named) knock out mice have a profound defect in defense against E.coli after intraperitoneal injection. This defect can be mimicked in wild-type mice by providing siderophore iron, which cannot be sequestered by NGAL, testifying to the specific role of NGAL as a siderophore binding protein in innate immunity. Megalin, a scavenger receptor functions as a receptor for NGAL and mediates uptake into endosomes, but other NGAL receptors are likely to exist.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Lipocalin 2 is a bacteriostatic protein that binds the siderophore enterobactin, an iron-chelating molecule produced by Escherichia coli (E. coli) that is required for bacterial growth. Infection of ...the lungs by E. coli is rare despite a frequent exposure to this commensal bacterium. Lipocalin 2 is an effector molecule of the innate immune system and could therefore play a role in hindering growth of E. coli in the lungs.
Lipocalin 2 knock-out and wild type mice were infected with two strains of E. coli. The lungs were removed 48 hours post-infection and examined for lipocalin 2 and MMP9 (a myeloid marker protein) by immunohistochemical staining and western blotting. Bacterial numbers were assessed in the lungs of the mice at 2 and 5 days after infection and mortality of the mice was monitored over a five-day period. The effect of administering ferrichrome (an iron source that cannot be bound by lipocalin 2) along with E.coli was also examined.
Intratracheal installation of E. coli in mice resulted in strong induction of lipocalin 2 expression in bronchial epithelium and alveolar type II pneumocytes. Migration of myeloid cells to the site of infection also contributed to an increased lipocalin 2 level in the lungs. Significant higher bacterial numbers were observed in the lungs of lipocalin 2 knock-out mice on days 2 and 5 after infection with E. coli (p < 0.05). In addition, a higher number of E. coli was found in the spleen of surviving lipocalin 2 knock-out mice on day 5 post-infection than in the corresponding wild-type mice (p < 0.05). The protective effect against E. coli infection in wild type mice could be counteracted by the siderophore ferrichrome, indicating that the protective effect of lipocalin 2 depends on its ability to sequester iron.
Lipocalin 2 is important for protection of airways against infection by E. coli.
Full text
Available for:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
MicroRNAs and cancer COWLAND, JACK B.; HOTHER, CHRISTOFFER; GRØNBÆK, KIRSTEN
APMIS : acta pathologica, microbiologica et immunologica Scandinavica,
10/2007, Volume:
115, Issue:
10
Journal Article
Peer reviewed
Open access
MicroRNAs (miRNAs) are a recently discovered group of small RNA molecules involved in the regulation of gene expression. Analogously to mRNAs, the non‐protein‐encoding pri‐miRNAs are synthesized by ...RNA polymerase II and post‐transcriptionally modified by addition of a 5′‐cap and a 3′‐poly (A) tail. Subsequently, the pri‐miRNA undergoes a number of processing steps in the nucleus and cytoplasm, and ends up as a mature ∼22 nt miRNA, which can exert its function by binding to the 3′‐untranslated region of a subset of mRNAs. Binding of the miRNA to the mRNA results in a reduced translation rate and/or increased degradation of the mRNA. In this way a large number of cellular pathways, such as cellular proliferation, differentiation, and apoptosis, are regulated by mi‐RNAs. As corruption of these pathways is the hallmark of many cancers, dysregulation of miRNA biogenesis or expression levels may lead to tumorigenesis. The mechanisms that alter the expression of miRNAs are similar to those that change the expression levels of mRNAs of tumor suppressor‐ and oncogenes, i.e. gross genomic aberrations, epigenetic changes, and minor mutations affecting the expression level, processing, or target‐interaction potential of the miRNA. Furthermore, expression profiling of miRNAs has been found to be useful for classification of different tumor types. Taken together, miRNAs can be classified as onco‐miRs or tumor suppressor‐miRs, and may turn out to be potential targets for cancer therapy.
Full text
Available for:
BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
Abstract
Neutrophil gelatinase-associated lipocalin (NGAL) is a siderophore-binding protein that exerts a bacteriostatic effect by sequestering iron. Strong induction of NGAL synthesis has been ...observed in inflamed epithelium of the lungs and colon. Expression of NGAL is up-regulated in the lung epithelial cell line A549 by IL-1β, but not by TNF-α, despite an induction of NF-κB binding to the NGAL promoter by both cytokines. In this study, we present evidence that the IL-1β specificity is caused by a requirement of the NGAL promoter for the NF-κB-binding cofactor IκB-ζ for transcriptional activation. Up-regulation of NGAL expression in A549 cells following IL-1β stimulation was dependent on de novo protein synthesis and was greatly diminished by a small interfering against IκB-ζ mRNA. Cotransfection of A549 cells with a plasmid expressing IκB-ζ made TNF-α capable of inducing NGAL transcription, indicating that IκB-ζ induction is the only factor discriminating between IL-1β and TNF-α in their ability to induce NGAL expression. Coexpression of the cofactor Bcl-3, which is closely related to IκB-ζ, did not enable TNF-α to induce NGAL transcription. A functional NF-κB site of the NGAL promoter was required for IκB-ζ to exert its effect. The human β defensin 2 gene also required IκB-ζ for its IL-1β-specific induction in A549 cells. Our findings indicate that a common regulatory mechanism has evolved to control expression of a subset of antimicrobial proteins expressed in epithelial cells.
PDF
