Neutrophil-attracting Chemokines Research Articles

PLAG ameliorates LPS-induced ALI by attenuation of neutrophil infiltration into alveolar via a prompt resolution of TLR4 signaling.

Abstract Acute lung injury (ALI) is an acute respiratory failure that is associated with excessive neutrophil recruitment into the bronchoalveolar space and results in severe mortality. To evaluate 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG) as a therapeutic agent for ALI, PLAG was administered orally to mice intranasally challenged with lipopolysaccharide (LPS). The excessive neutrophil infiltration in the bronchoalveolar lavage fluid (BALF) was detected in LPS-treated mice. Intranasally introduced LPS especially stimulates tissue-resident macrophages in the pulmonary tissue and induces neutrophil-attracting chemokine production such as MIP-2. Co-administrated PLAG dramatically ameliorated neutrophil infiltration into the bronchoalveolar region via modification of TLR4 signaling. We found that PLAG effectively accelerated endocytosis of LPS-TLR4 complex and promoted the NADPH oxidase activity through the formation of Rac, p47phox assembly into membrane for ROS production which results in elimination of exotoxin in Raw264.7 cells. PLAG also triggered a prompt TLR4 signals occurred in endosome mediated by TRIF and terminated signaling including MIP-2 expression when endocytosed exotoxin is cleared. Moreover, immunofluorescence microscopes of RAW264.7 cells showed that PLAG accelerated the endocytosis of the LPS-TLR4 complex and the clearance of the internalized LPS. Our results suggest that PLAG promotes the clearance of invaded exotoxin and eventually triggers an earlier termination of MIP-2 secretion in the exotoxin-cleared macrophages, and might be used as a potential therapeutic agent to prevent ALI through speedy resolution of exotoxin.

Intestinal Epithelial Cell-specific Deletion of α-Mannosidase II Ameliorates Experimental Colitis.

Inflammatory bowel disease (IBD) is a refractory disease of the gastrointestinal tract that is believed to develop in genetically susceptible individuals. Glycosylation, a type of post-translational modification, is involved in the development of a wide range of diseases, including IBD, by modulating the function of various glycoproteins. To identify novel genes contributing to the development of IBD, we analyzed single nucleotide polymorphisms (SNPs) of glycosylation-related genes in IBD patients and identified MAN2A1, encoding alpha-mannosidase II (α-MII), as a candidate gene. α-MII plays a crucial, but not exclusive, role in the maturation of N-glycans. We also observed that intestinal epithelial cells (IECs), which establish the first-line barrier and regulate gut immunity, selectively expressed α-MII with minimal expression of its isozyme, alpha-mannosidase IIx (α-MIIx). This led us to hypothesize that IEC-intrinsic α-MII is implicated in the pathogenesis of IBD. To test this hypothesis, we generated IEC-specific α-MII-deficient (α-MIIΔIEC) mice. Although α-MII deficiency has been shown to have a minimal effect on N-glycan maturation in most cell types due to the compensation by α-MIIx, ablation of α-MII impaired the maturation of N-glycans in IECs. α-MIIΔIEC mice were less susceptible to dextran sulfate sodium-induced colitis compared with control littermates. In accordance with this, neutrophil infiltration in the colonic mucosa was attenuated in α-MIIΔIEC mice. Furthermore, gene expression levels of neutrophil-attracting chemokines were downregulated in the colonic tissue. These results suggest that IEC-intrinsic α-MII promotes intestinal inflammation by facilitating chemokine expression. We propose SNPs in MAN2A1 as a novel genetic factor for IBD.Key words: inflammatory bowel disease, alpha-mannosidase II, intestinal epithelial cell, N-glycosylation.

Correction: Targeting Neutrophils to Prevent Malaria-Associated Acute Lung Injury/Acute Respiratory Distress Syndrome in Mice.

[This corrects the article DOI: 10.1371/journal.ppat.1006054.].

Immune-modulating Activity of Hydrogel Microparticles Contributes to the Host Defense in a Murine Model of Cutaneous Anthrax.

We recently reported that the open-mesh (0.7 μ) polyacrylamide microparticles (MPs) with internally-coupled Cibacron affinity dye demonstrate protective effect in mice challenged into footpads with high doses (200 LD50) of anthrax (Sterne) spores. A single injection of MPs before spore challenge reduces inflammatory response, delays onset of mortality and promotes survival. In this study, we show that the effect of MPs was substantially increased at the lower spore dose (7 LD50). The inflammation of footpads was reduced to the background level, and 60% of animals survived for 16 days while all untreated infected animals died within 6 days with strong inflammation. The effects of MPs were promoted when the MPs were loaded with a combination of neutrophil-attracting chemokines IL-8 and MIP-1α which delayed the onset of mortality in comparison with untreated mice for additional 8 days. The MPs were not inherently cytotoxic against the bacteria or cultured murine Raw 264.7 cells, but stimulated these cells to release G-CSF, MCP-1, MIP-1α, and TNF-α. Consistent with this finding the injection of MPs induced neutrophil influx into footpads, stimulated production of TNF-α associated with migration of pERK1/2-positive cells with the Langerhans phenotype from epidermis to regional lymph nodes. Our data support the mechanism of protection in which the immune defense induced by MPs along with the exogenous chemokines counterbalances the suppressive effect caused by anthrax infection.

Heme molecule functions as an endogenous agonist of astrocyte TLR2 to contribute to secondary brain damage after intracerebral hemorrhage

Toll-like receptor 2 (TLR2) was recently shown to contribute to secondary brain damage after intracerebral hemorrhage (ICH), although the molecular mechanisms of this contribution are elusive. In this study, we tested the hypothesis that hemin functions as a TLR2 endogenous agonist, causing proinflammatory astrocyte activation and secondary brain damage after ICH. Hemin administration to the mouse brain striatum induced ICH injury and neurological deficits, however, the brain injury volume and neurological deficits due to hemin injection were significantly reduced in TLR2 knock-out (KO) mice. Hemin administration induced neutrophil infiltration and upregulated neutrophil-attracting chemokine and proinflammatory cytokine expression in wild-type (WT) mice; these effects were ameliorated in TLR2 KO mice. Likewise, ICH-induced blood-brain barrier (BBB) damage was also decreased in TLR2 KO mice. This effect was most likely due to reduced matrix metalloproteinase 9 (MMP9) activity in the TLR2 KO mice compared to WT mice. In primary astrocytes, hemin directly induced MMP9 activity as well as proinflammatory cytokine and chemokine expression in a TLR2-dependent manner. Finally, hemin-induced MMP9 activity and proinflammatory gene expression were almost completely blocked by TLR2-neutralizing antibodies. Taken together, our data propose that heme released to the brain parenchyma after ICH injury activates TLR2 in astrocytes and induces inflammatory gene expression and BBB damage, which contribute to secondary brain damage after ICH.

Targeting Neutrophils to Prevent Malaria-Associated Acute Lung Injury/Acute Respiratory Distress Syndrome in Mice.

Malaria remains one of the greatest burdens to global health, causing nearly 500,000 deaths in 2014. When manifesting in the lungs, severe malaria causes acute lung injury/acute respiratory distress syndrome (ALI/ARDS). We have previously shown that a proportion of DBA/2 mice infected with Plasmodium berghei ANKA (PbA) develop ALI/ARDS and that these mice recapitulate various aspects of the human syndrome, such as pulmonary edema, hemorrhaging, pleural effusion and hypoxemia. Herein, we investigated the role of neutrophils in the pathogenesis of malaria-associated ALI/ARDS. Mice developing ALI/ARDS showed greater neutrophil accumulation in the lungs compared with mice that did not develop pulmonary complications. In addition, mice with ALI/ARDS produced more neutrophil-attracting chemokines, myeloperoxidase and reactive oxygen species. We also observed that the parasites Plasmodium falciparum and PbA induced the formation of neutrophil extracellular traps (NETs) ex vivo, which were associated with inflammation and tissue injury. The depletion of neutrophils, treatment with AMD3100 (a CXCR4 antagonist), Pulmozyme (human recombinant DNase) or Sivelestat (inhibitor of neutrophil elastase) decreased the development of malaria-associated ALI/ARDS and significantly increased mouse survival. This study implicates neutrophils and NETs in the genesis of experimentally induced malaria-associated ALI/ARDS and proposes a new therapeutic approach to improve the prognosis of severe malaria.

Chemokine-Releasing Microparticles Improve Bacterial Clearance and Survival of Anthrax Spore-Challenged Mice

In this study the hydrogel microparticles (MPs) were used to enhance migration of neutrophils in order to improve outcome of anthrax infection in a mouse model. Two MP formulations were tested. In the first one the polyacrylamide gel MPs were chemically coupled with Cibacron Blue (CB) affinity bait. In the second one the bait molecules within the MPs were additionally loaded with neutrophil-attracting chemokines (CKs), human CXCL8 and mouse CCL3. A non-covalent interaction of the bait with the CKs provided their gradual release after administration of the MPs to the host. Mice were challenged into footpads with Bacillus anthracis Sterne spores and given a dose of MPs a few hours before and/or after the spores. Pre-treatment with a single dose of CK-releasing MPs without any additional intervention was able to induce influx of neutrophils to the site of spore inoculation and regional lymph nodes correlating with reduced bacterial burden and decreased inflammatory response in footpads. On average, in two independent experiments, up to 53% of mice survived over 13 days. All control spore-challenged but MP-untreated mice died. The CB-coupled particles were also found to improve survival likely due to the capacity to stimulate release of endogenous CKs, but were less potent at decreasing the inflammatory host response than the CK-releasing MPs. The CK post-treatment did not improve survival compared to the untreated mice which died within 4 to 6 days with a strong inflammation of footpads, indicating quick dissemination of spores though the lymphatics after challenge. This is the first report on the enhanced innate host resistance to anthrax in response to CKs delivered and/or endogenously induced by the MPs.

Epithelial Cell-Derived Secreted and Transmembrane 1a Signals to Activated Neutrophils during Pneumococcal Pneumonia.

Airway epithelial cell responses are critical to the outcome of lung infection. In this study, we aimed to identify unique contributions of epithelial cells during lung infection. To differentiate genes induced selectively in epithelial cells during pneumonia, we compared genome-wide expression profiles from three sorted cell populations: epithelial cells from uninfected mouse lungs, epithelial cells from mouse lungs with pneumococcal pneumonia, and nonepithelial cells from those same infected lungs. Of 1,166 transcripts that were more abundant in epithelial cells from infected lungs compared with nonepithelial cells from the same lungs or from epithelial cells of uninfected lungs, 32 genes were identified as highly expressed secreted products. Especially strong signals included two related secreted and transmembrane (Sectm) 1 genes, Sectm1a and Sectm1b. Refinement of sorting strategies suggested that both Sectm1 products were induced predominantly in conducting airway epithelial cells. Sectm1 was induced during the early stages of pneumococcal pneumonia, and mutation of NF-κB RelA in epithelial cells did not diminish its expression. Instead, type I IFN signaling was necessary and sufficient for Sectm1 induction in lung epithelial cells, mediated by signal transducer and activator of transcription 1. For target cells, Sectm1a bound to myeloid cells preferentially, in particular Ly6G(bright)CD11b(bright) neutrophils in the infected lung. In contrast, Sectm1a did not bind to neutrophils from uninfected lungs. Sectm1a increased expression of the neutrophil-attracting chemokine CXCL2 by neutrophils from the infected lung. We propose that Sectm1a is an epithelial product that sustains a positive feedback loop amplifying neutrophilic inflammation during pneumococcal pneumonia.

IL-22 derived from γδ T cells restricts Staphylococcus aureus infection of mechanically injured skin

Staphylococcus aureus is an opportunistic pathogen that colonizes the skin of patients with atopic dermatitis (AD) and aggravates their disease. Neutrophils and the cytokines IL-17A and IL-17F, which drive the expression of the neutrophil-attracting chemokines, are important for the clearance of S aureus infection. The cytokine IL-22 is often coproduced by IL-17-secreting cells. The levels of IL-22 are elevated in AD skin lesions. We sought to determine the role of IL-22 in the clearance of S aureus infection of mouse skin subjected to tape stripping, a surrogate for scratching, a cardinal feature of AD. S aureus was applied to the tape-stripped skin of wild-type and Il22-/- mice. Bacterial burden was evaluated by enumerating colony-forming units. Quantitative PCR and ELISA were performed to quantify Il22 mRNA and IL-22 protein in mouse and human skin. Flow cytometry was used to enumerate neutrophils in the skin. Scratching the skin of healthy adults and tape stripping of mouse skin induced local expression of Il22 mRNA and IL-22 protein. Induction of Il22 expression by tape stripping was dependent on IL-23 and γδ Tcells. Clearance of S aureus from tape-stripped skin was significantly impaired in Il22-/- mice. Neutrophil infiltration and upregulation of expression of genes encoding the antimicrobial peptides antigen-6/urokinase-type plasminogen activator receptor related protein-1 and β-DEFENSIN 14 and the chemokine (C-X-C motif) ligand following tape stripping were significantly impaired in Il22-/- mice. These findings show that IL-22 is important for limiting the growth of S aureus on mechanically injured skin and caution that IL-23 and IL-22 blockade in patients with ADmay enhance susceptibility to staphylococcal skin infection.

NKT cells mediate the recruitment of neutrophils by stimulating epithelial chemokine secretion during colitis

Ulcerative colitis (UC) is a kind of inflammatory bowel diseases characterized by chronic inflammation and ulcer in colon, and UC patients have increased risk of getting colorectal cancer. NKT cells are cells that express both NK cell markers and semi-invariant CD1d-restricted TCRs, can regulate immune responses via secreting a variety of cytokines upon activation. In our research, we found that the NKT cell-deficient CD1d−/− mice had relieved colitis in the DSS-induced colitis model. Further investigations revealed that the colon of CD1d−/− mice expressed less neutrophil-attracting chemokine CXCL 1, 2 and 3, and had decreased neutrophil infiltration. Infiltrated neutrophils also produced less reactive oxygen species (ROS) and TNF-α, indicating they may cause less epithelial damage. In addition, colitis-associated colorectal cancer was also relieved in CD1d−/− mice. During colitis, NKT cells strongly expressed TNF-α, which could stimulate CXCL 1, 2, 3 expressions by the epithelium. In conclusion, NKT cells can regulate colitis via the NKT cell-epithelium-neutrophil axis. Targeting this mechanism may help to improve the therapy of UC and prevent colitis-associated colorectal cancer.

IL-17F Promotes Tissue Injury in Autoimmune Kidney Diseases.

The TH17 immune response has a central role in the pathogenesis of autoimmune diseases, implicating the TH17 master cytokine, IL-17A, as the critical mediator of diseases such as human and experimental crescentic GN. However, the relative importance of additional TH17 effector cytokines, including IL-17F, in immune-mediated tissue injury remains to be fully elucidated. Here, using a mouse model of acute crescentic GN (nephrotoxic nephritis), we identified CD4+ T cells and γδ T cells as the major cellular source of IL-17F in the inflamed kidney. Interventional studies using IL-17F gene-deficient mice, IL-17F-neutralizing antibodies, and adoptive transfer experiments into Rag1-/- mice demonstrated that CD4+ T cell-derived IL-17F drives renal tissue injury in acute crescentic GN. Notably, IL-17F-deficient nephritic mice had fewer renal infiltrating neutrophils than wild-type nephritic mice, and neutrophil depletion did not affect the course of GN in IL-17F-deficient mice. Moreover, in the chronic model of pristane-induced SLE, IL-17F-deficient mice developed less severe disease than wild-type mice, with respect to survival and renal injury. Finally, we show that IL-17F induced expression of the neutrophil-attracting chemokines CXCL1 and CXCL5 in kidney cells. The finding that IL-17F has a nonredundant function in the development of renal tissue injury in experimental GN might be of great importance for the development of anti-IL-17 cytokine therapies in TH17-mediated human autoimmune diseases.

Neutrophil recruitment by allergens contribute to allergic sensitization and allergic inflammation.

To discuss the presence and role of neutrophils in asthma and allergic diseases, and outline the importance of pollen and cat dander-induced innate neutrophil recruitment in induction of allergic sensitization and allergic inflammation. Uncontrolled asthma is associated with elevated numbers of neutrophils, and levels of neutrophil-attracting chemokine IL-8 and IL-17 in bronchoalveolar lavage fluids. These parameters negatively correlate with lung function. Pollen allergens and cat dander recruit neutrophils to the airways in a toll-like receptor 4, myeloid differentiation protein-2, and chemokine (C-X-C motif) receptor (CXCR) 2-dependent manner. Repeated recruitment of activated neutrophils by these allergens facilitates allergic sensitization and airway inflammation. Inhibition of neutrophil recruitment with CXCR2 inhibitor, disruption of toll-like receptor 4, or small interfering RNA against myeloid differentiation protein-2 also inhibits allergic inflammation. The molecular mechanisms by which innately recruited neutrophils contribute to shifting the airway inflammatory response induced by allergens from neutrophilic to an eosinophilic-allergic is an area of active research. Recent studies have revealed that neutrophil recruitment is important in the development of allergic sensitization and inflammation. Inhibition of neutrophils recruitment may be a strategy to control allergic inflammation.

The Mechanism of Type I Interferon-Mediated Polarization of Tumor-Associated Neutrophils in Mice and Human

Neutrophils are the most abundant cells of all white blood cells and play a key role in host inflammatory responses. Importantly, inflammation has been associated with increased susceptibility for cancer and neutrophils, as a crucial component of this process, play essential role in inflammation-driven tumorigenesis. Neutrophils also represent an independent prognostic marker in a broad variety of neoplasias. The tumor microenvironment represents a special niche that is extremely influencing infiltrating immune cells. The concept of immune cell polarization was first described for macrophages (anti-tumor M1/pro-tumor M2). Recently neutrophil polarization has been postulated. Neutrophils appear to have diverse phenotypes in the tumor microenvironment i.e. tumor promoting (N2) or inhibiting (N1).Previously, we could show that significantly elevated numbers of neutrophils accumulate in tumors of mice that lack endogenous type I IFNs (Ifnb1-/-). Such tumor associated neutrophils (TANs) do not only efficiently support tumor angiogenesis and growth by up-regulating pro-angiogenic molecules (VEGF and MMP9), but also secrete higher amounts of neutrophil-attracting chemokines and display prolonged survival, compared to their WT counterparts thus representing pro-tumor N2 phenotype. Moreover, we could show that these N2 neutrophils efficiently support metastatic processes, due to up-regulation of pro-metastatic proteins, like Bv8, MMP9, S100A8 and S100A9, and due to impaired tumor cell killing. Treatment of such cells with rmIFNb reversed such an effect leading to anti-tumor N1 polarization.Here, we add further evidence emphasizing the importance of type I IFNs for neutrophil polarization in tumor microenvironment and reveal possible mechanism responsible for this phenomenon. In Ifnb1-/- mice, we observe a significant down-regulation of anti-tumor neutrophil markers, like ICAM1 and TNF-α. Moreover, neutrophils show reduced formation of NETs, accompanied by lower tumor killing capacity. Under these conditions, massively enhanced neutrophil turnover in combination with accumulation of immature neutrophils is observed. Importantly, therapeutic intervention in both Ifnb1-/- and WT mice using low dose IFN-β, induced anti-tumor activation of neutrophils. Correspondingly, in human melanoma patients undergoing type I IFN therapy, neutrophil anti-tumor characteristics were augmented, compared to untreated patients, suggesting effective outcome of this therapy.Further, we evaluated the mechanism of prolonged neutrophil survival in the absence of endogenous IFN-β. Importantly, we found that G-CSF mRNA expression levels in Ifnb1-/- neutrophils from different anatomical compartments as well as G-CSF blood serum levels were markedly up-regulated in such mice. G-CSF-expression levels were strongly reduced when the Ifnb1-/- neutrophils were incubated with rmIFN-β suggesting involvement of type I interferons in G-CSF down-regulation. Notably, we could recently show that G-CSF induces synthesis of enzyme Nicotinamide phosphoribosyltransferase (NAMPT), which is a rate-limiting enzyme converting nicotinamide (NA) into NAD+ that in turn activates NAD+ -dependent protein deacetylases sirtuins (SIRTs). NAMPT serves as an inhibitor of neutrophil apoptosis and as neutrophil chemoattractant by upregulation of CXCL8. It is a potent pro-inflammatory factor (upregulation of ROS release) and pro-angiogenic factor (smooth muscle maturation). At the same time, NAMPT was found to be strongly overexpressed in tumors and serum of leukemia patients. Analysis of NAMPT and SIRTs levels in tumor bearing Ifnb1-/- mice revealed highly upregulated levels of NAMPT and SIRT1 in blood neutrophils of these animals, in comparison to WT mice, which was in line with elevated levels of G-CSF. It also correlates with enhanced tumor angiogenesis, growth and metastasis. Based on these observations, we identified a new mechanism of interferon-mediated activation of pro-tumor neutrophils. Since tumor associated neutrophils represent a highly potent therapeutic target, these data highlight the therapeutic potential of interferons and NAMPT inhibitors, suggesting optimization of their clinical use as potent anti-tumor agent. DisclosuresNo relevant conflicts of interest to declare.

Matrix metalloproteinases contribute to the regulation of chemokine expression and pulmonary inflammation in Cryptococcus infection.

Matrix metalloproteinases (MMPs) are a family of extracellular proteases that play roles in regulating the immune response in inflammatory processes. Previous studies indicated that different MMPs were involved in the host defence and tissue damage in response to different pathogens. However, the contributions of MMPs during Cryptococcus infection have not been addressed clearly. Here, we examined the expression and activity of MMPs during Cryptococcus infection. Among MMP family members, we found significant increases of MMP-3 and MMP-12 mRNA levels and MMP12 zymographic activities in response to C. neoformans but not C. gattii infection. The expression of MMP12 was induced in RAW cells after C. neoformans treatment and in alveolar macrophages purified from C. neoformans-infected mice. Interestingly, administration of MMP inhibitor GM6001 into C. neoformans-infected mice resulted in a significantly increased pulmonary fungal burden with attenuated inflammatory cell infiltration. Corresponding to this finding, the expression of the macrophage- and neutrophil-attracting chemokines CCL2 and CXCL1 was inhibited in the GM6001-treated group and MMP12 levels were found to be correlated strongly with CCL2 mRNA expression. Thus, our data suggest that the induction of MMPs by C. neoformans infection potentiates inflammatory cell infiltration by modulating pulmonary chemokines, thereby promoting effective host immunity to pulmonary Cryptococcus infection.

Redox Stimulation of Human THP-1 Monocytes in Response to Cold Physical Plasma.

In plasma medicine, cold physical plasma delivers a delicate mixture of reactive components to cells and tissues. Recent studies suggested a beneficial role of cold plasma in wound healing. Yet, the biological processes related to the redox modulation via plasma are not fully understood. We here used the monocytic cell line THP-1 as a model to test their response to cold plasma in vitro. Intriguingly, short term plasma treatment stimulated cell growth. Longer exposure only modestly compromised cell viability but apparently supported the growth of cells that were enlarged in size and that showed enhanced metabolic activity. A significantly increased mitochondrial content in plasma treated cells supported this notion. On THP-1 cell proteome level, we identified an increase of protein translation with key regulatory proteins being involved in redox regulation (hypoxia inducible factor 2α), differentiation (retinoic acid signaling and interferon inducible factors), and cell growth (Yin Yang 1). Regulation of inflammation is a key element in many chronic diseases, and we found a significantly increased expression of the anti-inflammatory heme oxygenase 1 (HMOX1) and of the neutrophil attractant chemokine interleukin-8 (IL-8). Together, these results foster the view that cold physical plasma modulates the redox balance and inflammatory processes in wound related cells.

Endothelial CD36 Contributes to Postischemic Brain Injury by Promoting Neutrophil Activation via CSF3.

Ischemic stroke is a leading cause of death and disability worldwide with limited therapeutic options. The inflammatory response initiated by cerebral ischemia-reperfusion contributes to ischemic brain injury and is a potential therapeutic target. Here we report that CD36, an innate immunity receptor involved in the initiation of postischemic inflammation, is a previously unrecognized regulator of neutrophil cytotoxicity. The effect is mediated by endothelial CD36 via upregulation of the neutrophil activator CSF3 in cerebral endothelial cells. Therefore, approaches to modulate cerebral endothelial CD36 signaling or to neutralize CSF3 may provide novel therapeutic opportunities to ameliorate postischemic inflammatory injury.

Dendritic cell immunoreceptor 1 alters neutrophil responses in the development of experimental colitis

BackgroundUlcerative colitis, an inflammatory bowel disease, is associated with the massive infiltration of neutrophils. Although the initial infiltration of neutrophils is beneficial for killing bacteria, it is presumed that persistent infiltration causes tissue damage by releasing antibacterial products as well as inflammatory cytokines. A murine C-type lectin receptor, dendritic cell immunoreceptor 1 (Dcir1), is expressed on CD11b+ myeloid cells, such as macrophages, dendritic cells and neutrophils. It was reported that Dcir1 is required to maintain homeostasis of the immune system to prevent autoimmunity, but it is also involved in the development of infectious disease resulting in the enhanced severity of cerebral malaria. However, the role of Dcir1 in intestinal immune responses during colitis remains unclear. In this study, we investigated the role of Dcir1 in intestinal inflammation using an experimental colitis model induced with dextran sodium sulfate (DSS).ResultsIn contrast to wild type (WT) mice, Dcir1−/− mice exhibited mild body weight loss during the course of DSS colitis accompanied by reduced colonic inflammation. Dcir1 deficiency caused a reduced accumulation of neutrophils in the inflamed colon on day 5 of DSS colitis compared with WT mice. Consistently, the production of a neutrophil-attracting chemokine, MIP-2, was also decreased in the Dcir1−/− colon compared with the WT colon on day 5. There were fewer myeloperoxidase-positive neutrophils in the inflamed colon of Dcir1−/− mice than in that of WT mice. Moreover, bone marrow neutrophils from Dcir1−/− mice produced less reactive oxygen species (ROS) by lipopolysaccharide stimulation than those from WT mice. This suggests that Dcir1 deficiency decreases the accumulation of tissue destructive neutrophils during DSS colitis.ConclusionDcir1 enhances the pathogenesis of DSS colitis by altering neutrophil recruitment and their functions.

Sex differences in the expression of lung inflammatory mediators in response to ozone.

Sex differences in the incidence of respiratory diseases have been reported. Women are more susceptible to inflammatory lung disease induced by air pollution and show worse adverse pulmonary health outcomes than men. However, the mechanisms underlying these differences remain unknown. In the present study, we hypothesized that sex differences in the expression of lung inflammatory mediators affect sex-specific immune responses to environmental toxicants. We focused on the effects of ground-level ozone, a major air pollutant, in the expression and regulation of lung immunity genes. We exposed adult male and female mice to 2 ppm of ozone or filtered air (control) for 3 h. We compared mRNA levels of 84 inflammatory genes in lungs harvested 4 h postexposure using a PCR array. We also evaluated changes in lung histology and bronchoalveolar lavage fluid cell counts and protein content at 24 and 72 h postexposure. Our results revealed sex differences in lung inflammation triggered by ozone exposure and in the expression of genes involved in acute phase and inflammatory responses. Major sex differences were found in the expression of neutrophil-attracting chemokines (Ccl20, Cxcl5, and Cxcl2), the proinflammatory cytokine interleukin-6, and oxidative stress-related enzymes (Ptgs2, Nos2). In addition, the phosphorylation of STAT3, known to mediate IL-6-related immune responses, was significantly higher in ozone-exposed mice. Together, our observations suggest that a differential regulation of the lung immune response could be implicated in the observed increased susceptibility to adverse health effects from ozone observed in women vs. men.

Increased neutrophil infiltration, IL-1 production and a SAPHO syndrome-like phenotype in PSTPIP2-deficient mice.

Proline-serine-threonine-phosphatase-interacting protein 2 (PSTPIP2) is involved in macrophage activation, neutrophil motility and osteoclast differentiation. However, the role of PSTPIP2 in inflammation and autoinflammatory diseases is still not clear. In this study, we generated PSTPIP2 knockout (Pstpip2(-/-)) mice to investigate its phenotype and role in autoinflammatory diseases. We constructed a Pstpip2-targeting vector and generated Pstpip2(-/-) mice. The phenotype and immunopathology of Pstpip2(-/-) mice were analysed. All Pstpip2(-/-) mice developed paw swelling, synovitis, hyperostosis and osteitis, resembling SAPHO syndrome, an inflammatory disorder of the bone, skin and joints. Multifocal osteomyelitis was found in inflamed paws, with increased macrophage and marked neutrophil infiltrations in the bone, joint and skin. Profound osteolytic lesions with markedly decreased bone volume density developed in paws and limbs. Neutrophil-attracting chemokines and IL-1β were markedly elevated in inflamed tissues. Our study suggests that PSTPIP2 could play a role in innate immunity and development of autoinflammatory bone disorders, and may be associated with the pathogenesis of human SAPHO syndrome.

Blocking cold-inducible RNA-binding protein protects liver from ischemia-reperfusion injury.

Cold-inducible RNA-binding protein (CIRP) is a nuclear protein that has been recently identified as a novel inflammatory mediator in hemorrhagic shock and sepsis. We hypothesized that CIRP acts as a potent inflammatory mediator in hepatic ischemia-reperfusion (I/R), and thus blocking CIRP protects against I/R-induced liver injury. Male C57BL/6 mice were subjected to 70% hepatic ischemia by microvascular clamping of the hilum of the left and median liver lobes for 60 min, followed by reperfusion. Anti-CIRP antibody (1 mg/kg body weight) or vehicle (normal saline) in 0.2 mL was injected via the internal jugular vein at the beginning of the reperfusion. Blood and liver tissues were collected 24 h after I/R for various measurements, and a 10-day survival study was performed. Cold-inducible RNA-binding protein released into the circulation was significantly increased 24 h after hepatic I/R. Anti-CIRP antibody treatment markedly reduced hepatocellular damage markers and significantly improved the liver microarchitecture. Anti-CIRP also reduced the systemic and local inflammation demonstrated by attenuation in both serum and hepatic levels of interleukin 6. The expression of neutrophil-attracting chemokine as well as liver neutrophil infiltration was reduced by anti-CIRP treatment. Anti-CIRP also dramatically decreased the amount of apoptosis and nitrosative stress, evidenced by decrease in TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) staining and inducible nitric oxide synthase and cyclooxygenase 2 levels, respectively. Finally, the 10-day survival rate was increased from 37.5% in the vehicle group to 75% in the anti-CIRP treatment group. Thus, targeting CIRP offers potential therapeutic implications in the treatment of hepatic I/R injury.