The development of adhesions in the peritoneal and pelvic cavities, which commonly form after surgery or infection, cause significant morbidity and mortality. However, the pathogenesis of adhesion formation is still poorly understood. Because T cells are important in orchestrating fibrinogenic tissue disorders, we hypothesized that they play a critical role in the pathogenesis of peritoneal adhesion formation. Using a cecal abrasion surgical model in rodents, T cell depletion and adoptive transfer experiments demonstrated that this host response is dependent on CD4+ alphabeta T cells. These cells were also critical to adhesion formation associated with experimental intraabdominal sepsis. T cell transfer studies with mice deficient in signal transducer and activator of transcription (Stat)4 and Stat6 revealed that adhesion formation was dependent on a T helper 1 response. Activated T cells homed to the peritoneal cavity 6 hours after cecal abrasion surgery and predominated at this site during adhesiogenesis. Increased levels of the T cell-derived proinflammatory cytokine interleukin (IL)-17 and of neutrophil chemoattractant CXC chemokines macrophage inflammatory protein-2/CXCL8 and cytokine-induced neutrophil chemoattractant/CXCL1 were associated with adhesion formation. The production of these chemokines was dependent on T cells. Furthermore, the administration of neutralizing antibodies specific for IL-17 or the receptor that binds these CXC chemokines, CXC chemokine receptor 2, significantly reduced the degree of adhesion formation. These results demonstrate for the first time that the immunopathogenesis of adhesion formation is under the control of T cells and that T cell-derived cytokines and chemokines play important roles in the development of this deleterious host response.

OBJECTIVE

Eosinophils reside in the colonic mucosa and increase significantly during disease. Although a number of studies have suggested that eosinophils contribute to the pathogenesis of GI inflammation, the expanding scope of eosinophil-mediated activities indicate that they also regulate local immune responses and modulate tissue inflammation. We sought to define the impact of eosinophils that respond to acute phases of colitis in mice.

METHODS

Acute colitis was induced in mice by administration of dextran sulfate sodium, 2,4,6-trinitrobenzenesulfonic acid or oxazolone to C57BL/6J (control) or eosinophil deficient (PHIL) mice. Eosinophils were also depleted from mice using antibodies against interleukin (IL)-5 or by grafting bone marrow from PHIL mice into control mice. Colon tissues were collected and analysed by immunohistochemistry, flow cytometry and reverse transcription PCR; lipids were analysed by mass spectroscopy.

RESULTS

Eosinophil-deficient mice developed significantly more severe colitis, and their colon tissues contained a greater number of neutrophils, than controls. This compensatory increase in neutrophils was accompanied by increased levels of the chemokines CXCL1 and CXCL2, which attract neutrophils. Lipidomic analyses of colonic tissue from eosinophil-deficient mice identified a deficiency in the docosahexaenoic acid-derived anti-inflammatory mediator 10, 17- dihydroxydocosahexaenoic acid (diHDoHE), namely protectin D1 (PD1). Administration of an exogenous PD1-isomer (10S, 17S-DiHDoHE) reduced the severity of colitis in eosinophil-deficient mice. The PD1-isomer also attenuated neutrophil infiltration and reduced levels of tumour necrosis factor-α, IL-1β, IL-6 and inducible NO-synthase in colons of mice. Finally, in vitro assays identified a direct inhibitory effect of PD1-isomer on neutrophil transepithelial migration.

CONCLUSIONS

Eosinophils exert a protective effect in acute mouse colitis, via production of anti-inflammatory lipid mediators.

Neuropathic pain resulting from damage or dysfunction of the nervous system is a highly debilitating chronic pain state and is often resistant to currently available treatments. It has become clear that neuroinflammation, mainly mediated by proinflammatory cytokines and chemokines, plays an important role in the establishment and maintenance of neuropathic pain. Chemokines were originally identified as regulators of peripheral immune cell trafficking and were also expressed in neurons and glial cells in the central nervous system. In recent years, accumulating studies have revealed the expression, distribution and function of chemokines in the spinal cord under chronic pain conditions. In this review, we provide evidence showing that several chemokines are upregulated after peripheral nerve injury and contribute to the pathogenesis of neuropathic pain via different forms of neuron-glia interaction in the spinal cord. First, chemokine CX3CL1 is expressed in primary afferents and spinal neurons and induces microglial activation via its microglial receptor CX3CR1 (neuron-to-microglia signaling). Second, CCL2 and <em>CXCL1</em> are expressed in spinal astrocytes and act on CCR2 and CXCR2 in spinal neurons to increase excitatory synaptic transmission (astrocyte-to-neuron signaling). Third, we recently identified that <em>CXCL1</em>3 is highly upregulated in spinal neurons after spinal nerve ligation and induces spinal astrocyte activation via receptor CXCR5 (neuron-to-astrocyte signaling). Strategies that target chemokine-mediated neuron-glia interactions may lead to novel therapies for the treatment of neuropathic pain.

Chemokines, including CXCL1, participate in neutrophil recruitment by triggering the activation of integrins, which leads to arrest from rolling. The downstream signaling pathways which lead to integrin activation and neutophil arrest following G-protein-coupled receptor engagement are incompletely understood. To test whether Galpha(i2) is involved, mouse neutrophils in their native whole blood were investigated in mouse cremaster postcapillary venules and in flow chambers coated with P-selectin, ICAM-1, and CXCL1. Gnai2(-/-) neutrophils showed significantly reduced CXCL1-induced arrest in vitro and in vivo. Similar results were obtained with leukotriene B(4) (LTB(4)). Lethally irradiated mice reconstituted with Gnai2(-/-) bone marrow showed a similar defect in chemoattractant-induced arrest as that of Gnai2(-/-) mice. In thioglycollate-induced peritonitis and lipopolysaccaride (LPS)-induced lung inflammation, chimeric mice lacking Galpha(i2) in hematopoietic cells showed about 50% reduced neutrophil recruitment similar to that seen in Gnai2(-/-) mice. These data show that neutrophil Galpha(i2) is necessary for chemokine-induced arrest, which is relevant for neutrophil recruitment to sites of acute inflammation.

Protective responses in mice immunized with an interferon-gamma producing strain of Cryptococcus neoformans, H99γ, are associated with IL-17A production by neutrophils. Neutrophil depletion in H99γ-immunized mice did not affect pulmonary fungal burden, indicating that neutrophils are not required for clearance. However, we observed an increase in IL-17A in the lungs of neutrophil-depleted H99γ infected mice, which corresponded to an increase in IL-17A+ γδ+ T cells. Moreover, we observed increased IL-17A+/ CD3+ cells and IL-17A+/γδ+ cells, but decreased IL-17A+/Ly6G+ neutrophils in the lungs of IL-17 receptor (R)A deficient mice compared to wild-type mice. Increased production of IL-17A in neutropenic mice coincided with increased IL-6 and CXCL1, but not Th17 inducing cytokines TGF-β, IL-21 and IL-23. Concurrent depletion of neutrophils and γδ+ T cells reduced IL-17A levels. Our results suggest that γδ+ T cells mediate significant IL-17A production in neutropenic mice during the protective response to C. neoformans infection.

The melanoma growth stimulatory activity/growth-regulated protein, CXCL1, is constitutively expressed at high levels during inflammation and progression of melanocytes into malignant melanoma. It has been shown previously that CXCL1 overexpression in melanoma cells is due to increased transcription as well as stability of the CXCL1 message. The transcription of CXCL1 is regulated through several cis-acting elements including Sp1, NF-kappaB, HMGI(Y), and the immediate upstream region (IUR) element (nucleotides -94 to -78), which lies immediately upstream to the nuclear factor kappaB (NF-kappaB) element. Previously, it has been shown that the IUR is necessary for basal and cytokine-induced transcription of the CXCL1 gene. UV cross-linking and Southwestern blot analyses indicate that the IUR oligonucleotide probe selectively binds a 115-kDa protein. In this study, the IUR element has been further characterized. We show here that proximity of the IUR element to the adjacent NF-kappaB element is critical to its function as a positive regulatory element. Using binding site oligonucleotide affinity chromatography, we have selectively purified the 115-kDa IUR-F. Mass spectrometry/mass spectrometry/matrix-assisted laser desorption ionization/time of flight spectroscopy and amino acid analysis as well as microcapillary reverse phase chromatography electrospray ionization tandem mass spectrometry identified this protein as the 114-kDa poly(ADP-ribose) polymerase (PARP1). Furthermore, 3-aminobenzamide, an inhibitor of PARP-specific ADP-ribosylation, inhibits CXCL1 promoter activity and reduces levels of CXCL1 mRNA. The data point to the possibility that PARP may be a coactivator of CXCL1 transcription.

BACKGROUND

Notch signaling regulates vascular development. However, the implication of the Notch ligand Delta-like 4 (Dll4) in postischemic angiogenesis remains unclear.

OBJECTIVE

We investigated the role of Dll4/Notch signaling in reparative angiogenesis using a mouse model of ischemia.

RESULTS

We found Dll4 weakly expressed in microvascular endothelial cells of normoperfused muscles. Conversely, Dll4 is upregulated following ischemia and localized at the forefront of sprouting capillaries. We analyzed the effect of inhibiting endogenous Dll4 by intramuscular injection of an adenovirus encoding the soluble form of Dll4 extracellular domain (Ad-sDll4). Dll4 inhibition caused the formation of a disorganized, low-perfused capillary network in ischemic muscles. This structural abnormality was associated to delayed blood flow recovery and muscle hypoxia and degeneration. Analysis of microvasculature at early stages of repair revealed that Dll4 inhibition enhances capillary sprouting in a chaotic fashion and causes excessive leukocyte infiltration of ischemic muscles. Furthermore, Dll4 inhibition potentiated the elevation of the leukocyte chemoattractant CXCL1 (chemokine [C-X-C motif] ligand 1) following ischemia, without altering peripheral blood levels of stromal cell-derived factor-1 and monocyte chemoattractant protein-1. In cultured human monocytes, Dll4 induces the transcription of Notch target gene Hes-1 and inhibits the basal and tumor necrosis factor-alpha-stimulated production of interleukin-8, the human functional homolog of murine CXCL1. The inhibitory effect of Dll4 on interleukin-8 was abolished by DAPT, a Notch inhibitor, or by coculturing activated human monocytes with Ad-sDll4-infected endothelial cells.

CONCLUSIONS

Dll4/Notch interaction is essential for proper reparative angiogenesis. Moreover, Dll4/Notch signaling regulates sprouting angiogenesis and coordinates the interaction between inflammation and angiogenesis under ischemic conditions.

Vascular endothelial growth factor (VEGF) and interleukin-8/CXCL8 (IL-8) are prominent pro-angiogenic and pro-metastatic proteins that represent negative prognostic factors in many types of cancer. Hypoxia is thought to be the primary environmental cause of VEGF and IL-8 expression in solid tumors. We hypothesized that a lack of nutrients other than oxygen could stimulate the expression of these factors and previously demonstrated that expression of VEGF and IL-8 is responsive to amino acid deprivation. In the present study, we examined the effect of glutamine availability on the expression of these factors as well as the role of transcription factors NFkappaB and activating protein-1 (AP-1) in the response of TSE human breast carcinoma cells to glutamine deprivation. VEGF and IL-8 secretion and mRNA levels were dramatically induced by glutamine deprivation. mRNA stabilization contributed to this response. Glutamine deprivation increased NFkappaB (p65/p50) and AP-1 (Fra-1/c-Jun+JunD) DNA-binding activities. Blocking NFkappaB and AP-1 activation with curcumin as well as expression of dominant inhibitors, inhibitor of nuclear factor-kappaB (IkappaB) super repressor (IkappaBM), and a mutant form of c-Fos (A-Fos) demonstrated that the activation of NFkappaB and AP-1 transcription factors was necessary for the induction of IL-8 expression but dispensable for the induction of VEGF expression. A macro-array containing 111 NFkappaB target genes identified a total of 17 that were up-regulated 2-fold or more in response to glutamine deprivation. These included growth regulated oncogene alpha (GROalpha/GRO1/CXCL1), another neutrophil chemoattractant implicated in tumor angiogenesis and metastasis.

Despite the long-appreciated in vivo role of the redox-active virulence factor pyocyanin in Pseudomonas airway infections and the importance of airway epithelial cells in combating bacterial pathogens, little is known about pyocyanin's effect on airway epithelial cells. We find that exposure of bronchiolar epithelial cells to pyocyanin results in MUC2/MUC5AC induction and mucin secretion through release of inflammatory cytokines and growth factors (interleukin (IL)-1β, IL-6, heparin-bound epidermal growth factor, tissue growth factor-α, tumor necrosis factor-α) that activate the epidermal growth factor receptor pathway. These changes are mediated by reactive oxygen species produced by pyocyanin. Microarray analysis identified 286 pyocyanin-induced genes in airway epithelial cells, including many inflammatory mediators elevated in cystic fibrosis (granulocyte colony-stimulating factor (G-CSF), granulocyte-monocyte CSF, chemokine (C-X-C motif) ligand 1 (CXCL1), serum amyloid, IL-23) and several novel pyocyanin-responsive genes of potential importance in the infection process (IL-24, CXCL2, CXCL3, CCL20, CXCR4). This comprehensive study uncovers numerous details of pyocyanin's proinflammatory action and establishes airway epithelial cells as key responders to this microbial toxin.

Chronic lung infections by Pseudomonas aeruginosa strains are a major cause of morbidity and mortality in cystic fibrosis (CF) patients. Although there is no clear evidence for a primary defect in the immune system of CF patients, the host is generally unable to clear P. aeruginosa from the airways. PTX3 is a soluble pattern recognition receptor that plays nonredundant roles in the innate immune response to fungi, bacteria, and viruses. In particular, PTX3 deficiency is associated with increased susceptibility to P. aeruginosa lung infection. To address the potential therapeutic effect of PTX3 in P. aeruginosa lung infection, we established persistent and progressive infections in mice with the RP73 clinical strain RP73 isolated from a CF patient and treated them with recombinant human PTX3. The results indicated that PTX3 has a potential therapeutic effect in P. aeruginosa chronic lung infection by reducing lung colonization, proinflammatory cytokine levels (CXCL1, CXCL2, CCL2, and IL-1β), and leukocyte recruitment in the airways. In models of acute infections and in in vitro assays, the prophagocytic effect of PTX3 was maintained in C1q-deficient mice and was lost in C3- and Fc common γ-chain-deficient mice, suggesting that facilitated recognition and phagocytosis of pathogens through the interplay between complement and FcγRs are involved in the therapeutic effect mediated by PTX3. These data suggested that PTX3 is a potential therapeutic tool in chronic P. aeruginosa lung infections, such as those seen in CF patients.

In the course of Type 1 diabetes pro-inflammatory cytokines (e.g., IL-1β, IFN-γ and TNF-α) produced by islet-infiltrating immune cells modify expression of key gene networks in β-cells, leading to local inflammation and β-cell apoptosis. Most known cytokine-induced transcription factors have pro-apoptotic effects, and little is known regarding "protective" transcription factors. To this end, we presently evaluated the role of the transcription factor CCAAT/enhancer binding protein delta (C/EBPδ) on β-cell apoptosis and production of inflammatory mediators in the rat insulinoma INS-1E cells, in purified primary rat β-cells and in human islets. C/EBPδ is expressed and up-regulated in response to the cytokines IL-1β and IFN-γ in rat β-cells and human islets. Small interfering RNA-mediated C/EBPδ silencing exacerbated IL-1β+IFN-γ-induced caspase 9 and 3 cleavage and apoptosis in these cells. C/EBPδ deficiency increased the up-regulation of the transcription factor CHOP in response to cytokines, enhancing expression of the pro-apoptotic Bcl-2 family member BIM. Interfering with C/EBPδ and CHOP or C/EBPδ and BIM in double knockdown approaches abrogated the exacerbating effects of C/EBPδ deficiency on cytokine-induced β-cell apoptosis, while C/EBPδ overexpression inhibited BIM expression and partially protected β-cells against IL-1β+IFN-γ-induced apoptosis. Furthermore, C/EBPδ silencing boosted cytokine-induced production of the chemokines CXCL1, 9, 10 and CCL20 in β-cells by hampering IRF-1 up-regulation and increasing STAT1 activation in response to cytokines. These observations identify a novel function of C/EBPδ as a modulatory transcription factor that inhibits the pro-apoptotic and pro-inflammatory gene networks activated by cytokines in pancreatic β-cells.

The exact pathogenesis of plaque psoriasis remains to be fully determined, but it is thought to depend on environmental and genetic factors that stimulate dysregulated innate and adaptive immune responses in the skin. The cytokine interleukin (IL)-17A plays a key role in host defence against extracellular bacteria and fungi. An increasing body of evidence suggests that IL-17A is also important in psoriasis pathogenesis. While IL-17A is a key product of Th17 cells, it is also produced by neutrophils, mast cells and Tc17 cells. Each of these cell types is found in psoriatic lesions. IL-17A acts on keratinocytes to increase expression of chemokines (e.g. CCL20, CXCL1, CXCL3, CXCL5, CXCL6 and CXCL8) involved in recruiting myeloid dendritic cells, Th17 cells and neutrophils to the lesion site. IL-17A induces production of antimicrobial peptides and proinflammatory cytokines that, in turn, may help sustain immune responses in the skin. Blocking IL-17A improved psoriasis-like pathology in experimental models, and reductions in IL-17 signalling have been associated with response to tumour necrosis factor-α blockers in patients with psoriasis. Agents that inhibit IL-17 are in development and preliminary clinical results for IL-17 inhibitors indicate the importance of IL-17A in psoriasis pathophysiology. In a proof-of-concept and two phase II trials, three agents markedly reduced disease severity in patients with moderate-to-severe plaque psoriasis. One agent downregulated cytokines, chemokines and proteins associated with inflammatory responses in lesional skin. In summary, IL-17A is an attractive therapeutic target, which may allow selective intervention to address the dysregulated immune system in plaque psoriasis.

This study aimed to analyze the role of endothelial progenitor cell (EPC)-derived angiogenic factors and chemokines in the multistep process driving angiogenesis with a focus on the recently discovered macrophage migration inhibitory factor (MIF)/chemokine receptor axis. Primary murine and murine embryonic EPCs (eEPCs) were analyzed for the expression of angiogenic/chemokines and components of the MIF/CXC chemokine receptor axis, focusing on the influence of hypoxic versus normoxic stimulation. Hypoxia induced an upregulation of CXCR2 and CXCR4 but not CD74 on EPCs and triggered the secretion of <em>CXCL1</em>2, <em>CXCL1</em>, MIF, and vascular endothelial growth factor (VEGF). These factors stimulated the transmigration activity and adhesive capacity of EPCs, with MIF and VEGF exhibiting the strongest effects under hypoxia. MIF-, VEGF-, <em>CXCL1</em>2-, and <em>CXCL1</em>-stimulated EPCs enhanced tube formation, with MIF and VEGF exhibiting again the strongest effect following hypoxia. Tube formation following in vivo implantation utilizing angiogenic factor-loaded Matrigel plugs was only promoted by VEGF. Coloading of plugs with eEPCs led to enhanced tube formation only by <em>CXCL1</em>2, whereas MIF was the only factor which induced differentiation towards an endothelial and smooth muscle cell (SMC) phenotype, indicating an angiogenic and differentiation capacity in vivo. Surprisingly, <em>CXCL1</em>2, a chemoattractant for smooth muscle progenitor cells, inhibited SMC differentiation. We have identified a role for EPC-derived proangiogenic MIF, VEGF and MIF receptors in EPC recruitment following hypoxia, EPC differentiation and subsequent tube and vessel formation, whereas <em>CXCL1</em>2, a mediator of early EPC recruitment, does not contribute to the remodeling process. By discerning the contributions of key angiogenic chemokines and EPCs, these findings offer valuable mechanistic insight into mouse models of angiogenesis and help to define the intricate interplay between EPC-derived angiogenic cargo factors, EPCs, and the angiogenic target tissue.

In prior studies, we demonstrated that 1) CXCL1/KC is essential for NF-κB and MAPK activation and expression of CXCL2/MIP-2 and CXCL5/LPS-induced CXC chemokine in Klebsiella-infected lungs, and 2) CXCL1 derived from hematopoietic and resident cells contributes to host immunity against Klebsiella. However, the role of CXCL1 in mediating neutrophil leukotriene B(4) (LTB(4)), reactive oxygen species (ROS), and reactive nitrogen species (RNS) production is unclear, as is the contribution of these factors to host immunity. In this study, we investigated 1) the role of CXCL1 in LTB(4), NADPH oxidase, and inducible NO synthase (iNOS) expression in lungs and neutrophils, and 2) whether LTB(4) postinfection reverses innate immune defects in CXCL1(-/-) mice via regulation of NADPH oxidase and iNOS. Our results demonstrate reduced neutrophil influx, attenuated LTB(4) levels, and decreased ROS and iNOS production in the lungs of CXCL1(-/-) mice after Klebsiella pneumoniae infection. Using neutrophil depletion and repletion, we found that neutrophils are the predominant source of pulmonary LTB(4) after infection. To treat immune defects in CXCL1(-/-) mice, we intrapulmonarily administered LTB(4). Postinfection, LTB(4) treatment reversed immune defects in CXCL1(-/-) mice and improved survival, neutrophil recruitment, cytokine/chemokine expression, NF-κB/MAPK activation, and ROS/RNS production. LTB(4) also enhanced myeloperoxidase, H(2)O(2,) RNS production, and bacterial killing in K. pneumoniae-infected CXCL1(-/-) neutrophils. These novel results uncover important roles for CXCL1 in generating ROS and RNS in neutrophils and in regulating host immunity against K. pneumoniae infection. Our findings suggest that LTB(4) could be used to correct defects in neutrophil recruitment and function in individuals lacking or expressing malfunctional CXCL1.

17β-Estradiol (E2) treatment limits the pathology associated with pulmonary diseases caused by pathogens, allergens, and asthma, partly by reducing the production of proinflammatory cytokines and chemokines. To test the hypothesis that E2 protects against influenza A virus (IAV) infection by altering the recruitment and activity of innate immune cells and T cells, chemokine concentrations were measured and innate and adaptive immune cells were enumerated from the lungs of E2- and placebo-treated ovariectomized female C57BL/6 mice following infection. Females treated with E2 experienced less morbidity but had similar lung virus titers to placebo-treated females. Females treated with E2 had lower induction of CCL2 but higher CCL3 and CXCL1 responses in their lungs than placebo-treated females. Pulmonary recruitment of neutrophils, NK cells, macrophages, and dendritic cells was increased following infection, but only neutrophil numbers were greater in E2-treated than placebo-treated females. Neutrophils enhance the responses of influenza virus-specific CD8 T cells to promote virus clearance and improve the outcome of infection. Total numbers of virus-specific CD8 T cells were not altered by treatment with E2, but the proportion of gamma interferon (IFN-γ)- and tumor necrosis factor alpha (TNF-α)-producing, virus-specific CD8 T cells was increased. Neutrophil depletion in E2-treated females increased morbidity, reduced pulmonary production of chemoattractants for neutrophils, and reduced IFN-γ production by virus-specific CD8 T cells. Neutrophils mediate both inflammation and tissue repair during IAV infection and are regulated by E2 to improve the outcome of influenza in females.

OBJECTIVE

Severe influenza is associated with excessive inflammation that leads to tissue damage. We demonstrate that estradiol (E2) is a potent anti-inflammatory hormone that reduces the severity of influenza A virus infection in females. Treatment of female C57BL/6 mice with E2 does not affect virus replication but rather alters the production of chemokines, pulmonary recruitment of neutrophils, and the cytokine responses of virus-specific CD8 T cells to protect females against severe influenza.

Although previous studies reported the involvement of the TLR4-TRIF pathway in alcohol-induced liver injury, the role of TLR2 and TLR9 signaling in alcohol-mediated neutrophil infiltration and liver injury has not been elucidated. Since alcohol binge drinking is recognized to induce more severe form of alcohol liver disease, we used a chronic-binge ethanol-feeding model as a mouse model for early stage of alcoholic hepatitis. Whereas a chronic-binge ethanol feeding induced alcohol-mediated liver injury in wild-type mice, TLR2- and TLR9-deficient mice showed reduced liver injury. Induction of neutrophil-recruiting chemokines, including Cxcl1, Cxcl2, and Cxcl5, and hepatic neutrophil infiltration were increased in wild-type mice, but not in TLR2- and TLR9-deficient mice. In vivo depletion of Kupffer cells (KCs) by liposomal clodronate reduced liver injury and the expression of Il1b, but not Cxcl1, Cxcl2, and Cxcl5, suggesting that KCs are partly associated with liver injury, but not neutrophil recruitment, in a chronic-binge ethanol-feeding model. Notably, hepatocytes and hepatic stellate cells (HSCs) produce high amounts of CXCL1 in ethanol-treated mice. The treatment with TLR2 and TLR9 ligands synergistically upregulated CXCL1 expression in hepatocytes. Moreover, the inhibitors for CXCR2, a receptor for CXCL1, and MyD88 suppressed neutrophil infiltration and liver injury induced by chronic-binge ethanol treatment. Consistent with the above findings, hepatic CXCL1 expression was highly upregulated in patients with alcoholic hepatitis. In a chronic-binge ethanol-feeding model, the TLR2 and TLR9-dependent MyD88-dependent pathway mediates CXCL1 production in hepatocytes and HSCs; the CXCL1 then promotes neutrophil infiltration into the liver via CXCR2, resulting in the development of alcohol-mediated liver injury.

A rise in tissue-embedded macrophages displaying "M1-like" proinflammatory polarization is a hallmark of metabolic inflammation during a high fat diet or obesity. Here we show that bone marrow-derived macrophages (BMDM) from high fat-fed mice retain a memory of their dietary environment in vivo (displaying the elevated proinflammatory genes Cxcl1, Il6, Tnf, Nos2) despite 7-day differentiation and proliferation ex vivo. Notably, 6-h incubation with palmitoleate (PO) reversed the proinflammatory gene expression and cytokine secretion seen in BMDM from high fat-fed mice. BMDM from low fat-fed mice exposed to palmitate (PA) for 18 h ex vivo also showed elevated expression of proinflammatory genes (Cxcl1, Il6, Tnf, Nos2, and Il12b) associated with M1 polarization. Conversely, PO treatment increased anti-inflammatory genes (Mrc1, Tgfb1, Il10, Mgl2) and oxidative metabolism, characteristic of M2 macrophages. Therefore, saturated and unsaturated fatty acids bring about opposite macrophage polarization states. Coincubation of BMDM with both fatty acids counteracted the PA-induced Nos2 expression in a PO dose-dependent fashion. PO also prevented PA-induced IκBα degradation, RelA nuclear translocation, NO production, and cytokine secretion. Mechanistically, PO exerted its anti-inflammatory function through AMP-activated protein kinase as AMP kinase knockout or inhibition by Compound C offset the PO-dependent prevention of PA-induced inflammation. These results demonstrate a nutritional memory of BMDM ex vivo, highlight the plasticity of BMDM polarization in response to saturated and unsaturated fatty acids, and identify the potential to reverse diet- and saturated fat-induced M1-like polarization by administering palmitoleate. These findings could have applicability to reverse obesity-linked inflammation in metabolically relevant tissues.

BACKGROUND

Pancreatic cancer (PC) is a lethal malignancy primarily driven by activated Kras mutations and characterized by the deregulation of several genes including mucins. Previous studies on mucins have identified their significant role in both benign and malignant human diseases including PC progression and metastasis. However, the initiation of MUC expression during PC remains unknown because of lack of early stage tumor tissues from PC patients.

METHODS

In the present study, we have evaluated stage specific expression patterns of mucins during mouse PC progression in (Kras(G12D);Pdx1-Cre (KC)) murine PC model from pancreatic intraepithelial neoplasia (PanIN) to pancreatic ductal adenocarcinoma (PDAC) by immunohistochemistry and quantitative real-time PCR.

RESULTS

In agreement with previous studies on human PC, we observed a progressive increase in the expression of mucins particularly Muc1, Muc4 and Muc5AC in the pancreas of KC (as early as PanIN I) mice with advancement of PanIN lesions and PDAC both at mRNA and protein levels. Additionally, mucin expression correlated with the increased expression of inflammatory cytokines IFN-γ (p < 0.0062), CXCL1 (p < 0.00014) and CXCL2 (p < 0.08) in the pancreas of KC mice, which are known to induce mucin expression. Further, we also observed progressive increase in inflammation in pancreas of KC mice from 10 to 50 weeks of age as indicated by the increase in the macrophage infiltration. Overall, this study corroborates with previous human studies that indicated the aberrant overexpression of MUC1, MUC4 and MUC5AC mucins during the progression of PC.

CONCLUSIONS

Our study reinforces the potential utility of the KC murine model for determining the functional role of mucins in PC pathogenesis by crossing KC mice with corresponding mucin knockout mice and evaluating mucin based diagnostic and therapeutic approaches for lethal PC.

Mesenchymal stem cells (MSCs) ameliorate injury and accelerate repair in many organs, including the kidney, although the reparative mechanisms and interaction with macrophages have not been elucidated. This study investigated the reparative potential of human bone marrow-derived MSCs and traced their homing patterns following administration to mice with ischemia-reperfusion (IR) injury using whole body bioluminescence imaging. The effect of MSCs on macrophage phenotype following direct and indirect coculture was assessed using qPCR. Human cytokine production was measured using multiplex arrays. After IR, MSCs homed to injured kidneys where they afforded protection indicated by decreased proximal tubule kidney injury molecule-1 expression, blood urea nitrogen, and serum creatinine levels. SDS-PAGE and immunofluorescence labeling revealed MSCs reduced collagen α1(I) and IV by day 7 post-IR. Gelatin zymography confirmed that MSC treatment significantly increased matrix metalloproteinase-9 activity in IR kidneys, which contributed to a reduction in total collagen. Following direct and indirect coculture, macrophages expressed genes indicative of an anti-inflammatory "M2" phenotype. MSC-derived human GM-CSF, EGF, CXCL1, IL-6, IL-8, MCP-1, PDGF-AA, and CCL5 were identified in culture supernatants. In conclusion, MSCs home to injured kidneys and promote repair, which may be mediated by their ability to promote M2 macrophage polarization.

Hepatocellular carcinoma (HCC) develops on the background of chronic hepatitis. Leukocytes found within the HCC microenvironment are implicated as regulators of tumour growth. We show that diethylnitrosamine (DEN)-induced murine HCC is attenuated by antibody-mediated depletion of hepatic neutrophils, the latter stimulating hepatocellular ROS and telomere DNA damage. We additionally report a previously unappreciated tumour suppressor function for hepatocellular nfkb1 operating via p50:p50 dimers and the co-repressor HDAC1. These anti-inflammatory proteins combine to transcriptionally repress hepatic expression of a S100A8/9, CXCL1 and CXCL2 neutrophil chemokine network. Loss of nfkb1 promotes ageing-associated chronic liver disease (CLD), characterized by steatosis, neutrophillia, fibrosis, hepatocyte telomere damage and HCC. Nfkb1(S340A/S340A)mice carrying a mutation designed to selectively disrupt p50:p50:HDAC1 complexes are more susceptible to HCC; by contrast, mice lacking S100A9 express reduced neutrophil chemokines and are protected from HCC. Inhibiting neutrophil accumulation in CLD or targeting their tumour-promoting activities may offer therapeutic opportunities in HCC.

The chemokine receptor CXCR7, belonging to the membrane-bound G protein-coupled receptor superfamily, is expressed in several tumor types. Inhibition of CXCR7 with either small molecules or small interference (si)RNA has shown promising therapeutic benefits in several tumor models. With the increased interest and effectiveness of biologicals inhibiting membrane-bound receptors we made use of the "Nanobody platform" to target CXCR7. Previously we showed that Nanobodies, i.e. immunoglobulin single variable domains derived from naturally occurring heavy chain-only camelids antibodies, represent new biological tools to efficiently tackle difficult drug targets such as G protein-coupled receptors. In this study we developed and characterized highly selective and potent Nanobodies against CXCR7. Interestingly, the CXCR7-targeting Nanobodies displayed antagonistic properties in contrast with previously reported CXCR7-targeting agents. Several high affinity CXCR7-specific Nanobodies potently inhibited CXCL1CXCL1 from head and neck cancer cells in vitro, thus acting here as inverse agonists, and subsequent angiogenesis in vivo. Hence, with this novel class of CXCR7 inhibitors, we further substantiate the therapeutic relevance of targeting CXCR7 in head and neck cancer.

The fungal pathogens Fusarium solani and Fusarium oxysporum cause severe corneal disease in the United States and worldwide and were the causative organisms in a recent outbreak of contact lens-associated keratitis. To characterize innate immunity in Fusarium keratitis, we developed a murine model in which conidia are injected into the corneal stroma. Immunocompetent C57BL/6 mice rapidly developed severe corneal opacification associated with neutrophil infiltration and clearance of Fusarium hyphae. In contrast, neutrophil infiltration was delayed in MyD88-/- mice, resulting in uncontrolled growth of Fusarium hyphae in the corneal stroma and anterior chamber, and eventually resulting in corneal perforation. Corneal opacification scores in TLR2-/-, TLR4-/-, and TLR2/4-/- mice were similar to those of C57BL/6 mice; however, TLR4-/- and TLR2/4-/- mice had impaired antifungal responses. The phenotype of infected IL-1R1-/- mice was similar to that of MyD88-/- mice, with uncontrolled fungal growth resulting in corneal perforation. IL-1R1-/- mice also produced significantly less CXCL1/KC in the corneal stroma compared with C57BL/6 mice consistent with delayed neutrophil recruitment to the corneal stroma. Together, these findings indicate that IL-1R1 and MyD88 regulate CXC chemokine production and neutrophil recruitment to the cornea, and that TLR4 has an important role in controlling growth and replication of these pathogenic fungi.

The expression of neutrophil-specific chemokines is known to be regulated via adenine-uridine-rich sequence elements in the 3'-untranslated regions of their mRNAs that confer a high degree of mRNA instability. Although the presence of intron sequences in eukaryotic genes is known to enhance expression, the effect of intron content on the rate of mature, translatable mRNA degradation has not been demonstrated. In this study, we have determined the effects of intron content on the rate of decay of the chemokine CXCL1 (KC) mRNA. The half-life of KC mRNA was markedly prolonged when the primary transcript was obtained from a genomic clone containing three introns as compared with the half-life observed with sequence-identical KC mRNA derived from an intron-free cDNA construct. The effect of intron content was achieved with a single intron, and neither the intron sequences nor the intron positions were critical determinants of the outcome. The intron content produced the same effect when expressed in multiple cell types and when the sequences were stably integrated into the genome. The differential decay rates were not a consequence of differential nuclear to cytoplasmic transport. The intron content of the primary transcript did not influence the rate of KC mRNA translation and did not modulate the ability of interleukin-1 stimulation to stabilize the otherwise unstable mRNA. The intron effect on mRNA decay was seen with mRNAs containing two distinct instability determinants. These findings document that intron content marks the mRNA sequence leading to enhanced stability that is particularly evident in short lived ARE-containing mRNAs.

OBJECTIVE

Chemokines are soluble mediators involved in angiogenesis, cellular growth control and immunomodulation. In the present study we investigated the effects of various chemokines on proliferation of acute myelogenous leukemia (AML) cells and constitutive chemokine release by primary AML cells.

METHODS

Native human AML cells derived from 68 consecutive patients were cultured in vitro. We investigated AML cell proliferation (3H-thymidine incorporation, colony formation), chemokine receptor expression, constitutive chemokine release and chemotaxis of normal peripheral blood mononuclear cells.

RESULTS

Exogenous chemokines usually did not have any effect on AML blast proliferation in the absence of hematopoietic growth factors, but when investigating growth factor-dependent (interleukin 3 + granulocyte-macrophage colony-stimulating factor + stem cell factor) proliferation in suspension cultures the following patient subsets were identified: (i) patients whose cells showed chemokine-induced growth enhancement (8 patients); (ii) divergent effects on proliferation (15 patients); and (iii) no effect (most patients). These patient subsets did not differ in chemokine receptor expression, but, compared to CD34- AML cells, CD34+ cells showed higher expression of several receptors. Chemokines also increased the proliferation of clonogenic AML cells from the first subset of patients. Furthermore, a broad constitutive chemokine release profile was detected for most patients, and the following chemokine clusters could be identified: CCL2-4/CXCL1/8, CCL5/CXCL9-11 (possibly also CCL23) and CCL13/17/22/24/CXCL5 (possibly also CXCL6). Only the CCL2-4/CXCL1/8 cluster showed significant correlations between corresponding mRNA levels and NFkB levels/activation. The chemotaxis of normal immunocompetent cells for patients without constitutive chemokine release was observed to be decreased.

CONCLUSIONS

Differences in chemokine responsiveness as well as chemokine release contribute to patient heterogeneity in AML. Patients with AML can be classified into distinct subsets according to their chemokine responsiveness and chemokine release profile.