Tumor bearing decreases systemic acute inflammation in rats – role of mast cell degranulation

Objective and design:  To investigate the effect of experimental tumor bearing on acute inflammation models in rats. Methods:  Four and 7 days after Walker tumor implantation in the right armpit, carrageenan or dextran– induced edema in the contralateral paw, carrageenan induced neutrophil migration into peritoneal cavities, cutaneous vascular permeability induced by bradykinin, histamine, serotonin, substance P, capsaicin or compound 48/80, and mesenteric mast cell degranulation induced by compound 48/80 were evaluated. The control group did not receive tumor implantation. Statistical analysis was performed using one way analysis of variance (ANOVA) followed by the Bonferroni test. Results:  On the 7^th day after tumor inoculation, there were significant decreases in both carrageenan and dextran- induced paw edema. Tumor bearing did not change the neutrophil infiltration induced by carrageenan. There were decreases in cutaneous vascular permeability induced by compound 48/80, serotonin or bradykinin, but not that induced by histamine, substance P. A significant inhibition of mesenteric mast cell degranulation induced by compound 48/80 was observed, on the 4^th and 7^th days after tumor inoculation. Conclusion:  Tumor bearing can limit mast cell function and vascular events in acute systemic inflammation in rats, without changes in neutrophil migration. Received 20 July 2008; returned for revision 27 August 2008; received from final revision 4 November 2008; accepted by A. Falus 6 November 2008     

Induction of neutrophil infiltration by rat chemotactic cytokine (CINC) and its inhibition by dexamethasone in rats

In vivo effects of cytokine-induced neutrophil chemotactic factor (CINC) derived from rats on neutrophil infiltration were investigated using an air-pouch-type inflammation model in rats, and effects of dexamethasone on neutrophil infiltration induced by CINC was also examined in order to gain further insight into the mechanism of antiinflammutory activity of glucocorticoids. Injection of CINC into the air pouch made on the dorsum of rats induced a marked infiltration of neutrophils into the pouch fluid but not mononuclear cells and eosinophils during a 30-min interval after the injection. Maximum effect was induced at a dose of 1.4g/pouch. Treatment with dexamethasone 3 h before the injection of CINC suppressed the neutrophil infiltration in a dose-dependent manner, but no complete inhibition was observed. CINC injection into the air pouch of rats that had been sacrificed by bleeding in order to minimize neutroph il infiltration from blood stream also stimulated neutrophil infiltration into the pouch fluid when the carcass was incubated at 37C for 30 min, but the number of infiltrated neutrophils was about 35% of CINC-induced neutrophil infiltration in intact ruts. CINC-induced neutrophil infiltration in the carcass, which is supposed to be a reflection of neutrophil migration from extravascular space in subcutaneous tissues to pouch fluid, was not inhibited by dexamethasone treatment. Therefore, the inhibition of neutrophil infiltration by dexamethasone might be due to inhibition of the extravasation of peripheral neutrophils but not due to inhibition of neutrophil chemotaxis from subcutaneous extravascular space to pouch fluid. These findings suggest that clinical effects of steroidal antiinflammatory drugs on neutrophil infiltration in inflammatory disease is partly due to inhibition of neutrophil extravasation induced by preformed neutrophil chemotactic factors in the inflammatory site.     

Modulation of infection‐mediated migration of neutrophils and CXCR2 trafficking by osteopontin

Osteopontin (OPN) is a pro‐inflammatory protein that paradoxically protects against inflammation and bone destruction in a mouse model of endodontic infection. Here we have tested the hypothesis that this effect of OPN is mediated by effects on migration of innate immune cells to the site of infection. Using the air pouch as a model of endodontic infection in mice, we showed that neutrophil accumulation at the site of infection with a mixture of endodontic pathogens is significantly reduced in OPN‐deficient mice. Reduced neutrophil accumulation in the absence of OPN was accompanied by an increase in bacterial load. OPN‐deficiency did not affect neutrophil survival, CXCR2 ligand expression, or the production of inflammatory cytokines in the air pouch. In vitro, OPN enhanced neutrophil migration to CXCL1, whereas in vivo, inhibition of CXCR2 suppressed cellular infiltration in air pouches of infected wild‐type mice by > 50%, but had no effect in OPN‐deficient mice. OPN increased cell surface expression of CXCR2 on bone marrow neutrophils in an integrin‐α_v‐dependent manner, and suppressed the internalization of CXCR2 in the absence of ligand. Together, these results support a model where the protective effect of OPN results from enhanced initial neutrophil accumulation at sites of infection resulting in optimal bacterial killing. We describe a novel mechanism for this effect of OPN: integrin‐α_v‐dependent suppression of CXCR2 internalization in neutrophils, which increases the ability of these cells to migrate to sites of infection in response to CXCR2 ligands.     

Temporal expression of cyclooxygenase-2 in peritoneal macrophages of rats and effects of panax notoginseng saponins

Objective:  To explore the temporal expression pattern of cyclooxygenase (COX)-2 and effects of panax notogensing saponins (PNS) in peritoneal macrophages of rats. Materials and methods:  Phagocytosis function of peritoneal macrophages was measured by chicken red blood cell phagocytosis assay in vitro. Expression of COX-2 mRNA and protein, PGE₂ and PGD₂ production were determined with real-time PCR, Western blotting and radioimmunoassay, respectively. Results:  Phagocytosis function of macrophages increased significantly after stimulation and reached peak during 2–3h. Expression of COX-2 mRNA and its protein increased markedly after stimulation and reached the first peak at 2 h and 3h, respectively; and then decreased to reach a minimum at 24h. The second peak appeared at 36h. PNS (50, 100, 200 mg/kg) increased the phagocytosis function obviously at 2h, decreased the expression level of COX-2 and PGE₂ production at 2 h and elevated COX-2 expression and PGD₂ production at 36 h, respectively. Conclusion:  COX-2 expression in peritoneal macrophages has a double-hump feature after stimulation. PNS enhanced phagocytosis, inhibiting COX-2 expression at an early stage and elevating it at a later stage. Received 29 February 2008; returned for revision 27 March 2008; received from final revision 14 May 2008; accepted by G. Wallace 9 June 2008 The first two authors contributed equally to this work.     

Daily variation in macrophage phagocytosis is clock-independent and dispensable for cytokine production

Innate immune responses vary in a circadian manner, and more recent investigations aim to understand the underlying molecular mechanisms. Cytokine production varies significantly over the course of a day depending on the time of stimulation by pathogens or Toll-like receptor ligands, and multiple signaling pathways linked to the cell-autonomous circadian clock modulate innate immunity. Recognition of foreign material, especially by innate immune cells, engages a myriad of receptors, which trigger inflammatory responses, as well as endocytosis and degradation and/or processing for antigen presentation. Because of the close connection between particle engulfment and inflammation, it has been proposed that phagocytic uptake may drive cytokine production in phagocytes. Here we show that bacterial particle ingestion by mouse peritoneal macrophages displays temporal variation, but is independent of the cell-intrinsic circadian clock in an ex vivo setting. Although cytokine production is dependent on phagocytosis, uptake capacity across 12 hr does not translate into 24-hr rhythms in cytokine production. In vivo, time-of-day variations in phagocytic capacity are not found, whereas a time of day and clock-dependent cytokine response is maintained. These data show that efficiency of bacterial phagocytosis and the 24-hr rhythmicity of cytokine production by macrophages are independent of one another and should be studied separately.     

Neutrophil haptotaxis induced by mouse MNCF: interactions with extracellular matrix glycoproteins probably contribute to overcoming the anti-inflammatory action of dexamethasone

Objective and design: The Macrophage-derived Neutrophil Chemotactic Factor (MNCF) has been characterized as a dexamethasone-resistant neutrophil chemotactic lectin produced by rat macrophages. This study was undertaken to evaluate different MNCF cellular sources and investigate the mechanisms by which MNCF overcomes the anti-inflammatory actions of dexamethasone. Material and methods: The mouse macrophage-like cell line P388D1 and thioglycollate-elicited mouse macrophages were studied regarding their capacity to release MNCF. Neutrophil migration assays were performed in vivo and in vitro, in either the presence or absence of extracellular matrix glycoproteins (ECM). Results: Mouse and P388D1 macrophages release a lectin that reproduces the activities of rat MNCF. The ability of MNCF to induce neutrophil adhesion and haptotaxis is enhanced through its interaction with laminin and fibronectin. These properties are not inhibited by dexamethasone. Conclusions: Together, our results suggest that dexamethasone-resistant neutrophil migration induced by MNCF occurs probably because of its interactions with ECM. Received 27 September 2006; returned for revision 6 February 2007; accepted by M. Katori 23 April 2007     

Impact of Resolvin E1 on Murine Neutrophil Phagocytosis in Type 2 Diabetes

Diabetic complications involve inflammation-mediated microvascular and macrovascular damage, disruption of lipid metabolism, glycosylation of proteins, and abnormalities of neutrophil-mediated events. Resolution of inflamed tissues to health and homeostasis is an active process mediated by endogenous lipid agonists, including lipoxins and resolvins. This proresolution system appears to be compromised in type 2 diabetes (T2D). The goal of this study was to investigate unresolved inflammation in T2D. Wild-type (WT) and genetically engineered mice, including T2D mice (db/db), transgenic mice overexpressing the human resolvin E1 (RvE1) receptor (ERV1), and a newly bred strain of db/ERV1 mice, were used to determine the impact of RvE1 on the phagocytosis of Porphyromonas gingivalis in T2D. Neutrophils were isolated and incubated with fluorescein isothiocyanate-labeled P. gingivalis, and phagocytosis was measured in a fluorochrome-based assay by flow cytometry. Mitogen-activated protein kinase (MAPK) (p42 and p44) and Akt (Thr308 and Ser473) phosphorylation was analyzed by Western blotting. The mouse dorsal air pouch model was used to evaluate the in vivo impact of RvE1. Results revealed that RvE1 increased the neutrophil phagocytosis of P. gingivalis in WT animals but had no impact in db/db animals. In ERV1-transgenic and ERV1-transgenic diabetic mice, phagocytosis was significantly increased. RvE1 decreased Akt and MAPK phosphorylation in the transgenic animals. In vivo dorsal air pouch studies revealed that RvE1 decreases neutrophil influx into the pouch and increases neutrophil phagocytosis of P. gingivalis in the transgenic animals; cutaneous fat deposition was reduced, as was macrophage infiltration. The results suggest that RvE1 rescues impaired neutrophil phagocytosis in obese T2D mice overexpressing ERV1.     

Earlier onset of neutrophil-mediated inflammation in the ultraviolet-exposed skin of mice deficient in myeloperoxidase and NADPH oxidase

Objective and design This study examined the role of neutrophil-derived reactive oxygen species (ROS) in neutrophil recruitment into ultraviolet B (UVB)-exposed skin of mice. Methods Mouse dorsal skin was irradiated with UVB (600 mJ/cm²). Accumulation of neutrophils within the inflammatory sites was observed histochemically. Keratinocyte-derived chemokine (KC) and macrophage inflammatory protein 2 (MIP-2) were quantified, and in vivo chemotaxis of neutrophils toward KC and MIP-2 was examined. Results UVB exposure of mice deficient in myeloperoxidase (MPO), NADPH oxidase, or both, caused skin neutrophil infiltration peaking at 60, 48, and 48 h, respectively, which was earlier than the 72-h peak in wild-type mice. MIP-2 level was higher in mutant than wild-type mice. Mutant neutrophils produced more MIP-2 in vitro. Neutrophil migration toward a localized source of KC was higher in mutant than wild type mice. NADPH oxidase deficiency had a greater effect on migration than MPO deficiency. Conclusions These results suggest that ROS produced by neutrophils regulate expression of MIP-2 and migration of neutrophils toward KC. This may explain the earlier infiltration of mutant neutrophils in response to UVB. Received 21 July 2005; returned for revision 23 December 2005; accepted by M. Parnham 23 January 2006     

The β2-adrenoceptor agonist clenbuterol reduces the neuroinflammatory response,neutrophil infiltration and apoptosis following intra-striatal IL-1β administration to rats

Objectives: Clenbuterol is a brain penetrant β₂-adrenoceptor agonist with anti-inflammatory and putative neuroprotective properties. In the present investigation, the effect of clenbuterol was assessed in a rat model of acute brain injury induced by intra-striatal administration of the pro-inflammatory cytokine IL-1β.

Methods: Clenbuterol (0.5?mg/kg; i.p.) was administered one hour prior to stereotactically delivered IL-1β (100?ng) into the striatum. Four hours postinjection, rats were anesthetized, blood samples were collected for circulating cytokine and chemokine analysis, and the ipsilateral striatum and liver tissue were harvested for mRNA expression analysis of target genes.

Results: Intrastriatal IL-1β provoked an inflammatory response with increased expression of IL-1β and the pro-inflammatory cytokine TNF-α. TNF-α expression was also increased in the liver and circulating concentrations of the chemokine cytokine-induced neutrophil chemoattractant 1 (CINC-1) were raised in response to intrastriatal IL-1β administration. The striatal response was accompanied by NFκB activation and 24?hours postinjection, increased immunoreactivity of the neutrophil marker MBS-2, indicative of cell infiltration and increased TUNEL staining, a cell marker of apoptosis. Treatment with clenbuterol attenuated all IL-1β-induced changes in the striatum including MBS-2 immunoreactivity and TUNEL?+?staining. Clenbuterol also attenuated IL-1β-induced expression of TNF-α in the liver and the increase in circulating CINC-1 concentrations.

Conclusions: The results provide evidence that clenbuterol elicits anti-inflammatory effects, suppresses the peripheral acute phase response and reduces the infiltration of neutrophils and apoptotic response to acute IL-1β–induced brain injury. Suppression of both the central and peripheral response following clenbuterol administration may contribute to its protective properties following brain injury.     

Mitigation of inflammation using the intravenous anesthetic dexmedetomidine in the mouse air pouch model

Dexmedetomidine, an α₂-adrenergic/imidazoline receptor agonist, is a widely used intravenous anesthetic. Its primary current usage is for sedation of patients in the intensive care unit. The mouse air pouch model is versatile in studying the anti-inflammatory effect of a drug on a local inflammation, which is induced by a variety of substances. In the present study, using the carrageenan-induced air pouch inflammation model, we tested whether dexmedetomidine mitigates inflammation occurring locally in the mouse air pouch. We found that dexmedetomidine dose-dependently inhibited the production of tumor necrosis factor (TNF)-α and interleukin (IL)-6 in the pouch and decreased the number of white blood cells (WBC) recruited into the pouch. Dexmedetomidine also dose-dependently inhibited the production of neutrophil chemokines, cxcl1 and cxcl2. Furthermore, the dexmedetomidine-induced decreased recruitment of WBC into the pouch was successfully reversed with intra-pouch administration of cxcl1/cxcl2, but not TNF-α or IL-6. Lastly, the inhibition of the production of the cytokines and chemokines with dexmedetomidine was reversed by the treatment of yohimbine, suggesting that dexmedetomidine’s anti-inflammatory effect is primarily via the stimulation of the α₂-adrenergic receptor. We conclude that dexmedetomidine has an anti-inflammatory property in the carrageenan-induced mouse air pouch inflammation model, and that the dexmedetomidine-induced inhibition of production of the neutrophil chemokines, cxcl1 and cxcl2, may be related, at least in part, to the inhibition of WBC intra-pouch recruitment.     

Nicotine Exerts an Anti-inflammatory Effect in a Murine Model of Acute Lung Injury

Activation of the cholinergic anti-inflammatory pathway through direct activation of nicotinic acetylcholine receptors on immune cells can inhibit pro-inflammatory chemokine and cytokine release and thereby protect in a variety of inflammatory diseases. The aim of this study was to investigate whether nicotine treatment protected against acute lung inflammation. Mice challenged with intratracheal lipopolysaccharide (LPS, 50 μg) were treated with nicotine (0.2 or 0.4 mg/kg, sc). After 24 h, bronchoalveolar lavage fluid (BALF) was obtained to measure leukocyte infiltration, lung edema, and pro-inflammatory chemokine (MIP-1α, MIP-2, and eotaxin) and cytokine (IL-1, IL-6, and TNF-α) levels. Nicotine treatment reduced the LPS-mediated infiltration of leukocytes and edema as evidenced by decreased BALF inflammatory cells, myeloperoxidase, and protein. Nicotine also downregulated lung production of pro-inflammatory chemokines and cytokines. These data support the proposal that activation of the cholinergic anti-inflammatory pathway may represent a useful addition to the therapy of acute respiratory distress syndrome.     

Thyrotropic hormone (TSH) regulation of triiodothyronine (T3) concentration in immune cells

Objective:  Cells of the immune system (peritoneal lymphocytes, monocytes, granulocytes and mast cells as well as thymocytes) contain triiodothyronine (T₃). The aim of the present experiments was to study whether thyrotropic hormone (TSH) regulates or not the T₃ concentration of these cells. Methods:  Peritoneal fluid and thymus cells of adult rats were studied by immunocytochemistry, combined with flow cytometry for triiodothyronine content with or without in-vitro TSH treatment. In addition, adult female CD1 mice were treated in vivo with 10 or 40 mU TSH and after 1 hour peritoneal immune cells were studied using the above mentioned method. Results:  Both in vitro (in rat) and in vivo (in mice) TSH treatments significantly elevated the T₃ content in each cell type. In vitro TSH 0.1 mU/ml cell suspension was enough to provoke about 50 % increase in T₃ production. Conclusion:  T₃ concentration in immune cells seems to be regulated by TSH, similarly to the T₃ in the thyroid. Considering the large number of immune cells in an organism, TSH regulation of their T₃ content could have an important physiological and pathological role, both in and beyond the immune system. Received 15 April 2008; returned for revision 19 May 2008; received from final revision 20 May 2008; accepted by I. Ahnfeld-R?nne 23 June 2008     

Anti-inflammatory activity of PAS-1, a protein component of Ascaris suum

Background: Recently, we identified a 200 kDa protein (PAS-1) from Ascaris suum worms, that suppresses the humoral immune response. Here, the effect of PAS-1 on inflammatory leukocyte migration induced by bacterial lipopolysaccharide (LPS) was investigated.Methods: Cellular migration and cytokine release, stimulated by LPS or LPS+PAS-1, were analyzed in air pouches induced in the shaved back of BALB/c mice. Cytokines were determined by ELISA and RT-PCR on air pouch exudates and in vitro stimulated peritoneal macrophages.Results: The significant cellular influx induced by LPS, consisting predominantly of neutrophils, was highly suppressed in the presence of PAS-1, but not a non-related protein. PAS-1 led also to a marked reduction of TNF-, IL-1 and IL-6 levels in both LPS-stimulated air pouches and peritoneal macrophage cultures. In contrast, PAS-1 induced a significant increase of IL-10 and TGF- production.Conclusions: These results demonstrate that PAS-1 has a potent anti-inflammatory activity, probably due to the stimulation of regulatory cytokines in macrophages, thus leading to the inhibition of pro-inflammatory cytokine production.Received 2 June 2004; returned for revision 16 July 2004; accepted by A. Falus 7 September 2004     

Signal transduction pathways involving p38 MAPK, JNK, NFκB and AP-1 influences the response of chondrocytes cultured in agarose constructs to IL-1β and dynamic compression

Objective and Design:  To examine whether inhibitors of the MAPK pathways will influence the response of bovine chondrocytes cultured in agarose constructs to IL-1β and dynamic compression. Methods:  Dose-response studies were conducted under IL-1β conditions with either SB203580, SP600125, PDTC or curcumin. In separate experiments, constructs were treated with IL-1β and an appropriate concentration of inhibitor and subjected to 15% dynamic compression. Nitrite and PGE₂ release, ³⁵SO₄ and [³H]-thymidine incorporation were subsequently measured using biochemical assays. Results:  All inhibitors reduced the IL-1β induced nitrite and PGE₂ release in a dose-dependent manner. The inhibition of [³H]-thymidine incorporation by IL-1β was partially reversed with SB203580, SP600125 or curcumin, but not PDTC. In most cases, the inhibitors reduced ³⁵SO₄ incorporation with IL-1β. For the mechanical loading studies, the inhibitors reduced the compression-induced inhibition of nitrite and PGE₂ release and restored [³H]-thymidine and ³⁵SO₄ incorporation. Conclusions:  The MAPK, AP-1 and NF-κB signalling pathways are involved in the upregulation of NO and PGE₂ release by IL-1β. Dynamic compression stimulates cell proliferation and proteoglycan synthesis in the presence of IL-1β and/or inhibitors of the MAPKs and NFκB and AP-1 signalling pathways. This experimental approach could provide valuable information for the biophysical/pharmacological treatment of OA. Received 11 July 2007; returned for revision 27 September 2007; received from final revision 15 January 2008; accepted by J. Di Battista 15 January 2008     

Comparison of Pulmonary Inflammatory and Antioxidant Responses to Intranasal Live and Heat-Killed Streptococcus pneumoniae in Mice

Inflammatory and antioxidant responses, in male C57Bl6J mice, to single intranasal inoculations with live or heat-killed Streptococcus pneumoniae were studied in order to tease out differences in responses. Heat-killed bacteria elicited weak lung neutrophil infiltration and raised concentrations (peak 6–8 h), in serum or lung tissue, of CXCL1 and 2, tumor necrosis factor alpha (TNFα), interleukin-6 (IL-6), and granulocyte-macrophage-colony stimulating factor, with later increases in CCL2 and IL-1β. Live bacteria induced profound pulmonary neutrophil infiltration and acute chemokine/cytokine elevations. After 72–96 h, live S. pneumoniae induced a delayed rise in chemokines CXCL2 and CCL2, preceded by increases in TNFα, IL-1β, and IL-6 and mononuclear infiltration of lungs. With both live and heat-killed bacteria, alveolar epithelial type II cells and alveolar macrophages were the main sources of TNFα and IL-1β. Only live bacteria caused an acute decrease in lung glutathione peroxidase, an increase in superoxide dismutase, and a sustained increase in serum amyloid protein A. Acute innate immune responses to live and heat-killed S. pneumoniae are similar. In response to live bacteria, inflammation is greater, accompanied by changes in antioxidant enzymes and has an additional, later mononuclear component.     

Cytokine expression in CD4+ cells exposed to the monocyte locomotion inhibitory factor produced by Entamoeba histolytica

Entamoeba histolytica produces monocyte locomotion inhibitory factor (MLIF), a pentapeptide with in vitro and in vivo anti-inflammatory properties. MLIF may interfere with leukocyte migration, disturbing the balance of pro- and anti-inflammatory cytokines secreted by CD4⁺ T lymphocytes. We evaluated the effect of MLIF on expression of pro- and anti-inflammatory cytokines in human CD4⁺ T lymphocytes. Regulatory cytokines [interleukin-1 beta (IL-1β), IL-2, interferon gamma (IFN-γ), IL-5, IL-6, and IL-10] were studied by enzyme-linked immunosorbent assay method in CD4⁺-cell supernatant fluids. Proinflammatory cytokines were produced per se by MLIF (IL-1β, IL-2, and IFN-γ) and also anti-inflammatory cytokines (IL-5, IL-6, and IL-10) with 1-phorbol-12 myristate-13 acetate + MLIF; the IL-1β, IFN-γ, IL-5 and IL-6 production was inhibited but not that of IL-10 which disclosed increase in its expression. MLIF disturbs the pro- and anti-inflammatory balance, and it induces inhibition of IL-1β (principal proinflammatory cytokine) and increases IL-10 (prototype of an anti-inflammatory cytokine).     

Downward regulation of neutrophil infiltration by endogenous histamine without affecting vascular permeability responses in air-pouch-type carrageenin inflammation in rats

The role of histamine in neutrophil infiltration and vascular permeability response in carrageenin air pouch inflammation in rats was examined. Injection of carrageenin solution into an air pouch induced a gradual increase in histamine content in the pouch fluid and histidine decarboxylase activity of pouch wall tissues, with a maximum attained at 24 h. Local administration of the H₂ antagonists cimetidine and famotidine, but not the H₁ antagonist pyrilamine, induced an increase in neutrophil infiltration at 24 h. Both types of histamine antagonists failed to suppress the vascular permeability response. In addition, H₂ antagonists attenuated the inhibitory effect of indomethacin on neutrophil infiltration without affecting the indomethacin-induced suppression of vascular permeability response. These results suggest that histamine produced in the inflammatory locus exerts a downward regulation of neutrophil infiltration through H₂ receptors but does not play any significant role in the vascular permeability response. Furthermore, the inhibition by indomethacin of neutrophil infiltration might be ascribed to the increase in histamine level in the pouch fluid.     

Interleukin-17/interleukin-17 receptor axis elicits intestinal neutrophil migration,restrains gut dysbiosis and lipopolysaccharide translocation in high-fat diet-induced metabolic syndrome model

Sound evidence supports a role for interleukin-17 (IL-17) -producing γδ T cells and IL-17-producing helper T (Th17) cells in intestinal homeostasis, especially in intestinal barrier integrity. In the present study, we aimed to evaluate the role of IL-17 cytokine in the regulation of intestinal immunity and obesity-induced metabolic syndrome (MetS) in an experimental murine model. C57BL/6 wild-type (WT) mice and mice lacking the IL-17 cytokine receptor (IL-17RA^−/−) were fed either a control diet (CD) or a high-fat diet (HFD) for 9 weeks. Our data demonstrate that IL-17RA^−/− mice are protected against obesity, but develop hyperglycemia, hyperinsulinemia and insulin resistance. In parallel, HFD-fed IL-17RA^−/− mice display intense inflammation in the ileum compared with WT mice on the HFD. IL-17RA^−/− mice fed the HFD exhibit impaired neutrophil migration to the intestinal mucosa and reduced gene expression of the CXCL-1 chemokine and CXCR-2 receptor in the ileum. Interestingly, the populations of neutrophils (CD11b⁺ Ly6G⁺) and anti-inflammatory macrophages (CD11b⁺ CX3CR1⁺) are increased in the mesenteric lymph nodes of these mice. IL-17RA^−/− mice on the HFD also display increased commensal bacterial translocation into the bloodstream and elevated lipopolysaccharide (LPS) levels in the visceral adipose tissue (VAT). Metagenomic analysis of bacterial 16S gene revealed increased Proteobacteria and Bacteroidetes phyla, the main representatives of Gram-negative bacteria, and reduced Akkermansia muciniphila in the fecal samples of IL-17RA^−/− mice fed the HFD. Together, these data indicate that the IL-17/IL-17R axis drives intestinal neutrophil migration, limits gut dysbiosis and attenuates LPS translocation to VAT, resulting in protection to MetS.     

TRPV1 Ablation Aggravates Inflammatory Responses and Organ Damage during Endotoxic Shock

To test the hypothesis that ablation of transient receptor potential vanilloid type 1 (TRPV1) channels leads to exacerbated inflammatory responses and organ damage during endotoxic shock, lipopolysaccharide (LPS; 5 million endotoxin units/kg of body weight) was injected intraperitoneally (i.p.) into wild-type (WT) and TRPV1-null mutant (TRPV1^−/−) mice. Mean arterial pressure and heart rate, determined by radiotelemetry, were severely depressed after LPS injection into WT and TRPV1^−/− mice, with no distinction between the two strains. At 24 h after LPS injection, renal glomerular hypercellularity and hepatocellular injury were observed in both strains, accompanying further elevated serum levels of creatinine and alanine aminotransferase in TRPV1^−/− mice compared to those in WT mice. At 6 or 24 h after LPS injection, neutrophil recruitment into kidneys and livers, serum cytokine (tumor necrosis factor alpha [TNF-α], interleukin 1β [IL-1β], IL-6) and renal chemokine (KC, macrophage inflammatory protein 2 [MIP-2]) levels, and renal VCAM-1 and ICAM-1 expression were greater in TRPV1^−/− mice than WT mice. In addition, increased plasma calcitonin gene-related peptide (CGRP) levels observed in WT mice 6 h after LPS injection were absent in TRPV1^−/− mice. Thus, TRPV1 ablation aggravates inflammatory responses, including neutrophil infiltration, proinflammatory cytokine production, and adhesion molecule expression, leading to intensified organ damage during endotoxic shock in the absence of worsened circulatory failure. The data indicate that TRPV1 activation may attenuate endotoxin-induced organ damage, possibly via its anti-inflammatory action rather than alteration of hemodynamics.