Deciphering the mechanisms of the IL-6/CXCL1 and NOD-like receptor signaling pathways in otitis media with effusion in rodents.

BACKGROUND: Otitis media with effusion (OME) often leads to pediatric hearing loss and is influenced by innate and adaptive immune responses. Innate immunity serves as the non-specific first line of defense against OME. METHODS: We induced OME in rats using ovalbumin. We administered IL-6 monoclonal antibodies intranasally to inhibit IL-6, and we injected an NF-κB inhibitor intraperitoneally to explore the role of IL-6 in innate immunity and its interaction with the NOD-like receptor signaling pathway. We analyzed RNA-sequencing data with Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathways to assess signaling pathways involved in OME. We also utilized Western blot, quantitative real-time PCR, and immunohistochemistry on middle ear samples and used microscopy to identify immune cells in ear wash fluids. RESULTS: Our study suggests a pivotal role for IL-6 in the immune pathways of rats with OME via the regulation of CXCL1-mediated pathways. Increased levels of IL-6 and CXCL1 were observed in the middle ear tissues, and activation of the NLRP3 inflammasome in OME rats led to an immune response via NF-κB, thus promoting IL-6 and CXCL1 production, which was reduced by IL-6 antibody treatment. CONCLUSIONS: Our findings confirm that IL-6 and CXCL1 play significant roles in the innate immune response in OME in rodents, predominantly via the NOD-like receptor signaling pathway and NLRP3 inflammasome activation. This research sheds light on OME pathogenesis and its immune-related mechanisms.

Generation and characterization of a humanized anti-IL-17A rabbit monoclonal antibody.

Interleukin-17A (IL-17A) produced by Th17 cells, contributes to the pathogenesis of various autoimmune diseases by stimulating the release of cytokines and chemokines and its regulation. Anti-IL-17A antibody which blocks the function of IL-17A has been proved to be an effective treatment of autoimmune disease. The aim of our study was to generate a potential humanized anti-IL-17A therapeutic monoclonal antibody (mAb) through a comprehensive panel of in vitro and in vivo biological activity studies, as well as physicochemical characterization. HZD37-5, a humanized monoclonal antibody specifically recognizing N78 loci of IL-17A, binds to human and rhesus monkeys, blocks IL-17 induced signal transduction and the release of IL-6, IL-8, CXCL-1 and G-GSF. In an in vivo efficacy mouse model, HZD37-5 significantly inhibited human IL-17A induced-keratinocyte chemoattractant (KC) secretion in a dose-dependent manner. The pharmacokinetics (PK) study result of HZD37-5 in rhesus monkeys indicated that HZD37-5 had favorable PK characteristics with limited distribution (78.0-78.8 ml/kg), slow elimination (5.00-6.45 ml/day/kg), long half-life (9.1-10.7 days) and high bioavailability (103%) following a single IV or SC dose at 1.5 mg/kg. These findings provided a comprehensive preclinical characterization of HZD37-5 and supported that it may be developed as a potential therapeutic for the treatment of autoimmune diseases, including psoriasis, psoriatic arthritis, axial spondyloarthritis, etc.

Interleukin-22 signaling attenuates necrotizing enterocolitis by promoting epithelial cell regeneration.

Necrotizing enterocolitis (NEC) is a deadly intestinal inflammatory disorder that primarily affects premature infants and lacks adequate therapeutics. Interleukin (IL)-22 plays a critical role in gut barrier maintenance, promoting epithelial regeneration, and controlling intestinal inflammation in adult animal models. However, the importance of IL-22 signaling in neonates during NEC remains unknown. We investigated the role of IL-22 in the neonatal intestine under homeostatic and inflammatory conditions by using a mouse model of NEC. Our data reveal that Il22 expression in neonatal murine intestine is negligible until weaning, and both human and murine neonates lack IL-22 production during NEC. Mice deficient in IL-22 or lacking the IL-22 receptor in the intestine display a similar susceptibility to NEC, consistent with the lack of endogenous IL-22 during development. Strikingly, treatment with recombinant IL-22 during NEC substantially reduces inflammation and enhances epithelial regeneration. These findings may provide a new therapeutic strategy to attenuate NEC.

Age-related changes in the local milieu of inflamed tissues cause aberrant neutrophil trafficking and subsequent remote organ damage.

Aging is associated with dysregulated immune functions. Here, we investigated the impact of age on neutrophil diapedesis. Using confocal intravital microscopy, we found that in aged mice, neutrophils adhered to vascular endothelium in inflamed tissues but exhibited a high frequency of reverse transendothelial migration (rTEM). This retrograde breaching of the endothelium by neutrophils was governed by enhanced production of the chemokine CXCL1 from mast cells that localized at endothelial cell (EC) junctions. Increased EC expression of the atypical chemokine receptor 1 (ACKR1) supported this pro-inflammatory milieu in aged venules. Accumulation of CXCL1 caused desensitization of the chemokine receptor CXCR2 on neutrophils and loss of neutrophil directional motility within EC junctions. Fluorescent tracking revealed that in aged mice, neutrophils undergoing rTEM re-entered the circulation and disseminated to the lungs where they caused vascular leakage. Thus, neutrophils stemming from a local inflammatory site contribute to remote organ damage, with implication to the dysregulated systemic inflammation associated with aging.

Cultured Human Uveal Melanocytes Express/secrete CXCL1 and CXCL2 Constitutively and Increased by Lipopolysaccharide via Activation of Toll-like Receptor 4.

Purpose: Lipopolysaccharide (LPS) can activate Toll-like receptor 4 (TLR4) and increase the expression of CXCL1 and CXCL2, the potent neutrophils chemoattractants, in various cell types. These effects have not been previously reported in the uveal melanocytes. This study was designed to investigate the effects of LPS on the activation of TLR4 and expression of CXCL1/CXCL2 in cultured human uveal melanocytes and the relevant signal pathways.Methods: Effects of LPS on the expression of TLR4 were tested using real-time PCR, flow cytometry and fluorescence immunostaining. Effects of LPS-induced expression/secretion of CXCL1/CXCL2 were studied using real-time PCR in cell lysates and ELISA in conditioned media of cultured uveal melanocytes. Activated NF-κB and phosphorylated MAPK signals were tested in cells with and without LPS treatment using flow cytometry. Effects of various signal inhibitors on p38, ERK1/2, JNK1/2 and NF-κB on the secretion of CXCL1/CXCL2 were tested by ELISA. The effects of neutralized antibodies of CXCL1/CXCL2 on the severity of LPS-induced uveitis were tested in a mouse model.Results: LPS stimulation increased the expression of TLR4 mRNA and protein in culture uveal melanocytes. Constitutive secretion of CXCL1/CXCL2 was detected in uveal melanocytes and was significantly increased dose- and time-dependently by LPS stimulation. LPS mainly increased the activated NF-κB and phosphorylated JNK1/2. LPS-induced expression of CXCL1/CXCL2 was blocked by NF-κB and JNK1/2 inhibitors. The severity of LPS-induced uveitis was significantly inhibited by neutralizing antibody to CXCL1/CXCL2Conclusions: This is the first report on the LPS-induced expression of CXCL1 and CXCL2 by uveal melanocytes via the activation of TLR4. These results suggest that uveal melanocytes may play a role in the immune reaction that eliminates the invading pathogens. Conversely, an excessive LPS-induced inflammatory reaction may also lead to the development of inflammatory ocular disorders, such as non-infectious uveitis.

GSDMD contributes to host defence against Staphylococcus aureus skin infection by suppressing the Cxcl1-Cxcr2 axis.

Gasdermin D (GSDMD), a member of the gasdermin protein family, is a caspase substrate, and its cleavage is required for pyroptosis and IL-1ß secretion. To date, the role and regulatory mechanism of GSDMD during cutaneous microbial infection remain unclear. Here, we showed that GSDMD protected against Staphylococcus aureus skin infection by suppressing Cxcl1-Cxcr2 signalling. GSDMD deficiency resulted in larger abscesses, more bacterial colonization, exacerbated skin damage, and increased inflammatory cell infiltration. Although GSDMD deficiency resulted in defective IL-1ß production, the critical role of IL-1ß was counteracted by the fact that Caspase-1/11 deficiency also resulted in less IL-1ß production but did not aggravate disease severity during S. aureus skin infection. Interestingly, GSDMD-deficient mice had increased Cxcl1 secretion accompanied by increased recruitment of neutrophils, whereas Caspase-1/11-deficient mice presented similar levels of Cxcl1 and neutrophils as wild-type mice. Moreover, the absence of GSDMD promoted Cxcl1 secretion in bone marrow-derived macrophages induced by live, dead, or different strains of S. aureus. Corresponding to higher transcription and secretion of Cxcl1, enhanced NF-κB activation was shown in vitro and in vivo in the absence of GSDMD. Importantly, inhibiting the Cxcl1-Cxcr2 axis with a Cxcr2 inhibitor or anti-Cxcl1 blocking antibody rescued host defence defects in the GSDMD-deficient mice. Hence, these results revealed an important role of GSDMD in suppressing the Cxcl1-Cxcr2 axis to facilitate pathogen control and prevent tissue damage during cutaneous S. aureus infection.

Monovalent antibody-conjugated lipid-polymer nanohybrids for active targeting to desmoglein 3 of keratinocytes to attenuate psoriasiform inflammation.

To improve the treatment of psoriasiform inflammation, we developed actively targeted nanocarriers loaded with the phosphodiesterase 4 inhibitor AN2728. Methods: Phospholipid-poly(lactic-co-glycolic acid) nanohybrids were prepared and conjugated with monovalent anti-desmoglein 3 antibody to bind keratinocytes. Results: The actively targeted nanohybrids were 229 nm in mean size with a nearly neutral surface charge. Flow cytometry and confocal microscopy showed a 9-fold increase in keratinocyte uptake of targeted nanohybrids relative to non-targeted nanoparticles. The nanoparticles localized mainly in lysosomes after internalization. AN2728-loaded antibody-conjugated nanocarriers inhibited cytokine/chemokine overexpression in activated keratinocytes without affecting cell viability. The targeted nanohybrids also suppressed neutrophil migration by reducing CXCL1 and CXCL2 release from keratinocytes. Following subcutaneous administration in mice, the nanohybrids distributed to the epidermis and hair follicles. In a psoriasis-like skin mouse model, the actively targeted nanoparticles were superior to free drug and non-targeted nanoparticles in mitigating skin inflammation. Intervention with the targeted nanosystem reduced the epidermal thickness of the psoriasiform lesion from 191 to 42 µm, decreased the Psoriasis Area Severity Index by 74%, restored barrier function, and returned chemokine levels to baseline. Conclusions: Our developed nanosystem was safe and demonstrated efficient targeting properties for the treatment of cutaneous inflammation.

Fatigue Is Common in Immunoglobulin G Subclass Deficiency and Correlates With Inflammatory Response and Need for Immunoglobulin Replacement Therapy.

Purpose: Individuals with immunoglobulin G deficiency (IgGsd) often complain of fatigue. The correlation between systemic inflammation and fatigue is unknown. In this study perceived quality of life (QoL) and fatigue in individuals with IgGsd, on and off immunoglobulin replacement therapy (IgRT) were correlated to inflammatory markers in plasma to identify the subgroup that benefits from IgRT. Method: Thirty-five IgGsd-patients were sampled on three occasions: at baseline, after being on IgRT for at least 18 months, and 18 months after discontinuation of IgRT. Short form 36, EQ-5D-5L visual analogue scale and fatigue impact scale questionnaires were used for evaluation of QoL and fatigue. Furthermore, a panel of 92 inflammatory markers were analysed in plasma. Thirty-two gender- and age-matched healthy individuals were included as controls and sampled on one occasion. Results: QoL was lower and perceived fatigue higher in IgGsd compared to the controls. Severe fatigue and low QoL were associated with the need to restart IgRT (which is considered in IgGsd-individuals with a high burden of infections in Sweden). Twenty-five inflammatory factors were dysregulated in IgGsd and the plasma protein patterns were similar regardless of whether IgRT was ongoing or not. Enrichment analysis indicated IL-10 signalling as the most affected pathway. Severe fatigue was associated with decreased levels of the neurotrophic factors VEGFA and CSF-1. Conclusion: Fatigue is a major contributory factor to impaired health-related QoL in IgGsd and is related to the need for IgRT. Low-grade systemic inflammation is a potential driver of fatigue. In addition to the burden of infections, we suggest the degree of fatigue should be considered when the decision to introduce IgRT is made.

Peritoneal dialysate-range hypertonic glucose promotes T-cell IL-17 production that induces mesothelial inflammation.

Peritoneal dialysis (PD) employs hypertonic glucose to remove excess water and uremic waste. Peritoneal membrane failure limits its long-term use. T-cell cytokines promote this decline. T-cell differentiation is critically determined by the microenvironment. We here study how PD-range hypertonic glucose regulates T-cell polarization and IL-17 production. In the human peritoneal cavity, CD3+ cell numbers increased in PD. Single cell RNA sequencing detected expression of T helper (Th) 17 signature genes RORC and IL23R. In vitro, PD-range glucose stimulated spontaneous and amplified cytokine-induced Th17 polarization. Osmotic controls l-glucose and d-mannose demonstrate that induction of IL-17A is a substance-independent, tonicity dose-dependent process. PD-range glucose upregulated glycolysis and increased the proportion of dysfunctional mitochondria. Blockade of reactive-oxygen species (ROS) prevented IL-17A induction in response to PD-range glucose. Peritoneal mesothelium cultured with IL-17A or IL17F produced pro-inflammatory cytokines IL-6, CCL2, and CX3CL1. In PD patients, peritoneal IL-17A positively correlated with CX3CL1 concentrations. PD-range glucose-stimulated, but neither identically treated Il17a-/- Il17f-/- nor T cells cultured with the ROS scavenger N-acetylcysteine enhanced mesothelial CX3CL1 expression. Our data delineate PD-range hypertonic glucose as a novel inducer of Th17 polarization in a mitochondrial-ROS-dependent manner. Modulation of tonicity-mediated effects of PD solutions may improve membrane survival.

Fonsecaeapedrosoi Conidia and Hyphae Activate Neutrophils Distinctly: Requirement of TLR-2 and TLR-4 in Neutrophil Effector Functions.

Chromoblastomycosis is a chronic and progressive subcutaneous mycosis caused mainly by the fungus Fonsecaea pedrosoi. The infection is characterized by erythematous papules and histological sections demonstrating an external layer of fibrous tissue and an internal layer of thick granulomatous inflammatory tissue containing mainly macrophages and neutrophils. Several groups are studying the roles of the innate and adaptive immune systems in F. pedrosoi infection; however, few studies have focused on the role of neutrophils in this infection. In the current study, we verify the importance of murine neutrophils in the killing of F. pedrosoi conidia and hyphae. We demonstrate that phagocytosis and reactive oxygen species during infection with conidia are TLR-2- and TLR-4-dependent and are essential for conidial killing. Meanwhile, hyphal killing occurs by NET formation in a TLR-2-, TLR-4-, and ROS-independent manner. In vivo experiments show that TLR-2 and TLR-4 are also important in chromoblastomycosis infection. TLR-2KO and TLR-4KO animals had lower levels of CCL3 and CXCL1 chemokines and impaired neutrophil migration to the infected site. These animals also had higher fungal loads during infection with F. pedrosoi conidia, confirming that TLR-2 and TLR-4 are essential receptors for F. pedrosoi recognition and immune system activation. Therefore, this study demonstrates for the first time that neutrophil activation during F. pedrosoi is conidial or hyphal-specific with TLR-2 and TLR-4 being essential during conidial infection but unnecessary for hyphal killing by neutrophils.

Differential lung inflammation and injury with tobacco smoke exposure in Wistar Kyoto and spontaneously hypertensive rats.

OBJECTIVE: Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide and has been associated with periods of intense lung inflammation. The objective of this study was to characterize whether similar rat strains, possessing different genetic predispositions, might play a role in exacerbating the pathophysiology of COPD-like cellular and structural changes with progressive 12-week exposure to tobacco smoke (TS). Normotensive Wistar Kyoto (WKY) and spontaneously hypertensive (SH) rats were compared. MATERIALS AND METHODS: WKY and SH rats were exposed to filtered air or to tobacco smoke at a particulate concentration of 80 mg/m3 for 4, 8, or 12 weeks. Necropsy was performed 24 h after the last exposure to obtain cells by bronchoalveolar lavage for total cell and differential counts. Scoring of lung tissues and immunohistochemical staining for M1 (pro-inflammatory) and M2 (anti-inflammatory) macrophages were performed on paraffin-embedded lung sections. RESULTS AND DISCUSSION: With progressive exposure, TS-exposed SH rats demonstrated significant airspace enlargement, mucin production, and lung inflammation compared to their FA control and TS-matched WKY rats. Moreover, SH rats also demonstrated increased expression of the M1 marker in alveolar macrophages compared to FA control, as well as the M2 marker compared to controls and TS-exposed WKY rats. CONCLUSION: The progressive tobacco smoke exposure contributes to persistent lung injury and inflammation that can be significantly enhanced by rat strain susceptibility in the genesis of COPD.

Streptococcus bovis Contributes to the Development of Colorectal Cancer via Recruiting CD11b⁺TLR-4⁺ Cells.

BACKGROUND An increasing number of studies have demonstrated that Streptococcus bovis and its concomitant inflammatory factors concentrate in the intestine in colorectal cancer (CRC). However, the molecular mechanism of S. bovis on colorectal tumorigenesis remains unclear. This study aimed to explore the role of S. bovis in carcinogenesis and its potential mechanism in CRC of mice orally pretreated with S. bovis. MATERIAL AND METHODS The colons of experimental mice were collected and evaluated for the extent of neoplasm. In addition, comparative feces DNA sequencing was adopted to verify the abundance change of S. bovis during the progression of CRC in patients. RESULTS The results of this study found that S. bovis is more likely to be present at higher levels in patients with progressive colorectal carcinoma compared to those adenoma patients and healthy volunteers (P<0.05). Pretreatment with S. bovis aggravated tumor formation in mice, resulting in more substantial and a higher number of tumor nodes (P<0.05). A cytokine expression pattern with increased levels of IL-6, Scyb1, Ptgs2, IL-1ß, TNF, and Ccl2 was detected in S. bovis pretreated CRC mice (all P<0.05). Furthermore, S. bovis recruited myeloid cells, especially CD11b⁺TLR-4⁺ cells, which could promote pro-tumor immunity in the tumor microenvironment (P<0.05). CONCLUSIONS Collectively, our study indicates that S. bovis may induce a suppressive immunity that is conducive to CRC by recruiting tumor-infiltrating CD11b⁺TLR-4⁺ cells. In conclusion, S. bovis contributes to colorectal tumorigenesis via recruiting CD11b⁺TLR-4⁺ cells.

A role for mast cells and mast cell tryptase in driving neutrophil recruitment in LPS-induced lung inflammation via protease-activated receptor 2 in mice.

OBJECTIVE: This study aims to investigate the role of protease-activated receptor (PAR) 2 and mast cell (MC) tryptase in LPS-induced lung inflammation and neutrophil recruitment in the lungs of C57BL/6 mice. METHODS: C57BL/6 mice were pretreated with the PAR2 antagonist ENMD-1068, compound 48/80 or aprotinin prior to intranasal instillation of MC tryptase or LPS. Blood leukocytes, C-X-C motif chemokine ligand (CXCL) 1 production leukocytes recovered from bronchoalveolar lavage fluid (BALF), and histopathological analysis of the lung were evaluated 4 h later. Furthermore, we performed experiments to determine intracellular calcium signaling in RAW 264.7 cells stimulated with LPS in the presence or absence of a protease inhibitor cocktail or ENMD-1068 and evaluated PAR2 expression in the lungs of LPS-treated mice. RESULTS: Pharmacological blockade of PAR2 or inhibition of proteases reduced neutrophils recovered in BALF and LPS-induced calcium signaling. PAR2 blockade impaired LPS-induced lung inflammation, PAR2 expression in the lung and CXCL1 release in BALF, and increased circulating blood neutrophils. Intranasal instillation of MC tryptase increased the number of neutrophils recovered in BALF, and MC depletion with compound 48/80 impaired LPS-induced neutrophil migration. CONCLUSION: Our study provides, for the first time, evidence of a pivotal role for MCs and MC tryptase in neutrophil migration, lung inflammation and macrophage activation triggered by LPS, by a mechanism dependent on PAR2 activation.

Protective and Detrimental Roles of p38α Mitogen-Activated Protein Kinase in Different Stages of Nonalcoholic Fatty Liver Disease.

BACKGROUND AND AIMS: Neutrophil infiltration is a hallmark of nonalcoholic steatohepatitis (NASH), but how this occurs during the progression from steatosis to NASH remains obscure. Human NASH features hepatic neutrophil infiltration and up-regulation of major neutrophil-recruiting chemokines (e.g., chemokine [C-X-C motif] ligand 1 [CXCL1] and interleukin [IL]-8). However, mice fed a high-fat diet (HFD) only develop fatty liver without significant neutrophil infiltration or elevation of chemokines. The aim of this study was to determine why mice are resistant to NASH development and the involvement of p38 mitogen-activated protein kinase (p38) activated by neutrophil-derived oxidative stress in the pathogenesis of NASH. APPROACH AND RESULTS: Inflamed human hepatocytes attracted neutrophils more effectively than inflamed mouse hepatocytes because of the greater induction of CXCL1 and IL-8 in human hepatocytes. Hepatic overexpression of Cxcl1 and/or IL-8 promoted steatosis-to-NASH progression in HFD-fed mice by inducing liver inflammation, injury, and p38 activation. Pharmacological inhibition of p38α/ß or hepatocyte-specific deletion of p38a (a predominant form in the liver) attenuated liver injury and fibrosis in the HFD+Cxcl1 -induced NASH model that is associated with strong hepatic p38α activation. In contrast, hepatocyte-specific deletion of p38a in HFD-induced fatty liver where p38α activation is relatively weak exacerbated steatosis and liver injury. Mechanistically, weak p38α activation in fatty liver up-regulated the genes involved in fatty acid ß-oxidation through peroxisome proliferator-activated receptor alpha phosphorylation, thereby reducing steatosis. Conversely, strong p38α activation in NASH promoted caspase-3 cleavage, CCAAT-enhancer-binding proteins homologous protein expression, and B cell lymphoma 2 phosphorylation, thereby exacerbating hepatocyte death. CONCLUSIONS: Genetic ablation of hepatic p38a increases simple steatosis but ameliorates oxidative stress-driven NASH, indicating that p38α plays distinct roles depending on the disease stages, which may set the stage for investigating p38α as a therapeutic target for the treatment of NASH.

Stromal Cells Covering Omental Fat-Associated Lymphoid Clusters Trigger Formation of Neutrophil Aggregates to Capture Peritoneal Contaminants.

The omentum is a visceral adipose tissue rich in fat-associated lymphoid clusters (FALCs) that collects peritoneal contaminants and provides a first layer of immunological defense within the abdomen. Here, we investigated the mechanisms that mediate the capture of peritoneal contaminants during peritonitis. Single-cell RNA sequencing and spatial analysis of omental stromal cells revealed that the surface of FALCs were covered by CXCL1+ mesothelial cells, which we termed FALC cover cells. Blockade of CXCL1 inhibited the recruitment and aggregation of neutrophils at FALCs during zymosan-induced peritonitis. Inhibition of protein arginine deiminase 4, an enzyme important for the release of neutrophil extracellular traps, abolished neutrophil aggregation and the capture of peritoneal contaminants by omental FALCs. Analysis of omental samples from patients with acute appendicitis confirmed neutrophil recruitment and bacterial capture at FALCs. Thus, specialized omental mesothelial cells coordinate the recruitment and aggregation of neutrophils to capture peritoneal contaminants.

Correlation Analysis of Morphological Changes of Structural and Functional Areas of Mesenteric Lymph Nodes with Cytokines of Lymph of Thoracic Lymphatic Duct in Experimental Breast Cancer.

We performed a correlation analysis of the morphometric parameters of mesenteric lymph nodes and cytokine content in the lymph of thoracic duct in rats with chemically induced breast cancer. The study showed that activity of the local immune response in the lymph nodes in breast cancer is aimed at antitumor protection. In breast cancer, the area of the paracortical zone remained at the level of the intact group, while the area of lymphoid nodules with germinative centers and the area of medullary substance increased; the number of macrophages in the thymus-dependent zone and zone responsible for humoral immunity also increased. The following positive correlations were revealed: in germinative centers and medullary substance, number of mitotic cells correlated with cytokine IL-5 content and the number of medium lymphocytes correlated with the content of chemokine MIP-1α; in the germinative centers, the number of immunoblasts correlated with the level of cytokine GRO/KC, in the paracortical zone, the number of macrophages correlated with the level of chemokine MCP-1, the number of reticular cells correlated with IL-6 and M-CSF content; in medullary substance, the number of small lymphocytes and mature cells plasma cells (their content was reduced) correlated with the level of chemokine GRO/KC, which can be caused by their migration from the lymph node.

TRAF1 suppresses antifungal immunity through CXCL1-mediated neutrophil recruitment during Candida albicans intradermal infection.

BACKGROUND: Candida albicans is the most common opportunistic human fungal pathogen. The chemokine ligand CXCL1 plays a protective role in fungal infection through the recruitment of neutrophils. TRAF1 (tumor necrosis factor-associated factor 1) can be highly induced by proinflammatory stimuli such as LPS and TNF and has been implicated in septic shock. However, the role of TRAF1 in infection, especially fungal infection, remains elusive. Herein, we reveal that TRAF1 suppresses the antifungal immune response to Candida albicans intradermal infection through the regulation of CXCL1 induction and neutrophil recruitment. METHODS: A mouse model of C. albicans intradermal infection was established. The Traf1-/- mice and Traf1-/- immortalized human keratinocytes were generated. The p65 inhibitor triptolide, STAT1 inhibitor fludarabine, neutrophil-depletion antibody Ly6G, and neutralizing antibody for CXCL1 were utilized. The expression of proinflammatory cytokines and chemokines was assessed by real-time PCR and ELISA, and the activation of signaling molecules was analyzed by Western blotting. Hematoxylin and eosin staining and periodic acid Schiff staining were used for histology or fungal detection, respectively. The immunofluorescence and flow cytometry analyses were employed in the assessment of immune cell infiltration. Bone marrow transplantation and adoptive transfer experiments were conducted to establish a role for TRAF1 in the macrophage compartment in fungal skin infection. RESULTS: TRAF1-deficient mice demonstrated improved control of Candida albicans intradermal infection, and concomitant increase in neutrophil recruitment and reduction in fungal burden. The chemokine CXCL1 was upregulated in the TRAF1-deficient macrophages treated with heat-killed C. albicans. Mechanistically, TRAF1-deficient macrophages showed increased activation of transcription factor NFκB p65. The human CXCL8 was also highly induced in the TRAF1-deficient human keratinocytes upon TNF stimulation through decreasing the activation of transcription factor STAT1. TRAF1-deficient macrophages played a critical role in containing the C. albicans skin infection in vivo. CONCLUSION: TRAF1-deficient mice can better control fungal infection in the skin, a process attributable to the CXCL-neutrophil axis. Mechanistically, TRAF1 likely regulates CXCL1 expression in both macrophages and keratinocytes through the transcriptional factor NFκB and STAT1, respectively. Our finding offers new insight into the understanding of the immune regulatory mechanisms in host defense against C. albicans infection.

Mechanism of berberine in treating Helicobacter pylori induced chronic atrophic gastritis through IRF8-IFN-γ signaling axis suppressing.

AIMS: In this study, we will investigate the therapeutic effects of berberine (BBR) in Helicobacter pylori (H. pylori) induced chronic atrophic gastritis (CAG). Furthermore, potential mechanisms of BBR in regulating IRF8-IFN-γ signaling axis will also be investigated. MATERIALS AND METHODS: H. pylori were utilized to establish CAG model of rats. Therapeutic effects of BBR on serum supernatant indices, and histopathology of stomach were analyzed in vivo. Moreover, GES-1 cells were infected by H. pylori, and intervened with BBR in vitro. Cell viability, morphology, proliferation, and quantitative analysis were detected by high-content screening (HCS) imaging assay. To further investigate the potential mechanisms of BBR, relative mRNA, immunohistochemistry and protein expression in IRF8-IFN-γ signaling axis were measured. KEY FINDINGS: Results showed serum supernatant indices including IL-17, CXCL1, and CXCL9 were downregulated by BBR intervention, while, G-17 increased significantly. Histological injuries of gastric mucosa induced by H. pylori also were alleviated. Moreover, cell viability and morphology changes of GES-1 cells were improved by BBR intervention. In addition, proinflammatory genes and IRF8-IFN-γ signaling axis related genes, including Ifit3, Upp1, USP18, Nlrc5, were suppressed by BBR administration in vitro and in vivo. The proteins expression related to IRF8-IFN-γ signaling axis, including Ifit3, IRF1 and Ifit1 were downregulated by BBR intervention.

S1PR4-dependent CCL2 production promotes macrophage recruitment in a murine psoriasis model.

The sphingolipid sphingosine-1-phosphate (S1P) fulfills distinct functions in immune cell biology via binding to five G protein-coupled receptors. The immune cell-specific sphingosine-1-phosphate receptor 4 (S1pr4) was connected to the generation of IL-17-producing T cells through regulation of cytokine production in innate immune cells. Therefore, we explored whether S1pr4 affected imiquimod-induced murine psoriasis via regulation of IL-17 production. We did not observe altered IL-17 production, although psoriasis severity was reduced in S1pr4-deficient mice. Instead, ablation of S1pr4 attenuated the production of CCL2, IL-6, and CXCL1 and subsequently reduced the number of infiltrating monocytes and granulocytes. A connection between S1pr4, CCL2, and Mϕ infiltration was also observed in Zymosan-A induced peritonitis. Boyden chamber migration assays functionally linked reduced CCL2 production in murine skin and attenuated monocyte migration when S1pr4 was lacking. Mechanistically, S1pr4 signaling synergized with TLR signaling in resident Mϕs to produce CCL2, likely via the NF-κB pathway. We propose that S1pr4 activation enhances TLR response of resident Mϕs to increase CCL2 production, which attracts further Mϕs. Thus, S1pr4 may be a target to reduce perpetuating inflammatory responses.

Intravascular adhesion and recruitment of neutrophils in response to CXCL1 depends on their TRPC6 channels.

Here we report a novel role for TRPC6, a member of the transient receptor potential (TRPC) channel family, in the CXCL1-dependent recruitment of murine neutrophil granulocytes. Representing a central element of the innate immune system, neutrophils are recruited from the blood stream to a site of inflammation. The recruitment process follows a well-defined sequence of events including adhesion to the blood vessel walls, migration, and chemotaxis to reach the inflammatory focus. A common feature of the underlying signaling pathways is the utilization of Ca2+ ions as intracellular second messengers. However, the required Ca2+ influx channels are not yet fully characterized. We used WT and TRPC6-/- neutrophils for in vitro and TRPC6-/- chimeric mice (WT mice with WT or TRPC6-/- bone marrow cells) for in vivo studies. After renal ischemia and reperfusion injury, TRPC6-/- chimeric mice had an attenuated TRPC6-/- neutrophil recruitment and a better outcome as judged from the reduced increase in the plasma creatinine concentration. In the cremaster model CXCL1-induced neutrophil adhesion, arrest and transmigration were also decreased in chimeric mice with TRPC6-/- neutrophils. Using atomic force microscopy and microfluidics, we could attribute the recruitment defect of TRPC6-/- neutrophils to the impact of the channel on adhesion to endothelial cells. Mechanistically, TRPC6-/- neutrophils exhibited lower Ca2+ transients during the initial adhesion leading to diminished Rap1 and ß2 integrin activation and thereby reduced ICAM-1 binding. In summary, our study reveals that TRPC6 channels in neutrophils are crucial signaling modules in their recruitment from the blood stream in response to CXCL1. KEY POINT: Neutrophil TRPC6 channels are crucial for CXCL1-triggered activation of integrins during the initial steps of neutrophil recruitment.