The plexin C1 receptor promotes acute inflammation

Acute inflammation is the pathophysiological basis of important clinical conditions associated with organ failure. The initial inflammatory response is controlled by the chemokine system, yet recent data have indicated that the neuronal guidance cues are significantly involved in the orchestration of this process. Previous work has shown the proinflammatory capacity of the guidance cue semaphorin (Sema) 7a, but the role of one of its target receptors, the plexin C1 (PLXNC1) receptor is to date unknown. We report here that PLXNC1 is expressed outside the nervous system and induced during acute inflammation. PLXNC1^?/? mice with C57BL/6 background demonstrated decreased inflammatory responses during zymosan A (ZyA)‐induced peritonitis. Subsequent in vivo studies revealed altered rolling, adhesion, and transmigration properties of PLXNC1^?/? leukocytes. Blockade of PLXNC1 was associated with attenuated chemotactic transendothelial migration properties in vitro. Studies in chimeric mice revealed that hematopoietic PLXNC1^?/? animals demonstrated an attenuated inflammatory response. To probe the therapeutic potential of PLXNC1 we treated C57BL/6 WT mice with an anti‐PLXNC1 antibody and a PLXNC1 binding peptide. Both of these interventions significantly dampened ZyA‐induced peritonitis. These results implicate an important role of PLXNC1 during an acute inflammatory response and indicate PLXNC1 as a potential target for the control of conditions associated with acute inflammation.     

Interleukin-1β induces autophagy by affecting calcium homeostasis and trypsinogen activation in pancreatic acinar cells

The strong up-regulation of inflammatory mediators has been reported to play a key role in acute pancreatitis (AP). Elevated serum levels of interleukin-1β (IL-1β) are associated with the development of AP. However, the precise effect and mechanism of IL-1β in AP remains obscure. In this study, we investigated the potential role and mechanism of IL-1β in AP. We measured autophagy activation in response to IL-1β in AR42J cells. The disrupting effects of IL-1β on cellular Ca²⁺ were observed. To determine whether the disruption of Ca²⁺ signaling has protective effects in vivo during AP, male C57BL/6 mice were treated with cerulein to induce AP. We found that the treatment of AR42J cells with IL-1β triggered autophagy and that the autophagic flux was impaired. In addition, IL-1β induced Ca²⁺ release from the ER. Furthermore, the expression of the ER stress markers GRP78 and IRE1 also increased. 2APB, an antagonist of the InsP₃ receptor, inhibited increased expression of autophagy markers. Subsequent biochemical assays revealed that co-culture with IL-1β could induce the activation of trypsinogen to trypsin and reduce the viability of acinar cells. Pathological changes of the pancreas were also observed in vivo. We found that the pathological injuries of the pancreas were significantly alleviated in mice co-treated with 2APB. Taken together, our results indicate that IL-1β can induce trypsin activation and decrease cellular viability in pancreatic acinar cells. These effects depend on impaired autophagy via intracellular calcium changes. Ca²⁺ signaling may become a promising therapeutic target in the treatment of pancreatitis.     

Rtp801 Suppression of Epithelial mTORC1 Augments Endotoxin-Induced Lung Inflammation

The mechanistic target of rapamycin (mTOR) is a central regulator of cellular responses to environmental stress. mTOR (and its primary complex mTORC1) is, therefore, ideally positioned to regulate lung inflammatory responses to an environmental insult, a function directly relevant to disease states such as the acute respiratory distress syndrome. Our previous work in cigarette smoke–induced emphysema identified a novel protective role of pulmonary mTORC1 signaling. However, studies of the impact of mTORC1 on the development of acute lung injury are conflicting. We hypothesized that Rtp801, an endogenous inhibitor of mTORC1, which is predominantly expressed in alveolar type II epithelial cells, is activated during endotoxin-induced lung injury and functions to suppress anti-inflammatory epithelial mTORC1 responses. We administered intratracheal lipopolysaccharide to wild-type mice and observed a significant increase in lung Rtp801 mRNA. In lipopolysaccharide-treated Rtp801^−/− mice, epithelial mTORC1 activation significantly increased and was associated with an attenuation of lung inflammation. We reversed the anti-inflammatory phenotype of Rtp801^−/− mice with the mTORC1 inhibitor, rapamycin, reassuring against mTORC1-independent effects of Rtp801. We confirmed the proinflammatory effects of Rtp801 by generating a transgenic Rtp801 overexpressing mouse, which displayed augmented inflammatory responses to intratracheal endotoxin. These data suggest that epithelial mTORC1 activity plays a protective role against lung injury, and its inhibition by Rtp801 exacerbates alveolar injury caused by endotoxin.In the past decade, increasing scientific attention has been devoted to the role of the mechanistic (formerly mammalian) target of rapamycin (mTOR) in the maintenance of cellular homeostasis.¹ mTOR signaling occurs via two well-defined, evolutionarily conserved complexes named mTORC1 and mTORC2. mTORC1, the best characterized of the mTOR complexes, primarily functions in the transduction of cell growth signals. mTORC1 signaling is activated during states of nutrient (eg, amino acids, lipids, and glucose) availability and growth factor stimulation. Activated mTORC1, in turn, activates downstream targets such as ribosomal S6 kinase, promoting protein synthesis and cell growth.² Accordingly, nutrient deprivation and environmental stress attenuate mTORC1 signaling, mediated by several upstream pathways that converge on the mTORC1 inhibitory complex TSC-1 (hamartin)/TSC-2 (tuberin).Acute respiratory distress syndrome (ARDS) is a common and morbid critical illness characterized by the diffuse and rapid onset of neutrophilic pulmonary inflammation in response to either a direct (eg, pneumonia) or an indirect (eg, nonpulmonary sepsis) pulmonary insult.³ Several known modifiers of mTOR signaling have been implicated in the pathophysiological characteristics of ARDS, such as oxidative stress and localized hypoxia (both of which inhibit mTORC1^4,5), as well as local inflammatory cytokine expression (associated with mTORC1 activation⁶). Interestingly, published reports conflict regarding the impact of mTORC1 signaling in ARDS.^7–10 Because these conflicting studies were on the basis of the systemic use of the pharmacological mTORC1 inhibitor rapamycin, their discrepant results could reflect varied effects of mTORC1 across the complex multicellular microenvironment of the injured alveolus. Furthermore, few studies have addressed the endogenous regulation of mTORC1 signaling during the onset and progression of lung injury.In mice, cigarette smoke inhalation increases pulmonary expression of Rtp801 (alias Redd1 or Ddit4), an endogenous activator of TSC-2, and, consequently, inhibitor of mTORC1.⁴ Within the lungs, Rtp801 is primarily localized to type II alveolar epithelial cells.⁴ Rtp801-mediated inhibition of epithelial mTORC1 activity during cigarette smoke inhalation augments alveolar injury, contributing to emphysema formation. Concordantly, RTP801 expression is increased in lung samples collected from human subjects with emphysema.⁴ These findings indicate that Rtp801/mTORC1 signaling functions to sense environmental stressors, integrating epithelial injury responses within the lungs.Given that bacterial-originated lipopolysaccharide (LPS) might be recognized as an environmental threat, we hypothesized that Rtp801 expression would increase in a mouse LPS model of ARDS, with the ensuing suppression of epithelial mTORC1 consequently augmenting lung inflammation. We investigated this hypothesis by using a model of direct (intratracheal LPS) lung injury in wild-type (WT) mice and Rtp801-knockout (Rtp801^−/−) mice. These investigations were complemented by the development of transgenic mice that overexpressed Rtp801, to determine whether mTORC1 inhibition would lower the threshold for LPS-induced lung injury. Neutrophilic inflammation was correlated to cell-specific measures of mTORC1 activity, demonstrating the complex cellular heterogeneity of mTORC1 activity within the injured lung.     

Protein tyrosine phosphatase PTPN22 regulates IL‐1β dependent Th17 responses by modulating dectin‐1 signaling in mice

A single nucleotide polymorphism within the PTPN22 gene is a strong genetic risk factor predisposing to the development of multiple autoimmune diseases. PTPN22 regulates Syk and Src family kinases downstream of immuno‐receptors. Fungal β‐glucan receptor dectin‐1 signals via Syk, and dectin‐1 stimulation induces arthritis in mouse models. We investigated whether PTPN22 regulates dectin‐1 dependent immune responses. Bone marrow derived dendritic cells (BMDCs) generated from C57BL/6 wild type (WT) and Ptpn22^?/? mutant mice, were pulsed with OVA_323‐339 and the dectin‐1 agonist curdlan and co‐cultured in vitro with OT‐II T‐cells or adoptively transferred into OT‐II mice, and T‐cell responses were determined by immunoassay. Dectin‐1 activated Ptpn22^?/? BMDCs enhanced T‐cell secretion of IL‐17 in vitro and in vivo in an IL‐1β dependent manner. Immunoblotting revealed that compared to WT, dectin‐1 activated Ptpn22^?/? BMDCs displayed enhanced Syk and Erk phosphorylation. Dectin‐1 activation of BMDCs expressing Ptpn22^R619W (the mouse orthologue of human PTPN22^R620W) also resulted in increased IL‐1β secretion and T‐cell dependent IL‐17 responses, indicating that in the context of dectin‐1 Ptpn22^R619W operates as a loss‐of‐function variant. These findings highlight PTPN22 as a novel regulator of dectin‐1 signals, providing a link between genetically conferred perturbations of innate receptor signaling and the risk of autoimmune disease.     

Staphylococcal Enterotoxin B-Induced MicroRNA-155 Targets SOCS1 To Promote Acute Inflammatory Lung Injury

Staphylococcal enterotoxin B (SEB) causes food poisoning in humans. It is considered a biological weapon, and inhalation can trigger lung injury and sometimes respiratory failure. Being a superantigen, SEB initiates an exaggerated inflammatory response. While the role of microRNAs (miRNAs) in immune cell activation is getting increasing recognition, their role in the regulation of inflammatory disease induced by SEB has not been studied. In this investigation, we demonstrate that exposure to SEB by inhalation results in acute inflammatory lung injury accompanied by an altered miRNA expression profile in lung-infiltrating cells. Among the miRNAs that were significantly elevated, miR-155 was the most overexpressed. Interestingly, miR-155^−/− mice were protected from SEB-mediated inflammation and lung injury. Further studies revealed a functional link between SEB-induced miR-155 and proinflammatory cytokine gamma interferon (IFN-γ). Through the use of bioinformatics tools, suppressor of cytokine signaling 1 (SOCS1), a negative regulator of IFN-γ, was identified as a potential target of miR-155. While miR-155^−/− mice displayed increased expression of Socs1, the overexpression of miR-155 led to its suppression, thereby enhancing IFN-γ levels. Additionally, the inhibition of miR-155 resulted in restored Socs1expression. Together, our data demonstrate an important role for miR-155 in promoting SEB-mediated inflammation in the lungs through Socs1 suppression and suggest that miR-155 may be an important target in preventing SEB-mediated inflammation and tissue injury.     

RCAN1 deficiency protects against Salmonella intestinal infection by modulating JNK activation

ObjectiveRCAN1 (regulator of calcineurin 1) has been shown to be involved in various physiological and pathological processes. However, the biological implications of RCAN1 during gastrointestinal tract infection remain unclear. In this study, we tried to determine the role of RCAN1 in acute Salmonella infectious colitis.MethodsWild type and RCAN1-deficient mice or macrophages were used to characterize the impacts of RCAN1 on intestinal inflammation, inflammatory cytokines production, animal survival, and pathogen clearance following Salmonella challenge.ResultsHistologic and quantitative assessments showed increased inflammation and elevated proinflammatory cytokines production in RCAN1-deficient mice. The aberrant inflammatory response was recapitulated in primary bone marrow-derived macrophages. In addition, we reveal a novel regulatory role for RCAN1 in the proinflammatory JNK signaling both in vitro and in vivo. Further analysis showed that the increased inflammation in RCAN1-deficient mice contributed to pathogen clearance and host survival.ConclusionsThe present study demonstrates that RCAN1 deficiency protects against Salmonella intestinal infection by enhancing proinflammatory JNK signaling.     

Suppression of monosodium urate crystal-induced inflammation by inhibiting TGF-β-activated kinase 1-dependent signaling: role of the ubiquitin proteasome system

Monosodium urate (MSU) crystals activate inflammatory pathways that overlap with interleukin-1β (IL-1β) signaling. However, the post-translational mechanisms involved and the role of signaling proteins in this activation are unknown. In the present study, we investigated the intracellular signaling mechanisms involved in MSU-induced activation of THP-1 macrophages and human nondiseased synovial fibroblasts (NLSFs) and the in vivo efficacy of an inhibitor of tumor growth factor-β (TGF-β)-activated kinase 1 (TAK1), 5Z-7-oxozeaenol, in MSU-induced paw inflammation in C57BL/6 mice. THP-1 macrophage activation with MSU crystals (25–200 µg/ml) resulted in the rapid and sustained phosphorylation of interleukin-1 receptor-activated kinase 1 (IRAK1 Thr²⁰⁹) and TAK1 (Thr^184/187) and their association with the E3 ubiquitin ligase TRAF6. At the cellular level, MSU inhibited the deubiquitinases A20 and UCHL2 and increased 20s proteasomal activity, leading to a global decrease in K⁶³-linked ubiquitination and increase in K⁴⁸-linked ubiquitination in THP-1 macrophages. While MSU did not stimulate cytokine production in NLSFs, it significantly amplified IL-1β-induced IL-6, IL-8, and ENA-78/CXCL5 production. Docking studies and MD simulations followed by TAK1 in vitro kinase assays revealed that uric acid molecules are capable of arresting TAK1 in an active-state conformation, resulting in sustained TAK1 kinase activation. Importantly, MSU-induced proinflammatory cytokine production was completely inhibited by 5Z-7-oxozeaenol but not IRAK1/4 or TRAF6 inhibitors. Administration of 5Z-7-oxozeaenol (5 or 15 mg/kg; orally) significantly inhibited MSU-induced paw inflammation in C57BL/6 mice. Our study identifies a novel post-translational mechanism of TAK1 activation by MSU and suggests the therapeutic potential of TAK1 in regulating MSU-induced inflammation.     

Geniposide regulates the miR-101/MKP-1/p38 pathway and alleviates atherosclerosis inflammatory injury in ApoE-/- mice

Atherosclerosis (AS) is the common pathological basis of chronic cardiovascular diseases and is associated with inflammation and lipid metabolism dysfunction. Geniposide, the main active ingredient of Gardenia jasminoides Ellis fruit, exhibits a variety of anti-inflammatory and anti-oxidative functions; however, its role in AS remains unclear. The aim of this study was to investigate the mechanisms of geniposide in alleviating inflammation and thereby attenuating the development of AS. ApoE^?/? mice were fed a high fat diet to induce AS and were treated with geniposide (50?mg/kg) for 12 weeks. Blood glucose and lipid levels were measured by biochemical analysis. H&E, Masson and Oil red O staining were performed to observe morphological changes and lipid deposition in the aorta and liver. Serum inflammatory cytokines were detected by ELISA. Dual-luciferase reporter gene assay was used to verify the target relationship between microRNA-101 (miR-101) and mitogen-activated protein kinase phosphatase-1 (MKP-1). The levels of miR-101, p-p38, and MKP-1 in the aorta were detected by qPCR and western blotting. The anti-inflammatory effect of geniposide in vitro was investigated in the RAW264.7 macrophage cell line. A miR-101 mimic and an inhibitor were used to study the effect of miR-101 on regulating the expression of the target MKP-1 and the downstream inflammatory cytokines. Geniposide treatment reduced lipid levels and plaque size in the mouse model of AS. Geniposide downregulated miR-101 to upregulate MKP-1 and suppress the production of inflammatory factors in vitro and in vivo. Geniposide suppressed the levels of inflammatory factors in the presence of the miR-101 mimic, whereas no obvious effect was observed in the miR-101 inhibitor group. We concluded that geniposide reduced the plaque size and alleviated inflammatory injury in ApoE^?/? mice and RAW264.7 cells. The specific anti-inflammatory mechanism was related to the miR-101/ MKP-1/p38 signaling pathway.     

HOIL1 regulates group 2 innate lymphoid cell numbers and type 2 inflammation in the small intestine

Patients with mutations in HOIL1 experience a complex immune disorder including intestinal inflammation. To investigate the role of HOIL1 in regulating intestinal inflammation, we employed a mouse model of partial HOIL1 deficiency. The ileum of HOIL1-deficient mice displayed features of type 2 inflammation including tuft cell and goblet cell hyperplasia, and elevated expression of Il13, Il5 and Il25 mRNA. Inflammation persisted in the absence of T and B cells, and bone marrow chimeric mice revealed a requirement for HOIL1 expression in radiation-resistant cells to regulate inflammation. Although disruption of IL-4 receptor alpha (IL4Rα) signaling on intestinal epithelial cells ameliorated tuft and goblet cell hyperplasia, expression of Il5 and Il13 mRNA remained elevated. KLRG1^hi CD90^lo group 2 innate lymphoid cells were increased independent of IL4Rα signaling, tuft cell hyperplasia and IL-25 induction. Antibiotic treatment dampened intestinal inflammation indicating commensal microbes as a contributing factor. We have identified a key role for HOIL1, a component of the Linear Ubiquitin Chain Assembly Complex, in regulating type 2 inflammation in the small intestine. Understanding the mechanism by which HOIL1 regulates type 2 inflammation will advance our understanding of intestinal homeostasis and inflammatory disorders and may lead to the identification of new targets for treatment.     

Thrombospondin-1 triggers macrophage IL-10 production and promotes resolution of experimental lung injury

Mononuclear phagocyte recognition of apoptotic cells triggering suppressive cytokine signaling is a key event in inflammation resolution from injury. Mice deficient in thrombospondin (TSP)-1 (thbs1^−/−), an extracellular matrix glycoprotein that bridges cell–cell interactions, are prone to lipopolysaccharide-induced lung injury and show defective macrophage interleukin (IL)-10 production during the resolution phase of inflammation. Reconstitution of IL-10 rescues thbs1^−/− mice from persistent neutrophilic lung inflammation and injury and thbs1^−/− alveolar macrophages show defective IL-10 production following intratracheal instillation of apoptotic neutrophils despite intact efferocytosis. Following co-culture with apoptotic neutrophils, thbs1^−/− macrophages show a selective defect in IL-10 production, whereas prostaglandin E2 and transforming growth factor beta 1 responses remain intact. Full macrophage IL-10 responses require the engagement of TSP-1 structural repeat 2 domain and the macrophage scavenger receptor CD36 LIMP-II Emp sequence homology (CLESH) domain in vitro. Although TSP-1 is not essential for macrophage engulfment of apoptotic neutrophils in vivo, TSP-1 aids in the curtailment of inflammatory responses during the resolution phase of injury in the lungs by providing a means by which apoptotic cells are recognized and trigger optimal IL-10 production by macrophages.     

NLRP6 function in inflammatory monocytes reduces susceptibility to chemically induced intestinal injury

NLRP6 is a member of the Nod-like receptor family, whose members are involved in the recognition of microbes and/or tissue injury. NLRP6 was previously demonstrated to regulate the production of interleukin (IL)-18 and is important for protecting mice against chemically induced intestinal injury and colitis-associated colon cancer. However, the cellular mechanisms by which NLRP6 reduces susceptibility to colonic inflammation remain unclear. Here, we determined that NLRP6 expression is specifically upregulated in Ly6C^hi inflammatory monocytes that infiltrate into the colon during dextran sulfate sodium (DSS)-induced inflammation. Adoptive transfer of wild-type (WT) Ly6C^hi inflammatory monocytes into Nlrp6^−/− mice was sufficient to protect them from mortality, significantly reducing intestinal permeability and damage. NLRP6-deficient inflammatory monocytes were defective in tumor necrosis factor α (TNFα) production, which was important for reducing DSS-induced mortality and was dependent on autocrine IL-18 signaling by inflammatory monocytes. Our data reveal a previously unappreciated role for NLRP6 in inflammatory monocytes, which are recruited after DSS-induced intestinal injury to promote barrier function and limit bacteria-driven inflammation. This study highlights the importance of early cytokine responses, particularly NLRP6-dependent and IL-18-dependent TNFα production, in preventing chronic dysregulated inflammation.     

MyD88 signaling contributes to early pulmonary responses to Aspergillus fumigatus

Toll-like receptors and the β-glucan receptor, dectin-1, mediate macrophage inflammatory responses to Aspergillus fumigatus through MyD88-dependent and -independent signaling mechanisms; however, pulmonary inflammatory responses in MyD88-deficient mice challenged with A. fumigatus are poorly defined. The role of MyD88 signaling in early pulmonary inflammation and fungal clearance was evaluated in C57BL/6J wild-type (WT) and MyD88-deficient (MyD88^−/−) mice. Early (<48 h) after infection, MyD88^−/− mice had higher fungal burdens than those of WT mice, although fungal burdens rapidly declined (>72 h) in both. MyD88^−/− mice had less consolidated inflammation, with fewer NK cells, in lung tissue early (24 h) after infection than did WT mice. At the latter time point, MyD88^−/− mouse lungs were characterized by a large amount of necrotic cellular debris and fibrin, while WT lungs had organized inflammation. Although there were equivalent numbers of macrophages in WT and MyD88^−/− mouse lung tissues, MyD88^−/− cells demonstrated delayed uptake of green fluorescent protein-expressing A. fumigatus (GFP-Af293); histologically, MyD88^−/− mouse lungs had more hyphal invasion of terminal airways and vessels, the appearance of bronchiolar epithelial cell necrosis, and necrotizing vasculitis. MyD88^−/− lung homogenates contained comparatively decreased amounts of interleukin-1β (IL-1β), IL-6, KC, and gamma interferon and paradoxically increased amounts of tumor necrosis factor alpha and macrophage inflammatory protein 1α. These data indicate that the MyD88-dependent pathway mediates acute pulmonary fungal clearance, inflammation, and tissue injury very early after infection. Resolution of abnormalities within a 3-day window demonstrates the importance of redundant signaling pathways in mediating pulmonary inflammatory responses to fungi.     

Spontaneous insertion of a b2 element in the ptpn6 gene drives a systemic autoinflammatory disease in mice resembling neutrophilic dermatosis in humans

We found a spontaneous autosomal mutation in a mouse leading to neutrophil infiltration with ulceration in the upper dermis of homozygous offspring. These animals had increased neutrophil numbers, associated with normal lymphocyte count, in peripheral blood and bone marrow, suggesting a myeloproliferative disorder; however, granulocyte precursor proliferation in bone marrow was actually reduced (because circulating neutrophils were less susceptible to apoptosis). Neutrophil infiltration of the skin and other organs and high serum levels of immunoglobulins and autoantibodies, cytokines, and acute-phase proteins were additional abnormalities, all of which could be reduced by high-dose corticosteroid treatment or neutrophil depletion by antibodies. Use of genome-wide screening localized the mutation within an 0.4-Mbp region on mouse chromosome 6. We identified insertion of a B2 element in exon 6 of the Ptpn6 gene (protein tyrosine phosphatase, non-receptor type 6; also known as Shp-1). This insertion involves amino acid substitutions that significantly reduced the enzyme activity in mice homozygous for the mutation. Disease onset was delayed, and the clinical phenotype was milder than the phenotypes of other Ptpn6-mutants described in motheaten (me, mev) mice; we designated this new genotype as Ptpn6(meB2/meB2) and the phenotype as meB2. This new phenotype encompasses an autoinflammatory disease showing similarities to many aspects of the so-called neutrophilic dermatoses, a heterogeneous group of skin diseases with unknown etiology in humans.     

The RAGE signaling pathway is involved in intestinal inflammation and represents a promising therapeutic target for Inflammatory Bowel Diseases

Inflammatory Bowel Diseases (IBD) are chronic inflammatory conditions of the intestinal tract. IBD are believed to result from an inappropriate immune response against the intestinal flora in genetically predisposed patients. The precise etiology of these diseases is not fully understood, therefore treatments rely on the dampening of symptoms, essentially inflammation, rather than on the cure of the disease. Despite the availability of biologics, such as anti-TNF antibodies, some patients remain in therapeutic failure and new treatments are thus needed. The multiligand receptor for advanced glycation end-products (RAGE) is a pattern recognition receptor implicated in inflammatory reactions and immune system activation. Here, we investigated the role of RAGE in intestinal inflammation and its potential as a therapeutic target in IBD. We showed that RAGE was upregulated in inflamed tissues from IBD patients compared to controls. Rage^−/− mice were less susceptible to intestinal and colonic inflammation development than WT mice. WT mice treated with the RAGE-specific inhibitor FPS-ZM1 experienced less severe enteritis and colitis. We demonstrated that RAGE could induce intestinal inflammation by promoting oxidative stress and endothelial activation which were diminished by FPS-ZM1 treatment. Our results revealed the RAGE signaling pathway as a promising therapeutic target for IBD patients.     

Lack of galectin-3 increases Jagged1/Notch activation in bone marrow-derived dendritic cells and promotes dysregulation of T helper cell polarization

Galectin-3, an endogenous glycan-binding protein, is abundantly expressed at sites of inflammation and immune cell activation. Although this lectin has been implicated in the control of T helper (Th) polarization, the mechanisms underlying this effect are not well understood. Here, we investigated the role of endogenous galectin-3 during the course of experimental Leishmania major infection using galectin-3-deficient (Lgals3^−/−) mice in a BALB/c background and the involvement of Notch signaling pathway in this process. Lgals3^−/− mice displayed an augmented, although mixed Th1/Th2 responses compared with wild-type (WT) mice. Concomitantly, lymph node and footpad lesion cells from infected Lgals3^−/− mice showed enhanced levels of Notch signaling components (Notch-1, Jagged1, Jagged2 and Notch target gene Hes-1). Bone marrow-derived dendritic cells (BMDCs) from uninfected Lgals3^−/− mice also displayed increased expression of the Notch ligands Delta-like-4 and Jagged1 and pro-inflammatory cytokines. In addition, activation of Notch signaling in BMDCs upon stimulation with Jagged1 was more pronounced in Lgals3^−/− BMDCs compared to WT BMDCs; this condition resulted in increased production of IL-6 by Lgals3^−/− BMDCs. Finally, addition of exogenous galectin-3 to Lgals3^−/− BMDCs partially reverted the increased sensitivity to Jagged1 stimulation. Our results suggest that endogenous galectin-3 regulates Notch signaling activation in BMDCs and influences polarization of T helper responses, thus increasing susceptibility to L. major infection.     

Distinct Tlr4-expressing cell compartments control neutrophilic and eosinophilic airway inflammation

Allergic asthma is a chronic, inflammatory lung disease. Some forms of allergic asthma are characterized by T helper type 2 (Th2)-driven eosinophilia, whereas others are distinguished by Th17-driven neutrophilia. Stimulation of Toll-like receptor 4 (TLR4) on hematopoietic and airway epithelial cells (AECs) contributes to the inflammatory response to lipopolysaccharide (LPS) and allergens, but the specific contribution of TLR4 in these cell compartments to airway inflammatory responses remains poorly understood. We used novel, conditionally mutant Tlr4^fl/fl mice to define the relative contributions of AEC and hematopoietic cell Tlr4 expression to LPS- and allergen-induced airway inflammation. We found that Tlr4 expression by hematopoietic cells is critical for neutrophilic airway inflammation following LPS exposure and for Th17-driven neutrophilic responses to the house dust mite (HDM) lysates and ovalbumin (OVA). Conversely, Tlr4 expression by AECs was found to be important for robust eosinophilic airway inflammation following sensitization and challenge with these same allergens. Thus, Tlr4 expression by hematopoietic and airway epithelial cells controls distinct arms of the immune response to inhaled allergens.     

Renal expression of proto-oncogene Ets-1 on matrix remodeling in experimental diabetic nephropathy

The molecular mechanisms of glomerulosclerosis and tubulointerstitial fibrosis in diabetic nephropathy (DN) have received scant attention. Ets-1 proto-oncogene plays a role in matrix remodeling by regulating matrix-degrading enzymes. We investigated the possible role of Ets-1 in the pathogenesis of DN. 6-week-old male Sprague-Dawley rats were divided into two experimental groups as follows: control group (n = 30) and a Diabetes mellitus group (n = 40) induced by injection of streptozotozin (STZ). The rats were investigated at 1, 4, 8, 12 and 16 weeks after STZ-treatment. By means of immunohistochemistry, the expression of Ets-1 in glomeruli was significantly increased in STZ-treated rat kidneys from week 1 (P < 0.05) and reached the peak at week 4 (P < 0.05), followed by a downward trend at subsequent time points. Similarly, the expression of Ets-1 in the tubulointerstitium was also markedly increased from week 1 (P < 0.05) and reached a maximum at week 8 (P < 0.05). By double immunostaining, Ets-1-positive cells were frequently found to co-express matrix metalloproteinase-2 (MMP-2) in STZ-treated rat kidneys. Increased expression of tissue inhibitor of metalloproteinase-2 (TIMP-2) coincided with increased expression of α-smooth muscle actin (α-SMA) in STZ-induced DN. A positive relationship was observed between the expression of Ets-1 in glomeruli or tubulointerstitium and the expression of MMP-2 (P < 0.01; P < 0.01, respectively) in STZ-treated rat kidneys. The ratio of MMP-2 and TIMP-2 in glomeruli or tubulointerstitium was negatively correlated with deposition of type IV collagen (P < 0.01; P < 0.01, respectively). These findings suggest that Ets-1 may play a critical role in fine-tuning matrix remodeling of STZ-induced DN.