CD68-expressing cells can prime T cells and initiate autoimmune arthritis in the absence of reactive oxygen species

It is widely believed that DC, but not macrophages, prime naïve T cells in vivo. Here, we investigated the ability of CD68‐expressing cells (commonly defined as macrophages) in priming autoreactive T cells and initiating collagen‐induced arthritis (CIA) in the mouse. For this purpose, a transgenic mouse was developed (MBQ mouse) where macrophages exclusively expressed the MHC class II H2‐A^q (A^q) on an H2‐A^p (A^p) background. A^q, but not A^p expression mediates susceptibility to CIA through presentation of type II collagen (CII) to T cells. CIA severity is enhanced by a mutation in the Ncf1 gene, impairing reactive oxygen species (ROS) production by the phagocyte NADPH oxidase (NOX2) complex. Expression of functional Ncf1 on macrophages was previously shown to protect from severe CIA. To study the effect of ROS on macrophage‐mediated priming of T cells, the Ncf1 mutation was introduced in the MBQ mouse. Upon CII immunization, Ncf1‐mutated MBQ mice, but not Ncf1 wild‐type MBQ mice nor Ncf1‐mutated A^p mice, activated autoreactive T cells and developed CIA. These findings demonstrate for the first time that macrophages can initiate arthritis and that the process is negatively regulated by ROS produced via the NOX2 complex.     

Macrophage‐derived reactive oxygen species protects against autoimmune priming with a defined polymeric adjuvant

Understanding the nature of adjuvants and the immune priming events in autoimmune diseases, such as rheumatoid arthritis, is a key challenge to identify their aetiology. Adjuvants are, however, complex structures with inflammatory and immune priming properties. Synthetic polymers provide a possibility to separate these functions and allow studies of the priming mechanisms in vivo. A well‐balanced polymer, poly‐N‐isopropyl acrylamide (PNiPAAm) mixed with collagen type II (CII) induced relatively stronger autoimmunity and arthritis compared with more hydrophilic (polyacrylamide) or hydrophobic (poly‐N‐isopropylacrylamide‐co‐poly‐N‐tertbutylacrylamide and poly‐N‐tertbutylacrylamide) polymers. Clearly, all the synthesized polymers except the more hydrophobic poly‐N‐tertbutylacrylamide induced arthritis, especially in Ncf1‐deficient mice, which are deficient in reactive oxygen species (ROS) production. We identified macrophages as the major infiltrating cells present at PNiPAAm‐CII injection sites and demonstrate that ROS produced by the macrophages attenuated the immune response and the development of arthritis. Our results reveal that thermo‐responsive polymers with high immune priming capacity could trigger an autoimmune response to CII and the subsequent arthritis development, in particular in the absence of NOX2 derived ROS. Importantly, ROS from macrophages protected against the autoimmune priming, demonstrating a critical regulatory role of macrophages in immune priming events.     

Increased ILC3s associated with higher levels of IL‐1β aggravates inflammatory arthritis in mice lacking phagocytic NADPH oxidase

The role of redox regulation in immune‐mediated arthritis has been previously described. However, the relationship between innate immune cells, including innate lymphoid cells (ILCs) and phagocyte‐derived ROS, in this process remains unclear. Here, we characterize ILCs and measure the IL‐1 family cytokines along with other cytokines relevant to ILC functions and development in serum‐induced arthritic joints in wild type and phagocytic NADPH oxidase (NOX2)‐deficient Ncf1^?/? mice. We found more severe serum‐induced joint inflammation and increased NCR⁺ ILC3s in inflamed joints of Ncf1^?/? mice. Furthermore, in vitro stimulation with IL‐1β on Tbet⁺ ILC1s from joints facilitated their differentiation into ROR‐γt⁺ ILC3s. Moreover, treatment with IL‐1 antagonists effectively lowered the proportions of NCR⁺ ILC3s and IL‐17A producing ILC3s in Ncf1^?/? arthritic mice and ameliorated the joint inflammation. These results suggest that NOX2 is an essential regulator of ILC transdifferentiation and may mediate this process in a redox‐dependent manner through IL‐1β production in the inflammatory joint. Our findings shed important light on the role of ILCs in the initiation and progression in tissue inflammation and delineate a novel innate immune cell‐mediated pathogenic mechanism through which redox regulation may determine the direction of immune responses in joints.     

Hyperinflammation of chronic granulomatous disease is abolished by NOX2 reconstitution in macrophages and dendritic cells

Chronic granulomatous disease (CGD), caused by a lack of reactive oxygen species (ROS) generation by the phagocyte NADPH oxidase NOX2, leads to massively increased inflammatory responses. In order to identify the type of phagocyte which requires NOX2 activity to limit inflammation, we investigated mice with a loss of function mutation in the Ncf1 gene coding for the p subunit of NOX2 and mice with transgenic rescue of Ncf1 under control of the CD68 promoter. To induce CGD hyperinflammation, different mouse genotypes were injected intradermally with β‐glucan. Ncf1 mutant mice showed massive and prolonged hyperinflammation. Hyperinflammatory lesions were characterized by persistent neutrophilic infiltration, along with ulceration and necrosis. In contrast, in CD68 promoter rescue mice inflammation resolved within days, as seen in wild‐type animals. Measurements of ROS in rescue mice demonstrated functional NOX2 in mononuclear phagocytes (macrophages and dendritic cells) but not in neutrophils. This absence of NOX2 function was also confirmed in inflammatory tissue neutrophils. Lack of functional NOX2 in mononuclear phagocytes increased the secretion of IL‐1β at early time points and of IL‐6 and TNFα at later time points. Thus, CGD hyperinflammation is a redox dysregulation in mononuclear phagocytes, demonstrating a cell type‐specific anti‐inflammatory function of NOX2. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

PTEN/PI3k/AKT Regulates Macrophage Polarization in Emphysematous mice

Macrophages play an important role in the pathogenesis of COPD. Macrophage polarization towards the M2 phenotype has been observed in the lung tissues of COPD patients and cigarette smokers. The molecular basis of this process remains unclear, and it has not been completely illuminated in animal models of emphysema. In our study, we combined cigarette smoke (CS) exposure with intraperitoneal injection of cigarette smoke extract (CSE) to build an emphysema model. We found by immunohistochemical staining and flow cytometry that the expression level of CD206 and the ratio of M2 to M1 macrophages was increased in emphysematous mice. We also demonstrated that decreased protein level for phosphatase and tensin homology deleted on chromosome ten (PTEN) and increased total protein levels for phosphorylation ‐protein kinase B (p‐AKT) in the lung tissue of emphysematous mice and in CSE‐treated RAW264.7 cells. In both bone marrow‐derived macrophages (BMDMs) from emphysematous mice and CSE‐treated RAW264.7 cells, we observed by RT‐PCR that the mRNA levels of M2 macrophage‐related markers and cytokines were increased. Furthermore, M1 macrophage‐related markers and cytokines were decreased. Meanwhile we treated BMDMs from emphysematous mice and CSE‐treated RAW264.7 cells with the phosphoinositide 3‐kinase (PI3K)/Akt inhibitor (LY294002), we observed a reduction in RNA levels of M2 macrophage‐related markers and cytokines. In conclusion, we confirmed that macrophage M2 polarization was induced in emphysematous mice generated by CS exposure combined with intraperitoneal injection of CSE. We also showed that M2 polarization was mediated through PTEN/PI3k/AKT pathway activation.     

Germ‐free mice deficient of reactive oxygen species have increased arthritis susceptibility

The NADPH oxidase 2 (NOX2) complex is responsible for the production of ROS in phagocytic cells. Genetic defects in NOX2 lead to opportunistic infections and inflammatory manifestations such as granulomas in humans, also known as chronic granulomatous disease (CGD). This condition is mirrored in mice with defective ROS production and interestingly both species are predisposed to autoimmune diseases. An unresolved question is whether the hyper‐inflammation and tendency to develop autoimmunity are secondary to the increased infections, or whether these are parallel phenomena. We generated germ‐free ROS deficient Ncf1 mutant mice that when reared in specific pathogen‐free condition, are highly susceptible to collagen‐induced arthritis compared with wild‐type mice. Strikingly, arthritis incidence and severity was almost identical in germ‐free and specific pathogen‐free ROS‐deficient mice. In addition, partial reduction of the microbial flora by antibiotics treatment did not alter the disease course. Taken together, this shows that ROS has a clear immune regulatory function that is decoupled from its function in host defence.     

Three‐dimensional accurate detection of lung emphysema in rats using ultra‐short and zero echo time MRI

Emphysema is a life‐threatening pathology that causes irreversible destruction of alveolar walls. In vivo imaging techniques play a fundamental role in the early non‐invasive pre‐clinical and clinical detection and longitudinal follow‐up of this pathology. In the present study, we aimed to evaluate the feasibility of using high resolution radial three‐dimensional (3D) zero echo time (ZTE) and 3D ultra‐short echo time (UTE) MRI to accurately detect lung pathomorphological changes in a rodent model of emphysema.Porcine pancreas elastase (PPE) was intratracheally administered to the rats to produce the emphysematous changes. 3D ZTE MRI, low and high definition 3D UTE MRI and micro‐computed tomography images were acquired 4 weeks after the PPE challenge. Signal‐to‐noise ratios (SNRs) were measured in PPE‐treated and control rats. T₂* values were computed from low definition 3D UTE MRI. Histomorphometric measurements were made after euthanizing the animals. Both ZTE and UTE MR images showed a significant decrease in the SNR measured in PPE‐treated lungs compared with controls, due to the pathomorphological changes taking place in the challenged lungs. A significant decrease in T₂* values in PPE‐challenged animals compared with controls was measured using UTE MRI. Histomorphometric measurements showed a significant increase in the mean linear intercept in PPE‐treated lungs. UTE yielded significantly higher SNR compared with ZTE (14% and 30% higher in PPE‐treated and non‐PPE‐treated lungs, respectively).This study showed that optimized 3D radial UTE and ZTE MRI can provide lung images of excellent quality, with high isotropic spatial resolution (400 µm) and SNR in parenchymal tissue (>25) and negligible motion artifacts in freely breathing animals. These techniques were shown to be useful non‐invasive instruments to accurately and reliably detect the pathomorphological alterations taking place in emphysematous lungs, without incurring the risks of cumulative radiation exposure typical of micro‐computed tomography. Copyright © 2015 John Wiley & Sons, Ltd.     

NOX2 in autoimmunity,tumor growth and metastasis

Myeloid cell NADPH oxidase isoform 2 (NOX2) generates reactive oxygen species (ROS) that participate in defense against microbial pathogens. Humans with compromised NOX2-mediated ROS formation develop chronic granulomatous disease characterized by recurrent bacterial and fungal infections. Additionally, impaired NOX2 function entails hyperactive lymphocytes and autoimmunity in humans and in murine models. The impact of NOX2 and ROS on cancer development is only partly explored. Recent research published in the Journal of Pathology showed that genetic depletion of any of the NOX2 subunits Cyba, Cybb, Ncf1, Ncf2 and Ncf4 reduced the formation of lung metastases following intravenous injection of murine tumor cells. These findings, together with the role of NOX2 in maintaining self-tolerance, imply that NOX2 is a targetable immune checkpoint in cancer. In particular, the possibility of modulating NOX2 to improve lymphocyte-mediated control of metastatic cells merits further investigation. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.     

Absence of phagocyte NADPH oxidase 2 leads to severe inflammatory response in lungs of mice infected with Coccidioides

Production of reactive oxygen species (ROS) resulting from phagocytic NADPH oxidase (NOX2) activity has been reported to contribute to host defense against numerous microbial pathogens. In this study we explored the role of NOX2 production in experimental coccidioidomycosis, a human respiratory disease caused by a soil-borne fungal pathogen. Activated and non-activated macrophages isolated from either NOX2^−/− knock-out or wild type (WT) mice showed comparable ROS production and killing efficiency in vitro when infected with parasitic cells of Coccidioides. Both mouse strains also revealed similar fungal burden in their lungs and spleen at 7 and 11 days after intranasal challenge with Coccidioides spores, although the NOX2^−/− mice died earlier than the WT strain. Immunization of the NOX2^−/− and WT mice with a live, attenuated vaccine strain of Coccidioides also resulted in comparable reduction of the fungal burden in both lungs and spleen. These combined results initially suggested that NOX2 activity and ROS production are not essential for protection against Coccidioides infection. However, the reduced survival of non-vaccinated NOX2^−/− mice correlated with high, sustained numbers of lung-infiltrated neutrophils on days 7 and 11 postchallenge, an expansion of the regulatory T cell population in infected lungs in the knock-out mice, and elevated concentrations of pro-inflammatory cytokines and chemokines in lung homogenates compared to infected WT mice. Although NOX2-derived ROS appeared to be dispensable for both innate and acquired immunity to pulmonary Coccidioides infection, evidence is presented that NOX2 production plays a role in limiting pathogenic inflammation in this murine model of coccidioidomycosis.     

B‐cell epitope spreading and inflammation in a mouse model of arthritis is associated with a deficiency in reactive oxygen species production

Autoantibody‐mediated inflammation contributes to the development of rheumatoid arthritis (RA), and anti‐type II collagen (CII) antibodies are present in the serum, synovial fluid, and cartilage of RA patients. We had previously generated and characterized knock‐in mice expressing a germline‐encoded, CII‐specific IgH (B10Q.ACB), which demonstrated positive selection of self‐reactive B cells. Here, we show that despite the spontaneous production of CII‐specific autoantibodies, B10Q.ACB mice are protected from collagen‐induced arthritis. Introducing a mutation in the Ncf1 gene, leading to ROS deficiency, breaks this strong arthritis resistance. Disease development in Ncf1‐mutated B10Q.ACB mice is associated with an enhanced germinal center formation but without somatic mutations of the auto‐reactive B cells, increased T‐cell responses and intramolecular epitope‐spreading. Thus, ROS‐mediated B‐cell tolerance to a self‐antigen could operate by limiting the expansion of the auto‐reactive B‐cell repertoire, which has important implications for the understanding of epitope spreading phenomena in rheumatoid arthritis and other autoimmune diseases.     

IL‐1α induces CD11blow alveolar macrophage proliferation and maturation during granuloma formation

Macrophages play a central role in immune and tissue responses of granulomatous lung diseases induced by pathogens and foreign bodies. Circulating monocytes are generally viewed as central precursors of these tissue effector macrophages. Here, we provide evidence that granulomas derive from alveolar macrophages serving as a local reservoir for the expansion of activated phagocytic macrophages. By exploring lung granulomatous responses to silica particles in IL‐1‐deficient mice, we found that the absence of IL‐1α, but not IL‐1β, was associated with reduced CD11b^high phagocytic macrophage accumulation and fewer granulomas. This defect was associated with impaired alveolar clearance and resulted in the development of pulmonary alveolar proteinosis (PAP). Reconstitution of IL‐1α^?/? mice with recombinant IL‐1α restored lung clearance functions and the pulmonary accumulation of CD11b^high phagocytic macrophages. Mechanistically, IL‐1α induced the proliferation of CD11b^low alveolar macrophages and differentiated these cells into CD11b^high macrophages which perform critical phagocytic functions and organize granuloma. We newly discovered here that IL‐1α triggers lung responses requiring macrophage proliferation and maturation from tissue‐resident macrophages. Copyright © 2014 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Lung injury induced by leukocytic proteases.

Human polymorphonuclear neutrophilic leukocytes (PMNs) contain large amounts of neutral proteases that can degrade elastin, collagen, proteoglycan, and basement membrane. The instillation of one of the purified enzymes (elastase) into dog lungs in vivo causes degradation of elastic fibers and other alveolar septal components and results in anatomic changes similar to those of human pulmonary emphysema. Cigarette smoking is a major risk factor associated with pulmonary emphysema in man. One mechanism for this association may be interference with the regulation of PMN elastase activity by alveolar antiproteases. This possibility is supported by the observation that the oxidizing activity of tobacco smoke inactivates alpha 1-proteinase inhibitor in vitro. Macrophages also secrete an elastolytic protease, albeit at low levels. The short-term exposure of cultured mouse macrophages to cigarette smoke augments the rate of elastase secretion by these cells. Mouse macrophage elastase is not inhibited by alpha 1-proteinase inhibitor or alpha 2-macroglobulin. This unusual property of macrophage elastase may facilitate its attack upon elastin over prolonged intervals despite very low levels of macrophage elastase production. A unified hypothesis of lung injury in pulmonary emphysema is presented, involving both PMN and macrophage elastases and the actions of cigarette smoke. (Am J Pathol 97:111--136, 1979).     

Immunoelectron-microscopic demonstration of elastase in emphysematous lungs of tight-skin mice

The tight-skin (Tsk) mouse has recently been proposed as a genetic model of emphysema. A morphometric study has shown that emphysema develops quickly, between 15 days and 1 month after birth. Previous biochemical and ultrastructural investigations of the lungs of 1- and 2-month-old Tsk mice revealed the presence of an ongoing elastolytic process. The goal of the present study was to investigate the role of mouse leukocyte elastase (MLE) in the development of emphysema in 1-month-old Tsk mice. Using electron microscopy and an immunogold labeling technique with rabbit anti-MLE IgG, MLE was localized within the lung neutrophils of control and Tsk mice. MLE was also found associated with elastin in the alveolar septa of Tsk but not of control mice. Little or no labeling was associated with other components (collagen, pneumocytes, and endothelium) of alveolar septa of Tsk mice. Lung elastin of control mice, or of control mice rendered emphysematous with porcine pancreatic elastase, showed negligible gold particle density when incubated with gold-conjugated rabbit IgG. Thus, under the present experimental conditions, an aspecific labeling of elastin is unlikely. This study indicates that MLE may be one of the factors responsible for the rapid development of emphysema in Tsk mice.     

Interleukin‐33 and alveolar macrophages contribute to the mechanisms underlying the exacerbation of IgE‐mediated airway inflammation and remodelling in mice

Allergen‐specific IgE has long been regarded as a major molecular component of allergic asthma. Additionally, there is increasing evidence of the important roles of interleukin‐33 (IL‐33) in the disease. Here, we show that IL‐33 and alveolar macrophages play essential roles in the exacerbation of IgE‐mediated airway inflammation and remodelling. BALB/c mice passively sensitized with ovalbumin (OVA)‐specific IgE monoclonal antibody (mAb) were challenged with OVA seven times intratracheally. The seventh challenge exacerbated airway inflammation and remodelling compared with the fourth challenge; furthermore, markedly increased expression of IL‐33 in the lungs was observed at the fourth and seventh challenges. When anti‐IL‐33 or anti‐ST2 antibody was administered during the fourth to seventh challenge, airway inflammation and remodelling were significantly inhibited at the seventh challenge. Because increases of IL‐33⁺ and ST2⁺ alveolar macrophages and ST2⁺ CD4⁺ T cells in the lungs were observed at the fourth challenge, the roles of macrophages and CD4⁺ cells were investigated. Depletion of macrophages by 2‐chloroadenosine during the fourth to seventh challenge suppressed airway inflammation and remodelling, and IL‐33 production in the lung at the seventh challenge; additionally, anti‐CD4 mAb inhibited airway inflammation, but not airway remodelling and IL‐33 production. Meanwhile, treatment with 2‐chloroadenosine or anti‐CD4 mAb decreased IL‐33‐induced airway inflammation in normal mice; airway remodelling was repressed only by 2‐chloroadenosine. These results illustrate that macrophage‐derived IL‐33 contributes to the exacerbation of IgE‐mediated airway inflammation by mechanisms associated with macrophages and CD4⁺ cells, and airway remodelling through the activation of macrophages.     

Dexamethasone increases ROS production and T cell suppressive capacity by anti-inflammatory macrophages

Macrophages have been demonstrated to suppress T cell responses by producing reactive oxygen species (ROS) leading to the subsequent induction of T regulatory cells in a ROS-dependent manner. Macrophages may therefore be instrumental in downregulating T cell responses in situations of exacerbated immune responses. Here we investigated the effect of immunosuppressive drugs on ROS production by macrophage subsets and the subsequent effects on T cell activation. Macrophage types 1 and 2 were differentiated with GM-CSF or M-CSF, in presence or absence of dexamethasone, cyclosporine A, FK506, rapamycin, or mycophenolic acid. The ROS producing capacity of fully differentiated Mph was highest in anti-inflammatory Mph2 and not affected by exposure to immunosuppressive drugs. However, presence of rapamycin during Mph2 differentiation decreased the ROS production of these cells. In contrast, other immunosuppressive drugs, with dexamethasone being the most potent, increased the ROS producing capacity of Mph2. Intriguingly although the ROS producing ability of Mph1 was unaffected, dexamethasone strongly increased the ROS producing capabilities of dendritic cells. Both at the mRNA and protein level we found that dexamethasone enhanced the expression of NOX2 protein p47^phox. Functionally, dexamethasone further enhanced the capacity of Mph2 to suppress T cell mediated IFN-γ and IL-4 production. In vivo, only in rats with normal ROS production (congenic DA.Ncf1^E3/E3) it was observed that dexamethasone injection resulted in long-lasting upregulation of ROS production by macrophages and induced higher levels of Treg in a ROS-dependent manner. In conclusion, we show that the anti-inflammatory drug dexamethasone increases the ROS producing capacity of macrophages.     

The xanthine oxidase–NFAT5 pathway regulates macrophage activation and TLR‐induced inflammatory arthritis

NFAT5 (nuclear factor of activated T cells), a well‐known osmoprotective factor, can be activated by isotonic stimuli such as Toll‐like receptor (TLR) triggering. However, it is unclear how NFAT5 discriminates between isotonic and hypertonic stimuli to produce different functional and molecular outcomes. Here, we identified a novel XO–ROS–p38 MAPK–NFAT5 pathway (XO is xanthine oxidase, ROS is reactive oxygen species) that is activated in RAW 264.7 macrophages upon isotonic TLR stimulation. Unlike what is seen under hypertonic conditions, XO‐derived ROS were selectively required for the TLR‐induced NFAT5 activation and NFAT5 binding to the IL‐6 promoter in RAW 264.7 macrophages under isotonic conditions. In mouse peritoneal macrophages and human macrophages, TLR ligation also induced NFAT5 activation, which was dependent on XO and p38 kinase. The involvement of XO in NFAT5 activation by TLR was confirmed in RAW 264.7 macrophages implanted in BALB/c mice. Moreover, allopurinol, an XO inhibitor, suppressed arthritis severity and decreased the expression of NFAT5 and IL‐6 in splenic macrophages in C57BL/6 mice. Collectively, these data support a novel function of the XO–NFAT5 axis in macrophage activation and TLR‐induced arthritis, and suggest that XO inhibitor(s) could serve as a therapeutic agent for chronic inflammatory arthritis.     

Over‐expression of prothymosin‐α antagonizes TGFβ signalling to promote the development of emphysema

Emphysema, a major consequence of chronic obstructive pulmonary disease (COPD), is characterized by the permanent airflow restriction resulting from enlargement of alveolar airspace and loss of lung elasticity. Transforming growth factor‐β (TGFβ) signalling regulates the balance of matrix metalloproteinase (MMP)/tissue inhibitor of matrix metalloproteinase (TIMP) to control matrix homeostasis. Patients with COPD have dysregulated TGFβ signalling and reduced histone deacetylase (HDAC) activity through epigenetic up‐regulation of histone acetylation in the promoters of pro‐inflammatory genes. However, the potential link between decreased HDAC activity and dysregulated TGFβ signalling in emphysema pathogenesis remains to be determined. Prothymosin α (ProT), a highly conserved acidic nuclear protein, plays a role in the acetylation of histone and non‐histone proteins. The aim of this study was to test the hypothesis that ProT inhibits TGFβ–Smad signalling through Smad7, thereby contributing to emphysema pathogenesis. We show that ProT enhances Smad7 acetylation by decreasing its association with HDAC and thereby down‐regulates TGFβ–Smad signalling. ProT caused an imbalance between MMP and TIMP through acetylated Smad7 in favour of MMP expression. In addition to interfering with R‐Smad activation and targeting receptors for degradation in the cytoplasm, acetylated Smad7 potentiated by ProT competitively antagonized binding of the pSmad2/3–Smad4 complex to the TIMP‐3 promoter, resulting in reduced TIMP‐3 expression. These effects were detected in ProT‐over‐expressing cells, lungs of ProT transgenic mice displaying an emphysema phenotype and in emphysema patients. Importantly, increased Smad7 and reduced TIMP‐3 were found in the lungs of emphysema patients and mice with cigarette smoke extract (CSE)‐induced emphysema. Such effects could be abrogated by silencing endogenous ProT expression. Collectively, our results uncover acetylated Smad7 regulated by ProT as an important determinant in dysregulated TGFβ signalling that contributes to emphysema pathogenesis. Copyright © 2015 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Antigen‐specific airway IL‐33 production depends on FcγR‐mediated incorporation of the antigen by alveolar macrophages in sensitized mice

Although interleukin (IL)‐33 is a candidate for the aggravation of asthma, the mechanisms underlying antigen‐specific IL‐33 production in the lung are unclear. Therefore, we analysed the mechanisms in mice. Intra‐tracheal administration of ovalbumin (OVA) evoked increases in IL‐33 and IL‐33 mRNA in the lungs of both non‐sensitized and OVA‐sensitized mice, and the increases in the sensitized mice were significantly higher than in the non‐sensitized mice. However, intra‐tracheal administration of bovine serum albumin did not increase the IL‐33 level in the OVA‐sensitized mice. Depletion of neither mast cells/basophils nor CD4⁺ cells abolished the OVA‐induced IL‐33 production in sensitized mice, suggesting that the antigen recognition leading to the IL‐33 production was not related with either antigen‐specific IgE‐bearing mast cells/basophils or memory CD4⁺ Th2 cells. When a fluorogenic substrate‐labelled OVA (DQ‐OVA) was intra‐tracheally administered, the lung cells of sensitized mice incorporated more DQ‐OVA than those of non‐sensitized mice. The lung cells incorporating DQ‐OVA included B‐cells and alveolar macrophages. The allergic IL‐33 production was significantly reduced by treatment with anti‐FcγRII/III mAb. Depletion of alveolar macrophages by clodronate liposomes significantly suppressed the allergic IL‐33 production, whereas depletion of B‐cells by anti‐CD20 mAb did not. These results suggest that the administered OVA in the lung bound antigen‐specific IgG Ab, and then alveolar macrophages incorporated the immune complex through FcγRII/III on the cell surface, resulting in IL‐33 production in sensitized mice. The mechanisms underlying the antigen‐specific IL‐33 production may aid in development of new pharmacotherapies.     

Arginase 1 activity worsens lung‐protective immunity against Streptococcus pneumoniae infection

Type 2 helper cell (Th2) dominated chronic lung diseases such as asthma are characterized by an increased risk for bacterial lung infections. However, the underlying mechanisms are poorly defined. Arginase 1 (Arg1) has been suggested to play an important role in the pathophysiology of asthma, and is rapidly induced in lung macrophages by Th2 cytokines, thereby limiting macrophage‐derived antimicrobial nitric oxide (NO) production. Here we examined the effect of Th2 cytokine induced upregulation or lung myeloid cell specific conditional knockdown of Arg1 on lung resistance against Streptococcus pneumoniae (Spn) in mice. Lung macrophages responded with a profound induction of Arg1 mRNA and protein to treatment with IL‐13 both in vitro and in vivo. IL‐13‐induced Arg1 activity in the lungs of mice led to significantly attenuated lung‐protective immunity against Spn, while conditional Arg1 knockdown had no effect on lung‐protective immunity against Spn. Collectively, the data show that Th2 cytokine induced increased Arg1 activity worsens lung‐protective immunity against Spn, and interventions to block Th2 cytokine induced lung Arg1 activity may thus be a novel immunomodulatory strategy to lower the risk of bacterial infections in asthmatic patients.