Inflammation
Abstract
Extracellular cold-inducible RNA-binding protein (eCIRP) is a damage-associated molecular pattern, whose effect on macrophages is not entirely elucidated. Here we identified that eCIRP promotes macrophage endotoxin tolerance. Septic mice had higher serum levels of eCIRP; this was associated with a reduced ex vivo immune response of their splenocytes to LPS. Pretreatment of macrophages with recombinant murine (rm) CIRP resulted in a tolerance to LPS stimulation as demonstrated by a significant reduction of TNF-α production. We found that eCIRP increased phosphorylation of STAT3 (pSTAT3) in macrophages. A STAT3 inhibitor, Stattic, rescued macrophages from rmCIRP-induced tolerance by restoring the release of TNF-α in response to LPS stimulation. We discovered strong binding affinity between eCIRP and IL-6R as revealed by Biacore, FRET, and their co-localization in macrophages by immunostaining assays. Blockade of IL-6R with its neutralizing Ab significantly inhibited eCIRP-induced pSTAT3 and restored LPS-stimulated TNF-α release in macrophages. Incubation of macrophages with rmCIRP skewed them towards a M2 phenotype, while treatment with anti-IL-6R Ab prevented rmCIRP-induced M2 polarization. Thus, we have demonstrated that eCIRP activates pSTAT3 via a novel receptor IL-6R to promote macrophage endotoxin tolerance. Targeting eCIRP appears to be a new therapeutic option to correct immune-tolerance in sepsis.
Authors
Mian Zhou, Monowar Aziz, Naomi-Liza Denning, Hao-Ting Yen, Gaifeng Ma, Ping Wang
Abstract
Inducible nitric oxide synthase (iNOS) and arginase-2 (ARG2) share a common substrate, arginine. Higher expression of iNOS and exhaled NO are linked to airway inflammation in patients. iNOS deletion in animal models suggests that eosinophilic inflammation is regulated by arginine metabolism. Moreover, ARG2 is a regulator of Th2 response, as shown by the development of severe eosinophilic inflammation in ARG2–/– mice. However, potential synergistic roles of iNOS and ARG2 in asthma have not been explored. Here, we hypothesized that arginine metabolic fate via iNOS and ARG2 may govern airway inflammation. In an asthma cohort, ARG2 variant genotypes were associated with arginase activity. ARG2 variants with lower arginase activity, combined with levels of exhaled NO, identified a severe asthma phenotype. Airway inflammation was present in WT, ARG2–/–, iNOS–/–, and ARG2–/–/iNOS–/– mice but was greatest in ARG2–/–. Eosinophilic and neutrophilic infiltration in the ARG2–/– mice was abrogated in ARG2–/–/iNOS–/– animals. Similarly, angiogenic airway remodeling was greatest in ARG2–/– mice. Cytokines driving inflammation and remodeling were highest in lungs of asthmatic ARG2–/– mice and lowest in the iNOS–/–. ARG2 metabolism of arginine suppresses inflammation, while iNOS metabolism promotes airway inflammation, supporting a central role for arginine metabolic control of inflammation.
Authors
Kewal Asosingh, Chris D. Lauruschkat, Mario Alemagno, Matthew Frimel, Nicholas Wanner, Kelly Weiss, Sean Kessler, Deborah A. Meyers, Carole Bennett, Weiling Xu, Serpil Erzurum
Abstract
Interleukin-3 (IL3) receptor α (IL3Rα) is the alpha subunit of the ligand-specific IL3 receptor and initiates intracellular signaling in response to IL3. IL3 amplifies pro-inflammatory signaling and cytokine storm in murine sepsis models. Here we found that RNFT2 (RING finger transmembrane-domain containing protein 2, also TMEM118), a previously uncharacterized RING finger ubiquitin E3 ligase, negatively regulated IL3-dependent cellular responses through IL3Rα ubiquitination and degradation in the proteasome. In vitro, IL3 stimulation promoted IL3Rα proteasomal degradation dependent on RNFT2, and we identified IL3Rα Lysine 357 as a ubiquitin acceptor site. We determined that LPS-priming reduces RNFT2 abundance, extends IL3Rα half-life, and sensitizes cells to the effects of IL3, acting synergistically to increase pro-inflammatory signaling. In vivo, IL3 synergized with LPS to exacerbate lung inflammation in LPS and Pseudomonas aeruginosa-challenged mice; conversely, IL3 neutralization reduced LPS-induce lung injury. Further, RNFT2 over-expression reduced lung inflammation and injury, whereas Rnft2 knockdown exacerbated inflammatory responses in LPS-induced murine lung injury. Lastly, we examined RNFT2 and IL3Rα in human lung explants from patients with Cystic Fibrosis, and also showed that IL3 is elevated in mechanically-ventilated critically ill humans at risk for Acute Respiratory Distress Syndrome (ARDS). These results identify RNFT2 as a negative regulator of IL3Rα, and show a potential role for the RNFT2/IL3Rα/IL3 axis in regulating innate immune responses in the lung.
Authors
Yao Tong, Travis B. Lear, John Evankovich, Yanwen Chen, James D. Londino, Michael M. Myerburg, Yingze Zhang, Iulia D. Popescu, John F. McDyer, Bryan J. McVerry, Karina C. Lockwood, Michael J. Jurczak, Yuan Liu, Bill B. Chen
Abstract
Alcohol abuse is a major public health problem worldwide causing a wide range of preventable morbidity and mortality. In this translational study, we show that heavy drinking (HD) (≥6 standard drinks/day) is independently associated to a worse outcome of ischemic stroke patients. To study the underlying mechanisms of this deleterious effect of HD, we then performed an extensive analysis of the brain inflammatory responses of mice exposed or not to 10% alcohol before and after ischemic stroke. Inflammatory responses were analyzed at the parenchymal, perivascular and vascular levels by using transcriptomic, immunohistochemical, in vivo two-photon microscopy and molecular MRI analyses. Alcohol-exposed mice show, in the absence of any other insult, a neurovascular inflammatory priming [i.e., an abnormal inflammatory status including an increase in brain perivascular macrophages (PVM)] associated to exacerbated inflammatory responses after a secondary insult (ischemic stroke or LPS challenge). Similar to our clinical data, alcohol-exposed mice showed larger ischemic lesions. We show here that PVM are key players on this aggravating effect of alcohol, since their specific depletion blocks the alcohol-induced aggravation of ischemic lesions. This study opens new therapeutic avenues aiming at blocking alcohol-induced exacerbation of the neurovascular inflammatory responses triggered after ischemic stroke.
Authors
Antoine Drieu, Anastasia Lanquetin, Damien Levard, Martina Glavan, Francisco Campos, Aurélien Quenault, Eloïse Lemarchand, Mikael Naveau, Anne Lise Pitel, José Castillo, Denis Vivien, Marina Rubio
Abstract
Colitis, an inflammatory bowel disease, is caused by a variety of factors, but luminal microbiota are thought to play crucial roles in disease development and progression. Indole is produced by gut microbiota and is believed to protect the colon from inflammatory damage. In the current study, we investigated whether indole-3-carbinol (I3C), a naturally occurring plant product found in numerous cruciferous vegetables, can prevent colitis-associated microbial dysbiosis and attempted to identify the mechanisms. Treatment with I3C led to repressed colonic inflammation and prevention of microbial dysbiosis caused by colitis, increasing a subset of gram-positive bacteria known to produce butyrate. I3C was shown to increase production of butyrate, and when mice with colitis were treated with butyrate, there was reduced colonic inflammation accompanied by suppression of Th17 and induction of Tregs, protection of the mucus layer, and upregulation in Pparg expression. Additionally, IL-22 was increased only after I3C but not butyrate administration, and neutralization of IL-22 prevented the beneficial effects of I3C against colitis, as well as blocked I3C-mediated dysbiosis and butyrate induction. This study suggests that I3C attenuates colitis primarily through induction of IL-22, which leads to modulation of gut microbiota that promote antiinflammatory butyrate.
Authors
Philip B. Busbee, Lorenzo Menzel, Haider Alrafas, Nicholas Dopkins, William Becker, Kathryn Miranda, Chaunbing Tang, Saurabh Chatterjee, Udai Singh, Mitzi Nagarkatti, Prakash S. Nagarkatti
Abstract
Integrins, the extracellular matrix receptors that facilitate cell adhesion and migration, are necessary for organ morphogenesis; however, their role in maintaining adult tissue homeostasis is poorly understood. To define the functional importance of β1 integrin in adult mouse lung, we deleted it post-development in type 2 alveolar epithelial cells (AECs). Aged β1 integrin-deficient mice exhibited chronic obstructive pulmonary disease (COPD)-like pathology characterized by emphysema, lymphoid aggregates, and increased macrophage infiltration. These histopathological abnormalities were preceded by β1 integrin-deficient AEC dysfunction such as excessive reactive oxygen species production and up-regulation of NF-κB-dependent chemokines, including CCL2. Genetic deletion of the CCL2 receptor, Ccr2, in mice with β1 integrin-deficient type 2 AECs impaired recruitment of monocyte-derived macrophages and resulted in accelerated inflammation and severe premature emphysematous destruction. These lungs exhibited reduced AEC efferocytosis and excessive numbers of inflamed type 2 AECs, demonstrating the requirement for recruited monocyte-macrophages in limiting lung injury and remodeling in the setting of a chronically inflamed epithelium. These studies support a critical role for β1 integrin in alveolar homeostasis in the adult lung.
Authors
Erin J. Plosa, John T. Benjamin, Jennifer M. Sucre, Peter M. Gulleman, Linda A. Gleaves, Wei Han, Seunghyi Kook, Vasiliy V. Polosukhin, Scott M. Haake, Susan H. Guttentag, Lisa R. Young, Ambra Pozzi, Timothy S. Blackwell, Roy Zent
Abstract
Dystrophic muscle is characterised by chronic injury, and a steady recruitment of inflammatory Ly6Chi monocytes. Recent studies have identified the spleen as the dominant reservoir of these cells during chronic inflammation. Here we investigated the hitherto unexplored contribution of splenic Ly6Chi monocytes to dystrophic muscle pathology. Using the mdx mouse model of muscular dystrophy, we show that Ly6Chi monocytes accumulate in great numbers in the spleen over the course of the disease. The chemokine receptor CCR2 was upregulated on Ly6Chi monocytes in mdx spleen before disease onset, thereby enabling their recruitment to dystrophic muscle. Splenectomy performed before disease onset significantly reduced the number of Ly6Chi monocytes infiltrating dystrophic limb muscle. Moreover, in the absence of splenic Ly6Chi monocytes there was a significant reduction in dystrophic muscle inflammation and necrosis, along with improved regeneration during early disease. However, during late disease, lack of splenic Ly6Chi monocytes adversely affected muscle fiber repair, due to a delay in the phenotypic shift of pro-inflammatory F4/80+/Ly6Chi/CD206lo to anti-inflammatory F4/80+/Ly6Clo/CD206+ macrophages. Overall, we show that the spleen is an indispensable source of Ly6Chi monocytes in muscular dystrophy, and that splenic monocytes are critical players in both muscle fiber injury and repair.
Authors
Giuseppe Rizzo, Rosanna Di Maggio, Anna Benedetti, Jacopo Morroni, Marina Bouche, Biliana Lozanoska-Ochser
Abstract
The MEK1/2–ERK1/2 pathway has been implicated in regulating the inflammatory response to lung injury and infection, and pharmacologic MEK1/2 inhibitor compounds are reported to reduce detrimental inflammation in multiple animal models of disease, in part through modulation of leukocyte responses. However, the specific contribution of myeloid MEK1 in regulating acute lung injury (ALI) and its resolution remain unknown. Here, the role of myeloid Mek1 was investigated in a murine model of LPS-induced ALI (LPS-ALI) by genetic deletion using the Cre-floxed system (LysMCre × Mekfl), and human alveolar macrophages from healthy volunteers and patients with acute respiratory distress syndrome (ARDS) were obtained to assess activation of the MEK1/2–ERK1/2 pathway. Myeloid Mek1 deletion results in a failure to resolve LPS-ALI, and alveolar macrophages lacking MEK1 had increased activation of MEK2 and the downstream target ERK1/2 on day 4 of LPS-ALI. The clinical significance of these findings is supported by increased activation of the MEK1/2–ERK1/2 pathway in alveolar macrophages from patients with ARDS compared with alveolar macrophages from healthy volunteers. This study reveals a critical role for myeloid MEK1 in promoting resolution of LPS-ALI and controlling the duration of macrophage proinflammatory responses.
Authors
Matthew E. Long, Ke-Qin Gong, William E. Eddy, Joseph S. Volk, Eric D. Morrell, Carmen Mikacenic, T. Eoin West, Shawn J. Skerrett, Jean Charron, W. Conrad Liles, Anne M. Manicone
Abstract
Immune activation is associated with increased risk of tuberculosis (TB) disease in infants. We performed a case control analysis to identify drivers of immune activation and disease risk. Among 49 infants who developed TB disease over the first two years of life, and 129 matched controls who remained healthy, we found the cytomegalovirus (CMV) stimulated IFNγ response at age 4-6 months to be associated with CD8+ T cell activation (Spearmans rho, P = 6 x 10-8). A CMV specific IFNγ response was also associated with increased risk of developing TB disease (Conditional Logistic Regression, P = 0.043, OR 2.2, 95% CI 1.02-4.83), and shorter time to TB diagnosis (Log Rank Mantel-Cox P = 0.037). CMV positive infants who developed TB disease had lower expression of natural killer cell associated gene signatures and a lower frequency of CD3−CD4−CD8− lymphocytes. We identified transcriptional signatures predictive of risk of TB disease among CMV ELISpot positive (AUROC 0.98, accuracy 92.57%) and negative (AUROC 0.9, accuracy 79.3%) infants; the CMV negative signature validated in an independent infant study (AUROC 0.71, accuracy 63.9%). Understanding and controlling the microbial drivers of T cell activation, such as CMV, could guide new strategies for prevention of TB disease in infants.
Authors
Julius Müller, Rachel Tanner, Magali Matsumiya, Margaret A. Snowden, Bernard Landry, Iman Satti, Stephanie A. Harris, Matthew K. O'Shea, Lisa Stockdale, Leanne Marsay, Agnieszka Chomka, Rachel Harrington-Kandt, Zita-Rose Manjaly Thomas, Elena Stylianou, Vivek Naranbhai, Stanley Kimbung Mbandi, Mark Hatherill, Gregory Hussey, Hassan Mahomed, Michele Tameris, J. Bruce McClain, Willem A. Hanekom, Thomas G. Evans, Thomas J. Scriba, Helen McShane, Helen A. Fletcher
Abstract
Worldwide, over a billion people suffer from chronic liver diseases, which often lead to fibrosis and then cirrhosis. Treatments for fibrosis remain experimental, in part because no unifying mechanism has been identified that initiates liver fibrosis. Necroptosis has been implicated in multiple liver diseases. Here, we report that O-linked β-N-acetylglucosamine (O-GlcNAc) modification protects against hepatocyte necroptosis and initiation of liver fibrosis. Decreased O-GlcNAc levels were seen in patients with alcoholic liver cirrhosis and in mice with ethanol-induced liver injury. Liver-specific O-GlcNAc transferase–KO (OGT-LKO) mice exhibited hepatomegaly and ballooning degeneration at an early age and progressed to liver fibrosis and portal inflammation by 10 weeks of age. OGT-deficient hepatocytes underwent excessive necroptosis and exhibited elevated protein expression levels of receptor-interacting protein kinase 3 (RIPK3) and mixed lineage kinase domain-like (MLKL), which are key mediators of necroptosis. Furthermore, glycosylation of RIPK3 by OGT is associated with reduced RIPK3 protein stability. Taken together, these findings identify OGT as a key suppressor of hepatocyte necroptosis, and OGT-LKO mice may serve as an effective spontaneous genetic model of liver fibrosis.
Authors
Bichen Zhang, Min-Dian Li, Ruonan Yin, Yuyang Liu, Yunfan Yang, Kisha A. Mitchell-Richards, Jin Hyun Nam, Rui Li, Li Wang, Yasuko Iwakiri, Dongjun Chung, Marie E. Robert, Barbara E. Ehrlich, Anton M. Bennett, Jun Yu, Michael H. Nathanson, Xiaoyong Yang
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