Idiopathic pulmonary fibrosis (IPF) causes progressive fibrosis and worsening pulmonary function. Prognosis is poor and no effective therapies exist. We show that programmed cell death 5 (PDCD5) ...expression is increased in the lungs of patients with IPF and in mouse models of lung fibrosis. Lung fibrosis is significantly diminished by club cell-specific deletion of Pdcd5 gene. PDCD5 mediates β-catenin/Smad3 complex formation, promoting TGF-β-induced transcriptional activation of matricellular genes. Club cell Pdcd5 knockdown reduces matricellular protein secretion, inhibiting fibroblast proliferation and collagen synthesis. Here, we demonstrate the club cell-specific role of PDCD5 as a mediator of lung fibrosis and potential therapeutic target for IPF.
Chitin, the second most abundant polysaccharide in nature after cellulose, consist exoskeleton of lower organisms such as fungi, crustaceans and insects except mammals. Recently, several studies ...evaluated immunologic effects of chitin in vivo and in vitro and revealed new aspects of chitin regulation of innate and adaptive immune responses. It has been shown that exogenous chitin activates macrophages and other innate immune cells and also modulates adaptive type 2 allergic inflammation. These studies further demonstrate that chitin stimulate macrophages by interacting with different cell surface receptors such as macrophage mannose receptor, toll-like receptor 2 (TLR-2), C-type lectin receptor Dectin-1, and leukotriene B4 receptor (BLT1). On the other hand, a number of chitinase or chitinase-like proteins (C/CLP) are ubiquitously expressed in the airways and intestinal tracts from insects to mammals. In general, these chitinase family proteins confer protective functions to the host against exogenous chitin-containing pathogens. However, substantial body of recent studies also set light on new roles of C/CLP in the development and progression of allergic inflammation and tissue remodeling. In this review, recent findings on the role of chitin and C/CLP in allergic inflammation and tissue remodeling will be highlighted and controversial and unsolved issues in this field of studies will be discussed.
Despite numerous previous studies, the full action mechanism of the pathogenesis of asthma remains undiscovered, and the need for further investigation is increasing in order to identify more ...effective target molecules. Recent attempts to develop more efficacious treatments for asthma have incorporated mesenchymal stem cell (MSC)-based cell therapies. This study aimed to evaluate the anti-asthmatic effects of MSCs primed with Liproxstatin-1, a potent ferroptosis inhibitor. In addition, we sought to examine the changes within macrophage populations and their characteristics in asthmatic conditions. Seven-week-old transgenic mice, constitutively overexpressing lung-specific interleukin (IL)-13, were used to simulate chronic asthma. Human umbilical cord-derived MSCs (hUC-MSCs) primed with Liproxstatin-1 were intratracheally administered four days prior to sampling. IL-13 transgenic mice demonstrated phenotypes of chronic asthma, including severe inflammation, goblet cell hyperplasia, and subepithelial fibrosis. Ly6C
M2 macrophages, found within the pro-inflammatory CD11c
CD11b
macrophages, were upregulated and showed a strong correlation with lung eosinophil counts. Liproxstatin-1-primed hUC-MSCs showed enhanced ability to downregulate the activation of T helper type 2 cells compared to naïve MSCs in vitro and reduced airway inflammation, particularly Ly6C
M2 macrophages population, and fibrosis in vivo. In conclusion, intratracheal administration is an effective method of MSC delivery, and macrophages hold great potential as an additional therapeutic target for asthma.
Members of the 18 glycosyl hydrolase (GH 18) gene family have been conserved over species and time and are dysregulated in inflammatory, infectious, remodeling, and neoplastic disorders. This is ...particularly striking for the prototypic chitinase-like protein chitinase 3-like 1 (Chi3l1), which plays a critical role in antipathogen responses where it augments bacterial killing while stimulating disease tolerance by controlling cell death, inflammation, and remodeling. However, receptors that mediate the effects of GH 18 moieties have not been defined. Here, we demonstrate that Chi3l1 binds to interleukin-13 receptor α2 (IL-13Rα2) and that Chi3l1, IL-13Rα2, and IL-13 are in a multimeric complex. We also demonstrate that Chi3l1 activates macrophage mitogen-activated protein kinase, protein kinase B/AKT, and Wnt/β-catenin signaling and regulates oxidant injury, apoptosis, pyroptosis, inflammasome activation, antibacterial responses, melanoma metastasis, and TGF-β1 production via IL-13Rα2-dependent mechanisms. Thus, IL-13Rα2 is a GH 18 receptor that plays a critical role in Chi3l1 effector responses.
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•Chi3l1 binds to IL-13Rα2 and stimulates MAPK, Akt/PKB, and Wnt//β-catenin signaling•Chi3l1 regulates oxidant injury, apoptosis, and pyroptosis via IL-13Rα2•Chi3l1 regulates antibacterial response and inflammasome activation via IL-13Rα2•Chi3l1 regulates melanoma metastasis and TGF-β1 production via IL-13Rα2
The prototypic chitinase-like protein chitinase 3-like 1 (Chi3l1) plays critical roles in antipathogen responses where it augments bacterial killing, stimulates disease tolerance, and controls cell death, inflammation, and remodeling. However, receptors that mediate the effects of Chi3l1 or any other 18 glycosyl hydrolase gene family member have not been defined. Here, Elias and colleagues demonstrate that Chi3l1 binds to, signals, and regulates oxidant injury, apoptosis, pyroptosis, inflammasome activation, antibacterial responses, melanoma metastasis, and TGF-β1 via IL-13 receptor α2 (IL-13Rα2).
The 18 glycosyl hydrolase family of chitinases is an ancient gene family that is widely expressed from prokaryotes to eukaryotes. In mammals, despite the absence of endogenous chitin, a number of ...chitinases and chitinase-like proteins (C/CLPs) have been identified. However, their roles have only recently begun to be elucidated. Acidic mammalian chitinase (AMCase) inhibits chitin-induced innate inflammation; augments chitin-free, allergen-induced Th2 inflammation; and mediates effector functions of IL-13. The CLPs BRP-39/YKL-40 (also termed chitinase 3-like 1) inhibit oxidant-induced lung injury, augments adaptive Th2 immunity, regulates apoptosis, stimulates alternative macrophage activation, and contributes to fibrosis and wound healing. In accord with these findings, levels of YKL-40 in the lung and serum are increased in asthma and other inflammatory and remodeling disorders and often correlate with disease severity. Our understanding of the roles of C/CLPs in inflammation, tissue remodeling, and tissue injury in health and disease is reviewed below.
Background
Chitinase 3‐like 1 protein (CHI3L1) (YKL‐40 in humans and breast regression protein BRP‐39 in mice) is required for optimal allergen sensitization and Th2 inflammation in various chronic ...inflammatory diseases including asthma. However, the role of CHI3L1 in airway inflammation induced by respiratory viruses has not been investigated. The aim of this study was to investigate the relationship between CHI3L1 and airway inflammation caused by respiratory syncytial virus (RSV) infection.
Methods
We measured YKL‐40 levels in human nasopharyngeal aspirate (NPA) from hospitalized children presenting with acute respiratory symptoms. Wild‐type (WT) and BRP‐39 knockout (KO) C57BL/6 mice were inoculated with live RSV (A2 strain). Bronchoalveolar lavage fluid and lung tissue samples were obtained on day 7 after inoculation to assess lung inflammation, airway reactivity, and expression of cytokines and BRP‐39.
Results
In human subjects, YKL‐40 and IL‐13 levels in NPA were higher in children with RSV infection than in control subjects. Expression of BRP‐39 and Th2 cytokines, IL‐13 in particular, was increased following RSV infection in mice. Airway inflammation caused by RSV infection was reduced in BRP‐39 KO mice as compared to WT mice. Th2 cytokine levels were not increased in the lungs of RSV‐infected BRP‐39 KO mice. BRP‐39 regulated M2 macrophage activation in RSV‐infected mice. Additionally, treatment with anti‐CHI3L1 antibody attenuated airway inflammation and Th2 cytokine production in RSV‐infected WT mice.
Conclusion
These findings suggest that CHI3L1 could contribute to airway inflammation induced by RSV infection. CHI3L1 could be a potential therapeutic candidate for attenuating Th2‐associated immunopathology during RSV infection.
Respiratory syncytial virus infection induces increased expression of BRP‐39 by macrophages and epithelial cells that is related to Th2 inflammation. A lack of BRP‐39 attenuates RSV‐induced airway inflammation and IL‐13 responses. BRP‐39 is an important regulator of RSV infection and suggested as a potential therapeutic target for RSV‐related respiratory illness.
Host antibacterial responses include mechanisms that kill bacteria, but also those that protect or tolerize the host to potentially damaging antibacterial effects. We determined that Chitinase ...3-like-1 (Chi3l1), a conserved prototypic chitinase-like protein, is induced by Streptococcus pneumoniae and plays central roles in promoting bacterial clearance and mediating host tolerance. S. pneumoniae-infected Chi3l1 null mice exhibit exaggerated lung injury, inflammation and hemorrhage, more frequent bacterial dissemination, decreased bacterial clearance, and enhanced mortality compared to controls. Chi3l1 augments macrophage bacterial killing by inhibiting caspase-1-dependent macrophage pyroptosis and augments host tolerance by controlling inflammasome activation, ATP accumulation, expression of ATP receptor P2X7R, and production of thymic stromal lymphopoietin and type 1, type 2, and type 17 cytokines. These data demonstrate that Chi3l1 is induced during infection, where it promotes bacterial clearance while simultaneously augmenting host tolerance, and that these roles likely contributed to the retention of Chi3l1 over species and evolutionary time.
► Chi3l1 plays a critical role in anti-Streptococcus pneumoniae responses ► Chi3l1 augments bacterial killing by inhibiting caspase-1-dependent pyroptosis ► Chi3l1 augments host tolerance by controlling inflammasome and purinergic activation ► Chi3l1 regulates type1, type 2, and type 17 immune responses
ABSTRACT
Pulmonary fibrosis is a progressive and often fatal condition that is believed to be partially orchestrated by macrophages. Mechanisms that control migration of these cells into and within ...the lung remain undefined. We evaluated thecontributions of the semaphorinreceptor, plexinC1 (PLXNC1), andtheexocytic calcium sensor, synaptotagmin 7 (Syt7), in these processes. Weevaluated the role of PLXNC1 in macrophagemigration by using Boyden chambers and scratch tests, characterized its contribution to experimentally induced lung fibrosis inmice, and defined themechanism for our observations. Our findings reveal that relative to controlparticipants, patients with idiopathic pulmonary fibrosis demonstrate excessive monocyte migration and underexpression of PLXNC1 in the lungs and circulation, a finding that is recapitulated in the setting of scleroderma‐related interstitial lung disease. Relative to wild type, PLXNC1‐/‐ mouse macrophages are excessively migratory, and PLXNC1‐/‐ mice show exacerbated collagen accumulation in response to either inhaled bleomycin or inducible lung targeted TGF‐β1 overexpression. These findings are ameliorated by replacement of PLXNC1 on bone marrow–derived cells or by genetic deletion of Syt7. These data demonstrate the previously unrecognized observation that PLXNC1 deficiency permits Syt7‐mediated macrophage migration and enhances mammalian lung fibrosis.—Peng, X., Moore, M., Mathur, A., Zhou, Y., Sun, H., Gan, Y., Herazo‐Maya, J. D., Kaminski, N., Hu, X., Pan, H., Ryu, C., Osafo‐Addo, A., Homer, R. J., Feghali‐Bostwick, C., Fares, W.H., Gulati, M.,Hu, B., Lee, C.‐G., Elias, J. A.,Herzog, E. L. Plexin C1 deficiency permits synaptotagmin 7–mediated macrophage migration and enhances mammalian lung fibrosis. FASEB J. 30, 4056–4070 (2016). www.fasebj.org
Chitin is the second most abundant biopolymer in nature, where it protects crustaceans, parasites, fungi, and other pathogens from the adverse effects of their environments, hosts, or both. Because ...chitin does not exist in mammals, it had been assumed that the chitinases that degrade it are also restricted to lower life forms. However, chitinases and chitinase-like proteins have recently been noted in mice and human subjects. The prototypic chitinase, acidic mammalian chitinase, was also noted to be induced during TH2 inflammation through an IL-13-dependent mechanism. It was also shown to play an important role in the pathogenesis of TH2 inflammation and IL-13 effector pathway activation and demonstrated to be expressed in an exaggerated fashion in human asthmatic tissues. The finding that chitinases contribute to host antiparasite responses and asthmatic TH2 inflammation support the concept that asthma might be a parasite-independent antiparasite response.
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