Chuan Hua He

Chitinase 3-like 1 Regulates Cellular and Tissue Responses via IL-13 Receptor α2

SUMMARY 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.

Bcl-2-related protein A1 is an endogenous and cytokine-stimulated mediator of cytoprotection in hyperoxic acute lung injury

Hyperoxic acute lung injury (HALI) is characterized by a cell death response with features of apoptosis and necrosis that is inhibited by IL-11 and other interventions. We hypothesized that Bfl-1/A1, an antiapoptotic Bcl-2 protein, is a critical regulator of HALI and a mediator of IL-11-induced cytoprotection. To test this, we characterized the expression of A1 and the oxygen susceptibility of WT and IL-11 Tg(+) mice with normal and null A1 loci. In WT mice, 100% O(2) caused TUNEL(+) cell death, induction and activation of intrinsic and mitochondrial-death pathways, and alveolar protein leak. Bcl-2 and Bcl-xl were also induced as an apparent protective response. A1 was induced in hyperoxia, and in A1-null mice, the toxic effects of hyperoxia were exaggerated, Bcl-2 and Bcl-xl were not induced, and premature death was seen. In contrast, IL-11 stimulated A1, diminished the toxic effects of hyperoxia, stimulated Bcl-2 and Bcl-xl, and enhanced murine survival in 100% O(2). In A1-null mice, IL-11-induced protection, survival advantage, and Bcl-2 and Bcl-xl induction were significantly decreased. VEGF also conferred protection via an A1-dependent mechanism. In vitro hyperoxia also stimulated A1, and A1 overexpression inhibited oxidant-induced epithelial cell apoptosis and necrosis. A1 is an important regulator of oxidant-induced lung injury, apoptosis, necrosis, and Bcl-2 and Bcl-xl gene expression and a critical mediator of IL-11- and VEGF-induced cytoprotection.

Chitinase 3-like-1 Promotes Streptococcus pneumoniae Killing and Augments Host Tolerance to Lung Antibacterial Responses

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.

Studies of Vascular Endothelial Growth Factor in Asthma and Chronic Obstructive Pulmonary Disease

Vascular endothelial growth factor (VEGF) is a potent stimulator of vascular angiogenesis, permeability, and remodeling that also plays important roles in wound healing and tissue cytoprotection. To begin to define the roles of VEGF in diseases like asthma and COPD, we characterized the effects of lung-targeted transgenic VEGF(165) and defined the innate immune pathways that regulate VEGF tissue responses. The former studies demonstrated that VEGF plays an important role in Th2 inflammation because, in addition to stimulating angiogenesis and edema, VEGF induced eosinophilic inflammation, mucus metaplasia, subepithelial fibrosis, myocyte hyperplasia, dendritic cell activation, and airways hyperresponsiveness via IL-13-dependent and -independent mechanisms. VEGF was also produced at sites of aeroallergen-induced Th2 inflammation, and VEGF receptor blockade ameliorated adaptive Th2 inflammation and Th2 cytokine elaboration. The latter studies demonstrated that activation of the RIG-like helicase (RLH) innate immune pathway using viral pathogen-associated molecular patterns such as Poly(I:C) or viruses ameliorated VEGF-induced tissue responses. In accord with these findings, Poly(I:C)-induced RLH activation also abrogated aeroallergen-induced Th2 inflammation. When viewed in combination, these studies suggest that VEGF excess can contribute to the pathogenesis of Th2 inflammatory disorders such as asthma and that abrogation of VEGF signaling via RLH activation can contribute to the pathogenesis of viral disorders such as virus-induced COPD exacerbations. They also suggest that RLH activation may be a useful therapeutic strategy in asthma and related disorders.

Acidic Mammalian Chitinase Regulates Epithelial Cell Apoptosis via a Chitinolytic-Independent Mechanism

Acidic mammalian chitinase (AMCase) is produced during and plays an important role in the pathogenesis of Th2-mediated diseases and antiparasite responses. However, the effector responses of AMCase in these settings have not been adequately defined and the relationship(s) between its chitinolytic and other biologic properties have not been investigated. In these studies, we demonstrate that AMCase protects airway epithelial cells from Fas ligand- and growth factor withdrawal-induced apoptosis. This cytoprotection was associated with Akt phosphorylation and abrogated when the PI3K/Akt pathway was inhibited. Comparable cytoprotection was also seen in experiments comparing wild-type AMCase and mutant AMCase that lacked chitinolytic activity. Importantly, the apoptosis-inhibiting effect of enzymatically active and inactive AMCase was abrogated by treatment with allosamidin. These studies demonstrate that secreted AMCase feeds back in an autocrine and/or paracrine manner to protect pulmonary epithelial cells from growth factor withdrawal- and Fas ligand-induced apoptosis. They also demonstrate that the cytoprotection is mediated via a PI3K/Akt-dependent and allosamidin-sensitive pathway that is independent of the chitinolytic activity of this chitinase.

Acidic Mammalian Chitinase Is Secreted via an ADAM17/Epidermal Growth Factor Receptor-dependent Pathway and Stimulates Chemokine Production by Pulmonary Epithelial Cells

Acidic mammalian chitinase (AMCase) is expressed in an exaggerated fashion in epithelial cells at sites of pulmonary T helper cell type 2 inflammation and plays important roles in the pathogenesis of anti-parasite and asthma-like responses. However, the mechanisms that control epithelial cell AMCase secretion and its effector responses have not been adequately defined. To address these issues, we used in vivo and in vitro experimental systems to define the pathways of epithelial AMCase secretion and its epithelial regulatory effects. Here we demonstrate that, in murine T helper cell type 2 modeling systems, AMCase colocalizes with the epidermal growth factor receptor (EGFR) and ADAM17 (a membrane disintegrin and metallopeptidase 17) in lung epithelial cells. In vitro cotransfection experiments in A549 cells demonstrated that AMCase and EGFR physically interact with each other. Cotransfection of AMCase and EGFR also increased, whereas EGFR inhibition decreased AMCase secretion. Interestingly, AMCase secretion was not significantly altered by treatment with EGF but was significantly decreased when the upstream EGFR transactivator ADAM17 was inhibited. AMCase secretion was also decreased when the EGFR-downstream Ras was blocked. Transfected and recombinant AMCase induced epithelial cell production of CCL2, CCL17, and CXCL8. These studies demonstrate that lung epithelial cells secrete AMCase via an EGFR-dependent pathway that is activated by ADAM17 and mediates its effects via Ras. They also demonstrate that the AMCase that is secreted feeds back in an autocrine and/or paracrine fashion to stimulate pulmonary epithelial cell chemokine production.

Chitinase 3–like–1 and its receptors in Hermansky-Pudlak syndrome–associated lung disease

Hermansky-Pudlak syndrome (HPS) comprises a group of inherited disorders caused by mutations that alter the function of lysosome-related organelles. Pulmonary fibrosis is the major cause of morbidity and mortality in patients with subtypes HPS-1 and HPS-4, which both result from defects in biogenesis of lysosome-related organelle complex 3 (BLOC-3). The prototypic chitinase-like protein chitinase 3-like-1 (CHI3L1) plays a protective role in the lung by ameliorating cell death and stimulating fibroproliferative repair. Here, we demonstrated that circulating CHI3L1 levels are higher in HPS patients with pulmonary fibrosis compared with those who remain fibrosis free, and that these levels associate with disease severity. Using murine HPS models, we also determined that these animals have a defect in the ability of CHI3L1 to inhibit epithelial apoptosis but exhibit exaggerated CHI3L1-driven fibroproliferation, which together promote HPS fibrosis. These divergent responses resulted from differences in the trafficking and effector functions of two CHI3L1 receptors. Specifically, the enhanced sensitivity to apoptosis was due to abnormal localization of IL-13Rα2 as a consequence of dysfunctional BLOC-3-dependent membrane trafficking. In contrast, the fibrosis was due to interactions between CHI3L1 and the receptor CRTH2, which trafficked normally in BLOC-3 mutant HPS. These data demonstrate that CHI3L1-dependent pathways exacerbate pulmonary fibrosis and suggest CHI3L1 as a potential biomarker for pulmonary fibrosis progression and severity in HPS.

IL-13Rα2 uses TMEM219 in chitinase 3-like-1-induced signalling and effector responses

Recent studies demonstrated that chitinase 3-like-1 (Chi3l1) binds to and signals via IL-13Rα2. However, the mechanism that IL-13Rα2 uses to mediate the effects of Chi3l1 has not been defined. Here, we demonstrate that the membrane protein, TMEM219, is a binding partner of IL-13Rα2 using yeast two-hybrid, co-immunoprecipitation, co-localization and bimolecular fluorescence complementation assays. Furthermore, fluorescence anisotropy nanodisc assays revealed a direct physical interaction between TMEM219 and IL-13Rα2-Chi3l1 complexes. Null mutations or siRNA silencing of TMEM219 or IL-13Rα2 similarly decreased Chi3l1-stimulated epithelial cell HB-EGF production and macrophage MAPK/Erk and PKB/Akt activation. Null mutations of TMEM219 or IL-13Rα2 also phenocopied one another as regards the ability of Chi3l1 to inhibit oxidant-induced apoptosis and lung injury, promote melanoma metastasis and stimulate TGF-β1. TMEM219 also contributed to the decoy function of IL-13Rα2. These studies demonstrate that TMEM219 plays a critical role in Chi3l1-induced IL-13Rα2 mediated signalling and tissue responses.

Galectin-3 Interacts with the CHI3L1 Axis and Contributes to Hermansky–Pudlak Syndrome Lung Disease

Hermansky–Pudlak syndrome (HPS) comprises a group of inherited disorders caused by mutations that alter the function of lysosome-related organelles. Pulmonary fibrosis is the major cause of morbidity and mortality in HPS-1 and HPS-4 patients. However, the mechanisms that underlie the exaggerated injury and fibroproliferative repair responses in HPS have not been adequately defined. In particular, although Galectin-3 (Gal-3) is dysregulated in HPS, its roles in the pathogenesis of HPS have not been adequately defined. In addition, although chitinase 3-like 1 (CHI3L1) and its receptors play major roles in the injury and repair responses in HPS, the ability of Gal-3 to interact with or alter the function of these moieties has not been evaluated. In this article, we demonstrate that Gal-3 accumulates in exaggerated quantities in bronchoalveolar lavage fluids, and traffics abnormally and accumulates intracellularly in lung fibroblasts and macrophages from bleomycin-treated pale ear, HPS-1–deficient mice. We also demonstrate that Gal-3 drives epithelial apoptosis when in the extracellular space, and stimulates cell proliferation and myofibroblast differentiation when accumulated in fibroblasts and M2-like differentiation when accumulated in macrophages. Biophysical and signaling evaluations also demonstrated that Gal-3 physically interacts with IL-13Rα2 and CHI3L1, and competes with TMEM219 for IL-13Rα2 binding. By doing so, Gal-3 diminishes the antiapoptotic effects of and the antiapoptotic signaling induced by CHI3L1 in epithelial cells while augmenting macrophage Wnt/β-catenin signaling. Thus, Gal-3 contributes to the exaggerated injury and fibroproliferative repair responses in HPS by altering the antiapoptotic and fibroproliferative effects of CHI3L1 and its receptor complex in a tissue compartment-specific manner.

Corrigendum: IL-13Rα2 uses TMEM219 in chitinase 3-like-1-induced signalling and effector responses.

Corrigendum: IL-13Rα2 uses TMEM219 in chitinase 3-like-1-induced signalling and effector responses