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.

TGF-β1 is a critical mediator of tissue fibrosis in health and disease whose effects are augmented by chitinase 1 (CHIT1). However, the mechanisms that CHIT1 uses to regulate TGF-β1–mediated fibrotic responses have not been defined. Here, we demonstrate that CHIT1 enhances TGF-β1–stimulated fibrotic cellular and tissue responses and TGF-β1 signaling. Importantly, we also demonstrate that these effects are mediated by the ability of CHIT1 to inhibit TGF-β1 induction of its feedback inhibitor, SMAD7. CHIT1 also interacted with TGF-β receptor associated protein 1 (TGFBRAP1) and forkhead box O3 (FOXO3) with TGFBRAP1 playing a critical role in CHIT1 enhancement of TGF-β1 signaling and effector responses and FOXO3 playing a critical role in TGF-β1 induction of SMAD7. These pathways were disease relevant because the levels of CHIT1 were increased and inversely correlated with SMAD7 in tissues from patients with idiopathic pulmonary fibrosis or scleroderma-associated interstitial lung disease. These studies demonstrate that CHIT1 regulates TGF-β1/SMAD7 axis via TGFBRAP1 and FOXO3 and highlight the importance of these pathways in the pathogenesis of pulmonary fibrosis.

Chitinase 1 (CHIT1) plays a role in the pathogenesis of pulmonary fibrosis by modulating canonical and noncanonical TGF-β signaling via interaction with TGFBRAP1 and FOXO3. These findings highlight the CHIT1/SMAD7 axis as a potential biomarker and therapeutic target of pulmonary fibrosis.

Objective: The objective of this study is to screen the therapeutic targets of pain of traditional Chinese medicine Chonglou and explore the relevant mechanism by network pharmacology techniques and methods. Materials and Methods: The chemical components of Chonglou were collected according to chemistry database and related literature. SwissADME was used to collect the potential active ingredients from all the chemical components of Chonglou and SwissTarget Prediction was utilized to predict their targets. The genes related to pain were collected from GeneCards and Online Mendelian Inheritance in Man databases. Joint genes were uploaded to the online string database for the analysis and the PPI network was constructed. The “Chonglou-active component-target-pain” network was constructed by Cytoscape 3.7.1 software, Gene Ontology (GO) functional enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were performed for key target proteins. The top three active components with most targets in the network were docked with the target proteins by the molecular docking technique. Results: A total of nine potential active compounds of Chonglou, 264 potential target genes, 2385 targets of pain disorder, and 128 common targets for drug and disease were screened. One hundred and thirty-one GO items were identified by the GO enrichment analysis, and 23 related signaling pathways were identified by the KEGG pathway enrichment analysis. Molecular-docking results show that pennogenin is the optimal butt ligand of PIK3CA, STAT3, mitogen-activated protein kinase 14, and ADORA1. Conclusion: It is preliminarily revealed that Chonglou might treat pain through multiple targets, multiple biology processes and multiple pain-related signaling pathways, providing reference for the subsequent experimental research.