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BACKGROUND & AIMS: Activation of TGFB (transforming growth factor b) promotes liver fibrosis by activating hepatic stellate cells (HSCs), but the mechanisms of TGFB activation are not clear. We investigated the role of ECM1 (extracellular matrix protein 1), which interacts with extracellular and structural proteins, in TGFB activation in mouse livers. METHODS:We performed studies with C57BL/6J mice (controls), ECM1-knockout (ECM1-KO) mice, and mice with hepatocyte-specific knockout of EMC1 (ECM1 Dhep ). ECM1 or soluble TGFBR2 (TGFB receptor 2) were expressed in livers of mice after injection of an adeno-associated virus vector. Liver fibrosis was induced by carbon tetrachloride (CCl 4 ) administration. Livers were collected from mice and analyzed by histology, immunohistochemistry, in situ hybridization, and immunofluorescence analyses. Hepatocytes and HSCs were isolated from livers of mice and incubated with ECM1; production of cytokines and activation of reporter genes were quantified. Liver tissues from patients with viral or alcohol-induced hepatitis (with different stages of fibrosis) and individuals with healthy livers were analyzed by immunohistochemistry and in situ hybridization. RESULTS: ECM1-KO mice spontaneously developed liver fibrosis and died by 2 months of age without significant hepatocyte damage or inflammation. In liver tissues of mice, we found that ECM1 stabilized extracellular matrix-deposited TGFB in its inactive form by interacting with av integrins Gastroenterology 2019;157:1352-1367 BASIC AND TRANSLATIONAL LIVER * Authors share co-first authorship.Abbreviations used in this paper: AAV, adeno-associated virus; CLD, chronic liver disease; CCl 4 , carbon tetrachloride; ECM1, extracellular matrix protein 1; ECM1 D;hep , hepatocyte-specific deletion of extracellular matrix protein 1; GAPDH, glyceraldehyde 3-phosphate dehydrogenase;

Interleukin (IL)-33, an epithelial cell-derived cytokine that responds rapidly to environmental insult, has a critical role in initiating airway in ammation, such as that in asthma. However, the molecular mechanism underlying IL-33 secretion following allergen exposure is not clear. Here, we demonstrated that Gasdermin D (Gsdmd) functions as a conduit for IL-33 secretion following allergen protease exposure. Gsdmd was rapidly cleaved into a functional neo-form, the N-terminal p40 fragment (p40 NT-Gsdmd), in the murine airway epithelium when cells were exposed to allergen proteases from fungi, house dust mites (HDMs), or bacteria. This cleavage event that produces the p40 Gsdmd fragment was independent of in ammatory caspases-1/11, as it could not be inhibited by caspase-1 and caspase-11 de ciency in murine cells. The functional p40 NT-Gsdmd fragment directly contributed to the secretion of both the nuclear full-length form and cytosolic mature form of IL-33. Both Gsdmd de ciency and blockade of the generation of p40 by amino acid mutation or deletion of residues 308-313 (ELRQQ) in the Gsdmd sequence could e ciently prevent IL-33 release in airway epithelial cells. In mice, Gsdmd de ciency prevented IL-33 release and hindered the activation of group 2 innate lymphoid cells (ILC2s), thus alleviating airway in ammation and lung tissue damage after stimulation with HDMs or papain. Our ndings uncovered a mechanism of Gsdmd-mediated IL-33 release under allergen exposure and offer insight into Gsdmd cleavage prevention as a potential approach to reduce allergic airway in ammation.