Chemotherapies are known often to induce severe gastrointestinal tract toxicity but the underlying mechanism remains unclear. This study considers the widely applied cytotoxic agent irinotecan (CPT-11) as a representative agent and demonstrates that treatment induces massive release of double-strand DNA from the intestine that accounts for the dose-limiting intestinal toxicity of the compound. Specifically, "self-DNA" released through exosome secretion enters the cytosol of innate immune cells and activates the AIM2 (absent in melanoma 2) inflammasome. This leads to mature IL-1β and IL-18 secretion and induces intestinal mucositis and late-onset diarrhoea. Interestingly, abrogation of AIM2 signalling, either in AIM2-deficient mice or by a pharmacological inhibitor such as thalidomide, significantly reduces the incidence of drug-induced diarrhoea without affecting the anticancer efficacy of CPT-11. These findings provide mechanistic insights into how chemotherapy triggers innate immune responses causing intestinal toxicity, and reveal new chemotherapy regimens that maintain anti-tumour effects but circumvent the associated adverse inflammatory response.

Uncontrolled immune responses to intracellular DNA have been shown to induce autoimmune diseases. Homeostasis regulation of immune responses to cytosolic DNA is critical for limiting the risk of autoimmunity and survival of the host. Here, we report that the E3 ubiquitin ligase tripartite motif protein 30α (TRIM30α) was induced by herpes simplex virus type 1 (HSV-1) infection in dendritic cells (DCs). Knockdown or genetic ablation of TRIM30α augmented the type I IFNs and interleukin-6 response to intracellular DNA and DNA viruses. Trim30α-deficient mice were more resistant to infection by DNA viruses. Biochemical analyses showed that TRIM30α interacted with the stimulator of interferon genes (STING), which is a critical regulator of the DNA-sensing response. Overexpression of TRIM30α promoted the degradation of STING via K48-linked ubiquitination at Lys275 through a proteasome-dependent pathway. These findings indicate that E3 ligase TRIM30α is an important negative-feedback regulator of innate immune responses to DNA viruses by targeting STING.

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;