Gores, G. J.

Cholangiopathies comprise a spectrum of chronic intrahepatic and extrahepatic biliary tract disorders culminating in progressive cholestatic liver injury, fibrosis, and often cirrhosis and its sequela. Treatment for these diseases is limited, and collectively, they are one of the therapeutic “black boxes” in clinical hepatology. The etiopathogenesis of the cholangiopathies likely includes disease-specific mediators but also common cellular and molecular events driving disease progression (eg, cholestatic fibrogenesis, inflammation, and duct damage). The common pathways involve cholangiocytes, the epithelial cells lining the intrahepatic and extrahepatic bile ducts, which are central to the pathogenesis of these disorders. Current information suggests that cholangiocytes function as a signaling “hub” in biliary tract-associated injury. Herein, we review the pivotal role of cholangiocytes in cholestatic fibrogenesis, focusing on the crosstalk between cholangiocytes and portal fibroblasts and HSCs. The proclivity of these cells to undergo a senescence-associated secretory phenotype, which is proinflammatory and profibrogenic, and the intrinsic intracellular activation pathways resulting in the secretion of cytokines and chemokines are reviewed. The crosstalk between cholangiocytes and cells of the innate (neutrophils and macrophages) and adaptive (T cells and B cells) immune systems is also examined in detail. The information will help consolidate information on this topic and guide further research and potential therapeutic strategies for these diseases.

Abstract Genes encoding SWI/SNF chromatin remodeling complex subunits are recurrently mutated across human cancers. In cholangiocarcinoma (CCA), AT-rich interaction domain-1A (ARID1A) and polybromo-1 (PBRM1) loss of function mutations occur in approximately 18 and 10% of cases respectively. Yet our mechanistic understanding and ability to therapeutically exploit ARID1A and PBRM1 deficiency are immature. Genetically accurate preclinical models are needed to define the role of ARID1A and PBRM1 and test therapeutic approaches in CCA. Analysis of human CCA tumors showed that loss of function mutations in ARID1A and PBRM1 frequently co-occur with each other and with PI3K/AKT pathway activation. Therefore, we developed novel murine models of cholangiocarcinoma initiated by Arid1a knockout or dual Arid1a/Pbrm1 knockout in the context of AKT activation, employing a surgical biliary transfection method for somatic gene editing with CRISPR/Cas9. Mice with cholangiocyte Arid1a knockout and AKT activation (AAC) or dual Arid1a/Pbrm1 knockout and AKT activation (APAC) formed numerous liver tumors within 8 months. Histologically, tumors were predominantly CCA and mixed HCC/CCA, with a similar spectrum of tumors across AAC and APAC mice. Gene editing with CRISPR/Cas9 was confirmed at the DNA level, and loss of protein expression was confirmed in tumor cells by immunohistochemistry. Similar to human CCA, many tumors were densely infiltrated with cancer-associated fibroblasts and a variable degree of CD45+ immune cells. To generate scalable models for preclinical testing, tumors from AAC and APAC mice were dissociated to create cell lines for in vitro studies and propagated by orthotopic transplantation for in vivo studies. Cell lines and orthotopic tumors were validated and retained the genetic features and histologic characteristics of the parental tumors. Collectively these studies have produced a suite of novel, well-characterized, genetically relevant mouse models of epigenetic dysregulation in CCA due to ARID1A and PBRM1 deficiency, which can be used broadly for discovery research and preclinical testing of novel treatment approaches. Citation Format: Caitlin B. Conboy, Jennifer L. Tomlinson, Ryan D. Watkins, Jayla T. Millender, Danielle M. Carlson, Rory L. Smoot, Keith D. Robertson, Greg J. Gores. Novel murine models of ARID1A and PBRM1-deficient cholangiocarcinoma for preclinical discovery and development [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr A048.

Background and Aims We conducted a comprehensive serum transcriptomic analysis to explore the roles of microRNAs (miRNAs) in alcohol‐associated hepatitis (AH) pathogenesis and their prognostic significance. Approach and Results Serum miRNA profiling was performed in 15 controls, 20 heavy drinkers without liver disease, and 65 patients with AH and compared to publicly available hepatic miRNA profiling in AH patients. Among the top 26 miRNAs, expression of miR‐30b‐5p, miR‐20a‐5p, miR‐146a‐5p, and miR‐26b‐5p were significantly reduced in both serum and liver of AH patients. Pathway analysis of the potential targets of these miRNAs uncovered the genes related to DNA synthesis and cell‐cycle progression pathways, including ribonucleotide reductase regulatory subunit M2 (RRM2), cyclin D1 (CCND1), cyclin D2 (CCND2), MYC proto‐oncogene (MYC), and phorbol‐12‐myristate‐13‐acetate‐induced protein 1 (PMAIP1). We found a significant increase in the protein expression of RRM2, CCND1, and CCND2, but not MYC and PMAIP1, in AH patients who underwent liver transplantation; miR‐26b‐5p and miR‐30b‐5p inhibited the 3′‐UTR (untranslated region) luciferase activity of RRM2 and CCND2, and miR‐20a‐5p reduced the 3′‐UTR luciferase activity of CCND1 and CCND2. During a median follow‐up of 346 days, 21% of AH patients died; these patients had higher body mass index (BMI), Model for End‐Stage Liver Disease (MELD), and serum miR‐30b‐5p, miR‐20a‐5p, miR‐146a‐5p, and miR‐26b‐5p than those who survived. Cox regression analysis showed that BMI, MELD score, miR‐20a‐5p, miR‐146a‐5p, and miR‐26b‐5p predicted mortality. Conclusions Patients with AH attempt to deal with hepatocyte injury by down‐regulating specific miRNAs and up‐regulating genes responsible for DNA synthesis and cell‐cycle progression. Higher expression of these miRNAs, suggestive of a diminished capacity in liver regeneration, predicts short‐term mortality in AH patients.

Hepatocytes do not express Bcl-2, a repressor of apoptosis. In contrast, cholangiocytes, which are in direct contact with bile, do express Bcl-2. Because cholestasis results in the retention of bile within hepatocytes, we reasoned cholestasis may induce hepatocellular expression of Bcl-2. Thus our aim was to determine whether hepatocytes express Bcl-2 or alter expression of other Bcl-2 family members in cholestasis using the bile duct-ligated (BDL) rat as a model of cholestasis. De novo Bcl-2 expression was observed in hepatocytes of BDL rats assessed by reverse transcriptase-polymerase chain reaction and immunoblot analysis. Immunohistochemistry demonstrated that Bcl-2 expression in hepatocytes was greater in periportal hepatocytes than pericentral hepatocytes. Expression of Bcl-x (an antiapoptotic Bcl-2 family protein) was not altered by bile duct ligation, whereas expression of Bax (a proapoptotic Bcl-2 family protein) increased slightly as determined by Northern and Western blot analyses. Bcl-2-positive hepatocytes isolated from BDL rats were resistant to induction of apoptosis by 50 microM glycochenodeoxycholate. Our results demonstrate, for the first time, expression of Bcl-2 by hepatocytes during cholestasis. We suggest that hepatocellular expression of Bcl-2 during cholestasis is an adaptive phenomenon to resist apoptosis by toxic bile salts.

Calpain proteases contribute to hepatocyte necrosis during anoxia. Our aim was to ascertain the mechanism causing calpain activation during anoxia. In rat hepatocytes, a twofold increase in calpain activity occurred despite the lack of an increase in cytosolic Ca2+ concentration ([Ca2+]i). The increase in calpain activity was not associated with an increase in calpain mRNA or a decrease in calpastatin mRNA expression. Because phospholipid degradation products generated by phospholipases can activate calpains at physiological [Ca2+]i, we determined the effect of phospholipase inhibitors and activators on calpain activity. Pretreatment of hepatocytes with fluphenazine, a phospholipase inhibitor, decreased calpain activation and improved cell survival. Melittin, a phospholipase A2 activator, increased calpain activity and potentiated cell killing. Finally, phospholipid degradation preceded the increase in calpain activity. Thus the enhanced calpain activity occurring in hepatocytes during anoxia 1) is regulated at the posttranslational level and 2) appears to be dependent on phospholipase activity. These data suggest a novel cascade for degradative hydrolase activity during hepatocyte necrosis by anoxia with phospholipase-mediated activation of calpains.

Interleukin-22 (IL-22) is a Th17 cell hepatoprotective cytokine that is undergoing clinical trials to treat patients with alcoholic hepatitis (AH). Lipopolysaccharide (LPS) activation of macrophage is implicated in hepatocyte cell death and pathogenesis of AH. The role of IL-22 production from macrophage, its regulation by LPS, and effects on alcohol-induced hepatocyte cell death are unexplored and were examined in this study. Low levels of IL-22 mRNA/protein were detected in macrophage but were significantly upregulated by 6.5-fold in response to the tissue reparative cytokine IL-10. Conversely, LPS significantly decreased IL-22 mRNA levels in a temporal and concentration-dependent manner with a maximum reduction of 5-fold. LPS downregulation of IL-22 mRNA levels was rescued in the presence of a pharmacological inhibitor of c-Jun NH 2 -terminal kinase (JNK) and by JNK knockdown. Next, we explored whether macrophage-derived IL-22 regulated ethanol-induced hepatocyte death. Conditioned media from IL-10-stimulated macrophages attenuated ethanol-induced hepatocyte caspase-3/7 activity, and apoptosis as assessed by fluorometric assay and TdT-mediated dUTP nick-end labeling (TUNEL) staining, respectively. This effect was diminished in conditioned media from macrophages with IL-22 knockdown. Cytokine analysis in sera samples of patients with AH revealed that IL-22 levels were significantly elevated compared with healthy controls and heavy-drinking controls, implying a state of IL-22 resistance in human AH. Macrophage-derived IL-22 protects hepatocytes from ethanol-induced cell death. IL-22 downregulation is a new regulatory target of LPS in the pathogenesis of AH.