Alb-Cre Mice Research Articles

233-LB: Ranolazine Fails to Improve Glycemia in Obese Liver-Specific Pyruvate Dehydrogenase–Deficient Mice

Background: Nonalcoholic fatty liver disease (NAFLD) increases risk for obesity-related insulin resistance and type 2 diabetes. Recent studies have demonstrated that stimulating pyruvate dehydrogenase (PDH) , the rate-limiting enzyme in glucose oxidation, can reverse obesity-induced NAFLD. Moreover, our lab has observed that treatment with the antianginal drug, ranolazine, augments hepatic PDH activity, leading to a reversal of obesity-induced glucose intolerance and NAFLD in mice. Our aim herein was to determine whether ranolazine's ability to mitigate obesity-induced NAFLD and hyperglycemia requires increases in hepatic PDH activity. Methods: We generated liver-specific PDH deficient (PDHLiver-/-) mice by crossing floxed Pdha1 mice with albumin-Cre (Alb-Cre) mice. PDHLiver-/- and Alb-Cre mice were placed on a high-fat diet for 12-weeks to induce obesity, whereas their lean controls were fed a low-fat diet. Mice were randomized to treatment with either vehicle control or ranolazine (50 mg/kg) once daily via oral gavage for 5-weeks, following which we assessed glucose homeostasis and hepatic steatosis. Results: Lean PDHLiver-/- mice exhibited no overt phenotypic differences (e.g. adiposity, glucose tolerance) from their Alb-Cre littermates, though a mild but nonsignificant worsening of pyruvate tolerance was observed. Similar findings were observed in obese PDHLiver-/- mice compared to their Alb-Cre littermates. Of interest, ranolazine treatment produced mild improvements in glucose tolerance in obese Alb-Cre mice, but not in obese PDHLiver-/- mice. However, this improvement in ranolazine treated Alb-Cre mice appears to be independent of decreases in hepatic triacylglycerol content. Conclusions: Although hepatic PDH activity appears to contribute to the glucose-lowering actions of ranolazine, this appears to be dissociated from its actions on hepatic steatosis, and impaired hepatic PDH activity per se is not sufficient to produce an NAFLD phenotype. Disclosure C. T. Saed: None. S. Tabatabaei dakhili: None. A. A. Greenwell: None. J. S. F. Chan: None. K. Yang: None. K. Gopal: None. F. Eaton: None. J. R. Ussher: None.

Targeting of GSDMD sensitizes HCC to anti-PD-1 by activating cGAS pathway and downregulating PD-L1 expression

BackgroundGasdermin D (GSDMD) is well known as a downstream of inflammasomes. However, the roles of GSDMD itself in hepatocellular carcinoma (HCC) remain unclear.MethodsTwo independent cohorts of patients with HCC were...

Enhanced Vascular Endothelial NLRP3 Inflammasome Activation by Plasma Exosomes from Liver‐specific Acid Ceramidase Gene Knockout Mice on the High Fat Diet

Circulatory exosomes have been reported to induce vascular endothelial injury and neointima proliferation in mice with liver‐specific deletion of acid ceramidase gene (Asah1fl/fl/Albcre, Asah1 is mouse code of this gene). However, the precise mechanism mediating this exosome‐induced endothelial injury remains unknown. The present study tested a hypothesis that plasma exosomes from Asah1fl/fl/Albcre mice on the high fat diet (HFD) activate endothelial NLRP3 inflammasome activation leading to endothelial dysfunction. To test this hypothesis, wild type (WT/WT) mice and Asah1fl/fl/Albcre mice were fed with normal diet (ND) or HFD for 2 months. Using immunofluorescence confocal microscopy, we confirmed that ceramide levels significantly increased in the liver of Asah1fl/fl/Albcre mice compared to its WT/WT littermates and that HFD further enhanced lysosome ceramide levels in the liver as shown by the colocalization of ceramide with lysosome marker, lamp‐1. Then, isolated exosomes from the plasma of these mice were used to treat the primary cultured WT/WT endothelial cells from the carotid artery. It was found that exosomes isolated from HFD‐treated mice (HFD‐Exo) even from WT/WT mice significantly stimulated NLRP3 inflammasome formation and activation as shown by the significant increases in the colocalization of NLRP3 with Caspase‐1 or ASC, caspase‐1 activity and interleukin 1 beta (IL‐1β) level in the endothelial cells compared to exosomes from ND treated mice (ND‐Exo). This inflammasome formation and activation were remarkably enhanced if endothelial cells were treated by HFD‐Exo isolated from Asah1fl/fl/Albcre mice. To confirm whether lysosomal ceramide contributes to HFD‐Exo‐induced endothelial NLRP3 inflammasome activation, we further treated endothelial cells with C(2)‐ceramide, which was shown similar effects comparable to that induced by HFD‐Exo. Using dibutyryl‐cAMP, a blocker of ceramide‐induced action significantly attenuated C(2)‐ceramide‐ or HDF‐Exo‐induced enhancement of endothelial NLRP3 inflammmasome activation. Together, these results suggest that liver‐specific deletion of lysosomal Asah1 gene promotes release of HFD‐Exos that may contain high ceramide, activating endothelial NLRP3 inflammasome and thereby resulting in endothelial dysfunction during HFD‐induced liver steatosis.

Hepatic CDP-diacylglycerol synthase 2 deficiency causes mitochondrial dysfunction and promotes rapid progression of NASH and fibrosis

Nonalcoholic fatty liver disease (NAFLD) encompasses a spectrum of pathologies, ranging from steatosis to nonalcoholic steatohepatitis (NASH). The factors promoting the progression of steatosis to NASH are still unclear. Recent studies suggest that mitochondrial lipid composition is critical in NASH development. Here, we showed that CDP-DAG synthase 2 (Cds2) was downregulated in genetic or diet-induced NAFLD mouse models. Liver-specific deficiency of Cds2 provoked hepatic steatosis, inflammation and fibrosis in five-week-old mice. CDS2 is enriched in mitochondria-associated membranes (MAMs), and hepatic Cds2 deficiency impaired mitochondrial function and decreased mitochondrial PE levels. Overexpression of phosphatidylserine decarboxylase (PISD) alleviated the NASH-like phenotype in Cds2f/f;AlbCre mice and abnormal mitochondrial morphology and function caused by CDS2 deficiency in hepatocytes. Additionally, dietary supplementation with an agonist of peroxisome proliferator-activated receptor alpha (PPARα) attenuated mitochondrial defects and ameliorated the NASH-like phenotype in Cds2f/f;AlbCre mice. Finally, Cds2 overexpression protected against high-fat diet-induced hepatic steatosis and obesity. Thus, Cds2 modulates mitochondrial function and NASH development.

Role of Mcpip1 in obesity-induced hepatic steatosis as determined by myeloid and liver-specific conditional knockouts.

Monocyte chemoattractant protein‐induced protein 1 (MCPIP1, alias Regnase 1) is a negative regulator of inflammation, acting through cleavage of transcripts coding for proinflammatory cytokines and by inhibition of NFκB activity. Moreover, it was demonstrated that MCPIP1 regulates lipid metabolism both in adipose tissue and in hepatocytes. In this study, we investigated the effects of tissue‐specific Mcpip1 deletion on the regulation of hepatic metabolism and development of nonalcoholic fatty liver disease (NAFLD). We used control Mcpip1fl/fl mice and animals with deletion of Mcpip1 in myeloid leukocytes (Mcpip1fl/flLysMCre) and in hepatocytes (Mcpip1fl/flAlbCre), which were fed chow or a high‐fat diet (HFD) for 12 weeks. Mcpip1fl/flLysMCre mice fed a chow diet were characterized by a significantly reduced hepatic expression of genes regulating lipid and glucose metabolism, which subsequently resulted in low plasma glucose level and dyslipidemia. These animals also displayed systemic inflammation, demonstrated by increased concentrations of cytokines in the plasma and high Tnfa, Il6, IL1b mRNA levels in the liver and brown adipose tissue (BAT). Proinflammatory leukocyte infiltration into BAT, together with low expression of Ucp1 and Ppargc1a, resulted in hypothermia of 22‐week‐old Mcpip1fl/flLysMCre mice. On the other hand, there were no significant changes in phenotype in Mcpip1fl/flAlbCre mice. Although we detected a reduced hepatic expression of genes regulating glucose metabolism and β‐oxidation in these mice, they remained asymptomatic. Upon feeding with a HFD, Mcpip1fl/flLysMCre mice did not develop obesity, glucose intolerance, nor hepatic steatosis, but were characterized by low plasma glucose level and dyslipidemia, along with proinflammatory phenotype. Mcpip1fl/flAlbCre animals, following a HFD, became hypercholesterolemic, but accumulated lipids in the liver at the same level as Mcpip1fl/fl mice, and no changes in the level of soluble factors tested in the plasma were detected. We have demonstrated that Mcpip1 protein plays an important role in the liver homeostasis. Depletion of Mcpip1 in myeloid leukocytes, followed by systemic inflammation, has a more pronounced effect on controlling liver metabolism and homeostasis than the depletion of Mcpip1 in hepatocytes.

Mechanism of hepatocyte mitochondrial NDUFA13 deficiency-induced liver fibrogenesis: the role of abnormal hepatic stellate cell activation

To investigate the role of hepatocyte mitochondrial NDUFA13 loss in the liver fibrogenesis in mice and explore the possible mechanisms. We used liver-specific NDUFA13 heterozygous knockout mouse models (NDUFA13fl/-; Alb-Cre) established previously by intercrossing NDUFA13fl/fl and Alb-Cre mice, with their littermate control NDUFA13fl/fl mice as the control (n=8). The mice were euthanized at the age of 4 weeks and 2 years, and the liver tissues were collected for HE and Masson staining to observe the pathological changes and fibrosis phenotypes. Western blotting was performed to detect the expression of NDUFA13 protein in the liver tissues, and the infiltration of F4/80+ macrophages and the expressions of TGF-β1, TNF-α and IL-1β were analyzed by immunofluorescence assay. The expression levels of α-SMA, matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of matrix metalloproteases 1 (TIMP-1), collagen-Ⅰ and collagen-Ⅲ were assayed by immunohistochemistry. HE and Masson staining showed obvious inflammatory infiltration but no significant fibrosis in the liver tissues of 4-week-old NDUFA13fl/- mice, but severe liver damage with massive fibrosis was observed in 2-year-old NDUFA13fl/- mice. NDUFA13 expression in 2-year-old NDUFA13fl/- mice markedly decreased compared with that in the control NDUFA13fl/fl mice as shown by Western blotting (P < 0.05). Immunohistochemistry showed obvious infiltration of F4/80+ macrophages in the liver tissue with a large amount of TGF-β1 production (P < 0.05) and TNF-α and IL-1β secretions in NDUFA13fl/- mice (P < 0.05). NDUFA13 knockout obviously promoted α-SMA expression (P < 0.05) and collagen-Ⅰ and collagen-Ⅲ deposition (P < 0.05) while significantly decreased MMP-9 and increased TIMP-1 expression in the liver (P < 0.05). Hepatocytes-specific NDUFA13 deficiency can trigger spontaneous and chronic liver fibrosis phenotypes in mice probably in association with abnormal activation of hepatic stellate cells induced by macrophages and inflammatory factors.

Liver-specific deletion of mechanistic target of rapamycin does not protect against acetaminophen-induced liver injury in mice

BackgroundAcetaminophen (APAP) overdose can cause liver injury and liver failure, which is one of the most common causes of drug-induced liver injury in the United States. Pharmacological activation of autophagy by inhibiting mechanistic target of rapamycin (mTOR) protects against APAP-induced liver injury likely via autophagic removal of APAP-adducts and damaged mitochondria. In the present study, we aimed to investigate the role of genetic ablation of mTOR pathways in mouse liver in APAP-induced liver injury and liver repair/regeneration. MethodsAlbumin-Cre (Alb-Cre) mice, mTORf/f and Raptorf/f mice (C57BL/6J background) were crossbred to produce liver-specific mTOR knockout (L-mTOR KO, Alb Cre+/-, mTORf/f) and liver-specific Raptor KO (L-Raptor, Alb Cre+/-, Raptor f/f) mice. Alb-Cre littermates were used as wild-type (WT) mice. These mice were treated with APAP for various time points for up to 48 h. Liver injury, cell proliferation, autophagy and mTOR activation were determined. ResultsWe found that genetic deletion of neither Raptor, an important adaptor protein in mTOR complex 1, nor mTOR, in the mouse liver significantly protected against APAP-induced liver injury despite increased hepatic autophagic flux. Genetic deletion of Raptor or mTOR in mouse livers did not affect APAP metabolism and APAP-induced c-Jun N-terminal kinase (JNK) activation, but slightly improved mouse survival likely due to increased hepatocyte proliferation. ConclusionsOur results indicate that genetic ablation of mTOR in mouse livers does not protect against APAP-induced liver injury but may slightly improve liver regeneration and mouse survival after APAP overdose.

Pathogenic role of NDUFA13 inactivation in spontaneous hepatitis in mice and the mechanism

To investigate the role of NDUFA13 inactivation in the pathogenesis of spontaneous hepatitis in mice and explore the possible mechanisms. Hepatocyte-specific NDUFA13 knockout (NDUFA13fl/-) mice were generated by intercrossing NDUFA13fl/fl and Alb-Cre mice based on Cre/loxP transgenic technology, and tail and liver DNA of the mice was genotyped by PCR analysis. Ten NDUFA13fl/- mice and 10 littermate control NDUFA13fl/fl mice were housed, and in each group, 5 mice were euthanized at the age of 4 weeks and the other 5 at two years for pathological examination of the liver tissues with HE staining. Immunohistochemistry was used to verify the expression levels of NDUFA13, NF-κB/p65, NF-κB/p-p65 and inflammasome NLRP3. The total intracellular ROS and mitochondrial ROS levels were measured with a ROS staining kit. The expressions of the inflammatory cell markers (CD45, MPO, and F4/80) and inflammatory cytokines (IL1β and IL33) in the liver were detected with immunohistochemistry and immunofluorescence assay. Liver-specific NDUFA13 heterozygous knockout mice were successfully constructed as verified by PCR results. HE staining revealed severe liver damage in both 4- week-old and 2-year-old NDUFA13fl/- mice as compared with their littermate controls. Immunohistochemistry showed a significant decrease of NDUFA13 expression in both 4-week-old and 2-year-old NDUFA13fl/- mice (P < 0.05). The expression levels of NF-κB signals p65, p-p65 and NLRP3 inflammasomes were all significantly increased in NDUFA13fl/- mice (P < 0.05). The total intracellular ROS and mitochondrial ROS levels in NDUFA13fl/- mice were also significantly increased. NDUFA13 knockout obviously promoted the expression of the inflammatory cell markers (CD45, MPO and F4/80) and the secretion of IL-1β and IL-33 in the liver tissue of the mice (P < 0.05). Hepatocytes-specific NDUFA13 ablation can trigger spontaneous hepatitis in mice possibly mediated by the activation of ROS/NF-κB/NLRP3 signaling.

BRG1 Mediates Nephronectin Activation in Hepatocytes to Promote T Lymphocyte Infiltration in ConA-Induced Hepatitis.

Fulminant hepatitis (FH) is a major cause of acute liver failure. Concanavalin A (ConA) belongs to the lectin family and is frequently used as an inducer of FH in animal models. ConA induced FH is characterized by massive accumulation of T lymphocytes in the liver. A host of chemoattractive substances are known to promote T cell homing to the liver during acute hepatitis. Here we investigated the involvement of Brahma-related gene 1 (BRG1), a chromatin remodeling protein, in FH. BRG1-flox mice were crossed to Alb-Cre mice to generate hepatocyte conditional BRG1 knockout (LKO) mice. The mice were peritoneally injected with a single dose of ConA to induce FH. BRG1 deficiency mitigated ConA-induced FH in mice. Consistently, there were fewer T lymphocyte infiltrates in the LKO livers compared to the wild type (WT) livers paralleling downregulation of T cell specific cytokines. Further analysis revealed that BRG1 deficiency repressed the expression of several chemokines critical for T cell homing including nephronectin (Npnt). BRG1 knockdown blocked the induction of Npnt in hepatocytes and attenuated T lymphocyte migration in vitro, which was reversed by the addition of recombinant nephronectin. Mechanistically, BRG1 interacted with β-catenin to directly bind to the Npnt promoter and activate Npnt transcription. Importantly, a positive correlation between infiltration of CD3+ T lymphocyes and nephronectin expression was detected in human acute hepatitis biopsy specimens. In conclusion, our data identify a novel role for BRG1 as a promoter of T lymphocyte trafficking by activating Npnt transcription in hepatocytes. Targeting the BRG1-Npnt axis may yield novel therapeutic solutions for FH.

Targeting tumor associated macrophages through blockade of GM-CSF sensitizes cholangiocarcinoma to adaptive immunity

Presenter: Luis Ruffolo MD | University of Rochester Background: Cholangiocarcinoma (CCA), is an aggressive malignancy with poor survival and increasing incidence. Immunotherapies offer the promise for better disease control, yet a thorough understanding of mechanisms of T cell exclusion in CCA remains undescribed. Here were report the immunosuppressive priming of the tumor microenvironment (TME) driven by CCA derived Granulocyte-Macrophage-Colony Stimulating Factor (GM-CSF) in a spontaneous model of CCA. Methods: KRAS(G12D); TP53(-/-); Alb-Cre mice (KPPC) develop spontaneous CCA. Disease was monitored with high frequency ultrasonography. Novel murine tumor cell lines were derived from syngeneic KPPC tumors and injected orthotopically. Histology and immunohistochemistry (IHC) staining was performed on mouse and human CCA for stromal and immunophenotypic markers. Murine tumor and immune compartments were processed for flow cytometry analysis. Genomic analysis of tumor and normal parenchyma was performed by quantitative real time polymerase chain reaction (qRT-PCR) and whole exome RNA sequencing (RNA seq). Therapeutic blockade of GM-CSF was achieved by administration of monoclonal antibody (mab), or appropriate control. The study was approved by UCAR and RSRB at the University of Rochester. Results: The human CCA TME is heavily desmoplastic with a predominant myeloid leukocyte infiltrate (CD11b+). CD68+ tumor associated macrophages (TAMs) are the most abundant leukocyte and their presence within the TME correlates with a worse overall survival after resection (p = 0.03). KPPC tumors closely recapitulate human CCA, and are similarly heavily infiltrated with TAMs and myeloid derived suppressor cells (MDSCs). Outside of the TME, myeloid leukocytes are elevated in the peripheral blood, spleen, and bone marrow of tumor bearing mice compared to littermate controls (P < 0.001). qRT-PCR of bulk tumor vs. normal parenchyma demonstrates increased transcription of myelopoietic cytokines, with GM-CSF being 1000 fold overexpressed compared to littermate controls (P < 0.001). Therapeutic blockade with anti-GM-CSF mAb slowed disease growth and onset of metastases, and prolonged survival in spontaneous tumor bearing mice (P = 0.015) (Figure). Flow cytometry analysis of treated and untreated murine CCA tumors demonstrated a significant decrease in TAMs and peripheral blood monocytes. Furthermore, GM-CSF blockade resulted in a reduction in expression of programmed cell death ligand 1 (PD-L1) and arginase (Arg1) by both TAMs and MDSCs within the TME. Concomitantly, CD8+ effector T cells were found to be increased in prevalence compared to untreated tumor bearing mice, and these cells exhibited increased expression of programmed cell death receptor 1 indicative of activation. RNA seq analysis of tumor educated macrophages treated with anti-GM-CSF mAb demonstrated repolarization away from an M2 phenotype, with reduction in CD206, Arg1, PD-L1, PD-L2, and IL6 (all p-values < 0.01). GM-CSF was found to be over expressed by human CCA tumors compared to normal liver, and tumors with a higher expression of GM-CSF conferred a worse overall survival in resected patients (P = 0.008). Conclusion: CCA induces myelopoiesis and recruitment of TAMs and MDSCs resulting in an immunosuppressive TME. GM-CSF is a key driver of myeloid cell production and immunosuppressive programming, and therapeutic blockade of GM-CSF potently inhibits TAMs resulting in enhanced cytotoxic T cell penetration and activation. GM-CSF represents a novel target which should be explored in advanced biliary malignancies.

Generation and validation of a conditional knockout mouse model for desmosterolosis

AbstractThe enzyme 3β-hydroxysterol-Δ24 reductase (DHCR24, EC 1.3.1.72) catalyzes the conversion of desmosterol to cholesterol and is obligatory for post-squalene cholesterol synthesis. Genetic loss of this enzyme results in desmosterolosis (MIM #602398), a rare disease that presents with multiple congenital anomalies, features of which overlap with subjects with the Smith-Lemli-Opitz syndrome (another post-squalene cholesterol disorder). Global knockout (KO) of Dhcr24 in mice recapitulates the biochemical phenotype, but pups die within 24 h from a lethal dermopathy, limiting its utility as a disease model. Here, we report a conditional KO mouse model (Dhcr24flx/flx) and validate it by generating a liver-specific KO (Dhcr24flx/flx,Alb-Cre). Dhcr24flx/flx,Alb-Cre mice showed normal growth and fertility, while accumulating significantly elevated levels of desmosterol in plasma and liver. Of interest, despite the loss of cholesterol synthesis in the liver, hepatic architecture, gene expression of sterol synthesis genes, and lipoprotein secretion appeared unchanged. The increased desmosterol content in bile and stool indicated a possible compensatory role of hepatobiliary secretion in maintaining sterol homeostasis. This mouse model should now allow for the study of the effects of postnatal loss of DHCR24, as well as role of tissue-specific loss of this enzyme during development and adulthood.

SIRT1 alleviates hepatic ischemia-reperfusion injury via the miR-182-mediated XBP1/NLRP3 pathway

The hepatoprotection of histone deacetylase sirtuin 1 (SIRT1) has been identified to attenuate ischemia-reperfusion (IR)-triggered inflammation and liver damage. This study was performed to characterize the function of SIRT1 in hepatic IR injury. In in vivo assays on liver-specific knockout mice of SIRT1, we first validated the effect of SIRT1 knockout on liver damage and XBP1/NLRP3 inflammasome activation. Next, we examined whether knockdown of XBP1/NLRP3 or miR-182 agomir could reverse the effect of SIRT1 knockout. In in vitro assays, NCTC1469 cells subjected to hypoxia/reoxygenation (H/R) were transduced with small interfering RNA (siRNA)/activator of SIRT1 or miR-182 agomir to confirm the effect of SIRT1 on NCTC1469 cell behaviors as well as the regulation of miR-182 and the XBP1/NLRP3 signaling pathway. Hepatic IR injury was appreciably aggravated in SIRT1 knockout mice, and SIRT1 knockdown abolished the inhibition of XBP1/NLRP3 inflammasome activation, which was reversed by NLRP3 knockdown, XBP1 knockdown, or miR-182 agomir. Mechanistically, miR-182 expression was positively regulated by SIRT1 in hepatic IR injury in mice, and miR-182 inhibited the expression of XBP1 by binding to the 3′ untranslated region (UTR) of XBP1. The histone deacetylase SIRT1 inhibits the downstream XBP1/NLRP3 inflammatory pathway by activating miR-182, thus alleviating hepatic IR injury in mice.

YAP Dependent Induction of CD47-Enriched Extracellular Vesicles Inhibit Dendritic Cells Activation and Ameliorate Hepatic Ischemia-Reperfusion Injury

Hepatic ischemia-reperfusion injury (IRI) is a major cause of liver damage during liver transplantation and hepatectomy, and its amelioration is an urgent unmet clinical need. Excess inflammatory response and oxidative stress contributes to the injury and Yes-associated protein (YAP) in the Hippo signaling pathway has been proved participating in it. In this study, using hepatocyte-specific YAP knockout (YAP-HKO) by crossing Yapflox/flox mice with Alb-Cre mice, we surprisingly noticed in the serum of these mice, the amount of serum extracellular vesicles (EVs) decreased after IRI. Then we found that YAP from hepatocytes regulate EVs secretion through F-actin by increasing membrane formation, as well as inhibiting the fusion of multivesicular body (MVB) and lysosomes. We further explored the essential element of YAP-induced EVs by mass spectrometry, and noticed CD47 was one of the target that highly expressed on hepatocyte-derived EVs in YAP-dependent manner. In addition, we found that CD47+ EVs can inhibit dendritic cells (DCs) activation and inflammatory responses via binding to CD172α on the surface of DCs. Finally, we isolated CD47+ EVs in IRI model and found IRI being ameliorated after treatment, suggesting that CD47+ EVs could be a potential therapeutic strategy for the treating hepatic IRI. Our data showed that CD47-enriched EVs were released in a YAP dependent manner by hepatocytes, which could inhibit DCs activation and contribute to the amelioration of hepatic IRI. Funding Statement: National Key RD the China Postdoctoral Science Foundation, Grant/Award Number: 2020M672980; the National 13th Five-Year Science and Technology Plan Major Projects of China, Grant/Award Number: 2017ZX10203205-006-001; National Natural Science Foundation of China, Grant/Award Number: 81702393, 81770648, 81670601, 81570593, 81802897, 81802897, 81900886; Key Scientific and Technological Projects of Guangdong Province, China, Grant/Award Number: 2015B020226004, 2015A030312013, 2017A030311034; Guangdong Natural Science Foundation, China, Grant/Award Number: 2017A030310373; Science and Technology Planning Project of Guangdong Province, China, Grant/Award Number:2017B030314027, 2017B020209004, 20169013, 2017A020215178; Science and Technology Planning Project of Guangzhou, China, Grant/Award Number: 2014Y2-00200, 2014Y2-00544, 201607010024, 201604020001, 201508020262, 201400000001-3 2017. Declaration of Interests: The authors have declared no conflict of interest. Ethics Approval Statement: The study protocol was approved by the Clinical Ethics Review Board of the Third Affiliated Hospital of Sun Yat- sen University. Informed consent was obtained according to the Declaration of Helsinki. All animal studies were approved and monitored by the animal experimental ethics committee of the Third Affiliated hospital of Sun-Yat Sen University.

HFE and ALK3 act in the same signaling pathway

Hepcidin deficiency leads to iron overload by increased dietary iron uptake and iron release from storage cells. The most frequent mutation in Hfe leads to reduced hepcidin expression and thereby causes iron overload. Recent findings suggested that HFE activates hepcidin expression predominantly via the BMP type I receptor ALK3. Here, we investigated whether HFE exclusively utilizes ALK3 or other signaling mechanisms also. We generated mice with double deficiency of Hfe and hepatocyte-specific Alk3 and compared the iron overload phenotypes of these double knockout mice to single hepatocyte-specific Alk3 deficient or Hfe knockout mice. Double Hfe−/−/hepatic Alk3fl/fl;Alb-Cre knockouts develop a similar iron overload phenotype compared to single hepatocyte-specific Alk3 deficient mice hallmarked by serum iron levels, tissue iron content and hepcidin levels of similar grades. HFE protein levels were increased in Alk3fl/fl;Alb-Cre mice compared to Alk3fl/fl mice, which was caused by iron overload – and not by Alk3 deficiency. The data provide evidence by genetic means that 1. HFE exclusively uses the BMP type I receptor ALK3 to induce hepcidin expression and 2. HFE protein expression is induced by iron overload, which further emphasizes the iron sensing function of HFE.

Abstract 1626: A novel mouse model of hepatocellular carcinoma induced by c-myc overexpression

Abstract Hepatocellular carcinoma is a fatal liver cancer, and there are limited treatment options for this cancer. c-Myc is a key oncogene in liver cancer, but the specific mechanism of carcinogenesis in liver is unknown. Animal models are widely used to explore the molecular pathogenesis of HCC and test new drug candidates. In this poster, we reported a c-Myc conditional over-expression mouse model (LSL-Myc), which inserts the CAG-Loxp-stop-Loxp-c-Myc-polyA expression cassette into the H11 site. The expression of the Myc gene in this mouse model is regulated by Cre recombinase, which is not normally expressed, but only expressed in Cre-expressing tissue cells. LSL-Myc / Alb-cre double-positive mice were produced by crossing LSL-Myc hybrid mice with Alb-cre mice. In this mouse model, c-Myc was specifically expressed in liver cells. LSL-Myc / Alb-cre double-positive mice show a typical HCC phenotype and show accelerated tumor initiation and rapid HCC progression. Mice can detect significant liver tumorigenesis at 2 months of age, and 100% mice can occur hepatocellular carcinoma. The liver cancer tissues from LSL-Myc / Alb-cre double-positive mice can be transplanted to C57BL/6 mice to establish a mouse-derived PDX model. In summary, this model has the advantages of rapid oncogenesis and high incidence of liver cancer. It is an ideal model for studying the mechanism of c-Myc-driven liver cancer and c-Myc targeted therapy. Citation Format: Jinjin Wang, Dan Feng, Haiyan Zhu, Lei Ci, Zhipeng Wan, Ruilin Sun. A novel mouse model of hepatocellular carcinoma induced by c-myc overexpression [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1626.

AMPK activator C24 inhibits hepatic lipogenesis and ameliorates dyslipidemia in HFHC diet-induced animal models.

Dyslipidemia is a chronic metabolic disease characterized by elevated levels of lipids in plasma. Recently, various studies demonstrate that the increased activity of adenosine 5'-monophosphate-activated protein kinase (AMPK) causes health benefits in energy regulation. Thus, great efforts have been made to develop AMPK activators as a metabolic syndrome treatment. In the present study, we investigated the effects of the AMPK activator C24 on dyslipidemia and the potential mechanisms. We showed that C24 (5-40 μM) dose-dependently increased the phosphorylation of AMPKα and acetyl-CoA carboxylase (ACC), and inhibited lipogenesis in HepG2 cells. Using compound C, an AMPK inhibitor, or hepatocytes isolated from liver tissue-specific AMPK knockout AMPKα1α2fl/fl;Alb-cre mice (AMPKLKO), we demonstrated that the lipogenesis inhibition of C24 was dependent on hepatic AMPK activation. In rabbits with high-fat and high-cholesterol diet-induced dyslipidemia, administration of C24 (20, 40, and 60 mg · kg-1· d-1, ig, for 4 weeks) dose-dependently decreased the content of TG, total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C) in plasma and played a role in protecting against hepatic dysfunction by decreasing lipid accumulation. A lipid-lowering effect was also observed in high-fat and high-cholesterol diet-fed hamsters. In conclusion, our results demonstrate that the small molecular AMPK activator C24 alleviates hyperlipidemia and represents a promising compound for the development of a lipid-lowering drug.

Exploration of cardiometabolic and developmental significance of angiotensinogen expression by cells expressing the leptin receptor or agouti-related peptide.

Angiotensin II (ANG II) Agtr1a receptor (AT1A) is expressed in cells of the arcuate nucleus of the hypothalamus that express the leptin receptor (Lepr) and agouti-related peptide (Agrp). Agtr1a expression in these cells is required to stimulate resting energy expenditure in response to leptin and high-fat diets (HFDs), but the mechanism activating AT1A signaling by leptin remains unclear. To probe the role of local paracrine/autocrine ANG II generation and signaling in this mechanism, we bred mice harboring a conditional allele for angiotensinogen (Agt, encoding AGT) with mice expressing Cre-recombinase via the Lepr or Agrp promoters to cause cell-specific deletions of Agt (AgtLepr-KO and AgtAgrp-KO mice, respectively). AgtLepr-KO mice were phenotypically normal, arguing against a paracrine/autocrine AGT signaling mechanism for metabolic control. In contrast, AgtAgrp-KO mice exhibited reduced preweaning survival, and surviving adults exhibited altered renal structure and steroid flux, paralleling previous reports of animals with whole body Agt deficiency or Agt disruption in albumin (Alb)-expressing cells (thought to cause liver-specific disruption). Surprisingly, adult AgtAgrp-KO mice exhibited normal circulating AGT protein and hepatic Agt mRNA expression but reduced Agt mRNA expression in adrenal glands. Reanalysis of RNA-sequencing data sets describing transcriptomes of normal adrenal glands suggests that Agrp and Alb are both expressed in this tissue, and fluorescent reporter gene expression confirms Cre activity in adrenal gland of both Agrp-Cre and Alb-Cre mice. These findings lead to the iconoclastic conclusion that extrahepatic (i.e., adrenal) expression of Agt is critically required for normal renal development and survival.

Loss of Integrin αvβ8 in Murine Hepatocytes Accelerates Liver Regeneration

Recent fate-mapping studies in mice have provided substantial evidence that mature adult hepatocytes are a major source of new hepatocytes after liver injury. In other systems, integrin αvβ8 has a major role in activating transforming growth factor (TGF)-β, a potent inhibitor of hepatocyte proliferation. We hypothesized that depletion of hepatocyte integrin αvβ8 would increase hepatocyte proliferation and accelerate liver regeneration after injury. Using Itgb8flox/flox;Alb-Cre mice to deplete hepatocyte αvβ8, after partial hepatectomy, hepatocyte proliferation and liver-to-body weight ratio were significantly increased in Itgb8flox/flox;Alb-Cre mice compared with control mice. Antibody-mediated blockade of hepatocyte αvβ8 in vitro, with assessment of TGF-β signaling pathways by real-time quantitative PCR array, supported the hypothesis that integrin αvβ8 inhibition alters hepatocyte TGF-β signaling toward a pro-regenerative phenotype. A diethylnitrosamine-induced model of hepatocellular carcinoma, used to examine the possibility that this pro-proliferative phenotype might be oncogenic, revealed no difference in either tumor number or size between Itgb8flox/flox;Alb-Cre and control mice. Immunohistochemistry for integrin αvβ8 in healthy and injured human liver demonstrated that human hepatocytes express integrin αvβ8. Depletion of hepatocyte integrin αvβ8 results in increased hepatocyte proliferation and accelerated liver regeneration after partial hepatectomy in mice. These data demonstrate that targeting integrin αvβ8 may represent a promising therapeutic strategy to drive liver regeneration in patients with a broad range of liver diseases.

PO-137 Liver specific NEMO ablation induces mixed hepatocellular-cholangiocarcinoma in MYC-overexpressing mice

IntroductionThe MYC oncogene appears to be critically involved in the pathogenesis of HCC. The role of NF- κB in liver cancer is complex, either acts as a tumor-promoter or tumor-suppressor in liver carcinogenesis. However, the role of NF- κB in MYC-induced liver carcinogenesis has not been reported. In the present study, we have generated a mouse model of MYC-induced HCC with or without liver specific NEMO deletion. Our aim is to study the effect of inhibiting the IKK/NF-κB signalling in MYC-induced liver carcinogenesis.Material and methodsLAP-tTA mice were first crossed to Alb-cre transgenic mice. Double transgenic offspring were crossed to NEMOfl mice to obtain LAP-tTA+/Alb-cre+/NEMOfl/wt mice, which later were crossed with tetO-Myc +mice. MYC expression was conditionally regulated by doxycycline (DOX) treatment. The combination of all these genetically modified mouse lines resulted in mice that expressed MYC in a liver-specific fashion (MYCLAP-tTA) and had deleted NEMO in liver parenchymal cells (NEMOΔLPC). Mice were analysed at 35 days and 45 days old. Survival curve was plotted and compared. Serum liver enzymes were measured, and analysis was based mainly on histology, protein and gene expression levels.Results and discussionsMacroscopic analyses of the livers of mice with MYC overexpression revealed substantially enlarged livers with multiple visible tumour nodules. MYCLAP-tTA/NEMOΔLPC mice showed significantly reduced survival time than MYCLAP-tTA mice. A significant increase of AST, ALP, GGT and bilirubin levels were observed in MYCLAP-tTA/NEMOΔLPC mice compared to MYCLAP-tTA mice. Unlike the solid tumour nodules present in the MYCLAP-tTA mice, the tumour nodules in the MYCLAP-tTA/NEMOΔLPC mice contained multiple cyst-like/glandular structures, positively stained for CK19, which have been described in human intrahepatic cholangiocarcinoma (ICC). MYCLAP-tTA/NEMOΔLPC mice showed stronger proliferation, apoptosis and fibrosis and an upregulation of progenitor genes expression compared to MYCLAP-tTA mice. We found an activation of RAF/MEK/ERK pathway in MYCLAP-tTA/NEMOΔLPC mice. 10 days DOX treatment could reverse tumorigenesis in MYC transgenic mice.ConclusionWe showed that liver specific NEMO deletion together with MYC overexpression induce a mixed tumour type of HCC-ICC. Deregulation of the IKK/NF-κB signalling may be one of the possible triggers for the development of mixed HCC-ICC and therefore may act as a tumour suppressor in liver carcinogenesis. MYC-driven liver tumorigenesis is reversible by DOX treatment.

PO-140 Cellular localization of survivin influences the response of colorectal cancer cells to topoisomerase I inhibitors

IntroductionThe MYC oncogene appears to be critically involved in the pathogenesis of HCC. The role of NF- κB in liver cancer is complex, either acts as a tumor-promoter or tumor-suppressor in liver carcinogenesis. However, the role of NF- κB in MYC-induced liver carcinogenesis has not been reported. In the present study, we have generated a mouse model of MYC-induced HCC with or without liver specific NEMO deletion. Our aim is to study the effect of inhibiting the IKK/NF-κB signalling in MYC-induced liver carcinogenesis.Material and methodsLAP-tTA mice were first crossed to Alb-cre transgenic mice. Double transgenic offspring were crossed to NEMOfl mice to obtain LAP-tTA+/Alb-cre+/NEMOfl/wt mice, which later were crossed with tetO-Myc +mice. MYC expression was conditionally regulated by doxycycline (DOX) treatment. The combination of all these genetically modified mouse lines resulted in mice that expressed MYC in a liver-specific fashion (MYCLAP-tTA) and had deleted NEMO in liver parenchymal cells (NEMOΔLPC). Mice were analysed at 35 days and 45 days old. Survival curve was plotted and compared. Serum liver enzymes were measured, and analysis was based mainly on histology, protein and gene expression levels.Results and discussionsMacroscopic analyses of the livers of mice with MYC overexpression revealed substantially enlarged livers with multiple visible tumour nodules. MYCLAP-tTA/NEMOΔLPC mice showed significantly reduced survival time than MYCLAP-tTA mice. A significant increase of AST, ALP, GGT and bilirubin levels were observed in MYCLAP-tTA/NEMOΔLPC mice compared to MYCLAP-tTA mice. Unlike the solid tumour nodules present in the MYCLAP-tTA mice, the tumour nodules in the MYCLAP-tTA/NEMOΔLPC mice contained multiple cyst-like/glandular structures, positively stained for CK19, which have been described in human intrahepatic cholangiocarcinoma (ICC). MYCLAP-tTA/NEMOΔLPC mice showed stronger proliferation, apoptosis and fibrosis and an upregulation of progenitor genes expression compared to MYCLAP-tTA mice. We found an activation of RAF/MEK/ERK pathway in MYCLAP-tTA/NEMOΔLPC mice. 10 days DOX treatment could reverse tumorigenesis in MYC transgenic mice.ConclusionWe showed that liver specific NEMO deletion together with MYC overexpression induce a mixed tumour type of HCC-ICC. Deregulation of the IKK/NF-κB signalling may be one of the possible triggers for the development of mixed HCC-ICC and therefore may act as a tumour suppressor in liver carcinogenesis. MYC-driven liver tumorigenesis is reversible by DOX treatment.