Hepatic fibrogenesis is a pathophysiological outcome of chronic liver injury hallmarked by excessive accumulation of extracellular matrix proteins. Fibrosis is a dynamic process that involves ...cross-talk between parenchymal cells (hepatocytes), hepatic stellate cells, sinusoidal endothelial cells and both resident and infiltrating immune cells. In this review, we focus on key cell-types that contribute to liver fibrosis, cytokines, and chemokines influencing this process and what it takes for fibrosis to regress. We discuss how mitochondria and metabolic changes in hepatic stellate cells modulate the fibrogenic process. We also briefly review how the presence of fibrosis affects development of hepatocellular carcinoma.
Impact statement
Advanced liver fibrosis results in cirrhosis, portal hypertension, and liver failure and often requires liver transplantation. Advanced liver fibrosis and cirrhosis are also major risk factors for hepatocellular carcinoma (HCC). Hepatic stellate cells (HSCs) play a pivotal role in the pathogenesis of liver fibrosis. In this review, we summarize the basic mechanisms that influence liver fibrosis development and how oxidative stress, mitochondrial dysfunction, and metabolic remodeling modulate HSC activation and indicate areas of potential therapeutic intervention.
How fully differentiated cells that experience carcinogenic insults become proliferative cancer progenitors that acquire multiple initiating mutations is not clear. This question is of particular ...relevance to hepatocellular carcinoma (HCC), which arises from differentiated hepatocytes. Here we show that one solution to this problem is provided by CD44, a hyaluronic acid receptor whose expression is rapidly induced in carcinogen-exposed hepatocytes in a STAT3-dependent manner. Once expressed, CD44 potentiates AKT activation to induce the phosphorylation and nuclear translocation of Mdm2, which terminates the p53 genomic surveillance response. This allows DNA-damaged hepatocytes to escape p53-induced death and senescence and respond to proliferative signals that promote fixation of mutations and their transmission to daughter cells that go on to become HCC progenitors.
Display omitted
•CD44 promotes HCC initiation by protecting DNA-damaged hepatocytes•MDM2 nuclear translocation is facilitated by CD44-coupled EGFR-AKT signaling axis•CD44 terminates DNA damage-induced p53 response, cell-cycle exit, and apoptosis•STAT3 regulates Cd44 expression in hepatocytes
Dhar et al. show that CD44 expression induced in carcinogen-exposed hepatocytes potentiates AKT signaling to activate Mdm2, which terminates the p53 genomic surveillance response. This allows DNA-damaged hepatocytes to respond to proliferative signals, leading their daughter cells to become HCC progenitors.
The role of adaptive immunity in early cancer development is controversial. Here we show that chronic inflammation and fibrosis in humans and mice with non-alcoholic fatty liver disease is ...accompanied by accumulation of liver-resident immunoglobulin-A-producing (IgA
) cells. These cells also express programmed death ligand 1 (PD-L1) and interleukin-10, and directly suppress liver cytotoxic CD8
T lymphocytes, which prevent emergence of hepatocellular carcinoma and express a limited repertoire of T-cell receptors against tumour-associated antigens. Whereas CD8
T-cell ablation accelerates hepatocellular carcinoma, genetic or pharmacological interference with IgA
cell generation attenuates liver carcinogenesis and induces cytotoxic T-lymphocyte-mediated regression of established hepatocellular carcinoma. These findings establish the importance of inflammation-induced suppression of cytotoxic CD8
T-lymphocyte activation as a tumour-promoting mechanism.
The ability to identify a specific cancer using minimally invasive biopsy holds great promise for improving the diagnosis, treatment selection, and prediction of prognosis in cancer. Using ...whole-genome methylation data from The Cancer Genome Atlas (TCGA) and machine learning methods, we evaluated the utility of DNA methylation for differentiating tumor tissue and normal tissue for four common cancers (breast, colon, liver, and lung). We identified cancer markers in a training cohort of 1,619 tumor samples and 173 matched adjacent normal tissue samples. We replicated our findings in a separate TCGA cohort of 791 tumor samples and 93 matched adjacent normal tissue samples, as well as an independent Chinese cohort of 394 tumor samples and 324 matched adjacent normal tissue samples. The DNA methylation analysis could predict cancer versus normal tissue with more than 95% accuracy in these three cohorts, demonstrating accuracy comparable to typical diagnostic methods. This analysis also correctly identified 29 of 30 colorectal cancer metastases to the liver and 32 of 34 colorectal cancer metastases to the lung. We also found that methylation patterns can predict prognosis and survival. We correlated differential methylation of CpG sites predictive of cancer with expression of associated genes known to be important in cancer biology, showing decreased expression with increased methylation, as expected. We verified gene expression profiles in a mouse model of hepatocellular carcinoma. Taken together, these findings demonstrate the utility of methylation biomarkers for the molecular characterization of cancer, with implications for diagnosis and prognosis.
Heterogeneity of HSCs in a Mouse Model of NASH Rosenthal, Sara Brin; Liu, Xiao; Ganguly, Souradipta ...
Hepatology,
August 2021, 2021-08-00, 20210801, Letnik:
74, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Background and Aims
In clinical and experimental NASH, the origin of the scar‐forming myofibroblast is the HSC. We used foz/foz mice on a Western diet to characterize in detail the phenotypic changes ...of HSCs in a NASH model.
Approach and Results
We examined the single‐cell expression profiles (scRNA sequencing) of HSCs purified from the normal livers of foz/foz mice on a chow diet, in NASH with fibrosis of foz/foz mice on a Western diet, and in livers during regression of NASH after switching back to a chow diet. Selected genes were analyzed using immunohistochemistry, quantitative real‐time PCR, and short hairpin RNA knockdown in primary mouse HSCs. Our analysis of the normal liver identified two distinct clusters of quiescent HSCs that correspond to their acinar position of either pericentral vein or periportal vein. The NASH livers had four distinct HSC clusters, including one representing the classic fibrogenic myofibroblast. The three other HSC clusters consisted of a proliferating cluster, an intermediate activated cluster, and an immune and inflammatory cluster. The livers with NASH regression had one cluster of inactivated HSCs, which was similar to, but distinct from, the quiescent HSCs.
Conclusions
Analysis of single‐cell RNA sequencing in combination with an interrogation of previous studies revealed an unanticipated heterogeneity of HSC phenotypes under normal and injured states.
Display omitted
•Hepatic myofibroblasts progressively accumulate in the livers of Mdr2−/− mice.•Myofibroblasts mostly originate from hepatic stellate cells or portal fibroblasts.•Meanwhile, ...fibrocytes minimally contribute to myofibroblasts in Mdr2−/− mice.•In addition to collagen production, myofibroblasts serve as a source of NADPH oxidase (NOX).•Therapeutic blocking of NOX1/4 ameliorates cholestatic fibrosis in Mdr2−/− mice.
Chronic liver injury often results in the activation of hepatic myofibroblasts and the development of liver fibrosis. Hepatic myofibroblasts may originate from 3 major sources: hepatic stellate cells (HSCs), portal fibroblasts (PFs), and fibrocytes, with varying contributions depending on the etiology of liver injury. Here, we assessed the composition of hepatic myofibroblasts in multidrug resistance gene 2 knockout (Mdr2−/−) mice, a genetic model that resembles primary sclerosing cholangitis in patients.
Mdr2−/− mice expressing a collagen-GFP reporter were analyzed at different ages. Hepatic non-parenchymal cells isolated from collagen-GFP Mdr2−/− mice were sorted based on collagen-GFP and vitamin A. An NADPH oxidase (NOX) 1/4 inhibitor was administrated to Mdr2−/− mice aged 12–16 weeks old to assess the therapeutic approach of targeting oxidative stress in cholestatic injury.
Thy1+ activated PFs accounted for 26%, 51%, and 54% of collagen-GFP+ myofibroblasts in Mdr2−/− mice at 4, 8, and 16 weeks of age, respectively. The remaining collagen-GFP+ myofibroblasts were composed of activated HSCs, suggesting that PFs and HSCs are both activated in Mdr2−/− mice. Bone-marrow-derived fibrocytes minimally contributed to liver fibrosis in Mdr2−/− mice. The development of cholestatic liver fibrosis in Mdr2−/− mice was associated with early recruitment of Gr1+ myeloid cells and upregulation of pro-inflammatory cytokines (4 weeks). Administration of a NOX inhibitor to 12-week-old Mdr2−/− mice suppressed the activation of myofibroblasts and attenuated the development of cholestatic fibrosis.
Activated PFs and activated HSCs contribute to cholestatic fibrosis in Mdr2−/− mice, and serve as targets for antifibrotic therapy.
Activated portal fibroblasts and hepatic stellate cells, but not fibrocytes, contributed to the production of the fibrous scar in livers of Mdr2−/− mice, and these cells can serve as targets for antifibrotic therapy in cholestatic injury. Therapeutic inhibition of the enzyme NADPH oxidase (NOX) in Mdr2−/− mice reversed cholestatic fibrosis, suggesting that targeting NOXs may be an effective strategy for the treatment of cholestatic fibrosis.
Hepatocellular carcinoma (HCC) is a slowly developing malignancy postulated to evolve from premalignant lesions in chronically damaged livers. However, it was never established that premalignant ...lesions actually contain tumor progenitors that give rise to cancer. Here, we describe isolation and characterization of HCC progenitor cells (HcPCs) from different mouse HCC models. Unlike fully malignant HCC, HcPCs give rise to cancer only when introduced into a liver undergoing chronic damage and compensatory proliferation. Although HcPCs exhibit a similar transcriptomic profile to bipotential hepatobiliary progenitors, the latter do not give rise to tumors. Cells resembling HcPCs reside within dysplastic lesions that appear several months before HCC nodules. Unlike early hepatocarcinogenesis, which depends on paracrine IL-6 production by inflammatory cells, due to upregulation of LIN28 expression, HcPCs had acquired autocrine IL-6 signaling that stimulates their in vivo growth and malignant progression. This may be a general mechanism that drives other IL-6-producing malignancies.
Display omitted
•Hepatocellular carcinoma (HCC) progenitor cells (HcPCs) are premalignant cells•The ability of HcPCs to progress into HCC depends on autocrine IL-6 production•Autocrine IL-6 production by HcPCs depends on elevated LIN28 expression•Cells with elevated IL-6 and LIN28 exist in mouse and human premalignant lesions
The progenitor cells of hepatocellular carcinoma, unlike normal hepatocytes, produce IL-6, and this autocrine signal is essential for progression of these progenitors to malignancy.
Reaction of NBu4LCuIIOH with excess ROOH (R = cumyl or tBu) yielded NBu4LCuIIOOR, the reversible one-electron oxidation of which generated novel species with CuOOR2+ cores (formally CuIIIOOR), ...identified by spectroscopy and theory for the case R = cumyl. This species reacts with weak O–H bonds in TEMPO-H and 4-dimethylaminophenol (NMe2PhOH), the latter yielding LCu(OPhNMe2), which was also prepared independently. With the identification of CuOOR2+ complexes, the first precedent for this core in enzymes is provided, with implications for copper monooxygenase mechanisms.
The stretching frequency, ν(Cu–O), of the CuOH2+ core in the complexes LCuOH (L = N,N′-bis(2,6-diisopropyl-4-R-phenyl)pyridine-2,6-dicarboxamide, R = H or NO2, or ...N,N′-bis(2,6-diisopropylphenyl)-1-methylpiperidine-2,6-dicarboxamide) was determined to be ∼630 cm–1 by resonance Raman spectroscopy and verified by isotopic labeling. In efforts to use Badger’s rule to estimate the bond distance corresponding to ν(Cu–O), a modified version of the rule was developed through use of stretching frequencies normalized by dividing by the appropriate reduced masses. The modified version was found to yield excellent fits of normalized frequencies to bond distances for >250 data points from theory and experiment for a variety of M–X and X–X bond distances in the range ∼1.1–2.2 Å (root mean squared errors for the predicted bond distances of 0.03 Å). Using the resulting general equation, the Cu–O bond distance was predicted to be ∼1.80 Å for the reactive CuOH2+ core. Limitations of the equation and its use in predictions of distances in a variety of moieties for which structural information is not available were explored.
Despite expression of oncogenic KRAS, premalignant pancreatic intraepithelial neoplasia 1 (PanIN1) lesions rarely become fully malignant pancreatic ductal adenocarcinoma (PDAC). The molecular ...mechanisms through which established risk factors, such as chronic pancreatitis, acinar cell damage, and/or defective autophagy increase the likelihood of PDAC development are poorly understood. We show that accumulation of the autophagy substrate p62/SQSTM1 in stressed KrasG12D acinar cells is associated with PDAC development and maintenance of malignancy in human cells and mice. p62 accumulation promotes neoplastic progression by controlling the NRF2-mediated induction of MDM2, which acts through p53-dependent and -independent mechanisms to abrogate checkpoints that prevent conversion of differentiated acinar cells to proliferative ductal progenitors. MDM2 targeting may be useful for preventing PDAC development in high-risk individuals.
Display omitted
•IKKα-deficiency-induced p62 accumulation drives PDAC progression•MDM2 links the autophagy substrate p62 to neoplastic progression in the pancreas•A p62-NRF2-MDM2 module acts via p53-dependent and -independent mechanisms•A p62-NRF2-MDM2 module converts acinar cells into progenitor-like cells
Todoric et al. demonstrate that pancreatitis-induced accumulation of the autophagy substrate p62/SQSTM1 in the context of oncogenic KRAS promotes progression to pancreatic ductal adenocarcinoma. This p62 function relies on NRF2-driven induction of MDM2 and both p53 dependent and independent activity of MDM2.
PDF
