Nuclear Translocation of RELB Is Increased in Diseased Human Liver and Promotes Ductular Reaction and Biliary Fibrosis in Mice

IAN: An Intelligent System for Omics Data Analysis and Discovery

IAN is an R package that addresses the challenge of integrating, analyzing and interpreting high-throughput "omics" data, using a multi-agent artificial intelligence (AI) system. IAN leverages popular pathway and regulatory datasets (KEGG, WikiPathways, Reactome, GO, ChEA) and the STRING database for protein-protein interactions to perform standard enrichment analysis. The individual enrichment results are then used to generate insightful summaries, for each of the datasets, using a large language model (LLM) through a multi-agent architecture. These summaries are then contextually integrated and interpreted by the LLM, guided by carefully engineered prompts and grounding instructions, to provide insightful explanations, system overview, key regulators, novel observations etc. We demonstrate IAN's potential to facilitate biological discovery from complex omics data, by reanalyzing two already published data and evaluating the results. We also show remarkable performance of IAN, in terms of avoiding hallucination. IAN package, along with installation instructions and example usage, is available on https://github.com/NIH-NEI/IAN.

Targeting the TNF and TNFR superfamilies in autoimmune disease and cancer

The first anti-tumour necrosis factor (TNF) monoclonal antibody, infliximab (Remicade), celebrated its 25th anniversary of FDA approval in 2023. Inhibitors of TNF have since proved clinically efficacious at reducing inflammation associated with several autoimmune diseases, including rheumatoid arthritis, psoriasis and Crohn's disease. The success of TNF inhibitors raised unrealistic expectations for targeting other members of the TNF superfamily (TNFSF) of ligands and their receptors, with difficulties in part related to their more limited, variable expression and potential redundancy. However, there has been a resurgence of interest and investment, with many of these cytokines or their cognate receptors now under clinical investigation as targets for modulation of autoimmune and inflammatory diseases, as well as cancer. This Review assesses TNFSF-targeted biologics currently in clinical development for immune system-related diseases, highlighting ongoing challenges and future directions.

Lymphotoxin beta-activated LTBR/NIK/RELB axis drives proliferation in cholangiocarcinoma

BACKGROUND AND AIMS

Cholangiocarcinoma (CCA) is an aggressive malignancy arising from the intrahepatic (iCCA) or extrahepatic (eCCA) bile ducts with poor prognosis and limited treatment options. Prior evidence highlighted a significant contribution of the non-canonical NF-κB signalling pathway in initiation and aggressiveness of different tumour types. Lymphotoxin-β (LTβ) stimulates the NF-κB-inducing kinase (NIK), resulting in the activation of the transcription factor RelB. However, the functional contribution of the non-canonical NF-κB signalling pathway via the LTβ/NIK/RelB axis in CCA carcinogenesis and progression has not been established.

METHODS

Human CCA-derived cell lines and organoids were examined to determine the expression of NF-κB pathway components upon activation or inhibition. Proliferation and cell death were analysed using real-time impedance measurement and flow cytometry. Immunoblot, qRT-PCR, RNA sequencing and in situ hybridization were employed to analyse gene and protein expression. Four in vivo models of iCCA were used to probe the activation and regulation of the non-canonical NF-κB pathway.

RESULTS

Exposure to LTα1/β2 activates the LTβ/NIK/RelB axis and promotes proliferation in CCA. Inhibition of NIK with the small molecule inhibitor B022 efficiently suppresses RelB expression in patient-derived CCA organoids and nuclear co-translocation of RelB and p52 stimulated by LTα1/β2 in CCA cell lines. In murine CCA, RelB expression is significantly increased and LTβ is the predominant ligand of the non-canonical NF-κB signalling pathway.

CONCLUSIONS

Our study confirms that the non-canonical NF-κB axis LTβ/NIK/RelB drives cholangiocarcinogenesis and represents a candidate therapeutic target.

Mendelian randomization analysis of causal and druggable circulating inflammatory proteins in schizophrenia

Background

Schizophrenia (SZ) is a severe mental disorder with complex origins. Observational studies suggested that inflammatory factors may play a role in the pathophysiology of SZ and we aim to investigate the potential genetic connection between them by examining the causal impact of circulating inflammatory proteins on SZ.

Methods

We utilized Mendelian randomization (MR) analysis to assess the causal relationship between circulating inflammatory proteins and SZ and the GWAS summary datasets were sourced from public databases. The SZ dataset comprised 74,776 cases and 101,023 controls, while the summary results for 91 plasma proteins in 14,824 participants were obtained through the Olink Target platform. Moreover, to identify and evaluate potential drug targets, we searched the Drug-Gene Interaction Database (DGIdb).

Results

The results of the MR study confirmed that nine inflammatory proteins had a causal effect on SZ. Among these proteins, IL1A (OR: 0.93), TNFB (OR: 0.94), TNFSF14 (OR: 0.96), and CD40 (OR: 0.95) exhibited protective effects against SZ. Conversely, CCL23 (OR: 1.04), CCL19 (OR: 1.04), 4EBP1 (OR: 1.06), TWEAK (OR: 1.08), and DNER (OR: 1.10) were associated with an increased risk of SZ. The MR-Egger and weighted median methods also supported the direction of these effects. According to the Gene-Drug analysis, LTA, IL1A, CD40, and 4EBP1 can serve as drug targets.

Conclusions

Our study established causal relationships between circulating inflammatory proteins and SZ. It may be beneficial to personalize the treatment of SZ by incorporating inflammation management into the treatment regimen.

Deletion of Tgm2 suppresses BMP-mediated hepatocyte-to-cholangiocyte metaplasia in ductular reaction

Transglutaminase 2 (Tgm2) plays an essential role in hepatic repair following prolonged toxic injury. During cholestatic liver injury, the intrahepatic cholangiocytes undergo dynamic tissue expansion and remodelling, referred to as ductular reaction (DR), which is crucial for liver regeneration. However, the molecular mechanisms governing the dynamics of active cells in DR are still largely unclear. Here, we generated Tgm2-knockout mice (Tgm2-/-) and Tgm2-CreERT2-Rosa26-mTmG flox/flox (Tgm2CreERT2-R26T/Gf/f) mice and performed a three-dimensional (3D) collagen gel culture of mouse hepatocytes to demonstrate how Tgm2 signalling is involved in DR to remodel intrahepatic cholangiocytes. Our results showed that the deletion of Tgm2 adversely affected the functionality and maturity of the proliferative cholangiocytes in DR, thus leading to more severe cholestasis during DDC-induced liver injury. Additionally, Tgm2 hepatocytes played a crucial role in the regulation of DR through metaplasia. We unveiled that Tgm2 regulated H3K4me3Q5ser via serotonin to promote BMP signalling activation to participate in DR. Besides, we revealed that the activation or inhibition of BMP signalling could promote or suppress the development and maturation of cholangiocytes in DDC-induced DR. Furthermore, our 3D collagen gel culture assay indicated that Tgm2 was vital for the development of cholangiocytes in vitro. Our results uncovered a considerable role of BMP signalling in controlling metaplasia of Tgm2 hepatocytes in DR and revealed the phenotypic plasticity of mature hepatocytes.

Central role for cholangiocyte pathobiology in cholestatic liver diseases

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.

Etiology-independent activation of the LTβ-LTβR-RELB axis drives aggressiveness and predicts poor prognosis in HCC

BACKGROUND AND AIMS

HCC is the most common primary liver tumor, with an increasing incidence worldwide. HCC is a heterogeneous malignancy and usually develops in a chronically injured liver. The NF-κB signaling network consists of a canonical and a noncanonical branch. Activation of canonical NF-κB in HCC is documented. However, a functional and clinically relevant role of noncanonical NF-κB and its downstream effectors is not established.

APPROACH AND RESULTS

Four human HCC cohorts (total n = 1462) and 4 mouse HCC models were assessed for expression and localization of NF-κB signaling components and activating ligands. In vitro , NF-κB signaling, proliferation, and cell death were measured, proving a pro-proliferative role of v-rel avian reticuloendotheliosis viral oncogene homolog B (RELB) activated by means of NF-κB-inducing kinase. In vivo , lymphotoxin beta was identified as the predominant inducer of RELB activation. Importantly, hepatocyte-specific RELB knockout in a murine HCC model led to a lower incidence compared to controls and lower maximal tumor diameters. In silico , RELB activity and RELB-directed transcriptomics were validated on the The Cancer Genome Atlas HCC cohort using inferred protein activity and Gene Set Enrichment Analysis. In RELB-active HCC, pathways mediating proliferation were significantly activated. In contrast to v-rel avian reticuloendotheliosis viral oncogene homolog A, nuclear enrichment of noncanonical RELB expression identified patients with a poor prognosis in an etiology-independent manner. Moreover, RELB activation was associated with malignant features metastasis and recurrence.

CONCLUSIONS

This study demonstrates a prognostically relevant, etiology-independent, and cross-species consistent activation of a lymphotoxin beta/LTβR/RELB axis in hepatocarcinogenesis. These observations may harbor broad implications for HCC, including possible clinical exploitation.

P4HA2 induces hepatic ductular reaction and biliary fibrosis in chronic cholestatic liver diseases

BACKGROUNDS

Prolyl-4-hydroxylases (P4Hs) are key enzymes in collagen synthesis. The P4HA subunit (P4HA1, P4HA2, and P4HA3) contains a substrate binding and catalyzation domain. We postulated that P4HA2 would play a key role in the cholangiocyte pathology of cholestatic liver diseases.

METHODS

We studied humans with primary biliary cholangitis (PBC) and Primary sclerosing cholangitis (PSC), P4HA2 -/- mice injured by DDC, and P4HA2 -/- /MDR2 -/- double knockout mice. A parallel study was performed in patients with PBC, PSC, and controls using immunohistochemistry and immunofluorescence. In the murine model, the level of ductular reaction and biliary fibrosis were monitored by histology, qPCR, immunohistochemistry, and Western blotting. Expression of Yes1 Associated Transcriptional Regulator (YAP) phosphorylation was measured in isolated mouse cholangiocytes. The mechanism of P4HA2 was explored in RBE and 293T cell lines by using qPCR, Western blot, immunofluorescence, and co-immunoprecipitation.

RESULTS

The hepatic expression level of P4HA2 was highly elevated in patients with PBC or PSC. Ductular reactive cholangiocytes predominantly expressed P4HA2. Cholestatic patients with more severe liver injury correlated with levels of P4HA2 in the liver. In P4HA2 -/- mice, there was a significantly reduced level of ductular reaction and fibrosis compared with controls in the DDC-induced chronic cholestasis. Decreased liver fibrosis and ductular reaction were observed in P4HA2 -/- /MDR2 -/- mice compared with MDR2 -/- mice. Cholangiocytes isolated from P4HA2 -/- /MDR2 -/- mice displayed a higher level of YAP phosphorylation, resulting in cholangiocytes proliferation inhibition. In vitro studies showed that P4HA2 promotes RBE cell proliferation by inducing SAV1 degradation, eventually resulting in the activation of YAP.

CONCLUSIONS

P4HA2 promotes hepatic ductular reaction and biliary fibrosis by regulating the SAV1-mediated Hippo signaling pathway. P4HA2 is a potential therapeutic target for PBC and PSC.

Bcl-xL as prognostic marker and potential therapeutic target in cholangiocarcinoma

Intrahepatic, perihilar, and distal cholangiocarcinoma (iCCA, pCCA, dCCA) are highly malignant tumours with increasing mortality rates due to therapy resistances. Among the mechanisms mediating resistance, overexpression of anti-apoptotic Bcl-2 proteins (Bcl-2, Bcl-x_L , Mcl-1) is particularly important. In this study, we investigated whether antiapoptotic protein patterns are prognostically relevant and potential therapeutic targets in CCA. Bcl-2 proteins were analysed in a pan-cancer cohort from the NCT/DKFZ/DKTK MASTER registry trial (n = 1140, CCA n = 72) via RNA-sequencing and transcriptome-based protein activity interference revealing high ranks of CCA for Bcl-x_L and Mcl-1. Expression of Bcl-x_L , Mcl-1, and Bcl-2 was assessed in human CCA tissue and cell lines compared with cholangiocytes by immunohistochemistry, immunoblotting, and quantitative-RT-PCR. Immunohistochemistry confirmed the upregulation of Bcl-x_L and Mcl-1 in iCCA tissues. Cell death of CCA cell lines upon treatment with specific small molecule inhibitors of Bcl-x_L (Wehi-539), of Mcl-1 (S63845), and Bcl-2 (ABT-199), either alone, in combination with each other or together with chemotherapeutics was assessed by flow cytometry. Targeting Bcl-x_L induced cell death and augmented the effect of chemotherapy in CCA cells. Combined inhibition of Bcl-x_L and Mcl-1 led to a synergistic increase in cell death in CCA cell lines. Correlation between Bcl-2 protein expression and survival was analysed within three independent patient cohorts from cancer centers in Germany comprising 656 CCA cases indicating a prognostic value of Bcl-x_L in CCA depending on the CCA subtype. Collectively, these observations identify Bcl-x_L as a key protein in cell death resistance of CCA and may pave the way for clinical application.

Triptolide increases resistance to bile duct ligation-induced liver injury and fibrosis in mice by inhibiting RELB

Cholestasis is a common, chronic liver disease that may cause fibrosis and cirrhosis. Tripterygium wilfordii Hook.f (TWHF) is a species in the Euonymus family that is commonly used as a source of medicine and food in Eastern and Southern China. Triptolide (TP) is an epoxy diterpene lactone of TWHF, as well as the main active ingredient in TWHF. Here, we used a mouse model of common bile duct ligation (BDL) cholestasis, along with cultured human intrahepatic biliary epithelial cells, to explore whether TP can relieve cholestasis. Compared with the control treatment, TP at a dose of 70 or 140 μg/kg reduced the serum levels of the liver enzymes alanine transaminase, aspartate aminotransferase, and alkaline phosphatase in mice; hematoxylin and eosin staining also showed that TP reduced necrosis in tissues. Both in vitro and in vivo analyses revealed that TP inhibited cholangiocyte proliferation by reducing the expression of RelB. Immunohistochemical staining of CK19 and Ki67, as well as measurement of Ck19 mRNA levels in hepatic tissue, revealed that TP inhibited the BDL-induced ductular reaction. Masson 3 and Sirius Red staining for hepatic hydroxyproline showed that TP alleviated BDL-induced hepatic fibrosis. Additionally, TP substantially inhibited BDL-induced hepatic inflammation. In summary, TP inhibited the BDL-induced ductular reaction by reducing the expression of RelB in cholangiocytes, thereby alleviating liver injury, fibrosis, and inflammation.

Biliary NIK promotes ductular reaction and liver injury and fibrosis in mice

Excessive cholangiocyte expansion (ductular reaction) promotes liver disease progression, but the underlying mechanism is poorly understood. Here we identify biliary NF-κB-inducing kinase (NIK) as a pivotal regulator of ductular reaction. NIK is known to activate the noncanonical IKKα/NF-κB2 pathway and regulate lymphoid tissue development. We find that cholangiocyte NIK is upregulated in mice with cholestasis induced by bile duct ligation (BDL), 5-diethoxycarbonyl-1,4-dihydrocollidine (DDC), or α-naphtyl-isothiocyanate (ANIT). DDC, ANIT, or BDL induces ductular reaction, liver injury, inflammation, and fibrosis in mice. Cholangiocyte-specific deletion of NIK, but not IKKα, blunts these pathological alterations. NIK inhibitor treatment similarly ameliorates DDC-induced ductular reaction, liver injury, and fibrosis. Biliary NIK directly increases cholangiocyte proliferation while suppressing cholangiocyte death, and it also promotes secretion of cholangiokines from cholangiocytes. Cholangiokines stimulate liver macrophages and hepatic stellate cells, augmenting liver inflammation and fibrosis. These results unveil a NIK/ductular reaction axis and a NIK/cholangiokine axis that promote liver disease progression.

Excessive expansion of cholangiocytes in the liver leads to ductular reaction and liver disease. Here, the authors show that genetic ablation, or pharmacological inhibition, of biliary NIK blocks ductular reaction, liver inflammation, and liver fibrosis in mice by modulating secretion of cholangiokines that mediate liver inflammation and fibrosis.

Progress and Prospects of Non-Canonical NF-κB Signaling Pathway in the Regulation of Liver Diseases

Non-canonical nuclear factor kappa B (NF-κB) signaling pathway regulates many physiological and pathological processes, including liver homeostasis and diseases. Recent studies demonstrate that non-canonical NF-κB signaling pathway plays an essential role in hyperglycemia, non-alcoholic fatty liver disease, alcoholic liver disease, liver regeneration, liver injury, autoimmune liver disease, viral hepatitis, and hepatocellular carcinoma. Small-molecule inhibitors targeting to non-canonical NF-κB signaling pathway have been developed and shown promising results in the treatment of liver injuries. Here, the recent advances and future prospects in understanding the roles of the non-canonical NF-κB signaling pathways in the regulation of liver diseases are discussed.

Amino acid sensor GCN2 promotes SARS-CoV-2 receptor ACE2 expression in response to amino acid deprivation

Angiotensin-converting enzyme 2 (ACE2) has been identified as a primary receptor for severe acute respiratory syndrome coronaviruses 2 (SARS-CoV-2). Here, we investigated the expression regulation of ACE2 in enterocytes under amino acid deprivation conditions. In this study, we found that ACE2 expression was upregulated upon all or single essential amino acid deprivation in human colonic epithelial CCD841 cells. Furthermore, we found that knockdown of general control nonderepressible 2 (GCN2) reduced intestinal ACE2 mRNA and protein levels in vitro and in vivo. Consistently, we revealed two GCN2 inhibitors, GCN2iB and GCN2-IN-1, downregulated ACE2 protein expression in CCD841 cells. Moreover, we found that increased ACE2 expression in response to leucine deprivation was GCN2 dependent. Through RNA-sequencing analysis, we identified two transcription factors, MAFB and MAFF, positively regulated ACE2 expression under leucine deprivation in CCD841 cells. These findings demonstrate that amino acid deficiency increases ACE2 expression and thereby likely aggravates intestinal SARS-CoV-2 infection.

Amino acid deprivation increases ACE2 expression in the gut, potentially aggravating SARS-CoV-2 infection.

Role of Immune Cells in Biliary Repair

The biliary system is comprised of cholangiocytes and plays an important role in maintaining liver function. Under normal conditions, cholangiocytes remain in the stationary phase and maintain a very low turnover rate. However, the robust biliary repair is initiated in disease conditions, and different repair mechanisms can be activated depending on the pathological changes. During biliary disease, immune cells including monocytes, lymphocytes, neutrophils, and mast cells are recruited to the liver. The cellular interactions between cholangiocytes and these recruited immune cells as well as hepatic resident immune cells, including Kupffer cells, determine disease outcomes. However, the role of immune cells in the initiation, regulation, and suspension of biliary repair remains elusive. The cellular processes of cholangiocyte proliferation, progenitor cell differentiation, and hepatocyte-cholangiocyte transdifferentiation during biliary diseases are reviewed to manifest the underlying mechanism of biliary repair. Furthermore, the potential role of immune cells in crucial biliary repair mechanisms is highlighted. The mechanisms of biliary repair in immune-mediated cholangiopathies, inherited cholangiopathies, obstructive cholangiopathies, and cholangiocarcinoma are also summarized. Additionally, novel techniques that could clarify the underlying mechanisms of biliary repair are displayed. Collectively, this review aims to deepen the understanding of the mechanisms of biliary repair and contributes potential novel therapeutic methods for treating biliary diseases.

Blockade of the Notch Signaling Pathway Promotes M2 Macrophage Polarization to Suppress Cardiac Fibrosis Remodeling in Mice With Myocardial Infarction

Myocardial infarction (MI) is regarded as a serious ischemic heart disease on a global level. The current study set out to explore the mechanism of the Notch signaling pathway in the regulation of fibrosis remodeling after the occurrence of MI. First, experimental mice were infected with recombination signal binding protein J (RBP-J) shRNA and empty adenovirus vector, followed by the establishment of MI mouse models and detection of cardiac function. After 4 weeks of MI, mice in the sh-RBP-J group were found to exhibit significantly improved cardiac function relative to the sh-NC group. Moreover, knockdown of RBP-J brought about decreased infarct area, promoted cardiac macrophages M2 polarization, reduced cardiac fibrosis, and further decreased transcription and protein expressions of inflammatory factors and fibrosis-related factors. Furthermore, downregulation of cylindromatosis (CYLD) using si-CYLD reversed the results that knockdown of RBP-J inhibited fibrogenesis and the release of inflammatory factors. Altogether, our findings indicated that the blockade of Notch signaling promotes M2 polarization of cardiac macrophages and improves cardiac function by inhibiting the imbalance of fibrotic remodeling after MI.

Transforming Growth Factor-β Activated Kinase 1 (Tak1) Is Activated in Hepatocellular Carcinoma, Mediates Tumor Progression, and Predicts Unfavorable Outcome

Simple Summary

Chronic inflammation is known to drive cancer initiation and progression in the liver and other organs. In different genetic mouse models, the role of the pro-inflammatory kinase Tak1 in liver cancer development has been controversial so far. To clarify the role of Tak1 in human hepatocellular carcinoma (HCC), we investigated the expression of Tak1 in a large and clinicopathologically well-characterized patient cohort with HCC. In human livers and HCCs, Tak1 is predominantly present in its isoform Tak1A localizing to the cell nucleus. Tak1 is upregulated in HCCs of the diethylnitrosamine mouse model as well as in human HCCs, independent of etiology, and is further induced in distant metastases. Overexpression of the isoform Tak1A in the HCC cell line Huh7 resulted in increased tumor cell migration, whereas overexpression of full-length Tak1 had no significant effect. In human HCCs, high nuclear Tak1 expression is associated with vascular invasion and short overall survival.

Abstract

Although knowledge on inflammatory signaling pathways driving cancer initiation and progression has been increasing, molecular mechanisms in hepatocarcinogenesis are still far from being completely understood. Hepatocyte-specific deletion of the MAPKKK Tak1 in mice recapitulates important steps of hepatocellular carcinoma (HCC) development, including the occurrence of cell death, steatohepatitis, dysplastic nodules, and HCCs. However, overactivation of Tak1 in mice upon deletion of its deubiquitinase Cyld also results in steatohepatitis and HCC development. To investigate Tak1 and Cyld in human HCCs, we created a tissue microarray to analyze their expression by immunohistochemistry in a large and well-characterized cohort of 871 HCCs of 561 patients. In the human liver and HCC, Tak1 is predominantly present as its isoform Tak1A and predominantly localizes to cell nuclei. Tak1 is upregulated in diethylnitrosamine-induced mouse HCCs as well as in human HCCs independent of etiology and is further induced in distant metastases. A high nuclear Tak1 expression is associated with short survival and vascular invasion. When we overexpressed Tak1A in Huh7 cells, we observed increased tumor cell migration, whereas overexpression of full-length Tak1 had no significant effect. A combined score of low Cyld and high Tak1 expression was an independent prognostic marker in a multivariate Cox regression model.

Novel Therapeutic Targets in Liver Fibrosis

Liver fibrosis is end-stage liver disease that can be rescued. If irritation continues due to viral infection, schistosomiasis and alcoholism, liver fibrosis can progress to liver cirrhosis and even cancer. The US Food and Drug Administration has not approved any drugs that act directly against liver fibrosis. The only treatments currently available are drugs that eliminate pathogenic factors, which show poor efficacy; and liver transplantation, which is expensive. This highlights the importance of clarifying the mechanism of liver fibrosis and searching for new treatments against it. This review summarizes how parenchymal, nonparenchymal cells, inflammatory cells and various processes (liver fibrosis, hepatic stellate cell activation, cell death and proliferation, deposition of extracellular matrix, cell metabolism, inflammation and epigenetics) contribute to liver fibrosis. We highlight discoveries of novel therapeutic targets, which may provide new insights into potential treatments for liver fibrosis.

HCV eradication with IFN-based therapy does not completely restore gene expression in PBMCs from HIV/HCV-coinfected patients

Objective

To evaluate the impact of hepatitis C virus (HCV) elimination via interferon (IFN)-based therapy on gene expression profiles related to the immune system in HIV/HCV-coinfected patients.

Methods

We conducted a prospective study in 28 HIV/HCV-coinfected patients receiving IFN-based therapy at baseline (HIV/HCV-b) and week 24 after sustained virological response (HIV/HCV-f). Twenty-seven HIV-monoinfected patients (HIV-mono) were included as a control. RNA-seq analysis was performed on peripheral blood mononuclear cells (PBMCs). Genes with a fold-change (FC) ≥ 1.5 (in either direction) and false discovery rate (FDR) ≤ 0.05 were identified as significantly differentially expressed (SDE).

Results

HIV/HCV-b showed six SDE genes compared to HIV-mono group, but no significantly enriched pathways were observed. For HIV/HCV-f vs. HIV/HCV-b, we found 58 SDE genes, 34 upregulated and 24 downregulated in the HIV/HCV-f group. Of these, the most overexpressed were CXCL2, PDCD6IP, ATP5B, IGSF9, RAB26, and CSRNP1, and the most downregulated were IFI44 and IFI44L. These 58 SDE genes revealed two significantly enriched pathways (FDR < 0.05), one linked to Epstein-Barr virus infection and another related to p53 signaling. For HIV/HCV-f vs. HIV-mono group, we found 44 SDE genes that revealed 31 enriched pathways (FDR < 0.05) related to inflammation, cancer/cell cycle alteration, viral and bacterial infection, and comorbidities associated with HIV/HCV-coinfection. Five genes were overrepresented in most pathways (JUN, NFKBIA, PIK3R2, CDC42, and STAT3).

Conclusion

HIV/HCV-coinfected patients who eradicated hepatitis C with IFN-based therapy showed profound gene expression changes after achieving sustained virological response. The altered pathways were related to inflammation and liver-related complications, such as non-alcoholic fatty liver disease and hepatocellular carcinoma, underscoring the need for active surveillance for these patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12929-021-00718-6.

Noncanonical NF-κB Signaling Pathway in Liver Diseases

The noncanonical NF-κB signaling pathway is an important branch of NF-κB signaling. It is involved in regulating multiple important biological processes, including inflammation and host immune response. A central adaptor protein of the noncanonical NF-κB pathway is NF-κB-inducing kinase (NIK), which activates the downstream kinase IKKα to process p100 to p52, thereby forming the RelB/p52 heterodimer to initiate the expression of target genes. Currently, many specific inhibitors and monoclonal antibodies targeting or triggering this pathway are being developed and tested for various diseases, including cancers, autoimmune diseases, and virus infection. Given that aberrant activation of the noncanonical NF-κB pathway is frequently observed in various liver diseases, targeting this pathway may be a promising therapeutic strategy to alleviate liver inflammation. Moreover, activation of this pathway may contribute to the antiviral immune response and promote the clearance of persistent hepatotropic virus infection. Here, we review the role of the noncanonical NF-κB pathway in the occurrence and development of different liver diseases, and discuss the potency and application of modulating the noncanonical NF-κB pathway for treatment of these liver diseases.

RelB promotes liver fibrosis via inducing the release of injury-associated inflammatory cytokines

Liver fibrosis is a serious chronic disease that developed by a coordinated interplay of many cell types, but the underlying signal transduction in individual cell type remains to be characterized. Nuclear factor‐κB (NF‐κB) is a widely accepted central player in the development of hepatic fibrosis. However, the precise role of each member of NF‐κB in different cell type is unclear. Here, we generated a mouse model (Relb^Δhep) with hepatocyte‐specific deletion of RelB, a member of NF‐κB family. Relb^Δhep mice born normally and appear normal without obvious abnormality. However, in the CCl4‐induced liver fibrosis, Relb^Δhep mice developed less severe disease compared with wide‐type (WT) mice. The denaturation and necrosis of hepatocytes as well as the formation of false lobules in Relb^Δhep mice were significantly reduced compared with WT mice. The production of α‐SMA and the level of collagen I and Collagen III were greatly reduced in Relb^Δhep mice comparing with WT mice. Furthermore, in patients with liver fibrosis, RelB is up‐regulated along with the stage of diseases. Consistently, CCl4 treatment could up‐regulate the expression of RelB as well as inflammatory cytokines such as IL‐6 and TGF‐β1 in hepatoma cell as well as in WT mice. Knockdown the expression of RelB in hepatoma cells greatly reduced the expression of CCl4‐induced inflammatory cytokines. In summary, we provide the genetic evidence to demonstrate the critical and hepatocellular role of RelB in liver fibrosis. RelB is an important transcription factor to drive the expression of inflammatory cytokines in the initiation phase of injury.

The Spectrum of Reactive Cholangiocytes in Primary Sclerosing Cholangitis

Cholangiocytes are the target of a group of chronic liver diseases termed the "cholangiopathies," in which cholangiocytes react to exogenous and endogenous insults, leading to disease initiation and progression. In primary sclerosing cholangitis (PSC), the focus of this review, the cholangiocyte response to genetic or environmental insults can lead to a heterogeneous response; that is, a subpopulation acquires a ductular reactive and proliferative phenotype, while another subpopulation undergoes senescence and growth arrest. Both ductular reactive cholangiocytes and senescent cholangiocytes can modify the periductal microenvironment through their ability to secrete various cytokines, chemokines, and growth factors, initiating and perpetuating inflammatory and profibrotic responses. This review discusses the similarities and differences, the interrelationships, and the potential pathogenic roles of these reactive proliferative and senescent cholangiocyte subpopulations in PSC.

Liver Progenitors and Adult Cell Plasticity in Hepatic Injury and Repair: Knowns and Unknowns

The liver is a complex organ performing numerous vital physiological functions. For that reason, it possesses immense regenerative potential. The capacity for repair is largely attributable to the ability of its differentiated epithelial cells, hepatocytes and biliary epithelial cells, to proliferate after injury. However, in cases of extreme acute injury or prolonged chronic insult, the liver may fail to regenerate or do so suboptimally. This often results in life-threatening end-stage liver disease for which liver transplantation is the only effective treatment. In many forms of liver injury, bipotent liver progenitor cells are theorized to be activated as an additional tier of liver repair. However, the existence, origin, fate, activation, and contribution to regeneration of liver progenitor cells is hotly debated, especially since hepatocytes and biliary epithelial cells themselves may serve as facultative stem cells for one another during severe liver injury. Here, we discuss the evidence both supporting and refuting the existence of liver progenitor cells in a variety of experimental models. We also debate the validity of developing therapies harnessing the capabilities of these cells as potential treatments for patients with severe and chronic liver diseases.