Semaphorin 3E secreted by damaged hepatocytes regulates the sinusoidal regeneration and liver fibrosis during liver regeneration

Liver sinusoidal endothelial cell: An important yet often overlooked player in the liver fibrosis

Liver sinusoidal endothelial cells (LSECs) are liver-specific endothelial cells with the highest permeability than other mammalian endothelial cells, characterized by the presence of fenestrae on their surface, the absence of diaphragms and the lack of basement membrane. Located at the interface between blood and other liver cell types, LSECs mediate the exchange of substances between the blood and the Disse space, playing a crucial role in maintaining substance circulation and homeostasis of multicellular communication. As the initial responders to chronic liver injury, the abnormal LSEC activation not only changes their own physicochemical properties but also interrupts their communication with hepatic stellate cells and hepatocytes, which collectively aggravates the process of liver fibrosis. In this review, we have comprehensively updated the various pathways by which LSECs were involved in the initiation and aggravation of liver fibrosis, including but not limited to cellular phenotypic change, the induction of capillarization, decreased permeability and regulation of intercellular communications. Additionally, the intervention effects and latest regulatory mechanisms of anti-fibrotic drugs involved in each aspect have been summarized and discussed systematically. As we studied deeper into unraveling the intricate role of LSECs in the pathophysiology of liver fibrosis, we unveil a promising horizon that pave the way for enhanced patient outcomes.

The role of semaphorins in allergic diseases

Semaphorins were originally identified as guidance molecules in neural development. However, accumulating evidence indicates that 'immune semaphorins' are critically involved in regulating immune cell activation, differentiation, mobility and migration. Semaphorins are also intimately associated with the pathogenesis of allergic diseases including asthma, allergic rhinitis, atopic dermatitis, allergic conjunctivitis, and eosinophilic chronic rhinosinusitis. Interestingly, reflecting their function in positive or negative regulation of immune cells, levels of some semaphorins are increased while others are decreased in patients with allergic diseases. This review presents the pathogenic functions of immune semaphorins in allergic inflammation and discusses the potential use of these molecules as therapeutic targets for allergic diseases.

Semaphorin 3C exacerbates liver fibrosis

BACKGROUND AND AIMS

Chronic liver disease is a growing epidemic, leading to fibrosis and cirrhosis. TGF-β is the pivotal profibrogenic cytokine that activates HSC, yet other molecules can modulate TGF-β signaling during liver fibrosis. Expression of the axon guidance molecules semaphorins (SEMAs), which signal through plexins and neuropilins (NRPs), have been associated with liver fibrosis in HBV-induced chronic hepatitis. This study aims at determining their function in the regulation of HSCs.

APPROACH AND RESULTS

We analyzed publicly available patient databases and liver biopsies. We used transgenic mice, in which genes are deleted only in activated HSCs to perform ex vivo analysis and animal models. SEMA3C is the most enriched member of the semaphorin family in liver samples from patients with cirrhosis. Higher expression of SEMA3C in patients with NASH, alcoholic hepatitis, or HBV-induced hepatitis discriminates those with a more profibrotic transcriptomic profile. SEMA3C expression is also elevated in different mouse models of liver fibrosis and in isolated HSCs on activation. In keeping with this, deletion of SEMA3C in activated HSCs reduces myofibroblast marker expression. Conversely, SEMA3C overexpression exacerbates TGF-β-mediated myofibroblast activation, as shown by increased SMAD2 phosphorylation and target gene expression. Among SEMA3C receptors, only NRP2 expression is maintained on activation of isolated HSCs. Interestingly, lack of NRP2 in those cells reduces myofibroblast marker expression. Finally, deletion of either SEMA3C or NRP2, specifically in activated HSCs, reduces liver fibrosis in mice.

CONCLUSION

SEMA3C is a novel marker for activated HSCs that plays a fundamental role in the acquisition of the myofibroblastic phenotype and liver fibrosis.

Gene-regulation modules in nonalcoholic fatty liver disease revealed by single-nucleus ATAC-seq

We investigated the progression of nonalcoholic fatty liver disease from fatty liver to steatohepatitis using single-nucleus and bulk ATAC-seq on the livers of rats fed a high-fat diet (HFD). Rats fed HFD for 4 wk developed fatty liver, and those fed HFD for 8 wk further progressed to steatohepatitis. We observed an increase in the proportion of inflammatory macrophages, consistent with the pathological progression. Utilizing machine learning, we divided global gene regulation into modules, wherein transcription factors within a module could regulate genes within the same module, reaffirming known regulatory relationships between transcription factors and biological processes. We identified core genes-central to co-expression and protein-protein interaction-for the biological processes discovered. Notably, a large part of the core genes overlapped with genes previously implicated in nonalcoholic fatty liver disease. Single-nucleus ATAC-seq, combined with data-driven statistical analysis, offers insight into in vivo global gene regulation as a combination of modules and assists in identifying core genes of relevant biological processes.

Axon guidance molecules in liver pathology: Journeys on a damaged passport

BACKGROUND AND AIMS

The liver is an innervated organ that develops a variety of chronic liver disease (CLD). Axon guidance cues (AGCs), of which ephrins, netrins, semaphorins and slits are the main representative, are secreted or membrane-bound proteins that can attract or repel axons through interactions with their growth cones that contain receptors recognizing these messengers. While fundamentally implicated in the physiological development of the nervous system, the expression of AGCs can also be reinduced under acute or chronic conditions, such as CLD, that necessitate redeployment of neural networks.

METHODS

This review considers the ad hoc literature through the neglected canonical neural function of these proteins that is also applicable to the diseased liver (and not solely their observed parenchymal impact).

RESULTS

AGCs impact fibrosis regulation, immune functions, viral/host interactions, angiogenesis, and cell growth, both at the CLD and HCC levels. Special attention has been paid to distinguishing correlative and causal data in such datasets in order to streamline data interpretation. While hepatic mechanistic insights are to date limited, bioinformatic evidence for the identification of AGCs mRNAs positive cells, protein expression, quantitative regulation, and prognostic data have been provided. Liver-pertinent clinical studies based on the US Clinical Trials database are listed. Future research directions derived from AGC targeting are proposed.

CONCLUSION

This review highlights frequent implication of AGCs in CLD, linking traits of liver disorders and the local autonomic nervous system. Such data should contribute to diversifying current parameters of patient stratification and our understanding of CLD.

Luteolin Alleviates Liver Fibrosis in Rat Hepatic Stellate Cell HSC-T6: A Proteomic Analysis

BACKGROUND

Traditional Chinese medicine (TCM) with single or compound materials is an effective cure for liver fibrosis. Hepatic stellate cells (HSCs) play a key role in liver fibrosis pathology and have become a novel drug target for this condition.

METHODS

CCK-8 assay was used to determine the cytotoxicity of four components, SYPA, HSYPA, Apigenin, and Luteolin, from Deduhonghua-7 powder on HSC-T6 cells. Transforming Growth Factor β 1 (TGFβ1)-induced fibrotic cell model and CCI4-induced fibrotic rat model were constructed, the expression of fibrosis-related genes, the pathological changes and serum biochemical markers were evaluated. Proteomic analysis was performed to determine the mechanism by which luteolin attenuated liver fibrosis, which were further confirmed by Western blot.

RESULTS

Luteolin attenuates liver fibrosis in HSC-T6 cells and luteolin decreases the liver fibrosis index level in vivo. A total of 5000 differentially expressed proteins (DEPs) were obtained using proteomic analysis. KEGG analysis found that DEPs were concentrated in various metabolic pathways, including DNA replication and repair and lysosomal signaling. GO analysis showed that molecular functions included the activity and binding of various enzymes, related cellular components included the extracellular space, lysosomal lumen, mitochondrial matrix, and nucleus, and biological processes included collagen organization and biosynthesis and the positive regulation of cell migration. Western blot results showed that CCR1, CD59, and NAGA were downregulated in TGFβ1 treatment, while upregulated both in Lut2 and Lut10 treatment. Meanwhile, eight proteins, ITIH3, MKI67, KIF23, DNMT1, P4HA3, CCDC80, APOB, FBLN2, that were upregulated in TGFβ1 treatment, while downregulated both in Lut2 and Lut10 treatment.

CONCLUSION

Luteolin was shown to have a strong protective effect on liver fibrosis. CCR1, CD59, and NAGA may promote liver fibrosis while ITIH3, MKI67, KIF23, DNMT1, P4HA3, CCDC80, APOB, and FBLN2 may facilitate protection against fibrosis.

Cell atlas of CCl 4-induced progressive liver fibrosis reveals stage-specific responses

Chronic liver injury leads to progressive liver fibrosis and ultimately cirrhosis, a major cause of morbidity and mortality worldwide. However, there are currently no effective anti-fibrotic therapies available, especially for late-stage patients, which is partly attributed to the major knowledge gap regarding liver cell heterogeneity and cell-specific responses in different fibrosis stages. To reveal the multicellular networks regulating mammalian liver fibrosis from mild to severe phenotypes, we generated a single-nucleus transcriptomic atlas encompassing 49 919 nuclei corresponding to all main liver cell types at different stages of murine carbon tetrachloride (CCl 4)-induced progressive liver fibrosis. Integrative analysis distinguished the sequential responses to injury of hepatocytes, hepatic stellate cells and endothelial cells. Moreover, we reconstructed cell-cell interactions and gene regulatory networks implicated in these processes. These integrative analyses uncovered previously overlooked aspects of hepatocyte proliferation exhaustion and disrupted pericentral metabolic functions, dysfunction for clearance by apoptosis of activated hepatic stellate cells, accumulation of pro-fibrotic signals, and the switch from an anti-angiogenic to a pro-angiogenic program during CCl 4-induced progressive liver fibrosis. Our dataset thus constitutes a useful resource for understanding the molecular basis of progressive liver fibrosis using a relevant animal model.

Targeting the Semaphorin3E-plexinD1 complex in allergic asthma

Asthma is a heterogenous airway disease characterized by airway inflammation and remodeling. It affects more than 300 million people worldwide and poses a significant burden on society. Semaphorins, discovered initially as neural guidance molecules, are ubiquitously expressed in various organs and regulate multiple signaling pathways. Interestingly, Semaphorin3E is a critical molecule in lung pathophysiology through its role in both lung development and homeostasis. Semaphorin3E binds to plexinD1, mediating regulatory effects on cell migration, proliferation, and angiogenesis. Recent in vitro and in vivo studies have demonstrated that the Semaphorin3E-plexinD1 axis is implicated in asthma, impacting inflammatory and structural cells associated with airway inflammation, tissue remodeling, and airway hyperresponsiveness. This review details the Semaphorin3E-plexinD1 axis in various aspects of asthma and highlights future directions in research including its potential role as a therapeutic target in airway allergic diseases.

Serum Proteomics Uncovers Biomarkers of Clinical Portal Hypertension in Children With Biliary Atresia

Children with biliary atresia (BA) often develop portal hypertension (PHT) and its complications, which are associated with high morbidity and mortality. The goal of this study was to identify serum biomarkers of PHT by using large-scale proteomics. We applied the slow off-rate modified aptamer scan (SOMAscan) to measure 1,305 proteins in serum samples of children with BA with and without clinical evidence of PHT in validation and discovery cohorts enrolled in the Biliary Atresia Study of Infants and Children. Serum proteomics data was analyzed using logistic regression to identify protein(s) with an area under the receiver operating characteristic curve (AUROC) ≥ 0.90. Immunostaining was used to characterize the cellular localization of the new biomarker proteins in liver tissues. We identified nine proteins in the discovery cohort (n = 40 subjects) and five proteins in the validation cohort (n = 80 subjects) that individually or in combination predicted clinical PHT with AUROCs ≥ 0.90. Merging the two cohorts, we found that semaphorin 6B (SEMA6B) alone and three other protein combinations (SEMA6B+secreted frizzle protein 3 [SFRP3], SEMA6B+COMM domain containing 7 [COMMD7], and vascular cell adhesion molecule 1 [VCAM1]+BMX nonreceptor tyrosine kinase [BMX]) had AUROCs ≥ 0.90 in both cohorts, with high positive- and negative-predictive values. Immunostaining of the new protein biomarkers showed increased expression in hepatic endothelial cells, cholangiocytes, and immune cells within portal triads in BA livers with clinical PHT compared to healthy livers. Conclusion: Large-scale proteomics identified SEMA6B, SFRP3, COMMD7, BMX, and VCAM1 as biomarkers highly associated with clinical PHT in BA. The expression of the biomarkers in hepatic epithelial, endothelial, and immune cells support their potential role in the pathophysiology of PHT.

Innervation in organogenesis

Proper innervation of peripheral organs helps to maintain physiological homeostasis and elicit responses to external stimuli. Disruptions to normal function can result in pathophysiological consequences. The establishment of connections and communication between the central nervous system and the peripheral organs is accomplished through the peripheral nervous system. Neuronal connections with target tissues arise from ganglia partitioned throughout the body. Organ innervation is initiated during development with stimuli being conducted through several types of neurons including sympathetic, parasympathetic, and sensory. While the physiological modulation of mature organs by these nerves is largely understood, their role in mammalian development is only beginning to be uncovered. Interactions with cells in target tissues can affect the development and eventual function of several organs, highlighting their significance. This chapter will cover the origin of peripheral neurons, factors mediating organ innervation, and the composition and function of organ-specific nerves during development. This emerging field aims to identify the functional contribution of innervation to development which will inform future investigations of normal and abnormal mammalian organogenesis, as well as contribute to regenerative and organ replacement efforts where nerve-derived signals may have significant implications for the advancement of such studies.

Lingonberry Anthocyanins Inhibit Hepatic Stellate Cell Activation and Liver Fibrosis via TGFβ/Smad/ERK Signaling Pathway

Phytochemicals from lingonberry have rich pharmacological value and may play an essential role in treating liver diseases. We investigated the regulatory role of lingonberry anthocyanins (LA) on HSC activation in vitro and liver fibrogenesis in vivo. The viability of HSCs treated with LA was significantly reduced in a dose-dependent manner at the concentration of 25-100 μg/mL, in which the monomers of LA also reduced the proliferation of HSCs via IC50 assay. The inducer transforming growth factor β1 (TGFβ1) and the effector α-smooth muscle actin (α-SMA) of HSC activation were all decreased both in protein and RNA levels treated by LA. Moreover, LA alleviated CCl₄-induced liver fibrosis in rats, reducing collagen aggregation and production and decreasing the hydroxyproline (HYP) and malondialdehyde (MDA) levels in the liver tissue. Moreover, LA reduced the indexes of serum liver fibrosis and reversed the index of serum liver function in CCl₄-induced rats. Furthermore, the antioxidant enzymes, including superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT), in the liver tissue and serum were significantly increased upon treatment with LA. Importantly, LA promoted hepatic parenchymal cell proliferation and inhibited the expression of TGFβ/Smad/extracellular regulated protein kinase (ERK) signaling pathway-related genes. This study demonstrates the anti-liver fibrosis activity of LA and investigates its mechanism, which may provide a novel strategy for treating liver fibrosis using lingonberry.

FXR-Deoxycholic Acid-TNF-α Axis Modulates Acetaminophen-Induced Hepatotoxicity

The idiosyncratic characteristics and severity of acetaminophen (APAP) overdose-induced hepatotoxicity render identifying the predisposing factors and mechanisms of APAP-induced liver toxicity necessary and urgent. Farnesoid X receptor (FXR) controls bile acid homeostasis and modulates the progression of various liver diseases. Although global FXR deficiency in mice enhances APAP intoxication, the mechanism remains elusive. In this study, an increased sensitivity to APAP-induced toxicity was found in global Fxr-null (Fxr-/-) mice, but was not observed in hepatocyte-specific or macrophage-specific Fxr-null mice, suggesting that global FXR deficiency enhances APAP hepatotoxicity via disruption of systematic bile acid homeostasis. Indeed, more bile acid accumulation was found in global Fxr-/- mice, while 2% cholestyramine diet feeding decreased serum bile acids and alleviated APAP hepatotoxicity in global Fxr-/- mice, suggesting that bile acid accumulation contributes to APAP toxicity. Bile acids were suspected to induce macrophage to release tumor necrosis factor-α (TNF-α), which is known to enhance the APAP hepatotoxicity. In vitro, deoxycholic acid (DCA), a secondary bile acid metabolite, significantly induced Tnfa mRNA and dose-dependently enhanced TNF-α release from macrophage, while the same dose of DCA did not directly potentiate APAP toxicity in cultured primary hepatocytes. In vivo, DCA enhanced TNF-α release and potentiated APAP toxicity, both of which were abolished by the specific TNF-α antagonist infliximab. These results reveal an FXR-DCA-TNF-α axis that potentiates APAP hepatotoxicity, which could guide the clinical safe use of APAP.

Feedback repression of PPARα signaling by Let-7 microRNA

Peroxisome proliferator-activated receptor α (PPARα) controls hepatic lipid homeostasis and is the target of lipid-lowering fibrate drugs. PPARα activation represses expression of let-7 microRNA (miRNA), but the function of let-7 in PPARα signaling and lipid metabolism is unknown. In the current study, a hepatocyte-specific let-7b/c2 knockout (let7b/c2ΔHep) mouse line is generated, and these mice are found to exhibit pronounced resistance to diet-induced obesity and fatty liver. Let-7 inhibition by hepatocyte-specific let-7 sponge expression shows similar phenotypes as let7b/c2ΔHep mice. RNA sequencing (RNA-seq) analysis reveals that hepatic PPARα signaling is repressed in let7b/c2ΔHep mice. Protein expression of the obligate PPARα heterodimer partner retinoid X receptor α (RXRα) is reduced in the livers of let7b/c2ΔHep mice. Ring finger protein 8 (Rnf8), which is a direct target of let-7, is elevated in let7b/c2ΔHep mouse liver and identified as a E3 ubiquitin ligase for RXRα. This study highlights a let-7-RNF8-RXRα regulatory axis that modulates hepatic lipid catabolism.

ENO3 promoted the progression of NASH by negatively regulating ferroptosis via elevation of GPX4 expression and lipid accumulation

Background

ENO3 expression is upregulated in Non-alcoholic fatty liver disease (NAFLD) patient tissues, demonstrated that ENO3 might play crucial roles in NAFLD. However, the mechanism of ENO3 in NAFLD remains unclear. Therefore, this study aimed to investigate the regulatory mechanism of ENO3 in the progression of non-alcoholic steatohepatitis (NASH) in vivo and vitro NASH model.

Methods

In vivo and vitro NASH model were established by methionine-choline deficient (MCD)-diet feeding and high free fatty acid (HFFA) induction in L02 cells. Loss and gain function of ENO3 and GPX4 was performed to study the mechanism in NASH. Western blot was used to detect the expression of ENO3 and GPX4. Hematoxylin and eosin (H&E), picrosirius Red and Oil Red O staining was used to evaluate histopathology of liver in NASH model. Ferroptosis indicators were measured by assay kits according to the manufacturer's instructions.

Results

NASH mouse model was successfully established induced by MCD diet with steatosis, inflammatory infiltration, ballooning and fibrosis observed in the liver tissue. The expression of ENO3 and GPX4 was significantly elevated while ferroptosis was inhibited in NASH mice and cell model. Upregulation of both ENO3 and GPX4 could promote the lipid accumulation in L02 cells. In addition, overexpressed ENO3 attenuated the status of ferroptosis.

Conclusions

In the present study, we demonstrate that ENO3 promoted the progression of NASH by negatively regulating ferroptosis via elevating GPX4 expression and lipid accumulation. These findings provided solid foundation for the mechanism of ferroptosis on the progression of NASH regulated by ENO3, suggesting that ENO3 may be a potential therapeutic target for NASH.

Lipid peroxidation and the subsequent cell death transmitting from ferroptotic cells to neighboring cells

Ferroptosis regulated cell death due to the iron-dependent accumulation of lipid peroxide. Ferroptosis is known to constitute the pathology of ischemic diseases, neurodegenerative diseases, and steatohepatitis and also works as a suppressing mechanism against cancer. However, how ferroptotic cells affect surrounding cells remains elusive. We herein report the transfer phenomenon of lipid peroxidation and cell death from ferroptotic cells to nearby cells that are not exposed to ferroptotic inducers (FINs). While primary mouse embryonic fibroblasts (MEFs) and NIH3T3 cells contained senescence-associated β-galactosidase (SA-β-gal)-positive cells, they were decreased upon induction of ferroptosis with FINs. The SA-β-gal decrease was inhibited by ferroptotic inhibitors and knockdown of Atg7, pointing to the involvement of lipid peroxidation and activated autophagosome formation during ferroptosis. A transfer of cell culture medium of cells treated with FINs, type 1 or 2, caused the reduction in SA-β-gal-positive cells in recipient cells that had not been exposed to FINs. Real-time imaging of Kusabira Orange-marked reporter MEFs cocultured with ferroptotic cells showed the generation of lipid peroxide and deaths of the reporter cells. These results indicate that lipid peroxidation and its aftereffects propagate from ferroptotic cells to surrounding cells, even when the surrounding cells are not exposed to FINs. Ferroptotic cells are not merely dying cells but also work as signal transmitters inducing a chain of further ferroptosis.

Semaphorin 3E Protects against Chlamydial Infection by Modulating Dendritic Cell Functions

Recent studies have identified semaphorin 3E (Sema3E) as a novel mediator of immune responses. However, its function in immunity to infection has yet to be investigated. Using a mouse model of chlamydial lung infection, we show that Sema3E plays a significant role in the host immune response to the infection. We found that Sema3E is induced in the lung after chlamydial infection, and Sema3E deficiency has a detrimental impact on disease course, dendritic cell (DC) function, and T cell responses. Specifically, we found that Sema3E knockout (KO) mice exhibited higher bacterial burden, severe body weight loss, and pathological changes after Chlamydia muridarum lung infection compared with wild-type (WT) mice. The severity of disease in Sema3E KO mice was correlated with reduced Th1/Th17 cytokine responses, increased Th2 response, altered Ab response, and a higher number of regulatory CD4 T cells. Moreover, DCs isolated from Sema3E KO mice showed lower surface expression of costimulatory molecules and production of IL-12, but higher expression of PD-L1, PD-L2, and IL-10 production. Functional DC-T cell coculture studies revealed that DCs from infected Sema3E KO mice failed to induce Th1 and Th17 cell responses compared with DCs from infected WT mice. Upon adoptive transfer, mice receiving DCs from Sema3E KO mice, unlike those receiving DCs from WT mice, were not protected against challenge infection. In conclusion, our data evidenced that Sema3E acts as a critical factor for protective immunity against intracellular bacterial infection by modulating DC functions and T cell subsets.

[Liver regeneration: solved and problem issues]

It is known that liver is able to restore own dimensions and functional properties in response to various injuries. Despite extensive injuries, liver can preserve functional activity. Analysis of liver regeneration mechanisms allowed us to obtain significant results in the treatment of hepatitis, cirrhosis and liver failure. Liver regeneration processes substantiate the development of hepatocellular cancer following cirrhosis. Modern experimental and clinical data on liver regeneration, as well as current methods of stimulating this process are summarized in the manuscript. Despite significant advances in this issue, there are still many questions in scientific understanding of liver regeneration.

Ginsenoside Rg3 promotes regression from hepatic fibrosis through reducing inflammation-mediated autophagy signaling pathway

Inflammation and autophagy occur during hepatic fibrosis development caused by various pathogens, and effectively curbing of autophage may delay the occurrence of hepatic fibrosis. The current study aimed to unravel the inhibitory effects of Ginsenoside Rg3 (G-Rg3) on inflammation-mediated hepatic autophagy to curb hepatic fibrosis caused by thioacetamide (TAA)-induced subacute and chronic hepatic injury. TAA is mainly metabolized in the liver to cause liver dysfunction. After intraperitoneal injection of TAA for 4 or 10 weeks (TAA-chronic mouse models), severe inflammatory infiltration and fibrosis occurred in the liver. Treatment with G-Rg3 alleviated hepatic pathological changes and reversed hepatic fibrosis in the TAA-chronic models with decreased deposition of collagen fibers, reduced expression of HSCs activation marker (α-SMA), and reduced secretion of profibrogenic factors (TGF-β1). G-Rg3 decreased expressions of autophagy-related proteins in mice of TAA-chronic models. Notably, G-Rg3 inhibited the survival of activated rat hepatic stellate cells (HSC-T6), but had no cytotoxicity on human hepatocytes (L02 cell lines). G-Rg3 dose-dependently inhibited autophagy in vitro with less expression of p62 and fewer LC3a transformation into LC3b in inflammatory inducer lipopolysaccharide (LPS)-induced rat HSC-T6 cells. Furthermore, G-Rg3 enhanced the phosphorylation of phosphatidylinositol 3-kinase (PI3K) and protein kinase B (Akt) in vivo and in vitro. Besides, mTOR inhibitor Rapamycin and PI3K inhibitors LY294002 were employed in LPS-treated HSC-T6 cell cultures to verify that Rg3 partially reversed the increase in autophagy in hepatic fibrosis in vitro. Taken together, G-Rg3 exerted anti-fibrosis effect through the inhibition of autophagy in TAA-treated mice and LPS-stimulated HSC-T6 cells. These data collectively unravel that G-Rg3 may serve a promising anti-hepatic fibrosis drug.

Hepatic ferroptosis plays an important role as the trigger for initiating inflammation in nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is a metabolic liver disease that progresses from simple steatosis to the disease state of inflammation and fibrosis. Previous studies suggest that apoptosis and necroptosis may contribute to the pathogenesis of NASH, based on several murine models. However, the mechanisms underlying the transition of simple steatosis to steatohepatitis remain unclear, because it is difficult to identify when and where such cell deaths begin to occur in the pathophysiological process of NASH. In the present study, our aim is to investigate which type of cell death plays a role as the trigger for initiating inflammation in fatty liver. By establishing a simple method of discriminating between apoptosis and necrosis in the liver, we found that necrosis occurred prior to apoptosis at the onset of steatohepatitis in the choline-deficient, ethionine-supplemented (CDE) diet model. To further investigate what type of necrosis is involved in the initial necrotic cell death, we examined the effect of necroptosis and ferroptosis inhibition by administering inhibitors to wild-type mice in the CDE diet model. In addition, necroptosis was evaluated using mixed lineage kinase domain-like protein (MLKL) knockout mice, which is lacking in a terminal executor of necroptosis. Consequently, necroptosis inhibition failed to block the onset of necrotic cell death, while ferroptosis inhibition protected hepatocytes from necrotic death almost completely, and suppressed the subsequent infiltration of immune cells and inflammatory reaction. Furthermore, the amount of oxidized phosphatidylethanolamine, which is involved in ferroptosis pathway, was increased in the liver sample of the CDE diet-fed mice. These findings suggest that hepatic ferroptosis plays an important role as the trigger for initiating inflammation in steatohepatitis and may be a therapeutic target for preventing the onset of steatohepatitis.

Dead cell phagocytosis and innate immune checkpoint

The human body loses several billions of cells daily. When cells die in vivo, the corpse of each dead cell is immediately cleared. Specifically, dead cells are efficiently recognized and cleared by multiple types of neighboring phagocytes. Early research on cell death focused more on molecular mechanisms of cell death regulation while the cellular corpses were merely considered cellular debris. However, it has come to light that various biological stimuli following cell death are important for immune regulation. Clearance of normal dead cells occurs silently in immune tolerance. Exogenous or mutated antigens of malignant or infected cells can initiate adaptive immunity, thereby inducing immunogenicity by adjuvant signals. Several pathogens and cancer cells have strategies to limit the adjuvant signals and escape immune surveillance. In this review, we present an overview of the mechanisms of dead cell clearance and its immune regulations.

Neutrophils alleviate fibrosis in the CCl4-induced mouse chronic liver injury model

Tribbles pseudokinase 1 (Trib1) is a negative regulator of CCAAT/enhancer binding protein α (C/EBPα) and is known to induce granulopoiesis while suppressing monocyte differentiation. Loss of Trib1 was previously shown to increase the neutrophil population in the spleen but lead to M2-like macrophage reduction. Because M2 macrophages are anti-inflammatory and promote tissue repair by producing fibrogenic factors, we investigated liver fibrosis in Trib1-deficient mice. Interestingly, loss of Trib1 suppressed fibrosis in the CCl4-induced chronic liver injury model. Trib1 knockout increased neutrophils but had a minimal effect on the macrophage population in the liver. Hepatic expressions of neutrophil matrix metalloproteinases (Mmp)8 and Mmp9 were increased, but the production of fibrogenic factors, including transforming growth factor β1, was not affected by loss of Trib1. These results suggest that neutrophils are responsible for the suppression of fibrosis in Trib1-deficient liver. Consistently, transplantation of Trib1-deficient bone marrow cells into wild-type mice alleviated CCl4-induced fibrosis. Furthermore, expression of chemokine (C-X-C motif) ligand 1 (Cxcl1) by adeno-associated viral vector in the normal liver recruited neutrophils and suppressed CCl4-induced fibrosis; infusion of wild-type neutrophils in CCl4-treated mice also ameliorated fibrosis. Using recombinant adeno-associated virus-mediated expression of Mmp8 and Mmp9 alleviated liver fibrosis. Finally, neutrophil depletion by infusion of Ly6G antibody significantly enhanced CCl4-induced fibrosis. Conclusion: While neutrophils are well known to exacerbate acute liver injury, our results demonstrate a beneficial role of neutrophils in chronic liver injury by promoting fibrolysis. (Hepatology Communications 2018;2:703-717).

Transcriptome Analysis of Porcine PBMCs Reveals the Immune Cascade Response and Gene Ontology Terms Related to Cell Death and Fibrosis in the Progression of Liver Failure

BACKGROUND

The key gene sets involved in the progression of acute liver failure (ALF), which has a high mortality rate, remain unclear. This study aims to gain a deeper understanding of the transcriptional response of peripheral blood mononuclear cells (PBMCs) following ALF.

METHODS

ALF was induced by D-galactosamine (D-gal) in a porcine model. PBMCs were separated at time zero (baseline group), 36 h (failure group), and 60 h (dying group) after D-gal injection. Transcriptional profiling was performed using RNA sequencing and analysed using DAVID bioinformatics resources.

RESULTS

Compared with the baseline group, 816 and 1,845 differentially expressed genes (DEGs) were identified in the failure and dying groups, respectively. A total of five and two gene ontology (GO) term clusters were enriched in 107 GO terms in the failure group and 154 GO terms in the dying group. These GO clusters were primarily immune-related, including genes regulating the inflammasome complex and toll-like receptor signalling pathways. Specifically, GO terms related to cell death, including apoptosis, pyroptosis, and autophagy, and those related to fibrosis, coagulation dysfunction, and hepatic encephalopathy were enriched. Seven Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, cytokine-cytokine receptor interaction, hematopoietic cell lineage, lysosome, rheumatoid arthritis, malaria, and phagosome and pertussis pathways were mapped for DEGs in the failure group. All of these seven KEGG pathways were involved in the 19 KEGG pathways mapped in the dying group.

CONCLUSION

We found that the dramatic PBMC transcriptome changes triggered by ALF progression was predominantly related to immune responses. The enriched GO terms related to cell death, fibrosis, and so on, as indicated by PBMC transcriptome analysis, seem to be useful in elucidating potential key gene sets in the progression of ALF. A better understanding of these gene sets might be of preventive or therapeutic interest.

Constitutive and Inducible Systems for Genetic In Vivo Modification of Mouse Hepatocytes Using Hydrodynamic Tail Vein Injection

In research models of liver cancer, regeneration, inflammation, and fibrosis, flexible systems for in vivo gene expression and silencing are highly useful. Hydrodynamic tail vein injection of transposon-based constructs is an efficient method for genetic manipulation of hepatocytes in adult mice. In addition to constitutive transgene expression, this system can be used for more advanced applications, such as shRNA-mediated gene knock-down, implication of the CRISPR/Cas9 system to induce gene mutations, or inducible systems. Here, the combination of constitutive CreER expression together with inducible expression of a transgene or miR-shRNA of choice is presented as an example of this technique. We cover the multi-step procedure starting from the preparation of sleeping beauty-transposon constructs, to the injection and treatment of mice, and the preparation of liver tissue for analysis by immunostaining. The system presented is a reliable and efficient approach to achieve complex genetic manipulations in hepatocytes. It is specifically useful in combination with Cre/loxP-based mouse strains and can be applied to a variety of models in the research of liver disease.

Oncostatin M causes liver fibrosis by regulating cooperation between hepatic stellate cells and macrophages in mice

Fibrosis is an important wound-healing process in injured tissues, but excessive fibrosis is often observed in patients with chronic inflammation. Although oncostatin M (OSM) has been reported to play crucial roles for recovery from acute liver injury by inducing tissue inhibitor of metalloproteinase 1 (Timp1) expression, the role of OSM in chronic liver injury (CLI) is yet to be elucidated. Here, we show that OSM exerts powerful fibrogenic activity by regulating macrophage activation during CLI. Genetic ablation of the OSM gene alleviated fibrosis in a mouse model of chronic hepatitis. Conversely, continuous expression of OSM in a normal mouse liver by hydrodynamic tail vein injection (HTVi) induced severe fibrosis without necrotic damage of hepatocytes, indicating that OSM is involved in the fundamental process of liver fibrosis (LF) after hepatitis. In a primary coculture of hepatic stellate cells (HSCs) and hepatic macrophages (HMs), OSM up-regulated the expression of fibrogenic factors, such as transforming growth factor-β and platelet-derived growth factor in HMs, while inducing Timp1 expression in HSCs, suggesting the synergistic roles of OSM for collagen deposition in the liver. Fluorescence-activated cell sorting analyses using OSM-HTVi and OSM knockout mice have revealed that bone-marrow-derived monocyte/macrophage are responsive to OSM for profibrotic activation. Furthermore, depletion or blocking of HMs by administration of clodronate liposome or chemokine inhibitor prevented OSM-induced fibrosis.

CONCLUSION

OSM plays a crucial role in LF by coordinating the phenotypic change of HMs and HSCs. Our data suggest that OSM is a promising therapeutic target for LF. (Hepatology 2018;67:296-312).

Semaphorin 3E Alleviates Hallmarks of House Dust Mite-Induced Allergic Airway Disease

Semaphorins are an essential family of guidance cues ubiquitously expressed in various organs, which play diverse developmental, homeostatic, and pathological roles. Semaphorin 3E (Sema3E), initially identified as a neuronal chemorepellent, is involved in the regulation of cell migration, proliferation, and angiogenesis. However, expression and function of Sema3E in allergic asthma has not been extensively investigated. We determined the expression of Sema3E in the airways and its effect on airway inflammation, hyperresponsiveness, and remodeling as pathological features of allergic asthma provoked by house dust mite in vivo. Our data indicate that exposure to house dust mite markedly reduces Sema3E expression in mouse airways. More important, replenishment of Sema3E by intranasal administration of exogenous Sema3E protects mice from allergic asthma by reducing eosinophilic inflammation, serum IgE level, and T helper cell 2/T helper cell 17 cytokine response. The regulatory effect of Sema3E on cytokine response was sustained on allergen recall response in the lymph nodes and spleen. Furthermore, goblet cell hyperplasia, collagen deposition, and airway hyperresponsiveness were significantly diminished on Sema3E treatment. The inhibitory effect of Sema3E was associated with a reduction of pulmonary CD11b⁺ conventional dendritic cells and regulation of CD4⁺ T-cell cytokine response. Collectively, our data represent a novel approach to treating allergic asthma via regulation of immune response to house dust mite.

Semaphorin 3A in Ankylosing Spondylitis

BACKGROUND/PURPOSE

To determine serum semaphorin 3A (Sema 3A) levels in ankylosing spondylitis (AS).

METHODS

Serum Sema 3A was measured in 46 AS patients and 30 healthy controls (HCs). For the patients, we recorded demographic data, disease activity, functional index & global assessment, detected human leukocyte antigen-B27 (HLA-B27), and measured erythrocyte sedimentation rate (ESR) & C-reactive protein (CRP).

RESULTS

Sema 3A was higher in AS patients than in HCs (3.98 ± 2.57 vs. 1.34 ± 0.48 ng/ml, p = 0.013). Area under the curve (AUC) of standard receiver operating characteristic (ROC) has suggested that Sema 3A > 2 ng/ml is better to predict the higher Bath Ankylosing Spondylitis Disease Activity Index (BASDAI, > 4) than ESR or CRP. There were good correlations between higher Sema 3A and uveitis, Schöber's test, as well as interstitial lung disease. AS patients undergoing anti-tumor necrosis factor therapies for 3 months exhibited a positive correlation of change in Sema 3A (ΔSema 3A) with disease activity fluctuation [ΔBASDAI, ΔBath Ankylosing Spondylitis Functional Index (BASFI) and ΔBath Ankylosing Spondylitis - Global score (BAS-G)].

CONCLUSION

Serum Sema 3A level was increased in AS patients and was inversely correlated to Schöber's test. Serum Sema 3A is better as a bio-marker than ESR or CRP to correlate with high disease activity in AS patients, and it is also a good indicator for monitoring disease activity and functional status during anti-TNF treatment. Also, Sema 3A may be taken as a predictor for extra-articular presentations in AS, but this needs further study to elucidate.

Expression and localization of sterile alpha motif domain containing 5 is associated with cell type and malignancy of biliary tree

Cholangiocarcinoma (CC) is a type of relatively rare neoplasm in adenocarcinoma. The characteristics of CCs as well as biliary epithelial cells are heterogeneous at the different portion of the biliary tree. There are two candidate stem/progenitor cells of the biliary tree, i.e., biliary tree stem/progenitor cell (BTSC) at the peribiliary gland (PBG) of large bile ducts and liver stem/progenitor cell (LPC) at the canals of Hering of peripheral small bile duct. Although previous reports suggest that intrahepatic CC (ICC) can arise from such stem/progenitor cells, the characteristic difference between BTSC and LPC in pathological process needs further investigation, and the etiology of CC remains poorly understood. Here we show that Sterile alpha motif domain containing 5 (SAMD5) is exclusively expressed in PBGs of large bile ducts in normal mice. Using a mouse model of cholestatic liver disease, we demonstrated that SAMD5 expression was upregulated in the large bile duct at the hepatic hilum, the extrahepatic bile duct and PBGs, but not in proliferating intrahepatic ductules, suggesting that SAMD5 is expressed in BTSC but not LPC. Intriguingly, human ICCs and extrahepatic CCs exhibited striking nuclear localization of SAMD5 while the normal hilar large bile duct displayed slight-to-moderate expression in cytoplasm. In vitro experiments using siRNA for SAMD5 revealed that SAMD5 expression was associated with the cell cycle regulation of CC cell lines. Conclusion: SAMD5 is a novel marker for PBG but not LPC in mice. In humans, the expression and location of SAMD5 could become a promising diagnostic marker for the cell type as well as malignancy of bile ducts and CCs.

Human liver epigenetic alterations in non-alcoholic steatohepatitis are related to insulin action

Both genetic and lifestyle factors contribute to the risk of non-alcoholic steatohepatitis (NASH). Additionally, epigenetic modifications may also play a key role in the pathogenesis of NASH. We therefore investigated liver DNA methylation, as a marker for epigenetic alterations, in individuals with simple steatosis and NASH, and further tested if these alterations were associated with clinical phenotypes. Liver biopsies obtained from 95 obese individuals (age: 49.5 ± 7.7 years, BMI: 43 ± 5.7 kg/m2, type 2 diabetes [T2D]: 35) as a wedge biopsy during a Roux-en-Y gastric bypass operation were investigated. Thirty-four individuals had a normal liver phenotype, 35 had simple steatosis, and 26 had NASH. Genome-wide DNA methylation pattern was analyzed using the Infinium HumanMethylation450 BeadChip. mRNA expression was analyzed from 42 individuals using the HumanHT-12 Expression BeadChip. We identified 1,292 CpG sites representing 677 unique genes differentially methylated in liver of individuals with NASH (q < 0.001), independently of T2D, age, sex, and BMI. Focusing on the top-ranking 30 and another 37 CpG sites mapped to genes enriched in pathways of metabolism (q = 0.0036) and cancer (q = 0.0001) all together, 59 NASH-associated CpG sites correlated with fasting insulin levels independently of age, fasting glucose, or T2D. From these, we identified 30 correlations between DNA methylation and mRNA expression, for example LDHB (r = -0.45, P = 0.003). We demonstrated that NASH, more than simple steatosis, associates with differential DNA methylation in the human liver. These epigenetic alterations in NASH are linked with insulin metabolism.

Liver regeneration and fibrosis after inflammation

The liver is a unique organ with an extraordinary capacity to regenerate upon various injuries. In acute and transient liver injury by insults such as chemical hepatotoxins, the liver in rodents returns to the original architecture by proliferation and remodeling of the remaining cells within a week. In contrast, chronic liver inflammation due to various etiologies, e.g., virus infection and metabolic and immune disorders, results in liver fibrosis, often leading to cirrhosis and carcinogenesis. In both acute and chronic inflammation, a variety of immune and non-immune cells in the liver is involved in the processes resulting in either regeneration or fibrosis. In addition, chronic hepatitis often accompanies proliferation of atypical biliary cells, also known as liver progenitor cells or oval cells. Although the origin of liver progenitor cells and its contribution to hepatic repair is still under intense debate, recent studies have revealed a regulatory role for immune cells in progenitor proliferation and differentiation. In this review, we summarize recent studies on liver regeneration and fibrosis in the viewpoint of inflammation.

Immune Regulation by Dead Cell Clearance

When cell death occurs in vivo, cell corpses are not left untreated, but are recognized and engulfed by phagocytes, such as macrophages and dendritic cells. In the past, cell death had been considered the final process of a cell's life, and cell corpses had been viewed as debris that is simply to be cleared by phagocytes. Recently, however, it has become clearer that various biological responses are induced with dead cells as the starting point. Most of these biological responses followed by cell death are thought to be mediated by macrophages and dendritic cells. In this review, we present the overview of molecular mechanisms and biological significance of dead cell clearance.