Diverse potential of secretome from natural killer cells and monocyte-derived macrophages in activating stellate cells.

Chronic liver diseases, such as non-alcoholic steatohepatitis (NASH)-induced cirrhosis, are characterized by an increasing accumulation of stressed, damaged, or dying hepatocytes. Hepatocyte damage triggers the activation of resident immune cells, such as Kupffer cells (KC), as well as the recruitment of immune cells from the circulation toward areas of inflammation. After infiltration, monocytes differentiate into monocyte-derived macrophages (MoMF) which are functionally distinct from resident KC. We herein aim to compare the in vitro signatures of polarized macrophages and activated hepatic stellate cells (HSC) with ex vivo-derived disease signatures from human NASH. Furthermore, to shed more light on HSC activation and liver fibrosis progression, we investigate the effects of the secretome from primary human monocytes, macrophages, and NK cells on HSC activation. Interleukin (IL)-4 and IL-13 treatment induced transforming growth factor beta 1 (TGF-ß1) secretion by macrophages. However, the supernatant transfer did not induce HSC activation. Interestingly, PMA-activated macrophages showed strong induction of the fibrosis response genes COL10A1 and CTGF, while the supernatant of IL-4/IL-13-treated monocytes induced the upregulation of COL3A1 in HSC. The supernatant of PMA-activated NK cells had the strongest effect on COL10A1 induction in HSC, while IL-15-stimulated NK cells reduced the expression of COL1A1 and CTGF. These data indicate that other factors, aside from the well-known cytokines and chemokines, might potentially be stronger contributors to the activation of HSCs and induction of a fibrotic response, indicating a more diverse and complex role of monocytes, macrophages, and NK cells in liver fibrosis progression.

mmu-miR-374b-5p modulated inflammatory factors via downregulation of C/EBP ß/NF-κB signaling in Kupffer cells during Echinococcus multilocularis infection.

BACKGROUND: Alveolar echinococcosis (AE) is an important infectious disease caused by the metacestode larvae of Echinococcus multilocularis, seriously threatening global public health security. Kupffer cells (KCs) play important roles in liver inflammatory response. However, their role in hepatic alveolar echinococcosis has not yet been fully elucidated. METHODS: In this study, qRT-PCR was used to detect the expression level of miR-374b-5p in KCs. The target gene of miR-374b-5p was identified through luciferase reporter assays and loss of function and gains. Critical genes involved in NFκB signaling pathway were analyzed by qRT-PCR and western blot. RESULTS: This study reported that miR-374b-5p was significantly upregulated in KCs during E. multilocularis infection and further showed that miR-374b-5p was able to bind to the 3'-UTR of the C/EBP ß gene and suppressed its expression. The expression levels of NF-κBp65, p-NF-κBp65 and pro-inflammatory factors including iNOS, TNFα and IL6 were attenuated after overexpression of miR-374b-5p while enhanced after suppression of miR-374b-5p. However, the Arg1 expression level was promoted after overexpression of miR-374b-5p while suppressed after downregulation of miR-374b-5p. Additionally, increased protein levels of NF-κBp65 and p-NF-κBp65 were found in the C/EBP ß-overexpressed KCs. CONCLUSIONS: These results demonstrated that miR-374b-5p probably regulated the expression of inflammatory factors via C/EBP ß/NF-κB signaling. This finding is helpful to explore the mechanism of inflammation regulation during E. multilocularis infection.

Fructose regulates the pentose phosphate pathway and induces an inflammatory and resolution phenotype in Kupffer cells.

Over-consumption of fructose in adults and children has been linked to increased risk of non-alcoholic fatty liver disease (NAFLD). Recent studies have highlighted the effect of fructose on liver inflammation, fibrosis, and immune cell activation. However, little work summarizes the direct impact of fructose on macrophage infiltration, phenotype, and function within the liver. We demonstrate that chronic fructose diet decreased Kupffer cell populations while increasing transitioning monocytes. In addition, fructose increased fibrotic gene expression of collagen 1 alpha 1 (Col1a1) and tissue metallopeptidase inhibitor 1 (Timp1) as well as inflammatory gene expression of tumor necrosis factor alpha (Tnfa) and expression of transmembrane glycoprotein NMB (Gpnmb) in liver tissue compared to glucose and control diets. Single cell RNA sequencing (scRNAseq) revealed fructose elevated expression of matrix metallopeptidase 12 (Mmp12), interleukin 1 receptor antagonist (Il1rn), and radical S-adenosyl methionine domain (Rsad2) in liver and hepatic macrophages. In vitro studies using IMKC and J774.1 cells demonstrated decreased viability when exposed to fructose. Additionally, fructose increased Gpnmb, Tnfa, Mmp12, Il1rn, and Rsad2 in unpolarized IMKC. By mass spectrometry, C13 fructose tracing detected fructose metabolites in glycolysis and the pentose phosphate pathway (PPP). Inhibition of the PPP further increased fructose induced Il6, Gpnmb, Mmp12, Il1rn, and Rsad2 in nonpolarized IMKC. Taken together, fructose decreases cell viability while upregulating resolution and anti-inflammatory associated genes in Kupffer cells.

The nuclear factor ID3 endows macrophages with a potent anti-tumour activity.

Macrophage activation is controlled by a balance between activating and inhibitory receptors1-7, which protect normal tissues from excessive damage during infection8,9 but promote tumour growth and metastasis in cancer7,10. Here we report that the Kupffer cell lineage-determining factor ID3 controls this balance and selectively endows Kupffer cells with the ability to phagocytose live tumour cells and orchestrate the recruitment, proliferation and activation of natural killer and CD8 T lymphoid effector cells in the liver to restrict the growth of a variety of tumours. ID3 shifts the macrophage inhibitory/activating receptor balance to promote the phagocytic and lymphoid response, at least in part by buffering the binding of the transcription factors ELK1 and E2A at the SIRPA locus. Furthermore, loss- and gain-of-function experiments demonstrate that ID3 is sufficient to confer this potent anti-tumour activity to mouse bone-marrow-derived macrophages and human induced pluripotent stem-cell-derived macrophages. Expression of ID3 is therefore necessary and sufficient to endow macrophages with the ability to form an efficient anti-tumour niche, which could be harnessed for cell therapy in cancer.

Activation of GPR3-ß-arrestin2-PKM2 pathway in Kupffer cells stimulates glycolysis and inhibits obesity and liver pathogenesis.

Kupffer cells are liver resident macrophages and play critical role in fatty liver disease, yet the underlying mechanisms remain unclear. Here, we show that activation of G-protein coupled receptor 3 (GPR3) in Kupffer cells stimulates glycolysis and protects mice from obesity and fatty liver disease. GPR3 activation induces a rapid increase in glycolysis via formation of complexes between ß-arrestin2 and key glycolytic enzymes as well as sustained increase in glycolysis through transcription of glycolytic genes. In mice, GPR3 activation in Kupffer cells results in enhanced glycolysis, reduced inflammation and inhibition of high-fat diet induced obesity and liver pathogenesis. In human fatty liver biopsies, GPR3 activation increases expression of glycolytic genes and reduces expression of inflammatory genes in a population of disease-associated macrophages. These findings identify GPR3 activation as a pivotal mechanism for metabolic reprogramming of Kupffer cells and as a potential approach for treating fatty liver disease.

Treadmill exercise can regulate the redox balance in the livers of APP/PS1 mice and reduce LPS accumulation in their brains through the gut-liver-kupffer cell axis.

A growing body of clinical data has shown that patients with Alzheimer's disease (AD) have symptoms such as liver dysfunction and microbial-gut-brain axis dysfunction in addition to brain pathology, presenting a systemic multisystemic pathogenesis. Considering the systemic benefits of exercise, here, we first observed the effects of long-term treadmill exercise on liver injuries in APP/PS1 transgenic AD mice and explored the potential mechanisms of the gut-liver-brain axis's role in mediating exercise's ability to reduce bacterial lipopolysaccharide (LPS) pathology in the brain. The results showed that the livers of the AD mice were in states of oxidative stress, while the mice after long-term treadmill exercise showed alleviation of their oxidative stress, their intestinal barriers were protected, and the ability of their Kupffer cells to hydrolyze LPS was improved, in addition to the accumulation of LPS in their brains being reduced. Notably, the livers of the AD mice were in immunosuppressed states, with lower pro-oxidative and antioxidative levels than the livers of the wild-type mice, while exercise increased both their oxidative and antioxidative levels. These results suggest that long-term exercise modulates hepatic redox homeostasis in AD mice, attenuates oxidative damage, and reduces the accumulation of LPS in the brain through the combined action of the intestine-liver-Kupffer cells.

LncRNA 220, a newly discovered long non-conding RNA inhibiting apoptosis and autophagy in Kupffer cells in LPS-induced endotoxemic mice through the XBP1u-PI3K-AKT pathway.

Sepsis is recognized as a potentially fatal condition characterized by acute organ dysfunction resulting from an imbalanced immune response to infection. Acute liver injury (ALI) arises as an inflammatory outcome of immune response dysregulation associated with sepsis. Kupffer cells, which are liver-specific macrophages, are known to have a significant impact on ALI, although the precise regulatory mechanism remains unclear. Numerous studies have showcased the regulatory impact of long non-coding RNAs (lncRNAs) on the progression of diverse ailments, yet their precise regulatory mechanisms remain predominantly unexplored. In this study, a novel long non-coding RNA (lncRNA), referred to as lncRNA 220, was discovered using high-throughput sequencing. The expression of lncRNA 220 was found to be significantly elevated in the livers of mice with lipopolysaccharide (LPS)-induced endotoxemia, specifically during the 8-hour time period. Furthermore, in Kupffer cells treated with LPS, lncRNA 220 was observed to inhibit apoptosis and autophagy by activating the PI3K-AKT-mTORC1 pathway. This effect was achieved through the reduction of X-box protein 1 unspliced (Xbp1u) mRNA stability and suppression of its translation in the context of endoplasmic reticulum stress (ERS). Ultimately, this intervention mitigated the progression of LPS-induced ALI. To summarize, our study establishes lncRNA 220 as a newly identified regulator that suppresses apoptosis and autophagy in Kupffer cells subjected to LPS treatment, indicating its potential as a molecular target for ALI in endotoxemic mice.

Extracellular vesicles derived from liver sinusoidal endothelial cells inhibit the activation of hepatic stellate cells and Kupffer cells in vitro.

Liver sinusoidal endothelial cells (LSECs) play a crucial role in maintaining liver microcirculation and exchange of nutrients in the liver and are thought to be involved in the pathogenesis of metabolic dysfunction-associated steatotic liver disease (MASLD). The activation of hepatic stellate cells (HSCs) and Kupffer cells (KCs) has been considered to be responsible for the onset of liver fibrosis and the aggravation of liver injury. However, the paracrine regulatory effects of LSECs in the development of MASLD, in particular the role of LSEC-derived extracellular vesicles (EVs) remains unclear. Therefore, the aim of the present study was to investigate the influence of LSEC-derived EVs on HSCs and KCs. Primary rat LSECs, HSCs and KCs were isolated from male Wistar rats. LSEC-derived EVs were isolated from conditioned medium by ultracentrifugation and analyzed by nanoparticle tracking analysis, and expression of specific markers. LSEC-derived EVs reduced the expression of activation markers in activated HSCs but did not affect quiescent HSCs. Also, LSEC-derived EVs suppressed proliferation of activated HSCs activation, as assessed by Xcelligence and BrdU assay. LSEC-derived EVs also increased the expression of inflammatory genes in HSCs that normally are lowly expression during their activation. In contrast, EVs decreased the expression of inflammatory genes in activated KCs. In summary, our results suggest that LSEC-derived EVs may attenuate the fibrogenic phenotype of activated HSCs and the inflammatory phenotype of KCs. Our results show promise for LSEC-derived EVs as therapeutic moieties to treat MASLD. In addition, these EVs might prove of diagnostic value.

STING modulates iron metabolism to promote liver injury and inflammation in acute immune hepatitis.

The pathogenesis of Autoimmune Hepatitis (AIH) is closely associated with perturbations in iron ion metabolism, during which Stimulator of Interferon Genes (STING) plays an important role. However, the precise regulatory mechanism remains elusive. In this study, we investigated the relationship between iron dysregulation and STING activation in Concanavalin A (ConA)-induced AIH liver injury. STING knockout (STING-/-) mice and AAV (Adeno-Associated virus)-Sting1-RNAi-treated mice were involved and subjected in AIH. We observed that increased iron dysregulation was linked with STING activation, but this effect was effectively reversed by the administration of iron chelating agent Desferoxamine (DFO) and the antioxidant Ferrostatin-1 (Fer-1). Notably, the iron transport protein Transferrin (TF) and Transferrin Receptor (TfR) exhibited significant accumulation in AIH along with upregulated expression of ferritin protein. Additionally, the deficiency of STING reduced hepatic iron accumulation, mitigated oxidative stress, and attenuated macrophage activation during ConA treatment. Furthermore, liver-specific knockdown of STING using AAV-Sting1-RNAi significantly ameliorated liver iron dysregulation and oxidative stress response induced by Kupffer cells (KCs). KC-derived STING exacerbates liver damage severity in AIH through promoting disturbances in hepatic iron ion metabolism as well as oxidative stress response. These findings provide valuable insights into the pathogenesis of AIH and may pave the way for potential therapeutic strategies targeting STING and iron metabolism in the future.

Role of Hepatic Stellate and Liver Sinusoidal Endothelial Cells in a Human Primary Cell Three-Dimensional Model of Nonalcoholic Steatohepatitis.

Nonalcoholic steatohepatitis (NASH) is an inflammatory and fibrotic liver disease that has reached epidemic proportions and has no approved pharmacologic therapies. Research and drug development efforts are hampered by inadequate preclinical models. This research describes a three-dimensional bioprinted liver tissue model of NASH built using primary human hepatocytes and nonparenchymal liver cells (hepatic stellate cells, liver sinusoidal endothelial cells, and Kupffer cells) from either healthy or NASH donors. Three-dimensional tissues bioprinted with cells sourced from diseased patients showed a NASH phenotype, including fibrosis. More importantly, this NASH phenotype occurred without the addition of disease-inducing agents. Bioprinted tissues composed entirely of healthy cells exhibited significantly less evidence of disease. The role of individual cell types in driving the NASH phenotype was examined by producing chimeric bioprinted tissues composed of healthy cells together with the addition of one or more diseased nonparenchymal cell types. These experiments reveal a role for both hepatic stellate and liver sinusoidal endothelial cells in the disease process. This model represents a fully human system with potential to detect clinically active targets and eventually therapies.

Liver macrophages and sinusoidal endothelial cells execute vaccine-elicited capture of invasive bacteria.

Vaccination has substantially reduced the morbidity and mortality of bacterial diseases, but mechanisms of vaccine-elicited pathogen clearance remain largely undefined. We report that vaccine-elicited immunity against invasive bacteria mainly operates in the liver. In contrast to the current paradigm that migrating phagocytes execute vaccine-elicited immunity against blood-borne pathogens, we found that invasive bacteria are captured and killed in the liver of vaccinated host via various immune mechanisms that depend on the protective potency of the vaccine. Vaccines with relatively lower degrees of protection only activated liver-resident macrophage Kupffer cells (KCs) by inducing pathogen-binding immunoglobulin M (IgM) or low amounts of IgG. IgG-coated pathogens were directly captured by KCs via multiple IgG receptors FcγRs, whereas IgM-opsonized bacteria were indirectly bound to KCs via complement receptors of immunoglobulin superfamily (CRIg) and complement receptor 3 (CR3) after complement C3 activation at the bacterial surface. Conversely, the more potent vaccines engaged both KCs and liver sinusoidal endothelial cells by inducing higher titers of functional IgG antibodies. Endothelial cells (ECs) captured densely IgG-opsonized pathogens by the low-affinity IgG receptor FcγRIIB in a "zipper-like" manner and achieved bacterial killing predominantly in the extracellular milieu via an undefined mechanism. KC- and endothelial cell-based capture of antibody-opsonized bacteria also occurred in FcγR-humanized mice. These vaccine protection mechanisms in the liver not only provide a comprehensive explanation for vaccine-/antibody-boosted immunity against invasive bacteria but also may serve as in vivo functional readouts of vaccine efficacy.

BRISC is required for optimal activation of NF-κB in Kupffer cells induced by LPS and contributes to acute liver injury.

BRISC (BRCC3 isopeptidase complex) is a deubiquitinating enzyme that has been linked with inflammatory processes, but its role in liver diseases and the underlying mechanism are unknown. Here, we investigated the pathophysiological role of BRISC in acute liver failure using a mice model induced by D-galactosamine (D-GalN) plus lipopolysaccharide (LPS). We found that the expression of BRISC components was dramatically increased in kupffer cells (KCs) upon LPS treatment in vitro or by the injection of LPS in D-GalN-sensitized mice. D-GalN plus LPS-induced liver damage and mortality in global BRISC-null mice were markedly attenuated, which was accompanied by impaired hepatocyte death and hepatic inflammation response. Constantly, treatment with thiolutin, a potent BRISC inhibitor, remarkably alleviated D-GalN/LPS-induced liver injury in mice. By using bone marrow-reconstituted chimeric mice and cell-specific BRISC-deficient mice, we demonstrated that KCs are the key effector cells responsible for protection against D-GalN/LPS-induced liver injury in BRISC-deficient mice. Mechanistically, we found that hepatic and circulating levels of TNF-α, IL-6, MCP-1, and IL-1ß, as well as TNF-α- and MCP-1-producing KCs, in BRISC-deleted mice were dramatically decreased as early as 1 h after D-GalN/LPS challenge, which occurred prior to the elevation of the liver injury markers. Moreover, LPS-induced proinflammatory cytokines production in KCs was significantly diminished by BRISC deficiency in vitro, which was accompanied by potently attenuated NF-κB activation. Restoration of NF-κB activation by two small molecular activators of NF-κB p65 effectively reversed the suppression of cytokines production in ABRO1-deficient KCs by LPS. In conclusion, BRISC is required for optimal activation of NF-κB-mediated proinflammatory cytokines production in LPS-treated KCs and contributes to acute liver injury. This study opens the possibility to develop new strategies for the inhibition of KCs-driven inflammation in liver diseases.

Zaluzanin C Alleviates Inflammation and Lipid Accumulation in Kupffer Cells and Hepatocytes by Regulating Mitochondrial ROS.

Zaluzanin C (ZC), a sesquiterpene lactone isolated from Laurus nobilis L., has been reported to have anti-inflammatory and antioxidant effects. However, the mechanistic role of ZC in its protective effects in Kupffer cells and hepatocytes has not been elucidated. The purpose of this study was to elucidate the efficacy and mechanism of action of ZC in Kupffer cells and hepatocytes. ZC inhibited LPS-induced mitochondrial ROS (mtROS) production and subsequent mtROS-mediated NF-κB activity in Kupffer cells (KCs). ZC reduced mRNA levels of pro-inflammatory cytokines (Il1b and Tnfa) and chemokines (Ccl2, Ccl3, Ccl4, Cxcl2 and Cxcl9). Tumor necrosis factor (TNF)-α-induced hepatocyte mtROS production was inhibited by ZC. ZC was effective in alleviating mtROS-mediated mitochondrial dysfunction. ZC enhanced mitophagy and increased mRNA levels of fatty acid oxidation genes (Pparα, Cpt1, Acadm and Hadha) and mitochondrial biosynthetic factors (Pgc1α, Tfam, Nrf1 and Nrf2) in hepatocytes. ZC has proven its anti-lipid effect by improving lipid accumulation in hepatocytes by enhancing mitochondrial function to facilitate lipid metabolism. Therefore, our study suggests that ZC may be an effective compound for hepatoprotection by suppressing inflammation and lipid accumulation through regulating mtROS.

Global Profiling of Lysine Acetylation and Lactylation in Kupffer Cells.

Among the various cell types that constitute the liver, Kupffer cells (KCs) are responsible for the elimination of gut-derived foreign products. Protein lysine acetylation (Kac) and lactylation (Kla) are dynamic and reversible post-translational modifications, and various global acylome studies have been conducted for liver and liver-derived cells. However, no such studies have been conducted on KCs. In this study, we identified 2198 Kac sites in 925 acetylated proteins and 289 Kla sites in 181 lactylated proteins in immortalized mouse KCs using global acylome technology. The subcellular distributions of proteins with Kac and Kla site modifications differed. Similarly, the specific sequence motifs surrounding acetylated or lactylated lysine residues also showed differences. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed to better understand the differentially expressed proteins in the studies by Kac and Kla. In the newly identified Kla, we found K82 lactylation in the high-mobility group box-1 protein in the neutrophil extracellular trap formation category using KEGG enrichment analyses. Here, we report the first proteomic survey of Kac and Kla in KCs.

Monocyte-derived Kupffer cells dominate in the Kupffer cell pool during liver injury.

Healthy Kupffer cell (KC) pool is dominated by embryonic KCs (EmKCs), preserving liver homeostasis. How the KC pool varies upon injury remains unclear. Using chimeric mice with bone marrow (BM) cells labeled with enhanced green fluorescent protein, we identify that BM monocyte-derived KCs (MoKCs) become dominant in cholestatic- or toxic-injured livers via immunofluorescence and mass cytometry. Single-cell RNA sequencing (scRNA-seq) unveils the enhanced proliferative, anti-apoptotic properties and repair potential of MoKCs compared with EmKCs, which are confirmed in vivo and ex vivo through flow cytometry, qPCR, Cell Counting Kit-8, and immunofluorescence. Furthermore, compared with EmKC-dominated livers, MoKC-dominated livers exhibit less functional damage, necrosis, and fibrosis under damage, as tested by serum alanine aminotransferase activity detection, H&E and Sirius red staining, qPCR, and western blot. Collectively, we highlight that MoKCs dominate the KC pool in injured livers and show enhanced proliferative and anti-apoptotic properties while also promoting repair and attenuating fibrosis.

CXCL5 promotes lipotoxicity of hepatocytes through upregulating NLRP3/Caspase-1/IL-1ß signaling in Kupffer cells and exacerbates nonalcoholic steatohepatitis in mice.

Immune-inflammatory responses play a key role in the development of nonalcoholic steatohepatitis (NASH). Previous studies have demonstrated that CXC motif chemokine ligand 5 (CXCL5) correlates positively with obesity and type 2 diabetes. This study is to explore the functional role of CXCL5 in the pathogenesis of NASH. To establish a NASH model, mice were fed with methionine-and choline-deficient high-fat diet for 6 weeks and anti-CXCL5 mAb was injected during the same period. An in vitro NASH model was established by treating palmitic acid (PA), using a trans-well co-culture system of mouse primary hepatocytes and Kupffer cells (KCs), and recombinant mouse (rm) CXCL5 was treated after PA administration. Our data showed that hepatic CXCL5 levels were highly expressed in the NASH mouse model. CXCL5 neutralization significantly alleviated the severity of NASH livers, demonstrated by pathological analysis, decreased biochemicals, and inflammation. Besides, neutralizing CXCL5 reduced lipid accumulation, cell death, and fibrosis in injured livers. In vitro, rmCXCL5 could not affect the activation of hepatic stellate cells. Also, rmCXCL5 exacerbated PA-induced hepatotoxicity and lipid deposition in hepatocytes co-cultured with KCs rather than in single-cultured hepatocytes. Mechanistically, rmCXCL5 not only promoted NOD-like receptor pyrin domain-containing protein 3 (NLRP3) expression, Cleaved caspase-1 expression, and interleukin 1 beta (IL-1ß) secretion in single-cultured and co-cultured KCs but also increased lipid deposition in co-cultured hepatocytes. In addition, MCC950, an inhibitor of NLRP3, almost abolished the effects of rmCXCL5 on PA-treated co-culture system. Therefore, CXCL5 could exacerbate NASH by promoting lipotoxicity of hepatocytes via upregulating NLRP3/Caspase-1/IL-1ß signaling in KCs.

Suppression of FOXO1 attenuates inflamm-aging and improves liver function during aging.

The liver is a key metabolic organ that maintains whole-body nutrient homeostasis. Aging-induced liver function alterations contribute to systemic susceptibility to aging-related diseases. However, the molecular mechanisms of liver aging remain insufficiently understood. In this study, we performed bulk RNA-Seq and single-cell RNA-Seq analyses to investigate the underlying mechanisms of the aging-induced liver function changes. We found that liver inflammation, glucose intolerance, and liver fat deposition were aggravated in old mice. Aging significantly increased pro-inflammation in hepatic macrophages. Furthermore, we found that Kupffer cells (KCs) were the major driver to induce pro-inflammation in hepatic macrophages during aging. In KCs, aging significantly increased pro-inflammatory levels; in monocyte-derived macrophages (MDMs), aging had a limited effect on pro-inflammation but led to a functional quiescence in antigen presentation and phagosome process. In addition, we identified an aging-responsive KC-specific (ARKC) gene set that potentially mediates aging-induced pro-inflammation in KCs. Interestingly, FOXO1 activity was significantly increased in the liver of old mice. FOXO1 inhibition by AS1842856 significantly alleviated glucose intolerance, hepatic steatosis, and systemic inflammation in old mice. FOXO1 inhibition significantly attenuated aging-induced pro-inflammation in KCs partially through downregulation of ARKC genes. However, FOXO1 inhibition had a limited effect on aging-induced functional quiescence in MDMs. These results indicate that aging induces pro-inflammation in liver mainly through targeting KCs and FOXO1 is a key player in aging-induced pro-inflammation in KCs. Thus, FOXO1 could be a potential therapeutic target for the treatment of age-associated chronic diseases.

Ligustrazine improves the compensative effect of Akt survival signaling to protect liver Kupffer cells in trauma-hemorrhagic shock rats.

Trauma-hemorrhagic shock (THS) is a medical emergency that is encountered by physicians in the emergency department. Chuan Xiong is a traditional Chinese medicine and ligustrazine is a natural compound from it. Ligustrazine improves coronary blood flow and reduces cardiac ischemia in animals through Ca2+ and ATP-dependent vascular relaxation. It also decreases the platelets' bioactivity and reduces reactive oxygen species formation. We hypothesized that ligustrazine could protect liver by decreasing the inflammation response, protein production, and apoptosis in THS rats. Ligustrazine at doses of 100 and 1000 µg/mL was administrated in Kupffer cells isolated from THS rats. The protein expressions were detected via western blot. The THS showed increased inflammation response proteins, mitochondria-dependent apoptosis proteins, and had a compensation effect on the Akt pathway. After ligustrazine treatment, the hemorrhagic shock Kupffer cells decreased inflammatory response and mitochondria-dependent apoptosis and promoted a more compensative effect of the Akt pathway. It suggests ligustrazine reduces inflammation response and mitochondria-dependent apoptosis induced by THS in liver Kupffer cells and promotes more survival effects by elevating the Akt pathway. These findings demonstrate the beneficial effects of ligustrazine against THS-induced hepatic injury, and ligustrazine could be a potential medication to treat the liver injury caused by THS.

CXCL5 Promotes Acetaminophen-Induced Hepatotoxicity by Activating Kupffer Cells.

Kupffer cells (KCs) play a key part in the pathological process of acetaminophen (APAP)-induced acute liver injury (ALI), the leading cause of acute liver failure in the world. CXC motif chemokine ligand 5 (CXCL5) exerts proinflammatory effects in acute respiratory distress syndrome and arthritis. In the current study, we aim to reveal the effects of CXCL5 on the activation of KCs and the role of CXCL5 in the pathogenesis of APAP-induced hepatotoxicity. The in vivo study, conducted on mice intraperitoneally injected with APAP (300 mg/kg) to establish the ALI model and then treated with Anti-CXCL5 mAb at 30 min and 12 h after the APAP challenge, showed that CXCL5 expression significantly increased in injured livers, and Anti-CXCL5 mAb mitigated the degree of APAP-evoked ALI in mice which was proven through biochemicals and histological examination. Also, neutralization of CXCL5 had no significant effect on APAP metabolism in the liver but exhibited anti-inflammatory effects and ameliorated hepatocellular death in the injured liver. The in vitro data displayed that recombinant mouse CXCL5 treatment promoted APAP-induced cellular toxicity in primary hepatocytes co-cultured with KCs, compared with single-cultured hepatocytes. Consistent with the result, we found that the Anti-CXCL5 mAb gradient decreased LPS-induced expression of inflammatory cytokines in single-cultured KCs. Therefore, CXCL5 could stimulate KCs to produce inflammatory mediators, therefore damaging hepatocytes from APAP toxicity.

Humanized mouse liver reveals endothelial control of essential hepatic metabolic functions.

Hepatocytes, the major metabolic hub of the body, execute functions that are human-specific, altered in human disease, and currently thought to be regulated through endocrine and cell-autonomous mechanisms. Here, we show that key metabolic functions of human hepatocytes are controlled by non-parenchymal cells (NPCs) in their microenvironment. We developed mice bearing human hepatic tissue composed of human hepatocytes and NPCs, including human immune, endothelial, and stellate cells. Humanized livers reproduce human liver architecture, perform vital human-specific metabolic/homeostatic processes, and model human pathologies, including fibrosis and non-alcoholic fatty liver disease (NAFLD). Leveraging species mismatch and lipidomics, we demonstrate that human NPCs control metabolic functions of human hepatocytes in a paracrine manner. Mechanistically, we uncover a species-specific interaction whereby WNT2 secreted by sinusoidal endothelial cells controls cholesterol uptake and bile acid conjugation in hepatocytes through receptor FZD5. These results reveal the essential microenvironmental regulation of hepatic metabolism and its human-specific aspects.