Metabolic dysfunction-associated steatotic liver disease (MASLD) comprises a spectrum of liver injuries, including steatosis to steatohepatitis (MASH), liver fibrosis, cirrhosis, and relevant complications. The liver mainly comprises hepatocytes, liver sinusoidal endothelial cells (LSECs), Kupffer cells (KCs), immune cells (T cells, B cells), and hepatic stellate cells (HSCs). Crosstalk among these different liver cells, endogenous aberrant glycolipid metabolism, and altered gut dysbiosis are involved in the pathophysiology of MASLD. This review systematically examines advances in understanding the molecular pathogenesis of MASLD, with a focus on emerging therapeutic targets and translational clinical trials. We first delineate the crucial regulatory mechanisms involving diverse liver cells and the gut-liver axis in MASLD development. These cell-specific pathogenic insights offer valuable perspectives for advancing precision medicine approaches in MASLD treatment. Furthermore, we evaluate potential therapeutic targets and summarize clinical trials currently underway. By comprehensively updating the MASLD pathophysiology and identifying promising strategies, this review aims to facilitate the development of novel pharmacotherapies for this increasingly prevalent condition.
Humans ; Fatty Liver/therapy* ; Animals ; Liver/pathology* ; Kupffer Cells/metabolism* ; Hepatocytes/metabolism* ; Hepatic Stellate Cells/metabolism*

OBJECTIVES: This study aimed to explore the functions and potential regulatory targets of local macrophages in nonalcoholic fatty liver combined with Porphyromonas gingivalis (P. gingivalis)infection. METHODS: Single-cell RNA sequencing was used to analyze the phenotypes and functional changes in various cells in the liver tissue of nonalcoholic steatohepatitis (NASH) mice fed with P. gingivalis. Real-time polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay, and immunofluorescence staining were applied to observe the inflammation and expression levels of macrophage antigen presenting functional markers in the NASH liver. Oil red staining was performed to observe the accumulation of local adipose tissue in the NASH liver. Results were verified through RT-PCRand RNA sequencing using P. gingivalis-lipopolysaccharide treated mouse peritoneal macrophages. RESULTS: In comparison with healthy livers with Kupffer cells, the NASH liver combined with P. gingivalis infection-related macrophages showed significant heterogeneity. C1qb, C1qc, Mafb, Apoe, and Cd14 were highly expressed, but Cd209a, H2-Aa, H2-Ab1, and H2-DMb1, which are related to the antigen presentation function, were weakly expressed. Further in vivo and in vitro investigations indicated that the activation and infiltration of these macrophages may be due to local P. gingivalis-lipopolysaccharide accumulation. CONCLUSIONS P. gingivalis-lipopolysaccharide induces a local macrophage immunotolerance phenotype in nonalcoholic fatty liver, which may be the key mechanism of periodontitis pathogen infection that promotes NASH inflammation and pathogenesis. This study further clarifies the dysfunction and regulatory mechanisms of macrophages in the pathogenesis of P. gingivalis-infected NASH, thereby providing potential therapeutic targets for its clinical treatment.
Mice ; Animals ; Non-alcoholic Fatty Liver Disease/pathology* ; Kupffer Cells/pathology* ; Porphyromonas gingivalis ; Lipopolysaccharides/metabolism* ; Inflammation/pathology* ; Macrophages/metabolism* ; Mice, Inbred C57BL

OBJECTIVE: To investigate the role of cathepsin B in hepatic Kupffer cells (KCs) in activating Toll-like receptor 4(TLR- 4)-independent inflammatory pathways in mice with lipopolysaccharide (LPS)-induced sepsis. METHODS: Eighteen wild-type (WT) mice and 18 TLR4-knockout (TLR4) mice were both divided into 3 groups for intraperitoneal injections of a lethal dose (54 mg/kg) of LPS, LPS and CA-074(a cathepsin B inhibitor), or normal saline, and the survival of the mice were observed. Another 36 WT mice and 36 TLR4mice were also divided into 3 groups and subjected to intraperitoneal injections of normal saline, 20 mg/kg LPS, or LPS with CA-074 pretreatment.After the treatments, KCs were collected from the mice for assessing the protein level and activity of cathepsin B.The histopathological changes of the liver were observed with HE staining, and the serum levels of IL-1α, IL-1β, TNF-α and IL-18 were detected. RESULTS: Compared with the WT mice,TLR4mice receiving the lethal dose of LPS had significantly longer survival time (up to 84 h) after the injection,but were still unable to fully resist LPS challenge.CA-074 pretreatment prolonged the survival time of WT mice and TLR4mice to 60 h and 132 h,respectively.In the mouse models of sepsis,20 mg/kg LPS induced significantly enhanced activity of cathepsin B without affecting its expression level in the KCs (<0.05) and increased the serum levels of the inflammatory cytokines.CA-074 pretreatment of the mice obviously lessened the detrimental effects of LPS in TLR4mice by significantly lowering cathepsin B activity in the KCs,alleviating hepatocyte apoptosis and reducing the serum levels of inflammatory cytokines. CONCLUSIONS Cathepsin B plays an important role in activating TLR4-independent inflammatory pathways in mice with LPS-induced sepsis.
Animals ; Cathepsin B ; antagonists & inhibitors ; physiology ; Dipeptides ; pharmacology ; Gene Knockout Techniques ; Hepatocytes ; Inflammation ; metabolism ; Interleukin-18 ; blood ; Interleukin-1alpha ; blood ; Interleukin-1beta ; blood ; Kupffer Cells ; metabolism ; Lipopolysaccharides ; Liver ; pathology ; Mice ; Sepsis ; etiology ; metabolism ; Toll-Like Receptor 4 ; genetics ; Tumor Necrosis Factor-alpha ; blood

OBJECTIVETo investigate the effects of inhibiting TIM-4 function in Kupffer cells (KCs) on liver graft rejection in mice and explore the underlying mechanism.

METHODSMouse models of orthotopic liver transplantation were treated with a control mAb group and TIM-4 mAb. The activated KCs were assayed with immunohistochemistry after operation. The expression of TIM-4 in KCs were assayed with Western blotting and RT-PCR and the levels of AST, ALT, TBIL, TNF-α, IFN-γ and CCL2 were assayed detected. The expression of TIM-4 in KCs was observed with laser confocal microscopy. HE staining was used to observe the microstructure of the liver tissues, and the number of CD25Foxp3T cells was determined using with flow cytometry; the proteins levels of p-P65and p-P38 were assayed with Western blotting. The donor mice were treated with clodronate liposomes to destroy the KCs in the liver before transplantation, and the liver grafts were examined for graft rejection.

RESULTSThe number of activated KCs in the liver graft increased progressively over time. Compared with the sham-operated group, the liver graft showed significantly increased TIM-4 protein and mRNA levels at 1, 3, and 7 days after transplantation (P<0.05) and increased levels of AST, ALT, TBIL, TNF-α, IFN-γ and CCL2 at 7 days (P<0.05). The graft in TIM-4 mAb group showed mild pathological changes with a mean RAI score of 2.67∓0.75, which was significantly lower than that in control mAb group (P<0.05). The mean survival time of the recipient mice was 53.8∓6.4 days in TIM-4 mAb group, significantly longer than that in the control mAB group (14.5∓2.9 days, P<0.05). Donor treatment with clodronate liposomes resulted in comparable RAI scores in TIM-4 mAb and control mAb groups (8.01∓0.64 vs 7.93∓0.56, P>0.05). The protein levels of p-P65 and p-P38 in TIM-4 mAb group were significantly lower than those in control mAb group (P<0.05), and CD25Foxp3T cells in the liver graft increased significantly in TIM-4 mAb group.

CONCLUSIONInhibition of TIM-4 function in KCs reduces the production of inflammatory factors after liver transplantation possibly by inhibiting the NF-κB and MAPK signaling pathways and promoting the proliferation of Foxp3Treg cells to induce allograft tolerance.

Animals ; Antibodies, Monoclonal ; pharmacology ; Graft Rejection ; Immunohistochemistry ; Kupffer Cells ; drug effects ; metabolism ; Liver ; surgery ; Liver Transplantation ; Male ; Membrane Proteins ; antagonists & inhibitors ; Mice ; NF-kappa B ; metabolism ; T-Lymphocytes, Regulatory ; immunology

OBJECTIVE: To evaluate whether dexmedetomidine hydrochloride, an α(2)-adrenergic receptor agonist, can prevent H(2)O(2)-induced oxidative stress and inflammatory response in Kupffer cells.
 METHODS: H(2)O(2)-induced oxidative damage model of Kupffer cell was established. Kupffer cells were pre-conditioned by dexmedetomidine hydrochloride or Yohimbine for 24 h. MTT colorimetry was used to demonstrate the survival rate of Kupffer cells. The levels of lactate dehydrogenase (LDH), malonaldehyde (MDA) and TNF-α in the culture medium were assessed by corresponding kits.
 RESULTS: Dexmedetomidine hydrochloride protected Kupffer cells from H(2)O(2)-induced oxidative damage, showing an increase in the cell survival rate while a decrease in LDH, MDA and TNF-α release in the culture supernatant. Yohimbine, an α(2)-adrenergic receptor antagonist, completely neutralized the protective effect of Dexmedetomidine hydrochloride on Kupffer cells. Yohimbine itself had no effect on H(2)O(2)-induced oxidative damage and inflammatory response.
 CONCLUSION Dexmedetomidine hydrochloride can prevent H(2)O(2)-induced oxidative stress and inflammatory response in Kupffer cells through activation of α(2)-adrenergic receptors.
Adrenergic alpha-2 Receptor Antagonists ; pharmacology ; Cell Survival ; Cells, Cultured ; Dexmedetomidine ; pharmacology ; Humans ; Hydrogen Peroxide ; pharmacology ; Kupffer Cells ; cytology ; drug effects ; L-Lactate Dehydrogenase ; metabolism ; Malondialdehyde ; metabolism ; Oxidative Stress ; drug effects ; Receptors, Adrenergic, alpha-2 ; metabolism ; Tumor Necrosis Factor-alpha ; metabolism ; Yohimbine ; pharmacology

The inducible form of nitric oxide synthase (iNOS) is expressed in hepatic cells in pathological conditions. Its induction is involved in the development of liver fibrosis, and thus iNOS could be a therapeutic target for liver fibrosis. This review summarizes the role of iNOS in liver fibrosis, focusing on 1) iNOS biology, 2) iNOS-expressing liver cells, 3) iNOS-related therapeutic strategies, and 4) future directions.
Endothelial Cells/metabolism ; Hepatic Stellate Cells/metabolism ; Humans ; Kupffer Cells/metabolism ; Liver Cirrhosis/metabolism/*pathology ; Nitric Oxide/*metabolism ; Nitric Oxide Synthase Type II/antagonists & inhibitors/genetics/*metabolism ; Polymorphism, Single Nucleotide ; RNA, Untranslated/metabolism

OBJECTIVETo investigate the effect of high mobility group box protein 1 (HMGB1) on the production of pro-inflammatory cytokines by Kupffer cell (KC) of rats with severe burn and the role of receptor for advanced glycation end products (RAGE) in the process.

METHODSModel of 30% TBSA full-thickness burn was reproduced in 32 SD rats through immersing the back in 98°C water for 12 s. KC (32 samples) was isolated from rat liver 24 h after injury and inoculated in 24-well plate in the concentration of 1×10(6) cell per well. (1) Cells were divided into control group (cultured with 1 mL PBS) and HMGB1 group (stimulated with 100 ng/mL HMGB1 in the volume of 1 mL) according to the random number table, with 8 samples in each group. At post culture hour (PCH) 48, the expression of RAGE (denoted as grey value ratio) was detected with Western blotting. (2) Another portion of cells were divided into control group (cultured with 1 mL PBS), HMGB1 group (treated with 100 ng/mL HMGB1 in the volume of 1 mL), HMGB1 + anti-RAGE antibody group (treated with 100 ng/mL HMGB1 in the volume of 1 mL after being pre-incubated with 20 µg/mL anti-RAGE monoclonal antibody in the volume of 1 mL for 2 hours), HMGB1 + recombinant rat RAGE/Fc chimera (rrRAGE/Fc) group (treated with the mixture of 100 ng/mL HMGB1 in the volume of 0.5 mL and 5 µg/mL rrRAGE/Fc in the volume of 0.5 mL which were pre-incubated for 2 hours) according to the random number table, with 8 samples in each group. At PCH 48, the protein levels of TNF-α and IL-1β in supernatant were determined with enzyme-linked immunosorbent assay, while the mRNA expression of TNF-α and IL-1β (denoted as grey value ratio) were determined with Northern blotting. Data were processed with one-way analysis of variance, t test, and LSD test.

RESULTS(1) The expression of RAGE in HMGB1 group (1.036 ± 0.101) was significantly higher than that of control group at PCH 48 (0.191 ± 0.024, t = -23.158, P = 0.000). (2) In HMGB1 group, HMGB1 + anti-RAGE antibody group, and HMGB1 + rrRAGE/Fc group, the contents of TNF-α in supernatant were respectively (10.59 ± 1.39), (9.91 ± 1.68), (11.51 ± 2.27) ng/mL; the contents of IL-1β in supernatant were respectively (2.49 ± 0.33), (2.08 ± 0.32), (2.42 ± 0.42) ng/mL; the mRNA levels of TNF-α in cells were respectively 0.311 ± 0.009, 0.301 ± 0.047, 0.326 ± 0.016; the mRNA levels of IL-1β in cells were respectively 0.237 ± 0.021, 0.244 ± 0.041, 0.245 ± 0.013. There were no statistically significant differences in the above indexes among these three groups (with P values all above 0.05). Their levels were all significantly higher than those of control group [with contents of TNF-α and IL-1β in supernatant respectively (2.69 ± 0.14), (0.43 ± 0.05) ng/mL, and mRNA levels of TNF-α and IL-1β in cells respectively 0.140 ± 0.022, 0.077 ± 0.005, P values all below 0.01].

CONCLUSIONSHMGB1 can induce the production of pro-inflammatory cytokines TNF-α and IL-1β from the KC in rats with severe burn. However, RAGE does not play a predominant role in this process.

Animals ; Burns ; metabolism ; Cytokines ; metabolism ; Disease Models, Animal ; HMGB1 Protein ; pharmacology ; Interleukin-1beta ; metabolism ; Kupffer Cells ; drug effects ; metabolism ; Male ; Rats ; Rats, Sprague-Dawley ; Receptor for Advanced Glycation End Products ; Receptors, Immunologic ; metabolism ; Tumor Necrosis Factor-alpha ; metabolism

Animals ; Disease Progression ; Fatty Liver ; metabolism ; pathology ; Humans ; Inflammation ; Kupffer Cells ; metabolism ; Non-alcoholic Fatty Liver Disease

OBJECTIVETo observe the effects of different therapeutic methods and the recipes of Chinese medicine (CM) on the activation of c-Jun N-terminal kinase (JNK) in Kupffer cells of rats with fatty liver disease and to explore the mechanisms of these therapeutic methods.

METHODSBy using a random number table, 98 rats were randomly divided into 7 groups: control group, model group, and 5 treatment groups, including soothing Liver (Gan) recipe group, invigorating Spleen (Pi) recipe group, dispelling dampness recipe group, promoting blood recipe group, and complex recipe group. Rats in the control group were fed with normal food and distilled water by gastric perfusion, while rats in the model group were fed with high-fat food and distilled spirits by gastric perfusion. Rats in the 5 treatment groups were fed with high-fat food and corresponding recipes by gastric perfusion. Twelve weeks later, all rats were sacrificed and liver tissues were stained for pathohistological observation. Kupffer cells were isolated from livers of rats to evaluate JNK and phospho-JNK expressions by Western blotting.

RESULTSThe grade of hepatic steatosis was higher in the model group than the control group (P<0.05). Compared with the model group, the grade of fatty degeneration in soothing Liver recipe group and invigorating Spleen recipe group were significantly ameliorated (P<0.05). Expressions of JNK and phospho-JNK in Kupffer cells were significantly higher in the model group than those in the control group (P<0.05, P<0.01). Compared with the model group, expressions of JNK in all treatment groups decreased, especially in invigorating Spleen recipe group and promoting blood recipe group (P<0.05). Compared with the model group, expressions of phospho-JNK in all treatment groups declined significantly (P<0.01), especially in soothing Live recipe group and invigorating Spleen recipe group.

CONCLUSIONSThe high expressions of JNK and phospho-JNK in Kupffer cells might play an important role in the pathogenesis of fatty liver disease in rats. The recipes of CM, especially invigorating Spleen recipe and soothing Liver recipe, might protect liver against injury by reducing the total JNK protein content and inhibiting the activation of JNK protein in Kupffer cells of fatty liver model rats, which showed beneficial effects on fatty liver disease.

Animals ; Cell Survival ; drug effects ; Drugs, Chinese Herbal ; pharmacology ; Enzyme Activation ; drug effects ; Fatty Liver ; enzymology ; pathology ; therapy ; Hepatocytes ; drug effects ; enzymology ; pathology ; JNK Mitogen-Activated Protein Kinases ; metabolism ; Kupffer Cells ; drug effects ; enzymology ; pathology ; Liver ; drug effects ; enzymology ; pathology ; Phosphorylation ; drug effects ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo investigate the relationship of NOR-1 with the inhibition of inflammatory reaction in mice Kupffer cells (KCs) induced by lipopolysaccharide (LPS) via liver X receptor alpha (LXR alpha).

METHODSKCs from male KM mice were isolated by density gradient centrifugation, incubated and then randomly assigned to three groups: control group, LPS treated group and LPS+T0901317 treated group.

RESULTSThe mRNA and protein expressions of LXR alpha and NOR-1 in each group were determined by RT-PCR, immunofluorescent assay and western blot, respectively. The densities of TNF alpha and IL-10 in supernatants were evaluated by enzyme linked immunosorbent assay (ELISA). The mRNA and protein expression levels of LXR alpha in LPS + T0901317 group were the highest as compared to the other two groups (0.748+/-0.072 and 1.217+/-0.133 respectively), The mRNA and protein expression levels of NOR-1 in LPS+ T0901317 group were the highest as compared to the other two groups (2.726+/-0.065 and 0.842+/-0.058 respectively). The densities of supernatant TNF alpha in LPS group and IL-10 in LPS+T0901317 group were the highest [(450.89+/-78.52) ng/L and (537.41+/-36.41) ng/L respectively].

CONCLUSIONSPromoting the expression of LXR alpha in KCs can elevate the NOR-1 expression and then inhibit inflammatory reaction.

Animals ; Cells, Cultured ; DNA-Binding Proteins ; metabolism ; Inflammation ; metabolism ; Interleukin-10 ; metabolism ; Kupffer Cells ; metabolism ; Liver X Receptors ; Male ; Mice ; Mice, Inbred Strains ; Nerve Tissue Proteins ; metabolism ; Orphan Nuclear Receptors ; metabolism ; Receptors, Steroid ; metabolism ; Receptors, Thyroid Hormone ; metabolism ; Tumor Necrosis Factor-alpha ; metabolism