Kupffer cell inactivation ameliorates immune liver injury via TNF-α/TNFR1 signal pathway in trichloroethylene sensitized mice

The effect of Jian Gan powder on the proliferation, migration and polarization of macrophages and relative mechanism

CONTEXT

Jian Gan powder (JGP) is a Chinese medicine compound comprised ginseng, Radix Paeoniae Alba, Radix Astragali, Salvia miltiorrhiza, Yujin, Rhizoma Cyperi, Fructus aurantii, Sophora flavescens, Yinchen, Bupleurum and licorice.

OBJECTIVE

This study explored the inhibitory effects, polarization and potential mechanisms associated with JGP in macrophages.

MATERIALS AND METHODS

RAW264.7 cells were randomly divided into six groups for 24 h: control, lipopolysaccharide (LPS), overexpression, 1% JGP, 2% JGP, 4% JGP, 8% JGP and 16% JGP. The effects of JGP on RAW264.7 cell proliferation were assessed using colony formation assays and cell counting kit-8 (CCK-8) assays. The Transwell assay was used to evaluate its impact on RAW264.7 cell migration. Moreover, we analysed the interleukin-6 (IL-6)/signal transducer and activator of the transcription 3 (IL-6/STAT3) signaling pathway using quantitative real-time PCR and Western blotting. Furthermore, we examined the M1/M2 polarization levels.

RESULTS

Unlike LPS stimulation, JGP serum treatment markedly suppressed macrophage proliferation and migration capacity, while STAT3 overexpression enhanced RAW264.7 cell proliferation and migration. JGP inhibited the proliferation and migration of RAW264.7 cells by attenuating the IL-6/STAT3 signaling pathway. Furthermore, it inhibited macrophage M1 polarization, promoting M2 polarization.

DISCUSSION AND CONCLUSIONS

JGP effectively suppressed the cellular function of RAW264.7 cells by down-regulating the IL-6/STAT3 signaling pathway and modulating macrophage M1/M2 polarization. These findings provide valuable theoretical and experimental basis for considering the potential clinical application of JGP in the treatment of immune-mediated liver injury in clinical practice.

Histone demethylase KDM4A mediating macrophage polarization: A potential mechanism of trichloroethylene induced liver injury

Trichloroethylene (TCE) is a commonly used organic solvent in industry. Our previous studies have found that TCE can cause liver injury accompanied by macrophage polarization, but the specific mechanism is unclear. The epigenetic regulation of macrophage polarization is mainly focused on histone modification. Histone lysine demethylase 4A (KDM4A) is involved in the activation of macrophages. In this study, we used a mouse model we investigated the role of KDM4A in the livers of TCE-drinking mice and found that the expression of KDM4A, M1-type polarization indicators, and related inflammatory factors in the livers of TCE-drinking mice. In the study, BALB/c mice were randomly divided into four groups: 2.5 mg/mL TCE dose group and 5.0 mg/mL TCE dose group, the vehicle control group, and the blank control group. We found that TCE triggered M1 polarization of mouse macrophages, characterized by the expression of CD11c and robust production of inflammatory cytokines. Notably, exposure to TCE resulted in markedly increased expression of KDM4A in macrophages. Functionally, the increased expression of KDM4A significantly impaired the expression of H3K9me3 and H3K9me2 and increased the expression of H3K9me1. In addition, KDM4A potentially represents a novel epigenetic modulator, with its upregulation connected to β-catenin activation, a signal critical for the pro-inflammatory activation of macrophages. Furthermore, KDM4A inhibitor JIB-04 treatment resulted in a decrease in β-catenin expression and prevented TCE-induced M1 polarization and the expression of the pro-inflammatory cytokines TNF-α and IL-1β. These results suggest that the association of KDM4A and Wnt/β-catenin cooperatively establishes the activation and polarization of macrophages and global changes in H3K9me3/me2/me1. Our findings identify KDM4A as an essential regulator of the polarization of macrophages and the expression of inflammatory cytokines, which might serve as a potential target for preventing and treating liver injury caused by TCE.

Hepatocyte mitochondrial DNA mediates macrophage immune response in liver injury induced by trichloroethylene

We have previously shown that excessive activation of macrophage proinflammatory activity plays a key role in TCE-induced immune liver injury, but the mechanism of polarization is unclear. Recent studies have shown that TLR9 activation plays an important regulatory role in macrophage polarization. In the present study, we demonstrated that elevated levels of oxidative stress in hepatocytes mediate the release of mtDNA into the bloodstream, leading to the activation of TLR9 in macrophages to regulate macrophage polarization. In vivo experiments revealed that pretreatment with SS-31, a mitochondria-targeting antioxidant peptide, reduced the level of oxidative stress in hepatocytes, leading to a decrease in mtDNA release. Importantly, SS-31 pretreatment inhibited TLR9 activation in macrophages, suggesting that hepatocyte mtDNA may activate TLR9 in macrophages. Further studies revealed that pharmacological inhibition of TLR9 by ODN2088 partially blocked macrophage activation, suggesting that the level of macrophage activation is dependent on TLR9 activation. In vitro experiments involving the extraction of mtDNA from TCE-sensitized mice treated with RAW264.7 cells further confirmed that hepatocyte mtDNA can activate TLR9 in mouse peritoneal macrophages, leading to macrophage polarization. In summary, our study comprehensively confirmed that TLR9 activation in macrophages is dependent on mtDNA released by elevated levels of oxidative stress in hepatocytes and that TLR9 activation in macrophages plays a key role in regulating macrophage polarization. These findings reveal the mechanism of macrophage activation in TCE-induced immune liver injury and provide new perspectives and therapeutic targets for the treatment of OMDT-induced immune liver injury.

Macrophage autophagy contributes to immune liver injury in trichloroethylene sensitized mice: Critical role of TNF-α mediating mTOR pathway

Trichloroethylene (TCE) induces occupational medicamentosa-like dermatitis due to TCE (OMDT) with immune liver injury, and TNF-α plays an important role in macrophage polarization and liver injury. However, TNF-α regulating macrophage polarization in liver injury induced by TCE is still unknown. Thus, on the basis of our previous research, we established the TCE-sensitized BALB/c mouse model with R7050, a specific inhibitor of TNFR1. Then, we observed significant decreases in autophagy related protein and gene levels in M1 macrophage in TCE positive group, and R7050 can relieve M1 macrophage autophagy. We also found the phosphorylated form of mammalian target of Rapamycin (mTOR) was activated and the expression of p-mTOR protein increased induce by TCE. In vitro, we found TNFR1 and CD11c were increased in RAW264.7 cell line with TNF-α. And then we use Zafirlukast (Zaf), an TNFR1 antagonist, CD11c and TNFR1 reduced significantly, we also found p-mTOR expression increased after TNF-α treatment, but decreased in TNF-α + Zaf group. Further, we used Rapamycin (RAP), a mTOR-specific inhibitor, to establish a TCE-sensitized mice model and found the expression levels of p62 and p-mTOR proteins increased and LC3B decreased in the TCE positive group, while RAP treatment reversed the trends of all of these proteins. Rapamycin prevented the TNF-α-induced p-mTOR increase and dramatically downregulated IL-1β expression in the RAW264.7 cell line with TNF-α treatment. The results uncover a novel role for TNF-α/TNFR1, which promotes M1 polarization of macrophage and suppresses macrophage autophagy via the mTOR pathway.

GRK6 palmitoylation increasing its membrance translocation promotes LPS-induced inflammation by PI3K/ AKT pathway in kuppfer cells

BACKGROUND

G protein-coupled receptor kinases 6 (GRK6) is one kinase of GPCRs, previous studies have shown that GRK6 is involved in the regulation of inflammatory processes. However, the role of GRK6 in inflammation is not well understood and what is the effect of its palmitoylation modification on inflammatory response in macrophage are still largely unknown.

METHODS

LPS stimulated Kupffer cells to simulate inflammatory injury model. SiGRK6 and GRK6 lentiviral plasmids were used to alter cellular GRK6 levels. Subcellular localization of GRK6 was detected using Membrane and Cytoplasmic Protein Extraction Kit and immunofluorescence. Palmitoylated Protein Assay Kit (Red) and modified Acyl-RAC method were used to detect palmitoylation levels.

RESULTS

GRK6 mRNA and protein expression decreased in LPS-induced inflammatory response in Kupffer cells (P < 0.05). Overexpression of GRK6 promoted inflammatory response, while silencing GRK6 reduced inflammatory response (P < 0.05). In terms of molecular mechanisms, LPS induced increased palmitoylation of GRK6 and promoted the translocation of GRK6 to cell membranes (P < 0.05). Subsequently, GRK6 functioned through the PI3K/ AKT signaling pathway (P < 0.05). Inhibition of palmitoylation level of GRK6 can inhibit its membrane translocation and reduce inflammatory response (P < 0.05).

CONCLUSION

Inhibition of palmitoylation level of GRK6 might relieve LPS-induced inflammation in Kupffer cells by blocking GRK6 membrane translocation and subsequent inflammatory signaling pathway, providing a theoretical basis for targeting GRK6 to regulate inflammation.

The effect of miR-155-5p on M1 polarization of Kupffer cells and immune response during liver transplantation through regulating the expression of KDM5D

BACKGROUND

To explore the effect and its specific mechanism of miR-155-5p on M1 polarization of Kupffer cells (KCs) and immune response in liver transplantation (LT) through KDM5D.

METHODS

Primary KCs were isolated from Wistar rats and identified by cell culture, ink-swallowing test and flow cytometry. The cells identified as KCs were induced into LT acute rejection (AR) model cells by LPS/IFN-γ, flow cytometry was used for cell sorting and apoptosis detection. Enzyme-linked immunosorbent assay (ELISA) kit was used to detect the levels of inflammatory factors, macrophages and liver function markers. RT-qPCR detected the expression of miR-155-5p and KDM5D mRNA. The protein expression of KDM5D was detected by Western blot. Dual luciferase reporter gene experiment verified the targeting relationship between miR-155-5p and KDM5D.

RESULTS

The separated KCs adhered after being cultured for 24 h, had pseudopodia and phagocytosis, and the proportion of F4/80 positive cells was more than 90%. The expression of miR-155-5p was increased in LPS/IFN-γ-induced KCs. And knockdown of miR-155-5p inhibited H3K4me3 and H3K27me3 of TNF-α promoter, M1 polarization of KCs and the immune response of AR model cells by upregulating KDM5D. In animal experiments, knockdown of miR-155-5p was found to inhibit liver damage and immune response in rats with allogeneic orthotopic LT.

CONCLUSION

These results confirmed that miR-155-5p inhibited M1 polarization of KCs induced by LPS/IFN-γ, thereby alleviating AR and liver function impairment after LT by upregulating KDM5D.

Tannic acid through ROS/TNF-α/TNFR 1 antagonizes atrazine induced apoptosis, programmed necrosis and immune dysfunction of grass carp hepatocytes

Atrazine (ATR) is a commonly used triazine herbicide, which will remain in the water source, soil and biological muscle tissue for a long time, threatening the survival of related organisms and future generations. Tannic acid (TAN), a glucosyl compound found in gallnuts, has previously been shown to antagonize heavy metal toxicity, antioxidant activity, and inflammation. However, it is unclear whether TAN can antagonize ATR-induced Grass carp hepatocytes (L8824 cells) cytotoxicity. Therefore, we treated L8824 cells with 3 μg mL^-1 ATR for 24 h to establish a toxic group model. The experimental data of flow cytometry and AO/EB staining together showed that the ratio of apoptosis and necrosis in L8824 cells after ATR exposure was significantly higher than that in the control group. Furthermore, RT-qPCR showed that inflammatory factors (TNF-α, IL-1β, IL-6, INF-γ) were up-regulated and antimicrobial peptides (hepcidin, β-defensin and LEAP2) were induced down-regulated in L8824 cells, leading to immune dysfunction. The measurement results of oxidative stress-related indicators showed that the levels of ROS and MDA increased after ATR exposure, the overall anti-oxidative system was down-regulated. Western blotting confirmed that TNF-α/TNFR 1-related genes were also up-regulated. This indicates that ATR stimulates oxidative stress in L8824 cells, which in turn promotes the binding of TNF-α to TNFR 1. In addition, TRADD, FADD, Caspase-3, P53, RIP1, RIP3 and MLKL were found to be significantly up-regulated by Western blotting and RT-qPCR. Conditioned after ATR exposure compared to controls. It indicates that ATR activates apoptosis and necrosis of TNF-α/TNFR 1 pathway by inducing oxidative stress in L8824 cells. Furthermore, the use of TAN (5 μM) significantly alleviated the toxic effects of ATR on L8824 cells mentioned above. In conclusion, TAN restrains ATR-induced apoptosis, programmed necrosis and immune dysfunction through the ROS/TNF-α/TNFR 1 pathway.

TNF-α/TNFR1 regulates the polarization of Kupffer cells to mediate trichloroethylene-induced liver injury

We have previously shown trichloroethylene (TCE) induced immune liver injury, and TNF-α/TNFR1 pathway as a probably mechanism underlying the immune damage, but the pathogenic mechanism is still unclear. The study aims to investigate whether TNF-α and its receptors regulate Kupffer cell polarization and downstream inflammation signaling pathways during TCE sensitization, to clarify the mechanism of TCE-mediated immune liver injury. 6-8 weeks old SPF BALB/c female mice were used to establish a TCE sensitization model. We found that in the TCE sensitization positive group, liver injury was aggravated, Kupffer cells activated and polarized to M1 type. The expression of M1 Kupffer cell marker proteins CD11c and CD16/32 increased in the TCE positive group, so did TNF-α and TNFR1 in liver. The expression of P-IKK protein, PP65 protein and P-STAT3 protein increased in the TCE sensitization positive group, and the downstream inflammatory factors IL-1β and IL-6 also increased in the TCE sensitization positive group. After using the TNFR1 inhibitor R7050, we found that M1 Kupffer cell polarization, TNF-α expression, signal pathway expression and inflammatory factors IL-1β and IL-6 expression declined, and the liver damage relieved. Briefly, the use of R7050 to inhibit TNF-α/TNFR1 changing the polarization of liver M1 Kupffer cell, thereby inhibiting the activation of related downstream signaling pathways and reducing the secretion of inflammatory factors. TNF-α/TNFR1 regulates the polarization of M1 Kupffer cells inflammatory play an important role in liver immune damage.

DHA/AA alleviates LPS-induced Kupffer cells pyroptosis via GPR120 interaction with NLRP3 to inhibit inflammasome complexes assembly

Pyroptosis is a novel type of programmed cell death associated with the pathogenesis of many inflammatory diseases. Docosahexaenoic acid (DHA) and Arachidonic acid (AA) is widely involved in inflammatory pathological processes. However, the effect and mechanism of DHA and AA on pyroptosis in Kupffer cells are poorly understood. The present study demonstrated that DHA and AA ameliorated lipopolysaccharide (LPS)-induced Kupffer cells pyroptosis by reversing the increased expression of NLRP3 inflammasome complex, GSDMD, IL-1β, IL-18, and PI-stained positive rate. Next, the study revealed that GPR120 silencing eliminated the anti-pyroptosis of DHA and AA in LPS-induced Kupffer cells, suggesting that DHA and AA exerted their effect through GPR120 signaling. Importantly, GPR120 endocytose and binds to NLRP3 under LPS stimulation. Furthermore, co-immunoprecipitation showed that DHA and AA promoted the interaction between GPR120 and NLRP3 in LPS-exposed Kupffer cells, thus inhibiting the self-assembly of NLRP3 inflammasome complex. Finally, the study verified that DHA and AA alleviated hepatic injury through inhibiting Kupffer cells pyroptosis in vivo. The findings indicated that DHA and AA alleviated LPS-induced Kupffer cells pyroptosis via GPR120 interaction with NLRP3, it might become a potential therapeutic approach hepatic injury.