Therapeutic Role of Inducible Nitric Oxide Synthase Expressing Myeloid-Derived Suppressor Cells in Acetaminophen-Induced Murine Liver Failure

Fecal microbiota transplantation modulates myeloid-derived suppressor cells and attenuates renal fibrosis in a murine model

BACKGROUND

Renal fibrosis is a hallmark of progressive chronic kidney disease (CKD), with emerging evidence linking gut microbiota dysbiosis to disease progression. Myeloid-derived suppressor cells (MDSCs) have demonstrated renoprotective effects, yet the impact of fecal microbiota transplantation (FMT) on MDSC-mediated modulation of renal fibrosis remains unclear.

METHODS

C57BL/6J mice underwent unilateral ureteral obstruction (UUO) to induce renal fibrosis, followed by FMT administration via gavage. Flow cytometry was used to quantify granulocytic (G-MDSCs) and monocytic (M-MDSCs) MDSC populations in peripheral blood, kidney, and spleen. To elucidate the role of MDSCs in FMT-mediated effects, MDSCs were depleted or adoptively transferred in vivo. Renal fibrosis severity and inflammatory cytokine expression were subsequently analyzed.

RESULTS

FMT altered MDSC distribution, increasing M-MDSC accumulation in the blood and kidney. This was associated with downregulation of proinflammatory cytokines and attenuation of renal fibrosis. Adoptive MDSC transfer similarly produced anti-inflammatory and antifibrotic effects, reinforcing their therapeutic role in FMT-mediated renal protection.

CONCLUSIONS

FMT enhances M-MDSC-mediated immunomodulation, reducing inflammation and renal fibrosis in UUO-induced CKD. These findings suggest a potential therapeutic strategy targeting the gut-kidney axis in CKD management.

The Roles of Myeloid-Derived Suppressor Cells in Liver Disease

Liver disease-related mortality is a major cause of death worldwide. Hepatic innate and adaptive immune cells play diverse roles in liver homeostasis and disease. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells. MDSCs can be broadly divided into monocytic MDSCs and polymorphonuclear or granulocytic MDSCs, and they functionally interact with both liver parenchymal and nonparenchymal cells, such as hepatocytes and regulatory T cells, to impact liver disease progression. The infiltration and activation of MDSCs in liver disease can be regulated by inflammatory chemokines and cytokines, tumor-associated fibroblasts, epigenetic regulation factors, and gut microbiota during liver injury and cancer. Given the pivotal roles of MDSCs in advanced liver diseases, they can be targeted to treat primary and metastatic liver cancer, liver generation, alcoholic and nonalcoholic liver disease, and autoimmune hepatitis. Currently, several treatments such as the antioxidant and anti-inflammatory agent berberine are under preclinical and clinical investigation to evaluate their therapeutic efficacy on liver disease and their effect on MDSC infiltration and function. Phenotypic alteration of MDSCs in different liver diseases that are in a model-dependent manner and lack special markers for distinct MDSCs are challenges for targeting MDSCs to treat liver disease. Multi-omics study is an option to uncover the features of disease-specific MDSCs and potential gene or protein targets for liver disease treatment. In summary, MDSCs play important roles in the pathogenesis and progression of liver disease by regulating both intrahepatic innate and adaptive immune responses.

Bioinformatics approach and experimental validation reveal the hepatoprotective effect of pachyman against acetaminophen-associated liver injury

Pachyman, known as Poria cocos polysaccharides, refers to the bioactive compounds isolated from Poria cocos. Pachyman is thought to exert cytoprotective action. However, the detailed mechanisms of pachyman action for hepatoprotection remain unknown. In this study, we aimed to assess the therapeutic actions, molecular mechanisms, and key target proteins of pachyman in the treatment of liver injury through network pharmacology and molecular docking assays. Furthermore, these bioinformatic findings were validated by an acetaminophen (APAP)-induced liver injury in vivo. Primarily using bioinformatic analysis, we screened and characterized 12 genes that act as potential therapeutic targets of pachyman against APAP-induced liver injury, in which all core targets were obtained. By using enrichment analysis, these core target genes of pachyman were characterized to reveal the pharmacological functions and molecular mechanisms of anti-liver injury induced by APAP. A molecular docking simulation was further performed to certain anti-liver injury target proteins of pachyman, including cytochrome P450 3A4 enzyme (CYP3A4) and inducible nitric oxide synthase (NOS2). In animal experiments, pachyman exerted potent hepatoprotective activities in prenatal APAP-exposed offspring livers, characterized by activated hepatocellular CYP3A4 and NOS2 expressions. These current findings have thus indicated that pachyman exerts hepatoprotective effects and may be the promising nutraceuticals for the treatment of APAP-induced liver injury.

Effect of Proton Therapy on Tumor Cell Killing and Immune Microenvironment for Hepatocellular Carcinoma

Radiotherapy with proton therapy (PT) has dosimetric advantages over photon therapy, which helps to enlarge the therapeutic window of radiotherapy for hepatocellular carcinoma (HCC). We evaluated the response of HCC to PT and examined the underlying mechanisms. The human liver cancer cell lines HepG2 and HuH7 and the murine liver cancer cell line Hepa1-6 were selected for cell and animal experiments to examine the response induced by PT irradiation. Biological changes and the immunological response following PT irradiation were examined. In vitro experiments showed no significant difference in cell survival following PT compared with photon radiotherapy. In a murine tumor model, the tumors were obviously smaller in size 12 days after PT irradiation. The underlying changes included increased DNA damage, upregulated IL-6 levels, and a regulated immune tumor microenvironment. Protein analysis in vitro and in vivo showed that PT increased the level of programmed cell death ligand 1 (PD-L1) expressed in tumor cells and recruited myeloid-derived suppressor cells (MDSCs). The increase in PD-L1 was positively correlated with the irradiation dose. In Hepa1-6 syngeneic mouse models, the combination of PT with anti-PD-L1 increased tumor growth delay compared with PT alone, which was associated with increased tumor-infiltrating T cells and attenuated MDSC recruitment in the microenvironment. Furthermore, when PT was applied to the primary HCC tumor, anti-PD-L1 antibody-treated mice showed smaller synchronous unirradiated tumors. In conclusion, the response of HCC to PT was determined by tumor cell killing and the immunological response in the tumor microenvironment. The combination with the anti-PD-L1 antibody to enhance antitumor immunity was responsible for the therapeutic synergism for HCC treated with PT. Based on our results, we suggest that PT combined with anti-PD-L1 may be a promising therapeutic policy for HCC.

The Function and Therapeutic Implications of TNF Signaling in MDSCs

Myeloid-derived suppressor cells (MDSCs) are a group of immature and heterogeneous myeloid cells with immunosuppressive functions. MDSCs play important roles in the pathogenesis of cancer, chronic inflammatory diseases, and many autoimmune disorders. The accumulation and activation of MDSCs can be regulated by tumor necrosis factor α (TNF-α). In this review, we summarize the roles played by TNF-α in the recruitment, immunosuppressive functions, and chemotaxis of MDSCs, and discuss the potential therapeutic effects of TNF-α upon these cells in tumor growth and some inflammatory disorders.

Pharmacological modulation of myeloid-derived suppressor cells to dampen inflammation

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous cell population with potent suppressive and regulative properties. MDSCs’ strong immunosuppressive potential creates new possibilities to treat chronic inflammation and autoimmune diseases or induce tolerance towards transplantation. Here, we summarize and critically discuss different pharmacological approaches which modulate the generation, activation, and recruitment of MDSCs in vitro and in vivo, and their potential role in future immunosuppressive therapy.

MCC950 Ameliorates Acute Liver Injury Through Modulating Macrophage Polarization and Myeloid-Derived Suppressor Cells Function

Acute liver injury (ALI) raises high mortality rates due to a rapid pathological process. MCC950, a highly selective nod-like receptor family pyrin domain containing 3 (NLRP3) inhibitor, has already been reported to show strong hepatoprotective effects in many different liver diseases. In this study, we unveiled the role of MCC950 in carbon tetrachloride (CCl₄)-induced ALI and its underlying molecular mechanisms on days 1, 2, and 3. MCC950 could significantly inhibit liver injury, evidenced by decreased serum alamine aminotransferase (ALT) and aspartate aminotransferase (AST) levels on days 1 and 2, increased Albumin (ALB) level on day 3, and decreased histological score during the whole period. Moreover, lower M1 macrophage related to pro-inflammatory genes expression was observed in MCC950-treated ALI mice on day 1, while MCC950 pretreatment also polarized macrophage to M2 phenotype indicating anti-inflammatory response on days 2 and 3. Additionally, MDSC was significantly increased in blood, liver, and spleen in ALI mice at different time courses. Specifically, upregulated myeloid-derived suppressor cell (MDSC) proportions were found in blood and spleen on days 1 and 2, but showed decreased trend on day 3. However, liver MDSC numbers were increased on days 2 and 3, but no significance on day 1. In conclusion, MCC950 pretreatment alleviates CCl₄-induced ALI through enhanced M2 macrophage and MDSC function at different time points of ALI. Further understanding of MCC950 in ALI may be a new potential therapeutic strategy.

The complex roles of neutrophils in APAP-induced liver injury

Acetaminophen (APAP) is a widely applied drug for the alleviation of pain and fever, which is also a dose‐depedent toxin. APAP‐induced acute liver injury has become one of the primary causes of liver failure which is an increasingly serious threat to human health. Neutrophils are the major immune cells in human serving as the first barrier against the invasion of pathogen. It has been reported that neutrophils patriciate in the occurrence and development of APAP‐induced liver injury. However, evolving evidences suggest that neutrophils also contribute to tissue repair and actively orchestrate resolution of inflammation. Here, we addressed the complex roles in APAP‐induced liver injury on the basis of brief introduction of neutrophil's activation, recruitment and migration.