Thymosin β4 Regulates Tissue Inflammatory Response in Mouse Nonalcoholic Fatty Liver Disease by Promoting Macrophage M2-Type Polarization.
This study investigated whether Thymosin β4 (Tβ4), a bioactive polypeptide, could regulate liver inflammation in nonalcoholic fatty liver disease (NAFLD) by influencing macrophage polarization. Researchers used a mouse model of NAFLD induced by a methionine and choline-deficient (MCD) diet in C57 mice, with liver Tβ4 knocked down via tail-vein-injected siRNA. Macrophage involvement was assessed using clodronate liposome depletion. Additionally, in vitro experiments co-cultured THP-1 macrophage cells with oleic acid-treated LO2 hepatocytes at varying Tβ4 concentrations. The study found that Tβ4 treatment was associated with reduced liver inflammation and steatosis in mice, while Tβ4 knockdown worsened steatosis. Tβ4 appeared to shift macrophages toward an M2 (anti-inflammatory) phenotype, reduce M1 marker expression, decrease hepatocyte apoptosis, downregulate STAT1 phosphorylation, and increase SOCS1/3 expression. A publicly available dataset was also used to assess Tβ4 expression in hepatocellular carcinoma-adjacent fatty tissue. Limitations include reliance primarily on animal and in vitro models, a relatively small experimental scope, and no direct human clinical data, leaving the translational relevance of these findings uncertain.
Why this grade: The study's primary findings are derived from a mouse NAFLD model and cell-culture experiments, with no human clinical trial data on Tβ4 treatment outcomes.
Introduction Nonalcoholic fatty liver disease (NAFLD) is characterized by hepatic steatosis, insulin resistance, and systemic pro-inflammatory response. Thymosin β4 (Tβ4) is a bioactive polypeptide that inhibits extracellular matrix (ECM) deposition and protects the liver. It can achieve immune homeostasis by regulating the polarization of liver macrophages and is a potential treatment for NAFLD. Methods A dataset was used to evaluate the expression of Tβ4 in fatty and non-fatty adjacent tissues of primary hepatocellular carcinoma. NAFLD was induced in C57 mice with methionine and choline-deficient diet (MCD), siRNATβ4 was injected into the tail vein to reduce liver Tβ4, and the therapeutic effect of Tβ4 was observed by phagocytosis of macrophages with clodronate liposomes. Hematoxylin and Eosin staining (HE) staining was used to observe the inflammation of mice in each group, and oil red O staining was used to determine the lipid accumulation. Macrophage polarization was detected by immunofluorescence assay. In the extrachromosomal experiment of oil red O, human myeloid leukemia mononuclear (THP-1) cells was co-cultured with human hepatic (LO2) constructed with oleic acid to detect the changes of aspartate transaminase (AST) and alanine transaminase (ALT) in supernatant and the apoptosis of LO2 under the intervention of different concentrations of Tβ4. Results Tβ4 allowed the mice to recover from NAFLD and reduce liver inflammation more effectively. Liver steatosis was more severe in sirnat4 mice. Macrophages are involved in Tβ4 treatment of NAFLD. The expression level of M1 phenotype in macrophages treated with Tβ4 decreased, and the apoptosis of hepatocytes decreased. At the same time, Tβ4 down-regulates signal transduction and activator of transcription1 (STAT1) phosphorylation and increases suppressor of cytokine signaling1/3 (SOCS1/3) expression in hepatocytes. Discussion This study revealed the molecular mechanism of the effective effect of Tβ4 on the polarization of liver macrophages, suggesting that Tβ4 may be a potential therapeutic measure for NAFLD.
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