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Acute liver failure (ALF) is a complex syndrome characterized by overactivation of innate immunity, and the recruitment and differentiation of immune cells at inflammatory sites. The present study aimed to explore the role of microRNA (miRNA/miR)-21 and its potential mechanisms underlying inflammatory responses in ALF. Baseline serum miR-21 was analyzed in patients with ALF and healthy controls. In addition, miR-21 antagomir was injected via the tail vein into C57BL/6 mice, and lipopolysaccharide/D-galactosamine (LPS/GalN) was injected into mice after 48 h. The expression levels of miR-21, Krüppel-like-factor-6 (KLF6), autophagy-related proteins and interleukin (IL)-23, and hepatic pathology were then assessed in the liver tissue. Furthermore, THP-1-derived macrophages were transfected with a miRNA negative control, miR-21 inhibitor, miR-21 mimics or KLF6 overexpression plasmid, followed by treatment with or without rapamycin, and the expression levels of miR-21, KLF6, autophagy-related proteins and IL-23 were evaluated. The results revealed that baseline serum miR-21 levels were significantly upregulated in patients with ALF. In addition, LPS/GalN-induced ALF was attenuated in the antagomir-21 mouse group. KLF6 was identified as a target of miR-21-5p with one putative seed match site identified by TargetScan. A subsequent luciferase activity assay demonstrated a direct interaction between miR-21-5p and the 3′-UTR of KLF6 mRNA. Further experiments suggested that miR-21 promoted the expression of IL-23 via inhibiting KLF6, which regulated autophagy. In conclusion, in the present study, baseline serum miR-21 levels were highly upregulated in patients with ALF, antagomir-21 attenuated LPS/GalN-induced ALF in a mouse model, and miR-21 could promote the expression of IL-23 via inhibiting KLF6. [ABSTRACT FROM AUTHOR]

Background/Aims: Serum procalcitonin (PCT) is elevated in acute liver failure (ALF), but the expression of PCT in the liver has not been elucidated. We aimed to clarify the regulation of hepatic PCT expression and the cell sources in ALF. Methods: Human monocytic leukemia line U937 cells were treated with 12-O-tetradecanoylphorbol-l3-acetate (PMA) (100 ng/ mL) for 24 h to induce activated macrophages. In the presence of lipopolysaccharide (LPS, 1 μg/mL), activated macrophages and human hepatocyte line L02 cells were incubated with LPS or co-cultured for 0, 2, 6, and 24 h. In an in vivo experiment, male C57BL/6 mice were challenged with intraperitoneal LPS/D-galactosamine (LPS/D-GalN). Serum liver enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured using an automatic chemical analyzer. Inflammatory mediators were measured by real-time PCR and liver histology was examined by hematoxylin-eosin (HE) staining and immunohistochemistry (IHC). Results: LPS induced the upregulation of PCT mRNA in U937-activated macrophages but not in L02 cells. When co-cultured with L02 cells, the expression of PCT mRNA of activated macrophages was upregulated compared to controls; however, the activated macrophages did not induce the expression of PCT mRNA in L02 cells in the presence of LPS. Moreover, serum liver enzymes (ALT, AST), inflammation, necrosis, and hepatic expression of PCT were significantly elevated in the LPS/D-GalN-challenged ALF mouse model. IHC revealed that PCT expression was co-localized with hepatic macrophages. Conclusions: Hepatic PCT expression is upregulated in ALF. Hepatic macrophages but not hepatocytes are the cell source of hepatic PCT expression. [ABSTRACT FROM AUTHOR]