Inflammatory stress potentiates emodin-induced liver injury in rats

Abstract

Herbal medicines containing emodin, widely used for the treatment of hepatitis in clinic, have been reported with hepatotoxicity in individuals. A modest inflammatory stress potentiating liver injury has been linked to the idiosyncratic drug-induced liver injury (IDILI). In this study, we investigated the hypothesis that lipopolysaccharide (LPS) interacts with emodin could synergize to cause liver injury in rats. Emodin (ranging from 20, 40, to 80 mg/kg), which is in the range of liver protection, was administered to rats, before LPS (2.8 mg/kg) or saline vehicle treatment. The biochemical tests showed that non-toxic dosage of LPS coupled with emodin caused significant increases of plasma ALT and AST activities as compared to emodin alone treated groups (P < 0.05). In addition, with LPS or emodin alone could not induce any changes in ALT and AST activity, as compared with the control group (0.5% CMC-Na treatment). Meanwhile, the plasma proinflammatory cytokines, TNF-α, IL-1β, and IL-6 increased significantly in the emodin/LPS groups compared to either emodin groups or the LPS (P < 0.05). Histological analysis showed that liver damage was only found in emodin/LPS cotreatmented rat livers samples. These results indicate that non-toxic dosage of LPS potentiates the hepatotoxicity of emodin. This discovery raises the possibility that emodin and herbal medicines containing it may induce liver injury in the inflammatory stress even in their therapeutic dosages.

Keywords: emodin; hepatotoxicity; idiosyncratic drug-induced liver injury; lipopolysaccharide; proinflammatory mediators; therapeutic dosages.

FIGURE 1

The Plasma biochemical indicators in the absence and presence of LPS with emodin. Rats were treated with various doses of emodin (20, 40, or 80 mg/kg, i.g.) or its vehicle (0.5% CMC-Na). After 3 h, LPS or emodin/LPS groups animals received LPS (2.8 mg/kg, i.v.) or its vehicle (0.5% CMC-Na). (A) and (B) Blood samples were taken at 7 h after the administration of LPS, and plasma ALT and AST levels were measured. (C) Plasma TBA content were measured from the same conditions. The results were presented as mean ± SD from of 10 rats. Significance of differences was from the value of emodin/LPS rats (*P < 0.05, **P < 0.01 vs emodin groups). For groups, “+” and “–” represent “presence” and “absence,” respectively.

FIGURE 2

Chemokine and cytokine expression in rats cotreated with LPS and emodin. Rats were treated with emodin (20, 40, or 80 mg/kg, i.g.) or its vehicle (0.5% CMC-Na) and LPS (2.8 mg/kg, i.v.) or its vehicle (0.5% CMC-Na) as described in Figure 1. (A–C) Showed Plasma proinflammatory cytokine levels determined by ELISA for IL-1β, IL-6, and TNF-α respectively. The data were presented as mean ± SD of 10 rats, and statistically significant difference (*P < 0.05, vs emodin groups; ΔP < 0.05, vs LPS group; #P < 0.05 and ##P < 0.01, vs control).

FIGURE 3

Histopathological damage in rats liver given LPS, emodin only and cotreated with LPS/emodin. (A) Liver sections from rats were treated with vehicle (0.5% CMC-Na); (B) with LPS (2.8 mg/kg); (C) emodin (20 mg/kg); (D) emodin (40 mg/kg); (E) emodin (80 mg/kg); (F) LPS/emodin (20 mg/kg); (G) LPS/emodin (40 mg/kg); (H) LPS/emodin (80 mg/kg). Liver samples were collected at 7 h after LPS tail intravenously injection (HE stained, × 200 magnification) and HE staining was performed to investigate the histological changes in all experimental groups.