Protective effect of Acanthopanax senticosus extract against endotoxic shock in mice

Abstract

Aim of the study

In this study, we evaluated protective effect of Acanthopanax senticosus extract (ASE) and a possible signaling pathway involved during endotoxic shock induced by intraperitoneal injection lipopolysaccharide (LPS) and D-galactosamine (D-GalN) in BALB/c mice.

Materials and methods

Mice were intraperitoneal administrated with ASE (100, 200 or 400 mg/kg) prior to injection of 50 μg/kg LPS and 1 g/kg D-GalN. The levels of tumor necrosis-alpha (TNF-α) and interleukin-10 (IL-10) in serum and liver.

Nitric oxide (NO) production in serum and inducible nitric oxide synthase (iNOS) protein level were investigated. Nuclear factor-kappa B (NF-κB) activation in liver was determined. Furthermore, we evaluated the effect of ASE pretreatment on infiltration of inflammatory cells into the heart, liver and lung of mice.

Results

Treatment of mice with ASE prior to LPS/D-GalN injection significantly improved the survival rate. ASE pretreatment inhibited the elevation of TNF-α in serum and liver. ASE also decreased iNOS level in liver and the overproduction of nitric oxide (NO) in serum. In addition, IL-10 levels in serum and liver were markedly enhanced. ASE pretreatment inhibited NF-κB activation in liver of mice. Moreover, infiltration of inflammatory cells into the heart, liver and lung of mice was also attenuated by ASE pretreatment.

Conclusions

These results suggested that ASE protected mice against LPS/D-GalN-induced endotoxic shock involving inhibition of NF-κB activation, which caused down-regulation of TNF-α and involved up-regulation of IL-10. Acanthopanax senticosus may thus prove beneficial in the prevention of endotoxic shock.

Introduction

Acanthopanax senticosus (Rupr. & Maxim.) Harms. (Syn. Eleutherococcus senticosus (Rupr. and Maxim.) Maxim.), also termed Siberian ginseng, belongs to the family Araliaceae and is a 1.5–2.6 m high shrub found in China, Korea, Japan and Russia. In China, Japan and Russia (Brekhman and Dardymov, 1969, Frasnsworth et al., 1985), the extract of the root bark of Acanthopanax senticosus has been used for the control of blood pressure, for mental and emotional problems, as analeptic or agents to cope with stress. In addition, the roots and stems of Acanthopanax senticosus have been reported to have pharmacological action in the treatment of various diseases, such as chronic renal failure, rheumatics, diabetes mellitus, chronic bronchitis, hypertension, gastric ulcers and ischemic heart diseases (Nishibe et al., 1990, Fujikawa et al., 1996, Davydov and Krikorian, 2000). In Korea, the stems have also been used clinically for the treatment of allergy (Yi et al., 2002). Our previous studies have shown that Acanthopanax senticosus extract (ASE) inhibits the production of nitric oxide (NO) and reactive oxygen species in murine macrophages in vitro and in vivo (Lin et al., 2007a, Lin et al., 2007b), which led us design more in vivo studies to verify its potent anti-inflammatory effects.

Sepsis is generally considered a systemic inflammatory disorder. It can be defined as a progressive failure of the circulation, characterized clinically by systemic hypotension, hyporeactiveness to vasoconstrictors and subsequent organ perfusion and functional changes followed by multiple organ failure (Bone et al., 1997). Septic shock is a serious clinical problem with high mortality. Most cases of human septic shock are caused by Gram-negative bacterial endotoxins (Bone et al., 1997, Friedman et al., 1998, Wheeler and Bernard, 1999, Angus et al., 2001). Many pathophysiological cascades of Gram-negative shock are triggered by the outer membrane component of bacterial cell walls, i.e., lipopolysaccharide (LPS). In experimental animals, LPS challenge leads to pathophysiological changes similar to the human septic shock syndrome. Sensitization with d-galactosamine (d-GalN) greatly increases the sensitivity of animals to LPS and augments the lethal activity of LPS. The lethal effect of LPS in d-GalN-sensitized mice is usually considered an experimental model for clinical endotoxic shock or septic shock (Galanos et al., 1979).

Most effects of LPS act via endogenous mediators, such as cytokines (Takemura and Werb, 1984). Among these cytokines, tumor necrosis factor-alpha (TNF-α) seems to be particularly important for endotoxic effects because it has been shown to induce most characteristics of endotoxic shock (Jansen et al., 1996). Interleukin-10 (IL-10) is known as an anti-inflammatory cytokine to decrease circulating TNF-α and offer protection against endotoxic shock (Fiorentino et al., 1991, Howard et al., 1993). Induction of IL-10 can therefore be considered as being part of endogenous host-protective mediation during endotoxic shock.

The excessive generation of NO via induction of inducible nitric oxide synthase (iNOS) has been suggested to lead to LPS-induced hypotension, vascular hyporeactivity and death, indicating that the overproduction of NO plays an important role in septic shock (Szabo et al., 1995, Yang et al., 2002). Inducible NOS is the key enzyme involved in NO production by macrophages stimulated by bacterial endotoxin of LPS and proinflammatory cytokines such as interferon-gamma (interferon-γ) and TNF-α (Moncada et al., 1992, Nathan and Xie, 1994). Activity of the iNOS is regulated at different levels, from transcriptional, posttranscriptional, translational, through to posttranslational steps (Nathan and Xie, 1994, Rao, 2000). Expression of the iNOS gene in macrophages is regulated mainly at the transcriptional level, particularly by nuclear factor-kappa B (NF-κB) (Xie et al., 1994).

In this study, we studied whether ASE could protect mice against LPS/d-GalN induced endotoxic shock and investigated a possible signaling pathway involved.