Sinomenine reduces iNOS expression via inhibiting the T-bet IFN-γ pathway in experimental autoimmune encephalomyelitis in rats

Bingjie Gu,Yanying Zeng,Cheng Yin,Huijiuan Wang,Xiaofan Yang,Song Wang,Xiaohui Ji

doi:10.7555/jbr.26.20110114

Abstract

Sinomenine is a bioactive alkaloid isolated from the Chinese medicinal plant Sinomenium acutum. It is widely used as an immunosuppressive drug for treating rheumatic and arthritic diseases. In our previous studies, we found that sinomenine reduced cellular infiltration within the spinal cord and alleviated experimental autoimmune encephalomyelitis (EAE) in rats. In this study, we further investigated the mechanisms of sinomenine treatment in EAE rats. In EAE rats, treatment with sinomenine exerted an anti-inducible NO synthase (anti-iNOS) effect, which is related to the reductions of Th1 cytokine interferon-γ (IFN-γ) and its transcription factor, T-bet, in spinal cords. Moreover, sinomenine treatment of splenocytes stimulated with anti-CD3 antibody and recombinant rat interleukin 12 reduced the expression of T-bet and IFN-γ in vitro and also reduced the capability of supernatants of splenocyte culture to induce iNOS expression by primary astrocytes. However, sinomenine had no direct inhibitory effect on iNOS produced by astrocytes cultured with IFN-γ and tumor necrosis factor αin vitro. In conclusion, the anti-iNOS effect of sinomenine on EAE is mediated via the suppression of T-bet/IFN-γ pathway.

Highlights

Multiple sclerosis (MS) is a chronic, neurodegenerative disease that is associated with central nervous system (CNS) demyelination[1]
We examined the expression of inducible NO synthase (iNOS) in spinal cord sections from control, EAE, and sinomenine-treated EAE rats
Consistent with mRNA levels, iNOS protein levels were significantly increased in astrocytes stimulated with IFN-γ and tumor necrosis factor-α (TNF-α); the GAPDH CON EAE SIN50 SIN100 SIN200

Summary

INTRODUCTION

Multiple sclerosis (MS) is a chronic, neurodegenerative disease that is associated with central nervous system (CNS) demyelination[1]. The specific mechanisms that cause damage to the CNS involve the secretion of cytokines by T cells, and the activation of glial cells to secrete both proinflammatory cytokines and inflammatory mediators such as tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6 and nitric oxide (NO)[4,5]. Overall, this process eventually leads to the destruction of the myelin sheath, axonal loss and damage. The anti-iNOS effect of sinomenine is correlated with blocking of IFN-γ, an important inducer of iNOS, which resulted from the inhibition of the transcription factor T-bet rather than direct suppression of iNOS production by astrocytes

MATERIALS AND METHODS

RESULTS

DISCUSSION