iNOS Induction by Polysaccharide Isolated from Astragalus membranaceus / 체질인류학회지

ABSTRACT

Astragalus membranaceus is used as a natural herbal medicine in East Asia for preventing carcinogenesis and reducing side effects induced by chemotherapy in cancer patients. Although the mechanism of anti-tumor activity is not known, the polysaccharides may potentiate the host defense mechanism through the activation of immune system. The objective of this study is to investigate the mechanism by which APS activates macrophages. To analyze macrophage activation and iNOS gene expression, we performed nitrite generation assay, immunohistochemistry, and RT-PCR. In the present study we show that a polysaccharide isolated from the Astragalus membranaceus (Astragalus Polysaccharide, APS) significantly induces nitric oxide (NO). Immunohistochemical staining of inducible NO synthase (iNOS) showed that the increase of NO was due to the induction of iNOS production. To further study the mechanism responsible for the induction of iNOS, we investigated the effect of APS on the iNOS mRNA expression. RT-PCR analysis showed that APS produced significant induction of iNOS gene expression. In conclusion, we demonstrate that a polysaccharide isolated from Astragalus membranaceus stimulates macrophages to generate NO through the activation of iNOS gene expression.