Pro-inflammatory cytokine gene expression and nitric oxide regulation of aqueous extracted Astragali radix in RAW 264.7 macrophage cells

Abstract

Astragali radix, which has tonifying and circulatory effect as well as immune response, is one of the oldest and most frequently used crude drug for oriental medicine in many Asian countries. The present study was conducted to evaluate the effect of aqueous extract of Astragali radix (ARE) on the functions of murine macrophage cell line, RAW 264.7 macrophage cells. In the cell proliferation assay, methotrexate (MTX), an agent of immune suppression, decreased the cell proliferation of RAW 264.7 macrophage cells (IC 50: 100 μg/ml), but the suppression of cell proliferation was significantly protected by ARE treatment in RAW 264.7 macrophage cells. The expressions of cytokine gene by ARE were investigated using reverse transcription polymerase chain reaction (RT-PCR). In RT-PCR, IL-1α, IL-1β and IL-6 mRNA expressions was induced in ARE-treated RAW 264.7 macrophage cells. We also investigated the effect of the nitric oxide (NO) synthesis and inducible nitric oxide synthase (iNOS) mRNA expression by ARE. ARE alone had no effect on NO synthesis and iNOS mRNA expression in RAW 264.7 cells. In the case of lipopolysaccharide (LPS) stimulation, NO production and iNOS mRNA expression were detected in RAW 264.7 cells. However, NO production and iNOS mRNA expression which is induced by LPS decreased after treatment of ARE. These data demonstrate that ARE can reduce the suppression of macrophage cell proliferation induced by MTX, and induce IL-1α, IL-1β and IL-6 mRNA expressions in RAW 264.7 macrophage cells. Also, ARE inhibit NO production in LPS-stimulated RAW 264.7 macrophage cells, and the inhibition of NO production may be associated with the inhibition of iNOS mRNA expression.