Anisodamine Inhibits Shiga Toxin Type 2-Mediated Tumor Necrosis Factor-α Production in Vitro and in Vivo 1

Abstract

Cytokines, in particular tumor necrosis factor (TNF), appear to be necessary to develop the pathological process of Shiga toxin-producing Escherichia coll (STEC) infection. In this study we examined the effect of anisodamine, a vasoactive drug, on TNF-α production in Shiga toxin type 2 (Stx2)-stimulated human monocytic cells in vitro and in Stx2-injected mice sera in vivo. Human monocytes and THP-1 cells were stimulated by Stx2 (1–100 ng/ml) with or without anisodamine addition (1–400 μg/ml). For in vivo evaluations, C57BL/6 mice were given a single intraperitoneal injection of anisodamine (6–50 mg/kg) or saline after intraperitoneal injection of Stx2 (50 ng/kg). The results showed that anisodamine suppressed Stx2-induced TNF-α production in a dose- and time-dependent manner. Anisodamine also suppressed Stx2-induced TNF-α mRNA expression. Further study showed that endogenous prostaglandin E2 may be involved in this inhibitory effect. In contrast to TNF-α mRNA, anisodamine at concentrations as high as 400 μg/ml did not decrease Stx2-induced IL-1β and IL-8 mRNA levels. In addition, anisodamine (>50 μg/ml) increased Stx2-stimulated THP-1 cell viability. Levels of TNF-α in anisodamine-treated mice sera were significantly lower than those in the saline-treated group 1.5 and 24 hr after Stx2 injection. Anisodamine induced a lower percentage of death in Stx2-injected mice. Taken together, our results indicate that anisodamine has an important regulatory effect on Stx2-induced TNF-α production in vitro and in vivo. The present study suggested that this drug should be further investigated for its effects on Stx2-mediated diseases in humans.