Heat-killed Tsukamurella inchonensis reduces lipopolysaccharide-induced inflammatory responses in activated murine peritoneal macrophages

Abstract

Tsukamurella inchonensis (T. inchonensis) is an aerobic species of Actinomycetales which has immunomodulatory activities when used as a suspension of killed bacilli. Here, the effects of T. inchonensis on lipopolysaccharide-induced inflammatory responses in mouse peritoneal macrophages have been examined. Peritoneal macrophages were harvested by lavaging with ice cold phosphate-buffered saline. Macrophages acquired from mice treated with different doses of T. inchonensis for seven days were cultured with 20 U/ml interferon-γ and 10 µg/ml lipopolysaccharide for in vivo assays. Nitrite levels were measured by using the diazotization method based on the Griess reaction, an indirect technique to determine nitric oxide (NO) production. T. inchonensis inhibited lipopolysaccharide-stimulated NO production in mouse peritoneal macrophages from mice previously exposed to concentrations of 108 and 5 × 10⁷ CFU per flask. Also, T. inchonensis decreased lipopolysaccharide-induced production of pro-inflammatory cytokines, including interleukin-6 and tumor necrosis factor-α. Thus, it can be concluded that T. inchonensis is a powerful inhibitor of lipopolysaccharide-induced NO production in activated murine macrophages, and T. inchonensis may be useful as a novel agent for chemoprevention in inflammatory diseases.