Aims: Josamycin has immunomodulatory properties independent of its antibacterial actions. This study was designed to explore the influences and associated mechanisms of josamycin upon the generation of proinflammatory mediators in murine macrophages activated with lipopolysaccharide (LPS) from Prevotella intermedia, a pathogenic bacterium associated with periodontal disease.
Main methods: LPS was purified by employing phenol-water extraction protocol. Culture supernatants were analyzed for nitric oxide (NO) and interleukin (IL)-1β. Real-time PCR and immunoblotting were conducted to quantify mRNA and protein expression, respectively. The expression levels of IL-1β were analyzed by confocal laser scanning microscopy. NF-κB-dependent SEAP levels were estimated by reporter assay.
Key findings: Josamycin significantly attenuated NO production elicited by P. intermedia LPS as well as induction of iNOS protein and mRNA in RAW264.7 cells. While the release of IL-1β from cells stimulated by LPS was suppressed in the presence of josamycin, josamycin failed to reduce the degree of IL-1β mRNA expression. Josamycin did not reduce the stability of IL-1β mRNA induced by P. intermedia LPS, at the same time josamycin also failed to suppress the LPS-induced intracellular IL-1β expression. Josamycin augmented HO-1 induction in cells exposed to P. intermedia LPS, and SnPP, an inhibitor of HO-1 activity, reversed the suppressive impact of josamycin upon NO generation induced by LPS. Josamycin diminished NF-κB transcriptional activity induced by P. intermedia LPS. Further, josamycin enhanced SOCS1 mRNA level in cells activated with LPS.
Significance: Josamycin suppressed P. intermedia LPS-induced generation of NO and IL-1β in RAW264.7 macrophages via the inhibition of NF-κB activation as well as HO-1 and SOCS1 induction. Josamycin may have benefits as a host modulatory agent in treating periodontal disease.
Keywords: HO-1; NF-κB; SOCS1; interleukin-1β; josamycin; nitric oxide.
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