O. tsutsugamushi inhibits tumor necrosis factor-alpha production without affecting NF-kB pathway in murine macrophages

초록

We have previously reported that O. tsutsugamushi (OT) induces little TNF-α by the infected macrophages. However, it was not clear whether this was a consequence of a "silent" invasion or live OT actively interfered with the production of TNF-α. J774 macrophages were first infected by OT for various time and then treated with LPS or zymosan for 6 h. Preinfection by OT inhibited LPS- or zymosan-induced TNF-α production. Within 30 min of OT infection, the level of TNF-α was reduced to about a half of zymosan-induced level. Many microorganisms suppress the production of pro-inflammatory cytokines by interfering the activation of NF-κB, allowing them to interfere with the transcription of immune response genes. Therefore, we examined whether the OT activates the NF-κB pathway. However, OT doesn't inhibit LPS- and zymosan- induced nuclear translocation of NF-κB. These results suggest that OT actively inhibit the production of TNF-α by the mechanism that does not affect the activation of NF-κB.