Dynamin 2-mediated endocytosis of BLT1 is required for IL-8 production in HMC-1 cells induced by Trichomonas vaginalis-derived secretory products

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We previously reported that leukotriene B4 (LTB4) contained in Trichomonas vaginalis-derived secretory products (TvSP) play an essential role in interleukin-8 (IL-8) production in human mast cell line (HMC-1 cells) via LTB4 receptor (BLT)-mediated Nuclear Factor-kappa B (NF-кB) activation. Dynamin, a GTPase, has been known to be involved in endocytosis of receptors for signaling of production of cytokine or chemokines. In the present study, we investigated the role of dynamin-mediated BLT1 endocytosis in TvSP-induced IL-8 production. When HMC-1 cells were transfected with BLT1 or BLT2 siRNA, TvSP-induced IL-8 production was significantly inhibited compared with that in cells transfected with control siRNA. In addition, pretreatment of HMC-1 cells with a dynamin inhibitor (Dynasore) reduced IL-8 production induced by TvSP or LTB4. TvSP- or LTB4- induced phosphorylation of NF-кB was also attenuated by pretreatment with Dynasore. After exposing HMC-1 cells to TvSP or LTB4, BLT1 was translocated from the intracellular compartments to the plasma membrane within 30 min. At 60 min after stimulation with TvSP or LTB4, BLT1 remigrated from the cell surface to intracellular areas. Pretreatment of HMC-1 cells with dynamin-2 siRNA blocked internalization of BLT1 induced by TvSP or LTB4. Co-immunoprecipitation experiments revealed that dynamin-2 strongly interacted with BLT1 60 min after stimulation with TvSP or LTB4. These results suggest that T. vaginalis-secreted LTB4 induces IL-8 production in HMC-1 cells via dynamin 2-mediated endocytosis of BLT1 and phosphorylation of NF-кB.

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