SNAP23-Dependent Surface Translocation of Leukotriene B ₄ (LTB ₄ ) Receptor 1 Is Essential for NOX2-Mediated Exocytotic Degranulation in Human Mast Cells Induced by Trichomonas vaginalis-Secreted LTB ₄

Abstract

Trichomonas vaginalis is a sexually transmitted parasite that causes vaginitis in women and itself secretes lipid mediator leukotriene B 4 (LTB 4 ). Mast cells are important effector cells of tissue inflammation during infection with parasites.Membrane-bridging SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) complexes are critical for fusion during exocytosis. Although T. vaginalis-derived secretory products (TvSP) have been shown to induce exocytosis in mast cells, information regarding the signaling mechanisms between mast cell activation and TvSP is limited. In this study, we found that SNAP23-dependent surface trafficking of LTB 4 receptor 1 (BLT1) is required for nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2)-mediated exocytotic degranulation of mast cells induced by TvSP. First, stimulation with TvSP induced exocytotic degranulation and reactive oxygen species (ROS) generation in HMC-1 cells. Next, TvSP-induced ROS generation and exocytosis were strongly inhibited by transfection of BLT1 small interfering RNA (siRNA). TvSP induced trafficking of BLT1 from the cytosol to the plasma membrane. We also found that knockdown of SNAP23 abrogated TvSPinduced ROS generation, exocytosis, and surface trafficking of BLT1 in HMC-1 cells. By coimmunoprecipitation, there was a physical interaction between BLT1 and SNAP23 in TvSP-stimulated HMC-1 cells. Taken together, our results suggest that SNAP23-dependent surface trafficking of BLT1 is essential for exocytosis in human mast cells induced by T. vaginalis-secreted LTB 4 . Our data collectively demonstrate a novel regulatory mechanism for SNAP23-dependent mast cell activation of T. vaginalis-secreted LTB 4 involving surface trafficking of BLT1. These results can help to explain how the cross talk mechanism between parasite and host can govern deliberately tissue inflammatory responses.KEYWORDS Trichomonas vaginalis, LTB 4 , human mast cells, SNAP23, NOX2, BLT1, surface trafficking, exocytotic degranulation T richomonas vaginalis is a lumen-dwelling protozoan parasite with flagella, which infects the genitourinary tract in humans via sexual intercourse (1, 2). Of note, in women it causes vaginitis or cervicitis leading to inflammatory and allergic symptoms, including vaginal discharge with a foul odor and an increased number of leukocytes, and vulvovaginal pruritus (3-6). During the infection, tight junctional proteins between

The Dynamics of the Skin’s Immune System

“…While a multitude of immune cell types express the machinery to produce some of the LTs, mast cells and eosinophils produce the complete battery of LTs. LTB4 has been shown to be effective in attracting neutrophils to sites of inflammation and cell death [63] and is a potent inducer of mast cell degranulation [184]. However, excess LTB4 amounts in the skin can lead to ineffective defense against Staphylococcus aureus infections in diabetic mice [185].…”