Vesicle-associated membrane protein 7-mediated eosinophil degranulation promotes allergic airway inflammation in mice

Abstract

Eosinophil degranulation is a determining factor in allergy-mediated airway pathology. Receptor-mediated degranulation in eosinophils requires vesicle-associated membrane protein 7 (VAMP-7), a principal component of the SNARE fusion machinery. The specific contribution of eosinophil degranulation to allergen-induced airway responses remains poorly understood. We generated mice with VAMP-7 gene deficiency exclusively in eosinophils (eoCRE/V7) from a cross using eosinophil-specific Cre recombinase-expressing mice crossed with VAMP-7f/f mice. Eosinophils from eoCRE/V7 mice showed deficient degranulation responses in vitro, and responses continued to be decreased following ex vivo intratracheal adoptive transfer of eoCRE/V7 eosinophils into IL-5/hE2/EPX−/− mice. Consistent with diminished degranulation responses, reduced airway hyperresponsiveness was observed in ovalbumin-sensitized and challenged eoCRE/V7 mice following methacholine inhalation. Therefore, VAMP-7 mediates eosinophil degranulation both in vitro and ex vivo, and this event augments airway hyperresponsiveness.

The Release Kinetics of Eosinophil Peroxidase and Mitochondrial DNA Is Different in Association with Eosinophil Extracellular Trap Formation

“…We investigated the effects of different physiological (C5a, PAF, eotaxin) stimuli on the cytokine-primed [ 34 ] and non-physiological (PMA [ 35 ], ionomycin [ 30 ]) agonists on unprimed eosinophils. IL-5 priming has been reported to increase eosinophil granule protein release [ 36 ].…”

“…Eosinophils from the peripheral blood were isolated as previously described [ 30 ]. In brief, peripheral blood was layered on top of Histopaque 1119 (density of 1.119 g/mL) (Sigma-Aldrich) and centrifuged at 800× g for 20 min.…”

Charcot-Leyden crystal protein/galectin-10 interacts with cationic ribonucleases and is required for eosinophil granulogenesis

“…45 Our finding that CLC/Gal-10 rapidly becomes associated with both CD63-positive secondary granules and EDN during the process of IFN-g-induced eosinophil activation is indicative of a possible role for CLC/Gal-10 in the vesicular transport of the cationic RNases. Extended studies on actively secreting eosinophils on the colocalization of CLC/ Gal-10 with components of the vesicular transport pathway expressed by eosinophils (including the vesicle-associated membrane proteins [VAPMs] VAMP-2, VAMP-7, and VAMP-8, syntaxin-4, and synaptosome-associated protein 23) [71][72][73] will further elucidate the role of CLC/Gal-10 in the process of PMD.…”

“…3,6,[82][83][84][85] The effect of CLC/Gal-10 deficiency on the activation and degranulation of in vitro-differentiated eosinophils was assessed by measuring the secretion of EDN and EPX following stimulation of the cells with PAF. PAF is a well-studied eosinophil secretagogue shown to induce eosinophil degranulation via both exocytosis 73 and piecemeal degranulation, 86 although the exact mechanism of its action on eosinophils is unknown. 87 Stimulation with PAF resulted in a dose-dependent secretion of EPX and EDN, suggesting that CLC/Gal-10-deficient eosinophils do not have a generalized defect in degranulation.…”

The emerging roles of eosinophils in mucosal homeostasis

“…IL-33 also functions as a potent modulator of eosinophil function, driving changes in the transcriptional profile and/or promoting degranulation. 23,44 For example, Bouffi et al, 23 show that IL-33 stimulation of eosinophils results in the alteration of over 500 genes resulting in the upregulation of various factors such as IL-6, IL-13, CCL17, and TGF-β. In addition, IL-33 stimulation of eosinophils results in autocrine production of IL-4, which synergizes with ongoing IL-33 signaling to regulate the eosinophil transcriptome through an NFκB-dependent mechanism.…”