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Front. Immunol. | doi: 10.3389/fimmu.2019.02703

Pannexin-1 channels are essential for mast cell degranulation triggered during Type I hypersensitivity reactions

 Paloma A. Harcha1, 2*,  Ximena Lopez1, 2,  Pablo J. Sáez1, 2, 3, Paola Fernández2,  Iván Barría2 and  Juan C. Sáez2, 4*
  • 1Department of Physiology, Faculty of Biological Sciences, Pontifical Catholic University of Chile, Chile
  • 2Centro Interdisciplinario de Neurociencia de Valparaiso, Universidad de Valparaíso, Chile
  • 3UMR144 Compartimentation et dynamique cellulaires (CDC), France
  • 4Pontifical Catholic University of Chile, Chile

Mast cells (MCs) release pro-inflammatory mediators through a process called degranulation response. The latter may be induced by several conditions, including antigen recognition through immunoglobulin E (IgE) or “cross-linking”, classically associated with Type I hypersensitivity reactions. Early in this reaction, Ca2+ influx and subsequent increase of intracellular free Ca2+ concentration are essential for MC degranulation. Several membrane channels that mediate Ca2+ influx have been proposed, but their role remain elusive. Here, we evaluated the possible contribution of pannexin-1 channels (Panx1 Chs), well-known as ATP releasing channels, in the increase of intracellular Ca2+ triggered during cross-linking reaction of MCs. The contribution of Panx1 Chs in the degranulation response was evaluated in MCs from wild type (WT) and Panx1 knock out (Panx1-/-) mice after anti-ovalbumin (OVA) IgE sensitization. Notably, the degranulation response (toluidine blue and histamine release) was absent in Panx1-/- MCs. Moreover, WT MCs showed a rapid and transient increase in Ca2+ signal followed by a sustained increase after antigen stimulation. However, the sustained increase in Ca2+ signal triggered by OVA was absent in Panx1-/- MCs. Furthermore, OVA stimulation increased the membrane permeability assessed by dye uptake, a prevented response by Panx1 Ch but not by connexin hemichannel blockers and without effect on Panx1-/- MCs. Interestingly, the increase in membrane permeability of WT MCs was also prevented by suramin, a P2 purinergic inhibitor, suggesting that Panx1 Chs act as ATP releasing channels impermeable to Ca2+. Accordingly, stimulation with exogenous ATP restored the degranulation response and sustained increase in Ca2+ signal of OVA stimulated Panx1-/- MCs. Moreover, opening of Panx1 Chs in Panx1 transfected HeLa cells increased dye uptake and ATP release but did not promote Ca2+ influx, confirming that Panx1 Chs permeable to ATP are not permeable to Ca2+. These data strongly suggest that during antigen recognition, Panx1 Chs contribute to the sustained Ca2+ signal increase via release of ATP that activates P2 receptors, playing a critical role in the sequential events that leads to degranulation response during Type I hypersensitivity reactions.

Keywords: Inflammation, inmune system, Ovalbumin, degranulation, ATP, Histamine

Received: 18 Jul 2019; Accepted: 04 Nov 2019.

Copyright: © 2019 Harcha, Lopez, Sáez, Fernández, Barría and Sáez. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence:
PhD. Paloma A. Harcha, Department of Physiology, Faculty of Biological Sciences, Pontifical Catholic University of Chile, Santiago, Chile,
Prof. Juan C. Sáez, Centro Interdisciplinario de Neurociencia de Valparaiso, Universidad de Valparaíso, Valparaiso, Chile,