Pannexin-1 Channels Are Essential for Mast Cell Degranulation Triggered During Type I Hypersensitivity Reactions

• Published in: Frontiers in immunology Vol. 10; p. 2703
• Main Authors: Harcha, Paloma A, López, Ximena, Sáez, Pablo J, Fernández, Paola, Barría, Iván, Martínez, Agustín D, Sáez, Juan C
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 29.11.2019
• Subjects: degranulation; histamine; immune cells; Immunology; inflammation; ovalbumin; pannexon; pannexon; histamine; inflammation; ovalbumin; immune cells; degranulation; ATP
• ISSN: 1664-3224; 1664-3224
• DOI: 10.3389/fimmu.2019.02703

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, Ca influx and subsequent increase of intracellular free Ca concentration are essential for MC degranulation. Several membrane channels that mediate Ca influx have been proposed, but their role remains elusive. Here, we evaluated the possible contribution of pannexin-1 channels (Panx1 Chs), well-known as ATP-releasing channels, in the increase of intracellular Ca 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 Ca signal followed by a sustained increase after antigen stimulation. However, the sustained increase in Ca 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 Ca . Accordingly, stimulation with exogenous ATP restored the degranulation response and sustained increase in Ca 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 Ca influx, confirming that Panx1 Chs permeable to ATP are not permeable to Ca . These data strongly suggest that during antigen recognition, Panx1 Chs contribute to the sustained Ca 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.