BackgroundHouse dust mite (HDM) affects the immunological and physical barrier function of airway epithelium, leading to allergic sensitization, airway remodeling, and eosinophilic inflammation in mouse models, although the mechanisms are still largely unknown. ObjectiveGiven the implications for adenosine triphosphate (ATP)-dependent Ca2+ signaling in allergic sensitization in mice, we sought to determine the role of intracellular Ca2+ concentration ([Ca2+](i)) in HDM-induced barrier dysfunction and pro-inflammatory activity of bronchial epithelium. MethodsWe investigated the effect of HDM on accumulation of [Ca2+](i) levels, barrier function, and CCL20 release in human bronchial epithelial 16HBE cells and primary bronchial epithelial cells (PBECs) from healthy subjects and asthma patients. Involvement of ATP-dependent activation of purinergic receptors and downstream Ca2+ influx was studied, using the ATP hydrolyzing agent apyrase, the purinergic receptor agonist PPADS, the calcium chelator BAPTA-AM, and calpain inhibitors. ResultsAsthma PBECs were more susceptible to HDM-induced barrier dysfunction, CCL20 secretion, and Ca2+ influx than healthy PBECs. Furthermore, we show that the HDM-induced increase in CCL20 in PBECs and 16HBE cells and the HDM-induced barrier dysfunction in 16HBE cells are dependent on [Ca2+](i) accumulation. Additionally, we demonstrate that [Ca2+](i) accumulation is initiated partly through the activation of purinergic receptors, which contributes to HDM-induced epithelial barrier dysfunction by disruption of cell-cell contacts, but not CCL20 secretion. ConclusionOur data show for the first time that Ca2+ signaling plays a crucial role in barrier dysfunction and the pro-inflammatory response of bronchial epithelium upon HDM exposure and may thus have important implications for the development of allergic asthma.