Chronic Airway Infection/Inflammation Induces a Ca2+i-dependent Hyperinflammatory Response in Human Cystic Fibrosis Airway Epithelia

Abstract Hyperinflammatory responses to infection have been postulated as a component of cystic fibrosis (CF) lung disease. Studies have linked intracellular calcium (Ca2+i) mobilization with inflammatory responses in several systems. We have reported that the pro-inflammatory mediator bradykinin (BK) promotes larger Ca2+i signals in CF compared with normal bronchial epithelia, a response that reflects endoplasmic reticulum (ER)/Ca2+ store expansion induced by chronic luminal airway infection/inflammation. The present study investigated whether CF airway epithelia were hyperinflammatory and, if so, whether the hyperinflammatory CF phenotype was linked to larger Ca2+ stores in the ER. We found that ΔF508 CF bronchial epithelia were hyperinflammatory as defined by an increased basal and mucosal BK-induced interleukin (IL)-8 secretion. However, the CF hyperinflammation expressed in short-term (6–11-day-old) primary cultures of ΔF508 bronchial epithelia was lost in long-term (30–40-day-old) primary cultures of ΔF508 bronchial epithelia, indicating this response was independent of mutant cystic fibrosis transmembrane conductance regulator. Exposure of 30–40-day-old cultures of normal airway epithelia to supernatant from mucopurulent material (SMM) from CF airways reproduced the increased basal and mucosal BK-stimulated IL-8 secretion of short-term CF cultures. The BK-triggered increased IL-8 secretion in SMM-treated cultures was mediated by an increased Ca2+i mobilization consequent to an ER expansion associated with increases in protein synthesis (total, cytokines, and antimicrobial factors). The increased ER-dependent, Ca2+i-mediated hyperinflammatory epithelial response may represent a general beneficial airway epithelial adaptation to transient luminal infection. However, in CF airways, the Ca2+i-mediated hyperinflammation may be ineffective in promoting the eradication of infection in thickened mucus and, consequently, may have adverse effects in the lung.