Aeroallergens derived from Alternaria alternata evoke ATP release and chronic increases in intracellular Ca2+ in bronchial epithelial cells by a mechanism involving oxidative stress (869.4)

Abstract

Alternaria aeroallergens have been previously shown to stimulate allergic inflammation and exacerbation of respiratory distress in patients with asthma. An early event following exposure to Alternaria extract is the sustained release of ATP and a persistent increase in intracellular [Ca2+] ([Ca2+]i) resulting from uptake of Ca2+ ions from the extracellular solution. In the present study we tested the hyopothesis that the release of ATP and the subsequent increase in [Ca2+]i was due to oxidative stress induced by exposure to Alternaria. ATP release following apical stimulation with Alternaria was measured in human primary bronchial epithelial cells using a luciferase/luciferin ATP measurement kit in combination with a modified luminometer that allows for tracking ATP release in real time. Pretreatment with glutathione (GSH) produced a concentration‐dependent inhibition of ATP release with an EC50 = 500 μM. Furthermore, GSH blocked the increase in [Ca2+]i typically observed following apical exposure to Alternaria. Moreover an increase in the expression of specific antioxidant protein mRNAs was also observed after 12 hours of treatment with Alternaria extract. These proteins included peroxiredoxins 1‐6, keratin 1, cyclooxygenase 2 (COX2) and oxidative stress responsive 1 protein with COX2 having the highest level of expression (~20 fold). These results implicate oxidative stress as an important initiating event in Alternaria evoked airway inflammation.Grant Funding Source: Supported by NIH: HL110539