Cigarette smoke extract attenuates adenosine‐mediated wound repair in bronchial epithelial cells

Abstract

Cigarette smoke (CS) exposure can lead to tissue destruction either through direct toxic effects or indirectly by initiating inflammatory responses. CS is a major risk factor for a number of diseases including asthma, emphysema and chronic obstructive pulmonary disease. Adenosine, a purine nucleoside, has been implicated as a potent regulator of inflammation. We have demonstrated that adenosine modulates airway wound repair in bronchial epithelial cells via activation of its specific adenosine receptors (A1, A2A, A2B, A3). Understanding that CS alters the imbalance between tissue destruction and tissue repair, we hypothesized that cigarette smoke extract (CSE) attenuates adenosine-mediated wound repair in bronchial epithelial cells (BECs). To test this hypothesis, both human bronchial epithelial cell line (BEAS-2B) and primary bovine bronchial epithelial cells (BBECs) were used. Utilizing an in vitro wounding model, BECs were exposed ± 5% CSE for 1 h, wounded and stimulated with either 10 μM adenosine (ADO) or with the specific A2A receptor agonist, 5′-(N-Cyclopropyl)-carboxamido-adenosine (CPCA; 10 μM) and assessed for wound closure. In the absence of 5% CSE, optimal wound closure occurred by 6 h in both ADO and/or CPCA stimulated cells as compared to media control. In the presence of 5% CSE, there was a significantly delay in both ADO and/or CPCA-mediated wound closure. In addition, CSE-treated cells revealed no significant release of lactate dehydrogenase, an enzyme that is indicative of cytotoxicity. Collectively, the data suggest cigarette smoke impairs adenosine-mediated airway wound repair. Supported by: VA Merit Review, NIH-AA08769 and NE DHHD-LB506