Smoke Extract Impairs Adenosine Wound Healing. Implications of Smoke-Generated Reactive Oxygen Species

Abstract

Adenosine concentrations are elevated in the lungs of patients with asthma and chronic obstructive pulmonary disease, where it balances between tissue repair and excessive airway remodeling. We previously demonstrated that the activation of the adenosine A 2A receptor promotes epithelial wound closure. However, the mechanism by which adenosine-mediated wound healing occurs after cigarette smoke exposure has not been investigated. The present study investigates whether cigarette smoke exposure alters adenosine-mediated reparative properties via its ability to induce a shift in the oxidant/ antioxidant balance. Using an in vitro wounding model, bronchial epithelial cells were exposed to 5% cigarette smoke extract, were wounded, and were then stimulated with either 10 mM adenosine or the specific A 2A receptor agonist, 59-(N-cyclopropyl)-carboxamidoadenosine (CPCA; 10 mM), and assessed for wound closure. In a subset of experiments, bronchial epithelial cells were infected with adenovirus vectors encoding human superoxide dismutase and/or catalase or control vector. In the presence of 5% smoke extract, significant delay was evident in both adenosine-mediated and CPCA-mediated wound closure. However, cells pretreated with N-acetylcysteine (NAC), a nonspecific antioxidant, reversed smoke extract-mediated inhibition. We found that cells overexpressing mitochondrial catalase repealed the smoke extract inhibition of CPCA-stimulated wound closure, whereas superoxide dismutase overexpression exerted no effect. Kinase experiments revealed that smoke extract significantly reduced the A 2A -mediated activation of cyclic adenosine monophosphate-dependent protein kinase. However, pretreatment with NAC reversed this effect. In conclusion, our data suggest that cigarette smoke exposure impairs A 2A -stimulated wound repair via a reactive oxygen species-dependent mechanism, thereby providing a better understanding of adenosine signaling that may direct the development of pharmacological tools for the treatment of chronic inflammatory lung disorders.

Effects of cigarette smoke extract on human airway smooth muscle cells in COPD

“…One study about the effect of CSE on the function of the human lung has shown that CSE reduces the migration and contractile activity of normal human bronchial smooth muscle cells [42]. In another study it was shown that CSE impairs the wound healing of bovine bronchial epithelial cells via a reactive oxygen species dependent mechanism [43]. Another study has shown CSE inhibits the proliferation of human lung fibroblasts [44], but whether these fibroblasts were derived from patients with COPD or not was not clear.…”

Cigarette Smoke Modulates Repair and Innate Immunity following Injury to Airway Epithelial Cells

“…The direct effects of CS on wound repair of airway epithelial cells have been primarily studied by applying an aqueous extract of CS on undifferentiated submerged cultures of airway or alveolar epithelial cell lines or primary airway epithelial cells [7, 11, 12]. However, to gain more insight in the effect of smoking on airway epithelial repair, further research is required using conditions that better reflect the local conditions in lungs of smokers.…”

Cigarette Smoke Impairs A2A Adenosine Receptor Mediated Wound Repair through Up-regulation of Duox-1 Expression

“…We previously demonstrated that CS-generated ROS, particularly H 2 O 2 , is implicated in blunting ADO-mediated wound repair of airway epithelial cells12. However, the mechanism by which CS-generated H 2 O 2 contributes to the dysregulation of ADO-stimulated wound repair remains unknown.…”

“…Cyclic nucleotides such as cAMP and cGMP are key messengers in modulating cell shape and attachment as well as cell movement in many model systems78. We recently demonstrated that CS exposure blunts ADO-mediated activation of cAMP-dependent Protein Kinase A (PKA) and this was facilitated by the robust activation of PKC signaling2. Moreover, we showed previously that PKC activation retards wound repair9.…”