Adenosine Promotion of Cellular Migration in Bronchial Epithelial Cells is Mediated by the Activation of Cyclic Adenosine Monophosphate–Dependent Protein Kinase A

Migration of neighboring cells into the injury is important for rapid repair of damaged airway epithelium. We previously reported that activation of the A_2A receptors (A_2AARs) mediates adenosine-stimulated epithelial wound healing, suggesting a role for adenosine in migration. Because A_2AAR increases cyclic adenosine monophosphate (cAMP) levels in many cells, we hypothesized that cAMP-dependent protein kinase A (PKA) is involved in adenosine-mediated cellular migration.

To test this hypothesis, we stimulated a human bronchial epithelial cell line with adenosine and/or A_2AAR agonist (5′-(N-cyclopropyl)-carboxamido-adenosine [CPCA]) in the presence or absence of adenosine deaminase inhibitor (erythro-9-(2-hydroxy-3-nonyl) adenine hydrochloride [EHNA]).

Cells treated with adenosine or CPCA demonstrated a concentration-dependent increase in migration. Similar results were observed in the presence and absence of EHNA. To confirm A_2A involvement, we pretreated the cells for 1 hour with the A_2A receptor antagonist ZM241385 and then stimulated them with either adenosine or CPCA. To elucidate PKA's role, cells were pretreated for 1 hour with either a PKA inhibitor (KT5720) or a cAMP antagonist analogue (Rp-cAMPS) and then stimulated with adenosine and/or CPCA. Pretreatment with KT5720 or Rp-cAMPS resulted in a significant decrease in adenosine-mediated cellular migration. PKA activity confirmed that bronchial epithelial migration requires cAMP and PKA activity. When cells were wounded and stimulated with CPCA, an increase in PKA activity occurred. Pretreatment for 1 hour with either KT5720 or Rp-cAMPS resulted in a significant decrease in adenosine-mediated PKA activation.

These data suggest that adenosine activation of A_2AAR augments epithelial repair by increasing airway cellular migration by PKA-dependent mechanisms.