ATP Mediates NADPH Oxidase/ROS Generation and COX-2/PGE₂ Expression in A549 Cells: Role of P2 Receptor-Dependent STAT3 Activation

Background: Up-regulation of cyclooxygenase (COX)-2 and its metabolite prostaglandin E₂ (PGE₂) are frequently implicated in lung inflammation. Extracellular nucleotides, such as ATP have been shown to act via activation of P2 purinoceptors, leading to COX-2 expression in various inflammatory diseases, such as lung inflammation. However, the mechanisms underlying ATP-induced COX-2 expression and PGE₂ release remain unclear. Principal Findings: Here, we showed that ATPγS induced COX-2 expression in A549 cells revealed by western blot and real-time PCR. Pretreatment with the inhibitors of P2 receptor (PPADS and suramin), PKC (Gö6983, Gö6976, Ro318220, and Rottlerin), ROS (Edaravone), NADPH oxidase [diphenyleneiodonium chloride (DPI) and apocynin], Jak2 (AG490), and STAT3 [cucurbitacin E (CBE)] and transfection with siRNAs of PKCα, PKCι, PKCμ, p47^phox, Jak2, STAT3, and cPLA₂ markedly reduced ATPγS-induced COX-2 expression and PGE₂ production. In addition, pretreatment with the inhibitors of P2 receptor attenuated ^phox translocation ₂ production via a P2 receptor/PKC/NADPH oxidase/ROS/Jak2/STAT3/cPLA₂ signaling pathway in A549 cells. Increased understanding of signal transduction mechanisms underlying COX-2 gene regulation will create opportunities for the development of anti-inflammation therapeutic strategies.