RATIONALE: Extracellular nucleotides can mediate a variety of cellular functions via interactions with purinergic receptors. We have previously shown that mechanical ventilation (MV) induces airway IL-6 and ATP release, modifies the luminal nucleotide composition, and alters lung purinoceptor expression. Here, we hypothesize that extracellular nucleotides induce secretion of IL-6 by small airway epithelial cells (SAEC). METHODS: Human SAEC were stimulated with nucleotides in the presence or absence of inhibitors. Supernatants were analyzed for IL-6, and lysates for p38MAPK activity, by ELISA. RNA was analyzed by real-time RT-PCR. Fifty-one rats were randomized to: control, small-volume MV, large-volume MV, large-volume MV/intratracheal apyrase, or small-volume MV/intratracheal ATPS. Following one hour of MV, bronchoalveolar lavage fluid was analyzed for ATP and IL-6, via luminometry and ELISA. RESULTS: ATP and ATPS increased SAEC IL-6 secretion in a time and dose-dependent manner, an effect inhibited by apyrase. Agonist rank order was: ATPS>ATP=UTP>ADP=Adenosine>2-MeS-ADP=Ctrl. Nucleotide effects decreased with SB203580, but not UO126 or JNK1 inhibitor. Additionally, nucleotides induced p38MAPK phosphorylation. IL-6 release was decreased by inhibitors of calcium signaling, phospholipase C, transcription, and translation. Furthermore, nucleotides increased IL-6 expression. In vivo, large-volume MV resulted in increased airway ATP and IL-6 concentrations. Moreover, IL-6 release was decreased by apyrase and increased by ATPS. CONCLUSION: Extracellular nucleotides induce P2Y₂-mediated secretion of IL-6 by SAEC via Ca²⁺, phospholipase C, and p38MAPK-dependent pathways. This effect is dependent upon transcription and translation. Our findings were confirmed in an in vivo model, thus demonstrating a novel mechanism of nucleotide-induced IL-6 secretion by airway epithelia.