Nucleotides induce IL-6 release from human airway epithelia via P2Y2 and p38 MAPK-dependent pathways

Nucleotides induce IL-6 release from human airway epithelia via P2Y(2) and p38 MAPK-dependent pathways. Am J Physiol Lung Cell Mol Physiol 291: L734-L746, 2006. First published April 21, 2006; doi: 10.1152/ajplung. 00389.2005.-Extracellular nucleotides can mediate a variety of cellular functions via interactions with purinergic receptors. We previously showed that mechanical ventilation (MV) induces airway IL-6 and ATP release, modifies 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). Human SAEC were stimulated with nucleotides in the presence or absence of inhibitors. Supernatants were analyzed for IL-6 and lysates for p38 MAPK activity by ELISA. RNA was analyzed by real-time RT-PCR. Rats (n = 51) were randomized to groups as follows: control, small-volume MV, large-volume MV, large-volume MV-intratracheal apyrase, or small-volume MV-intratracheal adenosine 5'-O-(3-thiotriphosphate) (ATP gamma S). After 1 h of MV, bronchoalveolar lavage fluid was analyzed for ATP and IL-6 by luminometry and ELISA. ATP and ATP gamma S increased SAEC IL-6 secretion in a time- and dose-dependent manner, an effect inhibited by apyrase. Agonists were ranked in the following order: ATP gamma S > ATP = UTP > ADP = adenosine > 2-methylthio-ADP = control. SB-203580, but not U-0126 or JNK1 inhibitor, decreased nucleotide effects. Additionally, nucleotides induced p38 MAPK phosphorylation. Inhibitors of Ca2+ signaling, phospholipase C, transcription, and translation decreased IL-6 release. Furthermore, nucleotides increased IL-6 expression. In vivo, large-volume MV increased airway ATP and IL-6 concentrations. IL-6 release was decreased by apyrase and increased by ATP gamma S. Extracellular nucleotides induce P2Y(2)- mediated secretion of IL-6 by SAEC via Ca2+, phospholipase C, and p38 MAPK-dependent pathways. This effect is dependent on 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.