OLE OF PURINERGIC RECEPTORS IN THE ACTS VATS ON OF HUMAN AIRWAY SMOOTH MUSCLE CELLS BY THE PEPTIDE LL-37

摘要

Inflammatory cells that infiltrate and surround the airway smooth muscle (ASM) layer express antimicrobial peptides including the cathelicidin LL-37. LL-37 has been shown to activate epithelial cells by transactivation of the epidermal growth factor receptor (EGFR). Previously, we have shown that LL-37-induced IL-8 release by ASM cells was not dependent on either formyl peptide receptors or the EGFR (ATS 2005). In monocytes LL-37 induces processing of IL-1|1 through activation of the purinergic P2X_7 receptor. Therefore, the aim of our study was to evaluate the role of purinergic receptors in LL-37-induced activation of ASM cells, and to explore the involvement of several intracellular signalling pathways.ASM cells were cultured and serum-deprived 24 hours before stimulation with LL-37 (10 ng ml~(-1)). The purinergic receptor antagonist suramin and inhibitors of ERK1 2. p38, Src and PI3K were preincubated for one hour. ERK1-2 phosphorylation was assessed by Western Blot, and IL-8 release was determined in supernatants using a sandwich ELISA. RT-PCR was performed for P2X_7 on untreated ASM cells. LL-37 induced ERK1.2 phosphorylation and IL-8 release: both were inhibited by suramin (IL-8: 86%). Inhibitors of ERK1 2. p38 and Src signalling also reduced LL-37-induced IL-8 release (by 67%. 63% and 76%, respectively), suggesting a role for these pathways. P2X_7 mRNA was expressed in ASM cells.These data show that LL-37-induced IL-8 release is mediated via purinergic receptors. ERK1.2 activation, p38 and Src signalling. Our PCR data are in line with the hypothesis that also in ASM P2X_7 is the purinergic receptor involved in LL-37 signalling, although this needs further investigation.