Role of c‐jun N‐terminal kinase in the induced release of GM‐CSF, RANTES and IL‐8 from human airway smooth muscle cells

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Abstract
Human airway smooth muscle cells (HASMC) contribute to airway inflammation in asthma by virtue of their capacity to produce several inflammatory mediators including IL‐8, GM‐CSF and RANTES. The intracellular signal pathway underlying the production of these cytokines in HASMC is not entirely elucidated. We examined the role of the mitogen‐activated protein kinase (MAPK) c‐jun N‐terminal kinase (JNK) in TNFα‐ and IL‐1β‐induced GM‐CSF, RANTES and IL‐8 production in HASMC by using a novel specific inhibitor for JNK (SP600125). Confluent HASMC were treated with TNFα or IL‐1β (10 ng ml−1) for 24 h in the presence or absence of SP600125 (1–100 μM). JNK activity was determined by a kinase assay. Phosphorylation of JNK, p38 MAPK and ERK was examined by Western blotting. Culture supernatants were assayed for GM‐CSF, RANTES and IL‐8 content by ELISA. Maximum TNFα‐ or IL‐1β‐induced phosphorylation of JNK in HASMC occurred after 15 min and returned to baseline levels after 4 h. SP600125 inhibited TNFα‐ and IL‐1β‐induced JNK activity in HASMC as shown by the reduced phosphorylation of its substrate c‐jun. Furthermore, GM‐CSF, RANTES and to a lesser extent IL‐8 release from HASMC treated with TNFα and IL‐1β was inhibited dosedependently by SP600125. JNK activation is involved in TNFα‐ and IL‐1β‐induced GM‐CSF, RANTES and IL‐8 production from HASMC. JNK may therefore represent a critical pathway for cytokine production in HASMC. British Journal of Pharmacology (2003) 139, 1228–1234. doi:10.1038/sj.bjp.0705345