Transcriptional regulation of lysophosphatidic acid-induced interleukin-8 expression and secretion by p38 MAPK and JNK in human bronchial epithelial cells.
HBEpCs (human bronchial epithelial cells) contribute to airway inflammation by secreting a variety of cytokines and chemokines in response to allergens, pathogens, viruses and environmental toxins and pollutants. The potent neutrophil chemoattractant, IL-8 (interleukin-8), is a major cytokine secreted by HBEpCs. We have recently demonstrated that LPA (lysophosphatidic acid) stimulated IL-8 production in HBEpCs via protein kinase C delta dependent signal transduction. However, mechanisms of IL-8 expression and secretion are complex and involve multiple protein kinases and transcriptional factors. The present study was undertaken to investigate MAPK (mitogen-activated protein kinase) signalling in the transcriptional regulation of IL-8 expression and secretion in HBEpCs. Exposure of HBEpCs to LPA (1 microM) enhanced expression and secretion of IL-8 by 5-8-fold and stimulated threonine/tyrosine phosphorylation of ERK (extracellular-signal-regulated kinase), p38 MAPK and JNK (c-Jun N-terminal kinase). The LPA-induced secretion of IL-8 was blocked by the p38 MAPK inhibitor SB203580, by p38 MAPK siRNA (small interfering RNA), and by the JNK inhibitor JNK(i) II, but not by the MEK (MAPK/ERK kinase) inhibitor, PD98059. LPA enhanced the transcriptional activity of the IL-8 gene; that effect relied on activation of the transcriptional factors NF-kappaB (nuclear factor kappaB) and AP-1 (activator protein-1). Furthermore, SB203580 attenuated LPA-dependent phosphorylation of IkappaB (inhibitory kappaB), NF-kappaB and phospho-p38 translocation to the nucleus, NF-kappaB transcription and IL-8 promoter-mediated luciferase reporter activity, without affecting the JNK pathway and AP-1 transcription. Similarly, JNK(i) II only blocked LPA-mediated phosphorylation of JNK and c-Jun, AP-1 transcription and IL-8 promoter-mediated luciferase reporter activity, without blocking p38 MAPK-dependent NF-kappaB transcription. Additionally, siRNA for LPA(1-3) receptors partially blocked LPA-induced IL-8 production and activation of MAPKs. The LPA1 and LPA3 receptors, as compared with LPA2, were most efficient in transducing LPA-mediated IL-8 production. These results show an independent role for p38 MAPK and JNK in LPA-induced IL-8 expression and secretion via NF-kappaB and AP-1 transcription respectively in HBEpCs.
Saatian
Bahman
B
Division of Pulmonary and Critical Care Medicine and Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Zhao
Yutong
Y
He
Donghong
D
Georas
Steve N
SN
Watkins
Tonya
T
Spannhake
Ernst Wm
EW
Natarajan
Viswanathan
V
D001980:Bronchi / Q000166:cytology*; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008246:Lysophospholipids / Q000494:pharmacology*; D016328:NF-kappa B / Q000378:metabolism; D010766:Phosphorylation; D021381:Protein Transport; D020545:Respiratory Mucosa / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D016209:Interleukin-8; D008246:Lysophospholipids; D016328:NF-kappa B; D018808:Transcription Factor AP-1; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C032881:lysophosphatidic acid