| Summary: | 碩士 === 國立陽明大學 === 生理學研究所 === 97 === Inhalation of toxic smoke causes severe pulmonary inflammation, which is life-threatening. Because their accessibility to toxic smoke, lung epithelial cells (LECs) play a critical role in the initiation and progression of this pulmonary inflammation. Direct exposure of LECs to inflammatory stimuli other than toxic smoke has been shown to induce increases in the production of various chemokines including interleukin-8 (IL-8). Indeed, IL-8 has been recognized as the key chemokine for trafficking of inflammatory cells to the alveolar spaces. In LECs, the up-regulation of IL-8 induced by these stimuli involves signaling pathways such as mitogen-activated protein kinases (MAPKs) and requires transcriptional factors such as signal transducers and activators of transcription protein (STAT) and nuclear factor-kappa B signaling pathway. Whether toxic smoke can stimulate LECs leading to up-regulation of IL-8 remains unclear. To this end, AMP-activated protein kinase (AMPK), a serine/threonine kinase possessing energy-sensing capability, is well known for its function in the activation of ATP-generating pathway. However, recent evidence suggests that AMPK may functionally modulate acute inflammatory responses in cell type other than LECs. For example, activation of AMPK increases the production of inflammatory cytokines via p38/NF-�羠 signaling pathway in human synovial fibroblast. Contrastingly, activation of AMPK attenuates lipopolysaccharide-induced neutrophil pro-inflammatory activity. Accordingly, the objectives of this study were to investigate 1) whether exposure of cultured human bronchial epithelial cells (HBECs) to wood smoke extract (SE) may up-regulate IL-8 and, if so, 2) the signaling pathways responsible for this IL-8 induction. We found that SE exposure increased protein expression of IL-8 in a dose- and time-dependant manner. Studies using specific pharmacological inhibitors revealed that the SE-induced up-regulation of IL-8 was mediated through AMPK, ERK (one major member of MAPKs) and JNK (one major member of MAPKs) signaling pathways, and depended on transcriptional factors NF-kappa B and STAT. Further investigations indicated that SE exposure increased phosphorylation of AMPK and promoted the NF-kappa B and STAT3 translocation to nucleus, but not STAT5, and Ikappa B-alpha degradation in the cytosol. Pharmacological inhibition of AMPK resulted in a reduction of SE-induced activation of NF-kappa B and STAT3. Additionally, in presence of PD98059 or SP600125 (a specific inhibitor of ERK or JNK), SE-induced translocation of NF-kappa B and STAT3 were reduced. Furthermore, the SE-induced activation of ERK and JNK was mediated through AMPK phosphorylation. These results suggest that SE-induced up-regulation of IL-8 is mediated through AMPK activation, which leads to NF-kappa B and STAT3 translocation to nucleus via ERK and JNK phosphprylation
|
|---|
