Inhibition of IL-1β-induced COX-2 and IL-8 Expression by Histone Deacetylase Inhibitor Trichostatin A (TSA) in Human Lung Adenocarcinoma Cells

• Main Authors: Meng-Lun Lu, 呂孟倫
• Other Authors: Yuh-Lin Wu
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/21082418530547281607

碩士 === 國立陽明大學 === 生理學研究所 === 98 === Chronic inflammation has been proposed to be associated with cancer progression, and indeed the pro-inflammatory cytokine interleukin (IL)-1β was shown to up-regulate the expression of several inflammation-related genes, such as cyclooxygenase (COX)-2 and IL-8, both of which have been regarded as critical players in carcinogenesis. Previous studies have also demonstrated that histone deacetylase (HDAC) may regulate COX-2 and IL-8 expression in inflammation-related diseases. Thus, this project aimed to clarify whether HDAC may involve in IL-1β-mediated COX-2 and/or IL-8 expression in the human lung adenocarcinoma A549 cell line by using a specific HDAC inhibitor trichostatin A (TSA). By employing western blot analysis and ELISA, we first revealed that TSA could significantly attenuate IL-1β-induced protein expression of COX-2 and IL-8, as well as the secretion of prostaglandin E2 (PGE2) and IL-8. By examining the cell proliferation parameters with MTT and alamarBlue analyses, we observed that TSA did not result in significant changes in the readouts, indicating that the suppression effect of TSA on IL-1β regulation of COX-2 and IL-8 was not due to its cytotoxic effect. By monitoring the protein degradation profiles, we noted that TSA did not alter the stability of IL-1β-induced COX-2 and IL-8 proteins. With reverse transcription-polymerase chain reaction (RT-PCR) assay, we discovered that TSA was able to inhibit IL-1β-mediated COX-2 and IL-8 mRNA expression. Transient transfection of A549 cells with COX-2 and IL-8 promoter constructs and luciferase assay demonstrated that instead of blunting IL-1β-induced promoter activation, TSA appeared to up-regulate the promoter activities; combination of IL-1β and TSA resulted in even higher activities of both promoter constructs. These data implied that TSA did not seem to inhibit IL-1β-induced COX-2 or IL-8 transcriptional activation. By utilization of MAP kinase inhibitors (SB203580, SP600125, and PD98059) as well as NF-?菣B inhibitor (APDC) and PI3K inhibitor (LY294002) to pinpoint the signaling pathway(s) involved in IL-1β-provoked COX-2 and IL-8 expression, we found that the MAPK p38, JNK and PI3K pathways seemed to be critical. Biochemical analyses further identified that TSA was capable of reducing IL-1β-stimulated JNK and PI3K activation (phosphorylation). Our current findings suggest that HDAC inhibitor TSA may affect IL-1β-regulated COX-2 and IL-8 expression at the mRNA level, at least in part by targeting to MAPK JNK and PI3K signaling pathways.