Abstract
Objective and design: The histone acetylation processes, which are believed to play a critical role in the regulation of many inflammatory genes, are reversible and regulated by histone acetyltransferases (HATs), which promote acetylation, and histone deacetylases (HDACs), which promote deacetylation. We studied the effects of lipopolysaccharide (LPS) on histone acetylation and its role in the regulation of interleukin (IL)-8 expression. Material: A human alveolar epithelial cell line A549 was used in vitro. Methods: Histone H4 acetylation at the IL-8 promoter region was assessed by a chromatin immunoprecipitation (ChIP) assay. The expression and production of IL-8 were evaluated by quantitative polymerase chain reaction and specific immunoassay. Effects of a HDAC inhibitor, trichostatin A (TSA), and a HAT inhibitor, anacardic acid, were assessed. Results: Escherichia coli-derived LPS showed a dose- and time-dependent stimulatory effect on IL-8 protein production and mRNA expression in A549 cells in vitro. LPS showed a significant stimulatory effect on histone H4 acetylation at the IL-8 promoter region by ChIP assay. Pretreatment with TSA showed a dose-dependent stimulatory effect on IL-8 release from A549 cells as compared to LPS alone. Conversely, pretreatment with anacardic acid inhibited IL-8 production and expression in A549 cells. Conclusion: These data suggest that LPS-mediated proinflammatory responses in the lungs might be modulated via changing chromatin remodeling by HAT inhibition.
Highlights
Pneumonia is an important socio-medical problem and one of the leading causes of death in the world[1]
LPS induced expression of IL-8 gene in A549 cells A549 cells were stimulated by 10μg/ml LPS, and the time course in levels of IL-8 mRNA was analyzed by Quantitative reverse transcription polymerase chain reaction (qRT-PCR)
IL-8 mRNA levels showed a gradual increase in response to LPS, reaching a maximum level 2 h after initial stimulation with 10μg/ml, which decreased after that point (Figure 2)
Summary
Pneumonia is an important socio-medical problem and one of the leading causes of death in the world[1]. Once inhaled via respiratory routes, LPS stimulate alveolar structural as well resident cells to release many kinds of bioactive agents such as proinflammatory cytokines into local microenvironments[2]. Upon infectious agents and their products being inhaled into the respiratory systems, activated lung epithelium may contribute to the regulation of the immune response as the first-line defense mechanism[6]. Among those defense responses, it seems important that alveolar epithelial cells express and release a variety of proinflammatory cytokines and chemokines into alveolar microenvironments[6,7]. The NF-κB binds to its specific binding sites on the promoter regions and enhances the expression of IL-8 gene[12,13]
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