組蛋白乙醯基轉移酵素在脂多醣體刺激

組蛋白乙醯基轉移酵素在脂多醣體刺激 RAW 264.7 巨噬細胞引發環氧 酵素 -2 表現之角色探討

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在過去的研究證實，內毒素是誘導巨噬細胞活化的重要因子，巨噬細 胞釋放的前列腺素 E (Prostaglandin E2 ， PGE2) 為誘導發炎反應的重 要因子之一；而 PGE2 的生成會受到 COX-2 的調控。研究指出內毒 素可經由 HAT 誘導轉錄因子活化以調控基因表現。本論文所要探討 的是在 RAW 264.7 巨噬細胞中，組蛋白乙醯基轉移酵素 (Histone ace tyltransferase, HAT) 在內毒素誘導環氧化酵素 -2 (Cyclooxygenase-2 ， COX-2) 表現分子機轉中所扮演的角色。結果顯示在 RAW 264.7 巨噬 細胞中，給予 anacardic acid ( HAT 抑制劑 ) 可抑制 lipopolysacchari de (LPS) 誘導 COX-2 蛋白表現，使用 p300 siRNA 會降低 LPS 誘導 COX-2 蛋白表現，且發現 anacardic acid 抑制 LPS 會誘導 HAT 活 性。我們也發現 LPS 會誘導 p65 及 Histone H3 產生乙醯化，進一步 發現給予 anacardic acid 可抑制 LPS 誘導 p65 乙醯化及 ? 羠 -lucif erase 的活性。給予 anacardic acid 抑制 LPS 誘導 Histone H3 乙醯 化。且 LPS 會誘導 p65 及 p300 結合在 COX-2 promoter region 。 綜合以上結果發現 p300 將 p65 及 Histone H3 乙醯化在 LPS 誘導 CO X-2 蛋白表現扮演重要角色，藉此研究可以提供發展控制發炎反應及 敗血性休克的新方法。

Role of Histone Acetyltransferase in Lipopolysaccharide -Induced Cycl ooxygenase-2 Expression in RAW 264.7 Macrophages

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Previous study shown that endotoxin is an important factor increased macrophage a

ctivity. Among the bioactive substances produced by macrophages including of pro

staglandin E2 (PGE2) has been found the important mediators of inflammation. Th

e PGE2 synthesis is dependent on the cyclooxygenase-2 (COX-2) expression. Previ

ous study shown that endotoxin increased histone acetyltransferase (HAT) activity

which mediates transcription factor activation and induces gene expression. In this

study, we examined the role of HAT in endotoxin-induced COX-2 expression in R

AW 264.7 macrophages. Pretreatment of anacardic acid (inhibitor of HAT) inhibite

d lipopolysaccharide (LPS)-induced COX-2 expression in a dose-dependent manne

r in RAW 264.7 macrophages. p300 siRNA inhibited LPS-induced COX-2 expressi

on and anacardic acid inhibited LPS-induced HAT activity in RAW 264.7 macroph

ages.. We found that LPS-induced p65 acetylation and ? 綑 stone H3 acetylation. F

urthermore, pretreatment of anacardic acid inhibited LPS-induced p65 acetylation a

nd ? 羠 -luciferase activity, and Histone H3 acetylaion. Moreover, LPS increased bi

nding of p65 and p300 to COX-2 promoter region. Taken together, we demonstrate

d that Histone H3 and p65 acetylation play crucial roles in LPS-induced COX-2 ex

pression, and provided a new target for development of novel therapy in inflammati

on and septic shock.