TNFα是一種作用很強的細(xì)胞因子,除對腫瘤細(xì)胞有特異的殺傷作用外,還有抗病毒、激活T細(xì)胞、促進(jìn)細(xì)胞因子分泌和誘發(fā)炎癥反應(yīng)等重要生物功能。本組實驗觀察到,TNFα刺激16HBE引起ICAM1mRNA表達(dá)增高,與以往的報道類似〔7〕,TNFα可誘導(dǎo)一系列與炎癥有關(guān)的細(xì)胞因子〔如IL1、IL6、IL8、粒細(xì)胞巨噬細(xì)胞集落刺激因子(GMCSF)〕、黏附分子〔如ICAM1、血管細(xì)胞間黏附因子1(VCAM1)〕的生成,通過誘導(dǎo)這些因子的產(chǎn)生和釋放,造成機體炎癥損傷,同時,通過再激活炎癥效應(yīng)細(xì)胞,釋放更多的炎性因子,使炎癥信號進(jìn)一步放大和加強。本實驗還顯示,不同濃度EM作用于16HBE 24 h或48 h后,再用TNFα刺激16 h,與僅用TNFα刺激組比較,16HBE ICAM1mRNA表達(dá)均降低,提示有濃度和時間依賴性。本實驗從分子水平上說明EM能抑制ICAM1mRNA表達(dá),且與其作用濃度和時間相關(guān),這一機制可能是EM抗炎作用機制之一。在國外,Suzuki等〔8〕研究發(fā)現(xiàn),EM抑制病毒感染人氣管上皮細(xì)胞導(dǎo)致的ICAM1分泌從而調(diào)節(jié)氣道炎癥。Sanz等〔9〕報告在老鼠體內(nèi)實驗中,EM抑制白細(xì)胞在肺內(nèi)的聚集,其機制是通過下調(diào)ICAM1mRNA和VCAM1 mRNA表達(dá)。Li等〔10,11〕研究結(jié)果顯示大環(huán)內(nèi)酯類抗生素能抑制博來霉素誘導(dǎo)大鼠的急性肺損傷和肺纖維,其作用機制主要是通過抑制ICAM1mRNA和VCAM1mRNA表達(dá)從而抑制白細(xì)胞特別是中性粒細(xì)胞向氣道內(nèi)遷移。有臨床實驗證明,長期小劑量EM治療COPD患者,可顯著減少患者感冒發(fā)生率,對阻止COPD患者病情惡化有良好的效果,這種效果是EM的抗炎而非抗菌機制所致,可能與EM能抑制16HBE表達(dá)和釋放IL6、IL8和ICAM1有關(guān)〔12〕。
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