摘要目的 研究机械拉伸对γ-干扰素(IFN-γ)诱导肺泡上皮细胞(A549细胞)人β-防御素-3(HBD-3)表达的影响并探讨HBD-3在呼吸机相关性肺炎(VAP)发病机制中的作用.方法 体外培养A549细胞,分别给予机械拉伸(S组),10 ng/ml IFN-γ(I组)和10.ng/ml IFN-γ+机械拉伸(IS组)3种处理,未处理的细胞为对照组(C组),处理的时间为2 h、4 h和6 h.拉伸由细胞FlexerceH-4000TM拉伸系统提供,拉伸的幅度为20%,速率为30次/min.处理后实时定量逆转录-多聚酶链反应(RT-PCR)检测HBD-3 mRNA的表达;处理6 h的细胞继续培养至24 h,激光扫描共聚焦显微镜检测HBD-3的表达.采用单因素方差分析和q检验对实验数据进行统计学分析.结果 单独的机械拉伸不能使HBD-3mRNA的表达发生显著变化.10 ng/ml IFN-γ处理2 h、4 h和6 h后,HBD-3 mRNA表达量较之C组分别增加了(2.63±0.60),(8.02±1.63)和(12.21±2.35)倍.10 rig/ml IFN-γ+机械拉伸处理2 h、4 h和6 h后,HBD-3 mRNA表达量较之C组分别增加了(1.54±0.16),(4.37±0.87)和(6.99 4-1.32)倍,但均显著低于I组(P<0.01).6 h机械拉伸后,IS组HBD-3的表达显著少于I组(P<0.01),同C组差异无统计学意义.结论 机械拉伸能显著抑制IFN-γ诱导肺泡上皮细胞HBD-3表达的上调,这可能是机械通气(MV)的患者易于发生VAP的原因之一.

abstractsObjective To study the effect of mechanical stretch on the expression of human beta-defensin-3 (HBD-3) in alveolar epithelial cells(A549 cells) elicited by interferon-gamma(IFN-γ) and to investigate the role of HBD-3 in the pathogenesis of ventilator-associated pneumonia (VAP) . Method A549 cells cultured in vitro were treated with mechanical stretch (group S), 10 ng/ml IFN-γ (group I) ,and 10 ng/ml IFN-γ with mechanical stretch (group IS), respectively. Cells without treatment served as controls (group C). Cells were stretched by 20% amplitude of stretch at 30 cycles/mm by Flexercell-4000[TM] Unit for 2 h, 4 h, and 6 hours. The HBD-3 mRNA expression was determined by real-time RT-PCR after treatment. After 6 hours, treatment, cells were cultured for 24 hours and the expression of HBD-3 was examined by laser scanning confocal microscope. The experimental data were statistically analyzed by using one-way ANOVA analysis and q-test. Results The expression of HBD-3 mRNA in A549 cells could not significantly be changed by mechanical stretch alone. Compared with group C,the HBD-3 mRNA expression after treatment with 10 ng/ml IFN-γ for 2 hours,4 hours and 6 hours increased significantly by (2.63 C,the HBD-3 mRNA expression after treatment with 10 ng/ml IFN-γ and mechanical stretch for 2 hours,4 hours and 6 hours increased by (1.54 were significantly lower than those in group I (P < 0.01). The HBD-3 expression in group IS after mechanical stretch for 6 significantly different from than in group C. Conclusions Mechanical stretch can significantly suppress the up-regulation of HBD-3 in alveolar epithelial cells elicited by IFN-γ, and this may be one of the explaina-tions that patients under mechanical ventilatiori(MV) have a higher risk of VAP.