摘要目的:探讨细胞外组蛋白参与脂多糖（LPS）诱导的肺泡巨噬细胞损伤的作用及机制。方法:体外培养小鼠肺泡巨噬细胞株（MH-S）并传代，取融合生长至80%时的细胞进行实验，用1 mg/L的LPS刺激细胞3 h后以50 mg/L的外源性组蛋白分别刺激细胞3、6、12、24 h（LPS +组蛋白3、6、12、24 h组），并设磷酸盐缓冲液（PBS）对照组（PBS组）、LPS单独刺激组（LPS组）、外源性组蛋白单独刺激组（组蛋白组）及肝素预处理组蛋白组（肝素+ LPS +组蛋白组）。各组细胞经相应处理后，采用酶联免疫吸附试验（ELISA）检测上清液中乳酸脱氢酶（LDH）及炎性因子表达，用FluxOR TMⅡ绿色钾离子通道检测试剂盒检测细胞内K +浓度，采用蛋白质免疫印迹试验（Western Blot）测定钾离子通道蛋白（TWIK2）、炎症小体（NLRP3）及凋亡相关斑点样蛋白（ASC）的表达。 结果:与PBS组比较，单用LPS刺激可使LDH及白细胞介素（IL-1β、IL-18）、肿瘤坏死因子-α（TNF-α）等炎性因子水平显著升高。与LPS组比较，加用外源性组蛋白处理后LDH及炎性因子水平显著升高，当组蛋白刺激时间为3 h时达到峰值〔LDH（U/L）：123.10±1.83比85.32±1.66，IL-1β（mg/L）：40.75±2.60比18.78±1.37，IL-18（mg/L）：49.94±2.45比30.19±1.82，TNF-α（mg/L）：36.51±1.56比20.84±1.61，均 P<0.01〕。Western Blot结果显示，与LPS组比较，NLRP3、ASC及TWIK2蛋白在LPS +组蛋白组表达均明显上调（NLRP3/GAPDH：0.80±0.02比0.57±0.02，ASC/GAPDH：0.57±0.02比0.38±0.01，TWIK2/GAPDH：0.65±0.01比0.41±0.01，均 P<0.01），而肝素预处理后上述蛋白表达均明显下调（NLRP3/GAPDH：0.28±0.02比0.80±0.02，ASC/GAPDH：0.25±0.02比0.57±0.02，TWIK2/GAPDH：0.35±0.01比0.65±0.01，均 P<0.01），表明组蛋白可通过TWIK2活化NLRP3参与炎症反应。此外，LPS +组蛋白组细胞内K +浓度较LPS组明显下降（荧光强度：35.48±2.53比83.92±3.11， P<0.01）；与LPS +组蛋白比较，给予肝素预处理后K +浓度明显上升（荧光强度：72.10±1.78比35.48±2.53， P<0.01），表明细胞外组蛋白可通过TWIK2致K +大量外流从而介导NLRP3活化参与肺泡巨噬细胞炎症损伤。 结论:细胞外组蛋白可致肺泡巨噬细胞炎症损伤，其作用机制可能与细胞外组蛋白激活TWIK2通道促进K +外流从而活化NLRP3有关。

abstractsObjective:To explore the role and mechanism of extracellular histones involved in lipopolysaccharide (LPS)-induced alveolar macrophage injury.Methods:The mouse alveolar macrophage cell line (MH-S) was cultured in vitro and passaged, and the cells were cultured to 80% of cells for cell proliferation. The cells were stimulated with 1 mg/L LPS for 3 hours and 50 mg/L exogenous histones for 3, 6, 12, and 24 hours, respectively (LPS+histones 3, 6, 12, 24 h groups), and other groups included phosphate buffered saline (PBS) control group (PBS group), LPS alone stimulation group (LPS group), the exogenous histones alone stimulation group (histones group) and heparin pretreatment histones group (heparin+LPS+histones group). The cells in each group were challenged with different reagent, the expression of lactate dehydrogenase (LDH) and inflammatory factors in the supernatant were detected by enzyme linked immunosorbent assay (ELISA), and the change of intracellular K + concentration was detected by FluxOR TMⅡgreen potassium channel. The proteins such as potassium channel protein (TWIK2), inflammasome (NLRP3), and apoptosis associated speck like protein containing a CARD (ASC) were determined by Western Blot. Results:Compared with the PBS group, the levels of LDH and inflammatory factors such as interleukin (IL-1β, IL-18) and tumor necrosis factor-α (TNF-α) were significantly increased after LPS stimulation group. Compared with the LPS group, the levels of LDH and inflammatory factors were significantly increased after the treatment with exogenous histones, and reached a peak after 3 hours of the histones stimulation [LDH (U/L): 123.10±1.83 vs. 85.32±1.66, IL-1β (mg/L): 40.75±2.60 vs. 18.78±1.37, IL-18 (mg/L): 49.94±2.45 vs. 30.19±1.82, TNF-α (mg/L): 36.51±1.56 vs. 20.84±1.61, all P < 0.01]. Western Blot results showed that compared with the LPS group, NLRP3, ASC and TWIK2 protein expression were significantly up-regulated in the LPS+histones group (NLRP3/GAPDH: 0.80±0.02 vs. 0.57±0.02, ASC/GAPDH: 0.57±0.02 vs. 0.38±0.01, TWIK2/GAPDH: 0.65±0.01 vs. 0.41±0.01, all P < 0.01), and the expression of the above proteins were significantly down-regulated after heparin pretreatment (NLRP3/GAPDH: 0.28±0.02 vs. 0.80±0.02, ASC/GAPDH: 0.25±0.02 vs. 0.57±0.02, TWIK2/GAPDH: 0.35±0.01 vs. 0.65±0.01, all P < 0.01), indicating that histones could activate NLRP3 through TWIK2 to participate in inflammatory reaction. In addition, intracellular K + concentration in LPS+histones group decreased significantly compared with the LPS group (fluorescence intensity: 35.48±2.53 vs. 83.92±3.11, P < 0.01). Compared with LPS+histones group, K + concentration increased significantly after pretreatment with heparin (fluorescence intensity: 72.10±1.78 vs. 35.48±2.53, P < 0.01), indicating that extracellular histones could cause K + massive efflux through TWIK2, and thus mediate NLRP3 activation and participate in inflammatory injury of alveolar macrophages. Conclusion:Extracellular histones can cause inflammatory damage in alveolar macrophages, and its mechanism may be related to the activation of NLRP3 by extracellular histones activation of TWIK2 channel to promote K + efflux.