目的:研究大鼠出生后早期大气细颗粒物(PM2.5)吸入暴露对其部分免疫指标及卵清蛋白(OVA)致敏原反应性的影响及机制.方法:SD妊娠大鼠随机分为过滤空气-生理盐水(FA-NS)组、FA-OVA组、PM2.5-NS组和PM2.5-OVA组,每组10只.PM2.5各组置于暴露柜中吸入环境浓度的PM2.5,从出生后第0天至第27天连续暴露28 d;FA各组置于滤除大气颗粒物的对照柜中.第9、15天腹腔注射0.5μg OVA,第24～26天雾化吸入1％OVA 30 min诱导OVA过敏;未致敏组给予等量载液.第27天检测各组大鼠IL-4、IL-5和IFN-γ含量、肺GATA结合蛋白3(GATA3)、T细胞特异性转录因子(T-bet)和脾miRNA-146a/b表达水平.结果:PM2.5-NS、FA-OVA或PM2.5-OVA组血浆IL-4水平较FA-NS组显著升高,PM2.5-OVA组较PM2.5-NS或FA-OVA组显著升高;FA-OVA或PM2.5-OVA组IL-5水平较FA-NS或PM2.5-NS组显著升高;FA-OVA组IFN-γ水平较FA-NS、PM2.5-NS或PM2.5-OVA组显著升高(P<0.05).FA-OVA或PM2.5-OVA组肺GATA3水平较FA-NS组显著升高,PM2.5-OVA较PM2.5-NS显著升高;FA-OVA、PM2.5-OVA组T-bet水平较FA-NS组或PM2.5-NS组显著降低,PM2.5-OVA组较FA-OVA组显著降低(P<0.05).PM2.5-OVA组脾miRNA-146a表达水平较FA-NS组、PM2.5-NS组或FA-OVA组显著升高,FA-OVA组较PM2.5-NS组显著升高;miRNA-146b表达FA-OVA、PM2.5-OVA组较FA-NS组或PM2.5-NS组显著升高(P<0.05).结论:出生后早期环境水平PM2.5吸入暴露对幼鼠免疫系统具有不良影响,OVA致敏幼鼠不良效应更为显著,可能与免疫调节异常和炎症反应有关.

Objective To investigate the effects of maternal exposure to ambient fine particles (PM2.5) in Fuzhou during pregnancy on immune responses to ovalbumin (OVA) in neonatal rats and the possible mechanisms.Methods Pregnant Sprague-Dawley rats were randomly assigned into four groups (ten in each):filtered air (FA) plus normal saline (NS),airborne PM2.5 plus NS (PM2.5-NS),FA plus OVA (FA-OVA) and PM2.5 plus OVA (PM2.5-OVA) groups.Pregnant dams in the PM2.5 exposure groups were placed in a PM2.5 exposure chamber in which the PM2.5 concentration was equal to the ambient air from the beginning of gestation till delivery,whereas the other dams inhaling air without particulate matters were put into a clean chamber.OVA sensitization was conducted through intraperitoneal injection of OVA at 50 μ g per dam at 4 and 9 days of gestation,followed by inhalation of atomized 1％ OVA for 30 min at 18,19 and 20 days of gestation.Dams without OVA sensitization were given NS in the same way.Levels of interleukin (IL)-4,IL-5 and interferon-γ (IFN-γ) in neonatal rats' plasma were measured by enzyme-linked immunosorbent assay just after birth.Protein levels of transcription factors GATA-3 and T-bet in lung were analyzed by Western-blotting.Changes in microRNA(miR)-146a and miR-146b in spleen were detected by real-time polymerase chain reaction.Histological changes in lung were observed under light microscope.One-way analysis of variance and LSD test were used as statistical methods.Results (1) IL-4 level in plasma was significantly increased in PM2.5-NS [(18.56±7.04) ng/L],FA-OVA [(34.04±7.06) ng/L] and PM2.5-OVA groups [(45.67±8.18) ng/L] as compared with that in FA-NS group [(10.51 ±2.88) ng/L],and the level of IL-4 in PM2.5-OVA group was higher than that in PM2.5-NS and FA-OVA groups (F=54.667,P＜0.001).Significantly increased IL-5 level in plasma was found in FA-OVA and PM2.5-OVA groups as compared with that in FA-NS group (F=6.253,P=0.023).Among the four groups,FA-OVA group showed significantly increased IFN-γ level in plasma (F=28.604,P＜0.001).(2) GATA-3 level in lung tissues was significantly increased in PM2.5-NS (31.09 + 3.54),FA-OVA (35.24± 5.00) and PM2.5-OVA groups (47.81 ±3.63) as compared with that in FA-NS group (24.19±3.12),and higher in PM2.5-OVA group than in PM2.5-NS and FA-OVA groups (F=96.581,P＜0.001).T-bet level was significantly lower in FA-OVA and PM2.5-OVA groups than in FA-NS group.Moreover,PM2.5-OVA group showed decreased T-bet level as compared with that in PM2.5-NS and FA-OVA groups (F=30.852,P＜0.001).(3) Expression of miR-146a in spleen was significantly enhanced in PM2.5-NS (1.72±0.27),FA-OVA (1.56±0.37) and PM2.5-OVA groups (3.06± 0.52) than in FA-NS group (1.05 ±0.25).Moreover,PM2.5-OVA group showed enhanced expression of miR-146a as compared with that in PM2.5-NS and FA-OVA groups (F=42.276,P＜0.001).Changes in the expressions of miR-146b were similar to those in miR-146a (F=28.776,P＜0.001).(4) Stenosis or disappearance of alveolar spaces,accompanied with infiltration of inflammatory cells in interstitial substance and congestion in alveolar septum,was seen in FA-OVA and PM2.5-OVA groups and conditions in the latter group were more severe.Conclusions Intrauterine exposure to ambient PM2.5 negatively affects fetal lung development and immunological function in rats,especially when the dams are sensitized with OVA during pregnancy.