PM2.5短期暴露对大鼠子宫组织的损伤及其作用机制

Effect and mechanism of short-term exposure to PM2.5 on the rat uterine injury

目的为研究PM2.5(空气动力学直径≤2.5μm的颗粒物)短期暴露对大鼠子宫的损伤作用及可能的分子机制。方法30只雌性SD大鼠随机分为生理盐水对照组、1.5 mg/(kg·bw)PM2.5低剂量暴露组和6 mg/(kg·bw)PM2.5高剂量暴露组,连续暴露30 d。HE染色病理学检查观察PM2.5暴露后子宫组织损伤情况。采用TUNEL法和检测cleaved caspase-3蛋白表达量的方法观察各组大鼠子宫组织细胞凋亡情况。荧光定量PCR法检测子宫中葡萄糖调节蛋白78(GRP78)、蛋白激酶样内质网激酶(PERK)、真核翻译起始因子2α(eIF2α)和C/EBP同源蛋白(CHOP)mRNA表达水平。Western blot检测子宫内质网应激相关蛋白表达水平。结果PM2.5短期暴露后,子宫内膜上皮细胞萎缩,细胞间隙增大,且细胞出现空泡化;同时腺体也出现萎缩。TUNEL检测结果显示,对照组大鼠子宫组织细胞的凋亡率为(9.93±1.66)%,低剂量和高剂量暴露组子宫组织细胞凋亡率分别为(29.40±6.96)%和(43.58±8.23)%,暴露组细胞凋亡率明显高于对照组,差异有统计学意义(P<0.05)。与对照组相比,暴露组子宫中GRP78、PERK、eIF2α和CHOP基因和蛋白表达水平均明显升高,差异有统计学意义(P<0.05)。暴露组子宫cleaved caspase-3蛋白表达量明显高于对照组(P<0.05)。结论PM2.5短期暴露可损伤大鼠子宫组织形态,其作用机制可能与PERK-eIF2α-CHOP信号通路介导子宫组织发生内质网应激反应,进而诱导子宫组织细胞凋亡有关。

Objective This study was designed to evaluate the effect of short-term exposure to the particulate matter with diameters that are generally 2.5μm and smaller(PM2.5)on the rat uterine injury,and to determine its mechanism.Methods Thirty Sprague-Dawley rats were randomly divided into:a control group,a 1.5 mg/kg body-weight(bw)low-dose PM2.5 exposure group and a 6 mg/(kg·bw)high-dose PM2.5 exposure group,all of which were followed for 30 days.The pathological uterine changes were observed with hematoxylin-eosin staining(HE staining).Uterine apoptosis was evaluated with the TUNEL method,and the expression levels of cleaved caspase-3 were measured.In addition,the mRNA expression levels of glucose-regulated protein 78(GRP78),PER-like ER kinase(PERK),eukaryotic initiation factor 2α(eIF2α)and C/EBP homologous protein(CHOP)were measured with quantitative real-time PCR,and the protein levels involved in the PERK-eIF2α-CHOP signal pathway were tested using western blot assay.Results After short-term exposure,PM2.5 resulted in atrophy and vacuolization of endometrial epithelial cells and glands.The apoptosis rates were(9.93±1.66)%,(29.40±6.96)%and(43.58±8.23)%in the uteruses in the control,low-dose exposure and high-dose exposure groups,respectively.Furthermore,the apoptosis rate was significantly higher(P<0.05)in the two exposure groups than in the control group.At the same time,the cleaved caspase-3 protein expression levels in the two exposure groups were significantly increased(P<0.05).The results of qPCR and western blot showed that the mRNA and protein levels of GRP78,PERK,eIF2αand CHOP in the two exposure groups were significantly higher than those in the control group(P<0.05).Conclusions After short-term exposure to PM2.5,the uterine structure of the rats is damaged,possibly as a consequence of PM2.5 inducing uterine cell apoptosis via ERs,mediated by the PERK-eIF2α-CHOP pathway.