微囊藻毒素急性暴露对斑马鱼卵巢的损伤效应

Ovary Damage in Zebrafish Resulting from Acute Exposure to MC-LR

为了探究蓝藻(Cyanobacteria)大量爆发产生的微囊藻毒素(microcystins,MCs)对鱼类的生殖毒性,以斑马鱼(Danio rerio)为实验对象,采取腹腔注射毒性最强的microcystin-LR(MC-LR)方式,研究MC-LR对斑马鱼卵巢的损伤效应及其作用机制。对性成熟雌性斑马鱼腹腔注射50μg/kg和200μg/kg MC-LR,在注射3、9、24、48 h后取卵巢分析其生理活性指标的变化。结果显示,染毒24 h后,200μg/kg剂量组斑马鱼性腺指数(gonad somatic index,GSI)14.14与对照组性腺指数16.98相比显著降低(P<0.05),其他组别无显著变化;卵巢发生卵母细胞空泡化、卵母细胞膜与滤泡细胞层连接组织缺失等病理现象;MC-LR显著抑制了斑马鱼卵巢蛋白磷酸酶(protein phosphatase 2A,PP2A)活性,并激活促成熟因子(maturation promoting factor,MPF)活性;MC-LR处理后,斑马鱼卵巢内丝裂原活化蛋白激酶(mitogen-activated protein kinase,MAPK)家族中的p 38MAPK、ERK1/2的转录水平显著上调,JNK未发生显著变化。研究表明,MC-LR抑制斑马鱼卵巢PP2A活性,并激活MPF活性与MAPK信号通路中ERK1/2与p 38MAPK的转录水平,进而干扰其卵母细胞的发育进程并产生生殖毒性。

Cyanobacterial blooms caused by water eutrophication severely damage the aquatic environment.Microcystins(MCs)released by algae threatens the health of aquatic organisms and human health,and the most toxic MC is microcystin-LR(MC-LR).Studies have shown that,after the liver,gonads are the organ most susceptible to MC toxicity.The reproductive toxicity of MC-LR on egg production,fertilization rate,sex hormone levels and parental transmission have been demonstrated,but further research is needed on the toxic mechanism.In this study,the effect of MCs on zebrafish(Danio rerio)ovaries and the mechanism of toxicity were investigated by intraperitoneal injection of MC-LR into the abdominal cavity.Four-month-old sexually mature female zebrafish were selected for the test and three treatments were set:a control group and two treatment groups receiving MC-LR by intraperitoneal injection at 50μg/kg and 200μg/kg of body weight(BW).Ovaries for each treatment were sampled at 3,9,24 and 48 h after injection for analysis.The gonadosomatic index(GSI)of zebrafish in the 200μg/kg treatment group decreased significantly at 24 h after MC-LR injection(P<0.05),but no significant changes were found in the 50μg/kg treatment group.However,pathology,such as vacuolization of oocytes and loss of connective tissue between the oocyte membrane and the follicular cell layer was observed in both treatment groups.MC-LR significantly inhibited ovarian protein phosphatase 2A(PP2A)activity and activated the maturation promoting factor(MPF).There was also a significant up-regulation in the transcription of the MAPK family of genes,but c-junamino-terminal kinase(JNK)activity did not change significantly.To summarize,acute exposure of zebrafish to MC-LR results in damage to ovarian tissue,a decrease in the GSI,decreased ovarian PP2A activity,activation of MPF and up-regulation of ERK1/2 and p38MAPK transcription.As a result of these multiple effects,we conclude that the reproductive toxicity of MC-LR in zebrafish results from interference with oocyte development.