富含半胱氨酸残基蛋白介导低剂量镉暴露胎盘屏障的机制探讨

Cadmium, harmful to human health, is highly paid attention because of its occupational exposure and environment pollution. Although placenta is one of the target organs of cadmium, it has obvious effect of placenta barrier effect blocking cadmium entering the embryo, which is quite different from lead and mercury. Some evidences suggest that enrich cysteine residue protein plays an important role in cadmium placenta barrier, but the molecular mechanism of the protein remains to be elucidated. To detect the mechanisms of enrich cysteine residue protein mediating the cadmium placenta barrier, we are to establish a low-cadmium exposure animal model with enriched stable isotope 112Cd by imitating the level of occupational cadmium exposure. Enrich cysteine residue protein in placenta is quantificationally analyzed with technics of proteomics. Key proteins affecting the functions of placenta barrier are to be screened and confirmed with western blotting and immunohistochemistry. On the other hand, the functions of these key proteins are to be studied in the cells exposed the different doses of cadmium.Finally, candidate protein as a biomarker will be validated in cadmium-exposed workers in epidemiological investigation. This study will reveal the key target proteins after low level cadmium exposure and understand their roles in the placental barrier, as well as their relationships with secondary adverse effects in cadmium reproductive toxicity. Furthermore, this study also provides the basis to develop the enrich cysteine residue protein as sensitive biomarkers for cadmium exposure.

镉是危害人体健康的环境污染物，近年来由于其职业暴露和环境污染逐渐加重而益发引起高度关注。胎盘是镉蓄积的靶器官之一，与铅、汞等重金属的通透性不同，胎盘对镉具有明显的屏障作用，富含半胱氨酸残基蛋白与屏障作用密切相关，但有关作用方式和机制不明。为明确富含半胱氨酸残基蛋白介导胎盘对镉屏障作用的机制，本研究通过模拟职业人群的实际暴露水平，采用镉富集稳定同位素示踪技术，建立低剂量镉暴露的动物模型，利用蛋白质组学技术定量分析胎盘的富含半胱氨酸残基蛋白，筛选镉暴露胎盘屏障作用的关键靶蛋白，蛋白印迹确认，免疫组化定位，体外细胞染毒研究其功能，并进一步在镉暴露人群中加以验证。本研究将揭示胎盘对镉暴露屏障作用的关键靶蛋白，确定其在胎盘组织的具体定位，阐明其与屏障作用的机制关系，为镉暴露早期监测生物标志物的基础研究提供依据。

镉是危害人体健康的环境污染物，近年来由于其职业暴露和环境污染逐渐加重而益发引起高度关注。胎盘是镉蓄积的靶器官之一，与铅、汞等重金属的通透性不同，胎盘对镉具有明显的屏障作用，但有关作用方式和机制不明。为明确何种靶蛋白介导胎盘对镉屏障作用的机制，本研究通过模拟职业人群的实际暴露水平，建立低剂量镉暴露的一代繁殖动物模型，利用蛋白质组学技术定量分析胎盘的差异蛋白，筛选镉暴露胎盘屏障作用的关键靶蛋白，经蛋白印迹确认以及免疫组化定位，并进一步利用细胞染毒进行体外验证。.实验结果显示，(1)孕期满20d时，低镉暴露组雌鼠的黄体数、每窝产仔数、活胎率、死胎率和吸收胎率等繁殖指数分别与对照组比较，差异均无统计学意义（Ｐ＞0.05）。说明在1mg/kg体质量的低镉暴露剂量下未导致明显的繁殖毒性，符合本实验低剂量镉暴露的染毒要求。(2)与对照组相比，低镉暴露组和高镉暴露组共有15个蛋白质点表达差异1.5倍以上。通过与Uniprot数据库比对，并结合候选蛋白质的功能，初步确定了ATP结合转运蛋白家族（The ATP-binding cassette transporter superfamily）之一的ABCG2和ABCB4蛋白进行下一步的验证。同时Western blot分析显示，ABCG2和ABCB4蛋白在镉暴露组表达下降，与对照组相比差异有统计学意义（P＜0.05），而且蛋白的下降趋势呈现剂量反应关系。说明ABCG2和ABCB4蛋白可能涉及镉在胎盘的转运。(3)与对照组正常胎盘相比，低镉暴露组出现部分轻微的滋养层细胞退化，而在中、高镉暴露组，退化程度不仅明显加重，而且出现组织充血及糖原细胞减少。说明伴随染毒剂量的加大，胎盘作为镉暴露的靶器官呈现相应的毒性改变。（4）体外细胞急性镉暴露24h后，ABCG2蛋白表达增高。说明在体外实验中ABCG2蛋白有助于保护胎盘免受镉的干扰。.本研究初步揭示了胎盘对镉暴露屏障作用的关键靶蛋白，不仅为研究镉的生殖发育毒性和筛选早期监测的生物标志物提供了依据，而且为今后借助转运蛋白影响镉转运的功能研究，寻求临床诊疗指引了新方向，具有重大的科学意义和社会效应。

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