线粒体功能变化在无机汞诱导肾小球足细胞损伤中的机制研究

The incidence of patients with nephrotic syndrome induced by inorganic mercury increased gradually in recent years after exposure to mercury-containing compounds.Mercury-containing compounds have historically been used in dental amalgams, Chinese traditional medicines, and skin- lightening creams. Mercury can be absorbed into the human body by inhalation, ingestion, or intact skin. It has toxicities for kidneys, nerves, and gastrointestinal tracts. Histopathological analysis of renal biopsies suggested heavy injuries of podocytes. The physiology of of kidney makes it vulnerable to inorganic mercury injuries. However, the mechanism of such jnjury remains unknown and is lack of systemic research. Podocytes are highly differentiated cells with numerous foot processes. The foot process of neighboring podocytes interdigitate sharing filtration slits bridged by the slit diaphragm. Foot processes and their slit diaphragms constitute an architectural element of the permeability barrier and become effacement during podocyte injury due to acquired factor. In our preliminary studies, an agonist for cAMP/PKA prevented mitochondrial membrane potential collapse when podocytes were injuried, suggesting that cAMP/PKA protect podocyte via regulate mitochondrial function. In the present project, we will focus on the role of mitochondrial dysfunction, including mitochondrial fusion/fission, oxidative phosphorylation, biogenesis in podocytes after exposure to inorganic mercury（HgCl2）. We will evaluate mitochondrial function and cAMP/PKA signaling in inorganic mercury-induced injured podocytes. We believe that these work will help us to the diagnosis, treatment and prognosis of patients with mercury poisoning-associated glomerulonephropathy.

慢性汞中毒性肾病发病率呈逐年上升趋势。传统观念认为无机汞能导致近端肾小管上皮细胞损伤。但近年研究发现，长期无机汞接触还会造成肾小球足细胞损伤。我们在患者肾脏病理研究中也证实存在明显足细胞损伤，同时体外实验证实无机汞可引起足细胞骨架结构损伤和细胞凋亡，并且发现：无机汞诱导足细胞损伤过程中，其线粒体膜电位降低，而加入cAMP/PKA激动剂可改善其损伤时的降低线粒体膜电位。为深入研究其具体的分子机制，本项目拟通过分子生物学方法，从体内和体外实验中观察无机汞对足细胞线粒体分裂/融合、氧化磷酸化及线粒体生成的影响，同时进一步观察cAMP/PKA信号通路在无机汞诱导足细胞损伤中的保护作用。本项目实施可让我们进一步了解无机汞诱导足细胞损伤的分子机制，阐明线粒体功能改变在无机汞诱导足细胞损伤中的作用，探索（cAMP/PKA信号通路）新的治疗干预靶点，为慢性汞中毒性肾病的临床治疗和提高远期预后提供新的思路。

接触无机汞导致的肾病发病率逐渐增加，肾活检病理及体外实验均证实汞中毒相关肾损害时存在明显的肾小球足细胞损伤，但其分子机制尚不清楚。我们前期工作发现无机汞诱导足细胞损伤过程中，其线粒体膜电位降低，而加入cAMP/PKA激动剂可逆转上述损伤。为深入研究无机汞对足细胞损伤的分子机制，本研究通过分子生物学方法，从体内外实验中观察无机汞对足细胞线粒体功能的影响，同时进一步观察cAMP/PKA信号通路在无机汞诱导足细胞损伤中的保护作用。我们的体外研究发现，氯化汞诱导足细胞骨架结构损伤和足细胞相关蛋白neprin，podocin和CD2AP表达异常。随着氯化汞浓度增加，足细胞活性下降，凋亡逐渐增加。cAMP/PKA信号介导了氯化汞诱导的足细胞相关蛋白及线粒体损伤过程，pCPT（PKA激动剂）抑制氯化汞诱导的足细胞损伤，改善线粒体数量、形态及功能。实验动物体内研究发现，伴随着足细胞相关蛋白nephrin和podocin表达下降，氯化汞可诱导大鼠肾皮质线粒体内氧化应激指标（MDA含量、Mn-SOD活力）表达异常。因此我们认为，无机汞诱导的足细胞损伤过程中，cAMP/PKA信号通路介导的线粒体功能异常起了重要作用。针对cAMP/PKA信号通路的干预可能成为无机汞中毒性肾病治疗的新思路。