Tang Weifeng, Xie Jianxun, Shaikh Zahir A
Department of Biomedical and Pharmaceutical Sciences and Center for Molecular Toxicology, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, USA.
Toxicology. 2006 Jun 15;223(3):202-8. doi: 10.1016/j.tox.2006.03.017. Epub 2006 Apr 4.
Glycine treatment is reported to protect against the nephrotoxicity of cadmium (Cd) in rats. The purpose of the present study was to explore the mechanism of this protection using a renal epithelial cell line, LLC-PK(1). The cells were incubated with 10-30 microM Cd in serum-free DMEM and cytotoxicity was evaluated by LDH leakage into the incubation medium. Under these conditions, 20 and 30 microM Cd concentrations were cytotoxic. As compared to the non-Cd-exposed cells, the LDH release was elevated more than six-fold in cells exposed to 30 microM Cd for 24h. Co-treatment with 5-50mM glycine was cytoprotective in a concentration-dependent manner. Prior treatment with 50 mM glycine for 16 h, or co-treatment for 24h, reduced LDH leakage due to 30 microM Cd exposure by 60 and 66%, respectively. Co-incubation with 50 mM alanine was also protective but only about half as effective as with glycine. During the first 4h, prior to the onset of any significant cell membrane damage, the Cd-exposed cells accumulated 0.55 microg Cd/mg protein. Glycine pre-treatment or co-treatment reduced Cd accumulation by about one-quarter or one-half, respectively. To delineate the mechanism of glycine's effect on Cd accumulation, the efflux of Cd was studied after a 30 min pulse exposure. The results suggested that pre-treatment reduced Cd accumulation by increasing its efflux from the cells. In contrast, co-treatment reduced Cd efflux, suggesting that the co-treatment lowered Cd accumulation by suppressing its uptake. When co-incubated, Cd and glycine formed a complex that was apparently responsible for the marked reduction in Cd uptake. It is concluded that, regardless of the mode of treatment, glycine is cytoprotective against Cd and that it may do so by lowering the intracellular Cd burden.
据报道，甘氨酸处理可保护大鼠免受镉（Cd）的肾毒性。本研究的目的是使用肾上皮细胞系LLC-PK(1)探索这种保护作用的机制。将细胞在无血清DMEM中与10-30微摩尔的Cd一起孵育，并通过乳酸脱氢酶（LDH）泄漏到孵育培养基中来评估细胞毒性。在这些条件下，20和30微摩尔的Cd浓度具有细胞毒性。与未暴露于Cd的细胞相比，暴露于30微摩尔Cd 24小时的细胞中LDH释放增加了六倍以上。与5-50毫摩尔甘氨酸共同处理具有浓度依赖性的细胞保护作用。用50毫摩尔甘氨酸预处理16小时或共同处理24小时，可分别将因暴露于30微摩尔Cd而导致的LDH泄漏减少60%和66%。与50毫摩尔丙氨酸共同孵育也具有保护作用，但效果仅约为甘氨酸的一半。在任何明显的细胞膜损伤开始之前的最初4小时内，暴露于Cd的细胞积累了0.55微克Cd/毫克蛋白质。甘氨酸预处理或共同处理分别将Cd积累减少了约四分之一或二分之一。为了阐明甘氨酸对Cd积累影响的机制，在30分钟脉冲暴露后研究了Cd的流出。结果表明，预处理通过增加Cd从细胞中的流出而减少了Cd积累。相反，共同处理减少了Cd流出，表明共同处理通过抑制其摄取而降低了Cd积累。当共同孵育时，Cd和甘氨酸形成了一种复合物，这显然是Cd摄取显著减少的原因。结论是，无论处理方式如何，甘氨酸对Cd都具有细胞保护作用，并且它可能通过降低细胞内Cd负荷来实现这一点。
