Department of Pharmacology and Toxicology, Rutgers University Ernest Mario School of Pharmacy, Piscataway, New Jersey (X.W., D.K., L.M.A.); Environmental and Occupational Health Sciences Institute, Rutgers University, Piscataway, New Jersey (X.W., R.Z., C.D., B.B., E.B., L.M.A.); and Department of Biostatistics and Epidemiology, Rutgers School of Public Health, Piscataway, New Jersey (R.Z., E.B.).
Department of Pharmacology and Toxicology, Rutgers University Ernest Mario School of Pharmacy, Piscataway, New Jersey (X.W., D.K., L.M.A.); Environmental and Occupational Health Sciences Institute, Rutgers University, Piscataway, New Jersey (X.W., R.Z., C.D., B.B., E.B., L.M.A.); and Department of Biostatistics and Epidemiology, Rutgers School of Public Health, Piscataway, New Jersey (R.Z., E.B.)
Drug Metab Dispos. 2021 Aug;49(8):629-637. doi: 10.1124/dmd.121.000446. Epub 2021 Jun 1.
Exposure to the environmental pollutant cadmium is ubiquitous, as it is present in cigarette smoke and the food supply. Over time, cadmium enters and accumulates in the kidneys, where it causes tubular injury. The breast cancer resistance protein (BCRP, ATP-Binding Cassette G2 ) is an efflux transporter that mediates the urinary secretion of pharmaceuticals and toxins. The genetic variant Q141K exhibits altered membrane trafficking that results in reduced efflux of BCRP substrates. Here, we sought to 1) evaluate the in vitro and in vivo ability of BCRP to transport cadmium and protect kidney cells from toxicity and 2) determine whether this protection is impaired by the Q141K variant. Cadmium concentrations, cellular stress, and toxicity were quantified in human embryonic kidney 293 cells expressing an empty vector (EV), BCRP wild-type (WT), or variant (Q141K) gene. Treatment with CdCl resulted in greater accumulation of cadmium and apoptosis in EV cells relative to WT cells. Exposure to CdCl induced expression of stress-related genes and proteins including MT-1A/MT-2A, NAD(P)H quinone dehydrogenase 1, and heme oxygenase-1 to a higher extent in EV cells compared with WT cells. Notably, the Q141K variant protected against CdCl-induced activation of stress genes and cytotoxicity, but this protection was to a lesser magnitude than observed with WT BCRP. Lastly, concentrations of cadmium in the kidneys of Bcrp knockout mice were 40% higher than in WT mice, confirming that cadmium is an in vivo substrate of BCRP. In conclusion, BCRP prevents the accumulation of cadmium and protects against toxicity, a response that is impaired by the Q141K variant. SIGNIFICANCE STATEMENT: The breast cancer resistance protein transporter lowers cellular accumulation of the toxic heavy metal cadmium. This protective function is partially attenuated by the Q141K genetic variant in the gene.
镉作为一种环境污染物无处不在，它存在于香烟烟雾和食物供应中。随着时间的推移，镉进入并积累在肾脏中，导致肾小管损伤。乳腺癌耐药蛋白（BCRP，ATP 结合盒 G2）是一种外排转运体，可介导药物和毒素的尿分泌。基因变异 Q141K 表现出改变的膜转运，导致 BCRP 底物的外排减少。在这里，我们试图 1）评估 BCRP 在体外和体内运输镉的能力，并保护肾脏细胞免受毒性，2）确定这种保护是否因 Q141K 变异而受损。在表达空载体 (EV)、BCRP 野生型 (WT) 或变异体 (Q141K) 基因的人胚肾 293 细胞中定量测定镉浓度、细胞应激和毒性。与 WT 细胞相比，CdCl 处理导致 EV 细胞中镉的积累和凋亡增加。与 WT 细胞相比，EV 细胞中应激相关基因和蛋白质（包括 MT-1A/MT-2A、NAD(P)H 醌脱氢酶 1 和血红素加氧酶-1）的表达在 CdCl 诱导下显著升高。值得注意的是，与 WT BCRP 相比，Q141K 变异体可防止 CdCl 诱导的应激基因激活和细胞毒性。最后，BCRP 敲除小鼠肾脏中的镉浓度比 WT 小鼠高 40%，证实镉是 BCRP 的体内底物。总之，BCRP 可防止镉的积累并防止毒性，而 Q141K 变异部分削弱了这种保护作用。
