College of Animal Science and Technology, Northeast Agricultural University, Harbin 150030, PR. China.
Institute of Agricultural Quality Standards and Testing Technology, Xinjiang Academy of Agricultural Sciences, Urumqi 830091, PR. China.
Aquat Toxicol. 2023 Aug;261:106570. doi: 10.1016/j.aquatox.2023.106570. Epub 2023 May 17.
Toxic effect of heavy metal cadmium (Cd) on fish kidneys had been reported. Mitochondrion is an important organelle for maintaining kidney function, while its role in Cd-induced kidney injury in common carp remained unclarified. In this experiment, we established a poisoning model of common carp with Cd exposure (0.26 mg/L) for 15, 30, and 45 days. Serum biochemistry determination, histological observation, TUNEL assay, qRT-PCR, Western blot, and integrated biomarker response (IBR) were applied to assess the nephrotoxicity of Cd to common carp. Our results displayed that Cd exposure increased the levels of serum biochemical indexes (UREA, CRE, and UA), indicating kidney injury. We further revealed via histological observation that Cd damaged structural integrity of kidneys, as evidenced by renal glomerulus and renal tubular injury, hallmark phenotypes of apoptosis, and mitochondrial damage, suggesting that mitochondria damage and apoptosis were involved in Cd-induced kidney injury. Moreover, Cd exposure decreased ATPase (Na/K-ATPase, Ca-ATPase, Mg-ATPase, and CaMg-ATPase) activities as well as PGC-1a and Mfn2 levels, while increased Drp1 and PINK1 levels as well as LC3-II/LC3-I ratio, which indicated that Cd-impaired renal energy metabolism was related to mitochondrial dysfunction. Additionally, we found that Cd induced oxidative stress (abnormal levels of SOD, CAT, GPX, MDA, and HO) in kidneys, which was involved in triggering mitochondrial dysfunction and further impairing mitochondrial energy metabolism. Moreover, the occurrence of mitochondria-dependent apoptosis was found after Cd-exposure in common carp kidneys, as indicated by enhanced levels of Bax, CytC, APAF1, Caspase-9, and Caspase-3, while declined level of Bcl-2. Subsequently, we confirmed a time-dependent nephrotoxicity of Cd to common carp via IBR assessment. In conclusion, Cd induced time-dependent nephrotoxicity in common carp via mitochondrial pathway. This mitochondria-oriented study shed light on underlying mechanisms of Cd-induced renal pathologies and provided a theoretical basis for evaluating Cd toxicity to aquatic organisms.
重金属镉(Cd)对鱼类肾脏的毒性作用已有报道。线粒体是维持肾脏功能的重要细胞器,但其在鲤鱼镉诱导肾损伤中的作用尚不清楚。在本实验中,我们建立了鲤鱼镉暴露(0.26mg/L)15、30 和 45 天的中毒模型。采用血清生化测定、组织学观察、TUNEL 检测、qRT-PCR、Western blot 和整合生物标志物响应(IBR)评估 Cd 对鲤鱼的肾毒性。结果显示,Cd 暴露增加了血清生化指标(UREA、CRE 和 UA)的水平,表明肾脏损伤。通过组织学观察进一步发现,Cd 破坏了肾脏的结构完整性,表现为肾小球和肾小管损伤、凋亡的标志性表型以及线粒体损伤,提示线粒体损伤和凋亡参与了 Cd 诱导的肾脏损伤。此外,Cd 暴露降低了 ATP 酶(Na/K-ATPase、Ca-ATPase、Mg-ATPase 和 CaMg-ATPase)的活性以及 PGC-1a 和 Mfn2 的水平,同时增加了 Drp1 和 PINK1 的水平以及 LC3-II/LC3-I 比值,表明 Cd 损害肾脏能量代谢与线粒体功能障碍有关。此外,我们发现 Cd 诱导肾脏氧化应激(SOD、CAT、GPX、MDA 和 HO 异常水平),这涉及触发线粒体功能障碍并进一步损害线粒体能量代谢。此外,在鲤鱼肾脏中发现了 Cd 暴露后线粒体依赖性细胞凋亡的发生,表现为 Bax、CytC、APAF1、Caspase-9 和 Caspase-3 水平升高,而 Bcl-2 水平降低。随后,我们通过 IBR 评估证实了 Cd 对鲤鱼的时间依赖性肾毒性。综上所述,Cd 通过线粒体途径诱导鲤鱼时间依赖性肾毒性。这项以线粒体为导向的研究揭示了 Cd 诱导肾脏病变的潜在机制,并为评估 Cd 对水生生物的毒性提供了理论依据。