Graduate School of Environmental Science, Hokkaido University, Sapporo, 060-0810, Japan.
Faculty of Environmental Earth Science, Hokkaido University, Sapporo, 060-0810, Japan; Department of Environmental Science, Jahangirnagar University, Dhaka, 1342, Bangladesh.
Ecotoxicol Environ Saf. 2020 Apr 1;192:110238. doi: 10.1016/j.ecoenv.2020.110238. Epub 2020 Feb 6.
Mercury (Hg) is an extremely dangerous environmental contaminant, responsible for human diseases including neurological disorders. However, the mechanisms of inorganic Hg (iHg)-induced cell death and toxicity are little known. Dihydrolipoic acid (DHLA) is the reduced form of a naturally occurring compound lipoic acid, which act as a potent antioxidant through multiple mechanisms. So we hypothesized that DHLA has an inhibitory role on iHg-cytotoxicity. The purposes of this research were to investigate mechanism/s of cytotoxicity of iHg, as well as, the cyto-protection of DHLA against iHg induced toxicity using PC12 cells. Treatment of PC12 cells with HgCl (Hg) (0-2.5 μM) for 48 h resulted in significant toxic effects, such as, cell viability loss, high level of lactate dehydrogenase (LDH) release, DNA damage, cellular glutathione (GSH) level decrease and increased Hg accumulation. In addition, protein level expressions of akt, p-akt, mTOR, GR, NFkB, ERK1, Nrf2 and HO-1 in cells were downregulated; and cleaved caspase 3 and cytochrome c release were upregulated after Hg (2.5 μM) exposure and thus inducing apoptosis. Hginduced apoptosis was also confirmed by flow cytometry. However, pretreatment with DHLA (50 μM) for 3 h before Hg (2.5 μM) exposure showed inhibition against iHg-induced cytotoxicity by reversing cell viability loss, LDH release, DNA damage, GSH decrease and inhibiting Hg accumulation. Moreover, DHLA pretreatment reversed the protein level expressions of akt, p-akt, mTOR, GR, NFkB, ERK1, Nrf2, HO-1, cleaved caspase 3 and cytochrome c. In conclusion, results showed that DHLA could attenuate Hg-induced cytotoxicity via limiting Hg accumulation, boosting up of antioxidant defense, and inhibition of apoptosis in cells.
汞（Hg）是一种极其危险的环境污染物，可导致包括神经紊乱在内的人类疾病。然而，无机汞（iHg）诱导细胞死亡和毒性的机制知之甚少。二氢硫辛酸（DHLA）是一种天然存在的化合物硫辛酸的还原形式，通过多种机制发挥强大的抗氧化作用。因此，我们假设 DHLA 对 iHg 细胞毒性具有抑制作用。本研究的目的是探讨 iHg 细胞毒性的机制，以及 DHLA 对 iHg 诱导毒性的细胞保护作用，使用 PC12 细胞进行研究。用 HgCl（Hg）（0-2.5 μM）处理 PC12 细胞 48 h 会导致明显的毒性作用，如细胞活力丧失、高水平的乳酸脱氢酶（LDH）释放、DNA 损伤、细胞内谷胱甘肽（GSH）水平下降和 Hg 积累增加。此外，Hg（2.5 μM）暴露后细胞中 akt、p-akt、mTOR、GR、NFkB、ERK1、Nrf2 和 HO-1 的蛋白水平表达降低，并且 cleaved caspase 3 和细胞色素 c 释放增加，从而诱导细胞凋亡。Hg 诱导的细胞凋亡也通过流式细胞术得到证实。然而，在 Hg（2.5 μM）暴露前用 DHLA（50 μM）预处理 3 h 可通过逆转细胞活力丧失、LDH 释放、DNA 损伤、GSH 减少和抑制 Hg 积累来抑制 iHg 诱导的细胞毒性。此外，DHLA 预处理逆转了 akt、p-akt、mTOR、GR、NFkB、ERK1、Nrf2、HO-1、cleaved caspase 3 和细胞色素 c 的蛋白水平表达。总之，结果表明 DHLA 可通过限制 Hg 积累、增强抗氧化防御和抑制细胞凋亡来减轻 Hg 诱导的细胞毒性。
