Methylmercury induces acute oxidative stress, altering Nrf2 protein level in primary microglial cells.
The neurotoxicity of methylmercury (MeHg) is well documented in both humans and animals. MeHg causes acute and chronic damage to multiple organs, most profoundly the central nervous system (CNS). Microglial cells are derived from macrophage cell lineage, making up approximately 12% of cells in the CNS, yet their role in MeHg-induced neurotoxicity is not well defined. The purpose of the present study was to characterize microglial vulnerability to MeHg and their potential adaptive response to acute MeHg exposure. We examined the effects of MeHg on microglial viability, reactive oxygen species (ROS) generation, glutathione (GSH) level, redox homeostasis, and Nrf2 protein expression. Our data showed that MeHg (1-5 microM) treatment caused a rapid (within 1 min) concentration- and time-dependent increase in ROS generation, accompanied by a statistically significant decrease in the ratio of GSH and its oxidized form glutathione disulfide (GSSG) (GSH:GSSG ratio). MeHg increased the cytosolic Nrf2 protein level within 1 min of exposure, followed by its nuclear translocation after 10 min of treatment. Consistent with the nuclear translocation of Nrf2, quantitative real-time PCR revealed a concentration-dependent increase in the messenger RNA level of Ho-1, Nqo1, and xCT 30 min post MeHg exposure, whereas Nrf2 knockdown greatly reduced the upregulation of these genes. Furthermore, we observed increased microglial death upon Nrf2 knockdown by the small hairpin RNA approach. Taken together, our study has demonstrated that microglial cells are exquisitely sensitive to MeHg and respond rapidly to MeHg by upregulating the Nrf2-mediated antioxidant response.
Ni
Mingwei
M
Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.
Li
Xin
X
Yin
Zhaobao
Z
Jiang
Haiyan
H
Sidoryk-Wegrzynowicz
Marta
M
Milatovic
Dejan
D
Cai
Jiyang
J
Aschner
Michael
M
D027182:Amino Acid Transport System y+ / Q000235:genetics; D026922:Amino Acid Transport Systems, Acidic; D000818:Animals; D002478:Cells, Cultured; D005978:Glutathione / Q000378:metabolism; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics; D015850:Interleukin-6 / Q000096:biosynthesis; D008767:Methylmercury Compounds / Q000633:toxicity*; D017628:Microglia / Q000187:drug effects* / Q000378:metabolism; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000235:genetics; D051267:NF-E2-Related Factor 2 / Q000032:analysis* / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley
D027182:Amino Acid Transport System y+; D026922:Amino Acid Transport Systems, Acidic; D005978:Glutathione; D006419:Heme Oxygenase (Decyclizing); D015850:Interleukin-6; D008767:Methylmercury Compounds; D016660:NAD(P)H Dehydrogenase (Quinone); D051267:NF-E2-Related Factor 2; C495637:Nfe2l2 protein, rat; C491523:Hmox1 protein, rat; C507703:NQO1 protein, rat; C000723960:Slc7a11 protein, rat