Methylmercury causes oxidative stress and cytotoxicity in microglia: Attenuation by 15-deoxy-delta 12, 14-Prostaglandin J₂

Abstract 

Methylmercury (MeHg) causes severe neurological disorders in the central nervous system. This study focused on the effects of MeHg on microglia, macrophage-like cells that reside in the CNS important in neuro-immune interactions. The murine N9 microglial cell line was used in this set of study. MeHg caused reactive oxygen species generation, mitochondrial depolarization and aconitase inactivation, all of which were signs of cellular oxidative stress. MeHg greatly increased microglial IL-6 secretion despite the fact that it severely inhibited protein synthesis. The concentration that caused 50% cell death in 24 h was ∼9 μM. Pretreatment of microglia with the prostaglandin derivative, 15-deoxy-delta 12, 14-Prostaglandin J₂ attenuated MeHg induced cell death. The saving effect did not appear to be mediated through activation of peroxisome proliferator activated receptors (PPAR) since other agonists of these receptors did not prevent MeHg induced microglial death.

Abbreviations: 15d-PGJ₂, 15-deoxy-delta 12, 14-Prostaglandin J₂, FCCP, carbonyl cyanide p-trifluoromethoxyphenylhydrazone, FU, fluorescence units, H₂DCF-DA, 2′, 7′-dichlorodihydrofluorescein diacetate, HBSS, Hank's Balanced Salt Solution, IL-6, interleukin-6, JC-1, 5,5′, 6,6′-tetrachloro-1, 1′, 3,3′-tetraethylbenzimidazolocarbocyanine iodide, MeHg, methylmercury, MMP, mitochondrial membrane potential (ΔΨm), MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), NADP⁺, β-nicotinamide adenine dinucleotide phosphate disodium salt, OD, optical density, PBS, phosphate buffered saline, PPARs, peroxisome proliferator-activated receptors, ROS, reactive oxygen species

Keywords: 15d-PGJ₂, Aconitase, Methylmercury, MMP (mitochondrial membrane potential), N9 microglia, Oxidative stress