Methylmercury Decreases AMPA Receptor Subunit GluA2 Levels in Cultured Rat Cortical Neurons

Methylmercury (MeHg) is a well-known environmental pollutant that has harmful effects on the central nervous systems of humans and animals. The molecular mechanisms of MeHg-induced neurotoxicity at low concentrations are not fully understood. Here, we investigated the effects of low-concentration MeHg on the cell viability, Ca²⁺ homeostasis, and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunit GluA2 levels, which determine Ca²⁺ permeability of AMPA receptors, in rat primary cortical neurons. Exposure of cortical neurons to 100 and 300 nM MeHg for 7 d resulted in a decrease in GluA2 levels, an increase in basal intracellular Ca²⁺ concentration, increased phosphorylation levels of extracellular signal-regulated kinase (ERK)1/2 and p38, and decreased cell viability. Moreover, glutamate stimulation exacerbated the decrease in cell viability and increased intracellular Ca²⁺ levels in MeHg-treated neurons compared to control neurons. MeHg-induced neuronal cell death was ameliorated by 1-naphthyl acetyl spermine, a specific antagonist of Ca²⁺-permeable, GluA2-lacking AMPA receptors. Our findings raise the possibility that decreased neuronal GluA2 levels and the subsequent increase in intracellular Ca²⁺ concentration may contribute to MeHg-induced neurotoxicity.