Effect of Glutathione on Apoptosis Induced by Methyl Mercury Chloride

Youm, Jung Ho; Koh, Dai Ha; Kwon, Keun Sang; Lee, Me Yae

Abstract

OBJECTIVES
This study was performed to evaluate the critical role of glutathione(GSH) in methyl mercury chloride(MeHgCl)induced cell apoptosis.
METHODS
The effect of GSH in MeHgCl induced cell apoptosis was observed in mouse macrophage-derived RAW 264.7 cells in vitro. The cells were cultured in Dulbecco's modified Eagle's medium(DMEM).
RESULTS
MeHgCl exerted a dose dependent cytotoxicity,as demonstrated by the MTT assay, which is an assay dependent partially on the mitochondrial function. Moreover, in the presence of NAC, a GSH precursor, the MeHgCl induced cytotoxicity was significantly decreased whereas BSO, a specific GSH synthesis inhibitor,increased the MeHgCl induced cytotoxicity.The MeHgCl induced DNA fragmentation and chromatin condensation was consistent with the morphological alterations. The MeHgCl treated cells exhibited increasing annexin V-FITC binding to the phos-phatidylserine(PS)translocated from the inner to the outer leaflet of the plasma membrane and those cells with NAC pretreatment significantly exhibited decreasing annexin V-FITC binding compared to the cells treated with MeHgCl only. However BSO pretreatment markedly exhibited the increasing annexin V-FITC binding. The MeHgCl treated cells generated ROS, which was evidenced by the oxidation of dihydroethidine and the generation of the fluorescent product, ethidium. In addition, BSO pretreatment further enhanced the extent of ROS generation caused by MeHgCl whereas NAC pretreatment decreased the amount of ROS generation. MeHgCl led to a dose dependent decrease in the GSH content. Although MeHgCl exposure significantly reduced the GSH level, those cells that had a NAC pretreatment contained a higher level of GSH compared to the cells treated with MeHgCl only. In contrast, BSO pretreatment futher enhanced the extent of GSH depletion caused by MeHgCl.
CONCLUSIONS
These results indicate that MeHgCl reduced the GSH content and impaired the defense against oxidative damage caused by ROS formation in RAW 264.7 cells. It is possible that these factors leads to the activation of the apoptosis signaling pathway. Ultimately these results suggest that GSH plays a crucial role in protecting the activity against MeHgCl induced apoptosis.