Original Contribution
Multiple roles of microsomal glutathione transferase 1 in cellular protection: A mechanistic study

https://doi.org/10.1016/j.freeradbiomed.2010.08.013Get rights and content

Abstract

The aim of this study was to investigate the involvement of membrane-bound microsomal glutathione transferase 1 (MGST1) in cellular resistance against oxidative stress as well as its mechanism of protection. MGST1 is ubiquitously expressed and predominantly located in the endoplasmic reticulum and outer mitochondrial membrane. Utilizing MCF7 cells overexpressing MGST1 we show significant protection against agents that are known to induce lipid peroxidation (e.g., cumene hydroperoxide and tert-butylhydroperoxide) and an end-product of lipid peroxidation (e.g., 4-hydroxy-2-nonenal). Furthermore, our results demonstrate that MGST1 protection can be enhanced by vitamin E when toxicity depends on oxidative stress, but not when direct alkylation is the dominant mechanism. Mitochondria in MGST1-overexpressing cells were shown to be protected from oxidative insult as measured by calcium loading capacity and respiration. MGST1 induces cellular resistance against cisplatin. Here we used vitamin E to elucidate whether oxidative stress caused by cisplatin is significant for cell toxicity. The results indicate that oxidative stress and induction of lipid peroxidation are not the most prominent toxic mechanism of cisplatin in our cell system. We thus conclude that MGST1 protects cells (and mitochondria) by both conjugation and glutathione peroxidase functions. A new protective mechanism against cisplatin is also indicated.

Section snippets

Chemicals

All cell culture media and their ingredients were obtained from GIBCO BRL (Midlothian, UK). Geneticin (G418) was purchased from GE Healthcare. CuOOH was obtained from Merck. ECL kit was from Amersham Biosciences. Tert-butylhydroperoxide (BuOOH) was obtained from Riedel de Haёn (Germany). 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT), dimethyl sulfoxide (DMSO), EDTA, HNE, α-tocopheryl acetate (vitamin E), and formaldehyde were all purchased from Sigma–Aldrich (St. Louis, MO,

MGST1 protects cells from lipophilic hydroperoxides

We, and others, have previously shown that MGST1 can protect cells from oxidative stress induced by hydrogen peroxide, CuOOH, or oxidized docosahexaenoic acid [22], [23]. Here we extend these findings by comparing the cellular effects of CuOOH and BuOOH, which are both substrates for MGST1. The latter, however, displays fivefold lower specific activity (data not shown). We find that MGST1 efficiently protects cells from both these organic hydroperoxides (comparing overexpressing cells to vector

Conclusion

This study shows that MGST1 is important in protecting cells and that the protection occurs by multiple mechanisms (Fig. 7). We show that MGST1-overexpressing cells are protected against substrates (CuOOH, HNE), poor substrates (BuOOH), and nonsubstrates (cisplatin). We suggest that MGST1 protects cells by direct reduction of toxicants (CuOOH/BuOOH) and downstream protection against lipid peroxidation (CuOOH/BuOOH) as well as against a toxic end-product of lipid peroxidation (HNE) by direct

Acknowledgments

This study was supported by the Swedish Research Council, AstraZeneca, and funds from the Karolinska Institutet.

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