Enhancement of endogenous glutathione and NQO1 by triterpenoid CDDO-Im in SH-SY5Y cells: protection against neurotoxicant-mediated cytotoxicity

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Adam M. Speen (Creator)
The University of North Carolina at Greensboro (UNCG )
Web Site: http://library.uncg.edu/
Zhenquan Jia

Abstract: Evidence suggests oxidative and electrophilic stress as a major factor contributing to the neuronal cell death in neurodegenerative disorders, especially Parkinson's disease (PD). Early depletion in the levels of thiol antioxidant glutathione (GSH), which may lead to generation of reactive oxygen species, is an important biochemical feature of PD. However, whether induction of endogenous antioxidative enzymes by a novel triterpenoid CDDO-Im (2-cyano-3,12 dioxooleana-1,9 dien-28-oyl imidazoline) affords protection against oxidative and electrophilic neurocytotoxicity has not been carefully investigated. Retinoic acid-induced differentiation of human neuroblastoma SH-SY5Y cells are known to possess properties of mature neurons and thus have been widely used in vitro model for the study of neurotoxicity and neuroprotection. In this study, we showed that incubation of retinoic acid-induced differentiation of human neuroblastoma SH-SY5Y cells with nanomolar concentrations of CDDO-IM (1- 400 nM) for 24 h resulted in significant increased in the levels of reduced glutathione (GSH) and NAD(P)H:quinone oxidoreductase 1 (NQO1), two critical cellular defenses in detoxification of reactive oxygen species and electrophilic quinone molecules. Pretreatment of the cells with CDDO-IM was found to afford remarkable protection against the neurocytotoxicity elicited by 4-hydroxynonenal, 3-morpholinosynonimine hydrochloride, xanthine oxidase/xanthine, and hydrogen peroxide. When studied using Buthionine Sulphoximine (BSO), a known GSH inhibitor, in the presence of acrolein CDDO-IM treatment no longer induces such remarkable protection. Taken together, this study demonstrates for the first time that CDDO-IM potently induces the cellular GSH system and NQO1 in retinoic acid-induced differentiation of human neuroblastoma SH-SY5Y cells, which is accompanied by dramatically increased resistance of these cells to the damage induced by various neurotoxicants. The results of this study may have important implications for the development of novel neuroprotective strategies. Acrolein is a ubiquitous unsaturated aldehyde product occurring in the combustion of organic matter including exhausts and pollutants. A product of lipid peroxidation, acrolein has been implicated in the pathogenesis of various neurological disorders including Parkinson's disease where acrolein-protein adducts have been observed in post mortem studies. However, limited study has been conducted into potential therapeutic protection against acrolein-induced cytotoxicity in neuronal cells via upregulation of cellular aldehyde-detoxification defenses. In this study we have utilized RA-differentiated human SH-SY5Y neuroblastoma cells to investigate the induction of glutathione (GSH), glutathione-s-transferase (GST), and aldose reductase (AR) by the synthetic triterpenoid 2-Cyano-3,12-dixooleana-1,9-dien-28-imidazolide (CDDO-Im); and the protective effects CDDO-Im mediated antioxidant defenses on acrolein-induced toxicity. Incubation of RA-differentiated SH-SY5Y cells with CDDO-Im (100nM) resulted in a significant increase in cellular GSH but not GST or AR. Acrolein exposure (40µM) to RA-differentiated SH-SY5Y cells resulted in a significant time dependent depletion of cellular GSH preceding a reduction in cell viability and LDH release. Pretreatment of the cells with 100nM CDDO-Im afforded a dramatic protection against acrolein-induced cytotoxicity as assessed by lactate dehydrogenase relase (LDH), 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium (MTT) reduction, and morphological changes. Further, we demonstrate the predominance of cellular GSH in protection against acrolein-induced cytotoxicity. Buthionine sulfoximine (BSO) at 25µM dramatically depleted GSH and significantly potentiated acrolein-induced cytotoxicity. Pretreatment of RA-differentiated SH-SY5Y cells with both 25µM BSO and 100nM CDDO was found to prevent the CDDO-Im mediated GSH induction and partially reverse the cytoprotective effects of CDDO-Im treatment on acrolein-induced toxicity. Overall, this study represents for the first time the CDDO-Im mediated- up regulation of GSH is a predominant mechanism against acrolein-induced neurotoxicity.

Additional Information

Language: English
Date: 2013
Acrolein, CDDO-Im, GSH, SH-SY5Y
Triterpenoid saponins $x Therapeutic use
Antioxidants $x Physiological effect
Nervous system $x Degeneration
Molecular neurobiology

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