Cooperative interaction between ascorbate and glutathione during mitochondrial impairment in mesencephalic cultures

Abstract

A decrease in total glutathione, and aberrant mitochondrial bioenergetics have been implicated in the pathogenesis of Parkinson's disease. Our previous work exemplified the importance of glutathione (GSH) in the protection of mesencephalic neurons exposed to malonate, a reversible inhibitor of mitochondrial succinate dehydrogenase/complex II. Additionally, reactive oxygen species (ROS) generation was an early, contributing event in malonate toxicity. Protection by ascorbate was found to correlate with a stimulated increase in protein-glutathione mixed disulfide (Pr-SSG) levels. The present study further examined ascorbate-glutathione interactions during mitochondrial impairment. Depletion of GSH in mesencephalic cells with buthionine sulfoximine potentiated both the malonate-induced toxicity and generation of ROS as monitored by dichlorofluorescein diacetate (DCF) fluorescence. Ascorbate completely ameliorated the increase in DCF fluorescence and toxicity in normal and GSH-depleted cultures, suggesting that protection by ascorbate was due in part to upstream removal of free radicals. Ascorbate stimulated Pr-SSG formation during mitochondrial impairment in normal and GSH-depleted cultures to a similar extent when expressed as a proportion of total GSH incorporated into mixed disulfides. Malonate increased the efflux of GSH and GSSG over time in cultures treated for 4, 6 or 8 h. The addition of ascorbate to malonate-treated cells prevented the efflux of GSH, attenuated the efflux of GSSG and regulated the intracellular GSSG/GSH ratio. Maintenance of GSSG/GSH with ascorbate plus malonate was accompanied by a stimulation of Pr-SSG formation. These findings indicate that ascorbate contributes to the maintenance of GSSG/GSH status during oxidative stress through scavenging of radical species, attenuation of GSH efflux and redistribution of GSSG to the formation of mixed disulfides. It is speculated that these events are linked by glutaredoxin, an enzyme shown to contain both dehydroascorbate reductase as well as glutathione thioltransferase activities.

Efficacy of Antioxidant Treatment in Reducing Resistin Serum Levels: A Randomized Study

“…In the experimental group, NT levels were significantly reduced after the supplementation, while a very slight increase was evident in the control group. These changes might be due to the direct protective antioxidant effect of vitamin C. Ascorbic acid could stimulate reduced glutathione synthesis, and, thus, might be responsible for the statistically significant incremental increase in its levels found in the experimental group [40]. …”

The interplay between iron accumulation, mitochondrial dysfunction, and inflammation during the execution step of neurodegenerative disorders

“…IRP1 activation leads to increased DMT1 and TfR1 expression (Lee et al, 2009; Mena et al, 2011) [3] and the ensuing iron accumulation (Asenjo, 1968; Dexter et al, 1987; Faucheux et al, 2003; Michaeli et al, 2007) [4]. Increased ROS and increased redox-active iron promotes the consumption of intracellular reductants such as GSH and ascorbate (Perry et al, 1982; Ehrhart and Zeevalk, 2003; Núñez et al, 2004; Jomova et al, 2010) [5], resulting in a further decrease in mitochondrial activity and ISC synthesis (Harley et al, 1993; Gu et al, 1998b; Jha et al, 2000; Chinta et al, 2007; Danielson et al, 2011). Another input to this cycle is contributed by inflammatory cytokines liberated by activated microglia and astrocytes (Mogi et al, 1994) [6], which enhance mitochondrial dysfunction (Tatsumi et al, 2000; Xie et al, 2004; Hunter et al, 2007; Djafarzadeh et al, 2011) [7], increase ROS production (Grzybicki et al, 1996) [8] and increase iron accumulation by modifying the expression of the iron transporters DMT1 and FPN1 (Urrutia et al, 2013; Wang et al, 2013) [9].…”

Restorative potential of dopaminergic grafts in presence of antioxidants in rat model of Parkinson's disease

“…Their depletion has been shown to cause inability to scavenge free radicals resulting in lipid peroxidation (Nakamura et al, 2000). Recently a co-operative interaction between these two antioxidants has been reported on the event of oxidative stress where it has been shown that under such conditions AA promotes the glutathionylation of protein and hence helps in maintaining cellular GSH/GSSG redox environment and together can provide a useful strategy to protect against free radical mediated oxidative stress (Choi et al, 2000;Ehrhart and Zeevalk, 2003). In the present study the effect of VMC and GSH + AA cotransplantation was investigated in 6-OHDA lesioned rat model of PD.…”

“…Both of these are major cellular antioxidants, required for the normal cell functioning and participate in various enzymatic and non-enzymatic processes that protect cells against oxidative stress (Machlin and Bendich, 1987;Dringen and Hirrlinger, 2003) and have been reported to act co-operatively in such conditions (Ehrhart and Zeevalk, 2003). Further, an insufficiency in antioxidant defence could be highly damaging to dopamine neurons.…”