Acute exposure of Drosophila melanogaster to paraquat causes oxidative stress and mitochondrial dysfunction.

Paraquat (PQ; 1, 1'-dimethyl-4-4'-bipyridinium), an herbicide and model neurotoxicant, is identified to be one of the prime risk factors in Parkinson's disease (PD). In the Drosophila system, PQ is commonly used to measure acquired resistance against oxidative stress (PQ resistance test). Despite this, under acute PQ exposure, data on the oxidative stress response and associated impact on mitochondria among flies is limited. Accordingly, in this study, we measured markers of oxidative stress and mitochondrial dysfunctions among adult male flies (8-10 days old) exposed to varying concentrations of PQ (10, 20, and 40 mM in 5% sucrose solution) employing a conventional filter disc method for 24 h. PQ exposure resulted in significant elevation in the levels of oxidative stress biomarkers (malondialdehyde: 43% increase: hydroperoxide: 32-39% increase), with concomitant enhancement in reduced glutathione and total thiol levels in cytosol. Higher activity of antioxidant enzymes were also evident along with increased free iron levels. Furthermore, PQ exposure caused a concentration-dependent increase in mitochondrial superoxide generation and activity of manganese-superoxide dismutase (Mn-SOD). The activity levels of complex I-III, complex II-III, and Mg+2 adinosine triphosphatase (ATPase) were also decreased significantly. A robust diminution in the activity of succinate dehydrogenase and moderate decline in the citrate synthase activity suggested a specific effect on citric acid cycle enzymes. Collectively, these data suggest that acute PQ exposure causes significant oxidative stress and mitochondrial dysfunction among flies in vivo. It is suggested that in various experimental settings, while conducting the "PQ resistance stress test" incorporation of selected biochemical end points is likely to enhance the quality of the data.

Hosamani R ，Muralidhara 《-》

Prophylactic treatment with Bacopa monnieri leaf powder mitigates paraquat-induced oxidative perturbations and lethality in Drosophila melanogaster.

Hosamani R ，Muralidhara 《INDIAN JOURNAL OF BIOCHEMISTRY & BIOPHYSICS》

Longterm melatonin administration alleviates paraquat mediated oxidative stress in Drosophila melanogaster.

Medina-Leendertz S ，Paz M ，Mora M ，Bonilla E ，Bravo Y ，Arcaya JL ，Terán R ，Villalobos V ... -  《INVESTIGACION CLINICA》

Evidence of neuroprotective effects of saffron and crocin in a Drosophila model of parkinsonism.

Evidence suggests that saffron and its major bioactives exhibit significant neuromodulatory effects in various animal models. However, specific data related to their efficacy to attenuate oxidative stress and neurotoxicity in animal models of Parkinson's disease (PD) are limited. Hence, we investigated the neuroprotective efficacy of saffron methanolic extract (SME) and its active constituent, crocin (CR) employing a Drosophila model of parkinsonism. We focussed on attenuation of Rotenone (ROT)-induced locomotor phenotype, oxidative stress, mitochondrial dysfunction and neurotoxicity in this model. SME and CR-enrichment significantly reduced ROT (500μM) induced mortality, rescued the locomotor phenotype and diminished the enhanced levels of oxidative stress markers in head/body regions of flies. The reduced levels of reduced glutathione (GSH) and total thiols (TSH) resulting from ROT exposure were significantly restored with concomitant enhancement of the antioxidant enzymes activities. Further, ROT-induced mitochondrial dysfunctions (MTT reduction, activities of SDH and NADH-Cyt C reductase (complexes I-III) enzymes) were markedly attenuated by SME/CR enrichment. While ROT elevated the activity of acetylcholinesterase (AChE) in head/body regions, both the treatments caused marked diminution of AChE activity and restored the dopamine levels suggesting their effectiveness to mitigate cholinergic function. Interestingly, SME/CR enrichment significantly delayed the onset of locomotor deficits and extended life span of flies among ROT (50μM)-stressed flies. In a satellite study, flies provided with SME/CR prophylaxis exhibited marked resistance to an acute Paraquat (PQ) challenge as evidenced by the lower incidence of lethality and improved locomotor phenotype. Taken together, the neuroprotective effects of saffron and crocin in the fly model may be largely attributable to its antioxidant action. Based on our findings, we propose that saffron may be exploited as a supplementary therapeutic agent in PD and other oxidative stress mediated neurodegenerative conditions.

Rao SV ，Muralidhara ，Yenisetti SC ，Rajini PS ... -  《-》

Protective role of glutathione reductase in paraquat induced neurotoxicity.

Paraquat (PQ), a widely used herbicide is a well-known free radical producing agent. The mechanistic pathways of PQ neurotoxicity were examined by assessing oxidative/nitrosative stress markers. Focus was on the role of glutathione (GSH) cycle and to examine whether the pre-treatment with enzyme glutathione reductase (GR) could protect the vulnerable brain regions (VBRs) against harmful oxidative effect of PQ. The study was conducted on Wistar rats, randomly divided in five groups: intact-control group, (n = 8) and four experimental groups (n = 24). All tested compounds were administered intrastriatally (i.s.) in one single dose. The following parameters of oxidative status were measured in the striatum, hippocampus and cortex, at 30 min, 24 h and 7 days post treatment: superoxide anion radical (O₂·⁻), nitrate (NO₃⁻), malondialdehyde (MDA), superoxide dismutase (SOD), total GSH (tGSH) and its oxidized, disulfide form (GSSG) and glutathione peroxidase (GPx). Results obtained from the intact and the sham operated groups were not statistically different, confirming that invasive i.s. route of administration would not influence the reliability of results. Also, similar pattern of changes were observed between ipsi- and contra- lateral side of examined VBRs, indicating rapid spatial spreading of oxidative stress. Mortality of the animals (10%), within 24h, along with symptoms of Parkinsonism, after awakening from anesthesia for 2-3 h, were observed in the PQ group, only. Increased levels of O₂·⁻, NO₃⁻ and MDA, increased ratio of GSSG/GSH and considerably high activity of GPx were measured at 30 min after the treatment. Cytotoxic effect of PQ was documented by drastic drop of all measured parameters and extremely high peak of the ratio GSSG/GSH at 24th hrs after the PQ i.s. injection. In the GR+PQ group, markedly low activity of GPx and low content of NO₃⁻ (in striatum and cortex) were measured during whole experiment, while increase value was observed only for O₂·⁻, at 7th days. We concluded that oxidative/nitrosative stress and excitotoxicity are the most important events since the early stage of PQ induced neurotoxicity. Based on the ratio GSSG/GSH, the oxidation of GSH to GSSG is probably dominant way of GHS depletion and main reason for reduced antioxidative defense against PQ harmful oxidative effect. The GR pre-treatment resulted in the absence of Parkinson's disease-like symptoms and mortality of the rats. Additionally, oxidative/nitrosative stress did not developed, as well as almost diminished metabolism of the VBRs at 24th hours (as has been documented in the PQ group) did not occurred in the GR+PQ, suggesting a neuroprotective role for the GR in PQ induced neurotoxicity.

Djukic MM ，Jovanovic MD ，Ninkovic M ，Stevanovic I ，Ilic K ，Curcic M ，Vekic J ... -  《-》