Ribose-cysteine and levodopa abrogate Parkinsonism via the regulation of neurochemical and redox activities in alpha-synuclein transgenic Drosophila melanogaster models

Abstract

Parkinson's disease (PD), the most prevalent type of parkinsonism, is a progressive neurodegenerative condition marked by several non-motor and motor symptoms. PD is thought to have a complex aetiology that includes a combination of age, genetic predisposition, and environmental factors. Increased expression of α-synuclein (α-Syn) protein is central to the evolvement of neuropathology in this devastating disorder, but the potential of ribose-cysteine and levodopa in abating pathophysiologic changes in PD model is unknown. Crosses were set up between flies conditionally expressing a pathological variant of human α-Syn (UAS-α-Syn) and those expressing GAL4 in neurons (elav-GAL4) to generate offspring referred to as PD flies. Flies were randomly assigned to five groups (n = 40) from the total population of flies, with each group having five replicates. Groups of PD flies were treated with either 500 mg/kg ribose-cysteine diet, 250 mg/kg levodopa diet, or a combination of the two compounds for 21 days, whereas the control group (w¹¹¹⁸) and the PD group were exposed to a diet without ribose-cysteine or levodopa. In addition to various biochemical and neurochemical assays, longevity, larval motility, and gravitaxis assays were carried out. Locomotive capability, lifespan, fecundity, antioxidant state, and neurotransmitter systems were all significantly (p < 0.05) compromised by overexpression of α-Syn. However, flies treated both ribose cysteine and levodopa showed an overall marked improvement in motor functions, lifespan, fecundity, antioxidant status, and neurotransmitter system functions. In conclusion, ribose-cysteine and levodopa, both singly and in combination, potentiated a therapeutic effect on alpha-synuclein transgenic Drosophila melanogaster models of Parkinsonism.

Keywords: Alpha-synuclein; Drosophila melanogaster; Parkinsonism; levodopa; neurochemical; ribose-cysteine; transgenic.

Figure 1.

Percentage survival at varied ribose-cysteine concentrations (a): ribose-cysteine prolonged longevity in a dose-dependent manner. Gravitaxis performance index on varied ribose-cysteine exposure (b): there is a significant increase in gravitaxis performance in all the PD groups exposed to ribose-cysteine compared to the group without ribose-cysteine treatment. Data is presented as mean ± S.E.M. at ****: p < 0.0001 compared to PD. (RC: ribose-cysteine, PD: PD flies).

Figure 2.

Distance covered on the larval motility assay (a), performance index on the gravitaxis assay (b), number of offspring emergence (c), and survival assay (d). There was a statistically significant decrease in larval motility, adult gravitaxis, and eclosion rate in all the PD groups compared to the control. On the other hand, all the PD groups exposed to ribose-cysteine and levodopa showed a statistically significant increase in these parameters when compared to the PD group fed on a normal diet. On the survival assay, the highest longevity was observed in the control group, while the groups exposed to ribose-cysteine and levodopa showed extended longevity over the PD group which were on a normal diet. The result is expressed as mean ± S.E.M. at **: p < 0.01, ****: p < 0.0001 compared to control; ##: p < 0.01, ###: p < 0.001, ####: p < 0.0001 compared to PD; λ: p < 0.05, λλ: p < 0.01 compared to PD + RC + LD (control: w¹¹¹⁸, RC: ribose-cysteine, LD: levodopa, PD: Parkinson’s disease).

Figure 3.

Dopamine level (a), serotonin level (b), and acetylcholine level (c). Compared to control, the levels of dopamine in the PD, PD + RC, and PD + RC + LD groups decreased significantly, but not in the PD + LD group. Further, a statistically significant increase in the levels of dopamine was observed in all the groups exposed to ribose-cysteine and levodopa compared to the PD group fed on a normal diet. Moreover, serotonin and acetylcholine levels were significantly lower in all the PD groups compared to the control. A significant increase in the levels of serotonin and acetylcholine was observed in all the groups exposed to ribose-cysteine and levodopa compared to the PD group which were on normal diet. The analysis is presented as mean ± S.E.M. at **: p < 0.01, ****: p < 0.0001 compared to control; ####: p < 0.0001 compared to PD; λλλ: p < 0.001, λλλλ: p< 0.0001 compared to PD + RC + LD (control: w¹¹¹⁸, RC: ribose-cysteine, LD: levodopa, PD: PD flies).

Figure 4.

Schematic illustration of the research protocol to study ribose-cysteine and levodopa effect on alpha-synuclein transgenic Drosophila melanogaster.

Figure 5.

Malondialdehyde level (a), nitric oxide level (b), glutathione S-transferase activity (c), acetylcholine esterase activity (d), total thiol level (e), and cell viability (f). A significant increase in the level of MDA was observed in all the PD groups, as well as a significantly increased level of NO in the PD, PD + RC, and PD + LD groups, but not in the PD + RC + LD group compared to the control. However, the level of MDA was significantly decreased in all the groups exposed to ribose-cysteine and levodopa compared to the PD group fed on a diet without ribose-cysteine or levodopa, as well as decreased NO levels in the PD + RC and PD + RC + LD groups, but not in the PD + LD group compared to the PD group fed on a diet without ribose-cysteine or levodopa. Moreover, there is a statistically significant decrease in GST activity in all the PD groups, as well as a significantly elevated AChE activity in the PD, PD + RC, and PD + LD groups, but not in the PD + RC + LD group compared to the control. However, GST activity was significantly increased, with decreased AChE activity in all the groups exposed to ribose-cysteine and levodopa compared to the PD group fed on a diet without ribose-cysteine or levodopa. Also, there is a statistically significant concurrent decrease in total thiol level and percentage cell viability observed in all the PD groups compared to the control. Conversely, there is a statistically significant increase in total thiol level and percentage cell viability in all the groups exposed to ribose-cysteine and levodopa compared to the PD group fed on a diet without ribose-cysteine or levodopa. The result is expressed as mean ± S.E.M. at **: p < 0.01, ****: p < 0.0001 compared to control; ####: p < 0.0001 compared to PD; λλλ: p < 0.001, λλλλ: p < 0.0001 compared to PD + RC + LD. (control: w¹¹¹⁸, RC: ribose-cysteine, LD: levodopa, PD: PD flies).