D-ribose-L-cysteine protects against rotenone-induced neurotoxicity in Drosophila via redox, neurotransmitter, and DDC gene regulation.

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by both motor and non-motor dysfunctions. Although the underlying mechanisms are multifactorial, oxidative stress, inflammation, and dopaminergic deficits are central to its pathogenesis. D-Ribose-L-Cysteine (DRLC), a glutathione (GSH) precursor, has shown potential protective effects in models of human diseases. This study investigates the neuroprotective effects of DRLC against rotenone (ROT)-induced PD-like pathology in Drosophila melanogaster. Adult Drosophila (Harwich strain) were segregated into five groups and administered either a control diet, 500 μM ROT, or ROT in conjunction with DRLC (125, 250, or 500 μM) for a duration of 14 days. Longevity, locomotor, and olfactory assays were performed. Biochemical analysis of dissected fly brains assessed redox status markers, pro-inflammatory cytokines, apoptosis indicators, neurotransmitter levels, and dopa-decarboxylase (DDC) gene expression. ROT exposure reduced survival by 25%, significantly impaired motor and olfactory functions, increased reactive oxygen species (ROS) levels, disrupted neurotransmission, elevated TNF-α and caspase-3 levels, and downregulated DDC gene expression. DRLC co-treatment improved survival and motor performance in a dose-dependent manner while also decreasing ROS, TNF-α, and caspase-3 expression. DRLC restored dopamine and acetylcholine levels and GSH concentrations compared to the ROT-only group. DRLC also upregulated DDC gene expression. In conclusion, DRLC mitigates ROT-induced PD-like neurotoxicity in Drosophila through antioxidant, anti-inflammatory, and anti-apoptotic mechanisms, possibly via enhanced GSH synthesis and dopamine regulation. Although we cannot fully rule out the possibility that DRLC affected rotenone ingestion or feeding behavior, the fact that ROT-dependent phenotypes persisted in the absence of DRLC and were only selectively reversed by DRLC suggests a neuroprotective effect.