D-ribose-L-cysteine Attenuates manganese-induced Oxidative Stress, Neuromorphological Deficits, Bax/Bcl-2 Response and TNF-α/ERK Signalling in Rats.

Manganese (Mn), though an essential trace element, can become neurotoxic after excessive exposure. Established mechanisms of Mn neurotoxicity include oxidative stress, apoptotic signalling, and inflammatory responses. D-ribose-L-cysteine (RibCys), a cysteine derivative, is reported to mitigate oxidative damage. In this study, we investigated its effects on B-cell lymphoma 2-associated X protein (Bax)/B-cell lymphoma 2 (Bcl-2) apoptotic signaling, tumor necrosis factor-alpha (TNF-α) inflammatory response, and extracellular signal-regulated kinase (ERK) pathway across various brain regions. Adult male Wistar rats were treated with saline (control), Mn (25 mg/kg intraperitoneally for 2 weeks, 8 doses at 48-hour intervals), RibCys (200 mg/kg orally for 2 weeks), or both Mn and RibCys. Biochemical assays for oxidative stress and antioxidant activity, Golgi staining for dendritic morphology, and immunohistochemistry for key protein markers were performed. Results showed that RibCys reduced Mn-induced distortions in brain neurochemistry and dendritic morphology. Mn increased lipid peroxidation, myeloperoxidase, and nitric oxide levels while decreasing glutathione peroxidase and sulfhydryl content, and these effects were attenuated by RibCys. Mn also disrupted dendritic arborization, which improved with RibCys treatment. Furthermore, Mn exposure elevated Bax/Bcl-2, TNF-α, and ERK1/2 expression in selected brain regions. RibCys co-administration mitigated these molecular alterations. Our findings suggest that RibCys is a promising therapeutic agent against Mn-induced neurotoxicity with potential for broader application. A notable limitation of this study was the absence of direct measurements of reduced and oxidized glutathione, and cysteine. Future studies should include these key antioxidant markers, assess long-term outcomes of RibCys treatment, and incorporate female animal models to evaluate potential sex-specific responses to Mn toxicity and intervention.