Aqueous leaf extract of Phyllanthus amarus protects against oxidative stress and misfiring of dopaminergic neurons in Paraquat-induced Parkinson’s disease-like model of adult Wistar rats

Abstract

Abstract Background of the study: Phyllanthus amarus has high nutritional value and is beneficial in managing and treating diverse ailments. This study assessed the role of aqueous leaf extract of Phyllanthus amarus on Paraquat (PQ) induced neurotoxicity in the substantia nigra of Wistar rats. Materials and methods: The role of aqueous leaves extract of Phyllanthus amarus was assessed using an open field test (OFT) for motor activity, oxidative stress biomarkers [Catalase (CAT), and Superoxide Dismutase (SOD)], histological examination (H and E stained) for cytoarchitectural changes and immunohistochemical studies using tyrosine hydroxylase (TH) as a marker for dopaminergic neurons. Forty-two (42) rats were categorized into six groups (n = 7); group 1: control was administered 0.5 ml/kg distilled water, group 2: received 10 mg/kg PQ + 10 mg/kg L‑dopa as reference drug, group 3; received 10 mg/kg PQ, while group 4: received 10 mg/kg PQ + 200 mg/kg P. amarus, group 5: received 10 mg/kg PQ + 300 mg/kg P. amarus, and group 6: received 10 mg/kg PQ + 400 mg/kg P. amarus respectively, for 14 days. All administrations were done orally; a significant difference was set at p<0.05. Results and discussion: The study's open field test (OFT) revealed no motor activity deficit with Paraquat (PQ) exposure. Also, cytoarchitectural distortions were not observed with Paraquat (PQ) only treatment group compared to the control and other groups pretreated with P. amarus and L-dopa. Moreover, the Paraquat (PQ) only treatment group showed oxidative stress by significantly decreasing the antioxidant enzyme (SOD) compared to the control and L-dopa pretreated group. A significant decrease in tyrosine hydroxylase (TH) expressing dopaminergic neurons was also observed in Paraquat (PQ) only treatment. However, P. amarus treatment showed therapeutic properties by significantly increasing tyrosine hydroxylase (TH) expressing dopaminergic neuron levels relative to control. Conclusion:Aqueous leaf extract of Phyllanthus amarus possesses therapeutic properties against Paraquat (PQ) induced changes in the substantia nigra of Wistar rats.