Alleviative and Anti-Inflammatory effects of tuna blood hydrolysates on MPP+ and TNF-α - induced Parkinson-Like disease model through the regulation of Keap1-Nrf2 antioxidant pathway and apoptosis

The pathophysiology of Parkinson's disease (PD) is linked to oxidative stress and inflammatory-induced cell death of dopaminergic neurons in substantia nigra pars compacta (SNpc). The current study aims to investigate the effects of tuna blood hydrolysate (TBH) on the neurodegeneration of Parkinson-like disease models using neurotoxin-induced SH-SY5Y cells differentiated to be dopaminergic-like neurons. It was found that TBH at concentrations ranging from 5 to 250 µg/ml can reduce differentiated SH-SY5Y cell death after exposure to 1-methyl-4-phenylpyridinium (MPP+) co-treated with TBH for 24 h. Real-time PCR results indicated that TBH enhanced the expressions of NAD(P)H quinone dehydrogenase 1 (NQO1), catalase (CAT), and thioredoxin reductase (TrxR1), which are Nrf2 downstream antioxidant genes. Bioinformatic analysis and molecular docking revealed that the peptide found in TBH, IPGQPGLPGPPGPPGPPGLG, could penetrate the cell and blood–brain barrier and strongly bind the Keap1-Kelch domain, causing Nrf2 nuclear translocation. Consequently, the upregulation of antioxidant genes ameliorates ROS and reduces dopaminergic neuron death. Another, TBH can reduce differentiated SH-SY5Y cell death and intracellular ROS after exposure to 24 h of co-treatment between TBH and tumor necrosis factor-alpha (TNF-α). Western blot analysis was performed to investigate apoptosis-related proteins. Bcl2 and BDNF are dramatically increased, while BAX, cytochrome c, caspase3, caspase9, and cleaved caspase9 are significantly decreased in co-treating differentiated SH-SY5Y cells with TBH and TNF-α. These findings demonstrated that TBH can suppress the apoptosis of inflammatory differentiated SH-SY5Y cells. Taken together, this study suggests that TBH can alleviate neurodegeneration and has anti-inflammatory effects on dopaminergic-like neurons in the simulation of a PD condition.