a Experimental protocol of cell death test and proliferation test. b Cell viability analysis of U251 cells in cell death and proliferation, U251 cells were treated with ligand 6 in various concentration (0, 0.1, 1, 10 μΜ). c Cell viability analysis of U251 cells, based on CCK assay. d Western blot (WB) analysis against anti-4HNE and cleaved caspase-3 reveals that ligand 6 (1 µM) and antioxidant, NAC (1 µM), treatment for 48 h reduces oxidative stress levels, and apoptosis triggered by AA (100 µM) in αSyn-overexpressing U251 cells. e Quantification of 4-HNE in Triton-soluble fractions, based on WB analysis, is illustrated (n = 4). f Quantification of cleaved caspase-3 in Triton-soluble fractions, based on WB analysis, is illustrated (n = 4). g Western blot (WB) analysis against anti-RIPK1 reveals that ligand 6 treatment for 48 h reduces RIPK1 cleaving triggered by AA (100 µM) in αSyn-overexpressing U251 cells. h The quantification of total RIPK1 in Triton-soluble fractions, based on WB analysis, is illustrated (n = 6). i The quantification of cleaved RIPK1 in Triton-soluble fractions, based on WB analysis, is illustrated (n = 6). The data are shown as mean ± standard error of the mean and were obtained using one-way analysis of variance. *P < 0.05; **P < 0.01; #P < 0.05; ##P < 0.01. αSyn alpha-synuclein, AA arachidonic acid, NS not statistically significant, NAC N-acetyl-L-cysteine, 4-HNE 4-Hydroxynonenal, RIPK1, receptor-interacting protein kinase 1.