Fig. 3: Effect of PARL knockdown and overexpress on apoptosis in PD cellular and animal models.

A TH expression changes in C57BL/6 J mouse striatum and midbrain 8 weeks post-PARL-shRNA lentivirus injection. Quantitative analysis shows significant TH reduction (***p < 0.001 vs. control, n = 3). B, DTH immunofluorescence (red) in substantia nigra pars compacta (SNpc). PARL knockdown reduced TH+ neurons (**p < 0.01). Scale bar: 500 µm. C PARL silencing in MPTP-induced PD mice increased apoptosis markers: BAX/BCL-2 ratio and Cleaved Caspase-3 (C-Casp3) increased (***p < 0.001). β-actin served as loading control. E–I Quantitative analysis of TH, BCL-2, BAX, Caspase3 and Cleaved-Caspase3(C-Caspase3) protein expressions in different Groups. J Successful PARL knockdown in SH-SY5Y cells via shRNA (p < 0.001). K PARL-deficient SH-SY5Y cells exhibited pro-apoptotic shifts: BAX/BCL-2 ratio and C-Casp3 increased (***p < 0.001). L CCK8 assay: PARL knockdown reduced SH-SY5Y viability (***p < 0.001). M PARL-Myc overexpression in SH-SY5Y cells. Western blot confirms PARL expression (Myc-tagged) 24 h post-transfection (Lipofectamine 3000, 3 µg plasmid/10⁶ cells). β-actin served as loading control. N Rescue of MPP⁺-induced apoptosis by PARL overexpression. Cells co-transfected with PARL plasmid (2 µg/well) for 24 h were treated with MPP⁺ (1 mM, 24 h). Immunoblot analysis shows BCL-2 restoration (vs. MPP⁺ alone), BAX suppression, and Cleaved Caspase-3 (C-Casp3) reduction (**p < 0.01, n = 3, one-way ANOVA with Tukey’s post hoc). Representative blot from three biological replicates.