Figure 6.

The Caspase-3 activity and intracellular ROS generation in MPP⁺- and H₂O₂-treated SH-SY5Y cells that were stably GPR4-OE or GPR4-KO. 24 h serum-starved SH-SY5Y cells were treated with MPP⁺ (1 mM) for 24 h in serum-free culture media for an immunoblot and a caspase activity assay. SH-SY5Y, GPR4-OE, and GPR4-KO cells were treated with H₂O₂ (300 µM) for 1 h in serum-free culture media for a 2′,7′-dichlorofluorescein diacetate (DCFDA) assay. (A) An immunoblot of the pro caspase & cleaved Caspase-3 and β-Actin. (B) Caspase-3 activity was measured using a colorimetric assay kit (Sigma, CAS No. CASP-3-C) in MPP⁺-induced apoptotic cells. (C) The relative intracellular ROS level after 1 h of H₂O₂ (300 µM) treatment of 24 h serum-starved SH-SY5Y, GPR4-OE, and GPR4-KO cells. β-Actin was utilised as an internal control. Mean ± SEM (n = 3) was employed to express the data. Tukey’s multiple comparison test was performed using a one-way ANOVA. Each * p < 0.05 refers to the sample concentration compared with the same group of non-treated cells.