Figure 8.

Morphological alterations of human neuronal SH-SY5Y cells treated with drug combinations (guarana, caffeine, and taurine) and effects on the intracellular production of reactive oxygen species (ROS). (a) Phase contrast microscopy (PCM) of human neuronal SH-SY5Y cells after treatments with guarana (12.5 mg/mL), caffeine (0.5 mg/mL), taurine (4 mg/mL), and their combinations for 2 hours in FBS-free culture medium. Scale bar represents 30 μm. (b) Intracellular ROS production was examined by incubating the cells for 2 hours with 100 μM of DCFH-DA dissolved in 1% FBS-containing culture medium. Then, medium was discarded, and human neuronal SH-SY5Y cells were treated with H₂O₂ (1 mM; positive control for intracellular ROS production), guarana (12.5 mg/mL), caffeine (0.5 mg/mL), taurine (4 mg/mL), and their combinations for 2 hours. Finally, DCF fluorescence was read (endpoint; 2 hours) at 37°C in a fluorescence plate reader (Spectra Max M2, Molecular Devices, USA) with an emission wavelength set at 535 nm and an excitation wavelength set at 485 nm. Values are expressed as mean ± SEM of three independent experiments (n = 3). Statistical difference compared to control was determined by one-way ANOVA followed by Dunnett's multiple comparison test (*P < 0.05; **P < 0.01; ***P < 0.001).