Protective effects of unsaponifiable matter of rice bran and γ-oryzanol on 6-OHDA-induced reactive oxygen species and apoptosis in PC12 cells

Tremor, stiffness, difficulty walking and disturbance in the balance and coordination of movement are the main characteristics of Parkinson’s disease. At the molecular level, oxidative stress increases free radicals and cell apoptosis in dopaminergic neurons. γ-oryzanol is a combination of ferulic acid esters of triterpene alcohols and plant sterols that have various therapeutic effects with potential health benefits for neurological disorders. This study was designed to investigate the protective effects of γ-oryzanol and unsaponifiable matter of rice bran on the toxicity and oxidative damage of 6-OHDA in PC12 cells as an appropriate model of Parkinson’s neural injury.

First, the antioxidant activity of extracted γ-oryzanol and unsaponifiable matter of rice bran were analyzed by 2,2′-diphenyl-1-picrylhydrazyl radical (DPPH) and ferric reducing antioxidant power (FRAP) methods. PC12 cells pretreated with γ-oryzanol (0.1–100 µg/ml) and unsaponifiable matter of rice bran (0.1–50 µg/ml) for 24 h, then cells exposed to 6-OHDA (200 µM) for 24 h, and the protective effect were determined using resazurin viability assay, 2′,7′-dichlorofluorescin diacetate reactive oxygen species (ROS) assay and flow cytometry of propidium iodide (PI) stained cells for apoptosis detection.

γ-oryzanol 0.1–100 µg/ml and unsaponifiable matter of rice bran (0.1–50 µg/ml) significantly decreased the 6-OHDA cytotoxicity. Also, γ-oryzanol (10–100 µg/ml) and unsaponifiable matter of rice bran (10, 20 and 50 µg/ml) decreased the amount of ROS. Treatment with 6-OHDA (200 μM) increased the rate of apoptosis in PC12 cells compared to the control and pretreatment with γ-oryzanol (10 µg/ml) and unsaponifiable matter of rice bran (10, 20 and 50 µg/ml) reduced cell apoptosis.

The results show that unsaponifiable matter of rice bran is effective in reducing the toxicity of 6-OHDA on neural PC12 cells and attenuate the apoptosis.