Glycyrrhizic acid and 18β-glycyrrhetinic acid protect against ischemic and 6-hydroxydopamine induced damage and its possible mechanism in rat pheochromocytoma PC12 cells

• Main Authors: Tzu-Chein Kao, 高滋鍵
• Other Authors: Gow-Chin Yen
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/94317684630319175423

碩士 === 中興大學 === 食品暨應用生物科技學系 === 95 === Licorice is a common herb plant that has been used in traditional Chinese medicine for thousand years. The active compound in licorice, glycyrrhizic acid, has been used to treat many liver diseases. Some studies also demonstrate that glycrrhizic acid can improve the recovery of kidney and heart tissues from ischemic damage and block the activation of NF-κB in primary neurons. This suggests that GA can protect against Parkinson''s disease-induced cell damage. In this study, rat pheochromcytoma PC12 cells were used as a model to evaluate neuroprotective activities of glycyrrhizic acid (GA) and 18β-glycyrrhetinic acid (18GA) against oxidative stress-induced damage in PC12 cells. Result of ischemic injury experiment induced by serum/glucose deprivation showed that cells co-incubated with GA (3.1-12.5 μM) for 12 h could significantly (p<0.05) decrease the intracellular ROS levels and increase the glutathione peroxidase (GPx) and catalase activity that leading to prevent the cell damage cause by ROS overproduction. It also increased the mRNA expression of gamma-glutamylcysteine synthetase (γ-GCS) and modulated intracellular GSH content. After co-incubated with GA for 3 h, Bax/Bcl-2 ratio was significantly (p<0.05) decreased, and led into the decrease of caspase-9 and caspase-3 activity. This phenomenon indicated that serum/glucose deprivation induced the disruption of mitochondria and resulted in apoptosis. Result of 6-Hydroxydopamine (6-OHDA) induced neural cell damage mimic neurotoxin-related Parkinson’s disease showed that GA and 18GA could significantly (p<0.05) protect cells against 6-OHDA-induced cytotoxicity. GA and 18GA also decreased the Bax/Bcl-2 ratio by increasing the level of Bcl-2 after co-incubation for 6 h. Furthermore, after 4 h of co-incubation, GA and 18GA increased the expression of PI3K and p-Akt. Pre-treatment of PI3K inhibitor (LY294002) with sample and 6-OHDA proved that the protective ability of GA and 18GA certainly regulated the pathway. Moreover, the activity of neutral sphingomyelinase (N-SMase) was also tested. The result demonstrated the elevation the activity of N-SMase that stimulated by 6-OHDA was attenuated by GA and 18GA. In conclusion, GA and 18GA could decrease the Bax/Bcl-2 ratio by increase the Bcl-2 expression and protect PC12 cell from ischemic and neurotoxin induced cell injury by maintaining the integrity of mitochondria. Otherwise, GA and 18GA also increased the activities of GPx and catalase by modulating PI3K/Akt pathway, and elevated the mRNA level of γ-GCS, which led to decrease of intracellular ROS levels and N-SMase activity to prevent cell apoptosis. Result also demonstrated the attenuated N-SMase after GA and 18GA treatment. All data suggest that GA and 18GA treatment could protect the PC12 cells from apoptosis after ischemic and neurotoxin induced cell injury.