Different effects of olive leaf extract on antioxidant enzyme activities in midbrain and dopaminergic neurons of Substantia Nigra in young and old rats

Abstract

Objectives: Study of the effects of olive leaf extract on antioxidant enzyme activities in midbrain and dopaminergic neurons of Substantia Nigra in young and old rats. Methods: Male wistar rats age 4 and 18 months were randomized into control and experimental groups. A single daily dose of 50 mg/kg of olive leaf extract was administered orally by gavage to each rat for 6 months. The control group received only distilled water. All rats were sacrificed 2 hours after the last gavage and their midbrains were separated for Malondialdehyde (MDA) and antioxidant enzyme activitiy analysis. TUNEL assay and immunohistochemical (IHC) staining were used for evaluation of the number of neurons in the Substantia Nigra. Results: The level of Catalase, Glutathione Peroxidase and Superoxide Dismutase enzyme activity were significantly increased in experimental young and old groups compared to their control groups. However the level of Superoxide Dismutase enzyme activity was significantly increased in experimental old group when compared to control group (P<0.01), the level of Superoxide Dismutase enzyme activity was not significantly changed in young groups. MDA level was decreased significantly in experimental young and old rats compared to their control groups. Histological analysis demonstrated that the number of neurons in Substantia Nigra of experimental old group was more than the control group (P<0.01). The number of apoptotic cells was significantly decreased in experimental old group compared to the corresponding control group (P<0.05). In IHC and TUNEL assay, no change was observed in the number of neurons between experimental and control young groups. Conclusion: Long term treatment with olive leaf extract increases antioxidant enzyme activity and protects the neurons in Substantia Nigra against oxidative stress.