Antioxidant effects of Dendropanax morbifera Léveille extract in the hippocampus of mercury-exposed rats

Abstract

Background: Dendropanax morbifera Léveille has been employed for the treatment of infectious diseases using folk medicine. In this study, we evaluated the antioxidant effects of a leaf extract of Dendropanax morbifera Léveille in the hippocampus of mercury-exposed rats.

Methods: Seven-week-old Sprague-Dawley rats received a daily intraperitoneal injection of 5 μg/kg dimethylmercury and/or oral Dendropanax morbifera Léveille leaf extract (100 mg/kg) for 4 weeks. Animals were sacrificed 2 h after the last dimethylmercury and/or leaf extract treatment. Mercury levels were measured in homogenates of hippocampal tissue, a brain region that is vulnerable to mercury toxicity. In addition, we measured reactive oxygen species production, lipid peroxidation levels, and antioxidant levels in these hippocampal homogenates.

Results: Treatment with Dendropanax morbifera Léveille leaf extract significantly reduced mercury levels in hippocampal homogenates and attenuated the dimethylmercury-induced increase in the production of reactive oxygen species and formation of malondialdehyde. In addition, this leaf extract treatment significantly reversed the dimethylmercury-induced reduction in the hippocampal activities of Cu, Zn-superoxide dismutase, catalase, glutathione peroxidase, and glutathione-S-transferase.

Conclusion: These results suggest that a leaf extract of Dendropanax morbifera Léveille had strong antioxidant effects in the hippocampus of mercury-exposed rats.

Fig. 1

Serum mercury (Hg) levels, hippocampal production of reactive oxygen species as determined by 2′,7’-dichlorofluorescein (DCF) levels, and malondialdehyde (MDA) levels in rats. ^* Indicates a significant difference between the control and dimethylmercury (MeHg) groups or between the Dendropanax morbifera leaf extract (DML) and DML-MeHg groups (P < 0.05); ^# indicates a significant difference between the control and DML groups or between the MeHg and DML-MeHg groups (p < 0.05; n = 7 per group). Serum Hg, hippocampal DCF, and MDA levels are significantly increased in the MeHg group and are reduced by DML treatment. The data represent means ± standard error of the mean (SEM)

Fig. 2

Rat hippocampal activities of Cu, Zn-superoxide dismutase 1 (SOD1), catalase (CAT), and glutathione peroxidase (GPx). ^* Indicates a significant difference between the control and dimethylmercury (MeHg) groups or between the Dendropanax morbifera leaf extract (DML) and DML-MeHg groups (p < 0.05); ^# indicates a significant difference between the control and DML or between the MeHg and DML-MeHg groups (p < 0.05; n = 7 per group). The activities of SOD1, CAT, and GPx are significantly decreased in the MeHg group, but DML administration significantly attenuates these effects. The data represent means ± standard error of the mean (SEM)

Fig. 3

Levels of total sulfhydryl (TSH), glutathione-S-transferase (GST), and glutathione reductase (GR) in the hippocampi of control, DML, MeHg, and DML-MeHg groups following 4 weeks of DML and/or MeHg treatment. ^* Indicates a significant difference between the control and MeHg groups or DML and DML-MeHg groups (p < 0.05); ^# indicates a significant difference between the control and DML or between MeHg and DML-MeHg groups (p < 0.05; n = 7 per group). TSH levels and GR activity are significantly decreased in the MeHg group, while GST activity is significantly increased. The administration of DML reduces the changes of these parameters. The data represent means ± standard error of the mean (SEM)