Compound Dihuang Granule Attenuates the Da Neuron Loss and Motor Deficits in 6-OHDA  Induced Parkinson’s Disease Rats

Abstract Background: Parkinson’s disease (PD) is a multifactorial neurodegenerative disorder characterized by progressive loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc) and the presence of Lewy bodies (LBs) consisting of misfolded α-synuclein protein in the substantia nigra pars compacta (SNpc). Compound Dihuang Granule (CDG), a famous traditional Chinese medicine (TCM) has been clinically used in PD therapy with curative effects. However, the specific functions and the mechanism of action remained unclear. This paper study assesses the preventive and therapeutic effect of CDG on motor deficits and DA neuron loss of PD induced by 6-OHDA and the underlying mechanisms.Methods: PD rat model was induced by unilaterally stereotactic injection of 6-OHDA into the SNpc of midbrain then the motor deficits were evaluated with apomorphine (APO) induced abnormal rotational behaviors. The striatal contents of neurotransmitters were detected by high performance liquid chromatography with electrochemical detection (HPLC-ECD). The number of DA neurons were determined with immunohistochemistry (IHC) staining. Protein expression levels were determined with Western blotting assay. Indicators of oxidative stress were determined with colorimetric method. Apoptotic cells were detected by Transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) assay. The expression of neurotrophic factors was examined with IHC staining.Results: With a 6-week treatment, CDG significantly attenuated the 6-OHDA induced abnormal rotational behaviors and alleviated the loss of DA neurons in the nigrostriatal axis. Consistently, the striatal contents of DA and its metabolites including DOPAC and HVA of PD rats were all significantly increased with CDG treatment. The 6-OHDA induced oxidative stress indicated with decreased superoxide dismutase (SOD), glutathione (GSH), glutathione peroxidase (GSH-Px) and increased malondialdehyde (MDA)was also suppressed by CDG. Moreover, CDG treatment inhibited the 6-OHDA induced cell apoptosis indicated with decreased apoptotic cells in the SNpc and increased protein expression ratio of Bcl-2/Bax in the striatum. The expression levels of neurotrophic factors including nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and glial-derived neurotrophic factor (GDNF)in the SNpc of PD rats were also increased by CDG.Conclusion: CDG could ameliorate the 6-OHDA induced brain injuries and motor symptoms mainly by inhibition of the oxidative stress and cell apoptosis in the nigrostriatal axis, and enhancing the expression of neurotrofic factors in the midbrain of rats.