Scutellaria barbata flavonoids inhibits NFT aggregation and regulatory mechanism in rats induced by composited Aβ

AIM: To investigate the effects of Scutellaria barbata flavonoids (SBF) on neurofibrillary tangle (NFT) aggregation, tau protein phosphorylation and the regulated mechanism of glycogen synthase kinase (GSK) 3β and protein phosphatase (PP) 2A in the rats induced by amyloid β protein 25-35 (Aβ_25-35) in combination with AlCl₃ and recombinant human transforming growth factor (RHTGF)-β1(composited Aβ). METHODS: The male SD rats were used to establish the simulated Alzheimer disease (AD) model by intracerebroventricular injection of composited Aβ. The Morris water maze was applied for screening the successful model rats with learning and memory deficits. The successful model rats were daily and orally administrated with SBF at doses of 35, 70 and 140 mg/kg or positive control drug Ginkgo biloba leaves flavonoids (GLF) at 140 mg/kg for 37 d. The silver nitrate staining was used to determine the cortical NFT. The protein levels of total tau, phosphorylated protein of tau at Ser199 and Ser214 sites, GSK3β and PP2A in hippocampus and cortex were determined by Western blot. The mRNA expression of GSK3β and PP2A in the hippocampus and cortex was detected by RT-PCR. RESULTS: Compared with sham group, the cell number of positive NFT with silver nitrate staining in model rat cerebral cortex was significantly increased. The protein levels of phosphorylated tau protein at Ser199 and Ser214 sites, GSK3β in the hippocampus and cerebral cortex in the model rats dramatically elevated, and PP2A was marked decreased as compared with the sham group rats. Meanwhile, the mRNA expression of GSK-3β significantly increased but PP2A was decreased. However, these above abnormalities were differently attenuated by treating with SBF at different doses or GLF at 140 mg/kg for 37 d. CONCLUSION: SBF suppresses the NFT aggregation by inhibition of the regulatory functions of GSK-3β and PP2A, thus reducing the phosphorylation of tau protein.     

Effects of Scutellaria barbata flavonoids on abnormal expression of NOS,HSP70 and apoE induced by Aβ 25-35 in rat astrocytes

AIM:To study the effects of Scutellaria barbata flavonoids (SBF) on abnormal expression of nitric oxide synthase (NOS), heat-shock protein 70 (HSP70) and apolipoprotein E (apoE) induced by Aβ 25-35 in rat astrocytes. METHODS:The third generation of cultured rat astrocytes was divided into 5 groups. The cells in 3 drug treatment groups were given SBF at dose of 17.5 mg/L, 35 mg/L and 70 mg/L for 24 h, and then the cells in model group and 3 doses of SBF groups were exposed to Aβ 25-35 at concentration of 100 μmol/L for 24 h. The expression of endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS) and neuronal nitric oxide synthase (nNOS) in the cultured cells was assayed by immunohistochemical method. The expression of HSP70 was estimated by Western blotting and the mRNA expression of apoE was assessed by RT-PCR. RESULTS:Compared with control group, the protein level of eNOS were significantly decreased and the protein level of iNOS increased (P<0.01) in model group. The protein expression of HSP70 and mRNA expression of apoE were notably increased (P<0.01) in model group. However, these disturbances were attenuated by SBF at dose of 17.5, 35 and 70 mg/L (P<0.01). CONCLUSION:SBF has an obvious protective effect on damaged astrocytes induced by Aβ 25-35, suggesting that SBF may be helpful for the treatment of Alzheimer disease.