Neuroprotective effects of Astragaloside IV in 6-hydroxydopamine-treated primary nigral cell culture.

Parkinson's disease (PD) is caused by a progressive degeneration of dopaminergic neurons in the substantia nigra. Oxidative stress and neural degeneration are suggested to be involved in the pathogenesis of Parkinson's disease. In the present study, Astragaloside IV (AS-IV) extracted from the dried root of Astragalus membranaceus, a well-known Chinese medicine used for the treatment of neurodegenerative diseases, was investigated for its capacity to protect dopaminergic neurons in experimental Parkinson's disease. By examining the effect of AS-IV on 6-hydroxydopamine (6-OHDA)-induced loss of dopaminergic neurons in primary nigral culture, we found that AS-IV pretreatment significantly and dose-dependently attenuated 6-OHDA-induced loss of dopaminergic neurons. Neuronal fiber length studies showed that massive neuronal cell death with degenerated neurons was observed in those cultures incubated with 6-OHDA, whereas in AS-IV co-treatments most dopaminergic neurons were seen to be intact and sprouting. In flow cytometric analysis, AS-IV resulted in a marked and dose-dependent rescue in tyrosine hydrolase (TH)-immunopositive cells from 6-OHDA-induced degeneration of dopaminergic neurons. Double immunofluorescence revealed that AS-IV treatment alone at concentrations of 100 and 200 microM increased the level of TH and NOS (nitrite oxide synthase) immunoreactivities; however, the protective effect of AS-IV on TH and NOS immunopositive cells in 6-OHDA treated nigral cell cultures was only seen at a concentration of 100 microM. These findings show that AS-IV can protect dopaminergic neurons against 6-OHDA-induced degeneration. Besides the neuroprotective effect, AS-IV alone promoted neurite outgrowth and increased TH and NOS immunoreactive of dopaminergic neurons. The neuroprotective and neurosprouting effects of AS-IV are specific for dopaminergic neurons and it has therapeutic potential in the treatment of PD.

Salvianolic acid B inhibits Abeta fibril formation and disaggregates preformed fibrils and protects against Abeta-induced cytotoxicty.

One of the major pathological features of Alzheimer's disease (AD) is the appearance of senile plaques characterized by extracellular aggregation of amyloid beta-peptide (Abeta) fibrils. Inhibition of Abeta fibril aggregation is therefore viewed as one possible method to halt the progression of AD. Salvianolic acid B (Sal B) is an active ingredient isolated from Salvia miltiorrhiza, a Chinese herbal medicine commonly used for the treatment of cardiovascular and cerebrovascular disorders. Recent findings show that Sal B prevents Abeta-induced cytotoxicity in a rat neural cell line. To understand the mechanism of Sal B-mediated neuroprotection, its effects on the inhibition of Abeta1-40 fibril formation and destabilization of the preformed Abeta1-40 fibrils were studied. The results were obtained using Thioflavin T fluorescence assay and Abeta aggregating immunoassay. We found that Sal B can inhibit fibril aggregation (IC(50): 1.54-5.37 microM) as well as destabilize preformed Abeta fibril (IC(50): 5.00-5.19 microM) in a dose- and time-dependent manner. Sal B is a better aggregation inhibitor than ferulic acid but less active than curcumin in the inhibition of Abeta1-40 aggregation. In electron microscope study, Sal B-treated Abeta1-40 fibrils are seen in various stages of shortening or wrinkling with numerous deformed aggregates of amorphous structure. Circular dichroism data indicate that Sal B dose dependently prevents the formation of beta-structured aggregates of Abeta1-40. Addition of preincubated Sal B with Abeta1-42 significantly reduces its cytotoxic effects on human neuroblastoma SH-SY5Y cells. These results suggest that Sal B has therapeutic potential in the treatment of AD, and warrant its study in animal models.