Investigation Of The Material Basis And Mechanism Of Danggui-Shaoyao-San Against Alzheimer’s Disease

Alzheimer’s disease（AD） is a neurodegenerative disorder characterized by a progressive memory deficiency with the formation of senile plaques and neurofibrillary tangles and the loss of synapses in the selected regions of the brain. With the average life-span of humans on the rise, ageing in the worldwide has drawn considerable attentions. An obvious negative consequence of ageing is the significant increase in the number of people with AD（50% 75%） and other related dementias（about 25%）. The high incidence rate of AD brings incubus to family and society.Several hypotheses of AD, including the β-amyloid peptide（Aβ） cascade hypothesis and the cholinergic hypothesis, have been frequently applied to investigate the etiology of AD. Nowadays, the clinical drugs used for AD including AChE inhibitor, NMDA receptor blocker, antioxidant and estrogens only relieve some symptoms of AD. They can not cure AD thoroughly. Specially, the associated adverse effects always limit their clinical uses. Therefore, many herbal formula or drugs and their active ingredients are recently used to protect against chemical-induced cognitive deficits.Danggui-Shaoyao-San（DSS）, as a traditional Chinese medicinal prescription widely used in oriental countries, consists of six Chinese herbs, Radix Angelica sinensis, Radix Paeonia lactiflora, Rhizoma Ligusticum chuanxiong, Poria cocos, Rhizoma Atractylodes macrocephalae and Rhizoma Alisma orientalis. It was originally described in “Jin Kui Yao Lue”, a medical classic written by Zhongjing Zhang in the Eastern Han Dynasty, and also called Toki-shakuyaku-san or Dangguijakyak-san. For more than thousands years, DSS has been used to improve post-menopausal disorders with neurological symptoms, and regulate hypothalamic-pituitary-endocrine system and immune-neuroendocrine functions in China. Recently, many studies have showed that DSS had therapeutic efficacy for senile dementia by enhancing the cognitive behavior, improving the mitochondrial impairment and inhibiting neuronal damage. These abovementioned findings provide some pharmacological basis for the dementia prevention function of DSS. Our previous study has shown that DSS reversed the superoxide dismutase（SOD） activity and malondialdehyde（MDA） level to improving aging in the D-gal-induced mice. However, the exact mechanism and material basis are not indentified. On the basis of the findings abovementioned, studies have been carried out to further clarify the material basis and mechanisms as follows:First, we investigated the actions of ethanol extract of DSS（DE） on cognitive ability, oxidative stress biomarkers and neuronal apoptosis in the hippocampus of aging mice induced by D-gal to elucidate the underlying molecular mechanisms. The results of this study showed that D-gal-induced mimetic aging was associated with an increase of oxidative stress and the consequent damage of hippocampal neurons by triggering apoptosis cascades leading to cognitive dysfunction, whereas DE prevented the effect by enhancing the cognitive performances, improving activities of antioxidant defense systems, and regulating the expressions of Bcl-2, Bax and caspase-3 proteins. Therefore, it can be concluded that DE attenuates oxidative stress and promotes anti-apoptotic response in the hippocampus of D-gal-induced aging mice, and affects the behavioral changes.Second, the effects of ingredients in DE on AD were investigated using AChE inhibitor model and the primary neurons induced by Aβ_1-42 in vitro. The results showed that DE, paeoniflorin and Z-ligustilide could inhibit the activity of AChE, and could enhance the viability of neurons.Third, we further investigated the actions of DE, paeoniflorin and Z-ligustilide on the cognitive ability in the Aβ（1-42）-treated rats, and to elucidate the potential molecular mechanisms. The results manifested that DE and paeoniflorin ameliorated the spatial learning and memory deficits in the Aβ（1-42）-treated rats. Attenuating oxidative stress, as well as regulating NGF-related signaling to strengthen cholinergic functions, was confirmed as the main pathways mediating the actions of DE and paeoniflorin in the hippocampus of Aβ（1-42）-treated rats. The results also showed that Z-ligustilide ameliorated the spatial learning and memory deficits in the Aβ（1-42）-treated rats through attenuating oxidative stress and maintained the cholinergic nerve functions. Furthermore, the effects of DE and paeoniflorin were investigated in the primary neurons induced by Aβ（1-42） in vitro. The results showed that DE and paeoniflorin reduced the production of ROS and cells apoptosis, and up-regulated the mRNA levels of NGF, TrkA, TIMP-1 and CREB, down-regulated the MMP-9 mRNA level.In summary, these studies manifest that DE is the active fraction of DSS against AD. Synergistic interactions of different ingredients in DE are potentiated each other’s effect. Paeoniflorin and Z-ligustilide can effectively protect against AD. Especially, the effect of paeoniflorin is as well as DE. They ameliorate the spatial learning and memory deficits in the Aβ（1-42）-treated rats, attenuate oxidative stress, regulate NGF-related signaling to strengthen cholinergic functions, and reduce the neurons apoptosis.