Protective effects of dibenzocyclooctadiene lignans from Schisandra chinensis against beta-amyloid and homocysteine neurotoxicity in PC12 cells

Network pharmacology-based study on the mechanism of Schisandra chinensis for treating Alzheimer's disease

BACKGROUND:

Alzheimer's disease (AD) is a mental illness that poses a serious threat to human health worldwide. Schisandra chinensis is a natural herb that can treat the effects of AD, but its specific mechanism is still unclear. The purpose of this study was to explore the potential components and pharmacological pathways of S. chinensis in the treatment of AD.

MATERIALS AND METHODS:

In this study, we investigated the compound of S. chinensis and the effects of it on AD by network pharmacology. Meanwhile, the potential mechanism was proved in vitro.

RESULTS:

The results showed that S. chinensis contained 173 compounds. Compound-target network confirmed that (E)-9-Isopropyl-6-Methyl-5,9-Decadiene-2-One, 1-Phenyl-1,3-Butanedion, nootkatone and phenyl-2-Propanone were the main chemical constituents which highly aimed at APOE, CACNA1D, GRIN2A, and PTGS2. KEGG and GO enrichment analysis indicated that the main pathways involved neural-related signaling pathways and functions, such as nicotine addiction, GABAergic synapse, Ca²⁺ signaling pathway, AD, and so on. Validation experiments showed that nootkatone was able to exert anti-apoptotic effects related to Ca²⁺ signaling pathway by inhibiting nitric oxide production, enhancing the activity of antioxidant enzymes, upregulating the expression of anti-oxidation and anti-apoptotic proteins in vitro.

CONCLUSIONS:

These results illustrated that S. chinensis could regulate neuronal apoptosis through the calcium signaling pathway to exert anti-AD by integrating multi-component, multi-target and multi-pathway.

The protective underlying mechanisms of Schisandrin on SH-SY5Y cell model of Alzheimer's disease

The extract of Schisandrin a traditional Chinese medicine was postulated to be effective in prevention and treatment of Alzheimer's disease (AD). The aim of this study was to examine the underlying protective actions of Schizandrin using a human neuroblastoma cell line (SH-SY5Y). In particular Schizandrin-mediated effects on expression of glycogen synthase kinase (GSK)-3β, protein kinase B (Akt) and Tau protein, known to be altered in AD were determined. In preliminary assays, various concentrations of Schisandrin were incubated SH-SY5Y cells to establish effects on cell viability and potential toxicity in further experimentation. Amyloid-β (Aβ_1-42) peptide 10 μmol/L was used to induce in vitro AD model in SH-SY5Y. Exposure to Aβ_1-42 significantly reduced cell viability. Treatment with Schisandrin to Aβ_1-42 exposed cells increased cell viability compared to amyloid peptide; however only the 10 μmol/L Schisandrin concentration was effective in restoring cell viability to control. Western blot analysis demonstrated that Aβ_1-42 produced a significant decrease in p-Akt protein expression levels accompanied by marked elevation in p-tau and p-GSK-3β protein expression levels. Addition of 10 μmol/L Schisandrin to amyloid-treated SH-SY5Y cells was found to significantly increase protein expression levels of p-Akt associated with reduction in expression levels of p-tau and p-GSK-3β protein. Treatment with 10 μmol/L Schisandrin of SH-SY5Y cells with the p-Akt inhibitor LY294002 demonstrated that the herbal-induced rise in p-Akt protein expression was diminished by this inhibitor indicating that signal transduction occurred in the observed cellular effects. Evidence indicates that Schisandrin inhibition of Aβ_1-42 -mediated cellular damage in AD neurons may involve activation of the PI3K/Akt signaling pathway where up-regulation of p-Akt activity consequently leads downstream to decreased activity of p-GSK-3β phosphorylation accompanied by reduced tau protein. Consequently, restoration of neuronal cell viability was noted. Our findings suggest that the use of Schisandrin may be considered beneficial as a therapeutic agent in AD.

Synergistic Neuroprotective Effect of Schisandra chinensis and Ribes fasciculatum on Neuronal Cell Death and Scopolamine-Induced Cognitive Impairment in Rats

Mild cognitive impairment (MCI) is considered as a transitional stage between aging and Alzheimer’s disease. In the present study, we examined the protective effect of Schisandra chinensis (SC) and Ribes fasciculatum (RF) on neuronal cell death in vitro and scopolamine-induced cognitive impairment in Sprague Dawley^® rats in vivo. A mixture of SC and RF extracts (SC+RF) significantly protected against hydrogen peroxide-induced PC12 neuronal cell death. The neuroprotective effect of SC+RF on scopolamine-induced memory impairment in rats was evaluated using the passive avoidance test and the Morris water maze test. In the passive avoidance test, SC+RF-treated rats showed an increased latency to escape, compared to the scopolamine-treated rats. Moreover, SC+RF treatment significantly reduced escape latency in water maze test, compared to treatment with scopolamine alone. To verify the long-term memory, we performed probe test of water maze test. As a result, rat treated with SC+RF spent more time in the target quadrant. Consistent with enhancement of memory function, the brain derived neurotrophic factor (BDNF) and its downstream molecules (pERK, pATK, and pCREB) are increased in SC+RF treatment in hippocampal area compared with scopolamine treated group. These results suggest that a mixture of SC and RF extracts may be a good therapeutic candidate for preventing mild cognitive impairment.

Scutellarein suppresses Aβ-induced memory impairment via inhibition of the NF-κB pathway in vivo and in vitro

The flavonoid compound scutellarin (Scu) is a traditional Chinese medicine used to treat a variety of diseases; however, the use of scutellarein (Scue), the hydrolysate of Scu, and its mechanisms of action in Alzheimer's disease (AD) have not been fully elucidated. In the present study, the effects of Scue on amyloid β (Aβ)-induced AD-like pathology were investigated. An in vitro model of inflammation and an aged rat model were used to confirm the effects of Scue. In vitro MTT assays and flow cytometry were used to assess the effects of Scue on cell viability and apoptosis, respectively. A Morris water maze was used to evaluate spatial learning and memory, and the levels of Aβ deposition, superoxide dismutase, malondialdehyde, apoptosis, neuro-inflammatory factors and nuclear factor-κB (NF-κB) activation in hippocampal tissues in vivo were measured to determine the effect of Scue in AD. Scue may be protective, as it decreased the apoptosis of hippocampal cells in vitro, inhibited Aβ-induced cognitive impairment, suppressed hippocampal neuro-inflammation and suppressed activation of NF-κB in vivo. Therefore, Scue may be a useful agent for the treatment of Aβ-associated pathology in the central nervous system through inhibition of the protein kinase B/NF-κB signaling pathway and thus, future studies are required to investigate the efficacy of Scue in patients with AD.

Cognitive enhancement of volatile oil from the stems of Schisandra chinensis Baill. in Alzheimer’s disease rats

The volatile oil (VO), extracted from the stems of Schisandra chinensis Baill. (SCS), was separated and identified by gas chromatography – mass spectrometry. The study was devised to investigate the effects of VO on oxidative stress and cognitive deficits induced by amyloid-β (Aβ(1-42)). Alzheimer’s disease (AD) models were established by injecting Aβ(1-42) into the rat hippocampus and the effects of learning and memory were observed by a Morris water maze test, immunohistological alterations, and correlative indicators covering nerve growth (brain-derived neurotrophic factor, glial-cell-derived trophic factor, and nerve growth factor), interleukin 1β, tumor necrosis factor, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), malondialdehyde (MDA), glial fibrillary acidic protein (GFAP), and microglial CD11b in AD rats. And activities of SOD, MDA, and GSH-Px were ameliorated by VO. The neurotrophic factors GFAP and microglial CD11b were noticeably improved in histopathologic changes. These data suggested that VO from SCS had potential activities for the prevention and treatment of AD.

Effects of Lignans from Schisandra chinensis Rattan Stems against Aβ1-42-Induced Memory Impairment in Rats and Neurotoxicity in Primary Neuronal Cells

Oxidative stress, which is caused by Amyloid-β deposition in brain, plays an important role in Alzheimer’s disease. In this study, we found that lignans from Schisandra chinensis rattan stems (rsSCH-L) could reduce the escape latency and the distance travelled by the Aβ_1–42 injected rats while the crossing platform time was enhanced in the Morris water maze test. Further research demonstrated that lignans from rsSCH-L attenuated Aβ_1-42-induced neuronal cell injury by increasing the content of SOD and GSH-Px and decreasing the levels of LDH, ROS, and MDA. Moreover, rsSCH-L also inhibited the apoptosis of primary neuronal cells. The mechanisms of the apoptosis were related with the downregulation of caspase-3, caspase-8, Bax, and upregulation of Bcl-2. Taken together, the results show that rsSCH-L can improve cognitive ability in vivo. Meanwhile rsSCH-L exhibit a neuroprotective environment against oxidative stress and apoptosis in vitro. Therefore, rsSCH-L may be a potential therapeutic agent for this neurodegenerative disease.

Reduction of Aβ Generation by Schisandrin B through Restraining Beta-Secretase 1 Transcription and Translation

BACKGROUND Beta-secretase 1 (BACE1) is a rate-limiting enzyme in the generation of amyloid beta peptides, which are associated with Alzheimer's disease (AD). It has been reported that Schisandrin B could improve cognitive functions in animal models of AD, but the underlying mechanisms are not completely understood. MATERIAL AND METHODS In this research, in order to investigate the effects of Schisandrin B on amyloid-β (Aβ) metabolism and its mechanisms, amyloid precursor protein (APP) and its proteolytic products were determined by enzyme-linked immunosorbent assay (ELISA), western blotting, and RT-PCR after incubation of N2a/Swe cells with Schisandrin B. RESULTS The results indicated that Schisandrin B can significantly reduce the level of secretion of Aβ40 and Aβ42 secreted in N2a/Swe cells. Additionally, there was nonsignificant change in APP level after Schisandrin B treatment. Treatment of Schisandrin B dramatically reduced the mRNA and protein expression levels of BACE1. Moreover, Schisandrin B treatment resulted in a reduction of protein level of sAPPβ, an APP fragment cleavage by BACE1. CONCLUSIONS These results suggest that Schisandrin B inhibits the transcription and translation of BACE1, suppresses the activity of BACE1, and ultimately attenuates Aβ generation, which provides a novel mechanism for the regulation of Aβ metabolism by Schisandrin B.

Dihuang Yinzi, a Classical Chinese Herbal Prescription, for Amyotrophic Lateral Sclerosis: A 12-Year Follow-up Case Report

Amyotrophic lateral sclerosis (ALS) is a devastating progressive neurodegenerative disease with no effective treatment and death within 2 to 5 years after symptom onset. Here, we reported a case of ALS patient using modified Dihuang Yinzi (DHYZ), a classical traditional Chinese medicine (TCM) prescription, who has survived 12 years with significant improvement in bulbar paralysis.A 41-year-old Chinese Han nationality woman was admitted to the hospital with complaints of weakened bilateral grip, slurred speech, stumbling, and muscle twitching for 3 years. The electromyography showed neurogenic injury in bilateral upper limbs and tongue. She was diagnosed with ALS according to the revised El escorial criteria. The patient was orally administrated with Riluzole 100 mg daily for 10 months and then stopped. Subsequently, she resorted to TCM. Based on the TCM theory, the patient was diagnosed with Yinfei syndrome because of kidney deficiency. DHYZ was chosen because it has the function of replenishing kidney essence to treat Yinfei syndrome. Up to now, she has been using modified DHYZ continuously for 12 years. The patient survived with ALS and did not require permanent continuous ventilator. In addition, the symptoms of choking on liquids are improved, and the utility of 30 mL water swallow test was improved with grade 2. The symptoms of muscle fibrillations of limbs are also reduced. However, muscle strength worsened slowly. The repeated electromyography showed motor conduction amplitude reducing gradually and velocity not changing more when compared with the initial electromyography.Our findings suggested that DHYZ can be potentially used in ALS patients because of its multi-targeted neuroprotection and general safety, although ALS does not have a cure. In addition, we identified the area that is worthy of further study and DHYZ as a promising candidate for further clinical application and ALS trials. Rigorous randomized controlled trials are needed in the future.

Schisandrin B Ameliorates ICV-Infused Amyloid β Induced Oxidative Stress and Neuronal Dysfunction through Inhibiting RAGE/NF-κB/MAPK and Up-Regulating HSP/Beclin Expression

Amyloid β (Aβ)-induced neurotoxicity is a major pathological mechanism of Alzheimer’s disease (AD). Our previous studies have demonstrated that schisandrin B (Sch B), an antioxidant lignan from Schisandra chinensis, could protect mouse brain against scopolamine- and cisplatin-induced neuronal dysfunction. In the present study, we examined the protective effect of Sch B against intracerebroventricular (ICV)-infused Aβ-induced neuronal dysfunction in rat cortex and explored the potential mechanism of its action. Our results showed that 26 days co-administration of Sch B significantly improved the behavioral performance of Aβ (1–40)-infused rats in step-through test. At the same time, Sch B attenuated Aβ-induced increases in oxidative and nitrosative stresses, inflammatory markers such as inducible nitric oxide syntheses, cyclooxygenase-2, interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α, and DNA damage. Several proteins such as receptor for advanced glycation end products (RAGE), nuclear factor-κB, mitogen-activated protein kinases, and apoptosis markers were over expressed in Aβ-infused rats but were significantly inhibited by Sch B treatment. Furthermore, Sch B negatively modulated the Aβ level with simultaneous up-regulation of HSP70 and beclin, autophagy markers in Aβ-infused rats. The aforementioned effects of Sch B suggest its protective role against Aβ-induced neurotoxicity through intervention in the negative cycle of RAGE-mediated Aβ accumulation during AD patho-physiology.

Overexpression of estrogen receptor beta alleviates the toxic effects of beta-amyloid protein on PC12 cells via non-hormonal ligands

After binding to the estrogen receptor, estrogen can alleviate the toxic effects of beta-amyloid protein, and thereby exert a therapeutic effect on Alzheimer's disease patients. Estrogen can increase the incidence of breast carcinoma and endometrial cancer in post-menopausal women, so it is not suitable for clinical treatment of Alzheimer's disease. There is recent evidence that the estrogen receptor can exert its neuroprotective effects without estrogen dependence. Real-time quantitative PCR and flow cytometry results showed that, compared with non-transfected PC12 cells, adenovirus-mediated estrogen receptor β gene-transfected PC12 cells exhibited lower expression of tumor necrosis factor α and interleukin 1β under stimulation with beta-amyloid protein and stronger protection from apoptosis. The Akt-specific inhibitor Abi-2 decreased the anti-inflammatory and anti-apoptotic effects of estrogen receptor β gene-transfection. These findings suggest that overexpression of estrogen receptor β can alleviate the toxic effect of beta-amyloid protein on PC12 cells, without estrogen dependence. The Akt pathway is one of the potential means for the anti-inflammatory and anti-apoptotic effects of the estrogen receptor.

3-N-butylphthalide improves neuronal morphology after chronic cerebral ischemia

3-N-butylphthalide is an effective drug for acute ischemic stroke. However, its effects on chronic cerebral ischemia-induced neuronal injury remain poorly understood. Therefore, this study ligated bilateral carotid arteries in 15-month-old rats to simulate chronic cerebral ischemia in aged humans. Aged rats were then intragastrically administered 3-n-butylphthalide. 3-N-butylphthalide administration improved the neuronal morphology in the cerebral cortex and hippocampus of rats with chronic cerebral ischemia, increased choline acetyltransferase activity, and decreased malondialdehyde and amyloid beta levels, and greatly improved cognitive function. These findings suggest that 3-n-butylphthalide alleviates oxidative stress caused by chronic cerebral ischemia, improves cholinergic function, and inhibits amyloid beta accumulation, thereby improving cerebral neuronal injury and cognitive deficits.

Tanshinone IIA protects PC12 cells from β-amyloid(25-35)-induced apoptosis via PI3K/Akt signaling pathway

For the aging populations of any nation, Dementia is becoming a primary problem and Alzheimer’s dementia (AD) is the most common type. However, until now, there is no effective treatment for AD. Tanshinone IIA (Tan IIA) has been reported for neuroprotective potential to against amyloid β peptides (Aβ)-induced cytotoxicity in the rat pheochromocytoma cell line PC-12, which is widely used as AD research model, but the mechanism still remains unclear. To investigate the effect of Tan IIA and the possible molecular mechanism in the apoptosis of PC12 cells, we induced apoptosis in PC12 cells with β-amyloid(25-35), and treated cells with Tan IIA. After 24 h treatment, we found that Tan IIA increased the cell viability and reduced the number of apoptotic cells induced by Aβ(25-35). However, neuroprotection of Tan IIA was abolished by PI3K inhibitor LY294002. Meanwhile, Treatment with lithium chloride, a phosphorylation inhibitor of GSK3β, which is a downstream target of PI3K/Akt, can block Aβ(25-35)-induced cell apoptosis in a Tan IIA-like manner. Our findings suggest that Tan IIA is an effective neuroprotective agent and a viable candidate in AD therapy and PI3K/Akt activation and GSK3β phosphorylation are involved in the neuroprotection of Tan IIA.

Response surface modeling and optimization of accelerated solvent extraction of four lignans from fructus schisandrae

A new method based on accelerated solvent extraction (ASE) combined with response surface methodology (RSM) modeling and optimization has been developed for the extraction of four lignans in Fructus Schisandrae (the fruits of Schisandra chinensis Baill). The RSM method, based on a three level and three variable Box-Behnken design (BBD), was employed to obtain the optimal combination of extraction condition. In brief, the lignans schizandrin, schisandrol B, deoxyschizandrin and schisandrin B were optimally extracted with 87% ethanol as extraction solvent, extraction temperature of 160 °C, static extraction time of 10 min, extraction pressure of 1,500 psi, flush volume of 60% and one extraction cycle. The 3D response surface plot and the contour plot derived from the mathematical models were applied to determine the optimal conditions. Under the above conditions, the experimental value of four lignans was 14.72 mg/g, which is in close agreement with the value predicted by the model.