Synergistic Action of Flavonoids, Baicalein, and Daidzein in Estrogenic and Neuroprotective Effects: A Development of Potential Health Products and Therapeutic Drugs against Alzheimer's Disease.

Despite the classical hormonal effect, estrogen has been reported to mediate neuroprotection in the brain, which leads to the searching of estrogen-like substances for treating neurodegenerative diseases. Flavonoids, a group of natural compounds, are well known to possess estrogenic effects and used to substitute estrogen, that is, phytoestrogen. Flavonoid serves as one of the potential targets for the development of natural supplements and therapeutic drugs against different diseases. The neuroprotection activity of flavonoids was chosen for a possible development of anti-Alzheimer's drugs or food supplements. The estrogenic activity of two flavonoids, baicalein and daidzein, were demonstrated by their strong abilities in stimulating estrogen receptor phosphorylation and transcriptional activation of estrogen responsive element in MCF-7 breast cells. The neuroprotection effects of flavonoids against ß -amyloid (A ß ) were revealed by their inhibition effects on in vitro A ß aggregation and A ß -induced cytotoxicity in PC12 neuronal cells. More importantly, the estrogenic and neuroprotective activities of individual flavonoid could be further enhanced by the cotreatment in the cultures. Taken together, this synergistic effect of baicalein and daidzein might serve as a method to improve the therapeutic efficacy of different flavonoids against A ß , which might be crucial in developing those flavonoidsin treating Alzheimer's disease in the future.

A chinese herbal decoction, danggui buxue tang, stimulates proliferation, differentiation and gene expression of cultured osteosarcoma cells: genomic approach to reveal specific gene activation.

Danggui Buxue Tang (DBT), a Chinese herbal decoction used to treat ailments in women, contains Radix Astragali (Huangqi; RA) and Radix Angelicae Sinensis (Danggui; RAS). When DBT was applied onto cultured MG-63 cells, an increase of cell proliferation and differentiation of MG-63 cell were revealed: both of these effects were significantly higher in DBT than RA or RAS extract. To search for the biological markers that are specifically regulated by DBT, DNA microarray was used to reveal the gene expression profiling of DBT in MG-63 cells as compared to that of RA- or RAS-treated cells. Amongst 883 DBT-regulated genes, 403 of them are specifically regulated by DBT treatment, including CCL-2, CCL-7, CCL-8, and galectin-9. The signaling cascade of this DBT-regulated gene expression was also elucidated in cultured MG-63 cells. The current results reveal the potential usage of this herbal decoction in treating osteoporosis and suggest the uniqueness of Chinese herbal decoction that requires a well-defined formulation. The DBT-regulated genes in the culture could serve as biological responsive markers for quality assurance of the herbal preparation.

A flavonol glycoside, isolated from roots of Panax notoginseng, reduces amyloid-beta-induced neurotoxicity in cultured neurons: signaling transduction and drug development for Alzheimer's disease.

A Radix Notoginseng flavonol glycoside (RNFG), quercetin 3-O-beta-D-xylopyranosyl-beta-D-galactopyranoside, was isolated from roots of Panax notoginseng. Among different biological properties tested, RNFG possessed a strong activity in preventing amyloid-beta (Abeta)-induced cell death. In an in vitro assay, RNFG inhibited the aggregation of Abeta in a dose-dependent manner. Moreover, application of RNFG in cultured cortical neurons, or PC12 cells, reduced the Abeta-induced cell death in time- and dose-dependent manners, with the suppression of Abeta-induced DNA fragmentation and caspase-3 activation. In cultured neurons, the pre-treatment of RNFG abolished the increase of Ca(2+) mobilization triggered by Abeta. The neuroprotective properties of RNFG required a specific sugar attachment within the main chemical backbone because the flavonol backbone by itself did not show any protective effect. In memory impairment experiments using the passive avoidance task, the administration of RNFG reduced brain damage in scopolamine-treated rats. These results therefore reveal a novel function of Radix Notoginseng and its flavonol glycoside that could be very useful in developing food supplements for the prevention, or potential treatment, of Alzheimer's disease.

Expression and Localization of PRiMA-linked globular form acetylcholinesterase in vertebrate neuromuscular junctions.

Acetylcholinesterase (AChE) is well known to process different molecular forms via the distinct interacting partners. Proline-rich membrane anchor (PRiMA)-linked tetrameric globular AChE (G4 AChE) is mainly found in the vertebrate brain; however, recent studies from our laboratory have suggested its existence at neuromuscular junctions (nmjs). Both muscle and motor neuron express AChE at the nmjs. In muscle, the expression of PRiMA-linked AChE is down-regulated during myogenic differentiation and by motor neuron innervation. As compared with muscle, spinal cord possessed higher total AChE activity and contained PRiMA-linked AChE forms. The spinal cord expression of this form increased during development. More importantly, PRiMA-linked G4 AChE identified as aggregates localized at nmjs. These findings suggest that the restricted localization of PRiMA-linked G4 AChE at the nmjs could be contributed by the pre-synaptic motor neuron and/or the post-synaptic muscle fiber.

A new variant of proline-rich membrane anchor (PRiMA) of acetylcholinesterase in chicken: expression in different muscle fiber types.

Proline-rich membrane anchor (PRiMA) is a molecule to organize acetylcholinesterase (AChE) into tetrameric globular form (G(4)) that anchors onto the plasma membrane in brain and muscle. In mammal, PRiMA is encoded by a single gene with two splicing variants, PRiMA I and PRiMA II: PRiMA II is different to PRiMA I by its absence of a C-terminal cytoplasmic domain. The existence of these isoforms has not been revealed in avian specie. By using RT-PCR and bioinformatic analyses, two splicing variants of PRiMA were identified in chicken cerebrum. One variant contains very similar domains as compared to mammalian PRiMA I. The other variant, named as PRiMA II, has a very distinct cytoplasmic C-terminus of having 26 amino acids. Both forms of chicken PRiMA were able to organize the formation of G(4) AChE when that was over expressed together with AChE(T) subunit in cultured cells. The level of PRiMA mRNA, mainly PRiMA I, was higher in slow-twitch muscle than that of in fast-twitch muscle of chicken. This finding suggests that the muscle fiber type-specific expression of G(4) AChE in chicken could be a result of the different expression pattern of PRiMA in fast- and slow-twitch muscles.

Hibifolin, a flavonol glycoside, prevents beta-amyloid-induced neurotoxicity in cultured cortical neurons.

The toxicity of aggregated beta-amyloid (A beta) has been implicated as a critical cause in the development of Alzheimer's disease (AD). Hibifolin, a flavonol glycoside derived from herbal plants, possessed a strong protective activity against cell death induced by aggregated A beta. Application of hibifolin in primary cortical neurons prevented the A beta-induced cell death in a dose-dependent manner. In cultured cortical neurons, the pre-treatment of hibifolin abolished A beta-induced Ca(2+) mobilization, and also reduced A beta-induced caspase-3 and caspase-7 activation. Moreover, DNA fragmentation induced by A beta could be suppressed by hibifolin. In addition to such protection mechanisms, hibifolin was able to induce Akt phosphorylation in cortical neurons, which could be another explanation for the neuroprotection activity. These results therefore provided the first evidence that hibifolin protected neurons against A beta-induced apoptosis and stimulated Akt activation, which would be useful in developing potential drugs or food supplements for treating AD.

Estrogenic and neuroprotective properties of scutellarin from Erigeron breviscapus: a drug against postmenopausal symptoms and Alzheimer's disease.

Besides the classical hormonal effect, estrogen possesses neuroprotective effects in the brain, which leads to the searching of novel treatments for neurodegenerative diseases such as Alzheimer's disease. Scutellarin is a major flavone derived from Herba Erigerontis, a Chinese medicine derived from Erigeron breviscapus, which has been shown here to possess both estrogenic and neuroprotective properties. Scutellarin showed the estrogenic effects by activating the estrogen responsive elements and phosphorylation of estrogen receptor alpha in cultured MCF-7 cells: the activation was in a dose-dependent manner. On the other hand, scutellarin inhibited the aggregation of beta-amyloid in vitro, and prevented the cell death mediated by beta-amyloid when applied to cultured neuronal PC12 cells. These results therefore suggested that Herba Erigerontis and its component scutellarin might have therapeutic effects against postmenopausal symptoms and Alzheimer's disease.

Myocyte enhancer factor 2 mediates acetylcholine-induced expression of acetylcholinesterase-associated collagen ColQ in cultured myotubes.

The collagenous protein (ColQ) characterizes the collagen-tailed forms of acetylcholinesterase (AChE) in vertebrate muscles. Two ColQ transcripts, ColQ-1 and ColQ-1a, driven by two distinct promoters are expressed differentially in mammalian slow- and fast-twitch muscles, respectively. Such expression patterns are determined by the contractile activity in different muscle fiber types. To reveal the regulatory role of muscular activity on ColQ expression, acetylcholine and nicotine were applied onto C2C12 muscle cells: the challenge increased the expression of ColQ-1/ColQ-1a mRNAs. The agonist challenge induced the phosphorylation of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII). In parallel, over expression of an active mutant of CaMKII enhanced both ColQ-1/ColQ-1a mRNA levels in cultured C2C12 myotubes. Moreover, the over expression of myocyte enhancer factor 2 (MEF2), a downstream mediator of CaMKII, in the myotubes potentiated the CaMKII-induced ColQ expression. The current results reveal a signaling cascade that drives the expression profiles of ColQ in responding to activity challenge in cultured myotubes.

Transcriptional control of different subunits of AChE in muscles: signals triggered by the motor nerve-derived factors.

Acetylcholinesterase (AChE) is a highly polymorphic enzyme. Alternative splicing in the 3' region of the primary transcript generates different subunits that contain the same catalytic domain but with distinct carboxyl termini. In mammals, the AChE(R) variant produces a soluble monomer that is up-regulated in the brain during stress. The AChE(H) variant produces a GPI-anchored dimer that is mainly expressed in blood cells, while AChE(T) variant is largely predominant in the brain and muscle. AChE(T) subunits associate with a collagen tail subunit (ColQ) forming asymmetric AChE species (A(4), A(8), and A(12) AChE) in muscle, and also form amphiphilic tetramers associated with a proline-rich membrane anchor (PRiMA) as globular AChE (G(4) AChE) in brain and muscle. The formation of these AChE forms depends on the physiological status of the muscles, and on the innervating nerves. The motor nerves achieve this regulation by two distinct mechanisms: release of the trophic factor calcitonin gene-related peptide (CGRP) and nerve-evoked electrical activity, which differentially regulate the expression levels of AChE(T), PRiMA and ColQ via different downstream signaling cascades. The regulatory mechanisms provided by the nerve are important to account for the different expression patterns of AChE and associated proteins in fast- and slow-twitch muscles.

Flavonoids possess neuroprotective effects on cultured pheochromocytoma PC12 cells: a comparison of different flavonoids in activating estrogenic effect and in preventing beta-amyloid-induced cell death.

Despite the classical hormonal effect, estrogen possesses a neuroprotective effect in the brain, which has led many to search for novel treatments for neurodegenerative diseases. Flavonoids, a group of compounds mainly derived from vegetables, share a resemblance, chemically, to estrogen, and indeed, some have been used as estrogen substitutes. To search for potential therapeutic agents against neurodegenerative diseases, different subclasses of flavonoids were analyzed and compared with estrogen. First, the estrogenic activities of these flavonoids were determined by activating the estrogen-responsive elements in cultured MCF-7 breast cancer cells. Second, the neuroprotective effects of flavonoids were revealed by measuring its inhibition effects on the formation of reactive oxygen species, the aggregation of beta-amyloid, and the induction of cell death by beta-amyloid in cultured neuronal PC12 cells. Among these flavonoids, baicalein, scutellarin, hibifolin, and quercetin-3'-glucoside possessed the strongest effect in neuroprotection; however, the neuroprotective activity did not directly correlate with the estrogenic activity of the flavonoids. Identification of these flavonoids could be very useful in finding potential drugs, or food supplements, for treating Alzheimer's disease.

Danggui buxue tang--a Chinese herbal decoction activates the phosphorylations of extracellular signal-regulated kinase and estrogen receptor alpha in cultured MCF-7 cells.

Danggui buxue tang (DBT), a Chinese herbal decoction used to treat ailments in women, contains radix Astragali (Huangqi; RA) and radix Angelicae Sinensis (Danggui; RAS). The weight ratio of RA to RAS used in DBT must be 5:1 as stipulated as early as AD 1247; however, DBT's mechanism of action has never been described. Here, the estrogenic effects of DBT were investigated by determining the phosphorylations of estrogen receptor alpha (ER alpha) and extracellular signal-regulated kinase 1/2 (Erk1/2) in cultured MCF-7 cells. The application of DBT triggered the phosphorylation of ER alpha and Erk1/2 in a time-dependent manner. In contrast to the effect of estrogen, DBT triggered ER alpha phosphorylation at both S118 and S167. This DBT-specific phosphorylation was not triggered by an extract of one of the individual herbs, or by mixing the extracts of RA and RAS. DBT-induced downstream signals are described here. These signals suggest the uniqueness of this Chinese herbal decoction that requires a well-defined formulation.