Molecular profiling of ginsenoside metabolites to identify estrogen receptor alpha activity.

20(S)-Protopanaxadiol (PPD) and 20(S)-Protopanaxatriol (PPT) are major metabolites of ginseng in humans and are considered to have estrogenic activity in cellular bioassays. In this study, we conducted in silico analyses to determine whether PPD and PPT interact with estrogen receptor alpha (ERα) and compared them with ERα agonists, partial agonists, and antagonists to identify their ERα activity. The transcriptome profile of 17ß-estradiol (E2), PPD, and PPT in MCF-7 cells expressing ERα was further compared to understand the ERα activity of ginsenoside metabolites. The results showed that PPD and PPT interacted with the 1ERE, 1GWR, and 3UUD ERα proteins in the E2 interaction model, the 3ERD protein in the diethylstilbestrol (DES) interaction model, and the 1X7R protein in the genistein (GEN) interaction model. Conversely, neither the 4PP6 protein of the interaction model with the antagonist resveratrol (RES) nor the 1ERR protein of the interaction model with the antagonist raloxifene (RAL) showed the conformation of amino acid residues. When E2, PPD, and PPT were exposed to MCF-7 cells, cell proliferation and gene expression were observed. The transcriptomic profiles of E2, PPD, and PPT were compared using a knowledge-based pathway. PPD-induced transcription profiling was similar to that of E2, and the neural transmission pathway was detected in both compounds. In contrast, PPT-induced transcription profiling displayed characteristics of gene expression associated with systemic lupus erythematosus. These results suggest that ginsenoside metabolites have ERα agonist activity and exhibit neuroprotective effects and anti-inflammatory actions. However, a meta-analysis using public microarray data showed that the mother compounds GRb1 and GRg1 of PPD and PPT showed metabolic functions in insulin signaling pathways, condensed DNA repair and cell cycle pathways, and immune response and synaptogenesis. These results suggest that the ginsenoside metabolites have potent ERα agonist activity; however, their gene expression profiles may differ from those of E2.

Effect of the natural compound trans­resveratrol on human MCM4 gene transcription.

trans­Resveratrol (Rsv) is a natural compound contained in red wine and grape skins that has various beneficial effects for organisms such as lengthening of their life span. Rsv induces expression of the human TP53 and HELB genes, which are involved in the regulation of DNA maintenance. In the present study, a luciferase expression vector containing 309 bp of the 5' upstream end of the human MCM4 gene was transfected into HeLa S3 cells. A luciferase assay revealed that Rsv treatment increased the minichromosome maintenance 4 (MCM4) gene promoter activity by GC­box and GGAA (TTCC) motifs. Electro phoretic mobility shift assay revealed that the specific binding factor (complex) contains PU.1 (SPI1). Quantitative reverse transcription­polymerase chain reaction analysis indicated that MCM4 gene expression was transiently induced by Rsv. Moreover, western blotting revealed that the SP1/PU.1 ratio markedly increased after Rsv treatment, indicating that a balance or profile of these transcription factors may control Rsv­inducible initiation of transcription. These observations indicated that the beneficial effects of Rsv can be attributed to induction of the chromosomal DNA maintenance factor encoding gene expression.

Characterization of the human zinc finger nfx­1­type containing 1 encoding ZNFX1 gene and its response to 12­O­tetradecanoyl­13­acetate in HL­60 cells.

Human promyelocytic HL­60 cells can be differentiated into macrophage­like cells by treatment with 12­O­tetra decanoylphorbol­13­acetate (TPA). Certain 5' upstream regions of the zinc finger protein (ZNF)­encoding genes contain duplicated GGAA motifs, which are frequently found in the TPA­responding gene promoter regions. To examine transcriptional responses to TPA, 5'flanking regions of human zinc finger CCCH­type containing, antiviral, ZNF252, ZNF343, ZNF555, ZNF782 and zinc finger nfx­1­type containing 1 (ZNFX1) genes were isolated by polymerase chain reaction (PCR) and ligated into a multiple­cloning site of the pGL4.10[luc2] vector. Transient transfection and a luciferase assay revealed that the ZNFX1 promoter most prominently responded to the TPA treatment. Deletion and point mutation experiments indicated that the duplicated GGAA motif in the 100­bp region positively responded to TPA. In addition, reverse transcription­quantitative PCR and western blotting showed that the mRNA and protein of ZNFX1 accumulate during the differentiation of HL­60 cells. These results indicated that expression of the TPA­inducible ZNFX1 gene, which belongs to the group of interferon­responsive genes, is regulated by the cis­action of the duplicated GGAA motif.

Characterization of the human E2F4 promoter region and its response to 12-O-tetradecanoylphorbol-13-acetate.

The E2F transcription factors (TFs), which control the progression of the cell cycle in response to DNA-damage and various stresses, are known to interact with a tumour suppressor, Retinoblastoma 1 (RB1). We previously showed that the response of the human RB1 promoter to a 12-O-tetradecanoylphorbol-13-acetate (TPA) in HL-60 cells is mediated by a duplicated GGAA motif, which is also present in the 5'-upstream of the E2F family genes. The motifs are especially rich in the 5'-upstream of the E2F4 gene. In the present study, we constructed luciferase (Luc) expression vectors containing a 466 bp of the 5'-upstream of the human E2F4 gene. The transfection of this plasmid and deletion/mutation-introduced derivatives into HL-60 cells and a Luc reporter assay showed that duplicated and triplicated GGAA (TTCC) motifs in the E2F4 promoter respond to TPA. As expected, electrophoretic mobility shift assay indicated that SPI1 (PU.1) binds to the GGAA motif-containing element. A quantitative RT-PCR and western blotting showed that the E2F4 transcripts and its encoding proteins accumulate during the differentiation of HL-60 into macrophage-like cells. In contrast, the expression of the E2F1 gene and the protein, which possibly acts as a cell cycle accelerator, was greatly diminished.

Elucidating Pathogenic Mechanisms of Early-onset Alzheimer's Disease in Down Syndrome Patients.

Down syndrome (DS) patients demonstrate the neuropathology of Alzheimer's disease (AD) characterized by the formation of senile plaques and neurofibrillary tangles by age 40-50 years. It has been considered for a number of years that 1.5-fold expression of the gene for the amyloid precursor protein (APP) located on chromosome 21 leading to overproduction of amyloid-ß peptide (Aß) results in the early onset of AD in adults with DS. However, the mean age of onset of familial AD with the Swedish mutation on APP which has high affinity for ß-secretase associated with a dramatic increase in Aß production is about 55 years. This paradox indicates that there is a poor correlation between average ages of AD onset and the theoretical amount of Aß production and that there are factors exacerbating AD on chromosome 21. We therefore focused on dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A), since overexpressing transgenic mice show AD-like brain pathology. The overexpression of DYRK1A caused suppression of the activity of neprilysin (NEP), which is a major Aß-degrading enzyme in the brain, and phosphorylation at the NEP cytoplasmic domain. NEP activity was markedly reduced in fibroblasts derived from DS patients compared with that in fibroblasts derived from healthy controls. This impaired activity of NEP was rescued by DYRK1A inhibition. These results show that DYRK1A overexpression causes suppression of NEP activity through its phosphorylation in DS patients. Our results suggest that DYRK1A inhibitors could be effective against AD not only in adults with DS but also in sporadic AD patients.

Neprilysin Is Suppressed by Dual-Specificity Tyrosine-Phosphorylation Regulated Kinase 1A (DYRK1A) in Down-Syndrome-Derived Fibroblasts.

Amyloid-ß peptide (Aß) accumulation is a triggering event leading to the Alzheimer's disease (AD) pathological cascade. Almost all familial AD-linked gene mutations increase Aß production and accelerate the onset of AD. The Swedish mutation of amyloid precursor protein (APP) affects ß-secretase activity and increases Aß production up to ca. 6-fold in cultured cells; the onset age is around 50. Down syndrome (DS) patients with chromosome 21 trisomy present AD-like pathologies at earlier ages (40s) compared with sporadic AD patients, because APP gene expression is 1.5-fold higher than that in healthy people, thus causing a 1.5-fold increase in Aß production. However, when comparing the causal relationship of Aß accumulation with the onset age between the above two populations, early DS pathogenesis does not appear to be accounted for by the increased Aß production alone. In this study, we found that neprilysin, a major Aß-degrading enzyme, was downregulated in DS patient-derived fibroblasts, compared with healthy people-derived fibroblasts. Treatment with harmine, an inhibitor of dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A), which is located in the DS critical region of chromosome 21, and gene knockdown of DYRK1A, upregulated neprilysin in fibroblasts. These results suggest that a decrease in the Aß catabolic rate may be, at least in part, one of the causes for accelerated AD-like pathogenesis in DS patients if a similar event occurs in the brains, and that neprilysin activity may be regulated directly or indirectly by DYRK1A-mediated phosphorylation. DYRK1A inhibition may be a promising disease-modifying therapy for AD via neprilysin upregulation.

Perturbed Calcineurin-NFAT Signaling Is Associated with the Development of Alzheimer's Disease.

Down syndrome (DS), the most common genetic disorder, is caused by trisomy 21. DS is accompanied by heart defects, hearing and vision problems, obesity, leukemia, and other conditions, including Alzheimer's disease (AD). In comparison, most cancers are rare in people with DS. Overexpression of dual specificity tyrosine-phosphorylation-regulated kinase 1A and a regulator of calcineurin 1 located on chromosome 21 leads to excessive suppression of the calcineurin-nuclear factor of activated T cells (NFAT) signaling pathway, resulting in reduced expression of a critical angiogenic factor. However, it is unclear whether the calcineurin-NFAT signaling pathway is involved in AD pathology in DS patients. Here, we investigated the association between the calcineurin-NFAT signaling pathway and AD using neuronal cells. Short-term pharmacological stimulation decreased gene expression of tau and neprilysin, and long-term inhibition of the signaling pathway decreased that of amyloid precursor protein. Moreover, a calcineurin inhibitor, cyclosporine A, also decreased neprilysin activity, leading to increases in amyloid-ß peptide levels. Taken together, our results suggest that a dysregulation in calcineurin-NFAT signaling may contribute to the early onset of AD in people with DS.

Cathepsin K-mediated Notch1 activation contributes to neovascularization in response to hypoxia.

Cysteine proteases play important roles in pathobiology. Here we reveal that cathepsin K (CatK) has a role in ischaemia-induced neovascularization. Femoral artery ligation-induced ischaemia in mice increases CatK expression and activity, and CatK-deficient mice show impaired functional recovery following hindlimb ischaemia. CatK deficiency reduces the levels of cleaved Notch1 (c-Notch1), Hes1 Hey1, Hey2, vascular endothelial growth factor, Flt-1 and phospho-Akt proteins of the ischaemic muscles. In endothelial cells, silencing of CatK mimicked, whereas CatK overexpression enhanced, the levels of c-Notch1 and the expression of Notch downstream signalling molecules, suggesting CatK contributes to Notch1 processing and activates downstream signalling. Moreover, CatK knockdown leads to defective endothelial cell invasion, proliferation and tube formation, and CatK deficiency is associated with decreased circulating endothelial progenitor cells-like CD31(+)/c-Kit(+) cells in mice following hindlimb ischaemia. Transplantation of bone marrow-derived mononuclear cells from CatK(+/+) mice restores the impairment of neovascularization in CatK(-/-) mice. We conclude that CatK may be a potential therapeutic target for ischaemic disease.

Global brain delivery of neprilysin gene by intravascular administration of AAV vector in mice.

Accumulation of amyloid-ß peptide (Aß) in the brain is closely associated with cognitive decline in Alzheimer's disease (AD). Stereotaxic infusion of neprilysin-encoding viral vectors into the hippocampus has been shown to decrease Aß in AD-model mice, but more efficient and global delivery is necessary to treat the broadly distributed burden in AD. Here we developed an adeno-associated virus (AAV) vector capable of providing neuronal gene expression throughout the brains after peripheral administration. A single intracardiac administration of the vector carrying neprilysin gene in AD-model mice elevated neprilysin activity broadly in the brain, and reduced Aß oligomers, with concurrent alleviation of abnormal learning and memory function and improvement of amyloid burden. The exogenous neprilysin was localized mainly in endosomes, thereby effectively excluding Aß oligomers from the brain. AAV vector-mediated gene transfer may provide a therapeutic strategy for neurodegenerative diseases, where global transduction of a therapeutic gene into the brain is necessary.

An alternative metabolic pathway of amyloid precursor protein C-terminal fragments via cathepsin B in a human neuroglioma model.

γ-Secretase catalyzes the cleavage of the intramembrane region of the Alzheimer amyloid precursor protein (APP), generating p3, amyloid-ß peptide (Aß), and the APP intracellular domain (AICD). Although a γ-secretase inhibitor has been shown to cause an accumulation of the APP C-terminal fragments (CTFs) α and ß and to decrease levels of p3 or Aß and AICD, we found that treatment with a lysosomotropic weak base, such as chloroquine or ammonium chloride, caused simultaneous accumulation of both CTFs and AICD, suggesting that lysosomal proteases are also involved in processing of APP. This observation was reinforced by the results that cysteine protease inhibitor E-64d and cathepsin B specific inhibitor CA-074Me caused the accumulation of both CTFs and AICD with no change in known secretase activities. γ-Secretase preferentially cleaved phosphorylated CTFs to produce Aß, but cathepsin B degraded CTFs regardless of phosphorylation. Our results suggest that cathepsin B plays novel roles in the metabolism of APP and that an inhibition of APP phosphorylation is an attractive therapeutic target for Alzheimer's disease.

Efficient four-drug cocktail therapy targeting amyloid-ß peptide for Alzheimer's disease.

Cocktail treatment is an effective multidrug medication therapy for some diseases, such as cancer and AIDS, because of the additive or synergistic effect of each medicine and relief from adverse effects. Amyloid-ß peptide (Aß), which is now recognized as central to the development of Alzheimer's disease (AD), is derived from the sequential proteolysis of amyloid precursor protein (APP) by ß- and γ-secretases. Secretase inhibitors are one of most attractive targets for therapeutic intervention in AD. However, because ß- and γ-secretases cleave not only APP but also other substrate proteins, strong inhibition of these secretases leads to severe adverse effects. Some nonsteroidal antiinflammatory drugs (NSAIDs) and cholesterol-lowering drugs (statins) can modify the production of Aß. Here, we report that a cocktail treatment with four drugs (NSAID, statin, and ß- and γ-secretase inhibitors) had additive effects on the reduction of Aß levels in cultured cells without competing with each other. Moreover, the four-drug cocktail treatment caused no changes in processing of the γ-secretase substrate Notch. This is suggests that this cocktail treatment could be a new therapeutic approach for AD.

1,3-Capryloyl-2-arachidonoyl glycerol activates alpha-secretase activity and suppresses Abeta40 secretion in A172 cells.

Alzheimer's disease (AD) is characterized by the deposition of amyloid beta-peptide (Abeta), derived from amyloid precursor protein (APP). Membrane states, such as lipid components or membrane fluidity, are important for enzymes related to APP processing in meeting their substrates efficiently. We analyzed the effects of triglycerides combined with polyunsaturated fatty acids (PUFAs) and/or caprylic acids on APP proteolysis. Our results showed that 1,3-capryloyl-2-arachidonoyl glycerol (8A8) moderately increased alpha-secretase activity (18%) in A172 cells. beta-Secretase activity was not statistically significantly changed in HEK293 cells stably expressing BACE1. However, Abeta40 secretion decreased by 22%. Thus, we conclude that 8A8 is a useful lipid compound for activating alpha-secretase activity and suppressing Abeta40 secretion.

Putative function of ADAM9, ADAM10, and ADAM17 as APP alpha-secretase.

The putative alpha-secretase cleaves the amyloid precursor protein (APP) of Alzheimer's disease in the middle of the amyloid beta peptide (Abeta) domain. It is generally thought that the alpha-secretase pathway mitigates Abeta formation in the normal brain. Several studies have suggested that ADAM9, ADAM10, and ADAM17 are candidate alpha-secretases belonging to the ADAM (a disintegrin and metalloprotease) family, which are membrane-anchored cell surface proteins. In this comparative study of ADAM9, ADAM10, and ADAM17, we examined the physiological role of ADAMs by expressing these ADAMs in COS-7 cells, and both "constitutive" and "regulated" alpha-secretase activities of these ADAMs were determined. We tried to suppress the expression of these ADAMs in human glioblastoma A172 cells, which contain large amounts of endogenous alpha-secretase, by lipofection of the double-stranded RNA (dsRNA) encoding each of these ADAMs. The results indicate that ADAM9, ADAM10, and ADAM17 catalyze alpha-secretory cleavage and therefore act as alpha-secretases in A172 cells. This is the first report that to suggest the endogenous alpha-secretase is composed of several ADAM enzymes.

BACE1 interacts with nicastrin.

Beta-amyloid peptide (Abeta) is generated through the proteolytic cleavage of beta-amyloid precursor protein (APP) by beta- and gamma-secretases. The beta-secretase, BACE1, initiates Abeta formation followed by gamma-cleavage within the APP transmembrane domain. Although BACE1 localizes in the transGolgi network (TGN), its physiological substrates and modulators are not known. In addition, the relationship to other secretase(s) also remains unidentified. Here, we demonstrate that BACE1 binds to nicastrin, a component of gamma-secretase complexes, in vitro, and that nicastrin activates beta-secretase activity in COS-7 cells.