Yongfang Zhang

Anti-Cancer Activities of Tea Epigallocatechin-3-Gallate in Breast Cancer Patients under Radiotherapy

The purpose of this study was to test the hypothesis that administration of epigallocatechin-3-gallate (EGCG), a polyphenol present in abundance in widely consumed tea, inhibits cell proliferation, invasion, and angiogenesis in breast cancer patients. EGCG in 400 mg capsules was orally administered three times daily to breast cancer patients undergoing treatment with radiotherapy. Parameters related to cell proliferation, invasion, and angiogenesis were analyzed while blood samples were collected at different time points to determine efficacy of the EGCG treatment. Compared to patients who received radiotherapy alone, those given radiotherapy plus EGCG for an extended time period (two to eight weeks) showed significantly lower serum levels of vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF), and reduced activation of metalloproteinase-9 and metalloproteinase-2 (MMP9/MMP2). Addition of sera obtained from patients treated with combination of radiotherapy and EGCG feeding for 2-8 weeks to in vitro cultures of highly-metastatic human MDA-MB-231 breast cancer cells resulted in the following significant changes: (1) suppression of cell proliferation and invasion; (2) arrest of cell cycles at the G0/G1 phase; (3) reduction of activation of MMP9/MMP2, expressions of Bcl-2/Bax, c-Met receptor, NF-κB, and the phosphorylation of Akt. MDA-MB-231 cells exposed to 5-10 μM EGCG also showed significant augmentation of the apoptosis inducing effects of γ-radiation, concomitant with reduced NF-κB protein level and AKT phosphorylation. These results provide hitherto unreported evidence that EGCG potentiated efficacy of radiotherapy in breast cancer patients, and raise the possibility that this tea polyphenol has potential to be a therapeutic adjuvant against human metastatic breast cancer.

Neuroprotective effects of PACAP27 in mice model of Parkinson’s disease involved in the modulation of KATP subunits and D2 receptors in the striatum

Pituitary adenylate cyclase activating polypeptide (PACAP) exhibits a protective effect against neural injury in vitro and in vivo. However, it has not been reported whether peripheral intravenous administration of PACAP could confer benefits in animal models of Parkinsons disease (PD). Furthermore, the underlying molecular mechanisms responsible for these effects are poorly understood. In the present experiments, we determined the effects and mechanism of action of intravenously administered PACAP27 in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice. Our results indicate that intravenous injection of PACAP27 offers neuroprotective effects in the MPTP-induced PD mouse model which may not be directly associated with the expression levels of the monoamine transporters. However, this effect may be correlated with its ability to selectively regulate not only K(ATP) subunits, but D2 receptors in the striatum. Our findings suggest that the benefit of PACAP may accompany with changes not only in dopaminergic neurotransmission, but also in cholinergic neurotransmission that are relatively associated with the K(ATP) subunits and D2 receptors in the striatum.

Harpagoside attenuates MPTP/MPP+ induced dopaminergic neurodegeneration and movement disorder via elevating glial cell line‐derived neurotrophic factor

J. Neurochem. (2012) 120, 1072–1083.

Harpagoside ameliorates the amyloid-β-induced cognitive impairment in rats via up-regulating BDNF expression and MAPK/PI3K pathways

So far, no effective disease-modifying therapies for Alzheimers disease (AD) aiming at protecting or reversing neurodegeneration of the disease have been established yet. The present work aims to elucidate the effect of Harpagoside (abbreviated HAR), an iridoid glycosides purified from the Chinese medicinal herb Scrophularia ningpoensis, on neurodegeneration induced by β-amyloid peptide (Aβ) and the underlying molecular mechanism. Here we show that HAR exerts neuroprotective effects against Aβ neurotoxicity. Rats injected aggregated Aβ₁₋₄₀ into the bilateral hippocampus displayed impaired spatial learning and memory ability in a Y-maze test and novel object recognition test, while HAR treatment ameliorated Aβ₁₋₄₀-induced behavioral deficits. Moreover, administration of HAR increased the expression levels of brain-derived neurotrophic factor (BDNF) and activated the extracellular-regulated protein kinase (ERK) and the phosphatidylinositol 3-kinase (PI3-kinase) pathways both in the cerebral cortex and hippocampus of the Aβ₁₋₄₀-insulted rat model. Furthermore, in cultured primary cortical neurons, Aβ₁₋₄₂ induced significant decrease of choline acetyltransferase (ChAT)-positive neuron number and neurite outgrowth length, both of which were dose dependently increased by HAR. In addition, HAR pretreatment also significantly attenuated the decrease of cell viability in Aβ₁₋₄₂-injured primary cortical neurons. Finally, when K252a, an inhibitor of Trk tyrosine kinases, and a BDNF neutralizing antibody were added to the culture medium 2 h prior to HAR addition, the protective effect of HAR on Aβ₁₋₄₂-induced neurodegeneration in the primary cortical neuron was almost inhibited. Taken together, HAR exerting neuroprotection effect and ameliorating learning and memory deficit appears to be associated, at least in part, with up-regulation of BDNF content as well as activating its downstream signaling pathways, e.g., MAPK/PI3K pathways. It raises the possibility that HAR has potential to be a therapeutic agent against AD.

Role of glial cell derived neurotrophic factor in the protective effect of smilagenin on rat mesencephalic dopaminergic neurons damaged by MPP

Tyrosine hydroxylase immunohistochemical analysis revealed that in cultured mesencephalic dopaminergic neurons smilagenin (SMI), added prior to 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPP+), protected against the drop of neuron number and neurite outgrowth length caused by MPP+. Addition of anti‐GDNF and/or anti‐GFRα1 functional antibodies to the medium prior to SMI, eliminated mostly, though incompletely, the action of SMI. The expression of glial cell derived neurotrophic factor (GDNF) mRNA, but not GDNF receptor alpha1 (GFRα1) or receptor tyrosine kinase mRNA in MPP+ intoxicated neurons was markedly elevated as early as 2 h after the addition of SMI with a peak at 24–48 h. Therefore, an important route of the protective action of SMI on dopaminergic neurons is to stimulate intrinsic GDNF expression.

Role of CREB in the regulatory action of sarsasapogenin on muscarinic M1 receptor density during cell aging.

This work studied the role of cyclic AMP responsive element binding protein (CREB) in the up‐regulation of M1 muscarinic acetylcholine receptor (M1 receptor) density by sarsasapogenin (ZMS) in CHO cells transfected with M1 receptor gene (CHOm1 cells). During cell aging, sarsasapogenin elevated M1 receptor density as well as CREB and phosphor‐CREB (pCREB) levels. CREB peaked earliest, followed by pCREB and M1 receptor density peaked last. When CREB synthesis was blocked by antisense oligonucleotides, the elevation effect of sarsasapogenin on M1 receptor density was abolished. These results suggest that sarsasapogenin up‐regulates M1 receptor density in aged cells by promoting CREB production and phosphorylation. Furthermore, the results support the hypothesis that pCREB regulates M1 receptor gene expression through heterodimer formation.

MicroRNA-146a suppresses ROCK1 allowing hyperphosphorylation of tau in Alzheimer's disease.

MicroRNA-146a is upregulated in the brains of patients with Alzheimer’s disease (AD). Here, we show that the rho-associated, coiled-coil containing protein kinase 1 (ROCK1) is a target of microRNA-146a in neural cells. Knockdown of ROCK1 mimicked the effects of microRNA-146a overexpression and induced abnormal tau phosphorylation, which was associated with inhibition of phosphorylation of the phosphatase and tensin homolog (PTEN). The ROCK1/PTEN pathway has been implicated in the neuronal hyperphosphorylation of tau that occurs in AD. To determine the function of ROCK1 in AD, brain tissue from 17 donors with low, intermediate or high probability of AD pathology were obtained and analyzed. Data showed that ROCK1 protein levels were reduced and ROCK1 colocalised with hyperphosphorylated tau in early neurofibrillary tangles. Intra-hippocampal delivery of a microRNA-146a specific inhibitor (antagomir) into 5xFAD mice showed enhanced hippocampal levels of ROCK1 protein and repressed tau hyperphosphorylation, partly restoring memory function in the 5xFAD mice. Our in vitro and in vivo results confirm that dysregulation of microRNA-146a biogenesis contributes to tau hyperphosphorylation and AD pathogenesis, and inhibition of this microRNA could be a viable novel in vivo therapy for AD.

Peripheral Blood MicroRNA Expression Profiles in Alzheimer’s Disease: Screening, Validation, Association with Clinical Phenotype and Implications for Molecular Mechanism

A series of investigations have been performed regarding microRNA (miRNA, miR) of Alzheimer’s disease (AD) patients. However, most of these used microarray with neither validation by PCR nor any follow-up on the biological mechanism implicated by findings. Further, there were rarely any analyses linking clinical phenotype of de novo, drug-naive patients to cellular pathogenic mechanism(s) to date. Microarray screening followed by validation via quantitative PCR (Q-PCR) assays and the relationship between miRNAs and phenotypic indices were evaluated. Additionally, the cellular mechanism of miRNAs through effects of β-site amyloid precursor protein (APP) cleaving enzyme (BACE1) was assessed. We identified 2 specific differentially expressed (DE) miRNAs (miR-339 and miR-425) as potential diagnostic biomarkers for AD and revealed that these DE miRNAs could be involved in modulating the pathogenesis of AD via BACE1 protein inhibition. The findings presented here reveal a detailed snapshot of the profile of peripheral blood mononuclear cells (PBMC) miRNA changes in AD patients, association with clinical phenotype, and potential roles in cellular pathogenesis.

MicroRNA‐146a represses LRP2 translation and leads to cell apoptosis in Alzheimer's disease

MicroRNA regulation of transcript expression has been reported in patients with Alzheimers disease (AD). Here, we investigate the role of microRNA‐146a (miRNA‐146a), a brain‐enriched miRNA, which is upregulated in AD patients. Through analysis of predicted targets of miRNA‐146a, low‐density lipoprotein receptor‐related protein‐2 (Lrp2), a member of the LDLR family that is known to play a protective role in AD, was identified. Overexpression of miRNA‐146a in SH‐SY5Y cells significantly decreased Lrp2 expression, resulting in a reduction of Akt activation and induction of proapoptotic caspase‐3, thereby increasing cell apoptosis. Thus, specific miRNA‐146a regulation may contribute to AD by downregulating the Lrp2/Akt pathway.

Catalpol protects synaptic proteins from beta-amyloid induced neuron injury and improves cognitive functions in aged rats

Synapse loss is one of the common factors contributing to cognitive disorders, such as Alzheimers disease (AD), which is manifested by the impairment of basic cognitive functions including memory processing, perception, problem solving, and language. The current therapies for patients with cognitive disorders are mainly palliative; thus, regimens preventing and/or delaying dementia progression are urgently needed. In this study, we evaluated the effects of catalpol, isolated from traditional Chinese medicine Rehmannia glutinosa, on synaptic plasticity in aged rat models. We found that catalpol markedly improved the cognitive function of aged male Sprague-Dawley rats and simultaneously increased the expression of synaptic proteins (dynamin 1, PSD-95, and synaptophysin) in the cerebral cortex and hippocampus, respectively. In beta-amyloid (Aβ) injured primary rat, catalpol did not increase the viability of neuron but extended the length of microtubule-associated protein 2 (MAP-2) positive neurites and reversed the suppressive effects on expression of synaptic proteins induced by Aβ. Additionally, the effects of catalpol on stimulating the growth of MAP-2 positive neurites and the expression of synaptic proteins were diminished by a PKC inhibitor, bisindolylmaleimide I, suggesting that PKC may be implicated in catalpols function of preventing the neurodegeneration induced by Aβ. Altogether, our study indicates that catalpol could be a potential disease-modifying drug for cognitive disorders such as AD.Synapse loss is one of the common factors contributing to cognitive disorders, such as Alzheimer’s disease (AD), which is manifested by the impairment of basic cognitive functions including memory processing, perception, problem solving, and language. The current therapies for patients with cognitive disorders are mainly palliative; thus, regimens preventing and/or delaying dementia progression are urgently needed. In this study, we evaluated the effects of catalpol, isolated from traditional Chinese medicine Rehmannia glutinosa, on synaptic plasticity in aged rat models. We found that catalpol markedly improved the cognitive function of aged male Sprague-Dawley rats and simultaneously increased the expression of synaptic proteins (dynamin 1, PSD-95, and synaptophysin) in the cerebral cortex and hippocampus, respectively. In beta-amyloid (Aβ) injured primary rat’s cortical neuron, catalpol did not increase the viability of neuron but extended the length of microtubule-associated protein 2 (MAP-2) positive neurites and reversed the suppressive effects on expression of synaptic proteins induced by Aβ. Additionally, the effects of catalpol on stimulating the growth of MAP-2 positive neurites and the expression of synaptic proteins were diminished by a PKC inhibitor, bisindolylmaleimide I, suggesting that PKC may be implicated in catalpol’s function of preventing the neurodegeneration induced by Aβ. Altogether, our study indicates that catalpol could be a potential disease-modifying drug for cognitive disorders such as AD.