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Yi Wen

Publications and source records attributed to Yi Wen.

At least 37 records · Page 2Linked to original sources
PubMed2005

Role of parvalbumin in estrogen protection from ethanol withdrawal syndrome.

BACKGROUND: Parvalbumin (PA) is a calcium-binding protein that has been implicated in protecting neurons from hyperexcitability by sequestering intracellular calcium. This study examined whether ethanol exposure and/or ethanol withdrawal (EW) alter the levels of PA in a manner that is protected by 17beta-estradiol (E2). METHODS: Ovariectomized rats implanted with E2 (EW/E2) or oil pellets (EW/Oil) received chronic ethanol (7.5% w/v, 5 weeks) or control dextrin (Dex/Oil and Dex/E2) diets. At 0 hr, 24 hr, and 2 weeks of EW, three brain areas (the cerebellum, hippocampus, and cortex) were prepared for immunoblotting and immunohistological assessment of PA. RESULTS: At 24 hr of EW, the EW/Oil group showed reduced levels of PA protein and PA-positive neurons in the cerebellum and hippocampus compared with the dextrin control and the EW/E2 groups. At 2 weeks of EW, the reduced levels of PA persisted in the cerebellum but recovered toward the control levels in the hippocampus. The cortex showed no change in PA levels in any of the treatment groups. When tested at 24 hr of EW, the magnitude of EW signs inversely correlated with the levels of PA in the cerebellum and hippocampus. Ethanol exposure itself did not affect PA levels. CONCLUSION: These data suggest that EW, rather than ethanol exposure, reduces PA levels in a manner that is brain region specific and that is protected by estrogen. Disturbed PA homeostasis is hypothesized to play a role in the hyperexcitability of EW signs.

Animals↗
PubMed2005

Acid acclimation by Helicobacter pylori.

Helicobacter pylori is a Gram-negative neutralophile associated with peptic ulcers and gastric cancer. It has a unique ability to colonize the human stomach by acid acclimation. It uses the pH-gated urea channel, UreI, to enhance urea access to intrabacterial urease and a membrane-anchored periplasmic carbonic anhydrase to regulate periplasmic pH to approximately 6.1 in acidic media, whereas other neutralophiles cannot regulate periplasmic pH and thus only transit the stomach.

Adaptation, Physiological↗
PubMed2005

Role of nonfeminizing estrogens in brain protection from cerebral ischemia: an animal model of Alzheimer's disease neuropathology.

Estrogens are potent and efficacious neuroprotectants both in vitro and in vivo in a variety of models of neurotoxicity. We determined the structural requirements for neuroprotection in in vitro assays using a library of more than 70 novel estratrienes, synthesized to reduce or eliminate estrogen receptor (ER) binding. We observed that neuroprotection could be enhanced by as much as 200-fold through modifications that positioned a large, bulky group at the C2 and/or C4 position of the phenolic A ring of the estratriene. Further, substitutions on the B, C, or D rings either reduced or did not markedly change neuroprotection. For this library of compounds, there was a negative correlation between ER binding and neuroprotection, as the more potent compounds showed weaker or no ER binding. In an in vivo model for neuroprotection, transient cerebral ischemia, efficacious compounds were active in protection of brain tissue from this pro-oxidant insult. Finally, estradiol protected brains from insult-induced Alzheimer's disease (AD) neuropathology, including activation of apoptosis, stimulation of Abeta production, hyperphosphorylation of tau, activation of cyclin-dependent kinases, and activation of catastrophic attempts at neuronal mitosis. Collectively, these results demonstrate that nonfeminizing estrogens are neuroprotective and protect the brain from the induction of AD-like neuropathology in an animal model. These features of nonfeminizing estrogens make them attractive compounds for assessment of efficacy in AD and stroke, because they are not expected to show the side effects of chronic estrogen therapy that are ER mediated in the liver, uterus, and breast.

Alzheimer Disease↗
PubMed2005

[Heteroplasmy: a common phenomenon of mitochondrial genome mutations in human tumor tissues].

To explore the status of heteroplasmy and homoplasmy of Mitochondrial DNA somatic mutations in different tumors. DNA from 149 tumors and corresponding normal tissues were extracted and entire mitochondrial genome was amplified using 32 pairs of overlapping primers. The somatic mutations were screened by temporal temperature gradient gel electrophoresis and their heteroplasmic statute were identified by sequencing. The results showed that the incidence rate of heteroplasmy of mitochondrial DNA somatic mutations varies in different tumors. There is a high rate of heteroplasmic mutation in oral cancer (65%) and esophageal cancer (64%), followed by breast cancer (45%). The frequency of four transfer types is Hm (homoplasmy)-->Hm (heteroplasmy) > Hm-->Ht > Ht-->Hm > Ht-->Ht. The main transfer forms of transition and transversion mutations are Hm-->Hm and Hm-->Ht respectively. Heteroplasmy is a common phenomenon in mitochondrial DNA somatic mutations of human tumors.

Breast Neoplasms↗
PubMed2004

Ethanol withdrawal reduces cerebellar parvalbumin expression in a manner reversed by estrogens.

Parvalbumin (PA) is a calcium-binding protein that has been implicated in neuroprotection. We examined whether the stimulus effect of ethanol withdrawal (EW) alters the expression of PA in a manner that is prevented by 17beta-estradiol (E2). Ovariectomized rats implanted with E2 (EW/E2) or oil (EW/Oil) pellets received chronic ethanol (7.5%, w/v, 5 weeks) or control dextrin diets (Dex/Oil). At 24h of EW, rats were tested for overt EW signs, and the cerebellum was prepared for immunoblotting and immunohistological assessment for PA. The EW/Oil group showed a higher EW sign score, a lower PA expression, and fewer PA-positive Purkinje neurons than the dextrin control group. In the EW/E2 group, EW sign scores, PA expression, and PA-positive Purkinje neurons were not significantly different from those in the control dextrin group. These data suggest that E2 treatment protects against the PA-suppression associated with EW toxicity.

Animals↗
PubMed2004

Transient cerebral ischemia induces site-specific hyperphosphorylation of tau protein.

Neurofibrillary tangles (NFTs) are a pathological hallmark of many neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease (PD), and frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP17). However, the cellular origin and the consequence of the NFT formation are poorly understood. Epidemiological evidence suggests a much higher occurrence of dementia in stroke patients. This may represent the pathogenesis of sporadic AD, which accounts for the majority of AD occurrence. Here we show that after a transient cerebral ischemia, hyperphosphorylated tau accumulates in cortical neurons in a site-specific manner. The hyperphosphorylated tau presents a conformation similar to those present in human tauopathies, and colocalizes largely with signs of apoptosis. Our current study suggests that tau hyperphosphorylation may contribute to the brain damage induced by transient cerebral ischemia, and may be involved in the pathogenesis of neurodegenerative disorders in patients after stroke. Further, these results indicate that ischemic neuronal damage and apoptosis associates with tau hyperphosphorylation, and potentially NFTs formation. Finally, our results also suggest that neuronal apoptosis may be a therapeutic target in preventing tauopathy-related neurodegenerative diseases.

Analysis of Variance↗
PubMed2004

nNOS is involved in estrogen mediated neuroprotection in neuroblastoma cells.

Estrogens exert neuroprotective activity in both in vivo and in vitro model systems. Herein, we report that both 17beta-estradiol and low concentrations of nitric oxide (NO) attenuate hydrogen peroxide (H2O2) induced toxicity in SK-N-SH cells, which express the neuronal nitric oxide synthase (nNOS). 17beta-estradiol rapidly induced an increase in NO levels. A nNOS inhibitor was able to block the neuroprotection of 17beta-estradiol. Cyclic guanylyl mono-phosphate (cGMP) also protected against H2O2 induced toxicity, while NO's protection was attenuated by ODQ, a soluble guanylyl cyclase (sGC) inhibitor. In SK-N-SH cells, the major estrogen receptor isoforms is estrogen receptor beta. Our current study suggests that increased activity of nNOS may be involved in the neuroprotection conferred by 17beta-estradiol.

Cell Line, Tumor↗
PubMed2004

Increased beta-secretase activity and expression in rats following transient cerebral ischemia.

The aberrant proteolytic processing of the amyloid precursor protein (APP) by beta- and gamma-secretases is key to amyloid plaque formation in Alzheimer's disease (AD). Identification of an aspartyl protease as the beta-secretase (beta-site APP cleaving enzyme, BACE) involved in APP processing provides a pharmaceutical target for potential AD treatment. In the present studies, we demonstrate that transient cerebral ischemia in female rats caused a 30% increase in beta-secretase activity. alpha-Secretase activity did not increase significantly. We examined protein levels of BACE1, and its analogue BACE2, in ischemic brain extracts. BACE1 protein levels increased 67%, while BACE2 protein level did not change after such a transient ischemia. Immunohistochemical studies demonstrated that BACE1 protein was increased in the ischemic neocortex, when compared with its contralateral cortex. Further, colocalization assessment indicated that BACE1 strongly associated with staining for the apoptotic marker, TUNEL. These results may partially explain epidemiological study, which demonstrate a higher incidence of dementia after stroke. Further, our results support the hypothesis that apoptosis and aberrant APP processing are correlated events in AD brain, and suggest that inhibition of BACE may have a therapeutic effect in the prevention of dementia after stroke recovery.

Amyloid Precursor Protein Secretases↗
PubMed2004

Estrogen attenuates nuclear factor-kappa B activation induced by transient cerebral ischemia.

The protective effects of estrogens have been widely reported in a number of animal and cell culture models, but the molecular mechanisms of this potent neuroprotective activity are not well understood. Both in vitro and in vivo studies indicate that in the central nervous system and peripheral tissues, estrogen treatment reduces cytokine production and inflammatory responses. Nuclear factor-kappa B (NFkappaB) plays an essential role in the regulation of post-ischemic inflammation, which is detrimental to recovery from an ischemic stroke. We investigated the role of NFkappaB in neuronal survival in rats that received transient middle cerebral artery (MCA) occlusion, and observed that this transient cerebral ischemia induced substantial apoptosis and inflammatory responses, including IkappaB phosphorylation, NF-kappaB activation and iNOS over-expression. 17 beta-estradiol (E2) treatment produced strong protective effects by reducing infarct volume, neuronal apoptosis, and inflammatory responses. These findings provide evidence for a novel molecular and cellular interaction between the sex hormone and the immunoresponsive system. These studies also provide evidence that suppression of post-ischemic inflammation may play a critical role in estrogen-mediated neuroprotection.

Actins↗
PubMed2004

Mitochondrial localization of estrogen receptor beta.

Estrogen receptors (ERs) are believed to be ligand-activated transcription factors belonging to the nuclear receptor superfamily, which on ligand binding translocate into the nucleus and activate gene transcription. To date, two ERs have been identified: ERalpha and ERbeta. ERalpha plays major role in the estrogen-mediated genomic actions in both reproductive and nonreproductive tissue, whereas the function of ERbeta is still unclear. In this study, we used immunocytochemistry, immunoblotting, and proteomics to demonstrate that ERbeta localizes to the mitochondria. In immunocytochemistry studies, ERbeta was detected with two ERbeta antibodies and found to colocalize almost exclusively with a mitochondrial marker in rat primary neuron, primary cardiomyocyte, and a murine hippocampal cell line. The colocalization of ERbeta and mitochondrial markers was identified by both fluorescence and confocal microscopy. No translocation of ERbeta into the nucleus on 17beta-estradiol treatment was seen by using immunocytochemistry. Immunoblotting of purified human heart mitochondria showed an intense signal of ERbeta, whereas no signals for nuclear and other organelle markers were found. Finally, purified human heart mitochondrial proteins were separated by SDS/PAGE. The 50,000-65,000 M(r) band was digested with trypsin and subjected to matrix-assisted laser desorption/ionization mass spectrometric analysis, which revealed seven tryptic fragments that matched with those of ERbeta. In summary, this study demonstrated that ERbeta is localized to mitochondria, suggesting a role for mitochondrial ERbeta in estrogen effects on this important organelle.

Animals↗
PubMed2004

Transient cerebral ischemia induces aberrant neuronal cell cycle re-entry and Alzheimer's disease-like tauopathy in female rats.

Aberrant mitosis occurs in many tauopathy-related neurodegenerative diseases and is believed to precede the formation of neurofibrillary tangles. In this study, we report for the first time that transient cerebral ischemia induces aberrant mitotic proteins and hyperphosphorylation of tau protein with neurofibrillary tangle-like conformational epitopes in adult female rat cortex. Following transient cerebral ischemia in rats, initiation of apoptosis precedes and is potentially integrated with subsequent aberrant mitosis and tau hyperphosphorylation. Furthermore, inhibition of mitosis-related cyclin-dependent kinases (Cdks) by roscovitine significantly reduced the hyperphosphorylation of tau. Administration of the female sex steroid and potent neuroprotective agent, 17beta-estradiol, reduced ischemia-reperfusion-induced cerebral damage and the subsequent aberrant mitosis and tauopathies. These results provide a neuropathological basis for the higher prevalence of dementia in stroke patients and support the hypothesis that apoptosis and aberrant mitosis are integrated pathological events in neurons that may play a critical role in the development of Alzheimer's disease and other tauopathy-related neuropathology.

Alzheimer Disease↗
PubMed2004

Estrogen protects against brain lipid peroxidation in ethanol-withdrawn rats.

This study examined whether 17beta-estradiol (E2) administration protects against ethanol withdrawal (EW)-associated oxidative insults by assessing oxidative markers thiobarbituric-acid-reacting-substances (TBARS). Ovariectomized rats implanted with E2 (EW/E2) or oil pellets (EW/Oil) received chronic ethanol (7.5% wt./vol., 5 weeks) or control dextrin diet (Dextrin/Oil). At 24 or 48 h of EW, rats were tested for overt EW signs and the cerebellum, hippocampus, and cortex were prepared for TBARS assessment in the presence and absence of FeCl3. For control experiments, we assessed E2 effects on blood ethanol concentrations and TBARS levels during ethanol exposure prior to EW. The EW/Oil group showed enhanced endogenous- and FeCl3-stimulated membrane TBARS levels in the cerebellum and hippocampus in a manner inhibited by E2 treatment. There was a relationship between the severity of EW and elevation of TBARS levels, particularly in the cerebellum. The enhanced TBARS levels at 24 h of EW appeared to diminish at 48 h in the hippocampus, but persisted in the cerebellum. E2 treatment did not alter blood ethanol concentrations and ethanol exposure alone did not enhance TBARS levels. These data suggest that EW rather than ethanol enhances brain lipid peroxidation that is transient and brain-region specific. Estrogens protect against the brain lipid peroxidation in a manner independent of blood ethanol concentrations.

Alcohol Drinking↗
PubMed2004

Genes of Helicobacter pylori regulated by attachment to AGS cells.

Reciprocal interactions between Helicobacter pylori and cells of the gastric epithelium to which it adheres may affect colonization. Changes in gene expression of H. pylori induced by adhesion to AGS gastric cancer cells by coculture were compared to changes in gene expression of H. pylori cultured without AGS cells by using cDNA filter macroarrays. Adhesion was quantitatively verified by confocal microscopy of green fluorescent protein-expressing bacteria. Four experiments showed that 22 and 21 H. pylori genes were consistently up- and down-regulated, respectively. The up-regulated genes included pathogenicity island, motility, outer membrane protein, and translational genes. The sigma(28) factor antagonist flgM, flgG, the stress response gene, flaA, omp11, and the superoxide dismutase gene (sodB) were down-regulated. The up-regulation of cag3, flgB, tonB, rho, and deaD was confirmed by quantitative PCR, and the up-regulation of lpxD, omp6, secG, fabH, HP1285, HP0222, and HP0836 was confirmed by reverse transcription (RT)-PCR. The down-regulation of flaA, sodB, and HP0874 was confirmed by quantitative PCR, and the down-regulation of omp11 was confirmed by RT-PCR. The alteration of gene expression in H. pylori after adhesion to gastric cells in vitro suggests that changes in motility, outer membrane composition, and stress responses, among other changes, may be involved in gastric colonization.

Bacterial Adhesion↗
PubMed2004

Inhibitory effects of antisense oligodeoxynucleotide on expression of vascular endothelia growth factor by human hepatocarcinoma cells.

BACKGROUND: It is widely recognized that the growth of solid tumor depends on angiogenesis. Vascular endothelia growth factor (VEGF) is an endothelial cell-specific mitogen that promotes angiogenesis in solid tumor. Inhibition of angiogenesis is considered a promising approach for cancer therapy, and treatments including administration of antisense drugs and RNA interference for the VEGF gene are geared to the suppression of tumor angiogenesis. METHODS: As a new approach for gene therapy of hepatocellular carcinoma (HCC), four groups of antisense oligodeoxynucleotide (ASODN) (A-Cap, A-AUG, A-UGA and A-Exon-3) were used to block the expression of VEGF, then VEGF mRNA and protein were detected by RT-PCR and Western blot. RESULTS: After treatment with ASODN, the relative VEGF mRNA levels of A-Cap, A-AUG, A-UGA, and A-Exon-3 were decreased significantly to (32+/-9)%, (63+/-1)%, (86+/-3)%, and (70+/-5)%, respectively(F=64.18, P<0.001). The relative VEGF protein levels of A-Cap, A-AUG, A-UGA and A-Exon-3 were decreased significantly to (41+/-5)%, (59+/-3)%, (88+/-7)%, and (79+/-9)% respectively (F=60.64, P<0.001). CONCLUSIONS: Among the four ASODNs, the ASODN for Cap structure showed the strongest inhibitory effect and that for A-UGA, the least (P<0.05 ). The inhibitory effect of ASODN on the expression of VEGF proteins was similar to that of VEGF mRNA expression.

Blotting, Western↗
PubMed2003

Acid-adaptive genes of Helicobacter pylori.

Helicobacter pylori is the only neutralophile that has been able to colonize the human stomach by using a variety of acid-adaptive mechanisms. One of the adaptive mechanisms is increased buffering due to expression of an acid-activated inner membrane urea channel, UreI, and a neutral pH-optimum intrabacterial urease. To delineate other possible adaptive mechanisms, changes in gene expression in response to acid exposure were examined using genomic microarrays of H. pylori exposed to different levels of external pH (7.4, 6.2, 5.5, and 4.5) for 30 min in the absence and presence of 5 mM urea. Gene expression was correlated with intrabacterial pH measured using 2',7'-bis-(2-carboxyethyl)-5-carboxyfluorescein and compared to that observed with exposure to 42 degrees C for 30 min. Microarrays containing the 1,534 open reading frames of H. pylori strain 26695 were hybridized with cDNAs from control (pH 7.4; labeled with Cy3) and acidic (labeled with Cy5) conditions. The intrabacterial pH was 8.1 at pH 7.4, fell to 5.3 at pH 4.5, and rose to 6.2 with urea. About 200 genes were up-regulated and approximately 100 genes were down-regulated at pH 4.5 in the absence of urea, and about half that number changed in the presence of urea. These genes included pH-homeostatic, transcriptional regulatory, motility, cell envelope, and pathogenicity genes. The up-regulation of some pH-homeostatic genes was confirmed by real-time PCR. There was little overlap with the genes induced by temperature stress. These results suggest that H. pylori has evolved multifaceted acid-adaptive mechanisms enabling it to colonize the stomach that may be novel targets for eliminating infection.

Adaptation, Physiological↗
PubMed2002

Speciation and bioavailability of EDTA complexed copper in the microenvironment of fish gills.

Carp were exposed to a synthetic solution with varied concentrations of Cu-EDTA and constant levels of other copper species and the amount of copper accumulated in the fish gills was measured. The distributions of copper species in both the bulk solution and the fish gill microenvironment were modeled using MINTEQA2. Under experimental conditions without EDTA, Cu(OH)2 was the most dominant species in the bulk solution while Cu-mucus dominated the gill microenvironment. When Cu-EDTA was added to the solution, copper accumulation in the fish gills increased significantly, suggesting a change in copper speciation. The amount of copper accumulated in the fish gills correlated positively to the concentration of Cu-mucus, rather than to free copper.

Animals↗
PubMedDate not supplied

Role of protein kinase C in estrogen protection against apoptotic cerebellar cell death in ethanol-withdrawn rats.

Results of studies from our laboratory have shown that administration of 17beta-estradiol (E(2)) reduces cerebellar neuronal damage during ethanol withdrawal (EW). In the current study, we examined mechanisms underlying E(2) protection against EW-associated cerebellar damage by assessing apoptotic indicators: DNA fragmentation, caspase-3 activity, and protein kinase C (PKC) activity. Ovariectomized rats, implanted with E(2) or oil pellets, received ethanol [7.5% weight/volume (wt./vol.)] (EW/E(2) group and EW/Oil group, respectively) chronically (for 5 weeks) or control dextrin diet (Dextrin/Oil group). At day 14 of EW, cerebelli were collected for the terminal deoxynucleotidyltransferase (TdT)-mediated dUDP-biotin nick end labeling (TUNEL) assay to detect DNA fragmentation and for immunohistochemistry to detect caspase-3 activation. A separate group of rat cerebelli was prepared to assess for total PKC activity, as well as for activity of a specific PKC isozyme, epsilon (PKCepsilon), by using an in vitro [gamma-(32)P]ATP phosphorylation assay at days 1 and 14 of EW. Results indicated that rats in the EW/Oil group had more DNA fragments and caspase-3-positive neuronal cells than observed for control rats, and these effects were inhibited by E(2) treatment. For total PKC activity at day 1 of EW, rats in the EW/E(2) group had a lower cytosolic PKC activity than observed for either rats in the EW/Oil group or control rats. At day 14 of EW, both EW groups had a lower total PKC activity than observed for control rats. For PKCepsilon activity, rats in the EW/E(2) group had a lower cytosolic PKCepsilon activity than observed for rats in the EW/Oil group or for control rats at day 1, and they had a lower membrane PKCepsilon activity at day 14 of EW than observed for control rats. These findings support the suggestion that E(2) protects against cerebellar neuronal damage in ethanol-withdrawn rats by inhibition of DNA fragmentation and caspase-3 activation, and that reduced PKC activity may be involved in the protection.

Animals↗