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Biomedical subjects

M Fu

Publications and source records attributed to M Fu.

At least 19 recordsLinked to original sources
PubMed2006

Phenotype of early cardiomyopathic changes induced by active immunization of rats with a synthetic peptide corresponding to the second extracellular loop of the human beta-adrenergic receptor.

In the failing human heart, due to idiopathic dilated cardiomyopathy, it has been suggested that the beta1-adrenergic receptor (beta1AR) is a potential pathogenic autoantigen. The aim of the present study was to investigate whether immunization of rats with a synthetic peptide corresponding to the second extracellular loop of the beta1AR (beta1AR EC(II)) was able to induce the early stage of cardiomyopathy and also to investigate immunological and receptor functional parameters at a transcriptional level to permit insights into the autoimmune mechanism in cardiomyopathy. Eleven Whistar Fur rats were immunized with a beta1AR EC(II) peptide (H26R) once a month during 12 months and seven control rats were injected with vehicle according to the same procedure used for the immunized group. Cardiac function, beta1AR autoantibodies and their functional effects on cardiomyocytes were analysed. beta1AR receptor signalling, immunological and cardiomyocyte stretch markers were determined on transcriptional level. In H26R immunized rats, beta1AR autoantibodies were shown to be present and functionally active, cardiac functions in terms of fractional shortening were decreased and beta1-adrenergic receptor kinase (GRK2) mRNA were increased compared with the control group. These data have shown that immunization of rats with a putative antigenic peptide was able to induce an early stage phenotype of cardiomyopathy in the form of cardiac dysfunction and up-regulation of GRK2 as the first step in the desensitization process of the beta1AR, implying the pathological importance of the beta1AR autoantibody.

Animals↗
PubMed2006

A polysaccharopeptide complex and a condensed tannin with antioxidant activity from dried rose (Rosa rugosa) flowers.

In this study, the fraction (P) from an aqueous extract of dried rose (Rosa rugosa) flowers was obtained by ethanol precipitation. P was chromatographed on DEAE-cellulose. The components retained on DEAE-cellulose were eluted with a linear gradient of 0-2 M NaCl solution. Two fractions, eluted at concentrations of 0.5 M NaCl and 1 M NaCl, respectively, were obtained. These two components were designated as P1 and P2, respectively. P1 was further purified using gel filtration on Sephadex G-200. P(1) yielded two peaks, and the two components were designated as P(1-a) and P(1-b), respectively. P(1-a) was a polysaccharide-peptide complex, and P(1-b) exhibited chemical properties of a condensed tannin as revealed by FTIR and NMR assay of carbohydrate and protein contents and HPLC-ESI-MS. The molecular masses of P(1-a) and P(1-b) were 150 kDa and 8 kDa, respectively. Both P(1-a) and P(1-b) possessed antioxidant activity, with the activity of P(1-b) higher than that of P(1-a). This study demonstrated that different components from rose flowers exhibited antioxidant activity.

Animals↗
PubMed2006

Compounds from rose (Rosa rugosa) flowers with human immunodeficiency virus type 1 reverse transcriptase inhibitory activity.

The aqueous extracts and ethanol precipitates of aqueous extracts of 18 medicinal herbs traditionally used in China were screened for their ability to inhibit human immunodeficiency virus type-1 reverse transcriptase (HIV-1 RT) in-vitro. Among the samples screened at a concentration of 500 microg mL-1, dried rose (Rosa rugosa) flowers showed the strongest inhibition. The ethanol precipitate of the aqueous extract of R. rugosa was processed and two components (P1 and P2) were obtained after ion exchange chromatography on DEAE-cellulose. Then, P1-a (Mr 150 kDa) and P1-b (Mr 8 kDa) were isolated from P1 by gel filtration on Sephadex G-200. They inhibited the activity of HIV-1 RT with an IC50 of 158 nM and 148.16 microg mL-1 (18.5 microM), respectively. Further structural analyses revealed that P1-a was a polysaccharide-peptide complex, and P1-b was a polymer consisting of acteoside and acteoside derivatives identified by Fourier transform infrared spectroscopy, nuclear magnetic resonance, assays of carbohydrate and protein contents and high-performance liquid chromatography electrospray ionization mass spectrometry.

Chromatography, Gel↗
PubMed2006

Toxicological mechanisms of Aconitum alkaloids.

The toxic effects of Aconitum alkaloids are known to affect mainly the central nervous system, heart and muscle tissues. Their toxicological mechanisms may involve interaction with voltage-dependent Na+ channels, modulation of neurotransmitter release and related receptors, promotion of lipid peroxidation and induction of cell apoptosis in heart, liver or other organs. Of them, the mechanism of interaction with voltage-dependent Na+ channels is quite well known, but the other factors are still unclear, and need to be further studied. This review focuses on the toxicological mechanisms of Aconitum alkaloids.

Aconitum↗
PubMed2005

Antioxidant activity of gallic acid from rose flowers in senescence accelerated mice.

The activities of the antioxidant enzymes catalase (CAT) and glutathione peroxidase (GPx) in the blood and liver of the aging model induced by injection of different doses of D-gal into normal mice, and in senescence accelerated mice (SAM) of different ages, were determined. The results showed that the enzyme activities in the D-gal treated mice did not alter appreciably but the enzyme activities in blood of the SAM declined significantly with the increase in age, especially in the 9-month-old SAM. When gallic acid purified from rose flowers was used to treat the 9-month-old male SAM, it not only reinstated the activities of CAT and GPx but also significantly reduced the amount of malondialdehyde (MDA) in the liver, brain and kidney. The results demonstrated that 9-month-old male SAM represent an appropriate animal model to evaluate the antioxidant activities of natural products.

Aging↗
PubMed2005

Identification of a novel HLA-A*0278 allele in a Chinese family.

A novel human leukocyte antigen-A (HLA-A) allele, A*0278, has been identified in a Chinese family using DNA-based typing and molecular cloning methods. The alleles A*0278 differs from its closest matching HLA sequence of A*0256 by a silent substitution at 102 A > C and by two replacement substitutions, 98T > A and 292 C > G in exon 2, resulting in a change of codon 33 from Phe (TTC) to Tyr (TAC) and codon 98 from His (CAC) to Asp (GAC). Serology study revealed that A*0278 is associated with HLA-A2 broad specificity. A polymerase chain reaction-sequence-specific primers-based assay was developed to identify A*0278. Family study indicated that the propositus inhered his father's HLA haplotype A*0278, B*35, DRB1*15. No further individuals of A*0278 were found in 5000 Chinese bone marrow donor volunteers.

Alleles↗
PubMed2005

Rose (Rosa rugosa)-flower extract increases the activities of antioxidant enzymes and their gene expression and reduces lipid peroxidation.

The effects of rose-flower extract on antioxidant enzymes were studied. The activities of catalase (CAT) and glutathione peroxidase (GPx) in 9-month-old senescence-accelerated mice (SAM mice) were lower than those in 6-month-old SAM mice. Therefore, 9-month-old SAM mice were the most appropriate targets for treatment with the rose-flower extract. The activities of CAT and GPx in SAM mice treated with rose-flower extract showed a marked increase in whole blood and liver. At the same time, the gene-expression level of CAT and GPx was upregulated in the liver, while malondialdehyde content in liver and brain decreased. Male SAM mice were more sensitive than female SAM mice. The mean and the longest lifespan of SAM mice were longer after treatment with rose-flower extract.

Aging↗
PubMed2004

Embryonic development of the ganglion plexuses and the concentric layer structure of human gut: a topographical study.

In this study, we performed a detailed topographical study on the development of ganglion plexuses and the smooth muscle layers of human embryonic and fetal gut. Neuron and glia differentiation was investigated with anti-PGP9.5 and anti-S100 antibodies respectively. The differentiation of smooth muscle and interstitial cells of Cajal (ICC) was studied with anti-smooth muscle alpha-actin and anti-C-Kit antibodies respectively. By week 7, rostro-caudal neural crest cell (NCC) colonization of the gut was complete, and NCCs have differentiated into neurons and glia. At the foregut, neurons and glia were aggregated into ganglion plexus in the myenteric region, and the longitudinal and circular muscle layers have started to differentiate; however, neurons and glia were not found in the submucosa. At the hindgut, neurons and glia were dispersed within the mesenchyme. Myenteric plexus, longitudinal and circular muscle layers formed along the entire gut by week 9. Scattered and individual neurons and glia, and small ganglion plexuses were detected in the foregut and midgut submucosa by week 12. Ganglion plexus was not seen in the hindgut submucosa until week 14. Muscularis mucosae was formed at the foregut and midgut by week 12 but was only discernible at the hindgut 2 weeks later. As the gut wall developed, ganglion plexus increased in size with more neurons and glia, and the formation of intra-plexus nerve fascicle. ICCs were localized in the ganglion plexus as early as week 7. ICCs were initially dispersed in the plexus and were preferentially localized at the periphery of the plexus by week 20. The specification of the annular layers of human embryonic and fetal gut follows a strict spatio-temporal pattern in a rostro-caudal and centripetal manner suggesting that interaction between (1) homotypic and/or heterotypic cells; and (2) cells and the extracellular matrix is critical for the embryonic development of the gut mesenchyme and the enteric nervous system.

Actins↗
PubMed2004

Clinical and electrophysiological features in Chinese patients with Kennedy's disease.

Kennedy's disease is a X-linked neuromuscular disorder caused by an expanded trinucleotide repeat in the androgen receptor gene. To ascertain the clinical diagnosis of Kennedy's disease in a Chinese population, we used a rapid, accurate PCR-based sizing method for the CAG repeat allelotype. The clinical and electrophysiological features of affected patients are described. The CAG repeats ranged from 43 to 53 and were inversely correlated with the age of onset (r = -0.63; P < 0.005).

Action Potentials↗
PubMed2004

Exposure to L-ascorbic acid or alpha-tocopherol facilitates the development of porcine denuded oocytes from metaphase I to metaphase II and prevents cumulus cells from fragmentation.

It is known that alpha-tocopherol (vitamin E) and L-ascorbic acid (vitamin C) can modulate many biochemical processes intracellularly or extracellularly as antioxidants. The objective of the present study was to investigate the effects of alpha-tocopherol and L-ascorbic acid on porcine oocyte meiotic maturation, viability and the functions of cumulus cells. In two independent experiments, porcine oocytes with or free from cumulus cells were exposed to different levels of alpha-tocopherol (0, 10, 100 and 200 microM) or L-ascorbic acid (0, 50, 250 and 750 microM). Cumulus expansion, cumulus cell DNA fragmentation, meiotic maturation and degeneration of oocytes were assessed 48 h after in vitro culture. The results showed that: (1) neither alpha-tocopherol nor L-ascorbic acid influenced cumulus expansion but both prevented cumulus cell DNA fragmentation. (2) Alpha-tocopherol lowered the percentage of denuded oocytes (DOs) arrested at germinal vesicle stage (GV). Among the oocytes undergoing germinal vesicle breakdown (GVBD) proportion, fewer DOs treated by alpha-tocopherol were at metaphase I (MI) and more at metaphase II (MII). L-ascorbic acid caused lower percentage of DOs arrested at GV stage and higher percentage of DOs undergoing GVBD, especially at MII. The influences of alpha-tocopherol and L-ascorbic acid were not obvious in cumulus-enclosed oocytes (CEOs). (3) Both vitamins compromised the viability of CEOs and DOs. These results indicate that exposure to alpha-tocopherol or L-ascorbic acid promotes the development of porcine DOs from MI to MII and prevents cumulus cell DNA fragmentation at certain levels, especially 10 microM alpha-tocopherol or 250 microM L-ascorbic acid.

Animals↗
PubMed2003

Thiazolidinediones, a class of anti-diabetic drugs, inhibit Id2 expression through a PPARgamma-independent pathway in human aortic smooth muscle cells.

Inhibitor of DNA binding (Id2) is a member of the helix-loop-helix family of transcription regulators that is known to play important roles in the proliferation and differentiation of many cell types. Overexpression of Id2 has been reported to result in significant enhancement of vascular smooth muscle cell growth via increased S phase entry. We hypothesized that downregulation of Id2 gene expression by thiazolidinediones (TZDs), a class of anti-diabetic drugs and peroxisome proliferator-activated receptor gamma (PPARgamma) activators, might contribute to the anti-atherosclerotic and anti-hypertensive effects of the PPARgamma. Here we document that TZDs, including troglitazone and ciglitazone, repress Id2 gene expression in a doses- and time-dependent manner. However, GW7845, a high-affinity and non-TZD PPARgamma activator, had no inhibitory effect on Id2 gene expression. In addition, PPARgamma antagonist GW9662 did not rescue TZD-induced Id2 repression. Taken together, our data suggest that TZDs repress Id2 expression through a PPARgamma-independent pathway.

Anilides↗
PubMed2001

Platelet-derived growth factor promotes the expression of peroxisome proliferator-activated receptor gamma in vascular smooth muscle cells by a phosphatidylinositol 3-kinase/Akt signaling pathway.

Vascular diseases such as atherosclerosis are characterized by abnormal accumulation of vascular smooth muscle cells (VSMCs) within the intimal lining. The intimal VSMCs exhibit an increased expression of peroxisome proliferator-activated receptor gamma (PPARgamma), and the administration of pharmacological PPARgamma agonists attenuates vascular lesion formation. The factors that regulate PPARgamma expression in the vasculature are poorly defined. Here we report that platelet-derived growth factor (PDGF) upregulates PPARgamma by the phosphatidylinositol 3-kinase (PI3-kinase)/Akt signaling pathway. Using Northern-blotting and Western-blotting analyses, we observed that the levels of PPARgamma mRNA and protein were increased by 2- to 3.5-fold in human aortic smooth muscle cells (HASMCs) treated with PDGF (20 ng/mL). This was abolished by preincubation of HASMCs with a PI3-kinase inhibitor (LY294002, 50 micromol/L), and partially inhibited by a MEK1 inhibitor (U0126, 10 micromol/L), but not affected by a p38 kinase inhibitor (SB202190, 10 micromol/L). In addition, overexpression of the dominant-negative p85 subunit of PI3-kinase or Akt proteins blocked the PDGF-induced PPARgamma expression. Taken together, our results suggest that PDGF induces PPARgamma expression in VSMCs by a PI3-kinase/Akt signaling pathway. The characterization of factors and signaling pathways that modulate PPARgamma expression in VSMCs may have important implications for understanding the pathogenesis of vascular diseases.

Aorta↗
PubMed2001

Peroxisome proliferator-activated receptor gamma inhibits transforming growth factor beta-induced connective tissue growth factor expression in human aortic smooth muscle cells by interfering with Smad3.

Activation of peroxisome proliferator-activated receptor gamma (PPAR gamma) after balloon injury significantly inhibits VSMC proliferation and neointima formation. However, the precise mechanisms of this inhibition have not been determined. We hypothesized that activation of PPAR gamma in vascular injury could attenuate VSMC growth and matrix production during vascular lesion formation. Since connective tissue growth factor (CTGF) is a key factor regulating extracellular matrix production, abrogation of transforming growth factor beta (TGF-beta)-induced CTGF production by PPAR gamma activation may be one of the mechanisms through which PPAR gamma agonists inhibit neointima formation after vascular injury. In this study, we demonstrate that the PPAR gamma natural ligand (15-deoxyprostaglandin J(2)) and a synthetic ligand (GW7845) significantly inhibit TGF-beta-induced CTGF production in a dose-dependent manner in HASMCs. In addition, suppression of CTGF mRNA expression is relieved by pretreatment with an antagonist of PPAR gamma (GW9662), suggesting that the inhibition of CTGF expression is mediated by PPAR gamma. To elucidate further the molecular mechanism by which PPAR gamma inhibits CTGF expression, an approximately 2-kilobase pair CTGF promoter was cloned. We found that PPAR gamma activation inhibits TGF-beta-induced CTGF promoter activity in a dose-dependent manner, and suppression of CTGF promoter activity by PPAR gamma activation is completely rescued by overexpression of Smad3, but not by Smad4. Furthermore, PPAR gamma physically interacts with Smad3 but not Smad4 in vitro in glutathione S-transferase pull-down experiments. Taken together, the data suggest that PPAR gamma inhibits TGF-beta-induced CTGF expression in HASMCs by directly interfering with the Smad3 signaling pathway.

Aorta↗
PubMed2001

beta(1)-Adrenoceptor antibodies induce positive inotropic response in isolated cardiomyocytes.

beta(1)-Adrenoceptor autoantibodies are present in approximately 30% of patients suffering from dilated cardiomyopathy. The inotropic effects mediated by these antibodies remain to be studied. Monoclonal antibodies were raised against a peptide corresponding to the second extracellular loop of the human beta(1)-adrenoceptor in balb/C mouse (n=6), and were characterized by enzyme immunoassay after purification by protein A. Purified immunoglobulin G from non-immunized animals (controls) did not influence Ca(2+) transient and cell shortening of rat cardiomyocytes measured by confocal-laser-scanning-microscopy. beta(1)-adrenoceptor antibodies caused a dose-related increase in Ca(2+) transient (dilution 1:2: +35.3+/-5.1%), and in cell shortening (dilution 1:2: +40.5+/-6.3%) (P<0.01 vs. controls). The effect of the beta(1)-adrenoceptor antibodies was blocked by the antigenic peptide and by the antagonist metoprolol. In addition, beta(1)-adrenoceptor antibodies induced a dose-dependent increase of the cyclic adenosine monophosphate. The inotropic response induced by isoproterenol was attenuated by the beta(1)-adrenoceptor antibody. beta(1)-adrenoceptor antibodies as partial agonists induce a specific positive inotropic effect via the protein-kinase-A-cascade.

Adrenergic beta-Agonists↗
PubMed2001

Histone acetylation and the cell-cycle in cancer.

A number of distinct surveillance systems are found in mammalian cells that have the capacity to interrupt normal cell-cycle progression. These are referred to as cell cycle check points. Surveillance systems activated by DNA damage act at three stages, one at the G1/S phase boundary, one that monitors progression through S phase and one at the G2/M boundary. The initiation of DNA synthesis and irrevocable progression through G1 phase represents an additional checkpoint when the cell commits to DNA synthesis. Transition through the cell cycle is regulated by a family of protein kinase holoenzymes, the cyclin-dependent kinases (Cdks), and their heterodimeric cyclin partner. Orderly progression through the cell-cycle checkpoints involves coordinated activation of the Cdks that, in the presence of an associated Cdk-activating kinase (CAK), phosphorylate target substrates including members of the "pocket protein" family. One of these, the product of the retinoblastoma susceptibility gene (the pRB protein), is phosphorylated sequentially by both cyclin D/Cdk4 complexes and cyclin E/Cdk2 kinases. Recent studies have identified important cross talk between the cell-cycle regulatory apparatus and proteins regulating histone acetylation. pRB binds both E2F proteins and histone deacetylase (HDAC) complexes. HDAC plays an important role in pRB tumor suppression function and transcriptional repression. Histones are required for accurate assembly of chromatin and the induction of histone gene expression is tightly coordinated. Recent studies have identified an important alternate substrate of cyclin E/Cdk2, NPAT (nuclear protein mapped to the ATM locus) which plays a critical role in promoting cell-cycle progression in the absence of pRB, and contributes to cell-cycle regulated histone gene expression. The acetylation of histones by a number of histone acetyl transferases (HATs) also plays an important role in coordinating gene expression and cell-cycle progression. Components of the cell-cycle regulatory apparatus are both regulated by HATs and bind directly to HATs. Finally transcription factors have been identified as substrate for HATs. Mutations of these transcription factors at their sites of acetylation has been associated with constitutive activity and enhanced cellular proliferation, suggesting an important role for acetylation in transcriptional repression as well as activation. Together these studies provide a working model in which the cell-cycle regulatory kinases phosphorylate and inactivate HDACs, coordinate histone gene expression and bind to histone acetylases themselves. The recent evidence for cross-talk between the cyclin-dependent kinases and histone gene expression on the one hand and cyclin-dependent regulation of histone acetylases on the other, suggests chemotherapeutics targeting histone acetylation may have complex and possibly complementary effects with agents targeting Cdks.

Acetylation↗
PubMed2001

Direct acetylation of the estrogen receptor alpha hinge region by p300 regulates transactivation and hormone sensitivity.

Regulation of nuclear receptor gene expression involves dynamic and coordinated interactions with histone acetyl transferase (HAT) and deacetylase complexes. The estrogen receptor (ERalpha) contains two transactivation domains regulating ligand-independent and -dependent gene transcription (AF-1 and AF-2 (activation functions 1 and 2)). ERalpha-regulated gene expression involves interactions with cointegrators (e.g. p300/CBP, P/CAF) that have the capacity to modify core histone acetyl groups. Here we show that the ERalpha is acetylated in vivo. p300, but not P/CAF, selectively and directly acetylated the ERalpha at lysine residues within the ERalpha hinge/ligand binding domain. Substitution of these residues with charged or polar residues dramatically enhanced ERalpha hormone sensitivity without affecting induction by MAPK signaling, suggesting that direct ERalpha acetylation normally suppresses ligand sensitivity. These ERalpha lysine residues also regulated transcriptional activation by histone deacetylase inhibitors and p300. The conservation of the ERalpha acetylation motif in a phylogenetic subset of nuclear receptors suggests that direct acetylation of nuclear receptors may contribute to additional signaling pathways involved in metabolism and development.

Acetylation↗
PubMed2001

Presenilin 1 negatively regulates beta-catenin/T cell factor/lymphoid enhancer factor-1 signaling independently of beta-amyloid precursor protein and notch processing.

In addition to its documented role in the proteolytic processing of Notch-1 and the beta-amyloid precursor protein, presenilin 1 (PS1) associates with beta-catenin. In this study, we show that this interaction plays a critical role in regulating beta-catenin/T Cell Factor/Lymphoid Enhancer Factor-1 (LEF) signaling. PS1 deficiency results in accumulation of cytosolic beta-catenin, leading to a beta-catenin/LEF-dependent increase in cyclin D1 transcription and accelerated entry into the S phase of the cell cycle. Conversely, PS1 specifically represses LEF-dependent transcription in a dose-dependent manner. The hyperproliferative response can be reversed by reintroducing PS1 expression or overexpressing axin, but not a PS1 mutant that does not bind beta-catenin (PS1Deltacat) or by two different familial Alzheimer's disease mutants. In contrast, PS1Deltacat restores Notch-1 proteolytic cleavage and Abeta generation in PS1-deficient cells, indicating that PS1 function in modulating beta-catenin levels can be separated from its roles in facilitating gamma-secretase cleavage of beta-amyloid precursor protein and in Notch-1 signaling. Finally, we show an altered response to Wnt signaling and impaired ubiquitination of beta-catenin in the absence of PS1, a phenotype that may account for the increased stability in PS1-deficient cells. Thus, PS1 adds to the molecules that are known to regulate the rapid turnover of beta-catenin.

Alzheimer Disease↗