Biomedical subjects

Fang Sun

Publications and source records attributed to Fang Sun.

33 records · Page 2Linked to original sources

PubMed2004

Matrix metalloproteinases are down-regulated in rat lenses exposed to oxidative stress.

Matrix metalloproteinases are important biological effectors of tissue remodelling. Increased MMP expression occurs during injury, inflammation, cellular transformation, and oxidative stress. Oxidative stress in the lens, a causal factor in cataractogenesis, has been shown to induce MMP secretion. The objective of this study was to assess the expression of MMPs and their regulators in an oxidative stress model of cataract, where epithelial cell death and cortical fibre cell swelling occurs in rat lenses after exposure to riboflavin, oxygen, and light. Two time points (4 and 7 hr of exposure) were chosen in order to compare transparent lenses with partially opaque lenses. MMP activity, protein, and mRNA levels were measured. The results show that MMP-2, MMP-9, MT1-MMP, and MT3-MMP are down-regulated by oxidative stress and that the down-regulation is most likely due to reduced gene transcription. In contrast, genes for catalase, glutathione peroxidase, and GAPDH are essentially unaffected, while beta-actin mRNA and protein levels are markedly increased at both time points. The down-regulation of MMPs occurs in lenses still seemingly transparent after 4 hr of exposure, indicating that reduced MMP activity is a relatively early response to the oxidative stress. Moreover, in our model system, MMP inhibition, not induction, is associated with cataractogenesis.

Actins↗

PubMed2004

The effect of stress withdrawal on gene expression and certain biochemical and cell biological properties of peroxide-conditioned cell lines.

Maturity onset cataract is a disease that afflicts >25% of the U.S. population over 65. Oxidative stress is believed to be a major factor in the development of this disease and peroxides are suspected to be prominent stressing agents. To elucidate mechanisms involved in the protection of cells against oxidative stress, immortal murine lens epithelial cells (alphaTN4-1) have been conditioned to survive lethal concentrations of either tertiary butyl hydroperoxide, TBOOH (a lipid peroxide prototype) (T cells), or H2O2 (H cells). It was found that T cells survived exposure to H2O2 but H cells were killed by TBOOH. In this communication, biological characteristics of the T cells are reported. It is shown that the T cell's ability to survive TBOOH is lost if the cells are grown in the absence of this peroxide (denoted as T- cells). By comparing the differential gene expression of 12,422 genes and ESTs from T and T- and the unconditioned control cells, 16 genes were found that may account for the loss of resistance to TBOOH. They include 5 glutathione-S-transferases, superoxide dismutase 1, zeta crystallin, a NADPH quinone reductase, as well as genes involved in detoxifying aldehydes, controlling iron metabolism, and degrading toxic lipoproteins.

Animals↗

PubMed2004

[Effect of anti-HPV16 E6-ribozyme on cell proliferation and invasiveness of cervical carcinoma cell line CaSKi].

OBJECTIVE: To investigate the effects of anti-HPV16-ribozyme on the cell proliferation and invasiveness of cultured cervical cancer cell line CaSKi. METHODS: CaSKi cells were transfected with anti-HPV16 E6-ribozyme and empty eukaryotic expression plasmids via lipofectin and designated as CaSKi-R and CaSKi-P cells respectively. The growth rate, cell colony-forming ability on soft agar, invasiveness and tumorigenicity of CaSKi-R, CaSKi-P, and CaSKi cells were studied using corresponding methods. The expressions of cox-2 and vascular endothelial growth factor (VEGF) mRNA of the 3 cell strains were determined with one-step reverse transcriptional PCR (RT-PCR), and immunocytochemistry was employed for detecting the expressions of COX-2 and VEGF antigens. RESULTS: No distinct differences in the growth rate, colony-forming ability on soft agar, cell invasiveness and tumorigenicity were observed between CaSKi and CaSKi-P cells, whereas by comparison, CaSKi-R cells exhibited decreased growth rate, colony-forming ability, the cell invasiveness and tumorgenicity, with also lowered expression levels of cox-2 and VEGF mRNA as shown by RT-PCR analysis. Expressions of COX-2 and VEGF antigens were detected in all the 3 cell strains immunocytochemically, but compared with CaSKi and CaSKi-P cells, the antigen expressions in CaSKi-R cells were significantly weaker. CONCLUSION: Anti-HPV16 E6-ribozyme may partially inhibit the proliferation and reduce the invasiveness of CaSKi cells possibly through decreasing cox-2 and VEGF expressions, which are the important agents for tumor invasion.

Cell Line, Tumor↗

PubMed2004

[Protective effect of hydroxysafflor yellow A against rat cortex mitochondrial injuries induced by cerebral ischemia].

AIM: To study the effects of hydroxysafflor yellow A (HSYA) on the mitochondrial function of cortex mitochondrial during cerebral ischemia in rats. METHODS: Rat focal cerebral ischemia model in rats was established by ligation of middle cerebral central artery. Cortex mitochondria were isolated and prepared for the measurement of membrane fluidity, swelling, respiratory function, activities of mitochondrial respiratory enzymes and superoxide dismutase (SOD), contents of phospholipid, malondial dehyde (MDA) and Ca2+ to evaluate the function of mitochondria. RESULTS: Focal cerebral ischemia resulted in severe neuronal mitochondrial injuries, which could be alleviated by i.v. HSYA (10, 20 mg x kg(-1)), and nimodipine (Nim, 1.0 mg x kg(-1)). The swelling of mitochondria was ameliorated, the decomposability of membrane phospholipid was decreased, the membrane fluidity of mitochondria was increased, HSYA also significantly inhibited the decrease in the activities of respiratory enzymes and SOD of mitochondria, and the increase in MDA and Ca2+ levels caused by cerebral ischemia in rats. CONCLUSION: HSYA showed a protective action against the cortex mitochondrial injuries in rats induced by cerebral ischemia. The mechanisms may be derived from reducing lipid peroxides, inhibiting Ca2+ overload, scavenging free radicals and improving the energy metabolism.

Animals↗

PubMed2003

Caloric restriction retards age-related changes in rat retina.

The neural retina of mammals consists of light sensitive photoreceptors and connecting neural cells that receive and send visual signal to the brain. Dietary caloric restriction (CR) is the only experimental intervention that can reliably retard the age-related degeneration of the retina in a normal mammalian model. Here, we studied the effect of CR on various biochemical parameters in the retina of male Brown Norway rats at different ages. We found that CR slowed the age-dependent protein insolubilization, blunted the declines in the total soluble thiols, and reduced glutathione and ascorbic acid levels in neural retina. We also observed that CR retarded the age-related decline in the levels of taurine, a vital amino acid in neural retina. These data are the first to implicate that CR may retard the age-related degeneration of retina by attenuating the oxidative stress and/or by sustaining the pool of protective factors in the neural retina.

Aging↗

PubMed2003

Evaluation of oxidative stress during apoptosis and necrosis caused by D-galactosamine in rat liver.

Eighteen and twenty-four hours after intraperitoneal administration of D-galactosamine (1g/kg body weight) to rats, the activity of caspase-3-like protease in the liver increased significantly compared with that in the control group given saline. Histological examinations including the in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) method found apoptotic hepatocytes 18 hr after the administration of D-galactosamine. Caspase-3 activity was barely detectable in the plasma of control rats, but increased significantly 24 hr after drug administration along with a dramatic increase in glutamate-oxaloacetate transaminase (GOT). These results indicated that D-galactosamine causes apoptosis in the liver by activating caspase-3, which is released to the plasma by secondary necrosis. The concentration of lipid hydroperoxides in the liver increased significantly 24 hr after D-galactosamine administration. In contrast, the concentration of vitamin C in the liver decreased significantly 18 and 24 hr after D-galactosamine administration. These results suggest that D-galactosamine induces severe oxidative stress in the liver, leading to extensive necrosis.

Animals↗

PubMed2003

Peroxide toxicity in conditioned lens epithelial cells--evaluation of multi-defense systems.

Immortal murine lens epithelial cells which were conditioned to survive peroxide stress were found to have a remarkable increase in catalase activity as well as lesser changes in a number of other antioxidative defense systems [Invest. Ophthalmol. Vis. Sci. 43 (2002) 3251]. Furthermore, the gene expression of hundreds of other genes was altered. In order to determine the relative importance of catalase, other enzyme systems which maintain the reducing environment of the cell and the involvement of Fenton chemistry, an analysis of the effect of inhibiting catalase, disruption of the cells' reducing environment by inhibition of GSSG reductase (GR) and chelation of metal ion was investigated. It was found that inhibition of catalase caused peroxide resistant cells to die within 48-72 hr when exposed to normally tolerated concentrations of peroxide. If 1,10-phenanthroline (OP), an effective metal ion chelator was present, the cells were not affected by catalase inhibition and survived peroxide stress. Peroxide vulnerable unconditioned control cells were similarly protected by the chelator. The results demonstrate that H2O2 itself has minimal toxicity and that it is the products resulting from interaction with metal ion that produces lethal toxicity. In stark contrast, however, metal chelation did not protect the cells when GR was inhibited by BCNU. Examination of non-protein thiol (NP-SH), which is primarily GSH, indicated that rapid and extensive oxidation occurred almost immediately after exposure to peroxide under all conditions. However, NP-SH returns to the normal range in the conditioned cells even though later cell death is observed in some cases, suggesting fatal damage during the period when the cell is exposed to an oxidizing environment. Examination of DNA damage by alkaline elution indicated that H2O2 caused little observed strand breakage in peroxide resistant cells even if catalase is inhibited, suggesting that such cells have developed other systems to protect DNA and that H2O2 induced death is probably not related to DNA single strand breaks. In contrast, unconditioned cells (C cells) show extensive H2O2 induced DNA damage which is prevented by OP. Thus, depending on the conditions, DNA damage may contribute to cell death. The overall results indicate that the conditioned cell lines are not simply dependent on catalase activity but have developed a complex defense which includes GSH dependent systems and possibly more effective regulation of metal ion concentrations to resist oxidative stress.

Animals↗

PubMed2003

HSV-1 amplicon peptide display vector.

There are significant uses for expressing foreign peptide epitopes in viral surface attachment proteins in terms of investigating viral targeting, biology, and immunology. HSV-1 attachment, followed by fusion and entry, is mediated in large part by the binding of viral surface glycoproteins to cell surface receptors, primarily through heparan sulfate (HS) glycosaminoglycan residues. We constructed a HSV-1 amplicon plasmid (pCONGA) carrying the gC primary attachment protein gene with unique restriction sites flanking the HS binding domain (HSBD) (residues 33-176) to allow rapid, high efficiency substitution with foreign peptide domains. To test this system, a His tag with an additional unique restriction site (for selection and assay digests) was recombined into the pCONGA HSBD site to create pCONGAH. Infection of pCONGAH transfected Vero cells with HSV-1 helper virus (gCdelta2-3 or hrR3) produced His-modified gC as demonstrated by western blot analysis with co-localization of anti-gC and anti-His tag antibodies to a protein of appropriate molecular weight (50 kd). As CONGA and CONGAH amplicons carry a GFP transgene and the gCdelta2-3 and hrR3 viruses carry a lacZ transgene, vector stocks produced from 1 x 10(5) Vero cells could be titered for competent vector on cell monolayers and were demonstrated to contain 2 x 10(5) amplicon vector transducing units (t.u.)/ml and 1 x 10(7) virus t.u./ml. As the amplicon plasmids also contain the neomycin resistance gene (neo(r)), long term vector producer cell lines were created using G418 selection. This amplicon system provides means to rapidly and efficiently generate HSV-1 amplicon and viral vector expressing surface attachment proteins modified with different peptide epitopes for investigational and therapeutic uses, with the advantages of an amplicon plasmid that can be used with interchangeable helper virus vectors, is designed specifically for easy manipulation, and carries GFP and neo(r) transgenes for marker and selection functions.

Animals↗

PubMed2002

Very low vitamin C activity of orally administered L-dehydroascorbic acid.

The biological activity of L-dehydroascorbic acid (DHA), which is easily formed from L-ascorbic acid (ASC) during storage and cooking processes, has been considered to be equivalent to that of ASC on the basis of studies made several decades ago, when a specific method to determine ASC was not available. The nutritional activity of orally ingested DHA has now been evaluated by comparing ASC concentrations in 12 tissues of rats administered four different doses of ASC. Determinations were made by using the specific and sensitive method, which had been developed by us. Here it is shown that the efficiency of DHA was almost 10% of that of ASC on a molar basis, based on animal experiments using the inherently scorbutic ODS rat, which is a convenient human model animal to investigate the metabolism of vitamin C. On the basis of these findings, it is proposed that it is necessary to reevaluate the nutritional requirement of vitamin C based on both ASC and DHA contents of foods.

Administration, Oral↗

PubMed2002

The effect of H2O2 and tertiary butyl hydroperoxide upon a murine immortal lens epithelial cell line, alphaTN4-1.

The effect of comparable concentrations of H(2)O(2) and tertiary butyl hydroperoxide (TBHP) upon an immortal murine lens epithelial cell line was examined as part of an ongoing effort to delineate differences in the mechanism by which these peroxides cause cell death. Both compounds result in cell death of normal, unconditioned cells within 24hr. It was found that with similar conditions, TBHP conditioned alphaTN4-1 cells survive H(2)O(2) stress while H(2)O(2) conditioned cells are killed by TBHP. To better understand how these peroxides act, their effect upon unconditioned cells has been investigated. Both peroxides cause a rapid loss of GSH and disruption of pump activity as illustrated by (14)C-choline transport and (86)Rb uptake. While H(2)O(2) exposure resulted in extensive DNA damage, TBHP had a minimal effect. DNA damage caused by H(2)O(2) was shown to activate polyADP-ribosyl polymerase (PARP), leading to depletion of NAD and ATP. H(2)O(2) induced cell death could be delayed by addition of 3-aminobenzamide (3AB), an inhibitor of PARP. ATP levels in cells subjected to H(2)O(2) were also maintained by the presence of 3AB. H(2)O(2) stress also disrupted glycolysis and mitochondrial activity but these parameters were not affected by TBHP. TBHP induced cell death, under the relatively mild conditions used in this work, appears to be caused by membrane disruption and loss of a reducing environment.

Adenosine Triphosphate↗

PubMed2002

Contribution of genetic polymorphisms in ethanol-metabolizing enzymes to problem drinking behavior in middle-aged Japanese men.

Among ethanol-metabolizing enzymes, the ALDH2*2 allele, ADH2*2 allele, and c2 allele of the cytochrome P450-2E1 (CYP2E1) gene are unique to Orientals. This prompted us to analyze their contribution to drinking behavior in 322 middle-aged Japanese men. The ALDH2*2 allele, detected in nearly half of the subjects, showed an overwhelming protective effect against a high level of alcohol consumption and problem drinking behavior, as determined by the Kurihama Alcoholism Screening Test (KAST). The ADH2*2 allele, in 95% of the subjects, exhibited an additive suppressive effect on alcohol consumption, whereas the c2 allele of CYP2E1, in 40% of the subjects, was associated with greater alcohol consumption. Problem drinkers showing a KAST score of 2.0 or higher were frequent among the few subjects with the ADH2*1/1 genotype, but not in the large number of subjects having the c2 allele of CYP2E1. These findings may explain, at least in part, why in Japan the number of alcoholic patients is small relative to the number of heavy drinkers.

Adult↗

PubMed2002

Differential amplification of gene expression in lens cell lines conditioned to survive peroxide stress.

PURPOSE: The response of lens systems to oxidative stress is confusing. Antioxidative defense systems are not mobilized as expected, and unanticipated defenses appear important. Therefore, mouse lens cell lines conditioned to survive different peroxide stresses have been analyzed to determine their global changes in gene expression. METHODS: The immortal mouse lens epithelial cell line alphaTN4-1 was conditioned to survive 125 microM H2O2 (H cells) or a combination of both 100 microM tertiary butyl hydroperoxide (TBHP) and 125 microM H2O2 (HT cells), by a methodology previously described. The total RNA was isolated from the different cell lines and analyzed with oligonucleotide mouse expression microarrays. Four microarrays were used for each cell line. Microarray results were confirmed by real-time RT-PCR. RESULTS: A new cell line resistant to both 125 microM H2O2 and 100 micro M TBHP was developed, because cells resistant to H2O2 were killed by TBHP. Analysis of classic antioxidative enzyme activities showed little change between cells that survive H2O2 (H) and those that survive H2O2 and TBHP (HT). Therefore, the global change in gene expression in these cell lines was determined with gene expression microarrays. The fluorescent signal changes of the genes within the three cell lines, H, HT, and control (C), were analyzed by statistical methods including Tukey analysis. It was found that from the 12,422 gene fragments and expressed sequence tags (ESTs) analyzed--based on a one-way ANOVA with a stringent cutoff of one false positive per 1000 genes and correcting for microarray background and noise--approximately 950 (7.6%) genes had a significant change in expression in comparing the C, H, and HT groups. A small group of antioxidative defense genes were found in this population, including catalase, members of the glutathione (GSH)-S-transferase family, NAD(P)H menadione oxidoreductase 1, and the ferritin light chain. The remaining genes are involved in a broad spectrum of other biological systems. In the HT versus H comparison, only a few genes were found that had increased expression in the HT line compared with expression in the H line, including GSH-S-transferase alpha 3 and hephaestin. Many genes that are frequently considered antioxidative defense genes, including most of the GSH peroxidases, unexpectedly showed little change. CONCLUSIONS: An unusual and generally unexpected small group of antioxidative defense genes appear to have increased expression in response to H2O2 stress. Cell lines resistant to H2O2 do not appear to survive challenge with another type of peroxide, TBHP, a lipid peroxide prototype. However, acquisition of TBHP resistance by H cells was found to be accompanied by significantly amplified expression of only a few additional antioxidative defense genes. Many of the amplified genes do not appear to be involved with antioxidative systems, reflecting the complexity of the cells' response to oxidative stress.

Animals↗

PubMed2002

[Blood lead level of children in the urban areas in China].

OBJECTIVE: The purpose of this study was to investigate the blood lead level of 3 - 5 year old children living in the cities in China and to provide scientific data for making policy on environmental lead pollution for children health protection. METHODS: Six thousand five hundred and two vein blood samples from 3 - 5 year old children in nineteen cities of nine provinces were sampled. Inductively coupled plasma-mass spectrometry (ICP-MS) were employed to determine lead level in whole blood after microwave digestion for sample preparation and questionnaire survey was also performed. Data were analyzed with multiple regression on factors which affecting blood lead levels. RESULTS: Results showed that mean blood lead level was 88.3 micro g/L for 3 - 5 year old children living in the cities in China and mean blood lead level of boys (91.1 micro g/L) was higher than that of girls (87.3 micro g/L). Twenty-nine point nine one per cent of the children's blood lead level exceeded 100 micro g/L. The research finding showed: (1) higher blood lead levels had negative effects on children's physical growth, language ability etc. (2) behavior of parents had certain effects on children's blood lead levels. (3) blood lead levels of children were affected by unhealthy habits. CONCLUSIONS: Problem of childhood lead poisoning in China has become more serious. During the past ten years, blood lead levels of children has been increased in China while decreasing in developed countries. Blood lead levels of children in China are higher than that of developed countries, which called for special concern by government and society.

Child, Preschool↗

PubMed1998

Chiroptical Properties of the Ketene and Diazo Chromophores. 1. Conformation and Optical Activity of 1-Alken-1-ones and 1-Diazoalkanes vs Aldehydes.

Ab initio methods have been employed to study the conformational behavior and chiroptical properties of acyclic, structurally related aldehydes, ketenes, and diazoalkanes of the type MeCHRCH=XY. The study involved aldehydes 1, 4, and 7 (XY = O, R = H, Me, Et, correspondingly), ketenes (1-alken-1-ones) 2, 5, and 8 (XY = CO, R = H, Me, Et), and 1-diazoalkanes 3, 6, and 9 (XY = NN, R = H, Me, Et). Geometries were optimized at the B3LYP/6-31G level, stationary points were characterized by vibrational frequency analysis, and final energies of 7-9 were obtained at the B3LYP/6-311+G//B3LYP/6-31G level. The chiroptical properties were calculated by the CIS/6-31+G method. It was found that rotational barriers of the functional group (CHXY) about the CC bond are lowered in the following order: aldehydes (1.5-2.1 kcal mol(-1)) > ketenes (1.3-1.6) > diazoalkanes (0.5-0.7). A conformer with the C=X bond eclipsed by an alpha-hydrogen is the global minimum of the ketenes and diazoalkanes, unlike the aldehydes where eclipsing by an alpha-alkyl group is preferred over a hydrogen. In all three classes of compounds, the optical rotational strength of the n-pi transition is greatest for conformers with the dihedral angle, CCCX, in the range 80-100 degrees. Within this range, the signs of the n-pi rotational strengths for the ketenes and diazoalkanes are opposite to ones for the aldehydes. As a whole, the torsional dependencies of the n-pi rotational strength of the ketene and diazo chromophores can be explained within the framework of a model of "through-bond" perturbation. CD spectra of (S)-alpha-methyl-substituted butanal (7), 1-penten-1-one (8), and 1-diazobutane (9) were obtained experimentally. The calculated chiroptical properties of equilibrium mixtures of conformers of compounds 7-9 are in agreement with experimental data.

Journal Article↗

PubMedDate not supplied

A sublethal dose of TNFalpha potentiates kainate-induced excitotoxicity in optic nerve oligodendrocytes.

Glutamate receptor-induced cell death, known as excitotoxicity in both neurons and oligodendrocytes, has been implicated as a common pathway of cell death in numerous central nervous system (CNS) diseases and trauma. Research in both neuronal and oligodendrocyte excitotoxicity has examined glutamate's receptor-mediated effects on CNS cells, and explored strategies to protect cells exposed to the elevated glutamate levels that occur in CNS trauma and disease. Proinflammatory cytokines are also elevated in the injured CNS, and have also been implicated in CNS cell death. Recently, several laboratories have examined cytokines' effects on neuronal and glial excitotoxicity. Here, we review literature concerning the dynamic susceptibility of both neurons and oligodendrocytes to excitotoxicity, and present new data from our laboratory showing that the susceptibility of oligodendrocytes to excitotoxicity is acutely potentiated by the proinflammatory cytokine TNFalpha.

Animals↗