Biomedical subjects

Feng Li

Publications and source records attributed to Feng Li.

At least 91 records · Page 5Linked to original sources

PubMed2005

Bright cyclic light accelerates photoreceptor cell degeneration in tubby mice.

Photoreceptor cell death is an irreversible, pathologic event in many blinding retinal diseases including retinitis pigmentosa, age-related macular disease, and retinal detachment. Light exposure can exacerbate a variety of human retinal diseases by increasing the rate of photoreceptor cell death. In the present study, we characterize the kinetics of photoreceptor cell death in Tubby (homozygous tub/tub, which have inherited, progressive retinal degeneration) mice born and raised in a bright cyclic light environment. Our data show that raising tub/tub mice in a bright cyclic light environment induces rapid loss of photoreceptors. This effect can be slowed, but not prevented, by raising animals in constant darkness, which suggests the involvement of phototransduction in the accelerated death of photoreceptors in this animal. We further demonstrated that the activities of cytosolic cytochrome c and caspases-3 and -9 were significantly increased in the retinas of tub/tub mice. Raising animals in darkness significantly reduced the increased activities of caspases-3 and -9, as well as cytosolic cytochrome c. We also observed that rhodopsin, a phototransduction protein, is not restricted to the rod outer segment, but is distributed throughout the rod cell, including the inner segments, cell bodies, and synapses. In addition, the light-dependent translocation and compartmentalization of arrestin and transducin are affected by the tubby mutation. Our results support the interpretation that problems in protein trafficking in the photoreceptors of the tub/tub mouse may contribute to retinal degeneration.

Adaptor Proteins, Signal Transducing↗

PubMed2005

Ribosome dysfunction is an early event in Alzheimer's disease.

Alzheimer's disease (AD) is a progressive and devastating disorder that is often preceded by mild cognitive impairment (MCI). In the present study, we report that in multiple cortical areas of MCI and AD subjects, there is a significant impairment in ribosome function that is not observed in the cerebellum of the same subjects. The impairment in ribosome function is associated with a decreased rate and capacity for protein synthesis, decreased ribosomal RNA and tRNA levels, and increased RNA oxidation. No alteration in the level of initiation factors was observed in the brain regions exhibiting impairments in protein synthesis. Together, these data indicate for the first time that impairments in protein synthesis may be one of the earliest neurochemical alterations in AD and directly demonstrate that the polyribosome complex is adversely affected early in the development of AD. These data have important implications for AD studies involving proteomics and studies analyzing proteolysis in AD, indicate that oxidative damage may contribute to decreased protein synthesis, and suggest a role for alterations in protein synthesis as a novel contributor to the onset and development of AD.

Aged↗

PubMed2005

The mimecan gene expressed in human pituitary and regulated by pituitary transcription factor-1 as a marker for diagnosing pituitary tumors.

CONTEXT: Mimecan, a secretory protein, belongs to a family of small leucine-rich proteoglycans (SLRPs). The physiological functions of mimecan have not been fully understood. OBJECTIVE: We hypothesize that the mimecan gene expressed in the human pituitary and regulated by pituitary transcription factor-1 (Pit-1) might act as a marker for diagnosing pituitary tumors. DESIGN: The clinical aspect of our work was a cross-sectional study. SETTING AND PATIENTS: In total, 20 pituitary tumor samples were collected from January 1, 2002, to December 30, 2002, in Ruijin Hospital, Shanghai, China. INTERVENTION: The number of pituitary tumors was limited. Collection of more pituitary tumor samples for additional observation will be necessary. MAIN OUTCOME MEASURES: The main outcomes were measured by Northern blot, in situ hybridization, immunohistochemical analysis, and so on. RESULTS: The mimecan gene was expressed at a moderate level in the mouse pituitary gland by Northern blot analysis. Expression of mimecan mRNA and protein is also observed in the human anterior pituitary gland. Luciferase reporter analysis and electrophoretic mobility shift assays show that Pit-1 activates the human mimecan promoter through Pit-1 response element sites. In addition, our data also show that almost all the ACTH- or GH-positive pituitary tumors likely express mimecan protein, and only a portion of prolactin-, TSH-, FSH-, and LH-positive pituitary tumors express mimecan protein. CONCLUSIONS: This work provides insight into the regulating mechanism of mimecan in pituitary and suggests that mimecan may be an unidentified pituitary secretory protein, and certain pituitary cells secreting ACTH or GH also secrete mimecan.

Animals↗

PubMed2005

Down-regulation of signal transducer and activator of transcription 3 expression using vector-based small interfering RNAs suppresses growth of human prostate tumor in vivo.

PURPOSE: Signal transducer and activator of transcription 3 (Stat3) is constitutively activated in a variety of cancers and it is a common feature of prostate cancer. Thus, Stat3 represents a promising molecular target for tumor therapy. We applied a DNA vector-based Stat3-specific RNA interference approach to block Stat3 signaling and to evaluate the biological consequences of Stat3 down-modulation on tumor growth using a mouse model. EXPERIMENTAL DESIGN: To investigate the therapeutic potential of blocking Stat3 in cancer cells, three small interfering RNAs (siRNA; Stat3-1, Stat3-2, and Stat3-3) specific for different target sites on Stat3 mRNA were designed and used with a DNA vector-based RNA interference approach expressing short hairpin RNAs to knockdown Stat3 expression in human prostate cancer cells in vitro as well as in vivo. RESULTS: Of the three equivalently expressed siRNAs, only Stat3-3 and Stat3-2, which target the region coding for the SH2 domain and the coiled-coil domain, respectively, strongly suppressed the expression of Stat3 in PC3 and LNCaP cells. The Stat3-1 siRNA, which targeted the DNA-binding domain, exerted no effect on Stat3 expression, indicating that the gene silencing efficiency of siRNA may be dependent on the local structure of Stat3 mRNA. The Stat3 siRNAs down-regulated the expression of Bcl-2 (an anti-apoptotic protein), and cyclin D1 and c-Myc (cell growth activators) in prostate cancer cells. Inhibition of Stat3 and its related genes was accompanied by growth suppression and induction of apoptosis in cancer cells in vitro and in tumors implanted in nude mice. CONCLUSIONS: These data indicate that Stat3 signaling is a promising molecular target for prostate cancer therapy and that vector-based Stat3 siRNA may be useful as a therapeutic agent for treatment of prostate cancer.

Animals↗

PubMed2005

Effects of dietary supplementation with vitamin E and selenium on rat hepatic stellate cell apoptosis.

AIM: To evaluate the effects of dietary supplementation with vitamin E and selenium on proliferation and apoptosis of hepatic stellate cells (HSCs), in acute liver injury induced by CCl(4), and to explore their role in the recovery from hepatic fibrosis phase. METHODS: An acute liver damage model of rats was established by intraperitoneal injection of carbon tetrachloride (0.3 mL/100 g body weight) twice a week, then the rats were killed at 6, 24, 48, and 72 h after the first and third injection, respectively. A liver fibrosis model was established by the same injection for 8 wk. Then three rats were killed at 3, 7, 14, and 28 d after the last injection, respectively. The rats from the intervention group were fed with chow supplemented with vitamin E (250 mg/kg) and selenium (0.2 mg/kg), and the rats in the normal control group and pathological group were given standard chow. Livers were harvested and stained with hematoxylin and eosin, Sirius red. Activated HSCs were determined by alpha-smooth muscle actin immunohistochemistry staining. Apoptotic HSCs were determined by dual staining with the terminal deoxynucleotidyl transferase UTP nick end labeling (TUNEL) and alpha-smooth muscle actin immunohistochemistry. Serum alanine aminotransferase and aspartate aminotransferase were also analyzed. RESULTS: In the acute liver damage model, the degree of liver injury was more serious in the pathological group than in the intervention group. At each time point, the number of activated HSCs was less in the intervention group than in the pathological group, while the number of apoptotic HSCs was more in the intervention group than in the pathological group. In the liver fibrosis model, the degree of liver fibrosis was more serious in the pathological group than in the intervention group. At each time point, the number of activated HSCs was less in the intervention group than in the pathological group, and the number of apoptotic HSCs was more in the intervention group than in the pathological group. CONCLUSION: Vitamin E and selenium supplementation at the given level can inhibit CCl(4)-induced activation and proliferation of HSCs and promote the apoptosis of activated HSCs in acute damage phase. Vitamin E and selenium can also effectively decrease the degree of hepatic fibrosis and promote the recovery process.

Animals↗

PubMed2005

Speciation analysis of inorganic arsenic by microchip capillary electrophoresis coupled with hydride generation atomic fluorescence spectrometry.

A novel method for speciation analysis of inorganic arsenic was developed by on-line hyphenating microchip capillary electrophoresis (chip-CE) with hydride generation atomic fluorescence spectrometry (HG-AFS). Baseline separation of As(III) and As(V) was achieved within 54 s by the chip-CE in a 90 mm long channel at 2500 V using a mixture of 25 mmol l(-1) H3BO3 and 0.4 mmol l(-1) CTAB (pH 8.9) as electrolyte buffer. The precisions (RSD, n=5) ranged from 1.9 to 1.4% for migration time, 2.1 to 2.7% for peak area, and 1.8 to 2.3% for peak height for the two arsenic species at 3.0 mg l(-1) (as As) level. The detection limits (3sigma) for As(III) and As(V) based on peak height measurement were 76 and 112 microg l(-1) (as As), respectively. The recoveries of the spikes (1 mg l(-1) (as As) of As(III) and As(V)) in four locally collected water samples ranged from 93.7 to 106%.

Argon↗

PubMed2005

Gene expression analysis of six GC-rich Gram-negative phytopathogens.

Predicted highly expressed (PHX) genes are comparatively analyzed for six GC-rich Gram-negative phytopathogens, i.e., Ralstonia solanacearum, Agrobacterium tumefaciens, Xanthomonas campestris pv. campestris (Xcc), Xanthomonas axonopodis pv. citri (Xac), Pseudomonas syringae pv. tomato, and Xylella fastidiosa. Enzymes involved in energy metabolism, such as ATP synthase, and genes involved in TCA cycle, are PHX in most bacteria except X. fastidiosa, which prefers an anaerobic environment. Most pathogenicity-related factors, including flagellar proteins and some outer membrane proteins, are PHX, except that flagellar proteins are missing in X. fastidiosa which is spread by insects and does not need to move during invasion. Although type III secretion system apparatus are homologous to flagellar proteins, none of them is PHX, which support the viewpoint that the two types of genes have evolved independently. Furthermore, it is revealed that some biosynthesis-related enzymes are highly expressed in certain bacteria. The PHX genes may provide potential drug targets for the design of new bactericide.

Bacterial Proteins↗

PubMed2005

An essential role of Pak1 phosphorylation of SHARP in Notch signaling.

The p21-activated kinases (Paks), an evolutionarily conserved family of serine/threonine kinases, play an important role in cytoskeletal reorganization in mammalian cells. The Notch signaling pathway plays an important role in the determination of cell fate/differentiation in a number of organs. Notch signaling is a complex process, and the mechanism by which Notch regulates multiple cellular processes is intriguing. The expression of both Notch and Pak1 has been shown to be deregulated in several human cancers. Using yeast two-hybrid screening, we identified SHARP, one of the Notch signaling components, as a Pak1-interacting protein. We found that SHARP is a physiologic interacting substrate of Pak1, and that this interaction enhances SHARP-mediated repression of Notch target genes. Pak1 phosphorylation sites in SHARP were mapped to Ser3486 and Thr3568 within the SHARP repression domain. Mutation of Pak1 phosphorylation sites in SHARP, inhibition of Pak1 functions by a Pak1-autoinhibitory fragment (amino acids 83-149), or expression of Pak1-specific siRNA interfered with SHARP-mediated repression of Notch target reporter gene activation. These results demonstrate that Pak1-SHARP interaction plays an essential role in enhancing the corepressor functions of SHARP, thereby modulating Notch signaling in human cancer cells.

3T3 Cells↗

PubMed2005

The protective effect of dantrolene on ischemic neuronal cell death is associated with reduced expression of endoplasmic reticulum stress markers.

The endoplasmic reticulum (ER) plays an important role in ischemic neuronal cell death. In order to determine the effect of dantrolene, a ryanodine receptor antagonist, on ER stress response and ischemic brain injury, we investigated changes in ER stress-related molecules, that is phosphorylated form of double-stranded RNA-activated protein kinase (PKR)-like ER kinase (p-PERK), phosphorylated form of eukaryotic initiation factor 2alpha (p-eIF2alpha), activating transcription factor-4 (ATF-4), and C/EBP-homologous protein (CHOP), as well as terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) in the peri-ischemic area and ischemic core region of rat brain after transient middle cerebral artery occlusion (MCAO). In contrast to the cases treated with vehicle, the infarct volume and TUNEL-positive cells were significantly reduced at 24 h of reperfusion by treatment with dantrolene. The immunoreactivities for p-PERK, p-eIF2alpha, ATF-4, and CHOP were increased at the ischemic peripheral region after MCAO, which were partially inhibited by dantrolene treatment. The present results suggest that dantrolene significantly decreased infarct volume and provided neuroprotective effect on rats after transient MCAO by reducing ER stress-mediated apoptotic signal pathway activation in the ischemic area.

Activating Transcription Factor 4↗

PubMed2005

A tumor necrosis factor receptor family protein serves as a cellular receptor for the macrophage-tropic equine lentivirus.

Characterization of cellular receptors for human, simian, and feline immunodeficiency viruses that are tropic for lymphocytes and macrophages have revealed a common theme of a sequential binding of viral envelope proteins with two coreceptors to mediate virus infection of target cells. In contrast to these dual tropic immunodeficiency viruses, the ungulate lentiviruses, including equine infectious anemia virus (EIAV), exclusively infect cells of the monocyte-macrophage lineage to cause progressive degenerative diseases without clinical immunodeficiency. EIAV causes a uniquely dynamic disease that is characterized by recurrent disease episodes including fever, diarrhea, lethargy, anemia, and thrombocytopenia. Although EIAV provides an important animal model for lentivirus disease resulting from macrophage infection, to date there has been no definition of the specific cellular receptor(s) used by the equine lentivirus to infect target cells. In the current study, we have identified and cloned a functional receptor for EIAV, designated equine lentivirus receptor-1 (ELR1), related to the family of TNF receptor (TNFR) proteins. ELR1 was shown to be expressed in various equine cells permissive for EIAV replication in vitro, including monocytes and macrophages. In contrast, EIAV-resistant human, murine, and simian cells were negative for ELR1 expression but became susceptible to virus infection when transduced with a recombinant murine retrovirus expressing the ELR1. Thus, these results identify a specific functional receptor for a macrophagetropic lentivirus and indicate that infection by EIAV may be mediated by a single receptor, in contrast to coreceptors used by the lymphotropic immunodeficiency lentiviruses.

Amino Acid Sequence↗

PubMed2005

Involvement of inflammation, degradation, and apoptosis in a mouse model of glaucoma.

Glaucoma is a common cause of blindness affecting at least 66 million people worldwide. Pigmentary glaucoma is one of the most common forms of secondary glaucoma, and its pathogenesis remains unclear. Interleukin-18 (IL-18) is an important regulator of innate and acquired immune responses and plays an important role in inflammatory/autoimmunity diseases. Using the DBA/2J mouse as an animal model of human pigmentary glaucoma, we demonstrated for the first time that the expression of the IL-18 protein and gene in the iris/ciliary body and level of IL-18 protein in the aqueous humor of DBA/2J mice are dramatically increased with age. This increase precedes the onset of clinical evidence of pigmentary glaucoma, implying a pathogenic role of inflammation/immunity in this disease. We also observed that activated NF-kappaB and phosphorylated MAPK are increased in the iris/ciliary body of DBA/2J mice, suggesting that both signaling pathways may be involved in IL-18 mediated pathogenesis of pigmentary glaucoma in the eyes of DBA/2J mice. In addition, matrix metalloproteinase-2 (MMP-2) expression in the iris/ciliary body and the activity of MMP-2 in the aqueous humor are increased whereas tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) expression in the iris/ciliary body is decreased, indicating that the degradation process is involved in this mouse model of pigmentary glaucoma. Furthermore, the expressions of apoptosis-related genes, caspase-8, Fas, FADD, FAP, and FAF, and the activity of caspase-3 are increased in the iris/ciliary body of DBA/2J mice. Elucidation of biochemical and molecular mechanisms of IL-18 participation in the pathogenesis of pigmentary glaucoma should provide approaches for developing improved and targeted treatments to ameliorate this blinding disease. The possibility that altered IL-18 expression in the eye of DBA/2J mice initiates and/or amplifies the pathogenesis of pigmentary glaucoma requires further investigation.

Aging↗

PubMed2005

Preparation of polymer-supported Ru-TsDPEN catalysts and use for enantioselective synthesis of (S)-fluoxetine.

Polymer-supported chiral ligands 9 and 17 were prepared based on Noyori's (1S,2S)- or (1R,2R)-N-(p-tolylsulfonyl)-1,2-diphenylethylenediamine. The combination with [RuCl2(p-cymene)]2 has been shown to exhibit high activities and enantioselectivities for heterogeneous asymmetric transfer hydrogenation of aromatic ketones (19a-c) with formic acid-triethylamine azeotrope as the hydrogen donor, whereby affording the respective optically active alcohols 20a-c, the key precursors of chiral fluoxetine. As exemplified by ligand 17 for substrate 19c, the catalysts can be recovered and reused in three consecutive runs with no significant decline in enantioselectivity. The procedure avoids the plausible contamination of fluoxetine by the toxic transition metal species.

Catalysis↗

PubMed2005

A new chain-like cadmium(II) coordination polymer containing chains of water molecules.

The title cadmium(II) polymer, catena-poly[[[bis(4-aminopyridine-kappaN)aquacadmium(II)]-mu-1,4-phenylenediacetato-kappa(4)O,O':O'',O'''] dihydrate], {[Cd(C10H8O4)(C5H6N2)2(H2O)].2H2O}n, comprises one-dimensional wave-like chains, in which the Cd atom is coordinated by 1,4-phenylenediacetate and 4-aminopyridine molecules. The 1,4-phenylenediacetate ligands lie about inversion centres. Extensive hydrogen-bonding interactions between the chains lead to a three-dimensional structure. Free water molecules form chains in the structure.

Journal Article↗

PubMed2005

Growth factor regulation of a 26S proteasomal subunit in breast cancer.

PURPOSE: We sought to gain insight into the mechanisms of heregulin-beta1 (HRG) action on breast epithelial cells by identifying and characterizing HRG-regulated proteins. EXPERIMENTAL DESIGN: Differential display mRNA screening of human breast cancer cells grown in the presence or absence of HRG was used to identify HRG-regulated genes. Biochemical and functional studies were undertaken to examine the impact of HRG and the therapeutic antibody herceptin on protein expression, localization, and function. RESULTS: We identified the ATPase subunit 4 (S4) of the 26S proteasome as a HRG-regulated target. Both S4 mRNA and protein levels were increased by HRG; however, this HRG-stimulated increase was blocked by the therapeutic antibody herceptin. S4 expression was significantly increased in primary human breast tumors and in estrogen receptor-negative tumors. Coimmunoprecipitation, immunofluorescence, and ATPase activity assays suggested that HRG also induced S4 activity and formation of a functional proteasome complex. CONCLUSIONS: This is the first demonstration of growth factor-regulated expression, localization, and activity of the S4 subunit of the 26S proteasome in human breast cancer cells. These findings now provide a potential mechanistic rationale for the use of proteasome inhibitors in breast cancers with active HRG signaling.

Adenosine Triphosphatases↗

PubMed2005

Identification of the immunogenic domains in HBsAg preS1 region using overlapping preS1 fragment fusion proteins.

AIM: The incorporation of hepatitis B virus (HBV) preS1 region into epitope-based vaccines against HBV has been accepted widely, but the incorporate site and size of preS1 sequence is controversial. Therefore our purpose was to further investigate its immunogenic domains for the epitope-based hepatitis B vaccine design. METHODS: Eight GST fusion proteins containing overlapping preS1 fragments in preS1 (21-119) region were expressed in E.coli. Using these purified fusion proteins, the immunogenic domains in preS1 region were identified in detail in mice and humans by Western blot analysis and ELISA. RESULTS: The results in mice showed that the immu-nogenic domains mainly existed in preS1 (21-59) and preS1 (95-109). Similarly, these fragments had strong immunogenicity in humans; whereas the other parts except for preS1 (60-70) also had some immunogenicity. More importantly, a major immunogenic domain, preS1 (34-59), which has much stronger immunogenicity, was identified. Additionally, the antibodies against some preS1 fragments, especially preS1 (34-59), were speculated to be virus-neutralizing. CONCLUSION: Eight GST fusion proteins containing overlapping preS1 fragments were prepared successfully. They were used for the study on the immunogenic dom-ains in preS1 (21-119) region. The preS1 (34-59) fragments were the major immunogenic domains in the preS1 region, and the antibodies against these fragments were speculated to be virus-neutralizing. Therefore, the incorporation of preS1 (34-59) fragments into epitope-based HBV vaccines may be efficient for enhancement of immune response. Additionally, the results also imply that there are more complex immune responses to preS1 region and more abundant immunogenic domains in humans.

Animals↗

PubMed2005

Functional complementation of Trypanosoma brucei RNA in vitro editing with recombinant RNA ligase.

The approximately 20S RNA ligase-containing complex (L-complex) in trypanosomatid mitochondria interacts by means of RNA linkers with at least two other multiprotein complexes to mediate the editing of mitochondrial cryptogene transcripts. The L-complex contains approximately 16 proteins, including the two RNA-editing ligases (RELs), REL1 and REL2. Leishmania tarentolae REL1 and REL2 and Trypanosoma brucei REL1 were expressed as enzymatically active tandem affinity purification-tagged proteins in a Baculovirus system. When these proteins were added to mitochondrial lysates from T. brucei procyclic cells that were depleted of the cognate endogenous ligase by RNA interference down-regulation of expression, the added proteins were integrated into the L-complex, and, in the case of REL1, there was a complementation of in vitro-precleaved U-insertion and U-deletion editing activities of the 20S L-complex. Integration of the recombinant proteins did not occur or occurred at a very low level with noncognate ligase-depleted L-complex or with wild-type L-complex. A C-terminal region of the T. brucei recombinant REL1 downstream of the catalytic domain was identified as being involved in integration into the L-complex. The ability to perform functional complementation in vitro provides a powerful tool for molecular dissection of the editing reaction.

Animals↗

PubMed2005

Fabrication of colloidal crystals with tubular-like packings.

Methods are reported for the fabrication of colloidal crystal wires with tubular packings. Both free and silica-encased wires have been prepared. Porous silicon membranes are infiltrated with silica spheres, treated with silane, and annealed. After removal of the silicon template, short annealing times were found to result in colloidal crystal wires with varied packing geometries, while repeated annealing cycles produced a thin translucent silica sheath around the wires. Packing in the wires varies with the channel diameter of the Si membrane. The channels used in this study typically produce colloidal crystal wires with six strands, though wires with four to seven strands have been observed. Both chiral and achiral packings are also possible.

Biocompatible Materials↗

PubMed2005

Expression of neurocan after transient middle cerebral artery occlusion in adult rat brain.

Neurocan is one of the major chondroitin sulfate proteoglycans in the nervous tissues. The expression and proteolytic cleavage of neurocan are developmentally regulated in the normal rat brain, and the full-length neurocan is detected in juvenile brains but not in normal adult brains. Recently, some studies showed that the full-length neurocan was detectable even in the adult brain when it was exposed to mechanical incision or epileptic stimulation. In the present study, we demonstrated by Western blot analysis that the full-length neurocan transiently appeared in the peri-ischemic region of transient middle cerebral artery occlusion (tMCAO) in adult rat with a peak level at 4 days after tMCAO. Immunohistochemical analysis showed that a clear positive signal of neurocan was observed 4 days after tMCAO in the peri-ischemic region of cerebral cortex and caudate, where cells strongly positive in GFAP expression were also distributed. These results indicate that accumulation of the full-length neurocan produced by reactive astrocytes may be one of the processes for tissue repair and reconstruction of neural networks after focal brain ischemia as well.

Animals↗