Biomedical subjects

Ling Chen

Publications and source records attributed to Ling Chen.

At least 55 records · Page 3Linked to original sources

PubMed2005

Structure-controlled solventless thermolytic synthesis of uniform silver nanodisks.

Monodisperse silver nanodisks are synthesized on the gram scale from a well-characterized layered silver thiolate precursor via thermolysis at 180-225 degrees C under a N(2) atmosphere. XRD, TEM, HRTEM, and AFM analyses indicate that the nanodisks generated at 180 degrees C over 2 h have an average diameter of about 16.1 nm (sigma = +/-12%) and a thickness of 2.3 nm (sigma = +/-14%), and they lie on their (111) faces. The disk shape is considered to be predestined by the crystal structure of the precursor. Important aspects regarding the stability of the precursor, the thermolysis temperature, and the annealing time, as well as a possible conversion mechanism, are discussed.

Journal Article↗

PubMed2005

Chronic administration of dehydroepiandrosterone sulfate (DHEAS) primes for facilitated induction of long-term potentiation via sigma 1 (sigma1) receptor: optical imaging study in rat hippocampal slices.

Dehydroepiandrosterone sulfate (DHEAS), one of the most abundant neurosteroids synthesized de novo in the nervous system, has well characterized effects on memory and cognitive performances. However, little is known about the underlying synaptic mechanisms. In this study, we investigated the effects of chronic administration of DHEAS (20 mg/kg for 7 days) on the plasticity of Schaffer collateral-CA1 synapses by applying an optical recording technique on the hippocampal slices stained with voltage-sensitive dyes. We report here that chronically administered DHEAS significantly facilitated the induction of frequency-dependent LTP, termed DHEAS-facilitated LTP. While tetanus of at least 50 pulses (at 100 Hz) were required to induce LTP in control rats, only 20 pulses were needed in DHEAS-treated animals. In contrast DHEA, the non-sulfated form of DHEAS, had no facilitating effect on the induction of LTP. We found that chronically administered DHEAS did not alter the presynaptic glutamate release in response to both single pulse and tetanic stimulation, suggesting that certain alterations happened in postsynaptic neurons. Co-administration of the sigma 1 (sigma1) receptor antagonists, haloperidol or NE100, with DHEAS completely inhibited the DHEAS-facilitated LTP. However, acute administration of sigma1 receptor antagonists to the slices did not affect the induction of DHEAS-facilitated LTP, suggesting that sigma1 receptor is a key target of chronic actions of DHEAS but is not involved in the induction of DHEAS-facilitated LTP. Our findings provide evidence that chronically administered DHEAS plays a priming role in inducing a facilitated synaptic plasticity probably via a chronic activation of sigma1 receptor in rat hippocampal CA1 pyramidal cells.

6-Cyano-7-nitroquinoxaline-2,3-dione↗

PubMed2005

alpha7 Nicotinic acetylcholine receptor as a target to rescue deficit in hippocampal LTP induction in beta-amyloid infused rats.

Continuous intracerebroventricular infusion of beta-amyloid peptide 1-40 (Abeta(1-40)) in animal models induces learning and memory impairment associated with dysfunction of the cholinergic neuronal system, which has been considered to be a pathological model of Alzheimer's disease [Nitta, A., Itoh, A., Hasegawa, T., Nabeshima, T., 1994. Beta-amyloid protein-induced Alzheimer's disease animal model. Neurosci. Lett. 170, 63-66.]. Here, using a real-time optical recording technique, we demonstrate that basal synaptic transmission and several forms of synaptic plasticity, including long-term potentiation (LTP), post-tetanic potentiation (PTP) and paired-pulse facilitation (PPF) are deficient at the Schaffer collateral-CA1 synapse in hippocampal slices from Abeta-infused brain. Throughout this study, an effort was made to address whether the alpha7 nicotinic acetylcholine receptor (alpha7nAChR), which is believed to be a primary target of Abeta [Wang, H.Y., Lee, D.H., Davis, C.B., Shank, R.P., 2000a. Amyloid peptide Abeta (1-42) binds selectively and with picomolar affinity to alpha 7 nicotinic acetylcholine receptors. J. Neurochem. 75, 1155-1161.], is responsible for the deficits in synaptic plasticity observed in the Abeta-infused rats. First, we found that Abeta-infusion markedly depressed the response of alpha7nAChR to a selective alpha7nAChR agonist [3-(2,4-dimethoxybenzylidene)-anabaseine] (DMXB). Second, blockade of alpha7nAChR with either methyllycaconitine (MLA) or alpha-bungarotoxin (alpha-BTX) in control rats inhibited LTP induction, suggesting that the activation of alpha7nAChR is required for LTP induction. Finally, pre-treatment of the slices from Abeta-infused rats with 10 microM DMXB rescued CA1 synapses from the deficit in LTP and PPF. These results suggest that Abeta-impaired LTP and PPF arise as a consequence of dysfunctional alpha7nAChR, and that alpha7nAChR may be an important target to help ameliorate AD patient cognitive deficits.

Amyloid beta-Peptides↗

PubMed2005

Sodium pump alpha2 subunits control myogenic tone and blood pressure in mice.

A key question in hypertension is: How is long-term blood pressure controlled? A clue is that chronic salt retention elevates an endogenous ouabain-like compound (EOLC) and induces salt-dependent hypertension mediated by Na(+)/Ca(2)(+) exchange (NCX). The precise mechanism, however, is unresolved. Here we study blood pressure and isolated small arteries of mice with reduced expression of Na(+) pump alpha1 (alpha1(+/-)) or alpha2 (alpha2(+/-)) catalytic subunits. Both low-dose ouabain (1-100 nm; inhibits only alpha2) and high-dose ouabain (> or =1 microm; inhibits alpha1) elevate myocyte Ca(2)(+) and constrict arteries from alpha1(+/-), as well as alpha2(+/-) and wild-type mice. Nevertheless, only mice with reduced alpha2 Na(+) pump activity (alpha2(+/-)), and not alpha1 (alpha1(+/-)), have elevated blood pressure. Also, isolated, pressurized arteries from alpha2(+/-), but not alpha1(+/-), have increased myogenic tone. Ouabain antagonists (PST 2238 and canrenone) and NCX blockers (SEA0400 and KB-R7943) normalize myogenic tone in ouabain-treated arteries. Only the NCX blockers normalize the elevated myogenic tone in alpha2(+/-) arteries because this tone is ouabain independent. All four agents are known to lower blood pressure in salt-dependent and ouabain-induced hypertension. Thus, chronically reduced alpha2 activity (alpha2(+/-) or chronic ouabain) apparently regulates myogenic tone and long-term blood pressure whereas reduced alpha1 activity (alpha1(+/-)) plays no persistent role: the in vivo changes in blood pressure reflect the in vitro changes in myogenic tone. Accordingly, in salt-dependent hypertension, EOLC probably increases vascular resistance and blood pressure by reducing alpha2 Na(+) pump activity and promoting Ca(2)(+) entry via NCX in myocytes.

Animals↗

PubMed2005

Glycine modulates the center response of ON type rod-dominant bipolar cells in carp retina.

Effects of glycine on ON type rod-dominant bipolar cells (RBCs) were studied in isolated, superfused carp retina by intracellular recording technique and in carp retinal slice preparation by whole cell recording. Glycine of 4mM hyperpolarized RBCs and potentiated their light responses to large light spots, which was reversed by co-application of 10 microM strychnine. It was further found that illumination of the receptive field surround did not affect the depolarizing center response of RBCs. The above result therefore suggests that glycine modulates the center response of RBCs. Focal application of glycine to either dendrites or axon terminals of RBCs failed to induce any currents in both isolated cell and retinal slice preparations. On the other hand, glycine of 4mM increased the amplitude of the scotopic electroretinographic PIII component, which reflects the activity of rod photoreceptors. It seems likely that modulation by glycine of the RBC center response may be in part ascribed to a consequence of the potentiation of rod responses by glycine.

Animals↗

PubMed2005

Hyperglycemia inhibits the uptake of dehydroascorbate in tubular epithelial cell.

BACKGROUND/AIMS: Oxidative stress has been considered to be a common pathogenetic factor of diabetic nephropathy. But the reason why renal cells are susceptible to oxidative injury in diabetes is not clear. Vitamin C plays a central role in the antioxidant defense system and exists in two major forms. The charged form, ascorbate, is taken up into cells via sodium-dependent facilitated transport. The uncharged form, dehydroascorbate, enters cells via glucose transporter and is then converted back to ascorbate within these cells. Because dehydroascorbate and glucose compete for glucose transporters, hyperglycemia will exclude vitamin C from the cell and resulted in a decreased antioxidant capacity in some cell type that is dehydroascorbate dependent. As such, we hypothesized that some renal cells were dehydroascorbate dependent and the susceptibility of renal cells to glucose-induced injury was mediated by hyperglycemic exclusion of dehydroascorbate uptake through competing for glucose transporter. The aims of the present study were to determine whether tubular epithelial cell was dehydroascorbate dependent and the effect of dehydroascorbate on the production of reactive oxygen species in cells incubated by high glucose. METHODS: Tubular epithelial cell was cultured in RPMI-1640 medium containing 10% newborn calf serum. Intracellular ascorbate and dehydroascorbate contents were measured with vitamin C assay system. The intracellular formation of reactive oxygen species was detected with the fluorescent probe CM-H(2)DCFDA by using confocal microscopy. RESULTS: Ascorbate entry into the cells was not significantly different from background noise. In contrast, we observed a significant increase in the uptake of dehydroascorbate in tubular cell. At a dehydroascorbate concentration of 1 mM, increasing concentrations of glucose competitively inhibited dehydroascorbate entry into the cells such that the accumulation of dehydroascorbate was smaller than half maximal at about 22 mM glucose. Cytochalasin B, a kind of hexose transporter inhibitor, inhibited dehydroascorbate entry into the cells. At a glucose concentration of 25 mM, increasing concentrations of dehydroascorbate reduced reactive oxygen species generation in a dose-dependent manner when dehydroascorbate concentration was smaller than 4 mM. However, the inhibitory effect was not observed at 8 mM of dehydroascorbate. CONCLUSIONS: Tubular epithelial cells are dehydroascorbate dependent. Vitamin C exclusion from tubular epithelial cells through competition of glucose and dehydroascorbate for common transport mechanism in diabetes will deprive the cells of antioxidant ability and could lead to reactive oxygen species accumulation.

Animals↗

PubMed2005

Photomutagenicity of retinyl palmitate by ultraviolet a irradiation in mouse lymphoma cells.

Retinyl palmitate (RP), a storage form of vitamin A, is frequently used as a cosmetic ingredient, with more than 700 RP-containing cosmetic products on the U.S. market in 2004. There are concerns for the possible genotoxicity and carcinogenicity of RP when it is exposed to sunlight. To evaluate the photomutagenicity of RP in cells when exposed to ultraviolet A (UVA) light, L5178Y/Tk+/- mouse lymphoma cells were treated with different doses of RP alone/or in the presence of UVA light. Treatment of the cells with RP alone at the dose range of 25-100 microg/ml did not increase mutant frequencies (MFs) over the negative control, whereas treatment of cells with 1-25 microg/ml RP under UVA light (82.8 mJ/cm2/min for 30 min) produced a dose-dependent mutation induction. The mean induced MF (392 x 10(-6)) for treatment with 25 microg/ml RP under UVA exposure was about threefold higher than that for UVA alone (122 x 10(-6)), a synergistic effect. To elucidate the underlying mechanism of action, we examined the mutants for loss of heterozygosity (LOH) at four microsatellite loci spanning the entire chromosome 11, on which the Tk gene is located. The mutational spectrum for the RP + UVA treatment was significantly different from the negative control, but not significantly different from UVA exposure alone. Ninety four percent of the mutants from RP + UVA treatment lost the Tk+ allele, and 91% of the deleted sequences extended more than 6 cM in chromosome length, indicating clastogenic events affecting a large segment of the chromosome. These results suggest that RP is photomutagenic in combination with UVA exposure in mouse lymphoma cells, with a clastogenic mode-of-action.

Animals↗

PubMed2005

The hydroxyurea-induced small GTP-binding protein SAR modulates gamma-globin gene expression in human erythroid cells.

Hydroxyurea (HU), a drug effective in the treatment of sickle cell disease, is thought to indirectly promote fetal hemoglobin (Hb F) production by perturbing the maturation of erythroid precursors. The molecular mechanisms involved in HU-mediated regulation of gamma-globin expression are currently unclear. We identified an HU-induced small guanosine triphosphate (GTP)-binding protein, secretion-associated and RAS-related (SAR) protein, in adult erythroid cells using differential display. Stable SAR expression in K562 cells increased gamma-globin mRNA expression and resulted in macrocytosis. The cells appeared immature. SAR-mediated induction of gamma-globin also inhibited K562 cell growth by causing arrest in G1/S, apoptosis, and delay of maturation, cellular changes consistent with the previously known effects of HU on erythroid cells. SAR also enhanced both gamma- and beta-globin transcription in primary bone marrow CD34+ cells, with a greater effect on gamma-globin than on beta-globin. Although up-regulation of GATA-2 and p21 was observed both in SAR-expressing cells and HU-treated K562 cells, phosphatidylinositol 3 (PI3) kinase and phosphorylated ERK were inhibited specifically in SAR-expressing cells. These data reveal a novel role of SAR distinct from its previously known protein-trafficking function. We suggest that SAR may participate in both erythroid cell growth and gamma-globin production by regulating PI3 kinase/extracellular protein-related kinase (ERK) and GATA-2/p21-dependent signal transduction pathways.

Antigens, CD34↗

PubMed2005

Oxidative stress and left ventricular function with chronic intermittent hypoxia in rats.

RATIONALE AND OBJECTIVES: Obstructive sleep apnea (OSA) is associated with oxidative stress and myocardial dysfunction. We hypothesized that the chronic intermittent hypoxia (CIH) component of OSA is sufficient to lead to these adverse effects. METHODS AND RESULTS: Rats were exposed to CIH (nadir O2, 4-5%) for 8 hours/day, 5 days/week, for 5 weeks. Results were compared with similarly handled controls (HC). Outcomes included blood pressure (tail cuff plethysmograph), echocardiographic and invasive measures of left-ventricular (LV) function, and indices of oxidative stress that included levels of myocardial lipid peroxides and Cu/Zn superoxide dismutase. Blood pressure was greater in CIH (n=22) than in HC (n=22) after 2 weeks of exposure (136+/-12 vs. 128+/-8 mm Hg; p<0.05). However, the difference disappeared by 5 weeks (127+/-13 vs. 127+/-13 mm Hg). LV weight/heart weight was greater with CIH (CIH, 0.52+/-0.05; HC, 0.47+/-0.06; p<0.005). Echocardiograms revealed LV dilation, as well as decreased LV fractional shortening (CIH, 29.7+/-9.8%; HC, 37.4+/-7.1%; p<0.001). LV end-diastolic pressure was increased with CIH (CIH, 13.7+/-5.5; HC, 8.0+/-2.9 mm Hg; p<0.001), decreased LV dp/dtmax (CIH, 5072+/-2191; HC, 6596+/-720 mm Hg/second; p<0.039), and decreased cardiac output (CIH, 48.2+/-10.5; HC, 64.1+/-10.9 ml/minute; p<0.001). LV myocardial lipid peroxides were greater (CIH, 1,258+/-703; HC 715+/-240 microm/mg protein; p<0.05) and LV myocardial superoxide dismutase levels were lower (CIH, 10.3+/-4.9; HC, 18.6+/-8.2 U/mg protein; p<0.05) with CIH. CONCLUSIONS: CIH leads to oxidative stress and LV myocardial dysfunction.

Animals↗

PubMed2005

Presynaptic modulation of synaptic transmission by pregnenolone sulfate as studied by optical recordings.

The effects of pregnenolone sulfate (PREGS), a putative neurosteroid, on the transmission of perforant path-granule cell synapses were investigated with an optical recording technique in rat hippocampal slices stained with voltage-sensitive dyes. Application of PREGS to the bath solution resulted in an acute augmentation of EPSP in a dose-dependent manner. The PREGS effect was dependent on the extracellular Ca(2+) concentration ([Ca(2+)](o)), but independent of NMDA receptor activation. PREGS caused a decrease in paired-pulse facilitation, which implies that PREGS positively modulates presynaptic neurotransmitter releases. Firmer support for this mechanism was that PREGS augmented the synaptically induced glial depolarization (SIGD) that reflects the activity of electrogenic glutamate transporters in glial cells during the uptake of released glutamate. The selective alpha7nAChR antagonist alpha-BGT or MLA prevented the SIGD increase by PREGS. Furthermore DMXB, a selective alpha7nAChR agonist, mimicked the PREGS effect on SIGD and antagonized the effect of PREGS. The presynaptic effect of PREGS was partially attenuated by the L-type Ca(2+) channel (VGCC) blocker nifedipine. Based on these findings, we proposed a novel mechanism underlying the facilitated synaptic transmission by PREGS: this neurosteroid sensitizes presynaptic alpha7nAChR that is followed by an activation of L-type VGCC to increase the presynaptic glutamate release.

2-Amino-5-phosphonovalerate↗

PubMed2005

Protection of beagle dogs from mucosal challenge with canine oral papillomavirus by immunization with recombinant adenoviruses expressing codon-optimized early genes.

Replication-deficient adenoviral (rAd5) vaccines containing codon-optimized E1, E2, E4, and E7 genes of canine oral papillomavirus (COPV) were tested singly or in combination to determine which vaccines could protect against mucosal challenge with COPV. In three studies, groups of 4-6 beagle dogs were immunized subcutaneously (s.c.) with 10(11) rAd5 at 8-10 weeks and 4-6 weeks prior to challenge with infectious COPV particles at multiple oral mucosal sites. Control dogs were immunized with equivalent doses of rAd5 expressing human papillomavirus (HPV) type 16 L1 (rAd5-HPV-16 L1). In the first study, complete protection from COPV-induced papillomas was achieved by immunization with rAd5 vaccine combinations expressing either E1 + E2 or E1 + E2 + E4 + E7; whereas two of six dogs immunized with rAd5-E4 + rAd5-E7 and six of six rAd5-HPV16-L1-immunized control dogs developed oral papillomas. In two subsequent studies, rAd5-E1 and rAd5-E2 vaccines were tested singly or in combination to assess levels of protective immunity to COPV challenge. Subcutaneous immunization with either one or two doses of rAd5 expressing the COPV E1 and E2 genes could protect > 90% of challenged dogs from wart formation. In contrast, all eight dogs immunized with rAd5-HPV-16 L1 developed papillomas at multiple sites. Protection was accompanied by significant IFN-gamma responses to COPV E1 and E2 peptides. Partial protection was conferred by two immunizations with either rAd5-E1 (6 of 9 protected) or rAd5-E2 (8 of 9 protected). These data indicate that rAd5 expressing papillomavirus E1 and E2 proteins can induce strong protective responses even in outbred populations under practical immunization conditions.

Adenoviridae↗

PubMed2005

Core-corona structure of cubic silsesquioxane-poly(ethylene oxide) in aqueous solution: fluorescence, light scattering, and TEM studies.

Well-defined amphiphilic cubic silsesquioxane-poly(ethylene oxide) (CSSQ-PEO) was prepared from octakis (dimethylsiloxy)octasilsesquioxane (Q8M8(H)) and allyl-PEO through a hydrosilylation reaction. The structure of CSSQ-PEO was characterized by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), and gel permeation chromatography (GPC). The amphiphilic properties and aggregation process of CSSQ-PEO in aqueous solution were investigated by fluorescence, dynamic and static light scattering (DLS and SLS), and transmission electron microscopy (TEM). The critical aggregation concentration (CAC) determined by fluorescence measurements was found to be 0.28 mg/mL. Combinations of DLS, SLS, and TEM studies showed the existence of core-corona micelle with hydrophobic CSSQ as the core and hydrophilic PEO as the corona in aqueous solution. The observation of two size distribution peaks from DLS measurements revealed the coexistence of small amounts of unassociated unimolecular micelles (approximately 10% of the scattered intensity) together with micellar aggregates when the CSSQ-PEO concentration was < or = 2 mg/mL. The hydrodynamic radii (R(h)) of unassociated unimolecular micelle and micellar aggregates were found to be 26 and 79 nm, respectively. A large R(g)/R(h) ratio (1.46) and the extremely small value of average chain density (4 x 10(-4) g/cm3) indicate the small hydrophobic CSSQ core was surrounded by the extended PEO coronae. The aggregation number (N(agg)) of CSSQ-PEO in aqueous solution was found to be 38 +/- 2 from SLS and 31-40 from TEM, respectively. The long PEO segments act as a spacer between the spherical aggregates, which facilitate the formation of a network-like structure at high concentration.

Chemical Phenomena↗

PubMed2005

Metal-rich chalcogenides. Synthesis, structure, and bonding of the layered Lu11Te4. Comparison with the similar Sc8Te3 and Ti11Se4.

The high-yield synthesis of Lu11Te4 by reaction of the components and annealing at 1200 degrees C is described. The structure determined by single-crystal diffraction means is monoclinic C2/m, Z = 6, a = 30.412(3) A, b = 3.9504(4) A, c = 21.073(2) A, beta = 102.96 degrees and consists of two independent condensed puckered sheets of Lu separated by individual Te atoms. Notwithstanding, the geometric structure is closely related to but distinctly different from those of both Sc8Te3 and Ti11Se4 (also C2/m), principally through displacements of pairs of atoms (the structure of the last was determined by electron diffraction). Further, close electronic similarities among the three structures are demonstrated by EHTB results in terms of both effective atom charge and bond overlap population trends between equivalent positions or functions.

Journal Article↗

PubMed2005

Preparation of highly exfoliated epoxy/clay nanocomposites by "slurry compounding": process and mechanisms.

Epoxy/clay nanocomposites with a high degree of exfoliation were achieved using a so-called "slurry-compounding" process with which the dispersed state of clay in water can be successfully transferred to an epoxy matrix. In this process sodium montmorillonite was first exfoliated and suspended in water. This suspension was further treated with acetone to form a clay-acetone slurry followed by chemical modification using silane. The modified slurry was then mixed extensively with epoxy to form epoxy/nanoclay composites. It has been shown that the morphologies of clay before and after curing are quite similar and the exfoliation process is termed "slurry compounding". Furthermore, the amount of organic modifier used is only 5 wt % of clay, in contrast to conventional organoclays which normally contain at least 25-45 wt % of organic surfactant. The resulting epoxy/nanoclay composites exhibit a high degree of clay exfoliation and a better thermal mechanical property.

Journal Article↗

PubMed2005

Hippocampal synaptic modulation by the phosphotyrosine adapter protein ShcC/N-Shc via interaction with the NMDA receptor.

N-Shc (neural Shc) (also ShcC), an adapter protein possessing two phosphotyrosine binding motifs [PTB (phosphotyrosine binding) and SH2 (Src homology 2) domains], is predominantly expressed in mature neurons of the CNS and transmits neurotrophin signals from the TrkB receptor to the Ras/mitogen-activated protein kinase (MAPK) pathway, leading to cellular growth, differentiation, or survival. Here, we demonstrate a novel role of ShcC, the modulation of NMDA receptor function in the hippocampus, using ShcC gene-deficient mice. In behavioral analyses such as the Morris water maze, contextual fear conditioning, and novel object recognition tasks, ShcC mutant mice exhibited superior ability in hippocampus-dependent spatial and nonspatial learning and memory. Consistent with this finding, electrophysiological analyses revealed that hippocampal long-term potentiation in ShcC mutant mice was significantly enhanced, with no alteration of presynaptic function, and the effect of an NMDA receptor antagonist on its expression in the mutant mice was notably attenuated. The tyrosine phosphorylation of NMDA receptor subunits NR2A and NR2B was also increased, suggesting that ShcC mutant mice have enhanced NMDA receptor function in the hippocampus. These results indicate that ShcC not only mediates TrkB-Ras/MAPK signaling but also is involved in the regulation of NMDA receptor function in the hippocampus via interaction with phosphotyrosine residues on the receptor subunits and serves as a modulator of hippocampal synaptic plasticity underlying learning and memory.

Amino Acid Motifs↗

PubMed2005

Induction of apoptosis in primary meningioma cultures by fenretinide.

Fenretinide, a synthetic retinoid that induces apoptosis in tumor cells in vitro, is being evaluated in clinical trials as a chemotherapeutic agent against several malignancies. Due to its ease of administration, long-term tolerability, and low incidence of long-term side effects, we explored its potential as a therapeutic agent against meningiomas by examining its efficacy in vitro against such cells in primary culture. Cells, cultured from freshly resected benign, atypical, or malignant meningiomas, were exposed to fenretinide (10 mumol/L). Treatment effects were assessed using flow cytometry, Western blot analysis, semiquantitative reverse transcription-PCR for retinoid receptor expression, and changes in insulin-like growth factor-I (IGF-I)-induced proliferation. Fenretinide induced apoptosis in the three grades of meningioma primary cells tested, as shown by the appearance of a sub-G(1) fraction in flow cytometric analysis and by the detection of poly-adenosyl ribonucleotidyl phosphorylase cleavage indicating caspase activation. Fenretinide treatment also increased levels of the death receptor DR5 and caused mitochondrial membrane depolarization. The levels of the retinoid receptors, retinoic acid receptor alpha and retinoid X receptor gamma, were up-regulated in response to fenretinide, suggestive of ligand-induced receptor up-regulation. IGF-I-induced proliferation in the meningioma cells was abolished by fenretinide. We conclude that fenretinide induces apoptosis in all three histologic subtypes of meningioma and exerts diverse cellular effects, including DR5 up-regulation, modulation of retinoid receptor levels, and inhibition of IGF-I-induced proliferation. These results provide preliminary evidence that fenretinide has activity against meningiomas and suggest that further studies are warranted to explore its potential as a therapeutic agent against meningiomas.

Antineoplastic Agents↗

PubMed2005

Mutagenic effects of 4-hydroxynonenal triacetate, a chemically protected form of the lipid peroxidation product 4-hydroxynonenal, as assayed in L5178Y/Tk+/- mouse lymphoma cells.

The lipid peroxidation product 4-hydroxynon-2-enal (4-HNE) is cytotoxic and genotoxic at superphysiological concentrations. To characterize the mechanism of action of 4-HNE, we assessed genotoxic damage by 4-HNE and by 4-HNE triacetate [4-HNE(Ac)(3)] using the mouse lymphoma assay that measures the mutant frequency in the Tk gene. As a strong electrophile, 4-HNE reacts readily with nucleophilic centers on cellular components. When added extracellularly, it may react preferentially with proteins in culture medium or on the cell surface and not reach deeper cellular targets such as nuclear DNA. Therefore, 4-HNE(Ac)(3), a protected form of 4-HNE that is metabolically converted to 4-HNE in cells (Neely MD, Amarnath V, Weitlauf C, and Montine TJ, Chem Res Toxicol 15:40-47, 2002), was assayed in addition to 4-HNE. When added in serum-containing medium, 4-HNE was not mutagenic in the mouse lymphoma assay up to 38 muM (cytotoxicity = 13%). In contrast, exposure to 4-HNE(Ac)(3), which mimics intracellular formation of 4-HNE, resulted in dose-dependent induction of mutations. At 17 muM 4-HNE(Ac)(3) (cytotoxicity = 33%), the mutant frequency was 719 x 10(-6) (>7-fold higher than the spontaneous mutant frequency). Loss of heterozygosity analysis in the Tk mutants revealed that the majority of mutations induced by 4-HNE(Ac)(3) resulted from clastogenic events affecting a large segment of the chromosome. The results indicate that, in the presence of serum that approximates physiological conditions, 4-HNE generated intracellularly but not extracellularly is a strong mutagen via a clastogenic action at concentrations that may occur during oxidative stress.

Aldehydes↗

PubMed2005

[ERK1/2 and p38 kinases are important regulators in P2Y receptor-mediated prostate cancer invasion].

OBJECTIVE: To explore whether ERK1/2 and p38 pathways mediate P2Y receptor-induced prostate cancer invasion. METHODS: The two subclones from the PC-3 human prostate carcinoma cell line: 1E8 (highly metastatic) and 2B4 (non-metastatic), were cultured and transfected with the plasmid pcDNA3-KA-MEK1 containing the dominant negative mutant of MEK1 (KA-MEK1) and wild type MKP-5 (a dual-specificity phosphatase of p38). P2Y receptor-activated ERK1/2 and p38 kinases were detected using phospho-specific antibodies directed against the dually phosphorylated active forms of these kinases by Western blotting. P2Y receptor agonists ATP and P2Y receptor antagonist suramin were used respectively to observe their effects on the activity of ERK1/2. The roles ERK1/2 and p38 pathways play in P2Y receptor-induced in vitro invasion were detected by in vitro invasion assay. The cells were pre-treated with ATP, SB203580, a p38 inhibitor, and PD98059, a blocker of ERK1/2 pathway, respectively. RESULTS: ATP activated ERK1/2 and p38 kinase time-dependently. Suramin significantly inhibited the activation of ERK1/2 and p38 kinase by ATP. ATP stimulated prostate cancer cell invasion. The stimulated cancer cell invasion was significantly inhibited by pretreatment of the cells with PD98059 or SB203580. Transfected of 1E8 cells with KA-MEK1 or up-regulation of MKP-5 both, while inhibiting phosphorylation of ERK1/2 or p38, significantly reduced the invasion of prostate cancer cells in vitro. CONCLUSION: P2Y receptor-induced prostate cancer cell invasion is mainly regulated through ERK1/2 and p38 pathways.

Cell Line, Tumor↗