Significant Concentration-dependent Reduction Research Articles

A Model for the Investigation of Allergic Sinus Congestion and Treatment

Sinus congestion and increased difficulty breathing are prominent symptoms of allergic upper airway inflammation in humans. In order to test the efficacy of putative drugs that might ameliorate these symptoms, we developed a model of sinus congestion in the guinea pig (GP), which has relevant histamine-driven allergic similarities to humans. GP's were administered ragweed pollen (RWP; 0-50ug) intranasally once per day, for 5 days, to determine both the dose-response relationship of sinus airway inflammation, and the maximal effect dose against which to test intranasal anti-inflammatory steroids, dexamethasone, mometasone, and fluticasone. After administration of RWP with and without steroid treatment, sinus cavity filling was measured as an index of allergic sinus congestion, and compared across treatments by ANOVA. Significant concentration-dependent increments in sinus congestion were observed with increasing concentrations of RWP, to levels that indicated up to 80% sinus occlusion at the highest concentrations of RWP tested (P<0.05). Significant concentration-dependent reductions of sinus congestion were produced by treatment with all three steroids, such that all steroids tested were able to completely abolish sinus congestion, to levels similar to RWP-vehicle-treated controls (n.s.). These results indicate proof-of-concept for this GP sinus congestion model, as being reliable for both measurement of the induction of allergic sinus congestion associated with upper airway inflammation, and its reduction with anti-inflammatory compounds typically used to treat nasal congestion both therapeutically (fluticasone, mometasone), and experimentally (dexamethasone). We conclude that this model should be suitable for evaluating novel compounds for developed for the treatment of allergic sinus inflammation and congestion.

Anthocyanin-rich Açai (Euterpe oleracea Mart.) Fruit Pulp Fractions Attenuate Inflammatory Stress Signaling in Mouse Brain BV-2 Microglial Cells

Age-related diseases of the brain compromise memory, learning, and movement and are directly linked with increases in oxidative stress and inflammation. Previous research has shown that supplementation with berries can modulate signaling in primary hippocampal neurons or BV-2 mouse microglial cells. Because of their high polyphenolic content, fruit pulp fractions of açai ( Euterpe oleracea Mart.) were explored for their protective effect on BV-2 mouse microglial cells. Freeze-dried açai pulp was fractionated using solvents with different polarities and analyzed using HPLC for major anthocyanins and other phenolics. Fractions extracted using methanol (MEOH) and ethanol (ETOH) were particularly rich in anthocyanins such as cyanidin, delphinidin, malvidin, pelargonidin, and peonidin, whereas the fraction extracted using acetone (ACE) was rich in other phenolics such as catechin, ferulic acid, quercetin, resveratrol, and synergic and vanillic acids. Studies were conducted to investigate the mitigating effects of açai pulp extracts on lipopolysaccharide (LPS, 100 ng/mL) induced oxidative stress and inflammation; treatment of BV-2 cells with acai fractions resulted in significant (p < 0.05) decreases in nitrite production, accompanied by a reduction in inducible nitric oxide synthase (iNOS) expression. The inhibition pattern was emulated with the ferulic acid content among the fractions. The protection of microglial cells by açai pulp extracts, particularly that of MEOH, ETOH, and ACE fractions, was also accompanied by a significant concentration-dependent reduction in cyclooxygenase-2 (COX-2), p38 mitogen-activated protein kinase (p38-MAPK), tumor necrosis factor-α (TNFα), and nuclear factor κB (NF-κB). The current study offers valuable insights into the protective effects of açai pulp fractions on brain cells, which could have implications for improved cognitive and motor functions.

Thein vitroeffects of antibiotics on cell viability and gene expression of equine bone marrow‐derived mesenchymal stromal cells

To investigate the effects of commonly used antibiotics on cell viability and gene expression of equine bone marrow-derived mesenchymal stromal cells (MSC) in vitro. Bone marrow-derived MSC were cultured in media containing gentamicin, amikacin, penicillin, enrofloxacin or ceftiofur at concentrations of 50, 100, 200 and 500 µg/ml. The alamarBlue fluorescence assay was used to assess cell viability over 48 h. After 5 days the cells were released and lysed prior to RNA extraction and reverse transcription. RNA levels were assessed using spectrophotometry and quantitative PCR was used to analyse gene expression of COL1A2, COL5A1, TNC, TNFα, CASP3, BCl2 and TGFβR2 relative to the reference gene GAPDH. Enrofloxacin produced a significant concentration-dependent reduction in cell viability at 200 µg/ml and higher concentrations (P = 0.009). Amikacin significantly reduced cell viability at 500 µg/ml (P = 0.002). Penicillin had no effect on cell viability at the concentrations tested (P = 0.18). Gentamicin and ceftiofur showed some interaction with the assay but had no overall effect on cell viability. At 500 µg/ml gentamicin (P<0.001), amikacin (P = 0.03), enrofloxacin (P<0.001) and ceftiofur (P<0.001) caused significant reductions in RNA levels. At 50 µg/ml gentamicin (P<0.001) and amikacin (P = 0.019) reduced BCl2 expression. Enrofloxacin produced a significant increase in COL1A2 expression (P<0.001). Enrofloxacin reduced MSC viability in vitro and may require cautious use in clinical situations. Penicillin has minimal detrimental effects on MSC in vitro and its use in conjunction with MSC at implantation appears safe. Further work is needed to fully investigate the effects of gentamicin, amikacin and ceftiofur. Clinicians using local antibiotic administration should consider the potential for local toxicity as well as the need for effective concentrations of the antibiotic.

A Novel Mechanism of Modulation of 5-HT3A Receptors by Hydrocortisone

Modulation of Cys-loop receptors by steroids is of physiological and therapeutical relevance. Nonetheless, its molecular mechanism has not been elucidated for serotonin (5-HT) type 3 receptors. We deciphered the mechanism of action of hydrocortisone (HC) at 5-HT type 3A receptors. Single-channel currents from the high-conductance form (∼4.7 pA, −70 mV) appear as a series of long opening events forming bursts, which group into long clusters. Although they are very infrequent, subconductance events (∼2.4 pA) are detected within clusters. HC produces a significant concentration-dependent reduction in open and burst durations, demonstrating open-channel block. In addition, it increases the appearance of subconductance levels in a concentration- and slightly voltage-dependent manner. The amplitude of the subconductance level does not change with HC concentration and its open duration is briefer than that of full amplitude events, indicating lower open-channel stability. Dual effects are distinguished from macroscopic responses: HC reduces amplitude by acting from either open or closed states, and it increases decay rates from the open state. Thus, HC acts as a negative modulator of 5-HT type 3A receptors by different mechanisms: It acts as an open-channel blocker and it favors opening to a preexisting subconductance level. The latter constitutes a novel, to our knowledge, mechanism of channel modulation, which might be applicable to other steroids and channels.

Waterborne fluoxetine disrupts the reproductive axis in sexually mature male goldfish, Carassius auratus

Fluoxetine (FLX) is a pharmaceutical acting as a selective serotonin reuptake inhibitor and is used to treat depression in humans. Fluoxetine and the major active metabolite norfluoxetine (NFLX) are released to aquatic systems via sewage-treatment effluents. They have been found to bioconcentrate in wild fish, raising concerns over potential endocrine disrupting effects. The objective of this study was to determine effects of waterborne FLX, including environmental concentrations, on the reproductive axis in sexually mature male goldfish. We initially cloned the goldfish serotonin transporter to investigate tissue and temporal expression of the serotonin transporter, the FLX target, in order to determine target tissues and sensitive exposure windows. Sexually mature male goldfish, which showed the highest levels of serotonin transporter expression in the neuroendocrine brain, were exposed to FLX at 0.54 μg/L and 54 μg/L in a 14-d exposure before receiving vehicle or sex pheromone stimulus consisting of either 4.3 nM 17,20β-dihydroxy-4-pregnene-3-one (17,20P) or 3 nM prostaglandin F 2α (PGF 2α). Reproductive endpoints assessed included gonadosomatic index, milt volume, and blood levels of the sex steroids testosterone and estradiol. Neuroendocrine function was investigated by measuring blood levels of luteinizing hormone, growth hormone, pituitary gene expression of luteinizing hormone, growth hormone and follicle-stimulating hormone and neuroendocrine brain expression of isotocin and vasotocin. To investigate changes at the gonadal level of the reproductive axis, testicular gene expression of the gonadotropin receptors, both the luteinizing hormone receptor and the follicle-stimulating hormone receptor, were measured as well as expression of the growth hormone receptor. To investigate potential impacts on spermatogenesis, testicular gene expression of the spermatogenesis marker vasa was measured and histological samples of testis were analyzed qualitatively. Estrogen indices were measured by expression and activity analysis of gonadal aromatase, as well as liver expression analysis of the estrogenic marker, esr1. After 14d, basal milt volume significantly decreased at 54 μg/L FLX while pheromone-stimulated milt volume decreased at 0.54 μg/L and 54 μg/L FLX. Fluoxetine (54 μg/L) inhibited both basal and pheromone-stimulated testosterone levels. Significant concentration-dependent reductions in follicle-stimulating hormone and isotocin expression were observed with FLX in the 17,20P- and PGF 2α-stimulated groups, respectively. Estradiol levels and expression of esr1 concentration-dependently increased with FLX. This study demonstrates that FLX disrupts reproductive physiology of male fish at environmentally relevant concentrations, and potential mechanisms are discussed.

The action of nitric oxide to enhance cell survival in chick cardiomyocytes is mediated through a cGMP and ERK1/2 pathway while p38 mitogen‐activated protein kinase‐dependent pathways do not alter cell death

The objective of this study was to determine whether the dual action of nitric oxide (NO) on cardiomyocyte cell viability is mediated through p38 mitogen-activated protein kinase (MAPK)-induced cell death and extracellular signal-regulated kinase (ERK1/2)-mediated cell survival pathways, and whether either of these is mediated through a cGMP-protein kinase G (PKG) pathway. Cell viability of embryonic chick cardiomyocytes was assessed by the MTT assay, which is based on the ability of viable cells to reduce 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide. The NO donor sodium nitroprusside (SNP) produced a significant (P < 0.01) concentration-dependent reduction in cell viability or increase in cell death. Sodium nitroprusside induced ERK1/2 phosphorylation, and the mitogen-activated protein kinase (MEK1/2) inhibitor PD 98059 significantly increased cell death. In contrast, SB202190, a relatively selective inhibitor of p38 MAPK, did not affect SNP-induced cell death. The cardioprotective effect of NO was prbably mediated in part via cGMP because 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, a selective inhibitor of NO-sensitive guanylyl cyclase, produced a significant enhancement of SNP-induced cell death. In contrast, the PKG inhibitor KT5823 did not affect cell viability. In summary, these data suggest that NO, via stimulation of soluble guanylyl cyclase, activates MEK1/2 whose product, ERK1/2, protects against cell death. In contrast, SNP-induced p38 MAPK activation does not modulate NO-induced cardiomyocyte cell death. Not all cGMP targets affect NO-induced cell death, since the PKG pathway does not enhance or suppress NO-induced cardiomyocyte cell death. Enhancement of the ERK1/2 responses to NO may permit the beneficial effects of NO to predominate.

β3‐Adrenoceptors modulate left ventricular relaxation in the rat heart via the NO‐cGMP‐PKG pathway

Using a model of isolated and Langendorff-perfused rat heart we analysed whether activation of beta3-adrenergic receptors (beta3-ARs) influences ventricular lusitropic performance. We also focused on the NOS/NO/cGMP/PKG cascade as the signal transduction mechanism. Hearts were treated with increasing concentrations (from 10(-12) to 10(-6) m) of BRL(37344), a selective beta3-AR agonist, and cardiac performance was evaluated by analysing both lusitropic parameters and coronary motility. Cardiac preparations were also perfused with BRL(37344) in the presence of either isoproterenol (ISO) or nadolol, or pertussis toxin (PTx), or selective inhibitors of the NOS/NO/cGMP/PKG pathway. BRL(37344) caused a significant concentration-dependent reduction in (LVdP/dt)(min), a decrease in half time relaxation significant starting from 10(-12) m, and an increase in (LVdP/dt)(max)/(LVdP/dt)(min) ratio (T/-t). BRL(37344) abolished the ISO-mediated positive lusitropism. beta3-AR-dependent effects on relaxation were insensitive to beta(1)/beta2-AR inhibition by nadolol (100 nm), and were abolished by G(i/o) protein inhibition by PTx (0.01 nm). NO scavenging by haemoglobin (10 microm), and nitric oxide synthase (NOS) inhibition by NG-monomethyl-l-arginine (10 microm) revealed the involvement of NO signalling in BRL(37344) response. Pre-treatment with inhibitors of either soluble guanylate cyclase (ODQ; 10 microm) or PKG (KT(5823); 100 nm) abolished beta3-AR-dependent negative lusitropism. In contrast, anantin (10 nm), an inhibitor of particulate guanylate cyclase, did not modify the effect of BRL(37344) on relaxation. Taken together, our findings provide functional evidence for beta3-AR modulation of ventricular relaxation in the rat heart which involves PTx-sensitive inhibitory Gi protein and occurs via an NO-cGMP-PKG cascade. Whether the effects of beta3-AR stimulation on lusitropism are beneficial or detrimental remains to be established.

Omapatrilat enhances adrenomedullin's reduction of cardiomyocyte cell death

The objective of this study was to determine whether adrenomedullin, a vasodilator peptide, modulates the process of cell death in cardiomyocytes and whether its effect would be enhanced by the endopeptidase inhibitor omapatrilat, which reduces adrenomedullin degradation. Further, we sought to determine whether the effect of adrenomedullin involved an action to preserve mitochondrial transmembrane potential (Δ Ψ m). Cardiomyocytes in culture were treated with agents that interrupted the mitochondrial electron transport chain, inhibiting glycolysis and oxidative phosphorylation. Cell death was evaluated by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay and Δ Ψ m was assessed by fluorescent microscopy. Cytochrome c loss from mitochondria and appearance in cytosol was determined by Western blotting. Potassium cyanide (KCN) plus deoxyglucose or antimycin A, for 24 h, produced significant ( p < 0.01) concentration-dependent reductions in cell viability or increases in cell death. Adrenomedullin reduced cell death produced in this manner and the effect of adrenomedullin was enhanced by treatment with omapatrilat. In contrast, there was no additional reduction in cell death by lisinopril treatment. Omapatrilat plus adrenomedullin reduced the KCN plus deoxyglucose-induced increase in cytosolic cytochrome c. A likely mechanism centers on the ability of adrenomedullin plus omapatrilat to prevent the decline in mitochondrial Δ Ψ m produced by KCN plus deoxyglucose treatment. In summary, adrenomedullin plus omapatrilat limited the decline in mitochondrial Δ Ψ m that accompanies interruption of mitochondrial metabolism and limited the extent of cell death in cardiomyocytes treated with KCN plus deoxyglucose or antimycin. Adrenomedullin plus the endopeptidase inhibitor omapatrilat may be a useful strategy to protect cardiomyocytes from cell death, in conditions associated with impairment of mitochondrial function.

The mitogen-activated/extracellular signal-regulated kinase kinase 1/2 inhibitor U0126 induces glial fibrillary acidic protein expression and reduces the proliferation and migration of C6 glioma cells

The extracellular signal-regulated kinase (ERK) signaling pathway has been implicated in diverse cellular functions. ERK and its activating kinase, mitogen-activated/extracellular signal-regulated kinase kinase (MEK), are downstream of cell surface receptors known to be up-regulated in many malignant gliomas. We sought to investigate the role of ERK in glioma cell migration, proliferation and differentiation using the rat-derived C6 glioma cell line and the MEK inhibitor, U0126. Treatment of C6 cells with U0126 caused a significant concentration-dependent reduction in cell proliferation and migration and also induced expression of glial fibrillary acidic protein, a marker of astrocytic differentiation. These results suggest that the ERK pathway regulates glioma cell proliferation, migration and differentiation.

Toxicological Interactions in the Respiratory System after Inhalation of Ozone and Sulfuric Acid Aerosol Mixtures

A factorial design study was performed to examine the acute effects of inhaled acid particles alone and in mixtures with ozone to test the hypothesis that acid particles and ozone would act synergistically. Sprague-Dawley rats were exposed nose-only for a single 4-h period to all 9 possible combinations of purified air and 2 concentrations each of O3 (0.3 and 0.6 ppm) and submicrometer (0.3 μm mass median diameter [MMD]) sulfuric acid aerosols H2SO4 (0.5 and 1.0 mg/m3). Respiratory-tract injury and impairment of alveolar macrophage functions were evaluated. Two-way analyses of variance were used to test for significance of main effects and statistical interactions, and Tukey multiple comparison tests were used to test the significance of differences between group mean values. Addition of H2SO4 to O3-containing atmospheres resulted in significant H2SO4 concentration-dependent reductions in O3-induced inflammatory responses, and H2SO4, alone and in combination with O3, depressed some functions of innate immunity. DNA synthesis in nasal, tracheal, and lung tissue following pollutant exposure, which is an index of injury or killing of epithelial cells, was significantly increased by O3 but not by H2SO4 when administered alone, compared to purified air. When administered with O3, H2SO4 did not reduce the effects of O3 on DNA synthesis in the trachea or the lung, but did reduce the DNA synthesis response to O3 in the nose. No significant changes in antibody-directed Fc receptor (FcR) binding of sheep red blood cells by alveolar macrophages were observed, but macrophage phagocytic activity was significantly reduced by the pollutant exposures. In summary, the results of this study indicate significant interactions between O3 and H2SO4 in concurrent exposures; however, the findings do not support the hypothesis that O3 and H2SO4 act synergistically in rats after single 4-h exposures.

Nonylphenol Alters Connexin 43 Levels and Connexin 43 Phosphorylation Via an Inhibition of the p38-Mitogen-Activated Protein Kinase Pathway1

Endocrine-disrupting chemicals are exogenous compounds that mimic or inhibit the action of estrogens or other hormones. Nonylphenol, an environmental contaminant distributed along the St. Lawrence River, has been reported to act as a weak estrogen. Previous studies from our laboratory have shown that rats that were fed fish taken from nonylphenol contaminated sites have altered spermatogenesis and decreased sperm count. The mechanism responsible for this effect is unknown. Gap junctional intercellular communication (GJIC) in the testis is critical for coordinating spermatogenesis. The objectives of the study were to determine the effects of nonylphenol on GJIC and connexin 43 (Cx43) in a murine Sertoli cell line, TM4. Cells were exposed for 24 h to different concentrations (1 to 50 microM) of either nonylphenol or 17beta-estradiol. GJIC was determined using a microinjection approach in which Lucifer yellow was injected directly into a single cell, and GJIC was assessed 3 min postinjection. Nonylphenol exposure decreased GJIC between adjacent cells by almost 80% relative to controls. A significant concentration-dependent reduction in GJIC was observed at nonylphenol concentrations between 1 and 50 microM. Cx43 immunofluorescent staining was reduced at both 10 and 50 microM doses of nonylphenol. Cx43 phosphorylation, as determined by Western blot analysis, was reduced at both 10 and 50 microM concentrations, which may explain, at least in part, the inhibition of GJIC. In contrast, no effect on GJIC or Cx43 protein was observed in cells exposed to 17beta-estradiol at these concentrations. Cx43 has been reported to be phosphorylated via the p38-mitogen-activated protein kinase (MAPK) pathway. P38-MAPK activity was assessed in both control and nonylphenol-exposed cells. A dose-dependent decrease in p38-MAPK activity was observed in nonylphenol-exposed Sertoli cells. Protein kinase C activity was also measured and was not influenced by nonylphenol. These results suggest that nonylphenol inhibits GJIC between Sertoli cells and that this is modulated via nonestrogenic pathways.

Fertilization‐Induced Changes in Growth Parameters and Antioxidant Activity of Medicinal Plants Used in Traditional Arab Medicine

In response to increased popularity and greater demand for medicinal plants, a number of conservation groups are recommending that wild medicinal plants be brought into cultivation systems. We collected four medicinal herbs Cichorium pumilum, Eryngium creticum, Pistacia palaestina and Teucrium polium used in traditional Arab medicine for greenhouse cultivation to assess the effects of different fertilization regimes on their growth and antioxidant activity. Wild seedlings were collected and fertilized with either 100% Hoagland solution, 50% Hoagland solution, 20% Hoagland solution or irrigated with tap water. Plant height was measured and the number of green leaves and branches counted weekly. Thereafter, the aboveground parts of plants were harvested for preparing a water-soluble powder extracts of which antioxidant activity was measured by their ability to suppress the oxidation of β-carotene. Of the fertilization regimes, we found either 20 or 50% Hoagland solution produced the most consistent response of the plant growth parameters. All powders prepared from the four wild growing plants inhibited oxidation of β-carotene. Increasing the amount of fertilizer caused a significant concentration-dependent increase in antioxidant activity of the cultivated T. polium compared with the wild type. In contrast, increasing the amount of fertilizer caused a significant concentration-dependent reduction in the antioxidant activity of powders prepared from the cultivated E. creticum when compared with wild plants. Our results showed that cultivation success should not rely solely on parameters of growth but should incorporate assessment related to indices of therapeutic potential.

Bortezomib Targets Multiple Myeloma Endothelial Cells.

Introduction: Bone marrow (BM) angiogenesis is an important hallmark of multiple myeloma (MM) which correlates with progression. Although MM remains incurable despite conventional and high-dose chemotherapy, the proteasome inhibitor Bortezomib (Velcade, formerly PS-341), can overcome conventional drug resistance in vitro and in vivo and it has recently been FDA approved for treatment of relapsed and refractory multiple myeloma. Here we evaluated whether anti-angiogenesis may contribute to the anti-MM activity of PS-341. We examined the effect of PS-341 on the angiogenic phenotype of endothelial cells (ECs) isolated from BM of patients with MM.Methods: MMECs were extracted from BM of patients with active MM using a lectin-based method. The MMEC population contained >95% factor VIII-related antigen (FVIII-RA)+ and CD31+ cells, as assessed by fluorescence activated cell sorting (FACS). Contamination by macrophages and plasma cells was <5%, evaluated by FACS for CD14 and CD38 positivity, respectively, as well as by RT-PCR and Western blot for CD38. Viability, assessed by trypan blue was >90%. MTT assay and [3H] thymidine uptake were used to evaluate the effects of PS-341 on survival and proliferation, respectively, of MMECs. Proliferation of MM.1S cells cocoltured with MMECs was measured by [3H] thymidine uptake. Cytokine (IL-6, VEGF) levels were quantitated by ELISA. Other in vitro angiogenesis functions examined included chemotaxis, spreading on fibronectin (FN), and morphogenesis on Matrigel. Ongoing work is looking at the effect of PS-341 on angiogenesis in vivo by using a chick embryo chorioallantoic membrane (CAM) model.Results: PS-341, at concentrations achievable in the plasma of patients, inhibited in vitro MMEC and HUVEC functions related to angiogenesis, including proliferation, chemotaxis, spreading on FN, and capillary formation on Matrigel. All these functions were affected in a dose-dependent fashion. A significant concentration-dependent reduction of VEGF and IL-6 production was observed in the presence of PS-341, as demonstrated by ELISA. Importantly, binding of MM.1S cells to MMECs triggers tumor cell proliferation, and PS-341 inhibits proliferation of adherent MM.1S cells in a dose-dependent fashion. Similar data were demonstrated in HUVECs.Conclusions: These data therefore demonstrate that PS-341 acts both directly and indirectly against MMECs, another mechanism which may contribute to the anti-MM activity of PS-341.

Fumonisin blunts nitric oxide-induced and nitroprusside-induced cardiomyocyte death

The objective of this study was to determine whether nitric oxide (NO)-induced cell death in cardiomyocytes was operative through de novo synthesis of ceramide by determining whether the ceramide synthase inhibitor fumonisin blocked NO-mediated cell death. Neonatal mouse cardiomyocytes in culture were pretreated with fumonisin B1 (FB1). FB1 is a competitive inhibitor of sphinganine N-acyl transferase, also known as ceramide synthase (EC 2.3.1.24). Cell viability was assessed by the (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay, which is based on the ability of viable cells to reduce MTT. Treatment with the NO donor nitroso-glutathione (NO-GSH) for 24 h produced a significant ( p<0.05) concentration-dependent reduction in OD 570 or an increase in cell death. Sodium nitroprusside (SNP) treatment for 24 h produced a significant ( p<0.001) concentration-dependent reduction in OD 570 and an increase in cardiomyocyte cell death but the effects of SNP were greater than those of NO-GSH. FB1 significantly ( p<0.05) reduced cell death induced by either SNP or NO-GSH. The SNP (0.1 mM) increase in cell death of 36.9±2.8% was significantly ( p<0.05) reduced to 24.7±1.8% by FB1 (10 μM). The effect of FB1 was not mediated through inhibition of the cell death effects of H 2O 2, which is produced by SNP, as FB1 did not prevent H 2O 2-induced cell death. Confirmation of the ability of ceramide to produce cell death was demonstrated by the cell-permeable ceramide analogue, C 2-ceramide (100 and 200 μM), which induced, respectively, 23.4±11.3 and 78.0±3.7% increases in cell death. The cell death effects of SNP and NO-GSH are likely independent of cGMP signal transduction pathways, which are activated by either SNP or NO-GSH, as there was no significant concentration-dependent change in cardiomyocyte viability after treatment with the cell-permeable analogue dibutyryl–GMP. These data show that FB1 blunts SNP- and NO-induced cardiomyocyte death and raise the novel possibility of preventing some of SNP- or NO-induced cardiomyocyte cell death by ceramide synthase inhibition.

Lovastatin induces cell death in cardiomyocytes that is not reversible by coenzyme Q 10.

Lovastatin induces cell death in cardiomyocytes that is not reversible by coenzyme Q 10.

Physiological levels of β-amyloid induce cerebral vessel dysfunction and reduce endothelial nitric oxide production

β-amyloid (Aβ), the major component of senile plaques in Alzheimer's disease (AD), normally circulates in the blood at nanomolar levels but is elevated in AD. Previous studies have found that high concentrations (10-5 -10-4 M) of Aβ result in neuronal cell death. Here we show that physiological levels of soluble Aβ can induce dysfunction in perfused rat cerebral vessels and in cultured endothelial cells. At concentrations of 10-9 -10-6 M, Aβ induced a significant concentration-dependent reduction of NO production in endothelial cells. At 10-8 M, Aβ significantly decreased the sensitivity of cerebral vessels to acetylcholine (ACh), an endothelium dependent vasodilator. At 10-7 M and higher concentrations, Aβ significantly reduced the maximum response of vessels to ACh, and induced significant endothelial cell death. Aβ (10-9 -10-5 M) did not cause any detectable change in nitric oxide synthase levels. The results suggest that a modest increase in the concentration of Aβ above its normal physiological level in the circulation, as found in the early stages of AD, results in decreased NO production and vessel sensitivity to endothelium-dependent vasodilation that could lead to constricted blood vessels and ischemia in the surrounding tissue. Further increases in Aβ concentration, which may occur in the later stages of AD, result in cell death and decreased maximum vasodilator response of cerebral vessels. [Neurol Res 2001; 23: 506-512]

Haemolytic potential of three chemotherapeutic agents and aspirin in glucose-6-phosphate dehydrogenase deficiency

The potential haemolytic effect of three chemotherapeutic drugs and aspirin was tested in vitro by gluthathione stability tests. Blood was collected from the local population of Basra, Iraq where previous studies had found a high frequency of glucose-6-phosphate dehydrogenase (G6PD) deficiency. Primaquine, chloramphenicol and sulfanilamide caused significant concentration-dependent reductions of glutathione levels in G6PD-deficient red cells when compared to normal red cells. Acetylsalicylic acid had no effect on glutathione level. The G6PD-deficient erythrocytes behaved as previously reported, probably due to similar patterns in the distribution of its variants. Studies on each local variant are warranted and new drugs should be tested for haemolytic potential prior to their introduction in areas where the deficiency is common.

Near-site monitoring of the antiplatelet drug abciximab using the hemodyne analyzer and modified thrombelastograph

Objective: This investigation examines the hypothesis that the antiplatelet effect of abciximab and its reversal can be monitored using the Hemodyne (Hemodyne, Inc, Midlothian, VA) analyzer and modified Thrombelastograph (Haemoscope, Skokie, IL). Design: In vitro dose-response and reversal study. Setting: Anesthesia Research (Dallas, TX) and Special Studies Coagulation Laboratories (Washington, DC). Participants: Nine healthy volunteers. Interventions: The addition of increasing concentrations of abciximab, 0 to 10 μg/mL, and purified fibrinogen, 50 to 400 mg/dL. The reversal of abciximab, 4 μg/mL, with the addition of fresh platelet-rich plasma (PRP) sufficient to increase the platelet concentration by approximately 10%. Measurements and Main Results: Platelet aggregation and platelet contractile force using the Hemodyne analyzer were used as platelet-specific measurements. The Thrombelastograph maximum amplitude (MA) for platelets (MA PLT) was calculated by subtracting the MA from a platelet-poor plasma (PPP) sample (MA ppp) determined in one thromboelastography well from that of whole-blood MA (MA WB) run simultaneously in the second thromboelastography well. The addition of abciximab, 0 to 10 μg/mL, resulted in significant concentration-dependent reductions in platelet aggregation ( p < 0.001), platelet contractile force ( p < 0.001), and MA PLT ( p < 0.001). Platelet contractile force ( p < 0.03) and MA PLT ( p < 0.05) were significantly more responsive than MA WB to the effect of abciximab, 4 μg/mL, and its reversal with the addition of fresh PRP. Purified fibrinogen concentration directly correlated with thromboelastography MA ( r s = 0.97; p < 0.001), yet had no effect on platelet contractile force. The addition of abciximab had no measurable influence on the MA PPP. Conclusion: This in vitro study suggests that the Hemodyne analyzer and modified Thrombelastograph might be clinically useful methods to monitor the platelet inhibitory effects of agents such as abciximab.

Dopaminergic modulation of early signs of excitotoxicity in visualized rat neostriatal neurons

Cell swelling induced by activation of excitatory amino acid receptors is presumably the first step in a toxic cascade that may ultimately lead to cell death. Previously we showed that bath application of N-methyl-D-aspartate (NMDA) or kainate (KA) produces swelling of neostriatal cells. The present experiments examined modulation of NMDA and KA-induced cell swelling by dopamine (DA) and its receptor agonists. Nomarski optics and infra-red videomicroscopy were utilized to visualize neostriatal medium-sized neurons in thick slices from rat pups (12-18 postnatal days). Increase in somatic cross-sectional area served as the indicator of swelling induced by bath application of glutamate receptor agonists. NMDA induced cell swelling in a dose-dependent manner. Activation of DA receptors in the absence of NMDA did not produce swelling. DA and the D1 receptor agonist SKF 38393, increased the magnitude of swelling produced by NMDA. This effect was reduced in the presence of the D1 receptor antagonist, SCH 23390. In contrast, activation of D2 receptors by quinpirole decreased the magnitude of NMDA-induced cell swelling. DA slightly attenuated cell swelling induced by activation of KA receptors. Quinpirole produced a significant concentration-dependent reduction in KA-induced swelling while SKF38393 increased KA-induced swelling, but only at a low concentration of KA. Together, these results provide additional support for the hypothesis that the direction of DA modulation depends on the glutamate receptor subtype, as well as the DA receptor subtype activated. One possible consequence of these observations is that endogenous DA may be an important contributing factor in the mechanisms of cell death in Huntington's disease.

Nucleoside diphosphate kinase associated with rat pancreatic membranes regulates CCK receptor affinity

We have previously demonstrated in permeabilized rat pancreatic acini that the existence of two affinity states of the pancreatic cholecystokinin (CCK) receptor seen in intact cells depends on the presence of ATP. In the present study, we demonstrate that this effect of ATP is mediated by the enzyme nucleoside diphosphate kinase (NDPK). Northern blot hybridization analysis demonstrated NDPK mRNA in pancreas. Furthermore, pancreatic membranes possessed NDPK activity, which transferred high-energy phosphate groups to [8-3H]GDP. This enzyme also utilized UTP and ITP as a source of gamma-phosphate for GTP formation while guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) was formed in the presence of adenosine 5'-O-(3-thiotriphosphate) (ATP gamma S). However, adenylyl (beta, gamma-methylene)-diphosphate (AMP-PCP) did not serve as a substrate for NDPK. Analysis of 125I-Bolton-Hunter-labeled CCK octapeptide ([125I]BH-CCK-8) binding data in the absence of nucleotides was consistent with a single affinity state with dissociation constant (Kd) equal to 80 pM and maximal binding equal to 50.8 fmol/mg. ATP, UTP, ITP, ATP gamma S, and GTP gamma S all induced two CCK binding affinity states, which in the presence of 1 mM ATP were Kd = 74 pM for high-affinity sites and Kd = 4.3 nM for low-affinity sites: AMP-PCP did not induce two affinity states. GDP at 10 microM had no effect on CCK binding but potentiated the effect of ATP. GTP gamma S, in addition to inducing high- and low-affinity states, also elicited a significant concentration-dependent reduction in the total number of measurable CCK receptors.(ABSTRACT TRUNCATED AT 250 WORDS)