U937 Cells (u937 + cell)

Distribution by Scientific Domains


Selected Abstracts


The MHC class,II transactivator (CIITA) mRNA stability is critical for the HLA class,II gene expression in myelomonocytic cells

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 2 2005
Andrea De Lerma Barbaro
Abstract The human promyelocytic U937 cells express detectable levels of MHC class,II (MHC-II) molecules. Treatment with 12-o- - tetradecanoyl phorbol 13-acetate (TPA), inducing macrophage-like differentiation, produces a dramatic decrease of MHC-II expression as result of down-modulation of the activation of immune response gene,1 (AIR-1)-encoded MHC-II transactivator (CIITA). This event is specific, as MHC class,I remains unaffected. Similar results are observed with U937 cells expressing an exogenous full-length CIITA. Molecular studies demonstrate that TPA treatment affects the stability of CIITA mRNA rather than CIITA transcription. Importantly, cis -acting elements within the distal 650,bp of the 1035-bp 3,,untranslated region (3,UTR, nucleotides 3509,4543) are associated to transcript instability. Transcription inhibitors actinomycin,D and 5,6-dichlororibofuranosyl benzimidazole, and the translation inhibitor cycloheximide significantly rescue the accumulation of CIITA mRNA in TPA-treated cells. A similar effect is also observed after treatment with staurosporine and the PKC-specific inhibitor GF109203X. The instability of CIITA mRNA produced by TPA in U937 cells is not seen in B,cells. These results demonstrate the presence of an additional level of control of MHC-II expression in the macrophage cell lineage depending upon the control of CIITA mRNA stability, most likely mediated by differentiation-induced, 3,UTR-interacting factors which require kinase activity for their destabilizing function. [source]


Reduced FAS transcription in clones of U937 cells that have acquired resistance to Fas-induced apoptosis

FEBS JOURNAL, Issue 2 2009
Jeanette Blomberg
Susceptibility to cell death is a prerequisite for the elimination of tumour cells by cytotoxic immune cells, chemotherapy or irradiation. Activation of the death receptor Fas is critical for the regulation of immune cell homeostasis and efficient killing of tumour cells by apoptosis. To define the molecular changes that occur during selection for insensitivity to Fas-induced apoptosis, a resistant variant of the U937 cell line was established. Individual resistant clones were isolated and characterized. The most frequently observed defect in the resistant cells was reduced Fas expression, which correlated with decreased FAS transcription. Clones with such reduced Fas expression also displayed partial cross-resistance to tumour necrosis factor-, stimulation, but the mRNA expression of tumour necrosis factor receptors was not decreased. Reintroduction of Fas conferred susceptibility to Fas but not to tumour necrosis factor-, stimulation, suggesting that several alterations could be present in the clones. The reduced Fas expression could not be explained by mutations in the FAS coding sequence or promoter region, or by silencing through methylations. Protein kinase B and extracellular signal-regulated kinase, components of signalling pathways downstream of Ras, were shown to be activated in some of the resistant clones, but none of the three RAS genes was mutated, and experiments using chemical inhibitors could not establish that the activation of these proteins was the cause of Fas resistance as described in other systems. Taken together, the data illustrate that Fas resistance can be caused by reduced Fas expression, which is a result of an unidentified mode of regulation. [source]


Regulated expression and intracellular localization of cystatin F in human U937 cells

FEBS JOURNAL, Issue 22 2002
Carl-Michael Nathanson
Cystatin F is a cysteine peptidase inhibitor recently discovered in haematopoietic cells by cDNA cloning. To further investigate the expression, distribution and properties of the native human inhibitor the promyeloid cell line U937 has been studied. The cells expressed relatively large quantities of cystatin F, which was found both secreted and intracellularly. The intracellular levels were unusually high for a secreted cystatin (, 25% of the cystatin F in 2- or 4-day culture medium). By contrast, U937 cells contained only 3,4% of the related inhibitor, cystatin C. Cystatin F purified from lysates of U937 cells showed three major forms carrying two, one or no carbohydrate chains. Immunocytochemistry demonstrated a marked cytoplasmic cystatin F staining in a granular pattern. Double staining with a marker for endoplasmic reticulum revealed no colocalization for cystatin F. Analysis of the promoter region of the cystatin F gene (CST7) showed that it, like that of the cystatin C gene (CST3), is devoid of typical TATA- and CAAT-box elements. In contrast to the cystatin C promoter, it does not contain multiple Sp1 binding sites, but has a unique site for C/EBP,, possibly explaining the restricted expression of the cystatin F gene. Cells stimulated with all- trans retinoic acid to differentiate them towards a granulocytic pathway, showed a strong (, 18-fold) down-regulation of intracellular cystatin F and almost abolished secreted levels of the inhibitor. Stimulation with tetradecanoyl phorbol acetate, causing monocytic differentiation, also resulted in down-regulation (two fold to threefold) of cystatin F expression, whereas the cystatin C expression was essentially unaltered in both experiments. The results suggest that cystatin F as an intracellular cysteine peptidase inhibitor with readily regulated expression, may be a candidate to control the cysteine peptidase activity known to be essential for antigen presentation in different blood cell lineages. [source]


Interleukin-8 fails to induce human immunodeficiency virus-1 expression in chronically infected promonocytic U1 cells but differentially modulates induction by proinflammatory cytokines

IMMUNOLOGY, Issue 1 2000
C. T. Tiemessen
Summary This study addresses the role of interleukin (IL)-8, a CXC-chemokine, the level of which is reported to be raised in the peripheral circulation of human immunodeficiency virus-1 (HIV-1)-infected individuals, during the induction of HIV-1 expression from latency and during cytokine-mediated HIV-1 up-regulation. IL-8 at the higher concentrations tested (, 100 ng/ml) was unable to induce HIV-1 expression in the chronically infected promonocytic U1 cell line, as measured by p24 antigen enzyme-linked immunosorbent assay (ELISA), whereas at lower concentrations of 1 and 10 ng/ml, constitutive HIV-1 expression was only marginally reduced. HIV-1 replication in acutely infected U937 cells was also significantly reduced by IL-8. The potent up-regulation of HIV-1 expression in U1 cells by tumour necrosis factor-, (TNF-,) remained unaffected by the addition of IL-8. HIV-1 induction by IL-1,, IL-6 and TNF-,, cytokines grouped here as intermediate HIV-1 inducers, was suppressed by IL-8 at concentrations of 1 and 10 ng/ml. However, IL-8 at 100 ng/ml did not significantly alter the effect of IL-1,, synergized with IL-6 in enhancing, and marginally suppressed TNF-,-induced HIV-1 expression. IL-8 suppressed granulocyte,macrophage colony-stimulating factor (GM-CSF) and enhanced interferon-, (IFN-,)-induced HIV-1 expression in a dose-dependent manner. Pretreatment of U1 cells with IL-8 did not alter the IL-8-mediated effects on cytokine-induced HIV-1 expression, suggesting that this chemokine exerts its effect at the time of HIV-1 induction or at a postinduction stage. Furthermore, IL-8 was itself induced by cytokines that up-regulate HIV-1 expression in U1 cells and the levels produced correlated directly with the levels of p24 antigen produced, suggesting common pathways for cytokine induction of both HIV-1 and IL-8. These results show that IL-8, typically a non-inducer, can differentially modulate HIV-1 expression in U1 cells and that this is dependent on the inducing cytokine and on the concentration of IL-8. [source]


In vitro evaluation of the chemoprotective action mechanisms of leontopodic acid against aflatoxin B1 and deoxynivalenol-induced cell damage

JOURNAL OF APPLIED TOXICOLOGY, Issue 1 2009
Stefano Costa
Abstract Several in vitro studies showed that free radical scavengers possess chemopreventive properties against mycotoxin-induced cell damage which are at least partially associated with the induction of phase II detoxifying enzymes and antioxidant enzymes like glutathione S -transferase (GST) and glutathione peroxidase (GPx). The aim of this project was to study the chemopreventive effects of leontopodic acid (LA), a potent natural occurring free radical scavenger isolated from the aerial parts of Leontopodium alpinum. Different mycotoxins were evaluated in two different cell lines on the basis of their specific toxicity: aflatoxin B1 (AFB1) on HepG2 cells and deoxynivalenol (DON) on U937 cells. Cell viability and reactive oxygen species concentration were determined, and the effects of pre-treatment with LA on these parameters were investigated together with the GST and GPx activity as well as the concentration of reduced glutathione. The results show that LA protects U937 cells from DON-induced cell damage but not HepG2 cells from AFB1. Moreover LA is able to enhance GPx activity in U937, but not GST activity in HepG2. We hypothesize that the increase in detoxifying enzymes is probably the main mechanism of antioxidant mediated chemoprevention. Copyright 2008 John Wiley & Sons, Ltd. [source]


The role of calcium in apoptosis induced by 7,-hydroxycholesterol and cholesterol-5,,6,-epoxide

JOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 5 2009
Sinad Lordan
Abstract Oxysterols, such as 7,-hydroxy-cholesterol (7,-OH) and cholesterol-5,,6,-epoxide (,-epoxide), may have a central role in promoting atherogenesis. This is thought to be predominantly due to their ability to induce apoptosis in cells of the vascular wall and in monocytes/macrophages. Although there has been extensive research regarding the mechanisms through which oxysterols induce apoptosis, much remains to be clarified. Given that experimental evidence has long associated alterations of calcium (Ca2+) homeostasis to apoptotic cell death, the aim of the present study was to determine the influence of intracellular Ca2+ changes on apoptosis induced by 7,-OH and ,-epoxide. Ca2+ responses in differentiated U937 cells were assessed by epifluorescence video microscopy, using the ratiometric dye fura-2. Over 15-min exposure of differentiated U937 cells to 30 ,M of 7,-OH induced a slow but significant rise in fura-2 ratio. The Ca2+ channel blocker nifedipine and the chelating agent EGTA blocked the increase in cytoplasmic Ca2+. Moreover, dihydropyridine (DHP) binding sites identified with BODIPY-FLX-DHP were blocked following pretreatment with nifedipine, indicating that the influx of Ca2+ occurred through L-type channels. However, following long-term incubation with 7,-OH, elevated levels of cytoplasmic Ca2+ were not maintained and nifedipine did not provide protection against apoptotic cell death. Our results indicate that the increase in Ca2+ may be an initial trigger of 7,-OH,induced apoptosis, but following chronic exposure to the oxysterol, the influence of Ca2+ on apoptotic cell death appears to be less significant. In contrast, Ca2+ did not appear to be involved in ,-epoxide,induced apoptosis. 2009 Wiley Periodicals, Inc. J Biochem Mol Toxicol 23:324,332, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20295 [source]


Jun N-terminal kinase pathway enhances signaling of monocytic differentiation of human leukemia cells induced by 1,25-dihydroxyvitamin D3

JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 6 2003
Qing Wang
Abstract Recent studies revealed that the MEK/ERK module of the mitogen-activated protein kinase (MAPK) signaling cascades is up-regulated in the early stages of 1,,25-dihydroxyvitamin D3 (1,25D3)-induced monocytic differentiation of human leukemia cells HL60. In the present study, we investigated whether another MAPK module, the JNK pathway, also participates in this form of differentiation. We found that the dependence on the concentration of the inducer, the vitamin-hormone 1,25D3, in two types of human leukemia cells, HL60 and U937, and the kinetics of monocytic differentiation in HL60 cells, parallel the degree of the activation of the JNK pathway. A blockade of JNK signaling by a stable expression of dominant negative (dn) JNK1 mutant in U937 cells resulted in reduced c-jun phosphorylation, and the differentiation of these cells was markedly decreased. Similarly, inhibition of JNK1 and JNK2 activities by the selective inhibitor SP600125 led to both dose-dependent reduction of c-jun and ATF-2 phosphorylation, and of the differentiation of HL60 cells. In addition, we found that JNK activity is essential for the AP-1 DNA binding induced by 1,25D3 in HL60 and U937 cells. The results indicate that in cultured human leukemia cells, the JNK pathway participates in the induction of monocytic differentiation by 1,25D3, probably by activating the AP-1 transcription factor. 2003 Wiley-Liss, Inc. [source]


PML/RAR, fusion protein mediates the unique sensitivity to arsenic cytotoxicity in acute promyelocytic leukemia cells: Mechanisms involve the impairment of cAMP signaling and the aberrant regulation of NADPH oxidase,

JOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2008
Lingna Li
Acute promyelocytic leukemia (APL) cells are characterized by PML/RAR, fusion protein, high responsiveness to arsenic trioxide (ATO)-induced cytotoxicity and an abundant generation of reactive oxygen species (ROS). In this study we investigated the association among these three features in APL-derived NB4 cells. We found that NADPH oxidase-derived ROS generation was more abundant in NB4 cells compared with monocytic leukemia U937 cells. By using PR9, a sub-line of U937 stably transduced with the inducible PML/RAR, expression vectors, we attributed disparities on ROS generation and ATO sensitivity to the occurrence of PML/RAR, fusion protein, since PML/RAR,-expressing cells appeared higher NADPH oxidase activity, higher ROS level and higher sensitivity to ATO. On the other hand, the basal intensity of cAMP signaling pathway was compared between NB4 and U937 as well as between PR9 cells with or without PML/RAR,, demonstrating that PML/RAR,-expressing cells had an impaired cAMP signaling pathway which relieved its inhibitory effect on NADPH oxidase derived ROS generation. In summary, the present study demonstrated the correlation of PML/RAR, with cAMP signaling pathway, NADPH oxidase and ROS generation in APL cells. PML/RAR, that bestows NB4 cells various pathological features, paradoxically also endows these cells with the basis for susceptibility to ATO-induced cytotoxcity. J. Cell. Physiol. 217: 486,493, 2008. 2008 Wiley-Liss, Inc. [source]


Gas chromatography,mass spectrometry analysis of endogenous cannabinoids in healthy and tumoral human brain and human cells in culture

JOURNAL OF NEUROCHEMISTRY, Issue 2 2001
Mauro Maccarrone
Endocannabinoids are lipid mediators thought to modulate central and peripheral neural functions. We report here gas chromatography,electron impact mass spectrometry analysis of human brain, showing that lipid extracts contain anandamide and 2-arachidonoylglycerol (2-AG), the most active endocannabinoids known to date. Human brain also contained the endocannabinoid-like compounds N -oleoylethanolamine, N -palmitoylethanolamine and N -stearoylethanolamine. Anandamide and 2-AG (0.16 0.05 and 0.10 0.05 nmol/mg protein, respectively) represented 7.7% and 4.8% of total endocannabinoid-like compounds, respectively. N -Palmitoyethanolamine was the most abundant (50%), followed by N -oleoyl (23.6%) and N -stearoyl (13.9%) ethanolamines. A similar composition in endocannabinoid-like compounds was found in human neuroblastoma CHP100 and lymphoma U937 cells, and also in rat brain. Remarkably, human meningioma specimens showed an approximately six-fold smaller content of all N -acylethanolamines, but not of 2-AG, and a similar decrease was observed in a human glioblastoma. These ex vivo results fully support the purported roles of endocannabinoids in the nervous system. [source]


Apoptosis inducing activity of viscin, a lipophilic extract from Viscum album L.

JOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 1 2005
K. Urech
Detection of antiproliferative activity and bioactivity-guided fractionation of viscin, a lipophilic extract from Viscum album L., led to the isolation of betulinic acid, oleanolic acid and ursolic acid as active components. Viscin, betulinic acid, oleanolic acid and ursolic acid inhibited growth and induced apoptotic cell death in Molt4, K562 and U937 leukaemia cells. The growth inhibitory effect of viscin was more pronounced in Molt4 and U937 cells (IC50 (concentration that inhibited cell proliferation by 50%): 118 24 and 138 24 ,g mL,1) than in K562 cells (IC50: 252 37 ,g mL,1). Oleanolic acid was the least effective in all cell lines (7.5,45.5% inhibition at 10 ,g mL,1) and ursolic acid the most active in Molt4 and U937 cells (81.8 and 97.8% inhibition, respectively, at 5 ,g mL,1). A dose-dependent loss of membrane phospholipid asymmetry associated with apoptosis was induced in all cell lines as shown in flow cytometry by the externalization of phosphatidylserine and morphological changes in cell size and granularity. There were differences in individual cell lines' response towards the apoptosis-inducing effect of viscin, betulinic acid, oleanolic acid and ursolic acid. The triterpenoids ,-amyrin, ,-amyrinacetate, lupeol, lupeolacetate, ,-sitosterol and stigmasterol, and the fatty acids oleic acid, linoleic acid, palmitic acid and stearic acid were also present in the lipophilic extract. [source]


Alcohol-Induced Up-Regulation of Fibrinolytic Activity and Plasminogen Activators in Human Monocytes

ALCOHOLISM, Issue 8 2002
Edlue M. Tabengwa
Background Moderate alcohol consumption is associated with reduced risk for coronary heart disease. This may due, in part to increased fibrinolysis. Monocytes synthesize fibrinolytic proteins, tissue plasminogen activator (t-PA), urokinase plasminogen activator (u-PA), and their receptors. These studies were carried out to determine the effect of low alcohol on monocyte fibrinolytic activity and PA messenger RNA (mRNA) synthesis. Methods Peripheral blood monocytes and U937 cells were incubated in absence/presence of low alcohol (0.1%, v/v) for various times (0,1 hr), followed by incubations in the absence of alcohol (0,24 hr) before measurement of fibrinolytic activity and PA mRNA levels (reverse transcriptase polymerase chain reaction). Results Brief exposure (15 min, 4C) of U937 cells to low alcohol resulted in an approximately 2- to 3-fold increase (269.0 5.6 fmol/1 106 cells versus 656.0 94.0 fmol/1 106 cells) in fibrinolytic activity. Preincubation of U937 cells and peripheral blood monocytes in low alcohol (1 hr, 37C) followed by incubation in the absence of alcohol (24 hr) resulted in a sustained approximately 4- to 5-fold increase (414.0 174.7 vs. 965.33.0 104.8 fmol/1 106 cells) and an approximately 3- to 4-fold (20.5 2.14 vs. 74 2.28 fmol/2 106 cells, respectively) increase in fibrinolytic activity. Preincubation of monocytes with low alcohol (1 hr, 37C) followed by incubation in the absence of alcohol (6 hr) resulted in an approximately 5- to 6-fold (0.06 0.02 vs. 0.42 0.02) and an approximately 2- to 3-fold (0.89 0.04 vs. 2.07 0.29) increase in t-PA and u-PA mRNA (reverse transcriptase polymerase chain reaction; PA/glyceraldehyde-3-phosphate dehydrogenase ratio), respectively. Conclusions These data suggest that low alcohol exerts a rapid, direct, and sustained effect on monocyte fibrinolytic activity, which may be, due in part, to increased monocyte t-PA/u-PA expression. These data provide a feasible molecular mechanism by which alcohol effects on monocyte fibrinolysis may contribute to the cardioprotective benefit associated with moderate alcohol consumption. [source]


Thimerosal induces apoptosis and G2/M phase arrest in human leukemia cells,

MOLECULAR CARCINOGENESIS, Issue 9 2006
Kyung Jin Woo
Abstract Thimerosal is an organomercury compound with sulfhydryl-reactive properties. The ability of thimerosal to act as a sulfhydryl group is related to the presence of mercury. Due to its antibacterial effect, thimerosal is widely used as preservatives and has been reported to cause chemically mediated side effects. In the present study, we showed that the molecular mechanism of thimerosal induced apoptosis in U937 cells. Thimerosal was shown to be responsible for the inhibition of U937 cells growth by inducing apoptosis. Treatment with 2.5,5 M thimerosal but not thiosalicylic acid (structural analog of thimerosal devoid of mercury) for 12 h produced apoptosis, G2/M phase arrest, and DNA fragmentation in a dose-dependent manner. Treatment with caspase inhibitor significantly reduced thimerosal-induced caspase 3 activation. In addition, thimerosal-induced apoptosis was attenuated by antioxidant Mn (III) meso-tetrakis (4-benzoic acid) porphyrin (Mn-TBAP). These data indicate that the cytotoxic effect of thimerosal on U937 cells is attributable to the induced apoptosis and that thimerosal-induced apoptosis is mediated by reactive oxygen species generation and caspase-3 activation. 2006 Wiley-Liss, Inc. [source]


Anti,citrullinated protein antibodies bind surface-expressed citrullinated Grp78 on monocyte/macrophages and stimulate tumor necrosis factor , production

ARTHRITIS & RHEUMATISM, Issue 5 2010
Ming-Chi Lu
Objective Anti,citrullinated protein antibodies (ACPAs), which are the most specific autoantibody marker in patients with rheumatoid arthritis (RA), correlate with disease activity; however, the role of ACPAs in RA pathogenesis has not been elucidated. We hypothesized that ACPAs may directly stimulate mononuclear cells to produce inflammatory cytokines. Thus, we identified cognate antigens of ACPAs on monocyte/macrophages and examined their immunopathologic roles in the pathogenesis of RA. Methods ACPAs were purified from pooled ACPA-positive RA sera by cyclic citrullinated peptide,conjugated affinity column. After coculture of U937 cells with ACPAs, the tumor necrosis factor , (TNF,) production and NF-,B DNA binding activity of the cells were measured by enzyme-linked immunosorbent assay. The cognate antigens of ACPAs on the U937 cell surface were probed by ACPAs, and the reactive bands were examined via proteomic analysis. Results ACPAs specifically enhanced TNF, production and increased the DNA-binding activity of NF-,B in U937 cells. Proteomic analysis revealed that Grp78 protein (72 kd) was one of the cognate antigens of ACPAs. The truncated form of cell surface,expressed Grp78 (55 kd) on U937 cells contained citrulline capable of binding with ACPAs. After citrullination, glutathione S-transferase,tagged recombinant Grp78 (97.52 kd) became a 72-kd fragment and bound with ACPAs. ACPAs also bound to human monocytes and lymphocytes to promote TNF, production. Conclusion We clearly demonstrated that ACPAs enhance NF-,B activity and TNF, production in monocyte/macrophages via binding to surface-expressed citrullinated Grp78. [source]


Mechanism of cell death by 5-aminolevulinic acid-based photodynamic action and its enhancement by ferrochelatase inhibitors in human histiocytic lymphoma cell line U937

CELL BIOCHEMISTRY AND FUNCTION, Issue 8 2009
Takashi Amo
Abstract Photodynamic therapy (PDT) for tumors is based on the tumor-selective accumulation of a photosensitizer, protoporphyrin IX (PpIX), followed by irradiation with visible light. However, the molecular mechanism of cell death caused by PDT has not been fully elucidated. The 5-aminolevulinic acid (ALA)-based photodynamic action (PDA) was dependent on the accumulation of PpIX, the level of which decreased rapidly by eliminating ALA from the incubation medium in human histiocytic lymphoma U937 cells. PDA induced apoptosis characterized by lipid peroxidation, increase in Bak and Bax/Bcl-xL, decrease in Bid, membrane depolarization, cytochrome c release, caspase-3 activation, phosphatidylserine (PS) externalization. PDT-induced cell death seemed to occur predominantly via apoptosis through distribution of PpIX in mitochondria. These cell death events were enhanced by ferrochelatase inhibitors. These results indicated that ALA-based-PDA induced apoptotic cell death through a mitochondrial pathway and that ferrochelatase inhibitors might enhanced the effect of PDT for tumors even at low concentrations of ALA. Copyright 2009 John Wiley & Sons, Ltd. [source]


New Anacardic Acid-Inspired Benzamides: Histone Lysine Acetyltransferase Activators

CHEMMEDCHEM, Issue 9 2010

Abstract A series of N -(4-cyano-3-trifluoromethyl-phenyl)-2-ethoxy-6-alkyl (and alkenyl) benzamides related to the anacardic acid derivative CTPB have been prepared from 2,6-dihydroxybenzoic acid with a Suzuki coupling and addition of the anion of 4-cyano-3-trifluoromethylphenylamine to a benzodioxinone as the key steps. In U937 cells, these analogues, in particular 7,c, 7,d, 7,f and 7,j, induced cell-cycle arrest in the G1 phase, caused apoptosis in about 20,% of the cells, and increased the acetylation levels of H3. These activities correlate with the enzymatic activation of histone lysine acetyltransferases (KATs): CBP and PCAF. [source]


Montelukast inhibits tumour necrosis factor-,-mediated interleukin-8 expression through inhibition of nuclear factor-,B p65-associated histone acetyltransferase activity

CLINICAL & EXPERIMENTAL ALLERGY, Issue 5 2008
F. Tahan
Summary Background Montelukast is a potent cysteinyl leukotriene-1 receptor antagonist possessing some anti-inflammatory effects although the molecular mechanism of these anti-inflammatory effects is unknown. In this study, we aimed to investigate the effect of montelukast on nuclear factor (NF)-,B-associated histone acetylation activity in phorbol myristate acetate (PMA)-differentiated U937 cells. Methods We examined the inhibitory effects of montelukast on TNF-,-induced IL-8 production in PMA-differentiated U-937 cells. U-937 cells were exposed to PMA (50 ng/mL) for 48 h to allow differentiation to macrophages. Macrophages were then exposed to TNF-, (10 ng/mL) in the presence or absence of montelukast (0.01,10 ,m) for 24 h. After this time, the concentration of IL-8 in the culture supernatant was measured by sandwich-type ELISA kit. The effect of signalling pathways on TNF-,-induced IL-8 release was examined pharmacologically using selective NF-,B/IKK2 (AS602868, 3 ,m), (PD98059, 10 ,m) and p38 mitogen activated protein kinase (MAPK) (SB203580, 1 ,m) inhibitors. NF-,B DNA binding activity was measured by a DNA-binding ELISA-based assay. NF-,B-p65-associated histone acetyltransferase (HAT) activity was measured by immunoprecipitation linked to commercial flourescent HAT. Results TNF-,-induced IL-8 release was suppressed by an NF-,B inhibitor but not by MEK or p38 MAPK inhibitors. Montelukast induced a concentration-dependent inhibition of TNF-,-induced IL-8 release and mRNA expression that reached a plateau at 0.1 ,m without affecting cell viability. Montelukast did not affect NF-,B p65 activation as measured by DNA binding but suppressed NF-,B p65-associated HAT activity. Conclusion Montelukast inhibits TNF-,-stimulated IL-8 expression through changes in NF-,B p65-associated HAT activity. Drugs targeting these enzymes may enhance the anti-inflammatory actions of montelukast. [source]


Elevated neutrophil membrane expression of proteinase 3 is dependent upon CD177 expression

CLINICAL & EXPERIMENTAL IMMUNOLOGY, Issue 1 2010
M. Abdgawad
Summary Proteinase 3 (PR3) is a major autoantigen in anti-neutrophil cytoplasmic antibodies (ANCA)-associated systemic vasculitis (AASV), and the proportion of neutrophils expressing PR3 on their membrane (mPR3+) is increased in AASV. We have shown recently that mPR3 and CD177 are expressed on the same cells in healthy individuals. In this study we try to elucidate mechanisms behind the increased mPR3 expression in AASV and its relationship to CD177. All neutrophils in all individuals were either double-positive or double-negative for mPR3 and CD177. The proportion of double-positive neutrophils was increased significantly in AASV and systemic lupus erythematosus patients. The proportion of mPR3+/CD177+ cells was not correlated to general inflammation, renal function, age, sex, drug treatment and levels of circulating PR3. AASV patients had normal levels of granulocyte colony-stimulating factor and granulocyte,macrophage colony-stimulating factor. Pro-PR3 was found to constitute 10% of circulating PR3 but none of the mPR3. We found increased mRNA levels of both PR3 and CD177 in AASV, but they did not correlate with the proportion of double-positive cells. In cells sorted based on membrane expression, CD177,mRNA was several-fold higher in mPR3+ cells. When exogenous PR3 was added to CD177-transfected U937 cells, only CD177+ cells bound PR3 to their membrane. In conclusion, the increased membrane expression of PR3 found in AASV is not linked directly to circulating PR3 or PR3 gene transcription, but is dependent upon CD177 expression and correlated with the transcription of the CD177 gene. [source]