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N Topley

Publications and source records attributed to N Topley.

At least 73 records · Page 4Linked to original sources
PubMed1992

Down-regulation of cyclooxygenase product generation by human peritoneal macrophages.

Isolated human peritoneal macrophages under resting conditions synthesize and release significant quantities of the cyclooxygenase products prostaglandin E2 (PGE2) and thromboxane B2 (TXB2). These increased linearly with time and were dependent on de novo protein synthesis. Following the addition of calcium ionophore A23187 there was a marked decrease in total generation of immunoreactive cyclooxygenase products. In contrast, there was a concomitant increase in the release of 5-lipoxygenase products. The down-regulation of both PGE2 and TXB2 was not due to diversion of substrate from the cyclooxygenase pathway to the 5-lipoxygenase pathway nor was it due to inhibitory effects of products of the 5-lipoxygenase pathway on the generation of cyclooxygenase products. Instead, the inhibitory effects of A23187 were thought to be due to a down-regulation of cyclooxygenase itself, a hypothesis supported by the finding that TXA2 synthase proved to be unaltered and Western analysis of crude peritoneal macrophage (PM phi) membranes demonstrated lesser quantities of cyclooxygenase in membranes from A23187-treated PM phi than in those prepared from control cells.

Adult↗
PubMed1992

Biocompatibility of peritoneal dialysis fluids.

The various studies cited here clearly demonstrate that peritoneal dialysis solutions reduce the viability of leukocytes and mesothelial cells, and compromise their capacity for phagocytosis, bacterial killing, and production of cytokines. The inhibitory capacity of the CAPD fluids appears to be related to their low pH, high osmolality, and high glucose concentrations. In some of the experimental settings, lactate was also identified as suppressive factor, but only at low pH. In clinical CAPD, the pH is rapidly buffered following the dialysate instillation, and the high glucose concentrations and osmolality are also partially equilibrated. Nevertheless, for a certain period of time following the dialysate exchange, peritoneal host defense systems are exposed to an unphysiological environment known to compromise important immune-cell functions. Moreover, certain leukocyte properties, such as the production of cytokines, are impaired even following longer i.p. dwell periods. Thus conventional CAPD solutions induce an at least transitory impairment of peritoneal host defense, reflecting a bioincompatibility of the commercial CAPD fluids and underscoring the need for developing fluids with a more physiological formulation.

Biocompatible Materials↗
PubMed1991

Regulation of TNF-alpha, IL-1 and IL-6 synthesis in differentiating human monoblastoid leukemic U937 cells.

The human monoblastoid tumor cell line U937 was induced to differentiate along the monocyte/macrophage lineage by treatment with 5 x 10(-9) M 12-O-tetradecanoyl phorbol-13-acetate (TPA). Between 2 h and 4 h following TPA-treatment U937 cells started to release significant amounts of TNF-alpha which remained detectable until 8-10 days. A significant IL-1 beta release was measured 24 h-48 h post stimulation and increased levels of IL-1 beta persisted until 20-22 days of culture. In contrast no release of either IL-1 alpha or IL-6 could be detected with 5 x 10(-9) M TPA during the whole time course of the experiments. The sequential induction of TNF-alpha and IL-1 beta appeared to be independently regulated since TNF-alpha release was not required for the onset of IL-1 beta production. Northern-blot analysis confirmed the sequential induction and the long term expression of TNF-alpha and IL-1 beta mRNAs. Western-blot analysis predominantly showed a high molecular weight IL-1 beta protein of about 35 kD. Further investigations on the regulation of cytokine production and release by TPA-differentiated U937 cells revealed that TNF-alpha and IL-1 beta synthesis was not influenced by exogenously added rhTNF-alpha or PGE2, whereas rh gamma-IFN specifically enhanced the IL-1 beta production. Thus, the regulation and intracellular processing of cytokines generated by differentiating U937 cells shows some differences when compared to mature monocytes/macrophages which may be related to the tumorigenic origin of U937 cells or to an incomplete differentiation.

Blotting, Northern↗
PubMed1991

Regulation of mesangial cell proliferation.

Mesangial cell proliferation constitutes a frequent finding in a number of glomerular diseases that progress to glomerular sclerosis. The factors responsible for mesangial cell growth regulation in vivo are ill defined. However, cell culture data indicate that an array of mediators may have mitogenic or antimitogenic effects on these cells. This brief review discusses the relevance of selected factors such as platelet-derived growth factor (PDGF) in this context. In vitro data indicate that PDGF is one of the most potent mesangial cell mitogens, that it may have autoregulatory properties, and that it may represent the final common pathway for a number of other mitogenic peptides. In contrast to PDGF, the relevance of inflammatory cytokines such as interleukin-1 (IL-1), tumor necrosis factor (TNF) or interleukin-6 (IL-6) for mesangial cell proliferation is less evident, with growth-inhibitory to weakly growth-promoting effects on mesangial cells. Transforming growth factor beta (TGF beta) appears to be unique in that it has a concentration-dependent mitogenic or antimitogenic effect on mesangial cells. Prostaglandins may also have variable effects, ranging from mitogenic (PGE2 alpha) to growth inhibitory (PGI2, PGF2, TxA2). These data support the notion that mesangial cell growth in vivo is regulated by a complex network of synergistic or antagonistic growth factors. The relative importance of each of these growth factors in the in vivo situation will have to be elucidated by future studies using specific receptor antagonists or neutralizing antibodies.

Animals↗
PubMed1991

Leukotriene release from peripheral and peritoneal leukocytes following exposure to peritoneal dialysis solutions.

During continuous ambulatory peritoneal dialysis (CAPD), peritoneal host defence mechanisms are repeatedly exposed to dialysis solutions (with unphysiological composition) which may compromise peritoneal immune cell functions. In this context, the current study focused on the capacity of peripheral and peritoneal PMN to release leukotrienes following exposure to conventional CAPD dialysates. PMN were obtained from peripheral blood of healthy volunteers and from the peritoneal effluent of CAPD patients with acute peritonitis. Following isolation, cells were incubated in fresh CAPD dialysates or control buffer, and calcium ionophore A23187-stimulated leukotriene synthesis was measured. Additional experiments included RP-HPLC analysis and radioactivity monitoring of lipoxygenase products in PMN labelled with 14C-arachidonic acid. Leukotriene B4 and leukotrienes C4/D4/E4 were determined by radioimmunoassay. Ionophore-triggered leukotriene release from cells exposed to control buffer was pronounced in inflammatory peritoneal PMN (70.4 +/- 31.3 ng/5 x 10(6) cells LTB4 and 13.4 +/- 19.8 ng/5 x 10(6) cells LTC4/D4/E4, mean +/- SD, n = 14) when compared to healthy peripheral PMN (26.6 +/- 16.9 ng/ml LTB4 and 6.3 +/- 6.6 ng/ml LTC4/D4/E4, n = 12). Incubation in fresh solutions for peritoneal dialysis severely depressed leukotriene release from both cell populations. These results indicate a severe inhibition of cellular responsiveness as a consequence of dialysate exposure which could contribute to the impairment of host defence early in the CAPD cycle.

Adult↗
PubMed1991

In vitro testing of a potentially biocompatible continuous ambulatory peritoneal dialysis fluid.

In the present study a newly formulated dialysis solution (HDF) was tested for its effects on phagocyte viability and function as well as its ability to support bacterial growth. This solution differs from standard CAPD solution (NPD) by the inclusion of histidine to buffer the fluid to pH 6.7. Low-dextrose HDF (1.36% w/v dextrose) did not significantly decrease the viability or inhibit any of the PMN functional parameters measured (phagocytosis, LTB4 release or respiratory burst activation) when compared to control buffer. NPD (1.36% w/v dextrose) at low pH as well as all high-dextrose dialysis solutions (NPD and HDF) significantly inhibited most PMN functions independently of reduced viability. Peritoneal mesothelial cell viability was unaffected by either low- or high-dextrose HDF but was significantly reduced by NPD (1.36 and 3.86% dextrose) at pH 5.2. The inhibitory effects of low dextrose dialysis solutions were confirmed as being partly related to their low initial pH. High-dextrose dialysis fluids, however, inhibit PMN function by a mechanism which, in addition to initial pH, appears to be directly related to their dextrose content but not their osmolality.

Bacteria↗
PubMed1991

Mitogenic effect of platelet-derived growth factor in human glomerular mesangial cells: modulation and/or suppression by inflammatory cytokines.

Glomerular mesangial cell proliferation constitutes a frequent pathological alteration in glomerulonephritis. In addition to platelet-derived growth factor (PDGF) inflammatory cytokines such as IL-1, IL-6 or tumour necrosis factor-alpha (TNF-alpha) have been proposed to have mitogenic activity for mesangial cells. A model was therefore established in which human mesangial cells (HMC) could be reversibly growth-arrested for prolonged times in serum-free medium without suffering irreversible functional or morphological changes. In this model 24 h stimulation with rhPDGF-BB induced an increase of the 3H-thymidine incorporation of 1190 +/- 280 (50 ng/ml) % +/- s.e.m. of medium control. Less growth induction was noted after stimulation with 50 ng/ml rhPDGF-AB (925 +/- 126%) or rhPDGF-AA (575 +/- 24%). Northern analysis confirmed the presence of both alpha- and beta-PDGF receptor subunit mRNA in growth-arrested HMCs. rhIL-1 alpha, rhIL-1 beta, rhTNF-alpha or rhIL-6 at various doses and times, despite increasing cellular PGE2-release, did not induce significant proliferation in HMCs. Inhibition of PGE2-release did not change the lack of mitogenicity of IL-1, TNF-alpha or IL-6. IL-6 did not alter the mitogenic response of the cells towards PDGF. In contrast, both IL-1 alpha and IL-1 beta (5 ng/ml) induced a delay but not augmentation of the PDGF growth response. This delay could be reversed by the concomitant addition of recombinant IL-6 or of anti-IL-1 antibody but not by inhibition of prostaglandin synthesis. High doses of TNF-alpha suppressed PDGF-induced proliferation. These data suggest that in growth-arrested HMCs inflammatory cytokines have a growth-modulating or -suppressive rather than (co-)mitogenic effect while PDGF-BB and -AB and to a lesser degree PDGF-AA are potent mitogens. The findings support the notion that the control of HMC proliferation in pathological situations depends on a complex network of interacting stimuli.

Blotting, Northern↗
PubMed1990

Leukotriene B4 generation by human monocytes and neutrophils stimulated by uropathogenic strains of Escherichia coli.

The generation of the 5-lipoxygenase product, leukotriene B4 (LTB4) by human mononuclear phagocytes (monocytes) following incubation with 25 different uropathogenic strains of Escherichia coli correlated with the haemolytic activity of the strains (r = 0.572, P less than 0.01). LTB4 generation by human neutrophils (PMN), however, was unrelated to this haemolytic potential (r = 0.164). In contrast, both prelabelled monocytes and PMN were stimulated by haemolytic strains of E. coli and by haemolytic culture supernatants to release significant amounts of [3H]arachidonic acid. There was a significant correlation between haemolytic activity and [3H]arachidonic acid release generated by individual strains from monocytes (r = 0.804, P less than 0.001) and PMN (r = 0.888, P less than 0.001). In addition, nonhaemolytic strains but not their culture supernatants were capable of causing slow release of both [3H]arachidonic acid and LTB4 from PMN and mononuclear cells. These results suggest that both the possession of haemolytic activity, and the direct interaction of bacteria with the leukocyte surface are mechanisms by which uropathogenic strains of E. coli may cause the release and metabolism of arachidonic acid. In addition, there was synergistic augmentation by nonhaemolytic bacteria of the PMN LTB4 response to haemolytic culture supernatants or to low doses of the calcium ionophore A23187. These results support an ionophore-like mechanism for the activation of the cell by haemolysin. LTB4 generation by PMN incubated with haemolytic supernatants was also augmented by particulate zymosan in a manner dependent on the dose of zymosan, suggesting that the direct interaction of E. coli with PMN may involve an activation mechanism similar to that for zymosan. These results demonstrate differing responses of peripheral mononuclear cells and PMN from the same donors to identical strains of E. coli and suggest that the generation of the potent chemotactic agent LTB4 in response to E. coli infection in vivo need not depend solely on the elaboration of cytotoxic haemolysins by individual strains.

Adenosine Triphosphate↗
PubMed1990

Differential augmentation by recombinant human tumor necrosis factor-alpha of neutrophil responses to particulate zymosan and glucan.

Zymosan (Z) and its major insoluble carbohydrate component beta-linked glucan activate human neutrophils (PMN) through a trypsin-sensitive recognition mechanism. This mechanism is believed to involve the PMN CR3R. Both Z and glucan generated dose and time-dependent release of the secondary lysosomal granule marker vitamin B12 binding protein, leukotriene B4 (LTB4) and superoxide from PMN and were phagocytosed with similar dose-dependent kinetics. The PMN superoxide and LTB4 responses to glucan; however, were consistently greater than those to the same doses of Z. The phagocytosis of both particles was significantly reduced after partial digestion with beta-laminarinase but not beta-glucosidase or alpha-mannosidase suggesting a recognition mechanism dependent on intact beta-1,3-glucosidic bonds in both particles. TNF-alpha (rhTNF-alpha) promoted a time- and dose-dependent increase in the expression of PMN CR3 up to 60 min. The increased expression of CR3 was paralleled by the release of the secondary lysosomal granule marker vitamin B12-binding protein. This granule contains a population of CR3R in its boundary membrane and it is the fusion of this membrane with the plasma membrane that may represent the mechanism by which CR3 expression is increased. Preincubation of PMN with 10(-9)M rhTNF-alpha augmented phagocytosis, LTB4, and superoxide generation by PMN in response to activation by Z. In contrast, none of the responses to glucan was significantly increased after incubation with rhTNF-alpha. These differences suggest a lack of absolute homology between the recognition mechanisms for zymosan and glucan and that there is a component of the recognition mechanism for zymosan that is independent of that for glucan and is up-regulated after rhTNF-alpha pretreatment.

Glucans↗
PubMed1990

Human glomerular mesangial cells inactivate leukotriene B4 by reduction into dihydro-leukotriene B4 metabolites.

Due to its potent chemotactic properties leukotriene B4 is an important mediator of inflammatory reactions. Cultured human kidney mesangial cells converted exogenously added leukotriene B4 efficiently into three different more lipophilic metabolites, two of them probably representing dihydro-leukotriene B4 isomers. This represents an alternative metabolic pathway, in contrast to leukotriene B4 omega-oxidation found in human polymorphonuclear leukocytes. Both dihydro-leukotriene B4 isomers had nearly completely lost their ability to induce leukocyte chemotaxis as compared to leukotriene B4.

Cells, Cultured↗
PubMed1990

Activation of the inflammatory response of neutrophils by Tamm-Horsfall glycoprotein.

The activation of human polymorphonuclear leukocytes (PMN) by particulate Tamm-Horsfall glycoprotein (THG) represents an interaction hitherto unrecognized. The potential pathophysiological effect of this phenomenon within the interstitium of the kidney is highlighted by the activation of the respiratory burst, as well as by comprehensive PMN degranulation. Products of the interaction are expressed in terms of phagocytosis, luminol-dependent chemiluminescence, granule marker enzyme release and arachidonic acid metabolism. Significant quantities of the primary, secondary and tertiary granule markers, myeloperoxidase, vitamin B12 binding protein and N-acetyl-beta-D-glucosaminidase, respectively, were secreted in a dose and time-dependent manner. Phagocytosis of the glycoprotein was accompanied by the generation of significant quantities of leukotriene B4. Furthermore, the ability of such a particulate ligand to activate the alternative pathway of complement clearly represents a capacity to augment the inflammatory response. Should the interaction of THG with PMN take place within the interstitium of the kidney, augmented by the deposition of complement proteins on the surface of insoluble aggregates, the resulting inflammatory response may lead to marked tissue damage and eventually result in interstitial fibrosis.

Complement Pathway, Alternative↗
PubMed1990

Interleukin 1-alpha and tumor necrosis factor-alpha induce oxygen radical production in mesangial cells.

Adherent human mesangial cells (HMC) were unable to phagocytose serum-treated zymosan (STZ), nevertheless this stimulus (1 mg/ml) induced a marked immediate increase of H2O2 and O2- release at a rate of 3.15 +/- 0.35 and 3.40 +/- 0.12 nmol/10(6) HMC/hr, respectively. Zymosan alone resulted in no release of either H2O2 or O2-. Phorbol myristate acetate (PMA, 2 X 10(-6) M) had only marginal effects on HMC leading to the generation of 0.273 +/- 0.014 nmol O2-/10(6) HMC/hr. After a lag period, human recombinant tumor necrosis factor-alpha (TNF-alpha) and human recombinant interleukin 1-alpha IL-1 alpha) both induced significant O2- production measured as SOD inhibitable reduction of cytochrome c, 5 X 10(-5) M, by adherent HMC for up to five hours, the maximum rates being 3.04 +/- 0.08 and 3.2 +/- 0.08 nmol/10(6) HMC/hr for IL-1 alpha and TNF-alpha, respectively. Significant O2- release was detectable at 0.625 ng/ml (37 pM) IL-1 alpha or 1 ng/ml (59 pM) TNF-alpha (P less than 0.05). Catalase inhibitable H2O2 production was also induced by IL-1 alpha and TNF-alpha in a dose dependent manner. Using scopoletin (40 nM) and 1 microM peroxidase we fluorimetrically measured 1.73 +/- 0.14 and 1.49 +/- 0.19 nmol H2O2/10(6) HMC/hr induced by IL-1 alpha (25 ng/ml) and TNF-alpha (20 ng/ml). Finally, we ascertained the type of radical species produced by HMC stimulated by cytokines employing ESR-spin-trapping with DMPO.2+ These results demonstrated that O2- was the primary radical species formed.(ABSTRACT TRUNCATED AT 250 WORDS)

Glomerular Mesangium↗
PubMed1990

Monokines and platelet-derived growth factor modulate prostanoid production in growth arrested, human mesangial cells.

Previous studies have demonstrated considerable prostanoid production by cultured proliferating rat mesangial cells (MC). In this study, human mesangial cells (HMC) were examined during serum-free culture in which the cells were reversibly growth arrested and did not suffer obvious irreversible functional changes. Non-stimulated cells released 2 to 10 pg/24 hr/micrograms cellular protein of PGE2, PGF2 alpha, 6-keto-PGF1 alpha, while TXB2 was not detectable. Stimulation with interleukin-1 beta (IL-1 beta) or tumor necrosis factor alpha (TNF alpha) induced up to 18-fold (IL-1 beta) or up to fourfold (TNF alpha) increases of prostanoid release. Combinations of the two monokines resulted in significant synergistic induction of PGE2 and 6-keto-PGF1 alpha up to 38 times that of control cells. Interleukin-6 (IL-6) and the HMC-mitogen, platelet-derived growth factor-BB (PDGF-BB) only induced marginal increases in HMC prostanoid generation. However, when PDGF-BB or -AB was combined with IL-1 beta or IL-6, prostanoid generation by HMC was synergistically increased up to 222-fold (IL-1 beta) or 12-fold (IL-6) above the control values, with the induction of PGE2 greater than 6-keto-PGF1 alpha greater than PGF2 alpha much greater than TXB2. In the case of IL-1 beta + PDGF-BB the induction of PGE2 release was at least partly due to the synergistic induction of cyclooxygenase activity. These findings demonstrate that both proliferating and reversibly growth arrested HMCs release prostaglandins in response to various inflammatory stimulators and combinations thereof. The findings support the important role of HMC in the regulation of glomerular hemodynamics during inflammatory processes.

Cell Division↗
PubMed1989

Prostaglandin E2 production is synergistically increased in cultured human glomerular mesangial cells by combinations of IL-1 and tumor necrosis factor-alpha 1.

Both IL-1 alpha and IL-1 beta and TNF-alpha induced a time- and dose-dependent release of authentic PGE2 from cultured human glomerular mesangial cells (HMC). This release became significant only after a 4- to 6-h lag phase, and was abolished by inhibition of protein synthesis, and was not related to cell proliferation. Combinations of IL-1 and TNF-alpha when added simultaneously to HMC resulted in a dose-dependent synergistic increase in PGE2 production. These stimulatory effects were specifically inhibited by anticytokine antibodies and the synergistic effect required the simultaneous presence of both IL-1 and TNF-alpha. Arachidonic acid (AA) release experiments and measurement of cyclooxygenase activity, revealed that while both were increased by IL-1 beta and TNF-alpha alone (IL-1 beta greater than TNF-alpha), combinations of IL-1 beta and TNF-alpha resulted in only additive increases in AA release and cyclooxygenase activity. Taken together, these data suggest that stimulation of PGE2 in HMC, by combinations of these cytokines, is not rate limited by AA release or cyclooxygenase activation, but may be related to the induction of the distal enzymes controlling specific PG synthesis.

Adult↗
PubMed1989

The assessment of relative surface hydrophobicity as a factor involved in the activation of human polymorphonuclear leukocytes by uropathogenic strains of Escherichia coli.

The initiation of the respiratory burst and the degranulation of human polymorphonuclear leukocytes (PMN) in response to stimulation by uropathogenic strains of Escherichia coli is dependent on the expression of Type 1 fimbriae by those strains. These PMN responses correlate with an increasing tendency of the interacting E. coli strain to be retained on hydrophobic columns. The present work assessed the measurement of relative surface hydrophobicity in relation to PMN activation. Type 1 fimbriate organisms bound most readily to Octyl-Sepharose columns and were strongly agglutinated in the salt aggregation test. In contrast, the same organisms partitioned to the dextran-rich (hydrophilic) phase of aqueous two-polymer phase systems. Electron microscopic observation of the organisms eluted from the Octyl-Sepharose columns and of the organisms recovered from both phases of the aqueous two-phase systems demonstrated, however, that both Type 1 and P-fimbriate organisms were retained on the columns and partitioned into the dextran-rich phase as a consequence of their being fimbriate and failed to identify this as a major factor in the activation of PMN. In addition electron microscopy demonstrated that each P-fimbriate population had fewer organisms expressing fimbriae than did Type 1 fimbriate populations, confirming the importance of phase variation as a factor affecting the physicochemical characteristics of a bacterial population.

Agglutination↗
PubMed1989

Variable expression of P fimbriae in Escherichia coli urinary tract infection.

Fresh urinary isolates were examined by immunofluorescence with polyclonal rabbit antibodies against type 1 and P fimbriae. This procedure showed P-fimbriate Escherichia coli in 22 of 24 samples from patients with asymptomatic bacteriuria, 24 of 26 samples from patients with cystitis, and 6 of 6 samples from patients with pyelonephritis. Type 1 fimbriae were expressed by less than 40% of isolates in all three groups. There was no relation between the presence of symptoms or the site of infection and fimbrial expression, of P or type 1, by bacteria adherent to freshly isolated uroepithelial cells.

Adolescent↗
PubMed1989

Type 1 fimbriate strains of Escherichia coli initiate renal parenchymal scarring.

The renal scarring which characterizes chronic pyelonephritis is initiated by bacterial infection and is independent on the activation of an inflammatory response. Although the presence of polymorphonuclear leukocytes (PMN) is essential for initiating the scarring process, the bacterial structures responsible for their activation have not been investigated. In an animal model of chronic pyelonephritis the surface area of the renal scars produced by Type 1 fimbriate escherichia coli (E. coli) was significantly greater than that of those produced by P fimbriate and non-fimbriate strains (P less than 0.01). The activation of human PMN by the same Type 1 fimbriate organisms resulted in a significant release of lysosomal neutral protease activity (P less than 0.001) and activation of the respiratory burst (P less than 0.01). The neutral protease release in response to P fimbriate and non-fimbriate organisms was not significantly increased. The extent of renal scarring also correlated with the release of neutral protease activity (P less than 0.02) and with the degree of activation of the respiratory burst (P less than 0.05). These results demonstrate that the ability of E. coli strains to cause renal scars may be related to their capacity to express Type 1 fimbria, which may be a causative factor in the in vivo activation of the inflammatory response.

Animals↗