Biomedical subjects

T Sundqvist

Publications and source records attributed to T Sundqvist.

At least 19 recordsLinked to original sources

PubMed1996

Leucocyte activation by anti-lactoferrin antibodies bound to vascular endothelium.

Human polymorphonuclear neutrophil leucocytes (PMNL) prestimulated with the formylated tripeptide f-Met-Leu-Phe (fMLP) were activated to an immediate chemiluminescence (CL) response by polyclonal rabbit antibodies against human lactoferrin (Lf). This activation, indicating the formation of reactive oxygen species, was induced by intact IgG antibodies but could not be brought about by F(ab')2 fragments. Human Lf was also shown to adhere to the surface of cultured bovine aorta endothelial cells (BEC). When Lf-coated BEC grown on microcarrier beads were reacted with anti-Lf antibodies, an immediate CL response was achieved also with nonprimed PMNL. Here, too, the reaction required intact IgG antibodies. Also, patient sera containing anti-Lf autoantibodies of IgG class were shown to activate fMLP-treated PMNL. The same effect was obtained (in a dose-dependent manner) with the gammaglobulin fraction from anti-Lf-positive serum. Further, anti-Lf-antibody-positive patient sera incubated with Lf-coated BEC beads were also able to activate non-stimulated PMNL to a chemiluminescence response. The results are discussed in relation to possible mechanisms of cell/tissue damage induced by anti-neutrophil cytoplasmic antibodies (ANCA).

Amino Acid Sequence↗

PubMed1995

Effects of hydrogen peroxide and phorbol myristate acetate on endothelial transport and F-actin distribution.

We have previously reported that both hydrogen peroxide (H2O2) and phorbol myristate acetate (PMA) can stimulate endocytosis in bovine aortic endothelial cells. Moreover, we have found that redistribution of filamentous actin (F-actin) in a low concentration of cytochalasin B also increases such endocytic activity. In the present study, the effects of H2O2 and PMA on endothelial transport and F-actin distribution were studied in bovine aortic endothelial monolayers. A low concentration of H2O2 (10(-5) M) had no effect on permeability, but did cause redistribution of F-actin, i.e., the diffuse arrangement of filaments changed to a clear stress-fiber pattern, but the dense peripheral filament bands were not affected. A 10-fold higher concentration of H2O2 (10(-4) M), which increases permeability as we reported previously, caused a disruption of F-actin dense peripheral bands. PMA had a concentration-dependent effect on endothelial permeability and F-actin distribution, i.e., 10(-7) M PMA had no observed effect on permeability and no effect on F-actin structure either, whereas 5 x 10(-7) M PMA caused decreased permeability during the first 1 to 1.5 h and thereafter increased permeability for up to 6 h. There was also a time-dependent reorganization of F-actin structure after the treatment with 5 x 10(-7) PMA: the number of dense peripheral bands increased after 1 h of exposure; these bands had a ruffled appearance after 2 h and were disrupted after 6 h. These results suggest that, in endothelial cells, F-actin plays a role in regulating the width of intercellular junctions and thereby controls the paracellular pathway of vascular permeability.

Actins↗

PubMed1995

Involvement of nitric oxide in permeability alteration and F-actin redistribution induced by phorbol myristate acetate in endothelial cells.

We have previously reported that phorbol myristate acetate (PMA) caused a decrease in endothelial permeability during the first 1 to 1.5 h of exposure and thereafter an increase for up to 6 h. This permeability alteration was correlated with a time-dependent redistribution of F-actin, i.e., an increase in dense peripheral bands was observed during the first hour of PMA incubation and a disruption of the bands after 6 h. In the present study, we found that this PMA-induced alteration of permeability is L-arginine dependent, since the low permeability prevailed for up to 6 h when extracellular L-arginine was available. Moreover, we noted that administration of N-nitro-L-arginine methylester (L-NAME) to PMA-treated cells caused a direct increase in permeability. The redistribution of F-actin induced by PMA was also L-arginine dependent, since the number of dense peripheral bands continued to increase for up to 6 h when extracellular L-arginine was available, and these bands were directly disrupted when L-NAME was added. These results suggest that the tight contact between PMA-treated endothelial cells is maintained by a redistribution of F-actin elicited by the endogenous production of nitric oxide.

Actins↗

PubMed1995

Nitric oxide reduces hydrogen peroxide production from human polymorphonuclear neutrophils.

Nitric oxide has been reported to affect both adhesion and respiratory burst of neutrophils. This indicates a possible role of nitric oxide in regulation of acute inflammatory responses. Release of oxygen metabolites from neutrophils can be measured using luminol-enhanced chemiluminescence and this method can detect both extracellularly and intracellularly released oxygen metabolites. Neutrophils treated with nitroprusside and activated with FMLP, type I collagen or PMA decreased their extracellular release of oxygen metabolites, while their intracellular release was almost unaffected. The effect of nitroprusside was mediated by nitric oxide since treatment with cyanide had the opposite effect. N-ethylmalemide treatment decreased both extra- and intracellular release of oxygen metabolites. This indicates that nitric oxide affects membrane-bound NADPH-oxidase either indirectly or directly, and not a cytosol factor of the oxidase as earlier shown for N-ethylmaleimide. In conclusion, extracellular nitric oxide attenuates extracellularly released oxygen metabolites from activated neutrophils in an inflammatory response.

Collagen↗

PubMed1995

Nitric oxide regulates the chemiluminescence from stimulated human neutrophils.

Nitric oxide produced from L-arginine by a variety of cells, is a biologically active compound that can react with iron and thiols. The objective of this study was to investigate the effects of nitric oxide on the respiratory burst from human neutrophils. Treatment with nitroprusside increased the chemiluminescence from neutrophils stimulated with PMA or collagen, but not from cells stimulated with FMLP. Addition of L-arginine increased the chemiluminescence after stimulation with any of the three stimuli, while N omega-nitro-L-arginine methyl ester decreased it. Low doses of nitric oxide, either endogenously or exogenously produced, probably inhibited catalase or glutathione, leading to an increase in hydrogen peroxide available for chemiluminescence detection. This indicates that nitric oxide may reduce the protection against hydrogen peroxide in tissue and in invading catalase-positive bacteria.

Catalase↗

PubMed1994

Different induction mechanisms of mRNA for inducible nitric oxide synthase in rat smooth muscle cells in culture and in aortic strips.

The expression of mRNA for the inducible form of nitric oxide synthase, (iNOS), was studied in rat aortic smooth muscle cells, (SMCs) in cell culture and in strips of rat aorta by reverse transcriptase coupled to the polymerase chain reaction. iNOS mRNA expression was weak in cultured SMCs when exposed to either interferon-gamma (IFN gamma) or lipopolysaccharide (LPS), but the combination LPS+IFN gamma enhanced the expression. In aortic strips LPS alone induced a pronounced expression, with no further increase by IFN gamma. Cycloheximide potentiated the expression of iNOS mRNA in SMCs in culture stimulated with LPS+IFN gamma but attenuated the response in aortic strips. The results indicate different cellular signaling pathways for the induction of iNOS mRNA by LPS and/or IFN gamma, in cultured SMCs and in rat aortic strips.

Amino Acid Oxidoreductases↗

PubMed1994

S-nitroso-N-acetylpenicillamine reduces leukocyte adhesion to type I collagen.

The initial step in the migration of neutrophils to the extravascular space is adhesion to the endothelium. We examined the effect of nitric oxide on this process by treating human neutrophils with S-nitroso-N-acetylpenicillamine (SNAP), a NO-producing compound. Since NO has been shown to increase the level of cGMP in other cell types, we used 8-Br-cGMP in order to mimic the effects of NO. Indeed, both these treatments resulted in a reduced adhesion of neutrophils to type I collagen coated surfaces. After a prolonged incubation with SNAP, the adhesion was the same as for untreated cells. SNAP incubation reduced the F-actin content in the cells whereas 8-Br-cGMP increased it, demonstrating different mechanisms of action on F-actin. These data suggest that endothelium-derived nitric oxide is an important endogenous modulator of neutrophil adhesion, but the effect is not mediated by a cGMP-dependent regulation of F-actin levels.

Actins↗

PubMed1994

Priming of oxidative response in human neutrophils by anti-CD18 monoclonal antibodies.

Type I collagen, the most abundant protein in the body, after acid extraction adheres to and can induce a respiratory burst from neutrophils. It has been proposed that the effects of collagen are mediated via the CD18 subfamily of integrins. In the present study, adhesion was measured by affinity chromatography in a column containing collagen-coated microcarriers, while oxygen metabolite production was measured with luminol-dependent chemiluminescence. Neutrophil adherence to collagen was attenuated by anti-CD18 monoclonal antibodies. The respiratory burst in response to collagen was not affected by the antibodies. Incubation of neutrophils with anti-CD18 antibodies prior to stimulation with FMLP increased both the extra- and intracellular respiratory burst. Treatment with antibodies prior to PMA stimulation increased only the extracellular respiratory burst. In conclusion, the respiratory burst from neutrophils is primed by pretreatment with anti-CD18 monoclonal antibodies. The collagen-stimulated respiratory burst is probably also primed, but the effect is hidden by the simultaneous attenuation of adhesion.

Antibodies, Monoclonal↗

PubMed1993

Microtubules are involved in transport of macromolecules by vesicles in cultured bovine aortic endothelial cells.

The macromolecular transport in bovine aortic endothelial monolayers, cultured in vitro, was studied by fluorescence microscopy, confocal laser scanning microscopy, and transmission electron microscopy. A fluid-phase endocytic tracer, fluorescein isothiocyanate dextran 70 kD (FITC-dextran 70), was found to be transported into and out of endothelial cells via vesicles arranged as chains stretching between the luminal surface and the cell interior and also from cell interior to the abluminal surface. The endocytic activity was reduced by colchicine, which disrupts microtubules, and increased during treatment with cytochalasin B, which blocks microfilament polymerization. These findings indicate that microtubules are required for fluid-phase endocytosis and that microfilaments hinder this process.

Actin Cytoskeleton↗

PubMed1993

The cGMP modulator, LY83583 alters oxygen metabolites differently in cultured endothelial cells and isolated neutrophilic granulocytes.

The present study was designed to assess the effect of LY83583 on H2O2/O2- production from endothelial cells and neutrophils, as determined by chemiluminiscence generation in vitro. We found that LY83583 increased H2O2/O2-production from endothelial cells, but inhibited the H2O2/O2- production from phorbol myristate acetate-stimulated neutrophils. Furthermore, LY83583 consumed NADPH under certain conditions. Since neutrophils generate superoxide anion radicals via an NADPH-oxidase, we suggest that the reduction of chemiluminiscence, seen after addition of LY83583 to phorbol myristate acetate-stimulated neutrophils, is due to increased consumption of NADPH. In endothelial cells, NADPH is required as a co-factor in the generation of nitric oxide, which may interact with superoxide anion. A consumption in NAPDH would therefore be expected to decrease the production of nitric oxide and increase H2O2/O2-generation. The consumption of NADPH in endothelial cells could also cause reduced scavenger functions of the glutathion system, resulting in a further increase in H2O2 release.

Aminoquinolines↗

PubMed1993

Hydrogen peroxide stimulates endocytosis in cultured bovine aortic endothelial cells.

Fluid-phase uptake of macromolecules by cultured bovine aortic endothelial cells was measured using FITC-dextran (70,000 Da). Low doses of hydrogen peroxide added extracellularly stimulated the uptake of macromolecules by the endothelial cells. There was no general increase in the passive permeation or the transport across the cell layer. Moreover, when endothelial cells were stimulated with phorbol myristate acetate (PMA), macromolecules uptake was also enhanced. The PMA effect was blocked with superoxide dismutase (SOD) and catalase, suggesting a pivotal role of oxygen metabolites in fluid phase uptake of macromolecules by endothelial cells.

Animals↗

PubMed1992

Reduced intestinal permeability measured by differently sized polyethylene glycols in acute uremic rats.

The effect of experimental acute renal failure on the intestinal permeability measured by differently sized polyethylene glycols (PEG) was studied in rats. The permeability was assessed by analysing the 24-hour urinary recovery of PEG molecules (size 326-1,162 D). Acute renal failure was induced by clamping the left renal artery and right-sided nephrectomy. The overall urinary recovery of PEG was decreased in the uremic rats. However, the relative recovery of larger molecules (range 590-1,162 D) was further reduced in the uremic rats. The results which are compared with a computer simulation by a multicompartment model, suggest that the intestinal permeability especially towards larger PEG is decreased in acute uremic rats.

Acute Kidney Injury↗

PubMed1991

Bovine aortic endothelial cells release hydrogen peroxide.

Endothelial cells grown on microcarriers are able to release H2O2 to the extracellular environment without any added stimulus. The extracellularly released H2O2 can be detected by luminol-amplified chemiluminescence (CL) if horseradish peroxidase is added. The CL response can be reduced by catalase and blocked by superoxide dismutase, indicating that O2- could be a precursor for H2O2. The CL kinetics, i.e., a long lag time followed by a rapid shift to a new level, indicate activation of an O2(-)-producing enzyme. The cells are also able to protect themselves from H2O2 stimulation by both catalase and the glutatione system. Bradykinin stimulates the H2O2 release, but if the effect is directly stimulatory or if it acts by reduction of the protective system is at present unclear. The extracellularly released H2O2 could be a cause of injury to the endothelial cells or to the subendothelial matrix.

Animals↗

PubMed1991

Intestinal permeability in patients with yersinia triggered reactive arthritis.

The passive intestinal permeability of patients with yersinia triggered reactive arthritis was studied using different sized polyethylene glycols (PEGs) contained in a mixture of PEG 400 and PEG 1000. The investigation was carried out at least one year after the onset of yersinia infection, and patients had neither acute gastrointestinal nor joint symptoms. The control groups included patients with uncomplicated yersiniosis as well as healthy subjects who were either HLA-B27 positive or negative. An altered intestinal barrier function to PEG molecules was detected in patients with a history of yersinia infection compared with healthy controls. No significant differences in the permeability were found between patients with or without reactive arthritis, nor was there any association of increased permeability with HLA-B27. The passive permeability of the intestinal mucosa to the larger molecules was increased for an unexpectedly long time after the acute yersinia infection, probably contributing to the perpetuation of joint symptoms in subjects susceptible to a chronic joint disease.

Adult↗

PubMed1991

Impaired intestinal barrier function measured by differently sized polyethylene glycols in patients with chronic renal failure.

The intestinal mucosa plays a fundamental role as the site for absorption of nutrients, and as an important barrier from potentially harmful agents in the intestinal lumen. Little is known of the permeability properties of the intestinal mucosa in uraemic patients. The intestinal permeability to differently sized polyethylene glycols (PEGs; range 326-1254 daltons) was studied in nine patients with chronic renal failure (24 hour endogeneous creatinine clearance 5-24 ml/minute). The maximum 24 hour urinary recovery of PEGs was decreased in the uraemic patients but relatively more of the larger than the smaller PEGs were found in these patients. The results suggest a reduced urinary recovery of PEGs caused by renal dysfunction but also a relatively increased intestinal permeability to larger PEGs in the uraemic patients.

Adult↗

PubMed1990

Increased intestinal permeability to differently sized polyethylene glycols in uremic rats: effects of low- and high-protein diets.

Intestinal mucosa forms an important barrier towards harmful agents in the intestinal lumen, besides being the site for absorption of nutrients. Little is known about the intestinal permeability properties in chronic uremia. The permeability toward differently sized polyethylene glycols (PEGs; range 326-1,162 Da) was studied in uremic groups compared to the control groups. The urinary recovery was also recovery of PEGs was increased in the uremic groups compared to the control groups. The urinary recovery was also increased in the groups on the high-protein diet compared to the corresponding group on the low-protein diet. This study suggests an increased permeability of PEG molecules in the range of 546-1,162 Da in uremic rats and a decreased intestinal permeability after a low-protein diet in both a uremic and nonuremic state. Thus, in chronic renal failure the intestinal barrier is impaired but returns towards normal with low-protein diets.

Animals↗

PubMed1990

Urinary excretion of differently sized polyethylene glycols after intravenous administration in uremic and control rats: effects of low- and high-protein diets.

The intestine constitutes a barrier towards potentially harmful agents in the intestinal lumen. Different-sized polyethylene glycols (PEGs; range 326-1,1162 Da) have been used to study the intestinal permeability properties in 5/6-nephrectomized rats on either a high- (22%) or low-protein (8%) diet. PEGs were administered intravenously, and the urinary recovery was measured. The 24-hour urinary recovery of PEGs was significantly reduced in the uremic groups. The ratios between different sizes of PEGs, indicating a size-selective escape of molecules from blood, were decreased in the uremic groups. The urinary recovery was in general increased in the control group on the high-protein diet compared to the control group on the low-protein diet. The results provide evidence for an increased permeability of larger PEGs (range 634-1,162 Da) in uremic rats and that the protein content of the diet might affect the permeability properties.

Animals↗

PubMed1989

Intestinal permeability to inert sugars and different-sized polyethyleneglycols in children with celiac disease.

Intestinal permeability was measured in a total of 42 children, 29 of whom had celiac disease. The celiac children were studied at presentation, during gluten-free diet, and/or at gluten challenge. The permeability was assessed by oral lactulose/L-rhamnose in all 42 children and also by different-sized polyethylene glycols (PEG) in 36 children. Results were compared with the findings of small intestinal biopsy. The mean of the permeability tests in children with enteropathy was significantly abnormal compared with the result in children with a normal mucosal morphology. The lactulose/L-rhamnose test and the PEG test gave equivalent results in the same child. In the celiac children abnormal permeability properties at presentation normalized during gluten-free diet and reappeared during gluten challenge. It is concluded that measurement of intestinal permeability may be a valuable tool in monitoring children with celiac disease, preferably when serial measurements are available in the same child.

Adolescent↗