Biomedical subjects

T Sundqvist

Publications and source records attributed to T Sundqvist.

At least 37 records · Page 2Linked to original sources

PubMed1999

Effects of HIV co-infection and chemotherapy on the urinary levels of nitric oxide metabolites in patients with pulmonary tuberculosis.

The presence of nitric oxide (NO) and its role as a factor in host defence against intracellular pathogens in human macrophages is controversial. We measured the metabolites of NO (nitrite (NO2-) and nitrate (NO3-)) in urine from Ethiopian patients suffering from tuberculosis. The urinary level of NO2-/NO3- in a group of healthy Ethiopians was 1020+/-471 microM (n = 22). Untreated HIV negative patients with active pulmonary tuberculosis (1574+/-588 microM, p<0.01, n = 12) and household contacts to tuberculosis patients (1949+/-812 microM, p = 0.006, n = 7) had significantly higher levels of urinary NO2-/NO3- than the control group. Untreated HIV positive patients with pulmonary tuberculosis did not have increased levels of urinary NO2-/NO3- (1101+/-614 microM, n = 6). Some of the HIV negative untreated patients with pulmonary tuberculosis (1710+/-519 microM, n = 6) were followed up after treatment and showed a reduction in the levels of urinary NO2-/NO3- 1 week after treatment (945+/-599 microM, p<0.05). We conclude that HIV negative patients with active pulmonary tuberculosis have increased urinary levels of nitric oxide metabolites with a reduction following specific anti-tuberculous chemotherapy.

Adolescent↗

PubMed1999

Increased levels of nitric oxide metabolites in urine from leprosy patients in reversal reaction.

We measured the metabolites of NO [nitrite (NO2-) and nitrate (NO3-)] in urine from Ethiopian patients suffering from leprosy. The urinary level of NO2-/NO3- in a group of healthy Ethiopians was 1020 +/- 471 microM (n = 22). Leprosy patients in reversal reaction had significantly higher levels of NO2-/NO3- (1817 +/- 492 microM, p < 0.001, n = 12) than both the control group and leprosy patients who were not in reversal reaction (1079 +/- 446 microM, n = 12). We conclude that the reversal reaction in leprosy in associated with increased urinary levels of nitric oxide metabolites.

Adult↗

PubMed1998

The ability to bind albumin is correlated with nitric oxide sensitivity in Moraxella catarrhalis.

Moraxella catarrhalis is sensitive to NO generators, e.g. S-nitroso-N-acetylpenicillamine (SNAP) and sodium nitroprusside (SNP), but can spontaneously develop higher SNP tolerance. Using SDS-PAGE of outer membrane proteins and immunoblotting for serum albumin, we found that the wild strain bound more blood-medium-derived albumin than the SNP-resistant variant did. There was a negative correlation between NO tolerance and the presence of serum albumin in the medium. We suggest that M. catarrhalis can change its surface properties to avoid binding albumin and thereby increase its resistance to NO. Growth of Moraxella is affected by iron, and that may have influenced our results. Using chrome azurol S plates as an indicator, we noted that both albumin and SNP have a strong affinity for iron(III).

Bacterial Outer Membrane Proteins↗

PubMed1998

Endogenous nitric oxide in MDCK-I cells modulates the Vibrio cholerae haemagglutinin/protease (HA/P)-mediated cytotoxicity.

Previously, we have shown that the Vibrio cholerae haemagglutinin/protease (HA/P) accounts for significant remaining toxicity of CVD110, an attenuated V. cholerae 01 El Tor live oral vaccine-strain. The present report demonstrates that endogenous nitric oxide (NO) production modulates HA/P-mediated cytotoxicity in Madin-Darby canine kidney cell strain I (MDCK-I) epithelial cells. The basal levels of endogenous NO suppressed the cytotoxicity of HA/P, whereas inhibition of NO production with nitro-L-arginine methyl-ester (L-NAME) made the MDCK-I cells susceptible even to low concentrations of the cytotoxin. The inhibition of NO production caused a reinforcement of the HA/P- mediated distortion of a tight junction-associated protein ZO-1 and increment of filamentous actin at the apical and the lateral membrane domains. The mechanism by which NO exerts its modulatory action is not likely to be from its direct interaction with the zinc-containing catalytic domain of HA/P, since two NO donors, sodium nitroprusside (SNP) and S-nitroso-N-acetyl-D, L-penicillamine (SNAP), did not affect the proteolytic activity of HA/P. In conclusion, the endogenous NO in the MDCK-I cells has a modulating effect on the cytotoxicity of HA/P and thus protects the cells against the cytotoxin.

Animals↗

PubMed1998

Children with celiac disease express inducible nitric oxide synthase in the small intestine during gluten challenge.

BACKGROUND: Childhood celiac disease in Sweden is presently seen at an incidence of around 1/250 and is thus one of the commonest chronic diseases in children. It has recently been shown that children with untreated celiac disease have increased levels of nitrate/nitrite in the urine, most likely reflecting an increased production of nitric oxide in the inflamed mucosa. Nitric oxide is produced from L-arginine by an inducible or a constitutive nitric oxide synthase. The inducible nitric oxide synthase (iNOS) can be stimulated in various cells by, for instance, inflammatory mediators. The present study has been done to find a possible source of nitric oxide in the small intestine that could result in the increased levels of nitrate/nitrite in the urine in children with active celiac disease. METHODS: Small-intestinal biopsy specimens from children with active celiac disease were labeled with rabbit-anti-human antibodies to iNOS and visualized with fluorescent pig anti-rabbit antibodies. The specimens were then analyzed with confocal microscopy to assess the labeling pattern. RESULTS: In all of seven specimens from children with increased levels of nitrate/nitrite in the urine, we detected antibodies to iNOS, whereas in five of six control specimens--that is, from children with normal nitrate/nitrite levels--we could not detect any iNOS. CONCLUSIONS: Children with active celiac disease have a gluten-induced nitric oxide production in the small intestine reflected by increased urine levels of nitrate/nitrite and iNOS expression in the intestine. We conclude that the increased production of nitric oxide could presumably, directly or indirectly, result in injury of the small-intestinal tissue.

Adolescent↗

PubMed1998

Significantly increased levels of nitric oxide products in urine of children with celiac disease.

BACKGROUND: Celiac disease is characterized by morphologic and functional aberrations of the small intestinal mucosa, i.e., crypt hyperplasia, villous atrophy, infiltration of intraepithelial lymphocytes, and alteration of permeability. Nitric oxide has been shown to affect mucosal permeability after ischemia-reperfusion, but little is known about the regulatory role of nitric oxide in celiac disease. The purpose of this study was to assess nitric oxide production in children with celiac disease and in control subjects. METHODS: The sum of nitrite and nitrate in the urine was measured with a colorimetric method in 137 children with a median age of 3 years, 84 patients and 53 reference children, all of whom underwent a small intestinal biopsy to confirm or overrule suspicion of celiac disease. RESULTS: Median urinary nitrite-nitrate concentration in celiac children was 3323 microM (4147 +/- 1102; mean +/- SEM) at first clinical examination and 2501 microM (2939 +/- 386) after gluten challenge, which was significantly higher than concentrations in reference children (1029 microM; 1174 +/- 116) and in children with celiac disease on a gluten-free diet (882 microM; 1369 +/- 360) (p < 0.0001). CONCLUSIONS: A gluten-containing diet is associated with an increased nitrite-nitrate secretion in the urine in children with celiac disease, presumably as a result of nitric oxide synthase activation and nitric oxide production in the diseased small intestinal mucosa.

Adolescent↗

PubMed1998

Intravenous endotoxin does not increase tissue extravasation of albumin in rats.

BACKGROUND: It is unclear whether activation of the inducible nitric oxide synthase (iNOS) increases or decreases the extravasation of plasma. METHODS: Chloralose anaesthetised male Wistar rats received E. coli lipopolysaccharide (LPS), 3 mg kg-1 i.v., or the corresponding volume of saline, 3 or 5 h before the end of the experiment. Mean arterial pressure (MAP) and heart rate (HR) were recorded. Tissue clearance of radio-labelled albumin, during the last 2 h of each experiment, was determined by a double-isotope method. In separate animals, the serum concentration of nitrite and nitrate was determined, 5 h after LPS or the solvent. MAIN RESULTS: LPS initially decreased MAP and lastingly increased HR. In the 3-h LPS animals (n = 8), tissue plasma clearance was lower in the heart and calf muscle and increased only in diaphragm, compared to corresponding control animals (n = 8). In the 5-h LPS rats, clearance was lowered (n = 8) in the entire gastrointestinal tract and in testes, compared to controls (n = 8). The serum nitrite/nitrate concentration was higher in animals given LPS (n = 6) than in controls (n = 6). CONCLUSION: After LPS, tissue clearance of albumin was not increased in any major tissue, in spite of increased serum levels of NO end products. Apparently, after activation of iNOS, the augmented release of NO is not necessarily associated with increased albumin extravasation.

Animals↗

PubMed1997

Nitric oxide and cGMP regulate endothelial permeability and F-actin distribution in hydrogen peroxide-treated endothelial cells.

We have previously reported that hydrogen peroxide (H2O2) has a concentration-dependent effect on endothelial permeability and F-actin distribution. In the present study, we considered the involvement of endogenous production of nitric oxide (NO) in the indicated effect of H2O2. This was done by measuring endothelial permeability to sodium fluorescein (MW 376 Da, Na-F) and to different-sized fluorescein-isothiocynate-labeled dextrans (FITC-dextrans) and by staining F-actin with rhodamine-labeled phalloidin in cultured bovine aortic endothelial cells growing on filters. A low concentration of H2O2 (10(-5) M) had no effect on either dense peripheral bands of F-actin (DPBs) or permeability. When N-nitro-l-arginine methylester (l-NAME), an inhibitor of NO production, was coadministrated with 10(-5) M H2O2, DPBs were disrupted and the permeability to FITC-dextran 40 and FITC-dextran 70, but not to Na-F and FITC-dextran 20, was increased. Combining of 10(-5) M H2O2 with l-arginine, a substrate for nitric oxide synthase, caused an increase in DPBs and a decrease in permeability to FITC-dextran 40 and FITC-dextran 70. l-arginine or l-NAME alone had no effect on either F-actin structure or endothelial permeability. A 10-fold higher concentration of H2O2 caused a disruption of DPBs and an increase in permeability; this could be prevented by adding l-arginine. An analogue of cGMP, i.e., 8-Br-cGMP, maintained DPBs and abolished the increase in permeability induced by the treatment with either 10(-4) M H2O2 or a combination of H2O2 and l-NAME. These results suggest that the endogenous production of NO is involved in maintaining endothelial junctions in H2O2-treated cells and that this involvement occurs via a cGMP-dependent mechanism.

Actin Cytoskeleton↗

PubMed1997

Nitric oxide-releasing particles inhibit phagocytosis in human neutrophils.

We have constructed a yeast (Saccharomyces cerevisiae) particle capable of releasing NO, by loading heat-killed yeast particles with a hydrophobic NO-generating substance, GEA-5171. This particle decreased phagocytosis in solution, as measured with flow cytometry, to about 80% of control values. Phagocytosis on a surface, as counted under the microscope, was also decreased by about 20%. The nitric oxide furthermore counteracted the production of oxygen metabolites by neutrophils to about 20% of control values. The inhibitory effect was most pronounced for the intracellular production, as could be seen when neutrophils preincubated with NO-releasing particles were stimulated with chemotactic agent (FMLP) or phorbol ester (PMA). In conclusion, NO has inhibitory effects on both phagocytosis and the respiratory burst of neutrophils. Since nitric oxide is a hydrophobic gas and an air pollutant, there is a possibility that it accumulates in particles which then become more resistant to elimination.

Actins↗

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↗