Biomedical subjects

D N Granger

Publications and source records attributed to D N Granger.

At least 127 records · Page 7Linked to original sources

PubMed1997

Soluble selectins and ICAM-1 modulate neutrophil-endothelial adhesion and diapedesis in vitro.

We observed that normal plasma dramatically reduces neutrophil-endothelial adhesion. Therefore, we identified factors in plasma which might limit PMN adhesion in vitro. We found that the anti-adhesive effect was not mediated by vasoactive lipids present in plasma. Immunoprecipitation of soluble adhesion molecules, P and E-selectins and ICAM-1 restored PMN adhesion to control values. We further examined whether soluble adhesion molecules in plasma might also regulate PMN endothelial migration in response to fMLP (10(-6) M). Plasma significantly reduced PMN migration, and this effect was prevented only by the simultaneous removal of soluble P and E selectins and ICAM-1 together, but not individually. These data show that soluble selectins and ICAM-1 may regulate PMN adhesion and diapedesis, and that alterations in the levels of these molecules may regulate PMN-endothelial interactions in vivo.

Adult↗

PubMed1997

Enhanced lymphocyte interaction in postcapillary venules of Peyer's patches during fat absorption in rats.

BACKGROUND & AIMS: Although dietary fat is known to modulate immune functions, there is a paucity of data concerning the effects of fat absorption on migration of lymphocytes in intestinal lymphoid tissue. The objective of this study was to assess the influence of fat absorption on T-lymphocyte migration in Peyer's patches. METHODS: T lymphocytes collected from rat intestinal lymph were labeled with carboxyfluorescein diacetate succinimidyl ester and injected into the jugular vein of recipient rats. Olive oil or octanoic acid was placed into the duodenum, and Peyer's patch microcirculation was observed by intravital fluorescence microscopy. RESULTS: Rolling and adherence of lymphocytes in postcapillary venules were noted in both fasted and fed rats. However, lymphocyte adherence was significantly greater in olive oil-fed rats than in fasted rats. Olive oil also significantly increased the transendothelial migration of T lymphocytes. Octanoic acid stimulated lymphocyte rolling but did not affect lymphocyte adherence. Olive oil enhanced the expression of both alpha4-integrin and L-selectin on lymphocytes, whereas octanoic acid only increased the expression of L-selectin. CONCLUSIONS: Lymphocyte rolling and adherence are enhanced by olive oil feeding, possibly through an interaction between activated adhesion molecules on lymphocytes and counter-receptors on endothelial cells.

Animals↗

PubMed1997

Effects of intestinal stasis on intercellular adhesion molecule 1 expression in the rat: role of enteric bacteria.

BACKGROUND & AIMS: The mechanisms underlying the inflammatory changes associated with intestinal stasis are poorly understood. The objective of this study was to assess whether endothelial expression of intercellular adhesion molecule 1 (ICAM-1) and leukocyte recruitment are altered after intestinal stasis. METHODS: ICAM-1 expression and granulocyte recruitment were quantified in different tissues of Sprague-Dawley rats using the double-radiolabeled monoclonal antibody technique and peroxidase activity, respectively. RESULTS: Both constitutive and endotoxin-induced ICAM-1 expression were significantly higher in the cecum than in distal colon, a finding that cannot be explained by a difference in endothelial surface area between the two organs. Surgical procedures to improve cecal stool flow (cecostomy, ileocecostomy) elicited a significant decrease in constitutive ICAM-1 expression in both cecum and distal colon. Tissue peroxidase activity was normally higher in cecum than in distal colon, and this difference was significantly reduced by ileocecostomy. Oral administration of antibiotics (kanamycin and/or metronidazole for 2 days) significantly reduced constitutive ICAM-1 expression in the cecum, but not in the distal colon. CONCLUSIONS: This study indicates that intestinal stasis is associated with an increased expression of ICAM-1 and granulocyte infiltration, which may be mediated by enteric bacteria.

Animals↗

PubMed1997

Ischemia/reperfusion-induced leukocyte-endothelial interactions in postcapillary venules.

The recruitment of leukocytes into postcapillary venules following reperfusion of ischemic tissues is a classical inflammatory response that is influenced by a balance of adhesive and hemodynamic forces. Initial periods of reperfusion are characterized by an elevation in low affinity adhesive interactions between leukocytes and endothelial cells, which permit the leukocytes to establish intimate contact with the vascular endothelial lining as they roll across it. This rolling behavior of leukocytes increases the probability that stronger adhesive interactions between leukocyte and endothelial cell will occur, allowing the leukocyte to firmly adhere to the endothelium and subsequently to emigrate across the venular wall into the interstitial compartment. Several factors appear to contribute to the leukocyte-endothelial cell adhesion that is elicited by ischemia/reperfusion, including: 1) the magnitude of adhesion molecule expression on leukocyte and/or endothelial cell surfaces, 2) reactive oxygen metabolites and lipid mediators released from stimulated leukocytes and endothelial cells and 3) hemodynamic dispersal forces that act to sweep leukocytes from the microvessel wall. Intravital microscopic techniques have allowed investigators to focus on inflammatory responses in postcapillary venules, which is the primary site of leukocyte adhesion and vascular protein leakage. This technology has also been employed to delineate the role of adhesive and hemodynamic factors in promoting leukocyte rolling, adhesion, and emigration in postcapillary venules exposed to ischemia/reperfusion.

Animals↗

PubMed1997

Enhanced mucosal permeability and nitric oxide synthase activity in jejunum of mast cell deficient mice.

BACKGROUND: Recent reports have described a modulating influence of nitric oxide (NO) on intestinal mucosal permeability and have implicated a role for mast cells in this NO mediated process. AIMS: To assess further the contribution of mast cells to the mucosal permeability changes elicited by the NO synthase (NOS) inhibitor NG-nitro-L-arginine methylester (L-NAME), using mast cell deficient (W/Wv) and mast cell replete mice (+/+). METHODS: Chromium-51 EDTA clearance (from blood to jejunal lumen), jejunal NOS and myeloperoxidase (MPO) activities, and plasma nitrate/nitrite levels were monitored. RESULTS: The increased EDTA clearance elicited by intraluminal L-NAME in W/Wv mice (4.4-fold) was significantly greater than the response observed in control (+/+) mice (1.8-fold). The exacerbated response in W/Wv mice was greatly attenuated by pretreatment with either dexamethasone (1.3-fold) or the selective inducible NOS inhibitor, aminoguanidine (1.4-fold), and partially attenuated by the mast cell stabiliser, lodoxamide (2.9-fold). Jejunal inducible NOS activity was significantly higher in W/Wv than in +/+ mice, while jejunal MPO was lower in W/Wv mice than in +/+ mice, suggesting that the higher inducible NOS in W/Wv does not result from the recruitment of inflammatory cells into the gut. The higher inducible NOS activity in the jejunum of W/Wv was significantly reduced by dexamethasone treatment. CONCLUSIONS: Our results suggest that mast cells normally serve to inhibit inducible NOS activity tonically in the gut and that inhibitors of NOS elicit a larger permeability response when this tonic inhibitory influence is released by mast cell depletion.

Animals↗

PubMed1997

Exogenous xanthine promotes neutrophil adherence to cultured endothelial cells.

Oxidants generated by endothelial xanthine oxidase (XO) can help trigger free radical-mediated tissue injury. An important event in oxidant-mediated tissue injury is neutrophil-endothelial adhesion. Although activation of endothelial XO increases adhesion, little is known about xanthine in the adhesive effect of XO. This study examined administered xanthine on the adhesion of neutrophils. Endothelial [human umbilical vein endothelial cells (HUVEC)] monolayers were exposed to xanthine (15 min), and neutrophils were allowed to adhere to HUVEC in an adhesion assay. Adhesion was dose dependently increased by xanthine (3-100 microM). Either catalase (1,000 U/ml), oxypurinol (XO inhibitor; 100 microM), or platelet-activating factor (PAF) receptor antagonist (WEB 2086; 10 microM) reduced neutrophil adhesion. Superoxide dismutase (1,000 U/ml) had no effect. Pretreatment of HUVEC with 50 microM tungsten also blocked xanthine-induced adherence. Adhesion was also inhibited by preincubation with 100 U/ml heparin. Finally, anti-P-selectin antibody (PB1.3; 20 micrograms/ml) attenuated adhesion. Our results indicate that xanthine may promote neutrophil-endothelial adhesion via a hydrogen peroxide- and PAF-mediated P-selectin expression.

Antioxidants↗

PubMed1997

Role of nitric oxide in gut ischemia-reperfusion-induced hepatic microvascular dysfunction.

The overall objective of this study was to assess the contribution of an altered bioavailability of nitric oxide (NO) to the leukocyte adhesion and hypoxic stress elicited in the liver by gut ischemia-reperfusion (I/R). The accumulation of leukocytes, number of nonperfused sinusoids (NPS), and NADH autofluorescence were monitored (by intravital microscopy) in mouse liver after 15 min of superior mesenteric artery occlusion and 60 min of reperfusion. Leukostasis, NPS, and NADH autofluorescence (indicating hypoxia) were all increased in the liver at 60 min after gut I/R. The NO synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) exaggerated the liver leukostasis elicited by gut I/R, responses that were prevented by coadministration of L-arginine. The NO donor diethylenetriamine-NO (DETA-NO) and L-arginine were both effective in attenuating the gut I/R-induced leukostasis and increased NADH autofluorescence, whereas neither DETA nor D-arginine exerted a protective action. These findings indicate that NO is an important determinant of the liver leukostasis, impaired sinusoidal perfusion, and tissue hypoxia elicited by gut I/R.

Alanine Transaminase↗

PubMed1997

Cell adhesion and migration. II. Leukocyte-endothelial cell adhesion in the digestive system.

The adhesion of leukocytes to vascular endothelial cells is a highly coordinated process that is governed by a number of factors, including the expression of specific adhesion glycoproteins, physical forces generated within the microcirculation, and inflammatory mediators released by a variety of activated cells. The digestive system, with its large resident population of immune cells and its tremendous capacity to generate inflammatory mediators, has proven to be a valuable source of information on the mechanisms involved in the regulation of leukocyte-endothelial cell adhesion. This article considers some of the evolving issues that have surfaced as a consequence of the rapidly growing body of literature on this topic. Particular emphasis is devoted to unresolved issues related to the expression and shedding of endothelial cell adhesion molecules, the contribution of capillaries to the inflammatory response, and the role of mast cells, macrophages and lymphocytes in the modulation of leukocyte-endothelial cell adhesion.

Animals↗

PubMed1997

Endothelial cell monolayers as a tool for studying microvascular pathophysiology.

Endothelial cells contribute to a variety of biological responses that facilitate organ function. This critical role of the endothelial cell has resulted in the development of different in vitro models that utilize monolayers of cultured cells to simulate conditions that exist in the intact animal. This review focuses on endothelial cell monolayers as a model system for research on certain pathophysiological conditions affecting the gastrointestinal tract. The advantages and limitations of endothelial cell monolayers are addressed, along with evolving technologies and strategies that hold promise for extending the utility of this in vitro model for studies of gastrointestinal function and disease.

Animals↗

PubMed1997

Modulation of P-selectin expression in the postischemic intestinal microvasculature.

The dual radiolabeled monoclonal antibody technique was used to 1) define the magnitude and kinetics of P-selectin expression in murine small intestine exposed to ischemia-reperfusion (I/R), and 2) determine the factor(s) responsible for initiating this response. Within 10 min after release of a 20-min arterial occlusion, intestinal P-selectin expression increased two- to threefold compared with control values. Peak (4-fold) expression of P-selectin was noted at 5 h after reperfusion, returning to the control value at 24 h. The early (10-30 min) I/R-induced upregulation of P-selectin appears to reflect mobilization of a performed pool of the adhesion molecule, whereas the later (5 h) rise appears to be transcription dependent. The early increase in P-selectin expression was not inhibited by pretreatment with either oxypurinol (inhibits xanthine oxidase), diphenhydramine (H1-receptor antagonist), or MK-571 (leukotriene C4/D4 antagonist), nor was it blunted in transgenic mice expressing three times the normal level of copper-zinc superoxide dismutase or in mast cell-deficient mice. However, significant inhibition was noted after treatment with either MK-886 (5-lipoxygenase inhibitor) or a nitric oxide (NO) donor (diethylenetriamine/NO). These findings indicate that the early I/R-induced increase in intestinal P-selectin expression is mediated by a 5-lipoxygenase-dependent NO-inhibitable mechanism.

Animals↗

PubMed1997

Ischemia/reperfusion-induced microvascular dysfunction: role of oxidants and lipid mediators.

The objective of this study was to define the role of oxidants and lipid mediators in the leukocyte-endothelial cell adhesion and albumin leakage elicited in rat mesenteric venules by ischemia-reperfusion (I/R). Intravital fluorescence microscopy was used to monitor leukocyte adherence and emigration, platelet-leukocyte aggregation, mast cell degranulation, and albumin leakage after release of a 20-min arterial occlusion. I/R elicited large increases in leukocyte-endothelial cell adhesion and albumin leakage. These responses were significantly attenuated in venules treated with either superoxide dismutase, oxypurinol (an inhibitor of xanthine oxidase), lodoxamide (a mast cell stabilizer), WEB-2086 (a platelet-activating factor antagonist), or SC-41930 (a leukotriene B4-receptor antagonist) but not by U-74006F (an inhibitor of lipid peroxidation). Platelet-leukocyte aggregates and mast cell degranulation induced by I/R were also attenuated by administration of either superoxide dismutase or lodoxamide. These results support the hypothesis that oxidants produced, in part, by xanthine oxidase promote the formation (by mast cells and endothelial cells) of platelet-activating factor and leukotriene B4, which recruit and activate leukocytes in postischemic venules. The adherent and emigrated leukocytes then mediate the increased albumin extravasation observed in the postcapillary venules.

Animals↗

PubMed1997

Reperfusion-induced leukocyte adhesion and vascular protein leakage in normal and hypercholesterolemic rats.

The objective of this study was to define the influence of hypercholesterolemia on ischemia-reperfusion (I/R)-induced leukocyte-endothelial cell adhesion and albumin leakage in rat mesenteric venules. The microvascular alterations normally elicited by I/R (leukocyte adherence and emigration, albumin leakage, and platelet aggregation) were more pronounced in hypercholesterolemic rats (compared with control rats). Monoclonal antibodies against the adhesion glycoproteins CD11/CD18 and intercellular adhesion molecule-1 attenuated the I/R-induced leukocyte adherence and emigration and albumin leakage. Leukocyte adherence, but not albumin leakage, was diminished in animals pretreated with a P-selectin-specific antibody. Platelet aggregation was reduced by antibodies directed against either P-selectin, CD18, or intercellular adhesion molecule-1, as well as a GPIIb-IIIa antagonist. These results indicate that the enhanced reperfusion-induced albumin leakage in hypercholesterolemic rats is dependent on leukocyte-endothelial cell adhesion. Furthermore, P-selectin- and CD11/CD18-dependent heterotypic and GPIIb-IIIa-mediated homotypic platelet aggregation appear to influence the extravasation of both leukocytes and albumin in postischemic venules of hypercholesterolemic rats.

Animals↗

PubMed1997

Endothelial cell adhesion molecule expression in gene-targeted mice.

Gene-targeted mice are now routinely employed as tools for defining the contribution of different leukocyte and endothelial cell adhesion molecules to the leukocyte recruitment and tissue injury associated with acute and chronic inflammation. The objective of this study was to determine whether gene-targeted mice that are deficient in CD11/CD18, intracellular adhesion molecule-1 (ICAM-1), or P-selectin exhibit an altered constitutive or induced expression of the endothelial cell adhesion molecules E- and P-selectin. The gene-targeted mice were all developed in the 129Sv mouse strain and backcrossed into C57B1/6J mice. The number of backcrosses ranged between 8 (P-selectin) and 10 (CD18 and ICAM-1) generations. The dual-radiolabeled monoclonal antibody technique was used to quantify E- and P-selectin expression in different vascular beds. In the unstimulated state, E-selectin expression was significantly elevated (relative to wild-type mice) in the stomach, large intestine, and brain of mutants deficient in ICAM-1. In general, constitutive expression of P-selectin did not differ between wild-type, ICAM-1-deficient, and CD11/CD18-deficient mutants. In CD11/CD18-deficient mice, tumor necrosis factor-alpha (TNF-alpha) administration elicited a more profound upregulation of P-selectin in several vascular beds, compared with wild-type and ICAM-1-deficient mice. E-selectin expression in brain of TNF-alpha-stimulated, ICAM-1-deficient, and P-selectin-deficient mice was attenuated compared with wild-type mice. These findings indicate that chronic deficiency of some of the adhesion glycoproteins that mediate leukocyte recruitment alters basal and induced surface expression of other adhesion molecules on endothelial cells.

Animals↗

PubMed1997

Postischemic endothelium-dependent vascular reactivity is preserved in adhesion molecule-deficient mice.

Previous studies utilizing monoclonal antibodies directed against specific leukocyte-endothelial cell adhesion proteins have suggested that neutrophils mediate endothelial cell injury in a number of vascular beds after ischemia-reperfusion (I/R). In the present study, we investigated superior mesenteric artery (SMA) vascular reactivity to acetylcholine (ACh) and sodium nitroprusside (SNP) after occlusion and reperfusion in wild-type (C57BL/6) mice and in gene-targeted mice that are deficient in either CD11/CD18, intercellular adhesion molecule 1 (ICAM-1), or P-selectin. All mice were 4 wk of age, and the SMA was occluded for 45 min and then reperfused for 45 min. Segments of SMA were isolated and suspended in organ chambers and contracted with phenylephrine (10(-5) M), and the maximal vasorelaxation to ACh (10(-6) M) and SNP (10(-6) M) was measured. SMA from sham-operated C57BL/6 mice relaxed 83.5 +/- 3.3% to ACh and 91.7 +/- 3.4% to SNP. In contrast, segments of SMA from C57BL/6 mice subjected to I/R demonstrated a marked impairment in vasorelaxation to ACh (51.3 +/- 4.7%, P < 0.01 vs. sham) without any impairment in the vasoreactivity to SNP (86.1 +/- 5.5%). In CD11/CD18-deficient mice, SMA reactivity to ACh (84.7 +/- 2.3%) and SNP (91.2 +/- 2.8%) was unaffected by I/R. Similarly, SMA rings from ICAM-1-deficient mice exhibited normal vasorelaxation to ACh and SNP with maximal vasorelaxation of 83.1 +/- 2.9 and 87.4 +/- 3.0%, respectively. We also observed profound preservation of endothelium-dependent vasorelaxation after I/R in P-selectin-deficient mice. These findings indicate that leukocyte-endothelial cell adhesion molecule deficiency is associated with the preservation of endothelium-dependent vascular responses after I/R.

Acetylcholine↗

PubMed1997

Molecular determinants of oxidized low-density lipoprotein-induced leukocyte adhesion and microvascular dysfunction.

Oxidized low-density lipoproteins (oxLDL) have been implicated in the leukocyte recruitment and microvascular dysfunction associated with atherosclerosis. The objectives of this study were to define the adhesion molecules that mediate oxLDL-induced leukocyte-endothelial cell adhesion and to determine whether leukocyte-endothelial cell adhesion contributes to the endothelial barrier dysfunction elicited by oxLDL. Leukocyte-endothelial cell adhesion and emigration, albumin extravasation, and mast cell degranulation were monitored in rat mesentery in response to native LDL (nLDL) or copper-oxidized LDL (oxLDL). Intra-arterial infusion of oxLDL but not nLDL elicited increases in leukocyte adherence and emigration, mast cell degranulation, and albumin leakage. The oxLDL-induced leukocyte adherence/emigration was attenuated by pretreatment with monoclonal antibodies directed against CD11/CD18, intercellular adhesion molecule-1, P-selectin, and L-selectin but not by pretreatment with a nonbinding monoclonal antibody. The albumin leakage and mast cell degranulation responses were attenuated by all of the same monoclonal antibodies except L-selectin. In addition, a peptide previously shown to inhibit leukocyte-endothelial cell adhesion in vitro also attenuated leukocyte adherence and mast cell degranulation in this model. These findings implicate CD11/ CD18, L-selectin, intercellular adhesion molecule-1, and P-selectin in the leukocyte recruitment elicited by oxLDL and invoke a role for adherent leukocytes in the accompanying increase in mast cell degranulation and albumin leakage.

Animals↗

PubMed1997

Effects of fluvastatin on leukocyte-endothelial cell adhesion in hypercholesterolemic rats.

The overall objective of this study was to determine whether peroral treatment with the 3-hydroxy-3-methyl-glutaryl coenzyme A (HMG-CoA) reductase inhibitor fluvastatin influences the leukocyte-endothelial cell adhesion (LECA) observed in postcapillary venules of hypercholesterolemic rats. Rats were fed either normal chow or a chow supplemented with 1% cholesterol for 10 days. Leukocyte adherence and extravasation, leukocyte rolling velocity, red blood cell velocity, and vessel diameter were monitored in mesenteric venules superfused with either 100 nmol/L platelet-activating factor (PAF) or 20 nmol/L leukotriene B4 (LTB4). Hypercholesterolemic rats exhibited an exaggerated LECA response compared with their normocholesterolemic counterparts. In hypercholesterolemic rats, treatment with fluvastatin significantly attenuated the leukocyte-adherence responses to PAF and LTB4 as well as the leukocyte emigration response to LTB4. Fluvastatin treatment also inhibited the PAF- and LTB4-induced reductions in leukocyte rolling velocity. These findings indicate that fluvastatin blunts the inflammatory responses elicited in post-capillary venules by lipid mediators.

Animals↗

PubMed1997

Effects of chronic arterial hypertension on constitutive and induced intercellular adhesion molecule-1 expression in vivo.

Recent reports indicate that bacterial endotoxin (lipopolysaccharide) and cytokines elicit a more profound increase in the surface expression of intercellular adhesion molecule-1 (ICAM-1) in cultured endothelial cells derived from spontaneously hypertensive (SHR) versus normotensive Wistar-Kyoto rats (WKY). Our objective in this study was to characterize and compare in vivo ICAM-1 expression in SHR and WKY under basal conditions and after 5 hours of endothelial cell activation with either lipopolysaccharide (5 mg/kg i.p.) or tumor necrosis factor-alpha (TNF-alpha; 1, 5, and 10 micrograms/kg i.p.). ICAM-1 expression was quantified in different tissues by the double-radiolabeled monoclonal antibody technique. When constitutive (baseline) ICAM-1 expression was corrected for endothelial cell surface area, significantly higher values were noted in SHR than WKY but only in splanchnic organs. Lipopolysaccharide and TNF-alpha elicited significant increases in ICAM-1 expression in all tissues of both WKY and SHR. However, the magnitude of the lipopolysaccharide-induced ICAM-1 upregulation in heart, stomach, skeletal muscle, and brain was significantly lower in SHR than WKY. A similar blunted ICAM-1 upregulation was noted in the stomach of SHR after administration of 5 micrograms/kg TNF-alpha. The differences in induced ICAM-1 expression between SHR and WKY do not appear to be due to differences in endothelial cell surface area or plasma glucocorticoid levels. These results suggest that chronic arterial hypertension results in altered ICAM-1 expression on the endothelium, which may contribute to the abnormal inflammatory responses associated with this disease.

Animals↗

PubMed1997

Low-density lipoprotein receptor knockout mice exhibit exaggerated microvascular responses to inflammatory stimuli.

The objective of this study was to determine whether genetically induced hypercholesterolemia affects leukocyte-endothelial cell interactions in postcapillary venules of the mouse cremaster muscle. Leukocyte adhesion, emigration, and other microvascular parameters were assessed in venules of normal (wild-type) and low-density lipoprotein receptor-deficient (LDLr-/-) mice maintained on either normal rodent chow or on a high cholesterol diet (HCD). Measurements were obtained under control conditions and after administration of either leukotriene B4 (LTB4), platelet-activating factor (PAF), or tumor necrosis factor-alpha (TNF-alpha). Elevated numbers of adherent and emigrated leukocytes were observed in venules of LDLr-/- (compared with wild-type) mice on HCD, both under baseline conditions and after exposure to either LTB4, PAF, or TNF-alpha. Plasma TNF-alpha levels were also elevated in LDLr-/- versus wild-type mice. Administration of blocking monoclonal antibodies demonstrated that intercellular adhesion molecule-1, but not vascular cell adhesion molecule-1, mediates the exaggerated leukocyte-endothelial cell adhesion observed in LDLr-/- mice. The results of these studies indicate that chronic hypercholesterolemia predisposes the microvasculature to intense leukocyte-endothelial cell adhesion in response to different inflammatory stimuli.

Animals↗