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D N Granger

Publications and source records attributed to D N Granger.

At least 19 recordsLinked to original sources
PubMed2001

Regulation of murine intestinal inflammation by reactive metabolites of oxygen and nitrogen: divergent roles of superoxide and nitric oxide.

Several reports have implicated reactive oxygen and nitrogen metabolites (RONS) in the initiation and/or progression of inflammatory bowel diseases (IBDs). We have investigated the role of three key RONS-metabolizing enzymes (inducible nitric oxide synthase [iNOS], superoxide dismutase [SOD], nicotinamide adenine dinucleotide phosphate [NADPH] oxidase) in a murine model of IBD. Mice genetically deficient ((-/-)) in either iNOS or the p47phox subunit of NADPH oxidase, transgenic (Tg) mice that overexpress SOD, and their respective wild-type (WT) littermates were fed dextran sulfate sodium (DSS) in drinking water for 7 days to induce colitis. In addition, the specific iNOS inhibitor 1400W was used in DSS-treated WT and p47phox(-/-) mice. WT mice responded to DSS feeding with progressive weight loss, bloody stools, elevated serum NO(X) and colonic mucosal injury with neutrophil infiltration. Both the onset and severity of colitis were significantly attenuated in iNOS(-/-) and 1400W-treated WT mice. While the responses to DSS did not differ between WT and p47phox(-/-) mice, enhanced protection was noted in 1400W-treated p47phox(-/-) mice. Interestingly, SOD(Tg) mice exhibited more severe colitis than their WT littermates. These findings reveal divergent roles for superoxide and iNOS-derived NO in intestinal inflammation.

Amidines↗
PubMed2001

Role of intercellular adhesion molecule 1 in indomethacin-induced ileitis.

Adhesion molecules have been implicated in the pathogenesis of inflammatory bowel diseases. We investigated their expression and contribution to leukocyte recruitment in experimental intestinal inflammation. Ileitis was induced in Sprague-Dawley rats by two injections of indomethacin (7.5 mg/kg), given 24 h apart. Endothelial intercellular adhesion molecule-1 (ICAM-1) expression was quantified using the dual radiolabeled monoclonal antibody technique and Mac-1 (CD11b/CD18) expression on leukocytes by flow cytometry. Leukocyte infiltration was monitored by tissue myeloperoxidase (MPO) activity. The first indomethacin injection induced a time- and site-dependent increase of ICAM-1 expression in ileal mucosa and muscularis. The second injection resulted in a reduction of ICAM-1 expression below constitutive levels whereas Mac-1 was upregulated. MPO changes paralleled lesion development over 48 h. ICAM-1 and MPO values were correlated for the first 24 h. Immunoneutralization of either ICAM-1 or Mac-1 attenuated mucosal injury. We conclude that (i) indomethacin-induced ileitis is associated with a temporally disassociated upregulation of ICAM-1 and (ii) despite a reduction in ICAM-1 after 24 h, ICAM-1, in concert with Mac-1, contributes to mucosal injury and leukocyte infiltration elicited by indomethacin.

Animals↗
PubMed2001

NAD(P)H oxidase-derived superoxide mediates hypercholesterolemia-induced leukocyte-endothelial cell adhesion.

Experimental animals placed on a high-cholesterol diet for 2 or more weeks exhibit an inflammatory response in postcapillary venules. The aims of this study were to determine (1) whether superoxide mediates the hypercholesterolemia-induced inflammatory response and (2) whether leukocyte and/or vessel wall NAD(P)H oxidase contributes to this response. Intravital videomicroscopy was used to quantify leukocyte-endothelial cell adhesion in cremasteric postcapillary venules of wild-type (WT) mice, CuZn-superoxide dismutase transgenic (SOD TgN) mice, and mice heterozygous (p47(phox)+/-) or homozygous (p47(phox)-/-) for NAD(P)H oxidase placed on either a normal diet or high-cholesterol diet (HCD) for 2 weeks. The number of adherent and emigrated leukocytes in postcapillary venules of WT HCD mice was significantly higher than that detected in venules of their normal-diet counterparts. However, the HCD-induced recruitment of adherent and emigrated leukocytes was not observed in SOD TgN mice. Whereas hypercholesterolemic p47(phox)+/- and WT mice exhibited similar inflammatory responses, p47(phox)-/- mice did not. Bone marrow chimeras were developed to selectively delete p47(phox) from either the vessel wall or circulating leukocytes. Whereas WT marrow transplanted into WT mice produced a normal inflammatory response of venules to HCD, chimeric mice with p47(phox) deficiency in either the vessel wall or leukocytes exhibited an attenuated inflammatory response to HCD that was comparable with that observed in p47(phox)-/- HCD mice. Our findings indicate that enhanced superoxide production is a critical event that initiates the leukocyte-endothelial cell adhesion in postcapillary venules of HCD mice. NAD(P)H oxidase appears to be an important source of this superoxide.

Animals↗
PubMed2001

Influence of hypercholesterolemia and hypertension on ischemia-reperfusion induced P-selectin expression.

Risk factors for cardiovascular disease have been shown to exacerbate the inflammatory response and microvascular dysfunction that is normally associated with ischemia-reperfusion. The objective of this study was to determine whether hypercholesterolemia and/or hypertension alter I/R-induced expression of P-selectin in the intestinal vasculature. Male control and hypertensive (HTN) rats were placed on either a normal diet or high cholesterol diet (HCD) for at least 3 weeks resulting in hypercholesterolemia (HC). Ischemia was induced by occlusion of the superior mesenteric artery for 15 min, followed by either 30 min or 4 h of reperfusion. The dual radiolabeled antibody technique was used to quantify the rapid (30 min) and transcription-dependent (4 h) expression of P-selectin. Tissue myeloperoxidase (MPO) was used to quantify neutrophil infiltration. The constitutive (basal) expression of P-selectin did not differ among the experimental groups. Although I/R significantly increased P-selectin expression in control, HC, and HTN+HC, P-selectin expression did not increase in HTN. The HC group exhibited the largest increments in P-selectin expression and tissue MPO after I/R. The increment in P-selectin expression was not significantly attenuated in HC rats that were rendered thrombocytopenic with anti-platelet serum. Treatment with an anti-P-selectin antibody largely prevented the exaggerated MPO increase noted in HC. These findings indicate that hypercholesterolemia in contrast to hypertension enhances the expression of P-selectin in the postischemic intestinal vasculature.

Animals↗
PubMed2001

Role of appendix and spleen in experimental colitis.

There is growing clinical evidence suggesting that certain secondary lymphoid tissues (e.g., appendix and spleen) contribute to the initiation and/or perpetuation of ulcerative colitis. In this study, the importance of secondary lymphoid tissues in inducing colitis was assessed experimentally by removing the spleen and/or appendix (or sham operation) prior to inducing colitis in mice. Feeding 2.5% dextran sulphate sodium (DSS) in drinking water over 7 days induced colitis. Clinical disease activity was assessed based on weight loss, stool consistency, and presence of blood in stools. Additional measurements included white blood cell count and hematocrit, and myeloperoxidase activity (MPO) in colon samples. Colonic injury was assessed by histology and computerized image analysis. DSS treatment in sham-operated mice produced colitis associated with weight loss, bloody diarrhea, and mucosal ulceration. Clinical assessment of DSS-treated mice subjected to appendectomy or combined appendectomy/splenectomy exhibited a delayed onset and course of disease activity. Histomorphologic examination revealed significantly lower damage scores and a reduction in ulcerated mucosal surface area. Colonic MPO activity, which correlated with tissue injury and disease activity, was lowest in appendectomized mice. No beneficial effects of splenectomy were observed after 7 days of colitis. These findings support the hypothesis that appendicular lymphoid tissue, but not the spleen, contributes to the development of colitis.

Animals↗
PubMed2001

Interferon-gamma and interleukin-10 reciprocally regulate endothelial junction integrity and barrier function.

Inflammatory bowel disease (IBD) is associated with Th1/Th2 cytokine dysregulation, leukocyte extravasation, and tissue edema, but the mechanisms for cytokine-mediated vascular dysfunction are not understood. To investigate how cytokines might control edema in IBD, we determined vascular permeability and IFN-gamma expression in two models of murine colitis: SCID mice reconstituted with CD45RB(high T-lymphocytes (CD45RB(high)/SCID mice), and interleukin-10 gene deficient (IL-10(-/-)) mice. We also investigated the in vitro effects of IFN-gamma and IL-10 on human endothelial solute barrier and junction protein expression. Vascular permeability in CD45RB(high)/SCID and IL-10(-/-) mice was quantified using tissue (131)I-IgG accumulation. The IFN-gamma message was quantified using the ribonuclease protection assay. Endothelial barrier integrity in vitro was measured by transmonolayer electrical resistance, and junctional proteins were examined by immunoblotting and fluorescence microscopy. Both CD45RB(high)/SCID and IL-10(-/-) mice exhibit enhanced colonic microvascular leakage and IFN-gamma message levels compared to their respective controls. In vitro, IFN-gamma also reduced endothelial barrier (monolayer electrical resistance, increased albumin permeability) and reduced tight junction (occludin) expression and staining. These effects were reversed by pretreatment of monolayers with IL-10. Therefore, in vivo IFN-gamma and IL-10 may modulate microvascular leakage in IBD partly by controlling the expression of intestinal endothelial tight junctional proteins.

Animals↗
PubMed2001

Adhesion molecules and their role in vascular disease.

A variety of recently discovered glycoproteins have been implicated in cell-cell interactions that are critical for normal hemostasis, immune surveillance, and vascular wall integrity. These cell adhesion molecules (CAM) are known to mediate blood cell (leukocyte, platelet)-endothelial cell interactions that can occur in all segments of the microvasculature under certain physiological (eg, hemostasis) and pathological (eg, inflammation) conditions. The multistep process of leukocyte recruitment illustrates how the coordinated and regulated expression of structurally and functionally distinct families of CAM can elicit a highly reproducible vascular response to inflammation. Selectins mediate the initial, low-affinity leukocyte-endothelial cell interaction that is manifested as leukocyte rolling. This transient binding results in further leukocyte activation and subsequent firm adhesion and transendothelial migration of leukocytes, both of which are mediated by interactions between members of the integrin and immunoglobulin superfamily of CAM. This CAM-regulated process of leukocyte recruitment often results in endothelial cell dysfunction, which can be manifested as either impaired endothelium-dependent vasorelaxation in arterioles, excess fluid filtration in capillaries, and enhanced protein extravasation in venules. Consequently, CAM have been implicated in a variety of vascular disorders (eg, ischemia/reperfusion, atherosclerosis, allograft dysfunction, and vasculitis) and an enhanced expression of these CAM has been invoked to explain the exaggerated microvascular dysfunction associated with some of the risk factors (hypertension, hypercholesterolemia, diabetes) for cardiovascular disease. Monoclonal antibodies and genetically engineered mice have proven to be valuable tools for defining the contribution of CAM to disease progression and provide hope for new diagnostic and therapeutic strategies for cardiovascular diseases.

Animals↗
PubMed2001

Endothelial expression of vascular cell adhesion molecule-1 correlates with metastatic pattern in spontaneous melanoma.

OBJECTIVE: Adhesive interactions between tumor cell surface receptors and endothelial cell adhesion molecules are thought to contribute to tumor cell arrest and extravasation during hematogenous metastasis. Recent reports suggest that melanoma cell integrin alpha4beta1 (very late antigen-4, VLA-4) interaction with the inducible cell adhesion molecule, vascular cell adhesion molecule-1 (VCAM-1), is critical for tumor cell arrest. However, no information is available regarding microvascular VCAM-1 expression during spontaneous melanoma metastasis. The objectives of this study were to evaluate VCAM-1 expression in pulmonary and extrapulmonary vascular beds during melanoma progression, and to determine whether there is an organ-specific profile for VCAM-1 expression which corresponds with the clinical pattern of melanoma metastasis. METHODS: The dual-radiolabeled monoclonal antibody (mAb) technique for quantification of VCAM-1 in different vascular beds was applied to a physiological model of melanoma (B16-BL6) metastasis. Measurements of VCAM-1 were obtained when primary tumors reached 5 mm in size, and every 7 days following removal of the primary lesion. Histological examinations were performed, and mice were placed into 2 groups, based on the presence (+colonies) or absence (-colonies) of pulmonary metastases. VCAM-1 measurements obtained from several organ systems were then compared between these 2 groups of mice. Localization of VCAM-1 was achieved through immunohistochemical staining of tissues. Plasma collected from each experimental animal, as well as melanoma-conditioned media, was assayed to determine levels of the cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-1alpha (IL-1alpha). RESULTS: Data collected from the dual-radiolabeled mAb technique indicate that 3 weeks following removal of the primary lesion, there is a tendency for VCAM-1 expression to increase in cardiac, hepatic, and cerebral vascular beds. Four weeks following primary resection, when pulmonary metastatic burden was maximal, VCAM-1 was significantly upregulated in each of these vascular beds. Results obtained from the lung indicate that VCAM-1 remains unchanged in pulmonary vessels at all time points examined. Immunohistochemical staining of heart and brain support the radiolabeled mAb measurements, and reveals that these organs exhibit an inflammatory phenotype in mice with heavy pulmonary tumor burden. Furthermore, 25% of these mice had histological evidence of melanoma metastases in heart and brain. Transplantation of liver fragments from mice with advanced pulmonary metastases into subcutaneous tissue of donor mice resulted in the formation of melanotic outgrowths. Plasma levels of the cytokines TNF-alpha and IL-1alpha were negligible in both groups of mice. CONCLUSIONS: Our results indicate that upregulation of VCAM-1 is not a prerequisite for the formation of pulmonary metastases during spontaneous melanoma metastases. However, once lung metastases become well established, organ-specific increases in VCAM-1 expression become apparent. Furthermore, these organ-specific increments in VCAM-1 expression correspond with documented clinical patterns of melanoma metastasis. The enhanced expression of VCAM-1 is independent of systemic levels of TNF-alpha and IL-1alpha, but may be the result of melanoma-induced alterations at the local level, as we found evidence of melanoma cell occupation in heart, brain, and liver in pulmonary metastases-bearing mice.

Animals↗
PubMed2001

Splanchnic ischaemia-reperfusion injury: mechanistic insights provided by mutant mice.

Reperfusion of ischaemic tissues often leads to microvascular dysfunction that is manifested as impaired endothelium-dependent dilation of arterioles, enhanced fluid filtration and leucocyte plugging in capillaries, and the trafficking of leucocytes and plasma protein extravasation in postcapillary venules. Efforts to define the mechanisms that underlie these microvascular responses to ischaemia and reperfusion have largely relied on pharmacological agents and monoclonal antibodies. Gene-targeting technology has been applied to the production of transgenic and knockout mice that are rapidly gaining acceptance as tools for mechanistic studies of ischaemia-reperfusion (I/R) injury that obviate some of the concerns (e.g. specificity) raised about previously employed experimental strategies. This review summarizes some of our efforts to apply gene-targeted mice to the study of I/R injury in the splanchnic vascular bed. A role for endothelial cell adhesion molecules (CAMs) and reactive oxygen metabolites is supported by results from mutant mice. Low density lipoprotein receptor mice also reveal that the microvascular and inflammatory responses to I/R are greatly exaggerated during chronic hypercholesterolaemia. The wide variety of mutant mice that have been produced for inflammation-related research makes this experimental strategy particularly promising for mechanistic investigations of the tissue responses to I/R.

Animals↗
PubMed2001

Inducible nitric oxide synthase (iNOS) and regulation of leucocyte/endothelial cell interactions: studies in iNOS-deficient mice.

It is well established that constitutive production of nitric oxide is central to numerous processes in the microvasculature, including controlling the trafficking of inflammatory leucocytes. However, during many inflammatory responses induction of inducible nitric oxide synthase (iNOS) increases nitric oxide production. The role of iNOS-derived nitric oxide in modulating leucocyte recruitment is less well understood, although recent studies using iNOS-deficient mice have begun to examine this issue. This article describes much of the work that implicates iNOS as having a role in controlling leucocyte recruitment, including the intravital microscopy studies which revealed that iNOS-deficient mice have elevated leucocyte-endothelial cell interactions during endotoxaemia. Furthermore in additional studies, we compared expression of endothelial adhesion molecules in wild-type and iNOS-deficient mice, under conditions in which iNOS was expressed. Adhesion molecule expression was measured using an in vivo dual radiolabel immunoassay. To induce iNOS, mice were treated with either 1 or 50 microg of bacterial lipopolysaccharide (LPS), and 4 h later expression of P-selectin, E-selectin and vascular cell adhesion molecule-1 was determined in eight different tissues. In nearly all cases, adhesion molecule expression did not differ between the two types of mice, either in the absence of an inflammatory stimulus, or following LPS treatment. These findings indicate that iNOS does not regulate expression of endothelial adhesion molecules either under basal conditions, or during the endotoxaemic response. This further suggests that alterations in leucocyte function may mediate the modulating effect of iNOS on leucocyte recruitment.

Animals↗
PubMed2001

Hemorrhagic shock induced up-regulation of P-selectin expression is mediated by factors in mesenteric lymph and blunted by mesenteric lymph duct interruption.

BACKGROUND: Previous studies have shown that mesenteric lymph duct interruption prevents lung injury and decreases lung neutrophil sequestration after hemorrhagic shock (HS). Since endothelial cells rapidly express P-selectin after ischemia/reperfusion injury and HS-induced lung injury appears to involve neutrophil-endothelial cell interactions, we tested the following two hypotheses. First, that HS increases endothelial cell P-selectin expression and that interruption of mesenteric lymph flow in vivo would diminish this expression. Second, that incubation of human umbilical vein endothelial cells with post-HS mesenteric lymph but not sham shock (SS) lymph or postshock portal vein plasma would up-regulate P-selectin expression. METHODS: Pulmonary microvascular P-selectin expression was measured in male rats subjected to 90 minutes of HS (30 mm Hg), SS, or HS with lymphatic ligation, with a dual radiolabeled monoclonal antibody technique. The lungs from these animals were subsequently harvested and P-selectin expression was expressed as mean +/- SEM nanograms of monoclonal antibody per gram of tissue. RESULTS: Pulmonary P-selectin expression was 2.0 +/- 0.4 after SS, 9.7 +/- 3.0 after HS, but decreased to 2.3 +/- 0.3 after HS with lymph interruption (p < 0.05 HS vs. SS or HS plus lymph ligation). Incubation of human umbilical vein endothelial cells with shock lymph collected 3 to 4 hours after shock resulted in a nearly fivefold increase in P-selectin expression (p < 0.001) as compared with SS lymph, lymph collected 6 hours after shock, or postshock portal vein plasma. CONCLUSION: These results support the concept that gut-derived lymph promotes HS-induced lung injury through up-regulation of microvascular adhesion molecules and that intestinal lymph duct interruption may prevent distant organ injury by blunting the expression of these molecules.

Animals↗
PubMed2001

Hypercholesterolemia alters endotoxin-induced endothelial cell adhesion molecule expression.

While there is a growing body of evidence suggesting that hypercholesterolemia prior to the onset of atherosclerosis renders tissues more susceptible to inflammation, the mechanisms that underlie this exaggerated inflammatory response remain poorly defined. The overall objective of this study was to assess the influence of hypercholesterolemia on endotoxin-induced endothelial cell adhesion molecule (CAM) expression in different vascular beds. Another objective was to determine whether the altered endothelial CAM expression in hypercholesterolemic animals is associated with a corresponding change in plasma cytokine levels. Male Sprague/Dawley rats (SD) were placed either on a normal (control) or high cholesterol (HC) diet for 3 weeks. The dual radiolabeled monoclonal antibody (mAb) technique was used to measure the expression of P-selectin, E-selectin, ICAM-1, and VCAM-1 in different vascular beds after intraperitoneal injection of endotoxin (LPS) derived from Salmonella abortus equi. LPS induced a significant increase in the expression of all endothelial CAMs in both normocholesterolemic and hypercholesterolemic groups. However, hypercholesterolemia enhanced LPS-induced expression of P-selectin, E-selectin, and ICAM-1 in several vascular beds, while VCAM-1 expression was unaffected. Thrombocytopenia, induced with anti-platelet serum, did not alter LPS-induced P-selectin expression in either group, suggesting that platelets do not contribute to this response. Hypercholesterolemia was associated with an exaggerated increase in plasma TNF-alpha, but not IL-1beta, after LPS treatment. These results indicate that hypercholesterolemia in rats may render tissues more vulnerable to the inflammatory effects of LPS by enhancing the expression of certain endothelial CAMs.

Animals↗
PubMed2001

CD8(+)-T-cell depletion ameliorates circulatory shock in Plasmodium berghei-infected mice.

The Plasmodium berghei-infected mouse model is a well-recognized model for human cerebral malaria. Mice infected with P. berghei exhibit (i) metabolic acidosis (pH < 7.3) associated with elevated plasma lactate concentrations, (ii) significant (P < 0.05) vascular leakage in their lungs, hearts, kidneys, and brains, (ii) significantly (P < 0.05) higher cell and serum glutamate concentrations, and (iv) significantly (P < 0.05) lower mean arterial blood pressures. Because these complications are similar to those of septic shock, the simplest interpretation of these findings is that the mice develop shock brought on by the P. berghei infection. To determine whether the immune system and specifically CD8(+) T cells mediate the key features of shock during P. berghei malaria, we depleted CD8(+) T cells by monoclonal antibody (mAb) treatment and assessed the complications of malarial shock. P. berghei-infected mice depleted of CD8(+) T cells by mAb treatment had significantly reduced vascular leakage in their hearts, brains, lungs, and kidneys compared with infected controls treated with rat immunoglobulin G. CD8-depleted mice were significantly (P < 0.05) protected from lactic acidosis, glutamate buildup, and diminished HCO(3)(-) levels. Although the blood pressure decreased in anti-CD8 mAb-treated mice infected with P. berghei, the cardiac output, as assessed by echocardiography, was similar to that of uninfected control mice. Collectively, our results indicate that (i) pathogenesis similar to septic shock occurs during experimental P. berghei malaria, (ii) respiratory distress with lactic acidosis occurs during P. berghei malaria, and (iii) most components of circulatory shock are ameliorated by depletion of CD8(+) T cells.

Acidosis, Lactic↗
PubMed2001

MAdCAM mediates lymphocyte-endothelial cell adhesion in a murine model of chronic colitis.

Previous studies have revealed that the expression of several endothelial cell adhesion molecules [e.g., intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and mucosal addressin cell adhesion molecule 1 (MAdCAM-1)] is dramatically elevated in the chronically inflamed colonic vasculature of severe combined immunodeficient (SCID) mice reconstituted with congenic CD4+, CD45RB(high) T lymphocytes. The objective of this study was to define the contribution of different endothelial cell adhesion molecules to the lymphocyte-endothelial cell (L/E) adhesion observed in the colonic microvasculature in this experimental model of inflammatory bowel disease. Fluorescently labeled T lymphocytes, isolated from spleens of normal BALB/C mice, were injected intravenously into SCID mice that had been reconstituted with CD4+, CD45RB(high) T lymphocytes either before (3 wk after reconstitution) or after (7 wk postreconstitution) the onset of clinical signs of colitis (i.e., diarrhea, loss of body wt). Intravital fluorescence microscopy was used to quantify L/E adhesion in different-sized venules of the colonic submucosa during the development of colitis. L/E adhesion was noted in some segments of the vasculature in precolitic SCID mice (3 wk after reconstitution) but not in similar-sized vessels of control (wild type and SCID) mice. L/E adhesion was observed in a greater proportion of venules and occurred with greater intensity in the mucosa of colitic mice (7 wk postreconstitution). Pretreatment with a blocking monoclonal antibody against MAdCAM-1, but not ICAM-1 or VCAM-1, significantly and profoundly reduced L/E adhesion in colitic mice. Immunohistochemical staining also revealed the localization of T cells on colonic endothelial cells expressing MAdCAM-1. These findings indicate that MAdCAM-1 is largely responsible for recruiting T lymphocytes into inflamed colonic tissue.

Animals↗
PubMed2001

Platelets modulate ischemia/reperfusion-induced leukocyte recruitment in the mesenteric circulation.

P-selectin-dependent leukocyte-endothelial cell adhesion has been implicated in the pathogenesis of ischemia/reperfusion (I/R) injury in several vascular beds, including the gut. Because platelet-endothelial (P/E) cell adhesion also occurs in postischemic venules, the possibility exists that the expression of P-selectin on the surface of platelets that are adherent to venular endothelial cells may mediate the leukocyte recruitment elicited by I/R. P-selectin expression [dual radiolabeled monoclonal antibody (MAb) technique] and neutrophil accumulation [myeloperoxidase (MPO) activity] were measured in the postischemic small intestine of untreated rats and rats treated with either antiplatelet serum (APS) or MAbs directed against either P-selectin, GPIIb/IIIa, or fibrinogen. The increases in P-selectin expression and tissue MPO normally elicited by I/R were significantly attenuated in the different treatment groups, suggesting that I/R-induced neutrophil recruitment is a platelet-dependent, P-selectin-mediated process. Intravital microscopy was then employed to examine this process relative to leukocyte-endothelial cell adhesion in postischemic rat mesenteric venules. The recruitment of adherent and emigrated leukocytes after I/R was attenuated by pretreatment with a MAb against, either P-selectin, GPIIb/IIIa, or fibrinogen, as well as an Arg-Gly-Asp peptide. Whereas thrombocytopenia greatly blunted leukocyte emigration, it did not alter the leukocyte adherence response to I/R. These findings suggest that platelet-associated P-selectin contributes to the accumulation of leukocytes in postischemic tissue via a mechanism that alters transendothelial leukocyte migration.

Animals↗
PubMed2001

Brain endothelial adhesion molecule expression in experimental colitis.

OBJECTIVES: 1) To determine if endothelial expression of adhesion molecules involved in leukocyte recruitment is increased in the brain and other organs in four different models of experimental colitis, and 2) to investigate whether leukocyte infiltration occurs in the brain of colitic animals. METHODS: Endothelial vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) expression was quantified, using the dual radiolabeled antibody technique in rats with trinitrobenzenesulfonic acid (TNBS)-induced colitis, in mice with dextran sulfate sodium (DSS)-induced colitis, in SCID mice reconstituted with CD45RBhigh T-cells, and in IL-10-/- mice. Leukocyte infiltration in the brain of TNBS-induced colitic rats was assessed by myeloperoxidase activity and immunohistochemical staining with anti-CD45 monoclonal antibody. RESULTS: Marked upregulation of brain endothelial VCAM-1 (2- to 5.5-fold) was consistently found in colitic animals in the four models studied. Brain VCAM-1 strongly correlated with colon VCAM-1 and colon weight. By contrast, upregulation of brain ICAM-1 in colitic animals was only observed in the CD45RBhigh transfer (3-fold) and the TNBS-induced (1.5-fold models). Heart and muscle VCAM-1 and ICAM-1 were not upregulated in colitic animals in the majority of models studied. There was no leukocyte infiltration into the brain of TNBS-induced colitic rats. CONCLUSIONS: Our study demonstrates a marked and specific upregulation of endothelial VCAM-1 in the brain of colitic animals. This activation of cerebral endothelial cells was not associated with an infiltration of leukocytes into brain tissue.

Animals↗
PubMed2001

Intercellular cell adhesion molecule-1 regulates lymphocyte movement into intestinal microlymphatics of rat Peyer's patches.

The objective of this study was to determine whether specific adhesion molecules modulate lymphocyte movement from Peyer's patches into intestinal microlymphatics. The fluorochrome acridine orange was injected via a micropipette into Peyer's patches to fill lymphatics. The flux of labeled lymphocytes into intestinal microlymphatics was monitored with intravital fluorescence microscopy. The lymphatic microvessels in the perifollicular area of Peyer's patches were filled with lymphocytes, most of which remained within the lymphatics. Some lymphocytes became detached and were drained into intestinal lymph. Administration of antibodies directed against ICAM-1 significantly increased lymphocyte flux into interfollicular lymphatics. The immunohistochemical study showed intense ICAM-1 expression on the lymphocytes densely packed in the lymphatics surrounding follicles in Peyer's patches. A large number of lymphocytes are normally sequestered in the lymphatic network of Peyer's patches. This sequestration of lymphocytes is largely mediated by ICAM-1-dependent cell-cell interactions.

Animals↗