Biomedical subjects

D Neil Granger

Publications and source records attributed to D Neil Granger.

At least 37 records · Page 2Linked to original sources

PubMed2005

Obesity exacerbates sepsis-induced inflammation and microvascular dysfunction in mouse brain.

OBJECTIVE: Obese patients with sepsis have higher morbidity and mortality than lean counterparts, but the mechanisms involved are unknown. The authors examined the inflammatory and thrombogenic responses of the cerebral microvasculature to sepsis induced by cecal ligation and perforation in obese and lean wild-type mice. METHODS: Leukocyte and platelet adhesion in cerebral microvasculature and behavioral responses were measured in wild-type and obese mice 4 h postperforation. P-selectin expression in different vascular beds was assessed 6 h postperforation. The effects of immunoblockade of P-selectin, ICAM-1, and CD18 on leukocyte and platelet recruitment were evaluated in obese septic animals. RESULTS: Cerebral venules of obese and wild-type mice assumed a proinflammatory and prothrombogenic phenotype 4 h post-perforation, with greatly exaggerated responses in obese mice compared to the lean counterparts. These enhanced responses were attenuated by blocking P-selectin, CD18, or ICAM-1. Obese mice also exhibited a more profound behavioral deficit after sepsis, which appears to be unrelated to the recruitment of leukocytes and platelets. Cecal ligation and perforation-induced P-selectin expression was greater in obese mice compared with lean counterparts. CONCLUSIONS: These findings suggest that the increased morbidity to sepsis in obesity may result from exaggerated microvascular inflammatory and thrombogenic responses that include the activation of endothelial cells with subsequent expression of adhesion molecules, such as P-selectin.

Animals↗

PubMed2005

Exposure of brain to high-dose, focused gamma rays irradiation produces increase in leukocytes-adhesion and pavementing in small intracerebral blood vessels.

OBJECTIVE: Radiosurgery is used to destroy a predetermined target within the brain, with minimal radiation injury to the surrounding tissue. We hereby present our in vivo model to study the effects of single-session, high-dose radiation on the cerebral vessels that are targeted with radiosurgery using the Leksell Gamma Knife. METHODS: The study was conducted in 29 adult male WT C57BL/6J mice weighing 21 to 28 g (6-8 wk old). The animals were exposed to 100 Gy single-session focused gamma ray irradiation using the Leksell Gamma Knife, and subsequently underwent intravital microscopy at different time intervals to study leukocytes and platelets adhesion patterns to the endothelium of the irradiated cerebral micro-vessels. RESULTS: The leukocyte adhesion response showed a bell-shaped curve upon quantitative analysis with a steady increase in the number of adherent cells during the first four hours and a subsequent plateau response that was maintained during the next 24 hours. The platelet adhesion response did not demonstrate any particular pattern similar to the leukocyte response. CONCLUSION: The experiment was able to establish in vivo increased leukocyte adhesion to the cerebral vascular endothelial cells in response to radiation injury and elaborate the time frame within which the leukocyte adhesion response increases, reaches a peak and then starts decreasing.

Animals↗

PubMed2005

Stroke and T-cells.

The microvasculature of the brain region affected by a stroke assumes an inflammatory phenotype that is characterized by endothelial cell activation and barrier dysfunction and the recruitment of adherent leukocytes. Although most attention has been devoted to the possible role of neutrophils in the tissue responses to ischemic stroke there is evidence that T-lymphocytes also accumulate in the postischemic brain. Although comparable detailed analyses of lymphocyte involvement in ischemic brain injury have not been performed, emerging findings suggest a role for T-cells in the pathogenesis of ischemic stroke. The recruitment of T-cells to the site of brain injury is critically dependent on the coordinated expression of adhesion molecules on the activated capillary endothelium. Whether the recruited lymphocytes are acting directly on brain tissue or indirectly through activation of other circulating blood cells and/or extravascular cells remain unclear. Cytotoxic CD8+ T-cells may induce brain injury through molecules released from their cytotoxic granules. CD4+ T-helper 1 (TH1) cells, which secrete proinflammatory cytokines, including interleukin-2 (IL-2), IL-12, interferon-gamma, and tumor necrosis factor-alpha, may play a key role in the pathogenesis of stroke, whereas CD4+TH2 cells may play a protective role through anti-inflammatory cytokines such as IL-4, IL-5, IL-10, and IL-13. T-cells should be considered as therapeutic targets for ischemic stroke. However, because infection is a leading cause of mortality in the postacute phase of ischemic stroke, and considering anti-inflammatory role of CD4+TH2, treatment targeting T-cells should be carefully designed to reduce deleterious and enhance protective actions of T-cells.

Brain↗

PubMed2005

Hypercholesterolemia: its impact on ischemia-reperfusion injury.

Ischemic diseases are a leading cause of death worldwide. It is becoming increasingly appreciated that atherosclerosis is a major cause of ischemia reperfusion. Hypercholesterolemia is a major risk factor for the development of atherosclerosis, and is associated with an increased incidence of ischemia reperfusion. Furthermore, elevated cholesterol levels exacerbate the vascular responses to ischemia-reperfusion, which intensifies the resulting organ dysfunction. One of the underlying features of both ischemia-reperfusion injury and hypercholesterolemia is the proinflammatory and prothrombogenic phenotype invoked in the microvasculature. This is manifested as an endothelial dysfunction, characterized by leukocyte and platelet recruitment, oxidative stress and angiotensin II receptor Type 1a activation. These common pathways of inflammation offer attractive targets for the development of drugs to combat cardiovascular disease and the associated ischemic disorders.

Animals↗

PubMed2004

The microcirculation: a motor for the systemic inflammatory response and large vessel disease induced by hypercholesterolaemia?

There is abundant evidence that links hypercholesterolaemia to both vascular inflammation and atherogenesis. While atherosclerosis is a large vessel disease that is characterized by leucocyte infiltration and lipid deposition in the wall of lesion-prone arteries, the inflammatory response does not appear to be confined to these locations. There is evidence supporting a systemic inflammatory response that is characterized by endothelial cell activation in multiple vascular beds and the appearance of activated immune cells and a wide range of inflammatory mediators in blood. The mechanism(s) responsible for initiating this systemic response remain poorly defined, although several inciting factors have been proposed, including infectious agents and oxidative stress resulting from one or more of the cardiovascular risk factors (e.g. hypercholesterolaemia, hypertension). While cells within lesion-prone arteries are often inferred as the source of circulating inflammatory mediators during atherogenesis, the fact that endothelial cells throughout the vasculature are activated raises the possibility that the microvasculature (which encompasses a vast endothelial surface area) may contribute to creating the systemic inflammatory milieu that is linked to atherogenesis. This review addresses evidence that links the microvasculature to the inflammatory responses induced by hypercholesterolaemia and offers the hypothesis that inflammatory events initiated within the microcirculation may contribute to initiation and/or progression of large vessel disease.

Animals↗

PubMed2004

Molecular determinants of the prothrombogenic phenotype assumed by inflamed colonic venules.

Although platelets have been implicated in the pathogenesis of human inflammatory bowel diseases, little is known about the magnitude of platelet accumulation in the inflamed bowel, what regulates this process, and its relevance to the overall inflammatory response. In this study, intravital video microscopy was used to monitor the trafficking of platelets and leukocytes and vascular permeability in colonic venules during the development of colonic inflammation induced by 3% dextran sodium sulfate (DSS). Blocking antibodies directed against different adhesion molecules as well as P-selectin-deficient mice were used to define the adhesive determinants of DSS-induced platelet recruitment. DSS induced an accumulation of adherent platelets that was temporally correlated with the appearance of adherent leukocytes and with disease severity. Platelet adhesion and, to a lesser extent, leukocyte adhesion were attenuated by immunoblockade of P-selectin and its ligand P-selectin glycoprotein ligand-1 (PSGL-1), with contributions from both platelet- and endothelial cell-associated P-selectin. DSS induced a rapid and sustained increase in vascular permeability that was greatly attenuated in P-selectin-deficient mice. P-selectin bone marrow chimeras revealed that both endothelial cell- and platelet-associated P-selectin contribute to the P-selectin expression detected in the inflamed colonic microvasculature, with endothelial P-selectin making a larger contribution. Our findings indicate that colonic inflammation is associated with the induction of a prothrombogenic phenotype in the colonic microcirculation, with P-selectin and its ligand PSGL-1 playing a major role in the recruitment of platelets.

Animals↗

PubMed2004

Contributions of LFA-1 and Mac-1 to brain injury and microvascular dysfunction induced by transient middle cerebral artery occlusion.

Although the beta2-integrins have been implicated in the pathogenesis of cerebral ischemia-reperfusion (I/R) injury, the relative contributions of the alpha-subunits to the pathogenesis of ischemic stroke remains unclear. The objective of this study was to determine whether and how genetic deficiency of either lymphocyte function-associated antigen-1 (LFA-1) or macrophage-1 (Mac-1) alters the blood cell-endothelial cell interactions, tissue injury, and organ dysfunction in the mouse brain exposed to focal I/R. Middle cerebral artery occlusion was induced for 1 h (followed by either 4 or 24 h of reperfusion) in wild-type mice and in mice with null mutations for either LFA-1 or Mac-1. Neurological deficit and infarct volume were monitored for 24 h after reperfusion. Platelet- and leukocyte-vessel wall adhesive interactions were monitored in cortical venules by intravital microscopy. Mice with null mutations for LFA-1 or Mac-1 exhibited significant reductions in infarct volume. This was associated with a significant improvement in the I/R-induced neurological deficit. Leukocyte adhesion in cerebral venules did not differ between wild-type and mutant mice at 4 h after reperfusion. However, after 24 h of reperfusion, leukocyte adhesion was reduced in both LFA-1- and Mac-1-deficient mice compared with their wild-type counterparts. Platelet adhesion was also reduced at both 4 and 24 h after reperfusion in the LFA-1- and Mac-1-deficient mice. These findings indicate that both alpha-subunits of the beta2-integrins contribute to the brain injury and blood cell-vessel wall interactions that are associated with transient focal cerebral ischemia.

Animals↗

PubMed2004

Inflammatory responses to ischemia and reperfusion in the cerebral microcirculation.

Ischemia and reperfusion (I/R) has been shown to elicit an inflammatory response that is characterized by an increased production of reactive oxygen species, and the rolling, firm adhesion, and transendothelial migration of leukocytes in postcapillary venules. A rate-determining role for leukocyte-endothelial cell (L/E) adhesion in the initiation and propagation of reperfusion injury is supported by several reports that describe attenuated microvascular dysfunction and tissue injury following I/R in animals receiving neutralizing antibodies directed against certain leukocyte adhesion receptors and in mutant mice that are genetically deficient in these adhesion receptors The technique of intravital videomicroscopy has been applied to several tissues, including the brain, in order to directly observe the microcirculatory alterations and inflammatory responses that are elicited by I/R. The leukocyte- and platelet-endothelial cell adhesion responses to cerebral I/R are addressed and compared to responses observed in other postischemic vascular beds. The limited data available for the brain microcirculation support the potential of anti-leukocyte and anti-platelet strategies for stroke therapy.

Animals↗

PubMed2004

Modulation of the inflammatory response in cardiovascular disease.

There is a growing body of evidence that inflammation might play an important role in the initiation and progression of cardiovascular diseases (CVDs). The designation of CVD as a chronic inflammatory process is further supported by evidence that the risk factors for CVD cause endothelial cells throughout the vascular tree to assume an inflammatory phenotype. These activated endothelial cells characteristically exhibit oxidative stress and increased adhesiveness for circulating leukocytes. Although initial efforts to define the mechanisms underlying the inflammatory phenotype in diseased endothelial cells have focused on the linkage between oxidative stress and adhesion molecule activation/expression, recent work has implicated a variety of additional factors that can modulate the magnitude and/or nature of the inflammatory responses in CVD. Platelets, angiotensin II, and the CD40/CD40 ligand signaling system are gaining recognition as contributors to the pathogenesis of CVD. These factors appear to converge with known pathways that link oxidative stress with adhesion molecule expression and help to explain the apparent integration of coagulation with inflammation in CVD. These factors also hold the promise of offering multiple sites for therapeutic intervention in CVD.

Angiotensin II↗

PubMed2004

Leukocyte dependence of platelet adhesion in postcapillary venules.

Reperfusion of ischemic tissues results in development of a proinflammatory, prothrombogenic phenotype, culminating in the recruitment of leukocytes and platelets within postcapillary venules. Recent studies have indicated an interdependence of platelet and leukocyte adhesion, suggesting that heterotypic blood cell interactions may account for postischemic platelet recruitment. The objectives of this study were to 1) determine whether ischemia-reperfusion (I/R)-induced platelet recruitment is leukocyte dependent and 2) quantify the contributions of leukocytes and endothelial cells in this platelet recruitment. Intravital microscopy was used to monitor the recruitment of fluorescently labeled platelets in postcapillary venules of the small intestine after 45-min ischemia and 4-h reperfusion. To assess the leukocyte dependence of platelet adhesion, platelets from wild-type mice were infused into mice deficient in neutrophils and/or lymphocytes and mice deficient in key leukocyte adhesion molecules (CD18 and ICAM-1). These antileukocyte strategies resulted in significantly reduced platelet recruitment. Simultaneous visualization of platelets and leukocytes enabled quantification of leukocyte-dependent and endothelium-dependent platelet adhesion. It was observed that in wild-type animals 74% of I/R-induced platelet adhesion was a result of platelet-leukocyte interactions. Although the majority of adherent platelets were associated with leukocytes, <50% of adherent leukocytes were platelet bearing, suggesting that not all adherent leukocytes support platelet adhesion. These results are consistent with leukocytes playing a major role in supporting I/R-induced platelet adhesion.

Animals↗

PubMed2004

Endothelial cell P-selectin mediates a proinflammatory and prothrombogenic phenotype in cerebral venules of sickle cell transgenic mice.

Whereas the adhesion of leukocytes and erythrocytes to vascular endothelium has been implicated in the vasooclusive events associated with sickle cell disease, the role of platelet-vessel wall interactions in this process remains undefined. The objectives of this study were to: 1) determine whether the adhesion of platelets and leukocytes in cerebral venules differs between sickle cell transgenic (betaS) mice and their wild-type (WT) counterparts (C57Bl/6) under both resting and posthypoxic conditions, and 2) define the contributions of P-selectin to these adhesion processes. Animals were anesthetized, and platelet and leukocyte interactions with endothelial cells of cerebral postcapillary venules were monitored and quantified using intravital fluorescence microscopy in WT, betaS, and chimeric mice produced by transplanting bone marrow from WT or betaS mice into WT or P-selectin-deficient (P-sel(-/-)) mice. Platelet and leukocyte adhesion to endothelial cells in both unstimulated and posthypoxic betaS mice were significantly elevated over WT levels. Chimeric mice involving bone marrow transfer from betaS mice to P-sel(-/-) mice exhibited a profound attenuation of both platelet and leukocyte adhesion compared with betaS bone marrow transfer to WT mice. These findings indicate that betaS mice assume both an inflammatory and prothrombogenic phenotype, with endothelial cell P-selectin playing a major role in mediating these microvascular responses.

Animals↗

PubMed2004

Impact of dextran sulfate sodium load on the severity of inflammation in experimental colitis.

In dextran sulfate sodium (DSS)-induced inflammatory bowel disease in mice the relationship between the amount of ingested DSS and the severity of colitis has not been systematically investigated. We examined whether (1) the severity of colitis is DSS load-dependent, and (2) there is a critical DSS load required to reliably induce colitis. DSS load was calculated as: (drinking volume (ml) x [DSS (g)/100 ml])/body weight (g). A minimum DSS load > or = 30 mg/g body weight over 7 days resulted in a significantly elevated colonic myeloperoxidase (MPO) activity, compared to mice receiving less DSS and controls (P < 0.05). Histomorphologic data correlated with MPO activity and revealed significantly higher damage scores once the DSS load was > or = 30 mg/g body weight. Our findings demonstrate the importance of monitoring DSS load in this model of experimental colitis.

Animals↗

PubMed2004

Differential expression of E- and P-selectin in the microvasculature of sickle cell transgenic mice.

OBJECTIVE: There is a growing body of evidence that endothelial cells assume an inflammatory phenotype in sickle cell disease. The authors determined whether (1) the expression of E- and P-selectin differs between sickle cell transgenic (beta(S)) mice and their wild-type counterparts, and (2) blood platelets and/or neutrophils contribute to the altered selectin expression. METHODS: Expression of E- and P-selectin was measured in different regional vascular beds of wild-type and beta(S) mice (with or without thrombocytopenia or neutropenia) using the dual radiolabeled monoclonal antibody technique. RESULTS: Constitutive expression of P-selectin was significantly increased in the heart, lungs, small bowel, large bowel, and penis of beta(S) versus WT mice. While thrombocytopenia reduced P-selectin expression in the small bowel and penis of beta(S) mice, neutropenia was associated with a reduction in P-selectin expression only in the penis. E-selectin expression was not significantly elevated in any vascular bed except the penis of beta(S) mice. CONCLUSIONS: Sickle cell disease promotes an increased P-selectin expression in several vascular beds. An accumulation of platelets may explain the increased P-selectin expression observed in some vascular beds.

Anemia, Sickle Cell↗

PubMed2004

The role of the complement system in ischemia-reperfusion injury.

Ischemia-reperfusion (I/R) injury is a common clinical event with the potential to seriously affect, and sometimes kill, the patient. Interruption of blood supply causes ischemia, which rapidly damages metabolically active tissues. Paradoxically, restoration of blood flow to the ischemic tissues initiates a cascade of pathology that leads to additional cell or tissue injury. I/R is a potent inducer of complement activation that results in the production of a number of inflammatory mediators. The use of specific inhibitors to block complement activation has been shown to prevent local tissue injury after I/R. Clinical and experimental studies in gut, kidney, limb, and liver have shown that I/R results in local activation of the complement system and leads to the production of the complement factors C3a, C5a, and the membrane attack complex. The novel inhibitors of complement products may find wide clinical application because there are no effective drug therapies currently available to treat I/R injuries.

Animals↗

PubMed2004

Signaling pathways for early brain injury after subarachnoid hemorrhage.

Few studies have examined the signaling pathways that contribute to early brain injury after subarachnoid hemorrhage (SAH). Using a rat SAH model, the authors explored the role of vascular endothelial growth factor (VEGF) and mitogen-activation protein kinase (MAPK) in early brain injury. Male Sprague-Dawley rats (n = 172) weighing 300 to 350 g were used for the experimental SAH model, which was induced by puncturing the bifurcation of the left anterior cerebral and middle cerebral arteries. The blood-brain barrier (BBB), brain edema, intracranial pressure, and mortality were evaluated at 24 hours after SAH. The phosphorylation of VEGF and different MAPK subgroups (ERK1/2, p38, and JNK) were examined in both the cortex and the major cerebral arteries. Experimental SAH increased intracranial pressure, BBB permeability, and brain edema and produced high mortality. SAH induced phosphorylation of VEGF and MAPKs in the cerebral arteries and, to a lesser degree, in the cortex. PP1, an Src-family kinase inhibitor, reduced BBB permeability, brain edema, and mortality and decreased the phosphorylation of VEGF and MAPKs. The authors conclude that VEGF contributes to early brain injury after SAH by enhancing the activation of the MAPK pathways, and that the inhibition of these pathways might offer new treatment strategies for SAH.

Animals↗

PubMed2004

Platelet-leukocyte-endothelial cell interactions after middle cerebral artery occlusion and reperfusion.

The adhesion of both leukocytes and platelets to microvascular endothelial cells has been implicated in the pathogenesis of ischemia/reperfusion (I/R) injury in several vascular beds. The objectives of this study were to (1) assess the platelet-leukocyte-endothelial cell interactions induced in the cerebral microvasculature by middle cerebral artery occlusion (MCAO)/reperfusion, and (2) define the molecular determinants of the prothrombogenic and inflammatory responses in this model of focal I/R. MCAO was induced for 1 hour in wild-type (WT) mice, WT mice treated with a monoclonal antibody (mAb) to either P-selectin or GPIIb/IIIa, and in P-selectin-/-(P-sel-/-) chimeras. Isolated platelets labeled with carboxyfluorescein diacetate succinimidyl ester (CFDASE) were administered intravenously and observed with intravital fluorescence microscopy. Leukocytes were observed after intravenous injection of rhodamine 6G. One hour of MCAO followed by 1 hour of reperfusion resulted in the rolling and adhesion of leukocytes in venules, and after 4 hours of reperfusion, the adhesion of both leukocytes and platelets was detected. Although both the P-selectin and GPIIb/IIIa mAbs significantly reduced the adhesion of leukocytes and platelets at 4 hours of reperfusion, the antiadhesive effects of the P-selectin mAb were much greater. The leukocyte and platelet adhesion responses were significantly attenuated in both P-sel-/- --> WT and WT --> P-sel-/- bone marrow chimeras, compared with WT --> WT chimeras. Neutropenia, induced by antineutrophil serum treatment, also reduced the recruitment of leukocytes and platelets after cerebral I/R. These findings implicate a major role for both platelet-associated and endothelial cell-associated P-selectin, as well as neutrophils in the inflammatory and prothrombogenic responses in the microcirculation after focal cerebral I/R.

Animals↗

PubMed2004

Mmp-9 deficiency enhances collagenase-induced intracerebral hemorrhage and brain injury in mutant mice.

Matrix metalloproteinase-9 (MMP-9) participates in the disregulation of blood-brain barrier during hemorrhagic transformation, and exacerbates brain injury after cerebral ischemia. However, the consequences of long-term inhibition or deficiency of MMP-9 activity (which might affect normal collagen or matrix homeostasis) remains to be determined. The authors investigated how MMP-9 gene deficiency enhances hemorrhage and increases mortality and neurologic deficits in a collagenase-induced intracerebral hemorrhage (ICH) model in MMP-9-knockout mice. MMP-9-knockout and corresponding wild-type mice at 20 to 35 weeks were used to model an aged population (because advanced age is a significant risk factor in human ICH). Collagenase VII-S (0.5 microL, 0.075 U) was injected into the right basal ganglia in mice and mortality, neurologic deficits, brain edema, and hemorrhage size measured. In addition, MMP-9 activity, brain collagen content, blood coagulation, cerebral arterial structure, and expressions of several MMPs were examined. Increased hemorrhage and brain edema that correlated with higher mortality and neurologic deficits were found in MMP-9-knockout mice. No apparent structural changes were observed in cerebral arteries, even though brain collagen content was reduced in MMP-9-knockout mice. MMP-9-knockout mice did exhibit an enhanced expression of MMP-2 and MMP-3 in response to ICH. The results indicate that a deficiency of MMP-9 gene in mutant mice increases collagenase-induced hemorrhage and the resulting brain injury. The intriguing relationship between MMP-9 deficiency and collagenase-induced ICH may reflect the reduction in collagen content and an enhanced expression of MMP-2 and MMP-3.

Animals↗

PubMed2004

Role of AT1 receptors and NAD(P)H oxidase in diabetes-aggravated ischemic brain injury.

The objective of the present study was to examine the role of the angiotensin II type 1 receptor (AT(1)-R) in the diabetes-aggravated oxidative stress and brain injury observed in a rat model of combined diabetes and focal cerebral ischemia. Diabetes was induced by an injection of streptozotoxin (STZ; 55 mg/kg iv) at 8 wk of age. Two weeks after the induction of diabetes, some animals received continuous subcutaneous infusion of the AT(1)-R antagonist candesartan (0.5 mg.kg(-1).day(-1)) for 14 days. Focal cerebral ischemia, induced by middle cerebral artery occlusion/reperfusion (MCAO), was conducted at 4 wk after STZ injection. Male Sprague-Dawley rats (n = 189) were divided into five groups: normal control, diabetes, MCAO, diabetes + MCAO, and diabetes + MCAO + candesartan. The major observations were that 1) MCAO produced typical cerebral infarction and neurological deficits at 24 h that were accompanied by elevation of NAD(P)H oxidase gp91(phox) and p22(phox) mRNAs, and lipid hydroperoxide production in the ipsilateral hemisphere; 2) diabetes enhanced NAD(P)H oxidase gp91(phox) and p22(phox) mRNA expression, potentiated lipid peroxidation, aggravated neurological deficits, and enlarged cerebral infarction; and 3) candesartan reduced the expression of gp91(phox) and p22(phox), decreased lipid peroxidation, lessened cerebral infarction, and improved the neurological outcome. We conclude that diabetes exaggerates the oxidative stress, NAD(P)H oxidase induction, and brain injury induced by focal cerebral ischemia. The diabetes-aggravated brain injury involves AT(1)-Rs. We have shown for the first time that candesartan reduces brain injury in a combined model of diabetes and cerebral ischemia.

Animals↗