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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Myocardial dysfunction following prolonged ischemia and reperfusion is at least partially dependent upon adhesion of neutrophils to myocardial and endothelial cells. Neutrophils are thought to contribute to reperfusion injury by two mechanisms: impairment of the microvasculature by physical obstruction, and secretion of products that damage microvasculature and myocardium. Cytokines have been shown to play several roles in neutrophil aggregation. Interleukin-6 (IL-6), along with IL-1 and tumor necrosis factor-alpha (TNF-alpha), induces the expression of intracellular adhesion molecule-1 (ICAM-1) in myocytes and endothelial cells, respectively. These cytokines also inhibit contractility and nitric oxide release (a vasodilator), and IL-1 and TNF-alpha have been found to reduce adrenergic stimulation of myocardial contractility by reducing intracellular cyclic AMP levels and uncoupling adenylate cyclase from beta receptors. The transforming growth factors, TGF-alpha and TGF-beta, also have a role in reperfusion injury. TGF-alpha reduces endothelial cell release of nitric oxide, while TGF-beta appears to protect against reperfusion injury by reducing plasma TGF-alpha levels, blocking neutrophil adherence, and promoting nitric oxide release. Although cytokines are likely to have important roles in reperfusion injury, their involvement in myocardial stunning is unclear.
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PMID:Cytokines and reperfusion injury. 846 22

Interleukin 2 (IL-2) mediates the regression of metastatic cancer, but its clinical use is limited by associated toxicities including hepatic dysfunction. To determine the mechanism for IL-2-induced hepatic dysfunction, we hypothesized that IL-2 activation of Kupffer cells causes leukocyte-endothelial adhesion and decreases hepatic sinusoidal blood flow. C57BL/6 mice were given injections of latex particles and prepared for intravital hepatic microscopy 2 h after i.p. IL-2 administration. Liver tissue was also prepared to quantitate hepatic tumor necrosis factor (TNF) mRNA and processed for light and electron microscopy. Phagocytosing Kupffer cells and leukocytes adherent to the endothelium were counted, and surface sinusoidal blood flow was quantitated. Kupffer cell activity was quantitated as the ratio of phagocytosing Kupffer cells to sinusoidal blood flow. IL-2 significantly increased Kupffer cell activity (0.56 +/- 0.05 for controls versus 0.84 +/- 0.05 for IL-2), significantly caused leukocyte-endothelial adhesion (26.7 +/- 7.9 for controls versus 87.0 +/- 27.6 for IL-2, WBC/mm2 endothelial surface), and significantly decreased the number of sinusoids containing blood flow per microscopic field (6.66 +/- 0.15 for controls versus 5.79 +/- 0.13 for IL-2) without causing changes in systemic hemodynamic parameters. In IL-2 treated livers, light and electron microscopy showed the constriction of sinusoids associated with swollen or ruptured mitochondria, which was consistent with hypoxic deterioration near central venules. Adherent platelets, neutrophils, and lymphocytes within sinusoids and central venules were also observed. PCR revealed that IL-2 significantly induced TNF mRNA expression in the liver. These data suggest that IL-2 activates Kupffer cells in association with the release of monokines including TNF, which causes activation of circulating leukocytes as well as hepatic sinusoidal endothelial cells. The resultant leukocyte and platelet adhesion to the endothelium may then physically impede the sinusoidal microcirculation, resulting in microscopic areas of hepatic ischemia and explaining the mechanism of IL-2-induced hepatic dysfunction.
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PMID:Mechanisms of interleukin-2-induced hepatic toxicity. 856 62

Cardiac surgery with cardiopulmonary bypass triggers an inflammatory response involving proinflammatory cytokines such as tumor necrosis factor-alpha, interleukin-6, and interleukin-8. To elucidate the pathophysiology of this cytokine response, we explored the possible differences in cytokine responses between patients undergoing heart transplantation and those undergoing coronary artery bypass grafting. Plasma levels of tumor necrosis factor-alpha, interleukin-6, interleukin-8, and interleukin-10 were measured in eight patients undergoing heart transplantation (mean age 44 years) and eight patients undergoing coronary artery bypass grafting (mean age 61 years). Duration of cardiopulmonary bypass and ischemic time were both longer in the heart transplantation group than in the coronary artery bypass grafting group (133 +/- 26 min vs 100 +/- 31 min, p < 0.05, and 130 +/- 47 min vs 58 +/- 21 min, p < 0.005, respectively). Samples were collected before heparin administration, at aortic crossclamping and declamping, and at 0.5, 1, 1.5, 2, 4, 12, and 24 hours after declamping. Tumor necrosis factor-alpha levels were significantly higher 30 minutes after aortic declamping in the heart transplantation group than in the coronary artery bypass grafting group (68 +/- 30 vs 18 +/- 5 pg/ml, p < 0.05). Interleukin-6 and interleukin-8 levels were also significantly higher 90 minutes after declamping in patients undergoing heart transplantation than in those undergoing coronary artery bypass grafting (310 +/- 63 vs 169 +/- 24 pg/ml, p < 0.05, and 73 +/- 17 vs 24 +/- 5 pg/ml, p < 0.01, respectively). Furthermore, interleukin-6 and interleukin-8 values 90 minutes after declamping were significantly correlated with the ischemic time (r = 0.72 and r = 0.82, respectively, both p < 0.05). Interleukin-10 levels in both groups rose to reach a peak value of around 115 pg/ml 1 hour after declamping. Patients undergoing heart transplantation exhibited a second peak of tumor necrosis factor-alpha, interleukin-8, and interleukin-10 levels 12 hours after declamping, probably related to the administration of rabbit antihuman thymocyte immunoglobulin (Thymoglobuline) 3 hours after declamping. Interleukin-6 levels decreased more significantly 12 and 24 hours after declamping in patients undergoing heart transplantation, probably related to methylprednisolone therapy. In conclusion, cardiopulmonary bypass is associated with the production of both proinflammatory and antiinflammatory cytokines. The production of proinflammatory cytokines in patients undergoing heart transplantation is higher than that in patients undergoing coronary artery bypass grafting, and this increase could be related to the longer duration of ischemia in the former group. The later course of cytokine levels after heart transplantation may be further influenced by immunosuppressive therapy.
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PMID:Human cytokine responses to cardiac transplantation and coronary artery bypass grafting. 875 37

Intestinal ischemia-reperfusion (I/R) causes local and distant tissue injury via neutrophil (PMN) activation and adhesion. Endothelial cell adhesion molecules (E-selectin, ICAM-1) mediate the adhesion and transmigration of PMN in the microcirculation. Expression of these receptors is influenced by cytokines. To determine the physiologic concentrations of two specific cytokines involved in I/R, tumor necrosis factor (TNF) and interleukin-1 (IL-1), human intestinal segments were exposed to 30 min of ischemia followed by reperfusion. Venous effluent samples were obtained; enzyme immunoassays measured maximum concentrations of TNF (30.5 +/ 1.0 pg/ml) and IL-1 (59.0 +/- 6.0 pg/ml). Cultured human endothelial cells were then exposed to physiologic concentrations of human recombinant TNF (10 pg/ml) and IL-1 (10 pg/ml), individually and in combination. Flow cytometric analysis of receptor expression demonstrated upregulation of E-selectin as early as 2 hr (P < 0.05) with maximum effects at 4 hr. At 4 hr, E-selectin expression (% shift from baseline) was greater with TNF and IL-1 combined (50.9 +/- 2.9, P < 0.01) than with either cytokine alone (TNF 34.6 +/- 4.0; IL-1 23.5 +/- 4.0, P < 0.01). ICAM-1 receptor expression began at 4 hr with maximum effects at 24 hr. ICAM-1 expression after TNF and IL-1 exposure (15.4 +/- 1.3, P < 0.001) was also greater than TNF (10.9 +/- 0.3, P < 0.01) or IL-1 (3.1 +/- 1.5) alone. TNF and IL-1 are present in venous effluent in concentrations capable of increasing PMN adhesion in the microcirculation. These findings support a role for these cytokines in local and distant organ injury from I/R. Since combined effects are greater than either cytokine alone, antagonism of both TNF and IL-1 may be required for a therapeutic benefit in clinical applications.
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PMID:Physiologic concentrations of TNFalpha and IL-1beta released from reperfused human intestine upregulate E-selectin and ICAM-1. 866 Dec 21

Granulocytes play a significant role in vascular diseases. The mechanisms of neutrophil-mediated vascular injury include their increased endothelial adhesion and activation with release of inflammatory mediators. Pentoxifylline (PTX) has a well-demonstrated ability to act on the activated neutrophils. It increases chemotaxis and decreases their adherence to endothelial cells, oxidative burst, and enzyme release. In this preliminary study, we investigated the effects of PTX on ischemia-induced changes in polymorphonuclear neutrophils (PMN) activation and cytokine release. A double-blind, randomized, placebo-controlled trial was carried out in 14 patients (age range 46-86 years) suffering from critical ischemia, as defined by the European Consensus Document, or subacute ischemia due to occlusive arterial disease of the lower limb. Femoral and antecubital venous blood samples on the side of the ischemic leg were obtained from patients immediately before (TO) and after infusion (T24) of PTX or placebo. PMN activation was evaluated by study of cell migration, beta 2 integrin expression (CD11b/ CD18), oxidative burst, and elastase release. Inflammation proteins were analyzed, such as tumor necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1), interleukin-6 (IL-6), C-reactive protein (CRP), and fibrinogen. Before treatment, our results demonstrate an important activation in both femoral and antecubital venous blood. PMN activation markers, cytokine release, and other inflammation proteins were significantly increased compared with normal subjects. In the experimental group there was no significant difference between femoral and antecubital venous blood. Six patients received PTX infusion and seven patients were in the placebo group. The effect of PTX was evaluated after 24 h of treatment (1,200 mg). In the PTX group the following variables were improved compared with the placebo group: CD11b expression on PMNs, elastase released from PMNs, fibrinogen, CRP, TNF-alpha, and IL6 in plasma. These preliminary results should be interpreted with caution because of the small sample size. Further trials may contribute to more complete understanding.
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PMID:Leukocyte activation study during occlusive arterial disease of the lower limb: effect of pentoxifylline infusion. 869 73

The effects of transient global ischemia using bilateral carotid artery occlusion on regional cytokine levels in gerbil brain were investigated using enzyme-linked immunoassay techniques. Brain concentrations of interleukin-6 (IL-6), interleukin-1 beta (IL-1 beta), and tumor necrosis factor-alpha (TNF-alpha) were increased during the early recirculation period ( < 6 h) after 10 min of ischemia, with lesser degrees of elevation following only 5 min of ischemia. TNF-alpha levels in the hippocampus and striatum were significantly increased as early as 1 h after recirculation, declining sharply to control levels by 12 h, then transiently increasing at 24 h. Elevated levels of IL-1 beta and IL-6 were not seen until 3-6 h post-occlusion. No significant increases in cytokine concentrations were observed in the cerebellum or thalamus. These results suggest that regionally selective increases in cytokines may be involved in the pathophysiological changes in hippocampus and striatum following transient cerebral ischemia.
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PMID:Early increases in TNF-alpha, IL-6 and IL-1 beta levels following transient cerebral ischemia in gerbil brain. 871 Jan 73

In this study, we investigated the effects of a glycine-containing diet (5%) on mortality and liver injury due to intravenous injection of endotoxin [Escherichia coli lipopolysaccharide (LPS)] in Sprague-Dawley rats in vivo. Fifty percent of the rats fed control diet died within 24 h after an intravenous injection of LPS (10 mg/kg), whereas feeding the rats glycine totally prevented mortality and markedly reduced an LPS-induced elevation of serum transaminase levels, hepatic necrosis, and lung injury. The elevation in serum tumor necrosis factor-alpha (TNF-alpha) due to LPS was also blunted and delayed significantly by glycine feeding. In a two-hit model (hepatic ischemia-reperfusion and injection of sublethal LPS), all rats fed control diet died, whereas 83% of glycine-fed animals survived with a significant reduction in transaminases and improved liver and lung histology. LPS elevated intracellular Ca2+ concentration ([Ca2+]i) in cultured Kupffer cells, an effect blocked almost completely by glycine. Glycine most likely reduces injury and mortality by preventing the LPS-induced elevation of [Ca2+]i in Kupffer cells, thereby minimizing toxic eicosanoid and cytokine production.
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PMID:A diet containing glycine improves survival in endotoxin shock in the rat. 876 Jan 12

We tested the hypothesis that gram-negative bacteremia (GNB) and brief (30 min) reductions in the hepatic O2 supply by low-flow ischemia differentially modulate tumor necrosis factor-alpha (TNF-alpha) gene expression owing to sequence-specific activation of cyclooxygenase vs. complement (C) pathways. Buffer-perfused Sprague-Dawley rat livers (n = 82) were studied over 180 min after intraportal 10(9) live E. coli serotype 055:B5 (EC) or 0.9% NaCl (NS) at t = 0. Compared with EC and NS controls receiving constant-flow perfusion, sequential GNB and ischemia/reperfusion (I/R) were studied in EC + 30 I/R and NS + 30 I/R livers, in which 30 min of ischemia (I) beginning 0.5 h after EC or NS was followed by 120 min of reperfusion (R). This sequence was reversed in 30 I/R + EC and 30 I/R + NS groups. Bacterial clearance, bioactive and antigenic TNF-alpha, prostaglandin E2 (PGE2), and hepatic O2 uptake and performance were serially assessed. Venous TNF-alpha increased in EC controls to peak at 155 +/- 29 U/ml after 180 min (P < 0.001 vs. NS controls) as did hepatic TNF-alpha mRNA. Both TNF-alpha transcripts and protein levels were markedly attenuated in EC + 30 I/R (P < 0.001 vs. EC) despite equivalent EC clearance by Kupffer cells. Indomethacin (10(-5) M) decreased I/R-induced PGE2 secretion and restored TNF-alpha to control levels. In contrast, TNF-alpha levels in 30 I/R + EC perfusates exceeded those of EC + 30 I/R livers (P < 0.05) and were indistinguishable from EC controls. Allopurinol pretreatment but not heat inactivation of C or infusion of soluble human complement receptor type 1 inhibited TNF-alpha production in 30 I/R + EC organs. These results identify a novel sequence-dependent interaction whereby hepatic O2 deprivation after GNB downregulates TNF-alpha via generation of cyclooxygenase metabolites, whereas ischemia preceding GNB increases cytokine expression via reactive O2 species but not C activation.
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PMID:Bidirectional effects of hepatic ischemia/reperfusion on E. coli-induced TNF-alpha gene expression. 876 13

Pulmonary edema following reperfusion is a major clinical problem. Changes in endothelial cell shape induced by oxidant injury may account for immediate capillary leakage associated with reperfusion injury. In these experiments we examined the role of tumor necrosis factor-alpha (TNF-alpha) in acute endothelial cell injury following ischemia-reperfusion. Sprague-Dawley rats were treated with a neutralizing antisera directed against TNF-alpha prior to production of distal ischemia. These rats demonstrated a significant reduction (P < 0.05) in acute lung edema in response to 4 hr of ischemia and 30 min of reperfusion when compared to rats undergoing the same procedure without antisera treatment. An in vitro model was developed to determine if TNF-alpha had a direct effect on endothelial cell response to ischemia-reperfusion. The effects of TNF-alpha and oxidant stress on the integrity of cultured endothelial cell monolayers was measured. Rat pulmonary artery endothelial cell monolayers reacted in vitro to oxidant stress by an increase in permeability. The cells changed shape and an increase in diffusion of 125I-albumin across cell monolayers resulted when these cells were exposed to 50 microM hydrogen peroxide (H2O2) or plasma from the ischemic hind limb of a Sprague-Dawley rat (50 microliters/ml). Pretreatment of cultured cells with low levels of recombinant mouse TNF-alpha significantly affected both the cell shape change and the increase in permeability (P < 0.05). Increased permeability of cell monolayers in vitro was not due to cell lysis as determined by media lactate dehydrogenase levels. The effect appeared to be due to cellular rounding and contraction seen using video time lapse microscopy. These data suggest a direct effect of TNF-alpha on endothelial cells, whereby the cells are rendered more susceptible to oxidant injury accompanying reperfusion.
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PMID:TNF-alpha potentiates oxidant and reperfusion-induced endothelial cell injury. 876 63

Ischemia is an interruption of oxygen and nutrient supply to a determined area of tissue for a period of time. Because of the heterogeneity of various tissues with regard to their microvascular flow reserve and oxidative capacity, as well as their markedly different metabolic needs, a single critical Po2 level below which ischemia occurs is unlikely. This is why there are variations of tolerance to hypoxia within and among organs. In general, when Pao2 reaches approximately 5 torr there is already evidence, in some organs, of altered cellular energetics. In addition, cessation of flow impairs the incoming transfer of nutrients such as glucose, and cells must depend on their own intracellular stores of carbon radicals, if available. Epidemiologic data suggest that there are deleterious effects of hypoxia on the immune system and that these effects result in increased susceptibility to infection. The histology of ischemic tissues demonstrates intravascular neutrophil (PMN) accumulation, vascular damage, and increased vascular permeability. Expression of PMN adhesion receptors is increased when oxygen is nearly completely removed from the medium. Expression of integrins on the cell surface is regulated by intracellular calcium; hypoxia causes a sustained and prolonged increase of intracellular calcium levels. Because both granule movement and functional expression of adhesion receptors on the cell surface are important in leukocyte motility, chemotaxis, and phagocytosis, these functions may be impaired by hypoxia. Exposure of a human macrophage cell line to nonlethal levels of hypoxia causes in vitro release of significant amounts of biologically active cytokines tumor necrosis factor (TNF) alpha, interleukin (IL)-1 and IL-8, as well as expression of intercellular adhesion molecule-1 and bound and soluble receptors for TNF alpha. Hypoxia markedly decreases T-lymphocyte IL-2 messenger RNA, a key cytokine responsible for B-cell proliferation and immunoglobulin secretion.
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PMID:Leukocyte responses to hypoxic/ischemic conditions. 877 94


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