Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The functional capacity of the hepatic reticuloendothelial system (RES) was studied under conditions of intestinal shock. Wistar rats underwent intestinal ischemia (60 min)-reperfusion or a sham procedure. One-half of each group received intravenous infusion of 2.6 x 10(-6) g/kg lipopolysaccharide B. Phagocytic clearance and phagocytic killing by the hepatic RES were quantitated using a double label bacteria clearance assay. Hepatic phagocytosis was unchanged 3 h after reperfusion of the ischemic intestine but hepatic killing was significantly decreased compared with the sham situation. The results were not different in animals who had received LPS B infusion. The plasma endotoxin levels correlated inversely to the hepatic killing efficiency (r = -.801) in the shocked animals given exogenous endotoxin. The decreased capacity of the hepatic RES to degrade bacteria present in the portal circulation could be an important pathophysiologic mechanism in the development of bacterial translocation.
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PMID:Hepatic reticuloendothelial system dysfunction after intestinal ischemia-reperfusion. 882 Nov 7

The etiology of chronic rejection of kidney allografts is unknown, although hyperfiltration, acute rejection, viral infection and initial graft ischemia have been implicated. To test whether endothelial activation may be the link between these factors and chronic rejection, the endotoxin (lipopolysaccharide-LPS), a potent activator of endothelial cells, was evaluated in an established chronic rejection model. Bilaterally nephrectomized Lewis recipients of orthotopically transplanted Fisher 344 kidneys were treated briefly with low dose cyclosporine (1.5 mg/kg/day x 10). Recipients were given a non-lethal dose of LPS (2 mg) i.p. at 8 weeks and compared to allografted controls treated with vehicle. Urine protein was measured every 4 weeks. Rats in the treated group were sacrificed at 12 and 16 weeks, control animals at 12, 16 and 24 weeks (20/group) and examined histologically. In the chronically rejecting control allografts, progressive interstitial and glomerular sclerosis and vascular intimal proliferation had become apparent by 12 weeks. Infiltration of glomeruli, particularly by macrophages (M phi), and the coincident presence of cytokines were prominent, peaking at 16 weeks. LPS treatment accelerated and intensified these changes; proteinuria was more pronounced (16 weeks: 79 mg/24 h vs. 49 mg/24 h, p < 0.05). Numbers of infiltrating M phi peaked at 12 weeks in LPS treated hosts (69 c/FV vs. 27 c/FV in untreated controls, p < 0.01), accompanied by an increased upregulation of MHC class II and cytokine expression, particularly TNF alpha and PDGF around arteries and areas of infiltration. BY 16 weeks, 35 +/- 3% of glomeruli in LPS treated recipients had become sclerotic vs. 15 +/- 6% (p < 0.05) in controls, again associated with increased expression of cytokines (PDGF, TNF alpha, TGF beta), adhesion molecules (ICAM-1) and extracellular matrix proteins. Overall, the extent of chronic rejection of grafts in LPS treated rats at 16 weeks was similar to that developing in non-treated rats at 24 weeks. Activation of graft endothelium and/or host leucocytes increased the pace of graft infiltration and the expression of cytokines and other molecules. These events accelerate the process of chronic rejection.
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PMID:Infections and reduced functioning kidney mass induce chronic rejection in rat kidney allografts. 883 48

Reactive oxygen species such as nitric oxide (NO) and/or superoxide have been proposed as mediators in the pathogenesis of reperfusion injury and acute endotoxemia. The purpose of this study was to examine the role of NO in a model of hepatic ischemia-reperfusion with endotoxemia (I/R + LPS). Rats subjected to 30 min of partial hepatic ischemia followed by reperfusion and LPS (Salmonella enteritidis, 1 mg/kg, i.v.,) administration, exhibited a marked, time-dependent increase in plasma alanine aminotransferase (ALT) levels compared to sham controls. An abrupt increase in liver nitrite/nitrate levels was also observed in I/R + LPS rats in association with the increases in plasma ALT. Although liver NO production in I/R + LPS rats increased with time, exacerbation of liver damage was not evident. Administration of L-NAME decreased NO production in plasma and liver but did not affect the liver damage in rats subjected to I/R + LPS. Superoxide levels in livers from I/R + LPS rats increased by threefold after 90 min reperfusion as compared to sham controls but dropped to control levels after 4 hr. There was a significant increase in neutrophils in liver lobes subjected to ischemia-reperfusion and LPS compared to sham controls and to non-ischemic lobes which received LPS. The number of neutrophils in the liver increased further in rats given L-NAME. These results suggest that the progressive injury seen in livers of I/R + LPS rats was possibly due to NO interaction with superoxide forming another reactive oxygen species such as peroxynitrite. However, inhibition of NO synthesis did not ameliorate liver damage, possibly because of an increase in tissue accumulation of activated polymorphonuclear leukocytes (PMN). Lung NO production increased in I/R + LPS rats after 4 hr reperfusion compared to sham controls. Prior administration of L-NAME did not prevent a significant rise in pulmonary NO generation (P < 0.05 at 90 min and 4 hr, compared to sham controls). This unexpected rise of pulmonary NO in the L-NAME treated group of rats was associated with a tendency for increased PMN accumulation (based on myeloperoxidase data) and superoxide generation. The results suggest that endogenous NO protected against excessive neutrophil infiltration in the lung in this model of hepatic ischemia-reperfusion and endotoxemia, and the use of L-NAME, a nonselective NOS inhibitor, may aggravate lung injury.
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PMID:Role of nitric oxide in hepatic ischemia-reperfusion with endotoxemia. 884 95

Ischaemia in wounds may modulate the expression of tumour necrosis factor-alpha (TNF-alpha) and granulocyte-macrophage colony-stimulating factor (GM-CSF). The release of these and other cytokines by stimulated macrophages influences wound healing. Our aim was to examine the separate and combined effects of hypoxia and glucose deprivation on TNF-alpha and GM-CSF mRNA levels in human monocytes isolated from peripheral blood by density gradient centrifugation and purified by adherence. Cells were incubated for a 16-hour period in a hypoxic (3% O2) or normoxic (21% O2) environment in the presence or absence of glucose followed by a further 4 h under normoxic conditions in the presence or absence of lipopolysaccharide (LPS, 100 pg/ml). These different incubation conditions had no effect on cell viability, cell number, lactate dehydrogenase release or superoxide anion generation (n = 5, p > 0.05, paired t test). However, Northern hybridisation showed that hypoxia decreased the expression of GM-CSF mRNA in LPS-stimulated human monocytes by 46% (n = 9, p < 0.05, paired t test) and increased the expression of TNF-alpha by 102% (n = 7, p < 0.05, paired t test). The increase in the level of immunoreactive TNF-alpha in the cell supernatants paralleled the increase in TNF-alpha mRNA. The combination of glucose deprivation and hypoxia decreased the expression of both GM-CSF and TNF-alpha mRNA in LPS-stimulated human monocytes. Similarly, a decrease in the level of TNF-alpha in the cell supernatants was observed (n = 3-5, p < 0.05, two-way ANOVA). These data suggest that incubation conditions simulating ischaemia reduce LPS-induced cytokine expression.
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PMID:Influence of hypoxia and glucose deprivation on tumour necrosis factor-alpha and granulocyte-macrophage colony-stimulating factor expression in human cultured monocytes. 954 21

Septic shock is an increasingly important clinical condition, characterized by systemic hypotension, ischemia, and ultimately organ failure. In Gram negative infection, the bacterial cell wall component, lipopolysaccharide (endotoxin, LPS), has been strongly linked to the pathophysiological responses that result in septic shock. LPS is bound in plasma to a protein called LPS-binding protein (LBP), which facilitates the binding of LPS to a cell surface receptor, CD14. Binding to CD14 stimulates cell signaling mechanisms that result in the production of inflammatory cytokines. However, the events which follow LPS binding to CD14 and which lead to the production of cytokines remain unclear. It has recently become evident that a number of phosphorylation cascades including MAP kinase pathways and NF-kappaB activation pathway are initiated by exposure of cells to LPS. These cascades act at both the transcriptional and translational levels to regulate cytokine production. This review will focus on the signaling pathways that are initiated by LPS and the cellular effects of the signaling pathways.
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PMID:Cellular activation mechanisms in septic shock. 956 Mar 58

Vasoactive intestinal peptide (VIP) is a neuropeptide synthesized by immune cells that can modulate several immune aspects, including the function of cells involved in the inflammatory response, such as macrophages and monocytes. Production and release of cytokines by activated mononuclear phagocytes is an important event in the pathogenesis of ischemia-reperfusion injury. VIP has been shown to attenuate the deleterious consequences of this pathologic phenomenon. We have investigated the effects of VIP and PACAP38 on the production of interleukin-6 (IL-6), a proinflammatory cytokine, by endotoxin-activated murine macrophages. Both neuropeptides exhibit a dual effect on the IL-6 production by peritoneal macrophages. Whereas VIP and PACAP inhibit with similar dose-response curves the release of IL-6 from macrophages stimulated with a LPS dose range from 100 pg/mL to 10 microg/mL, both neuropeptides enhance IL-6 secretion in unstimulated macrophages and in macrophages stimulated with very low LPS concentrations (1-10 pg/mL). The inhibition on LPS-induced IL-6 production is specific, presumably mediated through a subtype of the PACAP-R. VIP and PACAP regulate the production of IL-6 at a transcriptional level. These results were correlated with an inhibition on both IL-6 expression and release in endotoxemic mice in vivo. These findings support the idea that in the absence of stimulation or in the presence of low doses of LPS, VIP and PACAP could play a role in immune system homeostasis. However, under toxicity conditions associated with high LPS doses, VIP and PACAP could act as protective mediators that regulate the excessive release of IL-6 in order to reduce inflammation or shock.
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PMID:Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide modulate endotoxin-induced IL-6 production by murine peritoneal macrophages. 958 3

Inhaled nitric oxide (NO) is being used more and more in intensive care units as a modality to improve the outcome of patients with pulmonary complications. Our objective was to demonstrate that inhaled NO could impact upon a distally inflamed microvasculature-improving perfusion, leukocyte adhesive interactions, and endothelial dysfunction. Using intravital microscopy to visualize ischemia/reperfusion of postcapillary venules, we were able to demonstrate that the reduction in perfusion, the dramatic increase in leukocyte rolling, adhesion, and emigration, and the endothelial dysfunction could all be significantly abrogated with 80 ppm, but not 20 ppm inhaled NO. Perfusing whole blood directly over an inert P-selectin and CD18 ligand substratum incorporated in a flow chamber recruited the same number of rolling and adhering leukocytes from NO-ventilated and non-NO-ventilated animals, suggesting that inhaled NO was not directly affecting leukocytes. To demonstrate that inhaled NO was actually reaching the peripheral microvasculature in vivo, we applied a NO synthase inhibitor locally to the feline mesentery and demonstrated that the vasoconstriction, as well as leukocyte recruitment, were essentially abolished by inhaled NO, suggesting that a NO-depleted peripheral microvasculature could be replenished with inhaled NO in vivo. Finally, inhaled NO at the same concentration that was effective in ischemia/reperfusion did not affect vascular alterations, leukocyte recruitment, and endothelial dysfunction associated with endotoxemia in the feline mesentery. In conclusion, our data for the first time demonstrate a role for inhaled NO as a therapeutic delivery system to the peripheral microvasculature, showing tremendous efficacy as an antiadhesive, antivasoconstrictive, and antipermeabilizing molecule in NO-depleted tissues, but not normal microvessels or vessels that have an abundance of NO (LPS-treated). The notion that blood borne molecules have NO carrying capacity is conceptually consistent with our observations.
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PMID:Inhaled NO as a viable antiadhesive therapy for ischemia/reperfusion injury of distal microvascular beds. 961 21

Vasoactive intestinal peptide (VIP) is a neuropeptide synthesized by immune cells that can modulate several immune aspects, including the function of cells involved in the inflammatory response, such as macrophages and monocytes. The production and release of cytokines by activated phagocytes are important events in the pathogenesis of ischemia-reperfusion injury. There is abundant evidence that the proinflammatory cytokine TNF-alpha is an important mediator of shock and organ failure complicating Gram-negative sepsis. VIP has been shown to attenuate the deleterious consequences of this pathologic phenomenon. In this study we have investigated the effects of VIP and the structurally related neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP38) on the production of TNF-alpha by endotoxin-activated murine peritoneal macrophages. Both neuropeptides rapidly and specifically inhibit the LPS-stimulated production of TNF-alpha, exerting their action through the binding to VPAC1 receptor and the subsequent activation of the adenylate cyclase system. VIP and PACAP regulate the production of TNF-alpha at a transcriptional level. In vitro results were correlated with an inhibition of both TNF-alpha expression and release in endotoxemic mice in vivo. The immunomodulatory role of VIP in vivo is supported by the up-regulation of VIP release in serum and peritoneal fluid by LPS and proinflammatory cytokines such as TNF-alpha, IL-1beta, and IL-6. These findings support the idea that under toxicity conditions associated with high LPS doses, VIP and PACAP could act as protective mediators that regulate the excessive release of TNF-alpha to reduce inflammation or shock.
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PMID:Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit endotoxin-induced TNF-alpha production by macrophages: in vitro and in vivo studies. 997 16

Experimental models of sepsis using endotoxin challenges, including studies with sensitized animals with D-galactosamine, have largely contributed to the basic rationale for innovative clinical trials in human septic shock, which have, to date, failed. The ability of these models to reproduce human disease has been highly discussed. We report here that the widely used D-galactosamine/LPS model does not account for septic shock. Treatment with YVAD-CMK, a potent tetrapeptide inhibitor of caspases of the interleukin (IL)-1beta converting enzyme (ICE) family, protects from LPS-induced liver apoptosis and mortality in D-galactosamine-sensitized mice when administered either before or up to 2 h after the lethal challenge. This curative effect is related to complete inhibition of caspase-3 activity in the liver. However, YVAD-CMK does not affect LPS-induced release of IL-1beta and does not protect from a lethal dose of LPS in unsensitized mice. These experiments demonstrate the difference between these two widely recognized experimental models of sepsis. LPS toxicity in D-galactosamine-treated mice, leading to blocked gene transcription, results from tumor necrosis factor (TNF)-alpha-induced caspase-3-dependent liver injury, not from the systemic inflammatory response. These results provide evidence that inhibitors of the ICE caspase family can prevent or even overcome the ongoing hepatic injury induced by TNF-alpha during sepsis, ischemia-reperfusion, or severe hepatitis.
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PMID:LPS challenge in D-galactosamine-sensitized mice accounts for caspase-dependent fulminant hepatitis, not for septic shock. 1019 82

Studies were undertaken to define the role of 5-lipoxygenase (5-LO) products and, in particular, of leukotriene (LT) B4 in the polymorphonuclear leukocyte (PMN) emigration process using a rabbit model of dermal inflammation. Our results show that i.v. administration to rabbits of MK-0591, a compound that inhibits LT biosynthesis in blood and tissues when administered in vivo, significantly reduced 51Cr-labeled PMN accumulation in response to intradermally injected chemotactic agonists, including IL-8, FMLP, C5a, and LTB4 itself. In addition, pretreatment of the labeled PMN with MK-0591 ex vivo before their injection in recipient animals was equally effective in reducing 51Cr-labeled PMN emigration to dermal inflammatory sites. These results support a role for de novo synthesis of 5-LO metabolites by PMN for their chemotactic response to inflammatory mediators. Other studies demonstrated that elevated intravascular concentration of LTB4 interferes with PMN extravasation inasmuch as a continuous i.v. infusion of LTB4, in the range of 5-300 ng/min/kg, dose-dependently inhibited extravascular PMN accumulation to acute inflammatory skin sites elicited by the chemoattractants LTB4, FMLP, C5a, and IL-8 and by TNF-alpha, IL-1beta, and LPS; such phenomena may constitute a natural protective mechanism from massive tissue invasion by activated PMN in specific pathologic conditions such as ischemia (and reperfusion). These studies demonstrate additional functions of 5-LO products in the regulation of PMN trafficking, distinct from the well-characterized chemotactic activity of LTB4 present in the extravascular compartment.
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PMID:Role of 5-lipoxygenase products in the local accumulation of neutrophils in dermal inflammation in the rabbit. 1047 17


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