ISSN:1073-2322    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Although circulating levels of interleukin 8 (IL-8), a potent pro-inflammatory chemokine, and many other inflammatory mediators increase in response to cardiopulmonary bypass, only a small proportion of patients develop a clinically significant systemic inflammatory response. The natural mechanisms that control the inflammatory response are poorly understood. To investigate the role of IL-8 in a human inflammatory model, 15 adult patients undergoing cardiopulmonary bypass for elective coronary artery bypass grafting were studied. Following reperfusion, plasma IL-8 levels increased significantly from 58 pg/mL (pre-bypass) and 66 pg/mL (after 20 min of bypass) to 98 pg/mL (p= .02 and .04, respectively), but this was accompanied by a concomitant threefold decrease in the IL-8 binding affinity of circulating neutrophils (Dissociation constant (KLpost-reperfusion/KLpre-bypass = 3.2;KLpost-reperfusion/KLafter 20 min of bypass = 2.8). IL-8-triggered release of myeloperoxidase and elastase by peripheral blood neutrophilsex vivowas also down-regulated following reperfusion. There were no significant changes in β2 integrin expression or inositol polyphosphate metabolism of peripheral blood neutrophils. These changes in receptor affinity and neutrophil responsiveness to IL-8 may represent an importantin vivoregulatory mechanism which serves to prevent excessive tissue injury from inflammatory triggers.

ISSN:1073-2322    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Activation of the complement system is an integral part of the initiation and maintenance of the inflammatory process such as that occurring in traumatic shock, and is considered responsible for much of the trauma-induced microvascular injury. We investigated the effects of early complement blockade induced by a C1 esterase inhibitor (C1 INH) in a rat model of traumatic shock. Pentobarbital-anesthetized rats subjected to Noble-Collip drum trauma developed a shock state characterized by marked hypotension and a 83.3% mortality rate with a mean survival time of 157.5 ± 26 min. Accompanying these effects were significant endothelial dysfunction and elevated intestinal myeloperoxidase activity. Treatment with C1 INH 15 mg/kg administered intravenously 10 min post-trauma, increased survival rate to 66.7% (p < .05), and prolonged survival time to 248 ± 27 min (p < .05). C1 INH significantly preserved the endothelium-dependent relaxation to acetylcholine and attenuated the increases in myeloperoxidase activity in C1 INH-treated rats compared with untreated trauma rats (p < .05). Our results suggest that complement activation plays an important role in tissue injury associated with trauma, and that its inhibition at an early step in the complement cascade through a C1 esterase inhibitor is beneficial in rats experiencing traumatic shock. The mechanisms of the protective effect of C1 INH involves preservation of vascular endothelial function and diminished neutrophil accumulation leading to reduced neutrophil-mediated tissue injury.

ISSN:1073-2322    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Activated macrophages are important cell effectors in sepsis/endotoxemia. Superoxide (SO) and nitric oxide (NO) are produced by activated macrophages and are responsible for host defense against microorganisms. Using laser scanning confocal microscopy, we investigated the role of intracellular free calcium ([Ca2+]i) on SO and NO production by rat peritoneal macrophages activated by lipopolysaccharide (LPS). Calcium influx from the extracellular space versus release of calcium from intracellular stores was determined using calcium channel blockers (diltiazem [DIL], verapamil [VER], and nicardipine [NIC]) and dantrolene (DAN), respectively. Cells incubated with LPS had a 30–50 nM increase in [Ca2+]i(p< .05) compared with non-LPS-treated cells. When stimulated with phorbol myristate acetate, both control and LPS-treated cells sustained a comparable increase in [Ca2+]i, but [Ca2+]i, remained elevated 30 min later in LPS-treated cells. Calcium channel blockers and DAN reduced phorbol myristate acetate-stimulated SO and LPS-stimulated NO production at all concentrations tested (p< .05). Although increased extracellular calcium influx and calcium from intracellular stores are important regulators of SO and NO production in macrophages, extracellular calcium influx seems to have the predominant effect. Calcium antagonists may modulate the inflammatory response via their effects on macrophages.

ISSN:1073-2322    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Neuronally secreted peptides are important mediators of hemodynamic changes in the systemic inflammatory response. The inositol derivative d-myo-inositol[1,2,6]triphosphate (α-trinositol) has been demonstrated to be a specific nonpeptide antagonist of vasoconstriction induced by neuropeptide Y. We induced sepsis by a 48 h continuous infusion ofPseudomonas aeruginosa(106colony-forming unit/min intravenously [i.v.]) in 12 chronically instrumented, conscious sheep. After 24 h, the animals were randomized to receive either α-trinositol (i.v. bolus of 2 mg/kg, followed by a continuous infusion of 3.5 mg/kg/h) or the saline carrier. α-Trinositol increased the heart rate (108 ± 4 to 152 ± 9 beats per minute) and reduced the stroke volume index (65 ± 5 to 49 ± 2 mL/beat/m2) but did not change cardiac index. Left ventricular stroke work decreased significantly (80 ± 9 to 58 ± 7 g·m/m2). All blood flows except the infrarenal aortic flow were increased after 24 h, but treatment decreased only the flow to the hind limb region. Urine output and fractional sodium excretion significantly increased without osmotic diuretic effects after α-trinositol. In treated animals, we found significantly lower leukocyte counts in all organ tissues. We conclude that α-trinositol modulates the cardiac performance and the local inflammatory response in tissues, and improves the fluid balance in septic sheep.

ISSN:1073-2322    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Apoptosis is well described in invertebrates and recently documented in mammals. The prevalence and pathophysiology of mammalian apoptosis is unknown and may have clinical ramifications. The aim of this study is to investigate the apoptotic response during kidney ischemia-reperfusion (I/R) injury. Kidney I/R was initiated in anesthetized rats by occlusion of the renal pedicle for 45 min with or without pretreatment with .2 mg/kg verapamil: control animals received sham exposure. Flow was re-established after ischemia and the animals were allowed to recover for 24 h. Bilateral kidneys were harvested for DNA electrophoresis, Western analysis for p53, Northern analysis for c-myc expression, and light and electron microscopic analysis. Kidney I/R caused characteristic DNA laddering in the clamped kidney, and less extensive laddering was seen in the contralateral kidney. Light and electron microscopic analysis confirmed apoptotic morphology in the reperfused tissues. Verapamil pretreatment completely abolished DNA laddering and attenuated the microscopic evidence of apoptosis. p53 levels were increased by I/R in the ischemic kidney and moderately increased in the contralateral organ, c-myc mRNA levels were increased by the I/R insult. Kidney I/R injury may induce global apoptosis, which seems to be associated with an alteration in calcium homeostasis. The increase in p53 and c-myc mRNA levels seen with I/R may facilitate apoptosis. Calcium modulation seems to reduce apoptosis during I/R and may have therapeutic implications.

ISSN:1073-2322    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Up-regulation of the leukocyte β2integrin, CD18, is a key event in neutrophil-endothelial adhesion and neutrophil-mediated organ injury. Inhibition of CD18 with monoclonal antibodies reduces lung and liver neutrophil sequestration in animal models of Gram-negative bacteremia or endotoxemia. However, with a persistent septic challenge, interference with host leukocyte phagocytic defense could adversely affect outcome. To assess the effects of inhibiting CD18 on organ neutrophil responses, bacteremia, and organ injury after fecal peritonitis, mice underwent cecal ligation and puncture (CLP). At the time of CLP and 12 h later, mice received intravenous anti-CD18 antibody or control IgG. At 3, 6, and 18 h after CLP, lung and liver tissue neutrophil content were measured by myeloperoxidase (MPO) assay, peritoneal cells and blood leukocytes were differentially counted, blood was cultured, and serum aspartate aminotransferase was measured. There was a significant reduction in peritoneal neutrophil migration and an increase in blood neutrophils after anti-CD18 treatment compared with results from treatment with the control antibody. In the anti-CD18-treated group, liver MPO was increased fivefold at 6 and 18 h, while lung MPO was increased two-fold at 18 h when compared with the control antibody-treated group. The anti-CD18-treated group also had an increase in bacteria cultured from the blood at 6 and 18 h and an increase in serum aminotransferase at 18 h. Our data demonstrate that peritoneal neutrophil migration in response to an endogenous fecal challenge is CD18-dependent, and that this mechanism forms a vital part of host defense. Inhibition of CD18 increased neutrophil sequestration in the liver and lung and increased liver injury. This study demonstrates a paradoxical increase in organ neutrophil sequestration using a leukocyte anti-adhesion therapy during sepsis and suggests that anti-adhesion therapies targeted towards neutrophil may worsen outcome if given during an ongoing, localized infection.

ISSN:1073-2322    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Platelet-activating factor (PAF) is a potent vasoactive and inflammatory lipid mediator which has been implicated in the hemodynamic alterations of endotoxemia and sepsis. Different PAF receptor antagonists have been shown to attenuate the systemic and pulmonary disturbances of sepsis, but they were generally administered before the injection of endotoxin and their effects have not been consistent. To examine the effects of BB-882, a novel potent PAF receptor antagonist, on general hemodynamics and regional flow distribution in a canine endotoxic shock model, 14 anesthetized and ventilated dogs received 2 mg/kg ofEscherichia coliendotoxin intravenously (i.v.) followed by generous fluid resuscitation. Thirty minutes later, the dogs received either BB-882 (n = 7) as a continuous i.v. infusion with hourly increasing doses (2, 5, and 10 mg/kg·h, respectively) or a corresponding amount of saline (n = 7). The administration of BB-882 resulted in a dose-dependent reduction in cardiac output and an increase in systemic and pulmonary vascular resistance. Mesenteric and renal flow were not different from control values whereas femoral blood flow progressively decreased. Another group of 7 dogs received 5 mg/kg i.v. bolus of BB-882 30 min before endotoxin. Pretreatment significantly increased mesenteric blood flow by about 50% but did not show any significant hemodynamic effects. This study demonstrates that the administration of a PAF receptor antagonist following endotoxic shock in fluid resuscitated dogs does not offer significant hemodynamic benefit. Pretreatment with BB-882 at the dose used only enhanced mesenteric perfusion. These findings do not support beneficial effects of PAF receptor antagonists in septic shock.

ISSN:1073-2322    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Net pulmonary vascular tone is determined by the balance of pulmonary vasorelaxation and vasoconstriction. In endotoxemic rats, cGMP-mediated pulmonary vasorelaxation is impaired through neutrophil-dependent mechanisms, yet agonist stimulated vasoconstriction remains intact. Endotoxin-induced lung neutrophil accumulation is a transient response. In models of myocardial ischemia-reperfusion injury, “stunning” or reversible cardiac dysfunction is also associated with a reversible neutrophil presence. We hypothesized that lung neutrophil accumulation and dysfunction of cGMP-mediated pulmonary vasorelaxation is reversible after an endotoxin challenge. Our purpose was to examine lung neutrophil accumulation and endothelium-dependent and -independent mechanisms of cGMP-mediated pulmonary vasorelaxation 4 and 48 h after endotoxin challenge. Rats (n = 5 per group) were studied 4 and 48 h after injection of saline or endotoxin (500 μg/kg, intraperitoneal). Endothelium-dependent relaxation by receptor-dependent (acetylcholine) and -independent (A23187) mechanisms and endothelium-independent (sodium nitroprusside) relaxation were studied in isolated pulmonary artery rings preconstricted with phenylephrine. Lung neutrophil accumulation was examined by lung myeloperoxidase assay. Lung neutrophil accumulation was increased at 4 h (p< .05 vs. control) and was attenuated by 48 h (p< .05 vs. endotoxin × 4 h) following endotoxin challenge. Similarly, the endotoxin-induced dysfunction of endothelium-dependent and -independent cGMP-mediated pulmonary vasorelaxation at 4 h normalized by 48 h. Endotoxin appears to induce reversible dysfunction of pulmonary vasorelaxation through stunning of vascular endothelial and smooth muscle cells.

ISSN:1073-2322    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Induction of heat shock proteins (HSPs) confers protection against a variety of cytotoxic agents. We hypothesized that induction of HSPs would protect cultured human respiratory epithelium against nitric oxide (NO)-mediated injury. Incubation of a human bronchial epithelial cell line (BEAS-2B cells) at 43°C for 1.5 h induced expression of several HSPs. Prior induction of HSPs was associated with protection against the NO-donorsS-nitroso-N-acetyl penicillamine and 3-morpholinsydnonimine. Protection was evident as improved short term survival and improved ability of cells to recover and proliferate after exposure to NO. Prior induction of HSPs also attenuated NO-mediated decreases in cellular ATP levels, but did not decrease nitrotyrosine formation. Specific overexpression of HSP-70 by plasmid-directed gene transfer protected murine respiratory epithelial cells againstS-nitroso-N-acetyl penicillamine. We conclude that in cultured human respiratory epithelium induction of HSPs confers protection against NO-mediated cytotoxicity, possibly by preservation of cellular energetics. We also suggest that HSP-70 may play a specific role in protection.

ISSN:1073-2322    

出版商:OVID    

年代:1997

数据来源: OVID