Monoclonal antibody to tumor necrosis factor-alpha attenuates hemodynamic dysfunction secondary to intestinal ischemia/reperfusion in rats

Functional roles of tumor necrosis factor-alpha and interleukin 1-Beta in hypoxia and reoxygenation

BACKGROUND

Intercellular signaling plays an important role in the development of lung ischemia-reperfusion injury. However, the role of specific mediators remains poorly characterized. Alveolar macrophages (AM) produce soluble mediators early in reperfusion, which modulate the responses of endothelial and epithelial cells to oxidative stress. There is a burst of proinflammatory cytokine production in a variety of cells; however, interleukin 1-beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) localize to the AM. We hypothesized that these cytokines account for the costimulatory effects that AM exert on endothelial and epithelial cells.

METHODS

Activated AM media was placed on cultured rat type 2 pneumocytes and pulmonary artery endothelial cells, which were then subjected to hypoxia and reoxygenation. To assess the contributions of IL-1β and TNF-α, the cells were treated with control media or media that had been depleted of IL-1β or TNF-α. To deplete specific cytokines, activated media was passed through a column with immobilized IL-1β or TNF-α antibodies. Nuclear translocation of transcription factors, mitogen-activated protein kinase activation, and cytokine and chemokine production were assessed.

RESULTS

Depletion of IL-1β or TNF-α effectively eliminated the ability of AM media to enhance the response of endothelial and epithelial cells to oxidative stress. There were significant reductions in monocyte chemotactic protein 1 and cytokine-induced neutrophil chemoattractant (CINC) production (p < 0.05) at 4 hours of reperfusion. Additionally there was decreased nuclear translocation of nuclear factor-kappa B, and extracellular signal-regulated kinase phosphorylation.

CONCLUSIONS

Interleukin 1-beta and TNF-α are critical mediators in the intercellular communication pathways that allow the AM to enhance the response of surrounding cells to oxidative stress.

Dexamethasone pretreatment alleviates intestinal ischemia-reperfusion injury

BACKGROUND

Activated mast cells are involved in the pathogenesis of intestinal ischemia-reperfusion (I/R)-related injury. Dexamethasone has been widely used to protect organs from I/R injury. This study was conducted to investigate the impact of treatment with dexamethasone at different stages of the II/R process on mast cell infiltration and activity and intestinal injury.

METHODS

Kunming mice were randomized and subjected to a sham surgery or the II/R induction by clamping the superior mesenteric artery for 30 min and then reperfusion. During the II/R induction, the mice were treated intravenously with dexamethasone (10 mg/kg) for 30 min before ischemia (pretreatment group), at 5 min after clamping the superior mesenteric artery (isc-treatment group), or at the beginning of perfusion (rep-treatment group), respectively. The levels of intestinal injury, mast cell infiltration and activity, tumor necrosis factor α (TNFα) and myeloperoxidase (MPO) activity in the intestines, and mouse survival rates were measured.

RESULTS

The death rates, levels of intestinal injury, mast cell infiltration and activity, and tumor necrosis factor α and myeloperoxidase activity in the intestinal tissues from the II/R group were similar to those from the isc-treatment and rep-treatment groups of mice and were significantly higher than those from the sham group. In contrast, pretreatment with dexamethasone significantly mitigated the II/R-induced mast cell infiltration and activity, inflammation, and intestinal injury and reduced the death rates in mice.

CONCLUSIONS

Pretreatment with dexamethasone inhibits II/R injury by reducing mast cell-related inflammation in mice.

Protective role of μ opioid receptor activation in intestinal inflammation induced by mesenteric ischemia/reperfusion in mice

Intestinal ischemia is a clinical emergency with high morbidity and mortality. We investigated whether activation of μ opioid receptor (μOR) protects from the inflammation induced by intestinal ischemia and reperfusion (I/R) in mice. Ischemia was induced by occlusion of the superior mesenteric artery (45 min), followed by reperfusion (5 hr). Sham-operated (SO) and normal (N) mice served as controls. Each group received subcutaneously 1) saline solution, 2) the μOR selective agonist [D-Ala2, N-Me-Phe4, Gly5-ol]-enkephalin (DAMGO; 0.01 mg kg(-1) ), 3) DAMGO and the selective μOR antagonist [H-D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2] (CTAP; 0.1 mg kg(-1) ), or 4) CTAP alone. I/R induced intestinal inflammation as indicated by histological damage and the significant increase in myeloperoxidase (MPO) activity, an index of tissue neutrophil accumulation. Tumor necrosis factor-α (TNF-α) and interleukin-10 (IL-10) mRNA levels were also increased in I/R mice compared with SO. DAMGO significantly reduced tissue damage, MPO activity, and TNF-α mRNA levels in I/R, and these effects were reversed by CTAP. By contrast, DAMGO did not modify IL-10 mRNA levels or gastrointestinal transit. DAMGO's effects are receptor mediated and likely are due to activation of peripheral μORs, because it does not readily cross the blood-brain barrier. These findings suggest that activation of peripheral μOR protects from the inflammatory response induced by I/R through a pathway involving the proinflammatory cytokine TNF-α. Reduction of acute inflammation might prevent I/R complications, including motility impairment, which develop at a later stage of reperfusion and likely are due to inflammatory cell infiltrates.

Evaluation of early macrophage activation and NF-kappaB activity in pulmonary injury caused by deep hypothermia circulatory arrest: an experimental study

This study aimed to analyze changes in nuclear factor-kappa B (NF-kappaB), inflammation factors, and macrophages in pulmonary tissue under deep hypothermia circulatory arrest (DHCA) at different time points, which can be used to infer the role of early macrophage activation and NF-kappaB activity in pulmonary injury. The possible pathogenic mechanisms of DHCA-induced pulmonary injury were investigated in this study to provide an experimental basis for clinical lung protective strategies. Piglets (n = 12) were randomly divided into 2 groups, with 6 piglets in each group. The control group had ambient temperature cardiopulmonary bypass (CPB), and the experimental group had DHCA. Both groups had conventional CPB with 30 min of parallel circulation. Changes in NF-kappaB and inflammatory factors were examined in each group at 6 different time points. At 0.5 h after ischemia-reperfusion, NF-kappaB expression in the nucleus of pulmonary tissue reached its peak, and brown-stained nuclei were mainly polymorphonuclear antibodies. At 1 h after ischemia-reperfusion, plasma tumor-necrosis factor (TNF)-alpha in the experimental group was significantly increased compared with that before reperfusion (P < 0.05). The plasma levels of interleukin (IL)-8 and IL-6 in the experimental group were significantly increased at 1.5 h after ischemia-reperfusion compared with the levels before reperfusion (P < 0.05). Early activation of NF-kappaB under DHCA might play an important role in DHCA-induced pulmonary injury.

Activated protein C and normal saline infusion might prevent deleterious effects of remote acute lung injury caused by intestinal ischemia-reperfusion: an experimental study in the rat model

BACKGROUND

Intestinal ischemia-reperfusion is a common medical event associated with both clinical and experimental distant organ injury. In particular, the lung tissue appears to be susceptible to injury resulting from systemic inflammatory mediator activation. Drotrecogin α (activated) or recombinant human activated protein C has antithrombotic, anti-inflammatory, and profibrinolytic properties. We hypothesized that APC infusion would decrease lung inflammation and ameliorate lung injury resulting from intestinal ischemia-reperfusion (IIR). A rat model of intestinal ischemia-reperfusion was used to test this hypothesis, and several parameters of lung injury were measured in lung samples.

MATERIAL AND METHODS

Forty Wistar albino rats were divided into four groups: a sham-operated group (Sham), an ischemic control group (IIR), an APC-infusion group (IIR'APC), and a normal saline-infusion group (IIR'NS) (n = 10, each). A marker for lipid peroxidation, malondialdehyde (MDA), free radical scavenger glutathione peroxidase (GSH-Px), an index of polymorphonuclear neutrophils, myeloperoxidase (MPO) activity, and lung polymorphonuclear leukocytes (PMNL) were investigated in the lung tissue samples.

RESULTS

MDA and MPO levels, and lung PMNL sequestration were decreased, but GSH-Px levels were increased in APC treated group versus IIR group. MDA levels were decreased and GSH-Px levels were increased in NS treated group versus IIR group. MPO levels and lung PMNL counts were similar across the IIR and IIR'NS groups.

CONCLUSIONS

This study documents that APC attenuates acute lung injury in intestinal ischemia-reperfusion. NS infusion had also some favorable effects regarding MDA and MPO.

Lung injury after in vivo reperfusion: outcome at 27 hours after reperfusion

BACKGROUND

Although short-term findings after lung reperfusion have been extensively reported, in vivo animal studies have not described outcome beyond the immediate time period. Therefore, the authors evaluated lung injury 27 h after reperfusion. They also investigated whether attenuation of lung injury with the A3 adenosine receptor agonist MRS3558 was sustained beyond the immediate time period.

METHODS

In intact-chest, spontaneously breathing cats in which the left lower lung lobe was isolated and subjected to 2 h of ischemia and 3 h of reperfusion, MRS3558 was administered before reperfusion. Animals were killed 3 or 27 h after reperfusion.

RESULTS

When compared with 3 h of reperfusion, at 27 h the left lower lobe showed reduced apoptosis and no change in inflammation, but increased edema. Increased edema of the nonischemic right lung and hypoxemia were observed at 27 h after left lower lobe reperfusion. Increases in phosphorylated p38 levels were found at 3 h of reperfusion compared with control lung, with further increases at 27 h. The attenuation of injury observed with MRS3558 treatment at 3 h of reperfusion was sustained at 27 h.

CONCLUSIONS

Lung edema may worsen hours after the immediate postreperfusion period, even though lung apoptosis and inflammation are reduced or show no change, respectively. This was associated with further increases in phosphorylated p38 levels. The nonischemic lung may also be affected, suggesting a systemic response to reperfusion. In addition, early attenuation of injury is beneficial beyond the immediate period after reperfusion. Treatment aimed at inhibiting p38 activation, such as A3 receptor activation, should be further studied to explore its potential long-term beneficial effect.

Acute renal failure: much more than a kidney disease

Acute renal failure is a frequent clinical problem with an increasing incidence, an unacceptably high mortality rate that has not improved in more than 40 years, and no specific treatment, yet renal failure is not the usual cause of death. The role of inflammation has been documented in both acute renal injury and cardiac dysfunction. Several investigators have shown that congestive heart failure is associated with increased mortality in patients with acute renal failure. This article reviews some of the cardiac and other distant organ effects of acute renal injury that may be important in the morbidity and mortality observed clinically. Cardiac changes after experimental renal ischemia include cytokine induction, leukocyte infiltration, cell death by apoptosis, and impaired function. I propose that the extrarenal effects of kidney injury must be considered in designing therapies. Acute renal failure has systemic consequences and must be thought of as more than a kidney disease.

Functional significance of inflammatory mediators in a murine model of resuscitated hemorrhagic shock

The mechanisms that underlie the development of myocardial dysfunction after resuscitated hemorrhagic shock (HS) are not known. Recent studies suggest that systemic activation of inflammatory mediators may contribute to cellular dysfunction and/or cell death in various organs, including the heart. However, the precise role that inflammatory mediators play in the heart in the setting of resuscitated HS is not known. Accordingly, the purpose of the present study was to use a well-defined murine model of resuscitated HS to characterize the functional significance of inflammatory mediators in the heart in vivo. Mice were subjected to sham operation or resuscitated HS. Left ventricular (LV) function was assessed by two-dimensional echocardiography 6 h after resuscitation. Myocardial TNF, IL-1β, and IL-6 proteins were measured 1 and 6 h after resuscitation. To determine the role of TNF in HS-induced LV dysfunction, mice were treated with a soluble TNF receptor antagonist (etanercept) before HS or at the time of resuscitation. LV fractional shortening was significantly depressed ( P < 0.05) in resuscitated HS mice (28 ± 1.5%) compared with sham controls (35.8 ± 1.0%). TNF and IL-1β levels were significantly increased ( P < 0.05) in resuscitated HS mice. Pretreatment with etanercept abrogated resuscitated HS-induced LV dysfunction, whereas treatment at the time of resuscitation significantly attenuated, but did not abrogate, LV dysfunction. Together, these data suggest that TNF plays a critical upstream role in resuscitated HS-induced LV dysfunction; however, once the deleterious consequences of reperfusion injury are initiated, TNF contributes to, but is not necessary for, the development of LV dysfunction.

Tissue lipopolysaccharide-binding protein expression in rats after thermal injury: potential role of TNF-alpha

Recent studies have suggested that levels of lipopolysaccharide-binding protein (LBP) might play a harmful role by up-regulating the host's sensitivity to endotoxin. Our previous studies demonstrated that local endotoxin could up-regulate LBP expression after acute insults, however, the definite molecular mechanisms downstream of endotoxin action remain unclear. This study investigates whether tumor necrosis factor (TNF-alpha) might be responsible for the LBP formation during endogenous endotoxemia postburn. Wistar rats were anesthetized, and a 35% TBSA full-thickness burn was created. Animals were randomly divided into normal control, thermal injury and anti-TNF-alpha mAb treatment group. A significant elevation of plasma endotoxin concentration was observed after acute insults. TNF-alpha levels in plasma also rapidly increased after thermal injury. Meanwhile, LBP mRNA expression markedly increased in liver, lungs, kidneys and intestine postburn. There was no detectable TNF-alpha in the plasma of anti-TNF-alpha mAb treated animals. Treatment with anti-TNF-alpha mAb also resulted in significantly lower concentrations of LBP mRNA in local tissues. Additionally, several organ function parameter levels in plasma significantly decreased in treatment group. These results demonstrated that an increase of plasma TNF-alpha levels caused by burns might be associated with a marked elevation of tissue LBP mRNA expression, which could contribute to the development of multiple organ damage.

Early tumor necrosis factor-alpha release from the pulmonary macrophage in lung ischemia-reperfusion injury

OBJECTIVE

Tumor necrosis factor-alpha is a proinflammatory mediator required for the development of experimental lung ischemia-reperfusion injury. The alveolar macrophage is a rich source of tumor necrosis factor-alpha in multiple models of acute lung injury. The present study was undertaken to determine whether the alveolar macrophage is an important source of tumor necrosis factor-alpha in lung ischemia-reperfusion injury and whether suppression of its function protects against injury.

METHODS

Left lungs of Long-Evans rats underwent normothermic ischemia for 90 minutes and reperfusion for up to 4 hours. Treated animals received gadolinium chloride, a rare earth metal that inhibits macrophage function. Injury was quantitated via lung tissue neutrophil accumulation (myeloperoxidase content), lung vascular permeability, and bronchoalveolar lavage fluid leukocyte, cytokine, and chemokine content. Separate samples were generated for immunohistochemistry.

RESULTS

Tumor necrosis factor-alpha secretion occurred at 15 minutes of reperfusion and was localized to the alveolar macrophage by immunohistochemistry. In gadolinium-treated animals, lung vascular permeability was reduced by 66% at 15 minutes (P <.03) of reperfusion and by 34% at 4 hours (P <.02) of reperfusion. Suppression of macrophage function resulted in a 35% reduction in lung myeloperoxidase content (P <.03) and similar reductions in bronchoalveolar lavage leukocyte accumulation. Tumor necrosis factor-alpha and microphage inflammatory protein-1alpha protein levels were markedly reduced in the bronchoalveolar lavage of gadolinium-treated animals by enzyme-linked immunosorbent assay.

CONCLUSIONS

The alveolar macrophage secretes tumor necrosis factor-alpha protein by 15 minutes of reperfusion, which orchestrates the early events that eventually result in lung ischemia-reperfusion injury at 4 hours. Gadolinium pretreatment markedly reduces tumor necrosis factor-alpha elaboration, resulting in significant protection against lung ischemia-reperfusion injury.

Comparative anti-inflammatory activities of antagonists to C3a and C5a receptors in a rat model of intestinal ischaemia/reperfusion injury

1. Complement activation is implicated in the pathogenesis of intestinal ischaemia-reperfusion injury (I/R), although the relative importance of individual complement components is unclear. A C3a receptor antagonist N(2)-[(2,2-diphenylethoxy)acetyl]-l-arginine (C3aRA) has been compared with a C5a receptor antagonist (C5aRA), AcF-[OPdChaWR], in a rat model of intestinal I/R. 2. C3aRA (IC(50)=0.15 microm) and C5aRA (IC(50)=0.32 microm) bound selectively to human polymorphonuclear leukocyte (PMN) C3a and C5a receptors, respectively. Effects on circulating neutrophils and blood pressure in the rat were also assessed. 3. Anaesthetised rats, subjected to intestinal ischaemia (30 min) and reperfusion (120 min), were administered intravenously with either (A) the C3aRA (0.1-1.0 mg x kg(-1)); the C5aRA (1.0 mg x kg(-1)); the C3aRA+C5aRA (each 1.0 mg x kg(-1)); or vehicle, 45 min prior, or (B) the C3aRA (1.0 mg x kg(-1)) or vehicle, 120 min prior to reperfusion. 4. The C3aRA and C5aRA, administered 45 min prior to reperfusion, displayed similar efficacies at ameliorating several disease markers (increased oedema, elevated ALT levels and mucosal damage) of rat intestinal I/R. The combination drug treatment did not result in greater injury reduction than either antagonist alone. However, doses of the C3aRA (0.01-10 mg x kg(-1)) caused transient neutropaenia, and the highest dose (10 mg x kg(-1)) also caused a rapid and transient hypertension. 5. The C3aRA (1.0 mg x kg(-1)), delivered 120 min prior to reperfusion to remove the global effect of C3aRA-induced neutrophil sequestration, did not attenuate the markers of intestinal I/R, despite persistent C3aR antagonism at this time. 6. C3aR antagonism does not appear to be responsible for the anti-inflammatory actions of this C3aRA in intestinal I/R in the rat. Instead, C3aRA-mediated global neutrophil tissue sequestration during ischaemia and early reperfusion may account for the protective effects observed.

Cytokines in patients with polytrauma

Patients with multiple injuries have alterations in hemodynamic, metabolic, and immune responses that largely are orchestrated by endogenous mediators referred to as cytokines. At the molecular level cytokines act as architects constructing a blueprint which ultimately will become the clinical "Big Picture"; however, the exact role and extent each cytokine has is still in question. In addition, the surface of research opportunities has nearly been scratched regarding the best way to control or manipulate the cytokine response in efforts to improve care for the trauma patient. Systemically organisms respond to injury regardless of the cause (hemorrhage, ischemia, reperfusion, fracture, and tissue damage) by attempting to restore homeostasis, which involves a coordination of the immune, cardiovascular, endocrine, and nervous systems. This systemic response can result in severe immunologic compromise that threatens the survival of patients with trauma. It seems that it is this balance or imbalance of cytokines, along with other associative factors, that controls the eventual clinical pathway a patient will take. Blood mediator concentrations often parallel the inflammatory process, and high levels of cytokines can be followed by severe organ dysfunction. Certain cytokine levels, such as the interleukins, can be used in predictive ways to correlate organ failure in multiply injured patients. Although much more research must be done, there is great promise in the study of cytokines through basic science research and clinical trials.

Intestinal ischemia reperfusion injury and multisystem organ failure

Intestinal ischemia-reperfusion is a common pathway for many diseases in infants, children, and adults, and this may lead to multiple organ dysfunction syndrome and death. While several studies have investigated reperfusion injury in cardiac, cerebral, and hepatic disease, limited work has been published on intestinal ischemia-reperfusion and its multiorgan effects. The authors have developed models of intestinal ischemia-reperfusion in rats and have demonstrated that intestinal reperfusion causes liver energy failure at normothermia. This is followed by 100% mortality within 4 hours of reperfusion. Moderate hypothermia (32 degrees C to 33 degrees C) induced throughout ischemia and reperfusion prevents liver energy failure, intestinal damage, and neutrophil infiltration in the lungs. Moderate hypothermia in this model of intestinal ischemia and reperfusion prevents mortality. Further studies are needed to establish whether therapeutic hypothermia is a useful intervention in the treatment of infants and children with intestinal injuries caused by ischemia and reperfusion.

Splenectomy attenuates intestinal ischemia-reperfusion-induced acute lung injury

BACKGROUND/PURPOSE

Intestinal ischemia-reperfusion (IIR) induced acute lung injury (ALI) has been documented. Kupffer cell blockage with gadolinium chloride (GdCl(3)) has been shown to attenuate IIR-induced ALI. However, the effects of splenic monocytes/macrophages on IIR-induced ALI has not been studied previously. In the current study, the authors aimed to investigate the role of splenectomy in IIR-induced ALI.

METHODS

Forty-eight rats were divided randomly into 6 groups as follows: SHAM, SHAM + KCB, SHAM + SPLN, IIR, IIR + KCB, IIR + SPLN. Two hours of ischemia and 1 hour of reperfusion has been applied by clipping the SMA. GdCl3 was given 24 hours before experiment. Splenectomy was done just before SMA clipping. Lung levels of tumor necrosis-factor (TNF), interleukin (IL)-6, myeloperoxidase (MPO), and malondialdehyde (MDA) were assayed biochemically. Lung leukosequestration was determined by counting PMNLs histologically. Kruskal-Wallis and Mann-Whitney U tests were done; P values less than.003 were considered significant.

RESULTS

Polimorphonuclear leukocyte (PMNL) counts and biochemical parameters in the IIR group were significantly higher than the other groups (P <.003). When compared with IIR group, PMNL counts and biochemical parameters were significantly decreased in the IIR+KCB and IIR+SPLN groups, respectively (P <.003). However, they were still significantly higher than their sham-operated controls (P <.003).

CONCLUSIONS

This study documents that splenectomy attenuates ALI as well as Kupffer cell blockage. Spleen, an important component of mononuclear phagocytic system as liver Kupffer cells, might play an important role in the IIR-induced ALI.

Myocardial ischemia in intestinal postischemic shock: the effect of hypoxemic reperfusion

OBJECTIVE

The circulatory shock following intestinal ischemia-reperfusion injury has been attributed to hypovolemia. The purpose of the current study is to clarify the pathophysiology of this type of shock and to test the hypothesis that hypoxemic compared with normoxemic reperfusion improves hemodynamics.

DESIGN

Randomized animal study.

SETTING

Medical school laboratory.

SUBJECTS

Twenty-one pigs.

INTERVENTIONS

Pigs were subjected to 120 mins of intestinal ischemia by clamping the superior mesenteric artery. Upon declamping, the animals were randomized into two groups: a group that received hypoxemic reperfusion (HR group, n = 8) with a PaO2 = 30-35 and a control group reperfused with PaO2 = 100 mm Hg (control group, n = 13).

MEASUREMENTS AND MAIN RESULTS

Measurements included mean arterial pressure, cardiac index, pulmonary artery occlusion pressure, and requirements for fluids and epinephrine. Biopsies from the terminal ileal mucosa were taken for malondialdehyde measurements at baseline, at 120 mins of ischemia, and at 30 and 60 mins of reperfusion. A piece of left ventricle was obtained after 120 mins of reperfusion for histologic studies. Five of 13 animals of the control group died in intractable shock; no animal of the HR group died (p =.11). The decrease in the mean arterial pressure during reperfusion was more pronounced in the control group (p <.008) despite the larger doses of epinephrine administered, compared with the HR group (p <.02). During reperfusion, both groups exhibited a decrease in cardiac index; this was more pronounced in the control group (p =.0007). Pulmonary artery occlusion pressure increased during reperfusion in both groups and was more pronounced in the control group (p =.04 at 60 mins). Although mixed venous blood oxygen saturation of the control animals was higher at 30 mins of reperfusion (p =.005), it declined after 60 mins and became lower than that of HR animals at the end of reperfusion (p <.02). The myocardial histopathologic injury score was higher in the control group (2.0 +/- 0.69 and 3.4 +/- 0.89 for the HR and control groups, respectively; p <.03). The concentrations of intestinal mucosa malondialdehyde were significantly higher in the control group at 60 mins of reperfusion (p <.03).

CONCLUSIONS

Acute myocardial ischemia and left heart failure significantly contribute to the circulatory shock that follows intestinal ischemia/reperfusion injury and are attenuated by hypoxemic reperfusion.

Evaluation of the mechanism of vascular endothelial growth factor improvement of ischemic flap survival in rats

This study evaluated the effects of exogenous vascular endothelial growth factor (VEGF) on the regulation of cytokines in a rat dorsal ischemic skin flap model. Exogenous VEGF (1 microg/ml) was injected subdermally into the flaps of 12 rats before the flaps were sutured back in place. Another 12 rats with flaps received saline injections, as a control group. Biopsy specimens were obtained from the flaps treated with VEGF or saline solution, at positions 2.5, 5.5, and 8.5 cm from the distal edge of the flaps, at 12 hours (n = 6 for each group) and 24 hours (n = 6 for each group) after suturing of the flaps. Expression of cytokine, growth factor, and inducible nitric oxide synthase was measured. The results demonstrated that expression of tumor necrosis factor-alpha and nitric oxide synthase in the distal part of the VEGF-treated flaps was significantly decreased, compared with the control values, at 12 and 24 hours postoperatively. It was concluded that administration of exogenous VEGF could protect flaps from ischemia-reperfusion injury through the regulation of proinflammatory cytokines and the inhibition of cytotoxic nitric oxide production.

Role for complement in mediating intestinal nitric oxide synthase-2 and superoxide dismutase expression

Inducible nitric oxide synthase (iNOS) and superoxide dismutase (SOD) play an important role in the pathology of ischemia-reperfusion. This study sought to determine if the proinflammatory effects of complement modulate iNOS and SOD in the rat after gastrointestinal ischemia and reperfusion (GI/R). An inhibitory or noninhibitory anti-complement component 5 (C5) monoclonal antibody (18A or 16C, respectively) was administered before GI/R. RT-PCR revealed a significant increase in intestinal iNOS mRNA compared with sham after GI/R that was attenuated significantly by 18A. Immunohistochemistry demonstrated increased iNOS protein expression within the intestinal crypts after GI/R. Cu/Zn SOD (mRNA and protein) was unaffected by GI/R, whereas Cu/Zn SOD activity was reduced significantly. Mn SOD protein expression was decreased significantly by GI/R. Anti-C5 preserved Cu/Zn SOD activity and Mn SOD protein expression. Staining for nitrotyrosine showed that anti-C5 treatment reduced protein nitration in the reperfused intestine. Immunohistochemistry demonstrated prominent phosphorylated (p) inhibitory factor-kappaB (IkappaB)-alpha staining of intestinal tissue after GI/R, whereas anti-C5 reduced p-IkappaB-alpha expression. These data indicate that complement may mediate tissue damage during GI/R by increasing intestinal iNOS and decreasing the activity and protein levels of Cu/Zn SOD and Mn SOD, respectively.

Distant effects of experimental renal ischemia/reperfusion injury

Acute renal failure results in significant morbidity and mortality, yet renal failure is not the usual cause of death in the clinical situation. We have previously reported systemic increases in the inflammatory mediators tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1) after renal ischemia in the mouse. In the present study, an animal model of bilateral renal ischemia was used to test the hypothesis that cytokines released with renal ischemia have effects on other organ systems. Increased levels of immunoreactive TNF-alpha and IL-1 and intercellular adhesion molecule-1 mRNA were found in the heart after renal ischemia in the rat. This was accompanied by increases in myeloperoxidase activity, an index of tissue leukocyte infiltration, in the heart as well as the liver and lung. Functional changes in the heart 48 h after renal ischemia included increases in left ventricular end diastolic diameter, left ventricular end systolic diameter, and decreased fractional shortening by echocardiography. Evidence of apoptosis of cardiac cells was also found 48 h after an abbreviated period of renal ischemia insufficient to induce azotemia but not bilateral nephrectomy (which resulted in significant renal failure), suggesting that renal ischemia but not uremia is necessary for the apoptosis observed. It was also found that blocking the action of TNF-alpha limited cardiac apoptosis. Renal ischemia results in distant effects and the alterations observed in the heart may be important in the morbidity and mortality observed clinically.

The mRNA expression patterns of tumor necrosis factor-α and TNFR-I in some vital organs after thermal injury

AIM: To investigate changes of tumor necrosis factor-α (TNF-α) and TNFR-I expression in vital organs and their significance in the pathogenesis of multiple organ damage associated with endogenous endotoxin following major burns.

METHODS: Wistar rats subjected to a 35% full-thickness scald injury were sacrificed at 12 h, 24 h, 48 h, and 72 h postburn, respectively. Meanwhile, eight rats were taken as normal controls. Tissue samples from liver, spleen, kidney, lung and intestine were collected to assay tissue endotoxin levels and measure TNF-α and TNFR-I expression. In addition, blood samples were obtained for the determination of organ function parameters.

RESULTS: Endotoxin levels in liver, spleen and lung increased markedly after thermal injury, with the highest level in liver. The gene expression of TNF-α in liver, lung and kidney was up-regulated after thermal injury, while the TNFR-I mRNA expression in liver, lung, kidney and intestine was shown decreased throughout the observation period. Thus, the mRNA expression ratio of TNF-α to TNFR-I was significantly increased postburn, particularly in pulmonary tissue (67-fold). In addition, the significant correlations between the expression of TNFR-I or the expression ratio of TNF-α/TNFR mRNA in liver tissue and serum aspartate aminotransferase levels were noted (P < 0.05-0.01). Similar results were also obtained between pulmonary TNF-α mRNA expression and myeloperoxidase activities (P < 0.01), whereas there was a highly negative correlation between levels of renal TNFR-I mRNA expression and serum creatinine.

CONCLUSION: Burn injury could result in the translocation of gut-derived endotoxin that was mainly distributed in the liver, spleen and lung. The translocated endotoxin then made the expression of TNF-α and TNFR-I mRNA up-regulated and down-regulated respectively in various organs, which might be involved in the pathogenesis of multiple organ damage following burns.

The role of proinflammatory cytokines in lung ischemia-reperfusion injury

OBJECTIVE

Proinflammatory cytokines are known to play roles in ischemia-reperfusion injury of the heart, kidney, small bowel, skin, and liver. Little is known about their roles in ischemia-reperfusion injury of the lung. This study was undertaken to define the role of 2 proinflammatory cytokines, tumor necrosis factor alpha and interleukin 1beta, in ischemia-reperfusion injury of the lung.

METHODS

Left lungs of male rats were rendered ischemic for 90 minutes and reperfused for up to 4 hours. Treated animals received anti-tumor necrosis factor alpha or anti-interleukin 1beta antibody before reperfusion. Increased vascular permeability in the lung was measured by using iodine 125-labeled bovine serum albumin. Neutrophil sequestration in the lung parenchyma was determined on the basis of activity. Bronchoalveolar lavage was performed to measure cell counts. Separate tissue samples were processed for histology, cytokine protein, and messenger RNA content by using Western blotting and the ribonuclease protection assay.

RESULTS

Animals receiving anti-tumor necrosis factor alpha and anti-interleukin 1beta demonstrated reduced injury compared with that seen in positive control animals (vascular permeability of 48.7% and 29.4% lower, respectively; P <.001). Vascular injury was reduced by 71% when antibodies to tumor necrosis factor alpha and interleukin 1beta were administered together. Lung neutrophil accumulation was markedly reduced among animals receiving anti-tumor necrosis factor alpha and anti-interleukin 1beta (myeloperoxidase content of 30.9% and 38.5% lower, respectively; P <.04) and combination blockade afforded even greater protection (52.4% decrease, P <.01). Bronchoalveolar lavage leukocyte content was also reduced by treatment with anti-tumor necrosis factor alpha, anti-interleukin 1beta, and combination treatment. Reductions in permeability, myeloperoxidase, and bronchoalveolar lavage leukocyte content also resulted in a decrease in a histologic injury. Finally, anti-tumor necrosis factor alpha and anti-interleukin 1beta treatment resulted in decreased messenger RNA expression for a number of early response and regulatory cytokines.

CONCLUSION

Tumor necrosis factor alpha and interleukin 1beta help regulate the development of lung ischemia-reperfusion injury. They appear to promote injury by altering expression of proinflammatory and anti-inflammatory cytokines and influencing tissue neutrophil recruitment.

Kinetics of endotoxin concentration and tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6 activities in the systemic and portal circulation during small intestinal ischemia and reperfusion in dogs

OBJECTIVE

To determine whether small intestinal ischemia and reperfusion induces bacterial translocation and proinflammatory cytokine response in either the systemic or portal circulation in dogs.

ANIMALS

17 healthy adult Beagles.

PROCEDURE

The superior mesenteric artery (SMA) was occluded for 0 (group-3 dogs), 30 (group-1 dogs), or 60 (group-2 dogs) minutes, followed by reperfusion for 180 minutes; serum lactate and endotoxin concentrations and tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and IL-6 activities in the systemic and portal circulation and intramucosal pH were measured at various time points.

RESULTS

In group-2 dogs, TNFalpha activity was found to be significantly increased in the portal circulation, peaking at 60 minutes of reperfusion; TNF-alpha activity, in the systemic circulation, gradually increased from 60 minutes of reperfusion to the end of the experiment; however, the increase was not significant. In group-1 and -2 dogs, IL-6 activities significantly and gradually increased in the systemic and portal circulation during the reperfusion phase, and the magnitude of these increases was dependent on the duration of the ischemic phase. There were no significant changes in IL-1beta activity or endotoxin concentration in any dog group.

CONCLUSIONS AND CLINICAL RELEVANCE

Results of the our study indicate that intestinal ischemia and reperfusion leads to significant increases of the circulating TNF-alpha and IL-6 activities, depending on the duration of the ischemia phase, in the absence of detectable endotoxin in the circulation. This finding suggests that intestinal ischemia and reperfusion induces a systemic proinflammatory cytokine response in dogs.

Increased mortality and inflammation in tumor necrosis factor-stimulated gene-14 transgenic mice after ischemia and reperfusion injury

TSG-14/PTX3 is a gene inducible by tumor necrosis factor (TNF)-alpha, interleukin-1 beta, and lipopolysaccharide in fibroblasts, macrophages, and endothelial cells. It encodes a 42-kd secreted glycoprotein that belongs to the pentraxin family of acute-phase proteins. Recently, we demonstrated that TSG-14 transgenic mice (TSG-14tg) overexpressing the murine TSG-14 gene under control of its own promoter are more resistant to lipopolysaccharide-induced shock and to polymicrobial sepsis caused by cecal ligation and puncture. Here we show that after ischemia and reperfusion (I/R) injury, TSG-14tg mice have an impaired survival rate, which appeared secondary to a markedly increased inflammatory response, as assessed by the local (duodenum and ileum) and remote (lung) enhancement in vascular permeability, hemorrhage, and neutrophil accumulation. Moreover, tissue concentrations of TNF-alpha, interleukin-1 beta, KC, and MCP-1 were higher in TSG-14tg as compared to wild-type mice after I/R injury. Of note, elevated TNF-alpha concentrations in serum were only observed in TSG-14tg mice and blockage of TNF-alpha action prevented lethality of TSG-14tg mice. These results demonstrate that transgenic expression of TSG-14 induces an enhanced local and systemic injury and TNF-alpha-dependent lethality after I/R. Taken together, our data point to a critical role of TSG-14 in controlling acute inflammatory response in part via the modulation of TNF-alpha expression.

Effects of inhibition of PDE4 and TNF-alpha on local and remote injuries following ischaemia and reperfusion injury

1. The effects of phosphodiesterase (PDE)4 and TNF-alpha inhibition were assessed on the local and remote injuries following intestinal ischaemia and reperfusion (I/R) injury in rats. 2. The PDE4 inhibitor rolipram dose-dependently (1 - 10 mg kg(-1)) suppressed the local (intestine) and remote (lung) increases in vascular permeability and neutrophil recruitment following mild I/R injury. SB207499 (ariflo), a structurally-distinct PDE4 inhibitor, also suppressed the injuries following mild I/R injury. 3. In a severe model of I/R injury, treatment with rolipram (10 mg kg(-1)) partially reversed the local and remote increases in vascular permeability, neutrophil recruitment, intestinal haemorrhage and intestinal LTB(4) concentrations. The anti-TNF-alpha anti-serum was more effective than rolipram at inhibiting local and remote injuries and prevented the lethality associated with severe I/R. 4. Rolipram and anti-TNF-alpha prevented the increase in the concentrations of TNF-alpha in the lung and intestine, but rolipram only partially inhibited the elevation of this cytokine in serum. Rolipram had little effect on the increases of IL-1 beta concentrations in lung and serum, whereas treatment with anti-TNF-alpha markedly increased the concentration of this cytokine. Concentrations of IL-10 rose significantly in the lung and serum and these increases were blocked by rolipram or anti-TNF-alpha. 5. The capacity of PDE4 inhibitors to block the recruitment of neutrophils into tissues, the production of LTB(4) and of the pro-inflammatory cytokines TNF-alpha, IL-1 beta and IL-6 appear to underlie their anti-inflammatory effects in our model of I/R injury. Overall, PDE4 inhibition was less effective than inhibition of TNF-alpha for protection against I/R injury.

Contribution of serotonin to liver injury following canine small-intestinal ischemia and reperfusion

Intestinal ischemia and reperfusion (I/R) has been shown to be associated with multiple organ damages. Serotonin (5-hydroxytriptamine; 5-HT), which is synthesized in the enterochromaffin cells in the intestine and stored in platelets, is known to play an important role in platelet aggregation and vasoconstriction and may ultimately enhance such organ injuries. The purpose of this study was to investigate the association between liver damage and 5-HT levels in the liver after intestinal I/R. The entire canine small intestine, isolated on a vascular pedicle that consisted of the proximal superior mesenteric artery and superior mesenteric vein, was subjected to 4-h ischemia by clamping these vessels and the marginal arteries supplying the proximal and distal ends of the small intestine. Hepatic blood flow, liver tissue blood flow, bile flow rate, and hepatic venous ketone body ratio (HVKBR) were measured before and at the end of intestinal ischemia and at 5, 15, and 30 min, and 1 and 2 h after reperfusion. 5-HT levels in plasma of the portal vein and hepatic vein were assayed at the same intervals. Time-matched, sham-operated animals served as controls. Intestinal I/R significantly decreased the liver tissue flow, bile flow rate, and HVKBR. Compared to those in controls, 5-HT levels in the portal vein and hepatic vein were markedly increased after reperfusion. Furthermore, intravenous administration of 5-HT receptor antagonists attenuated the liver dysfunction after intestinal reperfusion. These results suggest that intestinal I/R induces continuous disturbance of hepatic microcirculation, leading to liver dysfunction, and that 5-HT may be implicated as one of the mediators of liver dysfunction after intestinal I/R.

TNF-alpha stimulates alveolar liquid clearance during intestinal ischemia-reperfusion in rats

Intestinal ischemia-reperfusion commonly occurs in critically ill patients and may lead to the development of remote organ injury, frequently involving the lungs. In the present study, alveolar liquid clearance was studied in ventilated, anesthetized rats subjected to 45 min of intestinal ischemia followed by 3 h of reperfusion. An isosmolar 5% albumin solution was instilled into the lungs, and alveolar liquid clearance was measured from the increase in alveolar protein concentration as water was reabsorbed over 45 min. Intestinal ischemia-reperfusion resulted in a 76% increase in alveolar liquid clearance compared with the control value (P < 0.05). The stimulated alveolar liquid clearance seen after intestinal ischemia-reperfusion was not inhibited by propranolol, indicating stimulation through a noncatecholamine-dependent pathway. Intestinal ischemia-reperfusion did not result in increased intracellular cAMP levels. Amiloride inhibited similar fractions in animals subjected to ischemia-reperfusion and control animals. Administration of a neutralizing polyclonal anti-tumor necrosis factor-alpha antibody before induction of intestinal ischemia completely inhibited the increased alveolar liquid clearance observed after intestinal ischemia-reperfusion. In conclusion, our results suggest that intestinal ischemia-reperfusion in rats leads to stimulation of alveolar liquid clearance and that this stimulation is mediated, at least in part, by a tumor necrosis factor-alpha-dependent mechanism.

Tumor necrosis factor-alpha in ischemia and reperfusion injury in rat lungs

The effects of both recombinant rat tumor necrosis factor-alpha (TNF-alpha) and an anti-TNF-alpha antibody were studied in isolated buffer-perfused rat lungs subjected to either 45 min of nonventilated [ischemia-reperfusion (I/R)] or air-ventilated (V/R) ischemia followed by 90 min of reperfusion and ventilation. In the I/R group, the vascular permeability, as measured by the filtration coefficient (Kfc), increased three- and fivefold above baseline after 30 and 90 min of reperfusion, respectively (P < 0.001). Over the same time intervals, the Kfc for the V/R group increased five- and tenfold above baseline values, respectively (P < 0.001). TNF-alpha measured in the perfusates of both ischemic models significantly increased after 30 min of reperfusion. Recombinant rat TNF-alpha (50,000 U), placed into perfusate after baseline measurements, produced no measurable change in microvascular permeability in control lungs perfused over the same time period (135 min), but I/R injury was significantly enhanced in the presence of TNF-alpha. An anti-TNF-alpha antibody (10 mg/rat) injected intraperitoneally into rats 2 h before the lung was isolated prevented the microvascular damage in lungs exposed to both I/R and V/R (P < 0.001). These results indicate that TNF-alpha is an essential component at the cascade of events that cause lung endothelial injury in short-term I/R and V/R models of lung ischemia.

Tumor necrosis factor-alpha hyporesponsiveness of rat intestinal mononuclear cells and whole portal venous blood after hemorrhagic shock

OBJECTIVE

To determine the effect of hemorrhagic shock on spontaneous and endotoxin-induced cytokine release from intestinal mononuclear cells compared with whole portal venous blood and splenic macrophages.

DESIGN

Random assignment to either unmanipulated control group, sham operation group, or hemorrhagic shock group.

SETTING

University animal laboratory.

SUBJECTS

Male Wistar rats, weighing between 300 and 350 g.

INTERVENTIONS

Rats were bled to 30 mm Hg for 30 mins by withdrawal/reinfusion of shed blood and Ringer's lactate equivalent to the shed blood volume.

MEASUREMENTS

Rats were killed immediately, 4 hrs, or 24 hrs after reperfusion. Portal venous blood, splenic macrophages, and small bowel mononuclear cells were obtained and spontaneous (unstimulated) and endotoxin-induced supernatant tumor necrosis factor (TNF)-alpha (WEHI 164 subclone 13) and interleukin (IL)-6 (B 13-29 clone 9) release was measured by bioassay.

MAIN RESULTS

Increased endotoxin-induced TNF release from gut mononuclear cells and portal venous blood was suppressed 4 and 24 hrs after reperfusion compared with sham operated animals (p < .05). TNF release from splenic macrophages could be significantly increased (p < .05) by addition of endotoxin in all groups with no difference between control, sham, and shock animals. In shock animals, endotoxin-stimulated IL-6 release was significantly greater (p < .05) than control and sham operated rats 4 hrs after reperfusion in portal blood and from splenic macrophages. In contrast to splenic macrophages, gut mononuclear cells and portal venous blood demonstrated high spontaneous IL-6 concentrations without further stimulation by endotoxin.

CONCLUSIONS

Hemorrhagic shock induced a hyporesponsiveness from gut mononuclear cells and whole portal venous blood 4 and 24 hrs after reperfusion. Spontaneous and endotoxin-induced stimulation of IL-6 indicates a different modulation of cytokines in gut, portal vein and spleen. The differences of gut mononuclear cells and portal blood compared with the splenic macrophages indicate a compartmentalized cytokine response.

Plasma D (-)-lactate as a new marker for diagnosis of acute intestinal injury following ischemia-reperfusion

AIM: To observe the kinetics of D (-)-lactate alteration in both portal and systemic circulation systems, and its relationship with intestinal injury in rats subjected to acute intestinal ischemia-reperfusion.

METHODS: Anesthetized rats underwent a 75-min superior mesenteric artery occlusion followed by a 6-h reperfusion. Plasma D (-)-lactate levels were measured by an enzymatic spectrophotometric assay.

RESULTS: Intestinal ischemia for 75 min resulted in a significant elevation of D (-)-lactate levels in the portal vein, as compared with the baseline values (P < 0.05). Plasma D (-)-lactate levels had a tendency to further increase after reperfusion, up to 6 h. Similar alterations in D (-)-lactate were also found in systemic circulation, and there were no significant differences between the portal and systemic circulations at any time point. Moreover, the macropathological evaluation scores were significantly correlated to the portal D (-)-lactate levels in animals at various time points (r = 0.415, P < 0.01). In addition, there was a remarkable rise of endotoxin concentration within the portal vein at the end of the 75-min ischemic period (P < 0.05), reaching a peak at 2 h post-reperfusion.

CONCLUSION: Acute intestinal ischemia is associated with failure of the mucosal barrier resulting in increased plasma D (-)-lactate levels in both portal and systemic blood. The subsequent reperfusion might further increase D (-)-lactate levels, which are correlated to the macropathological alterations. Plasma D (-)-lactate may be a useful marker of intestinal injury following both ischemia and reperfusion insults.

IL-6 release after intestinal ischemia/reperfusion in rats is under partial control of TNF

Although there is much evidence to substantiate the view that tumor necrosis factor (TNF) plays a pivotal role in the pathogenesis of multiple organ injury subsequent to intestinal ischemia/reperfusion (I/R), it is still unclear whether TNF is involved in triggering the release of other inflammatory mediators in this condition. The current study was designed to determine the potential effects of TNF blockade, by means of monoclonal antibody (TNF MoAb) treatment, on plasma interleukin 6 (IL-6) in rats after acute intestinal I/R injury. Anesthetized rats underwent 75-min occlusion of superior mesenteric artery followed by 6 hr of reperfusion. The animals were treated with TNF MoAb or control protein at a dose of 20 mg/kg i.v. 30 min before the onset of I/R. Similar IL-6 responses in both the portal and the systemic circulation were observed in animals subjected to intestinal I/R, who showed a progressive increase in plasma IL-6 concentration upon release of the clamp. In animals receiving TNF MoAb before I/R, the subsequent IL-6 release following reperfusion was significantly blunted compared to the levels in controls (P < 0.05). The present study demonstrates that the activation and/or release of IL-6 in the setting of acute gut I/R may, at least in part, be mediated via TNF-dependent mechanisms, providing further evidence that a complex interaction exists between TNF and IL-6.