Free radicals and pathogenesis during ischemia and reperfusion of the cat small intestine

Clinical Significance of Elevated Xanthine Dehydrogenase Levels and Hyperuricemia in Patients with Sepsis

Patient outcomes for severe sepsis and septic shock remain poor. Excessive oxidative stress accelerates organ dysfunction in severe acute illnesses. Uric acid (UA) is the most abundant antioxidant. We hypothesized that UA and related molecules, which play a critical role in antioxidant activity, might be markers of oxidative stress in sepsis. The study aimed to clarify the clinical significance of UA and the relationship between UA, molecules related to UA, and outcomes by measuring blood UA, xanthine dehydrogenase (XDH), and 8-hydroxy-2-deoxyguanosine (8-OHdG) levels over time. Blood UA levels in septic patients were correlated with the SOFA score (ρ = 0.36, p < 0.0001) and blood XDH levels (ρ = 0.27, p < 0.0001). Blood XDH levels were correlated with the SOFA score (ρ = 0.59, p < 0.0001) and blood 8-OHdG levels (ρ = -0.32, p < 0.0001). Blood XDH levels were persistently high in fatal cases. Blood XDH level (OR 8.84, 95% CI: 1.42-91.2, p = 0.018) was an independent factor of poor outcomes. The cutoff of blood XDH level was 1.38 ng/mL (sensitivity 92.8%, specificity 61.9%), and those 1.38 ng/mL or higher were associated with a significantly reduced survival rate (blood XDH level > 1.38 ng/mL: 23.7%, blood XDH level < 1.38 ng/mL: 96.3%, respectively, p = 0.0007). Elevated UA levels due to elevated blood XDH levels in sepsis cases may reduce oxidative stress. Countermeasures against increased oxidative stress in sepsis may provide new therapeutic strategies.

Effect of enteral ecoimmunonutrition support for patients undergoing hepatectomy: A meta-analysis of randomized controlled trials

BACKGROUND

Whether to conduct enteral ecoimmunonutrition (EEIN) in patients undergoing hepatectomy remains controversial. This study aimed to systematically explore the efficacy and safety of EEIN in patients undergoing hepatectomy.

SUBJECT

We performed searches in the Embase, PubMed, Medline, Cochrane Library, Chinese Scientific Journal Database (VIP), Chinese National Knowledge Infrastructure (CNKI) and Wanfang databases.

RESULTS

A total of 9 randomized controlled trials (705 patients) were included. The meta-analysis revealed a significantly shorter time to first postoperative flatus (h) (MD, -14.60; 95% CI, -16.06~-13.15; P < 0.00001); lower levels of alanine aminotransferase (µmol/L) (MD, -22.26; 95% CI, -28.42~-16.10; P < 0.00001), aspartate transaminase (µmol/L) (MD, -53.79; 95% CI, -57.37~-50.21; P < 0.00001), total bilirubin (µmol/L) (MD, -16.28; 95% CI, -17.77~-14.79; P < 0.00001), direct bilirubin (µmol/L) (MD, -8.77; 95% CI, -9.65~-7.88; P < 0.00001), endotoxin (ng/L) (MD, -0.78; 95% CI, -0.88~-0.68; P < 0.00001), tumor necrosis factor-α (pg/ml) (MD, -79.69; 95% CI, -99.90~-59.49; P < 0.00001), and interleukin-6 (pg/ml) (MD, -46.29; 95% CI, -50.24~-42.34; P < 0.00001); and higher levels of immunoglobulin A (g/L) (MD, 0.24; 95% CI, 0.14~0.35; P < 0.00001), immunoglobulin G (g/L) (MD, 1.52; 95% CI, 1.22~1.82; P < 0.00001), and immunoglobulin M (g/L) (MD, 0.12; 95% CI, 0.05~0.20; P = 0.0007) in the EEIN group than in the enteral or parenteral nutrition (EN/PN) groups.

CONCLUSION

Enteral ecoimmunonutrition support in patients undergoing hepatectomy may effectively protect liver function, reduce serum endotoxin levels and inflammatory factors, improve the immune function of patients, and promote the recovery of postoperative gastrointestinal function, which is worthy of clinical application.

Effects of bradykinin preconditioning in an experimental intestinal ischemia reperfusion model on rats

PURPOSE

To investigate the effects of bradykinin on reperfusion injury in an experimental intestinal ischemia reperfusion model.

METHODS

We used 32 Wistar-Albino rats. We composed 4 groups each containing 8 rats. Rats in sham group were sacrified at 100 minutes observation after laparotomy. Thirty minutes reperfusion was performed following 50 minutes ischaemia in control group after observing 20 minutes. Ischaemic preconditioning was performed in one group of the study. We performed the other study group pharmacologic preconditioning by infusional administration of 10 μg/kg/minute bradykinin intravenously. We sacrified all of the rats by taking blood samples to evaluate the lactate and lactate dehydrogenase (LDH) after resection of jejunum for detecting tissue myeloperoxidase (MPO) activity.

RESULTS

Lactate and LDH levels were significantly higher in control and study groups than the sham group (P<0.001). There is no difference between the study groups statistically. (P>0.05). The results were the same for MPO levels. Although definitive cell damage was determinated in the control group by hystopatological evaluation, the damage in the study groups observed was lower in different levels. However, there was no significant difference between the study groups statistically (P>0.05).

CONCLUSION

Either ischeamic preconditioning or pharmacologic preconditioning made by bradykinin reduced the ischemia reperfusion injury at jejunum.

Intestinal Stem Cell Isolation and Culture in a Porcine Model of Segmental Small Intestinal Ischemia

Intestinal ischemia remains a major cause of morbidity and mortality in human and veterinary patients. Many disease processes result in intestinal ischemia, when the blood supply and therefore oxygen is decreased to the intestine. This leads to intestinal barrier loss and damage to the underlying tissue. Intestinal stem cells reside at the base of the crypts of Lieberkühn and are responsible for intestinal renewal during homeostasis and following injury. Ex vivo cell culture techniques have allowed for the successful study of epithelial stem cell interactions by establishing culture conditions that support the growth of three-dimensional epithelial organ-like systems (termed "enteroids" and "colonoids" from the small and large intestine, respectively). These enteroids are composed of crypt and villus-like domains and mature to contain all of the cell types found within the epithelium. Historically, murine models have been utilized to study intestinal injury. However, a porcine model offers several advantages including similarity of size as well as gastrointestinal anatomy and physiology to that of humans. By utilizing a porcine model, we establish a protocol in which segmental loops of intestinal ischemia can be created within a single animal, enabling the study of differing time points of ischemic injury and repair in vivo. Additionally, we describe a method to isolate and culture the intestinal stem cells from the ischemic loops of intestine, allowing for the continued study of epithelial repair, modulated by stem cells, ex vivo.

Animal models of ischemia-reperfusion-induced intestinal injury: progress and promise for translational research

Research in the field of ischemia-reperfusion injury continues to be plagued by the inability to translate research findings to clinically useful therapies. This may in part relate to the complexity of disease processes that result in intestinal ischemia but may also result from inappropriate research model selection. Research animal models have been integral to the study of ischemia-reperfusion-induced intestinal injury. However, the clinical conditions that compromise intestinal blood flow in clinical patients ranges widely from primary intestinal disease to processes secondary to distant organ failure and generalized systemic disease. Thus models that closely resemble human pathology in clinical conditions as disparate as volvulus, shock, and necrotizing enterocolitis are likely to give the greatest opportunity to understand mechanisms of ischemia that may ultimately translate to patient care. Furthermore, conditions that result in varying levels of ischemia may be further complicated by the reperfusion of blood to tissues that, in some cases, further exacerbates injury. This review assesses animal models of ischemia-reperfusion injury as well as the knowledge that has been derived from each to aid selection of appropriate research models. In addition, a discussion of the future of intestinal ischemia-reperfusion research is provided to place some context on the areas likely to provide the greatest benefit from continued research of ischemia-reperfusion injury.

The role of epidermal growth factor in prevention of oxidative injury and apoptosis induced by intestinal ischemia/reperfusion in rats

Intestinal ischemia/reperfusion is a major problem which may lead to multiorgan failure and death. The aim of the study was to evaluate the effects of epidermal growth factor (EGF) on apoptosis, cell proliferation, oxidative stress and the antioxidant system in intestinal injury induced by ischemia/reperfusion in rats and to determine if EGF can ameliorate these toxic effects. Intestinal ischemia/reperfusion injury was produced by causing complete occlusion of the superior mesenteric artery for 60 min followed by a 60-min reperfusion period. Animals received intraperitoneal injections of 150 μg/kg human recombinant EGF 30 min prior to the mesenteric ischemia/reperfusion. Mesenteric ischemia/reperfusion caused degeneration of the intestinal mucosa, inhibition of cell proliferation, stimulation of apoptosis and oxidative stress in the small intestine of rats. In the ischemia/reperfusion group, lipid peroxidation was stimulated accompanied by increased intestinal catalase and glutathione peroxidase activities, however, glutathione levels and superoxide dismutase activities were markedly decreased. EGF treatment to rats with ischemia/reperfusion prevented the ischemia/reperfusion-induced oxidative injury by reducing apoptosis and lipid peroxidation, and by increasing antioxidant enzyme activities. These results demonstrate that EGF has beneficial antiapoptotic and antioxidant effects on intestinal injury induced by ischemia/reperfusion in rats.

The protective effect of methylene blue in lungs, small bowel and kidney after intestinal ischemia and reperfusion

PURPOSE

To study the role of methylene blue as an inhibitor of superoxide production by xanthine oxidase.

METHODS

Thirty-two Wistar rats were divided into 2 groups of 16 animals: the control group and the experimental group. All were submitted to a laparotomy for the occlusion of the cranial mesenteric artery during 60 minutes. The reperfusion was confirmed by the pulsation of the artery after the release of the temporary ligature and color change of the intestines. In the animals of the control group, 2 ml of saline were injected in the peritoneal cavity and in the animals of the experimental group, 2 ml of methylene blue were injected in the peritoneal cavity. After reperfusion for 4 hours, the animals were then sacrificed. The lungs were excised from all 32 rats. Simultaneously, the small intestine and kidneys were ressected in 20 animals (10 from the control group and 10 from the experimental group). Samples of the organs were taken to evaluate the action of xanthine-oxidase, for histopathology studies and for characterization of the edema.

RESULTS

In the animals of the experimental group, the inflammatory lesion as well as the edema in the lung was greater than in the control group. The intestinal and renal lesions were similar in both groups, but the lung damage was superior to that observed in the intestines and kidneys. .

CONCLUSION

Despite similar action of the xanthine oxidase in the control and the experimental group, after intestinal ischemia and reperfusion, the protective effect of methylene blue was observed only in the lungs of the experimental group.

Effect of bencyclane fumarate on intestinal ischaemia reperfusion injury

BACKGROUND

Post-ischaemic intestinal tissue damage appears to be due to the formation of oxygen radicals. Free radical-initiated lipid peroxidation following intestinal ischaemia/reperfusion (I/R) may disrupt mucosal integrity. Indirectly, the radicals trigger the accumulation of neutrophils within the affected tissue, initiating inflammatory processes that lead to severe mucosal lesions. We have investigated the protective effect of bencyclane fumarate, a vasodilating Ca(2+) channel blocker, which has been used for the treatment of peripheral arterial occlusive diseases, on intestinal ischaemia reperfusion (IR) injury in rats.

METHODS

Forty-eight Wistar albino rats were divided into three groups: a sham-operated group (no IR injury, n = 16), an ischaemic control group (IR, n = 16), and BF-treated group (pretreatment 5 mg/kg bencyclane fumarate + IR, n = 16). A marker for lipid peroxidation, namely malondialdehyde; free radical scavengers, glutathione peroxidase, catalase and superoxide dismutase levels; an index of polymorphonuclear neutrophils, myeloperoxidase activity and mucosal damage were investigated.

RESULTS

Malondialdehyde levels, myeloperoxidase activity and the severity of mucosal damage were decreased in the BF group. In addition, in the BF group, glutathione peroxidase, catalase and superoxide dismutase levels were higher compared with the IR group.

CONCLUSION

The pretreatment of rats with bencyclane fumarate before intestinal ischaemia attenuates the mucosal damage in intestinal IR injury, probably by altering lipid peroxidation, neutrophil accumulation and antioxidant activity.

LAMOTRIGINE REDUCES INTESTINAL I/R INJURY IN THE RAT

I/R injury of the intestine is a life-threatening emergency with mortality rates still more than 60%. We have investigated the protective effect of lamotrigine (LTG), an antiepileptic drug, which has an established neuroprotective effect, on intestinal I/R injury in rats. Forty-eight Wistar albino rats were divided into three groups: a sham-operated group (no I/R injury; n = 16), an ischemic control group (I/R, n = 16), and an LTG-treated group (pretreatment 5 mg kg-1 LTG + IR; n = 16). A marker for lipid peroxidation, malondialdehyde, free radical scavengers, glutathione peroxidase, catalase, and superoxide dismutase levels, an index of polymorphonuclear neutrophils, myeloperoxidase activity, and mucosal damage were investigated. Malondialdehyde levels, myeloperoxidase activity, and the severity of mucosal damage were decreased in the LTG group. Moreover, in the LTG group, glutathione peroxidase and superoxide dismutase levels were higher compared with the I/R group. The pretreatment of rats with LTG before intestinal ischemia ameliorates the mucosal damage in intestinal I/R injury probably by altering lipid peroxidation, neutrophil accumulation, and antioxidant activity.

Protective effects of ascorbic acid pretreatment in a rat model of intestinal ischemia-reperfusion injury: a histomorphometric study

BACKGROUND

Ascorbic acid has shown promise in attenuation of intestinal ischemia-reperfusion (I/R) injury. The aim of this study was to determine the protective effects of ascorbic acid on intestinal morphology during IR injury in rats.

MATERIALS AND METHODS

We examined morphological changes in the small intestine of Wistar rats after (i) 40 minutes of ischemia (I), (ii) ischemia followed by 30 min of reperfusion (IR), (iii) ischemia with ascorbic acid (IA), (iv) ischemia followed by reperfusion and ascorbic acid (IRA) and (v) in a sham group (S). We used morphometry to evaluate the amount of villous architecture, crypts, necrosis, hemorrhagic infarcts and inflammatory cells at the mesenteric and antimesenteric borders of the small intestine.

RESULTS

Ascorbic acid caused a significant reduction of antimesenteric villous hemorrhagic infarction (p<0.05) of the small intestine after ischemia followed by reperfusion as well as villous necrosis reduction at both borders after ischemia (p<0.05). The lesions found in the small intestine were more prominent along the antimesenteric margin.

CONCLUSIONS

Ascorbic acid pretreatment has a protective effect against the intestinal morphological lesions induced by ischemia-reperfusion injury in rats.

Role of the thrombin/protease-activated receptor 1 pathway in intestinal ischemia-reperfusion injury in rats

CXC chemokines, including human interleukin-8 and rat cytokine-induced neutrophil chemoattractant-1, play a crucial role in the pathogenesis of intestinal inflammation induced by ischemia-reperfusion (I-R). Thrombin and its specific receptor, protease-activated receptor 1 (PAR1), act as important players in inflammation. However, the association between thrombin activation and chemokine production during I-R has not been well studied. We investigated whether thrombin and PAR1 might be involved in the pathophysiology of intestinal I-R, using an in vivo model. Intestinal damage was induced by clamping the superior mesenteric artery for 30 min followed by reperfusion in male Wistar rats. Thrombin-antithrombin complex was measured as an indicator of thrombin activation. PAR1 expression in the intestine was evaluated by real-time PCR. The severity of the intestinal mucosal injury was evaluated on the distal segment of the ileum by several biochemical markers and histological findings. Reperfusion significantly increased the serum levels of thrombin-antithrombin complex and enhanced PAR1 expression in the intestinal mucosa. The levels of both intraluminal hemoglobin and protein were significantly increased in the I-R group. The mucosal myeloperoxidase activity and expressions and/or productions of cytokine-induced neutrophil chemoattractant-1 and TNF-alpha were significantly increased after I-R. These increases were inhibited by the treatment of rat with antithrombin intravenously before I-R at a dose of 30 U/kg. These results suggest that the thrombin/PAR1 pathway plays an important role in the production of these cytokines during I-R and that antithrombin exerts potent anti-inflammatory effects on this injury via inhibition of proinflammatory cytokines.

Effects of L-carnitine on neutrophil-mediated ischemia-reperfusion injury in rat stomach

Reactive oxygen metabolites play an important role in ischemia-reperfusion related gastric injury. Primary sources of reactive oxygen metabolites seem to be the xanthine/xanthine oxidase system and neutrophils accumulating within the reperfused tissue. Tissue myeloperoxidase activity is an important index of neutrophil accumulation. The purpose of the present study was to clarify the effect of L-carnitine on the accumulation of neutrophils and neutrophil-induced gastric mucosal damage in rats exposed to ischemia-reperfusion. Rats were randomly divided into three groups: sham-operated, ischemia-reperfusion and ischemia-reperfusion plus L-carnitine groups. Ischemia was induced by clamping the celiac artery for 30 min and then reperfusion was established for 60 min. Gastric injury was assessed by measuring myeloperoxidase activity in gastric tissue. The neutrophil accumulation and hemorrhagic lesions due to ischemia-reperfusion in gastric mucosa were ascertained in a histological study. L-Carnitine (100 mg kg(-1)) administrated intravenously 5 min before ischemia significantly reduced both the gastric injury and myeloperoxidase activity compared with the ischemia-reperfusion group. The results suggest that L-carnitine provides marked protection against ischemia-reperfusion-related gastric injury which could be due to its ability to reduce neutrophil accumulation in ischemic tissue.

CV-11974, angiotensin II type I receptor antagonist, protects against ischemia–reperfusion injury of the small intestine in rats

BACKGROUND

Angiotensin II has been implicated in the pathogenesis of vascular inflammation in various organs. The aim of the present study was to examine the effect of angiotensin II type I receptor antagonist, CV-11974, on reperfusion-induced small intestinal injury in rats.

METHODS

Intestinal damage was induced by clamping both the superior mesenteric artery and the celiac trunk for 30 min followed by reperfusion for 60 min in male Wistar rats. CV-11974 was given to the rats by intravenous injection 1 h before the vascular clamping. The intestinal mucosal injury and inflammation were evaluated by biochemical markers and histological findings. Thiobarbituric acid reactive substances and tissue-associated myeloperoxidase (MPO) activity were measured in the gastric mucosa as indices of lipid peroxidation and neutrophil infiltration. The expressions of pro-inflammatory cytokines (CINC-1) in intestinal mucosa were measured by enzyme-linked immunosorbent assay (ELISA) and reverse transcription-PCR (RT-PCR). In additional experiments with an in vitro flow system, human neutrophils were perfused on human umbilical vein endothelial cells (HUVEC) pretreated with anoxia-reoxygenation with or without CV-11974 and then the adhesive neutrophils were counted.

RESULTS

Reperfusion after ischemia resulted in an increase in luminal protein concentrations, hemoglobin concentrations, thiobarbituric acid reactive substances, and MPO activity. Pretreatment with CV-11974 significantly inhibited the increases in these parameters. CV-11974 also inhibited increases in intestinal CINC-1 protein and mRNA expression induced by ischemia-reperfusion. Moreover, in an in vitro study, CV-11974 significantly inhibited the adherence of neutrophils to HUVEC exposed to reoxygenation after anoxia.

CONCLUSIONS

These results suggest that the blockade of angiotensin II type I receptor by treatment with CV-11974 remarkably reduced the reperfusion-induced intestinal injury.

Therapeutic effects of xanthine oxidase inhibitors: renaissance half a century after the discovery of allopurinol

The prototypical xanthine oxidase (XO) inhibitor allopurinol, has been the cornerstone of the clinical management of gout and conditions associated with hyperuricemia for several decades. More recent data indicate that XO also plays an important role in various forms of ischemic and other types of tissue and vascular injuries, inflammatory diseases, and chronic heart failure. Allopurinol and its active metabolite oxypurinol showed considerable promise in the treatment of these conditions both in experimental animals and in small-scale human clinical trials. Although some of the beneficial effects of these compounds may be unrelated to the inhibition of the XO, the encouraging findings rekindled significant interest in the development of additional, novel series of XO inhibitors for various therapeutic indications. Here we present a critical overview of the effects of XO inhibitors in various pathophysiological conditions and also review the various emerging therapeutic strategies offered by this approach.

N-acetylcysteine in intestinal reperfusion injury: an experimental study in rats

BACKGROUND

The aim of the present study was to investigate the effect of N-acetylcysteine on intestinal reperfusion injury.

METHODS

Forty Sprague-Dawley rats were divided into four groups (n = 10): sham, sham + N-acetylcysteine, reperfusion, and reperfusion + N-acetylcysteine. Thirty minutes of ischaemia +/- 30 min of reperfusion was performed under 100 mg/kg N-acetylcysteine or placebo, administered 30 min before the operation in the groups where appropriate. Ileum samples were resected for histopathologic evaluation and tissue malondialdehyde and super oxide dismutase level determination.

RESULTS

The mean mucosal injury score and malondialdehyde level of the reperfusion and reperfusion + N-acetylcysteine groups were significantly higher than that of the control and control + N-acetylcysteine group (P < 0.01, P < 0.05, respectively). Mean super oxide dismutase level of the control + N-acetylcysteine group was significantly higher than that of the other groups (P < 0.05).

CONCLUSION

N-Acetylcysteine did not prevent intestinal reperfusion injury by means of histopathologic findings and malondialdehyde level.

Glutamine stimulates amino acid transport during ischemia-reperfusion in human intestinal epithelial cells1

BACKGROUND

The potential mechanism of intestinal ischemia-reperfusion (I/R) injury includes oxygen-derived toxic free radicals. We tested the hypothesis that glutamine increases intracellular glutathione, a protective substrate against oxidative stress, by stimulating membrane amino acid transport during I/R using human intestinal epithelial cell line Caco-2.

METHODS

Ischemic conditions were obtained by combining both hypoxic (1%O2-5%CO2-94% N2) and nutrient-deprived (Phosphate-Buffered Saline; PBS) conditions. After 2 h of ischemia, re-oxygenation (5%CO2-95% air) was initiated and the culture medium was changed to PBS, PBS supplemented with amino acids (A.A.), and PBS supplemented with 2 mm glutamine plus amino acids (Gln) (reperfusion). After 4 h of reperfusion, the transport of 3H-glutamine, 3H-glutamate, and 3H-leucine was assayed and intracellular glutathione was measured. 3H-thymidine incorporation was measured for the determination of DNA synthesis. Data (mean +/- SD) were analyzed by ANOVA.

RESULTS

Ischemia decreased Na+-dependent glutamine, Na+-dependent glutamate, and Na+-independent leucine transport compared with control (P < 0.01). After reperfusion, glutamine and glutamate transport in the PBS and A.A. groups decreased significantly compared with control (P < 0.01), whereas glutamine supplementation increased glutamine transport to the levels in control (P < 0.01) and partially increased glutamate transport (P < 0.01). Leucine transport significantly increased in the A.A. and Gln groups compared with the PBS group. Glutamine significantly increased intracellular glutathione and DNA synthesis compared with the PBS and A.A. groups (P < 0.01).

CONCLUSIONS

This study demonstrated that glutamine up-regulates amino acid transport during I/R in human intestinal epithelial cells, possibly resulting in increased intracellular glutathione and DNA synthesis.

Bradykinin B2 receptor antagonist FR173657 ameliorates small bowel ischemia-reperfusion injury in dogs

Bradykinin mediates acute inflammation by increasing microvascular permeability, vasodilation, leukocyte migration and accumulation, and the production of arachidonic acid via phospholipase A2 activation. Arachidonic acid metabolites, or eicosanoids, are potent modulators of biological functions, particularly inflammation. Bradykinin exerts its inflammatory effects via the bradykinin B2 receptor. The aim of this study was to evaluate the effect of a bradykinin B2 receptor antagonist, FR173657 (FR), on intestinal ischemia-reperfusion (I/R) injury. Twenty-eight mongrel dogs were divided into four groups (n = 7 per group). Group I underwent I/R alone, Group II underwent I/R and received FR treatment, Group III was sham operated, and Group IV was sham operated and received FR treatment. The FR treatment consisted of FR continuously from 30 min prior to ischemia to 2 hr after reperfusion. In the I/R procedure, the superior mesenteric artery (SMA) and vein were clamped for 2 hr and then released to permit reperfusion for 12 hr. The intramucosal pH (pHi), SMA blood flow, and mucosal tissue blood flow were measured during the reperfusion period. The serum thromboxane B2 and 6-keto-prostaglandin F1alpha levels were determined, and tissue samples were examined histologically. Results showed that tissue blood flow, pHi, and SMA blood flow after reperfusion were maintained in Group II in comparison with Group I. Histopathological examination showed less severe mucosal damage after reperfusion in Group II than in Group I. The serum thromboxane B2 and 6-keto-prostagland in F1alpha levels were significantly lower in Group II than in Group I (P < 0.05). We conclude that FR treatment appears to have clear protective effects on small bowel I/R injury by inhibiting the release of eicosanoids.

Hypoxemic reperfusion after 120 mins of intestinal ischemia attenuates the histopathologic and inflammatory response *

OBJECTIVE

It has been suggested that reactive oxygen species play a pivotal role in the initial organ-tissue injury during reperfusion, eliciting inflammatory reaction and multiple organ failure. It was investigated if hypoxemic reperfusion attenuates tissue injury and inflammatory response.

DESIGN

Randomized animal study.

SETTING

Medical school laboratory.

SUBJECTS

Twenty-five male pigs weighing 25-28 kg.

INTERVENTIONS

Pigs were subjected to 120 mins of intestinal ischemia by clamping the superior mesenteric artery. Upon declamping, the animals were randomly assigned to receive either hypoxemic reperfusion (HR group, n = 9) reperfused with a Pao2 = 30-35 or normoxemic reperfusion (control group, n = 16) reperfused with a Pao2 = 100 mm Hg for 120 mins. Fluids without inotropes were given to combat circulatory shock during reperfusion.

MEASUREMENTS AND MAIN RESULTS

Portal blood and intestinal and lung biopsies were collected at baseline, end of ischemia, and end of reperfusion. Histopathologic changes were scored, and interleukin-1beta, qualitative Limulus amebocyte, lysate test, and Pao2/Fio2 were measured. Eight of 16 animals of the control group and seven of nine of the HR group survived (p = .22). At the end of reperfusion, the intestinal (p = .004) and lung (p = .028) pathologic scores were lower in the HR group compared with controls. The only significant difference in concentration of interleukin-1beta in the portal blood between the two animal groups occurred 120 mins after reperfusion (p = .006). The number of HR animals with a positive Limulus test was significantly smaller compared with controls at 60 (p = .041) and 120 (p = .07) mins of reperfusion. During the period of ischemia, the Pao2/Fio2 decreased similarly in the control and HR group, whereas after 120 mins of reperfusion the rate was significantly higher in the HR group.

CONCLUSIONS

Hypoxemic reperfusion represents an intervention that may attenuate the triggering of multifactorial cascade and organ tissue injury.

Oxygen free radicals and redox biology of organelles

The presence and supposed roles of reactive oxygen species (ROS) were reported in literature in a myriad of instances. However, the breadth and depth of their involvement in cellular physiology and pathology, as well as their relationship to the redox environment can only be guessed from specialized reports. Whatever their circumstances of formation or consequences, ROS seem to be conspicuous components of intracellular milieu. We sought to verify this assertion, by collecting the available evidence derived from the most recent publications in the biomedical field. Unlike other reviews with similar objectives, we centered our analysis on the subcellular compartments, namely on organelles, grouped according to their major functions. Thus, plasma membrane is a major source of ROS through NAD(P)H oxidases located on either side. Enzymes of the same class displaying low activity, as well as their components, are also present free in cytoplasm, regulating the actin cytoskeleton and cell motility. Mitochondria can be a major source of ROS, mainly in processes leading to apoptosis. The protein synthetic pathway (endoplasmic reticulum and Golgi apparatus), including the nucleus, as well as protein turnover, are all exquisitely sensitive to ROS-related redox conditions. The same applies to the degradation pathways represented by lysosomes and peroxisomes. Therefore, ROS cannot be perceived anymore as a mere harmful consequence of external factors, or byproducts of altered cellular metabolism. This may explain why the indiscriminate use of anti-oxidants did not produce the expected "beneficial" results in many medical applications attempted so far, underlying the need for a deeper apprehension of the biological roles of ROS, particularly in the context of the higher cellular order of organelles.

Effects of flunixin meglumine or etodolac treatment on mucosal recovery of equine jejunum after ischemia

OBJECTIVE

To examine the effects of flunixin meglumine and etodolac treatment on recovery of ischemic-injured equine jejunal mucosa after 18 hours of reperfusion.

ANIMALS

24 horses.

PROCEDURE

Jejunum was exposed to 2 hours of ischemia during anesthesia. Horses received saline (0.9% NaCl) solution (12 mL, i.v., q 12 h), flunixin meglumine (1.1 mg/kg, i.v., q 12 h), or etodolac (23 mg/kg, i.v., q 12 h). Tissue specimens were obtained from ischemic-injured and nonischemic jejunum immediately after ischemia and 18 hours after recovery from ischemia. Transepithelial electric resistance (TER) and transepithelial flux of tritium-labeled mannitol measured mucosal permeability. Denuded villous surface area and mean epithelial neutrophil count per mm2 were calculated. Western blot analysis for cyclooxygenase (COX)-1 and -2 was performed. Pharmacokinetics of flunixin and etodolac and eicosanoid concentrations were determined.

RESULTS

Ischemic-injured tissue from horses treated with flunixin and etodolac had significantly lower TER and increased permeability to mannitol, compared with that from horses treated with saline solution. Epithelial denudation after ischemia and 18 hours after recovery was not significantly different among treatments. Both COX-1 and -2 were expressed in ischemic-injured and nonischemic tissues. Ischemia caused significant upregulation of both COX isoforms. Eicosanoid concentrations were significantly lower in tissues from flunixin and etodolac-treated horses, compared with that from horses treated with saline solution.

CONCLUSIONS AND CLINICAL RELEVANCE

Flunixin and etodolac treatment retarded recovery of intestinal barrier function in jejunal mucosa after 18 hours of reperfusion, whereas tissues from horses treated with saline solution recovered baseline values of TER and permeability to mannitol.

Alleviating ischemia-reperfusion injury in small bowel

An amino acid-based solution has been recently developed and has demonstrated significant protective effects during cold storage of small bowel (SB). This study was designed to examine the role of this novel solution in ameliorating intestinal injury in an in vivo model of ischemia-reperfusion (IR). The impact of luminal treatment with an amino acid-based (AA) solution was assessed throughout reperfusion after 60-min warm ischemia (WI) in rodent SB. Energetics (ATP and total adenylates) remained significantly elevated throughout 60-min reperfusion in AA-treated tissue compared with untreated controls. Increases in end-products (ammonia and alanine) and increases in alanine aminotransferase and glutaminase activity implicated greater amino acid metabolism in AA-treated tissues. After reperfusion, malondialdehyde levels were similar between all groups. Glutathione levels were consistently elevated in AA-treated tissues and by 60 min reperfusion values were sixfold greater than control. AA-mediated protection during IR resulted in reduced neutrophil infiltration suggesting a weaker inflammatory response. Barrier function and electrophysiology parameters exhibited a clear pattern of mucosal preservation in AA-treated tissues; histology supported these findings. This study raises the possibility of a role for a luminal nutrient-rich solution during ischemic storage of small bowel in the clinic.

In vivo investigation of the efficacy of a customized solution to attenuate injury following low-flow ischemia and reperfusion injury in the jejunum of horses

OBJECTIVE

To evaluate the efficacy of a customized solution to attenuate intestinal injury following 20% low-flow ischemia and reperfusion in the jejunum of horses.

ANIMALS

10 healthy adult horses.

PROCEDURE

Two 30.5-cm-long segments of jejunum were exteriorized through a ventral midline incision and the mesenteric artery and vein supplying that portion of the intestine were instrumented with flow probes. Blood flow was decreased to 20% of baseline for 90 minutes followed by 90 minutes of reperfusion. In 5 horses, 60 mL of the customized solution was placed in the lumen of each segment (treatment-group horses), and 60 mL of lactated Ringer's solution was placed in the lumen of 5 additional horses (control-group horses). Biopsy specimens were obtained from 1 segment in both groups for histologic evaluation. Aliquots of luminal fluid were obtained from the other segment in both groups for determination of albumin concentrations as an index of mucosal permeability.

RESULTS

Compared with control-group horses, treatment-group horses had a significant decrease in luminal albumin concentration following reperfusion. Although differences in mucosal grades were not significantly different between control- and treatment-group horses, treatment-group horses had significantly greater jejunal villous length and area, compared with that of control-group horses.

CONCLUSIONS AND CLINICAL RELEVANCE

Intraluminal administration of the customized solution in the jejunum, compared with lactated Ringer's solution, results in an improvement in histologic findings and mucosal translocation of albumin in horses with mild intestinal injury.

Treatment of gastrointestinal ischemic injury

Ischemic injury is one of the most important causes of mortality in equine veterinary medicine. Although treatment of reperfusion injury has been attempted in a number of experimental trials to reduce the level of injury subsequent to an ischemic episode, this research has not resulted in the development of useful clinical treatments. Nevertheless, recent studies assessing intraluminal application of solutions containing antioxidants, nutrients, and vasodilators are promising. Furthermore, focusing on improving mucosal recovery after an ischemic event may provide an alternative method of reducing mortality. Potential treatments include administration of basement membrane components like hyaluronic acid, gut-specific nutrients like glutamine, and early return to feeding to stimulate endogenous repair mechanisms. Finally, recent studies evaluating NSAIDs have revealed the potential of flunixin meglumine to retard the mucosal repair process, indicating the need for judicious use of this drug.

Protective effect of a novel antioxidant non-steroidal anti-inflammatory agent (compound IA) on intestinal viability after acute mesenteric ischemia and reperfusion

Reactive oxygen species play an important role in the basic pathophysiology of ischemia-reperfusion injury. We investigated whether the administration of a novel non-steroidal anti-inflammatory compound with antioxidant properties, the compound [5-(2-amino-ethylamino)-1-phenyl-2-pentanone] (compound IA), has a beneficial effect on the repair process of the intestinal mucosa after transient mesenteric ischemia in a randomized blind trial. Six groups of rats were subjected to a model of 60 min of intestinal ischemia that was produced by occluding the superior mesenteric artery. At the end of ischemia, compound IA was administered intravenously and the clamp was removed allowing reperfusion. At 60 min after reperfusion, animals were sacrificed and a 10 cm section of terminal ileum was resected. The outcome was evaluated by histopathologic assessment, measurement of polymorphonuclear leukocytes and the extent of lipid peroxidation measuring the small intestine tissue malondialdehyde. After 1 h of reperfusion, the mucosal damage was less in IA-treated rats compared with the control group. Moreover, the number of polymorphonuclear leukocytes in intestinal mucosa was significantly lower in IA group. Compound IA resulted in a statistically significant reduction of the concentration of small intestine tissue malondialdehyde, compared to those of controls. Administration of compound IA decreased the mucosal damage in rats that were subjected to 60 min of ischemia followed by 60 min of reperfusion. The mechanism of compound IA action is considered to be mediated via its potent antioxidant, free radical scavenging activities and inhibition of polymorphonuclear leukocytes infiltration.

Effects of in vivo freezing and mannitol in intestinal ischaemia-reperfusion injury

PURPOSE

The main purpose of this study was to investigate whether in vivo freezing and mannitol administration can protect the small intestine against ischaemia-reperfusion (I-R) injury.

METHODS

Fifty male Sprague-Dawley rats (200-225 g) were divided into 5 groups each containing 10 rats; group SO, sham operation group; group I, mesenteric ischaemia group; group R, ischaemia-reperfusion (I-R); group FR, I-R plus in vivo freezing; group MR, I-R plus mannitol treatment. Intestinal ischaemia for 30 min and reperfusion for 60 min were applied. Ileum specimens were obtained to determine the tissue levels of malondialdehyde (MDA) and histological changes.

RESULTS

The mucosal injury scores of group R were significantly higher than those of the group I (P<0.0001). The mucosal injury scores in the groups FR and MR were significantly lower than the group R (P<0.0001 and P<0.0001, respectively). In the group FR, mucosal injury scores were not significantly different from those of group I (P=0.123). However, mucosal injury scores of group MR were significantly less when compared to those of group I (P=0.01). Mean MDA levels of group R were significantly higher than those of the group I (P<0.0001). Mean MDA levels of groups FR and MR were significantly lower than those of group R (P<0.0001 and P<0.0001, respectively). In addition, MDA levels of group FR were significantly higher than those of group MR (P<0.0001).

CONCLUSION

In conclusion, these observations suggest that the in vivo freezing of SMA and the pre-treatment with mannitol before reperfusion period may be useful in preventing intestinal reperfusion injury.

Homocysteine prevents total parenteral nutrition (TPN)-induced cholestasis without changes in hepatic oxidative stress in the rat

BACKGROUND

The role of oxidative stress in total parenteral nutrition (TPN)-associated cholestasis with liver glutathione depletion was recently shown. The aims of this study were to test the appearance of cholestasis and oxidative stress during TPN, and the hypothesis that reducing oxidative stress with a precursor of glutathione (GSH), homocysteine, would restore bile flow.

METHODS

Three groups of rats (weight, 179-278 g) were studied: 1) D/aa group received dextrose and amino acids (3.4 g/d); 2) D/aa/L group received the same amount of amino acids, and lipids were added on an equicaloric basis (50 kcal/d) with a lowered amount of dextrose; and 3) a control group, which received dextrose perfusion and had free access to chow. A subgroup of D/aa/L rats (n = 6) received a TPN solution containing homocysteine. After 5 days of TPN, bile was collected during 2 hours. In liver homogenates, GSH, thiobarbituric acid reactive substances (TBARS), and carbonyl content of proteins (Prot-CO) were measured to test the level of oxidative stress and hepatic lipid and protein oxidation.

RESULTS

After TPN, bile flow was significantly lower in the D/aa group than in the control group. Addition of lipids further decreased bile flow. Addition of homocysteine to TPN with lipids significantly increased bile flow. Aspartate aminotransferase increased significantly in both TPN groups compared with the control group. gamma-Glutamyl transpeptidase was not different among TPN groups. An increased hepatic lipid oxidation was demonstrated by TBARS level in both TPN groups when compared with the control group. However, the liver GSH contents were not different. Protein oxidation was also significantly increased by TPN. The addition of homocysteine to TPN solution increased bile flow without liver injury or changes of lipid and protein oxidation.

DISCUSSION

This study shows that TPN administered to rats induces a decrease of bile flow and an oxidative stress but that the two changes are not directly correlated. Addition of lipids further impairs bile flow but does not increase the occurrence of liver injury. Consequently, it seems more likely that TPN primarily induces a cholestatic effect that in turn induces an oxidative stress rather than inducing an oxidative stress that leads to cholestasis. However, an association of both mechanisms is not totally excluded.

Ischemia-reperfusion injury following superior mesenteric artery occlusion and strangulation obstruction

BACKGROUND

Intestinal ischemia-reperfusion injury (IRI) is a serious and common clinical entity resulting in severe tissue injury. This study was designed to compare IRI in superior mesenteric artery (SMA) occlusion and strangulation obstruction (SO).

MATERIALS AND METHODS

Thirty Wistar-Albino rats were assigned randomly to three groups. In the control group, a sham operation was performed. In the SMA occlusion group, a vascular clamp was placed across the SMA to occlude arterial circulation. In the SO group, a 15-cm segment of small intestine was looped to prevent venous circulation. Sixty minutes of ischemia was followed by 60 min of reperfusion. Following reperfusion, biopsies of small intestine were taken to assess morphologic damage, tissue levels of malonyldialdehyde (MDA) as an index of lipid peroxidation reflecting oxygen free radicals (OFR) were determined, and serum biochemical analyses were performed.

RESULTS

The levels of tissue MDA were significantly higher in the SO group than in the SMA occlusion group (P < 0.05). Biochemical parameters of SO and SMA occlusion groups were higher than those in the control group and there was a significant difference between the SMA occlusion and the SO models, except for ALP levels. Histopathologically, transmural intestinal damage were present in seven cases of SO and in six cases in the SMA occlusion group.

CONCLUSIONS

Despite no significant difference between the two groups in terms of intestinal tissue damage, OFR-induced injury was higher in the strangulation obstruction group.

In vitro evaluation of an intraluminal solution to attenuate effects of ischemia and reperfusion in the small intestine of horses

OBJECTIVE

To evaluate the efficacy of intraluminal administration of a customized solution during low-flow ischemia and reperfusion in the jejunum of horses.

SAMPLE POPULATION

Segments of jejunum obtained from 13 healthy adult horses.

PROCEDURE

In isolated segments of jejunum maintained in an extracorporeal circuit, arterial flow was reduced to 20% of baseline for 40 minutes (ischemia) followed by 60 minutes of reperfusion. In 2 groups, a customized solution (concentrations, 12.5 and 25%, respectively) was placed in the lumen prior to low-flow ischemia and maintained during reperfusion. The control group received intraluminal lactated Ringer's solution for the same duration. Various metabolic, hemodynamic, histologic, and permeability variables were recorded.

RESULTS

The 12.5% solution resulted in less histomorphologic injury and reduced mucosal permeability to albumin, compared with the 25% solution and the lactated Ringer's solution. Morphologic injury and permeability were reduced in tissues that received the 25% solution, compared with the control group, but this difference was not significant.

CONCLUSIONS AND CLINICAL RELEVANCE

Use of a 12.5% customized solution appeared to minimize injury in the isolated extracoporeal jejunal loop, which provides some indication that it might be useful in clinical situations.

Prediction of graft viability from non-heart-beating donor pigs using hepatic microdialysate hypoxanthine levels

BACKGROUND

Non-heart-beating donors (NHBDs) are not yet acceptable in orthotopic liver transplantation (OLTX) because of the high frequency of primary graft nonfunction. In this study, we aimed to develop a new predictive method of graft viability in OLTX from NHBDs.

MATERIALS AND METHODS

(1) Pigs were subjected to 15 min of hepatic ischemia and reperfusion (I/R). (2) Porcine OLTX was performed using grafts obtained from NHBDs subjected to in situ warm ischemia (0, 30, and 60 min). During both operations, hepatic hypoxanthine levels were measured by a microdialysis method.

RESULTS

In the I/R model, hypoxanthine accumulated during ischemia and decreased after reperfusion, whereas marked xanthine and uric acid production were observed after reperfusion. In the NHBDs model, all of the 0-min group, 6 of 13 pigs in the 30-min group, and 1 of 6 pigs in the 60-min group survived more than 7 days. Significant increases of hypoxanthine levels were seen dependent on warm ischemic time. In the 30-min group, hypoxanthine levels were significantly higher in the pigs that died than in those that survived, and correlated with aspartate aminotransferase, lactate dehydrogenase, and adenosine triphosphate levels of recipients. Histological examination revealed that graft injury was severe in the pigs with higher hypoxanthine levels.

CONCLUSIONS

It is suggested that hepatic microdialysate hypoxanthine levels during warm ischemia in NHBDs were correlated with graft viability in the recipient. By using of this technique, prediction of the graft viability may be possible during donor operation.

Neutrophils increase paracellular permeability of restituted ischemic-injured porcine ileum

BACKGROUND

We have previously shown minimal evidence of neutrophil infiltration during early reperfusion of porcine ischemic ileum. However, we noted marked neutrophil infiltration 6 to 18 hours after ischemia during mucosal repair. We postulated such neutrophil infiltration would disrupt restituting epithelium.

METHODS

Pigs were pretreated with anti-CD11/CD18 monoclonal antibody, superoxide dismutase-polyethylene glycol, or saline solution before inducing 1 hour of ischemia. Pigs recovered for up to 18 hours, after which mucosal repair was assessed.

RESULTS

One hour of ischemia induced loss of 19 +/- 7% of the villous epithelial surface area. Epithelial restitution covered the mucosal defect within 2 hours, although full recovery of mucosal barrier function required 6 hours. By 18 hours, a significant decrease in transepithelial electrical resistance and increase in transmucosal mannitol flux was noted despite the continued presence of complete epithelial coverage. Accumulation of neutrophils within restituting epithelium was noted on histologic examination, associated with electron-microscopic evidence of widened paracellular spaces. Pretreatment with anti-CD11/CD18 monoclonal antibody and superoxide dismutase-polyethylene glycol significantly reduced neutrophil infiltration and normalized transepithelial electrical resistance and mannitol fluxes.

CONCLUSIONS

Mucosal inflammation during epithelial repair resulted in increased paracellular permeability as neutrophils traversed restituted epithelium. Blocking neutrophil adhesion or scavenging superoxide prevented mucosal dysfunction in recovering tissue.

Antioxidant enzyme levels in intestinal and renal tissues after a 60-minute exercise in untrained mice

The present study was designed to determine the effects of exercise on the antioxidant enzymatic system and lipid peroxidation in small intestine and kidney, during the post-exercise period in untrained mice. Two days after the last adaptation running exercise, animals were ran on the treadmill for 60 min at 18 m/min. 5 degrees slope. After the acute exercise the animals were killed by cervical dislocation, immediately (0 h), 3 hours (3 h) and 24 hours (24 h) after the exercise. Control animals were killed without running exercise. Their proximal small intestinal and renal tissues were quickly removed. Changes in the concentration of thiobarbituric acid reactive substance (TBARS), as an index of lipid peroxidation, in intestine and kidney were studied in mice after the running exercise and in unexercised control group. The activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx) were determined in these tissues. Tissue SOD, GPx activities and TBARS level were not increase by the exercise in kidney. Intestinal SOD activity decreased after exercise (0 h and 3 h respectively, p<0.05, p<0.01) and retumed to control levels. Intestinal GPx activity increased after exercise (0 h, p<0.05) and returned to control levels. There was no significant difference among groups in intestinal tissue TBARS levels. These findings could suggest that submaximal exercise may not cause oxidative stress in proximal small intestinal tissue and kidney.

Role of the mitochondrial permeability transition and cytochrome C release in hydrogen peroxide-induced apoptosis

We investigated the role of the mitochondrial inner membrane permeability transition and subsequent release of cytochrome c into the cytosol during oxidative stress-evoked apoptosis. Sublethal oxidative stress was applied by treating L929 cells with 0.5 mM H2O2 for 90 min. Then the cellular localization of cytochrome c was examined by immunofluorescent staining and Western blotting. H2O2 treatment caused the permeability transition and pore formation, resulting in membrane depolarization and translocation of cytochrome c from the mitochondria into the cytosol. Pretreatment with cyclosporin A and aristolochic acid (to inhibit pore formation) significantly attenuated a reduction of the mitochondrial membrane potential, as well as signs of apoptosis such as DNA fragmentation, increased plasma membrane permeability, and chromatin condensation. Therefore, exposure to H2O2 caused the opening of permeability transition pores in the inner mitochondrial membrane. An essential role of cytosolic cytochrome c in the execution of apoptosis was demonstrated by its direct microinjection into the cytosol, thus bypassing the need for cytochrome c release from the mitochondrial intermembrane space. Microinjection of cytochrome c caused caspase-dependent apoptosis.

Modification of 5-hydroxytryptophan-evoked 5-hydroxytryptamine formation of guinea pig colonic mucosa by reactive oxygen species

We studied whether reactive oxygen species (ROS) generated by normal colonic mucosa affect 5-hydroxytryptophan (5-HTP)-evoked 5-HT formation (measured as the sum of 5-HT plus 5-hydroxyindole acetic acid (5-HIAA) accumulation) of guinea pig's isolated colonic mucosa. Catalase (3000-6000 U/ml), a hydrogen peroxide (H2O2) scavenger or diphenylene iodonium (DPI, 10-100 microM), an NADPH oxidase inhibitor, concentration-dependently caused an increase of the sum of 5-HT plus 5-HIAA accumulation in the presence of 5-HTP (10 microM), but these drugs did not significantly affect the 5-HT-metabolite in the colonic mucosa measured as the ratio of 5-HIAA/5-HT. Exogenously applied H2O2 (10-100 microM) concentration-dependently inhibited the sum of 5-HT plus 5-HIAA accumulation. In contrast, neither superoxide dismutase (SOD, 100-300 U/ml), superoxide anion scavenger, nor dimetyl sulfoxide (1-5%, DMSO), a hydroxyl radical scavenger affected the sum of 5-HT plus 5-HIAA accumulation. Moreover, mucosa ROS generation was estimated using the chemiluminescence technique. SOD (100-300 U/ml), catalase (3000-6000 U/ml) or DPI (10-100 microM), concentration-dependently reduced luminol-enhanced chemiluminescence signal from the colonic mucosa, while allopurinol (10-100 microM), a xanthine oxidase inhibitor, did not affect the chemiluminescence signal. These results suggest that ROS is formed through an NADPH oxidase system in the guinea pig colonic mucosa, where it exerts a modulatory effect on mucosal 5-HT formation upon addition of 5-HTP. Thus, ROS formation from normal colonic mucosa could be considered to contribute to the control of 5-HT production in mucosa enterochromaffin cells.

Increase in gastric intramucosal hydrogen ion concentration following endotoxin challenge in the rat and the actions of nitric oxide synthase inhibitors

1. Cardiovascular events and outcome in septic shock may be predicted by monitoring the fall in intramural pH (pHi), as an index of splanchnic perfusion and mucosal ischaemia. In the present study, a small animal model for monitoring the changes of gastric pHi or intramucosal [H+] following challenge with the endotoxin lipopolysaccharide (LPS) was developed in the rat. The role of nitric oxide (NO) in these events in this model was evaluated using the non-selective NO synthase (NOS) inhibitors N(G)-nitro-L-arginine methyl ester (L-NAME) and N(G)-monomethyl-L-arginine (L-NMMA). 2. The pHi and intramucosal [H+] were evaluated in omeprazole-pretreated rats (30 mg/kg, i.p.) using the Henderson equation after estimating the PCO2 and the bicarbonate concentration in gastric wall. To measure gastric wall PCO2, the oesophagus was intubated and the pylorus ligated. The PCO2 was measured by a blood gas analyser in 2 mL saline instilled for 30 min in the gastric lumen to equilibrate with the gastric wall. The pHi was measured under basal conditions and 3 and 5 h after LPS (3 mg/kg) administration. Separate groups received treatment with L-NMMA (25-50 mg/kg) or L-NAME concomitantly or 2.5 h after administration of LPS. 3. Intravenous administration of Escherichia coli LPS provoked a significant fall in gastric pHi from 7.37 to 7.18 (median values; n =10-19) determined after 5 h. In groups treated concurrently with LPS and L-NAME (5 mg/kg; n = 19), there was a similar increase in intramucosal [H+] as that induced by LPS alone (n = 15) in those animals that survived. In contrast, L-NAME (5 mg/kg; n = 12), given 2.5 h after LPS challenge, at a time at which inducible NOS is known to be significantly expressed, prevented the increase in intramucosal [H+] at 3 and 5 h after LPS challenge. Similarly, L-NMMA (25-50 mg/kg; n = 23), given 2.5 h after LPS challenge, dose-dependently inhibited the increase in intramucosal [H+] at 3 and 5 h. 4. In conclusion, these findings indicate that this rat model could be useful in exploring the pathophysiology of acute endotoxin shock. Delayed administration of L-NAME and L-NMMA abolished the increase in gastric intramucosal [H+], supporting the involvement of excess NO in the tissue dysfunction associated with endotoxin shock. This suggests the potential value of this small animal model in evaluating the therapeutic activity of novel agents for use in septic shock.

Prostanoids mediate the protective effect of trefoil factor 3 in oxidant-induced intestinal epithelial cell injury: role of cyclooxygenase-2

Trefoil factors are small peptides found in several mammalian tissues including gut, respiratory tract and brain. Their physiological function is not well understood. Among them, trefoil factor 3 (intestinal trefoil factor) is known to be cytoprotective in the gut. However, the molecular mechanism and secondary mediators of trefoil factor 3 action are not known. In the present study, we examined whether the cyclooxygenase pathway is involved in trefoil factor 3 action. We showed that trefoil factor 3 significantly induces the production of prostaglandin E(2) and prostaglandin I(2) in IEC-18 cells (an intestinal epithelial cell line) in a dose dependent manner. Western blot and immunohistochemistry revealed that trefoil factor 3 (2.5 microM) up-regulates the expression of cyclooxygenase-2 but not cyclooxygenase-1 in IEC-18 cells. Treating cells with trefoil factor 3 (10 microM) significantly attenuated reactive oxygen species-induced IEC-18 cell injury. This effect is blocked by NS-398 (10 microM), a selective cyclooxygenase-2 inhibitor. Moreover, we demonstrated that exogenously administered carbacyclin (1 microM, a stable analogue of prostaglandin I(2)) and/or prostaglandin E(2) (1 microM) caused a significant reduction of reactive oxygen species-induced cell injury, mimicking the effect of trefoil factor 3. In summary, our results indicate that trefoil factor 3 activates cyclooxygenase-2 in intestinal epithelium to produce prostaglandin I(2) and prostaglandin E(2), which function as survival factors and mediate the cytoprotective action of trefoil factor 3 against oxidant injury.

Interaction of platelet activating factor, reactive oxygen species generated by xanthine oxidase, and leukocytes in the generation of hepatic injury after shock/resuscitation

OBJECTIVE

To evaluate the putative relation of platelet activating factor (PAF), xanthine oxidase, reactive oxidants, and leukocytes in the pathogenesis of hepatic injury after shock/resuscitation (S/R) in vivo.

BACKGROUND

Reactive oxygen metabolites generated by xanthine oxidase at reperfusion have been found to trigger postischemic injury in many organs, including the liver. However, the precise linear sequence of the mechanism of consequent hepatic injury after S/R remains to be characterized.

METHODS

Unheparinized male rats were bled to a mean blood pressure of 45 +/- 3 mmHg. After 2 hours of shock, they were resuscitated by reinfusion of shed blood (anticoagulated with citrate-phosphate-dextrose) and crystalloid and observed for the next 6 or 24 hours.

RESULTS

S/R caused the oxidation of hepatic glutathione and generated centrolobular leukocyte accumulation at 6 hours, followed by predominantly centrolobular hepatocellular injury at 24 hours. Each of these components was attenuated by PAF inhibition with WEB 2170, xanthine oxidase inhibition with allopurinol, antioxidant treatment with N-acetylcysteine, or severe leukopenia induced by vinblastine. In each case, the degree of leukocyte accumulation at 6 hours correlated with the hepatocellular injury seen at 24 hours. However, xanthine oxidase inhibition with allopurinol failed to attenuate further the small level of residual hepatocellular injury seen in leukopenic rats.

CONCLUSION

These findings suggest that reactive oxidants generated by xanthine oxidase at reperfusion, stimulated by PAF, mediate hepatocellular injury by triggering leukocyte accumulation, primarily within the centrolobular sinusoids.

Attenuation of intestinal ischemia/reperfusion injury with sodium nitroprusside: studies on mitochondrial function and lipid changes

Reactive oxygen species have been implicated in cellular injury during ischemia/reperfusion (I/R). Mitochondria are one of the main targets of oxygen free radicals and damage to this organelle leads to cell death. Reports suggest that nitric oxide (NO) may offer protection from damage during I/R. This study has looked at the functional changes and lipid alteration to mitochondria during intestinal I/R and the protection offered by NO. It was observed that I/R of the intestine is associated with functional alterations in the mitochondria as suggested by MTT reduction, respiratory control ratio and mitochondrial swelling. Mitochondrial lipid changes suggestive of activation of phospholipase A(2) and phospholipase D were also seen after (I/R) mediated injury. These changes were prevented by the simultaneous presence of a NO donor in the lumen of the intestine. These studies have suggested that structural and functional alterations of mitochondria are prominent features of I/R injury to the intestine which can be ameliorated by NO.

Heparin-binding epidermal growth factor-like growth factor protects rat intestine from ischemia/reperfusion injury

BACKGROUND

We have shown previously that heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) is cytoprotective for intestinal epithelial cells exposed to hypoxia in vitro. We now examine the effects of HB-EGF on the recovery of small intestine from ischemic injury in vivo.

METHODS

Segmental intestinal ischemia of 60-min duration was produced in adult rats by occlusion of a first-order branch of the superior mesenteric artery. Recombinant HB-EGF (100 microg) was injected intraluminally into the proximal small bowel after 45 min of ischemia in experimental animals, and buffered saline was injected in control animals. Animals were sacrificed after 48 h, and the affected bowel was resected, processed, and examined microscopically, with histologic grading of the ischemic injury. Additional animals were allowed to recover for up to 1 month to evaluate mortality differences.

RESULTS

Intraluminal administration of HB-EGF resulted in significantly decreased extent and severity of ischemia/reperfusion injury, with significantly decreased grade of injury in the HB-EGF-treated compared with nontreated animals (average injury grade 0.66 compared with 2.44, respectively). Moreover, the mortality rate was significantly lower in the HB-EGF-treated animals compared with nontreated animals (0% vs 25%, respectively). HB-EGF-treated animals had increased weight gain in the postischemia recovery period.

CONCLUSIONS

We conclude that HB-EGF, given intraluminally, reduces both the amount and the severity of ischemia/reperfusion injury in the small bowel, reduces the mortality associated with intestinal ischemia, and may enhance intestinal recovery. The in vitro and in vivo cytoprotective effects of this growth factor suggest that it may, in the future, be clinically useful in treating patients with intestinal ischemia.

Reactive oxygen species induced smooth muscle responses in the intestine, vessels and airways and the effect of antioxidants

Numerous experimental data confirm the importance of reactive oxygen species (ROS) in physiological activities of smooth muscles and in the pathogenesis of various diseases with altered function of smooth muscles. The present study shows that smooth muscles of the intestine, airways and vessels, as well as their epithelium, endothelium and innervations, might be important targets of the ROS action. We demonstrated differences among the actions of various ROS (endogenous, exogenous, produced enzymatically, non-enzymatically) as well as among their actions in different smooth muscle tissues. Our results indicate that ROS are involved in changes in muscle tone, membrane conductance, calcium homeostasis, calcium-dependent processes, as well as in eicosanoid and nitric oxide metabolism. The effects of antioxidative enzymes (superoxide dismutase, catalase), of several drugs of natural origin (e.g. Kampo Medicines) and synthetic agents (e.g. stobadine, nitrosopine, ACE inhibitors) suggest that smooth muscle tissues are useful models to study ROS action and drug intervention in ROS induced injuries.

Role of nitric oxide in intestinal ischaemia-reperfusion injury studied using electron paramagnetic resonance

BACKGROUND

The role of nitric oxide in intestinal ischaemia-reperfusion (I/R) remains poorly defined, partly because of difficulty in detecting the nitric oxide free radical. In this study nitric oxide production was assessed during intestinal I/R by direct measurement using electron paramagnetic resonance (EPR), and the production of nitric oxide in jejunum and ileum was correlated with their different abilities to resist I/R injury.

METHODS

Rats were given an electron spin trapper (diethyldithiocarbamate/ferrous citrate) by intraperitoneal injection. Thirty-six segments each of jejunum and ileum were subjected to 15-90 min of ischaemia and 25 min of reperfusion. Tissue samples were analysed for EPR signals using a spectrometer.

RESULTS

Mean(s.d.) basal nitric oxide level was significantly higher in ileum (3.39(1.42) units) than jejunum (0. 65(0.05) units) (P = 0.0005). Increasing ischaemic times in the ileum resulted in decreasing nitric oxide levels (85, 32 and 13 per cent of basal level at 30, 60 and 90 min respectively); reperfusion resulted in further nitric oxide reduction (mean decrease 26 per cent). Severe (grade 3) histological damage was observed in low nitric oxide states (after 15 min of I/R in jejunum, 60 min of I/R in ileum).

CONCLUSION

Nitric oxide can be measured in intestinal tissues directly by EPR. The findings support a protective role for nitric oxide in I/R, and offer an explanation for the greater resistance to I/R of ileum.

The characteristics of intestinal injury peripheral to strangulating obstruction lesions in the equine small intestine

Recent studies suggest that horses requiring surgical correction of strangulating intestinal obstruction may develop post operative complications as a result of ischaemia/reperfusion injury. Therefore, the mucosal and serosal margins of resected small intestine from 9 horses with small intestinal strangulating lesions were examined for evidence of ischaemia/reperfusion injury. Severe mucosal injury and marked elevations in myeloperoxidase activity were detected at ileal resection margins (n = 4), whereas the mucosa from proximal jejunal (n = 9) and distal jejunal (n = 5) resection margins was normal. However, the serosa from jejunal resection margins had evidence of haemorrhage and oedema, and the proximal jejunal serosa had significantly increased numbers of neutrophils. Histological injury in ileal stumps is indicative of the inability fully to resect the ileum in horses with distal small intestinal strangulations. One of 4 horses subjected to ileal resection was subjected to euthanasia and found to have a necrotic ileal stump. Evidence of serosal injury and neutrophil infiltration in the proximal jejunal resection margins may predispose horses to post operative adhesions. Four of 8 horses discharged from the hospital suffered from recurrent colic in the post operative period.

Anti-inflammatory effects of U74389F in a rat model of intestinal ischemia/reperfusion injury

OBJECTIVE

To investigate the role of eicosanoid generation and neutrophilic infiltration in the protective effects of U74389F against ischemia/reperfusion injury in the small intestines of rats.

DESIGN

Prospective, randomized, controlled study.

SETTING

University research laboratory.

SUBJECTS

Adult, male Sprague-Dawley rats weighing between 200 and 300 g.

INTERVENTIONS

Groups (5-8) of rats treated with U74389F or vehicle were subjected to a sham operation and 30 mins of ischemia by occlusion of the superior mesenteric artery or 30 mins of ischemia followed by 60 or 120 mins of reperfusion. U74389F (2.5 mg/kg i.v.) or vehicle (citrate buffer) were slowly injected 2 mins before ischemia.

MEASUREMENTS AND MAIN RESULTS

Ischemia significantly (p < .05) increased mucosal injury (0 [normal] to 5) in both U74389F and untreated rats. In contrast, U74389F significantly (p < .05) attenuated the severity of injury after reperfusion. In vehicle-treated rats, ischemia/reperfusion significantly reduced villus height in both U74389F and untreated groups. However, the surface epithelial layer was intact in the U74389F but not in the vehicle-treated group. In addition, compared with the vehicle-treated group, U74389F significantly reduced neutrophil infiltration and prevented the increase in leukotriene B4 and prostaglandin E2 in response to ischemia and reperfusion.

CONCLUSIONS

This study demonstrates that the mechanism of U74389F against mesenteric ischemia/reperfusion includes a delay and reduction of neutrophilic infiltrate, an inhibition of leukotriene B4 production, and a facilitation of mucosal restitution.

Tissue hypoxanthine reflects gut vulnerability in porcine endotoxin shock

OBJECTIVE

To study differences in organ sensitivity during progressive endotoxin shock tissue levels of hypoxanthine, used as an indicator of adenosine triphosphate depletion and cellular energy failure, were monitored simultaneously in several organs by in vivo microdialysis.

DESIGN

Prospective, controlled animal study.

SETTING

University research laboratory.

SUBJECTS

Seventeen landrace pigs.

MEASUREMENTS AND MAIN RESULTS

Tissue levels of hypoxanthine, assessed by in vivo microdialysis, were monitored (in the ileum, liver, lung, skeletal muscle, subcutaneous fat, and arterial blood) simultaneously in addition to central hemodynamics during endotoxin shock in ten pigs. Seven sham animals not receiving endotoxin served as controls. Marked changes were seen in central hemodynamic parameters in response to endotoxemia. Very prominent increases were seen in the ileum and liver, followed by the lung, whereas only limited changes were observed in subcutaneous fat. These results indicate a differentiated development of cellular energy failure in response to endotoxemia in different organs. By considering the high amounts of xanthine oxidase seen in the gut, the increases in hypoxanthine may provide an important substrate for reactive oxygen species formation in this organ. The limited changes seen in subcutaneous fat suggest that this tissue may provide limited sensitivity when monitoring the septic patient.

CONCLUSIONS

These findings support the concept of specific vulnerability of the gut during endotoxemia.