Intestinal energy metabolism after ischemia-reperfusion: Effects of moderate hypothermia and perfluorocarbons

Remote ischaemic pre-conditioning reduces intestinal ischaemia reperfusion injury in a newborn rat

OBJECTIVE

Remote ischaemic conditioning (RIC) has been shown to reduce ischaemia-reperfusion injury(IRI) in multiple organ systems. IRI is seen in multiple bowel pathologies in the newborn, including NEC. We investigated the potential of RIC as a novel therapy for various intestinal pathologies in the newborn.

METHODS

We used an established intestinal IRI model in rat pups which results in similar intestinal injury to necrotising enterocolitis (NEC). Animals were randomly allocated to IRI only(n = 14), IRI + RIC(n = 13) or sham laparotomy(n = 10). The macroscopic extent of intestinal injury is reported as a percentage of total small bowel. Injury severity was measured using Chiu-Park scoring. Neutrophil infiltration/activation was assayed by myeloperoxidase activity. Immunohistochemistry was used to assess the expression of hypoxia-inducible factor alpha (HIF-1α). Data are median (interquartile range).

RESULTS

Animals that underwent RIC showed a decreased extent of macroscopic injury from 100%(85-100%) in the IRI only group to 58%(15-84%, p = 0.003) in the IRI + RIC group. Microscopic injury score was significantly lower in animals that underwent RIC compared to IRI alone (3.5[1.25-5] vs 5.5[4-6], p = 0.014). Intestinal myeloperoxidase activity in animals exposed to IRI was 3.4 mU/mg of tissue (2.5-3.7) and 2.1 mU/mg(1.5-2.8) in the IRI + RIC group(p = 0.047). HIF-1α expression showed a non-significant trend towards reduced expression in the IRI + RIC group.

CONCLUSIONS

RIC reduces the extent and severity of bowel injury in this animal model, supporting the hypothesis that RIC has therapeutic potential for intestinal diseases in the newborn.

Hepatic oxidative injury: role of mitochondrial dysfunction in necrotizing enterocolitis

PURPOSE

Necrotizing enterocolitis (NEC) is a severe neonatal gastrointestinal disease that can cause damage to remote organs. Previous studies have shown that inflammatory and oxidative injury occur in the liver during NEC. Mitochondrial DNA (mtDNA) plays an important role in hepatic injuries of many other diseases. We aimed to investigate the mechanism of mitochondrial dysfunction in hepatic oxidative injury during NEC.

METHODS

NEC was induced in C57BL/6 mice (approval: 44032) by hypoxia, gavage feeding with hyperosmolar formula, and lipopolysaccharide administration from postnatal days 5 to 9 (n = 15). Two additional groups with hypoxia only (n = 10) and hypoxia and hyperosmolar formula (n = 13) were also examined. Breastfed pups were used as control (n = 15). Liver was harvested on postnatal day 9. Gene expressions of mtDNA markers cytochrome c oxidase subunit 3 (COX3), cytochrome b (CYTB) and NADH-ubiquinone oxidoreductase chain 1 (ND1) were measured by real-time qPCR. Mitochondrial morphology marker HSP60 and oxidative stress marker NRF2 were detected by immunofluorescence staining and compared between NEC and control. Data were presented as mean ± SD and compared using Student's t test; p < 0.05 was considered significant.

RESULTS

Gene expression of mtDNA markers (COX3, CYTB, and ND1) were significantly decreased in the liver of NEC mice relative to control, hypoxia alone, and hypoxia with hyperosmolar formula. Immunofluorescence showed depletion of HSP60 indicating decreased mitochondria in NEC liver relative to control. Furthermore, a higher protein expression of NRF2 was observed indicating higher oxidative stress in NEC liver relative to control.

CONCLUSIONS

Intestinal injury in experimental NEC leads to a systemic inflammatory response affecting the liver. Hepatic oxidative injury in NEC is characterized by decreased mitochondria and mtDNA depletion. This study provides insight into the mechanism of liver injury in NEC.

The intestinal injury caused by ischemia-reperfusion is attenuated by amniotic fluid stem cells via the release of tumor necrosis factor-stimulated gene 6 protein

Ischemia/reperfusion (I/R) is implicated in the pathogenesis of various acute intestinal injuries. Amniotic fluid stem cells (AFSC) are beneficial in experimental intestinal diseases. Tumor necrosis factor-induced protein 6 (TSG-6) has been shown to exert anti-inflammatory effects. We aimed to investigate if AFSC secreted TSG-6 reduces inflammation and rescues intestinal I/R injury. The superior mesenteric artery of 3-week-old rats was occluded for 90 minutes and green fluorescent protein-labeled AFSC or recombinant TSG-6 was injected intravenously upon reperfusion. AFSC distribution was evaluated at 24, 48, and 72 hours after I/R. AFSC and TSG-6 effects on the intestine were assessed 48 hours postsurgery. Intestinal organoids were used to study the effects of TSG-6 after hypoxia-induced epithelial damage. After I/R-induced intestinal injury, AFSC migrated preferentially to the ileum, the primary site of injury, through blood circulation. Engrafted AFSC reduced ileum injury, inflammation, and oxidative stress. These AFSC-mediated beneficial effects were dependent on secretion of TSG-6. Administration of TSG-6 protected against hypoxia-induced epithelial damage in intestinal organoids. Finally, TSG-6 attenuated intestinal damage during I/R by suppressing genes involved in wound and injury pathways. This study indicates that AFSC or TSG-6 have the potential of rescuing the intestine from the damage caused by I/R.

Necrotizing enterocolitis: controversies and challenges

Necrotizing enterocolitis is a devastating intestinal disease that affects ~5% of preterm neonates. Despite advancements in neonatal care, mortality remains high (30–50%) and controversy still persists with regards to the most appropriate management of neonates with necrotizing enterocolitis. Herein, we review some controversial aspects regarding the epidemiology, imaging, medical and surgical management of necrotizing enterocolitis and we describe new emerging strategies for prevention and treatment.

Minimal enteral nutrition during neonatal hypothermia treatment for perinatal hypoxic-ischaemic encephalopathy is safe and feasible

AIM

The safety and efficacy of enteral feeding during hypothermia treatment following hypoxic-ischaemic encephalopathy has not been studied before, resulting in variations in practice. Our study compared the benefits and safety of both early minimal and delayed enteral feeding during hypothermia treatment.

METHODS

Our retrospective cohort study, from January 2009 to December 2011, compared a Swedish cohort, who received early enteral feeding during hypothermia, and a UK cohort, who received delayed enteral feeding.

RESULTS

In Sweden (n = 51), enteral feeds were initiated at a median of 23.6 h and full oral feeding was achieved at 9 days (range 3-23). In the UK (n = 34), the equivalent figures were 100 h and 8 days (range 3-13) (p = 0.01). Both groups achieved enteral feeding at a median 6 days. The median length of hospital stay was 13 days in Sweden and 10 days in the UK (p = 0.04). More babies were fully breastfeeding or breastfed and bottle-fed at discharge in Sweden (85%) than the UK (67%) (p = 0.08). There were no significant differences between the two groups regarding adverse events.

CONCLUSION

Early minimal enteral feeding during hypothermia proved feasible, with no significant complications. Delayed enteral feeding did not affect time to full enteral feeding.

Multidirectional and simultaneous evaluation of gastroschisis-related intestinal damage in chick embryos

PURPOSE

In a chick model of gastroschisis, we aimed to investigate the morphological/cellular, molecular, and ultrastructural changes taking place in gastroschisis-related intestinal damage (GRID).

METHODS

13-Day fertilized eggs were divided into two groups.

CONTROL GROUP

chorio-amnio-allontoic membranes opened and abdominal wall exposed. Gastroschisis group: an anterior abdominal wall defect created after opening membranes. Embryos from both groups were surgically removed on post-fertilization day 19. Intestinal samples were obtained for histopathology, immunohistochemistry, molecular biology, and electron microscopy.

RESULTS

The histopathological grade of intestinal damage which primarily involved mucosal structures was significantly higher in the gastroschisis group when compared to the control group (p<0.001). Immunohistochemically, E-cadherin and synaptophysin immunoreactivity in the gastroschisis group was significantly lower than control group (p<0.05 and p<0.01, respectively), whereas there was no significant difference in laminin and type-4 collagen immunoreactivity between the groups (p>0.05). Molecular analyses indicated a significant decrease in NFκB and IκB expression in the gastroschisis group (p<0.05 and p=0.001, respectively). Electron microscopy showed that the gastroschisis group had considerable ultrastructural damage, manifested by apoptosis in all layers.

CONCLUSIONS

GRID affected all layers but was more prominent in mucosa. The damage may depend on E-cadherin and synaptophysin downregulation. Increased apoptotic activity, associated with decreased NFκB and IκB expression, may be an important component of this multifactorial damaging process.

Oxygenated Perfluorocarbons Protect the Intestine From the Ischemia/Reperfusion Injury in Rabbits

Objective: To investigate whether intraluminal administration of oxygenated perfluorocarbons (PFCs) protects the enterocyte from acute ischemia-reperfusion (I/R) injury. Materials and Methods: Twenty rabbits were divided in 4 groups: sham-operated controls (group A), acute I/R (group B), acute I/R plus infusion of oxygenated PFCs 30 minutes before ischemia (group C), and acute I/R plus infusion of oxygenated PFCs 30 minutes before reperfusion (group D). Serum creatine phosphokinase (CPK) and mucosal disaccharidase activity were examined. Intestinal biopsies were obtained for electron microscopy study. Results: Group B CPK mean values are 3495.2 ± 157.35 and 4855 ± 350.21 U/L. Group C: 2674.6 ± 265.87 and 3231 ± 232.30. Group D: 2382.2 ± 102.90 and 3217.6 ± 185.61 at 120 and 180 minutes (P < .05). At 180 minutes, maltase and sucrose values were 33.63, 51.88, 8.45, and 19.91, and 17.99, 22.87, 6.62, and 14.24 µmol/min per g for groups A, B, C, and D, respectively (P < .05). Histopathology showed the least cellular deterioration in PFC groups. Conclusion: Oxygenated PFCs protect the enterocyte during bowel I/R.

Hypothermia: novel approaches for premature infants

Hypothermia for hypoxic ischemic encephalopathy has recently permeated clinical practice for term infants. Speculation regarding a neuroprotective benefit of hypothermia for premature infants with HIE has been raised as a need for further research. Hypothermia for other indications including necrotizing enterocolitis with the hope of tissue preservation following injury is less well studied. A summary of evidence for hypothermia and premature infants is presented in this brief report.

Mild controlled hypothermia in preterm neonates with advanced necrotizing enterocolitis

OBJECTIVES

Necrotizing enterocolitis (NEC) with multiple organ dysfunction syndrome (MODS) carries significant morbidity and mortality. There is extensive experimental evidence to support investigation of therapeutic hypothermia in infants with these conditions. We aimed to establish the feasibility and safety of mild hypothermia in preterm neonates with NEC and MODS as a prelude to a randomized trial.

METHODS

This was a prospective, nonrandomized pilot study of 15 preterm infants who were referred for surgical intervention of advanced NEC and failure of at least 3 organs. Whole-body cooling was achieved by ambient temperature adjustment with or without cooling mattress. Three groups (n = 5 per group) were cooled to core temperatures of 35.5 degrees C (+/-0.5 degrees C), 34.5 degrees C, and 33.5 degrees C, respectively, for 48 hours before rewarming to 37 degrees C. Infants were carefully assessed to identify adverse effects that potentially were related to cooling and rewarming. A noncooled group (n = 10) with advanced surgical NEC and MODS was used for comparison. Data are medians (interquartile range).

RESULTS

Gestational age at birth was 27 weeks (26-30), admission weight was 1.1 kg (1.0-1.7), and admission age was 31 days (12-45). Core temperature was maintained within target range for 90% (88%-97%) of the intended time. Statistically significant relationships were identified between core temperature and heart rate (P < .0001), pH (P < .0001), base excess (P = .003), and blood clot dynamics (longer time to initial clot formation, slower rate of clot formation, and decrease in clot strength; all P < .001) as assessed by thromboelastography. No major clinical problems or adverse events were noted during cooling or rewarming. Comparison with the noncooled group revealed no increase in mortality, bleeding, infection, or need for inotropes in infants who were cooled.

CONCLUSIONS

Mild hypothermia for 48 hours in preterm neonates with severe NEC seems both feasible and safe. Additional investigation of the efficacy of this therapeutic intervention in this population is warranted.

The Protective Effect of Oxygenated Perfluorocarbons (PFCs) on Intestinal Ischemia Reperfusion Injury (I/R) in Rabbits

Objective: To evaluate the effect of intraluminal administration of oxygenated perfluorocarbons (PFCs) on small intestine’s viability in an experimental model of acute ischemia-reperfusion (I/R).

Methods: Twenty rabbits were divided in four groups: sham-operated controls (group A), acute I/R (group B), acute I/R plus infusion of PFCs 30 min before ischemia (group C), and acute I/R plus infusion of PFCs 30 min before reperfusion (group D). Malondialdehyde (MDA) tissue levels and d-lactate blood samples were taken. All tissue sections were examined under light microscope.

Results: Mean MDA levels in group A: 1.79 ± 0.97 at 0 min, 2.25 ± 1.76 at 120 min and 3.70 ± 1.76 nmols/g at 180 min. Group B: 2.60 ± 0.58 at 0 min, 4.20 ± 0.58 at 120 min and 5.48 ± 2.01 at 180 min. Group C: 1.54 ± 0.85 at 0 min, 1.14 ± 0.37 at 120 min and 0.59 ± 0.35 at 180 min. Group D: 2.12 ± 0.62 at 0 min, 3.97 ± 0.70 at 120 min and 2.32 ± 0.37 at 180 min (p < 0.05). Mean d-lactate levels in group A: at 0 min 36.45 ± 1.99, at 120 min 39.10 ± 2.37 and at 180 min 40.05 ± 2.13 mg/dl. Group B: 61.23 ± 11.03 at 0 min, 74.84 ± 10.70 at 120 min and 89.90 ± 9.29 at 180 min. Group C: at 0 min 51.05 ± 10.36, at 120 min 56.07 ± 11.27 and at 180 min 57.20 ± 11.19. Group D: 64.36 ± 5.26 at 0 min, 72.55 ± 7.19 at 120 min and 77.02 ± 9.41 at 180 min (p < 0.05). Histopathological analysis indicated a significant improvement in the groups of oxygenated PFCs compared with I/R group.

Conclusion: Intraluminal administration of oxygenated PFCs seems that protect the intestine from the I/R injury.

Mechanisms of action, physiological effects, and complications of hypothermia

BACKGROUND

Mild to moderate hypothermia (32-35 degrees C) is the first treatment with proven efficacy for postischemic neurological injury. In recent years important insights have been gained into the mechanisms underlying hypothermia's protective effects; in addition, physiological and pathophysiological changes associated with cooling have become better understood.

OBJECTIVE

To discuss hypothermia's mechanisms of action, to review (patho)physiological changes associated with cooling, and to discuss potential side effects.

DESIGN

Review article.

INTERVENTIONS

None.

MAIN RESULTS

A myriad of destructive processes unfold in injured tissue following ischemia-reperfusion. These include excitotoxicty, neuroinflammation, apoptosis, free radical production, seizure activity, blood-brain barrier disruption, blood vessel leakage, cerebral thermopooling, and numerous others. The severity of this destructive cascade determines whether injured cells will survive or die. Hypothermia can inhibit or mitigate all of these mechanisms, while stimulating protective systems such as early gene activation. Hypothermia is also effective in mitigating intracranial hypertension and reducing brain edema. Side effects include immunosuppression with increased infection risk, cold diuresis and hypovolemia, electrolyte disorders, insulin resistance, impaired drug clearance, and mild coagulopathy. Targeted interventions are required to effectively manage these side effects. Hypothermia does not decrease myocardial contractility or induce hypotension if hypovolemia is corrected, and preliminary evidence suggests that it can be safely used in patients with cardiac shock. Cardiac output will decrease due to hypothermia-induced bradycardia, but given that metabolic rate also decreases the balance between supply and demand, is usually maintained or improved. In contrast to deep hypothermia (<or=30 degrees C), moderate hypothermia does not induce arrhythmias; indeed, the evidence suggests that arrhythmias can be prevented and/or more easily treated under hypothermic conditions.

CONCLUSIONS

Therapeutic hypothermia is a highly promising treatment, but the potential side effects need to be properly managed particularly if prolonged treatment periods are required. Understanding the underlying mechanisms, awareness of physiological changes associated with cooling, and prevention of potential side effects are all key factors for its effective clinical usage.

Intestinal ischemia/reperfusion injury: defining the role of the gut microbiome

Intestinal ischemia/reperfusion (I/R) injury initiates a systemic inflammatory response syndrome with a high associated mortality rate. Early diagnosis is essential for reducing surgical mortality, yet current clinical biomarkers are insufficient. Metabonomics is a novel strategy for studying intestinal I/R, which may be used as part of a systems approach for quantitatively analyzing the intestinal microbiome during gut injury. By deconvolving the mammalian–microbial symbiotic relationship systems biology thus has the potential for personalized risk stratification in patients exposed to intestinal I/R. This review describes the mechanism of intestinal I/R and explores the essential role of the intestinal microbiota in the initiation of systemic inflammatory response syndrome. Furthermore, it analyzes current and future approaches for elucidating the mechanism of this condition.

Moderate hypothermia as a rescue therapy against intestinal ischemia and reperfusion injury in the rat

OBJECTIVE

Moderate hypothermia is protective when applied throughout experimental intestinal ischemia and reperfusion (I/R). However, therapeutic intervention is usually possible only after ischemia has occurred. The aim of this study was to evaluate moderate hypothermia when applied at reperfusion as a rescue therapy for intestinal I/R.

DESIGN

Prospective, randomized, controlled experiment.

SETTING

University research laboratory.

SUBJECTS

Adult male Sprague-Dawley rats (240-300 g).

INTERVENTIONS

In experiment I, rats underwent 60 mins of normothermic intestinal ischemia (36-38 degrees C) plus 300 mins of reperfusion at either normothermia or moderate hypothermia (30-32 degrees C) with or without rewarming. Hemodynamics were measured invasively and survival was assessed. In experiment II, rats underwent 60 mins of normothermic ischemia plus 120 mins of reperfusion at either normothermia or moderate hypothermia. At kill, organs and a blood sample were collected.

MEASUREMENTS AND MAIN RESULTS

In experiment I, all normothermic I/R rats died within 197 mins of reperfusion after developing severe tachycardia and hypotension, whereas hypothermic rats, with or without rewarming, were alive at 300 mins of reperfusion (p < .001 vs. I/R normothermia) and were hemodynamically stable. In experiment II, normothermic reperfusion caused histologic and biochemical damage to the gut, hepatic energy failure, and inflammatory infiltration of the lung. However, hypothermia reduced injury to the reperfused ileum and prevented distant organ injury by counteracting energy failure in the liver, systemic overproduction of nitric oxide, altered cardiac fatty acid metabolism, and infiltration of inflammatory cells in the lungs.

CONCLUSIONS

Hypothermia applied as a rescue therapy for intestinal I/R abolishes mortality even after rewarming. Hypothermic protection during early reperfusion appears to be mediated by several pathways, including prevention of intestinal and pulmonary neutrophil infiltration, reduction of oxidative stress in the ileum, and preservation of cardiac and hepatic energy metabolism. Moderate hypothermia may improve outcome in clinical conditions associated with intestinal I/R.

Can the kidney function as a lung? Systemic oxygenation and renal preservation during retrograde perfusion of the ischaemic kidney in rabbits

OBJECTIVE

To investigate renal preservation by a novel method of perfusion using an oxygenated perfluorocarbon (PFC) emulsion via retrograde access to the kidney, as preserving renal function during urological surgery has been elusive, and the recognized technique of nephron-sparing surgery has increased its application and practice in modern urology.

MATERIALS AND METHODS

After institutional review and approval, 30 New Zealand White rabbits were studied. In a solitary kidney model, each rabbit had the ureter catheterized before 40 min of renal artery occlusion. Each rabbit was randomized to one retrograde perfusion group, i.e. sham, normothermic PFC, chilled PFC, normothermic saline, and chilled saline. The rabbits were maintained for 2 weeks, during which renal function, urine output, systemic blood gases, weight and serum creatinine level were measured. After death, the kidneys were individually examined and graded by one renal pathologist unaware of the treatment.

RESULTS

The rabbits treated with retrograde PFC perfusion (normothermic and chilled) had less change in their creatinine clearance, at 3.6 and 4.0 mL/min per kg, than the sham group, at 7.8 mL/min per kg, while also having significantly higher systemic venous oxygenation, at 26.3 and 10.0 mmHg, than the sham group, at 0.2 mmHg. Normothermic and chilled perfusion with PFC was also associated with less histological evidence of ischaemic damage, with mean (sd) scores of 13.0 (13.5) and 8.7 (4.5), respectively, than in the sham group, at 33.3 (16.8), while favourably matching the contralateral control kidney group, at 5.5 (2.3). The rabbits treated with saline retrograde perfusion also had better outcomes than the sham cohort. There were no adverse effects in any of the study arms or with the use of PFC.

CONCLUSION

Retrograde oxygen delivery to the kidney through the urinary collecting system was successful in this pilot study. Renal function, laboratory and histological data indicate a trend towards renal preservation and even systemic oxygenation in the experimental groups compared with the sham rabbits, with no adverse effects attributed to this technique.

Mild Hypothermia Ameliorates Lung Ischemia Reperfusion Injury in an ex vivo Rat Lung Model

BACKGROUND

Ischemia reperfusion (I-R) injury of the lung frequently occurs after cardiopulmonary bypass, pulmonary thromboendarterectomy, lung transplantation, and major pulmonary resection with vascular reconstruction. Mild hypothermia ameliorates ischemia reperfusion injury of the brain and the liver. However, the effect of mild hypothermia on I-R injury of the lung has not been investigated.

METHODS

The lungs of Lewis rats underwent 80 min of ischemia followed by 60 min of reperfusion in an ex vivo perfusion model. The ambient temperature was maintained at either normothermia (38 degrees C, n=6) or mild hypothermia (35 degrees C, n=6) during the ischemia and reperfusion.

RESULTS

Pulmonary shunt fraction, peak inspiratory pressure, mean pulmonary arterial pressure during reperfusion, and the wet/dry weight ratio of the lung tissue at the end of reperfusion in the mild hypothermia group were significantly (p<0.05) lower than those in the normothermia group. Total adenine nucleotide, adenosine triphosphate, adenosine diphosphate, and adenosine monophosphate after reperfusion in the mild hypothermia group were significantly (p<0.05) higher than those in the normothermia group.

CONCLUSION

Mild hypothermia attenuates I-R injury of the lung with maintained levels of intrapulmonary high-energy phosphate compounds after reperfusion, suggesting its beneficial effect on warm lung I-R in clinical settings.

The effects of moderate hypothermia on energy metabolism and serum inflammatory markers during laparotomy

The objective of this study was to investigate energy metabolism of the gut and liver as well as serum inflammatory cytokines following exploratory laparotomy at moderate hypothermia. Two groups of rats were studied, (n=6-8/group); laparotomy at normothermia for 120 min and laparotomy at hypothermia (32-33 degrees C) for 120 min. Study 1: Intestinal glucose, succinate, lactate, phosphocreatine, and ATP as well as hepatic glucose, succinate, lactate, and ATP were measured in terms of micromole per gram using magnetic resonance spectroscopy. Study 2: Serum levels of TNF-alpha, IL-1beta, LPS-inducible chemokine (LIX), and sICAM-1 were measured by ELISA. Histology of the gut and liver were interpreted. Data are expressed as mean and SEM. In Study 1, laparotomy at hypothermia caused an increase in intestinal glucose levels (0.78+/-0.03 vs. 1.29+/-0.11, P=0.0012) with a decrease in hepatic lactate levels (0.82+/-0.04 vs. 0.44+/-0.06, P<0.001). There were no differences in the other metabolites between the two groups. In Study 2, there were no differences in serum TNF-alpha, IL-1beta, LIX, or sICAM-1 between the two groups. Histological features of the gut and liver among groups were comparable. In conclusion, the intestine and liver react to hypothermia differently. However, levels of high-energy phosphates in both organs are not affected by hypothermia suggesting adequate energy for the organs. It is unlikely that hypothermia induces either systemic inflammatory response or hypoxic damage to the intestine and liver in this model.

Amelioration of intestinal reperfusion injury by moderate hypothermia is associated with serum sICAM-1 levels

BACKGROUND

The aim of this study was to investigate the effects of moderate hypothermia on various serum markers involving in inflammation after intestinal ischemia-reperfusion (IR).

MATERIALS AND METHODS

The model of 30 min intestinal ischemia +90 min reperfusion was used. Three groups of rats were studied, n=7-8 per group: 1) sham at normothermia, 36.5 to 37.5 degrees C; 2) IR at normothermia and; 3) IR at moderate hypothermia, 32 to 33 degrees C. Serum levels of TNF-alpha, lipopolysaccharide-inducible CXC chemokine (LIX), and soluble intercellular adhesion molecule-1 (sICAM-1) were determined using ELISA technique. Histological features of terminal ileum were also graded.

RESULTS

Intestinal IR at normothermia caused remarkable tissue injury together with an elevation in serum TNF-alpha, LIX, and sICAM-1 levels. Moderate hypothermia significantly decreased the degree of mucosal damage and attenuated the elevation of serum sICAM-1 levels. However, there were no significant differences in serum TNF-alpha and LIX levels between IR at normothermia and IR at hypothermia.

CONCLUSIONS

Intestinal IR at normothermia induces the elevation of serum TNF-alpha, LIX, and sICAM-1 levels. Moderate hypothermia protects the small intestine from reperfusion injury. This beneficial effect is associated with serum sICAM-1 levels but not with serum TNF-alpha and LIX levels. We speculate that one of the mechanisms, by which hypothermia blunts the tissue injury, is at the step of firm adhesion between leukocytes and endothelial cells.

Reperfusion injury after critical intestinal ischemia and its correction with perfluorochemical emulsion "perftoran"

AIM

To investigate the anti-ischemic properties of perfluorochemical emulsion "perftoran" in mesenteric region.

METHODS

Experiments were conducted on 146 nonlinear white male rats weighing 200-350 g. Partial critical intestinal ischemia was induced by thorough atraumatic strangulation of 5-6 cm jejunal loop with its mesentery for 90 min. Global critical intestinal ischemia was made by atraumatic occlusion of the cranial mesenteric artery (CMA) for 90 min also. Perftoran (PF, 0.8-1.0 mL per 100 g) in experimental groups or 0.9% sodium chloride in control groups was injected at 75 min of ischemic period. Mean systemic arterial blood pressure (BP(M)) registration, intravital microscopy and morphological examination of ischemic intestine and its mesentery were performed in both groups.

RESULTS

During 90 min of reperfusion, BP(M) progressively decreased to 27.3+/-7.4% after PF administration vs 38.6+/-8.0% in the control group of rats with partial intestinal ischemia (NS) and to 50.3+/-6.9% vs 53.1+/-5.8% in rats after global ischemia (NS). During the reperfusion period, full restoration of microcirculation was never registered; parts with restored blood flow had leukocyte and erythrocyte stasis and intra-vascular clotting, a typical "non-reflow" phenomenon. The reduction of mesenteric 50-400 mum feeding artery diameter was significantly less in the PF group than in the control group (24+/-5.5% vs 45.2+/-3.6%, P<0.05) 5 min after partial intestinal ischemia. This decrease progressed but differences between groups minimized at the 90(th) min of reperfusion (41.5+/-4.2% and 50.3+/-2.8%, respectively). In reperfusion of rat's intestine, a significant mucosal alteration was registered. Villous height decreased 2.5-3 times and the quantity of crypts decreased more than twice. In the group of rats administered PF, intestinal mucosal layer was protected from irreversible post-ischemic derangement during reperfusion. Saved cryptal epithelial cells were the source of regeneration of the epithelium, which began to cover renewing intestinal villi after 24 h of blood flow restoration. View of morphological alterations was more heterogeneous in CMA groups.

CONCLUSION

Systemic administration of perftoran promotes earlier and more complete structural regeneration during reperfusion in rats after partial and global critical intestinal ischemia.

MODERATE HYPOTHERMIA PROTECTS AGAINST SYSTEMIC OXIDATIVE STRESS IN A RAT MODEL OF INTESTINAL ISCHEMIA AND REPERFUSION INJURY

Multisystem organ failure represents a major cause of mortality in intestinal ischemia and reperfusion (I/R), and oxidative stress plays a key role in its pathogenesis. Hypothermia is beneficial in I/R injury, but its effects on systemic oxidative stress have not been elucidated. The aim of this study was to evaluate the effects of moderate hypothermia on systemic oxidative stress after intestinal I/R injury. Anaesthetized adult rats (n = 10 per group) underwent 60 min of intestinal ischemia followed by 120 min of reperfusion or sham operation at normothermia (36 degrees C-38 degrees C) or moderate hypothermia (30 degrees C-32 degrees C). At sacrifice, ileum, liver, lungs, and kidneys were removed to determine the concentration of malondialdehyde (a marker of lipid peroxidation), reduced and oxidized glutathione (a major endogenous antioxidant), and glutathione redox state. Plasma malondialdehyde and nitrate plus nitrite (reflecting nitric oxide production) were also analyzed. A marked elevation of malondialdehyde was observed after I/R at normothermia in plasma, ileum, and lungs; however, hypothermia during I/R prevented this increase. I/R at normothermia caused a profound decrease in reduced glutathione and glutathione redox state in the ileum, but this was not observed in I/R at hypothermia. Interestingly, hypothermia increased glutathione content of control intestine. Nitric oxide production was increased only in normothermic I/R animals. Moderate hypothermia attenuates systemic oxidative stress associated with experimental intestinal I/R in an animal model by decreasing lipid peroxidation in plasma, ileum, lungs, and kidneys, by preventing the depletion of gut glutathione, and by reducing systemic nitric oxide production. However, whether these effects persist after rewarming is unknown.

The protective effect of moderate hypothermia during intestinal ischemia-reperfusion is associated with modification of hepatic transcription factor activation

BACKGROUND/PURPOSE

Moderate hypothermia throughout intestinal ischemia-reperfusion (IIR) injury reduces multiple organ dysfunction. Heat shock proteins (HSPs) have been shown to be protective against ischemia-reperfusion injury, and STAT (Signal Transducers and Activators of Transcription) proteins are pivotal determinants of the cellular response to reperfusion injury. The aim of this study is to investigate the mechanism of hypothermic protection during IIR.

METHODS

Adult rats underwent intestinal ischemia-reperfusion (IIR), 60-minute ischemia and 60-minute reperfusion, or sham (120 minutes) at either normothermia or moderate hypothermia. Four groups of animals were studied: (1) normothermic sham (NS), (2) normothermic IIR (NIIR), (3) hypothermic sham (HS), and (4) hypothermic IIR (HIIR). Western blotting measured heat shock protein expression, phosphorylated (p-) and total (T-) hepatic STAT-1 and STAT-3.

RESULTS

There were no differences in expression of HSPs 27, 47, 60, i70, c70, or 90 between any of the experimental groups. NIIR caused a significant increase in p-STAT-1 compared with normothermic sham (P <.05) and a highly significant increase in p-STAT-3 (P <.001), both these increases were completely abolished by moderate hypothermia (P <.01 v NIIR.)

CONCLUSIONS

The protective effect of moderate hypothermia on liver is not mediated by HSP expression at this time-point. Hypothermia may act by decreasing hepatic STAT activation, supporting the potential therapeutic role of moderate hypothermia. Modulation of STAT activation may also provide novel therapeutic targets.

Necrotizing enterocolitis

Necrotizing enterocolitis is the principal cause of surgical referral in preterm neonates and the most common gastrointestinal emergency among infants. Its pathophysiology is unclear and it carries high levels of mortality and morbidity. This article provides an overview of necrotizing enterocolitis including risk factors, preventative strategies and medical and surgical management.

Heart energy metabolism after intestinal ischaemia and reperfusion

BACKGROUND/PURPOSE

Multiple organ failure subsequent to intestinal ischaemia and reperfusion (I/R) includes cardiac failure, but little is known about heart energy metabolism in this setting. This study investigates the effects of intestinal I/R on heart energy metabolism and evaluates the effects of moderate hypothermia.

METHODS

Adult rats underwent intestinal ischaemia for 60 minutes followed by 120 minutes of reperfusion. Animals were maintained at either normothermia (36 degrees to 38 degrees C) or moderate hypothermia (30 degrees to 32 degrees C). In experiment A, 2 groups were studied: (1) sham at normothermia; (2) I/R at normothermia. After death, the heart was removed. Cardiac phosphoenergetics were assessed by 31P magnetic resonance spectroscopy; data are expressed as micromoles per gram. In experiment B, 4 groups were studied: (1) sham at normothermia, (2) I/R at normothermia, (3) sham at hypothermia, (4) I/R at hypothermia. At the end of the experiment, the heart was harvested. The activity of carnitine palmitoyl transferase I (CPT I), an important enzyme in the control of fatty acid oxidation, was measured; data are expressed as nanomoles per minute per unit citrate synthase. Results are expressed as mean +/- SEM.

RESULTS

In experiment A, there were no differences between the 2 study groups in cardiac phosphocreatine, inorganic phosphate, adenosine triphosphate (ATP), or in the ratio of inorganic phosphate to ATP. In experiment B, CPT I activity was decreased significantly after I/R at normothermia compared with normothermic sham, but this enzyme inhibition was prevented by hypothermia (3.9 +/- 0.2; v I/R).

CONCLUSIONS

These results suggest that although cardiac ATP supply was maintained during intestinal I/R at normothermia, the balance of substrate utilisation was shifted from fatty acid oxidation to carbohydrate utilisation. However, moderate hypothermia modified these changes. The beneficial effect of moderate hypothermia on cardiac metabolism during intestinal I/R has potential clinical application in various surgical conditions.

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.

Hypothermia throughout intestinal ischaemia-reperfusion injury attenuates lung neutrophil infiltration

BACKGROUND/PURPOSE

Secondary organ damage to the lungs is an important consequence of intestinal ischaemia reperfusion (IIR) injury. Moderate hypothermia ameliorates gut necrosis and liver energy failure after IIR but potential beneficial effects on lung neutrophil infiltration after reperfusion of ischaemic bowel have not been investigated.

METHODS

Adult Sprague-Dawley rats underwent 60 minutes intestinal ischaemia followed by 120 minutes of reperfusion. The animals were maintained at either normothermia (36 degrees to 38 degrees C) or moderate hypothermia (30 degrees to 32 degrees C). Four groups were studied: (A) sham normothermia; (B) IIR normothermia; (C) sham hypothermia; and (D) IIR hypothermia. Lungs and terminal ileum were removed for measurement of myeloperoxidase activity (a marker of neutrophil infiltration). Results are expressed as milliunits per milligrams protein, mean +/- SEM, and one-way analysis of variance (ANOVA) with Tukey post-test was used for group comparisons.

RESULTS

Lungs: IIR at normothermia significantly increased lung neutrophil infiltration assessed by myeloperoxidase activity compared with sham-operated controls (normothermia sham 4.6 +/- 1.0, n = 8; normothermia IIR 37.7 +/- 13.8, n = 8; P =.011). Moderate hypothermia during IIR significantly attenuated lung neutrophil infiltration (7.2 +/- 2.1, n = 9) compared with normothermia IIR (P =.016) such that myeloperoxidase activity was similar to that found in sham normothermia (4.6 +/- 1.0, n = 8) and sham hypothermia (3.1 +/- 1.3, n = 8). Intestine: Gut myeloperoxidase activity was 0.9 +/- 0.5 in sham normothermia (n = 9) and 2.3 +/- 0.6 after normothermic IIR (n = 8). After IIR at hypothermia gut myeloperoxidase activity (0.5 +/- 0.2; n = 8) was significantly less than normothermic IIR (P =.035) and higher than sham hypothermia (0.2 +/- 0.1, n = 9; P =.01).

CONCLUSIONS

These results indicate that moderate hypothermia may prevent damage to another distant organ, ie the lungs, by preventing recruitment of neutrophils. This may be of benefit in decreasing distal organ damage in diseases in which intestinal ischaemia-reperfusion is implicated in the pathogenesis.