Molecular and functional contractile sequelae of rat intestinal ischemia/reperfusion injury

The Effect of Antioxidant Astaxanthin on Intestinal Ischemia Reperfusion Damage in Rats

BACKGROUND

Mesenteric ischemia is a frequently encountered disease in surgical clinics, difficult to diagnose, and very mortal if not treated. Our study investigated the effects of astaxanthin, which is known to have potent antioxidant properties and is also known to have anti-inflammatory effects on ischemia-reperfusion (I/R) injury.

METHODS

A total of 32 healthy Wistar albino female rats were used in our study. Subjects were randomized and equally divided into 4 groups; control (laparotomy group only), I/R (transient mesenteric ischemia group only), astaxanthin 1 mg/kg and 10 mg/kg doses. The transient ischemia time was 60 minutes and the reperfusion time was 120 minutes. Tissue samples were taken from intracardiac blood and terminal ileum after reperfusion. Superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA) from blood samples, interleukin-1 (IL-1), IL-6, tumor necrosis factor-α (TNFα), Caspase-3, P53 tests from terminal ileum were studied. Tissue samples were also taken for histopathological evaluation.

RESULTS

At the end of the study, both doses of astaxanthin were found to significantly reduce MDA level, CAT, and SOD enzymatic activity, whereas higher doses of astaxanthin significantly reduced MDA level, CAT, and SOD enzyme activities. In addition, cytokines such as TNFα, IL-1 and IL-6 were found to be reduced at both doses of astaxanthin, but only significantly inhibited at higher doses. We observed that inhibition of apoptosis reduced caspase-3 activity and P53 and deoxyribonucleic acid (DNA) fragmentation.

CONCLUSION

Astaxanthin, a potent antioxidant, and anti-inflammatory, significantly reduces ischemia and reperfusion injury, especially when used at a dose of 10 mg/kg. These data need to be confirmed by larger animal series and clinical studies.

The effect of post-reperfusion levosimendan in an experimental intestinal ischemia-reperfusion model

BACKGROUND

Levosimendan has been reported to have a positive effect on ischemia-reperfusion injury. Herein, we aimed to evaluate the effects of levosimendan applied after reperfusion in an experimental intestinal injury-reperfusion (IR) model.

METHODS

Twenty-one Wistar-albino male rats were separated into three groups: Sham group (n = 7): solely superior mesenteric artery (SMA) was dissected after laparotomy; intestinal ischemia-reperfusion group (IIR, n = 7): SMA was clamped for 60 min and unclamped for 120 min to cause ischemia-reperfusion; IIR + levosimendan group (IIR + L, n = 7): levosimendan was administered in ischemia-reperfusion model. The mean arterial pressures (MAP) were measured in all groups. MAP measurements were performed at the end of stabilization, at the 15th, 30th, and 60th minute of ischemia; at the 15th, 30th, 60th, and 120th minute of reperfusion; and at the end of levosimendan bolus application and when levosimendan infusion concluded. Reperfusion injury was evaluated with tissue malondialdehyde (MDA) and by Chiu score.

RESULTS

MAP at 15 min, 30 min, and 60 min of reperfusion was lower in IIR and IIR + L groups compared with basal inter-group measurements. Decline in MAP at 30 min after reperfusion was statistically significant in IIR and IIR + L groups when compared with the sham group. There was no significant difference between MDA levels in the groups. Chiu score was significantly lower in the sham group when compared to IIR and IIR + L groups and higher in IIR when compared to the IIR + L group.

CONCLUSION

Levosimendan leads to a decrease in intestinal damage although it did not affect lipid peroxidation and MAP when administered after reperfusion in an experimental intestinal IR model.

Hyaluronan Regulates Neuronal and Immune Function in the Rat Small Intestine and Colonic Microbiota after Ischemic/Reperfusion Injury

BACKGROUND

Intestinal ischemia and reperfusion (IRI) injury induces acute and long-lasting damage to the neuromuscular compartment and dysmotility. This study aims to evaluate the pathogenetic role of hyaluronan (HA), a glycosaminoglycan component of the extracellular matrix, as a modulator of the enteric neuronal and immune function and of the colonic microbiota during in vivo IRI in the rat small intestine.

METHODS

mesenteric ischemia was induced in anesthetized adult male rats for 60 min, followed by 24 h reperfusion. Injured, sham-operated and non-injured animals were treated with the HA synthesis inhibitor, 4-methylumbelliferone (4-MU 25 mg/kg). Fecal microbiota composition was evaluated by Next Generation Sequencing. Neutrophil infiltration, HA homeostasis and toll like receptor (TLR2 and TLR4) expression in the small intestine were evaluated by immunohistochemical and biomolecular approaches (qRT-PCR and Western blotting). Neuromuscular responses were studied in vitro, in the absence and presence of the selective TLR2/4 inhibitor, Sparstolonin B (SsnB 10, 30 µM).

RESULTS

4-MU significantly reduced IRI-induced enhancement of potentially harmful Escherichia and Enterococcus bacteria. After IRI, HA levels, neutrophil infiltration, and TLR2 and TLR4 expression were significantly enhanced in the muscularis propria, and were significantly reduced to baseline levels by 4-MU. In the injured, but not in the non-injured and sham-operated groups, SsnB reduced both electrical field-stimulated (EFS, 0.1-40 Hz) contractions and EFS-induced (10 Hz) non-cholinergic non-adrenergic relaxations.

CONCLUSIONS

enhanced HA levels after intestinal IRI favors harmful bacteria overgrowth, increases neutrophil infiltration and promotes the upregulation of bacterial target receptors, TLR2 and TLR4, in the muscularis propria, inducing a pro-inflammatory state. TLR2 and TLR4 activation may, however, underlay a provisional benefit on excitatory and inhibitory neuronal pathways underlying peristalsis.

Intestinal resident macrophages: Multitaskers of the gut

BACKGROUND

Intestinal resident macrophages play a crucial role in homeostasis and have been implicated in numerous gastrointestinal diseases. While historically believed to be largely of hematopoietic origin, recent advances in fate-mapping technology have unveiled the existence of long-lived, self-maintaining populations located in specific niches throughout the gut wall. Furthermore, the advent of single-cell technology has enabled an unprecedented characterization of the functional specialization of tissue-resident macrophages throughout the gastrointestinal tract.

PURPOSE

The purpose of this review was to provide a panorama on intestinal resident macrophages, with particular focus to the recent advances in the field. Here, we discuss the functions and phenotype of intestinal resident macrophages and, where possible, the functional specialization of these cells in response to the niche they occupy. Furthermore, we will discuss their role in gastrointestinal diseases.

Involvement of hyaluronan in the adaptive changes of the rat small intestine neuromuscular function after ischemia/reperfusion injury

Intestinal ischemia/reperfusion (I/R) injury has severe consequences on myenteric neurons, which can be irreversibly compromised resulting in slowing of transit and hindered food digestion. Myenteric neurons synthesize hyaluronan (HA) to form a well-structured perineuronal net, which undergoes derangement when myenteric ganglia homeostasis is perturbed, i.e. during inflammation. In this study we evaluated HA involvement in rat small intestine myenteric plexus after in vivo I/R injury induced by clamping a branch of the superior mesenteric artery for 60 min, followed by 24 h of reperfusion. In some experiments, 4-methylumbelliferone (4-MU, 25 mg/kg), a HA synthesis inhibitor, was intraperitoneally administered to normal (CTR), sham-operated (SH) and I/R animals for 24 h. In longitudinal muscle myenteric plexus (LMMP) whole-mount preparations, HA binding protein staining as well as HA levels were significantly higher in the I/R group, and were reduced after 4-MU treatment. HA synthase 1 and 2 (HAS1 and HAS2) labelled myenteric neurons and mRNA levels in LMMPs increased in the I/R group with respect to CTR, and were reduced by 4-MU. The efficiency of the gastrointestinal transit was significantly reduced in I/R and 4-MU-treated I/R groups with respect to CTR and SH groups. In the 4-MU-treated I/R group gastric emptying was reduced with respect to the CTR, SH and I/R groups. Carbachol (CCh) and electrical field (EFS, 0.1–40 Hz) stimulated contractions and EFS-induced (10 Hz) NANC relaxations were reduced in the I/R group with respect to both CTR and SH groups. After I/R, 4-MU treatment increased EFS contractions towards control values, but did not affect CCh-induced contractions. NANC on-relaxations after I/R were not influenced by 4-MU treatment. Main alterations in the neurochemical coding of both excitatory (tachykinergic) and inhibitory pathways (iNOS, VIPergic) were also observed after I/R, and were influenced by 4-MU administration. Overall, our data suggest that, after an intestinal I/R damage, changes of HA homeostasis in specific myenteric neuron populations may influence the efficiency of the gastrointestinal transit. We cannot exclude that modulation of HA synthesis in these conditions may ameliorate derangement of the enteric motor function preventing, at least in part, the development of dysmotility.

Tachykinin Antagonists Reverse Ischemia/Reperfusion Gastrointestinal Motility Impairment in Rats

BACKGROUND

Supraceliac aortic clamping and unclamping produces ischemia-reperfusion (I/R) injury of the splanchnic organs. The protective effects of tachykinin receptor antagonists, SR140333 (NK₁ receptor), SR48968 (NK₂ receptor), and SB222200 (NK₃ receptor), against I/R-induced inhibition of intestinal motility were tested in rats.

MATERIAL AND METHODS

The intestinal transit of Evans blue was measured in untreated rats and animals subjected to skin incision, I/R (1 h superior mesenteric artery occlusion followed by 24 h reperfusion) or sham operation. Surgical procedures were conducted under diethyl ether anesthesia.

RESULTS

The gastrointestinal transit has not been markedly affected in rats, which were anesthetized or subjected to skin incision in comparison with untreated animals. In contrast, a sham operation and I/R have significantly reduced the intestinal motility. Pretreatment with NK_1-3 blockers (SR140333 [3-30 μg/kg]; SR48968 [3-100 μg/kg]; and SB222200 [10-100 μg/kg]) reversed dose dependently the effects of I/R to the level observed after sham operation only. A combination of NK₁+NK₂+NK₃ inhibitors exerted an additive effect compared with NK₁ and NK₂ antagonists used as single agents. Similarly, combined NK₁+NK₂ were more effective than NK₂ alone. Sham operation and I/R have shifted the in vitro carbachol concentration-response curves to the right in comparison with untreated animals, a phenomenon partially reversed by NK₁-NK₃ pretreatment.

CONCLUSIONS

Single-agent and combined treatment with NK_1-3 antagonists markedly attenuated the gastrointestinal dysmotility evoked by I/R injury. The pretreatment with NK₃ blocker proved to be the most active in this experimental setting.

Thymoquinone reduces ischemia and reperfusion-induced intestinal injury in rats, through anti-oxidative and anti-inflammatory effects

OBJECTIVES

The aim of the present study was to investigate the effect of thymoquinone on ischemia/reperfusion (I/R) injury at 150 min or/and 24 h of reperfusion in male Wistar Rats.

MATERIAL AND METHODS

The therapeutic value of thymoquinone on cellular damage caused by reactive oxygene species or inflammatory processes during intestinal ischemia/reperfusion was investigated using pharmacological function studies on smooth muscle contractile responses of acetylcholine (Ach) and KCl, along with myeloperoxidase activity, malondialdehyhde, glutathione and cytokine levels such as tumor necrosis factor (TNF)-α and interleukin (IL)-1β in serum and ileum tissue of rats. Thymoquinone was administered at a dose of 50 mg/kg orally for three times: 30 min, 24 h and 48 h prior to the surgical procedure. Soon after reperfusion timing (150 min or 24 h), the contractility traces to KCl and acetylcholine of the ileum smooth muscle were recorded through isolated organ bath.

RESULTS

Pretreatment with thymoquinone reversed the disrupted contractility of the ileum smooth muscle at the 24 h reperfusion. Increased malondialdehyde and depleted glutathione levels and high myeloperoxidase activity determined in the ileum I/R tissue returned to reasonable amounts by pretreatment of Thymoquinone, which attenuated malondialdehyde quantity, restored glutathione level and inhibited myeloperoxidase activity. In addition, both serum and tissue TNF-α and IL-1β activities were modulated by thymoquinone at 24 h of intestinal I/R.

CONCLUSION

The results indicate that thymoquinone may have therapeutic value due to its immunomodulating, radical scavenging and/or antioxidant effects in intestinal I/R injury including oxidant damage mechanisms.

Blockage of the P2X7 Receptor Attenuates Harmful Changes Produced by Ischemia and Reperfusion in the Myenteric Plexus

INTRODUCTION

Our work analyzed the effects of a P2X7 receptor antagonist, Brilliant Blue G (BBG), on rat ileum myenteric plexus following ischemia and reperfusion (ISR) induced by 45 min of ileal artery occlusion with an atraumatic vascular clamp with 24 h (ISR 24-h group) or 14 d of reperfusion (ISR 14-d group).

MATERIAL AND METHODS

Either BBG (50 mg/kg or 100 mg/kg, BBG50 or BBG100 groups) or saline (vehicle) was administered subcutaneously 1 h after ischemia in the ISR 24-h group or once daily for the 5 d after ischemia in the ISR 14-d group (n = 5 per group). We evaluated the neuronal density and profile area by examining the number of neutrophils in the intestinal layers, protein expression levels of the P2X7 receptor, intestinal motility and immunoreactivity for the P2X7 receptor, nitric oxide synthase, neurofilament-200, and choline acetyl transferase in myenteric neurons.

RESULTS

The neuronal density and profile area were restored by BBG following ISR. The ischemic groups showed alterations in P2X7 receptor protein expression and the number of neutrophils in the intestine and decreased intestinal motility, all of which were recovered by BBG treatment.

CONCLUSION

We concluded that ISR morphologically and functionally affected the intestine and that its effects were reversed by BBG treatment, suggesting the P2X7 receptor as a therapeutic target.

Analysis of the Effect of Intestinal Ischemia and Reperfusion on the Rat Neutrophils Proteome

Intestinal ischemia and reperfusion injury is a model system of possible consequences of severe trauma and surgery, which might result into tissue dysfunction and organ failure. Neutrophils contribute to the injuries preceded by ischemia and reperfusion. However, the mechanisms by which intestinal ischemia and reperfusion stimulate and activate circulating neutrophils is still not clear. In this work, we used proteomics approach to explore the underlying regulated mechanisms in Wistar rat neutrophils after ischemia and reperfusion. We isolated neutrophils from three different biological groups; control, sham laparotomy, and intestinal ischemia/reperfusion. In the workflow, we included iTRAQ-labeling quantification and peptide fractionation using HILIC prior to LC-MS/MS analysis. From proteomic analysis, we identified 2,045 proteins in total that were grouped into five different clusters based on their regulation trend between the experimental groups. A total of 417 proteins were found as significantly regulated in at least one of the analyzed conditions. Interestingly, the enzyme prediction analysis revealed that ischemia/reperfusion significantly reduced the relative abundance of most of the antioxidant and pro-survival molecules to cause more tissue damage and ROS production whereas some of the significantly up regulated enzymes were involved in cytoskeletal rearrangement, adhesion and migration. Clusters based KEGG pathways analysis revealed high motility, phagocytosis, directional migration, and activation of the cytoskeletal machinery in neutrophils after ischemia and reperfusion. Increased ROS production and decreased phagocytosis were experimentally validated by microscopy assays. Taken together, our findings provide a characterization of the rat neutrophil response to intestinal ischemia and reperfusion and the possible mechanisms involved in the tissue injury by neutrophils after intestinal ischemia and reperfusion.

Evaluation of the NMR-MOUSE as a new method for continuous functional monitoring of the small intestine during different perfusion states in a porcine model

Objective

The study aim was to evaluate a small low-field NMR (nuclear magnetic resonance) scanner, the NMR-MOUSE^®, for detecting changes in intestinal diffusion under different (patho-) physiological perfusion states.

Methods

Laparotomy was performed on 8 female landrace pigs (body weight 70±6 kg) and the feeding vessels of several intestinal loops were dissected. Successively, the intestinal loops were examined using O2C (oxygen to see, LEA Medizintechnik GmbH, Giessen, Germany) for microcirculatory monitoring and the NMR-MOUSE^® for diffusion measurement (fast and slow components). On each loop the baseline measurement (physiological perfusion) was followed by one of the following main procedures: method 1 –ischemia; method 2 –flow reduction; method 3 –intraluminal glucose followed by ischemia; method 4 –intraluminal glucose followed by flow reduction. Additionally, standard perioperative monitoring (blood pressure, ECG, blood gas analyses) and histological assessment of intestinal biopsies was performed.

Results

There was no statistical overall time and method effect in the NMR-MOUSE measurement (fast component: p_time = 0.6368, p_method = 0.9766, slow component: p_time = 0.8216, p_method = 0.7863). Yet, the fast component of the NMR-MOUSE measurement showed contrary trends during ischemia (increase) versus flow reduction (decrease). The slow-to-fast diffusion ratio shifted slightly towards slow diffusion during flow reduction. The O2C measurement showed a significant decrease of oxygen saturation and microcirculatory blood flow during ischemia and flow reduction (p < .0001). The local microcirculatory blood amount (rHb) showed a significant mucosal increase (p_{Clamping(method 1)} = 0.0007, p_{Clamping(method 3)} = 0.0119), but a serosal decrease (p_{Clamping(method 1)} = 0.0119, p_{Clamping(method 3)} = 0.0078) during ischemia. The histopathological damage was significantly higher with increasing experimental duration and at the end of methods 3 and 4 (p < .0001,Fisher-test).

Conclusion

Monitoring intestinal diffusion changes due to different perfusion states using the NMR-MOUSE is feasible under experimental conditions. Despite the lack of statistical significance, this technique reflects perfusion changes and therefore seems promising for the evaluation of different intestinal perfusion states in the future. Beforehand however, an optimization of this technology, including the optimization of the penetration depth, as well as further validation studies under physiological conditions and including older animals are required.

Intravital imaging of neutrophil recruitment in intestinal ischemia-reperfusion injury

BACKGROUND

Neutrophils are known to be key players in innate immunity. Activated neutrophils induce local inflammation, which results in pathophysiologic changes during intestinal ischemia-reperfusion injury (IRI). However, most studies have been based on static assessments, and few have examined real-time intravital neutrophil recruitment. We herein report a method for imaging and evaluating dynamic changes in the neutrophil recruitment in intestinal IRI using two-photon laser scanning microscopy (TPLSM).

METHODS

LysM-eGFP mice were subjected to 45 min of warm intestinal ischemia followed by reperfusion. Mice received an intravenous injection of tetramethylrhodamine isothiocyanate-labeled albumin to visualize the microvasculature. Using a time-lapse TPLSM technique, we directly observed the behavior of neutrophils in intestinal IRI.

RESULTS

We were able to image all layers of the intestine without invasive surgical stress. At low-magnification, the number of neutrophils per field of view continued to increase for 4 h after reperfusion. High-magnification images revealed the presence or absence of blood circulation. At 0-2 h after reperfusion, rolling and adhesive neutrophils increased along the vasculature. At 2-4 h after reperfusion, the irregularity of crypt architecture and transmigration of neutrophils were observed in the lamina propria. Furthermore, TPLSM imaging revealed the villus height, the diameters of the crypt, and the number of infiltrating neutrophils in the crypt. In the IRI group, the villus height 4 h after reperfusion was significantly shorter than in the control group.

CONCLUSIONS

TPLSM imaging revealed the real-time neutrophil recruitment in intestinal IRI. Z-stack imaging was useful for evaluating pathophysiological changes in the intestinal wall.

Rhamnolipids Enhance in Vivo Oral Bioavailability of Poorly Absorbed Molecules

PURPOSE

This report describes the effect of rhamnolipids (RLs) on the tight junctions (TJ) of the intestinal epithelium using the rat in-situ closed loop model.

METHODS

We investigated the transport of 5 (6)-carboxyfluorescein (CF) and fluorescein isothiocyanate-labeled dextrans with average molecular weights of 4.4 and 10 kDa (FD-4 and FD-10) when co-administered with different concentrations of RLs. Lactate dehydrogenase (LDH) leakage assay and histopathological examination of treated intestinal loops were used to assess potential toxicity of RLs. Further, the effect of kaempferol on accelerating the resealing of the tight junctions in vivo was also investigated RESULTS: Data shows that administration of different RLs concentrations (1.0-5.0% v/v) increased CF absorption through rat intestine by 2.84- and 15.82-folds with RLs concentrations of 1.0% and 5.0% v/v, respectively. RLs exhibited size-dependent increase on FD-4 and FD-10 absorption. Dosing RLs at 1.0% v/v didn't cause a significant LDH leakage or histopathological changes to intestinal mucosa compared to higher concentrations, which showed a progressive damaging effect. Using kaempferol, a natural flavonoid that stimulates the assembly of the TJs, proved to enhance the recovery of barrier properties of the intestinal mucosa treated with high concentrations of RLs (2.5% and 5% v/v).

CONCLUSIONS

These results collectively illustrate the ability of RLs to enhance oral bioavailability of different molecules across the intestinal epithelial membrane in a concentration- and time-dependent fashion.

High performance mass spectrometry based proteomics reveals enzyme and signaling pathway regulation in neutrophils during the early stage of surgical trauma

PURPOSE

In clinical conditions trauma is associated with high mortality and morbidity. Neutrophils play a key role in the development of multiple organ failure after trauma EXPERIMENTAL DESIGN: To have a detailed understanding of the neutrophil activation at primary stages after trauma, neutrophils are isolated from control and surgical trauma rats in this study. Extracted proteins are analyzed using nano liquid chromatography coupled with tandem mass spectrometry.

RESULTS

A total of 2924 rat neutrophil proteins are identified in our analysis, of which 393 are found differentially regulated between control and trauma groups. By using functional pathways analysis of the 190 proteins up-regulated in surgical trauma, we found proteins related to transcription initiation and protein biosynthesis. On the other hand, among the 203 proteins down-regulated in surgical trauma we found enrichment for proteins of the immune response, proteasome degradation and actin cytoskeleton. Overall, enzyme prediction analysis revealed that regulated enzymes are directly involved in neutrophil apoptosis, directional migration and chemotaxis. Our observations are then confirmed by in silico protein-protein interaction analysis.

CONCLUSIONS AND CLINICAL RELEVANCE

Collectively, our results reveal that neutrophils drastically regulate their biochemical pathways after the early stages of surgical trauma, showing lower activity. This implies higher susceptibility of the trauma patients to infection and bystander tissues damage.

Role of glutamatergic neurotransmission in the enteric nervous system and brain-gut axis in health and disease

Several studies have been carried out in the last 30 years in the attempt to clarify the possible role of glutamate as a neurotransmitter/neuromodulator in the gastrointestinal tract. Such effort has provided immunohistochemical, biomolecular and functional data suggesting that the entire glutamatergic neurotransmitter machinery is present in the complex circuitries of the enteric nervous system (ENS), which participates to the local coordination of gastrointestinal functions. Glutamate is also involved in the regulation of the brain-gut axis, a bi-directional connection pathway between the central nervous system (CNS) and the gut. The neurotransmitter contributes to convey information, via afferent fibers, from the gut to the brain, and to send appropriate signals, via efferent fibers, from the brain to control gut secretion and motility. In analogy with the CNS, an increasing number of studies suggest that dysregulation of the enteric glutamatergic neurotransmitter machinery may lead to gastrointestinal dysfunctions. On the whole, this research field has opened the possibility to find new potential targets for development of drugs for the treatment of gastrointestinal diseases. The present review analyzes the more recent literature on enteric glutamatergic neurotransmission both in physiological and pathological conditions, such as gastroesophageal reflux, gastric acid hypersecretory diseases, inflammatory bowel disease, irritable bowel syndrome and intestinal ischemia/reperfusion injury.

Neutrophil proteomic analysis reveals the participation of antioxidant enzymes, motility and ribosomal proteins in the prevention of ischemic effects by preconditioning

Intestinal ischemia and reperfusion injury are widely used models, which result into tissue injury and multiple organ failure also observed after trauma and surgery. Ischemic preconditioning (IPC) preceding ischemia and reperfusion (IR) was shown to attenuate this injury and has a potential therapeutic application; however the exact underlying mechanism is not clear. Neutrophils play an important role in the mechanism of injuries caused by ischemia and reperfusion while IPC led to a decrease in neutrophil stimulation and activation. The effect of preconditioning on the neutrophil proteome is unclear. Proteomic analysis has been ratified as an appropriate tool for studying complex systems. In order to evaluate the effect of IPC preceding 45min of ischemia on the proteome of neutrophils we used Wistar rats divided in four experimental groups: Control, sham laparotomy, intestinal ischemia reperfusion and ischemic preconditioning. After neutrophil separation, proteins were extracted, trypsin digested and the resulting peptides were iTRAQ labeled followed by HILIC fractionation and nLC-MS/MS analysis. After database searches, normalization and statistical analysis our proteomic analysis resulted in the identification of 2437 protein groups that were assigned to five different clusters based on the relative abundance profiles among the experimental groups. The clustering followed by statistical analysis led to the identification of significantly up and downregulated proteins in IR and IPC. Cluster based KEGG pathways analysis revealed up- regulation of actin cytoskeleton, metabolism, Fc gamma R mediated phagocytosis, chemokine signaling, focal adhesion and leukocyte transendothelial migration whereas downregulation in ribosome, spliceosome, RNA transport, protein processing in endoplasmic reticulum and proteasome, after intestinal ischemic preconditioning. Furthermore, enzyme prediction analysis revealed the regulation of some important antioxidant enzymes and having their role in reactive oxygen species production. To our knowledge, this work describes the most comprehensive and detailed quantitative proteomic study of the neutrophil showing the beneficial role of ischemic preconditioning and its effects on the neutrophil proteome. This data will be helpful to understand the effect of underlying protective mechanisms modulating the role of PMNs after IPC and provide a trustworthy basis for future studies.

BIOLOGICAL SIGNIFICANCE

Preconditioning is a relevant strategy to overcome clinical implications from ischemia and reperfusion. Such implications have the neutrophil as a major player. Although many publications describe specific biochemical and physiological roles of the neutrophil in such conditions, there is no report of a proteomic study providing a broader view of this scenario. Here we describe a group of proteins significantly regulated by ischemia and reperfusion being such regulation prevented by preconditioning. Such finding may provide relevant information for a deeper understanding of the mechanisms involved, as well as serve as basis for future biomarker or drug target assays.

The Effect of Perioperative Ischemia and Reperfusion on Multiorgan Dysfunction following Abdominal Aortic Aneurysm Repair

Abdominal aortic aneurysms (AAAs) are relatively common and are potentially life-threatening medical problems. The aim of this review is to provide an overview of the effect of I/R injury on multiorgan failure following AAA repair. The PubMed, CINAHL, EMBASE, Medline, Cochrane Review, and Scopus databases were comprehensively searched for articles concerning the pathophysiology of I/R and its systemic effects. Cross-referencing was performed using the bibliographies from the articles obtained. Articles retrieved were restricted to those published in English. One of the most prominent characteristics of AAA open repair is the double physiological phenomenon of ischemia-reperfusion (I/R) that happens either at the time of clamping or following the aortic clamp removal. Ischemia-reperfusion injury causes significant pathophysiological disturbances to distant organs, increasing the possibility for postoperative multiorgan failure. Although tissue injury is mediated by diverse mechanisms, microvascular dysfunction seems to be the final outcome of I/R.

Extracorporeal circulation increases proliferation in the intestinal mucosa in a large animal model

OBJECTIVE

Extracorporeal circulation induces ischemia/reperfusion injury in the small intestinal wall. One reason for this damage is a perfusion shift from the muscular toward the mucosal layer. This study investigated the effect of this perfusion shift on the small-intestinal apoptosis and proliferation.

METHODS

Twenty-eight pigs were randomly assigned to the following cohorts and underwent a thoracolaparotomy and a 1 hour main procedure: cohort I: control; cohort II: thoracic aortic cross-clamping (TAC) without perfusion; cohort III: TAC and distal aortic perfusion (DAP); cohort IV: TAC, DAP, and selective visceral perfusion. The main procedure was followed by 2 hours of reperfusion in all cohorts. Tissue samples were taken during the experiment, stained, and analyzed for apoptosis and proliferation (caspase-3, annexin-V, terminal deoxynucleotide transferase-mediated deoxy uridine triphosphate nick-end labeling, and proliferating cell nuclear antigen). Six animals died unexpectedly during the experiment and were excluded from the analysis.

RESULTS

Extensive tissue damage and necrosis was only found in cohort II after the main procedure. In the mucosa, the proliferation was increased in cohort III at the end of the experiment (P = .0157 cohort I vs II). In contrast, the annexin-V/proliferating cell nuclear antigen ratio was significantly higher in cohorts II and IV than in cohorts I and II at the end of the experiment (P = .0034). Furthermore, the caspase-3/annexin-V ratio was increased in all cohorts at the end of the experiment (P = .0015).

CONCLUSIONS

Mucosal proliferation is the early repair mechanism of the limited small intestinal ischemia/reperfusion injury after DAP. Furthermore, the extensive surgical trauma shifted the mucosal apoptosis into an advanced state.

Toll-like receptor 2 mediates ischemia-reperfusion injury of the small intestine in adult mice

Toll-like receptor 2 (TLR2) recognizes conserved molecular patterns associated with both gram-negative and gram-positive bacteria, and detects some endogenous ligands. Previous studies demonstrated that in ischemia-reperfusion (I/R) injury of the small intestine, the TLR2-dependent signaling exerted preventive effects on the damage in young mice, but did not have a significant effect in neonatal mice. We investigated the role of TLR2 in adult ischemia-reperfusion injury in the small intestine. Wild-type and TLR2 knockout mice at 16 weeks of age were subjected to intestinal I/R injury. Some wild-type mice received anti-Ly-6G antibodies to deplete circulating neutrophils. In wild-type mice, I/R induced severe small intestinal injury characterized by infiltration by inflammatory cells, disruption of the mucosal epithelium, and mucosal bleeding. Compared to wild-type mice, TLR2 knockout mice exhibited less severe mucosal injury induced by I/R, with a 35%, 33%, and 43% reduction in histological grading score and luminal concentration of hemoglobin, and the numbers of apoptotic epithelial cells, respectively. The I/R increased the activity of myeloperoxidase (MPO), a marker of neutrophil infiltration, and the levels of mRNA expression of tumor necrosis factor-α (TNF-α), intercellular adhesion molecule-1 (ICAM-1), and cyclooxygenase-2 (COX-2) in the small intestine of the wild-type mice by 3.3-, 3.2-, and 13.0-fold, respectively. TLR2 deficiency significantly inhibited the I/R-induced increase in MPO activity and the expression of mRNAs for TNF-α and ICAM-1, but did not affect the expression of COX-2 mRNA. I/R also enhanced TLR2 mRNA expression by 2.9-fold. TLR2 proteins were found to be expressed in the epithelial cells, inflammatory cells, and endothelial cells. Neutrophil depletion prevented intestinal I/R injury in wild-type mice. These findings suggest that TLR2 may mediate I/R injury of the small intestine in adult mice via induction of inflammatory mediators such as TNF-α and ICAM-1.

Pretreatment with mineralocorticoid receptor blocker reduces intestinal injury induced by ischemia and reperfusion: involvement of inhibition of inflammatory response, oxidative stress, nuclear factor κB, and inducible nitric oxide synthase

BACKGROUND

Spironolactone (Sp), a mineralocorticoid receptor antagonist, protects against the ischemia reperfusion (IR) injury of retina, kidney, heart, and brain. We aimed to investigate the effects of Sp on intestinal IR injury.

METHODS

Male Wistar rats were randomly divided into: (1) a sham control group; (2) an IR control group, subjected to 30 min ischemia and 3 h reperfusion; (3) a group treated with Sp (20 mg/kg) for 3 d before the IR; and (4) a sham-operated control group treated with Sp (20 mg/kg). After the reperfusion, blood and intestinal tissue samples were collected to evaluate histopathologic state, neutrophil infiltration (by measuring myeloperoxidase activity), levels of the cytokines (tumor necrosis factor α, interleukin 1α [IL-1α], interferon γ, monocyte chemotactic protein-1, granulocyte macrophage-colony stimulating factor, and IL-4), malondialdehyde (MDA) and reduced glutathione contents, and immunohistochemical expressions of nuclear factor κB, inducible nitric oxide synthase (iNOS), and caspase-3.

RESULTS

MDA content, myeloperoxidase activity, and plasma levels of tumor necrosis factor α, IL-1α, and monocyte chemotactic protein-1 were all elevated in IR, indicating the oxidative stress and local and systemic inflammatory response. Sp administration markedly reduced the MDA content and the cytokine levels. The pretreatment alleviated intestinal injury, neutrophil infiltration, and the expressions of caspase-3, iNOS, and NFκB.

CONCLUSIONS

The results implicate that Sp may have a strong protective effect against the intestinal IR injury. The effect can be mediated via suppression of both systemic inflammatory response and apoptosis through amelioration of oxidative stress and generation of proinflammatory cytokines, iNOS, caspase-3, and nuclear factor κB. Therefore, mineralocorticoid receptor antagonism might be of potential therapeutic benefit in cases of intestinal IR damage.

Microcirculatory perfusion shift in the gut wall layers induced by extracorporeal circulation

OBJECTIVE

Extracorporeal circulation (ECC) is regularly applied to maintain organ perfusion during major aortic and cardiovascular surgery. During thoracoabdominal aortic repair, ECC-driven selective visceral arterial perfusion (SVP) results in changed microcirculatory perfusion (shift from the muscularis toward the mucosal small intestinal layer) in conjunction with macrohemodynamic hypoperfusion. The underlying mechanism, however, is unclear. Therefore, the aim of this study was to assess in a porcine model whether ECC itself or the hypoperfusion induced by SVP is responsible for the mucosal/muscular shift in the small intestinal wall.

METHODS

A thoracoabdominal aortic approach was performed in 15 healthy pigs divided equally into three groups: group I, control; group II, thoracic aortic cross-clamping with distal aortic perfusion; and group III, thoracic aortic cross-clamping with distal aortic perfusion and SVP. Macrocirculatory and microcirculatory blood flow was assessed by transit time ultrasound volume flow measurement and fluorescent microspheres. In addition, markers for metabolism and intestinal ischemia-reperfusion injury were determined.

RESULTS

ECC with a roller pump induced a significant switch from the muscularis and mucosal layer of the small intestine, even with adequate macrocirculation (mucosal/muscular perfusion ratio: group I vs II, P = .005; group I vs III, P = .0018). Furthermore, the oxygen extraction ratio increased significantly in groups II (>30%) and III (>40%) in the beginning of the ECC compared with the control (group I vs II, P = .0037; group I vs III, P = .0062). Lactate concentrations and pH values did not differ between groups I and II; but group III demonstrated a significant shifting toward a lactate-associated acidosis (lactate: group I vs III, P = .0031; pH: group I vs III, P = .0001).

CONCLUSIONS

We demonstrated a significant shifting between the small intestinal gut wall layers induced by roller pump-driven ECC. The shift occurs independently of macrohemodynamics, with a significant effect on aerobic metabolism in the gut wall. Consequently, an optimal intestinal perfusion cannot be guaranteed by a roller pump; therefore, perfusion techniques need to be optimized.

The novel guanylhydrazone CPSI-2364 ameliorates ischemia reperfusion injury after experimental small bowel transplantation

BACKGROUND

Resident macrophages within the tunica muscularis are known to play a crucial role in initiating severe inflammation in response to ischemia reperfusion injury after intestinal transplantation contributing to graft dysmotility, bacterial translocation, and possibly, acute rejection. The p38 mitogen-activated protein kinase is a key player in the signaling of proinflammatory cytokine synthesis in macrophages. Therefore, we investigated the effects of CPSI-2364, an apparent macrophage-specific inhibitor of the p38 mitogen-activated protein kinase pathway in an isogenic intestinal rat transplantation model.

METHODS

Recipient and donor animals were treated perioperatively with CPSI-2364 (1 mg/kg, intravenously) or vehicle solution. Nontransplanted animals served as control. Animals were killed 30 min, 3 hr, and 18 hr after reperfusion.

RESULTS

CPSI-2364 treatment resulted in significantly less leukocyte infiltration and significantly improved graft motor function (18 hr). Messenger RNA expression of proinflammatory cytokines (interleukin 6) and kinetic active mediators (NO) was reduced by CPSI-2364 in the early phase after transplantation. Histologic evaluation revealed the protective effects of CPSI-2364 treatment by a significantly less destruction of mucosal integrity at all time points. Perioperative treatment with CPSI-2364 improves graft motor function through impaired inflammatory responses to ischemia reperfusion injury by inhibition of proinflammatory cytokines and suppression of nitric oxide production in macrophages.

CONCLUSIONS

CPSI-2364 presents as a promising complementary pharmacological approach preventing postoperative dysmotility for clinical intestinal transplantation.

Heparin-binding epidermal growth factor-like growth factor protects rat intestine after portal triad clamping

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a potent mitogen and chemotactic factor. HB-EGF attenuates intestinal ischemia/reperfusion injury caused by superior mesenteric artery occlusion. We examined whether HB-EGF offers protection against intestinal congestion/reperfusion (C/R) injury, which is caused by portal triad clamping. Male Sprague-Dawley rats were randomly divided into three equally sized groups: I, sham-operated; II, portal triad clamping (Pringle maneuver); III, II + intraluminal administration of HB-EGF. Compared with sham-operated rats, all rats in group II exhibited significant increases in intestinal histologic injury, pro-inflammatory cytokine expression, myeloperoxidase activity, malonaldehyde levels, and apoptosis indices. Intraluminal administration of HB-EGF in group III significantly reduced these indicators when compared with group II. Clamping of the portal triad followed by reperfusion causes intestinal C/R injury and intraluminal administration of HB-EGF reduces the severity of intestinal C/R injury in rats.

Role of neuronal and inducible nitric oxide synthases in the guinea pig ileum myenteric plexus during in vitro ischemia and reperfusion

BACKGROUND

Intestinal ischemia and reperfusion (I/R) injury leads to abnormalities in motility, namely delay of transit, caused by damage to myenteric neurons. Alterations of the nitrergic transmission may occur in these conditions. This study investigated whether an in vitro I/R injury may affect nitric oxide (NO) production from the myenteric plexus of the guinea pig ileum and which NO synthase (NOS) isoform is involved.

METHODS

The distribution of the neuronal (n) and inducible (i) NOS was determined by immunohistochemistry during 60 min of glucose/oxygen deprivation (in vitro ischemia) followed by 60 min of reperfusion. The protein and mRNA levels of nNOS and iNOS were investigated by Western-immunoblotting and real time RT-PCR, respectively. NO levels were quantified as nitrite/nitrate.

KEY RESULTS

After in vitro I/R the proportion of nNOS-expressing neurons and protein levels remained unchanged. nNOS mRNA levels increased 60 min after inducing ischemia and in the following 5 min of reperfusion. iNOS-immunoreactive neurons, protein and mRNA levels were up-regulated during the whole I/R period. A significant increase of nitrite/nitrate levels was observed in the first 5 min after inducing I/R and was significantly reduced by N(ω) -propyl-l-arginine and 1400 W, selective inhibitors of nNOS and iNOS, respectively.

CONCLUSIONS & INFERENCES

Our data demonstrate that both iNOS and nNOS represent sources for NO overproduction in ileal myenteric plexus during I/R, although iNOS undergoes more consistent changes suggesting a more relevant role for this isoform in the alterations occurring in myenteric neurons following I/R.

Activation of the MyD88 signaling pathway inhibits ischemia-reperfusion injury in the small intestine

Toll-like receptors (TLRs) recognize microbial components and trigger the signaling cascade that activates innate and adaptive immunity. Recent studies have shown that the activation of TLR-dependent signaling pathways plays important roles in the pathogenesis of ischemia-reperfusion (I/R) injuries in many organs. All TLRs, except TLR3, use a common adaptor protein, MyD88, to transduce activation signals. We investigated the role of MyD88 in I/R injury of the small intestine. MyD88 and cyclooxygenase-2 (COX-2) knockout and wild-type mice were subjected to intestinal I/R injury. I/R-induced small intestinal injury was characterized by infiltration of inflammatory cells, disruption of the mucosal epithelium, destruction of villi, and increases in myeloperoxidase activity and mRNA levels of TNF-α and the IL-8 homolog KC. MyD88 deficiency worsened the severity of I/R injury, as assessed using the histological grading system, measuring luminal contents of hemoglobin (a marker of intestinal bleeding), and counting apoptotic epithelial cells, while it inhibited the increase in mRNA expression of TNF-α and KC. I/R significantly enhanced COX-2 expression and increased PGE(2) concentration in the small intestine of wild-type mice, which were markedly inhibited by MyD88 deficiency. COX-2 knockout mice were also highly susceptible to intestinal I/R injury. Exogenous PGE(2) reduced the severity of injury in both MyD88 and COX-2 knockout mice to the level of wild-type mice. These findings suggest that the MyD88 signaling pathway may inhibit I/R injury in the small intestine by inducing COX-2 expression.

Knock out of neuronal nitric oxide synthase exacerbates intestinal ischemia/reperfusion injury in mice

Recent investigation of the intestine following ischemia and reperfusion (I/R) has revealed that nitric oxide synthase (NOS) neurons are more strongly affected than other neuron types. This implies that NO originating from NOS neurons contributes to neuronal damage. However, there is also evidence of the neuroprotective effects of NO. In this study, we compared the effects of I/R on the intestines of neuronal NOS knockout (nNOS(-/-)) mice and wild-type mice. I/R caused histological damage to the mucosa and muscle and infiltration of neutrophils into the external muscle layers. Damage to the mucosa and muscle was more severe and greater infiltration by neutrophils occurred in the first 24 h in nNOS(-/-) mice. Immunohistochemistry for the contractile protein, α-smooth muscle actin, was used to evaluate muscle damage. Smooth muscle actin occurred in the majority of smooth muscle cells in the external musculature of normal mice but was absent from most cells and was reduced in the cytoplasm of other cells following I/R. The loss was greater in nNOS(-/-) mice. Basal contractile activity of the longitudinal muscle and contractile responses to nerve stimulation or a muscarinic agonist were reduced in regions subjected to I/R and the effects were greater in nNOS(-/-) mice. Reductions in responsiveness also occurred in regions of operated mice not subjected to I/R. This is attributed to post-operative ileus that is not significantly affected by knockout of nNOS. The results indicate that deleterious effects are greater in regions subjected to I/R in mice lacking nNOS compared with normal mice, implying that NO produced by nNOS has protective effects that outweigh any damaging effect of this free radical produced by enteric neurons.

Strategies for modulating the inflammatory response after decompression from abdominal compartment syndrome

BACKGROUND

Management of the open abdomen is an increasingly common part of surgical practice. The purpose of this review is to examine the scientific background for the use of temporary abdominal closure (TAC) in the open abdomen as a way to modulate the local and systemic inflammatory response, with an emphasis on decompression after abdominal compartment syndrome (ACS).

METHODS

A review of the relevant English language literature was conducted. Priority was placed on articles published within the last 5 years.

RESULTS/CONCLUSION

Recent data from our group and others have begun to lay the foundation for the concept of TAC as a method to modulate the local and/or systemic inflammatory response in patients with an open abdomen resulting from ACS.

Effects of ischemia and reperfusion on P2X2 receptor expressing neurons of the rat ileum enteric nervous system

PURPOSE

We investigated the effects of ischemia/reperfusion in the intestine (I/R-i) on purine receptor P2X2-immunoreactive (IR) neurons of the rat ileum.

METHODS

The superior mesenteric artery was occluded for 45 min with an atraumatic vascular clamp and animals were sacrificed 4 h later. Neurons of the myenteric and submucosal plexuses were evaluated for immunoreactivity against the P2X2 receptor, nitric oxide synthase (NOS), choline acetyl transferase (ChAT), calbindin, and calretinin.

RESULTS

Following I/R-i, we observed a decrease in P2X2 receptor immunoreactivity in the cytoplasm and surface membranes of neurons of the myenteric and submucosal plexuses. These studies also revealed an absence of calbindin-positive neurons in the I/R-i group. In addition, the colocalization of the P2X2 receptor with NOS, ChAT, and calretinin immunoreactivity in the myenteric plexus was decreased following I/R-i. Likewise, the colocalization between P2X2 and calretinin in neurons of the submucosal plexus was also reduced. In the I/R-i group, there was a 55.8% decrease in the density of neurons immunoreactive (IR) for the P2X2 receptor, a 26.4% reduction in NOS-IR neuron, a 25% reduction in ChAT-IR neuron, and a 47% reduction in calretinin-IR neuron. The density of P2X2 receptor and calretinin-IR neurons also decreased in the submucosal plexus of the I/R-i group. In the myenteric plexus, P2X2-IR, NOS-IR, ChAT-IR and calretinin-IR neurons were reduced in size by 50%, 49.7%, 42%, and 33%, respectively, in the I/R-i group; in the submucosal plexus, P2X2-IR and calretinin-IR neurons were reduced in size by 56% and 72.6%, respectively.

CONCLUSIONS

These data demonstrate that ischemia/reperfusion of the intestine affects the expression of the P2X2 receptor in neurons of the myenteric and submucosal plexus, as well as density and size of neurons in this population. Our findings indicate that I/R-i induces changes in P2X2-IR enteric neurons that could result in alterations in intestinal motility.

Application of heme oxygenase-1, carbon monoxide and biliverdin for the prevention of intestinal ischemia/reperfusion injury

Intestinal ischemia/reperfusion (I/R) injury occurs frequently in a variety of clinical settings, including mesenteric artery occlusion, abdominal aneurism surgery, trauma, shock, and small intestinal transplantation, and is associated with substantial morbidity and mortality. Although the exact mechanisms involved in the pathogenesis of intestinal I/R injury have not been fully elucidated, it is generally believed that polymorphonuclear neutrophils, pro-inflammatory cytokines, and mediators generated in the setting of oxidative stress, such as reactive oxygen species (ROS), play important roles. Heme oxygenase (HO) is the rate-limiting enzyme that catalyzes the degradation of heme into equimolar quantities of biliverdin and carbon monoxide (CO), while the central iron is released. An inducible form of HO (HO-1), biliverdin, and CO, have been shown to possess generalized endogenous anti-inflammatory activities and provide protection against intestinal I/R injury. Further, recent observations have demonstrated that exogenous HO-1 expression, as well as exogenously administered CO and biliverdin, have potent cytoprotective effects on intestinal I/R injury as well. Here, we summarize the currently available data regarding the role of the HO system in the prevention intestinal I/R injury.

Protein kinase C modulates NMDA receptors in the myenteric plexus of the guinea pig ileum during in vitro ischemia and reperfusion

BACKGROUND

Ischemic episodes lead to profound functional and structural alterations of the gastrointestinal tract which may contribute to disorders of intestinal motility. Enhancement of glutamate overflow and the consequent activation of NMDA (N-methyl-D-aspartate) receptors may participate to such changes by modulating different enteric neurotransmitter systems, including cholinergic motor pathways.

METHODS

The molecular mechanism/s underlying activation of NMDA receptors in the guinea pig ileum were investigated after glucose/oxygen deprivation (in vitro ischemia) and during reperfusion.

KEY RESULTS

The number of ileal myenteric neurons positive for NR1, the functional subunit of NMDA receptors, and its mRNA levels were unchanged after in vitro ischemia/reperfusion. In these conditions, the protein levels of NR1, and of its phosphorylated form by protein kinase C (PKC), significantly increased in myenteric neurons, whereas, the levels of NR1 phosphorylated by protein kinase A (PKA) did not change, with respect to control values. Spontaneous glutamate overflow increased during in vitro ischemia/reperfusion. In these conditions, the NMDA receptor antagonists, D(-)-2-amino-5-phosphonopentanoic acid [(D)-AP5] (10 μmol L(-1)) and 5,7-dichlorokynurenic acid (5,7-diClKyn acid) (10 μmol L(-1)) and the PKC antagonist, chelerythrine (1 μmol L(-1)), but not the PKA antagonist, H-89 (1 μmol L(-1)), were able to significantly depress the increased glutamate efflux.

CONCLUSIONS & INFERENCES

The present data suggest that in the guinea pig ileum during in vitro ischemia/reperfusion, NR1 protein levels increase. Such event may rely upon posttranscriptional events involving NR1 phosphorylation by PKC. Increased NR1 levels may, at least in part, explain the ability of NMDA receptors to modulate a positive feedback on ischemia/reperfusion-induced glutamate overflow.

Anti-inflammatory role of glycine in reducing rodent postoperative inflammatory ileus

BACKGROUND

Inflammatory events within the intestinal muscularis, including macrophage activation and leukocyte recruitment, have been demonstrated to participate in causing postoperative ileus. Recently, glycine has gained attention due to its beneficial immunomodulatory effects in transplantation, shock and sepsis.

METHODS

Muscularis glycine receptors were investigated by immunohistochemistry. Gastrointestinal motility was assessed by in vivo transit distribution histograms with calculated geometric center analysis and jejunal circular smooth muscle contractility in a standard organ bath. The impact of glycine on the muscularis inflammatory responses to surgical manipulation of the intestine were measured by real-time PCR, nitric oxide Griess reaction, prostaglandin ELISA, Luminex and histochemistry.

KEY RESULTS

Glycine-gated chloride channels were immunohistochemically localized to muscularis macrophages and postoperative infiltrating leukocytes. Preoperative glycine treatment significantly improved postoperative gastrointestinal transit and jejunal circular muscle contractility. Preoperative glycine injection significantly reduced the induction of interleukin-6 (IL-6), tumor necrosis factor-α, inducible nitric oxide synthase and intercellular adhesion molecule-1 mRNAs, which was associated with the attenuation in postoperative leukocyte recruitment. Nitric oxide and prostanoid release from the postsurgical inflamed muscularis was diminished by glycine. The secretion of the inflammatory proteins IL-6, monocyte chemotactic protein-1/chemokine ligand 2 and macrophage inflammatory protein-1α/chemokine ligand 3 were also significantly decreased by glycine pretreatment.

CONCLUSIONS & INFERENCES

The data indicate that preoperative glycine reduces postoperative ileus via the early attenuation of primal inflammatory events within the surgically manipulated gut wall. Therapeutic modulation of resident macrophages by glycine is a potential novel pharmacological target for the prevention of postoperative ileus.

Damaging effects of ischemia/reperfusion on intestinal muscle

Periods of ischemia followed by restoration of blood flow cause ischemia/reperfusion (I/R) injury. In the intestine, I/R damage to the mucosa and neurons is prominent. Functionally, abnormalities occur in motility, most conspicuously a slowing of transit, possibly as a consequence of damage to neurons and/or muscle. Here, we describe degenerative and regenerative changes that have not been previously reported in intestinal muscle. The mouse small intestine was made ischemic for 1 h, followed by re-perfusion for 1 h to 7 days. The tissues were examined histologically, after hematoxylin/eosin and Masson's trichrome staining, and by myeloperoxidase histochemistry to detect inflammatory reactions to I/R. Histological analysis revealed changes in the mucosa, muscle, and neurons. The mucosa was severely but transiently damaged. The mucosal surface was sloughed off at 1-3 h, but re-epithelialization occurred by 12 h, and the epithelium appeared healthy by 1-2 days. Longitudinal muscle degeneration was followed by regeneration, but little effect on the circular muscle was noted. The first signs of muscle change were apparent at 3-12 h, and by 1 and 2 days, extensive degeneration within the muscle was observed, which included clear cytoplasm, pyknotic nuclei, and apoptotic bodies. The muscle recovered quickly and appeared normal at 7 days. Histological evidence of neuronal damage was apparent at 1-7 days. Neutrophils were not present in the muscle layers and were infrequent in the mucosa. However, they were often seen in the longitudinal muscle at 1-3 days and were also present in the circular muscle. Neutrophil numbers increased in the mucosa in both I/R and sham-operated animals and remained elevated from 1 h to 7 days. We conclude that I/R causes severe longitudinal muscle damage, which might contribute to the long-term motility deficits observed after I/R injury to the intestine.

A murine model for the study of edema induced intestinal contractile dysfunction

BACKGROUND

We have published extensively regarding the effects of edema on intestinal contractile function. However, we have found the need to expand our model to mice to take advantage of the much larger arsenal of research support, especially in terms of transgenic mouse availability and development. To that end, we have developed and validated a hydrostatic intestinal edema model in mice.

METHODS

Male C57 Black 6 mice were subjected to a combination of high volume crystalloid resuscitation and mesenteric venous hypertension in an effort to induce hydrostatic intestinal edema. Wet to dry ratios, myeloperoxidase activity, mucosal injury scoring, STAT-3 nuclear activation, phosphorylated STAT-3 levels, NF-κB nuclear activation, myosin light chain phosphorylation, intestinal contractile activity, and intestinal transit were measured to evaluate the effects of the model.

KEY RESULTS

High volume crystalloid resuscitation and mesenteric venous hypertension resulted in the development of significant intestinal edema without an increase in myeloperoxidase activity or mucosal injury. Edema development was associated with increases in STAT-3 and NF-κB nuclear activation as well as phosphorylated STAT-3. There was a decrease in myosin light chain phosphorylation, basal and maximally stimulated intestinal contractile activity, and intestinal transit.

CONCLUSION & INFERENCES

Hydrostatic edema in mice results in activation of a signal transduction profile that culminates in intestinal contractile dysfunction. This novel model allows for advanced studies into the pathogenesis of hydrostatic edema induced intestinal contractile dysfunction.

The reactions of specific neuron types to intestinal ischemia in the guinea pig enteric nervous system

Damage following ischemia and reperfusion (I/R) is common in the intestine and can be caused during abdominal surgery, in several disease states and following intestinal transplantation. Most studies have concentrated on damage to the mucosa, although published evidence also points to effects on neurons. Moreover, alterations of neuronally controlled functions of the intestine persist after I/R. The present study was designed to investigate the time course of damage to neurons and the selectivity of the effect of I/R damage for specific types of enteric neurons. A branch of the superior mesenteric artery supplying the distal ileum of anesthetised guinea pigs was occluded for 1 h and the animals were allowed to recover for 2 h to 4 weeks before tissue was taken for the immunohistochemical localization of markers of specific neuron types in tissues from sham and I/R animals. The dendrites of neurons with nitric oxide synthase (NOS) immunoreactivity, which are inhibitory motor neurons and interneurons, were distorted and swollen by 24 h after I/R and remained enlarged up to 28 days. The total neuron profile areas (cell body plus dendrites) increased by 25%, but the sizes of cell bodies did not change significantly. Neurons of type II morphology (intrinsic primary afferent neurons), revealed by NeuN immunoreactivity, were transiently reduced in cell size, at 24 h and 7 days. These neurons also showed signs of minor cell surface blebbing. Calretinin neurons, many of which are excitatory motor neurons, were unaffected. Thus, this study revealed a selective damage to NOS neurons that was observed at 24 h and persisted up to 4 weeks, without a significant change in the relative numbers of NOS neurons.

Interaction of hemorrhagic shock and subsequent polymicrobial sepsis on gastrointestinal motility

Understanding "two-hit" experimental models is crucial for the rational development of therapies for hemorrhagic shock (HS). We modeled the clinical scenario of HS followed by polymicrobial sepsis (cecal ligation and puncture [CLP]) to investigate the molecular and functional alterations that occur within the gastrointestinal tract. Control, HS, CLP, simultaneous HS + CLP, and HS + delayed CLP by 24 h groups of Sprague-Dawley rats were studied for gastrointestinal transit and in vitro colonic circular muscle contractility to bethanechol. Reverse transcription-polymerase chain reaction quantified IL-6, IL-10, and heme oxygenase 1 messenger RNA expression in the isolated colonic muscularis 6 h after insult. Myeloperoxidase-positive neutrophils were quantified in colonic muscularis whole mounts. Mortality at 24 h was significantly increased in simultaneous mild HS + CLP (88%) over control, mild HS, CLP alone, or HS + delayed CLP. Cecal ligation and puncture significantly delayed transit compared with controls and HS alone. Hemorrhagic shock + delayed CLP animals had normal transit. Colonic contractions were suppressed by 50% after CLP compared with controls and HS. In contrast, HS + delayed CLP displayed control levels of contractile responses to bethanechol. Cecal ligation and puncture and simultaneous HS + CLP caused significant inflammatory messenger RNA induction of IL-6, iNOS, IL-10, and heme oxygenase 1 compared with control and HS, and these responses were significantly suppressed in HS + delayed CLP colonic muscularis extracts. Neutrophils were significantly recruited into the colonic muscularis following CLP after 24 h compared with control and HS. This recruitment was significantly less in the HS + delayed CLP animals. These data demonstrate the ability of mild HS to precondition the animal and protect it against a delayed, but not simultaneous, polymicrobial event.

The effects of sildenafil on the functional and structural changes of ileum induced by intestinal ischemia-reperfusion in rats

There is evidence demonstrating the protective effect of cGMP-specific phosphodiesterase type 5 (PDE5) inhibitors against ischemic injury in certain tissues. In this study, sildenafil, a potent inhibitor of PDE5, was tested for its beneficial effects in the prevention of disrupted ileal contractility and damage to tissue caused by intestinal ischemia-reperfusion in rats. Male Sprague-Dawley rats were divided into four groups: sham-operated; sham-operated with sildenafil pretreatment; ischemia-reperfusion with vehicle pretreatment; and ischemia-reperfusion with sildenafil pretreatment. The superior mesenteric artery was occluded for 45 min to induce ischemia. The clamp was then removed for a 60 min period of reperfusion. Sildenafil (1 mg/kg, i.v.) or saline was administered prior to the surgical procedure in the ischemia-reperfusion and sham-operated groups. Isometric contractions of the ileal segments in response to acetylcholine or electrical field stimulation (120 V, 2 ms pulse for 5 s, 1-20 Hz) were recorded. Additionally, levels of thiobarbituric acid reactive substances and myeloperoxidase activity were measured in addition to a histopathological examination of the ileal tissue. The contractions induced by both acetylcholine and electrical field stimulations were markedly inhibited after ischemia-reperfusion. Sildenafil pretreatment (1 mg/kg, i.v.) abolished the inhibition of responses to acetylcholine. The increased levels of thiobarbituric acid reactive substances and myeloperoxidase activity caused by ischemia-reperfusion were reversed to control levels with sildenafil pretreatment. Intestinal ischemia-reperfusion caused severe ischemic injury in rat ileum, which was prevented by sildenafil. These results suggest that sildenafil pretreatment has a protective effect against ileal dysfunction and damage induced by intestinal ischemia-reperfusion in the rat.

Activated protein C prevents deleterious effects of remote reperfusion injury caused by intestinal ischemia on wound healing in the left colonic anastomoses: an experimental study in the murine model

BACKGROUND

Activated protein C (APC) is a serine protease with anticoagulant and antiinflammatory activities. The delaying effects of remote reperfusion injury on the wound-healing process in colonic anastomoses have been previously shown. In this study, we aimed to investigate whether APC protects against deleterious systemic effects of intestinal ischemia/reperfusion (I/R) injury on colonic anastomotic wound healing process.

METHODS

Male Wistar-albino rats were randomly allocated into 4 groups, and a left colonic anastomosis was performed in all animals: (1) sham-operated group, simultaneously with left colonic anastomosis, the superior mesenteric artery and collateral branches were divided from the celiac axis, and the inferior mesenteric artery were isolated but not occluded (group 1, n = 12), (2) sham + APC group, identical to group 1 except for APC treatment (100 microg/kg, intravenously, 15 minutes before construction of the colonic anastomosis), (group 2, n = 12), (3) intestinal I/R group, 60 minutes of superior mesenteric ischemia followed by reperfusion (group 3, n = 12), and (4) APC-treated group, (100 microg/kg, intravenously, 15 minutes before reperfusion) (group 4, n = 12). All animals were sacrificed, and colonic anastomotic bursting pressures were measured in vivo on day 7. Tissue samples were obtained for analysis of hydroxyproline contents, nitrate/nitrite levels, and activities of oxidative and antioxidative enzymes. The plasma levels of proinflammatory cytokines and D-dimer were also measured.

RESULTS

Intestinal I/R led to significant decreases in colonic anastomotic bursting pressures, tissue hydroxyproline contents, and activities of antioxidative enzymes, along with increases in tissue nitrate/nitrite levels, activities of oxidative enzymes, and plasma levels of proinflammatory cytokines and D-dimer (P < .05). However, APC treatment led to significant increases in colonic anastomotic bursting pressures, tissue hydroxyproline contents, and activities of antioxidative enzymes, along with decreases in tissue nitrate/nitrite levels, activities of oxidative enzymes, and plasma levels of proinflammatory cytokines and D-dimer (P < .05).

CONCLUSION

This study clearly showed that APC treatment prevented the delaying effects of remote I/R injury on colonic anastomotic wound healing process. Further clinical studies are required to determine whether APC has a useful role in the enhancement of colonic anastomotic wound healing after particular operations in which I/R injury occurs.

Mast cells reduce survival of myenteric neurons in culture

Mast cell-nerve interactions play a key role in intestinal inflammation and irritable bowel disease. Loss of enteric neurons has been reported in inflammatory conditions but the contribution of mast cells in this event is unknown. To study neuronal survival and plasticity of myenteric neurons in contact with mast cells a co-culture system using myenteric neurons from rat small intestine and peritoneal mast cells was set up. Dissociated myenteric neurons were cultured for 4 days before addition of mast cells isolated by peritoneal lavage. Neuronal survival and expression of vasoactive intestinal peptide (VIP) and nitric oxide synthase (NOS) were studied by immunocytochemistry and neuronal cell counting. Myenteric neurons cultured without mast cells were used to study the rate of neuronal survival after the addition of various mast cell mediators, proteinase-activated receptor(2) (PAR(2)) agonist, VIP or corticosteroid. A striking mast cell-induced neuronal cell death was found after co-culturing. It was counteracted by the addition of mast cell stabiliser doxantrazole, protease inhibitors, PAR(2) antagonist FSLLRY-amide, corticosteroid or VIP. In myenteric neurons cultured without mast cells the PAR(2) agonist SLIGRL-amide, prostaglandin D(2) and interleukin (IL) 6 reduced neuronal survival while histamine, serotonin, heparin, IL1beta and tumour necrosis factor alpha had no effect; corticosteroid and VIP enhanced neuronal survival. The relative numbers of VIP-, but not NOS-expressing myenteric neurons increased after co-culturing. Mast cell-induced neuronal cell death is suggested to be mediated via PAR(2) activation, IL6 and prostaglandin D(2). Corticosteroid and VIP are neuroprotective and able to prevent cell death of myenteric neurons in co-culture.