New insights in intestinal ischemia-reperfusion injury: implications for intestinal transplantation

Enteric fungi protect against intestinal ischemia-reperfusion injury via inhibiting the SAA1-GSDMD pathway

INTRODUCTION

Prophylactic antifungal therapy has been widely used for critical patients, but it has failed to improve patient prognosis and has become a hot topic. This may be related to disruption of fungal homeostasis, but the mechanism of fungi action is not clear. As a common pathway in critical patients, intestinal ischemia-reperfusion (IIR) injury is fatal and regulated by gut microbiota. However, the exact role of enteric fungi in IIR injury remains unclear.

OBJECTIVES

This is a clinical study that aims to provide new perspectives in clarifying the underlying mechanism of IIR injury and propose potential strategies that could be relevant for the prevention and treatment of IIR injury in the near future.

METHODS

ITS sequencing was performed to detect the changes in fungi before and after IIR injury. The composition of enteric fungi was altered by pretreatment with single-fungal strains, fluconazole and mannan, respectively. Intestinal morphology and function impairment were evaluated in the IIR injury mouse model. Intestinal epithelial MODE-K cells and macrophage RAW264.7 cells were cultured for in vitro tests.

RESULTS

Fecal fungi diversity revealed the obvious alteration in IIR patients and mice, accompanied by intestinal epithelial barrier dysfunction. Fungal colonization and mannan supplementation could reverse intestinal morphology and function impairment that were exacerbated by fluconazole via inhibiting the expression of SAA1 from macrophages and decreasing pyroptosis of intestinal epithelial cells. Clodronate liposomes were used to deplete the number of macrophages, and it was demonstrated that the protective effect of mannan was dependent on macrophage involvement.

CONCLUSION

This finding firstly validates that enteric fungi play a crucial role in IIR injury. Preventive antifungal treatment should consider damaging fungal balance. This study provides a novel clue to clarify the role of enteric fungi in maintaining intestinal homeostasis.

Intraluminal oxygen can keep small bowel mucosa intact in a segmental ischemia model

Intestinal preservation for transplantation is accompanied by hypoperfusion with long periods of ischemia with total blood cessation and absolute withdrawal of oxygen leading to structural damage. The application of intraluminal oxygen has been successfully tested in small-animal series during storage and transport of the organ but have been so far clinically unrelatable. In this study, we tested whether a simple and clinically approachable method of intraluminal oxygen application could prevent ischemic damage in a large animal model, during warm ischemia time. We utilised a local no-flow ischemia model of the small intestine in pigs. A low-flow and high-pressure intraluminal oxygen deliverance system was applied in 6 pigs and 6 pigs served as a control group. Mucosal histopathology, hypoxia and barrier markers were evaluated after two hours of no-flow conditions, in both treatment and sham groups, and in healthy tissue. Macro- and microscopically, the luminal oxygen delivered treatment group showed preserved small bowel's appearance, viability, and mucosal integrity. A gradual deterioration of histopathology and barrier markers and increase in hypoxia-inducible factor 1-α expression towards the sites most distant from the oxygen application was observed. Intraluminal low-flow, high oxygen delivery can preserve the intestinal mucosa during total ischemia of the small intestine. This finding can be incorporated in methods to overcome small bowel ischemia and improve intestinal preservation for transplantation.

Unveiling the molecular complexity of intestinal ischemia-reperfusion injury through omics technologies

Intestinal ischemia-reperfusion injury (IR) is implicated in various clinical conditions and causes damage to the intestinal epithelium resulting in intestinal barrier loss. This presents a substantial clinical challenge, emphasizing the importance of gaining a comprehensive understanding of molecular events to aid in the identification of novel therapeutic targets. This review systematically explores the extent to which omics technologies-transcriptomics, proteomics, metabolomics, and metagenomics-have already contributed to deciphering the molecular mechanisms contributing to intestinal IR injury, in in vivo and in vitro animal and human models, and in clinical samples. Recent breakthroughs involve applying omics methodologies on exosomes, organoids, and single cells, shedding light on promising avenues and valuable targets to reduce intestinal IR injury. Future directions aimed at expediting clinical translation are discussed as well and include multi-omics data integration to facilitate the identification of key regulatory nodes driving intestinal IR injury and advancing human organoid models based on the novel insights by single-cell omics technologies, offering hope for clinical application of therapeutic strategies in the years to come.

Nitric oxide protects intestinal mucosal barrier function and prevents acute graft rejection after intestinal transplantation: A mini-review

Intestinal transplantation is a complex technical procedure that provides patients suffering from end-stage intestinal failure an opportunity to enjoy improved quality of life, nutrition and survival. Compared to other types of organ transplants, it is a relatively new advancement in the field of organ transplantation. Nevertheless, great advances have been made over the past few decades to the present era, including the use of ischemic preconditioning, gene therapy, and addition of pharmacological supplements to preservation solutions. However, despite these strides, intestinal transplantation is still a challenging endeavor due to several factors. Notable among them is ischemia-reperfusion injury (IRI), which results in loss of cellular integrity and mucosal barrier function. In addition, IRI causes graft failure, delayed graft function, and decreased graft and recipient survival. This has necessitated the search for novel therapeutic avenues and improved transplantation protocols to prevent or attenuate intestinal IRI. Among the many candidate agents that are being investigated to combat IRI and its associated complications, nitric oxide (NO). NO is an endogenously produced gaseous signaling molecule with several therapeutic properties. The purpose of this mini-review is to discuss IRI and its related complications in intestinal transplantation, and NO as an emerging pharmacological tool against this challenging pathological condition. i.

Nutrition care for the adult post-intestinal transplant patient

Intestinal transplantation has emerged as an accepted treatment choice for individuals experiencing irreversible intestinal failure. This treatment is particularly relevant for those who are not candidates or have poor response to autologous gut reconstruction or trophic hormone therapy, and who can no longer be sustained on parenteral nutrition. One of the main goals of transplant is to eliminate the need for parenteral support and its associated complications, while safely restoring complete nutrition autonomy. An intestinal transplant is a complex process that goes beyond merely replacing the intestines to provide nourishment and ceasing parenteral support. It requires an integrated management approach in the pretransplant and posttransplant setting, and high-quality nutrition treatment is one of the cornerstones leading to favorable outcomes and long-term management. Since the outset of intestinal transplant in the early 2000s, there is observed improvement of achieving nutrition autonomy sooner in the initial posttransplant phase; however, the development of nutrition complications in the chronic posttransplant period remains a long-term risk. This review delineates the decision-making process and clinical protocols used to nutritionally manage and monitor pre- and post-intestine transplant patients.

Peptidome analysis reveals critical roles for peptides in a rat model of intestinal ischemia/reperfusion injury

Intestinal ischemia/reperfusion injury (IIRI) has the potential to be life threatening and is associated with significant morbidity and serious damage to distant sites in the body on account of disruption of the intestinal mucosal barrier. In the present study, we have explored this line of research by comparing and identifying peptides that originated from the intestinal segments of IIRI model rats by using liquid chromatography-mass spectrometry (LC-MS). We also analyzed the basic characteristics, cleavage patterns, and functional domains of differentially expressed peptides (DEPs) between the IIRI model rats and control (sham-operated) rats and identified bioactive peptides that are potentially associated with ischemia reperfusion injury. We also performed bioinformatics analyses in order to identify the biological roles of the DEPs based on their precursor proteins. Enrichment analysis demonstrated the role of several DEPs in impairment of the intestinal mucosal barrier caused by IIRI. Based on the results of comprehensive ingenuity pathway analysis, we identified the DEPs that were significantly correlated with IIRI. We identified a candidate precursor protein (Actg2) and seven of its peptides, and we found that Actg2-6 had a more significant difference in its expression, a longer half-life, and better lipophilicity, hydrophobicity, and stability than the other candidate Actg2 peptides examined. Furthermore, we observed that Actg2-6 might play critical roles in the protection of the intestinal mucosal barrier during IIRI. In summary, our study provides a better understanding of the peptidomics profile of IIRI, and the results indicate that Actg2-6 could be a useful target in the treatment of IIRI.

Idiopathic Ileal Ulceration After Intestinal Transplantation

Background

Idiopathic ileal ulceration after intestinal transplantation (ITx) has been discussed infrequently and has an uncertain natural history and relation to graft rejection. Herein, we review our experience with this pathology.

Methods

We retrospectively reviewed 225 ITx in 217 patients with minimum 1 y graft survival. Routine graft endoscopy was conducted up to twice weekly within the first 90 d after ITx, gradually decreasing to once yearly. Risks for ulceration over time were evaluated using Cox regression.

Results

Of 93 (41%) patients with ulcers, 50 were found within 90 d after ITx mostly via ileoscopy; delayed healing after biopsy appeared causal in the majority. Of the remaining 43 patients with ulcers found >90 d after ITx, 36 were after ileostomy closure. Multivariable modeling demonstrated within 90-d ulcer associations with increasing patient age (hazard ratio [HR], 1.027; P < 0.001) and loop ileostomy (versus Santulli ileostomy; HR, 0.271; P < 0.001). For ulcers appearing after ileostomy closure, their sole association was with absence of graft colon (HR, 7.232; P < 0.001). For ulcers requiring extended anti-microbial and anti-inflammatory therapy, associations included de novo donor-specific antibodies (HR, 3.222; P < 0.007) and nucleotide oligomerization domain mutations (HR, 2.772; P < 0.016). Whole-cohort post-ITx ulceration was not associated with either graft rejection (P = 0.161) or graft failure (P = 0.410).

Conclusions

Idiopathic ulceration after ITx is relatively common but has little independent influence on outcome; risks include ileostomy construction, colon-free ITx, immunologic mutation, and donor sensitization.

Preclinical Study of DCD and Normothermic Perfusion for Visceral Transplantation

Considering recent clinical and experimental evidence, expectations for using DCD-derived intestines have increased considerably. However, more knowledge about DCD procedure and long-term results after intestinal transplantation (ITx) is needed. We aimed to describe in detail a DCD procedure for ITx using normothermic regional perfusion (NRP) in a preclinical model. Small bowel was obtained from pigs donors after 1 h of NRP and transplanted to the recipients. Graft Intestinal samples were obtained during the procedure and after transplantation. Ischemia-reperfusion injury (Park-Chiu score), graft rejection and transplanted intestines absorptive function were evaluated. Seven of 8 DCD procedures with NRP and ITx were successful (87.5%), with a good graft reperfusion and an excellent recovery of the recipient. The architecture of grafts was well conserved during NRP. After an initial damage of Park-chiu score of 4, all grafts recovered from ischemia-reperfusion, with no or very subtle alterations 2 days after ITx. Most recipients (71.5%) did not show signs of rejection. Only two cases demonstrated histologic signs of mild rejection 7 days after ITx. Interestingly intestinal grafts showed good absorptive capacity. The study's results support the viability of intestinal grafts from DCD using NRP, contributing more evidence for the use of DCD for ITx.

Esculetin Alleviates Inflammation, Oxidative Stress and Apoptosis in Intestinal Ischemia/Reperfusion Injury via Targeting SIRT3/AMPK/mTOR Signaling and Regulating Autophagy

Aim

Intestinal ischemia/reperfusion (I/R) injury is a challenging pathological phenomenon accountable for significant mortality in clinical scenarios. Substantial evidence has supported the protective role of esculetin in myocardial I/R injury. This study is designed to reveal the specific impacts of esculetin on intestinal I/R injury and disclose the underlying mechanism.

Methods

First, intestinal I/R injury model and intestinal epithelial cell line hypoxia/reoxygenation (H/R) model were established. Pathologic damages to intestinal tissues were observed through H&E staining. Serum diamine oxidase (DAO) levels were examined. RT-qPCR and Western blot examined the expression of inflammatory mediators. Commercial kits were used for detecting the levels of oxidative stress markers. TUNEL assay and caspase 3 activity assay measured cell apoptosis. Immunofluorescence (IF) staining measured autophagy levels. Western blot analyzed the expression of apoptosis-, Sirtuin 3 (SIRT3)/AMP activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) signaling- and autophagy-related proteins. Molecular docking verified the interaction of esculetin with SIRT3. Cell viability was explored via CCK-8 assay.

Results

The experimental results revealed that esculetin treatment mitigated pathological damage of intestinal tissues, reduced serum DAO level, ameliorated inflammation, oxidative stress and apoptosis and promoted autophagy in intestinal I/R rats. Moreover, esculetin bond to SIRT3 and activated SIRT3/AMPK/mTOR signaling both in vitro and in vivo. Furthermore, esculetin treatment enhanced cell viability and SIRT3 silencing reversed the impacts of esculetin on autophagy, inflammation, oxidative stress and apoptosis in H/R cell model.

Conclusion

In a word, esculetin activated SIRT3/AMPK/mTOR signaling and autophagy to protect against inflammation, oxidative stress and apoptosis in intestinal I/R injury.

Transcription factor Krüppel-like factor 4 upregulated G protein-coupled receptor 30 alleviates intestinal inflammation and apoptosis, and protects intestinal integrity from intestinal ischemia-reperfusion injury

INTRODUCTION

Intestinal ischemia/reperfusion (I/R) injury is a common clinical event occurring during multiple clinical pathological processes. Here, we designed this paper to discuss the role of G protein-coupled receptor 30 (GPR30) playing in intestinal I/R injury.

METHODS

An oxygen-glucose deprivation/reoxygenation (OGD/R) cell model was established to simulate the pathological process of I/R injury. With the application of enzyme-linked immunosorbent assay, TUNEL, and transepithelial electrical resistance (TEER) assays, the levels of inflammatory cytokines, cell apoptosis, and intestinal integrity were estimated. The corresponding proteins were estimated by applying western blot. Immunofluorescence was conducted to examine N-terminal Gasdermin D (GSDMD-N) expression. The interplay between KLF4 and GPR30 was demonstrated by dual-luciferase reporter assay and chromatin immunoprecipitation.

RESULTS

The results showed that GPR30 was downregulated in Caco-2 cells exposed to OGD/R. GPR30 overexpression reduced the production of TNF-α, IL-6, IL-1β, and IL-18, the TUNEL-positive cells, as well as the contents of p-p65, Cox-2, Inos, Bax, and cleaved-PARP, but elevated the expression of Bcl-2 in OGD/R-induced Caco-2 cells. In addition, OGD/R-induced the reduction of TEER value and reduced expression of tight junction proteins in Caco-2 cells, which was partially restored by GPR30 overexpression. Furthermore, GPR30 suppressed nod-like receptor pyrin 3 inflammasome and GSDMD-N expression. It was evidenced that Krüppel-like factor 4 (KLF4) could directly bind to GPR30 promoter and positively regulate GPR30 expression. The regulation of GPR30 overexpression above was weakened by KLF4 knockdown.

CONCLUSION

Collectively, our findings suggested that KLF4 could transcriptionally upregulate GPR30, and GPR30 prevented intestine I/R injury by inhibiting inflammation and apoptosis, and maintaining intestinal integrity that provides potential targets for mitigating the I/R injury.

Effect of remote ischemic preconditioning on postoperative gastrointestinal function in patients undergoing laparoscopic colorectal cancer resection

PURPOSE

Patients undergoing laparoscopic colorectal cancer resection have a high incidence of postoperative gastrointestinal dysfunction (POGD). Remote ischemic preconditioning (RIPC) is an organ protection measure. The study investigated the effect of RIPC on postoperative gastrointestinal function.

METHODS

In this single-center, prospective, double-blinded, randomized, parallel-controlled trial, 100 patients undergoing elective laparoscopic colorectal cancer resection were randomly assigned in a 1:1 ratio to receive RIPC or sham RIPC (control). Three cycles of 5-min ischemia/5-min reperfusion induced by a blood pressure cuff placed on the right upper arm served as RIPC stimulus. Patients were followed up continuously for 7 days after surgery. The I-FEED score was used to evaluate the patient's gastrointestinal function after the surgery. The primary outcome of the study was the I-FEED score on POD3. Secondary outcomes include the daily I-FEED scores, the highest I-FEED score, the incidence of POGD, the changes in I-FABP and the inflammatory markers (IL-6 and TNF-α), and the time to first postoperative flatus.

RESULTS

A total of 100 patients were enrolled in the study, of which 13 patients were excluded. Finally, 87 patients were included in the analysis, 44 patients in the RIPC group and 43 patients in the sham-RIPC group. Patients assigned to the RIPC group had a lower I-FEED score on POD3 compared with the sham-RIPC group (mean difference 0.86; 95% CI: 0.06 to 1.65; P = 0.035). And patients in the RIPC group were also associated with a lower I-FEED score on POD4 vs the sham-RIPC group (mean difference 0.81; 95% CI: 0.03 to 1.60; P = 0.043). Compared with the sham-RIPC group, the incidence of POGD within 7 days after surgery was lower in the RIPC group (P = 0.040). At T₁, T₂, and T₃ time points, inflammatory factors and I-FABP were considerably less in the RIPC group compared to the sham-RIPC group. The time to the first flatus and the first feces was similar in both groups.

CONCLUSION

RIPC reduced I-FEED scores, decreased the incidence of postoperative gastrointestinal dysfunction, and lowered concentrations of I-FABP and inflammatory factors.

Protective Effect of Oxygen and Isoflurane in Rodent Model of Intestinal Ischemia-Reperfusion Injury

Animal research in intestinal ischemia-reperfusion injury (IRI) is mainly performed in rodent models. Previously, intraperitoneal (I.P.) injections with ketamine-xylazine mixtures were used. Nowadays, volatile anesthetics (isoflurane) are more common. However, the impact of the anesthetic method on intestinal IRI has not been investigated. We aim to analyze the different anesthetic methods and their influence on the extent of intestinal IRI in a rat model. Male Sprague-Dawley rats were used to investigate the effect of I.P. anesthesia on 60 min of intestinal ischemia and 60 min of reperfusion in comparison to hyperoxygenation (100% O₂) and volatile isoflurane anesthesia. In comparison to I.P. anesthesia with room air (21% O₂), supplying 100% O₂ improved 7-day survival by cardiovascular stabilization, reducing lactic acidosis and preventing vascular leakage. However, this had no effect on the intestinal epithelial damage, permeability, and inflammatory response observed after intestinal IRI. In contrast to I.P. + 100% O₂, isoflurane anesthesia reduced intestinal IRI by preventing ongoing low-flow reperfusion hypotension, limiting intestinal epithelial damage and permeability, and by having anti-inflammatory effects. When translating the aforementioned results of this study to clinical situations, such as intestinal ischemia or transplantation, the potential protective effects of hyperoxygenation and volatile anesthetics require further research.

Exosomes Derived from BMSCs Ameliorate Intestinal Ischemia-Reperfusion Injury by Regulating miR-144-3p-Mediated Oxidative Stress

BACKGROUND

Intestinal ischemia-reperfusion (I/R) injury is a critical pathophysiological process involved in many acute and critical diseases, and it may seriously threaten the lives of patients. Exosomes derived from bone marrow mesenchymal stem cells (BMSC-exos) may be an effective therapeutic approach for I/R injury.

AIMS

This study aimed to investigate the role and possible mechanism of BMSC-exos in intestinal I/R injury in vivo and in vitro based on the miR-144-3p and PTEN/Akt/Nrf2 pathways.

METHODS

BMSC-exos were isolated from mouse BMSCs by super centrifugation methods. The effects of BMSC-exos on I/R intestinal injury, intestinal cell apoptosis, oxidative stress and the PTEN/Akt/Nrf2 pathway were explored in vivo and in vitro. Furthermore, the relationship between miR-144-3p and PTEN was confirmed by a dual-luciferase reporter assay. The miR-144-3p mimic and inhibitor were used to further clarify the role of miR-144-3p in the mitigation of intestinal I/R by BMSC-exos.

RESULTS

BMSC-exos effectively alleviated intestinal pathological injury, reduced intestinal cell apoptosis, relieved oxidative stress and regulated the PTEN/Akt/Nrf2 pathway in vivo and in vitro. In addition, miR-144-3p was significantly reduced in the oxygen and glucose deprivation/reperfusion cell model, and miR-144-3p could directly target PTEN to regulate its expression. Additional studies showed that changing the expression of miR-144-3p in BMSC-exos significantly affected the regulation of intestinal injury, intestinal cell apoptosis, oxidative stress and the PTEN/Akt/Nrf2 pathway in I/R, suggesting that miR-144-3p in BMSC-exos plays an important role in regulating the PTEN/Akt/Nrf2 during intestinal I/R.

CONCLUSIONS

BMSC-exos carrying miR-144-3p alleviated intestinal I/R injury by regulating oxidative stress.

H151, A SMALL MOLECULE INHIBITOR OF STING AS A NOVEL THERAPEUTIC IN INTESTINAL ISCHEMIA-REPERFUSION INJURY

BACKGROUND

Intestinal ischemia-reperfusion (I/R) injury is a severe disease associated with high mortality. Stimulator of interferon genes (STING) is an intracellular protein that is activated by cytosolic DNA and is implicated in I/R injury, resulting in transcription of type I interferons (IFN-α and IFN-β) and other proinflammatory molecules. Extracellular cold-inducible RNA-binding protein (eCIRP), a damage-associated molecular pattern, induces STING activation. H151 is a small molecule inhibitor of STING that has not yet been studied as a potential therapeutic. We hypothesize that H151 reduces inflammation, tissue injury, and mortality after intestinal I/R. Methods: In vitro, RAW264.7 cells were pretreated with H151 then stimulated with recombinant murine (rm) CIRP, and IFN-β levels in the culture supernatant were measured at 24 hours after stimulation. In vivo, male C57BL/6 mice were subjected to 60-minute intestinal ischemia via superior mesenteric artery occlusion. At the time of reperfusion, mice were intraperitoneally instilled with H151 (10 mg/kg BW) or 10% Tween-80 in PBS (vehicle). Four hours after reperfusion, the small intestines, lungs, and serum were collected for analysis. Mice were monitored for 24 hours after intestinal I/R to assess survival. Results: In vitro, H151 reduced rmCIRP-induced IFN-β levels in a dose-dependent manner. In vivo, intestinal levels of pIRF3 were increased after intestinal I/R and decreased after H151 treatment. There was an increase in serum levels of tissue injury markers (lactate dehydrogenase, aspartate aminotransferase) and cytokine levels (interleukin 1β, interleukin 6) after intestinal I/R, and these levels were decreased after H151 treatment. Ischemia-reperfusion-induced intestinal and lung injury and inflammation were significantly reduced after H151 treatment, as evaluated by histopathologic assessment, measurement of cell death, chemokine expression, neutrophil infiltration, and myeloperoxidase activity. Finally, H151 improved the survival rate from 41% to 81% after intestinal I/R. Conclusions: H151, a novel STING inhibitor, attenuates the inflammatory response and reduces tissue injury and mortality in a murine model of intestinal I/R. H151 shows promise as a potential therapeutic in the treatment of this disease.

Blockade or deficiency of PD-L1 expression in intestinal allograft accelerates graft tissue injury in mice

The importance of PD-1/PD-L1 interaction to alloimmune response is unknown in intestinal transplantation. We tested whether PD-L1 regulates allograft tissue injury in murine intestinal transplantation. PD-L1 expression was observed on the endothelium and immune cells in the intestinal allograft. Monoclonal antibody treatment against PD-L1 led to accelerated allograft tissue damage, characterized by severe cellular infiltrations, massive destruction of villi, and increased crypt apoptosis in the graft. Interestingly, PD-L1^-/- allografts were more severely rejected than wild-type allografts, but the presence or absence of PD-L1 in recipients did not affect the degree of allograft injury. PD-L1^-/- allografts showed increased infiltrating Ly6G⁺ and CD11b⁺ cells in lamina propria on day 4, whereas the degree of CD4⁺ or CD8⁺ T cell infiltration was comparable to wild-type allografts. Gene expression analysis revealed that PD-L1^-/- allografts had increased mRNA expressions of Cxcr2, S100a8/9, Nox1, IL1rL1, IL1r2, and Nos2 in the lamina propria cells on day 4. Taken together, study results suggest that PD-L1 expression in the intestinal allograft, but not in the recipient, plays a critical role in mitigating allograft tissue damage in the early phase after transplantation. The PD-1/PD-L1 interaction may contribute to immune regulation of the intestinal allograft via the innate immune system.

Post-Cardiac Arrest Syndrome Is Not Associated with An Early Bacterial Translocation

BACKGROUND

The aim of this study was to investigate bacterial translocation and its possible role in the development of post-resuscitation inflammatory response following Cardio-Pulmonary Resuscitation (CPR) after cardiac arrest.

METHODS

Munich female swine were employed for a model of cardiac arrest via application of electrical current. After 7 min, CPR was initiated, and animals were either successfully return to spontaneous circulation (ROSC) within 40 min or not (no-ROSC). At the end of experimental period and prior to sacrifice, samples from the intestine, mesenteric lymph nodes (MLN), liver and portal vein blood were obtained. Evaluation of inflammation and gut permeability was performed; MLN, liver and portal vein samples were analyzed for 16 s rRNA detection and cytokine mRNA expression.

RESULTS

A decreased expression of the tight junction protein Occludin, with higher levels of inflammation, greater epithelial disintegration, ulceration, loss of crypts and villi height were found in the intestines of the ROSC swine in comparison to no-ROSC. The macrophage surface antigen CD-14 staining was relatively more intense in the ROSC than in no-ROSC. Higher levels of TNF-α mRNA expression were present in the liver of the ROSC group. Finally, despite the inflammatory response and the gut mucosal alterations in ROSC group, no bacterial translocation was detected in liver, MLN and portal vein.

CONCLUSIONS

We show that resuscitation from cardiac arrest induces inflammatory response and intestinal permeability in swine 4h after resuscitation, but not a bacterial translocation. Bacterial translocation is not an early phase phenomenon but probably part of the pathophysiologic sequelae.

Protective effect of parecoxib sodium against ischemia reperfusion‑induced intestinal injury

Ischemia reperfusion (I/R)-induced intestinal injury is a pathophysiological process leading to oxidative stress and inflammatory responses, and revealing its underlying mechanisms is essential for developing therapeutic strategies. Cyclooxygenase (COX) has been reported to be involved in I/R injury. Parecoxib sodium, a selective inhibitor for COX-2, exerts protective effects, such as reducing I/R-induced injuries in the heart, kidney and brain. However, the potential role of parecoxib sodium in protecting the small intestine against I/R-induced injury has rarely been investigated. Therefore, the aim of the present study was to elucidate the effects and potential mechanisms of parecoxib sodium in I/R-induced intestinal injury. In total, 60 Sprague-Dawley rats were randomly divided into four groups: Control (sham operation) group, intestinal I/R group, 10 mg/kg parecoxib sodium-pre-treated I/R (I/R + Pare/10) group and the 20 mg/kg parecoxib sodium-pre-treated I/R (I/R + Pare/20) group. A regular I/R model was established to induce the intestinal injury in rats. Parecoxib sodium at 10 or 20 mg/kg was intraperitoneally administered into rats in both I/R + Pare groups once daily for 5 consecutive days prior to ischemia. Blood samples and small intestinal tissues were collected at 2 h after reperfusion. Changes in the levels of malondialdehyde, nitric oxide, interleukin (IL)-1β, IL-8, intercellular cell adhesion molecule-1 and IL-10, as well as the total antioxidant capacity were determined using ELISA, as were the activities of superoxidase dismutase and myeloperoxidase. Furthermore, the protein expression levels of total caspase-3, cleaved caspase-3, Bcl-2 and Bax were examined via western blot analysis. In addition, the daily survival rate post-reperfusion was examined for 7 days. It was revealed that parecoxib sodium increased the levels of antioxidants and suppressed the intestinal oxidative injury induced by I/R. Moreover, parecoxib sodium downregulated the expression levels of the proinflammatory factors, but upregulated the expression levels of anti-inflammatory factors. The results also demonstrated that parecoxib sodium attenuated I/R-induced apoptosis and increased the survival rate of rats. Thus, administration of parecoxib sodium prior to intestinal I/R attenuated intestinal injury and increased the rat survival rate by inhibiting I/R-induced inflammation, oxidative stress and apoptosis.

Proteomics analysis of human intestinal organoids during hypoxia and reoxygenation as a model to study ischemia-reperfusion injury

Intestinal ischemia-reperfusion (IR) injury is associated with high mortality rates, which have not improved in the past decades despite advanced insight in its pathophysiology using in vivo animal and human models. The inability to translate previous findings to effective therapies emphasizes the need for a physiologically relevant in vitro model to thoroughly investigate mechanisms of IR-induced epithelial injury and test potential therapies. In this study, we demonstrate the use of human small intestinal organoids to model IR injury by exposing organoids to hypoxia and reoxygenation (HR). A mass-spectrometry-based proteomics approach was applied to characterize organoid differentiation and decipher protein dynamics and molecular mechanisms of IR injury in crypt-like and villus-like human intestinal organoids. We showed successful separation of organoids exhibiting a crypt-like proliferative phenotype, and organoids exhibiting a villus-like phenotype, enriched for enterocytes and goblet cells. Functional enrichment analysis of significantly changing proteins during HR revealed that processes related to mitochondrial metabolism and organization, other metabolic processes, and the immune response were altered in both organoid phenotypes. Changes in protein metabolism, as well as mitophagy pathway and protection against oxidative stress were more pronounced in crypt-like organoids, whereas cellular stress and cell death associated protein changes were more pronounced in villus-like organoids. Profile analysis highlighted several interesting proteins showing a consistent temporal profile during HR in organoids from different origin, such as NDRG1, SDF4 or DMBT1. This study demonstrates that the HR response in human intestinal organoids recapitulates properties of the in vivo IR response. Our findings provide a framework for further investigations to elucidate underlying mechanisms of IR injury in crypt and/or villus separately, and a model to test therapeutics to prevent IR injury.

Paneth Cell Alterations During Ischemia-reperfusion, Follow-up, and Graft Rejection After Intestinal Transplantation

BACKGROUND

Ischemia-reperfusion injury is inevitable during intestinal transplantation (ITx) and executes a key role in the evolution towards rejection. Paneth cells (PCs) are crucial for epithelial immune defense and highly vulnerable to ischemia-reperfusion injury. We investigated the effect of ITx on PC after reperfusion (T0), during follow-up, and rejection. Moreover, we investigated whether PC loss was associated with impaired graft homeostasis.

METHODS

Endoscopic biopsies, collected according to center protocol and at rejection episodes, were retrospectively included (n = 28 ITx, n = 119 biopsies) Biopsies were immunohistochemically co-stained for PC (lysozyme) and apoptosis, and PC/crypt and lysozyme intensity were scored.

RESULTS

We observed a decrease in PC/crypt and lysozyme intensity in the first week after ITx (W1) compared with T0. There was a tendency towards a larger decline in PC/crypt (P = 0.08) and lysozyme intensity (P = 0.08) in W1 in patients who later developed rejection compared with patients without rejection. Follow-up biopsies showed that the PC number recovered, whereas lysozyme intensity remained reduced. This persisting innate immune defect may contribute to the well-known vulnerability of the intestine to infection. There was no clear evidence that PCs were affected throughout rejection.

CONCLUSIONS

This study revealed a transient fall in PC numbers in the early post-ITx period but a permanent reduction in lysozyme intensity following ITx. Further research is needed to determine the potential clinical impact of PC impairment after ITx.

Sulforaphane Elicits Protective Effects in Intestinal Ischemia Reperfusion Injury

Intestinal ischemia reperfusion injury (IRI) is an inherent, unavoidable event of intestinal transplantation, contributing to allograft failure and rejection. The inflammatory state elicited by intestinal IRI is characterized by heightened leukocyte recruitment to the gut, which is amplified by a cross-talk with platelets at the endothelial border. Sulforaphane (SFN), a naturally occurring isothiocyanate, exhibits anti-inflammatory characteristics and has been shown to reduce platelet activation and block leukocyte adhesion. Thus, the aim of this study was to investigate protective effects and mechanism of action of SFN in a murine model of intestinal IRI. Intestinal IRI was induced by superior mesenteric artery occlusion for 30 min, followed by reperfusion for 2 h, 8 h or 24 h. To investigate cellular interactions, leukocytes were in vivo stained with rhodamine and platelets were harvested from donor animals and ex vivo stained. Mice (C57BL/6J) were divided into three groups: (1) control, (2) SFN treatment 24 h prior to reperfusion and (3) SFN treatment 24 h prior to platelet donation. Leukocyte and platelet recruitment was analyzed via intravital microscopy. Tissue was analyzed for morphological alterations in intestinal mucosa, barrier permeability, and leukocyte infiltration. Leukocyte rolling and adhesion was significantly reduced 2 h and 8 h after reperfusion. Mice receiving SFN treated platelets exhibited significantly decreased leukocyte and platelet recruitment. SFN showed protection for intestinal tissue with less damage observed in histopathological and ultrastructural evaluation. In summary, the data presented provide evidence for SFN as a potential therapeutic strategy against intestinal IRI.

Tissue Dependent Role of PTX3 During Ischemia-Reperfusion Injury

Reperfusion of an ischemic tissue is the treatment of choice for several diseases, including myocardial infarction and stroke. However, reperfusion of an ischemic tissue causes injury, known as Ischemia and Reperfusion Injury (IRI), that limits the benefit of blood flow restoration. IRI also occurs during solid organ transplantation. During IRI, there is activation of the innate immune system, especially neutrophils, which contributes to the degree of injury. It has been shown that PTX3 can regulate multiple aspects of innate immunity and tissue inflammation during sterile injury, as observed during IRI. In humans, levels of PTX3 increase in blood and elevated levels associate with extent of IRI. In mice, there is also enhanced expression of PTX3 in tissues and plasma after IRI. In general, absence of PTX3, as seen in PTX3-deficient mice, results in worse outcome after IRI. On the contrary, increased expression of PTX3, as seen in PTX3 transgenic mice and after PTX3 administration, is associated with better outcome after IRI. The exception is the gut where PTX3 seems to have a clear deleterious role. Here, we discuss mechanisms by which PTX3 contributes to IRI and the potential of taming this system for the treatment of injuries associated with reperfusion of solid organs.

Cold Storage Injury to Rat Small-bowel Transplants-Beneficial Effect of a Modified HTK Solution

BACKGROUND

The small bowel is prone to ischemic injury during transport before transplantation, an injury that endangers the recipient patient. The small-bowel mucosal microcirculation in particular appears to be highly sensitive to injury. Current preservation solutions such as histidine-tryptophan-ketoglutarate (HTK) solution provide some protection to the graft. However, these were developed decades ago and do not address several critical processes, such as hypoxia-induced membrane pores and free radical-mediated hypothermic injury.

METHODS

To protect the graft from cold ischemic injury, we implemented a modified HTK solution here, including glycine, alanine, and iron chelators in a heterotopic, syngeneic small-bowel transplantation model of the rat. The effects of the modified solution and its major components were compared against the conventional HTK solution using intravital microscopy in the early reperfusion period.

RESULTS

The amino acid glycine, added to HTK solution, slightly improved mucosal perfusion. Both, the modified base solution (without iron chelators) and iron chelators increased functional capillary density of the mucosa during the early reperfusion period. The complete modified solution (with glycine, alanine, and iron chelators) significantly increased the perfusion index, functional capillary density of the mucosa, and red blood cell velocity in the grafts after reperfusion in comparison with the grafts preserved with HTK.

CONCLUSIONS

The modified preservation solution improved the microcirculation of the transplants and needs detailed evaluation in further models of small-bowel transplantation.

Colonic anastomosis can be protected from ischemia reperfusion injury with intra-peritoneal Montelukast treatment

BACKGROUND

Ischemia reperfusion injury is unavoidable in the setting of transplantation and may lead to primary dysfunction of the transplanted organ. Similarly, intestinal ischemia reperfusion injury may have deleterious effects causing intestinal failure. Montelukast is a selective reversible cysteinyl-leukotriene type 1 receptor antagonist used in clinical practice for its anti-inflammatory effects. In this study, we investigated the effects of Montelukast on colon anastomosis performed after intestinal ischemia reperfusion injury.

METHODS

40 adult male Wistar Albino rats were used. All rats underwent intestinal ischemia reperfusion injury. Afterwards, the entire group was divided into two for either right or left colonic resection and anastomosis. Rats in the control groups were given intra-peritoneal normal saline for 1 week while the animals in the treatment groups were given intra-peritoneal Montelukast (10 mg/kg; 1 ml). All animals were subjected to ischemia reperfusion injury followed by either right or left colonic segmental resection and anastomosis in the first day of the experiment. On postoperative day 7 adhesion scoring, anastomotic bursting pressure, anastomotic tissue hydroxyproline content were assessed for all groups.

RESULTS

Significant differences were detected in adhesion scores between the treatment and control groups regardless of the colonic resection site. Anastomotic bursting pressures and hydroxyproline content of the anastomotic sites were significantly higher in the treatment groups when compared with the control groups. Anastomotic tissues treated with Montelukast showed more prominent vascularization in histopathological examinations.

CONCLUSION

Montelukast has a potential to attenuate the detrimental effects of ischemia reperfusion injury on intestinal anastomosis.

Activation of PD-1 Protects Intestinal Immune Defense Through IL-10/miR-155 Pathway After Intestinal Ischemia Reperfusion

BACKGROUND

To date, mechanisms of intestinal immunoglobulin (Ig) dysfunction following intestinal ischemia/reperfusion (I/R) remain unclear. Programmed death 1 (PD-1) is associated with immune responses of lymphocytes.

AIM

We aimed to verify the hypothesis that activation of PD-1 may improve intestinal immune dysfunction by regulating IL-10/miR-155 production after intestinal IR injury.

METHODS

Intestinal I/R injury was induced in mice by clamping the superior mesenteric artery for 1 h followed by 2-h reperfusion. PD-L1 fusion Ig, anti-interleukin (IL)-10 monoclonal antibody (mAb), and microRNA (miR)-155 agomir were administered. PD-1 expression, IL-10 mRNA, and protein expression in Peyer's patches (PP) CD4⁺ cells were measured. MiR-155 levels, tumor necrosis factor (TNF)-α and IL-1β concentration, and activation-induced cytidine deaminase (AID), a key enzyme for intestinal immune antibodies, in PP tissues were measured, respectively. Importantly, the production and cecal bacteria-binding capacity of IgA and IgM were detected.

RESULTS

Intestinal I/R led to decreased PD-1 expression, imbalanced production, and impaired bacteria-binding capacity of IgA and IgM. Activating PD-1 by PD-L1 Ig facilitated IL-10 synthesis, then decreased miR-155 levels, and subsequently promoted AID expression and reduced TNF-α, IL-1β concentration. Upregulation of AID improved the disruptions of intestinal immune barrier caused by IgA and IgM dysfunction. Anti-IL-10 mAb and miR-155 agomir abolished the protective effects of PD-L1 Ig on the intestinal immune defense.

CONCLUSION

Activation of PD-1 with PD-L1 Ig relieves intestinal immune defensive injury through IL-10/miR-155 pathway following intestinal I/R attack. PD-1, IL-10, and miR-155 may be potential targets for the damages of intestinal barrier and immunity.

Inhibition of ubiquitin-activating enzyme protects against organ injury after intestinal ischemia-reperfusion

Intestinal ischemia-reperfusion (I/R) occurs in various clinical settings, such as transplantation, acute mesenteric arterial occlusion, trauma, and shock. I/R injury causes severe systemic inflammation, leading to multiple organ dysfunction associated with high mortality. The ubiquitin proteasome pathway has been indicated in the regulation of inflammation, particularly through the NF-κB signaling pathway. PYR-41 is a small molecular compound that selectively inhibits ubiquitin-activating enzyme E1. A mouse model of intestinal I/R injury by clamping the superior mesenteric artery for 45 min was performed to evaluate the effect of PYR-41 treatment on organ injury and inflammation. PYR-41 was administered intravenously at the beginning of reperfusion. Blood and organ tissues were harvested at 4 h after reperfusion. PYR-41 treatment improved the morphological structure of gut and lung after I/R, as judged by hematoxylin and eosin staining. It also reduced the number of apoptotic terminal deoxynucleotidyl transferase dUTP nick end-labeling-positive cells and caspase-3 activity in the organs. PYR-41 treatment decreased the expression of proinflammatory cytokines IL-6 and IL-1β as well as chemokines keratinocyte chemoattractant and macrophage inflammatory protein-2 in the gut and lung, which leads to inhibition of neutrophils infiltrating into these organs. The serum levels of IL-6, aspartate aminotransferase, and lactate dehydrogenase were reduced by the treatment. The IκB degradation in the gut increased after I/R was inhibited by PYR-41 treatment. Thus, ubiquitination may be a potential therapeutic target for treating patients suffering from intestinal I/R. NEW & NOTEWORTHY Excessive inflammation contributes to organ injury from intestinal ischemia-reperfusion (I/R) in many clinical conditions. NF-κB signaling is very important in regulating inflammatory response. In an experimental model of gut I/R injury, we demonstrate that administration of a pharmacological inhibitor of ubiquitination process attenuates NF-κB activation, leading to reduction of inflammation, tissue damage, and apoptosis in the gut and lungs. Therefore, ubiquitination process may serve as a therapeutic target for treating patients with intestinal I/R injury.

Evaluation of small intestinal damage in a rat model of 6 Minutes cardiac arrest

BACKGROUND

Contribution of the small intestine to systemic inflammation after cardiac arrest (CA) is poorly understood. The objective was to evaluate whether an in vivo rat model of 6 min CA is suitable to initiate intestinal ischaemia-reperfusion-injury and to evaluate histomorphological changes and inflammatory processes in the small intestinal mucosa resp. in sera.

METHODS

Adult male Wistar rats were subjected to CA followed by cardio-pulmonary resuscitation. Proximal jejunum and serum was collected at 6 h, 24 h, 72 h and 7 d post return of spontaneous circulation (ROSC) and from a control group. The small intestine was evaluated histomorphologically. Cytokine concentrations were measured in jejunum lysates and sera.

RESULTS

Histomorphological evaluation revealed a significant increase in mucosal damage in the jejunum at all timepoints compared to controls (p < 0.0001). In jejunal tissues, concentrations of IL-1α, IL-1β, IL-10, and TNF-α showed significant peaks at 24 h and were 1.5- to 5.7-fold higher than concentrations at 6 h and in the controls (p < 0.05). In serum, a significant higher amount of cytokine was detected only for IL-1β at 24 h post-ROSC compared to controls (15.78 vs. 9.76 pg/ml).

CONCLUSION

CA resulted in mild small intestinal tissue damage but not in systemic inflammation. A rat model of 6 min CA is not capable to comprehensively mimic a post cardiac arrest syndrome (PCAS). Whether there is a vital influence of the intestine on the PCAS still remains unclear.

Protective effect of CDDO-imidazolide against intestinal ischemia/reperfusion injury in mice

Intestinal ischemia/reperfusion (I/R) is life-threatening and challenging in clinical practice. CDDO-imidazolide (CDDO-Im) is therapeutic in alleviating I/R injury. Nevertheless, there is a lack of investigation on the effects of CDDO-Im on intestinal I/R. Mice were randomly divided into four groups: (a) the sham group, (b) the CDDO-Im group, (c) the I/R group, and (d) the I/R + CDDO-Im group. Intestinal I/R was performed by clamping arteria mesenteric anterior for 45 min, followed by 24 h reperfusion. In addition, Kaplan–Meier method and the log-rank test were used to compare the survival rates among groups by observing for 24 h. Intestinal I/R in model group demonstrated severe injury of the intestinal mucosa, lung, kidney, and liver. The intestinal mucosal damage and intestinal barrier dysfunction were obviously attenuated in CDDO-Im-treated group compared with the model group. Also, preconditioning with CDDO-Im reduced pulmonary, hepatic and renal damage, and decreased oxidative stress (malondialdehyde (MDA), superoxide dismutase (SOD), and NO) and pro-inflammatory responses (tumor necrosis factor (TNF-α), interleukin 1β (IL-1β), and interleukin 6 (IL-6)) following I/R injury. Furthermore, we also observed that these protective properties of CDDO-Im were accomplished by the activation of nuclear factor E2-related factor 2 (Nrf2) signaling pathway and upregulation of its downstream antioxidant genes, including heme oxygenase (HO-1), NQO-1, and glutamate–cysteine ligase regulatory subunit (GCLM). Our data suggest that CDDO-Im exerts a beneficial effect on intestinal I/R-associated mucosal barrier dysfunction and distant organ injuries.

MicroRNA-378 protects against intestinal ischemia/reperfusion injury via a mechanism involving the inhibition of intestinal mucosal cell apoptosis

Intestinal ischemia/reperfusion (I/R) injury remains a major clinical event and contributes to high morbidity and mortality rates, but the underlying mechanisms remain elusive. Recent studies have demonstrated that microRNAs (miRNAs) have important roles in organ I/R injury, but the changes and potential roles of miRNAs in intestinal I/R-induced intestinal injury are unclear. This study was designed to analyze the miRNA expression profiles in intestinal mucosa after I/R injury and to explore the role of target miRNA during this process. Using miRNA microarray analysis, we found changes of 19 miRNAs from the expression profile of miRNAs in a mouse model of intestinal I/R and further verified them by RT-qPCR. Here, we report that miR-378 is one of the markedly decreased miRNAs and found the putative target mRNA that is linked to cell death after applying the TargetScan, miRanda, CLIP-Seq and miRDB prediction algorithms. Our results show that the overexpression of miR-378 significantly ameliorated intestinal tissue damage in wild-type and transgenic mice and oxygen glucose deprivation/reperfusion-challenged IEC-6 cell injury. Moreover, miR-378 overexpression reduced intestinal epithelial cell apoptosis in both in vivo and in vitro ischemic models and attenuated cleaved caspase-3 expression. Collectively, our results revealed that the suppression of caspase-3 activation by miRNA-378 overexpression may be involved in the protective effects of intestinal ischemic damage. MiRNA-378 may serve as a key regulator and therapeutic target in intestinal I/R injury.

Roles of amino acids in preventing and treating intestinal diseases: recent studies with pig models

Animal models are needed to study and understand a human complex disease. Because of their similarities in anatomy, structure, physiology, and pathophysiology, the pig has proven its usefulness in studying human gastrointestinal diseases, such as inflammatory bowel disease, ischemia/reperfusion injury, diarrhea, and cancer. To understand the pathogenesis of these diseases, a number of experimental models generated in pigs are available, for example, through surgical manipulation, chemical induction, microbial infection, and genetic engineering. Our interests have been using amino acids as therapeutics in pig and human disease models. Amino acids not only play an important role in protein biosynthesis, but also exert significant physiological effects in regulating immunity, anti-oxidation, redox regulation, energy metabolism, signal transduction, and animal behavior. Recent studies in pigs have shown that specific dietary amino acids can improve intestinal integrity and function under normal and pathological conditions that protect the host from different diseases. In this review, we summarize several pig models in intestinal diseases and how amino acids can be used as therapeutics in treating pig and human diseases.

Rutaecarpine alleviates renal ischemia reperfusion injury in rats by suppressing the JNK/p38 MAPK signaling pathway and interfering with the oxidative stress response

In the present study, the protective effect and the potential underlying mechanism of rutaecarpine (Ru) on renal ischemia reperfusion injury (IRI) in rats were investigated. A renal ischemia reperfusion mouse model was established. Ru at 30, 60 mg/kg administered intraperitoneally prior to reperfusion led to attenuated renal injury. The results demonstrated that Ru treatment significantly reduced the content of serum creatinine, urea nitrogen and neutrophil gelatinase‑associated lipocalin in rats with renal IRI. In addition, Ru treatment improved the degree of renal proximal tubular necrosis, decreased the content of inflammatory cytokines in reperfused renal tissue and increased serum superoxide dismutase levels to protect the kidney. The associated underlying mechanism may involve the inhibition of p38 kinase phosphorylation and c‑Jun N‑terminal kinase, anti‑lipid peroxidation, elimination of free radicals, and a reduction in the degree of apoptotic damage and oxidative stress injury induced by renal IRI. Therefore, Ru may be a suitable compound for the prevention and treatment of renal IRI.

Farnesoid X Receptor Activation Attenuates Intestinal Ischemia Reperfusion Injury in Rats

INTRODUCTION

The farnesoid X receptor (FXR) is abundantly expressed in the ileum, where it exerts an enteroprotective role as a key regulator of intestinal innate immunity and homeostasis, as shown in pre-clinical models of inflammatory bowel disease. Since intestinal ischemia reperfusion injury (IRI) is characterized by hyperpermeability, bacterial translocation and inflammation, we aimed to investigate, for the first time, if the FXR-agonist obeticholic acid (OCA) could attenuate intestinal ischemia reperfusion injury.

MATERIAL AND METHODS

In a validated rat model of intestinal IRI (laparotomy + temporary mesenteric artery clamping), 3 conditions were tested (n = 16/group): laparotomy only (sham group); ischemia 60min+ reperfusion 60min + vehicle pretreatment (IR group); ischemia 60min + reperfusion 60min + OCA pretreatment (IR+OCA group). Vehicle or OCA (INT-747, 2*30mg/kg) was administered by gavage 24h and 4h prior to IRI. The following end-points were analyzed: 7-day survival; biomarkers of enterocyte viability (L-lactate, I-FABP); histology (morphologic injury to villi/crypts and villus length); intestinal permeability (Ussing chamber); endotoxin translocation (Lipopolysaccharide assay); cytokines (IL-6, IL-1-β, TNFα, IFN-γ IL-10, IL-13); apoptosis (cleaved caspase-3); and autophagy (LC3, p62).

RESULTS

It was found that intestinal IRI was associated with high mortality (90%); loss of intestinal integrity (structurally and functionally); increased endotoxin translocation and pro-inflammatory cytokine production; and inhibition of autophagy. Conversely, OCA-pretreatment improved 7-day survival up to 50% which was associated with prevention of epithelial injury, preserved intestinal architecture and permeability. Additionally, FXR-agonism led to decreased pro-inflammatory cytokine release and alleviated autophagy inhibition.

CONCLUSION

Pretreatment with OCA, an FXR-agonist, improves survival in a rodent model of intestinal IRI, preserves the gut barrier function and suppresses inflammation. These results turn FXR into a promising target for various conditions associated with intestinal ischemia.

CD6 Receptor Regulates Intestinal Ischemia/Reperfusion-induced Injury by Modulating Natural IgM-producing B1a Cell Self-renewal

Intestinal ischemia/reperfusion (I/R) injury is a relatively common pathological condition that can lead to multi-organ failure and mortality. Regulatory mechanism for this disease is poorly understood, although it is established that circulating pathogenic natural IgM, which is primarily produced by B1a cells outside of the peritoneal cavity, are integrally involved. CD6 was originally identified as a marker for T cells and was later found to be present on some subsets of B cells in humans; however, whether CD6 plays any role in intestinal I/R-induced injury and, if so, the underlying mechanisms, remain unknown. Here we report that CD6^-/- mice were significantly protected from intestinal inflammation and mucosal damage compared with WT mice in a model of intestinal I/R-induced injury. Mechanistically, we found that CD6 was selectively expressed on B1 cells outside of the bone marrow and peritoneal cavity and that pathogenic natural IgM titers were reduced in the CD6^-/- mice in association with significantly decreased B1a cell population. Our results reveal an unexpected role of CD6 in the pathogenesis of intestinal IR-induced injury by regulating the self-renewal of B1a cells.

The Leuven Immunomodulatory Protocol Promotes T-Regulatory Cells and Substantially Prolongs Survival After First Intestinal Transplantation

Intestinal transplantation (ITx) remains challenged by frequent/severe rejections and immunosuppression-related complications (infections/malignancies/drug toxicity). We developed the Leuven Immunomodulatory Protocol (LIP) in the lab and translated it to the clinics. LIP consists of experimentally proven maneuvers, destined to promote T-regulatory (Tregs)-dependent graft-protective mechanisms: donor-specific blood transfusion (DSBT); avoiding high-dose steroids/calcineurin-inhibitors; and minimizing reperfusion injury and endotoxin translocation. LIP was tested in 13 consecutive ITx from deceased donors (2000-2014) (observational cohort study). Recipient age was 37 years (2.8-57 years). Five-year graft/patient survival was 92%. One patient died at 9 months due to aspergillosis, another at 12 years due to nonsteroidal anti-inflammatory drug-induced enteropathy. Early acute rejection (AR) developed in two (15%); late AR in three (23%); all were reversible. No chronic rejection (CR) occurred. No malignancies developed and estimated glomerular filtration rate remained stable post-Tx. At last follow-up (3.5 years [0.5-12.5 years]), no donor-specific antibodies were detected and 11 survivors were total parenteral nutrition free with a Karnofsky score >90% in 8 recipients (follow-up >1 years). A high frequency of circulating CD4⁺ CD45RA^- Foxp3^hi memory Tregs was found (1.8% [1.39-2.21]), comparable to tolerant kidney transplant (KTx) recipients and superior to stable immunosuppression (IS)-KTx, KTx with CR, and healthy volunteers. In this ITx cohort we show that DSBT in a low-inflammatory/pro-regulatory environment activates Tregs at levels similar to tolerant-KTx, without causing sensitization. LIP limits rejection under reduced IS and thereby prolongs long-term survival to an extent not previously attained after ITx.

The expanding role of the bile acid receptor farnesoid X in the intestine and its potential clinical implications

Knowledge about the role of farnesoid X receptor (FXR) in the intestine is rapidly expanding. In pre-clinical animal models of inflammatory bowel disease and bile duct ligation, FXR activation has proven to directly target the three pillars of intestinal homeostasis: intestinal permeability, inflammation and bacterial translocation. The protective role of FXR-ligands on this homeostasis has implications for many intestinal pathologies like inflammatory bowel disease, ischemia reperfusion injury, the metabolic syndrome, colon cancer and even diarrhea. In this review, we summarize the mechanisms by which FXR-activation exerts these protective effects and we discuss its potential clinical applications.

Murine Model of Intestinal Ischemia-reperfusion Injury

Intestinal ischemia is a life-threatening condition associated with a broad range of clinical conditions including atherosclerosis, thrombosis, hypotension, necrotizing enterocolitis, bowel transplantation, trauma and chronic inflammation. Intestinal ischemia-reperfusion (IR) injury is a consequence of acute mesenteric ischemia, caused by inadequate blood flow through the mesenteric vessels, resulting in intestinal damage. Reperfusion following ischemia can further exacerbate damage of the intestine. The mechanisms of IR injury are complex and poorly understood. Therefore, experimental small animal models are critical for understanding the pathophysiology of IR injury and the development of novel therapies. Here we describe a mouse model of acute intestinal IR injury that provides reproducible injury of the small intestine without mortality. This is achieved by inducing ischemia in the region of the distal ileum by temporally occluding the peripheral and terminal collateral branches of the superior mesenteric artery for 60 min using microvascular clips. Reperfusion for 1 hr, or 2 hr after injury results in reproducible injury of the intestine examined by histological analysis. Proper position of the microvascular clips is critical for the procedure. Therefore the video clip provides a detailed visual step-by-step description of this technique. This model of intestinal IR injury can be utilized to study the cellular and molecular mechanisms of injury and regeneration.

The Gastrointestinal Circulation: Physiology and Pathophysiology

The gastrointestinal (GI) circulation receives a large fraction of cardiac output and this increases following ingestion of a meal. While blood flow regulation is not the intense phenomenon noted in other vascular beds, the combined responses of blood flow, and capillary oxygen exchange help ensure a level of tissue oxygenation that is commensurate with organ metabolism and function. This is evidenced in the vascular responses of the stomach to increased acid production and in intestine during periods of enhanced nutrient absorption. Complimenting the metabolic vasoregulation is a strong myogenic response that contributes to basal vascular tone and to the responses elicited by changes in intravascular pressure. The GI circulation also contributes to a mucosal defense mechanism that protects against excessive damage to the epithelial lining following ingestion of toxins and/or noxious agents. Profound reductions in GI blood flow are evidenced in certain physiological (strenuous exercise) and pathological (hemorrhage) conditions, while some disease states (e.g., chronic portal hypertension) are associated with a hyperdynamic circulation. The sacrificial nature of GI blood flow is essential for ensuring adequate perfusion of vital organs during periods of whole body stress. The restoration of blood flow (reperfusion) to GI organs following ischemia elicits an exaggerated tissue injury response that reflects the potential of this organ system to generate reactive oxygen species and to mount an inflammatory response. Human and animal studies of inflammatory bowel disease have also revealed a contribution of the vasculature to the initiation and perpetuation of the tissue inflammation and associated injury response.

Pretreatment With Erythropoietin Attenuates Intestinal Ischemia Reperfusion Injury by Further Promoting PI3K/Akt Signaling Activation

BACKGROUND

Erythropoietin (EPO) has been shown to be beneficial in resolution of acute inflammation and intestinal ischemia/reperfusion (IR) injury is featured by the excessive immune response. The current research is designed to evaluate the effect and potential mechanisms of EPO on the intestinal IR injury. Therefore, the effect of EPO on intestinal IR injury was examined by the change of intestinal histology; the expression of pro-inflammatory cytokines tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), and interferon γ (IFN-γ); and the protein levels of EPOR, p-EPOR, p85, p-p85, Akt, p-Akt, IκΒ-α, p-p65, and p65.

MATERIALS AND METHODS

Thirty male Sprague-Dawley rats were randomly divided into three groups: sham group (sham), IR-saline group (IRI), and the IR-EPO group (EPO). Rats were treated with EPO (5000 U/kg) 1 hour before IR induction. A rat model of IR injury was established by ligating the superior mesenteric artery for 30 minutes, followed by reperfusion for 1 hour. Intestinal histology, pro-inflammatory cytokines, and mediators were assessed. The effect of EPO on PI3K/Akt/NF-κB signaling and EPOR were also measured.

RESULTS

EPO significantly decreased the pathologic changes of intestinal and reduced the elevation of pro-inflammatory cytokines TNF-α, IL-1β, and IFN-γ in intestinal and serum caused by IR which was associated with suppressing NF-κB activation by further promoting activation of PI3K/Akt signaling.

CONCLUSIONS

EPO ameliorated the acute intestinal injury caused by IR, which was associated with further activating PI3K/Akt signaling to suppress NF-κΒ-mediating inflammation. Our findings suggest that EPO could be useful for preventing IR-induced intestinal injury.

Gut epithelial inducible heat-shock proteins and their modulation by diet and the microbiota

The epidemic of metabolic diseases has raised questions about the interplay between the human diet and the gut and its microbiota. The gut has two vital roles: nutrient absorption and intestinal barrier function. Gut barrier defects are involved in many diseases. Excess energy intake disturbs the gut microbiota and favors body entry of microbial compounds that stimulate chronic metabolic inflammation. In this context, the natural defense mechanisms of gut epithelial cells and the potential to boost them nutritionally warrant further study. One such important defense system is the activation of inducible heat-shock proteins (iHSPs) which protect the gut epithelium against oxidative stress and inflammation. Importantly, various microbial components can induce the expression of iHSPs. This review examines gut epithelial iHSPs as the main targets of microbial signals and nutrients and presents data on diseases involving disturbances of gut epithelial iHSPs. In addition, a broad literature analysis of dietary modulation of gut epithelial iHSPs is provided. Future research aims should include the identification of gut microbes that can optimize gut-protective iHSPs and the evaluation of iHSP-mediated health benefits of nutrients and food components.

Intestinal transplantation: The anesthesia perspective

Intestinal transplantation is a complex and challenging surgery. It is very effective for treating intestinal failure, especially for those patients who cannot tolerate parenteral nutrition nor have extensive abdominal disease. Chronic parental nutrition can induce intestinal failure associated liver disease (IFALD). According to United Network for Organ Sharing (UNOS) data, children with intestinal failure affected by liver disease secondary to parenteral nutrition have the highest mortality on a waiting list when compared with all candidates for solid organ transplantation. Intestinal transplant grafts can be isolated or combined with the liver/duodenum/pancreas. Organ Procurement and Transplantation Network (OPTN) has defined intestinal donor criteria. Living donor intestinal transplant (LDIT) has the advantages of optimal timing, short ischemia time and good human leukocyte antigen matching contributing to lower postoperative complications in the recipient. Thoracic epidurals provide excellent analgesia for the donors, as well as recipients. Recipient management can be challenging. Thrombosis and obstruction of venous access maybe common due to prolonged parenteral nutrition and/or hypercoaguability. Thromboelastography (TEG) is helpful for managing intraoperative product therapy or thrombosis. Large fluid shifts and electrolyte disturbances may occur due to massive blood loss, dehydration, third spacing etc. Intestinal grafts are susceptible to warm and cold ischemia and ischemia-reperfusion injury (IRI). Post-reperfusion syndrome is common. Cardiac or pulmonary clots can be monitored with transesophageal echocardiography (TEE) and treated with recombinant tissue plasminogen activator. Vasopressors maybe used to ensure stable hemodynamics. Post-intestinal transplant patients may need anesthesia for procedures such as biopsies for surveillance of rejection, bronchoscopy, endoscopy, postoperative hemorrhage, anastomotic leaks, thrombosis of grafts etc. Asepsis, drug interactions between anesthetic and immunosuppressive agents and venous access are some of the anesthetic considerations for this group.

The protective role of montelukast against intestinal ischemia-reperfusion injury in rats

Several drugs are effective in attenuating intestinal ischemia-reperfusion injury (IRI); however little is known about the effect of montelukast. Fifty rats were randomly assigned to 3 groups: model group (operation with clamping), sham group (operation without clamping), and study group (operation with clamping and 0.2, 2 and 20 mg/kg montelukast pretreatment). Intestinal ischemia-reperfusion was performed by occlusion (clamping) of the arteria mesenterica anterior for 45 min, followed by 24 h reperfusion. Intestinal IRI in the model group led to severe damage of the intestinal mucosa, liver and kidney. The Chiu scores of the intestines from the study group (2 and 20 mg/kg) were lower than that of the model group. Intestinal IRI induced a marked increase in CysLTR1, Caspase-8 and -9 expression in intestine, liver and kidney, which were markedly reduced by preconditioning with 2 mg/kg montelukast. Preconditioning with 2 g/kg montelukast significantly attenuated hepatic tissue injury and kidney damage, and decreased plasma interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) levels in plasma after intestinal IRI. In conclusion, preconditioning with montelukast could attenuate intestinal IRI and the subsequent systemic inflammatory response in rats.

Intestinal preservation for transplantation: current status and alternatives for the future

PURPOSE OF REVIEW

Among transplantable abdominal organs the intestine has the shortest cold storage time, raising significant medical and logistical challenges. Herein, established and innovative, emerging concepts in intestinal preservation are summarized.

RECENT FINDINGS

The method of intestinal preservation using an in-situ vascular perfusion followed by static storage remained unchanged for almost 30 years, despite suboptimal results. Advanced preservation injury occurs within 12 h and is little influenced by the type of solution used. Recent reports indicate that several customized luminal solutions containing various amino acids and macromolecules may delay its development. In addition, gaseous interventions in the storage solutions or in the lumen seem promising and easily applicable tools that may further reduce the ischemia-reperfusion injury and safely prolong the preservation time. Rodent models are not entirely suitable for direct translation to clinical practice as the development of preservation injury is faster than in humans.

SUMMARY

The limitations of intestinal preservation originate in the methods (vascular perfusion and static storage) rather than in the solutions used. Several additional strategies promise to prolong the cold storage and reduce its impact on the intestinal graft and deserve further exploration in large animals and clinical studies.

Somatostatin Improved B Cells Mature in Macaques during Intestinal Ischemia-Reperfusion

AIMS

Intestinal ischemia-reperfusion has been taken as an important pathophysiological process for multiple organ dysfunctions in critical patients. Recent studies reported that dual expression programs of the B cells receptors and Toll-like receptors on B-lymphocytes permit these ubiquitous cells to integrate both adaptive and innate immune functions. Our previous studies found that somatostatin inhibited the intestinal inflammatory injury after ischemia-reperfusion in macaques. However, the changes of B cells and the effects of somatostatin on B cells after intestinal ischemia-reperfusion were unclear.

METHODS

15 macaques were divided into control, intestinal ischemia-reperfusion and somatostatin pretreatment groups. Immunohistochemistry was performed to identify the distributions of adaptive and innate immunity markers in the iliac mucosa. Hmy2.cir B lymphoblastoid cell line was cultured in vitro study. Enzyme-linked immunosorbent assay was used to measure IgM, IL-6 and SIgA, and the expressions of B cells transcription factors, PAX-5 and BLIMP-1, were detected by Western blotting.

RESULTS

B2 lymphocytes in normal Peyer's patches were presented the phenotype of PAX-5+CD20+CD5-. Ischemia-reperfusion increased the numbers and sizes of Peyer's patches but with PAX-5+CD20-CD5- B cells, an unmatured set of B cells. Somatostatin partly kept the phenotype of mature B cells during ischemia-reperfusion. The innate immunity of B cells was inhibited whereas the adaptive immunity was increased in the intestinal mucosa in the somatostatin group, compared to the ischemia-reperfusion group. In vitro, somatostatin significantly inhibited IL-6 and promoted IgM by increasing the expression of both PAX-5 and BLIMP-1 in the proinflammatory condition.

CONCLUSION

Intestinal ischemia-reperfusion resulted in the proliferation of unmatured B cells which were involved in the augmentation of innate immunity. Somatostatin, with a bi-directional regulation function on innate as well as adaptive immunity of B cells, greatly improved B cells mature in macaques during ischemia-reperfusion. Preventive supplements of somatostatin may greatly limit intestinal injury and bacterial translocation during ischemia-reperfusion.

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.

Porcine models of digestive disease: the future of large animal translational research

There is increasing interest in nonrodent translational models for the study of human disease. The pig, in particular, serves as a useful animal model for the study of pathophysiological conditions relevant to the human intestine. This review assesses currently used porcine models of gastrointestinal physiology and disease and provides a rationale for the use of these models for future translational studies. The pig has proven its utility for the study of fundamental disease conditions such as ischemia-reperfusion injury, stress-induced intestinal dysfunction, and short bowel syndrome. Pigs have also shown great promise for the study of intestinal barrier function, surgical tissue manipulation and intervention, as well as biomaterial implantation and tissue transplantation. Advantages of pig models highlighted by these studies include the physiological similarity to human intestine and mechanisms of human disease. Emerging future directions for porcine models of human disease include the fields of transgenics and stem cell biology, with exciting implications for regenerative medicine.

Protection of rat intestinal epithelial cells from ischemia/reperfusion injury by (D-Ala2, D-Leu5)-enkephalin through inhibition of the MKK7-JNK signaling pathway

Previous studies have demonstrated that (D‑Ala2, D‑Leu5)‑enkephalin (DADLE) protects rats from hepatic ischemia/reperfusion (I/R) injury. In the present study, DADLE was also observed to alleviate IR‑induced intestinal epithelial cell injury in rats by inhibiting mitogen‑activated protein kinase kinase 7 (MKK7)‑c‑Jun N‑terminal kinase (JNK) pathway signaling. To investigate the protective effect of DADLE on hypoxia/reoxygenation injury in rat intestinal epithelial cells, rat intestinal epithelial cells were treated with different concentrations of DADLE, following which the cell survival rate was determined using a tetrazolium (MTT) colorimetric assay, and apoptosis was determined using flow cytometry. To confirm whether the protective effect of DADLE was due to its effect on MKK7‑JNK signaling, the phosphorylation levels of MKK7 and JNK were analyzed using western blot analysis following treatment with different concentrations of DADLE. The results demonstrated that, following treatment with DADLE, the survival rate of the rat intestinal cells subjected to I/R‑induced injury increased significantly and the apoptotic rate decreased in a concentration‑dependent manner. In addition, the levels of phosphorylated MKK7 and JNK decreased in a concentration‑dependent manner following treatment with DADLE. Silencing the gene expression of MKK7 using small interfering RNA prior to DADLE treatment resulted in a reduction in the protective effects of DADLE on the rat intestinal epithelial cells subjected to I/R injury. Collectively, the results of the present study demonstrated that the protective effects of DADLE in I/R injury in rat intestinal cells occurred through inhibition of the MKK7‑JNK pathway.

Luminal injection of hydrogen-rich solution attenuates intestinal ischemia-reperfusion injury in rats

BACKGROUND

Luminal preservation of the intestine is an attractive method to locally mitigate preservation injury and ischemic-reperfusion injury in small bowel transplantation (SBT) because this method has a potential to maintain the intestinal graft integrity. Hydrogen is noted as an antioxidant material by reducing hydroxyl radicals. We hypothesized that hydrogen-containing solution can be an optimum material for luminal preservation method in SBT.

METHODS

Ischemic reperfusion was induced in Lewis rats by occlusion of the supramesenteric artery and vein for 90 min. Experimental protocols were divided into four groups: sham operation group, no luminal injection (control) group, luminal injection of 5% glucose saline (GS) solution group, and luminal injection of hydrogen-rich GS (HRGS) group. Two milliliters of experimental solution was locally injected into the lumen of the intestine before declamping of vessels. Oxidative stress markers, proinflammatory cytokines, apoptosis in the crypt cells, and morphologic changes of the intestine were assessed.

RESULTS

The production of malondialdehyde and 8-hydroxydeoxyguanosine, as oxidative stress markers, were markedly suppressed in HRGS group. The level of proinflammatory cytokines, such as inducible nitric oxide synthase and interleukin-6, was significantly inhibited in HRGS group. Crypt apoptosis was also significantly suppressed in HRGS group. Histopathologically, integrity of villus in intestine was maintained in HRGS group in comparison to the other groups.

CONCLUSION

Luminal injection of hydrogen-rich solution can reduce oxidative stress and consequently ameliorate ischemic-reperfusion injury. Hydrogen-containing solution can be a novel and promising luminal preservation material in SBT.

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

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