Acute necrosis of the intestinal mucosa with high serum levels of diamine oxidase

Analyzing the metabolic fate of oral administration drugs: A review and state-of-the-art roadmap

The key orally delivered drug metabolism processes are reviewed to aid the assessment of the current in vivo/vitro experimental systems applicability for evaluating drug metabolism and the interaction potential. Orally administration is the most commonly used state-of-the-art road for drug delivery due to its ease of administration, high patient compliance and cost-effectiveness. Roles of gut metabolic enzymes and microbiota in drug metabolism and absorption suggest that the gut is an important site for drug metabolism, while the liver has long been recognized as the principal organ responsible for drugs or other substances metabolism. In this contribution, we explore various experimental models from their development to the application for studying oral drugs metabolism of and summarized advantages and disadvantages. Undoubtedly, understanding the possible metabolic mechanism of drugs in vivo and evaluating the procedure with relevant models is of great significance for screening potential clinical drugs. With the increasing popularity and prevalence of orally delivered drugs, sophisticated experimental models with higher predictive capacity for the metabolism of oral drugs used in current preclinical studies will be needed. Collectively, the review seeks to provide a comprehensive roadmap for researchers in related fields.

The Probiotic Lactobacillus paracasei Ameliorates Diarrhea Cause by Escherichia coli O8via Gut Microbiota Modulation1

Introduction

Koumiss is a fermented horse milk food containing abundant probiotics. Lactobacillus paracasei is a bacterial strain isolated from koumiss that helps regulate the intestinal microbiota. One of the major cause of diarrhea is an imbalance of the intestinal flora. The aim of this study was to investigate whether Lactobacillus paracasei can ameliorate E. coli-induced diarrhea and modulate the gut microbiota.

Methods

Mouse models of diarrhea were established via intragastric E. coli O₈ administration. We then attempted to prevent or treat diarrhea in the mice via intragastric administration of a 3 × 10⁸ CFU/mL L. paracasei cell suspension. The severity of diarrhea was evaluated based on the body weight, diarrhea rate, and index, fecal diameter, ileum injury, hematoxylin-eosin (H&E) staining, and diamine oxidase (DAO) and zonulin expression. Expression of the tight junction (TJ) proteins claudin-1, occludin, and zona occludens (ZO-)1 were detected by immunohistochemistry (IHC). Gastrointestinal mRNA expression levels of interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α were detected by real-time polymerase chain reaction (RT-PCR). The microbial composition was analyzed by 16s rRNA sequencing.

Results

The L. paracasei demonstrated excellent therapeutic efficacy against diarrhea. It elevated the TJ protein levels and downregulated proinflammatory cytokines IL-6, IL-1β, TNF-α, and p65, myosin light chain 2 (MLC2), myosin light chain kinase (MLCK). Moreover L. paracasei increased those bacteria, which can product short-chain fatty acid (SCFA) such Alistipes, Odoribacter, Roseburia, and Oscillibacter.

Conclusion

L. paracasei ameliorated diarrhea by inhibiting activation of the nuclear factor kappa B (NF-κB)-MLCK pathway and increasing the abundance of gut microbiota that produce SCFA.

Cell death in the gut epithelium and implications for chronic inflammation

The intestinal epithelium has one of the highest rates of cellular turnover in a process that is tightly regulated. As the transit-amplifying progenitors of the intestinal epithelium generate ~300 cells per crypt every day, regulated cell death and sloughing at the apical surface keeps the overall cell number in check. An aberrant increase in the rate of intestinal epithelial cell (IEC) death underlies instances of extensive epithelial erosion, which is characteristic of several intestinal diseases such as inflammatory bowel disease and infectious colitis. Emerging evidence points to a crucial role of necroptosis, autophagy and pyroptosis as important modes of programmed cell death in the intestine in addition to apoptosis. The mode of cell death affects tissue restitution responses and ultimately the long-term risks of intestinal fibrosis and colorectal cancer. A vicious cycle of intestinal barrier breach, misregulated cell death and subsequent inflammation is at the heart of chronic inflammatory and infectious gastrointestinal diseases. This Review discusses the underlying molecular and cellular underpinnings that control programmed cell death in IECs, which emerge during intestinal diseases. Translational aspects of cell death modulation for the development of novel therapeutic alternatives for inflammatory bowel diseases and colorectal cancer are also discussed.

Relationship between postnatal days, serum Cu concentration and plasma diamine oxidase activity in Japanese Black calves

The aim of study was to investigate the relationships among serum diamine oxidase (DAO) activity, postnatal days and the plasma copper (Cu) concentration, using calves with or without diarrhea. In healthy calves, the serum DAO activity was significantly higher at 2 postnatal days than at ≥7 postnatal days, and no significant changes were observed after 7 postnatal days. In addition, no significant correlation was found between serum DAO activity and plasma Cu concentration at all postnatal days in healthy calves. Although, the serum DAO activity in 14 diarrheic calves (66.78 ± 14.37 IU/ml) was lower than that in 19 healthy calves (170.33 ± 97.83 IU/m, P<0.01), plasma Cu concentrations in all calves remained within the normal range.

Citrulline, A Potential Biomarker of Radiation-Induced Small Intestine Damage

Radiation damage assessment of the small intestine is important in nuclear accidents or routine radiotherapy of abdominal tumors. This article reviews the clinical symptoms and molecular mechanisms of radiation-induced small intestinal damage and summarizes recent research on biomarkers of such damage. Citrulline is the most promising biomarker for the evaluation of radiation-induced small intestinal damage caused by radiotherapy and nuclear accidents. This article also summarizes the factors influencing plasma citrulline measurement investigated in the latest research, as well as new findings on the concentration of citrulline in saliva and urine after different types of radiation.

Pyruvate Protects Against Intestinal Injury by Inhibiting the JAK/STAT Signaling Pathway in Rats With Hemorrhagic Shock

BACKGROUND

This study aimed to investigate the role of Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway in protection by peritoneal resuscitation (PR) using pyruvate-peritoneal dialysis solution (PY-PDS) against intestinal injury from hemorrhagic shock (HS) in rats.

MATERIALS AND METHODS

Sixty-four rats were assigned to eight groups: group SHAM; group intravenous resuscitation (VR); groups NS, LA, and PY in which the rats were subjected to HS and PR with normal saline (NS), lactate-peritoneal dialysis solution (LA-PDS), and PY-PDS, respectively, combined with VR; and groups DMSO, RPM, and AG490 in which the rats were subjected to HS and VR with pretreatment of dimethyl sulfoxide (DMSO), rapamycin (RPM), and tyrphostin B42 (AG490).

RESULTS

At 2 h after HS and resuscitation, the levels of diamine oxidase, 15-F_2t-isoprostane, thromboxane B₂, and endothelin-1, in the blood and the intestinal mucosal apoptotic index and caspase-3 were lower in groups PY, RPM, and AG490 than in groups VR, NS, LA, and DMSO. Group PY showed lower levels of malondialdehyde and myeloperoxidase and a higher level of superoxide dismutase than groups VR, NS, and LA. Phosphorylated JAK2 and phosphorylated STAT3 levels were lower in groups PY, RPM, AG490, and LA than in groups VR, NS, and DMSO.

CONCLUSIONS

The protection mechanism of PR with PY-PDS combined with VR was related to the inhibition of the JAK/STAT signaling pathway during HS and resuscitation. The process might include suppression of oxidative stress, reduction of neutrophil infiltration, regulation of microcirculation, and inhibition of apoptosis.

Fluoropyrimidine-induced intestinal mucosal injury is associated with the severity of chemotherapy-related diarrhea

BACKGROUND AND AIM

Although the fluoropyrimidines are effective chemotherapeutic agents for malignant gastrointestinal tumors, they sometimes cause enteritis with diarrhea. Severe treatment-related diarrhea may result in chemotherapy discontinuation. We investigated the relationship between diarrhea severity and fluoropyrimidine-induced small intestinal mucosal injury.

METHODS

We performed small bowel capsule endoscopy in patients undergoing chemotherapy including fluoropyrimidine for a malignant tumor between May 2017 and June 2018 and analyzed the relationship between the endoscopic findings and diarrhea severity. We also performed a cross-sectional analysis of patient factors and routes of chemotherapy to identify risk factors of fluoropyrimidine-induced small intestinal injury.

RESULTS

Small bowel capsule endoscopy was successfully completed in 16 eligible patients. The diarrhea grade (per the Common Terminology Criteria for Adverse Events, version 4.0) was significantly correlated with the percentage of patients with a small intestinal mucosal break (grade 0, 16.7%; grade 1, 57.1%; grade 2, 100%; p = .016, Cochran-Armitage trend test). Compared to patients receiving intravenous therapy, those receiving an orally administered fluoropyrimidine had a significantly greater number of small intestinal mucosal breaks (median number of breaks [range]; intravenous 5-fluorouracil, 0 [0-13]; oral fluoropyrimidine, 6.5 [1-20]; p = .0162, Mann-Whitney U test).

CONCLUSIONS

Many patients with diarrhea caused by chemotherapy including fluoropyrimidine had small intestinal mucosal breaks. Additionally, small intestinal mucosal breaks were more severe in patients receiving a regimen of oral treatment than in those receiving a regimen of intravenous therapy. These outcomes have important implications for investigations of new strategies for preventing anti-cancer drug-induced diarrhea.

Dexmedetomidine improves gastrointestinal motility after laparoscopic resection of colorectal cancer: A randomized clinical trial

BACKGROUND

To investigate the effects of intraoperative application of dexmedetomidine (Dex) on early gastrointestinal motility after laparoscopic resection of colorectal cancer.

METHODS

In this prospective, randomized double-blind investigation, 60 patients who underwent laparoscopic resection of colorectal cancer were randomly allocated to receive Dex (DEX group, n = 30) or saline (CON group, n = 30). In the DEX group, Dex was loaded (1 μg/kg) before anesthesia induction and was infused (0.3 μg/kg/h) during surgery. Time to postoperative first flatus (FFL) and first feces (FFE), and time to regular diet were recorded. Serum diamine oxidase (DAO) activity and intestinal fatty acid-binding protein (I-FABP) were detected.

RESULTS

Both the time to the FFL (44.41 ± 4.51 hours vs 61.03 ± 5.16 hours, P = 0.02) and the time to the FFE (60.67 ± 4.94 hours vs 82.50 ± 6.88 hours, P = 0.014) were significantly shorter in the DEX group than the CON group. Furthermore, the time to regular diet of the DEX group was shorter than that of the CON group (76.15 ± 4.11 hours vs 91.50 ± 5.70 hours, P = 0.037). Both DAO and I-FABP increased significantly from beginning of surgery to postoperative day 1 in the CON group (2.49 ± 0.41 ng/mL vs 4.48 ± 0.94 ng/mL for DAO, P = 0.028, 1.32 ± 0.09 ng/mL vs 2.17 ± 0.12 ng/mL for I-FABP, P = 0.045, respectively), whereas no significant change was observed in the DEX group. Furthermore, patients in the DEX group had stable hemodynamics and shorter hospital stay than those in the CON group.

CONCLUSION

Dex administration intraoperatively benefits recovery of gastrointestinal motility function after laparoscopic resection of colorectal cancer with stable hemodynamics during surgery though further studies are needed to explore the mechanisms of Dex on gastrointestinal motility.

Protective effects of Raphanus sativus extract on intestinal mucosal peroxide damage in rats with incomplete intestinal obstruction

AIM: To investigate the protective effects of Raphanus sativus extract (Rex) on intestinal mucosal peroxide damage in a rat model of incomplete intestinal obstruction (IIO).

METHODS: Sprague-Dawley rats were randomly divided into a normal group (group A, n = 14), a sham-operation group (group B, n = 14), an intestinal obstruction group (group C, n = 20) and an intestinal obstruction + Rex group (group D, n = 20). IIO was induced by surrounding the terminal ileum with a sterile pipe. After that, the animals in group D was given Rex (100 mg/kg body weight), while the rest groups were given equal volumes of saline. On days 5 and 7, the abdominal cavity was opened to collect 3 mL blood from the abdominal aorta for determining superoxide dismutase (SOD) and malondialdehyde (MDA) levels. Meanwhile, two segments of the small intestine were taken 4 cm above the obstructive for hematoxylin-eosin (HE) staining and for measuring diamine oxidase (DAO), respectively.

RESULTS: At each corresponding time point, compared with group B, SOD and DAO levels were significantly lower (P < 0.05 or P < 0.01) and MDA content and mucosal injury score were significantly higher (P < 0.01) in group C. Swelling, necrosis and shedding were visible in epithelial cells. Meanwhile, the submucosa, muscular and serosa had apparent congestion with infiltration of inflammatory cells. Compared with group C, treatment with Rex in group D significantly increased SOD activity (P < 0.05 or P < 0.01) and DAO content (P < 0.01), while MDA content and mucosal injury score were significantly decreased (P < 0.01). The damage of the ileum mucosa, infiltration of inflammatory cells and vascular responses in the ileum were significantly alleviated after treatment with Rex.

CONCLUSION: Rex can elevate serum SOD activity, reduce MDA content and increase tissue DAO levels in rats with IIO to protect the intestinal mucosal from being damaged by oxidative stress reaction effectively.

Protective effect of allopurinol against intestinal ischemia-reperfusion injury

AIM: To investigate the protective effect of allopurinol against intestinal ischemia-reperfusion injury.

METHODS: Thirty male SD rats were randomly divided into a sham operation group, an allopurinol group and a saline group, with 10 rats in each group. A rat model of intestinal ischemia was established. Serum content of diamine oxidase (DAO), tissue level of malondialdehyde (MDA) and activity of xanthine oxidase (XO) were detected by colorimetry.

RESULTS: Ileal mucosa Chiu's score differed significantly among the three groups (P < 0.05), and the score in the allopurinol group was significantly lower that in the saline group (P < 0.05), but significantly higher than that in the sham operation group (P < 0.05). Serum DAO levels differed significantly among the three groups (P < 0.05), and serum DAO levels in the allopurinol group was significantly higher than that in the sham operation group (P < 0.05), but significantly lower than that in the saline group (P < 0.05). MDA contents in the ileum differed significantly among the three groups (P < 0.05), and ileal tissue MDA in the allopurinol group was significantly higher than that in the sham operation group (P < 0.05), but significantly lower than that in the saline group (P < 0.05). XO activity differed significantly among the three groups (P < 0.05), and XO activity in the allopurinol group was significantly higher than that in the sham operation group (P < 0.05), but significantly lower than that in the saline group (P < 0.05).

CONCLUSION: Allopurinol has a protective effect against intestinal ischemia-reperfusion injury possibly through its antioxidant and free radical scavenging activities.

Serum diamine oxidase as a hemorrhagic shock biomarker in a rabbit model

Background

In prolonged hemorrhagic shock, reductions in intestinal mucosal blood perfusion lead to mucosal barrier damage and systemic inflammation. Gastrointestinal failure in critically ill patients has a poor prognosis, so early assessment of mucosal barrier injury in shock patients is clinically relevant. Unfortunately, there is no serum marker that can accurately assess intestinal ischemia-reperfusion injury.

Objective

The aim of this study was to assess if serum diamine oxidase levels can reflect intestinal mucosal injury subsequent to prolonged hemorrhagic shock.

Methods

Thirty New Zealand white rabbits were divided into three groups: a control group, a medium blood pressure (BP) group (exsanguinated to a shock BP of 50 to 41 mm Hg), and a low BP group (exsanguinated to a shock blood pressure of 40 to 31 mm Hg), in which the shock BP was sustained for 180 min prior to fluid resuscitation.

Results

The severity of hemorrhagic shock in the low BP group was significantly greater than that of the medium BP group according to the post-resuscitation BP, serum tumor necrosis factor (TNF)-α, and arterial lactate. Intestinal damage was significantly more severe in the low BP group according to Chiu’s scoring, claudin-1, intercellular adhesion molecule (ICAM)-1, and myeloperoxidase expression. Serum diamine oxidase was significantly increased in the low BP group compared to the medium BP and control groups and was negatively correlated with shock BP.

Conclusion

Serum diamine oxidase can be used as a serological marker in evaluating intestinal injury and shows promise as an indicator of hemorrhagic shock severity.

Changes in intestinal microflora in rats with acute respiratory distress syndrome

AIM

To implement high-throughput 16S rDNA sequencing to study microbial diversity in the fecal matter of rats with acute lung injury/acute respiratory distress syndrome (ALI/ARDS).

METHODS

Intratracheal instillation of lipopolysaccharide was used to induce ALI, and the pathological changes in the lungs and intestines were observed. D-lactate levels and diamine oxidase (DAO) activities were determined by enzymatic spectrophotometry. The fragments encompassing V4 16S rDNA hypervariable regions were PCR amplified from fecal samples, and the PCR products of V4 were sequenced by Illumina MiSeq.

RESULTS

Increased D-lactate levels and DAO activities were observed in the model group (P < 0.01). Sequencing results revealed the presence of 3780 and 4142 species in the control and model groups, respectively. The percentage of shared species was 18.8419%. Compared with the control group, the model group had a higher diversity index and a lower number of species of Fusobacteria (at the phylum level), Helicobacter and Roseburia (at the genus level) (P < 0.01). Differences in species diversity, structure, distribution and composition were found between the control group and early ARDS group.

CONCLUSION

The detection of specific bacteria allows early detection and diagnosis of ALI/ARDS.

Effects of penehyclidine hydrochloride on rat intestinal barrier function during cardiopulmonary bypass

AIM: To test the ability of penehyclidine hydrochloride (PHC) to attenuate intestinal injury in a rat cardiopulmonary bypass (CPB) model.

METHODS: Male Sprague-Dawley rats were randomly divided into six groups (eight each): sham-operated control; sham-operated low-dose PHC control (0.6 mg/kg); sham-operated high-dose PHC control (2.0 mg/kg); CPB vehicle control; CPB low-dose PHC (0.6 mg/kg); and CPB high-dose PHC (2.0 mg/kg). Blood samples were collected from the femoral artery 2 h after CPB for determination of plasma diamine oxidase (DAO), D-lactate and endotoxin levels. Spleen, liver, mesenteric lymph nodes and lung were removed for biochemical analyses. Intestinal tissue ultrastructure was examined by electron microscopy.

RESULTS: In the sham-operated groups, high- and low-dose-PHC had no significant impact on the levels of DAO, D-lactate and endotoxin, or the incidence of intestinal bacterial translocation (BT). Serum levels of DAO, D-lactate, endotoxin and the incidence of intestinal BT were significantly increased in the surgical groups, compared with the sham-operated groups (0.543 ± 0.061, 5.697 ± 0.272, 14.75 ± 2.46, and 0/40 vs 1.038 ± 0.252, 9.377 ± 0.769, 60.37 ± 5.63, and 30/40, respectively, all P < 0.05). PHC alleviated the biochemical and histopathological changes in a dose-dependent manner. Serum levels of DAO, D-lactate, and endotoxin and the incidence of intestinal BT in the high-dose PHC group were significantly lower than in the low-dose PHC group (0.637 ± 0.064, 6.972 ± 0.349, 29.64 ± 5.49, and 14/40 vs 0.998 ± 0.062, 7.835 ± 0.330, 38.56 ± 4.28, and 6/40, respectively, all P < 0.05).

CONCLUSION: PHC protects the structure and function of the intestinal mucosa from injury after CPB in rats.

Effects of simulated weightlessness on tight junction protein occludin and Zonula Occluden-1 expression levels in the intestinal mucosa of rats

This study investigated the tight junction (TJ) protein expression of the intestinal mucosa in a rat tail-suspension model under simulated weightlessness. Twenty-four Wistar rats were randomly divided into three groups: CON group (n=8), control; SUS-14 d group (n=8), tail-suspension for 14 days; SUS-21 d group (n=8), tail-suspension for 21 days. Occludin and Zonula Occluden-1 (ZO-1) expression levels were determined by immunohistochemical analysis and mRNA fluorescent quantitative PCR. Plasma levels of diamine oxidase (DAO) and d-lactate were determined using enzymatic spectrophotometry. Immunohistochemical results for occludin and ZO-1 showed disruption of the TJs in the intestinal mucosa in SUS-14 d and SUS-21 d groups. The expression levels of occludin and ZO-1 in SUS-21 d group were lower than those in SUS-14 d group, and significantly lower than those in CON group (Occldin: 0.86±0.02 vs 1.01±0.03 vs 1.63±0.03 and ZO-1: 0.82±0.01 vs 1.00±0.02 vs 1.55±0.01, P<0.01). Moreover, the levels of plasma DAO and d-lactate in SUS-21 d group were higher than those in SUS-14 d group, and significantly higher than those in CON group (DAO: 27.58±0.49 vs 20.74±0.49 vs 12.94±0.21 and d-lactate: 37.86±0.74 vs 28.26±1.01 vs 17.76±0.91, P<0.01). There were significant negative correlations between occludin or ZO-1 expression levels and DAO (r (2)=0.9014, r (2)=0.9355, P<0.01) or d-lactate levels (r (2)=0.8989, r (2)=0.9331, P<0.01). Occludin and Zo-1 were reduced in intestinal mucosa both in mRNA and protein levels in the rat tail-suspension model. The significant negative correlations between expression levels of TJs and plasma levels of DAO or d-lactate support the hypothesis that intestinal permeability is increased due to a decrease in TJ protein expression during tail-suspension from 14 days to 21 days.

Histidine decarboxylase is identified as a potential biomarker of intestinal mucosal injury in patients with acute intestinal obstruction

Various biomarkers currently used for the diagnosis of intestinal mucosal injury (IMI) in patients with acute intestinal obstruction have low sensitivity and specificity. In the present study, IMI, as indicated by the impaired expression of tight junction proteins, including zonula occludens-1, occludin and claudin-1, and inflammation were determined in colonic tissues of patients with 45 strangulated intestinal obstruction (STR-IO) and the adjacent "normal" colonic tissues of 35 patients with colon cancers by quantitative real-time polymerase chain reaction (QRT-PCR), Western blotting, immunohistochemistry and histological examination, respectively. Then, two-dimensional fluorescent difference gel electrophoresis coupled with linear trap quadrupole mass spectrometry was used to screen for potential biomarkers of IMI in the serum samples of 10 STR-IO, 10 simple intestinal obstruction (SIM-IO) and 10 normal healthy controls. A total of 35 protein spots were differentially expressed among the serum samples, and six of the proteins were identified as potential biomarkers. Among the six proteins, histidine decarboxylase (HDC) and ceruloplasmin (CP) were elevated significantly in patients with STR-IO, compared with patients with SIM-IO and healthy controls. Thus, HDC and CP were further validated by QRT-PCR, Western blotting, immunohistochemistry and enzyme-linked immunosorbent assay, respectively, in colonic tissues, serum and urine samples. Finally, the receiver operating characteristic curves were used to show the area under the curves of HDC, CP and several established biomarkers, followed by the determination of the appropriate cutoff values and their sensitivities and specificities. It was shown that for serum and urine, HDC levels achieved sensitivities and specificities compatible to or even greater than those of established biomarkers for the diagnosis of IMI in patients with acute intestinal obstruction, although further validation in a larger cohort is required.

Effects of cardiopulmonary bypass on tight junction protein expressions in intestinal mucosa of rats

AIM: To investigate the tight junction protein expressions of intestinal mucosa in an experimental model of cardiopulmonary bypass (CPB) in rats.

METHODS: Thirty anesthetized rats were randomly divided into two groups: Group S (n = 10) served as sham operation and group C (n = 20) served as CPB which underwent CPB for 1 h. Expression of occludin and zonula occludens-1 (ZO-1) were determined by Western blotting and immunocytochemistry, respectively. Plasma levels of diamine oxidase (DAO) and d-lactate were determined using an enzymatic spectrophotometry.

RESULTS: Immunohistochemical localization of occludin and ZO-1 showed disruption of the tight junctions in enterocytes lining villi at the end of CPB and 2 h after CPB. The intensities of the occludin and ZO-1 at the end of CPB were lower than those of control group (76.4% ± 22.5% vs 96.5% ± 28.5% and 62.4% ± 10.1% vs 85.5% ± 25.6%, P < 0.05) and were further lower at 2 h after CPB (50.5% ± 10.5% and 45.3% ± 9.5%, P < 0.05). Plasma d-lactate and DAO levels increased significantly (8.688 ± 0.704 vs 5.745 ± 0.364 and 0.898 ± 0.062 vs 0.562 ± 0.035, P < 0.05) at the end of CPB compared with control group and were significantly higher at 2 h after CPB than those at the end of CPB (9.377 ± 0.769 and 1.038 ± 0.252, P < 0.05). There were significant negative correlations between occludin or ZO-1 expression and DAO (r² = 0.5629, r² = 0.5424, P < 0.05) or d-lactate levels (r² = 0.6512, r² = 0.7073, P < 0.05) both at the end of CPB and 2 h after CPB.

CONCLUSION: CPB markedly down-regulates the expression of occludin and ZO-1 proteins in intestinal mucosa of rats. The close correlation between expression of tight junctions (TJs) and plasma levels of DAO or d-lactate supports the hypothesis that intestinal permeability increases during and after CPB because of decreases in the expressions of TJs.

Biomarkers for radiation-induced small bowel epithelial damage: An emerging role for plasma Citrulline

Reduction of cancer treatment-induced mucosal injury has been recognized as an important target for improving the therapeutic ratio as well as reducing the economic burden associated with these treatment related sequellae. Clinical studies addressing this issue are hampered by the fact that specific objective parameters, which enable monitoring of damage in routine clinical practice, are lacking. This review summarizes pros and cons of currently available endpoints for intestinal injury. The metabolic background and characteristics of plasma citrulline, a recently investigated biomarker specifically for small intestinal injury, are discussed in more detail.

Localization and Changes of Diamine Oxidase During Cardiopulmonary Bypass in Rabbits

BACKGROUND

We previously observed increased serum diamine oxidase activity during clinical cardiopulmonary bypass, indicating small intestinal mucosal ischemia followed by bacterial translocation.

MATERIALS AND METHODS

In seven female rabbits undergoing cardiopulmonary bypass for 1 h, we analyzed the localization of diamine oxidase immunohistochemically, and measured its activity in serum and abdominal organs before and after cardiopulmonary bypass (CPB).

RESULTS

Preoperatively, diamine oxidase activity and immunoreactivity were high in the small intestine, localized to villus tips. Serum activity increased significantly after CPB, whereas small intestinal diamine oxidase decreased with mucosal injury.

CONCLUSIONS

In this model serum diamine oxidase activity appeared to reflect CPB induced intestinal mucosal injury.

Infarcted intestine: a diagnostic void

The diagnostic approaches to infarction of the small intestine are reviewed in the present paper. The inadequacy of current methods, especially biochemical methods, are highlighted. Additionally, the benefits of a sensitive and specific test of intestinal infarction are discussed.

Diagnostic tests for intestinal ischemia

Mesenteric ischemia is a devastating disease. Without early diagnosis and intervention, the process proceeds to intestinal gangrene with its associated high morbidity and mortality rates. Although newer operative techniques and better intensive care unit management may improve patient outcome, it is only by obtaining an earlier diagnosis that greater patient survival rates will be possible. In an attempt to improve diagnostic accuracy, many modalities have been explored. These include serum biochemical markers, peritoneal fluid analysis, tonometry, radionuclide imaging, laparoscopy, and endoscopic techniques. At present, no single test has enabled the clinician to improve the patient's outcome. We are hopeful that the newer techniques, including radionuclide-labeled antibodies, tonometry, and reflectance spectrophotometry, may in the future be of assistance in improving the results for patients sustaining intestinal ischemia.

Nuclear magnetic resonance as a noninvasive method of diagnosing intestinal ischemia: technique and preliminary results

Despite the long-standing effort to identify a noninvasive method of diagnosing intestinal ischemia, no reliable biochemical or radiographic technique has evolved. We explored the use of phosphorus nuclear magnetic resonance (PNMR) as a method of detecting surgically induced intestinal ischemia. Using Lewis strain rats (250 to 300 g), small intestine ischemia was produced by ligation in succession from the ligament of Treitz to the ileocecal valve 1 of 2 (group I), 2 of 3 (group II), 3 of 4 (group III), and 4 of 5 (group IV) mesenteric terminal vessels. A sham-operated group was used as a control. Following the surgical procedure, the abdomen was closed and the rat positioned under the PNMR apparatus. Using phosphorus spectroscopy, data were analyzed using a computer program and plotted on a graph indicating relative peaks for the phosphate-based compounds. As a means of comparing groups, we devised an inorganic phosphate to phosphocreatine ratio ("ischemia index"), a qualitative measurement indicating trends used to evaluate ischemia. At the completion of the PNMR study, the abdomen was reopened and proximal, mid, and distal small intestine segments were harvested for histological evaluation using a previously established grading system for intestinal ischemia. Preoperatively, immediately postoperatively, and approximately 2 hours postoperatively, blood samples were obtained for hexosaminidase levels. With increasing vascular ligation, there was an upward trend in both the histological appearance of ischemia and the PNMR ischemia index indicative of increasing tissue ischemia. A similar trend was identified when the histological ischemia grade was directly correlated with the PNMR ischemia index. Hexosaminidase levels did not correlate with ischemia in this study.(ABSTRACT TRUNCATED AT 250 WORDS)

Intestinal diamine oxidase levels reflect ischemic injury

Mucosal diamine oxidase (DAO) decreases during intestinal ischemia and may be a useful marker of intestinal ischemic injury. Tissue DAO activity and histologic changes were studied in intestinal segments taken from the midpoint of the small intestine before and 2, 4, and 24 hr after manipulation of the intestinal blood supply in 24 mongrel dogs. Intestinal DAO activity decreased significantly (17 +/- 21% of control value) 24 hr after SMA ligation and was associated with abnormal histology (histology score 7.8 +/- 2.9 at 24 hr vs 0.3 +/- 0.5 at 0 hr). SMA occlusion for 2 hr resulted in a significant decrease in DAO activity (45 +/- 36% of control value) 4 hr after manipulation which returned to normal at 24 hr, as did the histologic injury. Ligation of both the mesenteric arteries and veins resulted in a more rapid decrease in DAO activity. Decreased DAO activity correlated with the extent of histologic injury. Intestinal ischemia is associated with decreased intestinal DAO activity, which is influenced by the mechanism and duration of intestinal ischemia.

Polarized secretion of diamine oxidase by intestinal epithelial cells and its stimulation by heparin

The Caco-2 cells have been used as a model system to study the pathways of diamine oxidase secretion by the intestinal epithelium. When grown in Transwell filter chamber devices, the polarized cell monolayers released the enzyme preferentially into the basal chamber. Heparin (1-10 USP U/mL) rapidly induced a marked stimulation of enzyme secretion only when in contact with the basolateral cell membrane, where high affinity binding sites for [3H]heparin were also exclusively located. Among the other glycosaminoglycans tested, only heparan sulfate (150 mg/mL) was able to induce enzyme release; chondroitin sulfate (150 mg/mL) and dermatan sulfate (150 mg/mL) were without effect. Four monoclonal antibodies specific for human diamine oxidase were produced and found to immunoprecipitate a single protein with a molecular weight of 95,000 (under reducing conditions) from the culture medium of Caco-2 cells. Immunofluorescence staining of cryostat sections of human small intestine with these four antibodies localized diamine oxidase at the lateral and basal sides of the villus cells. Staining was markedly reduced in specimens obtained from patients who received doses of heparin in vivo. This study concludes that release of diamine oxidase by intestinal cells occurs specifically at the basolateral aspect of the cells, most likely through the constitutive secretory pathway. Heparin may induce its marked stimulation of enzyme release by complexing with diamine oxidase bound to the cell surface or through interaction with specific binding sites also located in the basolateral membrane. In the intestinal mucosa in vivo, the basal aspect of the villus cells represents the main site of diamine oxidase storage in the presence of normal circulating levels of heparin.

Serum enzyme levels during intestinal ischemia

Because the intestinal mucosa is most sensitive to ischemia, serum levels of mucosal enzymes, such as diamine oxidase, may be most likely to indicate intestinal ischemia. Our aim was to compare serum levels of mucosal (diamine oxidase, alkaline phosphatase) and seromuscular (creatinine phosphokinase, lactic dehydrogenase, serum glutamic oxaloacetic transminase) enzymes during intestinal ischemia of varying extent and duration in dogs. Group 1 (n = 6) underwent sham laparotomy. Group 2 (n = 8) had 50% of the small intestine devascularized. Group 3 (n = 8) had the superior mesenteric artery occluded for 2 hours and released. Group 4 (n = 8) had the superior mesenteric artery ligated. Serum samples were obtained before and 2, 4, 8, and 24 hours after operation, and histologic specimens were examined at 4 hours. Creatinine phosphokinase levels became elevated within 4 hours of ischemic injury in group 2 (223 +/- 197 vs. 68 +/- 26, p less than 0.05) and group 4 (212 +/- 136 vs. 76 +/- 29, p less than 0.05). Significant elevation of serum enzymes levels, except diamine oxidase, occurred in groups 2, 3, and 4 at 24 hours, including those with normal histology after temporary superior mesenteric artery occlusion. Thus seromuscular enzymes, particularly creatinine phosphokinase, were more likely to be elevated during intestinal ischemia. Enzyme levels were not influenced by the extent and reversibility of the ischemic injury.