Influence of ischaemia-reperfusion injury on CD44 expression in rat small intestine

Mechanism of gut barrier failure associated with severe acute pancreatitis

Gut barrier failure is often present in severe acute pancreatitis (SAP), and it increases the gut permeability, leads to translocation of bacteria or endotoxin, causes severe infection and multiple organ dysfunction syndrome, and worsens the course of the disease. The injury of gut barrier may result from the interactions among microcirculation disturbance, ischemia-reperfusion injury, excessive release of inflammatory mediators, apoptosis, flora imbalance and so on. The research on the mechanism of gut barrier failure caused by SAP is of important significance for the treatment of SAP.

miR-34a-5p Inhibition Alleviates Intestinal Ischemia/Reperfusion-Induced Reactive Oxygen Species Accumulation and Apoptosis via Activation of SIRT1 Signaling

AIMS

Reactive oxygen species (ROS) generation and massive epithelial apoptosis are critical in the pathogenesis of intestinal ischemia/reperfusion (I/R) injury. We previously found that the Sirtuin 1 (SIRT1)-mediated antioxidant pathway was impaired in the intestine after I/R. Here, we investigate the potential role of SIRT1-targeting microRNAs (miRNAs) in regulating ROS accumulation and apoptosis in intestinal I/R, and the important role SIRT1 involved in.

RESULTS

C57BL/6 mice were subjected to intestinal I/R induced by occlusion of the superior mesenteric artery followed by reperfusion. Caco-2 cells were incubated under hypoxia/reoxygenation condition to mimic I/R in vivo. We find that SIRT1 is gradually repressed during the early reperfusion, and that this repression results in intestinal ROS accumulation and apoptosis. Using bioinformatics analysis and real-time PCR, we demonstrate that miR-34a-5p and miR-495-3p are significantly increased among the 41 putative miRNAs that can target SIRT1. Inhibition of miR-34a-5p, but not miR-495-3p, attenuates intestinal I/R injury, as demonstrated by repressing p66shc upregulation, manganese superoxide dismutase repression, and the caspase-3 activation in vitro and in vivo; it further alleviates systemic injury, as demonstrated by reducing inflammatory cytokine release, attenuating lung and liver lesions, and improving survival. Interestingly, SIRT1 plays an indispensable role in the protection afforded by miR-34a-5p inhibition.

INNOVATION

This study provides the first evidence of miRNAs in regulating oxidative stress and apoptosis in intestinal I/R.

CONCLUSION

miR-34a-5p knockdown attenuates intestinal I/R injury through promoting SIRT1-mediated suppression of epithelial ROS accumulation and apoptosis. This may represent a novel prophylactic approach to intestinal I/R injury. Antioxid. Redox Signal. 24, 961-973.

Effect of vitamin A on the CD44 expression in the small intestine of rats with obstructive jaundice

HYPOTHESIS

In this study, the influence of obstructive jaundice on the CD44 expression in the rat small intestine and the alterations of this CD44 expression by vitamin A given intraperitoneally (200 IU/g/day) are evaluated.

MATERIALS AND METHODS

In a prospective animal model study, 32 Sprague-Dawley rats were randomized into four groups: group A rats (n = 8) underwent sham operation and were given daily saline intraperitoneally for 2 weeks (sham + saline); group B animals (n = 8) underwent sham operation and were given daily vitamin A intraperitoneally for 2 weeks (sham + vitamin A); group C rats (n = 8) underwent common bile duct ligation and were given daily saline intraperitoneally for 2 weeks (obstructive jaundice + saline), and group D animals (n = 8) underwent common bile duct ligation and were given daily vitamin A intraperitoneally for 2 weeks (obstructive jaundice + vitamin A). After 2 weeks, standardized jejunum and ileum segments were harvested from all animals. The expression of CD44 on the cell surface was evaluated immunohistochemically. Comparisons among the four groups were done.

RESULTS

The plasma bilirubin, aspartate transaminase, alanine transaminase, alkaline phospatase, and gamma-glutamyltransferase levels in groups C and D (obstructive jaundice groups) were higher than those in groups A and B (sham groups; p < 0.05). There was no difference between groups A and B (sham groups) with regard to the number of cells expressing surface CD44 in jejunum and ileum. When groups A and B were compared with group C (obstructive jaundice + saline) animals, the number of cells expressing surface CD44 was significantly decreased in both jejunum and ileum in group C. The difference between sham groups (A and B) and group C was found to be significant (p < 0.05). When group D (obstructive jaundice + vitamin A) was compared with group C (obstructive jaundice + saline), the number of cells expressing surface CD44 was significantly increased in jejunum and ileum in group D animals (p < 0.05), higher than in the sham groups (A and B). The difference between group D and sham groups (A and B) was found to be significant (p < 0.05).

CONCLUSION

Obstructive jaundice for 2 weeks significantly decreased the CD44 expression in the rat small intestine. We found that daily intraperitoneal administration of vitamin A in rats with obstructive jaundice for 2 weeks significantly restored the impaired CD44 expression.

Role of the gut in the course of severe acute pancreatitis

INTRODUCTION

The pathogenesis of acute pancreatitis remains elusive. Sepsis and multiple organ failure continue to cause death (overall mortality rate, approximately 10%) despite immense improvements in supportive, radiologic, and surgical therapy. The gut appears to play a key role in the development of these complications.

AIM

To critically review the evidence implicating the gut in the pathogenesis of acute pancreatitis.

METHODS

Relevant English-language literature or abstracts cited in the MEDLINE database were reviewed.

RESULTS AND CONCLUSION

Gram-negative enteric organisms account for most infections of pancreatic necrosis and subsequent sepsis, which suggests the gut as a source. Intestinal permeability is increased early in patients with severe acute pancreatitis and correlates with endotoxemia, which suggests translocation as a possible mechanism. The pathogenesis of the deranged function of the gut mucosal barrier and the possible sites of increase in intestinal permeability are discussed. The gut also plays a role in priming neutrophils and the release of inflammatory cytokines, which initiate and propagate nearly all the detrimental consequences of severe inflammation and sepsis. Future research avenues and potential therapeutic measures that may restore and preserve gut barrier function are explored.

Growth hormone downregulated the excessive apoptosis of ileal intestinal epithelial cells in rats during the early course of acute necrotizing pancreatitis

INTRODUCTION

Growth hormone (GH) has beneficial effects in protecting the intestinal barrier integrity of rats with acute necrotizing pancreatitis (ANP), and the balance between apoptosis and proliferation of intestinal epithelium is one of the key factors in maintenance of the intestinal barrier homeostasis.

AIM

To evaluate further the effect of GH on cell apoptosis of intestinal epithelium in rats with ANP.

METHODOLOGY

Seventy-two rats were randomly divided into 3 groups: sham operation (SO) group (n = 24); ANP group (n = 24); and ANP with GH treatment group (n = 24). ANP in rats was established by injection of 5% sodium taurocholate into the biliopancreatic duct, and laparotomized animals without induction of ANP (sham operation) served as controls. The rats in the GH treatment group received human recombinant GH (0.75 U/kg body weight) subcutaneously once, immediately after operation. The segment of ileum was removed and the detached epithelial cells of ileum were harvested at 3 hours, 6 hours, 12 hours, and 24 hours after operation. Apoptosis of intestinal epithelium was studied by DNA gel electrophoresis, fluorescein isothiocyanate (FITC)-labeled annexin V and propidium iodide (PI) staining under flow cytometry, and the terminal deoxynucleotidyl transferase-mediated d-UTP-biotin nick end labeling (TUNEL) histochemical method.

RESULTS

All specimens harvested at different time points from rats with ANP showed a marked DNA ladder pattern after agarose gel electrophoresis, in comparison with those in the SO group, indicating DNA fragmentation appeared at the early stage in the ANP group. However, a DNA ladder pattern was seen only at 3 hours after operation in the GH-treated rats. The apoptotic percentage assayed by flow cytometry with use of an annexin V kit at 6 hours in the ANP group was significantly higher than in the control group (80% +/- 9% versus 28% +/- 6%; p < 0.01) and was decreased markedly in the GH treatment group (27% +/- 15% versus 80% +/- 9%, p < 0.01). The apoptotic index, studied by the TUNEL method, was obviously higher in the ANP group than in the control group (3 hours: 18 +/- 4 versus 6 +/- 2; 6 hours: 20 +/- 3 versus 8 +/- 2; 12 hours: 15 +/- 2 versus 11 +/- 1; 24 hours: 14 +/- 2 versus 5 +/- 1; p < 0.01), whereas the apoptotic index in the GH treatment group decreased at 3 hours and 6 hours (10 +/- 2 versus 18 +/- 4; 10 +/- 2 versus 20 +/- 3; p < 0.01). The same results were achieved for the apoptotic index of villi tips in the three groups.

CONCLUSION

Apoptosis is a principle model of intestinal epithelial cell death at the early stage of ANP, and GH may downregulate the apoptosis significantly. This action probably is involved in the mechanisms contributing to the protective effects of GH on intestinal barrier integrity in ANP.

Assessment of the intestinal permeability after a gastrectomy and the oral administration of anticancer drugs in rats: nitric oxide release in response to gut injury

BACKGROUND

Although intestinal permeability is known to increase in conditions of stress (such as endotoxemia, septic shock, and ischemia-reperfusion), the mechanism of gut barrier dysfunction during chemotherapy remains to be elucidated. We designed an experiment in which a gastrectomy and anticancer drugs were administered to rats to assess the extent of damage or an increase in permeability of the intestinal mucosa.

METHODS

The rats were separated into the following groups: group A, no operation without an anticancer drug (control rats); group B, a gastric operation; group C, chemotherapy; and group D, a gastric operation followed by chemotherapy. Six rats were placed in each group. The groups that were given the anticancer drug received 45 mg/kg for 7 and 14 days, respectively. Intestinal permeability was determined by an injection of fluorescein isothiocyanate-dextran (FITC-D) intravenously and the measurement of the amount of FITC-D leakage in the luminal lavage. The plasma nitric oxide concentrations were measured spectrophotometrically by the Griess reaction. The cell surface expression of CD44 in the rat small intestine was evaluated immunohistochemically.

RESULTS

During the entire experimental period, the FITC-D levels in the anticancer drug that was administrated to rats (groups C and D) were significantly higher than the levels in groups A and B (P <.001). Similarly, the plasma nitric oxide concentration increased significantly not only in groups C and D but also in group B (P <.05). A linear regression analysis revealed a positive significant correlation between FITC-D and the plasma nitric oxide levels (r = 0.617; P <.001). When the anticancer drug was administered, the intestine histologically revealed so-called mucosal atrophy and a decreased expression of CD44 within the intestinal mucosa.

CONCLUSIONS

The administration of anticancer drugs impairs the gut barrier function, possibly by reducing the cell-cell and cell-matrix interactions. This may contribute to the development of hyperpermeability that is induced by an overexpression of nitric oxide.

Pretreatment with glycine reduces the severity of warm intestinal ischemic-reperfusion injury in the rat

Free jejunal flaps may experience adverse effects immediately after revascularization because of ischemic-reperfusion injury. In this study the authors evaluated the ability of glycine to protect the small intestine against the effects of a warm ischemic-reperfusion injury. Male Wistar rats (N = 30) were randomized to either a baseline group (no intervention), a control group (local arterial infusion with normal saline), or a glycine group (local arterial infusion with 20% glycine). Pretreatment with 20% glycine increased significantly (p < 0.05) mucosal protein and deoxyribonucleic acid content, reduced intestinal myeloperoxidase activity, and maintained mucosal glutaminase activity. These results indicate that some of the indicators of ischemic-reperfusion injury are improved by pretreatment with a 20% glycine solution.