Beneficial effects of intraluminal nitroglycerin in intestinal ischemia-reperfusion injury in rats

Simvastatin nanoparticles attenuated intestinal ischemia/reperfusion injury by downregulating BMP4/COX-2 pathway in rats

The purpose of the research was to explore the therapeutic action of simvastatin-loaded poly(ethylene glycol)-b-poly(gamma-benzyl l-glutamate) (PEG-b-PBLG₅₀) on intestinal ischemia/reperfusion injury (II/RI) through downregulating bone morphogenetic protein 4 (BMP4)/cyclooxygenase-2 (COX-2) pathway as compared to free simvastatin (Sim). Sprague Dawley rats were preconditioned with 20 mg/kg Sim or simvastatin/PEG-b-PBLG₅₀ (Sim/P) compounds, and then subjected to 45 min of ischemia and 1 h of reperfusion. The blood and small intestines were collected, serum levels of interleukin-4 (IL-4), interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor-α, and nitric oxide (NO) were checked, and the dry/wet intestine ratios, superoxide dismutase activity, myeloperoxidase content, reactive oxygen species, endothelial nitric oxide synthase, protein 47 kDa phagocyte oxidase (p47phox), BMP4, COX-2, and p38 mitogen-activated protein kinase (p38MAPK) expressions were measured in intestinal tissues. Both Sim and Sim/P pretreatment reduced intestinal oxidative damnification, restricted inflammatory harm, and downregulated the BMP4 and COX-2 expressions as compared to II/RI groups, while Sim/P remarkably improved this effect.

Evidence of attenuation of intestinal ischemia-reperfusion injury following pre-treatment with methanolic extracts from Chromolena odorata in rats

BACKGROUND

Chromolena odorata is a tropical species of flowering shrub in the family Asteraceae, leaves of it have been reported to be widely used as herbal remedy for the treatment of various ailments. It is particularly reported to be useful in the healing of wounds.

METHODS

We investigated the possibility of amelioration of intestinal ischemia-reperfusion (IR) injury in rats treated with methanolic extract of C. odorata (MECO). Wistar albino rats were divided randomly into five groups of six animals each as control, IR-treated, IR+200 mg/kg MECO, IR+400 mg/kg MECO, and IR+200 mg/kg vitamin C. Pre-treatment with MECO or vitamin C was for 7 days.

RESULTS

The contents of hydrogen peroxide (H2O2) and malondialdehyde (MDA) were significantly reduced by MECO and vitamin C, while there were significant enhancements of the activities of superoxide dismutase (SOD), glutathione peroxidase (GPX), catalase (CAT), as well as the content of reduced glutathione (GSH) in pre-treated rats compared to IR-treated rats. Glutathione S-transferase (GST) activity was not significantly affected in all the groups. Histopathological examination of small intestinal mucosa revealed significant attenuation of intestinal pathology in animals pre-treated with MECO, while IR injury produced severe villi erosion, necrosis, and inflammatory cell infiltrations.

CONCLUSIONS

The present study highlights the antioxidant activities of MECO and its ability to inhibit inflammatory cell infiltration as mechanisms involved in its protection against IR injury in the intestine of rats, an effect that was largely comparable to that of vitamin C.

Hypoxia enhances protective effect of placental-derived mesenchymal stem cells on damaged intestinal epithelial cells by promoting secretion of insulin-like growth factor-1

Apoptosis and necrosis of intestinal epithelial cells (IECs), induced by ischemia-reperfusion (I/R) injury, can lead to dysfunction of the intestinal barrier, which could cause multiple organ dysfunction syndromes. Mesenchymal stem cells (MSCs) have the potential of providing protective effects on damaged IECs via paracrine action. This study investigated whether hypoxia can enhance the protective effect of placental-derived MSCs (pMSCs) on H2O2-treated-caco2 cells, and explored the possible mechanism. The pMSCs isolated by tissue culture were fibroblast-like, positive for CD73, CD90 and CD105 and can differentiate into chondrocytes and endothelial cells. Five days after treatment with H2O2, the numbers of living caco2 cells significantly decreased. More live H2O2-treated-caco2 cells were observed in pMSCs hypoxia culture medium (pMSCs-HCM) than pMSCs normoxia culture medium (pMSCs-NCM), and the application of a specific antibody that blocked insulin-like growth factor-1 (IGF-1) leads to a significant decrease of the protective effect of pMSCs-HCM. Hypoxia can promote IGF-1 expression of pMSCs at mRNA and protein levels, and caco2 stably expressed IGF-1 receptor. Knocking down IGF-1 expression in pMSCs by siRNA resulted in a significant attenuation of the increase in apoptosis of H2O2-treated-caco2 cultured in pMSCs-HCM. In conclusion, hypoxia can increase the protective effect of pMSCs on H2O2-treated-caco2 cells via a promotion of their paracrine actions, and the key cytokine involved is IGF-1.

Oxidative stress and ischemia-reperfusion injury in gastrointestinal tract and antioxidant, protective agents

Exacerbation of hypoxic injury after reoxygenation is a crucial mechanism mediating organ injury in transplantation, and in myocardial, hepatic, gastrointestinal, cerebral, renal, and other ischemic syndromes. The occlusion and reperfusion of the splanchnic artery is a useful animal model to elucidate the mechanism of gastrointestinal injury induced by ischemia-reperfusion (I/R). Although xanthine oxidase is a major source of reactive oxygen species (ROS), which plays an important role in the I/R-induced intestinal injury, there are many other sources of intracellular ROS. Various treatment modalities have been successfully applied to attenuate the I/R injury in animal models. This review focuses on the role of oxidant stress in the mechanism of I/R injury and the use of antioxidant agents for its treatment.

Effect of simvastatin on intestinal recovery following gut ischemia-reperfusion injury in a rat

BACKGROUND

Pleiotropic (lipid lowering-independent) effects of statins are attributed to their antiinflammatory, antioxidant, and/or vascular actions. Extensive studies in various experimental models have established that pretreatment with simvastatin significantly protects heart and kidney injured by ischemia-reperfusion (IR). The purpose of the present study was to examine the effect of simvastatin on intestinal recovery and enterocyte turnover after intestinal IR injury in rats.

METHODS

Male Sprague-Dawley rats were divided into three experimental groups: (1) sham rats underwent laparotomy, (2) IR-rats underwent occlusion of both superior mesenteric artery and portal vein for 30 min followed by 48 h of reperfusion, and (3) IR-SIM rats underwent IR and were treated with oral simvastatin (10 mg/kg) given by gavage immediately before and 24 h after operation. Intestinal structural changes, Park's injury score, enterocyte proliferation and enterocyte apoptosis were determined 24 h following IR. A non-parametric Kruskal-Wallis ANOVA test was used for statistical analysis with P less than 0.05 considered statistically significant.

RESULTS

Treatment with simvastatin resulted in a significant increase in bowel and mucosal weight in ileum, villus height and crypt depth in jejunum and ileum compared to IR animals. IR-SIM rats had also a significantly lower intestinal injury score as well as lower apoptotic index in jejunum and ileum compared to IR animals.

CONCLUSIONS

Treatment with simvastatin prevents gut mucosal damage and inhibits programmed cell death following intestinal IR in a rat.

Bone marrow mesenchymal stem cells reduce intestinal ischemia/reperfusion injuries in rats

BACKGROUND

Adult stem cells are promising novel therapies in regenerative medicine. We investigated effects of bone marrow-derived mesenchymal stem cells (MSCs) on intestinal mucosal permeability impaired by ischemia/reperfusion (I/R).

METHODS

We used a common I/R model in rats to induce intestinal injury by clamping and unclamping the superior mesenteric artery (SMA) in female Sprague-Dawley rats. MSCs were directly injected into the small intestinal submucosa of the syngenic female rats. Control group were injected with the same volume of 0.9% sodium chloride. Small intestine samples were examined for the engraftment of donor-derived mesenchymal stem cells (MSCs) by Y chromosome in situ hybridization analysis. The small intestinal permeability and histomorphologic alternations were measured to evaluate the therapeutic effect of MSCs transplantation.

RESULTS

Small intestinal permeability and villi injuries were significantly reduced in the MSCs administrated group compared with control group. MSCs administration accelerated the recovery of the intestinal barrier dysfunction.

CONCLUSION

We concluded that submucosal infusion of MSCs might exert protective effects on the integrity of intestinal barrier.

The effect of leptin on intestinal recovery following ischemia-reperfusion injury in a rat

Recent evidence suggests that the adipose tissue derived cytokine leptin (LEP) is involved in the modulation of growth and differentiation of normal small intestine. The purpose of the present study was to examine the effect of leptin on enterocyte turnover and intestinal recovery after ischemia-reperfusion (IR) injury in a rat. Male Sprague-Dawley rats were divided into three experimental groups: (1) sham rats underwent laparotomy, (2) IR-rats underwent occlusion of both superior mesenteric artery and portal vein for 30 min followed by 24 h of reperfusion, and (3) IR-LEP rats underwent IR and were treated with leptin given subcutaneously at a dose of 50 microg/kg once a day for 48 h before and 24 h following IR. Intestinal structural changes, enterocyte proliferation and enterocyte apoptosis were determined 24 h following IR. A non-parametric Kruskal-Wallis ANOVA test was used for statistical analysis with P < 0.05 considered statistically significant. Treatment with leptin resulted in a significant increase in bowel weight in ileum, mucosal weight in jejunum and ileum, mucosal DNA content in ileum, mucosal protein content in jejunum and ileum, villus height in jejunum and ileum, and crypt depth in jejunum compared to IR-animals. IR-LEP rats also had a significantly lower intestinal injury score as well as lower apoptotic index and higher cell proliferation index in jejunum and ileum compared to the IR-animals. In conclusion, pre-treatment with leptin prevents gut mucosal damage and improves intestinal rehabilitation following intestinal IR in a rat.

Protective Effects of Hyperoxygenated Solution Preconditioning on Intestinal Ischemia–Reperfusion Injury in Rabbits

BACKGROUND

The aim of this study was to investigate the protective effects of hyperoxygenated solution (HOS) preconditioning on intestinal ischemia-reperfusion (IR) injury in rabbits.

MATERIALS AND METHODS

Thirty-two rabbits were randomly divided into four groups as follows: (1) control group in which sham operation was performed (Sham group); (2) sham operation and HOS treatment group (sham+H group); (3) ischemia-reperfusion group (IR group); (4) ischemia-reperfusion and HOS treatment group (H group). Intestinal IR model was produced by clamping superior mesenteric artery with an atraumatic vascular clamp for 1 h, followed by reperfusion for 2 h. Animals in H group received intravenous HOS infusion (20 mL/kg) every day for 5 days before ischemia-reperfusion; animals in the sham+H group received the same amount of HOS before sham operation, and animals in IR group received the same amount of normal saline in the same way. At the end of reperfusion, histopathological changes of intestine were observed, and malondialdehyde (MDA) levels, superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities in intestinal tissues were also detected. Intestinal barrier function was assessed by blood d-lactate levels and bacterial translocation (BT).

RESULTS

The H group showed significantly lower MDA levels and higher activities of SOD, CAT, and GSH-Px in the intestinal tissue compared with the IR group. Furthermore, the mean d-lactate levels and incidence of BT in the H group were significantly lower than those in the IR group. Histopathological analysis also indicated that there were significant histological improvements in the H group compared with the IR group.

CONCLUSIONS

HOS preconditioning at an appropriate dose ameliorates the deleterious changes in intestinal mucosal injury and barrier function associated with IR by effectively preventing a decrease in the intestinal antioxidant defense system, which is another simple and effective measure to protect intestine from IR injury.

Mibefradil, a T-type Ca2+ channel blocker, protects against mesenteric ischemia-reperfusion-induced oxidative injury and histologic alterations in intestinal mucosa in rats

The purpose of the present study was to investigate whether mibefradil can reduce oxidative stress and histologic damage in the rat small bowel subjected to mesenteric ischemia and reperfusion injury. Thirty Sprague-Dawley rats weighing between 210 and 220 g were divided into three groups, each containing 10 rats: group 1, sham operation; group 2, untreated ischemia-reperfusion; and group 3, ischemia-reperfusion plus mibefradil treatment group. Intestinal ischemia for 45 min and reperfusion for 60 min were applied. Ileal specimens were obtained to determine the tissue levels of MDA, CAT, SOD, and GSH-Px and histologic changes. In group 2, MDA values were significantly increased compared to those in groups 1 and 3. In addition, SOD, CAT, and GSH-Px values decreased significantly in group 2 compared to groups 1 and 3. The intestinal injury score increased significantly in group 2 and 3 rats compared to group 1 rats. However, this increase was reduced in group 3 rats compared to group 2. Histopathologically, the rats in group 1 had essentially normal testicular architecture. In group 2 rats, the lesions varied between grade 3 and grade 5. In contrast, most of the specimens in the mibefradil-treated group 3 showed grade 1 injury. Mibefradil plays a role in attenuating reperfusion injury of the small intestine by depressing free radical production and mucosal injury score and regulating postischemic intestinal perfusion while restoring intestinal microcirculatory blood flow and encountered histologic injury.

The selective inhibition of inducible nitric oxide synthase prevents intestinal ischemia-reperfusion injury in mice

Nitric oxide (NO) involvement in intestinal ischemia-reperfusion (I/R) injury has been widely suggested but its protective or detrimental role remains still question of debate. Here, we examine the impact of supplementation or inhibition of NO availability on intestinal dysmotility and inflammation caused by mesenteric I/R in mice. Ischemia 45min and reperfusion 24h were performed by superior mesenteric artery occlusion in female Swiss mice. Saline-treated sham-operated (S) or normal mice without surgery (N) served as controls. Drugs were subcutaneously injected 0, 4, 8, and 18 h after ischemia. Upper gastrointestinal transit (GIT, estimated through black marker gavage), intestinal myeloperoxidase activity (MPO), intestinal malondialdehyde levels (MDA), Evans blue extravasation (EB), intestinal histological damage, and mean arterial pressure (MAP) were considered. In I/R mice, GIT was significantly delayed compared to S and N groups; MPO activity and EB extravasation enhanced, whereas MDA levels did not change. Compared to N and S groups, in I/R mice selective iNOS inhibitor P-BIT significantly prevented motor, MPO and EB changes; putative iNOS inhibitor aminoguanidine significantly counteracted GIT delay but not neutrophil recruitment and the increase in vascular permeability; NOS inhibitor l-NAME and NO precursor l-arginine were scarcely or no effective. Furthermore, in S mice aminoguanidine caused a significant increase of MPO activity reverted by H(1) histamine receptor antagonist pre-treatment. Unlike P-BIT, aminoguanidine and l-NAME injection increased MAP. These findings confirm a detrimental role for iNOS-derived NO overproduction during reperfusion. Aminoguanidine-associated neutrophil recruitment suggests that this drug could act through mechanisms additional to iNOS inhibition involving both eNOS blockade, as indicated by its hemodynamic effects, and indirect activation of H(1) histamine receptors.

Amelioration of intestinal ischemia-reperfusion injury with intraluminal hyperoxygenated solution: studies on structural and functional changes of enterocyte mitochondria

BACKGROUND

The aim of this study was to investigate the effects of intraluminal hyperoxygenated solution (HOS) on enterocyte mitochondrial structure and respiratory function after intestinal ischemia-reperfusion (IR) in rabbits.

MATERIALS AND METHODS

Thirty-two rabbits were divided randomly into four groups: control group in which sham operation was performed (Sham group), ischemia-reperfusion group (IR group), and two HOS treatment groups (H1 group and H2 group). Intestinal IR model was produced by clamping superior mesenteric artery (SMA) with an atraumatic vascular clamp for 1 h, followed by reperfusion for 2 h. Animals in the H1 group and H2 group received intraluminal HOS infusion for 1 h immediately after occlusion of SMA, and the rates of infusion were 10 and 20 mL/kg.h, respectively. After 2 h of reperfusion, enterocyte mitochondria morphological quantitative analysis was made with electron microscopy and biogenetics stereology, and the following parameters, including mitochondrial respiratory control ratio (RCR), intestinal O(2) extraction ratio (ER), and mucosal ATP contents, were measured, respectively.

RESULTS

After IR, the mitochondria was severely swollen with broken cristae, and mean transaction area, diameter, surface density, and volume density of the mitochondria increased significantly. Meanwhile, specific surface and numeral density of the mitochondria decreased significantly. The mitochondrial RCR, intestinal O(2) ER, and mucosal ATP contents were all decreased significantly. There were no differences in all parameters between the IR group and H1 group. In the H2 group, the mitochondria were slightly swollen, and mean transaction area, diameter, surface density, and volume density of the mitochondria were all significantly lower, with the specific surface and numeral density of the mitochondria significantly higher compared with the IR group. The mitochondrial RCR, intestinal O(2) ER and mucosal ATP contents in H2 group were all significantly higher than those in IR group.

CONCLUSIONS

Intraluminal HOS infusion at 20 mL/kg.h during ischemia ameliorates structural and functional changes of enterocyte mitochondria associated with intestinal IR injury, which is a safe, simple, and effective measure to protect the intestine from IR injury.

Oral arginine improves intestinal recovery following ischemia-reperfusion injury in rat

Arginine and nitric oxide are critical to the normal physiology of the gastrointestinal tract and maintain the mucosal integrity of the intestine in various intestinal disorders. In the present study, we evaluate the effects of oral arginine (ARG) supplementation on intestinal structural changes, enterocyte proliferation, and apoptosis following intestinal ischemia-reperfusion (IR) in the rat. Male Sprague-Dawley rats were divided into three experimental groups: sham rats underwent laparotomy and superior mesenteric artery mobilization, IR rats underwent superior mesenteric artery occlusion for 30 min following by 24 h of reperfusion, and IR-ARG rats were treated with enteral arginine given in drinking water (2%) 48 h before and following IR. Intestinal structural changes, enterocyte proliferation, and enterocyte apoptosis were determined 24 h following IR. A nonparametric Kruskal-Wallis ANOVA test was used for statistical analysis with p <0.05 considered statistically significant. IR rats demonstrated a significant decrease in bowel weight in duodenum and jejunum, mucosal weight in jejunum and ileum, and villus height in jejunum and ileum compared with control animals. IR rats also had a significantly lower cell proliferation index in jejunum and ileum and a higher apoptotic index in ileum compared with control rats. IR-ARG animals demonstrated greater duodenal and jejunal bowel weight; duodenal, jejunal, and ileal mucosal weight; and jejunal and ileal cell proliferation index compared with IR animals. In conclusion, oral ARG administration improves mucosal recovery following IR injury in the rat.

Review article: diagnosis and management of mesenteric ischaemia with an emphasis on pharmacotherapy

Mesenteric ischaemia results from decreased blood flow to the bowel, causing cellular injury from lack of oxygen and nutrients. Acute mesenteric ischaemia (AMI) is an uncommon disorder with high morbidity and mortality, but outcomes are improved with prompt recognition and aggressive treatment. Five subgroups of AMI have been identified, with superior mesenteric artery embolism (SMAE) the most common. Older age and cardiovascular disease are common risk factors for AMI, excepting acute mesenteric venous thrombosis (AMVT), which affects younger patients with hypercoaguable states. AMI is characterized by sudden onset of abdominal pain; a benign abdominal exam may be observed prior to bowel infarction. Conventional angiography and more recently, computed tomography angiography, are the cornerstones of diagnosis. Correction of predisposing conditions, volume resuscitation and antibiotic treatment are standard treatments for AMI, and surgery is mandated in the setting of peritoneal signs. Intra-arterial vasodilators are used routinely in the treatment of non-occlusive mesenteric ischaemia (NOMI) and also are advocated in the treatment of occlusive AMI to decrease associated vasospasm. Thrombolytics have been used on a limited basis to treat occlusive AMI. A variety of agents have been studied in animal models to treat reperfusion injury, which sometimes can be more harmful than ischaemic injury. Chronic mesenteric ischaemia (CMI) usually is caused by severe obstructive atherosclerotic disease of two or more splanchnic vessels, presents with post-prandial pain and weight loss, and is treated by either surgical revascularization or percutaneous angioplasty and stenting.

Differential nitros(yl)ation of blood and tissue constituents during glyceryl trinitrate biotransformation in vivo

Nitric oxide (NO)-derived products may modify tissue constituents, forming S- and N-nitroso adducts and metal nitrosyls implicated in NO signaling. Nitrovasodilator drugs have been in widespread use for more than a century, yet their biotransformation pathways to NO and their effects as NO donors across tissues remain ill defined. By using a metabonomics approach (termed "NObonomics") for detailing the global NO-related metabolism of the cornerstone nitrovasodilator, glyceryl trinitrate (GTN; 0.1-100 mg/kg), in the rat in vivo, we find that GTN biotransformation elicits extensive tissue nitros(yl)ation throughout all major organ systems. The corresponding reaction products remained detectable hours after administration, and vascular tissue was not a major nitros(yl)ation site. Extensive heart and liver modifications involved both S- and N-nitrosation, and RBC S-nitrosothiol formation emerged as a sensitive indicator of organic nitrate metabolism. The dynamics of GTN-derived oxidative NO metabolites in blood did not reflect the nitros(yl)ation patterns in the circulation or in tissues, casting doubt on the usefulness of plasma nitrite/nitrate as an index of NO/NO-donor biodynamics. Target-tissue NO metabolites varied in amount and type with GTN dose, suggesting a dose-sensitive shift in the prevailing routes of GTN biotransformation ("metabolic shunting") from thiol nitrosation to heme nitrosylation. We further demonstrate that GTN-induced nitros(yl)ation is modulated by a complex, tissue-selective interplay of enzyme-catalyzed pathways. These findings provide insight into the global in vivo metabolism of GTN at pharmacologically relevant doses and offer an additional experimental paradigm for the NObonomic analysis of NO-donor metabolism and signaling.