Effects of antioxidative agents on apoptosis induced by ischaemia-reperfusion in rat intestinal mucosa

Hypothermic machine perfusion alleviates ischemia-reperfusion injury of intestinal transplantation in pigs

Background

Intestinal transplantation (IT) has become an important procedure for the treatment of irreversible intestinal failure. However, IT is extremely vulnerable to ischemia-reperfusion injury (IRI). Due to the limitations of static cold storage (SCS), hypothermic machine perfusion (HMP) is rapidly gaining popularity. In this study, the intestinal HMP system is established and HMP is compared with SCS.

Methods

An intestinal HMP system was built. Ten miniature pigs were randomly divided into the HMP and SCS groups, and their intestines were perfused using the HMP device and SCS, respectively, followed by orthotopic auto-transplantation. Analysis was done on the grafts between the two groups.

Results

Operation success rates of the surgery were 100% in both groups. The 7-day survival rate was 100% in the HMP group, which was significantly higher than that of the SCS group (20%, P< 0.05). The pathological results showed that fewer injuries of grafts were in the HMP group. Endotoxin (ET), IL-1, IL-6, IFN-γ and TNF-α levels in the HMP group were significantly lower than in the SCS group (P<0.05), whereas IL-10 levels were significantly higher (P<0.05).The intestinal expression levels of ZO-1 and Occludin were higher in the HMP group compared to the SCS group, whereas Toll-like receptor 4 (TLR4), nuclear factor kappa B (NFκB), and caspase-3 were lower.

Conclusions

In this study, we established a stable intestinal HMP system and demonstrated that HMP could significantly alleviate intestinal IRI and improve the outcome after IT.

Dexmedetomidine reduces enteric glial cell injury induced by intestinal ischaemia-reperfusion injury through mitochondrial localization of TERT

This study was performed to uncover the effects of dexmedetomidine on oxidative stress injury induced by mitochondrial localization of telomerase reverse transcriptase (TERT) in enteric glial cells (EGCs) following intestinal ischaemia-reperfusion injury (IRI) in rat models. Following establishment of intestinal IRI models by superior mesenteric artery occlusion in Wistar rats, the expression and distribution patterns of TERT were detected. The IRI rats were subsequently treated with low or high doses of dexmedetomidine, followed by detection of ROS, MDA and GSH levels. Calcein cobalt and rhodamine 123 staining were also carried out to detect mitochondrial permeability transition pore (MPTP) and the mitochondrial membrane potential (MMP), respectively. Moreover, oxidative injury of mtDNA was determined, in addition to analyses of EGC viability and apoptosis. Intestinal tissues and mitochondria of EGCs were badly damaged in the intestinal IRI group. In addition, there was a reduction in mitochondrial localization of TERT, oxidative stress, whilst apoptosis of EGCs was increased and proliferation was decreased. On the other hand, administration of dexmedetomidine was associated with promotion of mitochondrial localization of TERT, whilst oxidative stress, MPTP and mtDNA in EGCs, and EGC apoptosis were all inhibited, and the MMP and EGC viability were both increased. A positive correlation was observed between different doses of dexmedetomidine and protective effects. Collectively, our findings highlighted the antioxidative effects of dexmedetomidine on EGCs following intestinal IRI, as dexmedetomidine alleviated mitochondrial damage by enhancing the mitochondrial localization of TERT.

Design, Synthesis, Molecular Docking, Antiapoptotic and Caspase-3 Inhibition of New 1,2,3-Triazole/Bis-2(1H)-Quinolinone Hybrids

A series of novel 1,2,3-triazoles hybridized with two quinolin-2-ones, was designed and synthesized through click reactions. The structures of the synthesized compounds were elucidated by NMR, IR, and mass spectra in addition to elemental analysis. The synthesized compounds were assessed for their antiapoptotic activity in testis, as testicular torsion is the main cause of male infertility. This effect was studied in light of decreasing tissue damage induced by I/R in the testis of rats using N-acetylcysteine (NAC) as an antiapoptotic reference. Compounds 6a-c were the most active antiapoptotic hybrids with significant measurements for malondialdehyde (MDA) and total antioxidant capacity (TAC) and the apoptotic biomarkers (testicular testosterone, TNFα, and caspase-3) in comparison to the reference. A preliminary mechanistic study was performed to improve the antiapoptotic activity through caspase-3 inhibition. A compound assigned as 6-methoxy-4-(4-(((2-oxo-1,2-dihydroquinolin-4-yl)oxy)methyl)-1H-1,2,3-triazol-1-yl)quinolin-2(1H)-one (6c) was selected as a representative of the most active hybrids in comparison to NAC. Assay of cytochrome C for 6c revealed an attenuation of cytochrome C level about 3.54 fold, comparable to NAC (4.13 fold). In caspases-3,8,9 assays, 6c was found to exhibit more potency and selectivity toward caspase-3 than other caspases. The testicular histopathological investigation was carried out on all targeted compounds 6a-g, indicating a significant improvement in the spermatogenesis process for compounds 6a-c if compared to the reference relative to the control. Finally, molecular docking studies were done at the caspase-3 active site to suggest possible binding modes. Hence, it could conceivably be hypothesized that compounds 6a-c could be considered good lead candidate compounds as antiapoptotic agents.

Protective effect of GYY4137, a water‑soluble hydrogen sulfide‑releasing molecule, on intestinal ischemia‑reperfusion

The present study aimed to clarify the protective effects of p‑methoxyphenyl morpholino‑phosphinodithioic acid (GYY4137), a water‑soluble hydrogen sulfide‑releasing molecule, on a rat model of intestinal ischemia‑reperfusion (IIR). A total of 40 healthy male Sprague Dawley (SD) rats were randomly divided into four groups (n=10/group): Group A, a sham‑surgery group; Group B, the IIR group; group C, rats with IIR that were administered an abdominal injection of low‑dose GYY4137 (40 mg/kg); and group D, rats with IIR that were administered high‑dose GYY4137 (80 mg/kg). Intestinal histomorphology was observed using hematoxylin and eosin staining, and the concentrations of malondialdehyde (MDA) and superoxide dismutase (SOD) were measured. Apoptotic index (AI) was determined by terminal deoxynucleotidyl‑transferase‑mediated dUTP nick end labeling. Reverse transcription‑quantitative PCR analysis was performed to assess the expression levels of intestinal caspase‑3, Bax and Bcl‑2. Notably, disordered arrangement of intestinal villi and mucosal necrosis were detected in group B, which was substantially improved by GYY4137 treatment (groups C and D). MDA content (nmol/mg) was 2.83±0.36, 9.23±0.78, 4.97±0.45 and 3.51±1.05 nmol/mg in groups A, B, C and D, respectively. In addition, SOD concentration (U/mg) was 135.37±3.34, 76.45±1.39, 95.13±1.64 and 115.13±2.54 in groups A, B, C and D, respectively. Furthermore, AI in group B (21.73±1.17%) was markedly higher than that in group A (4.53±0.28%) and in the GYY4137 intervention groups (9.53±0.96 and 6.53±0.76% in groups C and D, respectively). Compared with in group A, the mRNA expression levels of Bax and caspase‑3 were markedly higher in group B (P<0.05), whereas the expression of Bcl‑2 was significantly lower (P<0.05). Furthermore, compared with in group B, Bcl‑2 expression was higher, and Bax and caspase‑3 expression was lower in groups C and D (P<0.05). In conclusion, GYY4137 may alleviate IIR‑induced damage in SD rats.

Microbiome and intestinal ischemia/reperfusion injury

Intestinal ischemia/reperfusion injury is a severe disease associated with a high mortality. The mechanisms that cause ischemia/reperfusion injury are complex and many factors are involved in the injury formation process; however, the only available treatment is surgical intervention. Recent studies demonstrated that the intestinal microbiome plays a key role in intestinal ischemia/reperfusion injury and there are many factors associated with intestinal bacteria during the formation of the intestinal ischemia/reperfusion injury. Among the Toll-like receptors (TLR), TLR2, TLR4, and their adaptor protein, myeloid differentiation primary-response 88 (MyD88), have been reported to be involved in intestinal ischemia/reperfusion injury. Oxidative stress and nitric oxide are also associated with intestinal bacteria during the formation of the intestinal ischemia/reperfusion injury. This review focuses on our current understanding of the impact of the microbiome, including the roles of the TLRs, oxidative stress, and nitric oxide, on intestinal ischemia/reperfusion injury.

Preconditioning with Azadirachta indica ameliorates cardiorenal dysfunction through reduction in oxidative stress and extracellular signal regulated protein kinase signalling

BACKGROUND

Azadirachta indica is widely distributed in Africa, Asia and other tropical parts of the world. A. indica (AI) is traditionally used for the treatment of several conditions including cancer, hypertension, heart diseases and skin disorders. Intestinal ischaemia-reperfusion is a common pathway for many diseases and may lead to multiple organ dysfunction syndrome and death.

OBJECTIVE

In this study, we investigated the ameliorative effects of AI on intestinal ischaemia-reperfusion injury-induced cardiorenal dysfunction.

MATERIALS AND METHODS

Sixty rats were divided into 6 groups; each containing 10. Corn oil was orally administered to group A (control) rats for 7 days without intestinal ischaemia-reperfusion injury. Group B underwent intestinal ischaemia-reperfusion injury (IIRI) without any pre-treatment. Groups C, D, E and F were pre-treated orally for 7 days with 100 mg/kg AI (100 and (200 mg/kg) vitamin C (100 and 200 mg/kg) respectively and thereafter underwent IIRI on the 8th day.

RESULTS

The cardiac and renal hydrogen peroxide increased significantly whereas serum xanthine oxidase and myeloperoxidase levels were significantly elevated (p < 0.05) in IIRI only when compared to the control. The cardiac and renal reduced glutathione, glutathione peroxidase, protein thiol, non-protein thiol and serum nitric oxide (NO) decreased (p < 0.05) significantly following IIRI. Immunohistochemical evaluation of cardiac and renal tissues showed reduced expressions of the extracellular signal regulated kinase (ERK1/2) in rats with IIRI only. However, pre-treatment with A. indica and vitamin C significantly reduced markers of oxidative stress and inflammation together with improvement in antioxidant status. Also, reduced serum NO level was normalised in rats pre-treated with A. indica and vitamin C with concomitant higher expressions of cardiac and renal ERK1/2.

CONCLUSIONS

Together, A. indica and vitamin C prevented IRI-induced cardiorenal dysfunction via reduction in oxidative stress, improvement in antioxidant defence system and increase in the ERK1/2 expressions. Therefore, A. indica can be a useful chemopreventive agent in the prevention and treatment of conditions associated with intestinal ischaemia-reperfusion injury.

Protective effects of thymoquinone and melatonin on intestinal ischemia-reperfusion injury

BACKGROUND/AIM

In the present study, we aimed to compare the potential protective effects of thymoquinone and melatonin by using equivalent dose, on oxidative stress-induced ischemia-reperfusion (IR) injury in the intestinal tissue of rats.

MATERIALS AND METHODS

The study was performed using 32 male Wistar-Albino rats (weighing 180-200 g) randomly divided into four groups: Group I, sham group; Group II, IR group; Group III, IR with melatonin group; and Group IV, IR with thymoquinone group. After laparotomy, ischemia and reperfusion were performed for 60 and 120 min, respectively, on all the groups. Intestinal tissue sections were stained using routine histological methods and examined under the light microscope. In addition, the sections were immunohistochemically stained using the TUNEL method for determination of apoptosis. Superoxide dismutase (SOD) activity, glutathione peroxidase (GSH-Px) activity, and malondialdehyde (MDA) levels in the intestinal tissue were also measured.

RESULTS

The IR group had significantly elevated tissue SOD activity, GSH-Px activity, and MDA levels compared with the sham group. Administration of thymoquinone and melatonin efficiently reduced these increases. Statistically significant number of apoptotic cells was observed in the intestinal tissue of IR group rats compared with the sham group. Treatment with thymoquinone and melatonin markedly reduced the number of apoptotic cells.

CONCLUSION

The effects of melatonin and thymoquinone on IR-induced oxidative stress in rat intestines were similar. Our findings suggest that melatonin and thymoquinone protect against IR-induced injury to intestinal tissues.

Effect of montmorillonite powder and mesalazine on intestinal epithelial cell apoptosis in rats with ulcerative colitis

AIM: To assess the effect of montmorillonite powder (Smecta) and mesalazine, alone or in combination, on intestinal epithelial cell apoptosis in rats with 2,4,6-trinitrobenzene sulfonic acid (TNBS) induced colitis.

METHODS: Eighty-two male SD rats were randomly divided into a normal group, a model group and three intervention groups including Smecta group, mesalazine group, and mesalazine plus Smecta group. Ulcerative colitis (UC) was induced in rats by the TNBS/ethanol method. The model group was daily treated with normal saline, and the intervention groups were intragastrically treated with Smecta, mesalazine, mesalazine plus Smecta, respectively. Rats were killed on days 5 and 12 after treatment to collect colon specimens. Terminal-deoxynucleoitidyl transferase mediated nick end labeling (TUNEL) method was used to assay intestinal cell apoptosis rate.

RESULTS: The rats treated with TNBS/ethanol had diarrhea with bloody stools and weight loss 24 h after model creation. Light and electronic microscopic analyses showed large mucosal ulceration area accompanied by neutrophil infiltration, damaged gland structural and decreased goblet cells. Compared with the normal group, intestinal epithelial cell apoptosis rates in the model group and three intervention groups were significantly increased on days 5 and 12 (H₅ = 439.78, H₁₂ = 84.03, P = 0.000). Compared with the model group, intestinal epithelial cell apoptosis rates in the three intervention groups were significantly lower on days 5 and 12 (P = 0.000). The apoptosis rates in the combination group were more significantly lower than those in the two monotherapy groups (P = 0.000). The apoptosis rates in the three intervention groups on day 12 were more significantly lower than those on day 5 (P = 0.000).

CONCLUSION: Intestinal epithelial cell apoptosis is involved in the pathogenesis of UC. Montmorillonite powder combined with mesalazine therapy has a synergistic inhibitory effect on apoptosis. The inhibitory effect on apoptosis is better on day 12 than on day 5.

Transduced PEP-1-heme oxygenase-1 fusion protein protects against intestinal ischemia/reperfusion injury

BACKGROUND

Heme oxygenase-1 (HO-1) has been shown to have antioxidant and anti-apoptotic properties. The present study transduced HO-1 protein into intestinal tissues using PEP-1, a cell-penetrating peptide, and investigated its potentiality in prevention against intestinal ischemia/reperfusion (I/R) injury.

MATERIALS AND METHODS

PEP-1-HO-1 fusion protein was administered intravenously to explore the time and dose characteristics through measuring serum HO-1 levels. Twenty-four male Sprague-Dawley rats were randomly divided into three groups: sham, intestinal I/R (II/R), II/R + PEP-1-HO-1 fusion protein (HO). The model was established by occluding the superior mesenteric artery for 45 min followed by 120 min reperfusion. In HO group, PEP-1-HO-1 was administered intravenously 30 min before ischemia, whereas animals in sham and II/R groups received the equal volume of physiological saline. After the experiment, the intestines were harvested for determination of histologic injury, wet/dry ratio, enzyme activity, apoptosis, and His-probe protein (one part of PEP-1-HO-1).

RESULTS

Levels of serum HO-1 were dose- and time-dependent manner after intravenous injection of PEP-1-HO-1. I/R caused deterioration of histologic characteristics and increases in histologic injury scoring, wet/dry ratio, myeloperoxidase activity, malondialdehyde, and intestinal apoptosis. These changes were also accompanied by a decrease in superoxide dismutase activity (P < 0.05). PEP-1-HO-1 treatment significantly reversed these changes (P < 0.05). Furthermore, His-probe protein expression was only detected in PEP-1-HO-1-treated animals.

CONCLUSION

Treatment of PEP-1-HO-1 attenuates intestinal I/R injury, which might be attributable to its antioxidant and anti-apoptotic roles of HO-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.

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

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

Endotoxin level in ischemia-reperfusion injury in rats: effect of glutamine pretreatment on endotoxin levels and gut morphology

OBJECTIVE

We aimed to investigate the effect of enteral glutamine (Gln) pretreatment on plasma endotoxin level and intestinal histopathologic changes during intestinal ischemia-reperfusion (I/R) injury in rats.

METHODS

Intestinal I/R was induced by 60-min occlusion of the superior mesenteric artery followed by 60 min of reperfusion. Animals were pretreated with Gln by orogastric route for different periods and doses. To investigate the effects of gut decontamination on intestinal I/R injury, animals were pretreated with neomycin sulfate and erythromycin phosphate by orogastric route. In another series, dl-alpha-tocopherol hydrogen succinate was used to investigate the effects of vitamin E on intestinal I/R injury. Plasma endotoxin level was measured by the colorimetric "limulus amebocyte lysate" test. Intestinal mucosal injury was scored on a scale described by Chiu et al. (Archive in Surgery 1970;101:478-483).

RESULTS

Intestinal I/R increased the plasma endotoxin level and worsened the histopathologic score significantly. Gln pretreatment (1g/kg) for 4 d reduced the I/R-induced elevation of plasma endotoxin level. However, a significant improvement in histopathologic score could only be achieved when the pretreatment was given for 7 d. Antibiotic pretreatment lowered plasma endotoxin level without affecting the I/R-induced histopathologic changes, whereas vitamin E pretreatment affected plasma endotoxin level and histopathologic changes.

CONCLUSION

These results suggest a lack of association between plasma endotoxin level and intestinal histopathologic alterations in intestinal I/R.

The role of oxygen-free radical in the apoptosis of enterocytes and bacterial translocation in abdominal compartment syndrome

BACKGROUND

The purpose of this study was to study the impact of intra-abdominal hypertension (IAH) on the intestine.

MATERIALS AND METHODS

One hundred and twenty Sprague-Daley rats were divided into four groups. In the ACS group, the intra-abdominal pressure (IAP) was increased to 20 mmHg. In the ACS/DE group, increased IAP was followed by decompression. In the control1 and control2 groups, the IAP remained unchanged. Malondialdehyde (MDA), myeloperoxidase (MPO), glutathione (GSH) and glutathione peroxidase (GSH-Px) enzymes of the intestine were measured. Additionally, ileal tissues were obtained for histopathological examinations and apoptosis detection. Liver, spleen and mesenteric lymph nodes were obtained for microbiological analysis.

RESULTS

In the presence of IAH, MDA and MPO were increased, while GSH and GSH-Px were decreased. Microbiological analysis suggested bacterial translocation across the gut. Morphological examinations indicated that the Chiu's score and apoptotic index in the ACS/DE group were the highest in the four groups.

CONCLUSIONS

Oxidative stress plays an important role in the intestinal damage and bacterial translocation in abdominal compartment syndrome. Additionally, the influence of oxygen free radicals occurs mainly during the period of reperfusion rather than during the IAH period.

Advance in enteric epithelial barrier and inflammatory bowel disease

Enteric epithelial barrier injury is a new field of the study on the cellular and molecular pathegenesis of inflammatory bowel disease (IBD) in recent years. The enteric epithelial barrier is one of the most important line of defense. Once the enteric epithelial barrier, one of the most important defense line in intestinal mucosa, is damaged, the permeability of enteric epithelium will increase, which is significantly involved in the genesis of IBD. At present, most researches mainly concentrate on the changes of intestinal epithelial cells and the structure and function of intercellular tight junction. Maintenance and repair of enteric epithelial barrier may be the ideal strategy for IBD therapy.

Prophylaxis with mesna prevents oxidative stress induced by ischemia reperfusion in the intestine via inhibition of nuclear factor-kappaB activation

BACKGROUND AND AIM

Mesna (2-mercaptoethane-sulfonate) has been shown to attenuate oxidative injury induced by ischemia reperfusion (I/R) in the kidneys, the liver, and the intestine; however, its mechanism of action has not been fully elucidated. We sought to determine a prophylactic administration schedule of mesna that would confer optimal antioxidant protection on the intestinal mucosa following I/R and to investigate whether mesna's action is mediated via inhibition of nuclear factor-kappaB (NF-kappaB) activity.

METHODS

Wistar rats were subjected to one of the following: (a) induction of 30 min ischemia followed by 60 min reperfusion (I30/R60) of the intestine, (b) pretreatment with intraperitoneal or oral mesna at various time- and dose- administration schedules plus I30/R60, (c) sham operation, (d) no operation (controls), or (e) oral mesna alone. At the end of the reperfusion period or at various time points after mesna alone administration, the oxidative state of the intestinal mucosa was assessed in terms of glutathione to glutathione disulfide ratio, malondialdehyde concentration, and superoxide dismutase activity. In addition, NF-kappaB activity in the intestinal mucosa was assessed immunohistochemically in the oral mesna plus I/R and in the oral mesna alone groups.

RESULTS

Sham operation caused mild stress, while I/R caused substantial oxidative stress in the intestinal mucosa. Mesna pretreatment had an antioxidant effect which varied from attenuation to prevention of oxidative stress. Over the two routes of administration, the oral proved to be more effective and had a time- and dose- dependent effect. The antioxidant action of mesna was not related to enhancement of the intestinal mucosa oxidative state. Furthermore, I/R induced NF-kappaB activation in the intestinal mucosa which was inhibited by mesna pretreatment. In the absence of oxidative damage, mesna led to downregulation of activated NF-kappaB.

CONCLUSIONS

Prophylaxis with mesna prevents oxidative stress induced by I/R in the intestine via inhibition of NF-kappaB activation.

Enteral glutamine pretreatment does not decrease plasma endotoxin level induced by ischemia-reperfusion injury in rats

AIM: To investigate whether oral glutamine pretreatment prevents impairment of intestinal mucosal integrity during ischemia-reperfusion (I/R) in rats.

METHODS: The study was performed as two series with 40 rats in each. Each series of animals was divided into four groups. The first group was used as a control. Animals in the second group were only pretreated with oral glutamine, 1 g/kg for 4 d. The third group received a normal diet, and underwent intestinal I/R, while the fourth group was pretreated with oral glutamine in the same way, and underwent intestinal I/R. Intestinal mucosal permeability to ⁵¹Cr-labeled EDTA was measured in urine in the first series of animals. In the second series, histopathological changes in intestinal tissue and plasma endotoxin levels were evaluated.

RESULTS: Intestinal I/R produced a significant increase in intestinal permeability, plasma endotoxin level and worsened histopathological alterations. After intestinal I/R, permeability was significantly lower in glutamine-treated rats compared to those which received a normal diet. However, no significant change was observed in plasma endotoxin levels or histopathological findings.

CONCLUSION: Although glutamine pretreatment seems to be protective of intestinal integrity, upon I/R injury, such an effect was not observable in the histopathological changes or plasma endotoxin level.

Erythropoietin protects the intestine against ischemia/ reperfusion injury in rats

Previous studies have shown that erythropoietin (EPO) has protective effects against ischemia/reperfusion (I/R) injury in several tissues. The aim of this study was to determine whether EPO could prevent intestinal tissue injury induced by I/R. Wistar rats were subjected to intestinal ischemia (30 min) and reperfusion (60 min). A single dose of EPO (5000 U/kg) was administered intraperitoneally at two different time points: either at five minutes before the onset of ischemia or at the onset of reperfusion. At the end of the reperfusion period, jejunum was removed for examinations. Myeloperoxidase (MPO), malondialdehyde (MDA), and antioxidant defense system were assessed by biochemical analyses. Histological evaluation was performed according to the Chiu scoring method. Endothelial nitric oxide synthase (eNOS) was demonstrated by immunohistochemistry. Apoptotic cells were determined by TUNEL staining. Compared with the sham, I/R caused intestinal tissue injury (Chiu score, 3+/-0.36 vs 0.4+/-0.24, P<0.01) and was accompanied by increases in MDA levels (0.747+/-0.076 vs 0.492+/-0.033, P<0.05), MPO activity (10.51+/-1.87 vs 4.3+/-0.45, P<0.05), intensity of eNOS immunolabelling (3+/-0.4 vs 1.3+/-0.33, P<0.05), the number of TUNEL-positive cells (20.4+/-2.6 vs 4.6+/-1.2, P<0.001), and a decrease in catalase activity (16.83+/-2.6 vs 43.15+/-4.7, P<0.01). Compared with the vehicle-treated I/R, EPO improved tissue injury; decreased the intensity of eNOS immunolabelling (1.6+/-0.24 vs 3+/-0.4, P<0.05), the number of TUNEL-positive cells (9.2+/-2.7 vs 20.4+/-2.6, P<0.01), and the high histological scores (1+/-0.51 vs 3+/-0.36, P<0.01), and increased catalase activity (42.85+/-6 vs 16.83+/-2.6, P<0.01) when given before ischemia, while it was found to have decreased the levels of MDA (0.483+/-0.025 vs 0.747+/-0.076, P<0.05) and MPO activity (3.86+/-0.76 vs 10.51+/-1.87, P<0.05), intensity of eNOS immunolabelling (1.4+/-0.24 vs 3+/-0.4, P<0.01), the number of TUNEL-positive cells (9.1+/-3 vs 20.4+/-2.6, P<0.01), and the number of high histological scores (1.16+/-0.4 vs 3+/-0.36, P<0.05) when given at the onset of reperfusion. These results demonstrate that EPO protects against intestinal I/R injury in rats by reducing oxidative stress and apoptosis. We attributed this beneficial effect to the antioxidative properties of EPO.

“Systemic apoptotic response” after thermal burns

The systemic pathophysiologic changes following thermal injuries affect multiple organs and body systems leading to clinical manifestations including shock, intestinal alterations, respiratory and renal failure, immunosuppression and others. Recent advances in the comprehension of mechanisms underlying systemic complications of thermal injuries have contributed to uncover part of the cellular and molecular basis that underlie such changes. Recently, programmed cell death (apoptosis) has been considered playing an important role in the development of such pathological events. Therefore, investigators utilizing animal models and clinical studies involving human primates have produced a large body of information suggesting that apoptosis is associated with most of the tissue damages triggered by severe thermal injuries. In order to draw the attention on the important role of apoptosis on systemic complications of thermal injuries, in this review we describe most of these studies, discuss possible cellular and molecular mechanisms and indicate ways to utilize them for the development of therapeutic strategies by which apoptosis may be prevented or counteracted.

Hibernation confers resistance to intestinal ischemia-reperfusion injury

The damaging effects of intestinal ischemia-reperfusion (I/R) on the gut and remote organs can be attenuated by subjecting the intestine to a prior, less severe I/R insult, a process known as preconditioning. Because intestines of hibernating ground squirrels experience repeated cycles of hypoperfusion and reperfusion, we examined whether hibernation serves as a model for natural preconditioning against I/R-induced injury. We induced intestinal I/R in either the entire gut or in isolated intestinal loops using rats, summer ground squirrels, and hibernating squirrels during natural interbout arousals (IBA; body temperature 37-39 degrees C). In both models, I/R induced less mucosal damage in IBA squirrels than in summer squirrels or rats. Superior mesenteric artery I/R increased MPO activity in the gut mucosa and lung of rats and summer squirrels and the liver of rats but had no effect in IBA squirrels. I/R in isolated loops increased luminal albumin levels, suggesting increased gut permeability in rats and summer squirrels but not IBA squirrels. The results suggest that the hibernation phenotype is associated with natural protection against intestinal I/R injury.

Mesna Protects Intestinal Mucosa from Ischemia/Reperfusion Injury

BACKGROUND

Mesna is a thiol used for the prevention of oxazaphosphorine-induced hemorrhagic cystitis. However, its antioxidant properties on renal and hepatorenal oxidative damage, as well as its mucoprotective effect on the intestinal epithelium have also been shown. The aim of this study was to investigate the potential beneficial effect of mesna on ischemia/reperfusion (I/R)-induced oxidant damage of the intestinal mucosa.

MATERIALS AND METHODS

Wistar rats were subjected to intestinal I/R for 30 min, induced by occlusion of the superior mesenteric artery, followed by 60 min reperfusion. Mesna was administered at 3 time points relative to ischemia; 60 min before ischemia, at the onset of ischemia or at the onset of reperfusion. At the end of the study period, jejunal segments were excised and assessed for histopathologic score, apoptotic index using the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick-end labeling (TUNEL) assay and glutathione/glutathione disulfide (GSH/GSSG) ratio, as a marker of oxidative stress.

RESULTS

I/R caused deterioration of histological characteristics and induction of apoptosis and oxidative stress in the intestinal mucosa. Changes regarding histology and apoptosis were prevented when mesna was administered 60 min before ischemia, but were attenuated when mesna was administered at the onset of ischemia or reperfusion. In all mesna groups, oxidative stress was reduced.

CONCLUSIONS

Mesna can ameliorate or even prevent intestinal I/R injury by reducing oxidative stress.

The effect of thalidomide on spinal cord ischemia/reperfusion injury in a rabbit model

STUDY DESIGN

Randomized study.

OBJECTIVES

To evaluate the effects of thalidomide on spinal cord ischemia/reperfusion injury via reduced TNF-alpha production.

SETTING

Animal experimental laboratory, Clinical Research Institute of Seoul National University Hospital, Seoul, Korea.

METHODS

Spinal cord ischemia was induced in rabbits by occluding the infrarenal aorta. Rabbits in group N did not undergo ischemic insult, but rabbits in groups C (the untreated group), THA, and THB underwent ischemic insult for 15 min. The THA and THB groups received thalidomide (20 mg/kg) intraperitoneally (i.p.) before ischemia, but only the THB group received thalidomide (i.p., 20 mg/kg) after 24 and 48 h of reperfusion. After evaluating neurologic functions at 1.5 h, 3, and 5 days of reperfusion, rabbits were killed for histopathologic examination and Western blot analysis of TNF-alpha.

RESULTS

The THA and THB groups showed significantly less neurologic dysfunction than the C group at 1.5 h, 3, and 5 days of reperfusion. The number of normal spinal motor neurons in ventral gray matter was higher in THA and THB than in C, but no difference was observed between THA and THB. Western blot analysis showed a significantly higher level of TNF-alpha in C than in THA and THB at 1.5 h of reperfusion, but no difference was observed between C, THA, or THB at 3 or 5 days of reperfusion.

CONCLUSION

Thalidomide treatment before ischemic insult reduces early phase ischemia/reperfusion injury of the spinal cord in rabbits.

The inhibitory effects of rebamipide on cigarette smoke-induced airway mucin production

Cigarette smoke may be the main cause of chronic bronchitis. Exposure of cigarette smoke induces the recruitment of inflammatory cells in the airway epithelium, and release of the tumor necrosis factor alpha (TNFalpha) from airways. Previous reports have shown that cigarette smoke induces goblet cell metaplasia by activating an epidermal growth factor receptor (EGFR) cascade, and that this results in mucin production. Rebamipide (2-(4-chlorobenzoylamino)-3-[2(1H)-quinolinon-4-yl] propionic acid, OPC-12759) directly inhibits the production of superoxide (O2-) and inhibits proinflammatory cytokines (such as TNFalpha and IL-8). In the present study, we aimed to analyze the inhibitory effects of rebamipide on TNFalpha and EGFR activation after cigarette smoke treatment in vitro and in vivo. NCl-H292 cells and Sprague-Dawley rats were used for in vitro and in vivo studies. In vitro studies, cigarette smoke solution was found to increase TNFalpha secretion, and EGFR-specific tyrosine phosphorylation, and to elevate MUC5AC production. These effects were inhibited dose-dependently by pretreatment with rebamipide (MUC5AC protein levels were inhibited from 44% to 17%, P<0.05). In vivo studies, cigarette smoke was found to cause inflammatory cell recruitment and to increase the secretion of TNFalpha in bronchoalveolar lavage (BAL) fluids (from 198+/-78 to 2270+/-158 pg/ml, P<0.01). Moreover, the pretreatment of rats with rebamipide inhibited goblet cell metaplasia and TNFalpha secretion, dose-dependently (from 2270+/-158 to 1377+/-112 pg/ml, P<0.05). In conclusion, the exposure of airway epithelium to cigarette smoke-induced TNFalpha production, neutrophil recruitment, activated EGFR, and caused MUC5AC mucin synthesis. Moreover, rebamipide was found to prevent this cigarette smoke-induced TNFalpha release, and mucin production.

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Polyethylene glycol but not mifepristone prevents intestinal lymphocyte loss following treadmill exercise in mice

Circulating lymphocyte numbers decrease following intense physical activity, possibly due to exercise-induced apoptosis. Increased reactive oxygen species (ROS) and glucocorticoids (GC) following exercise contribute to lymphocyte apoptosis. Intestinal lymphocyte (IL) numbers also decrease following exercise.

AIM

The purpose of this study was to determine the contribution of GC to exercise-induced IL loss.

METHODS

Female C57BL/6 mice (n = 178) were randomized to five drug conditions: (1) single injection of the glucocorticoid receptor antagonist mifepristone (MIF) solubilized in polyethylene glycol (PEG); (2) three injections of MIF (repeated MIF) PEG; (3) single injection of PEG (PEG); (4) three injections of PEG (repeated PEG); or (5) repeated injections of saline (SAL). Within each drug group mice were further randomized to exercise conditions: (1) control condition (non-exercised); (2) treadmill running with sacrifice immediately following the exercise; or (3) treadmill running with sacrifice 24 h after completion of the exercise.

RESULTS

There was a significant exercise effect, across all T lymphocyte subsets, in SAL (P < 0.01), PEG (P < 0.01) and MIF (P < 0.01) treated mice but not in mice given repeated PEG or repeated MIF exposure. The exercise effect was due to reduced IL numbers 24 h post-exercise compared with non-exercised controls.

CONCLUSION

These results suggest that GC are not directly responsible for IL cell loss following exercise. Repeated exposure to PEG may confer protection in the gastrointestinal tract from exercise-induced lymphocyte depletion. Because PEG inhibits ROS generation in experimental cell injury, the mechanisms for IL loss after exercise may involve oxidative stress.

Adrenalectomy in mice does not prevent loss of intestinal lymphocytes after exercise

Exhaustive exercise is associated with an increase in circulating glucocorticoids (GCs), lymphocyte apoptosis, and a reduction in intestinal lymphocyte number. The present study examined the role of GCs on the numerical changes seen in intestinal lymphocytes after exercise. Female C57BL/6 mice were bilaterally adrenalectomized (ADX; n = 18) or given sham surgery (Sham; n = 18) and assigned to one of three exercise conditions: treadmill running (28 m/min, 90 min, 2 degrees slope) and killed immediately or after 24 h recovery, or not exercised and killed immediately after 90-min exposure to the treadmill environment. Lymphocytes were isolated from the intestines with CD45(+) cells collected by positive selection using magnetic bead separation columns, and lymphocyte subpopulations were analyzed by flow cytometry for CD45(+), CD3alphabeta(+), CD3gammadelta(+), CD8beta(+), CD8alpha(+), CD4(+), and NK(+) phenotypic markers. ADX mice had significantly more intestinal CD45(+) leukocytes (P < 0.05) and CD3alphabeta(+) (P < 0.05), CD3gammadelta(+) (P < 0.01), CD8alpha(+) (P < 0.001), and NK(+) (P < 0.05) intestinal lymphocytes than Sham mice. There was a significant effect of exercise condition on total intestinal CD45(+) leukocytes (P < 0.01) and CD3alphabeta(+) (P < 0.05), CD8alpha(+) (P < 0.001), and CD4(+) (P < 0.05) intestinal lymphocytes, with fewer cells at 24 h postexercise compared with the other treatment conditions. There were no surgical x exercise interaction effects on the CD3 and CD8 phenotype numbers. Plasma corticosterone was virtually nil in ADX mice regardless of exercise condition but was significantly elevated in Sham mice immediately postexercise (P < 0.001). The data indicate that ADX does not prevent the loss of lymphocytes from the intestinal mucosa 24 h after strenuous exercise and GCs are not directly causal in the leukopenia of exercise.

Ischemic preconditioning attenuates ischemia-reperfusion-induced mucosal apoptosis by inhibiting the mitochondria-dependent pathway in rat small intestine

Ischemic preconditioning provides a way of protecting organs from damage inflicted with prolonged ischemia-reperfusion. In this study, we investigated the mechanism of ischemic preconditioning involved in inhibition of prolonged ischemia-reperfusion-induced mucosal apoptosis in rat small intestine. Ischemic preconditioning was triggered by a transient occlusion of the superior mesenteric artery followed by reperfusion. Ischemia-reperfusion was induced by 60-min occlusion of the superior mesenteric artery followed by 60-min reperfusion in the small intestine. Ischemia-reperfusion alone induced mucosal apoptosis and mitochondrial respiratory dysfunction via promoted reactive oxygen species generation, reduced mitochondrial glutathione oxidation, increased mitochondrial lipid peroxidation, reduced mitochondrial membrane potential, and enhanced release of cytochrome c from mitochondria to activate caspase-9 and caspase-6 in the small intestine. Pretreatment with 20-min ischemia followed by 5-min reperfusion significantly inhibited the prolonged ischemia-reperfusion-induced mucosal apoptosis by 30%. Ischemic preconditioning ameliorated mitochondrial respiratory dysfunction by 50%, reduced reactive oxygen species generation by 38%, and suppressed mitochondrial lipid peroxidation by 36%, resulting in improvement of the mitochondrial membrane potential and prevention of cytochrome c release as well as caspase-6 activation. Results suggest that ischemic preconditioning attenuated ischemia-reperfusion-induced mucosal apoptosis partly by inhibiting the reactive oxygen species-mediated mitochondria-dependent pathway in the rat small intestine.