Different Intervals of Ischemic Preconditioning on Small Bowel Ischemia-Reperfusion Injury in Rats

Purpose

The purpose of this study was to establish morphologically the best time of vascular occlusion to induce ischemic preconditioning (IPC) for rat small bowel undergoing ischemia and reperfusion injury.

Methods

After approval by the Ethics Committee, 36 EPM-1 young adult Wistar rats from 300-350 g were distributed into 6 groups: sham (S); ischemia and reperfusion (IR), with 50 minutes of cranial mesenteric artery occlusion and 30 minutes of reperfusion; IPC with 1 cycle of 2 minutes (IPC-2), 5 minutes (IPC-5), 10 minutes (IPC-10), or 15 minutes (IPC-15), followed by sustained IR. The animals anesthetized with ketamine (60 mg/kg) and xylazine (10 mg/kg) intramuscular (IM), were maintained on mattress heat, hydrated with saline (80 mL/kg), and injected with 100 IU heparin. Samples of jejunum were stained with hematoxylin and eosin (HE) and classified according to Park et al. Statistical analysis of results was performed using Kruskal-Wallis tests (P < .05).

Results

The histological evaluation showed no difference between IR and IPC15 rats (5.2 and 5, respectively; P = .84). Greater jejunal injury was observed with IPC15 (5) compared with other groups (IPC2 = 3, P = .03; IPC5 = 3.2, P = .05; IPC10 = 2.8, P = .02, respectively). There was no difference between groups IPC2 × IPC5 × IPC10.

Conclusion

Morphologically, IPC with short times promoted greater intestinal protection against the IR lesion in rats.     

Effects of tetrandrine on ischemia/reperfusion injury in mouse liver

Objective

Hepatic ischemia/reperfusion injury (IRI) may cause acute inflammatory damage, producing significant organ dysfunction, an important problem for liver transplantation. Previous studies have demonstrated that Tetrandrine (Tet), a component of traditional Chinese herbal medicine, shows protective effects to scavenge active oxygen radicals and inhibit lipid peroxidation. In this study, we examined whether Tet has a protective effect on mouse hepatic IRI.

Materials and Methods

Male C57BL/6 mice were divided into sham, ischemic, and Tet-treated groups; 90 minutes of warm ischemia was performed on the left liver lobe. Tet (20 mg/kg) was injected intraperitoneally at 1 hour before ischemia with a second intravenous dose was injected just before reperfusion. Blood and liver samples were collected at 6 hours after reperfusion. We analyzed the hepatocellular injury, oxidative stress, neutrophil recruitment, and tumor necrosis factor-alpha (TNF-α) generation associated with hepatic IRI.

Results

Undergoing 90 minutes of ischemia and 6 hours reperfusion caused dramatic injuries in mouse livers. Administration of Tet (20 mg/kg) reduced serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH); decreased liver edema, TNF-α, myeloperoxidase (MPO) and malondialdehyde (MDA) contents; and ameliorated the down-regulation of superoxide dismutase (SOD) activity.

Conclusion

Tet showed protective effects on mouse hepatic IRI.     

Hepatic stellate cell activation and hepatic fibrosis induced by ischemia/reperfusion injury

Objective

Warm ischemia causes severe allograft damage in liver transplantation. However, the long-term effects of ischemia/reperfusion injury (IRI) on fibrosis have not been fully elucidated. In this study, we used a partial warm hepatic ischemia mouse model to monitor fibrosis in the ischemic liver.

Materials and Methods

Male BALB/c mice were divided into ischemic and sham groups (n = 30/group). Via a midline laparotomy, an atraumatic clip was used to interrupt the arterial and the portal venous blood supply to the left liver lobe. After 90 minutes of partial hepatic ischemia, the clip was removed initiating hepatic reperfusion. Samples from normal, sham, and ischemic liver tissues were collected at intervals of 1, 5, 10, 15, 20, or 30 days after operation (n = 5 for each time point) for hematoxylin-eosin (H&E), Mallory's trichrome, and alpha-smooth muscle actin (α-SMA) immunohistochemical stains for fibrosis and activation of hepatic stellate cell (HSCs).

Results

IRI caused significant HSC activation in the ischemic liver tissues. Mallory's trichrome stain demonstrated that IRI caused hepatic parenchymal fibrosis near portal tracts and central veins. With prolonged reperfusion time hepatic parenchymal fibrosis was aggravated, showing the same pattern of HSC activation. IRI also caused increased portal tract fibrosis in ischemic liver tissues, especially around biliary tracts.

Conclusions

Hepatic IRI caused HSC activation, increasing hepatic parenchymal and portal tract fibrosis in ischemic liver tissues.     

Sympathetic Nerves Do Not Affect Experimental Ischemia-Reperfusion Injury of Rat Liver

Background

We investigated whether sympathetic, noradrenergic nerves participate in experimental acute ischemia-reperfusion injury of the rat liver.

Methods

Female Wistar rats (200-250 g body weight) were anesthetized with pentobarbital. After tracheotomy, we cannulated a carotid artery and jugular vein. The rats were divided in 2 groups (n = 8 per group). The control group received NaCl IV and the test group received the sympatholytic agent, guanethidine (3 mg/kg, IV). After 30 minutes of drug equilibration, laparotomy was performed to arrange the liver for temporary occlusion (by a ligature) of its vascular supply, corresponding with 70% reduction in hepatic blood flow. The rats were then allowed 60 minutes of equilibration. Thereafter, regional ischemia was induced for 30 minutes. The animals were then monitored for 2 hours of reperfusion. Blood samples for alanine aminotransferase (ALT) estimation (as a measure of injury to the parenchyma) were drawn immediately before ischemia, as well as 60 and 120 minutes after reperfusion. Readings of mean arterial pressure were taken during these times.

Results

After 2 hours of reperfusion, there were no significant differences between the groups with regard to ALT or mean arterial pressure.

Conclusion

Sympathetic, noradrenergic nerves did not affect experimental ischemia-reperfusion injury of rat liver in the current model.     

Myocardial protection with postconditioning is not enhanced by ischemic preconditioning

Background

Ischemic preconditioning (IPC) has been used in off-pump coronary artery bypass surgery (OPCAB) to reduce potential injury secondary to ligation of the target vessel. Previous studies have shown that a brief period of repetitive coronary occlusion applied at the onset of reperfusion, postconditioning (postcon), attenuates myocardial injury. This study tested the hypothesis that coincident application of IPC and postcon would provide more cardioprotection than either intervention alone by inhibiting oxidant-mediated injury after ischemia and reperfusion.

Methods

Four groups of open-chest canines endured 60 minutes coronary occlusion followed by 3 hours reperfusion: control (n = 10), no intervention; IPC (n = 9), 5 minutes left anterior descending coronary artery occlusion preceded 10 minutes of reperfusion before prolonged occlusion; postcon (n = 10), 3 cycles of 30 seconds reperfusion-30 seconds reocclusion were imposed immediately upon reperfusion; IPC+postcon (n = 8), IPC and postcon algorithms were combined.

Results

Collateral blood flow during ischemia was similar in all groups. Compared to control (24% ± 2%), infarct size was comparably reduced in IPC (13% ± 2%* [* denotes p less than 0.05 compared with control]), and postcon (10% ± 1%*), consistent with a reduction in plasma creative kinase activity in these groups; infarct size was not further reduced by IPC+postcon (12% ± 3%*). Tissue water content in ischemic myocardium was comparably reduced in IPC, postcon, and IPC+postcon compared to control. Superoxide anion generation detected by dihydroethidium staining in area at risk myocardium was comparably reduced in all intervention groups relative to control. Plasma malondialdehyde (μM), a lipid peroxidation byproduct of oxidant injury, was less at 1 hour of reperfusion in IPC (2.2 ± 0.2*), postcon (2.1 ± 0.2*), and IPC+postcon (2.5 ± 0.2*) relative to control (3.3 ± 0.2). Ventricular fibrillation occurred less often in all intervention groups.

Conclusions

No additive cardioprotective effects by IPC and postcon were observed in a canine model of regional ischemia and reperfusion. The potent attenuation of myocardial injury by postcon may suggest a clinically applicable strategy during some surgical revascularization procedures (ie, OPCAB).     

Influence of ischemic preconditioning and nitric oxide on microcirculation and the degree of rat liver injury in the model of ischemia and reperfusion

The aim of this study was to assess the influence of ischemic preconditioning (IPC) on parenchymal liver blood flow during the early phase of reperfusion after 60 minutes of ischemia, additionally modified by adding N-nitro-L-arginine methyl ester (L-NAME). Our research involved 4 groups of rats (10 animals in each group), which underwent liver ischemia and 24 hours of reperfusion. Group I, ischemia/reperfusion (IR) was performed; group II, IPC, 10 minutes of ischemia and 10 minutes of reperfusion, and IR after that; group III, L-NAME (10 mg/kg intravenous [iv]), 10 minutes before IR; and group IV, L-NAME before IPC + IR. Activity of APAT, ALAT, GGTP, and FA was marked in serum in 90 minutes and 24 hours of reperfusion. In the liver biopsies at 24 hours of reperfusion, we analyzed reaction on adenosine-3-phosphatase stimulated by Mg++ and performed histological examination. The parenchymal perfusion was measured using a laser-doppler blood flowmeter (model PeriFlux System5000, Perimed Inc., United Kingdom). IPC during reperfusion led to minor injuries of the organ, with statistically significant normalization of enzymes compared with group 1, and a better reaction to the adenosine-3-phosphatase IPC produced faster and full return of perfusion to the 68.3 value at 24 hours (59.1 in the 60 minutes). In groups III and IV at 60 minutes, the perfusion was not statistically different from that in group 1. IPC causes full and faster blood return in the early phase of reperfusion and minor injury of liver parenchyma and liver sinus. The protective effect observed, especially in the first 60 minutes of reperfusion, was limited by L-NAME and was influenced by the action of nitric oxide.     

Ischemic preconditioning of small bowel mitigates the late phase of reperfusion injury: heme oxygenase mediates cytoprotection

Background

Ischemia and reperfusion (IR) injury of the intestine is a major cause of morbidity and mortality following small bowel transplantation. The current study evaluates the effect of ischemic preconditioning (IPC) on the intestinal microcirculation in the late phase of IR injury of the intestine.

Methods

Sixty rats were randomly allocated to 5 study groups (n = 12 per group): (1) sham, (2) IR (3) IPC, (4) pyrrolidine dithiocarbamate (PDTC) (HO-1 inducer), and (5) zinc protoporhyrin (ZnPP) (HO-1 inhibitor). Mucosal perfusion and leukocyte-endothelial interactions were measured with the aid of an intravital microscope. At the end of the experiments, blood samples for lactate dehydrogenase (LDH) levels and biopsies of ileum for histologic evaluation were obtained.

Results

IPC significantly improved the mucosal perfusion and decreased the leukocyte-endothelial interactions. Histologic examination showed that ileal mucosa was significantly less injured in the IPC and PDTC groups as compared with the IR group.

Conclusions

IPC protects the intestine from late reperfusion injury. HO-1 is involved in this protection. These findings may be of significant importance in clinical small bowel transplantation.     

Propofol attenuates ischemic reperfusion-induced formation of lipid peroxides in liver transplant recipients

Objective

Ischemic reperfusion (IR) injury is known to have an important influence on the success of transplant surgery and the occurrence of complications. Malondialdehyde (MDA) is an intermediate metabolite of lipid peroxidation resulting from IR-induced reactive oxygen species. This study was designed to investigate the protective effects of propofol on IR injury in liver transplant recipients.

Methods

We analyzed 19 recipients prospectively by measuring the blood levels of MDA at nine predefined intervals; before induction of anesthesia (baseline, T0), 1 hour after surgical incision (T1), 1 minute before reperfusion (T2), 30 seconds after reperfusion (T3), as well as 1, 3, 5, 30, and 60 minutes thereafter (T4-8). These patients were randomly allocated to two groups. The propofol group received an infusion (2 mg/kg per hr) after an induction bolus (2 mg/kg). The control group was prescribed midazolam (0.2 mg/kg) for induction without intravenous anesthetic infusion for maintenance.

Results

The highest MDA level occured at T6 in the controls and T7 in the propofol group. Compared with the blood levels at baseline, the MDA levels increased significantly at T2-T8 among controls versus T2, T3, T4, and T7 in the propofol group. Compared to the control group, propofol significantly lowered MDA values at T5-T8.

Conclusion

There were significantly higher MDA levels among the control versus the propofol group at 3, 5, 30, and 60 minutes after reperfusion in liver transplant recipients.     

Effects of the anti-ICAM-1 monoclonal antibody, allopurinol, and methylene blue on intestinal reperfusion injury

Purpose:

The aim of this study was to evaluate the effect of allopurinol, methylene blue, and a monoclonal antibody to the adhesion molecule ICAM-1 in intestinal ischemia and reperfusion injury.

Methods:

The rats were divided into 5 groups. CG (n = 8) was untreated controls, SISG (n = 11) received sterile isotonic saline solution, ICAMG (n = 12) received a monoclonal antibody to rat ICAM-1, ALLOG (n = 12) received allopurinol, and MBG (n = 14) received methylene blue. Intestinal ischemia was performed for 60 minutes followed by 60 minutes of reperfusion. The agents were injected 10 minutes before the reperfusion to animals. After 60 minutes of reperfusion, the plasma samples for myeloperoxidase (MPO) activity, tumor necrosis factor alpha (TNF-α) and uric acid levels, and the intestinal biopsies of ileum and jejunum for histopathologic examination were taken.

Results:

The mucosal damage was attenuated, and TNF-α level significantly decreased in ALLOG and ICAMG compared with SISG. The MPO activity was the lowest in ICAMG, and uric acid level was significantly decreased in ALLOG compared with the other groups. Methylene blue decreased TNF-α response to reperfusion injury but significantly increased the grade of the mucosal damage and the MPO activity.

Conclusions:

This study shows that prereperfusion application of allopurinol and monoclonal antibody to the adhesion molecule ICAM-1 may attenuate the damage caused by intestinal ischemia and reperfusion, but the different time-points for application, the effects observed in the different ischemia and reperfusion durations, and the long-term results also should be investigated in the same experimental model before the final conclusion. Methylene blue was not effective to prevent or attenuate the intestinal tissue injury, but because this was the first study examining the effect of methylene blue on intestinal reperfusion injury, further studies with the different doses, ischemic duration, and application times will be needed.     

Protective role of nitric oxide induced by ischemic preconditioning on cold ischemic-reperfusion injury of rat liver graft

Aims

To investigate the protective role of nitric oxide (NO) induced by ischemic preconditioning (IP) on cold ischemic-reperfusion (IR) injury of rat liver grafts.

Methods

One hundred twenty-eight male Sprague Dawley rats used for orthotopic liver transplantation were randomly divided into four groups (n = 32): administering heparin before ischemic reperfusion (control group); IP with 10-minute ischemia and 10-minute reperfusion before IR (IP group); adenosine before IR (Ade group); and L-NAME (NG-nitro-L-arginine methyl ester) + IP before IR (NAME group). Half of each group were used to investigate 1-week recipient survival rate, and another to obtain blood and hepatic tissue samples after 2-hour reperfusion.

Results

One-week survival bile production, serum NO, and antioxidase activity were higher but serum alanine aminotransferase, tumor necrosis factor-α, and superoxide levels in hepatic tissue were lower in the IP group and Ade group versus the control group or NAME group. Liver sinusoidal endothelial cells in the IP and Ade groups showed less injury than the other groups.

Conclusion

NO induced by IP can improve 1-week survival and rat liver function as well as protect liver sinusoidal endothelial cells.     

Delayed Ischemic Preconditioning Protects Against Liver Ischemia-Reperfusion Injury In Vivo

Objectives

Ischemic preconditioning (IP) affords resistance to liver ischemia-reperfusion (IR) injury, providing an early phase of protection. Development of delayed IP against IR injury was assessed using partial IR in rat liver.

Methods

The IP manuver (10 minutes of ischemia and up to 72 hours of reperfusion) was induced before 1 hour of ischemia and 20 hours of reperfusion. At the end of the reperfusion period, blood and liver samples were analyzed for serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), haptoglobin and tumor necrosis factor-α (TNF-α) levels, hepatic histology, protein carbonyl and glutathione (GSH) contents as well as nuclear factor-κB (NF-κB), and activating protein-1 (AP-1) DNA binding.

Results

The IP manuver significantly increased protein carbonyl/GSH ratios (275%), serum ALT (42%), and AST (58%); these changes normalized after 12 hours. Serum AST, ALT, and LDH levels were significantly increased by IR (4-, 5.6-, and 7.0-fold, respectively), with significant changes in liver histology, protein carbonyl/GSH ratio (481% enhancement), and serum TNF-α (6.1-fold increase). Delayed IP in IR animals reduced serum AST (66%), ALT (57%), and LDH (90%) and liver GSH depletion (89%), with normalization of protein carbonyl content, serum TNF-α levels, and liver histology. Enhanced AP-1/NF-κB DNA binding ratios and diminished haptoglobin expression induced by IR were normalized by IP.

Conclusion

These data support that delayed IP suppresses IR-induced liver injury, oxidative stress, and TNF-α response, which coincide with recovery of IR-altered signaling functions represented by normal AP-1/NF-κB DNA binding ratios and acute phase responses.     

Determination of apparent diffusion coefficient to quantitatively study partial hepatic ischemia reperfusion injury in a rabbit model

Background

Animal models of partial hepatic ischemia-reperfusion injury (IRI) have potential benefits for decision making and clinical management after liver transplantation or massive hepatic resection. We evaluated changes in apparent diffusion coefficient (ADC) in rabbits with partial hepatic IRI using 3.0 T magnetic resonance diffusion-weighted imaging (DWI).

Methods

Rabbits underwent 60 minutes of left lobar ischemia followed by 0.5, 2, 6, 12, 24, or 48 hours of reperfusion (n = 6 each). DWI spin echo-echo planar imaging (SE-EPI) was performed with b values of 50, 100, 200, 300, 500, and 600 s/mm².

Results

There was a significant difference between the ADCs at 0.5 hour and sham groups when b values were <300 s/mm² and between the six hour and sham groups with b = 50 and 100 s/mm². The ADC values were lower in the 24-hour group with b values of 50, 100, 200, and 300 s/mm² (all P < .01) but significantly increased in the 48-hour group when b = 500 and 600 s/mm² compared with the sham group (all P < .01). ADC did not change significantly in the 2-hour and 12-hour groups compared with the control group.

Conclusions

In this study 3.0 T DWI dynamically monitored the pathological processes of liver IRI, revealing the microvascular disorder with a perfusion-sensitive ADC at the lower b values (<300 s/mm²), particularly in the early stages.     

The role of CD14 and Toll-like receptor 4 of Kupffer cells in hepatic ischemia-reperfusion injury in rats

Objective

The objective of this study was to study the role of CD14 and Toll-like receptor 4 (TLR4) in Kupffer cells (KCs) on ischemia reperfusion injury (IRI) in rat liver grafts.

Methods

Isolated KCs were obtained from control, IRI, and IRI plus anti-CD14 antibody groups. We measured messenger RNA (mRNA) and protein expression of the lipopolysaccharide receptor CD14 and TLR4, nuclear factor kappa B (NF-κβ) activity, and TNF-α levels.

Results

mRNA and protein expressions of CD14 and TLR4 were significantly higher in the IRI than in the control group, as were protein expressions of CD14 and TLR4 by flow cytometry and by Western blots. NF-κβ activity and tumor necrosis factor-α level in the IRI group were significantly higher than in the control group (3.17 ± 0.21 and 0.28 ± 0.03 vs 654.2 ± 3.6 pg/mL and 147.4 ± 1.1 pg/mL; t value = 4.11 and 4.29 for each; P < .01). Compared with the IRI group they were greatly decreased after anti-CD14 antibody treatment: 2.14 ± 0.17 vs 3.17 ± 0.21, 298.7 ± 1.8 pg/mL vs 654.2 ± 3.6 pg/mL (t value = 2.52 and 2.92 for each; P < .05). They were still significantly higher than the control group (t values of 3.01 and 3.27 for each; P < .01).

Conclusion

IRI up-regulated CD14 and TLR4 gene expression in KCs, and subsequently activated NF-κβ to produce cytokines.     

Effect of necrosis modulator necrox-7 on hepatic ischemia-reperfusion injury in beagle dogs

Objective

The liver is susceptible to ischemia-reperfusion (IR) injury during inflow occlusion for hepatectomy. There is no effective pharmacologic agent available to prevent the release of high-mobility-group box 1 (HMGB1) or to ameliorate IR injury. This pilot study sought to develop a model in beagle dogs for the purpose of testing the efficacy of a necrosis modulator, necrox-7, to prevent hepatic IR injury in beagle dogs.

Methods

Six male beagle dogs were randomly assigned to the control group (group A; n = 3) or the treatment group (group B; n = 3). Under general anesthesia, group B received intravenous infusion of necrox-7 (13 mg/kg over 20 minutes) followed by 60 minutes of left hepatic inflow occlusion and 60 minutes of reperfusion. Both groups were tested for serum biochemicals, hematology values, liver biopsies, and plasma HMGB1 levels over a 48-hour period.

Results

The maximum alanine transferase (ALT), aspartate transferase (AST), and lactate dehydrogenase (LDH) levels among group A versus group B were: ALT 868.3 ± 337.4 IU/L vs 274.3 ± 72.6 IU/L (P = .041); AST 1,024.7 ± 246.5 IU/L vs 505.3 ± 66.7 IU/L (P = .024); and LDH 962.7 ± 226.2 IU/L vs 552.7 ± 62.4 IU/L (P = .039). Liver biopsy demonstrated marked necrosis and inflammatory infiltrates in group A, whereas group B showed little evidence of IR injury. The plasma HMGB1 concentration was significantly lower among group B versus A.

Conclusion

This pilot study developed a hepatic IR injury model, demonstrating that necrox-7 reduced hepatic necrosis secondary to IR injury in a large animal setting.     

Intestinal Ischemia/Reperfusion Injury Triggers Activation of Innate Toll-Like Receptor 4 and Adaptive Chemokine Programs

Background

Ischemia/reperfusion injury (IRI) is a major problem in intestinal transplantation. Toll-like receptor 4 (TLR4) has been implicated as a possible link between the innate and adaptive immune systems, however little data exists regarding TLR4 in intestinal IRI. The goal of this study is to evaluate the involvement of TLR4 in intestinal IRI and to assess the effect on T cell related chemokine programs.

Methods

C57BL6 mice underwent 100 minutes of warm intestinal ischemia by SMA clamping. Control WT mice underwent laparotomy without vascular occlusion. Separate survival and analysis groups were performed, and intestinal tissue was harvested at 1 hour, 2 hours, 4 hours, and 24 hours post-reperfusion. Analysis included histology, CD3 immunostaining, myeloperoxidase activity, Western blot, and PCR.

Results

Survival was significantly worse in the IRI group vs control (50% vs. 100%). IRI caused severe histopathological injury including mucosal erosions and villous congestion and hemorrhage. Myeloperoxidase activity increased in a time-dependent manner after IRI (2.71 0.25 at 1 hour, 2.92 0.25 at 2 hours, 4 0.16 at 4 hours, 5.1 0.25 at 24 hours vs 0.47 0.11 controls, P < .05). Protein expression of TLR4 followed by NF-κB was increased after IRI. Additionally, mRNA production of IP-10, MIP-2, MCP-1, and RANTES was increased at all time-points, as was mRNA for ICAM-1 and E-selectin.

Conclusion

This study is the first to demonstrate increased expression of TLR4 and NF-κB after warm intestinal IRI. This detrimental cascade may be initiated by TLR4 via NF-κB signaling pathways, implicating TLR4 as a potential therapeutic target for the prevention of intestinal IRI.