Schemes against ischemia; solutions for reperfusion (injury)?

Adenosine A1 receptor agonism protection mechanism in intestinal ischemia/reperfusion injury via activation of PI3K/Akt signaling

Intestinal ischemia/reperfusion (I/R) injury is a common clinical problem with a high mortality rate, resulting from loss of blood flow to an intestinal segment. Adenosine serves a protective role in intestinal I/R injury; however, its potential mechanism is not completely understood. The present study aimed to investigate the protective effects of adenosine A₁ receptor (A₁R) agonists CPA and LUF6941 and whether their mechanisms are associated with the PI3K/Akt signaling pathway. To simulate intestinal I/R injury, a cell oxygen-glucose deprivation/reoxygenation (OGD/R) model was established and the human colon cancer cell line (Caco-2) was incubated with A₁R agonists before OGD/R treatment. The viability of Caco-2 cells was detected by PI and Cell Counting Kit-8 assay, apoptosis was detected using flow cytometry and western blotting was used to analyze protein expression levels of PI3K, Akt and p53 in Caco-2 cells. A₁R agonist pretreatment protected Caco-2 cells against OGD/R-induced cell damage and activated PI3K/Akt signaling. Additionally, apoptosis was inhibited by downregulating phosphorylation of p53 protein, as evidenced by increased cell viability. These findings suggested that A₁R agonists decreased OGD/R damage in Caco-2 cells, which may be due to their anti-apoptotic effects and activation of the PI3K/Akt/p53 signal pathway.

Hemodynamic Influences on Mesenteric Blood Flow in Shock Conditions

The gastrointestinal (GI) system, is most vulnerable to hypoperfusion among the splanchnic organs. Disturbed perfusion of the mesenteric area may lead to GI dysfunction, cause further injury to the patients and even vital outcomes. However, due to the limitation of detection methods, the hemodynamic influences on mesenteric blood flow in clinical practice are not fully understood. By elucidating the underlying mechanisms, we may be able to recognize disturbed GI perfusion and eventually GI dysfunction at an early phase. Thus, in this review, we will focus on situations where mesenteric blood flow is disturbed due to hemodynamic causes in shock conditions, and the present research status will be discussed. English language articles published before 2020 were identified through a computerized PubMed search using the terms "mesenteric, gastrointestinal, intestinal, splanchnic, blood flow, perfusion" and the cofactors. Relevant publications were retrieved and scanned for additional sources. There were few clinical trials focusing on mesenteric blood flow in shock patients. Most were animal experiments. Based on the best current evidence from these sources, we described the major influences on mesenteric blood flow in the context of physiologic accommodation, disease-related effects and the consequences of medical interventions related to shock conditions. During circulatory shock, sepsis, and medical interventions related to shock treatment, mesenteric blood flow changes and shows different features. We need to carefully consider these issues when making medical decisions, and more work needs to be done on early detection of GI hypoperfusion and its accurate correlation with GI dysfunction.

The role of the exogenous supply of adenosine triphosphate in the expression of Bax and Bcl2L1 genes in intestinal ischemia and reperfusion in rats 1

PURPOSE

To investigate the role of the exogenous supply of adenosine triphosphate (ATP) in the expression of Bax and Bcl2L1 genes in intestinal ischemia and reperfusion (IR) in rats.

METHODS

The study was designed as a randomized controlled trial with a blinded assessment of the outcome. Eighteen adult male Wistar-EPM1 rats were housed under controlled temperature and light conditions (22-23°C, 12 h light/dark cycle). The animals were randomly divided into 3 groups: 1. Sham group (SG): no clamping of the superior mesenteric artery; 2. Ischemia and reperfusion group (IRG): 3. Ischemia and reperfusion plus ATP (IRG + ATP). ATP was injected in the femoral vein before and after ischemia. Afterwards, intestinal segments were appropriately removed and processed for Endothelial Cell Biology Rat RT2 Profiler PCR Array.

RESULTS

ATP promoted the upregulation of Bcl2L1 gene expression, whereas it did not have significant effects on Bax gene expression. In addition, the relation of Bax/Bcl2L1 gene expression in the IRG group was 1.39, whereas it was 0.43 in the IRG + ATP group. Bcl2L1 plays a crucial role in protecting against intestinal apoptosis after ischemia and reperfusion. Increased Bcl2L1 expression can inhibit apoptosis while decreased Bcl2L1 expression can trigger apoptosis.

CONCLUSION

Adenosine triphosphate was associated with antiapoptotic effects on the rat intestine ischemia and reperfusion by upregulating of Bcl2L1 gene expression.

Effects of lazaroid U-74389G on intestinal ischemia and reperfusion injury in porcine experimental model

BACKGROUND

The readmission of molecular oxygen into an ischemic tissue promotes the oxidation of resuscitated tissue with certain pathophysiologic mechanisms.

MATERIALS AND METHODS

Twenty four pigs (male or female) were randomized in this study. The animals were allocated to four groups with an equal number (n = 6) in each group: (1) control group-ischemia for 30 min and reperfusion for 60 min. (2) control group-ischemia for 30 min and reperfusion for 120 min. (3) ischemia for 30 min and immediate iv injection of lazaroid U-74389G and reperfusion for 60 min. (4) ischemia for 30 min and immediate iv injection of lazaroid U-74389G and reperfusion for 120 min.

RESULTS

We investigated further the role of an antioxidant molecule such as U-74389G and we concluded that there is statistically significant relation in MDA (malondialdeyde), TNF -α (tumor necrosis factor-α) measurement in tissue, while the histological score in the groups that the lazaroid was administered was improved.

CONCLUSIONS

In many emergency clinical situations, such as reperfusion of the intestine, the role of U-74389G can be protective.

Effect of ischemic preconditioning on injuries caused by ischemia and reperfusion in rat intestine

To study whether ischemic preconditioning (IPC) attenuated intestinal dysfunction caused by ischemia (I) and reperfusion (R), rats were underwent 60 minutes of I which was produced by occlusion of the superior mesenteric artery, and/or 120 minutes R. The IPC group had the I procedure previously stimulated for 5 minutes and the R for 10 minutes. IPC and sham groups were injected with saline solution (SS) via the femoral vein 5 minutes before the I and R, and for R. After I or I/R, 2-cm jejunal segments were mounted in an organ bath to study neurogenic contractions stimulated by electrical pulses or KCl using a digital recording system. Thin jejunal slices were stained with hematoxylin and eosin for optical microscopy. Compared with the sham group, jejunal contractions were similar in the IPC + I and the IPC + I/R groups, but reduced in the I + SS and the I/R + SS groups. The jejunal enteric nerves were damaged in the I + SS and the I/R + SS groups, but not in the IPC groups. These results suggested that ischemic preconditioning attenuated intestinal dysfunction caused by I and I/R.

Study of L-arginine in intestinal lesions caused by ischemia-reperfusion in rats

To examine whether treatment with L-arginine (ARG), a substrate of nitric oxide biosynthesis, attenuated intestinal dysfunction caused by ischemia (I) and reperfusion (R), we treated rats with ARG (100 mg/kg intravenously) or saline solution (SS) before 60 minutes of I produced by occlusion of the superior mesenteric artery and/or during 120 minutes of R. After I or I/R, we isolated 2-cm jejunal segments for mounting in an organ bath to study neurogenic contractions stimulated by electrical pulses or KCl with the use of a digital recording system. Thin jejunal slices were stained with hematoxylin and eosin for optical microscopy. Jejunal contractions were similar in the sham and I+ARG, but reduced in I+SS, I/R+SS, and I/R+ARG groups. Jejunal enteric nerves were damaged in I+SS, IR+SS, and IR+ARG, but not in the I+ARG group, suggesting that ARG attenuate intestinal dysfunctions due to I but not to R.

Study of heparin in intestinal ischemia and reperfusion in rats: morphologic and functional evaluation

To study whether treatment with heparin (HEP) attenuates intestinal dysfunction caused by ischemia (I) and reperfusion (R), rats were treated with HEP (100 U/kg intravenously) or saline solution (SS) before I (60 min), which was produced by occlusion of the superior mesenteric artery, and R (120 min). After I or I/R, we mounted 2-cm jejunal segment in an organ bath to study neurogenic contractions stimulated by electrical pulses or KCl, using a digital recording system. Thin jejunal slices were stained with hematoxylin and eosin for optical microscopy. Compared with the sham group, jejunal contractions were similar in the I + HEP and the I/R + HEP groups, but reduced in the I + SS and the I/R + SS groups. The jejunal enteric nerves were damaged in the I + SS and the I/R + SS, but not in the I + HEP and the I/R + HEP cohorts. These results suggested that HEP attenuated intestinal dysfunction caused by I and I/R.

Atenolol to treat intestinal ischemia and reperfusion in rats

To study whether treatment with the beta-blocker atenolol (AT) attenuates intestinal dysfunction caused by ischemia (I) and reperfusion (R), rats were treated with AT (1.5 mg · kg(-1), intravenously) or saline solution (SS) prior to I (60 minutes), which was produced by occlusion of the superior mesenteric artery, and/or R (120 minutes). After I or I/R, 2-cm jejunal segments were mounted in an organ bath to study neurogenic contractions stimulated by electrical pulses or KCl using a digital recording system. Thin jejunal slices were stained with hematoxylin and eosin for optical microscopy analysis. Compared to the sham group, jejunal contractions were similar in the I + AT and the I/R + AT groups, but reduced in the I + SS and the I/R + SS groups. The jejunal enteric nerves were damaged in the I + SS and the I/R + SS groups, but not in the I + AT and the I/R + AT. These results suggest that AT may attenuate intestinal dysfunction caused by I and I/R.

Effects of lazaroids on intestinal ischemia and reperfusion injury in experimental models

Mesenteric ischemia occurs in a number of clinically relevant pathophysiologic processes, including sepsis, hemorrhage, intestinal transplantation, severe burns, and mesenteric thrombosis. The readmission of molecular oxygen into an ischemic tissue promotes the oxidation of resuscitated tissue with certain pathophysiologic mechanisms. Depending on the duration and the intensity of ischemia, reoxygenation of the intestine that has been reperfused may further induce tissue injury. Intestinal ischemia and reperfusion injury can accelerate complex processes between the endothelium and different cell types leading to microvascular injury, cellular necrosis, and apoptosis. The injury due to reperfusion is found predominantly in the intestinal mucosa and submucosa, causing endothelial detachment. The 21-aminosteroids (lazaroids) are a family of compounds that inhibit lipid membrane peroxidation. Many of the performed studies show conflicting results, which reflect differences in experimental design, evolving time that (I/R) is induced, total or partial vascular occlusion, dosage of the lazaroid, and the exact period of time that the lazaroid is administered.

Effects of 5'-adenosine triphosphate on intestinal ischemia-reperfusion in rabbits

To study whether treatment with 5'-adenosine triphosphate (ATP), an agonist of P2 purine receptors, attenuated intestinal dysfunction caused by ischemia (I) and/or reperfusion (R), rabbits were treated with ATP (15 mgxkg(-1), intravenously) or saline solution (SS) 60 minutes before I by occlusion of the superior mesenteric artery and/or R (120 minutes). After I or I/R isolated 2-cm jejunal segments were mounted in an organ bath to study nerve-mediated contractions stimulated by electrical pulses or KCl using a digital recording system. Thin jejunal slices were stained (hematoxylin and eosin) for optical microscopy. Compared to a sham group, the jejunal contractions were similar to sham hosts among I + ATP, but reduced in I + SS, I/R + SS, and I/R + ATP groups. The jejunal-enteric nerves were damaged in I + SS, I/R + SS, and I/R + ATP, but not the I + ATP group. These results suggested that ATP attenuated intestinal dysfunction produced by I, but not that caused by R.

Role of L-arginine, a substrate of nitric oxide biosynthesis, on intestinal ischemia-reperfusion in rabbits

To study whether treatment with L-arginine (ARG), a substrate of nitric oxide biosynthesis, attenuates intestinal dysfunction caused by ischemia (I) and reperfusion (R), rabbits treated with ARG (100 mgxkg(-1), intravenously) or saline solution (SS) prior to I (60 minutes) by occlusion of superior mesenteric artery and/or during R (120 minutes). After I or I/R, 2-cm jejunal segments were isolated and mounted in an organ bath to study of neurogenic contractions stimulated by electrical pulses or KCl using a digital recording system. Thin jejunal slices were stained (hematoxylin and eosin) for analysis by optical microscopy. Compared to the sham group, jejunal contractions were similar in I + ARG, but reduced in I + SS, I/R + SS, and I/R + ARG groups. The jejunal enteric nerves were damaged in I + SS, I/R + SS, and I/R + ARG, but not in I + ARG group, suggesting that ARG can attenuate intestinal dysfunctions due to I, but not to R.

Sodium nitroprusside as a nitric oxide donor in a rat intestinal ischemia-reperfusion model

AIM

The aim of this study was to investigate the efficacy of sodium nitroprusside in the reduction of the intestinal ischemia-reperfusion injury as a nitric oxide donor after intraperitoneal administration.

METHODS

The histopathological examinations and tissue malonyldialdehyde levels of 35 Wistar albino rats that were subjected to ischemia-reperfusion, were performed in 5 groups. The groups include Control, Ischemia -reperfusion, Sodium nitroprusside, NG-Nitro-L-Arginine Methyl Ester (L-NAME) and Sodium nitroprusside+L-NAME. Each rat was subjected to ischemia for 40 minutes and reperfusion for 30 minutes, except the control group. The medications were done intraperitoneally as saline 4 ml/kg, Sodium nitroprusside 5 mg/kg, L-NAME 10 mg/kg just before reperfusions.

RESULTS

Significant tissue injury in histological sections and an increase in tissue levels of Malonyldialdehyde was detected in the I/R group. The efficacy of intraperitoneal administration of Sodium nitroprusside in both Sodium nitroprusside alone and Sodium nitroprusside+L-NAME groups was found statistically significant for the reducing of injury scores (p<0.05). The difference between the Ischemia/reperfusion and Sodium nitroprusside groups was found statistically significant as in the Ischemia/reperfusion and Sodium nitroprusside+L-NAME groups due to the tissue Malonyldialdehyde levels (p<0.05). There was no statistical difference between Ischemia/reperfusion and L-NAME groups.

CONCLUSION

Ischemia/reperfusion induced injury might be reduced by the intraperitoneal administration of Sodium nitroprusside, even in the presence of L-NAME, in the rat intestinal model.

Ischemia reperfusion injury, preconditioning and critical illness

The purpose of this review is to describe in more detail ischemia reperfusion injury and preconditioning, and to speculate on the potential role of preconditioning in the care of critically ill patients. Current hemodynamic treatment of hypotension and hypoperfusion in critically ill patients is directed at ensuring essential organ perfusion by maintaining intravascular volume and cardiac output, and ensuring adequate oxygen delivery by maintaining arterial oxygen partial pressure and hemoglobin levels. However, morbidity and mortality remain high and new approaches to critically ill patients are required. Treatments are needed that can protect against organ ischemia during periods of low blood flow. In recent years, there has been a growing appreciation of the importance of ischemia reperfusion injury. Ischemia associated with reperfusion may result in greater injury than ischemia alone. Ischemic preconditioning is used to describe the protective effect of short periods of ischemia to an organ or tissue against longer periods of ischemia. Although first described in the myocardium, there is now evidence that this phenomenon occurs in a wide variety of organs and tissues, including the brain and other nervous tissue such as the retina and spinal cord, liver, stomach, intestines, kidney, and the lungs. Preconditioning therapy may offer a new avenue of treatment in critically ill patients. Both traditional preconditioning methods and pharmacologic agents that mimic or induce such preconditioning may be used in the future. Clinical trials of pharmacologic agents are underway in patients with coronary artery disease. Further trials of such methods and agents are needed in critically ill patients suffering from sepsis or multiorgan system failure.

Cardiopulmonary bypass in man: role of the intestine in a self-limiting inflammatory response with demonstrable bacterial translocation

BACKGROUND

Cardiopulmonary bypass provokes a systemic inflammatory reaction that, in 1% to 2% of all cases, leads to multiorgan disfunction. The aim of this study was to evaluate the possible role of the intestine in the pathogenesis and development of this reaction.

METHODS

Eleven selected patients scheduled for elective coronary artery bypass graft surgery were enrolled in a open, prospective clinical study. Gastric tonometry, chromium-labeled test and double sugar intestinal absorption tests, polymerase chain reaction microbial DNA test, and measurement of cytokines and transcriptional factor (nuclear factor kappaB) activation were performed.

RESULTS

During the postoperative period, gastric pH remained stable (range,7.2 to 7.3). The partial pressure for carbon dioxide gradient between the gastric mucosa and arterial blood increased significantly (from 1 to 23 mm Hg), peaking in the sixth postoperative hour. Interleukin 6 increased significantly over basal levels, peaking 3 hours after cardiopulmonary bypass (96.3 versus 24 pg/mL). Nuclear factor kappaB never reached levels higher than those observed after lipopolysaccharide stimulation. Escherichia coli translocation was documented in 10 patients: in eight cases from removal of aortic cross-clamps and in two cases from the first postoperative hour. With respect to basal value (6.4%), the urine collection revealed a significant increase in excretion of the radioisotope during the first 24 hours after surgery (39.1%), although there were no significant variations with the double sugar test.

CONCLUSIONS

The results obtained showed a correlation between the damage of the gastrointestinal mucosa, subsequent increased permeability, E coli bacteremia, and the activation of a self-limited inflammatory response in the absence of significant macrocirculatory changes and postoperative complications.