Ischemic preconditioning ameliorates intestinal injury induced by ischemia-reperfusion in rats

Exploring the mechanism of Huanglian ointment in alleviating wound healing after anal fistula surgery through metabolomics and proteomics

Anal fistula is a common anal and intestinal disease. The wound of anal fistula surgery is open and polluting, which is the most difficult to heal among all surgical incisions. To investigate the mechanism of Huanglian ointment (HLO) on wound healing after anal fistula incision. The S. aureus infected wound in SD rats were used to imitate poor healing wound after anal fistula surgery. SD rats with wound sites (n = 24) were randomly divided into four groups (Control group, Model group, Potassium permanganate (PP) treatment group, and HLO treatment group). The wound healing rate was evaluated, HE staining was used to evaluate the pathological changes of each group, ELISA was used to detect the secretion of inflammatory factors in each group, and the mechanism was explored through metabolomics and proteomics in plasma rat. Compared to other groups, the rate of wound healing in the HLO group was higher on days 7 and 14. Histological analysis showed that collagen and fibroblast in HLO rats were significantly increased, inflammatory cells were reduced, and vascular endothelial permeability was increased. ELISA results showed that the secretion of inflammatory factors in HLO rats was significantly lower. Significant proteins and metabolites were identified in the wound tissues of the infected rats and HLO-treated rats, which were mainly attributed to Cdc42, Ctnnb1, Actr2, Actr3, Arpc1b, Itgam, Itgb2, Cttn, Linoleic acid metabolism, d-Glutamine and d-glutamate metabolism, Phenylalanine, tyrosine and tryptophan biosynthesis, Phenylalanine metabolism, alpha-Linolenic acid metabolism, and Ascorbate and aldarate metabolism. In conclusion, this study showed that HLO can promote S. aureus infected wound healing, and the data provide a theoretical basis for the treatment of wounds after anal fistula surgery with HLO.

Mitochondrial DNA Release Contributes to Intestinal Ischemia/Reperfusion Injury

Mitochondria release many damage-associated molecular patterns (DAMPs) when cells are damaged or stressed, with mitochondrial DNA (mtDNA) being. MtDNA activates innate immune responses and induces inflammation through the TLR-9, NLRP3 inflammasome, and cGAS-STING signaling pathways. Released inflammatory factors cause damage to intestinal barrier function. Many bacteria and endotoxins migrate to the circulatory system and lymphatic system, leading to systemic inflammatory response syndrome (SIRS) and even damaging the function of multiple organs throughout the body. This process may ultimately lead to multiple organ dysfunction syndrome (MODS). Recent studies have shown that various factors, such as the release of mtDNA and the massive infiltration of inflammatory factors, can cause intestinal ischemia/reperfusion (I/R) injury. This destroys intestinal barrier function, induces an inflammatory storm, leads to SIRS, increases the vulnerability of organs, and develops into MODS. Mitophagy eliminates dysfunctional mitochondria to maintain cellular homeostasis. This review discusses mtDNA release during the pathogenesis of intestinal I/R and summarizes methods for the prevention or treatment of intestinal I/R. We also discuss the effects of inflammation and increased intestinal barrier permeability on drugs.

Ischemic perconditioning on mesenteric ischemia/reperfusion injury in rats

Purpose:

To evaluate if the perconditioning affects the antioxidant capacity in mesenteric ischemia and reperfusion injury.

Methods:

Twenty-one Wistar rats were assigned into three groups, as follows: Sham, IR and rPER. The animals were subjected to mesenteric ischemia for 30 min. rPER consisted of three cycles of 5-min hindlimb ischemia followed by 5 min hindlimb perfusion at the same time to mesenteric ischemic period. After 5 minutes, blood and 5 cm of terminal ileum were harvested for thiobarbituric acid reactive substances (TBARS) and Trolox equivalent antioxidant capacity (TEAC) measurement.

Results:

rPER technique was able to reduce intestinal tissue TBARS levels (p<0.0001), but no statistic difference was observed in blood levels between groups, although it was verified similar results in rPER and Sham group. rPER technique also enhanced TEAC levels in both blood (p = 0.0314) and intestinal tissue (p = 0.0139), compared to IR group.

Conclusions:

rPER appears as the most promising technique to avoid IR injury. This technique reduced TBARS levels in blood and intestinal tissue and promoted the maintenance of antioxidant defense in mesenteric acute injury.

Intestinal ischemic reperfusion injury: Recommended rats model and comprehensive review for protective strategies

Intestinal ischemic reperfusion injury (IIRI) is a life-threatening condition with high morbidity and mortality in the clinic. IIRI was induced by intestinal ischemic diseases such as, small bowel transplantation, aortic aneurysm surgery, and strangulated hernias. Although related mechanisms have not been fully elucidated, during the last decade, researches have demonstrated that many factors are crucial in the pathological process, including oxidative stress (OS), epithelial barrier function disorder, and so on. Rats model, as the most applied animal IIRI model, provides specific targets for researches and therapeutic strategies. Moreover, various treatment strategies such as, anti-oxidative stress, anti-apoptosis, and anti-inflammation, have shown promising effects in alleviating IIRI. However, current researches cannot solve the clinical problems of IIRI, and specific treatment strategies are still needed to be exploited. This review focuses on a recommended experimental IIRI rat model and understanding of the involved mechanisms such as, OS, gut bacteria translocation, apoptosis, and necroptosis, aim at providing novel ideas for therapeutic strategies of IIRI.

The value of potassium, pH and D-dimer levels in early diagnosis of acute mesenteric ischemia: an experimental study on rats

INTRODUCTION

The aim of this randomized controlled experimental study was to evaluate the efficacy of potassium, pH and D-dimer levels in blood, as well as potassium and pH levels in peritoneal lavage fluid, in the early diagnosis of acute mesenteric ischemia.

MATERIAL AND METHODS

This study was conducted at the Istanbul University Center of Experimental Medicine after having received approval from the Istanbul University animal testing ethics committee. Male albino Wistar rats (n = 24; 250 to 350 g) were divided into two control groups and two ischemic groups. Levels of potassium, pH, and D-dimer in blood and levels of potassium and pH in peritoneal lavage fluid were analyzed for 1 h and 2 h after the induced acute mesenteric ischemia procedure. The degree of ischemic injury was determined using the histopathological damage score in tissue samples taken from the terminal ileum.

RESULTS

Ischemic groups had statistically significant differences in potassium and pH in blood and peritoneal lavage fluid compared to non-ischemic groups (p < 0.05). There was no significant difference between control and ischemic groups in terms of D-dimer and histologic grading results after 1 h (p = 0.132, p = 0.475 respectively), while there was a significant difference between control and ischemic groups after 2 h (p < 0.05).

CONCLUSIONS

The levels of potassium, pH, and D-dimer could be useful in daily practice for the early diagnosis of acute mesenteric ischemia.

EGFR monoclonal antibody panitumumab inhibits chronic proliferative cholangitis by downregulating EGFR

In hepatolithiasis, chronic proliferative cholangitis (CPC), an active and longstanding inflammation of stone-containing bile ducts with enhanced mucin-producing activity, not only affects the progression of the disease, it can also induce biliary carcinogenesis. The present study aimed to examine the effect of the epidermal growth factor receptor (EGFR) monoclonal antibody panitumumab (Pani) on CPC. Following the establishment of CPC rat models, periodic acid Schiff staining was used to observe the positive rate of EGFR expression. The expression levels of EGFR, mucin 5AC (MUC5AC), Ki-67, type I collagen and mammalian target of rapamycin (mTOR), and the activity of β-glucuronidase (β-G), were measured. The rats treated with Pani demonstrated a significantly lower degree of hyperproliferation of the epithelium and submucosal glands of the bile duct and collagen fibers of the bile duct wall, a significantly decreased positive rate of EGFR, reduced phosphorylation of mTOR, decreased expression of EGFR, MUC5AC, Ki-67 and type I collagen, and reduced β-G activity. The therapeutic effects in rats treated with 4 and 6 mg/kg of Pani were more marked than those in rats treated with 2 mg/kg of Pani. Collectively, the data obtained in the present study suggest that the EGFR monoclonal antibody Pani can effectively inhibit the excessive proliferation and stone-forming potential of bile duct mucosa in CPC with a receptor saturation effect. Therefore, Pani offers promise as a treatment for the prevention and control of intra-hepatic choledocholithiasis caused by CPC.

The role of ischemic preconditioning in gene expression related to inflammation in a rat model of intestinal ischemia-reperfusion injury

PURPOSE

To investigate the gene expression related to inflammation on mice subjected to intestinal ischemia and reperfusion (I/R) and treated with ischemic preconditioning (IPC).

METHODS

Thirty rats (EPM-Wistar), distributed in five groups of six animals each, were underwent anesthesia and laparotomy. The ischemia time was standardized in 60 minutes and the reperfusion time 120 minutes. IPC was standardized in 5 minutes of ischemia followed by 10 minutes of reperfusion accomplished before I/R. The control group was submitted only to anesthesia and laparotomy. The other groups were submitted to ischemia, I/R, ischemia + IPC and I/R + IPC. It was collected a small intestine sample to analyses by Quantitative Polymerase Chain Reaction in real Time (RT-qPCR) and histological analyses. It was studied 27 genes.

RESULTS

The groups that received IPC presented downregulation of genes, observed in of genes in IPC+ischemia group and IPC+I/R group. Data analysis by clusters showed upregulation in I/R group, however in IPC groups occurred downregulation of genes related to inflammation.

CONCLUSION

The ischemia/reperfusion promoted upregulation of genes related to inflammation, while ischemic preconditioning promoted downregulation of these genes.

The Role of O-GlcNAcylation for Protection against Ischemia-Reperfusion Injury

Ischemia reperfusion injury (IR injury) associated with ischemic heart disease contributes significantly to morbidity and mortality. O-linked β-N-acetylglucosamine (O-GlcNAc) is a dynamic posttranslational modification that plays an important role in numerous biological processes, both in normal cell functions and disease. O-GlcNAc increases in response to stress. This increase mediates stress tolerance and cell survival, and is protective. Increasing O-GlcNAc is protective against IR injury. Experimental cellular and animal models, and also human studies, have demonstrated that protection against IR injury by ischemic preconditioning, and the more clinically applicable remote ischemic preconditioning, is associated with increases in O-GlcNAc levels. In this review we discuss how the principal mechanisms underlying tissue protection against IR injury and the associated immediate elevation of O-GlcNAc may involve attenuation of calcium overload, attenuation of mitochondrial permeability transition pore opening, reduction of endoplasmic reticulum stress, modification of inflammatory and heat shock responses, and interference with established cardioprotective pathways. O-GlcNAcylation seems to be an inherent adaptive cytoprotective response to IR injury that is activated by mechanical conditioning strategies.

Chitosan-microcapsulated insulin alleviates mesenteric microcirculation dysfunction via modulating COX-2 and VCAM-1 expression in rats with diabetes mellitus

Background

The study of the experiment was to display the therapeutic function of insulin-loaded chitosan (insulin/chitosan) on mesenteric microcirculation via down-regulating cyclooxygenase-2 (COX-2) and vascular cell adhesion molecule (VCAM-1) expressions in rats with diabetes mellitus (DM) as compared to free insulin.

Methods

Diabetic rats were administrated with 24 U/kg insulin or 120 U/kg insulin/chitosan compounds. The blood and mesenteriums were collected, blood glucose levels, arteriole velocity, arteriole diameter, venular diameter, and hemodiapedesis were measured, and COX-2, VCAM-1 expressions were measured in mesenteriums tissues.

Results

Both insulin and insulin/chitosan administration decreased blood glucose and improved the state of mesenteric microcirculation through down-regulating COX-2 and VCAM-1 expressions as compared to DM groups, while insulin/chitosan remarkably augmented this functions.

Conclusion

Chitosan-microcapsulated insulin alleviates mesenteric microcirculation dysfunction via modulating COX-2 and VCAM-1 expressions in rats with DM.

Quercetin protects jejunal mucosa from experimental intestinal ischemia reperfusion injury by activation of CD68 positive cells

The aim of our study was to analyse the possible protective effect of quercetin application during the jejunal ischemia-reperfusion injury (IRI) in rats. Quercetin was administered intraperitoneally 30min before 1h ischemia of superior mesenteric artery with following 24h lasting reperfusion period. The male specific pathogen-free (SPF) Charles River Wistar rats were used. In the group with applied quercetin, the significantly increased (p<0.001) levels of anti-inflammatory cytokine IL10 were observed both in the blood serum and jejunal tissue. The improvement of the mucosal tissue morphology and proliferating and DNA repairing cell number measured by PCNA activity were recorded by more than 30% higher in the quercetin group. Simultaneously, significant elongation of the intestinal glands (p<0.001) and increase in the number of CD68-positive cells in the lamina propria mucosae (p<0.001) in comparison with control group were found. Based on our results, the preventive application of quercetin before induction of jejunal IRI stimulates faster jejunal mucosa restoration and it seems to have immunomodulatory and anti-inflammatory effects as well. CD68-positive macrophages could have crucial role in this process since they work as both growth factor and cytokine producers.

The expression of endothelial and inducible nitric oxide synthase and apoptosis in intestinal ischemia and reperfusion injury under the action of ischemic preconditioning and pentoxifylline

PURPOSE

To investigate the expression of nitric oxide synthase (NOS) and apoptosis associated with ischemic preconditioning (IPC) and pentoxifylline (PTX) in intestinal ischemia (I) and reperfusion (R) injury.

METHODS

Thirty male rats were assigned to 5 groups: (CG), no clamping of the superior mesenteric artery (90 minutes); (IR-SS) saline + ischemia (30 minutes) + reperfusion (60 minutes); (IR-PTX) PTX + ischemia (30 minutes) + reperfusion (60 minutes); (IPC-IR-SS) 5 minutes of ischemia + 5 minutes of reperfusion (IPC) + saline + I(30 minutes)+R(60 minutes); and (IPC-IR-PTX) IPC + PTX + I(30 minutes)+ R(60 minutes).

RESULTS

The application of IPC and PTX showed a significantly lower immunohistochemistry reaction for active caspase-3 (P<0.05) compared to IR+SS. The number of cells immunoreactive to BCL-2 was higher in the IR-PTX group (P>0.05). The NOS-2 expression (qRTPCR) in the IR-PTX group (P<0.05) was higher than the values for the IPC+IR-SS and IPC-IR-PTX groups. The NOS-3 expression was significantly upper in the IPC-IR-PTX group than in the CG (P<0.05), the IR-SS (P<0.05) and the IR-PTX (P<0.05) groups.

CONCLUSIONS

The BCL-2 and active caspase-3 showed beneficial effects on PTX and IPC. The expression of NOS-2 and NOS-3 in the IPC and IPC-PTX groups showed no synergistic effect.

Synergistic Effect of Ischemic Preconditioning and Antithrombin in Ischemia-Reperfusion Injury

OBJECTIVES

Our study aimed to determine whether antithrombin plays a synergistic role in accentuating the effects of intestinal ischemic preconditioning.

MATERIALS AND METHODS

Fifty rats were randomly allocated to 5 groups (10 rats/group) as follows: sham treatment (group 1); ischemia-reperfusion (group 2); ischemic preconditioning followed by ischemia-reperfusion (group 3); antithrombin + ischemia-reperfusion, similar to group 2 but including antithrombin administration (group 4); and antithrombin + ischemic preconditioning, similar to group 3 but including antithrombin administration (group 5). Blood samples and liver specimens were obtained for measurement of cytokines, myeloperoxidase, and malondialdehyde. Liver biopsies were examined by electron microscopy.

RESULTS

Intestinal ischemia-reperfusion induced a remote hepatic inflammatory response as evidenced by the striking increase of proinflammatory cytokines, myeloperoxidase, and malondialdehyde. Tumor necrosis factor-α levels in group 5 (12.48 ± 0.7 pg/mL) were significantly lower than in group 3 (13.64 ± 0.78 pg/mL; P = .014). Mean interleukin 1β was lower in group 5 (9.52 ± 0.67pg/mL) than in group 3 (11.05 ± 1.9 pg/mL; P > .99). Mean interleukin 6 was also significantly lower in group 5 (17.13 ± 0.54 pg/mL) than in group 3 (23.82 ± 1 pg/mL; P ≤ .001). Myeloperoxidase levels were significantly higher in group 3 (20.52 ± 2.26 U/g) than in group 5 (18.59 ± 1.03 U/g; P = .025). However, malondialdehyde levels did not significantly improve in group 5 (4.55 ± 0.46 μmol) versus group 3 (5.17 ± 0.61 μmol; P = .286). Tumor necrosis factor-α, interleukin 6, and myeloperoxidase findings show that antithrombin administration further attenuated the inflammatory response caused by ischemia-reperfusion, suggesting a synergistic effect with ischemic preconditioning. These findings were confirmed by electron microscopy.

CONCLUSIONS

The addition of antithrombin to ischemic preconditioning may act to attenuate or prevent damage from ischemia-reperfusion injury by inhibiting the release of cytokines and neutrophil infiltration.

Grape seed protects cholestatic rats liver from ischemia/reperfusion injury

PURPOSE

To determine the effect of grape-seed extract against ischemia/reperfusion injury in cholestatic liver.

METHODS

Eighteen Wistar albino rats were divided into three groups. In control and study groups, cholestasis was provided by bile duct ligation. Seven days later, the rats were subjected to 30 min hepatic ischemia, followed by 60 min of reperfusion. Oral administration of 50 mg/kg/day grape-seed extract was started 15 days before bile duct ligation and continued to the second operation in the study group. Serum, plasma and liver samples were taken. Laboratory analysis, tissue gluthation, malondialdehyde, myeloperoxidase levels and histopathological examination were performed.

RESULTS

Significant decrease in liver gluthation level and significant increase in malondialdehyde level and myeloperoxidase activity were observed after ischemia/reperfusion in cholestatic rats. Serum and plasma levels for laboratory analysis were also significantly higher in cholestatic I/R group. Hepatic necrosis and fibrosis were detected in histopathological examination. Oral grape-seed extract administiration reversed all these parameters and histopathological findings except serum bilirubin levels.

CONCLUSION

Oral grape-seed extract treatment can improve liver functions and attenuate the inflammation and oxidative stress in cholestatic ischemia/reperfusion injury.

Acute and Chronic Pretreatment With Atenolol Attenuates Intestinal Ischemia and Reperfusion Injury in Hypercholesterolemic Rats

OBJECTIVE

To evaluate the protective effects of preinjury atenolol (acute v chronic) on apoptosis, contractility, oxidative stress, and inflammatory markers in hypercholesterolemic rats undergoing intestinal ischemia-reperfusion (I/R) injury.

DESIGN

Prospective, experimental animal study.

SETTING

University laboratory.

PARTICIPANTS

Male Wistar rats (n = 32).

INTERVENTIONS

Rats were divided into the following 4 groups: 1 group was fed a normal diet (ND) (group ND+NoAT [no atenolol]), and the other 3 groups were fed a high-cholesterol diet (HCD)-group HCD+NoAT, group HCD+ChAT (chronic atenolol, 3 mg/kg/day for 8 weeks), and group HCD+AcAT (acute atenolol, 1.5 mg/kg, given 5 minutes before intestinal clamping). All rats underwent I/R injury. The superior mesenteric artery was clamped for 60 minutes, then opened for 120 minutes (reperfusion). Apoptotic cells and stimulated contractions of ileal segments were examined. Tissue markers of intestinal I/R injury were examined. Intestinal malondialdehyde, superoxide dismutase, and nitrate/nitrite levels were measured.

MEASUREMENTS AND MAIN RESULTS

The chronic atenolol group had fewer apoptotic cells and higher superoxide dismutase activity compared with the other groups. Intestinal contraction was higher in both atenolol pretreatment groups compared with the NoAT groups. Chronic and acute atenolol resulted in lower ileal levels of malondialdehyde and immunolabeling-positive cells (intestinal inducible nitric oxide synthase, endothelial nitric oxide synthase, interleukin-1, and interleukin-8) after I/R injury compared with the no atenolol groups.

CONCLUSIONS

Both chronic and acute pre-I/R injury treatment with atenolol attenuated I/R injury in this hypercholesterolemic rat model. These findings should encourage future studies of atenolol in hypercholesterolemic patients undergoing procedures with a high risk of intestinal ischemia.

Neutrophil proteomic analysis reveals the participation of antioxidant enzymes, motility and ribosomal proteins in the prevention of ischemic effects by preconditioning

Intestinal ischemia and reperfusion injury are widely used models, which result into tissue injury and multiple organ failure also observed after trauma and surgery. Ischemic preconditioning (IPC) preceding ischemia and reperfusion (IR) was shown to attenuate this injury and has a potential therapeutic application; however the exact underlying mechanism is not clear. Neutrophils play an important role in the mechanism of injuries caused by ischemia and reperfusion while IPC led to a decrease in neutrophil stimulation and activation. The effect of preconditioning on the neutrophil proteome is unclear. Proteomic analysis has been ratified as an appropriate tool for studying complex systems. In order to evaluate the effect of IPC preceding 45min of ischemia on the proteome of neutrophils we used Wistar rats divided in four experimental groups: Control, sham laparotomy, intestinal ischemia reperfusion and ischemic preconditioning. After neutrophil separation, proteins were extracted, trypsin digested and the resulting peptides were iTRAQ labeled followed by HILIC fractionation and nLC-MS/MS analysis. After database searches, normalization and statistical analysis our proteomic analysis resulted in the identification of 2437 protein groups that were assigned to five different clusters based on the relative abundance profiles among the experimental groups. The clustering followed by statistical analysis led to the identification of significantly up and downregulated proteins in IR and IPC. Cluster based KEGG pathways analysis revealed up- regulation of actin cytoskeleton, metabolism, Fc gamma R mediated phagocytosis, chemokine signaling, focal adhesion and leukocyte transendothelial migration whereas downregulation in ribosome, spliceosome, RNA transport, protein processing in endoplasmic reticulum and proteasome, after intestinal ischemic preconditioning. Furthermore, enzyme prediction analysis revealed the regulation of some important antioxidant enzymes and having their role in reactive oxygen species production. To our knowledge, this work describes the most comprehensive and detailed quantitative proteomic study of the neutrophil showing the beneficial role of ischemic preconditioning and its effects on the neutrophil proteome. This data will be helpful to understand the effect of underlying protective mechanisms modulating the role of PMNs after IPC and provide a trustworthy basis for future studies.

BIOLOGICAL SIGNIFICANCE

Preconditioning is a relevant strategy to overcome clinical implications from ischemia and reperfusion. Such implications have the neutrophil as a major player. Although many publications describe specific biochemical and physiological roles of the neutrophil in such conditions, there is no report of a proteomic study providing a broader view of this scenario. Here we describe a group of proteins significantly regulated by ischemia and reperfusion being such regulation prevented by preconditioning. Such finding may provide relevant information for a deeper understanding of the mechanisms involved, as well as serve as basis for future biomarker or drug target assays.

Preparation and Biological Activity of the Monoclonal Antibody against the Second Extracellular Loop of the Angiotensin II Type 1 Receptor

The current study was to prepare a mouse-derived antibody against the angiotensin II type 1 receptor (AT1-mAb) based on monoclonal antibody technology, to provide a foundation for research on AT1-AA-positive diseases. Balb/C mice were actively immunized with the second extracellular loop of the angiotensin II type 1 receptor (AT₁R-ECII). Then, mouse spleen lymphocytes were fused with myeloma cells and monoclonal hybridomas that secreted AT1-mAb were generated and cultured, after which those in logarithmic-phase were injected into the abdominal cavity of mice to retrieve the ascites. Highly purified AT1-mAb was isolated from mouse ascites after injection with 1 × 10⁷ hybridomas. A greater amount of AT1-mAb was purified from mouse ascites compared to the cell supernatant of hybridomas. AT1-mAb purified from mouse ascites constricted the thoracic aorta of mice and increased the beat frequency of neonatal rat myocardial cells via the AT₁R, identical to the effects of AT1-AA extracted from patients' sera. Murine blood pressure increased after intravenous injection of AT1-mAb via the tail vein. High purity and good biological activity of AT1-mAb can be obtained from mouse ascites after intraperitoneal injection of monoclonal hybridomas that secrete AT1-mAb. These data provide a simple tool for studying AT1-AA-positive diseases.

Hypoxemic reperfusion of ischemic states: an alternative approach for the attenuation of oxidative stress mediated reperfusion injury

Ischemia and reperfusion (I/R) - induced injury has been described as one of the main factors that contribute to the observed morbidity and mortality in a variety of clinical entities, including myocardial infarction, ischemic stroke, cardiac arrest and trauma. An imbalance between oxygen demand and supply, within the organ beds during ischemia, results in profound tissue hypoxia. The subsequent abrupt oxygen re-entry upon reperfusion, may lead to a burst of oxidative aggression through production of reactive oxygen species by the primed cells. The predominant role of oxidative stress in the pathophysiology of I/R mediated injury, has been well established. A number of strategies that target the attenuation of the oxidative burst have been tested both in the experimental and the clinical setting. Despite these advances, I/R injury continues to be a major problem in everyday medical practice. The aim of this paper is to review the existing literature regarding an alternative approach, termed hypoxemic reperfusion, that has exhibited promising results in the attenuation of I/R injury, both in the experimental and the clinical setting. Further research to clarify its underlying mechanisms and to assess its efficacy in the clinical setting is warranted.