A model of mitochondrial superoxide production during ischaemia-reperfusion injury for therapeutic development and mechanistic understanding

Ischaemia-reperfusion (IR) injury is the paradoxical consequence of the rapid restoration of blood flow to an ischaemic organ. Although reperfusion is essential for tissue survival in conditions such as myocardial infarction and stroke, the excessive production of mitochondrial reactive oxygen species (ROS) upon reperfusion initiates the oxidative damage that underlies IR injury, by causing cell death and inflammation. This ROS production is caused by an accumulation of the mitochondrial metabolite succinate during ischaemia, followed by its rapid oxidation upon reperfusion by succinate dehydrogenase (SDH), driving superoxide production at complex I by reverse electron transport. Inhibitors of SDH, such as malonate, show therapeutic potential by decreasing succinate oxidation and superoxide production upon reperfusion. To better understand the mechanism of mitochondrial ROS production upon reperfusion and to assess potential therapies, we set up an in vitro model of IR injury. For this, isolated mitochondria were incubated anoxically with succinate to mimic ischaemia and then rapidly reoxygenated to replicate reperfusion, driving a burst of ROS formation. Using this system, we assess the factors that contribute to the magnitude of mitochondrial ROS production in heart, brain, and kidney mitochondria, as well as screening for inhibitors of succinate oxidation with therapeutic potential.

Quantifying acute kidney injury in an Ischaemia-Reperfusion Injury mouse model using deep-learning-based semantic segmentation in histology

This study focuses on ischaemia-reperfusion injury (IRI) in kidneys, a cause of acute kidney injury (AKI) and end-stage kidney disease (ESKD). Traditional kidney damage assessment methods are semi-quantitative and subjective. This study aims to use a convolutional neural network (CNN) to segment murine kidney structures after IRI, quantify damage via CNN-generated pathological measurements, and compare this to conventional scoring. The CNN was able to accurately segment the different pathological classes, such as Intratubular casts and Tubular necrosis, with an F1 score of over 0.75. Some classes, such as Glomeruli and Proximal tubules, had even higher statistical values with F1 scores over 0.90. The scoring generated based on the segmentation approach statistically correlated with the semiquantitative assessment (Spearman's rank correlation coefficient=0.94). The heatmap approach localised the intratubular necrosis mainly in the outer stripe of the outer medulla, while the tubular casts were also present in more superficial or deeper portions of the cortex and medullary areas. This study presents a CNN model capable of segmenting multiple classes of interest, including acute IRI-specific pathological changes, in a whole mouse kidney section and can provide insights into the distribution of pathological classes within the whole mouse kidney section.

Cysteine hydropersulfide reduces lipid peroxidation and protects against myocardial ischaemia-reperfusion injury - Are endogenous persulfides mediators of ischaemic preconditioning?

Earlier studies revealed the presence of cysteine persulfide (CysSSH) and related polysulfide species in various mammalian tissues. CysSSH has both antioxidant and oxidant properties, modulates redox-dependent signal transduction and has been shown to mitigate oxidative stress. However, its functional relevance in the setting of myocardial ischaemia-reperfusion injury (IRI) remains unknown. The present study was undertaken to (1) study the dynamics of production and consumption of persulfides under normoxic and hypoxic conditions in the heart, and (2) determine whether exogenous administration of the CysSSH donor, cysteine trisulfide (Cys-SSS-Cys) at the onset of reperfusion rescues functional impairment and myocardial damage by interfering with lipid peroxidation. Utilising a well-established ex vivo Langendorff murine model, we here demonstrate that endogenous tissue concentrations of CysSSH are upregulated when oxygen supply is compromised (global myocardial ischaemia) and rapidly restored to baseline levels upon reperfusion, suggestive of active regulation. In a separate set of experiments, exogenous administration of Cys-SSS-Cys for 10 min at the onset of reperfusion was found to decrease malondialdehyde (MDA) concentrations, formation of 4-hydroxynonenal (4-HNE) protein adducts and rescue the heart from injury. Cys-SSS-Cys also restored post-ischaemic cardiac function, improving both coronary flow and left ventricular developed pressure (LVDP). Taken together, these results support the notion that endogenous CysSSH plays an important role as a "redox preconditioning" agent to combat the oxidative insult in myocardial IRI.

The Effects of Increasing Aortic Occlusion Times at the Level of the Highest Renal Artery (Zone II) in the Normovolemic Rabbit Model

PURPOSE

The purpose of this study was to evaluate the effects of increasing zone II resuscitative endovascular balloon occlusion of the aorta (REBOA) occlusion times on physiological, end-organ and inflammatory responses in rabbits to assess the safe aortic occlusion time in a normovolemic rabbit model.

METHODS

The zone ll aorta was occluded with a balloon in 32 rabbits (8 animals each for 15, 30, 60, and 90 min). 8 rabbits served as a control. ELISAs were used to examine the serum levels of ALT, AST, Cr, BUN, MDA, SOD, IL-8, IL-6, and TNF-α; HE staining was used to identify the morphological changes in the kidney; RT-PCR was used to detect the mRNA levels of IL-6, IL-8, TNF-α and NF-κB in the kidney and uterus; and Western blotting was used to measure the protein expression levels of IL-6, IL-8, TNF-α and NF-κB in the kidney and uterus.

RESULTS

Plasma concentrations of liver markers, kidney markers, inflammatory factors and oxidative stress indicators were significantly increased at the end of reperfusion in the 30 min, 60 min and 90 min groups. Damage to the kidney occurred in the 30 min, 60 min and 90 min groups. The mRNA and protein expression levels of IL-6, IL-8, TNF-α and NF-κB in the kidney and uterus were significantly increased at the end of reperfusion in the 30 min group, and as the time of occlusion extended, these levels continued to increase.

CONCLUSION

Activation of systemic inflammation and ischaemia-reperfusion injury of end-organs occurred when the occlusion time reached 30 min. Therefore, 15 min should be regarded as a safe period of REBOA in zone II.

Literature review of the mechanisms of acute kidney injury secondary to acute liver injury

People exposed to liver ischaemia reperfusion (IR) injury often develop acute kidney injury and the combination is associated with significant morbidity and mortality. Molecular mediators released by the liver in response to IR injury are the likely cause of acute kidney injury (AKI) in this setting, but the mediators have not yet been identified. Identifying the mechanism of injury will allow the identification of therapeutic targets which may modulate both liver IR injury and AKI following liver IR injury.

Hypoxic preconditioning in renal ischaemia-reperfusion injury: a review in pre-clinical models

Ischaemia-reperfusion injury (IRI) is a major cause of acute kidney injury (AKI) and chronic kidney disease, which consists of cellular damage and renal dysfunction. AKI is a major complication that is of particular concern after cardiac surgery and to a lesser degree following organ transplantation in the immediate post-transplantation period, leading to delayed graft function. Because effective therapies are still unavailable, several recent studies have explored the potential benefit of hypoxic preconditioning (HPC) on IRI. HPC refers to the acquisition of increased organ tolerance to subsequent ischaemic or severe hypoxic injury, and experimental evidences suggest a potential benefit of HPC. There are three experimental forms of HPC, and, for better clarity, we named them as follows: physical HPC, HPC via treated-cell administration and stabilised hypoxia-inducible factor (HIF)-1α HPC, or mimicked HPC. The purpose of this review is to present the latest developments in the literature on HPC in the context of renal IRI in pre-clinical models. The data we compiled suggest that preconditional activation of hypoxia pathways protects against renal IRI, suggesting that HPC could be used in the treatment of renal IRI in transplantation.

Daphnetin Preconditioning Decreases Cardiac Injury and Susceptibility to Ventricular Arrhythmia following Ischaemia-Reperfusion through the TLR4/MyD88/NF-Κb Signalling Pathway

BACKGROUND/AIMS

Daphnetin (7,8-dihydroxycoumarin, DAP) exhibits various bioactivities, such as anti-inflammatory and antioxidant activities. However, the role of DAP in myocardial ischaemia/reperfusion (I/R) injury and I/R-related arrhythmia is still uncertain. This study aimed to investigate the mechanisms underlying the effects of DAP on myocardial I/R injury and electrophysiological properties in vivo and in vitro.

METHODS

Myocardial infarct size was measured by triphenyltetrazolium chloride staining. Cardiac function was assessed by echocardiographic and haemodynamic analyses. The levels of creatine kinase-MB, lactate dehydrogenase, malondialdehyde, superoxide dismutase, interleukin-6 (IL-6), and tumour necrosis factor-alpha (TNF-α) were detected using commercial kits. Apoptosis was measured by terminal deoxynucleotidyl-transferase-mediated dUTP nick-end labelling staining and flow cytometry. The viability of H9c2 cells was determined by the Cell Counting Kit-8 assay. In vitro, the levels of IL-6 and TNF-α were measured by quantitative PCR. The expression levels of proteins associated with apoptosis, inflammation, and the Toll-like receptor 4/myeloid differentiation factor 88/nuclear factor kappa B (TLR4/MyD88/NF-κB) signalling pathway were detected by Western blot analysis. The RR, PR, QRS, and QTc intervals were assessed by surface ECG. The 90% action potential duration (APD90), threshold of APD alternans, and ventricular tachycardia inducibility were measured by the Langendorff perfusion technique.

RESULTS

DAP preconditioning decreased myocardial I/R injury and hypoxia/reoxygenation (H/R) injury in cells. DAP preconditioning improved cardiac function after myocardial I/R injury. DAP preconditioning also suppressed apoptosis, attenuated oxidative stress, and inhibited inflammatory responses in vivo and in vitro. Furthermore, DAP preconditioning decreased the susceptibility to ventricular arrhythmia after myocardial I/R. Finally, DAP preconditioning inhibited the expression of TLR4, MyD88, and phosphorylated NF-κB (p-NF-κB)/P65 in mice subjected to I/R and cells subjected to H/R.

CONCLUSIONS

DAP preconditioning protected against myocardial I/R injury and decreased susceptibility to ventricular arrhythmia by inhibiting the TLR4/MyD88/NF-κB signalling pathway.

MiR-126-3p-Enriched Extracellular Vesicles from Hypoxia-Preconditioned VSC 4.1 Neurons Attenuate Ischaemia-Reperfusion-Induced Pain Hypersensitivity by Regulating the PIK3R2-Mediated Pathway

Recent evidence suggests that hypoxia preconditioning can alter the microRNA (miRNA) profile of extracellular vesicles (EVs) and has better neuroprotective effects when enriched miRs are delivered to recipients. However, the roles of exosomal miRNAs in regulating ischaemia-reperfusion (IR)-induced pain hypersensitivity are largely unknown. Thus, we isolated EVs from normoxia-conditioned neurons (Nor-VSC EVs) and Hypo-VSC EVs by ultracentrifugation. After the initial screening by a microarray analysis and quantitative RT-PCR (qRT-PCR), miR-126-3p, which was detected as the most altered miR in the Hypo-VSC EVs, was further confirmed by applying GW4869 to inhibit exosomal secretion. Moreover, transfection with a miR-126 mimic obviously increased miR-126-3p expression in Nor-VSC EVs, whereas a miR-126 inhibitor prevented the increase in miR-126-3p in Hypo-VSC EVs. A rat model of pain was established by performing 8-min occlusion of the aorta. Following IR, compared with the Nor-VSC EVs- or antagomir-126-injected rats, the Hypo-VSC EVs-injected rats displayed improved pain hypersensitivity demonstrated as higher PWT and PWL values. Mechanistically, PIK3R2 is a target of miR-126-3p and might be a modulator of the phosphoinositide 3-kinase (PI3K)/Akt pathway as the PIK3R2 and PI3K immunoreactivities in each group were changed in opposite directions. Compared with the controls, higher protein levels of PI3K and phosphorylated Akt but lower levels of phosphorylated nuclear factor-κ B (NF-κB), tumour necrosis factor (TNF)-α and interleukin (IL)-1β were detected in the spinal cords of the Hypo-VSC EVs-injected rats, and these effects were impaired by an injection of Hypo-VSC EVs combined with antagomir-126. Collectively, the miR-126-3p-enriched Hypo-VSC EVs attenuated IR-induced pain hypersensitivity by restoring miR-126-3p expression in the injured spinal cord and subsequently modulating PIK3R2-mediated PI3K/Akt and NF-κB signalling pathways.

Diabetic cardiomyopathy attenuated the protective effect of ischaemic post-conditioning against ischaemia-reperfusion injury in the isolated rat heart model

The present study was designed to investigate the efficacy of post-conditioning (POC) in the diabetic heart with myopathy (DCM) against ischaemia-reperfusion (I/R) injury in an isolated rat heart model. Present work includes three groups of male Wistar rat viz., (i) normal, (ii) diabetes mellitus (DM) and (iii) DCM and each group was subdivided into normal perfusion, I/R, and POC. Isolated heart from the rats was analysed for tissue injury, contractile function, mitochondrial function, and oxidative stress. Results demonstrated that unlike in DM heart and normal heart, POC procedure failed to recover the DCM heart from I/R induced cardiac dysfunction (measured via cardiac hemodynamics and infarct size. POC was unsuccessful in preserving mitochondrial subsarcolemmal fraction during I/R when compared with DM and normal heart. To conclude, the development of myopathy in diabetic heart abolished the cardioprotective efficacy of POC and the underlying pathology was linked with the mitochondrial dysfunction.KEY MESSAGESEarly studies reported contradicting response of diabetic heart towards post-conditioning mediated cardioprotection.Deteriorated mitochondrial function underlines the failure of post-conditioning in DCM.Efficacy of cardioprotection depends on the varying pathology of different diabetes stages.

A post-preservation vascular flush removes significant populations of donor leukocytes prior to lung transplantation

BACKGROUND

Donor leukocytes are intrinsically involved in acute lung allograft rejection, via self-presentation of donor antigens to recipient leukocytes. Therapeutic modalities to remove donor leukocytes are currently unavailable. We evaluated if a vascular flush immediately following preservation can be used for this purpose.

METHODS

A post-preservation flush was performed with STEEN solution in n = 6 porcine lungs following static cold storage. The first 500 ml effluent from the left atrium was collected and an inflammatory profile performed.

RESULTS

A total of 1.17 billion (±2.8 × 10⁸) viable leukocytes were identified within the effluent. T cells were the dominant cell population, representing 82% of the total mobilised leukocytes, of which <0.01% were regulatory T cells. IL-18 was the most abundant cytokine, with a mean concentration of 84,216 pg (±153,552 pg). In addition, there was a mean concentration of 8819 ng (±4415) cell-free mitochondrial DNA.

CONCLUSION

There is an immediate transfer of donor leukocytes, cytokines and damage-associated molecular patterns following reperfusion. Such a pro-inflammatory donor load may enhance alloantigen presentation and drive recipient alloimmune responses. A post-preservation flush may therefore be an effective method for reducing the immune burden of the donor lung prior to transplantation.

Mitochondria in acute myocardial infarction and cardioprotection

Acute myocardial infarction (AMI) and the heart failure (HF) that often follows are among the leading causes of death and disability worldwide. As such, new treatments are needed to protect the myocardium against the damaging effects of the acute ischaemia and reperfusion injury (IRI) that occurs in AMI, in order to reduce myocardial infarct (MI) size, preserve cardiac function, and improve patient outcomes. In this regard, cardiac mitochondria play a dual role as arbiters of cell survival and death following AMI. Therefore, preventing mitochondrial dysfunction induced by acute myocardial IRI is an important therapeutic strategy for cardioprotection. In this article, we review the role of mitochondria as key determinants of acute myocardial IRI, and we highlight their roles as therapeutic targets for reducing MI size and preventing HF following AMI. In addition, we discuss the challenges in translating mitoprotective strategies into the clinical setting for improving outcomes in AMI patients.

Harpagide from Scrophularia protects rat cortical neurons from oxygen-glucose deprivation and reoxygenation-induced injury by decreasing endoplasmic reticulum stress

ETHNOPHARMACOLOGICAL RELEVANCE

Harpagide is the main ingredient in Scrophularia ningpoensis Hemsl which is used for the therapeutic purpose of treating encephalopathy. Harpagide has shown promise in the treatment of oxygen-glucose deprivation and reoxygenation (OGD/R)-induced brain injury. However, the underlying mechanisms remain unclear.

AIM OF STUDY

In this study, we aimed to determine the neuroprotective effect of harpagide on rat cortical neurons under OGD/R conditions that induce the development of ischaemia-reperfusion (I/R).

MATERIALS AND METHODS

To explore the biological function of harpagide in cerebral ischaemia-reperfusion injury (CIRI), The CIRI model was established by oxygen-glucose deprivation and reoxygenation (OGD/R) on rat cortical neurons. It tested cell survival rate by 3-(4,5-dimethylthiazol-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay, apoptosis by flow cytometry, intracellular Ca²⁺ concentration [Ca²⁺] _i by cofocal laser, and expressions related to endoplasmic reticulum stress (ERS) by RT-PCR and Western blot.

RESULTS

We found that pretreatment with harpagide (50 μM) prevented OGD/R-induced apoptotic cell death. Harpagide also significantly decreased the gene expression levels and protein production of ERS-related proteins. We found that harpagide also exerted a neuroprotective effect on TG-induced apoptosis in rat cortical neurons and decreased the gene expression levels and protein production of GRP78, caspase-12 and CHOP. We also measured the intracellular calcium ion concentration ([Ca²⁺]_i) in neurons and found that harpagide significantly decreased the [Ca²⁺]_i induced by OGD/R and TG.

CONCLUSION

These results suggest that harpagide protects against OGD/R-induced cell apoptosis, likely by decreasing ERS. Collectively, harpagide was demonstrated to be a prominent suppressor of ERS and prevented the apoptosis of rat cortical neurons. Based on the results, harpagide could potentially serve as a therapeutic agent of ischaemia-like injury associated with excessive ERS and apoptosis.

Riluzole protects against skeletal muscle ischaemia-reperfusion injury in a porcine model

INTRODUCTION

Skeletal muscle ischaemia-reperfusion injury (IRI) can be a life threatening condition. It is relevant to various aspects of the management of trauma and surgical patients. Currently there lacks a pharmacological agent that can be used to dampen the effects of IRI. Riluzole has been shown to reduce the effects of IRI on various organ systems, but there have yet to be any studies on the effects in IRI of skeletal muscle. Our aim was to investigate the effects of Riluzole on IRI in the skeletal muscle of pigs.

METHODS

Twenty-two pigs were randomly divided into groups. Riluzole was administered before ligation of the femoral artery to produce ischaemia in the tibialis anterior muscle in the experimental group but not the control group. The microscopic appearance of muscles were recorded, a TUNEL assay was used to identify DNA damage and glutathione levels were measured.

RESULTS

In the Riluzole group, muscle fibres appeared less wavy and less oedematous compared to the control group. The Riluzole group also had less evidence of DNA fragmentation on the TUNEL assay. The glutathione levels in the Riluzole group were also significantly greater than the control group.

DISCUSSION

Our findings suggest that Riluzole can potentially reduce the effects of IRI on skeletal muscle. This is potentially due to the ability of Riluzole to block sodium channels, decreasing action potentials and therefore glutamate release. It also acts to decrease intracellular calcium levels, which prevents apoptosis. Riluzole is a promising drug for the prevention of IRI in skeletal muscle, but further research is required.

Neuroprotective effect of salvianolate on cerebral ischaemia-reperfusion injury in rats by inhibiting the Caspase-3 signal pathway

Salvianolate has been widely used for the treatment of cerebrovascular diseases. However, the detailed molecular mechanism of how it alleviates cerebral ischaemia-reperfusion injury is not well understood. In the present study, we investigated the neuroprotective effects of salvianolate in acute cerebral infarction using the PC12 cell oxygen-glucose deprivation (OGD) model in vitro and the rat transient middle cerebral artery occlusion (MCAO) model in vivo. The results showed that the salvianolate significantly reduced the level of reactive oxygen species and inhibited the Caspase-3 signalling pathway in vitro; at the same time, in vivo experiments showed that salvianolate obviously reduced the infarct area (12.9%) and repaired cognitive function compared with the model group (28.28%). In conclusion, our data demonstrated that the salvianolate effectively alleviated cerebral ischaemia-reperfusion injury via suppressing the Caspase-3 signalling pathway.

Protective effect of hyperbaric oxygen treatment on rat intestinal mucosa after mesenteric ischaemia and reperfusion

INTRODUCTION

Mesenteric ischaemia results from a lack of adequate blood flow to and oxygenation of the mesentery and intestines. The aim of the present study was to evaluate the effect of hyperbaric oxygen treatment (HBOT) on the healing process in intestinal mucosa of rats undergoing mesenteric ischaemia and reperfusion.

METHODS

Thirty-two Wistar-Albino rats were divided into four groups of eight: 1) ischaemia/reperfusion (I/R); 2) sham operation; 3) I/R+HBOT started 6 hours after reperfusion; 4) I/R+HBOT started 12 hours after reperfusion. In the I/R groups, a vascular clamp was placed across the superior mesenteric artery to occlude arterial circulation for 60 minutes, followed by reperfusion. A dose of HBOT consisted of 100% oxygen breathing for 90 minutes at 2.5 atmospheres absolute pressure. Thirteen doses of HBOT were administered after ischaemia. The rats were sacrificed on the eighth day, and their intestinal tissues were harvested for histopathologic analysis. The tissue levels of catalase, malondialdehyde, and glutathione were determined.

RESULTS

The histopathological scores (HSCORE) were consistent with macroscopic examinations. The scores were significantly higher (worse) in Group 1 compared to Group 2, Group 3, and Group 4 (for all comparisons, P < 0.05). Group 4's HSCORE was significantly higher than those of Group 2 and Group 3 (for both comparisons P < 0.05). Group 3's HSCOREs were only marginally higher than Group 2. Group 3 exhibited higher glutathione levels than Group 1 (P < 0.05). There were no significant differences across the groups with respect to malondialdehyde and catalase levels.

CONCLUSION

A beneficial effect of HBOT was observed on oxidative stress and inflammation in acute mesenteric ischaemia-reperfusion.

Neuroprotection in Rats Following Ischaemia-Reperfusion Injury by GLP-1 Analogues-Liraglutide and Semaglutide

PURPOSE

A substantial number of ischaemic stroke patients who receive reperfusion therapy in the acute phase do not ever fully recover. This reveals the urgent need to develop new adjunctive neuroprotective treatment strategies alongside reperfusion therapy. Previous experimental studies demonstrated the potential of glucagon-like peptide-1 (GLP-1) to reduce acute ischaemic damage in the brain. Here, we examined the neuroprotective effects of two GLP-1 analogues, liraglutide and semaglutide.

METHODS

A non-diabetic rat model of acute ischaemic stroke involved 90, 120 or 180 min of middle cerebral artery occlusion (MCAO). Liraglutide or semaglutide was administered either i.v. at the onset of reperfusion or s.c. 5 min before the onset of reperfusion. Infarct size and functional status were evaluated after 24 h or 72 h of reperfusion.

RESULTS

Liraglutide, administered as a bolus at the onset of reperfusion, reduced infarct size by up to 90% and improved neuroscore at 24 h in a dose-dependent manner, following 90-min, but not 120-min or 180-min ischaemia. Semaglutide and liraglutide administered s.c. reduced infarct size by 63% and 48%, respectively, and improved neuroscore at 72 h following 90-min MCAO. Neuroprotection by semaglutide was abolished by GLP1-R antagonist exendin(9-39).

CONCLUSION

Infarct-limiting and functional neuroprotective effects of liraglutide are dose-dependent. Neuroprotection by semaglutide is at least as strong as by liraglutide and is mediated by GLP-1Rs.

Spermidine ameliorates liver ischaemia-reperfusion injury through the regulation of autophagy by the AMPK-mTOR-ULK1 signalling pathway

BACKGROUND

Hepatic ischaemia-reperfusion (IR) injury is a common clinical challenge lacking effective therapy. The aim of this study was to investigate whether spermidine has protective effects against hepatic IR injury through autophagy.

METHODS

Liver ischaemia reperfusion was induced in male C57BL/6 mice. Then, liver function, histopathology, cytokine production and immunofluorescence were evaluated to assess the impact of spermidine pre-treatment on IR-induced liver injury. Autophagosome formation was observed by transmission electron microscopy. Western blotting was used to explore the underlying mechanism and its relationship with autophagy, and TUNEL staining was conducted to determine the relationship between apoptosis and autophagy in the ischaemic liver.

RESULTS

The results of the transaminase assay, histopathological examination, and pro-inflammatory cytokine production and immunofluorescence evaluations demonstrated that mice pre-treated with spermidine showed significantly preserved liver function. Further experiments demonstrated that mice administered spermidine before the induction of IR exhibited increased autophagy via the AMPK-mTOR-ULK1 pathway, and TUNEL staining revealed that spermidine attenuated IR-induced apoptosis in the liver.

CONCLUSIONS

Our results provide the first line of evidence that spermidine provides protection against IR-induced injury in the liver by regulating autophagy through the AMPK-mTOR-ULK1 signalling pathway. These results suggest that spermidine may be beneficial for hepatic IR injury.

A pilot study into the use of Continuous Venous Hyperfiltration to manage patients in a critical state with dysregulated inflammation

INTRODUCTION

Haemofiltration paradigms used to manage critically ill patients with a dysregulated inflammatory response (DIR) assess kidney function to monitor its onset, adaptation, and completion. A Continuous Venous Hyperfiltration (CONVEHY) protocol is presented, in which a non-specific adsorption membrane (AN69-ST-Heparin Grafted) is used with citrate as an anticoagulant and substitution fluid. CONVEHY uses tools readily available to achieve kidney related and non-related objectives, and it is guided by the monitoring of pathophysiological responses.

OBJECTIVES

To compare the response to an AN69-ST-HG membrane when heparin (He, n=5: Standard protocol) or citrate (Ci, n=6: CONVEHY protocol) was used to evaluate whether a larger study into the benefits of this protocol would be feasible.

MATERIALS AND METHODS

In a retrospective pilot study, the benefits of the CONVEHY protocol to manage patients with a DIR in a surgical critical care unit (CCUs) were assessed by evaluating the SOFA (Sequential Organ Failure Assessment) (He 11 ± 2.35; Ci 11 ± 3.63: p=0.54) and APACHE II (He 28.60 ± 9.40; Ci 24 ± 8.46: p=0.93) scores.

RESULTS

Nights in hospital (He 35.2 ± 16.3 nights; Ci 9 ± 2.53: p=0.004), hospital admission after discharge from the CCUs (He 40.25 ± 21.82; Ci 13.2 ± 4.09: p=0.063), patients hospitalised >20 days (He 80%; Ci 0%: p=0.048), days requiring mechanical ventilation (He 16 ± 5.66; Ci 4 ± 1.72: p=0.004), and the predicted (55.39 ± 26.13%) versus real mortality in both groups (9.1%: p=0.004).

CONCLUSIONS

The CONVEHY protocol improves the clinical responses of patients with DIR, highlighting the potential value of performing larger and confirmatory studies.

Stromal cell-derived factor-1α signals via the endothelium to protect the heart against ischaemia-reperfusion injury

AIMS

The chemokine stromal derived factor-1α (SDF-1α) is known to protect the heart acutely from ischaemia-reperfusion injury via its cognate receptor, CXCR4. However, the timing and cellular location of this effect, remains controversial.

METHODS AND RESULTS

Wild type male and female mice were subjected to 40 min LAD territory ischaemia in vivo and injected with either saline (control) or SDF-1α prior to 2 h reperfusion. Infarct size as a proportion of area at risk was assessed histologically using Evans blue and triphenyltetrazolium chloride. Our results confirm the cardioprotective effect of exogenous SDF-1α in mouse ischaemia-reperfusion injury and, for the first time, show protection when SDF-1α is delivered just prior to reperfusion, which has important therapeutic implications. The role of cell type was examined using the same in vivo ischaemia-reperfusion protocol in cardiomyocyte- and endothelial-specific CXCR4-null mice, and by Western blot analysis of endothelial cells treated in vitro. These experiments demonstrated that the acute infarct-sparing effect is mediated by endothelial cells, possibly via the signalling kinases Erk1/2 and PI3K/Akt. Unexpectedly, cardiomyocyte-specific deletion of CXCR4 was found to be cardioprotective per se. RNAseq analysis indicated altered expression of the mitochondrial protein co-enzyme Q10b in these mice.

CONCLUSIONS

Administration of SDF-1α is cardioprotective when administered prior to reperfusion and may, therefore, have clinical utility. SDF-1α-CXCR4-mediated cardioprotection from ischaemia-reperfusion injury is contingent on the cellular location of CXCR4 activation. Specifically, cardioprotection is mediated by endothelial signalling, while cardiomyocyte-specific deletion of CXCR4 has an infarct-sparing effect per se.

Machine perfusion of the liver: Which is the best technique to mitigate ischaemia-reperfusion injury?

Longstanding research describes the mechanisms whereby the restoration of blood flow and reoxygenation (reperfusion) aggravates the ischaemic injury caused by a period of anoxia to a donor liver. This phenomenon, called ischaemia-reperfusion injury (IRI), leads to parenchymal cell death, microcirculatory failure, and inflammatory immune response. Clinically, IRI is the main factor responsible for the occurrence of posttransplant graft dysfunction and ischaemic-type biliary lesions. While extended criteria donor livers are more vulnerable to IRI, their utilisation is required to address the shortfall in donor organs. Thus, the mitigation of IRI should drive the setting of a new benchmark for marginal organ preservation. Herein, strategies incorporating different modalities of machine perfusion of the liver to alleviate IRI are discussed in conjunction with advantages and disadvantages of individual protocols. Techniques leading to reperfusion of the liver during machine perfusion (in situ normothermic regional perfusion and ex situ normothermic machine perfusion) may mitigate IRI by shortening the ischaemic period of the organs. This benefit potentially escalates from the minimum level, obtained following just partial alleviation of the ischaemic period, to the maximum level, which can be potentially achieved with ischaemia-free organ transplantation. Techniques that do not lead to reperfusion of the liver during machine perfusion (hypothermic, subnormothermic, and controlled-oxygenated rewarming) optimise mitochondrial oxidative function and replenish cellular energy stores, thereby lowering reactive oxygen species production as well as the activation of downstream inflammatory pathways during reperfusion. Further mechanistic insights into IRI may guide the development of donor-specific protocols of machine perfusion on the basis of the limitations of individual categories of extended criteria donor organs.

Cellular and acellular ex vivo lung perfusion preserve functional lung ultrastructure in a large animal model: a stereological study

Background

Ex vivo lung perfusion (EVLP) is used by an increasing number of transplant centres. It is still controversial whether an acellular or cellular (erythrocyte enriched) perfusate is preferable. The aim of this paper was to evaluate whether acellular (aEVLP) or cellular EVLP (cEVLP) preserves functional lung ultrastructure better and to generate a hypothesis regarding possible underlying mechanisms.

Methods

Lungs of 20 pigs were assigned to 4 groups: control, ischaemia (24 h), aEVLP and cEVLP (both EVLP groups: 24 h ischaemia + 12 h EVLP). After experimental procedures, whole lungs were perfusion fixed, samples for light and electron microscopic stereology were taken, and ventilation, diffusion and perfusion related parameters were estimated.

Results

Lung structure was well preserved in all groups. Lungs had less atelectasis and higher air content after EVLP. No significant group differences were found in alveolar septum composition or blood-air barrier thickness. Small amounts of intraalveolar oedema were detected in both EVLP groups but significantly more in aEVLP than in cEVLP.

Conclusions

Both EVLP protocols supported lungs well for up to 12 h and could largely prevent ischaemia ex vivo reperfusion associated lung injury. In both EVLP groups, oedema volume remained below the level of functional relevance. The group difference in oedema formation was possibly due to inferior septal perfusion in aEVLP.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0942-5) contains supplementary material, which is available to authorized users.

Glycocalyx Degradation after Pulmonary Transplantation Surgery

PURPOSE

Ischaemia-reperfusion injury (IRI) is a main cause of morbidity after pulmonary resection surgery. The degradation of glycocalyx, a dynamic layer of macromolecules at the luminal surface of the endothelium, seems to participate in tissue dysfunction after IRI. Lidocaine has a proven anti-inflammatory activity in several tissues but its modulation of glycocalyx has not been investigated. This work aimed to investigate the potential involvement of glycocalyx in lung IRI in a lung auto-transplantation model and the possible effect of lidocaine in modulating IRI.

METHODS

Three groups (sham-operated, control, and lidocaine), each consisting of 6 Large White pigs, were subjected to lung auto-transplantation. All groups received the same anaesthesia. In addition, the lidocaine group received a continuous IV administration of lidocaine (1.5 mg/kg/h). Lung tissue and plasma samples were taken before pulmonary artery clamp, before reperfusion, and 30 and 60 min post-reperfusion in order to analyse pulmonary oedema, glycocalyx components, adhesion molecules, and myeloperoxidase level.

RESULTS

Ischaemia caused pulmonary oedema, which was greater after reperfusion. This effect was accompanied by decreased levels of syndecan-1 and heparan sulphate in the lung samples, together with increased levels of both glycocalyx components in the plasma samples. After reperfusion, neutrophil activation and the expression of adhesion molecules were increased. All these alterations were significantly lower or absent in the lidocaine group.

CONCLUSION

Lung IRI caused glycocalyx degradation that contributed to neutrophil activation and adhesion. The administration of lidocaine was able to protect the lung from glycocalyx degradation.

Cardioprotective role of azafrin in against myocardial injury in rats via activation of the Nrf2-ARE pathway

BACKGROUND

The root of Centranthera grandiflora Benth. is a Chinese ethnodrug known as Ye-Can-Dou-Gen (YCDG) and has been widely used to treat cardiovascular diseases in Hmong, Yunnan Province, China; however, its mechanisms of action were largely unknown. Azafrin, a natural carotenoid, is one of the most abundant active ingredients in YCDG.

PURPOSE

We aimed to explore the cardioprotective effects of azafrin on myocardial infarction (MI) and myocardial ischaemia-reperfusion (MIR) injury and to clarify its underlying myocardial protective mechanisms.

METHODS

The in vitro cardioprotective effects of azafrin against oxidative stress injury in H9c2 cells were assessed by the ferric reducing antioxidant power (FRAP) assay and a viability assay in the presence of H₂O₂-induced oxidative insults, whereas the in vivo effects were assessed with the echocardiographic and histopathological evaluation together with 2,3,5-triphenyltetrazolium chloride (TTC) and serum biochemical analyses in vivo. Then, we used the luciferase reporter gene assay to measure Nrf2 transcriptional activity in HEK 293 cells and analysed the expression levels of enzymes downstream of Nrf2-ARE signalling by q-PCR and western blotting.

RESULTS

Azafrin showed higher FRAP values than FeSO₄ and exhibited prophylactic and therapeutic potency against H₂O₂-induced cell injury. Additionally, azafrin treatment dramatically improved cardiac function; ameliorated the infarct size and pathological changes in rats; decreased the levels of MDA, cTnI, and myocardial enzymes and elevated SOD activity in vivo. In addition, azafrin significantly elevated the transcriptional activity of Nrf2 in HEK 293 cells and up-regulated the mRNA expression levels of genes downstream of Nrf2-ARE pathway activation in H9c2 cells. Furthermore, the protein expression levels of HO-1 and NQO1 in the cytoplasm and Nrf2 in the nucleus were also up-regulated in both the in vivo and in vitro experiments.

CONCLUSION

Azafrin exhibited cardioprotective effects against myocardial injury via activation of the Nrf2-ARE pathway. As a natural carotenoid antioxidant, this molecule represents a promising cardioprotective adjuvant for the prophylaxis and treatment of ischaemic heart diseases.

Delta Opioid Receptors and Cardioprotection

The opioid receptor family, with associated endogenous ligands, has numerous roles throughout the body. Moreover, the delta opioid receptor (DORs) has various integrated roles within the physiological systems, including the cardiovascular system. While DORs are important modulators of cardiovascular autonomic balance, they are well-established contributors to cardioprotective mechanisms. Both endogenous and exogenous opioids acting upon DORs have roles in myocardial hibernation and protection against ischaemia-reperfusion (I-R) injury. Downstream signalling mechanisms governing protective responses alternate, depending on the timing and duration of DOR activation. The following review describes models and mechanisms of DOR-mediated cardioprotection, the impact of co-morbidities and challenges for clinical translation.

Mechanisms of autophagy activation in endothelial cell and their targeting during normothermic machine liver perfusion

Ischaemia-reperfusion injury (IRI) is the leading cause of injury seen in the liver following transplantation. IRI also causes injury following liver surgery and haemodynamic shock. The first cells within the liver to be injured by IRI are the liver sinusoidal endothelial cells (LSEC). Recent evidence suggests that LSEC co-ordinate and regulates the livers response to a variety of injuries. It is becoming increasingly apparent that the cyto-protective cellular process of autophagy is a key regulator of IRI. In particular LSEC autophagy may be an essential gatekeeper to the development of IRI. The recent availability of liver perfusion devices has allowed for the therapeutic targeting of autophagy to reduce IRI. In particular normothermic machine liver perfusion (NMP-L) allow the delivery of pharmacological agents to donor livers whilst maintaining physiological temperature and hepatic flow rates. In this review we summarise the current understanding of endothelial autophagy and how this may be manipulated during NMP-L to reduce liver IRI.

Sub-therapeutic doses of fluvastatin and valsartan are more effective than therapeutic doses in providing beneficial cardiovascular pleiotropic effects in rats: A proof of concept study

BACKGROUND

Statins and sartans can, in therapeutic doses, induce pleiotropic cardiovascular effects. Similar has recently been shown also for sub-therapeutic doses. We thus explored and compared the cardiovascular pleiotropic efficacy of sub-therapeutic vs. therapeutic doses.

METHODS

Wistar rats were randomly divided into 7 groups receiving fluvastatin, valsartan and their combination in sub-therapeutic and therapeutic doses, or saline. After 6weeks, the animals were euthanised, their hearts and thoracic aortas isolated, and blood samples taken. Endothelium-dependent relaxation of the thoracic aortae and ischaemic-reperfusion injury of the isolated hearts were assessed along with the related serum parameters and genes expression.

RESULTS

Fluvastatin and valsartan alone or in combination were significantly more effective in sub-therapeutic than therapeutic doses. The sub-therapeutic combination greatly increased thoracic aorta endothelium-dependent relaxation and maximally protected the isolated hearts against ischaemia-reperfusion injury and was thus most effective. Beneficial effects were accompanied by increased levels of nitric oxide (NO) and decreased levels of asymmetric dimethylarginine (ADMA) in the serum (again prominently induced by the sub-therapeutic combination). Furthermore, nitric oxide synthase 3 (NOS3) and endothelin receptor type A (EDNRA) genes expression increased, but only in both combination groups and without significant differences between them. In the therapeutic dose groups, fluvastatin and valsartan decreased cholesterol values and systolic blood pressure.

CONCLUSION

Sub-therapeutic doses of fluvastatin and valsartan are more effective in expressing cardiovascular pleiotropic effects than therapeutic doses of fluvastatin and/or valsartan. These results could be of significant clinical relevance.

Chronic β1-adrenoceptor blockade impairs ischaemic tolerance and preconditioning in murine myocardium

β-adrenoceptor antagonists are commonly used in ischaemic heart disease (IHD) patients, yet may impair signalling and efficacy of 'cardioprotective' interventions. We assessed effects of chronic β1-adrenoceptor antagonism on myocardial resistance to ischaemia-reperfusion (IR) injury and the ability of cardioprotective interventions [classic ischaemic preconditioning (IPC); novel sustained ligand-activated preconditioning (SLP)] to reduce IR injury in murine hearts. Young male C57Bl/6 mice were untreated or received atenolol (0.5g/l in drinking water) for 4 weeks. Subsequently, two cardioprotective stimuli were evaluated: morphine pellets implanted (to induce SLP, controls received placebo) 5 days prior to Langendorff heart perfusion, and IPC in perfused hearts (3×1.5min ischaemia/2min reperfusion). Atenolol significantly reduced in vivo heart rate. Untreated control hearts exhibited substantial left ventricular dysfunction (~50% pressure development recovery, ~20mmHg diastolic pressure rise) with significant release of lactate dehydrogenase (LDH, tissue injury indicator) after 25min ischaemia/45min reperfusion. Contractile dysfunction and elevated LDH were reduced >50% with IPC and SLP. While atenolol treatment did not modify baseline contractile function, post-ischaemic function was significantly depressed compared to untreated hearts. Atenolol pre-treatment abolished beneficial effects of IPC, whereas SLP protection was preserved. These data indicate that chronic β1-adrenoceptor blockade can exert negative effects on functional IR tolerance and negate conventional IPC (implicating β1-adrenoceptors in IR injury and IPC signalling). However, novel morphine-induced SLP is resistant to inhibition by β1-adrenoceptor antagonism.

Strategies to attenuate micro-vascular obstruction during P-PCI: the randomized reperfusion facilitated by local adjunctive therapy in ST-elevation myocardial infarction trial

Background

Microvascular obstruction (MVO) following primary percutaneous coronary intervention (PPCI) treatment of ST-segment elevation myocardial infarction (STEMI) contributes to infarct expansion, left ventricular (LV) remodelling, and worse clinical outcomes. The REFLO-STEMI trial tested whether intra-coronary (IC) high-dose adenosine or sodium nitroprusside (SNP) reduce infarct size and/or MVO determined by cardiac magnetic resonance (CMR).

Methods and results

REFLO-STEMI, a prospective, open-label, multi-centre trial with blinded endpoints, randomized (1:1:1) 247 STEMI patients with single vessel disease presenting within 6 h of symptom onset to IC adenosine (2–3 mg total) or SNP (500 μg total) immediately following thrombectomy and again following stenting, or to standard PPCI. The primary endpoint was infarct size % LV mass (%LVM) on CMR undertaken 24–96 h after PPCI (n = 197). Clinical follow-up was to 6 months. There was no significant difference in infarct size (%LVM, median, interquartile range, IQR) between adenosine (10.1, 4.7–16.2), SNP (10.0, 4.2–15.8), and control (8.3, 1.9–14.0), P = 0.062 and P = 0.160, respectively, vs. control. MVO (% LVM, median, IQR) was similar across groups (1.0, 0.0–3.7, P = 0.205 and 0.6, 0.0–2.4, P = 0.244 for adenosine and SNP, respectively, vs. control 0.3, 0.0–2.8). On per-protocol analysis, infarct size (%LV mass, 12.0 vs. 8.3, P = 0.031), major adverse cardiac events (hazard ratio, HR, 5.39 [1.18–24.60], P = 0.04) at 30 days and 6 months (HR 6.53 [1.46–29.2], P = 0.01) were increased and ejection fraction reduced (42.5 ± 7.2% vs. 45.7 ± 8.0%, P = 0.027) in adenosine-treated patients compared with control.

Conclusions

High-dose IC adenosine and SNP during PPCI did not reduce infarct size or MVO measured by CMR. Furthermore, adenosine may adversely affect mid-term clinical outcome.

Clinical Trial registration

ClinicalTrials.gov Identifier: NCT01747174; https://clinicaltrials.gov/ct2/show/NCT01747174

Post-conditioning through lower limb ischemia-reperfusion can alleviate lung ischemia-reperfusion injury

OBJECTIVE

Operation on the infrarenal aorta could cause ischemic-reperfusion (IR) injury in local tissues and remote organs (e.g. the lung). We aim to explore the method of reducing lung ischemia-reperfusion damage after lower limb IR with post conditioning (LIPC).

METHODS

Bilateral lower limb ischemia was performed in Sprague-Dawley (SD) rats, and then animals were divided into 4 groups: IR-Sham-operated, IR, post conditioned-IR (LIPC) and bilateral lower limb ischemia (LIR). The serum free radical, histological changes, Wet/Dry (W/D) ratio, levels of TNF-α, IL-6, cytokines and chemokines were tested and compared.

RESULTS

Post-conditioning could ameliorate histological injuries in the lung when compared to IR group. The serum free radical is significantly lower in LIPC group than IR groups. W/D ratio in LIPC groups is significantly lower. LIPC also could reduce the expression of cytokines and chemokines.

CONCLUSION

post conditioning could reduce long-term damages of the lung after lower limb ischemic-reperfusion injury.

Cardioprotection for percutaneous coronary intervention--reperfusion quality as well as quantity

Ischaemia-reperfusion (IR) injury is an important cause of myocardial damage during percutaneous coronary intervention (PCI). There are few therapies in widespread clinical use which impact on IR injury and it remains an important and underutilized target for treatment in acute myocardial infarction. This review will examine the translational scientific evidence for ischaemic conditioning and pharmacological agents including conditioning mimetics such as cyclosporine, anti-inflammatory agents, and those which modify myocardial glucose metabolism. We will address the reasons why many trials have failed to demonstrate clinical benefit and emphasize the need to deliver the right therapy to the right patient, at the right time to achieve successful translation of cardioprotection from bench-to-bedside. We critique trial design and offer advice for future translational trials in the field to ensure that effective treatments can be demonstrated clinically to improve patient outcomes during PCI.

Intravenous sodium nitrite in acute ST-elevation myocardial infarction: a randomized controlled trial (NIAMI)

AIM

Despite prompt revascularization of acute myocardial infarction (AMI), substantial myocardial injury may occur, in part a consequence of ischaemia reperfusion injury (IRI). There has been considerable interest in therapies that may reduce IRI. In experimental models of AMI, sodium nitrite substantially reduces IRI. In this double-blind randomized placebo controlled parallel-group trial, we investigated the effects of sodium nitrite administered immediately prior to reperfusion in patients with acute ST-elevation myocardial infarction (STEMI).

METHODS AND RESULTS

A total of 229 patients presenting with acute STEMI were randomized to receive either an i.v. infusion of 70 μmol sodium nitrite (n = 118) or matching placebo (n = 111) over 5 min immediately before primary percutaneous intervention (PPCI). Patients underwent cardiac magnetic resonance imaging (CMR) at 6-8 days and at 6 months and serial blood sampling was performed over 72 h for the measurement of plasma creatine kinase (CK) and Troponin I. Myocardial infarct size (extent of late gadolinium enhancement at 6-8 days by CMR-the primary endpoint) did not differ between nitrite and placebo groups after adjustment for area at risk, diabetes status, and centre (effect size -0.7% 95% CI: -2.2%, +0.7%; P = 0.34). There were no significant differences in any of the secondary endpoints, including plasma troponin I and CK area under the curve, left ventricular volumes (LV), and ejection fraction (EF) measured at 6-8 days and at 6 months and final infarct size (FIS) measured at 6 months.

CONCLUSIONS

Sodium nitrite administered intravenously immediately prior to reperfusion in patients with acute STEMI does not reduce infarct size.

The depletion of donor macrophages reduces ischaemia-reperfusion injury after mouse lung transplantation

OBJECTIVES

Macrophages (M) are one of the most important cells of the innate immune system for first line defense. Upon transplantation (Tx), M play a prominent role during lung ischaemia reperfusion (I/R) injury. Here, we hypothesize that the depletion of donor M ameliorates the post-transplant lung I/R injury.

METHODS

Orthotopic single-lung Tx was performed between syngeneic BALB/c mice after a cold ischaemic time of 8 h and a reperfusion time of 10 h. Prior to graft implantation, alveolar macrophages of donor lungs were selectively depleted applying the 'suicide technique' by intratracheal application of clodronate liposomes (experimental, n = 6) vs the application of empty liposomes (control, n = 6). Cell count (number of F4/80(+)-macrophages) and graft injury were evaluated by histology and immunohistochemistry, and levels of lactat dehydrogenase (LDH) (apoptosis assay), enzyme linked immunosorbent assay for nuclear protein high-mobility-group-protein B1 (HMGB1), tumor necrosis factor alpha (TNF-α) and transforming growth factor beta1 (TGF-β1) in plasma were analysed.

RESULTS

Clodronate liposomes successfully reduced 70% of M from donor lungs when compared with grafts treated with empty liposome only. M-depleted transplants showed improved histology and revealed considerably less graft damage when compared with control recipients (LDH, P = 0.03; HMGB1, P = 0.3). Oxygenation capacity was ameliorated in M-depleted transplants, if not significant (P = 0.114); however, wet/dry ratio did not differ between groups (P = 0.629). The inflammatory response was significantly reduced in M-depleted mice when compared with control recipients (TNF-α, P = 0.042; TGF-β1, P = 0.039).

CONCLUSIONS

The selective depletion of M in donor lung transplants can be successfully performed and results in a sustained anti-inflammatory response upon I/R-injury. The beneficial effect of this preconditioning method should be further evaluated as a promising tool for the attenuation of I/R prior to graft implantation in clinical Tx.

Addition of vardenafil into storage solution protects the endothelium in a hypoxia-reoxygenation model

OBJECTIVE

Based upon the well known protective effect of intracellular cyclic guanosine monophosphate (cGMP) accumulation, we tested the hypothesis that storage solution enriched with optimal concentration of the phosphodiestherase-5 inhibitor vardenafil could provide better protection of vascular grafts against reperfusion injury after long-term cold ischaemic storage.

METHODS

Isolated thoracic aorta obtained from rats underwent 24-h cold ischaemic preservation in physiological saline or vardenafil (10(-11) M)-supplemented saline solution. Reperfusion injury was simulated by hypochlorite (200 μM) exposure for 30 minutes. Endothelium-dependent vasorelaxation was assessed, and histopathological and molecular-biological examination of the aortic tissue were performed.

RESULTS

Compared with the control group, the saline group showed significantly attenuated endothelium-dependent maximal relaxation (Rmax) to acetylcholine after hypoxia-reoxygenation, which was significantly improved by vardenafil supplementation (Rmax control: 98 ± 1%; saline: 48 ± 6%; vardenafil: 75 ± 4%; p < .05). Vardenafil treatment significantly reduced DNA strand breaks (control: 10.6 ± 6.2%; saline: 72.5 ± 4.0%; vardenafil: 14.2 ± 5.2%; p < .05) and increased cGMP score in the aortic wall (control: 8.2 ± 0.6; saline: 4.5 ± 0.3; vardenafil: 6.7 ± 0.6; p < .05).

CONCLUSIONS

Our results support the view that impairment of intracellular cGMP signalling plays a role in the pathogenesis of the endothelial dysfunction induced by cold storage warm reperfusion, which can be effectively reversed by pharmacological phosphodiesterase-5 inhibition.