Nitric oxide ventilation of rat lungs from non-heart-beating donors improves posttransplant function

Therapeutic benefits of nitric oxide in lung transplantation

Lung transplantation is an evolutionary procedure from its experimental origin in the twentieth century and is now recognized as an established and routine life-saving intervention for a variety of end-stage pulmonary diseases refractory to medical management. Despite the success and continuous refinement in lung transplantation techniques, the widespread application of this important life-saving intervention is severely hampered by poor allograft quality offered from donors-after-brain-death. This has necessitated the use of lung allografts from donors-after-cardiac-death (DCD) as an additional source to expand the pool of donor lungs. Remarkably, the lung exhibits unique properties that may make it ideally suitable for DCD lung transplantation. However, primary graft dysfunction (PGD), allograft rejection and other post-transplant complications arising from unavoidable ischemia-reperfusion injury (IRI) of transplanted lungs, increase morbidity and mortality of lung transplant recipients annually. In the light of this, nitric oxide (NO), a selective pulmonary vasodilator, has been identified as a suitable agent that attenuates lung IRI and prevents PGD when administered directly to lung donors prior to donor lung procurement, or to recipients during and after transplantation, or administered indirectly by supplementing lung preservation solutions. This review presents a historical account of clinical lung transplantation and discusses the lung as an ideal organ for DCD. Next, the author highlights IRI and its clinical effects in lung transplantation. Finally, the author discusses preservation solutions suitable for lung transplantation, and the protective effects and mechanisms of NO in experimental and clinical lung transplantation.

Maximizing organs for donation: the potential for ex situ normothermic machine perfusion

Currently, there is a shortfall in the number of suitable organs available for transplant resulting in a high number of patients on the active transplant waiting lists worldwide. To address this shortfall and increase the utilization of donor organs, the acceptance criteria for donor organs is gradually expanding including increased use of organs from donation after circulatory death. Use of such extended criteria donors and exposure of organs to more prolonged periods of warm or cold ischaemia also increases the risk of primary graft dysfunction occurring. Normothermic machine perfusion (NMP) offers a unique opportunity to objectively assess donor organ function outside the donor body and potentially recondition those deemed unsuitable on initial evaluation prior to implantation in the recipient. Furthermore, NMP provides a platform to support the use of established and novel therapeutics delivered directly to the organ, without the need to worry about potential deleterious 'off-target' side effects typically considered when treating the whole patient. This review will explore some of the novel therapeutics currently being added to perfusion platforms during NMP experimentally in an attempt to improve organ function and post-transplant outcomes.

Redox-Mechanisms of Molecular Hydrogen Promote Healthful Longevity

Age-related diseases represent the largest threat to public health. Aging is a degenerative, systemic, multifactorial and progressive process, coupled with progressive loss of function and eventually leading to high mortality rates. Excessive levels of both pro- and anti-oxidant species qualify as oxidative stress (OS) and result in damage to molecules and cells. OS plays a crucial role in the development of age-related diseases. In fact, damage due to oxidation depends strongly on the inherited or acquired defects of the redox-mediated enzymes. Molecular hydrogen (H2) has recently been reported to function as an anti-oxidant and anti-inflammatory agent for the treatment of several oxidative stress and aging-related diseases, including Alzheimer's, Parkinson's, cancer and osteoporosis. Additionally, H2 promotes healthy aging, increases the number of good germs in the intestine that produce more intestinal hydrogen and reduces oxidative stress through its anti-oxidant and anti-inflammatory activities. This review focuses on the therapeutic role of H2 in the treatment of neurological diseases. This review manuscript would be useful in knowing the role of H2 in the redox mechanisms for promoting healthful longevity.

L-alanyl-L-glutamine modified perfusate improves human lung cell functions and extend porcine ex vivo lung perfusion

BACKGROUND

The clinical application of normothermic ex vivo lung perfusion (EVLP) has increased donor lung utilization for transplantation through functional assessment. To develop it as a platform for donor lung repair, reconditioning and regeneration, the perfusate should be modified to support the lung during extended EVLP.

METHODS

Human lung epithelial cells and pulmonary microvascular endothelial cells were cultured, and the effects of Steen solution (commonly used EVLP perfusate) on basic cellular function were tested. Steen solution was modified based on screening tests in cell culture, and further tested with an EVLP cell culture model, on apoptosis, GSH, HSP70, and IL-8 expression. Finally, a modified formula was tested on porcine EVLP. Physiological parameters of lung function, histology of lung tissue, and amino acid concentrations in EVLP perfusate were measured.

RESULTS

Steen solution reduced cell confluence, induced apoptosis, and inhibited cell migration, compared to regular cell culture media. Adding L-alanyl-L-glutamine to Steen solution improved cell migration and decreased apoptosis. It also reduced cold preservation and warm perfusion-induced apoptosis, enhanced GSH and HSP70 production, and inhibited IL-8 expression on an EVLP cell culture model. L-alanyl-L-glutamine modified Steen solution supported porcine lungs on EVLP with significantly improved lung function, well-preserved histological structure, and significantly higher levels of multiple amino acids in EVLP perfusate.

CONCLUSIONS

Adding L-alanyl-L-glutamine to perfusate may provide additional energy support, antioxidant, and cytoprotective effects to lung tissue. The pipeline developed herein, with cell culture, cell EVLP, and porcine EVLP models, can be used to further optimize perfusates to improve EVLP outcomes.

Synthesis of benzylated amine-substituted xanthone derivatives and their antioxidant and anti-inflammatory activities

Oxidative stress and its constant companion, inflammation, play a critical part in the pathogenesis of many acute and chronic illnesses. The discovery of new multi-targeted drug candidates with antioxidant and anti-inflammatory properties is deemed necessary. Thus, a series of novel xanthone derivatives with halogenated benzyl (4b-4d, 4f-4h) and methoxylated benzyl groups (4e) attached to the butoxy amine substituent were synthesized in this study. The synthesized xanthone derivatives exhibited stronger antioxidant activity against H₂ O₂ scavenging than the standard drug, α-tocopherol, but weaker towards DPPH scavenging and ferrous ion chelation. Besides that, 4b-4d, 4f-4h demonstrated good anti-inflammatory activities through NO production inhibition towards lipopolysaccharide (LPS)-induced RAW 264.7 cells and showed 2-4 times stronger effects than the standard drug, diclofenac sodium. Moreover, compound 4b with two brominated benzyl groups attached to the butoxy amine substituent suppressed the production of pro-inflammatory cytokines, TNF-α and IL-1β, significantly. Structure-activity relationship elucidated that the halogenated benzylamine substituent plays an important role in contributing the antioxidant and anti-inflammatory activities of xanthones. In summary, xanthone 4b was identified as a potential lead compound to be further developed into antioxidant and anti-inflammatory drugs. Thus, further studies on the related mechanisms of action of 4b are recommended.

A Randomized, Multicenter, Blinded Pilot Study Assessing the Effects of Gaseous Nitric Oxide in an Ex Vivo System of Human Lungs

INTRODUCTION

Normothermic ex vivo lung perfusion (EVLP) is used to evaluate and condition donor lungs for transplantation. The objective of this study was to determine whether administration of exogenous nitric oxide during EVLP contributes to improvement of lung health.

METHODS

A multicenter, blinded, two-arm, randomized pilot study evaluated the effect of gaseous nitric oxide (gNO) administered during EVLP on donor lungs rejected for transplantation. gNO introduced into the perfusate at 80 parts per million (ppm) was compared with perfusate alone (P). An open-label substudy assessed inhaled nitric oxide gas (iNO) delivered into the lungs at 20 ppm via a ventilator. Primary endpoints were an aggregate score of lung physiology indicators and total duration of stable EVLP time. Secondary endpoints included assessments of lung weight and left atrium partial pressure of oxygen (LAPO₂).

RESULTS

Twenty bilateral donor lungs (blinded study, n = 16; open-label substudy, n = 4) from three centers were enrolled. Median (min, max) total EVLP times for the gNO, P, and iNO groups were 12.4 (8.6, 12.6), 10.6 (6.0, 12.4), and 12.4 (8.7, 13.0) hours, respectively. In the blinded study, median aggregate scores were higher in the gNO group compared to the P group at most time points, suggesting better lung health with gNO (median score range [min, max], 0-3.5 [0, 7]) vs. P (0-2.0 [0, 5] at end of study). In the substudy, median aggregate scores did not improve for lungs in the iNO group. However, both the gNO and iNO groups showed improvements in lung weight and LAPO₂ compared to the P group.

CONCLUSIONS

The data suggest that inclusion of gNO during EVLP may potentially prolong duration of organ stability and improve donor lung health, which warrants further investigation.

The metabolic and molecular mechanisms of α‑mangostin in cardiometabolic disorders (Review)

α‑mangostin is a xanthone predominantly encountered in Garcinia mangostana. Extensive research has been carried out concerning the effects of this compound on various diseases, including obesity, cancer and metabolic disorders. The present review suggests that α‑mangostin exerts promising anti‑obesity, hepatoprotective, antidiabetic, cardioprotective, antioxidant and anti‑inflammatory effects on various pathways in cardiometabolic diseases. The anti‑obesity effects of α‑mangostin include the reduction of body weight and adipose tissue size, the increase in fatty acid oxidation, the activation of hepatic AMP‑activated protein kinase and Sirtuin‑1, and the reduction of peroxisome proliferator‑activated receptor γ expression. Hepatoprotective effects have been revealed, due to reduced fibrosis through transforming growth factor‑β 1 pathways, reduced apoptosis and steatosis through reduced sterol regulatory‑element binding proteins expression. The antidiabetic effects include decreased fasting blood glucose levels, improved insulin sensitivity and the increased expression of GLUT transporters in various tissues. Cardioprotection is exhibited through the restoration of cardiac functions and structure, improved mitochondrial functions, the promotion of M2 macrophage populations, reduced endothelial and cardiomyocyte apoptosis and fibrosis, and reduced acid sphingomyelinase activity and ceramide depositions. The antioxidant effects of α‑mangostin are mainly related to the modulation of antioxidant enzymes, the reduction of oxidative stress markers, the reduction of oxidative damage through a reduction in Sirtuin 3 expression mediated by phosphoinositide 3‑kinase/protein kinase B/peroxisome proliferator‑activated receptor‑γ coactivator‑1α signaling pathways, and to the increase in Nuclear factor‑erythroid factor 2‑related factor 2 and heme oxygenase‑1 expression levels. The anti‑inflammatory effects of α‑mangostin include its modulation of nuclear factor‑κB related pathways, the suppression of mitogen‑activated protein kinase activation, increased macrophage polarization to M2, reduced inflammasome occurrence, increased Sirtuin 1 and 3 expression, the reduced expression of inducible nitric oxide synthase, the production of nitric oxide and prostaglandin E2, the reduced expression of Toll‑like receptors and reduced proinflammatory cytokine levels. These effects demonstrate that α‑mangostin may possess the properties required for a suitable candidate compound for the management of cardiometabolic diseases.

Inhaled nitric oxide: role in the pathophysiology of cardio-cerebrovascular and respiratory diseases

Nitric oxide (NO) is a key molecule in the biology of human life. NO is involved in the physiology of organ viability and in the pathophysiology of organ dysfunction, respectively. In this narrative review, we aimed at elucidating the mechanisms behind the role of NO in the respiratory and cardio-cerebrovascular systems, in the presence of a healthy or dysfunctional endothelium. NO is a key player in maintaining multiorgan viability with adequate organ blood perfusion. We report on its physiological endogenous production and effects in the circulation and within the lungs, as well as the pathophysiological implication of its disturbances related to NO depletion and excess. The review covers from preclinical information about endogenous NO produced by nitric oxide synthase (NOS) to the potential therapeutic role of exogenous NO (inhaled nitric oxide, iNO). Moreover, the importance of NO in several clinical conditions in critically ill patients such as hypoxemia, pulmonary hypertension, hemolysis, cerebrovascular events and ischemia-reperfusion syndrome is evaluated in preclinical and clinical settings. Accordingly, the mechanism behind the beneficial iNO treatment in hypoxemia and pulmonary hypertension is investigated. Furthermore, investigating the pathophysiology of brain injury, cardiopulmonary bypass, and red blood cell and artificial hemoglobin transfusion provides a focus on the potential role of NO as a protective molecule in multiorgan dysfunction. Finally, the preclinical toxicology of iNO and the antimicrobial role of NO-including its recent investigation on its role against the Sars-CoV2 infection during the COVID-19 pandemic-are described.

A CLUE for better assessment of donor lungs: Novel technique in clinical ex vivo lung perfusion

BACKGROUND

The direCt Lung Ultrasound Evaluation (CLUE) technique was proven to be an accurate method for monitoring extravascular lung water in donor lungs during ex vivo lung perfusion (EVLP) in an experimental model. The aim of this study was to examine the application of CLUE in the clinical setting.

METHODS

Lungs were evaluated using acellular EVLP protocol. Ultrasound images were obtained directly from the lung surface. Images were graded according to the percentage of B-lines seen on ultrasound. CLUE scores were calculated at the beginning and end of EVLP for the whole lung, each side, and lobe based on the number (No.) of images in each grade and the total No. of images taken and evaluated retrospectively.

RESULTS

A total of 23 EVLP cases were performed resulting in 13 lung transplants (LTxs) with no hospital mortality. Primary graft dysfunction (PGD) occurred in only 1 recipient (PGD3, no PGD2). Significant differences were found between suitable and non-suitable lungs in CLUE scores (1.03 vs 1.85, p < 0.001), unlike the partial pressure of oxygen/fraction of inspired oxygen ratio. CLUE had the highest area under the receiver operating characteristic curve (0.98) compared with other evaluation parameters. The initial CLUE score of standard donor lungs was significantly better than marginal lungs. The final CLUE score in proned lungs showed improvement when compared with initial CLUE score, especially in the upper lobes.

CONCLUSIONS

The CLUE technique shows the highest accuracy in evaluating donor lungs for LTx suitability compared with other parameters used in EVLP. CLUE can optimize the outcomes of LTx by guiding the decision making through the whole process of clinical EVLP.

A method for translational rat ex vivo lung perfusion experimentation

The application of ex vivo lung perfusion (EVLP) has significantly increased the successful clinical use of marginal donor lungs. While large animal EVLP models exist to test new strategies to improve organ repair, there is currently no rat EVLP model capable of maintaining long-term lung viability. Here, we describe a new rat EVLP model that addresses this need, while enabling the study of lung injury due to cold ischemic time (CIT). The technique involves perfusing and ventilating male Lewis rat donor lungs for 4 h before transplanting the left lung into a recipient rat and then evaluating lung function 2 h after reperfusion. To test injury within this model, lungs were divided into groups and exposed to different CITs (i.e., 20 min, 6 h, 12 h, 18 h and 24 h). Experiments involving the 24-h-CIT group were prematurely terminated due to the development of severe edema. For the other groups, no differences in the ratio of arterial oxygen partial pressure to fractional inspired oxygen ([Formula: see text]/[Formula: see text]) were observed during EVLP; however, lung compliance decreased over time in the 18-h group (P = 0.012) and the [Formula: see text]/[Formula: see text] of the blood from the left pulmonary vein 2 h after transplantation was lower compared with 20-min-CIT group (P = 0.0062). This new model maintained stable lung function during 4-h EVLP and after transplantation when exposed to up to 12 h of CIT.

Increased Arginase Expression and Decreased Nitric Oxide in Pig Donor Lungs after Normothermic Ex Vivo Lung Perfusion

An established pig lung transplantation model was used to study the effects of cold ischemia time, normothermic acellular ex vivo lung perfusion (EVLP) and reperfusion after lung transplantation on l-arginine/NO metabolism in lung tissue. Lung tissue homogenates were analyzed for NO metabolite (NOx) concentrations by chemiluminescent NO-analyzer technique, and l-arginine, l-ornithine, l-citrulline and asymmetric dimethylarginine (ADMA) quantified using liquid chromatography-mass spectrometry (LC-MS/MS). The expression of arginase and nitric oxide synthase (NOS) isoforms in lung was measured by real-time polymerase chain reaction. EVLP preservation resulted in a significant decrease in concentrations of NOx and l-citrulline, both products of NOS, at the end of EVLP and after reperfusion following transplantation, compared to control, respectively. The ratio of l-ornithine over l-citrulline, a marker of the balance between l-arginine metabolizing enzymes, was increased in the EVLP group prior to reperfusion. The expression of both arginase isoforms was increased from baseline 1 h post reperfusion in EVLP but not in the no-EVLP group. These data suggest that EVLP results in a shift of the l-arginine balance towards arginase, leading to NO deficiency in the lung. The arginase/NOS balance may, therefore, represent a therapeutic target to improve lung quality during EVLP and, subsequently, transplant outcomes.

Ex Vivo Lung Perfusion: A Review of Research and Clinical Practices

End-stage lung disease is ultimately treated with lung transplantation. However, there is a paucity of organs with an increasing number of patients being diagnosed with end-stage lung disease. Ex vivo lung perfusion has emerged as a potential tool to assess the quality and to recondition marginal donor lungs prior to transplantation with the goal of increasing the donor pool. This technology has shown promise with similar results compared with the conventional technique of cold static preservation in terms of primary graft dysfunction and overall outcomes. This review provides an update on the results and uses of this technology. The review will also summarize clinical studies and techniques in reconditioning and assessing lungs on ex vivo lung perfusion. Last, we discuss how this technology can be applied to fields outside of transplantation such as thoracic oncology and bioengineering.

A New Approach for the Prevention and Treatment of Cardiovascular Disorders. Molecular Hydrogen Significantly Reduces the Effects of Oxidative Stress

Cardiovascular diseases are the most common causes of morbidity and mortality worldwide. Redox dysregulation and a dyshomeostasis of inflammation arise from, and result in, cellular aberrations and pathological conditions, which lead to cardiovascular diseases. Despite years of intensive research, there is still no safe and effective method for their prevention and treatment. Recently, molecular hydrogen has been investigated in preclinical and clinical studies on various diseases associated with oxidative and inflammatory stress such as radiation-induced heart disease, ischemia-reperfusion injury, myocardial and brain infarction, storage of the heart, heart transplantation, etc. Hydrogen is primarily administered via inhalation, drinking hydrogen-rich water, or injection of hydrogen-rich saline. It favorably modulates signal transduction and gene expression resulting in suppression of proinflammatory cytokines, excess ROS production, and in the activation of the Nrf2 antioxidant transcription factor. Although H2 appears to be an important biological molecule with anti-oxidant, anti-inflammatory, and anti-apoptotic effects, the exact mechanisms of action remain elusive. There is no reported clinical toxicity; however, some data suggests that H2 has a mild hormetic-like effect, which likely mediate some of its benefits. The mechanistic data, coupled with the pre-clinical and clinical studies, suggest that H2 may be useful for ROS/inflammation-induced cardiotoxicity and other conditions.

Lung transplantation, ex-vivo reconditioning and regeneration: state of the art and perspectives

Lung transplantation is the only therapeutic option for end-stage pulmonary failure. Nevertheless, the shortage of donor pool available for transplantation does not allow to satisfy the requests, thus the mortality on the waiting list remains high. One of the tools to overcome the donor pool shortage is the use of ex-vivo lung perfusion (EVLP) to preserve, evaluate and recondition selected lung grafts not otherwise suitable for transplantation. EVLP is nowadays a clinical reality and have several destinations of use. After a narrative review of the literature and looking at our experience we can assume that one of the chances to improve the outcome of lung transplantation and to overcome the donor pool shortage could be the tissue regeneration of the graft during EVLP and the immunomodulation of the recipient. Both these strategies are performed using mesenchymal stem cells (MSC). The results of the models of lung perfusion with MSC-based cell therapy open the way to a new innovative approach that further increases the potential for using of the lung perfusion platform.

Hydrogen gas inhalation during ex vivo lung perfusion of donor lungs recovered after cardiac death

BACKGROUND

Ex vivo lung perfusion (EVLP) is a system that circulates normothermic perfusate into procured lungs, allowing for improved lung function and lung assessment. We investigated whether ventilation with hydrogen gas during EVLP improves the donation after cardiac death lung function and whether this effect persists after actual transplantation.

METHODS

Ten pigs were randomly divided into a control group (n = 5) and a hydrogen group (n = 5). No treatment was administered to induce warm ischemic injury for 1 hour after cardiac arrest, and EVLP was applied in procured lungs for 4 hours. During EVLP, the control group was given room air for respiration, and the hydrogen group was given 2% hydrogen gas. After EVLP, the left lung graft was orthotopically transplanted into the recipient and reperfused for 3 hours. During EVLP and reperfusion, the functional parameters and arterial blood gas analysis (ABGA) were measured every hour. Superoxide dismutase, heme oxygenase, interleukin (IL)-6, IL-10, tumor necrosis factor-α, and nucleotide-binding oligomerization domain-like receptor protein 3 were evaluated in lung tissue after reperfusion. Pathologic evaluations were performed, and the degree of apoptosis was evaluated. The wet/dry ratio was measured.

RESULTS

During EVLP and reperfusion, functional parameters and ABGA results were better in the hydrogen group. The expressions of superoxide dismutase (p = 0.022) and heme oxygenase-1 (p = 0.047) were significantly higher in the hydrogen group. The expressions of IL-6 (p = 0.024) and nucleotide-binding oligomerization domain-like receptor protein 3 (p = 0.042) were higher in the control group, but IL-10 (p = 0.037) was higher in the hydrogen group. The lung injury severity score and the number of apoptotic cells were higher and the degree of pulmonary edema was more severe in the control group than in the hydrogen group.

CONCLUSIONS

Hydrogen gas inhalation during EVLP improved donation after cardiac death lung function via reduction of inflammation and apoptosis, and this effect persisted after LTx.

Organ preservation: from the past to the future

Organ transplantation is the most effective therapy for patients with end-stage disease. Preservation solutions and techniques are crucial for donor organ quality, which is directly related to morbidity and survival after transplantation. Currently, static cold storage (SCS) is the standard method for organ preservation. However, preservation time with SCS is limited as prolonged cold storage increases the risk of early graft dysfunction that contributes to chronic complications. Furthermore, the growing demand for the use of marginal donor organs requires methods for organ assessment and repair. Machine perfusion has resurfaced and dominates current research on organ preservation. It is credited to its dynamic nature and physiological-like environment. The development of more sophisticated machine perfusion techniques and better perfusates may lead to organ repair/reconditioning. This review describes the history of organ preservation, summarizes the progresses that has been made to date, and discusses future directions for organ preservation.

An anti-inflammatory molecular mechanism of action of α-mangostin, the major xanthone from the pericarp of Garcinia mangostana: an in silico, in vitro and in vivo approach

α-Mangostin (αMN) is a xanthone present in the pericarp of Garcinia mangostana Linn.

Lung inflation with hydrogen sulfide during the warm ischemia phase ameliorates injury in rat donor lungs via metabolic inhibition after cardiac death

BACKGROUND

Hydrogen sulfide attenuates lung ischemia-reperfusion injury when inhaled or administered intraperitoneally. This study investigated the effects of lung inflation with H₂S during the warm ischemia phase on lung grafts from rat donors after cardiac death.

METHODS

One hour after cardiac death, donor lungs were inflated in situ for 2 h with either O₂ or H₂S (O₂ or H₂S group) during the warm ischemia phase or were deflated as a control procedure (n = 8). After 3 h of cold preservation, lung transplantation was performed. During the warm ischemia phase, the metabolism and mitochondrial structures of donor lungs were analyzed. Arterial blood gas analysis was performed on the recipients. Protein expression in the graft of nuclear factor E2-related factor (Nrf)2 and nuclear factor kappa B (NF-κB) was analyzed by Western blotting, and static compliance, inflammation, oxidative stress, and cell apoptosis were assessed after 3 h of reperfusion.

RESULTS

When the O₂ and H₂S groups were compared with the control group, the mitochondrial structures were improved, and lactic acid levels, inflammation, oxidative stress, and cell apoptosis were significantly decreased; and glucose levels, as well as graft oxygenation and static compliance were increased. Simultaneously, the above indices showed further improvements, and the Nrf2 protein expression was significantly greater, and NF-κB protein expression was less in the H₂S group than the O₂ group.

CONCLUSION

Lung inflation with H₂S during the warm ischemia phase inhibited metabolism in donor lungs via mitochondrial protection, attenuated graft ischemic-reperfusion injury, and improved graft function through NF-κB-dependent anti-inflammatory and Nrf2-dependent antioxidative and antiapoptotic effects.

Current Antioxidant Treatments in Organ Transplantation

Oxidative stress is one of the key mechanisms affecting the outcome throughout the course of organ transplantation. It is widely believed that the redox balance is dysregulated during ischemia and reperfusion (I/R) and causes subsequent oxidative injury, resulting from the formation of reactive oxygen species (ROS). Moreover, in order to alleviate organ shortage, increasing number of grafts is retrieved from fatty, older, and even non-heart-beating donors that are particularly vulnerable to the accumulation of ROS. To improve the viability of grafts and reduce the risk of posttransplant dysfunction, a large number of studies have been done focusing on the antioxidant treatments for the purpose of maintaining the redox balance and thereby protecting the grafts. This review provides an overview of these emerging antioxidant treatments, targeting donor, graft preservation, and recipient as well.

Uncontrolled Donation After Circulatory Determination of Death Donors (uDCDDs) as a Source of Lungs for Transplant

In April 2014, the American Journal of Transplantation published a report on the first lung transplant in the United States recovered from an uncontrolled donation after circulatory determination of death donor (uDCDD), assessed by ex vivo lung perfusion (EVLP). The article identified logistical and ethical issues related to introduction of lung transplant from uDCDDs. In an open clinical trial, we have Food and Drug Administration and Institutional Review Board approval to transplant lungs recovered from uDCDDs judged suitable after EVLP. Through this project and other experiences with lung recovery from uDCDDs, we have identified solutions to many logistical challenges and have addressed ethical issues surrounding lung transplant from uDCDDs that were mentioned in this case report. Here, we discuss those challenges, including issues related to recovery of other solid organs from uDCDDs. Despite logistical challenges, uDCDDs could solve the critical shortage of lungs for transplant. Furthermore, by avoiding the deleterious impact of brain death and days of positive pressure ventilation, and by using opportunities to treat lungs in the decedent or during EVLP, lungs recovered from uDCDDs may ultimately prove to be better than lungs currently being transplanted from conventional brain-dead organ donors.

The effects of hydrogen gas inhalation during ex vivo lung perfusion on donor lungs obtained after cardiac death

OBJECTIVES

Lung transplantation is a well-established treatment of end-stage lung disease; however, it is limited by a shortage of donor lungs. To overcome this problem, donation after cardiac death (DCD) and ex vivo lung perfusion (EVLP) are being widely investigated. In this study, the effect of hydrogen gas, a known antioxidant, was investigated on a DCD lung model during EVLP.

METHODS

Ten pigs were randomized into either a control (n = 5) or a hydrogen group (n = 5). After fibrillation by electric shock, no further treatment was administered in order to induce warm ischaemic injury for 1 h. The lungs were then procured, followed by 4 h of EVLP. During EVLP, the lungs were ventilated with room air in the control group, and with 2% hydrogen gas in the hydrogen group. Oxygen capacity (OC), pulmonary vascular resistance (PVR) and peak airway pressure (PAP) were measured every hour, and the expressions of interleukin-1 beta (IL-1β), IL-6 (IL-6), IL-8 (IL-8) and tumour necrosis factor-alpha (TNF-α) were evaluated in lung tissue after EVLP. Pathological evaluations were performed using lung injury severity (LIS) scores and the wet/dry ratio was also measured.

RESULTS

The OC in the hydrogen group was higher than in the control group, but the difference was not statistically significant (P = 0.0862). PVR (P = 0.0111) and PAP (P = 0.0189) were statistically significantly lower in the hydrogen group. Compared with the control group, the hydrogen group had a statistically significantly lower expression of IL-1β (P = 0.0317), IL-6 (P = 0.0159), IL-8 (P = 0.0195) and TNF-α (P = 0.0159). The LIS scores (P = 0.0358) and wet/dry ratios (P = 0.040) were also significantly lower in the hydrogen group.

CONCLUSIONS

Hydrogen gas inhalation during EVLP improved the function of DCD lungs, which may increase the utilization of DCD lungs.

Mesenchymal stem cell pretreatment of non-heart-beating-donors in experimental lung transplantation

Background

Lung transplantation (LTx) is still limited by organ shortage. To expand the donor pool, lung retrieval from non-heart-beating donors (NHBD) was introduced into clinical practice recently. However, primary graft dysfunction with inactivation of endogenous surfactant due to ischemia/reperfusion-injury is a major cause of early mortality. Furthermore, donor-derived human mesenchymal stem cell (hMSC) expansion and fibrotic differentiation in the allograft results in bronchiolitis obliterans syndrome (BOS), a leading cause of post-LTx long-term mortality. Therefore, pretreatment of NHBD with recipient-specific bone-marrow-(BM)-derived hMSC might have the potential to both improve the postischemic allograft function and influence the long-term development of BOS by the numerous paracrine, immunomodulating and tissue-remodeling properties especially on type-II-pneumocytes of hMSC.

Methods

Asystolic pigs (n = 5/group) were ventilated for 3 h of warm ischemia (groups 2–4). 50x106 mesenchymal-stem-cells (MSC) were administered in the pulmonary artery (group 3) or nebulized endobronchially (group 4) before lung preservation. Following left-lung-transplantation, grafts were reperfused, pulmonary-vascular-resistance (PVR), oxygenation and dynamic-lung-compliance (DLC) were monitored and compared to control-lungs (group 2) and sham-controls (group 1). To prove and localize hMSC in the lung, cryosections were counter-stained. Intra-alveolar edema was determined stereologically. Statistics comprised ANOVA with repeated measurements.

Results

Oxygenation (p = 0.001) and PVR (p = 0.009) following endovascular application of hMSC were significantly inferior compared to Sham controls, whereas DLC was significantly higher in endobronchially pretreated lungs (p = 0.045) with overall sham-comparable outcome regarding oxygenation and PVR. Stereology revealed low intrapulmonary edema in all groups (p > 0.05). In cryosections of both unreperfused and reperfused grafts, hMSC were localized in vessels of alveolar septa (endovascular application) and alveolar lumen (endobronchial application), respectively.

Conclusions

Preischemic deposition of hMSC in donor lungs is feasible and effective, and endobronchial application is associated with significantly better DLC as compared to sham controls. In contrast, transvascular hMSC delivery results in inferior oxygenation and PVR. In the long term perspective, due to immunomodulatory, paracrine and tissue-remodeling effects on epithelial and endothelial restitution, an endobronchial NHBD allograft-pretreatment with autologous mesenchymal-stem-cells to attenuate limiting bronchiolitis-obliterans-syndrome in the long-term perspective might be promising in clinical lung transplantation. Subsequent work with chronic experiments is initiated to further elucidate this important field.

Electronic supplementary material

The online version of this article (doi:10.1186/s13019-014-0151-3) contains supplementary material, which is available to authorized users.

Advances in lung preservation

After a brief review of conventional lung preservation, this article discusses the rationale behind ex vivo lung perfusion and how it has shifted the paradigm of organ preservation from conventional static cold ischemia to the utilization of functional normothermia, restoring the lung's own metabolism and its reparative processes. Technical aspects and previous clinical experience as well as opportunities to address specific donor organ injuries in a personalized medicine approach are also reviewed.

The differential tissue expression of inflammatory, oxidative stress, and apoptosis markers in human uncontrolled non-heart-beating donors

BACKGROUND

Uncontrolled non-heart-beating donor (UNHBD) transplantation offers a major opportunity to ameliorate the effects of the donor shortage. However, little is known about the true status of the organs obtained from these donors. UNHBD transplantation is performed under unfavorable conditions and involves exposure to several harmful stimuli that have been identified as triggers for immediate inflammatory response, oxidative stress, and apoptotic phenomena. This adverse scenario could explain the higher rates of graft dysfunction due to primary nonfunction traditionally observed in NHBD. Our aim was to assess the expression of proinflammatory, oxidative, and apoptotic markers in liver, lung, and pancreas tissue samples obtained from UNHBD and to compare these expression levels with those observed in brain-dead donors (BDD).

METHODS

Samples from human type 2 NHBD and BDD were obtained at the end of cold storage. Interleukin (IL)-1β, tumor necrosis factor-α, IL-6, IL-10, endothelial nitric oxide synthase, inducible nitric oxide synthase, type 1 heme oxygenase, type 2 heme oxygenase, Bax, and Bcl-2 protein and mRNA expression, as well as catalase, glutathione peroxidase, and glutathione reductase tissue activity, were determined.

RESULTS

UNHBD showed similar or lower expression of proinflammatory mediators and apoptosis markers in all three organs without modifications to the anti-inflammatory cytokines. Although the major oxidative stress marker levels were also comparable in both types of donors, the type 1 heme oxygenase mRNA expression and antioxidant enzyme activity were slightly diminished in UNHBD.

CONCLUSIONS

The initial tissue damage generated during the UNHB donation process is at least comparable with that observed in BDD. However, although the expression of the immediate immune response and apoptosis markers is similar, a mild impairment of the local antioxidant activity was observed.

Early results in transplantation of initially rejected donor lungs after ex vivo lung perfusion: a case-control study

OBJECTIVES

An increasing number of studies have shown that ex vivo lung perfusion (EVLP) is safe and that rejected donor lungs can be resuscitated and used for lung transplantation (LTx). Early clinical outcomes in patients transplanted with reconditioned lungs at our centre were reviewed and compared with those of contemporary non-EVLP controls.

METHODS

During 18 months starting January 2011, 11 pairs of donor lungs initially deemed unsuitable for transplantation underwent EVLP. Haemodynamic (pulmonary flow, vascular resistance and artery pressure) and respiratory (peak airway pressure and compliance) parameters were analysed during evaluation. Lungs that improved (n = 11) to meet International Society of Heart and Lung Transplantation criteria were transplanted and compared with patients transplanted with non-EVLP lungs (n = 47) during the same time period.

RESULTS

Donor lungs were initially rejected due to either inferior PaO2/FiO2 ratio (n = 9), bilateral infiltrate on chest X-ray (n = 1) or ongoing extra corporeal membrane oxygenation (n = 1). The donor lungs improved from a mean PaO2/FiO2 ratio of 27.9 kPa in the donor to a mean of 59.6 kPa at the end of the EVLP (median improvement 28.4 kPa, range 21.0-50.7 kPa). Two single lungs were deemed unsuitable and not used for LTx. Eleven recipients from the regular waiting list underwent either single (n = 3) LTx or double (n = 8) LTx with EVLP-treated lungs. The median time to extubation (12 (range, 3-912) vs 6 (range, 2-1296) h) and median intensive care unit (ICU) stay (152 (range, 40-625) vs 48 (range, 22-1632) h) were longer in the EVLP group (P = 0.05 and P = 0.01, respectively). There were no differences in length of hospital stay (median 28 (range 25-93) vs 28 (18-209), P = 0.21). Two patients in the EVLP group and 6 in the control group had primary graft dysfunction >Grade 1 at 72 h postoperatively. Three patients in the control group died before discharge. All recipients of EVLP lungs were discharged alive from hospital.

CONCLUSIONS

The use of EVLP seems safe and indicates that lungs otherwise refused for LTx can be recovered and subsequently used for transplantation, although time to extubation and ICU stay were longer for the EVLP group.

Effect of a vascular endothelial cadherin antagonist in a rat lung transplant model

BACKGROUND

Adherens junctions are critically important in control of endothelial cell permeability. Bβ15-42 is a peptide product of fibrin degradation that binds to vascular endothelial cadherin, the major component of endothelial adherens junctions. We tested the hypothesis that Bβ15-42 improves lung function in our rat lung transplant model.

METHODS

Bβ15-42 was administered to donors before lung retrieval and to recipients by continuous intravenous infusion, or just to recipients, or neither. Recipients were monitored, anesthetized and ventilated, for 6 hours. Outcome measures were indices of lung function (edema [wet-to-dry weight ratio], oxygenation, dynamic compliance) and bronchoalveolar fluid measures of inflammation (protein, cell count, differential, and cytokines).

RESULTS

Bβ15-42 therapy was associated with improved graft lung function, including less edema, and improved oxygenation and airway pressure, particularly if Bβ15-42 was administered to both the donor and recipient. However, Bβ15-42 had little or no effect on bronchoalveolar fluid measures of inflammation. Analysis of bronchoalveolar fluid protein concentration showed Bβ15-42 may enhance alveolar fluid clearance.

CONCLUSIONS

Bβ15-42 may be a useful therapy to reduce edema and improve graft function after lung transplant, alone or as an adjunct to other therapies.

A novel organ preservation for small partial liver transplantations in rats: venous systemic oxygen persufflation with nitric oxide gas

The prognosis for recipients of small liver grafts is poor. The aim of this study was to determine the impact of venous systemic oxygen persufflation (VSOP) with nitric oxide (NO) gas for 30% partial liver preservation and transplantation in rats. After we determined optimal NO concentration as 40 ppm in vitro with the isolated perfused rat liver model, we assessed liver injury and regeneration in vivo at 1, 3, 24 and 168 h after transplantation in the following three groups after 3 h-cold storage (n = 20 per group): control group = static storage; VSOP group = oxygen persufflation and VSOP+NO group = oxygen with NO persufflation. The liver graft persufflation was achieved with medical gas via the suprahepatic vena cava; In comparison with control group after transplantation, VSOP+NO preservation (1) increased portal circulation, (2) reduced AST and ALT release, (3) upregulated hepatic endothelial NO synthase, (4) reduced hepatocyte and bileductule damage and (5) improved liver regeneration. These results suggest that gaseous oxygen with NO persufflation is a novel and safe preservation method for small partial liver grafts, not only alleviating graft injury but also improve liver regeneration after transplantation.

Postmortem and ex vivo carbon monoxide ventilation reduces injury in rat lungs transplanted from non-heart-beating donors

OBJECTIVE

We sought to determine whether ventilation of lungs after death in non-heart-beating donors with carbon monoxide during warm ischemia and ex vivo lung perfusion and after transplant would reduce ischemia-reperfusion injury and improve lung function.

METHODS

One hour after death, Sprague-Dawley rats were ventilated for another hour with 60% oxygen (control group) or 500 ppm carbon monoxide in 60% oxygen (CO-vent group; n=6/group). Then, lungs were flushed with 20 mL cold Perfadex, stored cold for 1 hour, then warmed to 37 °C in an ex vivo lung perfusion circuit perfused with Steen solution. At 37 °C, lungs were ventilated for 15 minutes with alveolar gas with or without 500 ppm carbon monoxide, then perfusion-cooled to 20 °C, flushed with cold Perfadex and stored cold for 2 hours. The left lung was transplanted using a modified cuff technique. Recipients were ventilated with 60% oxygen with or without carbon monoxide. One hour after transplant, we measured blood gases from the left pulmonary vein and aorta, and wet-to-dry ratio of both lungs. The RNA and protein extracted from graft lungs underwent real-time polymerase chain reaction and Western blotting, and measurement of cyclic guanosine monophosphate by enzyme-linked immunosorbent assay.

RESULTS

Carbon monoxide ventilation begun 1 hour after death reduced wet/dry ratio after ex vivo lung perfusion. After transplantation, the carbon monoxide-ventilation group had better oxygenation; higher levels of tissue cyclic guanosine monophosphate, heme oxidase-1 expression, and p38 phosphorylation; reduced c-Jun N-terminal kinase phosphorylation; and reduced expression of interleukin-6 and interleukin-1β messenger RNA.

CONCLUSIONS

Administration of carbon monoxide to the deceased donor and non-heart-beating donor lungs reduces ischemia-reperfusion injury in rat lungs transplanted from non-heart-beating donors. Therapy to the deceased donor via the airway may improve post-transplant lung function.

A physiologic and biochemical profile of clinically rejected lungs on a normothermic ex vivo lung perfusion platform

BACKGROUND

Although ex vivo lung perfusion (EVLP) is increasingly being used to evaluate and manipulate potential donor lungs before lung transplantation (LTx), data on the biochemistry of lungs during EVLP are limited. In this study, we examined the physiology and biochemistry of human lungs on an EVLP circuit.

METHODS

We recovered unallocated double lungs in standard fashion and split them into single lungs. All lungs received a nebulized arginase inhibitor, 2-S-amino-6-boronohexanoic acid (ABH), at either the onset (n = 6) or after 3 h (n = 8) of EVLP. Serial biochemical analysis included levels of arginase, endogenous nitric oxide synthase (eNOS), cyclic guanosine monophosphate, and reactive oxygen species. We considered lungs transplantable if they sustained a PaO2:FiO2 ≥ 350 in addition to stable pulmonary function during EVLP.

RESULTS

We recovered a total of 14 single lungs. We deemed three single lungs from different donors to be transplantable after EVLP. These lungs had superior oxygenation, lower carbon dioxide, and more stable pulmonary artery pressures. Transplantable lungs had higher baseline levels of eNOS and higher final levels of cyclic guanosine monophosphate than non-transplantable lungs. Early ABH administration was associated with a transient increase in dynamic compliance.

CONCLUSIONS

In this biochemical characterization of lungs deemed unsuitable for LTx, early levels of eNOS and late levels of cyclic guanosine monophosphate appear to be associated with improved allograft function during EVLP. In addition, nebulized ABH is associated with a significant increase in dynamic compliance. These data suggest that biochemical markers during EVLP may predict acceptable allograft function, and that this platform can be used to biochemically manipulate donor lungs before LTx.

Nebulized nitrite protects rat lung grafts from ischemia reperfusion injury

OBJECTIVES

Nebulization is a potential method for delivering therapeutic agents to lung grafts. Recent evidence suggests that nitrite may mitigate ischemia-reperfusion injury via a nitric oxide-dependent pathway.

METHODS

Syngeneic orthotopic left lung transplantation was performed in rats after 7 hours of cold ischemia. Sodium nitrite (3 mg) or phosphate-buffered saline (controls) was delivered before procurement via nebulization.

RESULTS

Nitrite treatment was associated with better oxygenation, lower peak airway pressure, lower wet/dry ratio, reduced myeloperoxidase level and macrophage infiltration, increased cyclic guanosine monophosphate (cGMP) levels, and decreased levels of interleukin 6, interleukin 1-β, inducible nitric oxide synthase, and intercellular adhesion molecule-1 at 2 hours after reperfusion. Treatment with 2-(4-carboxypheny)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, a nitric oxide scavenger, reversed the beneficial effects of nitrite and decreased cGMP concentration in grafts. A dose-response curve of nitrite was performed at the following doses: 0.3 mg (N0.1), 3.0 mg (N1.0), 5.25 mg (N1.75), 7.5 mg (N2.5), and 15.0 mg (N5.0). All treatments, excluding N1.0, resulted in poorer oxygenation, higher peak airway pressures, and higher wet/dry ratio. Higher dosage groups (N1.75, N2.5, and N5.0) exhibited positive immunostaining of nitrotyrosine and increased the intensity of nitrotyrosine in immunoblotting.

CONCLUSIONS

These data suggest that nebulized nitrite limits lung ischemia-reperfusion injury and may prove a clinically useful strategy but requires appropriate dosing to limit oxidative injury at high doses.

Nitrite reduces acute lung injury and improves survival in a rat lung transplantation model

Ischemia/reperfusion injury (IRI) is the most common cause of early mortality following lung transplantation (LTx). We hypothesized that nitrite, an endogenous source of nitric oxide (NO), may protect lung grafts from IRI. Rat lung grafts were stored in preservation solution at 4°C for 6 hours. Both grafts and recipients were treated with nitrite. Nitrite treatment was associated with significantly higher levels of tissue oxygenation, lower levels of cytokines and neutrophil/macrophage infiltration, lower myeloperoxidase activity, reduced oxidative injury and increased cGMP levels in grafts than in the controls. Treatment with either a nitric oxide scavenger or a soluble guanylyl cyclase (sGC) inhibitor diminished the beneficial effects of nitrite and decreased cGMP concentrations. These results suggest that nitric oxide, generated from nitrite, is the molecule responsible for the effects of nitrite via the nitric oxide/sGC/cGMP pathway. Allopurinol, a xanthine oxidoreductase (XOR) inhibitor, abrogated the protective effects of nitrite, suggesting that XOR is a key enzyme in the conversion of nitrite to nitric oxide. In vitro experiments demonstrated that nitrite prevented apoptosis in pulmonary endothelial cells. Nitrite also exhibits longer survival rate in recipients than control. In conclusion, nitrite inhibits lung IRI following cold preservation and had higher survival rate in LTx model.

Reconditioning of lungs donated after circulatory death with normothermic ex vivo lung perfusion

BACKGROUND

The use of donation-after-circulatory-death (DCD) donors for lung transplantation has come into practice. In this study we investigated whether DCD lungs can be resuscitated after warm ischemia with normothermic ex vivo lung perfusion (EVLP).

METHODS

Four hours after cardiac arrest, beagle dogs were divided into two groups (n = 6 each): those with static cold storage (SCS group) and those with normothermic EVLP (EVLP group), for 3.5 hours. Physiologic lung functions were evaluated during EVLP. In both groups, the left lungs were then transplanted and reperfused for 4 hours to evaluate post-transplant lung functions. Lung tissue adenosine triphosphate (ATP) levels were measured at given time-points.

RESULTS

Lung oxygenation was significantly improved with EVLP (p < 0.01), and lung oxygenation at the end of EVLP significantly reflected post-transplant lung oxygenation (r = 0.99, p < 0.01). Post-transplant lung oxygenation was significantly better in the EVLP group than in the SCS group (p < 0.05). Both dynamic pulmonary compliance and wet-to-dry lung weight ratio 4 hours after transplantation were also significantly better in the EVLP group than in the SCS group (p < 0.05). Microthrombi in the donor lungs before transplantation were microscopically detected more often in the SCS group. The lung tissue ATP levels 4 hours after transplantation were significantly higher in the EVLP group compared with the SCS group (p = 0.03).

CONCLUSIONS

Normothermic ex vivo lung perfusion could resuscitate DCD lungs injured by warm ischemia, and may ameliorate ischemia-reperfusion injury.

Medical gases: a novel strategy for attenuating ischemia-reperfusion injury in organ transplantation?

Ischemia reperfusion injury (IRI) is an inevitable clinical consequence in organ transplantation. It can lead to early graft nonfunction and contribute to acute and chronic graft rejection. Advanced molecular biology has revealed the highly complex nature of this phenomenon and few definitive therapies exist. This paper reviews factors involved in the pathophysiology of IRI and potential ways to attenuate it. In recent years, inhaled nitric oxide, carbon monoxide, and hydrogen sulfide have been increasingly explored as plausible novel medical gases that can attenuate IRI via multiple mechanisms, including microvascular vasorelaxation, reduced inflammation, and mitochondrial modulation. Here, we review recent advances in research utilizing inhaled nitric oxide, carbon monoxide, and hydrogen sulfide in animal and human studies of IRI and postulate on its future applications specific to solid organ transplantation.

Hydrogen sulfide decreases reactive oxygen in a model of lung transplantation

BACKGROUND

Ischemia-reperfusion injury is a common complication after lung transplantation. Ischemia-reperfusion injury is thought to be mediated by reactive oxygen species (ROS). Hydrogen sulfide (H(2)S) is a novel agent that has been previously shown to scavenge ROS and slow metabolism. We evaluated the effect of infused H(2)S on the presence of ROS after reperfusion in an ex vivo model of lung transplantation.

METHODS

Heart-Lung blocks were recovered from New Zealand white rabbits (n = 12) and cold stored in Perfadex solution for 18 h. After storage, the heart-lung blocks were reperfused ex vivo with donor rabbit blood. In the treatment group (n = 7), a bolus of sodium H(2)S was added at the beginning of reperfusion (100 μg/kg) and continuously infused throughout the 2-h experiment (1 mg/kg/h). The vehicle group (n = 5) received an equivalent volume of saline. Serial airway and pulmonary artery pressures and arterial and venous blood gases were measured.

RESULTS

Oxygenation and pulmonary artery pressures were similar between the 2 groups. However, treatment with H(2)S resulted in a dramatic reduction in the presence of ROS after 2 h of reperfusion (4,851 ± 2,139 versus 235 ± 462 related fluorescence units/mg protein; P = 0.003). A trend was seen toward increased levels of cyclic guanosine monophosphate in the H(2)S-treated group (3.08 ± 1.69 versus 1.73 ± 1.41 fmol/mg tissue; P = .23).

CONCLUSIONS

After prolonged ischemia, infusion of H(2)S during reperfusion was associated with a significant decrease in the presence of ROS, a suspected mediator of ischemia-reperfusion injury. To our knowledge, the present study represents the first reported therapeutic use of H(2)S in an experimental model of lung transplantation.

Impact of venous systemic oxygen persufflation supplemented with nitric oxide gas on cold-stored, warm ischemia-damaged experimental liver grafts

The increasing shortage of donor organs has led to the increasing use of organs from non-heart-beating donors. We aimed to assess the impact of venous systemic oxygen persufflation (VSOP) supplemented with nitric oxide (NO) gas during the cold storage (CS) of warm ischemia (WI)-damaged experimental liver grafts. Rat livers (n = 5 per group) were retrieved after 30 minutes of WI induced by cardiac arrest (the WI group) and were thereafter preserved for 24 hours by CS in histidine tryptophan ketoglutarate solution. During CS, gaseous oxygen was insufflated via the caval vein with 40 ppm NO (the VSOP-NO group) or without NO (the VSOP group). Cold-stored livers without WI served as controls. Liver viability was assessed after the preservation period by normothermic isolated reperfusion for 45 minutes with oxygenated Krebs-Henseleit buffer. After 45 minutes of reperfusion, the VSOP-NO-treated livers showed significantly lower alanine aminotransferase values than the WI-damaged livers (10.2 ± 0.2 versus 78.2 ± 14.6 IU/L), whereas the control livers showed no differences from the VSOP-NO-treated livers. The mitochondrial enzyme release was lower in the VSOP-NO group (4.0 ± 0.7 IU/L) versus the WI group (18.2 ± 4.9 IU/L). An increased portal vein pressure was observed throughout reperfusion (45 minutes) in the WI group (21.7 ± 0.2 mm Hg) versus the VSOP-NO group (12.2 ± 0.8 mm Hg) and the control group (19.9 ± 0.4 mm Hg). Furthermore, the NO concentration in the perfusate after 5 minutes of reperfusion was highest in the VSOP-NO group. The release of malondialdehyde into the perfusate was significantly reduced in the VSOP-NO group (0.9 ± 0.1 nmol/mL) versus the WI group (31.3 ± 5.3 nmol/mL). In conclusion, the resuscitation of livers after 30 minutes of WI to a level comparable to that of nonischemically damaged livers is possible with VSOP supplemented with NO gas. Moreover, the application of VSOP with NO minimizes the extent of injuries caused by oxygen free radicals during preservation.