Ischemia-reperfusion Injury In Lung Transplantation Research Articles

Cell death and ischemia-reperfusion injury in lung transplantation.

Lung transplantation is the most effective therapy for patients with end-stage lung disease. However, concern of donor lung damage and ischemia-reperfusion induced lung injury limits the use of "marginal" donor lungs. Recent transcriptomic studies have demonstrated that the enrichment of gene-clusters related to cell death and inflammation are the most profound signals during ischemia-reperfusion in human lung transplants. Herein, we focus on the relationship between inflammation and programmed cell death, especially necroptosis, mitochondrial permeability transition-initiated regulated necrosis, pyroptosis, ferroptosis, and autophagic cell death. Cell death-related molecules have been tested as potential biomarkers for donor lung assessment. Inhibitors for various types of cell death have been explored as therapeutics for ischemia reperfusion injury in lung transplantation. A deeper understanding of these mechanisms may help to improve donor management, organ preservation, prevention and treatment of primary graft dysfunction during and post transplantation. Moreover, evaluation and treatment of cell death and inflammation during ex vivo lung perfusion may be a game changer in donor organ management, assessment, repair, and reconditioning.

Ischemia-Reperfusion Injury in Lung Transplantation.

Lung transplantation has been established worldwide as the last treatment for end-stage respiratory failure. However, ischemia–reperfusion injury (IRI) inevitably occurs after lung transplantation. The most severe form of IRI leads to primary graft failure, which is an important cause of morbidity and mortality after lung transplantation. IRI may also induce rejection, which is the main cause of mortality in recipients. Despite advances in donor management and graft preservation, most donor grafts are still unsuitable for transplantation. Although the pulmonary endothelium is the primary target site of IRI, the pathophysiology of lung IRI remains incompletely understood. It is essential to understand the mechanism of pulmonary IRI to improve the outcomes of lung transplantation. Therefore, we reviewed the state-of-the-art in the management of pulmonary IRI after lung transplantation. Recently, the ex vivo lung perfusion (EVLP) system has been clinically introduced worldwide. Various promising therapeutic strategies for the protection of the endothelium against IRI, including EVLP, inhalation therapy with therapeutic gases and substances, fibrinolytic treatment, and mesenchymal stromal cell therapy, are awaiting clinical application. We herein review the latest advances in the field of pulmonary IRI in lung transplantation.

A Novel Natural Autoantibody Targeted Complement Inhibitor Protects against Lung Transplant Ischemia Reperfusion Injury

Purpose Chronic obstructive pulmonary disease is characterized by chronic inflammation and severe lung parenchyma damage that is in part driven by autoimmunity. Lung specific autoreactive antibodies (AAb) are indicative of disease progression and severity. The purpose of this study was to elucidate how pre-existing AAb contribute to ischemia reperfusion injury (IRI) and graft rejection following lung transplant (LTx). We hypothesize that pre-existing AAb bind cryptic antigens exposed during IRI which exacerbates lung graft injury in a complement (C)-dependent pathway. Methods We generated a clinically relevant cigarette smoke (CS)-induced mouse model that exhibits increased serum AAb compared to non-smoke exposed age-matched (NS) controls. We analyzed the impact of a full pre-existing AAb repertoire by creating an orthotopic syngeneic left lung LTx model in which we transplanted the left lungs from age-matched donor mice into NS and CS mice. Furthermore, we developed a novel bifunctional inhibitor that blocks IgM binding and inhibits complement. Results CS exposure significantly increased graft injury and immune infiltration 48 hours after LTx. Syngeneic LTx into Rag−/- mice reconstituted with serum from NS and CS mice demonstrated that AAb present in CS are responsible for the observed graft injury. Immunofluorescent staining showed that IgM/IgG binding was increased in CS recipients and colocalized with C3d deposition. These data suggested that AAb-mediated graft injury may occur via the C pathway. To elucidate the role of C in AAb-mediated graft injury, we treated CS LTx recipients with a novel bifunctional C inhibitor, C2scFv-Crry, that blocks IgM binding and C activation. C2scFv-Crry treatment following LTx dramatically reduced acute graft injury and immune infiltration, and significantly decreased de novo AAb production compared to CS control LTx mice. Conclusion Ultimately, these data reveal that CS induces pre-existing AAb production that exacerbate IRI following LTx in a C-dependent manner. Furthermore, we demonstrate the efficacy of a novel C inhibitor in reducing IRI and acute graft injury.

Anti-HMGB1 Monoclonal Antibody Ameliorates Lung Ischemia Reperfusion Injury in Mice

Purpose Lung ischemia reperfusion (IR) injury increases the mortality and morbidity in patients undergoing lung transplantation. Inflammatory mediators called Damage Associated Molecular Patterns (DAMPs) concern with inflammatory response to develop the organ damages during IR injury and High Mobility Group Box 1 (HMGB1) is one of the most important DAMPs. We had previously developed anti-HMGB1 monoclonal antibody (mAb) and assessed the therapeutic effect of the antibody in lung IR injury. Methods A mice hilar clamp model of IR was used, and animals were divided into sham groups and IR groups with or without administration of anti-HMGB 1 mAb. We analyzed the effect of anti-HMGB 1 mAb against IR injury by assessing lung oxygenation, injury, neutrophil infiltrations, expression of proinflammatory cytokines and chemokines, MAPK signaling and apoptosis. Results The severity of IR injury represented by oxygenation capacity, lung injury score and neutrophil infiltrations was significantly improved by anti-HMGB1 mAb treatment. The expressions of proinflammatory factors including IL-1b, IL-6, IL-12, TNFα, CXCL1 and CXCL2 and phosphorylation of p38 MAPK were significantly reduced by the anti-HMGB1 mAb treatment. Furthermore, the antibody decreased TUNEL positive cells to detect apoptosis. Conclusion Anti-HMGB1 mAb obviously ameliorated lung IR injury by reduction of inflammatory responses and apoptosis. Our findings indicate that anti-HMGB1 mAb have a potential as therapeutic drug to improve IR injury in lung transplantation.

Creatine Supply Attenuates Ischemia-Reperfusion Injury in Lung Transplantation in Rats

Ischemia-reperfusion injury (IRI) is one of the factors limiting the success of lung transplantation (LTx). IRI increases death risk after transplantation through innate immune system activation and inflammation induction. Some studies have shown that creatine (Cr) protects tissues from ischemic damage by its antioxidant action. We evaluated the effects of Cr supplementation on IRI after unilateral LTx in rats. Sixty-four rats were divided into four groups: water + 90 min of ischemia; Cr + 90 min of ischemia; water + 180 min of ischemia; and Cr + 180 min of ischemia. Donor animals received oral Cr supplementation (0.5 g/kg/day) or vehicle (water) for five days prior to LTx. The left lung was exposed to cold ischemia for 90 or 180 min, followed by reperfusion for 2 h. We evaluated the ventilatory mechanics and inflammatory responses of the graft. Cr-treated animals showed a significant decrease in exhaled nitric oxide levels and inflammatory cells in blood, bronchoalveolar lavage fluid and lung tissue. Moreover, edema, cell proliferation and apoptosis in lung parenchyma were reduced in Cr groups. Finally, TLR-4, IL-6 and CINC-1 levels were lower in Cr-treated animals. We concluded that Cr caused a significant decrease in the majority of inflammation parameters evaluated and had a protective effect on the IRI after LTx in rats.

Pegylated-Catalase Is Protective in Lung Ischemic Injury and Oxidative Stress

Lung transplant ischemia-reperfusion injury is typified by toxic metabolites and oxygen free radicals leading to worse graft function. Catalase is an enzyme involved in oxidative-stress detoxification. We hypothesize that direct delivery of highly concentrated polyethylene glycol-catalase (PEG-CAT) during normothermic exvivo lung perfusion (EVLP) significantly reduces ischemia-reperfusion injury. To demonstrate protection, primary culture porcine endothelial cells were treated with PEG-CAT (0 to 1250 U/mL) in a model of oxidative stress (400 μM H2o2). Invivo, rat lungs were subjected to 0 hours or 1 hour of warm ischemic injury and 2 hours of EVLP with or without PEG-CAT. Perfusate was collected throughout the perfusion duration and tissue was collected at the end. Tissue and perfusate underwent analysis for markers of apoptosis and a biometric signature of lung health. Uptake of PEG-CAT into primary endothelial cells was demonstrated with Alexa Fluor 488-labeled PEG-CAT. Oxidatively stressed cells pretreated with PEG-CAT had significantly decreased cytotoxicity and caspase 3/7 activity and increased cell viability and cell membrane integrity. In a rat model of warm ischemia with EVLP, PEG-CAT improved allograft viability as measured by indications of cell membrane integrity (lactate dehydrogenase and hyaluronic acid), presence of vasoconstrictive peptides (endothelin-1 and big endothelin-1) released from endothelial cells, and reduced apoptosis (terminal deoxynucleotidyl transferase dUTP nick-end labeling). Invitro and exvivo, PEG-CAT protects against oxidative stress-induced cytotoxicity, maintains cellular metabolism, and mitigates lung ischemia-reperfusion in an experimental model. Together, these data suggest that PEG-CAT is a potential therapeutic target for donor organs at risk for ischemia-reperfusion injury.

Heme oxygenase-1 modified mesenchymal stem cells in the treatment of ischemia-reperfusion injury in lung transplantation

Objective To explore the protective mechanism of Heme Oxygenase-1 (HO-1) modified mesenchymal stem cells (MSC) in the treatment of lung transplantation ischemia-reperfusion injury (IRI). Methods Sixty SD rats were randomly divided into Surgical control (Ⅰ), simple MSCs (Ⅱ), empty vector-MSCs (Ⅲ), HO-1 modified MSCs (Ⅳ) were established. After establishing orthotopic left lung transplantation model in rats, group Ⅱ, Ⅲ and Ⅳ were injected with MSCs, empty vector-MSCs and HO-1-MSCs from pulmonary artery fine needles of recipient rats. Four hours later, partial pressure of oxygen (PaO2), partial pressure of carbon dioxide (PaCO2), tumor necrosis factor-alpha (TNF-α), Interleukin-10 (IL-10), wet/dry ratio (W/D), superoxide dismutase (SOD), malondialdehyde (MDA) and myeloperoxidase (MPO) were measured. Histopathological examination. Detection of HO-1-mRNA expression in transplants by reverse transcription polymerase chain reaction (RT-PCR). Multigroup mean comparison using One-way ANOVA. Results PaO2: Group Ⅰ, Ⅱ, Ⅲ and Ⅳ were (70.40±4.64), (87.53±4.01), (87.27±4.06), (96.80±647) mmHg (1 mmHg=0.133 kPa) gradually increased (F=75.578, P 0.05). PaCO2: group Ⅰ, Ⅱ, Ⅲ and Ⅳ were (32.67±3.31), (27.80±2.98), (27.60±2.41), (19.87±3.02) mmHg gradually decreased (F=48.286, P 0.05). W/D: Group Ⅰ, Ⅱ, Ⅲ and Ⅳ were (4.96±0.22), (4.04±0.28), (4.11±0.31), (3.85±0.27) gradually decreased (F=48.992, P 0.05). MDA content: In group Ⅰ, Ⅱ, Ⅲ and Ⅳ, the levels of MDA were (126.80±11.14), (114.27±16.45), (114.06±17.68), (102.40±14.21) nmol/g gradually decreased (F=6.551, P 0.05). MPO content: group Ⅰ, Ⅱ, Ⅲ and Ⅳ were (53.51±3.06), (45.07±3, 32), (44.45±3.37), (40.60±2.47) U/g decreased gradually (F=46.907, P 0.05). SOD activity: In group Ⅰ, Ⅱ, Ⅲ and Ⅳ, SOD activity increased gradually [(304.60±34.74), (329.87±19.44), (329.87±19.44), (338.73±15.77) U/g, (F=6.038, P 0.05). TNF-α: In group Ⅰ, Ⅱ, Ⅲ and Ⅳ, the levels of TNF-αwere (61.56±2.83), (48.32±4.11), (48.53±4.20), (36.77±3.79) ng/L gradually decreased (F=108.215, P 0.05). IL-10: The levels of IL-10 in group Ⅰ, Ⅱ, Ⅲ and Ⅳ were (23.43±2.37), (34.96±3.04), (35.48±3.00), (41.16±3.12) ng/L gradually increased (F=98.751, P 0.05). Under light microscopy, neutrophils infiltrated pulmonary interstitium and inflammatory exudation was seen in alveolar cavity. Inflammation in group Ⅳ was the lightest in each group. The amplification bands of HO-1 mRNA in group IV were significantly stronger than other groups. Conclusion HO-1 gene modified MSCs have synergistic anti-injury effect in the treatment of lung transplantation IRI. Key words: Heme oxygenase-1; Mesenchymal stem cells; Lung transplantation ischemia-reperfusion injury

Mesenchymal stromal cell therapy during ex vivo lung perfusion ameliorates ischemia-reperfusion injury in lung transplantation.

The application of mesenchymal stromal cell (MSC)-based therapy during ex vivo lung perfusion (EVLP) could repair injured donor lungs before transplantation. The aim of this study was to determine the efficacy of MSC therapy performed during EVLP on ischemia-reperfusion injury using a pig lung transplant model. Following 24 hours of cold storage, pig lungs were randomly assigned to 2 groups (n = 6 each), the control group without MSC vs the MSC group, where 5 × 106 cells/kg MSCs were delivered through the pulmonary artery during EVLP. After 12 hours of EVLP, followed by a 1-hour second cold preservation period, the left lung was transplanted and reperfused for 4 hours. EVLP perfusate hepatocyte growth factor (HGF) level at 12 hours was significantly elevated in the MSC group compared with the control and was associated with a significant decrease in cell death markers, cleaved caspase-3 and terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells, in the MSC group. The MSC group showed significantly lower interleukin (IL)-18 and interferon gamma levels and a significantly higher IL-4 level in lung tissue at 12 hours of EVLP than the control group. After transplantation, the MSC group showed a significant increase in lung tissue HGF level compared with the control group, associated with a significantly reduced lung tissue wet-to-dry weight ratio. Lung tissue tumor necrosis factor-α level and pathological acute lung injury score were significantly lower in the MSC group than the control group. The administration of MSCs ameliorated ischemic injury in donor lungs during EVLP and attenuated the subsequent ischemia-reperfusion injury after transplantation.

Emphysema-associated Autoreactive Antibodies Exacerbate Post-Lung Transplant Ischemia-Reperfusion Injury.

Chronic obstructive pulmonary disease-associated chronic inflammation has been shown to lead to an autoimmune phenotype characterized in part by the presence of lung autoreactive antibodies. We hypothesized that ischemia-reperfusion injury (IRI) liberates epitopes that would facilitate preexisting autoantibody binding, thereby exacerbating lung injury after transplant. We induced emphysema in C57BL/6 mice through 6 months of cigarette smoke (CS) exposure. Mice with CS exposure had significantly elevated serum autoantibodies compared with non-smoke-exposed age-matched (NS) mice. To determine the impact of a full preexisting autoantibody repertoire on IRI, we transplanted BALB/c donor lungs into NS or CS recipients and analyzed grafts 48 hours after transplant. CS recipients had significantly increased lung injury and immune cell infiltration after transplant. Immunofluorescence staining revealed increased IgM, IgG, and C3d deposition in CS recipients. To exclude confounding alloreactivity and confirm the role of preexisting autoantibodies in IRI, syngeneic Rag1-/- (recombination-activating protein 1-knockout) transplants were performed in which recipients were reconstituted with pooled serum from CS or NS mice. Serum from CS-exposed mice significantly increased IRI compared with control mice, with trends in antibody and C3d deposition similar to those seen in allografts. These data demonstrate that pretransplant CS exposure is associated with increased IgM/IgG autoantibodies, which, upon transplant, bind to the donor lung, activate complement, and exacerbate post-transplant IRI.

A Novel Injury Site-Targeted Complement Inhibitor Which Protects against Lung Transplant Ischemia Reperfusion Injury

Purpose Self-reactive natural Abs initiate complement activation and injury following ischemia and reperfusion of certain tissues, but their role in post-ischemic lung injury is unknown. Here, we investigated the expression of two previously identified post-ischemic neoepitopes, namely a modified annexin IV epitope recognized by B4 IgM mAb, and an epitope consisting of a subset of phospholipids recognized by C2 IgM mAb, and additionally determined their role in lung transplant ischemia reperfusion injury (IRI). Methods Lungs from C57Bl/6 mice were orthotopically transplanted into Rag1-/- (antibody-deficient) mice reconstituted with either B4 and C2 mAbs. Results Rag1-/- mice were protected from lung IRI, but reconstitution with either B4 or C2 natural IgM mAbs restored lung IRI. The C2 mAb was more effective than the B4 mAb at restoring injury, as determined by histological and micro-CT analysis. Based on this information, we developed and characterized a therapeutic strategy that exploited the post-ischemia recognition system of natural antibodies. We constructed a single-chain antibody (scFv) derived from C2 mAb and linked it to Crry, an inhibitor of C3 activation (C2scFv-Crry). In models of syngeneic (B6-B6) and allogeneic (Balb/c-B6) lung transplant models in which recipients contain a full natural antibody repertoire, a single post-transplant injection of C2scFv-Crry blocked the binding of endogenous IgM to the graft, inhibited complement activation, and significantly reduced graft inflammation and injury as determined by histology, μCT, and immunhistochemical analysis. The severity of IRI is associated with the onset of acute rejection. Conclusion We identified pathophysiologically important epitopes expressed within the lung after lung ischemia and reperfusion post transplantation. We further describe a novel translatable strategy for complement inhibition that is specifically targeted to the transplanted lung, and that has several advantages over currently available approaches that rely on systemic complement inhibition. Significantly, the C2 epitope has been identified in both mouse and man, increasing the translational relevance of the approach.

Investigation of the preventive effect of proanthocyanidin in ischemia-reperfusion injury in lung transplantation: An experimental study.

This study aims to investigate the preventive effect of proanthocyanidin against ischemia-reperfusion injury after lung transplantation. The study included 12 swines (weighing 35±5 kg) and separated into four groups. Groups 1 and 3 were identified as control groups and left upper lobectomy was performed. Groups 2 and 4 were identified as transplantation groups and left lower lobectomy and heterotransplantation were performed. Proanthocyanidin was only given to groups 3 and 4. Tissue samples were analyzed under light microscope and histopathological findings were recorded. There was no statistically significant difference between control groups in terms of the numerical values of histopathological findings that include congestion (p=0.565), alveolar edema (p=0.197) and peribronchial inflammation (p=0.444). However, numerical values of acute cellular rejection were statistically significantly different between transplantation groups (p=0.048). Mean oxidative stress enzyme levels were higher in group 2 compared to group 4; however, the difference was not statistically significant (p>0.05). According to the findings of our experimental study, proanthocyanidin can be safely used in lung transplantation based on its preventive effect in ischemia-reperfusion injury that may lead to morbidity and mortality.

Update on ischemia-reperfusion injury in lung transplantation.

Primary graft failure, which represents one of the most frequent causes of early mortality, is mostly caused by ischemia-reperfusion injury (IRI). IRI may also induce rejection, which is the principal cause of mortality after transplantation. It is essential to understand the mechanism of pulmonary IRI for improving the outcomes of lung transplantation, and therefore we reviewed the state of the art concerning pulmonary IRI in lung transplantation. Numerous strategies have been conducted to reduce IRI after lung transplantation both from the experimental and clinical aspects. The greatest efforts have been done in the method of lung preservation and reperfusion. Recently, ex-vivo lung perfusion system was developed and has been clinically introduced. Furthermore, more experimental studies to understand the pathophysiology of IRI and to alleviate lung IRI have been performed worldwide, and various new treatment modalities including inhalation therapy with therapeutic gases and substances, fibrinolytic treatment, subzero preservation, and mesenchymal stromal cell therapy are going to be applied to the clinical practice. IRI, whose pathophysiology remains incompletely understood, is one of the most critical phenomena in lung transplantation, and therefore more studies to control pulmonary IRI are required for improving the outcomes of lung transplantation.

Interleukin-10 Delivery via Mesenchymal Stem Cells: A Novel Gene Therapy Approach to Prevent Lung Ischemia–Reperfusion Injury

Ischemia-reperfusion (IR) injury is an important cause of primary graft failure in lung transplantation. In this study, viral interleukin-10 (vIL-10)-engineered mesenchymal stem cells (MSCs) were tested for their ability to prevent lung IR injury. Bone marrow-derived MSCs were transduced with rvIL-10-retrovirus. After 120 min of warm left lung ischemia, rats received approximately 15 x 10(6) vIL-10-engineered MSCs (MSC-vIL-10), empty vector-engineered MSCs (MSC-vec), or saline intravenously. Mean blood oxygenation (PaO(2)/FiO(2) ratio, mmHg) was measured at 4 hr, 24 hr, 72 hr, and 7 days. As early as 4 hr post-IR injury with MSC-vIL-10 treatment, blood oxygenation was significantly (p < 0.05) improved (319 +/- 94; n = 7) compared with untreated (saline) controls (63 +/- 19; n = 6). At 24 hr post-IR injury, in the MSC-vIL-10-treated group there was a further increase in blood oxygenation (353 +/- 105; n = 10) compared with the MSC-vec group (138 +/- 86; n = 9) and saline group (87 +/- 39; n = 10). By 72 hr, oxygenation reached normal (475 +/- 55; n = 9) in the MSC-vIL-10-treated group but not in the saline-treated and MSC-vec-treated groups. At 4 hr after IR injury, lungs with MSC-vIL10 treatment had a lower (p < 0.05) injury score (0.9 +/- 0.4) compared with lungs of the untreated (saline) group (2.5 +/- 1.4) or MSC-vec-treated group (2 +/- 0.4). Lung microvascular permeability and wet-to-dry weight ratios were markedly lower in the MSC-vIL10 group compared with untreated (saline) controls. ISOL (in situ oligonucleotide ligation for DNA fragmentation detection) and caspase-3 staining demonstrated significantly (p < 0.05) fewer apoptotic cells in MSC-vIL10-treated lungs. Animals that received MSC-vIL10 therapy had fewer (p < 0.05) CD4(+) and CD8(+) T cells in bronchoalveolar lavage fluid compared with untreated control animals. A therapeutic strategy using vIL-10-engineered MSCs to prevent IR injury in lung transplantation seems promising.

Lung Transplant Ischemia Reperfusion Injury: Metalloprotease Inhibition Down-regulates Exposure of Type V Collagen, Growth-Related Oncogene-Induced Neutrophil Chemotaxis, and Tumor Necrosis Factor-α Expression

Immunity to type V collagen [col(V)] contributes to lung transplant rejection. Matrix metalloproteases (MMPs), which are induced by transplant-related ischemia-reperfusion injury (IRI), could expose col(V) and regulate local IRI-induced inflammation. To test the hypothesis that MMPs induce col(V) exposure and inflammation, Wistar-Kyoto rats were treated with the MMP inhibitor, COL-3, before inducing lung IRI without transplantation, and in parallel studies, Wistar-Kyoto lung donor and recipients were treated with COL-3 pre- and postisograft lung transplantation. Ischemia-reperfusion injury induced growth-related oncogene/CINC-1-dependent neutrophil influx, and up-regulated tumor necrosis factor-alpha. MMP2 and MMP9, induced at 4 and 24 hr after IRI, respectively, were associated with detection of antigenic col(V) in bronchoalveolar lavage and lung interstitium because of MMP-mediated matrix degradation. MMP-inhibitor treatment significantly reduced polymorphonuclear leukocytes, growth-related oncogene/CINC-1, and tumor necrosis factor-alpha; abrogated MMP-9 expression; and resulted in lower levels of antigenic col(V) in bronchoalveolar lavage. In the lung transplant model, inhibiting MMPs in the donor before lung harvest and in the recipient after lung transplantation resulted in improved oxygenation and diminished polymorphonuclear leukocyte influx into the isograft. MMP inhibition may be a potential therapy to prevent release of antigenic col(V) and ameliorate IRI in the transplant recipient.

Ischemic preconditioning modulates ischemia-reperfusion injury in the rat lung: Role of adenosine receptors

Recent studies have been focused on the protective role of ischemic preconditioning against ischemia-reperfusion injury of the lung occurring following cardiopulmonary by-pass surgery and lung or heart transplantation. The present study was undertaken to investigate the role of adenosine in ischemic preconditioning in the isolated buffer-perfused rat lung. Since the pulmonary perfusion flow rate and left atrial pressure were constant, changes in pulmonary arterial pressure directly reflect changes in pulmonary vascular resistance. When compared to control values, ischemia-reperfusion injury in the form of 2 h of normothermic ischemia significantly reduced the pulmonary vasoconstrictor response to phenylephrine and KCl, increased wet-to-dry lung weight ratios and increased malondialdehyde content of rat lungs. Ischemic preconditioning in the form of one cycle of 5 min of ischemia and reperfusion applied prior to ischemia-reperfusion, as well as, adenosine preconditioning in the form of adenosine infusion prior to ischemia-reperfusion independently prevented the reduction in pulmonary vasoconstrictor responses and the increases in pulmonary edema and malondialdehyde formation in response to ischemia-reperfusion injury. Pretreatment with adenosine receptor antagonists, theophylline or 8-cyclopentyl-1,3-dipropyl xanthine (DPCPX) prior to ischemic preconditioning or adenosine preconditioning abolished the protective effects of preconditioning by ischemic preconditioning and adenosine preconditioning. The present data demonstrate that ischemic preconditioning and adenosine preconditioning prevent the vascular and biochemical alterations studied in response to ischemia-reperfusion injury in the pulmonary vascular bed of the rat. Results of the present study suggest activation of adenosine A 1 receptors mediates the protective properties of ischemic preconditioning and adenosine preconditioning on ischemia-reperfusion injury in the lung. Moreover, the present data further suggest selective adenosine receptor agonists may be useful as pharmacologic preconditioning agents in preventing ischemia-reperfusion injury in lung transplantation and other forms of pulmonary vascular ischemia.

Glycine intravenous donor preconditioning is superior to glycine supplementation to low-potassium dextran flush preservation and improves graft function in a large animal lung transplantation model after 24 hours of cold ischemia

The potential role of glycine in combination with standard lung preservation with low-potassium dextran solution in lung ischemia-reperfusion injury has not been investigated in a preclinical porcine transplant model. In a control group (n = 6), donor lungs were flushed with 1 liter of low-potassium dextran solution. In a second group (LPD-glyc, n = 6), low-potassium dextran solution was supplemented with 3.75 g of glycine. In a third group (IV-glyc, n = 6), donor preconditioning was performed by intravenous administration of 3.75 g glycine 1 hour before low-potassium dextran preservation. Grafts were stored in low-potassium dextran at 4 degrees C for 24 hours. Posttransplant graft function was assessed throughout a 7-hour observation period. In the control group, 2 recipients died of right-sided heart failure caused by severe ischemia-reperfusion injury. All animals of the glycine groups survived the entire observation period. Pulmonary vascular resistance remained significantly (P < .01) lower in both glycine groups when compared with controls. At the end of the observation period pulmonary vascular resistance in the control group was higher (P < .01) compared with the glycine groups (1310 +/- 319 dyn x sec x cm(-5) vs 879 +/- 127 dyn x sec x cm(-5) [LPD-glyc] vs 663 +/- 191 dyn x sec x cm(-5) [IV-glyc]). Changes of lung tissue water content were lower in the IV-glyc group compared with the LPD-control (P < .01) and LPD-glyc lungs (P < .05). Oxygenation (PO2/FiO2) was higher in the IV-glyc group compared with the LPD-glyc and control lungs (445 +/- 110 mm Hg vs 388 +/- 124 mm Hg [P < .01] vs 341 +/- 224 mm Hg [P < .001], respectively). Modification of low-potassium dextran solution with glycine or donor preconditioning ameliorates ischemia-reperfusion injury in lung transplantation. This intriguing approach merits further evaluation with respect to the mechanisms involved and may improve results in clinical lung preservation.

Surfactant alterations and treatment of lung transplant ischemia–reperfusion injury

This review addresses surfactant alterations and treatment in lung transplant ischemia–reperfusion injury. Lung ischemia–reperfusion injury damages the endogenous surfactant system as a result of the production of reactive oxygen species, proteolytic enzymes and (phospho)lipases. Surfactant is composed of phospholipids and proteins and its main function is to reduce the surface tension inside the alveolus. Impairment of surfactant will cause atelectasis, influx of serum proteins, pulmonary edema, decreased lung compliance and impaired gas exchange. Surfactant therapy restores the quantity and composition of surfactant and reduces the inhibitory effect of serum proteins; other effects are that it serves as an antioxidant and anti-inflammatory agent. Pretreatment may be more beneficial than treatment after the development of lung ischemia–reperfusion injury. However, the cost of surfactant must be weighed against the clinical outcome.

CXCR2/CXCR2 Ligand Biology during Lung Transplant Ischemia-Reperfusion Injury

Lung transplantation is a therapeutic option for a number of end-stage pulmonary disorders. Early lung allograft dysfunction (ischemia-reperfusion injury) continues to be the most common cause of early mortality after lung transplantation and a significant risk factor for the development of bronchiolitis obliterans syndrome. Ischemia-reperfusion injury is characterized histopathologically by lung edema and a neutrophil predominate leukocyte extravasation. The specific mechanism(s) that recruit leukocytes to the lung during post-lung transplantation ischemia-reperfusion injury have not been fully elucidated. Because the ELR+ CXC chemokines are potent neutrophil chemoattractants, we investigated their role during post-lung transplantation ischemic-reperfusion injury. We found elevated levels of multiple ELR+ CXC chemokines in human bronchoalveolar lavage fluid from patients with ischemia-reperfusion injury. Proof of concept studies using a rat orthotopic lung transplantation model of "cold" ischemic-reperfusion injury demonstrated an increase in lung graft neutrophil sequestration and injury. In addition, lung expression of CXCL1, CXCL2/3, and their shared receptor CXCR2 paralleled lung neutrophil infiltration and injury. Importantly, inhibition of CXCR2/CXCR2 ligand interactions in vivo led to a marked reduction in lung neutrophil sequestration and graft injury. Taken together these experiments support the notion that increased expression of ELR+ CXC chemokines and their interaction with CXCR2 plays an important role in the pathogenesis of post-lung transplantation cold ischemia-reperfusion injury.

Inhibition of nuclear factor κB by IκB superrepressor gene transfer ameliorates ischemia-reperfusion injury after experimental lung transplantation

Ischemia-reperfusion injury after lung transplantation is associated with significant morbidity and mortality. The activation of the transcription factor nuclear factor kappaB is central to the 2 important pathways that characterize ischemia-reperfusion injury, namely the inflammatory response and apoptosis. The purpose of this study was to determine the effects of nuclear factor kappaB inhibition on experimental lung transplant ischemia-reperfusion injury with gene transfer of the nuclear factor kappaB inhibitor IkappaB in a superrepressor form (IkappaBSR). An orthotopic left lung transplant model in isogeneic rats was used, with 18 hours of prolonged cold storage of donor lung grafts used to create severe ischemia-reperfusion injury. Donor rats underwent endobronchial gene transfection with saline alone or adenovirus encoding either beta-galactosidase control or IkappaBSR 48 hours before harvest. The function of transplanted lung grafts was assessed on the basis of isolated graft oxygenation, wet/dry lung weight ratio, and myeloperoxidase activity. Nuclear factor kappaB activation was assessed by means of enzyme-linked immunosorbent assay. Apoptotic cell death was assessed by evaluating the levels of histone-associated DNA fragments and caspase-3 activity. Treatment of donor lung grafts with IkappaBSR resulted in significantly improved oxygenation compared with that seen in control tissue 24 hours after transplantation. IkappaBSR-treated lungs also demonstrated less pulmonary edema and reduced neutrophil infiltration 24 hours after reperfusion. Nuclear factor kappaB activation and apoptotic cell death induction 2 hours after transplantation was significantly reduced in IkappaBSR-treated lungs compared with in control lungs. Inhibition of nuclear factor kappaB activation by IkappaBSR gene transfer improves transplanted lung graft oxygenation, decreases pulmonary edema and neutrophil sequestration, and reduces apoptotic cell death after experimental lung transplantation.

Iloprost to improve surfactant function in porcine pulmonary grafts stored for twenty-four hours in low-potassium dextran solution

The optimal strategy for pulmonary graft preservation remains elusive. Experimental work and initial clinical experience support low-potassium dextran solutions as lung perfusates. We have previously shown a protective effect of prostaglandin E 1 on ischemia-reperfusion injury in lung transplantation by a shift from proinflammatory to anti-inflammatory cytokines in a rat lung transplantation model. In this study, we tested the hypothesis that the addition of a prostacyclin analog (iloprost) to low-potassium dextran might lead to improved surfactant and ultimately graft function. In a randomized, blinded study with a porcine left single-lung transplantation model, donor lungs were flushed with 1 L of either low-potassium dextran solution or low-potassium dextran solution modified by the addition of 250 microg iloprost (n = 6 in each group). Grafts were stored at 4 degrees C for 24 hours. After transplantation, the right bronchus and pulmonary artery were clamped, and the animals remained dependent on the graft. Posttransplantation graft function was assessed throughout a 7-hour observation period by measuring oxygenation (30-minute intervals), different pulmonary and systemic hemodynamic parameters, and wet/dry lung weight ratios. Bronchoalveolar lavage fluid was obtained before and 2 hours after reperfusion. Surfactant function was measured from bronchoalveolar lavage fluid with a pulsating bubble surfactometer. Neutrophil sequestration was assessed by a myeloperoxidase assay performed on lung tissue specimens taken at the end of the observation period. Pulmonary vascular resistance remained lower in the iloprost group than in the control group (P < .05). Tissue water content after 7 hours of reperfusion remained lower in the iloprost group (P < .05). In addition, significantly reduced myeloperoxidase tissue activity was observed in the iloprost group (P < .05). Although there was no difference in degradation of surface active surfactant large aggregates to small aggregates, the surface tension measured at minimal bubble diameter was lower in the iloprost group (P < .05). Modification of low-potassium dextran solution with the prostacyclin analog iloprost resulted in a significant amelioration of ischemia-reperfusion injury and improved preservation of surfactant function in transplanted lungs. This intriguing approach merits further evaluation with respect to the mechanisms involved and, ultimately, potential introduction into clinical lung transplantation.