Ischemic Lungs Research Articles

(672) - Transient Heat Stress Protects from Endothelial Injury During Prolonged Ex-Vivo Perfusion of Warm Ischemic Rat Lungs

(672) - Transient Heat Stress Protects from Endothelial Injury During Prolonged Ex-Vivo Perfusion of Warm Ischemic Rat Lungs

Hemopexin alleviates sterile inflammation in ischemia-reperfusion-induced lung injury.

Pulmonary ischemia-reperfusion (IR) injury (IRI) plays a significant role in various lung disorders and is a key factor in the development of primary graft dysfunction following lung transplantation. Hemopexin (Hx) is the major serum scavenger protein for heme, which is a prooxidant and pro-inflammatory compound. In the current study, we hypothesized that Hx could confer beneficial effects in sterile inflammation induced by IR-mediated lung injury. To examine this hypothesis, we administered Hx in an experimental mouse model of unilateral lung IRI. Our results demonstrate that treatment with Hx alleviated histopathological signs of inflammation in ischemic lungs, as evidenced by a reduction in the number of infiltrating neutrophils and decreased levels of perivascular edema. In addition, thrombotic vaso-occlusion in pulmonary blood vessels of IRI lungs was reduced by Hx. Immunohistochemical analysis revealed that Hx inhibited the up-regulation of heme oxygenase-1, an enzyme highly induced by heme, in ischemic lungs. Finally, Hx administration caused a decrease in the levels of circulating B- and CD8+ T-lymphocytes in the peripheral blood of mice with pulmonary IRI. These findings suggest that the serum heme scavenger protein Hx holds therapeutic promise in alleviating lung IRI-mediated sterile inflammation. Thus, Hx may represent a preemptive therapeutic approach in IR-related lung disorders such as primary graft dysfunction in lung transplantation.

Newly synthesized glycoprotein profiling to identify molecular signatures of warm ischemic injury in donor lungs.

Despite recent technological advances such as ex vivo lung perfusion (EVLP), the outcome of lung transplantation remains unsatisfactory with ischemic injury being a common cause for primary graft dysfunction. New therapeutic developments are hampered by limited understanding of pathogenic mediators of ischemic injury to donor lung grafts. Here, to identify novel proteomic effectors underlying the development of lung graft dysfunction, using bioorthogonal protein engineering, we selectively captured and identified newly synthesized glycoproteins (NewS-glycoproteins) produced during EVLP with unprecedented temporal resolution of 4 h. Comparing the NewS-glycoproteomes in lungs with and without warm ischemic injury, we discovered highly specific proteomic signatures with altered synthesis in ischemic lungs, which exhibited close association to hypoxia response pathways. Inspired by the discovered protein signatures, pharmacological modulation of the calcineurin pathway during EVLP of ischemic lungs offered graft protection and improved posttransplantation outcome. In summary, the described EVLP-NewS-glycoproteomics strategy delivers an effective new means to reveal molecular mediators of donor lung pathophysiology and offers the potential to guide future therapeutic development.NEW & NOTEWORTHY This study developed and implemented a bioorthogonal strategy to chemoselectively label, enrich, and characterize newly synthesized (NewS-)glycoproteins during 4-h ex vivo lung perfusion (EVLP). Through this approach, the investigators uncovered specific proteomic signatures associated with warm ischemic injury in donor lung grafts. These signatures exhibit high biological relevance to ischemia-reperfusion injury, validating the robustness of the presented approach.

Primary Graft Dysfunction: The Role of Aging in Lung Ischemia-Reperfusion Injury.

Transplant centers around the world have been using extended criteria donors to remedy the ongoing demand for lung transplantation. With a rapidly aging population, older donors are increasingly considered. Donor age, at the same time has been linked to higher rates of lung ischemia reperfusion injury (IRI). This process of acute, sterile inflammation occurring upon reperfusion is a key driver of primary graft dysfunction (PGD) leading to inferior short- and long-term survival. Understanding and improving the condition of older lungs is thus critical to optimize outcomes. Notably, ex vivo lung perfusion (EVLP) seems to have the potential of reconditioning ischemic lungs through ex-vivo perfusing and ventilation. Here, we aim to delineate mechanisms driving lung IRI and review both experimental and clinical data on the effects of aging in augmenting the consequences of IRI and PGD in lung transplantation.

Nicotinamide Adenine Dinucleotide (NAD+) improves lung function in rat lung ex-vivo lung perfusion model

Abstract Objective Ischemia-reperfusion injury compromises short- and long-term outcome after lung transplantation. The scarce existing data on the natural co-enzyme NAD+ suggest an antagonistic effect on hypoxia induced vasoconstriction, removal capacity on reactive oxygen species, and anti-inflammatory effects. We therefore investigated the impact of NAD+ on ischemic rat lungs during ex-vivo lung perfusion (EVLP). Methods Lungs were retrieved from 12 outbred Sprague Dawley male rats and exposed to 14 hours of cold ischemic storage. All lungs were then perfused in a rat EVLP system for 4 hours. Lung grafts were injected after 1, 2 and 3 hours with 2000 uM NAD + (N = 6) or placebo (N = 6) in the perfusate in proximity of the pulmonary artery. EVLP physiology and biochemistry were monitored. Results During the 4 hours of EVLP, the lung function increased significantly in the NAD+ group when compared to the placebo group. We monitored a higher vascular flow (p = 0.018), a lower mean pulmonary pressure (p = 0.007) and increased oxygenation capacity (p = 0.003). Lung compliance and weight were comparable. Tissue inflammation measured by myeloperoxidase was significantly lower in the NAD+ group (p = 0.015). In the perfusate, we observed in the NAD+ group significantly lower levels of pro-inflammatory interleukin-18 (p = 0.033) and a trend towards high levels of anti-inflammatory interleukin-10 (p = 0.080) and low levels of pro-inflammatory interleukin-12 (p = 0.146). Conclusion Findings from this preliminary study demonstrated that NAD+ is a promising agent with both anti-inflammatory properties and the ability to improve ischemic lung function. This observation should be validated in a large animal model.

Nicotinamide Adenine Dinucleotide (NAD+) Improves Lung Function in Rat Lung Ex-Vivo Lung Perfusion Model

Purpose Ischemia-reperfusion injury compromises short- and long-term outcome after lung transplantation. The scarce existing data on the natural co-enzyme NAD+ suggest an antagonistic effect on hypoxia induced vasoconstriction, removal capacity on reactive oxygen species, and anti-inflammatory effects. We therefore investigated the impact of NAD+ on ischemic rat lungs during ex-vivo lung perfusion (EVLP). Methods Lungs were retrieved from 12 outbred Sprague Dawley male rats and exposed to 14 hours of cold ischemic storage. All lungs were then perfused in a rat EVLP system for 4 hours. Lung grafts were injected after 1, 2 and 3 hours with 2000 uM NAD+ (N=6) or placebo (N=6) in the perfusate in proximity of the pulmonary artery. EVLP physiology and biochemistry were monitored. Results During the 4 hours of EVLP, the lung function increased significantly in the NAD+ group when compared to the placebo group. We monitored a higher vascular flow (p=0.018), a lower mean pulmonary pressure (p=0.007) and increased oxygenation capacity (p=0.003). Lung compliance and weight were comparable. Tissue inflammation measured by myeloperoxidase was significantly lower in the NAD+ group (p=0.015). In the perfusate, we observed in the NAD+ group significantly lower levels of pro-inflammatory interleukin-18 (p=0.033) and a trend towards high levels of anti-inflammatory interleukin-10 (p=0.080) and low levels of pro-inflammatory interleukin-12 (p=0.146). Conclusion Findings from this preliminary study demonstrated that NAD+ is a promising agent with both anti-inflammatory properties and the ability to improve ischemic lung function. This observation should be validated in a large animal model.

Functional Pulmonary Magnetic Resonance Imaging for Detection of Ischemic Injury in a Porcine Ex-Vivo Lung Perfusion System Prior to Transplantation

To evaluate the feasibility of multiparametric magnetic resonance imaging (MRI) of the lungs to detect impaired organ function in a porcine model of ischemic injury within an ex-vivo lung perfusion system (EVLP) prior to transplantation. Twelve pigs were anesthetized, and left lungs were clamped to induce warm ischemia for 3 hours. Right lungs remained perfused as controls. Lungs were removed and installed in an EVLP for 12 hours. Lungs in the EVLP were imaged repeatedly using computed tomography, proton MRI (1H-MRI) and fluorine MRI (19F-MRI). Dynamic contrast-enhanced derived parenchymal blood volume, oxygen washout times, and 19F washout times were calculated. PaO2 was measured for ischemic and normal lungs, wet/dry ratio was determined, histologic samples were assessed, and cytokines in the lung tissue were analyzed. Statistical analysis was performed using nonparametric testing. Eleven pigs were included in the final analysis. Ischemic lungs showed significantly higher wet/dry ratios (p = 0.024), as well as IL-8 tissue levels (p = 0.0098). Histologic assessment as well as morphologic scoring of computed tomography and 1H-MRI did not reveal significant differences between ischemic and control lungs. 19F washout (p = 0.966) and parenchymal blood flow (p = 0.32) were not significantly different. Oxygen washout was significantly prolonged in ischemic lungs compared to normal control lungs at the beginning (p = 0.018) and further prolonged at the end of the EVLP run (p = 0.005). Multiparametric pulmonary MRI is feasible in lung allografts within an EVLP system. Oxygen-enhanced imaging seems to be a promising marker for ischemic injury, enabling detection of affected lung segments prior to transplantation.

Lung injury pathways: Adenosine receptor 2B signaling limits development of ischemic bronchiolitis obliterans organizing pneumonia

ABSTRACTPurpose/Aim of the Study: Adenosine signaling was studied in bronchiolitis obliterans organizing pneumonia (BOOP) resulting from unilateral lung ischemia. Materials and Methods: Ischemia was achieved by either left main pulmonary artery or complete hilar ligation. Sprague–Dawley (SD) rats, Dahl salt sensitive (SS) rats and SS mutant rat strains containing a mutation in the A2B adenosine receptor gene (Adora2b) were studied. Adenosine concentrations were measured in bronchoalveolar lavage (BAL) by HPLC. A2A (A2AAR) and A2B adenosine receptor (A2BAR) mRNA and protein were quantified. Results: Twenty-four hours after unilateral PA ligation, BAL adenosine concentrations from ischemic lungs were increased relative to contralateral lungs in SD rats. A2BAR mRNA and protein concentrations were increased after PA ligation while miR27a, a negatively regulating microRNA, was decreased in ischemic lungs. A2AAR mRNA and protein concentrations remained unchanged following ischemia. A2BAR protein was increased in PA ligated lungs of SS rats after 7 days, and 4 h after complete hilar ligation in SD rats. SS-Adora2b mutants showed a greater extent of BOOP relative to SS rats, and greater inflammatory changes. Conclusion: Increased A2BAR and adenosine following unilateral lung ischemia as well as more BOOP in A2BAR mutant rats implicate a protective role for A2BAR signaling in countering ischemic lung injury.

Attenuation of Pulmonary Ischemia-Reperfusion Injury by Adenosine A2B Receptor Antagonism

Ischemia-reperfusion injury (IRI) is a major source of morbidity and mortality after lung transplantation. We previously demonstrated a proinflammatory role of adenosine A2B receptor (A2BR) in lung IR injury. The current study tests the hypothesis that A2BR antagonism is protective of ischemic lungs after invivo reperfusion or exvivo lung perfusion (EVLP). Mice underwent lung IR with or without administration of ATL802, a selective A2BR antagonist. A murine model of EVLP was also used to evaluate rehabilitation of donation after circulatory death (DCD) lungs. DCD lungs underwent ischemia, cold preservation, and EVLP with Steen solution with or without ATL802. A549 human type 2 alveolar epithelial cells were exposed to hypoxia-reoxygenation (HR) (3 hours/1 hour) with or without ATL802 treatment. Cytokines were measured in bronchoalveolar lavage (BAL) fluid and culture media by enzyme-linked immunoassay (ELISA). After IR, ATL802 treatment significantly improved lung function (increased pulmonary compliance and reduced airway resistance and pulmonary arterypressure) and significantly attenuated proinflammatory cytokine production, neutrophil infiltration, vascular permeability, and edema. ATL802 also significantly improved the function of DCD lungs after EVLP(increased compliance and reduced pulmonary artery pressure). After HR, A549 cells exhibited robust production of interleukin (IL)-8, a potent neutrophil chemokine, which was significantly attenuated by ATL802. These results demonstrate that A2BR antagonism attenuates lung IRI and augments reconditioning of DCD lungs by EVLP. The protective effects of ATL802 may involve targeting A2BRs onalveolar epithelial cells to prevent IL-8 production. A2BR may be a novel therapeutic target for mitigating IRI to increase the success of lung transplantation.

(464) - Reconditioning of Prolonged Warm Ischemic Lungs by High-Dose Bronchodilator Inhalation during Ex Vivo Lung Perfusion in a Canine Lung Transplantation Model

(464) - Reconditioning of Prolonged Warm Ischemic Lungs by High-Dose Bronchodilator Inhalation during Ex Vivo Lung Perfusion in a Canine Lung Transplantation Model

Evaluation of oxygen sensitivity of hyperpolarized helium imaging for the detection of pulmonary ischemia

In this study, a new model of pulmonary embolism in rats was developed and tested, to examine if hyperpolarized (HP) (3) He MR images can measure impairment of the exchange of oxygen from the airspaces to the blood during pulmonary embolism. HP (3) He MRI was used to image six treatment-group rats in which a branch of the pulmonary artery was embolized, and six control-group rats. HP (3) He MR images were used to calculate the initial partial pressure of oxygen (pO ) and the rate of oxygen depletion (R) in rat lungs. The pO was significantly higher in the ischemic lung than in the contralateral normal side, and pO was significantly higher in the ischemic lung than in both sides of the control lungs. Mean R in ischemic lungs was significantly lower than in the contralateral lungs, and mean R in ischemic lungs was also significantly lower than in both control lungs. These results demonstrate that pO and R, as measured by the T1 decay of HP (3) He, are sensitive to pulmonary ischemia in rats, confirming the findings in studies performed in large animal models of pulmonary ischemia.

Advance in study on endothelial colony-forming cells

Endothelial colony-forming cells (ECFCs), different from classical endothelial progenitor cells, are late endothelial progenitor cells with the capability to promote angiogenesis. Recent studies showed that ECFCs have a huge angiogenesis potential in the restoration of ischemic hearts, lungs or brains. They are also able to induce the expression of vascular related factor to promote angiogenesis in repair of limb ischemia or bone injury. Furthermore, ECFCs possess a strong homing effect for tumor, which is closely related to tumor occurrence, development and prognosis. Thus, ECFCs are a novel direction for vascular regeneration study, and may lead to ground-breaking progresses in fields of tissue regeneration and tumor.

Protective Effect of Surfactant Inhalation against Warm Ischemic Injury in an Isolated Rat Lung Ventilation Model

Warm ischemia-reperfusion injury remains a crucial issue in transplantation following the cardiac death of donors. Previously, we showed that surfactant inhalation during warm ischemia mitigated ischemia-reperfusion injury. This study investigated the mechanisms of surfactant inhalation protection of the warm ischemic lung after reoxygenation with ventilation alone. In an isolated rat lung ventilation model, cardiac arrest was induced in the CTRL (control) and SURF (surfactant treatment) groups by ventricular fibrillation. Ventilation was restarted 110 min later; the lungs were flushed, and a heart and lung block was procured. In the SURF group, a natural bovine surfactant (Surfacten®) was inhaled for 3 min at the end of warm ischemia. In the Sham (no ischemia) group, lungs were flushed, procured, and ventilated in the same way. Afterwards, the lungs were ventilated with room air without reperfusion for 60 min. Surfactant inhalation significantly improved dynamic compliance and airway resistance. Moreover, surfactant inhalation significantly decreased inducible nitric oxide synthase and caspase-3 transcript levels, and increased those of Bcl-2 and surfactant protein-C. Immunohistochemically, lungs in the SURF group showed weaker staining for 8-hydroxy-2′-deoxyguanosine, inducible nitric oxide synthase, and apoptosis, and stronger staining for Bcl-2 and surfactant protein-C. Our results indicate that surfactant inhalation in the last phase of warm ischemia mitigated the injury resulting from reoxygenation after warm ischemia. The reduction in oxidative damage and the inhibition of apoptosis might contribute to the protection of the warm ischemic lungs.

Rattus model utilizing selective pulmonary ischemia induces bronchiolitis obliterans organizing pneumonia.

Bronchiolitis obliterans organizing pneumonia (BOOP), a morbid condition when associated with lung transplant and chronic lung disease, is believed to be a complication of ischemia. Our goal was to develop a simple and reliable model of lung ischemia in the Sprague-Dawley rat that would produce BOOP. Unilateral ischemia without airway occlusion was produced by an occlusive slipknot placed around the left main pulmonary artery. Studies were performed 7 days later. Relative pulmonary and systemic flow to each lung was measured by injection of technetium Tc 99m macroaggregated albumin. Histological sections were examined for structure and necrosis and scored for BOOP. Apoptosis was detected by immunohistochemistry with an antibody against cleaved caspase 3. Pulmonary artery blood flow to left lungs was less than 0.1% of the cardiac output, and bronchial artery circulation was ∼2% of aortic artery flow. Histological sections from ischemic left lungs consistently showed Masson bodies, inflammation, and young fibroblasts filling the distal airways and alveoli, consistent with BOOP. In quantitative evaluation of BOOP using epithelial changes, inflammation and fibrosis were higher in ischemic left lungs than right or sham-operated left lungs. Apoptosis was increased in areas exhibiting histological BOOP, but there was no histological evidence of necrosis. Toll-like receptor 4 expression was increased in ischemic left lungs over right. An occlusive slipknot around the main left pulmonary artery in rats produces BOOP, providing direct evidence that ischemia without immunomodulation or coinfection is sufficient to initiate this injury. It also affords an excellent model to study signaling and genetic mechanisms underlying BOOP.

Prophylactic Surfactant Inhalation Attenuates Warm Ischemic Injury in Rat Lungs from Donation after Cardiac Death Donors

Background: To deal with the shortage of donor organs in lung transplantation, donation after cardiac death (DCD) has been introduced worldwide as one of the potential strategies to increase the donor pool. Considering ischemia-reperfusion injury in solid organ transplantation from DCD donors, it is very important to alleviate graft injury during warm ischemia. It was reported that surfactant function deteriorated with increasing warm ischemic time, resulting in graft injury. Therefore, we investigated the effect of surfactant inhalation against warm ischemic injury in rat lungs from DCD donors. In this experiment, only ventilation was initiated after warm ischemia, therefore, warm ischemic injury was assessed from the view of hypoxia-reoxygenation injury. Methods/Materials: Male Lewis rats were used. One hundred and ten minutes after cardiac arrest induced by ventricular fibrillation, the lungs were initiated to ventilate and flushed by Low Potassium Dextran solution. Thereafter, heart and lung block was isolated, and ex vivo lung ventilation (EVLV) was conducted. Rats were randomly allocated to 2 groups, the CTRL and SURF groups (n = 5 each). In the SURF group, surfactant was inhaled for 3 min, while nothing was inhaled in the CTRL group. Just after this inhalation period (total warm ischemic time: 135 min), dynamic compliance and airway resistance were evaluated on time throughout 60 min of ventilation. After 60 min of EVLV, lung tissue levels of ATP, ADP, and AMP were measured by high-performance liquid chromatography: messenger RNA (mRNA) expression of NO synthase (neuronal, inducible, endothelial), caspase-3, Bax, and Bcl-2 were measured by real-time RT-PCR: Hematoxylin-Eosin (H-E) staining, immunohistochemical staining for 8-hydroxy-2′-deoxyguanosine (8-OHdG), and in situ apoptosis detection (TUNEL assay) were examined. Results: During 60 min of ventilation, surfactant inhalation significantly increased dynamic compliance (p < 0.01), and decreased airway resistance (p < 0.001). Surfactant inhalation effectively increased lung tissue levels of ATP (p < 0.05). After 60 min of ventilation, mRNA levels of NO synthase (neuronal, inducible, endothelial) and caspase-3 were significantly lower, and mRNA levels of Bcl-2 were significantly higher in the SURF group than those in the CTRL group. In the histologic examination with H-E staining, both the CTRL and SURF groups showed no differences with relatively normal structure. However, in 8-OHdG stain and in TUNEL assay, there were fewer positive cells in the SURF group than those in the CTRL group. Conclusion: We confirmed that surfactant inhalation in the last phase of warm ischemia mitigated warm ischemic injury in an isolated rat lung ventilation model. Reduction of oxidative stress and inhibition of apoptosis might contribute to the protection of the warm ischemic lungs in our study.

Deguelin attenuates reperfusion injury and improves outcome after orthotopic lung transplantation in the rat.

The main goal of adequate organ preservation is to avoid further cellular metabolism during the phase of ischemia. However, modern preservation solutions do rarely achieve this target. In donor organs hypoxia and ischemia induce a broad spectrum of pathologic molecular mechanisms favoring primary graft dysfunction (PGD) after transplantation. Increased hypoxia-induced transcriptional activity leads to increased vascular permeability which in turn is the soil of a reperfusion edema and the enhancement of a pro-inflammatory response in the graft after reperfusion. We hypothesize that inhibition of the respiration chain in mitochondria and thus inhibition of the hypoxia induced mechanisms might reduce reperfusion edema and consecutively improve survival in vivo. In this study we demonstrate that the rotenoid Deguelin reduces the expression of hypoxia induced target genes, and especially VEGF-A, dose-dependently in hypoxic human lung derived cells. Furthermore, Deguelin significantly suppresses the mRNA expression of the HIF target genes VEGF-A, the pro-inflammatory CXCR4 and ICAM-1 in ischemic lungs vs. control lungs. After lung transplantation, the VEGF-A induced reperfusion-edema is significantly lower in Deguelin-treated animals than in controls. Deguelin-treated rats exhibit a significantly increased survival-rate after transplantation. Additionally, a downregulation of the pro-inflammatory molecules ICAM-1 and CXCR4 and an increase in the recruitment of immunomodulatory monocytes (CD163+ and CD68+) to the transplanted organ involving the IL4 pathway was observed. Therefore, we conclude that ischemic periods preceding reperfusion are mainly responsible for the increased vascular permeability via upregulation of VEGF. Together with this, the resulting endothelial dysfunction also enhances inflammation and consequently lung dysfunction. Deguelin significantly decreases a VEGF-A induced reperfusion edema, induces the recruitment of immunomodulatory monocytes and thus improves organ function and survival after lung transplantation by interfering with hypoxia induced signaling.

Early effects of the ex vivo evaluation system on graft function after swine lung transplantation

Ex vivo lung evaluation (ex vivo) has been developed as a useful method by which to assess lungs from donation-after-cardiac death (DCD) donors prior to transplant. However, the safety of the ex vivo circulation itself with respect to grafts has not been fully investigated. The aim of this study is to evaluate the effects of the ex vivo circuit using a swine lung transplant model. Lungs with or without 2-h warm ischemia were used. To assess post-transplant graft function, the left lung was transplanted after 2-h ex vivo or cold preservation; blood gas analysis of the left pulmonary vein (partial pressure of oxygen, PO(2)) was performed during the 6-h post-transplant follow-up period. Data were compared between the ex vivo (+) and ex vivo (-) groups. Partial pressure of oxygen/ inspired oxygen fraction (PO(2)/FiO(2)) in the ex vivo (-) group was significantly greater than that in the ex vivo (+) group until 3h after transplant. The PO(2)/FiO(2) levels in both groups then increased and became similar at 6 h after transplant, regardless of whether ischemic or non-ischemic lungs (p<0.001 and p=0.004, respectively) were used. Negative effects of the ex vivo system were limited and seen only in the immediate post-transplant period. Therefore, in DCD swine lung transplantation, the ex vivo system appears to be safe.

Influence of lung mechanical properties and alveolar architecture on the pathogenesis of ischemia-reperfusion injury

We tested the hypothesis that lung preservation techniques disarrange lung architecture, increase pulmonary impedance and lead to ischemia-reperfusion injury, which can be prevented by re-establishment of optimal lung geometry. In the first phase, fresh, cold ischemic, preserved lungs insufflated to total lung capacity (TLC) and preserved lungs ventilated with tidal volume prior to reperfusion were submitted to a 60-min ex-vivo reperfusion to evaluate the gas exchange, pulmonary hemodynamic and lung mechanics' properties. In the second phase, we evaluated the mechanical properties of lungs submitted to the same conditions of the first phase. Cold ischemic lungs developed fulminant edema during the first 15 min of ex-vivo reperfusion, whereas gas exchange, hemodynamic and mechanic properties of lungs insufflated to TLC and ventilated during 10 min prior to reperfusion were similar to fresh lungs. After the pulmonary vascular flush pulmonary impedance and alveolar collapsed area increased significantly. The insufflation to TLC and 10 min of tidal ventilation reduced the lung impedance and the percentage of alveolar collapsed area. Lung preservation techniques disarrange alveolar architecture, which lead to ischemia-reperfusion injury; recruitment maneuvers decrease the pulmonary inhomogeneities and protect the lungs against the ischemia-reperfusion injury.

The effects of adding methylprednisolone to low-potassium dextran solution on preserved ischemic lungs

To investigate the effects of adding methylprednisolone to low-potassium dextran solution on cold-preserved ischemic lungs. Materials and methods: The study included 42 rat lung blocks that were divided into 7 groups (n = 6). Lung blocks were preserved in 40 mL of cold Perfadex solution, to which 5, 15, 30, 60, and 120 mg kg-1 (approximately 40, 120, 240, 480, and 960 mg L-1) of methylprednisolone were added. After a 24-h preservation period, the lungs were removed from the solution and examined. Results: As compared to the Perfadex only group, cell death and degeneration were significantly higher in the Perfadex + methylprednisolone groups (P < 0.05). MDA and IL-8 levels were higher in all Perfadex + methylprednisolone groups. Statistically significant differences were observed between some of these groups. Antioxidant enzyme activity was generally higher in the Perfadex + methylprednisolone groups than in the Perfadex only group (P < 0.05). Conclusion: Adding methylprednisolone to low-potassium dextran solution does not have any beneficial effects but has possible deleterious effects in rat lung preservation.

PROTEASOME PEPTIDASE ACTIVITIES PARALLEL HISTOMORPHOLOGICAL AND FUNCTIONAL CONSEQUENCES OF ISCHEMIA-REPERFUSION INJURY IN THE LUNG

Several lines of evidence suggest that the proteasome contributes to ischemia-reperfusion injury (I-RI) of organs. Although I-RI contributes to multiple disease processes in the lung, the regulation of proteasome activities during pulmonary I-RI is unknown. Thus, the authors performed a pilot study to define time-related changes of lung proteasome peptidase activities and to evaluate if possible alterations correspond to morphological and functional consequences of I-RI using a rat model. Animals underwent 120 minutes of unilateral lung ischemia. Ischemic and contralateral lungs were harvested at multiple time points for up to 168 hours of reperfusion (I-R30min-168h). Chymotryptic-like (CT-L) and tryptic-like (T-L) proteasome peptidase activities were measured in lung extracts. An early I-R–associated inactivation of proteasome activities paralleled impairment of oxygenation, edema formation, and degree of histopathology, and resolved with restoration of function within 24 to 72 hours. Although functional and histomorphological baseline conditions were still not fully achieved at I-R168h, proteasome activities increased continuously 1.4-fold (CT-L) and 5.7-fold (T-L) until I-R168h. Apparent KM values for the CT-L/T-L substrates were not influenced by I-R. This pilot study establishes an initial link between proteasome activities and physiological relevant consequences of lung I-RI, and further points towards a possible role of the proteasome during the postischemic tissue repair process.