Lung preservation: the importance of endothelial and alveolar type II cell integrity

The effects of ischaemic conditioning on lung ischaemia-reperfusion injury

Ischaemia-reperfusion injury (IRI) encompasses the deleterious effects on cellular function and survival that result from the restoration of organ perfusion. Despite their unique tolerance to ischaemia and hypoxia, afforded by their dual (pulmonary and bronchial) circulation as well as direct oxygen diffusion from the airways, lungs are particularly susceptible to IRI (LIRI). LIRI may be observed in a variety of clinical settings, including lung transplantation, lung resections, cardiopulmonary bypass during cardiac surgery, aortic cross-clamping for abdominal aortic aneurysm repair, as well as tourniquet application for orthopaedic operations. It is a diagnosis of exclusion, manifesting clinically as acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). Ischaemic conditioning (IC) signifies the original paradigm of treating IRI. It entails the application of short, non-lethal ischemia and reperfusion manoeuvres to an organ, tissue, or arterial territory, which activates mechanisms that reduce IRI. Interestingly, there is accumulating experimental and preliminary clinical evidence that IC may ameliorate LIRI in various pathophysiological contexts. Considering the detrimental effects of LIRI, ranging from ALI following lung resections to primary graft dysfunction (PGD) after lung transplantation, the association of these entities with adverse outcomes, as well as the paucity of protective or therapeutic interventions, IC holds promise as a safe and effective strategy to protect the lung. This article aims to provide a narrative review of the existing experimental and clinical evidence regarding the effects of IC on LIRI and prompt further investigation to refine its clinical application.

Ischemia-Reperfusion Injury in a Simulated Lung Transplant Setting Differentially Regulates Transcriptomic Profiles between Human Lung Endothelial and Epithelial Cells

Current understanding of mechanisms of ischemia-reperfusion-induced lung injury during lung preservation and transplantation is mainly based on clinical observations and animal studies. Herein, we used cell and systems biology approaches to explore these mechanisms at transcriptomics levels, especially by focusing on the differences between human lung endothelial and epithelial cells, which are crucial for maintaining essential lung structure and function. Human pulmonary microvascular endothelial cells and human lung epithelial cells were cultured to confluent, subjected to different cold ischemic times (CIT) to mimic static cold storage with preservation solution, and then subjected to warm reperfusion with a serum containing culture medium to simulate lung transplantation. Cell morphology, viability, and transcriptomic profiles were studied. Ischemia-reperfusion injury induced a CIT time-dependent cell death, which was associated with dramatic changes in gene expression. Under normal control conditions, endothelial cells showed gene clusters enriched in the vascular process and inflammation, while epithelial cells showed gene clusters enriched in protein biosynthesis and metabolism. CIT 6 h alone or after reperfusion had little effect on these phenotypic characteristics. After CIT 18 h, protein-biosynthesis-related gene clusters disappeared in epithelial cells; after reperfusion, metabolism-related gene clusters in epithelial cells and multiple gene clusters in the endothelial cells also disappeared. Human pulmonary endothelial and epithelial cells have distinct phenotypic transcriptomic signatures. Severe cellular injury reduces these gene expression signatures in a cell-type-dependent manner. Therapeutics that preserve these transcriptomic signatures may represent new treatment to prevent acute lung injury during lung transplantation.

Methane Inhalation Protects Against Lung Ischemia-Reperfusion Injury in Rats by Regulating Pulmonary Surfactant via the Nrf2 Pathway

Methane (CH₄) exerted protective effects against lung ischemia-reperfusion (I/R) injury, but the mechanism remains unclear, especially the role of pulmonary surfactant. Therefore, this study aimed to explore the effects of CH₄ inhalation on pulmonary surfactant in rat lung I/R injury and to elucidate the mechanism. Rats were randomly divided into three groups (n = 6): the sham, I/R control, and I/R CH₄ groups. In the sham group, only thoracotomy was performed on the rats. In the I/R control and I/R CH₄ groups, the rats underwent left hilum occlusion for 90 min, followed by reperfusion for 180 min and ventilation with O₂ or 2.5% CH₄, respectively. Compared with those of the sham group, the levels of large surfactant aggregates (LAs) in pulmonary surfactant, lung compliance, oxygenation decreased, the small surfactant aggregates (SAs), inflammatory response, oxidative stress injury, and cell apoptosis increased in the control group (P < 0.05). Compared to the control treatment, CH₄ increased LA (0.42 ± 0.06 vs. 0.31 ± 0.09 mg/kg), oxygenation (201 ± 11 vs. 151 ± 14 mmHg), and lung compliance (16.8 ± 1.0 vs. 11.5 ± 1.3 ml/kg), as well as total antioxidant capacity and Nrf2 protein expression and decreased the inflammatory response and number of apoptotic cells (P < 0.05). In conclusion, CH₄ inhalation decreased oxidative stress injury, inflammatory response, and cell apoptosis, and improved lung function through Nrf2-mediated pulmonary surfactant regulation in rat lung I/R injury.

Targeting therapeutics to endothelium: are we there yet?

Vascular endothelial cells represent an important therapeutic target in many pathologies, including inflammation, oxidative stress, and thrombosis; however, delivery of drugs to this site is often limited by the lack of specific affinity of therapeutics for these cells. Selective delivery of both small molecule drugs and therapeutic proteins to the endothelium has been achieved through the use of targeting ligands, such as monoclonal antibodies, directed against endothelial cell surface markers, particularly cell adhesion molecules (CAMs). Careful selection of target molecules and targeting agents allows for precise delivery to sites of inflammation, thereby maximizing therapeutic drug concentrations at the site of injury. A good understanding of the physiological and pathological determinants of drug and drug carrier pharmacokinetics and biodistribution may allow for a priori identification of optimal properties of drug carrier and targeting agent. Targeted delivery of therapeutics such as antioxidants and antithrombotic agents to the injured endothelium has shown efficacy in preclinical models, suggesting the potential for translation into clinical practice. As with all therapeutics, demonstration of both efficacy and safety are required for successful clinical implementation, which must be considered not only for the individual components (drug, targeting agent, etc.) but also for the sum of the parts (e.g., the drug delivery system), as unexpected toxicities may arise with complex delivery systems. While the use of endothelial targeting has not been translated into the clinic to date, the preclinical results summarized here suggest that there is hope for successful implementation of these agents in the years to come.

Effects of Sildenafil and Tadalafil on Edema and Reactive Oxygen Species Production in an Experimental Model of Lung Ischemia-Reperfusion Injury

BACKGROUND

Lung ischemia-reperfusion injury is characterized by formation of reactive oxygen species and cellular swelling leading to pulmonary edema and primary graft dysfunction. Phosphodiesterase 5 inhibitors could ameliorate lung ischemia-reperfusion injury by interfering in many molecular pathways. The aim of this work was to evaluate and compare the effects of sildenafil and tadalafil on edema and reactive oxygen species formation in an ex vivo nonhuman animal model of lung ischemia-reperfusion injury.

METHODS

Thirty-two Wistar rats were distributed, treated, perfused and the cardiopulmonary blocks were managed as follows: control group: immediate excision and reperfusion without pretreatment; ischemia reperfusion group: treatment with dimethylsulfoxide 0.9% and excision 1 hour later; sildenafil group: treatment with sildenafil (0.7 mg/kg) and excision 1 hour later; and tadalafil group: treatment with tadalafil (0.15 mg/kg) and excision 2 hours later. All cardiopulmonary blocks except control group were preserved for 8 hours and then reperfused. Pulmonary arterial pressure, pulmonary venous pressure, and capillary filtration coefficient were measured. Reactive oxygen species were measured.

RESULTS

Edema was similar between control and sildenafil groups, but significantly greater in the ischemia-reperfusion (P ≤ .04) and tadalafil (P ≤ .003) groups compared with the sildenafil group. The malondialdehyde levels were significantly lower in the sildenafil (P ≤ .001) and tadalafil (P ≤ .001) groups than the ischemia-reperfusion group.

CONCLUSIONS

Administration of sildenafil, but not tadalafil, decreased edema in lung ischemia-reperfusion injury. Both drugs decreased reactive oxygen species formation in a lung ischemia-reperfusion injury model.

Variable Ventilation Improved Respiratory System Mechanics and Ameliorated Pulmonary Damage in a Rat Model of Lung Ischemia-Reperfusion

Lung ischemia-reperfusion injury remains a major complication after lung transplantation. Variable ventilation (VV) has been shown to improve respiratory function and reduce pulmonary histological damage compared to protective volume-controlled ventilation (VCV) in different models of lung injury induced by endotoxin, surfactant depletion by saline lavage, and hydrochloric acid. However, no study has compared the biological impact of VV vs. VCV in lung ischemia-reperfusion injury, which has a complex pathophysiology different from that of other experimental models. Thirty-six animals were randomly assigned to one of two groups: (1) ischemia-reperfusion (IR), in which the left pulmonary hilum was completely occluded and released after 30 min; and (2) Sham, in which animals underwent the same surgical manipulation but without hilar clamping. Immediately after surgery, the left (IR-injured) and right (contralateral) lungs from 6 animals per group were removed, and served as non-ventilated group (NV) for molecular biology analysis. IR and Sham groups were further randomized to one of two ventilation strategies: VCV (n = 6/group) [tidal volume (V_T) = 6 mL/kg, positive end-expiratory pressure (PEEP) = 2 cmH₂O, fraction of inspired oxygen (FiO₂) = 0.4]; or VV, which was applied on a breath-to-breath basis as a sequence of randomly generated V_T values (n = 1200; mean V_T = 6 mL/kg), with a 30% coefficient of variation. After 5 min of ventilation and at the end of a 2-h period (Final), respiratory system mechanics and arterial blood gases were measured. At Final, lungs were removed for histological and molecular biology analyses. Respiratory system elastance and alveolar collapse were lower in VCV than VV (mean ± SD, VCV 3.6 ± 1.3 cmH₂0/ml and 2.0 ± 0.8 cmH₂0/ml, p = 0.005; median [interquartile range], VCV 20.4% [7.9–33.1] and VV 5.4% [3.1–8.8], p = 0.04, respectively). In left lungs of IR animals, VCV increased the expression of interleukin-6 and intercellular adhesion molecule-1 compared to NV, with no significant differences between VV and NV. Compared to VCV, VV increased the expression of surfactant protein-D, suggesting protection from type II epithelial cell damage. In conclusion, in this experimental lung ischemia-reperfusion model, VV improved respiratory system elastance and reduced lung damage compared to VCV.

Autologous endothelial progenitor cells improve allograft survival in porcine lung transplantation with prolonged ischemia

BACKGROUND

As endothelial progenitor cells (EPCs) attenuated acute lung injury (ALI) in rabbit model, we hypothesized that autologous EPCs preserved lung graft function during the acute reperfusion period of lung transplantation and tested the therapeutic potential of EPCs in a porcine model of lung transplantation with prolonged graft ischemia.

METHODS

Day-7 EPCs isolated from the recipient subjects or plain culture media were administered into the left pulmonary artery immediately before restoration of pulmonary blood flow in a porcine lung allotransplantation model, with the transplantation surgeons blinded to the content of injection. Hemodynamics and arterial blood gas were recorded, and the right pulmonary artery was occluded 30 min after reperfusion to evaluate the lung graft function. The lung grafts were sectioned for histological examination at the end of experiments. The total ischemic time for lung graft was approximately 14 h.

RESULTS

All animals receiving plain medium died within 40 min after reperfusion, but 3 out of 5 (60%) piglets receiving EPCs survived up to 4 h after diversion of the entire cardiac output into the lung graft (P<0.01). The donor body weight, recipient body weight, cold ischemic time, and time for anastomosis were comparable between the EPC and control group (P=0.989, 0.822, 0.843, and 0.452, respectively). The mean aortic pressure decreased, and the cardiac output and mean pulmonary artery pressure elevated after right pulmonary artery occlusion. All these parameters were gradually compensated in the EPC group but decompensated in the control group. Better preservation of gas exchange function, reduced thrombi formation in the terminal pulmonary arterioles, and attenuated interstitial hemorrhage of the lung graft were observed in the EPC group.

CONCLUSIONS

We concluded autologous EPCs significantly enhanced the function of lung allograft and improved survival in a porcine model of lung transplantation with prolonged ischemia.

Critical Care Aspects of Lung Transplant Patients

Major strides have been made in lung transplantation during the 1990s and it has become an established treatment option for patients with advanced lung disease. Due to improvements in organ preservation, surgical techniques, postoperative intensive care, and immunosuppression, the risk of perioperative and early mortality (less than 3 months after transplantation) has declined [1]. The transplant recipient now has a greater chance of realizing the benefits of the long and arduous waiting period.

Despite these improvements, suboptimal long-term outcomes continue to be shaped by issues such as opportunistic infections and chronic rejection. Because of the wider use of lung transplantation and the longer life span of recipients, intensivists and ancillary intensive care unit (ICU) staff should be well versed with the care of lung transplant recipients.

In this clinical review, issues related to organ donation will be briefly mentioned. The remaining focus will be on the critical care aspects of lung transplant recipients in the posttransplant period, particularly ICU management of frequently encountered conditions. First, the groups of patients undergoing transplantation and the types of procedures performed will be outlined. Specific issues directly related to the allograft, including early graft dysfunction from ischemia-reperfusion injury, airway anastomotic complications, and infections in the setting of immunosuppression will be emphasized. Finally nonpulmonary aspects of posttransplant care and key pharmacologic points in the ICU will be covered.

Neonatal Type II Alveolar Epithelial Cell Transplant Facilitates Lung Reparation in Piglets With Acute Lung Injury and Extracorporeal Life Support

OBJECTIVES

Type II alveolar epithelial cells have potential for lung growth and reparation. Extracorporeal membrane oxygenation is used as life support for lung impairment resulting from acute respiratory distress syndrome. We hypothesized that intratracheal transplantation of isogeneic primary type II alveolar epithelial cells in combination with extracorporeal membrane oxygenation may facilitate lung reparation for acute lung injury (ALI).

DESIGN

A randomized, controlled experiment.

SETTING

An animal laboratory in a university pediatric center.

SUBJECTS

Twenty-eight 4- to 6-week young piglets, weighing 7-8 kg.

INTERVENTIONS

Type II alveolar epithelial cells from neonatal male piglet lungs were isolated, purified, cultured, and labeled with chemical stain PKH26. After 3-6 hours of induction of ALI by IV endotoxin and mechanical ventilation (MV), young female piglets were allocated to five groups (n = 5): ALI-MV, ALI treated with MV; ALI-EC, ALI treated with both MV and venovenous extracorporeal membrane oxygenation; ALI-EC-T, ALI-EC protocol plus intratracheal type II alveolar epithelial cell transplant; CON-MV, healthy animals treated with MV; and CON-EC-T, healthy animals treated with venovenous extracorporeal membrane oxygenation. After 24 hours, animals were weaned from treatment for recovery in the ensuing 14 days, with their lungs assessed for injury and reparation.

MEASUREMENTS AND MAIN RESULTS

Lung injury for animals in ALI-MV was moderate to severe, whereas much milder injuries in ALI-EC-T and ALI-EC were found. More PKH26-labeled type II alveolar epithelial cells were detected by fluorescence in the lungs of ALI-EC-T than in CON-EC-T as further verified by the expression of messenger RNA of sex-determining region of Y chromosome. Electromicroscopically intact type II alveolar epithelial cells and prominent lattice-like tubular myelin were also found in ALI-EC-T and CON-MV but not in ALI-EC. The hydroxyproline level in lung tissue was significantly lower in ALI-EC-T than in ALI-EC and ALI-MV, with most of the lung histopathologic and pathobiologic manifestations in favor of ALI-EC-T.

CONCLUSIONS

The preliminary data suggested that type II alveolar epithelial cell transplant facilitated lung reparation for ALI in this model.

Oxidative Stress and Lung Ischemia-Reperfusion Injury

Ischemia-reperfusion (IR) injury is directly related to the formation of reactive oxygen species (ROS), endothelial cell injury, increased vascular permeability, and the activation of neutrophils and platelets, cytokines, and the complement system. Several studies have confirmed the destructiveness of the toxic oxygen metabolites produced and their role in the pathophysiology of different processes, such as oxygen poisoning, inflammation, and ischemic injury. Due to the different degrees of tissue damage resulting from the process of ischemia and subsequent reperfusion, several studies in animal models have focused on the prevention of IR injury and methods of lung protection. Lung IR injury has clinical relevance in the setting of lung transplantation and cardiopulmonary bypass, for which the consequences of IR injury may be devastating in critically ill patients.

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.

NF-κB RNAi decreases the Bax/Bcl-2 ratio and inhibits TNF-α-induced apoptosis in human alveolar epithelial cells

OBJECTIVE

Apoptosis of alveolar epithelial cells (AECs) plays a key role in acute lung injury (ALI). Understanding the underlying mechanism is conducive to the treatment of ALI. The goal of this study was to determine the possible involvement of nuclear factor-κB (NF-κB)/p65 and Bax/Bcl-2 in tumor necrosis factor-α (TNF-α)-induced apoptosis in AECs.

METHODS

Type II AECs, A549, with or without NF-κB/p65 expression silenced by small interfering RNA (siRNA) were challenged with TNF-α. The levels of NF-κB/p65, Bcl-2 and Bax were detected by reverse transcription-polymerase chain reaction, Western blotting, and immunocytochemical staining. The apoptosis rate was measured by flow cytometry.

RESULTS

TNF-α challenge significantly increased the transcription and translation of NF-κB/p65 and Bax genes, but significantly decreased the Bcl-2 gene level. siRNA silencing of NF-κB/p65 reversed the effect of TNF-α on NF-κB/p65, Bcl-2 and Bax, and significantly decreased the TNF-α-induced apoptosis rate of AECs, as compared to the non-silenced cells.

CONCLUSIONS

This study indicates that NF-κB plays an important role in the process of TNF-α-induced apoptosis in AECs, via regulation of the expression of Bcl-2 and Bax.

Burkholderia mallei and Burkholderia pseudomallei stimulate differential inflammatory responses from human alveolar type II cells (ATII) and macrophages

Alveolar type II pneumocytes (ATII) and alveolar macrophages (AM) play a crucial role in the lung's innate immune response. Burkholderia pseudomallei (BP) and Burkholderia mallei (BM) are facultative Gram-negative bacilli that cause melioidosis and glanders, respectively. The inhalation of these pathogens can cause lethal disease and death in humans. We sought to compare the pathogenesis of and host responses to BP and BM through contact with human primary ATII cells and monocytes-derived macrophages (MDM). We hypothesized that because BP and BM induce different disease outcomes, each pathogen would induce distinct, unique host immune responses from resident pulmonary cells. Our findings showed that BP adhered readily to ATII cells compared to BM. BP, but not BM, was rapidly internalized by macrophages where it replicated to high numbers. Further, BP-induced significantly higher levels of pro-inflammatory cytokine secretion from ATII cells (IL-6, IL-8) and macrophages (IL-6, TNFα) at 6 h post-infection compared to BM (p < 0.05). Interestingly, BM-induced the anti-inflammatory cytokine, IL-10, in ATII cells and macrophages at 6 h post-infection, with delayed induction of inflammatory cytokines at 24 h post-infection. Because BP is flagellated and produces LPS, we confirmed that it stimulated both Toll-like receptor (TLR) 4 and TLR5 via NF-κb activation while the non-flagellated BM stimulated only TLR4. These data show the differences in BP and BM pathogenicity in the lung when infecting human ATII cells and macrophages and demonstrate the ability of these pathogens to elicit distinct immune responses from resident lung cells which may open new targets for therapeutic intervention to fight against these pathogens.

Studies of isolated global brain ischaemia: III. Influence of pulsatile flow during cerebral perfusion and its link to consistent full neurological recovery with controlled reperfusion following 30 min of global brain ischaemia

OBJECTIVE

Brain damage is universal in the rare survivor of unwitnessed cardiac arrest. Non-pulsatile-controlled cerebral reperfusion offsets this damage, but may simultaneously cause brain oedema when delivered at the required the high mean perfusion pressure. This study analyses pulsatile perfusion first in control pigs and then using controlled reperfusion after prolonged normothermic brain ischaemia (simulating unwitnessed arrest) to determine if it might provide a better method of delivery for brain reperfusion.

METHODS

Initial baseline studies during isolated brain perfusion in 12 pigs (six non-pulsatile and six pulsatile) examined high (750 cc/min) then low (450 cc/min) fixed flow before and after transient (30 s) ischaemia, while measuring brain vascular resistance and oxygen metabolism. Twelve subsequent pigs underwent 30 min of normothermic global brain ischaemia followed by either uncontrolled reperfusion with regular blood (n = 6) or pulsatile-controlled reperfusion (n = 6) before unclamping brain inflow vessels. Functional neurological deficit score (NDS; score: 0, normal; 500, brain death) was evaluated 24 h post-reperfusion.

RESULTS

High baseline flow rates with pulsatile and non-pulsatile perfusion before and after transient ischaemia maintained normal arterial pressures (90-100 mmHg), surface oxygen levels IN Vivo Optical Spectroscopy (INVOS) and oxygen uptake. In contrast, oxygen uptake fell after 30 s ischaemia at 450 cc/min non-pulsatile flow, but improved following pulsatile perfusion, despite its delivery at lower mean cerebral pressure. Uncontrolled (normal blood) reperfusion after 30 min of prolonged ischaemia, caused negligible INVOS O(2) uptake (<10-15%), raised conjugated dienes (CD; 1.75 ± 0.15 A(233 mn)), one early death, multiple seizures, high NDS (243 ± 16) and extensive cerebral infarcts (2,3,5-triphenyl tetrazolium chloride stain) and oedema (84.1 ± 0.6%). Conversely, pulsatile-controlled reperfusion pigs exhibited normal O(2) uptake, low CD levels (1.31 ± 0.07 A(233 mn); P < 0.01 versus uncontrolled reperfusion), no seizures and a low NDS (32 ± 14; P < 0.001 versus uncontrolled reperfusion); three showed complete recovery (NDS = 0) and all could sit and eat. Post-mortem brain oedema was minimal (81.1 ± 0.5; P < 0.001 versus uncontrolled reperfusion) and no infarctions occurred.

CONCLUSIONS

Pulsatile perfusion lowers cerebral vascular resistance and improves global O(2) uptake to potentially offset post-ischaemic oedema following high-pressure reperfusion. The irreversible functional and anatomic damage that followed uncontrolled reperfusion after a 30-min warm global brain ischaemia interval was reversed by pulsatile-controlled reperfusion, as its delivery resulted in consistent near complete neurological recovery and absent brain infarction.

Alveolar preservation with high inflation pressure and intermediate oxygen concentration reduces ischemia-reperfusion injury of the lung

BACKGROUND

This study investigated the optimal alveolar oxygen concentration and inflation pressure during ischemia that reduces lung ischemia-reperfusion injury (LIRI).

METHODS

Male Sprague-Dawley rats (n = 66) underwent 150 minutes of left lung ischemia by hilar clamping at an airway inflation pressure (P) of 5 or 30 cm H(2)O and an oxygen (O) concentration of 0%, 30%, or 100% (P(5)O(0), P(5)O(30), P(5)O(100), P(30)O(0), P(30)O(30) and P(30)O(100) groups). Lungs preserved with 0% oxygen were inflated with 100% nitrogen. Measurements of arterial blood gas values, pulmonary compliance, histology, flow cytometry of bronchoalveolar lavage fluid were performed on day 2 postoperatively.

RESULTS

Inflation with 30 cm H(2)O resulted in increased partial pressure of arterial oxygen (Pao(2)) and lung compliance, decreased diffuse alveolar damage, and less infiltration of CD4(+) and CD8(+) lymphocytes and major histocompatibility complex class II-positive (MHCII(+)) antigen-presenting cells (APCs) in the left lung on day 2 compared with clamping at an airway inflation pressure of 5 cm H(2)O. The 100% oxygen groups demonstrated a lower Pao(2) and a decreased pulmonary compliance than 30% oxygen groups. More CD8(+) lymphocytes and MHCII(+) APCs were found in the P(5)O(100) group than in the P(5)O(0) and P(5)O(30) groups.

CONCLUSION

Alveolar inflation with a pressure of 30 cm H(2)O and an oxygen concentration of 30% decreases the severity of LIRI. The protective effect is mainly due to hyperinflation and, to a lesser extent, through oxygen concentration.

Targeted endothelial delivery of nanosized catalase immunoconjugates protects lung grafts donated after cardiac death

BACKGROUND

Donor organ shortage represents a major problem in lung transplantation. Donation after cardiac death could help to expand the pool of organs, but the additional period of warm ischemia after cardiac arrest aggravates primary graft dysfunction. The pulmonary endothelium of the graft constitutes an important source and target of reactive oxygen species generated during ischemia and reperfusion. Targeted protection of graft pulmonary endothelial cells by the antioxidant enzyme catalase, conjugated with a platelet/endothelial cell adhesion molecule-1 (PECAM-1) antibody to nanosized particles (anti-PECAM/catalase conjugates), might improve outcome in lung transplantation using donors after cardiac death and prolonged hypothermic preservation.

METHODS

Left lung transplantation was performed in 18 pigs. Before cardiac arrest, donors received anti-PECAM/catalase, unconjugated component mixture or vehicle solution. After 90-min warm and 18-hr hypothermic ischemia, lungs were transplanted, and function was assessed during 6 hr after reperfusion. Samples of bronchoalveolar lavage fluid and lung tissue were taken thereafter. Six sham-operated animals served as controls.

RESULTS

During 6-hr reperfusion, anti-PECAM/catalase significantly ameliorated graft function, evidenced by major improvements of gas exchange and reduced intrapulmonary shunt fraction. Furthermore, lipid peroxidation, alveolar leakage, and edema formation were reduced in protected grafts. Similarly moderate lung pathology was seen after transplantation.

CONCLUSIONS

Augmentation of the antioxidant capacity of graft pulmonary endothelial cells with anti-PECAM/catalase nanoparticles represents a straightforward approach to enable a safe transplantation of prolonged preserved donation after cardiac death lungs. Anti-PECAM/catalase protection alleviated oxidative stress and allowed immediate reconstitution of normal gas exchange and pulmonary microcirculation, a prerequisite for improved graft and patient outcome.

Lung ischemia-reperfusion injury: a molecular and clinical view on a complex pathophysiological process

Lung ischemia-reperfusion injury remains one of the major complications after cardiac bypass surgery and lung transplantation. Due to its dual blood supply system and the availability of oxygen from alveolar ventilation, the pathogenetic mechanisms of ischemia-reperfusion injury in the lungs are more complicated than in other organs, where loss of blood flow automatically leads to hypoxia. In this review, an extensive overview is given of the molecular and cellular mechanisms that are involved in the pathogenesis of lung ischemia-reperfusion injury and the possible therapeutic strategies to reduce or prevent it. In addition, the roles of neutrophils, alveolar macrophages, cytokines, and chemokines, as well as the alterations in the cell-death related pathways, are described in detail.

Protective mechanism of ultrafiltration against cardiopulmonary bypass-induced lung injury

BACKGROUND

We previously demonstrated a negative effect of cardiopulmonary bypass (CPB) in a canine model of single-lung graft function and an improved effect with ultrafiltration during CPB.

OBJECTIVE

To investigate the mechanism of these effects, focusing on cytokines and pulmonary surfactants using real-time quantitative reverse transcriptase-polymerase chain reaction (RT-PCR).

MATERIALS AND METHODS

Fifteen left-sided single-lung transplant procedures were performed in pairs of dogs. The animals were divided into 3 groups. In one group, transplantation was performed without CPB (non-CPB group); in a second group, transplantation was performed with CPB and CPB flow was decreased slowly and pulmonary artery pressure was controlled (CPB group; and in the third group, transplantation was performed with CPB and ultrafiltration (CPB+UF group). Grafted lung specimens were harvested for RT-PCR of cytokines (IL-6, IL-8, and IL-10) and surfactant proteins (SP-A, SP-B, and SP-C).

RESULTS

Real-time quantitative RT-PCR demonstrated increased IL-6 expression in the CPB group compared with the non-CPB group. IL-6 gene expression was suppressed and pulmonary surfactant restored using ultrafiltration. Gene expression of surfactant protein (SP)-A, SP-B, and SP-C was decreased in the CPB group compared with normal lung and ultrafiltration groups, which demonstrated sustained gene expression of SP-A and SP-B.

CONCLUSION

Cardiopulmonary bypass has negative effects on grafts; however, ultrafiltration attenuates acute lung dysfunction by decreasing the inflammatory response and increasing pulmonary surfactant.

Recipient treatment with L-arginine attenuates donor lung injury associated with hemorrhagic shock

BACKGROUND

Organ donors are frequently trauma victims, but the impact of donor hemorrhagic shock and resuscitation (HSR) on pulmonary graft function has not been assessed. L-arginine treatment during reperfusion increases the production of endothelial nitric oxide and thus ameliorates ischemia-reperfusion injury. Objective of the present porcine study was to investigate the effect of donor hemorrhage on pulmonary graft function and potential beneficial effects of L-arginine administration.

METHODS

In the control-group (n=6), lungs were harvested from donors without hypotensive periods. In the HSR-group (n=6) and HSR-Arg-group (n=6), donors were subjected to hemorrhagic shock (40% blood shed) and resuscitation before harvest. Left lungs were transplanted after hypothermic preservation of 18 hr, and graft function was observed for 6 hr after reperfusion. Recipients in the HSR-Arg-group received a bolus of L-arginine (50 mg/kg BW) intravenously 5 min before reperfusion followed by a continuous intravenous administration of L-arginine 200 mg/kg BW for 2 hr. Tissue specimens and bronchoalveolar lavage fluid were obtained at the end of the observation period.

RESULTS

Donor lung function did not differ between study groups. Compared with the control group, pulmonary graft gas exchange was significantly impaired in the HSR-group. Graft function in the HSR-Arg-group did not differ from control organs. Neutrophil fraction, protein content, and malondialdehyde levels in the bronchoalveolar lavage fluid in the HSR-group were higher compared with control and HSR-Arg-Group.

CONCLUSION

Although fulfilling ideal donor criteria, pulmonary graft function of lungs harvested from donors subjected to HSR is impaired, but improves significantly when l-arginine is administered during reperfusion.

Protection from pulmonary ischemia-reperfusion injury by adenosine A2A receptor activation

Background

Lung ischemia-reperfusion (IR) injury leads to significant morbidity and mortality which remains a major obstacle after lung transplantation. However, the role of various subset(s) of lung cell populations in the pathogenesis of lung IR injury and the mechanisms of cellular protection remain to be elucidated. In the present study, we investigated the effects of adenosine A_2A receptor (A_2AAR) activation on resident lung cells after IR injury using an isolated, buffer-perfused murine lung model.

Methods

To assess the protective effects of A_2AAR activation, three groups of C57BL/6J mice were studied: a sham group (perfused for 2 hr with no ischemia), an IR group (1 hr ischemia + 1 hr reperfusion) and an IR+ATL313 group where ATL313, a specific A_2AAR agonist, was included in the reperfusion buffer after ischemia. Lung injury parameters and pulmonary function studies were also performed after IR injury in A_2AAR knockout mice, with or without ATL313 pretreatment. Lung function was assessed using a buffer-perfused isolated lung system. Lung injury was measured by assessing lung edema, vascular permeability, cytokine/chemokine activation and myeloperoxidase levels in the bronchoalveolar fluid.

Results

After IR, lungs from C57BL/6J wild-type mice displayed significant dysfunction (increased airway resistance, pulmonary artery pressure and decreased pulmonary compliance) and significant injury (increased vascular permeability and edema). Lung injury and dysfunction after IR were significantly attenuated by ATL313 treatment. Significant induction of TNF-α, KC (CXCL1), MIP-2 (CXCL2) and RANTES (CCL5) occurred after IR which was also attenuated by ATL313 treatment. Lungs from A_2AAR knockout mice also displayed significant dysfunction, injury and cytokine/chemokine production after IR, but ATL313 had no effect in these mice.

Conclusion

Specific activation of A_2AARs provides potent protection against lung IR injury via attenuation of inflammation. This protection occurs in the absence of circulating blood thereby indicating a protective role of A_2AAR activation on resident lung cells such as alveolar macrophages. Specific A_2AAR activation may be a promising therapeutic target for the prevention or treatment of pulmonary graft dysfunction in transplant patients.

Advances with surfactant

In this article, the physiology of surfactant is reviewed along with the research that lead to its current clinical uses. Acute lung injury (ALI) and Acute Respiratory Distress Syndrome (ARDS) will also be reviewed because they represent pulmonary disease processes in which secondary deficiency and surfactant inactivation occur, for which surfactant may prove to be an effective treatment. Finally, research using surfactant as a treatment for other pulmonary diseases, such as bronchiolitis and asthma, will be briefly highlighted. These studies may one day lead to new treatment opportunities in the realm of emergency medicine.

Exogenous surfactant application in a rat lung ischemia reperfusion injury model: effects on edema formation and alveolar type II cells

Background

Prophylactic exogenous surfactant therapy is a promising way to attenuate the ischemia and reperfusion (I/R) injury associated with lung transplantation and thereby to decrease the clinical occurrence of acute lung injury and acute respiratory distress syndrome. However, there is little information on the mode by which exogenous surfactant attenuates I/R injury of the lung. We hypothesized that exogenous surfactant may act by limiting pulmonary edema formation and by enhancing alveolar type II cell and lamellar body preservation. Therefore, we investigated the effect of exogenous surfactant therapy on the formation of pulmonary edema in different lung compartments and on the ultrastructure of the surfactant producing alveolar epithelial type II cells.

Methods

Rats were randomly assigned to a control, Celsior (CE) or Celsior + surfactant (CE+S) group (n = 5 each). In both Celsior groups, the lungs were flush-perfused with Celsior and subsequently exposed to 4 h of extracorporeal ischemia at 4°C and 50 min of reperfusion at 37°C. The CE+S group received an intratracheal bolus of a modified natural bovine surfactant at a dosage of 50 mg/kg body weight before flush perfusion. After reperfusion (Celsior groups) or immediately after sacrifice (Control), the lungs were fixed by vascular perfusion and processed for light and electron microscopy. Stereology was used to quantify edematous changes as well as alterations of the alveolar epithelial type II cells.

Results

Surfactant treatment decreased the intraalveolar edema formation (mean (coefficient of variation): CE: 160 mm³ (0.61) vs. CE+S: 4 mm³ (0.75); p < 0.05) and the development of atelectases (CE: 342 mm³ (0.90) vs. CE+S: 0 mm³; p < 0.05) but led to a higher degree of peribronchovascular edema (CE: 89 mm³ (0.39) vs. CE+S: 268 mm³ (0.43); p < 0.05). Alveolar type II cells were similarly swollen in CE (423 μm³(0.10)) and CE+S (481 μm³(0.10)) compared with controls (323 μm³(0.07); p < 0.05 vs. CE and CE+S). The number of lamellar bodies was increased and the mean lamellar body volume was decreased in both CE groups compared with the control group (p < 0.05).

Conclusion

Intratracheal surfactant application before I/R significantly reduces the intraalveolar edema formation and development of atelectases but leads to an increased development of peribronchovascular edema. Morphological changes of alveolar type II cells due to I/R are not affected by surfactant treatment. The beneficial effects of exogenous surfactant therapy are related to the intraalveolar activity of the exogenous surfactant.

Length of pressure-controlled reperfusion is critical for reducing ischaemia-reperfusion injury in an isolated rabbit lung model

Background

Ischaemia-reperfusion injury is still a major problem after lung transplantation. Several reports describe the benefits of controlled graft reperfusion. In this study the role of length of the initial pressure-controlled reperfusion (PCR) was evaluated in a model of isolated, buffer-perfused rabbit lungs.

Methods

Heart-lung blocks of 25 New Zealand white rabbits were used. After measurement of baseline values (haemodynamics and gas exchange) the lungs were exposed to 120 minutes of hypoxic warm ischaemia followed by repeated measurements during reperfusion. Group A was immediately reperfused using a flow of 100 ml/min whereas groups B, C and D were initially reperfused with a maximum pressure of 5 mmHg for 5, 15 or 30 minutes, respectively. The control group had no period of ischaemia or PCR.

Results

Uncontrolled reperfusion (group A) caused a significant pulmonary injury with increased pulmonary artery pressures (PAP) and pulmonary vascular resistance and a decrease in oxygen partial pressure (PO₂), tidal volume and in lung compliance. All groups with PCR had a significantly higher PO₂ for 5 to 90 min after start of reperfusion. At 120 min there was also a significant difference between group B (264 ± 91 mmHg) compared to groups C and D (436 ± 87 mmHg; 562 ± 20 mmHg, p < 0.01). All PCR groups showed a significant decrease of PAP compared to group A.

Conclusion

Uncontrolled reperfusion results in a severe lung injury with rapid oedema formation. PCR preserves pulmonary haemodynamics and gas exchange after ischaemia and might allows for recovery of the impaired endothelial function. 30 minutes of PCR provide superior results compared to 5 or 15 minutes of PCR.

Impact of preservation solution on the extent of blood-air barrier damage and edema formation in experimental lung transplantation

A major aim in lung transplantation is to prevent the loss of structural integrity due to ischemia and reperfusion (I/R) injury. Preservation solutions protect the lung against I/R injury to a variable extent. We compared the influence of two extracellular-type preservation solutions (Perfadex, or PX, and Celsior, or CE) on the morphological alterations induced by I/R. Pigs were randomly assigned to sham (n = 4), PX (n = 5), or CE (n = 2) group. After flush perfusion with PX or CE, donor lungs were excised and stored for 27 hr at 4 degrees C. The left donor lung was implanted into the recipient, reperfused for 6 hr, and, afterward, prepared for light and electron microscopy. Intra-alveolar, septal, and peribronchovascular edema as well as the integrity of the blood-air barrier were determined stereologically. Intra-alveolar edema was more pronounced in CE (219.80 +/- 207.55 ml) than in PX (31.46 +/- 15.75 ml). Peribronchovascular (sham: 13.20 +/- 4.99 ml; PX: 15.57 +/- 5.53 ml; CE: 31.56 +/- 5.78 ml) and septal edema (thickness of alveolar septal interstitium, sham: 98 +/- 33 nm; PX: 84 +/- 8 nm; CE: 249 +/- 85 nm) were only found in CE. The blood-air barrier was similarly well preserved in sham and PX but showed larger areas of swollen and fragmented epithelium or endothelium in CE. The present study shows that Perfadex effectively prevents intra-alveolar, septal, and peribronchovascular edema formation as well as injury of the blood-air barrier during I/R. Celsior was not effective in preserving the lung from morphological I/R injury.

Role of primary human alveolar epithelial cells in host defense against Francisella tularensis infection

Francisella tularensis, an intracellular pathogen, is highly virulent when inhaled. Alveolar epithelial type I (ATI) and type II (ATII) cells line the majority of the alveolar surface and respond to inhaled pathogenic bacteria via cytokine secretion. We hypothesized that these cells contribute to the lung innate immune response to F. tularensis. Results demonstrated that the live vaccine strain (LVS) contacted ATI and ATII cells by 2 h following intranasal inoculation of mice. In culture, primary human ATI or ATII cells, grown on transwell filters, were stimulated on the apical (AP) surface with virulent F. tularensis Schu 4 or LVS. Basolateral (BL) conditioned medium (CM), collected 6 and 24 h later, was added to the BL surfaces of transwell cultures of primary human pulmonary microvasculature endothelial cells (HPMEC) prior to the addition of polymorphonuclear leukocytes (PMNs) or dendritic cells (DCs) to the AP surface. HPMEC responded to S4- or LVS-stimulated ATII, but not ATI, CM as evidenced by PMN and DC migration. Analysis of the AP and BL ATII CM revealed that both F. tularensis strains induced various levels of a variety of cytokines via NF-kappaB activation. ATII cells pretreated with an NF-kappaB inhibitor prior to F. tularensis stimulation substantially decreased interleukin-8 secretion, which did not occur through Toll-like receptor 2, 2/6, 4, or 5 stimulation. These data indicate a crucial role for ATII cells in the innate immune response to F. tularensis.

Venovenous Extracorporeal Life Support After Pulmonary Endarterectomy: Indications, Techniques, and Outcomes

BACKGROUND

Pulmonary endarterectomy is the accepted therapy for thromboembolic pulmonary hypertension. A recognized complication of this surgery is the postoperative development of reperfusion edema, a potentially fatal cause of respiratory failure. Because reperfusion edema can be a reversible process, temporizing support measures may be life saving.

METHODS

We retrospectively reviewed our experience with venovenous extracorporeal life support (V-V ECLS) from July 1990 to February 2006, in 20 adult patients (mean age 50.5 +/- 14.5 years) presenting with potentially reversible respiratory failure after pulmonary endarterectomy. This subset of patients comprised 1.12% of our total pulmonary endarterectomy experience during that time (1,790 cases).

RESULTS

Overall in-hospital survival was 30.0% for patients requiring ECLS support after pulmonary endarterectomy versus 94.2% for patients who underwent pulmonary endarterectomy alone during the same timeframe. V-V ECLS was instituted at a mean of 86.8 hours after surgery. The mean duration of V-V ECLS was 123.4 +/- 71.3 hours. The most common cause of death in ECLS patients after pulmonary endarterectomy was pulmonary hemorrhage. Survival was greater in patients cannulated within 120 hours of surgery (46.2% survival; 6 of 13 patients) compared with those cannulated after 120 hours (0 of 7 patients). Multiple logistic regression identified long duration of mechanical ventilation pre-ECLS and severity of preoperative pulmonary hypertension together as predictors of mortality.

CONCLUSIONS

A small subset of patients undergoing pulmonary endarterectomy develop temporary life-threatening respiratory failure secondary to severe reperfusion edema. In those patients with satisfactory hemodynamic outcome, V-V ECLS is a therapeutic option when all other conventional strategies have been exhausted.

In situ cooling in a lung hilar clamping model of ischemia-reperfusion injury

Experimental models for studying transplantation have up to now been unable to isolate reperfusion injury with minimal surgical manipulation and without the interference of graft rejection. Six pigs were subjected to left hilum preparation only (control group), and eight pigs were subjected to left hilum preparation plus in situ cooling ischemia and reperfusion of the lung (experimental group). The hilum was dissected free from other tissues in both groups. Lung preservation was achieved by antegrade flush perfusion via the left pulmonary artery. Pulmonary veins were clamped at the left atrium and a vent was created. The left main bronchus was clamped. Lung temperature was maintained at 4 degrees -8 degrees C, while core temperature was kept at 38 degrees C. After 3 hrs of cold ischemia the clamps were removed and the lung was reperfused. Elevated pulmonary vascular resistance and local and systemic aspects of ischemia-reperfusion syndrome were consistently reproduced. This large-animal model of in situ unilateral lung cold ischemia with warm reperfusion proved to be very reliable in reproducing all aspects of ischemia-reperfusion injury. It excludes the interference of rejection and extensive surgical manipulation. We therefore propose its use in experimental studies investigating pharmaceutical or cooling modifications affecting lung ischemia-reperfusion outcomes.

Ischemic and endotoxin pre-conditioning reduce lung reperfusion injury-induced surfactant alterations

BACKGROUND

Pulmonary ischemia/reperfusion injury represents a common clinical phenomenon after lung transplantation, pulmonary embolism, and cardiac surgery with extracorporeal circulation. We investigated the influence of ischemic and endotoxin pre-conditioning on gas exchange and surfactant properties in a canine model of ischemia/reperfusion injury.

METHODS

Twenty-six foxhounds underwent 3 hours of warm ischemia of the left lung, followed by 8 hours of reperfusion. Ischemic pre-conditioning was performed for either 5 minutes (IPC-5) or by 2 10-minute ischemic periods (IPC-10), before ischemia. For endotoxin pre-conditioning, dogs were pre-treated by a daily intravenous application of increasing amounts of endotoxin for 6 days. No pre-conditioning was performed in the controls. Bronchoalveolar lavage was performed before ischemia/reperfusion injury (baseline) and after the 8-hour reperfusion period in the non-injured right and in the reperfused left lung. Bronchoalveolar lavage fluids were analyzed for the phospholipid-protein ratio, the content of large surfactant aggregates, the phospholipid and neutral lipid profile, the surfactant protein (SP) content, and for biophysical activity.

RESULTS

Severe surfactant alterations were observed in the ischemia/reperfusion-injured left lung, with increased protein concentrations and depressed concentrations of large surface aggregates, SP-B, dipalmitoylated phosphatidylcholine, and phosphatidylglycerol. Endotoxin pre-conditioning and IPC-5 were both capable of greatly preventing the ischemia/reperfusion injury-related deterioration of surfactant properties. IPC-10 exerted no effects. Endotoxin pre-conditioning and IPC-5, but not IPC-10, also prevented loss of gas exchange.

CONCLUSIONS

Ischemic and endotoxin pre-conditioning may protect against impairment of gas exchange in ischemia/reperfusion injury by restoring physiological surfactant properties.

Neutrophil Elastase Inhibitor Ameliorates Reperfusion Injury in a Canine Model of Lung Transplantation

BACKGROUND

We investigated the effects of neutrophil elastase inhibitor ONO-5046 Na on lung ischemia-reperfusion injury in a canine model of single lung transplantation.

METHODS

24 mongrel dogs, 12 donors and 12 recipients, were used for single lung transplantation. Lung grafts were preserved for 18 h by cold ischemia then transplanted into the left thoracic cavity of recipients. In 6 recipients (ONO group), a bolus of ONO-5046 Na (10 mg/kg) was introduced before reperfusion and followed by continuous infusion (10 mg/kg/h). The remaining 6 recipients (control group) did not receive ONO-5046 Na and thus served as controls. We evaluated lung function and respiratory parameters over 240 min.

RESULTS

The total cell number in bronchoalveolar lavage fluid increased significantly in the control group in comparison to that in the ONO group. Histologic scores after 4 h of reperfusion and myeloperoxidase activity were significantly lower in the ONO group than in the control group.

CONCLUSION

Neutrophil elastase inhibitor ONO-5046 Na may be useful in ameliorating lung reperfusion injury after transplantation.

Does Perfadex Affect Outcomes In Clinical Lung Transplantation?

BACKGROUND

The use of a low-potassium-based preservation solution improves gas exchange in experimental models of lung transplantation. However, its efficacy in reducing the incidence of primary graft dysfunction (PGD) and improving patient outcomes in the clinical setting is controversial.

METHODS

In this study we measured: oxygenation index (OI); International Society of Heart and Lung Transplantation (ISHLT) PGD grades; extubation times; intensive care unit (ICU) and hospital length of stay; 30-day, 90-day and 1-year survival rates; and bronchiolitis obliterans syndrome (BOS)-free survival. We compared 115 consecutive (2001 to 2004) lung recipients who received allografts preserved with Perfadex, a low-potassium dextran (LPD) solution, and compared the results with the previous 116 consecutive (1999 to 2001) lung recipients who received allografts preserved with modified Euro-Collins (MEC) solution. Recipients were classified as having severe PGD (ISHLT Grade III) if the lowest arterial oxygenation (P) to fraction of inspired oxygen (F) (P/F ratio) within 48 hours post-transplantation was <200.

RESULTS

Baseline characteristics of the 2 cohorts were similar except for recipient age (LPD 53.5 vs MEC 49.9 years; p = 0.03). There were no differences in donor age, gender, category of transplant, indication for transplant, use of cardiopulmonary bypass or pre-operative pulmonary artery pressures. When gas-exchange parameters were measured upon arrival to the ICU (T0), at 24 hours post-transplant (T24) and at 48 hours post-transplant (T48), the only significant finding was that the incidence of ISHLT Grade III PGD at T24 was lower in the LPD group compared with the MEC group (8% vs 20%, p = 0.03). The incidence of severe PGD at other timepoints was not statistically different (LPD vs MEC: T0, 17% vs 26%; T0 to T48, 25% vs 31%). Both groups had similar extubation rates at 48 hours post-transplant (LPD 64% vs MEC 67%). The 30-day survival (LPD 93% vs MEC 95%), 90-day survival (LPD 89% vs MEC 89%), 1-year patient survival (LPD 80% vs MEC 77%) and 1-year BOS-free survival (LPD 70% vs MEC 74%) were not statistically different.

CONCLUSIONS

Lung preservation with LPD as compared with MEC does not improve early gas exchange or impact 90-day and 1-year mortality. Continued investigation into lung preservation solution composition is necessary to reduce the incidence of PGD.

The biology of exhaled nitric oxide (NO) in ischemia–reperfusion-induced lung injury: A tale of dynamism of NO production and consumption

The main objective of this paper is to review the potential diagnostic roles of exhaled nitric oxide (NO) in evaluating ischemia-reperfusion-induced lung injury associated with cardiac surgery. We shall start by elaborating on current clinical practice of cardiac surgery and to arrive at the conclusion that clinically important ischemia-reperfusion injury is a common scenario of many forms of these surgical procedures. We shall conclude this part by establishing the clinical need for biomarkers of inflammation in cardiothoracic surgery and by proposing that exhaled NO could be an important new addition to our anaesthetic monitoring repertoire based on our expertise with exhaled breath monitoring. We shall then take a closer look at mechanisms of ischemia-reperfusion injury and will propose the role of reactive oxygen and nitrogen species as mediators and biomarkers of acute lung injury. This analysis will provide a good opportunity to highlight major potential mechanisms of altered NO production and bioactivity of NO. We shall conclude that multiple relevant mechanisms may either lead to increased production of NO or enhance consumption of NO, leaving us with the paradigm that NO maybe used either as a positive or negative biomarker of inflammation. In order to explore this dilemma further, we will investigate the predominant effect of oxidative stress on NO bioactivity in cell culture models of ischemia-reperfusion injury. We will then turn to animal models of ischemia-reperfusion injury to elucidate the ultimate effects of this condition on lung NO production and concentrations of NO in the lung. Finally, we shall complete this journey by highlighting the human relevance of these observations by reviewing our own experience at Harefield Hospital, UK, and that of others, regarding exhaled NO in ischemia-reperfusion injury associated with cardiac surgery and lung transplantation.

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.

Inhalative Pre-Treatment of Donor Lungs Using the Aerosolized Prostacyclin Analog Iloprost Ameliorates Reperfusion Injury

BACKGROUND

Lung transplantation is effective for end-stage pulmonary disease, but its successful application is still limited by organ shortage and sub-optimal preservation techniques. Therefore, optimal allograft protection is essential to reduce organ dysfunction, especially in the early post-operative period. Intravenous prostanoids are routinely used to ameliorate reperfusion injury. However, the latest evidence suggests similar efficacy using inhaled prostacyclin. Thus, we evaluated the impact of donor pre-treatment using the prostacyclin analog, iloprost, on post-ischemic function of Perfadex-protected allografts.

METHODS

In Group 1, 5 pig lungs were preserved with Perfadex (PER group) solution and stored for 27 hours. In Group 2, 100 microg of iloprost was aerosolized over 30 minutes using a novel mobile ultrasonic nebulizer (Optineb) before identical organ harvest (PER-ILO group). After left lung transplantation and contralateral lung exclusion, hemodynamic variables, Po2/Fio2 and dynamic compliance were monitored for 6 hours and compared with sham-operated controls. Pulmonary edema was determined stereologically and by wet-to-dry (W/D) weight ratio. Statistical assessment included analysis of variance (ANOVA) with repeated measures.

RESULTS

Dynamic compliance and pulmonary vascular resistance (PVR) were superior in iloprost-treated compared with untreated organs (p < 0.05), whereas oxygenation was comparable between groups. W/D ratio revealed a significantly smaller amount of lung water in PER-ILO organs (p = 0.048), whereas stereologic data showed a trend toward less intra-alveolar edema.

CONCLUSIONS

Endobronchial application of iloprost in donor lungs before Perfadex preservation decreases post-ischemic edema and significantly improves lung compliance and vascular resistance. This innovative approach is easily applicable in the clinical setting and offers a new strategy for improvement of pulmonary allograft preservation.

Protective effect of erythropoietin on type II pneumocyte cells after traumatic brain injury in rats

BACKGROUND

The main objective was to evaluate the protective effect of erythropoietin on lung ultrastructure against damage in rats after traumatic brain injury.

METHODS

We used forty Wistar-Albino female rats weighing 170-200 gr. The rats were allocated into five groups. The first group was the control and the second was the craniotomy without trauma. The third group was the trauma group. The fourth and fifth groups were erythropoietin (1000 IU/kg) and vehicle (0.4 mL/rat) groups, respectively. A weight-drop method was used for achieving head trauma. Samples were obtained from pulmonary lobes 24-hour post injury. Lipid peroxidation levels were determined and electron microscopic scoring model was used to reveal the ultrastructural changes.

RESULTS

Ultrastructural evaluation revealed pathologic changes in the trauma group compared with the control group (p < 0.05). Lipid peroxidation levels were found to be higher in the trauma group (p < 0.05). Erythropoietin significantly reduced both the ultrastructural pathologic changes and the lipid peroxidation levels in the treatment group (p < 0.05).

CONCLUSIONS

Erythropoietin protects the ultrastructure of pneumocyte type II cells against damage after traumatic brain injury.

Donor pretreatment using the aerosolized prostacyclin analogue iloprost optimizes post-ischemic function of non-heart beating donor lungs

BACKGROUND

Ischemia-reperfusion injury accounts for one-third of early deaths after lung transplantation. To expand the limited donor pool, lung retrieval from non-heart beating donors (NHBD) has been introduced recently. However, because of potentially deleterious effects of warm ischemia on microvascular integrity, use of NHBD lungs is limited by short tolerable time periods before preservation. After intravenous prostanoids are routinely used to ameliorate reperfusion injury, the latest evidence suggests similar efficacy of inhaled prostacyclin. Therefore, the impact of donor pretreatment with the prostacyclin analogue iloprost on postischemic NHBD lung function and preservation quality was evaluated.

METHODS

Asystolic pigs (5 per group) were ventilated for 180 minutes of warm ischemia (Group 2). In Group 3, 100 microg iloprost was aerosolized during the final 30 minutes of ventilation with a novel mobile ultrasonic nebulizer. Lungs were then retrogradely preserved with Perfadex and stored for 3 hours. After left lung transplantation and contralateral lung exclusion, hemodynamics, rO2/FiO2, and dynamic compliance were monitored for 6 hours and compared with sham-operated controls (Group 1). Pulmonary edema was determined both stereologically and by wet-to-dry weight ratio (W/D). Statistics comprised analysis of variance with repeated measures and Mann-Whitney test.

RESULTS

Flush preservation pressures, dynamic compliance, inspiratory pressures, and W/D were significantly superior in iloprost-treated lungs, and oxygenation and pulmonary hemodynamics were comparable between groups. Stereology revealed a trend toward lower intraalveolar edema formation in iloprost-treated lungs compared with untreated grafts.

CONCLUSIONS

Alveolar deposition of Iloprost and NHBD lungs before preservation ameliorates postischemic edema and significantly improves lung compliance. This easily applicable innovation approach, which uses a mobile ultrasonic nebulizer, offers an important strategy for improvement of pulmonary preservation quality and might expand the pool of donor lungs.

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

OBJECTIVES

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

Early expression of adhesion molecules after lung transplantation: evidence for a role of aggregated P-selectin-positive platelets in human primary graft failure

BACKGROUND

Primary graft failure (PGF) secondary to ischemia-reperfusion injury is the main cause of death in the first month after lung transplantation. The aim of this study was to identify early cellular and immunologic events associated with PGF in human lung transplants.

METHODS

Induction of P-selectin, E-selectin and intercellular adhesion molecule-1 (ICAM-1) and evaluation of leukocytes and platelets accumulation were investigated in 18 post-reperfusion surgical specimens of lung allografts by an immunohistochemical technique.

RESULTS

Selectins were restricted to the venular plexus after reperfusion as in the normal lung, whereas ICAM-1 was induced in all cases on alveolar capillaries. Numerous polymorphonuclear cells (18 of 18 cases) and aggregated platelets (7 of 18 cases) were identified along the venular plexus after reperfusion. Compared with the other patients, those with aggregated P-selectin-positive platelets were characterized by a longer duration of mechanical ventilation (p < 0.01), a lower PaO2/FiO2 ratio (p < 0.01) and the presence of radiologic edema (p < 0.05) within the first 3 post-operative days.

CONCLUSIONS

We showed in the reperfused lung a distinct expression of adhesion molecules on venous and capillary pulmonary endothelia that may influence the role of leukocytes and platelets during the early course of transplantation. Furthermore, the knowledge of an association between the presence of P-selectin-positive platelet aggregates and PGF criteria might have implications for graft management and therapeutic strategies.

Hyperinflation during lung preservation and increased reperfusion injury1

BACKGROUND

Reperfusion injury after lung transplantation remains a perplexing and unpredictable problem. Most surgeons preserve the lung inflated, but the amount of inflation that should be used is not well documented. Therefore, we studied the effect of high inflation during organ preservation on lung function during reperfusion. Our hypothesis is that donor lung hyperinflation during storage contributes to early allograft dysfunction during reperfusion.

METHODS

To test our hypothesis we used an isolated, blood-perfused, ventilated rabbit lung model. Group I lungs (control) underwent immediate reperfusion after harvest. Group II lungs (low-inflation, maintained at 6 mmHg airway pressure) and group III lungs (high-inflation, maintained at 20 mmHg airway pressure) were stored for 4 h in 4 degrees C Euro-Collins solution after harvest. All lungs were then reperfused with whole blood for 1 h, and measurements of arterial oxygenation (PO2, mmHg), pulmonary artery pressure (PAP, mmHg), peak inspiratory pressure (PIP, cm H2O), and wet-to-dry weight ratio (WTD) were obtained.

RESULTS

Throughout the 1 h reperfusion period group III lungs had significantly lower oxygenation compared to groups I and II. In addition, throughout reperfusion, group III lungs showed significantly higher PAP and PIP compared to group II. WTD did not differ significantly between groups, however, there was a trend toward increased edema in group III.

CONCLUSIONS

These results indicate that high inflation during cold storage results in acute pulmonary dysfunction. Careful monitoring of airway inflation pressure during storage, especially to prevent hyperinflation, should be maintained in the current practice for lung transplantation.

Occurence of lipid bodies in canine type II pneumocytes during hypothermic lung ischemia

Type II pneumocytes defend the pulmonary alveolus by synthesis and secretion of surfactant and by contributing to alveolar epithelial regeneration. Lipid bodies are regarded as intracellular domains for the synthesis of eicosanoid mediators that can be induced by inflammatory stimuli. The aim of the present study was to establish whether hypothermic ischemic lung storage without further preservation measures leads to an induction of lipid body formation in canine type II pneumocytes. The lungs of 18 dogs were fixed for transmission electron microscopy (TEM) immediately after cardiac arrest (six double lungs) and after ischemic storage in Tutofusin solution at 4 degrees C for 20 min, 4 hr, 8 hr, and 12 hr (six single lungs, respectively). Type II pneumocytes were analyzed qualitatively by conventional TEM (CTEM) and quantitatively by stereology. The relative phosphorus content of surfactant containing lamellar bodies, lipid bodies, and intermediate forms was investigated by energy-filtering TEM (EFTEM). By CTEM, lipid bodies as well as forms intermediate between lipid bodies and lamellar bodies were already noted in the control group but were more pronounced in the ischemia groups. Beginning at 20 min of ischemic storage, a significant increase in the volume density of lipid bodies was noted in the ischemic groups as compared to the control group. By EFTEM, the highest intracellular phosphorus signals were recorded over lamellar bodies and lamellar areas of intermediate forms in all experimental groups, while lipid bodies and homogeneous areas of intermediate forms did not show a clear phosphorus signal. These results indicate that the formation of lipid bodies in canine type II pneumocytes is induced early during ischemic lung storage.

Cellular infiltrates and injury evaluation in a rat model of warm pulmonary ischemia-reperfusion

Introduction

Beside lung transplantation, cardiopulmonary bypass, isolated lung perfusion and sleeve resection result in serious pulmonary ischemia–reperfusion injury, clinically known as acute respiratory distress syndrome. Very little is known about cells infiltrating the lung during ischemia–reperfusion. Therefore, a model of warm ischemia–reperfusion injury was applied to differentiate cellular infiltrates and to quantify tissue damage.

Methods

Fifty rats were randomized into eight groups. Five groups underwent warm ischemia for 60 min followed by 30 min and 1–4 hours of warm reperfusion. An additional group was flushed with the use of isolated lung perfusion after 4 hours of reperfusion. One of two sham groups was also flushed. Neutrophils and oedema were investigated by using samples processed with hematoxylin/eosin stain at a magnification of ×500. Immunohistochemistry with antibody ED-1 (magnification ×250) and antibody 1F4 (magnification ×400) was applied to visualize macrophages and T cells. TdT-mediated dUTP nick end labelling was used for detecting apoptosis. Statistical significance was accepted at P < 0.05.

Results

Neutrophils were increased after 30 min until 4 hours of reperfusion as well as after flushing. A doubling in number of macrophages and a fourfold increase in T cells were observed after 30 min until 1 and 2 hours of reperfusion, respectively. Apoptosis with significant oedema in the absence of necrosis was seen after 30 min to 4 hours of reperfusion.

Conclusions

After warm ischemia–reperfusion a significant increase in infiltration of neutrophils, T cells and macrophages was observed. This study showed apoptosis with serious oedema in the absence of necrosis after all periods of reperfusion.

Efeito da ventilação com diferentes frações inspiradas de oxigênio e do alopurinol na isquemia-reperfusão pulmonar em ratos

OBJETIVO: Avaliar o efeito da ventilação associada a frações inspiradas de oxigênio a 0,21 e 1,00 e do alopurinol (antioxidante) na isquemia-reperfusão pulmonar. MÉTODO: Foram utilizados 60 ratos Wistar, distribuídos aleatoriamente em seis grupos. O grupo 1 foi o controle; no grupo 2 os animais foram ventilados durante a isquemia-reperfusão pulmonar com FiO2 de 0,21; e no grupo 3, com FiO2 de 1,00. Os três grupos restantes 1A, 2A e 3A foram medicados com 100 mg/kg de alopurinol no pré-operatório e submetidos a procedimentos semelhantes aos grupos 1, 2 e 3, respectivamente. O modelo utilizado foi de isquemia-reperfusão normotérmica, in situ. O tempo de isquemia foi de 30 minutos, e o de reperfusão, de 10 minutos. Como parâmetros de avaliação foram utilizados a pressão arterial média sistêmica (PAM), a relação da pressão parcial de oxigênio/fração inspirada de oxigênio (PaO2/FiO2), a dosagem das substâncias reativas ao ácido tiobarbitúrico (TBARS) no tecido pulmonar e a relação entre peso pulmonar úmido e peso pulmonar seco. RESULTADOS: Em relação à PAM, ocorreu diminuição significante (p<0,05) entre os grupos 3 x 1, 2 x 2A e 3 x 3A. Na PaO2/FiO2 ocorreu diminuição significante (p<0,05) entre os grupos 3 x 2 e 3 x 3A. Nas TBARS ocorreu diminuição significante (p<0,05) entre os grupos 3 x 3A. Na relação peso pulmonar úmido/seco ocorreu aumento significante (p<0,05) entre os grupos 3 x 2, 2 x 2A e 3 x 3A. CONCLUSÕES: A ventilação com oxigênio a 21%, quando comparada à ventilação com oxigênio a 100%, apresentou diminuição menos acentuada da PAM, melhor relação entre PaO2/FiO2, e menor edema pulmonar. O uso de alopurinol no pré-operatório mostrou uma diminuição menos acentuada da PAM, melhor relação entre PaO2/FiO2, menor produção de TBARS e menor edema pulmonar, quando comparado aos resultados dos grupos que não o utilizaram.