Complement inhibition attenuates human lung transplant reperfusion injury: a multicenter trial

Rosmarinic Acid Ameliorates Pulmonary Ischemia/Reperfusion Injury by Activating the PI3K/Akt Signaling Pathway

Pulmonary ischemia/reperfusion (IR) injury is the leading cause of acute lung injury, which is mainly attributed to reactive oxygen species (ROS) induced cell injuries and apoptosis. Since rosmarinic acid (RA) has been identified as an antioxidant natural ester, this natural compound might protect against pulmonary IR injury. In this study, the mice were given RA daily (50, 75, or 100 mg/kg) by gavage for 7 days before the pulmonary IR injury. We found that hypoxemia, pulmonary edema, and serum inflammation cytokines were aggravated in pulmonary IR injury. RA pretreatment (75 and 100 mg/kg) effectively reversed these parameters, while 50 mg/kg RA pretreatment was less pronounced. Our data also indicated RA pretreatment mitigated the upregulation of pro-oxidant NADPH oxidases (NOX2 and NOX4) and the downregulation of anti-oxidant superoxide dismutases (SOD1 and SOD2) upon IR injury. In vitro studies showed RA preserved the viability of anoxia/reoxygenation (AR)-treated A549 cells (a human lung epithelial cell line), and the results showed the protective effect of RA started at 5 μM concentration, reached its maximum at 15 μM, and gradually decreased at 20–25 μM. Besides, RA pretreatment (15 μM) greatly reduced the lactate dehydrogenase release levels subjected to AR treatment. Moreover, the results of our research revealed that RA eliminated ROS production and reduced alveolar epithelial cell apoptosis through activating the phosphatidylinositol 3 kinase (PI3K)/protein kinase B (Akt) signaling pathway, which was supported by using wortmannin, because in the presence of wortmannin, the RA-mediated protection was blocked. Meanwhile, wortmannin also reversed the protective effects of RA in mice. Together, our results demonstrate the beneficial role of RA in pulmonary IR injury via PI3K/Akt-mediated anti-oxidation and anti-apoptosis, which could be a promising therapeutic intervention for pulmonary IR injury.

A novel injury site-natural antibody targeted complement inhibitor protects against lung transplant injury

Complement is known to play a role in ischemia and reperfusion injury (IRI). A general paradigm is that complement is activated by self-reactive natural IgM antibodies (nAbs), after they engage postischemic neoepitopes. However, a role for nAbs in lung transplantation (LTx) has not been explored. Using mouse models of LTx, we investigated the role of two postischemic neoepitopes, modified annexin IV (B4) and a subset of phospholipids (C2), in LTx. Antibody deficient Rag1-/- recipient mice were protected from LTx IRI. Reconstitution with either B4 or C2nAb restored IRI, with C2 significantly more effective than B4 nAb. Based on these information, we developed/characterized a novel complement inhibitor composed of single-chain antibody (scFv) derived from the C2 nAb linked to Crry (C2scFv-Crry), a murine inhibitor of C3 activation. Using an allogeneic LTx, in which recipients contain a full nAb repertoire, C2scFv-Crry targeted to the LTx, inhibited IRI, and delayed acute rejection. Finally, we demonstrate the expression of the C2 neoepitope in human donor lungs, highlighting the translational potential of this approach.

Primary Graft Dysfunction

Primary graft dysfunction (PGD) is a form of acute lung injury after transplantation characterized by hypoxemia and the development of alveolar infiltrates on chest radiograph that occurs within 72 hours of reperfusion. PGD is among the most common early complications following lung transplantation and significantly contributes to increased short-term morbidity and mortality. In addition, severe PGD has been associated with higher 90-day and 1-year mortality rates compared with absent or less severe PGD and is a significant risk factor for the subsequent development of chronic lung allograft dysfunction. The International Society for Heart and Lung Transplantation released updated consensus guidelines in 2017, defining grade 3 PGD, the most severe form, by the presence of alveolar infiltrates and a ratio of PaO₂:FiO₂ less than 200. Multiple donor-related, recipient-related, and perioperative risk factors for PGD have been identified, many of which are potentially modifiable. Consistently identified risk factors include donor tobacco and alcohol use; increased recipient body mass index; recipient history of pulmonary hypertension, sarcoidosis, or pulmonary fibrosis; single lung transplantation; and use of cardiopulmonary bypass, among others. Several cellular pathways have been implicated in the pathogenesis of PGD, thus presenting several possible therapeutic targets for preventing and treating PGD. Notably, use of ex vivo lung perfusion (EVLP) has become more widespread and offers a potential platform to safely investigate novel PGD treatments while expanding the lung donor pool. Even in the presence of significantly prolonged ischemic times, EVLP has not been associated with an increased risk for PGD.

Methamphetamine use association with pulmonary diseases: a retrospective investigation of hospital discharges in California from 2005 to 2011

BACKGROUND

Methamphetamine can have acute and long-term adverse health consequences. Our objective was to determine whether methamphetamine use is associated with more hospitalisation codes for asthma exacerbation, chronic obstructive pulmonary disease (COPD) exacerbation, pneumonia and acute respiratory failure (ARF).

METHODS

The Health Care Utilization Project (HCUP) database includes retrospective inpatient discharge abstracts from 2005 through 2011 from the California state inpatient databases (SIDs). ICD-9 codes were used to identify hospitalisations for asthma exacerbation, COPD exacerbation, acute pneumonia, ARF and methamphetamine use from discharges with complete demographic data and ages 18 to 75 years. Adjusted rate ratios comparing methamphetamine users with nonusers were estimated separately for each pulmonary disease diagnosis by sex using negative binomial regression models.

RESULTS

We included 21 125 249 inpatient discharges from 2005 through 2011 in California in our analysis; 182 766 (0.87%) had methamphetamine use. The rate ratio comparing pneumonia in discharges with methamphetamine use versus those without were 1.40 (95% CI 1.18, 1.67) for women and 1.18 (95% CI 1.04, 1.35) for men; comparing ARF 1.77 (95% CI 1.59, 1.98) for women and 1.24 (95% CI 1.12, 1.37) for men; and comparing COPD exacerbation 1.40 (95% CI 1.18, 1.67) for women and 0.90 (95% CI 0.79, 1.02) for men.

CONCLUSIONS

A positive association was found when comparing inpatient hospital discharge diagnoses for methamphetamine use and those for pneumonia and ARF in both sexes. This association was not seen when comparing discharge diagnoses for methamphetamine and those for asthma exacerbation in both sexes or COPD exacerbation in men. While future investigation for is warranted, this finding may help to further characterise the pulmonary toxicity of methamphetamine.

Donor pretreatment with nebulized complement C3a receptor antagonist mitigates brain-death induced immunological injury post-lung transplant

Donor brain death (BD) is an inherent part of lung transplantation (LTx) and a key contributor to ischemia-reperfusion injury (IRI). Complement activation occurs as a consequence of BD in other solid organ Tx and exacerbates IRI, but the role of complement in LTx has not been investigated. Here, we investigate the utility of delivering nebulized C3a receptor antagonist (C3aRA) pretransplant to BD donor lungs in order to reduce post-LTx IRI. BD was induced in Balb/c donors, and lungs nebulized with C3aRA or vehicle 30 minutes prior to lung procurement. Lungs were then cold stored for 18 hours before transplantation into C57Bl/6 recipients. Donor lungs from living donors (LD) were removed and similarly stored. At 6 hours and 5 days post-LTx, recipients of BD donor lungs had exacerbated IRI and acute rejection (AR), respectively, compared to recipients receiving LD lungs, as determined by increased histopathological injury, immune cells, and cytokine levels. A single pretransplant nebulized dose of C3aRA to the donor significantly reduced IRI as compared to vehicle-treated BD donors, and returned IRI and AR grades to that seen following LD LTx. These data demonstrate a role for complement inhibition in the amelioration of IRI post-LTx in the context of donor BD.

Primary graft dysfunction: lessons learned about the first 72 h after lung transplantation

PURPOSE OF REVIEW

In 2005, the International Society for Heart and Lung Transplantation published a standardized definition of primary graft dysfunction (PGD), facilitating new knowledge on this form of acute lung injury that occurs within 72 h of lung transplantation. PGD continues to be associated with significant morbidity and mortality. This article will summarize the current literature on the epidemiology of PGD, pathogenesis, risk factors, and preventive and treatment strategies.

RECENT FINDINGS

Since 2011, several manuscripts have been published that provide insight into the clinical risk factors and pathogenesis of PGD. In addition, several transplant centers have explored preventive and treatment strategies for PGD, including the use of extracorporeal strategies. More recently, results from several trials assessing the role of extracorporeal lung perfusion may allow for much-needed expansion of the donor pool, without raising PGD rates.

SUMMARY

This article will highlight the current state of the science regarding PGD, focusing on recent advances, and set a framework for future preventive and treatment strategies.

[Ischemia-reperfusion injury after lung transplantation]

Lung ischemia-reperfusion is characterized by diffuse alveolar damage arising from the first hours after transplantation. The first etiology of the primary graft dysfunction in lung is ischemia-reperfusion. It is burdened by an important morbi-mortality. Lung ischemia-reperfusion increases the oxidative stress, inactivates the sodium pump, increases the intracellular calcium, leads to cellular death and the liberation of pro-inflammatory mediators. Researches relative to the reduction of the lung ischemia-reperfusion injuries are numerous but few of them found a place in common clinical practice, because of an insufficient level of proofs. Ex vivolung evaluation is a suitable technique in order to evaluate therapeutics supposed to limit lung ischemia-reperfusion injuries.

Anti-inflammatory strategies to enhance islet engraftment and survival

Early innate inflammatory reaction strongly affects islet engraftment and survival after intrahepatic transplantation. This early immune response is triggered by ischemia-reperfusion injury and instant blood mediated inflammatory reaction (IBMIR) occurring hours and days after islet infusion. Evidence in both mouse model and in human counterpart suggest the involvement of coagulation, complement system, and proinflammatory chemokines/cytokines. Identification and targeting of pathway(s), playing a role as "master regulator(s)" in post-transplant detrimental inflammatory events, is now mandatory to improve islet transplantation success. This review will focus on inflammatory pathway(s) differentially modulated by islet isolation and mainly associated with the early post-transplant events. Moreover, we will take into account anti-inflammatory strategies that have been tested at 2 levels: on the graft, ex vivo, during islet culture (i.e., donor) and/or on the graft site, in vivo, early after islet infusion (i.e., recipient).

Managing complications following lung transplantation

Lung transplantation has become a proven therapeutic option for patients with end-stage lung disease, extending life and providing improved quality of life to those who otherwise would continue to be breathless and oxygen-dependent. Over the past 20 years, considerable experience has been gained in understanding the multitude of medical and surgical issues that impact upon patient survival. Today, clinicians have an armamentarium of tools to manage diverse problems such as primary graft dysfunction, acute and chronic allograft rejection, airway anastomotic issues, infectious complications, renal dysfunction, diabetes and osteoporosis, hematological and gastrointestinal problems, malignancy, and other unique issues that confront immunosuppressed solid organ transplant recipients.

Primary graft dysfunction

Primary graft dysfunction (PGD) is the most important cause of early morbidity and mortality following lung transplantation. PGD affects up to 25% of all lung transplant procedures and currently has no proven preventive therapy. Lung transplant recipients who recover from PGD may have impaired long-term function and an increased risk of bronchiolitis obliterans syndrome. This article aims to provide a state-of-the-art review of PGD epidemiology, outcomes, and risk factors, and to summarize current efforts at biomarker development and novel strategies for prevention and treatment.

The effect of hyperbaric oxygen treatment on aspiration pneumonia

We have studied whether hyperbaric oxygen (HBO) prevents different pulmonary aspiration materials-induced lung injury in rats. The experiments were designed in 60 Sprague-Dawley rats, ranging in weight from 250 to 300 g, randomly allotted into one of six groups (n = 10): saline control, Biosorb Energy Plus (BIO), hydrochloric acid (HCl), saline + HBO treated, BIO + HBO treated, and HCl + HBO treated. Saline, BIO, HCl were injected into the lungs in a volume of 2 ml/kg. A total of seven HBO sessions were performed at 2,4 atm 100% oxygen for 90 min at 6-h intervals. Seven days later, rats were sacrificed, and both lungs in all groups were examined biochemically and histopathologically. Our findings show that HBO inhibits the inflammatory response reducing significantly (P < 0.05) peribronchial inflammatory cell infiltration, alveolar septal infiltration, alveolar edema, alveolar exudate, alveolar histiocytes, interstitial fibrosis, granuloma, and necrosis formation in different pulmonary aspiration models. Pulmonar aspiration significantly increased the tissue HP content, malondialdehyde (MDA) levels and decreased (P < 0.05) the antioxidant enzyme (SOD, GSH-Px) activities. HBO treatment significantly (P < 0.05) decreased the elevated tissue HP content, and MDA levels and prevented inhibition of SOD, and GSH-Px (P < 0.05) enzymes in the tissues. Furthermore, there is a significant reduction in the activity of inducible nitric oxide synthase, TUNEL and arise in the expression of surfactant protein D in lung tissue of different pulmonary aspiration models with HBO therapy. It was concluded that HBO treatment might be beneficial in lung injury, therefore, shows potential for clinical use.

Elevated Serum Concentrations of Triggering Receptor Expressed on Myeloid Cells-1 in Diffuse Cutaneous Systemic Sclerosis: Association with Severity of Pulmonary Fibrosis

Objective.

To determine serum concentrations and clinical association of soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) in patients with systemic sclerosis (SSc).

Methods.

Serum sTREM-1 levels from 17 patients with limited cutaneous SSc (lSSc), 24 patients with diffuse cutaneous SSc (dSSc), and 29 healthy control individuals were examined by ELISA.

Results.

Total SSc patients exhibited significantly elevated serum sTREM-1 levels relative to controls (p < 0.01). Serum sTREM-1 levels were significantly elevated in patients with dSSc compared to controls (p < 0.005) and lSSc patients (p < 0.05). By contrast, sTREM-1 levels in lSSc were similar to those in controls. Serum sTREM-1 levels were significantly elevated in SSc patients with decreased percentage vital capacity (%VC). Consistent with this, serum sTREM-1 levels in SSc patients correlated negatively with %VC (r = −0.24, p < 0.005). Among SSc patients with pulmonary fibrosis, sTREM-1 levels were significantly increased in patients with decreased %VC or decreased percentage of diffusion capacity for carbon monoxide relative to those with normal values (p < 0.05).

Conclusion.

Serum sTREM-1 levels were elevated in dSSc patients and correlated with severity of pulmonary fibrosis, suggesting that serum sTREM-1 is a novel serological marker for the disease severity of SSc.

Complement inhibition as a proposed neuroprotective strategy following cardiac arrest

Out-of-hospital cardiac arrest (OHCA) is a devastating disease process with neurological injury accounting for a disproportionate amount of the morbidity and mortality following return of spontaneous circulation. A dearth of effective treatment strategies exists for global cerebral ischemia-reperfusion (GCI/R) injury following successful resuscitation from OHCA. Emerging preclinical as well as recent human clinical evidence suggests that activation of the complement cascade plays a critical role in the pathogenesis of GCI/R injury following OHCA. In addition, it is well established that complement inhibition improves outcome in both global and focal models of brain ischemia. Due to the profound impact of GCI/R injury following OHCA, and the relative lack of effective neuroprotective strategies for this pathologic process, complement inhibition provides an exciting opportunity to augment existing treatments to improve patient outcomes. To this end, this paper will explore the pathophysiology of complement-mediated GCI/R injury following OHCA.

The complement cascade as a therapeutic target in intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is the second most common and deadliest form of stroke. Currently, no pharmacologic treatment strategies exist for this devastating disease. Following the initial mechanical injury suffered at hemorrhage onset, secondary brain injury proceeds through both direct cellular injury and inflammatory cascades, which trigger infiltration of granulocytes and monocytes, activation of microglia, and disruption of the blood-brain barrier with resulting cerebral edema. The complement cascade has been shown to play a central role in the pathogenesis of secondary injury following ICH, although the specific mechanisms responsible for the proximal activation of complement remain incompletely understood. Cerebral injury following cleavage of complement component 3 (C3) proceeds through parallel but interrelated pathways of anaphylatoxin-mediated inflammation and direct toxicity secondary to membrane attack complex-driven erythrocyte lysis. Complement activation also likely plays an important physiologic role in recovery following ICH. As such, a detailed understanding of the variation in functional effects of complement activation over time is critical to exploiting this target as an exciting translational strategy for intracerebral hemorrhage.

Elevated serum concentrations of polymorphonuclear neutrophilic leukocyte elastase in systemic sclerosis: association with pulmonary fibrosis

OBJECTIVE

To determine the serum concentrations and clinical association of polymorphonuclear neutrophilic leukocyte (PMN) elastase in patients with systemic sclerosis (SSc).

METHODS

Serum PMN elastase levels from 21 patients with limited cutaneous SSc (lSSc) and 32 with diffuse cutaneous SSc (dSSc) were examined by ELISA.

RESULTS

Serum PMN elastase levels were elevated in patients with SSc, especially dSSc, compared to healthy controls. SSc patients with elevated serum PMN elastase levels had more frequent presence of pulmonary fibrosis, arthritis, contracture of phalanges, and diffuse pigmentation. Anticentromere antibody was detected less frequently in SSc patients with elevated serum PMN elastase levels than in controls. Consistently, serum PMN elastase levels also correlated positively with serum levels of KL-6 and surfactant protein-D, serological markers for pulmonary fibrosis. Serum PMN elastase levels were also associated with levels of serum 8-isoprostane, an oxidative stress marker in SSc.

CONCLUSION

Serum PMN elastase levels were elevated in patients with SSc, and it was more prominent in patients with pulmonary fibrosis, suggesting that serum PMN elastase is a novel serological marker for SSc-related pulmonary fibrosis.

Identification of a complement receptor 1 peptide for inhibition of immune hemolysis

Complement sensitization of red blood cells (RBCs) can cause life-threatening hemolytic anemias. We have previously shown that complement receptor 1 (CR1) derivatives specifically the N-terminal region with decay accelerating activity (DAA) for inactivation of a key enzyme in the complement cascade can reduce complement-mediated RBC destruction in vitro and in an in vivo mouse model of hemolytic transfusion reaction. In the present study, we have modeled the N-terminal CR1 molecule based on the X-ray crystal structure of decay accelerating factor and the NMR structure of a homologous CR1 domain. Based on the homology model, we identified a 34-mer peptide encompassing the putative DAA which in vitro reduced hemolysis, C3a release and surface C3 deposition. More importantly, this peptide at 0.6 mM was effective in prolonging survival of transfused incompatible RBCs in vivo. Our results indicate that CR1-based structure-function studies may provide insights for developing structure-derived transfusion therapeutics in the future.

Inflammatory response to pulmonary ischemia-reperfusion injury

Lung ischemia-reperfusion (IR) injury is one of the most important complications following lung transplant and cardiopulmonary bypass. The pulmonary dysfunction following lung IR has been well documented. Recent studies have shown that ischemia and reperfusion of the lung may each play significant yet differing roles in inducing lung injury. The mechanisms of injury involving neutrophil activation, and the release of numerous inflammatory mediators and oxygen radicals also contributes to lung cellular injury, pneumocyte necrosis, and apoptosis. We herein review the current understanding of the underlying mechanism involved in lung IR injury. The biomolecular mechanisms and interactions which lead to the inflammatory response, pneumocyte necrosis, and apoptosis following lung IR therefore warrant further investigation.

Development of complement therapeutics for inhibition of immune-mediated red cell destruction

A major objective of my National Blood Foundation (NBF)-funded proposal was to produce recombinant soluble forms of a complement regulatory protein called complement receptor 1 (CR1) that carries the Knops blood group system antigens to perform antibody neutralization studies. By generating these recombinant proteins, we were able to inhibit several Knops antibodies in patient serum samples, thereby demonstrating their usefulness for clinical use. Interestingly, the recombinant CR1 proteins generated through NBF funding were also found to strongly reduce complement-mediated red cell destruction in a mouse hemolytic transfusion model. In this review, I will outline our NBF-funded studies, give an overview of recent advances from our group and others in the development of complement therapeutics, and highlight their potential use in the transfusion medicine setting.

Controlling the complement system for prevention of red cell destruction

PURPOSE OF REVIEW

Complement sensitization of red blood cells (RBCs) can lead to both intravascular and extravascular red cell destruction. Altered levels of naturally occurring complement regulatory proteins on red cells can result in hemolysis, while defective expression of these proteins on immune cells can cause breakdown of tolerance to self antigens and is associated with autoimmune disease.

RECENT FINDINGS

To date several complement inhibitors, including recombinant forms of complement regulatory proteins, humanized antibodies, and synthetic molecules have been described that limit complement activation by interfering with different steps in the complement cascade. However, few have been evaluated for prevention of complement-mediated RBC destruction. In this review, possible applications of these complement inhibitors for treatment of complement-mediated hemolysis in specific disease states are described. Furthermore, the implication of the regulatory role of complement in the development of autoimmune hemolytic anemia is discussed.

SUMMARY

Complement therapeutics has potential for effective and safe prophylactic use and treatment of hemolytic transfusion reactions and complement-mediated hemolytic diseases. Furthermore, the regulatory function of complement may be exploited to prevent and treat autoimmune hemolytic anemia.

Complement membrane attack complex and hemodynamic changes during human orthotopic liver transplantation

Hemodynamic changes and elevation of intracellular calcium following reperfusion in human liver transplantation occur rapidly and do not match the time course of cytokine expression, therefore, we postulate involvement of other, pre-formed substances, such as complement. We studied 40 adult patients undergoing liver transplantation. Blood was drawn for estimation of C3, C4, C3 degradation product, membrane attack complex, and CH100 levels and elastase (a marker of neutrophil activation) at induction of anesthesia, 5 minutes before reperfusion, 5 minutes and 60 minutes after reperfusion. Cardiac output was measured by thermodilution and systemic vascular resistance was calculated at these same time points. There was a significant rise in C5b-9 membrane attack complex (P =.0012) with a corresponding fall in C3 (P =.0013) and C4 (P =.0002) levels and a rise in C3 degradation product levels (P =.0006). There was no significant change in CH100. These changes very closely followed the hemodynamic changes of a significant fall in systemic vascular resistance index (P =.0024) and increase in cardiac index (P =.0005). Elastase rose from 356 +/- 53 to 557 +/- 40 microg/L (P <.0001). There is complement activation and neutrophil activation at reperfusion in liver transplantation. Dilution alone cannot explain the fall in C3 and C4 levels as there is a corresponding increase in membrane attack complex and C3 degradation product levels with time. As both C3 and C4 are consumed, the classical pathway must be active, though alternative and lectin activated pathways may also be involved. These findings may, at least in part, explain the hemodynamic changes typically seen at reperfusion in liver transplantation.

Ischaemia–reperfusion is an event triggered by immune complexes and complement

Background

Reperfusion injury is a common clinical problem that lacks effective therapy. Two decades of research implicating oxygen free radicals and neutrophils has not led to a single successful clinical trial.

Methods

The aim was to review new clinical and preclinical data pertaining to the alleviation of reperfusion injury. A review of the literature was undertaken by searching the MEDLINE database for the period 1966–2003 without language restrictions.

Results and conclusion

Evidence now points to complement and immune complexes as critical players in mediating reperfusion injury. Ischaemia is postulated to induce a phenotypical cellular change through the surface expression of a neoantigen. Preformed circulating natural IgM antibodies are then trapped and complement is activated. Final events leading to reperfusion injury include formation of the membrane attack complex and mast cell degranulation.

Lung transplantation. Lung preservation

Over the past decade, improvements in the technique of lung preservation have led to significant reduction in the incidence of ischemia-reperfusion-induced lung injury after lung transplantation. The challenge remains to improve the number of donor lungs available for transplantation. While the number of patients on the waiting list is constantly increasing, only 10% to 30% of donor lungs are currently being used for transplantation. Hence, the development of new strategies to assess, repair, and improve the quality of the lungs could have a tremendous impact on the number of transplants performed. In addition, an improved understanding of the mechanisms involved in lung preservation might help elucidate the potential link between acute lung injury and chronic graft dysfunction. In the future, genetic analysis using novel technologies such as microarray analysis will help researchers determine which genes control the injury seen in the transplantation process. Hopefully, this information will provide new insights into the mechanisms of injury and reveal potential new strategies and targets for therapies to improve lung preservation.

Complement receptor 2-mediated targeting of complement inhibitors to sites of complement activation

In a strategy to specifically target complement inhibitors to sites of complement activation and disease, recombinant fusion proteins consisting of a complement inhibitor linked to a C3 binding region of complement receptor (CR) 2 were prepared and characterized. Natural ligands for CR2 are C3 breakdown products deposited at sites of complement activation. Fusion proteins were prepared consisting of a human CR2 fragment linked to either the N terminus or C terminus of soluble forms of the membrane complement inhibitors decay accelerating factor (DAF) or CD59. The targeted complement inhibitors bound to C3-opsonized cells, and all were significantly more effective (up to 20-fold) than corresponding untargeted inhibitors at protecting target cells from complement. CR2 fusion proteins also inhibited CR3-dependent adhesion of U937 cells to C3 opsonized erythrocytes, indicating a second potential anti-inflammatory mechanism of CR2 fusion proteins, since CR3 is involved in endothelial adhesion and diapedesis of leukocytes at inflammatory sites. Finally, the in vivo validity of the targeting strategy was confirmed by the demonstration that CR2-DAF, but not soluble DAF, targets to the kidney in mouse models of lupus nephritis that are associated with renal complement deposition.

Ischemia-reperfusion-induced lung injury

Ischemia-reperfusion-induced lung injury is characterized by nonspecific alveolar damage, lung edema, and hypoxemia occurring within 72 hours after lung transplantation. The most severe form may lead to primary graft failure and remains a significant cause of morbidity and mortality after lung transplantation. Over the past decade, better understanding of the mechanisms of ischemia-reperfusion injury, improvements in the technique of lung preservation, and the development of a new preservation solution specifically for the lung have been associated with a reduction in the incidence of primary graft failure from approximately 30 to 15% or less. Several strategies have also been introduced into clinical practice for the prevention and treatment of ischemia-reperfusion-induced lung injury with various degrees of success. However, only three randomized, double-blinded, placebo-controlled trials on ischemia-reperfusion-induced lung injury have been reported in the literature. In the future, the development of new agents and their application in prospective clinical trials are to be expected to prevent the occurrence of this potentially devastating complication and to further improve the success of lung transplantation.

Pulmonary activity on labeled leukocyte images: physiologic, pathologic, and imaging correlation

Accurate interpretation of labeled leukocyte images requires knowledge of pulmonary labeled leukocyte uptake: its prevalence and patterns and its correlation with technical, physiologic, and pathologic conditions as well as with other imaging findings. Images obtained shortly after injection of labeled cells are characterized by diffuse pulmonary activity, which decreases over time, until about 4 hours after injection when it becomes indistinguishable from background activity, remaining constant thereafter. Focal pulmonary uptake that is segmental or lobar in appearance is most often associated with bacterial pneumonia. Focal pulmonary uptake that is not segmental or lobar results from technical problems during labeling or reinfusion and is not usually associated with infection. Diffuse pulmonary uptake on images obtained more than 4 hours after reinjection of labeled cells is associated with a variety of pathologic conditions, some of the more common being opportunistic infection, radiation pneumonitis, pulmonary drug toxicity, adult respiratory distress syndrome, and sepsis. However, this pattern is almost never seen in bacterial pneumonia. When pulmonary uptake patterns are analyzed and correlated with the clinical situation, labeled leukocyte scintigraphy can provide useful information about pulmonary disease.

Differential role of CD18 integrins in mediating lung neutrophil sequestration and increased microvascular permeability induced by Escherichia coli in mice

The in vivo contributions of CD18 integrin-dependent and -independent mechanisms in mediating the increases in lung neutrophil (polymorphonuclear leukocyte; PMN) sequestration and microvascular permeability are not well understood. We determined the time course of these responses to Gram-negative sepsis in the mouse lung and addressed the specific contributions of CD18 integrins and ICAM-1. PMN sequestration in the lung was assessed by morphometric analysis, and transalveolar PMN migration was assessed by bronchoalveolar lavage. Lung tissue PMN number increased by 6-fold within 1 h after i.p. Escherichia coli challenge; this value peaked at 3 h (7-fold above control) and decreased at 12 h (3.5-fold above control). PMN migration into the airspace was delayed; the value peaked at 6 h and remained elevated up to 12 h. Saturating concentrations of anti-CD18 and anti-ICAM-1 mAbs reduced lung tissue PMN sequestration and migration; however, peak responses at 3 and 6 h were inhibited by 40%, indicating that only a small component of PMN sequestration and migration was CD18 dependent at these times. In contrast to the time-dependent decreased role of CD18 integrins in mediating PMN sequestration and migration, CD18 and ICAM-1 blockade prevented the increase in lung microvascular permeability and edema formation at all times after E. coli challenge. Thus, Gram-negative sepsis engages CD18/ICAM-1-independent mechanisms capable of the time-dependent amplification of lung PMN sequestration and migration. The increased pulmonary microvascular permeability induced by E. coli is solely the result of engagement of CD18 integrins even when PMN accumulation and migration responses are significantly CD18 independent.

sCR1sLe ameliorates ischemia/reperfusion injury in experimental lung transplantation

BACKGROUND

The nonspecific immune response with activation of the complement system and polymorphonuclear leukocytes is important for the mediation of reperfusion injury after lung transplantation. In this study, we investigated the combined blockade of the complement system and leukocyte adhesion by a novel drug combining soluble complement receptor type 1 (sCR1, CD35) with the selectin ligand sialyl Lewis X (sLe(X), CD15s) synthesized to sCR1sLe(X). Both sCR1 and sCR1sLe(X) were supplied by AVANT Immunotherapeutics, Inc, Needham, Massachusetts.

METHODS

Orthotopic allogeneic single left lung transplantation was performed in male rats (Brown Norway to Fischer F344; n = 5 in all groups) after a total ischemic time of 20 hours. Recipients received either no specific treatment (control) or administration of sCR1 (10 mg/kg) or sCR1sLe(X) (10 mg/kg) 15 minutes before reperfusion by intracardiac injection. Twenty-four hours after reperfusion, the native contralateral lung was occluded to assess gas exchange of the graft only. In additional animals (5 per group), lung tissue was frozen 24 hours after reperfusion and assessed for myeloperoxidase activity as a measurement of neutrophil migration into the graft and thiobarbituric acid reactive substances to quantify lipid peroxidation.

RESULTS

Graft function as assessed by arterial PO (2) in recipients treated with sCR1sLeX was superior not only to that of controls (383 +/- 53 vs 56 +/- 7 mm Hg, P =. 000095) but also to that of animals treated with sCR1 (243 +/- 45 mm Hg, P =.031). This improvement was confirmed by significant reduction of neutrophil migration (0.33 +/- 0.05 vs control, 1.0 +/- 0.09 DeltaOD/mg/min, P =.0000024) and lipid peroxidation (6.2 +/- 0. 38 vs control, 10.6 +/- 0.54 pmol/g, P =.00021).

CONCLUSIONS

Our data indicate that combined inhibition of complement activation and leukocyte adhesion with sCR1sLe(X) reduces reperfusion injury significantly and that both mechanisms are effectively inhibited in this model.

Overview and future practice patterns in cardiac and pulmonary preservation

Heart and lung transplantation have become standard therapy for many patients with end-stage heart and lung disease. Successful transplantation requires preservation of allografts until they can be implanted and reperfused. In the decades since the transplantation of thoracic organs became a clinical reality, many advances have been made in preoperative donor management, procurement, and preservation techniques. This article summarizes the state of the art in heart and lung preservation and review some of the areas of current research that may lead to improvements in preservation techniques in the future.

Pulmonary transplantation

Anesthetic technique for pulmonary transplantation varies with recipient's underlying lung disease, procedure performed and regional practice. The pulmonary allograft is vulnerable to mechanical and biochemical injury throughout the harvesting, preservation and engraftment procedures. Mechanisms of allograft injury are reviewed, with suggestions for incorporation of strategies to minimize injury into clinical practice. Particular emphasis is placed on the use of nitric oxide for treatment of reperfusion injury.