Chung-Wai Chow

Normothermic Ex Vivo Lung Perfusion in Clinical Lung Transplantation

BACKGROUND More than 80% of donor lungs are potentially injured and therefore not considered suitable for transplantation. With the use of normothermic ex vivo lung perfusion (EVLP), the retrieved donor lung can be perfused in an ex vivo circuit, providing an opportunity to reassess its function before transplantation. In this study, we examined the feasibility of transplanting high-risk donor lungs that have undergone EVLP. METHODS In this prospective, nonrandomized clinical trial, we subjected lungs considered to be high risk for transplantation to 4 hours of EVLP. High-risk donor lungs were defined by specific criteria, including pulmonary edema and a ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen (PO(2):FIO(2)) less than 300 mm Hg. Lungs with acceptable function were subsequently transplanted. Lungs that were transplanted without EVLP during the same period were used as controls. The primary end point was primary graft dysfunction 72 hours after transplantation. Secondary end points were 30-day mortality, bronchial complications, duration of mechanical ventilation, and length of stay in the intensive care unit and hospital. RESULTS During the study period, 136 lungs were transplanted. Lungs from 23 donors met the inclusion criteria for EVLP; in 20 of these lungs, physiological function remained stable during EVLP and the median PO(2):FIO(2) ratio increased from 335 mm Hg in the donor lung to 414 and 443 mm Hg at 1 hour and 4 hours of perfusion, respectively (P<0.001). These 20 lungs were transplanted; the other 116 lungs constituted the control group. The incidence of primary graft dysfunction 72 hours after transplantation was 15% in the EVLP group and 30% in the control group (P=0.11). No significant differences were observed for any secondary end points, and no severe adverse events were directly attributable to EVLP. CONCLUSIONS Transplantation of high-risk donor lungs that were physiologically stable during 4 hours of ex vivo perfusion led to results similar to those obtained with conventionally selected lungs. (Funded by Vitrolife; ClinicalTrials.gov number, NCT01190059.).

Proteases and lung injury.

ObjectiveAcute respiratory distress syndrome (ARDS) represents an inflammatory process that is initiated by diverse systemic and/or pulmonary insults, resulting in a clinical syndrome of severe respiratory distress and refractory hypoxemia. Neutrophils and their cytotoxic products, including oxidants and proteases, such as elastase, have been implicated as playing a key role in the pathophysiology of ARDS. This article reviews some of the physiologic actions of proteases, specifically elastase, the evidence for neutrophil elastase involvement in ARDS, and the potential therapeutic use of neutrophil elastase inhibitors in lung injury. Data SourceA review of published literature (original articles and reviews) in English from 1965 to 2002. ConclusionAlthough the data support a key role for neutrophil elastase in the pathogenesis of ARDS, further study is needed to fully define the actions of neutrophil elastase, and how these actions affect host functions, before we can exploit this knowledge for therapeutic benefit.

Syk Associates with Clathrin and Mediates Phosphatidylinositol 3-Kinase Activation during Human Rhinovirus Internalization

Human rhinovirus (HRV) causes the common cold. The most common acute infection in humans, HRV is a leading cause of exacerbations of asthma and chronic obstruction pulmonary disease because of its ability to exacerbate airway inflammation by altering epithelial cell biology upon binding to its receptor, ICAM-1. ICAM-1 regulates not only viral entry and replication but also signaling pathways that lead to inflammatory mediator production. We recently demonstrated the Syk tyrosine kinase to be an important mediator of HRV-ICAM-1 signaling: Syk regulates replication-independent p38 MAPK activation and IL-8 expression. In leukocytes, Syk regulates receptor-mediated internalization via PI3K. Although PI3K has been shown to regulate HRV-induced IL-8 expression and clathrin-mediated endocytosis of HRV, the role of airway epithelial Syk in this signaling pathway is not known. We postulated that Syk regulates PI3K activation and HRV endocytosis in the airway epithelium. Using confocal microscopy and immunoprecipitation, we demonstrated recruitment of the normally cytosolic Syk to the plasma membrane upon HRV16-ICAM-1 binding, along with Syk-clathrin coassociation. Subsequent incubation at 37°C to permit internalization revealed redistribution of Syk to punctate structures resembling endosomes and colocalization with HRV16. Internalized HRV was not detected in cells overexpressing the kinase inactive SykK396R mutant, indicating that kinase activity was necessary for endocytosis. HRV-induced PI3K activation was dependent on Syk; Syk knockdown by small interfering RNA significantly decreased phosphorylation of the PI3K substrate Akt. Together, these data reveal Syk to be an important mediator of HRV endocytosis and HRV-induced PI3K activation.

Functional outcomes and quality of life after normothermic ex vivo lung perfusion lung transplantation

BACKGROUND Ex vivo lung perfusion (EVLP) is an effective method to assess and improve the function of otherwise unacceptable lungs, alleviating the shortage of donor lungs. The early results with EVLP have been encouraging, but longer-term results, including functional and patient-reported outcomes, are not well characterized. METHODS This retrospective single-center study included all lung transplants performed between September 2008 and December 2012. We investigated whether survival or rate of chronic lung allograft dysfunction (CLAD) differed in recipients of EVLP-treated lungs compared with contemporaneous recipients of conventional donor lungs. We also studied functional (highest forced expiratory volume in 1 second predicted, change in 6-minute walk distance, number of acute rejection episodes) and quality of life outcomes. RESULTS Of 403 lung transplants that were performed, 63 patients (15.6%) received EVLP-treated allografts. Allograft survival for EVLP and conventional donor lung recipients was 79% vs 85%, 71% vs 73%, and 58% vs 57% at 1, 3, and 5 years after transplant, respectively (log-rank p = not significant). Freedom from CLAD was also similar (log-rank p = 0.53). There were no significant differences in functional outcomes such as highest forced expiratory volume in 1 second predicted (76.5% ± 23.8% vs 75.8% ± 22.8%, p = 0.85), change in 6-minute walk distance (194 ± 108 meters vs 183 ± 126 meters, p = 0.57), or the number of acute rejection episodes (1.5 ± 1.4 vs 1.3 ± 1.3, p = 0.36). The EVLP and conventional donor groups both reported a significantly improved quality of life after transplantation, but there was no intergroup difference. CONCLUSION EVLP is a safe and effective method of assessing and using high-risk donor lungs before transplantation and leads to acceptable long-term survival, graft function, and improvements of quality of life that are comparable with conventionally selected donor lungs.

Survival in Sensitized Lung Transplant Recipients With Perioperative Desensitization

Donor‐specific HLA antibodies (DSA) have an adverse effect on short‐term and long‐term lung transplant outcomes. We implemented a perioperative strategy to treat DSA‐positive recipients, leading to equivalent rejection and graft survival outcomes. Pretransplant DSA were identified to HLA‐A, B, C, DR and DQ antigens. DSA‐positive patients were transplanted if panel reactive antibody (PRA) ≥30% or medically urgent and desensitized with perioperative plasma exchange, intravenous immune globulin, antithymocyte globulin (ATG), and mycophenolic acid (MPA). PRA‐positive/DSA‐negative recipients received MPA. Unsensitized patients received routine cyclosporine, azathioprine and prednisone without ATG. From 2008–2011, 340 lung‐only first transplants were performed: 53 DSA‐positive, 93 PRA‐positive/DSA‐negative and 194 unsensitized. Thirty‐day survival was 96 %/99%/96% in the three groups, respectively. One‐year graft survival was 89%/88%/86% (p = 0.47). DSA‐positive and PRA‐positive/DSA‐negative patients were less likely to experience any ≥ grade 2 acute rejection (9% and 9% vs. 18% unsensitized p = 0.04). Maximum predicted forced expiratory volume (1 s) (81%/74%/76%, p = NS) and predicted forced vital capacity (81%/77%/78%, respectively, p = NS) were equivalent between groups. With the application of this perioperative treatment protocol, lung transplantation can be safely performed in DSA/PRA‐positive patients, with similar outcomes to unsensitized recipients.

De Novo DQ Donor-Specific Antibodies Are Associated with Chronic Lung Allograft Dysfunction after Lung Transplantation

RATIONALE Despite increasing evidence about the role of donor-specific human leukocyte antigen (HLA) antibodies in transplant outcomes, the incidence and impact of de novo donor-specific antibodies (dnDSA) after lung transplantation remains unclear. OBJECTIVES To describe the incidence, characteristics, and impact of dnDSA after lung transplantation. METHODS We investigated a single-center cohort of 340 lung transplant recipients undergoing transplant during 2008 to 2011. All patients underwent HLA-antibody testing quarterly pretransplant and at regular intervals over the first 24 months after transplant. The patients received modified immunosuppression depending on their pretransplant sensitization status. Risk factors for dnDSA development, as well as the associations of dnDSA with patient survival and chronic lung allograft dysfunction (CLAD), were determined using multivariable analysis. MEASUREMENTS AND MAIN RESULTS The cumulative incidence of dnDSA was 47% at a median of 86 days (range, 44-185 d) after lung transplantation. Seventy-six percent of recipients with dnDSA had DQ-DSA. Male sex and the use of ex vivo lung perfusion were associated with an increased risk of dnDSA, whereas increased HLA-DQB1 matching was protective. DQ-dnDSA preceded or coincided with the diagnosis of CLAD in all cases. Developing dnDSA (vs. no dnDSA) was associated with a twofold increased risk of CLAD (hazard ratio, 2.04; 95% confidence interval, 1.13-3.69). This association appeared to be driven by the development of DQ-dnDSA. CONCLUSIONS dnDSA are common after lung transplantation, with the majority being DQ DSA. DQ-dnDSA are associated with an increased risk of CLAD. Strategies to prevent or treat DQ-dnDSA may improve outcomes for lung transplant recipients.

The combined effects of physicochemical properties of size-fractionated ambient particulate matter on in vitro toxicity in human A549 lung epithelial cells

Epidemiological and toxicological studies have suggested that the health effects associated with exposure to particulate matter (PM) are related to the different physicochemical properties of PM. These effects occur through the initiation of differential cellular responses including: the induction of antioxidant defenses, proinflammatory responses, and ultimately cell death. The main objective of this study was to investigate the effects of size-fractionated ambient PM on epithelial cells in relation to their physicochemical properties. Concentrated ambient PM was collected on filters for three size fractions: coarse (aerodynamic diameter [AD] 2.5–10 μm), fine (0.15–2.5 μm), and quasi-ultrafine (<0.2 μm), near a busy street in Toronto, Ontario, Canada. Filters were extracted and analyzed for chemical composition and redox activity. Chemical analyses showed that the coarse, fine, and quasi-ultrafine particles were comprised primarily of metals, water-soluble species, and organic compounds, respectively. The highest redox activity was observed for fine PM. After exposure of A549 cells to PM (10–100 μg/ml) for 4 h, activation of antioxidant, proinflammatory and cytotoxic responses were assessed by determining the expression of heme oxygenase (HMOX-1, mRNA), interleukin-8 (IL-8, mRNA), and metabolic activity of the cells, respectively. All three size fractions induced mass-dependent antioxidant, proinflammatory, and cytotoxic responses to different degrees. Quasi-ultrafine PM caused significant induction of HMOX-1 at the lowest exposure dose. Correlation analyses with chemical components suggested that the biological responses correlated mainly with transition metals and organic compounds for coarse and fine PM and with organic compounds for quasi-ultrafine PM. Overall, the observed biological responses appeared to be related to the combined effects of size and chemical composition and thus both of these physicochemical properties should be considered when explaining PM toxicity.

Comparative cardiopulmonary effects of size-fractionated airborne particulate matter

Context: Strong epidemiological evidence exists linking particulate matter (PM) exposures with hospital admissions of individuals for cardiopulmonary symptoms. The PM size is important in influencing the extent of infiltration into the respiratory tract and systemic circulation and directs the differential physiological impacts. Objective: To investigate the differential effects of the quasi-ultrafine (PM0.2), fine (PM0.15-2.5), and coarse PM (PM2.5-10) size fractions on pulmonary and cardiac function. Methods: Female BALB/c mice were exposed to HEPA-filtered laboratory air or concentrated coarse, fine, or quasi-ultrafine PM using Harvard Ambient Particle Concentrators in conjunction with our nose-only exposure system. These exposures were conducted as part of the “Health Effects of Aerosols in Toronto (HEAT)” campaign. Following a 4 h exposure, mice underwent assessment of respiratory function and recording of electrocardiograms using the flexiVent® system. Results: Exposure to coarse and fine PM resulted in a significant reduction in quasistatic compliance of the lung. Baseline total respiratory resistance and maximum responsiveness to methacholine were augmented after coarse PM exposures but were not affected by quasi-ultrafine PM exposures. In contrast, quasi-ultrafine PM alone had a significant effect on heart rate and in reducing heart rate variability. Conclusion: These findings indicate that coarse and fine PM influence lung function and airways responsiveness, while ultrafine PM can perturb cardiac function. This study supports the hypothesis that coarse and fine PM exerts its predominant physiologic effects at the site of deposition in the airways, whereas ultrafine PM likely crosses the alveolar epithelial barrier into the systemic circulation to affect cardiovascular function.

Spleen tyrosine kinase inhibition attenuates airway hyperresponsiveness and pollution-induced enhanced airway response in a chronic mouse model of asthma

BACKGROUND Asthma is a chronic inflammatory disease characterized by airways hyperresponsiveness (AHR), reversible airflow obstruction, airway remodeling, and episodic exacerbations caused by air pollutants, such as particulate matter (PM; PM <2.5 μm in diameter [PM(2.5)]) and ozone (O(3)). Spleen tyrosine kinase (Syk), an immunoregulatory kinase, has been implicated in the pathogenesis of asthma. OBJECTIVE We sought to evaluate the effect of Syk inhibition on AHR in a chronic mouse model of allergic airways inflammation and pollutant exposure. METHODS We used a 12-week chronic ovalbumin (OVA) sensitization and challenge mouse model of airways inflammation followed by exposure to PM(2.5) plus O(3). Respiratory mechanics and methacholine (MCh) responsiveness were assessed by using the flexiVent system. The Syk inhibitor NVP-QAB-205 was nebulized intratracheally by using a treatment-based protocol 15 minutes before assessment of MCh responsiveness. RESULTS Syk expression increased significantly in the airway epithelia of OVA-sensitized and OVA-challenged (OVA/OVA) mice compared with OVA-sensitized but PBS-challenged (OVA/PBS) control mice. OVA/OVA mice exhibited AHR to MCh, which was attenuated by a single administration of NVP-QAB-205 (0.3 and 3 mg/kg). PM(2.5) plus O(3) significantly augmented AHR to MCh in the OVA/OVA mice, which was abrogated by NVP-QAB-205. Total inflammatory cell counts were significantly higher in the bronchoalveolar lavage fluid from OVA/OVA than OVA/PBS mice and were unaffected by PM(2.5) plus O(3) or NVP-QAB-205. CONCLUSION NVP-QAB-205 reduced AHR and the enhanced response to PM(2.5) plus O(3) to normal levels in an established model of chronic allergic airways inflammation, suggesting that Syk inhibitors have promise as a therapy for asthma.

Syk: A Novel Target for Treatment of Inflammation in Lung Disease

Spleen Tyrosine Kinase (Syk) is widely expressed in the immune system and functions in the transmission of inflammatory signals via ITAM-bearing cell surface receptors. The broad expression pattern and importance of Syk in regulating innate immunity and the inflammatory response have led to significant interest from the pharmaceutical industry to developing anti-Syk therapeutics for the treatment of inflammatory disorders such as allergic rhinitis and rheumatoid arthritis. While the function and regulation of Syk has been well-described in leukocytes, where its primary role is an early transducer of signaling following immunoreceptor engagement, Syk has recently been described in non-immune cells, such as the airway epithelium, that also play an important role in mediating the inflammatory response. This manuscript will focus on the expression and function of Syk in the context of inflammatory lung diseases, and review recent data that have demonstrated novel roles for Syk in airway epithelial cells, particularly its role in mediating the human rhinovirus (HRV) induced inflammatory response and viral cell entry. In addition, data describing the efficacy of novel Syk inhibitors in the management of inflammatory diseases in animal models and early clinical trials are also reviewed.