Imatinib Is Protective Against Ischemia-Reperfusion Injury in an Ex Vivo Rabbit Model of Lung Injury

The endothelium: gatekeeper to lung ischemia-reperfusion injury

The success of lung transplantation is limited by the high rate of primary graft dysfunction due to ischemia-reperfusion injury (IRI). Lung IRI is characterized by a robust inflammatory response, lung dysfunction, endothelial barrier disruption, oxidative stress, vascular permeability, edema, and neutrophil infiltration. These events are dependent on the health of the endothelium, which is a primary target of IRI that results in pulmonary endothelial barrier dysfunction. Over the past 10 years, research has focused more on the endothelium, which is beginning to unravel the multi-factorial pathogenesis and immunologic mechanisms underlying IRI. Many important proteins, receptors, and signaling pathways that are involved in the pathogenesis of endothelial dysfunction after IR are starting to be identified and targeted as prospective therapies for lung IRI. In this review, we highlight the more significant mediators of IRI-induced endothelial dysfunction discovered over the past decade including the extracellular glycocalyx, endothelial ion channels, purinergic receptors, kinases, and integrins. While there are no definitive clinical therapies currently available to prevent lung IRI, we will discuss potential clinical strategies for targeting the endothelium for the treatment or prevention of IRI. The accruing evidence on the essential role the endothelium plays in lung IRI suggests that promising endothelial-directed treatments may be approaching the clinic soon. The application of therapies targeting the pulmonary endothelium may help to halt this rapid and potentially fatal injury.

Imatinib attenuates reperfusion injury in a rat model of acute myocardial infarction

Following an acute myocardial infarction, reperfusion of an occluded coronary artery is often accompanied by microvascular injury, leading to worse long-term prognosis. Experimental studies have revealed the potential of tyrosine-kinase inhibitor imatinib to reduce vascular leakage in various organs. Here, we examined the potential of imatinib to attenuate microvascular injury in a rat model of myocardial reperfusion injury. Isolated male Wistar rat hearts (n = 20) in a Langendorff system and male Wistar rats (n = 37) in an in vivo model were randomly assigned to imatinib or placebo and subjected to ischaemia and reperfusion. Evans-blue/Thioflavin-S/TTC staining and Cardiac Magnetic Resonance Imaging were performed to assess the extent of reperfusion injury. Subsequently, in vivo hearts were perfused ex vivo with a vascular leakage tracer and fluorescence and electron microscopy were performed. In isolated rat hearts, imatinib reduced global infarct size, improved end-diastolic pressure, and improved rate pressure product recovery compared to placebo. In vivo, imatinib reduced no-reflow and infarct size with no difference between imatinib and placebo for global cardiac function. In addition, imatinib showed lower vascular resistance, higher coronary flow, and less microvascular leakage in the affected myocardium. At the ultrastructural level, imatinib showed higher preserved microvascular integrity compared to placebo. We provide evidence that low-dose imatinib can reduce microvascular injury and accompanying myocardial infarct size in a rat model of acute myocardial infarction. These data warrant future work to examine the potential of imatinib to reduce reperfusion injury in patients with acute myocardial infarction.

High-Sensitivity Cardiac Troponin T in Prediction and Diagnosis of Early Postoperative Hypoxemia after Off-Pump Coronary Artery Bypass Grafting

To investigate the relationship of preoperative high-sensitivity cardiac troponin T (hs-cTnT) with early postoperative hypoxemia (EPH) following off-pump coronary artery bypass grafting (OPCAB). Records of patients undergoing OPCAB between 2018 and 2022 were reviewed. Baseline characteristics and postoperative arterial blood gas analysis were derived from the cardiovascular surgery electronic medical records. Preoperative hs-cTnT levels were measured routinely in all patients. Logistic regression analyses were performed to test the association of preoperative hs-cTnT with EPH. A total of 318 OPCAB patients were included, who had a preoperative hs-cTnT test available for review. Before surgery, 198 patients (62%) had a rise in hs-cTnT level (≥14 ng/L) and 127 patients (40%) had a more severe hs-cTnT level (≥25 ng/L). The preoperative hs-cTnT level was associated with EPH (odds ratio per ng/L, 1.86; 95% confidence interval 1.30−2.68; p < 0.001), prolonged intensive care unit stay (odds ratio, 1.58; 95% confidence interval 1.08−2.32; p = 0.019), and delayed extubating time (odds ratio, 1.63; 95% confidence interval 1.15−2.34; p = 0.007). On multivariable analysis, adjusted for BMI, hypertension, smoking status, serum creatinine, and cardiac function, preoperative hs-cTnT remained an independent factor associated with EPH. Elevation of hs-cTnT concentrations are significantly associated with EPH after OPCAB. Review of presurgical hs-cTnT concentration may help identify patients who would benefit from OPCAB to improve surgical risk assessment.

Novel approaches for long-term lung transplant survival

Allograft failure remains a major barrier in the field of lung transplantation and results primarily from acute and chronic rejection. To date, standard-of-care immunosuppressive regimens have proven unsuccessful in achieving acceptable long-term graft and patient survival. Recent insights into the unique immunologic properties of lung allografts provide an opportunity to develop more effective immunosuppressive strategies. Here we describe advances in our understanding of the mechanisms driving lung allograft rejection and highlight recent progress in the development of novel, lung-specific strategies aimed at promoting long-term allograft survival, including tolerance.

Pseudomonas aeruginosa outer membrane vesicles ameliorates lung ischemia-reperfusion injury by regulating the balance of regulatory T cells and Th17 cells through Tim-3 and TLR4/NF-κB pathway

OBJECTIVE

Regulatory T cells (Tregs) and T helper (Th) 17 cells are two subsets of CD4 + T cells with opposite effects which play a crucial role in the pathogenesis of lung injury. In this study, we aim to investigate the protective effect of Pseudomonas aeruginosa outer membrane vesicles (OMVs) preconditioning on lung ischemia-reperfusion (I/R) injury and potential mechanisms.

METHODS

Pathogen-free C57BL/6 mice were randomly divided into four groups: control, Control + OMVs, I/R and I/R + OMVs groups. Bronchoalveolar lavage fluid (BALF), serum, and lung tissues were collected and analyzed for pathophysiology and immune mechanism.

RESULTS

OMVs not only attenuated tissue injury and respiratory physiologic function but also mediated the downregulation of lung wet-to-dry weight ratio and the reduction of total protein concentration. The numbers of total cells, macrophages, neutrophils, and lymphocytes were markedly decreased in the I/R mice following OMVs preconditioning. OMVs also decreased inflammatory cytokines associated with CD4 + T cells in both BALF and serum. In addition, the level of Tregs and its transcription factor forkhead box P3 (Foxp3) were significantly increased, while the level of Th17 cells and its transcription factor retinoid-related orphan receptor γ (RORγt) were significantly decreased following OMVs preconditioning. In the process of exploring the underlying protection mechanisms of OMVs, we found that OMVs preconditioning significantly reduced protein expression of Toll-like receptor 4 (TLR4), which in turn not only inactivated myeloid differentiation factor 88 (MyD88) and Phosphorylated nuclear factor kappa B (p-NF-κB), but also simultaneously increased the levels of T-cell immunoglobulin and mucin domain-containing protein 3 (Tim-3).

CONCLUSIONS

These results suggest that OMVs preconditioning may ameliorate lung I/R injury by regulating the balance of Tregs and Th17 cells through Tim-3 and TLR4/NF-κB pathway.

Repurposing anticancer drugs for the management of COVID-19

Since its outbreak in the last December, coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 has rapidly spread worldwide at a pandemic proportion and thus is regarded as a global public health emergency. The existing therapeutic options for COVID-19 beyond the intensive supportive care are limited, with an undefined or modest efficacy reported so far. Drug repurposing represents an enthusiastic mechanism to use approved drugs outside the scope of their original indication and accelerate the discovery of new therapeutic options. With the emergence of COVID-19, drug repurposing has been largely applied for early clinical testing. In this review, we discuss some repurposed anticancer drugs for the treatment of COVID-19, which are under investigation in clinical trials or proposed for the clinical testing.

Normothermic machine perfusion of donor-lungs ex-vivo: promoting clinical adoption

PURPOSE OF REVIEW

Lung transplantation offers the only realistic therapeutic option for patients with end-stage lung disease. However, this is impacted by a shortfall in availability of suitable donor-lungs. Normothermic machine perfusion of donor-lungs outside the donor body also known as ex-vivo lung perfusion (EVLP) offers a potential solution through objective assessment, reconditioning and treatment of donor-lungs initially deemed unsuitable for use. This review discusses key advances and challenges in the wider clinical adoption of this technology.

RECENT FINDINGS

This review will summarize key research within the following areas: recent clinical trials utilizing EVLP, logistical challenges, EVLP protocol innovations, novel assessment methods and current research into therapeutic modulation of lung function during EVLP.

SUMMARY

Normothermic machine perfusion of donor-lungs ex-vivo offers a promising platform to assess and modulate donor-lung quality prior to transplantation. Consensus on how and when to best utilize EVLP is yet to be reached, meaning that widespread clinical adoption of the technology has not yet become a reality. Further work is needed on agreed indications, perfusion protocols and organization of services before becoming a regularly used procedure prior to lung transplantation.

Arg mediates LPS-induced disruption of the pulmonary endothelial barrier

Acute Respiratory Distress Syndrome (ARDS) is a devastating disease process that involves dysregulated inflammation and decreased alveolar-capillary barrier function. Despite increased understanding of the pathophysiology, no effective targeted therapies exist to treat ARDS. Recent preclinical studies suggest that the multi-tyrosine kinase inhibitor, imatinib, which targets the Abl kinases c-Abl and Arg, has the potential to restore endothelial dysfunction caused by inflammatory agonists. Prior work demonstrates that imatinib attenuates LPS (lipopolysaccharide)-induced vascular leak and inflammation; however, the mechanisms underlying these effects remain incompletely understood. In the current study, we demonstrate that imatinib inhibits LPS-induced increase in the phosphorylation of CrkL, a specific substrate of Abl kinases, in human pulmonary endothelial cells. Specific silencing of Arg, and not c-Abl, attenuated LPS-induced pulmonary vascular permeability as measured by electrical cellular impedance sensing (ECIS) and gap formation assays. In addition, direct activation of Abl family kinases with the small molecule activator DPH resulted in endothelial barrier disruption that was attenuated by Arg siRNA. In complementary studies to characterize the mechanisms by which Arg mediates endothelial barrier function, Arg silencing was found to inhibit LPS-induced disruption of adherens junctions and phosphorylation of myosin light chains (MLC). Overall, these results characterize the mechanisms by which imatinib protects against LPS-induced endothelial barrier disruption and suggest that Arg inhibition may represent a novel strategy to enhance endothelial barrier function.

Ex-vivo lung perfusion

PURPOSE OF REVIEW

Ex-vivo lung perfusion (EVLP) has been developed to expand the donor pool for lung transplantation recipients. The role of EVLP in organ preservation, evaluation and potential reconditioning is reviewed.

RECENT FINDINGS

EVLP has been shown to significantly increase the utilization of donor lungs for transplantation. Evidence suggests that patient outcomes from EVLP lungs are comparable to standard procurement technique. Novel strategies are being developed to treat and recondition injured donor lungs. EVLP may also prove to be a tool for translational research of lung diseases.

SUMMARY

EVLP has been shown to be an effective system to expand donor pool for lung transplantation without detriment to recipients. Future potential ex-vivo developments may further improve patient outcomes as well as increasing availability of donor organs.