Cell death in human lung transplantation: apoptosis induction in human lungs during ischemia and after transplantation

Thyroid hormone protects human lung epithelial cells from cold preservation and warm reperfusion-induced injury

BACKGROUND

Cellular stress associated with static-cold storage (SCS) and warm reperfusion of donor lungs can contribute to ischemia-reperfusion (IR) injury during transplantation. Adding cytoprotective agents to the preservation solution may be conducive to reducing graft deterioration and improving post-transplant outcomes.

METHODS

SCS and warm reperfusion were simulated in human lung epithelial cells (BEAS-2B) by exposing cells to low potassium dextran glucose solution at 4 °C for different periods and then switching back to serum-containing culture medium at 37 °C. Transcriptomic analysis was used to explore potential cytoprotective agents. Based on its results, cell viability, caspase activity, cell morphology, mitochondrial function, and inflammatory gene expression were examined under simulated IR conditions with or without thyroid hormones (THs).

RESULTS

After 18 h SCS followed by 2 h warm reperfusion, genes related to inflammation and cell death were upregulated, and genes related to protein synthesis and metabolism were downregulated in BEAS-2B cells, which closely mirrored gene profiles found in thyroid glands of mice with congenital hypothyroidism. The addition of THs (T3 or T4) to the preservation solution increases cell viability, inhibits activation of caspase 3, 8 and 9, preserves cell morphology, enhances mitochondrial membrane potential, reduces mitochondrial superoxide production, and suppresses inflammatory gene expression.

CONCLUSION

Adding THs to lung preservation solutions may protect lung cells during SCS by promoting mitochondrial function, reducing apoptosis, and inhibiting pro-inflammatory pathways. Further in vivo testing is warranted to determine the potential clinical application of adding THs as therapeutics in lung preservation solutions.

Advances in lung ischemia/reperfusion injury: unraveling the role of innate immunity

BACKGROUND

Lung ischemia/reperfusion injury (LIRI) is a common occurrence in clinical practice and represents a significant complication following pulmonary transplantation and various diseases. At the core of pulmonary ischemia/reperfusion injury lies sterile inflammation, where the innate immune response plays a pivotal role. This review aims to investigate recent advancements in comprehending the role of innate immunity in LIRI.

METHODS

A computer-based online search was performed using the PubMed database and Web of Science database for published articles concerning lung ischemia/reperfusion injury, cell death, damage-associated molecular pattern molecules (DAMPs), innate immune cells, innate immunity, inflammation.

RESULTS

During the process of lung ischemia/reperfusion, cellular injury even death can occur. When cells are injured or undergo cell death, endogenous ligands known as DAMPs are released. These molecules can be recognized and bound by pattern recognition receptors (PRRs), leading to the recruitment and activation of innate immune cells. Subsequently, a cascade of inflammatory responses is triggered, ultimately exacerbating pulmonary injury. These steps are complex and interrelated rather than being in a linear relationship. In recent years, significant progress has been made in understanding the immunological mechanisms of LIRI, involving novel types of cell death, the ability of receptors other than PRRs to recognize DAMPs, and a more detailed mechanism of action of innate immune cells in ischemia/reperfusion injury (IRI), laying the groundwork for the development of novel diagnostic and therapeutic approaches.

CONCLUSIONS

Various immune components of the innate immune system play critical roles in lung injury after ischemia/reperfusion. Preventing cell death and the release of DAMPs, interrupting DAMPs receptor interactions, disrupting intracellular inflammatory signaling pathways, and minimizing immune cell recruitment are essential for lung protection in LIRI.

Mitsugumin 53 mitigation of ischemia-reperfusion injury in a mouse model

OBJECTIVE

Primary graft dysfunction is often attributed to ischemia-reperfusion injury, and prevention would be a therapeutic approach to mitigate injury. Mitsugumin 53, a myokine, is a component of the endogenous cell membrane repair machinery. Previously, exogenous administration of recombinant human (recombinant human mitsugumin 53) protein has been shown to mitigate acute lung injury. In this study, we aimed to quantify a therapeutic benefit of recombinant human mitsugumin 53 to mitigate a transplant-relevant model of ischemia-reperfusion injury.

METHODS

C57BL/6J mice were subjected to 1 hour of ischemia (via left lung hilar clamp), followed by 24 hours of reperfusion. mg53-/- mice were administered exogenous recombinant human mitsugumin 53 or saline before reperfusion. Tissue, bronchoalveolar lavage, and blood samples were collected at death and used to quantify the extent of lung injury via histology and biochemical assays.

RESULTS

Administration of recombinant human mitsugumin 53 showed a significant decrease in an established biometric profile of lung injury as measured by lactate dehydrogenase and endothelin-1 in the bronchoalveolar lavage and plasma. Biochemical markers of apoptosis and pyroptosis (interleukin-1β and tumor necrosis factor-α) were also significantly mitigated, overall demonstrating recombinant human mitsugumin 53's ability to decrease the inflammatory response of ischemia-reperfusion injury. Exogenous recombinant human mitsugumin 53 administration showed a trend toward decreasing overall cellular infiltrate and neutrophil response. Fluorescent colocalization imaging revealed recombinant human mitsugumin 53 was effectively delivered to the endothelium.

CONCLUSIONS

These data demonstrate that recombinant human mitsugumin 53 has the potential to prevent or reverse ischemia-reperfusion injury-mediated lung damage. Although additional studies are needed in wild-type mice to demonstrate efficacy, this work serves as proof-of-concept to indicate the potential therapeutic benefit of mitsugumin 53 administration to mitigate ischemia-reperfusion injury.

MG53 mitigates warm ischemic lung injury in a murine model of transplantation

OBJECTIVES

Lung transplant warm ischemia-reperfusion injury (IRI) results in cellular injury, inflammation, and poor graft function. Mitsugumin 53 (MG53) is an endogenous protein with cell membrane repair properties and the ability to modulate the inflammasome. We hypothesize that the absence of circulating MG53 protein in the recipient increases IRI, and higher levels of circulating MG53 protein mitigate IRI associated with lung transplantation.

METHODS

To demonstrate protection, wild-type (wt) lung donor allografts were transplanted into a wt background, a MG53 knockout (mg53-/-), or a constitutively overexpressed MG53 (tissue plasminogen activator-MG53) recipient mouse after 1 hour of warm ischemic injury. Mice survived for 5 days after transplantation. Bronchioalveolar lavage, serum, and tissue were collected at sacrifice. Bronchioalveolar lavage, serum, and tissue markers of apoptosis and a biometric profile of lung health were analyzed.

RESULTS

mg53-/- mice had significantly greater levels of markers of overall cell lysis and endothelial cell injury. Overexpression of MG53 resulted in a signature similar to that of wt controls. At the time of explant, tissue plasminogen activator-MG53 recipient tissue expressed significantly greater levels of MG53, measured by immunohistochemistry, compared with mg53-/-, demonstrating uptake of endogenous overexpressed MG53 into donor tissue.

CONCLUSIONS

In a warm IRI model of lung transplantation, the absence of MG53 resulted in increased cell injury and inflammation. Endogenous overexpression of MG53 in the recipient results in protection in the wt donor. Together, these data suggest that MG53 is a potential therapeutic agent for use in lung transplantation to mitigate IRI.

Protective Effect of Calpain Inhibition During Cold Ischemia on Ischemia-reperfusion Injury After Lung Transplantation

BACKGROUND

Necroptosis, one of the types of regulated necrosis, causes ischemia-reperfusion (IR) lung injury. N-acetyl-leucyl-leucyl-norleucinal (ALLN), a calpain inhibitor, is known to attenuate necroptosis and apoptosis, and the purpose of this study was to evaluate the protective effect of ALLN during cold ischemia against IR injury in a rat lung transplant model.

METHODS

Male Lewis rats (250-350 g) were divided into 3 groups: sham group (n = 4), nontransplantation; control group (n = 8), transplantation with IR lung injury; and ALLN group (n = 8), transplantation with IR lung injury/ALLN. Rats in the sham group underwent a simple thoracotomy, and the remaining 2 groups of rats underwent an orthotopic left lung transplant. Cold ischemic time was 15 h. After 2 h of reperfusion, physiological function, inflammatory cytokine expression, pathway activation, and the degrees of necroptosis and apoptosis were evaluated.

RESULTS

Lung gas exchange (PaO 2 /FiO 2 ) was significantly better, and pulmonary edema was significantly improved in the ALLN group compared with the control group ( P = 0.0009, P = 0.0014). Plasma expression of interleukin-1β was significantly lower in the ALLN group than in the control group ( P = 0.0313). The proportion of necroptotic and apoptotic cells was significantly lower in the ALLN group than in the control group ( P = 0.0009), whereas the proportion of apoptotic cells remained unchanged ( P = 0.372); therefore, the calpain inhibitor was thought to suppress necroptosis.

CONCLUSIONS

The administration of ALLN during cold ischemia appears to improve IR lung injury in a lung transplant animal model via the inhibition of necroptosis.

Biometric Profiling to Quantify Lung Injury Through Ex Vivo Lung Perfusion Following Warm Ischemia

Standard physiologic assessment parameters of donor lung grafts may not accurately reflect lung injury or quality. A biometric profile of ischemic injury could be identified as a means to assess the quality of the donor allograft. We sought to identify a biometric profile of lung ischemic injury assessed during ex vivo lung perfusion (EVLP). A rat model of lung donation after circulatory death (DCD) warm ischemic injury with subsequent EVLP evaluation was utilized. We did not observe a significant correlation between the classical physiological assessment parameters and the duration of the ischemic. In the perfusate, solubilized lactate dehydrogenase (LDH) as well as hyaluronic acid (HA) significantly correlated with duration of ischemic injury and length of perfusion ( p < 0.05). Similarly, in perfusates, the endothelin-1 (ET-1) and Big ET-1 correlated ischemic injury ( p < 0.05) and demonstrated a measure of endothelial cell injury. In tissue protein expression, heme oxygenase-1 (HO-1), angiopoietin 1 (Ang-1), and angiopoietin 2 (Ang-2) levels were correlated with the duration of ischemic injury ( p < 0.05). Cleaved caspase-3 levels were significantly elevated at 90 and 120 minutes ( p < 0.05) demonstrating increased apoptosis. A biometric profile of solubilized and tissue protein markers correlated with cell injury is a critical tool to aid in the evaluation of lung transplantation, as accurate evaluation of lung quality is imperative and improved quality leads to better results. http://links.lww.com/ASAIO/B49.

The crosstalk between gut barrier impairment, mitochondrial dysfunction, and microbiota alterations in people living with HIV

Functional and structural damage of the intestinal mucosal barrier significantly contribute to translocation of gut microbial products into the bloodstream and are largely involved in HIV-1 associated chronic immune activation. This microbial translocation is largely due to a progressive exhaustion of intestinal macrophage phagocytic function, which leads to extracellular accumulation of microbial derived components and results in HIV-1 disease progression. This study aims to better understand whether the modulation of gut microbiota promotes an intestinal immune restoration in people living with HIV (PLWH). Long-term virologically suppressed PLWH underwent blood, colonic, and fecal sampling before (T0) and after 6 months (T6) of oral bacteriotherapy. Age- and gender-matched uninfected controls (UC) were also included. 16S rRNA gene sequencing was applied to all participants' fecal microbiota. Apoptosis machinery, mitochondria, and apical junctional complex (AJC) morphology and physiological functions were analyzed in gut biopsies. At T0, PLWH showed a different pattern of gut microbial flora composition, lower levels of occludin (p = 0.002) and zonulin (p = 0.01), higher claudin-2 levels (p = 0.002), a reduction of mitochondria number (p = 0.002), and diameter (p = 0.002), as well as increased levels of lipopolysaccharide (LPS) (p = 0.018) and cCK18 (p = 0.011), compared to UC. At T6, an increase in size (p = 0.005) and number (p = 0.008) of mitochondria, as well as amelioration in AJC structures (p < 0.0001) were observed. Restoration of bacterial richness (Simpson index) and biodiversity (Shannon index) was observed in all PLWH receiving oral bacteriotherapy (p < 0.05). Increased mitochondria size (p = 0.005) and number (p = 0.008) and amelioration of AJC structure (p < 0.0001) were found at T6 compared to T0. Moreover, increased occludin and zonulin concentration were observed in PLWH intestinal tracts and decreased levels of claudin-2, LPS, and cCK18 were found after oral bacteriotherapy (T0 vs. T6, p < 0.05 for all these measures). Oral bacteriotherapy supplementation might restore the balance of intestinal flora and support the structural and functional recovery of the gut mucosa in antiretroviral therapy treated PLWH.

Functional Blockage of S100A8/A9 Ameliorates Ischemia–Reperfusion Injury in the Lung

(1) Background: Lung ischemia–reperfusion (IR) injury increases the mortality and morbidity of patients undergoing lung transplantation. The objective of this study was to identify the key initiator of lung IR injury and to evaluate pharmacological therapeutic approaches using a functional inhibitor against the identified molecule. (2) Methods: Using a mouse hilar clamp model, the combination of RNA sequencing and histological investigations revealed that neutrophil-derived S100A8/A9 plays a central role in inflammatory reactions during lung IR injury. Mice were assigned to sham and IR groups with or without the injection of anti-S100A8/A9 neutralizing monoclonal antibody (mAb). (3) Results: Anti-S100A8/A9 mAb treatment significantly attenuated plasma S100A8/A9 levels compared with control IgG. As evaluated by oxygenation capacity and neutrophil infiltration, the antibody treatment dramatically ameliorated the IR injury. The gene expression levels of cytokines and chemokines induced by IR injury were significantly reduced by the neutralizing antibody. Furthermore, the antibody treatment significantly reduced TUNEL-positive cells, indicating the presence of apoptotic cells. (4) Conclusions: We identified S100A8/A9 as a novel therapeutic target against lung IR injury.

Successful 3-day lung preservation using a cyclic normothermic ex vivo lung perfusion strategy

Background

Methods

Findings

Interpretation

Funding

Mitochondrial PKM2 deacetylation by procyanidin B2-induced SIRT3 upregulation alleviates lung ischemia/reperfusion injury

Apoptosis is a critical event in the pathogenesis of lung ischemia/reperfusion (I/R) injury. Sirtuin 3 (SIRT3), an important deacetylase predominantly localized in mitochondria, regulates diverse physiological processes, including apoptosis. However, the detailed mechanisms by which SIRT3 regulates lung I/R injury remain unclear. Many polyphenols strongly regulate the sirtuin family. In this study, we found that a polyphenol compound, procyanidin B2 (PCB2), activated SIRT3 in mouse lungs. Due to this effect, PCB2 administration attenuated histological lesions, relieved pulmonary dysfunction, and improved the survival rate of the murine model of lung I/R injury. Additionally, this treatment inhibited hypoxia/reoxygenation (H/R)-induced A549 cell apoptosis and rescued Bcl-2 expression. Using Sirt3-knockout mice and specific SIRT3 knockdown in vitro, we further found that SIRT3 strongly protects against lung I/R injury. Sirt3 deficiency or enzymatic inactivation substantially aggravated lung I/R-induced pulmonary lesions, promoted apoptosis, and abolished PCB2-mediated protection. Mitochondrial pyruvate kinase M2 (PKM2) inhibits apoptosis by stabilizing Bcl-2. Here, we found that PKM2 accumulates and is hyperacetylated in mitochondria upon lung I/R injury. By screening the potential sites of PKM2 acetylation, we found that SIRT3 deacetylates the K433 residue of PKM2 in A549 cells. Transfection with a deacetylated mimic plasmid of PKM2 noticeably reduced apoptosis, while acetylated mimic transfection abolished the protective effect of PKM2. Furthermore, PKM2 knockdown or inhibition in vivo significantly abrogated the antiapoptotic effects of SIRT3 upregulation. Collectively, this study provides the first evidence that the SIRT3/PKM2 pathway is a protective target for the suppression of apoptosis in lung I/R injury. Moreover, this study identifies K433 deacetylation of PKM2 as a novel modification that regulates its anti-apoptotic activity. In addition, PCB2-mediated modulation of the SIRT3/PKM2 pathway may significantly protect against lung I/R injury, suggesting a novel prophylactic strategy for lung I/R injury.

N6-methyladenosine reader YTH N6-methyladenosine RNA binding protein 3 or insulin like growth factor 2 mRNA binding protein 2 knockdown protects human bronchial epithelial cells from hypoxia/reoxygenation injury by inactivating p38 MAPK, AKT, ERK1/2, and NF-κB pathways

Lung ischemia/reperfusion (I/R) injury (LIRI) is a common complication after lung transplantation, embolism, and trauma. N6-methyladenosine (m6A) methylation modification is implicated in the pathogenesis of I/R injury. However, there are no or few reports of m6A-related regulators in LIRI till now. In this text, dysregulated genes in lung tissues of LIRI rats versus the sham group were identified by RNA sequencing (RNA-seq). RNA-seq outcomes revealed that only YTH N6-methyladenosine RNA binding protein 3 (YTHDF3) and insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2) were differentially expressed in the LIRI versus sham group among 20 m6A-related regulators. Next, the functions and molecular mechanisms of YTHDF3 and IGF2BP2 in LIRI were investigated in a hypoxia/reoxygenation-induced BEAS-2B cell injury model in vitro. Results showed that YTHDF3 or IGF2BP2 knockdown attenuated hypoxia/reoxygenation-mediated inhibitory effects on cell survival and cell cycle progression and inhibited hypoxia/reoxygenation-induced cell apoptosis and pro-inflammatory cytokine secretion in BEAS-2B cells. Genes that could be directly regulated by YTHDF3 or IGF2BP2 were identified based on prior experimental data and bioinformatics analysis. Moreover, multiple potential downstream pathways of YTHDF3 and IGF2BP2 were identified by the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) enrichment analysis of the above-mentioned genes. Among these potential pathways, we demonstrated that YTHDF3 or IGF2BP2 knockdown inhibited hypoxia/reoxygenation-activated p38, ERK1/2, AKT, and NF-κB pathways in BEAS-2B cells. In conclusion, YTHDF3 or IGF2BP2 knockdown weakened hypoxia/reoxygenation-induced human lung bronchial epithelial cell injury by inactivating p38, AKT, ERK1/2, and NF-κB pathways.

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.

Protective effects of anti-HMGB1 monoclonal antibody on lung ischemia reperfusion injury in mice

During ischemia reperfusion (IR) injury, high mobility group box 1 (HMGB1), a chromatin binding protein, is released from necrotic cells and triggers inflammatory responses. We assessed the therapeutic effect of a neutralizing anti-HMGB1 monoclonal antibody (mAb) on lung IR injury. A murine hilar clamp model of IR was used, where mice were divided into sham and IR groups with intravenous administration of anti-HMGB 1 mAb or control mAb. We analyzed the effect of anti-HMGB1 mAb against IR injury by assessing lung oxygenation, lung injury score, neutrophil infiltration, expression of proinflammatory cytokines and chemokines, levels of mitogen-activated protein kinase (MAPK) signaling, and measurement of apoptotic cells. Anti-HMGB1 mAb significantly decreased the plasma level of HMGB1 elevated by IR. The severity of IR injury represented by oxygenation capacity, lung injury score, and neutrophil infiltration was significantly improved by anti-HMGB1 mAb treatment. The expression of proinflammatory factors, including IL-1β, IL-6, IL-12, TNF-α, CXCL-1, and CXCL-2, and phosphorylation of p38 MAPK were both significantly reduced by anti-HMGB1 mAb treatment. Furthermore, anti-HMGB1 mAb treatment suppressed apoptosis, as determined through TUNEL assays. Overall, anti-HMGB1 mAb ameliorated lung IR injury by reducing inflammatory responses and apoptosis. Our findings indicate that anti-HMGB1 mAb has potential for use as a therapeutic to improve IR injury symptoms during lung transplantation.

Static lung storage at 10°C maintains mitochondrial health and preserves donor organ function

[Figure: see text].

Pilot Trial of Extended Hypothermic Lung Preservation to Analyze Ischemia-reperfusion Injury in Pigs

BACKGROUND

In lung transplantation (LT), the length of ischemia time is controversial as it was arbitrarily stablished. We ought to explore the impact of extended cold-ischemia time (CIT) on ischemia-reperfusion injury in an experimental model.

METHODS

Experimental, randomized pilot trial of parallel groups and final blind analysis using a swine model of LT. Donor animals (n=8) were submitted to organ procurement. Lungs were subjected to 6h (n=4) or 12h (n=4) aerobic hypothermic preservation. The left lung was transplanted and re-perfused for 4h. Lung biopsies were obtained at (i) the beginning of CIT, (ii) the end of CIT, (iii) 30min after reperfusion, and (iv) 4h after reperfusion. Lung-grafts were histologically assessed by microscopic lung injury score and wet-to-dry ratio. Inflammatory response was measured by determination of inflammatory cytokines. Caspase-3 activity was determined as apoptosis marker.

RESULTS

We observed no differences on lung injury score or wet-to-dry ratio any given time between lungs subjected to 6h-CIT or 12h-CIT. IL-1β and IL6 showed an upward trend during reperfusion in both groups. TNF-α was peaked within 30min of reperfusion. IFN-γ was hardly detected. Caspase-3 immunoexpression was graded semiquantitatively by the percentage of stained cells. Twenty percent of apoptotic cells were observed 30min after reperfusion.

CONCLUSIONS

We observed that 6 and 12h of CIT were equivalent in terms of microscopic lung injury, inflammatory profile and apoptosis in a LT swine model. The extent of lung injury measured by microscopic lung injury score, proinflammatory cytokines and caspase-3 determination was mild.

Innate immunity in lung transplantation

Innate immune pathways early after pulmonary transplantation have been shown to cause primary graft dysfunction (PGD) and also predispose to late graft failure. Recent studies in animal models have elucidated critical mechanisms governing such innate immune responses. Here, we discuss pathways of inflammatory cell death, triggers for sterile and infectious inflammation, and signaling cascades that mediate lung injury early after transplantation. These studies highlight potential avenues for lung-specific therapies early following lung transplantation to dampen innate immune responses and improve outcomes.

Effect of Intravenous Lidocaine on Inflammatory and Apoptotic Response of Ischemia-Reperfusion Injury in Pigs Undergoing Lung Resection Surgery

Background

Ischemia-reperfusion injury is one of the most critical phenomena in lung transplantation and causes primary graft failure. Its pathophysiology remains incompletely understood, although the inflammatory response and apoptosis play key roles. Lidocaine has anti-inflammatory properties. The aim of this research is to evaluate the effect of intravenous lidocaine on the inflammatory and apoptotic responses in lung ischemia-reperfusion injury.

Methods

We studied the histological and immunohistochemical changes in an experimental model of lung transplantation in pigs. Twelve pigs underwent left pneumonectomy, cranial lobectomy, caudal lobe reimplantation, and 60 minutes of graft reperfusion. Six of the pigs made up the control group, while six other pigs received 1.5 mg/kg of intravenous lidocaine after induction and a 1.5 mg/kg/h intravenous lidocaine infusion during surgery. In addition, six more pigs underwent simulated surgery. Lung biopsies were collected from the left caudal lobe 60 minutes after reperfusion. We conducted a double study on these biopsies and assessed the degree of inflammation, predominant cell type (monocyte-macrophage, lymphocytes, or polymorphous), the degree of congestion, and tissue edema by hematoxylin and eosin stain. We also conducted an immunohistochemical analysis with antibodies against CD68 antigens, monocyte chemoattractant protein-1 (MCP-1), Bcl-2, and caspase-9.

Results

The lungs subjected to ischemia-reperfusion injury exhibited a higher degree of inflammatory infiltration. The predominant cell type was monocyte-macrophage cells. Both findings were mitigated by intravenous lidocaine administration. Immunohistochemical detection of anti-CD68 and anti-MCP-1 showed higher infiltration in the lungs subjected to ischemia-reperfusion injury, while intravenous lidocaine decreased the expression. Ischemia-reperfusion induced apoptotic changes and decreased Bcl-2 expression. The group treated with lidocaine showed an increased number of Bcl-2-positive cells. No differences were observed in caspase-9 expression.

Conclusions

In our animal model, intravenous lidocaine was associated with an attenuation of the histological markers of lung damage in the early stages of reperfusion.

Atelectasis in primary graft dysfunction survivors after lung transplantation

BACKGROUND

Primary graft dysfunction (PGD) is an important contributor to early mortality in lung transplant recipients and is associated with impaired lung function. The radiographic sequelae of PGD on computed tomography (CT) have not been characterized.

METHODS

We studied adult double lung transplant recipients from 2010 to 2016 for whom protocol 3-month post-transplant CT scans were available. We assessed CTs for changes including pleural effusions, ground glass opacification, atelectasis, centrilobular nodularity, consolidation, interlobular septal thickening, air trapping and fibrosis, and their relationship to prior post-transplant PGD, future lung function, post-transplant baseline lung allograft dysfunction (BLAD), and chronic lung allograft dysfunction (CLAD).

RESULTS

Of 237 patients studied, 50 (21%) developed grade 3 PGD (PGD3) at 48 or 72 h. PGD3 was associated with increased interlobular septal thickening (p = .0389) and atelectasis (p = .0001) at 3 months, but only atelectasis remained associated after correction for multiple testing. Atelectasis severity was associated with lower peak forced expiratory volume in 1 s (FEV1) and increased risk of BLAD (p = .0014) but not with future CLAD onset (p = .7789).

CONCLUSIONS

Severe PGD was associated with atelectasis on 3-month post-transplant CT in our cohort. Atelectasis on routine CT may be an intermediary identifiable stage between PGD and future poor lung function.

Inflammatory responses in lungs from donation after brain death: Mechanisms and potential therapeutic targets

The vast majority of lungs used in clinical transplantation are donated after brain death (DBD). The utilization of DBD lungs is low due to brain death-induced lung injury. Moreover, inflammatory responses in DBD lungs used for transplantation contribute to ischemia-reperfusion injury and primary graft dysfunction. Work from human observational studies has demonstrated overexpression of cytokines, activation of endothelial cells, and cell death in DBD lungs, are associated with the activation of signaling pathways. Animal models have characterized the pulmonary injury induced by brain death and identified potential strategies to improve donor management. Interestingly, transcriptomic studies comparing DBD and donated after circulatory death (DCD) lungs have found that inflammatory responses are elevated in DBD lungs, while cell death pathways are elevated in DCD lungs. Development of the ex vivo lung perfusion technique, has made it possible to assess donor lungs using inflammation and cell death biomarkers. In the future, identification of potential therapeutic targets and development of novel treatments strategies may allow for lung repair during EVLP prior to transplantation.

Pilot Trial of Extended Hypothermic Lung Preservation to Analyze Ischemia-reperfusion Injury in Pigs

BACKGROUND

In lung transplantation (LT), the length of ischemia time is controversial as it was arbitrarily stablished. We ought to explore the impact of extended cold-ischemia time (CIT) on ischemia-reperfusion injury in an experimental model.

METHODS

Experimental, randomized pilot trial of parallel groups and final blind analysis using a swine model of LT. Donor animals (n=8) were submitted to organ procurement. Lungs were subjected to 6h (n=4) or 12h (n=4) aerobic hypothermic preservation. The left lung was transplanted and re-perfused for 4h. Lung biopsies were obtained at (i) the beginning of CIT, (ii) the end of CIT, (iii) 30min after reperfusion, and (iv) 4h after reperfusion. Lung-grafts were histologically assessed by microscopic lung injury score and wet-to-dry ratio. Inflammatory response was measured by determination of inflammatory cytokines. Caspase-3 activity was determined as apoptosis marker.

RESULTS

We observed no differences on lung injury score or wet-to-dry ratio any given time between lungs subjected to 6h-CIT or 12h-CIT. IL-1β and IL6 showed an upward trend during reperfusion in both groups. TNF-α was peaked within 30min of reperfusion. IFN-γ was hardly detected. Caspase-3 immunoexpression was graded semiquantitatively by the percentage of stained cells. Twenty percent of apoptotic cells were observed 30min after reperfusion.

CONCLUSIONS

We observed that 6 and 12h of CIT were equivalent in terms of microscopic lung injury, inflammatory profile and apoptosis in a LT swine model. The extent of lung injury measured by microscopic lung injury score, proinflammatory cytokines and caspase-3 determination was mild.

The Effects of Volatile Anesthetics on Lung Ischemia-Reperfusion Injury: Basic to Clinical Studies

Case reports from as early as the 1970s have shown that intravenous injection of even a small dose of volatile anesthetics result in fatal lung injury. Direct contact between volatile anesthetics and pulmonary vasculature triggers chemical damage in the vessel walls. A wide variety of factors are involved in lung ischemia-reperfusion injury (LIRI), such as pulmonary endothelial cells, alveolar epithelial cells, alveolar macrophages, neutrophils, mast cells, platelets, proinflammatory cytokines, and surfactant. With a constellation of factors involved, the assessment of the protective effect of volatile anesthetics in LIRI is difficult. Multiple animal studies have reported that with regards to LIRI, sevoflurane demonstrates an anti-inflammatory effect in immunocompetent cells and an anti-apoptotic effect on lung tissue. Scattered studies have dismissed a protective effect of desflurane against LIRI. While a single-center randomized controlled trial (RCT) found that volatile anesthetics including desflurane demonstrated a lung-protective effect in thoracic surgery, a multicenter RCT did not demonstrate a lung-protective effect of desflurane. LIRI is common in lung transplantation. One study, although limited due to its small sample size, found that the use of volatile anesthetics in organ procurement surgery involving "death by neurologic criteria" donors did not improve lung graft survival. Future studies on the protective effect of volatile anesthetics against LIRI must examine not only the mechanism of the protective effect but also differences in the effects of different types of volatile anesthetics, their optimal dosage, and the appropriateness of their use in the event of marked alveolar capillary barrier damage.

Inhibition of ACSL4 attenuates ferroptotic damage after pulmonary ischemia-reperfusion

Lung ischemia-reperfusion (IR) injury is a common clinical pathology associated with high mortality. Ferroptosis, a novel mode of cell death elicited by iron-dependent phospholipid peroxidation, has been implicated in ischemic events. Acyl-CoA synthetase long-chain family member 4 (ACSL4) is one of the main enzymes in pro-ferroptotic lipid metabolism. In this study, the involvement of ferroptotic death in different durations of reperfusion was evaluated by assessing the iron content, malondialdehyde, and glutathione levels, ferroptosis-related protein expression, and mitochondria morphology. The roles of ferroptosis-specific inhibitor, liproxastin-1 (Lip-1), and ACSL4 modulation in a preventive regimen were assessed in vivo and in vitro. The hallmarks of pulmonary function, such as histological lung injury score, wet/dry ratio, and oxygenation index, were evaluated as well. Results showed that lung IR increased the tissue iron content and lipid peroxidation accumulation, along with key protein (GPX4 and ACSL4) expression alteration during reperfusion. Pretreatment with Lip-1 inhibited ferroptosis and ameliorated lung IR-induced injury in animal and cell models. In addition, administering ACSL4 inhibitor rosiglitazone before ischemia diminished the ferroptotic damage in IR-injured lung tissue, consistent with the protective effect of ACSL4 knockdown on lung epithelial cells subjected to hypoxia/reoxygenation. Thus, this study delineated that IR-induced ferroptotic cell death in lung tissue and ACSL4 were correlated with this process. Inhibition of ferroptosis and ACSL4 mitigated the ferroptotic damage in IR-induced lung injury by reducing lipid peroxidation and increasing the glutathione and GPX4 levels.

Protective effects of hydrogen inhalation during the warm ischemia phase against lung ischemia-reperfusion injury in rat donors after cardiac death

BACKGROUND

Successful amelioration of long-term warm ischemia lung injury in donors after cardiac death (DCDs) can remarkably improve outcomes. Hydrogen gas provides potent anti-inflammatory and antioxidant effects against ischemia-reperfusion injury (IRI). This study observed the effects of hydrogen inhalation on lung grafts during the warm ischemia phase in cardiac death donors.

METHODS

After cardiac death, rat donor lungs (n = 8) underwent mechanical ventilation with 40% oxygen plus 60% nitrogen (control group) or 3% hydrogen and 40% oxygen plus 57% nitrogen (hydrogen group) for 2 h during the warm ischemia phase in situ. Then, lung transplantation was performed after 2 h of cold storage and 3 h of recipient reperfusion prior to lung graft assessment. Rats that underwent left thoracotomy without transplantation served as the sham group (n = 8). The results of static compliance and arterial blood gas analysis were assessed in the recipients. The wet-to-dry weight ratio (W/D), inflammation, oxidative stress, cell apoptosis and histologic changes were evaluated after 3 h of reperfusion. Nuclear factor kappa B (NF-κB) protein expression in the graft was analyzed by Western blotting.

RESULTS

Compared with the sham group, lung function, W/D, inflammatory reaction, oxidative stress and histological changes were decreased in both transplant groups (control and hydrogen groups). However, compared with the control group, exposure to 3% hydrogen significantly improved lung graft static compliance and oxygenation and remarkably decreased the wet-to-dry weight ratio, inflammatory reactions, and lipid peroxidation. Furthermore, hydrogen improved the lung graft histological changes, decreased the lung injury score and apoptotic index and reduced NF-κB nuclear accumulation in the lung grafts.

CONCLUSION

Lung inhalation with 3% hydrogen during the warm ischemia phase attenuated lung graft IRI via NF-κB-dependent anti-inflammatory and antioxidative effects in rat donors after cardiac death.

Involvement of pulmonary arteriopathy in the development and severity of reperfusion pulmonary edema after pulmonary endarterectomy

Reperfusion pulmonary edema (RPE) is a common complication after pulmonary endarterectomy (PEA) in patients with chronic thromboembolic pulmonary hypertension (CTEPH). However, the precise mechanisms underlying the development of RPE remain unclear. To evaluate the effects of pulmonary vasculopathy on RPE, the severity of the pulmonary arteriopathies and venopathies of lung tissues biopsied during PEA were pathologically quantified in 33 CTEPH patients. The severity of RPE was classified from grade 0 (no RPE) to 4 (death due to RPE) based on the arterial oxygen tension/inspiratory oxygen fraction (P/F ratio) and necessity of respiratory management. Among the 33 patients (27 women; mean age = 63.3 years), 17 (51.5%) patients developed RPE. The severity of pulmonary arteriopathy (obstruction ratio) correlated with the grade of RPE (r = 0.576, P = 0.0005). The obstruction ratio also correlated with the P/F ratio (r = −0.543, P = 0.001) and the perioperative mean pulmonary arterial pressure (r = 0.445, P = 0.009). Multivariate logistic regression analysis revealed that the obstruction ratio was a significant independent determinant for the development of RPE (odds ratio = 15.7; 95% confidence interval = 2.29–108.00, P = 0.005). In conclusion, pulmonary arteriopathy could be a determinant of the development and severity of RPE after PEA.

The protective effects of heat shock protein 22 in lung ischemia-reperfusion injury mice

Lung ischemia-reperfusion injury (LIRI) often results in respiratory insufficiency after pulmonary embolism, lung transplantation, etc. To investigate the role of HSP22 in LIRI mice, ischemia-reperfusion injury was established in the left lung of an HSP22 overexpression transgenic mouse. Twelve HSP22 transgenic (TG) mice and twelve wild-type (WT) mice were randomly divided into 2 groups: the sham-operated group (SO: TG-SO, WT-SO) and the ischemia-reperfusion group (I/R: TG-I/R, WT-I/R), respectively. We tested the PaO₂, W/D ratio, and MDA level; observed morphology changes; and calculated the index of alveolar damage. HSP22 expression was examined in lung tissues of TG and WT C57BL mice by immunohistochemistry. TUNEL assay was performed to measure apoptosis. We found that HSP22 was significantly overexpressed in TG mice. There was no difference in PaO₂ among the four groups. In the I/R group, the W/D ratio, MDA and index of alveolar damage were higher than those in the SO group. Moreover, compared with WT-I/R group, the W/D ratio, MDA and index of alveolar damage in the TG-I/R group were significantly decreased. Apoptosis in the I/R groups was increased compared to that in the SO groups, while apoptosis in the TG-I/R groups was decreased compared to that in the WT-I/R groups. Our results showed that HSP22 TG mice and the LIRI model were successfully established. In addition, HSP22 overexpression has protective effects on LIRI by inhibiting lipid peroxidation and apoptosis.

Cellular and acellular ex vivo lung perfusion preserve functional lung ultrastructure in a large animal model: a stereological study

Background

Ex vivo lung perfusion (EVLP) is used by an increasing number of transplant centres. It is still controversial whether an acellular or cellular (erythrocyte enriched) perfusate is preferable. The aim of this paper was to evaluate whether acellular (aEVLP) or cellular EVLP (cEVLP) preserves functional lung ultrastructure better and to generate a hypothesis regarding possible underlying mechanisms.

Methods

Lungs of 20 pigs were assigned to 4 groups: control, ischaemia (24 h), aEVLP and cEVLP (both EVLP groups: 24 h ischaemia + 12 h EVLP). After experimental procedures, whole lungs were perfusion fixed, samples for light and electron microscopic stereology were taken, and ventilation, diffusion and perfusion related parameters were estimated.

Results

Lung structure was well preserved in all groups. Lungs had less atelectasis and higher air content after EVLP. No significant group differences were found in alveolar septum composition or blood-air barrier thickness. Small amounts of intraalveolar oedema were detected in both EVLP groups but significantly more in aEVLP than in cEVLP.

Conclusions

Both EVLP protocols supported lungs well for up to 12 h and could largely prevent ischaemia ex vivo reperfusion associated lung injury. In both EVLP groups, oedema volume remained below the level of functional relevance. The group difference in oedema formation was possibly due to inferior septal perfusion in aEVLP.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0942-5) contains supplementary material, which is available to authorized users.

Pluripotent Stem Cell-Derived Cardiomyocytes as a Platform for Cell Therapy Applications: Progress and Hurdles for Clinical Translation

Cardiovascular diseases are the leading cause of morbidity and mortality worldwide. Regenerative therapy has been applied to restore lost cardiac muscle and cardiac performance. Induced pluripotent stem cells (iPSCs) can provide an unlimited source of cardiomyocytes and therefore play a key role in cardiac regeneration. Despite initial encouraging results from pre-clinical studies, progress toward clinical applications has been hampered by issues such as tumorigenesis, arrhythmogenesis, immune rejection, scalability, low graft-cell survival, and poor engraftment. Here, we review recent developments in iPSC research on regenerating injured heart tissue, including novel advances in cell therapy and potential strategies to overcome current obstacles in the field.

Inhibition of regulated necrosis attenuates receptor-interacting protein kinase 1-mediated ischemia-reperfusion injury after lung transplantation

BACKGROUND

Increasing evidence indicates that regulated necrosis plays a critical role during cell death caused by ischemia-reperfusion (IR) injury. Necroptosis is one form of regulated necrosis. Necrostatin-1 (Nec-1), an inhibitor of receptor-interacting protein kinase 1 (RIPK1), is known to reduce necroptosis. We investigated the effect of Nec-1 treatment on IR-induced lung injury in a rat lung transplant model.

METHODS

Lewis rats were divided into 4 groups (n = 6 each): (1) Control (no treatment), (2) Donor treatment (D), (3) Recipient treatment (R), and (4) Donor plus Recipient treatment (D+R) groups. Donor lungs were flushed and preserved for 18 hours at 4ºC before transplantation. Recipient animals underwent a left single lung transplant. After 2 hours of reperfusion, we assessed the physiologic function, cytokine expression, pathway activation, and the extent of necrosis.

RESULTS

Pulmonary gas exchange in D+R group was significantly better than in the other 3 groups (p = 0.003). Lung edema was significantly lower in the D+R group compared with the Control group (p = 0.006). The expression of interleukin-6 in lung tissue and plasma was significantly reduced in the D+R group compared with the Control group (p = 0.036). The percentage of necrotic cells in D+R group was significantly lower than in the Control and D groups (p = 0.01), indicating Nec-1inhibited regulated necrosis.

CONCLUSIONS

The administration of Nec-1 to both donor and recipient improved graft function after lung transplantation through the reduction of necroptosis. The inhibition of regulated necrosis appears to be a promising strategy to attenuate IR lung injury after lung transplantation.

Association between ACE2/ACE balance and pneumocyte apoptosis in a porcine model of acute pulmonary thromboembolism with cardiac arrest

Acute pulmonary embolism (APE) is frequently reported in patients with cardiac arrest (CA) in emergency care. Pneumocyte apoptosis is commonly observed in the lungs following an APE. An important pathological mechanism evoking apoptosis during a lipopolysaccharide-induced acute lung injury is the angiotensin-converting enzyme 2 (ACE2)/ACE imbalance. The present study uses a porcine model to examine the anti-apoptotic effects of captopril on APE-CA and the return of spontaneous circulation (ROSC). Pigs were randomly assigned into four groups: Control, APE-CA, ROSC-saline, and ROSC-captopril. Surviving pigs were euthanized at 6 h and lungs were isolated for analysis using several biochemical assays. Compared with the control group, the ACE2/ACE ratio was lower in the APE-CA and ROSC pigs. In addition, APE-CA pigs had higher Bcl-2-associated X protein (Bax) and cleaved caspase-3 levels, and lower B-cell lymphoma-2 (Bcl-2) level compared to control pigs. Captopril treatment reduced lung apoptosis, as demonstrated by lower TUNEL-positive cells, higher Bcl-2, and lower cleaved caspase-3 protein levels in the lung. Notably, the ACE2/ACE ratio was positively correlated with Bcl-2 protein levels and Bcl-2/Bax ratio. In conclusion, captopril has a protective effect against lung apoptosis following ROSC and that maintaining the balance of the ACE2/ACE axis is important for inhibiting pulmonary apoptosis during APE.

Stereological assessment of the blood-air barrier and the surfactant system after mesenchymal stem cell pretreatment in a porcine non-heart-beating donor model for lung transplantation

More frequent utilization of non-heart-beating donor (NHBD) organs for lung transplantation has the potential to relieve the shortage of donor organs. In particular with respect to uncontrolled NHBD, concerns exist regarding the risk of ischaemia/reperfusion (IR) injury-related graft damage or dysfunction. Due to their immunomodulating and tissue-remodelling properties, bone-marrow-derived mesenchymal stem cells (MSCs) have been suspected of playing a beneficial role regarding short- and long-term survival and function of the allograft. Thus, MSC administration might represent a promising pretreatment strategy for NHBD organs. To study the initial effects of warm ischaemia and MSC application, a large animal lung transplantation model was generated, and the structural organ composition of the transplanted lungs was analysed stereologically with particular respect to the blood-gas barrier and the surfactant system. In this study, porcine lungs (n = 5/group) were analysed. Group 1 was the sham-operated control group. In pigs of groups 2-4, cardiac arrest was induced, followed by a period of 3 h of ventilated ischaemia at room temperature. In groups 3 and 4, 50 × 10⁶ MSCs were administered intravascularly via the pulmonary artery and endobronchially, respectively, during the last 10 min of ischaemia. The left lungs were transplanted, followed by a reperfusion period of 4 h. Then, lungs were perfusion-fixed and processed for light and electron microscopy. Samples were analysed stereologically for IR injury-related structural parameters, including volume densities and absolute volumes of parenchyma components, alveolar septum components, intra-alveolar oedema, and the intracellular and intra-alveolar surfactant pool. Additionally, the volume-weighted mean volume of lamellar bodies (lbs) and their profile size distribution were determined. Three hours of ventilated warm ischaemia was tolerated without eliciting histological or ultrastructural signs of IR injury, as revealed by qualitative and quantitative assessment. However, warm ischaemia influenced the surfactant system. The volume-weighted mean volume of lbs was reduced significantly (P = 0.024) in groups subjected to ischaemia (group medians of groups 2-4: 0.180-0.373 μm³) compared with the sham control group (median 0.814 μm³). This was due to a lower number of large lb profiles (size classes 5-15). In contrast, the intra-alveolar surfactant system was not altered significantly. No significant differences were encountered comparing ischaemia alone (group 2) or ischaemia plus application of MSCs (groups 3 and 4) in this short-term model.

Pro-Regenerative Hydrogel Restores Scarless Skin during Cutaneous Wound Healing

The transformation of fibrotic healing process to regenerative one has great potential to fully restore wounded skin. The M2 macrophage phenotype promotes constructive tissue remodeling and instructs tissue repair in a regenerative manner. It is hypothesized that hydrogels that can establish robustness of endogenous cells to regulate M2 phenotype will promote constructive dermal remodeling. Toward this end, a series of dextran-based bioabsorbable hydrogels are developed and self-crosslinkable dextran-isocyanatoethyl methacrylate-ethylamine (DexIEME) is identified as the potential scaffold. The initial screening study revealed that DexIEME has superior biocompatibility in varying concentrations. Although DexIEME brings about low proinflammatory responses, it promotes M2 macrophage phenotype. Then the optimized hydrogel formulation is tested for acute skin injuries using both murine and porcine models. Preliminary data demonstrated that the innovative DexIEME hydrogel promotes complete skin regeneration with hair regrowth on pre-existing scars, while untreated scars remain intact. Preclinical studies further demonstrated that the DexIEME hydrogel regenerated perfect skin during deep porcine wound healing. Overall, the approach to investigate immune-modulated hydrogels yields pro-regenerative DexIEME hydrogel, which may lead to greater clinical success in treating deep dermal injury and attenuating scar formation.

Role of autophagy and its signaling pathways in ischemia/reperfusion injury

This study was conducted to investigate the mechanism of autophagy and its signaling pathways in ischemia/reperfusion injury (IRI). Pulmonary microvascular endothelial cells (PMVECs) were used to construct I/R models. The cells were then treated with autophagy inhibitor 3-MA and infected with adenovirus expressing Beclin 1-shRNA. The expression of CD31, LC3-II, Bcl-2, Bax, LC3-II, Beclin 1, AKT, p-AKT, AMPK and p-AMPK, apoptosis, cell viability and migration ability were determined. Over 95% isolated PMVECs were positive for CD31. The expression of LC3-II and Beclin 1 was up-regulated in I/R cells. 3-MA and Beclin 1 knockdown inhibited the expression of LC3-II and Beclin 1 and autophagosome formation. Autophagy induced by hypoxia was antagonistic against apoptosis, which increased after treatment with 3-MA and knockdown of Beclin 1. 3-MA and Beclin 1 knockdown downregulated and upregulated the expression of Bcl-2 and Bax, respectively. Apoptosis mediated by hypoxia and reperfusion-induced autophagy was reduced by 3-MA and Beclin-1 knockdown, which increased and reduced the expression of Bcl-2 and Bax, respectively, leading to significant decreased Bax/Bcl-2 ratio. In these cells, expression of p-AKT, p-AMPK and p-mTOR was up-regulated. After treatment with 3-MA and Beclin 1 knockdown, expression of p-AKT and p-AMPK was significantly reduced.

Anesthesia for Lung Transplantation

Perioperative management of patients undergoing lung transplantation is challenging and requires constant communication among the surgical, anesthesia, perfusion, and nursing teams. Although all aspects of anesthetic management are important, certain intraoperative strategies (mechanical ventilation, fluid management, extracorporeal mechanical support deployment) have tremendous impact on the subsequent evolution of the lung transplant recipient, especially with respect to allograft function, and should be carefully considered. This review highlights some of the intraoperative anesthetic challenges and opportunities during lung transplantation.

Higher M30 and high mobility group box 1 protein levels in ex vivo lung perfusate are associated with primary graft dysfunction after human lung transplantation

BACKGROUND

Ex vivo lung perfusion (EVLP) enables assessment of marginal donor lungs for transplantation, with similar clinical outcomes to conventional lung transplantation. We investigated whether cell death-related proteins in the EVLP perfusate could predict primary graft dysfunction (PGD) after transplantation.

METHODS

M30 (indicating epithelial apoptosis), M65 (indicating total epithelial cell death), and high mobility group box 1 (HMGB-1, related to cell death and inflammation) protein levels in EVLP perfusate were measured by enzyme-linked immunosorbent assay and correlated with clinical outcomes.

RESULTS

From 100 sequential EVLP patients, 79 lungs were transplanted. Patients who were bridged with extracorporeal life support (ECLS, n = 6) or who received lobar/single lung (n = 25) were excluded. PGD grade 3 (partial pressure of arterial oxygen/fraction of inspired oxygen <200 or need for ECLS) developed in 11 at any time within 72 hours after transplantation (PGD Group). PGD grade 3 did not develop in 34 patients (Control Group). M30 was significantly higher in the PGD Group than in the Control Group at 1 hour (PGD: 73.3 ± 24.9, control: 53.9 ± 15.9 U/liter; p < 0.01) and at 4 hours (PGD: 137.0 ± 146.6, Control: 72.4 ± 40.0 U/liter; p = 0.046) of EVLP. The increase of HMGB-1 from 1 to 4 hours of EVLP was significantly greater in the PGD Group (PGD: 37.0 ± 25.4, Control: 7.2 ± 16.8 ng/ml; p < 0.001). Higher levels of or a greater increase in M30 and a greater increase in HMGB-1 were associated with higher mortality in Cox regression.

CONCLUSIONS

Levels of M30 and HMGB-1 in the EVLP perfusate correlate with PGD after lung transplantation and might therefore be useful biomarkers to improve donor lung assessment during EVLP.

Alda-1 Attenuates Lung Ischemia-Reperfusion Injury by Reducing 4-Hydroxy-2-Nonenal in Alveolar Epithelial Cells

OBJECTIVES

Excessive oxidative stress is a main cause of lung ischemia-reperfusion injury, which often results in respiratory insufficiency after open-heart surgery for a cardiopulmonary bypass. Previous studies demonstrate that the activation of aldehyde dehydrogenase-2 could significantly reduce the oxidative stress mediated by toxic aldehydes and attenuate cardiac and cerebral ischemia-reperfusion injury. However, both the involvement of aldehydes and the protective effect of the aldehyde dehydrogenase-2 agonist, Alda-1, in lung ischemia-reperfusion injury remain unknown.

DESIGN

Prospective laboratory and animal investigation were conducted.

SETTING

State Key Laboratory of Cardiovascular Disease.

SUBJECTS

Primary human pulmonary alveolar epithelial cells, human pulmonary microvascular endothelial cells, and Sprague-Dawley rats.

INTERVENTIONS

A hypoxia/reoxygenation cell-culture model of human pulmonary alveolar epithelial cell, human pulmonary microvascular endothelial cell, and an isolated-perfused lung model were applied to mimic lung ischemia-reperfusion injury. We evaluated the effects of Alda-1 on aldehyde dehydrogenase-2 quantity and activity, on aldehyde levels and pulmonary protection.

MEASUREMENTS AND MAIN RESULTS

We have demonstrated that ischemia-reperfusion-induced pulmonary injury concomitantly induced aldehydes accumulation in human pulmonary alveolar epithelial cells and lung tissues, but not in human pulmonary microvascular endothelial cells. Moreover, Alda-1 pretreatment significantly elevated aldehyde dehydrogenase-2 activity, increased surfactant-associated protein C, and attenuated elevation of 4-hydroxy-2-nonenal, apoptosis, intercellular adhesion molecule-1, inflammatory response, and the permeability of pulmonary alveolar capillary barrier, thus alleviated injury.

CONCLUSIONS

Our study indicates that the accumulation of 4-hydroxy-2-nonenal plays an important role in lung ischemia-reperfusion injury. Alda-1 pretreatment can attenuate lung ischemia-reperfusion injury, possibly through the activation of aldehyde dehydrogenase-2, which in turn removes 4-hydroxy-2-nonenal in human pulmonary alveolar epithelial cells. Alda-1 pretreatment has clinical implications to protect lungs during cardiopulmonary bypass.

The role of autophagy in lung ischemia/reperfusion injury after lung transplantation in rats

BACKGROUND

The aim of this study was to explore the role of autophagy in the cold I/R injury following lung transplantation.

METHODS

The rat orthotopic lung transplantation model was established to perform the level of autophagy in the cold I/R injury in this study. The pretreatment of inhibitor (3-Methyladenine [3-MA]) and activator (rapamycin [RAPA]) of autophagy were performed to assess the role of autophagy in the cold I/R injury following lung transplantation in rats.

RESULTS

After lung transplantation, the autophagy, lung cell apoptosis and lung injury were aggravated and peaked at 6 h following the transplantation. The inhibition of autophagy by 3-MA induced downregulated of autophagy, decreased cell apoptosis. Meanwhile, the lung injury, which was indicated by calculating the peak inspiratory pressure (PIP), pulmonary vein blood gas analysis (PO2) and ratio of wet to dry in lung (W/D), was ameliorated after treatment with 3-MA. The activation of autophagy by RAPA causing the upregulated of autophagy and apoptosis of lung cells, and enhanced the lung injury.

CONCLUSION

All the results suggested that the autophagy was involved in the cold I/R injury in lung transplantation model, and played a potential role on the regulation of I/R injury after lung transplantation.

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.

Annexin V homodimer protects against ischemia reperfusion-induced acute lung injury in lung transplantation

OBJECTIVE

We hypothesized that administration of a homodimer of recombinant annexin V, diannexin, could shield phosphatidylserine on the endothelium, and inhibit leukocyte and platelet adhesion, thereby potentially reducing ischemia reperfusion injury (IRI) in lung transplantation. This hypothesis was tested using a rat syngeneic single left-lung transplant model.

METHODS

Rats were randomly assigned to receive diannexin (DN group; n = 10) or normal saline (control group; n = 10). Diannexin (1000 μg/kg) was administered to the donor lung in the pulmonary flush solution, and to the recipient intravenously, 5 minutes after initiation of reperfusion. Grafts were reperfused for 2 hours.

RESULTS

The transplanted grafts in the DN group performed significantly better in gas exchange with higher partial pressure of oxygen (control group: 179 ± 121 vs DN group: 330 ± 54 mm Hg; P = .007) and lower partial pressure of carbon dioxide (control: 55.1 ± 26 vs DN: 34.2 ± 11 mm Hg; P = .04), as well as lower peak airway pressure (control: 20.5 ± 8.5 vs DN: 12.0 ± 7.9 cm H2O; P = .035) after 2 hours of reperfusion. Wet-to-dry lung weight ratio (P = .054), and alveolar fibrin deposition score (P = .04), were reduced in the DN group. Caspase-cleaved cytokeratin 18 in plasma (a marker of epithelial apoptosis) was significantly reduced in the DN group (P = .013). Furthermore, gene-expression levels of proinflammatory cytokines in the transplanted graft, including interleukin-6 (P = .04) and macrophage inflammatory protein 2 (P = .03) were significantly decreased in the DN group.

CONCLUSIONS

A homodimer of recombinant annexin V reduced ischemia reperfusion injury in a lung transplant animal model, by reducing cell death and tissue inflammation.

Therapeutic lymphangiogenesis ameliorates established acute lung allograft rejection

Lung transplantation is the only viable option for patients suffering from otherwise incurable end-stage pulmonary diseases such as chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis. Despite aggressive immunosuppression, acute rejection of the lung allograft occurs in over half of transplant recipients, and the factors that promote lung acceptance are poorly understood. The contribution of lymphatic vessels to transplant pathophysiology remains controversial, and data that directly address the exact roles of lymphatic vessels in lung allograft function and survival are limited. Here, we have shown that there is a marked decline in the density of lymphatic vessels, accompanied by accumulation of low-MW hyaluronan (HA) in mouse orthotopic allografts undergoing rejection. We found that stimulation of lymphangiogenesis with VEGF-C156S, a mutant form of VEGF-C with selective VEGFR-3 binding, alleviates an established rejection response and improves clearance of HA from the lung allograft. Longitudinal analysis of transbronchial biopsies from human lung transplant recipients demonstrated an association between resolution of acute lung rejection and decreased HA in the graft tissue. Taken together, these results indicate that lymphatic vessel formation after lung transplantation mediates HA drainage and suggest that treatments to stimulate lymphangiogenesis have promise for improving graft outcomes.

Alternative solution for ex vivo lung perfusion, experimental study on donated human lungs non-accepted for transplantation

PURPOSE

To evaluate a new perfusate solution to be used for ex vivo lung perfusion.

METHODS

Randomized experimental study using lungs from rejected brain-dead donors harvested and submitted to 1 hour of ex vivo lung perfusion (EVLP) using mainstream solution or the alternative.

RESULTS

From 16 lungs blocs tested, we found no difference on weight after EVLP: Steen group (SG) = 1,097±526g; Alternative Perfusion Solution (APS) = 743±248g, p=0.163. Edema formation, assessed by Wet/dry weigh ratio, was statistically higher on the Alternative Perfusion Solution group (APS = 3.63 ± 1.26; SG = 2.06 ± 0.28; p = 0.009). No difference on PaO2 after EVLP (SG = 498±37.53mmHg; APS = 521±55.43mmHg, p=0.348, nor on histological analyses: pulmonary injury score: SG = 4.38±1.51; APS = 4.50±1.77, p=0.881; apoptotic cells count after perfusion: SG = 2.4 ± 2.0 cells/mm2; APS = 4.8 ± 6.9 cells/mm2; p = 0.361).

CONCLUSION

The ex vivo lung perfusion using the alternative perfusion solution showed no functional or histological differences, except for a higher edema formation, from the EVLP using Steen Solution(r) on lungs from rejected brain-dead donors.

Geranylgeranylacetone ameliorates lung ischemia/reperfusion injury by HSP70 and thioredoxin redox system: NF-kB pathway involved

Geranylgeranylacetone (GGA) has been clinically used as an anti-ulcer drug. In the present study, we explored the protective effects of GGA on lung ischemia/reperfusion injury (IRI) and the underlying mechanism. The results demonstrated that GGA ameliorated the lung biochemical and histological alterations induced by IRI, which was reversed by HSP70 inhibition. To further explore the mechanism of GGA action, we focused on NF-kB and thioredoxin (Trx) redox system. It was shown that GGA induced the HSP70 and Trx-1 expression, NF-kB nuclear translocation and activated thioredoxin reductase (TrxR). The Trx-1 expression and TrxR activity was suppressed by HSP70 and NF-kB inhibition, while the nuclear NF-kB p65 expression was suppressed by HSP70 inhibitor. These results indicated that GGA may protect rat lung against IRI by HSP70 and Trx redox system, in which NF-kB pathway may be involved.

Low-dose adrenomedullin-2/intermedin(8-47) reduces pulmonary ischemia/reperfusion injury

Adrenomedullin-2/intermedin stabilizes the pulmonary microvascular barrier challenged by application of thrombin ex vivo and by experimental ventilation in vivo. Here, we test the hypothesis that adrenomedullin-2/intermedin(8-47) protects mouse lungs from ischemia/reperfusion injury in vivo. C57BL/6 mice were anesthetized, intubated, ventilated, and heparinized. Blood vessels and the main bronchus of the left lung were clamped for 90min. Thereafter, lungs were reperfused for 120min. Five min before clamping and before reperfusion, mice obtained intravenous injections of adrenomedullin-2/intermedin(8-47). After reperfusion, mice were sacrificed and bronchoalveolar lavage of the left and the right lung was performed separately. The integrity of the blood-air barrier was investigated by electron microscopy using stereological methods. In response to ischemia/reperfusion injury, intraalveolar leukocytes accumulated in the ischemic lung. Two applications of 10ng/kg body weight adrenomedullin-2/intermedin(8-47) dramatically reduced leukocyte infiltration to about 15% (p≤0.001). Also the proportion of the subpopulation of neutrophil granulocytes decreased (12% vs 5%, p=0.013). Electron microscopy revealed a protection of the blood-air barrier by adrenomedullin-2/intermedin(8-47). Adrenomedullin-2/intermedin(8-47) ameliorates early ischemia/reperfusion injury in mouse lungs by protecting the integrity of the blood-air barrier and by potently reducing leukocyte influx into the alveolar space. Adrenomedullin-2/intermedin(8-47) might be of therapeutic interest in lung transplantation and cardiopulmonary bypass.

Cold ischemia-induced autophagy in rat lung tissue

Autophagy is a highly conserved pathway that permits recycling of nutrients within the cell and is rapidly upregulated during starvation or cell stress. Autophagy has been implicated in the pathophysiological process of warm ischemia-reperfusion injury in the rat lung. Cold ischemia (CI) preservation for lung transplantation also exhibits cell stress and nutrient deprivation, however, little is known with regard to the involvement of autophagy in this process. In the present study, CI preservation-induced autophagy and apoptosis was investigated in the lungs of Sprague Dawley rats. Sprague Dawley rat lungs were flushed and preserved at 4°C (i.e. CI) for various durations (0, 3, 6, 12 and 24 h). The levels of autophagy, autophagic cell death and apoptosis were measured at each time point following CI. The results revealed that autophagy was induced by CI preservation, which was initiated at 3 h, peaked at 6 h after CI and declined thereafter. Additionally, a coexistence of autophagic cell death and apoptosis was observed in rat lung tissues following prolonged CI. These findings demonstrate that autophagy is involved in the pathophysiological process of lung CI. Furthermore, autophagic cell death in addition to necrosis and apoptosis occurs following CI in the lung. CI preservation may therefore be a potential mechanism of lung injury during organ preservation prior to lung transplantation.

Infusion of mesenchymal stem cells protects lung transplants from cold ischemia-reperfusion injury in mice

BACKGROUND

Cold ischemia-reperfusion injury (IRI) is a major cause of graft failure in lung transplantation. Despite therapeutic benefits of mesenchymal stem cells (MSCs) in attenuating acute lung injury, their protection of lung transplants from cold IRI remains elusive. The present study was to test the efficacy of MSCs in the prevention of cold IRI using a novel murine model of orthotopic lung transplantation.

METHODS

Donor lungs from C57BL/6 mice were exposed to 6 h of cold ischemia before transplanted to syngeneic recipients. MSCs were isolated from the bone marrows of C57BL/6 mice for recipient treatment. Gas exchange was determined by the measurement of blood oxygenation, and lung injury and inflammation were assessed by histological analyses.

RESULTS

Intravenously delivered MSC migration/trafficking to the lung grafts occurred within 4-hours post-transplantation. As compared to untreated controls, the graft arterial blood oxygenation (PaO2/FiO2) capacity was significantly improved in MSC-treated recipients as early as 4 h post-reperfusion and such improvement continued over time. By 72 h, oxygenation reached normal level that was not seen in controls. MSCs treatment conferred significant protection of the grafts from cold IRI and cell apoptosis, which is correlated with less cellular infiltration, a decrease in proinflammatory cytokines (TNF-α, IL-6) and toll-like receptor 4, and an increase in anti-inflammatory TSG-6 generation.

CONCLUSIONS

MSCs provide significant protection against cold IRI in lung transplants, and thus may be a promising strategy to improve outcomes after lung transplantation.