Mechanisms of lung ischemia-reperfusion injury. Curr Opin Organ Transplant. 2016;21:246-252. [PMID: 26945320 DOI: 10.1097/mot.0000000000000304]

Intermittent hypoxia-reoxygenation-induced miRNAs inhibit expression of IRF and interferon genes but activate NF-κB and expression of pulmonary fibrosis markers in human small airway epithelial cells

AIM

Intermittent hypoxia-reoxygenation (H/R) has been demonstrated to be associated with aviation and various respiratory diseases, and hence it is of interest to unravel the regulatory mechanisms underlying the H/R-induced innate immune and inflammatory responses in both healthy and COPD-diseased human small airway epithelial cells (SAECs).

MAIN METHODS

The normal healthy and COPD-diseased SAECs (i.e., N-SAECs and D-SAECs) were purchased from PromoCell biotechnology company and respectively cultured under normoxia (21 % O2) or 12/12-h cycles of H/R (i.e., 1 % O2 and 21 % O2 alternately) for 6 days in total for 2D cultures and 21 days in total for the air-liquid interface 3D cultures, followed by qPCR analyses, miRNA fluorescence in situ hybridization, luciferase reporter assays, and immunofluorescence staining.

KEY FINDINGS

Human SAECs cultured under 12/12-h cycles of H/R showed dramatically increased expression of HIF1A and the H/R-inducible miRNAs miR-129-1-3p, miR-1290 and miR-193b-5p, with miR-129-1-3p and miR-193b-5p targeting and inhibiting IRF5 and IRF7 mRNAs, hence downregulating both the type I and II interferon genes in SAECs cultured under H/R. In addition, miR-129-1-3p, miR-1290 and miR-193b-5p all targeted and inhibited SOCS3 mRNA, hence upregulating transactivation of NF-κB and in turn inducing expression of the inflammatory chemokine genes and pulmonary fibrosis-associated marker genes.

SIGNIFICANCE

We show for the first time that intermittent H/R upregulates the NF-κB-induced proinflammatory and fibrosis marker genes whereas downregulates the IRF5/7-induced type I/II interferon expression in human SAECs through distinct HIF1A-inducible miRNAs miR-129-1-3p, miR-193b-5p and miR-1290, which may serve as promising therapeutic targets for airway inflammation and pulmonary fibrosis.

MiR-146a engineered extracellular vesicles derived from mesenchymal stromal cells more potently attenuate ischaemia-reperfusion injury in lung transplantation

BACKGROUND

The limited donor lung pool for lung transplantation (LTx) is largely due to concerns over ischaemia-reperfusion injury (IRI), a major cause of primary graft dysfunction (PGD). NLRP3 inflammasome activation is known to play a pivotal role in the onset of IRI. While human umbilical cord mesenchymal stromal cell-derived extracellular vesicles (hucMSC-EVs) have shown potential in reducing acute lung injury, their effects on NLRP3 activation in the context of LTx remain unclear.

METHODS

In this study, engineered hucMSC-EVs were delivered via nebulisation to mitigate IRI in rat LTx models. We utilised both a rat orthotopic LTx model and a cell cold preservation reperfusion model to evaluate the therapeutic efficacy of hucMSC-EVs. Bulk-RNA sequencing, single-cell sequencing analysis, immunofluorescence and Western blot techniques were employed to assess NLRP3 inflammasome activation and inflammation.

RESULTS

Nebulised hucMSC-EVs were efficiently internalised by alveolar macrophages (AMs), significantly reducing lung injury and improving oxygenation in the LTx models. Mechanistically, the engineered hucMSC-EVs, which enhance the expression of miR-146a, can more effectively suppress the activation of the NLRP3 inflammasome by targeting the IRAK1/TRAF6/NF-κB pathway, resulting in decreased levels of IL-1β, IL-18 and other inflammatory cytokines. These findings highlight the potential of miR-146a-modified EVs in modulating innate immune responses to alleviate IRI.

CONCLUSION

Our results demonstrate that nebulised delivery of engineered hucMSC-EVs effectively mitigates IRI in LTx by inhibiting NLRP3 inflammasome activation. This innovative approach presents a promising strategy for enhancing donor lung preservation and improving post-transplant outcomes in LTx.

HIGHLIGHTS

Nebulized Delivery of miR-146a Engineered hucMSC-EVs Mitigates Ischemia-Reperfusion Injury (IRI) in Lung Transplantation. This study demonstrates the therapeutic potential of nebulized, engineered human umbilical cord mesenchymal stromal cell-derived extracellular vesicles (hucMSC-EVs) modified with miR-146a to alleviate IRI in rat lung transplantation models. The treatment significantly improved lung oxygenation and reduced inflammation, highlighting the efficacy of this novel approach in enhancing donor lung preservation. Mechanistic Insights: Inhibition of NLRP3 Inflammasome Activation. Engineered hucMSC-EVs efficiently targeted alveolar macrophages and suppressed NLRP3 inflammasome activation through the IRAK1/TRAF6/NF-κB pathway. This modulation of innate immune responses played a crucial role in reducing IRI-induced lung injury and inflammation, offering a promising strategy to manage primary graft dysfunction in lung transplantation. Superior Efficacy of miR-146a-Modified EVs in Reducing Inflammatory Cytokines. The miR-146a modification enhanced the anti-inflammatory properties of hucMSC-EVs, leading to a more significant reduction in pro-inflammatory cytokines (IL-1β, IL-18, and TNF-α) compared to unmodified EVs. This targeted intervention presents a potential therapeutic avenue for improving lung transplant outcomes and mitigating IRI. Innovative Therapeutic Approach: Non-Invasive Nebulization for Direct Lung Delivery. The use of nebulized EVs for direct delivery to donor lungs represents a non-invasive and efficient method for lung-targeted therapy. This strategy could expand the applicability of MSC-EV-based treatments for improving lung transplantation outcomes, particularly in enhancing donor lung preservation during the procurement process.

Preconditioning donor lungs with lung-derived exosomes mitigates ischemia-reperfusion injury in a warm ischemia porcine DCD model

BACKGROUND

Donation after circulatory death (DCD) donors remain an underutilized source in the United States due to concerns of ischemia-reperfusion injury (IRI) after prolonged ischemic times. Lung-derived exosomes have shown potential in mitigating pulmonary fibrosis by promoting lung repair. Here, we sought to investigate the potential of lung-derived exosomes to prevent and repair lung IRI.

METHODS

We used a porcine DCD model to induce lung injury. Following the determination of optimal warm ischemic time (WIT), donor pigs were allocated into 3 study groups (n = 5, each): control, pre-DCD exosome treatment, and post-DCD exosomes treatment. Lungs were assessed using ex-vivo lung perfusion (EVLP) for functional parameters, histologic evaluation, and molecular analysis of inflammatory markers and oxidative stress.

RESULTS

A 1-hour WIT induced consistent lung injury, which was ameliorated with pre-DCD exosome treatment exhibiting significantly improved lung function during EVLP compared to controls. This group presented higher pO2, better lung compliance, lower airway pressures, and reduced pulmonary vascular resistance. Histologic analysis indicated reduced edema, vascular congestion, and leukocyte infiltration. Key inflammatory cytokines such as IL-6, IL-1β, and TNF-α were significantly downregulated, and reactive oxygen species levels were lower than controls. Despite inferior response compared to pre-DCD treatment, post-DCD exosome treatment also improved lung function and reduced edema formation, with significant decrease in inflammation.

CONCLUSIONS

Lung-derived exosome therapy significantly mitigates IRI in a porcine DCD model, improving lung function and reducing inflammation and oxidative stress. These findings support the potential of exosome therapy to increase donor lung utilization, warranting further mechanistic and clinical studies.

FLRT3 Overexpression Attenuates Ischemia-Reperfusion Induced Vascular Hyperpermeability and Lung Injury Through RND3

PURPOSE

Pulmonary ischemia/reperfusion injury (IRI) causes endothelial barrier dysfunction and increased vascular permeability. Fibronectin leucine-rich transmembrane protein-3 (FLRT3) is known to regulate endothelial cell function, but its role in pulmonary IRI remains unexplored.

METHODS

We established both a mouse lung I/R model and a hypoxia/reoxygenation (H/R) cell culture model using human pulmonary microvascular endothelial cells (HPMECs). The effects of FLRT3 manipulation were assessed through lentiviral-mediated overexpression and knockdown approaches. Lung injury was evaluated by histological analysis, immunohistochemistry, and lung injury scoring. Endothelial barrier function was assessed using transmission electron microscopy, Evans blue extravasation, and endothelial permeability assays.

RESULTS

FLRT3 expression was predominantly localized in pulmonary endothelial cells and was downregulated following I/R injury. Lentiviral vectors overexpressing FLRT3 (LV-FLRT3, 1 × 109 TU/ml) via tail vein injection before I/R surgery. FLRT3 overexpression effectively protected against lung injury by maintaining vascular integrity and reducing edema formation in I/R-challenged mice. In H/R-treated HPMECs, we identified that FLRT3 protein underwent autophagic-lysosomal degradation. Mechanistically, FLRT3 preserved endothelial barrier function through interaction with Rho family GTPase 3 (RND3), which prevented RhoA pathway-mediated cytoskeletal disruption. FLRT3 overexpression in HPMECs promoted cell migration, maintained cytoskeletal structure, and reduced endothelial hyperpermeability under H/R conditions. Importantly, RND3 knockdown in vivo significantly attenuated FLRT3's protective effects against I/R injury, as evidenced by increased lung injury scores, vascular permeability, and RhoA pathway activation.

CONCLUSIONS

Our findings reveal FLRT3, a critical regulator of endothelial barrier function during IRI through the RND3-RhoA pathway, is a potential therapeutic target for pulmonary IRI.

Vagus nerve stimulation: A targeted approach for reducing tissue-specific ischemic reperfusion injury

Vagus Nerve Stimulation (VNS), a neuromodulation technique of applying controlled electrical impulses to the vagus nerve, has now emerged as a potential therapeutic approach for ischemia-reperfusion insults. It provides a pivotal link in improving functional outcomes for the central nervous system and multiple target organs affected by ischemia-reperfusion injury (I/RI). Reduced blood flow during ischemia and subsequent resumption of blood supply during reperfusion to the tissue compromises cellular health because of the combination of mitochondrial dysfunction, oxidative stress, cytokine release, inflammation, apoptosis, intracellular calcium overload, and endoplasmic reticulum stress, which ultimately leads to cell death and irreversible tissue damage. Furthermore, inflammation and apoptosis also play critical roles in the acute progression of ischemic injury pathology. Emerging evidence indicates that VNS in I/RI may act in an anti-inflammatory capacity, reducing oxidative stress and apoptosis, while also improving endothelial and mitochondrial function leading to reduced infarct sizes and cytoprotection in skeletal muscle, gastrointestinal tract, liver, kidney, lung, heart, and brain tissue. In this review, we attempt to shed light on the mechanistic links between tissue-specific damage following I/RI and the therapeutic approach of VNS in attenuating damage, considering both direct and remote I/RI scenarios. Thus, we want to advance the understanding of VNS that could further warrant its clinical implementation, especially as a treatment for I/RI.

Dexmedetomidine Blocks NCOA4-Dependent Ferritinophagy to Confer Ferroptosis Resistance in Lung Ischemia Reperfusion Injury via Targeting NRF2

Lung ischemia reperfusion injury (LIRI) represents an evitable but significant pathologic complication post pulmonary transplantation. Dexmedetomidine (Dex) that is extensively applied as an anesthetic adjuvant in the intensive care setting has increasingly presented outstandingly protective effect on LIRI. This article concerns the elaborate role of Dex in ferroptosis after LIRI and the correlative downstream mechanism. Upon hypoxia/reoxygenation (H/R) in human (A549) and mouse (MLE-12) alveolar epithelial cells, reverse transcription-quantitative PCR and western blot analysis tested nuclear receptor coactivator 4 (NCOA4) expression. CCK-8 kit determined cell viability. Western blot analysis and immunofluorescence assay estimated ferritinophagy. C11-BODIPY 581/591 staining, western blot analysis, assay kits and ferro-orange staining appraised ferroptosis. Molecular docking technology investigated the binding affinity between Dex and nuclear factor erythroid 2-related factor 2 (NRF2). Cell viability was eliminated and ferritinophagy was aggravated in A549 and MLE-12 cells in response to H/R. Disturbance of NCOA4 or treatment with Dex suppressed the ferroptosis in H/R-stimulated cells. Also, Dex docked with NRF2 and upregulated NRF2 to concentration-dependently obstruct NCOA4-mediated ferritinophagy and ferroptosis in H/R-challenged cells. Collectively, Dex might protect against NCOA4-mediated ferritinophagy through targeting NRF2, thereby alleviating ferroptosis during LIRI.

Lung injury in myocardial infarction-associated cardiogenic shock supported by venoarterial extracorporeal membrane oxygenation: a scoping review

BACKGROUND

Acute lung injury and acute respiratory failure are frequent complications of cardiogenic shock and are associated with increased morbidity and mortality. Even with increased use of temporary mechanical circulatory support, such as venoarterial extracorporeal membrane oxygenation (VA-ECMO), acute lung injury related to cardiogenic shock continues to have a determinantal effect on patient outcomes.

OBJECTIVES

To summarize potential mechanisms of acute lung injury described in patients with cardiogenic shock supported by VA-ECMO and determine current knowledge gaps.

METHODS

We searched literature from January 1st, 2010, to December 31st, 2023, using MEDLINE, EMBASE, and Web of Science databases on February 27th, 2024. The search strategy was split into two main domains: (a) cardiogenic shock and ECMO and (b) Acute respiratory failure and ECMO.

RESULTS

The search yielded 2246 citations. After 743 duplicates were removed, 1465 citations remained. Of these studies, 1456 were excluded based on the exclusion criteria, leaving the final eight studies we included in our scoping review. We identified disruption of the pulmonary blood flow in patients with cardiogenic shock, with cardiac arrest being an extreme form of cardiogenic shock. Placing the patient on VA-ECMO could intensify this process of lung injury.

CONCLUSION

Acute lung injury in patients with cardiogenic shock, especially when supported by VA ECMO, is a significant complication that is associated with increased morbidity and mortality. There is a limited understanding of the underlying mechanisms that could represent opportunities for future research to mitigate its development and provide the best approach to protecting and monitoring lung function.

Myrtenol-loaded niosomes can prevent lung ischemia-reperfusion injury model in rats by balancing the Nrf2/Keap1 and NF-κB signaling pathways

Lung Ischemia-reperfusion injury (LIRI) is a risk during lung transplantation that can cause acute lung injury and organ failure. In LIRI, the NF-E2-related factor 2(Nrf2)/ Kelch-like ECH-associated protein 1 (Keap1) signaling pathway and the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway are two major pathways involved in regulating oxidative stress and inflammation, respectively. Myrtenol, a natural compound with anti-inflammatory and antioxidant properties, has potential protective effects against IRI. This study aimed to explore the impact of myrtenol encapsulated within niosomes on the prevention of LIRI and examine the role of the two pathways mentioned in this process. Wistar rats were segregated into four groups. Animals received the myrtenol (MN) (32 mg/kg) or vehicle through daily inhalation for a week before LIRI. Expression of IκB, p-IκB, Nrf2, Keap1, Heme Oxygenase-1(HO-1), NF-κB signaling proteins, reactive oxygen species (ROS) level, caspase-3 expression, arterial blood gases, lung edema, and histopathological indices were assessed. Niosomal myrtenol significantly reduced lung edema, ROS, Keap1, p-IκB, NF-kB, Caspase-3, PaCO2 (the carbon dioxide pressure in arterial blood), and histopathological indices. Additionally, the expression of IκB, Nrf2, HO-1, and PaO2 (the oxygen pressure in arterial blood) increased significantly in the pretreated group compared to the IR group. Overall, inhalation of the niosomal myrtenol protects against lung ischemia-reperfusion injury, presumably through the balance between Nrf2/Keap1 and NF-κB pathways. The findings suggest that the niosomal form of myrtenol may be a potential candidate for developing new drugs to prevent and treat LIR damage.

Fibroblast growth factor 21 attenuates pulmonary ischemia/reperfusion injury via inhibiting endoplasmic reticulum stress-induced ferroptosis though FGFR1/PPARδ signaling pathway

BACKGROUND

Acute lung injury is a critical life-threatening complication of pulmonary and cardiac surgery with a high rate of morbidity and mortality. Fibroblast growth factor 21 (FGF21) has been reported to play an important role in protecting vital organs from damage. This study aims to investigate the potential protective role and mechanism of FGF21 in pulmonary ischemia/reperfusion (I/R)-induced acute lung injury.

METHODS

A pulmonary epithelial cell line was treated with hypoxia/regeneration (H/R) in vitro and a mouse model of acute lung injury was induced with pulmonary I/R in vivo. Lung injury after pulmonary I/R was compared between FGF21-konckout (KO) mice and wild-type (WT) mice. Recombinant FGF21 was administrated in vivo and in vitro to determine its therapeutic effect.

RESULTS

Circulating levels of FGF21 in mice with pulmonary I/R injury were significantly higher than in those without pulmonary I/R injury. Lung injury was aggravated in FGF21-KO mice compared with WT mice and the administration of FGF21 alleviated lung injury in mouse treated with I/R and pulmonary epithelial cell injury treated with H/R. FGF21 treatment decreased endoplasmic reticulum (ER) stress, Fe2+ and lipid reactive oxygen species (ROS) contents and GPX4 expression and increased PTGS2 levels. Mechanistically, FGF21 upregulated the expression of FGFR1 and PPARδ, ameliorated ER stress and ER stress induced-ferroptosis. Furthermore, FGF21 increased the expression level of PPARδ in pulmonary epithelial cell exposed to H/R, which was inhibited by FGFR1 inhibitor (PD173074). The protective effects of FGF21 were abolished by co-treatment with PPARδ inhibitor (GSK0660), indicating FGF21 attenuated ER stress-induced ferroptosis by dependent on FGFR1/PPARδ signaling pathway.

CONCLUSION

Our study reveals that FGF21 protects against pulmonary I/R injury via inhibiting ER stress-induced ferroptosis though FGFR1/PPARδ signaling pathway. Boosting endogenous FGF21 or the administration of recombinant FGF21 could be promising therapeutic strategies for pulmonary IRI.

Neutrophil PPIF exacerbates lung ischemia-reperfusion injury after lung transplantation by promoting calcium overload-induced neutrophil extracellular traps formation

Lung ischemia-reperfusion (I/R) injury is the main risk factor for primary graft dysfunction and patient death after lung transplantation (LTx). It is widely accepted that the main pathological mechanism of lung I/R injury are calcium overload, oxygen free radical explosion and neutrophil-mediated damage, which leading to the lack of effective treatment options. The aim of this study was to further explore the mechanisms of lung I/R injury after LTx and to provide potential therapeutic strategies. Our bioinformatics analysis revealed that the neutrophil extracellular traps (NETs) formation was closely involved in lung I/R injury after LTx, which was accompanied by up-regulation of peptidylprolyl isomerase F (PPIF) and peptidyl arginine deiminase 4 (PADI4). We further established an orthotopic LTx mouse model to simulate lung I/R injury in vivo, and found that PPIF and PADI4 inhibitors effectively reduced neutrophil infiltration, NETs formation, inflammatory response, and lung I/R injury. In the neutrophil model induced by HL-60 cell line in vitro, we found that PPIF inhibitor cyclosporin A (Cys A) better alleviated calcium overload induced inflammatory response, reactive oxygen species content and NETs formation. Further study demonstrated that interfering with neutrophil PPIF protected mitochondrial function by alleviating store-operated calcium entry (SOCE) during calcium overload and played the above positive role. On this basis, we found that the reduction of calcium content in neutrophils was accompanied by the inhibition of calcineurin (CN) and nuclear factor of activated T cells (NFAT). In conclusion, our findings suggested that neutrophil PPIF could serve as a novel biomarker and potential therapeutic target of lung I/R injury after LTx, which provided new clues for its treatment by inhibiting calcium overload-induced NETs formation.

Bone marrow mesenchymal stem cells-derived exosomal miR-381 alleviates lung ischemia-reperfusion injury by activating Treg differentiation through inhibiting YTHDF1 expression

AIM

Our study aimed to investigate whether BMSCs-derived exosomal miR-381 promotes Treg cell differentiation in lung ischemia-reperfusion injury (LIRI), and the underlying mechanism.

METHODS

The in vitro and in vivo models of LIRI were established by hypoxia/reoxygenation (H/R) treatment and lung ischemia/reperfusion (I/R) surgery, respectively. BMSCs-derived exosomes were isolated and identified by western blot, nanoparticle tracking analysis, and transmission electron microscopy. Cell viability, proliferation, and apoptosis were assessed by CCK-8, EdU, and flow cytometry assay, respectively. IL-18 secretion level in lung microvascular endothelial cells (LMECs) and lung tissue homogenate was examined by ELISA. Treg cell differentiation was determined using flow cytometry. The relationships between miR-381, YTHDF1, and IL-18 were investigated using dual-luciferase reporter gene, RIP, and/or RNA pull-down assays. MeRIP assay was employed to determine m6A modification of IL-18 mRNA in LMECs. The ubiquitination level of Foxp3 protein in CD4+ T cells was analyzed by Co-IP assay.

RESULTS

BMSCs-derived exosomes reduced LMECs injury and increased Treg cell differentiation in LIRI, whereas miR-381 inhibition in BMSCs weakened these impacts. Mechanistically, miR-381 inhibited IL-18 translation in LMECs by inhibiting YTHDF1 expression via binding to its 3'-UTR. As expected, YTHDF1 overexpression in LMECs abolished the effects of miR-381-overexpressed exosomes on LMECs injury and Treg cell differentiation. Moreover, LMECs-secreted IL-18 inhibited Treg cell differentiation by promoting the ubiquitination degradation of Foxp3 protein.

CONCLUSION

BMSCs-derived exosomal miR-381 suppressed IL-18 translation in LMECs through binding to YTHDF1 3'-UTR, thus suppressing the ubiquitination degradation of Foxp3 in CD4+ T cells, which promoted Treg cell differentiation and mitigated LIRI development.

Precision cut lung slices: an innovative tool for lung transplant research

Lung ischemia-reperfusion injury (IRI), a common complication after lung transplantation (LTx), plays a crucial role in both primary graft dysfunction (PGD) and chronic lung allograft dysfunction (CLAD) thereby adversely impacting the clinical outcomes in these patient cohorts. Lung IRI is characterized by several molecular events including immune cell infiltration, reactive oxygen species (ROS) generation, calcium overload, inflammation and various forms of cell death pathways. Currently, no therapeutic agents are available to clinically prevent lung IRI. While animal and cell culture models are highly valuable in understanding the pathophysiology of lung IRI, they may not completely recapitulate the complexity of human lung tissue pathology. This limitation necessitates the requirement for developing innovative preclinical human research tools that can supplement available scientific modalities. Emerging evidence suggests that precision-cut lung slices (PCLS) have become an indispensable tool in scientific research to study lung biology in an ex vivo tissue system. Recent studies using PCLS have investigated lung diseases including asthma, chronic obstructive pulmonary disease (COPD), and lung cancer. Although PCLS can be successfully employed to determine the deleterious events in the pathogenesis of lung IRI, including cell-cell interactions as well as hallmarks of inflammation and oxidative stress-dependent pathways, detailed studies employing PCLS to decipher these molecular events in post-LTx injury are currently limited. This review focuses on the applicability and unexplored potential of PCLS as a powerful tool in lung IRI research for understanding the pathophysiology and consequent development of new therapeutic modalities.

Experimental Lung Transplantation Related With HIF-1, VEGF, ROS. Assessment of HIF-1alpha, VEGF, and Reactive Oxygen Species After Competitive Blockade of Chetomin for Lung Transplantation in Rats

Primary graft failure occurs 15 to 30 % of the time after transplantation. Although there have been improvements in preserving the lungs in good condition, there have not been studies on the regulation of transcription factors.

METHODS

We carried out an experimental study involving lung transplantation to indirectly evaluate reactive oxygen species (ROS) production and VEGF expression by competitive blockade of HIF-1alpha with chetomin. There were 5 groups: Group-1: Lung blocks were perfused with 0.9 % SSF, immediately harvested, and preserved. Group-2 (I-T): Immediate transplantation and then reperfusion for 1 h. Group-3 (I-R): Lung blocks were harvested and preserved in LPD solution for 6 h and reperfused for 1 h. Group-4 (DMSO): Lung blocks were treated for 4 h with DMSO, preserved for 6 h and transplanted to a receptor treated with DMSO. Group-5 (chetomin): Lung blocks were treated for 4 h with chetomin, preserved for 6 h and transplanted to a receptor treated with chetomin. ROS, mRNA, and protein levels of HIF-1alpha and EG-VEGF were determined.

RESULTS

The DMSO and chetomin groups had significantly lower ROS levels. Compared with those in the I-R group, the chetomin group exhibited the lowest level of HIF-1alpha.

CONCLUSIONS

Addition of chetomin to the donor and the receptor results in a significant reduction in HIF-1A, VEGF and ROS.

Exploring the research progression and evolutionary trends of lung ischemia-reperfusion injury: A bibliometric analysis from 1979 to 2023

BACKGROUND

Lung ischemia-reperfusion injury (LIRI) poses a significant challenge in various clinical scenarios. Despite extensive research on the pathogenesis and potential treatments of LIRI, there is a notable absence of bibliometric analysis.

MATERIALS AND METHODS

We summarized the results of LIRI research through two searches on the Web of Science, covering data from 1979 to 2023 with topic words "lung" and "reperfusion injury". The collected data were analyzed and visualized based on country, author(s), and keywords by bibliometric software. The keyword "programmed cell death" was further added to explore the hotspot of the LIRI research field.

RESULTS

The initial analysis of 1648 research articles showed a total of 40 countries and 7031 researchers were involved in the publications, with America being the most productive country in the research field of LIRI. Keyword analysis revealed that the evolving focus of LIRI research has progressively transitioned from, lung transplantation, primary graft dysfunction, inflammation, oxidative stress, and ex vivo lung perfusion to cell death. Subsequently, 212 publications specifically addressing programmed cell death (PCD) in LIRI were identified, which clarified the recent hotspot of the LIRI field.

CONCLUSION

With closer international cooperation and increasing research scale, the LIRI research focused mainly on the pathogenesis and potential therapeutic interventions for LIRI. PCD in LIRI is becoming a trending topic and will continue to be a hotspot in this field. Our study may offer valuable guidance for future research endeavors concerning LIRI.

Transient receptor potential vanilloid 4 channel inhibition attenuates lung ischemia-reperfusion injury in a porcine lung transplant model

OBJECTIVE

Transient receptor potential vanilloid 4 (TRPV4) is a nonselective cation channel important in many physiological and pathophysiological processes, including pulmonary disease. Using a murine model, we previously demonstrated that TRPV4 mediates lung ischemia-reperfusion injury, the major cause of primary graft dysfunction after transplant. The current study tests the hypothesis that treatment with a TRPV4 inhibitor will attenuate lung ischemia-reperfusion injury in a clinically relevant porcine lung transplant model.

METHODS

A porcine left-lung transplant model was used. Animals were randomized to 2 treatment groups (n = 5/group): vehicle or GSK2193874 (selective TRPV4 inhibitor). Donor lungs underwent 30 minutes of warm ischemia and 24 hours of cold preservation before left lung allotransplantation and 4 hours of reperfusion. Vehicle or GSK2193874 (1 mg/kg) was administered to the recipient as a systemic infusion after recipient lung explant. Lung function, injury, and inflammatory biomarkers were compared.

RESULTS

After transplant, left lung oxygenation was significantly improved in the TRPV4 inhibitor group after 3 and 4 hours of reperfusion. Lung histology scores and edema were significantly improved, and neutrophil infiltration was significantly reduced in the TRPV4 inhibitor group. TRPV4 inhibitor-treated recipients had significantly reduced expression of interleukin-8, high mobility group box 1, P-selectin, and tight junction proteins (occludin, claudin-5, and zonula occludens-1) in bronchoalveolar lavage fluid as well as reduced angiopoietin-2 in plasma, all indicative of preservation of endothelial barrier function.

CONCLUSIONS

Treatment of lung transplant recipients with TRPV4 inhibitor significantly improves lung function and attenuates ischemia-reperfusion injury. Thus, selective TRPV4 inhibition may be a promising therapeutic strategy to prevent primary graft dysfunction after transplant.

Salidroside inhibits the ferroptosis to alleviate lung ischemia reperfusion injury via the JAK2/STAT3 signalling pathway

OBJECTIVE

The present study aims to investigate the protective potential of salidroside in both lung ischemia/reperfusion injury (LIRI) mice model and cell hypoxia/reoxygenation (H/R)model and the involvement of ferroptosis and JAK2/STAT3 pathway.

MATERIALS AND METHODS

After we established the IR-induced lung injury model in mice, we administered salidroside and the ferroptosis inhibitor, ferrostatin-1, then assessed the lung tissue injury, ferroptosis (levels of reactive oxygen species level, malondialdehyde and glutathione), and inflammation in lung tissues. The levels of ferroptosis-related proteins (glutathione peroxidase 4, fibroblast-specific protein 1, solute carrier family 1 member 5 and glutaminase 2) in the lung tissue were measured with Western blotting. Next, BEAS-2B cells were used to establish an H/R cell model and treated with salidroside or ferrostatin-1 before the cell viability and the levels of lactate dehydrogenase (LDH), inflammatory factor, ferroptosis-related proteins were measured. The activation of the JAK2/STAT3 signaling pathway was measured with Western blotting, then its role was confirmed with STAT3 knockdown.

RESULTS

Remarkably, salidroside was found to alleviate ferroptosis, inflammation, and lung injury in LIRI mice and the cell injury in H/R cell model. Severe ferroptosis were observed in LIRI mice models and H/R-induced BEAS-2B cells, which was alleviated by salidroside. Furthermore, salidroside could inhibit JAK2/STAT3 activation induced by LIRI. STAT3 knockdown could enhance the effect of salidroside treatment on H/R-induced cell damage and ferroptosis in vitro.

CONCLUSIONS

Salidroside inhibits ferroptosis to alleviate lung ischemia reperfusion injury via the JAK2/STAT3 signaling pathway.

MerTK-dependent efferocytosis by monocytic-MDSCs mediates resolution of ischemia/reperfusion injury after lung transplant

Lung transplantation (LTx) outcomes are impeded by ischemia/reperfusion injury (IRI) and subsequent chronic lung allograft dysfunction (CLAD). We examined the undefined role of receptor Mer tyrosine kinase (MerTK) on monocytic myeloid-derived suppressor cells (M-MDSCs) in efferocytosis to facilitate resolution of lung IRI. Single-cell RNA sequencing of lung tissue and bronchoalveolar lavage (BAL) from patients after LTx were analyzed. Murine lung hilar ligation and allogeneic orthotopic LTx models of IRI were used with BALB/c (WT), Cebpb-/- (MDSC-deficient), Mertk-/-, or MerTK-cleavage-resistant mice. A significant downregulation in MerTK-related efferocytosis genes in M-MDSC populations of patients with CLAD was observed compared with healthy individuals. In the murine IRI model, a significant increase in M-MDSCs, MerTK expression, and efferocytosis and attenuation of lung dysfunction was observed in WT mice during injury resolution that was absent in Cebpb-/- and Mertk-/- mice. Adoptive transfer of M-MDSCs in Cebpb-/- mice significantly attenuated lung dysfunction and inflammation. Additionally, in a murine orthotopic LTx model, increases in M-MDSCs were associated with resolution of lung IRI in the transplant recipients. In vitro studies demonstrated the ability of M-MDSCs to efferocytose apoptotic neutrophils in a MerTK-dependent manner. Our results suggest that MerTK-dependent efferocytosis by M-MDSCs can substantially contribute to the resolution of post-LTx IRI.

Tree-based ensemble machine learning models in the prediction of acute respiratory distress syndrome following cardiac surgery: a multicenter cohort study

BACKGROUND

Acute respiratory distress syndrome (ARDS) after cardiac surgery is a severe respiratory complication with high mortality and morbidity. Traditional clinical approaches may lead to under recognition of this heterogeneous syndrome, potentially resulting in diagnosis delay. This study aims to develop and external validate seven machine learning (ML) models, trained on electronic health records data, for predicting ARDS after cardiac surgery.

METHODS

This multicenter, observational cohort study included patients who underwent cardiac surgery in the training and testing cohorts (data from Nanjing First Hospital), as well as those patients who had cardiac surgery in a validation cohort (data from Shanghai General Hospital). The number of important features was determined using the sliding windows sequential forward feature selection method (SWSFS). We developed a set of tree-based ML models, including Decision Tree, GBDT, AdaBoost, XGBoost, LightGBM, Random Forest, and Deep Forest. Model performance was evaluated using the area under the receiver operating characteristic curve (AUC) and Brier score. The SHapley Additive exPlanation (SHAP) techinque was employed to interpret the ML model. Furthermore, a comparison was made between the ML models and traditional scoring systems. ARDS is defined according to the Berlin definition.

RESULTS

A total of 1996 patients who had cardiac surgery were included in the study. The top five important features identified by the SWSFS were chronic obstructive pulmonary disease, preoperative albumin, central venous pressure_T4, cardiopulmonary bypass time, and left ventricular ejection fraction. Among the seven ML models, Deep Forest demonstrated the best performance, with an AUC of 0.882 and a Brier score of 0.809 in the validation cohort. Notably, the SHAP values effectively illustrated the contribution of the 13 features attributed to the model output and the individual feature's effect on model prediction. In addition, the ensemble ML models demonstrated better performance than the other six traditional scoring systems.

CONCLUSIONS

Our study identified 13 important features and provided multiple ML models to enhance the risk stratification for ARDS after cardiac surgery. Using these predictors and ML models might provide a basis for early diagnostic and preventive strategies in the perioperative management of ARDS patients.

Impact of Pre-Transplant Left Ventricular Diastolic Pressure on Primary Graft Dysfunction after Lung Transplantation: A Narrative Review

Lung transplantation (LT) constitutes the last therapeutic option for selected patients with end-stage respiratory disease. Primary graft dysfunction (PGD) is a form of severe lung injury, occurring in the first 72 h following LT and constitutes the most common cause of early death after LT. The presence of pulmonary hypertension (PH) has been reported to favor PGD development, with a negative impact on patients' outcomes while complicating medical management. Although several studies have suggested a potential association between pre-LT left ventricular diastolic dysfunction (LVDD) and PGD occurrence, the underlying mechanisms of such an association remain elusive. Importantly, the heterogeneity of the study protocols and the various inclusion criteria used to define the diastolic dysfunction in those patients prevents solid conclusions from being drawn. In this review, we aim at summarizing PGD mechanisms, risk factors, and diagnostic criteria, with a further focus on the interplay between LVDD and PGD development. Finally, we explore the predictive value of several diastolic dysfunction diagnostic parameters to predict PGD occurrence and severity.

Donor Inhalation of Nebulized Dexmedetomidine Alleviates Ischemia-Reperfusion Injury in Rat Lung Transplantation

INTRODUCTION

The occurrence of lung ischemia-reperfusion injury (LIRI) after lung transplantation results in primary graft dysfunction (PGD) in more than 50% of cases, which seriously affects the prognosis of recipients. Currently, donor lung protection is the focus of research on improving graft survival in lung transplant recipients. Dexmedetomidine (Dex) is a widely used general anesthesia adjuvant in clinical practice to alleviate ischemia-reperfusion injury in the lungs, liver, heart, kidneys, and brain. However, intravenous infusion of Dex can cause negative effects on the cardiovascular system. Inhaling nebulized Dex can directly act on the alveolar tissue and alleviate its cardiovascular inhibitory effect by reducing drug intake. This study aimed to investigate the effect of donor nebulized Dex inhalation on LIRI after lung transplantation in rats.

METHODS

We randomly divided the male Sprague-Dawley rats into donor rats and recipient rats, and allowed the donor rats to inhale nebulized Dex or physiological saline 15 min before surgery. The donor lung was refrigerated for 8 h before each single-lung transplant. After 2 h of reperfusion of the transplanted lung, serum and transplanted lung tissue were collected. The wet-to-dry weight ratio of the lung tissue was measured, arterial blood gas was detected, and histopathology changes, oxidative stress, inflammatory reactions, and apoptosis were evaluated.

RESULTS

Pretransplant inhalation of Dex through the donor's lung reduced the injury of the transplanted lung, increased the levels of malondialdehyde and myeloperoxidase, and decreased the levels of superoxide dismutase and glutathione in the lung tissue. Moreover, nebulized Dex inhalation of the donor lung inhibited LIRI-induced tumor necrosis factor-α, interleukin-6, and inducible nitric oxide synthase expression and also suppressed nuclear factor kappa B phosphorylation. Nebulized Dex inhalation reduced the rate of cell apoptosis in the transplanted lung tissue by inhibiting the upregulation of Bax, downregulation of Bcl-2, and increase in caspase-3 lysis caused by LIRI.

CONCLUSION

Inhalation of atomized Dex is a potential donor lung protection strategy, which can be used to reduce LIRI after lung transplantation and may be helpful to improve the occurrence of PGD and prognosis of lung transplant recipients.

Transient heat stress protects from severe endothelial damage and dysfunction during prolonged experimental ex-vivo lung perfusion

Introduction

The pulmonary endothelium is the primary target of lung ischemia-reperfusion injury leading to primary graft dysfunction after lung transplantation. We hypothesized that treating damaged rat lungs by a transient heat stress during ex-vivo lung perfusion (EVLP) to elicit a pulmonary heat shock response could protect the endothelium from severe reperfusion injury.

Methods

Rat lungs damaged by 1h warm ischemia were reperfused on an EVLP platform for up to 6h at a constant temperature (T°) of 37°C (EVLP37°C group), or following a transient heat stress (HS) at 41.5°C from 1 to 1.5h of EVLP (EVLPHS group). A group of lungs exposed to 1h EVLP only (pre-heating conditions) was added as control (Baseline group). In a first protocol, we measured lung heat sock protein expression (HSP70, HSP27 and Hsc70) at selected time-points (n=5/group at each time). In a second protocol, we determined (n=5/group) lung weight gain (edema), pulmonary compliance, oxygenation capacity, pulmonary artery pressure (PAP) and vascular resistance (PVR), the expression of PECAM-1 (CD31) and phosphorylation status of Src-kinase and VE-cadherin in lung tissue, as well as the release in perfusate of cytokines (TNFα, IL-1β) and endothelial biomarkers (sPECAM, von Willebrand Factor -vWF-, sE-selectin and sICAM-1). Histological and immunofluorescent studies assessed perivascular edema and formation of 3-nitrotyrosine (a marker of peroxinitrite) in CD31 lung endothelium.

Results

HS induced an early (3h) and persisting expression of HSP70 and HSP27, without influencing Hsc70. Lungs from the EVLP37°C group developed massive edema, low compliance and oxygenation, elevated PAP and PVR, substantial release of TNFα, IL-1β, s-PECAM, vWF, E-selectin and s-ICAM, as well as significant Src-kinase activation, VE-cadherin phosphorylation, endothelial 3-NT formation and reduced CD31 expression. In marked contrast, all these alterations were either abrogated or significantly attenuated by HS treatment.

Conclusion

The therapeutic application of a transient heat stress during EVLP of damaged rat lungs reduces endothelial permeability, attenuates pulmonary vasoconstriction, prevents src-kinase activation and VE-cadherin phosphorylation, while reducing endothelial peroxinitrite generation and the release of cytokines and endothelial biomarkers. Collectively, these data demonstrate that therapeutic heat stress may represent a promising strategy to protect the lung endothelium from severe reperfusion injury.

Experımental Study: The Effect Of 20% Intralıpıd Emulsıon Therapy In Cerebral Ischemıc Reperfusıon

BACKGROUND

This experimental study was conducted to investigate the effect of 20% Intralipid Emulsion (ILE) treatment on Cerebral Ischemia Reperfusion Injury (CIRI) after reperfusion in acute ischemic stroke.

METHODS

In this experimental study, seven rats without any intervention (control group), seven rats (sham group) for which CIRI was created after the common carotid artery was ligated for 2 hours, and seven rats who were treated with 20% ILE after CIRI (CIRI + ILE group) were sacrificed after 24 hours, and histopathological findings were investigated.

RESULTS

In rats that were not treated after CIRI, 52.7% had level-1, 32.7% had level-2. and 14.5% had level-3. histopathological findings. While 72.2% of the rats treated with ILE had level-1 and 27.8% had level-2 findings, no level-3 histopathological findings were detected in any of the rats. While no signs of coagulative necrosis, spongiosis of surrounding tissue and polymorphonuclear leukocytes were observed histopathological in any of the rats given ILE, there was no macrophages finding in 85.6% of the rats. ILE treatment also reduced the histopathological findings of eosinophilic neurons, astrogliosis, neovascularization, vascular thrombosis and mononuclear inflammatory cells.

CONCLUSION

This study showed that 20% ILE treatment reduces the histopathological damage seen in cerebral ischemia and CIRI.

A novel modified Steen solution limits inflammatory processes during ex vivo lung perfusion and improves graft function post-transplantation

Background

Ex vivo lung perfusion allows donor lung preservation, assessment, and reconditioning before transplantation, but is associated with increased inflammatory injury over time. Addition of antioxidative and anti-inflammatory agents to perfusate formulations could limit iatrogenic injury during perfusion. The effectiveness of a modified Steen solution containing acetyl salicylic acid, retinoic acid, and methylprednisolone was examined using a porcine extended criteria donor ex vivo lung perfusion and transplantation model.

Methods

Porcine donor lungs underwent 24 hours cold storage and were then randomized to 4 hours normothermic ex vivo lung perfusion with modified Steen or original Steen, followed by single lung transplantation into a recipient pig. RNA-sequencing was used to assess tissue inflammatory changes during perfusion. Organ function was examined during perfusion and following transplantation and compared between groups.

Results

Lungs perfused with modified Steen showed reduced pulmonary vascular resistance (p = 0.0391) and stable pulmonary artery pressure despite achieving higher flows (p = 0.0001) compared to Steen. Lung tissue showed negative enrichment of the tumor necrosis factor-α (TNF-α) signaling via nuclear factor-κB (NF-κB) pathway (p = 0.0040) in modified Steen compared to Steen. Recipients of lungs perfused with modified Steen also showed improved post-transplantation oxygenation (p = 0.0462).

Conclusions

This study highlights the superiority of modified Steen compared with original Steen. The modifications to Steen solution appear to limit inflammatory injury via the NF-κB signaling pathway during perfusion, leading to improved post-transplant function. Modified Steen provides the potential to improve post-transplant outcomes following ex vivo lung perfusion of extended criteria lungs and could also facilitate extended assessment and preservation, as well as administration of advanced therapies.

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.

Effects of high-intensity inspiratory muscle training on systemic inflammatory response in cardiac surgery - A randomized clinical trial

PURPOSE

Preoperative inspiratory muscle training reduces the incidence of postoperative pulmonary complications after cardiac surgery, but training protocols vary widely in terms of intensity. Currently, the mechanisms underlying the effectiveness of this practice are not known. The purpose of the present study is to determine whether preoperative high-intensity inspiratory muscle training (HI-IMT) modulates the perioperative systemic inflammatory response in cardiac surgery patients.

METHODS

Participants awaiting surgical aortic valve replacement were randomized to 3 to 6 weeks preoperative home-based HI-IMT or same duration low-intensity inspiratory muscle training (LI-IMT). The primary outcome was the preoperative value of the soluble tumor necrosis factor receptor 1 (sTNFR1). Secondary outcomes assessed perioperative evolution of the cytokines: sTNFR1, Tumor necrosis factor-α, Interleukin (IL)-6, IL-8, IL10, IL1β, and their combined z-score; reflecting post-training and postoperative inflammatory response. Perioperative pulmonary function and postoperative clinical outcomes were collected.

RESULTS

Between February 2018 and March 30, 2019 patients were randomized, to HI-IMT or LI-IMT. There were no differences between the groups in terms of baseline characteristics. The median (IQR) training duration was 34 (28-44) days. After training, the median (IQR) predicted maximal inspiratory pressure was higher in the HI-IMT vs LI-IMT group (119 (96-142%) vs 97 (81-107%); p = .04) Levels of the sTNFR1 cytokine increased during training in the HI-IMT group, pre vs post training (Median (IQR) 1073 (920; 1219) vs 1172 (965; 1368) ng/L; p = .03). The 24-h postoperative global inflammatory score was lower in the HI-IMT than in the LI-IMT group (Median (IQR), -0.37 (-0.62, 0.03) vs -0.10 (-0.17, 0.49), p = .04). Global inflammatory scores were not different at other time points. There were no significant differences between the groups in post-operative pulmonary function and postoperative clinical outcome.

CONCLUSION

High intensity inspiratory muscle training shows immunomodulatory properties. These properties could explain why preoperative inspiratory muscle training can lead to lung protection after cardiac surgery.

Ex Vivo Optimization of Donor Lungs with Inhaled Sevoflurane during Normothermic Ex Vivo Lung Perfusion (VITALISE): A Pilot and Feasibility Study in Sheep

Volatile anesthetics have been shown in different studies to reduce ischemia reperfusion injury (IRI). Ex vivo lung perfusion (EVLP) facilitates graft evaluation, extends preservation time and potentially enables injury repair and improvement of lung quality. We hypothesized that ventilating lungs with sevoflurane during EVLP would reduce lung injury and improve lung function. We performed a pilot study to test this hypothesis in a slaughterhouse sheep DCD model. Lungs were harvested, flushed and stored on ice for 3 h, after which EVLP was performed for 4 h. Lungs were ventilated with either an FiO2 of 0.4 (EVLP, n = 5) or FiO2 of 0.4 plus sevoflurane at a 2% end-tidal concentration (Cet) (S-EVLP, n = 5). Perfusate, tissue samples and functional measurements were collected and analyzed. A steady state of the target Cet sevoflurane was reached with measurable concentrations in perfusate. Lungs in the S-EVLP group showed significantly better dynamic lung compliance than those in the EVLP group (p = 0.003). Oxygenation capacity was not different in treated lungs for delta partial oxygen pressure (PO2; +3.8 (-4.9/11.1) vs. -11.7 (-12.0/-3.2) kPa, p = 0.151), but there was a trend of a better PO2/FiO2 ratio (p = 0.054). Perfusate ASAT levels in S-EVLP were significantly reduced compared to the control group (198.1 ± 93.66 vs. 223.9 ± 105.7 IU/L, p = 0.02). We conclude that ventilating lungs with sevoflurane during EVLP is feasible and could be useful to improve graft function.

Metformin alleviates lung ischemia-reperfusion injury in a rat lung transplantation model

Background: Lung ischemia-reperfusion injury (LIRI) is among the complications observed after lung transplantation and is associated with morbidity and mortality. Preconditioning of the donor lung before organ retrieval may improve organ quality after transplantation. We investigated whether preconditioning with metformin (Met) ameliorates LIRI after lung transplantation. Methods: Twenty Lewis rats were randomly divided into the sham, LIRI, and Met groups. The rats in the LIRI and Met groups received saline and Met, respectively, via oral gavage. Subsequently, a donor lung was harvested and kept in cold storage for 8 h. The LIRI and Met groups then underwent left lung transplantation. After 2 h of reperfusion, serum and transplanted lung tissues were examined. Results: The partial pressure of oxygen (PaO2) was greater in the Met group than in the LIRI group. In the Met group, wet-to-dry (W/D) weight ratios, inflammatory factor levels, oxidative stress levels and apoptosis levels were notably decreased. Conclusions: Met protects against ischemia-reperfusion injury after lung transplantation in rats, and its therapeutic effect is associated with its anti-inflammatory, antioxidative, and antiapoptotic properties.

The Immunopathology of Pulmonary Rejection after Murine Lung Transplantation

To improve outcomes following lung transplantation, it is essential to understand the immunological mechanisms that result in chronic graft failure. The associated clinical syndrome is termed chronic lung allograft dysfunction (CLAD), which is known to be induced by alloimmune-dependent (i.e., rejection) and alloimmune-independent factors (e.g., infections, reflux and environmental factors). We aimed to explore the alloimmune-related mechanism, i.e., pulmonary rejection. In this study, we use a murine orthotopic left lung transplant model using isografts and allografts (C57BL/6 or BALB/c as donors to C57BL/6 recipients), with daily immunosuppression (10 mg/kg cyclosporin A and 1.6 mg/kg methylprednisolone). Serial sacrifice was performed at days 1, 7 and 35 post-transplantation (n = 6 at each time point for each group). Left transplanted lungs were harvested, a single-cell suspension was made and absolute numbers of immune cells were quantified using multicolor flow cytometry. The rejection process followed the principles of a classic immune response, including innate but mainly adaptive immune cells. At day 7 following transplantation, the numbers of interstitial macrophages, monocytes, dendritic cells, NK cells, NKT cells, CD4+ T cells and CD8+ T and B cells were increased in allografts compared with isografts. Only dendritic cells and CD4+ T cells remained elevated at day 35 in allografts. Our study provides insights into the immunological mechanisms of true pulmonary rejection after murine lung transplantation. These results might be important in further research on diagnostic evaluation and treatment for CLAD.

MerTK-dependent efferocytosis by monocytic-MDSCs mediates resolution of post-lung transplant injury

Rationale

Patients with end stage lung diseases require lung transplantation (LTx) that can be impeded by ischemia-reperfusion injury (IRI) leading to subsequent chronic lung allograft dysfunction (CLAD) and inadequate outcomes.

Objectives

We examined the undefined role of MerTK (receptor Mer tyrosine kinase) on monocytic myeloid-derived suppressor cells (M-MDSCs) in efferocytosis (phagocytosis of apoptotic cells) to facilitate resolution of lung IRI.

Methods

Single-cell RNA sequencing of lung tissue and BAL from post-LTx patients was analyzed. Murine lung hilar ligation and allogeneic orthotopic LTx models of IRI were used with Balb/c (WT), cebpb -/- (MDSC-deficient), Mertk -/- or MerTK-CR (cleavage resistant) mice. Lung function, IRI (inflammatory cytokine and myeloperoxidase expression, immunohistology for neutrophil infiltration), and flow cytometry of lung tissue for efferocytosis of apoptotic neutrophils were assessed in mice.

Measurements and Main Results

A significant downregulation in MerTK-related efferocytosis genes in M-MDSC populations of CLAD patients compared to healthy subjects was observed. In the murine IRI model, significant increase in M-MDSCs, MerTK expression and efferocytosis was observed in WT mice during resolution phase that was absent in cebpb -/- Land Mertk -/- mice. Adoptive transfer of M-MDSCs in cebpb -/- mice significantly attenuated lung dysfunction, and inflammation leading to resolution of IRI. Additionally, in a preclinical murine orthotopic LTx model, increases in M-MDSCs were associated with resolution of lung IRI in the transplant recipients. In vitro studies demonstrated the ability of M-MDSCs to efferocytose apoptotic neutrophils in a MerTK-dependent manner.

Conclusions

Our results suggest that MerTK-dependent efferocytosis by M-MDSCs can significantly contribute to the resolution of post-LTx IRI.

MicroRNA-141-3p reduces pulmonary hypoxia/reoxygenation injury through suppression of Beclin-1-dependent autophagy

Alterations in autophagy are involved in pulmonary hypoxia/reoxygenation (H/R)-induced injury. Here, we intended to explain the function of microRNA-141-3p (miR-141-3p) in regulating autophagy under the H/R condition. Rat pulmonary microvascular endothelial cells (PMVECs) were applied for H/R cell model establishment, followed by tracing of autophagy formation. SIRT1 plays a critical role in controlling the lifespan of yeast, flies, and mice. Interaction between SIRT1 and Beclin-1, an indicator protein for autophagy, and between miR-141-3p and SIRT1 was assayed with their roles in PMVEC injury. Autophagy of PMVECs was activated after hypoxia treatment and further activated after H/R treatment. The binding of miR-141-3p and SIRT1 was verified. In H/R-treated PMVECs, the binding of miR-141-3p and SIRT1 was reduced. Furthermore, SIRT1 acted as a deacetylase to stabilize the Beclin-1 protein, promoting autophagy and PMVEC injury. H/R rat models were established, and in vivo, experiments further confirmed that miR-141-3p regulated autophagy and lung injury in H/R rats through SIRT1/Beclin-1 axis. The current study highlighted that reduced miR-141-3p in H/R-treated PMVECs promoted deacetylation of Beclin-1 by SIRT1, thus causing PMVEC injury.

Translational medicine for acute lung injury

Acute lung injury (ALI) is a complex disease with numerous causes. This review begins with a discussion of disease development from direct or indirect pulmonary insults, as well as varied pathogenesis. The heterogeneous nature of ALI is then elaborated upon, including its epidemiology, clinical manifestations, potential biomarkers, and genetic contributions. Although no medication is currently approved for this devastating illness, supportive care and pharmacological intervention for ALI treatment are summarized, followed by an assessment of the pathophysiological gap between human ALI and animal models. Lastly, current research progress on advanced nanomedicines for ALI therapeutics in preclinical and clinical settings is reviewed, demonstrating new opportunities towards developing an effective treatment for ALI.

Lung transplantation in children

Lung transplantation is a well-established treatment for children facing advanced lung disease and pulmonary vascular disorders. However, organ shortage remains highest in children. For fitting the small chest of children, transplantation of downsized adult lungs, lobes, or even segments were successfully established. The worldwide median survival after pediatric lung transplantation is currently 5.7 years, while under consideration of age, underlying disease, and peri- and posttransplant center experience, median survival of more than 10 years is reported. Timing of referral for transplantation, ischemia-reperfusion injury, primary graft dysfunction, and acute and chronic rejection after transplantation remain the main challenges.

Role of gut microbes in acute lung injury/acute respiratory distress syndrome

Acute lung injury (ALI) is an acute, diffuse inflammatory lung condition triggered by factors of severe infections, trauma, shock, burns, ischemia-reperfusion, and mechanical ventilation. It is primarily characterized by refractory hypoxemia and respiratory distress. The more severe form, acute respiratory distress syndrome (ARDS), can progress to multi-organ failure and has a high mortality rate. Despite extensive research, the exact pathogenesis of ALI and ARDS remains complex and not fully understood. Recent advancements in studying the gut microecology of patients have revealed the critical role that gut microbes play in ALI/ARDS onset and progression. While the exact mechanisms are still under investigation, evidence increasingly points to the influence of gut microbes and their metabolites on ALI/ARDS. This review aims to summarize the role of gut microbes and their metabolites in ALI/ARDS caused by various triggers. Moreover, it explores potential mechanisms and discusses how gut microbe-targeting interventions might offer new clinical strategies for the treatment of ALI/ARDS.

Intraoperative Extracorporeal Support during Lung Transplantation: Not Just for the High-Risk Patient

The use of intraoperative mechanical support during lung transplantation has traditionally been a controversial topic. Trends for intraoperative mechanical support strategies swing like a pendulum. Historically, cardiopulmonary bypass (CPB) was the modality of choice during transplantation. It provides full hemodynamic support including oxygenation and decarboxylation. Surgical exposure is improved by permitting the drainage of the heart and provides more permissive retraction. CPBs contain drainage reservoirs with hand-held pump suction catheters promoting blood conservation through collection and re-circulation. But CPB has its disadvantages. It is known to cause systemic inflammation and coagulopathy. CPB requires high doses of heparinization, which increases bleeding risks. As transplantation progressed, off-pump transplantation began to trend as a preferable option. ECMO, however, has many of the benefits of CPB with less of the risk. Outcomes were improved with ECMO compared to CPB. CPB has a higher blood transfusion requirement, a higher need for post-operative ECMO support, a higher re-intubation rate, high rates of kidney injury and need for hemodialysis, longer ICU stays, higher incidences of PGD grade 3, as well as overall in-hospital mortality when compared with ECMO use. The focus now shifts to using intraoperative mechanical support to protect the graft, helping to reduce ischemia-reperfusion injury and allowing for lung protective ventilator settings. Studies show that the routine use of ECMO during transplantation decreases the rate of primary graft dysfunction and many adverse outcomes including ventilator time, need for tracheostomy, renal failure, post-operative ECMO requirements, and others. As intraoperative planned ECMO is considered a safe and effective approach, with improved survival and better overall outcomes compared to both unplanned ECMO implementation and off-pump transplantation, its routine use should be taken into consideration as standard protocol.

Hydroxycitric Acid Alleviated Lung Ischemia-Reperfusion Injury by Inhibiting Oxidative Stress and Ferroptosis through the Hif-1α Pathway

Lung ischemia-reperfusion injury (LIRI) is a prevalent occurrence in various pulmonary diseases and surgical procedures, including lung resections and transplantation. LIRI can result in systemic hypoxemia and multi-organ failure. Hydroxycitric acid (HCA), the primary acid present in the peel of Garcinia cambogia, exhibits anti-inflammatory, antioxidant, and anticancer properties. However, the effects of HCA on LIRI remain unknown. To investigate the impact of HCA on LIRI in mice, the mice were randomly divided into four groups: the control group, the I/R model group, and the I/R + low- or high-dose HCA groups. Human umbilical vein endothelial cells (HUVECs) were subjected to hypoxia for 12 h followed by reoxygenation for 6 h to simulate in vitro LIRI. The results demonstrated that administration of HCA effectively attenuated lung injury, inflammation, and edema induced by ischemia reperfusion. Moreover, HCA treatment significantly reduced malondialdehyde (MDA) and reactive oxygen species (ROS) levels while decreasing iron content and increasing superoxide dismutase (SOD) levels after ischemia-reperfusion insult. Mechanistically, HCA administration significantly inhibited Hif-1α and HO-1 upregulation both in vivo and in vitro. We found that HCA could also alleviate endothelial barrier damage in H/R-induced HUVECs in a concentration-dependent manner. In addition, overexpression of Hif-1α counteracted HCA-mediated inhibition of H/R-induced endothelial cell ferroptosis. In summary, these results indicate that HCA alleviated LIRI by inhibiting oxidative stress and ferroptosis through the Hif-1α pathway.

Bioinformatics analyses of immune-related genes and immune infiltration associated with lung ischemia-reperfusion injury

BACKGROUND

Ischemia-reperfusion injury (IRI) is a significant complication that can occur following lung transplantation and is known to contribute to poor prognosis. Our research aimed to investigate the potential molecular targets and mechanisms involved in lung IRI (LIRI), in order to improve our understanding of this condition.

METHOD

We downloaded gene expression datasets (GSE127003 and GSE18995) linked to LIRI from the GEO database. Using WGCNA, we identified LIRI-related modules. Functional enrichment analyses were performed on the modules showing significant correlation with LIRI. Core immune-related genes (IRGs) were identified and validated using the GSE18995 dataset. A rat LIRI model was established to validate the expression changes of core IRGs. The LIRI groups were subjected to 60 min of warm ischemia followed by 120 min of reperfusion. Additionally, the xCell algorithm was used to characterize the immune landscape and analyze the relationships between hub IRGs and infiltrating immune cells.

RESULTS

A total of 483 genes from the turquoise module were identified through WGCNA, with a predominant enrichment in immune- and inflammation-related pathways. Three IRGs (PTGS2, CCL2, and RELB) were found to be up-regulated after reperfusion in both GSE127003 and GSE18995 datasets, and this was further confirmed using the rat LIRI model. The xCell analysis revealed that immune score, CD8+ naive T cells, eosinophils, neutrophils, NK cells, and Tregs were upregulated after reperfusion. PTGS2, CCL2, and RELB showed positive correlations with CD8+ naive T cells, monocytes, neutrophils, and Tregs.

CONCLUSION

PTGS2, CCL2, and RELB were found to be potential biomarkers for LIRI. Immune and microenvironment scores were higher after reperfusion compared to before reperfusion. PTGS2, CCL2, and RELB appear to play a crucial role in the development of LIRI and may contribute to it by increasing the number of immune cells. Our findings offer new perspectives on potential treatment targets and the pathogenesis of LIRI.

Therapeutic benefits of nitric oxide in lung transplantation

Lung transplantation is an evolutionary procedure from its experimental origin in the twentieth century and is now recognized as an established and routine life-saving intervention for a variety of end-stage pulmonary diseases refractory to medical management. Despite the success and continuous refinement in lung transplantation techniques, the widespread application of this important life-saving intervention is severely hampered by poor allograft quality offered from donors-after-brain-death. This has necessitated the use of lung allografts from donors-after-cardiac-death (DCD) as an additional source to expand the pool of donor lungs. Remarkably, the lung exhibits unique properties that may make it ideally suitable for DCD lung transplantation. However, primary graft dysfunction (PGD), allograft rejection and other post-transplant complications arising from unavoidable ischemia-reperfusion injury (IRI) of transplanted lungs, increase morbidity and mortality of lung transplant recipients annually. In the light of this, nitric oxide (NO), a selective pulmonary vasodilator, has been identified as a suitable agent that attenuates lung IRI and prevents PGD when administered directly to lung donors prior to donor lung procurement, or to recipients during and after transplantation, or administered indirectly by supplementing lung preservation solutions. This review presents a historical account of clinical lung transplantation and discusses the lung as an ideal organ for DCD. Next, the author highlights IRI and its clinical effects in lung transplantation. Finally, the author discusses preservation solutions suitable for lung transplantation, and the protective effects and mechanisms of NO in experimental and clinical lung transplantation.

Differentiation between lung allograft rejection and infection using donor-derived cell-free DNA and pathogen detection by metagenomic next-generation sequencing

Background

In lung transplant recipients (LTRs), the primary causes of mortality are rejection and infection, which often present similar symptoms, making differentiation challenging. This study aimed to explore the diagnostic efficacy of plasma donor-derived cell-free DNA (dd-cfDNA) in conjunction with metagenomic next-generation sequencing (mNGS) for pathogen detection in differentiation between lung allograft rejection and infection in LTRs experiencing new-onset pulmonary complications.

Methods

We conducted a retrospective study on 188 LTRs who underwent lung or heart-lung transplantation at our institution from 2015 to 2021. The LTRs were categorized into three groups: stable, rejection, and infection. We measured plasma dd-cfDNA levels and utilized both mNGS and culture methods to identify pathogens in the bronchoalveolar lavage fluid (BALF).

Results

The rejection group exhibited the highest levels of plasma dd-cfDNA (median 1.34 %, interquartile range [IQR] 1.06-2.19 %) compared to the infection group (median 0.72 %, IQR 0.62-1.07 %) and the stable group (median 0.69 %, IQR 0.58-0.78 %) (both p < 0.001). Within the infection group, a significantly higher level of dd-cfDNA was observed in the cytomegalovirus infection subgroup (p < 0.001), but not in the fungal (p > 0.05) or bacterial infection subgroups (p > 0.05), when compared to the stable group. Elevated dd-cfDNA levels, in combination with negative mNGS results, strongly indicated lung allograft rejection, with a positive predictive value and negative predictive value of 88.7 % and 99.2 %, respectively.

Conclusions

Plasma dd-cfDNA in combination with BALF pathogen detection by mNGS shows satisfactory accuracy in differentiating lung allograft rejection from infectious complications.

Pulmonary reperfusion injury in post-palliative intervention of oligaemic cyanotic CHD: a new catastrophic consequence or just revisiting the same old story?

Pulmonary reperfusion injury is a well-recognised clinical entity in the setting pulmonary artery angioplasty for pulmonary artery stenosis or chronic thromboembolic disease, but not much is known about this complication in post-palliative intervention of oligaemic cyanotic CHD. The pathophysiology of pulmonary reperfusion injury in this population consists of both ischaemic and reperfusion injury, mainly resulting in oxidative stress from reactive oxygen species generation, followed by endothelial dysfunction, and cytokine storm that may induce multiple organ dysfunction. Other mechanisms of pulmonary reperfusion injury are "no-reflow" phenomenon, overcirculation from high pressure in pulmonary artery, and increased left ventricular end-diastolic pressure. Chronic hypoxia in cyanotic CHD eventually depletes endogenous antioxidant and increased the risk of pulmonary reperfusion injury, thus becoming a concern for palliative interventions in the oligaemic subgroup. The incidence of pulmonary reperfusion injury varies depending on multifactors. Despite its inconsistence occurrence, pulmonary reperfusion injury does occur and may lead to morbidity and mortality in this population. The current management of pulmonary reperfusion injury is supportive therapy to prevent deterioration of lung injury. Therefore, a general consensus on pulmonary reperfusion injury is necessary for the diagnosis and management of this complication as well as further studies to establish the use of novel and potential therapies for pulmonary reperfusion injury.

Purinergic P2Y2 receptor-induced activation of endothelial TRPV4 channels mediates lung ischemia-reperfusion injury

Lung ischemia-reperfusion injury (IRI), characterized by inflammation, vascular permeability, and lung edema, is the major cause of primary graft dysfunction after lung transplantation. Here, we investigated the cellular mechanisms underlying lung IR-induced activation of endothelial TRPV4 channels, which play a central role in lung edema and dysfunction after IR. In a left lung hilar-ligation model of IRI in mice, we found that lung IRI increased the efflux of ATP through pannexin 1 (Panx1) channels at the endothelial cell (EC) membrane. Elevated extracellular ATP activated Ca2+ influx through endothelial TRPV4 channels downstream of purinergic P2Y2 receptor (P2Y2R) signaling. P2Y2R-dependent activation of TRPV4 channels was also observed in human and mouse pulmonary microvascular endothelium in ex vivo and in vitro models of IR. Endothelium-specific deletion of P2Y2R, TRPV4, or Panx1 in mice substantially prevented lung IRI-induced activation of endothelial TRPV4 channels and lung edema, inflammation, and dysfunction. These results identify endothelial P2Y2R as a mediator of the pathological sequelae of IRI in the lung and show that disruption of the endothelial Panx1-P2Y2R-TRPV4 signaling pathway could be a promising therapeutic strategy for preventing lung IRI after transplantation.

Acellular ex vivo lung perfusate silences pro-inflammatory signaling in human lung endothelial and epithelial cells

BACKGROUND

Ischemia-reperfusion injury is a key complication following lung transplantation. The clinical application of ex vivo lung perfusion (EVLP) to assess donor lung function has significantly increased the utilization of "marginal" donor lungs with good clinical outcomes. The potential of EVLP on improving organ quality and ameliorating ischemia-reperfusion injury has been suggested.

METHODS

To determine the effects of ischemia-reperfusion and EVLP on gene expression in human pulmonary microvascular endothelial cells and epithelial cells, cell culture models were used to simulate cold ischemia (4 °C for 18 h) followed by either warm reperfusion (DMEM + 10% FBS) or EVLP (acellular Steen solution) at 37 °C for 4 h. RNA samples were extracted for bulk RNA sequencing, and data were analyzed for significant differentially expressed genes and pathways.

RESULTS

Endothelial and epithelial cells showed significant changes in gene expressions after ischemia-reperfusion or EVLP. Ischemia-reperfusion models of both cell types showed upregulated pro-inflammatory and downregulated cell metabolism pathways. EVLP models, on the other hand, exhibited downregulation of cell metabolism, without any inflammatory signals.

CONCLUSION

The commonly used acellular EVLP perfusate, Steen solution, silenced the activation of pro-inflammatory signaling in both human lung endothelial and epithelial cells, potentially through the lack of serum components. This finding could establish the basic groundwork of studying the benefits of EVLP perfusate as seen from current clinical practice.

Risk of prolonged ischemic time linked to use of cardiopulmonary bypass during implantation for lung transplantation in the United Kingdom

BACKGROUND

Some degree of ischemia is inevitable in organ transplantation, and for most, if not all organs, there is a relationship between ischemic time and transplant outcome. The contribution of ischemic time to lung injury is unclear, with conflicting recent data. In this study, we investigate the impact of ischemia time on survival after lung transplantation in a large national cohort.

METHODS

We studied the outcomes for 1,565 UK adult lung transplants over a 12-year period, for whom donor, transplant, and recipient data were available from the UK Transplant Registry. We examined the effect of ischemia time (defined as donor cross-clamp to recipient reperfusion) and whether standard cardiopulmonary bypass was used using Cox proportional hazards models, adjusting for other risk factors.

RESULTS

The total ischemic time increased from a median under 5 hours in 2003 to over 6.2 hours in 2013. Our findings show that, when the cardiopulmonary bypass was used, there was an increase in the hazard of death (of 13% [95% CI: 5%-21%] for 1-year patient survival) for each hour of total ischemic time. However, if the cardiopulmonary bypass was not used for implantation, this link disappeared-there was no statistically significant change in mortality with increasing ischemic time.

CONCLUSIONS

We document that avoidance of bypass may remove ischemic time, within the limits of our observed range of ischemic times, as a risk factor for poor outcomes. Our data add to the evidence that bypass may be harmful to the donor lung.

Galectin-3 as TREM2 upstream factor contributes to lung ischemia-reperfusion injury by regulating macrophage polarization

Lung ischemia-reperfusion injury (LIRI) is a complex "aseptic" inflammatory response, macrophage play a pivotal role in the pathogenesis of LIRI. Galectin-3 (Gal3), a lectin implicated inflammation, has received limited attention in LIRI. Studies have reported Gal3 as a ligand for triggering receptor expressed on myeloid cell 2 (TREM2) in macrophages in Alzheimer's disease. Hence, we established LIRI C57BL/6 mice model and hypoxia/glucose deprivation and reoxygenation (OGD/R) model to investigate the relationship among Gal3, TREM2, and macrophage polarization. Our result demonstrated inhibition of Gal3 significantly reduced M1-type macrophage polarization while markedly increased M2-type in LIRI. In addition, we observed colocalization of Gal3 and TREM2 in macrophages, inhibition of Gal3 could recover the downregulation of TREM2 induced by LIRI while promoting TREM2 expression could attenuate lung injury in LIRI. In summary, our findings suggest Gal3 as an upstream factor of TREM2, play a crucial role in LIRI by regulating macrophage polarization.

Neutrophils for Revascularization Require Activation of CCR6 and CCL20 by TNFα

BACKGROUND

Activation of immune-inflammatory pathways involving TNFα (tumor necrosis factor alpha) signaling is critical for revascularization and peripheral muscle tissue repair after ischemic injury. However, mechanisms of TNFα-driven inflammatory cascades directing recruitment of proangiogenic immune cells to sites of ischemia are unknown.

METHODS

Muscle tissue revascularization after permanent femoral artery ligation was monitored in mutant mice by laser Doppler imaging and light sheet fluorescence microscopy. TNFα-mediated signaling and the role of the CCL20 (C-C motif chemokine ligand 20)-CCR6 (C-C chemokine receptor 6) axis for formation of new vessels was studied in vitro and in vivo using bone marrow transplantation, flow cytometry, as well as biochemical and molecular biological techniques.

RESULTS

TNFα-mediated activation of TNFR (tumor necrosis factor receptor) 1 but not TNFR2 was found to be required for postischemic muscle tissue revascularization. Bone marrow-derived CCR6+ neutrophil granulocytes were identified as a previously undescribed TNFα-induced population of proangiogenic neutrophils, characterized by increased expression of VEGFA (vascular endothelial growth factor A). Mechanistically, postischemic activation of TNFR1 induced expression of the CCL20 in vascular cells and promoted translocation of the CCL20 receptor CCR6 to the cell surface of neutrophils, essentially conditioning VEGFA-expressing proangiogenic neutrophils for CCL20-dependent recruitment to sites of ischemia. Moreover, impaired revascularization of ischemic peripheral muscle tissue in diabetic mice was associated with reduced numbers of proangiogenic neutrophils and diminished CCL20 expression. Administration of recombinant CCL20 enhanced recruitment of proangiogenic neutrophils and improved revascularization of diabetic ischemic skeletal muscles, which was sustained by sequential treatment with fluvastatin.

CONCLUSIONS

We demonstrate that site-specific activation of the CCL20-CCR6 axis via TNFα recruits proangiogenic VEGFA-expressing neutrophils to sites of ischemic injury for initiation of muscle tissue revascularization. The findings provide an attractive option for tissue revascularization, particularly under diabetic conditions.

Extracorporeal cytokine adsorption reduces systemic cytokine storm and improves graft function in lung transplantation

Objectives

Ischemia-reperfusion injury often coincides with a cytokine storm, which can result in primary graft dysfunction following lung transplantation. Our previous research has demonstrated allograft improvement by cytokine adsorption during ex vivo lung perfusion. The aim of this study was to investigate the effect of in vivo extracorporeal cytokine adsorption in a large animal model.

Materials and Methods

Pig left lung transplantation was performed following 24 hours of cold ischemic storage. Observation period after transplantation was 24 hours. In the treatment group (n = 6), extracorporeal CytoSorb adsorption was started 30 minutes before reperfusion and continued for 6 hours. A control group (n = 3) did not receive adsorber treatment.

Results

During adsorption, we consistently noticed a significant decrease in plasma proinflammatory interleukin (IL)-2, trends of less proinflammatory, tumor necrosis factor- α, IL-1α, and granulocyte-macrophage colony-stimulating factor as well as significantly reduced systemic neutrophils. In addition, a significantly lower peak airway pressure was detected during the 6 hours of adsorption. After 24 hours of observation, when evaluating the left lung allograft independently, we observed significantly improved CO2 removal, partial pressure of oxygen/inspired oxygen fraction ratio, and less acidosis in the treatment group. At autopsy, bronchoalveolar lavage results exhibited significantly lower recruitment of cells and less pro-inflammatory IL-1α, IL-1β, IL-6, and IL-8 in the treatment group. Histologically, the treatment group had a strong trend, indicating less neutrophil invasion into the alveolar space.

Conclusions

Based on our findings, cytokine adsorption during and after reperfusion is a viable approach to reducing posttransplant inflammation following lung transplantation. CytoSorb may increase the acceptance of extended criteria donor lungs, which are more susceptible to ischemia-reperfusion injury.

Primary Graft Dysfunction in Lung Transplantation: A Review of Mechanisms and Future Applications

Lung allograft recipients have worse survival than all other solid organ transplant recipients, largely because of primary graft dysfunction (PGD), a major form of acute lung injury affecting a third of lung recipients within the first 72 h after transplant. PGD is the clinical manifestation of ischemia-reperfusion injury and represents the predominate cause of early morbidity and mortality. Despite PGD's impact on lung transplant outcomes, no targeted therapies are currently available; hence, care remains supportive and largely ineffective. This review focuses on molecular and innate immune mechanisms of ischemia-reperfusion injury leading to PGD. We also discuss novel research aimed at discovering biomarkers that could better predict PGD and potential targeted interventions that may improve outcomes in lung transplantation.

Tackling regulated cell death yields enhanced protection in lung grafts

Background: Effective preservation strategies to ameliorate lung graft ischaemia injury are needed to rescue 'extended criteria' or 'marginal' lung grafts, and to improve recipient outcomes after transplantation. Methods: Lung grafts from male Lewis rats were extracted after 40 min of cardiocirculatory death, and healthy human lung tissues were collected from patients undergoing a lobectomy. Lung samples were then preserved in a 4°C preservation solution supplemented with 0.1 nM Dexmedetomidine (Dex, α2-adrenoceptor agonist) for 16 h. In vitro, human lung epithelial A549 cells were preserved in the 4°C preservation solution with 0.1 nM Dex for 24 h, then re-cultured in the cell culture medium at 37°C to mimic the clinical scenario of cold ischaemia and warm reperfusion. Lung tissues and cells were then analysed with various techniques including western blot, immunostaining and electron microscope, to determine injuries and the protection of Dex. Results: Prolonged warm ischaemia after cardiocirculatory death initiated Rip kinase-mediated necroptosis, which was exacerbated by cold storage insult and enhanced lung graft injury. Dex supplementation significantly reduced necroptosis through upregulating Nrf2 activation and reducing oxidative stress, thereby significantly improving lung graft morphology. Dex treatment also attenuated endoplasmic reticulum stress, stabilised lysosomes and promoted cell membrane resealing function, consequently reducing cell death and inflammatory activation after hypothermic hypoxia-reoxygenation in A549 cells. Conclusions: Inhibition of regulated cell death through Dex supplementation to the graft preservation solution improves allograft quality which may aid to expand the donor lung pool and enhance lung transplant outcomes per se.

Bone marrow mesenchymal stem cell-derived exosomes miR-202-5p inhibited pyroptosis to alleviate lung ischemic-reperfusion injury by targeting CMPK2

Bone mesenchymal stem cell-derived exosome (BMSC-exosome) is a potential candidate for lung ischemia-reperfusion injury (LIRI) treatment. This study aims to investigate the anti-pyroptosis effect of BMSC-exosomes in LIRI. The LIRI cell model was established by hypoxia/reoxygenation (H/R) treatment. Interleukin (IL)-1β and IL-18 levels were examined by enzyme-linked immunosorbent assay. Cell viability was assessed by 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay. Lactate dehydrogenase (LDH) release was examined using a LDH assay kit. The interaction between microRNA (miR)-202-5p and cytidine monophosphate kinase 2 (CMPK2) was analyzed using dual-luciferase reporter assay and RNA immunoprecipitation. BMSC-exosomes promoted cell viability and suppressed pyroptosis in H/R-treated mouse lung epithelial. miR-202-5p was enriched in BMSC-exosomes, and exosomal miR-202-5p inhibition upregulated pyroptosis-associated proteins, including cleaved N-terminal Gasdermin D, nucleotide-binding domain-like receptor family member pyrin domain-containing protein 3, and Caspase1. Meanwhile, miR-202-5p suppressed CMPK2 expression by directly targeting CMPK2. Expectedly, CMPK2 knockdown reversed the promoting effect of exosomal miR-202-5p inhibition on pyroptosis in LIRI. Therefore, BMSC-derived exosome miR-202-5p repressed pyroptosis to inhibit LIRI progression by targeting CMPK2.

Purinergic P2Y2 Receptor-Induced Activation of Endothelial TRPV4 Channels Mediates Lung Ischemia-Reperfusion Injury

Lung ischemia-reperfusion injury (IRI), characterized by inflammation, vascular permeability, and lung edema, is the major cause of primary graft dysfunction after lung transplantation. We recently reported that endothelial cell (EC) TRPV4 channels play a central role in lung edema and dysfunction after IR. However, the cellular mechanisms for lung IR-induced activation of endothelial TRPV4 channels are unknown. In a left-lung hilar ligation model of IRI in mice, we found that lung IR increases the efflux of extracellular ATP (eATP) through pannexin 1 (Panx1) channels at the EC membrane. Elevated eATP activated elementary Ca2+ influx signals through endothelial TRPV4 channels through purinergic P2Y2 receptor (P2Y2R) signaling. P2Y2R-dependent activation of TRPV4 channels was also observed in human and mouse pulmonary microvascular endothelium in ex vivo and in vitro surrogate models of lung IR. Endothelium-specific deletion of P2Y2R, TRPV4, and Panx1 in mice had substantial protective effects against lung IR-induced activation of endothelial TRPV4 channels, lung edema, inflammation, and dysfunction. These results identify endothelial P2Y2R as a novel mediator of lung edema, inflammation, and dysfunction after IR, and show that disruption of endothelial Panx1-P2Y2R-TRPV4 signaling pathway could represent a promising therapeutic strategy for preventing lung IRI after transplantation.

Evaluation of the effects of empagliflozin on acute lung injury in rat intestinal ischemia-reperfusion model

BACKGROUND

Empagliflozin is a selective sodium-glucose co-transporter (SGLT2) inhibitor that is approved for the treatment of type 2 diabetes. The beneficial effects of empagliflozin on other organ systems including the heart and kidneys have been proven. The aim of this study is to evaluate the role of empagliflozin on acute lung injury induced by intestinal ischemia-reperfusion (I/R).

MATERIALS AND METHODS

A total of 27 male Wistar albino rats were divided into three groups: sham, I/R, and I/R + empagliflozin; each group containing nine animals. Sham group rats underwent laparotomy without I/R injury. Rats in the I/R group underwent laparotomy, 1 h of after ischemia-reperfusion injury (superior mesenteric artery ligation was followed by 2 h of reperfusion). Rats in I/R were given empagliflozin (30 mg/kg) by gastric gavage for 7 days before the ischemia-reperfusion injury. All animals were killed at the end of reperfusion and lung tissue samples were obtained for immunohistochemical staining and histopathological investigation in all groups.

RESULTS

Serum glucose, AST, ALT, creatinine, native thiol, total thiol, and disulfide levels and disulfide-native thiol, disulfide-total thiol, and native thiol-total thiol ratios as well as the IMA levels were analyzed and compared among the groups. While intestinal I/R significantly increases serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and creatinine levels; did not cause any change in homeostasis parameters and IMA level. Empagliflozin treatment had no significant effect on biochemical parameters. Empagliflozin treatment induced a significant decrease in positive immunostaining for IL-1, IL-6, TNF-alpha, caspase 3, caspase 8, and caspase 9 compared to the I/R group in lung tissue samples. Intestinal I/R caused severe histopathological injury including edema, hemorrhage, increased thickness of the alveolar wall, and infiltration of inflammatory cells into alveolar spaces. Empagliflozin treatment significantly attenuated the severity of intestinal I/R injury.

CONCLUSIONS

It was concluded that empagliflozin treatment may have beneficial effects in acute lung injury, and, therefore, has the potential for clinical use.