Therapeutic reconditioning of damaged lungs by transient heat stress during ex vivo lung perfusion

Optimal duration of ex vivo lung perfusion for heat stress-mediated therapeutic reconditioning of damaged rat donor lungs

OBJECTIVES

Transient heat stress (HS) application during experimental ex vivo lung perfusion (EVLP) of warm ischaemic (WI) rat lungs produces a range of therapeutic benefits. Here, we explored whether different EVLP durations after HS application would influence its therapeutic effects.

METHODS

In protocol 1, WI rat lungs were exposed to HS (41.5°C, 60-90 min EVLP), and EVLP was maintained for 3, 4.5 or 6 h (n = 5/group), followed by physiological measurements (compliance, oedema, oxygenation capacity). In protocol 2, WI rat lungs treated with (HS groups) or without HS (control groups) were maintained for 3 or 4.5 h EVLP (n = 5/group), followed by physiological evaluation and measurements (lung tissue) of heat shock proteins (HSP70, HSP27, HS90, GRP78), endogenous proteins (surfactant protein-D, CC16, platelet endothelial cell adhesion molecule-1), anti-apoptotic (Bcl2, Bcl-xL) and pro-apoptotic proteins (Bcl2-associated X protein, CCAAT/enhancer binding-protein homologous protein), antioxidant enzymes (heme-oxygenase-1, nicotinamide di-phospho-nucleotide dehydrogenase quinone-1) and nitrotyrosine (oxidative stress biomarker).

RESULTS

In protocol 1, physiological variables were stable after 3 and 4.5 h but deteriorated after 6 h. In protocol 2, at 3 h EVLP, HS-treated lungs differed from controls by higher expression of HSP70 and heme-oxygenase-1, and lower CC16 expression. In contrast, at 4.5 h EVLP, HS-treated lungs displayed improved physiology, higher levels of all HSPs, preserved or increased expression of surfactant protein-D, CC-16 and platelet endothelial cell adhesion molecule-1, increased antioxidant and anti-apoptotic proteins, and reduced pro-apoptotic proteins and nitrotyrosine.

CONCLUSIONS

The protective effects of HS application during EVLP of WI-damaged rat lungs strictly depend on the duration of post-HS recovery. An EVLP duration of 4.5 h appears to optimize the therapeutic potential of HS, while maintaining lungs in a stable physiological state.

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.

Racial and Gender Disparities in Transplantation of Hepatitis C+ Hearts and Lungs

BACKGROUND

Transplanting organs from hepatitis C virus (HCV)-infected donors into HCV-negative recipients has led to thousands of more transplants in the United States since 2016. Studies have demonstrated disparities in utilization of kidneys from these donors due to gender and education. It is still unknown, however, if the same disparities are seen in heart and lung transplantation.

METHODS

We used Organ Procurement and Transplantation/United Network for Organ Sharing data on all isolated heart and lung transplants from November 1, 2018, to March 31, 2023, classifying donors based on their HCV nucleic acid test (NAT) result: HCV-NAT- vs HCV-NAT+. We fit separate mixed-effects logistic regression models (outcome: HCV-NAT+ donor) for heart and lung transplants. Primary covariates included (1) race/ethnicity, (2) sex, (3) education level, (4) insurance type, and (5) transplant year.

RESULTS

The study included 26,108 adults (14,189 isolated heart transplant recipients and 11,919 isolated lung transplant recipients). A total of 993 (7.0%) heart transplants involved an HCV-NAT+ donor, compared to 457 (3.8%) lung transplants. In multivariable models among all isolated heart transplant recipients, women were significantly less likely to receive an HCV-NAT+ donor heart (odds ratio [OR]: 0.79, 95% confidence interval [CI]: 0.67-0.92, p = 0.003), as were Asian patients (OR: 0.52, 95% CI: 0.31-0.86, p = 0.01). In multivariable models among all isolated lung transplant recipients, Asians were significantly less likely to receive HCV-NAT+ transplants (OR: 0.31, 95% CI: 0.12-0.77, p = 0.01).

CONCLUSIONS

There are disparities in utilization of heart and lungs from HCV-NAT+ donors, with women and Asian patients being significantly less likely to receive these transplants.

Erythropoietin alleviates lung ischemia-reperfusion injury by activating the FGF23/FGFR4/ERK signaling pathway

Background

The purpose of the present study was to investigate the effect of erythropoietin (EPO) on lung ischemia-reperfusion injury (LIRI).

Methods

Sprague Dawley rats and BEAS-2B cells were employed to construct an ischemia-reperfusion (I/R)-induced model in vivo and in vitro, respectively. Afterward, I/R rats and tert-butyl hydroperoxide (TBHP)-induced cells were treated with different concentrations of EPO. Furthermore, 40 patients with LIRI and healthy controls were enrolled in the study.

Results

It was observed that lung tissue damage, cell apoptosis and the expression of BAX and caspase-3 were higher in the LIRI model in vivo and in vitro than in the control group, nevertheless, the Bcl-2, FGF23 and FGFR4 expression level was lower than in the control group. EPO administration significantly reduced lung tissue damage and cell apoptosis while also up-regulating the expression of FGF23 and FGFR4. Rescue experiments indicated that EPO exerted a protective role associated with the FGF23/FGFR4/p-ERK1/2 signal pathway. Notably, the expression of serum EPO, FGF23, FGFR4 and Bcl-2 was decreased in patients with LIRI, while the expression of caspase-3 and BAX was higher.

Conclusion

EPO could effectively improve LIRI, which might be related to the activation of the FGF23/FGFR4/p-ERK1/2 signaling pathway.