Trigger for intercellular adhesion molecule-1 expression in rat lungs transplanted from non-heart-beating donors

Prophylactic efficacy of Quercetin in ameliorating the hypoxia induced vascular leakage in lungs of rats

The objective of the study was to find out the prophylactic efficacy of Quercetin in ameliorating the hypoxia induced vascular leakage in lungs of rats. Male SD rats received different doses of quercetin @ 25mg, 50mg, 100mg and 200mg/Kg BW, 1h prior to hypobaric hypoxia exposure (7,620m, for 6h). Quercetin 50 mg/kg BW supplemented orally 1h prior to hypoxia exposure was considered to be the optimum dose, due to significant reduction (p<0.001) in lung water content and lung transvascular leakage compared to control (hypoxia, 6h). Further, biochemical analysis (ROS, MDA, GSH, GPx, LDH, and albumin) and differential expressions of proteins (IKK-α/β, NFĸB, Nrf-2,TNF-α, ICAM-1, VCAM, P-selectin, Hif-1α, VEGF, TNF-α, TGF-β, INF-γ and IL-4) were determined by western blotting and ELISA. Changes in lung parenchyma were assessed by histopathology. Quercetin (50 mg/kg BW) prophylaxis under hypoxia showed significant reduction in oxidative stress (ROS and MDA), concomitant increase in antioxidants (GSH, GPx and SOD) followed by decreased LDH and albumin extravasation in BAL fluid over hypoxia. Quercetin prophylaxis significantly down regulated hypoxia induced increase in IKKα/β and NFĸB expressions leading to reduction in the levels of pro-inflammatory cytokines (TNF-α and INF-γ) followed by up regulation of anti-inflammatory cytokines (IL-4 and INF-γ) in lungs. Further, hypoxia mediated increase in HIF-1α was stabilized and VEGF levels in lungs were significantly down regulated by quercetin supplementation, leading to reduction in vascular leakage in lungs of rats under hypoxia. However, Quercetin has also enacted as Nrf-2 activator which significantly boosted up the synthesis of GSH under hypoxic condition compared to hypoxia. Histopathological observations further confirmed that quercetin preconditioning has an inhibitory effect on progression of oxidative stress and inflammation via attenuation of NFκB and stabilization HIF-1α in lungs of rats under hypoxia.These studies indicated that quercetin prophylaxis abrogates the possibility of hypobaric hypoxia induced pulmonary edema in rats.

Emerging understanding of roles for arterioles in inflammation

Arterioles, capillaries, and venules all actively change their cellular functions and phenotypes during inflammation in ways that are essential for maintenance of homeostasis and self-defense, and are also associated with many inflammatory disorders. ECs, together with pericytes and ECM proteins, can regulate blood flow, the coagulation cascade, fluid and solute exchange, and leukocyte trafficking. While capillary and venular functions in inflammation are well characterized, the arteriolar contribution to inflammation has only recently come into focus. Arterioles differ from venules in structure, EC morphology, shear environment, expression, and distribution of surface ligands; hence, regulation and function of arteriolar wall cells during inflammation may also be distinct from venules. Recent work indicates that in response to proinflammatory stimuli, arterioles alter barrier function, and support leukocyte and platelet interactions through upregulation of adhesion molecules. This suggests that in addition to their role in blood flow regulation, arterioles may also participate in inflammatory responses. In this review, we will discuss mechanisms that characterize arteriolar responses to proinflammatory stimuli. We will detail how distinct arteriolar features contribute to regulation of barrier function and leukocyte-EC interactions in inflammation, and further highlight the potential priming effects of arteriolar responses on venular function and progression of inflammatory responses.

Animal models of ex vivo lung perfusion as a platform for transplantation research

Ex vivo lung perfusion (EVLP) is a powerful experimental model for isolated lung research. EVLP allows for the lungs to be manipulated and characterized in an external environment so that the effect of specific ventilation/perfusion variables can be studied independent of other confounding physiologic contributions. At the same time, EVLP allows for normal organ level function and real-time monitoring of pulmonary physiology and mechanics. As a result, this technique provides unique advantages over in vivo and in vitro models. Small and large animal models of EVLP have been developed and each of these models has their strengths and weaknesses. In this manuscript, we provide insight into the relative strengths of each model and describe how the development of advanced EVLP protocols is leading to a novel experimental platform that can be used to answer critical questions in pulmonary physiology and transplant medicine.

Impact of prolonged cold preservation on the graft function and gene expression levels in an experimental lung transplantation model

PURPOSE

Ischemia reperfusion injury (IRI) remains a significant cause of morbidity and mortality after lung transplantation. Early growth response-1 (EGR1) drives the expression of inflammatory mediators and has an important role in IRI. We hypothesized that the severe IRI caused by a long preservation induces a specific expression pattern of EGR1 and its target genes which would correlate with the lung graft function.

METHODS

SD rat lungs were preserved at 4 °C for 3 or 18 h, then transplanted and reperfused. Pulmonary grafts were evaluated for the blood gas oxygenation and pathological findings. The intra-graft mRNA levels of EGR1 and its downstream target genes were measured by real-time PCR. A Western blotting analysis of the EGR1 expression was used to validate the changes in the protein level.

RESULTS

There was upregulation of EGR1, MIP-2 and PAI-1 when there was prolonged hypothermic preservation. The expression levels of MIP-2 and PAI-1 were observed to increase for up to 4 h in the 18 h preserved lungs. There were no differences in the expression levels of IL-1β and ICAM-1 between the lungs subjected to short and long periods of ischemia.

CONCLUSIONS

Our data showed that prolonged hypothermic graft preservation deteriorates the pulmonary graft function, which was associated with the induction of EGR1 and its downstream target genes, which may aggravate IRI following lung transplantation.

Novel critical role of Toll-like receptor 4 in lung ischemia-reperfusion injury and edema

Toll-like receptors (TLRs) of the innate immune system contribute to noninfectious inflammatory processes. We employed a murine model of hilar clamping (1 h) with reperfusion times between 15 min and 3 h in TLR4-sufficient (C3H/OuJ) and TLR4-deficient (C3H/HeJ) anesthetized mice with additional studies in chimeric and myeloid differentiation factor 88 (MyD88)- and TLR4-deficient mice to determine the role of TLR4 in lung ischemia-reperfusion injury. Human pulmonary microvascular endothelial monolayers were subjected to simulated warm ischemia and reperfusion with and without CRX-526, a competitive TLR4 inhibitor. Functional TLR4 solely on pulmonary parenchymal cells, not bone marrow-derived cells, mediates early lung edema following ischemia-reperfusion independent of MyD88. Activation of MAPKs and NF-kappaB was significantly blunted and/or delayed in lungs of TLR4-deficient mice as a consequence of ischemia-reperfusion injury, but edema development appeared to be independent of activation of these signaling pathways. Pretreatment with a competitive TLR4 inhibitor prevented edema in vivo and reduced actin cytoskeletal rearrangement and gap formation in pulmonary microvascular endothelial monolayers subjected to simulated warm ischemia and reperfusion. In addition to its well-accepted role to alter gene transcription, functioning TLR4 on pulmonary parenchymal cells plays a key role in very early and profound pulmonary edema in murine lung ischemia-reperfusion injury. This may be due to a novel mechanism: regulation of endothelial cell cytoskeleton affecting microvascular endothelial cell permeability.

Plasma intercellular adhesion molecule-1 and von Willebrand factor in primary graft dysfunction after lung transplantation

Primary graft dysfunction (PGD), a form of acute lung injury occurring within 72 h following lung transplantation, is characterized by pulmonary edema and diffuse alveolar damage. We hypothesized that higher concentrations of intercellular adhesion molecule-1 (ICAM-1) and von Willebrand factor (vWF) would be associated with the occurrence of PGD. A total of 128 lung transplant recipients among 7 lung transplant centers were enrolled in a multicenter, prospective, cohort study. Blood specimens were collected preoperatively and at 6, 24, 48 and 72 h following lung transplantation. The primary outcome was Grade 3 PGD at 72 h after transplant. Logistic regression and generalized estimating equations (GEE) were used to analyze plasma ICAM-1 and vWF. At each postoperative timepoint, mean plasma ICAM-1 concentrations were higher for patients with PGD versus no PGD. The GEE contrast estimate for the association of plasma ICAM-1 with PGD was 107.5 ng/mL (95% CI 38.7, 176.3), p = 0.002. In the multivariate analyses, this finding was independent of all clinical variables except pulmonary artery pressures prior to transplant. There was no association between plasma vWF levels and PGD. We conclude that higher levels of plasma ICAM-1 are associated with PGD following lung transplantation.

Sivelestat reduces reperfusion injury of lungs harvested from endotoxin-primed rats by inhibition of neutrophil-mediated inflammation

BACKGROUND

Although liberalization of donor criteria may be one of the solutions to the current serious lung donor shortage, the use of non-standard donor lungs would increase the risk of post-operative complications. In the present study, we investigated the effect of sivelestat, a neutrophil elastase inhibitor, on reperfusion injury of a donor lung that was harvested from endotoxin-primed animals in a rat lung transplantation model.

METHODS

Donor rats received an intraperitoneal injection of Escherichia coli endotoxin (5 mg/kg) 2 hours before lung harvesting. The donor lungs were flushed with an organ preservation solution with or without sivelestat (300 microg/ml), and the left lung was immediately transplanted to the recipient by the cuff technique.

RESULTS

Endotoxin priming did not cause significant lung injury before harvesting. Although these lungs looked normal macroscopically, they were found to contain numerous neutrophils in the alveolar capillaries, even after lung flushing. There was no significant difference in the neutrophil count between the lungs flushed with and without sivelestat. The endotoxin-primed donor lung without sivelestat treatment became edematous immediately after reperfusion. In addition, the recipient's native right lungs were also pathologic. Treatment with sivelestat significantly reduced injury in both the donor and the recipient's native lungs. Treatment with sivelestat also inhibited the increase in tumor necrosis factor-alpha and cytokine-induced neutrophil chemoattractant-1 levels in the recipient circulation after reperfusion.

CONCLUSIONS

We conclude that sivelestat could reduce lung injury after transplantation by inhibiting the deleterious burst of inflammatory reactions that are initiated by reperfusion of the lungs from endotoxin-primed rats.

Ex-vivo perfusion and ventilation of rat lungs from non-heart-beating donors before transplant

BACKGROUND

We developed an ex-vivo circuit to evaluate human lungs retrieved from non-heart-beating donors. We assessed the effect of a similar circuit on the function of transplanted rat lungs retrieved from non-heart-beating donors.

METHODS

One hour after death, Sprague-Dawley rat heart-lung blocks were flushed with 20 mL of cold Perfadex, stored cold for 1 hour, then warmed to 37 degrees C in a circuit perfused with Earle's crystalloid solution with or without washed porcine erythrocytes (hematocrit 12% to 15%). At 37 degrees C, lungs were ventilated for 15 minutes with alveolar gas, perfusion-cooled to 20 degrees C, flushed again with cold Perfadex, and then stored cold for 2.5 hours. The left lung was transplanted using a modified cuff technique with flow probes on the main and left pulmonary arteries. After 1 hour of reperfusion, arterial blood gases from the left pulmonary vein and wet/dry weight ratio (W/D) of both donor lungs were determined. Lungs transplanted after retrieval from heart-beating or non-heart-beating donors served as controls (n = 6 per group).

RESULTS

Lungs gained weight in the circuit but W/D and PO2 were similar after transplantation for all groups. After transplantation, vascular resistance was higher and dynamic compliance was lower for lungs perfused in the circuit. Myeloperoxidase and conjugated diene levels were modestly elevated in lungs transplanted from non-heart-beating donors irrespective of perfusion in the circuit.

CONCLUSIONS

Rat lungs are suitable for transplant after ex-vivo perfusion and ventilation. This model closely mimics methods used to evaluate the function of lungs retrieved from human non-heart-beating donors and can economically evaluate ex-vivo therapies for lungs retrieved from non-heart-beating donors.

Lung Transplantation: Current Status and Challenges

The lung is an anatomically complex vital organ whose normal physiology depends on actively regulated ventilation and perfusion, and maintenance of a delicate blood-air barrier over a huge surface area in direct contact with a potentially hostile environment. Despite significant progress over the past 25 years, both short- and long-term outcomes remain significantly inferior for lung recipients relative to other "solid" organs. This review summarizes the current status of lung transplantation so as to frame the principle challenges currently facing end-stage lung-failure patients and the practitioners who care for them.

ICAM-1 and LFA-1 play critical roles in LPS-induced neutrophil recruitment into the alveolar space

Neutrophil recruitment into lung constitutes a major response to airborne endotoxins. In many tissues endothelial intercellular adhesion molecule-1 (ICAM-1) interacts with lymphocyte function associated antigen-1 (LFA-1) on neutrophils, and this interaction plays a critical role in neutrophil recruitment. There are conflicting reports about the role of ICAM-1 in neutrophil recruitment into lungs. We studied neutrophil recruitment into alveolar space in a murine model of aerosolized LPS-induced lung inflammation. LPS induces at least a 100-fold increase in neutrophil numbers in alveolar space, as determined by flow cytometry of bronchoalveolar lavage fluid. Neutrophil recruitment was reduced by 54% in ICAM-1 null mice and by 45% in LFA-1 null mice. In wild-type mice treated with anti-ICAM-1 and anti-LFA-1 antibodies, there was 51 and 58% reduction in the neutrophil recruitment, respectively. In chimeric mice, generated by the transplantation of mixtures of bone marrows from LFA-1 null and wild-type mice, the normalized recruitment of LFA-1 null neutrophils was reduced by 60% compared with wild-type neutrophils. Neither the treatment of ICAM-1 null mice with a function-blocking antibody to LFA-1 nor the treatment of LFA-1 null mice with anti-ICAM-1 antibody resulted in further reduction in the recruitment compared with untreated ICAM-1 null and LFA-1 null mice. We conclude that ICAM-1 and LFA-1 play critical roles in the recruitment of neutrophils into the alveolar space in aerosolized LPS-induced lung inflammation, and LFA-1 serves as a ligand of ICAM-1 in the lung.

Non-heart-beating donors

The widespread application of lung transplantation is limited by the shortage of suitable donor organs resulting in longer waiting times for listed patients with a substantial risk of dying before transplantation. To overcome this critical organ shortage, some transplant programs have now begun to explore the use of lungs from circulation-arrested donors, so called non-heart-beating donors (NHBDs). This review outlines the different categories of NHBDs, the relevant published experimental data that support the use of lungs coming from these donors and the clinical experience worldwide so far. Techniques for NHBD lung preservation and pretransplant functional assessment are reviewed. Ethical issues involved in transplanting lungs from asystolic donors are discussed.