Mast cells in a murine lung ischemia-reperfusion model of primary graft dysfunction

Loading Imatinib inside targeted nanoparticles to prevent Bronchiolitis Obliterans Syndrome

Bronchiolitis Obliterans Syndrome seriously reduces long-term survival of lung transplanted patients. Up to now there is no effective therapy once BOS is established. Nanomedicine introduces the possibility to administer drugs locally into lungs increasing drug accumulation in alveola reducing side effects. Imatinib was loaded in gold nanoparticles (GNP) functionalized with antibody against CD44 (GNP-HCIm). Lung fibroblasts (LFs) were derived from bronchoalveolar lavage of BOS patients. GNP-HCIm cytotoxicity was evaluated by MTT assay, apoptosis/necrosis and phosphorylated-cAbl (cAbl-p). Heterotopic tracheal transplantation (HTT) mouse model was used to evaluate the effect of local GNP-HCIm administration by Alzet pump. GNP-HCIm decreased LFs viability compared to Imatinib (44.4 ± 1.8% vs. 91.8 ± 3.2%, p < 0.001), inducing higher apoptosis (22.68 ± 4.3% vs. 6.43 ± 0.29; p < 0.001) and necrosis (18.65 ± 5.19%; p < 0.01). GNP-HCIm reduced cAbl-p (0.41 GNP-HCIm, 0.24 Imatinib vs. to control; p < 0.001). GNP-HCIm in HTT mouse model by Alzet pump significantly reduced tracheal lumen obliteration (p < 0.05), decreasing apoptosis (p < 0.05) and TGF-β-positive signal (p < 0.05) in surrounding tissue. GNP-HCIm treatment significantly reduced lymphocytic and neutrophil infiltration and mast cells degranulation (p < 0.05). Encapsulation of Imatinib into targeted nanoparticles could be considered a new option to inhibit the onset of allograft rejection acting on BOS specific features.

Role of Mast Cells and Type 2 Innate Lymphoid (ILC2) Cells in Lung Transplantation

The multifunctional role of mast cells (MCs) in the immune system is complex and has not fully been explored. MCs reside in tissues and mucous membranes such as the lung, digestive tract, and skin which are strategically located at interfaces with the external environment. These cells, therefore, will encounter external stimuli and pathogens. MCs modulate both the innate and the adaptive immune response in inflammatory disorders including transplantation. MCs can have pro- and anti-inflammatory functions, thereby regulating the outcome of lung transplantation through secretion of mediators that allow interaction with other cell types, particularly innate lymphoid cells (ILC2). ILC2 cells are a unique population of hematopoietic cells that coordinate the innate immune response against a variety of threats including infection, tissue damage, and homeostatic disruption. In addition, MCs can modulate alloreactive T cell responses or assist in T regulatory (Treg) cell activity. This paper outlines the current understanding of the role of MCs in lung transplantation, with a specific focus on their interaction with ILC2 cells within the engrafted organ.

Degranulation of gastrointestinal mast cells contributes to hepatic ischemia-reperfusion injury in mice

The pathological changes following liver damage, including those caused by ischemia and reperfusion (I/R), are closely related to gastrointestinal dysregulation. Mast cells (MCs) are tissue-resident immune cells abundant in the gastrointestinal system that play diverse roles. In view of the characteristic localization of MCs around the microvasculature, we hypothesized that a stimulus-specific set of mediators released through degranulation of gastrointestinal MCs, which are enriched in hepatic sinusoids via the hepatic system, subsequently participate in associated pathological development within the liver. To elucidate the biological role of gastrointestinal MC granules in liver damage, we employed an experimental liver I/R model that allows conditional ablation of MCs. Marked degranulation was detected during I/R, which showed a significant positive correlation with liver damage. Our experiments further disclosed that MC degranulation primarily enhanced the cycle of inflammatory damage in I/R liver consisting of liver sinusoidal endothelial cell death, neutrophil infiltration, and formation of a neutrophil extracellular trap, with a concomitant increase in adhesion molecules, inflammatory cytokines, chemokines, and oxidative stress. Based on the collective results, we propose that suppression of activity or number of MCs may present an effective strategy for protection against hepatic I/R injury.

Mechanisms of lung ischemia-reperfusion injury

PURPOSE OF REVIEW

Lungs are extremely susceptible to injury, and despite advances in surgical management and immunosuppression, outcomes for lung transplantation are the worst of any solid organ transplant. The success of lung transplantation is limited by high rates of primary graft dysfunction because of ischemia-reperfusion injury characterized by robust inflammation, alveolar damage, and vascular permeability. This review will summarize major mechanisms of lung ischemia-reperfusion injury with a focus on the most recent findings in this area.

RECENT FINDINGS

Over the past 18 months, numerous studies have described strategies to limit lung ischemia-reperfusion injury in experimental settings, which often reveal mechanistic insight. Many of these strategies involved the use of various antioxidants, anti-inflammatory agents, mesenchymal stem cells, and ventilation with gaseous molecules. Further advancements have been achieved in understanding mechanisms of innate immune cell activation, neutrophil infiltration, endothelial barrier dysfunction, and oxidative stress responses.

SUMMARY

Methods for prevention of primary graft dysfunction after lung transplant are urgently needed, and understanding mechanisms of ischemia-reperfusion injury is critical for the development of novel and effective therapeutic approaches. In doing so, both acute and chronic outcomes of lung transplant recipients will be significantly improved.

Fluid Management in Lung Transplant Patients

Overall, there is a lack of randomized controlled trials examining the correlation between fluid volume delivery and outcomes in postoperative lung transplant patients. However, using thoracic surgery patients as a guide, the evidence suggests that hypervolemia correlates with pulmonary edema and should be avoided in lung transplant patients. However, it is recognized that patients with hemodynamic instability may require volume for attenuation of this situation, but it can likely be mitigated with the use of inotropic medication to maintain adequate perfusion and avoid the development of edema.

Mechanisms of graft rejection after lung transplantation

PURPOSE OF REVIEW

To date, outcomes after lung transplantation are far worse than after transplantation of other solid organs. New insights into mechanisms that contribute to graft rejection and tolerance after lung transplantation remain of great interest. This review examines the recent literature on the role of innate and adaptive immunity in shaping the fate of lung grafts.

RECENT FINDINGS

Innate and adaptive immune cells orchestrate allograft rejection after transplantation. Innate immune cells such as neutrophils are recruited to the lung graft early after reperfusion and subsequently promote allograft rejection. Although it is widely recognized that CD4 T lymphocytes in concert with CD8 T cells promote graft rejection, regulatory Foxp3 CD4 T, central memory CD8 T cells, and natural killer cells can facilitate tolerance.

SUMMARY

This review highlights interactions between innate and adaptive immune pathways and how they contribute to lung allograft rejection. These findings lay a foundation for the design of new therapeutic strategies that target both innate and adaptive immune responses.

The putative role of mast cells in lung transplantation

Mast cells (MCs) were primarily recognized as effector cells of allergy. These cells are acting predominantly at the interface between the host and the external environment, such as skin, gastrointestinal and the respiratory tract. Only recently, MCs have gained increased recognition as cells of functional plasticity with immune-regulatory properties that influence both the innate and the adaptive immune response in inflammatory disorders, cancer and transplantation. Through the secretion of both proinflammatory and antiinflammatory mediators, MCs can either ameliorate or deteriorate the course and outcome in lung transplantation. Recent research from other models recognized the immune-protective activity of MCs including its role as an important source of IL-10 and TGF-β for the modulation of alloreactive T cell responses or assistance in Treg activity. This paper summarizes the current understanding of MCs in lung transplantation and discusses MC-mediated immune-mechanisms by which the outcome of the engrafted organ is modulated.

Longitudinal quantification of radical bursts during pulmonary ischaemia and reperfusion

OBJECTIVES

Pulmonary ischaemia-reperfusion injury (IRI) is associated with several life-threatening pulmonary disorders, and may severely compromise the outcome of lung transplantation. Highly reactive molecules such as superoxide, nitric oxide (NO) and peroxynitrite (ONOO(-)) are presumed to contribute to IRI pathogenesis, but this assumption is based on indirect measurements. We use electron spin resonance (ESR) to directly quantify free radical formation after pulmonary ischaemia and reperfusion.

METHODS

Five groups of 10 Swiss mice were subjected to left pulmonary hilum clamping for 1 h of ischaemia followed by 0, 1, 4 and 24 h of reperfusion or to sham thoracotomy alone as control procedure. In five mice per group, ESR was used to measure iron-diethyldithio-carbamate trihydrate-trapped NO in the lung. In the other group of 5, reactive oxygen species generation in the lung and in blood was quantified with ESR by detection of ascorbyl radical and CMH spin probe, respectively. Pulmonary ONOO(-) was monitored with nitrotyrosine Western blotting.

RESULTS

After 1 h of reperfusion, a pulmonary NO peak (14.69 ± 0.91 × 10(4) Arbitrary Units (A.U.). vs 1.84 ± 0.75 × 10(4) A.U. in sham; P < 0.001) coincided with a significant increase in nitrosated proteins (0.105 ± 0.015 A.U.) compared with sham (0.047 ± 0.006 A.U.); P < 0.005). Peripheral blood showed a significant free radical burst after 1 h of ischaemia (11 774 ± 728 A.U. vs 6660 ± 833 A.U. in sham; P < 0.001).

CONCLUSIONS

Longitudinal quantification of free radicals during IRI reveals the occurrence of two major radical bursts. The radical peak in peripheral blood after ischaemia may be related to systemic hypoxia. After 1 h of reperfusion, the lung tissue shows a significant increase of superoxide, NO and their reaction products, which are probably involved in IRI pathogenesis.