Sumiharu Yamamoto

Bcl3 prevents acute inflammatory lung injury in mice by restraining emergency granulopoiesis

Granulocytes are pivotal regulators of tissue injury. However, the transcriptional mechanisms that regulate granulopoiesis under inflammatory conditions are poorly understood. Here we show that the transcriptional coregulator B cell leukemia/lymphoma 3 (Bcl3) limits granulopoiesis under emergency (i.e., inflammatory) conditions, but not homeostatic conditions. Treatment of mouse myeloid progenitors with G-CSF--serum concentrations of which rise under inflammatory conditions--rapidly increased Bcl3 transcript accumulation in a STAT3-dependent manner. Bcl3-deficient myeloid progenitors demonstrated an enhanced capacity to proliferate and differentiate into granulocytes following G-CSF stimulation, whereas the accumulation of Bcl3 protein attenuated granulopoiesis in an NF-κB p50-dependent manner. In a clinically relevant model of transplant-mediated lung ischemia reperfusion injury, expression of Bcl3 in recipients inhibited emergency granulopoiesis and limited acute graft damage. These data demonstrate a critical role for Bcl3 in regulating emergency granulopoiesis and suggest that targeting the differentiation of myeloid progenitors may be a therapeutic strategy for preventing inflammatory lung injury.

Emergency granulopoiesis promotes neutrophil-dendritic cell encounters that prevent mouse lung allograft acceptance

The mechanisms by which innate immune signals regulate alloimmune responses remain poorly understood. In the present study, we show by intravital 2-photon microscopy direct interactions between graft-infiltrating neutrophils and donor CD11c(+) dendritic cells (DCs) within orthotopic lung allografts immediately after reperfusion. Neutrophils isolated from the airways of lung transplantation recipients stimulate donor DCs in a contact-dependent fashion to augment their production of IL-12 and expand alloantigen-specific IFN-γ(+) T cells. DC IL-12 expression is largely regulated by degranulation and induced by TNF-α associated with the neutrophil plasma membrane. Extended cold ischemic graft storage enhances G-CSF-mediated granulopoiesis and neutrophil graft infiltration, resulting in exacerbation of ischemia-reperfusion injury after lung transplantation. Ischemia reperfusion injury prevents immunosuppression-mediated acceptance of mouse lung allografts unless G-CSF-mediated granulopoiesis is inhibited. Our findings identify granulopoiesis-mediated augmentation of alloimmunity as a novel link between innate and adaptive immune responses after organ transplantation.

Cutting Edge: Pseudomonas aeruginosa Abolishes Established Lung Transplant Tolerance by Stimulating B7 Expression on Neutrophils

The mechanisms that link bacterial infection to solid organ rejection remain unclear. In this study, we show that following the establishment of lung allograft acceptance in mice, Pseudomonas aeruginosa airway infection induces a G-CSF–dependent neutrophilia that stimulates acute rejection. Graft-infiltrating neutrophils sharply upregulate the B7 molecules CD80 and CD86, but they do not express CD40 or MHC class II in response to P. aeruginosa infection. Neutrophil B7 promotes naive CD4+ T cell activation and intragraft IL-2+, IFN-γ+, and IL-17+ T lymphocyte accumulation. Intravital two-photon microscopy reveals direct interactions between neutrophils and CD4+ T cells within pulmonary allografts. Importantly, lung rejection in P. aeruginosa-infected recipients is triggered by CD80/86 on neutrophils and can be prevented by B7 blockade without affecting clearance of this pathogen. These data show that neutrophils enhance T cell activation through B7 trans-costimulation and suggest that inhibiting neutrophil-mediated alloimmunity can be accomplished without compromising bacterial immune surveillance.

Suppression of Inflammatory Cytokines During Ex Vivo Lung Perfusion With an Adsorbent Membrane

BACKGROUND Lung grafts can be perfused ex vivo for 2 hours without edema formation; however, prolonged ex vivo lung perfusion (EVLP) eventually induces lung injury. This study evaluated the change in proinflammatory cytokines of the perfusate during EVLP and investigated the effect of cytokine removal using an adsorbent membrane. METHODS Porcine heart-lung blocks were harvested after electrically induced cardiac arrest and underwent 12-hour EVLP with an adsorbent membrane (membrane group: n = 5) and without an adsorbent membrane (control group: n = 6). RESULTS In the control group, both tumor necrosis factor-alpha and interleukin 8 levels were elevated in the perfusate 2 hours after perfusion. Although tumor necrosis factor-alpha and interleukin 8 levels were significantly lower in the membrane group than in the control group during the EVLP period, there was no significant difference in oxygenation, pulmonary vascular resistance, edema formation, or myeloperoxidase activity between the two groups. CONCLUSIONS Tumor necrosis factor-alpha and interleukin 8 levels of the perfusate were elevated during EVLP. Although adverse effects of these inflammatory cytokines were anticipated, removal of inflammatory cytokines by the adsorbent membrane did not improve lung function during prolonged EVLP. Factors other than the cytokines may play a major role in causing lung injury during EVLP. Further research is needed to investigate the real mechanism of lung graft injury during prolonged EVLP and to establish longer EVLP duration for graft treatment. This strategy could contribute to the salvage of potentially damaged lungs, especially from cardiac death donors, and to expansion of the donor pool.

Increased T Cell Glucose Uptake Reflects Acute Rejection in Lung Grafts

Although T cells are required for acute lung rejection, other graft–infiltrating cells such as neutrophils accumulate in allografts and are also high glucose utilizers. Positron emission tomography (PET) with the glucose probe [18F]fluorodeoxyglucose ([18F]FDG) has been employed to image solid organ acute rejection, but the sources of glucose utilization remain undefined. Using a mouse model of orthotopic lung transplantation, we analyzed glucose probe uptake in the grafts of syngeneic and allogeneic recipients with or without immunosuppression treatment. Pulmonary microPET scans demonstrated significantly higher [18F]FDG uptake in rejecting allografts when compared to transplanted lungs of either immunosuppressed or syngeneic recipients. [18F]FDG uptake was also markedly attenuated following T cell depletion therapy in lung recipients with ongoing acute rejection. Flow cytometric analysis using the fluorescent deoxyglucose analog 2‐NBDG revealed that T cells, and in particular CD8+ T cells, were the largest glucose utilizers in acutely rejecting lung grafts followed by neutrophils and antigen‐presenting cells. These data indicate that imaging modalities tailored toward assessing T cell metabolism may be useful in identifying acute rejection in lung recipients.

Five-year update on the mouse model of orthotopic lung transplantation: Scientific uses, tricks of the trade, and tips for success

It has been 5 years since our team reported the first successful model of orthotopic single lung transplantation in the mouse. There has been great demand for this technique due to the obvious experimental advantages the mouse offers over other large and small animal models of lung transplantation. These include the availability of mouse-specific reagents as well as knockout and transgenic technology. Our laboratory has utilized this mouse model to study both immunological and non-immunological mechanisms of lung transplant physiology while others have focused on models of chronic rejection. It is surprising that despite our initial publication in 2007 only few other laboratories have published data using this model. This is likely due to the technical complexity of the surgical technique and perioperative complications, which can limit recipient survival. As two of the authors (XL and WL) have a combined experience of over 2500 left and right single lung transplants, this review will summarize their experience and delineate tips and tricks necessary for successful transplantation. We will also describe technical advances made since the original description of the model.

Perioperative supplementation with bifidobacteria improves postoperative nutritional recovery, inflammatory response, and fecal microbiota in patients undergoing colorectal surgery: a prospective, randomized clinical trial

The use of probiotics has been widely documented to benefit human health, but their clinical value in surgical patients remains unclear. The present study investigated the effect of perioperative oral administration of probiotic bifidobacteria to patients undergoing colorectal surgery. Sixty patients undergoing colorectal resection were randomized to two groups prior to resection. One group (n=31) received a probiotic supplement, Bifidobacterium longum BB536, preoperatively for 7–14 days and postoperatively for 14 days, while the other group (n=29) received no intervention as a control. The occurrences of postoperative infectious complications were recorded. Blood and fecal samples were collected before and after surgery. No significant difference was found in the incidence of postoperative infectious complications and duration of hospital stay between the two groups. In comparison to the control group, the probiotic group tended to have higher postoperative levels of erythrocytes, hemoglobin, lymphocytes, total protein, and albumin and lower levels of high sensitive C-reactive proteins. Postoperatively, the proportions of fecal bacteria changed significantly; Actinobacteria increased in the probiotic group, Bacteroidetes and Proteobacteria increased in the control group, and Firmicutes decreased in both groups. Significant correlations were found between the proportions of fecal bacteria and blood parameters; Actinobacteria correlated negatively with blood inflammatory parameters, while Bacteroidetes and Proteobacteria correlated positively with blood inflammatory parameters. In the subgroup of patients who received preoperative chemoradiotherapy treatment, the duration of hospital stay was significantly shortened upon probiotic intervention. These results suggest that perioperative oral administration of bifidobacteria may contribute to a balanced intestinal microbiota and attenuated postoperative inflammatory responses, which may subsequently promote a healthy recovery after colorectal resection.

Maintenance of IKKβ activity is necessary to protect lung grafts from acute injury

Background. Signaling pathways that target I-&kgr;B kinase &bgr; (IKK&bgr;) activation stimulate the expression of nuclear factor (NF)-&kgr;B-dependent genes and are thus believed to primarily promote inflammation and injury in solid organ grafts. Methods. We examined the role of IKK&bgr; in a mouse model of lung transplantation-mediated ischemia-reperfusion injury using NF-&kgr;B essential modulator (NEMO)-binding domain (NBD) peptide to pharmacologically inhibit IKK activation. As myeloid cells are primarily responsible for the production of acute inflammatory mediators after lung transplantation, we also investigated the effects of myeloid cell-specific IKK&bgr; gene deletion on acute lung graft injury by transplanting mutant mice. Results. When NBD was administered at a dose that partially inhibits IKK&bgr; activation, we observed attenuated lung graft injury and blunted expression of intragraft proinflammatory mediators. Surprisingly, when the dose of NBD was increased to a level that ablates intragraft IKK&bgr; activation, graft inflammation, and injury were significantly worse compared with recipients treated with control peptide. Similar to lung recipients with pharmacologically ablated IKK&bgr; activity, donor-recipient transplant combinations with a myeloid cell-specific IKK&bgr; gene deletion had marked intragraft inflammation and poor lung function. Conclusions. Our data show maintenance of IKK&bgr; activity is critical for promoting graft homeostasis with important implications for targeting NF-&kgr;B-dependent signaling pathways for treating acute lung injury.

Early Growth Response-1 Plays an Important Role in Ischemia-Reperfusion Injury in Lung Transplants by Regulating Polymorphonuclear Neutrophil Infiltration.

Background Early growth response-1 (Egr-1) has been shown to be a trigger-switch transcription factor that is involved in lung ischemia-reperfusion injury (IRI). Methods Mouse lung transplants were performed in wild-type (WT) C57BL/6 and Egr1-knockout (KO) mice in the following donor → recipient combinations: WT → WT, KO → WT, WT → KO, and KO → KO to determine whether the presence of Egr-1 in the donor or recipient is the most critical factor for IRI. Pulmonary grafts were retrieved after 18 hours of ischemia after 4 hours of reperfusion. We analyzed graft function by analyzing arterial blood gas and histology in each combination and assessed the effects of Egr1 depletion on inflammatory cytokines that are regulated by Egr-1 as well on polymorphonuclear neutrophil (PMN) infiltration. Results Deletion of Egr1 improved pulmonary graft function in the following order of donor → recipient combinations: WT → WT < WT → KO < KO → WT < KO → KO. Polymerase chain reaction assays for Il1B, Il6, Mcp1, Mip2, Icam1, and Cox2 showed significantly lower expression levels in the KO → KO group than in the other groups. Immunohistochemistry demonstrated clear Egr-1 expression in the nuclei of pulmonary artery endothelial cells and PMN cytoplasm in the WT grafts. Flow cytometry analysis showed that Egr1 deletion reduced PMN infiltration and that the extent of reduction correlated with graft function. Conclusions Both graft and recipient Egr-1 played a role in lung IRI, but the graft side contributed more to this phenomenon through regulation of PMN infiltration. Donor Egr-1 expression in pulmonary artery endothelial cells may play an important role in PMN infiltration, which results in IRI after lung transplantation.

Activations of mitogen-activated protein kinases and regulation of their downstream molecules after rat lung transplantation from donors after cardiac death.

OBJECTIVES Accepting organs donated after cardiac death (DCD) is an effective approach to the donor shortage. However, lung transplantations from DCD donors show severe rapid pulmonary graft dysfunction (PGD) followed by warm ischemia-reperfusion injury (IRI). This study sought to clarify the molecular mediators in warm IRI, including activation of mitogen-activated protein kinase (MAPK) and the downstream cascades. METHODS We performed single left lung transplantation using organs from male Sprague-Dawley rats after 0 (CIT group), 30 (30WIT group), or 180 (180WIT group) minutes of warm ischemia time. Pulmonary graft functions were estimated by blood gas analysis. At 1 hour after reperfusion, the phosphorylation status of MAPKs (ERK, p38, and JNK) and the gene expression levels of transcription factors (Egr-1 and ATF-3) and immune mediators (MCP-1, MIP-2, PAI-1, ICAM-1, TNF-α, IL-1β, IL-6, and COX-2) in the grafts were examined using Western blotting and real-time polymerase chain reaction assays. RESULTS Severe PGD was observed in the 180WIT group compared with transplanted lungs in the other groups, which exhibited good pulmonary graft function. ERK and JNK activations, as well as mRNA levels of transcription factors (Egr-1 and ATF3) significantly increased with greater warm ischemic times. The pattern of JNK activation correlated with the severity of PGD. MCP-1, ICAM-1, IL-1β, IL-6, and COX-2 were also up-regulated among the 180WIT group, although MIP-2 and PAI-1 showed no significant differences among the groups. CONCLUSIONS We suggest that the ERK and JNK pathways may play important roles to induce the injury caused by prolonged warm ischemia followed by reperfusion in the setting of lung transplantation from DCD donors.