Yusuke Kumamoto

Up-regulation of oxygen-derived free radicals by interleukin-1 in hepatic ischemia/reperfusion injury

BACKGROUND Oxygen-derived free radicals (FRs) are critical mediators of ischemia/reperfusion injury. Inflammatory cytokines have been shown to play important roles in tissue injury. To examine the relationship between FRs and interleukin-1 (IL-1) in hepatic ischemia/reperfusion injury, we used interleukin-1 receptor antagonist (IL-1ra) to block endogenous IL-1 production in a rat model of hepatic ischemia/reperfusion. METHODS Female SD rats were subjected to 30 min of hepatic ischemia followed by reperfusion. The animals were divided into two groups, control group and IL-1ra-treated group, according to the rinse solution. In both groups, FR production, histological changes, and interactions between leukocytes and endothelial cells were analyzed in the course of reperfusion. RESULTS In the control group, production of FRs increased significantly after 60 min of reperfusion. After 60 and 180 min of reperfusion, histological examination showed atrophy and degeneration of hepatocytes. Hepatic microcirculation demonstrated a marked increase in the number of leukocytes adherent to endothelial cells and of injured cells after reperfusion. In the IL-1ra-treated group, IL-1ra pretreatment markedly reduced FR production after 60 min of reperfusion, the number of leukocytes adherent to endothelial cells, and tissue injury. CONCLUSION These data clearly show an important role for IL-1 in the induction of FR production, leukocyte adhesion, and tissue injury after hepatic ischemia/reperfusion injury.

Efficacy of intraportal infusion of prostaglandin E1 to improve the hepatic blood flow and graft viability in porcine liver transplantation

BACKGROUND Prostaglandin E1 (PGE1) has been reported to have a protective effect in experimental and clinical models of liver damage. The aim of this study was to elucidate the effects of the intraportal infusion of PGE1 on hepatic blood flow and graft viability after orthotopic liver transplantation in pigs. METHODS First, the hepatic arterial flow (HAF), portal venous flow (PVF), and liver tissue blood flow (LTBF) were measured during the continuous intravenous or intraportal infusion of PGE1. Second, two groups of pigs underwent orthotopic liver transplantation: group A, untreated controls; and group B, animals that received intraportal PGE1 for 2 hr after vascular reconstruction of the allograft. Changes in HAF, PVF, LTBF, and hepatic function were measured. RESULTS The intraportal infusion of PGE1 significantly increased HAF and had no effect on blood pressure, PVF, or LTBF. In group B, HAF and LTBF increased significantly with time. In group A, HAF remained unchanged and a decrease in LTBF was observed. Group B exhibited a higher arterial ketone body ratio and a greater bile flow compared with group A. A significant elevation in serum glutamic oxaloacetic transaminase concentration was observed in group A, but not in group B. CONCLUSIONS This study demonstrates that the intraportal infusion of PGE1 improves hepatic allograft blood flow, predominantly through an effect on HAF, and may improve graft viability after orthotopic liver transplantation.

Partial resection of the second portion of the duodenum for gastrointestinal stromal tumor after effective transarterial embolization.

We report herein the case of 64-year-old man with gastrointestinal stromal tumor (GIST), who was treated by partial resection of the duodenum after preoperative transarterial embolization. He presented to our hospital with a history of tarry stools, dizziness, and severe anemia (hemoglobin, 7.5 g/dl). Gastroduodenal endoscopy revealed the presence of a submucosal tumor in the second portion of the duodenum. The presence of the tumor was subsequently confirmed by double-contrast gastrointestinal radiography and abdominal computed tomography. Super-selective angiography showed tumor staining fed from the anterior and posterior superior pancreaticoduodenal arteries, and the inferior pancreaticoduodenal artery. Two weeks after transarterial embolization through these vessels, the tumor size was found to have shrunk to 40% of its original size. Partial resection of the duodenum was performed and absence of tumor cells at the surgical margin was confirmed by intraoperative frozen-section examination. Histopathological examination revealed that the duodenal submucosal tumor consisted of spindle cells, and immunohistochemical analysis revealed positive tumor staining for c-kit protein, CD34 and α-smooth muscle actin (SMA), and negative staining for desmin and S-100; the positivity rate for MIB-1 staining was 2.2%. Based on these findings, the tumor was diagnosed as a GIST of low-grade malignancy, classified as the muscular type. It is considered that preoperative treatment of duodenal GISTs, such as transarterial embolization, may be useful for reducing the extent of resection, from pancreaticoduodenenctomy to a partial resection.

Superoxide, NO and CO in liver microcirculation: Physiology and pathophysiology

Superoxide anion (O2−), nitric oxide (NO), and carbon monoxide (CO) are metabolites of molecular oxygen endogenously generated through oxygen activation by a variety of oxidases and oxygenases such as xanthine oxidase and NADPH oxidase, NO synthase, and heme oxygenase, respectively. There is an increasing body of evidence showing that these active oxygen metabolites not only exert their cytotoxic properties but also play a modulatory role in regulation of cell function in and around hepatic sinusoidal vessels. Among them, CO generated by heme oxygenase is a novel vasodilatory mediator which can upregulate cGMP in fatstoring Ito cells, liver-specific microvascular pericytes which encircle sinusoidal walls, and thereby control the microvascular tone under control conditions. When exposed to endotoxemia, Kupffer cells and hepatocytes can express inducible NO synthase activity which serves as a NO-dependent cytotoxic mechanisms involving peroxynitrite formation. Disclosure of the whole picture of NO- and CO-dependent mechanisms for regulation of hepatic microcirculation gives a clue to understanding the physiology and pathophysiology of liver function.

Anti-TIRC7 Antibody Treatment Prevents Rejection of Mice Cardiac Allografts while Immune Competency to Viral and Bacterial Antigens Remain Normal

Introduction T cell immune response c-DNA (TIRC7) is expressed in activated lymphocytes binding to its ligand HLA-class II protein in response to alloantigens. Notably, TIRC7 is mainly induced in activated lymphocytes at the site of the inflammation. Thus, unlike other immunosuppressive agents, treatment with an anti-TIRC7 does not interfere with an overall immune competency. Here, anti-TIRC7 antibody (mAb) treatment was compared with Cyclosporin A (CyA) treatment in a mouse cardiac transplant model. As currenty used therapeutics to prevent rejection act unspecifically with severe side effects including infections, we tested the overall immue competency in the presence of anti-TIRC7 mAb treatment and challanged mice with infectious antigens. Method Fully vascularized heterotopic allogeneic heart transplants were performed across a full-mismatch barrier (C57BL/10 into CBA). Recipients mice received anti-TIRC7 mAb (40mg/kg, day 0-7) and compared to treatments with CyA (10mg/kg for either 7 or 14 days or an untreated control n=5-7/group. In an additional experiment, two experimental model systems for viral infections - non-cytopathic lymphocytic choriomeningitis virus (LCMV) and acutely cytopathic vesicular stomatitis virus (VSV) in addition to Listeria monocytogenes (LM) infections were used to analyse fundamentally different types of antiviral and bacterial antibody responses in the presence or absence of anti-TIRC7 mAb. LCMV responses were examined after injecting 200pfu LCMV into the footpad of B6 mice and response was assessed by CTL assays. VSV triggers the production of IFN-I in mice leading to augmentation of specific B cell responses. IgG and IgM titer against VSV was analyzed up to 20d post infection. Listeria monocytogenes (LM) provides a means for introducing antigens into the class I pathway of antigen presentation and induces CD4 response. 1000cfu LM was injected i.v and LM-titers were assessed in spleen and liver (n=4/experiment). Results Mean cardiac allograft survival in anti-TIRC7 mAb treated mice was 52 days with some grafts working > 140 days, in sharp contrast to CyA treated mice and controls with a mean graft function of 8days. Morphology of allografts showed diminished lymphocyte infiltration in anti-TIRC7 mAb treated allografts. Mice cleared the LCMV infection within 15 d. Anti-VSV IgG and IgM antibody titers were highest at 15 d post infection. Mice liver and spleen infected with LM were protected in anti-TIRC7 mAb treated mice as assessed at day 4 post infection. Conclusion Ligation of TIRC7 regulates immune activation at the site of inflammation while the function of peripheral blood lymphocytes remains normal. Mice treated with anti-TIRC7 mAb mounted normal immune responses to infections. Thus, targeting TIRC7 may provide a novel therapeutic approach to specifically modulate alloimmune responses.