Yohichi Yasunami

CD4+ Vα14 natural killer T cells are essential for acceptance of rat islet xenografts in mice

Pancreatic islet transplantation represents a potential treatment for insulin-dependent diabetes mellitus. However, the precise cellular and molecular mechanisms of the immune reactions against allogeneic and xenogeneic transplanted islets remain unclear. Here, we demonstrate that CD4(+) Valpha14 natural killer T (NKT) cells, a recently identified lymphoid cell lineage, are required for the acceptance of intrahepatic rat islet xenografts. An anti-CD4 mAb, administrated after transplantation, allowed islet xenografts to be accepted by C57BL/6 mice, with no need for immunosuppressive drugs. The dose of anti-CD4 mAb was critical, and the beneficial effect appeared to be associated with the reappearance of CD4(+) NKT cells at around 14 days after transplantation. Interestingly, rat islet xenografts were rejected, despite the anti-CD4 mAb treatment, in Valpha14 NKT cell-deficient mice, which exhibit the normal complement of conventional lymphoid cells; adoptive transfer of Valpha14 NKT cells into Valpha14 NKT cell-deficient mice restored the acceptance of rat islet xenografts. In addition, rat islet xenografts were accepted by Valpha14 NKT mice having only Valpha14 NKT cells and no other lymphoid cells. These results indicate that Valpha14 NKT cells play a crucial role in the acceptance of rat islet xenografts in mice treated with anti-CD4 antibody, probably by serving as immunosuppressive regulatory cells.

Meat,fish and fat intake in relation to subsite-specific risk of colorectal cancer.The Fukuoka Colorectal Cancer Study

High intake of red meat has been associated with increased risk of colorectal cancer in Western countries. There has been much interest in the role of n‐3 polyunsaturated fatty acids (PUFA) in colorectal cancer prevention, but epidemiological findings are limited and inconsistent. The objective of our study was to examine associations of meat, fish and fat intake with risk of colorectal cancer, paying particular attention to the subsite within the colorectum. Data were from the Fukuoka Colorectal Cancer Study, a population‐based case‐control study, covering 782 cases and 793 controls. Diet was assessed by interview, using newly developed personal‐computer software for registering semiquantitative food frequencies. The intake of beef/pork, processed meat, total fat, saturated fat or n‐6 PUFA showed no clear association with the overall or subsite‐specific risk of colorectal cancer. There was an almost significant inverse association between n‐3 PUFA and the risk of colorectal cancer; the covariate‐adjusted odds ratio for the highest (median 3.94 g/day) versus lowest (median 1.99 g/day) quintile of energy‐adjusted intake was 0.74 (95% confidence interval 0.52–1.06, trend P = 0.050). The consumption of fish and fish products was similarly inversely related to the risk although the association was not statistically significant. These associations were more evident for distal colon cancer; adjusted odds ratio for the highest versus lowest quintile of n‐3 PUFA intake was 0.56 (95% confidence interval 0.34–0.92, trend P = 0.02). Our findings do not support the hypothesis that consumption of red meat increases colorectal cancer risk but do suggest that high intake of fish may decrease the risk, particularly of distal colon cancer. (Cancer Sci 2007; 98: 590–597)

High-mobility group box 1 is involved in the initial events of early loss of transplanted islets in mice

Islet transplantation for the treatment of type 1 diabetes mellitus is limited in its clinical application mainly due to early loss of the transplanted islets, resulting in low transplantation efficiency. NKT cell-dependent IFN-gamma production by Gr-1(+)CD11b(+) cells is essential for this loss, but the upstream events in the process remain undetermined. Here, we have demonstrated that high-mobility group box 1 (HMGB1) plays a crucial role in the initial events of early loss of transplanted islets in a mouse model of diabetes. Pancreatic islets contained abundant HMGB1, which was released into the circulation soon after islet transplantation into the liver. Treatment with an HMGB1-specific antibody prevented the early islet graft loss and inhibited IFN-gamma production by NKT cells and Gr-1(+)CD11b(+) cells. Moreover, mice lacking either of the known HMGB1 receptors TLR2 or receptor for advanced glycation end products (RAGE), but not the known HMGB1 receptor TLR4, failed to exhibit early islet graft loss. Mechanistically, HMGB1 stimulated hepatic mononuclear cells (MNCs) in vivo and in vitro; in particular, it upregulated CD40 expression and enhanced IL-12 production by DCs, leading to NKT cell activation and subsequent NKT cell-dependent augmented IFN-gamma production by Gr-1(+)CD11b(+) cells. Thus, treatment with either IL-12- or CD40L-specific antibody prevented the early islet graft loss. These findings indicate that the HMGB1-mediated pathway eliciting early islet loss is a potential target for intervention to improve the efficiency of islet transplantation.

Vα14 NK T cell–triggered IFN-γ production by Gr-1+CD11b+ cells mediates early graft loss of syngeneic transplanted islets

Pancreatic islet transplantation is a highly promising approach for the treatment of insulin-dependent diabetes mellitus. However, the procedure remains experimental for several reasons, including its low efficiency caused by the early graft loss of transplanted islets. We demonstrate that Gr-1+CD11b+ cells generated by transplantation and their IFN-γ production triggered by Vα14 NKT cells are an essential component and a major cause of early graft loss of pancreatic islet transplants. Gr-1+CD11b+ cells from Vα14 NKT cell–deficient (Jα281−/−) mice failed to produce IFN-γ, resulting in efficient islet graft acceptance. Early graft loss was successfully prevented through the repeated administration of α-galactosylceramide, a specific ligand for Vα14 NKT cells, resulting in dramatically reduced IFN-γ production by Gr-1+CD11b+ cells, as well as Vα14 NKT cells. Our study elucidates, for the first time, the crucial role of Gr-1+CD11b+ cells and the IFN-γ they produce in islet graft rejection and suggests a novel approach to improving transplantation efficiency through the modulation of Vα14 NKT cell function.

Methylenetetrahydrofolate reductase C677T and A1298C polymorphisms and colorectal cancer: the Fukuoka Colorectal Cancer Study.

Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme regulating folate metabolism, which affects DNA synthesis and methylation. This study investigated the relation of MTHFR C677T and A1298C polymorphisms to colorectal cancer in a case‐control study in Fukuoka, Japan. The subjects comprised 685 incident cases of histologically confirmed colorectal adenocarcinomas and 778 community controls selected randomly in the study area. The genotype was determined by the PCR‐RFLP method using genomic DNA extracted from buffy coat. Alcohol use was ascertained by in‐person interview. Statistical adjustment was made for gender, age class, area, and alcohol use. The MTHFR 677TT genotype was associated with a statistically significant decrease in the risk with an adjusted odds ratio of 0.69 (95% confidence interval 0.51–0.93) compared with the 677CC and 677CT combined, and the decrease was most evident in individuals with no alcohol consumption. While the A1298C polymorphism showed no measurable association with the overall risk of colorectal cancer, the 1298CC genotype was associated with a statistically significant increase in the risk when alcohol consumption was high, and was also associated with an approximately 2‐fold increase in the risk of each of proximal and distal colon cancer. The findings add to evidence that individuals with the MTHFR 677TT genotype have a decreased risk of colorectal cancer in the absence of folate depletion, suggesting a protective role of folate by ensuring a sufficient thymidylate pool for DNA synthesis. Because very few individuals had the 1298CC genotype, the findings regarding the A1298C polymorphism need careful interpretation and confirmation in larger studies.

Intratesticular Transplants of Islet Xenografts (Rat to Mouse)

Freshly isolated rat islets were transplanted into the testis of diabetic mice. The intratesticular islet xenografts produced normoglycemia in the diabetic recipients. The survival time of the intratesticular xenografts was significantly longer than intrasplenic, intrahepatic, and renal subcapsular sites of transplantation of xenografts of freshly isolated rat islets. Three of the recipients with intratesticular islet grafts were still normoglycemic at 60 days after transplantation, and orchidectomy resulted in a return to the diabetic state. The findings indicate that the testis provided a more privileged immunologic site than either the spleen, liver, or kidney and the lower temperature of the testis apparently did not affect the function of the islet grafts since the recipients became normoglycemic.

An improved method for the isolation of islets from the beef pancreas.

An improved method for the isolation of islets from the beef and pig pancreas Is described. The procedure involves the use of strips of Velcro that retain the partially-digested collagen during the isolation of islets by the collagenase technique. The spiny portion of the Velcro Is ideally suited to retain the collagen and yet permit the separation of islets from the pancreatic parenchyma. A remarkably high yield of islets has been obtained from the beef and pig pancreas USing this procedure.

A new site for islet transplantation ― A peritoneal-omental pouch

A new site for islet transplantation is described. A peritoneal-omental pouch was constructed in diabetic rats by encasing the omentum in a pouch formed from a strip of parietal peritoneum obtained from the recipient. Isografts of rat islets placed in the pouch maintained normoglycemia in the recipients and removal of the pouch resulted in a rapid return to a diabetic state. This site may be applicable to the transplantation of islets in human diabetes.

Physical activity and colorectal cancer: the Fukuoka Colorectal Cancer Study.

The number of cases of colorectal cancer in Japan has increased over the past few decades, and incidence rates are now among the highest in the world. The present investigation within the Fukuoka Colorectal Cancer Study, including 778 cases and 767 controls aged 20–74 years, examined the association between physical activity and colorectal cancer risk by subsite. Employment‐associated and leisure time physical activity was assessed by a questionnaire and interview. Division of sites into the proximal and distal colon, as well as the rectum, revealed clear site‐dependent protective effects, with adjustment for smoking, alcohol consumption, BMI and age. In males, greater job‐related physical activity was associated with significant reduction of risk in the distal colon and rectum (P = 0.047 and 0.02, respectively), whereas total and moderate or hard non‐job physical activity exerted effects limited to the rectum (P = 0.01 and 0.004, respectively). In females, job‐related physical activity and moderate or hard non‐job physical activity was also protective, but only in the distal colon. Separate assessment of the influence of BMI 10 years previous to the study showed increase in risk with obesity in males but not in females, limited to distal colon and rectum. The results of the present study indicate that physical activity associated with work and leisure‐time exerts beneficial effects in Japanese, but not on the proximal colon. (Cancer Sci 2006; 97: 1099–1104)

Hepatocyte growth factor is essential for amelioration of hyperglycemia in streptozotocin-induced diabetic mice receiving a marginal mass of intrahepatic islet grafts.

BACKGROUND It is crucial for clinical islet transplantation to find a procedure to improve the success rate of insulin independence after islet transplantation. In the present study, we determined whether hepatocyte growth factor (HGF) has a favorable effect on amelioration of hyperglycemia in streptozotocin (STZ, 200 mg/kg)-induced diabetic mice (C57BL/6) receiving a marginal mass of intrahepatic islet isografts. METHODS Isolated syngeneic islets were transplanted into the liver of recipients. HGF with dextran sulfate (DS) was administered intraperitoneally once a day at day 0, 2, 4, 6, and 8 relative to islet transplantation. DS has been known to enhance the effect of HGF. RESULTS It was found that the number of 250 islets was a marginal mass as donor islets in this model, in which 2 out of 14 diabetic mice receiving 250 islets became normoglycemic by 90 days after transplantation. The treatment with HGF (100 microg) in conjunction with DS (200 microg) produced normoglycemia in all mice (n = 5). Morphological study as well as intraperitoneal glucose tolerance test revealed the beneficial effects of HGF. To our surprise, six out of nine mice receiving 250 islets and treated with DS alone became normoglycemic. Additional anti-HGF antibody treatment (100 microg, day -1, 0, 2, 4, 6, and 8) abolished the effects of DS, indicating that the effect by DS is mediated via the endogenous HGF. The effects of DS were not observed when the renal subcapsular space was the site of islet transplantation. There was a significant increase in plasma HGF levels in mice after the intrahepatic grafts but not the renal subcapsular one. CONCLUSIONS These findings demonstrate that HGF is essential for amelioration of hyperglycemia in STZ-induced diabetic mice when a marginal mass of islets was grafted into the liver. As the liver is the site of clinical islet transplantation and the inability to achieve insulin independence after transplantation is a major obstacle for successful transplantation, HGF may facilitate to overcome such an important issue for clinical islet transplantation.