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Akio Koyama

Publications and source records attributed to Akio Koyama.

At least 19 recordsLinked to original sources
PubMed2006

Time-dependent expression of renal vaso-regulatory molecules in LPS-induced endotoxemia in rat.

To elucidate roles of microvascular factors in the pathogenesis of renal complications during endotoxemia, that is characterized by renal vasoconstriction and systemic hypotension/generalized non-renal vasodilation, we profile the expression pattern and time-course of three key vaso-regulators, namely endothelin (ET)-1, nitric oxide (NO), and angiotensin II (Ang II). We hypothesize that disruption of the overall balance between vasodilatation and vasoconstriction in the kidney, during the early phase of sepsis, contribute to its (kidney) predisposition to acute renal failure. Adult male Wistar rats were rendered endotoxemic at different time points (1, 3, 6 and 10 h) by a single i.p. injection of lipopolysaccharide (LPS) (15 mg/kg) dissolved in saline. Control group was injected vehicle only (saline). Both systolic and diastolic blood pressures significantly decreased at different time points after LPS administration. Surprisingly, renal histopathological evaluation showed no remarkable changes in LPS-induced endotoxemia. However, overall, levels of the vaso-regulators and, where applicable, their respective receptors were upregulated: (1) plasma ET-1 increased 25-fold and peaked, as renal ET-1 mRNA, at 3 h; renal ET-1 protein and its receptors, ET type A (ET(A)) receptor (vasoconstrictive) and ET type B (ET(B)) receptor (vasodilatatory) increased in a time-dependent fashion, (2) Ang II increased by 53% compared to control, peaking at 6 h. However, while levels of Ang II type 1 (AT1) receptor increased over time after LPS injection, those of Ang II type 2 (AT2) receptor were downregulated, (3) data of NO system (NO-NOS), the key vasodilator, were the most intriguing. Whereas levels of renal NO increased time-dependently following LPS administration, with a 2240-fold increase in renal iNOS expression, levels of eNOS, were almost unchanged. In conclusion, the present study overall reveals intriguing and complex dynamics between levels of vasoconstrictors and vasodilators during the early phase of LPS-induced endotoxemia. These shifts in molecular expressions are likely triggered by compensatory mechanisms aimed at counteracting the undesirable and dominant effects of one group of vaso-regulatory moiety over the other.

Angiotensin II↗
PubMed2006

Tissue-specific distribution of an alternatively spliced COL4A5 isoform and non-random X chromosome inactivation reflect phenotypic variation in heterozygous X-linked Alport syndrome.

A novel type of hereditary transmission of COL4A5 in a Japanese family with X-linked Alport syndrome was detected through analysis of cDNA sequences and an X-chromosome inactivation assay. A female patient with moderately altered renal function, who was diagnosed with Alport syndrome by renal biopsy, and her mother, who was undergoing maintenance haemodialysis, showed similar tissue-specific expression of a truncated isoform of COL4A5, which was generated by alternative splicing without a splice-site mutation. Expression of the truncated isoform occurred in the renal specimen derived from the patient, but not in specimens from controls. Genomic analysis revealed two point mutations (c.4821 + 121, T>C; c.4822-151_150, ins T) in intron 49 of COL4A5 from the patient. The peripheral blood mononuclear cells of the patient and her mother showed non-random lyonization. While the females showed only renal impairment, an affected male in the same family suffered from severe renal insufficiency, visual defect and hearing disturbances. Hence, we suggest that this type of heredity COL4A5 presents with phenotypic variation in female heterozygous X-linked Alport syndrome patients.

Adult↗
PubMed2006

Mulberry latex rich in antidiabetic sugar-mimic alkaloids forces dieting on caterpillars.

Since ancient times, mulberry leaves (Morus spp.) have been used to rear the silkworm Bombyx mori. Because the silkworm grows well on mulberry leaves, the toxicities and defensive activities of these leaves against herbivorous insects have been overlooked. Here we show that mulberry leaves are highly toxic to caterpillars other than the silkworm B. mori, because of the ingredients of the latex, a milky sap exuded from mulberry leaf veins. The toxicity of mulberry leaves was lost when the latex was eliminated from the leaves, and artificial diets containing latex showed toxicity. Mulberry latex contained very high concentrations of alkaloidal sugar-mimic glycosidase inhibitors reported to have antidiabetic activities, such as 1,4-dideoxy-1,4-imino-D-arabinitol, 1-deoxynojirimycin, and 1,4-dideoxy-1,4-imino-D-ribitol. The overall concentrations of these inhibitors in latex reached 1.5-2.5% (8-18% dry weight) in several mulberry varieties, which were approximately 100 times the concentrations previously reported from whole mulberry leaves. These sugar-mimic alkaloids were toxic to caterpillars but not to the silkworm B. mori, indicating that the silkworm can circumvent the mulberry tree's defense. Our results suggest that latex ingredients play key roles in defense of this tree and of other plants against insect herbivory, and they imply that plant latexes are treasuries of bioactive substances useful as medicines and pesticides.

1-Deoxynojirimycin↗
PubMed2006

Overexpression of c-Maf contributes to T-cell lymphoma in both mice and human.

c-Maf translocation or overexpression has been observed in human multiple myeloma. Although c-maf might function as an oncogene in multiple myeloma, a role for this gene in other cancers has not been shown. In this study, we have found that mice transgenic for c-Maf whose expression was direct to the T-cell compartment developed T-cell lymphoma. Moreover, we showed that cyclin D2, integrin beta(7), and ARK5 were up-regulated in c-Maf transgenic lymphoma cells. Furthermore, 60% of human T-cell lymphomas (11 of 18 cases), classified as angioimmunoblastic T-cell lymphoma, were found to express c-Maf. These results suggest that c-Maf might cause a type of T-cell lymphoma in both mice and humans and that ARK5, in addition to cyclin D2 and integrin beta(7), might be downstream target genes of c-Maf leading to malignant transformation.

Animals↗
PubMed2006

Testing various fruits for anti-thrombotic effect: i. Mulberries.

Prevention of arterial thrombotic disease has high priority in developed countries. As inappropriate diet predispose to acute thrombotic events, regular intake of an antithrombotic diet may be a convenient and effective way of prevention. The present study was performed to examine antithrombotic effect of mulberry varieties. A shear-induced in vitro platelet reactivity/thrombolysis test (Gorog Thrombosis Test) was used to screen for antiplatelet and thrombolytic activities. In case of effectiveness, it was followed by an in vivo test of laser-induced thrombosis in mice. Antioxidant capacity was assessed by superoxide anion and radical scavenging activities. Total polyphenolics, anthocyanin and citrate contents were also measured. The tested varieties showed different effect in vitro on platelet reactivity and endogenous thrombolytic activity. Varieties inhibiting platelet reactivity were antithrombotic in vivo regardless inhibition or enhancement of thrombolysis. Those mulberry varieties, which enhanced platelet reactivity in vitro, were prothrombotic only if inhibitory activity on endogenous thrombolysis coexisted with the platelet effect. Antioxidant activities and polyphenolics content did not affect platelets and the overall thrombotic status. However, antioxidant activities and polyphenolics content significantly correlated with the endogenous thrombolytic activity. These data showed that mulberry varieties can be grouped into subclasses with either anti- or prothrombotic activities. Antioxidant activities and polyphenolic contents do not affect platelets but may enhance endogenous thrombolysis, thus causing an overall antithrombotic effect.

Animals↗
PubMed2006

Critical role of M. tuberculosis for dendritic cell maturation to induce collagen-induced arthritis in H-2b background of C57BL/6 mice.

Collagen-induced arthritis (CIA) can be induced even in CIA-resistant H-2(b) background of C57BL/6 mice when these mice are immunized with type II collagen (CII) emulsified in complete Freund's adjuvant (CFA) containing high, but not low, dose of Mycobacterium tuberculosis. Here, we investigated the pathogenesis of CIA in C57BL/6 mice induced by the immunizing protocol. We examined expressions of cytokines, costimulatory molecules and major histocompatibility complex (MHC) class II in draining lymph nodes (DLN) in CIA-induced C57BL/6 mice by quantitative reverse transcription-polymerase chain reaction. We also examined an effect of M. tuberculosis on the expression of these molecules on dendritic cells (DC) in vitro by flow cytometry. We finally examined an effect of M. tuberculosis in CFA used for immunization with CII antigen on priming of CD4+ helper T cells specific to CII in DLN of CIA-induced C57BL/6 mice. The expression of interferon-gamma (IFN-gamma), Interleukin-12p40 (IL-12p40), costimulatory molecules CD40, CD80 and CD86 and MHC class II were up-regulated in DLN of CIA-induced C57BL/6 mice. Expressions of these costimulatory molecules were also up-regulated on DC after stimulation with high, but not low, dose of M. tuberculosis in vitro. Furthermore, priming of CD4+ helper T cells specific to CII antigen in DLN required immunization with CII using CFA containing high, but not low, dose of M. tuberculosis. These results suggested that high dose of M. tuberculosis were required for maturation of DC enough to prime CD4+ helper T cells specific to CII antigen in DLN of H-2b background of C57BL/6 mice.

Adjuvants, Immunologic↗
PubMed2005

Normalizing renal reducing ability prevents adriamycin-induced proteinuria.

Reactive oxygen species play an important role in adriamycin (ADR) nephropathy. We showed by in vivo electron paramagnetic resonance (EPR) that renal reducing ability (RRA) declined on the 7th day after ADR administration. Proteinuria appeared after the decline in RRA. The aim of this study was to prove by in vivo EPR whether the decline in RRA is altered by scavengers such as dimethyl sulfoxide (DMSO) and dimethylthiourea (DMTU) and that it is this change which is responsible for the proteinuria in ADR nephropathy. By showing that DMSO and DMTU ameliorate the RRA, we demonstrate that the decline in RRA is related to ADR-induced proteinuria.

Animals↗
PubMed2005

Murine metanephric mesenchyme possesses characteristics of vascular endothelial cells in vitro.

BACKGROUND/AIMS: Although the renal microvasculature, including the glomerular capillaries, is generally considered to develop from the metanephric mesenchyme, this has not been unequivocally demonstrated. Using a murine metanephric mesenchymal cell line (MS7), we tested whether the metanephric mesenchyme expresses phenotypic characteristics of endothelial cells and differentiates into vascular endothelial cells in vitro. METHODS: MS7 cells were examined for the mRNA expression of endothelial markers by reverse transcription (RT)-PCR. Moreover, we attempted to induce the appearance of new endothelial markers by stimulation with growth factors and exposure to hypoxia. RESULTS: Before induction, MS7 cells expressed mRNA of fetal liver kinase 1 (Flk1), fms-like tyrosine kinase (Flt1), tyrosine kinase with Ig and EGF homology domains 2 (Tie2), CD31, and podocalyxin. However, they did not express mRNA for vascular endothelial-cadherin (VE-cadherin) or von Willebrand factor (vWF), which are markers specific for endothelial cells and mature endothelial cells. In the immunocytochemical analysis, MS7 absorbed DiI-acetylated LDL virtually, but the results of staining with anti-VE-cadherin, vWF, or CD31 antibodies were negative. MS7 cells that were cultured for 14 days after reaching confluence began to express VE-cadherin and vWF mRNA. In addition, immunofluorescence showed abundant granules stained with anti-vWF antibody in the cytoplasm. Stimulation with vascular endothelial growth factor (VEGF), or basic fibroblast growth factor (bFGF), or exposure to a hypoxic condition did not influence their characteristic changes. CONCLUSION: Our results suggest that metanephric mesenchymal (MS7) cells possess some characteristics of endothelial cells, and they are potent to differentiate into mature vascular endothelium in vitro.

Animals↗
PubMed2005

Tissue Prx I in the protection against Fe-NTA and the reduction of nitroxyl radicals.

Peroxiredoxin I (Prx I) is a key cytoplasmic peroxidase that reduces intracellular hydroperoxides in concert with thioredoxin. To study the role of tissue Prx I in protection from oxidative stress, we generated Prx I-/- mice by gene trapping. We then evaluated the acute-phase tissue damage caused by ferric-nitrilotriacetate (Fe-NTA). Increases in serum aspartate aminotransferase and alanine aminotransferase levels were significantly greater in Prx I-/- than wild-type mice, 4 and 12 h after the injection of Fe-NTA. Using real-time EPR imaging, we examined the reduction of the stable paramagnetic nitroxyl radical 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl in vivo, and found that the half-life of this spin probe in the liver and kidney was significantly prolonged in the Prx I-/- mice. These results demonstrate that Prx I-/- mice have less reducing activity and are more susceptible to the damage mediated by reactive oxygen species in vivo than wild-type mice.

Alanine Transaminase↗
PubMed2005

Evaluation of adriamycin nephropathy by an in vivo electron paramagnetic resonance.

A rat model for human minimal change nephropathy was obtained by the intravenous injection of adriamycin (ADR) at 5 mg/kg. By using an in vivo electron paramagnetic resonance (EPR) spectrometer operating at 700 MHz, the temporal changes in signal intensities of a nitroxide radical, 4-hydroxyl-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL), in the kidneys of rats with ADR nephropathy were investigated. The decay rate of the EPR signal intensity obtained in the kidney is indicative of the renal reducing ability. It was found that the reducing ability in the kidney declined on the 7th day after ADR administration and recovered after the 14th day. Impairment of the reducing ability occurred before the appearance of continuous urinary protein. The in vitro EPR study showed that this impairment of in vivo renal reducing ability is related to impairment of the reducing ability in the mitochondria.

Animals↗
PubMed2005

Apheresis for MPO-ANCA-associated RPGN-indications and efficacy: lessons learned from Japan nationwide survey of RPGN.

A national survey concerning rapidly progressive glomerulonephritis (RPGN) was conducted in Japan between 1989 and 2000 and resulted in the registration of 715 patients with RPGN. Among the documented patients, the most frequent primary disease was primary pauci-immune crescentic glomerulonephritis (n = 283), and the second most frequent was microscopic polyangitis (n = 127). Overall, 370 patients had MPO-ANCA, and 23 patients had PR3-ANCA. We found that both renal and patient survivals were significantly worse in patients with MPO-ANCA-associated RPGN than patients with PR3-ANCA. Fifty-three patients received apheresis therapy with various combinations of immunosuppressive regimens. They had higher serum creatinine, higher CRP, and a higher frequency of complicated pulmonary involvements as compared to the controls without apheresis therapy. In dialysis-dependent patients, no additional benefit from apheresis therapy was observed. Only pulmonary renal syndrome patients with CRP > 6 mg/dl at presentation showed a slightly better prognosis (patient survival with apheresis; 66.7%, without apheresis; 56.7%). Furthermore, a rapid MPO-ANCA titer reduction was observed in patients treated with apheresis. Patients with MPO-ANCA-associated RPGN were older, and had more chronic and sclerotic lesions than patients with PR3-ANCA-associated RPGN. Based on these findings, we suggest that a lower dose of immunosuppressant should be considered in order to avoid opportunistic infection. In this situation, cytapheresis is the treatment of choice. Nevertheless, in patients with an aggressive form of RPGN with rapid deterioration of renal function like the PR3-ANCA-associated RPGN, or pulmonary renal syndrome complicated severe inflammation, or relapses with high MPO-ANCA titer, we conclude that apheresis therapy should be considered.

Antibodies, Antineutrophil Cytoplasmic↗
PubMed2005

Identification of immature podocyte specific antigen using retrovirus-mediated gene transfer and cell sorting.

BACKGROUND: For identifying an antigen recognizable by a monoclonal antibody (mAb), the cDNA cloning method using expression cDNA library has become increasingly popular. For analysis of the mAb clone 2E3, which recognizes the cell membrane surface of immature podocytes, we developed an expression cloning strategy that identified the targeted antigen using retrovirus-mediated gene transfer and enrichment by cell sorting. METHODS: In this experiment, the NIH3T3 cell line was infected by a retrovirally amplified cDNA library derived from the same fetal murine kidneys that provided the immunized antigen. Infected NIH3T3 staining for mAb clone 2E3 was concentrated by cell sorting, followed by identification of the integrated gene. RESULTS: The infected cells reacted with mAb were highly enriched by two rounds of cell sorting. As a result of sequencing the inserted gene from the enriched cells, we isolated the low-affinity nerve growth factor receptor (NGFR) gene. Furthermore, the NIH3T3 cell line that was enforced by recovery of NGFR cDNA reacted with mAb clone 2E3. CONCLUSIONS: Monoclonal antibodies recognizing cell membrane surface molecules are essential tools for immunohistochemistry and flow cytometry analysis, and the application of a combination of retrovirus-mediated gene transfer and cell sorting is beneficial for identifying the targeted antigen.

Animals↗