[Transgenic and knockout models for the kallikrein-kinin system].
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Animals↗
Biomedical subjects
Sadayoshi Ito
Publications and source records attributed to Sadayoshi Ito.
[Perspectives of vasopressin receptor antagonists].
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Animals↗
[Glomerular hyperfiltration in diabetic nephropathy].
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Animals↗
[Elevated plasma concentration of IP-10 in patients with type 2 diabetes mellitus].
Recent studies have shown the important role of proinflammatory cytokines and chemokines in the pathogenesis of atherosclerosis and diabetes mellitus(DM). Interferon-inducible protein of 10 kD (IP-10/ CXCL10), a member of the C-X-C chemokine superfamily, is a potent chemoattractant for activated T lymphocytes and is reported to be involved in various disease states including atheroma plaque formation, inhibition of tumor angiogenesis and maintenance of podocyte function. However, the involvement of IP-10 in type 2 DM, especially in its vascular and renal complications, is largely unknown. To elucidate the etiopathological role of IP-10 in type 2 DM, we measured the concentrations of IP-10 together with IFN-gamma, TNF-alpha, IL-18, IL-6 and MCP-1 in plasma samples from 103 type 2 DM patients with various degrees of nephropathy. A significant difference in the plasma level of IP-10 was observed between the patients and the control subjects (183.3+/-12.5 pg/m/ vs 65.6+/-9.3 pg/ml, p<0.05). IP-10 correlated IL-18, IL-6, TNF-alpha and MCP-1. The IFN-gamma level was below the detectable range. IP-10 levels became higher with the progression of nephropathy : IP-10 levels were 148.9+/-14.5, 174.2+/-17.2 and 231.9+/-31.3 pg/m/ in patients with an urinary albumin creatinine ratio of <30, 30 to 300 and >300 microg/mg Cr, respectively. Similarly, IL-18, IL-6, MCP-1 and TNF-alpha levels in patients with overt albuminuria were significantly higher as compared with those without albuminuria (IL-18, 367.3 45.6 vs 203.5+/-17.6 pg/ml; IL-6, 1.61+/-0.26 vs 0.87+/-0.13 pg/ml; TNF-alpha, 1.83+/-0.48 vs 0.61+/-0.07 pg/ml; p<0.05, respectively) in consistent with previous reports. These results suggested that IP-10 may have an etiopathogenic role in type2 DM and diabetic nephropathy as one of the downstream effectors of proinflammatory cytokines.
Adult↗
PDZ binding motif-dependent localization of K+ channel on the basolateral side in distal tubules.
Kir5.1, a nonfunctional inwardly rectifying K(+) channel by itself, can form functional channels by assembling with other proteins. We previously showed that Kir5.1 assembled with Kir4.1 and functioned as an acid-base regulator in the kidney. In this study, we examined the intrarenal distribution of Kir5.1 by RT-PCR analysis on dissected nephron segments and immunohistochemical analysis with the specific anti-Kir5.1 antibody. Strong expression of Kir5.1 was detected in distal convoluted tubules, and weak expression was also detected in thick ascending limb of Henle's loop. Colocalization of Kir5.1 with Kir4.1 indicated expression of Kir5.1/Kir4.1 heteromer in these nephron segments. In a renal epithelial cell line, Madin-Darby canine kidney cells, heteromer formation with Kir4.1 changed the localization of Kir5.1 from intracellular components to the cell surface. The COOH-terminal cytoplasmic portion that includes the PDZ binding motif of Kir4.1 was responsible for this intracellular localization. These data suggest the signals on the COOH terminus of Kir4.1, including PDZ binding motif, determine the intracellular localization of Kir5.1/Kir4.1 heteromer in distal tubules.
Animals↗
Transcription suppression of peroxisome proliferator-activated receptor gamma2 gene expression by tumor necrosis factor alpha via an inhibition of CCAAT/ enhancer-binding protein delta during the early stage of adipocyte differentiation.
TNFalpha is known to inhibit adipocyte differentiation and induce insulin resistance. Moreover, TNFalpha is known to down-regulate peroxisome proliferator-activated receptor (PPAR)gamma2, an adipocyte-specific nuclear receptor of insulin-sensitizer thiazolidinediones. To clarify molecular mechanisms of TNFalpha- mediated PPARgamma2 down-regulation, we here examined the effect of TNFalpha on transcription regulation of PPARgamma2 gene expression during the early stage of adipocyte differentiation. 3T3-L1 preadipocytes (2 d after 100% confluent) were incubated in a differentiation mixture (dexamethasone, insulin, 3-isobutyl-1-methlxanthine), with or without 50 ng/ml TNFalpha, for 24 h. TNFalpha significantly decreased PPARgamma2 expression both at mRNA and protein levels (to approximately 40%), as well as aP2 mRNA expression. The mouse PPARgamma2 gene promoter region (2.2-kb) was isolated and was used for luciferase reporter assays by transient transfection. TNFalpha significantly suppressed PPARgamma2 gene transcription (to approximately 50%), and deletion analyses demonstrated that the suppression was mediated via CCAAT/enhancer-binding protein (C/EBP) binding elements at the -320/-340 region of the promoter. Moreover, TNFalpha significantly decreased expression of C/EBPdelta mRNA and protein levels (to approximately 40%). EMSA, using 3T3-L1 cells nuclear extracts with the -320/-340 region as a probe, demonstrated the binding of C/EBPdelta to the element, which was significantly decreased by TNFalpha treatment. Overexpression of CEBP/delta prevented the TNFalpha-mediated suppression of PPARgamma2 transactivation. Taken together, TNFalpha suppresses PPARgamma2 gene transcription by the inhibition of C/EBPdelta expression and its DNA binding during the early stage of adipocyte differentiation, which may contribute to the inhibition of adipocyte differentiation, as well as the induction of insulin resistance.
3T3-L1 Cells↗
[Thiazide-induced hypercalcemic nephropathy in a patient with secondary hypoparathyroidism].
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Aged↗
Isolation and characterization of a digoxin transporter and its rat homologue expressed in the kidney.
Digoxin, which is one of the most commonly prescribed drugs for the treatment of heart failure, is mainly eliminated from the circulation by the kidney. P-glycoprotein is well characterized as a digoxin pump at the apical membrane of the nephron. However, little is known about the transport mechanism at the basolateral membrane. We have isolated an organic anion transporter (OATP4C1) from human kidney. Human OATP4C1 is the first member of the organic anion transporting polypeptide (OATP) family expressed in human kidney. The isolated cDNA encodes a polypeptide of 724 aa with 12 transmembrane domains. The genomic organization consists of 13 exons located on chromosome 5q21. Its rat counterpart, Oatp4c1, is also isolated from rat kidney. Human OATP4C1 transports cardiac glycosides (digoxin, K(m) = 7.8 microM and ouabain, K(m) = 0.38 microM), thyroid hormone (triiodothyronine, K(m) = 5.9 microM and thyroxine), cAMP, and methotrexate in a sodium-independent manner. Rat Oatp4c1 also transports digoxin (K(m) = 8.0 microM) and triiodothyronine (K(m) = 1.9 microM). Immunohistochemical analysis reveals that rat Oatp4c1 protein is localized at the basolateral membrane of the proximal tubule cell in the kidney. These data suggest that human OATP4C1/rat Oatp4c1 might be a first step of the transport pathway of digoxin and various compounds into urine in the kidney.
Amino Acid Sequence↗
A Kruppel-like factor KLF15 contributes fasting-induced transcriptional activation of mitochondrial acetyl-CoA synthetase gene AceCS2.
Acetyl-CoA synthetase 2 (AceCS2) produces acetyl-CoA for oxidation through the citric acid cycle in the mitochondrial matrix. AceCS2 is highly expressed in the skeletal muscle and is robustly induced by fasting. Quantification of AceCS2 transcripts both in C2C12 and human myotubes indicated that fasting-induced AceCS2 gene expression appears to be independent on insulin action. Characterization of 5'-flanking region of the mouse AceCS2 gene demonstrates that Krüppel-like factor 15 (KLF15) plays a key role in the trans-activation of the AceCS2 gene. Deletion and mutation analyses of AceCS2 promoter region revealed that the most proximal KLF site is a curtail site for the trans-activation of the AceCS2 gene by KLF15. Using Sp-null Drosophila SL2 cells, we showed that the combination of KLF15 and Sp1 resulted in a synergistic activation of the AceCS2 promoter. Mutation analyses of three GC-boxes in the AceCS2 promoter indicated that the GC-box, located 8 bases downstream of the most proximal KLF15 site, is the most important GC-box in the synergistic trans-activation of the AceCS2 gene by KLF15 and Sp1. GST pull-down assays showed that KLF15 interacts with Sp1 in vitro. Quantification of various KLF transcripts revealed that 48 h fasting robustly induced the KLF15 transcripts in the skeletal muscle. Together with the trans-activation of the AceCS2 promoter, it is suggested that fasting-induced AceCS2 expression is largely contributed by KLF15. Furthermore, KLF15 overexpression induced the levels of AceCS2 transcripts both in myoblasts and in myotubes, indicating that AceCS2 gene expression in vivo is indeed induced by KLF15.
Acetate-CoA Ligase↗
Adult onset Fanconi syndrome: extensive tubulo-interstitial lesions and glomerulopathy in the early stage of Chinese herbs nephropathy.
A 33-year-old woman was transferred to our hospital with a 5-month history of taking Chinese herbal medicine containing aristolochic acid. She presented with metabolic acidosis, severe anemia, hypophosphatemia and uric aciduria, and generalized aminoaciduria and glycosuria, features which were consistent with the clinical manifestations of Fanconi syndrome. Renal biopsy was performed when her plasma creatinine was 0.7 mg/dl and creatinine clearance was 46 ml/min per 1.73 m(2). The renal specimen showed extensive interstitial edema with focal fibrosis, tubular atrophy, and focal glomerulopathy, which suggested the presence of glomerular endothelial damage or glomerular ischemia. Although steroid therapy ameliorated the plasma electrolyte levels, renal failure progressed, and hemodialysis therapy was initiated approximately 18 months after the time of renal biopsy. This patient demonstrated the early renal lesions of Chinese herbs nephropathy in association with various clinical manifestations. The characteristic glomerulopathy found in the present patient is considered to be an additional renal lesion, leading to the renal failure.
Adult↗
Experimental autoimmune thyroiditis in nonobese diabetic mice lacking interferon regulatory factor-1.
Interferon regulatory factor-1 (IRF-1) is pivotal in the regulation of interferon (IFN)-mediated immune reactions, and studies suggest that IRF-1 is involved in the development of autoimmune diseases. IRF-1+/+, +/-, and -/- nonobese diabetic (NOD) mice were immunized with mouse thyroglobulin (mTg) to determine whether IRF-1 is required in experimental autoimmune thyroiditis (EAT), a murine model for Hashimoto's thyroiditis (HT). IRF-1-deficient mice developed EAT and anti-mTg antibodies comparable to IRF-1+/+ and +/- mice. Whereas both CD4+ and CD8+ T cells were found in thyroids of IRF-1+/+ mice, the latter was not in IRF-1-/- mice. Major histocompatibility complex class II antigen was comparably expressed in thyroids of IRF-1+/+ and -/- mice. Lack of IRF-1 resulted in decreased CD8+ T cell number in the spleen and reduced IFNgamma production by splenocytes. Our results suggest that IRF-1 is not pivotal in EAT in NOD mice.
Animals↗
Altered expression of NDST-1 messenger RNA in puromycin aminonucleoside nephrosis.
Sulfated portions of glycosaminoglycan (GAG) side chains in heparan sulfate proteoglycan (HSPG) are thought to play an important role in charge-dependent selectivity of glomerular filtration against plasma proteins. Heparan sulfate N-acetylglucosamine N-deacetylase/adenosine 3'-phosphate 5'-phosphosulfate: unsubstituted glucosamine N-sulfotransferase (NDST) is the key enzyme regulating sulfation of GAG chains. In this study we investigated transcriptional expression of NDST-1, 1 of 4 isozymes of NDST, in glomeruli of rats with puromycin aminonucleoside (PAN) nephrosis. Nephrosis was induced in rats with a single intraperitoneal injection of 150 mg/kg PAN. On days 10 and 35, expression of NDST-1 messenger RNA (mRNA) in glomeruli was analyzed with the use of Northern-blot analysis. Immunohistochemical studies were also performed with the use of monoclonal antibodies that react specifically with the N-sulfated portion of the GAG chain of HSPG and agrin, a major core protein of HSPG in glomerular basement membrane (GBM). In addition, we studied the expression of NDST-1 mRNA in cultured glomerular epithelial cells (GECs) and glomerular mesangial cells in the presence of PAN. On day 10, when significant proteinuria developed, the ratios of glomerular expression of NDST-1 mRNA against glyceraldehyde-phosphate dehydrogenase mRNA in PAN-treated rats were decreased to 48% +/- 6% of those in controls (P<.05). Immunohistochemical studies revealed that staining for N-sulfated GAG chains of HSPG on GBM was markedly reduced on day 10 in PAN-treated rats but that staining for agrin was unchanged. In contrast, on day 35, when PAN-treated rats recovered from proteinuria, we noted no differences in glomerular expression of NDST-1 mRNA and staining intensity for N-sulfated GAG chains on GBM between PAN-treated rats and controls. Incubation of GECs for 24 hours in the presence of 50 ng/mL PAN resulted in the reduction of the expression of NDST-1 mRNA (67% +/- 12% of those in controls, P<.05). In summary, we found alteration of the expression of NDST-1 mRNA, accompanying a loss of N-sulfated GAG chains of HSPG on GBM without changes in the core protein agrin, in the course of PAN nephrosis. These data suggest an important role for this enzyme in heparan sulfate assembly in GBM and GEC and in the pathogenesis of proteinuria in PAN nephrosis.
Amidohydrolases↗
Elevated plasma levels of immunoreactive urotensin II and its increased urinary excretion in patients with Type 2 diabetes mellitus: association with progress of diabetic nephropathy.
Urotensin II (UII) is the most potent vasoconstrictor peptide ever identified. In order to clarify the pathophysiological role of UII in diabetes mellitus, we examined plasma immunoreactive UII levels and urinary excretion of immunoreactive UII in 10 control subjects and 48 patients with Type 2 diabetes mellitus. The patients were divided into three groups according to the renal function: Group I with Ccr > or = 70 ml/min, group II with 30 < or = Ccr <70 ml/min and group III with Ccr <30 ml/min. Plasma immunoreactive UII levels were elevated in the three diabetic groups compared with normal controls (P <0.05). Group III patients had significantly higher plasma immunoreactive UII levels (15.9 +/- 2.2 fmol/ml, mean +/- S.E.M., n=6) by approximately 1.6-fold than did group I (10.9 +/- 0.9 fmol/ml, n=17) and group II (10.8 +/- 0.8 fmol/ml, n=25) (P <0.05). Urinary excretion of immunoreactive UII was significantly increased in group III patients (52.4 +/- 14.8 pmol/day) by more than 1.8-fold compared with control subjects, groups I and II (P <0.005). Fractional excretion of immunoreactive UII significantly increased as renal function decreased. Presence of diabetic retinopathy or neuropathy had negligible effects on plasma immunoreactive UII levels and urinary immunoreactive UII excretion. Reverse phase HPLC analyses showed three immunoreactive peaks in normal plasma extracts and multiple immunoreactive peaks in normal urine extracts. Thus, Type 2 diabetes mellitus itself is a factor to elevate plasma immunoreactive UII levels, and accompanying renal failure is another independent factor for the increased plasma immunoreactive UII levels in Type 2 diabetic patients. Increased urinary immunoreactive UII excretion in Type 2 diabetic patients with advanced diabetic nephropathy may be due not only to the elevated plasma immunoreactive UII levels but also to increased UII production and/or decreased UII degradation in the diseased kidney.
Adult↗
Artifactually elevated serum-free thyroxine levels measured by equilibrium dialysis in a pregnant woman with familial dysalbuminemic hyperthyroxinemia.
Familial dysalbuminemic hyperthyroxinemia (FDH) is a familial autosomal dominant syndrome caused by abnormal albumin with an increased affinity for thyroxine (T4). Two types of mutations in the albumin gene, replacing the normal arginine 218 with a histidine (R218H) or a proline (R218P), have been reported to cause FDH. Here, we report a pregnant Japanese woman with FDH caused by the mutant albumin R218P. She had extremely elevated total T4 levels but normal TSH. While the majority of T4was bound to albumin, T4 binding to thyroxine-binding globulin (TBG) was progressively increased throughout pregnancy. Her infant also had elevated serum T4 but normal thyrotropin (TSH). The presence of a guanine to cytosine transition in the second nucleotide of codon 218 of the albumin gene, resulting in a substitution of proline for the normal arginine (R218P), was revealed in the proband. Serum free thyroxine (FT4) levels were increased when measured with some commercial kits including equilibrium dialysis followed by radioimmunoassay (RIA) but not when determined by RIA after ultrafiltration of sera. These results indicate an increased T4 binding to TBG during pregnancy in the patients with FDH. Furthermore, our results suggest that normal serum FT4 determined by equilibrium dialysis is not an ultimate standard for the diagnosis of FDH in the patients with the mutant albumin R218P.
Adult↗
Role of renal eicosanoids in the control of intraglomerular and systemic blood pressure during development of hypertension.
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Animals↗
Expression of peroxisome proliferator-activated receptor isoform proteins in the rat kidney.
Peroxisome proliferator-activated receptors (PPARs) are nuclear hormone receptors mediating ligand-dependent transactivation. Among the 3 isoforms, PPAR- alpha is involved in lipid metabolism in the liver, while PPAR-gamma(-gamma1 and -gamma2) is involved in adipocyte differentiation. Recently, PPARs have been suggested to be involved in renal electrolyte metabolism as well as atherosclerosis. PPAR-alpha is known to regulate cytochrome P450 gene expression, and may possibly affect sodium retention in the kidney. Moreover, PPAR-gamma is involved in the transcription regulation of blood pressure regulatory genes, including thromboxane and angiotensin II type 1 receptors. In the kidney, although expression of PPARs has been reported, detailed immunohistochemical analyses have not been performed. We here generated isoform-specific anti-PPAR antibodies to localize their proteins in the kidney. Anti-PPAR antibodies were raised against synthetic peptides. Their isoform specificity was confirmed by immunoblot analyses, immunoprecipitations, and antibody supershift experiments by electrophoretic mobility shift assay. We therefore studied the protein expression of PPARs in the kidney of adult Sprague-Dawley rats using these antibodies. Immunoblot analyses demonstrated protein expression of PPAR-alpha and -gamma1, but not of -gamma2, in the kidney nuclear extracts. Immunohistochemical analyses demonstrated that both PPAR-alpha and -gamma1 proteins were widely expressed in the nuclei of mesangial and epithelial cells in glomeruli, proximal and distal tubules, the loop of Henle, medullary collecting ducts, and intima/media of renal vasculatures. PPAR-alpha and -gamma1 proteins are thus widely expressed along the nephron segments, and may affect gene expression at these segments. Further studies will be needed to identify additional target genes for PPARs along the nephron segments.
Animals↗
Hepatocyte growth factor stimulates nitric oxide production through endothelial nitric oxide synthase activation by the phosphoinositide 3-kinase/Akt pathway and possibly by mitogen-activated protein kinase kinase in vascular endothelial cells.
Hepatocyte growth factor (HGF) has recently been the focus of attention due to its angiogenic effects, which are similar to those of vascular endothelial growth factor (VEGF); because of these effects, HGF is considered to be a novel therapeutic agent against vascular disorders, including atherosclerotic angiopathies. Although nitric oxide (NO), which is derived from vascular endothelial cells (ECs), is also involved in angiogenesis, little is known regarding the interactions between HGF and NO. We therefore examined the effects of HGF on NO production as well as endothelial NO synthase (eNOS) phosphorylation, and investigated their mechanisms. In bovine aortic ECs, HGF induced a rapid (5 min) increase of NO production measured by diaminofluorescein-2 diacetate. Moreover, HGF rapidly (2.5 min) stimulated eNOS phosphorylation (Ser-1179) as determined by Western immunoblot analyses. Both of these effects were almost completely suppressed by the phosphoinositide 3-kinase (PI3K) inhibitor LY294002, and were partially suppressed by the mitogen-activated protein kinase (MAPK) kinase 1/2 inhibitor U0126. HGF also stimulated Akt phosphorylation (Ser-473), which was completely suppressed by LY294002 and was partially suppressed by U0126. Moreover, HGF stimulated extracellular signal-regulated kinase 1/2 phosphorylation (Thr-202/Tyr-204), which was completely suppressed by U0126 and was partially suppressed by LY294002. Taken together, these results indicate that HGF not only phosphorylates eNOS through the PI3K/Akt pathway, but also partially through the MAPK pathway, and that these two pathways may interact. Compared with VEGF, HGF was more potent in both NO production and eNOS phosphorylation. Our study thus demonstrates a novel activity of HGF-the stimulation of NO production-which occurs via eNOS phosphorylation that may in turn be mediated by cross-talk between the PI3K/Akt and MAPK pathways.
Animals↗
The organic anion transporter (OATP) family.
In the last decade, many organic anion transporters have been isolated, characterized their distribution and substrates. The recently identified organic anion transporter family OATP (organic anion transporting polypeptide)/LST (liver-specific transporter) family, transport bile acids, hormones as well as eicosanoids, various compounds (BSP, HMG-CoA reductase inhibitor, angiotensin converting enzyme inhibitor, etc.). The isolation of the family revealed that not only hydrophilic compounds, drugs and hormones of lipophilic nature need a membrane transport system to penetrate cell membrane. In this family, the nomenclature becomes very complicated and the physiological role of this family is still unclear except about few organs such as the brain, liver and kidney. Even in such organs, the co-existence of the OATP/LST family and similar substrate specificity hamper the progress and clear characterization identifying the real role of the transporter family. Here, recent progress and an insight of this field are reviewed.
Animals↗