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ABSTRACT: Chronic hypoxia has been recognized as a key regulator in renal tubulointerstitial fibrosis, as seen in diabetic nephropathy, which is associated with the activation of hypoxia-inducible factor (HIF)-1α. We assess here the effects of the biguanide, metformin, on the expression of HIF-1α in diabetic nephropathy using renal proximal tubular cells and type 2 diabetic rats.
We explored the effects of metformin on the expression of HIF-1α using human renal proximal tubular epithelial cells (HRPTECs). Male Zucker diabetic fatty (ZDF; Gmi-fa/fa) rats were treated from 9 to 39 weeks with metformin (250 mg ⋅ kg(-1) ⋅ day(-1)) or insulin.
Metformin inhibited hypoxia-induced HIF-1α accumulation and the expression of HIF-1-targeted genes in HRPTECs. Although metformin activated the downstream pathways of AMP-activated protein kinase (AMPK), neither the AMPK activator, AICAR, nor the mTOR inhibitor, rapamycin, suppressed hypoxia-induced HIF-1α expression. In addition, knockdown of AMPK-α did not abolish the inhibitory effects of metformin on HIF-1α expression. The proteasome inhibitor, MG-132, completely eradicated the suppression of hypoxia-induced HIF-1α accumulation by metformin. The inhibitors of mitochondrial respiration similarly suppressed hypoxia-induced HIF-1α expression. Metformin significantly decreased ATP production and oxygen consumption rates, which subsequently led to increased cellular oxygen tension. Finally, metformin, but not insulin, attenuated tubular HIF-1α expression and pimonidazole staining and ameliorated tubular injury in ZDF rats.
Our data suggest that hypoxia-induced HIF-1α accumulation in diabetic nephropathy could be suppressed by the antidiabetes drug, metformin, through the repression of oxygen consumption.
Diabetes 01/2011; 60(3):981-92. · 8.29 Impact Factor
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ABSTRACT: High glucose evokes a variety of signals in mesangial cells that alter cellular functions responsible for the development of diabetic glomerulopathy. The hypoxia-inducible factor-1alpha (HIF-1alpha) regulates cellular homeostasis under hypoxic conditions, but it also has pleiotropic effects in response to cellular stresses at normoxia. Here we determined whether HIF-1alpha has a role in the regulation of mesangial cells in hyperglycemia. In the streptozotocin-induced diabetic mouse model, glomerular mesangial cells had a significant increase in HIF-1alpha expression in the nucleus. In cultured mesangial cells, high glucose enhanced the expression of HIF-1alpha and its target genes known to be involved in the development of diabetic glomerulopathy. A glucose-responsive carbohydrate response element binding protein (ChREBP) was found to have a critical role in the transcriptional upregulation of HIF-1alpha and downstream gene expression in mesangial cells exposed to high glucose. Knockdown of HIF-1alpha or ChREBP in mesangial cells abrogated the high glucose-mediated perturbation of gene expression. Our results show that ChREBP and HIF-1alpha mediate gene regulation in mesangial cells. Further studies will be needed to find out whether these findings are relevant to the development of the diabetic nephropathy.
Kidney International 04/2010; 78(1):48-59. · 6.61 Impact Factor
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ABSTRACT: In order to clarify the importance of Interleukin (IL)-18 in the development of diabetic nephropathy (DN), we evaluated the expressions of IL-18 in diabetic kidney.
We performed immmunohistochemical analysis of IL-18 and IL-18 receptor (IL-18 R) in human kidney tissue derived from 12 subjects with type 2 diabetes and overt nephropathy, and compared with those in 7 subjects with minimal change nephrotic syndrome (MCNS). In addition, we examined the regulation of IL-18 expression using human renal proximal tubular epithelial cells (HRPTECs) in culture.
IL-18 expression in tubular cells was observed in higher rate (83%) in patients with diabetes, whereas one positive specimen (14.3%) for IL-18 in patients with MCNS. In contrast, IL-18 R was expressed in glomerular mesangial cells and endothelial cells as well as tubular cells, similarly in almost of both groups. Exposure to transforming growth factor beta (TGF-beta(1)) led to two-fold increase in IL-18 gene expression in HRPTECs, and mitogen-activated protein kinases (MAPK) inhibitors abolished TGF-beta(1)-induced IL-18 mRNA expression. Western blot analysis showed the IL-18 protein in HRPTECs.
The present data indicate that IL-18 is overexpressed in human tubular epithelial cells in diabetic nephropathy, probably through the activation of MAPK pathways induced by TGF-beta(1).
Diabetes research and clinical practice 01/2009; 83(2):190-9. · 2.16 Impact Factor
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ABSTRACT: Dendritic cells (DCs) are considered to be the most powerful antigen-presenting cells (APCs). DCs are thought to be associated with Th1 or Th2 polarization and with polarization-induced disease such as atopic dermatitis, asthma and allergic rhinitis, but its mechanism is not well known. In this study, we analyzed the mRNA expression of DCs between birch pollen allergic rhinitis and healthy controls by using cDNA array. We found that the expressions of CCL22/macrophage-derived chemokine (MDC) differed significantly. We also revealed that CCL22/MDC production was higher in patients than in healthy donors. By chemotaxis assay, CCL22/MDC can enhance the migration of patient's T cells rather than those of healthy controls. Surface marker analysis of migrated cells revealed that the most of migrated cells expressed CCR4, which were considered to be Th2 cells. Furthermore, CD1a(+) CD83(+) cells located in the nasal mucosa expressed CCL22/MDC in vivo. To the best of our knowledge, this is the first report clearly indicating the role of CCL22/MDC in allergic rhinitis.
Clinical Immunology 01/2008; 125(3):291-8. · 4.05 Impact Factor
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ABSTRACT: Retinoid X receptors (RXRs) are ligand-inducible transcription factors that belong to the superfamily of nuclear hormone receptors. Because RXRs heterodimerize with thyroid hormone receptor, retinoic acid receptor, vitamin D(3) receptor, and peroxisome proliferator-activated receptor, they play central roles in regulating a number of signaling pathways. To understand the roles of RXRs in human thyroid carcinogenesis, we have investigated the immunohistochemical expression of RXRs in normal and neoplastic thyroid tissues. Whereas nontumorous human thyroid cells exhibited distinct nuclear staining for the RXRs, thyroid carcinomas showed decreased nuclear expression of all three RXR isoforms. In particular, some thyroid carcinoma cells showed intense RXR-alpha cytoplasmic staining accompanied by decreased immunoreactivity in their nuclei. This subcellular localization of RXR-alpha was confirmed by Western blot analysis, which showed both lower nuclear expression levels of RXR-alpha and a cytosolic presence of RXR-related protein in neoplastic regions. We present here, for the first time, the histological distribution of each RXR protein (alpha, beta, and gamma) in human thyroid follicular cells. In addition, we found that the nuclear expression of RXRs was lower in thyroid carcinomas than in normal tissue. The differential expressions of these RXRs in thyroid carcinomas might be implicated in the pathogenesis of thyroid cancers.
Journal of Clinical Endocrinology & Metabolism 12/2004; 89(11):5851-61. · 6.50 Impact Factor
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Kensuke Oikawa,
Shoji Kimura,
Naoko Aoki,
Yoshiaki Atsuta, Yumi Takiyama,
Toshihiro Nagato,
Mitsuru Yanai,
Hiroya Kobayashi,
Keisuke Sato,
Tadahiro Sasajima,
Masatoshi Tateno
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ABSTRACT: Visinin-like protein-3, which is one of the neuronal calcium sensors, has been shown to be mainly expressed in cerebellar Purkinje cells, but cellular function of this protein has not yet been elucidated. We examined the tissue distribution of murine visinin-like protein-3 transcripts using real-time reverse transcription-PCR. Visinin-like protein-3 mRNA was found to be expressed in peripheral tissues. Particularly, the expression of the transcript in the thymus was significantly higher than in other peripheral tissues. In addition, B6RVTC1 thymoma cells robustly expressed visinin-like protein-3 mRNA. To identify a target protein of visinin-like protein-3, we performed a pull-down experiment using glutathione S-transferase-tagged visinin-like protein-3 and two-dimensional electrophoresis. We demonstrated that microsomal cytochrome b(5) was a Ca(2+)-dependent binding partner of visinin-like protein-3. In a co-immunoprecipitation experiment, it was observed that hippocalcin, as well as visinin-like protein-3, could interact with cytochrome b(5). Furthermore, we confirmed that the sequence Val(114)-Tyr(127) at the C-terminal tail of cytochrome b(5) is the minimal structural requirement for binding to visinin-like protein-3. In addition, the loop His(19)-His(25) at the N terminus of visinin-like protein-3 is essential for binding to cytochrome b(5). Microsomal cytochrome b(5) was also shown to be a potential activator of cytochrome P450. The present findings raise the possibility that visinin-like protein-3 may link Ca(2+) signaling to the machinery of microsomal monooxygenase complex composed of cytochrome b(5), cytochrome P450, and some reductases. This report provides the first evidence of an interaction between visinin-like protein-3 and microsomal cytochrome b(5).
Journal of Biological Chemistry 05/2004; 279(15):15142-52. · 4.77 Impact Factor
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Hitoshi Nochi,
Naoko Aoki,
Kensuke Oikawa,
Mitsuru Yanai, Yumi Takiyama,
Yoshiaki Atsuta,
Hiroya Kobayashi,
Keisuke Sato,
Masatoshi Tateno,
Takeo Matsuno,
Makoto Katagiri,
Zhou Xing,
Shoji Kimura
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ABSTRACT: DAP12 (also known as KARAP) is a novel ITAM-bearing transmembrane adapter molecule that is expressed on the cell surface of natural killer cells, monocytes, dendritic cells, and macrophages. Several myeloid cell-specific DAP12-associating receptors, such as TREM receptor family, SIRP-beta1, and MDL-1 have been identified. The in vivo function of DAP12 and its associating molecules in inflammation has remained primarily unknown. To investigate DAP12 signaling during chronic inflammation, we constructed two adenoviral gene transfer vectors to express FLAG/DAP12 (Ad-FDAP12) and the extracellular domain of mouse TREM-1 and the Fc portion of human IgG1 (Ad-TREM-1 Ig), respectively, and observed their modulatory activities in a mouse model of hepatic granulomatous inflammation elicited by zymosan A. Mice were injected with zymosan A intravenously and 24 hours after zymosan A, they were injected with Ad-FDAP12 or Ad-TREM-1 Ig. Zymosan A-induced hepatic granuloma formation peaked at day 7 and markedly declined by day 10. Although adenoviral-mediated DAP12 gene transfer did not enhance granuloma formation by day 7, it sustained and enhanced granuloma formation beyond day 7. However, an anti-FLAG monoclonal antibody used to potentiate the signaling of adenoviral-derived DAP12, enhanced granuloma formation at day 7. In sharp contrast to the effect by Ad-FDAP12, transgene expression in the liver of soluble form of extracellular domain of TREM-1 as an antagonist of DAP12 signaling, remarkably inhibited zymosan A-induced granuloma formation at all time points examined. Our findings thus suggest that both DAP12 and TREM-1 are involved in the development of granulomatous responses in the liver.
American Journal Of Pathology 05/2003; 162(4):1191-201. · 4.89 Impact Factor
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ABSTRACT: Interleukin (IL)-18 is a cloned cytokine that was identified originally as a factor having potent interferon (IFN)-gamma-inducing activity on Kupffer cells. First, we analyzed IL-18 gene expression by reverse transcription-polymerase chain reaction (RT-PCR) in rat thyroid FRTL-5 cells and human thyroid tissue samples. The expression of IL-18 mRNA in FRTL-5 cells was enhanced by thryoid-stimulating hormone (TSH) in a dose-dependent manner. 8-Bromo-cyclic adenosine monophosphate (cAMP) also increased in IL-18 mRNA levels. Furthermore, TGCT clones that exhibited an increase in intracellular cAMP accumulation showed an increased IL-18 mRNA signal when compared to controls. Taken together, these data suggested that the effect of TSH on IL-18 gene expression was mediated by activating protein kinase A. Treatment of FRTL-5 cells with the antithyroid drug, methimazole (MMI), suppressed this stimulatory action of TSH on IL-18 gene expression. Next, we examined IL-18 expression in human thyroid tissue derived from patients with autoimmune thyroid diseases (ATD). RT-PCR and immunohistology demonstrated that human thyroid follicular cells expressed IL-18. Especially in thyroid tissue from a patient with Hashimoto's thyroiditis, expression was more diffuse and extensive, generally observed in close relation to a lymphocytic infiltrate. Also, IL-18 protein was distributed in the same follicles that express Fas-L and HLA-DR. This study is the first to demonstrate the detection of IL-18 in the thyroid gland. The frequent expression of IL-18 in thyrocytes suggests that IL-18 itself might be a secreted immunomodulator in ATD.
Thyroid 12/2002; 12(11):935-43. · 4.79 Impact Factor
