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Articles by H Kimura
Total Records ( 2 ) for H Kimura
  H Kimura , X Li , K Torii , T Okada , K Kamiyama , D Mikami , N Takahashi and H. Yoshida

Background. Long-term treatment with glucocorticoids (GCs) reportedly exaggerates renal fibrosis in chronic progressive inflammatory kidney disease. GCs induce the gene expression of plasminogen activator inhibitor-1 (PAI-1), a fibrosis enhancer in non-renal cells. Tumour necrosis factor-alpha (TNF-) reduces the gene expression of 11β-hydroxysteroid dehydrogenase (HSD) 2, an inactivator of GCs, and may enhance GC activity. However, the individual and collective effects of adrenal steroids, TNF- and HSD2 status on PAI-1 production are unknown in human proximal renal tubular epithelial cells (HPTECs).

Methods. Confluent HPTECs were treated with adrenal steroids (10 nM to 10 µM) or TNF- (10 ng/ml) for up to 48 h. The mRNA amounts of the target genes were determined by TaqMan quantitative PCR, and the PAI-1 protein amounts were measured by an immunoassay.

Results. Dexamethasone (DXA) maximally increased the amounts of PAI-1 mRNA and protein at 100 nM. Aldosterone (Ald) increased PAI-1 expression dose dependently, but the effect was over 100-fold weaker than that of DXA. The PAI-1-increasing effects of DXA and Ald were abolished completely by U-486, a specific inhibitor of the glucocorticoid receptor (GR) but not by spironolactone, a specific inhibitor of the mineralocorticoid receptor. The effect of DXA was also blocked partially by AG1478 and herbimycin A, tyrosine kinase inhibitors. DXA further increased TNF--stimulated PAI-1 expression via the GR. Although TNF- treatment caused an 80% reduction in the gene expression of HSD2, an inactivator of GCs, HSD2 inhibition did not enhance DXA-induced PAI-1 production.

Conclusions. DXA induces basal and TNF--stimulated PAI-1 expression via the GR pathway, regardless of HSD2 status in HPTECs. Excess GCs may serve as a pro-fibrotic factor in chronic inflammatory kidney diseases.

  S Ugi , K Shi , Y Nishio , S Shimizu , B Guo , O Sekine , K Ikeda , K Egawa , T Yoshizaki , Y Nagai , D Koya , T Takada , R Torii , H Kimura , A Kashiwagi and H. Maegawa

Protein-tyrosine phosphatase 1B (PTP1B) is a major regulator of insulin sensitivity. We have described a novel action of PTP1B in the induction of sterol regulatory element-binding protein-1 (SREBP-1) gene expression through activation of protein phosphatase 2A (PP2A). PTP1B is anchored to the endoplasmic reticulum membrane via its C-terminal tail. We have previously reported that membrane localization of PTP1B is essential for PP2A activation, which is crucial for enhancing SREBP-1 gene expression in in vitro experiments. In this study, we further investigated the physiological importance of membrane localization of PTP1B in vivo. We found that transient liver-specific overexpression of wild-type PTP1B (PTP1B-WT) using adenovirus-mediated gene transfer was associated with hypertriglyceridaemia and enhanced hepatic SREBP-1 gene expression in mice. However, overexpression of the C-terminal truncated PTP1B (PTP1BCT) failed to increase hepatic SREBP-1 expression or serum triglyceride levels, despite causing insulin resistance. Our results indicate that activation of PTP1B in the liver could induce hypertriglyceridaemia and that anchoring of PTP1B to the membrane is crucial for its action.

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