| Co-Investigator(Kenkyū-buntansha) |
YOSHIDA Haruyoshi University of Fukui, Faculty of Medical Sciences, Professor, 医学部, 教授 (80135574)
FUJII Hiroshi Niigata University, School of Medicine, Associate Professor, 医歯学系, 助教授 (90165340)
HIROTA Kiichi Kyoto University, Graduate School of Medicine, Lecturer, 大学院医学研究科, 講師 (00283606)
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| Research Abstract |
1. Effects of hypoxia and inflammation on expression of lipophilic transcriptional factors in cultured human proximal renal tubular epithelial cells (HPTECs).
(1) In HPTECs under normoxia and hypoxia, mRNA amounts of lipophilic transcriptional factors (PPAR-α, β, γ, RXR-α, β, RAR-α, β, FXR) were determined using cDNA array system. Under normoxia, all the genes were significantly expressed in the cells. Relative mRNA amounts of RXR, FXR, and PPAR-γ were 10.1, 5.4, and 2.1, respectively, when the amount of PPA-α was set to 1.0. Hypoxia reduced PPA-α by 20%, PPAR-γ by 70% and RX-α by 30% at mRNA levels, while FXR mRNA expression was unchanged under hypoxia.
(2) Hypoxia reduced PPAR-γ mRNA levels by 57% at 24 hours and by 80% at 48 hours compared with those in normoxic cells at 24 hours, while under normoxia PPAR-γ mRNA levels did not differ at 24 and 48 hours. Hypoxia also reduced PPAR-γ protein levels by 20% at 24 hours and by 30% at 48 hours. Treatment TNF-α(10ng/ml) had no influence on a
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mounts of PPAR-γ mRNA or protein.
2. Effects of hypoxia on L-fatty acid-binding protein (L-FABP) expression in HPTECs.
L-FABP mRNA expression was up-regulated by 3.4-fold after hypoxic treatment for 48 hours.
3. PPAR-γ activation by PGJ2 and effects of PGJ2 on expression of MCP-1 and PAI-1 in HPTECs.
(1) In HPTECs, a considerable amount of PPAR-g was identified, and treatment with PGJ2 (5 μM) enhanced PPRE-mediated transcriptional activity by 3-fold compared with no treatment. PGJ2 and pioglitazone reduced basal and TNF-α-stimulated MCP-1 expression, which was 30% and 100% PPAR-γ-dependent, respectively. PGJ2 induced further hypoxia-, TNF-α-, and hypoxia plus TNF-α-stimulated PAI-1 expression, which was mediated probably by MAPK and tyrosine kinase, independently of PPAR-γ action. Pioglitazone had no effect on PAI-1 expression.
(2) The inhibitory effect of PGJ2 and pioglitazone on MCP-1 expression decreased under hypoxia, while the stimulatory effect of PGJ2 on PAI-1 expression increased under hypoxia. This multiplicity of PGJ2's effects may be explained in part by the PPAR-γ-independent action. Less
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