A novel PPAR response element in the murine iNOS promoter

被引:43
作者
Crosby, MB
Svenson, J
Gilkeson, GS
Nowling, TK
机构
[1] Med Univ S Carolina, Dept Med, Div Rheumatol, Charleston, SC 29425 USA
[2] Ralph H Johnson VAMC, Med Res Serv, Charleston, SC 29425 USA
关键词
PPAR gamma; iNOS; TZD; gene regulation;
D O I
10.1016/j.molimm.2004.12.009
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The nuclear hormone receptor peroxisome proliferation activated receptor gamma (PPAR gamma) is a modulator of inflammation including down-regulation of inducible nitric oxide synthase (iNOS) and nitric oxide (NO) production. PPAR gamma agonists reduce iNOS expression and NO production in a dose-dependent manner in macrophages, mesangial cells and other inflammatory cells. However, the mechanisms involved in the inhibition of iNOS expression by PPAR gamma and its agonists are not fully understood. Here we show that the PPAR gamma agonist ciglitazone dose-dependently inhibited a murine iNOS-luciferase reporter construct by up to 50% in transfected mesangial cells. Blocking de novo protein synthesis in mesangial cells had no effect on PPAR gamma agonist activity, indicating that ciglitazone acts directly to inhibit iNOS transcription. We identified a novel PPAR response element (PPRE) in the murine iNOS promoter that is homologous to the PPRE consensus sequence. In binding assays PPAR gamma directly binds to this response element in vitro and can function as a positive element in response to PPAR gamma agonists when placed in front of a reporter gene. Site-directed mutagenesis of this PPRE in a murine iNOS promoter/reporter construct did not block the inhibitory activity of a synthetic PPAR gamma agonist on the iNOS promoter/reporter construct in transfected mesangial cells. However, the mutated construct exhibited lower basal expression, and higher expression in response to inflammatory stimuli compared to the intact construct. These data suggest that the iNOS PPRE contributes to positive basal expression and negative expression of iNOS in response to inflammatory stimuli. The PPRE is not necessary, however, for synthetic PPAR gamma agonists to inhibit iNOS expression. (c) 2005 Elsevier Ltd. All rights reserved.
引用
收藏
页码:1303 / 1310
页数:8
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