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Involvement of iNOS and NO in TNF‐α–downregulated Resistin Gene Expression in 3T3‐L1 Adipocytes
Author(s) -
Juan ChiChang,
Lien ChihChen,
Chang ChihLing,
Huang YuHan,
Ho LowTone
Publication year - 2008
Publication title -
obesity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.438
H-Index - 199
eISSN - 1930-739X
pISSN - 1930-7381
DOI - 10.1038/oby.2008.200
Subject(s) - resistin , tumor necrosis factor alpha , endocrinology , medicine , nitric oxide synthase , nitric oxide , 3t3 l1 , blot , downregulation and upregulation , chemistry , sodium nitroprusside , gene expression , adipocyte , biology , adipose tissue , adiponectin , biochemistry , insulin resistance , insulin , gene
Objective: In order to characterize the regulation of resistin gene expression, we explore the effect of tumornecrosis factor‐α (TNF‐α) on resistin mRNA expression and its underlying mechanism in 3T3‐L1 adipocytes. Methods and Procedures: Differentiated 3T3‐L1 adipocytes were treated for 24 h with 0–10 ng/ml of TNF‐α or with 2.5 ng/ml of TNF‐α for 0–24 h, and then resistin mRNA levels were measured by northern blotting. To further explore the involvement of nitric oxide (NO) in TNF‐α–regulated resistin expression, the effect of the NO donor, sodium nitroprusside (SNP), on resistin mRNA levels in adipocytes and the effect of the nitric oxide synthase (NOS) inhibitors, N G ‐nitro‐ l ‐arginine methyl ester ( l ‐NAME), and S, S′−1,3‐phenylene‐bis(1,2‐ethanediyl)‐bis‐isothiourea·2HBr (PBITU), on the TNF‐α effect in adipocytes were examined. The effects of TNF‐α on inducible NOS (iNOS) protein expression in adipocytes were also measured by western blotting. Results: Our results showed that TNF‐α caused a dose‐dependent reduction in resistin mRNA levels. This effect seemed to be associated with the TNF‐α–induced expression of iNOS. The results showed that TNF‐α induced iNOS expression and release of NO after 24‐h treatment of differentiated 3T3‐L1 adipocytes. Pretreatment with l ‐NAME and PBITU significantly reversed the TNF‐α–induced downregulation of resistin expression, while treatment with SNP mimicked the inhibitory effect of TNF‐α on resistin expression. In addition, pretreatment with protein tyrosine kinase (PTK) inhibitors, genistein and AG‐1288, prevented TNF‐α–induced iNOS expression and subsequent resistin downregulation. Discussion: Our data suggest that TNF‐α suppresses resistin expression by inducing iNOS expression, thus causing overproduction of NO, which downregulates resistin gene expression.