Involvement of iNOS and NO in TNF-alpha-downregulated resistin gene expression in 3T3-L1 adipocytes.
OBJECTIVE
In order to characterize the regulation of resistin gene expression, we explore the effect of tumornecrosis factor-alpha (TNF-alpha) on resistin mRNA expression and its underlying mechanism in 3T3-L1 adipocytes.


METHODS
Differentiated 3T3-L1 adipocytes were treated for 24 h with 0-10 ng/ml of TNF-alpha or with 2.5 ng/ml of TNF-alpha 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-alpha-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-alpha effect in adipocytes were examined. The effects of TNF-alpha on inducible NOS (iNOS) protein expression in adipocytes were also measured by western blotting.


RESULTS
Our results showed that TNF-alpha caused a dose-dependent reduction in resistin mRNA levels. This effect seemed to be associated with the TNF-alpha-induced expression of iNOS. The results showed that TNF-alpha 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-alpha-induced downregulation of resistin expression, while treatment with SNP mimicked the inhibitory effect of TNF-alpha on resistin expression. In addition, pretreatment with protein tyrosine kinase (PTK) inhibitors, genistein and AG-1288, prevented TNF-alpha-induced iNOS expression and subsequent resistin downregulation.


CONCLUSIONS
Our data suggest that TNF-alpha suppresses resistin expression by inducing iNOS expression, thus causing overproduction of NO, which downregulates resistin gene expression.
Juan
Chi-Chang
CC
Department of Physiology, School of Medicine, National Yang-Ming University, Taipei, Taiwan. ccjuan@ym.edu.tw
Lien
Chih-Chen
CC
Chang
Chih-Ling
CL
Huang
Yu-Han
YH
Ho
Low-Tone
LT
D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D051379:Mice; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D009599:Nitroprusside / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D052243:Resistin / Q000235:genetics / Q000378:metabolism*; D013890:Thiourea / Q000031:analogs & derivatives / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D012333:RNA, Messenger; D052243:Resistin; C118852:S,S'-1,4-phenylene-bis(1,2-ethanediyl)bis-isothiourea; D014409:Tumor Necrosis Factor-alpha; D009599:Nitroprusside; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D013890:Thiourea; D019331:NG-Nitroarginine Methyl Ester