Thiazolidinediones inhibit the expression of beta3-adrenergic receptors at a transcriptional level.
The effect of the thiazolidinediones (TZDs) darglitazone and troglitazone on beta3-adrenergic receptor (AR) expression was studied in cultured cell lines representing several tissues. After 24 h of exposing HIB-1B brown adipocytes to 30 micromol/l darglitazone or 20 micromol/l troglitazone, beta3-AR mRNA levels were reduced by 75%. This effect was significant within 1 h of exposure to a maximal dose of these drugs, with the full effect obtained within 10 h. The darglitazone ID50 was approximately 10 nmol/l, similar to the Kd of TZDs binding to peroxisome proliferator-activated receptor-gamma (PPAR-gamma). These drugs also decreased beta3-AR mRNA in 3T3-F442A white adipocytes, but not in SK-N-MC cells, which lack PPAR-gamma2. A luciferase reporter gene containing 1.4 kb of 5' flanking sequence of the mouse beta3-AR was transiently transfected, with or without PPAR-gamma2, in SK-N-MC cells. The vigorous expression of luciferase driven by the beta3-AR gene sequence was inhibited by TZDs in a PPAR-gamma2-dependent manner. The half-lives of gamma3-AR precursor RNA and mRNA were short, approximately 40 and approximately 100 min, respectively, and remained unaffected by TZD treatment. Exposure of HIB-1B cells to 30 micromol/l darglitazone was associated with reduced beta3-AR mRNA levels, as well as decreased response of uncoupling protein 1 to norepinephrine + propranolol (a beta1 beta2-AR antagonist) or the specific beta3-AR agonist CL 316, 243. Both the beta3-AR mRNA level and response to these stimuli fully recovered by 24 h of removing the drug, indicating that the beta3-AR protein and its coupling to adenylyl cyclase rapidly followed the changes in mRNA. Thus, TZDs can rapidly reduce beta3-AR expression at the transcriptional level, acting through PPAR-gamma2. The rapid turnover and responses of beta3-AR to perturbations, along with numerous other factors reported to regulate its expression, suggest a tight control of beta3-AR and function. Lastly, leptin being the only other known gene suppressed by TZDs, the present studies support a concerted lipogenic effect of these drugs.
Bakopanos
E
E
Lady Davis Institute for Medical Research, Division of Endocrinology and Metabolism, Jewish General Hospital, McGill University, Montreal, Quebec, Canada.
Silva
J E
JE
D016475:3T3 Cells; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D002839:Chromans / Q000494:pharmacology*; D004149:Dioxoles / Q000494:pharmacology; D004338:Drug Combinations; D006207:Half-Life; D007473:Ion Channels; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D024101:Mitochondrial Proteins; D009638:Norepinephrine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D012333:RNA, Messenger / Q000037:antagonists & inhibitors*; D011943:Receptors, Adrenergic, beta / Q000235:genetics*; D018160:Receptors, Cytoplasmic and Nuclear / Q000502:physiology; D013844:Thiazoles / Q000494:pharmacology*; D045162:Thiazolidinediones; D014157:Transcription Factors / Q000502:physiology; D000077288:Troglitazone; D000071256:Uncoupling Protein 1
D000318:Adrenergic beta-Agonists; D002352:Carrier Proteins; D002839:Chromans; D004149:Dioxoles; D004338:Drug Combinations; D007473:Ion Channels; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D012333:RNA, Messenger; D011943:Receptors, Adrenergic, beta; D018160:Receptors, Cytoplasmic and Nuclear; D013844:Thiazoles; D045162:Thiazolidinediones; D014157:Transcription Factors; C000604372:Ucp1 protein, mouse; D000071256:Uncoupling Protein 1; C076126:disodium (R,R)-5-(2-((2-(3-chlorophenyl)-2-hydroxyethyl)-amino)propyl)-1,3-benzodioxole-2,3-dicarboxylate; D011433:Propranolol; C089948:darglitazone; D000077288:Troglitazone; D009638:Norepinephrine