Differential regulation by tumor necrosis factor-alpha of beta(1)-, beta(2)-, and beta(3)-adrenoreceptor gene expression in 3T3-F442A adipocytes

Modulation of beta-adrenoreceptor expression by tumor necrosis factor-alpha (TNF-alpha) was investigated in murine 3T3-F442A adipocytes. TNF-alpha treatment of mature adipocytes decreased beta(3)-adrenoreceptor mRNA content in a time-and concentration-dependent manner, with a 8.5-fold decrease observed after a 6-h exposure to 300 pM TNF-alpha. beta(1)-Adrenoreceptor mRNA abundance was slightly decreased by TNF-alpha treatment, while beta(2)-adrenoreceptor mRNA levels were potently induced (6-fold increase at 6 h), (-)-[I-125]Iodocyanopindolol saturation and competition binding experiments indicated that TNF-alpha induced a 2-fold decrease in beta(3)-adrenoreceptor number, a nonsignificant reduction in beta(1)-subtype population, and a similar to 4.5-fold increase in beta(2)-adrenoreceptor density, This correlated with a lower EC value measured for epinephrine in stimulating adenylyl cyclase, whereas the EC50 value for norepinephrine increased. Nuclear run-on assays on isolated nuclei and mRNA stability measurements showed that TNF-alpha increased both beta(2)-adrenoreceptor gene transcription and beta(2)-adrenoreceptor mRNA half-life, while beta(1)- and beta(3)-adrenoreceptor gene expression was modulated only at the transcriptional level by the cytokine. These findings demonstrate a differential modulation by TNF-alpha of the three beta-adrenoreceptor subtypes in adipocytes, which may contribute to metabolic disorders induced by the cytokine in the adipocyte.