Tumor necrosis factor alpha enhances the expression of the interleukin (IL)-4 receptor alpha-chain on endothelial cells increasing IL-4 or IL-13-induced Stat6 activation

Functional receptors for interleukin (IL)-4 and IL-13 on endothelial cells consist of the 130-kDa IL-4 receptor alpha-chain (IL-4R alpha) and a 65-75-kDa IL-13 binding subunit that are expressed in a ratio of about 1:3, respectively. The restricted number of IL-4R alpha limits subunit heterodimerization and in turn receptor-mediated signaling, We report here, the effects of tumor necrosis factor alpha (TNF-alpha) on the expression of the receptor subunits for IL-4 and IL-13. By flow cytofluorometry and receptor-binding analysis of iodinated IL-4 and IL-13, stimulation with TNF-alpha-induced a 23-fold increase of the IL-4R alpha expression, The up-regulation was also confirmed at the transcriptional level by reverse transcription-polymerase chain reaction, Radioligand cross-linking experiments revealed no change in the subunit composition of the TNF-alpha-induced receptor complex, Nevertheless, TNF-alpha stimulation led to increased activation of the IL-4-specific signal transducers and activators of transcription protein (Stat6) by IL-4 and IL-13. Thus, TNF-alpha corrects the subunit imbalance of the endothelial IL-4 IL-13 receptor complex thereby increasing receptor heterodimerization and in turn the signaling capability by IL-4 and IL-13.