IL-4 and IL-13 activate the JAK2 tyrosine kinase and Stat6 in cultured human vascular endothelial cells through a common pathway that does not involve the gamma c chain.

IL-4 and IL-13 each act on human endothelial cells (ECs) to induce expression of vascular cell adhesion molecule-1. On hematopoietic cells. IL-4 responses may be mediated either through a pathway involving gc, the common signaling subunit of the IL-2, IL-4, IL-7, IL-9, and IL-15 receptors, or through a gc-independent pathway that may be alternatively activated by IL-13. We find that human ECs do not express gc, as detected by indirect immunofluorescence and FACS analysis or by a reverse transcription-PCR method. Like IL-4, IL-13 activates a protein tyrosine kinase that phosphorylates the IL-4R binding protein. In addition, we find that IL-4 and IL-13 each induce tyrosine phosphorylation of the JAK2 tyrosine kinase. Furthermore, both IL-4 and IL-13 induce binding of the Stat6 transcription factor to a consensus sequence oligonucleotide. We conclude that the IL-4 response of human ECs involves the IL-13 shared pathway that is independent of gc, and uses JAK2-Stat6 signaling.

IL-4 induction of VCAM-1 on endothelial cells involves activation of a protein tyrosine kinase.

IL-4 triggers tyrosine phosphorylation of a single major substrate (M(r) 145,000) in cultured human endothelial cells (EC) as detected by Western blot of whole cell lysates or of anti-phosphotyrosine immunoprecipitates. Phosphorylation of this substrate depends on IL-4 concentration (appearance at 10 U/ml, maximal at 300 to 1000 U/ml) and time of treatment (onset by 1 min, peak at 5 to30 min, duration of 60 to 120 min). Immunoprecipitation with specific mAb identified the phosphorylated substrate as the IL-4R. Treatment of EC with IL-4 alone causes only a small increase in the expression of vascular cell adhesion molecule-1 (VCAM-1), but IL-4 significantly augments the level of VCAM-1 expression induced by PMA. Pretreatment of EC with herbimycin A (0.5 to 1.0 microgram/ml) for 12 to 18 h abrogates both IL-4-induced tyrosine phosphorylation and IL-4-augmented VCAM-1 expression. This concentration of herbimycin A does not inhibit and may augment PMA-induced VCAM-1 expression in replicate wells. These observations suggest that IL-4 induction of VCAM-1 in EC involves the activation of an as yet unidentified protein tyrosine kinase that phosphorylates the IL-4R.