Activation of eotaxin-3/CCL26 gene expression in human dermal fibroblasts is mediated by STAT6

Allergic inflammatory conditions such as asthma are characterized by an acc umulation of eosinophils at sites of inflammation. Eotaxin-3/CCL26 is a mem ber of the family of CC chemokines, which are known to be potent chemoattra ctants for eosinophils. This chemokine was shown to be up-regulated by IL-4 and IL-13 in endothelial cells. This study demonstrates that eotaxin-3 tra nscription and eotaxin-3 protein expression are stimulated by IL-4 and IL-1 3 in a time- and dose-dependent fashion in human dermal fibroblasts. In con trast to eotaxin-1/CCL11, TNF-alpha could not act as inducer on its own nor did it synergize with IL-4. The activities of eotaxin-3 promoter luciferas e constructs were significantly increased by IL-4 and IL-13 in human dermal fibroblasts. This effect was mediated by a binding site for the transcript ion factor STAT6 in the eotaxin-3 promoter sequence. Mutations in the STAT6 binding site abrogated up-regulation of eotaxin-3 promoter activity. In ST AT6-defective human embryonic kidney 293 cells, the wild-type luciferase co nstruct, but not the STAT6 binding mutant, was inducible by IL-4 only upon cotransfection of STAT6 expression vector. In addition, eotaxin-3 protein w as detectable in the supernatants of STAT6-transfected human embryonic kidn ey 293 cells upon IL-4 or IL-13 stimulation. In the same experiments, TNF-a lpha induced activation of the monocyte chemoattractant protein-1/CCL2 gene was independent of STAT6 transfection. These results indicate that IL-4 an d IL-13 activate eotaxin-3 gene expression in a STAT6-dependent fashion. Al though both eotaxin-1 and -3 are regulated by this transcription factor, th e response of the eotaxin-3 gene to TNF-alpha stimulation appears to be dif ferent.