The IKK-2/I Kappa B alpha /NF- Kappa B Pathway Plays a Key Role in the Regulation of CCR3 and eotaxin-1 in Fibroblasts: A critical link to dermatitis in I Kappa B alpha -deficient mice

Tumor necrosis factor (TNF)- alpha -induced phosphorylation of the I Kappa B proteins by the I Kappa B kinase (IKK) complex containing IKK-2 and subsequent degradation of the I Kappa B proteins are prerequisites for NF- Kappa B activation, resulting in the stimulation of a variety of pro-inflammatory target genes. The C-C chemokine eotaxin-1 is a potent chemoattractant for eosinophils and Th2 lymphocytes, may play an important role in the pathogenesis of atopic dermatitis, and acts via binding to its receptor CCR3. To investigate the role of NF- Kappa B signaling in the regulation of these genes, we stably expressed a transdominant mutant of I Kappa B alpha and a constitutively active mutant of IKK-2 in mouse NIH3T3 fibroblasts. The transdominant I Kappa B alpha mutant completely inhibited TNF- alpha -mediated induction of both eotaxin-1 and CCR3, whereas expression of constitutively active IKK-2 was sufficient to drive almost full expression of these two genes in the absence of TNF- alpha . Moreover, we observed elevated expression levels of CCR3 and eotaxin-1 protein levels in the skin of I Kappa B alpha -deficient mice characterized by a widespread dermatitis. Finally, using dermal fibroblasts derived from I Kappa B alpha -deficient mice, we observed elevated basal expression, enhanced inducibility by TNF- alpha , and attenuated down-regulation upon TNF- alpha withdrawal of both CCR3 and eotaxin-1 mRNA levels. These results demonstrate that the IKK-2/I Kappa B alpha /NF- Kappa B pathway plays a critical role for CCR3 and eotaxin-1 expression in fibroblasts and suggests a critical link to the pathogenesis of atopic dermatitis.