Activation of NFκB signal pathways in keloid fibroblasts

Keloids are characterized as an "over-exuberant" healing response resulting in a disproportionate extracellular matrix (ECM) accumulation and tissue fibrosis. In view of the integral role of inflammation and cytokines in the healing response, it is logical to assume that they may play a part in orchestrating the pathology of this "abnormal" healing process. Tumor necrosis factor-alpha (TNF-alpha) is a potent proinflammatory cytokine involved in activation of signaling events and transcriptional programs, such as NFkappaB. This study attempts to determine the difference in NFkappaB and its related genes expression and DNA binding activity between keloid and normal skin fibroblasts. Three keloid and normal skin tissues (NSk) and their derived fibroblasts were used to determine NFkappaB signaling pathway expression using specific cDNA microarrays, Western blot analysis and immunohistochemistry. Electrophoretic mobility gel shift assay (EMSA) was used to assess NFkappaB-binding activity, all assays were performed in the presence and absence of TNF-alpha. TNF-alpha up-regulated 15% of NFkappaB signal pathway related genes in keloid fibroblast compared to normal skin. At the protein level, keloid fibroblasts and tissues showed higher basal levels of TNF- receptor-associated factors-TRAF1, TRAF2-TNF-alpha, inhibitor of apoptosis (c-IAP-1), and NFkappaB, compared with NSk. Keloid fibroblasts showed a constitutive increase in NFkappaB-binding activity in comparison to NSk both with and without TNF-alpha treatment. NFkappaB and its targeted genes, especially the antiapoptotic genes, could play a role in keloid pathogenesis; targeting NFkappaB could help in developing therapeutic interventions for the treatment of keloid scarring.