Dimethylfumarate inhibits TNF-induced nuclear entry of NF-κB/p65 in human endothelial cells

Fumaric acid esters, mainly dimethylfumarate (DMF), have been successfully used to treat psoriasis. Based on previous observations that DMF inhibited expression of several TNF-induced genes in endothelial cells, we wished to explore the molecular basis of DMF function in greater detail. In first experiments we analyzed DMF effects on tissue factor expression in human endothelial cells in culture, because tissue factor is expressed by two independent sets of transcription factors, by NF-kappaB via TNF and by early gene response-1 transcription factor via vascular endothelial growth factor (VEGF). We show that DMF inhibits TNF-induced tissue factor mRNA and protein expression as well as TNF-induced DNA binding of NF-kappaB proteins, but not VEGF-induced tissue factor protein, mRNA expression, or VEGF-induced early gene response-1 transcription factor/DNA binding. To determine where DMF interferes with the TNF/NF-kappaB signaling cascade, we next analyzed DMF effects on IkappaB and on the subcellular distribution of NF-kappaB. DMF does not inhibit TNF-induced IkappaBalpha phosphorylation and IkappaB degradation; thus, NF-kappaB is properly released from IKB complexes even in the presence of DMF. Importantly, DMF inhibits the TNF-induced nuclear entry of NF-kappaB proteins, and this effect appears selective for NF-kappaB after the release from 1kappaB, because the constitutive shuttling of inactive NF-kappaB/IkappaB complexes into and out from the nucleus is not blocked by DMF. Moreover, DMF does not block NF-kappaB/DNA binding. In conclusion, DMF appears to selectively prevent the nuclear entry of activated NF-kappaB, and this may be the basis of its beneficial effect in psoriasis.