U-0126

U-0126 (Bis[amino[(2-aminophenyl)thio]methylene]butanedinitrile) is a novel, potent and selective MEK inhibitor (MEK1; IC₅₀=72nM, MEK2; IC₅₀=58nM). Inhibits AP-1 transcription activity. Blocks the production of inflammatory cytokines and matrix metalloproteinases.

Binding of extracellular growth factors to cell surface receptors often results in actiavtion of the mitogen-ativated protein kinase (MAPK).  MAPK is regulated by MAPK kinase , also called MEK. Deprivation of growth factors during cell culture or intracellular MEK inhibition leads to inhibition of proliferation and apoptotic cell death. N Blank et al. (2002) have shown that U0126, a common used MEK inhibitor and compound that itself has no intrinsic fluorescence in vitro but develops an intensive fluorsecence during cell culture which can be observed in all fluorescence channels with a predominance in the FL1 channel (525nm). Therefore either the use of PD98,059 or PD184352 as an alternative for U126 or nonfluorometric methods for detection of apoptosis should be considered.