Effect of tumor necrosis factor-alpha converting enzyme (TACE) and metalloprotease inhibitor on amyloid precursor protein metabolism in human neurons

Tumor necrosis factor-alpha (TNF-alpha) is implicated in inflammatory processes and much effort is being directed at inhibiting the release of TNF-alpha for treatment of inflammatory conditions. In this context, the drug CP-661,631 has been developed to inhibit the TNF-alpha converting enzyme (TACE). However, TACE is also implicated in amyloid precursor protein secretion. Amyloid precursor protein (APP) undergoes constitutive and regulated secretion by alpha-secretase endoproteolytic cleavage within the amyloid beta peptide (Abeta) domain. Alternative cleavage at the N- and C-terminus of the Abeta domain by beta- and gamma-secretases results in the production of Abeta. In many cellular and in vivo animal models, increased secretion of APP results in a concomitant decrease in the production of Abeta suggesting that the two pathways are intricately linked. However, in human primary neuron cultures, increased APP secretion is not associated with a decrease in total Abeta production. To determine if the use of CP-661,631 may enhance amyloidogenic processing in human brain, we have assessed the effect of CP-661,631 on APP metabolism in primary cultures of human neurons. Our results show that CP-661,631 effectively prevents regulated APP secretion but does not increase total Abeta levels in human primary neuron cultures.