Effect of Caffeine and Other Methylxanthines on A beta-Homeostasis in SH-SY5Y Cells
Authors: Janitschke, Daniel; Nelke, Christopher; Lauer, Anna Andrea; Regner, Liesa; Winkler, Jakob; Thiel, Andrea; Grimm, Heike Sabine; Hartmann, Tobias; Grimm, Marcus Otto Walter
Methylxanthines (MTX) are alkaloids derived from the purine-base xanthine. Whereas especially caffeine, the most prominent known MTX, has been formerly assessed to be detrimental, this point of view has changed substantially. MTXs are discussed to have beneficial properties in neurodegenerative diseases, however, the mechanisms of action are not completely understood. Here we investigate the effect of the naturally occurring caffeine, theobromine and theophylline and the synthetic propentofylline and pentoxifylline on processes involved in Alzheimer's disease (AD). All MTXs decreased amyloid-beta (A beta) level by shifting the amyloid precursor protein (APP) processing from the A beta-producing amyloidogenic to the non-amyloidogenic pathway. The alpha-secretase activity was elevated whereas beta-secretase activity was decreased. Breaking down the molecular mechanism, caffeine increased protein stability of the major alpha-secretase ADAM10, downregulated BACE1 expression and directly decreased beta-secretase activity. Additionally, APP expression was reduced. In line with literature, MTXs reduced oxidative stress, decreased cholesterol and a decreased in A beta 1-42 aggregation. In conclusion, all MTXs act via the pleiotropic mechanism resulting in decreased A beta and show beneficial properties with respect to AD in neuroblastoma cells. However, the observed effect strength was moderate, suggesting that MTXs should be integrated in a healthy diet rather than be used exclusively to treat or prevent AD.
Dissecting the interaction between tissue inhibitor of metalloproteinases-3 (TIMP-3) and low density lipoprotein receptor-related protein-1 (LRP-1): Development of a "TRAP" to increase levels of TIMP-3 in the tissue
Authors: Scilabra, Simone D.; Yamamoto, Kazuhiro; Pigoni, Martina; Sakamoto, Kazuma; Mueller, Stephan A.; Papadopoulou, Alkmini; Lichtenthaler, Stefan F.; Troeberg, Linda; Nagase, Hideaki; Kadomatsu, Kenji
Tissue inhibitor of metalloproteinases 3 (TIMP-3) is a key regulator of extracellular matrix turnover for its ability to inhibit matrix metalloproteinases (MMPs), adamalysin-like metalloproteinases (ADAMs) and ADAMs with thrombospondin motifs (ADAMTSs). TIMP-3 is a secreted protein whose extracellular levels are regulated by endocytosis via the low-density-lipoprotein receptor-related protein-1 (LRP-1). In this study we developed a molecule able to "trap" TIMP-3 extracellularly, thereby increasing its tissue bioavailability. LRP-1 contains four ligand-binding clusters. In order to investigate the TIMP-3 binding site on LRP-1, we generated soluble minireceptors (sLRPs) containing the four distinct binding clusters or part of each cluster. We used an array of biochemical methods to investigate the binding of TIMP-3 to different sLRPs. We found that TIMP-3 binds to the ligand-binding cluster II of the receptor with the highest affinity and a soluble minireceptor containing the N-terminal half of cluster II specifically blocked TIMP-3 internalization, without affecting the turnover of metalloproteinases. Mass spectrometry-based secretome analysis showed that this minireceptor, named T3TRAP, selectively increased TIMP-3 levels in the extracellular space and inhibited constitutive shedding of a number of cell surface proteins. In conclusion, T3TRAP represents a biological tool that can be used to modulate TIMP-3 levels in the tissue and could be potentially developed as a therapy for diseases characterized by a deficit of TIMP-3, including arthritis. (C) 2016 Elsevier B.V. All rights reserved.