Bivalent Compound 17MN Exerts Neuroprotection through Interaction at Multiple Sites in a Cellular Model of Alzheimer’s Disease

Abstract

Multiple pathogenic factors have been suggested in playing a role in the development of Alzheimer’s disease (AD). The multifactorial nature of AD also suggests the potential use of compounds with polypharmacology as effective disease-modifying agents. Recently, we have developed a bivalent strategy to include cell membrane anchorage into the molecular design. Our results demonstrated that the bivalent compounds exhibited multifunctional properties and potent neuroprotection in a cellular AD model. Herein, we report the mechanistic exploration of one of the representative bivalent compounds, 17MN, in MC65 cells. Our results established that MC65 cells die through a necroptotic mechanism upon the removal of tetracycline (TC). Furthermore, we have shown that mitochondrial membrane potential (MMP) and cytosolic Ca2+ levels are increased upon removal of TC. Our bivalent compound 17MN can reverse such changes and protect MC65 cells from TC removal induced cytotoxicity. The results also suggest that 17MN may function between the Aβ species and RIPK1 in producing its neuroprotection. Colocalization studies employing a fluorescent analog of 17MN and confocal microscopy demonstrated the interactions of 17MN with both mitochondria and endoplasmic reticulum (ER), thus suggesting that 17MN exerts its neuroprotection via a multiple-site mechanism in MC65 cells. Collectively, these results strongly support our original design rationale of bivalent compounds and encourage further optimization of this bivalent strategy to develop more potent analogs as novel disease-modifying agents for AD.

Bivalent ligands incorporating curcumin and diosgenin as multifunctional compounds against Alzheimer’s disease

“…Our recent studies also demonstrated that our bivalent compounds not only localize into the cell membrane, but also to intracellular organelles, such as the endoplasmic reticulum and mitochondria, and exert their neuroprotection via a multi-target mechanism. [10] In addition, our results demonstrated that the ‘P’ attachment compounds can also bind to Aβ 42 (data not shown), thus further suggesting that the observed protective activities originate from multiple factors. Taken together, the results echo and reassure our previous conclusion that the bivalent nature of these compounds is essential for their biological outcomes, and this strategy not only provides multifunctionality but also compounds with novel mechanisms of action.…”

“…[22–24] From our previous studies, we observed that our bivalent compounds retain the antioxidative effects of curcumin, and these effects might be due to interaction with the mitochondria. [10] Furthermore, our previous results also suggested the involvement of all three parts of the bivalent compounds, rather than just the curcumin moiety, are in involved in chelating biometals. Therefore, to examine whether the replacement of the anchor moiety with diosgenin will affect such properties, compounds 33 and 38 were evaluated for their antioxidative function in MC65 cells and biometal binding ability.…”

“…This is somewhat consistent with our recent findings using another bivalent compound with cholesterylamine that showed that the anchor moiety and spacer length can affect the cellular localization of these compounds, thus leading to different mechanisms of action with regard to interacting with mitochondria or endoplasmic reticulum (unpublished data). [10] Again, this suggests that the bivalent strategy not only provides compounds with multifunctionality similar to the parent molecules, but also with novel mechanisms of action, and this functionality can be fine-tuned by modification of one of the various structural components of these compounds, as well.…”

“…Recently, we have successfully employed this concept in the creation of two series of bivalent, multifunctional compounds as potential neuroprotectants for AD in our laboratory. [8–10] These compounds included curcumin ( 1 ) as the multifunctional inhibitor “warhead” connected to a steroid moiety, acting as a lipid raft/membrane (LR/M) anchor. The key concept here is to localize the beneficial effects of the multifunctional “warhead” to the lipid rafts, where Aβ oligomer (AβO) and ROS production is known to occur, thus improving the efficiency.…”

Insights into the Impact of a Membrane-Anchoring Moiety on the Biological Activities of Bivalent Compounds As Potential Neuroprotectants for Alzheimer’s Disease

“…29, 31, 33 Notably, our studies suggested that the spacer length and the anchor moiety of the bivalent compounds may determine the sub-cellular localization of these bivalent compounds with different, yet overlapping, biological activities. 28, 30 In addition, bivalent compounds with different spacers showed different profiles with respect to their biometal chelating properties. 29 Although our bivalent compounds exhibited promising activities as potential neuroprotectants for AD, these results were derived from analogs with structural modifications on both the spacer composition/length and the anchor moiety at the same time.…”