Site-specific quantification of lysine acetylation in the N-terminal tail of histone H4 using a double-labelling, targeted UHPLC MS/MS approach

We developed a targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the site-specific quantification of lysine acetylation in the N-terminal region of histone H4 by combining chemical derivatization at the protein and peptide levels with digestion using chymotrypsin and trypsin. Unmodified epsilon-amino groups were first modified with propionic acid anhydride and the derivatized protein digested with trypsin and chymotrypsin. The newly formed peptide N-termini were subjected to a second derivatization step with d(6)- (heavy) or d(0)- (light) acetic acid anhydride. Samples were mixed at different ratios and peptides monitored by multiple reaction monitoring (MRM) LC-MS/MS. The method was validated in terms of linearity (R (2) a parts per thousand yenaEuro parts per thousand 0.94), precision (RSD a parts per thousand currency signaEuro parts per thousand 10 %), and accuracy (a parts per thousand currency sign27 %) and used to assess the effect of the histone deacetylase (HDAC) inhibitors SAHA and MS-275 in the murine macrophage-like cell line RAW 264.7. SAHA and MS-275 showed site-specific effects on the acetylation levels of K5 and K8 with the K5(Ac)-K8 and K5-K8(Ac) peptides increasing 2.5-fold and 5-fold upon treatment with SAHA and MS-275, respectively. Assessing lysine acetylation in a site-specific manner is important for gaining a better understanding of the effects of HDAC inhibitors and for clarifying disease mechanisms where lysine acetylation plays a role

Investigating in vitro amyloid peptide 1-42 aggregation: impact of higher molecular weight stable adducts

The self-assembly of amyloid peptides (Aβ), in particular Aβ1–42, into oligomers and fibrils is one of the main pathological events related to Alzheimer’s Disease (AD). Recent studies have demonstrated the ability of carbon monoxide releasing molecules (CORMs) to protect neurons and astrocytes from Aβ1-42 toxicity. In fact, CORMs are able to carry and release controlled levels of CO and are known to exert a wide range of anti-inflammatory and anti-apoptotic activities at physiologically relevant concentrations. In order to investigate the direct effects of CORMs on Aβ1–42, we studied the reactivity of CORM-2 and CORM-3 with Aβ1–42 in vitro and the potential inhibition of its aggregation by mass spectrometry (MS), as well as fluorescence and circular dichroism (CD) spectroscopies. The application of an electrospray ionisation-mass spectrometry (ESI-MS) method allowed the detection of stable Aβ1–42/CORMs adducts, involving the addition of the Ru(CO)2 portion of CORMs at histidine residues on the Aβ1-42 skeleton. Moreover, CORMs showed anti-aggregating properties through formation of stable adducts with Aβ1–42 as demonstrated by a thioflavin T (ThT) fluorescence assay and MS analysis. As a further proof, comparison of the CD spectra of Aβ1–42 recorded in the absence and in the presence of CORM-3 at 1:1 molar ratio showed the ability of CORM-3 to stabilize the peptide in its soluble, unordered conformation, thereby preventing its misfolding and aggregation. This multi-methodological investigation revealed novel interactions between Aβ1–42 and CORMs, contributing new insights into the proposed neuroprotective mechanisms mediated by CORMs and disclosing a new strategy to divert amyloid aggregation and toxicity

Multitarget drug design strategy in Alzheimer’s disease: focus on cholinergic transmission and amyloid-β aggregation

Background: Alzheimer pathogenesis has been associated with a network of processes working simultaneously and synergistically. Over time, much interest has been focused on cholinergic transmission and its mutual interconnections with other active players of the disease. Besides the cholinesterase mainstay, the multifaceted interplay between nicotinic receptors and amyloid is actually considered to have a central role in neuroprotection. Thus, the multitarget drug-design strategy has emerged as a chance to face the disease network. Results: By exploiting the multitarget approach, the present study provides new molecules able to target the cholinergic pathway, by joining direct nicotinic receptor stimulation to acetylcholinesterase inhibition, and to inhibit Aβ aggregation. Conclusions: These new compounds emerged as a suitable starting point for a further optimization process

Synthesis, in vitro profiling, and in vivo efficacy studies of a new family of multitarget anti-Alzheimer compounds

Simultaneous modulation of several targets or pathological events with a key pathogenic role is a promising strategy to tackle thus far difficult-to-cure or incurable multifactorial diseases, such as Alzheimer's disease (AD). In this scenario, multitarget compounds, i.e., single molecules that hit several targets, are superior to other multitarget strategies that are based on the use of more than one drug (drug cocktails, fixed-dose combinations), in terms of simpler drug development and better patient compliance, efficiency, and safety. In the frame of our research line devoted to the development of novel anti-AD drug candidates, we have recently prepared a new class of multitarget compounds, which were designed by combining pharmacophoric moieties of a known antioxidant agent (7-methoxy-2,2- dimethylchroman-6-ol (CR-6)) and an acetylcholinesterase (AChE) inhibitor (6-chlorotacrine), to primarily address two important pathological events of AD, namely oxidative stress and cholinergic deficit. Here, we present the synthesis of three short series of CR-6-chlorotacrine hybrids, featuring different linker functionalities (amide, inverse amide, or amine) and lengths, and their in vitro biological activities against AChE, butyrylcholinesterase, BACE-1, and β-amyloid and tau protein aggregation, their antioxidant activity, and BBB permeability. We will also show the results of the in vivo efficacy studies of two selected compounds in double transgenic APP/PS1 mice, a wellestablished mouse model of AD (behavioral studies, effects on amyloid pathology and oxidative stress)

From virtual screening hits targeting a cryptic pocket in BACE-1 to a nontoxic brain permeable multitarget anti-Alzheimer lead with disease-modifying and cognition-enhancing effects

Starting from six potential hits identified in a virtual screening campaign directed to a cryptic pocket of BACE-1, at the edge of the catalytic cleft, we have synthesized and evaluated six hybrid compounds, designed to simultaneously reach BACE-1 secondary and catalytic sites and to exert additional activities of interest for Alzheimer's disease (AD). We have identified a lead compound with potent in vitro activity towards human BACE-1 and cholinesterases, moderate Ab42 and tau antiaggregating activity, and brain permeability, which is nontoxic in neuronal cells and zebrafish embryos at concentrations above those required for the in vitro activities. This compound completely restored short- and long-term memory in a mouse model of AD (SAMP8) relative to healthy control strain SAMR1, shifted APP processing towards the non-amyloidogenic pathway, reduced tau phosphorylation, and increased the levels of synaptic proteins PSD95 and synaptophysin, thereby emerging as a promising disease-modifying, cognitionenhancing anti-AD lead

A novel class of multitarget anti-Alzheimer benzohomoadamantane‒chlorotacrine hybrids modulating cholinesterases and glutamate NMDA receptors

The development of multitarget compounds against multifactorial diseases, such as Alzheimer's disease, is an area of very intensive research, due to the expected superior therapeutic efficacy that should arise from the simultaneous modulation of several key targets of the complex pathological network. Here we describe the synthesis and multitarget biological profiling of a new class of compounds designed by molecular hybridization of an NMDA receptor antagonist fluorobenzohomoadamantanamine with the potent acetylcholinesterase (AChE) inhibitor 6-chlorotacrine, using two different linker lengths and linkage positions, to preserve or not the memantine-like polycyclic unsubstituted primary amine. The best hybrids exhibit greater potencies than parent compounds against AChE (IC50 0.33 nM in the best case, 44-fold increased potency over 6-chlorotacrine), butyrylcholinesterase (IC50 21 nM in the best case, 24-fold increased potency over 6-chlorotacrine), and NMDA receptors (IC50 0.89 µM in the best case, 2-fold increased potency over the parent benzohomoadamantanamine and memantine), which suggests an additive effect of both pharmacophoric moieties in the interaction with the primary targets. Moreover, most of these compounds have been predicted to be brain permeable. This set of biological properties makes them promising leads for further anti-Alzheimer drug development