Hybrids of oxoisoaporphine-tetrahydroisoquinoline: novel multi-target inhibitors of inflammation and amyloid-β aggregation in Alzheimer's disease

Presenilin 1 M139I mutation regulates the microRNA-34a-mediated neurogenic locus notch homolog protein 1 signaling pathway in an early-onset Alzheimer disease cell model

Presenilin 1 (PSEN1) mutations are the leading cause of early-onset Alzheimer disease (EOAD). A recent study found that the PSEN1 M139I mutation is associated with EOAD. In this study, we examined the impact of the PSEN1 M139I mutation in an EOAD in vitro model. Our findings reveal that the PSEN1 M139I mutation leads to increased levels of Aβ42/40, Hairy and Enhancer of Split-1 (Hes1), neurogenic locus notch homolog intracellular domain, and microRNA-34a, accompanied by a decrease in the level of neurogenic locus notch homolog protein 1 (NOTCH-1). Computational predictions indicate that NOTCH-1 is a direct target of microRNA-34a. Transfection of microRNA-34a mimics into PSEN1 M139I mutant SH-SY5Y cells increased the ratio of Aβ42/40 and induced Hes1, cysteine-aspartic acid protease 3 (Caspase-3), and apoptosis while reducing the NOTCH-1 expression and inhibiting cell proliferation. Conversely, downregulating microRNA-34a expression by transfecting microRNA-34a inhibitors mitigated these effects, thereby restoring NOTCH-1 production and cell proliferation and reversing the increases in Aβ42/40 ratio, Hes1, Caspase-3, and apoptosis induced by the PSEN1 M139I mutation. In summary, the PSEN1 M139I mutation identified in EOAD may influence amyloid-β (Aβ) production and apoptosis by regulating the microRNA-34a-mediated NOTCH-1 signaling pathway.

Analysis of skeletal diversity of multi-target directed ligands (MTDLs) targeting Alzheimer's disease

Alzheimer's disease (AD) remains a significant healthcare challenge, necessitating innovative therapeutic approaches to address its complex and multifactorial nature. Traditional drug discovery strategies targeting single molecular targets are not sufficient for the effective treatment of AD. In recent years, MTDLs have emerged as promising candidates for AD therapy, aiming to simultaneously modulate multiple pathological targets. Among the various strategies employed in MTDL design, pharmacophore hybridization offers a versatile approach to integrate diverse pharmacophoric features within a single molecular scaffold. This strategy provides access to a wide array of chemical space for the design and development of novel therapeutic agents. This review, therefore, provides a comprehensive overview of skeletal diversity exhibited by MTDLs designed recently for AD therapy based on pharmacophore hybridization approach. A diverse range of pharmacophoric elements and core scaffolds hybridized to construct MTDLs that has the potential to target multiple pathological features of AD including amyloid-beta aggregation, tau protein hyperphosphorylation, cholinergic dysfunction, oxidative stress, and neuroinflammation are discussed. Through the comprehensive analysis and integration of structural insights of key biomolecular targets, this review aims to enhance optimization efforts in MTDL design, ultimately striving towards a comprehensive cure for the multifaceted pathophysiology of the disease.

Development of novel melatonin-isatin hybrids as multifunctional agents for Alzheimer's disease

The development of multifunctional agents has been a heated area of research for AD treatment in recent years. In this work, a series of melatonin-isatin hybrids were designed, synthesized, and evaluated as multifunctional agents for treating AD. In vitro studies indicated that most of the synthesized compounds displayed moderate to good MAO-B inhibition activities and good antioxidant activities. In particular, compounds IM-5 and IM-10 exhibited the best inhibitory activities with IC50 value of 12.4 μM and 15.6 μM against MAO-B, and potent antioxidant activities with their ORAC-FL values of 4.6 and 5.2 at 5 μM, respectively. ThT assay revealed compounds IM-5 and IM-10 exhibited the optimal Aβ1-42 self-induced aggregation inhibitory activities with the inhibition ratio of 72.8% and 69.7% at 20 μM. In addition, compounds IM-5 and IM-10 exhibited low cytotoxicities and significant neuroprotective effects on Aβ1-42-induced and H2O2-induced SH-SY5Y cell injury. More importantly, compounds IM-5 and IM-10 could significantly ameliorate the memory impairment and cognition injury in scopolamine-induced mice. The SwissADME program was used to predict drug-like properties of compounds IM-5 and IM-10 which exhibited they had good pharmacokinetics and drug-likeness properties. Molecular docking study further manifested that compounds IM-5 and IM-10 showed high hMAO-B inhibitory potency. In summary, all above results revealed compounds IM-5 and IM-10 might be promising multifunctional agents for AD treatment.

Design, synthesis, and evaluation of 2,2'-bipyridyl derivatives as bifunctional agents against Alzheimer's disease

Alzheimer's disease (AD) is a complex multifactorial neurodegenerative disease. Metal ion dyshomeostasis and Aβ aggregation have been proposed to contribute to AD progression. Metal ions can bind to Aβ and promote Aβ aggregation, and ultimately lead to neuronal death. Bifunctional (metal chelation and Aβ interaction) compounds are showing promise against AD. In this work, eleven new 3,3'-diamino-2,2'-bipyridine derivatives 4a-4k were synthesized, and evaluated as bifunctional agents for AD treatment. In vitro Aβ aggregation inhibition assay confirmed that most of the synthesized compounds exhibited significant self-induced Aβ1-42 aggregation inhibition. Among them, compound 4d displayed the best inhibitory potency of self-induced Aβ1-42 aggregation with IC50 value of 9.4 µM, and it could selectively chelate with Cu2+ and exhibited 66.2% inhibition of Cu2+-induced Aβ1-42 aggregation. Meanwhile, compound 4d showed strong neuroprotective activity against Aβ1-42 and Cu2+-treated Aβ1-42 induced cell damage. Moreover, compound 4d in high dose significantly reversed Aβ-induced memory impairment in mice.

A comprehensive review on the progress and challenges of tetrahydroisoquinoline derivatives as a promising therapeutic agent to treat Alzheimer's disease

Alzheimer's disease (AD) is the most common and irreversible neurodegenerative disorder worldwide. While the precise mechanism behind this rapid progression and multifaceted disease remains unknown, the numerous drawbacks of the available therapies are prevalent, necessitating effective alternative treatment methods. In view of the rising demand for effective AD treatment, numerous reports have shown that tetrahydroisoquinoline (THIQ) is a valuable scaffold in various clinical medicinal molecules and has a promising potential as a therapeutic agent in treating AD due to its significant neuroprotective, anti-inflammatory, and antioxidative properties via several mechanisms that target the altered signaling pathways. Therefore, this review comprehensively outlines the potential application of THIQ derivatives in AD treatment and the challenges in imparting the action of these prospective therapeutic agents. The review emphasizes a number of THIQ derivatives, including Dauricine, jatrorrhizine, 1MeTIQ, and THICAPA, that have been incorporated in AD studies in recent years. Subsequently, a dedicated section of the review briefly discusses the emerging potential benefits of multi-target therapeutics, which lie in their ability to be integrated with alternative therapeutics. Eventually, this review elaborates on the rising challenges and future recommendations for the development of therapeutic drug agents to treat AD effectively. In essence, the valuable research insights of THIQ derivatives presented in this comprehensive review would serve as an integral reference for future studies to develop potent therapeutic drugs for AD research.

Targeting Alzheimer's Disease: Evaluating the Efficacy of C-1 Functionalized N-Aryl-Tetrahydroisoquinolines as Cholinergic Enzyme Inhibitors and Promising Therapeutic Candidates

We have synthesized 22 C-1 functionalized-N-aryl-1,2,3,4-tetrahydroisoquinoline derivatives showing biological activities towards cholinergic enzymes. Synthesis was performed using visible-light-promoted photo-redox chemistry, starting from a common intermediate, and the application of this synthetic methodology drastically simplified synthetic routes and purification of desired compounds. All synthesized derivates were divided into four groups based on the substituents in the C-1 position, and their inhibition potencies towards two cholinergic enzymes, acetyl- and butyrylcholinesterase were evaluated. Most potent derivatives were selected, and kinetic analysis was further carried out to obtain insights into the mechanisms of inhibition of these two enzymes. Further validation of the mode of inhibition of cholinergic enzymes by the two most potent THIQ compounds, 3c and 3i, was performed using fluorescence-quenching titration studies. Molecular docking studies further confirmed the proposed mechanism of enzymes' inhibition. In silico predictions of physicochemical properties, pharmacokinetics, drug-likeness, and medicinal chemistry friendliness of the selected most potent derivatives were performed using Swiss ADME tool. This was followed by UPLC-assisted log P determination and in vitro BBB permeability studies performed in order to assess the potential of the synthesized compounds to pass the BBB.

Carnosine Protects Macrophages against the Toxicity of Aβ1-42 Oligomers by Decreasing Oxidative Stress

Carnosine (β-alanyl-L-histidine) is a naturally occurring endogenous peptide widely distributed in excitable tissues such as the brain. This dipeptide has well-known antioxidant, anti-inflammatory, and anti-aggregation activities, and it may be useful for treatment of neurodegenerative disorders such as Alzheimer’s disease (AD). In this disease, peripheral infiltrating macrophages play a substantial role in the clearance of amyloid beta (Aβ) peptides from the brain. Correspondingly, in patients suffering from AD, defects in the capacity of peripheral macrophages to engulf Aβ have been reported. The effects of carnosine on macrophages and oxidative stress associated with AD are consequently of substantial interest for drug discovery in this field. In the present work, a model of stress induced by Aβ1-42 oligomers was investigated using a combination of methods including trypan blue exclusion, microchip electrophoresis with laser-induced fluorescence, flow cytometry, fluorescence microscopy, and high-throughput quantitative real-time PCR. These assays were used to assess the ability of carnosine to protect macrophage cells, modulate oxidative stress, and profile the expression of genes related to inflammation and pro- and antioxidant systems. We found that pre-treatment of RAW 264.7 macrophages with carnosine counteracted cell death and apoptosis induced by Aβ1-42 oligomers by decreasing oxidative stress as measured by levels of intracellular nitric oxide (NO)/reactive oxygen species (ROS) and production of peroxynitrite. This protective activity of carnosine was not mediated by modulation of the canonical inflammatory pathway but instead can be explained by the well-known antioxidant and free-radical scavenging activities of carnosine, enhanced macrophage phagocytic activity, and the rescue of fractalkine receptor CX3CR1. These new findings obtained with macrophages challenged with Aβ1-42 oligomers, along with the well-known multimodal mechanism of action of carnosine in vitro and in vivo, substantiate the therapeutic potential of this dipeptide in the context of AD pathology.

Medicinal chemistry perspectives of 1,2,3,4-tetrahydroisoquinoline analogs - biological activities and SAR studies

Isoquinoline alkaloids are a large group of natural products in which 1,2,3,4-tetrahydroisoquinolines (THIQ) form an important class. THIQ based natural and synthetic compounds exert diverse biological activities against various infective pathogens and neurodegenerative disorders. Due to these reasons, the THIQ heterocyclic scaffold has garnered a lot of attention in the scientific community which has resulted in the development of novel THIQ analogs with potent biological activity. The present review provides a much-needed update on the biological potential of THIQ analogs, their structural-activity relationship (SAR), and their mechanism of action. In addition, a note on commonly used synthetic strategies for constructing the core scaffold has also been discussed.