Identification of tetrahydrocarbazoles as novel multifactorial drug candidates for treatment of Alzheimer's disease

The significance of calcium ions in cerebral ischemia-reperfusion injury: mechanisms and intervention strategies

Cerebral ischemia-reperfusion injury (CIRI) represents a multifaceted pathological phenomenon characterized by an array of molecular and cellular mechanisms, which significantly contribute to neurological dysfunction. Evidence suggests that calcium ions play an indispensable role in this context, as abnormal elevations in calcium concentrations exacerbate neuronal injury and intensify functional deficits. These ions are integral not only for intracellular signaling pathways but also for various pathological processes, such as programmed cell death, inflammatory responses, and oxidative stress. This review article elucidates the physiological framework of calcium homeostasis and the precise mechanisms through which calcium ions influence CIRI. Moreover, it addresses potential intervention strategies, including calcium channel blockers, calmodulin (CaM) inhibitors, antioxidants, and anti-inflammatory agents. Despite the proposal of certain intervention strategies, their effectiveness and safety in clinical settings warrant further scrutiny. In conclusion, the article highlights the limitations of current research and anticipates future investigative trajectories, aiming to provide a theoretical foundation and reference for the development of more efficacious treatment modalities.

Enantioselective Synthesis of Tetrahydro-1H-1,3-methanocarbazoles by Formal (3 + 3)-Cycloaddition Using Bicyclo[1.1.0]butanes

Asymmetric synthesis presents many challenges, with the selective formation of chiral bridged polyheterocycles being a notable example. Cycloadditions using bicyclo[1.1.0]butanes (BCB) offer a promising solution along those lines, yet, despite significant advances in that emerging area, asymmetric control has remained limited thus far. Here, we describe an organocatalytic, enantioselective formal (3 + 3)-cycloaddition of BCBs with 1H-indol-3-yl((hetero)aryl)methanol derivatives. This approach enables the rapid and efficient synthesis of chiral tetrahydro-1H-1,3-methanocarbazole derivatives (34 examples) from readily available starting materials, with very good stereochemical control (up to 98:2 er). Successful scale-up experiments and product modification demonstrated the potential of this methodology. Control experiments and DFT calculations provide insights into the mechanistic pathway.

Insulin signaling and oxidative stress: Bridging the gap between type 2 diabetes mellitus and Alzheimer's disease

BACKGROUND

Type 2 diabetes mellitus (T2D) and Alzheimer's disease (AD) are two prevalent chronic diseases that pose significant global health challenges. Increasing evidence suggests a complex bidirectional relationship between these conditions, where T2D elevates the risk of AD, and AD exacerbates glucose metabolism abnormalities in T2D.

OBJECTIVE

This review explores the molecular mechanisms linking T2D and AD, focusing on the role of insulin signaling pathways and oxidative stress.

METHODS

A comprehensive literature search from PubMed, Web of Science, and other relevant databases was conducted and analyzed.

RESULTS

Insulin resistance in T2D leads to impaired insulin signaling in the brain, contributing to cognitive decline and the development of AD. Hyperglycemia-induced oxidative stress exacerbates neuronal damage, promoting the formation of amyloid-β plaques and neurofibrillary tangles characteristic of AD. Clinically antidiabetic drugs such as metformin show potential against AD in preclinical studies; Many natural products such as Dendrobium nobile Lindl. have anti-T2D efficacy and are also effective against AD in various in vivo and in vitro models.

CONCLUSIONS

Improving insulin resistance and reducing oxidative stress are important strategies in the treatment of T2D and AD. To understand the bridging role of insulin singling and oxidative stress in T2D and AD will provide insights and broader applications in alleviating T2D and AD.

Recent approaches to the synthesis of tetrahydrocarbazoles

The tetrahydrocarbazole (THC) motif is ubiquitous in natural products and biologically active compounds.

Drug Screening with Genetically Encoded Fluorescent Sensors: Today and Tomorrow

Genetically-encoded fluorescent sensors have been actively developed over the last few decades and used in live imaging and drug screening. Real-time monitoring of drug action in a specific cellular compartment, organ, or tissue type; the ability to screen at the single-cell resolution; and the elimination of false-positive results caused by low drug bioavailability that is not detected by in vitro testing methods are a few of the obvious benefits of using genetically-encoded fluorescent sensors in drug screening. In combination with high-throughput screening (HTS), some genetically-encoded fluorescent sensors may provide high reproducibility and robustness to assays. We provide a brief overview of successful, perspective, and hopeful attempts at using genetically encoded fluorescent sensors in HTS of modulators of ion channels, Ca2+ homeostasis, GPCR activity, and for screening cytotoxic, anticancer, and anti-parasitic compounds. We discuss the advantages of sensors in whole organism drug screening models and the perspectives of the combination of human disease modeling by CRISPR techniques with genetically encoded fluorescent sensors for drug screening.

Dysregulation of Neuronal Calcium Signaling via Store-Operated Channels in Huntington's Disease

Huntington's disease (HD) is a progressive neurodegenerative disorder that is characterized by motor, cognitive, and psychiatric problems. It is caused by a polyglutamine expansion in the huntingtin protein that leads to striatal degeneration via the transcriptional dysregulation of several genes, including genes that are involved in the calcium (Ca²⁺) signalosome. Recent research has shown that one of the major Ca²⁺ signaling pathways, store-operated Ca²⁺ entry (SOCE), is significantly elevated in HD. SOCE refers to Ca²⁺ flow into cells in response to the depletion of endoplasmic reticulum Ca²⁺ stores. The dysregulation of Ca²⁺ homeostasis is postulated to be a cause of HD progression because the SOCE pathway is indirectly and abnormally activated by mutant huntingtin (HTT) in γ-aminobutyric acid (GABA)ergic medium spiny neurons (MSNs) from the striatum in HD models before the first symptoms of the disease appear. The present review summarizes recent studies that revealed a relationship between HD pathology and elevations of SOCE in different models of HD, including YAC128 mice (a transgenic model of HD), cellular HD models, and induced pluripotent stem cell (iPSC)-based GABAergic medium spiny neurons (MSNs) that are obtained from adult HD patient fibroblasts. SOCE in MSNs was shown to be mediated by currents through at least two different channel groups, Ca²⁺ release-activated Ca²⁺ current (I_CRAC) and store-operated Ca²⁺ current (I_SOC), which are composed of stromal interaction molecule (STIM) proteins and Orai or transient receptor potential channel (TRPC) channels. Their role under physiological and pathological conditions in HD are discussed. The role of Huntingtin-associated protein 1 isoform A in elevations of SOCE in HD MSNs and potential compounds that may stabilize elevations of SOCE in HD are also summarized. Evidence is presented that shows that the dysregulation of molecular components of SOCE or pathways upstream of SOCE in HD MSN neurons is a hallmark of HD, and these changes could lead to HD pathology, making them potential therapeutic targets.

Design, synthesis and biological evaluation of novel naturally-inspired multifunctional molecules for the management of Alzheimer's disease

In our overall goal to overcome the limitations associated with natural products for the management of Alzheimer's disease and to develop in-vivo active multifunctional cholinergic inhibitors, we embarked on the development of ferulic acid analogs. A systematic SAR study to improve upon the cholinesterase inhibition of ferulic acid with analogs that also had lower logP was carried out. Enzyme inhibition and kinetic studies identified compound 7a as a lead molecule with preferential acetylcholinesterase inhibition (AChE IC₅₀ = 5.74 ± 0.13 μM; BChE IC₅₀ = 14.05 ± 0.10 μM) compared to the parent molecule ferulic acid (% inhibition of AChE and BChE at 20 μM, 15.19 ± 0.59 and 19.73 ± 0.91, respectively). Molecular docking and dynamics studies revealed that 7a fits well into the active sites of AChE and BChE, forming stable and strong interactions with key residues Asp74, Trp286, and Tyr337 in AChE and with Tyr128, Trp231, Leu286, Ala328, Phe329, and Tyr341 in BChE. Compound 7a was found to be an efficacious antioxidant in a DPPH assay (IC₅₀ = 57.35 ± 0.27 μM), and it also was able to chelate iron. Data from atomic force microscopy images demonstrated that 7a was able to modulate aggregation of amyloid β_1-42. Upon oral administration, 7a exhibited promising in-vivo activity in the scopolamine-induced AD animal model and was able to improve spatial memory in cognitive deficit mice in the Y-maze model. Analog 7a could effectively reverse the increased levels of AChE and BChE in scopolamine-treated animals and exhibited potent ex-vivo antioxidant properties. These findings suggest that 7a can act as a lead molecule for the development of naturally-inspired multifunctional molecules for the management of Alzheimer's and other neurodegenerative disorders.

Computer-Aided Multi-Target Management of Emergent Alzheimer's Disease

Alzheimer's disease (AD) represents an enormous global health burden in terms of human suffering and economic cost. AD management requires a shift from the prevailing paradigm targeting pathogenesis to design and develop effective drugs with adequate success in clinical trials. Therefore, it is of interest to report a review on amyloid beta (Aβ) effects and other multi-targets including cholinesterase, NFTs, tau protein and TNF associated with brain cell death to be neuro-protective from AD. It should be noted that these molecules have been generated either by target-based or phenotypic methods. Hence, the use of recent advancements in nanomedicine and other natural compounds screening tools as a feasible alternative for circumventing specific liabilities is realized. We review recent developments in the design and identification of neuro-degenerative compounds against AD generated using current advancements in computational multi-target modeling algorithms reflected by theragnosis (combination of diagnostic tests and therapy) concern.

Tetrahydrocarbazoles are a novel class of potent P-type ATPase inhibitors with antifungal activity

We have identified a series of tetrahydrocarbazoles as novel P-type ATPase inhibitors. Using a set of rationally designed analogues, we have analyzed their structure-activity relationship using functional assays, crystallographic data and computational modeling. We found that tetrahydrocarbazoles inhibit adenosine triphosphate (ATP) hydrolysis of the fungal H⁺-ATPase, depolarize the fungal plasma membrane and exhibit broad-spectrum antifungal activity. Comparative inhibition studies indicate that many tetrahydrocarbazoles also inhibit the mammalian Ca²⁺-ATPase (SERCA) and Na⁺,K⁺-ATPase with an even higher potency than Pma1. We have located the binding site for this compound class by crystallographic structure determination of a SERCA-tetrahydrocarbazole complex to 3.0 Å resolution, finding that the compound binds to a region above the ion inlet channel of the ATPase. A homology model of the Candida albicans H⁺-ATPase based on this crystal structure, indicates that the compounds could bind to the same pocket and identifies pocket extensions that could be exploited for selectivity enhancement. The results of this study will aid further optimization towards selective H⁺-ATPase inhibitors as a new class of antifungal agents.

Focused design of polypharmacophoric neuroprotective compounds: Conjugates of γ-carbolines with carbazole derivatives and tetrahydrocarbazole

Alzheimer’s disease has a complex multifactorial nature; therefore, a promising approach for the development of efficient therapeutic agents is the concept of multitarget drugs, which affect several biological targets involved in the pathogenesis of the disease. We developed a synthetic algorithm for conjugating several pharmacophoric ligands acting on the key stages of pathogenesis of several neurodegenerative diseases and synthesized hybrid structures combining the γ-carboline fragment of Dimebon with carbazole and tetrahydrocarbazole moieties. Using the complex primary screening system the structures have been revealed that combine the high inhibitory activity and selectivity towards butyrylcholinesterase with the radical-scavenging activity and the ability to potentiate tubulin polymerization to microtubules with a normal structure and/or prevent mitochondrial permeability transition. The lead compound was identified for future optimization and development of new multi-target drugs against neurodegenerative diseases combining the cognitive-stimulating and neuroprotective potentials.

Tetrahydrocarbazoles decrease elevated SOCE in medium spiny neurons from transgenic YAC128 mice, a model of Huntington's disease

Huntington's disease (HD) is a hereditary neurodegenerative disease caused by a polyglutamine expansion within the huntingtin (HTT) gene. One of the cellular functions that is dysregulated in HD is store-operated calcium entry (SOCE), a process in which the depletion of Ca²⁺ from the endoplasmic reticulum (ER) induces Ca²⁺ influx from the extracellular space. We detected an enhanced activity of SOC channels in medium spiny neurons (MSNs) from YAC128 mice, a transgenic model of HD, and investigated whether this could be reverted by tetrahydrocarbazoles. The compound 6-bromo-N-(2-phenylethyl)-2,3,4,9-tetrahydro-1H-carbazol-1-amine hydrochloride was indeed able to restore the disturbed Ca²⁺ homeostasis and stabilize SOCE in YAC128 MSN cultures. We also detected a beneficial effect of this compound on the mitochondrial membrane potential. Since dysregulated Ca²⁺ homeostasis is believed to be one of the pathological hallmarks of HD, this compound might be a lead structure for HD treatment.