Synthesis of novel cognition enhancers with pyrazolo[5,1-c][1,2,4]benzotriazine core acting at γ-aminobutyric acid type A (GABA(A)) receptor

Plant-mediated green synthesis of gold nanoparticles using an aqueous extract of Passiflora ligularis, optimization, characterizations, and their neuroprotective effect on propionic acid-induced autism in Wistar rats

The current study was conducted to examine an innovative method for synthesizing gold nanoparticles (AuNPs) from an aqueous sweet granadilla (Passiflora ligularis Juss) P. ligularis. Furthermore, the synthesized AuNPs were used to explore their potential neuroprotective impact against propionic acid (PPA)-induced autism. A sweet granadilla extract was used to achieve the synthesis of AuNPs. The structural and dimensional dispersion of AuNPs were confirmed by different techniques, including UV-Vis spectrophotometer (UV-Vis), X-ray Diffraction (XRD) Pattern, Energy Dispersive X-ray (EDX), Zeta potential, and High-Resolution Transmission Electron Microscopy (HRTEM) analysis. The AuNPs mediated by P. ligularis adopt a spherical shape morphology and the particle size was distributed in the range of 8.43-13 nm without aggregation. Moreover, in vivo, the anti-autistic effects of AuNPs administration were higher than those of P. ligularis extract per second. In addition, the reduced anxiety and neurobehavioral deficits of AuNPs were observed in autistic rats which halted the brain oxidative stress, reduced inflammatory cytokines, ameliorated neurotransmitters, and neurochemical release, and suppressed apoptotic genes (p < 0.05). The alleviated antiapoptotic gene expression and histopathological analysis confirmed that the treatment of AuNPs showed significant neural pathways that aid in reducing tissue damage and necrosis. The results emphasize that the biomedical activity was increased by using the green source synthesis P. ligularis -AuNPs. Additionally, the formulation of AuNPs demonstrates strong neuroprotective effects against PPA-induced autism that were arbitrated by a range of different mechanisms, such as anti-inflammatory, antioxidant, neuromodulator, and antiapoptotic effects.

Therapeutic potential of quinazoline derivatives for Alzheimer's disease: A comprehensive review

Quinazolines are considered as a promising class of bioactive heterocyclic compounds with broad properties. Particularly, the quinazoline scaffold has an impressive role in the design and synthesis of new CNS-active drugs. The drug-like properties and pharmacological characteristics of quinazoline could lead to different drugs with various targets. Among CNS disorders, Alzheimer's disease (AD) is a progressive neurodegenerative disorder with memory loss, cognitive decline and language dysfunction. AD is a complex and multifactorial disease therefore, the need for finding multi-target drugs against this devastative disease is urgent. A literature survey revealed that quinazoline derivatives have diverse therapeutic potential for AD as modulators/inhibitors of β-amyloid, tau protein, cholinesterases, monoamine oxidases, and phosphodiesterases as well as other protective effects. Thus, we describe here the most relevant and recent studies about anti-AD agents with quinazoline structure which can further aid the development and discovery of new anti-AD agents.

Soluble β-amyloid impaired the GABA inhibition by mediating KCC2 in early APP/PS1 mice

Alzheimer's disease (AD) is a neurodegenerative disorder, which has become the leading cause of dementia cases globally. Synaptic failure is an early pathological feature of AD. However, the cause of synaptic failure in AD, especially the GABAergic synaptic activity remains unclear. Extensive evidence indicates that the presence of soluble amyloid-β is an early pathological feature in AD, which triggers synaptic dysfunction and cognitive decline. Our recent study explored the relation of GABAergic transmission and soluble Aβ in early APP/PS1 mice. Firstly, we found soluble Aβ42 levels were significantly increased in serum, hippocampus and prefrontal cortex in 3-4 months APP/PS1 mice, which was much earlier than Aβ plagues formation. In addition, we found TNF-α and BDNF expression levels were increased, while KCC2 and GABA_AR expression were decreased in 3-4 months APP/PS1 hippocampus. When we treated 3-4 months APP/PS1 mice with a potent γ-secretase inhibitor, LY411575, which can reduce the soluble Aβ42 levels, the TNF-α and BDNF protein levels were decreased, while KCC2 and GABA_AR levels were increased. In conclusion, our study suggested soluble Aβ may impaired the GABA inhibition by mediating KCC2 levels in early APP/PS1 mice. KCC2 may be served as a potential biomarker for AD.

Rational approaches for the design of various GABA modulators and their clinical progression

GABA (γ-amino butyric acid) is an important inhibitory neurotransmitter in the central nervous system. Attenuation of GABAergic neurotransmission plays an important role in the etiology of several neurological disorders including epilepsy, Alzheimer's disease, Huntington's chorea, migraine, Parkinson's disease, neuropathic pain, and depression. Increase in the GABAergic activity may be achieved through direct agonism at the GABAA receptors, inhibition of enzymatic breakdown of GABA, or by inhibition of the GABA transport proteins (GATs). These functionalities make GABA receptor modulators and GATs attractive drug targets in brain disorders associated with decreased GABA activity. There have been several reports of development of GABA modulators (GABA receptors, GABA transporters, and GABAergic enzyme inhibitors) in the past decade. Therefore, the focus of the present review is to provide an overview on various design strategies and synthetic approaches toward developing GABA modulators. Furthermore, mechanistic insights, structure-activity relationships, and molecular modeling inputs for the biologically active derivatives have also been discussed. Summary of the advances made over the past few years in the clinical translation and development of GABA receptor modulators is also provided. This compilation will be of great interest to the researchers working in the field of neuroscience. From the light of detailed literature, it can be concluded that numerous molecules have displayed significant results and their promising potential, clearly placing them ahead as potential future drug candidates.

GABAergic Inhibitory Interneuron Deficits in Alzheimer's Disease: Implications for Treatment

Alzheimer’s disease (AD) is a neurodegenerative disorder characterized clinically by severe cognitive deficits and pathologically by amyloid plaques, neuronal loss, and neurofibrillary tangles. Abnormal amyloid β-protein (Aβ) deposition in the brain is often thought of as a major initiating factor in AD neuropathology. However, gamma-aminobutyric acid (GABA) inhibitory interneurons are resistant to Aβ deposition, and Aβ decreases synaptic glutamatergic transmission to decrease neural network activity. Furthermore, there is now evidence suggesting that neural network activity is aberrantly increased in AD patients and animal models due to functional deficits in and decreased activity of GABA inhibitory interneurons, contributing to cognitive deficits. Here we describe the roles played by excitatory neurons and GABA inhibitory interneurons in Aβ-induced cognitive deficits and how altered GABA interneurons regulate AD neuropathology. We also comprehensively review recent studies on how GABA interneurons and GABA receptors can be exploited for therapeutic benefit. GABA interneurons are an emerging therapeutic target in AD, with further clinical trials urgently warranted.

GABAergic dysfunction in excitatory and inhibitory (E/I) imbalance drives the pathogenesis of Alzheimer's disease

OBJECTIVE

To propose a new hypothesis that GABAergic dysfunction in excitatory and inhibitory (E/I) imbalance drives the pathogenesis of Alzheimer's disease (AD).

BACKGROUND

Synaptic dysfunction and E/I imbalance emerge decades before the appearance of cognitive decline in AD patients, which contribute to neurodegeneration. Initially, E/I imbalance was thought to occur first, due to dysfunction of the glutamatergic and cholinergic systems. However, new evidence has demonstrated that the GABAergic system, the counterpart of E/I balance and the major inhibitory neurotransmitter system in the central nervous system, is altered enormously and that this contributes to E/I imbalance and further AD pathogenesis.

NEW HYPOTHESIS

Alterations to the GABAergic system, induced by multiple AD pathogenic or risk factors, contribute to E/I imbalance and AD pathogenesis.

MAJOR CHALLENGES FOR THE HYPOTHESIS

This GABAergic hypothesis accounts for many critical questions and common challenges confronting a new hypothesis of AD pathogenesis. More specifically, it explains why amyloid beta (Aβ), β-secretase (BACE1), apolipoprotein E4 gene (APOE ε4), hyperactive glia cells, contributes to AD pathogenesis and why age and sex are the risk factors of AD. GABAergic dysfunction promotes the spread of Aβ pathology throughout the AD brain and associated cognitive impairments, and the induction of dysfunction induced by these varied risk factors shares this common neurobiology leading to E/I imbalance. In turn, some of these factors exacerbate GABAergic dysfunction and E/I imbalance. Moreover, the GABAergic system modulates various brain functions and thus, the GABAergic hypothesis accounts for nonamnestic manifestations. Furthermore, corrections of E/I balance through manipulation of GABAergic functions have shown positive outcomes in preclinical and clinical studies, suggesting the potential of the GABAergic system as a therapeutic target in AD.

LINKAGE TO OTHER MAJOR THEORIES

Dysfunction of the GABAergic system is induced by multiple critical signaling pathways, which include the existing major theories of AD pathogenesis, such as the Aβ and neuroinflammation hypotheses. In a new perspective, this GABAergic hypothesis accounts for the E/I imbalance and related excitotoxicity, which contribute to cognitive decline and AD pathogenesis. Therefore, the GABAergic system could be a key target to restore, at least partially, the E/I balance and cognitive function in AD patients.

Regioselective Ring Expansion of 3-Ylideneoxindoles with Tosyldiazomethane (TsDAM): A Metal-Free and Greener Approach for the Synthesis of Pyrazolo-[1,5-c]quinazolines

An efficient, metal-free approach to access pyrazolo-[1,5-c]quinazolines with 3-ylideneoxindoles and tosyldiazomethane (TsDAM) under mild aqueous reaction conditions has been developed and the solvent involvement in the present reaction has also been explored for the first time. This greener approach involves 1,3-dipolar cycloaddition, regioselective ring expansion, followed by the elimination of tosyl group with aqueous base in a single operation, and the product can be isolated in high purity without column chromatographic separation. The method is also compatible with a large variety of functional groups, providing good to excellent yields in water, thus resulting in a decrease of environmental impact in the pharmaceutical industry.

Allosteric GABAA Receptor Modulators-A Review on the Most Recent Heterocyclic Chemotypes and Their Synthetic Accessibility

GABAA receptor modulators are structurally almost as diverse as their target protein. A plethora of heterocyclic scaffolds has been described as modulating this extremely important receptor family. Some made it into clinical trials and, even on the market, some were dismissed. This review focuses on the synthetic accessibility and potential for library synthesis of GABAA receptor modulators containing at least one heterocyclic scaffold, which were disclosed within the last 10 years.

Implications of GABAergic Neurotransmission in Alzheimer's Disease

Alzheimer's disease (AD) is characterized pathologically by the deposition of β-amyloid peptides (Aβ) and the accumulation of neurofibrillary tangles (NFTs) composed of hyper-phosphorylated tau. Regardless of the pathological hallmarks, synaptic dysfunction is widely accepted as a causal event in AD. Of the two major types of synapses in the central nervous system (CNS): glutamatergic and GABAergic, which provide excitatory and inhibitory outputs respectively, abundant data implicate an impaired glutamatergic system during disease progression. However, emerging evidence supports the notion that disrupted default neuronal network underlies impaired memory, and that alterations of GABAergic circuits, either plays a primary role or as a compensatory response to excitotoxicity, may also contribute to AD by disrupting the overall network function. The goal of this review is to provide an overview of the involvement of Aβ, tau and apolipoprotein E4 (apoE4), the major genetic risk factor in late-onset AD (LOAD), in GABAergic neurotransmission and the potential of modulating the GABAergic function as AD therapy.