Beneficial Effect of Flavone Derivatives on Aβ-Induced Memory Deficit Is Mediated by Peroxisome Proliferator-Activated Receptor γ Coactivator 1α: A Comparative Study

Berberine Improves Behavioral and Cognitive Deficits in a Mouse Model of Alzheimer's Disease via Regulation of β-Amyloid Production and Endoplasmic Reticulum Stress

Alzheimer's disease (AD) is a neurodegenerative disease characterized by β-amyloid (Aβ), neurofibrillary tangles, and neuronal cell death. Aggressive Aβ accumulation accelerates senile plaque formation and perturbs endoplasmic reticulum (ER) function. Aβ accumulation-induced changes stimulate the unfolded protein response (UPR), which can trigger neuronal apoptosis. Protein kinase RNA-like endoplasmic reticulum kinase (PERK), whose activation is stress-dependent, increases the phosphorylation of eukaryotic translation initiation factor-2α (eIF2α). eIF2α promotes the synthesis of β-site APP cleavage enzyme 1 (BACE1), which in turn facilitates Aβ generation and subsequent neuronal apoptosis. In this study, we investigated whether berberine could improve cognitive deficits in the triple-transgenic mouse model of Alzheimer's disease (3 × Tg AD) mice. Our results revealed that berberine treatment may inhibit PERK/eIF2α signaling-mediated BACE1 translation, thus reducing Aβ production and resultant neuronal apoptosis. Further, berberine may have neuroprotective effects, via attenuation of ER stress and oxidative stress. In sum, our study demonstrates the therapeutic potential of berberine for treating AD.

Natural products as pharmacological modulators of mitochondrial dysfunctions for the treatments of Alzheimer's disease: A comprehensive review

Alzheimer's disease (AD) is the most common progressive neurodegenerative disorder characterized by neuronal loss and cognitive impairment that harshly affect the elderly individuals. Currently, the available anti-AD pharmacological approaches are purely symptomatic to alleviate AD symptoms, and the curative effects of novel anti-AD drugs focused on Aβ target are disappointing. Hence, there is a tremendous need to adjust AD therapeutic targets and discover novel anti-AD agents. In AD, mitochondrial dysfunction gradually triggers neuronal death from different aspects and worsens the occurrence and progress of AD. Consequently, it has been proposed that the intervention of impaired mitochondria represents an attractive breakthrough point for AD treatments. Due to chemical diversity, poly-pharmacological activities, few adverse effects and multiple targeting, natural products (NPs) have been identified as a valuable treasure for drug discovery and development. Multiple lines of studies have scientifically proven that NPs display ameliorative benefits in AD treatment in relation to mitochondrial dysfunction. This review surveys the complicated implications for mitochondrial dysregulation and AD, and then summarizes the potentials of NPs and their underlying molecular mechanisms against AD via reducing or improving mitochondrial dysfunction. It is expected that this work may open the window to speed up the development of innovative anti-AD drugs originated from NPs and improve upcoming AD therapeutics.

99mTc-labeled Small Molecules for Diagnosis of Alzheimer’s Disease: Past, Recent and Future Perspectives

Background:

Alzheimer’s disease (AD) is an age-related progressive neurodegenerative disease. Its prominent hallmarks are extracellular deposition of β-amyloids (amyloid plaques), intracellular neurofibrillary tangles (NTFs), neurodegeneration and finally loss of cognitive function. Hence, AD diagnosis in the early stage and monitoring of the disease are of great importance.

Methods:

In this review article, we have reviewed recent efforts for design, synthesis and evaluation of 99mTc labeled small molecule for AD imaging purposes.

Results:

These small molecules include derivatives of Congo red, benzothiazole, benzofuran, benzoxazole, naphthalene, biphenyl, chalcone, flavone, aurone, stilbene, curcumin, dibenzylideneacetone, quinoxaline, etc. The different aspects of 99mTc-labeled small molecules including chemical structure, their affinity toward amyloid plaques, BBB permeation and in vivo/vitro stability will be discussed.

Conclusion:

The findings of this review confirm the importance of 99mTc-labeled small molecules for AD imaging. Future studies based on the pharmacophore of these designed compounds are needed for improvement of these molecules for clinical application.

Mechanisms of dietary flavonoid action in neuronal function and neuroinflammation

Flavonoids are a class of plant-derived dietary polyphenols that have attracted attention for their pro-cognitive and anti-inflammatory effects. The diversity of flavonoids and their extensive in vivo metabolism suggest that a variety of cellular targets in the brain are likely to be impacted by flavonoid consumption. Initially characterized as antioxidants, flavonoids are now believed to act directly on neurons and glia via the interaction with major signal transduction cascades, as well as indirectly via interaction with the blood-brain barrier and cerebral vasculature. This review discusses potential mechanisms of flavonoid action in the brain, with a focus on two critical transcription factors: cAMP response element-binding protein (CREB) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). To advance beyond current understanding of cellular targets, critical bioavailability studies need to be performed to verify the identity and concentration of flavonoid metabolites reaching the brain after ingestion and to validate that these metabolites are produced not just in rodent models but also in humans. Recent advances in human induced pluripotent stem cell (iPSC) differentiation protocols to generate human neuronal and glial cell types could also provide a unique tool for clinically relevant in vitro investigation of the mechanisms of action of bioavailable flavonoid metabolites in humans.

Prevention of recognition memory loss and moderation of mitochondrial dynamic tendency toward fusion by flavone derivatives in Aβ-injected rats: a comparison between two flavonoids with different polarity

Growing evidence sheds light on the use of flavonoids as the promising alternatives for the treatment of chronic conditions, including cancer and neurodegenerative disorders. Accordingly, in the present study, we aimed at evaluating the effects of oral intake of two structurally different flavonoids 5-hydroxy-6,7,4'-trimethoxyflavone (flavone 1) and 5,7,4'-trihydroxyflavone (flavone 2) on recognition memory, hippocampal protein level of immediate early gene cFos and mitochondrial dynamic markers in Amyloid β (Aβ)-injected rats. Recognition aspect of memory and level of proteins were measured using novel object recognition test and Western blot, respectively. Our data indicated that even though flavone 1 was more effective than flavone 2 to prevent memory impairment, feeding with both flavones alleviated memory in Aβ-injected rats. Furthermore, in flavones-administered rats, mitochondrial dynamic balancing returned to the control level by the decline in Dynamin-related protein-1 protein level, a known marker for mitochondrial fission, and elevation in protein level of mitochondrial fusion factors Mitofusins 1 and 2. In parallel with behavior results, flavone 1 was more effectual on mitochondrial dynamic moderating. The more neuroprotective effects of flavone 1 could be attributed to its methylated structure leading to crossing of the blood-brain barrier with ease and metabolic stability and bioactivity.

Disease chemopreventive effects and molecular mechanisms of hydroxylated polymethoxyflavones

Recent increasing attention in research of polymethoxyflavones (PMFs) from Citrus genus because of their wide range of biological properties has been reported in various studies. Hydroxylated PMFs are unique flavones and recognized as the methoxy group of PMFs that is substituted for hydroxyl one. Hydroxylated PMFs are naturally existed in citrus peel and other plants as well as occurred as metabolites of their PMFs counterparts. Several in vitro and in vivo studies have documented the chemopreventive effects of hydroxylated PMFs including anti-cancer, anti-inflammation, anti-atherosclerosis, and neuroprotection. They function to regulate cell death, proliferation, differentiation, repair, and metabolism through acting on modulation of signaling cascade, gene transcription, and protein function and enzyme activity. The mechanisms of action of hydroxylated PMFs in disease chemoprevention depend on their structure, the number, and position of hydroxyl group. Although the efficacy of hydroxylated PMFs in chemoprevention and the oral bioavailability requires further investigation, they still provide great promise for improving human health. This review highlights the recent published data of hydroxylated PMFs with chemopreventive potential and the underlying mechanism involved.