The impact of curcumin and its modified formulations on Alzheimer's disease

Potential Therapeutic Role of Phytochemicals to Mitigate Mitochondrial Dysfunctions in Alzheimer's Disease

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder characterized by a decline in cognitive function and neuronal damage. Although the precise pathobiology of AD remains elusive, accumulating evidence suggests that mitochondrial dysfunction is one of the underlying causes of AD. Mutations in mitochondrial or nuclear DNA that encode mitochondrial components may cause mitochondrial dysfunction. In particular, the dysfunction of electron transport chain complexes, along with the interactions of mitochondrial pathological proteins are associated with mitochondrial dysfunction in AD. Mitochondrial dysfunction causes an imbalance in the production of reactive oxygen species, leading to oxidative stress (OS) and vice versa. Neuroinflammation is another potential contributory factor that induces mitochondrial dysfunction. Phytochemicals or other natural compounds have the potential to scavenge oxygen free radicals and enhance cellular antioxidant defense systems, thereby protecting against OS-mediated cellular damage. Phytochemicals can also modulate other cellular processes, including autophagy and mitochondrial biogenesis. Therefore, pharmacological intervention via neuroprotective phytochemicals can be a potential strategy to combat mitochondrial dysfunction as well as AD. This review focuses on the role of phytochemicals in mitigating mitochondrial dysfunction in the pathogenesis of AD.

Nano-soldiers Ameliorate Silibinin Delivery: A Review Study

Flavonoids are a large group of naturally occurring compounds, which are of interest due to their great pharmacological effects and health-promoting impacts. These properties have led to their extensive application in a variety of pathological conditions, particularly cancer. Flavonoids are used in large quantities in a human's daily diet and a high amount of flavonoids are found in the intestine after oral usage. However, flavonoid concentrations in tissue/plasma are low because of their low bioavailability, the leading to the low efficacy of flavonoids in different clinical disorders. For this reason, nanotechnology application for delivering flavonoids to tumor sites has recently received significant attention. Silibinin is a key member of flavonoids and a bioactive component of silymarin, which is widely isolated from Silybum marianum. This plant-derived chemical has a number of valuable biological and therapeutic activities such as antioxidant, anti-inflammatory, neuroprotective, anti-tumor, hepatoprotective, cardioprotective and anti-diabetic. These beneficial effects have been demonstrated in in vivo and in vitro experiments. However, it seems that silibinin has a variety of limitations and poor bioavailability is the most important factor restricting its wide application. Hence, there have been attempts to improve the bioavailability of silibinin and it has been suggested that nano-soldiers are potential candidates for this aim. In the present review, we describe the different drug delivery systems for improving the bioavailability of silibinin.

Preparation, optimization and preliminary pharmacokinetic study of curcumin encapsulated turmeric oil microemulsion in zebra fish

The present investigation aimed to develop curcumin loaded turmeric oil microemulsion for brain targeting. An effort has been made to investigate the role of functional components in developing brain targeted formulation which could enhance the bioavailability and uptake of drug in the brain upon oral administration. Preliminary studies like solubility study, emulsification study and construction of the pseudo ternary phase diagram were performed for screening components. The formulation was optimized by using extreme vertices mixture design. The optimized formulation was characterized for appearance, stability to centrifugation, dilution potential, globule size, zeta potential and drug content. Furthermore, ex-vivo permeation in chicken gut sac non everted technique and pharmacokinetic study in adult zebra fishes were carried out. The optimized formulation was found to clear, yellow-colored with the absence of phase separation and precipitation denoted the stability of formulation to centrifugation and dilution. The mean globule size, polydispersity index, zeta potential and drug content was observed as 29.13± 0.12 nm, 0.23 ± 0.01,-12.33 ± 1.37 mV and 99.10±3.91 %, respectively. Ex vivo permeation study revealed 2.41 fold enhancement in the steady-state flux when compared to curcumin solution. Furthermore, optimized formulation showed shorter T_max (5 min) and higher AUC_(0-∞) (7.93 μg/brain*min) compared to the curcumin solution which showed similar T_max and AUC_(0-∞) of 2.78 μg/brain*min after oral administration to zebra fishes revealing 3.97 fold enhancement. The results revealed enhanced ex vivo oral absorption and enhanced in vivo brain pharmacokinetics of curcumin via functional microemulsion in the zebra fish model.

Neuroprotection: Targeting Multiple Pathways by Naturally Occurring Phytochemicals

With the increase in the expectancy of the life span of humans, neurodegenerative diseases (NDs) have imposed a considerable burden on the family, society, and nation. In defiance of the breakthroughs in the knowledge of the pathogenesis and underlying mechanisms of various NDs, very little success has been achieved in developing effective therapies. This review draws a bead on the availability of the nutraceuticals to date for various NDs (Alzheimer's disease, Parkinson's disease, Amyotrophic lateral sclerosis, Huntington's disease, vascular cognitive impairment, Prion disease, Spinocerebellar ataxia, Spinal muscular atrophy, Frontotemporal dementia, and Pick's disease) focusing on their various mechanisms of action in various in vivo and in vitro models of NDs. This review is distinctive in its compilation to critically review preclinical and clinical studies of the maximum phytochemicals in amelioration and prevention of almost all kinds of neurodegenerative diseases and address their possible mechanism of action. PubMed, Embase, and Cochrane Library searches were used for preclinical studies, while ClinicalTrials.gov and PubMed were searched for clinical updates. The results from preclinical studies demonstrate the efficacious effects of the phytochemicals in various NDs while clinical reports showing mixed results with promise for phytochemical use as an adjunct to the conventional treatment in various NDs. These studies together suggest that phytochemicals can significantly act upon different mechanisms of disease such as oxidative stress, inflammation, apoptotic pathways, and gene regulation. However, further clinical studies are needed that should include the appropriate biomarkers of NDs and the effect of phytochemicals on them as well as targeting the appropriate population.

Liposomal Encapsulated Curcumin Effectively Attenuates Neuroinflammatory and Reactive Astrogliosis Reactions in Glia Cells and Organotypic Brain Slices

Introduction

The polyphenolic spice and food coloring ingredient curcumin has beneficial effects in a broad variety of inflammatory diseases. Amongst them, curcumin has been shown to attenuate microglia reaction and prevent from glial scar formation in spinal cord and brain injuries.

Methods

We developed a protocol for the efficient encapsulation of curcumin as a model for anti-inflammatory drugs yielding long-term stable, non-toxic liposomes with favorable physicochemical properties. Subsequently, we evaluate the effects of liposomal curcumin in experimental models for neuroinflammation and reactive astrogliosis.

Results

We could show that liposomal curcumin can efficiently reduce the reactivity of human microglia and astrocytes and preserve tissue integrity of murine organotypic cortex slices.

Discussion and Perspective

In perspective, we want to administer this curcumin formulation in brain implant coatings to prevent neuroinflammation and glial scar formation as foreign body responses of the brain towards implanted materials.

Neuroinflammation in pathogenesis of Alzheimer's disease: Phytochemicals as potential therapeutics

Accumulation of neurotoxic forms of amyloid-β proteins in senile plaques and hyperphosphorylated tau proteins in neurofibrillary tangles is a well-known pathophysiological hallmark of Alzheimer's disease (AD). However, clinical trials with drugs targeting amyloid-β and tau have failed to demonstrate efficacy in treating AD. All currently FDA-approved anti-AD drugs have symptomatic effects only and are not able to cure this disease. This makes necessary to search for alternative therapeutic targets. Accumulating evidence suggests that systemic inflammation and related vascular dysfunction play important etiological roles in AD and precede its clinical manifestation. Therefore, novel therapeutic modalities targeted at these pathophysiological components of AD are intensively developed now. Phytochemicals such as resveratrol, curcumin, quercetin, genistein and catechins are promising anti-AD therapeutics due to their ability to affect major pathogenetic mechanisms of AD, including oxidative stress, neuroinflammation and mitochondrial dysfunction. The implementation of innovative approaches for phytochemical delivery, including the nanotechnology-based ones which enable to significantly enhance their oral bioavailability, would likely provide an opportunity to address many challenges of conventional anti-AD therapies. In this review, roles of inflammation and vascular dysregulation in AD are described and phytobioactive compound-based treatment strategies for AD are discussed.

Exercise Attenuates Brain Aging by Rescuing Down-Regulated Wnt/β-Catenin Signaling in Aged Rats

Down-regulated Wnt signaling is involved in brain aging with declined cognitive capacity due to its modulation on neuronal function and synaptic plasticity. However, the molecular mechanisms are still unclear. In the present study, the naturally aged rat model was established by feeding rats from 6 months old to 21 months old. The cognitive capacity of aged rats was compared with young rats as the controls and the aged rats upon 12-week exercise interventions including treadmill running, resistance exercise, and alternating exercise with resistance exercise and treadmill running. Wnt signaling was examined in hippocampal tissues of the rats from different groups. Results indicated that the expression of Dickkopf-1 (DKK-1) as an antagonist of Wnt signal pathway, the activation of GSK-3β, and the hyperphosphorylated Tau were markedly increased as the extension of age. Meanwhile, higher p-β-catenin^{Ser33, 37, Thr41} promoted neuronal degradation of aged rats. In contrast, three kinds of exercise interventions rescued the abnormal expression of DKK-1 and synaptophysin such as PSD-93 and PSD-95 in hippocampal tissues of the aged rats; especially 12-week treadmill running suppressed DKK-1 up-regulation, GSK-3β activation, β-catenin phosphorylation, and hyperphosphorylated Tau. In addition, the down-regulated PI3K/AKT and Wnt signal pathways were observed in aged rats, but could be reversed by resistance exercise and treadmill running. Moreover, the increased Bax and reduced Bcl-2 levels in hippocampal tissues of aged rats were also reversed upon treadmill running intervention. Taken together, down-regulated Wnt signaling suppressed PI3K/Akt signal pathway, aggravated synaptotoxicity, induced neuron apoptosis, and accelerated cognitive impairment of aged rats. However, exercise interventions, especially treadmill running, can attenuate their brain aging process via restoring Wnt signaling and corresponding targets.

Targeting the Wnt/β-catenin pathway in neurodegenerative diseases: recent approaches and current challenges

INTRODUCTION

Wnt/β-catenin signaling is an evolutionarily conserved pathway having a crucial role in embryonic and adult life. Specifically, the Wnt/β-catenin axis is pivotal to the development and homeostasis of the nervous system, and its dysregulation has been associated with various neurological disorders, including neurodegenerative diseases. Therefore, this signaling pathway has been proposed as a potential therapeutic target against neurodegeneration.

AREAS COVERED

This review focuses on the role of Wnt/β-catenin pathway in the pathogenesis of neurodegenerative diseases, including Parkinson's, Alzheimer's Diseases and Amyotrophic Lateral Sclerosis. The evidence showing that defects in the signaling might be involved in the development of these diseases, and the pharmacological approaches tested so far, are discussed. The possibilities that this pathway offers in terms of new therapeutic opportunities are also considered.

EXPERT OPINION

The increasing interest paid to the role of Wnt/β-catenin pathway in the onset of neurodegenerative diseases demonstrates how targeting this signaling for therapeutic purposes could be a great opportunity for both neuroprotection and neurorepair. Without overlooking some licit concerns about drug safety and delivery to the brain, there is growing and more convincing evidence that restoring this signaling in neurodegenerative diseases may strongly increase the chance to develop disease-modifying treatments for these brain pathologies.

Carbon dots as versatile nanoarchitectures for the treatment of neurological disorders and their theranostic applications: A review

The development of novel methods plays a fundamental role in early diagnosis and controlling of neurological disorders (NDs). Blood-brain barrier (BBB) is the most challenging barrier for the development of neuro drug delivery systems due to its inhibiting ability to enter drugs and agents into central nervous system (CNS). Carbon dots (CDs) have shown to be very promising and outstanding agents for various biomedical applications (bio imaging studies, treatment of NDs and brain tumors). They exhibit remarkable properties such as biocompatibility, small size (less than 10 nm, enabling penetration into BBB), tunable optical properties, photostability and simple synthetic procedures, allowing them to act as ideal candidates in various fields of science. Therefore, the objective of this review is to overview the recent studies on CDs for the development of neuro drug delivery systems to reach CNS via crossing of BBB. Primarily, this review briefly outlines the unique optical properties and toxicity of CDs. The development of novel neuro drug delivery systems for various neurological disorders using CDs as carriers is described. This review also covers the potential applications of CDs in brain tumors imaging and treatment of neurodegenerative diseases. Finally, the sensing applications and future prospects of CDs are summarized.

AR ubiquitination induced by the curcumin analog suppresses growth of temozolomide-resistant glioblastoma through disrupting GPX4-Mediated redox homeostasis

Drug resistance is the main obstacle in the improvement of chemotherapeutic efficacy in glioblastoma. Previously, we showed that dehydroepiandrosterone (DHEA), one kind of androgen/neurosteroid, potentiates glioblastoma to acquire resistance through attenuating DNA damage. Androgen receptor (AR) activated by DHEA or other types of androgen was reported to promote drug resistance in prostate cancer. However, in DHEA-enriched microenvironment, the role of AR in acquiring resistance of glioblastoma remains unknown. In this study, we found that AR expression is significantly correlated with poor prognosis, and AR obviously induced the resistance to temozolomide (TMZ) treatment. Herein, we observed that ALZ003, a curcumin analog, induces FBXL2-mediated AR ubiquitination, leading to degradation. Importantly, ALZ003 significantly inhibited the survival of TMZ-sensitive and -resistant glioblastoma in vitro and in vivo. The accumulation of reactive oxygen species (ROS), lipid peroxidation and suppression of glutathione peroxidase (GPX) 4, which are characteristics of ferroptosis, were observed in glioblastoma cell after treatment of ALZ003. Furthermore, overexpression of AR prevented ferroptosis in the presence of GPX4. To evaluate the therapeutic effect in vivo, we transplanted TMZ-sensitive or -resistant U87MG cells into mouse brain followed by intravenous administration with ALZ003. In addition to inhibiting the growth of glioblastoma, ALZ003 significantly extended the survival period of transplanted mice, and significantly decreased AR expression in the tumor area. Taken together, AR potentiates TMZ resistance for glioblastoma, and ALZ003-mediated AR ubiquitination might open a new insight into therapeutic strategy for TMZ resistant glioblastoma.

Restoring Wnt/β-catenin signaling is a promising therapeutic strategy for Alzheimer's disease

Alzheimer’s disease (AD) is an aging-related neurological disorder characterized by synaptic loss and dementia. Wnt/β-catenin signaling is an essential signal transduction pathway that regulates numerous cellular processes including cell survival. In brain, Wnt/β-catenin signaling is not only crucial for neuronal survival and neurogenesis, but it plays important roles in regulating synaptic plasticity and blood-brain barrier integrity and function. Moreover, activation of Wnt/β-catenin signaling inhibits amyloid-β production and tau protein hyperphosphorylation in the brain. Critically, Wnt/β-catenin signaling is greatly suppressed in AD brain via multiple pathogenic mechanisms. As such, restoring Wnt/β-catenin signaling represents a unique opportunity for the rational design of novel AD therapies.