Abstract
Several nutraceuticals have been investigated for preventing or retarding the progression of different neurodegenerative diseases, including Alzheimer's disease (AD). Because Nigella sativa (NS) and its isolated compound thymoquinone (TQ) have significant anti-oxidant and anti-inflammatory proprieties, they could represent effective neuroprotective agents. The purpose of this manuscript is to analyze and to recapitulate the results of in vitro and in vivo studies on the potential role of NS/TQ in AD's prevention and treatment. The level of evidence for each included animal study has been assessed by using a modified CAMARADES (Collaborative Approach to Meta-Analysis and Review of Animal Data from Experimental Studies) 10-item checklist. We used MEDLINE and EMBASE databases to screen relevant articles published up to July 2017. A manual search was also performed. The database search yielded 38 studies, of which 18 were included in this manuscript. Results from these approaches suggest that NS or TQ could represent an effective strategy against AD due to the balancing of oxidative processes and the binding to specific intracellular targets. The overall effects mainly regard the prevention of hippocampal pyramidal cell loss and the increased cognitive functions.
Highlights
The knowledge of the exact pathophysiological mechanisms remains an unresolved issue, an emerging evidence underlines the role of the oxidative damage and microglia-mediated neuro-inflammatory responses in the initiation of neurodegenerative disorders including Alzheimer’s disease (AD) (Mosher and Wyss-Coray, 2014)
Experimental findings demonstrated that in AD pathogenesis, the 4.2-kD amyloid β peptide (Aβ)-dependent microglial activation leads to neuronal injury through a complex cascade by involving the secretion of various pro-inflammatory molecules such as tumor necrosis factor-α (TNF-α), interleukin (IL) IL-6, IL-1β, reactive oxygen species (ROS), and reactive nitrogen species (NOS) (Agostinho et al, 2010)
We divided the available studies into two categories: in vitro studies: an overview on the molecular mechanism underlying the anti-Alzheimer effects of Nigella sativa (NS) or TQ, and Pre-clinical in vivo studies on the preventive effects of NS or TQ on AD
Summary
The knowledge of the exact pathophysiological mechanisms remains an unresolved issue, an emerging evidence underlines the role of the oxidative damage and microglia-mediated neuro-inflammatory responses in the initiation of neurodegenerative disorders including Alzheimer’s disease (AD) (Mosher and Wyss-Coray, 2014). In addition to the clinical investigations most experimental studies have been conducted in vitro or in animal models of AD to test natural compounds with antioxidants proprieties such as epigallocatechin gallate (EGCG) (Cascella et al, 2017a), quercetin (Schültke et al, 2003), kaempferol (Lei et al, 2012), resveratrol (Zhao et al, 2015) as potential protective factors to neurodegeneration induced by oxidative stress (Mecocci et al, 2014; Essa et al, 2016; De Domenico and Giudetti, 2017). Other researchers focused the studies on their anticancer activities (Kundu et al, 2014) as well as on their potential role in the prevention and/or treatment of toxic effects of anticancer drugs (e.g., chemotherapy-induced nephrotoxicity) (Cascella et al, 2017b). The two reviewers agreed on 95% of the selected article and reached consensus on all included studies through collective discussions with a third reviewer (M.R.M.)
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