Potential therapeutic roles of retinoids for prevention of neuroinflammation and neurodegeneration in Alzheimer's disease

Herpotrichone A Exerts Neuroprotective Effects by Relieving Ferroptosis

Inhibition of oxidative stress and ferroptosis is currently considered to be a promising therapeutic approach for neurodegenerative diseases. Herpotrichones, a class of compounds derived from insect symbionts, have shown potential for neuroprotective activity with low toxicity. However, the specific mechanisms through which herpotrichones exert their neuroprotective effects remain to be fully elucidated. In this study, the natural [4 + 2] adducts herpotrichone A (He-A) and its new analogues were isolated from the isopod-associated fungus Herpotrichia sp. SF09 and exhibited significantly protective effects in H2O2-, 6-OHDA-, and RSL3-stimulated PC12 cells and LPS-stimulated BV-2 cells. Moreover, He-A was able to relieve ferroptotic cell death in RSL3-stimulated PC12 cells and 6-OHDA-induced zebrafish larvae. Interestingly, He-A can activate antioxidant elements and modulate the SLC7A11 pathway without capturing oxidic free radical and chelating iron. These findings highlight He-A as a novel hit that protects against ferroptosis-like neuronal damage in the treatment of neurodegenerative diseases.

Impact of micronutrients and nutraceuticals on cognitive function and performance in Alzheimer's disease

Alzheimer's disease (AD) is a major global health problem today and is the most common form of dementia. AD is characterized by the formation of β-amyloid (Aβ) plaques and neurofibrillary clusters, leading to decreased brain acetylcholine levels in the brain. Another mechanism underlying the pathogenesis of AD is the abnormal phosphorylation of tau protein that accumulates at the level of neurofibrillary aggregates, and the areas most affected by this pathological process are usually the cholinergic neurons in cortical, subcortical, and hippocampal areas. These effects result in decreased cognitive function, brain atrophy, and neuronal death. Malnutrition and weight loss are the most frequent manifestations of AD, and these are also associated with greater cognitive decline. Several studies have confirmed that a balanced low-calorie diet and proper nutritional intake may be considered important factors in counteracting or slowing the progression of AD, whereas a high-fat or hypercholesterolemic diet predisposes to an increased risk of developing AD. Especially, fruits, vegetables, antioxidants, vitamins, polyunsaturated fatty acids, and micronutrients supplementation exert positive effects on aging-related changes in the brain due to their antioxidant, anti-inflammatory, and radical scavenging properties. The purpose of this review is to summarize some possible nutritional factors that may contribute to the progression or prevention of AD, understand the role that nutrition plays in the formation of Aβ plaques typical of this neurodegenerative disease, to identify some potential therapeutic strategies that may involve some natural compounds, in delaying the progression of the disease.

Mitochondria-Targeted Oligomeric α-Synuclein Induces TOM40 Degradation and Mitochondrial Dysfunction in Parkinson's Disease and Parkinsonism-Dementia of Guam

Mitochondrial dysfunction is a central aspect of Parkinson's disease (PD) pathology, yet the underlying mechanisms are not fully understood. This study investigates the link between α-Synuclein (α-Syn) pathology and the loss of translocase of the outer mitochondrial membrane 40 (TOM40), unraveling its implications for mitochondrial dysfunctions in neurons. We discovered that TOM40 protein depletion occurs in the brains of patients with Guam Parkinsonism Dementia (Guam PD) and cultured neurons expressing α-Syn proteinopathy, notably, without corresponding changes in TOM40 mRNA levels. Cultured neurons expressing α-Syn mutants, with or without a mitochondria-targeting signal (MTS) underscore the role of α-Syn's mitochondrial localization in inducing TOM40 degradation. Parkinson's Disease related etiological factors, such as 6-hydroxy dopamine or ROS/metal ions stress, which promote α-Syn oligomerization, exacerbate TOM40 depletion in PD patient-derived cells with SNCA gene triplication. Although α-Syn interacts with both TOM40 and TOM20 in the outer mitochondrial membrane, degradation is selective for TOM40, which occurs via the ubiquitin-proteasome system (UPS) pathway. Our comprehensive analyses using Seahorse technology, mitochondrial DNA sequencing, and damage assessments, demonstrate that mutant α-Syn-induced TOM40 loss results in mitochondrial dysfunction, characterized by reduced membrane potential, accumulation of mtDNA damage, deletion/insertion mutations, and altered oxygen consumption rates. Notably, ectopic supplementation of TOM40 or reducing pathological forms of α-Syn using ADP-ribosylation inhibitors ameliorate these mitochondrial defects, suggesting potential therapeutic avenues. In conclusion, our findings provide crucial mechanistic insights into how α-Syn accumulation leads to TOM40 degradation and mitochondrial dysfunction, offering insights for targeted interventions to alleviate mitochondrial defects in PD.

A Combinational Therapy for Preventing and Delaying the Onset of Alzheimer's Disease: A Focus on Probiotic and Vitamin Co-Supplementation

Alzheimer's disease is a progressive neurodegenerative disorder with a complex etiology, and effective interventions to prevent or delay its onset remain a global health challenge. In recent years, there has been growing interest in the potential role of probiotic and vitamin supplementation as complementary strategies for Alzheimer's disease prevention. This review paper explores the current scientific literature on the use of probiotics and vitamins, particularly vitamin A, D, E, K, and B-complex vitamins, in the context of Alzheimer's disease prevention and management. We delve into the mechanisms through which probiotics may modulate gut-brain interactions and neuroinflammation while vitamins play crucial roles in neuronal health and cognitive function. The paper also examines the collective impact of this combinational therapy on reducing the risk factors associated with Alzheimer's disease, such as oxidative stress, inflammation, and gut dysbiosis. By providing a comprehensive overview of the existing evidence and potential mechanisms, this review aims to shed light on the promise of probiotic and vitamin co-supplementation as a multifaceted approach to combat Alzheimer's disease, offering insights into possible avenues for future research and clinical application.

The role and impact of abnormal vitamin levels in autism spectrum disorders

The prevalence of autism spectrum disorder (ASD), a neurodevelopmental disorder with a predominance of social behavioral disorders, has increased dramatically in various countries in recent decades. The interplay between genetic and environmental factors is believed to underlie ASD pathogenesis. Recent analyses have shown that abnormal vitamin levels in early life are associated with an increased risk of autism. As essential substances for growth and development, vitamins have been shown to have significant benefits for the nervous and immune systems. However, it is unknown whether certain vitamin types influence the emergence or manifestation of ASD symptoms. Several studies have focused on vitamin levels in children with autism, and neurotypical children have provided different insights into the types of vitamins and their intake. Here, we review the mechanisms and significance of several vitamins (A, B, C, D, E, and K) that are closely associated with the development of ASD in order to prevent, mitigate, and treat ASD. Efforts have been made to discover and develop new indicators for nutritional assessment of children with ASD to play a greater role in the early detection of ASD and therapeutic remission after diagnosis.

Epigallocatechin-3-Gallate and Genistein for Decreasing Gut Dysbiosis, Inhibiting Inflammasomes, and Aiding Autophagy in Alzheimer's Disease

There are approximately 24 million cases of Alzheimer's disease (AD) worldwide, and the number of cases is expected to increase four-fold by 2050. AD is a neurodegenerative disease that leads to severe dementia in most patients. There are several neuropathological signs of AD, such as deposition of amyloid beta (Aβ) plaques, formation of neurofibrillary tangles (NFTs), neuronal loss, activation of inflammasomes, and declining autophagy. Several of these hallmarks are linked to the gut microbiome. The gastrointestinal (GI) tract contains microbial diversity, which is important in regulating several functions in the brain via the gut-brain axis (GBA). The disruption of the balance in the gut microbiota is known as gut dysbiosis. Recent studies strongly support that targeting gut dysbiosis with selective bioflavonoids is a highly plausible solution to attenuate activation of inflammasomes (contributing to neuroinflammation) and resume autophagy (a cellular mechanism for lysosomal degradation of the damaged components and recycling of building blocks) to stop AD pathogenesis. This review is focused on two bioflavonoids, specifically epigallocatechin-3-gallate (EGCG) and genistein (GS), as a possible new paradigm of treatment for maintaining healthy gut microbiota in AD due to their implications in modulating crucial AD signaling pathways. The combination of EGCG and GS has a higher potential than either agent alone to attenuate the signaling pathways implicated in AD pathogenesis. The effects of EGCG and GS on altering gut microbiota and GBA were also explored, along with conclusions from various delivery methods to increase the bioavailability of these bioflavonoids in the body.

The ameliorative effect of Piper trioicum in attenuating cognitive deficit in scopolamine induced neurotoxicity in experimental rats

ETHNOPHARMACOLOGICAL RELEVANCE

In traditional system of medicine, Piper species, or its components are widely used to treat many diseases including memory improvement. One of the wild species Piper trioicum Roxb. (Piperaceae) is found in South Asian countries. The whole plant is used as folk medicine to improve memory.

AIM OF THE STUDY

To our knowledge, no previous research has investigated the neuroprotective activities of P. trioicum. So, we studied the ameliorative effect of P. trioicum in attenuating cognitive deficit in scopolamine induced neurotoxicity in experimental rats.

MATERIALS AND METHODS

Wistar rats were exposed to scopolamine (3 mg/kg, i. p.) for 14 consecutive days, and the effect of P. trioicum (HAPT; oral, 300, 400 mg/kg) on scopolamine-invoked neurotoxicity in brain were studied. During the experimental period, behaviour analyses of rats were observed 30 min post-drug administration. The role of antioxidants of HAPT in scavenging cellular oxygen/peroxyl radicals were studied. Acetylcholinesterase and butyrylcholinesterase inhibitions, and mode of inhibition kinetics of HAPT were studied. Pathogenic cellular oxidative (MDA, GSH, SOD, and CAT), DNA damage (8-oxodG), neurochemical (acetyl- and, butyryl-cholinesterase), β-secretase (BACE-1 and 2), MAPτ, and neuroinflammation (IL-6, TNF-α) biomarkers in extension to the histopathological observation of brain cortex were studied. GC-MS/MS analysis was carried out to investigate the presence of bioactive constituents in HAPT.

RESULTS

HAPT, a rich source of phenol and flavonoid type antioxidants were responsible in quenching oxygen/peroxyl radicals and protected the cellular membrane, and lipoproteins against ROS in DPPH, ORAC, and CAPe tests. HAPT inhibited acetylcholinesterase and butyrylcholinesterase activities, and showed competitive-inhibition (reversible) towards cholinesterase activities. HAPT-400 significantly improved the learning and memory-impairment by restoring oxidative MDA, GSH, SOD, CAT, and DNA damage (8-oxodG) markers of serum, and cortex. It also improved acetyl- and, butyryl-cholinesterase, β-secretase, and MAPτ level in brain by restoring proinflammatory cytokines IL-6, and TNF-α indicators in neurotoxic rats. GC-MS/MS reported therapeutic significance active compounds were molecular-docked towards target proteins, found that proscillaridin showed the highest affinity towards AChE, BuChE, BACE1, and BACE2 with binding energy of ΔGb -9.1, ΔGb -10.2, ΔGb -11.4 and ΔGb -11.5 Kcal/mol, respectively. Cymarin and morphine-3-glucuronide showed the second highest binding affinity towards AChE (ΔGb -8.8) and BuChE (ΔGb -10.0), respectively. In BACE-1, betulin showed the second highest binding affinity ΔGb -10.7 Kcal/mol and in BACE-2, morphine-3-glucuronide showed the second highest binding affinity ΔGb -9.8 Kcal/mol.

CONCLUSIONS

Synergistic impact of proscillaridin, Cymarin, morphine-3-glucuronide, betulin like compounds in HAPT improved memory impairment, healing of tissue architecture of cortex with the restoration of neurochemical, neuroinflammation, and oxidative indicators in neurotoxic rats.

9-cis beta-carotene-enriched diet significantly improved cognition and decreased Alzheimer's disease neuropathology and neuroinflammation in Alzheimer's disease-like mouse models

A significant progressive decline in beta-carotene (βC) levels in the brain is associated with cognitive impairment and a higher prevalence of Alzheimer's disease (AD). In this study, we investigated whether the administration of 9-cis beta-carotene (9CBC)-rich powder of the alga Dunaliella bardawil, the best-known source of βC in nature, inhibits the development of AD-like neuropathology and cognitive deficits. We demonstrated that in 3 AD mouse models, Tg2576, 5xFAD, and apoE4, 9CBC treatment improved long- and short-term memory, decreased neuroinflammation, and reduced the prevalence of β-amyloid plaques and tau hyperphosphorylation. These findings suggest that 9CBC has the potential to be an effective preventive and symptomatic AD therapy.

Nutritional Factors: Benefits in Glaucoma and Ophthalmologic Pathologies

Glaucoma is a chronic optic neuropathy that can lead to irreversible functional and morphological damage if left untreated. The gold standard therapeutic approaches in managing patients with glaucoma and limiting progression include local drops, laser, and/or surgery, which are all geared at reducing intraocular pressure (IOP). Nutrients, antioxidants, vitamins, organic compounds, and micronutrients have been gaining increasing interest in the past decade as integrative IOP-independent strategies to delay or halt glaucomatous retinal ganglion cell degeneration. In our minireview, we examine the various nutrients and compounds proposed in the current literature for the management of ophthalmology diseases, especially for glaucoma. With respect to each substance considered, this minireview reports the molecular and biological characteristics, neuroprotective activities, antioxidant properties, beneficial mechanisms, and clinical studies published in the past decade in the field of general medicine. This study highlights the potential benefits of these substances in glaucoma and other ophthalmologic pathologies. Nutritional supplementation can thus be useful as integrative IOP-independent strategies in the management of glaucoma and in other ophthalmologic pathologies. Large multicenter clinical trials based on functional and morphologic data collected over long follow-up periods in patients with IOP-independent treatments can pave the way for alternative and/or coadjutant therapeutic options in the management of glaucoma and other ocular pathologies.

Retinoic acid administration normalizes aberrant microglial activation via regulating TREM2 transcription in the PFC of valproic acid induced autism rat

Autism spectrum disorder (ASD) is a complex neurodevelopmental disease with an unclear underlying pathogenesis. Disruption of retinoic acid (RA)-retinoic acid receptor α (RARα) signaling and aberrant microglial activation were reported to be involved in the pathogenesis of ASD. However, the effect of RA-RARα signaling on microglial activation in ASD and the underlying mechanisms are unknown. Herein, we found inhibited RA-RARα signaling and increased microglial activation in valproic acid (VPA)-induced autism rats. Furthermore, we administered RA to VPA rats and found that RA ameliorated autism-like behaviors, inhibited microglial activation and normalized microglial polarization in VPA rats. Additionally, the expression levels of RARα and triggering receptor expressed on myeloid cells 2 (TREM2) were increased in the prefrontal cortex (PFC) of VPA rats given RA. Chromatin immunoprecipitation (ChIP) and dual luciferase reporter assays confirmed that RARα can regulate the transcriptional activity of the TREM2 gene by binding to its promoter. We conclude that RA administration ameliorates autism-like behaviors in VPA rats by inhibiting microglial activation and normalizing microglial polarization through the regulation of TREM2 transcription by RARα.

Common Genetic Factors and Pathways in Alzheimer's Disease and Ischemic Stroke: Evidences from GWAS

Alzheimer's disease (AD) and ischemic stroke (IS) are common neurological disorders, and the comorbidity of these two brain diseases is often seen. Although AD and IS were regarded as two distinct disease entities, in terms of different etiologies and clinical presentation, recent genome-wide association studies (GWASs) revealed that there were common risk genes between AD and IS, indicating common molecular pathways and their common pathophysiology. In this review, we summarize AD and IS risk single nucleotide polymorphisms (SNPs) and their representative genes from the GWAS Catalog database, and find thirteen common risk genes, but no common risk SNPs. Furthermore, the common molecular pathways associated with these risk gene products are summarized from the GeneCards database and clustered into inflammation and immunity, G protein-coupled receptor, and signal transduction. At least seven of these thirteen genes can be regulated by 23 microRNAs identified from the TargetScan database. Taken together, the imbalance of these molecular pathways may give rise to these two common brain disorders. This review sheds light on the pathogenesis of comorbidity of AD and IS, and provides molecular targets for disease prevention, manipulation, and brain health maintenance.

Effect of vitamin A on recovery from the acute phase of multiple sclerosis-related optic neuritis, double-blind, randomized, placebo-controlled trial

Background

Optic neuritis (ON) is one of the main neuro-ophthalmic presentations of multiple sclerosis (MS), and it causes optic nerve atrophy and axonal loss. However, so far, there is no effective treatment to improve long-term outcomes.

Methods

In a double-blind placebo-controlled randomized clinical trial, 50 patients with MS-related ON were allocated into two arms (24 in the control group and 26 in the intervention group) receiving either 25000IU retinyl palmitate or an identical placebo for six months. Visual evoked potential (VEP), visual acuity, and the retinal nerve fiber layer (RNFL) thickness were evaluated and compared before and after the treatment.

Results

RNFL thickness reduction in the affected eyes at sixth month compared to the baseline were 14.81 and 19.46 μm, in the intervention and control groups, respectively (P=0.017). However, VitA therapy did not affect visual acuity and VEP.

Conclusion

Vitamin A supplementation in the patients with acute ON in MS could lessen optic nerve axonal loss.

Bidirectional communication between brain and visceral white adipose tissue: Its potential impact on Alzheimer's disease

A variety of axes between brain and abdominal organs have been reported, but the interaction between brain and visceral white adipose tissue (vWAT) remains unclear. In this review, we summarized human studies on the association between brain and vWAT, and generalized their interaction and the underlying mechanisms according to animal and cell experiments. On that basis, we come up with the concept of the brain-vWAT axis (BVA). Furthermore, we analyzed the potential mechanisms of involvement of BVA in the pathogenesis of Alzheimer's disease (AD), including vWAT-derived fatty acids, immunological properties of vWAT, vWAT-derived retinoic acid and vWAT-regulated insulin resistance. The proposal of BVA may expand our understanding to some extent of how the vWAT impacts on brain health and diseases, and provide a novel approach to study the pathogenesis and treatment strategies of neurodegenerative disorders.

Identification of changed proteins by retinoic acid in cerebral ischemic damage: a proteomic study

Ischemic stroke is a severe neurodegenerative disease with a high mortality rate. Retinoic acid is a representative metabolite of vitamin A. It has many beneficial effects including anti-inflammatory, anti-apoptotic, and neuroprotective effects. The purpose of this study is to identify specific proteins that are regulated by retinoic acid in ischemic stroke. Middle cerebral artery occlusion (MCAO) was performed to induce focal cerebral ischemia. Retinoic acid (5 mg/kg) or vehicle was injected intraperitoneally into male rats for four days prior to MCAO operation. Neurobehavioral tests were performed 24 hr after MCAO and the cerebral cortex was collected for proteomic study. Retinoic acid alleviates neurobehavioral deficits and histopathological changes caused by MCAO. Furthermore, we identified various proteins that were altered by retinoic acid in MCAO damage. Among these identified proteins, adenosylhomocysteinase, isocitrate dehydrogenase [NAD+] subunit α, glycerol-3-phosphate dehydrogenase, Rab GDP dissociation inhibitor β, and apolipoprotein A1 were down-regulated in MCAO animals with vehicle treatment, whereas retinoic acid treatment alleviated these reductions. However, heat shock protein 60 was up-regulated in MCAO animals with vehicle, while retinoic acid treatment attenuated this increase. The changes in these expressions were confirmed by reverse transcription-PCR. These proteins regulate cell metabolism and mediate stress responses. Our results demonstrated that retinoic acid attenuates the neuronal damage by MCAO and regulates the various protein expressions that are involved in the survival of cells. Thus, we can suggest that retinoic acid exerts neuroprotective effects on focal cerebral ischemia by modulation of specific proteins.

Therapeutic insights elaborating the potential of retinoids in Alzheimer’s disease

Alzheimer’s disease (AD) is perceived with various pathophysiological characteristics such oxidative stress, senile plaques, neuroinflammation, altered neurotransmission immunological changes, neurodegenerative pathways, and age-linked alterations. A great deal of studies even now are carried out for comprehensive understanding of pathological processes of AD, though many agents are in clinical trials for the treatment of AD. Retinoids and retinoic acid receptors (RARs) are pertinent to such attributes of the disease. Retinoids support the proper functioning of the immunological pathways, and are very potent immunomodulators. The nervous system relies heavily on retinoic acid signaling. The disruption of retinoid signaling relates to several pathogenic mechanisms in the normal brain. Retinoids play critical functions in the neuronal organization, differentiation, and axonal growth in the normal functioning of the brain. Disturbed retinoic acid signaling causes inflammatory responses, mitochondrial impairment, oxidative stress, and neurodegeneration, leading to Alzheimer’s disease (AD) progression. Retinoids interfere with the production and release of neuroinflammatory chemokines and cytokines which are located to be activated in the pathogenesis of AD. Also, stimulating nuclear retinoid receptors reduces amyloid aggregation, lowers neurodegeneration, and thus restricts Alzheimer’s disease progression in preclinical studies. We outlined the physiology of retinoids in this review, focusing on their possible neuroprotective actions, which will aid in elucidating the critical function of such receptors in AD pathogenesis.

Genetic association between epigenetic aging-acceleration and the progression of mild cognitive impairment to Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder and previous studies have showed its association with accelerated aging. In this study, we hypothesized that SNPs that contributed to aging acceleration are also associated with the progression from mild cognitive impairment (MCI) to AD. By applying genetic correlation analysis and single-locus survival analysis, we investigated the associations between intrinsic- and extrinsic-epigenetic-age-acceleration (IEAA and EEAA) related SNPs and the progression time from mild cognitive impairment (MCI) to AD dementia using the data of 767 MCI participants from the ADNI study and 1373 MCI patients from the NACC study. Genetic correlations were found between IEAA/EEAA and AD (positive for IEAA-AD and negative for EEAA-AD). We revealed that 70 IEAA and 81 EEAA SNPs had associations with the progression time from MCI to AD with Bayesian false-discovery probability (BFDP) ≤ 0.8 in the ADNI study, with 22 IEAA SNPs and 16 EEAA SNPs being replicated in the NACC study (P < 0.05). Polygenic risk score (PRS) analysis showed that EEAA PRS but not IEAA PRS was associated with AD progression and the trend of decreasing Fusiform gyrus volume in two datasets. Risk models incorporating both EAA PRSs did not show any significant improvement in predictive accuracy. Our results identified multiple genetic variants with pleiotropic effects on both EAA and AD, which suggested shared genetic architecture between epigenetic age acceleration and AD progression.

Retinoic Acid Signaling Is Compromised in DSS-Induced Dysbiosis

Obesity and malnutrition both cause dysbiosis and dampen retinoic acid (RA) signaling pathways, which play pivotal roles in biological processes. The current study evaluates a hypothesis that colitis-associated dysbiosis also has systemic negative impacts on RA signaling. Thus, we studied the effects of inflammation, under a vitamin A-sufficient condition, on RA signaling using mouse colitis models induced by dextran sulfate sodium. That data showed that intestinal inflammation resulted in reduced RA signaling in the liver, brain, gut, and adipose tissues measured by analyzing the expression of genes encoding for the synthesis, oxidation, transport, and receptor of RA. The expression of RA-regulated gut homing molecules including α4β7 integrin, and CCR9, along with MADCAM1 were all reduced in colitis mice revealing compromised immunity due to reduced RA signaling. The data also showed that the development of colitis was accompanied by dysbiosis featured with reduced Lactobacillaceae and Verrucomicrobiaceae but an expansion of Erysipelotrichaceae and others. Colitis resulted in reduced butyrate-producing bacteria and increased methane-generating bacteria. Additionally, dysbiosis was associated with induced Il-1β, Ifn-γ, and Tnf-α mRNA but reduced Il-22, Il-17f, and Rorγt transcripts in the colon. Together, intestinal inflammation inhibits RA signaling in multiple organs. RA is essential in regulating various biological processes, it is critical to detect RA signaling reduction in tissues even when vitamin A deficiency is absent. Moreover, probiotics can potentially prevent dysbiosis and reverse compromised RA signaling, having systemic health benefits.

Fenretinide in Cancer and Neurological Disease: A Two-Face Janus Molecule

Recently, several chemotherapeutic drugs have been repositioned in neurological diseases, based on common biological backgrounds and the inverse comorbidity between cancer and neurodegenerative diseases. Fenretinide (all-trans-N-(4-hydroxyphenyl) retinamide, 4-HPR) is a synthetic derivative of all-trans-retinoic acid initially proposed in anticancer therapy for its antitumor effects combined with limited toxicity. Subsequently, fenretinide has been proposed for other diseases, for which it was not intentionally designed for, due to its ability to influence different biological pathways, providing a broad spectrum of pharmacological effects. Here, we review the most relevant preclinical and clinical findings from fenretinide and discuss its therapeutic role towards cancer and neurological diseases, highlighting the hormetic behavior of this pleiotropic molecule.

Retinoic acid regulates the ubiquitin-proteasome system in a middle cerebral artery occlusion animal model

Background

Retinoic acid is a major metabolite of vitamin A and exerts beneficial effects including anti-oxidant and anti-inflammatory activities in neurons. The ubiquitin–proteasome system is an important biological system that regulates cell survival. Ubiquitination regulates protein degradation and plays an important role in oxidative stress. Deubiquitinating enzymes cleave ubiquitin from proteins and control ubiquitination-induced degradation. We detected decreases in ubiquitin carboxy-terminal hydrolase L1, ubiquitin thioesterase OTUB1, and proteasome subunit alpha types 1 and 3 in cerebral ischemic damage. In this study, we investigated whether retinoic acid regulates the expression of deubiquitinating enzymes ubiquitin carboxy-terminal hydrolase L1, ubiquitin thioesterase OTUB1, and proteasome subunit alpha types 1 and 3 in cerebral ischemic injury. Right middle cerebral artery occlusion (MCAO) was performed to induce cerebral ischemic damage in male rats. Retinoic acid (5 mg/kg) or vehicle was intraperitoneally injected every day from 4 days before surgery. Neurological behavioral tests were performed 24 h after MCAO, and right cerebral cortical tissues were collected.

Results

MCAO damage caused neurological behavioral dysfunction, and retinoic acid alleviated these deficits. The identified proteins decreased in MCAO animals with vehicle, while retinoic acid treatment attenuated these decreases. The results of proteomic study were confirmed by a reverse transcription-PCR technique. Expressions of ubiquitin carboxy-terminal hydrolase L1, ubiquitin thioesterase OTUB1, and proteasome subunit alpha types 1 and 3 were decreased in MCAO animals treated with vehicle. Retinoic acid treatment alleviated these MCAO-induced reductions. The ubiquitin–proteasome system plays an essential role in maintaining cell function and preserving cell shape against ischemic damage.

Conclusions

These findings suggest that retinoic acid regulates ubiquitin- and proteasome-related proteins including ubiquitin carboxy-terminal hydrolase L1, ubiquitin thioesterase OTUB1, and proteasome subunit alpha types 1 and 3 in a brain ischemia model. Changes in these proteins are involved in the neuroprotective effects of retinoic acid.

Revisiting APP secretases: an overview on the holistic effects of retinoic acid receptor stimulation in APP processing

Alzheimer's disease (AD) is the leading cause of dementia worldwide and is characterized by the accumulation of the β-amyloid peptide (Aβ) in the brain, along with profound alterations in phosphorylation-related events and regulatory pathways. The production of the neurotoxic Aβ peptide via amyloid precursor protein (APP) proteolysis is a crucial step in AD development. APP is highly expressed in the brain and is complexly metabolized by a series of sequential secretases, commonly denoted the α-, β-, and γ-cleavages. The toxicity of resulting fragments is a direct consequence of the first cleaving event. β-secretase (BACE1) induces amyloidogenic cleavages, while α-secretases (ADAM10 and ADAM17) result in less pathological peptides. Hence this first cleavage event is a prime therapeutic target for preventing or reverting initial biochemical events involved in AD. The subsequent cleavage by γ-secretase has a reduced impact on Aβ formation but affects the peptides' aggregating capacity. An array of therapeutic strategies are being explored, among them targeting Retinoic Acid (RA) signalling, which has long been associated with neuronal health. Additionally, several studies have described altered RA levels in AD patients, reinforcing RA Receptor (RAR) signalling as a promising therapeutic strategy. In this review we provide a holistic approach focussing on the effects of isoform-specific RAR modulation with respect to APP secretases and discuss its advantages and drawbacks in subcellular AD related events.

Systems Analysis Reveals Ageing-Related Perturbations in Retinoids and Sex Hormones in Alzheimer's and Parkinson's Diseases

Neurodegenerative diseases, including Alzheimer's (AD) and Parkinson's diseases (PD), are complex heterogeneous diseases with highly variable patient responses to treatment. Due to the growing evidence for ageing-related clinical and pathological commonalities between AD and PD, these diseases have recently been studied in tandem. In this study, we analysed transcriptomic data from AD and PD patients, and stratified these patients into three subclasses with distinct gene expression and metabolic profiles. Through integrating transcriptomic data with a genome-scale metabolic model and validating our findings by network exploration and co-analysis using a zebrafish ageing model, we identified retinoids as a key ageing-related feature in all subclasses of AD and PD. We also demonstrated that the dysregulation of androgen metabolism by three different independent mechanisms is a source of heterogeneity in AD and PD. Taken together, our work highlights the need for stratification of AD/PD patients and development of personalised and precision medicine approaches based on the detailed characterisation of these subclasses.

The Role of Vitamins in Neurodegenerative Disease: An Update

Acquiring the recommended daily allowance of vitamins is crucial for maintaining homeostatic balance in humans and other animals. A deficiency in or dysregulation of vitamins adversely affects the neuronal metabolism, which may lead to neurodegenerative diseases. In this article, we discuss how novel vitamin-based approaches aid in attenuating abnormal neuronal functioning in neurodegeneration-based brain diseases such as Alzheimer's disease, Parkinson's disease, Huntington's disease, Amyotrophic lateral sclerosis, and Prion disease. Vitamins show their therapeutic activity in Parkinson's disease by antioxidative and anti-inflammatory activity. In addition, different water- and lipid-soluble vitamins have also prevented amyloid beta and tau pathology. On the other hand, some results also show no correlation between vitamin action and the prevention of neurodegenerative diseases. Some vitamins also exhibit toxic activity too. This review discusses both the beneficial and null effects of vitamin supplementation for neurological disorders. The detailed mechanism of action of both water- and lipid-soluble vitamins is addressed in the manuscript. Hormesis is also an essential factor that is very helpful to determine the effective dose of vitamins. PubMed, Google Scholar, Web of Science, and Scopus were employed to conduct the literature search of original articles, review articles, and meta-analyses.

Biological Significance of the Protein Changes Occurring in the Cerebrospinal Fluid of Alzheimer's Disease Patients: Getting Clues from Proteomic Studies

The fact that cerebrospinal fluid (CSF) deeply irrigates the brain together with the relative simplicity of sample extraction from patients make this biological fluid the best target for biomarker discovery in neurodegenerative diseases. During the last decade, biomarker discovery has been especially fruitful for the identification new proteins that appear in the CSF of Alzheimer's disease (AD) patients together with amyloid-β (Aβ42), total tau (T-tau), and phosphorylated tau (P-tau). Thus, several proteins have been already stablished as important biomarkers, due to an increase (i.e., CHI3L1) or a decrease (i.e., VGF) in AD patients' CSF. Notwithstanding this, only a deep analysis of a database generated with all the changes observed in CSF across multiple proteomic studies, and especially those using state-of-the-art methodologies, may expose those components or metabolic pathways disrupted at different levels in AD. Deep comparative analysis of all the up- and down-regulated proteins across these studies revealed that 66% of the most consistent protein changes in CSF correspond to intracellular proteins. Interestingly, processes such as those associated to glucose metabolism or RXR signaling appeared inversely represented in CSF from AD patients in a significant manner. Herein, we discuss whether certain cellular processes constitute accurate indicators of AD progression by examining CSF. Furthermore, we uncover new CSF AD markers, such as ITAM, PTPRZ or CXL16, identified by this study.

Medicinal herbs and nutritional supplements for dementia therapy: potential therapeutic targets and clinical evidence

Spices and herbs have been used for medicinal purposes for centuries. Also, in the last decades, the use of different nutritional supplements has been implemented to treat all kinds of diseases, including those that present an alteration in cognitive functioning. Dementia is a clinical syndrome in which a person's mental and cognitive capacities gradually decline. As the disease progresses, the person's autonomy diminishes. As there is not an effective treatment to prevent progressive deterioration in many of these pathologies, nutritional interventions have been, and still are, one of the most widely explored therapeutic possibilities. In this review, we have discussed a great number of potentially interesting plants, nutritional derivatives and probiotics for the treatment of dementia around the world. Their action mechanisms generally involve neuroprotective effects via anti-inflammatory, antioxidant, anti-apoptotic, b-amyloid and tau anti-aggregate actions; brain blood flow improvement, and effects on synaptic cholinergic and dopaminergic neurotransmission, which may optimize cognitive performance in patients with cognitive impairment. As for their efficacy in patients with cognitive impairment and/or dementias, evidence is still scarce and/or their outcomes are controversial. We consider that many of these substances have promising therapeutic properties. Therefore, the scientific community has to continue with a more complete research focused on both identifying possible action mechanisms and carrying out clinical trials, preferably randomized double-blind ones, with a greater number of patients, a long-term follow-up, dose standardization and the use of current diagnosis criteria.

Accurate characterization of β-amyloid (Aβ40, Aβ42) standards using species-specific isotope dilution by means of HPLC-ICP-MS/MS

The amyloid β peptide, as one of the main components in senile plaque, represents a defining pathological feature for Alzheimer’s disease, and is therefore commonly used as a biomarker for this disease in clinical analysis. However, the selection of suitable standards is limited here, since only a few are commercially available, and these suffer from varying purity. Hence, the accurate characterization of these standards is of great importance. In this study, we developed a method for the traceable quantification of the peptide content using species-specific isotope dilution and ICP-MS/MS detection. It is based on the separation of the sulfur-containing amino acids methionine and cysteine after oxidation and hydrolysis of the peptide. Using a strong anion exchange column, both amino acids could be separated from each other, as well as from their oxidized forms and sulfate. The sulfur content was determined via ICP-MS/MS using oxygen as reaction gas. Species-specific isotope dilution was enabled by using a ³⁴S-labeled yeast hydrolysate, containing methionine sulfone and cysteic acid with different isotopic composition. The peptide contents of Aβ standards (Aβ40,42), as well as myoglobin and lysozyme with different degrees of purity, were determined. For validation purposes, the standard reference material NIST 2389a, which contains the amino acids in a similar concentration, was subjected to the developed sample preparation and analysis method. In addition to accounting for errors during sample preparation, high levels of accuracy and precision could be obtained using this method, making it fit-for-purpose for the characterization of peptide standards.

Linking Oxidative Stress and Proteinopathy in Alzheimer's Disease

Proteinopathy and excessive production of reactive oxygen species (ROS), which are the principal features observed in the Alzheimer’s disease (AD) brain, contribute to neuronal toxicity. β-amyloid and tau are the primary proteins responsible for the proteinopathy (amyloidopathy and tauopathy, respectively) in AD, which depends on ROS production; these aggregates can also generate ROS. These mechanisms work in concert and reinforce each other to drive the pathology observed in the aging brain, which primarily involves oxidative stress (OS). This, in turn, triggers neurodegeneration due to the subsequent loss of synapses and neurons. Understanding these interactions may thus aid in the identification of potential neuroprotective therapies that could be clinically useful. Here, we review the role of β-amyloid and tau in the activation of ROS production. We then further discuss how free radicals can influence structural changes in key toxic intermediates and describe the putative mechanisms by which OS and oligomers cause neuronal death.

Shotgun lipidomics of liver and brain tissue of Alzheimer's disease model mice treated with acitretin

Alzheimer’s disease (AD) is a very frequent neurodegenerative disorder characterized by an accumulation of amyloid-β (Aβ). Acitretin, a retinoid-derivative and approved treatment for Psoriasis vulgaris, increases non-amyloidogenic Amyloid-Precursor-Protein-(APP)-processing, prevents Aβ-production and elicits cognitive improvement in AD mouse models. As an unintended side effect, acitretin could result in hyperlipidemia. Here, we analyzed the impact of acitretin on the lipidome in brain and liver tissue in the 5xFAD mouse-model. In line with literature, triglycerides were increased in liver accompanied by increased PCaa, plasmalogens and acyl-carnitines, whereas SM-species were decreased. In brain, these effects were partially enhanced or similar but also inverted. While for SM and plasmalogens similar effects were found, PCaa, TAG and acyl-carnitines showed an inverse effect in both tissues. Our findings emphasize, that potential pharmaceuticals to treat AD should be carefully monitored with respect to lipid-homeostasis because APP-processing itself modulates lipid-metabolism and medication might result in further and unexpected changes. Moreover, deducing effects of brain lipid-homeostasis from results obtained for other tissues should be considered cautiously. With respect to acitretin, the increase in brain plasmalogens might display a further positive probability in AD-treatment, while other results, such as decreased SM, indicate the need of medical surveillance for treated patients.

Targeting autophagy in neurodegenerative diseases: From molecular mechanisms to clinical therapeutics

Many neurodegenerative diseases are associated with pathological aggregation of proteins in neurons. Autophagy is a natural self-cannibalization process that can act as a powerful mechanism to remove aged and damaged organelles as well as protein aggregates. It has been shown that promoting autophagy can attenuate or delay neurodegeneration by removing protein aggregates. In this paper, we will review the role of autophagy in Alzheimer's disease (AD), Parkinson's Disease (PD), and Huntington's Disease (HD) and discuss opportunities and challenges of targeting autophagy as a potential therapeutic avenue for treatment of these common neurodegenerative diseases.

Retinoic acid exerts neuroprotective effects against focal cerebral ischemia by preventing apoptotic cell death

Cerebral ischemia is a neurological disorder that leads to cognitive decline and high mortality. Retinoic acid is a metabolite of vitamin A that has anti-inflammatory and anti-apoptotic effects. This study investigated whether retinoic acid prevents neuronal cell damage on focal cerebral ischemia through modulating apoptosis signaling pathway. Middle cerebral artery occlusion (MCAO) was performed to induce focal cerebral ischemia in adult male rats. Retinoic acid (5 mg/kg) or vehicle was injected intraperitoneally for 4 days prior to MCAO. Neurological behavior deficit tests were performed 24 h after MCAO. Brain edema and infarct volume were measured, and TUNEL histochemistry was carried out. We also investigated the changes in apoptosis-related proteins including bcl-2 family proteins and caspases. MCAO injury induced severe neurological behavior deficits and brain edema. It also increased infarct volume, histopathological damages, and the number of TUNEL-positive cells in cerebral cortex. However, retinoic acid pretreatment attenuated MCAO-induced neurological behavior deficits, brain edema, and infarction. It also alleviated histopathological lesion and decreased the number of TUNEL-positive cells. Bcl-2 and bax proteins are representative bcl-2 family proteins. MCAO injury induced a decrease in bcl-2 expression and an increase in bax expression, and retinoic acid pretreatment alleviated these changes. MCAO injury caused a decrease in bcl-2/bax expression ratio in cerebral cortex, while retinoic acid restored this decrease by MCAO. Moreover, our result showed increases in caspase-9, caspase-3, PARP protein levels in MCAO-operated animals. Retinoic acid pretreatment prevented these increases. We identified the changes in cleaved forms of these proteins, similar to the changes in full-length protein. Activation of caspases and PARP proteins are considered to be representative apoptosis indicators. This study showed that retinoic acid regulates bcl-2 family proteins and caspase proteins in focal cerebral ischemia. Thus, our findings demonstrate that retinoic acid exhibits a neuroprotective effect against ischemic damage by modulating apoptosis signaling pathway.

Serum retinol levels are associated with cognitive function among community-dwelling older Mexican adults

BACKGROUND

Vitamin A (VA) provides neuroprotection against oxidative stress and brain inflammation. VA deficiency (VAD) increases the risk of neurodegeneration in animal models, but results are inconclusive in humans: particularly in the older adult (OA) population which is at higher risk for micronutrient deficiencies and cognitive impairment.

OBJECTIVE

To estimate the association between serum retinol levels and cognitive function (CF) in older Mexican adults.

METHODS

Cross-sectional study with 803 adults aged ≥60 years with fasting blood sample from the southern region of Mexico, collected in summer of 2015. Low serum retinol (LSR) was defined if serum retinol ≤20 µg/dl. CF was evaluated using Semantic Verbal Fluency Test (SVFT). Mild cognitive impairment (MCI) was defined using normative values for SVFT. Linear and logistic regression models were used to estimate the association of LSR with CF and MCI, respectively.

RESULTS

Prevalence of MCI was 9.35% and LSR 3.36%. OA with LSR evoked less words in the SVFT (β = -2.8, CI95% -4.6, -0.9) and had higher probability of MCI (OR =  2.7, CI95% 0.9, 7.7). Associations remained significant when considered IL-6.

CONCLUSION

Frequency of LSR in older Mexican adults was low, but strongly associated with MCI. This result suggests that VA plays a role in maintaining CF in the elderly population. Since VAD is a reversible condition, further studies are needed in order to identify the main causes of LSR and prevent MCI in populations which are at higher risk for malnutrition.Trial registration: ClinicalTrials.gov identifier: NCT04820465.

Biofortified orange corn increases xanthophyll density and yolk pigmentation in egg yolks from laying hens

Plant breeding has developed corn genotypes with grain higher in levels of carotenoids. Dietary consumption of specific carotenoids by humans has been associated with improved eye health, notably with some protection against age-related macular degeneration. Increasing dietary sources of macular carotenoids in the standard American diet might be accomplished by using high carotenoid Orange Corn in poultry diets to increase macular carotenoid concentrations in egg yolks. Three hundred sixty laying hens (Novogen White) were fed three different diets over 31 days. Each diet had six replicates of 20 hens housed in enrichable colony cages. The only difference was the type of corn included - white, yellow, and orange, in order to assess the impact of each type of corn on egg production, yolk pigmentation, and carotenoid deposition. This study assessed yolk color and carotenoid densities using a portable colorimeter and the DSM YolkFan, and by high performance liquid chromatography (HPLC) on eggs from the feeding study and on 43 cartons of 12 eggs commercially available and produced in various production settings: conventional cage, cage-free, cage-free organic, free-range/pasture, and free-range/pasture organic. Yolks from hens fed with the Orange Corn diet produced eggs with higher (P < 0.01) DSM yolk color (6 to 10) and total xanthophylls (23.5 to 35.3 μg/g of egg yolk) compared to the yellow diet (5 to 6 DSM and 12.3 to 17.7 μg/g xanthophylls) and white diet (1 to 2 DSM and 2.5 to 3.0 μg/g xanthophylls). Egg yolks reached a maximum xanthophyll accumulation with the Orange Corn diet (35.3 μg/g of egg yolk) after twelve days of treatment and maintained steady levels at subsequent time points. In general, xanthophyll levels in yolks from the Orange Corn diet were superior (30–61% higher) to any of the commercial egg brands, suggesting that feeding high carotenoid Orange Corn increases xanthophyll density in eggs.

Pouteria sapota (Red Mamey Fruit): Chemistry and Biological Activity of Carotenoids

BACKGROUND

Red mamey fruit known as P. sapota, comes from trees found in Mesoamerica and Asia. This fruit is considered a nutraceutical food due to it's a food and has multiple beneficial health including anti-amyloidogenic activity and potential anti-tumorigenic property. Red mamey fruit contain a variety of carotenoids including novel ketocarotenoids such as sapotexanthin and cryptocapsin. A ketocarotenoid is a chemical compound with a carbonyl group present in the β-ring or in the double bond chain of a carotenoid. In red mamey, the 3'-deoxy-k-end group in sapotexanthin has proved to be an important pro-vitamin A source, which is essential for maintaining a healthy vision and cognitive processes.

OBJECTIVE

Summarize the chemistry and biological activity of the studied carotenoids present in this fruit until now.

METHOD

An exhaustive extraction is the most usual methodology to isolate and thoroughly characterize the carotenoids present in this fruit. High performance liquid chromatography is used to determine the profile of total carotenoid and its purity. Atmospheric pressure chemical ionization is used to determine the molecular weight of carotenoid. Nuclear magnetic resonance is used to determine the structure of carotenoids.

RESULT

For each 100 g of fresh weight, 0.12 mg of total carotenoid from this fruit can be obtained. Out of the more than 47 reported carotenoids in red mamey, only 34 have a detailed characterization.

CONCLUSION

it is important to continue studying the chemical composition and biological activity of this unique tropical fruit with commercial and nutritional value.

The link between nutrition and Alzheimer's disease: from prevention to treatment

Alzheimer's disease (AD) is the most common cause of dementia. To date, there is no effective pharmacological strategy to slow or stop disease progression. In this context, multiple alternative therapeutic strategies have been investigated for AD. This review addresses the potential role of nutrition interventions in AD prevention and treatment. Nutritional strategies for AD have been based on four pillars: maintaining a healthy weight (i.e., prevention and/or treatment of obesity, especially in midlife and prevention of weight loss in the later stages of AD); correction of nutritional deficiencies; adequate consumption of micronutrients (vitamins and minerals), especially those implicated in the pathways of AD pathophysiology; and microbiota modulation.

Distinctive Microbial Signatures and Gut-Brain Crosstalk in Pediatric Patients with Coeliac Disease and Type 1 Diabetes Mellitus

Coeliac disease (CD) and Type 1 diabetes mellitus (T1DM) are immune-mediated diseases. Emerging evidence suggests that dysbiosis in the gut microbiome plays a role in the pathogenesis of both diseases and may also be associated with the development of neuropathy. The primary goal in this cross-sectional pilot study was to identify whether there are distinct gut microbiota alterations in children with CD (n = 19), T1DM (n = 18) and both CD and T1DM (n = 9) compared to healthy controls (n = 12). Our second goal was to explore the relationship between neuropathy (corneal nerve fiber damage) and the gut microbiome composition. Microbiota composition was determined by 16S rRNA gene sequencing. Corneal confocal microscopy was used to determine nerve fiber damage. There was a significant difference in the overall microbial diversity between the four groups with healthy controls having a greater microbial diversity as compared to the patients. The abundance of pathogenic proteobacteria Shigella and E. coli were significantly higher in CD patients. Differential abundance analysis showed that several bacterial amplicon sequence variants (ASVs) distinguished CD from T1DM. The tissue transglutaminase antibody correlated significantly with a decrease in gut microbial diversity. Furthermore, the Bacteroidetes phylum, specifically the genus Parabacteroides was significantly correlated with corneal nerve fiber loss in the subjects with neuropathic damage belonging to the diseased groups. We conclude that disease-specific gut microbial features traceable down to the ASV level distinguish children with CD from T1DM and specific gut microbial signatures may be associated with small fiber neuropathy. Further research on the mechanisms linking altered microbial diversity with neuropathy are warranted.

Recent advances in the design of RAR α and RAR β agonists as orally bioavailable drugs. A review

Retinoic acid receptors (RARs) α, β, and γ are members of the nuclear receptor superfamily. Compounds which bind to and activate the RARs are termed retinoids which regulate a wide variety of biological processes such as vertebrate embryonic morphogenesis and organogenesis, cell growth arrest, differentiation, and apoptosis, as well as their disorders. Although many synthetic selective RARα, RARβ, and RARγ agonists have been designed and prepared, these have generally been lipophilic acids without good drug-like properties and with low oral bioavailability. Recently this has been changing and drug design approaches to highly potent and selective RARα and RARβ agonists with low lipophilicity that are orally bioavailable and less toxic have been developed, that have a range of potential therapeutic uses. This review covers these new advances.

Decoding the role of zebrafish neuroglia in CNS disease modeling

Neuroglia, including microglia and astrocytes, is a critical component of the central nervous system (CNS) that interacts with neurons to modulate brain activity, development, metabolism and signaling pathways. Thus, a better understanding of the role of neuroglia in the brain is critical. Complementing clinical and rodent data, the zebrafish (Danio rerio) is rapidly becoming an important model organism to probe the role of neuroglia in brain disorders. With high genetic and physiological similarity to humans and rodents, zebrafish possess some common (shared), as well as some specific molecular biomarkers and features of neuroglia development and functioning. Studying these common and zebrafish-specific aspects of neuroglia may generate important insights into key brain mechanisms, including neurodevelopmental, neurodegenerative, neuroregenerative and neurological processes. Here, we discuss the biology of neuroglia in humans, rodents and fish, its role in various CNS functions, and further directions of translational research into the role of neuroglia in CNS disorders using zebrafish models.

Protective role of anticancer drugs in neurodegenerative disorders: A drug repurposing approach

The disease heterogeneity and little therapeutic progress in neurodegenerative diseases justify the need for novel and effective drug discovery approaches. Drug repurposing is an emerging approach that reinvigorates the classical drug discovery method by divulging new therapeutic uses of existing drugs. The common biological background and inverse tuning between cancer and neurodegeneration give weight to the conceptualization of repurposing of anticancer drugs as novel therapeutics. Many studies are available in the literature, which highlights the success story of anticancer drugs as repurposed therapeutics. Among them, kinase inhibitors, developed for various oncology indications evinced notable neuroprotective effects in neurodegenerative diseases. In this review, we shed light on the salient role of multiple protein kinases in neurodegenerative disorders. We also proposed a feasible explanation of the action of kinase inhibitors in neurodegenerative disorders with more attention towards neurodegenerative disorders. The problem of neurotoxicity associated with some anticancer drugs is also highlighted. Our review encourages further research to better encode the hidden potential of anticancer drugs with the aim of developing prospective repurposed drugs with no toxicity for neurodegenerative disorders.

FGF21 attenuates neurodegeneration through modulating neuroinflammation and oxidant-stress

Previous studies indicate that FGF21 has ability to repair nerve injury, but the specific mechanism is less studied. The present study was designed to investigate the effects of FGF21 on neurodegeneration changes in aging and diabetic mice and its mechanism. The diabetic and aging mice were used to study the effects of FGF21 on neurodegeneration and possible mechanisms. These mice were administrated with PBS, FGF21 or metformin once daily for 4 or 6 months, then the mechanism was studied in SH-SY5Y cells. The relevant gene expression for neurodegeneration was assessed by Quantitative Real Time-PCR, Western blot, H&E staining, immunohistochemistry and ELISA. The Western blot results of NeuN showed that FGF21 inhibited the loss of neurons in diabetic and aging mice. H&E staining results showed that the karyopyknosis and tissue edema around dentate gyrus and Cornu Amonis 3 (CA3) area of hippocampus were also inhibited by FGF21 in aging and diabetes mice. In vivo results revealed that administration of FGF21 suppressed the aggregation of tau and β-amyloid_1-42 in the brains of diabetic and aging mice. The aggregation resulted in apoptosis of neurons. Meanwhile, FGF21 significantly reduced the expression of Iba1, NF-κB, IL6 and IL8 (p < 0.05) and enhanced anti-oxidant enzymes (p < 0.05) in aging and diabetic mice. In addition, the phosphorylation of AKT and AMPKα were increased by FGF21 treatment. In vitro experiment showed that the aggregation of tau and β-amyloid_1-42 wereincreased by LPS in SH-SY5Y cells, and FGF21 inhibited the aggregation through inhibiting the expression of NF-κB and promoting the phosphorylation of AKT and AMPKα. In conclusion, FGF21 attenuates neurodegeneration by reducing neuroinflammation and oxidant stress through regulating the NF-κB pathway and AMPKα/AKT pathway, which enhances the protective effect on mitochondria in neurons.

Genetic ablation of bone marrow beta-adrenergic receptors in mice modulates miRNA-transcriptome networks of neuroinflammation in the paraventricular nucleus

Elucidating molecular pathways regulating neuroimmune communication is critical for therapeutic interventions in conditions characterized by overactive immune responses and dysfunctional autonomic nervous system. We generated a bone marrow-specific adrenergic beta 1 and beta 2 knockout mouse chimera (AdrB1.B2 KO) to determine how sympathetic drive to the bone affects transcripts and miRNAs in the hypothalamic paraventricular nucleus (PVN). This model has previously exhibited a dampened systemic immune response and decreased blood pressure compared with control animals. Reduced sympathetic responsiveness of the bone marrow hematopoietic cells of AdrB1.B2 KO chimera led to suppression of transcriptional networks that included leukocyte cell adhesion and migration and T cell-activation and recruitment. Transcriptome responses related to IL-17a signaling and the renin-angiotensin system were also suppressed in the PVN. Based on the transcriptome response, we next computationally predicted miRNAs in the PVN that may underscore the reduced sympathetic responsiveness of the bone marrow cells. These included miR-27b-3p, miR-150, miR-223-3p, and miR-326. Using real-time PCR, we measured a downregulation in the expression of miR-150-5p, miR-205-5p, miR-223-3p, miR-375-5p, miR-499a-5p, miR-27b-3p, let-7a-5p, and miR-21a-5p in the PVN of AdrB1.B2 KO chimera, confirming computational predictions that these miRNAs are associated with reduced neuro-immune responses and the loss of sympathetic responsiveness in the bone marrow. Intriguingly, directional responses of the miRNA corresponded to mRNAs, suggesting complex temporal or circuit-dependent posttranscriptional control of gene expression in the PVN. This study identifies molecular pathways involved in neural-immune interactions that may act as targets of therapeutic intervention for a dysfunctional autonomic nervous system.

Stability of motor endplates is greater in the biceps than in the interossei in a rat model of obstetric brachial plexus palsy

The time window for repair of the lower trunk is shorter than that of the upper trunk in patients with obstetric brachial plexus palsy. The denervated intrinsic muscles of the hand become irreversibly atrophic much faster than the denervated biceps. However, it is unclear whether the motor endplates of the denervated interosseous muscles degenerate more rapidly than those of the denervated biceps. In this study, we used a rat model of obstetric brachial plexus palsy of the right upper limb. C5–6 was lacerated distal to the intervertebral foramina, with concurrent avulsion of C7–8 and T1, with the left upper limb used as the control. Bilateral interossei and biceps were collected at 5 and 7 weeks. Immunofluorescence was used to assess the morphology of the motor endplates. Real-time quantitative polymerase chain reaction and western blot assay were used to assess mRNA and protein expression levels of acetylcholine receptor subunits (α, β and δ), rapsyn and β-catenin. Immunofluorescence microscopy showed that motor endplates in the denervated interossei were fragmented, while those in the denervated biceps were morphologically intact with little fragmentation. The number and area of motor endplates, relative to the control side, were significantly lower in the denervated interossei compared with the denervated biceps. mRNA and protein expression levels of acetylcholine receptor subunits (α, β and δ) were significantly lower, whereas β-catenin protein expression was higher, in the denervated interossei compared with the denervated biceps. The protein expression of rapsyn was higher in the denervated biceps than in the denervated interossei at 7 weeks. Our findings demonstrate that motor endplates of interossei are destabilized, whereas those of the biceps remain stable, in the rat model of obstetric brachial plexus palsy. All procedures were approved by the Experimental Animal Ethics Committee of Fudan University, China (approval No. DF-187) in January 2016.

Low and High Molecular Weight FGF-2 Have Differential Effects on Astrocyte Proliferation, but Are Both Protective Against Aβ-Induced Cytotoxicity

Astrocytes are the most abundant type of glial cells in the brain, and they play a key role in Alzheimer’s disease (AD). Fibroblast Growth Factor-2 (FGF-2) has been implicated as a potential therapeutic agent for treating AD. In the present study, we investigated the protective effects of low molecular weight (LMW; 17 KDa) and high molecular weight (HMW; 23 KDa) forms of FGF-2 on Aβ_1–42-induced toxicity, and proliferation in astrocytes. We show that both isoforms of FGF-2 have similar protective effects against Aβ_1–42-induced cytotoxicity in primary cultured cortical astrocytes as measured by Lactate Dehydrogenase (LDH) release assay. Additionally, 17 KDa FGF-2 significantly promoted astrocyte proliferation as measured by Trypan Blue, DRAQ5 and 5-ethynyl-2’-deoxyuridine (EdU) staining, but not 23 kDa FGF-2. Furthermore, our results demonstrated that AKT signaling pathway was required for the protective and proliferative effects of FGF-2. Downstream effector studies indicated that 17 kDa FGF-2 promoted astrocyte proliferation by enhanced expression of c-Myc, Cyclin D1, Cyclin E. Furthermore, our data suggested that Cyclin D1 was required for the proliferative effect of LMW FGF2 in astrocytes. Taken together, our findings provide important information for the similarities and differences between 23 kDa and17 kDa isoforms of FGF-2 on astrocyte survival and proliferation.

Jidong cognitive impairment cohort study: objectives, design, and baseline screening

The risk of dementia increases in patients with cognitive impairment. However, it is not clear what factors contribute to the onset of dementia in those with cognitive impairment. In this prospective cohort study, we will investigate the every-five-year incidence of cognitive impairment and prognostic factors for cognitive impairment. The Jidong cognitive impairment cohort was established from April 2012 to August 2015, during which we recruited 5854 healthy participants (55.1% male) older than 45 years (mean, 57 years). Participants received a health examination in the Staff Hospital, Jidong Oilfield Branch, China National Petroleum Corporation. Baseline data and blood samples were collected. Cognitive impairment was evaluated using the Mini-Mental State Examination, and was defined as a Mini-Mental State Examination score of less than 24. Dementia was assessed using the criteria of Diagnostic and Statistical Manual of Mental Disorders (Fourth edition), the International Working Group criteria, and the Mini-Mental State Examination score. The follow-up will continue until December 2024, during which a prognostic model will be constructed. The primary outcome is the presence/absence of dementia and the secondary outcome is quality of life. Baseline screening results showed the following: (1) Cognitive impairment was apparent in 320 participants (5.5%). These participants will be excluded from the Jidong cohort study, and the remaining participants will be followed up. (2) Of the 320 participants with cognitive impairment, there was a significantly higher prevalence of illiteracy than other education levels (35.9%, P < 0.05). Age, arterial hypertension, alcohol consumption, and passive smoking differed significantly between the cognitive impairment and healthy groups (P < 0.05). Multivariate logistic regression models showed that age (odds ratio [OR] = 1.059, 95% confidence interval [CI]: 1.044–1.074) and arterial hypertension (OR = 1.665, 95% CI: 1.143–2.427) were risk factors for mild cognitive impairment. With the increase of educational level (illiteracy, primary school, junior high school, high school, university, and above), cognitive impairment gradually decreased (OR < 1, P < 0.05). (3) This cohort study has initially screened for several risk factors for cognitive impairment at baseline, and subsequent prospective data will further describe, validate, and evaluate the effects of these risk factors on cognitive impairment and dementia. These results can provide clinical evidence for the early prevention of cognitive impairment and dementia. The study was approved by the Ethics Committee of Kailuan General Hospital of Tangshan City and the Medical Ethics Committee, Staff Hospital, Jidong Oilfield Branch, China National Petroleum Corporation on July 12, 2013 (approval No. 2013 YILUNZI 1).

Role of miR-124 in the regulation of retinoic acid-induced Neuro-2A cell differentiation

Retinoic acid can cause many types of cells, including mouse neuroblastoma Neuro-2A cells, to differentiate into neurons. However, it is still unknown whether microRNAs (miRNAs) play a role in this neuronal differentiation. To address this issue, real-time polymerase chain reaction assays were used to detect the expression of several differentiation-related miRNAs during the differentiation of retinoic acid-treated Neuro-2A cells. The results revealed that miR-124 and miR-9 were upregulated, while miR-125b was downregulated in retinoic acid-treated Neuro-2A cells. To identify the miRNA that may play a key role, miR-124 expression was regulated by transfection of miRNA mimics or inhibitors. Morphological analysis results showed that inhibition of miR-124 expression reversed the effects of retinoic acid on neurite outgrowth. Moreover, miR-124 overexpression alone caused Neuro-2A cells to differentiate into neurons, and its inhibitor could block this effect. These results suggest that miR-124 plays an important role in retinoic acid-induced differentiation of Neuro-2A cells.

Decay in Retinoic Acid Signaling in Varied Models of Alzheimer's Disease and In-Vitro Test of Novel Retinoic Acid Receptor Ligands (RAR-Ms) to Regulate Protective Genes

Retinoic acid has been previously proposed in the treatment of Alzheimer's disease (AD). Here, five transgenic mouse models expressing AD and frontotemporal dementia risk genes (i.e., PLB2APP, PLB2TAU, PLB1Double, PLB1Triple, and PLB4) were used to investigate if consistent alterations exist in multiple elements of the retinoic acid signaling pathway in these models. Many steps of the retinoic acid signaling pathway including binding proteins and metabolic enzymes decline, while the previously reported increase in RBP4 was only consistent at late (6 months) but not early (3 month) ages. The retinoic acid receptors were exceptional in their consistent decline in mRNA and protein with transcript decline of retinoic acid receptors β and γ by 3 months, before significant pathology, suggesting involvement in early stages of disease. Decline in RBP1 transcript may also be an early but not late marker of disease. The decline in the retinoic acid signaling system may therefore be a therapeutic target for AD and frontotemporal dementia. Thus, novel stable retinoic acid receptor modulators (RAR-Ms) activating multiple genomic and non-genomic pathways were probed for therapeutic control of gene expression in rat primary hippocampal and cortical cultures. RAR-Ms promoted the non-amyloidogenic pathway, repressed lipopolysaccharide induced inflammatory genes and induced genes with neurotrophic action. RAR-Ms had diverse effects on gene expression allowing particular RAR-Ms to be selected for maximal therapeutic effect. Overall the results demonstrated the early decline of retinoic acid signaling in AD and frontotemporal dementia models and the activity of stable and potent alternatives to retinoic acid as potential therapeutics.

20S proteasome and glyoxalase 1 activities decrease in erythrocytes derived from Alzheimer's disease patients

As a result of accumulating methylglyoxal and advanced glycation end products in the brains of patients with Alzheimer's disease, it is considered a protein precipitation disease. The ubiquitin proteasome system is one of the most important mechanisms for cells to degrade proteins, and thus is very important for maintaining normal physiological function of the nervous system. This study recruited 48 individuals with Alzheimer's disease (20 males and 28 females aged 75 ± 6 years) and 50 healthy volunteers (21 males and 29 females aged 72 ± 7 years) from the Affiliated Hospital of Youjiang Medical University for Nationalities (Baise, China) between 2014 and 2017. Plasma levels of malondialdehyde and H₂O₂ were measured by colorimetry, while glyoxalase 1 activity was detected by spectrophotometry. In addition, 20S proteasome activity in erythrocytes was measured with a fluorescent substrate method. Ubiquitin and glyoxalase 1 protein expression in erythrocyte membranes was detected by western blot assay. The results demonstrated that compared with the control group, patients with Alzheimer's disease exhibited increased plasma malondialdehyde and H₂O₂ levels, and decreased glyoxalase 1 activity; however, expression level of glyoxalase 1 protein remained unchanged. Moreover, activity of the 20S proteasome was decreased and expression of ubiquitin protein was increased in erythrocytes. These findings indicate that proteasomal and glyoxalase activities may be involved in the occurrence of Alzheimer's disease, and erythrocytes may be a suitable tissue for Alzheimer's disease studies. This study was approved by the Ethics Committee of Youjiang Medical University for Nationalities (approval No. YJ12017013) on May 3, 2017.