Microdose Lithium NP03 Diminishes Pre-Plaque Oxidative Damage and Neuroinflammation in a Rat Model of Alzheimer’s-like Amyloidosis

Lithium and disease modification: A systematic review and meta-analysis in Alzheimer's and Parkinson's disease

The role of lithium as a possible therapeutic strategy for neurodegenerative diseases has generated scientific interest. We systematically reviewed and meta-analyzed pre-clinical and clinical studies that evidenced the neuroprotective effects of lithium in Alzheimer's (AD) and Parkinson's disease (PD). We followed the PRISMA guidelines and performed the systematic literature search using PubMed, EMBASE, Web of Science, and Cochrane Library. A total of 32 articles were identified. Twenty-nine studies were performed in animal models and 3 studies were performed on human samples of AD. A total of 17 preclinical studies were included in the meta-analysis. Our analysis showed that lithium treatment has neuroprotective effects in diseases. Lithium treatment reduced amyloid-β and tau levels and significantly improved cognitive behavior in animal models of AD. Lithium increased the tyrosine hydroxylase levels and improved motor behavior in the PD model. Despite fewer clinical studies on these aspects, we evidenced the positive effects of lithium in AD patients. This study lends further support to the idea of lithium's therapeutic potential in neurodegenerative diseases.

Oxidative damage in neurodegeneration: roles in the pathogenesis and progression of Alzheimer disease

Alzheimer disease (AD) is associated with multiple etiologies and pathological mechanisms, among which oxidative stress (OS) appears as a major determinant. Intriguingly, OS arises in various pathways regulating brain functions, and it seems to link different hypotheses and mechanisms of AD neuropathology with high fidelity. The brain is particularly vulnerable to oxidative damage, mainly because of its unique lipid composition, resulting in an amplified cascade of redox reactions that target several cellular components/functions ultimately leading to neurodegeneration. The present review highlights the "OS hypothesis of AD," including amyloid beta-peptide-associated mechanisms, the role of lipid and protein oxidation unraveled by redox proteomics, and the antioxidant strategies that have been investigated to modulate the progression of AD. Collected studies from our groups and others have contributed to unraveling the close relationships between perturbation of redox homeostasis in the brain and AD neuropathology by elucidating redox-regulated events potentially involved in both the pathogenesis and progression of AD. However, the complexity of AD pathological mechanisms requires an in-depth understanding of several major intracellular pathways affecting redox homeostasis and relevant for brain functions. This understanding is crucial to developing pharmacological strategies targeting OS-mediated toxicity that may potentially contribute to slow AD progression as well as improve the quality of life of persons with this severe dementing disorder.

The Effect of Fat Intake with Increased Omega-6-to-Omega-3 Polyunsaturated Fatty Acid Ratio in Animal Models of Early and Late Alzheimer's Disease-like Pathogenesis

This work aims to clarify the effect of dietary polyunsaturated fatty acid (PUFA) intake on the adult brain affected by amyloid pathology. McGill-R-Thy1-APP transgenic (Tg) rat and 5xFAD Tg mouse models that represent earlier or later disease stages were employed. The animals were exposed to a control diet (CD) or an HFD based on corn oil, from young (rats) or adult (mice) ages for 24 or 10 weeks, respectively. In rats and mice, the HFD impaired reference memory in wild-type (WT) animals but did not worsen it in Tg, did not cause obesity, and did not increase triglycerides or glucose levels. Conversely, the HFD promoted stronger microglial activation in Tg vs. WT rats but had no effect on cerebral amyloid deposition. IFN-γ, IL-1β, and IL-6 plasma levels were increased in Tg rats, regardless of diet, while CXCL1 chemokine levels were increased in HFD-fed mice, regardless of genotype. Hippocampal 3-nitrotyrosine levels tended to increase in HFD-fed Tg rats but not in mice. Overall, an HFD with an elevated omega-6-to-omega-3 ratio as compared to the CD (25:1 vs. 8.4:1) did not aggravate the outcome of AD regardless of the stage of amyloid pathology, suggesting that many neurobiological processes relevant to AD are not directly dependent on PUFA intake.

Botanical Mixture Containing Nitric Oxide Metabolite Enhances Neural Plasticity to Improve Cognitive Impairment in a Vascular Dementia Rat Model

Vascular dementia (VD), caused by impaired cerebral blood flow, is the most common form of dementia after Alzheimer's disease (AD) in the elderly and is characterized by severe neuronal damage and cognitive decline. Nitric oxide (NO) is an important determinant of vascular homeostasis, and its deficiency is associated with the progression of VD. In this study, we investigated the role of nitrite ion, a NO metabolite in a botanical mixture (BM) of fermented garlic, fermented Scutellaria baicalensis, and Rhodiola rosea on neuron loss and cognitive impairment using a VD rat model. The BM containing the NO metabolite alleviated cognitive deficits and enhanced neural plasticity, as reflected by an increase in long-term potentiation. The BM also alleviated neuron apoptosis, decreased GFAP expression, and oxidative stress, and increased parvalbumin and brain-derived neurotrophic factor (BDNF) levels. These results indicate that BM exerts neuroprotective effects and alleviates cognitive dysfunction while enhancing neuroplasticity, and thus has therapeutic potential against VD.

Oxidative Stress in Brain in Amnestic Mild Cognitive Impairment

Amnestic mild cognitive impairment (MCI), arguably the earliest clinical stage of Alzheimer disease (AD), is characterized by normal activities of daily living but with memory issues but no dementia. Oxidative stress, with consequent damaged key proteins and lipids, are prominent even in this early state of AD. This review article outlines oxidative stress in MCI and how this can account for neuronal loss and potential therapeutic strategies to slow progression to AD.

Drug Discovery and Development Targeting Dementia

Dementia, most often associated with neurodegenerative diseases, affects millions of people worldwide, predominantly the elderly. Unfortunately, no treatment is still available. Therefore, there is an urgent need to address this situation. This review presents the state of the art of drug discovery and developments in targeting dementia. Several approaches are discussed, such as drug repurposing, the use of small molecules, and phosphodiesterase inhibitors. Furthermore, the review also provides insights into clinical trials of these molecules. Emphasis has been placed on small molecules and multi-target-directed ligands, as well as disease-modifying therapies. Finally, attention is drawn to the possibilities of applications of nanotechnology in managing dementia.

Nicotinamide as potential biomarker for Alzheimer's disease: A translational study based on metabolomics

Introduction: The metabolic routes altered in Alzheimer's disease (AD) brain are poorly understood. As the metabolic pathways are evolutionarily conserved, the metabolic profiles carried out in animal models of AD could be directly translated into human studies. Methods: We performed untargeted Nuclear Magnetic Resonance metabolomics in hippocampus of McGill-R-Thy1-APP transgenic (Tg) rats, a model of AD-like cerebral amyloidosis and the translational potential of these findings was assessed by targeted Gas Chromatography-Electron Impact-Mass Spectrometry in plasma of participants in the German longitudinal cohort AgeCoDe. Results: In rat hippocampus 26 metabolites were identified. Of these 26 metabolites, nine showed differences between rat genotypes that were nominally significant. Two of them presented partial least square-discriminant analysis (PLS-DA) loadings with the larger absolute weights and the highest Variable Importance in Projection (VIP) scores and were specifically assigned to nicotinamide adenine dinucleotide (NAD) and nicotinamide (Nam). NAD levels were significantly decreased in Tg rat brains as compared to controls. In agreement with these results, plasma of AD patients showed significantly reduced levels of Nam in respect to cognitively normal participants. In addition, high plasma levels of Nam showed a 27% risk reduction of progressing to AD dementia within the following 2.5 years, this hazard ratio is lost afterwards. Discussion: To our knowledge, this is the first report showing that a decrease of Nam plasma levels is observed couple of years before conversion to AD, thereby suggesting its potential use as biomarker for AD progression.

Lithium, a Treatment Option for Alzheimer's Disease? A Review of Existing Evidence and Discussion on Future Perspectives

After over 50 years of use, lithium-salts remain the first-line therapy for the management of bipolar disorder. Throughout this period, the potential for lithium salts has been extensively studied and numerous data favor its use in the treatment of neurodegenerative disorders such as Alzheimer's disease (AD). We reviewed existing evidence gathered from clinical case reports and studies on the effect of lithium on neuropsychological symptoms of AD and as a disease-modifying treatment acting on cognitive symptoms. The review summarizes the molecular pathways, involving GSK-3β inhibition and neuroprotection, through which lithium is proposed to exert its effect. Limitations to its current use in AD are discussed and future perspectives as a potential treatment option for AD are considered in regard to ongoing clinical trials using different forms of lithium.

Role of Intracellular Amyloid β as Pathway Modulator, Biomarker, and Therapy Target

The β- and γ-secretase-driven cleavage of the amyloid precursor protein (APP) gives rise to the amyloid β peptide, which is believed to be the main driver of neurodegeneration in Alzheimer’s disease (AD). As it is prominently detectable in extracellular plaques in post-mortem AD brain samples, research in recent decades focused on the pathological role of extracellular amyloid β aggregation, widely neglecting the potential meaning of very early generation of amyloid β inside the cell. In the last few years, the importance of intracellular amyloid β (iAβ) as a strong player in neurodegeneration has been indicated by a rising number of studies. In this review, iAβ is highlighted as a crucial APP cleavage fragment, able to manipulate intracellular pathways and foster neurodegeneration. We demonstrate its relevance as a pathological marker and shed light on initial studies aiming to modulate iAβ through pharmacological treatment, which has been shown to have beneficial effects on cognitive properties in animal models. Finally, we display the relevance of viral infections on iAβ generation and point out future directions urgently needed to manifest the potential relevance of iAβ in Alzheimer’s disease.

A review on α-mangostin as a potential multi-target-directed ligand for Alzheimer's disease

Alzheimer's disease (AD) is an age-related neurodegenerative disease characterized by progressive memory loss, declining language skills and other cognitive disorders. AD has brought great mental and economic burden to patients, families and society. However due to the complexity of AD's pathology, drugs developed for the treatment of AD often fail in clinical or experimental trials. The main problems of current anti-AD drugs are low efficacy due to mono-target method or side effects, especially high hepatotoxicity. To tackle these two main problems, multi-target-directed ligand (MTDL) based on "one molecule, multiple targets" has been studied. MTDLs can regulate multiple biological targets at the same time, so it has shown higher efficacy, better safety. As a natural active small molecule, α-mangostin (α-M) has shown potential multi-factor anti-AD activities in a series of studies, furthermore it also has a certain hepatoprotective effect. The good availability of α-M also provides support for its application in clinical research. In this work, multiple activities of α-M related to AD therapy were reviewed, which included anti-cholinesterase, anti-amyloid-cascade, anti-inflammation, anti-oxidative stress, low toxicity, hepatoprotective effects and drug formulation. It shows that α-M is a promising candidate for the treatment of AD.

Connecting the "Dots": From Free Radical Lipid Autoxidation to Cell Pathology and Disease

Our understanding of lipid peroxidation in biology and medicine is rapidly evolving, as it is increasingly implicated in various diseases but also recognized as a key part of normal cell function, signaling, and death (ferroptosis). Not surprisingly, the root and consequences of lipid peroxidation have garnered increasing attention from multiple disciplines in recent years. Here we "connect the dots" between the fundamental chemistry underpinning the cascade reactions of lipid peroxidation (enzymatic or free radical), the reactive nature of the products formed (lipid-derived electrophiles), and the biological targets and mechanisms associated with these products that culminate in cellular responses. We additionally bring light to the use of highly sensitive, fluorescence-based methodologies. Stemming from the foundational concepts in chemistry and biology, these methodologies enable visualizing and quantifying each reaction in the cascade in a cellular and ultimately tissue context, toward deciphering the connections between the chemistry and physiology of lipid peroxidation. The review offers a platform in which the chemistry and biomedical research communities can access a comprehensive summary of fundamental concepts regarding lipid peroxidation, experimental tools for the study of such processes, as well as the recent discoveries by leading investigators with an emphasis on significant open questions.

NP03, a Microdose Lithium Formulation, Blunts Early Amyloid Post-Plaque Neuropathology in McGill-R-Thy1-APP Alzheimer-Like Transgenic Rats

Epidemiological, preclinical, and clinical studies have suggested a role for microdose lithium in reducing Alzheimer's disease (AD) risk by modulating key mechanisms associated with AD pathology. The novel microdose lithium formulation, NP03, has disease-modifying effects in the McGill-R-Thy1-APP transgenic rat model of AD-like amyloidosis at pre-plaque stages, before frank amyloid-β (Aβ) plaque deposition, during which Aβ is primarily intraneuronal. Here, we are interested in determining whether the positive effects of microdose lithium extend into early Aβ post-plaque stages. We administered NP03 (40μg Li/kg; 1 ml/kg body weight) to McGill-R-Thy1-APP transgenic rats for 12 weeks spanning the transition phase from plaque-free to plaque-bearing. The effect of NP03 on remote working memory was assessed using the novel object recognition task. Levels of human Aβ38, Aβ40, and Aβ42 as well as levels of pro-inflammatory mediators were measured in brain-extracts and plasma using electrochemiluminescent assays. Mature Aβ plaques were visualized with a thioflavin-S staining. Vesicular acetylcholine transporter (VAChT) bouton density and levels of chemokine (C-X-C motif) ligand 1 (CXCL1), interleukin-6 (IL-6), and 4-hydroxynonenal (4-HNE) were probed using quantitative immunohistochemistry. During the early Aβ post-plaque stage, we find that NP03 rescues functional deficits in object recognition, reduces loss of cholinergic boutons in the hippocampus, reduces levels of soluble and insoluble cortical Aβ42 and reduces hippocampal Aβ plaque number. In addition, NP03 reduces markers of neuroinflammation and cellular oxidative stress. Together these results indicate that microdose lithium NP03 is effective at later stages of amyloid pathology, after appearance of Aβ plaques.

Neuroinflammation in Alzheimer's Disease: Microglia, Molecular Participants and Therapeutic Choices

Alzheimer's disease is the world's most common dementing illness. It is pathologically characterized by β-amyloid accumulation, extracellular senile plaques and intracellular neurofibrillary tangles formation, and neuronal necrosis and apoptosis. Neuroinflammation has been widely recognized as a crucial process that participates in AD pathogenesis. In this review, we briefly summarized the involvement of microglia in the neuroinflammatory process of Alzheimer's disease. Its roles in the AD onset and progression are also discussed. Numerous molecules, including interleukins, tumor necrosis factor alpha, chemokines, inflammasomes, participate in the complex process of AD-related neuroinflammation and they are selectively discussed in this review. In the end of this paper from an inflammation- related perspective, we discussed some potential therapeutic choices.

The effect of amyloid on microglia-neuron interactions before plaque onset occurs independently of TREM2 in a mouse model of Alzheimer's disease

Genetic studies identified mutations in several immune-related genes that confer increased risk for developing Alzheimer’s disease (AD), suggesting a key role for microglia in AD pathology. Microglia are recruited to and actively modulate the local toxicity of amyloid plaques in models of AD through these cells’ transcriptional and functional reprogramming to a disease-associated phenotype. However, it remains unknown whether microglia actively respond to amyloid accumulation before plaque deposition in AD. We compared microglial interactions with neurons that exhibit amyloid accumulation to those that do not in 1-month-old 5XFAD mice to determine which aspects of microglial morphology and function are altered by early 6E10+ amyloid accumulation. We provide evidence of preferential microglial process engagement of amyloid laden neurons. Microglia, on exposure to amyloid, also increase their internalization of neurites even before plaque onset. Unexpectedly, we found that triggering receptor expressed on myeloid cells 2 (TREM2), which is critical for microglial responses to amyloid plaque pathology later in disease, is not required for enhanced microglial interactions with neurons or neurite internalization early in disease. However, TREM2 was still required for early morphological changes exhibited by microglia. These data demonstrate that microglia sense and respond to amyloid accumulation before plaques form using a distinct mechanism from the TREM2-dependent pathway required later in disease.

Early intraneuronal amyloid triggers neuron-derived inflammatory signaling in APP transgenic rats and human brain

This work provides evidence that soluble and oligomeric amyloid protein stokes neuronal inflammation during the earliest stages of Alzheimer’s disease. Identifying neuron-derived factors that engage the brain’s immune system will provide insight into how vulnerable neurons might interact with other immune cells to propagate cytotoxic signaling cascades and cellular dysfunction during disease development.

Chronic inflammation during Alzheimer’s disease (AD) is most often attributed to sustained microglial activation in response to amyloid-β (Aβ) plaque deposits and cell death. However, cytokine release and microgliosis are consistently observed in AD transgenic animal models devoid of such pathologies, bringing into question the underlying processes that may be at play during the earliest AD-related immune response. We propose that this plaque-independent inflammatory reaction originates from neurons burdened with increasing levels of soluble and oligomeric Aβ, which are known to be the most toxic amyloid species within the brain. Laser microdissected neurons extracted from preplaque amyloid precursor protein (APP) transgenic rats were found to produce a variety of potent immune factors, both at the transcript and protein levels. Neuron-derived cytokines correlated with the extent of microglial activation and mobilization, even in the absence of extracellular plaques and cell death. Importantly, we identified an inflammatory profile unique to Aβ-burdened neurons, since neighboring glial cells did not express similar molecules. Moreover, we demonstrate within disease-vulnerable regions of the human brain that a neuron-specific inflammatory response may precede insoluble Aβ plaque and tau tangle formation. Thus, we reveal the Aβ-burdened neuron as a primary proinflammatory agent, implicating the intraneuronal accumulation of Aβ as a significant immunological component in the AD pathogenesis.

Experimental Pharmacology in Transgenic Rodent Models of Alzheimer's Disease

This Mini Review discusses the merits and shortfalls of transgenic (tg) rodents modeling aspects of the human Alzheimer’s disease (AD) pathology and their application to evaluate experimental therapeutics. It addresses some of the differences between mouse and rat tg models for these investigations. It relates, in a condensed fashion, the experience of our research laboratory with the application of anti-inflammatory compounds and S-adenosylmethionine (SAM) at the earliest stages of AD-like amyloid pathology in tg mice. The application of SAM was intended to revert the global brain DNA hypomethylation unleashed by the intraneuronal accumulation of amyloid-β-immunoreactive material, an intervention that restored levels of DNA methylation including of the bace1 gene. This review also summarizes experimental pharmacology observations made in the McGill tg rat model of AD-like pathology by applying “nano-lithium” or a drug with allosteric M1 muscarinic and sigma 1 receptor agonistic properties (AF710B). Extremely low doses of lithium (up to 400 times lower than used in the clinic) had remarkable beneficial effects on lowering pathology and improving cognitive functions in tg rats. Likewise, AF710B treatment, even at advanced stages of the pathology, displayed remarkable beneficial effects. This drug, in experimental conditions, demonstrated possible “disease-modifying” properties as pathology was frankly diminished and cognition improved after a month of “wash-out” period. The Mini-Review ends with a discussion on the predictive value of similar experimental pharmacological interventions in current rodent tg models. It comments on the validity of some of these approaches for early interventions at preclinical stages of AD, interventions which may be envisioned once definitive diagnosis of AD before clinical presentation is made possible.

Platelets Bioenergetics Screening Reflects the Impact of Brain Aβ Plaque Accumulation in a Rat Model of Alzheimer

Alzheimer's disease (AD) is associated to depressed brain energy supply and impaired cortical and hippocampal synaptic function. It was previously reported in McGill-R-Thy1-APP transgenic (Tg(+/+)) rats that Aβ deposition per se is sufficient to cause abnormalities in glucose metabolism and neuronal connectivity. These data support the utility of this animal model as a platform for the search of novel AD biomarkers based on bioenergetic status. Recently, it has been proposed that energy dysfunction can be dynamically tested in platelets (PLTs) of nonhuman primates. PLTs are good candidates to find peripheral biomarkers for AD because they may reflect in periphery the bioenergetics deficits and the inflammatory and oxidative stress processes taking place in AD brain. In the present study, we carried out a PLTs bioenergetics screening in advanced-age (12-14 months old) control (WT) and Tg(+/+) rats. Results indicated that thrombin-activated PLTs of Tg(+/+) rats showed a significantly lower respiratory rate, as compared to that measured in WT animals, when challenged with the same dose of FCCP (an uncoupler of oxidative phosphorylation). In summary, our results provide original evidence that PLTs bioenergetic profiling may reflect brain bioenergetics dysfunction mediated by Aβ plaque accumulation. Further studies on human PLTs from control and AD patients are required to validate the usefulness of PLTs bioenergetics as a novel blood-based biomarker for AD.