Lithium inhibits Alzheimer's disease-like tau protein phosphorylation in neurons

Impact of chronic hyperglycemia and high-fat diet on Alzheimer's disease-related pathology in CX3CR1 knockout mice

Diabetes mellitus (DM), obesity, and metabolic syndrome are related disorders with wide-ranging and devastating effects that are comorbid with many other diseases. Clinical and epidemiological studies have found that type II diabetes mellitus (T2DM), including chronic hyperglycemia and hyperinsulinemia, significantly increases the risk of Alzheimer's disease (AD) and other forms of dementia in the elderly. Insulin has slightly different functions in the peripheral body than in the central nervous system and the dysregulation of these functions may contribute to the onset and progression of late-life neurodegenerative disease. To investigate cognitive function and AD-related disease pathology, we utilized two different models of key features of diabetes, one model characterized by hyperglycemia resulting from a diabetogenic compound that selectively targets insulin-producing pancreatic β-cells, and the other model based on diet-induced obesity. Additionally, these diabetic models were combined with fractalkine receptor knockout mice (CX3CR1-/-), a genetic mouse model of inflammation, to explore the additive effects of multiple AD risk factors. The CX3CR1 receptor has been implicated in modulating neuroinflammation associated with AD, and its dysregulation can exacerbate metabolic disturbances and neurodegenerative markers. We found that diabetic-status, regardless of whether it was drug- or diet-induced, resulted in profound impairments in learning and memory and AD-related alterations within the hippocampus.

RhoA/ROCK/GSK3β Signaling: A Keystone in Understanding Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive cognitive decline and loss of neuronal integrity. Emerging evidence suggests that RhoA, Rho-associated coiled-coil kinase (ROCK), and their downstream effector molecule glycogen synthase 3β (GSK3β) interact within a complex signaling pathway (RhoA/ROCK/GSK3β) that plays a crucial role in the pathogenesis of AD. RhoA, a small GTPase, along with its downstream effector, ROCK, regulates various cellular processes, including actin cytoskeleton dynamics, apoptosis, and synaptic plasticity. GSK3β, a serine/threonine kinase, plays a key role in neuronal function and AD pathology, including the regulation of tau phosphorylation and amyloid-beta cleavage. Overactive GSK3β has been closely linked to tau hyperphosphorylation, neurodegeneration, and the progression of AD. Thus, GSK3β has been considered as a promising therapeutic target for treating AD and mitigating cognitive impairment. However, clinical trials of GSK3β in AD have faced considerable challenges due to the complexity of the specific neuronal inhibition of GSK3β. In this review, we summarize the literature regarding the relationship of RhoA/ROCK and GSK3β signaling pathways in AD pathogenesis. We further discuss recent findings of the sTREM2-transgelin-2 (TG2) axis as a potential mediator of this complex pathway and provide our review on a novel targeting strategy for AD.

Intracellular effects of lithium in aging neurons

Lithium therapy received approval during the 1970s, and it has been used for its antidepressant, antimanic, and anti-suicidal effects for acute and long-term prophylaxis and treatment of bipolar disorder (BPD). These properties have been well established; however, the molecular and cellular mechanisms remain controversial. In the past few years, many studies demonstrated that at the cellular level, lithium acts as a regulator of neurogenesis, aging, and Ca2+ homeostasis. At the molecular level, lithium modulates aging by inhibiting glycogen synthase kinase-3β (GSK-3β), and the phosphatidylinositol (PI) cycle; latter, lithium specifically inhibits inositol production, acting as a non-competitive inhibitor of inositol monophosphatase (IMPase). Mitochondria and peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) have been related to lithium activity, and its regulation is mediated by GSK-3β degradation and inhibition. Lithium also impacts Ca2+ homeostasis in the mitochondria modulating the function of the lithium-permeable mitochondrial Na+-Ca2+exchanger (NCLX), affecting Ca2+ efflux from the mitochondrial matrix to the endoplasmic reticulum (ER). A close relationship between the protease Omi, GSK-3β, and PGC-1α has also been established. The purpose of this review is to summarize some of the intracellular mechanisms related to lithium activity and how, through them, neuronal aging could be controlled.

Molecular mechanisms and therapeutic potential of lithium in Alzheimer's disease: repurposing an old class of drugs

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline and memory loss. Despite advances in understanding the pathophysiological mechanisms of AD, effective treatments remain scarce. Lithium salts, recognized as mood stabilizers in bipolar disorder, have been extensively studied for their neuroprotective effects. Several studies indicate that lithium may be a disease-modifying agent in the treatment of AD. Lithium's neuroprotective properties in AD by acting on multiple neuropathological targets, such as reducing amyloid deposition and tau phosphorylation, enhancing autophagy, neurogenesis, and synaptic plasticity, regulating cholinergic and glucose metabolism, inhibiting neuroinflammation, oxidative stress, and apoptosis, while preserving mitochondrial function. Clinical trials have demonstrated that lithium therapy can improve cognitive function in patients with AD. In particular, meta-analyses have shown that lithium may be a more effective and safer treatment than the recently FDA-approved aducanumab for improving cognitive function in patients with AD. The affordability and therapeutic efficacy of lithium have prompted a reassessment of its use. However, the use of lithium may lead to potential side effects and safety issues, which may limit its clinical application. Currently, several new lithium formulations are undergoing clinical trials to improve safety and efficacy. This review focuses on lithium's mechanism of action in treating AD, highlighting the latest advances in preclinical studies and clinical trials. It also explores the side effects of lithium therapy and coping strategies, offering a potential therapeutic strategy for patients with AD.

Heavy metals toxicity on epigenetic modifications in the pathogenesis of Alzheimer's disease (AD)

Alzheimer's disease (AD) is a progressive decline in cognitive ability and behavior which eventually disrupts daily activities. AD has no cure and the progression rate varies unlikely. Among various causative factors, heavy metals are reported to be a significant hazard in AD pathogenesis. Metal-induced neurodegeneration has been focused globally with thorough research to unravel the mechanistic insights in AD. Recently, heavy metals suggested to play an important role in epigenetic alterations which might provide evidential results on AD pathology. Epigenetic modifications are known to play towards novel therapeutic approaches in treating AD. Though many studies focus on epigenetics and heavy metal implications in AD, there is a lack of research on heavy metal influence on epigenetic toxicity in neurological disorders. The current review aims to elucidate the plausible role of cadmium (Cd), iron (Fe), arsenic (As), copper (Cu), and lithium (Li) metals on epigenetic factors and the increase in amyloid beta and tau phosphorylation in AD. Also, the review discusses the common methods of heavy metal detection to implicate in AD pathogenesis. Hence, from this review, we can extend the need for future research on identifying the mechanistic behavior of heavy metals on epigenetic toxicity and to develop diagnostic and therapeutic markers in AD.

Age-associated temporal decline in butyrate-producing bacteria plays a key pathogenic role in the onset and progression of neuropathology and memory deficits in 3×Tg-AD mice

Alterations in the gut-microbiome-brain axis are increasingly being recognized to be involved in Alzheimer's disease (AD) pathogenesis. However, the functional consequences of enteric dysbiosis linking gut microbiota and brain pathology in AD progression remain largely undetermined. The present work investigated the causal role of age-associated temporal decline in butyrate-producing bacteria and butyrate in the etiopathogenesis of AD. Longitudinal metagenomics, neuropathological, and memory analyses were performed in the 3×Tg-AD mouse model. Metataxonomic analyses showed a significant temporal decline in the alpha diversity marked by a decrease in butyrate-producing bacterial communities and a concurrent reduction in cecal butyrate production. Inferred metagenomics analysis identified the bacterial acetyl-CoA pathway as the main butyrate synthesis pathway impacted. Concomitantly, there was an age-associated decline in the transcriptionally permissive acetylation of histone 3 at lysines 9 and 14 (H3K9/K14-Ac) in hippocampal neurons. Importantly, these microbiome-gut-brain changes preceded AD-related neuropathology, including oxidative stress, tau hyperphosphorylation, memory deficits, and neuromuscular dysfunction, which manifest by 17-18 months. Initiation of oral administration of tributyrin, a butyrate prodrug, at 6 months of age mitigated the age-related decline in butyrate-producing bacteria, protected the H3K9/K14-Ac status, and attenuated the development of neuropathological and cognitive changes associated with AD pathogenesis. These data causally implicate age-associated decline in butyrate-producing bacteria as a key pathogenic feature of the microbiome-gut-brain axis affecting the onset and progression of AD. Importantly, the regulation of butyrate-producing bacteria and consequent butyrate synthesis could be a significant therapeutic strategy in the prevention and treatment of AD.

Astrocytic uptake of neuronal corpses promotes cell-to-cell spreading of tau pathology

Tau deposits in astrocytes are frequently found in Alzheimer's disease (AD) and other tauopathies. Since astrocytes do not express tau, the inclusions have been suggested to be of neuronal origin. However, the mechanisms behind their appearance and their relevance for disease progression remain unknown. Here we demonstrate, using a battery of experimental techniques that human astrocytes serve as an intermediator, promoting cell-to-cell spreading of pathological tau. Human astrocytes engulf and process, but fail to fully degrade dead neurons with tau pathology, as well as synthetic tau fibrils and tau aggregates isolated from AD brain tissue. Instead, the pathogenic tau is spread to nearby cells via secretion and tunneling nanotube mediated transfer. By performing co-culture experiments we could show that tau-containing astrocytes induce tau pathology in healthy human neurons directly. Furthermore, our results from a FRET based seeding assay, demonstrated that the tau proteoforms secreted by astrocytes have an exceptional seeding capacity, compared to the original tau species engulfed by the cells. Taken together, our study establishes a central role for astrocytes in mediating tau pathology, which could be of relevance for identifying novel treatment targets for AD and other tauopathies.

Lithium Provides Broad Therapeutic Benefits in an Alzheimer's Disease Mouse Model

BACKGROUND

Alzheimer's disease (AD) is a chronic neurodegenerative disorder with a progressive loss of cognitive function. Currently, no effective treatment regimen is available. Lithium, a mood stabilizer for bipolar disorder, exerts broad neuroprotective and neurotrophic actions and improves cognitive function.

OBJECTIVE

The study investigated if lithium stabilizes Ca2+ signaling abnormalities in hippocampal neurons and subsequently normalize downstream effects on AD neuropathology and synaptic plasticity in young AD mice.

METHODS

Four-month-old 3xTg-AD mice were treated with a LiCl diet chow for 30 days. At the end of the lithium treatment, a combination of two-photon Ca2+ imaging, electrophysiology, and immunohistochemistry assays were used to assess the effects of the LiCl treatment on inositol trisphosphate receptor (IP3R)-dependent endoplasmic reticulum (ER) Ca2+ and voltage-gated Ca2+ channel (VGCC)-mediated Ca2+ signaling in CA1 neurons, neuronal nitric oxide synthase (nNOS) and hyperphosphorylated tau (p-tau) levels and synaptic plasticity in the hippocampus and overlying cortex from 3xTg-ADmice.

RESULTS

Thirty-day LiCl treatment reduced aberrant IP3R-dependent ER Ca2+ and VGCC-mediated Ca2+ signaling in CA1 pyramidal neurons from 3xTg-AD mice and restored neuronal nitric oxide synthase (nNOS) and hyperphosphorylated tau (p-tau) levels to control levels in the hippocampal subfields and overlying cortex. The LiCl treatment enhanced post-tetanic potentiation (PTP), a form of short-term plasticity in the hippocampus.

CONCLUSION

The study found that lithium exerts therapeutic effects across several AD-associated early neuronal signaling abnormalities including aberrant Ca2+ signaling, nNOS, and p-tau formation and enhances short-term synaptic plasticity. Lithium could serve as an effective treatment or co-therapeutic for AD.

Clinical Biomarkers and Novel Drug Targets to Cut Gordian Knots of Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD), the primary cause of dementia, escalating worldwide, has no proper diagnosis or effective treatment. Neuronal cell death and impairment of cognitive abilities, possibly triggered by several brain mechanisms, are the most significant characteristic of this disorder.

METHODS

A multitude of pharmacological targets have been identified for potential drug design against AD. Although many advances in treatment strategies have been made to correct various abnormalities, these often exhibit limited clinical significance because this disease aggressively progresses into different regions of the brain, causing severe deterioration.

RESULTS

These biomarkers can be game-changers for early detection and timely monitoring of such disorders.

CONCLUSION

This review covers clinically significant biomarkers of AD for precise and early monitoring of risk factors and stages of this disease, the potential site of action and novel targets for drugs, and pharmacological approaches to clinical management.

Probiotic supplement as a promising strategy in early tau pathology prevention: Focusing on GSK-3β?

Neurofibrillary tangles (NFT) is one of the hallmarks of Alzheimer's disease (AD). Recent research suggests that pretangle tau, the soluble precursor of NFT, is an initiator for AD pathogenesis, thus targeting pretangle tau pathology may be a promising early intervention focus. The bidirectional communications between the gut and the brain play a crucial role in health. The compromised gut-brain axis is involved in various neurodegenerative diseases including AD. However, most research on the relationship between gut microbiome and AD have focused on amyloid-β. In this mini review, we propose to target preclinical pretangle tau stages with gut microbiota interventions such as probiotic supplementation. We discuss the importance of targeting pretangle tau that starts decades before the onset of clinical symptoms, and potential intervention focusing on probiotic regulation of tau hyperphosphorylation. A particular focus is on GSK-3β, a protein kinase that is at the interface between tau phosphorylation, AD and diabetes mellitus.

Diabetes: Risk factor and translational therapeutic implications for Alzheimer's disease

Type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD) commonly co-occur. T2DM increases the risk for AD by approximately twofold. Animal models provide one means of interrogating the relationship of T2DM to AD and investigating brain insulin resistance in the pathophysiology of AD. Animal models show that persistent hyperglycaemia results in chronic low-grade inflammation that may contribute to the development of neuroinflammation and accelerate the pathobiology of AD. Epidemiological studies suggest that patients with T2DM who received treatment with specific anti-diabetic agents have a decreased risk for the occurrence of AD and all-cause dementia. Agents such as metformin ameliorate T2DM and may have other important systemic effects that lower the risk of AD. Glucagon-like peptide 1 (GLP-1) agonists have been associated with a decreased risk for AD in patients with T2DM. Both insulin and non-insulin anti-diabetic treatments have been evaluated for the treatment of AD in clinical trials. In most cases, patients included in the trials have clinical features of AD but do not have T2DM. Many of the trials were conducted prior to the use of diagnostic biomarkers for AD. Trials have had a wide range of durations and population sizes. Many of the agents used to treat T2DM do not cross the blood brain barrier, and the effects are posited to occur via lowering of peripheral hyperglycaemia and reduction of peripheral and central inflammation. Clinical trials of anti-diabetic agents to treat AD are ongoing and will provide insight into the therapeutic utility of these agents.

Lithium Enhances Hippocampal Glucose Metabolism in an In Vitro Mice Model of Alzheimer's Disease

Impaired cerebral glucose metabolism is an early event that contributes to the pathogenesis of Alzheimer's disease (AD). Importantly, restoring glucose availability by pharmacological agents or genetic manipulation has been shown to protect against Aβ toxicity, ameliorate AD pathology, and increase lifespan. Lithium, a therapeutic agent widely used as a treatment for mood disorders, has been shown to attenuate AD pathology and promote glucose metabolism in skeletal muscle. However, despite its widespread use in neuropsychiatric disorders, lithium's effects on the brain have been poorly characterized. Here we evaluated the effect of lithium on glucose metabolism in hippocampal neurons from wild-type (WT) and APPSwe/PS1ΔE9 (APP/PS1) mice. Our results showed that lithium significantly stimulates glucose uptake and replenishes ATP levels by preferential oxidation of glucose through glycolysis in neurons from WT mice. This increase was also accompanied by a strong increase in glucose transporter 3 (Glut3), the major carrier responsible for glucose uptake in neurons. Similarly, using hippocampal slices from APP-PS1 mice, we demonstrate that lithium increases glucose uptake, glycolytic rate, and the ATP:ADP ratio in a process that also involves the activation of AMPK. Together, our findings indicate that lithium stimulates glucose metabolism and can act as a potential therapeutic agent in AD.

Experimental data on lithium salts: From neuroprotection to multi-organ complications

Lithium-salts stand on the first line of therapy for the management of specific psychiatric conditions, mainly bipolar mood disorder. It is also known to protect the brain against neurodegenerative processes such as Alzheimer's disease. Despite the mentioned merits, recent studies have revealed that high dose or prolonged lithium intake deteriorate the function of multiple key organs including heart, ovaries, thyroid gland and kidneys. Mechanistically, both positive and negative effects of lithium are mediated through methylation of β-catenin nuclear-binding proteins which is potentiated by lithium-induced inhibition of GSK-3 or inositol monophosphatase. The current study briefly reviews the recent experimental data on lithium therapy considering both positive (i.e., neuroprotective) and negative aspects. In this regard, the question is that whether doses of lithium administered in experimental research are comparable with the therapeutic doses, as currently prescribed in clinical practice. It should be noted that the experimental data on animal studies, as widely reviewed here, could not be directly generalized to clinic. This is mainly because lithium doses applied in animal models are usually higher than therapeutic doses, however, there are evidence indicating that even animal to human translated doses of lithium, cause serious complications and this has been reported by meta-analyses on human studies. Therefore, we suggest the clinicians to use lithium-salts with precaution particularly in pregnancy and precisely adjust lithium concentration considering the patient's general health status to avoid lithium toxicity. Indeed, alternative approaches are recommended when the subject is pregnant, prolonged therapy is required or specific organ dysfunction is diagnosed.

Alzheimer risk gene product Pyk2 suppresses tau phosphorylation and phenotypic effects of tauopathy

BACKGROUND

Genetic variation at the PTK2B locus encoding the protein Pyk2 influences Alzheimer's disease risk. Neurons express Pyk2 and the protein is required for Amyloid-β (Aβ) peptide driven deficits of synaptic function and memory in mouse models, but Pyk2 deletion has minimal effect on neuro-inflammation. Previous in vitro data suggested that Pyk2 activity might enhance GSK3β-dependent Tau phosphorylation and be required for tauopathy. Here, we examine the influence of Pyk2 on Tau phosphorylation and associated pathology.

METHODS

The effect of Pyk2 on Tau phosphorylation was examined in cultured Hek cells through protein over-expression and in iPSC-derived human neurons through pharmacological Pyk2 inhibition. PS19 mice overexpressing the P301S mutant of human Tau were employed as an in vivo model of tauopathy. Phenotypes of PS19 mice with a targeted deletion of Pyk2 expression were compared with PS19 mice with intact Pyk2 expression. Phenotypes examined included Tau phosphorylation, Tau accumulation, synapse loss, gliosis, proteomic profiling and behavior.

RESULTS

Over-expression experiments from Hek293T cells indicated that Pyk2 contributed to Tau phosphorylation, while iPSC-derived human neuronal cultures with endogenous protein levels supported the opposite conclusion. In vivo, multiple phenotypes of PS19 were exacerbated by Pyk2 deletion. In Pyk2-null PS19 mice, Tau phosphorylation and accumulation increased, mouse survival decreased, spatial memory was impaired and hippocampal C1q deposition increased relative to PS19 littermate controls. Proteomic profiles of Pyk2-null mouse brain revealed that several protein kinases known to interact with Tau are regulated by Pyk2. Endogenous Pyk2 suppresses LKB1 and p38 MAPK activity, validating one potential pathway contributing to increased Tau pathology.

CONCLUSIONS

The absence of Pyk2 results in greater mutant Tau-dependent phenotypes in PS19 mice, in part via increased LKB1 and MAPK activity. These data suggest that in AD, while Pyk2 activity mediates Aβ-driven deficits, Pyk2 suppresses Tau-related phenotypes.

Revisiting the grammar of Tau aggregation and pathology formation: how new insights from brain pathology are shaping how we study and target Tauopathies

Converging evidence continues to point towards Tau aggregation and pathology formation as central events in the pathogenesis of Alzheimer's disease and other Tauopathies. Despite significant advances in understanding the morphological and structural properties of Tau fibrils, many fundamental questions remain about what causes Tau to aggregate in the first place. The exact roles of cofactors, Tau post-translational modifications, and Tau interactome in regulating Tau aggregation, pathology formation, and toxicity remain unknown. Recent studies have put the spotlight on the wide gap between the complexity of Tau structures, aggregation, and pathology formation in the brain and the simplicity of experimental approaches used for modeling these processes in research laboratories. Embracing and deconstructing this complexity is an essential first step to understanding the role of Tau in health and disease. To help deconstruct this complexity and understand its implication for the development of effective Tau targeting diagnostics and therapies, we firstly review how our understanding of Tau aggregation and pathology formation has evolved over the past few decades. Secondly, we present an analysis of new findings and insights from recent studies illustrating the biochemical, structural, and functional heterogeneity of Tau aggregates. Thirdly, we discuss the importance of adopting new experimental approaches that embrace the complexity of Tau aggregation and pathology as an important first step towards developing mechanism- and structure-based therapies that account for the pathological and clinical heterogeneity of Alzheimer's disease and Tauopathies. We believe that this is essential to develop effective diagnostics and therapies to treat these devastating diseases.

Inflammation: A Major Target for Compounds to Control Alzheimer's Disease

Several hypotheses have been postulated to explain how Alzheimer's disease is triggered, but none of them provide a unified view of its pathogenesis. The dominant hypothesis based on build-ups of the amyloid-β peptide has been around for longer than three decades; however, up to today, numerous clinical trials based on the amyloid postulates have been attempted, but all of them have failed. Clearly, the revisited tau hypothesis provides a better explanation of the clinical observations of patients, but it needs to integrate the cumulative observations on the onset of this disease. In this context, the neuroimmuno modulation theory, based on the involvement of inflammatory events in the central nervous system, accounts for all these observations. In this review we intend to emphasize the idea that neuroinflammation is a main target for the search of new therapeutic strategies to control Alzheimer's disease. Beyond mono-targeting approaches using synthetic drugs that control only specific pathophysiological events, emerging therapeutics views based on multi targeting compounds appear to provide a new pathway for Alzheimer's disease treatment.

Isoform-selective decrease of glycogen synthase kinase-3-beta (GSK-3β) reduces synaptic tau phosphorylation, transcellular spreading, and aggregation

It has been suggested that aberrant activation of glycogen synthase kinase-3-beta (GSK-3β) can trigger abnormal tau hyperphosphorylation and aggregation, which ultimately leads to neuronal/synaptic damage and impaired cognition in Alzheimer disease (AD). We examined if isoform-selective partial reduction of GSK-3β can decrease pathological tau changes, including hyperphosphorylation, aggregation, and spreading, in mice with localized human wild-type tau (hTau) expression in the brain. We used adeno-associated viruses (AAVs) to express hTau locally in the entorhinal cortex of wild-type and GSK-3β hemi-knockout (GSK-3β-HK) mice. GSK-3β-HK mice had significantly less accumulation of hyperphosphorylated tau in synapses and showed a significant decrease of tau protein spread between neurons. In primary neuronal cultures from GSK-3β-HK mice, the aggregation of exogenous FTD-mutant tau was also significantly reduced. These results show that a partial decrease of GSK-3β significantly represses tau-initiated neurodegenerative changes in the brain, and therefore is a promising therapeutic target for AD and other tauopathies.

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Genetic reduction of GSK-3β decreases synaptic accrual of GSK-3β and p-Tau in mice

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Reduction of GSK-3β lowers the trans-cellular spread of tau in vivo and in vitro

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Reduction of GSK-3β diminishes the formation of tau aggregates in vitro

Human gut microbiota Agathobaculum butyriciproducens improves cognitive impairment in LPS-induced and APP/PS1 mouse models of Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease, and is characterized by the accumulation and presence of amyloid plaques (Aβ), tangles, dementia, and cognitive impairment. Currently, there is no known cure for AD; however, recently, the association between alteration of the gut microbiota and AD pathology has been explored to find novel therapeutic approaches. Microbiota-targeted intervention has been suggested as an attractive therapeutic approach for AD. Agathobaculum butyriciproducens (SR79) is a strict anaerobic and butyric acid-producing bacteria. We hypothesized that administration of SR79 might have a beneficial effect on cognitive deficits and AD pathologies. To determine the therapeutic effects of SR79 on AD pathologies, APP/PS1 transgenic and lipopolysaccharide -induced cognitive impairment mouse models were used. In the lipopolysaccharide -induced cognitive deficit model, the administration of SR79 improved cognitive function and decreased microglia activation. In addition, the administration of SR79 to APP/PS1 mice significantly improved novel object recognition and percent alteration results in novel object recognition and Y-maze alteration tests. Furthermore, Aβ plaque deposition and microglial activation were markedly reduced in the parietal cortex and hippocampus after SR79 treatment in APP/PS1 mice. SR79 treatment significantly decreased gene expression levels of IL-1β and C1QB and increased the gene expression levels of IGF-1 and thereby the downstream signaling pathway in the cortex of APP/PS1 mice. In conclusion, SR79 administration improved cognitive function and AD pathologies through the regulation of neuroinflammation and IGF-1 signaling in an animal model.

β-amyloid redirects norepinephrine signaling to activate the pathogenic GSK3β/tau cascade

The brain noradrenergic system is critical for normal cognition and is affected at early stages in Alzheimer's disease (AD). Here, we reveal a previously unappreciated direct role of norepinephrine signaling in connecting β-amyloid (Aβ) and tau, two key pathological components of AD pathogenesis. Our results show that Aβ oligomers bind to an allosteric site on α2A adrenergic receptor (α2AAR) to redirect norepinephrine-elicited signaling to glycogen synthase kinase 3β (GSK3β) activation and tau hyperphosphorylation. This norepinephrine-dependent mechanism sensitizes pathological GSK3β/tau activation in response to nanomolar accumulations of extracellular Aβ, which is 50- to 100-fold lower than the amount required to activate GSK3β by Aβ alone. The significance of our findings is supported by in vivo evidence in two mouse models, human tissue sample analysis, and longitudinal clinical data. Our study provides translational insights into mechanisms underlying Aβ proteotoxicity, which might have strong implications for the interpretation of Aβ clearance trial results and future drug design and for understanding the selective vulnerability of noradrenergic neurons in AD.

Regulation of Inositol Biosynthesis: Balancing Health and Pathophysiology

Inositol is the precursor for all inositol compounds and is essential for viability of eukaryotic cells. Numerous cellular processes and signaling functions are dependent on inositol compounds, and perturbation of their synthesis leads to a wide range of human diseases. Although considerable research has been directed at understanding the function of inositol compounds, especially phosphoinositides and inositol phosphates, a focus on regulatory and homeostatic mechanisms controlling inositol biosynthesis has been largely neglected. Consequently, little is known about how synthesis of inositol is regulated in human cells. Identifying physiological regulators of inositol synthesis and elucidating the molecular mechanisms that regulate inositol synthesis will contribute fundamental insight into cellular processes that are mediated by inositol compounds and will provide a foundation to understand numerous disease processes that result from perturbation of inositol homeostasis. In addition, elucidating the mechanisms of action of inositol-depleting drugs may suggest new strategies for the design of second-generation pharmaceuticals to treat psychiatric disorders and other illnesses.

Regulation of Diabetes: a Therapeutic Strategy for Alzheimer's Disease?

Accumulated evidence suggests that sporadic cases of Alzheimer's disease (AD) make up more than 95% of total AD patients, and diabetes has been implicated as a strong risk factor for the development of AD. Diabetes shares pathological features of AD, such as impaired insulin signaling, increased oxidative stress, increased amyloid-beta (Aβ) production, tauopathy and cerebrovascular complication. Due to shared pathologies between the two diseases, anti-diabetic drugs may be a suitable therapeutic option for AD treatment. In this article, we will discuss the well-known pathologies of AD, including Aβ plaques and tau tangles, as well as other mechanisms shared in AD and diabetes including reactive glia and the breakdown of blood brain barrier in order to evaluate the presence of any potential, indirect or direct links of pre-diabetic conditions to AD pathology. In addition, clinical evidence of high incidence of diabetic patients to the development of AD are described together with application of anti-diabetic medications to AD patients.

Poor Diet, Stress, and Inactivity Converge to Form a "Perfect Storm" That Drives Alzheimer's Disease Pathogenesis

North American incidence of Alzheimer's disease (AD) is expected to more than double over the coming generation. Although genetic factors surrounding the production and clearance of amyloid-β and phosphorylated tau proteins are known to be responsible for a subset of early-onset AD cases, they do not explain the pathogenesis of the far more prevalent sporadic late-onset variant of the disease. It is thus likely that lifestyle and environmental factors contribute to neurodegenerative processes implicated in the pathogenesis of AD. Herein, we review evidence that (1) excess sucrose consumption induces AD-associated liver pathologies and brain insulin resistance, (2) chronic stress overdrives activity of locus coeruleus neurons, leading to loss of function (a common event in neurodegeneration), (3) high-sugar diets and stress promote the loss of neuroprotective sex hormones in men and women, and (4) Western dietary trends set the stage for a lithium-deficient state. We propose that these factors may intersect as part of a "perfect storm" to contribute to the widespread prevalence of neurodegeneration and AD. In addition, we put forth the argument that exercise and supplementation with trace lithium can counteract many of the deleterious consequences associated with excessive caloric intake and perpetual stress. We conclude that lifestyle and environmental factors likely contribute to AD pathogenesis and that simple lifestyle and dietary changes can help counteract their effects.

GSK-3β at the Intersection of Neuronal Plasticity and Neurodegeneration

In neurons, Glycogen Synthase Kinase-3β (GSK-3β) has been shown to regulate various critical processes underlying structural and functional synaptic plasticity. Mouse models with neuron-selective expression or deletion of GSK-3β present behavioral and cognitive abnormalities, positioning this protein kinase as a key signaling molecule in normal brain functioning. Furthermore, mouse models with defective GSK-3β activity display distinct structural and behavioral abnormalities, which model some aspects of different neurological and neuropsychiatric disorders. Equalizing GSK-3β activity in these mouse models by genetic or pharmacological interventions is able to rescue some of these abnormalities. Thus, GSK-3β is a relevant therapeutic target for the treatment of many brain disorders. Here, we provide an overview of how GSK-3β is regulated in physiological synaptic plasticity and how aberrant GSK-3β activity contributes to the development of dysfunctional synaptic plasticity in neuropsychiatric and neurodegenerative disorders.

cis pT231-Tau Drives Neurodegeneration in Bipolar Disorder

Bipolar disorder is a complex neuropsychiatric disorder, characterized by intermittent episodes of mania and depression. Recent studies have indicated argyrophilic grains, composed of hyperphosphorylated tau, are observable in postmortem brains of bipolar patients. It remains uncertain how tau hyperphosphorylation results in neurodegeneration upon the disease. Recent studies have demonstrated that phosphorylated tau at Thr231 exists in two distinct cis and trans conformations, in which cis pT231-tau is highly neurotoxic and acts as an early driver of tauopathy in several neurodegenerative diseases. We herein employed an in vitro model, which resembles some aspects of bipolar disorder, to study the cis p-tau mediatory role. We established GSK3β overexpressing SH-SY5Y cells and examined cell viability, cis p-tau formation, and lithium effects by immunofluorescence and flow cytometry. We found an increase in cis p-tau levels as well as viability decrease in the cell model. Furthermore, we discovered that lithium treatment inhibits cis p-tau formation, resulting in diminished cell death. We also examined BD and healthy human brain samples and detected cis p-tau in the patients' brains. Our results show that tauopathy, observed in bipolar disorder, is being mediated through cis p-tau and that a conformer could be the cause of neurodegeneration upon the disease. Our findings would suggest novel therapeutic target to fight the devastating disorder.

Modulating Protein Phosphatase 2A Rescues Disease Phenotype in Neurodegenerative Tauopathies

Alzheimer's disease (AD) is the leading cause of dementia worldwide accounting for around 70% of all cases. There is currently no treatment for AD beyond symptom management and attempts at developing disease-modifying therapies have yielded very little. These strategies have traditionally targeted the peptide Aβ, which is thought to drive pathology. However, the lack of clinical translation of these Aβ-centric strategies underscores the need for diverse treatment strategies targeting other aspects of the disease. Metal dyshomeostasis is a common feature of several neurodegenerative diseases such as AD, Parkinson's disease, and frontotemporal dementia, and manipulation of metal homeostasis has been explored as a potential therapeutic avenue for these diseases. The copper ionophore glyoxalbis-[N4-methylthiosemicarbazonato]Cu(II) (Cu^II(gtsm)) has previously been shown to improve the cognitive deficits seen in an AD animal model; however, the molecular mechanism remained unclear. Here we report that the treatment of two animal tauopathy models (APP/PS1 and rTg4510) with Cu^II(gtsm) recovers the cognitive deficits seen in both neurodegenerative models. In both models, markers of tau pathology were significantly reduced with Cu^II(gtsm) treatment, and in the APP/PS1 model, the levels of Aβ remained unchanged. Analysis of tau kinases (GSK3β and CDK5) revealed no drug induced changes; however, both models exhibited a significant increase in the levels of the structural subunit of the tau phosphatase, PP2A. These findings suggest that targeting the tau phosphatase PP2A has therapeutic potential for preventing memory impairments and reducing the tau pathology seen in AD and other tauopathies.

Expression of Gas1 in Mouse Brain: Release and Role in Neuronal Differentiation

Growth arrest-specific 1 (Gas1) is a pleiotropic protein that induces apoptosis of tumor cells and has important roles during development. Recently, the presence of two forms of Gas1 was reported: one attached to the cell membrane by a GPI anchor; and a soluble extracellular form shed by cells. Previously, we showed that Gas1 is expressed in different areas of the adult mouse CNS. Here, we report the levels of Gas1 mRNA protein in different regions and analyzed its expressions in glutamatergic, GABAergic, and dopaminergic neurons. We found that Gas1 is expressed in GABAergic and glutamatergic neurons in the Purkinje-molecular layer of the cerebellum, hippocampus, thalamus, and fastigial nucleus, as well as in dopaminergic neurons of the substantia nigra. In all cases, Gas1 was found in the cell bodies, but not in the neuropil. The Purkinje and the molecular layers show the highest levels of Gas1, whereas the granule cell layer has low levels. Moreover, we detected the expression and release of Gas1 from primary cultures of Purkinje cells and from hippocampal neurons as well as from neuronal cell lines, but not from cerebellar granular cells. In addition, using SH-SY5Y cells differentiated with retinoic acid as a neuronal model, we found that extracellular Gas1 promotes neurite outgrowth, increases the levels of tyrosine hydroxylase, and stimulates the inhibition of GSK3β. These findings demonstrate that Gas1 is expressed and released by neurons and promotes differentiation, suggesting an important role for Gas1 in cellular signaling in the CNS.

Antiviral effect of lithium chloride on porcine epidemic diarrhea virus in vitro

Porcine epidemic diarrhea virus (PEDV), a member of the Coronaviridae family, causes acute diarrhea, vomiting, dehydration, and high mortality rates in neonatal piglets. Severe outbreaks of PEDV variants have re-emerged in Asia and North America since 2010, causing tremendous economic losses to the swine industry. The lack of effective therapeutic treatment promotes the research for new antivirals. Lithium chloride (LiCl) has been reported as a potential antiviral drug for certain viruses. In this study, the antiviral effect of LiCl on PEDV in Vero cells was evaluated. Real-time quantitative PCR and indirect immunofluorescence assay indicated that LiCl effectively inhibited the entry and replication of PEDV in Vero cells. The expression of viral RNA and protein of PEDV in Vero cells was suppressed in a dose-dependent manner by LiCl. Moreover, addition of LiCl inhibited both early and late cell apoptosis induced by PEDV. Our data implied that LiCl could be a potential antiviral drug against PEDV infection. Further studies are required to explore the antiviral effect of lithium chloride on PEDV infection in vivo.

Secretion of full-length Tau or Tau fragments in cell culture models. Propagation of Tau in vivo and in vitro

The microtubule-associated protein Tau plays a crucial role in stabilizing neuronal microtubules. In Tauopathies, Tau loses its ability to bind microtubules, detach from them and forms intracellular aggregates. Increasing evidence in recent years supports the notion that Tau pathology spreading throughout the brain in AD and other Tauopathies is the consequence of the propagation of specific Tau species along neuroanatomically connected brain regions in a so-called “prion-like” manner. A number of steps are assumed to be involved in this process, including secretion, cellular uptake, transcellular transfer and/or seeding, although the precise mechanisms underlying propagation of Tau pathology are not fully understood yet. This review summarizes recent evidence on the nature of the specific Tau species that are propagated and the different mechanisms of Tau pathology spreading.

Prevention of Amyloid-β and Tau Pathologies, Associated Neurodegeneration, and Cognitive Deficit by Early Treatment with a Neurotrophic Compound

To date, neither any effective treatment nor prevention of Alzheimer's disease (AD), a major dementia causing disorder, are available. Herein, we investigated the secondary prevention of neurodegeneration, amyloid-β (Aβ) and tau pathologies with a neurotrophic compound P021 in 3xTg-AD mice. Previous work found that P021 can rescue at mild to moderate stages Aβ and tau pathologies in 3xTg-AD mice. To determine its potential clinical application, we sought to test the preventive effect of P021 on Aβ and tau pathologies by starting the treatment during the period of synaptic compensation several months before the appearance of any overt pathology in 3xTg-AD mice. We started a continuous treatment with P021 in 3-month-old female animals and followed its effect at 9-, 15- and 18-months post-treatment. Neurodegeneration at the above time points was studied using Fluorojade C staining, and tau and Aβ pathologies both immunohistochemically and by Western blots. Cognitive performance was studied by assessing episodic memory with Novel Object Recognition task at 16-17-months post-treatment. We found that P021 treatment initiated during the synaptic compensation period can prevent neurodegeneration, Aβ and tau pathologies, rescue episodic memory impairment, and markedly reduce mortality rate. These findings for the first time show effective prevention of AD changes with a neurotrophic compound that targets neurogenesis and synaptic plasticity, suggesting that improving the health of the neuronal network can prevent AD.

Lithium chloride inhibits early stages of foot-and-mouth disease virus (FMDV) replication in vitro

Foot‐and‐mouth disease virus (FMDV) causes an economically important and highly contagious disease of cloven‐hoofed animals such as cattle, swine, and sheep. FMD vaccine is the traditional way to protect against the disease, which can greatly reduce its occurrence. However, the use of FMD vaccines to protect early infection is limited. Therefore, the alternative strategy of applying antiviral agents is required to control the spread of FMDV in outbreak situations. As previously reported, LiCl has obviously inhibition effects on a variety of viruses such as transmissible gastroenteritis virus (TGEV), infectious bronchitis coronavirus (IBV), and pseudorabies herpesvirus and EV‐A71 virus. In this study, our findings were the first to demonstrate that LiCl inhibition of the FMDV replication. In this study, BHK‐21 cell was dose‐dependent with LiCl at various stages of FMDV. Virus titration assay was calculated by the 50% tissue culture infected dose (TCID₅₀) with the Reed and Muench method. The cytotoxicity assay of LiCl was performed by the CCK8 kit. The expression level of viral mRNA was measured by RT‐qPCR. The results revealed LiCl can inhibit FMDV replication, but it cannot affect FMDV attachment stage and entry stage in the course of FMDV life cycle. Further studies confirmed that the LiCl affect the replication stage of FMDV, especially the early stages of FMDV replication. So LiCl has potential as an effective anti‐FMDV drug. Therefore, LiCl may be an effective drug for the control of FMDV. Based on that, the mechanism of the antiviral effect of LiCl on FMDV infection is need to in‐depth research in vivo.

Inhibition of glycogen synthase kinase-3 by BTA-EG4 reduces tau abnormalities in an organotypic brain slice culture model of Alzheimer's disease

Organotypic brain slice culture models provide an alternative to early stage in vivo studies as an integrated tissue system that can recapitulate key disease features, thereby providing an excellent platform for drug screening. We recently described a novel organotypic 3xTg-AD mouse brain slice culture model with key Alzheimer’s disease-like changes. We now highlight the potential of this model for testing disease-modifying agents and show that results obtained following in vivo treatment are replicated in brain slice cultures from 3xTg-AD mice. Moreover, we describe novel effects of the amyloid-binding tetra (ethylene glycol) derivative of benzothiazole aniline, BTA-EG₄, on tau. BTA-EG₄ significantly reduced tau phosphorylation in the absence of any changes in the amounts of amyloid precursor protein, amyloid-β or synaptic proteins. The reduction in tau phosphorylation was associated with inactivation of the Alzheimer’s disease-relevant major tau kinase, GSK-3. These findings highlight the utility of 3xTg-AD brain slice cultures as a rapid and reliable in vitro method for drug screening prior to in vivo testing. Furthermore, we demonstrate novel tau-directed effects of BTA-EG₄ that are likely related to the ability of this agent to inactivate GSK-3. Our findings support the further exploration of BTA-EG₄ as a candidate therapeutic for Alzheimer’s disease.

Lithium suppression of tau induces brain iron accumulation and neurodegeneration

Lithium is a first-line therapy for bipolar affective disorder. However, various adverse effects, including a Parkinson-like hand tremor, often limit its use. The understanding of the neurobiological basis of these side effects is still very limited. Nigral iron elevation is also a feature of Parkinsonian degeneration that may be related to soluble tau reduction. We found that magnetic resonance imaging T₂ relaxation time changes in subjects commenced on lithium therapy were consistent with iron elevation. In mice, lithium treatment lowers brain tau levels and increases nigral and cortical iron elevation that is closely associated with neurodegeneration, cognitive loss and parkinsonian features. In neuronal cultures lithium attenuates iron efflux by lowering tau protein that traffics amyloid precursor protein to facilitate iron efflux. Thus, tau- and amyloid protein precursor-knockout mice were protected against lithium-induced iron elevation and neurotoxicity. These findings challenge the appropriateness of lithium as a potential treatment for disorders where brain iron is elevated (for example, Alzheimer's disease), and may explain lithium-associated motor symptoms in susceptible patients.

The Tyr216 phosphorylated form of GSK3β contributes to tau phosphorylation at PHF-1 epitope in response to Aβ in the nucleus of SH-SY5Y cells

AIMS

GSK3β activation in Aβ conditions leading to tau phosphorylation at pathological sites is a well-known phenomenon. However, the serine/tyrosine phosphorylation processes implied in Aβ-induced GSK3β activation and responsible for tau phosphorylation, especially at the GSK3β specific Ser396/Ser404 (PHF-1) site, are still debated.

MAIN METHODS

Experiments were performed on SH-SY5Y cells exposed to 20μM Aβ1-42 in a time ranging from 5min to 8h. The phophorylated forms (Ser9 and Tyr216) of GSK3β and pTau at PHF-1 epitope were measured by immunoblotting in nuclear extracts.

KEY FINDINGS

We showed a superimposable time-dependent increase of nuclear pGSK3βTyr216 and nuclear pTau at PHF-1 site, both reaching their maximal level after 8h of Aβ1-42 exposure. In addition, nuclear accumulation of pTau is accompanied by its cytoplasmic decrease suggesting that pTau is translocated in response to Aβ treatment. Besides, our experiments showed that specific pGSK3βTyr216 inhibition is required to drop nuclear pTau, ensuring the involvement of Tyr216 phosphorylation in Aβ-mediated tau phosphorylation at PHF-1 epitope.

SIGNIFICANCE

These data suggested that in response to Aβ exposure in SH-SY5Y cells, GSK3β activation is performed through Tyr216 phosphorylation and resulted in tau phosphorylation at PHF-1 epitope and in its translocation.

Animal models of bipolar mania: The past, present and future

Bipolar disorder (BD) is the sixth leading cause of disability in the world according to the World Health Organization and affects nearly six million (∼2.5% of the population) adults in the United State alone each year. BD is primarily characterized by mood cycling of depressive (e.g., helplessness, reduced energy and activity, and anhedonia) and manic (e.g., increased energy and hyperactivity, reduced need for sleep, impulsivity, reduced anxiety and depression), episodes. The following review describes several animal models of bipolar mania with a focus on more recent findings using genetically modified mice, including several with the potential of investigating the mechanisms underlying 'mood' cycling (or behavioral switching in rodents). We discuss whether each of these models satisfy criteria of validity (i.e., face, predictive, and construct), while highlighting their strengths and limitations. Animal models are helping to address critical questions related to pathophysiology of bipolar mania, in an effort to more clearly define necessary targets of first-line medications, lithium and valproic acid, and to discover novel mechanisms with the hope of developing more effective therapeutics. Future studies will leverage new technologies and strategies for integrating animal and human data to reveal important insights into the etiology, pathophysiology, and treatment of BD.

Inositol depletion, GSK3 inhibition and bipolar disorder

Valproic acid and lithium are widely used to treat bipolar disorder, a severe illness characterized by cycles of mania and depression. However, their efficacy is limited, and treatment is often accompanied by serious side effects. The therapeutic mechanisms of these drugs are not understood, hampering the development of more effective treatments. Among the plethora of biochemical effects of the drugs, those that are common to both may be more related to therapeutic efficacy. Two common outcomes include inositol depletion and GSK3 inhibition, which have been proposed to explain the efficacy of both valproic acid and lithium. Here, we discuss the inositol depletion and GSK3 inhibition hypotheses, and introduce a unified model suggesting that inositol depletion and GSK3 inhibition are inter-related.

A Simple Model to Study Tau Pathology

Tau proteins play a role in the stabilization of microtubules, but in pathological conditions, tauopathies, tau is modified by phosphorylation and can aggregate into aberrant aggregates. These aggregates could be toxic to cells, and different cell models have been used to test for compounds that might prevent these tau modifications. Here, we have used a cell model involving the overexpression of human tau in human embryonic kidney 293 cells. In human embryonic kidney 293 cells expressing tau in a stable manner, we have been able to replicate the phosphorylation of intracellular tau. This intracellular tau increases its own level of phosphorylation and aggregates, likely due to the regulatory effect of some growth factors on specific tau kinases such as GSK3. In these conditions, a change in secreted tau was observed. Reversal of phosphorylation and aggregation of tau was found by the use of lithium, a GSK3 inhibitor. Thus, we propose this as a simple cell model to study tau pathology in nonneuronal cells due to their viability and ease to work with.

Novel antiviral effect of lithium chloride on mammalian orthoreoviruses in vitro

Reovirus not only causes considerable economic loss in the swine industry of the United States and other countries, but also threatens the public health due to its zoonotic potential. According to previous reports, LiCl has antiviral activity against a number of viruses. The inhibitory effects of LiCl on reovirus life cycle in Vero cells were evaluated. The unpaired t-test and one-way ANOVA were used to analyze the differences between experimental groups. We first found that LiCl treatment significantly inhibited reovirus replication in a dose-dependent manner. Furthermore, we found that this antiviral activity of LiCl targets the early stage of viral replication. LiCl could be a potential drug against reovirus infection.

Lithium in Medicine: Mechanisms of Action

In this chapter, we review the mechanism of action of lithium salts from a chemical perspective. A description on how lithium salts are used to treat mental illnesses, in particular bipolar disorder, and other disease states is provided. Emphasis is not placed on the genetics and the psychopharmacology of the ailments for which lithium salts have proven to be beneficial. Rather we highlight the application of chemical methodologies for the characterization of the cellular targets of lithium salts and their distribution in tissues.

Glycation alter the process of Tau phosphorylation to change Tau isoforms aggregation property

The risk of tauopathies depends in part on the levels and modified composition of six Tau isoforms in the human brain. Abnormal phosphorylation of the Tau protein and the shift of the ratio of 3R Tau to 4R Tau are presumed to result in neurofibrillary pathology and neurodegeneration. Glycation has recently been linked to dementia and metabolic syndrome. To determine the contribution of Tau protein glycation and phosphorylation on Tau aggregation propensity, the assembled kinetics were examined in vitro using Thioflavin T fluorescence assays. We found that glycation and phosphorylation have different effects on aggregation propensity in different Tau isoforms. Different Tau proteins play important parts in each tauopathies, but 3R0N, fetal Tau protein, has no effect on tauopathies. Conversely, 4R2N has more modified sites and a higher tendency to aggregate, playing the most important role in 4R tauopathies. Finally, Glycation, which could modulate Tau phosphorylation, may occur before any other modification. It also regulates the 3R to 4R ratio and promotes 4R2N Tau protein aggregation. Decreasing the sites of glycation, as well as shifting other Tau proteins to 3R0N Tau proteins has potential therapeutic implications for tauopathies.

Potential application of lithium in Parkinson's and other neurodegenerative diseases

Lithium, the long-standing hallmark treatment for bipolar disorder, has recently been identified as a potential neuroprotective agent in neurodegeneration. Here we focus on introducing numerous in vitro and in vivo studies that have shown lithium treatment to be efficacious in reducing oxidative stress and inflammation, increasing autophagy, inhibiting apoptosis, and decreasing the accumulation of α-synulcein, with an emphasis on Parkinson's disease. A number of biological pathways have been shown to be involved in causing these neuroprotective effects. The inhibition of GSK-3β has been the mechanism most studied; however, other modes of action include the regulation of apoptotic proteins and glutamate excitotoxicity as well as down-regulation of calpain. This review provides a framework of the neuroprotective effects of lithium in neurodegenerative diseases and the putative mechanisms by which lithium provides the protection. Lithium-only treatment may not be a suitable therapeutic option for neurodegenerative diseases due to inconsistent efficacy and potential side-effects, however, the use of low dose lithium in combination with other potential or existing therapeutic compounds may be a promising approach to reduce symptoms and disease progression in neurodegenerative diseases.

Valproic Acid Modifies Synaptic Structure and Accelerates Neurite Outgrowth Via the Glycogen Synthase Kinase-3β Signaling Pathway in an Alzheimer's Disease Model

AIM

Tau hyperphosphorylation and amyloid β-peptide overproduction, caused by altered localization or abnormal activation of glycogen synthase kinase-3β (GSK-3β), is a pathogenic mechanism in Alzheimer's disease (AD). Valproic acid (VPA) attenuates senile plaques and neuronal loss. Here, we confirmed that VPA treatment improved spatial memory in amyloid precursor protein (APP)/presenilin 1 (PS 1) double-transgenic mice and investigated the effect of VPA on synaptic structure and neurite outgrowth.

METHODS

We used ultrastructural analysis, immunocytochemistry, immunofluorescence staining, and Western blot analysis to assess the effect of VPA treatment in mice.

RESULTS

VPA treatment thickened the postsynaptic density, increased the number of presynaptic vesicles, and upregulated the expression of synaptic markers PSD-95 and GAP43. VPA increased neurite length of hippocampal neurons in vivo and in vitro. In VPA-treated AD mouse brain, inactivated GSK-3β (pSer9-GSK-3β) was markedly increased, while hyperphosphorylation of tau at Ser396 and Ser262 was decreased; total tau levels remained similar. VPA treatment notably improved pSer133-cAMP response element-binding protein (CREB) and brain-derived neurotrophic factor (BDNF) levels, which are associated with synaptic function and neurite outgrowth.

CONCLUSION

VPA improves behavioral deficits in AD, modifies synaptic structure, and accelerates neurite outgrowth, by inhibiting the activity of GSK-3β, decreasing hyperphosphorylated tau, enhancing CREB and BDNF expression.

Antiviral effect of lithium chloride on infection of cells by canine parvovirus

Canine parvovirus type 2 causes significant viral disease in dogs, with high morbidity, high infectivity, and high mortality. Lithium chloride is a potential antiviral drug for viruses. We determined the antiviral effect of Lithium Chloride on canine parvovirus type 2 in feline kidney cells. The viral DNA and proteins of canine parvovirus were suppressed in a dose-dependent manner by lithium chloride. Further investigation verified that viral entry into cells was inhibited in a dose-dependent manner by lithium chloride. These results indicated that lithium chloride could be a potential antiviral drug for curing dogs with canine parvovirus infection. The specific steps of canine parvovirus entry into cells that are affected by lithium chloride and its antiviral effect in vivo should be explored in future studies.

Antiviral effect of lithium chloride on infection of cells by porcine parvovirus

Porcine parvovirus (PPV) causes reproductive failure in pigs, which leads to economic losses to the industry. As reported previously, LiCl efficiently impairs the replication of a variety of viruses, including the coronavirus infectious bronchitis virus (IBV), transmissible gastroenteritis virus (TGEV), and pseudorabies herpesvirus. We demonstrate for the first time that inhibition of PPV replication in swine testis (ST) cells by LiCl is dose-dependent, and that the antiviral effect of LiCl occurred in the early phase of PPV replication. These results indicate that LiCl might be an effective anti-PPV drug to control PPV disease. Further studies are required to explore the mechanism of the antiviral effect of LiCl on PPV infection in vivo.

Lithium prevents parkinsonian behavioral and striatal phenotypes in an aged parkin mutant transgenic mouse model

Lithium has long been used as a treatment for the psychiatric disease bipolar disorder. However, previous studies suggest that lithium provides neuroprotective effects in neurodegenerative diseases such as Parkinson's disease (PD) and Alzheimer's disease. The exact mechanism by which lithium exerts these effects still remains unclear. In the present study, we evaluated the effects of low-dose lithium treatment in an aged mouse model expressing a parkin mutation within dopaminergic neurons. We found that low-dose lithium treatment prevented motor impairment as demonstrated by the open field test, pole test, and rearing behavior. Furthermore, lithium prevented dopaminergic striatal degeneration in parkin animals. We also found that parkin-induced striatal astrogliosis and microglial activation were prevented by lithium treatment. Our results further corroborate the use of this parkin mutant transgenic mouse line as a model for PD for testing novel therapeutics. The findings of the present study also provide further validation that lithium could be re-purposed as a therapy for PD and suggest that anti-inflammatory effects may contribute to its neuroprotective mechanisms.