A recent case study reported a PSEN2 mutation carrier with high amyloid burden but unexpectedly restricted tau pathology and preserved cognition. While genetic and proteomic factors were explored, the patient's lifelong occupational heat exposure may represent an overlooked contributor to resilience. We highlight evidence from preclinical, clinical, and epidemiological studies suggesting that elevated body temperature promotes tau clearance via enhanced proteostasis. This observation invites deeper investigation into thermoregulation as a modifiable factor in tau homeostasis and Alzheimer's disease vulnerability, with implications for both biomarker interpretation and therapeutic strategies targeting tau-mediated neurodegeneration.

Background : Alzheimer’s disease (AD) is an age-related brain disorder associated with metabolic and thermoregulatory deficits. Here, we tested whether enhancing thermogenesis through pharmacological stimulation of brown adipose tissue (BAT) with a β3-adrenergic receptor (β3-AR) agonist can protect against cold-induced tau phosphorylation in a mouse model of AD neuropathology. Methods: A b3-AR agonist (CL-316,243) was administered to old (18 months), male 3xTg-AD and NonTg mice for 4 weeks at a dose of 1 mg.kg -1 .day -1 i.p. Mice were then subjected to an acute cold exposure (4°C) during 24h, to enhance tau hyperphosphorylation. A group of saline-treated mice was kept at room temperature (22°C) as controls. Results: Chronic administration of b3-AR agonist induced weight loss, improved peripheral glucose and insulin metabolism, enhanced thermogenesis and modulated FGF21 in both NonTg and 3xTg-AD mice. While b3-AR agonist treatment slightly decreased the ratio of soluble Ab42/Ab40 in the cortex, it almost completely blunted the cold-induced soluble tau hyperphosphorylation (pTau) in the hippocampus of 3xTg-AD mice. Acute cold exposure also led to the detection of pTau-217 in the plasma, which was attenuated by β3-AR stimulation. Conclusions: Our results indicate that BAT stimulation through pharmacological activation of b3-AR protected against cold-induced tau hyperphosphorylation and attenuated Ab pathology in 18-month-old 3xTg-AD mice. Treatment with a b3-AR agonist could represent a therapeutic strategy in AD by counteracting both metabolic deficits and neuropathology.

Background and Purpose: Exposure to chronic stress and high levels of glucocorticoid hormones in adulthood has been associated with cognitive deficits and increased risk of Alzheimer's disease (AD). Dazucorilant has recently emerged as a selective glucocorticoid receptor (NR3C1) modulator, exhibiting efficacy in counteracting amyloid-beta toxicity in an acute model of AD. We aim to assess the therapeutic potential of dazucorilant in reversing amyloid and tau pathologies through the inhibition of glucocorticoid receptor pathological activity, and providing additional evidence for its consideration in AD treatment. Experimental Approach: The efficacy of dazucorilant was evaluated in two transgenic mouse models of amyloid pathology. The slowly progressing J20 and the aggressively pathological 5xFAD mice. Behavioural analysis was conducted to evaluate welfare, cognitive performances and anxiety levels. The activity of the glucocorticoid receptor system, neuroinflammation, amyloid burden and tau phosphorylation were examined in hippocampi. Key Results: In both AD models, chronic treatment with dazucorilant improved working and long-term spatial memories along with the inhibition of glucocorticoid receptor-dependent pathogenic processes and the normalization of plasma glucocorticoid levels. Dazucorilant treatment also resulted in a reduction in tau hyperphosphorylation and amyloid production and aggregation. Additionally, dazucorilant seemed to mediate a specific re-localization of activated glial cells onto amyloid plaques in J20 mice, suggesting a restoration of physiological neuroinflammatory processes. Conclusion and Implications: Dazucorilant exhibited sustained disease-modifying effects in two AD models. Given that this compound has demonstrated safety and tolerability in human subjects, our results provide pre-clinical support for conducting clinical trials to evaluate its potential in AD.

RyR1-related myopathies (RyR1-RMs) include a wide range of genetic disorders that result from mutations in the RYR1 gene. Pathogenic variants lead to defective intracellular calcium homeostasis and muscle dysfunction. Fixing intracellular calcium leaks by stabilizing the RyR1 calcium channel has been identified as a promising therapeutic target. Gene therapy via prime editing also holds great promise as it can cure diseases by correcting genetic mutations. However, as more than 700 variants have been identified in the RYR1 gene, a universal treatment would be a more suitable solution for patients. Our investigation into the RyR1-S2843A mutation has yielded promising results. Using a calcium leak assay, we determined that the S2843A mutation was protective when combined with pathogenic mutations and significantly reduced the Ca2+ leak of the RyR1 channel. Our study demonstrated that prime editing can efficiently introduce the protective S2843A mutation. In vitro experiments using the RNA electroporation of the prime editing components in human myoblasts achieved a 31% introduction of this mutation. This article lays the foundation for a new therapeutic approach for RyR1-RM, where a unique once-in-a-lifetime prime editing treatment could potentially be universally applied to all patients with a leaky RyR1 channel.

Aggregates of hyperphosphorylated tau protein are a hallmark of Alzheimer's disease (AD) and other tauopathies. Sleep disturbances—common in AD—have been associated with altered tau phosphorylation and secretion in both animal models and humans, and insufficient sleep is recognized as a potential risk factor for AD. Moreover, sleep deprivation affects mRNA splicing, polyadenylation, and miRNA-mediated degradation. However, how tau phosphorylation, secretion, and splicing are physiologically regulated across the sleep–wake cycle remains unknown. Here, we combine in vitro, in vivo and clinical methods to investigate whether tau phosphorylation, secretion and splicing are governed by circadian rhythms linked to sleep and body temperature (BT). To elucidate underlying mechanisms, we exposed neuronal cells to the physiological temperatures observed under each condition. We found that tau phosphorylation undergoes sleep-driven circadian variations, as it is hyperphosphorylated during sleep, when BT is lower. Similar changes in tau phosphorylation were reproduced in neuronal cells exposed to temperatures recorded during the sleep–wake cycle. In addition, we reveal a novel pathway by which BT modulates tau secretion, with higher temperature increasing extracellular and circulating tau levels. Tau splicing also varied with temperature, as lower temperatures favored exon 10 exclusion. Finally, in humans, the increase in CSF tau levels observed post-wakefulness correlated with BT increase during wakefulness. Overall, these findings demonstrate that tau phosphorylation, secretion, and splicing follow a circadian pattern primarily regulated by BT and sleep. Given the prevalence of sleep disruptions and thermoregulatory deficits in AD, this study offers new insight into how tau pathology may develop and spread.

This scientific commentary refers to ‘Proteostasis as a fundamental principle of Tau immunotherapy’ by Cruz et al. (https://doi.org/10.1093/brain/awae254).

Sleep disturbance is bidirectionally associated with an increased risk of Alzheimer's disease and other tauopathies. While the sleep-wake cycle regulates interstitial and cerebrospinal fluid (CSF) tau levels, the underlying mechanisms remain unknown. Understanding these mechanisms is crucial, given the evidence that tau pathology spreads through neuron-to-neuron transfer, involving the secretion and internalization of pathological tau forms. Here, we combined in vitro, in vivo, and clinical methods to reveal a pathway by which changes in body temperature (BT) over the sleep-wake cycle modulate extracellular tau levels. In mice, a higher BT during wakefulness and sleep deprivation increased CSF and plasma tau levels, while also upregulating unconventional protein secretion pathway I (UPS-I) events including (a) intracellular tau dephosphorylation, (b) caspase 3-mediated cleavage of tau (TauC3), and (c) membrane translocation of tau through binding to phosphatidylinositol 4,5-bisphosphate (PIP2) and syndecan 3. In humans, the increase in CSF and plasma tau levels observed after wakefulness correlated with BT increases during wakefulness. By demonstrating that sleep-wake variation in BT regulates extracellular tau levels, our findings highlight the importance of thermoregulation in linking sleep disturbances to tau-mediated neurodegeneration and the preventative potential of thermal interventions.

Phosphorylation of Tau is a key post-translational modification implicated in tauopathies, such as Alzheimer’s disease (AD), leading to microtubule dysfunction and Tau aggregation. Recent preclinical evidence suggests that deletion or pharmacological inhibition of the adenosine A2A receptor improves outcomes in both amyloid and Tau models. We recently developed a novel fluorinated derivative of the approved A2A receptor antagonist, Istradefylline (approved for Parkinson’s disease), named MB204, for potential use in AD and depression. Here, we investigate the acute effects of oral MB204 on Tau phosphorylation in a non-transgenic mouse model of Tau hyperphosphorylation. Eight-week-old CD-1 male mice (n=6 per group) were dosed with MB204 (2.5 mg/kg, p.o.) or the positive control lithium chloride (LiCl, 25.6 mg/kg, i.p.) daily for three days. One hour after the final dose, general anesthesia (1.3% isoflurane) was administered to lower body temperature and induce Tau hyperphosphorylation, as described previously. Brain tissue was collected 3 hours after anesthesia administration for quantitative western blot analysis targeting multiple Tau phosphorylation epitopes. Multiple Tau epitopes were studied. In the cortex : reductions were seen in the phosphorylation at AT270, AT8 were seen in both MB204 and Li treatment (both p<0.001). A reduction was only seen with MB204 for pT205 (p<0.001) and only seen with lithium for the pS409 epitope (p<0.001). In the hippocampus : reductions were seen in the phosphorylation at pS40K were seen in both MB204 and Li treatment (both p<0.05 and 0.001 respectively). A reduction was only seen with MB204 for the AT8 epitope (p<0.05) and only seen for lithium for the AT270 and pT205 epitope (p<0.01 and 0.001) Acute oral treatment of mice with MB204 reduced anesthesia induced Tau hyperphosphorylation at key clinically relevant Tau epitopes. These findings highlight MB204 potential as a therapeutic agent for AD and related tauopathies.

Alzheimer's disease (AD) is a multifactorial neurodegenerative disease with a complex origin, thought to involve a combination of genetic, biological and environmental factors. Insulin dysfunction has emerged as a potential factor contributing to AD pathogenesis, particularly in individuals with diabetes, and among those with insulin deficiency or undergoing insulin therapy. The intraperitoneal administration of streptozotocin (STZ) is widely used in rodent models to explore the impact of insulin deficiency on AD pathology, although prior research predominantly focused on young animals, with no comparative analysis across different age groups. Our study aimed to fill this gap by analyzing the impact of insulin dysfunction in 7 and 23 months 3xTg-AD mice, that exhibit both amyloid and tau pathologies. Our objective was to elucidate the age-specific consequences of insulin deficiency on AD pathology. STZ administration led to insulin deficiency in the younger mice, resulting in an increase in cortical amyloid-β (Aβ) and tau aggregation, while tau phosphorylation was not significantly affected. Conversely, older mice displayed an unexpected resilience to the peripheral metabolic impact of STZ, while exhibiting an increase in both tau phosphorylation and aggregation without significantly affecting amyloid pathology. These changes were paralleled with alterations in signaling pathways involving tau kinases and phosphatases. Several markers of blood-brain barrier (BBB) integrity declined with age in 3xTg-AD mice, which might have facilitated a direct neurotoxic effect of STZ in older mice. Overall, our research confirms the influence of insulin signaling dysfunction on AD pathology, but also advises careful interpretation of data related to STZ-induced effects in older animals.

Huntington’s disease (HD) is a rare genetic neurodegenerative disorder caused by an expansion of CAG repeats in the Huntingtin (HTT) gene. One hypothesis suggests that the mutant HTT gene contributes to HD neuropathology through transcriptional dysregulation involving microRNAs (miRNAs). In particular, the miR-132/212 cluster is strongly diminished in the HD brain. This study explores the effects of miR-132/212 deficiency specifically in adult HD zQ175 mice. The absence of miR-132/212 did not impact body weight, body temperature, or survival rates. Surprisingly, miR-132/212 loss seemed to alleviate, in part, the effects on endogenous Htt expression, HTT inclusions, and neuronal integrity in HD zQ175 mice. Additionally, miR-132/212 depletion led to age-dependent improvements in certain motor functions. Transcriptomic analysis revealed alterations in HD-related networks in WT- and HD zQ175-miR-132/212-deficient mice, including significant overlap in BDNF and Creb1 signaling pathways. Interestingly, however, a higher number of miR-132/212 gene targets was observed in HD zQ175 mice lacking the miR-132/212 cluster, especially in the striatum. These findings suggest a nuanced interplay between miR-132/212 expression and HD pathogenesis, providing potential insights into therapeutic interventions. Further investigation is needed to fully understand the underlying mechanisms and therapeutic potential of modulating miR-132/212 expression during HD progression.

The sleep-wake cycle regulates interstitial fluid and cerebrospinal fluid (CSF) tau levels in both mouse and human by mechanisms that remain unestablished. Here, we reveal a novel pathway by which wakefulness increases extracellular tau levels in mouse and humans. In mice, higher body temperature (BT) associated with wakefulness and sleep deprivation increased CSF tau. In vitro, wakefulness temperatures upregulated tau secretion via a temperature-dependent increase in activity and expression of unconventional protein secretion pathway-1 components, namely caspase-3-mediated C-terminal cleavage of tau (TauC3), and membrane expression of PIP2 and syndecan-3. In humans, the increase in both CSF and plasma tau levels observed post-wakefulness correlated with BT increase during wakefulness. Our findings suggest sleep-wake variation in BT may contribute to regulating extracellular tau levels, highlighting the importance of thermoregulation in pathways linking sleep disturbance to neurodegeneration, and the potential for thermal intervention to prevent or delay tau-mediated neurodegeneration.

Tau is a microtubule-associated protein enriched in the axonal compartment. Its most well-known function is to bind and stabilize microtubules. In Alzheimer's disease and other neurodegenerative diseases known as tauopathies, tau undergoes several abnormal post-translational modifications including hyperphosphorylation, conformational changes, oligomerization, and aggregation. Numerous mouse models of tauopathies have been developed, and Western blotting remains an invaluable tool in studying tau protein physiological and pathological changes in these models. However, many of the antibodies that have been developed to analyze tau post-translational modifications are mouse monoclonal, which are at risk of producing artifactual signals in Western blotting procedures. This risk does not arise due to their lack of specificity, but rather because the secondary antibodies used to detect them will also react with the heavy chain of endogenous mouse immunoglobulins (Igs), leading to a non-specific signal at the same molecular weight as tau protein (around 50 kDa). Here, we present the use of anti-light-chain secondary antibodies as a simple and efficient technique to prevent non-specific Ig signals around 50 kDa. We demonstrate the efficacy of this method by either eliminating or identifying artifactual signals when using monoclonal antibodies directed at non-phosphorylated epitopes (T49, Tau3R, Tau4R), phosphorylated epitopes (MC6, AT180, CP13), or an abnormal tau conformation (MC1), in wild-type (WT) mice with tau hyperphosphorylation (hypothermic), transgenic mice overexpressing human tau (hTau mice), and tau knockout (TKO) mice.

The intracellular accumulation of microtubule-associated protein tau is a characteristic feature of tauopathies, a group of neurodegenerative diseases including Alzheimer's disease. Formation of insoluble tau aggregates is initiated by the abnormal hyperphosphorylation and oligomerization of tau. Over the past decades, multiple transgenic rodent models mimicking tauopathies have been develop, showcasing this neuropathological hallmark. The biochemical analysis of insoluble tau in these models has served as a valuable tool to understand the progression of tau-related pathology. In this chapter, we provide a comprehensive review of the two primary methods for isolating insoluble tau, namely, sarkosyl and formic acid extraction (and their variants), which are employed for biochemical analysis in transgenic mouse models of tauopathy. We also analyze the strengths and limitations of these methods.

disease (HD) is an inherited neurodegenerative disorder caused by an expansion of CAG repeats in the Huntingtin (HTT) gene. Accumulating evidence suggests that the microtubule-associated tau pro-tein participates in the pathogenesis of HD. Recently, we have identified changes in tau alternative splicing of exons 2, 3 and 10 in the putamen of HD patients (St-Amour et al, 2018). In this study, we sought to determine whether tau mis-splicing events were equally observed in other brain regions that are less prone to neurodegen-eration. Using Western blot and PCR, we characterized the relationship between MAPT splicing of exons 2, 3 and 10, tauopathy and Htt pathologies, as well as neurodegeneration markers in matching putamen and cortical sam -ples from HD (N = 48) and healthy control (N = 25) subjects. We first show that levels of 4R-tau (exon 10 inclu-sion) isoforms are higher in both the putamen and the cortex of individuals with HD, consistent with earlier findings. On the other hand, higher 0N-tau (exclusion of exons 2 and 3) and lower 1N-tau (exclusion of exon 3) isoforms were seen exclusively in the putamen of HD individuals. Interestingly, investigated splicing factors were deregulated in both regions whereas exon 2 differences coincided with increased tau hyperphosphorylation, aggregation and markers of neurodegeneration. Overall, these results imply a differential regulation of tau exon 2 and exon 10 alternative splicing in HD putamen that could provide a useful biomarker or therapeutic target. This article is part of a Special Issue entitled: SI: The Molecular Bases of Tauopathies. (c) 2022 IBRO. Published by Elsevier Ltd. All rights reserved.

Propagation of hyperphosphorylated and aggregated tau protein is a hallmark of Alzheimer’s disease (AD). Previously, we demonstrated that tau phosphorylation is inversely correlated with body temperature (BT) variations during the sleep/wake cycle. Tau is hyperphosphorylated during sleep (when BT is lower), compared to wakefulness (when BT is higher). Interestingly, it has been shown that tau in ISF and CSF is increased during wakefulness, suggesting increased secretion. We thus hypothesized that tau secretion might be regulated by BT during the sleep/wake cycle.

In preclinical research on Alzheimer's disease and related tauopathies, tau phosphorylation analysis is routinely employed in both cellular and animal models. However, recognizing the sensitivity of tau phosphorylation to various extrinsic factors, notably temperature, is vital for experimental accuracy. Hypothermia can trigger tau hyperphosphorylation, while hyperthermia leads to its dephosphorylation. Nevertheless, the rapidity of tau phosphorylation in response to unintentional temperature variations remains unknown. In cell cultures, the most significant temperature change occurs when the cells are removed from the incubator before harvesting, and in animal models, during anesthesia prior to euthanasia. In this study, we investigate the kinetics of tau phosphorylation in N2a and SH-SY5Y neuronal cell lines, as well as in mice exposed to anesthesia. We observed changes in tau phosphorylation within the few seconds upon transferring cell cultures from their 37°C incubator to room temperature conditions. However, cells placed directly on ice post-incubation exhibited negligible phosphorylation changes. In vivo, isoflurane anesthesia rapidly resulted in tau hyperphosphorylation within the few seconds needed to lose the pedal withdrawal reflex in mice. These findings emphasize the critical importance of preventing temperature variation in researches focused on tau. To ensure accurate results, we recommend avoiding anesthesia before euthanasia and promptly placing cells on ice after removal from the incubator. By controlling temperature fluctuations, the reliability and validity of tau phosphorylation studies can be significantly enhanced.

Huntington's disease is classically described as a neurodegenerative disorder of monogenic aetiology. The disease is characterized by an abnormal polyglutamine expansion in the huntingtin gene, which drives the toxicity of the mutated form of the protein. However, accumulation of the microtubule-associated protein tau, which is involved in a number of neurological disorders, has also been observed in patients with Huntington's disease. In order to unravel the contribution of tau hyperphosphorylation to hallmark features of Huntington's disease, we administered weekly intraperitoneal injections of the anti-tau pS202 CP13 monoclonal antibody to zQ175 mice and characterized the resulting behavioral and biochemical changes. After 12 weeks of treatment, motor impairments, cognitive performance and general health were improved in zQ175 mice along with a significant reduction in hippocampal pS202 tau levels. Despite the lack of effect of CP13 on neuronal markers associated with Huntington's disease pathology, tau-targeting enzymes and gliosis, CP13 was shown to directly impact mutant huntingtin aggregation such that brain levels of amyloid fibrils and huntingtin oligomers were decreased, while larger huntingtin protein aggregates were increased. Investigation of CP13 treatment of Huntington's disease patient-derived induced pluripotent stem cells (iPSCs) revealed a reduction in pS202 levels in differentiated cortical neurons and a rescue of neurite length. Collectively, these findings suggest that attenuating tau pathology could mitigate behavioral and molecular hallmarks associated with Huntington's disease.

Polyunsaturated fatty acids (PUFAs) are a class of fatty acids that are closely associated with the development and function of the brain. The most abundant PUFA is docosahexaenoic acid (DHA, 22:6 n-3). In humans, low plasmatic concentrations of DHA have been associated with impaired cognitive function, low hippocampal volumes, and increased amyloid deposition in the brain. Several studies have reported reduced brain DHA concentrations in Alzheimer’s disease (AD) patients’ brains. Although a number of epidemiological studies suggest that dietary DHA consumption may protect the elderly from developing cognitive impairment or dementia including AD, several review articles report an inconclusive association between omega-3 PUFAs intake and cognitive decline. The source of these inconsistencies might be because DHA is highly oxidizable and its accessibility to the brain is limited by the blood–brain barrier. Thus, there is a pressing need for new strategies to improve DHA brain supply. In the present study, we show for the first time that the intranasal administration of nanovectorized DHA reduces Tau phosphorylation and restores cognitive functions in two complementary murine models of AD. These results pave the way for the development of a new approach to target the brain with DHA for the prevention or treatment of this devastating disease.

Although epilepsies and neurodegenerative disorders show pathophysiological similarities, their direct functional associations are unclear. Here, we tested the hypothesis that experimental seizures can induce tau hyperphosphorylation and amyloidogenic modifications over time, with intersections with neuroinflammation.

In Alzheimer’s disease (AD), hyper-phosphorylation and aggregation of tau correlates with clinical progression and represents a valid therapeutic target. A recent 20-year prospective study revealed an association between moderate to high frequency of Finnish sauna bathing and a lower incidence of dementia and AD, but the molecular mechanisms underlying these benefits remain uncertain. Here, we tested the hypothesis that sauna-like conditions could lower tau phosphorylation by increasing body temperature. We observed a decrease in tau phosphorylation in wild-type and hTau mice as well as in neuron-like cells when exposed to higher temperatures. These effects were correlated with specific changes in phosphatase and kinase activities, but not with inflammatory or heat-shock responses. We also used a drug strategy to promote thermogenesis. Topical application of menthol led to a sustained increase in body temperature in hTau mice concomitant with a significant decrease in tau phosphorylation. Our results suggest that sauna-like conditions or menthol treatment could lower tau pathology through mild hyperthermia, and may provide promising therapeutic strategies for AD and other tauopathies.