Transgenic Mouse Model Of Alzheimer's Disease Research Articles

Enhancing of cerebral Abeta clearance by modulation of ABC transporter expression: a review of experimental approaches.

Clearance of amyloid-beta (Aβ) from the brain is impaired in both early-onset and late-onset Alzheimer's disease (AD). Mechanisms for clearing cerebral Aβ include proteolytic degradation, antibody-mediated clearance, blood brain barrier and blood cerebrospinal fluid barrier efflux, glymphatic drainage, and perivascular drainage. ATP-binding cassette (ABC) transporters are membrane efflux pumps driven by ATP hydrolysis. Their functions include maintenance of brain homeostasis by removing toxic peptides and compounds, and transport of bioactive molecules including cholesterol. Some ABC transporters contribute to lowering of cerebral Aβ. Mechanisms suggested for ABC transporter-mediated lowering of brain Aβ, in addition to exporting of Aβ across the blood brain and blood cerebrospinal fluid barriers, include apolipoprotein E lipidation, microglial activation, decreased amyloidogenic processing of amyloid precursor protein, and restricting the entrance of Aβ into the brain. The ABC transporter superfamily in humans includes 49 proteins, eight of which have been suggested to reduce cerebral Aβ levels. This review discusses experimental approaches for increasing the expression of these ABC transporters, clinical applications of these approaches, changes in the expression and/or activity of these transporters in AD and transgenic mouse models of AD, and findings in the few clinical trials which have examined the effects of these approaches in patients with AD or mild cognitive impairment. The possibility that therapeutic upregulation of ABC transporters which promote clearance of cerebral Aβ may slow the clinical progression of AD merits further consideration.

Behavioral and Neuronal Characterizations, across Ages, of the TgSwDI Mouse Model of Alzheimer's Disease.

Alzheimer's disease (AD) is a neurodegenerative disorder that currently affects as many as 50 million people worldwide. It is neurochemically characterized by an aggregation of β-amyloid plaques and tau neurofibrillary tangles that result in neuronal dysfunction, cognitive decline, and a progressive loss of brain function. TgSwDI is a well-studied transgenic mouse model of AD, but no longitudinal studies have been performed to characterize cognitive deficits or β-amyloid plaque accumulation for use as a baseline reference in future research. Thus, we use behavioral tests (T-Maze, Novel Object Recognition (NOR), Novel Object Location (NOL)) to study long-term and working memory, and immunostaining to study β-amyloid plaque deposits, as well as brain size, in hippocampal, cerebellum, and cortical slices in TgSwDI and wild-type (WT) mice at 3, 5, 8, and 12 months old. The behavioral results show that TgSwDI mice exhibit deficits in their long-term spatial memory starting at 8 months old and in long-term recognition memory at all ages, but no deficits in their working memory. Immunohistochemistry showed an exponential increase in β-amyloid plaque in the hippocampus and cortex of TgSwDI mice over time, whereas there was no significant accumulation of plaque in WT mice at any age. Staining showed a smaller hippocampus and cerebellum starting at 8 months old for the TgSwDI compared to WT mice. Our data show how TgSwDI mice differ from WT mice in their baseline levels of cognitive function and β-amyloid plaque load throughout their lives.

Electrochemical Nanopipette Sensor for In Vitro/In Vivo Detection of Cu2+ Ions.

In vitro/in vivo detection of copper ions is a challenging task but one which is important in the development of new approaches to the diagnosis and treatment of cancer and hereditary diseases such as Alzheimer's, Wilson's, etc. In this paper, we present a nanopipette sensor capable of measuring Cu2+ ions with a linear range from 0.1 to 10 μM in vitro and in vivo. Using the gold-modified nanopipette sensor with a copper chelating ligand, we evaluated the accumulation ability of the liposomal form of an anticancer Cu-containing complex at three levels of biological organization. First, we detected Cu2+ ions in a single cell model of human breast adenocarcinoma MCF-7 and in murine melanoma B16 cells. The insertion of the nanoelectrode did not result in leakage of the cell membrane. We then evaluated the distribution of the Cu-complex in MCF-7 tumor spheroids and found that the diffusion-limited accumulation was a function of the depth, typical for 3D culture. Finally, we demonstrated the use of the sensor for Cu2+ ion detection in the brain of an APP/PS1 transgenic mouse model of Alzheimer's disease and tumor-bearing mice in response to injection (2 mg kg-1) of the liposomal form of the anticancer Cu-containing complex. Enhanced stability and selectivity, as well as distinct copper oxidation peaks, confirmed that the developed sensor is a promising tool for testing various types of biological systems. In summary, this research has demonstrated a minimally invasive electrochemical technique with high temporal resolution that can be used for the study of metabolism of copper or copper-based drugs in vitro and in vivo.

O-GlcNAc regulates the mitochondrial integrated stress response by regulating ATF4.

Accumulation of mitochondrial dysfunctional is a hallmark of age-related neurodegeneration including Alzheimer's disease (AD). Impairment of mitochondrial quality control mechanisms leading to the accumulation of damaged mitochondria and increasing neuronal stress. Therefore, investigating the basic mechanisms of how mitochondrial homeostasis is regulated is essential. Herein, we investigate the role of O-GlcNAcylation, a single sugar post-translational modification, in controlling mitochondrial stress-induced transcription factor Activating Transcription Factor 4 (ATF4). Mitochondrial dysfunction triggers the integrated stress response (ISRmt), in which the phosphorylation of eukaryotic translation initiation factor 2α results in the translation of ATF4. We used patient-derived induced pluripotent stem cells, a transgenic mouse model of AD, SH-SY5Y neuroblastoma and HeLa cell-lines to examine the effect of sustained O-GlcNAcase inhibition by Thiamet-G (TMG) on ISRmt using biochemical analyses. We show that TMG elevates ATF4 protein levels upon mitochondrial stress in SH-SY5Y neuroblastoma and HeLa cell-lines. An indirect downstream target of ATF4 mitochondrial chaperone glucose-regulated protein 75 (GRP75) is significantly elevated. Interestingly, knock-down of O-GlcNAc transferase (OGT), the enzyme that adds O-GlcNAc, in SH-SY5Y increases ATF4 protein and mRNA expression. Additionally, ATF4 target gene Activating Transcription Factor 5 (ATF5) is significantly elevated at both the protein and mRNA level. Brains isolated from TMG treated mice show elevated levels of ATF4 and GRP75. Importantly, ATF4 occupancy increases at the ATF5 promoter site in brains isolated from TMG treated mice suggesting that O-GlcNAc is regulating ATF4 targeted gene expression. Interestingly, ATF4 and GRP75 are not induced in TMG treated familial Alzheimer's Disease mice model. The same results are seen in a human in vitro model of AD. Together, these results indicate that in healthy conditions, O-GlcNAc regulates the ISRmt through regulating ATF4, while manipulating O-GlcNAc in AD has no effect on ISRmt.

Targeting SIK3 to modulate hippocampal synaptic plasticity and cognitive function by regulating the transcription of HDAC4 in a mouse model of Alzheimer's disease.

Cognitive deterioration and memory decline associated with the progression of Alzheimer's disease (AD) primarily results from synaptic failure. However, current understanding of the upstream regulatory mechanisms controlling synaptic plasticity remains limited. Salt-inducible kinase 3 (SIK3) is central to the signal pathway and is involved in neuronal regulation of sleep duration in mice. We speculated that the SIK3 cascade signaling pathway might contribute to the pathogenesis of AD. Thus, the present study employed AD transgenic mouse models, Morris Water Maze, virus-mediated gene transfer, electrophysiology, co-immunoprecipitation, western blotting, quantitative polymerase chain reaction, immunofluorescence, ChIP-qPCR, Golgi-Cox staining and dendritic spine analysis to investigate this connection. Our results revealed that SIK3 mRNA/protein expression was significantly reduced in middle-aged AD transgenic mouse models and AD patients. Conditional deletion of SIK3 gene in dorsal hippocampal neurons of 5×FAD mice further accelerated cognitive deterioration and impaired synaptic plasticity. In hippocampal neuronal cultures, SIK3 formed a complex with HDAC4, directly phosphorylated HDAC4 and regulated its nuclear cytoplasmic shuttle. Overexpression of SIK3 could facilitate the expression of synaptic plasticity-related genes by directly repressing mef2c or involving the recruitment of histone deacetylase to promoter regions of target genes through regulation of p-HDAC4, and vice versa. Moreover, up-regulation of SLP-S, the truncated fragment of SIK3, in dorsal hippocampal neurons, restored the synaptic plasticity and alleviates the cognitive impairment in 5×FAD mice. Collectively, these findings revealed a novel and important role of SIK3-HDAC4 regulation of synaptic plasticity and propose a new target for therapeutic approaches of cognitive deficits associated with AD.

A conformationally-locked p-hydroxybenzylidene imidazolinone derivative for detecting Aβ42 aggregation

Alzheimer’s disease (AD) is a common type of neurodegenerative disease, which can only be symptomatically relieved but does not yet have a cure. Among the different Aβ species, amyloid-β 42 (Aβ42) aggregates are proposed to be more neurotoxic than that of Aβ40, and oligomeric Aβ42 is thought to play a harmful role in the pathophysiology of AD. Therefore, the detection of Aβ42 aggregation is very meaningful in the AD field. We herein report a conformationally-locked p- hydroxybenzylidene imidazolinone derivative, BDI, which exhibits selectivity and specificity towards Aβ42 aggregation and remarkable fluorescent enhancement with a large Stokes shift (more than 100 nm). In the fluorescent co-localization study, BDI can sensitively detect a large population of Aβ42 aggregation over that of Aβ40 in the brain tissues of AD transgenic mouse models. Therefore, this new probe could provide a useful tool for the rapid detection of important Aβ species in AD.

In vivo three-dimensional brain imaging with chemiluminescence probes in Alzheimer's disease models.

Optical three-dimensional (3D) molecular imaging is highly desirable for providing precise distribution of the target-of-interest in disease models. However, such 3D imaging is still far from wide applications in biomedical research; 3D brain optical molecular imaging, in particular, has rarely been reported. In this report, we designed chemiluminescence probes with high quantum yields, relatively long emission wavelengths, and high signal-to-noise ratios to fulfill the requirements for 3D brain imaging in vivo. With assistance from density-function theory (DFT) computation, we designed ADLumin-Xs by locking up the rotation of the double bond via fusing the furan ring to the phenyl ring. Our results showed that ADLumin-5 had a high quantum yield of chemiluminescence and could bind to amyloid beta (Aβ). Remarkably, ADLumin-5's radiance intensity in brain areas could reach 4 × 107 photon/s/cm2/sr, which is probably 100-fold higher than most chemiluminescence probes for in vivo imaging. Because of its strong emission, we demonstrated that ADLumin-5 could be used for in vivo 3D brain imaging in transgenic mouse models of Alzheimer's disease.

Inhibiting tau-induced elevated nSMase2 activity and ceramides is therapeutic in an Alzheimer’s disease mouse model

BackgroundCognitive decline in Alzheimer’s disease (AD) is associated with hyperphosphorylated tau (pTau) propagation between neurons along synaptically connected networks, in part via extracellular vesicles (EVs). EV biogenesis is triggered by ceramide enrichment at the plasma membrane from neutral sphingomyelinase2 (nSMase2)-mediated cleavage of sphingomyelin. We report, for the first time, that human tau expression elevates brain ceramides and nSMase2 activity.MethodsTo determine the therapeutic benefit of inhibiting this elevation, we evaluated PDDC, the first potent, selective, orally bioavailable, and brain-penetrable nSMase2 inhibitor in the transgenic PS19 AD mouse model. Additionally, we directly evaluated the effect of PDDC on tau propagation in a mouse model where an adeno-associated virus (AAV) encoding P301L/S320F double mutant human tau was stereotaxically-injected unilaterally into the hippocampus. The contralateral transfer of the double mutant human tau to the dentate gyrus was monitored. We examined ceramide levels, histopathological changes, and pTau content within EVs isolated from the mouse plasma.ResultsSimilar to human AD, the PS19 mice exhibited increased brain ceramide levels and nSMase2 activity; both were completely normalized by PDDC treatment. The PS19 mice also exhibited elevated tau immunostaining, thinning of hippocampal neuronal cell layers, increased mossy fiber synaptophysin immunostaining, and glial activation, all of which were pathologic features of human AD. PDDC treatment reduced these changes. The plasma of PDDC-treated PS19 mice had reduced levels of neuronal- and microglial-derived EVs, the former carrying lower pTau levels, compared to untreated mice. In the tau propagation model, PDDC normalized the tau-induced increase in brain ceramides and significantly reduced the amount of tau propagation to the contralateral side.ConclusionsPDDC is a first-in-class therapeutic candidate that normalizes elevated brain ceramides and nSMase2 activity, leading to the slowing of tau spread in AD mice.

Aβ in the Lens of the Eye: A Noninvasively Detectable Early Biomarker of Alzheimer’s Disease β‐Amyloidopathy in Humans and Transgenic Mouse Model

AbstractBackgroundAmyloid‐ß (Aß) accumulation in brain is an early hallmark of Alzheimer’s disease (AD). We discovered Aß deposition, ß‐amyloidopathy, and colocalizing supranuclear cataracts (SNC) in lenses from people with AD (Goldstein LE et al., Lancet, 2003) and Down syndrome (DS; Moncaster JA et al., PLoS One, 2010), but not other neurodegenerative diseases or normal aging. These findings spurred development of an investigational drug‐device lens Aß eye scanner (Sapphire II, Cognoptix) that combines an Aß‐binding fluorescent ligand (Aftobetin) and specialized laser scanning ophthalmoscope for noninvasive measurement of lens Aß (FDA Breakthrough Device, 2021). Early clinical results indicate that lens Aß is an ideal biomarker for early AD detection. Here, we investigated Aß accumulation and amyloidopathy in lens and brain.MethodTg2576 transgenic (Tg+) mice express Swedish mutant human amyloid precursor protein (hAPP‐Swe), human Aß (hAß), ß‐amyloidopathy, and cognitive deficits (Hsiao et al., Science, 1996). Non‐transgenic (Tg–) littermates were used as controls. Lenses were examined by ex vivo lens stereomicroscopy. Brains and lenses were analyzed by Aß immunohistochemistry, amyloid histopathology, anti‐Aß immunogold electron microscopy, tryptic digest mass spectrometry, anti‐hAß ELISA/immunoblotting. Quasi‐elastic light scattering hAß‐lens protein aggregation analysis.ResultTg2576 Tg+ mice, but not Tg– controls, age‐dependently express hAPP, accumulate hAß, and develop hAß molecular pathology in the lens and exhibit age‐dependent Aß supranuclear opacification that recapitulates lens pathology and SNC phenotype expression in human AD and DS. We detected hAß in conditioned medium from Tg+ but not Tg– lens explant cultures. hAß potently promotes mouse lens protein aggregation in vitro.ConclusionThese results support mechanistic (genotype‐phenotype) linkage between age‐dependent Aß pathology and AD‐related phenotypes in lens and brain. Collectively, our findings identify Aß pathology as the shared molecular etiology of age‐dependent supranuclear cataracts associated with two human diseases (AD, DS) and homologous murine cataracts in the Tg2576 transgenic mouse model of AD. These results represent the first evidence of AD‐related Aß pathology outside the brain and support lens Aß as an optically‐accessible biomarker for early detection and longitudinal monitoring of AD.

Aβ in the Lens of the Eye: A Noninvasively Detectable Early Biomarker of Alzheimer’s Disease β‐Amyloidopathy in Humans and Transgenic Mouse Model

AbstractBackgroundAmyloid‐β (Aβ) accumulation in brain is an early hallmark of Alzheimer’s disease (AD). We discovered Aβ deposition, β‐amyloidopathy, and colocalizing supranuclear cataracts (SNC) in lenses from people with AD (Goldstein LE et al., Lancet, 2003) and Down syndrome (DS; Moncaster JA et al., PLoS One, 2010), but not other neurodegenerative diseases or normal aging. These findings spurred development of an investigational drug‐device lens Aβ eye scanner (Sapphire II, Cognoptix) that combines an Aβ‐binding fluorescent ligand (Aftobetin) and specialized laser scanning ophthalmoscope for noninvasive measurement of lens Aβ (FDA Breakthrough Device, 2021). Early clinical results indicate that lens Aβ is an ideal biomarker for early AD detection. Here, we investigated Aβ accumulation and amyloidopathy in lens and brain.MethodTg2576 transgenic (Tg+) mice express Swedish mutant human amyloid precursor protein (hAPP‐Swe), human Aβ (hAβ), β‐amyloidopathy, and cognitive deficits (Hsiao et al., Science, 1996). Non‐transgenic (Tg–) littermates were used as controls. Lenses were examined by ex vivo lens stereomicroscopy. Brains and lenses were analyzed by Aβ immunohistochemistry, amyloid histopathology, anti‐Aβ immunogold electron microscopy, tryptic digest mass spectrometry, anti‐hAβ ELISA/immunoblotting. Quasi‐elastic light scattering hAβ‐lens protein aggregation analysis.ResultTg2576 Tg+ mice, but not Tg– controls, age‐dependently express hAPP, accumulate hAβ, and develop hAβ molecular pathology in the lens and exhibit age‐dependent Aβ supranuclear opacification that recapitulates lens pathology and SNC phenotype expression in human AD and DS. We detected hAβ in conditioned medium from Tg+ but not Tg– lens explant cultures. hAβ potently promotes mouse lens protein aggregation in vitro.ConclusionThese results support mechanistic (genotype‐phenotype) linkage between age‐dependent Aβ pathology and AD‐related phenotypes in lens and brain. Collectively, our findings identify Aβ pathology as the shared molecular etiology of age‐dependent supranuclear cataracts associated with two human diseases (AD, DS) and homologous murine cataracts in the Tg2576 transgenic mouse model of AD. These results represent the first evidence of AD‐related Aβ pathology outside the brain and support lens Aβ as an optically‐accessible biomarker for early detection and longitudinal monitoring of AD.

The effect of oral galactose on oxidative stress in the brain of a transgenic mice model of Alzheimer’s disease

AbstractBackgroundChanges in the brain energy metabolism and oxidative stress can be found before development of Aβ plaques in Alzheimer’s disease (AD) and galactose showed potential therapeutic effect in Tg2576 mice AD model. We aimed to investigate changes in the hippocampal (HPC) energy status and oxidative stress before and after galactose treatment in this model.MethodAdult male B6; SJL‐Tg(APPSWE)2576Kha transgenic (TG) mice (Tg2576) and wild types (WT) aged 5 (5M) and 10 (10M) months were used. Oral galactose therapy was given to half of WT (WT+G) and half of TG (TG+G) group for 2 months (200mg/kg/day), while another half of each group received water ad libitum. Protein expression of insulin receptor substrate (total and phosphorylated; IRS, pIRS), AMP‐activated protein kinase (AMPK, p‐AMPK) was measured by western blot. Corticosterone levels were measured by ELISA, and spectrophotometry were used to measure the parameters of oxidative stress (MnSOD; TBARS). Data were analyzed by Kruskal‐Wallis and Mann‐Whitney U‐test (p<0.05).ResultThe levels of corticosterone were decreased in 5M TG mice (p = 0.0055; n = 8) and galactose (5M TG+G) increased it to the levels of control. Galactose decreased MnSOD (p = 0.0329;n = 5) in 10M TG mice. The decrement in p/t IRS ratio (p = 0.043; n = 5) was seen only in 10M TG mice, and galactose (10M TG+G) reversed it to the levels of control. Increased AMPAK levels were found in 5M TG+G (p = 6,5e‐04; n = 5) and 5M WT+G (p = 8,6e‐05; n = 5) groups, while pAMPK was increased only in 5M TG (p = 0.013; n = 5), and decreased in 5M TG+G group after galactose treatment (p = 0.034: n = 5).ConclusionGalactose increased the corticosterone and AMPK levels in young TG mice, while in older TG mice oral galactose had the effect on the level of MnSOD and p/t IRS ratio. The potential therapeutic impact of oral galactose in Tg2576 mice seems to be connected to maintaining of oxidative stress and energy balance and depends on the animal age and AD stage at which the treatment was initiated. Supported by HRZZ IP‐2018‐01‐8938 and the Scientific Centre of Excellence for Basic, Clinical and Translational Neuroscience (project “Experimental and clinical research of hypoxic‐ischemic damage in perinatal and adult brain”, GA KK01.1.1.01.0007 funded by the European Union)

Sovateltide prevents loss of spatial memory retention and reduces neuroinflammation in a transgenic mouse model of Alzheimer’s disease

AbstractBackgroundAmyloid‐β (Aβ) accumulation, fibrillary tangles, neuroinflammation, and memory loss are hallmarks of Alzheimer’s disease (AD). We still lack an effective treatment for AD. Our group has demonstrated that endothelin B receptors (ETBR) in the brain could be a potential drug target to treat AD. However, a direct link between ETBR stimulation and regulation of AD‐related pro‐inflammatory cytokines is still lacking. In this study, we aimed to investigate the effect of sovateltide, an ETBR agonist, on inflammation and cognitive function improvement in transgenic AD (APP/PS1) mice.MethodWe assessed Aβ load, neuroinflammation, and cognitive changes in 3, 6, and 12 months old APP/PS1 transgenic mice. Animals were treated with vehicle or sovateltide (5 µg/kg) intravenously, and memory deficit was assessed using the Morris water maze test. In addition, the levels of beta‐amyloid plaques and inflammatory cytokines in the mouse brain were evaluated by immunoblotting.ResultOur results showed a significant (p<0.001) increased expression of pro‐inflammatory cytokines IL‐2 and IL‐6 and decreased expression of anti‐inflammatory cytokines IL‐4 and IL‐10 in APP/PS1 transgenic mice at 6 and 12 months of age. The expression of IL‐2 and IL‐6 was significantly (p<0.001) decreased, and IL‐4 and IL‐10 increased following sovateltide treatment in these mice, indicating an association of ETBR in regulating inflammatory factors. Moreover, APP/PS1 transgenic mice showed significant (p<0.001) impairment in spatial memory with elevated amounts of Aβ plaque. While treatment with sovateltide rescued learning and memory deficits and significantly (p<0.001) decreased Aβ plaque load compared to vehicle in 6 and 12 months aged transgenic mice. There were no changes in the expression of any of these markers at three months.ConclusionAltogether, our work suggests a novel strategy by improving memory deficits and reducing Aβ plaque load and neuroinflammation by targeting ETBR and suggests that sovateltide could be an effective therapeutic option to treat AD.

A randomized, double‐blind, placebo‐controlled phase 1b study to evaluate the safety, tolerability, and pharmacodynamics of an anti‐amyloid‐β antibody SHR‐1707 in patients with mild cognitive impairment and mild Alzheimer’s disease

AbstractBackgroundSHR‐1707 is a humanized monoclonal antibody against amyloid‐β (Aβ). Pharmacodynamic studies in vitro showed that SHR‐1707 is more potent than lecanemab. SHR‐1707 had similar affinity to Aβ fibrils and protofibrils and relatively higher affinity to Aβ monomers than lecanemab. In 5xFAD transgenic mouse model of Alzheimer’s disease (AD), SHR‐1707 safely reduced brain Aβ deposition and ameliorated memory deficits. Phase 1 studies in China (NCT04973189) and Australia (NCT04745104) had demonstrated the safety and tolerability of SHR‐1707 in healthy young adults and elderly subjects at up to 60 mg/kg. The preclinical and clinical evidence support further development of SHR‐1707. Hence, we designed a phase 1b trial of SHR‐1707 to evaluate the safety, effective dosage, and effects on brain Aβ deposition in patients with mild cognitive impairment (MCI) due to AD or mild AD.MethodThis is a randomized, double‐blind, dose‐escalation, placebo‐controlled phase 1b study (NCT05681819; Figure 1). Patients with MCI due to AD or mild AD aged 55‐85 years will be randomized to placebo or intravenous SHR‐1707 at escalated doses of 5, 10, 20, and 40 mg/kg every 2 weeks for 26 weeks. Randomization will be based on the treatment to placebo ratio of 3:2 for 5 mg/kg dose group (N = 5, ≥3 ApoE ε4 carriers) and 10:2 for the remaining dose groups (for each group: N = 12, ≥5 ApoE ε4 carriers). In the following open‐label extension study, all patients will be assigned to SHR‐1707 for 52 weeks. The primary objective is to assess the safety and tolerability of 26‐week treatment of SHR‐1707. Secondary objectives are to assess effects on brain Aβ deposition by positron‐emission tomography, pharmacokinetic and pharmacodynamic profiles in blood and cerebrospinal fluid, immunogenicity, and clinical efficacy with 26‐week treatment of SHR‐1707; and long‐term safety, tolerability, and effects on brain Aβ deposition with 78‐week treatment. Figure 2 lists all study endpoints.ResultThe study is ongoing in China. Topline results are expected in Q1 2024.ConclusionThis trial will obtain safety, tolerability, pharmacokinetics, pharmacodynamics, immunogenicity, and clinical efficacy data of SHR‐1707 to support advancement to confirmatory phase 2 or 3 studies in patients with MCI due to AD and mild AD.

Effects of Mutations in Tau’s Proline Rich Region on Epileptic Activity and Sleep in Mouse Models of Epilepsy

AbstractBackgroundGenetic ablation of tau prevents seizures, memory loss, and premature mortality in transgenic mouse models of Alzheimer’s disease, but the exact mechanisms are unknown. We tested the hypothesis that variants in tau’s proline rich domain, which affect binding to SH3‐containing proteins, prevent epileptic activity in epilepsy models.MethodWe used the following lines: 1) AxxA6 (P‐to‐A substitutions in 6th PxxP motif in tau) and 2) R221A: R‐to‐A substitution at amino acid corresponding to 221 in human 2N4R tau. Tau knockout mice were used as a benchmark. We injected kainic acid (25 mg/kg, ip), and analyzed latency to different seizure severity levels (SSL) over 3 hours: 1 to grade 8. We also crossed AxxA6 and R221A mice with the Kv1.1 knockout (Kcna1–/–) model of epilepsy and performed 24‐hour epidural video‐electroencephalography and electromyography in mice ages 5‐8 weeks. We used ex vivo slice electrophysiology and measured burst frequency in CA3 after bath‐applied picrotoxin and 4‐amino‐pyridine.ResultTau knockout mice exhibited higher latency to seizure stages than wildtype mice (WT) after kainic acid injections (p<0.05, One‐way ANOVA), consistent with previous studies. Heterozygous AxxA6 mice showed reduced susceptibility to seizures (n = 4‐6 per genotype; SSL 4‐8: ∼ 9.5 vs WT: 4.5 seconds, p<0.05, One‐Way ANOVA). The heterozygous R221A tau variant decreased mortality in Kcna1 KO mice (p<0.05). Epileptic spikes in Kcna1 KO mice averaged 22 spikes/hour (AxxA6 n = 4, R221A n = 7), and AxxA6 (homozygous and heterozygous) tau variants decreased epileptic activity to ∼2 spikes/hour (p<0.05, One‐Way ANOVA, excluding statistical outliers) in Kcna1 KO mice. Kcna1 KO mice showed a higher percentage in the awake state during light and dark phases compared to WT mice (n = 5, p<0.05, t‐test). The AxxA6 and R221A tau variants did not alter sleep‐wake cycle in Kcna1 KO mice. Kcna1 KO mice showed increase burst frequency in CA3, and heterozygous and homozygous R221A tau variants reduced bursting frequency (p<0.05, One‐Way ANOVA).ConclusionThe AxxA6 and R221A tau lines show partial reduction in seizure susceptibility in models of epilepsy compared to the tau knockout line. The tau protein variants do not affect regulation of the sleep‐wake cycle in the Kcna1 model.

A light at the end of the tunnel – from mutation identification to a potential treatment for Alzheimer’s disease

Recent advances have driven the development of immunotherapies that act by either promoting or suppressing a patient’s immune system to treat inflammation, autoimmune disease, cardiovascular disease, infectious diseases, and several cancers. In addition, research conducted over the past 25 years has identified therapeutic targets and indicated that immunotherapy could be used to treat Alzheimer’s disease (AD). Despite a number of setbacks, this approach has now led to the development of the first disease-modifying treatments for this devastating disease. A key neuropathological feature of AD is the accumulation of a ~40-amino acid peptide known as amyloid β (Aβ) in the brain and cerebrovasculature. Our detection of an Aβ precursor protein mutation that caused early-onset AD in a Swedish family by enhancing Aβ protofibril formation sharpened the focus on soluble Aβ aggregates (oligomers and protofibrils) as viable therapeutic targets. Initial studies developed and tested a mouse monoclonal antibody (mAb158) with specific conformation-dependent binding to these soluble Aβ aggregates. Treatment with mAb158 selectively reduced Aβ protofibrils in the brain and cerebrospinal fluid of a transgenic mouse model of AD. A humanized version of mAb158 (lecanemab) subsequently entered clinical trials. Based on promising Phase 2 data showing plaque clearance and reduced cognitive decline, a Phase 3 trial found that lecanemab slowed decline on the primary cognitive endpoint by 27% over 18 months and also produced positive effects on secondary clinical endpoints and key biomarkers. In July 2023, the FDA granted lecanemab a full approval, and this therapeutic antibody will be marketed as Leqembi®. This represents a significant advance for patients with AD, although many challenges remain. In particular, it is now more important than ever to identify individuals who are vulnerable to AD, so that treatment can be initiated at an early stage in the disease process.

Multimodal Gamma Stimulation Improves Activity but not Memory in Aged Tgf344-AD Rats.

Multimodal sensory gamma stimulation is a treatment approach for Alzheimers disease that has been shown to improve pathology and memory in transgenic mouse models of Alzheimer's. Because rats are closer to humans in evolution, we tested the hypothesis that the transgenic rat line bearing human APP and PS1, line TgF344-AD, would be a good supplemental candidate to test the efficacy of this treatment. Current therapy approaches under investigation seek to utilize the immune response to minimize or degrade the accumulation of β-amyloid plaque load in mouse models designed to overexpress Aβ. However, many of these models lack some of the hallmarks of Alzheimer's disease, such as hyperphosphorylated tau and neuronal cell loss. The TgF344-AD transgenic rat model is a good candidate to bridge the gap between mouse models and clinical efficacy in humans. The objective of this study was to use multimodal gamma stimulation at light and auditory modalities simultaneously to test whether this enhances memory performance as measured by the object location task and the spontaneous alternation task. In our study, we designed and built a low-cost, easy-to-construct multimodal light and sound gamma stimulator. Our gamma stimulation device was built using an Arduino microcontroller, which drives lights and a speaker at the gamma frequency. We have included in this paper our device's parts, hardware design, and software architecture for easy reproducibility. We then performed an experiment to test the effect of multimodal gamma stimulation on the cognitive performance of fourteen-month-old TgF344-AD rats. Rats were randomly assigned to either an experimental group that received gamma stimulation or a control group that did not. Performance in a Novel Object Location (NOL) task and spontaneous alternation task was evaluated in both groups before and after the treatment. Multimodal gamma stimulation did not improve memory compared to unstimulated TgF344-AD rats. However, the gamma-stimulated rats did spend significantly more time exploring objects in the novel location task than the unstimulated rats. In the spontaneous alternation task, gamma-stimulated rats exhibited significantly greater exploratory activity than unstimulated controls. Multimodal gamma stimulation did not enhance memory performance in the object location task or the spontaneous alternation task. However, in both tasks, the treatment group had improved measures of exploratory activity relative to the untreated group. We conclude that several limitations could have contributed to this mixed effect, including aging complications, different animal models, or light cycle effects.

Increased Heat Pain Tolerance but Hyperalgesia to Tonic Inflammatory Pain in the CRND8 Mouse Model of Alzheimer's Disease.

The effects of Alzheimer's disease (AD) pathology on the experience of pain are poorly understood. To understand the pathophysiological mechanisms underlying pain sensory transmission in the transgenic mouse model of AD, CRND8. We explored AD-related pathology in the spinal cord and dorsal root ganglia of 18-week-old female CRND8 mice. We assessed nociceptive responses to both acute heat stimuli and persistent inflammatory pain in CRND8 mice and non-transgenic (non-Tg) littermates. In addition, we searched for differences in biochemical correlates of inflammatory pain between CRND8 and non-Tg mice. Finally, we investigated the excitability of dorsal horn noc iceptive neurons in spinal cord slices from CRND8 and non-Tg mice. We demonstrated the presence of intracellular AD-like pathology in the spinal cord and in the dorsal root ganglia nociceptive sensory neurons of CRND8 mice. We found that CRND8 mice had a reduced susceptibility to acute noxious heat stimuli and an increased sensitivity to tonic inflammatory pain. Tonic inflammatory pain correlated with a lack of induction of pro-opiomelanocortin in the spinal cord of CRND8 mice as compared to non-Tg mice. Electrophysiological recording in acute spinal cord slice preparations indicated an increased probability of glutamate release at the membrane of dorsal horn nociceptive neurons in CRND8 mice. This study suggests that an increased thermal tolerance and a facilitation of nociception by peripheral inflammation can coexist in AD.

Genetic background influences the 5XFAD Alzheimer's disease mouse model brain proteome.

There is an urgent need to improve the translational validity of Alzheimer's disease (AD) mouse models. Introducing genetic background diversity in AD mouse models has been proposed as a way to increase validity and enable the discovery of previously uncharacterized genetic contributions to AD susceptibility or resilience. However, the extent to which genetic background influences the mouse brain proteome and its perturbation in AD mouse models is unknown. In this study, we crossed the 5XFAD AD mouse model on a C57BL/6J (B6) inbred background with the DBA/2J (D2) inbred background and analyzed the effects of genetic background variation on the brain proteome in F1 progeny. Both genetic background and 5XFAD transgene insertion strongly affected protein variance in the hippocampus and cortex (n = 3,368 proteins). Protein co-expression network analysis identified 16 modules of highly co-expressed proteins common across the hippocampus and cortex in 5XFAD and non-transgenic mice. Among the modules strongly influenced by genetic background were those related to small molecule metabolism and ion transport. Modules strongly influenced by the 5XFAD transgene were related to lysosome/stress responses and neuronal synapse/signaling. The modules with the strongest relationship to human disease-neuronal synapse/signaling and lysosome/stress response-were not significantly influenced by genetic background. However, other modules in 5XFAD that were related to human disease, such as GABA synaptic signaling and mitochondrial membrane modules, were influenced by genetic background. Most disease-related modules were more strongly correlated with AD genotype in the hippocampus compared with the cortex. Our findings suggest that the genetic diversity introduced by crossing B6 and D2 inbred backgrounds influences proteomic changes related to disease in the 5XFAD model, and that proteomic analysis of other genetic backgrounds in transgenic and knock-in AD mouse models is warranted to capture the full range of molecular heterogeneity in genetically diverse models of AD.

Apolipoprotein E genotype-dependent accumulation of amyloid β in APP-knock-in mouse model of Alzheimer's disease

Apolipoprotein E4 (APOE4), the strongest risk factor for late-onset Alzheimer's disease (AD), has been revealed to cause greater accumulation of extracellular amyloid β (Aβ) aggregates than does APOE3 in traditional transgenic mouse models of AD. However, concerns that the overexpression paradigm might have affected the phenotype remain. Amyloid precursor protein (APP)-knock-in (KI) mice, incorporating APP mutations associated with AD development, offer an alternative approach for overproducing pathogenic Aβ without needing overexpression of APP. Here, we present the results of comprehensive analyses of pathological and biochemical traits in the brains of APP-KI mice harboring APP-associated familial AD mutations (APPNL-G-F/NL-G-F mice) crossed with human APOE-KI mice. Immunohistochemical and biochemical analyses revealed the APOE genotype-dependent increase in Aβ pathology and glial activation, which was evident within 8 months in the mouse model. These results suggested that this mouse model may be valuable for investigating APOE pathobiology within a reasonable experimental time frame. Thus, this model can be considered in investigating the interaction between APOE and Aβ in vivo, which may not be addressed appropriately by using other transgenic mouse models.

RhoA-LIMK Signaling Axis Reveals Rostral-Caudal Plane and Spatial Dysregulation in the Brain of Alzheimer's Disease Mouse Models.

RhoA signaling is widely reported to be dysregulated in Alzheimer's disease (AD), but its therapeutic targeting demonstrated mixed outcomes. We hypothesize that the activation and inactivation states of RhoA and LIMK are different in the cortex and in subregions of hippocampus along the rostral-caudal dimensions. We intended to elucidate the plane and spatial dependent RhoA signaling in association with AD. We applied antibody pRhoA that recognizes an inactive state of RhoA (S188 phosphorylation) and antibody pLIMK against an active state of LIMK (T508 phosphorylation) to investigate RhoA signaling in wildtype (WT) and triple transgenic AD (3xTg-AD) mouse model. We prepared serial sections from the rostral to caudal coronal planes of the entire mouse brain followed by immunofluorescence staining with pRhoA and pLIMK antibodies. Both pRhoA and pLIMK elicited a shift of expression pattern from rostral to caudal planes. Additionally, pRhoA demonstrated dynamic redistribution between the nucleus and cytoplasm. pLIMK did not show such nucleus and cytoplasm redistribution but the expression level was changed from rostral to caudal planes. At some planes, pRhoA showed an increasing trend in expression in the cortex but a decreasing trend in the dentate gyrus of the 3xTg-AD mouse hippocampus. pLIMK tends to decrease in the cortex but increase in the dentate gyrus of 3xTg-AD mouse hippocampus. RhoA activation is dysregulated in both human and mouse AD brains, and the RhoA-LIMK signaling axis reveals spatial dysregulation along the rostral-caudal plane dimensions.