Presenilin Research Articles

4 Association Between Plasma Neurofilament Light Chain (NfL) and Non-Verbal Abstract Reasoning in a Colombian Cohort with Autosomal Dominant Alzheimer’s Disease

Objective:Neurofilament light chain (NfL), a plasma-based biomarker for neurodegeneration, is a promising marker for early Alzheimer disease (AD) detection in individuals at increased risk. We previously reported that Presenilin1 (PSEN1) E280A carriers have increased levels of plasma NfL relative to non-carrier family members twenty years before the onset of clinical symptoms. Abstract reasoning is one of the first cognitive abilities to deteriorate in AD. Here, we examined whether levels of plasma NfL were associated with non-verbal abstract reasoning performance in non-demented PSEN1-E280A carriers and non-carriers.Participants and Methods:A total of 798 members of the Colombian kindred with the PSEN1 E280A mutation (462 cognitively-unimpaired and 336 non-carriers; mean age= 34.02 (10.53), mean education= 8.23(4.60), 57% females and 43% males) were included in the study. Participants completed the Raven’s Progressive Matrices (RPM), Mini Mental State Examination (MMSE), and underwent blood sampling. Plasma NfL concentrations were measured with a single molecule array (Simoa) method. Mann-Whitney U test and education-adjusted Spearman partial correlation were used to examine group differences and associations between abstract reasoning performance and NfL levels.Results:Non-carriers were older (p<.001) and had higher levels of education than carriers (p=.025). Compared to non-carriers, carriers had higher levels of NfL (p=.014), lower performance on the MMSE (p<.001) and on the RPM (p=.001). In the whole sample, performance on the RPM was significantly associated with age (r= -.144, p<.001), and MMSE score (r=.198, p<.001). In carriers only, performance on the RPM was negatively associated with NfL levels (r=-.121, p=.009). This association was not significant in non-carriers.Conclusions:Our findings support the hypothesis that plasma NfL levels may be indicators of disease progression and early cognitive dysfunction in autosomal dominant AD. Future work with NfL, abstract reasoning and memory with larger samples across the preclinical/prodromal spectrum will allow a more comprehensive examination of these associations.

33 Associations Between Long-Term Forgetting and Slow Wave Activity in Autosomal-Dominant Alzheimer’s Disease: Findings from the Colombia-Boston (COLBOS) Biomarker Study

Objective:Sleep contributes to memory retention and recall. Alzheimer’s disease (AD) patients experience decreased slow wave activity (SWA) during sleep. This decrease in SWA is associated with impaired memory consolidation (Lee et al., 2020). Long-term forgetting (LTF) over days or weeks has been linked to memory consolidation deficits and has been suggested as an early marker of AD that could be useful for identifying at-risk individuals for preclinical AD trials (Weston et al., 2018). Here, we examined associations between LTF and SWA in a sample of Presenilin-1 (PSEN1) E280A mutation carriers with autosomal dominant Alzheimer’s disease and non-carrier family members. Carriers of this mutation usually develop dementia in their forties (Fuller et al., 2019).Participants and Methods:Fourteen cognitively unimpaired PSEN1-E280A mutation carriers and sixteen age-matched non-carriers (mean age: 34.2 years) from the Colombia-Boston (COLBOS) biomarker study were included. Participants completed an overnight polysomnogram (PSG) and memory testing (NEUROPSI Word List) at 3-time points: 1) the night before PSG: immediate recall (Day1-ImmRecall) and a 20-minute delayed recall (Day1-DelayedRecall), 2) recall the following day (Day2-recall), and 3) recall one week later (Day7-recall). SWA was measured as the ratio 0. 6-1Hz/0.6-4Hz in frontopolar and frontotemporal regions and was calculated for sleep stages N2+N3 (slow wave sleep) based on an automated staging algorithm. Each participant’s LTF was calculated as the percent retention between Day 1 immediate recall and Day 7 recall (Butler, 2009). Mann-Whitney U tests were used to compare differences in recall, SWA, and LTF between groups. Spearman’s correlation was used to examine the associations between memory recall at different time points and SWA, as well as between LTF and SWA.Results:On Day 1, carriers had lower performance in immediate recall (p=0.02), compared to non-carriers, but there were no group differences in the 20-minute delayed recall. Carriers also recalled fewer words on Day 2 (p=0.03) and Day 7 (p=0.009) and had greater LTF (p=0.03). There were no group differences in SWA. In our overall sample, worse performance on word list delayed recall on Day 1, Day 2, and Day 7 was associated with less SWA across both frontotemporal (Day1: p=0.04, Day2: p=0.02, Day7: p=0.02) and frontopolar (all Ps<0.01) regions. In carriers, only worse performance on Day 1 delayed recall was associated with lower SWA in the frontopolar region (r= 0.535; p=0.049). Memory recall on other days was not associated with SWA in any brain regions. Additionally, greater LTF was associated with less SWA across both frontopolar (r= 0.507; p=0.005) and frontotemporal regions (r= 0.463 p= 0.01).Conclusions:Preliminary findings suggest that long-term forgetting is associated with less slow- wave activity in preclinical autosomal dominant Alzheimer’s disease. These results also suggest that SWA may be related to pre-sleep learning and subsequent overnight memory consolidation processes. LTF testing may be useful in selecting individuals for preclinical AD trials. Future research on the impact of slow wave activity on LTF may be useful in identifying ways to enhance short- and long-term memory consolidation in individuals at greater risk for dementia.

37 The MAPP Room Memory Task: Examining Contextual Memory Using a Novel Computerized Task in Cognitively-Unimpaired Individuals with Autosomal Dominant Alzheimer’s Disease from the Colombia-Boston Biomarker Study

Objective:Contextual memory, which refers to the ability to remember spatial or temporal circumstances related to an event, is affected early in Alzheimer’s Disease (AD). Computerized cognitive tasks have been suggested to be an ecological way to assess memory, but there are few studies that utilize these tools. Studying contextual memory via a computerized task in a Colombian kindred with autosomal dominant AD due to the Presenilin-1 (PSEN1) E280A mutation and a well-characterized disease progression may help us understand contextual memory changes in the preclinical AD stage. In this study we investigated whether a novel computerized task examining contextual memory can help identify those at increased risk for dementia.Participants and Methods:A group of 31 non-carriers (mean age=38.97±6.11; mean education=11.45±4.34) and 15 cognitively unimpaired PSEN1E280A mutation carriers from the Colombia-Boston (COLBOS) Biomarker Study (mean age=35.67±5.50), mean education=10.60±3.83) performed the “MAPP Room Memory Task” on a computer. As part of this task, participants are asked to remember ten rooms and the specific location of a few objects for later recall. During the immediate recall phase, participants are asked to recognize the objects presented in each room (Immediate Object Recognition) and their location (Immediate Object Placement). During the subsequent delay phase of the task, participants are asked to select the correct room in which an object was first presented (Delayed Room Recognition) and place the objects previously seen in each room (Delayed Object Placement). We conducted Mann Whitney U tests to analyze differences between groups and Spearman Rho correlations to examine associations among the Room Memory Task performance, age, education, and Mini Mental State Examination (MMSE).Results:There were no differences in age or education between carriers and non-carriers (p>0.05, for both). Carriers had worse Delayed Room Recognition than non-carriers (Carriers mean score=0.893±0.18, non-carriers mean score=0.987±0.05; U=168.0, p=0.02), while there were no differences in the other task conditions (all p>0.05). In carriers, education was positively associated with Immediate Object Placement (rs=0.61, p=0.02), Delayed Object Placement (rs=0.76, p=0.001), and Delayed Room Recognition (rs=0.68, p=0.006). There were no significant associations between Room Memory Task conditions and age or MMSE scores in carriers. Further, no significant associations were observed between Room Memory Task performance, and age, education or MMSE scores in non-carriers.Conclusions:Our preliminary findings show that the MAPP Room Memory Task, in particular the Delayed Room Recognition condition, may be helpful to discriminate those at increased risk of dementia. Future studies with larger samples using the Room Memory Task and AD-related biomarkers are needed to examine whether this task can be sensitive to early preclinical changes associated with AD and can potentially help track disease progression in those at risk.

An Alternative View of Familial Alzheimer's Disease Genetics.

Probabilistic and parsimony-based arguments regarding available genetics data are used to propose that Hardy and Higgin's amyloid cascade hypothesis is valid but is commonly interpreted too narrowly to support, incorrectly, the primacy of the amyloid-β peptide (Aβ) in driving Alzheimer's disease pathogenesis. Instead, increased activity of the βCTF (C99) fragment of AβPP is the critical pathogenic determinant altered by mutations in the APP gene. This model is consistent with the regulation of APP mRNA translation via its 5' iron responsive element. Similar arguments support that the pathological effects of familial Alzheimer's disease mutations in the genes PSEN1 and PSEN2 are not exerted directly via changes in AβPP cleavage to produce different ratios of Aβ length. Rather, these mutations likely act through effects on presenilin holoprotein conformation and function, and possibly the formation and stability of multimers of presenilin holoprotein and/or of the γ-secretase complex. All fAD mutations in APP, PSEN1, and PSEN2 likely find unity of pathological mechanism in their actions on endolysosomal acidification and mitochondrial function, with detrimental effects on iron homeostasis and promotion of "pseudo-hypoxia" being of central importance. Aβ production is enhanced and distorted by oxidative stress and accumulates due to decreased lysosomal function. It may act as a disease-associated molecular pattern enhancing oxidative stress-driven neuroinflammation during the cognitive phase of the disease.

Depressive symptoms and hippocampal volume in autosomal dominant Alzheimer's disease.

Depressive symptoms are among early behavioral changes in Alzheimer's disease (AD); however, the relationship between neurodegeneration and depressive symptoms remains inconclusive. To better understand this relationship in preclinical AD, we examined hippocampal volume and depressive symptoms in cognitively unimpaired carriers of the presenilin-1 (PSEN1) E280A mutation for autosomal dominant AD. A total of 27 PSEN1 mutation carriers and 26 non-carrier family members were included. Linear regression was used to test the relationship between hippocampal volume and 15-item Geriatric Depression Scale. Carriers and non-carriers did not differ in depressive symptoms or hippocampal volume. Within carriers, lower hippocampal volume was associated with greater depressive symptoms, which remained significant after adjusting for age and cognition. This relationship was not significant in non-carriers. Hippocampal neurodegeneration may underlie depressive symptoms in preclinical autosomal dominant AD. These findings provide support for the utility of targeting depressive symptoms in AD prevention. We compared unimpaired autosomal dominant Alzheimer's disease (AD) mutation carriers and non-carriers. Carriers and non-carriers did not differ in severity of depressive symptoms. In carriers, hippocampal volume was inversely associated with depressive symptoms. Depressive symptoms may be a useful target in AD prevention.

Human Presenilin-1 delivered by AAV9 rescues impaired γ-secretase activity, memory deficits, and neurodegeneration in Psen mutant mice

Mutations in the Presenilin (PSEN1 and PSEN2) genes are the major cause of early-onset familial Alzheimer's disease (FAD). Presenilin (PS) is the catalytic subunit of the γ-secretase complex, which cleaves type I transmembrane proteins, such as Notch and the amyloid precursor protein (APP), and plays an evolutionarily conserved role in the protection of neuronal survival during aging. FAD PSEN1 mutations exhibit impaired γ-secretase activity in cell culture, in vitro, and knockin (KI) mouse brains, and the L435F mutation is the most severe in reducing γ-secretase activity and is located closest to the active site of γ-secretase. Here, we report that introduction of the codon-optimized wild-type human PSEN1 cDNA by adeno-associated virus 9 (AAV9) results in broadly distributed, sustained, low to moderate levels of human PS1 (hPS1) expression and rescues impaired γ-secretase activity in the cerebral cortex of Psen mutant mice either lacking PS or expressing the Psen1 L435F KI allele, as evaluated by endogenous γ-secretase substrates of APP and recombinant γ-secretase products of Notch intracellular domain and Aβ peptides. Furthermore, introduction of hPS1 by AAV9 alleviates impairments of synaptic plasticity and learning and memory in Psen mutant mice. Importantly, AAV9 delivery of hPS1 ameliorates neurodegeneration in the cerebral cortex of aged Psen mutant mice, as shown by the reversal of age-dependent loss of cortical neurons and elevated microgliosis and astrogliosis. These results together show that moderate hPS1 expression by AAV9 is sufficient to rescue impaired γ-secretase activity, synaptic and memory deficits, and neurodegeneration caused by Psen mutations in mouse models.

H - 06 Associations between Non-verbal Reasoning Abilities and Brain Pathology in a Colombian Cohort with Autosomal Dominant Alzheimer's Disease.

Declines in non-verbal reasoning abilities have been linked to Alzheimer's disease (ad) progression. Individuals with autosomal dominant ad (ADAD) are genetically determined to develop early-onset dementia. We examined the relation between non-verbal reasoning abilities and brain pathology in a Colombian cohort with ADAD due to the Presenilin-1 (PSEN1) E280A mutation. A total of 25 carriers of the PSEN1 E280A mutation (16 cognitively-unimpaired carriers [x- age = 35.25 +/- 4.04]; 9 with mildly impaired (age = 45.56 +/- 2.60), and 27 non-carriers (age = 36.11 +/- 5.59) were included. A summary non-verbal reasoning score was calculated from performance on the Judgment of Line Orientation and the Spanish WAIS-IV Matrix Reasoning and Visual Puzzles subtests. Participants also completed the Mini-mental State Examination (MMSE) and underwent amyloid and tau PET imaging. Mann-Whitney U test and education-adjusted Spearman partial correlations were used to examine group differences and associations between pathology levels and non-verbal reasoning. Compared to carriers, non-carriers had higher MMSE and non-verbal reasoning scores (p = 0.006). In carriers only, lower non-verbal reasoning was associated with greater mean cortical amyloid (r = -0.427, p = 0.037) and greater precuneus tau (r = -0.516, p = 0.010). No significant associations were observed after excluding the impaired carriers from the analyses. Our findings suggest that changes in non-verbal reasoning abilities are evident in early symptomatic ADAD stages and are related to ad brain pathology. Future longitudinal work is needed to characterize the progression of non-verbal reasoning deficits in ADAD. Future research should also examine performance between older adults and people at risk for sporadic ad.

Ginkgolide attenuates memory impairment and neuroinflammation by suppressing the NLRP3/caspase-1 pathway in Alzheimer's disease.

The NLRP3 inflammasome is involved in the neuroinflammatory pathway of Alzheimer's disease (AD). The aim of this study is to explore the roles and underlying mechanisms of ginkgolide (Baiyu®) on amyloid precursor protein (APP)/presenilin 1 (PS1) transgenic mice and a murine microglial cell line, BV-2. In the present study, the APP/PS1 mice were administered with ginkgolide, followed by a Morris water maze test. The mice were then euthanized to obtain brain tissue for histological and Aβ analysis. Additionally, BV-2 cells were pretreated with ginkgolide and then incubated with Aβ1-42 peptide. NLRP3, ASC, and caspase-1 mRNA and protein expression in brain tissue of mice and BV-2 cells were quantified by real-time PCR and western blotting, as well as reactive oxygen species (ROS) production, interleukin (IL)-1β and IL-18 levels by lucigenin technique and ELISA. Compared with the APP/PS1 mice, ginkgolide-treated mice demonstrated the shortened escape latency, reduced plaques, less inflammatory cell infiltration and neuron loss in the hippocampi of APP/PS1 mice. The levels of NLRP3, ASC, caspase-1, ROS, IL-1β, and IL-18 were also decreased in the brain tissue of APP/PS1 mice or Aβ1-42-treated BV-2 cells following ginkgolide treatment. Ginkgolide exerted protective effects on AD, at least partly by inactivating the NLRP3/caspase-1 pathway.

Supplementation of Medium-Chain Triglycerides Combined with Docosahexaenoic Acid Inhibits Amyloid Beta Protein Deposition by Improving Brain Glucose Metabolism in APP/PS1 Mice.

The deterioration of brain glucose metabolism predates the clinical onset of Alzheimer's disease (AD). Medium-chain triglycerides (MCTs) and docosahexaenoic acid (DHA) positively improve brain glucose metabolism and decrease the expression of AD-related proteins. However, the effects of the combined intervention are unclear. The present study explored the effects of the supplementation of MCTs combined with DHA in improving brain glucose metabolism and decreasing AD-related protein expression levels in APP/PS1 mice. The mice were assigned into four dietary treatment groups: the control group, MCTs group, DHA group, and MCTs + DHA group. The corresponding diet of the respective groups was fed to mice from the age of 3 to 11 months. The results showed that the supplementation of MCTs combined with DHA could increase serum octanoic acid (C8:0), decanoic acid (C10:0), DHA, and β-hydroxybutyrate (β-HB) levels; improve glucose metabolism; and reduce nerve cell apoptosis in the brain. Moreover, it also aided with decreasing the expression levels of amyloid beta protein (Aβ), amyloid precursor protein (APP), β-site APP cleaving enzyme-1 (BACE1), and presenilin-1 (PS1) in the brain. Furthermore, the supplementation of MCTs + DHA was significantly more beneficial than that of MCTs or DHA alone. In conclusion, the supplementation of MCTs combined with DHA could improve energy metabolism in the brain of APP/PS1 mice, thus decreasing nerve cell apoptosis and inhibiting the expression of Aβ.

Presenilin-1, mutated in familial Alzheimer’s disease, maintains genome stability via a γ-secretase dependent way

Mutations in Presenilin-1 (PS1) account for over 80 % mutations linked to familial Alzheimer’s disease (AD). However, the mechanisms of action of PS1 mutations in causing familial AD are not fully understood, limiting opportunities to develop targeted disease-modifying therapies for individuals carrying PS1 mutation. To gain more comprehensive insights into the impact of PS1 mutations on genome stability, we knocked down PS1 in SH-SY5Y, HMC3 and A549 cells. This revealed that PS1 knockdown (KD) dramatically induces genome instability (GIN) in all cell types, as indicated by the increased incidence of micronuclei, nucleoplasmic bridges and/or nuclear buds. Although amyloid β (Aβ) was able to induce GIN, PS1-KD was associated with decreased expression of Aβ in SH-SY5Y cells, suggesting Aβ is not the primary cause of GIN in PS1-KD cells. In contrast, inhibiting the PS1 γ-secretase activity by DAPT recapitulated GIN phenotype as seen in PS1-KD cells, indicating that the induction of GIN following PS1 KD can be attributed to the loss of γ-secretase activity. PS1 KD or γ-secretase inhibition markedly sensitizes SH-SY5Y to the genotoxicity of mitomycin C. Interestingly, overexpression of the wildtype PS1 dramatically increased GIN in SH-SY5Y. Collectively, our study demonstrates the potential of PS1 and its γ-secretase activity in maintaining genome stability, highlighting a novel potential link between PS1 loss-of-function or gain-of-function mutations and familial AD through GIN. Several mechanisms by which GIN induced by PS1 dys-expression may contribute to AD are discussed.

Preferential Regulation of Γ-Secretase-Mediated Cleavage of APP by Ganglioside GM1 Reveals a Potential Therapeutic Target for Alzheimer's Disease.

A hallmark of Alzheimer's disease (AD) is the senile plaque, which contains β-amyloid peptides (Aβ). Ganglioside GM1 is the most common brain ganglioside. However, the mechanism of GM1 in modulating Aβ processing is rarely known. Aβ levels are detected by using Immunohistochemistry (IHC) and enzyme-linked immune-sorbent assay (ELISA). Cryo-electron microscopy (Cryo-EM) is used to determine the structure of γ-secretase supplemented with GM1. The levels of the cleavage of amyloid precursor protein (APP)/Cadherin/Notch1 are detected using Western blot analysis. Y maze, object translocation, and Barnes maze are performed to evaluate cognitive functions. GM1 leads to conformational change of γ-secretase structure and specifically accelerates γ-secretase cleavage of APP without affecting other substrates including Notch1, potentially through its interaction with the N-terminal fragment of presenilin 1 (PS1). Reduction of GM1 levels decreases amyloid plaque deposition and improves cognitive dysfunction. This study reveals the mechanism of GM1 in Aβ generation and provides the evidence that decreasing GM1 levels represents a potential strategy in AD treatment. These results provide insights into the detailed mechanism of the effect of GM1 on PS1, representing a step toward the characterization of its novel role in the modulation of γ-secretase activity and the pathogenesis of AD.

Presenilin-1-Derived Circular RNAs: Neglected Epigenetic Regulators with Various Functions in Alzheimer's Disease.

The presenilin-1 (PSEN1) gene is crucial in developing Alzheimer's disease (AD), a progressive neurodegenerative disorder and the most common cause of dementia. Circular RNAs (circRNAs) are non-coding RNA generated through back-splicing, resulting in a covalently closed circular molecule. This study aimed to investigate PSEN1-gene-derived circular RNAs (circPSEN1s) and their potential functions in AD. Our in silico analysis indicated that circPSEN1s (hsa_circ_0008521 and chr14:73614502-73614802) act as sponge molecules for eight specific microRNAs. Surprisingly, two of these miRNAs (has-mir-4668-5p and has-mir-5584-5p) exclusively interact with circPSEN1s rather than mRNA-PSEN1. Furthermore, the analysis of pathways revealed that these two miRNAs predominantly target mRNAs associated with the PI3K-Akt signaling pathway. With sponging these microRNAs, circPSEN1s were found to protect mRNAs commonly targeted by these miRNAs, including QSER1, BACE2, RNF157, PTMA, and GJD3. Furthermore, the miRNAs sequestered by circPSEN1s have a notable preference for targeting the TGF-β and Hippo signaling pathways. We also demonstrated that circPSEN1s potentially interact with FOXA1, ESR1, HNF1B, BRD4, GATA4, EP300, CBX3, PRDM9, and PPARG proteins. These proteins have a prominent preference for targeting the TGF-β and Notch signaling pathways, where EP300 and FOXA1 have the highest number of protein interactions. Molecular docking analysis also confirms the interaction of these hub proteins and Aβ42 with circPSEN1s. Interestingly, circPSEN1s-targeted molecules (miRNAs and proteins) impacted TGF-β, which served as a shared signaling pathway. Finally, the analysis of microarray data unveiled distinct expression patterns of genes influenced by circPSEN1s (WTIP, TGIF, SMAD4, PPP1CB, and BMPR1A) in the brains of AD patients. In summary, our findings suggested that the interaction of circPSEN1s with microRNAs and proteins could affect the fate of specific mRNAs, interrupt the function of unique proteins, and influence cell signaling pathways, generally TGF-β. Further research is necessary to validate these findings and gain a deeper understanding of the precise mechanisms and significance of circPSEN1s in the context of AD.

Interictal spikes in Alzheimer's disease: Preclinical evidence for dominance of the dentate gyrus and cholinergic control by the medial septum

Interictal spikes (IIS) are a common type of abnormal electrical activity in Alzheimer's disease (AD) and preclinical models. The brain regions where IIS are largest are not known but are important because such data would suggest sites that contribute to IIS generation. Because hippocampus and cortex exhibit altered excitability in AD models, we asked which areas dominate the activity during IIS along the cortical-CA1-dentate gyrus (DG) dorso-ventral axis. Because medial septal (MS) cholinergic neurons are overactive when IIS typically occur, we also tested the novel hypothesis that silencing the MS cholinergic neurons selectively would reduce IIS.We used mice that simulate aspects of AD: Tg2576 mice, presenilin 2 (PS2) knockout mice and Ts65Dn mice. To selectively silence MS cholinergic neurons, Tg2576 mice were bred with choline-acetyltransferase (ChAT)-Cre mice and offspring were injected in the MS with AAV encoding inhibitory designer receptors exclusively activated by designer drugs (DREADDs). We recorded local field potentials along the cortical-CA1-DG axis using silicon probes during wakefulness, slow-wave sleep (SWS) and rapid eye movement (REM) sleep.We detected IIS in all transgenic or knockout mice but not age-matched controls. IIS were detectable throughout the cortical-CA1-DG axis and occurred primarily during REM sleep. In all 3 mouse lines, IIS amplitudes were significantly greater in the DG granule cell layer vs. CA1 pyramidal layer or overlying cortex. Current source density analysis showed robust and early current sources in the DG, and additional sources in CA1 and the cortex also. Selective chemogenetic silencing of MS cholinergic neurons significantly reduced IIS rate during REM sleep without affecting the overall duration, number of REM bouts, latency to REM sleep, or theta power during REM. Notably, two control interventions showed no effects.Consistent maximal amplitude and strong current sources of IIS in the DG suggest that the DG is remarkably active during IIS. In addition, selectively reducing MS cholinergic tone, at times when MS is hyperactive, could be a new strategy to reduce IIS in AD.

Abstract 106: Vascular Dysfunction In The Mesenteric Resistance Arteries Occurs Prior To The Occurrence Of Early-onset Alzheimer’S Disease In A Sex-dependent Manner

Alzheimer’s Disease (AD) and cardiovascular diseases (CVDs) are a major cause ofdisability and death among the older population. Familial Alzheimer’s Disease (FAD) islinked with an early onset AD (EOAD) pathology (<65years) that manifests throughpathogenic mutations in the presenilin (PSEN)1 and PSEN2 genes, leading to theincreased production of central amyloid β (Aβ) peptides. There is increasing evidencethat elevated blood pressure and peripheral arterial stiffness contribute to thedevelopment and increase the risk of β-amyloid deposition in the brain leading to cognitivedecline later in life. We hypothesized that peripheral vascular remodeling and vasculardysfunction in the aorta and mesenteric resistance arteries (MRA) would be observedprior to the development of EOAD. The MRA of male and female C57Bl/6J (control) andAD mice (B6. CApptm1DboTg(APPswe,PSEN1dE9)85Dbo) at 9-weeks-old were isolatedprior to the onset of AD. Acetylcholine-induced relaxation (1pM-30μM) andphenylephrine-induced contraction (0.1nM-30μM) were evaluated using wire myography.Pulse wave velocity (PWV) and H&E staining were used to measure vascular stiffnessand morphology, respectively. Data were analyzed as non-linear curve regression andmaximum response (Rmax) using the Student t test ( p <0.05*). MRA from AD miceshowed impaired relaxation in both males (Rmax: control 90±0.9 vs. AD 59±6.4* %, n=3-4) and females (Rmax: control 90±2.8 vs. AD 70±8.3*%, n=4-6). Interestingly,phenylephrine-induced contraction was reduced in arteries from males (Rmax: control11.7±0.9 vs . AD 7.7±0.8* mN, n=3-4), but not in arteries from females (Rmax: control9.3±1.3 vs. AD 8.1±0.6 mN, n=6-7). However, no differences were observed in the aortawall thickness in the male (control 51.8±2.9 vs. AD 72±9.2 μm, n=3-4), or female (control63.7±9.8 vs. AD 54±4.8μm, n=2-3) AD mice, as well as the PWV analysis from male ADmice (control 2.41±0.44 vs. AD 4.05±1.4 mm/ms, n=6). These data suggest that thechanges observed in the peripheral microvasculature prior to the onset of AD could laterhave direct effects on cerebral blood flow leading to areas of altered blood perfusion andmicrovascular damage, thus contributing to the genesis and maintenance of AD.

In Silico Structural Analysis Exploring Conformational Folding of Protein Variants in Alzheimer's Disease.

Accurate protein structure prediction using computational methods remains a challenge in molecular biology. Recent advances in AI-powered algorithms provide a transformative effect in solving this problem. Even though AlphaFold's performance has improved since its release, there are still limitations that apply to its efficacy. In this study, a selection of proteins related to the pathology of Alzheimer's disease was modeled, with Presenilin-1 (PSN1) and its mutated variants in the foreground. Their structural predictions were evaluated using the ColabFold implementation of AlphaFold, which utilizes MMseqs2 for the creation of multiple sequence alignments (MSAs). A higher number of recycles than the one used in the AlphaFold DB was selected, and no templates were used. In addition, prediction by RoseTTAFold was also applied to address how structures from the two deep learning frameworks match reality. The resulting conformations were compared with the corresponding experimental structures, providing potential insights into the predictive ability of this approach in this particular group of proteins. Furthermore, a comprehensive examination was performed on features such as predicted regions of disorder and the potential effect of mutations on PSN1. Our findings consist of highly accurate superpositions with little or no deviation from experimentally determined domain-level models.

Treating Alzheimer’s and ATTR using CRISPR-Cas9 to target amyloidosis

Approximately 50 million people live with Alzheimer’s (Alz) and 50,000 people are living with Transthyretin Amyloidosis (ATTR) worldwide. Both Alz and ATTR are types of amyloidosis, a disease where amyloid protein builds up in the body’s organs. Alz and ATTR are conditions with no known cures and similar etiologies but different manifestations in the brain and heart, respectively. Alzheimer’s disease is irreversible, which causes lifelong suffering for patients and their families. ATTR is a potentially fatal disease that causes heart problems for patients. Amyloidosis arises due to genetic mutations in the amyloid precursor protein (APP) or proteins involved in the generation of APP such as BACE1, PSEN1, PSEN2, APOE and transthyretin (TTR) genes, which result in the overexpression and accumulation of amyloid protein. CRISPR-Cas9 is a breakthrough gene editing technology that is capable of editing mutations in multiple genes with high specificity. This technology has the capability of treating both Alz and ATTR through targeted gene editing of the mutations that contribute to these diseases. This review will focus on BACE1, PSEN1, PSEN2, and APOE as targets for Alz and TTR as a treatment for ATTR through the use of CRISPR-Cas9. Various delivery mechanisms and current clinical trials will be discussed to identify the best delivery route of these treatments for the respective disease . A CRISPR-Cas9 derived treatment would bring new hope for patients with these diseases and could propel cures for other types of amyloidosis.

Discovery of brain permeable 2-Azabicyclo[2.2.2]octane sulfonamides as a novel class of presenilin-1 selective γ-secretase inhibitors

This paper describes the rational design, synthesis, structure-activity relationship (SAR), and biological profile of presenilin-1 (PSEN-1) complex selective γ-secretase inhibitors, assessed for selectivity using a unique set of four γ-secretase subtype complexes. A set of known PSEN-1 selective γ-Secretase inhibitors (GSIs) was analyzed to understand the pharmacophoric features required for selective inhibition. Conformational modeling suggests that a characteristic 'U' shape orientation between aromatic sulfone/sulfonamide and aryl ring is crucial for PSEN-1 selectivity and potency. Using these insights, a series of brain-penetrant 2-azabicyclo[2,2,2]octane sulfonamides was devised and synthesized as a new class of PSEN-1 selective inhibitors. Compounds 13c and 13k displayed high potency towards PSEN1-APH1B complex but moderate selectivity towards PSEN2 complexes. However, compound (+)-13b displayed low nanomolar potency towards the PSEN1-APH1B complex, little (∼4-fold) selectivity towards PSEN1-APH1A, and high selectivity (>350-fold) versus PSEN2 complexes. Excellent brain penetration, no significant CYP inhibition, or cardiotoxicity, good solubility, and permeability make (+)-13b an excellent candidate for further lead optimization.

Developing a Gene Therapy for the Treatment of Autosomal Dominant Alzheimer's Disease.

Autosomal dominant Alzheimer's disease (ADAD) is a rare early-onset form of Alzheimer's disease, caused by dominant mutations in one of three genes: presenilin 1, presenilin 2, and amyloid β precursor protein (APP). Mutations in the presenilin 1 gene (PSEN1) account for the majority of cases, and individuals who inherit a single-mutant PSEN1 allele go on to develop early-onset dementia, ultimately leading to death. The presenilin 1 protein (PS1) is the catalytic subunit of the γ-secretase protease, a tetrameric protease responsible for cleavage of numerous transmembrane proteins, including Notch and the APP. Inclusion of a mutant PS1 subunit in the γ-secretase complex leads to a loss of enzyme function and a preferential reduction of shorter forms of Aβ peptides over longer forms, an established biomarker of ADAD progression in human patients. In this study, we describe the development of a gene therapy vector expressing a wild-type (WT) copy of human PSEN1 to ameliorate the loss of function associated with PSEN1 mutations. We have carried out studies in mouse models using a recombinant AAV9 vector to deliver the PSEN1 gene directly into the central nervous system (CNS) and shown that we can normalize γ-secretase function and slow neurodegeneration in both PSEN1 conditional knockout and PSEN1 mutant knockin models. We have also carried out biodistribution studies in nonhuman primates (NHPs) and demonstrated the ability to achieve broad PS1 protein expression throughout the cortex and the hippocampus, two regions known to be critically involved in ADAD progression. These studies demonstrate preclinical proof of concept that expression of a WT human PSEN1 gene in cells harboring a dominant PSEN1 mutation can correct the γ-secretase dysfunction. In addition, direct administration of the recombinant AAV9 into the NHP brain can achieve broad expression at levels predicted to provide efficacy in the clinic.

Loss of normal Alzheimer's disease-associated Presenilin 2 function alters antiseizure medicine potency and tolerability in the 6-Hz focal seizure model.

Patients with early-onset Alzheimer's disease (EOAD) experience seizures and subclinical epileptiform activity, which may accelerate cognitive and functional decline. Antiseizure medicines (ASMs) may be a tractable disease-modifying strategy; numerous ASMs are marketed with well-established safety. However, little information is available to guide ASM selection as few studies have rigorously quantified ASM potency and tolerability in traditional seizure models in rodents with EOAD-associated risk factors. Presenilin 2 (PSEN2) variants evoke EOAD, and these patients experience seizures. This study thus established the anticonvulsant profile of mechanistically distinct ASMs in the frontline 6-Hz limbic seizure test evoked in PSEN2-knockout (KO) mice to better inform seizure management in EOAD. The median effective dose (ED50) of prototype ASMs was quantified in the 6-Hz test in male and female PSEN2-KO and wild-type (WT) C57BL/6J mice (3-4 months old). Minimal motor impairment (MMI) was assessed to estimate a protective index (PI). Immunohistological detection of cFos established the extent to which 6-Hz stimulation activates discrete brain regions in KO vs. WT mice. There were significant genotype-related differences in the potency and tolerability of several ASMs. Valproic acid and levetiracetam were significantly more potent in male KO than in WT mice. Additionally, high doses of valproic acid significantly worsened MMI in KO mice. Conversely, carbamazepine was significantly less potent in female KO vs. WT mice. In both male and female KO mice vs. WTs, perampanel and lamotrigine were equally potent. However, there were marked genotype-related shifts in PI of both carbamazepine and perampanel, with KO mice exhibiting less MMI at the highest doses tested. Gabapentin was ineffective against 6-Hz seizures in KO mice vs. WTs without MMI changes. Neuronal activation 90 min following 6-Hz stimulation was significantly increased in the posterior parietal association cortex overlying CA1 and in the piriform cortex of WT mice, while stimulation-induced increases in cFos immunoreactivity were absent in KO mice. Acute ASM potency and tolerability in the high-throughput 6-Hz test may be significantly altered with loss of normal PSEN2 function. Seizures in discrete EOAD populations may benefit from precisely selected medicines optimized for primary ASM pharmacological mechanisms.

Presenilin-2 knock-In mice show severe depressive behavior via DVL3 downregulation.

Alzheimer's disease (AD) is the most common form of dementia. Depression is one of the most critical psychiatric complications of AD, and 20%-30% of patients with AD experience symptoms of depression. Phospho-glycogen synthase kinase-3 beta (GSK3β) is known to be associated with AD and depression. Furthermore, the role of disheveled (DVL) is known to regulate GSK3β. Moreover, presenilin-2 (PS2) and DVL have cross-talk with each other. Also, it is widely hypothesized that stress leads to hypersecretion of cortisol and is thus associated with depression. Dickkopf WNT signaling pathway inhibitor-1 (DKK-1) is a crucial factor regulating depression and both amyloid beta (Aβ) and phosphorylation of tau are widely known as a biomarker of AD. To investigate the relationship between AD and depression, and possible pathways connecting the two diseases, we examined memory function and depression-related behavior test results in PS2 knock-in AD mice (PS2 MT). Next, we confirmed that there are relationships between DVL, depression, and cognitive disease through the comparative toxicogenomics database (https://ctdbase.org) and STRING (https://string-db.org) database. PS2 knock-in mice showed much more severe memory impairment and depression than PS2 wild-type mice (PS2 WT). In AD-related behavioral experiments, PS2 MT mice showed more memory dysfunction compared with PS2 WT group mice. Moreover, Aβ and phosphorylation of tau showed higher expression in PS2 MT mice than in PS2 WT mice. Depression-related behavioral tests showed that PS2 MT mice exhibited more depressive behaviors than PS2 WT mice. Furthermore, both higher cortisol levels and higher expression of DKK-1 were found in PS2 MT mice relative to PS2 WT mice. The results indicated that there is a relationship between DVL and the release of AD-related mediators and expression of the depression-related glucocorticoid receptor and DKK-1. In the PS2 knock-in group, DVL was significantly decreased compared with the PS2 WT group. Depression increases the risk of developing AD and other forms of dementia. Recent evidence indicates that depression symptoms could trigger changes in memory and thinking over time. However, it is recognized that there are no drugs to facilitate a full recovery for both AD and depression. However, our results suggest that AD and depression could be associated, and DVL could be a significant target for the association between AD and depression.