The Positively Charged Cluster in the N-terminal Disordered Region may Affect Prion Protein Misfolding: Cryo-EM Structure of Hamster PrP(23-144) Fibrils.

Prions, the misfolding form of prion proteins, are contagious proteinaceous macromolecules. Recent studies have shown that infectious prion fibrils formed in the brain and non-infectious fibrils formed from recombinant prion protein in a partially denaturing condition have distinct structures. The amyloid core of the in vitro-prepared non-infectious fibrils starts at about residue 160, while that of infectious prion fibrils formed in the brain involves a longer sequence (residues ∼90-230) of structural conversion. The C-terminal truncated prion protein PrP(23-144) can form infectious fibrils under certain conditions and cause disease in animals. In this study, we used cryogenic electron microscopy (cryo-EM) to resolve the structure of hamster sHaPrP(23-144) fibrils prepared at pH 3.7. This 2.88 Å cryo-EM structure has an amyloid core covering residues 94-144. It comprises two protofilaments, each containing five ß-strands arranged as a long hairpin plus an N-terminal ß-strand. This N-terminal ß-strand resides in a positively charged cluster region (named PCC2; sequence 96-111), which interacts with the turn region of the opposite protofilaments' hairpin to stabilize the fibril structure. Interestingly, this sHaPrP(23-144) fibril structure differs from a recently reported structure formed by the human or mouse counterpart at pH 6.5. Moreover, sHaPrP(23-144) fibrils have many structural features in common with infectious prions. Whether this structure is infectious remains to be determined. More importantly, the sHaPrP(23-144) structure is different from the sHaPrP(108-144) fibrils prepared in the same fibrillization buffer, indicating that the N-terminal disordered region, possibly the positively charged cluster, influences the misfolding pathway of the prion protein.

Comparing tonic and phasic dendritic calcium in cholinergic pedunculopontine neurons and dopaminergic substantia nigra neurons.

Several brainstem nuclei degenerate in Parkinson's disease (PD). In addition to the well-characterized dopaminergic neurons of the substantia nigra pars compacta (SNc), the cholinergic neurons of the pedunculopontine nucleus (PPN) also degenerate in PD. One leading hypothesis of selective vulnerability is that pacemaking activity and the activation of low-threshold L-type calcium current are major contributors to tonic calcium load and cellular stress in SNc dopaminergic neurons. However, it is not yet clear whether the vulnerable PPN cholinergic neurons share this property. Therefore, we used two-photon dendritic calcium imaging and whole-cell electrophysiology to evaluate the role of L-type calcium channels in tonic and phasic dendritic calcium signals in PPN and SNc neurons. In addition, we investigated N- and P/Q-type calcium channel regulation of firing properties and dendritic calcium in PPN neurons. We found that blocking L-type channels reduces tonic firing rate and dendritic calcium levels in SNc neurons. By contrast, the tonic calcium load in PPN neurons did not depend on L-, N- or P/Q-type channels. However, we found that blocking either L-type (with nifedipine) or N- and P/Q-type (with omega-conotoxin MVIIC) channels reduces phasic calcium influx in PPN dendrites. Together, these findings show that L-type calcium channels play different roles in the activity of SNc and PPN neurons, and suggest that low-threshold L-type channels are not responsible for tonic calcium levels in PPN cholinergic neurons and are therefore not likely to be a source of selective vulnerability in these cells.

Mediating Effect of White Blood Cells and Tobacco Exposure on Cervical Neoplasm Risk Among Taiwanese Women.

Background: Both the high-risk human papillomavirus (HR-HPV) infection and tobacco exposure are significantly associated with cervical neoplasm risk. Immune cells play important roles in carcinogenesis. However, it is still unclear whether immune cells have a mediating effect on the HR-HPV infection and tobacco exposure with cervical neoplasm development. Aim: The aim of this study was to determine how the increased white blood cell (WBC) count affects the relationship between HR-HPV DNA load and tobacco exposure in the development of cervical neoplasia. Methods: A hospital-based case-control study design was conducted with a total of 108 cases of Taiwanese women with ≥ cervical intraepithelial neoplasia (CIN) I confirmed by biopsy, and 222 healthy Taiwanese female subjects with negative findings on a Pap smear were assigned to the control group. The study evaluated HR-HPV status and immune cell counts (WBCs, natural killer (NK) cells) and tobacco exposure by a self-construct questionnaire. Results: Both HR-HPV DNA load and tobacco exposure significantly independently increased cervical neoplasm risk (AORs: 1.28 and 1.42, respectively). Similar significant results were found for WBCs and NK cells, with respective AORs of 1.20 and 1.00. Moreover, increased WBCs (ß = 0.04, 95% CI corrected: 0.01-0.07) and tobacco exposure (ß = 0.02, 95% CI corrected: 0.01-0.04) mediated the relationship between the high-risk HPV DNA load and cervical neoplasm risk. Conclusions: Elevated WBC count acts as both predictor and mediator in cervical neoplasm development linked to HR-HPV DNA load. Monitoring and maintaining WBC levels within the normal range could be a preventive strategy for cervical neoplasm development.

Immunoglobulin replacement products protect against SARS-CoV-2 infection in vivo despite poor neutralizing activity.

Immunoglobulin (IG) replacement products are used routinely in patients with immune deficiency and other immune dysregulation disorders who have poor responses to vaccination and require passive immunity conferred by commercial antibody products. The binding, neutralizing, and protective activity of intravenously administered IG against SARS-CoV-2 emerging variants remains unknown. Here, we tested 198 different IG products manufactured from December 2019 to August 2022. We show that prepandemic IG had no appreciable cross-reactivity or neutralizing activity against SARS-CoV-2. Anti-spike antibody titers and neutralizing activity against SARS-CoV-2 WA1/2020 D614G increased gradually after the pandemic started and reached levels comparable to vaccinated healthy donors 18 months after the diagnosis of the first COVID-19 case in the United States in January 2020. The average time between production to infusion of IG products was 8 months, which resulted in poor neutralization of the variant strain circulating at the time of infusion. Despite limited neutralizing activity, IG prophylaxis with clinically relevant dosing protected susceptible K18-hACE2-transgenic mice against clinical disease, lung infection, and lung inflammation caused by the XBB.1.5 Omicron variant. Moreover, following IG prophylaxis, levels of XBB.1.5 infection in the lung were higher in FcγR-KO mice than in WT mice. Thus, IG replacement products with poor neutralizing activity against evolving SARS-CoV-2 variants likely confer protection to patients with immune deficiency disorders through Fc effector function mechanisms.

Machine Learning Model to Extract Malnutrition Data from Nursing Notes.

Malnutrition is a severe health problem that is prevalent in older people residing in residential aged care facilities. Recent advancements in machine learning have made it possible to extract key insight from electronic health records. To date, few researchers applied these techniques to classify nursing notes automatically. Therefore, we propose a model based on ClinicalBioBert to identify malnutrition notes. We evaluated our approach with two mainstream approaches. Our approach had the highest F1-score of 0.90.

Measuring the effects of a nurse-led intervention on frailty status of older people living in the community in Ethiopia: A protocol for a quasi-experimental study.

BACKGROUND: The recent recognition of the multidimensional features of frailty has emphasised the need for individualised multicomponent interventions. In the context of sub-Saharan Africa, few studies have examined: a) the frailty status of the older population; b) the level of frailty and its health implications and; c) the impact of a nurse-led intervention to reduce frailty. OBJECTIVES: This study aims to design, implement, and evaluate a nurse-led intervention to reduce frailty and associated health consequences among older people living in Ethiopia. METHODS: The study will be conducted on 68 older persons using a pre-, post-, and follow-up single-group quasi-experimental design. Residents of Ethiopia, ≥60 years and living in the community will be invited to participate in a 24-week program designed to decrease frailty and associated health consequences. Data will be collected at three-time points: baseline, immediately after the intervention, and 12 weeks post-intervention. To determine the effect of the intervention, changes in frailty, nutritional status, activities of daily living, depression and quality of life scores will be measured. To measure the effect of a nurse-led intervention on the level of frailty among older people a generalised linear model (GLM) using repeated measures ANOVA will be used. Statistical significances will be set at p-values < 0.05. DISCUSSION: The results of this study will determine the impact of a nurse-led intervention to reduce frailty amongst community-dwelling older people living in Ethiopia. The results of this study will inform the development of future interventions designed to reduce frailty in lower-income countries. TRIAL REGISTRATION: The trial was registered in ClinicalTrials.gov with the identifier of NCT05754398.

Effects of simulation-based education module on delirium care in undergraduate nursing students: A quasi-experimental study.

AIM: To examine the effects of a delirium education module on undergraduate nursing students' knowledge of and perceived confidence and competence in delirium care. BACKGROUND: Delirium is common in intensive care units (ICUs) and leads to poor clinical outcomes. The under recognition of delirium is a major problem in ICU medicine. Nurses, as first-line health care providers, can address this by recognizing patients who are experiencing delirium. Since undergraduate nursing students will be the future ICU nurses, it is important to deliver the knowledge regarding delirium care. However, education about assessing delirium in ICUs among undergraduate nursing students is lacking. DESIGN: Quasi-experimental study. METHODS: A total of 74 undergraduate students were divided into an intervention group (n=34) and a comparison group (n=40). A 2-hour simulation-based delirium education module integrated into a critical care curriculum was delivered to the intervention group only. The classroom-based intervention was administered at a medical university in northern Taiwan. Study outcomes were measured using a structured survey including (1) a 16-item delirium care knowledge quiz, (2) confidence in delirium care scale and (3) competence in delirium care scale. The survey was distributed to students before and after the module in December 2020. The Mann-Whitney U test, chi-square test and Fisher's exact test were adopted to test the differences of all variables between groups. A generalized estimating equation model was used to investigate the adjusted treatment effects. RESULTS: The participants had a median age of 22 years and 81% were female. The delirium education module yielded greater knowledge (B = 3.04, 95% confidence interval = 2.20-3.88), confidence (B = 4.20, 95% confidence interval = 2.67-5.73) and competence (B = 4.82, 95% confidence interval = 3.33-6.30) in delirium care when the treatment and control groups were compared. CONCLUSIONS: For undergraduate nursing students, simulation-based education module is effective in improving the knowledge of and confidence and competence in delirium care. It is recommended that this be included in critical care nursing curricula.

A broadly reactive antibody targeting the N-terminal domain of SARS-CoV-2 spike confers Fc-mediated protection.

Most neutralizing anti-SARS-CoV-2 monoclonal antibodies (mAbs) target the receptor binding domain (RBD) of the spike (S) protein. Here, we characterize a panel of mAbs targeting the N-terminal domain (NTD) or other non-RBD epitopes of S. A subset of NTD mAbs inhibits SARS-CoV-2 entry at a post-attachment step and avidly binds the surface of infected cells. One neutralizing NTD mAb, SARS2-57, protects K18-hACE2 mice against SARS-CoV-2 infection in an Fc-dependent manner. Structural analysis demonstrates that SARS2-57 engages an antigenic supersite that is remodeled by deletions common to emerging variants. In neutralization escape studies with SARS2-57, this NTD site accumulates mutations, including a similar deletion, but the addition of an anti-RBD mAb prevents such escape. Thus, our study highlights a common strategy of immune evasion by SARS-CoV-2 variants and how targeting spatially distinct epitopes, including those in the NTD, may limit such escape.

The effectiveness of nurse-led interventions to manage frailty in community-dwelling older people: a systematic review.

BACKGROUND: The global increase in the number of frail older people and the accompanying increase in chronic conditions underline the need to develop effective health promotion and preventive interventions for these population groups. Wide ranging of physical, psychological, and social health factors influence frailty in older people and leads to increased vulnerability to many adverse outcomes. To reverse or reduce the progression of frailty, nurses play a pivotal role in delivering health promotion and preventive interventions. The purpose of the review is to determine the effectiveness of nurse-led interventions in reducing frailty in community-dwelling older people. METHODS: The following electronic databases: PubMed, MEDLINE, Web of Science, SCOPUS, CINAHL, PsychInfo, and WHO Global Index Medicus were searched until June 2022. Nurse-led, "nurse led", education, training, intervention, program, teaching, frail*, fragile*, "frailty syndrome", debility, infirmity, elder*, aged*, old*, geriatric, "community based settings", "community-based", "community setting", community were the search terms. Before data extraction, eligible articles were assessed for their methodological quality. The JBI critical appraisal checklist for reporting experimental studies was utilised to appraise the methodological quality of the studies. Data were systematically examined using a narrative review to determine the effectiveness of the intervention. RESULTS: Of the 156 studies identified, from the search, six studies with samples ranging from 40 to 1387 older people were eligible for inclusion in the review. Two quasi-experimental studies and one Randomised Controlled Trial (RCT) showed a moderate risk of bias. The Nurse-led frailty interventions used a multi-component intervention approach across the studies. The interventions reversed frailty progression, improve physical functioning, nutritional status, and quality of life, enhance perceptions of social support, improve mental health, and reduce depression. CONCLUSIONS: Few studies have explored the effectiveness of a nurse-led intervention to decrease frailty in older people. Evaluating physical functioning, nutritional status, mental health, and quality of life in community-dwelling frail older people can contribute to developing appropriate interventions. SYSTEMATIC REVIEW REGISTRATION: PROSPERO ID of CRD42022348064.

Visualizing the membrane disruption action of antimicrobial peptides by cryo-electron tomography.

The abuse of antibiotics has led to the emergence of multidrug-resistant microbial pathogens, presenting a pressing challenge in global healthcare. Membrane-disrupting antimicrobial peptides (AMPs) combat so-called superbugs via mechanisms different than conventional antibiotics and have good application prospects in medicine, agriculture, and the food industry. However, the mechanism-of-action of AMPs has not been fully characterized at the cellular level due to a lack of high-resolution imaging technologies that can capture cellular-membrane disruption events in the hydrated state. Previously, we reported PepD2M, a de novo-designed AMP with potent and wide-spectrum bactericidal and fungicidal activity. In this study, we use cryo-electron tomography (cryo-ET) and high-speed atomic force microscopy (HS-AFM) to directly visualize the pepD2M-induced disruption of the outer and inner membranes of the Gram-negative bacterium Escherichia coli, and compared with a well-known pore-forming peptide, melittin. Our high-resolution cryo-ET images reveal how pepD2M disrupts the E. coli membrane using a carpet/detergent-like mechanism. Our studies reveal the direct membrane-disrupting consequence of AMPs on the bacterial membrane by cryo-ET, and this information provides critical insights into the mechanisms of this class of antimicrobial agents.

Comparing tonic and phasic calcium in the dendrites of vulnerable midbrain neurons.

Several midbrain nuclei degenerate in Parkinson's Disease (PD). Many of these nuclei share the common characteristics that are thought to contribute to their selective vulnerability, including pacemaking activity and high levels of calcium influx. In addition to the well-characterized dopaminergic neurons of the substantia nigra pars compacta (SNc), the cholinergic neurons of the pedunculopontine nucleus (PPN) also degenerate in PD. It is well established that the low-threshold L-type calcium current is a main contributor to tonic calcium in SNc dopaminergic neurons and is hypothesized to contribute to their selective vulnerability. However, it is not yet clear whether the vulnerable PPN cholinergic neurons share this property. Therefore, we used two-photon dendritic calcium imaging and whole-cell electrophysiology to evaluate the role of L-type calcium channels in the tonic and phasic activity of PPN neurons and the corresponding dendritic calcium signal and directly compare these characteristics to SNc neurons. We found that blocking L-type channels reduces tonic firing rate and dendritic calcium levels in SNc neurons. By contrast, the calcium load in PPN neurons during pacemaking did not depend on L-type channels. However, we find that blocking L-type channels reduces phasic calcium influx in PPN dendrites. Together, these findings show that L-type calcium channels play different roles in the activity of SNc and PPN neurons, and suggest that low-threshold L-type channels are not responsible for tonic calcium levels in PPN cholinergic neurons and are therefore not likely to be a source of selective vulnerability in these cells.

Developmentally distinct architectures in top-down circuits.

The medial prefrontal cortex (mPFC) plays a key role in learning, mood and decision making, including in how individuals respond to threats 1-6 . mPFC undergoes a uniquely protracted development, with changes in synapse density, cortical thickness, long-range connectivity, and neuronal encoding properties continuing into early adulthood 7-21 . Models suggest that before adulthood, the slow-developing mPFC cannot adequately regulate activity in faster-developing subcortical centers 22,23 . They propose that during development, the enhanced influence of subcortical systems underlies distinctive behavioural strategies of juveniles and adolescents and that increasing mPFC control over subcortical structures eventually allows adult behaviours to emerge. Yet it has remained unclear how a progressive strengthening of top-down control can lead to nonlinear changes in behaviour as individuals mature 24,25 . To address this discrepancy, here we monitored and manipulated activity in the developing brain as animals responded to threats, establishing direct causal links between frontolimbic circuit activity and the behavioural strategies of juvenile, adolescent and adult mice. Rather than a linear strengthening of mPFC synaptic connectivity progressively regulating behaviour, we uncovered multiple developmental switches in the behavioural roles of mPFC circuits targeting the basolateral amygdala (BLA) and nucleus accumbens (NAc). We show these changes are accompanied by axonal pruning coinciding with functional strengthening of synaptic connectivity in the mPFC-BLA and mPFC-NAc pathways, which mature at different rates. Our results reveal how developing mPFC circuits pass through distinct architectures that may make them optimally adapted to the demands of age-specific challenges.

Delirium assessment tools among hospitalized older adults: A systematic review and metaanalysis of diagnostic accuracy.

Delirium is a common neuropsychiatric syndrome that is often overlooked in clinical settings. The most accurate instrument for screening delirium has not been established. This study aimed to compare the diagnostic accuracy of the 4 'A's Test (4AT), Nursing Delirium Screening Scale (Nu-DESC), and Confusion Assessment Method (CAM) in detecting delirium among older adults in clinical settings. These assessment tools feature concise item sets and straightforward administration procedures. Five electronic databases were systematically searched from their inception to September 7, 2022. Studies evaluating the sensitivity and specificity of the 4AT, Nu-DESC, and CAM against the Diagnostic and Statistical Manual of Mental Disorders or International Classification of Diseases as the reference standard were included. Bivariate random effects model was used to summarize the sensitivity and specificity results. A total of 38 studies involving 7378 patients were included. The 4AT, Nu-DESC, and CAM had comparable sensitivity in detecting delirium (0.76, 0.78, and 0.80, respectively). However, the specificity of the CAM was higher than that of the 4AT (0.98 vs 0.89, P = .01) and Nu-DESC 0.99 vs 0.90, P = .003). Diagnostic accuracy was moderated by the percentage of women, acute care setting, sample size, and assessors. The three tools exhibit comparable sensitivity, and the CAM has the highest specificity. Based on the feasibility of the tools, nurses and clinical staffs could employ the Nu-DESC and the 4AT on screening out positive delirium cases and integrate these tools into daily practice. Further investigations are warranted to verify our findings.

Brain-Wide Projections and Differential Encoding of Prefrontal Neuronal Classes Underlying Learned and Innate Threat Avoidance.

To understand how the brain produces behavior, we must elucidate the relationships between neuronal connectivity and function. The medial prefrontal cortex (mPFC) is critical for complex functions including decision-making and mood. mPFC projection neurons collateralize extensively, but the relationships between mPFC neuronal activity and brain-wide connectivity are poorly understood. We performed whole-brain connectivity mapping and fiber photometry to better understand the mPFC circuits that control threat avoidance in male and female mice. Using tissue clearing and light sheet fluorescence microscopy (LSFM), we mapped the brain-wide axon collaterals of populations of mPFC neurons that project to nucleus accumbens (NAc), ventral tegmental area (VTA), or contralateral mPFC (cmPFC). We present DeepTraCE (deep learning-based tracing with combined enhancement), for quantifying bulk-labeled axonal projections in images of cleared tissue, and DeepCOUNT (deep-learning based counting of objects via 3D U-net pixel tagging), for quantifying cell bodies. Anatomical maps produced with DeepTraCE aligned with known axonal projection patterns and revealed class-specific topographic projections within regions. Using TRAP2 mice and DeepCOUNT, we analyzed whole-brain functional connectivity underlying threat avoidance. PL was the most highly connected node with functional connections to subsets of PL-cPL, PL-NAc, and PL-VTA target sites. Using fiber photometry, we found that during threat avoidance, cmPFC and NAc-projectors encoded conditioned stimuli, but only when action was required to avoid threats. mPFC-VTA neurons encoded learned but not innate avoidance behaviors. Together our results present new and optimized approaches for quantitative whole-brain analysis and indicate that anatomically defined classes of mPFC neurons have specialized roles in threat avoidance.SIGNIFICANCE STATEMENT Understanding how the brain produces complex behaviors requires detailed knowledge of the relationships between neuronal connectivity and function. The medial prefrontal cortex (mPFC) plays a key role in learning, mood, and decision-making, including evaluating and responding to threats. mPFC dysfunction is strongly linked to fear, anxiety and mood disorders. Although mPFC circuits are clear therapeutic targets, gaps in our understanding of how they produce cognitive and emotional behaviors prevent us from designing effective interventions. To address this, we developed a high-throughput analysis pipeline for quantifying bulk-labeled fluorescent axons [DeepTraCE (deep learning-based tracing with combined enhancement)] or cell bodies [DeepCOUNT (deep-learning based counting of objects via 3D U-net pixel tagging)] in intact cleared brains. Using DeepTraCE, DeepCOUNT, and fiber photometry, we performed detailed anatomic and functional mapping of mPFC neuronal classes, identifying specialized roles in threat avoidance.

Cross-Cultural Adaptation, Validity, and Reliability Testing of the Tilburg Frailty Indicator (TFI) Amharic Version for Screening Frailty in Community-Dwelling Ethiopian Older People.

Background: Frailty is a global health problem, including in African countries. Despite this, no reliable or valid frailty instruments incorporate any African language, and no research exists to cross-culturally adapt and test the validity and reliability of instruments commonly used in other countries for use within African countries. The Tilburg Frailty Indicator (TFI) is a reliable and validated instrument with the potential to be relevant for older populations living in Africa. This study aimed to develop the TFI Amharic (TFI-AM) version for use within Ethiopia. Methods: This study employed psychometric testing and the evaluation of a translated and adapted instrument. The original English language version of the TFI was translated and culturally adapted into Amharic using the World Health Organization process of translation and adaptation of an instrument. A convenience sample of ninety-six community-dwelling older people 60 years and over was recruited. Cronbach's alpha was used for the analysis of the internal consistency of the TFI Amharic (TFI-AM) version using IBM SPSS 26.0 (IBM Corp., Armonk, NY, USA). Face and content validities of the TFI-AM were determined. Results: The TFI-AM total mean score was 5.76 (±2.89). The internal consistency of the TFI-AM was very good with an overall Cronbach alpha value of 0.82. The physical domain showed the highest reliability with a 0.75 Cronbach's alpha value while the social domain was the lowest with a 0.68 Cronbach's alpha value. The Cronbach's alpha reliability coefficients of the instrument ranged from 0.68 to 0.75. The item content validity index value ranged from 0.83 to 1.0 and the total content validity index average for the instrument was 0.91. Conclusion: The TFI-AM is reliable, valid, and reproducible for the assessment of frailty among community-dwelling older populations in Ethiopia. TFI-AM proved an easy-to-administer, applicable and fast instrument for assessing frailty in community-dwelling older populations.

Malnutrition and its contributing factors for older people living in residential aged care facilities: Insights from natural language processing of aged care records.

BACKGROUND: Malnutrition is a serious health risk facing older people living in residential aged care facilities. Aged care staff record observations and concerns about older people in electronic health records (EHR), including free-text progress notes. These insights are yet to be unleashed. OBJECTIVE: This study explored the risk factors for malnutrition in structured and unstructured electronic health data. METHODS: Data of weight loss and malnutrition were extracted from the de-identified EHR records of a large aged care organization in Australia. A literature review was conducted to identify causative factors for malnutrition. Natural language processing (NLP) techniques were applied to progress notes to extract these causative factors. The NLP performance was evaluated by the parameters of sensitivity, specificity and F1-Score. RESULTS: The NLP methods were highly accurate in extracting the key data, values for 46 causative variables, from the free-text client progress notes. Thirty three percent (1,469 out of 4,405) of the clients were malnourished. The structured, tabulated data only recorded 48% of these malnourished clients, far less than that (82%) identified from the progress notes, suggesting the importance of using NLP technology to uncover the information from nursing notes to fully understand the health status of the vulnerable older people in residential aged care. CONCLUSION: This study identified 33% of older people suffered from malnutrition, lower than those reported in the similar setting in previous studies. Our study demonstrates that NLP technology is important for uncovering the key information about health risks for older people in residential aged care. Future research can apply NLP to predict other health risks for older people in this setting.

Cholesterol twists the transmembrane Di-Gly region of amyloid-precursor protein.

Nearly 95% of Alzheimer's disease (AD) occurs sporadically without genetic linkage. Aging, hypertension, high cholesterol content, and diabetes are known nongenomic risk factors of AD. Aggregation of Aß peptides is an initial event of AD pathogenesis. Aß peptides are catabolic products of a type I membrane protein called amyloid precursor protein (APP). Aß40 is the major product, whereas the 2-residue-longer version, Aß42, induces amyloid plaque formation in the AD brain. Since cholesterol content is one risk factor for sporadic AD, we aimed to explore whether cholesterol in the membrane affects the structure of the APP transmembrane region, thereby modulating the γ-secretase cutting behavior. Here, we synthesized several peptides containing the APP transmembrane region (sequence 693-726, corresponding to the Aß22-55 sequence) with one or two Cys mutations for spin labeling. We performed three electron spin resonance experiments to examine the structural changes of the peptides in liposomes composed of dioleoyl phosphatidylcholine and different cholesterol content. Our results show that cholesterol increases membrane thickness by 10% and peptide length accordingly. We identified that the di-glycine region of Aß36-40 (sequence VGGVV) exhibits the most profound change in response to cholesterol compared with other segments, explaining how the presence of cholesterol affects the γ-secretase cutting site. This study provides spectroscopic evidence showing how cholesterol modulates the structure of the APP transmembrane region in a lipid bilayer.