Androgen alleviates neurotoxicity of β-amyloid peptide (Aβ) by promoting microglial clearance of Aβ and inhibiting microglial inflammatory response to Aβ

Leveraging research into sex differences and steroid hormones to improve brain health

Sex differences, driven in part by steroid hormones, shape the structure and function of the brain throughout the lifespan and manifest across brain health and disease. The influence of steroid hormones on neuroplasticity, particularly in the adult hippocampus, differs between the sexes, which has important implications for disorders and diseases that compromise hippocampus integrity, such as depression and Alzheimer disease. This Review outlines the intricate relationship between steroid hormones and hippocampal neuroplasticity across the adult lifespan and explores how the unique physiology of male and female individuals can affect health and disease. Despite calls to include sex and gender in research, only 5% of neuroscience studies published in 2019 directly investigated the influence of sex. Drawing on insights from depression, Alzheimer disease and relevant hippocampal plasticity, this Review underscores the importance of considering sex and steroid hormones to achieve a comprehensive understanding of disease susceptibility and mechanisms. Such consideration will enable the discovery of personalized treatments, ultimately leading to improved health outcomes for all.

Androgen deprivation exacerbates AD pathology by promoting the loss of microglia in an age-dependent manner

AIMS

Microglial cells are integral to the pathogenesis of Alzheimer's disease (AD). The observed sex disparity in AD prevalence, with a notable predominance in women, implies a potential influence of sex hormones, such as androgens, on disease mechanisms. Despite this, the specific effects of androgens on microglia remain unclear. This study is designed to delineate the interplay between androgens and the survival and inflammatory profile of microglial cells, as well as to explore their contribution to the progression of AD.

METHODS AND KEY FINDINGS

To create a chronic androgen deficiency model, 3-month-old wild-type (WT) mice and APP/PS1 mice underwent bilateral orchiectomy (ORX), with age-matched sham-operated controls. Cognitive and memory were evaluated at 5 and 12 months, paralleled by assessments of amyloid-beta (Aβ) and microglial morphology in hippocampal and cortical areas. The ORX treatment in mice resulted in diminished microglial populations and morphological alterations, alongside an increase in Aβ plaques and a concomitant decline in cognitive performance that exacerbated over time. In vitro, dihydrotestosterone (DHT) was found to stimulate microglial proliferation and ameliorate Aβ1-42-induced apoptosis.

SIGNIFICANCE

These findings suggested that androgens may exert a protective role, maintaining the normal proliferation and functionality of microglial cells. This preservation could potentially slow the progression of AD. As a result, our study provided a conceptual framework for the development of novel therapeutic strategies for AD.

Causal effects of genetically predicted testosterone on Alzheimer's disease: a two-sample mendelian randomization study

OBJECTIVE

Although several studies have reported that testosterone may protect against Alzheimer's disease, no evidence of a causal relationship has been demonstrated.

METHODS

A Mendelian randomization (MR) study was performed to determine the causal role of testosterone in Alzheimer's disease. The study utilized public databases obtained from separately published genome-wide associationstudies (GWAS). Single-nucleotide polymorphisms (SNPs) for testosterone were extracted from the most recent and largest published GWAS meta-analysis (178,782 participants), and SNPs for Alzheimer's disease were extracted from UK Biobank (954 AD cases and 487,331 controls). The odds ratio (OR) of the inverse variance weighting (IVW) approach was the primary outcome, and the weighted median and MR Egger regression were used for sensitivity analysis.

RESULTS

Through IVW, we observed a causal association between genetically predicted testosterone and the risk of Alzheimer's disease, with an OR of 0.99 (95% confidence interval [CI] = 0.998-0.999, p = 0.047). In the sensitivity analyses, the weighted median regression showed directionally similar estimates (OR = 0.99, 95% CI = 0.998-0.999, p = 0.048). The MR Egger regression showed similar estimates (OR = 0.99, 95% CI = 0.998-1.00, p = 0.35), but with lower precision. Funnel plots, MR Egger intercepts, and Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) analysis indicated the absence of directional pleiotropy effects.

CONCLUSION

In conclusion, our MR study provides evidence of a causal relationship between testosterone levels and Alzheimer's disease; however, this relationship must be validated in future studies with larger sample sizes. Early testosterone monitoring may enable the prevention of Alzheimer's and related diseases.

Biomaterials-based anti-inflammatory treatment strategies for Alzheimer's disease

The current therapeutic drugs for Alzheimer's disease only improve symptoms, they do not delay disease progression. Therefore, there is an urgent need for new effective drugs. The underlying pathogenic factors of Alzheimer's disease are not clear, but neuroinflammation can link various hypotheses of Alzheimer's disease; hence, targeting neuroinflammation may be a new hope for Alzheimer's disease treatment. Inhibiting inflammation can restore neuronal function, promote neuroregeneration, reduce the pathological burden of Alzheimer's disease, and improve or even reverse symptoms of Alzheimer's disease. This review focuses on the relationship between inflammation and various pathological hypotheses of Alzheimer's disease; reports the mechanisms and characteristics of small-molecule drugs (e.g., nonsteroidal anti-inflammatory drugs, neurosteroids, and plant extracts); macromolecule drugs (e.g., peptides, proteins, and gene therapeutics); and nanocarriers (e.g., lipid-based nanoparticles, polymeric nanoparticles, nanoemulsions, and inorganic nanoparticles) in the treatment of Alzheimer's disease. The review also makes recommendations for the prospective development of anti-inflammatory strategies based on nanocarriers for the treatment of Alzheimer's disease.

Recent Research Progress in Fluorescent Probes for Detection of Amyloid-β In Vivo

Alzheimer's disease (AD) is a neurodegenerative disease. Due to its complex pathological mechanism, its etiology is not yet clear. As one of the main pathological markers of AD, amyloid-β (Aβ) plays an important role in the development of AD. The deposition of Aβ is not only related to the degeneration of neurons, but also can activate a series of pathological events, including the activation of astrocytes and microglia, the breakdown of the blood-brain barrier, and the change in microcirculation, which is the main cause of brain lesions and death in AD patients. Therefore, the development of efficient and reliable Aβ-specific probes is crucial for the early diagnosis and treatment of AD. This paper focuses on reviewing the application of small-molecule fluorescent probes in Aβ imaging in vivo in recent years. These probes efficiently map the presence of Aβ in vivo, providing a pathway for the early diagnosis of AD and providing enlightenment for the design of Aβ-specific probes in the future.

Advances in the Study of the Pathology and Treatment of Alzheimer's Disease and Its Association with Periodontitis

Alzheimer's disease (AD) has become one of the leading causes of health problems in the elderly, and studying its causes and treatments remains a serious challenge for researchers worldwide. The two main pathological features of Alzheimer's disease are the extracellular deposition of β-amyloid (Aβ) to form senile plaques and the intracellular aggregation of hyperphosphorylated Tau protein to form neurofibrillary tangles (NFTs). Researchers have proposed several hypotheses to elucidate the pathogenesis of AD, but due to the complexity of the pathophysiologic factors involved in the development of AD, no effective drugs have been found to stop the progression of the disease. Currently, the mainstay drugs used to treat AD can only alleviate the patient's symptoms and do not have a therapeutic effect. As researchers explore interactions among diseases, much evidence suggests that there is a close link between periodontitis and AD, and that periodontal pathogenic bacteria can exacerbate Aβ deposition and Tau protein hyperphosphorylation through neuroinflammatory mechanisms, thereby advancing the pathogenesis of AD. This article reviews recent advances in the pathogenesis of AD, available therapeutic agents, the relevance of periodontitis to AD, and mechanisms of action.

Sex-based differences in effector cells of the adaptive immune system during Alzheimer's disease and related dementias

Neurological conditions such as Alzheimer's disease (AD) and related dementias (ADRD) present with many challenges due to the heterogeneity of the related disease(s), making it difficult to develop effective treatments. Additionally, the progression of ADRD-related pathologies presents differently between men and women. With two-thirds of the population affected with ADRD being women, ADRD has presented itself with a bias toward the female population. However, studies of ADRD generally do not incorporate sex-based differences in investigating the development and progression of the disease, which is detrimental to understanding and treating dementia. Additionally, recent implications for the adaptive immune system in the development of ADRD bring in new factors to be considered as part of the disease, including sex-based differences in immune response(s) during ADRD development. Here, we review the sex-based differences of pathological hallmarks of ADRD presentation and progression, sex-based differences in the adaptive immune system and how it changes with ADRD, and the importance of precision medicine in the development of a more targeted and personalized treatment for this devastating and prevalent neurodegenerative condition.

Lipin2 ameliorates diabetic encephalopathy via suppressing JNK/ERK-mediated NLRP3 inflammasome overactivation

OBJECTIVES

Diabetic encephalopathy (DE) is a common complication of diabetes in the central nervous system, which can cause cognitive dysfunction in patients. However, its pathophysiological mechanism has not been elucidated, and thus effective prevention and treatment methods are still lacking.Previous studies reported that neuroinflammation involved in the central neuropathy, while lipin2 plays an important role in inflammatory response.Therefore, we aimed to investigate the effects of lipin2 on regulating inflammatory response in the pathogenesis of DE.

METHODS

BV2 cells were treated with high glucose and infected with lipin2 overexpression or knockdown virus to observe the cell viability. Then, we constructed a mouse model of DE, and constructed a lipin2 knockdown or overexpression model by injecting lentivirus into the brain with stereotaxis. The expression of lipin2 in inflammatory bodies and related inflammatory factor signaling pathway-related proteins were examined by western blot and quantitative real-time PCR. Morris water maze was used to evaluate the spatial learning and memory of mice.

RESULTS

High glucose decreased the expression of lipin2 in BV2 cells, while overexpression of lipin2 in BV2 cells significantly suppressed the inflammatory response and apoptosis induced by high glucose. Meanwhile, the expression of lipin2 was down-regulated in the hippocampus in a DE mice model. Up-regulation of lipin2 in the hippocampus of DE mice inhibited JNK/ERK signaling pathway, reduced NLRP3 inflammasome-mediated inflammatory response, down-regulated IL-1/TNF-α expression, and improved synaptic plasticity and cognitive dysfunction in mice. Conversely, knockdown of lipin2 increased NLRP3 inflammasome overactivation, caused neuronal abnormalities and cognitive impairment in mice.

CONCLUSIONS

Lipin2 may play a neuroprotective role in DE by inhibiting JNK/ERK-mediated NLRP3 inflammasome overactivation and subsequent inflammatory responses. It may be a potential therapeutic target for DE therapy.

Recent advances in demystifying O-glycosylation in health and disease

O-Glycosylation is one of the most common protein post-translational modifications (PTM) and plays an essential role in the pathophysiology of diseases. However, the complexity of O-glycosylation and the lack of specific enzymes for the processing of O-glycans and their O-glycopeptides make O-glycosylation analysis challenging. Recently, research on O-glycosylation has received attention owing to technological innovation and emerging O-glycoproteases. Several serine/threonine endoproteases have been found to specifically cleave O-glycosylated serine or threonine, allowing for the systematic analysis of O-glycoproteins. In this review, we first assessed the field of protein O-glycosylation over the past decade and used bibliometric analysis to identify keywords and emerging trends. We then summarized recent advances in O-glycosylation, covering several aspects: O-glycan release, site-specific elucidation of intact O-glycopeptides, identification of O-glycosites, characterization of different O-glycoproteases, mass spectrometry (MS) fragmentation methods for site-specific O-glycosylation assignment, and O-glycosylation data analysis. Finally, the role of O-glycosylation in health and disease was discussed.

Alternative Pharmacological Strategies for the Treatment of Alzheimer's Disease: Focus on Neuromodulator Function

Alzheimer's disease (AD) is a neurodegenerative disorder, comprising 70% of dementia diagnoses worldwide and affecting 1 in 9 people over the age of 65. However, the majority of its treatments, which predominantly target the cholinergic system, remain insufficient at reversing pathology and act simply to slow the inevitable progression of the disease. The most recent neurotransmitter-targeting drug for AD was approved in 2003, strongly suggesting that targeting neurotransmitter systems alone is unlikely to be sufficient, and that research into alternate treatment avenues is urgently required. Neuromodulators are substances released by neurons which influence neurotransmitter release and signal transmission across synapses. Neuromodulators including neuropeptides, hormones, neurotrophins, ATP and metal ions display altered function in AD, which underlies aberrant neuronal activity and pathology. However, research into how the manipulation of neuromodulators may be useful in the treatment of AD is relatively understudied. Combining neuromodulator targeting with more novel methods of drug delivery, such as the use of multi-targeted directed ligands, combinatorial drugs and encapsulated nanoparticle delivery systems, may help to overcome limitations of conventional treatments. These include difficulty crossing the blood-brain-barrier and the exertion of effects on a single target only. This review aims to highlight the ways in which neuromodulator functions are altered in AD and investigate how future therapies targeting such substances, which act upstream to classical neurotransmitter systems, may be of potential therapeutic benefit in the sustained search for more effective treatments.

[Testosterone and Alzheimer's disease]

Alzheimer's disease (AD) is a neurodegenerative disease that causes dementia in half of the cases. Asthma is usually found in people over 65 years of age. The etiopathogenesis of the disease is multifactorial and includes genetic factors, nutritional disorders, mitochondrial dysfunction, oxidative stress, and aging. Sex hormones have an important influence on the development of AD, as evidenced by a higher incidence in women than in men. Considering the significant influence of T on the maintenance of normal brain function, the present study is aimed at evaluating the impact of androgen deprivation therapy (ADT), as well as testosterone therapy, on the risk of AD development and progression. Although there is some clinical inconsistency between studies, androgens have a significant effect on brain function and are beneficial for AD patients. Low levels of circulating androgens should be considered as a significant risk factor for the development of AD and memory loss. With a reduced level of T in the plasma of men, its administration improves cognitive performance and memory, treatment should be started at an early stage of the disease. In men and women with AD, androgens improve mental state and slow the progression of the disease, providing a protective effect. In the future, it is necessary to conduct studies on a large population, taking into account personality factors and a more specific approach to assessing cognitive functions and the causal relationship of T administration in AD.

Impact of Testosterone on Alzheimer's Disease

Alzheimer’s disease (AD) is a neurodegenerative disease responsible for almost half of all dementia cases in the world and progressively increasing. The etiopathology includes heritability, genetic factors, aging, nutrition, but sex hormones play a relevant role. Animal models demonstrated that testosterone (T) exerted a neuroprotective effect reducing the production of amyloid-beta (Aβ), improving synaptic signaling, and counteracting neuronal death. This study aims to evaluate the impact of T deprivation and T administration in humans on the onset of dementia and AD. A search was conducted on MEDLINE and Scopus for the “androgen deprivation therapy” and “testosterone therapy” with “dementia” and “Alzheimer’s.” Studies lasting twenty years with low risk of bias, randomized clinical trial, and case-controlled studies were considered. Twelve articles on the effect of androgen deprivation therapy (ADT) and AD and seventeen on T therapy and AD were retrieved. Men with prostate cancer under ADT showed a higher incidence of dementia and AD. The effect of T administration in hypogonadal men with AD and cognitive impairment has evidenced some positive results. The majority of studies showed the T administration improved memory and cognition in AD while others did not find any benefit. Although some biases in the studies are evident, T therapy for AD patients may represent an essential clinical therapy to reduce dementia incidence and AD progression. However, more specific case-controlled trials on the effect of androgens therapy in men and women to reducing the onset of AD are necessary.

Changes in resting-state measures of prostate cancer patients exposed to androgen deprivation therapy

The aim of the present work is to describe the differences in rs-fMRI measures (Amplitude of low frequency fluctuations [ALFF], Regional Homogeneity [ReHo] and Functional Connectivity [FC]) between patients exposed to Androgen deprivation therapy (ADT) and a control group. Forty-nine ADT patients and fifteen PC-non-ADT patients (Controls) were included in the study. A neuropsychological evaluation and a resting-state fMRI was performed to evaluate differences in ALFF and ReHo. Region of interest (ROI) analysis was also performed. ROIs were selected among those whose androgen receptor expression (at RNA-level) was the highest. FC analysis was performed using the same ROIs. Higher ALFF in frontal regions and temporal regions was identified in Controls than in ADT patients. In the ROI analysis, higher activity for Controls than ADT patients was shown in the left inferior frontal gyrus and in the left precentral gyrus. Lower ALFF in the right hippocampus and the lateral geniculate nucleus of the right thalamus was identified for Controls than ADT patients. Higher ReHo was observed in Controls in the left parietal-occipital area. Finally, ADT patients presented an increase of FC in more regions than Controls. These differences may reflect an impairment in brain functioning in ADT users.

Hijacking Sexual Immuno-Privilege in GBM-An Immuno-Evasion Strategy

Regulatory T-cells (Tregs) are immunosuppressive T-cells, which arrest immune responses to 'Self' tissues. Some immunosuppressive Tregs that recognize seminal epitopes suppress immune responses to the proteins in semen, in both men and women. We postulated that GBMs express reproductive-associated proteins to manipulate reproductive Tregs and to gain immune privilege. We analyzed four GBM transcriptome databases representing ≈900 tumors for hypoxia-responsive Tregs, steroidogenic pathways, and sperm/testicular and placenta-specific genes, stratifying tumors by expression. In silico analysis suggested that the presence of reproductive-associated Tregs in GBM tumors was associated with worse patient outcomes. These tumors have an androgenic signature, express male-specific antigens, and attract reproductive-associated Related Orphan Receptor C (RORC)-Treg immunosuppressive cells. GBM patient sera were interrogated for the presence of anti-sperm/testicular antibodies, along with age-matched controls, utilizing monkey testicle sections. GBM patient serum contained anti-sperm/testicular antibodies at levels > six-fold that of controls. Myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs) are associated with estrogenic tumors which appear to mimic placental tissue. We demonstrate that RORC-Tregs drive poor patient outcome, and Treg infiltration correlates strongly with androgen levels. Androgens support GBM expression of sperm/testicular proteins allowing Tregs from the patient's reproductive system to infiltrate the tumor. In contrast, estrogen appears responsible for MDSC/TAM immunosuppression.

A high fat, sugar, and salt Western diet induces motor-muscular and sensory dysfunctions and neurodegeneration in mice during aging: Ameliorative action of metformin

Aims

To explore the novel linkage between a Western diet combining high saturated fat, sugar, and salt (HFSS) and neurological dysfunctions during aging as well as Metformin intervention, we assessed cerebral cortex abnormalities associated with sensory and motor dysfunctions and cellular and molecular insights in brains using HFSS‐fed mice during aging. We also explored the effect of Metformin treatment on these mice.

Methods

C57BL/6 mice were fed with HFSS and treated with metformin from 20 to 22 months of age, resembling human aging from 56 to 68 years of age (an entry phase of the aged portion of lifespan).

Results

The motor and sensory cortexes in mice during aging after HFSS diet showed: (A) decreased motor‐muscular and sensory functions; (B) reduced inflammation‐resolving Arg‐1⁺ microglia; (C) increased inflammatory iNOs⁺ microglia and TNFα levels; (D) enhanced abundance of amyloid‐β peptide and of phosphorylated Tau. Metformin attenuated these changes.

Conclusion

A HFSS‐combined diet caused motor‐muscular and sensory dysfunctions, neuroinflammation, and neurodegeneration, whereas metformin counteracted these effects. Our findings show neuroinflammatory consequences of a HFSS diet in aging. Metformin curbs the HFSS‐related neuroinflammation eliciting neuroprotection.

Investigation of common risk factors between polycystic ovary syndrome and Alzheimer's disease: a narrative review

BACKGROUND

The most common endocrine and metabolic disorders in premenopausal women is polycystic ovary syndrome (PCOS), characterized by hyperandrogenism, chronic anovulation, and/or ultrasound evidence of small ovarian cysts. Obesity and insulin resistance are also the main factors influencing the clinical manifestations of this syndrome. Alzheimer's disease (AD) is the most typical progressive neurodegenerative disorder of the brain, and recent studies suggest a relationship between endocrinal dysregulation and neuronal loss during AD pathology.

AIM

This study aimed to evaluate the common risk factors for Alzheimer's and PCOS based on previous studies. Knowing the common risk factors and eliminating them may prevent neurodegenerative Alzheimer's disease in the future.

METHOD

In this narrative review, international databases, including Google Scholar, Scopus, PubMed, and the Web of Science, were searched to retrieve the relevant studies. The relevant studies' summaries were categorized to discuss the possible pathways that may explain the association between Alzheimer's and PCOS signs/symptoms and complications.

RESULTS

According to our research, the factors involved in Alzheimer's and PCOS disorders may share some common risk factors. In patients with PCOS, increased LH to FSH ratio, decreased vitamin D, insulin resistance, and obesity are some of the most important factors that may increase the risk of Alzheimer's disease.

New insights in drug development for Alzheimer's disease based on microglia function

One of the biggest challenges in drug development for Alzheimer's disease (AD) is how to effectively remove deposits of amyloid-beta (Aβ). Recently, the relationship between microglia and Aβ has become a research hotspot. Emerging evidence suggests that Aβ-induced microglia-mediated neuroinflammation further aggravates the decline of cognitive function, while microglia are also involved in the process of Aβ clearance. Hence, microglia have become a potential therapeutic target for the treatment or prevention of AD. An in-depth understanding of the role played by microglia in the development of AD will help us to broaden therapeutic strategies for AD. In this review, we provide an overview of the dual roles of microglia in AD progression: the positive effect of phagocytosis of Aβ and its negative effect on neuroinflammation after over-activation. With the advantages of novel structure, high efficiency, and low toxicity, small-molecule compounds as modulators of microglial function have attracted considerable attention in the therapeutic areas of AD. In this review, we also summarize the therapeutic potential of small molecule compounds (SMCs) and their structure-activity relationship for AD treatment through modulating microglial phagocytosis and inhibiting neuroinflammation. For example, the position and number of phenolic hydroxyl groups on the B ring are the key to the activity of flavonoids, and the substitution of hydroxyl groups on the benzene ring enhances the anti-inflammatory activity of phenolic acids. This review is expected to be useful for developing effective modulators of microglial function from SMCs for the amelioration and treatment of AD.

Network-based analysis on genetic variants reveals the immunological mechanism underlying Alzheimer's disease

Alzheimer's Disease (AD) is a neurodegenerative disorder characterized by the impairment of cognitive function and loss of memory. Previous studies indicate an essential role of immune response in AD, but the detailed mechanisms remain unclear. In this study, we obtained 1664 credible risk variants (CRVs) based on the most significant SNP detected by International Genomics of Alzheimer's Project, from which 99 genes (CRVs-related genes) were identified. Function analysis revealed that these genes were mainly involved in immune response and amyloid-β and its precursor metabolisms, indicating a potential role of immune response in regulating neurobiological processes in the etiology of neurodegenerative disease. Pathway crosstalk analysis revealed the complicated connections between immune-related pathways. Further, we found that the CRVs-related genes showed temporal-specific expression in the thalamus in adolescence developmental period. Cell type-specific expression analysis found that CRVs-related genes might be specifically expressed in brain cells such as astrocytes and oligodendrocytes. Protein-protein interaction network analysis identified the highly interconnected 'hub' genes, all of which were susceptible loci of AD. These results indicated that the CRVs may exert a potential influence in AD by regulating immune response, thalamus development, astrocytes activities, and amyloid-β binding. Our results provided hints for further experimental verification of AD pathophysiology.

Activated microglia-induced neuroinflammatory cytokines lead to photoreceptor apoptosis in Aβ-injected mice

Age-related macular degeneration (AMD) is mainly characterized by the progressive accumulation of drusen deposits and loss of photoreceptors and retinal pigment epithelial (RPE) cells. Because amyloid β (Aβ) is the main component of drusen, Aβ-induced activated microglia most likely lead to neuroinflammation and play a critical role in the pathogenesis of AMD. However, the relationship between activated microglia-mediated neuroinflammatory cytokines and photoreceptor death has not been clarified. By subretinal injection of Aβ₄₂ in mice, we mimicked an inflammatory milieu of AMD to better understand how activated microglia-induced neuroinflammatory cytokines lead to photoreceptor apoptosis in the AMD progression. We demonstrated that subretinal injection of Aβ₄₂ induces microglial activation and increases inflammatory cytokine release, which gives rise to photoreceptor apoptosis in mice. Our results were verified in vitro by co-culture of Aβ₄₂ activated primary microglia and the photoreceptor cell line 661W. We also demonstrated that the p38 mitogen-activated protein kinase (MAPK) signaling pathway was involved in Aβ₄₂-induced microglial activation and inflammatory cytokine release. Overall, our findings indicate that activated microglia-derived neuroinflammatory cytokines could contribute to photoreceptor apoptosis under the stimulation of Aβ₄₂. Moreover, this study may provide a potential therapeutic approach for AMD. KEY MESSAGES: Further explore the association between activated microglia-derived neuroinflammatory cytokine secretion and photoreceptor apoptosis under the stimulation of Aβ₄₂. Subretinal injection of Aβ₄₂ induces the activation of microglia and increases proinflammatory cytokines IL-1β and COX-2 expression in the retina, which could give rise to the deterioration of visual function and aggravate photoreceptor apoptosis in mice. Primary microglial are activated and the levels of proinflammatory cytokines are increased by Aβ₄₂ stimulation, which could increase the apoptosis of photoreceptor cell line 661W in vitro. The p38 MAPK signaling pathway is involved in microglial activation and photoreceptor apoptosis under Aβ₄₂ treatment.

Neuroprotection of dihydrotestosterone via suppression of the toll-like receptor 4/nuclear factor-kappa B signaling pathway in high glucose-induced BV-2 microglia inflammatory responses

Hyperglycemia is considered to induce neuronal apoptosis via activating microglia inflammatory responses, thus involving in the development and progression of diabetic encephalopathy and neurodegenerative disorders. Increasing evidences suggest that androgen exerts neuroprotective functions including antiapoptosis, anti-inflammation and antioxidative stress. In this study, we investigate the anti-inflammatory role of dihydrotestosterone (DHT) in high glucose (HG)-induced neuroinflammatory response in BV-2 microglia. Our results revealed that DHT significantly inhibited HG-induced production of nitric oxide and prostaglandin E2 through suppressing the expression of corresponding regulatory enzymes - inducible NO synthase and cyclooxygenase-2. Also, DHT inhibited HG-induced expression of TNF-α and IL-1β. Moreover, DHT suppressed the toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB) signaling pathway. Furthermore, when SH-SY5Y neurons were cultured in HG-treated BV-2 microglial supernatant, DHT pretreatment significantly increased neuronal survival, indicating the neuroprotective role of DHT. Collectively, these results suggest that DHT could protect SH-SY5Y neurons from HG-mediated BV-2 microglia inflammatory damage through inhibiting TLR4/NF-κB signaling, suggesting that maintenance of androgen level in brain might have potential benefit in neurodegenerative diseases, especially in diabetes patients combined with cognitive disorders.

Steroids and Alzheimer's Disease: Changes Associated with Pathology and Therapeutic Potential

Alzheimer's disease (AD) is a multifactorial age-related neurodegenerative disease that today has no effective treatment to prevent or slow its progression. Neuroactive steroids, including neurosteroids and sex steroids, have attracted attention as potential suitable candidates to alleviate AD pathology. Accumulating evidence shows that they exhibit pleiotropic neuroprotective properties that are relevant for AD. This review focuses on the relationship between selected neuroactive steroids and the main aspects of AD disease, pointing out contributions and gaps with reference to sex differences. We take into account the regulation of brain steroid concentrations associated with human AD pathology. Consideration is given to preclinical studies in AD models providing current knowledge on the neuroprotection offered by neuroactive (neuro)steroids on major AD pathogenic factors, such as amyloid-β (Aβ) and tau pathology, mitochondrial impairment, neuroinflammation, neurogenesis and memory loss. Stimulating endogenous steroid production opens a new steroid-based strategy to potentially overcome AD pathology. This article is part of a Special Issue entitled Steroids and the Nervous System.

Berberine attenuates Aβ42-induced neuronal damage through regulating circHDAC9/miR-142-5p axis in human neuronal cells

BACKGROUND

Berberine plays a neuroprotective role in neurodegenerative diseases, including Alzheimer's disease (AD). Circular RNAs (circRNAs) function as crucial players in AD pathogenesis. In the current work, we aimed to investigate whether circRNA histone deacetylase 9 (circHDAC9) was involved in the regulation of berberine in AD.

METHODS

Cell viability and apoptosis were determined by the Cell Counting Kit-8 (CCK-8) assay and flow cytometry, respectively. Enzyme-linked immunosorbent assay (ELISA) was used to assess caspase-3 activity and the production of interleukin-1β (IL-1β), IL-6 and tumor necrosis factor-α (TNF-α). The levels of circHDAC9 and miR-142-5p were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Subcellular fractionation assays were performed to evaluate the localization of circHDAC9. The direct interaction between circHDAC9 and miR-142-5p was confirmed by dual-luciferase reporter, RNA immunoprecipitation (RIP) and RNA pull-down assays.

RESULTS

Our data indicated that circHDAC9 was indeed a circular transcript and mainly localized in the cytoplasm. 42-residue β-amyloid (Aβ42) triggered a significant down-regulation in circHDAC9 and a striking up-regulation in miR-142-5p in human neuronal (HN) cells. Berberine relieved Aβ42-induced HN cell neurotoxicity. Moreover, berberine resulted in increased circHDAC9 expression and decreased miR-142-5p level in Aβ42-treated HN cells. Berberine alleviated Aβ42-induced neuronal damage in HN cells by up-regulating circHDAC9. Furthermore, circHDAC9 acted as a molecular sponge of miR-142-5p. CircHDAC9 overexpression alleviated Aβ42-induced HN cell neurotoxicity via miR-142-5p.

CONCLUSION

Our current study suggested that berberine protected HN cell from Aβ42-induced neuronal damage at least partly through regulating the circHDAC9/miR-142-5p axis, highlighting novel evidence for the neuroprotective effect of berberine in AD.

5-HT1AR alleviates Aβ-induced cognitive decline and neuroinflammation through crosstalk with NF-κB pathway in mice

The 5-hydroxytryptamine (5-HT) receptor is significant for the regulation of mood and memory. However, the role of 5-HT1AR in β-Amyloid protein (Aβ)-induced cognitive decline, neuroinflammation and the possible mechanism remains elusive. Thus, we aimed to evaluate the effects of 5-HT1AR on Aβ-induced learning and memory decline and neuroinflammation in mice. Novel object recognition and Morris water maze tests were performed to observe learning and memory behavior in mice. Protein levels of Iba1, GFAP, MAP2, TNF-α, Tβ4, C-fos, IKK-β, IKB-α, NF-κBp65, phospho-NF-κBp65 in the hippocampus were examined by immunostaining or western blotting. Aβ1-42-treatment inducing learning and memory decline was shown in novel object recognition and Morris water maze tests; neuroinflammation shown in immunostaining. Our study found out that 5-HT1AR inhibitor WAY100635 showed significant improvement in Aβ-induced learning and memory decline. Moreover, WAY100635 decreases levels of Iba1, GFAP, and TNF-α in the hippocampus, which were related to neuroinflammation. While treatment with 5-HT1AR agonist 8-OH-DPAT or ERK inhibitor U0126 exerted no effects or even aggravated Aβ-induced learning and memory decline. In addition, WAY100635 could downregulate phospho-NF-κB in the hippocampus of Aβ1-42-injected mice. These results provide new insight into the mechanism, for 5-HT1AR in Aβ-induced cognitive impairments through crosstalk with the NF-κB signaling pathway. Our data indicated that WAY100635 was involved in the protective effects against neuroinflammation and improvement of learning and memory in Alzheimer's disease.

Formyl Peptide Receptor 2 Deficiency Improves Cognition and Attenuates Tau Hyperphosphorylation and Astrogliosis in a Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is characterized by progressive loss of memory and other cognitive functions. Accumulation of amyloid-β (Aβ) and hyperphosphorylated tau are two major neuropathological features of AD. Formyl peptide receptor 2 (FPR2), contributing to innate immunity and inflammation, has been implicated in the uptake and clearance of Aβ. It remains unclear whether FPR2 affects cognition and tau phosphorylation. The effects of FPR2 in cognition and tau phosphorylation were examined using FPR2 knock-out (Fpr2-/-) mice receiving intracerebroventricular (ICV) injection of streptozotocin (STZ). The general behaviors and cognitive functions were evaluated using rotarod, open field test, and Morris water maze test. The alteration in tau hyperphosphorylation and activation of astrocytes were determined by using western blotting and/or immunofluorescence staining. ICV injection of STZ impaired spatial learning and memory of mice in Morris water maze. FPR2 deficiency improved spatial learning and memory of ICV-STZ mice. In the hippocampus and cortex of ICV-STZ mice, a marked increase was observed in tau phosphorylation at Ser199, Thr205, and Ser396 compared with ICV-saline control mice. However, FPR2 deficiency attenuated the hyperphosphorylation of tau at Ser199 and Ser396. In addition, the expression of GFAP was significantly increased in hippocampus and cortex of ICV-STZ mice. FPR2 deletion reduced the increase of GFAP expression induced by ICV injection of STZ. These results indicate that FPR2 deficiency is associate with improved cognition, reduced tau hyperphosphorylation, and activation of astrocytes in the mouse AD model tested. FPR2 may be a potential target in AD prevention and therapy.

Neuroprotection by dihydrotestosterone in LPS-induced neuroinflammation

Microglia-induced neuroinflammation plays a vital role in the etiology and progression of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease and multiple sclerosis. The neuroprotective role of androgens, including testosterone and its metabolite dihydrotestosterone (DHT), has been increasingly demonstrated in these diseases, but few studies investigated the effects of androgen on neuroinflammation. This study investigated the role of DHT in lipopolysaccharide (LPS)-induced neuroinflammation, neuronal damage and behavioral dysfunction, as well as underlying mechanisms. We showed that DHT inhibited LPS-induced release of proinflammatory factors, including TNF-α, IL-1β, IL-6; iNOS, COX-2, NO, and PGE2 in BV2 cells and primary microglia by suppressing the TLR4-mediated NF-κB and MAPK p38 signaling pathways, thus protecting SH-SY5Y neurons from inflammatory damage induced by activated microglia. In an LPS-induced neuroinflammation mouse model, endogenous DHT depletion by castration exacerbated inflammatory responses by upregulating the levels of TNF-α, IL-1β, IL-6, iNOS, and COX-2 in the serum and brain by increasing the LR4-mediated NF-κB and MAPK pathway activation, but these effects were restored by exogenous DHT supplementation. Moreover, DHT also regulated the mRNA levels of the anti-inflammatory cytokines IL-10 and IL-13 in the brain. In addition, DHT modulated the expression of Aβ, the apoptotic proteins caspase-3, Bcl-2, and Bax, and synaptophysin, as well as neuronal damage in LPS-treated mouse brains. Further behavioral tests revealed that DHT ameliorated LPS-induced spatial and learning impairment and motor incoordination, and partly improved the locomotor activity in LPS-injected mice. Therefore, this study suggests that DHT exerts anti-neuroinflammatory and neuroprotective effects; thus, androgen replacement therapy is a potential therapeutic strategy for improving cognitive and behavioral function in neuroinflammation-related diseases.

Sex differences in steroid levels and steroidogenesis in the nervous system: Physiopathological role

The nervous system, in addition to be a target for steroid hormones, is the source of a variety of neuroactive steroids, which are synthesized and metabolized by neurons and glial cells. Recent evidence indicates that the expression of neurosteroidogenic proteins and enzymes and the levels of neuroactive steroids are different in the nervous system of males and females. We here summarized the state of the art of neuroactive steroids, particularly taking in consideration sex differences occurring in the synthesis and levels of these molecules. In addition, we discuss the consequences of sex differences in neurosteroidogenesis for the function of the nervous system under healthy and pathological conditions and the implications of neuroactive steroids and neurosteroidogenesis for the development of sex-specific therapeutic interventions.

An Updated Review: Androgens and Cognitive Impairment in Older Men

Androgens are some of the most important sex hormones in men, and they maintain important physiological activities in the human body. Cognitive impairment is one of the most common manifestations of aging in the elderly population and an important factor affecting the quality of life of elderly individuals. The levels of sex hormones in elderly people decrease with age, and low levels of androgens in older male individuals have been closely linked to the development of cognitive impairment. Basic studies have shown that androgens have neuroprotective effects and that androgen deficiency impairs cognitive function by increasing oxidative stress and decreasing synaptic plasticity, among other effects. Additionally, clinical studies have also shown that androgen deficiency is closely related to cognitive impairment. This article reviews the relationship between low androgen levels and cognitive impairment, their potential mechanisms, and the effects of testosterone supplementation in improving cognition.

EGb 761 inhibits Aβ1-42-induced neuroinflammatory response by suppressing P38 MAPK signaling pathway in BV-2 microglial cells

Ginkgo biloba extract EGb 761 possesses a variety of biological effects and has been proved to be beneficial in Alzheimer's disease. This study aimed to explore the anti-inflammatory mechanisms of EGb 761 on the Aβ1-42-induced BV-2 microglial cells. We analyzed the production and gene expression of proinflammatory cytokines by enzyme-linked immunosorbent assay and qRT-PCR, examined phosphorylation of MAPKs by western blot and measured nuclear factor-κB nuclear translocation. Compared with Aβ1-42-treated group, EGb 761 inhibited release and gene expression of tumor necrosis factor-α and interleukin-1β, suppressed nuclear translocation of nuclear factor-κB and attenuated phosphorylation of p38 MAPK in a concentration-dependent manner, but not ERK and JNK. In summary, the results suggested that EGb 761 could attenuate Aβ1-42-induced neuroinflammatory response.

Androgen deprivation therapy increases brain ageing

BACKGROUND

Prostate cancer (PC) is the most frequent neoplasia in the male population and androgen deprivation therapy (ADT) is frequently used in the management of the disease.

AIM

To evaluate the effect of ADT exposure on cognitive status, grey matter volume (GMV) and white matter lesion (WML) load.

METHODS

Fifty ADT patients and fifteen PC-non-ADT (control) patients were included in the study. A neuropsychological evaluation was performed and a magnetic resonance imaging (MRI), with anatomical T1 and FLAIR sequences, was performed to evaluate the GMV and the WML burden.

RESULTS

Most of the patients included in the study presented a significant cognitive impairment (CI). No significant differences were identified in the cognitive assessment between the studied groups, but when considering the educational background intragroup differences were found.No significant difference of GMV and WML volume were identified between groups, but a negative relationship between the ADT period and the GMV was identified. Furthermore, a significant positive association between the age and the lesion volume was found in the ADT group (β=.406; p=.004).

CONCLUSION

PC patients exposed to ADT present an acceleration of age-related brain changes, such as WML development and GMV loss.

Oxymatrine exhibits anti-neuroinflammatory effects on Aβ1-42-induced primary microglia cells by inhibiting NF-κB and MAPK signaling pathways

Oxymatrine (OMT), isolated from Sophora flavescens or Sophora alopecuroides, possesses various pharmacological and biological activities, including anti-inflammatory, anti-oxidant, and anti-diabetic properties. Microglia cells, the resident immune cells in the central nervous system (CNS), play a key role in neurodegenerative diseases. In this study, the neuroinflammatory effects of OMT and its mechanisms were investigated by Aβ_1-42-induced rat brain tissue model and primary microglia cells model. The hematoxylin-eosin (HE) staining and immunohistochemistry results showed that OMT could reduce neuronal damage and inhibit microglia activation in the model tissue. The in vitro experiments revealed that OMT could decrease the levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and nitric oxide (NO), and down-regulate the expression of iNOS and COX-2 in a dose-dependent manner. Furthermore, OMT inhibited phosphorylation of JNK, ERK 1/2, P-p38 and NF-κB in Aβ_1-42-induced microglia cells. In summary, OMT exhibits anti-neuroinflammatory effects and the anti-inflammatory activity of OMT is related to the regulation of MAPK and NF-κB signaling pathways.

Supraphysiologic-dose anabolic-androgenic steroid use: A risk factor for dementia?

Supraphysiologic-dose anabolic-androgenic steroid (AAS) use is associated with physiologic, cognitive, and brain abnormalities similar to those found in people at risk for developing Alzheimer's Disease and its related dementias (AD/ADRD), which are associated with high brain β-amyloid (Aβ) and hyperphosphorylated tau (tau-P) protein levels. Supraphysiologic-dose AAS induces androgen abnormalities and excess oxidative stress, which have been linked to increased and decreased expression or activity of proteins that synthesize and eliminate, respectively, Aβ and tau-P. Aβ and tau-P accumulation may begin soon after initiating supraphysiologic-dose AAS use, which typically occurs in the early 20s, and their accumulation may be accelerated by other psychoactive substance use, which is common among non-medical AAS users. Accordingly, the widespread use of supraphysiologic-dose AAS may increase the numbers of people who develop dementia. Early diagnosis and correction of sex-steroid level abnormalities and excess oxidative stress could attenuate risk for developing AD/ADRD in supraphysiologic-dose AAS users, in people with other substance use disorders, and in people with low sex-steroid levels or excess oxidative stress associated with aging.

Effects of Androgens on the Amyloid-β Protein in Alzheimer's Disease

Age-related androgen depletion has been implicated in compromised neuroprotection and is involved in the pathogenesis of neurodegenerative disease, including Alzheimer's disease (AD), the leading cause of dementia. Emerging data revealed that reduction of both serum and brain androgen levels in males is associated with increased amyloid-β (Aβ) accumulation, a putative cause of AD. It has been demonstrated that androgens can function as the endogenous negative regulators of Aβ. However, the mechanisms by which androgens regulate Aβ production, degradation, and clearance, as well as the Aβ-induced pathological process in AD, are still elusive. This review emphasizes the contributions of androgen to Aβ metabolism and toxicity in AD and thus may provide novel strategies for prevention and therapeutics.

Identification of novel immune-relevant drug target genes for Alzheimer's Disease by combining ontology inference with network analysis

AIMS

Alzheimer's disease (AD) is one of the leading causes of death in elderly people. Its pathogenesis is greatly associated with the abnormality of immune system. However, only a few immune-relevant AD drug target genes have been discovered up to now, and it is speculated that there are still many potential drug target genes of AD (at least immune-relevant genes) to be discovered. Thus, this study was designed to identify novel AD drug target genes and explore their biological properties.

METHODS

A combinatorial approach was adopted for the first time to discover AD drug targets by collectively considering ontology inference and network analysis. Moreover, a novel strategy limiting the distance of reasoning and in turn reducing noise interference was further proposed to improve inference performance. Potential AD drug target genes were discovered by integrating information of multiple popular databases (TTD, DrugBank, PharmGKB, AlzGene, and BioGRID). Then, the enrichment analyses of the identified drug targets genes based on nine well-known pathway-related databases were conducted to explore the function of the identified potential drug target genes.

RESULTS

Eighteen potential drug target genes were finally identified, and 13 of them had been reported to be closely associated with AD. Enrichment analyses of these identified drug target genes, based on nine pathway-related databases, revealed that the enriched terms were primarily focus on immune-relevant biological processes. Four of those identified drug target genes are involved in the classical complement pathway and process of antigen presenting.

CONCLUSION

The well-reproducible results showed the good performance of the combinatorial approach, and the remaining five new targets could be a good starting point for our understanding of the pathogenesis and drug discovery of AD. Moreover, this study supported validity of the combinatorial approach integrating ontology inference with network analysis in the discovery of novel drug target for neurological diseases.

Computer-Aided Multi-Target Management of Emergent Alzheimer's Disease

Alzheimer's disease (AD) represents an enormous global health burden in terms of human suffering and economic cost. AD management requires a shift from the prevailing paradigm targeting pathogenesis to design and develop effective drugs with adequate success in clinical trials. Therefore, it is of interest to report a review on amyloid beta (Aβ) effects and other multi-targets including cholinesterase, NFTs, tau protein and TNF associated with brain cell death to be neuro-protective from AD. It should be noted that these molecules have been generated either by target-based or phenotypic methods. Hence, the use of recent advancements in nanomedicine and other natural compounds screening tools as a feasible alternative for circumventing specific liabilities is realized. We review recent developments in the design and identification of neuro-degenerative compounds against AD generated using current advancements in computational multi-target modeling algorithms reflected by theragnosis (combination of diagnostic tests and therapy) concern.

Androgen alleviates neurotoxicity of β-amyloid peptide (Aβ) by promoting microglial clearance of Aβ and inhibiting microglial inflammatory response to Aβ

AIMS

Lower androgen level in elderly men is a risk factor of Alzheimer's disease (AD). It has been reported that androgen reduces amyloid peptides (Aβ) production and increases Aβ degradation by neurons. Activated microglia are involved in AD by either clearing Aβ deposits through uptake of Aβ or releasing cytotoxic substances and pro-inflammatory cytokines. Here, we investigated the effect of androgen on Aβ uptake and clearance and Aβ-induced inflammatory response in microglia, on neuronal death induced by Aβ-activated microglia, and explored underlying mechanisms.

METHODS

Intracellular and extracellular Aβ were examined by immunofluorescence staining and Western blot. Amyloid peptides (Aβ) receptors, Aβ degrading enzymes, and pro-inflammatory cytokines were detected by RT-PCR, real-time PCR, and ELISA. Phosphorylation of MAP kinases and NF-κB was examined by Western blot.

RESULTS

We found that physiological concentrations of androgen enhanced Aβ42 uptake and clearance, suppressed Aβ42 -induced IL-1β and TNFα expression by murine microglia cell line N9 and primary microglia, and alleviated neuronal death induced by Aβ42 -activated microglia. Androgen administration also reduced Aβ42 -induced IL-1β expression and neuronal death in murine hippocampus. Mechanistic studies revealed that androgen promoted microglia to phagocytose and degrade Aβ42 through upregulating formyl peptide receptor 2 and endothelin-converting enzyme 1c expression, and inhibited Aβ42 -induced pro-inflammatory cytokines expression via suppressing MAPK p38 and NF-κB activation by Aβ42 , in an androgen receptor independent manner.

CONCLUSION

Our study demonstrates that androgen promotes microglia to phagocytose and clear Aβ42 and inhibits Aβ42 -induced inflammatory response, which may play an important role in reducing the neurotoxicity of Aβ.