Human mitochondrial transcriptional factor A breaks the mitochondria-mediated vicious cycle in Alzheimer's disease

The neuroimmune nexus: unraveling the role of the mtDNA-cGAS-STING signal pathway in Alzheimer's disease

The relationship between Alzheimer's disease (AD) and neuroimmunity has gradually begun to be unveiled. Emerging evidence indicates that cyclic GMP-AMP synthase (cGAS) acts as a cytosolic DNA sensor, recognizing cytosolic damage-associated molecular patterns (DAMPs), and inducing the innate immune response by activating stimulator of interferon genes (STING). Dysregulation of this pathway culminates in AD-related neuroinflammation and neurodegeneration. A substantial body of evidence indicates that mitochondria are involved in the critical pathogenic mechanisms of AD, whose damage leads to the release of mitochondrial DNA (mtDNA) into the extramitochondrial space. This leaked mtDNA serves as a DAMP, activating various pattern recognition receptors and immune defense networks in the brain, including the cGAS-STING pathway, ultimately leading to an imbalance in immune homeostasis. Therefore, modulation of the mtDNA-cGAS-STING pathway to restore neuroimmune homeostasis may offer promising prospects for improving AD treatment outcomes. In this review, we focus on the mechanisms of mtDNA release during stress and the activation of the cGAS-STING pathway. Additionally, we delve into the research progress on this pathway in AD, and further discuss the primary directions and potential hurdles in developing targeted therapeutic drugs, to gain a deeper understanding of the pathogenesis of AD and provide new approaches for its therapy.

Mitochondrial DNA copy number alterations: Key players in the complexity of glioblastoma (Review)

Renowned as a highly invasive and lethal tumor derived from neural stem cells in the central nervous system, glioblastoma (GBM) exhibits substantial histopathological variation and genomic complexity, which drive its rapid progression and therapeutic resistance. Alterations in mitochondrial DNA (mtDNA) copy number (CN) serve a crucial role in GBM development and progression, affecting various aspects of tumor biology, including energy production, oxidative stress regulation and cellular adaptability. Fluctuations in mtDNA levels, whether elevated or diminished, can impair mitochondrial function, potentially disrupting oxidative phosphorylation and amplifying reactive oxygen species generation, thereby fueling tumor growth and influencing treatment responses. Understanding the mechanisms of mtDNA‑CN variations, and their interplay with genetic and environmental elements in the tumor microenvironment, is essential for advancing diagnostic and therapeutic strategies. Targeting mtDNA alterations could strengthen treatment efficacy, mitigate resistance and ultimately enhance the prognosis of patients with this aggressive brain tumor. The present review summarizes the existing literature on mtDNA alterations, specifically emphasizing variations in mtDNA‑CN and their association with GBM by surveying articles published between 1996 and 2024, sourced from databases such as Scopus, PubMed and Google Scholar. In addition, the review provides a brief overview of mitochondrial genome architecture, knowledge regarding the regulation of mtDNA integrity and CN, and how mitochondria significantly impact GBM tumorigenesis. This review further presents information on therapeutic approaches for restoring mtDNA‑CN that contribute to optimized mitochondrial function and improved health outcomes.

Beneficial effects of the herbal medicine zuo gui wan in a mice model of Alzheimer's disease via Drp1-Mediated inhibition of mitochondrial fission and activation of AMPK/PGC-1α-regulated mitochondrial bioenergetics

ETHNOPHARMACOLOGICAL RELEVANCE

Zuo Gui Wan (ZGW) is a well-known traditional Chinese medicine decoction used for approximately 400 years to treat age-related degenerative conditions, including cognitive impairment in older adults, osteoporosis, and general aging. However, the mechanism of action for ZGW remains unclear.

AIMS OF THE STUDY

This study aims to investigate the efficacy of ZGW in improving cognitive function in Alzheimer's disease (AD) animal models and to explore the underlying mechanisms, presenting a novel perspective in the field.

MATERIALS AND METHODS

Six-month-old male APP/PS1 mice were divided into three groups that received either metformin (200 mg/kg daily) or ZGW (6 and 12 g/kg daily). High-performance liquid chromatography was conducted for ZGW's quality control. Cognitive function was assessed using the Morris water maze test. Neuronal loss, synaptic plasticity, and β-amyloid (Aβ) deposition were evaluated through Western blot or immunofluorescence staining. The underlying molecular mechanisms were investigated using ELISA, Western blot, qRT-PCR, co-immunoprecipitation assay, ATP assay, and cytochrome c oxidase assay.

RESULTS

ZGW, administered in both low and high doses, significantly enhanced cognitive performance, notably decreased neuronal loss and Aβ deposition, and reduced levels of Aβ1-40/42. It also inhibited excessive mitochondrial division primarily by suppressing phosphorylated dynamin-related protein 1 (Drp1), especially at high doses of ZGW. Co-immunoprecipitation experiments further confirmed that ZGW inhibited the interaction between Aβ and p-Drp1. Furthermore, similar to the effects of the AMP-activated Protein Kinase (AMPK) activator metformin, ZGW led to a marked increase in the mitochondrial DNA copy number and upregulated the AMPK/PGC-1α/NRF1/TFAM pathway. Improvements in mitochondrial function were evident from the increased ATP production, elevated expression of superoxide dismutase 2, and upregulated cytochrome c oxidase activity. Additionally, the excess byproduct of reactive oxygen species, 4-hydroxy-2-nonenal, decreased in the group treated with ZGW.

CONCLUSION

This study provides compelling evidence that ZGW improves cognitive impairment in APP/PS1 mice by activating AMPK/PGC-1α-regulated mitochondrial bioenergetics and inhibiting Aβ-induced mitochondrial fragmentation, highlighting its potential as an effective therapeutic strategy for AD.

Is the Relationship Between Cardiovascular Disease and Alzheimer's Disease Genetic? A Scoping Review

BACKGROUND/OBJECTIVES

Cardiovascular disease (CVD) and Alzheimer's disease (AD) are two diseases highly prevalent in the aging population and often co-occur. The exact relationship between the two diseases is uncertain, though epidemiological studies have demonstrated that CVDs appear to increase the risk of AD and vice versa. This scoping review aims to examine the current identified overlapping genetics between CVDs and AD at the individual gene level and at the shared pathway level.

METHODS

Following PRISMA-ScR guidelines for a scoping review, we searched the PubMed and Scopus databases from 1990 to October 2024 for articles that involved (1) CVDs, (2) AD, and (3) used statistical methods to parse genetic relationships.

RESULTS

Our search yielded 2918 articles, of which 274 articles passed screening and were organized into two main sections: (1) evidence of shared genetic risk; and (2) shared mechanisms. The genes APOE, PSEN1, and PSEN2 reportedly have wide effects across the AD and CVD spectrum, affecting both cardiac and brain tissues. Mechanistically, changes in three main pathways (lipid metabolism, blood pressure regulation, and the breakdown of the blood-brain barrier (BBB)) contribute to subclinical and etiological changes that promote both AD and CVD progression. However, genetic studies continue to be limited by the availability of longitudinal data and lack of cohorts that are representative of diverse populations.

CONCLUSIONS

Highly penetrant familial genes simultaneously increase the risk of CVDs and AD. However, in most cases, sets of dysregulated genes within larger-scale mechanisms, like changes in lipid metabolism, blood pressure regulation, and BBB breakdown, increase the risk of both AD and CVDs and contribute to disease progression.

Differential DNA methylation profiles of Alzheimer's disease-related genomic pathways in the blood of cognitively-intact individuals with and without high impact chronic pain

Background

Chronic pain and Alzheimer's disease (AD) are prevalent in older age and their etiologies remain to be understoodand evidence supports potential associations between the two. Both high impact pain and AD have been previously associated with differences in the epigenome. Interactions with the epigenome may serve as a possible underlying mechanism linking high impact pain and AD.

Objective

To complete epigenetic canonical pathways analyses related to AD in individuals with and without high-impact knee pain.

Methods

This manuscript aimed to explore differences in DNA methylation patterns in genes and pathways associated with AD. Blood samples of cognitively intact, community-dwelling adults with high impact knee painmversus pain-free controls were compared on their DNA methylation levels of AD-related genes. Pathway enrichment analysis was performed on significantly different DNA Methylation probes by pain group.

Results

There were significant DNA methylation differences between the high impact versus the pain-free control groups in genes and pathways associated with AD (p < 0.05). We found a total of 17,563 differentially methylated CpG probes, including 13,411 hypermethylated CpG probes and 4152 hypomethylated CpG probes. Further, pathway analysis revealed these differences were significantly associated with AD-related pathways associated with AD progression.

Conclusions

This study sample showed AD-related DNA methylation differences and associated potential canonical pathways in those with and without high impact knee pain. These results highlight the need to study overlapping epigenetic modifications underlying high impact pain and AD pathologies. Further studies, including gene expression, are needed to further explore the relationship between epigenetics, chronic pain, and AD.

Transcriptomics analysis reveals molecular alterations underpinning spaceflight dermatology

BACKGROUND

Spaceflight poses a unique set of challenges to humans and the hostile spaceflight environment can induce a wide range of increased health risks, including dermatological issues. The biology driving the frequency of skin issues in astronauts is currently not well understood.

METHODS

To address this issue, we used a systems biology approach utilizing NASA's Open Science Data Repository (OSDR) on space flown murine transcriptomic datasets focused on the skin, biochemical profiles of 50 NASA astronauts and human transcriptomic datasets generated from blood and hair samples of JAXA astronauts, as well as blood samples obtained from the NASA Twins Study, and skin and blood samples from the first civilian commercial mission, Inspiration4.

RESULTS

Key biological changes related to skin health, DNA damage & repair, and mitochondrial dysregulation are identified as potential drivers for skin health risks during spaceflight. Additionally, a machine learning model is utilized to determine gene pairings associated with spaceflight response in the skin. While we identified spaceflight-induced dysregulation, such as alterations in genes associated with skin barrier function and collagen formation, our results also highlight the remarkable ability for organisms to re-adapt back to Earth via post-flight re-tuning of gene expression.

CONCLUSION

Our findings can guide future research on developing countermeasures for mitigating spaceflight-associated skin damage.

TFAM is an autophagy receptor that limits inflammation by binding to cytoplasmic mitochondrial DNA

When cells are stressed, DNA from energy-producing mitochondria can leak out and drive inflammatory immune responses if not cleared. Cells employ a quality control system called autophagy to specifically degrade damaged components. We discovered that mitochondrial transcription factor A (TFAM)-a protein that binds mitochondrial DNA (mtDNA)-helps to eliminate leaked mtDNA by interacting with the autophagy protein LC3 through an autolysosomal pathway (we term this nucleoid-phagy). TFAM contains a molecular zip code called the LC3 interacting region (LIR) motif that enables this binding. Although mutating TFAM's LIR motif did not affect its normal mitochondrial functions, more mtDNA accumulated in the cell cytoplasm, activating inflammatory signalling pathways. Thus, TFAM mediates autophagic removal of leaked mtDNA to restrict inflammation. Identifying this mechanism advances understanding of how cells exploit autophagy machinery to selectively target and degrade inflammatory mtDNA. These findings could inform research on diseases involving mitochondrial damage and inflammation.

Gastrodin alleviates mitochondrial dysfunction by regulating SIRT3-mediated TFAM acetylation in vascular dementia

BACKGROUND

Mitochondrial dysfunction is key to the pathogenesis of vascular dementia (VaD). Sirtuin-3 (SIRT3), an essential member of the sirtuins family, has been proven to be a critical sirtuin in regulating mitochondrial function. The phenolic glucoside gastrodin (GAS), a bioactive ingredient from Gastrodiae Rhizome (known in Chinese as Tian ma) demonstrates significant neuroprotective properties against central nervous system disorders; however, the precise mechanisms through which GAS modulates VaD remain elusive.

PURPOSE

This study aims to investigate whether GAS confers a protective role against VaD, and to figure out the underlying molecular mechanisms.

METHODS

A bilateral common carotid artery occlusion (BCCAO)-mediated chronic cerebral hypoperfusion (CCH) VaD rat model and a hypoxia model using HT22 cells were employed to investigate pharmacological properties of GAS in mitigating mitochondrial dysfunction. A SIRT3 agonist resveratrol (RES), a SIRT3 inhibitor 3-TYP and SIRT3-knockdown in vitro were used to explore the mechanism of GAS in association with SIRT3. The ability of SIRT3 to bind and deacetylate mitochondrial transcription factor A (TFAM) was detected by immunoprecipitation assay, and TFAM acetylation sites were further validated using mass spectrometry.

RESULTS

GAS increased SIRT3 expression and ameliorated mitochondrial structure, mitochondrial respiration, mitochondrial dynamics along with upregulated TFAM, mitigating oxidative stress and senescence. Comparable results were noted with the SIRT3 agonist RES, indicating an impactful neuroprotection played by SIRT3. Specifically, the attenuation of SIRT3 expression through knockdown techniques or exposure to the SIRT3 inhibitor 3-TYP in HT22 cells markedly abrogated GAS-mediated mitochondrial rescuing function. Furthermore, our findings elucidate a novel facet: SIRT3 interacted with and deacetylated TFAM at the K5, K7, and K8 sites. Decreased SIRT3 is accompanied by hyper-acetylated TFAM.

CONCLUSION

The present results were the first to demonstrate that the SIRT3/TFAM pathway is a protective target for reversing mitochondrial dysfunction in VaD. The findings suggest that GAS-mediated modulation of the SIRT3/TFAM pathway, a novel mechanism, could ameliorate CCH-induced VaD, offering a potentially beneficial therapeutic strategy for VaD.

Intranasal administration of induced pluripotent stem cell-derived cortical neural stem cell-secretome as a treatment option for Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is the most common neurodegenerative disorder in the elderly, resulting in gradual destruction of cognitive abilities. Research on the development of various AD treatments is underway; however, no definitive treatment has been developed yet. Herein, we present induced pluripotent stem cell (iPSC)-derived cortical neural stem cell secretome (CNSC-SE) as a new treatment candidate for AD and explore its efficacy.

METHODS

We first assessed the effects of CNSC-SE treatment on neural maturation and electromagnetic signal during cortical nerve cell differentiation. Then to confirm the efficacy in vivo, CNSC-SE was administered to the 5×FAD mouse model through the nasal cavity (5 μg/g, once a week, 4 weeks). The cell-mediated effects on nerve recovery, amyloid beta (Aβ) plaque aggregation, microglial and astrocyte detection in the brain, and neuroinflammatory responses were investigated. Metabolomics analysis of iPSC-derived CNSC-SE revealed that it contained components that could exert neuro-protective effects or amplify cognitive restorative effects.

RESULTS

Human iPSC-derived CNSC-SE increased neuronal proliferation and dendritic structure formation in vitro. Furthermore, CNSC-SE-treated iPSC-derived cortical neurons acquired electrical network activity and action potential bursts. The 5×FAD mice treated with CNSC-SE showed memory restoration and reduced Aβ plaque accumulation.

CONCLUSIONS

Our findings suggest that the iPSC-derived CNSC-SE may serve as a potential, non-invasive therapeutic option for AD in reducing amyloid infiltration and restoring memory.

Interactions of amyloidogenic proteins with mitochondrial protein import machinery in aging-related neurodegenerative diseases

Most mitochondrial proteins are targeted to the organelle by N-terminal mitochondrial targeting sequences (MTSs, or "presequences") that are recognized by the import machinery and subsequently cleaved to yield the mature protein. MTSs do not have conserved amino acid compositions, but share common physicochemical properties, including the ability to form amphipathic α-helical structures enriched with basic and hydrophobic residues on alternating faces. The lack of strict sequence conservation implies that some polypeptides can be mistargeted to mitochondria, especially under cellular stress. The pathogenic accumulation of proteins within mitochondria is implicated in many aging-related neurodegenerative diseases, including Alzheimer's, Parkinson's, and Huntington's diseases. Mechanistically, these diseases may originate in part from mitochondrial interactions with amyloid-β precursor protein (APP) or its cleavage product amyloid-β (Aβ), α-synuclein (α-syn), and mutant forms of huntingtin (mHtt), respectively, that are mediated in part through their associations with the mitochondrial protein import machinery. Emerging evidence suggests that these amyloidogenic proteins may present cryptic targeting signals that act as MTS mimetics and can be recognized by mitochondrial import receptors and transported into different mitochondrial compartments. Accumulation of these mistargeted proteins could overwhelm the import machinery and its associated quality control mechanisms, thereby contributing to neurological disease progression. Alternatively, the uptake of amyloidogenic proteins into mitochondria may be part of a protein quality control mechanism for clearance of cytotoxic proteins. Here we review the pathomechanisms of these diseases as they relate to mitochondrial protein import and effects on mitochondrial function, what features of APP/Aβ, α-syn and mHtt make them suitable substrates for the import machinery, and how this information can be leveraged for the development of therapeutic interventions.

In utero and post-natal opioid exposure followed by mild traumatic brain injury contributes to cortical neuroinflammation, mitochondrial dysfunction, and behavioral deficits in juvenile rats

Maternal opioid use poses a significant health concern not just to the expectant mother but also to the fetus. Notably, increasing numbers of children born suffering from neonatal opioid withdrawal syndrome (NOWS) further compounds the crisis. While epidemiological research has shown the heightened risk factors associated with NOWS, little research has investigated what molecular mechanisms underly the vulnerabilities these children carry throughout development and into later life. To understand the implications of in utero and post-natal opioid exposure on the developing brain, we sought to assess the response to one of the most common pediatric injuries: minor traumatic brain injury (mTBI). Using a rat model of in utero and post-natal oxycodone (IUO) exposure and a low force weight drop model of mTBI, we show that not only neonatal opioid exposure significantly affects neuroinflammation, brain metabolites, synaptic proteome, mitochondrial function, and altered behavior in juvenile rats, but also, in conjunction with mTBI these aberrations are further exacerbated. Specifically, we observed long term metabolic dysregulation, neuroinflammation, alterations in synaptic mitochondria, and impaired behavior were impacted severely by mTBI. Our research highlights the specific vulnerability caused by IUO exposure to a secondary stressor such as later life brain injury. In summary, we present a comprehensive study to highlight the damaging effects of prenatal opioid abuse in conjunction with mild brain injury on the developing brain.

Piceatannol Protects PC-12 Cells against Oxidative Damage and Mitochondrial Dysfunction by Inhibiting Autophagy via SIRT3 Pathway

Oxidative stress has been identified as a major cause of cellular injury in a variety of neurodegenerative disorders. This study aimed to investigate the cytoprotective effects of piceatannol on hydrogen peroxide (H₂O₂)-induced pheochromocytoma-12 (PC-12) cell damage and explore the underlying mechanisms. Our findings indicated that piceatannol pre-treatment significantly attenuated H₂O₂-induced PC-12 cell death. Furthermore, piceatannol effectively improved mitochondrial content and mitochondrial function, including enhancing mitochondrial reactive oxygen species (ROS) elimination capacity and increasing mitochondrial transcription factor (TFAM), peroxisome-proliferator-activated receptor-γ coactivator-1α (PGC-1α) and mitochondria Complex IV expression. Meanwhile, piceatannol treatment inhibited mitochondria-mediated autophagy as demonstrated by restoring mitochondrial membrane potential, reducing autophagosome formation and light chain 3B II/I (LC3B II/I) and autophagy-related protein 5 (ATG5) expression level. The protein expression level of SIRT3 was significantly increased by piceatannol in a concentration-dependent manner. However, the cytoprotective effect of piceatannol was dramatically abolished by sirtuin 3 (SIRT3) inhibitor, 3-(1H-1,2,3-Triazol-4-yl) pyridine (3-TYP), which led to an exacerbated mitochondrial dysfunction and autophagy in PC-12 cells under oxidative stress. In addition, the autophagy activator (rapamycin) abrogated the protective effects of piceatannol on PC-12 cell death. These findings demonstrated that piceatannol could alleviate PC-12 cell oxidative damage and mitochondrial dysfunction by inhibiting autophagy via the SIRT3 pathway.

A systematic study on the use of multifunctional nanodiamonds for neuritogenesis and super-resolution imaging

BACKGROUND

Regeneration of defective neurons in central nervous system is a highlighted issue for neurodegenerative disease treatment. Various tissue engineering approaches have focused on neuritogenesis to achieve the regeneration of damaged neuronal cells because damaged neurons often fail to achieve spontaneous restoration of neonatal neurites. Meanwhile, owing to the demand for a better diagnosis, studies of super-resolution imaging techniques in fluorescence microscopy have triggered the technological development to surpass the classical resolution dictated by the optical diffraction limit for precise observations of neuronal behaviors. Herein, the multifunctional nanodiamonds (NDs) as neuritogenesis promoters and super-resolution imaging probes were studied.

METHODS

To investigate the neuritogenesis-inducing capability of NDs, ND-containing growing medium and differentiation medium were added to the HT-22 hippocampal neuronal cells and incubated for 10 d. In vitro and ex vivo images were visualized through custom-built two-photon microscopy using NDs as imaging probes and the direct stochastic optical reconstruction microscopy (dSTORM) process was performed for the super-resolution reconstruction owing to the photoblinking properties of NDs. Moreover, ex vivo imaging of the mouse brain was performed 24 h after the intravenous injection of NDs.

RESULTS

NDs were endocytosed by the cells and promoted spontaneous neuritogenesis without any differentiation factors, where NDs exhibited no significant toxicity with their outstanding biocompatibility. The images of ND-endocytosed cells were reconstructed into super-resolution images through dSTORM, thereby addressing the problem of image distortion due to nano-sized particles, including size expansion and the challenge in distinguishing the nearby located particles. Furthermore, the ex vivo images of NDs in mouse brain confirmed that NDs could penetrate the blood-brain barrier (BBB) and retain their photoblinking property for dSTORM application.

CONCLUSIONS

It was demonstrated that the NDs are capable of dSTORM super-resolution imaging, neuritogenic facilitation, and BBB penetration, suggesting their remarkable potential in biological applications.

More than a Feeling: Dermatological Changes Impacted by Spaceflight

Spaceflight poses a unique set of challenges to humans and the hostile Spaceflight environment can induce a wide range of increased health risks, including dermatological issues. The biology driving the frequency of skin issues in astronauts is currently not well understood. To address this issue, we used a systems biology approach utilizing NASA's Open Science Data Repository (OSDR) on spaceflown murine transcriptomic datasets focused on the skin, biomedical profiles from fifty NASA astronauts, and confirmation via transcriptomic data from JAXA astronauts, the NASA Twins Study, and the first civilian commercial mission, Inspiration4. Key biological changes related to skin health, DNA damage & repair, and mitochondrial dysregulation were determined to be involved with skin health risks during Spaceflight. Additionally, a machine learning model was utilized to determine key genes driving Spaceflight response in the skin. These results can be used for determining potential countermeasures to mitigate Spaceflight damage to the skin.

The Breakthroughs and Caveats of Using Human Pluripotent Stem Cells in Modeling Alzheimer's Disease

Modeling Alzheimer's disease (AD) using human-induced pluripotent stem cells (iPSCs) is a field now spanning 15 years. Developments in the field have shown a shift in using simple 2D cortical neuron models to more advanced tri-cultures and 3D cerebral organoids that recapitulate more features of the disease. This is largely due to development and optimization of new cell protocols. In this review, we highlight recent major breakthroughs in the AD field and the implications this has in modeling AD using iPSCs (AD-iPSCs). To date, AD-iPSCs have been largely used to recapitulate and study impaired amyloid precursor protein (APP) processing and tau phosphorylation in both familial and sporadic AD. AD-iPSCs have also been studied for varying neuronal and glial dysfunctions. Moreover, they have been useful for discovering new molecular mechanisms, such as identifying proteins that bridge APP processing with tau phosphorylation and for identifying molecular pathways that bridge APP processing dysfunction with impaired cholesterol biosynthesis. Perhaps the greatest use of AD-iPSCs has been in discovering compounds via drug screening, that reduce amyloid beta (Aβ) in neurons, such as the anti-inflammatory compound, cromolyn, and antiparasitic drugs, avermectins. In addition, high content screening using AD-iPSCs has led to the identification of statins that can reduce levels of phosphorylated tau (p-Tau) in neurons. Some of these compounds have made it through to testing in human clinical trials. Improvements in omic technologies including single cell RNA sequencing and proteomics as well as advances in production of iPSC-cerebral organoids and tri-cultures is likely to result in the further discovery of new drugs and treatments for AD. Some caveats remain in the field, including, long experimental conditions to create mature neurons, high costs of media that limit research capabilities, and a lack of reproducibility using current iPSC-cerebral organoid protocols. Despite these current limitations, AD-iPSCs remain an excellent cellular model for studying AD mechanisms and for drug discovery.

Mitochondrial protective effects caused by the administration of mefenamic acid in sepsis

The pathophysiology of sepsis may involve the activation of the NOD-type receptor containing the pyrin-3 domain (NLPR-3), mitochondrial and oxidative damages. One of the primary essential oxidation products is 8-oxoguanine (8-oxoG), and its accumulation in mitochondrial DNA (mtDNA) induces cell dysfunction and death, leading to the hypothesis that mtDNA integrity is crucial for maintaining neuronal function during sepsis. In sepsis, the modulation of NLRP-3 activation is critical, and mefenamic acid (MFA) is a potent drug that can reduce inflammasome activity, attenuating the acute cerebral inflammatory process. Thus, this study aimed to evaluate the administration of MFA and its implications for the reduction of inflammatory parameters and mitochondrial damage in animals submitted to polymicrobial sepsis. To test our hypothesis, adult male Wistar rats were submitted to the cecal ligation and perforation (CLP) model for sepsis induction and after receiving an injection of MFA (doses of 10, 30, and 50 mg/kg) or sterile saline (1 mL/kg). At 24 h after sepsis induction, the frontal cortex and hippocampus were dissected to analyze the levels of TNF-α, IL-1β, and IL-18; oxidative damage (thiobarbituric acid reactive substances (TBARS), carbonyl, and DCF-DA (oxidative parameters); protein expression (mitochondrial transcription factor A (TFAM), NLRP-3, 8-oxoG; Bax, Bcl-2 and (ionized calcium-binding adaptor molecule 1 (IBA-1)); and the activity of mitochondrial respiratory chain complexes. It was observed that the septic group in both structures studied showed an increase in proinflammatory cytokines mediated by increased activity in NLRP-3, with more significant oxidative damage and higher production of reactive oxygen species (ROS) by mitochondria. Damage to mtDNA it was also observed with an increase in 8-oxoG levels and lower levels of TFAM and NGF-1. In addition, this group had an increase in pro-apoptotic proteins and IBA-1 positive cells. However, MFA at doses of 30 and 50 mg/kg decreased inflammasome activity, reduced levels of cytokines and oxidative damage, increased bioenergetic efficacy and reduced production of ROS and 8-oxoG, and increased levels of TFAM, NGF-1, Bcl-2, reducing microglial activation. As a result, it is suggested that MFA induces protection in the central nervous system early after the onset of sepsis.

Alzheimer's disease is associated with disruption in thiamin transport physiology: A potential role for neuroinflammation

Alzheimer's disease (AD) is a neurodegenerative disease characterized by Amyloid-β peptide (Aβ) containing plaques and cognitive deficits. The pathophysiology of AD also involves neuroinflammation. Vitamin B1 (thiamin) is indispensable for normal cellular energy metabolism. Thiamin homeostasis is altered in AD, and its deficiency is known to aggravate AD pathology. Little, however, is known about possible alterations in level of expression of thiamin transporters-1 and -2 (THTR-1 and -2) in the brain of AD, and whether pro-inflammatory cytokines affect thiamin uptake by brain cells. We addressed these issues using brain tissue samples [prefrontal cortex (PFC) and hippocampus (HIP)] from AD patients and from 5XFAD mouse model of AD, together with cultured human neuroblastoma SH-SY5Y cells as model. Our results revealed a significantly lower expression of both THTR-1 and THTR-2 in the PFC and HIP of AD patients and 5XFAD mouse model of AD compared to appropriate normal controls. Further, we found that exposure of the SH-SY5Y cells to pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) led to a significant inhibition in thiamin uptake. Focusing on IL-1β, we found the inhibition in thiamin uptake to be time-dependent and reversible; it was also associated with a substantial reduction in expression of THTR-1 (but not THTR-2) protein and mRNA as well as a decrease in promoter activity of the SLC19A2 gene (which encodes THTR-1). Finally, using transcriptomic analysis, we found that thiamin availability in SH-SY5Y cells caused changes in the expression of genes relevant to AD pathways. These studies demonstrate, for the first time, that thiamin transport physiology/molecular biology parameters are negatively impacted in AD brain and that pro-inflammatory cytokines inhibit thiamin uptake by neuroblastoma cells. The results also support a possible role for thiamin in the pathophysiology of AD.

Role of melatonin in Alzheimer's disease: From preclinical studies to novel melatonin-based therapies

Melatonin and novel melatonin-based therapies such as melatonin-containing hybrid molecules, melatonin analogues, and melatonin derivatives have been investigated as potential therapeutics against Alzheimer's disease (AD) pathogenesis. In this review, we examine the developmental trends of melatonin therapies for AD from 1997 to 2021. We then highlight the neuroprotective mechanisms of melatonin therapy derived from preclinical studies. These mechanisms include the alleviation of amyloid-related burden, neurofibrillary tangle accumulation, oxidative stress, neuroinflammation, apoptosis, mitochondrial dysfunction, and impaired neuroplasticity and neurotransmission. We further illustrate the beneficial effects of melatonin on behavior in animal models of AD. Next, we discuss the clinical effects of melatonin on sleep, cognition, behavior, psychiatric symptoms, electroencephalography findings, and molecular biomarkers in patients with mild cognitive impairment and AD. We then explore the effectiveness of novel melatonin-based therapies. Lastly, we discuss the limitations of current melatonin therapies for AD and suggest two emerging research themes for future study.

Human iPSC-Derived Neural Models for Studying Alzheimer's Disease: from Neural Stem Cells to Cerebral Organoids

During the past two decades, induced pluripotent stem cells (iPSCs) have been widely used to study mechanisms of human neural development, disease modeling, and drug discovery in vitro. Especially in the field of Alzheimer’s disease (AD), where this treatment is lacking, tremendous effort has been put into the investigation of molecular mechanisms behind this disease using induced pluripotent stem cell-based models. Numerous of these studies have found either novel regulatory mechanisms that could be exploited to develop relevant drugs for AD treatment or have already tested small molecules on in vitro cultures, directly demonstrating their effect on amelioration of AD-associated pathology. This review thus summarizes currently used differentiation strategies of induced pluripotent stem cells towards neuronal and glial cell types and cerebral organoids and their utilization in modeling AD and potential drug discovery.

Amelioration of Alzheimer's Disease by Gut-Pancreas-Liver-Brain Interaction in an App Knock-In Mouse Model

In this study, we observed disease progression, changes in the gut microbiota, and interactions among the brain, liver, pancreas, and intestine in a mouse model of Alzheimer's disease (AD), in addition to attempting to inhibit disease progression through the dietary supplementation of L-arginine and limonoids. Wild-type mice (WC) and AD mice were fed a normal diet (AC), a diet supplemented with L-arginine and limonoids (ALA), or a diet containing only limonoids (AL) for 12-64 weeks. The normal diet-fed WC and AC mice showed a decrease in the diversity of the gut microbiota, with an increase in the Firmicutes/Bacteroidetes ratio, and bacterial translocation. Considerable bacterial translocation to the pancreas and intense inflammation of the pancreas, liver, brain, and intestinal tissues were observed in the AC mice from alterations in the gut microbiota. The ALA diet or AL diet-fed mice showed increased diversity of the bacterial flora and suppressed oxidative stress and inflammatory responses in hepatocytes and pancreatic cells, bacterial translocation, and neurodegeneration of the brain. These findings suggest that L-arginine and limonoids help in maintaining the homeostasis of the gut microbiota, pancreas, liver, brain, and gut in AD mice.

How an increase in the copy number of HSV-1 during latency can cause Alzheimer's disease: the viral and cellular dynamics according to the microcompetition model

Numerous studies observed a link between the herpes smplex virus-1 (HSV-1) and Alzheimer's disease. However, the exact viral and cellular dynamics that lead from an HSV-1 infection to Alzheimer's disease are unknown. In this paper, we use the microcompetition model to formulate these dynamics by connecting seemingly unconnected observations reported in the literature. We concentrate on four pathologies characteristic of Alzheimer's disease. First, we explain how an increase in the copy number of HSV-1 during latency can decrease the expression of BECN1/Beclin1, the degradative trafficking protein, which, in turn, can cause a dysregulation of autophagy and Alzheimer's disease. Second, we show how an increase in the copy number of the latent HSV-1 can decrease the expression of many genes important for mitochondrial genome metabolism, respiratory chain, and homeostasis, which can lead to oxidative stress and neuronal damage, resulting in Alzheimer's disease. Third, we describe how an increase in this copy number can reduce the concentration of the NMDA receptor subunits NR1 and NR2b (Grin1 and Grin2b genes), and brain derived neurotrophic factor (BDNF), which can cause an impaired synaptic plasticity, Aβ accumulation and eventually Alzheimer's disease. Finally, we show how an increase in the copy number of HSV-1 in neural stem/progenitor cells in the hippocampus during the latent phase can lead to an abnormal quantity and quality of neurogenesis, and the clinical presentation of Alzheimer's disease. Since the current understanding of the dynamics and homeostasis of the HSV-1 reservoir during latency is limited, the proposed model represents only a first step towards a complete understanding of the relationship between the copy number of HSV-1 during latency and Alzheimer's disease.

Contribution of Mitochondrial Dysfunction Combined with NLRP3 Inflammasome Activation in Selected Neurodegenerative Diseases

Alzheimer's disease and Parkinson's disease are the most common forms of neurodegenerative illnesses. It has been widely accepted that neuroinflammation is the key pathogenic mechanism in neurodegeneration. Both mitochondrial dysfunction and enhanced NLRP3 (nucleotide-binding oligomerization domain (NOD)-like receptor protein 3) inflammasome complex activity have a crucial role in inducing and sustaining neuroinflammation. In addition, mitochondrial-related inflammatory factors could drive the formation of inflammasome complexes, which are responsible for the activation, maturation, and release of pro-inflammatory cytokines, including interleukin-1β (IL-1β) and interleukin-18 (IL-18). The present review includes a broadened approach to the role of mitochondrial dysfunction resulting in abnormal NLRP3 activation in selected neurodegenerative diseases. Moreover, we also discuss the potential mitochondria-focused treatments that could influence the NLRP3 complex.

Role of Oxidative Damage in Alzheimer's Disease and Neurodegeneration: From Pathogenic Mechanisms to Biomarker Discovery

Alzheimer’s disease (AD) is a neurodegenerative disorder accounting for over 50% of all dementia patients and representing a leading cause of death worldwide for the global ageing population. The lack of effective treatments for overt AD urges the discovery of biomarkers for early diagnosis, i.e., in subjects with mild cognitive impairment (MCI) or prodromal AD. The brain is exposed to oxidative stress as levels of reactive oxygen species (ROS) are increased, whereas cellular antioxidant defenses are decreased. Increased ROS levels can damage cellular structures or molecules, leading to protein, lipid, DNA, or RNA oxidation. Oxidative damage is involved in the molecular mechanisms which link the accumulation of amyloid-β and neurofibrillary tangles, containing hyperphosphorylated tau, to microglia response. In this scenario, microglia are thought to play a crucial role not only in the early events of AD pathogenesis but also in the progression of the disease. This review will focus on oxidative damage products as possible peripheral biomarkers in AD and in the preclinical phases of the disease. Particular attention will be paid to biological fluids such as blood, CSF, urine, and saliva, and potential future use of molecules contained in such body fluids for early differential diagnosis and monitoring the disease course. We will also review the role of oxidative damage and microglia in the pathogenesis of AD and, more broadly, in neurodegeneration.

A high-fat diet exacerbates the Alzheimer's disease pathology in the hippocampus of the AppNL-F/NL-F knock-in mouse model

Insulin resistance and diabetes mellitus are major risk factors for Alzheimer's disease (AD), and studies with transgenic mouse models of AD have provided supportive evidence with some controversies. To overcome potential artifacts derived from transgenes, we used a knock‐in mouse model, App^{NL−F/NL−F}, which accumulates Aβ plaques from 6 months of age and shows mild cognitive impairment at 18 months of age, without the overproduction of APP. In the present study, 6‐month‐old male App^{NL−F/NL−F} and wild‐type mice were fed a regular or high‐fat diet (HFD) for 12 months. HFD treatment caused obesity and impaired glucose tolerance (i.e., T2DM conditions) in both wild‐type and App^{NL−F/NL−F} mice, but only the latter animals exhibited an impaired cognitive function accompanied by marked increases in both Aβ deposition and microgliosis as well as insulin resistance in the hippocampus. Furthermore, HFD‐fed App^{NL−F/NL−F} mice exhibited a significant decrease in volume of the granule cell layer in the dentate gyrus and an increased accumulation of 8‐oxoguanine, an oxidized guanine base, in the nuclei of granule cells. Gene expression profiling by microarrays revealed that the populations of the cell types in hippocampus were not significantly different between the two mouse lines, regardless of the diet. In addition, HFD treatment decreased the expression of the Aβ binding protein transthyretin (TTR) in App^{NL−F/NL−F} mice, suggesting that the depletion of TTR underlies the increased Aβ deposition in the hippocampus of HFD‐fed App^{NL−F/NL−F} mice.

DRD1 agonist A-68930 improves mitochondrial dysfunction and cognitive deficits in a streptozotocin-induced mouse model

Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder characterized by irreversible cognitive deficits and memory dysfunction. Dopamine is the most abundant catecholaminergic neurotransmitter in the brain which regulates motivation, reward, movement, and cognition. Recently, increasing evidences have shown that dopaminergic system is disturbed in AD conditions, and pharmacological interventions targeting dopamine D1 receptor (DRD1) exhibit certain therapeutic benefits in AD models. However, the underlying link between DRD1 and AD remains elusive. This study sought to test whether the selective DRD1 agonist A-68930 could improve streptozotocin (STZ)-induced cognitive impairment in mice. Here we found that A-68930 treatment through intraperitoneal injection efficiently alleviated STZ-induced cognitive deficits in mice. Moreover, our mechanism researches revealed that the DRD1 signaling induced by A-68930 significantly rescued STZ-induced mitochondrial biogenesis deficit, mitochondrial dysfunction, Aβ overexpression, and tau phosphorylation in mice hippocampus and cortex and SH-SY5Y cells, which may be mediated through stimulating AMPK/PGC-1α pathway. This study indicates that DRD1 agonist A-68930 can improve STZ-induced cognitive deficits and mitochondrial dysfunction in vivo and in vitro, and DRD1 may represent an appropriate target candidate for AD drug development.

Transthyretin: From Structural Stability to Osteoarticular and Cardiovascular Diseases

Transthyretin (TTR) is a tetrameric protein transporting hormones in the plasma and brain, which has many other activities that have not been fully acknowledged. TTR is a positive indicator of nutrition status and is negatively correlated with inflammation. TTR is a neuroprotective and oxidative-stress-suppressing factor. The TTR structure is destabilized by mutations, oxidative modifications, aging, proteolysis, and metal cations, including Ca2+. Destabilized TTR molecules form amyloid deposits, resulting in senile and familial amyloidopathies. This review links structural stability of TTR with the environmental factors, particularly oxidative stress and Ca2+, and the processes involved in the pathogenesis of TTR-related diseases. The roles of TTR in biomineralization, calcification, and osteoarticular and cardiovascular diseases are broadly discussed. The association of TTR-related diseases and vascular and ligament tissue calcification with TTR levels and TTR structure is presented. It is indicated that unaggregated TTR and TTR amyloid are bound by vicious cycles, and that TTR may have an as yet undetermined role(s) at the crossroads of calcification, blood coagulation, and immune response.

Exploring the Physiological Role of Transthyretin in Glucose Metabolism in the Liver

Transthyretin (TTR), a 55 kDa evolutionarily conserved protein, presents altered levels in several conditions, including malnutrition, inflammation, diabetes, and Alzheimer’s Disease. It has been shown that TTR is involved in several functions, such as insulin release from pancreatic β-cells, recovery of blood glucose and glucagon levels of the islets of Langerhans, food intake, and body weight. Here, the role of TTR in hepatic glucose metabolism was explored by studying the levels of glucose in mice with different TTR genetic backgrounds, namely with two copies of the TTR gene, TTR+/+; with only one copy, TTR+/−; and without TTR, TTR−/−. Results showed that TTR haploinsufficiency (TTR+/−) leads to higher glucose in both plasma and in primary hepatocyte culture media and lower expression of the influx glucose transporters, GLUT1, GLUT3, and GLUT4. Further, we showed that TTR haploinsufficiency decreases pyruvate kinase M type (PKM) levels in mice livers, by qRT-PCR, but it does not affect the hepatic production of the studied metabolites, as determined by 1H NMR. Finally, we demonstrated that TTR increases mitochondrial density in HepG2 cells and that TTR insufficiency triggers a higher degree of oxidative phosphorylation in the liver. Altogether, these results indicate that TTR contributes to the homeostasis of glucose by regulating the levels of glucose transporters and PKM enzyme and by protecting against mitochondrial oxidative stress.

Dementia and cognitive impairment in adults as sequels of HSV-1-related encephalitis: a review

Considering the variety of mechanisms of Herpes simplex virus (HSV-1) contamination and its broad invasive potential of the nervous system, a life-long latent infection is established. Infected adult individuals may be susceptible to viral reactivation when under the influence of multiple stressors, especially regarding immunocompromised patients. This guides a series of neuroinflammatory events on the cerebral cortex, culminating, rarely, in encephalitis and cytotoxic / vasogenic brain edema. A sum of studies of such processes provides an explanation, even though not yet completely clarified, on how the clinical evolution to cognitive impairment and dementia might be enabled. In addition, it is of extreme importance to recognize the current dementia and cognitive deficit worldwide panorama. The aim of this literature review is to elucidate the available data upon the pathophysiology of HSV-1 infection as well as to describe the clinical panorama of the referred afflictions.

MTH1 and OGG1 maintain a low level of 8-oxoguanine in Alzheimer's brain, and prevent the progression of Alzheimer's pathogenesis

8-Oxoguanine (8-oxoG), a major oxidative base lesion, is highly accumulated in Alzheimer’s disease (AD) brains during the pathogenic process. MTH1 hydrolyzes 8-oxo-dGTP to 8-oxo-dGMP, thereby avoiding 8-oxo-dG incorporation into DNA. 8-OxoG DNA glycosylase-1 (OGG1) excises 8-oxoG paired with cytosine in DNA, thereby minimizing 8-oxoG accumulation in DNA. Levels of MTH1 and OGG1 are significantly reduced in the brains of sporadic AD cases. To understand how 8-oxoG accumulation in the genome is involved in AD pathogenesis, we established an AD mouse model with knockout of Mth1 and Ogg1 genes in a 3xTg-AD background. MTH1 and OGG1 deficiency increased 8-oxoG accumulation in nuclear and, to a lesser extent, mitochondrial genomes, causing microglial activation and neuronal loss with impaired cognitive function at 4–5 months of age. Furthermore, minocycline, which inhibits microglial activation and reduces neuroinflammation, markedly decreased the nuclear accumulation of 8-oxoG in microglia, and inhibited microgliosis and neuronal loss. Gene expression profiling revealed that MTH1 and OGG1 efficiently suppress progression of AD by inducing various protective genes against AD pathogenesis initiated by Aß/Tau accumulation in 3xTg-AD brain. Our findings indicate that efficient suppression of 8-oxoG accumulation in brain genomes is a new approach for prevention and treatment of AD.

Mitochondrial ubiquitin ligase alleviates Alzheimer's disease pathology via blocking the toxic amyloid-β oligomer generation

Mitochondrial pathophysiology is implicated in the development of Alzheimer's disease (AD). An integrative database of gene dysregulation suggests that the mitochondrial ubiquitin ligase MITOL/MARCH5, a fine-tuner of mitochondrial dynamics and functions, is downregulated in patients with AD. Here, we report that the perturbation of mitochondrial dynamics by MITOL deletion triggers mitochondrial impairments and exacerbates cognitive decline in a mouse model with AD-related Aβ pathology. Notably, MITOL deletion in the brain enhanced the seeding effect of Aβ fibrils, but not the spontaneous formation of Aβ fibrils and plaques, leading to excessive secondary generation of toxic and dispersible Aβ oligomers. Consistent with this, MITOL-deficient mice with Aβ etiology exhibited worsening cognitive decline depending on Aβ oligomers rather than Aβ plaques themselves. Our findings suggest that alteration in mitochondrial morphology might be a key factor in AD due to directing the production of Aβ form, oligomers or plaques, responsible for disease development.

Mitochondrial dysfunction in neurodegenerative diseases: A focus on iPSC-derived neuronal models

Progressive neuronal loss is a hallmark of many neurodegenerative diseases, including Alzheimer's and Parkinson's disease. These pathologies exhibit clear signs of inflammation, mitochondrial dysfunction, calcium deregulation, and accumulation of aggregated or misfolded proteins. Over the last decades, a tremendous research effort has contributed to define some of the pathological mechanisms underlying neurodegenerative processes in these complex brain neurodegenerative disorders. To better understand molecular mechanisms responsible for neurodegenerative processes and find potential interventions and pharmacological treatments, it is important to have robust in vitro and pre-clinical animal models that can recapitulate both the early biological events undermining the maintenance of the nervous system and early pathological events. In this regard, it would be informative to determine how different inherited pathogenic mutations can compromise mitochondrial function, calcium signaling, and neuronal survival. Since post-mortem analyses cannot provide relevant information about the disease progression, it is crucial to develop model systems that enable the investigation of early molecular changes, which may be relevant as targets for novel therapeutic options. Thus, the use of human induced pluripotent stem cells (iPSCs) represents an exceptional complementary tool for the investigation of degenerative processes. In this review, we will focus on two neurodegenerative diseases, Alzheimer's and Parkinson's disease. We will provide examples of iPSC-derived neuronal models and how they have been used to study calcium and mitochondrial alterations during neurodegeneration.

Mitochondrial DNA copy number in human disease: the more the better?

Most of the genetic information has been lost or transferred to the nucleus during the evolution of mitochondria. Nevertheless, mitochondria have retained their own genome that is essential for oxidative phosphorylation (OXPHOS). In mammals, a gene‐dense circular mitochondrial DNA (mtDNA) of about 16.5 kb encodes 13 proteins, which constitute only 1% of the mitochondrial proteome. Mammalian mtDNA is present in thousands of copies per cell and mutations often affect only a fraction of them. Most pathogenic human mtDNA mutations are recessive and only cause OXPHOS defects if present above a certain critical threshold. However, emerging evidence strongly suggests that the proportion of mutated mtDNA copies is not the only determinant of disease but that also the absolute copy number matters. In this review, we critically discuss current knowledge of the role of mtDNA copy number regulation in various types of human diseases, including mitochondrial disorders, neurodegenerative disorders and cancer, and during ageing. We also provide an overview of new exciting therapeutic strategies to directly manipulate mtDNA to restore OXPHOS in mitochondrial diseases.

Protective effects of BACE1 inhibitory ligand molecules against amyloid beta-induced synaptic and mitochondrial toxicities in Alzheimer's disease

Amyloid-β (Aβ) peptides are the major drivers of Alzheimer's disease (AD) pathogenesis, and are formed by successive cleavage of the amyloid precursor protein (APP) by the beta and gamma secretases. Mounting evidence suggests that Aβ and mitochondrial structural and functional abnormalities are critically involved in the loss of synapses and cognitive decline, in patients with AD. In AD brain, state the sequential proteolytic cleavage of APP by beta secretase 1 enzyme (BACE1) and γ-secretase leads to the production and release of Aβ40 and 42. BACE1 expression and activity increased in the brains of AD patients. Structurally, β-secretase has a very large binding site (1000 Å) with fewer hydrophobic domains that makes a challenge to identify the specific targets/binding sites of BACE1. In the present study, we constructed a BACE1 pharmacophore with pepstatin and screened through molecular docking studies. We found one potential candidate (referred as ligand 1) that binds to the key catalytic residues of BACE1 and predicts to inhibit abnormal APP processing and reduce Aβ levels in AD neurons. Using biochemical, molecular, transmission electron microscopy, immunoblotting and immunofluorescence analyses, we studied the protective effects of ligand 1 against Aβ-induced synaptic and mitochondrial toxicities in mouse neuroblastoma (N2a) cells that express mutant APP. We found interaction between ligand 1 and BACE1 and this interaction decreased BACE1 activity, Aβ40 and 42 levels. We also found increased mitochondrial biogenesis, mitochondrial fusion and synaptic activity and reduced mitochondrial fission in ligand 1-treated mutant APP cells. Based on these results, we cautiously conclude that ligand 1 reduces Aβ-induced mitochondrial and synaptic toxicities, and maintains mitochondrial dynamics and neuronal function in AD.

Exploring the role of mitochondrial proteins as molecular target in Alzheimer's disease

Brain is a fully differentiated organ and is sensitive towards oxidative damage of various compounds including lipids, proteins, and DNA that occurs during process of normal aging and is mainly due to its high energy metabolism and reduced activity of anti-oxidative defense mechanism. Mitochondria are dynamic ATP-generating organelles which constitutes cellular functions such as regulation of intracellular calcium, bio-energetic processes, and reduction-oxidation of cells. Such functioning is negatively affected due to the presence of amyloid β peptide (Aβ) which is involved in pathogenesis of Alzheimer disease (AD). Aβ interacts with mitochondria and leads to mitochondrial dysfunction. Mitochondrial dysfunction, abnormal interactions, oxidative stress, and mis-folding of synaptic proteins inside nervous system are explored and regarded as primary or initial features in insurgence of pathology (AD and other neurological disease). The major histopathological hallmarks of AD are characterized by presence of these hallmarks intracellularly, its further progression and exacerbation which leads to excessive accumulation of oligomeric as well as fibrillar-β-amyloid peptides (present extracellularly) and accumulation of neurofibrillary tangles intracellularly. The current review will focus on alterations and variation in mitochondria/mitochondrial DNA (mtDNA) and the rationale for involvement of related abnormalities in pathogenesis of AD.

Relationships between Mitochondrial Dysfunction and Neurotransmission Failure in Alzheimer's Disease

Besides extracellular deposition of amyloid beta and formation of phosphorylated tau in the brains of patients with Alzheimer's disease (AD), the pathogenesis of AD is also thought to involve mitochondrial dysfunctions and altered neurotransmission systems. However, none of these components can describe the diverse cognitive, behavioural, and psychiatric symptoms of AD without the pathologies interacting with one another. The purpose of this review is to understand the relationships between mitochondrial and neurotransmission dysfunctions in terms of (1) how mitochondrial alterations affect cholinergic and monoaminergic systems via disruption of energy metabolism, oxidative stress, and apoptosis; and (2) how different neurotransmission systems drive mitochondrial dysfunction via increasing amyloid beta internalisation, oxidative stress, disruption of mitochondrial permeabilisation, and mitochondrial trafficking. All these interactions are separately discussed in terms of neurotransmission systems. The association of mitochondrial dysfunctions with alterations in dopamine, norepinephrine, and histamine is the prospective goal in this research field. By unfolding the complex interactions surrounding mitochondrial dysfunction in AD, we can better develop potential treatments to delay, prevent, or cure this devastating disease.

Mitochondrial HMG-Box Containing Proteins: From Biochemical Properties to the Roles in Human Diseases

Mitochondrial DNA (mtDNA) molecules are packaged into compact nucleo-protein structures called mitochondrial nucleoids (mt-nucleoids). Their compaction is mediated in part by high-mobility group (HMG)-box containing proteins (mtHMG proteins), whose additional roles include the protection of mtDNA against damage, the regulation of gene expression and the segregation of mtDNA into daughter organelles. The molecular mechanisms underlying these functions have been identified through extensive biochemical, genetic, and structural studies, particularly on yeast (Abf2) and mammalian mitochondrial transcription factor A (TFAM) mtHMG proteins. The aim of this paper is to provide a comprehensive overview of the biochemical properties of mtHMG proteins, the structural basis of their interaction with DNA, their roles in various mtDNA transactions, and the evolutionary trajectories leading to their rapid diversification. We also describe how defects in the maintenance of mtDNA in cells with dysfunctional mtHMG proteins lead to different pathologies at the cellular and organismal level.

Mitochondria dysfunction in the pathogenesis of Alzheimer's disease: recent advances

Alzheimer's disease (AD) is one of the most prevalent neurodegenerative diseases, characterized by impaired cognitive function due to progressive loss of neurons in the brain. Under the microscope, neuronal accumulation of abnormal tau proteins and amyloid plaques are two pathological hallmarks in affected brain regions. Although the detailed mechanism of the pathogenesis of AD is still elusive, a large body of evidence suggests that damaged mitochondria likely play fundamental roles in the pathogenesis of AD. It is believed that a healthy pool of mitochondria not only supports neuronal activity by providing enough energy supply and other related mitochondrial functions to neurons, but also guards neurons by minimizing mitochondrial related oxidative damage. In this regard, exploration of the multitude of mitochondrial mechanisms altered in the pathogenesis of AD constitutes novel promising therapeutic targets for the disease. In this review, we will summarize recent progress that underscores the essential role of mitochondria dysfunction in the pathogenesis of AD and discuss mechanisms underlying mitochondrial dysfunction with a focus on the loss of mitochondrial structural and functional integrity in AD including mitochondrial biogenesis and dynamics, axonal transport, ER-mitochondria interaction, mitophagy and mitochondrial proteostasis.

Emerging perspectives on mitochondrial dysfunction and inflammation in Alzheimer's disease

Despite enduring diverse insults, mitochondria maintain normal functions through mitochondrial quality control. However, the failure of mitochondrial quality control resulting from excess damage and mechanical defects causes mitochondrial dysfunction, leading to various human diseases. Recent studies have reported that mitochondrial defects are found in Alzheimer’s disease (AD) and worsen AD symptoms. In AD pathogenesis, mitochondrial dysfunction-driven generation of reactive oxygen species (ROS) and their contribution to neuronal damage has been widely studied. In contrast, studies on mitochondrial dysfunction-associated inflammatory responses have been relatively scarce. Moreover, ROS produced upon failure of mitochondrial quality control may be linked to the inflammatory response and influence the progression of AD. Thus, this review will focus on inflammatory pathways that are associated with and initiated through defective mitochondria and will summarize recent progress on the role of mitochondria-mediated inflammation in AD. We will also discuss how reducing mitochondrial dysfunction-mediated inflammation could affect AD.

Modeling Alzheimer's disease with iPSC-derived brain cells

Alzheimer's disease is a devastating neurodegenerative disorder with no cure. Countless promising therapeutics have shown efficacy in rodent Alzheimer's disease models yet failed to benefit human patients. While hope remains that earlier intervention with existing therapeutics will improve outcomes, it is becoming increasingly clear that new approaches to understand and combat the pathophysiology of Alzheimer's disease are needed. Human induced pluripotent stem cell (iPSC) technologies have changed the face of preclinical research and iPSC-derived cell types are being utilized to study an array of human conditions, including neurodegenerative disease. All major brain cell types can now be differentiated from iPSCs, while increasingly complex co-culture systems are being developed to facilitate neuroscience research. Many cellular functions perturbed in Alzheimer's disease can be recapitulated using iPSC-derived cells in vitro, and co-culture platforms are beginning to yield insights into the complex interactions that occur between brain cell types during neurodegeneration. Further, iPSC-based systems and genome editing tools will be critical in understanding the roles of the numerous new genes and mutations found to modify Alzheimer's disease risk in the past decade. While still in their relative infancy, these developing iPSC-based technologies hold considerable promise to push forward efforts to combat Alzheimer's disease and other neurodegenerative disorders.

Cancer‑related fatigue during combined treatment of androgen deprivation therapy and radiotherapy is associated with mitochondrial dysfunction

Combined androgen deprivation therapy (ADT) and radiation therapy (RT) is the standard of care treatment for non-metastatic prostate cancer (NMPC). Despite the efficacy, treatment-related symptoms including fatigue greatly reduce the quality of life of cancer patients. The goal of the study is to examine the influence of combined ADT/RT on fatigue and understand its underlying mechanisms. A total of 64 participants with NMPC were enrolled. Fatigue was assessed using the Functional Assessment of Cancer Therapy-Fatigue. Mitochondrial function parameters were measured as oxygen consumption from peripheral blood mononuclear cells (PBMCs) extracted from participants' whole blood. An ADT/RT-induced fatigue mouse model was developed, with fatigue measured as a reduction in voluntary wheel-running activity (VWRA) in 54 mice. Mitochondrial function was assessed in the ADT/RT mouse brains using western blot analysis of glucose transporter 4 (GLUT4) and transcription factor A, mitochondrial (TFAM). The results demonstrated that fatigue in the ADT group was exacerbated during RT compared with the non-ADT group. This effect was specific to fatigue, as depressive symptoms were unaffected. PBMCs of fatigued subjects exhibited decreased ATP coupling efficiency compared to non-fatigued subjects, indicative of mitochondrial dysfunction. The ADT/RT mice demonstrated the synergistic effect of ADT and RT in decreasing VWRA. Brain tissues of ADT/RT mice exhibited decreased levels of GLUT4 and TFAM suggesting that impaired neuronal metabolic homeostasis may contribute to fatigue pathogenesis. In conclusion, these findings suggest that fatigue induced by ADT/RT may be attributable to mitochondrial dysfunction both peripherally and in the central nervous system (CNS). The synergistic effect of ADT/RT is behaviorally reproducible in a mouse model and its mechanism may be related to bioenergetics in the CNS.

Distinct Genetic Signatures of Cortical and Subcortical Regions Associated with Human Memory

Despite the discovery of gene variants linked to memory performance, understanding the genetic basis of adult human memory remains a challenge. Here, we devised an unsupervised framework that relies on spatial correlations between human transcriptome data and functional neuroimaging maps to uncover the genetic signatures of memory in functionally-defined cortical and subcortical memory regions.

Despite the discovery of gene variants linked to memory performance, understanding the genetic basis of adult human memory remains a challenge. Here, we devised an unsupervised framework that relies on spatial correlations between human transcriptome data and functional neuroimaging maps to uncover the genetic signatures of memory in functionally-defined cortical and subcortical memory regions. Results were validated with animal literature and showed that our framework is highly effective in identifying memory-related processes and genes compared to a control cognitive function. Genes preferentially expressed in cortical memory regions are linked to memory-related processes such as immune and epigenetic regulation. Genes expressed in subcortical memory regions are associated with neurogenesis and glial cell differentiation. Genes expressed in both cortical and subcortical memory areas are involved in the regulation of transcription, synaptic plasticity, and glutamate receptor signaling. Furthermore, distinct memory-associated genes such as PRKCD and CDK5 are linked to cortical and subcortical regions, respectively. Thus, cortical and subcortical memory regions exhibit distinct genetic signatures that potentially reflect functional differences in health and disease, and nominates gene candidates for future experimental investigations.

IGFBP-2 Signaling in the Brain: From Brain Development to Higher Order Brain Functions

Insulin-like growth factor-binding protein-2 (IGFBP-2) is a pleiotropic polypeptide that functions as autocrine and/or paracrine growth factors. IGFBP-2 is the most abundant of the IGFBPs in the cerebrospinal fluid (CSF), and developing brain showed the highest expression of IGFBP-2. IGFBP-2 expressed in the hippocampus, cortex, olfactory lobes, cerebellum, and amygdala. IGFBP-2 mRNA expression is seen in meninges, blood vessels, and in small cell-body neurons (interneurons) and astrocytes. The expression pattern of IGFBP-2 is often developmentally regulated and cell-specific. Biological activities of IGFBP-2 which are independent of their abilities to bind to insulin-like growth factors (IGFs) are mediated by the heparin binding domain (HBD). To execute IGF-independent functions, some IGFBPs have shown to bind with their putative receptors or to translocate inside the cells. Thus, IGFBP-2 functions can be mediated both via insulin-like growth factor receptor-1 (IGF-IR) and independent of IGF-Rs. In this review, I suggest that IGFBP-2 is not only involved in the growth, development of the brain but also with the regulation of neuronal plasticity to modulate high-level cognitive operations such as spatial learning and memory and information processing. Hence, IGFBP-2 serves as a neurotrophic factor which acts via metaplastic signaling from embryonic to adult stages.

White Matter Abnormalities Linked to Interferon, Stress Response, and Energy Metabolism Gene Expression Changes in Older HIV-Positive Patients on Antiretroviral Therapy

Neurocognitive impairment (NCI) remains a significant cause of morbidity in human immunodeficiency virus (HIV)-positive individuals despite highly active antiretroviral therapy (HAART). White matter abnormalities have emerged as a key component of age-related neurodegeneration, and accumulating evidence suggests they play a role in HIV-associated neurocognitive disorders. Viral persistence in the brain induces chronic inflammation associated with lymphocytic infiltration, microglial proliferation, myelin loss, and cerebrovascular lesions. In this study, gene expression profiling was performed on frontal white matter from 34 older HIV+ individuals on HAART (18 with NCI) and 24 HIV-negative controls. We used the NanoString nCounter platform to evaluate 933 probes targeting inflammation, interferon and stress responses, energy metabolism, and central nervous system-related genes. Viral loads were measured using single-copy assays. Compared to HIV- controls, HIV+ individuals exhibited increased expression of genes related to interferon, MHC-1, and stress responses, myeloid cells, and T cells and decreased expression of genes associated with oligodendrocytes and energy metabolism in white matter. These findings correlated with increased white matter inflammation and myelin pallor, suggesting interferon (IRFs, IFITM1, ISG15, MX1, OAS3) and stress response (ATF4, XBP1, CHOP, CASP1, WARS) gene expression changes are associated with decreased energy metabolism (SREBF1, SREBF2, PARK2, TXNIP) and oligodendrocyte myelin production (MAG, MOG), leading to white matter dysfunction. Machine learning identified a 15-gene signature predictive of HIV status that was validated in an independent cohort. No specific gene expression patterns were associated with NCI. These findings suggest therapies that decrease chronic inflammation while protecting mitochondrial function may help to preserve white matter integrity in older HIV+ individuals.

The Neuroprotective Effect of the Adiponectin Receptor Agonist AdipoRon on Glutamate-Induced Cell Death in Rat Primary Retinal Ganglion Cells

Purpose: To determine whether the adiponectin receptor (AdipoR) agonist AdipoRon inhibits glutamate-induced neuronal cell death and to investigate the neuroprotective mechanism of AdipoRon in rat primary retinal ganglion cells (RGCs). Methods: The expression pattern of AdipoR1 and AdipoR2 in rat retina and primary RGCs was examined by immunostaining. The neuroprotective effect of AdipoRon on glutamate-induced cell death was evaluated in rat primary RGCs. Cellular levels of reactive oxygen species (ROS) were also measured. Peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), estrogen-related receptor-α (Esrra), mitochondrial transcription factor A (TFAM), peroxisome proliferator-activated receptor α (PPARα), and catalase mRNA levels were examined. Results: The expression of AdipoR1 and AdipoR2 was confirmed in rat retina and primary RGCs. AdipoRon significantly increased the survival rate of glutamate-induced cell death and decreased ROS production. Additionally, the mRNA levels of PGC-1α, Esrra, and TFAM were upregulated by AdipoRon. Conclusions: These results suggest that AdipoRon has a neuroprotective effect by inhibiting ROS production via upregulation of PGC-1α, Esrra, and TFAM against glutamate-induced RGC death.

Elucidation of the Molecular Mechanism Underlying Lippia citriodora(Lim.)-Induced Relaxation and Anti-Depression

Lippia citriodora ethanolic extract (VEE) and verbascoside (Vs), a phenypropanoid glycoside, have been demonstrated to exert relaxant and anxiolytic properties. However, the molecular mechanisms behind their effects are still unclear. In this work, we studied the effects and action mechanisms of VEE and Vs in vivo and in vitro, on human neurotypic SH-SY5Y cells.TST was conducted on mice treated orally with VEE (25, 50 and 100 mg/Kg), Vs (2.5 and 5 mg/Kg), Bupropion (20 mg/Kg) and Milli-Q water. Higher dose of VEE-treated mice showed an increase of immobility time compared to control groups, indicating an induction of relaxation. This effect was found to be induced by regulation of genes playing key roles in calcium homeostasis (calcium channels), cyclic AMP (cAMP) production and energy metabolism. On the other hand, low doses of VEE and Vs showed an antidepressant-like effect and was confirmed by serotonin, noradrenalin, dopamine and BDNF expressions. Finally, VEE and Vsenhancedcell viability, mitochondrial activity and calcium uptake in vitro confirming in vivo findings. Our results showed induction of relaxation and antidepressant-like effects depending on the administered dose of VEE and Vs, through modulation of cAMP and calcium.

Mitochondrial complex IV mutation increases reactive oxygen species production and reduces lifespan in aged mice

AIM

Mitochondrial DNA (mtDNA) mutations can negatively influence lifespan and organ function. More than 250 pathogenic mtDNA mutations are known, often involving neurological symptoms. Major neurodegenerative diseases share key etiopathogenetic components ie mtDNA mutations, mitochondrial dysfunction and oxidative stress.

METHODS

Here, we characterized a conplastic mouse strain (C57BL/6 J-mtNOD) carrying an electron transport chain complex IV mutation that leads to an altered cytochrome c oxidase subunit III. Since this mouse also harbours adenine insertions in the mitochondrial tRNA for arginine, we chose the C57BL/6 J-mtMRL as control strain which also carries a heteroplasmic stretch of adenine repetitions in this tRNA isoform.

RESULTS

Using MitoSOX fluorescence, we observed an elevated mitochondrial superoxide production and a reduced gene expression of superoxide dismutase 2 in the 24-month-old mtNOD mouse as compared to control. Together with the decreased expression of the fission-relevant gene Fis1, these data confirmed that the ageing mtNOD mouse had a mitochondrial dysfunctional phenotype. On the functional level, we could not detect significant differences in synaptic long-term potentiation, but found a markedly poor physical constitution to perform the Morris water maze task at the age of 24 months. Moreover, the median lifespan of mtNOD mice was significantly shorter than of control animals.

CONCLUSION

Our findings demonstrate that a complex IV mutation leads to mitochondrial dysfunction that translates into survival.

Herpes Simplex Virus Type 1 Infection of the Central Nervous System: Insights Into Proposed Interrelationships With Neurodegenerative Disorders

Herpes simplex virus type 1 (HSV-1) is highly prevalent in humans and can reach the brain without evident clinical symptoms. Once in the central nervous system (CNS), the virus can either reside in a quiescent latent state in this tissue, or eventually actively lead to severe acute necrotizing encephalitis, which is characterized by exacerbated neuroinflammation and prolonged neuroimmune activation producing a life-threatening disease. Although HSV-1 encephalitis can be treated with antivirals that limit virus replication, neurological sequelae are common and the virus will nevertheless remain for life in the neural tissue. Importantly, there is accumulating evidence that suggests that HSV-1 infection of the brain both, in symptomatic and asymptomatic individuals could lead to neuronal damage and eventually, neurodegenerative disorders. Here, we review and discuss acute and chronic infection of particular brain regions by HSV-1 and how this may affect neuron and cognitive functions in the host. We review potential cellular and molecular mechanisms leading to neurodegeneration, such as protein aggregation, dysregulation of autophagy, oxidative cell damage and apoptosis, among others. Furthermore, we discuss the impact of HSV-1 infection on brain inflammation and its potential relationship with neurodegenerative diseases.

Important advances in Alzheimer's disease from the use of induced pluripotent stem cells

Among the various types of dementia, Alzheimer’s disease (AD) is the most prevalent and is clinically defined as the appearance of progressive deficits in cognition and memory. Considering that AD is a central nervous system disease, getting tissue from the patient to study the disease before death is challenging. The discovery of the technique called induced pluripotent stem cells (iPSCs) allows to reprogram the patient’s somatic cells to a pluripotent state by the forced expression of a defined set of transcription factors. Many studies have shown promising results and made important conclusions beyond AD using iPSCs approach. Due to the accumulating knowledge related to this topic and the important advances obtained until now, we review, using PubMed, and present an update of all publications related to AD from the use of iPSCs. The first iPSCs generated for AD were carried out in 2011 by Yahata et al. (PLoS One 6:e25788, 2011) and Yaqi et al. (Hum Mol Genet 20:4530–9, 2011). Like other authors, both authors used iPSCs as a pre-clinical tool for screening therapeutic compounds. This approach is also essential to model AD, testing early toxicity and efficacy, and developing a platform for drug development. Considering that the iPSCs technique is relatively recent, we can consider that the AD field received valuable contributions from iPSCs models, contributing to our understanding and the treatment of this devastating disorder.

The Disease-modifying Drug Candidate, SAK3 Improves Cognitive Impairment and Inhibits Amyloid beta Deposition in App Knock-in Mice

Alzheimer's disease (AD) is a progressive neurodegenerative disease and the most common form of elderly dementia in the world. At present, acetylcholine inhibitors, such as donepezil, galantamine and rivastigmine, are used for AD therapy, but the therapeutic efficacy is limited. We recently proposed T-type voltage-gated Ca²⁺ channels' (T-VGCCs) enhancer as a new therapeutic candidate for AD. In the current study, we confirmed the pharmacokinetics of SAK3 in the plasma and brain of mice using ultra performance liquid chromatography-tandem mass spectrometry. We also investigated the effects of SAK3 on the major symptoms of AD, such as cognitive dysfunction and amyloid beta (Aβ) accumulation, in App^NL-F knock-in (NL-F) mice, which have been established as an AD model. Chronic SAK3 (0.5 mg/kg/day) oral administration for 3 months from 9 months of age improved cognitive function and inhibited Aβ deposition in 12-month-old NL-F mice. Using microarray and real-time PCR analysis, we discovered serum- and glucocorticoid-induced protein kinase 1 (SGK1) as one of possible genes involved in the inhibition of Aβ deposition and improvement of cognitive function by SAK3. These results support the idea that T-VGCC enhancer, SAK3 could be a novel candidate for disease-modifying therapeutics for AD.