Mitochondrial dysfunction: the missing link between aging and sporadic Alzheimer's disease

N1-methylation of adenosine (m1A) in ND5 mRNA leads to complex I dysfunction in Alzheimer's disease

One mechanism of particular interest to regulate mRNA fate post-transcriptionally is mRNA modification. Especially the extent of m1A mRNA methylation is highly discussed due to methodological differences. However, one single m1A site in mitochondrial ND5 mRNA was unanimously reported by different groups. ND5 is a subunit of complex I of the respiratory chain. It is considered essential for the coupling of oxidation and proton transport. Here we demonstrate that this m1A site might be involved in the pathophysiology of Alzheimer's disease (AD). One of the pathological hallmarks of this neurodegenerative disease is mitochondrial dysfunction, mainly induced by Amyloid β (Aβ). Aβ mainly disturbs functions of complex I and IV of the respiratory chain. However, the molecular mechanism of complex I dysfunction is still not fully understood. We found enhanced m1A methylation of ND5 mRNA in an AD cell model as well as in AD patients. Formation of this m1A methylation is catalyzed by increased TRMT10C protein levels, leading to translation repression of ND5. As a consequence, here demonstrated for the first time, TRMT10C induced m1A methylation of ND5 mRNA leads to mitochondrial dysfunction. Our findings suggest that this newly identified mechanism might be involved in Aβ-induced mitochondrial dysfunction.

Putative Molecular Mechanisms Underpinning the Inverse Roles of Mitochondrial Respiration and Heme Function in Lung Cancer and Alzheimer's Disease

Mitochondria are the powerhouse of the cell. Mitochondria serve as the major source of oxidative stress. Impaired mitochondria produce less adenosine triphosphate (ATP) but generate more reactive oxygen species (ROS), which could be a major factor in the oxidative imbalance observed in Alzheimer's disease (AD). Well-balanced mitochondrial respiration is important for the proper functioning of cells and human health. Indeed, recent research has shown that elevated mitochondrial respiration underlies the development and therapy resistance of many types of cancer, whereas diminished mitochondrial respiration is linked to the pathogenesis of AD. Mitochondria govern several activities that are known to be changed in lung cancer, the largest cause of cancer-related mortality worldwide. Because of the significant dependence of lung cancer cells on mitochondrial respiration, numerous studies demonstrated that blocking mitochondrial activity is a potent strategy to treat lung cancer. Heme is a central factor in mitochondrial respiration/oxidative phosphorylation (OXPHOS), and its association with cancer is the subject of increased research in recent years. In neural cells, heme is a key component in mitochondrial respiration and the production of ATP. Here, we review the role of impaired heme metabolism in the etiology of AD. We discuss the numerous mitochondrial effects that may contribute to AD and cancer. In addition to emphasizing the significance of heme in the development of both AD and cancer, this review also identifies some possible biological connections between the development of the two diseases. This review explores shared biological mechanisms (Pin1, Wnt, and p53 signaling) in cancer and AD. In cancer, these mechanisms drive cell proliferation and tumorigenic functions, while in AD, they lead to cell death. Understanding these mechanisms may help advance treatments for both conditions. This review discusses precise information regarding common risk factors, such as aging, obesity, diabetes, and tobacco usage.

BNIP3 as a new tool to promote healthy brain aging

The article "Neuronal induction of BNIP3-mediated mitophagy slows systemic aging in Drosophila" reveals BCL2-interacting protein 3 as a therapeutic target to counteract brain aging and prolong overall organismal health with age. In this spotlight, we consider the roles of BNIP3, a mitochondrial outer membrane protein, in the adult nervous system, including its induction of mitophagy and prevention of dysfunctional mitochondria in the aged brain. Implications for other tissue types to reduce the burden of aging are further considered.

Elucidating the relationship between breast cancer and brain cortical structure: a Mendelian randomization study

Cancer-associated cognitive impairment is a significant challenge for individuals who have survived breast cancer, affecting their quality of life. In this study, we conducted an inaugural comprehensive Mendelian randomization analysis discerning the causal relationship between breast cancer, including its two subtypes, and the cerebral cortical structure. Our analysis indicated that estrogen receptor-negative breast cancer significantly decreased surface area (β = -593.01 mm2, 95% CI: -1134.9 to -51.1 mm2, P = 0.032). At the regional level, estrogen receptor-negative breast cancer showed a significant association with surface area and thickness in 17 cortical regions. These regions included the insula, posterior cingulate, superior frontal, precuneus, fusiform, lateral occipital, and rostral middle frontal. Specifically, estrogen receptor-negative breast cancer had a significant impact on decreasing the surface area of the insula without considering global weight (β = -14.09 mm2, 95% CI: -22.91 to -5.27 mm2, P = 0.0017). The results from meta-analysis and LD Score Regression provide support for our findings. This investigation unveils the correlations between breast cancer, its various subcategories, and the cerebral cortical structure. Notably, breast cancer of the estrogen receptor-negative variety may elicit more widespread cerebral atrophy.

Role of Autophagy and Mitophagy in Neurodegenerative Disorders

Autophagy is a self-destructive cellular process that removes essential metabolites and waste from inside the cell to maintain cellular health. Mitophagy is the process by which autophagy causes disruption inside mitochondria and the total removal of damaged or stressed mitochondria, hence enhancing cellular health. The mitochondria are the powerhouses of the cell, performing essential functions such as ATP (adenosine triphosphate) generation, metabolism, Ca2+ buffering, and signal transduction. Many different mechanisms, including endosomal and autophagosomal transport, bring these substrates to lysosomes for processing. Autophagy and endocytic processes each have distinct compartments, and they interact dynamically with one another to complete digestion. Since mitophagy is essential for maintaining cellular health and using genetics, cell biology, and proteomics techniques, it is necessary to understand its beginning, particularly in ubiquitin and receptor-dependent signalling in injured mitochondria. Despite their similar symptoms and emerging genetic foundations, Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS) have all been linked to abnormalities in autophagy and endolysosomal pathways associated with neuronal dysfunction. Mitophagy is responsible for normal mitochondrial turnover and, under certain physiological or pathological situations, may drive the elimination of faulty mitochondria. Due to their high energy requirements and post-mitotic origin, neurons are especially susceptible to autophagic and mitochondrial malfunction. This article focused on the importance of autophagy and mitophagy in neurodegenerative illnesses and how they might be used to create novel therapeutic approaches for treating a wide range of neurological disorders.

The potential role of creatine supplementation in neurodegenerative diseases

PURPOSE

The maintenance of energy balance in the body, especially in energy-demanding tissues like the muscles and the central nervous system, depends on creatine (Cr). In addition to improving muscle function, Cr is necessary for the bioenergetics of the central nervous system because it replenishes adenosine triphosphate without needing oxygen. Furthermore, Cr possesses anti-oxidant, anti-apoptotic, and anti-excitotoxic properties. Clinical research on neurodegenerative illnesses has shown that Cr supplementation results in less effective outcomes. With a brief update on the possible role of Cr in human, animal, and in vitro experiments, this review seeks to offer insights into the ideal dosage regimen.

METHODS

Using specified search phrases, such as "creatine and neurological disorder," "creatine supplementation and neurodegenerative disorders," and "creatine and brain," we searched articles in the PubMed database and Google Scholar. We investigated the association between creatine supplementation and neurodegenerative illnesses by examining references.

RESULTS

The neuroprotective effects of Cr were observed in in vitro and animal models of certain neurodegenerative diseases, while clinical trials failed to reproduce favorable outcomes.

CONCLUSION

Determining the optimal creatinine regime for increasing brain creatinine levels is essential for maintaining brain health and treating neurodegeneration.

Deciphering the interplay between LPS/TLR4 pathways, neurotransmitter, and deltamethrin-induced depressive-like behavior: Perspectives from the gut-brain axis

The improper use of deltamethrin (DM) can result in its accumulation in soil, water, food, and even the human body, which is associated with an elevated risk of neurotoxicity and behavioral abnormalities; however, the underlying mechanisms remain insufficiently investigated. Emerging evidence underscores the significance of the gut-brain axis in central nervous system (CNS) dysfunctions. Accordingly, this study investigates the role of the gut-brain axis in DM-induced behavioral anomalies in mice. The results showed that DM exposure induced depressive-like behavior, and the hippocampus, the region that is responsible for the modulation of emotional behavior, showed structural integrity disrupted (neuronal nuclear shrinkage and decreased tight junction protein expression). In addition, DM exposure led to compromised gut barrier integrity (disruptions on crypt surfaces and decreased tight junction protein expression), which might contribute to the gut bacterial-derived lipopolysaccharide (LPS) leakage into the bloodstream and reaching the brain, triggering LPS/toll-like receptor (TLR) 4 -mediated increases in brain pro-inflammatory cytokines. Subsequently, we observed a disturbance in neurotransmitter metabolic pathways following DM exposure, which inhibited the production of 5-hydroxytryptamine (5-HT). Additionally, DM exposure resulted in gut microbiota dysbiosis. Characteristic bacteria, such as Alistipes, Bifidobacterium, Gram-negative bacterium cTPY-13, and Odoribacter exhibited significant correlations with behavior, tight junction proteins, inflammatory response, and neurotransmitters. Further fecal microbiota transplantation (FMT) experiments suggested that DM-induced gut microbiota dysbiosis might contribute to depressive-like behavior. These results provide a new perspective on the toxicity mechanism of DM, indicating that its neurotoxicity may be partially regulated by the microbiota-gut-brain axis.

Neuroprotective effect of ropinirole against Aβ1-42 -induced neurochemical perturbations and cognitive impairments in a rodent model

The primary objective of this study was to investigate the protective effects of ropinirole (ROP) medication given for an extended period following the induction of cognitive decline, oxidative stress, and deterioration of mitochondria in a Wistar rat model by Aβ1-42 . This study aimed to examine the neuroprotective efficacy of ROP in a stereotaxis model of AD. The Wistar rats were randomly assigned into four groups. Group I was considered as a sham, group II served as Aβ-infusion alone, Group III was Aβ1-42 + ROP (5 mg/kg/i.p.), and Group IV was Aβ1-42 + ROP (10 mg/kg/i.p.). Our research revealed that ROP (10 mg/kg, b.wt.) attenuates the cognitive deficits caused by Aβ1-42 -infused, which also correlates with the barnes maze, where (10 mg/kg, b.w.t.) shows significant improvement in spatial learning and memory. At the same time, ROP was rescued from oxidative damage, decreased lipid peroxidation rates, and inhibited acetylcholinesterase activity caused, demonstrating antioxidant benefits. In addition, a higher dose of ROP restored mitochondrial membrane potential in Aβ1-42 rats. Furthermore, histopathological examination showed that ROP treatment reduced neuronal loss, especially in the hippocampus. We conclude that ROP's protective effects in reducing oxidative stress and modulating mitochondrial function might have a propensity in AD pathogenesis.

Consumption of cashew nut induced anxiolytic-like behavior in dyslipidemic rats consuming a high fat diet

This study aimed to evaluate the effect of cashew nut consumption on anxiety-like behavior in dyslipidemic rats. The groups formed were: Control (CONT), Dyslipidemic (DL) and Dyslipidemic cashew nuts (DLCN). Tests to assess anxiety parameters were performed after the treatment period. Brain fatty acid profiles were analyzed. The animals in the DLCN group showed more rearing than DL, without differing from the CONT and less grooming than either the DL and CONT in the Open Field. In the Elevated Plus Maze, DLCN spent more time on the open arms and in the central area compared to the other groups. As for brain fatty acids, there was a reduction in polyunsaturated fatty acids for the DLCN compared to the other groups. The cashew nut, rich in fatty acids, phenolic and flavonoid compounds, reduced the anxiogenic-like behavior caused by dyslipidemia in rats without altering brain fatty acids.

Neuroprotective Effects of Tinospora cordifolia via Reducing the Oxidative Stress and Mitochondrial Dysfunction against Rotenone-Induced PD Mice

Oxidative stress and mitochondrial dysfunction are leading mechanisms that play a crucial role in the progression of Parkinson's disease (PD). Tinospora cordifolia shows a wide range of biological activities including immunomodulatory, antimicrobial, antioxidant, and anti-inflammatory properties. This study explored the neuroprotective activities of T. cordifolia ethanolic extract (TCE) against Rotenone (ROT)-intoxicated Parkinsonian mice. Four experimental groups of mice were formed: control, ROT (2 mg/kg body wt, subcutaneously), TCE (200 mg/kg body wt, oral) + ROT, and TCE only. Mice were pretreated with TCE for a week and then simultaneously injected with ROT for 35 days. Following ROT-intoxication, motor activities, antioxidative potential, and mitochondrial dysfunction were analyzed. Decrease in the activity of the mitochondrial electron transport chain (mETC) complex, loss of mitochondrial membrane potential (Ψm), increase in Bax/Bcl-2 (B-cell lymphoma 2) ratio, and caspase-3 expression are observed in the ROT-intoxicated mice group. Our results further showed ROT-induced reactive oxygen species (ROS)-mediated alpha-synuclein (α-syn) accumulation and mitochondrial dysfunction. However, pre- and cotreatment with TCE along with ROT-intoxication significantly reduced α-syn aggregation and improved mitochondrial functioning in cells by altering mitochondrial potential and increasing mETC activity. TCE also decreases the Bax/Bcl-2 ratio and also the expression of caspase-3, thus reducing apoptosis of the cell. Altogether, TCE is effective in protecting neurons from rotenone-induced cytotoxicity in the Parkinsonian mouse model by modulating oxidative stress, ultimately reducing mitochondrial dysfunction and cell death.

Frontal adenosine triphosphate markers from 31P MRS are associated with cognitive performance in healthy older adults: preliminary findings

Aging is associated with declines in mitochondrial efficiency and energy production which directly impacts the availability of adenosine triphosphate (ATP), which contains high energy phosphates critical for a variety of cellular functions. Previous phosphorous magnetic resonance spectroscopy (31P MRS) studies demonstrate cerebral ATP declines with age. The purpose of this study was to explore the functional relationships of frontal and posterior ATP levels with cognition in healthy aging. Here, we measured frontal and posterior ATP levels using 31P MRS at 3 Tesla (3 T) and assessed cognition using the Montreal Cognitive Assessment (MoCA) in 30 healthy older adults. We found that greater frontal, but not posterior, ATP levels were significantly associated with better MoCA performance. This relationship remained significant after controlling for age, sex, years of education, and brain atrophy. In conclusion, our findings indicate that cognition is related to ATP in the frontal cortex. These preliminary findings may have important implications in the search for non-invasive markers of in vivo mitochondrial function and the impact of ATP availability on cognition. Future studies are needed to confirm the functional significance of regional ATP and cognition across the lifespan.

APPswe /PS1ΔE9 mice exhibit low oxygen saturation and alterations of erythrocytes preceding the neuropathology and cognitive deficiency during Alzheimer's disease

AIM

The molecular mechanism underlying Alzheimer's disease (AD) pathologies remains unclear. The brain is extremely sensitive to oxygen deprivation, and brief interruptions in oxygen supply may lead to permanent brain damage. The objective here was to access the red blood cell (RBC) physiological alterations and the changes in blood oxygen saturation of an AD model as well as to explore the possible mechanism underlying these pathologies.

METHODS

We used female APPswe /PS1ΔE9 mice as AD models. Data were collected at the age of 3, 6, and 9 months. In addition to examining classic features of AD, namely cognitive deficiency and Aβ depositions, 24 h blood oxygen saturation was monitored by Plus oximeters in real time. In addition, RBC physiological parameters were measured by blood cell counter using peripheral blood from the epicanthal veins. Furthermore, in the mechanism investigations, the expression of phosphorylated band 3 protein was examined by a series of Western blot analyses, and the levels of soluble Aβ40 and Aβ42 on the membrane of RBCs were determined by ELISA.

RESULTS

Our results showed that the blood oxygen saturation in the AD mice was significantly reduced as early as at 3 months of age, preceding the neuropathological changes and cognitive impairments. Meanwhile, the expression of phosphorylated band 3 protein and levels of soluble Aβ40 and Aβ42 were all elevated in the erythrocytes of the AD mice.

CONCLUSION

APPswe /PS1ΔE9 mice exhibited decreased oxygen saturation together with reduced RBC counts and hemoglobin concentrations at the early stage, which may aid in the development of predictive markers for AD diagnosis. The increased expression of band 3 protein and elevated Aβ40 and Aβ42 levels may contribute to the deformation of RBCs and, in turn, cause the subsequent AD development.

Talk to Me-Interplay between Mitochondria and Microbiota in Aging

The existence of mitochondria in eukaryotic host cells as a remnant of former microbial organisms has been widely accepted, as has their fundamental role in several diseases and physiological aging. In recent years, it has become clear that the health, aging, and life span of multicellular hosts are also highly dependent on the still-residing microbiota, e.g., those within the intestinal system. Due to the common evolutionary origin of mitochondria and these microbial commensals, it is intriguing to investigate if there might be a crosstalk based on preserved common properties. In the light of rising knowledge on the gut-brain axis, such crosstalk might severely affect brain homeostasis in aging, as neuronal tissue has a high energy demand and low tolerance for according functional decline. In this review, we summarize what is known about the impact of both mitochondria and the microbiome on the host's aging process and what is known about the aging of both entities. For a long time, bacteria were assumed to be immortal; however, recent evidence indicates their aging and similar observations have been made for mitochondria. Finally, we present pathways by which mitochondria are affected by microbiota and give information about therapeutic anti-aging approaches that are based on current knowledge.

Chronic cerebral hypoperfusion: a critical feature in unravelling the etiology of vascular cognitive impairment

Vascular cognitive impairment (VCI) describes a wide spectrum of cognitive deficits related to cerebrovascular diseases. Although the loss of blood flow to cortical regions critically involved in cognitive processes must feature as the main driver of VCI, the underlying mechanisms and interactions with related disease processes remain to be fully elucidated. Recent clinical studies of cerebral blood flow measurements have supported the role of chronic cerebral hypoperfusion (CCH) as a major driver of the vascular pathology and clinical manifestations of VCI. Here we review the pathophysiological mechanisms as well as neuropathological changes of CCH. Potential interventional strategies for VCI are also reviewed. A deeper understanding of how CCH can lead to accumulation of VCI-associated pathology could potentially pave the way for early detection and development of disease-modifying therapies, thus allowing preventive interventions instead of symptomatic treatments.

New indole derivatives as multitarget anti-Alzheimer's agents: synthesis, biological evaluation and molecular dynamics

Background: Alzheimer's disease is a neurological disorder that causes brain cells to shrink and die. Aim: Thirteen novel 'oxathiolanyl', 'pyrazolyl' and 'pyrimidinyl' indole derivatives were designed and synthesized as anti-Alzheimer's disease treatment. Method: In vitro enzyme assay was performed against both AChE and BChE enzymes. In addition, antioxidant assay and cytotoxicity on a normal cell line were determined. Molecular docking and dynamic simulations were conducted to confirm the binding mode in both esterases' active sites. In silico absorption, distribution, metabolism, excretion and toxicity studies were also carried out. Results & conclusion: Compounds 5, 7 and 11 exhibited superior inhibitory activity against acetylcholinesterase and butyrylcholinesterase, with IC₅₀ values of 0.042 and 3.003 μM, 2.54 and 0.207 μM and 0.052 and 2.529 μM, respectively, compared with donepezil.

The association between inflammatory markers in blood and cerebrospinal fluid: a systematic review and meta-analysis

BACKGROUND

Neuroinflammatory processes have been hypothesized to play a role in the pathogenesis of psychiatric and neurological diseases. Studies on this topic often rely on analysis of inflammatory biomarkers in peripheral blood. Unfortunately, the extent to which these peripheral markers reflect inflammatory processes in the central nervous system (CNS) is unclear.

METHODS

We performed a systematic review and found 29 studies examining the association between inflammatory marker levels in blood and cerebrospinal (CSF) samples. We performed a random effects meta-analysis of 21 studies (pooled n = 1679 paired samples) that reported the correlation of inflammatory markers in paired blood-CSF samples.

RESULTS

A qualitative review revealed moderate to high quality of included studies with the majority of studies reporting no significant correlation of inflammatory markers between paired blood-CSF. Meta-analyses revealed a significant low pooled correlation between peripheral and CSF biomarkers (r = 0.21). Meta-analyses of individual cytokines revealed a significant pooled correlation for IL-6 (r = 0.26) and TNFα (r = 0.3) after excluding outlier studies, but not for other cytokines. Sensitivity analyses showed that correlations were highest among participants with a median age above 50 (r = 0.46) and among autoimmune disorder patients (r = 0.35).

CONCLUSION

This systematic review and meta-analysis revealed poor correlation between peripheral and central inflammatory markers in paired blood-CSF samples, with increased correlations in certain study populations. Based on the current findings, peripheral inflammatory markers are a poor reflection of the neuroinflammatory profile.

Exploring Pro-Inflammatory Immunological Mediators: Unraveling the Mechanisms of Neuroinflammation in Lysosomal Storage Diseases

Lysosomal storage diseases are a group of rare and ultra-rare genetic disorders caused by defects in specific genes that result in the accumulation of toxic substances in the lysosome. This excess accumulation of such cellular materials stimulates the activation of immune and neurological cells, leading to neuroinflammation and neurodegeneration in the central and peripheral nervous systems. Examples of lysosomal storage diseases include Gaucher, Fabry, Tay–Sachs, Sandhoff, and Wolman diseases. These diseases are characterized by the accumulation of various substrates, such as glucosylceramide, globotriaosylceramide, ganglioside GM2, sphingomyelin, ceramide, and triglycerides, in the affected cells. The resulting pro-inflammatory environment leads to the generation of pro-inflammatory cytokines, chemokines, growth factors, and several components of complement cascades, which contribute to the progressive neurodegeneration seen in these diseases. In this study, we provide an overview of the genetic defects associated with lysosomal storage diseases and their impact on the induction of neuro-immune inflammation. By understanding the underlying mechanisms behind these diseases, we aim to provide new insights into potential biomarkers and therapeutic targets for monitoring and managing the severity of these diseases. In conclusion, lysosomal storage diseases present a complex challenge for patients and clinicians, but this study offers a comprehensive overview of the impact of these diseases on the central and peripheral nervous systems and provides a foundation for further research into potential treatments.

Spermidine Rescues Bioenergetic and Mitophagy Deficits Induced by Disease-Associated Tau Protein

Abnormal tau build-up is a hallmark of Alzheimer’s disease (AD) and more than 20 other serious neurodegenerative diseases. Mitochondria are paramount organelles playing a predominant role in cellular bioenergetics, namely by providing the main source of cellular energy via adenosine triphosphate generation. Abnormal tau impairs almost every aspect of mitochondrial function, from mitochondrial respiration to mitophagy. The aim of our study was to investigate the effects of spermidine, a polyamine which exerts neuroprotective effects, on mitochondrial function in a cellular model of tauopathy. Recent evidence identified autophagy as the main mechanism of action of spermidine on life-span prolongation and neuroprotection, but the effects of spermidine on abnormal tau-induced mitochondrial dysfunction have not yet been investigated. We used SH-SY5Y cells stably expressing a mutant form of human tau protein (P301L tau mutation) or cells expressing the empty vector (control cells). We showed that spermidine improved mitochondrial respiration, mitochondrial membrane potential as well as adenosine triphosphate (ATP) production in both control and P301L tau-expressing cells. We also showed that spermidine decreased the level of free radicals, increased autophagy and restored P301L tau-induced impairments in mitophagy. Overall, our findings suggest that spermidine supplementation might represent an attractive therapeutic approach to prevent/counteract tau-related mitochondrial impairments.

Galangin Rescues Alzheimer's Amyloid-β Induced Mitophagy and Brain Organoid Growth Impairment

Dysfunctional mitochondria and mitophagy are hallmarks of Alzheimer's disease (AD). It is widely accepted that restoration of mitophagy helps to maintain cellular homeostasis and ameliorates the pathogenesis of AD. It is imperative to create appropriate preclinical models to study the role of mitophagy in AD and to assess potential mitophagy-targeting therapies. Here, by using a novel 3D human brain organoid culturing system, we found that amyloid-β (Aβ_1-42,10 μM) decreased the growth level of organoids, indicating that the neurogenesis of organoids may be impaired. Moreover, Aβ treatment inhibited neural progenitor cell (NPC) growth and induced mitochondrial dysfunction. Further analysis revealed that mitophagy levels were reduced in the brain organoids and NPCs. Notably, galangin (10 μM) treatment restored mitophagy and organoid growth, which was inhibited by Aβ. The effect of galangin was blocked by the mitophagy inhibitor, suggesting that galangin possibly acted as a mitophagy enhancer to ameliorate Aβ-induced pathology. Together, these results supported the important role of mitophagy in AD pathogenesis and suggested that galangin may be used as a novel mitophagy enhancer to treat AD.

Long-term administration of CU06-1004 ameliorates cerebrovascular aging and BBB injury in aging mouse model

BACKGROUND

Age-related changes in the cerebrovasculature, including blood-brain barrier (BBB) disruption and vascular dementia, are emerging as potential risks for many neurodegenerative diseases. Therefore, the endothelial cells that constitute the cerebrovasculature may play key roles in preventing brain injury. Our previous study showed that CU06-1004, an endothelial cell dysfunction blocker, prevented vascular leakage, enhanced vascular integrity in ischemic reperfusion injury, and promoted the normalization of tumor vasculature. Here, we evaluated the effects of CU06-1004 on age-related cerebrovascular functional decline in the aged mouse brain.

RESULTS

In this study, we investigated the protective effects of CU06-1004 against oxidative stress-induced damage in human brain microvascular endothelial cells (HBMECs). HBMECs were treated with hydrogen peroxide (H₂O₂) to establish an oxidative stress-induced model of cellular injury. Compared with H₂O₂ treatment alone, pretreatment of HBMECs with CU06-1004 considerably reduced oxidative stress-induced cytotoxicity, reactive oxygen species generation, senescence-associated β-galactosidase activity, senescence marker expression, and the expression levels of inflammatory proteins. Based on the observed cytoprotective effects of CU06-1004 in HBMECs, we examined whether CU06-1004 displayed protective effects against cerebrovascular aging in mice. Long-term administration of CU06-1004 alleviated age-associated cerebral microvascular rarefaction and cerebrovascular senescence in the aged mouse brain. CU06-1004 supplementation also reduced the extravasation of plasma IgG by improving BBB integrity in the aged mouse brain, associated with reductions in neuronal injury. A series of behavioral tests also revealed improved motor and cognitive functions in aged mice that received long-term CU06-1004 administration.

CONCLUSIONS

These findings suggest that CU06-1004 may represent a promising therapeutic approach for delaying age-related cerebrovascular impairment and improving cognitive function in old age.

The Rat Brain Transcriptome: From Infancy to Aging and Sporadic Alzheimer's Disease-like Pathology

It has been suggested that functional traits of the adult brain-all of which are established early in life-may affect the brain's susceptibility to Alzheimer's disease (AD). Results of our previous studies on senescence-accelerated OXYS rats, a model of sporadic AD, support this hypothesis. Here, to elucidate the molecular genetic nature of the aberrations revealed during brain maturation, we analyzed transcriptomes (RNA-seq data) of the prefrontal cortex (PFC) and hippocampus of OXYS rats and Wistar (control) rats in the period of brain maturation critical for OXYS rats (ages P3 and P10; P: postnatal day). We found more than 1000 differentially expressed genes in both brain structures; functional analysis indicated reduced efficiency of the formation of neuronal contacts, presumably explained mainly by deficits of mitochondrial functions. Next, we compared differentially expressed genes in the rat PFC and hippocampus from infancy to the progressive stage of AD-like pathology (five ages in total). Three genes (Thoc3, Exosc8, and Smpd4) showed overexpression in both brain regions of OXYS rats throughout the lifespan. Thus, reduced efficiency of the formation of neural networks in the brain of OXYS rats in infancy likely contributes to the development of their AD-like pathology.

Effects of Exercise Training on Neurotrophic Factors and Blood-Brain Barrier Permeability in Young-Old and Old-Old Women

Aging and regular exercise may have opposite effects on brain health, and although oxidative stress and sirtuins may be involved in these effects, studies on this topic are limited. Accordingly, the present study aimed to verify the effect of exercise training on oxidant-antioxidant balance, neurotrophic factors, blood-brain barrier permeability, and sirtuins in young-old and old-old women. The study participants were 12 women aged 65-74 years (Young-Old group) and 12 women aged 75-84 years (Old-Old group). All of the selected participants performed exercise training consisting of treadmill walking and resistance band exercise three times a week for 12 weeks. Blood samples were collected before and after exercise training to analyze serum oxidant-antioxidant markers (reactive oxygen species [ROS], superoxide dismutase [SOD]), neurotrophic factor (brain-derived neurotrophic factor [BDNF], vascular endothelial growth factor [VEGF]) levels, and blood-brain barrier permeability marker (S100 calcium-binding protein β [S100β], matrix metalloproteinase-9 [MMP-9]) levels, and sirtuin (SIRT-1, SIRT-2, SIRT-3) levels. The Young-Old group showed significantly increased SOD, BDNF, VEGF, SIRT-1, and SIRT-3 levels after training in comparison with the levels before training (p < 0.05), and a significantly higher BDNF level than the Old-Old group after training (p < 0.05). On the other hand, the Old-Old group showed significantly higher SIRT-1 levels after training in comparison with the levels before training (p < 0.05). Thus, exercise training may be effective in increasing the levels of neurotropic factors and reducing blood-brain barrier permeability in the elderly women, and increased antioxidant capacity and elevated levels of sirtuins are believed to play a major role in these effects. The positive effect of exercise may be greater in participants of relatively young age.

Altered glucose metabolism in Alzheimer's disease: Role of mitochondrial dysfunction and oxidative stress

Increasing evidence suggests that abnormal cerebral glucose metabolism is largely present in Alzheimer's disease (AD). The brain utilizes glucose as its main energy source and a decline in its metabolism directly reflects on brain function. Weighing on recent evidence, here we systematically assessed the aberrant glucose metabolism associated with amyloid beta and phosphorylated tau accumulation in AD brain. Interlink between insulin signaling and AD highlighted the involvement of the IRS/PI3K/Akt/AMPK signaling, and GLUTs in the disease progression. While shedding light on the mitochondrial dysfunction in the defective glucose metabolism, we further assessed functional consequences of AGEs (advanced glycation end products) accumulation, polyol activation, and other contributing factors including terminal respiration, ROS (reactive oxygen species), mitochondrial permeability, PINK1/parkin defects, lysosome-mitochondrial crosstalk, and autophagy/mitophagy. Combined with the classic plaque and tangle pathologies, glucose hypometabolism with acquired insulin resistance and mitochondrial dysfunction potentiate these factors to exacerbate AD pathology. To this end, we further reviewed AD and DM (diabetes mellitus) crosstalk in disease progression. Taken together, the present work discusses the emerging role of altered glucose metabolism, contributing impact of insulin signaling, and mitochondrial dysfunction in the defective cerebral glucose utilization in AD.

Mechanistic and therapeutic role of Drp1 in the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD), a progressive neurodegenerative disorder, has emerged as the most common form of dementia in the elderly. Two major pathological hallmarks have been identified for AD: extracellular amyloid plaques and intracellular neurofibrillary tangles (NFT). Recently, dynamin-related protein 1 (Drp1) was recognized to contribute significantly towards the pathogenesis of AD. Drp1 is primarily located in the cytosol, from where it translocates to the mitochondrial outer membrane and drives the mitochondrial fission via GTP hydrolysis. Drp1 interacts with Aβ and phosphorylated tau, leading to excessive mitochondrial fragmentation, which in turn results in synaptic dysfunction, neuronal damage and cognitive decline. Several studies suggest an increase in the level of Drp1 in the post-mortem brain specimen collected from the AD patients and murine models of AD. Interestingly, heterozygous deletion of Drp1 in the transgenic murine model of AD ameliorates the mitochondrial dysfunction, improving learning and memory. The current review article discusses the possible mechanistic pathways by which Drp1 can influence the pathogenesis of AD. Besides, it will describe various inhibitors for Drp1 and their potential role as therapeutics for AD in the future.

Potential Protective Mechanisms of S-equol, a Metabolite of Soy Isoflavone by the Gut Microbiome, on Cognitive Decline and Dementia

S-equol, a metabolite of soy isoflavone daidzein transformed by the gut microbiome, is the most biologically potent among all soy isoflavones and their metabolites. Soy isoflavones are phytoestrogens and exert their actions through estrogen receptor-β. Epidemiological studies in East Asia, where soy isoflavones are regularly consumed, show that dietary isoflavone intake is inversely associated with cognitive decline and dementia; however, randomized controlled trials of soy isoflavones in Western countries did not generally show their cognitive benefit. The discrepant results may be attributed to S-equol production capability; after consuming soy isoflavones, 40-70% of East Asians produce S-equol, whereas 20-30% of Westerners do. Recent observational and clinical studies in Japan show that S-equol but not soy isoflavones is inversely associated with multiple vascular pathologies, contributing to cognitive impairment and dementia, including arterial stiffness and white matter lesion volume. S-equol has better permeability to the blood-brain barrier than soy isoflavones, although their affinity to estrogen receptor-β is similar. S-equol is also the most potent antioxidant among all known soy isoflavones. Although S-equol is available as a dietary supplement, no long-term trials in humans have examined the effect of S-equol supplementation on arterial stiffness, cerebrovascular disease, cognitive decline, or dementia.

Incorporating Mitochondrial Gene Expression Changes Within a Testable Mathematical Model for Alzheimer’s Disease: Stress Response Modulation Predicts Potential Therapeutic Targets

Background: Alzheimer’s disease is a specific form of dementia characterized by the aggregation of amyloid-β plaques and tau tangles. New research has found that the formation of these aggregates occurs after dysregulation of cellular respiration and the production of radical oxygen species. Proteomic data shows that these changes are also related to unique gene expression patterns. Objective: This study is designed to incorporate both proteomic and gene expression data into a testable mathematical model for AD. Manipulation of this new model allows the identification of potential therapeutic targets for AD. Methods: We investigate the impact of these findings on new therapeutic targets via metabolic flux analysis of sirtuin stress response pathways while also highlighting the importance of metabolic enzyme activity in maintaining proper respiratory activity. Results: Our results indicate that protective changes in SIRT1 and AMPK expression are potential avenues for therapeutics. Conclusion: Combining our mitochondrial gene expression analyses with available protein data allowed the construction of a new mathematical model for AD that provides a useful approach to test the efficacy of potential AD therapeutic targets.

Glucose metabolism patterns: A potential index to characterize brain ageing and predict high conversion risk into cognitive impairment

Exploring individual hallmarks of brain ageing is important. Here, we propose the age-related glucose metabolism pattern (ARGMP) as a potential index to characterize brain ageing in cognitively normal (CN) elderly people. We collected 18F-fluorodeoxyglucose (18F-FDG) PET brain images from two independent cohorts: the Alzheimer's Disease Neuroimaging Initiative (ADNI, N = 127) and the Xuanwu Hospital of Capital Medical University, Beijing, China (N = 84). During follow-up (mean 80.60 months), 23 participants in the ADNI cohort converted to cognitive impairment. ARGMPs were identified using the scaled subprofile model/principal component analysis method, and cross-validations were conducted in both independent cohorts. A survival analysis was further conducted to calculate the predictive effect of conversion risk by using ARGMPs. The results showed that ARGMPs were characterized by hypometabolism with increasing age primarily in the bilateral medial superior frontal gyrus, anterior cingulate and paracingulate gyri, caudate nucleus, and left supplementary motor area and hypermetabolism in part of the left inferior cerebellum. The expression network scores of ARGMPs were significantly associated with chronological age (R = 0.808, p < 0.001), which was validated in both the ADNI and Xuanwu cohorts. Individuals with higher network scores exhibited a better predictive effect (HR: 0.30, 95% CI: 0.1340 ~ 0.6904, p = 0.0068). These findings indicate that ARGMPs derived from CN participants may represent a novel index for characterizing brain ageing and predicting high conversion risk into cognitive impairment.

Gut microbiota dysbiosis induced by polychlorinated biphenyl 126 contributes to increased brain proinflammatory cytokines: Landscapes from the gut-brain axis and fecal microbiota transplantation

The pathogenesis of brain inflammation induced by polychlorinated biphenyl 126 (PCB126) has not yet been fully illustrated. Growing evidence highlights the relevance of the microbiota-gut-brain axis in central nervous system (CNS) dysfunction. Therefore, we aimed to study the role of the gut microbiota in PCB126-induced proinflammatory cytokine increases in the mouse brain. The results showed that PCB126 exposure significantly disordered gut bacterial communities, resulting in the enrichment of gram-negative bacteria (e.g., Bacteroidetes and Proteobacteria), further leading to elevated levels of the gram-negative bacterial lipopolysaccharide (LPS). Subsequently, colonic toll-like receptor 4 (TLR-4) was activated by bacterial LPS, which promoted proinflammatory cytokine generation and inhibited tight junction (TJ) protein expression. Then, bacterial LPS translocated from the gut lumen into the blood circulation and reached the brain, triggering LPS/TLR-4-mediated increases in brain proinflammatory cytokines. Further analysis after fecal microbiota transplantation (FMT) suggested that the gut microbiota disturbance caused by PCB126 could induce elevated bacterial LPS and trigger TLR-4-mediated increases in proinflammatory cytokines in the brain. This study highlights the possibility that PCB126-induced gut microbiota disorder contributes to increased brain proinflammatory cytokines. These results provide a new perspective for identifying the toxicity mechanisms of PCB126 and open up the possibility of modulating the gut microbiota as a therapeutic target for CNS disease caused by environmental pollution.

Critical appraisal on mitochondrial dysfunction in Alzheimer's disease

It is widely recognized that Alzheimer's disease (AD) is a common type of progressive neurodegenerative disorder that results in cognitive impairment over time. Approximately 152 million cases of AD are predicted to be reported by 2050. Amyloid plaques and tau proteins are two major hallmarks of AD which can be seen under electron microscope. Mitochondria plays a vital role in the pathogenesis of AD and mitochondria disruption leads to mitochondrial DNA (mtDNA) dysfunction, alteration of mitochondria dependent Ca2+ homeostasis, copper dysfunction, immune cell dysfunction, etc. In this review, we try to cover all the mechanisms related with mitochondrial dysfunction and mitochondrial pathogenesis that may help us to better understand AD as well as open a new era for therapeutic target of AD and treat this progressive disease.

Dietary Alterations in Impaired Mitochondrial Dynamics Due to Neurodegeneration

Alzheimer's disease is still an incurable disease with significant social and economic impact globally. Nevertheless, newly FDA-approved drugs and non-pharmacological techniques may offer efficient disease treatments. Furthermore, it is widely accepted that early diagnosis or even prognosis of Alzheimer's disease using advanced computational tools could offer a compelling alternative way of management. In addition, several studies have presented an insight into the role of mitochondrial dynamics in Alzheimer's development. In combination with diverse dietary and obesity-related diseases, mitochondrial bioenergetics may be linked to neurodegeneration. Considering the probabilistic expectations of Alzheimer's disease development or progression due to specific risk factors or biomarkers, we designed a Bayesian model to formulate the impact of diet-induced obesity with an impaired mitochondrial function and altered behavior. The applied probabilities are based on clinical trials globally and are continuously subject to updating and redefinition. The proposed multiparametric model combines various data types based on uniform probabilities. The program simulates all the variables with a uniform distribution in a sample of 1000 patients. First, the program initializes the variable age (30-95) and the four different diet types ("HFO_diet," "Starvation," "HL_diet," "CR") along with the factors that are related to prodromal or mixed AD (ATP, MFN1, MFN2, DRP1, FIS1, Diabetes, Oxidative_Stress, Hypertension, Obesity, Depression, and Physical_activity). Besides the known proteins related to mitochondrial dynamics, our model includes risk factors like Age, Hypertension, Oxidative Stress, Obesity, Depression, and Physical Activity, which are associated with Prodromal Alzheimer's. The outcome is the disease progression probability corresponding to a random individual ID related to diet choices and mitochondrial dynamics parameters. The proposed model and the programming code are adjustable to different parameters and values. The program is coded and executed in Python and is fully and freely available for research purposes and testing the correlation between diet type and Alzheimer's disease progression regarding various risk factors and biomarkers.

Ultrafine black carbon caused mitochondrial oxidative stress, mitochondrial dysfunction and mitophagy in SH-SY5Y cells

Exposure to ambient ultrafine black carbon (uBC, with aerodynamic diameter less than 100 nm) is associated with many neurodegenerative diseases. Oxidative stress is the predominantly reported neurotoxic effects caused by uBC exposure. Mitochondrion is responsible for production of majority of ROS in cells and mitochondrial dysfunction is closely related to adverse nervous outcomes. Mitophagy is an important cellular process to eliminate dysfunctional or damaged mitochondria. However, the mechanisms that modulate mitophagy and mitochondrial dysfunction initiated by uBC remain to be elucidated. The purpose of this study was to investigate how mitochondrial oxidative stress regulated mitochondrial dysfunction and mitophagy in human neuroblastoma cell line (SH-SY5Y) after uBC treatment. RNA interference was further applied to explore the roles of mitophagy in mitochondrial dysfunction. We found uBC triggered cell apoptosis via ROS-mitochondrial apoptotic pathway. The uBC also caused serious mitochondrial damage and respiratory dysfunction, indicated by the abnormalities in mitochondrial division and fusion related proteins, decreased mitochondria number and ATP level. Increased PTEN induced putative kinase 1 (PINK1) and Parkin protein levels and the autolysosome numbers suggested uBC could promote Pink1/Parkin-dependent mitophagy process in SH-SY5Y cells. Mitophagy inhibition could reserve mitochondria number and ATP activity, but not fusion and division related protein levels in SH-SY5Y cells exposed to uBC. Administration of a mitochondria-targeted antioxidant (mitoquinone) significantly eliminated uBC caused apoptosis, mitochondrial dysfunction and mitophagy. Our data suggested mitochondrial oxidative stress regulated uBC induced mitochondrial dysfunction and PINK1/Parkin-dependent mitophagy. PINK1/Parkin-dependent mitophagy probably participated in regulating uBC caused mitochondrial dysfunction but not by controlling mitochondrial fusion and division related proteins. Our results may provide some new insights and evidences to understand the mechanisms of neurotoxicity induced by uBC.

Mechanisms of Acupuncture in Improving Alzheimer's Disease Caused by Mitochondrial Damage

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases among the elderly and it accounts for nearly 80% of all dementias. The pathogenesis of AD is complicated and enigmatic thus far. The mitochondrial cascade hypothesis assumes that mitochondrial damage may mediate, drive, or contribute to a variety of AD pathologies and may be the main factor in late-onset AD. Currently, there are no widely recognized drugs able to attenuate mitochondrial damage in AD. Notably, increasing evidence supports the efficacy of acupuncture for improving the mitochondrial structure and protecting mitochondrial functions in AD. This review reports the mechanisms by which acupuncture regulates mitochondrial dynamics, energy metabolism, calcium homeostasis and apoptosis. In conclusion, these findings suggest that AD mitochondrial dysfunction represents a reasonable therapeutic target and acupuncture could play a significant role in preventing and treating AD.

Role of Creatine Supplementation in Conditions Involving Mitochondrial Dysfunction: A Narrative Review

Creatine monohydrate (CrM) is one of the most widely used nutritional supplements among active individuals and athletes to improve high-intensity exercise performance and training adaptations. However, research suggests that CrM supplementation may also serve as a therapeutic tool in the management of some chronic and traumatic diseases. Creatine supplementation has been reported to improve high-energy phosphate availability as well as have antioxidative, neuroprotective, anti-lactatic, and calcium-homoeostatic effects. These characteristics may have a direct impact on mitochondrion's survival and health particularly during stressful conditions such as ischemia and injury. This narrative review discusses current scientific evidence for use or supplemental CrM as a therapeutic agent during conditions associated with mitochondrial dysfunction. Based on this analysis, it appears that CrM supplementation may have a role in improving cellular bioenergetics in several mitochondrial dysfunction-related diseases, ischemic conditions, and injury pathology and thereby could provide therapeutic benefit in the management of these conditions. However, larger clinical trials are needed to explore these potential therapeutic applications before definitive conclusions can be drawn.

Significance of Brain Glucose Hypometabolism, Altered Insulin Signal Transduction, and Insulin Resistance in Several Neurological Diseases

Several neurological diseases share pathological alterations, even though they differ in their etiology. Neuroinflammation, altered brain glucose metabolism, oxidative stress, mitochondrial dysfunction and amyloidosis are biological events found in those neurological disorders. Altered insulin-mediated signaling and brain glucose hypometabolism are characteristic signs observed in the brains of patients with certain neurological diseases, but also others such as type 2 diabetes mellitus and vascular diseases. Thus, significant reductions in insulin receptor autophosphorylation and Akt kinase activity, and increased GSK-3 activity and insulin resistance, have been reported in these neurological diseases as contributing to the decline in cognitive function. Supporting this relationship is the fact that nasal and hippocampal insulin administration has been found to improve cognitive function. Additionally, brain glucose hypometabolism precedes the unmistakable clinical manifestations of some of these diseases by years, which may become a useful early biomarker. Deficiencies in the major pathways of oxidative energy metabolism have been reported in patients with several of these neurological diseases, which supports the hypothesis of their metabolic background. This review remarks on the significance of insulin and brain glucose metabolism alterations as keystone common pathogenic substrates for certain neurological diseases, highlighting new potential targets.

Heterogeneity in Alzheimer's Disease Diagnosis and Progression Rates: Implications for Therapeutic Trials

The clinical presentation and the pathological processes underlying Alzheimer's disease (AD) can be very heterogeneous in severity, location, and composition including the amount and distribution of AB deposition and spread of neurofibrillary tangles in different brain regions resulting in atypical clinical patterns and the existence of distinct AD variants. Heterogeneity in AD may be related to demographic factors (such as age, sex, educational and socioeconomic level) and genetic factors, which influence underlying pathology, the cognitive and behavioral phenotype, rate of progression, the occurrence of neuropsychiatric features, and the presence of comorbidities (e.g., vascular disease, neuroinflammation). Heterogeneity is also manifest in the individual resilience to the development of neuropathology (brain reserve) and the ability to compensate for its cognitive and functional impact (cognitive and functional reserve). The variability in specific cognitive profiles and types of functional impairment may be associated with different progression rates, and standard measures assessing progression may not be equivalent for individual cognitive and functional profiles. Other factors, which may govern the presence, rate, and type of progression of AD, include the individuals' general medical health, the presence of specific systemic conditions, and lifestyle factors, including physical exercise, cognitive and social stimulation, amount of leisure activities, environmental stressors, such as toxins and pollution, and the effects of medications used to treat medical and behavioral conditions. These factors that affect progression are important to consider while designing a clinical trial to ensure, as far as possible, well-balanced treatment and control groups.

Sex differences in Alzheimer's disease: metabolic reprogramming and therapeutic intervention

Studies on the sporadic form of Alzheimer's disease (AD) have revealed three classes of risk factor: age, genetics, and sex. These risk factors point to a metabolic dysregulation as the origin of AD. Adaptive alterations in cerebral metabolism are the rationale for the Metabolic Reprogramming (MR) Theory of the origin of AD. The theory contends that the progression toward AD involves three adaptive events: a hypermetabolic phase, a prolonged prodromal phase, and a metabolic collapse. This article exploits the MR Theory to elucidate the effect of hormonal changes on the origin and progression of AD in women. The theory invokes bioenergetic signatures of the menopausal transition to propose sex-specific diagnostic program and therapeutic strategies.

Tricholoma matsutake-Derived Peptides Ameliorate Inflammation and Mitochondrial Dysfunction in RAW264.7 Macrophages by Modulating the NF-κB/COX-2 Pathway

Tricholoma matsutake is an edible fungus that contains various bioactive substances, some of them with immunostimulatory properties. Presently, there is limited knowledge about the functional components of T. matsutake. Our aim was to evaluate the protective effects and molecular mechanisms of two T. matsutake-derived peptides, SDLKHFPF and SDIKHFPF, on lipopolysaccharide (LPS)-induced mitochondrial dysfunction and inflammation in RAW264.7 macrophages. Tricholoma matsutake peptides significantly ameliorated the production of inflammatory cytokines and inhibited the expression of COX-2, iNOS, IKKβ, p-IκB-α, and p-NF-κB. Immunofluorescence assays confirmed the inhibitory effect of T. matsutake peptides on NF-κB/p65 nuclear translocation. Furthermore, the treatment with T. matsutake peptides prevented the accumulation of reactive oxygen species, increased the Bcl-2/Bax ratio, reversed the loss of mitochondrial membrane potential, and rescued abnormalities in cellular energy metabolism. These findings indicate that T. matsutake peptides can effectively inhibit the activation of NF-κB/COX-2 and may confer an overall protective effect against LPS-induced cell damage.

Dissecting the Crosstalk between Endothelial Mitochondrial Damage, Vascular Inflammation, and Neurodegeneration in Cerebral Amyloid Angiopathy and Alzheimer's Disease

Alzheimer’s disease (AD) is the most prevalent cause of dementia and is pathologically characterized by the presence of parenchymal senile plaques composed of amyloid β (Aβ) and intraneuronal neurofibrillary tangles of hyperphosphorylated tau protein. The accumulation of Aβ also occurs within the cerebral vasculature in over 80% of AD patients and in non-demented individuals, a condition called cerebral amyloid angiopathy (CAA). The development of CAA is associated with neurovascular dysfunction, blood–brain barrier (BBB) leakage, and persistent vascular- and neuro-inflammation, eventually leading to neurodegeneration. Although pathologically AD and CAA are well characterized diseases, the chronology of molecular changes that lead to their development is still unclear. Substantial evidence demonstrates defects in mitochondrial function in various cells of the neurovascular unit as well as in the brain parenchyma during the early stages of AD and CAA. Dysfunctional mitochondria release danger-associated molecular patterns (DAMPs) that activate a wide range of inflammatory pathways. In this review, we gather evidence to postulate a crucial role of the mitochondria, specifically of cerebral endothelial cells, as sensors and initiators of Aβ-induced vascular inflammation. The activated vasculature recruits circulating immune cells into the brain parenchyma, leading to the development of neuroinflammation and neurodegeneration in AD and CAA.

Exercise-Induced Benefits for Alzheimer's Disease by Stimulating Mitophagy and Improving Mitochondrial Function

Neurons are highly specialized post-mitotic cells that are inherently dependent on mitochondria due to their higher bioenergetic demand. Mitochondrial dysfunction is closely associated with a variety of aging-related neurological disorders, such as Alzheimer’s disease (AD), and the accumulation of dysfunctional and superfluous mitochondria has been reported as an early stage that significantly facilitates the progression of AD. Mitochondrial damage causes bioenergetic deficiency, intracellular calcium imbalance and oxidative stress, thereby aggravating β-amyloid (Aβ) accumulation and Tau hyperphosphorylation, and further leading to cognitive decline and memory loss. Although there is an intricate parallel relationship between mitochondrial dysfunction and AD, their triggering factors, such as Aβ aggregation and hyperphosphorylated Tau protein and action time, are still unclear. Moreover, many studies have confirmed abnormal mitochondrial biosynthesis, dynamics and functions will present once the mitochondrial quality control is impaired, thus leading to aggravated AD pathological changes. Accumulating evidence shows beneficial effects of appropriate exercise on improved mitophagy and mitochondrial function to promote mitochondrial plasticity, reduce oxidative stress, enhance cognitive capacity and reduce the risks of cognitive impairment and dementia in later life. Therefore, stimulating mitophagy and optimizing mitochondrial function through exercise may forestall the neurodegenerative process of AD.

Effects of Urolithin A on Mitochondrial Parameters in a Cellular Model of Early Alzheimer Disease

(1) Background: Ellagitannins are natural products occurring in pomegranate and walnuts. They are hydrolyzed in the gut to release ellagic acid, which is further metabolized by the microflora into urolithins, such as urolithin A (UA). Accumulation of damaged mitochondria is a hallmark of aging and age-related neurodegenerative diseases. In this study, we investigated the neuroprotective activity of the metabolite UA against mitochondrial dysfunction in a cellular model of early Alzheimer disease (AD). (2) Methods: In the present study we used SH-SY5Y-APP695 cells and its corresponding controls (SH-SY5Ymock) to assess UA’s effect on mitochondrial function. Using these cells we investigated mitochondrial respiration (OXPHOS), mitochondrial membrane potential (MMP), adenosine triphosphate (ATP) production, autophagy and levels of reactive oxygen species (ROS) in cells treated with UA. Furthermore, we assessed UA’s effect on the expression of genes related to mitochondrial bioenergetics, mitochondrial biogenesis, and autophagy via quantitative real-time PCR (qRT-PCR). (3) Results: Treatment of SH-SY5Y-APP695 cells suggests changes to autophagy corresponding with qRT-PCR results. However, LC3B-I, LC3B-II, and p62 levels were unchanged. UA (10 µM) reduced MMP, and ATP-levels. Treatment of cells with UA (1 µM) for 24 h did not affect ROS production or levels of Aβ, but significantly increased expression of genes for mitochondrial biogenesis and OXPHOS. Mitochondrial Transcription Factor A (TFAM) expression was specifically increased in SH-SY5Y-APP695. Both cell lines showed unaltered levels of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), which is commonly associated with mitochondrial biogenesis. Results imply that biogenesis might be facilitated by estrogen-related receptor (ESRR) genes. (4) Conclusion: Urolithin A shows no effect on autophagy in SH-SY5Y-APP695 cells and its effect on mitochondrial function is limited. Instead, data suggests that UA treatment induces hormetic effects as it induces transcription of several genes related to mitochondrial biogenesis.

Adaptation of mitochondrial network dynamics and velocity of mitochondrial movement to chronic stress present in fibroblasts derived from patients with sporadic form of Alzheimer's disease

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases. Only 10% of all cases are familial form, the remaining 90% are sporadic form with unknown genetic background. The etiology of sporadic AD is still not fully understood. Pathogenesis and pathobiology of this disease are limited due to the limited number of experimental models. We used primary culture of fibroblasts derived from patients diagnosed with sporadic form of AD for investigation of dynamic properties of mitochondria, including fission-fusion process and localization of mitochondria within the cell. We observed differences in mitochondrial network organization with decreased mitochondrial transport velocity, and a drop in the frequency of fusion-fission events. These studies show how mitochondrial dynamics adapt to the conditions of long-term mitochondrial stress that prevails in cells of sporadic form of AD.

NADH Fluorescence Lifetime Imaging Microscopy Reveals Selective Mitochondrial Dysfunction in Neurons Overexpressing Alzheimer's Disease-Related Proteins

Alzheimer's disease (AD), the most prevalent form of dementia, affects globally more than 30 million people suffering from cognitive deficits and neuropsychiatric symptoms. Substantial evidence for the involvement of mitochondrial dysfunction in the development and/or progression of AD has been shown in addition to the pathological hallmarks amyloid beta (Aβ) and tau. Still, the selective vulnerability and associated selective mitochondrial dysfunction cannot even be resolved to date. We aimed at optically quantifying mitochondrial function on a single-cell level in primary hippocampal neuron models of AD, unraveling differential involvement of cell and mitochondrial populations in amyloid precursor protein (APP)-associated mitochondrial dysfunction. NADH lifetime imaging is a highly sensitive marker-free method with high spatial resolution. However, deciphering cellular bioenergetics of complex cells like primary neurons has still not succeeded yet. To achieve this, we combined highly sensitive NADH lifetime imaging with respiratory inhibitor treatment, allowing characterization of mitochondrial function down to even the subcellular level in primary neurons. Measuring NADH lifetime of the same neuron before and after respiratory treatment reveals the metabolic delta, which can be taken as a surrogate for cellular redox capacity. Correlating NADH lifetime delta with overexpression strength of Aβ-related proteins on the single-cell level, we could verify the important role of intracellular Aβ-mediated mitochondrial toxicity. Subcellularly, we could demonstrate a higher respiration in neuronal somata in general than dendrites, but a similar impairment of somatic and dendritic mitochondria in our AD models. This illustrates the power of NADH lifetime imaging in revealing mitochondrial function on a single and even subcellular level and its potential to shed light into bioenergetic alterations in neuropsychiatric diseases and beyond.

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.

Ascorbate deficiency decreases dopamine release in gulo-/- and APP/PSEN1 mice

Dopamine (DA) has important roles in learning, memory, and motivational processes and is highly susceptible to oxidation. In addition to dementia, Alzheimer's disease (AD) patients frequently exhibit decreased motivation, anhedonia, and sleep disorders, suggesting deficits in dopaminergic neurotransmission. Vitamin C (ascorbate, ASC) is a critical antioxidant in the brain and is often depleted in AD patients as a result of disease-related oxidative stress and dietary deficiencies. To probe the effects of ASC deficiency and AD pathology on the DAergic system, gulo-/- mice, which like humans depend on dietary ASC to maintain adequate tissue levels, were crossed with APP/PSEN1 mice and provided sufficient or depleted ASC supplementation from weaning until 12 months of age. Ex vivo fast-scan cyclic voltammetry showed that chronic ASC depletion and APP/PSEN1 genotype both independently decreased dopamine release in the nucleus accumbens, a hub for motivational behavior and reward, while DA clearance was similar across all groups. In striatal tissue containing nucleus accumbens, low ASC treatment led to decreased levels of DA and its metabolites 3,4-dihydroxyohenyl-acetic acid (DOPAC), 3-methoxytyramine (3-MT), and homovanillic acid (HVA). Decreased enzyme activity observed through lower pTH/TH ratio was driven by a cumulative effect of ASC depletion and APP/PSEN1 genotype. Together the data show that deficits in dopaminergic neurotransmission resulting from age and disease status are magnified in conditions of low ASC which decrease DA availability during synaptic transmission. Such deficits may contribute to the non-cognitive behavioral changes observed in AD including decreased motivation, anhedonia, and sleep disorders.

Vitamin E: necessary nutrient for neural development and cognitive function

Vitamin E, discovered in 1922, is essential for pregnant rats to carry their babies to term. However, 100 years later, the molecular mechanisms for the vitamin E requirement during embryogenesis remain unknown. Vitamin E's role during pregnancy has been difficult to study and thus, a vitamin E-deficient (E-) zebrafish embryo model was developed. Vitamin E deficiency in zebrafish embryos initiates lipid peroxidation, depletes a specific phospholipid (DHA-phosphatidyl choline), causes secondary deficiencies of choline, betaine and critical thiols (such as glutathione), and dysregulates energy metabolism. Vitamin E deficiency not only distorts the carefully programmed development of the nervous system, but it leads to defects in several developing organs. Both the α-tocopherol transfer protein and vitamin E are necessary for embryonic development, neurogenesis and cognition in this model and likely in human embryos. Elucidation of the control mechanisms for the cellular and metabolic pathways involved in the molecular dysregulation caused by vitamin E deficiency will lead to important insights into abnormal neurogenesis and embryonic malformations.

Design, synthesis, and biological evaluation of diosgenin-indole derivatives as dual-functional agents for the treatment of Alzheimer's disease

The complex pathogenesis of Alzheimer's disease (AD) has become a major obstacle in its treatment. An effective approach is to develop multifunctional agents that simultaneously target multiple pathological processes. Here, a series of diosgenin-indole compounds were designed, synthesized and evaluated for their neuroprotective effects against H₂O₂ (hydrogen peroxide), 6-OHDA (6-hydroxydopamine) and Aβ (beta amyloid) damages. Preliminary structure-activities relationship revealed that the introduction of indole fragment and electron-donating group at C-5 on ring indole could be beneficial for neuroprotective activities. Results indicated that compound 5b was the most promising candidate against cellular damage induced by H₂O₂ (52.9 ± 1.9%), 6-OHDA (38.4 ± 2.4%) and Aβ_1-42 (54.4 ± 2.7%). Molecular docking study suggested the affinity for 5b bound to Aβ_1-42 was -40.59 kcal/mol, which revealed the strong binding affinity of 5b to Aβ_1-42. The predicted values of brain/blood partition coefficient (-0.733) and polar surface area (85.118 Å²) indicated the favorable abilities of BBB permeation and absorption of 5b. In addition, 5b significantly decreased ROS (reactive oxygen species) production induced by H₂O₂. In the following in vivo experiment, 5b obviously attenuated memory and learning impairments of Aβ-injected mice. In summary, compound 5b could be considered as a promising dual-functional neuroprotective agent against AD.

Improving Age-Related Cognitive Decline through Dietary Interventions Targeting Mitochondrial Dysfunction

Aging is inevitable and it is one of the major contributors to cognitive decline. However, the mechanisms underlying age-related cognitive decline are still the object of extensive research. At the biological level, it is unknown how the aging brain is subjected to progressive oxidative stress and neuroinflammation which determine, among others, mitochondrial dysfunction. The link between mitochondrial dysfunction and cognitive impairment is becoming ever more clear by the presence of significant neurological disturbances in human mitochondrial diseases. Possibly, the most important lifestyle factor determining mitochondrial functioning is nutrition. Therefore, with the present work, we review the latest findings disclosing a link between nutrition, mitochondrial functioning and cognition, and pave new ways to counteract cognitive decline in late adulthood through diet.

Cholesterol alters mitophagy by impairing optineurin recruitment and lysosomal clearance in Alzheimer's disease

BACKGROUND

Emerging evidence indicates that impaired mitophagy-mediated clearance of defective mitochondria is a critical event in Alzheimer's disease (AD) pathogenesis. Amyloid-beta (Aβ) metabolism and the microtubule-associated protein tau have been reported to regulate key components of the mitophagy machinery. However, the mechanisms that lead to mitophagy dysfunction in AD are not fully deciphered. We have previously shown that intraneuronal cholesterol accumulation can disrupt the autophagy flux, resulting in low Aβ clearance. In this study, we examine the impact of neuronal cholesterol changes on mitochondrial removal by autophagy.

METHODS

Regulation of PINK1-parkin-mediated mitophagy was investigated in conditions of acute (in vitro) and chronic (in vivo) high cholesterol loading using cholesterol-enriched SH-SY5Y cells, cultured primary neurons from transgenic mice overexpressing active SREBF2 (sterol regulatory element binding factor 2), and mice of increasing age that express the amyloid precursor protein with the familial Alzheimer Swedish mutation (Mo/HuAPP695swe) and mutant presenilin 1 (PS1-dE9) together with active SREBF2.

RESULTS

In cholesterol-enriched SH-SY5Y cells and cultured primary neurons, high intracellular cholesterol levels stimulated mitochondrial PINK1 accumulation and mitophagosomes formation triggered by Aβ while impairing lysosomal-mediated clearance. Antioxidant recovery of cholesterol-induced mitochondrial glutathione (GSH) depletion prevented mitophagosomes formation indicating mitochondrial ROS involvement. Interestingly, when brain cholesterol accumulated chronically in aged APP-PSEN1-SREBF2 mice the mitophagy flux was affected at the early steps of the pathway, with defective recruitment of the key autophagy receptor optineurin (OPTN). Sustained cholesterol-induced alterations in APP-PSEN1-SREBF2 mice promoted an age-dependent accumulation of OPTN into HDAC6-positive aggresomes, which disappeared after in vivo treatment with GSH ethyl ester (GSHee). The analyses in post-mortem brain tissues from individuals with AD confirmed these findings, showing OPTN in aggresome-like structures that correlated with high mitochondrial cholesterol levels in late AD stages.

CONCLUSIONS

Our data demonstrate that accumulation of intracellular cholesterol reduces the clearance of defective mitochondria and suggest recovery of the cholesterol homeostasis and the mitochondrial scavenging of ROS as potential therapeutic targets for AD.

Nobiletin Exhibits Neuroprotective Effects against Mitochondrial Complex I Inhibition via Regulating Apoptotic Signaling

Nobiletin, a polymethoxylated flavonoid found in citrus, has been studied because of its modulatory functions in cellular signaling cascades, and effects to prevent mitochondrial calcium overload and neuronal cell death. Particularly, we previously reported that nobiletin induced changes in the mitochondrial membrane potential through K⁺ channel regulation, suggesting that nobiletin might exert neuroprotective effects via regulating mitochondrial functions associated with the electron transport chain (ETC) system. This study investigated whether nobiletin regulated mitochondrial dysfunction mediated by ETC system downregulation by inhibiting complex I (CI) and complex III (CIII) in pure mitochondria and the cortical neurons of rats. The results showed that nobiletin significantly reduced mitochondrial reactive oxygen species (ROS) production, inhibited apoptotic signaling, enhanced ATP production and then restored neuronal viability under conditions of CI inhibition, but not CIII inhibition. These effects were attributed to the downregulation of translocation of apoptosis-induced factor (AIF), and the upregulation of CI activity and the expression of antioxidant enzymes such as Nrf2 and HO-1. Together with our previous study, these results indicate that the neuroprotective effects of nobiletin under mitochondrial dysfunction may be associated with its function to activate antioxidant signaling cascades. Our findings suggest the possibility that nobiletin has therapeutic potential in treating oxidative neurological and neurodegenerative diseases mediated by mitochondrial dysfunction.