Alzheimer's brains harbor somatic mtDNA control-region mutations that suppress mitochondrial transcription and replication

Mitochondrial dysfunction, cause or consequence in neurodegenerative diseases?

Neurodegenerative diseases encompass a spectrum of conditions characterized by the gradual deterioration of neurons in the central and peripheral nervous system. While their origins are multifaceted, emerging data underscore the pivotal role of impaired mitochondrial functions and endolysosomal homeostasis to the onset and progression of pathology. This article explores whether mitochondrial dysfunctions act as causal factors or are intricately linked to the decline in endolysosomal function. As research delves deeper into the genetics of neurodegenerative diseases, an increasing number of risk loci and genes associated with the regulation of endolysosomal and autophagy functions are being identified, arguing for a downstream impact on mitochondrial health. Our hypothesis centers on the notion that disturbances in endolysosomal processes may propagate to other organelles, including mitochondria, through disrupted inter-organellar communication. We discuss these views in the context of major neurodegenerative diseases including Alzheimer's and Parkinson's diseases, and their relevance to potential therapeutic avenues.

Mechanism and Clinical Application Prospects of Mitochondrial DNA Single Nucleotide Polymorphism in Neurodegenerative Diseases

Mitochondrial dysfunction is well recognized as a critical component of the complicated pathogenesis of neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and Huntington's disease. This review investigates the influence of mitochondrial DNA single nucleotide polymorphisms on mitochondrial function, as well as their role in the onset and progression of these neurodegenerative diseases. Furthermore, the contemporary approaches to mitochondrial regulation in these disorders are discussed. Our objective is to uncover early diagnostic targets and formulate precision medicine strategies for neurodegenerative diseases, thereby offering new paths for preventing and treating these conditions.

Mitochondrial Quality Control in Alzheimer's Disease: Insights from Caenorhabditis elegans Models

Alzheimer's disease (AD) is a complex neurodegenerative disorder that is classically defined by the extracellular deposition of senile plaques rich in amyloid-beta (Aβ) protein and the intracellular accumulation of neurofibrillary tangles (NFTs) that are rich in aberrantly modified tau protein. In addition to aggregative and proteostatic abnormalities, neurons affected by AD also frequently possess dysfunctional mitochondria and disrupted mitochondrial maintenance, such as the inability to eliminate damaged mitochondria via mitophagy. Decades have been spent interrogating the etiopathogenesis of AD, and contributions from model organism research have aided in developing a more fundamental understanding of molecular dysfunction caused by Aβ and toxic tau aggregates. The soil nematode C. elegans is a genetic model organism that has been widely used for interrogating neurodegenerative mechanisms including AD. In this review, we discuss the advantages and limitations of the many C. elegans AD models, with a special focus and discussion on how mitochondrial quality control pathways (namely mitophagy) may contribute to AD development. We also summarize evidence on how targeting mitophagy has been therapeutically beneficial in AD. Lastly, we delineate possible mechanisms that can work alone or in concert to ultimately lead to mitophagy impairment in neurons and may contribute to AD etiopathology.

Norboldine improves cognitive impairment and pathological features in Alzheimer's disease by activating AMPK/GSK3β/Nrf2 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Lindera aggregata (Sims) Kosterm is a common traditional herb that has multiple bioactivities. Radix Linderae (LR), the dry roots of Lindera aggregata (Sims) Kosterm, is a traditional Chinese herbal medicine with antioxidant, anti-inflammatory and immunomodulatory properties, first found in Kaibao Era. Norboldine (Nor) is an alkaloid extracted from LR and is one of the primary active ingredients of LR. However, the pharmacological functions and mechanism of Nor in Alzheimer's disease (AD) are still unknown.

AIM OF THE STUDY

This study aims to investigate the effect and mechanism of Nor therapy in improving the cognitive impairment and pathological features of 3 × Tg mice.

MATERIALS AND METHODS

3 × Tg mice were treated with two concentrations of Nor for one month and then the memory and cognitive abilities of mice were assessed by novel object recognition experiment and Morris water maze. The impact of Nor on the pathology of ADwere examined in PC12 cells and animal tissues using western blotting and immunofluorescence. Finally, western blotting was used to verify the anti-apoptotic effect of Nor by activating AMPK/GSK3β/Nrf2 signaling pathway at animal and cellular levels.

RESULTS

In this study, we showed that Nor treatment improved the capacity of the learning and memory of 3 × Tg mice and alleviated AD pathology such as Aβ deposition. In addition, Nor restored the abnormalities of mitochondrial membrane potential, significantly reduced the production of intracellular ROS and neuronal cell apoptosis. Mechanistically, we combined network pharmacology and experimental verification to show that Nor may exert antioxidant stress and anti-apoptotic through the AMPK/GSK3β/Nrf2 signaling pathway.

CONCLUSION

Our data provide some evidence that Nor exerts a neuroprotective effect through the AMPK/GSK3β/Nrf2 pathway, thereby improving cognitive impairment in AD model mice. Natural products derived from traditional Chinese medicines are becoming increasingly popular in the process of new drug development and discovery, and our findings provide new perspectives for the discovery of improved treatment strategies for AD.

Signaling Pathways Concerning Mitochondrial Dysfunction: Implications in Neurodegeneration and Possible Molecular Targets

Mitochondrion is an important organelle present in our cells responsible for meeting energy requirements. All higher organisms rely on efficient mitochondrial bioenergetic machinery to sustain life. No other respiratory process can produce as much power as generated by mitochondria in the form of ATPs. This review is written in order to get an insight into the magnificent working of mitochondrion and its implications in cellular homeostasis, bioenergetics, redox, calcium signaling, and cell death. However, if this machinery gets faulty, it may lead to several disease states. Mitochondrial dysfunctioning is of growing concern today as it is seen in the pathogenesis of several diseases which includes neurodegenerative disorders, cardiovascular disorders, diabetes mellitus, skeletal muscle defects, liver diseases, and so on. To cover all these aspects is beyond the scope of this article; hence, our study is restricted to neurodegenerative disorders only. Moreover, faulty functioning of this organelle can be one of the causes of early ageing in individuals. This review emphasizes mutations in the mitochondrial DNA, defects in oxidative phosphorylation, generation of ROS, and apoptosis. Researchers have looked into new approaches that might be able to control mitochondrial failure and show a lot of promise as treatments.

Role of Mitochondrial Dysfunctions in Neurodegenerative Disorders: Advances in Mitochondrial Biology

Mitochondria, essential organelles responsible for cellular energy production, emerge as a key factor in the pathogenesis of neurodegenerative disorders. This review explores advancements in mitochondrial biology studies that highlight the pivotal connection between mitochondrial dysfunctions and neurological conditions such as Alzheimer's, Parkinson's, Huntington's, ischemic stroke, and vascular dementia. Mitochondrial DNA mutations, impaired dynamics, and disruptions in the ETC contribute to compromised energy production and heightened oxidative stress. These factors, in turn, lead to neuronal damage and cell death. Recent research has unveiled potential therapeutic strategies targeting mitochondrial dysfunction, including mitochondria targeted therapies and antioxidants. Furthermore, the identification of reliable biomarkers for assessing mitochondrial dysfunction opens new avenues for early diagnosis and monitoring of disease progression. By delving into these advancements, this review underscores the significance of understanding mitochondrial biology in unraveling the mechanisms underlying neurodegenerative disorders. It lays the groundwork for developing targeted treatments to combat these devastating neurological conditions.

The Protective Mechanism of TFAM on Mitochondrial DNA and its Role in Neurodegenerative Diseases

Mitochondrial transcription factor A (TFAM) is a mitochondrial protein encoded by nuclear genes and transported from the cytoplasm to the mitochondria. TFAM is essential for the maintenance, expression, and delivery of mitochondrial DNA (mtDNA) and can regulate the replication and transcription of mtDNA. TFAM is associated with the formation of mtDNA nucleomimetic structures, mtDNA repair, and mtDNA stability. However, the mechanism by which TFAM protects mtDNA is still being studied. This review provides a summary of the protective mechanism of TFAM on mtDNA including the discrete regulatory effects of TFAM acetylation and phosphorylation on mtDNA, the regulation of Ca2+ levels by TFAM to activate transcription in mitochondria, and the increased binding of TFAM to mtDNA damage hot spots. This review also discusses the association between TFAM and some neurodegenerative diseases.

Novel blood and tissue-based mitochondrial D-loop mutations detected in an Iranian NAFLD patient cohort

Non-alcoholic fatty liver disease (NAFLD) is an increasingly prevalent chronic liver disease characterized by an elusive etiology. In its advanced stages, this condition can pose life-threatening implications. Mitochondrial dysfunction due to its impact on hepatic lipid homeostasis, cytokine release, ROS production, and cell death, contributes to the pathogenesis of NAFLD. Previous research reveals a direct link between NAFLD genetic predictors and mitochondrial dysfunction. The emphasis on the D-loop stems from its association with impaired mtDNA replication, underscoring its crucial role in NAFLD progression. We included 38 Iranian NAFLD patients (comprising 16 patients with non-alcoholic fatty liver [NAFL] and 22 patients with non-alcoholic steatohepatitis [NASH]), with matched blood and liver tissue samples collected from each to compare variations in the mitochondrial D-loop sequence within samples. The mitochondrial DNA (mtDNA) D-loop region was amplified using PCR, and variations were identified through sequencing. The resultant sequences were compared with the reference sequence of human mtDNA available in the MITOMAP Database for comparative analysis. In this study, 97 somatic mutations in the mtDNA D-loop region were identified in NAFLD patients. Our study revealed significant difference between the NAFLD patients and control group in 13 detected mutations (P ≤ 0.05). Novel mutations were discovered in hepatic tissues, while mutation 16220-16221ins C was found in both tissues and blood. A significant difference was found in the distribution of D310 and mt514-mt523 (CA)n repeat variations between NAFLD patients and the control group (P < 0.001). C to T and T to C transitions were the prevalent substitution among patients. Identification of the 16220-16221ins C mutation in both blood and tissue samples from NAFLD patients holds substantial promise as a potential diagnostic marker. However, further research is imperative to corroborate these findings.

Involvement of mitochondria in Alzheimer's disease pathogenesis and their potential as targets for phytotherapeutics

Alzheimer's disease (AD) is the leading cause of dementia around the globe. The disease's genesis is multifaceted, and its pathophysiology is complicated. Malfunction of mitochondria has been regarded as one of the intracellular events that are substantially damaged in the onset of AD and are likely a common trait of other neurodegenerative illnesses. Several mitochondrial characteristics begin to diminish with age, eventually reaching a state of significant functional failure concurrent with the beginning of neurodegenerative diseases, however, the exact timing of these processes is unknown. Mitochondrial malfunction has a multitude of negative repercussions, including reduced calcium buffering and secondary excitotoxicity contributing to synaptic dysfunction, also free radical production, and activation of the mitochondrial permeability transition. Hence mitochondria are considered a therapeutic target in neurodegenerative disorders such as Alzheimer's. Traditional medicinal systems practiced in different countries employing various medicinal plants postulated to have potential role in the therapy and management of memory impairment including amnesia, dementia as well as AD. Although, the preclinical and clinical studies using these medicinal plants or plant products have demonstrated the therapeutic efficacy for AD, the precise mechanism of action is still obscure. Therefore, this review discusses the contribution of mitochondria towards AD pathogenesis and considering phytotherapeutics as a potential therapeutic strategy.

MitoH3: Mitochondrial Haplogroup and Homoplasmic/Heteroplasmic Variant Calling Pipeline for Alzheimer's Disease Sequencing Project

Background

Mitochondrial DNA (mtDNA) is a double-stranded circular DNA and has multiple copies in each cell. Excess heteroplasmy, the coexistence of distinct variants in copies of mtDNA within a cell, may lead to mitochondrial impairments. Accurate determination of heteroplasmy in whole-genome sequencing (WGS) data has posed a significant challenge because mitochondria carrying heteroplasmic variants cannot be distinguished during library preparation. Moreover, sequencing errors, contamination, and nuclear mtDNA segments can reduce the accuracy of heteroplasmic variant calling.

Objective

To efficiently and accurately call mtDNA homoplasmic and heteroplasmic variants from the large-scale WGS data generated from the Alzheimer's Disease Sequencing Project (ADSP), and test their association with Alzheimer's disease (AD).

Methods

In this study, we present MitoH3-a comprehensive computational pipeline for calling mtDNA homoplasmic and heteroplasmic variants and inferring haplogroups in the ADSP WGS data. We first applied MitoH3 to 45 technical replicates from 6 subjects to define a threshold for detecting heteroplasmic variants. Then using the threshold of 5% ≤variant allele fraction≤95%, we further applied MitoH3 to call heteroplasmic variants from a total of 16,113 DNA samples with 6,742 samples from cognitively normal controls and 6,183 from AD cases.

Results

This pipeline is available through the Singularity container engine. For 4,311 heteroplasmic variants identified from 16,113 samples, no significant variant count difference was observed between AD cases and controls.

Conclusions

Our streamlined pipeline, MitoH3, enables computationally efficient and accurate analysis of a large number of samples.

Mitochondrial Permeability Transition, Cell Death and Neurodegeneration

Neurodegenerative diseases are chronic conditions occurring when neurons die in specific brain regions that lead to loss of movement or cognitive functions. Despite the progress in understanding the mechanisms of this pathology, currently no cure exists to treat these types of diseases: for some of them the only help is alleviating the associated symptoms. Mitochondrial dysfunction has been shown to be involved in the pathogenesis of most the neurodegenerative disorders. The fast and transient permeability of mitochondria (the mitochondrial permeability transition, mPT) has been shown to be an initial step in the mechanism of apoptotic and necrotic cell death, which acts as a regulator of tissue regeneration for postmitotic neurons as it leads to the irreparable loss of cells and cell function. In this study, we review the role of the mitochondrial permeability transition in neuronal death in major neurodegenerative diseases, covering the inductors of mPTP opening in neurons, including the major ones-free radicals and calcium-and we discuss perspectives and difficulties in the development of a neuroprotective strategy based on the inhibition of mPTP in neurodegenerative disorders.

Targeted Treatment Strategies for Mitochondria Dysfunction: Correlation with Neurological Disorders

Mitochondria are an essential intracellular organelle for medication targeting and delivery since they seem to create energy and conduct many other cellular tasks, and mitochondrial dysfunctions and malfunctions lead to many illnesses. Many initiatives have been taken to detect, diagnose, and image mitochondrial abnormalities, and to transport and accumulate medicines precisely to mitochondria, all because of special mitochondrial aspects of the pathophysiology of cancer. In addition to the negative membrane potential and paradoxical mitochondrial dynamics, they include high temperatures, high levels of reactive oxygen species, high levels of glutathione, and high temperatures. Neurodegenerative diseases represent a broad spectrum of debilitating illnesses. They are linked to the loss of certain groups of neurons based on an individual's physiology or anatomy. The mitochondria in a cell are generally accepted as the authority with respect to ATP production. Disruption of this system is linked to several cellular physiological issues. The development of neurodegenerative disorders has been linked to mitochondrial malfunction, according to pathophysiological studies. There seems to be substantial evidence connecting mitochondrial dysfunction and oxidative stress to the development of neurodegenerative disorders. It has been extensively observed that mitochondrial malfunction triggers autophagy, which plays a role in neurodegenerative disorders. In addition, excitotoxicity and mitochondrial dysfunction have been linked to the development of neurodegenerative disorders. The pathophysiology of neurodegenerative illnesses has been linked to increased apoptosis and necrosis, as well as mitochondrial malfunction. A variety of synthetic and natural treatments have shown efficacy in treating neurodegenerative illnesses caused by mitochondrial failure. Neurodegenerative illnesses can be effectively treated with existing drugs that target mitochondria, although their precise formulations are poorly understood. Therefore, there is an immediate need to focus on creating drug delivery methods specifically targeted at mitochondria in the treatment and diagnosis of neurodegenerative disorders.

Oxidative damage in neurodegeneration: roles in the pathogenesis and progression of Alzheimer disease

Alzheimer disease (AD) is associated with multiple etiologies and pathological mechanisms, among which oxidative stress (OS) appears as a major determinant. Intriguingly, OS arises in various pathways regulating brain functions, and it seems to link different hypotheses and mechanisms of AD neuropathology with high fidelity. The brain is particularly vulnerable to oxidative damage, mainly because of its unique lipid composition, resulting in an amplified cascade of redox reactions that target several cellular components/functions ultimately leading to neurodegeneration. The present review highlights the "OS hypothesis of AD," including amyloid beta-peptide-associated mechanisms, the role of lipid and protein oxidation unraveled by redox proteomics, and the antioxidant strategies that have been investigated to modulate the progression of AD. Collected studies from our groups and others have contributed to unraveling the close relationships between perturbation of redox homeostasis in the brain and AD neuropathology by elucidating redox-regulated events potentially involved in both the pathogenesis and progression of AD. However, the complexity of AD pathological mechanisms requires an in-depth understanding of several major intracellular pathways affecting redox homeostasis and relevant for brain functions. This understanding is crucial to developing pharmacological strategies targeting OS-mediated toxicity that may potentially contribute to slow AD progression as well as improve the quality of life of persons with this severe dementing disorder.

Dual barrier system against xenomitochondrial contamination in mouse embryos

Heteroplasmic mammalian embryos between genetically distant species fail to develop to term, preventing transmission of xenomitochondrial DNA to progeny. However, there is no direct evidence indicating the mechanisms by which species specificity of the mitochondrial genome is ensured during mammalian development. Here, we have uncovered a two-step strategy underlying the prevention of xenomitochondrial DNA transmission in mouse embryos harboring bovine mitochondria (mtB-M embryos). First, mtB-M embryos showed metabolic disorder by transient increase of reactive oxygen species at the 4-cell stage, resulting in repressed development. Second, trophoblasts of mtB-M embryos led to implantation failure. Therefore, we tested cell aggregation with tetraploid embryos to compensate for the placentation of mtB-M embryos. The 14 mtB-M embryos harboring bovine mtDNAs developed to term at embryonic day 19.5. Taken together, our results show that contamination of bovine mtDNA is prohibited by embryonic lethality due to metabolic disruption and failure of placentation, suggesting these represent xenomitochondrial elimination mechanisms in mammalian embryos.

Understanding the neuronal synapse and challenges associated with the mitochondrial dysfunction in mild cognitive impairment and Alzheimer's disease

Synaptic mitochondria are crucial for maintaining synaptic activity due to their high energy requirements, substantial calcium (Ca2+) fluctuation, and neurotransmitter release at the synapse. To provide a continuous energy supply, neurons use special mechanisms to transport and distribute healthy mitochondria to the synapse while eliminating the damaged mitochondria from the synapse. Along the neuron, mitochondrial membrane potential (ψ) gradient exists and is highest in the somal region. Lower ψ in the synaptic region renders mitochondria more vulnerable to oxidative stress-mediated damage. Secondly, mitochondria become susceptible to the release of cytochrome c, and mitochondrial DNA (mtDNA) is not shielded from the reactive oxygen species (ROS) by the histone proteins (unlike nuclear DNA), leading to activation of caspases and pronounced oxidative DNA base damage, which ultimately causes synaptic loss. Both synaptic mitochondrial dysfunction and synaptic failure are crucial factors responsible for Alzheimer's disease (AD). Furthermore, amyloid beta (Aβ) and hyper-phosphorylated Tau, the two leading players of AD, exaggerate the disease-like pathological conditions by reducing the mitochondrial trafficking, blocking the bi-directional transport at the synapse, enhancing the mitochondrial fission via activating the mitochondrial fission proteins, enhancing the swelling of mitochondria by increasing the influx of water through mitochondrial permeability transition pore (mPTP) opening, as well as reduced ATP production by blocking the activity of complex I and complex IV. Mild cognitive impairment (MCI) is also associated with decline in cognitive ability caused by synaptic degradation. This review summarizes the challenges associated with the synaptic mitochondrial dysfunction linked to AD and MCI and the role of phytochemicals in restoring the synaptic activity and rendering neuroprotection in AD.

C17orf80 binds the mitochondrial genome to promote its replication

Serving as the power plant and signaling hub of a cell, mitochondria contain their own genome which encodes proteins essential for energy metabolism and forms DNA-protein assemblies called nucleoids. Mitochondrial DNA (mtDNA) exists in multiple copies within each cell ranging from hundreds to tens of thousands. Maintaining mtDNA homeostasis is vital for healthy cells, and its dysregulation causes multiple human diseases. However, the players involved in regulating mtDNA maintenance are largely unknown though the core components of its replication machinery have been characterized. Here, we identify C17orf80, a functionally uncharacterized protein, as a critical player in maintaining mtDNA homeostasis. C17orf80 primarily localizes to mitochondrial nucleoid foci and exhibits robust double-stranded DNA binding activity throughout the mitochondrial genome, thus constituting a bona fide new mitochondrial nucleoid protein. It controls mtDNA levels by promoting mtDNA replication and plays important roles in mitochondrial metabolism and cell proliferation. Our findings provide a potential target for therapeutics of human diseases associated with defective mtDNA control.

Evaluating genomic signatures of aging in brain tissue as it relates to Alzheimer's disease

Telomere length (TL) attrition, epigenetic age acceleration, and mitochondrial DNA copy number (mtDNAcn) decline are established hallmarks of aging. Each has been individually associated with Alzheimer's dementia, cognitive function, and pathologic Alzheimer's disease (AD). Epigenetic age and mtDNAcn have been studied in brain tissue directly but prior work on TL in brain is limited to small sample sizes and most studies have examined leukocyte TL. Importantly, TL, epigenetic age clocks, and mtDNAcn have not been studied jointly in brain tissue from an AD cohort. We examined dorsolateral prefrontal cortex (DLPFC) tissue from N = 367 participants of the Religious Orders Study (ROS) or the Rush Memory and Aging Project (MAP). TL and mtDNAcn were estimated from whole genome sequencing (WGS) data and cortical clock age was computed on 347 CpG sites. We examined dementia, MCI, and level of and change in cognition, pathologic AD, and three quantitative AD traits, as well as measures of other neurodegenerative diseases and cerebrovascular diseases (CVD). We previously showed that mtDNAcn from DLPFC brain tissue was associated with clinical and pathologic features of AD. Here, we show that those associations are independent of TL. We found TL to be associated with β-amyloid levels (beta = - 0.15, p = 0.023), hippocampal sclerosis (OR = 0.56, p = 0.0015) and cerebral atherosclerosis (OR = 1.44, p = 0.0007). We found strong associations between mtDNAcn and clinical measures of AD. The strongest associations with pathologic measures of AD were with cortical clock and there were associations of mtDNAcn with global AD pathology and tau tangles. Of the other pathologic traits, mtDNAcn was associated with hippocampal sclerosis, macroscopic infarctions and CAA and cortical clock was associated with Lewy bodies. Multi-modal age acceleration, accelerated aging on both mtDNAcn and cortical clock, had greater effect size than a single measure alone. These findings highlight for the first time that age acceleration determined on multiple genomic measures, mtDNAcn and cortical clock may have a larger effect on AD/AD related disorders (ADRD) pathogenesis than single measures.

Mitochondrial dynamics in health and disease: mechanisms and potential targets

Mitochondria are organelles that are able to adjust and respond to different stressors and metabolic needs within a cell, showcasing their plasticity and dynamic nature. These abilities allow them to effectively coordinate various cellular functions. Mitochondrial dynamics refers to the changing process of fission, fusion, mitophagy and transport, which is crucial for optimal function in signal transduction and metabolism. An imbalance in mitochondrial dynamics can disrupt mitochondrial function, leading to abnormal cellular fate, and a range of diseases, including neurodegenerative disorders, metabolic diseases, cardiovascular diseases and cancers. Herein, we review the mechanism of mitochondrial dynamics, and its impacts on cellular function. We also delve into the changes that occur in mitochondrial dynamics during health and disease, and offer novel perspectives on how to target the modulation of mitochondrial dynamics.

Quantifying human genome parameters in aging

Healthy human longevity is a global goal of the world health system. Determining the causes and processes influencing human longevity is the primary fundamental goal facing the scientific community. Currently, the main efforts of the scientific community are aimed at identifying the qualitative characteristics of the genome that determine the trait. At the same time, when evaluating qualitative characteristics, there are many challenges that make it difficult to establish associations. Quantitative traits are burdened with such problems to a lesser extent, but they are largely overlooked in current genomic studies of aging and longevity. Although there is a wide repertoire of quantitative trait analyses based on genomic data, most opportunities are ignored by authors, which, along with the inaccessibility of published data, leads to the loss of this important information. This review focuses on describing quantitative traits important for understanding aging and necessary for analysis in further genomic studies, and recommends the inclusion of the described traits in the analysis. The review considers the relationship between quantitative characteristics of the mitochondrial genome and aging, longevity, and age-related neurodegenerative diseases, such as the frequency of extensive mitochondrial DNA (mtDNA) deletions, mtDNA half-life, the frequency of A>G replacements in the mtDNA heavy chain, the number of mtDNA copies; special attention is paid to the mtDNA methylation sign. A separate section of this review is devoted to the correlation of telomere length parameters with age, as well as the association of telomere length with the amount of mitochondrial DNA. In addition, we consider such a quantitative feature as the rate of accumulation of somatic mutations with aging in relation to the lifespan of living organisms. In general, it may be noted that there are quite serious reasons to suppose that various quantitative characteristics of the genome may be directly or indirectly associated with certain aspects of aging and longevity. At the same time, the available data are clearly insufficient for definitive conclusions and the determination of causal relationships.

Targeted to neuronal organelles for CNS drug development

Significant evidences indicate that sub-cellular organelle dynamics is critical for both physiological and pathological events and therefore may be attractive drug targets displaying great therapeutic potential. Although the basic biological mechanism underlying the dynamics of intracellular organelles has been extensively studied, relative drug development is still limited. In the present review, we show that due to the development of technical advanced imaging tools, especially live cell imaging methods, intracellular organelle dynamics (including mitochondrial dynamics and membrane contact sites) can be dissected at the molecular level. Based on these identified molecular targets, we review and discuss the potential of drug development to target organelle dynamics, especially mitochondria dynamics and ER-organelle membrane contact dynamics, in the central nervous system for treating human diseases, including neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, Huntington's disease and amyotrophic lateral sclerosis.

Mitochondrial genome study in blood of maternally inherited ALS cases

BACKGROUND

ALS is a heterogeneous disease in which different factors such as mitochondrial phenotypes act in combination with a genetic predisposition. This study addresses the question of whether homoplasmic (total mitochondrial genome of a sample is affected) and/or heteroplasmic mutations (wildtype and mutant mitochondrial DNA molecules coexist) might play a role in familial ALS. Blood was drawn from familial ALS patients with a possible maternal pattern of inheritance according to their pedigrees, which was compared to blood of ALS patients without maternal association as well as age-matched controls. In two cohorts, we analyzed the mitochondrial genome from whole blood or isolated white blood cells and platelets using a resequencing microarray (Affymetrix MitoChip v2.0) that is able to detect homoplasmic and heteroplasmic mitochondrial DNA mutations and allows the assessment of low-level heteroplasmy.

RESULTS

We identified an increase in homoplasmic ND5 mutations, a subunit of respiratory chain complex I, in whole blood of ALS patients that allowed maternal inheritance. This effect was more pronounced in patients with bulbar onset. Heteroplasmic mutations were significantly increased in different mitochondrial genes in platelets of patients with possible maternal inheritance. No increase of low-level heteroplasmy was found in maternal ALS patients.

CONCLUSION

Our results indicate a contribution of homoplasmic ND5 mutations to maternally associated ALS with bulbar onset. Therefore, it might be conceivable that specific maternally transmitted rather than randomly acquired mitochondrial DNA mutations might contribute to the disease process. This stands in contrast with observations from Alzheimer's and Parkinson's diseases showing an age-dependent accumulation of unspecific mutations in mitochondrial DNA.

The contribution of mitochondrial DNA alterations to aging, cancer, and neurodegeneration

Mitochondrial DNA (mtDNA) is as a double-stranded molecule existing in hundreds to thousands copies in cells depending on cell metabolism and exposure to endogenous and/or environmental stressors. The coordination of mtDNA replication and transcription regulates the pace of mitochondrial biogenesis to guarantee the minimum number of organelles per cell. mtDNA inheritance follows a maternal lineage, although bi-parental inheritance has been reported in some species and in the case of mitochondrial diseases in humans. mtDNA mutations (e.g., point mutations, deletions, copy number variations) have been identified in the setting of several human diseases. For instance, sporadic and inherited rare disorders involving the nervous system as well higher risk of developing cancer and neurodegenerative conditions, including Parkinson's and Alzheimer's disease, have been associated with polymorphic mtDNA variants. An accrual of mtDNA mutations has also been identified in several tissues and organs, including heart and muscle, of old experimental animals and humans, which may contribute to the development of aging phenotypes. The role played by mtDNA homeostasis and mtDNA quality control pathways in human health is actively investigated for the possibility of developing targeted therapeutics for a wide range of conditions.

Modeling of mitochondrial genetic polymorphisms reveals induction of heteroplasmy by pleiotropic disease locus 10398A>G

Mitochondrial (MT) dysfunction has been associated with several neurodegenerative diseases including Alzheimer's disease (AD). While MT-copy number differences have been implicated in AD, the effect of MT heteroplasmy on AD has not been well characterized. Here, we analyzed over 1800 whole genome sequencing data from four AD cohorts in seven different tissue types to determine the extent of MT heteroplasmy present. While MT heteroplasmy was present throughout the entire MT genome for blood samples, we detected MT heteroplasmy only within the MT control region for brain samples. We observed that an MT variant 10398A>G (rs2853826) was significantly associated with overall MT heteroplasmy in brain tissue while also being linked with the largest number of distinct disease phenotypes of all annotated MT variants in MitoMap. Using gene-expression data from our brain samples, our modeling discovered several gene networks involved in mitochondrial respiratory chain and Complex I function associated with 10398A>G. The variant was also found to be an expression quantitative trait loci (eQTL) for the gene MT-ND3. We further characterized the effect of 10398A>G by phenotyping a population of lymphoblastoid cell-lines (LCLs) with and without the variant allele. Examination of RNA sequence data from these LCLs reveal that 10398A>G was an eQTL for MT-ND4. We also observed in LCLs that 10398A>G was significantly associated with overall MT heteroplasmy within the MT control region, confirming the initial findings observed in post-mortem brain tissue. These results provide novel evidence linking MT SNPs with MT heteroplasmy and open novel avenues for the investigation of pathomechanisms that are driven by this pleiotropic disease associated loci.

Systematic review of 31P-magnetic resonance spectroscopy studies of brain high energy phosphates and membrane phospholipids in aging and Alzheimer's disease

Many lines of evidence suggest that mitochondria have a central role in aging-related neurodegenerative diseases, such as Alzheimer's disease (AD). Mitochondrial dysfunction, cerebral energy dysmetabolism and oxidative damage increase with age, and are early event in AD pathophysiology and may precede amyloid beta (Aβ) plaques. In vivo probes of mitochondrial function and energy metabolism are therefore crucial to characterize the bioenergetic abnormalities underlying AD risk, and their relationship to pathophysiology and cognition. A majority of the research conducted in humans have used 18F-fluoro-deoxygluose (FDG) PET to image cerebral glucose metabolism (CMRglc), but key information regarding oxidative phosphorylation (OXPHOS), the process which generates 90% of the energy for the brain, cannot be assessed with this method. Thus, there is a crucial need for imaging tools to measure mitochondrial processes and OXPHOS in vivo in the human brain. 31Phosphorus-magnetic resonance spectroscopy (31P-MRS) is a non-invasive method which allows for the measurement of OXPHOS-related high-energy phosphates (HEP), including phosphocreatine (PCr), adenosine triphosphate (ATP), and inorganic phosphate (Pi), in addition to potential of hydrogen (pH), as well as components of phospholipid metabolism, such as phosphomonoesters (PMEs) and phosphodiesters (PDEs). Herein, we provide a systematic review of the existing literature utilizing the 31P-MRS methodology during the normal aging process and in patients with mild cognitive impairment (MCI) and AD, with an additional focus on individuals at risk for AD. We discuss the strengths and limitations of the technique, in addition to considering future directions toward validating the use of 31P-MRS measures as biomarkers for the early detection of AD.

The role of STING signaling in central nervous system infection and neuroinflammatory disease

The cyclic guanosine monophosphate-adenosine monophosphate (GMP-AMP) synthase-Stimulator of Interferon Genes (cGAS-STING) pathway is a critical innate immune mechanism for detecting the presence of double-stranded DNA (dsDNA) and prompting a robust immune response. Canonical cGAS-STING activation occurs when cGAS, a predominantly cytosolic pattern recognition receptor, binds microbial DNA to promote STING activation. Upon STING activation, transcription factors enter the nucleus to cause the production of Type I interferons, inflammatory cytokines whose primary function is to prime the host for viral infection by producing a number of antiviral interferon-stimulated genes. While the pathway was originally described in viral infection, more recent studies have implicated cGAS-STING signaling in a number of different contexts, including autoimmune disease, cancer, injury, and neuroinflammatory disease. This review focuses on how our understanding of the cGAS-STING pathway has evolved over time with an emphasis on the role of STING-mediated neuroinflammation and infection in the nervous system. We discuss recent findings on how STING signaling contributes to the pathology of pain, traumatic brain injury, and stroke, as well as how mitochondrial DNA may promote STING activation in common neurodegenerative diseases. We conclude by commenting on the current knowledge gaps that should be filled before STING can be an effective therapeutic target in neuroinflammatory disease. This article is categorized under: Neurological Diseases > Molecular and Cellular Physiology Infectious Diseases > Molecular and Cellular Physiology Immune System Diseases > Molecular and Cellular Physiology.

The Alzheimer's Disease Mitochondrial Cascade Hypothesis: A Current Overview

Viable Alzheimer's disease (AD) hypotheses must account for its age-dependence; commonality; association with amyloid precursor protein, tau, and apolipoprotein E biology; connection with vascular, inflammation, and insulin signaling changes; and systemic features. Mitochondria and parameters influenced by mitochondria could link these diverse characteristics. Mitochondrial biology can initiate changes in pathways tied to AD and mediate the dysfunction that produces the clinical phenotype. For these reasons, conceptualizing a mitochondrial cascade hypothesis is a straightforward process and data accumulating over decades argue the validity of its principles. Alternative AD hypotheses may yet account for its mitochondria-related phenomena, but absent this happening a primary mitochondrial cascade hypothesis will continue to evolve and attract interest.

Mitochondria Profoundly Influence Apolipoprotein E Biology

BACKGROUND

Mitochondria can trigger Alzheimer's disease (AD)-associated molecular phenomena, but how mitochondria impact apolipoprotein E (APOE; apoE) is not well known.

OBJECTIVE

Consider whether and how mitochondrial biology influences APOE and apoE biology.

METHODS

We measured APOE expression in human SH-SY5Y neuronal cells with different forms of mitochondrial dysfunction including total, chronic mitochondrial DNA (mtDNA) depletion (ρ0 cells); acute, partial mtDNA depletion; and toxin-induced mitochondrial dysfunction. We further assessed intracellular and secreted apoE protein levels in the ρ0 cells and interrogated the impact of transcription factors and stress signaling pathways known to influence APOE expression.

RESULTS

SH-SY5Y ρ0 cells exhibited a 65-fold increase in APOE mRNA, an 8-fold increase in secreted apoE protein, and increased intracellular apoE protein. Other models of primary mitochondrial dysfunction including partial mtDNA-depletion, toxin-induced respiratory chain inhibition, and chemical-induced manipulations of the mitochondrial membrane potential similarly increased SH-SY5Y cell APOE mRNA. We explored potential mediators and found in the ρ0 cells knock-down of the C/EBPα and NFE2L2 (Nrf2) transcription factors reduced APOE mRNA. The activity of two mitogen-activated protein kinases, JNK and ERK, also strongly influenced ρ0 cell APOE mRNA levels.

CONCLUSION

Primary mitochondrial dysfunction either directly or indirectly activates APOE expression in a neuronal cell model by altering transcription factors and stress signaling pathways. These studies demonstrate mitochondrial biology can influence the biology of the APOE gene and apoE protein, which are implicated in AD.

Therapeutics for mitochondrial dysfunction-linked diseases in Down syndrome

Genome-wide deregulation contributes to mitochondrial dysfunction and impairment in oxidative phosphorylation (OXPHOS) mechanism resulting in oxidative stress, increased production of reactive oxygen species (ROS) and cell death in individuals with Down syndrome (DS). The cells, which require more energy, such as muscles, brain and heart are greatly affected. Impairment in mitochondrial network has a direct link with patho-mechanism at cellular and systemic levels at the backdrop of generalized metabolic perturbations in individuals with DS. Myriads of clinico-phenotypic features, including intellectual disability, early aging and neurodegeneration, and Alzheimer disease (AD)-related dementia are inevitable in DS-population where mitochondrial dysfunctions play the central role. Collectively, the mitochondrial abnormalities and altered energy metabolism perturbs several signaling pathways, particularly related to neurogenesis, which are directly associated with cognitive development and early onset of AD in individuals with DS. Therefore, therapeutic challenges for amelioration of the mitochondrial defects were perceived to improve the quality of life of the DS population. A number of pharmacologically active natural compounds such as polyphenols, antioxidants and flavonoids have shown convincing outcome for reversal of the dysfunctional mitochondrial network and oxidative metabolism, and improvement in intellectual skill in mouse models of DS and humans with DS.

Mitochondrial Medicine: A Promising Therapeutic Option Against Various Neurodegenerative Disorders

Abnormal mitochondrial morphology and metabolic dysfunction have been observed in many neurodegenerative disorders (NDDs). Mitochondrial dysfunction can be caused by aberrant mitochondrial DNA, mutant nuclear proteins that interact with mitochondria directly or indirectly, or for unknown reasons. Since mitochondria play a significant role in neurodegeneration, mitochondriatargeted therapies represent a prosperous direction for the development of novel drug compounds that can be used to treat NDDs. This review gives a brief description of how mitochondrial abnormalities lead to various NDDs such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. We further explore the promising therapeutic effectiveness of mitochondria- directed antioxidants, MitoQ, MitoVitE, MitoPBN, and dimebon. We have also discussed the possibility of mitochondrial gene therapy as a therapeutic option for these NDDs.

CEND1 deficiency induces mitochondrial dysfunction and cognitive impairment in Alzheimer's disease

Alzheimer's disease (AD) is the most common form of neurodegenerative disease featured with memory loss and cognitive function impairments. Chronic mitochondrial stress is a vital pathogenic factor for AD and finally leads to massive neuronal death. However, the underlying mechanism is unclear. By proteomic analysis, we identified a new mitochondrial protein, cell-cycle exit and neuronal differentiation 1 (CEND1), which was decreased significantly in the brain of 5xFAD mice. CEND1 is a neuronal specific protein and locates in the presynaptic mitochondria. Depletion of CEND1 leads to increased mitochondrial fission mediated by upregulation of dynamin related protein 1 (Drp1), resulting in abnormal mitochondrial functions. CEND1 deficiency leads to cognitive impairments in mice. Overexpression of CEND1 in the hippocampus of 5xFAD mice rescued cognitive deficits. Moreover, we identified that CDK5/p25 interacted with and phosphorylated CEND1 which promoted its degradation. Our study provides new mechanistic insights in mitochondrial function regulations by CEND1 in Alzheimer's disease.

A Review of the Recent Advances in Alzheimer's Disease Research and the Utilization of Network Biology Approaches for Prioritizing Diagnostics and Therapeutics

Alzheimer's disease (AD) is a polygenic multifactorial neurodegenerative disease that, after decades of research and development, is still without a cure. There are some symptomatic treatments to manage the psychological symptoms but none of these drugs can halt disease progression. Additionally, over the last few years, many anti-AD drugs failed in late stages of clinical trials and many hypotheses surfaced to explain these failures, including the lack of clear understanding of disease pathways and processes. Recently, different epigenetic factors have been implicated in AD pathogenesis; thus, they could serve as promising AD diagnostic biomarkers. Additionally, network biology approaches have been suggested as effective tools to study AD on the systems level and discover multi-target-directed ligands as novel treatments for AD. Herein, we provide a comprehensive review on Alzheimer's disease pathophysiology to provide a better understanding of disease pathogenesis hypotheses and decipher the role of genetic and epigenetic factors in disease development and progression. We also provide an overview of disease biomarkers and drug targets and suggest network biology approaches as new tools for identifying novel biomarkers and drugs. We also posit that the application of machine learning and artificial intelligence to mining Alzheimer's disease multi-omics data will facilitate drug and biomarker discovery efforts and lead to effective individualized anti-Alzheimer treatments.

Mitochondrial biogenesis, telomere length and cellular senescence in Parkinson's disease and Lewy body dementia

Progressive age is the single major risk factor for neurodegenerative diseases. Cellular aging markers during Parkinson's disease (PD) have been implicated in previous studies, however the majority of studies have investigated the association of individual cellular aging hallmarks with PD but not jointly. Here, we have studied the association of PD with three aging hallmarks (telomere attrition, mitochondrial dysfunction, and cellular senescence) in blood and the brain tissue. Our results show that PD patients had 20% lower mitochondrial DNA copies but 26% longer telomeres in blood compared to controls. Moreover, telomere length in blood was positively correlated with medication (Levodopa Equivalent Daily Dose, LEDD) and disease duration. Similar results were found in brain tissue, where patients with Parkinson's disease (PD), Parkinson's disease dementia (PDD) and Dementia with Lewy Bodies (DLB) showed (46-95%) depleted mtDNA copies, but (7-9%) longer telomeres compared to controls. In addition, patients had lower mitochondrial biogenesis (PGC-1α and PGC-1β) and higher load of a cellular senescence marker in postmortem prefrontal cortex tissue, with DLB showing the highest effect among the patient groups. Our results suggest that mitochondrial dysfunction (copy number and biogenesis) in blood might be a valuable marker to assess the risk of PD. However, further studies with larger sample size are needed to evaluate these findings.

The role of mitochondrial genome abundance in Alzheimer's disease

Mitochondrial dysfunction is an early and prominent feature of Alzheimer's disease (AD), with impaired energy metabolism preceding the onset of clinical symptoms. Here we propose an update to the mitochondrial dysfunction hypothesis of AD based on recent results examining the role of mitochondrial genome abundance in AD. In a large post mortem study, we show that lower brain mitochondrial genome abundance is associated with a greater odds of AD neuropathological change and worse cognitive performance. We hypothesize that lower mitochondrial genome abundance impairs mitochondrial function by reducing mitochondrial bioenergetics, thereby impacting neuronal and glial cell function. However, it remains to be determined if mitochondrial dysfunction causes, mediates, or is a by-product of AD pathogenesis. Additional support for this hypothesis will be generated by linking peripheral blood mitochondrial genome abundance to AD and establishing clinical trials of compounds that upregulate total mitochondrial genome abundance or boost mitochondrial mass.

Mitochondrial dysfunction in microglia: a novel perspective for pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disease in the elderly globally. Emerging evidence has demonstrated microglia-driven neuroinflammation as a key contributor to the onset and progression of AD, however, the mechanisms that mediate neuroinflammation remain largely unknown. Recent studies have suggested mitochondrial dysfunction including mitochondrial DNA (mtDNA) damage, metabolic defects, and quality control (QC) disorders precedes microglial activation and subsequent neuroinflammation. Therefore, an in-depth understanding of the relationship between mitochondrial dysfunction and microglial activation in AD is important to unveil the pathogenesis of AD and develop effective approaches for early AD diagnosis and treatment. In this review, we summarized current progress in the roles of mtDNA, mitochondrial metabolism, mitochondrial QC changes in microglial activation in AD, and provide comprehensive thoughts for targeting microglial mitochondria as potential therapeutic strategies of AD.

Adult-Onset Deficiency of Mitochondrial Complex III in a Mouse Model of Alzheimer's Disease Decreases Amyloid Beta Plaque Formation

For decades, mitochondrial dysfunctions and the generation of reactive oxygen species have been proposed to promote the development and progression of the amyloid pathology in Alzheimer's disease, but this association is still debated. It is unclear whether different mitochondrial dysfunctions, such as oxidative phosphorylation deficiency and oxidative stress, are triggers or rather consequences of the formation of amyloid aggregates. Likewise, the role of the different mitochondrial oxidative phosphorylation complexes in Alzheimer's patients' brain remains poorly understood. Previous studies showed that genetic ablation of oxidative phosphorylation enzymes from early age decreased amyloid pathology, which were unexpected results. To better model oxidative phosphorylation defects in aging, we induced the ablation of mitochondrial Complex III (CIIIKO) in forebrain neurons of adult mice with amyloid pathology. We found that mitochondrial Complex III dysfunction in adult neurons induced mild oxidative stress but did not increase amyloid beta accumulation. On the contrary, CIIIKO-AD mice showed decreased plaque number, decreased Aβ42 toxic fragment, and altered amyloid precursor protein clearance pathway. Our results support the hypothesis that mitochondrial dysfunctions alone, caused by oxidative phosphorylation deficiency, is not the cause of amyloid accumulation.

Targeting Mitochondrial Function with Chemoptogenetics

Mitochondria are ATP-generating organelles in eukaryotic cells that produce reactive oxygen species (ROS) during oxidative phosphorylation (OXPHOS). Mitochondrial DNA (mtDNA) is packaged within nucleoids and, due to its close proximity to ROS production, endures oxidative base damage. This damage can be repaired by base excision repair (BER) within the mitochondria, or it can be degraded via exonucleases or mitophagy. Persistent mtDNA damage may drive the production of dysfunctional OXPHOS components that generate increased ROS, or OXPHOS components may be directly damaged by ROS, which then can cause more mtDNA damage and create a vicious cycle of ROS production and mitochondrial dysfunction. If mtDNA damage is left unrepaired, mtDNA mutations including deletions can result. The accumulation of mtDNA mutations has been associated with conditions ranging from the aging process to cancer and neurodegenerative conditions, but the sequence of events leading to mtDNA mutations and deletions is yet unknown. Researchers have utilized many systems and agents for generating ROS in mitochondria to observe the downstream effects on mtDNA, ROS, and mitochondrial function; yet, there are various drawbacks to these methodologies that limit their precision. Here, we describe a novel chemoptogenetic approach to target oxidative damage to mitochondria and mtDNA with a high spatial and temporal resolution so that the downstream effects of ROS-induced damage can be measured with a high precision in order to better understand the mechanism of mitochondrial dysfunction in aging, cancer, and neurodegenerative diseases.

Mitochondria - Nucleus communication in neurodegenerative disease. Who talks first, who talks louder?

Mitochondria - nuclear coadaptation has been central to eukaryotic evolution. The dynamic dialogue between the two compartments within the context of multiorganellar interactions is critical for maintaining cellular homeostasis and directing the balance survival-death in case of cellular stress. The conceptualisation of mitochondria - nucleus communication has so far been focused on the communication from the mitochondria under stress to the nucleus and the consequent signalling responses, as well as from the nucleus to mitochondria in the context of DNA damage and repair. During ageing processes this dialogue may be better viewed as an integrated bidirectional 'talk' with feedback loops that expand beyond these two organelles depending on physiological cues. Here we explore the current views on mitochondria - nucleus dialogue and its role in maintaining cellular health with a focus on brain cells and neurodegenerative disease. Thus, we detail the transcriptional responses initiated by mitochondrial dysfunction in order to protect itself and the general cellular homeostasis. Additionally, we are reviewing the knowledge of the stress pathways initiated by DNA damage which affect mitochondria homeostasis and we add the information provided by the study of combined mitochondrial and genotoxic damage. Finally, we reflect on how each organelle may take the lead in this dialogue in an ageing context where both compartments undergo accumulation of stress and damage and where, perhaps, even the communications' mechanisms may suffer interruptions.

Could Amyloid-β 1-42 or α-Synuclein Interact Directly with Mitochondrial DNA? A Hypothesis

The amyloid β (Aβ) and the α-synuclein (α-syn) are shown to be translocated into mitochondria. Even though their roles are widely investigated in pathological conditions, information on the presence and functions of Aβ and α-syn in mitochondria in endogenous levels is somewhat limited. We hypothesized that endogenous Aβ fragments or α-syn could interact with mitochondrial DNA (mtDNA) directly or influence RNAs or transcription factors in mitochondria and change the mtDNA transcription profile. In this review, we summarized clues of these possible interactions.

Perspectives on the Molecular Mediators of Oxidative Stress and Antioxidant Strategies in the Context of Neuroprotection and Neurolongevity: An Extensive Review

Molecules with at least one unpaired electron in their outermost shell are known as free radicals. Free radical molecules are produced either within our bodies or by external sources such as ozone, cigarette smoking, X-rays, industrial chemicals, and air pollution. Disruption of normal cellular homeostasis by redox signaling may result in cardiovascular, neurodegenerative diseases and cancer. Although ROS (reactive oxygen species) are formed in the GI tract, little is known about how they contribute to pathophysiology and disease etiology. When reactive oxygen species and antioxidants are in imbalance in our bodies, they can cause cell structure damage, neurodegenerative diseases, diabetes, hypercholesterolemia, atherosclerosis, cancer, cardiovascular diseases, metabolic disorders, and other obesity-related disorders, as well as protein misfolding, mitochondrial dysfunction, glial cell activation, and subsequent cellular apoptosis. Neuron cells are gradually destroyed in neurodegenerative diseases. The production of inappropriately aggregated proteins is strongly linked to oxidative stress. This review's goal is to provide as much information as possible about the numerous neurodegenerative illnesses linked to oxidative stress. The possibilities of multimodal and neuroprotective therapy in human illness, using already accessible medications and demonstrating neuroprotective promise in animal models, are highlighted. Neuroprotection and neurolongevity may improve from the use of bioactive substances from medicinal herbs like Allium stadium, Celastrus paniculatus, and Centella asiatica. Many neuroprotective drugs' possible role has been addressed. Preventing neuroinflammation has been demonstrated in several animal models.

Does protracted radon exposure play a role in the development of dementia?

Radon is a ubiquitous radioactive gas that decays into a series of solid radioactive decay products. Radon, and its decay products, enter the human body primarily through inhalation and can be delivered to various tissues including the brain through systemic circulation. It can also reach the brain by neuronal pathways via the olfactory system. While ionizing radiation has been suggested as a risk factor of dementia for decades, studies exploring the possible role of radon exposure in the development of Alzheimer's Diseases (AD) and other dementias are sparse. We systematically reviewed the literature and found several lines of evidence suggesting that radon decay products (RDPs) disproportionally deposit in the brain of AD patients with selective accumulation within the protein fractions. Ecologic study findings also indicate a significant positive correlation between geographic-level radon distribution and AD mortality in the US. Additionally, pathologic studies of radon shed light on the potential pathways of radon decay product induced proinflammation and oxidative stress that may result in the development of dementia. In summary, there are plausible underlying biological mechanisms linking radon exposure to the risk of dementia. Since randomized clinical trials on radon exposure are not feasible, well-designed individual-level epidemiologic studies are urgently needed to elucidate the possible association between radon (i.e., RDPs) exposure and the onset of dementia.

SIRT3 regulates mitochondrial biogenesis in aging-related diseases

Sirtuin 3 (SIRT3), the main family member of mitochondrial deacetylase, targets the majority of substrates controlling mitochondrial biogenesis via lysine deacetylation and modulates important cellular functions such as energy metabolism, reactive oxygen species production and clearance, oxidative stress, and aging. Deletion of SIRT3 has a deleterious effect on mitochondrial biogenesis, thus leading to the defect in mitochondrial function and insufficient ATP production. Imbalance of mitochondrial dynamics leads to excessive mitochondrial biogenesis, dampening mitochondrial function. Mitochondrial dysfunction plays an important role in several diseases related to aging, such as cardiovascular disease, cancer and neurodegenerative diseases. Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) launches mitochondrial biogenesis through activating nuclear respiratory factors. These factors act on genes, transcribing and translating mitochondrial DNA to generate new mitochondria. PGC1α builds a bridge between SIRT3 and mitochondrial biogenesis. This review described the involvement of SIRT3 and mitochondrial dynamics, particularly mitochondrial biogenesis in aging-related diseases, and further illustrated the role of the signaling events between SIRT3 and mitochondrial biogenesis in the pathological process of aging-related diseases.

Progress in biophysics and molecular biology proteostasis impairment and ALS

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive and fatal neurodegenerative disease that results from the loss of both upper and lower motor neurons. It is the most common motor neuron disease and currently has no effective treatment. There is mounting evidence to suggest that disturbances in proteostasis play a significant role in ALS pathogenesis. Proteostasis is the maintenance of the proteome at the right level, conformation and location to allow a cell to perform its intended function. In this review, we present a thorough synthesis of the literature that provides evidence that genetic mutations associated with ALS cause imbalance to a proteome that is vulnerable to such pressure due to its metastable nature. We propose that the mechanism underlying motor neuron death caused by defects in mRNA metabolism and protein degradation pathways converges on proteostasis dysfunction. We propose that the proteostasis network may provide an effective target for therapeutic development in ALS.

Mitochondrial genome mutations and neuronal dysfunction of induced pluripotent stem cells derived from patients with Alzheimer's disease

OBJECTIVES

Patient-derived induced pluripotent stem cells (iPSCs) are materials that can be used for autologous stem cell therapy. We screened mtDNA mutations in iPSCs and iPSC-derived neuronal cells from patients with Alzheimer's disease (AD). Also, we investigated whether the mutations could affect mitochondrial function and deposition of β-amyloid (Aβ) in differentiated neuronal cells.

MATERIALS AND METHODS

mtDNA mutations were measured and compared among iPSCs and iPSC-derived neuronal cells. The selected iPSCs carrying mtDNA mutations were subcloned, and then their growth rate and neuronal differentiation pattern were analyzed. The differentiated cells were measured for mitochondrial respiration and membrane potential, as well as deposition of Aβ.

RESULTS

Most iPSCs from subjects with AD harbored ≥1 mtDNA mutations, and the number of mutations was significantly higher than that from umbilical cord blood. About 35% and 40% of mutations in iPSCs were shared with isogenic iPSCs and their differentiated neuronal precursor cells, respectively, with similar or different heteroplasmy. Furthermore, the mutations in clonal iPSCs were stable during extended culture and neuronal differentiation. Finally, mtDNA mutations could induce a growth advantage with higher viability and proliferation, lower mitochondrial respiration and membrane potential, as well as increased Aβ deposition.

CONCLUSION

This study demonstrates that mtDNA mutations in patients with AD could lead to mitochondrial dysfunction and accelerated Aβ deposition. Therefore, early screening for mtDNA mutations in iPSC lines would be essential for developing autologous cell therapy or drug screening for patients with AD.

Cellular Senescence in Aging Lungs and Diseases

Cellular senescence represents a state of irreversible cell cycle arrest occurring naturally or in response to exogenous stressors. Following the initial arrest, progressive phenotypic changes define conditions of cellular senescence. Understanding molecular mechanisms that drive senescence can help to recognize the importance of such pathways in lung health and disease. There is increasing interest in the role of cellular senescence in conditions such as chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF) in the context of understanding pathophysiology and identification of novel therapies. Herein, we discuss the current knowledge of molecular mechanisms and mitochondrial dysfunction regulating different aspects of cellular senescence-related to chronic lung diseases to develop rational strategies for modulating the senescent cell phenotype in the lung for therapeutic benefit.

Targeting Mitochondrial bioenergetics as a promising therapeutic strategy in metabolic and neurodegenerative diseases

Mitochondria are the organelles that generate energy for the cells and act as biosynthetic and bioenergetic factories, vital for normal cell functioning and human health. Mitochondrial bioenergetics is considered an important measure to assess the pathogenesis of various diseases. Dysfunctional mitochondria affect or cause several conditions involving the most energy-intensive organs, including the brain, muscles, heart, and liver. This dysfunction may be attributed to an alteration in mitochondrial enzymes, increased oxidative stress, impairment of electron transport chain and oxidative phosphorylation, or mutations in mitochondrial DNA that leads to the pathophysiology of various pathological conditions, including neurological and metabolic disorders. The drugs or compounds targeting mitochondria are considered more effective and safer for treating these diseases. In this review, we make an effort to concise the available literature on mitochondrial bioenergetics in various conditions and the therapeutic potential of various drugs/compounds targeting mitochondrial bioenergetics in metabolic and neurodegenerative diseases.

Next-Generation Sequencing to Characterize Mitochondrial Genomic DNA Heteroplasmy

Mitochondria play a very important role in many crucial cellular functions. Each eukaryotic cell contains hundreds of mitochondria with hundreds of mitochondrial genomes. Mutant and wild-type mitochondrial DNA (mtDNA) may co-exist as heteroplasmy and cause human disease. The purpose of the protocols in this article is to simultaneously determine the mtDNA sequence and quantify the heteroplasmy level using parallel sequencing. The protocols include mitochondrial genomic DNA PCR amplification of two full-length products using two distinct sets of PCR primers. The PCR products are mixed at an equimolar ratio, and the samples are then barcoded and sequenced with high-throughput next-generation sequencing technology. This technology is highly sensitive, specific, and accurate in determining mtDNA mutations and the degree/level of heteroplasmy. © 2022 Wiley Periodicals LLC. Basic Protocol 1: PCR amplification of mitochondrial DNA Basic Protocol 2: Analysis of next-generation sequencing of mitochondrial DNA Basic Protocol 3: Mutect2 pipeline for automated sample processing and large-scale data analysis.

Dietary Supplements and Natural Products: An Update on Their Clinical Effectiveness and Molecular Mechanisms of Action During Accelerated Biological Aging

Accelerated biological aging, which involves the gradual decline of organ or tissue functions and the distortion of physiological processes, underlies several human diseases. Away from the earlier free radical concept, telomere attrition, cellular senescence, proteostasis loss, mitochondrial dysfunction, stem cell exhaustion, and epigenetic and genomic alterations have emerged as biological hallmarks of aging. Moreover, nutrient-sensing metabolic pathways are critical to an organism's ability to sense and respond to nutrient levels. Pharmaceutical, genetic, and nutritional interventions reverting physiological declines by targeting nutrient-sensing metabolic pathways can promote healthy aging and increase lifespan. On this basis, biological aging hallmarks and nutrient-sensing dependent and independent pathways represent evolving drug targets for many age-linked diseases. Here, we discuss and update the scientific community on contemporary advances in how dietary supplements and natural products beneficially revert accelerated biological aging processes to retrograde human aging and age-dependent human diseases, both from the clinical and preclinical studies point-of-view. Overall, our review suggests that dietary/natural products increase healthspan-rather than lifespan-effectively minimizing the period of frailty at the end of life. However, real-world setting clinical trials and basic studies on dietary supplements and natural products are further required to decisively demonstrate whether dietary/natural products could promote human lifespan.