The mitochondria-targeted antioxidant MitoQ inhibits memory loss, neuropathology, and extends lifespan in aged 3xTg-AD mice

The synergistic effect of curcumin and mitoquinol mesylate on cognitive impairment and the neuropathology of Alzheimer's disease

Given the complexity and heterogeneity of Alzheimer's disease (AD) pathology, targeted monotherapy drugs may not be effective. Therefore, synergistic combination therapy of curcumin and Mito Q was proposed and evaluated in a triple-transgenic AD model mice (3 × Tg-AD mice). The cognitive ability was assessed using behavioral tests and typical pathological changes were observed through Western blotting and histological analysis. The results demonstrated a significant enhancement in cognitive ability along with the mitigation of typical AD pathological features such as Aβ aggregation, tau phosphorylation, and synaptic damage. Notably, the combination therapy demonstrated superior efficacy over individual drugs alone. These findings provide valuable insights for optimizing the development of AD drugs.

Permeabilization of the outer mitochondrial membrane: Mechanisms and consequences

Permeabilization of the outer mitochondrial membrane is а physiological process that can allow certain molecules to pass through it, such as low molecular weight solutes required for cellular respiration. This process is also important for the development of various modes of cell death. Depending on the severity of this process, cells can die by autophagy, apoptosis, or necrosis/necroptosis. Distinct types of pores can be opened at the outer mitochondrial membrane depending on physiological or pathological stimuli, and different mechanisms can be activated in order to open these pores. In this comprehensive review, all these types of permeabilization, the mechanisms of their activation, and their role in various diseases are discussed.

Mitochondrial disorders leading to Alzheimer's disease-perspectives of diagnosis and treatment

Alzheimer's disease (AD) is a neurodegenerative disorder and the most common cause of dementia globally. The pathogenesis of AD remains still unclear. The three main features of AD are extracellular deposits of amyloid beta (Aβ) plaque, accumulation of abnormal formation hyper-phosphorylated tau protein, and neuronal loss. Mitochondrial impairment plays an important role in the pathogenesis of AD. There are problems with decreased activity of multiple complexes, disturbed mitochondrial fusion, and fission or formation of reactive oxygen species (ROS). Moreover, mitochondrial transport is impaired in AD. Mouse models in many research show disruptions in anterograde and retrograde transport. Both mitochondrial transportation and network impairment have a huge impact on synapse loss and, as a result, cognitive impairment. One of the very serious problems in AD is also disruption of insulin signaling which impairs mitochondrial Aβ removal.Discovering precise mechanisms leading to AD enables us to find new treatment possibilities. Recent studies indicate the positive influence of metformin or antioxidants such as MitoQ, SS-31, SkQ, MitoApo, MitoTEMPO, and MitoVitE on mitochondrial functioning and hence prevent cognitive decline. Impairments in mitochondrial fission may be treated with mitochondrial division inhibitor-1 or ceramide.

Mitochondrial dynamics dysfunction: Unraveling the hidden link to depression

Depression is a common mental disorder and its pathogenesis is not fully understood. However, more and more evidence shows that mitochondrial dynamics dysfunction may play an important role in the occurrence and development of depression. Mitochondria are the centre of energy production in cells, and are also involved in important processes such as apoptosis and oxidative stress. Studies have found that there are abnormalities in mitochondrial function in patients with depression, including mitochondrial morphological changes, mitochondrial dynamics disorders, mitochondrial DNA damage, and impaired mitochondrial respiratory chain function. These abnormalities may cause excessive free radicals and oxidative stress in mitochondria, which further damage cells and affect the balance of neurotransmitters, causing or aggravating depressive symptoms. Studies have shown that mitochondrial dynamics dysfunction may participate in the occurrence and development of depression by affecting neuroplasticity, inflammation and neurotransmitters. This article reviews the effects of mitochondrial dynamics dysfunction on the pathogenesis of depression and its potential molecular pathway. The restorers for the treatment of depression by regulating the function of mitochondrial dynamics were summarized and the possibility of using mitochondrial dynamics as a biomarker of depression was discussed.

Mechanistic insights and emerging therapeutic stratagems for Alzheimer's disease

Alzheimer's disease (AD), a multi-factorial neurodegenerative disorder has affected over 30 million individuals globally and these numbers are expected to increase in the coming decades. Current therapeutic interventions are largely ineffective as they focus on a single target. Development of an effective drug therapy requires a deep understanding of the various factors influencing the onset and progression of the disease. Aging and genetic factors exert a major influence on the development of AD. Other factors like post-viral infections, iron overload, gut dysbiosis, and vascular dysfunction also exacerbate the onset and progression of AD. Further, post-translational modifications in tau, DRP1, CREB, and p65 proteins increase the disease severity through triggering mitochondrial dysfunction, synaptic loss, and differential interaction of amyloid beta with different receptors leading to impaired intracellular signalling. With advancements in neuroscience tools, new inter-relations that aggravate AD are being discovered including pre-existing diseases and exposure to other pathogens. Simultaneously, new therapeutic strategies involving modulation of gene expression through targeted delivery or modulation with light, harnessing the immune response to promote clearance of amyloid deposits, introduction of stem cells and extracellular vesicles to replace the destroyed neurons, exploring new therapeutic molecules from plant, marine and biological sources delivered in the free state or through nanoparticles and use of non-pharmacological interventions like music, transcranial stimulation and yoga. Polypharmacology approaches involving combination of therapeutic agents are also under active investigation for superior therapeutic outcomes. This review elaborates on various disease-causing factors, their underlying mechanisms, the inter-play between different disease-causing players, and emerging therapeutic options including those under clinical trials, for treatment of AD. The challenges involved in AD therapy and the way forward have also been discussed.

TPP-based conjugates: potential targeting ligands

Mitochondria are one of the major sources of energy as well as regulators of cancer cell metabolism. Thus, they are potential targets for the effective treatment and management of cancer. Research has explored triphenylphosphonium (TPP) derivatives as potent cancer-targeting ligands because of their lipophilic nature and mitochondrial affinity. In this review, we summarize the utility of TPP-based conjugates targeting mitochondria in different types of cancer and other diseases, such as neurodegenerative and cardiovascular disorders. Such conjugates offer versatile therapeutic potential by modulating membrane potential, influencing reactive oxygen species (ROS) production, and coupling of molecular modifications (such as ATP metabolism and energy metabolism). Thus, we highlight TPP conjugates as promising mitochondria-targeting agents for use in targeted drug delivery systems.

Peripheral vascular dysfunction and the aging brain

Aging is the greatest non-modifiable risk factor for most diseases, including cardiovascular diseases (CVD), which remain the leading cause of mortality worldwide. Robust evidence indicates that CVD are a strong determinant for reduced brain health and all-cause dementia with advancing age. CVD are also closely linked with peripheral and cerebral vascular dysfunction, common contributors to the development and progression of all types of dementia, that are largely driven by excessive levels of oxidative stress (e.g., reactive oxygen species [ROS]). Emerging evidence suggests that several fundamental aging mechanisms (e.g., "hallmarks" of aging), including chronic low-grade inflammation, mitochondrial dysfunction, cellular senescence and deregulated nutrient sensing contribute to excessive ROS production and are common to both peripheral and cerebral vascular dysfunction. Therefore, targeting these mechanisms to reduce ROS-related oxidative stress and improve peripheral and/or cerebral vascular function may be a promising strategy to reduce dementia risk with aging. Investigating how certain lifestyle strategies (e.g., aerobic exercise and diet modulation) and/or select pharmacological agents (natural and synthetic) intersect with aging "hallmarks" to promote peripheral and/or cerebral vascular health represent a viable option for reducing dementia risk with aging. Therefore, the primary purpose of this review is to explore mechanistic links among peripheral vascular dysfunction, cerebral vascular dysfunction, and reduced brain health with aging. Such insight and assessments of non-invasive measures of peripheral and cerebral vascular health with aging might provide a new approach for assessing dementia risk in older adults.

CoQ10 and Mitochondrial Dysfunction in Alzheimer's Disease

The progress in understanding the pathogenesis and treatment of Alzheimer's disease (AD) is based on the recognition of the primary causes of the disease, which can be deduced from the knowledge of risk factors and biomarkers measurable in the early stages of the disease. Insights into the risk factors and the time course of biomarker abnormalities point to a role for the connection of amyloid beta (Aβ) pathology, tau pathology, mitochondrial dysfunction, and oxidative stress in the onset and development of AD. Coenzyme Q10 (CoQ10) is a lipid antioxidant and electron transporter in the mitochondrial electron transport system. The availability and activity of CoQ10 is crucial for proper mitochondrial function and cellular bioenergetics. Based on the mitochondrial hypothesis of AD and the hypothesis of oxidative stress, the regulation of the efficiency of the oxidative phosphorylation system by means of CoQ10 can be considered promising in restoring the mitochondrial function impaired in AD, or in preventing the onset of mitochondrial dysfunction and the development of amyloid and tau pathology in AD. This review summarizes the knowledge on the pathophysiology of AD, in which CoQ10 may play a significant role, with the aim of evaluating the perspective of the pharmacotherapy of AD with CoQ10 and its analogues.

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.

Mitochondrial-targeted antioxidant ingestion acutely blunts VO2max in physically inactive females

PURPOSE

To determine the acute effects of a mitochondrial targeting antioxidant (MitoQ) on the metabolic response during exercise.

METHODS

Nine (n = 9) physically inactive females (age 47 ± 22 years) performed two trials (Placebo and MitoQ) in a double-blind randomized cross-over design. In both trials, participants performed an exercise protocol consisting of 3-min stages at submaximal workloads followed by a ramp protocol to volitional exhaustion. Participants received either Placebo or MitoQ (80 mg) 1 h prior to exercise. Indirect calorimetry and cardiovascular measurements were collected throughout the duration of the exercise bout.

RESULTS

Submaximal metabolic and cardiovascular variables were not different between trials (p > 0.05). VO2max was higher (p = 0.03) during Placebo (23.5 ± 5.7 mL kg min-1 ) compared to MitoQ (21.0 ± 6.6 mL kg min-1 ). Maximal ventilation was also higher (p = 0.02) in Placebo (82.4 ± 17.7 L/min) compared to MitoQ (75.0 ± 16.8 L/min). Maximal cardiovascular variables and blood lactate were not different between trials (p > 0.05).

CONCLUSION

An acute dose of MitoQ blunted VO2max , which was primarily mediated by impairment of ventilatory function. These data suggest that the acute accumulation of exercise-induced mitochondrial reactive oxygen species (mtROS) are necessary for maximal aerobic capacity. Further research is warranted on mtROS-antioxidant cell signaling cascades, and how they relate to mitochondrial function during exercise.

Mitochondrial dysfunction and neurological disorders: A narrative review and treatment overview

Mitochondria play a vital role in the nervous system, as they are responsible for generating energy in the form of ATP and regulating cellular processes such as calcium (Ca2+) signaling and apoptosis. However, mitochondrial dysfunction can lead to oxidative stress (OS), inflammation, and cell death, which have been implicated in the pathogenesis of various neurological disorders. In this article, we review the main functions of mitochondria in the nervous system and explore the mechanisms related to mitochondrial dysfunction. We discuss the role of mitochondrial dysfunction in the development and progression of some neurological disorders including Parkinson's disease (PD), multiple sclerosis (MS), Alzheimer's disease (AD), depression, and epilepsy. Finally, we provide an overview of various current treatment strategies that target mitochondrial dysfunction, including pharmacological treatments, phototherapy, gene therapy, and mitotherapy. This review emphasizes the importance of understanding the role of mitochondria in the nervous system and highlights the potential for mitochondrial-targeted therapies in the treatment of neurological disorders. Furthermore, it highlights some limitations and challenges encountered by the current therapeutic strategies and puts them in future perspective.

Effects of Redox Homeostasis and Mitochondrial Damage on Alzheimer's Disease

Bioenergetic mitochondrial dysfunction is a common feature of several diseases, including Alzheimer's disease (AD), where redox imbalance also plays an important role in terms of disease development. AD is an age-related disease and begins many years before the appearance of neurodegenerative symptoms. Intracellular tau aggregation, extracellular β-amyloid (Aβ) deposition in the brain, and even the APOE4 genotype contribute to the process of AD by impairing redox homeostasis and mitochondrial dysfunction. This review summarizes the evidence for the redox imbalance and mitochondrial dysfunction in AD and demonstrates the current therapeutic strategies related to mitochondrial maintenance.

Anthracycline chemotherapy, vascular dysfunction and cognitive impairment: burgeoning topics and future directions

Anthracyclines, chemotherapeutic agents used to treat common forms of cancer, increase cardiovascular (CV) complications, thereby necessitating research regarding interventions to improve the health of cancer survivors. Vascular dysfunction, which is induced by anthracycline chemotherapy, is an established antecedent to overt CV diseases. Potential treatment options for ameliorating vascular dysfunction have largely been understudied. Furthermore, patients treated with anthracyclines have impaired cognitive function and vascular dysfunction is an independent risk factor for the development of mild cognitive impairment. Here, we will focus on: anthracycline chemotherapy associated CV diseases risk; how targeting mechanisms underlying vascular dysfunction may be a means to improve both CV and cognitive health; and research gaps and potential future directions for the field of cardio-oncology.

Coenzyme Q-related compounds to maintain healthy mitochondria during aging

Mitochondrial dysfunction is one of the main factors that affects aging progression and many age-related diseases. Accumulation of dysfunctional mitochondria can be driven by unbalanced mito/autophagy or by decrease in mitochondrial biosynthesis and turnover. Coenzyme Q is an essential component of the mitochondrial electron transport chain and a key factor in the protection of membrane and mitochondrial DNA against oxidation. Coenzyme Q levels decay during aging and this can be considered an accelerating factor in mitochondrial dysfunction and aging progression. Supplementation with coenzyme Q is successful for some tissues and organs but not for others. For this reason, the role of coenzyme Q in systemic aging is a complex picture that needs different strategies depending on the organ considered the main objective to be addressed. In this chapter we focus on the different effects of coenzyme Q and related compounds and the probable strategies to induce endogenous synthesis to maintain healthy aging.

Changing ROS, NAD and AMP: A path to longevity via mitochondrial therapeutics

Lifespan of many organisms, from unicellular yeast to extremely complex human organism, strongly depends on the genetic background and environmental factors. Being among most influential target energy metabolism is affected by macronutrients, their caloric values, and peculiarities of catabolism. Mitochondria are central organelles that respond for energy metabolism in eukaryotic cells. Mitochondria generate reactive oxygen species (ROS), which are lifespan modifying metabolites and a kind of biological clock. Oxidized nicotinamide adenine dinucleotide (NAD⁺) and adenosine monophosphate (AMP) are important metabolic intermediates and molecules that trigger or inhibit several signaling pathways involved in gene silencing, nutrient allocation, and cell regeneration and programmed death. A part of NAD⁺ and AMP metabolism is tied to mitochondria. Using substances that able to target mitochondria, as well as allotopic expression of specific enzymes, are envisioned to be innovative approaches to prolong lifespan by modulation of ROS, NAD⁺, and AMP levels. Among substances, an anti-diabetic drug metformin is believed to increase NAD⁺ and AMP levels, indirectly influencing histone deacetylases, involved in gene silencing, and AMP-activated protein kinase, an energy sensor of cells. Mitochondrially targeted derivatives of ubiquinone were found to interact with ROS. A mitochondrially targeted non-proton-pumping NADH dehydrogenase may influence both ROS and NAD⁺ levels. Chapter describes putative how mitochondria-targeted drugs and NADH dehydrogenase extend lifespan, perspectives of creating drugs with similar properties and their usage as senotherapeutic pills are discussed in the chapter.

Kai-Xin-San protects against mitochondrial dysfunction in Alzheimer's disease through SIRT3/NLRP3 pathway

BACKGROUND

Kai-Xin-San (KXS) has been reported to have a good curative impact on dementia. The purpose of the study was to determine whether KXS might ameliorate cognitive deficits in APP/PS1 mice and to evaluate its neuroprotective mechanism.

METHODS

APP/PS1 mice were employed as an AD animal model; Aβ_1-42 and KXS-containing serum were used in HT22 cells. Four different behavioral tests were used to determine the cognitive ability of mice. Nissl staining was utilized to detect hippocampal neuron changes. ROS, SOD, and MDA were used to detect oxidative stress levels. Transmission electron microscopy and Western blot were used to evaluate mitochondrial morphology, mitochondrial division, and fusion state. Western blotting and immunofluorescence identified PSD95, BDNF, NGF, SYN, SIRT3, and NLRP3 inflammasome levels.

RESULTS

The results indicated that KXS protected APP/PS1 mice against cognitive impairments. KXS suppressed neuronal apoptosis and oxidative stress among APP/PS1 mice. KXS and KXS-containing serum improved mitochondrial dysfunction and synaptic and neurotrophic factors regarding APP/PS1 mice. In addition, KXS and KXS-containing serum enhanced mitochondrial SIRT3 expression and reduced NLRP3 inflammasome expression in APP/PS1 mice.

CONCLUSION

KXS improves cognitive dysfunction among APP/PS1 mice via regulating SIRT3-mediated neuronal cell apoptosis. These results suggested that KXS was proposed as a neuroprotective agent for AD progression.

Disturb mitochondrial associated proteostasis: Neurodegeneration and imperfect ageing

The disturbance in mitochondrial functions and homeostasis are the major features of neuron degenerative conditions, like Parkinson’s disease, Amyotrophic Lateral Sclerosis, and Alzheimer’s disease, along with protein misfolding. The aberrantly folded proteins are known to link with impaired mitochondrial pathways, further contributing to disease pathogenesis. Despite their central significance, the implications of mitochondrial homeostasis disruption on other organelles and cellular processes remain insufficiently explored. Here, we have reviewed the dysfunction in mitochondrial physiology, under neuron degenerating conditions. The disease misfolded proteins impact quality control mechanisms of mitochondria, such as fission, fusion, mitophagy, and proteasomal clearance, to the detriment of neuron. The adversely affected mitochondrial functional roles, like oxidative phosphorylation, calcium homeostasis, and biomolecule synthesis as well as its axes and contacts with endoplasmic reticulum and lysosomes are also discussed. Mitochondria sense and respond to multiple cytotoxic stress to make cell adapt and survive, though chronic dysfunction leads to cell death. Mitochondria and their proteins can be candidates for biomarkers and therapeutic targets. Investigation of internetworking between mitochondria and neurodegeneration proteins can enhance our holistic understanding of such conditions and help in designing more targeted therapies.

Cobalt nanoparticles induce mitochondrial damage and β-amyloid toxicity via the generation of reactive oxygen species

Exposure to cobalt nanoparticles (CoNPs) has been associated with neurodegenerative disorders, while the mitochondrial-associated mechanisms that mediate their neurotoxicity have yet to be fully characterized. In this study, we reported that CoNPs exposure reduced the survival and lifespan in the nematodes, Caenorhabditis elegans (C. elegans). Moreover, exposure to CoNPs aggravated the induction of paralysis and the aggregation of β-amyloid (Aβ). These effects were accompanied by reactive oxygen species (ROS) overproduction, ATP reduction as well as mitochondrial fragmentation. Dynamin-related protein 1 (drp-1) activation and ensuing mitochondrial fragmentation have been shown to be associated with CoNPs-reduced survival. In order to address the role of mitochondrial damage and ROS production in CoNPs-induced Aβ toxicity, the mitochondrial reactive oxygen species scavenger mitoquinone (Mito Q) was used. Our results showed that Mito Q pretreatment alleviated CoNPs-induced ROS generation, rescuing mitochondrial dysfunction, thereby lessening the CoNPs-induced Aβ toxicity. Taken together, we show for the first time, that increasing of ROS and the upregulation of drp-1 lead to CoNPs-induced Aβ toxicity. Our novel findings provide in vivo evidence for the mechanisms of environmental toxicant-induced Aβ toxicity, and can afford new modalities for the prevention and treatment of CoNPs-induced neurodegeneration.

Mitochondria-Targeted Antioxidants, an Innovative Class of Antioxidant Compounds for Neurodegenerative Diseases: Perspectives and Limitations

Neurodegenerative diseases comprise a wide spectrum of pathologies characterized by progressive loss of neuronal functions and structures. Despite having different genetic backgrounds and etiology, in recent years, many studies have highlighted a point of convergence in the mechanisms leading to neurodegeneration: mitochondrial dysfunction and oxidative stress have been observed in different pathologies, and their detrimental effects on neurons contribute to the exacerbation of the pathological phenotype at various degrees. In this context, increasing relevance has been acquired by antioxidant therapies, with the purpose of restoring mitochondrial functions in order to revert the neuronal damage. However, conventional antioxidants were not able to specifically accumulate in diseased mitochondria, often eliciting harmful effects on the whole body. In the last decades, novel, precise, mitochondria-targeted antioxidant (MTA) compounds have been developed and studied, both in vitro and in vivo, to address the need to counter the oxidative stress in mitochondria and restore the energy supply and membrane potentials in neurons. In this review, we focus on the activity and therapeutic perspectives of MitoQ, SkQ1, MitoVitE and MitoTEMPO, the most studied compounds belonging to the class of MTA conjugated to lipophilic cations, in order to reach the mitochondrial compartment.

Ferroptosis-Related Metabolic Mechanism and Nanoparticulate Anticancer Drug Delivery Systems Based on Ferroptosis

Ferroptosis is a new type of cell death discovered in recent years that distinguishes from apoptosis and necrosis, mainly caused by the imbalance between the production and degradation of lipid reactive oxygen species in cells. Although the mechanism of ferroptosis is not yet clear, the phenomenon of ferroptosis has attracted widespread attention from researchers and has become a new hotspot in anti-tumor research. Studies have shown that ferroptosis is involved in the occurrence and development of a variety of diseases such as nervous system diseases, cardiovascular diseases and cancer. And inhibiting or inducing the occurrence of ferroptosis can effectively intervene in related diseases. At the same time, nanotechnology, by virtue of its distinct advantages, has been widely used in the development of nanodrug delivery systems. This review outlines current the advance on the intersection of ferroptosis and biomedical nanotechnology. In this review, the discovery and characteristics of ferroptosis, the mechanism of occurrence and the relationship with disease are summarized. More importantly, we summarized the strategies for inducing ferroptosis based on nanoparticulate drug delivery systems for cancer treatment.

Non-Enzymatic Antioxidants against Alzheimer's Disease: Prevention, Diagnosis and Therapy

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive memory loss and cognitive decline. Although substantial research has been conducted to elucidate the complex pathophysiology of AD, the therapeutic approach still has limited efficacy in clinical practice. Oxidative stress (OS) has been established as an early driver of several age-related diseases, including neurodegeneration. In AD, increased levels of reactive oxygen species mediate neuronal lipid, protein, and nucleic acid peroxidation, mitochondrial dysfunction, synaptic damage, and inflammation. Thus, the identification of novel antioxidant molecules capable of detecting, preventing, and counteracting AD onset and progression is of the utmost importance. However, although several studies have been published, comprehensive and up-to-date overviews of the principal anti-AD agents harboring antioxidant properties remain scarce. In this narrative review, we summarize the role of vitamins, minerals, flavonoids, non-flavonoids, mitochondria-targeting molecules, organosulfur compounds, and carotenoids as non-enzymatic antioxidants with AD diagnostic, preventative, and therapeutic potential, thereby offering insights into the relationship between OS and neurodegeneration.

Altered Mitochondrial Morphology and Bioenergetics in a New Yeast Model Expressing Aβ42

Alzheimer's disease (AD) is an incurable, age-related neurological disorder, the most common form of dementia. Considering that AD is a multifactorial complex disease, simplified experimental models are required for its analysis. For this purpose, genetically modified Yarrowia lipolytica yeast strains expressing Aβ42 (the main biomarker of AD), eGFP-Aβ42, Aβ40, and eGFP-Aβ40 were constructed and examined. In contrast to the cells expressing eGFP and eGFP-Aβ40, retaining "normal" mitochondrial reticulum, eGFP-Aβ42 cells possessed a disturbed mitochondrial reticulum with fragmented mitochondria; this was partially restored by preincubation with a mitochondria-targeted antioxidant SkQThy. Aβ42 expression also elevated ROS production and cell death; low concentrations of SkQThy mitigated these effects. Aβ42 expression caused mitochondrial dysfunction as inferred from a loose coupling of respiration and phosphorylation, the decreased level of ATP production, and the enhanced rate of hydrogen peroxide formation. Therefore, we have obtained the same results described for other AD models. Based on an analysis of these and earlier data, we suggest that the mitochondrial fragmentation might be a biomarker of the earliest preclinical stage of AD with an effective therapy based on mitochondria- targeted antioxidants. The simple yeast model constructed can be a useful platform for the rapid screening of such compounds.

Oxidative Stress and Natural Antioxidants: Back and Forth in the Neurological Mechanisms of Alzheimer's Disease

Alzheimer's disease (AD) is characterized by the progressive degeneration of neuronal cells. With the increase in aged population, there is a prevalence of irreversible neurodegenerative changes, causing a significant mental, social, and economic burden globally. The factors contributing to AD are multidimensional, highly complex, and not completely understood. However, it is widely known that aging, neuroinflammation, and excessive production of reactive oxygen species (ROS), along with other free radicals, substantially contribute to oxidative stress and cell death, which are inextricably linked. While oxidative stress is undeniably important in AD, limiting free radicals and ROS levels is an intriguing and potential strategy for deferring the process of neurodegeneration and alleviating associated symptoms. Therapeutic compounds from natural sources have recently become increasingly accepted and have been effectively studied for AD treatment. These phytocompounds are widely available and a multitude of holistic therapeutic efficiencies for treating AD owing to their antioxidant, anti-inflammatory, and biological activities. Some of these compounds also function by stimulating cholinergic neurotransmission, facilitating the suppression of beta-site amyloid precursor protein-cleaving enzyme 1, α-synuclein, and monoamine oxidase proteins, and deterring the occurrence of AD. Additionally, various phenolic, flavonoid, and terpenoid phytocompounds have been extensively described as potential palliative agents for AD progression. Preclinical studies have shown their involvement in modulating the cellular redox balance and minimizing ROS formation, displaying them as antioxidant agents with neuroprotective abilities. This review emphasizes the mechanistic role of natural products in the treatment of AD and discusses the various pathological hypotheses proposed for AD.

Mitochondrial dysfunctions, oxidative stress and neuroinflammation as therapeutic targets for neurodegenerative diseases: An update on current advances and impediments

Neurodegenerative diseases (NDs) such as Alzheimer disease (AD), Parkinson disease (PD), and Huntington disease (HD) represent a major socio-economic challenge in view of their high prevalence yet poor treatment outcomes affecting quality of life. The major challenge in drug development for these NDs is insufficient clarity about the mechanisms involved in pathogenesis and pathophysiology. Mitochondrial dysfunction, oxidative stress and inflammation are common pathways that are linked to neuronal abnormalities and initiation of these diseases. Thus, elucidating the shared initial molecular and cellular mechanisms is crucial for recognizing novel remedial targets, and developing therapeutics to impede or stop disease progression. In this context, use of multifunctional compounds at early stages of disease development unclogs new avenues as it acts on act on multiple targets in comparison to single target concept. In this review, we summarize overview of the major findings and advancements in recent years focusing on shared mechanisms for better understanding might become beneficial in searching more potent pharmacological interventions thereby reducing the onset or severity of various NDs.

Endurance training and MitoQ supplementation improve spatial memory, VEGF expression, and neurogenic factors in hippocampal tissue of rats

Background and Aim

The hippocampus has a key role in memory and learning, which means that this brain structure has high-energy demand. Accordingly, mitochondrial dysfunction in the hippocampus has deleterious effects on brain function. MitoQ is an antioxidant that accumulates selectively in mitochondria at high concentration. In this study, the effect of MitoQ alone and in combination with endurance training (ET) was investigated on spatial memory (distance, time, and number of passes in the target quarter), antioxidant status (superoxide dismutase [SOD] and glutathione peroxidase [GPx]), and neurogenic factor levels (vascular endothelial growth factor [VEGF] and brain-derived neurotrophic factor [BDNF]) in male Wistar rats.

Methods

Rats were assigned to a control (CTL) group, ET group, ET+MitoQ group, and a MitoQ group. Rats were trained on a treadmill for 8 weeks, 5 days/week, and 50 min/day. MitoQ (250 μM daily) was administered through drinking water for 8 weeks. Spatial memory (Morris water maze test), gene expression (real-time PCR), protein expression (Western blotting), and antioxidants (ELISA method) were determined.

Results

Distance and number of passes in the target quarter in the ET, MitoQ, and ET+MitoQ groups were higher than in the CTL group (P=0.001). MitoQ+ET had more impact on the abovementioned indices than MitoQ or ET alone. Simultaneous use of MitoQ and ET significantly increased gene and protein expression of VEGF (P=0.0001) and gene expression of BDNF (P=0.004) and Sestrin 2 (SESN2) (P=0.0001) in hippocampal tissue. The expression of VEGF (P=0.007) and SESN2 (P=0.001) was higher in the MitoQ group compared to the CTL group. Tissue GPx levels were increased following all three interventions (P≤0.013) compared to the CTL group while SOD levels remained unchanged in all groups.

Conclusions

The combination of ET and MitoQ has additive effects on spatial memory in rats by modulating parameters that are involved in hippocampal neurogenesis. In addition, MitoQ may have positive effects on the antioxidant defense by improving GPx activity.

Relevance for Patients

Considering the positive effects of MitoQ on improving the memory and the antioxidant defense, it seems that it can play a positive role in improving the diseases associated with memory loss in the long term, and ET along with this supplement can increase the possible positive effects.

Losartan Mitigates Oxidative Stress in the Brains of Aged and Inflamed IL-10-/- Mice

Chronic inflammation, oxidative stress, and dysregulation of the renin-angiotensin system are closely linked, and their crosstalk commonly contributes to age-related physical and cognitive decline. The primary dementia-protective benefits of Angiotensin II type 1 receptor (AT1R) blockers are believed to arise from systemic effects on blood pressure. However, there is an independently regulated brain-specific renin-angiotensin system. Here, we examined the impact of 4 weeks of oral Losartan treatment on the brains of aged (100 weeks old) IL-10-/- mice, an animal model of chronic inflammation and frailty. Our data show that aged IL-10-/- mice have higher AT1R and Nitrotyrosine (oxidative stress marker) levels in their frontal cortex tissue but not in cerebellar or hippocampal tissue compared to age- and sex-matched wild type mice. Losartan treatment for 4 weeks is associated with lower AT1R protein level, Nitrotyrosine, and Tau protein in the frontal cortex of aged IL-10-/- mice. Our results highlight the impact of Losartan, an AT1R blocker commonly prescribed for treating high blood pressure, on the brain-specific angiotensin system and AT1R-linked downstream effects such as brain oxidative stress damage and Tau burden in a frailty mouse model.

Effect of Tau Protein on Mitochondrial Functions

Alzheimer's disease is the most common age-related progressive neurodegenerative disorder of brain cortex and hippocampus leading to cognitive impairment. Accumulation of extracellular amyloid plaques and intraneuronal neurofibrillary tangles are believed to be the main hallmarks of the disease. Origin of Alzheimer's disease is not totally clear, multiple initiator factors are likely to exist. Intracellular impacts of Alzheimer's disease include mitochondrial dysfunction, oxidative stress, ER-stress, disruption of autophagy, severe metabolic challenges leading to massive neuronal apoptosis. Mitochondria are the key players in all these processes. This formed the basis for the so-called mitochondrial cascade hypothesis. This review provides current data on the molecular mechanisms of the development of Alzheimer's disease associated with mitochondria. Special attention was paid to the interaction between Tau protein and mitochondria, as well as to the promising therapeutic approaches aimed at preventing development of neurodegeneration.

Oxidative Stress in Tauopathies: From Cause to Therapy

Oxidative stress (OS) is the result of an imbalance between the production of reactive oxygen species (ROS) and the antioxidant capacity of cells. Due to its high oxygen demand, the human brain is highly susceptible to OS and, thus, it is not a surprise that OS has emerged as an essential component of the pathophysiology of several neurodegenerative diseases, including tauopathies. Tauopathies are a heterogeneous group of age-related neurodegenerative disorders characterized by the deposition of abnormal tau protein in the affected neurons. With the worldwide population aging, the prevalence of tauopathies is increasing, but effective therapies have not yet been developed. Since OS seems to play a key role in tauopathies, it has been proposed that the use of antioxidants might be beneficial for tau-related neurodegenerative diseases. Although antioxidant therapies looked promising in preclinical studies performed in cellular and animal models, the antioxidant clinical trials performed in tauopathy patients have been disappointing. To develop effective antioxidant therapies, the molecular mechanisms underlying OS in tauopathies should be completely understood. Here, we review the link between OS and tauopathies, emphasizing the causes of OS in these diseases and the role of OS in tau pathogenesis. We also summarize the antioxidant therapies proposed as a potential treatment for tauopathies and discuss why they have not been completely translated to clinical trials. This review aims to provide an integrated perspective of the role of OS and antioxidant therapies in tauopathies. In doing so, we hope to enable a more comprehensive understanding of OS in tauopathies that will positively impact future studies.

Secondary Mechanisms of Neurotrauma: A Closer Look at the Evidence

Traumatic central nervous system injury is a leading cause of neurological injury worldwide. While initial neuroresuscitative efforts are focused on ameliorating the effects of primary injury through patient stabilization, secondary injury in neurotrauma is a potential cause of cell death, oxidative stress, and neuroinflammation. These secondary injuries lack defined therapy. The major causes of secondary injury in neurotrauma include endoplasmic reticular stress, mitochondrial dysfunction, and the buildup of reactive oxygen or nitrogenous species. Stress to the endoplasmic reticulum in neurotrauma results in the overactivation of the unfolded protein response with subsequent cell apoptosis. Mitochondrial dysfunction can lead to the release of caspases and the buildup of reactive oxygen species; several characteristics make the central nervous system particularly susceptible to oxidative damage. Together, endoplasmic reticulum, mitochondrial, and oxidative stress can have detrimental consequences, beginning moments and lasting days to months after the primary injury. Understanding these causative pathways has led to the proposal of various potential treatment options.

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.

Mitochondria and Other Organelles in Neural Development and Their Potential as Therapeutic Targets in Neurodegenerative Diseases

The contribution of organelles to neural development has received increasing attention. Studies have shown that organelles such as mitochondria, endoplasmic reticulum (ER), lysosomes, and endosomes play important roles in neurogenesis. Specifically, metabolic switching, reactive oxygen species production, mitochondrial dynamics, mitophagy, mitochondria-mediated apoptosis, and the interaction between mitochondria and the ER all have roles in neurogenesis. Lysosomes and endosomes can regulate neurite growth and extension. Moreover, metabolic reprogramming represents a novel strategy for generating functional neurons. Accordingly, the exploration and application of mechanisms underlying metabolic reprogramming will be beneficial for neural conversion and regenerative medicine. There is adequate evidence implicating the dysfunction of cellular organelles—especially mitochondria—in neurodegenerative disorders, and that improvement of mitochondrial function may reverse the progression of these diseases through the reinforcement of adult neurogenesis. Therefore, these organelles have potential as therapeutic targets for the treatment of neurodegenerative diseases. In this review, we discuss the function of these organelles, especially mitochondria, in neural development, focusing on their potential as therapeutic targets in neurodegenerative disorders, including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and amyotrophic lateral sclerosis.

Mitochondrial and metabolic dysfunction in ageing and age-related diseases

Organismal ageing is accompanied by progressive loss of cellular function and systemic deterioration of multiple tissues, leading to impaired function and increased vulnerability to death. Mitochondria have become recognized not merely as being energy suppliers but also as having an essential role in the development of diseases associated with ageing, such as neurodegenerative and cardiovascular diseases. A growing body of evidence suggests that ageing and age-related diseases are tightly related to an energy supply and demand imbalance, which might be alleviated by a variety of interventions, including physical activity and calorie restriction, as well as naturally occurring molecules targeting conserved longevity pathways. Here, we review key historical advances and progress from the past few years in our understanding of the role of mitochondria in ageing and age-related metabolic diseases. We also highlight emerging scientific innovations using mitochondria-targeted therapeutic approaches.

Chronic Stress Induces Hippocampal Mitochondrial Damage in APPPS1 Model Mice and Wildtype Littermates

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative disorder and the most common cause of dementia worldwide. Despite decades of investigation, the etiology of AD is not fully understood, although emerging evidence suggest that chronic environmental and psychological stress plays a role in the mechanisms and contributes to the risk of developing AD. Thus, dissecting the impact of stress on the brain could improve our understanding of the pathological mechanisms.

OBJECTIVE

We aimed to study the effect of chronic stress on the hippocampal proteome in male APPPS1 transgenic mice and wildtype (WT) littermates.

METHODS

APPPS1 and WT mice were subjected to 4 weeks of chronic stress followed by 3 weeks of continued diurnal disruption. Hippocampal tissue was used for proteomics analysis using label-free quantitative DIA based LC-MS/MS analysis.

RESULTS

We identified significantly up- and downregulated proteins in both APPPS1 and WT mice exposed to chronic stress compared to the control groups. Via interaction network mapping, significant proteins could be annotated to specific pathways of mitochondrial function (oxidative phosphorylation and TCA cycle), metabolic pathways, AD pathway and synaptic functions (long term potentiation). In WT mice, chronic stress showed the highest impact on complex I of the oxidative phosphorylation pathway, while in APPPS1 mice this pathway was compromised broadly by chronic stress.

CONCLUSION

Our data shows that chronic stress and amyloidosis additively contribute to mitochondrial damage in hippocampus. Although these results do not explain all effects of chronic stress in AD, they add to the scientific knowledge on the topic.

Mitochondria targeting drugs for neurodegenerative diseases—design, mechanism and application

Neurodegenerative diseases (NDDs) such as Alzheimer's disease (AD) and Parkinson's disease (PD) are a heterogeneous group of disorders characterized by progressive degeneration of neurons. NDDs threaten the lives of millions of people worldwide and regretfully remain incurable. It is well accepted that dysfunction of mitochondria underlies the pathogenesis of NDDs. Dysfunction of mitochondria results in energy depletion, oxidative stress, calcium overloading, caspases activation, which dominates the neuronal death of NDDs. Therefore, mitochondria are the preferred target for intervention of NDDs. So far various mitochondria-targeting drugs have been developed and delightfully some of them demonstrate promising outcome, though there are still some obstacles such as targeting specificity, delivery capacity hindering the drugs development. In present review, we will elaborately address 1) the strategy to design mitochondria targeting drugs, 2) the rescue mechanism of respective mitochondria targeting drugs, 3) how to evaluate the therapeutic effect. Hopefully this review will provide comprehensive knowledge for understanding how to develop more effective drugs for the treatment of NDDs.

Antioxidant Therapy in Oxidative Stress-Induced Neurodegenerative Diseases: Role of Nanoparticle-Based Drug Delivery Systems in Clinical Translation

Free radicals are formed as a part of normal metabolic activities but are neutralized by the endogenous antioxidants present in cells/tissue, thus maintaining the redox balance. This redox balance is disrupted in certain neuropathophysiological conditions, causing oxidative stress, which is implicated in several progressive neurodegenerative diseases. Following neuronal injury, secondary injury progression is also caused by excessive production of free radicals. Highly reactive free radicals, mainly the reactive oxygen species (ROS) and reactive nitrogen species (RNS), damage the cell membrane, proteins, and DNA, which triggers a self-propagating inflammatory cascade of degenerative events. Dysfunctional mitochondria under oxidative stress conditions are considered a key mediator in progressive neurodegeneration. Exogenous delivery of antioxidants holds promise to alleviate oxidative stress to regain the redox balance. In this regard, natural and synthetic antioxidants have been evaluated. Despite promising results in preclinical studies, clinical translation of antioxidants as a therapy to treat neurodegenerative diseases remains elusive. The issues could be their low bioavailability, instability, limited transport to the target tissue, and/or poor antioxidant capacity, requiring repeated and high dosing, which cannot be administered to humans because of dose-limiting toxicity. Our laboratory is investigating nanoparticle-mediated delivery of antioxidant enzymes to address some of the above issues. Apart from being endogenous, the main advantage of antioxidant enzymes is their catalytic mechanism of action; hence, they are significantly more effective at lower doses in detoxifying the deleterious effects of free radicals than nonenzymatic antioxidants. This review provides a comprehensive analysis of the potential of antioxidant therapy, challenges in their clinical translation, and the role nanoparticles/drug delivery systems could play in addressing these challenges.

Targeting whole body metabolism and mitochondrial bioenergetics in the drug development for Alzheimer's disease

Aging is by far the most prominent risk factor for Alzheimer's disease (AD), and both aging and AD are associated with apparent metabolic alterations. As developing effective therapeutic interventions to treat AD is clearly in urgent need, the impact of modulating whole-body and intracellular metabolism in preclinical models and in human patients, on disease pathogenesis, have been explored. There is also an increasing awareness of differential risk and potential targeting strategies related to biological sex, microbiome, and circadian regulation. As a major part of intracellular metabolism, mitochondrial bioenergetics, mitochondrial quality-control mechanisms, and mitochondria-linked inflammatory responses have been considered for AD therapeutic interventions. This review summarizes and highlights these efforts.

Dendrobium nobile Lindl. Alkaloids Ameliorate Aβ25-35-Induced Synaptic Deficits by Targeting Wnt/β-Catenin Pathway in Alzheimer’s Disease Models

Background: Dendrobium nobile Lindl. alkaloids (DNLA) are effective in ameliorating cognitive deficit in SAMP8, AβPP/PS1, and LPS-induced AD animal models, and prevented Aβ-induced synaptic degeneration in cultured hippocampal neurons. However, the underlying mechanisms remain unexplored. Objective: This study investigated the protective effects of DNLA on synaptic damage in an Aβ 25-35-induced rat AD model, in primary cortical neuron cultures, and in PC12 cells transfected with human AβPP695, focusing on the Wnt/β-catenin pathway. Methods: Sprague-Dawley rats received a single Aβ 25-35 injection (10μg) into the bilateral hippocampi. DNLA (40 and 80 mg/kg/d) was intragastrically administrated 7d prior to Aβ injection and continued for 28 days. The spatial learning and memory, synaptic morphology, synapse-related proteins, and Wnt signaling components GSK3β and β-catenin phosphorylation were evaluated. Rat primary cortical neuron cultures and AβPP695-PC12 cells were used to evaluate axonal mitochondria distribution, reactive oxygen species production, amyloidogenesis, and Wnt pathway in the protection. Results: DNLA ameliorated Aβ-induced cognitive impairment, increased the number of synapses, elevated the postsynaptic density thickness and expression of synapsin and PSD95 in the hippocampus, and suppressed Aβ-mediated GSK3β activity and the β-catenin phosphorylation. In primary neurons and AβPP695-PC12 cells, DNLA restored Aβ 25-35 induced mitochondrial dysfunction and inhibited reactive oxygen species production and amyloidogenesis. Furthermore, the Wnt/β-catenin pathway inhibitor Dkk-1 blocked the effect of DNLA on the expression of Aβ 1-42 and PSD95. Conclusion: DNLA rescued Aβ-mediated synaptic and mitochondrial injury and inhibited amyloidogenesis in vivo and in vitro, probably through the activation of Wnt/β-catenin signaling pathway to protect synaptic integrity.

Coenzyme Q10 effects in neurological diseases

Coenzyme Q10 (CoQ10), a lipophilic substituted benzoquinone, is present in animal and plant cells. It is endogenously synthetized in every cell and involved in a variety of cellular processes. CoQ10 is an obligatory component of the respiratory chain in inner mitochondrial membrane. In addition, the presence of CoQ10 in all cellular membranes and in blood. It is the only endogenous lipid antioxidant. Moreover, it is an essential factor for uncoupling protein and controls the permeability transition pore in mitochondria. It also participates in extramitochondrial electron transport and controls membrane physicochemical properties. CoQ10 effects on gene expression might affect the overall metabolism. Primary changes in the energetic and antioxidant functions can explain its remedial effects. CoQ10 supplementation is safe and well-tolerated, even at high doses. CoQ10 does not cause any serious adverse effects in humans or experimental animals. New preparations of CoQ10 that are less hydrophobic and structural derivatives, like idebenone and MitoQ, are being developed to increase absorption and tissue distribution. The review aims to summarize clinical and experimental effects of CoQ10 supplementations in some neurological diseases such as migraine, Parkinson´s disease, Huntington´s disease, Alzheimer´s disease, amyotrophic lateral sclerosis, Friedreich´s ataxia or multiple sclerosis. Cardiovascular hypertension was included because of its central mechanisms controlling blood pressure in the brainstem rostral ventrolateral medulla and hypothalamic paraventricular nucleus. In conclusion, it seems reasonable to recommend CoQ10 as adjunct to conventional therapy in some cases. However, sometimes CoQ10 supplementations are more efficient in animal models of diseases than in human patients (e.g. Parkinson´s disease) or rather vague (e.g. Friedreich´s ataxia or amyotrophic lateral sclerosis).

Recent Advances in Molecular Pathways and Therapeutic Implications Targeting Mitochondrial Dysfunction for Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder which leads to mental deterioration due to aberrant accretion of misfolded proteins in the brain. According to mitochondrial cascade hypothesis, mitochondrial dysfunction is majorly involved in the pathogenesis of AD. Many drugs targeting mitochondria to treat and prevent AD are in different phases of clinical trials for the evaluation of safety and efficacy as mitochondria are involved in various cellular and neuronal functions. Mitochondrial dynamics is regulated by fission and fusion processes mediated by dynamin-related protein (Drp1). Inner membrane fusion takes place by OPA1 and outer membrane fusion is facilitated by mitofusin1 and mitofusin2 (Mfn1/2). Excessive calcium release also impairs mitochondrial functions; to overcome this, calcium channel blockers like nilvadipine are used. Another process acting as a regulator of mitochondrial function is mitophagy which is involved in the removal of damaged and non-functional mitochondria however this process is also altered in AD due to mutations in Presenilin1 (PS1) and Amyloid Precursor Protein (APP) gene. Mitochondrial dynamics is altered in AD which led to the discovery of various fission protein (like Drp1) inhibitors and drugs that promote fusion. Modulations in AMPK, SIRT1 and Akt pathways can also come out to be better therapeutic strategies as these pathways regulate functions of mitochondria. Oxidative phosphorylation is major generator of Reactive Oxygen Species (ROS) leading to mitochondrial damage; therefore reduction in production of ROS by using antioxidants like MitoQ, Curcumin and Vitamin Eis quiteeffective.

Disentangling Mitochondria in Alzheimer's Disease

Alzheimer's disease (AD) is a major cause of dementia in older adults and is fast becoming a major societal and economic burden due to an increase in life expectancy. Age seems to be the major factor driving AD, and currently, only symptomatic treatments are available. AD has a complex etiology, although mitochondrial dysfunction, oxidative stress, inflammation, and metabolic abnormalities have been widely and deeply investigated as plausible mechanisms for its neuropathology. Aβ plaques and hyperphosphorylated tau aggregates, along with cognitive deficits and behavioral problems, are the hallmarks of the disease. Restoration of mitochondrial bioenergetics, prevention of oxidative stress, and diet and exercise seem to be effective in reducing Aβ and in ameliorating learning and memory problems. Many mitochondria-targeted antioxidants have been tested in AD and are currently in development. However, larger streamlined clinical studies are needed to provide hard evidence of benefits in AD. This review discusses the causative factors, as well as potential therapeutics employed in the treatment of AD.

Mitochondrial dysfunction and beneficial effects of mitochondria-targeted small peptide SS-31 in Diabetes Mellitus and Alzheimer's disease

Diabetes and Alzheimer's disease are common chronic illnesses in the United States and lack clearly demonstrated therapeutics. Mitochondria, the "powerhouse of the cell", is involved in the homeostatic regulation of glucose, energy, and reduction/oxidation reactions. The mitochondria has been associated with the etiology of metabolic and neurological disorders through a dysfunction of regulation of reactive oxygen species. Mitochondria-targeted chemicals, such as the Szeto-Schiller-31 peptide, have advanced therapeutic potential through the inhibition of oxidative stress and the restoration of normal mitochondrial function as compared to traditional antioxidants, such as vitamin E. In this article, we summarize the pathophysiological relevance of the mitochondria and the beneficial effects of Szeto-Schiller-31 peptide in the treatment of Diabetes and Alzheimer's disease.

Mitochondrial quality control: Epigenetic signatures and therapeutic strategies

Mitochondria are semi-autonomous organelle staging a crucial role in cellular stress response, energy metabolism and cell survival. Maintaining mitochondrial quality control is very important for its homeostasis. Pathological conditions such as oxidative stress and neurodegeneration, disrupt this quality control, and involvement of genetic and epigenetic materials in this disruption have been reported. These regulatory factors trigger mitochondrial imbalance, as seen in many neurodegenerative diseases like Alzheimer's disease, Parkinson's disease, Amyotrophic lateral sclerosis, and Huntington's disease. The dynamic regulatory pathways i.e. mitophagy, biogenesis, permeability pore transitioning, fusion-fission are affected as a consequence and have been reviewed in this article. Moreover, several epigenetic mechanisms such as DNA methylation and histone modulation participating in such neurological disorders have also been discussed. Apart from it, therapeutic approaches targeting mitochondrial quality control have been tremendously explored showing ameliorative effects for these diseases, and have been discussed here with a novel perspective.

Mitochondria-targeted therapeutics, MitoQ and BGP-15, reverse aging-associated meiotic spindle defects in mouse and human oocytes

STUDY QUESTION

Do mitochondria-targeted therapies reverse ageing- and oxidative stress-induced spindle defects in oocytes from mice and humans?

SUMMARY ANSWER

Exposure to MitoQ or BGP-15 during IVM protected against spindle and chromosomal defects in mouse oocytes exposed to oxidative stress or derived from reproductively aged mice whilst MitoQ promoted nuclear maturation and protected against chromosomal misalignments in human oocytes.

WHAT IS KNOWN ALREADY

Spindle and chromosomal abnormalities in oocytes are more prevalent with maternal aging, increasing the risk of aneuploidy, miscarriage and genetic disorders such as Down's syndrome. The origin of compromised oocyte function may be founded in mitochondrial dysfunction and increased reactive oxygen species (ROS).

STUDY DESIGN, SIZE, DURATION

Oocytes from young and old mice were treated with MitoQ and/or BGP-15 during IVM. To directly induce mitochondrial dysfunction, oocytes were treated with H2O2, and then treated the MitoQ and/or BGP-15. Immature human oocytes were cultured with or without MitoQ. Each experiment was repeated at least three times, and data were analyzed by unpaired-sample t-test or chi-square test.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Immature germinal vesicle (GV) stage oocytes from 1-, 12- and 18-month-old mice were obtained from preovulatory ovarian follicles. Oocytes were treated with MitoQ and/or BGP-15 during IVM. GV-stage human oocytes were cultured with or without MitoQ. Mitochondrial membrane potential and mitochondrial ROS were measured by live-cell imaging. Meiotic spindle and chromosome alignments were visualized by immunofluorescent labeling of fixed oocytes and the 3-dimensional images were analyzed by Imaris.

MAIN RESULTS AND THE ROLE OF CHANCE

MitoQ or BGP-15 during IVM protects against spindle and chromosomal defects in oocytes exposed to oxidative stress and in oocytes from aged mice (P < 0.001). In human oocytes, the presence of MitoQ during IVM promoted nuclear maturation and had a similar positive effect in protecting against chromosomal misalignments (P < 0.001).

LIMITATIONS, REASONS FOR CAUTION

Our study identifies two excellent candidates that may help to improve fertility in older women. However, these potential therapies must be tested for efficacy in clinical IVM systems, and undergo thorough examination of resultant offspring in preclinical models before utilization.

WIDER IMPLICATIONS OF THE FINDINGS

Our results using in-vitro systems for oocyte maturation in both mouse and human provide proof of principle that mitochondrially targeted molecules such as MitoQ and BGP-15 may represent a novel therapeutic approach against maternal aging-related spindle and chromosomal abnormalities.

STUDY FUNDING/COMPETING INTEREST(S)

The project was financially supported by the National Health and Medical Research Council and Australian Research Council, Australia. U.A.-Z. was supported by the Iraqi Higher Education and Scientific Research Ministry PhD scholarship and O.C. was supported by TUBITAK-1059B191601275. M.P.M. consults for MitoQ Inc. and holds patents in mitochondria-targeted therapies. R.L.R. is an inventor on patents relating to the use of BGP-15 to improve gamete quality.

TRIAL REGISTRATION NUMBER

N/A.

Role of Mitochondrial Dysfunction in the Pathology of Amyloid-β

Mitochondrial dysfunction has been widely reported in several neurodegenerative disorders, including in the brains of patients with Alzheimer's disease (AD), Parkinson's disease, and Huntington disease. An increasing number of studies have implicated altered glucose and energy metabolism in patients with AD. There is compelling evidence of abnormalities in some of the key mitochondrial enzymes involved in glucose metabolism, including the pyruvate dehydrogenase and α-ketoglutarate dehydrogenase complexes, which play a great significance role in the pathogenesis of AD. Changes in some of the enzyme activities of the mitochondria found in AD have been linked with the pathology of amyloid-β (Aβ). This review highlights the role of mitochondrial function in the production and clearance of Aβ and how the pathology of Aβ leads to a decrease in energy metabolism by affecting mitochondrial function.

Dynamic Interplay between Copper Toxicity and Mitochondrial Dysfunction in Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder, affecting millions of people worldwide, a number expected to exponentially increase in the future since no effective treatments are available so far. AD is characterized by severe cognitive dysfunctions associated with neuronal loss and connection disruption, mainly occurring in specific brain areas such as the hippocampus, cerebral cortex, and amygdala, compromising memory, language, reasoning, and social behavior. Proteomics and redox proteomics are powerful techniques used to identify altered proteins and pathways in AD, providing relevant insights on cellular pathways altered in the disease and defining novel targets exploitable for drug development. Here, we review the main results achieved by both -omics techniques, focusing on the changes occurring in AD mitochondria under oxidative stress and upon copper exposure. Relevant information arises by the comparative analysis of these results, evidencing alterations of common mitochondrial proteins, metabolic cycles, and cascades. Our analysis leads to three shared mitochondrial proteins, playing key roles in metabolism, ATP generation, oxidative stress, and apoptosis. Their potential as targets for development of innovative AD treatments is thus suggested. Despite the relevant efforts, no effective drugs against AD have been reported so far; nonetheless, various compounds targeting mitochondria have been proposed and investigated, reporting promising results.

Coenzyme Q homeostasis in aging: Response to non-genetic interventions

Coenzyme Q (CoQ) is a key component for many essential metabolic and antioxidant activities in cells in mitochondria and cell membranes. Mitochondrial dysfunction is one of the hallmarks of aging and age-related diseases. Deprivation of CoQ during aging can be the cause or the consequence of this mitochondrial dysfunction. In any case, it seems clear that aging-associated CoQ deprivation accelerates mitochondrial dysfunction in these diseases. Non-genetic prolongevity interventions, including CoQ dietary supplementation, can increase CoQ levels in mitochondria and cell membranes improving mitochondrial activity and delaying cell and tissue deterioration by oxidative damage. In this review, we discuss the importance of CoQ deprivation in aging and age-related diseases and the effect of prolongevity interventions on CoQ levels and synthesis and CoQ-dependent antioxidant activities.

An Angiopep2-PAPTP Construct Overcomes the Blood-Brain Barrier. New Perspectives against Brain Tumors

A developing family of chemotherapeutics—derived from 5-(4-phenoxybutoxy)psoralen (PAP-1)—target mitochondrial potassium channel mtKv1.3 to selectively induce oxidative stress and death of diseased cells. The key to their effectiveness is the presence of a positively charged triphenylphosphonium group which drives their accumulation in the organelles. These compounds have proven their preclinical worth in murine models of cancers such as melanoma and pancreatic adenocarcinoma. In in vitro experiments they also efficiently killed glioblastoma cells, but in vivo they were powerless against orthotopic glioma because they were completely unable to overcome the blood-brain barrier. In an effort to improve brain delivery we have now coupled one of these promising compounds, PAPTP, to well-known cell-penetrating and brain-targeting peptides TAT_48–61 and Angiopep-2. Coupling has been obtained by linking one of the phenyl groups of the triphenylphosphonium to the first amino acid of the peptide via a reversible carbamate ester bond. Both TAT_48–61 and Angiopep-2 allowed the delivery of 0.3–0.4 nmoles of construct per gram of brain tissue upon intravenous (i.v.) injection of 5 µmoles/kg bw to mice. This is the first evidence of PAPTP delivery to the brain; the chemical strategy described here opens the possibility to conjugate PAPTP to small peptides in order to fine-tune tissue distribution of this interesting compound.

Ferroptosis: mechanisms and links with diseases

Ferroptosis is an iron-dependent cell death, which is different from apoptosis, necrosis, autophagy, and other forms of cell death. The process of ferroptotic cell death is defined by the accumulation of lethal lipid species derived from the peroxidation of lipids, which can be prevented by iron chelators (e.g., deferiprone, deferoxamine) and small lipophilic antioxidants (e.g., ferrostatin, liproxstatin). This review summarizes current knowledge about the regulatory mechanism of ferroptosis and its association with several pathways, including iron, lipid, and cysteine metabolism. We have further discussed the contribution of ferroptosis to the pathogenesis of several diseases such as cancer, ischemia/reperfusion, and various neurodegenerative diseases (e.g., Alzheimer's disease and Parkinson's disease), and evaluated the therapeutic applications of ferroptosis inhibitors in clinics.

The Crosstalk Between Pathological Tau Phosphorylation and Mitochondrial Dysfunction as a Key to Understanding and Treating Alzheimer's Disease

Alzheimer's disease (AD) is the most common progressive neurodegenerative disorder. A defining hallmark of the AD brain is the presence of intraneuronal neurofibrillary tangles (NFTs) which are made up of abnormally modified tau, with aberrant phosphorylation being the most studied posttranslational modification (PTM). Although the accumulation of tau as NFTs is an invariant feature of the AD brain, it has become evident that these insoluble aggregates are likely not the primary pathogenic form of tau, rather soluble forms of tau with abnormal PTMs are the mediators of toxicity. The most prevalent PTM on tau is phosphorylation, with the abnormal modification of specific residues on tau playing a key role in its toxicity. Even though it is widely accepted that tau with aberrant PTMs facilitates neurodegeneration, the precise cellular mechanisms remain unknown. Nonetheless, there is an evolving conceptual framework that an important contributing factor may be selective pathological tau species compromising mitochondrial biology. Understanding the mechanisms by which tau with site-specific PTM impacts mitochondria is crucial for understanding the role tau plays in AD. Here, we provide a brief introduction to tau and its phosphorylation and function in a physiological context, followed by a discussion of the impact of soluble phosphorylated tau species on neuronal processes in general and mitochondria more specifically. We also discuss how therapeutic strategies that attenuate pathological tau species in combination with treatments that improve mitochondrial biology could be a potential therapeutic avenue to mitigate disease progression in AD and other tauopathies.