Coenzyme Q10 and α-tocopherol reversed age-associated functional impairments in mice

Changes in the Mitochondria in the Aging Process-Can α-Tocopherol Affect Them?

Aerobic organisms use molecular oxygen in several reactions, including those in which the oxidation of substrate molecules is coupled to oxygen reduction to produce large amounts of metabolic energy. The utilization of oxygen is associated with the production of ROS, which can damage biological macromolecules but also act as signaling molecules, regulating numerous cellular processes. Mitochondria are the cellular sites where most of the metabolic energy is produced and perform numerous physiological functions by acting as regulatory hubs of cellular metabolism. They retain the remnants of their bacterial ancestors, including an independent genome that encodes part of their protein equipment; they have an accurate quality control system; and control of cellular functions also depends on communication with the nucleus. During aging, mitochondria can undergo dysfunctions, some of which are mediated by ROS. In this review, after a description of how aging affects the mitochondrial quality and quality control system and the involvement of mitochondria in inflammation, we report information on how vitamin E, the main fat-soluble antioxidant, can protect mitochondria from age-related changes. The information in this regard is scarce and limited to some tissues and some aspects of mitochondrial alterations in aging. Improving knowledge of the effects of vitamin E on aging is essential to defining an optimal strategy for healthy aging.

Synthesis and Pharmacological Characterization of a Difluorinated Analogue of Reduced Haloperidol as a Sigma-1 Receptor Ligand

Reduced haloperidol (1) was previously reported to act as a potent sigma-1 receptor (S1R) ligand with substantially lower affinity to the dopamine D2 receptor (D2R) compared to haloperidol. It was also found to facilitate brain-derived neurotrophic factor (BDNF) secretion from astrocytic glial cell lines in a sigma-1 receptor (S1R)-dependent manner. Although an increase in BDNF secretion may have beneficial effects in some neurological conditions, the therapeutic utility of reduced haloperidol (1) is limited because it can be oxidized back to haloperidol in the body, a potent dopamine D2 receptor antagonist associated with well-documented adverse effects. A difluorinated analogue of reduced haloperidol, (±)-4-(4-chlorophenyl)-1-(3,3-difluoro-4-(4-fluorophenyl)-4-hydroxybutyl)piperidin-4-ol (2), was synthesized in an attempt to minimize the oxidation. Compound (±)-2 was found to exhibit high affinity to S1R and facilitate BDNF release from mouse brain astrocytes. It was also confirmed that compound 2 cannot be oxidized back to the corresponding haloperidol analogue in liver microsomes. Furthermore, compound 2 was distributed to the brain following intraperitoneal administration in mice and reversed the learning deficits in active avoidance tasks. These findings suggest that compound 2 could serve as a promising S1R ligand with therapeutic potential for the treatment of cognitive impairments.

Coenzyme Q10 and Dementia: A Systematic Review

It is well known that coenzyme Q₁₀ (CoQ₁₀) has important antioxidant properties. Because one of the main mechanisms involved in the pathogenesis of Alzheimer's disease (AD) and other neurodegenerative diseases is oxidative stress, analysis of the concentrations of CoQ₁₀ in different tissues of AD patients and with other dementia syndromes and the possible therapeutic role of CoQ₁₀ in AD have been addressed in several studies. We performed a systematic review and a meta-analysis of these studies measuring tissue CoQ₁₀ levels in patients with dementia and controls which showed that, compared with controls, AD patients had similar serum/plasma CoQ₁₀ levels. We also revised the possible therapeutic effects of CoQ₁₀ in experimental models of AD and other dementias (which showed important neuroprotective effects of coenzyme Q₁₀) and in humans with AD, other dementias, and mild cognitive impairment (with inconclusive results). The potential role of CoQ₁₀ treatment in AD and in improving memory in aged rodents shown in experimental models deserves future studies in patients with AD, other causes of dementia, and mild cognitive impairment.

Coenzyme Q10 Levels Associated With Cognitive Functioning and Executive Function in Older Adults

Brain deterioration with age is associated with inflammation and oxidative stress that result in structural and functional changes. Recent studies have indicated that coenzyme Q10 (CoQ10) is associated with neurological oxidative stress and cognitive impairment. Studies with older people have shown a relationship between neurodegenerative diseases and CoQ10 levels. However, no studies have analyzed the relationship between CoQ10 and cognitive functioning in older adults. The aim of this study was to analyze the association between CoQ10 and cognitive functioning in an older adult sample, controlling for other factors that may influence aging, such as the level of physical activity and nutritional status. The sample consisted of 64 older adults aged 65-99 years (76.67 ± 8.16 years), among whom 48 were women (75%). The participants were recruited among those who attended community centers to voluntarily participate in leisure activities. According to previous studies, physical activity and nutritional status are positively associated with cognitive functioning. However, the main finding of this study was that plasma CoQ10, controlling for other measures, was significantly associated with cognitive functioning and executive function. The current findings suggest that a decline in cognitive capacities may be related to reduced antioxidant defenses, as reflected by low CoQ10 levels in older adults.

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.

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.

Preventive and Therapeutic Strategies in Alzheimer's Disease: Focus on Oxidative Stress, Redox Metals, and Ferroptosis

Significance: Alzheimer's disease (AD) is the most common cause of dementia in the elderly. AD is currently ranked as the sixth leading cause of death, but some sources put it as third, after heart disease and cancer. Currently, there are no effective therapeutic approaches to treat or slow the progression of chronic neurodegeneration. In addition to the accumulation of amyloid-β (Aβ) and tau, AD patients show progressive neuronal loss and neuronal death, also high oxidative stress that correlates with abnormal levels or overload of brain metals. Recent Advances: Several promising compounds targeting oxidative stress, redox metals, and neuronal death are under preclinical or clinical evaluation as an alternative or complementary therapeutic strategy in mild cognitive impairment and AD. Here, we present a general analysis and overview, discuss limitations, and suggest potential directions for these treatments for AD and related dementia. Critical Issues: Most of the disease-modifying therapeutic strategies for AD under evaluation in clinical trials have focused on components of the amyloid cascade, including antibodies to reduce levels of Aβ and tau, as well as inhibitors of secretases. Unfortunately, several of the amyloid-focused therapeutics have failed the clinical outcomes or presented side effects, and numerous clinical trials of compounds have been halted, reducing realistic options for the development of effective AD treatments. Future Directions: The focus of research on AD and related dementias is shifting to alternative or innovative areas, such as ApoE, lipids, synapses, oxidative stress, cell death mechanisms, neuroimmunology, and neuroinflammation, as well as brain metabolism and bioenergetics.

The effects of coenzyme Q10 supplement on blood lipid indices and hepatic antioxidant defense system in SD rats fed a high cholesterol diet

A total of 24 SD rats were allotted to four treatment groups such as the control (CON), 1% of cholesterol diet (CHO), 0.5% of coenzyme Q₁₀ (COQ) and 1% of cholesterol plus 0.5% of coenzyme Q₁₀ (CHCQ) groups to determine the effects of coenzyme Q₁₀ (CoQ₁₀) on the antioxidant defense system in rats. The body weight, weight gain, liver weight and abdominal fat pads were unaffected by 0.5% of CoQ₁₀ supplement in the rats. The level of triglyceride and HDL-cholesterol levels in the blood was significantly increased (p < 0.05) by the 1% of cholesterol supplement (CHO), whereas 0.5% of CoQ₁₀ supplement (COQ) did not alter these blood lipid indices. In the mRNA expression, there was a significant effect (P < 0.05) of the CoQ₁₀ supplement on the mRNA expression of superoxide dismutase (SOD), although the mRNA expression of glutathione peroxidase (GPX) and glutathione S-transferase (GST) was unaffected by cholesterol or the CoQ₁₀ supplement. Similar to mRNA expression of SOD, its activity was also significantly increased (P < 0.05) by CoQ₁₀, but not by the cholesterol supplement effect. The activities hepatic GPX and GST were unaffected by CoQ₁₀ and cholesterol supplements in rats. Lipid peroxidation in the CHO group resulted in a significant (p < 0.05) increase compared with that in the other groups, indicating that the CoQ₁₀ supplement to 1% of cholesterol-fed rats alleviated the production of lipid peroxidation in the liver. In conclusion, 0.5% of the CoQ₁₀ supplement resulted in positive effects on the hepatic antioxidant defense system without affecting blood lipid indices in 1% of cholesterol fed rats.

Age-related murine hippocampal CA1 laminae oxidative stress measured in vivo by QUEnch-assiSTed (QUEST) MRI: impact of isoflurane anesthesia

Age-related impairments in spatial learning and memory often precede non-familial neurodegenerative disease. Ex vivo studies suggest that physiologic age-related oxidative stress in hippocampus area CA1 may contribute to prodromal spatial disorientation and to morbidity. Yet, conventional blood or cerebrospinal fluid assays appear insufficient for early detection or management of oxidative stress within CA1 sub-regions in vivo. Here, we address this biomarker problem using a non-invasive MRI index of CA1 laminae oxidative stress based on reduction in R1 (= 1/T1) after anti-oxidant administration. An R1 reduction reflects quenching of continuous and excessive production of endogenous paramagnetic free radicals. Careful motion-correction image acquisition, and avoiding repeated exposure to isoflurane, facilitates detection of hippocampus CA1 laminae oxidative stress with QUEnch-assiSTed (QUEST) MRI. Intriguingly, age- and isoflurane-related oxidative stress is localized to the stratum lacunosum of the CA1 region. Our data raise the possibility of using QUEST MRI and FDA-approved anti-oxidants to remediate spatial disorientation and later neurodegeneration with age in animals and humans.

The effect of dietary coenzyme Q10 on plasma metabolites and hepatic gene expression in broiler breeder hens

1. This study was performed to evaluate the effects of dietary supplementation of coenzyme Q10 (CoQ10) on laying rate, body weight, plasma metabolites and some liver gene expression in broiler breeder hens. 2. A total of 128 broiler breeder hens (Arbor Acres Plus, 47 weeks of age) were randomly distributed to four dietary groups supplemented with different levels of CoQ10 (0, 300, 600 or 900 mg/kg diet) with four replicates of eight hens each. During 47-54 weeks of age, laying rate, egg mass and body weight were recorded weekly. To assay plasma biochemical indicators, blood samples were collected at 54 weeks of age. At the end of the experiment, for evaluating the abdominal fat weight, liver weight and expression of the adiponectin and proliferator-activated receptor-α (PPAR-α) genes in the liver, eight hens per treatment were selected, weighed and humanely killed by decapitation. 3. Dietary supplementation of CoQ10 linearly decreased abdominal fat weight, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities by increased levels of CoQ10. The plasma levels of glucose, cholesterol and alkaline phosphatase (ALP) activity were quadratically decreased by increased levels of CoQ10. The best plasma levels of glucose, cholesterol and ALP activity were estimated at 562.5, 633.3 and 517.8 mg CoQ10/kg diet, respectively. Adiponectin and PPARα gene expression exhibited a linear increased by increased levels of CoQ10. 4. In conclusion, addition of CoQ10 to the diet influenced lipid metabolism and expression of the adiponectin and PPAR-α genes, which might be partially due to the improvement in mitochondrial metabolism and energy production. However, further studies are necessary to determine the effects of CoQ10 on these indicators in broiler breeder hens during ageing.

Metformin and cognition from the perspectives of sex, age, and disease

Metformin is the safest and the most widely prescribed first-line therapy for managing hyperglycemia due to different underlying causes, primarily type 2 diabetes mellitus. In addition to its euglycemic properties, metformin has stimulated a wave of clinical trials to investigate benefits on aging-related diseases and longevity. Such an impact on the lifespan extension would undoubtedly expand the therapeutic utility of metformin regardless of glycemic status. However, there is a scarcity of studies evaluating whether metformin has differential cognitive effects across age, sex, glycemic status, metformin dose, and duration of metformin treatment and associated pathological conditions. By scrutinizing the available literature on animal and human studies for metformin and brain function, we expect to shed light on the potential impact of metformin on cognition across age, sex, and pathological conditions. This review aims to provide readers with a broader insight of (a) how metformin differentially affects cognition and (b) why there is a need for more translational and clinical studies examining multifactorial interactions. The outcomes of such comprehensive studies will streamline precision medicine practices, avoiding "fit for all" approach, and optimizing metformin use for longevity benefit irrespective of hyperglycemia.

Targeting Mitochondria in Alzheimer Disease: Rationale and Perspectives

A decline in mitochondrial function plays a key role in the aging process and increases the incidence of age-related disorders, including Alzheimer disease (AD). Mitochondria-the power station of the organism-can affect several different cellular activities, including abnormal cellular energy generation, response to toxic insults, regulation of metabolism, and execution of cell death. In AD subjects, mitochondria are characterized by impaired function such as lowered oxidative phosphorylation, decreased adenosine triphosphate production, significant increased reactive oxygen species generation, and compromised antioxidant defense. The current review discusses the most relevant mitochondrial defects that are considered to play a significant role in AD and that may offer promising therapeutic targets for the treatment/prevention of AD. In addition, we discuss mechanisms of action and translational potential of some promising mitochondrial and bioenergetic therapeutics for AD including compounds able to potentiate energy production, antioxidants to scavenge reactive oxygen species and reduce oxidative damage, glucose metabolism, and candidates that target mitophagy. While mitochondrial therapeutic strategies have shown promise at the preclinical stage, there has been little progress in clinical trials. Thus, there is an urgent need to better understand the mechanisms regulating mitochondrial homeostasis in order to identify powerful drug candidates that target 'in and out' the mitochondria to preserve cognitive functions.

Supplementation with N-Acetyl Cysteine Affects Motor and Cognitive Function in Young but Not Old Mice

BACKGROUND

N-acetyl cysteine (NAC) is a thiolic antioxidant that is thought to increase cellular glutathione (GSH) by augmenting the concentration of available cysteine, an essential precursor to GSH production. Manipulating redox status can affect brain function, and NAC intake has been associated with improving brain function in models of neurodegenerative diseases.

OBJECTIVES

The objective of the study was to determine if short-term dietary supplementation with NAC could ameliorate functional impairment associated with aging.

METHODS

C57BL/6J male mice aged 6, 12, or 24 mo were fed a control diet or the control diet supplemented with 0.3% NAC for a total of 12 wk. After 4 wk of dietary supplementation, mice began a series of behavioral tests to measure spontaneous activity (locomotor activity test), psychomotor performance (bridge-walking and coordinated running), and cognitive capacity (Morris water maze and discriminated active avoidance). The performance of the mice on these tests was analyzed through the use of analyses of variance with Age and Diet as factors.

RESULTS

Supplementation of NAC improved peak motor performance in a coordinated running task by 14% (P < 0.05), and increased the time spent around the platform by 24% in a Morris water maze at age 6 mo. However, the supplementation had no to minimal effect on the motor and cognitive functions of 12- and 24-mo-old mice.

CONCLUSIONS

The findings of this preclinical study support the claim that NAC has nootropic properties in 6-mo-old mice, but suggest that it may not be useful for improving motor and cognitive impairments in older mice.

Ameliorative Effects of α-Tocopherol and/or Coenzyme Q10 on Phenytoin-Induced Cognitive Impairment in Rats: Role of VEGF and BDNF-TrkB-CREB Pathway

Phenytoin is one of the most well-known antiepileptic drugs that cause cognitive impairment which is closely related to cAMP response element-binding protein (CREB) brain-derived neurotrophic factor (BDNF) signaling pathway. Moreover, vascular endothelial growth factor (VEGF), an endothelial growth factor, has a documented role in neurogenesis and neuronal survival and cognitive impairment. Therefore, this study aimed to investigate the influence of powerful antioxidants: α-Toc and CoQ10 alone or combined in the preservation of brain tissues and the maintenance of memory formation in phenytoin-induced cognitive impairment in rats. The following behavioral test novel object recognition and elevated plus maze were assessed after 14 days of treatment. Moreover, VEGF, BDNF, TrkB, and CREB gene expression levels in the hippocampus and prefrontal cortex were estimated using RT-PCR. Both α-Toc and CoQ10 alone or combined with phenytoin showed improvement in behavioral tests compared to phenytoin. Mechanistically, α-Toc and/or CoQ10 decreases the VEGF mRNA expression, while increases BDNF-TrKB-CREB mRNA levels in hippocampus and cortex of phenytoin-treated rats. Collectively, α-Toc and/or CoQ10 alleviated the phenytoin-induced cognitive impairment through suppressing oxidative damage. The underlying molecular mechanism of the treating compounds is related to the VEGF and enhancing BDNF-TrkB-CREB signaling pathway. Our study indicated the usefulness α-Toc or CoQ10 as an adjuvant to antiepileptic drugs with an advantage of preventing cognitive impairment and oxidative stress.

Current Perspective in the Discovery of Anti-aging Agents from Natural Products

Aging is a process characterized by accumulating degenerative damages, resulting in the death of an organism ultimately. The main goal of aging research is to develop therapies that delay age-related diseases in human. Since signaling pathways in aging of Caenorhabditis elegans (C. elegans), fruit flies and mice are evolutionarily conserved, compounds extending lifespan of them by intervening pathways of aging may be useful in treating age-related diseases in human. Natural products have special resource advantage and with few side effect. Recently, many compounds or extracts from natural products slowing aging and extending lifespan have been reported. Here we summarized these compounds or extracts and their mechanisms in increasing longevity of C. elegans or other species, and the prospect in developing anti-aging medicine from natural products.

Metformin Impairs Spatial Memory and Visual Acuity in Old Male Mice

Metformin is an oral anti-diabetic used as first-line therapy for type 2 diabetes. Because benefits of metformin extend beyond diabetes to other age-related pathology, and because its effect on gene expression profiles resembles that of caloric restriction, metformin has a potential as an anti-aging intervention and may soon be assessed as an intervention to extend healthspan. However, beneficial actions of metformin in the central nervous system have not been clearly established. The current study examined the effect of chronic oral metformin treatment on motor and cognitive function when initiated in young, middle-aged, or old male mice. C57BL/6 mice aged 4, 11, or 22 months were randomly assigned to either a metformin group (2 mg/ml in drinking water) or a control group. The mice were monitored weekly for body weight, as well as food and water intake and a battery of behavioral tests for motor, cognitive and visual function was initiated after the first month of treatment. Liver, hippocampus and cortex were collected at the end of the study to assess redox homeostasis. Overall, metformin supplementation in male mice failed to affect blood glucose, body weights and redox homeostasis at any age. It also had no beneficial effect on age-related declines in psychomotor, cognitive or sensory functions. However, metformin treatment had a deleterious effect on spatial memory and visual acuity, and reduced SOD activity in brain regions. These data confirm that metformin treatment may be associated with deleterious effect resulting from the action of metformin on the central nervous system.

The influence of vitamins E and C and exercise on brain aging

Age-related declines in motor and cognitive function have been associated with increases in oxidative stress. Accordingly, interventions capable of reducing the oxidative burden would be capable of preventing or reducing functional declines occurring during aging. Popular interventions such as antioxidant intake and moderate exercise are often recommended to attain healthy aging and have the capacity to alter redox burden. This review is intended to summarize the outcomes of antioxidant supplementation (more specifically of vitamins C and E) and exercise training on motor and cognitive declines during aging, and on measures of oxidative stress. Additionally, we will address whether co-implementation of these two types of interventions can potentially further their individual benefits. Together, these studies highlight the importance of using translationally-relevant parameters for interventions and to study their combined outcomes on healthy brain aging.

Exercise, but not antioxidants, reversed ApoE4-associated motor impairments in adult GFAP-ApoE mice

Motor dysfunction has been found to be predictive of cognitive dysfunction in Alzheimer's disease and to occur earlier than cognitive impairments. While apolipoprotein (Apo) E4 has been associated with cognitive impairments, it remains unclear whether it also increases risk for motor dysfunction. Exercise and antioxidants are often recommended to reduce cognitive declines, however it is unclear whether they can successfully improve motor impairments. This study was designed to determine the extent of the impact of apolipoprotein genotype on motor function, and whether interventions such as exercise and antioxidant intake can improve motor function. This study is the first to identify the nature of the interaction between antioxidant intake and exercise using a mouse model expressing either the human ApoE3 or ApoE4 isoforms under glial fibrillary acid protein promoter (GFAP-ApoE3 and GFAP-ApoE4 mice). The mice were fed either a control diet or the control diet supplemented with vitamins E and C (1.12 IU/g diet α-tocopheryl acetate and 1.65mg/g ascorbic acid). Each genotype/diet group was further divided into a sedentary group or a group that followed a 6 days a week exercise regimen. After 8 weeks on their respective treatment, the mice were administered a battery of motor tests to measure reflexes, strength, coordination and balance. GFAP-ApoE4 mice exhibited impaired motor learning and diminished strength compared to the GFAP-ApoE3 mice. Exercise alone was more efficient at improving motor function and reversing ApoE4-associated impairments than antioxidants alone, even though improvements were rather subtle. Contrarily to expected outcomes, combination of antioxidants and exercise did not yield further improvements of motor function. Interestingly, antioxidants antagonized the beneficial effects of exercise on strength. These data suggest that environmental and genetic factors influence the outcome of interventions on motor function and should be investigated more thoroughly and taken into consideration when implementing changes in lifestyles.

Alternative mitochondrial electron transfer for the treatment of neurodegenerative diseases and cancers: Methylene blue connects the dots

Brain has exceptional high requirement for energy metabolism with glucose as the exclusive energy source. Decrease of brain energy metabolism and glucose uptake has been found in patients of Alzheimer's, Parkinson's and other neurodegenerative diseases, providing a clear link between neurodegenerative disorders and energy metabolism. On the other hand, cancers, including glioblastoma, have increased glucose uptake and rely on aerobic glycolysis for energy metabolism. The switch of high efficient oxidative phosphorylation to low efficient aerobic glycolysis pathway (Warburg effect) provides macromolecule for biosynthesis and proliferation. Current research indicates that methylene blue, a century old drug, can receive electron from NADH in the presence of complex I and donates it to cytochrome c, providing an alternative electron transfer pathway. Methylene blue increases oxygen consumption, decrease glycolysis, and increases glucose uptake in vitro. Methylene blue enhances glucose uptake and regional cerebral blood flow in rats upon acute treatment. In addition, methylene blue provides protective effect in neuron and astrocyte against various insults in vitro and in rodent models of Alzheimer's, Parkinson's, and Huntington's disease. In glioblastoma cells, methylene blue reverses Warburg effect by enhancing mitochondrial oxidative phosphorylation, arrests glioma cell cycle at s-phase, and inhibits glioma cell proliferation. Accordingly, methylene blue activates AMP-activated protein kinase, inhibits downstream acetyl-coA carboxylase and cyclin-dependent kinases. In summary, there is accumulating evidence providing a proof of concept that enhancement of mitochondrial oxidative phosphorylation via alternative mitochondrial electron transfer may offer protective action against neurodegenerative diseases and inhibit cancers proliferation.

Mitochondrial proteases and protein quality control in ageing and longevity

Mitochondria have been implicated in the ageing process and the lifespan modulation of model organisms. Mitochondria are the main providers of energy in eukaryotic cells but also represent both a major source of reactive oxygen species and targets for protein oxidative damage. Since protein damage can impair mitochondrial function, mitochondrial proteases are critically important for protein maintenance and elimination of oxidized protein. In the mitochondrial matrix, protein quality control is mainly achieved by the Lon and Clp proteases which are also key players in damaged mitochondrial proteins degradation. Accumulation of damaged macromolecules resulting from oxidative stress and failure of protein maintenance constitutes a hallmark of cellular and organismal ageing and is believed to participate to the age-related decline of cellular function. Hence, age-related impairment of mitochondrial protein quality control may therefore contribute to the age-associated build-up of oxidized protein and alterations of mitochondrial redox and protein homeostasis.

Microglial cell dysregulation in brain aging and neurodegeneration

Aging is the main risk factor for neurodegenerative diseases. In aging, microglia undergoes phenotypic changes compatible with their activation. Glial activation can lead to neuroinflammation, which is increasingly accepted as part of the pathogenesis of neurodegenerative diseases, including Alzheimer’s disease (AD). We hypothesize that in aging, aberrant microglia activation leads to a deleterious environment and neurodegeneration. In aged mice, microglia exhibit an increased expression of cytokines and an exacerbated inflammatory response to pathological changes. Whereas LPS increases nitric oxide (NO) secretion in microglia from young mice, induction of reactive oxygen species (ROS) predominates in older mice. Furthermore, there is accumulation of DNA oxidative damage in mitochondria of microglia during aging, and also an increased intracellular ROS production. Increased ROS activates the redox-sensitive nuclear factor kappa B, which promotes more neuroinflammation, and can be translated in functional deficits, such as cognitive impairment. Mitochondria-derived ROS and cathepsin B, are also necessary for the microglial cell production of interleukin-1β, a key inflammatory cytokine. Interestingly, whereas the regulatory cytokine TGFβ1 is also increased in the aged brain, neuroinflammation persists. Assessing this apparent contradiction, we have reported that TGFβ1 induction and activation of Smad3 signaling after inflammatory stimulation are reduced in adult mice. Other protective functions, such as phagocytosis, although observed in aged animals, become not inducible by inflammatory stimuli and TGFβ1. Here, we discuss data suggesting that mitochondrial and endolysosomal dysfunction could at least partially mediate age-associated microglial cell changes, and, together with the impairment of the TGFβ1-Smad3 pathway, could result in the reduction of protective activation and the facilitation of cytotoxic activation of microglia, resulting in the promotion of neurodegenerative diseases.