Mitochondria take center stage in aging and neurodegeneration

Epalrestat improves motor symptoms by reducing oxidative stress and inflammation in the reserpine induced mouse model of Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is a progressive neurodegenerative disorder affecting a large number of elderly people worldwide. The current therapies for PD are symptom-based; they do not provide a cure but improve the quality of life. Muscular dysfunction is the hallmark clinical feature of PD and oxidative stress and inflammation play a critical role in its pathogenesis. Epalrestat is used for the treatment of diabetic neuropathy and is known to improve antioxidative defense mechanisms in the CNS. Therefore, in this study, we investigated the role of Epalrestat in the reserpine induced mouse model of PD.

METHOD

We used Swiss Albino mice for the PD model and tested for akinesia/bradykinesia, muscular rigidity, palpebral ptosis, and tremor, as well as conducting swim and open field tests. Brain samples were used to determine oxidative stress parameters and infiltration of immune cells.

RESULTS

Epalrestat treatment significantly improved akinesia and bradykinesia, muscular dysfunctions, tremor level, and gait functions compared to the reserpine group. It also improved the latency in the swim test. Eplarestat significantly reduced lipid peroxidation and NO concentration in different brain tissues and increased the activity of antioxidative enzymes, glutathione, catalase, and superoxide dismutase. Furthermore, Epalrestat reduced neuroinflammation by reducing the number of infiltrating immune cells.

CONCLUSION

Eplarestat improves muscular dysfunction in PD by reducing oxidative stress and inflammation.

Neuroprotective Effects of Lindleyin on Hydrogen Peroxide-Induced Cell Injury and MPTP-Induced Parkinson's Disease in C57BL/6 Mice

Oxidative stress (OS) is a crucial factor influencing the development of Parkinson's disease (PD). Here we first reported that Lindleyin (Lin), one of the major components of rhubarb, possessed neuroprotective effects against H₂O₂-induced SH-SY5Y cell injury and MPTP-induced PD of C57BL/6 mice. The results showed that Lin can decrease cell death and apoptotic rate induced by H₂O₂ through inhibiting mitochondrial apoptotic pathway and increasing the activities of SOD, GSH-Px, and CAT as well as decreasing the level of MDA. In addition, in vivo studies showed that oral administration of Lin (5 or 20 mg/kg) showed significant change in motor function deficits, antioxidant enzyme activities, apoptotic pathway, and tyrosine hydroxylase expression. Our results reveal that Lin might be a promising anti-PD agent by reducing OS and apoptosis.

Strategies for the Treatment of Parkinson's Disease: Beyond Dopamine

Parkinson’s disease (PD) is the second-leading cause of dementia and is characterized by a progressive loss of dopaminergic neurons in the substantia nigra alongside the presence of intraneuronal α-synuclein-positive inclusions. Therapies to date have been directed to the restoration of the dopaminergic system, and the prevention of dopaminergic neuronal cell death in the midbrain. This review discusses the physiological mechanisms involved in PD as well as new and prospective therapies for the disease. The current data suggest that prevention or early treatment of PD may be the most effective therapeutic strategy. New advances in the understanding of the underlying mechanisms of PD predict the development of more personalized and integral therapies in the years to come. Thus, the development of more reliable biomarkers at asymptomatic stages of the disease, and the use of genetic profiling of patients will surely permit a more effective treatment of PD.

Carnosine ameliorates age-related dementia via improving mitochondrial dysfunction in SAMP8 mice

Carnosine can improve mitochondrial dysfunction in the hippocampus of SAMP8 mice and reduce NLRP3 inflammasome and apoptosis by improving mitochondrial dysfunction.

Diphenyl diselenide protects a Caenorhabditis elegans model for Huntington's disease by activation of the antioxidant pathway and a decrease in protein aggregation

The effect of (PhSe)₂ in a C. elegans model for Huntington's disease. Treatment with (PhSe)₂ triggered the nuclear translocation and activation of DAF-16 transcription factor in C. elegans, inducing the expression of superoxide dismutase-3 (SOD-3) and heat shock protein-16.2 (HSP-16.2). SOD-3 acts on reactive oxygen species (ROS) detoxification, and HSP-16.2 decreases protein misfolding and aggregation, which occur in HD.

Ferulic acid reinstates mitochondrial dynamics through PGC1α expression modulation in 6-hydroxydopamine lesioned rats

Disruption of the tightly regulated mitochondrial dynamics and energy homeostasis leads to oxidative stress and apoptotic cell death, as observed in neurodegenerative disorders such as Parkinson's disease (PD). Polyphenolic plant derivatives have been shown to alleviate such pathological features and have been used in models of neurodegenerative disorders in previous reports. In the current study, we utilized a 6-hydroxydopamine (6-OHDA) lesioned rat model of PD to explore the protective efficacy of polyphenolic phytochemical ferulic acid (FA) against mitochondrial dysfunction and explored its effect on gene and protein expression of mitochondrial dynamics regulators dynamin-related protein 1 (Drp1)/mitofusin 2 (Mfn2) in lesioned animals. We also evaluated its effect on expression of mitochondrial biogenesis regulator PGC1α and apoptotic regulators BAX, cyt c, p53, and cleaved PARP. We found that oral FA supplementation alleviated 6-OHDA induced oxidative stress, DNA fragmentation, morphological changes, and blocked apoptotic cascade. FA also reduced mitochondrial Drp1 expression and increased gene and protein expression of PGC1α, thereby regulating expression of its downstream target Mfn2 and restoring mitochondrial dynamics in lesioned animals. Our data suggest that targeting mitochondrial dynamics through modulation of PGC1α can prove to be a potent preventive strategy against PD pathology.

The Role of Mitochondrial Impairment in Alzheimer´s Disease Neurodegeneration: The Tau Connection

Accumulative evidence has shown that mitochondrial dysfunction plays a pivotal role in the pathogenesis of Alzheimer's disease (AD). Mitochondrial impairment actively contributes to the synaptic and cognitive failure that characterizes AD. The presence of soluble pathological forms of tau like hyperphosphorylated at Ser396 and Ser404 and cleaved at Asp421 by caspase 3, negatively impacts mitochondrial bioenergetics, transport, and morphology in neurons. These adverse effects against mitochondria health will contribute to the synaptic impairment and cognitive decline in AD. Current studies suggest that mitochondrial failure induced by pathological tau forms is likely the result of the opening of the mitochondrial permeability transition pore (mPTP). mPTP is a mitochondrial mega-channel that is activated by increases in calcium and is associated with mitochondrial stress and apoptosis. This structure is composed of different proteins, where Ciclophilin D (CypD) is considered to be the primary mediator of mPTP activation. Also, new studies suggest that mPTP contributes to Aβ pathology and oxidative stress in AD. Further, inhibition of mPTP through the reduction of CypD expression prevents cognitive and synaptic impairment in AD mouse models. More importantly, tau protein contributes to the physiological regulation of mitochondria through the opening/interaction with mPTP in hippocampal neurons. Therefore, in this paper, we will discuss evidence that suggests an important role of pathological forms of tau against mitochondrial health. Also, we will discuss the possible role of mPTP in the mitochondrial impairment produced by the presence of tau pathology and its impact on synaptic function present in AD.

Up-regulation of PGC-1α in neurons protects against experimental autoimmune encephalomyelitis

Reactive oxygen species (ROS) generation and mitochondrial dysfunction are related to neuron loss in multiple sclerosis (MS). Although peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) appears to play a key role in modulating levels of mitochondrial ROS, antioxidants, and uncoupling proteins (UCPs), and PGC-1α expression is reduced in the neocortex of patients with MS, it is unclear what its role is in neurons and in the manifestation of clinical symptoms of MS. Here, we show in wild-type (WT) experimental autoimmune encephalomyelitis (EAE) mice that PGC-1α is decreased 13 d after EAE induction followed by a steady decline up to 20 d. These changes were accompanied by parallel alterations in levels of superoxide dismutase 2, peroxiredoxin 3, thioredoxin 2, UCP4, and UCP5. In transgenic (TG) mice with neuron-specific overexpression of PGC-1α (PGC-1α^f/fEno2-Cre), clinical symptoms after EAE induction were delayed and less severe than in WT mice. The degrees of apoptotic neuron loss and demyelination were also less severe in PGC-1α-TG mice. Overexpression of PGC-1α in neuronal neuroblastoma spinal cord 34 cells subjected to EAE inflammatory conditions showed similar results to those obtained in vivo. RNA sequencing analysis showed that apoptotic processes were significantly enriched in the top 10 significant gene ontology (GO) terms of differentially expressed genes, and the apoptotic pathway was significantly enriched in Kyoto Encyclopedia of Genes and Genomes pathway analysis. Our findings indicate that up-regulation of neuronal PGC-1α protected neurons from apoptosis in EAE. Manipulating PGC-1α levels in MS may help stave off this devastating disease.-Dang, C., Han, B., Li, Q., Han, R., Hao, J. Up-regulation of PGC-1α in neurons protects against experimental autoimmune encephalomyelitis.

N6-(2-hydroxyethyl)-adenosine from Cordyceps cicadae attenuates hydrogen peroxide induced oxidative toxicity in PC12 cells

N⁶-(2-hydroxyethyl)-adenosine (HEA), is one of the active molecule found in Cordyceps cicadae. The protective effect of HEA against H₂O₂ induced oxidative damage in PC12 cells and the mechanism of action was investigated. The cells were exposed to varying concentrations of HEA (5-40 μM) for a period of 24 h and further incubated with 100 μM of H₂O₂ for an another 12 h. Cell viability, LDH release, MMP collapse, Ca²⁺ overload, antioxidant parameters (reactive oxygen species generation (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), inflammatory mediators (interleukins 6 and 1β (IL-6 and IL-1β), tumor necrosis factor alpha (TNF-α) and NF-kB were evaluated. The results obtained showed that cells exposed to H₂O₂ toxicity showed reduced cell viability, increased LDH, ROS and Ca²⁺ overload. However, prior treatment of PC12 cells with HEA increased cell viability, reduced LDH release, MMP collapse, Ca²⁺ overload and ROS generation induced by H₂O₂ toxicity. Furthermore, HEA also increased the activities of antioxidant enzymes and inhibited lipid peroxidation as well as reduced IL-6, IL-1β, TNF-α and NF-kB. Thus, our results provided insight into the attenuative effect of HEA against H₂O₂ induced cell death through its antioxidant action by reducing ROS generation, oxidative stress and protecting mitochondrial function.

Age-related neurodegenerative diseases

Converging evidence indicates the dysregulation of unique cytosolic compartments called stress granules (SGs) might facilitate the accumulation of toxic protein aggregates that underlie many age-related neurodegenerative pathologies (ANPs). SG dynamics are particularly susceptible to the cellular conditions that are commonly induced by aging, including the elevation in reactive oxygen species and increased concentration of aggregate-prone proteins. In turn, the persistent formation of these compartments is hypothesized to serve as a seed for subsequent protein aggregation. Notably, the protein quality control (PQC) machinery responsible for inhibiting persistent SGs (e.g., Hsc70-BAG3) can become compromised with age, suggesting that the modulation of such PQC mechanisms could reliably inhibit pathological processes of ANPs. As exemplified in the context of accelerated aging syndromes (i.e., Hutchinson-Gilford progeria), PQC enhancement is emerging as a potential therapeutic strategy, indicating similar techniques might be applied to ANPs. Collectively, these recent findings advance our understanding of how the processes that might facilitate protein aggregation are particularly susceptible to aging conditions, and present investigators with an opportunity to develop novel targets for ANPs.

Protective effect of Cordyceps militaris against hydrogen peroxide-induced oxidative stress in vitro

BACKGROUND/OBJECTIVES

Excessive production of reactive oxygen species (ROS) such as hydroxyl (·OH), nitric oxide (NO), and hydrogen peroxide (H2O2) is reported to induce oxidative stress. ROS generated by oxidative stress can potentially damage glial cells in the nervous system. Cordyceps militaris (CM), a kind of natural herb widely found in East Asia. In this study, we investigated the free radical scavenging activity of the CM extract and its neuroprotective effects in H2O2-induced C6 glial cells.

MATERIALS/METHODS

The ethanol extract of CM (100-1,000 µg/mL) was used to measure DPPH, ·OH, and NO radical scavenging activities. In addition, hydrogen peroxide (H2O2)-induced C6 glial cells were treated with CM at 0.5-2.5 µg/mL for measurement of cell viability, ROS production, and protein expression resulting from oxidative stress.

RESULTS

The CM extract showed high scavenging activities against DPPH, ·OH, and NO radicals at concentration of 1,000 µg/mL. Treatment of CM with H2O2-induced oxidative stress in C6 glial cells significantly increased cell viability, and decreased ROS production. Cyclooxygenase-2 and inducible nitric oxide synthase protein expression was down-regulated in CM-treated groups. In addition, the protein expression level of phospho-p38 mitogen-activated protein kinase (p-p38 MAPK), phospho-c-Jun N-terminal kinase (p-JNK), and phospho-extracellular regulated protein kinases (p-ERK) in H2O2-induced C6 glial cells was down-regulated upon CM administration.

CONCLUSION

CM exhibited radical scavenging activity and protective effect against H2O2 as indicated by the increased cell viability, decreased ROS production, down-regulation of inflammation-related proteins as well as p-p38, p-JNK, and p-ERK protein levels. Therefore, we suggest that CM could play the protective role from oxidative stress in glial cells.

Mitochondrially-targeted APOBEC1 is a potent mtDNA mutator affecting mitochondrial function and organismal fitness in Drosophila

Somatic mutations in the mitochondrial genome (mtDNA) have been linked to multiple disease conditions and to ageing itself. In Drosophila, knock-in of a proofreading deficient mtDNA polymerase (POLG) generates high levels of somatic point mutations and also small indels, but surprisingly limited impact on organismal longevity or fitness. Here we describe a new mtDNA mutator model based on a mitochondrially-targeted cytidine deaminase, APOBEC1. mito-APOBEC1 acts as a potent mutagen which exclusively induces C:G>T:A transitions with no indels or mtDNA depletion. In these flies, the presence of multiple non-synonymous substitutions, even at modest heteroplasmy, disrupts mitochondrial function and dramatically impacts organismal fitness. A detailed analysis of the mutation profile in the POLG and mito-APOBEC1 models reveals that mutation type (quality) rather than quantity is a critical factor in impacting organismal fitness. The specificity for transition mutations and the severe phenotypes make mito-APOBEC1 an excellent mtDNA mutator model for ageing research.

Parkinson's disease protein DJ-1 regulates ATP synthase protein components to increase neuronal process outgrowth

Familial Parkinson’s disease (PD) protein DJ-1 mutations are linked to early onset PD. We have found that DJ-1 binds directly to the F₁F_O ATP synthase β subunit. DJ-1’s interaction with the β subunit decreased mitochondrial uncoupling and enhanced ATP production efficiency while in contrast mutations in DJ-1 or DJ-1 knockout increased mitochondrial uncoupling, and depolarized neuronal mitochondria. In mesencephalic DJ-1 KO cultures, there was a progressive loss of neuronal process extension. This was ameliorated by a pharmacological reagent, dexpramipexole, that binds to ATP synthase, closing a mitochondrial inner membrane leak and enhancing ATP synthase efficiency. ATP synthase c-subunit can form an uncoupling channel; we measured, therefore, ATP synthase F₁ (β subunit) and c-subunit protein levels. We found that ATP synthase β subunit protein level in the DJ-1 KO neurons was approximately half that found in their wild-type counterparts, comprising a severe defect in ATP synthase stoichiometry and unmasking c-subunit. We suggest that DJ-1 enhances dopaminergic cell metabolism and growth by its regulation of ATP synthase protein components.

A secret that underlies Parkinson's disease: The damaging cycle

Parkinson's disease (PD) is a movement disorder, and its common characteristics include the loss of dopaminergic neurons and the accumulation of a special type of cytoplasmic inclusions called Lewy bodies in the substantia nigra pars compacta, which are more prevalent in the elderly. However, the pathophysiology of PD is still elusive. In this review, we summarized five common factors involved in PD, namely, (i) oxidative stress, (ii) mitochondrial dysfunction, (iii) inflammation, (iv) abnormal α-synuclein, and (v) endogenous neurotoxins, and proposed a hypothesis involving a damaging cycle. Oxidative stress-triggered aldehydes react with biogenic amines to produce endogenous neurotoxins. They cause mitochondrial dysfunction and the formation of inflammasomes, which induce the activation of neuroglial cells and the infiltration of T lymphocytes. The synergistic effect of these processes fosters chronic inflammation and α-synuclein aggregation and further exacerbates the impact of oxidative stress to establish a damaging cycle that eventually results in the degeneration of dopaminergic neurons. This damaging cycle provides an explanation of progressive neuronal death during the pathogenesis of PD and provides new potential targets beneficial for developing new drugs and approaches for clinical neuroprotection.

De novo missense variant in the GTPase effector domain (GED) of DNM1L leads to static encephalopathy and seizures

DNM1L encodes a GTPase of the dynamin superfamily, which plays a crucial role in mitochondrial and peroxisomal fission. Pathogenic variants affecting the middle domain and the GTPase domain of DNM1L have been implicated in encephalopathy because of defective mitochondrial and peroxisomal fission 1 (EMPF1, MIM #614388). Patients show variable phenotypes ranging from severe hypotonia leading to death in the neonatal period to developmental delay/regression, with or without seizures. Familial pathogenic variants in the GTPase domain have also been associated with isolated optic atrophy. We present a 27-yr-old woman with static encephalopathy, a history of seizures, and nystagmus, in whom a novel de novo heterozygous variant was detected in the GTPase effector domain (GED) of DNM1L (c.2072A>G, p.Tyr691Cys). Functional studies in Drosophila demonstrate large, abnormally distributed peroxisomes and mitochondria, an effect very similar to that of middle domain missense alleles observed in pediatric subjects with EMPF1. To our knowledge, not only is this the first report of a disease-causing variant in the GED domain in humans, but this is also the oldest living individual reported with EMPF1. Longitudinal data of this kind helps to expand our knowledge of the natural history of a growing list of DNM1L-related disorders.

Experimental Motor Neuron Disease Induced in Mice with Long-Term Repeated Intraperitoneal Injections of Serum from ALS Patients

In an earlier study, signs of commencing degeneration of spinal motor neurons were induced in mice with short-term intraperitoneal injections of immunoglobulin G (IgG) taken from patients with amyotrophic lateral sclerosis (ALS). Since in that study, neither weakness nor loss of motor neurons was noted, to test whether the ALS IgG in this paradigm has the potential to evoke relentless degeneration of motor neurons, treatment with repeated injections over a longer period was carried out. Mice were systematically injected intraperitoneally with serum taken from ALS patients over a 75-day period. At selected time points, the isometric force of the limbs, number of spinal motor neurons and their intracellular calcium levels were determined. Furthermore, markers of glial activation and the motoneuronal uptake of human IgG were monitored. During this period, gliosis and progressive motoneuronal degeneration developed, which led to gradual loss of spinal motor neurons, more than 40% at day 21, along with decreasing muscle strength in the limbs. The inclusion-like accumulation of IgG appeared in the perikarya with the increase of intracellular calcium in the cell bodies and motor nerve terminals. Our results demonstrate that ALS serum can transfer motor neuron disease to mice.

An in silico investigation on the inhibitory potential of the constituents of Pomegranate juice on antioxidant defense mechanism: Relevance to neurodegenerative diseases

Elevation in the levels of reactive oxygen and nitrogen species (RONS), and downregulation of cellular antixoidants, have ubiquitously been reported from studies in animal models of neurodegenerative diseases, including Parkinson’s disease (PD) and Alzheimer’s disease (AD). Thus, plant-derived compounds are widely being investigated for their beneficial effects in these models. However, while studies have reported antioxidant potentials of several phytochemicals, a large number of studies have demonstrated different phytochemicals to be rather pro-oxidant and exaggerate oxidative stress (OS). One such study aimed to investigate possible ameliorative effect of Pomegranate juice (PJ) in rat model of toxin-induced parkinsonism revealed that PJ exacerbates OS, inflammation and promotes neurodegeneration. Thus, it remains to be investigated whether different constituents and metabolites of PJ are pro-oxidant or anti-oxidant. Using computational modeling, we investigated possible inhibitory potential of different constituents of PJ and their metabolites viz. delphinidin-3-glucoside, dimethylellagic acid-glucuronide, ellagic acid, ellagitannin, gallic acid, gallotannin 23, pelargonidin, punicalagin, urolithin A, urolithin A-glucuronide and urolithin B, on anti-oxidant defense system of the brain. The results indicate that the constituents of PJ have the potential to inhibit five key enzymes of the neuronal antioxidant defense system, viz. catalase, superoxide dismutase, glutathione peroxidase 4, glutathione reductase and glutathione-S-transferase. Thus, it is surmised that the constituents of PJ may contribute to OS and neurodegeneration by way of affecting antioxidant defense mechanism. This may particularly be more pronounced in neurodegenerative diseases, since neurons are known to be more vulnerable to OS. Thus, the present findings caution the use of PJ in patients prone to OS, especially those suffering from neurodegenerative diseases, and warrant further experimental studies to unveil the effects of individual components and metabolites of PJ on antioxidant defense system of brain.

Creatine as a Neuroprotector: an Actor that Can Play Many Parts

Creatine is a nitrogenous organic acid that plays a central role as an energy buffer in high energy demanding systems, including the muscular and the central nervous system. It can be acquired from diet or synthesized endogenously, and its main destination is the system creatine/phosphocreatine that strengthens cellular energetics via a temporal and spatial energy buffer that can restore cellular ATP without a reliance on oxygen. This compound has been proposed to possess secondary roles, such as direct and indirect antioxidant, immunomodulatory agent, and possible neuromodulator. However, these effects may be associated with its bioenergetic role in the mitochondria. Given the fundamental roles that creatine plays in the CNS, several preclinical and clinical studies have tested the potential that creatine has to treat degenerative disorders. However, although in vitro and in vivo animal models are highly encouraging, most clinical trials fail to reproduce positive results suggesting that the prophylactic use for neuroprotection in at-risk populations or patients is the most promising field. Nonetheless, the only clearly positive data of the creatine supplementation in human beings are related to the (rare) creatine deficiency syndromes. It seems critical that future studies must establish the best dosage regime to increase brain creatine in a way that can relate to animal studies, provide new ways for creatine to reach the brain, and seek larger experimental groups with biomarkers for prediction of efficacy.

CeVO4 Nanozymes Catalyze the Reduction of Dioxygen to Water without Releasing Partially Reduced Oxygen Species

In this study, we report a remarkably active CeVO₄ nanozyme that functionally mimics cytochrome c oxidase (CcO), the terminal enzyme in the respiratory electron transport chain, by catalyzing a four-electron reduction of dioxygen to water. The nanozyme catalyzes the reaction by using cytochrome c (Cyt c), the biological electron donor for CcO, at physiologically relevant pH. The CcO activity of the CeVO₄ nanozymes depends on the relative ratio of surface Ce³⁺ /Ce⁴⁺ ions, the presence of V⁵⁺ and the surface-Cyt c interactions. The complete reduction of oxygen to water takes place without release of any partially reduced oxygen species (PROS) such as superoxide, peroxide and hydroxyl radicals.

Garcinol, a multifaceted sword for the treatment of Parkinson's disease

Garcinol, the principal phytoconstituent of plants belonging to the genus Garcinia, is known for its anti-oxidant as well as anti-inflammatory properties, which can be extended to its possible neuroprotective role. Recent reports disseminate the capacity of garcinol to influence neuronal growth and survival, alter the neurochemical status in brain, as well as regulate memory and cognition. The concomitant neuro-rescue property of garcinol may render it as an effective compound in Parkinson's disease (PD) therapeutics since it is capable of ameliorating the related pathophysiological changes. Emerging pieces of evidence linking histone acetylation defects to the progression of neurodegenerative diseases provide an effective basis for targeting PD. Hyperacetylation of histones has been reported in Parkinsonian brain, which demands the use of pharmacological inhibitors of histone acetyltransferases (HAT). Garcinol serves as a potent natural HAT inhibitor and has unveiled promising results in molecular interaction studies against Monoamine oxidase B (MAO-B) and Catechol-O-Methyltransferase (COMT), as well as in L-DOPA induced dyskinesia. This review highlights the prospective implications of garcinol as a novel anti-Parkinsonian agent, and establishes a bridge between histone acetylation defects and the pathological aspects of PD.

Structure-Based Specific Detection and Inhibition of Monoamine Oxidases and Their Applications in Central Nervous System Diseases

Monoamine oxidases (MAOs) are the enzymes that catalyze the oxidation of monoamines, such as dopamine, norepinephrine, and serotonin, which serve as key neurotransmitters in the central nervous system (CNS). MAOs play important roles in maintaining the homeostasis of monoamines, and the aberrant expression or activation of MAOs underlies the pathogenesis of monoamine neurotransmitter disorders, including neuropsychiatric and neurodegenerative diseases. Clearly, detecting and inhibiting the activities of MAOs is of great value for the diagnosis and therapeutics of these diseases. Accordingly, many specific detection probes and inhibitors have been developed and substantially contributed to basic and clinical studies of these diseases. In this review, progress in the detecting and inhibiting of MAOs and their applications in mechanism exploration and treatment of neurotransmitter-related disorders is summarized. Notably, how the detection probes and inhibitors of MAOs were developed has been specifically addressed. It is hoped that this review will benefit the design of more effective and sensitive probes and inhibitors for MAOs, and eventually the treatment of monoamine neurotransmitter disorders.

Age-related loss of mitochondrial glutathione exacerbates menadione-induced inhibition of Complex I

The role of mitochondrial GSH (mGSH) in the enhanced age-related susceptibility to xenobiotic toxicity is not well defined. We determined mGSH status and indices of mitochondrial bioenergetics in hepatocytes from young and old F344 rats treated with 300 μM menadione, a concentration that causes 50% cell death in old. At this concentration, mGSH was significantly lost only in hepatocytes from old rats, and with near total depletion due to lower basal mGSH in aged cells. In old hepatocytes, menadione caused mitochondrial membrane potential to collapse, as well as significant deficits in maximal O2 consumption and respiratory reserve capacity, indicators of cellular bioenergetic resiliency. Further examination revealed that the menadione-mediated loss of respiratory reserve capacity in aged hepatocytes was from significant inhibition of Complex I activity and increased proton leak, for which an increase in Complex II activity was not able to compensate. These data demonstrate an age-related increase in mitochondrial susceptibility to a redox-cycling challenge, particularly in regards to Complex I activity, and provide a plausible mechanism to link this vulnerability to mGSH perturbations.

Mitochondrial genome variations in idiopathic dilated cardiomyopathy

Idiopathic dilated cardiomyopathy (DCM) is a structural heart disease with strong genetic background. The aim of this study was to assess the role of mitochondrial DNA (mtDNA) variations and haplogroups in Indian DCM patients. Whole mtDNA analysis of 221 DCM patients revealed 48 novel, 42 disease-associated and 97 private variations. The frequency of reported variations associated with hearing impairment, DEAF, SNHL and LHON are significantly high in DCM patients than controls. Haplogroups H and HV were over represented in DCM than controls. Functional analysis of two private variations (m.8812A>G & m.10320G>A) showed decrease in mitochondrial functions, suggesting the role of mtDNA variations in DCM.

NAD+ Deficiency Is a Common Central Pathological Factor of a Number of Diseases and Aging: Mechanisms and Therapeutic Implications

Increasing evidence has indicated critical roles of nicotinamide adenine dinucleotide, oxidized form (NAD⁺) in various biological functions. NAD⁺ deficiency has been found in models of a number of diseases such as cerebral ischemia, myocardial ischemia, and diabetes, and in models of aging. Applications of NAD⁺ or other approaches that can restore NAD⁺ levels are highly protective in these models of diseases and aging. NAD⁺ produces its beneficial effects by targeting at multiple pathological pathways, including attenuating mitochondrial alterations, DNA damage, and oxidative stress, by modulating such enzymes as sirtuins, glyceraldehyde-3-phosphate dehydrogenase, and AP endonuclease. These findings have suggested great therapeutic and nutritional potential of NAD⁺ for diseases and senescence. Recent Advances: Approaches that can restore NAD⁺ levels are highly protective in the models of such diseases as glaucoma. The NAD⁺ deficiency in the diseases and aging results from not only poly(ADP-ribose) polymerase-1 (PARP-1) activation but also decreased nicotinamide phosphoribosyltransferase (Nampt) activity and increased CD38 activity. Significant biological effects of extracellular NAD⁺ have been found. Increasing evidence has suggested that NAD⁺ deficiency is a common central pathological factor in a number of diseases and aging. Critical Issues and Future Directions: Future studies are required for solidly establishing the concept that "NAD⁺ deficiency is a common central pathological factor in a number of disease and aging." It is also necessary to further investigate the mechanisms underlying the NAD⁺ deficiency in the diseases and aging. Preclinical and clinical studies should be conducted to determine the therapeutic potential of NAD⁺ for the diseases and aging.

Inhibition of bioenergetics provides novel insights into recruitment of PINK1-dependent neuronal mitophagy

Contributions of damaged mitochondria to neuropathologies have stimulated interest in mitophagy. We investigated triggers of neuronal mitophagy by disruption of mitochondrial energy metabolism in primary neurons. Mitophagy was examined in cultured murine cerebellar granule cells after inhibition of mitochondrial respiratory chain by drugs rotenone, 3-nitropropionic acid, antimycin A, and potassium cyanide, targeting complexes I, II, III, and IV, respectively. Inhibitor concentrations producing slow cellular demise were determined from analyses of cellular viability, morphology of neuritic damage, plasma membrane permeability, and oxidative phosphorylation. Live cell imaging of dissipation of mitochondrial membrane potential (ΔΨ_m ) by drugs targeting mitochondrial complexes was referenced to complete depolarization by carbonyl cyanide m-chlorophenyl hydrazone. While inhibition of complexes I, III and IV effected rapid dissipation of ΔΨ_m , inhibition of complex II using 3-nitropropionic acid led to minimal depolarization of mitochondria. Nonetheless, all respiratory chain inhibitors triggered mitophagy as indicated by increased aggregation of mitochondrially localized PINK1. Mitophagy was further analyzed using a dual fluorescent protein biosensor reporting mitochondrial relocation to acidic lysosomal environment. Significant acidification of mitochondria was observed in neurons treated with rotenone or 3-nitropropionic acid, revealing mitophagy at distal processes. Neurons treated with antimycin A or cyanide failed to show mitochondrial acidification. Minor dissipation of ΔΨ_m by 3-nitropropionic acid coupled with vigorous triggering of mitophagy suggested depolarization of mitochondria is not a necessary condition to trigger mitophagy. Moreover, weak elicitation of mitophagy by antimycin A, subsequent to loss of ΔΨ_m , suggested that mitochondrial depolarization is not a sufficient condition for triggering robust neuronal mitophagy. Our findings provide new insight into complexities of mitophagic clearance of neuronal mitochondria.

Short-term air pollution exposure and emergency department visits for amyotrophic lateral sclerosis: A time-stratified case-crossover analysis

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a progressive and devastating neurodegenerative disease, eventually leading to respiratory failure. Although the only currently available therapeutic interventions merely slow the disease progression, few studies have examined risk factors associated with ALS exacerbation and progression.

OBJECTIVE

To investigate the association between exposure to short-term air pollution and acute exacerbation of ALS requiring emergency department (ED) visit.

METHODS

We identified from the national emergency database of Korea 617 patients who visited EDs in Seoul with ALS as a primary cause during the period 2008-2014. We estimated short-term exposure to particles <2.5 μm (PM_2.5), particles <10 μm (PM₁₀), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ozone (O₃), and carbon monoxide (CO). We conducted a conditional logistic regression with a time-stratified case-crossover design to examine the association between ED visits for ALS and short-term exposure to interquartile range (IQR) increase and upper quartile levels of air pollutants on the day of the ED visit, compared to the control days matched to day of the week, month, and year.

RESULTS

The risk of ED visits for ALS was significantly associated with an IQR increase of PM_2.5 [Odds ratio (OR) = 1.21; 95% confidence interval (CI): 1.08, 1.35], PM₁₀ [OR = 1.13; 95% CI: 1.02, 1.25], SO₂ [OR = 1.19; 95% CI: 1.01, 1.41], and CO [OR = 1.19; 95% CI: 1.03, 1.36]. Exposure to the highest quartiles of PM_2.5 and PM₁₀ showed higher associations with ED visits for ALS [OR = 1.40; 95% CI: 1.06, 1.85 and OR = 1.33; 95% CI: 1.00, 1.77].

DISCUSSION

We provide new evidence that exposure to short-term air pollution may increase the risk of acute exacerbation of ALS. Further studies are warranted to understand the underlying mechanisms.

Glucose Homeostasis Is Not Affected in a Murine Model of Parkinson's Disease Induced by 6-OHDA

There is a mutual relationship between metabolic and neurodegenerative diseases. However, the causal relationship in this crosstalk is unclear and whether Parkinson’s disease (PD) causes a posterior impact on metabolism remains unknown. Considering that, this study aimed to evaluate the appearance of possible changes in metabolic homeostasis due to 6-hydroxydopamine (6-OHDA) administration, a neurotoxin that damage dopaminergic neurons leading to motor impairments that resemble the ones observed in PD. For this, male Wistar rats received bilateral 6-OHDA administration in the dorsolateral striatum, and the motor and metabolic outcomes were assessed at 7, 21, or 35 days post-surgical procedure. Dexamethasone, a diabetogenic glucocorticoid (GC), was intraperitoneally administered in the last 6 days to challenge the metabolism and reveal possible metabolic vulnerabilities caused by 6-OHDA. Controls received only vehicles. The 6-OHDA-treated rats displayed a significant decrease in locomotor activity, exploratory behavior, and motor coordination 7 and 35 days after neurotoxin administration. These motor impairments paralleled with no significant alteration in body mass, food intake, glucose tolerance, insulin sensitivity, and biochemical parameters (plasma insulin, triacylglycerol, and total cholesterol levels) until the end of the experimental protocol on days 35–38 post-6-OHDA administration. Moreover, hepatic glycogen and fat content, as well as the endocrine pancreas mass, were not altered in rats treated with 6-OHDA at the day of euthanasia (38th day after neurotoxin administration). None of the diabetogenic effects caused by dexamethasone were exacerbated in rats previously treated with 6-OHDA. Thus, we conclude that bilateral 6-OHDA administration in the striatum causes motor deficits in rats with no impact on glucose and lipid homeostasis and does not exacerbate the adverse effects caused by excess GC. These observations indicate that neurodegeneration of dopaminergic circuits in the 6-OHDA rats does not affect the metabolic outcomes.

LRRK2 and mitochondria: Recent advances and current views

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene account for most common causes of familial and sporadic Parkinson's disease (PD) and are one of the strongest genetic risk factors in sporadic PD. Pathways implicated in LRRK2-dependent neurodegeneration include cytoskeletal dynamics, vesicular trafficking, autophagy, mitochondria, and calcium homeostasis. However, the exact molecular mechanisms still need to be elucidated. Both genetic and environmental causes of PD have highlighted the importance of mitochondrial dysfunction in the pathogenesis of PD. Mitochondrial impairment has been observed in fibroblasts and iPSC-derived neural cells from PD patients with LRRK2 mutations, and LRRK2 has been shown to localize to mitochondria and to regulate its function. In this review we discuss recent discoveries relating to LRRK2 mutations and mitochondrial dysfunction.

When safeguarding goes wrong: Impact of oxidative stress on protein homeostasis in health and neurodegenerative disorders

Cellular redox status is an established player in many different cellular functions. The buildup of oxidants within the cell is tightly regulated to maintain a balance between the positive and negative outcomes of cellular oxidants. Proteins are highly sensitive to oxidation, since modification can cause widespread unfolding and the formation of toxic aggregates. In response, cells have developed highly regulated systems that contribute to the maintenance of both the global redox status and protein homeostasis at large. Changes to these systems have been found to correlate with aging and age-related disorders, such as neurodegenerative pathologies. This raises intriguing questions as to the source of the imbalance in the redox and protein homeostasis systems, their interconnectivity, and their role in disease progression. Here we focus on the crosstalk between the redox and protein homeostasis systems in neurodegenerative diseases, specifically in Alzheimer's, Parkinson's, and ALS. We elaborate on some of the main players of the stress response systems, including the master regulators of oxidative stress and the heat shock response, Nrf2 and Hsf1, which are essential features of protein folding, and mediators of protein turnover. We illustrate the elegant mechanisms used by these components to provide an immediate response, including protein plasticity controlled by redox-sensing cysteines and the recruitment of naive proteins to the redox homeostasis array that act as chaperons in an ATP-independent manner.

Silent Free Fall at Disease Onset: A Perspective on Therapeutics for Progressive Multiple Sclerosis

Central nervous system (CNS) degeneration occurs during multiple sclerosis (MS) following several years of reversible autoimmune demyelination. Progressive CNS degeneration appears later during the course of relapsing-remitting MS (RRMS), although it starts insidiously at disease onset. We propose that there is an early subclinical phase also for primary-progressive (PP) MS. Consensus exists that many different cell types are involved during disease onset. Furthermore, the response to the initial damage, which is specific for each individual, would result in distinct pathological pathways that add complexity to the disease and the mechanisms underlying progressive CNS degeneration. Progressive MS is classified as either active or not active, as well as with or without progression. Different forms of progressive MS might reflect distinct or overlapping pathogenetic pathways. Disease mechanisms should be determined for each patient at diagnosis and the time of treatment. Until individualized and time-sensitive treatments that specifically target the molecular mechanisms of the progressive aspect of the disease are identified, combined therapies directed at anti-inflammation, regeneration, and neuroprotection are the most effective for preventing MS progression. This review presents selected therapeutics in support of the overall idea of a multidimensional therapy applied early in the disease. This approach could limit damage and increase CNS repair. By targeting several cellular populations (i.e., microglia, astrocytes, neurons, oligodendrocytes, and lymphocytes) and multiple pathological processes (e.g., inflammation, demyelination, synaptopathy, and excitatory/inhibitory imbalance) progressive MS could be attenuated. Early timing for such multidimensional therapy is proposed as the prerequisite for effectively halting progressive MS.

Mitochondrial dynamics, a key executioner in neurodegenerative diseases

Neurodegenerative diseases (NDs) are the group of disorder that includes brain, peripheral nerves, spinal cord and results in sensory and motor neuron dysfunction. Several studies have shown that mitochondrial dynamics and their axonal transport play a central role in most common NDs such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD) and Amyotrophic Lateral Sclerosis (ALS) etc. In normal physiological condition, there is a balance between mitochondrial fission and fusion process while any alteration to these processes cause defect in ATP (Adenosine Triphosphate) biogenesis that lead to the onset of several NDs. Also, mitochondria mediated ROS may induce lipid and protein peroxidation, energy deficiency environment in the neurons and results in cell death and defective neurotransmission. Though, mitochondria is a well-studied cell organelle regulating the cellular energy demands but still, its detail role or association in NDs is under observation. In this review, we have summarized an updated mitochondria and their possible role in different NDs with the therapeutic strategy to improve the mitochondrial functions.

In vitro rejuvenation of brain mitochondria by the inhibition of actin polymerization

The oxygen consumption rate (OCR) and cytochrome c oxidase (CcO) activity of respiratory complex IV (CIV) in brain mitochondria significantly decline in middle-aged male mice compared to younger male mice. To explore the mechanisms underlying the regulation of brain mitochondrial function, we examined CIV-associated proteins, and identified actin inside the isolated brain mitochondria. Inhibiting actin polymerization using cytochalasin B (CB) significantly enhanced the OCR and CcO activity of CIV in the mitochondria. These changes were accompanied by a significant reduction in the amount of CIV-bound cytochrome c (cyt c). Actin was also associated with respiratory complex III (CIII); however, the amount of CIII-bound cyt c increased significantly after treatment of the mitochondria with CB. In contrast, no significant alteration in the assembly or the CcO activity of CIV in CIV-containing supercomplexes or CIV monomers was induced by CB. These results suggest that mitochondrial actin plays a crucial role in the regulation of the CcO activity and OCR of CIV with modification of the retention of cyt c between CIV and CIII.

Forebrain cellular bioenergetics in neonatal mice

BACKGROUND

Hypoglycemia occurs frequently in the neonate and may result in neurologic dysfunction. Its impact on the kinetics of cellular respiration and bioenergetics in the neonatal brain remains to be explored.

AIMS

Develop murine model to investigate the effects of hypoglycemia on neonatal brain bioenergetics.

STUDY DESIGN

Forebrain fragments were excised from euthanized BALB/c pups aged <24 hours to 14 days. We measured cellular respiration (μM O2 min-1.mg-1) in phosphate-buffered saline with and without glucose, using phosphorescence oxygen analyzer, as well as cellular adenosine triphosphate (ATP, nmol.mg-1) using the luciferin-luciferase system.

RESULTS

In the presence of glucose, although cellular respiration was 11% lower in pups ≤3 days compared to those 3- 14 days old (0.48 vs. 0.54), that difference was not statistically significant (p = 0.14). Respiration driven by endogenous metabolic fuels (without added glucose) was 16% lower in pups ≤3 days compared to those 3- 14 days (0.35 vs. 0.42, p = 0.03), confirming their increased dependency on exogenous glucose. Although cellular ATP was similar between the two age groups (14.9 vs. 11.2, p = 0.32), the ATP content was more severely depleted without added glucose in the younger pups, especially in the presence of the cytochrome c oxidase inhibitor cyanide. The first-order rate constant of cellular ATP decay (hydrolysis) was 44% lower in 2-day-old pups compared to 14-day-old mice (0.43 vs. 0.77 min-1, p = 0.03).

CONCLUSIONS

Forebrain cellular respiration and ATP consumption are lower in young pups than older mice. In the absence of glucose, the support for these processes is reduced in young pups, explaining their brain hypersensitivity to hypoglycemia.

Thiamine Deficiency Induced Dietary Disparity Promotes Oxidative Stress and Neurodegeneration

Thiamine or vitamin B1 is a well known coenzyme and nutrient necessary for the assembly and right functioning of several enzymes involved in the energy metabolism. The present study evaluates oxidative stress and prevalence of neurodegenerative conditions in the brain following TD. The study was carried out on mice (Musmusculus) in three groups, namely control and thiamine-deficient group for 8 (TD 8) and 10 (TD 10) days. Lipid peroxidation was determined in terms of reduced glutathione (GSH) and thiobarbituric acid reactive substance (TBARS). The level of antioxidant enzymes such as catalase (CAT), glutathione reductase, glutathione peroxidase (GPx), superoxide dismutase (SOD) and glutathione transferase (GST) were measured along with histopathological studies in all the groups. There was significant increase in the TBARS levels in group II (TD 8) and group III (TD 10) animals in comparison to controls (Group I). The GSH levels were found to be lower in both the treated groups. The level of antioxidant enzymes CAT (p < 0.001), glutathione reductase (p < 0.001), GPx (p < 0.001), SOD (p < 0.0001) were found to be significantly reduced in group III (TD 10) in comparison to controls. Histopathological studies showed moderated to extensive neuronal loss in group II and group III in comparison to control group. The increase in LPO and reduction in enzymes CAT, glutathione reductase, GPx, SOD, and GST following TD suggests mitochondrial dysfunction, neuronal loss acute oxidative stress that may impair the functioning of the brain along with the rise of neurodegenerative conditions in the affected animals.

Cellular Proteostasis in Neurodegeneration

The term proteostasis reflects the fine-tuned balance of cellular protein levels, mediated through a vast network of biochemical pathways. This requires the regulated control of protein folding, post-translational modification, and protein degradation. Due to the complex interactions and intersection of proteostasis pathways, exposure to stress conditions may lead to a disruption of the entire network. Incorrect protein folding and/or modifications during protein synthesis results in inactive or toxic proteins, which may overload degradation mechanisms. Further, a disruption of autophagy and the endoplasmic reticulum degradation pathway may result in additional cellular stress which could ultimately lead to cell death. Neurodegenerative diseases such as Parkinson's disease, Alzheimer's disease, Huntington's disease, and Amyotrophic Lateral Sclerosis all share common risk factors such as oxidative stress, aging, environmental stress, and protein dysfunction; all of which alter cellular proteostasis. The differing pathologies observed in neurodegenerative diseases are determined by factors such as location-specific neuronal death, source of protein dysfunction, and the cell's ability to counter proteotoxicity. In this review, we discuss how the disruption in cellular proteostasis contributes to the onset and progression of neurodegenerative diseases.

The Therapeutic Potential of Metformin in Neurodegenerative Diseases

The search for treatments for neurodegenerative diseases is a major concern in light of today's aging population and an increasing burden on individuals, families, and society. Although great advances have been made in the last decades to understand the underlying genetic and biological cause of these diseases, only some symptomatic treatments are available. Metformin has long since been used to treat Type 2 Diabetes and has been shown to be beneficial in several other conditions. Metformin is well-tested in vitro and in vivo and an approved compound that targets diverse pathways including mitochondrial energy production and insulin signaling. There is growing evidence for the benefits of metformin to counteract age-related diseases such as cancer, cardiovascular disease, and neurodegenerative diseases. We will discuss evidence showing that certain neurodegenerative diseases and diabetes are explicitly linked and that metformin along with other diabetes drugs can reduce neurological symptoms in some patients and reduce disease phenotypes in animal and cell models. An interesting therapeutic factor might be how metformin is able to balance survival and death signaling in cells through pathways that are commonly associated with neurodegenerative diseases. In healthy neurons, these overarching signals keep energy metabolism, oxidative stress, and proteostasis in check, avoiding the dysfunction and neuronal death that defines neurodegenerative disease. We will discuss the biological mechanisms involved and the relevance of neuronal vulnerability and potential difficulties for future trials and development of therapies.

The Therapeutic Potential of Metformin in Neurodegenerative Diseases

The search for treatments for neurodegenerative diseases is a major concern in light of today's aging population and an increasing burden on individuals, families, and society. Although great advances have been made in the last decades to understand the underlying genetic and biological cause of these diseases, only some symptomatic treatments are available. Metformin has long since been used to treat Type 2 Diabetes and has been shown to be beneficial in several other conditions. Metformin is well-tested in vitro and in vivo and an approved compound that targets diverse pathways including mitochondrial energy production and insulin signaling. There is growing evidence for the benefits of metformin to counteract age-related diseases such as cancer, cardiovascular disease, and neurodegenerative diseases. We will discuss evidence showing that certain neurodegenerative diseases and diabetes are explicitly linked and that metformin along with other diabetes drugs can reduce neurological symptoms in some patients and reduce disease phenotypes in animal and cell models. An interesting therapeutic factor might be how metformin is able to balance survival and death signaling in cells through pathways that are commonly associated with neurodegenerative diseases. In healthy neurons, these overarching signals keep energy metabolism, oxidative stress, and proteostasis in check, avoiding the dysfunction and neuronal death that defines neurodegenerative disease. We will discuss the biological mechanisms involved and the relevance of neuronal vulnerability and potential difficulties for future trials and development of therapies.

Nicotine Modulates Cognitive Function in D-Galactose-Induced Senescence in Mice

Here, we tested the claim that nicotine attenuates the signs of brain dysfunction in the model of brain aging induced by D-galactose (DGal) in mice. We administered nicotine at doses of 0.1, 0.5 and 1 mg/kg by the subcutaneous (s.c.) or at 0.1 mg/kg by the intranasal (i.n.) routes in mice that had received DGal at the dose of 500 mg/kg subcutaneous (s.c.) for 6 weeks. We assessed animal withdrawal signs as the number of presented somatic signs, thermal hyperalgesia, elevated plus maze (EPM) and open field tests. We evaluated spatial memory and recognition with Barnes maze and novel object recognition (NOR) tests. We tested brain tissue for reactive oxygen species (ROS), mitochondrial membrane potential, caspase-3, Bax, Bcl-2, cytochrome C, brain-derived neurotrophic factor and nerve growth factor levels. Nicotine administration in model groups (0.5 mg/kg s.c. and 0.1 mg/kg i.n. doses) significantly attenuated impairment of spatial and episodic memories in comparison to normal saline-received model group. These doses also reduced mito-oxidative damage as well as apoptosis and raised neurotrophic factors level in model groups in comparison to normal saline-received model group. The 1 mg/kg s.c. dose nicotine revealed withdrawal signs compared with the other nicotine-received groups. Nicotine at specific doses and routes has the potential to attenuate age-related cognitive impairment, mito-oxidative damage, and apoptosis. The doses raise neurotrophic factors without producing withdrawal signs.

Differential effect of amyloid beta peptides on mitochondrial axonal trafficking depends on their state of aggregation and binding to the plasma membrane

Inhibition of mitochondrial axonal trafficking by amyloid beta (Aβ) peptides has been implicated in early pathophysiology of Alzheimer's Disease (AD). Yet, it remains unclear whether the loss of motility inevitably induces the loss of mitochondrial function, and whether restoration of axonal trafficking represents a valid therapeutic target. Moreover, while some investigations identify Aβ oligomers as the culprit of trafficking inhibition, others propose that fibrils play the detrimental role. We have examined the effect of a panel of Aβ peptides with different mutations found in familial AD on mitochondrial motility in primary cortical mouse neurons. Peptides with higher propensity to aggregate inhibit mitochondrial trafficking to a greater extent with fibrils inducing the strongest inhibition. Binding of Aβ peptides to the plasma membrane was sufficient to induce trafficking inhibition where peptides with reduced plasma membrane binding and internalization had lesser effect on mitochondrial motility. We also found that Aβ peptide with Icelandic mutation A673T affects axonal trafficking of mitochondria but has very low rates of plasma membrane binding and internalization in neurons, which could explain its relatively low toxicity. Inhibition of mitochondrial dynamics caused by Aβ peptides or fibrils did not instantly affect mitochondrial bioenergetic and function. Our results support a mechanism where inhibition of axonal trafficking is initiated at the plasma membrane by soluble low molecular weight Aβ species and is exacerbated by fibrils. Since trafficking inhibition does not coincide with the loss of mitochondrial function, restoration of axonal transport could be beneficial at early stages of AD progression. However, strategies designed to block Aβ aggregation or fibril formation alone without ensuring the efficient clearance of soluble Aβ may not be sufficient to alleviate the trafficking phenotype.

Neuroprotective action of tea polyphenols on oxidative stress-induced apoptosis through the activation of the TrkB/CREB/BDNF pathway and Keap1/Nrf2 signaling pathway in SH-SY5Y cells and mice brain

Many studies have shown that oxidative stress is a major cause of cellular injuries in a variety of human diseases including cognitive impairment. Tea polyphenols (TPs), natural plant flavonoids found in tea plant leaves, possess the bioactivity to affect the pathogenesis of several chronic diseases via antioxidant associated mechanisms. However, the possible antioxidant and neuroprotective properties of TPs in the brain of mice housed in constant darkness and in H₂O₂-stimulated SH-SY5Y cells are yet to be elucidated. In this study, pretreatment with TPs markedly attenuated H₂O₂-elicited cell viability loss and mitochondrial dysfunction, suppressed the induced apoptosis and reduced the elevated levels of intracellular ROS and H₂O₂. Additionally, TPs modulate the nuclear translocation of Nrf2 and the TrkB/CREB/BDNF signaling pathway by provoking the PI3K/AKT pathway and thus, they transcriptionally regulate the downstream expression of antioxidant enzymes including HO-1, NQO-1, and BDNF in SH-SY5Y cells. Furthermore, an in vivo study revealed that housing mice in constant darkness, simulating shift work disruption in humans, notably affects the AKT/CREB/BDNF signal pathway and the nuclear translocation of Nrf2 and its downstream phase II detoxification enzymes in brain tissue. Remarkably, TP supplementation through drinking water eliminated these changes. These results suggest that TPs possess protective effects against oxidative stress-triggered cognitive impairment, which might be a potential nutritional preventive strategy for neurodegenerative diseases implicated with oxidative stress in shift workers.

Swim Training Modulates Skeletal Muscle Energy Metabolism, Oxidative Stress, and Mitochondrial Cholesterol Content in Amyotrophic Lateral Sclerosis Mice

Recently, in terms of amyotrophic lateral sclerosis (ALS), much attention has been paid to the cell structures formed by the mitochondria and the endoplasmic reticulum membranes (MAMs) that are involved in the regulation of Ca²⁺ signaling, mitochondrial bioenergetics, apoptosis, and oxidative stress. We assumed that remodeling of these structures via swim training may accompany the prolongation of the ALS lifespan. In the present study, we used transgenic mice with the G93A hmSOD1 gene mutation. We examined muscle energy metabolism, oxidative stress parameters, and markers of MAMs (Caveolin-1 protein level and cholesterol content in crude mitochondrial fraction) in groups of mice divided according to disease progression and training status. The progression of ALS was related to the lowering of Caveolin-1 protein levels and the accumulation of cholesterol in a crude mitochondrial fraction. These changes were associated with aerobic and anaerobic energy metabolism dysfunction and higher oxidative stress. Our data indicated that swim training prolonged the lifespan of ALS mice with accompanying changes in MAM components. Swim training also maintained mitochondrial function and lowered oxidative stress. These data suggest that modification of MAMs might play a crucial role in the exercise-induced deceleration of ALS development.

A reciprocal relationship between reactive oxygen species and mitochondrial dynamics in neurodegeneration

Mitochondrial fragmentation due to fission/fusion imbalance has often been linked to mitochondrial dysfunction and apoptosis in neurodegeneration. Conventionally, it is believed that once mitochondrial morphology shifts away from its physiological tubular form, mitochondria become defective and downstream apoptotic signaling pathways are triggered. However, our study shows that beta-amyloid (Aβ) induces morphological changes in mitochondria where they become granular-shaped and are distinct from fragmented mitochondria in terms of both morphology and functions. Accumulation of mitochondrial reactive oxygen species triggers granular mitochondria formation, while mitoTEMPO (a mitochondria-targeted superoxide scavenger) restores tubular mitochondrial morphology within Aβ-treated neurons. Interestingly, modulations of mitochondria fission and fusion by genetic and pharmacological tools attenuated not only the induction of granular mitochondria, but also mitochondrial superoxide levels in Aβ-treated neurons. Our study shows a reciprocal relationship between mitochondrial dynamics and reactive oxygen species and provides a new potential therapeutic target at early stages of neurodegenerative disease pathogenesis.

Phasor analysis of NADH FLIM identifies pharmacological disruptions to mitochondrial metabolic processes in the rodent cerebral cortex

Investigating cerebral metabolism in vivo at a microscopic level is essential for understanding brain function and its pathological alterations. The intricate signaling and metabolic dynamics between neurons, glia, and microvasculature requires much more detailed understanding to better comprehend the mechanisms governing brain function and its disease-related changes. We recently demonstrated that pharmacologically-induced alterations to different steps of cerebral metabolism can be distinguished utilizing 2-photon fluorescence lifetime imaging of endogenous reduced nicotinamide adenine dinucleotide (NADH) fluorescence in vivo. Here, we evaluate the ability of the phasor analysis method to identify these pharmacological metabolic alterations and compare the method's performance with more conventional nonlinear curve-fitting analysis. Visualization of phasor data, both at the fundamental laser repetition frequency and its second harmonic, enables resolution of pharmacologically-induced alterations to mitochondrial metabolic processes from baseline cerebral metabolism. Compared to our previous classification models based on nonlinear curve-fitting, phasor-based models required fewer parameters and yielded comparable or improved classification accuracy. Fluorescence lifetime imaging of NADH and phasor analysis shows utility for detecting metabolic alterations and will lead to a deeper understanding of cerebral energetics and its pathological changes.

Toward a Reasoned Classification of Diseases Using Physico-Chemical Based Phenotypes

Background: Diseases and health conditions have been classified according to anatomical site, etiological, and clinical criteria. Physico-chemical mechanisms underlying the biology of diseases, such as the flow of energy through cells and tissues, have been often overlooked in classification systems.

Objective: We propose a conceptual framework toward the development of an energy-oriented classification of diseases, based on the principles of physical chemistry.

Methods: A review of literature on the physical chemistry of biological interactions in a number of diseases is traced from the point of view of the fluid and solid mechanics, electricity, and chemistry.

Results: We found consistent evidence in literature of decreased and/or increased physical and chemical forces intertwined with biological processes of numerous diseases, which allowed the identification of mechanical, electric and chemical phenotypes of diseases.

Discussion: Biological mechanisms of diseases need to be evaluated and integrated into more comprehensive theories that should account with principles of physics and chemistry. A hypothetical model is proposed relating the natural history of diseases to mechanical stress, electric field, and chemical equilibria (ATP) changes. The present perspective toward an innovative disease classification may improve drug-repurposing strategies in the future.

Cytoprotective effects of diosmetin against hydrogen peroxide-induced L02 cell oxidative damage via activation of the Nrf2-ARE signaling pathway

Oxidative stress is considered a crucial mediator in the pathogenesis of various liver diseases. The flavone diosmetin has been reported to exhibit antioxidant activities; however, the hepatoprotective effects of diosmetin against oxidative stress, and the underlying molecular mechanisms, remain unknown. The present study aimed to investigate the potential hepatoprotective effects of diosmetin on hydrogen peroxide (H2O2)‑induced oxidative damage in L02 cells and attempted to evaluate the role of the nuclear factor erythroid 2‑related factor 2 (Nrf2)/antioxidant response element pathway in this process. L02 cells were divided into groups: Control (DMSO, diosmetin), H2O2, Trolox or tertiary butylhydroquinone and diosmetin (different doses). Protective effects in L02 cells were determined by CCK‑8, cell apoptosis and lactate dehydrogenase leakage assays. Flow cytometry and inverted fluorescence microscope were used to measure the intracellular reactive oxygen species (ROS) and mitochondrial membrane potential (MMP). Protein expression levels were of Nrf2, heme oxygenase‑1 (HO‑1) and NAD(P)H quinone oxidoreductase‑1 (NQO1) were determined by western blotting and mRNA levels were determined by reverse transcription‑quantitative polymerase chain reaction. The results revealed that H2O2 induced notable injury to L02 cells, as demonstrated by decreased cell viability, increased lactate dehydrogenase release, apoptotic rate and intracellular ROS production, and by the loss of MMP. Conversely, diosmetin (20‑40 µM) significantly reversed the damaging effects of H2O2, which indicated that diosmetin may exhibit potent hepatoprotective potential against H2O2‑induced oxidative damage. Furthermore, pretreatment with diosmetin elevated mRNA and protein expression levels of Nrf2, HO‑1 and NQO1. The present study is the first, to the best of our knowledge, to demonstrate that activation of the Nrf2/NQO1‑HO‑1 signaling pathway maybe involved in the cytoprotective effects of diosmetin against oxidative stress. Therefore, diosmetin may be considered a promising therapeutic agent for the treatment of various liver diseases associated with oxidative stress.