Mitochondria take center stage in aging and neurodegeneration

Neurodegenerative disorders, metabolic icebergs, and mitohormesis

Neurodegenerative disorders are typically "split" based on their hallmark clinical, anatomical, and pathological features, but they can also be "lumped" by a shared feature of impaired mitochondrial biology. This leads us to present a scientific framework that conceptualizes Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD) as "metabolic icebergs" comprised of a tip, a bulk, and a base. The visible tip conveys the hallmark neurological symptoms, neurodegenerative regions, and neuronal protein aggregates for each disorder. The hidden bulk depicts impaired mitochondrial biology throughout the body, which is multifaceted and may be subdivided into impaired cellular metabolism, cell-specific mitotypes, and mitochondrial behaviours, functions, activities, and features. The underlying base encompasses environmental factors, especially modern industrial toxins, dietary lifestyles, and cognitive, physical, and psychosocial behaviours, but also accommodates genetic factors specific to familial forms of AD, PD, and ALS, as well as HD. Over years or decades, chronic exposure to a particular suite of environmental and genetic factors at the base elicits a trajectory of impaired mitochondrial biology that maximally impacts particular subsets of mitotypes in the bulk, which eventually surfaces as the hallmark features of a particular neurodegenerative disorder at the tip. We propose that impaired mitochondrial biology can be repaired and recalibrated by activating "mitohormesis", which is optimally achieved using strategies that facilitate a balanced oscillation between mitochondrial stressor and recovery phases. Sustainably harnessing mitohormesis may constitute a potent preventative and therapeutic measure for people at risk of, or suffering with, neurodegenerative disorders.

Progress of research on the treatment of depression by traditional Chinese medicine prescriptions

Depression is a common psychiatric disorder that belongs to the category of "Depression Syndrome" in traditional Chinese medicine (TCM), and its etiology and pathogenesis are complex and unclear. It is characterized by high prevalence, high disability rate, and high recurrence rate, which seriously affect human health, and its treatment has become a research hotspot worldwide. At present, the antidepressants commonly used in the clinic are mainly Western medicine (WM), but there are problems such as frequent side effects and poor efficacy. Studies have found that the use of TCM prescriptions in the treatment of depression can achieve the same effect as WM; and when TCM prescriptions are combined with WM, the efficacy can be enhanced while the adverse effects of WM can be reduced. Pharmacological studies related to the treatment of depression with traditional Chinese medicine prescriptions (TCMPs) have focused on the neurobiochemical system, gut microbes, and energy metabolism in mitochondria. No one has yet reviewed the pharmacological mechanism of TCMPs for depression. So, this paper reviews the pharmacological mechanism of TCMPs for depression from the perspective of TCMPs, introduces the progress of research on classical TCMPs for depression and their antidepressant mechanism. This article aims to promote the application of TCMPs in the clinic and provide a new therapeutic idea for the clinical treatment of depression.

Loss of MEF2C function by enhancer mutation leads to neuronal mitochondria dysfunction and motor deficits in mice

Genetic changes and epigenetic modifications are associated with neuronal dysfunction in the pathogenesis of neurodegenerative disorders. However, the mechanism behind genetic mutations in the non-coding region of genes that affect epigenetic modifications remains unclear. Here, we identified an ALS-associated SNP located in the intronic region of MEF2C (rs304152), residing in a putative enhancer element, using convolutional neural network. The enhancer mutation of MEF2C reduces own gene expression and consequently impairs mitochondrial function in motor neurons. MEF2C localizes and binds to the mitochondria DNA, and directly modulates mitochondria-encoded gene expression. CRISPR/Cas-9-induced mutation of the MEF2C enhancer decreases expression of mitochondria-encoded genes. Moreover, MEF2C mutant cells show reduction of mitochondrial membrane potential, ATP level but elevation of oxidative stress. MEF2C deficiency in the upper and lower motor neurons of mice impairs mitochondria-encoded genes, and leads to mitochondrial metabolic disruption and progressive motor behavioral deficits. Together, MEF2C dysregulation by the enhancer mutation leads to mitochondrial dysfunction and oxidative stress, which are prevalent features in motor neuronal damage and ALS pathogenesis. This genetic and epigenetic crosstalk mechanism provides insights for advancing our understanding of motor neuron disease and developing effective treatments.

Mitochondrial DNA abundance in blood is associated with Alzheimer's disease- and dementia-risk

The mitochondrial cascade hypothesis of Alzheimer's disease (AD) has been portrayed through molecular, cellular, and animal studies; however large epidemiological studies are lacking. This study aimed to explore the association of mitochondrial DNA copy number (mtDNAcn), a marker representative of mtDNA abundance per cell, with risk of incident all-cause dementia, AD, and vascular dementia diagnosis within 17 years and dementia-related blood biomarkers (P-tau181, GFAP, and NfL). Additionally, sex-stratified analyses were completed. In this German population-based cohort study (ESTHER), 9940 participants aged 50-75 years were enrolled by general practitioners and followed for 17 years. Participants were included in this study if information on dementia status and blood-based mtDNAcn measured via real-time polymerase chain reaction were available. In a nested case-control approach, a subsample of participants additionally had measurements of P-tau181, GFAP, and NfL in blood samples taken at baseline. Of 4913 participants eligible for analyses, 386 were diagnosed with incident all-cause dementia, including 130 AD and 143 vascular dementia cases, while 4527 participants remained without dementia diagnosis within 17 years. Participants with low mtDNAcn (lowest 10%) experienced 45% and 65% percent increased risk of incident all-cause dementia and AD after adjusting for age and sex (all-cause dementia: HRadj, 95%CI:1.45, 1.08-1.94; AD: HRadj, 95%CI: 1.65, 1.01-2.68). MtDNAcn was not associated to vascular dementia diagnosis and was more strongly associated with all-cause dementia among women. In the nested case-control study (n = 790), mtDNAcn was not significantly associated with the dementia-related blood biomarkers (P-tau181, GFAP, and NfL) levels in blood from baseline before dementia diagnosis. This study provides novel epidemiological evidence connecting mtDNA abundance, measured via mtDNAcn, to incident dementia and AD at the population-based level. Reduced mitochondrial abundance may play a role in pathogenesis, especially among women.

Ameliorating Mitochondrial Dysfunction for the Therapy of Parkinson's Disease

Parkinson's disease (PD) is currently the second most incurable central neurodegenerative disease resulting from various pathogenesis. As the "energy factory" of cells, mitochondria play an extremely important role in supporting neuronal signal transmission and other physiological activities. Mitochondrial dysfunction can cause and accelerate the occurrence and progression of PD. How to effectively prevent and suppress mitochondrial disorders is a key strategy for the treatment of PD from the root. Therefore, the emerging mitochondria-targeted therapy has attracted considerable interest. Herein, the relationship between mitochondrial dysfunction and PD, the causes and results of mitochondrial dysfunction, and major strategies for ameliorating mitochondrial dysfunction to treat PD are systematically reviewed. The study also prospects the main challenges for the treatment of PD.

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

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

Diosmetin as a promising natural therapeutic agent: In vivo, in vitro mechanisms, and clinical studies

Diosmetin, a natural occurring flavonoid, is primarily found in citrus fruits, beans, and other plants. Diosmetin demonstrates a variety of pharmacological activities, including anticancer, antioxidant, anti-inflammatory, antibacterial, metabolic regulation, cardiovascular function improvement, estrogenic effects, and others. The process of literature search was done using PubMed, Web of Science and ClinicalTrials databases with search terms containing Diosmetin, content, anticancer, anti-inflammatory, antioxidant, pharmacological activity, pharmacokinetics, in vivo, and in vitro. The aim of this review is to summarize the in vivo, in vitro and clinical studies of Diosmetin over the last decade, focusing on studies related to its anticancer, anti-inflammatory, and antioxidant activities. It is found that DIO has significant therapeutic effects on skin and cardiovascular system diseases, and its research in pharmacokinetics and toxicology is summarized. It provides the latest information for researchers and points out the limitations of current research and areas that should be strengthened in future research, so as to facilitate the relevant scientific research and clinical application of DIO.

Serine 39 in the GTP-binding domain of Drp1 is involved in shaping mitochondrial morphology

Continuous fusion and fission are critical for mitochondrial health. In this study, we further characterize the role played by dynamin-related protein 1 (Drp1) in mitochondrial fission. We show that a single amino acid change in Drp1 at position 39 from serine to alanine (S39A) within the GTP-binding (GTPase) domain results in a fused mitochondrial network in human SH-SY5Y neuroblastoma cells. Interestingly, the phosphorylation of Ser-616 and Ser-637 of Drp1 remains unaffected by the S39A mutation, and mitochondrial bioenergetic profile and cell viability in the S39A mutant were comparable to those observed in the control. This leads us to propose that the serine 39 residue of Drp1 plays a crucial role in mitochondrial distribution through its involvement in the GTPase activity. Furthermore, this amino acid mutation leads to structural anomalies in the mitochondrial network. Taken together, our results contribute to a better understanding of the function of the Drp1 protein.

Fumaria vaillantii extract protects PC12 cells against neurotoxicity induced by 6-OHDA

BACKGROUND

Parkinson's disease is a neurological disorder caused by the loss of dopaminergic neurons in the midbrain. Various mechanisms are involved in the incidence of the disease including oxidative stress. Several herbs and natural products may interfere with the oxidative-stress pathway due to their antioxidant effects.

OBJECTIVE

Herein, we aimed to investigate the neuroprotective role of F. vaillantii extract on Parkinson's in vitro and in vivo model owing to the presence of the bioactive agents with antioxidant properties.

METHODS

In vitro experments showed that 6-hydroxydopamine could induce toxicity in PC12 cells. The impact of F. vaillantii extract on cell viability was measured by using MTT assay. Nuclear morphological changes were qualitatively evaluated employing Hoechst staining. The antioxidant activity of the extract was determined by ROS and lipid peroxidation assays. Tyrosine hydroxylase protein expression was measured by western blotting in PC12 cells. For in vivo study, movement parameters were evaluated.

RESULTS

The results indicated that 75 µΜ of 6-OHDA induced 50% toxicity in PC12 cells for 24 h. Following post-treatment with F. vaillantii extract (0.1 mg/ml) for 72 h, we observed that the extract effectively prevented cell toxicity induced by 6-OHDA and reduced the apoptotic cell population. Furthermore, the extract attenuated the ROS level, lipid peroxidation and increased protein expression of TH after 72 h of treatment. In addition, oral administration of 300 mg/kg of F. vaillantii extract for 14 days improved locomotor activity, catalepsy, bradykinesia, motor coordination and reduced the apomorphine-caused rotation in 6-OHDA- induced Parkinson's disease-like symptoms in male rats.

CONCLUSION

The present study suggests a protective role for the extract of F. vaillantii against oxidative stress-induced cell damage in the PC12 cells exposed to neurotoxin 6-OHDA which was verified in in vivo model by reducing the motor defects induced by 6-OHDA. This extract could be a promising therapeutic agent for the prevention of PD progression.

The neuroprotective effects of ferulic acid in toxin-induced models of Parkinson's disease: A review

Parkinson's disease is predominantly caused by dopaminergic neuron loss in the substantia nigra pars compacta and the accumulation of alpha-synuclein protein. Though the general consensus is that several factors, such as aging, environmental factors, mitochondrial dysfunction, accumulations of neurotoxic alpha-synuclein, malfunctions of the lysosomal and proteasomal protein degradation systems, oxidative stress, and neuroinflammation, are involved in the neurodegeneration process of Parkinson's disease, the precise mechanism by which all of these factors are triggered remains unknown. Typically, neurotoxic compounds such as rotenone, 6-hydroxydopamine, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 1-methyl 4-phenyl pyridinium (mpp+), paraquat, and maneb are used to Preclinical models of Parkinson's disease Ferulic acid is often referred to by its scientific name, 4-hydroxy-3-methoxycinnamic acid (C10H10O4), and is found naturally in cereals, fruits, vegetables, and bee products. This substance exhibits neuroprotective effects against Parkinson's disease because of its intriguing potential, which includes anti-inflammatory and antioxidant qualities. This review goes into additional detail about Parkinson's disease and the neuroprotective properties of ferulic acid that may help prevent the condition.

Frontal-temporal regional differences in brain energy metabolism and mitochondrial function using 31P MRS in older adults

Aging is a major risk for cognitive decline and transition to dementia. One well-known age-related change involves decreased brain efficiency and energy production, mediated in part by changes in mitochondrial function. Damaged or dysfunctional mitochondria have been implicated in the pathogenesis of age-related neurodegenerative conditions like Alzheimer's disease (AD). The aim of the current study was to investigate mitochondrial function over frontal and temporal regions in a sample of 70 cognitively normal older adults with subjective memory complaints and a first-degree family history of AD. We hypothesized cerebral mitochondrial function and energy metabolism would be greater in temporal as compared to frontal regions based on the high energy consumption in the temporal lobes (i.e., hippocampus). To test this hypothesis, we used phosphorous (31P) magnetic resonance spectroscopy (MRS) which is a non-invasive and powerful method for investigating in vivo mitochondrial function via high energy phosphates and phospholipid metabolism ratios. We used a single voxel method (left temporal and bilateral prefrontal) to achieve optimal sensitivity. Results of separate repeated measures analyses of variance showed 31P MRS ratios of static energy, energy reserve, energy consumption, energy demand, and phospholipid membrane metabolism were greater in the left temporal than bilateral prefrontal voxels. Our findings that all 31P MRS ratios were greater in temporal than bifrontal regions support our hypothesis. Future studies are needed to determine whether findings are related to cognition in older adults.

AIF translocation into nucleus caused by Aifm1 R450Q mutation: generation and characterization of a mouse model for AUNX1

Mutations in AIFM1, encoding for apoptosis-inducing factor (AIF), cause AUNX1, an X-linked neurologic disorder with late-onset auditory neuropathy (AN) and peripheral neuropathy. Despite significant research on AIF, there are limited animal models with the disrupted AIFM1 representing the corresponding phenotype of human AUNX1, characterized by late-onset hearing loss and impaired auditory pathways. Here, we generated an Aifm1 p.R450Q knock-in mouse model (KI) based on the human AIFM1 p.R451Q mutation. Hemizygote KI male mice exhibited progressive hearing loss from P30 onward, with greater severity at P60 and stabilization until P210. Additionally, muscle atrophy was observed at P210. These phenotypic changes were accompanied by a gradual reduction in the number of spiral ganglion neuron cells (SGNs) at P30 and ribbons at P60, which coincided with the translocation of AIF into the nucleus starting from P21 and P30, respectively. The SGNs of KI mice at P210 displayed loss of cytomembrane integrity, abnormal nuclear morphology, and dendritic and axonal demyelination. Furthermore, the inner hair cells and myelin sheath displayed abnormal mitochondrial morphology, while fibroblasts from KI mice showed impaired mitochondrial function. In conclusion, we successfully generated a mouse model recapitulating AUNX1. Our findings indicate that disruption of Aifm1 induced the nuclear translocation of AIF, resulting in the impairment in the auditory pathway.

New cyclophilin D inhibitor rescues mitochondrial and cognitive function in Alzheimer's disease

Mitochondrial dysfunction is an early pathological feature of Alzheimer disease and plays a crucial role in the development and progression of Alzheimer's disease. Strategies to rescue mitochondrial function and cognition remain to be explored. Cyclophilin D (CypD), the peptidylprolyl isomerase F (PPIase), is a key component in opening the mitochondrial membrane permeability transition pore, leading to mitochondrial dysfunction and cell death. Blocking membrane permeability transition pore opening by inhibiting CypD activity is a promising therapeutic approach for Alzheimer's disease. However, there is currently no effective CypD inhibitor for Alzheimer's disease, with previous candidates demonstrating high toxicity, poor ability to cross the blood-brain barrier, compromised biocompatibility and low selectivity. Here, we report a new class of non-toxic and biocompatible CypD inhibitor, ebselen, using a conventional PPIase assay to screen a library of ∼2000 FDA-approved drugs with crystallographic analysis of the CypD-ebselen crystal structure (PDB code: 8EJX). More importantly, we assessed the effects of genetic and pharmacological blockade of CypD on Alzheimer's disease mitochondrial and glycolytic bioenergetics in Alzheimer's disease-derived mitochondrial cybrid cells, an ex vivo human sporadic Alzheimer's disease mitochondrial model, and on synaptic function, inflammatory response and learning and memory in Alzheimer's disease mouse models. Inhibition of CypD by ebselen protects against sporadic Alzheimer's disease- and amyloid-β-induced mitochondrial and glycolytic perturbation, synaptic and cognitive dysfunction, together with suppressing neuroinflammation in the brain of Alzheimer's disease mouse models, which is linked to CypD-related membrane permeability transition pore formation. Thus, CypD inhibitors have the potential to slow the progression of neurodegenerative diseases, including Alzheimer's disease, by boosting mitochondrial bioenergetics and improving synaptic and cognitive function.

Misfolded protein oligomers: mechanisms of formation, cytotoxic effects, and pharmacological approaches against protein misfolding diseases

The conversion of native peptides and proteins into amyloid aggregates is a hallmark of over 50 human disorders, including Alzheimer's and Parkinson's diseases. Increasing evidence implicates misfolded protein oligomers produced during the amyloid formation process as the primary cytotoxic agents in many of these devastating conditions. In this review, we analyze the processes by which oligomers are formed, their structures, physicochemical properties, population dynamics, and the mechanisms of their cytotoxicity. We then focus on drug discovery strategies that target the formation of oligomers and their ability to disrupt cell physiology and trigger degenerative processes.

Mechanisms and structure-activity relationships of polysaccharides in the intervention of Alzheimer's disease: A review

Alzheimer's disease (AD) is a complex neurodegenerative disease. Despite several decades of research, the development of effective treatments and responses for Alzheimer's disease remains elusive. The utilization of polysaccharides for Alzheimer's disease became more popular due to their beneficial characteristics, notably their multi-target activity and low toxicity. This review mainly focuses on the researches of recent 5 years in the regulation of AD by naturally derived polysaccharides, systematically lists the possible intervention pathways of polysaccharides from different mechanisms, and explores the structure-activity relationship between polysaccharide structural activities, so as to provide references for the intervention and treatment of AD by polysaccharides.

Glial Activation, Mitochondrial Imbalance, and Akt/mTOR Signaling May Be Potential Mechanisms of Cognitive Impairment in Heart Failure Mice

Heart failure (HF) is a major health burden worldwide, with approximately half of HF patients having a comorbid cognitive impairment (CI). However, it is still unclear how CI develops in patients with HF. In the present study, a mice model of heart failure was established by ligating the left anterior descending coronary artery. Echocardiography 1 month later confirmed the decline in ejection fraction and ventricular remodeling. Cognitive function was examined by the Pavlovian fear conditioning and the Morris water maze. HF group cued fear memory, spatial memory, and learning impairment, accompanied by activation of glial cells (astrocytes, microglia, and oligodendrocytes) in the hippocampus. In addition, the mitochondrial biogenesis genes TFAM and SIRT1 decreased, and the fission gene DRP1 increased in the hippocampus. Damaged mitochondria release excessive ROS, and the ability to produce ATP decreases. Damaged swollen mitochondria with altered morphology and aberrant inner-membrane crista were observed under a transmission electron microscope. Finally, Akt/mTOR signaling was upregulated in the hippocampus of heart failure mice. These findings suggest that activation of Akt/mTOR signaling, glial activation, and mitochondrial dynamics imbalance could trigger cognitive impairment in the pathological process of heart failure mice.

Polyherbal and Multimodal Treatments: Kaempferol- and Quercetin-Rich Herbs Alleviate Symptoms of Alzheimer's Disease

Alzheimer's Disease (AD) is a progressive neurodegenerative disorder impairing cognition and memory in the elderly. This disorder has a complex etiology, including senile plaque and neurofibrillary tangle formation, neuroinflammation, oxidative stress, and damaged neuroplasticity. Current treatment options are limited, so alternative treatments such as herbal medicine could suppress symptoms while slowing cognitive decline. We followed PRISMA guidelines to identify potential herbal treatments, their associated medicinal phytochemicals, and the potential mechanisms of these treatments. Common herbs, including Ginkgo biloba, Camellia sinensis, Glycyrrhiza uralensis, Cyperus rotundus, and Buplerum falcatum, produced promising pre-clinical results. These herbs are rich in kaempferol and quercetin, flavonoids with a polyphenolic structure that facilitate multiple mechanisms of action. These mechanisms include the inhibition of Aβ plaque formation, a reduction in tau hyperphosphorylation, the suppression of oxidative stress, and the modulation of BDNF and PI3K/AKT pathways. Using pre-clinical findings from quercetin research and the comparatively limited data on kaempferol, we proposed that kaempferol ameliorates the neuroinflammatory state, maintains proper cellular function, and restores pro-neuroplastic signaling. In this review, we discuss the anti-AD mechanisms of quercetin and kaempferol and their limitations, and we suggest a potential alternative treatment for AD. Our findings lead us to conclude that a polyherbal kaempferol- and quercetin-rich cocktail could treat AD-related brain damage.

Mitochondrial Neurodegenerative Diseases: Three Mitochondrial Ribosomal Proteins as Intermediate Stage in the Pathway That Associates Damaged Genes with Alzheimer's and Parkinson's

Currently, numerous research endeavors are dedicated to unraveling the intricate nature of neurodegenerative diseases. These conditions are characterized by the gradual and progressive impairment of specific neuronal systems that exhibit anatomical or physiological connections. In particular, in the last twenty years, remarkable efforts have been made to elucidate neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease. However, despite extensive research endeavors, no cure or effective treatment has been discovered thus far. With the emergence of studies shedding light on the contribution of mitochondria to the onset and advancement of mitochondrial neurodegenerative disorders, researchers are now directing their investigations toward the development of therapies. These therapies include molecules designed to protect mitochondria and neurons from the detrimental effects of aging, as well as mutant proteins. Our objective is to discuss and evaluate the recent discovery of three mitochondrial ribosomal proteins linked to Alzheimer's and Parkinson's diseases. These proteins represent an intermediate stage in the pathway connecting damaged genes to the two mitochondrial neurological pathologies. This discovery potentially could open new avenues for the production of medicinal substances with curative potential for the treatment of these diseases.

Dysfunctional energy and future perspective of low dose H2O2 as protective agent in neurodegenerative disease

The number of people with neurodegenerative disease continues to increase every year. A new perspective is needed to overcome this disease. In this review, researchers collected information about dysfunctional energy in neurodegenerative diseases driven by mitochondria. Mitochondrial dysregulation can cause damage to the neuron system. The increase in the amount and interaction of α-synuclein with SAMM50 and GABARAPL1 in the mitochondria is one of the factors causing neurodegenerative disease. As an energy provider in the body, the existence of harmonization in the regulation of mitochondria, specifically the mitochondrial outer membrane, is important. Low-dose hydrogen peroxide (H₂O₂) has neuroprotective abilities to overcome the impairment function of mitochondria in neurodegenerative patients. Based on computational simulation of this case, it can be used as a basic concept for the development of the role of H₂O₂ in neurodegenerative diseases.

Vascular disease risk factors in multiple sclerosis: Effect on metabolism and brain volumes

BACKGROUND

Vascular disease risk factors (VDRF) such as hypertension, hyperlipidemia, obesity, diabetes and heart disease likely play a role in disease progression in people with multiple sclerosis (PwMS) (Marrie, Rudick et al. 2010). Studies exploring the mechanistic connection between vascular disease and MS disease progression are scant. We hypothesized that phosphate energy metabolism impairment in PwMS with VDRFs (VDRF+) will be greater compared to PwMS without VDRFs (VDRF-) and is related to increased brain atrophy in VDRF+. To test this hypothesis, we planned to study the differences in the high energy phosphate (HEP) metabolites in cerebral gray matter as assessed by 31P magnetic resonance spectroscopic imaging (MRSI) and MRI brain volumetric in the VDRF+ and VDRF- PwMS at four different timepoints over a 3 yearlong period using a 7T MR system. We present here the results from the cross-sectional evaluation of HEP metabolites and brain volumes. We also evaluated the differences in clinical impairment, blood metabolic biomarkers and quality of life in VDRF+ and VDRF- PwMS in this cohort.

METHODS

Group differences in high energy phosphate metabolites were assessed from a volume of interest in the occipital region using linear mixed models. Brain parenchymal and white matter lesion volumes were determined from MR anatomic images. We present here the cross-sectional analysis of the baseline data collected as part of a longitudinal 3 yearlong study where we obtained baseline and subsequent 6-monthly clinical and laboratory data and annual 7T MRI volumetric and 31P MR spectroscopic imaging (MRSI) data on 52 PwMS with and without VDRF. Key clinical and laboratory outcomes included: body mass index (BMI), waist and thigh circumferences and disability [Expanded Disability Status Scale (EDSS)], safety (complete blood count with differential, complete metabolic), lipid panel including total cholesterol and HbA1C. We analyzed clinical and laboratory data for the group differences using student's t or χ2 test. We investigated relationship between phosphate metabolites and VDRF using mixed effect linear regression.

RESULTS

Complete MRI data were available for 29 VDRF+, age 56.3 (6.8) years [mean (SD)] (83% female), and 23 VDRF-, age 52.5 (7.5) years (57% female) individuals with MS. The mean value of normalized adenosine triphosphate (ATP) (calculated as the ratio of ATP to total phosphate signal in a voxel) was decreased by 4.5% (p < .05) in VDRF+ compared to VDRF- MS group. White matter lesion (WML) volume fraction in VDRF+ individuals {0.007 (0.007)} was more than doubled compared to VDRF- participants {0.003 (0.006), p= .02}.

CONCLUSIONS

We found significantly lower brain ATP and higher inorganic phosphate (Pi) in those PwMS with VDRFs compared to those without. ATP depletion may reflect mitochondrial dysfunction. Ongoing longitudinal data analysis from this study, not presented here, will evaluate the relationship of phosphate metabolites, brain atrophy and disease progression in PwMS with and without vascular disease.

Trends of mitochondrial changes in AD: a bibliometric study

Background

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive progress and memory loss, which eventually develops into dementia. It can cause personality disorders and decreased quality of life of patients. Currently, AD patients account for 60-70% of global dementia patients and the incidence rate of AD is increasing annually. AD not only causes pain to patients but also brings a heavy burden to the entire family. Studies have found that there is a connection between mitochondrial dysfunction and other biochemical changes in AD like classical neuropathological hallmarks (β-amyloid and tau protein), inflammation pathways, oxidative stress, and so on. Evidence shows that early treatment targeted directly to mitochondria could extend the lifespan of model mice and decrease the relevant neuropathological markers. Therefore, research on the mitochondrial dysfunction of AD can be of potential significance for clinical treatment. To date, few bibliometric analysis articles related to mitochondrial dysfunction of AD have been published. Bibliometric analysis refers to quantitatively analyzing certain aspects of articles like publishers, authors, and countries by using statistical and mathematical methods. Combined with statistical software, a large number of papers can be converted to visualization figures and tables, which provide vital information such as keyword hotspots and the names of contributing authors. Through the bibliometric analysis method, our study aimed to provide study trends and keyword hotpots for researchers to conduct further relevant research in this field.

Methods

We used the Web of Science core collection database as a literature retrieval tool to obtain data related to mitochondrial changes in Alzheimer's disease during the last 20 years. The retrieval type was [TS = (Alzheimer's disease)] ND [TS = (mitochondrion)], ranging from January 1, 2000 to June 30, 2022. VOSviewer v1.6.18, Arcgis 10.8, and HistCite pro 2.1 were used to conduct data visualization analysis. VOSviewer v1.6.18 made relevant network visualization maps of the cooperative relationship between relevant countries, institutions, and authors (co-authorship), the frequency of different keywords appearing together (co-occurrence), and the frequency of different articles cited together (co-cited). Arcgis 10.8 created the world map of publications distribution in this field and Histcite pro 2.1 was used to count the local citation score (LCS) of references. In addition, Journal Citation Reports were used to consult the latest journal import factor and JCI quartile.

Results

As of June 30, 2022, from the Web of Science core collection, we selected 2,474 original articles in English, excluding the document types of the news items, meeting abstracts, and some articles that had little relevance to our theme. The United States acted as the leader and enjoyed a high reputation in this field. The University of California System was the institution that made the greatest contribution (3.64% with 90 papers). Most articles were published in the Journal of Alzheimer's Disease (8.21%, with 203 papers). The most frequently co-cited journal in Q1 was the Journal of Biological Chemistry (8,666 citations, TLS: 1039591). Russel H. Swerdlow (55 publications) was the most productive author and PH Reddy was the most co-cited author with 1,264 citations (TLS: 62971). The hotpots of mitochondrial dysfunction in AD were as follows: "oxidative stress," "amyloid-beta-protein," "tau," "apoptosis," "inflammation," "autophagy," "precursor protein," "endoplasmic-reticulum," "dynamics" and "mitochondrial unfolded protein response."

Conclusion

This bibliometric analysis research will help readers rapidly identify current hotpots and milestone studies related to directions of interest in AD research.

Antioxidant and Anti-Inflammatory Effects of Carotenoids in Mood Disorders: An Overview

Depression has a multifactorial etiology comprising family history and unemployment. This review aims to summarize the evidence available for the antioxidant and anti-inflammatory effects of carotenoids in mood disorders. This review article’s methodologies were based on a search of the PubMed database for all linked published papers. Epidemiological studies indicate that a diet rich in vegetables, fruits, nuts, fish, and olive oil may prevent the development of depression. Antioxidant supplementation has been found to combat various stress-induced psychiatric disorders, including depression and anxiety. A growing body of evidence indicates that carotenoids have both antioxidant and anti-inflammatory. Studies also suggest that poor dietary intake, particularly low intakes of fruit and vegetables and high intakes of fast food and other convenience foods, may increase the risk of developing depression. Thus, dietary interventions have the potential to help mitigate the risk of mental health decline in both the general population and those with mood disorders. Considering that carotenoids have both antioxidant and anti-inflammatory effects, it is expected that they might exert a promising antidepressant effect. Nevertheless, further studies (including interventional and mechanistic studies) assessing the effect of carotenoids on preventing and alleviating depression symptoms are needed.

Is lithium neuroprotective? An updated mechanistic illustrated review

Neurodegeneration is a pathological process characterized by progressive neuronal impairment, dysfunction, and loss due to mitochondrial dysfunction, oxidative stress, inflammation, and apoptosis. Many studies have shown that lithium protects against neurodegeneration. Herein, we summarize recent clinical and laboratory studies on the neuroprotective effects of lithium against neurodegeneration and its potential to modulate mitochondrial dysfunction, oxidative stress, inflammation, and apoptosis. Recent findings indicate that lithium regulates critical intracellular pathways such as phosphatidylinositol-3 (PI3)/protein kinase B (Akt)/glycogen synthase kinase-3 (GSK3β) and PI3/Akt/response element-binding protein (CREB)/brain-derived neurotrophic factor (BDNF). We queried PubMed, Web of Science, Scopus, Elsevier, and other related databases using search terms related to lithium and its neuroprotective effect in various neurodegenerative diseases and events from January 2000 to May 2022. We reviewed the major findings and mechanisms proposed for the effects of lithium. Lithium's neuroprotective potential against neural cell degeneration is mediated by inducing anti-inflammatory factors, antioxidant enzymes, and free radical scavengers to prevent mitochondrial dysfunction. Lithium effects are regulated by two essential pathways: PI3/Akt/GSK3β and PI3/Akt/CREB/BDNF. Lithium acts as a neuroprotective agent against neurodegeneration by preventing inflammation, oxidative stress, apoptosis, and mitochondrial dysfunction using PI3/Akt/GSK3β and PI3/Akt/CREB/BDNF signaling pathways.

Competing endogenous RNA (ceRNA) networks in Parkinson's disease: A systematic review

Parkinson's disease (PD) is a distinctive clinical syndrome with several causes and clinical manifestations. Aside from an infectious cause, PD is a rapidly developing neurological disorder with a global rise in frequency. Notably, improved knowledge of molecular pathways and the developing novel diagnostic methods may result in better therapy for PD patients. In this regard, the amount of research on ceRNA axes is rising, highlighting the importance of these axes in PD. CeRNAs are transcripts that cross-regulate one another via competition for shared microRNAs (miRNAs). These transcripts may be either coding RNAs (mRNAs) or non-coding RNAs (ncRNAs). This research used a systematic review to assess validated loops of ceRNA in PD. The Prisma guideline was used to conduct this systematic review, which entailed systematically examining the articles of seven databases. Out of 309 entries, forty articles met all criteria for inclusion and were summarized in the appropriate table. CeRNA axes have been described through one of the shared vital components of the axes, including lncRNAs such as NEAT1, SNHG family, HOTAIR, MALAT1, XIST, circRNAs, and lincRNAs. Understanding the multiple aspects of this regulatory structure may aid in elucidating the unknown causal causes of PD and providing innovative molecular therapeutic targets and medical fields.

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.

Mitochondrial Medicine: A Promising Therapeutic Option Against Various Neurodegenerative Disorders

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

Mechanisms Underlying Neurodegenerative Disorders and Potential Neuroprotective Activity of Agrifood By-Products

Neurodegenerative diseases, characterized by progressive loss in selected areas of the nervous system, are becoming increasingly prevalent worldwide due to an aging population. Despite their diverse clinical manifestations, neurodegenerative diseases are multifactorial disorders with standard features and mechanisms such as abnormal protein aggregation, mitochondrial dysfunction, oxidative stress and inflammation. As there are no effective treatments to counteract neurodegenerative diseases, increasing interest has been directed to the potential neuroprotective activities of plant-derived compounds found abundantly in food and in agrifood by-products. Food waste has an extremely negative impact on the environment, and recycling is needed to promote their disposal and overcome this problem. Many studies have been carried out to develop green and effective strategies to extract bioactive compounds from food by-products, such as peel, leaves, seeds, bran, kernel, pomace, and oil cake, and to investigate their biological activity. In this review, we focused on the potential neuroprotective activity of agrifood wastes obtained by common products widely produced and consumed in Italy, such as grapes, coffee, tomatoes, olives, chestnuts, onions, apples, and pomegranates.

Role of Nrf2 in aging, Alzheimer's and other neurodegenerative diseases

Nuclear Factor-Erythroid Factor 2 (Nrf2) is an important transcription factor that regulates the expression of large number of genes in healthy and disease states. Nrf2 is made up of 605 amino acids and contains 7 conserved regions known as Nrf2-ECH homology domains. Nrf2 regulates the expression of several key components of oxidative stress, mitochondrial biogenesis, mitophagy, autophagy and mitochondrial function in all organs of the human body, in the peripheral and central nervous systems. Mounting evidence also suggests that altered expression of Nrf2 is largely involved in aging, neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's diseases, Amyotrophic lateral sclerosis, Stroke, Multiple sclerosis and others. The purpose of this article is to detail the essential role of Nrf2 in oxidative stress, antioxidative defense, detoxification, inflammatory responses, transcription factors, proteasomal and autophagic/mitophagic degradation, and metabolism in aging and neurodegenerative diseases. This article also highlights the Nrf2 structural and functional activities in healthy and disease states, and also discusses the current status of Nrf2 research and therapeutic strategies to treat aging and neurodegenerative diseases.

Nutritional intervention for diabetes mellitus with Alzheimer's disease

The combined disease burden of diabetes mellitus (DM) and Alzheimer's disease (AD) is increasing, and the two diseases share some common pathological changes. However, the pharmacotherapeutic approach to this clinical complexity is limited to symptomatic rather than disease-arresting, with the possible exception of metformin. Whether nutritional intervention might extend or synergize with these effects of metformin is of interest. In particular, dietary patterns with an emphasis on dietary diversity shown to affect cognitive function are of growing interest in a range of food cultural settings. This paper presents the association between diabetes and AD. In addition, the cross-cultural nutritional intervention programs with the potential to mitigate both insulin resistance (IR) and hyperglycemia, together with cognitive impairment are also reviewed. Both dietary patterns and nutritional supplementation showed the effects of improving glycemic control and reducing cognitive decline in diabetes associated with AD, but the intervention specificity remained controversial. Multi-nutrient supplements combined with diverse diets may have preventive and therapeutic potential for DM combined with AD, at least as related to the B vitamin group and folate-dependent homocysteine (Hcy). The nutritional intervention has promise in the prevention and management of DM and AD comorbidities, and more clinical studies would be of nutritional scientific merit.

The relationship of alpha-synuclein to mitochondrial dynamics and quality control

Maintenance of mitochondrial health is essential for neuronal survival and relies upon dynamic changes in the mitochondrial network and effective mitochondrial quality control mechanisms including the mitochondrial-derived vesicle pathway and mitophagy. Mitochondrial dysfunction has been implicated in driving the pathology of several neurodegenerative diseases, including Parkinson’s disease (PD) where dopaminergic neurons in the substantia nigra are selectively degenerated. In addition, many genes with PD-associated mutations have defined functions in organelle quality control, indicating that dysregulation in mitochondrial quality control may represent a key element of pathology. The most well-characterized aspect of PD pathology relates to alpha-synuclein; an aggregation-prone protein that forms intracellular Lewy-body inclusions. Details of how alpha-synuclein exerts its toxicity in PD is not completely known, however, dysfunctional mitochondria have been observed in both PD patients and models of alpha-synuclein pathology. Accordingly, an association between alpha-synuclein and mitochondrial function has been established. This relates to alpha-synuclein’s role in mitochondrial transport, dynamics, and quality control. Despite these relationships, there is limited research defining the direct mechanisms linking alpha-synuclein to mitochondrial dynamics and quality control. In this review, we will discuss the current literature addressing this association and provide insight into the proposed mechanisms promoting these functional relationships. We will also consider some of the alternative mechanisms linking alpha-synuclein with mitochondrial dynamics and speculate what the relationship between alpha-synuclein and mitochondria might mean both physiologically and in relation to PD.

Selective Unnatural Base Pairing and Recognition of 2-Hydroxy-2'-deoxyadenosine in DNA Using Pseudo-dC Derivatives

The formation of unnatural base pairs within duplex DNA would facilitate DNA nanotechnology and biotechnology. Iso-2'-deoxyguanosine (iso-dG) forms base pairs with iso-2'-deoxycytidine, and its use as an unnatural base pair was investigated. Iso-dG is one of the tautomers of 2-hydroxy-2'-deoxyadenosine (2-OH-dA), known as an oxidatively damaged nucleobase, and its selective recognition in DNA plays an important role in the diagnosis and pathogenesis of disease. Therefore, we focused on pseudo-dC (ψdC) as a suitable molecule that recognizes 2-OH-dA in DNA. Since 2-OH-dA shows tautomeric structures in DNA, we designed and used ψdC, which also has a tautomeric structure. We successfully synthesized a ψdC phosphoramidite compound for the synthesis of oligonucleotides (ODNs) as well as its triphosphate derivative (ψdCTP). T_m measurements revealed that ODNs including ψdC showed stable base pair formation with ODNs having 2-OH-dA. In contrast, low T_m values were observed for other bases (dG, dA, dC, and T). The results obtained for the single-nucleotide primer extension reaction revealed that ψdCTP was incorporated into the complementary position of 2-OH-dA in template DNA with high selectivity. In addition, the primer elongation reaction was confirmed to proceed in the presence of dNTPs. The present study reports an artificial nucleic acid that selectively and stably forms unnatural base pairs with 2-OH-dA in DNA.

The APP intracellular domain promotes LRRK2 expression to enable feed-forward neurodegenerative mechanisms in Parkinson's disease

Gain-of-function mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are common in familial forms of Parkinson's disease (PD), which is characterized by progressive neurodegeneration that impairs motor and cognitive function. We previously demonstrated that LRRK2-mediated phosphorylation of β-amyloid precursor protein (APP) triggers the production and nuclear translocation of the APP intracellular domain (AICD). Here, we connected LRRK2 to AICD in a feed-forward cycle that enhanced LRRK2-mediated neurotoxicity. In cooperation with the transcription factor FOXO3a, AICD promoted LRRK2 expression, thus increasing the abundance of LRRK2 that promotes AICD activation. APP deficiency in LRRK2^G2019S mice suppressed LRRK2 expression, LRRK2-mediated mitochondrial dysfunction, α-synuclein accumulation, and tyrosine hydroxylase (TH) loss in the brain, phenotypes associated with toxicity and loss of dopaminergic neurons in PD. Conversely, AICD overexpression increased LRRK2 expression and LRRK2-mediated neurotoxicity in LRRK2^G2019S mice. In LRRK2^G2019S mice or cultured dopaminergic neurons from LRRK2^G2019S patients, treatment with itanapraced reduced LRRK2 expression and was neuroprotective. Itanapraced showed similar effects in a neurotoxin-induced PD mouse model, suggesting that inhibiting the AICD may also have therapeutic benefits in idiopathic PD. Our findings reveal a therapeutically targetable, feed-forward mechanism through which AICD promotes LRRK2-mediated neurotoxicity in PD.

Putative role of mitochondria in SARS-CoV-2 mediated brain dysfunctions: a prospect

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of the COVID-19 pandemic. Though the virus primarily damages the respiratory and cardiovascular systems after binding to the host angiotensin-converting enzyme 2 (ACE2) receptors, it has the potential to affect all major organ systems, including the human nervous system. There are multiple clinical reports of anosmia, dizziness, headache, nausea, ageusia, encephalitis, demyelination, neuropathy, memory loss, and neurological complications in SARS-CoV-2 infected individuals. Though the molecular mechanism of these brain dysfunctions during SARS-CoV-2 infection is elusive, the mitochondria seem to be an integral part of this pathogenesis. Emerging research findings suggest that the dysfunctional mitochondria and associated altered bioenergetics in the infected host cells lead to altered energy metabolism in the brain of Covid-19 patients. The interactome between viral proteins and mitochondrial proteins during Covid-19 pathogenesis also provides evidence for the involvement of mitochondria in SARS-CoV-2-induced brain dysfunctions. The present review discusses the possible role of mitochondria in disturbing the SARS-CoV-2 mediated brain functions, with the potential to use this information to prevent and treat these impairments.

Mutation-related magnetization-transfer, not axon density, drives white matter differences in premanifest Huntington disease: Evidence from in vivo ultra-strong gradient MRI

White matter (WM) alterations have been observed in Huntington disease (HD) but their role in the disease-pathophysiology remains unknown. We assessed WM changes in premanifest HD by exploiting ultra-strong-gradient magnetic resonance imaging (MRI). This allowed to separately quantify magnetization transfer ratio (MTR) and hindered and restricted diffusion-weighted signal fractions, and assess how they drove WM microstructure differences between patients and controls. We used tractometry to investigate region-specific alterations across callosal segments with well-characterized early- and late-myelinating axon populations, while brain-wise differences were explored with tract-based cluster analysis (TBCA). Behavioral measures were included to explore disease-associated brain-function relationships. We detected lower MTR in patients' callosal rostrum (tractometry: p = .03; TBCA: p = .03), but higher MTR in their splenium (tractometry: p = .02). Importantly, patients' mutation-size and MTR were positively correlated (all p-values < .01), indicating that MTR alterations may directly result from the mutation. Further, MTR was higher in younger, but lower in older patients relative to controls (p = .003), suggesting that MTR increases are detrimental later in the disease. Finally, patients showed higher restricted diffusion signal fraction (FR) from the composite hindered and restricted model of diffusion (CHARMED) in the cortico-spinal tract (p = .03), which correlated positively with MTR in the posterior callosum (p = .033), potentially reflecting compensatory mechanisms. In summary, this first comprehensive, ultra-strong gradient MRI study in HD provides novel evidence of mutation-driven MTR alterations at the premanifest disease stage which may reflect neurodevelopmental changes in iron, myelin, or a combination of these.

Associations of Social Isolation and Loneliness With Later Dementia

BACKGROUND AND OBJECTIVES

To investigate the independent associations of social isolation and loneliness with incident dementia and to explore the potential neurobiological mechanisms.

METHODS

We utilized the UK Biobank cohort to establish Cox proportional hazard models with social isolation and loneliness as separate exposures. Demographic (sex, age, and ethnicity), socioeconomic (education level, household income, and Townsend deprivation index), biological (body mass index, APOE genotype, diabetes, cancer, cardiovascular disease, and other), cognitive (speed of processing and visual memory), behavioral (current smoker, alcohol intake, and physical activity), and psychological (social isolation or loneliness, depressive symptoms, and neuroticism) factors measured at baseline were adjusted. Then, voxel-wise brainwide association analyses were used to identify gray matter volumes (GMVs) associated with social isolation and with loneliness. Partial least squares regression was performed to test the spatial correlation of GMV differences and gene expression using the Allen Human Brain Atlas.

RESULTS

We included 462,619 participants (mean age at baseline 57.0 years [SD 8.1]). With a mean follow-up of 11.7 years (SD 1.7), 4,998 developed all-cause dementia. Social isolation was associated with a 1.26-fold increased risk of dementia (95% CI, 1.15-1.37) independently of various risk factors including loneliness and depression (i.e., full adjustment). However, the fully adjusted hazard ratio for dementia related to loneliness was 1.04 (95% CI, 0.94-1.16) and 75% of this relationship was attributable to depressive symptoms. Structural MRI data were obtained from 32,263 participants (mean age 63.5 years [SD 7.5]). Socially isolated individuals had lower GMVs in temporal, frontal, and other (e.g., hippocampal) regions. Mediation analysis showed that the identified GMVs partly mediated the association between social isolation at baseline and cognitive function at follow-up. Social isolation-related lower GMVs were related to underexpression of genes that are downregulated in Alzheimer disease and to genes that are involved in mitochondrial dysfunction and oxidative phosphorylation.

DISCUSSION

Social isolation is a risk factor for dementia that is independent of loneliness and many other covariates. Social isolation-related brain structural differences coupled with different molecular functions also support the associations of social isolation with cognition and dementia. Social isolation may thus be an early indicator of an increased risk of dementia.

Hallmarks and Molecular Tools for the Study of Mitophagy in Parkinson’s Disease

The best-known hallmarks of Parkinson’s disease (PD) are the motor deficits that result from the degeneration of dopaminergic neurons in the substantia nigra. Dopaminergic neurons are thought to be particularly susceptible to mitochondrial dysfunction. As such, for their survival, they rely on the elaborate quality control mechanisms that have evolved in mammalian cells to monitor mitochondrial function and eliminate dysfunctional mitochondria. Mitophagy is a specialized type of autophagy that mediates the selective removal of damaged mitochondria from cells, with the net effect of dampening the toxicity arising from these dysfunctional organelles. Despite an increasing understanding of the molecular mechanisms that regulate the removal of damaged mitochondria, the detailed molecular link to PD pathophysiology is still not entirely clear. Herein, we review the fundamental molecular pathways involved in PINK1/Parkin-mediated and receptor-mediated mitophagy, the evidence for the dysfunction of these pathways in PD, and recently-developed state-of-the art assays for measuring mitophagy in vitro and in vivo.

Molecular Mechanisms of Parthanatos and Its Role in Diverse Diseases

Differential evolution of apoptosis, programmed necrosis, and autophagy, parthanatos is a form of cell death mediated by poly(ADP-ribose) polymerase 1 (PARP1), which is caused by DNA damage. PARP1 hyper-activation stimulates apoptosis-inducing factor (AIF) nucleus translocation, and accelerates nicotinamide adenine dinucleotide (NAD⁺) and adenosine triphosphate (ATP) depletion, leading to DNA fragmentation. The mechanisms of parthanatos mainly include DNA damage, PARP1 hyper-activation, PAR accumulation, NAD⁺ and ATP depletion, and AIF nucleus translocation. Now, it is reported that parthanatos widely exists in different diseases (tumors, retinal diseases, neurological diseases, diabetes, renal diseases, cardiovascular diseases, ischemia-reperfusion injury...). Excessive or defective parthanatos contributes to pathological cell damage; therefore, parthanatos is critical in the therapy and prevention of many diseases. In this work, the hallmarks and molecular mechanisms of parthanatos and its related disorders are summarized. The questions raised by the recent findings are also presented. Further understanding of parthanatos will provide a new treatment option for associated conditions.

SIRT3 regulates mitochondrial biogenesis in aging-related diseases

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

Detailed insight into the pathophysiology and the behavioral complications associated with the Parkinson's disease and its medications

Background

The loss of dopamine neurons in the substantia nigra, as well as other mostly catecholaminergic neurons, causes many of the motor symptoms that define Parkinson's disease. Parkinson's disease is commonly thought of as a movement disorder, the significant prevalence of psychiatric complications such as cognitive impairment, and psychosis suggests it should be considered a neuropsychiatric illness, and all behavioral complications are linked to growing disability and the medication.

Main body

Apart from the disease-induced abnormalities, there are several other side effects of the disease and also from the medication used to prevent the disease. This article focuses on the pathogenesis of Parkinson’s disease and also the behavioral abnormalities caused by the disease and its medication. The study's data were gathered by searching several review articles and research papers from a variety of sources, including Elsevier, PubMed, Research Gate, Journal of Pharmaceutical Science, etc., from the year 1985 to 2021. Parkinson's disease is a neurodegenerative disease caused by a variety of complex processes. It is responsible not just for motor symptoms, but also for a variety of behavioral symptoms that can arise as a result of the disease and/or medication.

Conclusion

Only symptomatic drugs are available; thus, finding treatments that directly address the disease mechanisms causing Parkinson’s disease is essential. To alleviate the disease's burden on patients and their families, better treatments for the neuropsychiatric repercussions of Parkinson's disease are required.

Graphical Abstract

A comparative study between olive oil and corn oil on oxidative metabolism

Fats are an important part of diet, but not all lipids have the same structure and chemical properties. Unsaturated fatty acids have one or more double bonds in their structure and can be monounsaturated or polyunsaturated, respectively. Most vegetable oils, such as olive oil and corn oil, contain significant amounts of these fatty acids. The presence of double bonds in the molecule of a fatty acid constitutes vulnerable sites for oxidation reactions generating lipid peroxides, potentially toxic compounds that can cause cellular damage. In response to this oxidative damage, aerobic organisms have intracellular enzymatic antioxidant defense mechanisms. The aim of the present investigation was to study comparatively the effects of control liquid diets, of a defined composition, containing olive oil or corn oil as a lipid source respectively of monounsaturated and polyunsaturated fatty acids, on the oxidative metabolism of rats. Rats were divided into three groups which received a control animal feed diet (A.F.), olive oil liquid diet (O.O) and corn oil liquid diet (C.O) for 30 days. It was observed that the activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), increased in the liver and white fat tissue of rats fed with olive oil when compared to the corn oil group. However, in brown fat tissue and blood cells, the enzyme activities showed a tendency to decrease in the olive oil group. In addition, the effect of olive oil and corn oil on several glucose metabolism parameters (pyruvate, lactate, LDH, acetoacetate and beta-hydroxybutyrate) showed that corn oil impairs to a greater extent the cellular metabolism. All these results helped in concluding that some body tissues are more adversely affected than others by the administration of corn oil or olive oil, and their antioxidant defenses and cellular metabolism respond differently too.

Neuroprotective potential of curcuminoids in modulating Alzheimer's Disease via multiple signaling pathways

Alzheimer's disease (AD) is a progressive and frequent neurodegenerative disease of elderly people. In the 21st century, owing to the increasing prevalence of AD, there is a crucial need for finding better and effective pharmacotherapeutic approaches. This review article demonstrated the various sources and possible metabolic pathways of curcuminoids obtained from Curcuma longa herb, to prevent and treat AD but the information related to the metabolic fate of curcuminoids is deficient. Different in vitro and in vivo research studies demonstrating the mechanisms by which curcuminoids attenuated AD have been summarized. Administration of curcuminoids has been indicated to inhibit hyperphosphorylation of tau protein, deposition, and oligomerization of amyloid beta plaques in several AD models. Curcuminoids also chelate metals and form complexes, have antioxidant properties, mediates neuroinflammatory signaling pathways by modifying microglial cells activity, inhibit acetylcholinesterase activities and also modulates other associated signaling pathways including insulin signaling pathways and heme-oxygenase pathway. Briefly curcuminoids exhibit the capability to be more productive and efficacious compared to many recent treatments due to their antioxidant, delayed neuron degeneration and anti-inflammatory potential. Although their effectiveness as a curative agent is considered to be reduced due to their low bioavailability, If the issue of curcuminoids' low bioavailability is resolved then curcuminoid-based medications are hopefully on the horizon against AD.

The Role of Mitochondrial Genes in Neurodegenerative Disorders

Mitochondrial disorders are clinically heterogeneous, resulting from nuclear gene and mitochondrial mutations that disturb the mitochondrial functions and dynamics. There is a lack of evidence linking mtDNA mutations to neurodegenerative disorders, mainly due to the absence of noticeable neuropathological lesions in postmortem samples. This review describes various gene mutations in Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, multiple sclerosis, and stroke. These abnormalities, including PINK1, Parkin, and SOD1 mutations, seem to reveal mitochondrial dysfunctions due to either mtDNA mutation or deletion, the mechanism of which remains unclear in depth.

Brain Metabolic Alterations in Alzheimer's Disease

The brain is one of the most energy-consuming organs in the body. Satisfying such energy demand requires compartmentalized, cell-specific metabolic processes, known to be complementary and intimately coupled. Thus, the brain relies on thoroughly orchestrated energy-obtaining agents, processes and molecular features, such as the neurovascular unit, the astrocyte-neuron metabolic coupling, and the cellular distribution of energy substrate transporters. Importantly, early features of the aging process are determined by the progressive perturbation of certain processes responsible for adequate brain energy supply, resulting in brain hypometabolism. These age-related brain energy alterations are further worsened during the prodromal stages of neurodegenerative diseases, namely Alzheimer's disease (AD), preceding the onset of clinical symptoms, and are anatomically and functionally associated with the loss of cognitive abilities. Here, we focus on concrete neuroenergetic features such as the brain's fueling by glucose and lactate, the transporters and vascular system guaranteeing its supply, and the metabolic interactions between astrocytes and neurons, and on its neurodegenerative-related disruption. We sought to review the principles underlying the metabolic dimension of healthy and AD brains, and suggest that the integration of these concepts in the preventive, diagnostic and treatment strategies for AD is key to improving the precision of these interventions.

Evaluation of Blood-Brain-Barrier Permeability, Neurotoxicity, and Potential Cognitive Impairment by Pseudomonas aeruginosa’s Virulence Factor Pyocyanin

Pyocyanin (PCN) is a redox-active secondary metabolite produced by Pseudomonas aeruginosa as its primary virulence factor. Several studies have reported the cytotoxic potential of PCN and its role during infection establishment and progression. Considering its ability to diffuse through biological membranes, it is hypothesized that PCN can gain entry into the brain and induce oxidative stress across the blood-brain barrier (BBB), ultimately contributing towards reactive oxygen species (ROS) mediated neurodegeneration. Potential roles of PCN in the central nervous system (CNS) have never been evaluated, hence the study aimed to evaluate PCN's probable penetration into CNS through blood-brain barrier (BBB) using both in silico and in vivo (Balb/c mice) approaches and the impact of ROS generation via commonly used tests: Morris water maze test, novel object recognition, elevated plus maze test, and tail suspension test. Furthermore, evidence for ROS generation in the brain was assessed using glutathione S-transferase assay. PCN demonstrated BBB permeability albeit in minute quantities. A significant hike was observed in ROS generation (P < 0.0001) along with changes in behavior indicating PCN permeability across BBB and potentially affecting cognitive functions. This is the first study exploring the potential role of PCN in influencing the cognitive functions of test animals.

Saturation Transfer MRI for Detection of Metabolic and Microstructural Impairments Underlying Neurodegeneration in Alzheimer's Disease

Alzheimer's disease (AD) is one of the most common causes of dementia and difficult to study as the pool of subjects is highly heterogeneous. Saturation transfer (ST) magnetic resonance imaging (MRI) methods are quantitative modalities with potential for non-invasive identification and tracking of various aspects of AD pathology. In this review we cover ST-MRI studies in both humans and animal models of AD over the past 20 years. A number of magnetization transfer (MT) studies have shown promising results in human brain. Increased computing power enables more quantitative MT studies, while access to higher magnetic fields improves the specificity of chemical exchange saturation transfer (CEST) techniques. While much work remains to be done, results so far are very encouraging. MT is sensitive to patterns of AD-related pathological changes, improving differential diagnosis, and CEST is sensitive to particular pathological processes which could greatly assist in the development and monitoring of therapeutic treatments of this currently incurable disease.

Characteristics of Neural Network Changes in Normal Aging and Early Dementia

To understand the mechanisms underlying preserved and impaired cognitive function in healthy aging and dementia, respectively, the spatial relationships of brain networks and mechanisms of their resilience should be understood. The hub regions of the brain, such as the multisensory integration and default mode networks, are critical for within- and between-network communication, remain well-preserved during aging, and play an essential role in compensatory processes. On the other hand, these brain hubs are the preferred sites for lesions in neurodegenerative dementias, such as Alzheimer's disease. Disrupted primary information processing networks, such as the auditory, visual, and sensorimotor networks, may lead to overactivity of the multisensory integration networks and accumulation of pathological proteins that cause dementia. At the cellular level, the brain hub regions contain many synapses and require a large amount of energy. These regions are rich in ATP-related gene expression and had high glucose metabolism as demonstrated on positron emission tomography (PET). Importantly, the number and function of mitochondria, which are the center of ATP production, decline by about 8% every 10 years. Dementia patients often have dysfunction of the ubiquitin-proteasome and autophagy-lysosome systems, which require large amounts of ATP. If there is low energy supply but the demand is high, the risk of disease can be high. Imbalance between energy supply and demand may cause accumulation of pathological proteins and play an important role in the development of dementia. This energy imbalance may explain why brain hub regions are vulnerable to damage in different dementias. Here, we review (1) the characteristics of gray matter network, white matter network, and resting state functional network changes related to resilience in healthy aging, (2) the mode of resting state functional network disruption in neurodegenerative dementia, and (3) the cellular mechanisms associated with the disruption.

Molecular Strategies to Target Protein Aggregation in Huntington's Disease

Huntington's disease (HD) is a neurodegenerative disorder caused by the aggregation of the mutant huntingtin (mHTT) protein in nerve cells. mHTT self-aggregates to form soluble oligomers and insoluble fibrils, which interfere in a number of key cellular functions. This leads to cell quiescence and ultimately cell death. There are currently still no treatments available for HD, but approaches targeting the HTT levels offer systematic, mechanism-driven routes towards curing HD and other neurodegenerative diseases. This review summarizes the current state of knowledge of the mRNA targeting approaches such as antisense oligonucleotides and RNAi system; and the novel methods targeting mHTT and aggregates for degradation via the ubiquitin proteasome or the autophagy-lysosomal systems. These methods include the proteolysis-targeting chimera, Trim-Away, autophagosome-tethering compound, autophagy-targeting chimera, lysosome-targeting chimera and approach targeting mHTT for chaperone-mediated autophagy. These molecular strategies provide a knowledge-based approach to target HD and other neurodegenerative diseases at the origin.