Immortalized Parkinson's disease lymphocytes have enhanced mitochondrial respiratory activity

Mitochondrial Dysfunction in Sporadic Amyotrophic Lateral Sclerosis Patients: Insights from High-Resolution Respirometry

Amyotrophic lateral sclerosis is a severe neurodegenerative disease whose exact cause is still unclear. Currently, research attention is turning to the mitochondrion as a critical organelle of energy metabolism. Current knowledge is sufficient to confirm the involvement of the mitochondria in the pathophysiology of the disease, since the mitochondria are involved in many processes in the cell; however, the exact mechanism of involvement is still unclear. We used peripheral blood mononuclear cells isolated from whole fresh blood from patients with amyotrophic lateral sclerosis for measurement and matched an age- and sex-matched set of healthy subjects. The group of patients consisted of patients examined and diagnosed at the neurological clinic of the University Hospital Martin. The set of controls consisted of healthy individuals who were actively searched, and controls were selected on the basis of age and sex. The group consisted of 26 patients with sporadic forms of ALS (13 women, 13 men), diagnosed based on the definitive criteria of El Escorial. The average age of patients was 54 years, and the average age of healthy controls was 56 years. We used a high-resolution O2K respirometry method, Oxygraph-2k, to measure mitochondrial respiration. Basal respiration was lower in patients by 29.48%, pyruvate-stimulated respiration (respiratory chain complex I) was lower by 29.26%, and maximal respiratory capacity was lower by 28.15%. The decrease in succinate-stimulated respiration (respiratory chain complex II) was 26.91%. Our data confirm changes in mitochondrial respiration in ALS patients, manifested by the reduced function of complex I and complex II of the respiratory chain. These defects are severe enough to confirm this disease's hypothesized mitochondrial damage. Therefore, research interest in the future should be directed towards a deeper understanding of the involvement of mitochondria and respiratory complexes in the pathophysiology of the disease. This understanding could develop new biomarkers in diagnostics and subsequent therapeutic interventions.

Plate-Based Assays for the Characterization of Mitochondrial and Cellular Phenotypes

The mitochondria are essential to eukaryotic life, acting as key drivers of energy generation while also being involved in the regulation of many cellular processes including apoptosis, cell proliferation, calcium homeostasis, and metabolism. Mitochondrial diseases which disrupt these processes lead to a diverse range of pathologies and lack consistency in symptom presentation. In disease, mitochondrial activity and energy homeostasis can be adapted to cellular requirements, and studies using Dictyostelium and human lymphoblastoid cell lines have shown that such changes can be facilitated by the key cellular and energy regulators, TORC1 and AMPK. Fluorescence-based assays are increasingly utilized to measure mitochondrial and cell signalling function in mitochondrial disease research. Here, we describe a streamlined method for the simultaneous measurement of mitochondrial mass, membrane potential, and reactive oxygen species production using MitoTracker Green™ FM, MitoTracker Red™ CMXRos, and DCFH-DA probes. This protocol has been adapted for both Dictyostelium and human lymphoblastoid cell lines. We also describe a method for assessing TORC1 and AMPK activity simultaneously in lymphoblastoid cells. These techniques allow for the characterization of mitochondrial defects in a rapid and easy to implement manner.

Molecular phenotypes of mitochondrial dysfunction in clinically non-manifesting heterozygous PRKN variant carriers

Homozygous or compound heterozygous (biallelic) variants in PRKN are causal for PD with highly penetrant symptom expression, while the much more common heterozygous variants may predispose to PD with highly reduced penetrance, through altered mitochondrial function. In the presence of pathogenic heterozygous variants, it is therefore important to test for mitochondrial alteration in cells derived from variant carriers to establish potential presymptomatic molecular markers. We generated lymphoblasts (LCLs) and human induced pluripotent stem cell (hiPSC)-derived neurons from non-manifesting heterozygous PRKN variant carriers and tested them for mitochondrial functionality. In LCLs, we detected hyperactive mitochondrial respiration, and, although milder compared to a biallelic PRKN-PD patient, hiPSC-derived neurons of non-manifesting heterozygous variant carriers also displayed several phenotypes of altered mitochondrial function. Overall, we identified molecular phenotypes that might be used to monitor heterozygous PRKN variant carriers during the prodromal phase. Such markers might also be useful to identify individuals at greater risk of eventual disease development and for testing potential mitochondrial function-based neuroprotective therapies before neurodegeneration advances.

Characterization of Mitochondrial Alterations in Aicardi-Goutières Patients Mutated in RNASEH2A and RNASEH2B Genes

Aicardi-Goutières syndrome (AGS) is a rare encephalopathy characterized by neurological and immunological features. Mitochondrial dysfunctions may lead to mitochondrial DNA (mtDNA) release and consequent immune system activation. We investigated the role of mitochondria and mtDNA in AGS pathogenesis by studying patients mutated in RNASEH2B and RNASEH2A genes. Lymphoblastoid cell lines (LCLs) from RNASEH2A- and RNASEH2B-mutated patients and healthy control were used. Transmission Electron Microscopy (TEM) and flow cytometry were used to assess morphological alterations, reactive oxygen species (ROS) production and mitochondrial membrane potential variations. Seahorse Analyzer was used to investigate metabolic alterations, and mtDNA oxidation and VDAC1 oligomerization were assessed by immunofluorescence. Western blot and RT-qPCR were used to quantify mtTFA protein and mtDNA release. Morphological alterations of mitochondria were observed in both mutated LCLs, and loss of physiological membrane potential was mainly identified in RNASEH2A LCLs. ROS production and 8-oxoGuanine levels were increased in RNASEH2B LCLs. Additionally, the VDAC1 signal was increased, suggesting a mitochondrial pore formation possibly determining mtDNA release. Indeed, higher cytoplasmic mtDNA levels were found in RNASEH2B LCLs. Metabolic alterations confirmed mitochondrial damage in both LCLs. Data highlighted mitochondrial alterations in AGS patients' LCLs suggesting a pivotal role in AGS pathogenesis.

Pattern of Mitochondrial Respiration in Peripheral Blood Cells of Patients with Parkinson's Disease

Mitochondria are central in the pathogenesis of Parkinson’s disease (PD), as they are involved in oxidative stress, synaptopathy, and other immunometabolic pathways. Accordingly, they are emerging as a potential neuroprotection target, although further human-based evidence is needed for therapeutic advancements. This study aims to shape the pattern of mitochondrial respiration in the blood leukocytes of PD patients in relation to both clinical features and the profile of cerebrospinal fluid (CSF) biomarkers of neurodegeneration. Mitochondrial respirometry on the peripheral blood mononucleate cells (PBMCs) of 16 PD patients and 14 controls was conducted using Seahorse Bioscience technology. Bioenergetic parameters were correlated either with standard clinical scores for motor and non-motor disturbances or with CSF levels of α-synuclein, amyloid-β peptides, and tau proteins. In PD, PBMC mitochondrial basal respiration was normal; maximal and spare respiratory capacities were both increased; and ATP production was higher, although not significantly. Maximal and spare respiratory capacity was directly correlated with disease duration, MDS-UPDRS part III and Hoehn and Yahr motor scores; spare respiratory capacity was correlated with the CSF amyloid-β-42 to amyloid-β-42/40 ratio. We provided preliminary evidence showing that mitochondrial respiratory activity increases in the PBMCs of PD patients, probably following the compensatory adaptations to disease progression, in contrast to the bases of the neuropathological substrate.

Integrative Profiling of Amyotrophic Lateral Sclerosis Lymphoblasts Identifies Unique Metabolic and Mitochondrial Disease Fingerprints

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease with a rapid progression and no effective treatment. Metabolic and mitochondrial alterations in peripheral tissues of ALS patients may present diagnostic and therapeutic interest. We aimed to identify mitochondrial fingerprints in lymphoblast from ALS patients harboring SOD1 mutations (mutSOD1) or with unidentified mutations (undSOD1), compared with age-/sex-matched controls. Three groups of lymphoblasts, from mutSOD1 or undSOD1 ALS patients and age-/sex-matched controls, were obtained from Coriell Biobank and divided into 3 age-/sex-matched cohorts. Mitochondria-associated metabolic pathways were analyzed using Seahorse MitoStress and ATP Rate assays, complemented with metabolic phenotype microarrays, metabolite levels, gene expression, and protein expression and activity. Pooled (all cohorts) and paired (intra-cohort) analyses were performed by using bioinformatic tools, and the features with higher information gain values were selected and used for principal component analysis and Naïve Bayes classification. Considering the group as a target, the features that contributed to better segregation of control, undSOD1, and mutSOD1 were found to be the protein levels of Tfam and glycolytic ATP production rate. Metabolic phenotypic profiles in lymphoblasts from ALS patients with mutSOD1 and undSOD1 revealed unique age-dependent different substrate oxidation profiles. For most parameters, different patterns of variation in experimental endpoints in lymphoblasts were found between cohorts, which may be due to the age or sex of the donor. In the present work, we investigated several metabolic and mitochondrial hallmarks in lymphoblasts from each donor, and although a high heterogeneity of results was found, we identified specific metabolic and mitochondrial fingerprints, especially protein levels of Tfam and glycolytic ATP production rate, that may have a diagnostic and therapeutic interest.

Dysregulated Gene Expression in Lymphoblasts from Parkinson’s Disease

Parkinson’s disease is the second largest neurodegenerative disease worldwide and is caused by a combination of genetics and environment. It is characterized by the death of neurons in the substantia nigra of the brain but is not solely a disease of the brain, as it affects multiple tissues and organs. Studying Parkinson’s disease in accessible tissues such as skin and blood has increased our understanding of the disease’s pathogenesis. Here, we used lymphoblast cell lines generated from Parkinson’s disease patient and healthy age- and sex-matched control groups and obtained their whole-cell transcriptomes and proteomes. Our analysis revealed, in both the transcriptomes and the proteomes of PD cells, a global downregulation of genes involved in protein synthesis, as well as the upregulation of immune processes and sphingolipid metabolism. In contrast, we discovered an uncoupling of mRNA and protein expression in processes associated with mitochondrial respiration in the form of a general downregulation in associated transcripts and an upregulation in proteins. Complex V was different to the other oxidative phosphorylation complexes in that the levels of its associated transcripts were also lower, but the levels of their encoded polypeptides were not elevated. This may suggest that further layers of regulation specific to Complex V are in play.

A Transcriptome Analysis of mRNAs and Long Non-Coding RNAs in Patients with Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder. The number of cases of PD is expected to double by 2030, representing a heavy burden on the healthcare system. Clinical symptoms include the progressive loss of dopaminergic neurons in the substantia nigra of the midbrain, which leads to striatal dopamine deficiency and, subsequently, causes motor dysfunction. Certainly, the study of the transcriptome of the various RNAs plays a crucial role in the study of this neurodegenerative disease. In fact, the aim of this study was to evaluate the transcriptome in a cohort of subjects with PD compared with a control cohort. In particular we focused on mRNAs and long non-coding RNAs (lncRNA), using the Illumina NextSeq 550 DX System. Differential expression analysis revealed 716 transcripts with padj ≤ 0.05; among these, 630 were mRNA (coding protein), lncRNA, and MT_tRNA. Ingenuity pathway analysis (IPA, Qiagen) was used to perform the functional and pathway analysis. The highest statistically significant pathways were: IL-15 signaling, B cell receptor signaling, systemic lupus erythematosus in B cell signaling pathway, communication between innate and adaptive immune cells, and melatonin degradation II. Our findings further reinforce the important roles of mitochondria and lncRNA in PD and, in parallel, further support the concept of inverse comorbidity between PD and some cancers.

A Transcriptome Analysis of mRNAs and Long Non-Coding RNAs in Patients with Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder. The number of cases of PD is expected to double by 2030, representing a heavy burden on the healthcare system. Clinical symptoms include the progressive loss of dopaminergic neurons in the substantia nigra of the midbrain, which leads to striatal dopamine deficiency and, subsequently, causes motor dysfunction. Certainly, the study of the transcriptome of the various RNAs plays a crucial role in the study of this neurodegenerative disease. In fact, the aim of this study was to evaluate the transcriptome in a cohort of subjects with PD compared with a control cohort. In particular we focused on mRNAs and long non-coding RNAs (lncRNA), using the Illumina NextSeq 550 DX System. Differential expression analysis revealed 716 transcripts with padj ≤ 0.05; among these, 630 were mRNA (coding protein), lncRNA, and MT_tRNA. Ingenuity pathway analysis (IPA, Qiagen) was used to perform the functional and pathway analysis. The highest statistically significant pathways were: IL-15 signaling, B cell receptor signaling, systemic lupus erythematosus in B cell signaling pathway, communication between innate and adaptive immune cells, and melatonin degradation II. Our findings further reinforce the important roles of mitochondria and lncRNA in PD and, in parallel, further support the concept of inverse comorbidity between PD and some cancers.

Dictyostelium discoideum: A Model System for Neurological Disorders

Background: The incidence of neurological disorders is increasing due to population growth and extended life expectancy. Despite advances in the understanding of these disorders, curative strategies for treatment have not yet eventuated. In part, this is due to the complexities of the disorders and a lack of identification of their specific underlying pathologies. Dictyostelium discoideum has provided a useful, simple model to aid in unraveling the complex pathological characteristics of neurological disorders including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, neuronal ceroid lipofuscinoses and lissencephaly. In addition, D. discoideum has proven to be an innovative model for pharmaceutical research in the neurological field. Scope of review: This review describes the contributions of D. discoideum in the field of neurological research. The continued exploration of proteins implicated in neurological disorders in D. discoideum may elucidate their pathological roles and fast-track curative therapeutics.

A Conserved Role for LRRK2 and Roco Proteins in the Regulation of Mitochondrial Activity

Parkinson's Disease (PD) is the second most common neurodegenerative disease world-wide. Mutations in the multidomain protein Leucine Rich Repeat Kinase 2 (LRRK2) are the most frequent cause of hereditary PD. Furthermore, recent data suggest that independent of mutations, increased kinase activity of LRRK2 plays an essential role in PD pathogenesis. Isolated mitochondria of tissue samples from PD patients carrying LRRK2 mutations display a significant impairment of mitochondrial function. However, due to the complexity of the mitochondrial signaling network, the role of LRRK2 in mitochondrial metabolism is still not well understood. Previously we have shown that D. discoideum Roco4 is a suitable model to study the activation mechanism of LRRK2 in vivo. To get more insight in the LRRK2 pathways regulating mitochondrial activity we used this Roco4 model system in combination with murine RAW macrophages. Here we show that both Dictyostelium roco4 knockout and cells expressing PD-mutants show behavioral and developmental phenotypes that are characteristic for mitochondrial impairment. Mitochondrial activity measured by Seahorse technology revealed that the basal respiration of D. discoideum roco4- cells is significantly increased compared to the WT strain, while the basal and maximal respiration values of cells overexpressing Roco4 are reduced compared to the WT strain. Consistently, LRRK2 KO RAW 264.7 cells exhibit higher maximal mitochondrial respiration activity compared to the LRRK2 parental RAW264.7 cells. Measurement on isolated mitochondria from LRRK2 KO and parental RAW 264.7 cells revealed no difference in activity compared to the parental cells. Furthermore, neither D. discoideum roco4- nor LRRK2 KO RAW 264.7 showed a difference in either the number or the morphology of mitochondria compared to their respective parental strains. This suggests that the observed effects on the mitochondrial respiratory in cells are indirect and that LRRK2/Roco proteins most likely require other cytosolic cofactors to elicit mitochondrial effects.

Relationships between Mitochondrial Function, AMPK, and TORC1 Signaling in Lymphoblasts with Premutation Alleles of the FMR1 Gene

The X-linked FMR1 gene contains a non-coding trinucleotide repeat in its 5' region that, in normal, healthy individuals contains 20-44 copies. Large expansions of this region (>200 copies) cause fragile X syndrome (FXS), but expansions of 55-199 copies (referred to as premutation alleles) predispose carriers to a neurodegenerative disease called fragile X-associated tremor/ataxia syndrome (FXTAS). The cytopathological mechanisms underlying FXTAS are poorly understood, but abnormalities in mitochondrial function are believed to play a role. We previously reported that lymphoblastoid cell lines (LCLs, or lymphoblasts) of premutation carriers have elevated mitochondrial respiratory activities. In the carriers, especially those not clinically affected with FXTAS, AMP-activated protein kinase (AMPK) activity was shown to be elevated. In the FXTAS patients, however, it was negatively correlated with brain white matter lesions, suggesting a protective role in the molecular mechanisms. Here, we report an enlarged and extended study of mitochondrial function and associated cellular stress-signaling pathways in lymphoblasts isolated from male and female premutation carriers, regardless of their clinical status, and healthy controls. The results confirmed the elevation of AMPK and mitochondrial respiratory activities and reduction in reactive O2 species (ROS) levels in premutation cells and revealed for the first time that target of rapamycin complex I (TORC1) activities are reduced. Extensive correlation, multiple regression, and principal components analysis revealed the best fitting statistical explanations of these changes in terms of the other variables measured. These suggested which variables might be the most "proximal" regulators of the others in the extensive network of known causal interactions amongst the measured parameters of mitochondrial function and cellular stress signaling. In the resulting model, the premutation alleles activate AMPK and inhibit both TORC1 and ROS production, the reduced TORC1 activity contributes to activation of AMPK and of nonmitochondrial metabolism, and the higher AMPK activity results in elevated catabolic metabolism, mitochondrial respiration, and ATP steady state levels. In addition, the results suggest a separate CGG repeat number-dependent elevation of TORC1 activity that is insufficient to overcome the inhibition of TORC1 in premutation cells but may presage the previously reported activation of TORC1 in FXS cells.

Utilization of Human Samples for Assessment of Mitochondrial Bioenergetics: Gold Standards, Limitations, and Future Perspectives

Mitochondrial bioenergetic function is a central component of cellular metabolism in health and disease. Mitochondrial oxidative phosphorylation is critical for maintaining energetic homeostasis, and impairment of mitochondrial function underlies the development and progression of metabolic diseases and aging. However, measurement of mitochondrial bioenergetic function can be challenging in human samples due to limitations in the size of the collected sample. Furthermore, the collection of samples from human cohorts is often spread over multiple days and locations, which makes immediate sample processing and bioenergetics analysis challenging. Therefore, sample selection and choice of tests should be carefully considered. Basic research, clinical trials, and mitochondrial disease diagnosis rely primarily on skeletal muscle samples. However, obtaining skeletal muscle biopsies requires an appropriate clinical setting and specialized personnel, making skeletal muscle a less suitable tissue for certain research studies. Circulating white blood cells and platelets offer a promising primary tissue alternative to biopsies for the study of mitochondrial bioenergetics. Recent advances in frozen respirometry protocols combined with the utilization of minimally invasive and non-invasive samples may provide promise for future mitochondrial research studies in humans. Here we review the human samples commonly used for the measurement of mitochondrial bioenergetics with a focus on the advantages and limitations of each sample.

Interactions and Cytotoxicity of Human Neurodegeneration- Associated Proteins Tau and α-Synuclein in the Simple Model Dictyostelium discoideum

The abnormal accumulation of the tau protein into aggregates is a hallmark in neurodegenerative diseases collectively known as tauopathies. In normal conditions, tau binds off and on microtubules aiding in their assembly and stability dependent on the phosphorylation state of the protein. In disease-affected neurons, hyperphosphorylation leads to the accumulation of the tau protein into aggregates, mainly neurofibrillary tangles (NFT) which have been seen to colocalise with other protein aggregates in neurodegeneration. One such protein is α-synuclein, the main constituent of Lewy bodies (LB), a hallmark of Parkinson's disease (PD). In many neurodegenerative diseases, including PD, the colocalisation of tau and α-synuclein has been observed, suggesting possible interactions between the two proteins. To explore the cytotoxicity and interactions between these two proteins, we expressed full length human tau and α-synuclein in Dictyostelium discoideum alone, and in combination. We show that tau is phosphorylated in D. discoideum and colocalises closely (within 40 nm) with tubulin throughout the cytoplasm of the cell as well as with α-synuclein at the cortex. Expressing wild type α-synuclein alone caused inhibited growth on bacterial lawns, phagocytosis and intracellular Legionella proliferation rates, but activated mitochondrial respiration and non-mitochondrial oxygen consumption. The expression of tau alone impaired multicellular morphogenesis, axenic growth and phototaxis, while enhancing intracellular Legionella proliferation. Direct respirometric assays showed that tau impairs mitochondrial ATP synthesis and increased the "proton leak," while having no impact on respiratory complex I or II function. In most cases depending on the phenotype, the coexpression of tau and α-synuclein exacerbated (phototaxis, fruiting body morphology), or reversed (phagocytosis, growth on plates, mitochondrial respiratory function, Legionella proliferation) the defects caused by either tau or α-synuclein expressed individually. Proteomics data revealed distinct patterns of dysregulation in strains ectopically expressing tau or α-synuclein or both, but down regulation of expression of cytoskeletal proteins was apparent in all three groups and most evident in the strain expressing both proteins. These results indicate that tau and α-synuclein exhibit different but overlapping patterns of intracellular localisation, that they individually exert distinct but overlapping patterns of cytotoxic effects and that they interact, probably physically in the cell cortex as well as directly or indirectly in affecting some phenotypes. The results show the efficacy of using D. discoideum as a model to study the interaction of proteins involved in neurodegeneration.

Dysregulation of mitochondrial and proteolysosomal genes in Parkinson's disease myeloid cells

An increasing number of identified Parkinson's disease (PD) risk loci contain genes highly expressed in innate immune cells, yet their role in pathology is not understood. We hypothesize that PD susceptibility genes modulate disease risk by influencing gene expression within immune cells. To address this, we have generated transcriptomic profiles of monocytes from 230 individuals with sporadic PD and healthy subjects. We observed a dysregulation of mitochondrial and proteasomal pathways. We also generated transcriptomic profiles of primary microglia from brains of 55 subjects and observed discordant transcriptomic signatures of mitochondrial genes in PD monocytes and microglia. We further identified 17 PD susceptibility genes whose expression, relative to each risk allele, is altered in monocytes. These findings reveal widespread transcriptomic alterations in PD monocytes, with some being distinct from microglia, and facilitate efforts to understand the roles of myeloid cells in PD as well as the development of biomarkers.

The Parkinson's Disease-Associated Protein DJ-1 Protects Dictyostelium Cells from AMPK-Dependent Outcomes of Oxidative Stress

Mitochondrial dysfunction has been implicated in the pathology of Parkinson’s disease (PD). In Dictyostelium discoideum, strains with mitochondrial dysfunction present consistent, AMPK-dependent phenotypes. This provides an opportunity to investigate if the loss of function of specific PD-associated genes produces cellular pathology by causing mitochondrial dysfunction with AMPK-mediated consequences. DJ-1 is a PD-associated, cytosolic protein with a conserved oxidizable cysteine residue that is important for the protein’s ability to protect cells from the pathological consequences of oxidative stress. Dictyostelium DJ-1 (encoded by the gene deeJ) is located in the cytosol from where it indirectly inhibits mitochondrial respiration and also exerts a positive, nonmitochondrial role in endocytosis (particularly phagocytosis). Its loss in unstressed cells impairs endocytosis and causes correspondingly slower growth, while also stimulating mitochondrial respiration. We report here that oxidative stress in Dictyostelium cells inhibits mitochondrial respiration and impairs phagocytosis in an AMPK-dependent manner. This adds to the separate impairment of phagocytosis caused by DJ-1 knockdown. Oxidative stress also combines with DJ-1 loss in an AMPK-dependent manner to impair or exacerbate defects in phototaxis, morphogenesis and growth. It thereby phenocopies mitochondrial dysfunction. These results support a model in which the oxidized but not the reduced form of DJ-1 inhibits AMPK in the cytosol, thereby protecting cells from the adverse consequences of oxidative stress, mitochondrial dysfunction and the resulting AMPK hyperactivity.

Altered Transcriptional Profile of Mitochondrial DNA-Encoded OXPHOS Subunits, Mitochondria Quality Control Genes, and Intracellular ATP Levels in Blood Samples of Patients with Parkinson's Disease

Mitochondrial dysfunctions are significant contributors to neurodegeneration. One result or a cause of mitochondrial dysfunction might be the disruption of mtDNA transcription. Limited data indicated an altered expression of mtDNA encoded transcripts in Alzheimer's disease (AD) or Parkinson's disease (PD). The number of mitochondria is high in cells with a high energy demand, such as muscle or nerve cells. AD or PD involves increased risk of cardiomyopathy, suggesting that mitochondrial dysfunction might be systemic. If it is systemic, we should observe it in different cell types. Given that, we wanted to investigate any disruption in the regulation of mtDNA encoded gene expression in addition to PINK1, PARKIN, and ATP levels in peripheral blood samples of PD cases who are affected by a neurodegenerative disorder that is very well known by its mitochondrial aspects. Our results showed for the first time that: 1) age of onset > 50 PD sporadic (PDS) cases: mtDNA transcription and quality control genes were affected; 2) age of onset <50 PDS cases: only mtDNA transcription was affected; and 3) PD cases with familial background: only quality control genes were affected. mtDNA copy number was not a confounder. Intracellular ATP levels of PD case subgroups were significantly higher than those of healthy subjects. We suggest that a systemic dysregulation of transcription of mtDNA or mitochondrial quality control genes might result in the development of a sporadic form of the disease. Additionally, ATP elevation might be an independent compensatory and response mechanism. Hyperactive cells in AD and PD require further investigation.

Lymphoblastoid Cell Lines as Models to Study Mitochondrial Function in Neurological Disorders

Neurological disorders, including neurodegenerative diseases, are collectively a major cause of death and disability worldwide. Whilst the underlying disease mechanisms remain elusive, altered mitochondrial function has been clearly implicated and is a key area of study in these disorders. Studying mitochondrial function in these disorders is difficult due to the inaccessibility of brain tissue, which is the key tissue affected in these diseases. To overcome this issue, numerous cell models have been used, each providing unique benefits and limitations. Here, we focussed on the use of lymphoblastoid cell lines (LCLs) to study mitochondrial function in neurological disorders. LCLs have long been used as tools for genomic analyses, but here we described their use in functional studies specifically in regard to mitochondrial function. These models have enabled characterisation of the underlying mitochondrial defect, identification of altered signalling pathways and proteins, differences in mitochondrial function between subsets of particular disorders and identification of biomarkers of the disease. The examples provided here suggest that these cells will be useful for development of diagnostic tests (which in most cases do not exist), identification of drug targets and testing of pharmacological agents, and are a worthwhile model for studying mitochondrial function in neurological disorders.

Therapeutic Applications of Botulinum Neurotoxin for Autonomic Symptoms in Parkinson's Disease: An Updated Review

Parkinson's disease is the most common age-related motoric neurodegenerative disease. In addition to the cardinal motor symptoms of tremor, rigidity, bradykinesia, and postural instability, there are numerous non-motor symptoms as well. Among the non-motor symptoms, autonomic nervous system dysfunction is common. Autonomic symptoms associated with Parkinson's disease include sialorrhea, hyperhidrosis, gastrointestinal dysfunction, and urinary dysfunction. Botulinum neurotoxin has been shown to potentially improve these autonomic symptoms. In this review, the varied uses of botulinum neurotoxin for autonomic dysfunction in Parkinson's disease are discussed. This review also includes discussion of some additional indications for the use of botulinum neurotoxin in Parkinson's disease, including pain.

Dysregulated Provision of Oxidisable Substrates to the Mitochondria in ME/CFS Lymphoblasts

Although understanding of the biomedical basis of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is growing, the underlying pathological mechanisms remain uncertain. We recently reported a reduction in the proportion of basal oxygen consumption due to ATP synthesis by Complex V in ME/CFS patient-derived lymphoblast cell lines, suggesting mitochondrial respiratory inefficiency. This was accompanied by elevated respiratory capacity, elevated mammalian target of rapamycin complex 1 (mTORC1) signaling activity and elevated expression of enzymes involved in the TCA cycle, fatty acid β-oxidation and mitochondrial transport. These and other observations led us to hypothesise the dysregulation of pathways providing the mitochondria with oxidisable substrates. In our current study, we aimed to revisit this hypothesis by applying a combination of whole-cell transcriptomics, proteomics and energy stress signaling activity measures using subsets of up to 34 ME/CFS and 31 healthy control lymphoblast cell lines from our growing library. While levels of glycolytic enzymes were unchanged in accordance with our previous observations of unaltered glycolytic rates, the whole-cell proteomes of ME/CFS lymphoblasts contained elevated levels of enzymes involved in the TCA cycle (p = 1.03 × 10⁻⁴), the pentose phosphate pathway (p = 0.034, G6PD p = 5.5 × 10⁻⁴), mitochondrial fatty acid β-oxidation (p = 9.2 × 10⁻³), and degradation of amino acids including glutamine/glutamate (GLS p = 0.034, GLUD1 p = 0.048, GOT2 p = 0.026), branched-chain amino acids (BCKDHA p = 0.028, BCKDHB p = 0.031) and essential amino acids (FAH p = 0.036, GCDH p = 0.006). The activity of the major cellular energy stress sensor, AMPK, was elevated but the increase did not reach statistical significance. The results suggest that ME/CFS metabolism is dysregulated such that alternatives to glycolysis are more heavily utilised than in controls to provide the mitochondria with oxidisable substrates.

Cellular Bioenergetics and AMPK and TORC1 Signalling in Blood Lymphoblasts Are Biomarkers of Clinical Status in FMR1 Premutation Carriers

Fragile X Associated Tremor/Ataxia Syndrome (FXTAS) is a neurodegenerative disorder affecting carriers of premutation alleles (PM) of the X-linked FMR1 gene, which contain CGG repeat expansions of 55-200 range in a non-coding region. This late-onset disorder is characterised by the presence of tremor/ataxia and cognitive decline, associated with the white matter lesions throughout the brain, especially involving the middle cerebellar peduncles. Nearly half of older male and ~ 20% of female PM carriers develop FXTAS. While there is evidence for mitochondrial dysfunction in neural and some peripheral tissues from FXTAS patients (though less obvious in the non-FXTAS PM carriers), the results from peripheral blood mononuclear cells (PBMC) are still controversial. Motor, cognitive, and neuropsychiatric impairments were correlated with measures of mitochondrial and non-mitochondrial respiratory activity, AMPK, and TORC1 cellular stress-sensing protein kinases, and CGG repeat size, in a sample of adult FXTAS male and female carriers. Moreover, the levels of these cellular measures, all derived from Epstein- Barr virus (EBV)- transformed and easily accessible blood lymphoblasts, were compared between the FXTAS (N = 23) and non-FXTAS (n = 30) subgroups, and with baseline data from 33 healthy non-carriers. A significant hyperactivity of cellular bioenergetics components as compared with the baseline data, more marked in the non-FXTAS PMs, was negatively correlated with repeat numbers at the lower end of the CGG-PM distribution. Significant associations of these components with motor impairment measures, including tremor-ataxia and parkinsonism, and neuropsychiatric changes, were prevalent in the FXTAS subgroup. Moreover, a striking elevation of AMPK activity, and a decrease in TORC1 levels, especially in the non-FXTAS carriers, were related to the size of CGG expansion. The bioenergetics changes in blood lymphoblasts are biomarkers of the clinical status of FMR1 carriers. The relationship between these changes and neurological involvement in the affected carriers suggests that brain bioenergetic alterations are reflected in this peripheral tissue. A possible neuroprotective role of stress sensing kinase, AMPK, in PM carriers, should be addressed in future longitudinal studies. A decreased level of TORC1-the mechanistic target of the rapamycin complex, suggests a possible future approach to therapy in FXTAS.

Cytotoxicity and Mitochondrial Dysregulation Caused by α-Synuclein in Dictyostelium discoideum

Alpha synuclein has been linked to both sporadic and familial forms of Parkinson's disease (PD) and is the most abundant protein in Lewy bodies a hallmark of Parkinson's disease. The function of this protein and the molecular mechanisms underlying its toxicity are still unclear, but many studies have suggested that the mechanism of α-synuclein toxicity involves alterations to mitochondrial function. Here we expressed human α-synuclein and two PD-causing α-synuclein mutant proteins (with a point mutation, A53T, and a C-terminal 20 amino acid truncation) in the eukaryotic model Dictyostelium discoideum. Mitochondrial disease has been well studied in D. discoideum and, unlike in mammals, mitochondrial dysfunction results in a clear set of defective phenotypes. These defective phenotypes are caused by the chronic hyperactivation of the cellular energy sensor, AMP-activated protein kinase (AMPK). Expression of α-synuclein wild type and mutant forms was toxic to the cells and mitochondrial function was dysregulated. Some but not all of the defective phenotypes could be rescued by down regulation of AMPK revealing both AMPK-dependent and -independent mechanisms. Importantly, we also show that the C-terminus of α-synuclein is required and sufficient for the localisation of the protein to the cell cortex in D. discoideum.

Recent Advances: Molecular Mechanism of RNA Oxidation and Its Role in Various Diseases

Compared with the research on DNA damage, there are fewer studies on RNA damage, and the damage mechanism remains mostly unknown. Recent studies have shown that RNA is more vulnerable to damage than DNA when the cells are exposed to endogenous and exogenous insults. RNA injury may participate in a variety of disease occurrence and development. RNA not only has important catalytic functions and other housekeeping functions, it also plays a decisive role in the translation of genetic information and protein biosynthesis. Various kinds of stressors, such as ultraviolet, reactive oxygen species and nitrogen, can cause damage to RNA. It may involve in the development and progression of diseases. In this review, we focused on the relationship between the RNA damage and disease as well as the research progress on the mechanism of RNA damage, which is of great significance for the pathogenesis, diagnosis, and treatment of related diseases.

Genetic networks in Parkinson's and Alzheimer's disease

Parkinson’s disease (PD) and Alzheimer’s disease (AD) are the most common neurodegenerative diseases and there is increasing evidence that they share common physiological and pathological links. Here we have conducted the largest network analysis of PD and AD based on their gene expressions in blood to date. We identified modules that were not preserved between disease and healthy control (HC) networks, and important hub genes and transcription factors (TFs) in these modules. We highlighted that the PD module not preserved in HCs was associated with insulin resistance, and HDAC6 was identified as a hub gene in this module which may have the role of influencing tau phosphorylation and autophagic flux in neurodegenerative disease. The AD module associated with regulation of lipolysis in adipocytes and neuroactive ligand-receptor interaction was not preserved in healthy and mild cognitive impairment networks and the key hubs TRPC5 and BRAP identified as potential targets for therapeutic treatments of AD. Our study demonstrated that PD and AD share common disrupted genetics and identified novel pathways, hub genes and TFs that may be new areas for mechanistic study and important targets in both diseases.

Cell-Based Blood Biomarkers for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a devastating illness whose biomedical basis is now beginning to be elucidated. We reported previously that, after recovery from frozen storage, lymphocytes (peripheral blood mononuclear cells, PBMCs) from ME/CFS patients die faster in culture medium than those from healthy controls. We also found that lymphoblastoid cell lines (lymphoblasts) derived from these PBMCs exhibit multiple abnormalities in mitochondrial respiratory function and signalling activity by the cellular stress-sensing kinase Target Of Rapamycin Complex 1 (TORC1). These differences were correlated with disease severity, as measured by the Richardson and Lidbury weighted standing test. The clarity of the differences between these cells derived from ME/CFS patient blood and those from healthy controls suggested that they may provide useful biomarkers for ME/CFS. Here, we report a preliminary investigation into that possibility using a variety of analytical classification tools, including linear discriminant analysis, logistic regression and receiver operating characteristic (ROC) curve analysis. We found that results from three different tests—lymphocyte death rate, mitochondrial respiratory function and TORC1 activity—could each individually serve as a biomarker with better than 90% sensitivity but only modest specificity vís a vís healthy controls. However, in combination, they provided a cell-based biomarker with sensitivity and specificity approaching 100% in our sample. This level of sensitivity and specificity was almost equalled by a suggested protocol in which the frozen lymphocyte death rate was used as a highly sensitive test to triage positive samples to the more time consuming and expensive tests measuring lymphoblast respiratory function and TORC1 activity. This protocol provides a promising biomarker that could assist in more rapid and accurate diagnosis of ME/CFS.

An Isolated Complex V Inefficiency and Dysregulated Mitochondrial Function in Immortalized Lymphocytes from ME/CFS Patients

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is an enigmatic condition characterized by exacerbation of symptoms after exertion (post-exertional malaise or “PEM”), and by fatigue whose severity and associated requirement for rest are excessive and disproportionate to the fatigue-inducing activity. There is no definitive molecular marker or known underlying pathological mechanism for the condition. Increasing evidence for aberrant energy metabolism suggests a role for mitochondrial dysfunction in ME/CFS. Our objective was therefore to measure mitochondrial function and cellular stress sensing in actively metabolizing patient blood cells. We immortalized lymphoblasts isolated from 51 ME/CFS patients diagnosed according to the Canadian Consensus Criteria and an age- and gender-matched control group. Parameters of mitochondrial function and energy stress sensing were assessed by Seahorse extracellular flux analysis, proteomics, and an array of additional biochemical assays. As a proportion of the basal oxygen consumption rate (OCR), the rate of ATP synthesis by Complex V was significantly reduced in ME/CFS lymphoblasts, while significant elevations were observed in Complex I OCR, maximum OCR, spare respiratory capacity, nonmitochondrial OCR and “proton leak” as a proportion of the basal OCR. This was accompanied by a reduction of mitochondrial membrane potential, chronically hyperactivated TOR Complex I stress signaling and upregulated expression of mitochondrial respiratory complexes, fatty acid transporters, and enzymes of the β-oxidation and TCA cycles. By contrast, mitochondrial mass and genome copy number, as well as glycolytic rates and steady state ATP levels were unchanged. Our results suggest a model in which ME/CFS lymphoblasts have a Complex V defect accompanied by compensatory upregulation of their respiratory capacity that includes the mitochondrial respiratory complexes, membrane transporters and enzymes involved in fatty acid β-oxidation. This homeostatically returns ATP synthesis and steady state levels to “normal” in the resting cells, but may leave them unable to adequately respond to acute increases in energy demand as the relevant homeostatic pathways are already activated.

Misfolded α-synuclein causes hyperactive respiration without functional deficit in live neuroblastoma cells

The misfolding and aggregation of the largely disordered protein, α-synuclein, is a central pathogenic event that occurs in the synucleinopathies, a group of neurodegenerative disorders that includes Parkinson's disease. While there is a clear link between protein misfolding and neuronal vulnerability, the precise pathogenic mechanisms employed by disease-associated α-synuclein are unresolved. Here, we studied the pathogenicity of misfolded α-synuclein produced using the protein misfolding cyclic amplification (PMCA) assay. To do this, previous published methods were adapted to allow PMCA-induced protein fibrillization to occur under non-toxic conditions. Insight into potential intracellular targets of misfolded α-synuclein was obtained using an unbiased lipid screen of 15 biologically relevant lipids that identified cardiolipin (CA) as a potential binding partner for PMCA-generated misfolded α-synuclein. To investigate whether such an interaction can impact the properties of α-synuclein misfolding, protein fibrillization was carried out in the presence of the lipid. We show that CA both accelerates the rate of α-synuclein fibrillization and produces species that harbour enhanced resistance to proteolysis. Because CA is virtually exclusively expressed in the inner mitochondrial membrane, we then assessed the ability of these misfolded species to alter mitochondrial respiration in live non-transgenic SH-SY5Y neuroblastoma cells. Extensive analysis revealed that misfolded α-synuclein causes hyperactive mitochondrial respiration without causing any functional deficit. These data give strong support for the mitochondrion as a target for misfolded α-synuclein and reveal persistent, hyperactive respiration as a potential upstream pathogenic event associated with the synucleinopathies.This article has an associated First Person interview with the first author of the paper.

Aging, rather than Parkinson's disease, affects the responsiveness of PBMCs to the immunosuppression of bone marrow mesenchymal stem cells

Whether aging or Parkinson's disease (PD) affects the responses of peripheral blood mononuclear cells (PBMCs) to immunosuppression by bone marrow‑derived mesenchymal stem cell (BM‑MSCs) and which cytokines are more effective in inducing BM‑MSCs to be immunosuppressive remains to be elucidated. PBMCs were isolated from healthy young (age 26‑35), healthy middle‑aged (age 56‑60) and middle‑aged PD‑affected individuals. All the recruits were male. The mitogen‑stimulated PBMCs and proinflammatory cytokine‑pretreated BM‑MSCs were co‑cultured. The PBMC proliferation was measured using Cell Counting Kit‑8, while the cytokine secretion was assayed by cytometric bead array technology. The immunosuppressive ability of BM‑MSCs was confirmed in young healthy, middle‑aged healthy and middle‑aged PD‑affected individuals. Among the three groups, the PBMC proliferation and cytokine secretion of the young healthy group were suppressed more significantly compared with those of the middle‑aged healthy and middle‑aged PD‑affected group. No significant differences were identified in the PBMC proliferation and cytokine secretion between the patients with PD and the middle‑aged healthy subjects. Interferon (IFN)‑γ synergized with tumor necrosis factor (TNF)‑α, interleukin (IL)‑1α or IL‑1β was more effective than either one alone, and the combinations of IFN‑γ + IL‑1α and IFN‑γ + IL‑1β were more effective than IFN‑γ + TNF‑α in inducing BM‑MSCs to inhibit PBMC proliferation. The results of the present study suggested that aging, rather than PD, affects the response of PBMCs toward the suppression of BM‑MSC, at least in middle‑aged males. Patients with PD aged 56‑60 remain eligible for anti‑inflammatory BM‑MSC‑based therapy. Treatment of BM‑MSCs with IFN‑γ + IL‑1α or IFN‑γ + IL‑1β prior to transplantation may result in improved immunosuppressive effects.

The Spectrum of Neurological and White Matter Changes and Premutation Status Categories of Older Male Carriers of the FMR1 Alleles Are Linked to Genetic (CGG and FMR1 mRNA) and Cellular Stress (AMPK) Markers

The fragile X premutation (PM) allele contains a CGG expansion of 55-200 repeats in the FMR1 gene's promoter. Male PM carriers have an elevated risk of developing neurological and psychiatric changes, including an approximately 50% risk of the fragile X-associated tremor/ataxia syndrome (FXTAS). The aim of this study was to assess the relationships of regional white matter hyperintensities (wmhs) semi-quantitative scores, clinical status, motor (UPDRS, ICARS, Tremor) scales, and cognitive impairments, with FMR1-specific genetic changes, in a sample of 32 unselected male PM carriers aged 39-81 years. Half of these individuals were affected with FXTAS, while the non-FXTAS group comprised subcategories of non-affected individuals and individuals affected with non-syndromic changes. The dynamics of pathological processes at the cellular level relevant to the clinical status of PM carriers was investigated using the enzyme AMP-activated protein kinase (AMPK), which is a highly sensitive cellular stress-sensing alarm protein. This enzyme, as well as genetic markers - CGG repeat number and the levels of the FMR1 mRNA - were assessed in blood lymphoblasts. The results showed that the repeat distribution for FXTAS individuals peaked at 85-90 CGGs; non-FXTAS carriers were distributed within the lowest end of the PM repeat range, and non-syndromic carriers assumed an intermediate position. The size of the CGG expansion was significantly correlated, across all three categories, with infratentorial and total wmhs and with all motor scores, and the FMR1 mRNA levels with all the wmh scores, whilst AMPK activity showed considerable elevation in the non-FXTAS combined group, decreasing in the FXTAS group, proportionally to increasing severity of the wmhs and tremor/ataxia. We conclude that the size of the CGG expansion relates to the risk for FXTAS, to severity of infratentorial wmhs lesions, and to all three motor scale scores. FMR1 mRNA shows a strong association with the extent of wmhs, which is the most sensitive marker of the pathological process. However, the AMPK activity findings - suggestive of a role of this enzyme in the risk of FXTAS - need to be verified and expanded in future studies using larger samples and longitudinal assessment.

Exploring the Effect of Rotenone-A Known Inducer of Parkinson's Disease-On Mitochondrial Dynamics in Dictyostelium discoideum

Current treatments for Parkinson's disease (PD) only alleviate symptoms doing little to inhibit the onset and progression of the disease, thus we must research the mechanism of Parkinson's. Rotenone is a known inducer of parkinsonian conditions in rats; we use rotenone to induce parkinsonian cellular conditions in Dictyostelium discoideum. In our model we primarily focus on mitochondrial dynamics. We found that rotenone disrupts the actin and microtubule cytoskeleton but mitochondrial morphology remains intact. Rotenone stimulates mitochondrial velocity while inhibiting mitochondrial fusion, increases reactive oxygen species (ROS) but has no effect on ATP levels. Antioxidants have been shown to decrease some PD symptoms thus we added ascorbic acid to our rotenone treated cells. Ascorbic acid administration suggests that rotenone effects may be specific to the disruption of the cytoskeleton rather than the increase in ROS. Our results imply that D. discoideum may be a valid cellular PD model and that the rotenone induced velocity increase and loss of fusion could prevent mitochondria from effectively providing energy and other mitochondrial products in high demand areas. The combination of these defects in mitochondrial dynamics and increased ROS could result in degeneration of neurons in PD.

The Parkinson's disease-associated protein DJ-1 plays a positive nonmitochondrial role in endocytosis in Dictyostelium cells

The loss of function of DJ-1 caused by mutations in DJ1 causes a form of familial Parkinson's disease (PD). However, the role of DJ-1 in healthy and in PD cells is poorly understood. Even its subcellular localization in mammalian cells is uncertain, with both cytosolic and mitochondrial locations having been reported. We show here that DJ-1 is normally located in the cytoplasm in healthy Dictyostelium discoideum cells. With its unique life cycle, straightforward genotype-phenotype relationships, experimental accessibility and genetic tractability, D.discoideum offers an attractive model to investigate the roles of PD-associated genes. Furthermore, the study of mitochondrial biology, mitochondrial genome transcription and AMP-activated protein kinase-mediated cytopathologies in mitochondrial dysfunction have been well developed in this organism. Unlike mammalian systems, Dictyostelium mitochondrial dysfunction causes a reproducible and readily assayed array of aberrant phenotypes: defective phototaxis, impaired growth, normal rates of endocytosis and characteristic defects in multicellular morphogenesis. This makes it possible to study whether the underlying cytopathological mechanisms of familial PD involve mitochondrial dysfunction. DJ-1 has a single homologue in the Dictyostelium genome. By regulating the expression level of DJ-1 in D. discoideum, we show here that in unstressed cells, DJ-1 is required for normal rates of endocytic nutrient uptake (phagocytosis and, to a lesser extent, pinocytosis) and thus growth. Reduced expression of DJ-1 had no effect on phototaxis in the multicellular migratory ‘slug’ stage of the life cycle, but resulted in thickened stalks in the final fruiting bodies. This pattern of phenotypes is distinct from that observed in Dictyostelium to result from mitochondrial dyfunction. Direct measurement of mitochondrial respiratory function in intact cells revealed that DJ-1 knockdown stimulates whereas DJ-1 overexpression inhibits mitochondrial activity. Together, our results suggest positive roles for DJ-1 in endocytic pathways and loss-of-function cytopathologies that are not associated with impaired mitochondrial function.

Editor's choice: The Dictyostelium homologue of the Parkinson's disease-associated protein DJ-1 is located in the cytosol, and its loss causes cytopathological defects in endocytic and autophagic cell death pathways, but stimulates respiration by functionally normal mitochondrial respiratory complexes.

Metabolic Dysfunction in Parkinson's Disease: Bioenergetics, Redox Homeostasis and Central Carbon Metabolism

The loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and the accumulation of protein inclusions (Lewy bodies) are the pathological hallmarks of Parkinson's disease (PD). PD is triggered by genetic alterations, environmental/occupational exposures and aging. However, the exact molecular mechanisms linking these PD risk factors to neuronal dysfunction are still unclear. Alterations in redox homeostasis and bioenergetics (energy failure) are thought to be central components of neurodegeneration that contribute to the impairment of important homeostatic processes in dopaminergic cells such as protein quality control mechanisms, neurotransmitter release/metabolism, axonal transport of vesicles and cell survival. Importantly, both bioenergetics and redox homeostasis are coupled to neuro-glial central carbon metabolism. We and others have recently established a link between the alterations in central carbon metabolism induced by PD risk factors, redox homeostasis and bioenergetics and their contribution to the survival/death of dopaminergic cells. In this review, we focus on the link between metabolic dysfunction, energy failure and redox imbalance in PD, making an emphasis in the contribution of central carbon (glucose) metabolism. The evidence summarized here strongly supports the consideration of PD as a disorder of cell metabolism.

Neurodegenerative disease: models, mechanisms, and a new hope

Neurodegeneration is a feature of many debilitating, incurable diseases that are rapidly rising in prevalence, such as Parkinson's disease. There is an urgent need to develop new and more effective therapeutic strategies to combat these devastating diseases. Models - from cell-based systems, to unicellular organisms, to complex animals - have proven to be a useful tool to help the research community shed light on the mechanisms underlying neurodegenerative diseases, and these advances have now begun to provide promising therapeutic avenues. In this themed issue of Disease Models & Mechanisms, a special collection of articles focused on neurodegenerative diseases is introduced. The collection includes original research articles that provide new insights into the complex pathophysiology of such diseases, revealing candidate biomarkers or therapeutic targets. Some of the articles describe a new disease model that enables deeper exploration of key mechanisms. We also present a series of reviews that highlight some of the recent translational advances made in studies of neurodegenerative diseases. In this Editorial, we summarize the articles featured in this collection, emphasizing the impact that model-based studies have made in this exciting area of research.

A novel selective VPAC2 agonist peptide-conjugated chitosan modified selenium nanoparticles with enhanced anti-type 2 diabetes synergy effects

A novel neuroendocrine peptide, pituitary adenylate cyclase activating peptide (PACAP), was found to have an important role in carbohydrate or lipid metabolism and was susceptible to dipeptidyl peptidase IV degradation. It can not only mediate glucose-dependent insulin secretion and lower blood glucose by activating VPAC2 receptor, but also raise blood glucose by promoting glucagon production by VPAC1 receptor activation. Therefore, its therapeutic application is restricted by the exceedingly short-acting half-life and the stimulatory function for glycogenolysis. Herein, we generated novel peptide-conjugated selenium nanoparticles (SeNPs; named as SCD), comprising a 32-amino acid PACAP-derived peptide DBAYL that selectively binds to VPAC2, and chitosan-modified SeNPs (SeNPs-CTS, SC) as slow-release carrier. The circulating half-life of SCD is 14.12 h in mice, which is 168.4-and 7.1-fold longer than wild PACAP (~5 min) and DBAYL (~1.98 h), respectively. SCD (10 nmol/L) significantly promotes INS-1 cell proliferation, glucose uptake, insulin secretion, insulin receptor expression and also obviously reduces intracellular reactive oxygen species levels in H₂O₂-injured INS-1 cells. Furthermore, the biological effects of SCD are stronger than Exendin-4 (a clinically approved drug through its insulinotropic effect), DBAYL, SeNPs or SC. A single injection of SCD (20 nmol/kg) into db/db mice with type 2 diabetes leads to enhanced insulin secretion and sustained hypoglycemic effect, and the effectiveness and duration of SCD in enhancing insulin secretion and reducing blood glucose levels are much stronger than Exendin-4, SeNPs or SC. In db/db mice, chronic administration of SCD by daily injection for 12 weeks markedly improved glucose and lipid profiles, insulin sensitivity and the structures of pancreatic and adipose tissue. The results indicate that SC can play a role as a carrier for the slow release of bioactive peptides and SCD could be a hopeful therapeutic against type 2 diabetes through the synergy effects of DBAYL and SeNPs.