C9orf72 regulates energy homeostasis by stabilizing mitochondrial complex I assembly

Exploring the role of CD13 and inflammatory factors in radiation enteritis: insights from high-throughput proteomics and Mendelian randomization analysis

BACKGROUND

Radiation enteritis (RE) is an unavoidable complication during radiotherapy for pelvic malignancies, characterized by chronic inflammation, fibrosis, and vascular injury in the intestinal tissue. Currently, there is a lack of research that delves into the relationship between inflammatory factors and key proteins in RE.

METHODS

This study employed high-throughput proteomics to analyze intestinal tissues from RE rats and healthy controls, identifying differentially expressed key proteins. The degree of intestinal damage was validated through HE staining. Furthermore, five Mendelian randomization methods were used to analyze the causal relationship between 70 serum circulating inflammatory factors and CD13 levels. Sensitivity analyses, including heterogeneity tests, leave-one-out tests, and horizontal pleiotropy tests, were performed to ensure the robustness and reliability of the results.

RESULTS

CD13 was identified as a key differentially expressed protein, with its expression significantly upregulated in RE rats and positively correlated with disease severity. Bidirectional Mendelian randomization analysis revealed causal relationships between CD13 and four inflammatory factors: increased levels of CCL28 and EN-RAGE may promote the rise in CD13, while increased levels of TAM-binding protein may be associated with decreased CD13 levels. Additionally, higher CD13 levels were found to be associated with increased levels of interleukin-12. Sensitivity analyses indicated good consistency and reliability in terms of heterogeneity and pleiotropy for these exposure variables.

CONCLUSION

This study reveals the potential mechanistic role of CD13 in RE. Moreover, the identified CD13-associated inflammatory factors offer potential targets for the development of new prevention and treatment strategies, with significant clinical implications.

Protein kinases in neurodegenerative diseases: current understandings and implications for drug discovery

Neurodegenerative diseases (e.g., Alzheimer's, Parkinson's, Huntington's disease, and Amyotrophic Lateral Sclerosis) are major health threats for the aging population and their prevalences continue to rise with the increasing of life expectancy. Although progress has been made, there is still a lack of effective cures to date, and an in-depth understanding of the molecular and cellular mechanisms of these neurodegenerative diseases is imperative for drug development. Protein phosphorylation, regulated by protein kinases and protein phosphatases, participates in most cellular events, whereas aberrant phosphorylation manifests as a main cause of diseases. As evidenced by pharmacological and pathological studies, protein kinases are proven to be promising therapeutic targets for various diseases, such as cancers, central nervous system disorders, and cardiovascular diseases. The mechanisms of protein phosphatases in pathophysiology have been extensively reviewed, but a systematic summary of the role of protein kinases in the nervous system is lacking. Here, we focus on the involvement of protein kinases in neurodegenerative diseases, by summarizing the current knowledge on the major kinases and related regulatory signal transduction pathways implicated in diseases. We further discuss the role and complexity of kinase-kinase networks in the pathogenesis of neurodegenerative diseases, illustrate the advances of clinical applications of protein kinase inhibitors or novel kinase-targeted therapeutic strategies (such as antisense oligonucleotides and gene therapy) for effective prevention and early intervention.

Comprehensive characterization of respiratory genes based on a computational framework in pan-cancer to develop stratified treatment strategies

Abnormal cellular respiration plays a critical role in carcinogenesis. However, the molecular mechanisms underlying dysregulation of respiratory gene expression across different cancer types remain unclear. Here, we developed a computational framework that provides an analytical approach for exploring the molecular alterations and clinical relevance of respiratory genes in pan-cancer. We identified a total of 53 gene signatures in the three stages of respiration (including glycolysis, tricarboxylic acid cycle, and oxidative phosphorylation) through this framework and found that they were broadly differentially expressed and genetically altered across 33 cancer types. Pathway analysis manifested that the expression levels of almost all respiratory gene signatures were remarkably associated with the activation or inhibition of numerous oncogenic pathways, such as metabolism, angiogenesis, cell proliferation, and apoptosis. Survival analysis highlighted the oncogenic or tumor suppressor potential of the respiratory gene signatures. In particular, VCAN has shown significant oncogenic features in multiple cancer types. Finally, we identified a number of respiratory gene signatures that could be potential therapeutic targets, including VCAN. We also predicted small-molecule compounds targeting respiratory gene signatures or components of pathways regulated by them. Overall, our comprehensive analysis has greatly enhanced the understanding of molecular alterations of respiratory genes in tumorigenesis and progression, and provided insights into developing new therapeutic strategies.

GMRSP encoded by lncRNA H19 regulates metabolic reprogramming and alleviates aortic dissection

Metabolic disturbances are hallmarks of vascular smooth muscle cell (VSMC) phenotypic transitions, which play a critical role in the pathogenesis of aortic dissection (AD). In this study, we identify and characterize glucose metabolism regulatory protein (GMRSP), a protein encoded by lncRNA H19. Using VSMC-specific GMRSP induction in knock-in mice, adeno-associated virus-mediated GMRSP overexpression, and exosomal GMRSP delivery, we demonstrate significant improvements in AD and mitochondrial dysfunction. Mechanistically, GMRSP inhibits heterogeneous nuclear ribonucleoprotein (hnRNP) A2B1-mediated alternative splicing of pyruvate kinase M (PKM) pre-mRNA, leading to reduced PKM2 production and glycolysis. This reprogramming preserves the contractile phenotype of VSMCs and prevents their transition to a proliferative state. Importantly, pharmacological activation of PKM2 via TEPP-46 abrogates the protective effects of GMRSP in vivo and in vitro. Clinical relevance is shown by elevated plasma PKM2 levels in AD patients, which correlate with poor prognosis. Collectively, these findings indicate GMRSP as a key regulator of VSMC metabolism and phenotypic stability, highlighting its potential as a therapeutic target for AD.

Tandem repeat expansions and copy number variations as risk factors and diagnostic tools for amyotrophic lateral sclerosis

Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disorder leading to upper and lower motoneurons degeneration. Although several mechanisms potentially involved in disease development have been identified, its pathogenesis is not fully understood. From the patient side, ALS diagnosis, still based on clinical criteria, can be difficult and may take up to 1 year. More than 30 genes have been associated to genetically inherited ALS, among which four (C9ORF72, SOD1, TARDBP and FUS) would explain around 60-70% of cases. However, familial ALS represents only 5-10% of ALS cases while the remaining are sporadic, with genetics explaining 6-10% of such cases only. In this context, short tandem repeats (STRs) expansions, have recently been found in clinically diagnosed ALS patients. In this review, we discuss the recent discoveries on ALS associated STRs and their potential as biomarkers as well as prognosis and therapy targets.

Proteolytic regulation of mitochondrial magnesium channel by m-AAA protease and prohibitin complex

Mitochondrial membrane phospholipid cardiolipin is essential for the stability of several inner mitochondrial membrane protein complexes. We recently showed that the abundance of mitochondrial magnesium channel MRS2 is reduced in models of Barth syndrome, an X-linked genetic disorder caused by a remodeling defect in cardiolipin. However, the mechanism underlying the reduced abundance of MRS2 in cardiolipin-depleted mitochondria remained unknown. In this study, we utilized yeast mutants of mitochondrial proteases to identify an evolutionarily conserved m-AAA protease, Yta10/Yta12, responsible for degrading Mrs2. The activity of m-AAA protease is regulated by the inner mitochondrial membrane scaffolding complex prohibitin, and consistent with this role, we find that Mrs2 turnover is increased in yeast prohibitin mutants. Importantly, we find that deleting Yta10 in cardiolipin-deficient yeast cells restores the steady-state levels of Mrs2 to the wild-type cells, and the knockdown of AFG3L2, a mammalian homolog of Yta12, increases the abundance of MRS2 in a murine muscle cell line. Thus, our work has identified the m-AAA protease/prohibitin complex as an evolutionarily conserved regulator of Mrs2 that can be targeted to restore Mrs2 abundance in cardiolipin-depleted cells.

Targeting common disease pathomechanisms to treat amyotrophic lateral sclerosis

The motor neuron disease amyotrophic lateral sclerosis (ALS) is a devastating condition with limited treatment options. The past few years have witnessed a ramping up of translational ALS research, offering the prospect of disease-modifying therapies. Although breakthroughs using gene-targeted approaches have shown potential to treat patients with specific disease-causing mutations, the applicability of such therapies remains restricted to a minority of individuals. Therapies targeting more general mechanisms that underlie motor neuron pathology in ALS are therefore of considerable interest. ALS pathology is associated with disruption to a complex array of key cellular pathways, including RNA processing, proteostasis, metabolism and inflammation. This Review details attempts to restore cellular homeostasis by targeting these pathways in order to develop effective, broadly-applicable ALS therapeutics.

Kaempferol enhances ER-mitochondria coupling and protects motor neurons from mitochondrial dysfunction and ER stress in C9ORF72-ALS

Repeat expansions in the C9ORF72 gene are a frequent cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia. Considerable progress has been made in identifying C9ORF72-mediated disease and resolving its underlying etiopathogenesis. The contributions of intrinsic mitochondrial deficits as well as chronic endoplasmic reticulum stress to the development of the C9ORF72-linked pathology are well established. Nevertheless, to date, no cure or effective therapy is available, and thus attempts to find a potential drug target, have received increasing attention. Here, we investigated the mode of action and therapeutic effect of a naturally occurring dietary flavanol, kaempferol in preclinical rodent and human models of C9ORF72-ALS. Notably, kaempferol treatment of C9ORF72-ALS human patient-derived motor neurons/neurons, resolved mitochondrial deficits, promoted resiliency against severe ER stress, and conferred neuroprotection. Treatment of symptomatic C9ORF72 mice with kaempferol, normalized mitochondrial calcium uptake, restored mitochondria function, and diminished ER stress. Importantly, in vivo, chronic kaempferol administration ameliorated pathological motor dysfunction and inhibited motor neuron degeneration, highlighting the translational potential of kaempferol. Lastly, in silico modelling identified a novel kaempferol target and mechanistically the neuroprotective mechanism of kaempferol is through the iP3R-VDAC1 pathway via the modulation of GRP75 expression. Thus, kaempferol holds great promise for treating neurodegenerative diseases where both mitochondrial and ER dysfunction are causally linked to the pathophysiology.

NADH-bound AIF activates the mitochondrial CHCHD4/MIA40 chaperone by a substrate-mimicry mechanism

Mitochondrial metabolism requires the chaperoned import of disulfide-stabilized proteins via CHCHD4/MIA40 and its enigmatic interaction with oxidoreductase Apoptosis-inducing factor (AIF). By crystallizing human CHCHD4's AIF-interaction domain with an activated AIF dimer, we uncover how NADH allosterically configures AIF to anchor CHCHD4's β-hairpin and histidine-helix motifs to the inner mitochondrial membrane. The structure further reveals a similarity between the AIF-interaction domain and recognition sequences of CHCHD4 substrates. NMR and X-ray scattering (SAXS) solution measurements, mutational analyses, and biochemistry show that the substrate-mimicking AIF-interaction domain shields CHCHD4's redox-sensitive active site. Disrupting this shield critically activates CHCHD4 substrate affinity and chaperone activity. Regulatory-domain sequestration by NADH-activated AIF directly stimulates chaperone binding and folding, revealing how AIF mediates CHCHD4 mitochondrial import. These results establish AIF as an integral component of the metazoan disulfide relay and point to NADH-activated dimeric AIF as an organizational import center for CHCHD4 and its substrates. Importantly, AIF regulation of CHCHD4 directly links AIF's cellular NAD(H) sensing to CHCHD4 chaperone function, suggesting a mechanism to balance tissue-specific oxidative phosphorylation (OXPHOS) capacity with NADH availability.

Unraveling mitochondrial dysfunction: comprehensive perspectives on its impact on neurodegenerative diseases

Neurodegenerative diseases represent a significant challenge to modern medicine, with their complex etiology and progressive nature posing hurdles to effective treatment strategies. Among the various contributing factors, mitochondrial dysfunction has emerged as a pivotal player in the pathogenesis of several neurodegenerative disorders. This review paper provides a comprehensive overview of how mitochondrial impairment contributes to the development of neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis, driven by bioenergetic defects, biogenesis impairment, alterations in mitochondrial dynamics (such as fusion or fission), disruptions in calcium buffering, lipid metabolism dysregulation and mitophagy dysfunction. It also covers current therapeutic interventions targeting mitochondrial dysfunction in these diseases.

The transcriptional repressor HEY2 regulates mitochondrial oxidative respiration to maintain cardiac homeostasis

Energy deprivation and metabolic rewiring of cardiomyocytes are widely recognized hallmarks of heart failure. Here, we report that HEY2 (a Hairy/Enhancer-of-split-related transcriptional repressor) is upregulated in hearts of patients with dilated cardiomyopathy. Induced Hey2 expression in zebrafish hearts or mammalian cardiomyocytes impairs mitochondrial respiration, accompanied by elevated ROS, resulting in cardiomyocyte apoptosis and heart failure. Conversely, Hey2 depletion in adult mouse hearts and zebrafish enhances the expression of mitochondrial oxidation genes and cardiac function. Multifaceted genome-wide analyses reveal that HEY2 enriches at the promoters of genes known to regulate metabolism (including Ppargc1, Esrra and Cpt1) and colocalizes with HDAC1 to effectuate histone deacetylation and transcriptional repression. Consequently, restoration of PPARGC1A/ESRRA in Hey2- overexpressing zebrafish hearts or human cardiomyocyte-like cells rescues deficits in mitochondrial bioenergetics. Knockdown of Hey2 in adult mouse hearts protects against doxorubicin-induced cardiac dysfunction. These studies reveal an evolutionarily conserved HEY2/HDAC1-Ppargc1/Cpt transcriptional module that controls energy metabolism to preserve cardiac function.

Mechanism and Clinical Application Prospects of Mitochondrial DNA Single Nucleotide Polymorphism in Neurodegenerative Diseases

Mitochondrial dysfunction is well recognized as a critical component of the complicated pathogenesis of neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and Huntington's disease. This review investigates the influence of mitochondrial DNA single nucleotide polymorphisms on mitochondrial function, as well as their role in the onset and progression of these neurodegenerative diseases. Furthermore, the contemporary approaches to mitochondrial regulation in these disorders are discussed. Our objective is to uncover early diagnostic targets and formulate precision medicine strategies for neurodegenerative diseases, thereby offering new paths for preventing and treating these conditions.

C9orf72-Associated Dipeptide Repeat Expansions Perturb ER-Golgi Vesicular Trafficking, Inducing Golgi Fragmentation and ER Stress, in ALS/FTD

Hexanucleotide repeat expansions (HREs) in the chromosome 9 open reading frame 72 (C9orf72) gene are the most frequent genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Both are debilitating neurodegenerative conditions affecting either motor neurons (ALS) in the brain and spinal cord or neurons in the frontal and/or temporal cortical lobes (FTD). HREs undergo repeat-associated non-ATG (RAN) translation on both sense and anti-sense strands, generating five distinct dipeptide repeat proteins (DPRs), poly-GA, -GR, -GP, -PA and -PR. Perturbed proteostasis is well-recognised in ALS pathogenesis, including processes affecting the endoplasmic reticulum (ER) and Golgi compartments. However, these mechanisms have not been well characterised for C9orf72-mediated ALS/FTD. In this study we demonstrate that C9orf72 DPRs polyGA, polyGR and polyGP (× 40 repeats) disrupt secretory protein transport from the ER to the Golgi apparatus in neuronal cells. Consistent with this finding, these DPRs also induce fragmentation of the Golgi apparatus, activate ER stress, and inhibit the formation of the omegasome, the precursor of the autophagosome that originates from ER membranes. We also demonstrate Golgi fragmentation in cells undergoing RAN translation that express polyGP. Furthermore, dysregulated ER-Golgi transport was confirmed in C9orf72 patient dermal fibroblasts. Evidence of aberrant ER-derived vesicles in spinal cord motor neurons from C9orf72 ALS patients compared to controls was also obtained. These data thus confirm that ER proteostasis and ER-Golgi transport is perturbed in C9orf72-ALS in the absence of protein over-expression. Hence this study identifies novel molecular mechanisms associated with the ER and Golgi compartments induced by the C9orf72 HRE.

Role of oxidative stress in mitochondrial dysfunction and their implications in intervertebral disc degeneration: Mechanisms and therapeutic strategies

Background

Intervertebral disc degeneration (IVDD) is widely recognized as one of the leading causes of low back pain. Intervertebral disc cells are the main components of the intervertebral disc (IVD), and their functions include synthesizing and secreting collagen and proteoglycans to maintain the structural and functional stability of the IVD. In addition, IVD cells are involved in several physiological processes. They help maintain nutrient metabolism balance in the IVD. They also have antioxidant and anti-inflammatory effects. Because of these roles, IVD cells are crucial in IVDD. When IVD cells are subjected to oxidative stress, mitochondria may become damaged, affecting normal cell function and accelerating degenerative changes. Mitochondria are the energy source of the cell and regulate important intracellular processes. As a key site for redox reactions, excessive oxidative stress and reactive oxygen species can damage mitochondria, leading to inflammation, DNA damage, and apoptosis, thus accelerating disc degeneration.

Aim of review

Describes the core knowledge of IVDD and oxidative stress. Comprehensively examines the complex relationship and potential mechanistic pathways between oxidative stress, mitochondrial dysfunction and IVDD. Highlights potential therapeutic targets and frontier therapeutic concepts. Draws researchers' attention and discussion on the future research of all three.

Key scientific concepts of review

Origin, development and consequences of IVDD, molecular mechanisms of oxidative stress acting on mitochondria, mechanisms of oxidative stress damage to IVD cells, therapeutic potential of targeting mitochondria to alleviate oxidative stress in IVDD.

The translational potential of this article

Targeted therapeutic strategies for oxidative stress and mitochondrial dysfunction are particularly critical in the treatment of IVDD. Using antioxidants and specific mitochondrial therapeutic agents can help reduce symptoms and pain. This approach is expected to significantly improve the quality of life for patients. Individualized therapeutic approaches, on the other hand, are based on an in-depth assessment of the patient's degree of oxidative stress and mitochondrial functional status to develop a targeted treatment plan for more precise and effective IVDD management. Additionally, we suggest preventive measures like customized lifestyle changes and medications. These are based on understanding how IVDD develops. The aim is to slow down the disease and reduce the chances of it coming back. Actively promoting clinical trials and evaluating the safety and efficacy of new therapies helps translate cutting-edge treatment concepts into clinical practice. These measures not only improve patient outcomes and quality of life but also reduce the consumption of healthcare resources and the socio-economic burden, thus having a positive impact on the advancement of the IVDD treatment field.

Poly-GP accumulation due to C9orf72 loss of function induces motor neuron apoptosis through autophagy and mitophagy defects

The GGGGCC hexanucleotide repeat expansion (HRE) of the C9orf72 gene is the most frequent cause of amyotrophic lateral sclerosis (ALS), a devastative neurodegenerative disease characterized by motor neuron degeneration. C9orf72 HRE is associated with lowered levels of C9orf72 expression and its translation results in the production of dipeptide-repeats (DPRs). To recapitulate C9orf72-related ALS disease in vivo, we developed a zebrafish model where we expressed glycine-proline (GP) DPR in a c9orf72 knockdown context. We report that C9orf72 gain- and loss-of-function properties act synergistically to induce motor neuron degeneration and paralysis with poly(GP) accumulating preferentially within motor neurons along with Sqstm1/p62 aggregation indicating macroautophagy/autophagy deficits. Poly(GP) levels were shown to accumulate upon c9orf72 downregulation and were comparable to levels assessed in autopsy samples of patients carrying C9orf72 HRE. Chemical boosting of autophagy using rapamycin or apilimod, is able to rescue motor deficits. Proteomics analysis of zebrafish-purified motor neurons unravels mitochondria dysfunction confirmed through a comparative analysis of previously published C9orf72 iPSC-derived motor neurons. Consistently, 3D-reconstructions of motor neuron demonstrate that poly(GP) aggregates colocalize to mitochondria, thus inducing their elongation and swelling and the failure of their processing by mitophagy, with mitophagy activation through urolithin A preventing locomotor deficits. Finally, we report apoptotic-related increased amounts of cleaved Casp3 (caspase 3, apoptosis-related cysteine peptidase) and rescue of motor neuron degeneration by constitutive inhibition of Casp9 or treatment with decylubiquinone. Here we provide evidence of key pathogenic steps in C9ALS-FTD that can be targeted through pharmacological avenues, thus raising new therapeutic perspectives for ALS patients.

Harlequin mice exhibit cognitive impairment, severe loss of Purkinje cells and a compromised bioenergetic status due to the absence of Apoptosis Inducing Factor

The functional integrity of the central nervous system relies on complex mechanisms in which the mitochondria are crucial actors because of their involvement in a multitude of bioenergetics and biosynthetic pathways. Mitochondrial diseases are among the most prevalent groups of inherited neurological disorders, affecting up to 1 in 5000 adults and despite considerable efforts around the world there is still limited curative treatments. Harlequin mice correspond to a relevant model of recessive X-linked mitochondrial disease due to a proviral insertion in the first intron of the Apoptosis-inducing factor gene, resulting in an almost complete depletion of the corresponding protein. These mice exhibit progressive degeneration of the retina, optic nerve, cerebellum, and cortical regions leading to irremediable blindness and ataxia, reminiscent of what is observed in patients suffering from mitochondrial diseases. We evaluated the progression of cerebellar degeneration in Harlequin mice, especially for Purkinje cells and its relationship with bioenergetics failure and behavioral damage. For the first time to our knowledge, we demonstrated that Harlequin mice display cognitive and emotional impairments at early stage of the disease with further deteriorations as ataxia aggravates. These functions, corresponding to higher-order cognitive processing, have been assigned to a complex network of reciprocal connections between the cerebellum and many cortical areas which could be dysfunctional in these mice. Consequently, Harlequin mice become a suitable experimental model to test innovative therapeutics, via the targeting of mitochondria which can become available to a large spectrum of neurological diseases.

Investigating the prevalence of MFN2 mutations in amyotrophic lateral sclerosis: insights from an Italian cohort

The MFN2 gene encodes mitofusin 2, a key protein for mitochondrial fusion, transport, maintenance and cell communication. MFN2 mutations are primarily linked to Charcot-Marie-Tooth disease type 2A. However, a few cases of amyotrophic lateral sclerosis and amyotrophic lateral sclerosis/frontotemporal dementia phenotypes with concomitant MFN2 mutations have been previously reported. This study examines the clinical and genetic characteristics of an Italian cohort of amyotrophic lateral sclerosis patients with rare, non-synonymous MFN2 mutations. A group of patients (n = 385) diagnosed with amyotrophic lateral sclerosis at our Neurology Units between 2008 and 2023 underwent comprehensive molecular testing, including MFN2. After excluding pathogenic mutations in the main amyotrophic lateral sclerosis-related genes (i.e. C9orf72, SOD1, FUS and TARDBP), MFN2 variants were classified based on the American College of Medical Genetics and Genomics guidelines, and demographic and clinical data of MFN2-mutated patients were retrieved. We identified 12 rare, heterozygous, non-synonymous MFN2 variants in 19 individuals (4.9%). Eight of these variants, carried by nine patients (2.3%), were either pathogenic, likely pathogenic or variants of unknown significance according to the American College of Medical Genetics and Genomics guidelines. Among these patients, four exhibited a familial pattern of inheritance. The observed phenotypes included classic and bulbar amyotrophic lateral sclerosis, amyotrophic lateral sclerosis/frontotemporal dementia, flail arm, flail leg and progressive muscular atrophy. Median survival after disease onset was extremely variable, ranging from less than 1 to 13 years. This study investigates the prevalence of rare, non-synonymous MFN2 variants within an Italian cohort of amyotrophic lateral sclerosis patients, who have been extensively investigated, enhancing our knowledge of the underlying phenotypic spectrum. Further research is needed to understand whether MFN2 mutations contribute to motor neuron disease and to what extent. Improving our knowledge regarding the genetic basis of amyotrophic lateral sclerosis is crucial both in a diagnostic and therapeutic perspective.

Human neural stem cell-derived artificial organelles to improve oxidative phosphorylation

Oxidative phosphorylation (OXPHOS) in the mitochondrial inner membrane is a therapeutic target in many diseases. Neural stem cells (NSCs) show progress in improving mitochondrial dysfunction in the central nervous system (CNS). However, translating neural stem cell-based therapies to the clinic is challenged by uncontrollable biological variability or heterogeneity, hindering uniform clinical safety and efficacy evaluations. We propose a systematic top-down design based on membrane self-assembly to develop neural stem cell-derived oxidative phosphorylating artificial organelles (SAOs) for targeting the central nervous system as an alternative to NSCs. We construct human conditionally immortal clone neural stem cells (iNSCs) as parent cells and use a streamlined closed operation system to prepare neural stem cell-derived highly homogenous oxidative phosphorylating artificial organelles. These artificial organelles act as biomimetic organelles to mimic respiration chain function and perform oxidative phosphorylation, thus improving ATP synthesis deficiency and rectifying excessive mitochondrial reactive oxygen species production. Conclusively, we provide a framework for a generalizable manufacturing procedure that opens promising prospects for disease treatment.

C9orf72 controls hepatic lipid metabolism by regulating SREBP1 transport

Sterol regulatory element binding transcription factors (SREBPs) play a crucial role in lipid homeostasis. They are processed and transported to the nucleus via COPII, where they induce the expression of lipogenic genes. COPII maintains the homeostasis of organelles and plays an essential role in the protein secretion pathways in eukaryotes. The formation of COPII begins at endoplasmic reticulum exit sites (ERES), and is regulated by SEC16A, which provides a platform for the assembly of COPII. However, there have been few studies on the changes in SEC16A protein levels. The repetitive expansion of the hexanucleotide sequence GGGGCC within the chromosome 9 open reading frame 72 (C9orf72) gene is a prevalent factor in the development of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Here, we found that the absence of C9orf72 leads to a decrease in SEC16A protein levels, resulting in reduced localization of the guanine nucleotide exchange factor SEC12 at the ERES. Consequently, the small GTP binding protein SAR1 is unable to bind the endoplasmic reticulum normally, impairing the assembly of COPII. Ultimately, the disruption of SREBPs transport decreases de novo lipogenesis. These results suggest that C9orf72 acts as a novel role in regulating lipid homeostasis and may serve as a potential therapeutic target for obesity.

pTDP-43 levels correlate with cell type specific molecular alterations in the prefrontal cortex of C9orf72 ALS/FTD patients

Repeat expansions in the C9orf72 gene are the most common genetic cause of amyotrophic lateral sclerosis and familial frontotemporal dementia (ALS/FTD). To identify molecular defects that take place in the dorsolateral frontal cortex of patients with C9orf72 ALS/FTD, we compared healthy controls with C9orf72 ALS/FTD donor samples staged based on the levels of cortical phosphorylated TAR DNA binding protein (pTDP-43), a neuropathological hallmark of disease progression. We identified distinct molecular changes in different cell types that take place during FTD development. Loss of neurosurveillance microglia and activation of the complement cascade take place early, when pTDP-43 aggregates are absent or very low, and become more pronounced in late stages, suggesting an initial involvement of microglia in disease progression. Reduction of layer 2-3 cortical projection neurons with high expression of CUX2/LAMP5 also occurs early, and the reduction becomes more pronounced as pTDP-43 accumulates. Several unique features were observed only in samples with high levels of pTDP-43, including global alteration of chromatin accessibility in oligodendrocytes, microglia, and astrocytes; higher ratios of premature oligodendrocytes; increased levels of the noncoding RNA NEAT1 in astrocytes and neurons, and higher amount of phosphorylated ribosomal protein S6. Our findings reveal previously unknown progressive functional changes in major cell types found in the frontal cortex of C9orf72 ALS/FTD patients that shed light on the mechanisms underlying the pathology of this disease.

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.

NDUFA9 and its crotonylation modification promote browning of white adipocytes by activating mitochondrial function in mice

Protein crotonylation plays a role in regulating cellular metabolism, gene expression, and other biological processes. NDUFA9 (NADH dehydrogenase [ubiquinone] 1 alpha subcomplex subunit 9) is closely associated with the activity and function of mitochondrial respiratory chain complex I. Mitochondrial function and respiratory chain are closely related to browning of white adipocytes, it's speculated that NDUFA9 and its crotonylation are associated with browning of white adipocytes. Firstly, the effect of NDUFA9 on white adipose tissue was verified in white fat browning model mice, and it was found that NDUFA9 promoted mitochondrial respiration, thermogenesis, and browning of white adipose tissue. Secondly, in cellular studies, it was discovered that NDUFA9 facilitated browning of white adipocytes by enhancing mitochondrial function, mitochondrial complex I activity, ATP synthesis, and mitochondrial respiration. Again, the level of NDUFA9 crotonylation was increased by treating cells with vorinostat (SAHA)+sodium crotonate (NaCr) and overexpressing NDUFA9, it was found that NDUFA9 crotonylation promoted browning of white adipocytes. Meanwhile, the acetylation level of NDUFA9 was increased by treating cells with SAHA+sodium acetate (NaAc) and overexpressing NDUFA9, the assay revealed that NDUFA9 acetylation inhibited white adipocytes browning. Finally, combined with the competitive relationship between acetylation and crotonylation, it was also demonstrated that NDUFA9 crotonylation promoted browning of white adipocytes. Above results indicate that NDUFA9 and its crotonylation modification promote mitochondrial function, which in turn promotes browning of white adipocytes. This study establishes a theoretical foundation for the management and intervention of obesity, which is crucial in addressing obesity and related medical conditions in the future.

Evidence of mitochondrial dysfunction in ALS and methods for measuring in model systems

Metabolic dysfunction is a hallmark of multiple amyotrophic lateral sclerosis (ALS) models with a majority of ALS patients exhibiting hypermetabolism. The central sites of metabolism in the cell are mitochondria, capable of utilising a multitude of cellular substrates in an array of ATP-generating reactions. With reactive oxygen species (ROS) production occurring during some of these reactions, mitochondria can contribute considerably to oxidative stress. Mitochondria are also very dynamic organelles, interacting with other organelles, undergoing fusion/fission in response to changing metabolic states and being turned over by the cell regularly. Disruptions to many of these mitochondrial functions and processes have been reported in ALS models, largely indicating compromised mitochondrial function, increased ROS production by mitochondria, disrupted interactions with the endoplasmic reticulum and reduced turnover. This chapter summarises methods routinely used to assess mitochondria in ALS models and the alterations that have been reported in these models.

Osteopontin drives neuroinflammation and cell loss in MAPT-N279K frontotemporal dementia patient neurons

Frontotemporal dementia (FTD) is an incurable group of early-onset dementias that can be caused by the deposition of hyperphosphorylated tau in patient brains. However, the mechanisms leading to neurodegeneration remain largely unknown. Here, we combined single-cell analyses of FTD patient brains with a stem cell culture and transplantation model of FTD. We identified disease phenotypes in FTD neurons carrying the MAPT-N279K mutation, which were related to oxidative stress, oxidative phosphorylation, and neuroinflammation with an upregulation of the inflammation-associated protein osteopontin (OPN). Human FTD neurons survived less and elicited an increased microglial response after transplantation into the mouse forebrain, which we further characterized by single nucleus RNA sequencing of microdissected grafts. Notably, downregulation of OPN in engrafted FTD neurons resulted in improved engraftment and reduced microglial infiltration, indicating an immune-modulatory role of OPN in patient neurons, which may represent a potential therapeutic target in FTD.

Glucose hypometabolism prompts RAN translation and exacerbates C9orf72-related ALS/FTD phenotypes

The most prevalent genetic cause of both amyotrophic lateral sclerosis and frontotemporal dementia is a (GGGGCC)n nucleotide repeat expansion (NRE) occurring in the first intron of the C9orf72 gene (C9). Brain glucose hypometabolism is consistently observed in C9-NRE carriers, even at pre-symptomatic stages, but its role in disease pathogenesis is unknown. Here, we show alterations in glucose metabolic pathways and ATP levels in the brains of asymptomatic C9-BAC mice. We find that, through activation of the GCN2 kinase, glucose hypometabolism drives the production of dipeptide repeat proteins (DPRs), impairs the survival of C9 patient-derived neurons, and triggers motor dysfunction in C9-BAC mice. We also show that one of the arginine-rich DPRs (PR) could directly contribute to glucose metabolism and metabolic stress by inhibiting glucose uptake in neurons. Our findings provide a potential mechanistic link between energy imbalances and C9-ALS/FTD pathogenesis and suggest a feedforward loop model with potential opportunities for therapeutic intervention.

C9ORF72 hexanucleotide repeat expansion: From ALS and FTD to a broader pathogenic role?

The major gene underlying monogenic forms of amyotrophic lateral sclerosis (ALS) and fronto-temporal dementia (FTD) is C9ORF72. The causative mutation in C9ORF72 is an abnormal hexanucleotide (G4C2) repeat expansion (HRE) located in the first intron of the gene. The aim of this review is to propose a comprehensive update on recent developments on clinical, biological and therapeutics aspects related to C9ORF72 in order to highlight the current understanding of genotype-phenotype correlations, and also on biological machinery leading to neuronal death. We will particularly focus on the broad phenotypic presentation of C9ORF72-related diseases, that goes well beyond the classical phenotypes observed in ALS and FTD patients. Last, we will comment the possible therapeutical hopes for patients carrying a C9ORF72 HRE.

Multi-omics characterization of esophageal squamous cell carcinoma identifies molecular subtypes and therapeutic targets

Esophageal squamous cell carcinoma (ESCC) is the predominant form of esophageal cancer and is characterized by an unfavorable prognosis. To elucidate the distinct molecular alterations in ESCC and investigate therapeutic targets, we performed a comprehensive analysis of transcriptomics, proteomics, and phosphoproteomics data derived from 60 paired treatment-naive ESCC and adjacent nontumor tissue samples. Additionally, we conducted a correlation analysis to describe the regulatory relationship between transcriptomic and proteomic processes, revealing alterations in key metabolic pathways. Unsupervised clustering analysis of the proteomics data stratified patients with ESCC into 3 subtypes with different molecular characteristics and clinical outcomes. Notably, subtype III exhibited the worst prognosis and enrichment in proteins associated with malignant processes, including glycolysis and DNA repair pathways. Furthermore, translocase of inner mitochondrial membrane domain containing 1 (TIMMDC1) was validated as a potential prognostic molecule for ESCC. Moreover, integrated kinase-substrate network analysis using the phosphoproteome nominated candidate kinases as potential targets. In vitro and in vivo experiments further confirmed casein kinase II subunit α (CSNK2A1) as a potential kinase target for ESCC. These underlying data represent a valuable resource for researchers that may provide better insights into the biology and treatment of ESCC.

Focusing on mitochondria in the brain: from biology to therapeutics

Mitochondria have multiple functions such as supplying energy, regulating the redox status, and producing proteins encoded by an independent genome. They are closely related to the physiology and pathology of many organs and tissues, among which the brain is particularly prominent. The brain demands 20% of the resting metabolic rate and holds highly active mitochondrial activities. Considerable research shows that mitochondria are closely related to brain function, while mitochondrial defects induce or exacerbate pathology in the brain. In this review, we provide comprehensive research advances of mitochondrial biology involved in brain functions, as well as the mitochondria-dependent cellular events in brain physiology and pathology. Furthermore, various perspectives are explored to better identify the mitochondrial roles in neurological diseases and the neurophenotypes of mitochondrial diseases. Finally, mitochondrial therapies are discussed. Mitochondrial-targeting therapeutics are showing great potentials in the treatment of brain diseases.

KCNJ2 inhibition mitigates mechanical injury in a human brain organoid model of traumatic brain injury

Traumatic brain injury (TBI) strongly correlates with neurodegenerative disease. However, it remains unclear which neurodegenerative mechanisms are intrinsic to the brain and which strategies most potently mitigate these processes. We developed a high-intensity ultrasound platform to inflict mechanical injury to induced pluripotent stem cell (iPSC)-derived cortical organoids. Mechanically injured organoids elicit classic hallmarks of TBI, including neuronal death, tau phosphorylation, and TDP-43 nuclear egress. We found that deep-layer neurons were particularly vulnerable to injury and that TDP-43 proteinopathy promotes cell death. Injured organoids derived from C9ORF72 amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD) patients displayed exacerbated TDP-43 dysfunction. Using genome-wide CRISPR interference screening, we identified a mechanosensory channel, KCNJ2, whose inhibition potently mitigated neurodegenerative processes in vitro and in vivo, including in C9ORF72 ALS/FTD organoids. Thus, targeting KCNJ2 may reduce acute neuronal death after brain injury, and we present a scalable, genetically flexible cerebral organoid model that may enable the identification of additional modifiers of mechanical stress.

Targeting mitochondrial Ca2+ uptake for the treatment of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a rare adult-onset neurodegenerative disease characterized by progressive motor neuron (MN) loss, muscle denervation and paralysis. Over the past several decades, researchers have made tremendous efforts to understand the pathogenic mechanisms underpinning ALS, with much yet to be resolved. ALS is described as a non-cell autonomous condition with pathology detected in both MNs and non-neuronal cells, such as glial cells and skeletal muscle. Studies in ALS patient and animal models reveal ubiquitous abnormalities in mitochondrial structure and function, and disturbance of intracellular calcium homeostasis in various tissue types, suggesting a pivotal role of aberrant mitochondrial calcium uptake and dysfunctional calcium signalling cascades in ALS pathogenesis. Calcium signalling and mitochondrial dysfunction are intricately related to the manifestation of cell death contributing to MN loss and skeletal muscle dysfunction. In this review, we discuss the potential contribution of intracellular calcium signalling, particularly mitochondrial calcium uptake, in ALS pathogenesis. Functional consequences of excessive mitochondrial calcium uptake and possible therapeutic strategies targeting mitochondrial calcium uptake or the mitochondrial calcium uniporter, the main channel mediating mitochondrial calcium influx, are also discussed.

Developing a novel immune infiltration-associated mitophagy prediction model for amyotrophic lateral sclerosis using bioinformatics strategies

Background

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease, which leads to muscle weakness and eventual paralysis. Numerous studies have indicated that mitophagy and immune inflammation have a significant impact on the onset and advancement of ALS. Nevertheless, the possible diagnostic and prognostic significance of mitophagy-related genes associated with immune infiltration in ALS is uncertain. The purpose of this study is to create a predictive model for ALS using genes linked with mitophagy-associated immune infiltration.

Methods

ALS gene expression profiles were downloaded from the Gene Expression Omnibus (GEO) database. Univariate Cox analysis and machine learning methods were applied to analyze mitophagy-associated genes and develop a prognostic risk score model. Subsequently, functional and immune infiltration analyses were conducted to study the biological attributes and immune cell enrichment in individuals with ALS. Additionally, validation of identified feature genes in the prediction model was performed using ALS mouse models and ALS patients.

Results

In this study, a comprehensive analysis revealed the identification of 22 mitophagy-related differential expression genes and 40 prognostic genes. Additionally, an 18-gene prognostic signature was identified with machine learning, which was utilized to construct a prognostic risk score model. Functional enrichment analysis demonstrated the enrichment of various pathways, including oxidative phosphorylation, unfolded proteins, KRAS, and mTOR signaling pathways, as well as other immune-related pathways. The analysis of immune infiltration revealed notable distinctions in certain congenital immune cells and adaptive immune cells between the low-risk and high-risk groups, particularly concerning the T lymphocyte subgroup. ALS mouse models and ALS clinical samples demonstrated consistent expression levels of four mitophagy-related immune infiltration genes (BCKDHA, JTB, KYNU, and GTF2H5) with the results of bioinformatics analysis.

Conclusion

This study has successfully devised and verified a pioneering prognostic predictive risk score for ALS, utilizing eighteen mitophagy-related genes. Furthermore, the findings indicate that four of these genes exhibit promising roles in the context of ALS prognostic.

Neuromuscular organoids model spinal neuromuscular pathologies in C9orf72 amyotrophic lateral sclerosis

Hexanucleotide repeat expansions in the C9orf72 gene are the most common cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia. Due to the lack of trunk neuromuscular organoids (NMOs) from ALS patients' induced pluripotent stem cells (iPSCs), an organoid system was missing to model the trunk spinal neuromuscular neurodegeneration. With the C9orf72 ALS patient-derived iPSCs and isogenic controls, we used an NMO system containing trunk spinal cord neural and peripheral muscular tissues to show that the ALS NMOs could model peripheral defects in ALS, including contraction weakness, neural denervation, and loss of Schwann cells. The neurons and astrocytes in ALS NMOs manifested the RNA foci and dipeptide repeat proteins. Acute treatment with the unfolded protein response inhibitor GSK2606414 increased the glutamatergic muscular contraction 2-fold and reduced the dipeptide repeat protein aggregation and autophagy. This study provides an organoid system for spinal neuromuscular pathologies in ALS and its application for drug testing.

[Effects of Oxidative Stress on Mitochondrial Functions and Intervertebral Disc Cells]

Intervertebral disc degeneration is widely recognized as one of the main causes of lower back pain. Intervertebral disc cells are the primary cellular components of the discs, responsible for synthesizing and secreting collagen and proteoglycans to maintain the structural and functional stability of the discs. Additionally, intervertebral disc cells are involved in maintaining the nutritional and metabolic balance, as well as exerting antioxidant and anti-inflammatory effects within the intervertebral discs. Consequently, intervertebral disc cells play a crucial role in the process of disc degeneration. When these cells are exposed to oxidative stress, mitochondria can be damaged, which may disrupt normal cellular function and accelerate degenerative changes. Mitochondria serve as the powerhouse of cells, being the primary energy-producing organelles that control a number of vital processes, such as cell death. On the other hand, mitochondrial dysfunction may be associated with various degenerative pathophysiological conditions. Moreover, mitochondria are the key site for oxidation-reduction reactions. Excessive oxidative stress and reactive oxygen species can negatively impact on mitochondrial function, potentially leading to mitochondrial damage and impaired functionality. These factors, in turn, triggers inflammatory responses, mitochondrial DNA damage, and cell apoptosis, playing a significant role in the pathological processes of intervertebral disc cell degeneration. This review is focused on exploring the impact of oxidative stress and reactive oxygen species on mitochondria and the crucial roles played by oxidative stress and reactive oxygen species in the pathological processes of intervertebral disc cells. In addition, we discussed current cutting-edge treatments and introduced the use of mitochondrial antioxidants and protectants as a potential method to slow down oxidative stress in the treatment of disc degeneration.

Recent Research Trends in Neuroinflammatory and Neurodegenerative Disorders

Neuroinflammatory and neurodegenerative disorders including Alzheimer's disease (AD), Parkinson's disease (PD), traumatic brain injury (TBI) and Amyotrophic lateral sclerosis (ALS) are chronic major health disorders. The exact mechanism of the neuroimmune dysfunctions of these disease pathogeneses is currently not clearly understood. These disorders show dysregulated neuroimmune and inflammatory responses, including activation of neurons, glial cells, and neurovascular unit damage associated with excessive release of proinflammatory cytokines, chemokines, neurotoxic mediators, and infiltration of peripheral immune cells into the brain, as well as entry of inflammatory mediators through damaged neurovascular endothelial cells, blood-brain barrier and tight junction proteins. Activation of glial cells and immune cells leads to the release of many inflammatory and neurotoxic molecules that cause neuroinflammation and neurodegeneration. Gulf War Illness (GWI) and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) are chronic disorders that are also associated with neuroimmune dysfunctions. Currently, there are no effective disease-modifying therapeutic options available for these diseases. Human induced pluripotent stem cell (iPSC)-derived neurons, astrocytes, microglia, endothelial cells and pericytes are currently used for many disease models for drug discovery. This review highlights certain recent trends in neuroinflammatory responses and iPSC-derived brain cell applications in neuroinflammatory disorders.

Molecular hallmarks of ageing in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal, severely debilitating and rapidly progressing disorder affecting motor neurons in the brain, brainstem, and spinal cord. Unfortunately, there are few effective treatments, thus there remains a critical need to find novel interventions that can mitigate against its effects. Whilst the aetiology of ALS remains unclear, ageing is the major risk factor. Ageing is a slowly progressive process marked by functional decline of an organism over its lifespan. However, it remains unclear how ageing promotes the risk of ALS. At the molecular and cellular level there are specific hallmarks characteristic of normal ageing. These hallmarks are highly inter-related and overlap significantly with each other. Moreover, whilst ageing is a normal process, there are striking similarities at the molecular level between these factors and neurodegeneration in ALS. Nine ageing hallmarks were originally proposed: genomic instability, loss of telomeres, senescence, epigenetic modifications, dysregulated nutrient sensing, loss of proteostasis, mitochondrial dysfunction, stem cell exhaustion, and altered inter-cellular communication. However, these were recently (2023) expanded to include dysregulation of autophagy, inflammation and dysbiosis. Hence, given the latest updates to these hallmarks, and their close association to disease processes in ALS, a new examination of their relationship to pathophysiology is warranted. In this review, we describe possible mechanisms by which normal ageing impacts on neurodegenerative mechanisms implicated in ALS, and new therapeutic interventions that may arise from this.

Using cryo-EM to understand the assembly pathway of respiratory complex I

Complex I (proton-pumping NADH:ubiquinone oxidoreductase) is the first component of the mitochondrial respiratory chain. In recent years, high-resolution cryo-EM studies of complex I from various species have greatly enhanced the understanding of the structure and function of this important membrane-protein complex. Less well studied is the structural basis of complex I biogenesis. The assembly of this complex of more than 40 subunits, encoded by nuclear or mitochondrial DNA, is an intricate process that requires at least 20 different assembly factors in humans. These are proteins that are transiently associated with building blocks of the complex and are involved in the assembly process, but are not part of mature complex I. Although the assembly pathways have been studied extensively, there is limited information on the structure and molecular function of the assembly factors. Here, the insights that have been gained into the assembly process using cryo-EM are reviewed.

Rare and common genetic determinants of mitochondrial function determine severity but not risk of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease involving selective vulnerability of energy-intensive motor neurons (MNs). It has been unclear whether mitochondrial function is an upstream driver or a downstream modifier of neurotoxicity. We separated upstream genetic determinants of mitochondrial function, including genetic variation within the mitochondrial genome or autosomes; from downstream changeable factors including mitochondrial DNA copy number (mtCN). Across three cohorts including 6,437 ALS patients, we discovered that a set of mitochondrial haplotypes, chosen because they are linked to measurements of mitochondrial function, are a determinant of ALS survival following disease onset, but do not modify ALS risk. One particular haplotype appeared to be neuroprotective and was significantly over-represented in two cohorts of long-surviving ALS patients. Causal inference for mitochondrial function was achievable using mitochondrial haplotypes, but not autosomal SNPs in traditional Mendelian randomization (MR). Furthermore, rare loss-of-function genetic variants within, and reduced MN expression of, ACADM and DNA2 lead to ∼50 % shorter ALS survival; both proteins are implicated in mitochondrial function. Both mtCN and cellular vulnerability are linked to DNA2 function in ALS patient-derived neurons. Finally, MtCN responds dynamically to the onset of ALS independently of mitochondrial haplotype, and is correlated with disease severity. We conclude that, based on the genetic measures we have employed, mitochondrial function is a therapeutic target for amelioration of disease severity but not prevention of ALS.

Multi-Omics Profiling Identifies Microglial Annexin A2 as a Key Mediator of NF-κB Pro-inflammatory Signaling in Ischemic Reperfusion Injury

Cerebral stroke is one of the leading causes of mortality and disability worldwide. Restoring the cerebral circulation following a period of occlusion and subsequent tissue oxygenation leads to reperfusion injury. Cerebral ischemic reperfusion (I/R) injury triggers immune and inflammatory responses, apoptosis, neuronal damage, and even death. However, the cellular function and molecular mechanisms underlying cerebral I/R-induced neuronal injury are incompletely understood. By integrating proteomic, phosphoproteomic, and transcriptomic profiling in mouse hippocampi after cerebral I/R, we revealed that the differentially expressed genes and proteins mainly fall into several immune inflammatory response-related pathways. We identified that Annexin 2 (Anxa2) was exclusively upregulated in microglial cells in response to cerebral I/R in vivo and oxygen-glucose deprivation and reoxygenation (OGD/R) in vitro. RNA-seq analysis revealed a critical role of Anxa2 in the expression of inflammation-related genes in microglia via the NF-κB signaling. Mechanistically, microglial Anxa2 is required for nuclear translocation of the p65 subunit of NF-κB and its transcriptional activity upon OGD/R in BV2 microglial cells. Anxa2 knockdown inhibited the OGD/R-induced microglia activation and markedly reduced the expression of pro-inflammatory factors, including TNF-α, IL-1β, and IL-6. Interestingly, conditional medium derived from Anxa2-depleted BV2 cell cultures with OGD/R treatment alleviated neuronal death in vitro. Altogether, our findings revealed that microglia Anxa2 plays a critical role in I/R injury by regulating NF-κB inflammatory responses in a non-cell-autonomous manner, which might be a potential target for the neuroprotection against cerebral I/R injury.

Myeloid and lymphoid expression of C9orf72 regulates IL-17A signaling in mice

A mutation in C9ORF72 is the most common cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Patients with ALS or FTD often develop autoimmunity and inflammation that precedes or coincides with the onset of neurological symptoms, but the underlying mechanisms are poorly understood. Here, we knocked out murine C9orf72 in seven hematopoietic progenitor compartments by conditional mutagenesis and found that myeloid lineage C9orf72 prevents splenomegaly, loss of tolerance, and premature mortality. Furthermore, we demonstrated that C9orf72 plays a role in lymphoid cells to prevent interleukin-17A (IL-17A) production and neutrophilia. Mass cytometry identified early and sustained elevation of the costimulatory molecule CD80 expressed on C9orf72-deficient mouse macrophages, monocytes, and microglia. Enrichment of CD80 was similarly observed in human spinal cord microglia from patients with C9ORF72-mediated ALS compared with non-ALS controls. Single-cell RNA sequencing of murine spinal cord, brain cortex, and spleen demonstrated coordinated induction of gene modules related to antigen processing and presentation and antiviral immunity in C9orf72-deficient endothelial cells, microglia, and macrophages. Mechanistically, C9ORF72 repressed the trafficking of CD80 to the cell surface in response to Toll-like receptor agonists, interferon-γ, and IL-17A. Deletion of Il17a in C9orf72-deficient mice prevented CD80 enrichment in the spinal cord, reduced neutrophilia, and reduced gut T helper type 17 cells. Last, systemic delivery of an IL-17A neutralizing antibody augmented motor performance and suppressed neuroinflammation in C9orf72-deficient mice. Altogether, we show that C9orf72 orchestrates myeloid costimulatory potency and provide support for IL-17A as a therapeutic target for neuroinflammation associated with ALS or FTD.

Mitochondrial dysfunction in neurodegenerative disorders

Recent advances in understanding the role of mitochondrial dysfunction in neurodegenerative diseases have expanded the opportunities for neurotherapeutics targeting mitochondria to alleviate symptoms and slow disease progression. In this review, we offer a historical account of advances in mitochondrial biology and neurodegenerative disease. Additionally, we summarize current knowledge of the normal physiology of mitochondria and the pathogenesis of mitochondrial dysfunction, the role of mitochondrial dysfunction in neurodegenerative disease, current therapeutics and recent therapeutic advances, as well as future directions for neurotherapeutics targeting mitochondrial function. A focus is placed on reactive oxygen species and their role in the disruption of telomeres and their effects on the epigenome. The effects of mitochondrial dysfunction in the etiology and progression of Alzheimer's disease, amyotrophic lateral sclerosis, Parkinson's disease, and Huntington's disease are discussed in depth. Current clinical trials for mitochondria-targeting neurotherapeutics are discussed.

Pathomechanistic Networks of Motor System Injury in Amyotrophic Lateral Sclerosis

Amyotrophic Lateral Sclerosis (ALS) is the most common, adult-onset, progressive motor neurodegenerative disorder that results in death within 3 years of the clinical diagnosis. Due to the clinicopathological heterogeneity, any reliable biomarkers for diagnosis or prognosis of ALS have not been identified till date. Moreover, the only three clinically approved treatments are not uniformly effective in slowing the disease progression. Over the last 15 years, there has been a rapid advancement in research on the complex pathomechanistic landscape of ALS that has opened up new avenues for successful clinical translation of targeted therapeutics. Multiple studies suggest that the age-dependent interaction of risk-associated genes with environmental factors and endogenous modifiers is critical to the multi-step process of ALS pathogenesis. In this review, we provide an updated discussion on the dysregulated cross-talk between intracellular homeostasis processes, the unique molecular networks across selectively vulnerable cell types, and the multisystemic nature of ALS pathomechanisms. Importantly, this work highlights the alteration in epigenetic and epitranscriptomic landscape due to gene-environment interactions, which have been largely overlooked in the context of ALS pathology. Finally, we suggest that precision medicine research in ALS will be largely benefitted from the stratification of patient groups based on the clinical phenotype, onset and progression, genome, exposome, and metabolic identities.

Mitochondrial Quality Control via Mitochondrial Unfolded Protein Response (mtUPR) in Ageing and Neurodegenerative Diseases

Mitochondria play a key role in cellular functions, including energy production and oxidative stress regulation. For this reason, maintaining mitochondrial homeostasis and proteostasis (homeostasis of the proteome) is essential for cellular health. Therefore, there are different mitochondrial quality control mechanisms, such as mitochondrial biogenesis, mitochondrial dynamics, mitochondrial-derived vesicles (MDVs), mitophagy, or mitochondrial unfolded protein response (mtUPR). The last item is a stress response that occurs when stress is present within mitochondria and, especially, when the accumulation of unfolded and misfolded proteins in the mitochondrial matrix surpasses the folding capacity of the mitochondrion. In response to this, molecular chaperones and proteases as well as the mitochondrial antioxidant system are activated to restore mitochondrial proteostasis and cellular function. In disease contexts, mtUPR modulation holds therapeutic potential by mitigating mitochondrial dysfunction. In particular, in the case of neurodegenerative diseases, such as primary mitochondrial diseases, Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), Amyotrophic Lateral Sclerosis (ALS), or Friedreich's Ataxia (FA), there is a wealth of evidence demonstrating that the modulation of mtUPR helps to reduce neurodegeneration and its associated symptoms in various cellular and animal models. These findings underscore mtUPR's role as a promising therapeutic target in combating these devastating disorders.

Mitochondrial Dyshomeostasis as an Early Hallmark and a Therapeutic Target in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal multisystem disease characterized by progressive death of motor neurons, loss of muscle mass, and impaired energy metabolism. More than 40 genes are now known to be associated with ALS, which together account for the majority of familial forms of ALS and only 10% of sporadic ALS cases. To date, there is no consensus on the pathogenesis of ALS, which makes it difficult to develop effective therapy. Accumulating evidence indicates that mitochondria, which play an important role in cellular homeostasis, are the earliest targets in ALS, and abnormalities in their structure and functions contribute to the development of bioenergetic stress and disease progression. Mitochondria are known to be highly dynamic organelles, and their stability is maintained through a number of key regulatory pathways. Mitochondrial homeostasis is dynamically regulated via mitochondrial biogenesis, clearance, fission/fusion, and trafficking; however, the processes providing "quality control" and distribution of the organelles are prone to dysregulation in ALS. Here, we systematically summarized changes in mitochondrial turnover, dynamics, calcium homeostasis, and alterations in mitochondrial transport and functions to provide in-depth insights into disease progression pathways, which may have a significant impact on current symptomatic therapies and personalized treatment programs for patients with ALS.

Pectolinarigenin Improves Oxidative Stress and Apoptosis in Mouse NSC-34 Motor Neuron Cell Lines Induced by C9-ALS-Associated Proline-Arginine Dipeptide Repeat Proteins by Enhancing Mitochondrial Fusion Mediated via the SIRT3/OPA1 Axis

Amyotrophic lateral sclerosis (ALS) is considered a fatal progressive degeneration of motor neurons (MN) caused by oxidative stress and mitochondrial dysfunction. There are currently no treatments available. The most common inherited form of ALS is the C9orf72 mutation (C9-ALS). The proline-arginine dipeptide repeat protein (PR-DPR) produced by C9-ALS has been confirmed to be a functionally acquired pathogenic factor that can cause increased ROS, mitochondrial defects, and apoptosis in motor neurons. Pectolinarigenin (PLG) from the traditional medicinal herb Linaria vulgaris has antioxidant and anti-apoptotic properties. I established a mouse NSC-34 motor neuron cell line model expressing PR-DPR and confirmed the neuroprotective effect of PLG. The results showed that ROS production and apoptosis caused by PR-DPR could be improved by PLG treatment. In terms of mechanism research, PR-DPR inhibited the activity of the mitochondrial fusion proteins OPA1 and mitofusin 2. Conversely, the expression of fission protein fission 1 and dynamin-related protein 1 (DRP1) increased. However, PLG treatment reversed these effects. Furthermore, I found that PLG increased the expression and deacetylation of OPA1. Deacetylation of OPA1 enhances mitochondrial fusion and resistance to apoptosis. Finally, transfection with Sirt3 small interfering RNA abolished the neuroprotective effects of PLG. In summary, the mechanism by which PLG alleviates PR-DPR toxicity is mainly achieved by activating the SIRT3/OPA1 axis to regulate the balance of mitochondrial dynamics. Taken together, the potential of PLG in preclinical studies for C9-ALS drug development deserves further evaluation.

Mitochondria, a Key Target in Amyotrophic Lateral Sclerosis Pathogenesis

Mitochondrial dysfunction occurs in numerous neurodegenerative diseases, particularly amyotrophic lateral sclerosis (ALS), where it contributes to motor neuron (MN) death. Of all the factors involved in ALS, mitochondria have been considered as a major player, as secondary mitochondrial dysfunction has been found in various models and patients. Abnormal mitochondrial morphology, defects in mitochondrial dynamics, altered activities of respiratory chain enzymes and increased production of reactive oxygen species have been described. Moreover, the identification of CHCHD10 variants in ALS patients was the first genetic evidence that a mitochondrial defect may be a primary cause of MN damage and directly links mitochondrial dysfunction to the pathogenesis of ALS. In this review, we focus on the role of mitochondria in ALS and highlight the pathogenic variants of ALS genes associated with impaired mitochondrial functions. The multiple pathways demonstrated in ALS pathogenesis suggest that all converge to a common endpoint leading to MN loss. This may explain the disappointing results obtained with treatments targeting a single pathological process. Fighting against mitochondrial dysfunction appears to be a promising avenue for developing combined therapies in the future.

The many "Neurofaces" of Prohibitins 1 and 2: Crucial for the healthy brain, dysregulated in numerous brain disorders

Prohibitin 1 (PHB1) and prohibitin 2 (PHB2) are proteins that are nearly ubiquitously expressed. They are localized in mitochondria, cytosol and cell nuclei. In the healthy CNS, they occur in neurons and non-neuronal cells (oligodendrocytes, astrocytes, microglia, and endothelial cells) and fulfill pivotal functions in brain development and aging, the regulation of brain metabolism, maintenance of structural integrity, synapse formation, aminoacidergic neurotransmission and, probably, regulation of brain action of certain hypothalamic-pituitary hormones.With regard to the diseased brain there is increasing evidence that prohibitins are prominently involved in numerous major diseases of the CNS, which are summarized and discussed in the present review (brain tumors, neurotropic viruses, Alzheimer disease, Down syndrome, Fronto-temporal and vascular dementia, dementia with Lewy bodies, Parkinson disease, Huntington disease, Multiple sclerosis, Amyotrophic lateral sclerosis, stroke, alcohol use disorder, schizophrenia and autism). Unfortunately, there is no PHB-targeted therapy available for any of these diseases.

Cell-Type-Specific Mitochondrial Quality Control in the Brain: A Plausible Mechanism of Neurodegeneration

Neurodegeneration is an age-dependent progressive phenomenon with no defined cause. Aging is the main risk factor for neurodegenerative diseases. During aging, activated microglia undergo phenotypic alterations that can lead to neuroinflammation, which is a well-accepted event in the pathogenesis of neurodegenerative diseases. Several common mechanisms are shared by genetically or pathologically distinct neurodegenerative diseases, such as excitotoxicity, mitochondrial deficits and oxidative stress, protein misfolding and translational dysfunction, autophagy and microglia activation. Progressive loss of the neuronal population due to increased oxidative stress leads to neurodegenerative diseases, mostly due to the accumulation of dysfunctional mitochondria. Mitochondrial dysfunction and excessive neuroinflammatory responses are both sufficient to induce pathology in age-dependent neurodegeneration. Therefore, mitochondrial quality control is a key determinant for the health and survival of neuronal cells in the brain. Research has been primarily focused to demonstrate the significance of neuronal mitochondrial health, despite the important contributions of non-neuronal cells that constitute a significant portion of the brain volume. Moreover, mitochondrial morphology and function are distinctly diverse in different tissues; however, little is known about their molecular diversity among cell types. Mitochondrial dynamics and quality in different cell types markedly decide the fate of overall brain health; therefore, it is not justifiable to overlook non-neuronal cells and their significant and active contribution in facilitating overall neuronal health. In this review article, we aim to discuss the mitochondrial quality control of different cell types in the brain and how important and remarkable the diversity and highly synchronized connecting property of non-neuronal cells are in keeping the neurons healthy to control neurodegeneration.

PHB2 ameliorates Doxorubicin-induced cardiomyopathy through interaction with NDUFV2 and restoration of mitochondrial complex I function

BACKGROUND

Doxorubicin (DOX) is among the most widely employed antitumor agents, although its clinical applications have been largely hindered by severe cardiotoxicity. Earlier studies described an essential role of mitochondrial injury in the pathogenesis of DOX cardiomyopathy. PHB2 (Prohibitin 2) is perceived as an essential regulator for mitochondrial dynamics and oxidative phosphorylation (OXPHOS) although its involvement in DOX cardiomyopathy remains elusive.

METHODS

To decipher the possible role of PHB2 in DOX cardiomyopathy, tamoxifen-induced cardiac-specific PHB2 conditional knockout mice were generated and subjected to DOX challenge. Cardiac function and mitochondrial profiles were examined. Screening of downstream mediators of PHB2 was performed using proteomic profiling and bioinformatic analysis, and was further verified using co-immunoprecipitation and pulldown assays.

RESULTS

Our data revealed significantly downregulated PHB2 expression in DOX-challenged mouse hearts. PHB2CKO mice were more susceptible to DOX cardiotoxicity compared with PHB2flox/flox mice, as evidenced by more pronounced cardiac atrophy, interstitial fibrosis and decrease in left ventricular ejection fraction and fractional shortening. Mechanistically, PHB2 deficiency resulted in the impairment of mitochondrial bioenergetics and oxidative phosphorylation in DOX cardiotoxicity. Proteomic profiling and interactome analyses revealed that PHB2 interacted with NDUFV2 (NADH-ubiquinone oxidoreductase core subunit V2), a key subunit of mitochondrial respiratory Complex I to mediate regulatory property of PHB2 on mitochondrial metabolism. PHB2 governed the expression of NDUFV2 by promoting its stabilization, while PHB2 deficiency significantly downregulated NDUFV2 in DOX-challenged hearts. Cardiac overexpression of PHB2 alleviated mitochondrial defects in DOX cardiomyopathy both in vivo and in vitro.

CONCLUSIONS

Our study defined a novel role for PHB2 in mitochondrial dynamics and energetic metabolism through interacting with NDUFV2 in DOX-challenged hearts. Forced overexpression of PHB2 may be considered a promising therapeutic approach for patients with DOX cardiomyopathy.

Nutritional and metabolic factors in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a complex neurodegenerative disease that is classically thought to impact the motor system. Over the past 20 years, research has started to consider the contribution of non-motor symptoms and features of the disease, and how they might affect ALS prognosis. Of the non-motor features of the disease, nutritional status (for example, malnutrition) and metabolic balance (for example, weight loss and hypermetabolism) have been consistently shown to contribute to more rapid disease progression and/or earlier death. Several complex cellular changes observed in ALS, including mitochondrial dysfunction, are also starting to be shown to contribute to bioenergetic failure. The resulting energy depletion in high energy demanding neurons makes them sensitive to apoptosis. Given that nutritional and metabolic stressors at the whole-body and cellular level can impact the capacity to maintain optimal function, these factors present avenues through which we can identify novel targets for treatment in ALS. Several clinical trials are now underway evaluating the effectiveness of modifying energy balance in ALS, making this article timely in reviewing the evidence base for metabolic and nutritional interventions.

Mitochondrial Dysfunction in Repeat Expansion Diseases

Repeat expansion diseases are a group of neuromuscular and neurodegenerative disorders characterized by expansions of several successive repeated DNA sequences. Currently, more than 50 repeat expansion diseases have been described. These disorders involve diverse pathogenic mechanisms, including loss-of-function mechanisms, toxicity associated with repeat RNA, or repeat-associated non-ATG (RAN) products, resulting in impairments of cellular processes and damaged organelles. Mitochondria, double membrane organelles, play a crucial role in cell energy production, metabolic processes, calcium regulation, redox balance, and apoptosis regulation. Its dysfunction has been implicated in the pathogenesis of repeat expansion diseases. In this review, we provide an overview of the signaling pathways or proteins involved in mitochondrial functioning described in these disorders. The focus of this review will be on the analysis of published data related to three representative repeat expansion diseases: Huntington's disease, C9orf72-frontotemporal dementia/amyotrophic lateral sclerosis, and myotonic dystrophy type 1. We will discuss the common effects observed in all three repeat expansion disorders and their differences. Additionally, we will address the current gaps in knowledge and propose possible new lines of research. Importantly, this group of disorders exhibit alterations in mitochondrial dynamics and biogenesis, with specific proteins involved in these processes having been identified. Understanding the underlying mechanisms of mitochondrial alterations in these disorders can potentially lead to the development of neuroprotective strategies.