MAPT genotype-dependent mitochondrial aberration and ROS production trigger dysfunction and death in cortical neurons of patients with hereditary FTLD

KCTD20 suppression mitigates excitotoxicity in tauopathy patient organoids

Excitotoxicity is a major pathologic mechanism in patients with tauopathy and other neurodegenerative diseases. However, the key neurotoxic drivers and the most effective strategies for mitigating these degenerative processes are unclear. Here, we show that glutamate treatment of induced pluripotent stem cell (iPSC)-derived cerebral organoids induces tau oligomerization and neurodegeneration and that these phenotypes are enhanced in organoids derived from tauopathy patients. Using a genome-wide CRISPR interference (CRISPRi) screen, we find that the suppression of KCTD20 potently ameliorates tau pathology and neurodegeneration in glutamate-treated organoids and mice, as well as in transgenic mice overexpressing mutant human tau. KCTD20 suppression reduces oligomeric tau and improves neuron survival by activating lysosomal exocytosis, which clears pathological tau. Our results show that glutamate signaling can induce neuronal tau pathology and identify KCTD20 suppression and lysosomal exocytosis as effective strategies for clearing neurotoxic tau species.

Based exploration of the diagnostic value of oxidative stress-related key genes in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) ranks as the third most common contributor to global mortality. Oxidative stress has been recognized as a critical driver of multiple interacting mechanisms in COPD development. This research investigated the potential of oxidative stress-related genes (OSRGs) biomarkers and their potential molecular mechanisms for COPD clinical diagnosis and treatment through bioinformatics analyses. As a result, 5 hub genes, CA3, PPP1R15B, MAPT, MMP9, and ECT2, were yielded by LASSO, Boruta, and SVM-RFE, and the performance of the nomogram constructed based on hub genes was favorable. Correlation analyses between hub genes and oxidative stress biomarkers showed that MMP9 and MAPT genes had a high association with oxidative stress biomarkers. Immune cell infiltration identified follicular helper T cells, Γδ T cells, M0 macrophages, and CD8 T cells as significantly different in COPD. ROC of ECT2 and MMP9 showed a higher capability to discriminate COPD patients from normal samples. In addition, we collected clinical samples and analyzed the core gene expression, which revealed that the hub genes ECT2 and MMP9 had high discriminatory ability in the COPD samples. The epistasis of ECT2 and MMP9 was further verified by constructing animal models, pathological sections, qPCR, immunoblotting, immunohistochemistry, etc. The data indicated the crucial function of MMP9 in CSC-induced oxidative stress injury. Deprivation of MMP9 attenuated CSC-induced injury and promoted macrophage polarisation to M2 macrophages. MMP9 deprivation protected against CSC-induced injury, mainly related to the reduction of cell apoptosis, cell inflammation, and ROS injury in BEAS-2B. It promoted macrophage polarization from M1 to M2. In summary, we found ECT2 and MMP9 are related to oxidative stress in COPD, and MMP9 was related to cell apoptosis, cell inflammation, and ROS injury in BEAS-2B, and the macrophage polarization from M1 to M2.

Hippocampal mitophagy alterations in MAPT-associated frontotemporal dementia with parkinsonism

The enzyme pair PINK1 and PRKN together orchestrates a cytoprotective mitophagy pathway that selectively tags damaged mitochondria with phospho-serine 65 ubiquitin (pS65-Ub) and directs them for autophagic-lysosomal degradation (mitophagy). We previously demonstrated a significant accumulation of pS65-Ub signals in autopsy brains of sporadic Lewy body disease and Alzheimer's disease cases, which strongly correlated with early tau pathology. In this study, we extended our analysis to a series of pathologically confirmed cases of frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17) harboring different pathogenic mutations in MAPT, the gene encoding tau. We assessed the morphology, levels, and distribution of the mitophagy tag pS65-Ub in several affected brain regions and hippocampal subregions of these cases. While tau pathological burden was similarly increased across all FTDP-17 cases, pS65-Ub immunopositive signals were strongly accumulated in P301L cases and only weakly present in N279K cases. In the hippocampus of both mutation groups, the density of pS65-Ub positive cells was overall the greatest in the dentate gyrus followed by the subiculum, CA1, and CA2/3, with the CA4 showing only minimal presence. Notably, positive cells in the subiculum carried greater numbers and particularly vacuolar pS65-Ub structures, while cells in the dentate gyrus mostly contained fewer and rather granular pS65-Ub inclusions. Single cell analyses revealed differential co-localization of pS65-Ub with mitochondria, autophagosomes, and lysosomes in these two regions. Together, our study demonstrates distinct mitophagy alteration in different FTDP-17 MAPT cases and hint at selective organelle failure in the hippocampal subregions that was associated with the P301L mutation.

Transgenic iPSC Lines with Genetically Encoded MitoTimer to Study Mitochondrial Biogenesis in Dopaminergic Neurons with Tauopathy

Background: Tauopathy has been identified as a prevalent causative agent of neurodegenerative diseases, including frontotemporal dementia with parkinsonism-17 (FTDP-17). This rare hereditary neurodegenerative condition is characterised by the manifestation of parkinsonism and behavioural changes. The majority of cases of FTDP-17 are associated with mutations in the MAPT gene, which encodes the tau protein. MAPT mutations lead to disruption of the balance between 3R and 4R tau forms, which causes destabilisation of microtubules and impairment of cellular organelle functions, particularly mitochondrial dysfunction. The development of model systems and tools for studying the molecular, genetic, and biochemical mechanisms underlying FTDP-17 and testing therapies at the cellular level is an urgent necessity. Methods: In this study, we generated transgenic lines of induced pluripotent stem cells (iPSCs) from a patient carrying the pathogenic mutation c.2013T > G (rs63750756, p.N279K) of MAPT and a healthy donor. A doxycycline-controlled transgene of the genetically encoded biosensor MitoTimer was integrated into the AAVS1 locus of these cells. The MitoTimer biosensor allows for lifetime monitoring of the turnover of mitochondria in neuronal cells derived from directed iPSC differentiation. The fact that transcription of the transgene can be induced by doxycycline provides additional possibilities for pulse labelling of newly formed mitochondria. Results: Transgenic iPSC lines provide a unique tool to study the molecular and genetic mechanisms of FTDP-17 caused by the presence of the c.2013T > G (p.N279K) mutation, as well as to test potential drugs in vitro.

The Underestimated Role of Iron in Frontotemporal Dementia: A Narrative Review

The term frontotemporal dementia (FTD) comprises a group of neurodegenerative disorders characterized by the progressive degeneration of the frontal and temporal lobes of the brain with language impairment and changes in cognitive, behavioral and executive functions, and in some cases motor manifestations. A high proportion of FTD cases are due to genetic mutations and inherited in an autosomal-dominant manner with variable penetrance depending on the implicated gene. Iron is a crucial microelement that is involved in several cellular essential functions in the whole body and plays additional specialized roles in the central nervous system (CNS) mainly through its redox-cycling properties. Such a feature may be harmful under aerobic conditions, since it may lead to the generation of highly reactive hydroxyl radicals. Dysfunctions of iron homeostasis in the CNS are indeed involved in several neurodegenerative disorders, although it is still challenging to determine whether the dyshomeostasis of this essential but harmful metal is a direct cause of neurodegeneration, a contributor factor or simply a consequence of other neurodegenerative mechanisms. Unlike many other neurodegenerative disorders, evidence of the dysfunction in brain iron homeostasis in FTD is still scarce; nonetheless, the recent literature intriguingly suggests its possible involvement. The present review aims to summarize what is currently known about the contribution of iron dyshomeostasis in FTD based on clinical, imaging, histological, biochemical and molecular studies, further suggesting new perspectives and offering new insights for future investigations on this underexplored field of research.

Generation and characterization of two induced pluripotent stem cell lines (ICGi052-A and ICGi052-B) from a patient with frontotemporal dementia with parkinsonism-17 associated with the pathological variant c.2013T>G in the MAPT gene

Frontotemporal dementia with parkinsonism-17 is a neurodegenerative disease characterised by pathological aggregation of the tau protein with the formation of neurofibrillary tangles and subsequent neuronal death. The inherited form of frontotemporal dementia can be caused by mutations in several genes, including the MAPT gene on chromosome 17, which encodes the tau protein. As there are currently no medically approved treatments for frontotemporal dementia, there is an urgent need for research using in vitro cell models to understand the molecular genetic mechanisms that lead to the development of the disease, to identify targets for therapeutic intervention and to test potential drugs to prevent neuronal death. Analysis of exome sequencing data from a 46-year-old patient with a clinical diagnosis of Parkinson's disease revealed the presence of the pathological variant c.2013T>G (rs63750756) in the MAPT gene, which is associated with frontotemporal dementia with parkinsonism-17. By reprogramming the patient's peripheral blood mononuclear cells, we obtained induced pluripotent stem cells (iPSCs). Two iPSC lines were characterised in detail. Reprogramming was performed by transfection with non-integrating episomal vectors expressing the OCT4, SOX2, KLF4, LIN28, L-MYC and mp53DD proteins. The iPSC lines ICGi052-A and ICGi052-B proliferate stably, form colonies with a morphology characteristic of human pluripotent cells, have a normal diploid karyotype (46,XX), express endogenous alkaline phosphatase and pluripotency markers (OCT4, NANOG, SSEA-4 and TRA-1-60) and are able to differentiate into derivatives of three germ layers: ento-, ecto- and mesoderm. The iPSC lines obtained and characterised in detail in this work represent a unique tool for studying the molecular genetic mechanisms of the pathogenesis of frontotemporal dementia with parkinsonism-17, as well as for testing potential drugs in vitro.

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.

Caffeine improves mitochondrial dysfunction in the white matter of neonatal rats with hypoxia-ischemia through deacetylation: a proteomic analysis of lysine acetylation

Aims

White matter damage (WMD) is linked to both cerebral palsy and cognitive deficits in infants born prematurely. The focus of this study was to examine how caffeine influences the acetylation of proteins within the neonatal white matter and to evaluate its effectiveness in treating white matter damage caused by hypoxia-ischemia.

Main methods

We employed a method combining affinity enrichment with advanced liquid chromatography and mass spectrometry to profile acetylation in proteins from the white matter of neonatal rats grouped into control (Sham), hypoxic-ischemic (HI), and caffeine-treated (Caffeine) groups.

Key findings

Our findings included 1,999 sites of lysine acetylation across 1,123 proteins, with quantifiable changes noted in 1,342 sites within 689 proteins. Analysis of these patterns identified recurring sequences adjacent to the acetylation sites, notably YKacN, FkacN, and G * * * GkacS. Investigation into the biological roles of these proteins through Gene Ontology analysis indicated their involvement in a variety of cellular processes, predominantly within mitochondrial locations. Further analysis indicated that the acetylation of tau (Mapt), a protein associated with microtubules, was elevated in the HI condition; however, caffeine treatment appeared to mitigate this over-modification, thus potentially aiding in reducing oxidative stress, inflammation in the nervous system, and improving mitochondrial health. Caffeine inhibited acetylated Mapt through sirtuin 2 (SITR2), promoted Mapt nuclear translocation, and improved mitochondrial dysfunction, which was subsequently weakened by the SIRT2 inhibitor, AK-7.

Significance

Caffeine-induced changes in lysine acetylation may play a key role in improving mitochondrial dysfunction and inhibiting oxidative stress and neuroinflammation.

Overlaps and divergences between tauopathies and synucleinopathies: a duet of neurodegeneration

Proteinopathy, defined as the abnormal accumulation of proteins that eventually leads to cell death, is one of the most significant pathological features of neurodegenerative diseases. Tauopathies, represented by Alzheimer's disease (AD), and synucleinopathies, represented by Parkinson's disease (PD), show similarities in multiple aspects. AD manifests extrapyramidal symptoms while dementia is also a major sign of advanced PD. We and other researchers have sequentially shown the cross-seeding phenomenon of α-synuclein (α-syn) and tau, reinforcing pathologies between synucleinopathies and tauopathies. The highly overlapping clinical and pathological features imply shared pathogenic mechanisms between the two groups of disease. The diagnostic and therapeutic strategies seemingly appropriate for one distinct neurodegenerative disease may also apply to a broader spectrum. Therefore, a clear understanding of the overlaps and divergences between tauopathy and synucleinopathy is critical for unraveling the nature of the complicated associations among neurodegenerative diseases. In this review, we discuss the shared and diverse characteristics of tauopathies and synucleinopathies from aspects of genetic causes, clinical manifestations, pathological progression and potential common therapeutic approaches targeting the pathology, in the aim to provide a timely update for setting the scheme of disease classification and provide novel insights into the therapeutic development for neurodegenerative diseases.

Effects of oxidative stress on hepatic encephalopathy pathogenesis in mice

Oxidative stress plays a crucial role in the pathogenesis of hepatic encephalopathy (HE), but the mechanism remains unclear. GABAergic neurons in substantia nigra pars reticulata (SNr) contribute to the motor deficit of HE. The present study aims to investigate the effects of oxidative stress on HE in male mice. The results validate the existence of oxidative stress in both liver and SNr across two murine models of HE induced by thioacetamide (TAA) and bile duct ligation (BDL). Systemic mitochondria-targeted antioxidative drug mitoquinone (Mito-Q) rescues mitochondrial dysfunction and oxidative injury in SNr, so as to restore the locomotor impairment in TAA and BDL mice. Furthermore, the GAD2-expressing SNr population (SNr^GAD2) is activated by HE. Both overexpression of mitochondrial uncoupling protein 2 (UCP2) targeted to SNr^GAD2 and SNr^GAD2-targeted chemogenetic inhibition targeted to SNr^GAD2 rescue mitochondrial dysfunction in TAA-induced HE. These results define the key role of oxidative stress in the pathogenesis of HE.

Pure total flavonoids from citrus alleviate oxidative stress and inflammation in nonalcoholic fatty liver disease by regulating the miR-137-3p/NOXA2/NOX2 pathway

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) has become a global health issue owing to its large disease population and high morbidity. We previously reported that the improvement in oxidative stress (OS) using pure total flavonoids from citrus (PTFC), flavonoids isolated from the peel of Citrus changshan-huyou Y.B. Chan, is a crucial strategy for NAFLD treatment. However, OS-associated intervention pathways in NAFLD remain unclear.

METHODS

In this study, we used microRNA (miR)- and mRNA-sequencing to identify the pathway by which PTFC improve OS in NAFLD. Clinical data, mimic/inhibitor assays, and a dual-luciferase reporter assay were selected to verify the regulatory relationships of this pathway. Moreover, in vivo and in vitro experiments were used to confime the regulatory effect of PTFC on this pathway.

RESULTS

miR-seq, mRNA-seq, and bioinformatics analyses revealed that the miR-137-3p/neutrophil cytosolic factor 2 (NCF2, also known as NOXA2)/cytochrome b-245 beta chain (CYBB, also known as NOX2) pathway may be a target pathway for PTFC to improve OS and NAFLD. Additionally, bivariate logistic regression analysis combining the serum and clinical data of patients revealed NOX2 and NOXA2 as risk factors and total antioxidant capacity (indicator of OS level) as a protective factor for NAFLD. miR-137-3p mimic/inhibitor assays revealed that the upregulation of miR-137-3p is vital for improving cellular steatosis, OS, and inflammation. Dual-luciferase reporter assay confirmed that NOXA2 acts as an miR-137-3p sponge. These results co-determined that miR-137-3p/NOXA2/NOX2 is an essential pathway involved in NAFLD pathogenesis, including lipid accumulation, OS, and inflammation. In vivo and in vitro experiments further confirmed that the miR-137-3p/NOXA2/NOX2 pathway is regulated by PTFC.

CONCLUSION

PTFC alleviates OS and inflammation in NAFLD by regulating the miR-137-3p/NOXA2/NOX2 pathway.

NOX4-derived ROS are neuroprotective by balancing intracellular calcium stores

Hyperexcitability is associated with neuronal dysfunction, cellular death, and consequently neurodegeneration. Redox disbalance can contribute to hyperexcitation and increased reactive oxygen species (ROS) levels are observed in various neurological diseases. NOX4 is an NADPH oxidase known to produce ROS and might have a regulating function during oxidative stress. We, therefore, aimed to determine the role of NOX4 on neuronal firing, hyperexcitability, and hyperexcitability-induced changes in neural network function. Using a multidimensional approach of an in vivo model of hyperexcitability, proteomic analysis, and cellular function analysis of ROS, mitochondrial integrity, and calcium levels, we demonstrate that NOX4 is neuroprotective by regulating ROS and calcium homeostasis and thereby preventing hyperexcitability and consequently neuronal death. These results implicate NOX4 as a potential redox regulator that is beneficial in hyperexcitability and thereby might have an important role in neurodegeneration.