Metabolic Regulation of Mitochondrial Protein Biogenesis from a Neuronal Perspective

Excitotoxicity, Oxytosis/Ferroptosis, and Neurodegeneration: Emerging Insights into Mitochondrial Mechanisms

Mitochondrial dysfunction plays a pivotal role in the development of age-related diseases, particularly neurodegenerative disorders. The etiology of mitochondrial dysfunction involves a multitude of factors that remain elusive. This review centers on elucidating the role(s) of excitotoxicity, oxytosis/ferroptosis and neurodegeneration within the context of mitochondrial bioenergetics, biogenesis, mitophagy and oxidative stress and explores their intricate interplay in the pathogenesis of neurodegenerative diseases. The effective coordination of mitochondrial turnover processes, notably mitophagy and biogenesis, is assumed to be critically important for cellular resilience and longevity. However, the age-associated decrease in mitophagy impedes the elimination of dysfunctional mitochondria, consequently impairing mitochondrial biogenesis. This deleterious cascade results in the accumulation of damaged mitochondria and deterioration of cellular functions. Both excitotoxicity and oxytosis/ferroptosis have been demonstrated to contribute significantly to the pathophysiology of neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's Disease (HD), Amyotrophic Lateral Sclerosis (ALS) and Multiple Sclerosis (MS). Excitotoxicity, characterized by excessive glutamate signaling, initiates a cascade of events involving calcium dysregulation, energy depletion, and oxidative stress and is intricately linked to mitochondrial dysfunction. Furthermore, emerging concepts surrounding oxytosis/ferroptosis underscore the importance of iron-dependent lipid peroxidation and mitochondrial engagement in the pathogenesis of neurodegeneration. This review not only discusses the individual contributions of excitotoxicity and ferroptosis but also emphasizes their convergence with mitochondrial dysfunction, a key driver of neurodegenerative diseases. Understanding the intricate crosstalk between excitotoxicity, oxytosis/ferroptosis, and mitochondrial dysfunction holds potential to pave the way for mitochondrion-targeted therapeutic strategies. Such strategies, with a focus on bioenergetics, biogenesis, mitophagy, and oxidative stress, emerge as promising avenues for therapeutic intervention.

New insights into the role of mitochondrial dynamics in oxidative stress-induced diseases

The accumulation of excess reactive oxygen species (ROS) can lead to oxidative stress (OS), which can induce gene mutations, protein denaturation, and lipid peroxidation directly or indirectly. The expression is reduced ATP level in cells, increased cytoplasmic Ca2+, inflammation, and so on. Consequently, ROS are recognized as significant risk factors for human aging and various diseases, including diabetes, cardiovascular diseases, and neurodegenerative diseases. Mitochondria are involved in the production of ROS through the respiratory chain. Abnormal mitochondrial characteristics, including mitochondrial OS, mitochondrial fission, mitochondrial fusion, and mitophagy, play an important role in various tissues. However, previous excellent reviews focused on OS-induced diseases. In this review, we focus on the latest progress of OS-induced mitochondrial dynamics, discuss OS-induced mitochondrial damage-related diseases, and summarize the OS-induced mitochondrial dynamics-related signaling pathways. Additionally, it elaborates on potential therapeutic methods aimed at preventing oxidative stress from further exacerbating mitochondrial disorders.

Potential role of mitochondria and endoplasmic reticulum in the response elicited by D-aspartate in TM4 Sertoli cells

D-Aspartic Acid (D-Asp) affects spermatogenesis by enhancing the biosynthesis of the sex steroid hormones acting either through the hypothalamus-pituitary-testis axis or directly on Leydig cells. Recently, in vitro studies have also demonstrated the direct effects of D-Asp on the proliferation and/or activity of germ cells. However, although D-Asp is present in Sertoli cells (SC), the specific role of the amino acid in these cells remains unknown. This study investigated the effects of D-Asp on the proliferation and activity of TM4 SC, focusing on the mitochondrial compartment and its association with the endoplasmic reticulum (ER). We found that D-Asp enhanced the proliferation and activity of TM4 cells as evidenced by the activation of ERK/Akt/PCNA pathway and the increase in the protein levels of the androgen receptor. Furthermore, D-Asp reduced both the oxidative stress and apoptotic process. An increase in mitochondrial functionality and dynamics, as well as a reduction in ER stress, were also found in D-Asp-treated TM4 cells. It is known that mitochondria are closely associated with ER to form the Mitochondrial-Associated Endoplasmic Reticulum Membranes (MAM), the site of calcium ions and lipid transfer from ER to the mitochondria, and vice versa. The data demonstrated that D-Asp induced stabilization of MAM in TM4 cells. In conclusion, this study is the first to demonstrate a direct effect of D-Asp on SC activity and to clarify the cellular/molecular mechanism underlying these effects, suggesting that D-Asp could stimulate spermatogenesis by improving the efficiency of SC.

The critical role of P2XR/PGC-1α signalling pathway in hypoxia-mediated pyroptosis and M1/M2 phenotypic differentiation of mouse microglia

Microglia are endogenous immune cells in the brain, and their pyroptosis and phenotype dichotomy are proved to play roles in neurodegenerative diseases. We investigated whether and how hypoxia affected pyroptosis and phenotype polarization in mouse microglia. Primary mouse microglia and BV2 microglia were exposed to hypoxia. Pyroptosis and M1/M2 phenotype were assessed by measuring gasdermin D truncation and M1/M2 surface marker expression. Mechanisms including purinergic ionotropic receptor (P2XR), peroxisome proliferator-activated receptor coactivator-1α (PGC-1α) and NOD-like receptor protein 3 (NLRP3) inflammasome were investigated. We reported hypoxia (90% N2, 5% O2 and 5% CO2) induced pyroptosis and promoted M1 phenotype polarization in primary mouse microglia and BV2 microglia, and the effect appeared after 6 h exposure. Although hypoxia (90% N2, 5% O2 and 5% CO2, 6 h) had no effect on P2X1R and P2X7R expression, it increased P2X4R expression and decreased PGC-1α expression. Interestingly, blockade of P2X4R or P2X7R abolished hypoxia-modulated PGC-1α expression, pyroptosis and M1 polarization. PGC-1α overexpression or overactivation alleviated hypoxia-induced pyroptosis and M1 polarization, while PGC-1α knockdown or deactivation promoted pyroptosis and M1 polarization under normoxic situation. Further, hypoxia induced NLRP3 expression and activated caspase-1 and induced the phosphorylation of NF-κB and reduced the phosphorylation of STAT3/6. NLRP3 inhibitor and caspase-1 inhibitor abolished hypoxia-induced pyroptosis, while NF-κB inhibitor and STAT phosphorylation inducer ameliorated hypoxia-induced M1 polarization. In addition, NF-κB activator and STAT3/6 inhibitor caused microglia M1 polarization under normoxic situation. We concluded in cultured mouse microglia, hypoxia may induce pyroptosis via P2XR/PGC-1α/NLRP3/caspase-1 pathway and trigger M1 polarization through P2XR/PGC-1α/NF-κB/STAT3/6 pathway.

CLUH maintains functional mitochondria and translation in motoneuronal axons and prevents peripheral neuropathy

Transporting and translating mRNAs in axons is crucial for neuronal viability. Local synthesis of nuclear-encoded mitochondrial proteins protects long-lived axonal mitochondria from damage; however, the regulatory factors involved are largely unknown. We show that CLUH, which binds mRNAs encoding mitochondrial proteins, prevents peripheral neuropathy and motor deficits in the mouse. CLUH is enriched in the growth cone of developing spinal motoneurons and is required for their growth. The lack of CLUH affects the abundance of target mRNAs and the corresponding mitochondrial proteins more prominently in axons, leading to ATP deficits in the growth cone. CLUH interacts with ribosomal subunits, translation initiation, and ribosome recycling components and preserves axonal translation. Overexpression of the ribosome recycling factor ABCE1 rescues the mRNA and translation defects, as well as the growth cone size, in CLUH-deficient motoneurons. Thus, we demonstrate a role for CLUH in mitochondrial quality control and translational regulation in axons, which is essential for their development and long-term integrity and function.

Steroidogenesis Upregulation through Mitochondria-Associated Endoplasmic Reticulum Membranes and Mitochondrial Dynamics in Rat Testes: The Role of D-Aspartate

Mitochondria-Associated Endoplasmic Reticulum Membranes (MAMs) mediate the communication between the Endoplasmic Reticulum (ER) and the mitochondria, playing a fundamental role in steroidogenesis. This study aimed to understand how D-aspartate (D-Asp), a well-known stimulator of testosterone biosynthesis and spermatogenesis, affects the mechanism of steroidogenesis in rat testes. Our results suggested that D-Asp exerts this function through MAMs, affecting lipid trafficking, calcium signaling, ER stress, and mitochondrial dynamics. After 15 days of oral administration of D-Asp to rats, there was an increase in both antioxidant enzymes (SOD and Catalase) and in the protein expression levels of ATAD3A, FACL4, and SOAT1, which are markers of lipid transfer, as well as VDAC and GRP75, which are markers of calcium signaling. Additionally, there was a decrease in protein expression levels of GRP78, a marker of aging that counteracts ER stress. The effects of D-Asp on mitochondrial dynamics strongly suggested its active role as well. It induced the expression levels of proteins involved in fusion (MFN1, MFN2, and OPA1) and in biogenesis (NRF1 and TFAM), as well as in mitochondrial mass (TOMM20), and decreased the expression level of DRP1, a crucial mitochondrial fission marker. These findings suggested D-Asp involvement in the functional improvement of mitochondria during steroidogenesis. Immunofluorescent signals of ATAD3A, MFN1/2, TFAM, and TOMM20 confirmed their localization in Leydig cells showing an intensity upgrade in D-Asp-treated rat testes. Taken together, our results demonstrate the involvement of D-Asp in the steroidogenesis of rat testes, acting at multiple stages of both MAMs and mitochondrial dynamics, opening new opportunities for future investigation in other steroidogenic tissues.

Integrated Network Pharmacology and in vivo Experimental Validation Approach to Explore the Potential Antioxidant Effects of Annao Pingchong Decoction in Intracerebral Hemorrhage Rats

Background

Annao Pingchong decoction (ANPCD) is a traditional Chinese decoction which has definite effects on treating intracerebral hemorrhage (ICH) validated through clinical and experimental studies. However, the impact of ANPCD on oxidative stress (OS) after ICH remains unclear and is worth further investigating.

Aim

To investigate whether the therapeutic effects of ANPCD on ICH are related to alleviating OS damage and seek potential targets for its antioxidant effects.

Materials and Methods

The therapeutic candidate genes of ANPCD on ICH were identified through a comparison of the target genes of ANPCD, target genes of ICH and differentially expressed genes (DEGs). Protein-protein interaction (PPI) network analysis and functional enrichment analysis were combined with targets-related literature to select suitable antioxidant targets. The affinity between ANPCD and the selected target was verified using macromolecular docking. Subsequently, the effects of ANPCD on OS and the selected target were further investigated through in vivo experiments.

Results

Forty-eight candidate genes were screened, in which silent information regulator sirtuin 1 (SIRT1) is one of the core genes that has antioxidant effects and ICH significantly affected its expression. The good affinity between 6 compounds of ANPCD and SIRT1 was also demonstrated by macromolecular docking. The results of in vivo experiments demonstrated that ANPCD significantly decreased modified neurological severity scoring (mNSS) scores and serum MDA and 8-OHdG content in ICH rats, while significantly increasing serum SOD and CAT activity, complicated with the up-regulation of ANPCD on SIRT1, FOXO1, PGC-1α and Nrf2. Furthermore, ANPCD significantly decreased the apoptosis rate and the expression of apoptosis-related proteins (P53, cytochrome c and caspase-3).

Conclusion

ANPCD alleviates OS damage and apoptosis after ICH in rats. As a potential therapeutic target, SIRT1 can be effectively regulated by ANPCD, as are its downstream proteins.

Mitochondria in the Central Nervous System in Health and Disease: The Puzzle of the Therapeutic Potential of Mitochondrial Transplantation

Mitochondria, the energy suppliers of the cells, play a central role in a variety of cellular processes essential for survival or leading to cell death. Consequently, mitochondrial dysfunction is implicated in numerous general and CNS disorders. The clinical manifestations of mitochondrial dysfunction include metabolic disorders, dysfunction of the immune system, tumorigenesis, and neuronal and behavioral abnormalities. In this review, we focus on the mitochondrial role in the CNS, which has unique characteristics and is therefore highly dependent on the mitochondria. First, we review the role of mitochondria in neuronal development, synaptogenesis, plasticity, and behavior as well as their adaptation to the intricate connections between the different cell types in the brain. Then, we review the sparse knowledge of the mechanisms of exogenous mitochondrial uptake and describe attempts to determine their half-life and transplantation long-term effects on neuronal sprouting, cellular proteome, and behavior. We further discuss the potential of mitochondrial transplantation to serve as a tool to study the causal link between mitochondria and neuronal activity and behavior. Next, we describe mitochondrial transplantation's therapeutic potential in various CNS disorders. Finally, we discuss the basic and reverse-translation challenges of this approach that currently hinder the clinical use of mitochondrial transplantation.

The mitochondria in schizophrenia with 22q11.2 deletion syndrome: From pathogenesis to therapeutic promise of targeted natural drugs

Schizophrenia is a complex multi-factor neurological disorder that caused an array of severe indelible consequences to the individuals and society. Additionally, anti-schizophrenic drugs are unsuitable for treating negative symptoms and have more significant side effects and drug resistance. For better treatment and prevention, we consider exploring the pathogenesis of schizophrenia from other perspectives. A growing body of evidence of 22q11.2 deletion syndrome (22q11DS) suggested that the occurrence and progression of schizophrenia are related to mitochondrial dysfunction. So combing through the literature of 22q11DS published from 2000 to 2023, this paper reviews the mechanism of schizophrenia based on mitochondrial dysfunction, and it focuses on the natural drugs targeting mitochondria to enhance mitochondrial function, which are potential to improve the current treatment of schizophrenia.

The Synergistic Effect of Quince Fruit and Probiotics (Lactobacillus and Bifidobacterium) on Reducing Oxidative Stress and Inflammation at the Intestinal Level and Improving Athletic Performance during Endurance Exercise

Endurance exercise promotes damage at the intestinal level and generates a variety of symptoms related to oxidative stress processes, inflammatory processes, microbiota dysbiosis, and intestinal barrier damage. This study evaluated the effects of quince (Cydonia oblonga Mill.) and probiotics of the genera Lactobacillus and Bifidobacterium on intestinal protection and exercise endurance in an animal swimming model. Phytochemical characterization of the quince fruit demonstrated a total dietary fiber concentration of 0.820 ± 0.70 g/100 g and a fiber-bound phenolic content of 30,218 ± 104 µg/g in the freeze-dried fruit. UPLC-PDA-ESI-QqQ analyses identified a high content of polyphenol, mainly flavanols, hydroxycinnamic acids, hydroxybenzoic acids, flavonols, and, to a lesser extent, dihydrochalcones. The animal model of swimming was performed using C57BL/6 mice. The histological results determined that the consumption of the synbiotic generated intestinal protection and increased antioxidant (catalase and glutathione peroxidase enzymes) and anti-inflammatory (TNF-α and IL-6 and increasing IL-10) activities. An immunohistochemical analysis indicated mitochondrial biogenesis (Tom2) at the muscular level related to the increased swimming performance. These effects correlated mainly with the polyphenol content of the fruit and the effect of the probiotics. Therefore, this combination of quince and probiotics could be an alternative for the generation of a synbiotic product that improves exercise endurance and reduces the effects generated by the practice of high performance sports.

Chiisanoside Mediates the Parkin/ZNF746/PGC-1α Axis by Downregulating MiR-181a to Improve Mitochondrial Biogenesis in 6-OHDA-Caused Neurotoxicity Models In Vitro and In Vivo: Suggestions for Prevention of Parkinson's Disease

The degeneration of dopamine (DA) neurons is known to be associated with defects in mitochondrial biogenesis caused by aging, environmental factors, or mutations in genes, leading to Parkinson's disease (PD). As PD has not yet been successfully cured, the strategy of using small molecule drugs to protect and restore mitochondrial biogenesis is a promising direction. This study evaluated the efficacy of synthetic chiisanoside (CSS) identified in the leaves of Acanthopanax sessiliflorus to prevent PD symptoms. The results show that in the 6-hydroxydopamine (6-OHDA) model, CSS pretreatment can effectively alleviate the reactive oxygen species generation and apoptosis of SH-SY5Y cells, thereby lessening the defects in the C. elegans model including DA neuron degeneration, dopamine-mediated food sensitivity behavioral disorders, and shortened lifespan. Mechanistically, we found that CSS could restore the expression of proliferator-activated receptor gamma coactivator-1-alpha (PGC-1α), a key molecule in mitochondrial biogenesis, and its downstream related genes inhibited by 6-OHDA. We further confirmed that this is due to the enhanced activity of parkin leading to the ubiquitination and degradation of PGC-1α inhibitor protein Zinc finger protein 746 (ZNF746). Parkin siRNA treatment abolished this effect of CSS. Furthermore, we found that CSS inhibited 6-OHDA-induced expression of miR-181a, which targets parkin. The CSS's ability to reverse the 6-OHDA-induced reduction in mitochondrial biogenesis and activation of apoptosis was abolished after the transfection of anti-miR-181a and miR-181a mimics. Therefore, the neuroprotective effect of CSS mainly promotes mitochondrial biogenesis by regulating the miR-181a/Parkin/ZNF746/PGC-1α axis. CSS potentially has the opportunity to be developed into PD prevention agents.

The Translocase of the Outer Mitochondrial Membrane (TOM40) is required for mitochondrial dynamics and neuronal integrity in Dorsal Root Ganglion Neurons

Polymorphisms and altered expression of the Translocase of the Outer Mitochondrial Membrane - 40 kD (Tom40) are observed in neurodegenerative disease subjects. We utilized in vitro cultured dorsal root ganglion (DRG) neurons to investigate the association of TOM40 depletion to neurodegeneration, and to unravel the mechanism of neurodegeneration induced by decreased levels of TOM40 protein. We provide evidence that severity of neurodegeneration induced in the TOM40 depleted neurons increases with the increase in the depletion of TOM40 and is exacerbated by an increase in the duration of TOM40 depletion. We also demonstrate that TOM40 depletion causes a surge in neuronal calcium levels, decreases mitochondrial motility, increases mitochondrial fission, and decreases neuronal ATP levels. We observed that alterations in the neuronal calcium homeostasis and mitochondrial dynamics precede BCL-xl and NMNAT1 dependent neurodegenerative pathways in the TOM40 depleted neurons. This data also suggests that manipulation of BCL-xl and NMNAT1 may be of therapeutic value in TOM40 associated neurodegenerative disorders.

Role of SIRT3 in mitochondrial biology and its therapeutic implications in neurodegenerative disorders

Sirtuin 3 (SIRT3), a mitochondrial deacetylase expressed preferentially in high-metabolic-demand tissues including the brain, requires NAD⁺ as a cofactor for catalytic activity. It regulates various processes such as energy homeostasis, redox balance, mitochondrial quality control, mitochondrial unfolded protein response (UPRmt), biogenesis, dynamics and mitophagy by altering protein acetylation status. Reduced SIRT3 expression or activity causes hyperacetylation of hundreds of mitochondrial proteins, which has been linked with neurological abnormalities, neuro-excitotoxicity and neuronal cell death. A body of evidence has suggested, SIRT3 activation as a potential therapeutic modality for age-related brain abnormalities and neurodegenerative disorders.