Editorial: Mitochondrial Exchangers and Transporters in Cell Survival and Death

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.

SARS-CoV-2 and Mitochondrial Proteins in Neural-Derived Exosomes of COVID-19

OBJECTIVE

As SARS-CoV-2 is known to invade neural cell mitochondria, a plasma system for quantifying central nervous system proteins in living humans was used to investigate neuropathogenic mechanisms of long-COVID-19.

METHODS

SARS-CoV-2 proteins and mitochondrial proteins (MPs) in enriched plasma neuron-derived extracellular vesicles (NDEVs) and astrocyte-derived EVs (ADEVs) were quantified in resolved acute COVID-19 without post-acute sequelae of SARS-CoV-2 (PASC), PASC without neuropsychiatric manifestations (NP), PASC with NP and healthy controls.

RESULTS

NDEV and ADEV mean levels of SARS-CoV-2 S1 and nucleocapsid (N) proteins were higher in all PASC sub-groups than controls, but only N levels were higher in PASC with than without NP. Exosome marker CD81-normalized NDEV mean levels of subunit 6 of MP respiratory chain complex I and subunit 10 of complex III, and neuroprotective MPs Humanin and mitochondrial open-reading frame of the 12S rRNA-c (MOTS-c) all were decreased significantly in PASC with NP but not in PASC without NP relative to controls. NDEV levels of MPs voltage-dependent anion-selective channel protein 1 (VDAC1) and N-methyl-D-aspartate receptor 1 (NMDAR1) were decreased in PASC without and with NP, whereas those of calcium channel MPs mitochondrial calcium uniporter (MCU), sodium/calcium exchanger (NCLX) and leucine zipper EF-hand containing transmembrane 1 protein (LETM1) were decreased only in PASC with NP. ADEV levels of MCU and NCLX only were increased in PASC without and with NP.

INTERPRETATION

Abnormal NDEV and ADEV levels of SARS-CoV-2 N and S1 protein and MPs correlate with NP and may be biomarkers for long-COVID prognostics and therapeutic trials. ANN NEUROL 2022;91:772-781.