Coenzyme Q redox signalling and longevity

Endurance exercise preconditioning alleviates ferroptosis induced by doxorubicin-induced cardiotoxicity through mitochondrial superoxide-dependent AMPKα2 activation

Doxorubicin-induced cardiotoxicity (DIC) adversely impacts patients' long-term health and quality of life. Its underlying mechanism is complex, involving regulatory cell death mechanisms, such as ferroptosis and autophagy. Moreover, it is a challenge faced by patients undergoing cardiac rehabilitation. Endurance exercise (E-Exe) preconditioning effectively counters DIC injury, potentially through the adenosine monophosphate-activated protein kinase (AMPK) pathway. However, detailed studies on this process's mechanisms are scarce. Here, E-Exe preconditioning and DIC models were established using mice and primary cultured adult mouse cardiomyocytes (PAMCs). Akin to ferrostatin-1 (ferroptosis inhibitor), rapamycin (autophagic inducer), and MitoTEMPO (mitochondrial free-radical scavenger), E-Exe preconditioning effectively alleviated Fe2+ accumulation and oxidative stress and improved energy metabolism and mitochondrial dysfunction in DIC injury, as demonstrated by multifunctional, enzymatic, and morphological indices. However, erastin (ferroptosis inducer), 3-methyladenine (autophagic inhibitor), adenovirus-mediated AMPKα2 downregulation, and AMPKα2 inhibition by compound C significantly diminished these effects, both in vivo and in vitro. The results suggest a non-traditional mechanism where E-Exe preconditioning, under mild mitochondrial reactive oxygen species generation, upregulates and phosphorylates AMPKα2, thereby enhancing mitochondrial complex I activity, activating adaptive autophagy, and improving myocardial tolerance to DIC injury. Overall, this study highlighted the pivotal role of mitochondria in myocardial DIC-induced ferroptosis and shows how E-Exe preconditioning activated AMPKα2 against myocardial DIC injury. This suggests that E-Exe preconditioning could be a viable strategy for patients undergoing cardiac rehabilitation.

Mitochondrial Mechanisms in Immunity and Inflammatory Conditions: Beyond Energy Management

Significance: The growing importance of mitochondria in the immune response and inflammation is multifaceted. Unraveling the different mechanisms by which mitochondria have a relevant role in the inflammatory response beyond the energy management of the process is necessary for improving our understanding of the host immune defense and the pathogenesis of various inflammatory diseases and syndromes. Critical Issues: Mitochondria are relevant in the immune response at different levels, including releasing activation molecules, changing its structure and function to accompany the immune response, and serving as a structural base for activating intermediates as NLRP3 inflammasome. In this scientific journey of dissecting mitochondrial mechanisms, new questions and interesting aspects arise, such as the involvement of mitochondrial-derived vesicles in the immune response with the putative role of preventing uncontrolled situations. Recent Advances: Researchers are continuously rethinking the role of mitochondria in acute and chronic inflammation and related disorders. As such, mitochondria have important roles as centrally positioned signaling hubs in regulating inflammatory and immune responses. In this review, we present the current understanding of mitochondrial mechanisms involved, beyond the largely known mitochondrial dysfunction, in the onset and development of inflammatory situations. Future Directions: Mitochondria emerge as an interesting and multifaceted platform for studying and developing pharmaceutical and therapeutic approaches. There are many ongoing studies aimed to describe the effects of specific mitochondrial targeted molecules and treatments to ameliorate the consequences of exacerbated inflammatory components of pathologies and syndromes, resulting in an open area of increasing research interest.

ROS production by mitochondria: function or dysfunction?

In eukaryotic cells, ATP generation is generally viewed as the primary function of mitochondria under normoxic conditions. Reactive oxygen species (ROS), in contrast, are regarded as the by-products of respiration, and are widely associated with dysfunction and disease. Important signaling functions have been demonstrated for mitochondrial ROS in recent years. Still, their chemical reactivity and capacity to elicit oxidative damage have reinforced the idea that ROS are the products of dysfunctional mitochondria that accumulate during disease. Several studies support a different model, however, by showing that: (1) limited oxygen availability results in mitochondria prioritizing ROS production over ATP, (2) ROS is an essential adaptive mitochondrial signal triggered by various important stressors, and (3) while mitochondria-independent ATP production can be easily engaged by most cells, there is no known replacement for ROS-driven redox signaling. Based on these observations and other evidence reviewed here, we highlight the role of ROS production as a major mitochondrial function involved in cellular adaptation and stress resistance. As such, we propose a rekindled view of ROS production as a primary mitochondrial function as essential to life as ATP production itself.

New insights into brain injury in chickens induced by bisphenol A and selenium deficiency-Mitochondrial reactive oxygen species and mitophagy-apoptosis crosstalk homeostasis

Bisphenol A (BPA), a component of plastic products, can penetrate the blood-brain barrier and pose a threat to the nervous system. Selenium (Se) deficiency can also cause nervous system damage. Resulting from the rapid industrial development, BPA pollution and Se deficiency often coexist. However, it is unclear whether brain damage in chickens caused by BPA exposure and Se deficiency is related to the crosstalk disorder between mitophagy and apoptosis. In this study, 60 chickens (1 day old) were fed with a diet that contained 20 mg/kg BPA but was insufficient in Se (only 0.039 mg/kg) for 42 days to establish a chicken brain injury model. In vitro, the primary chicken embryo brain neurons were treated for 24 h with Se-deficient medium containing 75 μM BPA. The results showed that BPA exposure and Se deficiency inhibited the expression of the mitochondrial respiratory chain complex in brain neurons, and a large number of mitochondrial reactive oxygen species were released. Furthermore, the expression levels of mitochondrial fusion proteins (OPA1, Mfn1, and Mfn2) decreased, while the expression levels of mitochondrial fission proteins (Drp1, Mff, and Fis1) increased, thus exacerbating mitochondrial division. In addition, the results of immunofluorescence and flow cytometry analysis, as well as the elevated expressions of mitophagy related genes (PINK1, Parkin, ATG5, and LC3II/I) and pro-apoptotic markers (Bax, Cytc, Caspase3, and Caspase9) indicated that BPA exposure and Se deficiency disrupted the crosstalk homeostasis between mitophagy and apoptosis. However, this crosstalk homeostasis was restored after Mito-Tempo and Rapamycin treatment. In contrast, 3-methyladenine treatment exacerbated this crosstalk disorder. In conclusion, BPA exposure and Se deficiency can induce mitochondrial reactive oxygen species bursts and disorders of mitochondrial dynamics by destroying the mitochondrial respiratory chain complex. The result is indicative of an imbalance in mitochondrial autophagy and apoptosis crosstalk homeostasis, which damages the chicken brain.

An oviduct glycan increases sperm lifespan by diminishing the production of ubiquinone and reactive oxygen species†

Sperm storage by females after mating for species-dependent periods is used widely among animals with internal fertilization to allow asynchrony between mating and ovulation. Many mammals store sperm in the lower oviduct where specific glycans on oviduct epithelial cells retain sperm to form a reservoir. Binding to oviduct cells suppresses sperm intracellular Ca2+ and increases sperm longevity. We investigated the mechanisms by which a specific oviduct glycan, 3-O-sulfated Lewis X trisaccharide (suLeX), prolongs the lifespan of porcine sperm. Using targeted metabolomics, we found that binding to suLeX diminishes the abundance of 4-hydroxybenzoic acid, the precursor to ubiquinone (also known as Coenzyme Q), 30 min after addition. Ubiquinone functions as an electron acceptor in the electron transport chain (ETC). 3-O-sulfated Lewis X trisaccharide also suppressed the formation of fumarate. A component of the citric acid cycle, fumarate is synthesized by succinate-coenzyme Q reductase, which employs ubiquinone and is also known as Complex II in the ETC. Consistent with the reduced activity of the ETC, the production of harmful reactive oxygen species (ROS) was diminished. The enhanced sperm lifespan in the oviduct may be because of suppressed ROS production because high ROS concentrations have toxic effects on sperm.

Mitochondrial Damage-Associated Molecular Patterns and Metabolism in the Regulation of Innate Immunity

The innate immune system, as the host's first line of defense against intruders, plays a critical role in recognizing, identifying, and reacting to a wide range of microbial intruders. There is increasing evidence that mitochondrial stress is a major initiator of innate immune responses. When mitochondria's integrity is disrupted or dysfunction occurs, the mitochondria's contents are released into the cytosol. These contents, like reactive oxygen species, mitochondrial DNA, and double-stranded RNA, among others, act as damage-related molecular patterns (DAMPs) that can bind to multiple innate immune sensors, particularly pattern recognition receptors, thereby leading to inflammation. To avoid the production of DAMPs, in addition to safeguarding organelles integrity and functionality, mitochondria may activate mitophagy or apoptosis. Moreover, mitochondrial components and specific metabolic regulations modify properties of innate immune cells. These include macrophages, dendritic cells, innate lymphoid cells, and so on, in steady state or in stimulation that are involved in processes ranging from the tricarboxylic acid cycle to oxidative phosphorylation and fatty acid metabolism. Here we provide a brief summary of mitochondrial DAMPs' initiated and potentiated inflammatory response in the innate immune system. We also provide insights into how the state of activation, differentiation, and functional polarization of innate immune cells can be influenced by alteration to the metabolic pathways in mitochondria.

Bypassing mitochondrial defects rescues Huntington's phenotypes in Drosophila

Huntington's disease (HD) is a fatal neurodegenerative disease with limited treatment options. Human and animal studies have suggested that metabolic and mitochondrial dysfunctions contribute to HD pathogenesis. Here, we use high-resolution respirometry to uncover defective mitochondrial oxidative phosphorylation and electron transfer capacity when a mutant huntingtin fragment is targeted to neurons or muscles in Drosophila and find that enhancing mitochondrial function can ameliorate these defects. In particular, we find that co-expression of parkin, an E3 ubiquitin ligase critical for mitochondrial dynamics and homeostasis, produces significant enhancement of mitochondrial respiration when expressed either in neurons or muscles, resulting in significant rescue of neurodegeneration, viability and longevity in HD model flies. Targeting mutant HTT to muscles results in larger mitochondria and higher mitochondrial mass, while co-expression of parkin increases mitochondrial fission and decreases mass. Furthermore, directly addressing HD-mediated defects in the fly's mitochondrial electron transport system, by rerouting electrons to either bypass mitochondrial complex I or complexes III-IV, significantly increases mitochondrial respiration and results in a striking rescue of all phenotypes arising from neuronal mutant huntingtin expression. These observations suggest that bypassing impaired mitochondrial respiratory complexes in HD may have therapeutic potential for the treatment of this devastating disorder.

Antioxidants Improve the Proliferation and Efficacy of hUC-MSCs against H2O2-Induced Senescence

Human umbilical cord mesenchymal stem cells (hUC-MSCs) are broadly applied in clinical treatment due to convenient accessibility, low immunogenicity, and the absence of any ethical issues involved. However, the microenvironment of inflammatory tissues may cause oxidative stress and induce senescence in transplanted hUC-MSCs, which will further reduce the proliferation, migration ability, and the final therapeutic effects of hUC-MSCs. Beta-nicotinamide mononucleotide (NMN) and coenzyme Q10 (CoQ10) are famous antioxidants and longevity medicines that could reduce intracellular reactive oxygen species levels by different mechanisms. In this study, hUC-MSCs were treated in vitro with NMN and CoQ10 to determine if they could reduce oxidative stress caused by hydrogen peroxide (H₂O₂) and recover cell functions. The effects of NMN and CoQ10 on the cell proliferation, the mRNA levels of the inflammatory cytokine TNFα and the anti-inflammatory cytokine IL10, and the differentiation and cell migration ability of hUC-MSCs before and after H₂O₂ treatment were investigated. The findings revealed that NMN and CoQ10 reduced H₂O₂-induced senescence and increased hUC-MSCs' proliferation in the late phase as passage 12 and later. The TNFα mRNA level of hUC-MSCs induced by H₂O₂ was significantly decreased after antioxidant treatment. NMN and CoQ10 all reduced the adipogenic differentiation ability of hUC-MSCs. CoQ10 improved the chondrogenic differentiation ability of hUC-MSCs. Furthermore, NMN was found to significantly enhance the migration ability of hUC-MSCs. Transcriptomic analysis revealed that NMN and CoQ10 both increased DNA repair ability and cyclin expression and downregulated TNF and IL-17 inflammatory signaling pathways, thereby contributing to the proliferative promotion of senecent stem cells and resistance to oxidative stress. These findings suggest that antioxidants can improve the survival and efficacy of hUC-MSCs in stem cell therapy for inflammation-related diseases.

The mechanism of ferroptosis in early brain injury after subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a cerebrovascular accident with an acute onset, severe disease characteristics, and poor prognosis. Within 72 hours after the occurrence of SAH, a sequence of pathological changes occur in the body including blood-brain barrier breakdown, cerebral edema, and reduced cerebrovascular flow that are defined as early brain injury (EBI), and it has been demonstrated that EBI exhibits an obvious correlation with poor prognosis. Ferroptosis is a novel programmed cell death mode. Ferroptosis is induced by the iron-dependent accumulation of lipid peroxides and reactive oxygen species (ROS). Ferroptosis involves abnormal iron metabolism, glutathione depletion, and lipid peroxidation. Recent study revealed that ferroptosis is involved in EBI and is significantly correlated with poor prognosis. With the gradual realization of the importance of ferroptosis, an increasing number of studies have been conducted to examine this process. This review summarizes the latest work in this field and tracks current research progress. We focused on iron metabolism, lipid metabolism, reduction systems centered on the GSH/GPX4 system, other newly discovered GSH/GPX4-independent antioxidant systems, and their related targets in the context of early brain injury. Additionally, we examined certain ferroptosis regulatory mechanisms that have been studied in other fields but not in SAH. A link between death and oxidative stress has been described. Additionally, we highlight the future research direction of ferroptosis in EBI of SAH, and this provides new ideas for follow-up research.

How the Disruption of Mitochondrial Redox Signalling Contributes to Ageing

In the past, mitochondrial reactive oxygen species (mtROS) were considered a byproduct of cellular metabolism. Due to the capacity of mtROS to cause oxidative damage, they were proposed as the main drivers of ageing and age-related diseases. Today, we know that mtROS are cellular messengers instrumental in maintaining cellular homeostasis. As cellular messengers, they are produced in specific places at specific times, and the intensity and duration of the ROS signal determine the downstream effects of mitochondrial redox signalling. We do not know yet all the processes for which mtROS are important, but we have learnt that they are essential in decisions that affect cellular differentiation, proliferation and survival. On top of causing damage due to their capacity to oxidize cellular components, mtROS contribute to the onset of degenerative diseases when redox signalling becomes dysregulated. Here, we review the best-characterized signalling pathways in which mtROS participate and those pathological processes in which they are involved. We focus on how mtROS signalling is altered during ageing and discuss whether the accumulation of damaged mitochondria without signalling capacity is a cause or a consequence of ageing.

Pathways Affected by Falcarinol-Type Polyacetylenes and Implications for Their Anti-Inflammatory Function and Potential in Cancer Chemoprevention

Polyacetylene phytochemicals are emerging as potentially responsible for the chemoprotective effects of consuming apiaceous vegetables. There is some evidence suggesting that polyacetylenes (PAs) impact carcinogenesis by influencing a wide variety of signalling pathways, which are important in regulating inflammation, apoptosis, cell cycle regulation, etc. Studies have shown a correlation between human dietary intake of PA-rich vegetables with a reduced risk of inflammation and cancer. PA supplementation can influence cell growth, gene expression and immunological responses, and has been shown to reduce the tumour number in rat and mouse models. Cancer chemoprevention by dietary PAs involves several mechanisms, including effects on inflammatory cytokines, the NF-κB pathway, antioxidant response elements, unfolded protein response (UPR) pathway, growth factor signalling, cell cycle progression and apoptosis. This review summarises the published research on falcarinol-type PA compounds and their mechanisms of action regarding cancer chemoprevention and also identifies some gaps in our current understanding of the health benefits of these PAs.

An oviduct glycan increases sperm lifespan by diminishing ubiquinone and production of reactive oxygen species

Sperm storage by females after mating for species-dependent periods is used widely among animals with internal fertilization to allow asynchrony between mating and ovulation. Many mammals store sperm in the lower oviduct where specific glycans on epithelial cells retain sperm to form a reservoir. Binding to oviduct cells suppresses sperm intracellular Ca 2+ and increases sperm longevity. We investigated the mechanisms by which a specific oviduct glycan, 3-O-sulfated Lewis X trisaccharide (suLe X ), prolongs the lifespan of porcine sperm. Using targeted metabolomics, we report that binding to suLe X diminishes the abundance of the precursor to ubiquinone and suppresses formation of fumarate, a specific citric acid cycle component, diminishing the activity of the electron transport chain and reducing the production of harmful reactive oxygen species (ROS). The enhanced sperm lifespan in the oviduct may be due to suppressed ROS production as many reports have demonstrated toxic effects of high ROS concentrations on sperm.

Application of the fission yeast Schizosaccharomyces pombe in human nutrition

Fission yeast Schizosaccharomyces pombe (S. pombe) is renowned as a powerful genetic model for deciphering cellular and molecular biological phenomena, including cell division, chromosomal events, stress responses, and human carcinogenesis. Traditionally, Africans use S. pombe to ferment the beer called 'Pombe', which continues to be consumed in many parts of Africa. Although not as widely utilized as the baker's yeast Saccharomyces cerevisiae, S. pombe has secured several niches in the food industry for human nutrition because of its unique metabolism. This review will explore three specific facets of human nutrition where S. pombe has made a significant impact: namely, in wine fermentation, animal husbandry and neutraceutical supplementation coenzyme Q10 production. Discussions focus on the current gaps in these areas, and the potential research advances useful for addressing future challenges. Overall, gaining a better understanding of S. pombe metabolism will strengthen production in these areas and potentially spearhead novel future applications.

Recent Advances in the Study of Na+/K+-ATPase in Neurodegenerative Diseases

Na⁺/K⁺-ATPase (NKA), a large transmembrane protein, is expressed in the plasma membrane of most eukaryotic cells. It maintains resting membrane potential, cell volume and secondary transcellular transport of other ions and neurotransmitters. NKA consumes about half of the ATP molecules in the brain, which makes NKA highly sensitive to energy deficiency. Neurodegenerative diseases (NDDs) are a group of diseases characterized by chronic, progressive and irreversible neuronal loss in specific brain areas. The pathogenesis of NDDs is sophisticated, involving protein misfolding and aggregation, mitochondrial dysfunction and oxidative stress. The protective effect of NKA against NDDs has been emerging gradually in the past few decades. Hence, understanding the role of NKA in NDDs is critical for elucidating the underlying pathophysiology of NDDs and identifying new therapeutic targets. The present review focuses on the recent progress involving different aspects of NKA in cellular homeostasis to present in-depth understanding of this unique protein. Moreover, the essential roles of NKA in NDDs are discussed to provide a platform and bright future for the improvement of clinical research in NDDs.

Modulatory effect of exogenous Coenzyme Q10 on redox and inflammatory biomarkers during aging in rats

An impaired redox homeostasis is an important hallmark of biological aging. Coenzyme Q₁₀ is an endogenous lipophilic antioxidant that decreases with age and has been linked to oxidative stress. The purpose of this study was to evaluate the effect of CoQ₁₀ supplementation on redox homeostasis and levels of inflammatory cytokines in young and old rats. Male Wistar rats (young and old) were randomly divided into four groups (n = 6). Group I: young control, Group II: young rats treated with CoQ₁₀, Group III: old control, Group IV: old rats treated with CoQ₁₀. CoQ₁₀ (20 mg/kg) was administered daily to Group II and IV via oral gavage. After 28 days of treatment, rats were sacrificed and biomarkers of oxidative stress and inflammatory cytokines were evaluated. Results demonstrated a significant (p ≤ 0.05) increase in malondialdehyde, protein carbonyl oxidation, advanced oxidation protein products, inflammatory cytokines: CRP, IL-6, TNF-α, and a decline in levels of superoxide dismutase, catalase, reduced glutathione, ferric reducing antioxidant potential in plasma and plasma membrane redox system in old rats when compared to young rats. After treatment with CoQ₁₀ significant decrease in the level of MDA, PCO, AOPP, CRP, IL-6, and TNF-α was observed. Also, significant up-regulation of SOD, CAT, GSH, FRAP, and PMRS was observed. The results show that supplementing rats with CoQ₁₀ aids in the maintenance of redox equilibrium with replenishment of antioxidant reserves and down-regulation of inflammatory biomarkers. Thus CoQ₁₀ supplementation could be a potential anti-aging therapy.

Mitochondrial ROS signalling requires uninterrupted electron flow and is lost during ageing in flies

Mitochondrial reactive oxygen species (mtROS) are cellular messengers essential for cellular homeostasis. In response to stress, reverse electron transport (RET) through respiratory complex I generates high levels of mtROS. Suppression of ROS production via RET (ROS-RET) reduces survival under stress, while activation of ROS-RET extends lifespan in basal conditions. Here, we demonstrate that ROS-RET signalling requires increased electron entry and uninterrupted electron flow through the electron transport chain (ETC). We find that in old fruit flies, ROS-RET is abolished when electron flux is decreased and that their mitochondria produce consistently high levels of mtROS. Finally, we demonstrate that in young flies, limiting electron exit, but not entry, from the ETC phenocopies mtROS generation observed in old individuals. Our results elucidate the mechanism by which ROS signalling is lost during ageing.

Redox Signaling and Stress in Inherited Myopathies

Significance: Reactive oxygen species (ROS) are highly reactive compounds that behave like a double-edged sword; they damage cellular structures and act as second messengers in signal transduction. Mitochondria and endoplasmic reticulum (ER) are interconnected organelles with a central role in ROS production, detoxification, and oxidative stress response. Skeletal muscle is the most abundant tissue in mammals and one of the most metabolically active ones and thus relies mainly on oxidative phosphorylation (OxPhos) to synthesize adenosine triphosphate. The impairment of OxPhos leads to myopathy and increased ROS production, thus affecting both redox poise and signaling. In addition, ROS enter the ER and trigger ER stress and its maladaptive response, which also lead to a myopathic phenotype with mitochondrial involvement. Here, we review the role of ROS signaling in myopathies due to either mitochondrial or ER dysfunction. Recent Advances: Relevant advances have been evolving over the last 10 years on the intricate ROS-dependent pathways that act as modifiers of the disease course in several myopathies. To this end, pathways related to mitochondrial biogenesis, satellite cell differentiation, and ER stress have been studied extensively in myopathies. Critical Issues: The analysis of the chemistry and the exact quantitation, as well as the localization of ROS, are still challenging due to the intrinsic labile nature of ROS and the technical limitations of their sensors. Future Directions: The mechanistic studies of the pathogenesis of mitochondrial and ER-related myopathies offer a unique possibility to discover novel ROS-dependent pathways. Antioxid. Redox Signal. 37, 301-323.

What physiological role(s) does the alternative oxidase perform in animals?

Although the alternative oxidase, AOX, was known to be widespread in the animal kingdom by 2004, its exact physiological role in animals remains poorly understood. Here we present what evidence has accumulated thus far, indicating that it may play a role in enabling animals to resist various kinds of stress, including toxins, abnormal oxygen or nutrient levels, protein unfolding, dessication and pathogen attack. Much of our knowledge comes from studies in model organisms, where any benefits from exogenously expressed AOX may be masked by its unregulated expression, which may itself be stressful. The further question arises as to why AOX has been lost from some major crown groups, namely vertebrates, insects and cephalopods, if it plays important roles favouring the survival of other animals. We conclude by presenting some speculative ideas addressing this question, and an outline of how it might be approached experimentally.

Defining roles of specific reactive oxygen species (ROS) in cell biology and physiology

'Reactive oxygen species' (ROS) is a generic term that defines a wide variety of oxidant molecules with vastly different properties and biological functions that range from signalling to causing cell damage. Consequently, the description of oxidants needs to be chemically precise to translate research on their biological effects into therapeutic benefit in redox medicine. This Expert Recommendation article pinpoints key issues associated with identifying the physiological roles of oxidants, focusing on H₂O₂ and O₂^.-. The generic term ROS should not be used to describe specific molecular agents. We also advocate for greater precision in measurement of H₂O₂, O₂^.- and other oxidants, along with more specific identification of their signalling targets. Future work should also consider inter-organellar communication and the interactions of redox-sensitive signalling targets within organs and whole organisms, including the contribution of environmental exposures. To achieve these goals, development of tools that enable site-specific and real-time detection and quantification of individual oxidants in cells and model organisms are needed. We also stress that physiological O₂ levels should be maintained in cell culture to better mimic in vivo redox reactions associated with specific cell types. Use of precise definitions and analytical tools will help harmonize research among the many scientific disciplines working on the common goal of understanding redox biology.

Mitochondrial electron transport chain is necessary for NLRP3 inflammasome activation

The NLRP3 inflammasome is linked to sterile and pathogen-dependent inflammation, and its dysregulation underlies many chronic diseases. Mitochondria have been implicated as regulators of the NLRP3 inflammasome through several mechanisms including generation of mitochondrial reactive oxygen species (ROS). Here, we report that mitochondrial electron transport chain (ETC) complex I, II, III and V inhibitors all prevent NLRP3 inflammasome activation. Ectopic expression of Saccharomyces cerevisiae NADH dehydrogenase (NDI1) or Ciona intestinalis alternative oxidase, which can complement the functional loss of mitochondrial complex I or III, respectively, without generation of ROS, rescued NLRP3 inflammasome activation in the absence of endogenous mitochondrial complex I or complex III function. Metabolomics revealed phosphocreatine (PCr), which can sustain ATP levels, as a common metabolite that is diminished by mitochondrial ETC inhibitors. PCr depletion decreased ATP levels and NLRP3 inflammasome activation. Thus, the mitochondrial ETC sustains NLRP3 inflammasome activation through PCr-dependent generation of ATP, but via a ROS-independent mechanism.

XJB-5-131 Is a Mild Uncoupler of Oxidative Phosphorylation

BACKGROUND

Mitochondria (MT) are energy "powerhouses" of the cell and the decline in their function from oxidative damage is strongly correlated in many diseases. To suppress oxygen damage, we have developed and applied XJB-5-131 as a targeted platform for neutralizing reactive oxygen species (ROS) directly in MT. Although the beneficial activity of XJB-5-131 is well documented, the mechanism of its protective effects is not yet fully understood.

OBJECTIVE

Here, we elucidate the mechanism of protection for XJB-5-131, a mitochondrial targeted antioxidant and electron scavenger.

METHODS

The Seahorse Flux Analyzer was used to probe the respiratory states of isolated mouse brain mitochondria treated with XJB-5-131 compared to controls.

RESULTS

Surprisingly, there is no direct impact of XJB-5-131 radical scavenger on the electron flow through the electron transport chain. Rather, XJB-5-131 is a mild uncoupler of oxidative phosphorylation. The nitroxide moiety in XJB-5-131 acts as a superoxide dismutase mimic, which both extracts or donates electrons during redox reactions. The electron scavenging activity of XJB-5-131 prevents the leakage of electrons and reduces formation of superoxide anion, thereby reducing ROS.

CONCLUSION

We show here that XJB-5-131 is a mild uncoupler of oxidative phosphorylation in MT. The mild uncoupling property of XJB-5-131 arises from its redox properties, which exert a protective effect by reducing ROS-induced damage without sacrificing energy production. Because mitochondrial decline is a common and central feature of toxicity, the favorable properties of XJB-5-131 are likely to be useful in treating Huntington's disease and a wide spectrum of neurodegenerative diseases for which oxidative damage is a key component. The mild uncoupling properties of XJB-5-131 suggest a valuable mechanism of action for the design of clinically effective antioxidants.

Coenzyme Q at the Hinge of Health and Metabolic Diseases

Coenzyme Q is a unique lipidic molecule highly conserved in evolution and essential to maintaining aerobic metabolism. It is endogenously synthesized in all cells by a very complex pathway involving a group of nuclear genes that share high homology among species. This pathway is tightly regulated at transcription and translation, but also by environment and energy requirements. Here, we review how coenzyme Q reacts within mitochondria to promote ATP synthesis and also integrates a plethora of metabolic pathways and regulates mitochondrial oxidative stress. Coenzyme Q is also located in all cellular membranes and plasma lipoproteins in which it exerts antioxidant function, and its reaction with different extramitochondrial oxidoreductases contributes to regulate the cellular redox homeostasis and cytosolic oxidative stress, providing a key factor in controlling various apoptosis mechanisms. Coenzyme Q levels can be decreased in humans by defects in the biosynthesis pathway or by mitochondrial or cytosolic dysfunctions, leading to a highly heterogeneous group of mitochondrial diseases included in the coenzyme Q deficiency syndrome. We also review the importance of coenzyme Q levels and its reactions involved in aging and age-associated metabolic disorders, and how the strategy of its supplementation has had benefits for combating these diseases and for physical performance in aging.

The multiple roles of coenzyme Q in cellular homeostasis and their relevance for the pathogenesis of coenzyme Q deficiency

Coenzyme Q (CoQ) is a redox active lipid that plays a central role in cellular homeostasis. It was discovered more than 60 years ago because of its role as electron transporter in the mitochondrial respiratory chain. Since then it has become evident that CoQ has many other functions, not directly related to bioenergetics. It is a cofactor of several mitochondrial dehydrogenases involved in the metabolism of lipids, amino acids, and nucleotides, and in sulfide detoxification. It is a powerful antioxidant and it is involved in the control of programmed cell death by modulating both apoptosis and ferroptosis. CoQ deficiency is a clinically and genetically heterogeneous group of disorders characterized by the impairment of CoQ biosynthesis. CoQ deficient patients display defects in cellular bioenergetics, but also in the other pathways in which CoQ is involved. In this review we will focus on the functions of CoQ not directly related to the respiratory chain, and on how their impairment is relevant for the pathophysiology of CoQ deficiency. A better understanding of the complex set of events triggered by CoQ deficiency will allow to design novel approaches for the treatment of this condition.

Oxidative Stress and Endoplasmic Reticulum Stress in Rare Respiratory Diseases

Several studies have shown that some rare respiratory diseases, such as alpha-1 antitrypsin deficiency (AATD), idiopathic pulmonary fibrosis (IPF), cystic fibrosis (CF), and primary ciliary dyskinesia (PCD) present oxidative stress (OS) and endoplasmic reticulum (ER) stress. Their involvement in these pathologies and the use of antioxidants as therapeutic agents to minimize the effects of OS are discussed in this review.