Mitochondrial Respiration Rate Research Articles

Blocking the mineralocorticoid receptor prevents cardiac and mitochondrial dysfunction through the activation of NOX-4 in female hormone deprivation rats.

Young women exhibit lower rates of cardiovascular disease (CVD) than age-matched men, a protective effect often attributed to estrogen's influence on cardiac and mitochondrial function. The risk of CVD increases in post-menopausal women, likely due to estrogen deficiency and aldosterone's negative effects, including those on mitochondria and other cellular targets. This study aimed to explore the link between estrogen deficiency and mitochondrial dysfunction in cardiac health. We hypothesized that in estrogen-deprived conditions, aldosterone could stimulate NADPH oxidase, leading to mitochondrial dysfunction, and reduced cardiac contractility. Wistar rats were divided into four groups: Sham, Ovariectomy-induced hormone deprivation (Ovx), Ovx with apocynin treatment, and Ovx with spironolactone treatment for 60 days. Both apocynin and spironolactone countered the adverse effects of hormone deprivation by preserving myocardial contractility, improving cellular responses to calcium and isoproterenol, and normalizing the expression of key mitochondrial proteins. These compounds also attenuated the increase in reactive oxygen species (ROS) and maintained mitochondrial respiration rates. We concluded that estrogen deficiency contributes to cardiac oxidative stress via the NADPH oxidase and mitochondrial pathways. Apocynin and spironolactone offer significant protective effects, opening new avenues for treating cardiac issues related to estrogen deficiency.

From molecular to physiological responses: improved stress tolerance and longevity in Drosophila melanogaster under fluctuating thermal regimes.

Climate change introduces greater thermal variability, profoundly affecting ectothermic species whose body temperatures rely heavily on the environment. Understanding the physiological and metabolic responses to such variability is crucial for predicting how these species will cope with changing climates. This study investigates how chronic thermal stress impacts mitochondrial metabolism and physiological parameters in Drosophila melanogaster, hypothesizing that a fluctuating thermal regime (FTR) activates protective mechanisms enhancing stress tolerance and longevity. To test this, Drosophila were exposed to constant 24°C or to an FTR of 24°C:15°C (day:night) cycle following an initial 5day period at 24°C. The FTR group exhibited rapid transcript level changes after the first day of FTR, particularly those related to heat shock proteins, mitophagy and regulatory factors, which returned to initial levels after 5 days. Mitochondrial respiration rates initially decreased after 1 and 2 days of FTR, then recovered by day 5, indicating rapid acclimation. Enhanced antioxidant enzyme activities were observed early in the FTR group, after 1 day for mtSOD and SODcyt+ext and 3 days for both SOD and catalase, followed by a decline by day 5, suggesting efficient oxidative stress management. The FTR group showed lower CTmax on day 3, reflecting possible physiological strain at that time point, and complete recovery by day 5. Longevity increased under FTR, highlighting the activation of protective mechanisms with beneficial long-term effects. These results suggest that FTR prompts a temporal succession of rapid physiological adjustments at different levels of organisation, enhancing long-term survival in D. melanogaster.

Anticancer activity of salinomycin quaternary phosphonium salts.

In recent years salinomycin has emerged as a promising anticancer drug. Many literature reports have proved its remarkable antiproliferative activity. Moreover, chemical modifications of salinomycin lead to analogues with even higher cytotoxicity against cancer cell lines and a better selectivity index for malignant cells than those of the unmodified compound or a standard anticancer drug such as doxorubicin. In this paper we report the synthesis of a series of twelve novel salinomycin conjugates and their characterization by spectroscopic and spectrometric methods. Salinomycin was conjugated with different triphenylphosphonium cations in order to find out whether the conjugation with mitochondrial targeting vectors would have a beneficial impact on biological properties. Salinomycin and its novel conjugates were tested to determine their in vitro antiproliferative and antimicrobial activity. Taking into account the presence of triphenylphosphonium moiety, the impact of the obtained analogues on mitochondria activity was evaluated by MitoTrackers dyes, furthermore their apoptosis effect and cell cycle arrest were assessed. In addition, the changes in the mitochondrial membrane potential were measured and the ability to generate reactive oxygen species was assessed. Finally, we conducted biophysical studies to investigate the impact of the obtained salinomycin analogues on mitochondrial respiration rates and their electrophysiological properties. Results of this study have proved that conjugation of salinomycin with phosphonium cations leads to promising results in the search for promising anticancer agents.

Inhibition of the PI3K-AKT-MTORC1 axis reduces the burden of the m.3243A>G mtDNA mutation by promoting mitophagy and improving mitochondrial function

ABSTRACT Mitochondrial DNA (mtDNA) encodes genes essential for oxidative phosphorylation. The m.3243A>G mutation causes severe disease, including myopathy, lactic acidosis and stroke-like episodes (MELAS) and is the most common pathogenic mtDNA mutation in humans. We have previously shown that the mutation is associated with constitutive activation of the PI3K-AKT-MTORC1 axis. Inhibition of this pathway in patient fibroblasts reduced the mutant load, rescued mitochondrial bioenergetic function and reduced glucose dependence. We have now investigated the mechanisms that select against the mutant mtDNA under these conditions. Basal macroautophagy/autophagy and lysosomal degradation of mitochondria were suppressed in the mutant cells. Pharmacological inhibition of any step of the PI3K-AKT-MTORC1 pathway activated mitophagy and progressively reduced m.3243A>G mutant load over weeks. Inhibition of autophagy with bafilomycin A1 or chloroquine prevented the reduction in mutant load, suggesting that mitophagy was necessary to remove the mutant mtDNA. Inhibition of the pathway was associated with metabolic remodeling – mitochondrial membrane potential and respiratory rate improved even before a measurable fall in mutant load and proved crucial for mitophagy. Thus, maladaptive activation of the PI3K-AKT-MTORC1 axis and impaired autophagy play a major role in shaping the presentation and progression of disease caused by the m.3243A>G mutation. Our findings highlight a potential therapeutic target for this otherwise intractable disease. Abbreviation: ΔΨm: mitochondrial membrane potential; 2DG: 2-deoxy-D-glucose; ANOVA: analysis of variance; ARMS-qPCR: amplification-refractory mutation system quantitative polymerase chain reaction; Baf A1: bafilomycin A1; BSA: bovine serum albumin; CQ: chloroquine; Cybrid: cytoplasmic hybrid; CYCS: cytochrome c, somatic; DCA: dichloroacetic acid; DMEM: Dulbecco’s modified Eagle’s medium; DMSO: dimethylsulfoxide; EGFP: enhanced green fluorescent protein; LC3B-I: carboxy terminus cleaved microtubule-associated protein 1 light chain 3 beta; LC3B-II: lipidated microtubule-associated protein 1 light chain 3 beta; LY: LY290042; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MELAS: mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes; MFC: mitochondrial fragmentation count; mt-Keima: mitochondrial-targeted mKeima; mtDNA: mitochondrial DNA/mitochondrial genome; MTOR: mechanistic target of rapamycin kinase; MTORC1: MTOR complex 1; OA: oligomycin+antimycin A; OxPhos: oxidative phosphorylation; DPBS: Dulbecco’s phosphate-buffered saline; PPARGC1A/PGC-1α: PPARG coactivator 1 alpha; PPARGC1B/PGC-1β: PPARG coactivator 1 beta; PI3K: phosphoinositide 3-kinase; PINK1: PTEN induced kinase 1; qPCR: quantitative polymerase chain reaction; RNA-seq: RNA sequencing; RP: rapamycin; SQSTM1/p62: sequestosome 1; TEM: transmission electron microscopy; WT: wild-type

Endurance training enhances skeletal muscle mitochondrial respiration by promoting MOTS-c secretion.

The mitochondrial open reading frame of 12S rRNA-c (MOTS-c) is a biologically active mitochondria-derived peptide. However, the relationship between MOTS-c, skeletal muscle mitochondrial function, and endurance exercise adaptations is unknown. Here, we tested indices such as maximal oxygen uptake and serum MOTS-c levels in marathon runners and sedentary subjects. In addition, we tested aerobic exercise capacity, skeletal muscle mitochondrial respiration rate, and serum MOTS-c levels in mice subjected to long-term endurance training groups and sedentary groups. Our results indicated a close association between serum MOTS-c levels and aerobic exercise capacity. Circulating MOTS-c levels are expected to be an important indicator for predicting aerobic exercise capacity and assessing body fat status, endurance training load, and physical function. More importantly, we found that endurance training may enhance the mitochondrial respiratory function of skeletal muscle by promoting the secretion of MOTS-c and activating the AMPK/PGC-1α pathway.

NAD+ depletion is central to placental dysfunction in an inflammatory subclass of preeclampsia.

Preeclampsia (PE) is a hypertensive disorder of pregnancy and a major cause of maternal/perinatal adverse health outcomes with no effective therapeutic strategies. Our group previously identified distinct subclasses of PE, one of which exhibits heightened placental inflammation (inflammation-driven PE). In non-pregnant populations, chronic inflammation is associated with decreased levels of cellular NAD+, a vitamin B3 derivative involved in energy metabolism and mitochondrial function. Interestingly, specifically in placentas from women with inflammation-driven PE, we observed the increased activity of NAD+-consuming enzymes, decreased NAD+ content, decreased expression of mitochondrial proteins, and increased oxidative damage. HTR8 human trophoblasts likewise demonstrated increased NAD+-dependent ADP-ribosyltransferase (ART) activity, coupled with decreased mitochondrial respiration rates and invasive function under inflammatory conditions. Such adverse effects were attenuated by boosting cellular NAD+ levels with nicotinamide riboside (NR). Finally, in an LPS-induced rat model of inflammation-driven PE, NR administration (200 mg/kg/day) from gestational days 1-19 prevented maternal hypertension and fetal/placental growth restriction, improved placental mitochondrial function, and reduced inflammation and oxidative stress. This study demonstrates the critical role of NAD+ in maintaining placental function and identifies NAD+ boosting as a promising preventative strategy for PE.

Toxicological evaluation of environmental chemicals associated with AD identified using an exposomic framework

AbstractExposure to environmental chemicals has been associated with Alzheimer’s disease (AD); however, most studies have used a targeted approach to study this relationship. While targeted approaches have been critical to understand mechanisms, they do not reflect real world exposures where an individual is exposed to multiple chemicals at the same time. Exposomics provides the opportunity to use an ‐omics level approach to understand the environmental drivers of disease by measuring the burden of multiple chemicals at the same time. Using an exposomic approach, we found a metabolite of the legacy pesticide DDT to be associated with AD in an observational study. We then investigated whether DDT can exacerbate AD‐related pathology using a transgenic strain of the nematode model Caenorhabditis elegans (worm) that expresses a mutant tau protein fragment that is prone to aggregation.Exposure to 3µM DDT resulted in internal levels of 0.5 pg (SD: 0.01) p, p’‐DDT per worm and 0.1 pg (SD: 0.01) of its metabolite p, p’‐DDE. We found that exposure DDT significantly restricted growth in the transgenic strain more than it does in wildtype worms. Further, DDT significantly lowered mitochondrial respiration rates in both strains. High‐resolution mass spectrometry‐based metabolomics (HRMS) analysis using the whole worm showed reduced levels of several amino acids and an increase in adenosylselenohomocysteine in DDT exposed worms. DDT exposure in the transgenic strain significantly increased the amount of time spent curling. The curling phenotype has been previously associated with mitochondrial dysfunction. Our data suggest that low level exposure to DDT likely exacerbates the mitochondrial inhibitory effects of aggregating tau protein in C. elegans.We are investigating the relationship between persistent organic pollutants and age‐related cognitive decline in the Reference Ability Neural Network study. This study, conducted in healthy volunteers, allows us to consider the relationship between exposure and poor cognitive function without confounding by underlying disease. We plan to investigate the potential mechanism through which these chemicals affect neuronal health while considering them as a mixture using C. elegans. Recent advancements in predictive toxicology provide a starting point to consider the appropriate health and functional end points that should be investigated.

PERM1 regulates mitochondrial energetics through O-GlcNAcylation in the heart

PERM1 was initially identified as a new downstream target of PGC-1α and ERRs that regulates mitochondrial bioenergetics in skeletal muscle. Subsequently, we and other groups demonstrated that PERM1 is also a positive regulator of mitochondrial bioenergetics in the heart. However, the exact mechanisms of regulatory functions of PERM1 remain poorly understood. O-GlcNAcylation is a post-translational modification of proteins that are regulated by two enzymes: O-GlcNAc transferase (OGT) that adds O-GlcNAc to proteins; O-GlcNAcase (OGA) that removes O-GlcNAc from proteins. O-GlcNAcylation is a powerful signaling mechanism mediating cellular responses to stressors and nutrient availability, which, among other targets, may influence cardiac metabolism. We hypothesized that PERM1 regulates mitochondrial energetics in cardiomyocytes through modulation of O-GlcNAcylation. We found that overexpression of PERM1 decreased the total levels of O-GlcNAcylated proteins, concomitant with decreased OGT and increased OGA expression levels. Luciferase gene reporter assay showed that PERM1 significantly decreases the promoter activity of Ogt without changing the promoter activity of Oga. The downregulation of OGT by PERM1 overexpression was mediated through its interaction with E2F1, a known transcription repressor of Ogt. A deliberate increase of O-GlcNAcylation through Oga silencing in cardiomyocytes decreased the basal and maximal mitochondrial respiration and ATP production rates, all of which were completely restored by PERM1 overexpression. Furthermore, excessive O-GlcNAcylation caused by the loss of PERM1 led to the increase of O-GlcNAcylated PGC-1α, a master regulator of mitochondrial bioenergetics, concurrent with the dissociation of PGC-1α from PPARα, a well-known transcription factor that regulates fatty acid β-oxidation. We conclude that PERM1 positively regulates mitochondrial energetics, in part, via suppressing O-GlcNAcylation in cardiac myocytes.

Rapid modulation of interscapular brown adipose tissue mitochondrial activity by ketosis induced by 1,3-butanediol administration to rats.

Some studies indicate that brown adipose tissue (BAT) represents a promising target in the fight against dysmetabolic diseases, with indications suggesting it as a potential target for the effects of ketone bodies. We investigate whether the elevation of plasma levels of the ketone body β-hydroxybutyrate, achieved through the invivo administration of its precursor 1,3-butanediol (BD) to rats, could impact interscapular BAT (iBAT) mitochondrial biochemistry and functionality. We examined the effects induced by BD within 3 h and after 2 weeks of treatment. A large-scale quantitative proteomics approach, coupling liquid chromatography with tandem mass spectrometry (LC-MS/MS) analysis, and Western blot associated with functional studies by respirometry allowed us to evaluate the changes in iBAT mitochondrial protein expression and bioenergetics induced by BD. BD administration increased β-hydroxybutyrate plasma levels, which correlated with an enhancement in iBAT mitochondrial respiration rate, likely due to the activation of the respiratory chain and uncoupling protein-1. The proteomic analysis demonstrated that BD influenced the mitochondrial levels of specific subunits belonging to the five respiratory complexes, uncoupling protein-1, and proteins involved in propanoate metabolism. BD administration also induced lysine β-hydroxybutyrylation of mitochondrial proteins, including specific subunits of the respiratory chain complexes and uncoupling protein-1. Most of the BD-induced effects were observed within 3 h of its administration and persisted/increased after 2 weeks of treatment. In conclusion, by using BD to increase β-hydroxybutyrate levels, we provide evidence supporting the role of β-hydroxybutyrate as a signaling molecule capable of rapidly modulating BAT physiology by acting at the mitochondrial level.

Spontaneous reversal of small molecule-induced mitochondrial uncoupling: the case of anilinothiophenes.

Tissue specificity can render mitochondrial uncouplers more promising asleading compounds for creating drugs against serious diseases. In searchof tissue-specific uncouplers, we address anilinothiophenes as possible glutathione-S-transferase substrates (GST). Earlier, 'cyclic' uncoupling activity was reported for 5-bromo-N-(4-chlorophenyl)-3,4-dinitro-2-thiophenamine (BDCT) in isolated rat liver mitochondria (RLM). The mechanism by which BDCT induced two-phase changes in mitochondrial respiration (stimulation followed by deceleration) was unknown. To clarify this issue, we synthesized BDCT and its two analogues. Among these, 5-bromo-3,4-dinitro-N-(4-nitrophenyl)-2-thiophenamine (BDNT) appeared to be the most effective as a mitochondrial uncoupler, decreasing membrane potential and stimulating respiration at submicromolar concentrations. Importantly, BDNT exerted two-phase changes in both mitochondrial membrane potential and respiration rate of RLM, which were enhanced by the addition of glutathione (GSH) but inhibited by the compounds capable of GSH depleting, such as 1-chloro-2,4-dinitrobenzene (CDNB). By contrast, the phase of recoupling was not observed in rat heart mitochondria (RHM). Remarkably, BDNT elicited mitochondrial depolarization in primary human fibroblasts but not in cultured human liver (HepG2) cells. By detecting proton-selective electrical current through planar bilayer lipid membranes, we demonstrated the ability of BDCT and BDNT to transfer protons across membranes. BDNT proved to be an anionic protonophore with a pKa of 7.38. By using LC-MS and capillary electrophoresis, we directly showed the formation of BDNT conjugates with GSH upon incubation with RLM but not RHM. Therefore, we hypothesize that GST is involved in the disappearance of the anilinothiophene uncoupling activity in RLM, ensuring the tissue-specific behavior of the uncoupler.

Brief Magnetic Field Exposure Stimulates Doxorubicin Uptake into Breast Cancer Cells in Association with TRPC1 Expression: A Precision Oncology Methodology to Enhance Chemotherapeutic Outcome.

Background/Objectives: Doxorubicin (DOX) is commonly used as a chemotherapeutic agent for the treatment of breast cancer. Nonetheless, its systemic delivery via intravenous injection and toxicity towards healthy tissues commonly result in a broad range of detrimental side effects. Breast cancer severity was previously shown to be correlated with TRPC1 channel expression that conferred upon it enhanced vulnerability to pulsed electromagnetic field (PEMF) therapy. PEMF therapy was also previously shown to enhance breast cancer cell vulnerability to DOX in vitro and in vivo that correlated with TRPC1 expression and mitochondrial respiratory rates. Methods: DOX uptake was assessed by measuring its innate autofluorescence within murine 4T1 or human MCF7 breast cancer cells following magnetic exposure. Cellular vulnerability to doxorubicin uptake was assessed by monitoring mitochondrial activity and cellular DNA content. Results: Here, we demonstrate that 10 min of PEMF exposure could augment DOX uptake into 4T1 and MCF7 breast cancer cells. DOX uptake could be increased by TRPC1 overexpression, whereas inhibiting the activity of TRPC1 channels with SKF-96356 or genetic knockdown, precluded DOX uptake. PEMF exposure enhances DOX-mediated killing of breast cancer cells, reducing the IC50 value of DOX by half, whereas muscle cells, representative of collateral tissues, were less sensitive to PEMF-enhanced DOX-mediated cytotoxicity. Vesicular loading of DOX correlated with TRPC1 expression. Conclusions: This study presents a novel TRPC1-mediated mechanism through which PEMF therapy may enhance DOX cytotoxicity in breast cancer cells, paving the way for the development of localized non-invasive PEMF platforms to improve cancer outcomes with lower systemic levels of DOX.

Exploring the impact of mitochondrial-targeting anthelmintic agents with GLUT1 inhibitor BAY-876 on breast cancer cell metabolism

BackgroundCancer cells alter their metabolic phenotypes with nutritional change. Single agent approaches targeting mitochondrial metabolism in cancer have failed due to either dose limiting off target toxicities, or lack of significant efficacy in vivo. To mitigate these clinical challenges, we investigated the potential utility of repurposing FDA approved mitochondrial targeting anthelmintic agents, niclosamide, IMD-0354 and pyrvinium pamoate, to be combined with GLUT1 inhibitor BAY-876 to enhance the inhibitory capacity of the major metabolic phenotypes exhibited by tumors.MethodsTo test this, we used breast cancer cell lines MDA-MB-231 and 4T1 which exhibit differing basal metabolic rates of glycolysis and mitochondrial respiration, respectively. Metabolic characterization was carried out using Seahorse XFe96 Bioanalyzer and statistical analysis was carried out via ANOVA.ResultsHere, we found that specific responses to mitochondrial and glycolysis targeting agents elicit responses that correlate with tested cell lines basal metabolic rates and fuel preference, highlighting the potential to cater metabolism targeting treatment regimens based on specific tumor nutrient handling. Inhibition of GLUT1 with BAY-876 potently inhibited glycolysis in both MDA-MB-231 and 4T1 cells, and niclosamide and pyrvinium pamoate perturbed mitochondrial respiration that resulted in potent compensatory glycolysis in the cell lines tested.ConclusionIn this regard, combination of BAY-876 with both mitochondrial targeting agents resulted in inhibition of compensatory glycolysis and subsequent metabolic crisis. These studies highlight targeting tumor metabolism as a combination treatment regimen that can be tailored by basal and compensatory metabolic phenotypes.

Mitochondrial respiratory pathways in immature rat heart tissue using different cardioplegic solutions.

Minor defects in the mitochondrial ATP-generating system and post-cardioplegia oxidative phosphorylation can negatively impact cardiac function in immature hearts. This study aimed to examine the mitochondrial respiratory pathway using three different cardioplegic solutions (Custodiol HTK, St. Thomas, and Del Nido) during moderate (1h) and long (3h) ischemic periods. A total of 41 male Wistar albino rats were utilized in this study. Five experiments were conducted without the use of any cardioplegic solution (CP0 group). To assess both moderate and prolonged ischemic periods, six experiments were carried out in each of the following groups: CP1 group (St. Thomas solution), CP2 group (Custodiol HTK solution), and CP3 group (Del Nido solution). After 1h, the highest mitochondrial respiration rate was observed in the CP3 group and the lowest in the CP1 group (p = 0.006). After adding ADP substrate, the highest mitochondrial ATP-production-coupled respiration was recorded in the CP3 group, which was similar to the control group CP0. After 3h, while evaluating the ratio between mitochondrial respiration ATP-production coupled and basal respiration, significant differences were found between CP1 group and CP3 group (p = 0.035), as well as between the CP1 and CP0 groups (p = 0.045). Additionally, by assessing the condition of the outer mitochondrial membrane using the Cyt C effect (Cyt/Phos [ADP]), significant differences were observed between the CP1 and CP3 group (p = 0.004), as well as between CP1 and CP0 groups (p = 0.003). Del Nido cardioplegic solution provided optimal mitochondrial protection under moderate and long myocardial ischemia conditions.

Effect of mitochondrial oxidative stress on regulatory T cell manufacturing for clinical application in transplantation: Results from a pilot study

The manufacturing process of regulatory T (Treg) cells for clinical application begins with the positive selection of CD25+ cells using superparamagnetic iron oxide nanoparticle (SPION)-conjugated anti-CD25 antibodies (spCD25) and immunomagnetic cell separation technology. Our findings revealed that the interaction of spCD25 with its cell target induced the internalization of the complex spCD25–interleukin-2 receptor. Accumulation of intracellular spCD25 triggered oxidative stress, causing delayed Treg expansion and temporary reduction in suppressor activity. This activation delay hindered the efficient generation of clinically competent cells. During this early phase, Treg cells exhibited elevated mitochondrial superoxide and lipid peroxidation levels, with a concomitant decrease in mitochondrial respiration rates. The results uncovered the increased mitochondrial unfolded protein response. This protective, redox-sensitive activity is inherent in Tregs when contrasted with homologous, spCD25-treated, conventional T cells. Although the temporary effects of spCD25 on clinically competent cells did not impede their use in a safety/feasibility pilot study with kidney transplant recipients, it is reasonable to anticipate a potential reduction in their therapeutic efficacy. The mechanistic understanding of the adverse effects triggered by spCD25 is crucial for improving the manufacturing process of clinically competent Treg cells, a pivotal step in the successful implementation of immune cell therapy in transplantation.

Age-related increase of CD38 directs osteoclastogenic potential of monocytic myeloid-derived suppressor cells through mitochondrial dysfunction in male mice.

An aged immune system undergoes substantial changes where myelopoiesis dominates within the bone marrow. Monocytic-MDSCs (M-MDSCs) have been found to play an important role in osteoclastogenesis and bone resorption. In this study, we sought to provide a more comprehensive understanding of the osteoclastogenic potential of bone marrow M-MDSCs during normal aging through transcriptomic and metabolic changes. Using young mature and aged mice, detailed immunophenotypic analyses of myeloid cells revealed that the M-MDSCs were not increased in bone marrow, however M-MDSCS were significantly expanded in peripheral tissues. Although aged mice exhibited a similar number of M-MDSCs in bone marrow, these M-MDSCs had significantly higher osteoclastogenic potential and greater demineralization activity. Intriguingly, osteoclast progenitors from aged bone marrow M-MDSCs exhibited greater mitochondrial respiration rate and glucose metabolism. Further, transcriptomic analyses revealed the upregulation of mitochondrial oxidative phosphorylation and glucose metabolism genes. Interestingly, there was 8-fold increase in Cd38 mRNA gene expression, consistent with the Mouse Aging Cell Atlas transcriptomic database, and confirmed by qRT-PCR. CD38 regulates NAD+ availability, and 78c, a small molecule inhibitor of CD38, reduced the mitochondrial oxygen consumption rate and glucose metabolism and inhibited the osteoclastogenic potential of aged mice bone marrow-derived M-MDSCs. These results indicate that the age-related increase in Cd38 expression in M-MDSCs bias the transcriptome of M-MDSCs towards osteoclastogenesis. This enhanced understanding of the mechanistic underpinnings of M-MDSCs and their osteoclastogenesis during aging could lead to new therapeutic approaches for age-related bone loss and promote healthy aging.

ND-13 preserves mitochondrial integrity via the RhoA/ROCK1/Drp1-S616 pathway providing acute cardioprotection in myocardial infarction

Abstract Background Ischemia-reperfusion injury (IRI) following acute myocardial infarction is a major contributor to heart failure and mortality worldwide. Drp1-driven mitochondrial fragmentation disrupts mitochondrial function, increases cardiomyocyte death, and aggravates cardiac dysfunction. We investigated whether ND-13, a novel DJ-1-derived peptide, can acutely protect the heart by maintaining mitochondrial homeostasis and modulating Drp1 activity during IRI. Methods The effects of ND-13 on Drp1 activity were assessed by studying mitochondrial dynamics, function and survival signalling pathways. Cardioprotective effects of ND-13 were assessed using in vitro, ex vivo and in vivo models of IRI. Results ND-13 demonstrated acute cardioprotective effects in murine adult cardiomyocytes subjected to simulated IRI by a 42% reduction in cell death. The excessive mitochondrial fission following IRI was attenuated by inhibiting Drp1 phosphorylation at the Ser616 residue by reduced activity of the RhoA/ROCK1 pathway. This in turn enhanced mitochondrial function as seen through increased mitochondrial respiration rates (basal, maximal and spare respiratory capacity), increased ATP production, maintained mitochondrial membrane potential and reduced reactive oxygen species levels. The acute cardioprotective effect of ND-13 was reproduced in both an ex vivo Langendorff based model of IRI with a 43% reduction infarct size and an in vivo murine model of IRI with a 35% reduction of infarct size. These results indicate the robust effect of the peptide and its potential for clinical translation through intravenous delivery. Conclusion In this study, we demonstrate ND-13 as a small peptide that modulates mitochondrial dynamics through the RhoA/ROCK1/DRP1-S616 pathway, which highlights a potential new therapeutic target for myocardial IRI.

Hydrogen Sulfide Modulates Astrocytic Toxicity in Mouse Spinal Cord Cultures: Implications for Amyotrophic Lateral Sclerosis.

Hydrogen sulfide (H2S), a known inhibitor of the electron transport chain, is endogenously produced in the periphery as well as in the central nervous system, where is mainly generated by glial cells. It affects, as a cellular signaling molecule, many different biochemical processes. In the central nervous system, depending on its concentration, it can be protective or damaging to neurons. In the study, we have demonstrated, in a primary mouse spinal cord cultures, that it is particularly harmful to motor neurons, is produced by glial cells, and is stimulated by inflammation. However, its role on glial cells, especially astrocytes, is still under-investigated. The present study was designed to evaluate the impact of H2S on astrocytes and their phenotypic heterogeneity, together with the functionality and homeostasis of mitochondria in primary spinal cord cultures. We found that H2S modulates astrocytes' morphological changes and their phenotypic transformation, exerts toxic properties by decreasing ATP production and the mitochondrial respiration rate, disturbs mitochondrial depolarization, and alters the energetic metabolism. These results further support the hypothesis that H2S is a toxic mediator, mainly released by astrocytes, possibly acting as an autocrine factor toward astrocytes, and probably involved in the non-cell autonomous mechanisms leading to motor neuron death.

Orthogonal Persulfide Generation through Precision Tools Provides Insights into Mitochondrial Sulfane Sulfur.

The sulfane sulfur pool, comprised of persulfide (RS-SH) and polysulfide (RS-SnH) derived from hydrogen sulfide (H2S), has emerged as a major player in redox biochemistry. Mitochondria, besides energy generation, serve as significant cellular redox hubs, mediate stress response and cellular health. However, the effects of endogenous mitochondrial sulfane sulfur (MSS) remain largely uncharacterized as compared with their cytosolic counterparts, cytosolic sulfane sulfur (CSS). To investigate this, we designed a novel artificial substrate for mitochondrial 3-mercaptopyruvate sulfurtransferase (3-MST), a key enzyme involved in MSS biosynthesis. Using cells expressing a mitochondrion-localized persulfide biosensor, we demonstrate this tool's ability to selectively enhance MSS. While H2S was previously known to suppress human immunodeficiency virus (HIV-1), we found that MSS profoundly affected the HIV-1 life cycle, mediating viral reactivation from latency. Additionally, we provide evidence for the role of the host's mitochondrial redox state, membrane potential, apoptosis, and respiration rates in managing HIV-1 latency and reactivation. Together, dynamic fluctuations in the MSS pool have a significant and possibly conflicting effect on HIV-1 viral latency. The precision tools developed herein allow for orthogonal generation of persulfide within both mitochondria and the cytosol and will be useful in interrogating disease biology.

Potential role of peripheral blood mononuclear cell ' s mitochondrial respiratory dysfunction in heart failure severity prediction in patients with cardioverter-defibrillator implantation indications.

It has been reported that the mitochondrial respiratory dysfunction (MRD) is important mechanisms affecting the heart failure (HF) pathogenesis. We sought to evaluate the potential role of MRD of peripheral blood mononuclear cells (PBMC) in HF severity prediction in patients with cardioverter-defibrillator implantation indications. In this single-center study patients with HF of New York Heart Association (NYHA) I-III functional class (FC) and cardioverter-defibrillator implantation indications underwent transthoracic echocardiography (TTE) and MRD assessment using PBMC. Mitochondrial respiration rate (MRR) indicators (pyruvate + malate + adenosine diphosphate; succinate + adenosine diphosphate; pyruvate + malate - adenosine diphosphate [V4.1]; succinate - adenosine diphosphate) were calculated. Correlations between HF NYHA FC, TTE and MRR indicators were evaluated. Based on our data, we developed a risk model regarding HF severity. Of 53 (100.0%) HF patients, 33 (62.3%) had mild exercise intolerance (1st group) and 20 (37.7%) had moderate-to-severe exercise intolerance (2nd group). Patients with mild exercise intolerance were likely to have a higher V4.1 (P < 0.001) values. V4.1 was independently associated with moderate-to-severe exercise intolerance in univariate and multivariate logistic regression (OR = 0.932, 95% CI: 0.891-0.975, P < 0.001). The severity of HF is associated with PBMC mitochondrial respiratory dysfunction in patients with cardioverter-defibrillator implantation indications. Our HF severity risk model including V4.1 parameters is able to distinguish patients with mild and moderate-to-severe exercise intolerance. Further investigations of their predictive significance are warranted.

Exercise Alters Peripheral Blood Mononuclear Cell Mitochondrial Respiratory Rates in Persons with CKD: Results from the ESTEEM-VIDA Pilot Randomized Clinical Trial

Exercise Alters Peripheral Blood Mononuclear Cell Mitochondrial Respiratory Rates in Persons with CKD: Results from the ESTEEM-VIDA Pilot Randomized Clinical Trial