Gelsemium low doses protect against serum deprivation-induced stress on mitochondria in neuronal cells.

ETHNOPHARMACOLOGICAL RELEVANCE: Gelsemium dynamized dilutions (GDD) are known as a remedy for a wide range of behavioral and psychological symptoms of depression and anxiety at ultra-low doses, yet the underlying mechanisms of the mode of action of G. sempervirens itself are not well understood. AIM OF THE STUDY: The present study was designed to examine the neuroprotective effects of Gelsemium preparations in counteracting stress-related mitochondrial dysfunctions in neuronal cells. MATERIALS AND METHODS: We started by studying how serum deprivation affects the mitochondrial functions of human neuroblastoma (SH-SY5Y) cells. Next, we looked into the potential of various Gelsemium dilutions to improve cell survival and ATP levels. After identifying the most effective dilutions, 3C and 5C, we tested their ability to protect SH-SY5Y cells from stress-induced mitochondrial deficits. We measured total and mitochondrial superoxide anion radicals using fluorescent dyes dihydroethidium (DHE) and the red mitochondrial superoxide indicator (MitoSOX). Additionally, we assessed total nitric oxide levels with 4,5-diaminofluorescein diacetate (DAF-2DA), examined the redox state using pRA305 cells stably transfected with a plasmid encoding a redox-sensitive green fluorescent protein, and analyzed mitochondrial network morphology using an automated high-content analysis device, Cytation3. Furthermore, we investigated bioenergetics by measuring ATP production with a bioluminescence assay (ViaLighTM HT) and evaluated mitochondrial respiration (OCR) and glycolysis (ECAR) using the Seahorse Bioscience XF24 Analyzer. Finally, we determined cell survival using an MTT reduction assay. RESULTS: Our research indicates that Gelsemium dilutions (3C and 5C) exhibited neuroprotective effects by: - Normalizing total and mitochondrial superoxide anion radicals and total nitric oxide levels. - Regulating the mitochondrial redox environment and mitochondrial networks morphology. - Increasing ATP generation as well as OCR and ECAR levels, thereby reducing the viability loss induced by serum withdrawal stress. CONCLUSIONS: These findings highlight that dynamized Gelsemium preparations may have neuroprotective effects against stress-induced cellular changes in the brain by regulating mitochondrial functions, essential for the survival, plasticity, and function of neurons in depression.

Drug-Induced Mitochondrial Disruption in the Blood-Brain Barrier Cells: Overlooked Player in Drug Safety Evaluation.

The blood-brain barrier (BBB) is based on the unique pattern of the microvasculature of the central nervous system (CNS), which controls the transport of molecules between the CNS and the blood. The blood-brain barrier is mainly composed of endothelial cells, pericytes, and basement membrane, as well as the astrocytes and immune cells as perivascular macrophages and microglial cells. The dysfunction of this barrier can cause serious neuronal disorders due to the transport of hazardous molecules and immune cells to the CNS. Mitochondria plays a major role in cellular homeostasis in terms of health and disease. This review evaluated the published data about the effect of the drugs on the cells of BBB. Only seven articles were found that considered the effect of drugs on the barrier endothelial cells and mitochondria via different assays. Further studies are recommended to evaluate the impact of used medications on BBB cell bioenergetics. Also, the effect of the newly studied pharmaceutical agents on the BBB bioenergetics should be included within their safety profile studies.

Data mining of PubChem bioassay records reveals diverse OXPHOS inhibitory chemotypes as potential therapeutic agents against ovarian cancer.

Focused screening on target-prioritized compound sets can be an efficient alternative to high throughput screening (HTS). For most biomolecular targets, compound prioritization models depend on prior screening data or a target structure. For phenotypic or multi-protein pathway targets, it may not be clear which public assay records provide relevant data. The question also arises as to whether data collected from disparate assays might be usefully consolidated. Here, we report on the development and application of a data mining pipeline to examine these issues. To illustrate, we focus on identifying inhibitors of oxidative phosphorylation, a druggable metabolic process in epithelial ovarian tumors. The pipeline compiled 8415 available OXPHOS-related bioassays in the PubChem data repository involving 312,093 unique compound records. Application of PubChem assay activity annotations, PAINS (Pan Assay Interference Compounds), and Lipinski-like bioavailability filters yields 1852 putative OXPHOS-active compounds that fall into 464 clusters. These chemotypes are diverse but have relatively high hydrophobicity and molecular weight but lower complexity and drug-likeness. These chemotypes show a high abundance of bicyclic ring systems and oxygen containing functional groups including ketones, allylic oxides (alpha/beta unsaturated carbonyls), hydroxyl groups, and ethers. In contrast, amide and primary amine functional groups have a notably lower than random prevalence. UMAP representation of the chemical space shows strong divergence in the regions occupied by OXPHOS-inactive and -active compounds. Of the six compounds selected for biological testing, 4 showed statistically significant inhibition of electron transport in bioenergetics assays. Two of these four compounds, lacidipine and esbiothrin, increased in intracellular oxygen radicals (a major hallmark of most OXPHOS inhibitors) and decreased the viability of two ovarian cancer cell lines, ID8 and OVCAR5. Finally, data from the pipeline were used to train random forest and support vector classifiers that effectively prioritized OXPHOS inhibitory compounds within a held-out test set (ROCAUC 0.962 and 0.927, respectively) and on another set containing 44 documented OXPHOS inhibitors outside of the training set (ROCAUC 0.900 and 0.823). This prototype pipeline is extensible and could be adapted for focus screening on other phenotypic targets for which sufficient public data are available.Scientific contributionHere, we describe and apply an assay data mining pipeline to compile, process, filter, and mine public bioassay data. We believe the procedure may be more broadly applied to guide compound selection in early-stage hit finding on novel multi-protein mechanistic or phenotypic targets. To demonstrate the utility of our approach, we apply a data mining strategy on a large set of public assay data to find drug-like molecules that inhibit oxidative phosphorylation (OXPHOS) as candidates for ovarian cancer therapies.

Disruption of mitochondrial electron transport impairs urinary concentration via AMPK-dependent suppression of aquaporin-2.

Urinary concentration is an energy-dependent process that minimizes body water loss by increasing aquaporin-2 (AQP2) expression in collecting duct (CD) principal cells. To investigate the role of mitochondrial (mt) ATP production in renal water clearance, we disrupted mt electron transport in CD cells by targeting ubiquinone (Q) binding protein QPC (UQCRQ), a subunit of mt complex III essential for oxidative phosphorylation. QPC-deficient mice produced less concentrated urine than controls, both at baseline and after type 2 vasopressin receptor stimulation with desmopressin. Impaired urinary concentration in QPC-deficient mice was associated with reduced total AQP2 protein levels in CD tubules, while AQP2 phosphorylation and membrane trafficking remained unaffected. In cultured inner medullary CD cells treated with mt complex III inhibitor antimycin A, the reduction in AQP2 abundance was associated with activation of 5' adenosine monophosphate-activated protein kinase (AMPK) and was reversed by treatment with AMPK inhibitor SBI-0206965. In summary, our studies demonstrated that the physiological regulation of AQP2 abundance in principal CD cells was dependent on mt electron transport. Furthermore, our data suggested that oxidative phosphorylation in CD cells was dispensable for maintaining water homeostasis under baseline conditions, but necessary for maximal stimulation of AQP2 expression and urinary concentration.

Metabolic impairments in neurodegeneration with brain iron accumulation.

Neurodegeneration with brain iron accumulation (NBIA) is a broad, heterogeneous group of rare inherited diseases (1-3 patients/1,000,000 people) characterized by progressive symptoms associated with excessive abnormal iron deposition in the brain. Approximately 15,000-20,000 individuals worldwide are estimated to be affected by NBIA. NBIA is usually associated with slowly progressive pyramidal and extrapyramidal symptoms, axonal motor neuropathy, optic nerve atrophy, cognitive impairment and neuropsychiatric disorders. To date, eleven subtypes of NBIA have been described and the most common ones include pantothenate kinase-associated neurodegeneration (PKAN), PLA2G6-associated neurodegeneration (PLAN), mitochondrial membrane protein-associated neurodegeneration (MPAN) and beta-propeller protein-associated neurodegeneration (BPAN). We present a comprehensive overview of the evidence for disturbed cellular homeostasis and metabolic alterations in NBIA variants, with a careful focus on mitochondrial bioenergetics and lipid metabolism which drives a new perspective in understanding the course of this infrequent malady.

Assessing the physiological effects of microplastics on cultured mussels in the Mediterranean Sea.

Microplastics (MPs) pollution has gained attention due to its ecological threats and potential economic impacts. Yet significant knowledge gaps remain in understanding MPs effects on marine organisms' physiology. This study quantifies the physiological impacts of MPs on farmed mussels (Mytilus galloprovincialis) across various locations in the Mediterranean Sea by combining a laboratory experiment with a Dynamic Energy Budget (DEB) model. Mussels' clearance rates (CR) were measured under different conditions of microplastics and suspended sediment. The DEB model, driven by satellite data and an MPs distribution model, was validated with literature growth and CR data, supporting further the data extracted from the conducted experiment. Results indicate that while the physiological impacts are minimal in most areas, important reductions in CR (8-25%) were estimated in regions like the Gulf of Napoli, leading to reduced growth (6-16%) and reduced reproductive output (7-19%). In addition to microplastic concentrations, seasonal and spatial variations of food availability and suspended inorganic matter importantly control the impacts, with mussels in oligotrophic environments (such as the Gulf of Napoli) showing higher vulnerability to MPs compared to those in more eutrophic locations. This study underscores the utility of bioenergetics models, such as DEB, in evaluating the ecological risks of microplastics and suggests their broader application in MPs research.

Metabolic energetic adaptation of Atlantic salmon phagocytes to changes in carbon sources and exposure to PAMPs.

Phagocytic cells are pivotal for host homeostasis and infection defense, necessitating metabolic adaptations in glycolysis, the tricarboxylic acid (TCA) cycle, and oxidative phosphorylation (OXPHOS). While mammalian phagocytes shift towards glycolysis and glutaminolysis during polarization, research on fish phagocyte metabolic reprogramming is limited. To address this, the Atlantic salmon phagocytic cell line, SHK-1, serves as a valuable model. Using the Seahorse XFe96 Flux Analyzer, this study compares SHK-1 bioenergetics under glucose-restricted (L-15 medium) and glucose-supplemented (PM) conditions, providing insights into metabolic characteristics and responses to Piscirickettsia salmonis bacterium Pathogen-associated molecular patterns (PAMPs). A standardized protocol for the study of real-time changes in the metabolism study of SHK-1 in PM and L-15 media, determining oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) is shown. Exhibiting metabolic adaptations, SHK-1 cells in the PM medium have higher basal and maximal OCR and spare capacity (SRC), while those grown in the L-15 medium favor OXPHOS, showing minimal glycolytic function. Despite metabolic differences, intracellular ATP levels are comparable, highlighting the metabolic plasticity and adaptability of SHK-1 cells to various carbon sources. Exposure to PAMPs from Piscirickettsia salmonis induces a metabolic shift, increasing glycolysis and OXPHOS, influencing ATP, lactate, glutamine, and glutamate levels. These findings highlight the role of mitochondrial bioenergetics and metabolic plasticity in salmon phagocytes, offering novel nutritional strategies for host-pathogen interventions based on energy metabolism.

α-Synuclein pathology disrupts mitochondrial function in dopaminergic and cholinergic neurons at-risk in Parkinson's disease.

BACKGROUND: Pathological accumulation of aggregated α-synuclein (aSYN) is a common feature of Parkinson's disease (PD). However, the mechanisms by which intracellular aSYN pathology contributes to dysfunction and degeneration of neurons in the brain are still unclear. A potentially relevant target of aSYN is the mitochondrion. To test this hypothesis, genetic and physiological methods were used to monitor mitochondrial function in substantia nigra pars compacta (SNc) dopaminergic and pedunculopontine nucleus (PPN) cholinergic neurons after stereotaxic injection of aSYN pre-formed fibrils (PFFs) into the mouse brain. METHODS: aSYN PFFs were stereotaxically injected into the SNc or PPN of mice. Twelve weeks later, mice were studied using a combination of approaches, including immunocytochemical analysis, cell-type specific transcriptomic profiling, electron microscopy, electrophysiology and two-photon-laser-scanning microscopy of genetically encoded sensors for bioenergetic and redox status. RESULTS: In addition to inducing a significant neuronal loss, SNc injection of PFFs induced the formation of intracellular, phosphorylated aSYN aggregates selectively in dopaminergic neurons. In these neurons, PFF-exposure decreased mitochondrial gene expression, reduced the number of mitochondria, increased oxidant stress, and profoundly disrupted mitochondrial adenosine triphosphate production. Consistent with an aSYN-induced bioenergetic deficit, the autonomous spiking of dopaminergic neurons slowed or stopped. PFFs also up-regulated lysosomal gene expression and increased lysosomal abundance, leading to the formation of Lewy-like inclusions. Similar changes were observed in PPN cholinergic neurons following aSYN PFF exposure. CONCLUSIONS: Taken together, our findings suggest that disruption of mitochondrial function, and the subsequent bioenergetic deficit, is a proximal step in the cascade of events induced by aSYN pathology leading to dysfunction and degeneration of neurons at-risk in PD.

The evolving pathophysiology of TBI and the advantages of temporally-guided combination therapies.

Several clinical and experimental studies have demonstrated that traumatic brain injury (TBI) activates cascades of biochemical, molecular, structural, and pathological changes in the brain. These changes combine to contribute to the various outcomes observed after TBI. Given the breadth and complexity of changes, combination treatments may be an effective approach for targeting multiple detrimental pathways to yield meaningful improvements. In order to identify targets for therapy development, the temporally evolving pathophysiology of TBI needs to be elucidated in detail at both the cellular and molecular levels, as it has been shown that the mechanisms contributing to cognitive dysfunction change over time. Thus, a combination of individual mechanism-based therapies is likely to be effective when maintained based on the time courses of the cellular and molecular changes being targeted. In this review, we will discuss the temporal changes of some of the key clinical pathologies of human TBI, the underlying cellular and molecular mechanisms, and the results from preclinical and clinical studies aimed at mitigating their consequences. As most of the pathological events that occur after TBI are likely to have subsided in the chronic stage of the disease, combination treatments aimed at attenuating chronic conditions such as cognitive dysfunction may not require the initiation of individual treatments at a specific time. We propose that a combination of acute, subacute, and chronic interventions may be necessary to maximally improve health-related quality of life (HRQoL) for persons who have sustained a TBI.

Oxidized Carbon Nanoparticles Enhance Cellular Energetics With Application to Injured Brain.

Pro-energetic effects of functionalized, oxidized carbon nanozymes (OCNs) are reported. OCNs, derived from harsh acid oxidation of single-wall carbon nanotubes or activated charcoal are previously shown to possess multiple nanozymatic activities including mimicking superoxide dismutase and catalyzing the oxidation of reduced nicotinamide adenine dinucleotide (NADH) to NAD+. These actions are predicted to generate a glycolytic shift and enhance mitochondrial energetics under impaired conditions. Impaired mitochondrial energy metabolism is increasingly recognized as an important facet of traumatic brain injury (TBI) pathophysiology and decreases the efficiency of electron transport chain (ETC)-coupled adenosine triphosphate (ATP) and NAD+ regeneration. In vitro, OCNs promote a pro-aerobic shift in energy metabolism that persists through ETC inhibition and enhances glycolytic flux, glycolytic ATP production, and cellular generation of lactate, a crucial auxiliary substrate for energy metabolism. To address specific mechanisms of iron injury from hemorrhage, OCNs with the iron chelator, deferoxamine (DEF), covalently-linked were synthesized. DEF-linked OCNs induce a glycolytic shift in-vitro and in-vivo in tissue sections from a rat model of TBI complicated by hemorrhagic contusion. OCNs further reduced hemorrhage volumes 3 days following TBI. These results suggest OCNs are promising as pleiotropic mediators of cell and tissue resilience to injury.

Illusory movements for immobile patients with extensive burns (IMMOBILE): A randomized, controlled, cross-over trial.

INTRODUCTION: Patients who have sustained extensive burns frequently exhibit substantial damage to skeletal muscle and associated complications. The rehabilitation of these patients can be challenging due to the nature of the injury and the subsequent complications. Nevertheless, there is a possibility that functional proprioceptive stimulation (illusory movements) may facilitate effective rehabilitation in patients with limited physiotherapy options. Nevertheless, this approach has yet to be tested in patients with burn injuries. MATERIAL AND METHODOLOGY: A prospective, randomised, crossover trial was conducted at a burn centre in a tertiary teaching hospital. The objective was to assess the effects of illusory movements on energy metabolism, insulin sensitivity, and skeletal muscle biology in adult critically ill patients with deep burns covering 30 % or more of the total body surface area. Two 30-minute daily sessions of functional proprioceptive stimulation were administered in addition to the standard physical therapy or physical activity regimen. Subsequently, the patients proceeded to the next stage of the trial, which involved a two-week crossover period. MEASUREMENTS AND MAIN RESULTS: Daily indirect calorimetry and calculation of nitrogen balance. Skeletal muscle biopsies from vastus lateralis for high resolution respirometry and euglycemic clamps to assess whole body glucose disposal were performed three times: at baseline and then fortnightly after each intervention period. The intervention was feasible and well tolerated in both early and late stages of burn disease. It did not change energy expenditure (mean change -33 [95 % CI: -292;+227] kcal .24 h-1, p = 0.79), nitrogen balance (+2.0 [95 % CI: -3.1;+7.1] g N .1.73 m-2 BSA .24 h-1), or insulin sensitivity (mean change of insulin-mediated glucose disposal -0.33 [95 % CI: -1.18;+0.53] mmol.h-1). At the cellular level, the intervention increased the capacity of mitochondria to synthesize ATP by aerobic phosphorylation and tended to increase mitochondrial coupling. Functional capacities of fatty acid oxidation and electron transfer chain complexes I, II, and IV were unaffected. CONCLUSIONS: Compared to physical therapy alone, two daily sessions of functional proprioceptive stimulation in addition to usual physical therapy in patients with extensive burns did not change energy expenditure, insulin sensitivity, nitrogen balance, or energy substrate oxidation. At cellular level, the intervention improved the capacity of aerobic phosphorylation in skeletal muscle mitochondria. Clinical effects remain to be demonstrated in adequately powered trials.

A Mediterranean Diet-Oriented Intervention Rescues Impaired Blood Cell Bioenergetics in Patients with Metabolic Dysfunction-Associated Steatotic Liver Disease.

Background: Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD), a novel term for Non-Alcoholic Fatty Liver Disease (NAFLD), is associated with liver mitochondrial dysfunction. We previously demonstrated that mitochondrial respiratory capacity in peripheral blood mononuclear cells (PBMCs) was significantly reduced in patients with MASLD compared to non-MASLD controls. For MASLD treatment, guidelines recommend behavioral and dietary changes to reduce body weight. A recent 12-month clinical trial demonstrated that ameliorating patients' lifestyles through improved adherence to the Mediterranean diet and encouraged physical activity results in MASLD remission or regression. Methods: As a sub-study of the 12-month clinical trial, we evaluated the effects of the Mediterranean diet-oriented intervention on PBMC mitochondrial DNA content and respiratory parameters and on various biomarkers associated with MASLD. Results: Contrary to what was found at the baseline, after twelve months of intervention, systemic inflammatory and bioenergetics parameters did not differ between MASLD patients (N = 15) and control subjects (N = 17). PBMCs from MASLD subjects showed rescued basal respiration, ATP-linked respiration, maximal respiration, and spare respiratory capacity. The observed recovery coincided with a significant increase in the patients' adherence to the Mediterranean diet (Medscore). Conclusions: Our findings indicate that a Mediterranean diet-oriented intervention, without calorie reduction, preserves blood cell mitochondrial function in MASLD subjects. Thus, PBMC bioenergetics-based assays might be taken into account not only for diagnosing but also for monitoring therapeutic responses in MASLD.

Plant-derived compounds normalize platelet bioenergetics and function in hyperglycemia.

Background: Polyphenols have been shown to decrease oxidative stress and modulate glycemic response. Nevertheless, their effect on platelet bioenergetics and clot structure in diabetes and hyperglycemia is unknown. Objectives: To investigate the effect of polyphenols on human platelet bioenergetics and its subsequent effect on clot structure in normoglycemia vs acute hyperglycemia in vitro. Methods: Four polyphenols (resveratrol, hesperetin, epigallocatechin gallate [EGCG], and quercetin) were selected for initial analysis. Healthy volunteers' isolated platelets/platelet-rich plasma were treated with 5 or 25 mM glucose to represent normoglycemia and acute hyperglycemia, respectively. Platelet-derived reactive oxygen species (ROS), citrate synthase activity (mitochondrial density), mitochondrial calcium flux, and mitochondrial respiration were performed following exposure to polyphenols (20 µM, 1 hour) to determine their effects on platelet bioenergetics. Procoagulant platelets (annexin V) and fibrin fiber density (Alexa Fluor-488 fibrinogen; Invitrogen) were analyzed by laser scanning confocal microscopy, while clot porosity was determined using platelet-rich plasma following exposure to polyphenols (20 µM, 20 minutes). Results: Acute hyperglycemia increased ROS, mitochondrial calcium flux, maximal respiration, and procoagulant platelet number. Resveratrol, quercetin, and EGCG reduced platelet ROS in normoglycemic and acute hyperglycemic conditions. Mitochondrial density was decreased by quercetin and EGCG in normoglycemia. Resveratrol and EGCG reduced mitochondrial calcium flux in acute hyperglycemia. Resveratrol also decreased procoagulant platelet number and attenuated oxygen consumption rate in normoglycemia and acute hyperglycemia. No effect of hyperglycemia or polyphenols was observed on fibrin fiber density or clot pore size. Conclusion: Our results suggest polyphenols attenuate increased platelet activity stemming from hyperglycemia and may benefit thrombosis-preventative strategies in patients with diabetes.

New Insights into Mitochondria in Health and Diseases.

Mitochondria are a unique type of semi-autonomous organelle within the cell that carry out essential functions crucial for the cell's survival and well-being. They are the location where eukaryotic cells carry out energy metabolism. Aside from producing the majority of ATP through oxidative phosphorylation, which provides essential energy for cellular functions, mitochondria also participate in other metabolic processes within the cell, such as the electron transport chain, citric acid cycle, and ß-oxidation of fatty acids. Furthermore, mitochondria regulate the production and elimination of ROS, the synthesis of nucleotides and amino acids, the balance of calcium ions, and the process of cell death. Therefore, it is widely accepted that mitochondrial dysfunction is a factor that causes or contributes to the development and advancement of various diseases. These include common systemic diseases, such as aging, diabetes, Parkinson's disease, and cancer, as well as rare metabolic disorders, like Kearns-Sayre syndrome, Leigh disease, and mitochondrial myopathy. This overview outlines the various mechanisms by which mitochondria are involved in numerous illnesses and cellular physiological activities. Additionally, it provides new discoveries regarding the involvement of mitochondria in both disorders and the maintenance of good health.

Structural and functional mechanisms of cytochrome c oxidase.

Cytochrome c oxidase (CcO) is the terminal enzyme in the electron transfer chain in mitochondria. It catalyzes the four-electron reduction of O2 to H2O and harnesses the redox energy to drive unidirectional proton translocation against a proton electrochemical gradient. A great deal of research has been conducted to comprehend the molecular properties of CcO. However, the mechanism by which the oxygen reduction reaction is coupled to proton translocation remains poorly understood. Here, we review the chemical properties of a variety of key oxygen intermediates of bovine CcO (bCcO) revealed by time-resolved resonance Raman spectroscopy and the structural features of the enzyme uncovered by serial femtosecond crystallography, an innovative technique that allows structural determination at room temperature without radiation damage. The implications of these data on the proton translocation mechanism are discussed.

Bone Morphogenetic Protein 9 Protects Against Myocardial Infarction by Improving Lymphatic Drainage Function and Triggering DECR1-Mediated Mitochondrial Bioenergetics.

BACKGROUND: BMP9 (bone morphogenetic protein 9) is a member of the TGF-ß (transforming growth factor ß) family of cytokines with pleiotropic effects on glucose metabolism, fibrosis, and lymphatic development. However, the role of BMP9 in myocardial infarction (MI) remains elusive. METHODS: The expressional profiles of BMP9 in cardiac tissues and plasma samples of subjects with MI were determined by immunoassay or immunoblot. The role of BMP9 in MI was determined by evaluating the impact of BMP9 deficiency and replenishment with adeno-associated virus-mediated BMP9 expression or recombinant human BMP9 protein in mice. RESULTS: We show that circulating BMP9 and its cardiac levels are markedly increased in humans and mice with MI and are negatively associated with cardiac function. It is important to note that BMP9 deficiency exacerbates left ventricular dysfunction, increases infarct size, and augments cardiac fibrosis in mice with MI. In contrast, replenishment of BMP9 significantly attenuates these adverse effects. We further demonstrate that BMP9 improves lymphatic drainage function, thereby leading to a decrease of cardiac edema. In addition, BMP9 increases the expression of mitochondrial DECR1 (2,4-dienoyl-CoA reductase 1), a rate-limiting enzyme involved in ß-oxidation, which, in turn, promotes cardiac mitochondrial bioenergetics and mitigates MI-induced cardiomyocyte injury. Moreover, DECR1 deficiency exacerbates MI-induced cardiac damage in mice, whereas this adverse effect is restored by the treatment of adeno-associated virus-mediated DECR1. Consistently, DECR1 deletion abrogates the beneficial effect of BMP9 against MI-induced cardiomyopathy and cardiac damage in mice. CONCLUSIONS: These results suggest that BMP9 protects against MI by fine-tuning the multiorgan cross-talk among the liver, lymph, and the heart.

How Cryo-EM Revolutionized the Field of Bioenergetics.

Ten years ago, the term "resolution revolution" was used for the first time to describe how cryogenic electron microscopy (cryo-EM) marked the beginning of a new era in the field of structural biology, enabling the investigation of previously unsolvable protein targets. The success of cryo-EM was recognized with the 2017 Chemistry Nobel Prize and has become a widely used method for the structural characterization of biological macromolecules, quickly catching up to x-ray crystallography. Bioenergetics is the division of biochemistry that studies the mechanisms of energy conversion in living organisms, strongly focused on the molecular machines (enzymes) that carry out these processes in cells. As bioenergetic enzymes can be arranged in complexes characterized by conformational heterogeneity/flexibility, they represent challenging targets for structural investigation by crystallography. Over the last decade, cryo-EM has therefore become a powerful tool to investigate the structure and function of bioenergetic complexes; here, we provide an overview of the main achievements enabled by the technique. We first summarize the features of cryo-EM and compare them to x-ray crystallography, and then, we present the exciting discoveries brought about by cryo-EM, particularly but not exclusively focusing on the oxidative phosphorylation system, which is a crucial energy-converting mechanism in humans.

An evolving roadmap: using mitochondrial physiology to help guide conservation efforts.

The crucial role of aerobic energy production in sustaining eukaryotic life positions mitochondrial processes as key determinants of an animal's ability to withstand unpredictable environments. The advent of new techniques facilitating the measurement of mitochondrial function offers an increasingly promising tool for conservation approaches. Herein, we synthesize the current knowledge on the links between mitochondrial bioenergetics, ecophysiology and local adaptation, expanding them to the wider conservation physiology field. We discuss recent findings linking cellular bioenergetics to whole-animal fitness, in the current context of climate change. We summarize topics, questions, methods, pitfalls and caveats to help provide a comprehensive roadmap for studying mitochondria from a conservation perspective. Our overall aim is to help guide conservation in natural populations, outlining the methods and techniques that could be most useful to assess mitochondrial function in the field.

A global assessment of large terrestrial carnivore kill rates.

Through killing and instilling fear in their prey, large terrestrial carnivores shape the structure and function of ecosystems globally. Most large carnivore species have experienced severe range and population declines due to human activities, and many are now threatened with extinction. Consequently, the impacts of these predators on food webs have been diminished or lost completely from many ecosystems. Kill rates provide a fundamental metric for understanding large carnivore ecology and assessing and comparing predation within and across ecological communities. Our systematic review of large terrestrial mammalian carnivore kill rates reveals significant positive geographic (North America, Europe, and Africa) and taxonomic (grey wolf Canis lupus, puma Puma concolor, lion Panthera leo, and Eurasian lynx Lynx lynx) bias, with most studies apparently motivated by human-carnivore conflict over access to ungulate prey and wildlife management objectives. Our current understanding of the behaviour and functional roles of many large carnivore species and populations thus remains limited. By synthesising and comparing kill rates, we show that solitary carnivores (e.g. brown bears Ursus arctos and most felids) exhibit higher per capita kill rates than social carnivores. However, ungulate predation by bears is typically limited to predation of neonates during a short period. Lower per capita kill rates by social carnivores suggests group living significantly reduces energetic demands, or, alternatively, that group-living carnivores defend and consume a greater proportion of large prey carcasses, or may acquire more food through other means (e.g. scavenging, kleptoparasitism) than solitary hunters. Kill and consumption rates for Canidae - measured as kilograms of prey per kilogram of carnivore per day - are positively correlated with body mass, consistent with increasing energy costs associated with a cursorial hunting strategy. By contrast, ambush predators such as felids show an opposite trend, and thus the potential energetic advantage of an ambush hunting strategy for carnivores as body mass increases. Additionally, ungulate kill rates remain relatively constant across solitary felid body sizes, indicative of energetic constraints and optimal foraging. Kill rate estimates also reveal potential insights into trophic structuring within carnivore guilds, with subordinate carnivores often killing more than their larger counterparts, which may be indicative of having to cope with food losses to scavengers and dominant competitors. Subordinate carnivores may thus serve an important role in provisioning food to other trophic levels within their respective ecosystems. Importantly, kill rates also clarify misconceptions around the predatory behaviour of carnivores (e.g. spotted hyaenas Crocuta crocuta and wolverines Gulo gulo are often considered scavengers rather than the capable hunters that they are) and thus the potential impacts of various carnivore species on their ecological communities. Despite the importance of kill rates in understanding predator-prey interactions, their utility is not widely recognised, and insufficient research limits our ability to fully appreciate and predict the consequences of modified predation regimes, justify current management actions affecting carnivores, or inform effective conservation measures. Together with other important research on predator-prey interactions, robust kill rate studies that address the research deficiencies we highlight will provide a deeper understanding of the foraging behaviours and potential ecosystem impacts of many of the world's carnivores, thus aiding effective conservation and management actions.

Heterogeneous redox responses in NHDF cells primed to enhance mitochondrial bioenergetics.

Aging and lifestyle-related diseases, such as cardiovascular diseases, diabetes, cancer, and neurodegenerative disorders, are major global health challenges. These conditions are often linked to redox imbalances, where cells fail to regulate reactive redox species (RRS), leading to oxidative stress and cellular damage. Although antioxidants are known to neutralize harmful RRS, their clinical efficacy remains inconsistent. One reason for this inconsistency is the inadequacy of current in vitro models to accurately mimic in vivo redox conditions. This study addresses the gap in understanding the heterogeneity of redox responses in cells by using metabolically primed human dermal fibroblasts (NHDF), a model relevant for precision mitochondrial medicine. We investigated how metabolic priming, which enhances mitochondrial bioenergetics, influences redox responses to oxidative stress induced by hydrogen peroxide (H2O2) and tert-butyl hydroperoxide (tBHP). Specifically, we explored the impact of cell population density and cell cycle distribution on redox dynamics. Our findings indicate that NHDF cells cultured in oxidative phosphorylation-promoting medium (OXm) exhibit significantly larger variability in oxidative stress responses. This variability suggests that enhanced mitochondrial bioenergetics necessitates a constant regulation of the cellular redox machinery, potentially leading to heterogeneous responses. Additionally, cells grown in OXm showed increased mitochondrial polarization and a lower percentage of cells in the G2/M phase, contributing to the observed heterogeneity. Key factors influencing this variability included cell population density at the time of oxidant exposure and fluctuations in cell cycle distribution. Our results highlight the necessity of employing multiple oxidants in metabolic priming models to achieve a comprehensive understanding of oxidative stress responses and redox regulation mechanisms. Furthermore, the study emphasizes the need to refine in vitro models to better reflect in vivo conditions, which is crucial for the development of effective redox-based therapeutic strategies.