Mitochondrial ATP generation in stimulated platelets is essential for granule secretion but dispensable for aggregation and procoagulant activity

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ATP synthase K+- and H+-fluxes drive ATP synthesis and enable mitochondrial K+-‘uniporter’ function: I. Characterization of ion fluxes

ATP synthase (F1Fo) synthesizes daily our body's weight in ATP, whose production-rate can be transiently increased several-fold to meet changes in energy utilization. Using purified mammalian F1Fo-reconstituted proteoliposomes and isolated mitochondria, we show F1Fo can utilize both ΔΨm-driven H+- and K+-transport to synthesize ATP under physiological pH = 7.2 and K+ = 140 mEq/L conditions. Purely K+-driven ATP synthesis from single F1Fo molecules measured by bioluminescence photon detection could be directly demonstrated along with simultaneous measurements of unitary K+ currents by voltage clamp, both blocked by specific Fo inhibitors. In the presence of K+, compared to osmotically-matched conditions in which this cation is absent, isolated mitochondria display 3.5-fold higher rates of ATP synthesis, at the expense of 2.6-fold higher rates of oxygen consumption, these fluxes being driven by a 2.7:1 K+:H+ stoichiometry. The excellent agreement between the functional data obtained from purified F1Fo single molecule experiments and ATP synthase studied in the intact mitochondrion under unaltered OxPhos coupling by K+ presence, is entirely consistent with K+ transport through the ATP synthase driving the observed increase in ATP synthesis. Thus, both K+ (harnessing ΔΨm) and H+ (harnessing its chemical potential energy, ΔµH) drive ATP generation during normal physiology.

Role of Mitochondria in Physiology of Chondrocytes and Diseases of Osteoarthritis and Rheumatoid Arthritis

Purpose of Review Mitochondria are recognized to be one of the most important organelles in chondrocytes for their role in triphosphate (ATP) generation through aerobic phosphorylation. Mitochondria also participate in many intracellular processes involving modulating reactive oxygen species (ROS), responding to instantaneous hypoxia stress, regulating cytoplasmic transport of calcium ion, and directing mitophagy to maintain the homeostasis of individual chondrocytes. Designs To summarize the specific role of mitochondria in chondrocytes, we screened related papers in PubMed database and the search strategy is ((mitochondria) AND (chondrocyte)) AND (English [Language]). The articles published in the past 5 years were included and 130 papers were studied. Results In recent years, the integrity of mitochondrial structure has been regarded as a prerequisite for normal chondrocyte survival and defect in mitochondrial function has been found in cartilage-related diseases, such as osteoarthritis (OA) and rheumatoid arthritis (RA). However, the understanding of mitochondria in cartilage is still largely limited. The mechanism on how the changes in mitochondrial structure and function directly lead to the occurrence and development of cartilage-related diseases remains to be elusive. Conclusion This review aims to summarize the role of mitochondria in chondrocytes under the physiological and pathological changes from ATP generation, calcium homeostasis, redox regulation, mitophagy modulation, mitochondria biogenesis to immune response activation. The enhanced understanding of molecular mechanisms in mitochondria might offer some new cues for cartilage remodeling and pathological intervention.

Aflatoxin and Disruption of Energy Metabolism

Aflatoxins constitute a cluster of mycotoxins that are derived from fungal metabolites and are produced from diverse fungi species, especially Aspergillus. They are a collection of closely linked heterocyclic compounds produced predominantly by two filamentous fungi, Aspergillus flavus and Aspergillus parasiticus. They are also known to cause severe health threats to humans and animals, thereby resulting to several complications like immunotoxicity, teratogenicity hepatotoxicity. Aflatoxins interfere with normal metabolic processes. This interference encompasses the regulatory processes that occur throughout the progression of energy metabolism. Thus, the effects of aflatoxins are seen in the inhibition of ATP generation, carbohydrate and lipid metabolism, mitochondrial structure and proteins synthesis. This chapter will focus on the mechanisms of aflatoxin-induced disruption of lipids, carbohydrates, and proteins metabolism, and how they affect the bioenergetic systems.

High-intensity training induces non-stoichiometric changes in the mitochondrial proteome of human skeletal muscle without reorganisation of respiratory chain content

Mitochondrial defects are implicated in multiple diseases and aging. Exercise training is an accessible, inexpensive therapeutic intervention that can improve mitochondrial bioenergetics and quality of life. By combining multiple omics techniques with biochemical and in silico normalisation, we removed the bias arising from the training-induced increase in mitochondrial content to unearth an intricate and previously undemonstrated network of differentially prioritised mitochondrial adaptations. We show that changes in hundreds of transcripts, proteins, and lipids are not stoichiometrically linked to the overall increase in mitochondrial content. Our findings suggest enhancing electron flow to oxidative phosphorylation (OXPHOS) is more important to improve ATP generation than increasing the abundance of the OXPHOS machinery, and do not support the hypothesis that training-induced supercomplex formation enhances mitochondrial bioenergetics. Our study provides an analytical approach allowing unbiased and in-depth investigations of training-induced mitochondrial adaptations, challenging our current understanding, and calling for careful reinterpretation of previous findings.

Transcriptional responses of Trichodesmium to natural inverse gradients of Fe and P availability

The filamentous diazotrophic cyanobacterium Trichodesmium is responsible for a significant fraction of marine di-nitrogen (N2) fixation. Growth and distribution of Trichodesmium and other diazotrophs in the vast oligotrophic subtropical gyres is influenced by iron (Fe) and phosphorus (P) availability, while reciprocally influencing the biogeochemistry of these nutrients. Here we use observations across natural inverse gradients in Fe and P in the North Atlantic subtropical gyre (NASG) to demonstrate how Trichodesmium acclimates in situ to resource availability. Transcriptomic analysis identified progressive upregulation of known iron-stress biomarker genes with decreasing Fe availability, and progressive upregulation of genes involved in the acquisition of diverse P sources with decreasing P availability, while genes involved in N2 fixation were upregulated at the intersection under moderate Fe and P availability. Enhanced N2 fixation within the Fe and P co-stressed transition region was also associated with a distinct, consistent metabolic profile, including the expression of alternative photosynthetic pathways that potentially facilitate ATP generation required for N2 fixation with reduced net oxygen production. The observed response of Trichodesmium to availability of both Fe and P supports suggestions that these biogeochemically significant organisms employ unique molecular, and thus physiological responses as adaptations to specifically exploit the Fe and P co-limited niche they construct.

Abstract 11243: Novel Peptide for Cardiopulmonary Resuscitation

Introduction: While effective for out-of-hospital cardiac arrest, therapeutic hypothermia can be difficult to timely implement clinically. No drugs exist for improving neurologically intact survival. We have developed a novel peptide (TAT-PHLPP) that inhibits PH domain and Leucine rich repeat Protein Phosphatases (PHLPP), leading to Akt activation and mimicking of the protective effects of therapeutic hypothermia without the need of physical cooling. Hypothesis: We hypothesize that when administered intravenously during CPR, TAT-PHLPP improves neurologically intact survival. Methods: We conducted parallel studies in mouse and swine models. In C57BL6 mice (n = 72), we induced a 8 or 12-min asystolic cardiac arrest with KCl, followed by initiation of CPR and blinded randomized administration of TAT-PHLPP (7.5 mg/kg) or saline placebo. The primary outcomes were 4-h and 5-day survival, mean arterial blood pressure (MAP) and cerebral blood flow (CBF). We assessed PHLPP-NHERF1 binding and glucose utilization (via pyruvate dehydrogenase (PDH) phosphorylation and ATP generation). In 16 swine, we induced 5 min of VF followed by ACLS with vest CPR and administered two doses of TAT-PHLPP or saline. Survival (24 h) and neurological function were assessed. Plasma biomarkers taurine and glutamate levels in mice were measured and validated in CA patients (n=68) with a shockable rhythm at the time of hospital arrival, 6, 24, 48, and 72 h post-hospital arrival. Results: In mice, compared to saline, TAT-PHLPP significantly improved 4-h and 5-day survival, increased post-ROSC MAP and CBF, inhibited PHLPP-NHERF1 binding, increased p-Akt, decreased p-PDH (increased activity) at 15 min post-ROSC, enhanced ATP generation in both heart and brain, and reduced plasma taurine and glutamate levels. In swine, TAT-PHLPP improved 24 h neurologically intact survival (1/9 in control vs. 6/7 with peptide, p < 0.01). In patients, taurine levels were higher in non-survivors (n=44) than survivors (n=24) at 6 h of post-hospital arrival (65.9 ± 34.8 vs. 45.6 ±23.7, p< 0.001). Conclusions: TAT-PHLPP has high translational potential as a first-of-class biologic treatment to reproduce critical outcomes of therapeutic hypothermia and improve cardiac arrest survival.

Ethoxyquin Inhibits the Progression of Murine Ehrlich Ascites Carcinoma through the Inhibition of Autophagy and LDH

Cancer cells exhibit an increased glycolysis rate for ATP generation (the Warburg effect) to sustain an increased proliferation rate. In tumor cells, the oxidation of pyruvate in the Krebs cycle is substituted by lactate production, catalyzed by LDH. In this study, we use ethoxyquin (EQ) as a novel inhibitor to target LDH in murine Ehrlich ascites carcinoma (EAC) and as a combination therapy to improve the therapeutic efficacy of the conventional chemotherapy drug, cisplatin (CIS). We investigated the anti-tumor effect of EQ on EAC-bearing mice and checked whether EQ can sustain the anti-tumor potential of CIS and whether it influences LDH activity. Treatment with EQ had evident anti-tumor effects on EAC as revealed by the remarkable decrease in the expression of the anti-apoptotic gene Bcl-2 and by a significant increase in the expression of apoptotic genes (BAX and caspase-3). EQ also caused a significant decrease in the autophagic activity of EAC cells, as shown by a reduction in the fluorescence intensity of the autophagosome marker. Additionally, EQ restored the altered hematological and biochemical parameters and improved the disrupted hepatic tissues of EAC-bearing mice. Co-administration of EQ and CIS showed the highest anti-tumor effect against EAC. Collectively, our findings propose EQ as a novel inhibitor of LDH in cancer cells and as a combinatory drug to increase the efficacy of cisplatin. Further studies are required to validate this therapeutic strategy in different cancer models and preclinical trials.