Proton Leak Research Articles

Low oxygen levels can help to prevent the detrimental effect of acute warming on mitochondrial efficiency in fish.

Aerobic metabolism of aquatic ectotherms is highly sensitive to fluctuating climates. Many mitochondrial traits exhibit phenotypic plasticity in response to acute variations in temperature and oxygen availability. These responses are critical for understanding the effects of environmental variations on aquatic ectotherms' performance. Using the European seabass, Dicentrarchus labrax, we determined the effects of acute warming and deoxygenation in vitro on mitochondrial respiratory capacities and mitochondrial efficiency to produce ATP (ATP/O ratio). We show that acute warming reduced ATP/O ratio but deoxygenation marginally raised ATP/O ratio, leading to a compensatory effect of low oxygen availability on mitochondrial ATP/O ratio at high temperature. The acute effect of warming and deoxygenation on mitochondrial efficiency might be related to the leak of protons across the mitochondrial inner membrane, as the mitochondrial respiration required to counteract the proton leak increased with warming and decreased with deoxygenation. Our study underlines the importance of integrating the combined effects of temperature and oxygen availability on mitochondrial metabolism. Predictions on decline in performance of aquatic ectotherms owing to climate change may not be accurate, since these predictions typically look at respiratory capacity and ignore efficiency of ATP production.

Fetal programming of polycystic ovary syndrome: Effects of androgen exposure on prenatal ovarian development

Polycystic ovary syndrome (PCOS) is a common form of anovulatory infertility with a strong hereditary component but no candidate genes have been found. The inheritance pattern may be due to in utero androgen programming on gene expression and mitochondria. Mitochondria are maternally inherited and alterations to mitochondria after fetal androgen exposure may explain one of the mechanisms of fetal programming in PCOS. Our aim was to investigate the role of excessive prenatal androgens in ovarian development by identifying how hyperandrogenemia affects gene expression and mitochondria in neonatal ovary. Pregnant dams were injected with dihydrotestosterone on days 16–18 of pregnancy. Day 0 ovaries were collected for gene expression and mitochondrial studies. RNAseq showed differential gene expressions which were related to mitochondrial dysfunction, fetal gonadal development, oocyte maturation, metabolism, angiogenesis, and PCOS. Top 20 up and downregulated genes were validated with qPCR and Western Blot. Transcriptional pathways involved in folliculogenesis and genes involved in ovarian and mitochondrial function were dysregulated. Further, DHT exposure altered mitochondrial ultrastructure and function by increasing mitochondrial oxygen consumption and decreasing mitochondrial efficiency with increased proton leak within the first day of life. Our data indicates that one path that leads to PCOS begins at birth and is programmed in utero by androgens.

Teneurin C-Terminal Associated Peptide (TCAP)-3 Increases Metabolic Activity in Zebrafish

Teneurin C-terminal associated peptides (TCAP), bioactive peptides located on the C-terminal end of teneurin proteins, have been shown to regulate stress axis functions due to the high conservation between TCAP and corticotropin releasing factor (CRF). Additionally, recent work demonstrated that TCAP can increase metabolism in rats via glucose metabolism. These metabolic actions are not well described in other organisms, including teleosts. Here we investigated the expression of a tcap isoform, tcap-3, and the potential role of TCAP-3 as a regulator of metabolism across zebrafish life-stages. Using pcr-based analyses, tcap-3 appears to be independently transcribed, in relation to teneurin-3, in muscle tissue of adult zebrafish. Resazurin, respirometry chambers, and mitochondrial metabolism analyses were used to study the metabolic effects of synthetic rainbow trout TCAP-3 (rtTCAP-3) in larval and adult zebrafish. Overall, metabolic activity was enhanced by 48 h of rtTCAP-3 treatment in larvae (bath immersion) and adults (intraperitoneal injections). This metabolic activity increase was due to mitochondrial uncoupling, as mitochondrial respiration increase by rtTCAP-3 was due to proton leak. Additionally, rtTCAP-3 protected larval fish from reduced metabolic activity induced by low temperatures. Subsequently, rtTCAP-3 increased metabolic output in adult zebrafish subjected to accelerated swimming speeds, demonstrating the potent role of rtTCAP-3 in zebrafish metabolism regulation during metabolic challenges. Collectively, these results demonstrate the conserved roles for rtTCAP-3 as a metabolic activator in zebrafish.

Protective Effect of Mitochondrial ND2 C5178A Gene Mutation on Cell and Mitochondrial Functions.

Background Mitochondrial NADH dehydrogenase subunit 2 (MT-ND2) m. 5178C>A gene mutation has protective effects against various diseases, but the molecular mechanism is still unclear. In previous study, we found a heteroplasmy level of MT-ND2 m. 5178C>A mutation in normotensive controls. Peripheral blood samples were obtained from essential hypertension individuals carrying the mutation and healthy controls without gene mutation to establish immortalized lymphocyte lines. To investigate the effect of the MT-ND2 m. 5178C>A gene mutation, comparative analyses of the two group cell lines were performed, including measurements of cell proliferation, viability, ATP synthesis, mitochondrial oxidative stress, and oxidative phosphorylation. Results The cell proliferation rate and viability of the MT-ND2 m. 5178C>A mutant lymphocyte line were higher than those of the control group. Mitochondrial functions of the MT-ND2 m. 5178C>A mutant lymphocyte were increased, including increased ATP synthesis, decreased ROS production, increased mitochondrial membrane potential and Bcl-2 gene transcription and protein translation, decreased Caspase 3/7 activity, and decreased early apoptosis and late apoptosis. The oxygen consumption rate (OCR) of the mutant lymphocyte line was higher than that of the control group, including basal OCR, ATP-linked OCR, maximal OCR, proton leak OCR, and reserve OCR, and there was no significant difference in nonmitochondrial OCR. The activity of Mitochondrial Complex I of the mutant group was increased than that of the control group. Conclusions The MT-ND2 m. 5178C>A mutation is a protective mutation that may be related to improvement of mitochondrial functions and decrease in apoptosis.

Role of mTORC2 in biphasic regulation of brown fat metabolism in response to mild and severe cold

Nonshivering thermogenesis is essential for mammals to maintain body temperature. According to the canonical view, temperature is sensed by cutaneous thermoreceptors and nerve impulses transmitted to the hypothalamus, which generates sympathetic signals to ß-adrenergic receptors in brown adipocytes. The energy for heat generation is primarily provided by the oxidation of fatty acids derived from triglyceride hydrolysis and cellular uptake. Fatty acids also activate the uncoupling protein, UCP1, which creates a proton leak that uncouples mitochondrial oxidative phosphorylation from ATP production, resulting in energy dissipation as heat. Recent evidence supports the idea that in response to mild cold, ß-adrenergic signals stimulate not only lipolysis and fatty acid oxidation, but also act through the mTORC2-Akt signaling module to stimulate de novo lipogenesis. This opposing anabolic effect is thought to maintain lipid fuel stores during increased catabolism. We show here, using brown fat-specific Gs-alpha knockout mice and cultured adipocytes that, unlike mild cold, severe cold directly cools brown fat and bypasses ß-adrenergic signaling to inhibit mTORC2. This cell-autonomous effect both inhibits lipogenesis and augments UCP1 expression to enhance thermogenesis. These findings suggest a novel mechanism for overriding ß-adrenergic-stimulated anabolic activities while augmenting catabolic activities to resolve the homeostatic crisis presented by severe cold.

An exacerbated metabolism and mitochondrial reactive oxygen species contribute to mitochondrial alterations and apoptosis in CD4 T cells during the acute phase of Trypanosoma cruzi infection

Chagas disease caused by Trypanosoma cruzi parasite is an endemic infection in America. It is well known that T. cruzi causes a strong immunosuppression during the acute phase of infection. However, it is not clear whether T. cruzi infection is related to metabolic alterations in CD4 T cells that prevent downstream effector function. Here, we evaluated the CD4 T cell metabolic and mitochondrial profiles from non-infected (NI), acute phase (AP) and chronic phase (CP) T. cruzi infected mice. CD4 T cells from all groups showed increased glucose uptake after stimulation. Moreover, the bioenergetic analysis revealed a rise in glycolysis and a higher oxidative metabolism in CD4 T cells from the AP. These cells showed increased proton leak and uncoupling protein 3 (UCP3) expression that correlated with mitochondrial ROS (mROS) accumulation, mitochondrial membrane potential (MMP) depolarization and expression of PD-1. In addition, CD4 T cells with mitochondrial alteration displayed an activated phenotype, and were less functional and more prone to apoptosis. In contrast, mitochondrial alterations were not observed during in vivo activation of CD4 T cells in a model of OVA-immunization. The Mn-superoxide dismutase (SOD2) expression, which is involved in mROS detoxification, was increased during the AP and CP of infection. Remarkably, the apoptosis observed in CD4 T cells with MMP depolarization was prevented by incubation with N-acetyl cysteine (NAC). Thus, our results showed that infection triggered an exacerbated metabolism together with mROS production in CD4 T cells from the AP of infection. However, antioxidant availability may not be sufficient to avoid mitochondrial alterations rendering these cells more susceptible to apoptosis. Our investigation is the first to demonstrate an association between a disturbed metabolism and an impaired CD4 T cell response during T. cruzi infection.

Exploring the acid enrichment application of piperidinium-functionalized cross-linked poly(2,6-dimethyl-1,4-phenylene oxide) anion exchange membranes in electrodialysis

The use of electrodialysis (ED) fabricated with proton blocking anion exchange membranes (AEMs) is a promising method to realize waste acid reclamation. To develop AEMs with low proton leakage, in this work, we designed a series of N-methylpiperidine (MPRD)-functionalized poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) cross-linked by weak base 1,3-di-4-piperidylpropane (DiPRD). Our investigations demonstrate the weak base cross-linker could enhance the density of membrane matrix and reduce the hydrophilicity of AEM matrix, which have been verified by thermogravimetric analysis and water absorption with low swelling ratio of 2.43%. Benefit from the unique structure with denser membrane matrix and additional protonated weak base piperidine structure, the acid blocking performance of the optimized crosslinked AEM was enhanced with the H+ concentration of 1.98 M in concentrate cell during 24 h-ED process at current density of 20 mA cm−2 (initial H+ concentration: 1.0 M), outperforming the AEM without cross-linking structure (1.73 M). Nevertheless, it was found that the small-sized proton diffusion in ion-nanochannels of AEM and the aged membrane matrix in ED process with high sulfuric acid concentration resulted in proton leakage to some degree. As a result, a trade-off between the proton blocking and sulfate ion transport of the cross-linked AEMs is achieved. It is believed that this study can provide a guideline for designing advanced proton blocking AEMs.

Effects of Oxygen on Renal Function and Oxidative Stress During Hypothermic Machine Perfusion in an Experimental Porcine Model of Kidney Donation after Cardiac Death

The efficacy and safety of using high concentrations of oxygen during hypothermic machine perfusion (HMP) have not been fully elucidated to date. This study investigated the impact of administering high concentrations of oxygen on renal function during HMP in a porcine donation after circulatory death (DCD), as well as the metabolic and biochemical effects of this method. A randomized nonblinded cohort study was established in a porcine transplant (KT) model mimicking Maastricht type III DCD under oxygen-supplemented HMP (Ox-HMP) compared to non-supplemented (nOx-HMP) (LifePort® kidney transporter) conditions. The primary endpoint was evolution of renal function post-KT, whereas secondary endpoints included changes in perfusion dynamics, miRNA expression and cellular lesion measured by LDH and lactate levels in perfusate, lipid peroxidation in kidney biopsies, ATP generation, epithelial mesenchymal transition (EMT) and oxidative gene expression in cell cultures and histology evaluation. ATP generation and oxidative stress, as measured by lipid peroxidation, increased simultaneously after warm ischemia in the Ox-HMP group. Ox-HMP did not exhibit a significant effect on kidney function or animal survival. A significant increase in lipid peroxidation was observed in the Ox-HMP group. This resulted in a greater expression of the genes responsible for producing superoxide dismutase 1 (SOD-1) and catalase oxygenation enzymes, although only SOD-1 showed statistical significance. Respiratory chain dysfunction was maintained in the Ox-HMP group with a non-significant decrease in ATP production, increased proton leakage, and a decrease in respiratory reserve. Regarding epithelial-mesenchymal transition, an upward trend in the expression of vimentin, fibronectin, and collagen genes was observed only in the Ox-HMP group. Finally, the expression levels of miR-101 and miR-126, related to characteristic functions of the tubular epithelium, were significantly modified (miRNA levels expressed as DCT. A brief bubble Ox-HMP treatment did not show a clear positive effect on renal function and oxidative stress markers. The role and safety of adding oxygen during HMP still need to be elucidated. Currently, this Ox-HMP method cannot be considered standard practice.

The Associated Regulatory Mechanisms of Zinc Lactate in Redox Balance and Mitochondrial Function of Intestinal Porcine Epithelial Cells.

Zinc lactate (ZnLA) is a new organic zinc salt which has antioxidant properties in mammals and can improve intestinal function. This study explored the effects of ZnLA and ZnSO4 on cell proliferation, Zn transport, antioxidant capacity, mitochondrial function, and their underlying molecular mechanisms in intestinal porcine epithelial cells (IPEC-J2). The results showed that addition of ZnLA promoted cell proliferation, inhibited cell apoptosis and IL-6 secretion, and upregulated the mRNA expression and concentration of MT-2B, ZNT-1, and CRIP, as well as affected the gene expression and activity of oxidation or antioxidant enzymes (e.g., CuZnSOD, CAT, and Gpx1, GSH-PX, LDH, and MDA), compared to ZnSO4 or control. Compared with the control, ZnLA treatment had no significant effect on mitochondrial membrane potential, whereas it markedly increased the mitochondrial basal OCR, nonmitochondrial respiratory capacity, and mitochondrial proton leakage and reduced spare respiratory capacity and mitochondrial reactive oxygen (ROS) production in IPEC-J2 cells. Furthermore, ZnLA treatment increased the protein expression of Nrf2 and phosphorylated AMPK, but reduced Keap1 and p62 protein expression and autophagy-related genes LC3B-1 and Beclin mRNA abundance. Under H2O2-induced oxidative stress conditions, ZnLA supplementation markedly reduced cell apoptosis and mitochondrial ROS levels in IPEC-J2 cells. Moreover, ZnLA administration increased the protein expression of Nrf2 and decreased the protein expression of caspase-3, Keap1, and p62 in H2O2-induced IPEC-J2 cells. In addition, when the activity of AMPK was inhibited by Compound C, ZnLA supplementation did not increase the protein expression of nuclear Nrf2, but when Compound C was removed, the activities of AMPK and Nfr2 were both increased by ZnLA treatment. Our results indicated that ZnLA could improve the antioxidant capacity and mitochondrial function in IPEC-J2 cells by activating the AMPK-Nrf2-p62 pathway under normal or oxidative stress conditions. Our novel finding also suggested that ZnLA, as a new feed additive for piglets, has the potential to be an alternative for ZnSO4.

Reduction of Elevated Proton Leak Rejuvenates Mitochondria in the Aged Cardiomyocyte

Rational: Aging-associated diseases, including cardiac dysfunction, are increasingly common in the population. However, the mechanisms of physiologic aging in general, and cardiac aging in particular, remain poorly understood. While effective medical interventions are available for some kinds of heart failure, one age-related impairment, diastolic dysfunction in Heart Failure with Preserved Ejection Fraction (HFpEF) is lacking a clinically effective treatment. Methods and Results: Using the pH indicator cpYFP in the model of naturally aging mice and rats, we show direct evidence of increased mitochondrial proton leak in aged heart mitochondria following a pH gradient stress. Furthermore, we identified Adenine Nucleotide Translocator 1 (ANT1) as mediating the increased proton permeability of old cardiomyocytes. Most importantly, acute (2 hours) in vitro treatment with the tetra-peptide drug SS-31 (elamipretide) reverses age-related excess proton entry, decreases the mitochondrial flash activity and mitochondrial permeability transition pore (mPTP) opening and rejuvenates mitochondrial function. Moreover, we show that SS-31 benefits the old mitochondria by direct association with ANT1 and stabilization of the mitochondrial ATP synthasome, leading to substantial reversal of diastolic dysfunction. Conclusion: Our results uncover excessive mitochondrial proton leak as a novel mechanism of age-related cardiac dysfunction and elucidate how SS-31 is able to reverse this clinically important complication of cardiac aging.

Pistacia lentiscus extract enhances mammary epithelial cells\u2019 productivity by modulating their oxidative status

We assessed the potential of phenolic compounds from Pistacia lentiscus (lentisk) to enhance production of milk constituents in bovine mammary epithelial cells (MEC). MEC were exposed to 0 (control), 1 or 10 ppm of polyphenols from lentisk ethanolic extract (PLEE) for 24 h. PLEE were absorbed by the MEC plasma membrane, but also penetrated the cell to accumulate in and around the nucleus. PLEE increased triglyceride content in the cell and its secretion to the medium, and significantly increased intracellular lipid droplet diameter. Compared to control, PLEE increased dose-dependently the lactose synthesis, secretion of whey proteins, and contents of casein. To evaluate mitochondrial activity under pro-oxidant load, MEC were preincubated with PLEE and exposed for 2 h to H2O2. Exposure to H2O2 increased the proportion of cells with impaired mitochondrial membrane potential twofold in controls, but not in PLEE-pre-treated cells. Accordingly, proton leakage was markedly decreased by PLEE, and coupling efficiency between the respiratory chain and ATP production was significantly enhanced. Thus, lentisk polyphenols divert energy to production of milk fat, protein and lactose, with less energy directed to cellular damage control; alternatively, PLEE enables MEC to maintain energy and oxidative status under extreme metabolic rate required for milk production and secretion, and reduces the limitation on energy required to support production.

Cognitive impairment is associated with mitochondrial dysfunction in peripheral blood mononuclear cells of elderly population

Cognitive impairment is commonly found in the elderly population. Evidence suggests that mitochondrial function in lymphocytes are potential biomarkers in the progression of neurodegeneration, as peripheral mitochondrial function is associated with mild cognitive impairment (MCI) in the elderly population. Therefore, we hypothesize that impaired mitochondrial ATP production and oxidative stress in peripheral blood mononuclear cells (PBMCs) are associated with cognitive impairment in the elderly population. Data were collected from 897 participants from the EGAT (The Electricity Generating Authority of Thailand) cohort. The participants were classified to be in the normal cognition group (n = 428) or mild cognitive impairment group (n = 469), according to their MoCA score. The association of mitochondrial function and cognitive status was analyzed by binary logistic regression analysis. MCI participants had higher age, systolic blood pressure, waist/hip ratio, and lower plasma high- and low-density lipoprotein cholesterol levels, when compared to the normal cognition group. In addition, estimated glomerular filtration rate were lower in the MCI group than those in the normal cognition group. Collectively, MCI is associated with mitochondrial dysfunction in PBMCs as indicated by decreasing mitochondrial ATP production, increasing proton leak, and oxidative stress, in the elderly population, independently of the possible confounding factors in this study.

Antioxidant prevents clearance of hemostatically competent platelets after long-term cold storage.

Cold storage of platelets (PLTs) has the potential advantage of prolonging storage time while reducing posttransfusion infection given the decreased likelihood of bacterial outgrowth during storage and possibly beneficial effects in treating bleeding patients. However, cold storage reduces PLT survival through the induction of complex storage lesions, which are more accentuated when storage is prolonged. Whole blood-derived PLT-rich plasma concentrates from seven PLT pools (n = 5 donors per pool). PLT additive solution was added (67%/33% plasma) and the product was split into 50-mL bags. Split units were stored in the presence or absence of 1 mM of N-acetylcysteine (NAC) under agitation for up to 14 days at room temperature or in the cold and were analyzed for PLT activation, fibrinogen-dependent spreading, microparticle formation, mitochondrial respiratory activity, reactive oxygen species (ROS) generation, as well as in vivo survival and bleeding time correction in immunodeficient mice. Cold storage of PLTs for 7 days or longer induces significant PLT activation, cytoskeletal damage, impaired fibrinogen spreading, enhances mitochondrial metabolic decoupling and ROS generation, and increases macrophage-dependent phagocytosis and macrophage-independent clearance. Addition of NAC prevents PLT clearance and allows a correction of the prolonged bleeding time in thrombocytopenic, aspirin-treated, immunodeficient mice. Long-term cold storage induces mitochondrial uncoupling and increased proton leak and ROS generation. The resulting ROS is a crucial contributor to the increased macrophage-dependent and -independent clearance of functional PLTs and can be prevented by the antioxidant NAC in a magnesium-containing additive solution.

Abstract 12567: Circulating Factors Induce Cardiomyopathy After Burn Injury

Introduction: Our previous results in vivo indicated PDE5-cGMP-PKG was involved in burn-induced heart dysfunction and PDE5A inhibitor restored the dysfunction. It’s unknown if circulating factors after burn would injure cardiomyocytes. Hypothesis: Circulating factors released after burn induce cardiomyopathy. Methods: Human cardiomyocytes (AC16) were treated with sham-serum, burn-serum (24 hpb-serum) and burn/sildenafil-serum (24 hpb/SIL). We performed cut-edged biochemistry technologies and Illumina RNA sequencing (RNA-seq) in this study. GraphPad Prism 8.4.2 was used for statistics. Results: We found a significant decrease of cGMP level and an increase of cTN1 in 24 hpb-serum group. Treatment with the PDE5A inhibitor Sildenafil completely reversed this change similar to our in vivo work. To understand what bioactive molecules would be involved in the alterations by burn injury, human cardiomyocytes (Ac16) were employed to test the cardiomyocyte response to burn-induced circulating factors. We observed that 24 hpb-serum significantly 1) decreased cell viability and cell proliferation; as well as 2) increased cell cytotoxicity, cell apoptosis and cell ROS production. We also found 24 hpb-serum resulted in cell mitochondrial dysfunction by decreasing ATP production and mitochondrial membrane integrity/potential and increasing mitochondrial ROS. Seahorse and O2K approaches confirmed 24 hpb-serum-induced cardiomyocyte mitochondrial dysfunction as evidenced by decreases of mitochondrial basal respiration, proton leak, ATP production, and maximal respiration. 24 hpb/SIL serum rescued 24 hpb serum-induced Ac 16 cell response, at least partially. Advanced bioinformatic analyses identified 1415 upregulated genes and 1091 downregulated genes in 24 hpb-serum group and 776 upregulated genes and 113 downregulated genes restored in 24 hpb/SIL-serum group. We also analyzed and validated the differentially expressed genes. Conclusions: Our study not only confirmed burn induced heart dysfunction, but also provided evidence for understanding the pathogenic mechanism of circulating factors released after burn injury and preliminary genomic evidence for the mechanism for cardiomyopathy after burn injury.

BacFlash signals acid-resistance gene expression in bacteria.

Intracellular pH (pHi) homeostasis is crucial for cellular functions and signal transduction across all kingdoms of life. In particular, bacterial pHi homeostasis is important for physiology, ecology, and pathogenesis. Here we report an exquisite bacterial acid-resistance (AR) mechanism in which proton leak elicits a pre-emptive AR response. A single bacterial cell undergoes quantal electrochemical excitation, termed "BacFlash", which consists of membrane depolarization, transient pHi rise, and bursting production of reactive oxygen species. BacFlash ignition is dictated by acid stress in the form of proton leak across the plasma membrane and the rate of BacFlash occurrence is reversely correlated with the pHi buffering capacity. Through genome-wide screening, we further identify the ATP synthase Fo complex subunit a as the putative proton sensor for BacFlash biogenesis. Importantly, persistent BacFlash hyperactivity activates transcription of a panel of key AR genes and predisposes the cells to survive imminent extreme acid stress. These findings demonstrate a prototypical coupling between electrochemical excitation and nucleoid gene expression in prokaryotes.

Acyl-CoA Synthetase Long Chain Family Inhibition with Triacsin C Inhibits Multiple Myeloma Cell Proliferation and Survival

Multiple myeloma (MM) is defined by the clonal expansion of malignant plasma cells in the bone marrow (BM) and has a 5-year survival rate of 50% (Siegel el al. 2018, Cancer J. Clin.). MM remains incurable due to the development of resistance to current chemotherapies; therefore, it is paramount to investigate novel treatments and the mechanisms of drug resistance in MM cells. Interestingly, obesity correlates with increased incidence of MM and high body mass index correlates with a poor treatment response (Marinac et al. 2019, JNCI Cancer Spectr, Groß et al. 2017, Oncotarget). Obesity is a major risk factor for many cancers, however, given the complexity of obesity, there are an array of mechanisms by which obesity may support tumor cells. Studies of obesity and MM are mainly at the epidemiological level and have not extensively explored the mechanism of this relationship. Therefore, there is a critical need to understand how obesity contributes to support cancers such as MM. Possible mechanisms may be through the increased availability of free fatty acids or through other factors that are found in obese patients. We hypothesize that lipid metabolism contributes to obesity-linked cancers such as MM. Recently, changes in lipid metabolism have been shown to support the proliferation, migration and the development of drug resistance in other blood cancers such as acute myeloid leukemia (Tabe et al. 2017, Cancer Res, Tabe et al. 2018, Sci. Reports) and solid tumors such as breast (Wang et al. 2017, JCI Insights) and prostate (Mitra et al. 2017, BMC Cancer) cancer. However, the role of lipid metabolism in MM cells has been understudied. Therefore, we hypothesized that genes within the Hallmark Fatty Acid Metabolism gene set (https://www.gsea-msigdb.org) would be differentially expressed between healthy patients and those with MM. We mined the clinical data (GSE6477, Chng et al. 2007, Cancer Res.) and found that transcripts of an enzyme critical for lipid metabolism, acyl-CoA synthetase long chain member 1 (ACSL1), was significantly downregulated (Figure 1A, Log2(Fold Change)=-2.33, adjusted p value=1.64*10-5, false discovery rate) in patients with newly diagnosed MM relative to normal plasma cells. Therefore, we hypothesized that ACSL1 may act as a tumor suppressor in MM. In order to test the role of the ACSL family as tumor suppressors, we treated human (MM1.S, OPM2 and RPMI-8226) and mouse myeloma (5TGM1) cell lines with an inhibitor (Triacsin C, TriC) of four of the five human acyl-CoA synthetase long chain family members (ACSL1,3,4 and 5). Contrary to our hypothesis, TriC treatment significantly decreased MM cell proliferation (Figure 1B, p<0.0001, One-way ANOVA Tukey's multiple comparisons test is used throughout unless otherwise noted), increased apoptosis (Figure 1C, p<0.001) and caused G0 arrest (Figure1D, p<0.0001) in a dose-dependent manner. Motivated to understand if TriC's toxicity was due to changes in metabolic dynamics, MM1.S cells were treated with 1 μM TriC for 30 minutes and subjected to a metabolic flux assay (Seahorse XF, Agilent). TriC treatment significantly reduced ATP-dependent respiration from fatty acid oxidation (FAO) (Figure 1F, p<0.0001 Student's t-test) and increased proton leak (p<0.0001). Taken together, our data demonstrate that TriC-mediated ACSL inhibition in MM cells decreases proliferation, induces G0 arrest, apoptosis and decreases FAO-dependent respiration and mitochondrial function. It is unclear what ACSL family member is responsible for the phenotype we report here. To address these questions, future studies will focus on genetically targeting individual ACSL family members and characterizing the lipidomic profile of MM ACSL mutants. Our data also suggests that fatty acids are used as an energy source, therefore we will explore how FAO contributes to MM cell proliferation and survival. Disclosures No relevant conflicts of interest to declare.

Mitochondrial Dysfunction in Fragile-X Syndrome: Plugging the Leak May Save the Ship

Recent work by Licznerski etal. suggests that mutant FMRP linked to Fragile-X syndrome elevates the inner mitochondrial membrane proton leak, leading to increased metabolism and changes in protein synthesis that trigger impaired synaptic maturation and autistic behaviors.

Bardoxolone Methyl Displays Detrimental Effects on Endothelial Bioenergetics, Suppresses Endothelial ET-1 Release, and Increases Endothelial Permeability in Human Microvascular Endothelium.

Nrf2 is a master regulator of antioxidant cellular defence, and agents activating the Nrf2 pathway have been tested in various diseases. However, unexpected side effects of cardiovascular nature reported for bardoxolone methyl in patients with type 2 diabetes mellitus and stage 4 chronic kidney disease (the BEACON trial) still have not been fully explained. Here, we aimed to characterize the effects of bardoxolone methyl compared with other Nrf2 activators—dimethyl fumarate and L-sulforaphane—on human microvascular endothelium. Endothelial toxicity, bioenergetics, mitochondrial membrane potential, endothelin-1 (ET-1) release, endothelial permeability, Nrf2 expression, and ROS production were assessed in human microvascular endothelial cells (HMEC-1) incubated for 3 and 24 hours with 100 nM–5 μM of either bardoxolone methyl, dimethyl fumarate, or L-sulforaphane. Three-hour incubation with bardoxolone methyl (100 nM–5 μM), although not toxic to endothelial cells, significantly affected endothelial bioenergetics by decreasing mitochondrial membrane potential (concentrations ≥ 3 μM), decreasing spare respiratory capacity (concentrations ≥ 1 μM), and increasing proton leak (concentrations ≥ 500 nM), while dimethyl fumarate and L-sulforaphane did not exert such actions. Bardoxolone methyl at concentrations ≥ 3 μM also decreased cellular viability and induced necrosis and apoptosis in the endothelium upon 24-hour incubation. In turn, endothelin-1 decreased permeability in endothelial cells in picomolar range, while bardoxolone methyl decreased ET-1 release and increased endothelial permeability even after short-term (3 hours) incubation. In conclusion, despite that all three Nrf2 activators exerted some beneficial effects on the endothelium, as evidenced by a decrease in ROS production, bardoxolone methyl, the most potent Nrf2 activator among the tested compounds, displayed a distinct endothelial profile of activity comprising detrimental effects on mitochondria and cellular viability and suppression of endothelial ET-1 release possibly interfering with ET-1–dependent local regulation of endothelial permeability.

Inhibition of alcohol-induced inflammation and oxidative stress by astaxanthin is mediated by its opposite actions in the regulation of sirtuin 1 and histone deacetylase 4 in macrophages

We previously demonstrated that astaxanthin (ASTX), a xanthophyll carotenoid, repressed ethanol-induced inflammation and oxidative stress in macrophages. We explored the role of sirtuin 1 (SIRT1) and histone deacetylase 4 (HDAC4) in the inhibitory effect of ASTX on inflammation and oxidative stress in macrophages exposed to ethanol. Ethanol decreased mRNA and protein of SIRT1 while increasing those of HDAC4, which was attenuated by ASTX in RAW 264.7 macrophages and mouse bone marrow-derived macrophages (BMDMs). Inhibition of SIRT1 expression or activity augmented ethanol-induced Hdac4 expression, but SIRT1 activation elicited the opposite effect. Consistently, Hdac4 knockdown increased Sirt1 expression with decreases in ethanol-induced inflammatory gene expression, but its overexpression resulted in the opposite effects. Furthermore, BMDMs from mice with macrophage specific-deletion of Hdac4 (Hdac4MKO) showed significant decreases in ethanol-induced inflammatory genes and ROS accumulation but an increase in Sirt1 expression. Macrophage specific deletion of Hdac4 or ASTX abolished the changes in genes for mitochondrial biogenesis and glycolysis by ethanol. Ethanol increased mitochondrial respiration, ATP production, and proton leak, but decreased maximal respiration and spare respiratory capacity, all of which were abolished by ASTX in RAW 264.7 macrophages. The ethanol-induced alterations in mitochondrial respiration were abrogated in Hdac4MKO BMDMs. In conclusion, the anti-inflammatory and antioxidant properties of ASTX in ethanol-treated macrophages may be mediated, at least partly, by its opposite effect on SIRT1 and HDAC4 to empower SIRT1 to counteract ethanol-induced activation of HDAC4.

Modeling alcohol-induced neurotoxicity using human induced pluripotent stem cell-derived three-dimensional cerebral organoids

Maternal alcohol exposure during pregnancy can substantially impact the development of the fetus, causing a range of symptoms, known as fetal alcohol spectrum disorders (FASDs), such as cognitive dysfunction and psychiatric disorders, with the pathophysiology and mechanisms largely unknown. Recently developed human cerebral organoids from induced pluripotent stem cells are similar to fetal brains in the aspects of development and structure. These models allow more relevant in vitro systems to be developed for studying FASDs than animal models. Modeling binge drinking using human cerebral organoids, we sought to quantify the downstream toxic effects of alcohol (ethanol) on neural pathology phenotypes and signaling pathways within the organoids. The results revealed that alcohol exposure resulted in unhealthy organoids at cellular, subcellular, bioenergetic metabolism, and gene expression levels. Alcohol induced apoptosis on organoids. The apoptotic effects of alcohol on the organoids depended on the alcohol concentration and varied between cell types. Specifically, neurons were more vulnerable to alcohol-induced apoptosis than astrocytes. The alcohol-treated organoids exhibit ultrastructural changes such as disruption of mitochondria cristae, decreased intensity of mitochondrial matrix, and disorganized cytoskeleton. Alcohol exposure also resulted in mitochondrial dysfunction and metabolic stress in the organoids as evidenced by (1) decreased mitochondrial oxygen consumption rates being linked to basal respiration, ATP production, proton leak, maximal respiration and spare respiratory capacity, and (2) increase of non-mitochondrial respiration in alcohol-treated organoids compared with control groups. Furthermore, we found that alcohol treatment affected the expression of 199 genes out of 17,195 genes analyzed. Bioinformatic analyses showed the association of these dysregulated genes with 37 pathways related to clinically relevant pathologies such as psychiatric disorders, behavior, nervous system development and function, organismal injury and abnormalities, and cellular development. Notably, 187 of these genes are critically involved in neurodevelopment, and/or implicated in nervous system physiology and neurodegeneration. Furthermore, the identified genes are key regulators of multiple pathways linked in networks. This study extends for the first time animal models of binge drinking-related FASDs to a human model, allowing in-depth analyses of neurotoxicity at tissue, cellular, subcellular, metabolism, and gene levels. Hereby, we provide novel insights into alcohol-induced pathologic phenotypes, cell type-specific vulnerability, and affected signaling pathways and molecular networks, that can contribute to a better understanding of the developmental neurotoxic effects of binge drinking during pregnancy.