Glutamine sustains energy metabolism and alleviates liver injury in burn sepsis by promoting the assembly of mitochondrial HSP60-HSP10 complex via SIRT4 dependent protein deacetylation

Burns and burn sepsis, characterized by persistent and profound hypercatabolism, cause energy metabolism dysfunction that worsens organ injury and systemic disorders. Glutamine (Gln) is a key nutrient that remarkably replenishes energy metabolism in burn and sepsis patients, but its exact roles beyond substrate supply is unclear. In this study, we demonstrated that Gln alleviated liver injury by sustaining energy supply and restoring redox balance. Meanwhile, Gln also rescued the dysfunctional mitochondrial electron transport chain (ETC) complexes, improved ATP production, reduced oxidative stress, and protected hepatocytes from burn sepsis injury. Mechanistically, we revealed that Gln could activate SIRT4 by upregulating its protein synthesis and increasing the level of Nicotinamide adenine dinucleotide (NAD+), a co-enzyme that sustains the activity of SIRT4. This, in turn, reduced the acetylation of shock protein (HSP) 60 to facilitate the assembly of the HSP60-HSP10 complex, which maintains the activity of ETC complex II and III and thus sustain ATP generation and reduce reactive oxygen species release. Overall, our study uncovers a previously unknown pharmacological mechanism involving the regulation of HSP60-HSP10 assembly by which Gln recovers mitochondrial complex activity, sustains cellular energy metabolism and exerts a hepato-protective role in burn sepsis.

Cytotoxic response of tumor-infiltrating lymphocytes of head and neck cancer slice cultures under mitochondrial dysfunction

Background

Head and neck squamous cell carcinomas (HNSCC) are highly heterogeneous tumors. In the harsh tumor microenvironment (TME), metabolic reprogramming and mitochondrial dysfunction may lead to immunosuppressive phenotypes. Aerobic glycolysis is needed for the activation of cytotoxic T-cells and the absence of glucose may hamper the full effector functions of cytotoxic T-cells. To test the effect of mitochondrial dysfunction on cytotoxic T cell function, slice cultures (SC) of HNSCC cancer were cultivated under different metabolic conditions.

Methods

Tumor samples from 21 patients with HNSCC were collected, from which, SC were established and cultivated under six different conditions. These conditions included high glucose, T cell stimulation, and temporarily induced mitochondrial dysfunction (MitoDys) using FCCP and oligomycin A with or without additional T cell stimulation, high glucose and finally, a control medium. Over three days of cultivation, sequential T cell stimulation and MitoDys treatments were performed. Supernatant was collected, and SC were fixed and embedded. Granzyme B was measured in the supernatant and in the SC via immunohistochemistry (IHC). Staining of PD1, CD8/Ki67, and cleaved-caspase-3 (CC3) were performed in SC.

Results

Hematoxylin eosin stains showed that overall SC quality remained stable over 3 days of cultivation. T cell stimulation, both alone and combined with MitoDys, led to significantly increased granzyme levels in SC and in supernatant. Apoptosis following T cell stimulation was observed in tumor and stroma. Mitochondrial dysfunction alone increased apoptosis in tumor cell aggregates. High glucose concentration alone had no impact on T cell activity and apoptosis. Apoptosis rates were significantly lower under conditions with high glucose and MitoDys (p=0.03).

Conclusion

Stimulation of tumor-infiltrating lymphocytes in SC was feasible, which led to increased apoptosis in tumor cells. Induced mitochondrial dysfunction did not play a significant role in the activation and function of TILs in SC of HNSCC. Moreover, high glucose concentration did not promote cytotoxic T cell activity in HNSCC SC.

Status of Mitochondrial Oxidative Phosphorylation during the Development of Heart Failure

Mitochondria are specialized organelles, which serve as the "Power House" to generate energy for maintaining heart function. These organelles contain various enzymes for the oxidation of different substrates as well as the electron transport chain in the form of Complexes I to V for producing ATP through the process of oxidative phosphorylation (OXPHOS). Several studies have shown depressed OXPHOS activity due to defects in one or more components of the substrate oxidation and electron transport systems which leads to the depletion of myocardial high-energy phosphates (both creatine phosphate and ATP). Such changes in the mitochondria appear to be due to the development of oxidative stress, inflammation, and Ca2+-handling abnormalities in the failing heart. Although some investigations have failed to detect any changes in the OXPHOS activity in the failing heart, such results appear to be due to a loss of Ca2+ during the mitochondrial isolation procedure. There is ample evidence to suggest that mitochondrial Ca2+-overload occurs, which is associated with impaired mitochondrial OXPHOS activity in the failing heart. The depression in mitochondrial OXPHOS activity may also be due to the increased level of reactive oxygen species, which are formed as a consequence of defects in the electron transport complexes in the failing heart. Various metabolic interventions which promote the generation of ATP have been reported to be beneficial for the therapy of heart failure. Accordingly, it is suggested that depression in mitochondrial OXPHOS activity plays an important role in the development of heart failure.

Targeting Mitochondrial Oxidative Stress: Potential Neuroprotective Therapy for Spinal Cord Injury

Spinal cord injury (SCI) is a serious central nervous system (CNS) injury disease related to hypoxia-ischemia and inflammation. It is characterized by excessive reactive oxygen species (ROS) production, oxidative damage to nerve cells, and mitochondrial dysfunction. Mitochondria serve as the primary cellular origin of ROS, wherein the electron transfer chain complexes within oxidative phosphorylation frequently encounter electron leakage. These leaked electrons react with molecular oxygen, engendering the production of ROS, which culminates in the occurrence of oxidative stress. Oxidative stress is one of the common forms of secondary injury after SCI. Mitochondrial oxidative stress can lead to impaired mitochondrial function and disrupt cellular signal transduction pathways. Hence, restoring mitochondrial electron transport chain (ETC), reducing ROS production and enhancing mitochondrial function may be potential strategies for the treatment of SCI. This article focuses on the pathophysiological role of mitochondrial oxidative stress in SCI and evaluates in detail the neuroprotective effects of various mitochondrial-targeted antioxidant therapies in SCI, including both drug and non-drug therapy. The objective is to provide valuable insights and serve as a valuable reference for future research in the field of SCI.

Luteolin induces apoptosis by impairing mitochondrial function and targeting the intrinsic apoptosis pathway in gastric cancer cells

Gastric cancer is one of the most lethal cancers worldwide. Research has focused on exploring natural medicines to improve the systematic chemotherapy for gastric cancer. Luteolin, a natural flavonoid, possesses anticancer activities. Nevertheless, the mechanism of the anticancer effects of luteolin is still not clear. The present study aimed to verify the inhibitory effect of luteolin on gastric cancer HGC-27, MFC and MKN-45 cells and to explore the underlying mechanism. A Cell Counting Kit-8 cell viability assay, flow cytometry, western blot, an ATP content assay and an enzyme activity testing assay were used. Luteolin inhibited the proliferation of gastric cancer HGC-27, MFC and MKN-45 cells. Further, it impaired mitochondrial integrity and function by destroying the mitochondrial membrane potential, downregulating the activities of mitochondrial electron transport chain complexes (mainly complexes I, III and V), and unbalancing the expression of B cell lymphoma-2 family member proteins, eventually leading to apoptosis of gastric cancer HGC-27, MFC and MKN-45 cells. The intrinsic apoptosis pathway was involved in luteolin's anti-gastric cancer effects. Furthermore, mitochondria were the main target in luteolin-induced gastric cancer apoptosis. The present study may provide a theoretical basis for the research on the effect of luteolin on the mitochondrial metabolism in cancer cells, and pave the way for its practical application in the future.

The mystery of massive mitochondrial complexes: the apicomplexan respiratory chain

The mitochondrial respiratory chain is an essential pathway in most studied eukaryotes due to its roles in respiration and other pathways that depend on mitochondrial membrane potential. Apicomplexans are unicellular eukaryotes whose members have an impact on global health. The respiratory chain is a drug target for some members of this group, notably the malaria-causing Plasmodium spp. This has motivated studies of the respiratory chain in apicomplexan parasites, primarily Toxoplasma gondii and Plasmodium spp. for which experimental tools are most advanced. Studies of the respiratory complexes in these organisms revealed numerous novel features, including expansion of complex size. The divergence of apicomplexan mitochondria from commonly studied models highlights the diversity of mitochondrial form and function across eukaryotic life.

Disruption of mitochondrial complex III in cap mesenchyme but not in ureteric progenitors results in defective nephrogenesis associated with amino acid deficiency

Oxidative metabolism in mitochondria regulates cellular differentiation and gene expression through intermediary metabolites and reactive oxygen species. Its role in kidney development and pathogenesis is not completely understood. Here we inactivated ubiquinone-binding protein QPC, a subunit of mitochondrial complex III, in two types of kidney progenitor cells to investigate the role of mitochondrial electron transport in kidney homeostasis. Inactivation of QPC in sine oculis-related homeobox 2 (SIX2)-expressing cap mesenchyme progenitors, which give rise to podocytes and all nephron segments except collecting ducts, resulted in perinatal death from severe kidney dysplasia. This was characterized by decreased proliferation of SIX2 progenitors and their failure to differentiate into kidney epithelium. QPC inactivation in cap mesenchyme progenitors induced activating transcription factor 4-mediated nutritional stress responses and was associated with a reduction in kidney tricarboxylic acid cycle metabolites and amino acid levels, which negatively impacted purine and pyrimidine synthesis. In contrast, QPC inactivation in ureteric tree epithelial cells, which give rise to the kidney collecting system, did not inhibit ureteric differentiation, and resulted in the development of functional kidneys that were smaller in size. Thus, our data demonstrate that mitochondrial oxidative metabolism is critical for the formation of cap mesenchyme-derived nephron segments but dispensable for formation of the kidney collecting system. Hence, our studies reveal compartment-specific needs for metabolic reprogramming during kidney development.

PACAP-38 Induces Transcriptomic Changes in Rat Trigeminal Ganglion Cells Related to Neuroinflammation and Altered Mitochondrial Function Presumably via PAC1/VPAC2 Receptor-Independent Mechanism

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a broadly expressed neuropeptide which has diverse effects in both the peripheral and central nervous systems. While its neuroprotective effects have been shown in a variety of disease models, both animal and human data support the role of PACAP in migraine generation. Both PACAP and its truncated derivative PACAP(6-38) increased calcium influx in rat trigeminal ganglia (TG) primary sensory neurons in most experimental settings. PACAP(6-38), however, has been described as an antagonist for PACAP type I (known as PAC1), and Vasoactive Intestinal Polypeptide Receptor 2 (also known as VPAC2) receptors. Here, we aimed to compare the signaling pathways induced by the two peptides using transcriptomic analysis. Rat trigeminal ganglion cell cultures were incubated with 1 µM PACAP-38 or PACAP(6-38). Six hours later RNA was isolated, next-generation RNA sequencing was performed and transcriptomic changes were analyzed to identify differentially expressed genes. Functional analysis was performed for gene annotation using the Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Reactome databases. We found 200 common differentially expressed (DE) genes for these two neuropeptides. Both PACAP-38 and PACAP(6-38) treatments caused significant downregulation of NADH: ubiquinone oxidoreductase subunit B6 and upregulation of transient receptor potential cation channel, subfamily M, member 8. The common signaling pathways induced by both peptides indicate that they act on the same target, suggesting that PACAP activates trigeminal primary sensory neurons via a mechanism independent of the identified and cloned PAC1/VPAC2 receptor, either via another target structure or a different splice variant of PAC1/VPAC2 receptors. Identification of the target could help to understand key mechanisms of migraine.

Huoxue Qianyang Qutan recipe attenuates Ang II-induced cardiomyocyte hypertrophy by regulating reactive oxygen species production

Continuous and irreversible cardiac hypertrophy can induce cardiac maladaptation and cardiac remodeling, resulting in increased risk of developing cardiovascular diseases. The present study was conducted to investigate the therapeutic effect of Huoxue Qianyang Qutan recipe (HQQR) on angiotensin II (Ang II)-induced cardiomyocyte hypertrophy. Primary cardiomyocytes were isolated from the cardiac tissue of neonatal rats, followed by flow cytometry detection to confirm the proportion of primary cardiomyocytes. Cell Counting Kit-8 assay and immunofluorescence detection were performed to examine the effect of Ang II and HQQR on cardiomyocyte hypertrophy. Reactive oxygen species (ROS) and a series of metabolic indicators were quantified to investigate the effect of HQQR on Ang II-induced cardiomyocyte hypertrophy. Mitochondrial electron transport chain complex activity and related coding gene expression were determined to explore the effect of HQQR on mitochondrial function. HQQR significantly inhibited Ang II-induced cardiomyocyte hypertrophy and restored Ang II-induced ROS accumulation, metabolic indicators, and membrane potential levels. HQQR also regulated the mitochondrial function related to the sirtuin 1 pathway in Ang II-induced cardiomyocytes by increasing the activity of the mitochondrial electron transport chain complex and affecting the expression of genes encoding mitochondrial electron transport chain complex subunits. HQQR could alleviate Ang II-induced cardiomyocyte hypertrophy by modulating oxidative stress, accumulating ROS and increasing mitochondrial electron transport chain activity.

Co-occurrence of subunit B and C mutations in respiratory complex II confers high resistance levels to pyflubumide and cyenopyrafen in the two-spotted spider mite Tetranychus urticae (Acari: Tetranychidae)

BACKGROUND

Pyflubumide and cyenopyrafen are respiratory complex II (complex II) inhibitors. Previous quantitative trait locus analyses suggested associations of I260V and S56L in complex II subunit B (B-I260V) and subunit C (C-S56L) with pyflubumide and cyenopyrafen resistance, respectively, in Tetranychus urticae. However, although resistant strains had been selected separately by these acaricides, all strains were homozygous for both B-I260V and C-S56L. Hence, the effects of each mutation on resistance development remain unclear.

RESULTS

We established strains homozygous for B-I260V with C-S56 (B-I260V_I260V/C-S56_S56) and for C-S56L with B-I260 (B-I260_I260/C-S56L_S56L). High resistance levels (LC₅₀  > 1000 mg L^-1 ) to pyflubumide and cyenopyrafen was not conferred by B-I260V or C-S56L alone. Next, we prepared intermixed strains by crossing B-I260V_I260V/C-S56_S56 and B-I260_I260/C-S56L_S56L. Selection of the intermixed strains by either acaricide caused very high resistance levels (LC₅₀  ≥ 10 000 mg L^-1 ) to both acaricides and fixed both mutations. Allele-selected recoupling of the mutations without acaricide selection also conferred very high resistance levels to both acaricides in the intermixed strains. Unlike these, B-I260V or C-S56L alone conferred very high and high resistance levels to cyflumetofen, respectively.

CONCLUSION

We conclude that the effect of individual mutations characteristically varies among complex II inhibitors. Moreover, very high resistance levels to pyflubumide and cyenopyrafen is conferred by the co-occurrence of B-I260V and C-S56L mutations, which alone have limited effects on resistance level.

Quantitative Proteomics Reveal That Metabolic Improvement Contributes to the Cardioprotective Effect of T89 on Isoproterenol-Induced Cardiac Injury

Background

T₈₉, a traditional Chinese medicine, has passed phase II, and is undergoing phase III clinical trials for treatment of ischemic cardiovascular disease by the US FDA. However, the role of T₈₉ on isoproterenol (ISO)-induced cardiac injury is unknown. The present study aimed to explore the effect and underlying mechanism of T₈₉ on ISO-induced cardiac injury.

Methods

Male Sprague-Dawley rats received subcutaneous injection of ISO saline solution at 24 h intervals for the first 3 days and then at 48 h intervals for the next 12 days. T₈₉ at dose of 111.6 and 167.4 mg/kg was administrated by gavage for 15 consecutive days. Rat survival rate, cardiac function evaluation, morphological observation, quantitative proteomics, and Western blotting analysis were performed.

Results

T₈₉ obviously improved ISO-induced low survival rate, attenuated ISO-evoked cardiac injury, as evidenced by myocardial blood flow, heart function, and morphology. Quantitative proteomics revealed that the cardioprotective effect of T₈₉ relied on the regulation of metabolic pathways, including glycolipid metabolism and energy metabolism. T₈₉ inhibited the enhancement of glycolysis, promoted fatty acid oxidation, and restored mitochondrial oxidative phosphorylation by regulating Eno1, Mcee, Bdh1, Ces1c, Apoc2, Decr1, Acaa2, Cbr4, ND2, Cox 6a, Cox17, ATP5g, and ATP5j, thus alleviated oxidative stress and energy metabolism disorder and ameliorated cardiac injury after ISO. The present study also verified that T₈₉ significantly restrained ISO-induced increase of HSP70/HSP40 and suppressed the phosphorylation of ERK, further restored the expression of CX43, confirming the protective role of T₈₉ in cardiac hypertrophy. Proteomics data are available via ProteomeXchange with identifier PXD024641.

Conclusion

T₈₉ reduced mortality and improves outcome in the model of ISO-induced cardiac injury and the cardioprotective role of T₈₉ is correlated with the regulation of glycolipid metabolism, recovery of mitochondrial function, and improvement of myocardial energy.

ATF4-Induced Warburg Metabolism Drives Over-Proliferation in Drosophila

The mitochondrial electron transport chain (ETC) enables essential metabolic reactions; nonetheless, the cellular responses to defects in mitochondria and the modulation of signaling pathway outputs are not understood. We show that Notch signaling and ETC attenuation via knockdown of COX7a induces massive over-proliferation. The tumor-like growth is caused by a transcriptional response through the eIF2α-kinase PERK and ATF4, which activates the expression of metabolic enzymes, nutrient transporters, and mitochondrial chaperones. We find this stress adaptation to be beneficial for progenitor cell fitness, as it renders cells sensitive to proliferation induced by the Notch signaling pathway. Intriguingly, over-proliferation is not caused by transcriptional cooperation of Notch and ATF4, but it is mediated in part by pH changes resulting from the Warburg metabolism induced by ETC attenuation. Our results suggest that ETC function is monitored by the PERK-ATF4 pathway, which can be hijacked by growth-promoting signaling pathways, leading to oncogenic pathway activity.

Cadmium-Induced Cytotoxicity: Effects on Mitochondrial Electron Transport Chain

Cadmium (Cd) is a well-known heavy metal and environmental toxicant and pollutant worldwide, being largely present in every kind of item such as plastic (toys), battery, paints, ceramics, contaminated water, air, soil, food, fertilizers, and cigarette smoke. Nowadays, it represents an important research area for the scientific community mainly for its effects on public health. Due to a half-life ranging between 15 and 30 years, Cd owns the ability to accumulate in organs and tissues, exerting deleterious effects. Thus, even at low doses, a Cd prolonged exposure may cause a multiorgan toxicity. Mitochondria are key intracellular targets for Cd-induced cytotoxicity, but the underlying mechanisms are not fully elucidated. The present review is aimed to clarify the effects of Cd on mitochondria and, particularly, on the mitochondrial electron transport chain.

Mitochondrial Targeting in an Anti-Austerity Approach Involving Bioactive Metabolites Isolated from the Marine-Derived Fungus Aspergillus sp

The tumor microenvironment is a nutrient-deficient region that alters the cancer cell phenotype to aggravate cancer pathology. The ability of cancer cells to tolerate nutrient starvation is referred to as austerity. Compounds that preferentially target cancer cells growing under nutrient-deficient conditions are being employed in anti-austerity approaches in anticancer drug discovery. Therefore, in this study, we investigated physcion (1) and 2-(2',3-epoxy-1',3',5'-heptatrienyl)-6-hydroxy-5-(3-methyl-2-butenyl) benzaldehyde (2) obtained from a culture extract of the marine-derived fungus Aspergillus species (sp.), which were isolated from an unidentified marine sponge, as anti-austerity agents. The chemical structures of 1 and 2 were determined via spectroscopic analysis and comparison with authentic spectral data. Compounds 1 and 2 exhibited selective cytotoxicity against human pancreatic carcinoma PANC-1 cells cultured under glucose-deficient conditions, with IC₅₀ values of 6.0 and 1.7 µM, respectively. Compound 2 showed higher selective growth-inhibitory activity (505-fold higher) under glucose-deficient conditions than under general culture conditions. Further analysis of the mechanism underlying the anti-austerity activity of compounds 1 and 2 against glucose-starved PANC-1 cells suggested that they inhibited the mitochondrial electron transport chain.

Multiparametric real-time sensing of cytosolic physiology links hypoxia responses to mitochondrial electron transport

Hypoxia regularly occurs during plant development and can be induced by the environment through, for example, flooding. To understand how plant tissue physiology responds to progressing oxygen restriction, we aimed to monitor subcellular physiology in real time and in vivo. We establish a fluorescent protein sensor-based system for multiparametric monitoring of dynamic changes in subcellular physiology of living Arabidopsis thaliana leaves and exemplify its applicability for hypoxia stress. By monitoring cytosolic dynamics of magnesium adenosine 5'-triphosphate, free calcium ion concentration, pH, NAD redox status, and glutathione redox status in parallel, linked to transcriptional and metabolic responses, we generate an integrated picture of the physiological response to progressing hypoxia. We show that the physiological changes are surprisingly robust, even when plant carbon status is modified, as achieved by sucrose feeding or extended night. Inhibition of the mitochondrial respiratory chain causes dynamics of cytosolic physiology that are remarkably similar to those under oxygen depletion, highlighting mitochondrial electron transport as a key determinant of the cellular consequences of hypoxia beyond the organelle. A broadly applicable system for parallel in vivo sensing of plant stress physiology is established to map out the physiological context under which both mitochondrial retrograde signalling and low oxygen signalling occur, indicating shared upstream stimuli.

Deficiencies in the Mitochondrial Electron Transport Chain Affect Redox Poise and Resistance Toward Colletotrichum higginsianum

To investigate if and how the integrity of the mitochondrial electron transport chain (mETC) influences susceptibility of Arabidopsis toward Colletotrichum higginsianum, we have selected previously characterized mutants with defects at different stages of the mETC, namely, the complex I mutant ndufs4, the complex II mutant sdh2-1, the complex III mutant ucr8-1, and a mutant of the uncoupling protein ucp1-2. Relative to wild type, the selected complex I, II, and III mutants showed decreased total respiration, increased alternative respiration, as well as increased redox charge of the NADP(H) pool and decreased redox charge of the NAD(H) pool in the dark. In the light, mETC mutants accumulated free amino acids, albeit to varying degrees. Glycine and serine, which are involved in carbon recycling from photorespiration, and N-rich amino acids were predominantly increased in mETC mutants compared to the wild type. Taking together the physiological phenotypes of all examined mutants, our results suggest a connection between the limitation in the re-oxidation of reducing equivalents in the mitochondrial matrix and the induction of nitrate assimilation into free amino acids in the cytosol, which seems to be engaged as an additional sink for reducing power. The sdh2-1 mutant was less susceptible to C. higginsianum and did not show hampered salicylic acid (SA) accumulation as previously reported for SDH1 knock-down plants. The ROS burst remained unaffected in sdh2-1, emonstrating that subunit SDH2 is not involved in the control of ROS production and SA signaling by complex II. Moreover, the ndufs4 mutant showed only 20% of C. higginsianum colonization compared to wild type, with the ROS burst and the production of callose papillae being significantly increased compared to wild type. This indicates that a restriction of respiratory metabolism can positively affect pre-penetration resistance of Arabidopsis. Taking metabolite profiling data from all investigated mETC mutants, a strong positive correlation of resistance toward C. higginsianum with NADPH pool size, pyruvate contents, and other metabolites associated with redox poise and energy charge was evident, which fosters the hypothesis that limitations in the mETC can support resistance at post-penetration stages by improving the availability of metabolic power.

Alternative Type II NAD(P)H Dehydrogenases in the Mitochondria of Protists and Fungi

Plants, fungi, and some protists possess a more branched electron transport chain in their mitochondria compared to canonical one. In these organisms, the electron transport chain contains several rotenone-insensitive NAD(P)H dehydrogenases. Some are located on the outer surface, and others are located on the inner surface of the inner mitochondrial membrane. The putative role of these enzymes still remains elusive, but they may prevent the overreduction of the electron transport chain components and decrease the production of reaction oxygen species as a consequence. The last two decades resulted in the discovery of alternative rotenone-insensitive NAD(P)H dehydrogenases present in representatives of fungi and protozoa. The aim of this review is to gather and focus on current information concerning molecular and functional properties, regulation, and the physiological role of fungal and protozoan alternative NAD(P)H dehydrogenases.

Selection of Plasmodium falciparum cytochrome B mutants by putative PfNDH2 inhibitors

Malaria control is threatened by a limited pipeline of effective pharmaceuticals against drug-resistant strains of Plasmodium falciparum Components of the mitochondrial electron transport chain (ETC) are attractive targets for drug development, owing to exploitable differences between the parasite and human ETC. Disruption of ETC function interferes with metabolic processes including de novo pyrimidine synthesis, essential for nucleic acid replication. We investigated the effects of ETC inhibitor selection on two distinct P. falciparum clones, Dd2 and 106/1. Compounds CK-2-68 and RYL-552, substituted quinolones reported to block P. falciparum NADH dehydrogenase 2 (PfNDH2; a type II NADH:quinone oxidoreductase), unexpectedly selected mutations at the quinol oxidation (Q_o) pocket of P. falciparum cytochrome B (PfCytB). Selection experiments with atovaquone (ATQ) on 106/1 parasites yielded highly resistant PfCytB Y268S mutants seen in clinical infections that fail ATQ-proguanil treatment. In contrast, ATQ pressure on Dd2 yielded moderately resistant parasites carrying a PfCytB M133I or K272R mutation. Strikingly, all ATQ-selected mutants demonstrated little change or slight increase of sensitivity to CK-2-68 or RYL-552. Molecular docking studies demonstrated binding of all three ETC inhibitors to the Q_o pocket of PfCytB, where Y268 forms strong van der Waals interactions with the hydroxynaphthoquinone ring of ATQ but not the quinolone ring of CK-2-68 or RYL-552. Our results suggest that combinations of suitable ETC inhibitors may be able to subvert or delay the development of P. falciparum drug resistance.

Combination Drug Therapy of Pioglitazone and D-cycloserine Attenuates Chronic Orofacial Neuropathic Pain and Anxiety by Improving Mitochondrial Function Following Trigeminal Nerve Injury

OBJECTIVES

The study aim was to determine how peripheral trigeminal nerve injury affects mitochondrial respiration and to test efficacy of combined treatment with 2 Federal Drug Administration approved drugs with potential for improving mitochondrial bioenergetics, pain and anxiety-related behaviors in a chronic orofacial neuropathic pain mouse model.

METHODS

Efficacy of (R)-(+)-4-amino-3-isoxazolidinone (D-cycloserine, DCS), an N-Methyl-D-aspartate antagonist/agonist, and Pioglitazone (PIO), a selective agonist of nuclear receptor peroxisome proliferator-activated receptor gamma was investigate in the trigeminal inflammatory compression (TIC) neuropathic nerve injury mouse model. Combined low doses of these drugs (80 mg/kg DCS and 100 mg/kg PIO) were given as a single bolus or daily for 7 days post-TIC to test ability to attenuate neuropathic nociceptive and associated cognitive dependent anxiety behaviors. In addition, beneficial effects of the DCS/PIO drug combination were explored ex vivo in isolated cortex/brainstem mitochondria at 28 weeks post-TIC.

RESULTS

The DCS/PIO combination not only attenuated orofacial neuropathic pain and anxiety-related behaviors associated with trigeminal nerve injury, but it also improved mitochondrial bioenergetics.

DISCUSSION

The DCS/PIO combination uncoupled mitochondrial respiration in the TIC model to improve cortical mitochondrial dysfunction, as well as reduced nociceptive and anxiety behaviors present in mice with centralized chronic neuropathic nerve injury. Combining these drugs could be a beneficial treatment for patients with depression, anxiety, or other psychological conditions due to their chronic pain status.

The occurrence and control of nitric oxide generation by the plant mitochondrial electron transport chain

The plant mitochondrial electron transport chain (ETC) is bifurcated such that electrons from ubiquinol are passed to oxygen via the usual cytochrome path or through alternative oxidase (AOX). We previously showed that knockdown of AOX in transgenic tobacco increased leaf concentrations of nitric oxide (NO), implying that an activity capable of generating NO had been effected. Here, we identify the potential source of this NO. Treatment of leaves with antimycin A (AA, Qi -site inhibitor of Complex III) increased NO amount more than treatment with myxothiazol (Myxo, Qo -site inhibitor) despite both being equally effective at inhibiting respiration. Comparison of nitrate-grown wild-type with AOX knockdown and overexpression plants showed a negative correlation between AOX amount and NO amount following AA. Further, Myxo fully negated the ability of AA to increase NO amount. With ammonium-grown plants, neither AA nor Myxo strongly increased NO amount in any plant line. When these leaves were supplied with nitrite alongside the AA or Myxo, then the inhibitor effects across lines mirrored that of nitrate-grown plants. Hence the ETC, likely the Q-cycle of Complex III generates NO from nitrite, and AOX reduces this activity by acting as a non-energy-conserving electron sink upstream of Complex III.

Time-restricted feeding for prevention and treatment of cardiometabolic disorders

The soaring prevalence of obesity and diabetes is associated with an increase in comorbidities, including elevated risk for cardiovascular diseases (CVDs). CVDs continue to be among the leading causes of death and disability in the United States. While increased nutritional intake from an energy-dense diet is known to disrupt metabolic homeostasis and contributes to the disease risk, circadian rhythm disruption is emerging as a new risk factor for CVD. Circadian rhythms coordinate cardiovascular health via temporal control of organismal metabolism and physiology. Thus, interventions that improve circadian rhythms are prospective entry points to mitigate cardiometabolic disease risk. Although light is a strong modulator of the neural circadian clock, time of food intake is emerging as a dominant agent that affects circadian clocks in metabolic organs. We discovered that imposing a time-restricted feeding (TRF) regimen in which all caloric intakes occur consistently within ≤ 12 h every day exerts many cardiometabolic benefits. TRF prevents excessive body weight gain, improves sleep, and attenuates age- and diet-induced deterioration in cardiac performance. Using an integrative approach that combines Drosophila melanogaster (fruit fly) genetics with transcriptome analyses it was found that the beneficial effects of TRF are mediated by circadian clock, ATP-dependent TCP/TRiC/CCT chaperonin and mitochondrial electron transport chain components. Parallel studies in rodents have shown TRF reduces metabolic disease risks by maintaining metabolic homeostasis. As modern humans continue to live under extended periods of wakefulness and ingestion events, daily eating pattern offers a new potential target for lifestyle intervention to reduce CVD risk.

Mitochondrial dysfunction induced by Bisphenol A is a factor of its hepatotoxicity in rats

Bisphenol A (BPA), an estrogenic and endocrine disrupting agent, is widely used in manufacturing of polycarbonate plastics and epoxy resins. BPA and other endocrine disrupting chemicals (EDCs) act via multiple mechanisms including interference with mitochondrial functions. Mitochondria are the hub of cellular energy pool and hence are the target of many EDCs. We studied perturbation of activities of mitochondrial enzymes by BPA and its possible role in hepatotoxicity in Wistar rats. Rats were exposed to BPA (150 mg/kg, 250 mg/kg, 500 mg/kg per os, for 14 days) and activities of enzymes of mitochondrial electron transport chain (ETC) were measured. Besides, other biochemical parameters such as superoxide generation, protein oxidation, and lipid peroxidation (LPO) were also measured. Our results indicated a significant decrease in the activities of enzymes of mitochondrial ETC complexes, i.e., complex I, II, III, IV, and V along with significant increase in LPO and protein oxidation. Additionally, a significant increase in mitochondrial superoxide generation was also observed. All these findings could be attributed to enhanced oxidative stress, decrease in reduced glutathione level, and decrease in the activity of superoxide dismutase in rat liver mitochondria isolated from BPA-treated rats. BPA treatment also caused a significant increase in serum alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and lactate dehydrogenase indicating its potential hepatotoxicity. Furthermore, histopathological findings revealed marked edema formation, hepatocellular degeneration, and necrosis of liver tissue in BPA-exposed rats. In conclusion, this study provides an evidence of impaired mitochondrial bioenergetics and liver toxicity after high-dose BPA exposure in rats. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1922-1934, 2016.

Endothelium-Derived Hyperpolarization and Coronary Vasodilation: Diverse and Integrated Roles of Epoxyeicosatrienoic Acids, Hydrogen Peroxide, and Gap Junctions

Myocardial perfusion and coronary vascular resistance are regulated by signaling metabolites released from the local myocardium that act either directly on the VSMC or indirectly via stimulation of the endothelium. A prominent mechanism of vasodilation is EDH of the arteriolar smooth muscle, with EETs and H(2)O(2) playing important roles in EDH in the coronary microcirculation. In some cases, EETs and H(2)O(2) are released as transferable hyperpolarizing factors (EDHFs) that act directly on the VSMCs. By contrast, EETs and H(2)O(2) can also promote endothelial KCa activity secondary to the amplification of extracellular Ca(2+) influx and Ca(2+) mobilization from intracellular stores, respectively. The resulting endothelial hyperpolarization may subsequently conduct to the media via myoendothelial gap junctions or potentially lead to the release of a chemically distinct factor(s). Furthermore, in human isolated coronary arterioles dilator signaling involving EETs and H(2)O(2) may be integrated, being either complimentary or inhibitory depending on the stimulus. With an emphasis on the human coronary microcirculation, this review addresses the diverse and integrated mechanisms by which EETs and H(2)O(2) regulate vessel tone and also examines the hypothesis that myoendothelial microdomain signaling facilitates EDH activity in the human heart.

Salicylic acid binding of mitochondrial alpha-ketoglutarate dehydrogenase E2 affects mitochondrial oxidative phosphorylation and electron transport chain components and plays a role in basal defense against tobacco mosaic virus in tomato

Salicylic acid (SA) plays a critical role in plant defense against pathogen invasion. SA-induced viral defense in plants is distinct from the pathways mediating bacterial and fungal defense and involves a specific pathway mediated by mitochondria; however, the underlying mechanisms remain largely unknown. The SA-binding activity of the recombinant tomato (Solanum lycopersicum) alpha-ketoglutarate dehydrogenase (Slα-kGDH) E2 subunit of the tricarboxylic acid (TCA) cycle was characterized. The biological role of this binding in plant defenses against tobacco mosaic virus (TMV) was further investigated via Slα-kGDH E2 silencing and transient overexpression in plants. Slα-kGDH E2 was found to bind SA in two independent assays. SA treatment, as well as Slα-kGDH E2 silencing, increased resistance to TMV. SA did not further enhance TMV defense in Slα-kGDH E2-silenced tomato plants but did reduce TMV susceptibility in Nicotiana benthamiana plants transiently overexpressing Slα-kGDH E2. Furthermore, Slα-kGDH E2-silencing-induced TMV resistance was fully blocked by bongkrekic acid application and alternative oxidase 1a silencing. These results indicated that binding by Slα-kGDH E2 of SA acts upstream of and affects the mitochondrial electron transport chain, which plays an important role in basal defense against TMV. The findings of this study help to elucidate the mechanisms of SA-induced viral defense.

The signaling role of a mitochondrial superoxide burst during stress

Plant mitochondria are proposed to act as signaling organelles in the orchestration of defense responses to biotic stress and acclimation responses to abiotic stress. However, the primary signal(s) being generated by mitochondria and then interpreted by the cell are largely unknown. Recently, we showed that mitochondria generate a sustained burst of superoxide (O 2(-)) during particular plant-pathogen interactions. This O 2(-) burst appears to be controlled by mitochondrial components that influence rates of O 2(-) generation and scavenging within the organelle. The O 2(-) burst appears to influence downstream processes such as the hypersensitive response, indicating that it could represent an important mitochondrial signal in support of plant stress responses. The findings generate many interesting questions regarding the upstream factors required to generate the O 2(-) burst, the mitochondrial events that occur in support of and in parallel with this burst and the downstream events that respond to this burst.