scholarly journals O2-sensing signal cascade: clamping of O2 respiration, reduced ATP utilization, and inducible fumarate respiration

2008 ◽  
Vol 295 (1) ◽  
pp. C29-C37 ◽  
Author(s):  
Vijayalakshmi Sridharan ◽  
Jason Guichard ◽  
Chuan-Yuan Li ◽  
Robin Muise-Helmericks ◽  
Craig Cano Beeson ◽  
...  
Keyword(s):  
Turnover Rate ◽  
Lactic Acid Production ◽  
Hypoxia Inducible Factor ◽  
Terminal Electron Acceptor ◽  
Neonatal Cardiomyocytes ◽  
Atp Turnover ◽  
Transport Chain ◽  
Pathway Activation ◽  
Atp Generation ◽  
Purine Nucleotide Cycle

These studies explore the consequences of activating the prolyl hydroxylase (PHD) O2-sensing pathway in spontaneously twitching neonatal cardiomyocytes. Full activation of the PHD pathway was achieved using the broad-spectrum PHD inhibitor (PHI) dimethyloxaloylglycine (DMOG). PHI treatment of cardiomyocytes caused an 85% decrease in O2 consumption and a 300% increase in lactic acid production under basal conditions. This indicates a ∼75% decrease in ATP turnover rate, inasmuch as the increased ATP generation by glycolysis is inadequate to compensate for the lower respiration. To determine the extent to which decreased ATP turnover underlies the suppressed O2 consumption, mitochondria were uncoupled with 2,4-dinitrophenol. We were surprised to find that 2,4-dinitrophenol failed to increase O2 consumption by PHI-treated cells, indicating that electron transport chain activity, rather than ATP turnover rate, limits respiration in PHI-treated cardiomyocytes. Silencing of hypoxia-inducible factor-1α (HIF-1α) expression restored the ability of uncoupled PHI-treated myocytes to increase O2 consumption; however, basal O2 uptake rates remained low because of the unabated suppression of cellular ATP consumption. Thus it appears that respiration is actively “clamped” through an HIF-dependent mechanism, whereas HIF-independent mechanisms are responsible for downregulation of ATP consumption. In addition, we find that PHD pathway activation enables mitochondria to utilize fumarate as a terminal electron acceptor when cytochrome c oxidase is inactive. The source of fumarate for this unusual respiration is derived from aspartate via the purine nucleotide cycle. In sum, these studies show that the O2-sensing pathway is sufficient to actively “clamp” O2 consumption and independently suppress cellular ATP consumption. The PHD pathway also enables the mitochondria to utilize fumarate for respiration.

scholarly journals Hydroxylase-dependent regulation of the NF-κB pathway

2013 ◽  
Vol 394 (4) ◽  
pp. 479-493 ◽  
Author(s):  
Carsten C. Scholz ◽  
Cormac T. Taylor
Keyword(s):  
Molecular Oxygen ◽  
Hypoxia Inducible Factor ◽  
Chronic Inflammatory Disease ◽  
Therapeutic Approaches ◽  
Diverse Range ◽  
Terminal Electron Acceptor ◽  
Transport Chain ◽  
Factor Α ◽  
Α Subunits

Abstract Hypoxia is associated with a diverse range of physiological and pathophysiological processes, including development, wound healing, inflammation, vascular disease and cancer. The requirement that eukaryotic cells have for molecular oxygen as the terminal electron acceptor for the electron transport chain means that the maintenance of oxygen delivery is key for bioenergetic homeostasis. Metazoans have evolved an effective way to adapt to hypoxic stress at the molecular level through a transcription factor termed the hypoxia inducible factor. A family of oxygen-sensing hydroxylases utilizes molecular oxygen as a co-substrate for the hydroxylation of hypoxia inducible factor α subunits, thereby reducing its expression and transcriptional activity when oxygen is available. Recent studies have indicated that other hypoxia-responsive transcriptional pathways may also be hydroxylase-dependent. In this review, we will discuss the role of hydroxylases in the regulation of NF-κB, a key regulator of immunity and inflammation. Developing our understanding of the role of hydroxylases in hypoxic inflammation may identify novel therapeutic approaches in chronic inflammatory disease.

alpha-Glycerophosphate shuttle in a clonal beta-cell line

1989 ◽  
Vol 256 (1) ◽  
pp. E173-E178 ◽  
Author(s):  
M. D. Meglasson ◽  
K. M. Smith ◽  
D. Nelson ◽  
M. Erecinska
Keyword(s):  
Insulin Secretion ◽  
Cell Line ◽  
Electron Transport Chain ◽  
Direct Evidence ◽  
Mitochondrial Fraction ◽  
Secreting Cell ◽  
Transport Chain ◽  
Beta Cell Line ◽  
Atp Generation ◽  
Hit Cells

It has been proposed that the alpha-glycerophosphate (alpha-GOP) shuttle plays a crucial role in regulation of glycolysis in beta-cells by linking reoxidation of cytosolic NADH to formation of ATP in the electron transport chain (J. Biol. Chem. 265: 8287, 1981). Direct evidence for this suggestion is still lacking, however. In this work the operation of the alpha-GOP shuttle was investigated in the insulin-secreting cell line HIT-T15. The constituent enzymes of the pathway were found to be present in HIT cells. Flavin-linked alpha-GOP dehydrogenase was associated with the mitochondrial fraction, whereas NAD+-dependent alpha-GOP dehydrogenase was localized in the cytosol. In the presence of amobarbital (used to preserve the function of the alpha-GOP shuttle under conditions where oxidation of NADH by the respiratory chain was blocked), glucose increased insulin secretion, O2 consumption, and the cell [ATP]/[ADP] when compared with amobarbital alone. These results indicate that the alpha-GOP shuttle contributes to ATP generation in HIT cells and that its activation may be necessary for the initiation of insulin secretion by glucose.

scholarly journals 322 Melanoma-intrinsic hypoxia-inducible factor-1α results in diminished T cell accumulation within the tumor microenvironment

2021 ◽  
Vol 9 (Suppl 3) ◽  
pp. A347-A347
Author(s):  
Emily Higgs ◽  
Thomas Gajewski ◽  
Jonathan Trujillo
Keyword(s):  
T Cell ◽  
Tumor Microenvironment ◽  
Cancer Cell ◽  
Gene Expression Analysis ◽  
Hypoxia Inducible Factor ◽  
Gene Signature ◽  
T Cell Response ◽  
Pathway Activation ◽  
Cell Accumulation ◽  
The Impact

BackgroundThe hypoxia-inducible factor (HIF) system, consisting of the transcription factors HIF-1α and HIF-2α, mediates cellular adaptation to hypoxia, and can promote cancer progression, invasion, and metastasis. HIF pathway activation in the tumor microenvironment has been implicated in cancer immune evasion; however, a direct causal role for tumor cell-intrinsic HIF-1α and HIF-2α activation in mediating T cell exclusion and cancer cell resistance to immune checkpoint inhibitor therapy has not been demonstrated.MethodsWe performed gene expression analysis of melanoma tumors in the Cancer Genome Atlas (TCGA) data set to determine whether increased HIF-1α pathway activation correlated with reduced T cell-based inflammation. The magnitude of HIF-1α pathway activation across melanoma samples was determined by applying a quantitative scoring system on the expression of a melanocyte-specific hypoxia-induced, HIF-1α-target gene signature consisting of 81 genes. The Pearson correlation test was used to compare the HIF-1α activation score and our 160-gene T-cell-inflamed gene signature. To determine the impact of cancer cell-intrinsic HIF-1α or HIF-2α activation on the endogenous anti-tumor T cell response, we developed an inducible autochthonous mouse melanoma model driven by BRAFV600E expression and PTEN-deletion, with or without inducible expression of either a stabilized variant of HIF-1α or HIF-2α. These murine tumor models are being used to determine the impact of cancer cell-intrinsic HIF-1α or HIF-2α activation on tumor sensitivity to anti-PD-1/PD-L1 and anti-CTLA-4 treatment.ResultsGene expression analysis of human melanomas in the TCGA demonstrated a statistically significant inverse correlation between the HIF-1α activation score and T cell-inflammation score. Braf/PTEN murine melanomas with and without stabilized HIF-1α expression developed with comparable tumor onset and growth kinetics. Multiparameter immunofluorescence staining of melanoma tissue revealed a significant decrease in tumor-infiltrating T cells within Braf/PTEN melanoma tumors expressing stabilized HIF-1α compared to control Braf/PTEN melanomas.ConclusionsOur data demonstrate that tumor-cell intrinsic HIF-1α activation leads to diminished T cell accumulation within the tumor microenvironment, which has implications for cancer immunotherapy. The mechanism of this effect is being elucidated. These novel murine models will help elucidate the roles of cancer cell-intrinsic HIF-1α and HIF-2α activation in modulating the anti-tumor T cell response, providing mechanistic insight that will inform the evaluation of novel selective HIF inhibitors, which are showing promising anti-tumor activity in clinical trials in patients with advanced solid tumors.

scholarly journals Lactobacillus plantarum WCFS1 Electron Transport Chains

2009 ◽  
Vol 75 (11) ◽  
pp. 3580-3585 ◽  
Author(s):  
R. J. W. Brooijmans ◽  
W. M. de Vos ◽  
J. Hugenholtz
Keyword(s):  
Electron Transport ◽  
Lactobacillus Plantarum ◽  
Consumption Rate ◽  
Growth Media ◽  
Terminal Electron Acceptor ◽  
Glucose Levels ◽  
Transport Chain ◽  
Electron Transport Chains ◽  
Cofactor Biosynthesis ◽  
Isogenic Mutants

ABSTRACT Lactobacillus plantarum WCFS1 requires both heme and menaquinone to induce respiration-like behavior under aerobic conditions. The addition of these compounds enhanced both biomass production, without progressive acidification, and the oxygen consumption rate. When both heme and menaquinone were present, L. plantarum WCFS1 was also able to reduce nitrate. The ability to reduce nitrate was severely inhibited by the glucose levels that are typically found in L. plantarum growth media (1 to 2% [vol/vol] glucose). In contrast, comparable mannitol levels did not inhibit the reduction of nitrate. L. plantarum reduced nitrate with concomitant formation of nitrite and ammonia. Genes that encode a bd-type cytochrome (cydABCD) and a nitrate reductase (narGHJI) were identified in the genome of L. plantarum. The narGHJI operon is part of a cluster of genes that includes the molybdopterin cofactor biosynthesis genes and narK. Besides a menaquinone source, isogenic mutants revealed that cydA and ndh1 are required for the aerobic-respiration-like response and narG for nitrate reduction. The ndh1 mutant was still able to reduce nitrate. The existence of a nonredundant branched electron transport chain in L. plantarum WCFS1 that is capable of using oxygen or nitrate as a terminal electron acceptor is proposed.

Muscle ATP turnover rate during isometric contraction in humans

1986 ◽  
Vol 60 (6) ◽  
pp. 1839-1842 ◽  
Author(s):  
A. Katz ◽  
K. Sahlin ◽  
J. Henriksson
Keyword(s):  
Isometric Contraction ◽  
Turnover Rate ◽  
Knee Extensor ◽  
High Energy ◽  
High Energy Phosphates ◽  
Atp Turnover ◽  
Contraction Duration ◽  
Extensor Muscles ◽  
Before And After ◽  
Fast Twitch

ATP turnover and glycolytic rates during isometric contraction in humans have been investigated. Subjects contracted the knee extensor muscles at two-thirds maximal voluntary force to fatigue (mean +/- SE, 53 +/- 4 s). Biopsies were obtained before and after exercise and analyzed for high-energy phosphates and glycogenolytic-glycolytic intermediates. Total ATP turnover was 190 +/- 7 mmol/kg dry muscle, whereas the average turnover rate was 3.7 +/- 0.2 mmol . kg dry muscle-1 . S-1. The average ATP turnover rate was positively correlated with the percentage of fast-twitch fibers in the postexercise biopsy (r = 0.71; P less than 0.05) and negatively correlated with contraction duration to fatigue (r = -0.88; P less than 0.05). At fatigue, phosphocreatine ranged from 1 to 11 mmol/kg dry muscle (86–99% depletion of value at rest), whereas lactate ranged from 59 to 101. The mean glycolytic rate was 0.83 +/- 0.05 mmol . kg dry muscle-1 . S-1 and was positively correlated with the rate of glucose 6-phosphate accumulation (r = 0.83; P less than 0.05). It is concluded that a major determinant of the ATP turnover rate is the muscle fiber composition, which is probably explained by a higher turnover rate in fast-twitch fibers; fatigue is more closely related to a low phosphocreatine content than to a high lactate content; and the increase in prephosphofructokinase intermediates is important for stimulating glycolysis during contraction.

Role of Hypoxia and Hypoxia-Inducible-Factor 1α (HIF1A) In the BM Microenvironment-Mediated Protection of Leukemic Cells.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2586-2586
Author(s):  
Rodrigo Jacamo ◽  
Juliana Benito ◽  
Olga Frolova ◽  
Ye Chen ◽  
Hongbo Lu ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Conflicts Of Interest ◽  
Lactic Acid Production ◽  
Hypoxia Inducible Factor ◽  
Leukemic Cells ◽  
Hypoxia Inducible Factor 1Α ◽  
Hypoxic Conditions ◽  
Control Mscs ◽  
Culture Supernatants

Abstract Abstract 2586 Resistance to chemotherapy can be mediated by genetic, epigenetic and microenvironmental causes. Only recently the connection between leukemia growth and survival and the hypoxic state of the BM microenvironment has been appreciated, by work conducted by us and others (Fiegl M et.al. Blood 2009; 113: 1504–1512; Harrison JS et. al., Blood 2002; 99). In extension of this concept we investigated the role of Hypoxia-Inducible-Factor 1α (HIF1A), the master regulator of hypoxia induced responses, in the microenvironment and its relevance for leukemia progression. Here we focused on the role of hypoxia and HIF transcription factors in cells contributing to the BM microenvironment, the mesenchymal stromal cells (MSC). Co-culture of lymphoid (NALM6) and myeloid (OCI-AML3) leukemic cell lines with BM-derived MSC under hypoxic conditions (1% O2) stimulated the secretion of a number of pro-survival cytokines and chemokines (including IL-6, VEGF, Beta-NGF and SDF-1α) that were quantified in co-culture supernatants by Luminex flow cytometry (Table 1). These findings suggest that hypoxia, and possibly its main mediator, the transcription factor HIF1A, may be responsible for the increased production of these factors. Since the chemokine stromal cell-derived factor-1α (SDF-1α) is involved in the attraction of leukemic cells towards cells of the BM microenvironment, we next investigated the role of HIF1A expression in MSC and its effect on SDF-1 secretion and migration of leukemic cells under hypoxic conditions. To this end, we generated primary human BM MSC stably transduced with lentiviral-encoded shRNA against HIF1A. SDF-1α transcription levels measured by qRT-PCR were diminished (∼30%, p<0.01) in HIF1A-silenced MSCs compared to control MSCs expressing non-silencing shRNA. This correlated with significantly reduced transwell migration of OCI-AML3 cells towards HIF1A-silenced MSCs compared with control (non-silencing) MSCs (∼35%, p<0.05) under hypoxic conditions. We next examined the contribution of hypoxia and HIF1A in the protective role of the BM microenvironment against standard chemotherapy with AraC and Doxorubicin. To this end, we performed in vitro experiments co culturing OCI-AML3 cells with either HIF1A-silenced MSCs or control MSCs under hypoxic conditions. After 48h of drug treatment a significant decrease in chemotherapy-induced apoptosis in leukemic cells co-cultured with control MSCs compared to leukemic cells cultured alone was observed. In turn, chemoresistance was reduced in OCI-AML3 co-cultured with HIF1A-silenced MSC, suggesting that hypoxia mediates chemoresistance largely through its effects on cells of the BM microenvironment. It has been shown that leukemic cells seem to exhibit increased dependency on glycolysis for ATP generation, which is frequently associated with resistance to therapeutic agents. Therefore, we measured the production of lactic acid (LA) in leukemic cells co-cultured with MSC in hypoxia compared to normoxia. In agreement with previous observations, we found that REH and primary ALL cells produced more LA when they were co-cultured with MSC under hypoxia compared to normoxia (∼1.8 fold, p<0.05). When REH cells were co-cultured with HIF1A-silenced MSCs in hypoxic conditions the lactic acid production was slightly but significantly reduced (∼20%, p<0.05) compared with the values observed in REH-control MSCs co-culture supernatants. Altogether, these findings strongly point to hypoxia and HIF1A as pivotal components in the protection from chemotherapy mediated by the BM microenvironment. We propose that targeting HIF1A and hypoxia in the protective cells of the bone marrow niches may represent a new approach to increase chemosensitivity of leukemic cells and hopefully improve the existing therapeutic strategies. Table 1: Fold increase observed in leukemic cells-MSC co-culture supernatants in hypoxia compared to normoxia. OCI-AML3+MSC NALM6+MSC IL-6 ∼3.1 ∼1.2 VEGF ∼3 ∼2 B-NGF ∼8 ∼10 SDF-1 ∼1.5 ∼1.5 Disclosure: No relevant conflicts of interest to declare.

scholarly journals Inhibition of Mitochondrial Complex III in Candida Albicans ADH1 Deletion Mutant Attenuates Its Pathogenicity Significantly

2021 ◽  
Author(s):  
Hui Guo ◽  
Yi Shan Zhang ◽  
Yan Jun Song ◽  
Ya Jing Zhao ◽  
Shui Xiu Li ◽  
...  
Keyword(s):  
Mitochondrial Function ◽  
Alternative Oxidase ◽  
Oxidase Inhibitor ◽  
Complex Iii ◽  
Ros Production ◽  
Mitochondrial Complex ◽  
Aerobic Growth ◽  
Transport Chain ◽  
Atp Generation

Abstract Fermentation and aerobic respiration in mitochondria are coordinately regulated and compensated either when C. albicans grows in vitro or in the hosts, and the creature gain the strong viability. It’s insufficient to influent the growth, reproduction and pathogenicity of C. albicans by inhibiting the electron transport chain (ECT) CI, CII, CIII, CV, or fermentation related gene ADH1. Our study showed that the induction of AA (inhibitor of complex III) rather than SHAM (alternative oxidase inhibitor) abolishes the mitochondrial function completely （96% less ATP generation, 59% reduction in MMP), and increases ROS production significantly in ADH1-deleted mutant ( adh1Δ/ adh1Δ ) that in turn becomes hypersensitive to azole and apoptosis, less viable and more difficult to form hyphae. At the same time, the expression of virulence related genes ALS3 and HWP1 were significantly lower than that of WT under AA induction. Under the induction of AA, the mitochondrial function of WT was slightly damaged and cell apoptosis increased slightly，ROS production and sensitivity of azoles increased significantly, but mycelium formation and the growth of cells were not affected. Under aerobic growth, we observed an ADH1 - dependent mitochondrial effect in C. albicans demonstrated by 64% less ATP generation, 58% reduction in MMP and significant elevations of the ROS and apoptosis in ADH1 -deleted mutant. However, mycelium formation and azole susceptibility are not affected. Our results suggested that ADH1 plus CIII played an important role in antifungal activity by damaging mitochondrial function, inhibiting cell growth and hyphae formation, promoting apoptosis and reducing pathogenicity.

scholarly journals Mitochondrial Calcium Regulation of Redox Signaling in Cancer

Cells ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 432 ◽  
Author(s):  
Céline Delierneux ◽  
Sana Kouba ◽  
Santhanam Shanmughapriya ◽  
Marie Potier-Cartereau ◽  
Mohamed Trebak ◽  
...  
Keyword(s):  
Metabolic Flux ◽  
Cellular Proliferation ◽  
Atp Synthesis ◽  
Redox Signaling ◽  
Mitochondrial Enzymes ◽  
Cellular Processes ◽  
Transport Chain ◽  
Atp Generation ◽  
And Function ◽  
Ca2 Channels

Calcium (Ca2+) uptake into the mitochondria shapes cellular Ca2+ signals and acts as a key effector for ATP generation. In addition, mitochondria-derived reactive oxygen species (mROS), produced as a consequence of ATP synthesis at the electron transport chain (ETC), modulate cellular signaling pathways that contribute to many cellular processes. Cancer cells modulate mitochondrial Ca2+ ([Ca2+]m) homeostasis by altering the expression and function of mitochondrial Ca2+ channels and transporters required for the uptake and extrusion of mitochondrial Ca2+. Regulated elevations in [Ca2+]m are required for the activity of several mitochondrial enzymes, and this in turn regulates metabolic flux, mitochondrial ETC function and mROS generation. Alterations in both [Ca2+]m and mROS are hallmarks of many tumors, and elevated mROS is a known driver of pro-tumorigenic redox signaling, resulting in the activation of pathways implicated in cellular proliferation, metabolic alterations and stress-adaptations. In this review, we highlight recent studies that demonstrate the interplay between [Ca2+]m and mROS signaling in cancer.

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