Is absence of pyruvate dehydrogenase complex in mitochondria a possible explanation of significant aerobic glycolysis by normal human leukocytes
TL;DR: The oxygen consumption of leukocyte mitochondria of both healthy donors and leukemic patients was tested by using different respiratory substrates and results indicate that pyruvate could not be utilized by mitochondrias of normal leukocytes, whereas mitochondrians of leukeMic leuk cells could use pyruVate as a good respiratory substrate.
Abstract: The oxygen consumption of leukocyte mitochondria of both healthy donors and leukemic patients was tested by using different respiratory substrates. The results indicate that pyruvate could not be utilized by mitochondria of normal leukocytes, whereas mitochondria of leukemic leukocytes could use pyruvate as a good respiratory substrate. A search for the possible presence of pyruvate dehydrogenase complex (PDC) in leukocytes indicates that this enzyme is apparently absent in mitochondria of normal leukocytes but is quite active in mitochondria of leukemic leukocytes. The absence of PDC in normal leukocyte mitochondria can explain the phenomenon of significant aerobic glycolysis that has been observed in normal leukocytes.
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TL;DR: A marked upregulation of mitochondrial fission protein dynamin-related protein 1 (Drp1) expression is found in human invasive breast carcinoma and metastases to lymph nodes and treatment with a mitochondrial uncoupling agent or adenosine triphosphate synthesis inhibitor reduced lamellipodia formation and decreased breast cancer cell migration and invasion.
Abstract: Mitochondria are highly dynamic and undergo constant fusion and fission that are essential for maintaining physiological functions of cells. Although dysfunction of mitochondria has been implicated in tumorigenesis, little is known about the roles of mitochondrial dynamics in metastasis, the major cause of cancer death. In the present study, we found a marked upregulation of mitochondrial fission protein dynamin-related protein 1 (Drp1) expression in human invasive breast carcinoma and metastases to lymph nodes. Compared with non-metastatic breast cancer cells, mitochondria also were more fragmented in metastatic breast cancer cells that express higher levels of total and active Drp1 and less mitochondrial fusion protein 1 (Mfn1). Silencing Drp1 or overexpression of Mfn1 resulted in mitochondria elongation or clusters, respectively, and significantly suppressed metastatic abilities of breast cancer cells. In contrast, silencing Mfn proteins led to mitochondrial fragmentation and enhanced metastatic abilities of breast cancer cells. Interestingly, these manipulations of mitochondrial dynamics altered the subcellular distribution of mitochondria in breast cancer cells. For example, silencing Drp1 or overexpression of Mfn1 inhibited lamellipodia formation, a key step for cancer metastasis, and suppressed chemoattractant-induced recruitment of mitochondria to lamellipodial regions. Conversely, silencing Mfn proteins resulted in more cell spreading and lamellipodia formation, causing accumulation of more mitochondria in lamellipodia regions. More importantly, treatment with a mitochondrial uncoupling agent or adenosine triphosphate synthesis inhibitor reduced lamellipodia formation and decreased breast cancer cell migration and invasion, suggesting a functional importance of mitochondria in breast cancer metastasis. Together, our findings show a new role and mechanism for regulation of cancer cell migration and invasion by mitochondrial dynamics. Thus targeting dysregulated Drp1-dependent mitochondrial fission may provide a novel strategy for suppressing breast cancer metastasis.
543 citations
TL;DR: Accumulated lactate appears to convey the impression of "metabolic need" for vascularization, even in well-oxygenated and pH-neutral conditions.
Abstract: Hypoxia serves as a physiological cue to drive angiogenic response via HIF-dependent mechanisms. Interestingly, minor elevation of lactate levels in the tissue produces the same effect under aerobic conditions. Aerobic glycolysis contributes to lactate accumulation in the presence of oxygen especially under inflammatory conditions. We have previously postulated that aerobic lactate accumulation, already known to stimulate collagen deposition, will also stimulate angiogenesis. If substantiated, this concept would advance understanding of wound healing and aerobic angiogenesis because lactate accumulation has many aerobic sources. In this study, Matrigel® plugs containing a powdered, hydrolysable lactate polymer were implanted into the subcutaneous space of mice. Lactate monomer concentrations in the implant were consistent with wound levels for over 11 days. They induced little inflammation but considerable VEGF production and were highly angiogenic as opposed to controls. Arterial hypoxia abrogated angiogenesis. Furthermore, inhibition of lactate dehydrogenase using oxamate also prevented the angiogenic effects of lactate. Lactate monomer, at concentrations found in cutaneous wounds, stabilized HIF-1α and increased VEGF levels in aerobically cultured human endothelial cells. Accumulated lactate, therefore, appears to convey the impression of “metabolic need” for vascularization even in well-oxygenated and pH-neutral conditions. Lactate and oxygen both stimulate angiogenesis and matrix deposition.
219 citations
TL;DR: The host response to injury is usually appropriate in degree and is self-limited, but in more severe injury, the host response may persist inappropriately, leading to SIRS and MODS and possibly multiple organ failure.
Abstract: The host response to injury is usually appropriate in degree and is self-limited. In more severe injury, the host response may persist inappropriately, leading to SIRS and MODS and possibly multiple organ failure. The initial response to injury is mediated primarily by norepinephrine, and is directed toward preservation of circulation to the heart and brain at the expense of other vascular beds. If fluid resuscitation is adequate and necrotic tissue is debrided, a hypermetabolic state ensues, mediated by epinephrine and directed toward supporting repair of injured tissue by leukocytes. Inflammatory cells are recruited to the site of injury and elaborate cytokines, which promote repair locally, but in severe injury may be systemically released and trigger remote inflammation. Cytokine biology presently is poorly understood, and simple anticytokine strategies have failed to improve survival of critically ill patients. Current therapy of SIRS and MODS is directed toward symptoms. Presently, it is unclear how an abnormal stress response arises. Cytokine spillover into the systemic circulation may occur. Selective transcriptional failure may be the cellular basis of organ dysfunction. Inappropriate production of peroxynitrite or its precursor, NO, is implicated in mediating cellular injury in SIRS and MODS.
124 citations
TL;DR: An alternative perspective of the stages of wound healing eases recognition of the multiple sites where oxidative stress has an impact on wound healing and aids the focus on mechanistic events and the interplay among various cell types and biochemical processes.
Abstract: Significance: Oxidative stress is recognized as playing a role in stem cell mobilization from peripheral sites and also cell function. Recent Advances: This review focuses on the impact of hyperoxia on vasculogenic stem cells and elements of wound healing. Critical Issues: Components of the wound-healing process in which oxidative stress has a positive impact on the various cells involved in wound healing are highlighted. A slightly different view of wound-healing physiology is adopted by departing from the often used notion of sequential stages: hemostatic, inflammatory, proliferative, and remodeling and instead organizes the cascade of wound healing as overlapping events or waves pertaining to reactive oxygen species, lactate, and nitric oxide. This was done because hyperoxia has effects of a number of cell signaling events that converge to influence cell recruitment/chemotaxis and gene regulation/protein synthesis responses which mediate wound healing. Future Directions: Our alternative perspe...
70 citations
Cites background from "Is absence of pyruvate dehydrogenas..."
...Wound margin lactate concentrations remain elevated, however, because of endothelial cells and recruited leukocytes that preferentially rely on glycolysis, even in an aerobic environment (18, 51, 122)....
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TL;DR: It is reported that lactate accumulation commonly occurs in the presence of oxygen and is sufficient to instigate signals for angiogenesis and connective tissue deposition and these include vascular endothelial growth factor (VEGF), transforming growth factor beta (TGF beta), interleukin-1 (IL-1), and hypoxia-inducible factor (hif-1alpha).
Abstract: Lactate has been reconsidered! As we now know, most is produced aerobically We report that lactate accumulation commonly occurs in the presence of oxygen and is sufficient to instigate signals for angiogenesis and connective tissue deposition. These include vascular endothelial growth factor (VEGF), transforming growth factor beta (TGF beta), interleukin-1 (IL-1), and hypoxia-inducible factor (hif-1alpha). This paper, a mini-review, is occasioned by new data showing increased presence of VEGF and angiogenesis in an oxygenated site by adding a slow-release source of lactate into Matrigel® and implanting the Matrigel subcutaneously in mice.
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TL;DR: Procedures are described for measuring protein in solution or after precipitation with acids or other agents, and for the determination of as little as 0.2 gamma of protein.
Abstract: Since 1922 when Wu proposed the use of the Folin phenol reagent for the measurement of proteins, a number of modified analytical procedures utilizing this reagent have been reported for the determination of proteins in serum, in antigen-antibody precipitates, and in insulin. Although the reagent would seem to be recommended by its great sensitivity and the simplicity of procedure possible with its use, it has not found great favor for general biochemical purposes. In the belief that this reagent, nevertheless, has considerable merit for certain application, but that its peculiarities and limitations need to be understood for its fullest exploitation, it has been studied with regard to effects of variations in pH, time of reaction, and concentration of reactants, permissible levels of reagents commonly used in handling proteins, and interfering substances. Procedures are described for measuring protein in solution or after precipitation with acids or other agents, and for the determination of as little as 0.2 gamma of protein.
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TL;DR: It is concluded that insulin accelerates a step in the span pyruvate-->fatty acid as well as the control of fatty acid synthesis in adipose tissue and the role of cyclic AMP in mediating the effects of insulin on pyruVate dehydrogenase.
Abstract: 1 In epididymal adipose tissue synthesizing fatty acids from fructose in vitro, addition of insulin led to a moderate increase in fructose uptake, to a considerable increase in the flow of fructose carbon atoms to fatty acid, to a decrease in the steady-state concentration of lactate and pyruvate in the medium, and to net uptake of lactate and pyruvate from the medium It is concluded that insulin accelerates a step in the span pyruvate→fatty acid 2 Mitochondria prepared from fat-cells exposed to insulin put out more citrate than non-insulin-treated controls under conditions where the oxaloacetate moiety of citrate was formed from pyruvate by pyruvate carboxylase and under conditions where it was formed from malate This suggested that insulin treatment of fat-cells led to persistent activation of pyruvate dehydrogenase 3 Insulin treatment of epididymal fat-pads in vitro increased the activity of pyruvate dehydrogenase measured in extracts of the tissue even in the absence of added substrate; the activities of pyruvate carboxylase, citrate synthase, glutamate dehydrogenase, acetyl-CoA carboxylase, NADP–malate dehydrogenase and NAD–malate dehydrogenase were not changed by insulin 4 The effect of insulin on pyruvate dehydrogenase activity was inhibited by adrenaline, adrenocorticotrophic hormone and dibutyryl cyclic AMP (6-N,2′-O-dibutyryladenosine 3′:5′-cyclic monophosphate) The effect of insulin was not reproduced by prostaglandin E1, which like insulin may lower the tissue concentration of cyclic AMP (adenosine 3′:5′-cyclic monophosphate) and inhibit lipolysis 5 Adipose tissue pyruvate dehydrogenase in extracts of mitochondria is almost totally inactivated by incubation with ATP and can then be reactivated by incubation with 10mm-Mg2+ In this respect its properties are similar to that of pyruvate dehydrogenase from heart and kidney where evidence has been given that inactivation and activation are catalysed by an ATP-dependent kinase and a Mg2+-dependent phosphatase Evidence is given that insulin may act by increasing the proportion of active (dephosphorylated) pyruvate dehydrogenase 6 Cyclic AMP could not be shown to influence the activity of pyruvate dehydrogenase in mitochondria under various conditions of incubation 7 These results are discussed in relation to the control of fatty acid synthesis in adipose tissue and the role of cyclic AMP in mediating the effects of insulin on pyruvate dehydrogenase
330 citations
TL;DR: These and other regulatory aberrations in tumor cells appear to be reflections of a complex set of non-random phenotypic changes, initiated by expression of oncogenes.
Abstract: The central glycolytic and oxidative pathways and the ATP-producing mechanisms differ in sane and malignant cells by their regulation and dynamics. Fast-growing, poorly-differentiated cancer cells characteristically show high aerobic glycolysis. In the same way, cholesterol biosynthesis, which occurs by normal pathways in tumors, is deficient in feed-back regulation and in sterol-transport mechanisms. Other metabolic ways are deficient, as for example, intramitochondrial aldehyde catabolism, at the origin of a possible acetaldehyde toxicity, which can be circumvented by the synthesis of an unusual and neutral product for mammalian cells acetoin, through tumoral pyruvate dehydrogenase. If most of the glycolytic pyruvate is deviated to lactate production, little of the remaining carbons enter a truncated Krebs cycle where citrate is preferentially extruded to the cytosol where it feeds sterol synthesis. Glutamine is the major oxidizable substrate by tumor cells. Inside the mitochondrion, it is deaminated to glutamate through a phosphate-dependent glutaminase. Glutamate is then preferentially transaminated to alpha-ketoglutarate that enters the Krebs cycle. Glutamine may be completely oxidized through the abnormal Krebs cycle only if a way of forming acetyl CoA is present: cytosolic malate entering mitochondria is preferentially oxidized to pyruvate + CO2 through an intramitochondrial NAD(P)(+)-malic enzyme, whereas intramitochondrial malate is preferentially oxidized to oxaloacetate through malate dehydrogenase, thus providing a high level of intramitochondrial substrate compartmentation. These and other regulatory aberrations in tumor cells appear to be reflections of a complex set of non-random phenotypic changes, initiated by expression of oncogenes.
284 citations