Ubisemiquinone is the electron donor for superoxide formation by complex III of heart mitochondria

Turrens, Julio F.; Alexandre, Adolfo; Lehninger, Albert L.

doi:10.1016/0003-9861(85)90293-0

Cited by 1,132 publications

(717 citation statements)

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“…Antimycin A is a mitochondrial complex III inhibitor that stimulates superoxide production [40,41] and mimics the effects of maternal diabetes on Pax3 expression and NTD [39,47]. As shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Briefly, transient hyperglycaemia was induced by injecting 2 ml of 12.5% glucose-PBS solution subcutaneously approximately every 1-2 h between 09.00 and 17.00 h. Blood glucose concentrations were checked hourly, and animals were re-injected as needed to maintain the blood glucose concentration ≥300 mg/dl (16.65 mmol/l). Oxidative stress was induced with a single injection of 3 mg/kg antimycin A (Sigma Chemicals), a mitochondrial complex III inhibitor [40,41], dissolved in 25% (v/v) propylene glycol. Control mice were injected with PBS or propylene glycol.…”

Section: Methodsmentioning

confidence: 99%

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Expression of the gene encoding the high-K m glucose transporter 2 by the early postimplantation mouse embryo is essential for neural tube defects associated with diabetic embryopathy

Thorens

Loeken

2007

Diabetologia

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Aims/hypothesis Excess glucose transport to embryos during diabetic pregnancy causes congenital malformations. The early postimplantation embryo expresses the gene encoding the high-K m GLUT2 (also known as SLC2A2) glucose transporter. The hypothesis tested here is that high-K m glucose transport by GLUT2 causes malformations resulting from maternal hyperglycaemia during diabetic pregnancy. Materials and methods Glut2 mRNA was assayed by RT-PCR. The K m of embryo glucose transport was determined by measuring 0.5-20 mmol/l 2-deoxy[ 3 H]glucose transport. To test whether the GLUT2 transporter is required for neural tube defects resulting from maternal hyperglycaemia, Glut2 +/− mice were crossed and transient hyperglycaemia was induced by glucose injection on day 7.5 of pregnancy. Embryos were recovered on day 10.5, and the incidence of neural tube defects in wild-type, Glut2 +/− and Glut2 −/− embryos was scored. Results Early postimplantation embryos expressed Glut2, and expression was unaffected by maternal diabetes. Moreover, glucose transport by these embryos showed Michaelis-Menten kinetics of 16.19 mmol/l, consistent with transport mediated by GLUT2. In pregnancies made hyperglycaemic on day 7.5, neural tube defects were significantly increased in wild-type embryos, but Glut2 +/− embryos were partially protected from neural tube defects, and Glut2 −/− embryos were completely protected from these defects. The frequency of occurrence of wild-type, Glut2 +/− and Glut2 −/− embryos suggests that the presence of Glut2 alleles confers a survival advantage in embryos before day 10.5. Conclusions/interpretations High-K m glucose transport by the GLUT2 glucose transporter during organogenesis is responsible for the embryopathic effects of maternal diabetes.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Expression of the gene encoding the high-K m glucose transporter 2 by the early postimplantation mouse embryo is essential for neural tube defects associated with diabetic embryopathy

Thorens

Loeken

2007

Diabetologia

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“…There were no differences in consumption of control compared to supplemented chow (data not shown). To induce oxidative stress with antimycin A, a complex III electron transport inhibitor which increases mitochondrial production of superoxide and hydrogen peroxide [36,37] mice were injected s.c. once on gestational day 7.5 with 3 mg/kg body weight antimycin A (Sigma Chemicals) dissolved in 25% (v/v) propylene glycol. Control mice were injected with 25% (v/v) propylene glycol/saline, or 25% (w/v) glucose dissolved in saline at approximately hourly intervals to maintain blood glucose greater than or equal to 17 mmol/l over a 10-h period [25].…”

Section: Methodsmentioning

confidence: 99%

Oxidant regulation of gene expression and neural tube development: Insights gained from diabetic pregnancy on molecular causes of neural tube defects

et al. 2003

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Aims/hypothesis. Maternal diabetes increases oxidative stress in embryos. Maternal diabetes also inhibits expression of embryonic genes, most notably, Pax-3, which is required for neural tube closure. Here we tested the hypothesis that oxidative stress inhibits expression of Pax-3, thereby providing a molecular basis for neural tube defects induced by diabetic pregnancy. Methods. Maternal diabetes-induced oxidative stress was blocked with α-tocopherol (vitamin E), and oxidative stress was induced with the complex III electron transport inhibitor, antimycin A, using pregnant diabetic or non-diabetic mice, primary cultures of neurulating mouse embryo tissues, or differentiating P19 embryonal carcinoma cells. Pax-3 expression was assayed by quantitative RT-PCR, and neural tube defects were scored by visual inspection. Oxidation-induced DNA fragmentation in P19 cells was assayed by electrophoretic analysis.Results. Maternal diabetes inhibited Pax-3 expression and increased neural tube defects, and α-tocopherol blocked these effects. In addition, induction of oxidative stress with antimycin A inhibited Pax-3 expression and increased neural tube defects. In cultured embryo tissues, high glucose-inhibited Pax-3 expression, and this effect was blocked by α-tocopherol and GSHethyl ester, and Pax-3 expression was inhibited by culture with antimycin A. In differentiating P19 cells, antimycin A inhibited Pax-3 induction but did not induce DNA strand breaks. Conclusion/interpretation. Oxidative stress inhibits expression of Pax-3, a gene that is essential for neural tube closure. Impaired expression of essential developmental control genes could be the central mechanism by which neural tube defects occur during diabetic pregnancy, as well as other sources of oxidative stress. [Diabetologia (2003) 46:538-545]

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“…41,43,[47][48][49] Unlike complexes I and II, which generate superoxide into the mitochondrial matrix, [52][53][54][55] complex III can also release superoxide into the mitochondrial intermembrane space and subsequently, into the cytosol. [56][57][58] The Q cycle is initiated when complex I and complex II transfer electrons to reduce the lipid moiety ubiquinone to ubiquinol (Figure 3). Ubiquinol then enters the Q cycle (Figure 3).…”

Section: Regulation Of Hif Functionmentioning

confidence: 99%

Mitochondrial complex III regulates hypoxic activation of HIF

2008

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Decreases in oxygen levels are observed in physiological processes, such as development, and pathological situations, such as tumorigenesis and ischemia. In the complete absence of oxygen (anoxia), mammalian cells are unable to generate sufficient energy for survival, so a mechanism for sensing a decrease in the oxygen level (hypoxia) before it reaches a critical point is crucial for the survival of the organism. In response to decreased oxygen levels, cells activate the transcription factors hypoxiainducible factors (HIFs), which lead to metabolic adaptation to hypoxia, as well as to generate new vasculature to increase oxygen supply. How cells sense decreases in oxygen levels to regulate HIF activation has been hotly debated. Emerging evidence indicates that reactive oxygen species (ROS) generated by mitochondrial complex III are required for hypoxic activation of HIF. This review examines the current knowledge about the role of mitochondrial ROS in HIF activation, as well as implications of ROS-level regulation in pathological processes such as cancer. Oxygen Homeostasis and HIF Maintaining oxygen homeostasis is critical for survival and proper function of cells and organisms. 1 Reduced oxygen levels (hypoxia) initiates proper placental and vascular development. Hypoxia also has a causal role in pathological conditions such as ischemia-related diseases and cancer. A complete absence of oxygen (anoxia) results in cell death. 2 ATP synthesis is ablated, and most cells undergo apoptosis soon after anoxia exposure. 3-5 Cells exposed to hypoxia, or reduced oxygen levels, on the other hand, are able to maintain normal ATP synthesis and survive. 5,6 However, as cells replicate in a hypoxic environment, they reduce the oxygen supply even further and generate levels of local anoxia. Therefore, cells must respond quickly to decreasing oxygen levels before reaching an anoxic state (Figure 1).Mammalian cells respond to hypoxia by activating broadaction transcription factors named hypoxia-inducible factors, or HIFs, which are expressed by virtually all cells of the body. 7-9 Three members of the HIF family exist, named HIF1, HIF2 and HIF-3. 10-13 HIFs bind to hypoxia-responsive elements, consensus sequences in the promoter region of more than one hundred genes, activating the transcription of genes that allow the cell to adapt to and survive in the hypoxic environment. 14,15 Genes regulated by HIFs include glucose transporter that allow the cells to efficiently import glucose to continue generating ATP despite reduced nutrient availability; and genes that reorganize the microenvironment to bring in oxygen, such as vascular endothelial growth factor, which stimulates formation of new blood vessels. [16][17][18] Importantly for tumorigenesis, HIF also turns on genes such as insulin-like growth factor 2,19 which induces cellular survival and proliferation, as well as those that promote tumor invasion and migration, such as matrix metalloproteinase-2. 20 These factors contribute to tumor growth and invasion and metastasis, im...

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Ubisemiquinone is the electron donor for superoxide formation by complex III of heart mitochondria

Cited by 1,132 publications

References 23 publications

Expression of the gene encoding the high-K m glucose transporter 2 by the early postimplantation mouse embryo is essential for neural tube defects associated with diabetic embryopathy

Expression of the gene encoding the high-K m glucose transporter 2 by the early postimplantation mouse embryo is essential for neural tube defects associated with diabetic embryopathy

Oxidant regulation of gene expression and neural tube development: Insights gained from diabetic pregnancy on molecular causes of neural tube defects

Mitochondrial complex III regulates hypoxic activation of HIF

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