scholarly journals (+)-Catechin inhibits heart mitochondrial complex I and nitric oxide synthase: functional consequences on membrane potential and hydrogen peroxide production

2019 ◽  
Vol 10 (5) ◽  
pp. 2528-2537 ◽  
Author(s):  
Darío E. Iglesias ◽  
Silvina S. Bombicino ◽  
Alberto Boveris ◽  
Laura B. Valdez
Keyword(s):  
Nitric Oxide ◽  
Hydrogen Peroxide ◽  
Membrane Potential ◽  
Complex I ◽  
Mitochondrial Complex I ◽  
Mitochondrial Complex ◽  
Hydrogen Peroxide Production ◽  
Functional Consequences ◽  
Oxide Synthase

The aim was to study thein vitroeffect of nM to low μM concentration of (+)-catechin on the enzymatic activities of mitochondrial complex I and mtNOS, as well as the consequences on the membrane potential and H2O2production rate.

scholarly journals Hypothyroid Phenotype Is Contributed by Mitochondrial Complex I Inactivation Due to Translocated Neuronal Nitric-oxide Synthase

2005 ◽  
Vol 281 (8) ◽  
pp. 4779-4786 ◽  
Author(s):  
María C. Franco ◽  
Valeria G. Antico Arciuch ◽  
Jorge G. Peralta ◽  
Soledad Galli ◽  
Damián Levisman ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Nitric Oxide Synthase ◽  
Complex I ◽  
Neuronal Nitric Oxide Synthase ◽  
Mitochondrial Complex I ◽  
Mitochondrial Complex ◽  
Oxide Synthase

Abstract 404: High-throughput Screening Reveals the Mitochondrial Complex I Inhibitor Nornicotine is Cardioprotective in Ischemia-reperfusion Injury When Delivered at Reperfusion

2015 ◽  
Vol 117 (suppl_1) ◽  
Author(s):  
Jimmy Zhang ◽  
Marcin K Karcz ◽  
Sergiy M Nadtochiy ◽  
Paul S Brookes
Keyword(s):  
Infarct Size ◽  
Reperfusion Injury ◽  
Functional Recovery ◽  
Complex I ◽  
Ischemia Reperfusion ◽  
Mitochondrial Complex I ◽  
Mitochondrial Complex ◽  
Early Reperfusion ◽  
Perfused Hearts

Background: To date, there are no FDA-approved therapies for the reduction of infarct size in acute myocardial infarction. Previously, we developed a cell-based phenotypic assay of ischemia-reperfusion (IR) injury, which was used to identify novel cytoprotective agents delivered prior to ischemia. Herein, we sought to identify cytoprotective agents in a more clinically relevant model: drug delivery at reperfusion, and to investigate possible underlying mechanisms of protection. Methods: Primary adult mouse cardiomyocytes were subjected to simulated IR injury using a modified Seahorse XF24 apparatus with drug addition at the onset of reperfusion. Cell death was estimated using LDH release. Drugs which protected cardiomyocytes in vitro were tested in a Langendorff model of IR injury, measuring functional recovery and infarct size. In separate experiments, metabolites extracted from perfused hearts were resolved by HPLC. Results: Nornicotine was identified as a cardioprotective agent in the screen. In perfused hearts, 10 nM nornicotine injected at the onset of reperfusion improved functional recovery and decreased in infarct size (13.1% ± 2.4 vs 49.2% ± 2.5 in non-treated hearts, p<0.05, n=16-20). Nornicotine also exhibited profound inhibitory effects on mitochondrial complex I activity. Succinate is known to accumulate in ischemia, and its rapid consumption during early reperfusion exacerbates reperfusion injury via ROS generation from electron backflow through complex I [PMID: 25383517]. In non-treated hearts, we confirmed that high post ischemic levels of succinate rapidly declined during the first 2 min of reperfusion. In contrast, nornicotine slowed post-ischemic succinate consumption, suggesting that electron backflow through complex I is the major pathway driving succinate consumption. Conclusions: Herein, we demonstrated that nornicotine was cardioprotective when delivered at early reperfusion in vitro and ex vivo. The mechanism of cardioprotection may be due to inhibition of rapid succinate consumption during early reperfusion via reverse electron flow back through complex I.

scholarly journals The specificity of mitochondrial complex I for ubiquinones

1996 ◽  
Vol 313 (1) ◽  
pp. 327-334 ◽  
Author(s):  
Mauro ESPOSTI DEGLI ◽  
Anna NGO ◽  
Gabrielle L. McMULLEN ◽  
Anna GHELLI ◽  
Francesca SPARLA ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Electron Transport ◽  
Complex I ◽  
Reductase Activity ◽  
Redox Activity ◽  
Mitochondrial Complex I ◽  
Transport Activity ◽  
Mitochondrial Complex ◽  
Potential Generation ◽  
Electron Transport Activity

We report the first detailed study on the ubiquinone (coenzyme Q; abbreviated to Q) analogue specificity of mitochondrial complex I, NADH:Q reductase, in intact submitochondrial particles. The enzymic function of complex I has been investigated using a series of analogues of Q as electron acceptor substrates for both electron transport activity and the associated generation of membrane potential. Q analogues with a saturated substituent of one to three carbons at position 6 of the 2,3-dimethoxy-5-methyl-1,4-benzoquinone ring have the fastest rates of electron transport activity, and analogues with a substituent of seven to nine carbon atoms have the highest values of association constant derived from NADH:Q reductase activity. The rate of NADH:Q reductase activity is potently but incompletely inhibited by rotenone, and the residual rotenone-insensitive rate is stimulated by Q analogues in different ways depending on the hydrophobicity of their substituent. Membrane potential measurements have been undertaken to evaluate the energetic efficiency of complex I with various Q analogues. Only hydrophobic analogues such as nonyl-Q or undecyl-Q show an efficiency of membrane potential generation equivalent to that of endogenous Q. The less hydrophobic analogues as well as the isoprenoid analogue Q-2 are more efficient as substrates for the redox activity of complex I than for membrane potential generation. Thus the hydrophilic Q analogues act also as electron sinks and interact incompletely with the physiological Q site in complex I that pumps protons and generates membrane potential.

scholarly journals Molecular mechanism and physiological role of active–deactive transition of mitochondrial complex I

2013 ◽  
Vol 41 (5) ◽  
pp. 1325-1330 ◽  
Author(s):  
Marion Babot ◽  
Alexander Galkin
Keyword(s):  
Complex I ◽  
Physiological Role ◽  
Protective Mechanism ◽  
Mitochondrial Complex I ◽  
Mitochondrial Complex ◽  
The Status ◽  
Nitric Oxide Metabolites

The unique feature of mitochondrial complex I is the so-called A/D transition (active–deactive transition). The A-form catalyses rapid oxidation of NADH by ubiquinone (k ~104 min−1) and spontaneously converts into the D-form if the enzyme is idle at physiological temperatures. Such deactivation occurs in vitro in the absence of substrates or in vivo during ischaemia, when the ubiquinone pool is reduced. The D-form can undergo reactivation given both NADH and ubiquinone availability during slow (k ~1–10 min−1) catalytic turnover(s). We examined known conformational differences between the two forms and suggested a mechanism exerting A/D transition of the enzyme. In addition, we discuss the physiological role of maintaining the enzyme in the D-form during the ischaemic period. Accumulation of the D-form of the enzyme would prevent reverse electron transfer from ubiquinol to FMN which could lead to superoxide anion generation. Deactivation would also decrease the initial burst of respiration after oxygen reintroduction. Therefore the A/D transition could be an intrinsic protective mechanism for lessening oxidative damage during the early phase of reoxygenation. Exposure of Cys39 of mitochondrially encoded subunit ND3 makes the D-form susceptible for modification by reactive oxygen species and nitric oxide metabolites which arrests the reactivation of the D-form and inhibits the enzyme. The nature of thiol modification defines deactivation reversibility, the reactivation timescale, the status of mitochondrial bioenergetics and therefore the degree of recovery of the ischaemic tissues after reoxygenation.

scholarly journals Novel Nanomolar Potency Mitochondrial Complex I Inhibitor Iacs-1131 Selectively Kills Oxphos-Dependent AML Cells

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 622-622
Author(s):  
Polina Matre ◽  
Marina Protopopova ◽  
Ningping Feng ◽  
Jason Gay ◽  
Jennifer Greer ◽  
...  
Keyword(s):  
Cell Lines ◽  
Complex I ◽  
Bioluminescence Imaging ◽  
Luciferase Activity ◽  
Xenograft Model ◽  
Mitochondrial Complex I ◽  
Mitochondrial Complex ◽  
Oral Gavage ◽  
Nsg Mice

Abstract Recent studies indicate that acute myeloid leukemia (AML) cells, including leukemia-initiating cells, are highly dependent on oxidative phosphorylation (OXPHOS) for survival, while normal hematopoietic stem cells predominantly utilize glycolysis for energy homeostasis. We have reported development of a series of novel, highly potent mitochondrial complex I inhibitors, which in vitro inhibit complex I with IC50 values <10 nM (Marszalek et al., AACR 2014 Abstract #949). These inhibitors offer excellent therapeutic potential in the OXPHOS-dependent cancer models. IACS-1131 was selected as a preclinical tool compound from the series of more than 800 compounds across distinct structural classes. Here, we report the in vitro and in vivo efficacy of IACS-1131 in AML models. Analysis of a panel of AML cell lines showed that a subset of leukemias are markedly dependent on OXPHOS for growth and survival; in this subset, IACS-1131 treatment caused steep decreases in viable cell number via induction of apoptosis. In sensitive cell lines (HL-60, OCI-AML3, KG-1, MV4;11, Kasumi-1), IACS-1131 induced pronounced apoptosis with EC50 between 10 and 100nM, consistent with the IC50 required to inhibit OXPHOS. MOLM13 and OCI-AML2 cells were less sensitive (EC50 250nM and 120nM, and a failure to induce cell death). In primary AML samples from patients with newly diagnosed or relapsed/refractory AML (n=12), the average EC50 for IACS-1131 was 14 ± 8nM in 9 samples, and exceeded 100nM in 3 samples. Consistent with the findings in AML cell lines, 10nM IACS-1131 resulted in partial responses, and 100-250nM resulted in profound loss of viability due to apoptosis induction. In contrast, this treatment caused only a moderate decrease in CD34+ cell numbers and <10% increase in apoptosis in 6 normal bone marrow samples. The effects of IACS-1131 on the two major energy-generating pathways, mitochondrial OXPHOS and glycolysis, were investigated using the Seahorse Bioscience XF96 Analyzer. Treatment for 16 hrs caused a striking dose-dependent decrease in basal oxygen consumption rates (OCR), indicating OXPHOS inhibition; reduced ATP production; and decreased maximal respiratory capacity in OCI-AML3 cells and in primary AML blasts (n=9). We confirmed inhibition of complex I in AML cells using Seahorse mitochondrial electron flow assay. These changes preceded changes in viability or apoptotic markers; as such, loss of the mitochondrial membrane potential, annexin V positivity, and induction of mitochondrial reactive oxygen species were seen only at 72 hrs of exposure. Further time-course analysis demonstrated that 2 hrs of IACS-1131 exposure caused significant inhibition of OCR in both sensitive OCI-AML3 and resistant MOLM13 cells, but in MOLM13 cells there was a greater increase in extracellular acidification rates, suggesting compensation by glycolysis. In turn, inhibition of glycolysis with 2-DG, or blockade of pyruvate dehydrogenase kinase with dicholoroacetate (which forces entry into the TCA cycle) sensitized resistant cells to IACS-1131. The intracellular metabolome (polar fraction) of OCI-AML3 cells was characterized following 2, 4, 12 and 24 hrs of treatment with 100nm IACS-1131 using high-resolution magnetic resonance spectroscopy and high mass accuracy Orbitrap mass spectrometry. IACS-1131 modulated levels of the TCA intermediates, producing increased accumulation of citrate and fumarate and decreased succinate and malate, and increased glutathione, possibly because of the oxidative stress. Furthermore, the metabolic analysis indicated a strong effect on amino acid metabolism, whereby IACS-1131 reduced (between 25% and 62% of control) multiple anaplerotic amino acids (including arginine, leucine, isoleucine, valine, phenylalanine, asparagine, histidine, and glutamine, but not aspartate). Finally, IACS-1131 at 60 mg/kg QD po demonstrated robust anti-leukemia activity in an orthotopic OCI-AML3 model. At this dose, IACS-1131 was well tolerated for >50 days and increased median survival duration by more than 5 times (Fig. 1). Studies exploring the anti-AML efficacy of single-agent IACS-1131 in primary AML xenografts are ongoing. Taken together, these data strongly indicate that OXPHOS inhibition constitutes a novel therapeutic approach that targets a unique metabolic vulnerability of AML cells and indicate that further preclinical evaluation of OXPHOS inhibitors is warranted. Figure 1 Figure 1. Figure 1 Treatment with IACS-1131 prolongs survival in a OCI-AML3 xenograft model. Luciferase-expressing OCI-AML3 cells were injected in the tail vein of NSG mice. On day 16 after injection, engraftment was confirmed and mice were randomized on the basis of IVIS-based imaging of luciferase activity after luciferin injection. For the next 58 days, mice received either vehicle or 60 mg/kg/day of IACS-1131 via oral gavage. Mice were sacrificed when body weight was reduced by >20% or for signs of morbidity. Right, bioluminescence imaging before (D0) and 10 days after 1 st dose; left survival. Figure 1. Treatment with IACS-1131 prolongs survival in a OCI-AML3 xenograft model. Luciferase-expressing OCI-AML3 cells were injected in the tail vein of NSG mice. On day 16 after injection, engraftment was confirmed and mice were randomized on the basis of IVIS-based imaging of luciferase activity after luciferin injection. For the next 58 days, mice received either vehicle or 60 mg/kg/day of IACS-1131 via oral gavage. Mice were sacrificed when body weight was reduced by >20% or for signs of morbidity. Right, bioluminescence imaging before (D0) and 10 days after 1 st dose; left survival. Disclosures No relevant conflicts of interest to declare.

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