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Mitochondria QSARs Involving Chemical Effects
by Albert Leo Pomona College Medicinal Chemistry Project ( ) BioByte Corp. (1993-present)
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The Role of Mitochondria in Pharmacotoxicology
“The role of mitochondria in pharmacotoxicology: a reevaluation of an old, newly emerging topic” (R. Scatena, et al, Am. J. Physiol. Cell Physiol, 293, C12-C21, 2007) points out: Some antiviral nucleoside analogs display mitochondrial toxicity by inhibiting DNA polymerase-γ. The more hydrophobic NSAIDs act as UOP. Some mitochondrial toxicity of drugs depends upon free radical production.
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Mitochondria in QSAR 149 equations dealing with mitochondria
1290 unique chemical structures Available as a SMILES file on 26 equations containing 6-X-2,4-dinitro- phenols
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Beginnings of Cellular Life
In Beginnings of Cellular Life, Harold Morowitz (Yale University Press, 1992) says: “spontaneous formation of closed membrane vesicles was the initiating event in cellular evolution.” They maintain separate stable phases in an aqueous environment. They maintain different chemical compositions between intra- and extra- cellular compartments. They maintain substantial trans-bilayer electrical voltages, pH differences, and oxidation potentials.
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Precursors of Chloroplasts & Mitochondria
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Mitochondria Chloroplasts
The result of Intelligent Design, says Michael Behe (?)Are we intelligent enough to refrain from injuring them?
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Mitochondrial Function
Protonophore: weak acid and hydrophobic (log P > 4) Both ion and neutral forms in innter membrane.
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Di-Aryl Amines as Non-Classical Uncouplers
Fluazinam - anti-fungal Set 2447: log 1/C = 0.18 pKa – 1.57 bilin(pKa) log P’ ; n = 22; r2 = 0.96; OpKa = 6.96
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McGowan volume and/or CMR may help explain the difference.
‘Normal’ π Special’ π #Expls 2-Cl +0.72 -0.01 3 4-Cl -0.02 3-CF3 +0.90 +0.01 2-F +0.14 -0.07 1 2-Br +0.87 -0.24 2 3-CH3 +0.51 -0.31 4-OCF3 +1.00 -0.18 In most cases another (Y) group also present, and so 'buttressing" effect possible. McGowan volume and/or CMR may help explain the difference.
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Classical Uncouplers (Protonophores)
2,4-DNP, 6-t-Bu pKa 4.80; logP 3.55 Pentachlorophenol pKa 4.69; logP 5.12 Set 599: I-50 respiration, rat liver mitochondria Log 1/C = 1.73 CLOGP – 1.51 bilinCLOGP -0.51; n = 21; r2 = 0.89; OLP =~5.6
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Malonoben (SF-6847) insecticide Set 2257: 1/C = pKa P-F P-P NVE ; n = 39; r2 = 0.96
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Uncouplers in Treatment of Obesity
R = CH3 = BHT R = P+(Ph)3 = Mito-BHT (ant-obesity lead) 2,4-DNP (1930s) Binds to adenine nucleotide translocase Lowers membrane potential (ΔΨm)
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Fenfluramine N-Nitroso analog metabolism Mitochondrial toxicity: membrane swelling and release of Cyt-C.
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Pharmaceuticals with UOP action
Amiodarone - anti-arrhythmic Protonated logD ~ 5.0; inhibits complexes 1 & II Kebuzone - anti-rheumatic
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Complex I-II Inhibitors
Capsaicin Analogs Set 6878: log 1/C = 3.44 CLOGP – 0.28 (CLOGP)2 – n = 6; r2 = 0.98; OLP = 6.08
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Complex I-II Inhibitors
Rotenone & Annonacin Analogs Set 10754: Log 1/C = 0.14 CLOGP + 7.7; n = 5; r2 = 0.93
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Complex I-II Inhibitors
4,7-subs. Acridones Set 2373: Log 1/C = 0.74 CLOGP – 1.53 CLOGP2 – 1.36 σ ; n = 22; r2 = 0.90; OLP = 4.5
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2,3-alkyl-Quinolones Set 3876: log P = 0.73 CLOGP – BiLinCLOGP I-3Me ; n = 12; r2 = 0.96; OLP = 5.65 Set 3877: Log 1/C = 0.67 CLOGP – 0.93 BiLin CLOGP I-Me ; n = 13; r2 = 0.86; OLP = 5.6
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INHIBITORS OF COMPLEX II (Succinic Dehydrogenase)
Prototype: 3-nitropropionic acid (3-NP): O2N-CH2-CH2-CO2H A natural phytoalexin; present in loco weed (Astragalus); animal toxin. Human toxin in fungal-contaminated sugar cane (China) Used as neurotoxin model for Huntington's disease
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Complex II-III Inhibition
Set 611: inhibition of succinate dehydrogenase in cinerea botrytis mold Log 1/C = 0.58 CLOGP NVE – 0.219; n = 21; r2 = .88 Set 699: acting as fungicide on rice sheath blight Log 1/C = MgVol MgVol ; n = 24; r2 = 0.88; Opt.vol. = 1.9
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Complex II-III Inhibition
Set 1557: Benzanilides as fungicides inhibiting Complex II Log 1/C = 1.04 CLOGP – 1.7 Bilin CLOGP Es-X2 – B1-R σR ; n = 32; r2 = 0.89; OLP = 5.28
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Complex II-III Inhibition
Set 1720: Thiazole-anilides as fungicides Log 1/C = 0.64 CLOGP σ I 2, ; n = 42; r2 = 0.85 I2,6 shows that di-ortho substitution is especially strong
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Complex II-III Inhibition
Set 2425: Carboxins inhibiting Complex II of yeast pathogen c. laurentii Log 1/C = B1-4 – 0.72 σ – 1.32 I2, ; n = 14; r2 = 087 In this set, 2,6-disubstitution weakens inhibitory action.
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Complex IV Inhibition Set 1006: Inhibition of cytochrome-C from horse heart mitochondria by alkanols (including -diols) Log 1/C = 0.35 log P – 0.70; n = 7; r2 = 0.91 Set 1643: Inhibition of cytochrome-C by catechols (from same source) Log 1/C = σ ; n = 9; r2 = 0.97
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Complex IV Inhibition Set 3882: 4-quinolone analogs inhibiting bacterial cytochrome-C Log 1/C = 0.73 CLOGP – 0.83 bilinCLOGP n = 12; r2 = 0.95; OLP = 5.86 Set 4985: Very similar relationships with cytochrome-C from beef heart mitochondria Log 1/C = 0.86 CLOGP – 1.29 bilinCLOGP n = 21; r2 = 0.90; OLP = 6.35
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anilino-thiadiazoles
Inhibitors of mammary sarcomas Set 7095: C for maximal respiration release in rat liver mitochondria log 1/C = σ ; n = 5; r2 = 0.96 Set 7096: C for inhibition of ATP synthesis in rat liver mitochondria log 1/C = σ ; n = 6; r2 = 0.90
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Mitochondrial Function
Protonophore: weak acid and hydrophobic (log P > 4) Both ion and neutral forms in innter membrane.
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Chloroplast ATP Production
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Triazine inhibitors of Plastoquinone
Set 2252: Log 1/C = 0.61 log P bilinLogP WRB-X D-Y T1-Y -2.8 I-Me ; n = 47; r2 = 0.89; OLP = 4.5
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Plastoquinone (atrazine target) in chloroplasts
Ubiquinone CoQ in mitochondria
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Complex V Inhibition Set 8510: Salicylanilides on exchange of P with ATP in fly mitochondria Log 1/C = NVE ; n = 15; r2 = 0.95
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Complex V Inhibition Set 9574: N,N’-diphenyl thiorureas inducing maximal release of state and respiration in rat liver mitochondria Log 1/C = 1.91 σY = 0.54 L-X ; n = 12; r2 = 0.95
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Anilino-Thiadiazoles
Set 116: Rat liver mitochondria; 2-X-anilino-1,3,4- thiadiazoles; uncoupling oxidative phosphorylation Log 1/C = 1.01 I(CF3) σ ; n = 11; r2 = 0.89 Set 117: Spinach chloroplasts; 2-X-anilino-1,3,4- thiadiazoles; uncoupling photo-phosphorylation Log 1/C = 1.87 I(CF3) σ ; n = 13; r2 = 0.9
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Uncouplers in Both Mitochondria & Chloroplasts
Pendimethalin (UOP measured; contradicts 1999 EPA manual) Trifluralin (UOP measured in plant mitochondria) Oryzalin (probable)
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Measurement of Proton Gradient (ΔΨm)
Now available as a simple kit; e.g. Molecular Probes B-34,950, Mitotracker Why not used during drug and pesticide development? Basis for QSARs? MTT Assay for mitochondrial reductase: could it be basis for QSAR?
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Acknowledgements Dr. Gilman Veith: for his support, both moral and financial. Prof. Corwin Hansch: for his skill and persistence in accumulating and organizing the data for so many QSARs. Prof. Toshio Fujita: for his insight in creating and applying QSARs. Mr. Michael Medlin: for preparing the slides for this presentation.
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Consequence of Mitochondrial Dysfunction
Production of ROS (e.g. H2O2) from non-phosphorylating respiration results in oxidative stress. Disability of aging most commonly ascribed to this oxidative stress mDNA not as well protected nor as easily repaired as nDNA Mit.-dysfunction signaled to nucleus via RR (retrograde response) but this fails thru extensive use. In simpler life forms (yeast, C.elegans) a deficiency in complex IV (cytochrome-c) lengthens life span, but "quality of life" not a concern. Could be a major factor in degenerative diseases: Parkinson's, Alzheimer's, neuropathy, myopathy, Type II Diabetes. etc.
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