Papers by Patricia Sokolove
Analytical Biochemistry, 1993
Biochemical Pharmacology, 1993
Adriamycin (AdM) aglycones have dramatic effects on isolated heart mitochondria, oxidizing pyridi... more Adriamycin (AdM) aglycones have dramatic effects on isolated heart mitochondria, oxidizing pyridine nucleotides, modifying sulfhydryl groups, and triggering a permeability transition of the inner membrane that results in free passage of solutes smaller than 1500 Da. In this investigation, the role of glutathione (GSH) peroxidase in these actions of the aglycones was evaluated, by comparing mitochondria from selenium-deficient and selenium-supplemented rats, with the following results. Selenium deficiency was without effect on the permeability transition of heart mitochondria, followed via Ca2+ release and triggered by AdM aglycone or by t-butyl hydroperoxide (TBH) or H2O2, both of which are authentic substrates of the peroxidase. The permeability transition of liver mitochondria was delayed by selenium deficiency regardless of the triggering agent; however, substantial triggering by the aglycone and TBH persisted in mitochondria from selenium-deficient animals. Selenium deficiency inhibited thiol modification elicited by AdM aglycone and H2O2 in heart mitochondria and by the aglycone, TBH, and possibly H2O2 in liver mitochondria. It would thus appear that AdM aglycone, TBH, and H2O2 can induce the permeability transition of isolated heart mitochondria via a process (or processes) distinct from the catalytic activity of the peroxidase. Furthermore, even in liver, where involvement of the peroxidase is observed, mechanisms other than the GSH cycle can contribute to transition induction by the aglycone and by TBH. Finally, mitochondrial-SH group modification by the aglycones appeared not to be causally linked to induction of the permeability transition. This laboratory has suggested that the effects of aglycone metabolites of AdM on mitochondria mediate the cardiotoxicity that limits use of the parent drug. The data presented in this paper argue against the involvement of GSH peroxidase in that process. They are in agreement with in vivo studies, which have generally failed to find evidence for amelioration of AdM cardiotoxicity in selenium-deficient animals.
Calcium and Phosphate Transport Across Biomembranes, 1981
FEBS Letters, 1986
Bis(2-hydroxy-3-tert-butyl-5-methylphenyl)methane (bis-phenol) is the most potent inhibitor of th... more Bis(2-hydroxy-3-tert-butyl-5-methylphenyl)methane (bis-phenol) is the most potent inhibitor of the (Caz+ + MgZ+)-ATPase of skeletal muscle sarcoplasmic reticulum yet identified. The compound behaves as a reversible, tight-binding inhibitor with apparant K, =0.3 PM. Butylated hydroxytoluene, butylated hydroxyanisole, and 4-nonylphenol are also effective inhibitors. These observations are of particular interest in light of the widespread use of such phenolic antioxidants and stabilizers in the food industry and in the manufacture of rubbers and plastics and the ease with which the compounds are extracted into organic solvents.
Journal of Biological Chemistry, 1984
Anal Biochem, 1989
Arsenazo III-loaded liposomes are in wide use as model systems in the study of Ca2+ transport. Th... more Arsenazo III-loaded liposomes are in wide use as model systems in the study of Ca2+ transport. The most sophisticated method for quantitation of Ca2+ uptake [E. B. Smaal et al. (1985) Biochim. Biophys. Acta 816, 418] utilizes the absorbance changes (650-700 nm) elicited by sequential additions of EDTA and A23187 to distinguish Ca2+-Arsenazo complexes which are outside and inside the liposomes. In this paper, the analytical approach of Smaal and co-workers is reevaluated and a straightforward treatment that allows calculation both of the concentration of Ca2+ inside liposomes and of total Ca2+ uptake (in moles/mole phospholipid) is developed.
Integration of Mitochondrial Function, 1988
Duramycin is a polypeptide antibiotic (MR = 2012) isolated from culture broth of Streptoverticill... more Duramycin is a polypeptide antibiotic (MR = 2012) isolated from culture broth of Streptoverticillium cinnamomeus (formerly Streptomyces cinnamomeus forma azacoluta, NRRL B-1699) (Shotwell et al., 1958). The antibiotic interferes with the function of several membrane transport systems including the chloride transporter of clathrin-coated vesicles (Stone et al., 1984), the Ca2+-ATPase of rabbit sarcoplasmic reticulum (Navarro et al., 1985), and the proton secretion system of B. subtilis(Navarro et al., 1985). Recently duramycin has been reported to interact specifically with the non-bilayer lipids phosphatidylethanolamine (PE) and monogalactosyldiglyceride (MGDG) (Navarro et al., 1985).
International Journal of Biochemistry, 1994
Adriamycin and related anthracyclines are potent oncolytic agents, the clinical utility of which ... more Adriamycin and related anthracyclines are potent oncolytic agents, the clinical utility of which is limited by severe cardiotoxicity. Aglycone metabolites of Adriamycin (5-20 microM) induce a Ca(2+)-dependent increase in the permeability of the inner mitochondrial membrane of both heart and liver mitochondria to small (< 1,500 Da) solutes; this phenomenon is accompanied by release of mitochondrial Ca2+, mitochondrial swelling, collapse of the membrane potential, oxidation of mitochondrial pyridine nucleotides [NAD(P)H], uncoupling, and a transition from the condensed to the orthodox conformation and is inhibited by ATP, dithiothreitol, the immunosuppressant cyclosporin A, and the ubiquitous polyamine spermine. Aglycones also modify mitochondrial sulfhydryl groups and induce a Ca2+ independent oxidation of mitochondrial NAD(P)H which appears to reflect electron transport from NADH to oxygen, mediated by the aglycones and resulting in the production of superoxide (O2-). Selenium deficiency and butylated hydroxytoluene inhibit aglycone-induced Ca2+ release from liver, but not heart, mitochondria, suggesting that the interactions of the aglycones with mitochondria differ in these two tissues. It can be proposed that the effects of Adriamycin aglycones on heart mitochondria are responsible for the cardiotoxicity of the parent drug.
Life Sciences, 1996
Previously, we reported that the stress-induced protein metallothionein I (MT) modulated the oxyg... more Previously, we reported that the stress-induced protein metallothionein I (MT) modulated the oxygen consumption (VO2) of isolated rat liver mitochondria [Life Sci. 55 221-226, 1994]. We now present confirmation of this finding, and the additional observations that in rat liver mitochondria, MT caused swelling and depolarization. These actions of MT were inhibited by the aliphatic polyamine, spermine. Our findings suggest that mitochondrial function could be influenced by the balance between MT and spermine.
Journal of Bioenergetics and Biomembranes, 1996
Mitochondria undergo a permeability transition (PT)2, i.e., become nonselectively permeable to sm... more Mitochondria undergo a permeability transition (PT)2, i.e., become nonselectively permeable to small solutes, in response to a wide range of conditions/compounds. In general, opening of the permeability transition pore (PTP) is Ca2+- and P(i)-dependent and is blocked by cyclosporin A (CsA), trifluoperazine (TFP), ADP, and butylated hydroxytoluene (BHT). Gudz and coworkers have reported [7th European Bioenergetics Conference, EBEC Short Reports (1992) 7, 125], however, that, under some conditions, BHT increases mitochondrial permeability via a process that may not share all of these characteristics. Specifically, they determined that the BHT-induced permeability transition was independent of Ca2+ and was insensitive to CsA. We have used mitochondrial swelling to compare in greater detail the changes in permeability induced by BHT and by Ca2+ plus P(i) with the following results. (1) The dependence of permeability on BHT concentration is triphasic: there is a threshold BHT concentration (ca. 60 nmol BHT/ mg mitochondrial protein) below which no increase occurs; BHT enhances permeability in an intermediate concentration range; and at high BHT concentrations (>120 nmol/mg) permeability is again reduced. (2) The effects of BHT depend on the ratio of BHT to mitochondrial protein. (3) Concentrations of BHT too low to induce swelling block the PT induced by Ca2+ and P(i). (4) The dependence of the Ca2+-triggered PT on P(i) concentration is biphasic. Below a threshold of 50-100 mu M, no swelling occurs. Above this threshold swelling increases rapidly. (5) P(i) levels too low to support the Ca2+-induced PT inhibit BHT-induced swelling. (6) Swelling induced by BHT can be stimulated by agents and treatments that block the PT induced by Ca2+ plus P(i). These data suggest that BHT and Ca2+ plus P(i) increase mitochondrial permeability via two mutually exclusive mechanisms.
FEBS Letters, 1992
The effect of spermine on the permeability transition of the inner mitochondrial membrane of isol... more The effect of spermine on the permeability transition of the inner mitochondrial membrane of isolated rat heart mitochondria was evaluated. The permeability transition was triggered using a series of agents (t-butyl hydrol~roxide, phenylarsine oxide, carboxyatractylate, and elevated Ca 2. and inorganic phosphate concentrations), and was monitored via Ca'-"-release, mitochondrial swelling and pyridine nueleotide oxidation. By all three criteria, spermine inhibited the transition. A Qo of 0.38 + 0.06 (SD) mM was measured for inhibition.
Cancer Letters, 1985
Rates of hydrolysis of 3-hydroxybenzo[a] pyrenyl glucuronide by microsomal /I-glucuronidase from ... more Rates of hydrolysis of 3-hydroxybenzo[a] pyrenyl glucuronide by microsomal /I-glucuronidase from rat liver were 397 + 17 nmol/min per g protein and were half-maximal with about 100 PM substrate. Treatment of rats with phenobarbital or 3_methylcholanthrene, which elevates activities of glucuronosyltransferase(s), lowered rates of hydrolysis of benzo [ a] pyrene glucuronide by 25%. Hydrolysis of the glucuronide by microsomal /3glucuronidase was stimulated by micromolar concentrations of calcium in the range existing in cytosol of hepatocytes (apparent Km-0.2 MM). Thus, humoral factors that change intracellular concentrations of free calcium may alter the production and export of glucuronides of benzo[a] pyrene metabohtes from the liver.
Biochemical Pharmacology, 1985
The interaction of cardiolipin-containing, unilamellar liposomes with Ca2+ was assessed by flow d... more The interaction of cardiolipin-containing, unilamellar liposomes with Ca2+ was assessed by flow dialysis in the presence of 2-100 microM 45Ca2+, using vesicles formed from phosphatidylcholine (PC) and from PC and cardiolipin in mole ratios from 16:1 to 1:1. Control (PC only) vesicles bound no detectable Ca2+. In contrast, Ca2+ binding to cardiolipin-containing vesicles was substantial and dependent on vesicle concentration. Scatchard plots for the binding were concave upward. Resolution of the data, assuming the presence of two independent classes of binding sites, indicated a high-affinity site with apparent KD = 5.57 +/- 0.48 microM (S.D.) and a second site with KD in the millimolar range. Interaction of cardiolipin-containing liposomes with Ca2+ was insensitive to monovalent cations (Na+, K+, Rb+), but was inhibited by ruthenium red much greater than La3+ greater than Mn2+ greater than Mg2+. Progressive increases in the PC: cardiolipin ratio markedly increased the apparent KD for Ca2+ at the high-affinity site. Stoichiometry of Ca2+ binding at the site passed through a maximum at a PC: cardiolipin ratio of 4:1. The potent antineoplastic agent adriamycin also inhibited the interaction of Ca2+ with cardiolipin-containing liposomes in a dose-dependent manner; effects were detected at 10 microM antibiotic. Unlike PC, adriamycin altered the stoichiometry of the high-affinity interaction but not the apparent KD. Adriamycin effects increased with pH in the range of the pKA of its amino group. These results suggest that inhibition by adriamycin may result from a mechanism other than simple competition for the charged head group of cardiolipin.
Biochemical Pharmacology, 1988
The effect of adriamycin aglycones on Ca*+ retention by isolated, preloaded rat heart mitochondri... more The effect of adriamycin aglycones on Ca*+ retention by isolated, preloaded rat heart mitochondria was assessed. After an initial lag, which decreased with increasing drug concentration, the 7-hydroxy-aglycone (5-20 PM) triggered Ca2+ release. Aglycone-induced Ca'+ release was correlated with Caz+-dependent mitochondrial swelling, Ca2+-dependent collapse of the mitochondrial membrane potential, Ca*+-dependent oxidation of mitochondrial pyridine nucleotides, and a transition from the condensed to the orthodox con~guration. Anyone-induced Ca2' release was inhibited by dibucaine, dithiothreitol, ATF', and bovine serum albumin. It can be concluded , therefore, that aglycone-induced Caz+ release reflects the Ca2'-dependent increase in the permeability of the inner mitochondrial membrane to solutes of molecular weight < 1000 which has been observed with other triggering agents
Biochemical Pharmacology, 1984
Biochemical Pharmacology, 1987
Biochemical Pharmacology, 1990
Biochemical and Biophysical Research Communications, 1984
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1983
The interaction of cardiolipin with Ca 2+ was assessed by measuring the cardiolipin-mediated extr... more The interaction of cardiolipin with Ca 2+ was assessed by measuring the cardiolipin-mediated extraction of 45Ca2+ from an aqueous to an organic (methylene chloride) phase. Cardiolipin binds Ca 2+ with high affinity [Kd(apparent)=0.70+0.17 IxM (S.D.)]. Cation-cardiolipin interactions are selective. Interaction of cardiolipin with Ca 2+ is insensitive to Na +, but is inhibited by divalent cations with MnZ+> Zn2+> Mg z+. In addition La 3+ and Ruthenium red are particularly potent inhibitors of Ca 2+ binding by cardiolipin. Cardiolipin-mediated extraction of Ca 2+ into an aqueous phase is also inhibited by phosphatidylcholine. Inhibition of Ca2+-cardiolipin interaction by phosphatidylcholine (a phospholipid known to stabilize the bilayer conformation) may implicate inverted, non-bilayer lipid structures in the binding.
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Papers by Patricia Sokolove