Investigation of sesquiterpene lactones as protein synthesis inhibitors of P-388 lymphocytic leukemia cells

Liou, Y.F.; Hall, Iris H.; Lee, Kuo Hsiung̀; Williams, W.L.; Chaney, Stephen G.

doi:10.1016/0167-4781(83)90029-5

Cited by 10 publications

(7 citation statements)

References 23 publications

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“…Specifically, helenalin affords a Michael-type addition to functional thiol groups of enzymes (1,2,3) inhibiting the activities of thiol-bearing enzymes, i.e. DNA polymerase a, ribonucleotide reductase, and IMP dehydrogenase in the L-1210, P-388, KB, and Ehrlich ascites cells (3-5) and inhibits eIF-3 function and activated eIF-2 kinase activity in the initiation process of protein synthesis of P-388 cells and rabbit reticulocytes (6)(7)(8), thus suggesting selectivity for the thiol group bound by the drug rather than non-specific thiol binding to all cellular components.…”

Section: Introductionmentioning

confidence: 99%

Role of Thiol Agents in Protecting Against the Toxicity of Helenalin in Tumor Bearing Mice

Hall¹,

Grippo²,

Holbrook³

et al. 1989

Planta Med

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Helanalin, a sesquiterpene lactone antineoplastic agent, is toxic at therapeutic doses in murine tumors. The toxicity has been assumed to be correlated with the binding of the drug to cellular thiol groups. Studies were undertaken to increase the intracellular level of GSH in the liver, kidney and other tissues to eliminate the toxicity of helenalin in vivo. Combination of helenalin 8 mg/kg/day i.p.) with L-cysteine (100 mg/kg/day), beta-mercaptoethanolamine (20 mg/kg/day), 18-beta-glycyrrhetinic acid (15 mg/kg/day), or 4,4'-diaminodiphenylsulfone (10 mg/kg/day) afforded improvement in survival of mice bearing P-388 lymphocytic leukemia. However, other thiol-elevating agents, anti-oxidants, intracellular buffering agents, and cardiac treatment drugs were not effective. Hydrocortisone, Cortef, treatment with helenalin afforded improvement in life expectancy. Reduced glutathione (GSH) and non-protein sulfhydryl (NPS) levels were not reduced in the liver, kidney, or circulating red blood cells (rbc) by helenalin treatment. After three days treatment of mice with helenalin, GSH levels were reduced and NPS levels elevated in P-388 tumor cells. Administration of L-cysteine, beta-mercaptoethanolamine, 4,4'-diaminodiphenylsulfone, or 18-beta-glycyrrhetinic acid alone caused no alteration in liver GSH but elevated NPS levels; P388 cell GSH and NPS levels were lowered. Combination of any of these agents, after three days, with helenalin afforded increases in P-388 cell GSH and NPS levels. This data would suggest that helenalin toxicity is not related to the lowering of GSH or NPS levels in critical tissues of mice.

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Section: Introductionmentioning

confidence: 99%

Role of Thiol Agents in Protecting Against the Toxicity of Helenalin in Tumor Bearing Mice

Hall¹,

Grippo²,

Holbrook³

et al. 1989

Planta Med

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“…CTAB precipitable counts were determined as described by Safer et al (1979) helenalin and bis(helenalinyl) malonate needed to produce 100% inhibition varies slightly from lysate to lysate (due to small variations in endogenous glutathione levels), 100 yuM drug was chosen for most subsequent experiments in the low-lysate assay since that level was always effective. The level of 100 fiM helenalin and bis(helenalinyl) malonate is also the level used in previous studies with P-388 cell-free protein synthesizing systems (Liou et al, 1983). In experiments with higher lysate concentrations (175 /uL of lysate/260-^L assay volume, Figure 2B), 200 /uM drug concentrations were used to obtain a similar level of inhibition (higher drug concentrations were precluded by solubility limitations).…”

Section: Resultsmentioning

confidence: 99%

“…The mechanism of protein synthesis inhibition by helenalin has been studied in some detail. Helenalin specifically inhibits at the level of initiation in both P-388 (Liou et al, 1983) and rabbit reticulocyte (Williams et al, 1983) systems. With use of fractionated systems, it appears likely that eIF-3 is the only initiation factor directly sensitive to inactivation by helenalin (Liou et al, 1983;Williams et al, 1983).…”

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confidence: 99%

“…Helenalin specifically inhibits at the level of initiation in both P-388 (Liou et al, 1983) and rabbit reticulocyte (Williams et al, 1983) systems. With use of fractionated systems, it appears likely that eIF-3 is the only initiation factor directly sensitive to inactivation by helenalin (Liou et al, 1983;Williams et al, 1983). Thus, helenalin appears to possess a remarkable degree of selectivity as a sulfhydryl reagent.…”

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confidence: 99%

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Indirect inactivation of rabbit reticulocyte initiation factor eIF-2 by helenalin and bis(helenalinyl) malonate

Williams¹,

Chaney²,

Hall³

et al. 1984

Biochemistry

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Helenalin and bis(helenalinyl) malonate, sesquiterpene lactones that react primarily with exposed sulfhydryl groups, were shown to be equally effective inhibitors of endogenous protein synthesis in rabbit reticulocyte lysates. By use of partially fractionated systems, it was possible to show that helenalin preferentially inhibited the conversion of the ternary initiation complex to the 48S preinitiation complex. Previous experiments have shown that this preferential inhibition is due to selective inactivation of eIF-3 [Williams, W. L., Chaney, S. G., Willingham, W., Considine, R. T., Hall, I. H., & Lee, K.-H. (1983) Biochim. Biophys. Acta 740, 152-162]. Bis(helenalinyl) malonate was much less active as an inhibitor of 48S complex formation than helenalin and clearly did not possess sufficient activity in that assay to explain its effectiveness as a protein synthesis inhibitor in whole lysates. Kinetic studies also showed a clear difference between the mechanism of action of these two drugs. Bis(helenalinyl) malonate inactivated protein synthesis in reticulocyte lysates only after a lag of 10 min, and the inhibition of protein synthesis could be completely reversed by the addition of 5 mM cAMP. Helenalin showed more complex kinetics. While full inhibition only occurred after a lag of 10-15 min, a partial inhibition was observed from very early times. cAMP at 5 mM was only partially able to reverse inhibition by helenalin. Phosphorylation studies showed that both helenalin and bis(helenalinyl) malonate were equally effective at activating eIF-2 alpha kinase and indirectly causing phosphorylation of eIF-2.(ABSTRACT TRUNCATED AT 250 WORDS)

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“…However, vernolepin has other effects on cells besides those considered here (e.g., 36-38), one or more of which may be required, together with oxidant injury, for its cytolytic action. For example, inhibition of protein synthesis by sesquiterpene lactones (37,38), like inhibition of GSH synthesis by BSO (8), may block a main route of utilization of intracellular cysteine, thereby increasing the pool available for autoxidation (Fig. 5).…”

Section: Discussionmentioning

confidence: 99%

Hydrogen peroxide from cellular metabolism of cystine. A requirement for lysis of murine tumor cells by vernolepin, a glutathione-depleting antineoplastic.

Arrick¹,

Griffo²,

Cohn³

et al. 1985

J. Clin. Invest.

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The sesquiterpene lactone antineoplastic vernolepin acutely depletes murine tumor cell glutathione (GSH) and lyses the cells by an unknown mechanism that is enhanced synergistically by inhibition of GSH synthesis with buthionine sulfoximine (BSO) (Arrick et al. 1983. J. Clia. Invest. 71:258). We found here that iysis of P815 mastocytoma cells by vernolepin, with or without BSO, required cystine in the culture medium. Addition of catalase markedly suppressed vernolepin-mediated cytolysis in cystine-containing media, suggesting the involvement of hydrogen peroxide in the cytolytic action of vernolepin.Consistent with this, Inhibition of tumor cell glutathione disulfide reductase with 1,3-bis(2-chloroethyl)-1-nitrosourea or inhibition of endogenous catalase with aminotriazole synergistically augmented cytolysis by vernolepin. Moreover, H202 was released by suspensions of P815 cells in cystine-containing buffer (63 pmol/10' cells h). Omission of cystine reduced the rate of H202 accumulation 10-fold. No H202 was detected without cells. Cytolysis by vernolepin could be restored in cystine deficient medium by several other disulfides, themselves noncytolytic, such as disulfiram and oxidized Captopril, as well as by cysteine. In contrast, withholding two other essential amino acids (leucine or tryptophan) or adding cycloheximide did not interfere with cytolysis by vernolepin. These results suggest that cellular uptake of disulfides of physiologic and pharmacologic interest may be followed by their intracellular reduction and autooxidation with generation of H202. This previously unrecognized source of intracellular oxidant stress may be an important component of injury to GSH-depleted cells.

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Investigation of sesquiterpene lactones as protein synthesis inhibitors of P-388 lymphocytic leukemia cells

Cited by 10 publications

References 23 publications

Role of Thiol Agents in Protecting Against the Toxicity of Helenalin in Tumor Bearing Mice

Role of Thiol Agents in Protecting Against the Toxicity of Helenalin in Tumor Bearing Mice

Indirect inactivation of rabbit reticulocyte initiation factor eIF-2 by helenalin and bis(helenalinyl) malonate

Hydrogen peroxide from cellular metabolism of cystine. A requirement for lysis of murine tumor cells by vernolepin, a glutathione-depleting antineoplastic.

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