Stimulatory, permeabilizing, and toxic effects of amphotericin B on L cells

Brajtburg, J; Elberg, S; Medoff, Judith; Kobayashi, George S.; Schlessinger, David; Medoff, Gerald

doi:10.1128/aac.26.6.892

Cited by 29 publications

(20 citation statements)

References 26 publications

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“…We have proposed that the effects of AmB on cultured L cells can be divided into separate dose-dependent stages:' stimulation, permeabilization, and lethality (6). The stimulatory effect was observed at concentrations of AmB lower than those required for induction of permeability changes, and for this reason it could not be associated with changes in cell membrane permeability.…”

Section: Oxidation-dependent Events In Stimulatory and Lytic Or Lethamentioning

confidence: 99%

“…For example, the initial concentration-dependent increases in production of DNA or RNA by L cells (6) or oxidative bursts in macrophages (32) were followed by a decrease below the control level as the AmB concentrations were increased. It is obvious that stimulatory effects cannot be manifested by seriously damaged cells.…”

Section: Oxidation-dependent Events In Stimulatory and Lytic Or Lethamentioning

confidence: 99%

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Amphotericin B: current understanding of mechanisms of action

Brajtburg

Powderly

Kobayashi

et al. 1990

Antimicrob Agents Chemother

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479

263

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Section: Oxidation-dependent Events In Stimulatory and Lytic Or Lethamentioning

confidence: 99%

Section: Oxidation-dependent Events In Stimulatory and Lytic Or Lethamentioning

confidence: 99%

Amphotericin B: current understanding of mechanisms of action

Brajtburg

Powderly

Kobayashi

et al. 1990

Antimicrob Agents Chemother

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479

263

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“…Fungizone increases the uptake of metabolic precursors by L-929 cells, but its stimulatory action is limited by its toxicity to cells (9). To test the relationship between the toxic and stimulatory effects of Egam and Edam, we compared their effects on the growth (protein content per dish) of L-929 cells.…”

Section: Methodsmentioning

confidence: 99%

“…On each of the following 4 days, medium was aspirated from the cell monolayers and fresh medium containing the various formulations of AmB was added to the cells. On the fourth day, the medium was removed, cells were rinsed with 0.1 M MgCl2, and the protein content per dish was measured (9). RESULTS Dissociation of AmB from Fungizone, Egam, and Edam.…”

Section: Methodsmentioning

confidence: 99%

“…To measure the effects of AmB on the retention of K+, cells were grown to 60 to 70% confluency and then overlayed with minimal essential a-medium without serum; Fungizone, Egam, or Edam was added and samples were incubated for 1 h. At the end of the incubation period, the medium was removed by aspiration and the cells were rinsed with 0.1 M MgCl2. Cell-associated K+ was measured in a flame photometer as described previously (9).…”

Section: Methodsmentioning

confidence: 99%

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Amphotericin B incorporated into egg lecithin-bile salt mixed micelles: molecular and cellular aspects relevant to therapeutic efficacy in experimental mycoses

Brajtburg

Elberg

Kobayashi

et al. 1994

Antimicrob Agents Chemother

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The cellular activities of amphotericin B (AmB) used as Fungizone were compared with those of AmB complexed to either egg lecithin and glycocholate (Egam) or egg lecithin and deoxycholate (Edam). Under conditions in which leakage of K+ from erythrocytes and cultured L cells treated with Fungizone was almost complete, Egam and Edam containing concentrations of AmB severalfold greater than the concentration of AmB in Fungizone had no effect but retained the ability to decrease the level of retention of K+ in fungal cells.Analysis by absorption and circular dichroism spectroscopy demonstrated that when these formulations containing AmB at concentrations of less than 10-5 M were added to buffer, the AmB dissociated slowly as monomers from Egam or Edam and dissociated rapidly as a mixture of monomers and self-associated species from Fungizone. We propose that in Egam and Edam, the absence of free AmB in the self-associated form reduces the toxicity of AmB to mammalian cells, whereas the presence of monomeric AmB results in the retention of the antifungal activities of these complexes.Amphotericin B (AmB) formulated with deoxycholate and sodium phosphate as Fungizone is highly effective in the treatment of systemic fungal infections, but its usefulness is limited by toxicity to patients (13,31). The toxicity of AmB can be reduced by incorporating it into liposomes (29,30) or by complexing it to various lipids (1,14,32), and in these less toxic formulations, AmB can be given in higher, more effective doses. These formulations have been successful in treating systemic fungal infections in clinical trials (2), but despite current efforts to rationalize the research on AmB delivery systems (17,25,26), the molecular and cellular bases of the differences in the therapeutic efficacies of these lipid-based formulations and that of Fungizone are not completely elucidated.Recently, the therapeutic efficacies of novel formulations of AmB complexed to either egg lecithin and glycocholate (Egam) or to egg lecithin and deoxycholate (Edam) were compared with that of AmB as Fungizone in murine models of candidiasis and cryptococcosis (11). These formulations were nontoxic at doses 80-fold higher than the maximal tolerated doses in mice infected with Candida albicans and 40-fold higher than the maximal tolerated doses in mice infected with Cryptococcus neoformans. At these doses, Egam and Edam were therapeutically more effective in both models of infection than Fungizone given at maximal tolerated doses.The present study was designed to gain insights into the cellular and molecular bases of the different effects of AmB as Fungizone or complexed with egg lecithin and bile salt. To this end, we characterized the physical states of AmB dispersed in buffer as Fungizone, Egam, or Edam. AmB has characteristic absorption and circular dichroism (CD) spectra (5,12,15), and from spectral analyses of the various formulations, we were able to obtain information about the time and concentration * Corresponding author. Preparation of Egam and Edam...

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Amphotericin B both inhibits and enhances T-cell proliferation: Inhibitory effect is mediated through H2O2 production via cyclooxygenase pathway by macrophages

Kumar

Chakrabarti

2000

J. Cell. Biochem.

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Amphotericin B (AmB) has been shown to have both immunosuppressive and -enhancing effects, making its precise nature of action enigmatic. In the present study, we found that AmB inhibited concanavalin A (Con A)-induced T cell proliferation if added within first 30 min of stimulation, after which inhibition began to diminish rapidly. However, AmB did not inhibit T-cell proliferation induced by a combination of PMA and ionomycin. AmB inhibition of Con A-induced proliferation was completely overcome by cyclooxygenase inhibitor ibuprofen ([alpha-methyl-4-(isobutyl)phenylacetic acid]) and H(2)O(2) scavenger catalase. In fact, in the presence of ibuprofen and catalase, AmB enhanced, instead of suppressing, Con A-induced proliferation in a dose-dependent way. The effect of catalase was limited to the removal of extracellular H(2)O(2) only, as the enzyme did not enter the cells. AmB stimulated H(2)O(2) production by macrophages, but not by a lymphocyte population, which was inhibited by ibuprofen. Our T-cell preparation contained about 3% macrophages, and AmB inhibition of proliferation was further pronounced by increasing the macrophage number by as little as 1%. Finally, AmB inhibition of Con A-induced T-cell proliferation was completely overcome by 2-mercaptoethanol. On the basis of these results, we suggest that AmB stimulates H(2)O(2) production by macrophages through the activation of the cyclooxygenase pathway of arachidonate metabolism. H(2)O(2) then inhibits Con A-induced T-cell proliferation by interfering with an early step of the T-cell receptor signaling pathway through the oxidative modification of some signaling proteins. Our results also show that AmB enhances T-cell proliferation, which can be seen only after blocking its inhibitory effect.

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Stimulatory, permeabilizing, and toxic effects of amphotericin B on L cells

Abstract: Our results suggest that the dose-related stimulatory, permeabilizing, and toxic effects of AmB most probably have distinct mechanisms of action and may be independent of one another.

Cited by 29 publications

References 26 publications

Amphotericin B: current understanding of mechanisms of action

Amphotericin B: current understanding of mechanisms of action

Amphotericin B incorporated into egg lecithin-bile salt mixed micelles: molecular and cellular aspects relevant to therapeutic efficacy in experimental mycoses

Amphotericin B both inhibits and enhances T-cell proliferation: Inhibitory effect is mediated through H2O2 production via cyclooxygenase pathway by macrophages

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