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Interactions of liposome-incorporated amphotericin B with kidney epithelial cell cultures
1Department of Pharmacology, University of Texas Medical School, Houston 77025.
Abstract:
The polyene antibiotic amphotericin B (AmB) is profoundly cytotoxic to both fungal cells and mammalian cells. We have previously shown that the incorporation of AmB into phospholipid vesicles can markedly reduce the toxicity of the drug for mammalian cells (erythrocytes) without changing its antifungal potency [Mol. Pharmacol. 31:1-11 (1987)]. Because the primary site of in vivo toxicity of AmB is the kidney, here we investigate the effects of free AmB and liposomal AmB (L-AmB) on LLCPK1 cells, a porcine kidney cell line with many characteristics typical of proximal tubule cells. Acute exposure (2 hr) to free AmB inhibits protein synthesis and causes cell detachment and protein loss in LLCPK1 cells, with an IC50 of about 30 micrograms/ml. By contrast, certain formulations of L-AmB have little effect on protein synthesis/protein loss at concentrations of up to 2 mg/ml. The action of liposomes in protecting against acute AmB toxicity extends to effects on sugar transport and on cellular morphology in differentiated cultured kidney cells. Thus, the IC50 for inhibition of sodium-stimulated glucose transport by free AmB is 1.5 micrograms/ml whereas concentrations of L-AmB up to 1 mg/ml do not inhibit this process. However, chronic exposure of cells to L-AmB results in profound toxic effects as manifested by changes in cellular transport functions and cell morphology. Our results suggest that extended periods of proximity between cells and liposomes permit the transfer to toxic amounts of AmB. This may be of importance to the therapeutic use of AmB, for which protracted courses of drug administration are common.
Insights
Liposomal amphotericin B (L-AmB) protects kidney cells from acute toxicity, but prolonged exposure can lead to significant harm. This highlights potential risks with long-term L-AmB therapy.
Area of Science:
- Pharmacology
- Toxicology
- Cell Biology
Background:
- Amphotericin B (AmB) is a potent antifungal drug with significant mammalian cell toxicity.
- Liposomal formulations of AmB (L-AmB) have been developed to reduce toxicity.
- Kidney toxicity is a primary concern for in vivo AmB administration.
Purpose of the Study:
- To investigate the effects of free AmB and L-AmB on a porcine kidney proximal tubule cell line (LLCPK1).
- To compare the acute and chronic toxicity profiles of free AmB and L-AmB in kidney cells.
Main Methods:
- LLCPK1 cells were exposed to varying concentrations of free AmB and L-AmB.
- Assessed effects on protein synthesis, cell detachment, protein loss, and sodium-stimulated glucose transport.
- Evaluated cellular morphology and transport functions under acute (2 hr) and chronic exposure conditions.
Main Results:
- Acute exposure to free AmB caused significant toxicity (IC50 ~30 µg/ml for protein synthesis inhibition).
- Certain L-AmB formulations showed minimal acute toxicity, even at high concentrations (up to 2 mg/ml).
- Chronic L-AmB exposure led to substantial toxicity, including impaired transport and altered cell morphology, suggesting liposome-mediated AmB transfer.
Conclusions:
- Liposomes effectively reduce acute AmB toxicity in kidney cells.
- Prolonged contact between L-AmB and kidney cells can result in significant drug-induced toxicity.
- Findings suggest potential risks associated with long-term L-AmB therapeutic use due to drug transfer.