Influence of lipoproteins on renal cytotoxicity and antifungal activity of amphotericin B

We examined the influence of high-density lipoproteins (HDLs) and low- density lipoproteins (LDLs) on the toxicity of amphotericin B (AmpB) to fungal and renal cells. Candida albicans was incubated for 18 h at 37°C with AmpB and deoxycholate (Fungizone) or liposomal AmpB (L-AmpB) (0.1 to 2.0 μg of AmpB per ml) in the presence or absence of HDLs or LDLs (0.5 mg of protein per ml). The MICs of AmpB and L-AmpB, whether or not HDLs or LDLs were present, were similar. LLC PK1 renal cells, derived from primary cultures of pig proximal tubular cells, were incubated for 18 h at 37°C in serum-free medium that contained AmpB and deoxycholate or L-AmpB at 20 μg of AmpB per ml, HDLs or LDLs at 0.5 mg of protein per ml, mixtures of AmpB with HDLs or LDLs, and mixtures of L-AmpB with HDLs or LDLs. HDL-associated AmpB was less toxic than AmB to LLC PK1 cells (53.0% ± 2.5% versus 81.3% ± 3.6% cytotoxicity; P = 0.01), while LDL-associated AmpB was as toxic as AmpB. L- AmpB, HDL-associated L-AmpB, and LDL-associated L-AmpB were less toxic to LLC PK1 cells than was AmpB (48.3% ± 1.5%, 25.5% ± 2.2%, and 52.2% ± 2.5% versus 81.3% ± 3.6% cytotoxicity; P = 0.02). To further understand why HDL- associated AmpB reduced renal cytotoxic effects, the LLC PK1 cells were examined for the presence of HDL and LDL receptors. LLC PK1 cells expressed high-affinity (K(d) = 0.0538 ng/ml; 96,000 sites per cell) and low-affinity (K(d) = 222.22 ng/ml; 77 sites per cell) LDL receptors but only a low- affinity HDL receptor (K(d) = 71.43 ng/ml; 2 sites per cell). HDL-associated AmpB and LDL-associated AmpB were less toxic than AmpB to trypsinized LLC PK1 cells (46.6% ± 10.9% and 16.8% ± 15.98% versus 74.7% ± 7.7% cytotoxicity; P = 0.02). HDL-associated AmB and LDL-associated L-AmpB were also less toxic than AmpB to the cells (20.4% ± 6.2% and 13.5% ± 8.6% versus 74.7% ± 7.7% cytotoxicity; P = 0.01). The antifungal activities of AmpB and L-AmpB were not altered in the presence of HDLs or LDLs. We conclude that the reduced nephrotoxicity associated with the use of L-AmpB is related to a decreased uptake of AmpB by renal cells when AmpB is associated with HDLs because of the low level of expression of HDL receptors in these cells.