Inhibition of kidney lysosomal phospholipases A and C by aminoglycoside antibiotics: possible mechanism of aminoglycoside toxicity.

Nephrotoxicity is an important side effect of aminoglycoside antibiotics, which are used to control infections caused by Gram-negative bacteria. Accumulation of aminoglycosides and phospholipids in the lysosomes is a prominent and early feature of aminoglycoside nephrotoxicity and is characterized histologically by the presence of numerous multilamellar bodies in kidney proximal tubule cells. Previous studies have shown that the drug-induced phospholipid fatty liver in man and animals is due to concentration of certain cationic amphiphilic drugs in lysosomes with inhibition of lysosomal phospholipases. It seemed possible that this mechanism might also explain the elevated levels of phospholipid and increased numbers of multilamellar bodies reported in the kidney cortex in aminoglycoside nephrotoxicity. In this study, subcellular localization of acid phospholipases A and C has been shown to be lysosomal in rat kidney cortex. A soluble lysosomal protein fraction was isolated and found to contain both phospholipase A and phospholipase C activity. Streptomycin did not inhibit the release of fatty acids from [3H]dioleoylphosphatidylcholine. However, amikacin, dibekacin, gentamicin, and tobramycin inhibited both phospholipase A and phospholipase C. Our results suggest that the accumulation of phospholipids in lysosomes of kidney cortex, an early and pervasive feature of acute aminoglycoside nephrotoxicity, is due to inhibition of lysosomal phospholipases.