Cellular responses associated with dibucaine-induced phospholipidosis.

A wide range of cationic amphiphilic drugs (CADs) from different therapeutic areas are known to cause phospholipidosis both in vivo and in vitro. Although the relevance of this storage disorder for human health remains uncertain, CADs have been repeatedly associated with clinical side effects, and as a result, phospholipidosis is of major concern for drug development in the pharmaceutical industry. An important unresolved question in this field is whether phospholipidosis is really linked to cellular toxicity. This work was focused on studying cellular responses associated with CAD-induced phospholipidosis in cultured mammalian kidney cells. Dibucaine (2-butoxy-N-[2-diethylaminoethyl]quinoline-4-carboxamide), an amide-type anesthetic with poorly defined cytotoxic effects, was used to induce phospholipidosis in Vero cells. The results from several assays that measure cell viability, proliferation, and morphological changes indicated that dibucaine-induced lysosomal phospholipidosis was accompanied by cellular defense responses such as transient growth arrest and autophagy, under mild stress conditions. Conversely, when tolerance limits were exceeded treated Vero cells underwent extensive and irreparable injury, leading ultimately to cell death. Our data provide additional information that may be of considerable interest for drug safety assessment.