1: Toxicol Appl Pharmacol.  2004 Jan 15;194(2):101-10.  

Cocaine induces a mixed lysosomal lipidosis in cultured fibroblasts, by
inactivation of acid sphingomyelinase and inhibition of phospholipase A1.

Nassogne MC, Lizarraga C, N'Kuli F, Van Bambeke F, Van Binst R, Wallemacq P,
Tulkens PM, Mingeot-Leclercq MP, Levade T, Courtoy PJ.

Cell Biology Unit, Christian de Duve Institute of Cellular Pathology, Louvain
University Medical School, B-1200 Brussels, Belgium.

This paper reports that cocaine may induce a lysosomal storage disorder. Indeed,
culture of Rat-1 fibroblasts with 250-500 microM cocaine induced after 2-3 days
a major accumulation in lysosomes of electron-dense lamellar structures. By
subcellular fractionation, this was reflected by a selective decrease of the
buoyant density of several lysosomal enzymes, indicating lysosomal lipid
overload. Biochemical analysis confirmed an increased cellular content of major
phospholipids and sphingomyelin, but not of cholesterol. Cocaine, a
membrane-permeant weak base, is concentrated by acidotropic sequestration,
because its accumulation was abrogated by the proton ionophore, monensin and the
vacuolar ATPase inhibitor, bafilomycin A1. At its estimated lysosomal
concentration, cocaine almost completely inhibited phospholipase A1 activity on
liposomes. Cell incubation with cocaine, but not with its inactive metabolite,
benzoylecgonine, rapidly inactivated acid sphingomyelinase, as reflected by a
10-fold decrease in Vmax with identical Km. Acid sphingomyelinase inactivation
was fully prevented by the thiol proteinases inhibitors, leupeptin and E64,
indicating that cocaine induces selective sphingomyelinase proteolysis. Upon
cocaine removal, acid sphingomyelinase activity was rapidly restored, pointing
to its fast turnover. In contrast, the cellular content of several other
lysosomal hydrolases was increased up to 2-fold. Together, these data show that
acidotropic accumulation of cocaine in lysosomes rapidly inhibits acid
phospholipase A1 and inactivates acid sphingomyelinase, which can explain
induction of a mixed lysosomal lipidosis.

PMID: 14736491 [PubMed - indexed for MEDLINE]