1. Free Radic Biol Med. 2011 Nov 1;51(9):1656-65. Epub 2011 Jul 23.

Role of oxidative stress in lysosomal membrane permeabilization and apoptosis
induced by gentamicin, an aminoglycoside antibiotic.

Denamur S, Tyteca D, Marchand-Brynaert J, Van Bambeke F, Tulkens PM, Courtoy PJ, 
Mingeot-Leclercq MP.

Université catholique de Louvain, Louvain Drug Research Institute, Laboratory of 
Cellular and Molecular Pharmacology, UCL B1.73.05, avenue E. Mounier 73, B-1200
Bruxelles, Belgium.

Gentamicin, an aminoglycoside antibiotic used to treat severe bacterial
infections, may cause acute renal failure. At therapeutic concentrations,
gentamicin accumulates in lysosomes and induces apoptosis in kidney proximal
tubular cells. In gentamicin-treated renal LLC-PK1 cells, acridine orange release
from lysosomes, previously interpreted as lysosomal membrane permeabilization,
precedes the apoptotic cascade that develops during incubation with gentamicin.
However, the link between gentamicin lysosomal accumulation and apoptosis remains
unclear. We here examined if reactive oxygen species (ROS) production could
account for gentamicin-induced acridine orange release and apoptosis, and the
implication of iron in these events. We found that gentamicin induced ROS
production prior to, and at lower drug concentrations than required for, acridine
orange release and apoptosis. ROS antioxidant or scavenger, catalase, and
N-acetylcysteine largely prevented these events. Vital confocal imaging revealed 
that gentamicin-induced ROS production occurs in lysosomes. Deferoxamine, an iron
chelator, which is endocytosed and accumulates in lysosomes, largely prevented
gentamicin-induced ROS production as well as apoptosis. Direct evidence for
gentamicin-induced permeabilization of lysosomal membrane was provided by showing
the release into the cytosol of Lucifer yellow, a membrane-impermeant endocytic
tracer with a comparable molecular weight as gentamicin. Altogether, our data
demonstrate a key role of lysosomal iron and early ROS production in
gentamicin-induced lysosomal membrane permeabilization and apoptosis.

PMID: 21835240  [PubMed - in process]