title: Gentamicin-induced apoptosis in LLC-PK1 cells: involvement of lysosomes and mitochondria.
abstract: Gentamicin accumulates in lysosomes and induces apoptosis in kidney proximal tubules and renal cell lines. Using LLC-PK1 cells, we have examined the concentration- and time-dependency of the effects exerted by gentamicin (1-3 mM; 0-3 days) on (i) lysosomal stability; (ii) activation of mitochondrial pathway; (iii) occurrence of apoptosis (concentrations larger than 3 mM caused extensive necrosis as assessed by the measurement of lactate dehydrogenase release). Within 2 h, gentamicin induced a partial relocalization [from lysosomes to cytosol] of the weak organic base acridine orange. We thereafter observed (a) a loss of mitochondrial membrane potential (as from 10 h, based on spectrophotometric and confocal microscopy using JC1 probe) and (b) the release of cytochrome c from granules to cytosol, and the activation of caspase-9 (as from 12 h; evidenced by Western blot analysis). Increase in caspase-3 activity (assayed with Ac-DEVD-AFC in the presence of z-VAD-fmk]) and appearance of fragmented nuclei (DAPI staining) was then detected as from 16 to 24 h together with nuclear fragmentation. Gentamicin produces a fast (within 4 h) release of calcein from negatively-charged liposomes at pH 5.4, which was slowed down by raising the pH to 7.4, or when phosphatidylinositol was replaced by cardiolipin (to mimic the inner mitochondrial membrane). The present data provide temporal evidence that gentamicin causes apoptosis in LLC-PK1 with successive alteration of the permeability of lysosomes, triggering of the mitochondrial pathway, and activation of caspase-3.
authors.affiliation: Unité de pharmacologie cellulaire et moléculaire, Université catholique de Louvain, UCL 73.70 Avenue E. Mounier 73, B-1200 Brussels, Belgium.
authors.forename: Hélène
authors.initials: H
authors.lastname: Servais
authors.forename: Patrick
authors.initials: P
authors.lastname: Van Der Smissen
authors.forename: Gaëtan
authors.initials: G
authors.lastname: Thirion
authors.forename: Gauthier
authors.initials: G
authors.lastname: Van der Essen
authors.forename: Françoise
authors.initials: F
authors.lastname: Van Bambeke
authors.forename: Paul M
authors.initials: PM
authors.lastname: Tulkens
authors.forename: Marie-Paule
authors.initials: MP
authors.lastname: Mingeot-Leclercq
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases / Q000096:biosynthesis; D045304:Cytochromes c / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D005839:Gentamicins / Q000737:chemistry / Q000633:toxicity*; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000648:ultrastructure; D018374:LLC-PK1 Cells; D008051:Lipid Bilayers / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry; D008247:Lysosomes / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000378:metabolism / Q000502:physiology*; D009336:Necrosis; D010539:Permeability; D013552:Swine; D013997:Time Factors
chemical_list: D005839:Gentamicins; D008051:Lipid Bilayers; D008081:Liposomes; D045304:Cytochromes c; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases