Biochem Pharmacol 1990 Aug 1;40(3):489-97

Effect of acidic phospholipids on the activity of lysosomal phospholipases and
on their inhibition by aminoglycoside antibiotics--I. Biochemical analysis.

Mingeot-Leclercq MP, Piret J, Brasseur R, Tulkens PM

Labortoire de Chimie Physiologique, Universite Catholique de Louvain, Bruxelles,
Belgium.

Aminoglycoside antibiotics accumulate in lysosomes of kidney and cultured cells
and cause an impairment of phospholipid catabolism which is considered to be an
early and significant step in the development of their toxicity. Using
liposomes, wer previously demonstrated that the activity of lysosomal
phospholipases A1 and A2 towards phosphatidylcholine was markedly enhanced by
the inclusion of phosphatidylinositol in the bilayer, and that gentamicin
impaired this activity by binding to phosphatidylinositol. Since
gentamicin-induced inhibition was inversely related to the amount of
phosphatidylinositol included in the liposomes, we proposed that gentamicin
impairs activity of phospholipases by decreasing the quantity of available
negative charges carried by the bilayer surface (Mingeot-Leclercq et al.,
Biochem Pharmacol 37: 591-599, 1988). We now extend these observations to
phosphatidylserine and phosphatidic acid, and compare the inhibition caused by
gentamicin, amikacin and streptomycin towards lysosomal phospholipases on the
hydrolysis of phosphatidylcholine in the presence of each of these acidic
phospholipids. Inclusion of phosphatidic acid in liposomes, and, to a lesser
extent, phosphatidylserine, caused a larger increase in phospholipases activity
than phosphatidylinositol. In parallel, the three aminoglycosides tested were
found less inhibitory towards phospholipases activity measured on phosphatidic
acid-or phosphatidylserine-containing liposomes than was previously observed
with phosphatidylinositol, even though equilibrium dialysis experiments failed
to demonstrate significant difference in binding parameters of the drug towards
each of these liposomes populations. Yet, as for phosphatidylinositol-containing
liposomes, the inhibition was inversely related to the amount of phosphatidic
acid or phosphatidylserine included in the bilayer and the inhibitory potency of
the three drugs was consistently gentamicin greater than amikacin greater than
streptomycin with the three types of negatively-charged liposomes used. We
conclude that impairment of lysosomal phospholipases activity towards
phosphatidylcholine included in negatively-charged membranes by aminoglycoside
antibiotics is dependent upon drug binding to the bilayer, but that it is
modulated by the nature of the acidic phospholipid that binds the drug as well
as by that of the drug itself. A companion paper (Mingeot-Leclercq et al.,
Biochem Pharmacol 40: 499-506, 1990) will examine by computer-aided
conformational analysis the parameters (drug-phospholipid energy of interaction,
position of the drug in a monolayer and its accessibility to the aqueous phase)
which may be important for these effects.

PMID: 2383282, UI: 90343839