Da. Garcia et al., Flunitrazepam partitioning into natural membranes increases surface curvature and alters cellular morphology, CHEM-BIO IN, 129(3), 2000, pp. 263-277
In recent studies, we showed that flunitrazepam (FNTZ) and other benzodiaze
pines interact with artificial phospholipid membranes locating at the polar
head group region, inducing a membrane expansion, reducing the molecular p
acking and reorganising molecular dipoles. In the present paper we investig
ated the possibility that those phenomena could be transduced into changes
in the curvature of membranes from natural origin. Hence we studied the eff
ect of FNTZ on cellular morphology using human erythrocyte as a natural ass
ay system. Shape changes of erythrocytes were evaluated by light microscopy
and expressed as a morphological index (MI). FNTZ induced echinocytosis in
a time-dependent manner with MI values significantly higher than those of
control (without drug) or DMSO (vehicle) samples. Lidocaine, a local anesth
etic known to induce stomatocytosis by incorporating in the inner monolayer
, counterbalanced the concentration-dependent FNTZ crenating effects. FNTZ
induced protective effects, compared with control and DMSO, against time-de
pendent hemolysis. Hypotonic-induced hemolysis, was also lowered by FNTZ in
a concentration-dependent manner. Both antihemolytic effects suggested a d
rug-induced membrane expansion allowing a greater increase in cell volume b
efore lysis. In such a complex system like a cell, curvature changes trigge
red by drug partitioning towards the plasma membrane, might be an indirect
effect exerted through modifications of ionic-gradients or by affecting cyt
oskeleton membrane linkage. In spite of that, the curvature changes can be
interpreted as a mechanism suitable to relieve the tension generated initia
lly by drug incorporation into the bilayer and may be the resultant of the
dynamic interactions of many molecular fluxes leading to satisfy the sponta
neous membrane curvature. (C) 2000 Published by Elsevier Science Ireland Lt
d.