Amitriptyline-induced loss of tight junction integrity in a human endothelial-smooth muscle cell bi-layer model

Tricyclic antidepressants can, when taken in overdose, cause serious pulmon ary failure such as the adult respiratory distress syndrome (ARDS). In this study we have examined the effects of some tricyclic antidepressants (amit riptyline, imipramine, nortriptyline and desipramine) on the viability and morphology of human endothelial and smooth muscle cells derived from umbili cal cord. Effects of amitriptyline on endothelial cell fluidity, as well as permeability changes to an endothelial-smooth muscle cell bi-layer, were a lso studied. The tricyclic antidepressants induced acute, sub-lethal toxici ty in both cell types above 100 mu M as assessed by the MTT reduction assay . Morphological changes were also observed at these concentrations. Such ch anges were, however, absent at 33 mu M and below. Amitriptyline did, howeve r, cause a concentration-dependent fall in the electrical resistance of an endothelial-smooth muscle cell bi-layer, with significant effects already e vident at 33 mu M All of these observed effects were fairly rapid and appea red within 5-15 min of exposure. The rapidity of these permeabilisation eff ects suggests potential membrane perturbations, since tricyclic antidepress ants are lipophilic molecules with affinity for cell membranes. However, fl uorescence anisotropy measurements showed no significant difference in memb rane fluidity between amitriptyline-treated and control endothelial cells. Collectively, these data point to specific mechanisms of action of amitript yline, and probably also the other tricyclic antidepressants studied, on en dothelial permeability, which is a hallmark of ARDS. The data suggest that increased endothelial permeability could be due to impaired tight junction function. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.