Antidepressants cause lethal disruption of membrane function in the human protozoan parasite Leishmania

The antidepressant compounds clomipramine and nitroimipramine were cidal to extracellular promastigotes of both human protozoan parasites Leishmania donovani and Leishmania major. Clomipramine also killed amastigotes of both species within murine macrophages with no apparent toxicity to the host cells. Further, amastigotes were more sensitive than promastigotes to clomipramine. Clomipramine (100 micromoles per liter or 0.2 nanomole per 1 X 10(6) cells) inhibited L-proline transport in promastigotes. Synergistic inhibition of L-proline transport was observed with clomipramine after addition of either of the ionophores valinomycin or nigericin. These observations suggest that the cytotoxic effects of clomipramine result from its disruption of the proton electrochemical gradient of the parasite surface membrane.