The Cratylia mollis Seed Lectin Induces Membrane Permeability Transition in Isolated Rat Liver Mitochondria and a Cyclosporine A-Insensitive Permeability Transition in Trypanosoma cruzi Mitochondria

摘要

Previous results provided evidence that Cratylia mollis seed lectin (Cramoll 1,4) promotes Trypanosoma cruzi epimastigotes death by necrosis via a mechanism involving plasma membrane permeabilization to Ca2+ and mitochondrial dysfunction due to matrix Ca2+ overload. In order to investigate the mechanism of Ca2+-induced mitochondrial impairment, experiments were performed analyzing the effects of this lectin on T. cruzi mitochondrial fraction and in isolated rat liver mitochondria (RLM), as a control. Confocal microscopy of T. cruzi whole cell revealed that Cramoll 1,4 binding to the plasma membrane glyco-conjugates is followed by its internalization and binding to the mitochondrion. Electrical membrane potential (Delta Psi(m)) of T. cruzi mitochondrial fraction suspended in a reaction medium containing 10 mu M Ca2+ was significantly decreased by 50 mu g/ml Cramoll 1,4 via a mechanism insensitive to cyclosporine A (CsA, membrane permeability transition (MPT) inhibitor), but sensitive to catalase or 125 mM glucose. In RLM suspended in a medium containing 10 mu M Ca2+ this lectin, at 50 mu g/ml, induced increase in the rate of hydrogen peroxide release, mitochondrial swelling, and Delta Psi(m) disruption. All these mitochondrial alterations were sensitive to CsA, catalase, and EGTA. These results indicate that Cramoll 1, 4 leads to inner mitochondrial membrane permeabilization through Ca2+ dependent mechanisms in both mitochondria. The sensitivity to CsA in RLM characterizes this lectin as a MPT inducer and the lack of CsA effect identifies a CsA-insensitive MPT in T. cruzi mitochondria