Peroxynitrite affects Ca2+ transport in Trypanosoma cruzi

Macrophages play an important role against Trypanosoma cruzi infection, via superoxide: nitric oxide, and peroxynitrite production. Peroxynitrite has been shown to be highly cytotoxic against Trypanosoma cruzi epimastigotes. Calcium is involved in many vital functions of the parasites, being its int racellular concentration governed by several transport systems, involving m itochondrial and non-mitochondrial compartments. In this paper: we report t he effect of peroxynitrite on the calcium uptake systems, as studied by dig itonin-permeabilized trypanosomes in the presence of arsenate III. Peroxyni trite, at biologically relevant concentrations produced within phagosomes ( 250-750 IJ-M), inhibited calcium uptake in a dose-dependent manner. Peroxyn itrite decreased the mitochondrial membrane potential obtained in the prese nce of tetramethyl-p-phenylenediamine (TMPD)/ascorbate. In addition, a decr ease of the non-mitochondrial Ca2+-uptake, concomitant with the inactivatio n of a Ca2+-dependent ATPase activity, was observed. HPLC analyses of the c ellular adenine nucleotide pool showed a time-dependent decrease of ATP con tent and energy charge of the parasite; however this drop in ATP levels was significantly delayed with respect to decrease of the ATP-dependent Ca2+-t ransport. We conclude that the disruption of calcium homeostasis by peroxyn itrite may contribute to the observed cytotoxic effects of macrophages agai nst T, cruzi. (C) 1999 Published by Elsevier Science B.V. All rights reserv ed.