Safety profile of AZT derivatives: Organoselenium moieties confer different cytotoxic responses in fresh human erythrocytes during in vitro exposures.INTRODUCTION
 The incorporation of selenium in the structure of nucleosides is a promising strategy to develop novel therapeutic molecules.


 OBJECTIVE
 To assess the toxic effects of three AZT derivatives containing organoselenium moieties on human erythrocytes.


 Freshly human erythrocytes were acutely treated with AZT and selenium derivatives SZ1 (chlorophenylseleno), SZ2 (phenylseleno) and SZ3 (methylphenylseleno) at concentrations ranging from 10 to 500 μM.  Afterwards, parameters related to membrane damage, redox dyshomeostasis and eryptosis were determined in the cells.


 The effects of AZT and derivatives toward erythrocytes differed considerably.  Overall, the SZ3 exhibited similar effect profiles to the prototypal AZT, without causing cytotoxicity.  Contrary, the derivative SZ1 induced hemolysis and increased the membrane fragility of cells.  Reactive species generation, lipid peroxidation and thiol depletion were also substantially increased in cells after exposure to SZ1.  δ-ALA-D and Na+/K+-ATPase activities were inhibited by derivatives SZ1 and SZ2.  Additionally, both derivatives caused eryptosis, promoting cell shrinkage and translocation of phosphatidylserine at the membrane surface.  The size and granularity of erythrocytes were not modified by any compound.


 CONCLUSION
 The insertion of either chlorophenylseleno or, in a certain way, phenylseleno moietes in the structure of AZT molecule was harmful to erythrocytes and this effect seems to involve a pro-oxidant activity.  This was not true for the derivative encompassing methylphenylseleno portion, making it a promising candidate for pharmacological studies.
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