PHENOTYPE OF RECOMBINANT LEISHMANIA-DONOVANI AND TRYPANOSOMA-CRUZI WHICH OVER-EXPRESS TRYPANOTHIONE REDUCTASE - SENSITIVITY TOWARDS AGENTS THAT ARE THOUGHT TO INDUCE OXIDATIVE STRESS

Trypanothione reductase is thought to be important in maintaining an i ntracellular reducing environment in trypanosomatids. To investigate t he role of trypanothione reductase we transfected Leishmania donovani and Trypanosoma cruzi with an expression vector containing the L. dono vani trypanothione reductase gene and achieved over-expression of enzy me activity (10-14-fold) in transformed cells. Following treatment of L. donovani cells with the thiol-oxidizing agent diamide, the ability to regenerate dihydrotrypanothione from trypanothione disulphide was c onsiderably enhanced in cells which over-expressed trypanothione reduc tase. However, the growth of transformed and control cells was equally sensitive to inhibition by nifurtimox, nitrofurazone and gentian viol et, drugs that are thought to act by inducing oxidative damage. Likewi se, growth of transformed and control cells were equally susceptible t o inhibition by hydrogen peroxide, and control and transformed L donov ani promastigotes metabolized hydrogen peroxide at comparable rates. T hus, these experiments suggest that the ability to regenerate dihydrot rypanothione from trypanothione disulphide is not a rate-limiting step in the metabolism of hydrogen peroxide.