Ultrastructural alterations of Trypanosoma cruzi kinetoplast induced by the interaction of a trypanocidal drug (hydroxystilbamidine) with the kinetoplast DNA

Abstract

The trypanocide Hydroxystilbamidine (OHSA) interacts selectively with the kinetoplast DNA (K-DNA) in Trypanosoma cruzi . When the drug is added to trypanosome cultures at a concentration of 5 μ g/ml, it induces characteristic alterations of kinetoplast ultrastructure, not modifying any other cell component within a 7-day period. Three chronological periods occurring during drug treatment have been described: (1) Within the first 15 hours of OHSAtreatment, no ultrastructural modifications can be detected, although fluorescence shows that the drug has penetrated into the organelle. (2) Between 15 and 48 hours, the characteristic double-layered pattern of K-DNA is rearranged to form elongated fibrillar bodies. (3) During the period following 48 hours, all regular fibrillar structure disappears. The various and complex later stages are characterized by the progressive loss of the K-DNA. Dyskinetoplastic trypanosomes are formed after 6–7 days; their kinetoplast contains only a small amount of amorphous material. The induction of “dyskinetoplasty” by drugs interacting with mitochondrial and kinetoplast DNA has been compared with the cytoplasmic “petite” mutation in yeast, which is similarly induced by the same drugs. The kinetoplast is a specialized region of the mitochondrial system of trypanosomes. It is therefore an interesting model system to study the interaction of drugs with mitochondrial DNA in vivo .