Inhibition of mitochondrial and plastid activity of Plasmodium falciparum by minocycline.

We previously reported the superior effect of minocycline against drug-resistant Plasmodium falciparum in vitro. Here, we report that RT-PCR for falciparum parasites treated with minocycline revealed reduced levels of RNA transcripts of the mitochondrion-encoded genes such as the COI and Cyb genes, as well as the plastid-encoded RNA polymerase subunit (rpoB/C) gene. However, we detected no apparent effects of the antibiotic on the transcription of merozoite surface antigen and small subunit rRNA genes encoded by the nucleus. In addition, treatment with chloroquine and pyrimethamine showed no substantial reduction of any RT-PCR products. These findings suggest that tetracycline antibiotics selectively inhibit both mitochondrial and plastid activity.