Changes in mitochondrial RNA production in cells treated with nucleoside analogues.

BACKGROUND: To investigate mitochondrial (mt) toxicity of antiretroviral drugs further, we developed a novel real-time PCR-based assay for the quantification of mtRNA. We analysed the effects of stavudine (d4T), didanosine (ddl) and zidovudine (AZT) on the production of mtRNAs in different human cell lines and compared the production with the amount of mtDNA present in the same cells. MATERIALS AND METHODS: HUT78, CEM and U937 cells were exposed to different nucleoside reverse transcriptase inhibitors (NRTIs) for 7 days. Thereafter, nucleic acids were isolated and Taqman-based real-time PCR was used to quantify mtDNA and three different mtRNAs (ND1, CYTB and ND6 gene products). RESULTS: Different amounts of mtRNAs exist in different cell lines. When mtRNA was measured in cells exposed to an NRTI, a marked decrease was observed in cells treated with d4T, but not with ddl or AZT. Changes in mtRNA production did not always correspond to modifications in mtDNA content: 1 microM d4T significantly changed mtRNA but not mtDNA content. CONCLUSIONS: d4T, but not ddl or AZT, significantly alters mtRNA quantity and quality. The method we have developed can reveal changes that are not observed by measuring mtDNA content only, and can be used for ex vivo studies on drug toxicity.