Figure 4. (A-B) Cisplatin exposure reduces the expression of mitochondrial-DNA encoded proteins.

(A) Representative Western Blot of mitochondrial-encoded cytochrome c oxidase subunit 1 (MT-CO1) and succinate dehydrogenase subunit A (SDHA) expression in A549 cells exposed to cisplatin (CDDP) or carboplatin (CBCDA) at a IC50 dose (12 μM and 50 μM, respectively) for 24 h. Chloramphenicol (CLP) at 100 μg/mL was used as positive control. (B) Quantitative analysis of n=3 independent biological replicates. MT-CO1 expression was normalized over SDHA expression. Data are presented as fold change over control (no treatment). (C-D) Carboplatin is less efficient than cisplatin in impairing mtDNA transcription and generating ROS in cancer cells. (C) MT-CO1 mRNA levels following exposure to cisplatin and carboplatin. A549 cells were exposed to cisplatin and carboplatin at an IC50 dose (12 μM and 50 μM, respectively) and mRNA levels analyzed by qRT-PCR as described in Materials and Methods. Bar represent mean of n=5 experiments +/- SEM. Data are presented as fold change compared to control (no treatment, black dotted line). MT-CO1 mRNA expression levels in treated vs. non treated cells were analyzed by one-way ANOVA (p<0.005; Bonferroni post-test for multiple comparison:* p<0.05; **p<0.005 (D) ROS levels in A549 following exposure to cisplatin and carboplatin. A549 cells were exposed to cisplatin (CDDP) at an IC50 dose (12 µM) or a range of carboplatin (CBCDA) doses and total intracellular ROS levels were measured after 24 h by incubating with H₂DCFDA. ROS levels in treated vs. non treated cells were analyzed by one-way ANOVA (p<0.005; Bonferroni post-test for multiple comparison: *p<0.05, **p<0.01). Data are presented as fold increase over control (no treatment). Bars represent the mean of n=3 independent biological replicates +/- SD.