In the last decades, the number of cancer survivors has increased considerably due to the huge efficacy of anticancer therapies. Nevertheless, the side effects in these patients are still a major concern, namely in the cardiac tissue[1,2]. The mechanisms underlying the cardiotoxicity of doxorubicin (DOX) and mitoxantrone (MTX) are not completely understood, although they seem to disturb the mitochondrial dynamics and lead to oxidative stress. Our goal was to study the effects of DOX and MTX in the molecular mechanisms harbored in the heart of adult male CD-1 mice (3 months). A total of 6 intraperitoneal administrations were given to the animals, twice a week for three weeks: control mice received saline solution and DOX- and MTX-treated received a total cumulative dose of 9 mg/kg and 6 mg/kg, respectively. During the entire experimental period, animal welfare was assessed daily. Mice were euthanized one week after the last administration. The experiments were performed with the approval of the Portuguese National Authority for Animal Health (reference number 0421/000/000/2016) and of the ORBEA of ICBAS-UP (project number 140/2015). After excising, aliquots of whole cardiac tissue and corresponding enriched mitochondrial fractions were prepared and analyzed by immunoblot and enzymatic techniques. Additionally, enriched mitochondrial fractions were studied by mass spectrometry-based proteomics (GeLC-MS/MS). From this analysis 693 different proteins were identified, assigned to the biological processes “small molecule metabolic process”, “oxidation-reduction process” and “carboxylic acid metabolic process” according to String. The distribution analysis of the mitochondrial proteome data (using partial least squares-discriminant analysis; PLS-DA) showed clustering among the conditions. Indeed, MTX treatment presented less similarities with control. Comparative analysis of the mitochondrial proteomes revealed upregulation of fatty acid metabolism induced by DOX administration and upregulation of antioxidant activity in response of MTX treatment. Moreover, DOX and MTX administration promoted a decrease on mitochondrial density, given by citrate synthase activity. Concomitantly, metabolic adaptations were noticed, more evident in the heart of DOX treated mice. Indeed, increased glyceraldehyde-3-phosphate dehydrogenase-to-ATP and electron transfer flavoprotein dehydrogenase-to-ATP ratios were observed. Thus, more than differences in cardiac mitochondrial proteome, these drugs seem to decrease this organelle density.
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This work was supported by national funds by Fundação para a Ciência e a Tecnologia (FCT, Portugal) and co-financed by FEDER and COMPETE for the project “PTDC/DTP-FTO/1489/2014 – POCI-01-0145-FEDER-016537” and the QOPNA research unit (FCT UID/QUI/00062/2019). SRB, ARM and VMC acknowledge FCT for their grants (SFRH/BD/138202/2018, SFRH/BD/129359/2017 and SFRH/BPD/110001/2015) and VMC’s grant is funded by FCT, I.P., under the Norma Transitória – DL57/2016/CP1334/CT0006.