Cisplatin compromises myocardial contractile function and mitochondrial ultrastructure: Role of endoplasmic reticulum stress Heng Ma,* † Kyla R Jones,* Rui Guo,* Peisheng Xu,* Youqing Shen ‡ and Jun Ren* † *Division of Pharmaceutical Science, Center for Cardiovascular Research and Alternative Medicine, ‡ Department of Chemical and Petroleum Engineering, University of Wyoming, Laramie, WY, USA and † Department of Physiology, Fourth Military Medical University, Xi’an, China SUMMARY 1. Cisplatin is a potent chemotherapeutic agent with broad- spectrum antineoplastic activity against various types of tumours. However, a major factor limiting treatment with cis- platin is its acute and cumulative cardiotoxicity. The aim of the present study was to explore the effect of cisplatin on myo- cardial contractile function and the possible underlying cellular mechanisms. 2. C57 mice were treated with cisplatin (10 mg / kg per day, i.v.) or vehicle (0.9% NaCl) for 1 week and myocardial function was assessed using the Langendorff and cardiomyocyte edge- detection systems. Transmission electron microscopy, mitochon- drial membrane potential, indices of endoplasmic reticulum (ER) stress and caspase 3 activity were evaluated. 3. Cisplatin-treated mice developed myocardial contractile dysfunction, as evidenced by a reduction in left ventricular devel- oped pressure (LVDP) and the first derivative of LVDP (+ / )dP / dt). Cisplatin treatment significantly prolonged time to 90% relengthening, depressed peak shortening, maximal velo- city of shortening / relengthening (+ / )dL / dt) and augmented the frequency-elicited depression in peak shortening. The JC-1 fluorescent assay demonstrated that cispatin-induced cardiac dysfunction was associated with mitochondrial membrane depo- larization. Transmission electron microscopy revealed that cis- platin induces ultrastructural abnormalities of the mitochondria. Following cisplatin treatment, cardiomyocytes show activation of the ER stress response, increased caspase 3 activity and increased terminal deoxyribonucleotidyl transferase-mediated dUTP– digoxigenin nick end-labelling (TUNEL) staining. 4. The data indicate that cisplatin is cardiotoxic and may lead to left ventricular dysfunction and depressed cardiomyocyte con- traction associated with mitochondrial abnormalities, enhanced ER stress and apoptosis. This work should shed some light on the management of cisplatin-induced cardiac injury. Key words: cardiotoxicity, cisplatin, endoplasmic reticulum stress, mitochondrial abnormalities. INTRODUCTION Cisplatin is a potent chemotherapeutic agent with broad-spectrum antineoplastic activity against various types of tumours. 1 Cisplatin treatment results in remissions of both adult and paediatric malignan- cies, including of the lung, head and neck, 2 and especially those of the genito-urinary system. 3,4 Several clinical trials, as well as in vitro models, have demonstrated a steep dose–response relationship for cisplatin in a variety of tumour types, but numerous toxic side-effects have been reported, limiting its use. Some of the reported side-effects include bilateral high-frequency hearing loss 5 and nephrotoxicity. 6 A major factor limiting cisplatin treatment is concern regarding its acute and cumulative cardiotoxicity. 7,8 Clinical reports regarding acute cis- platin treatment have identified myocardial infarction and severe ven- tricular arrhythmias in young patients. 9,10 Those studies suggested that the use of cisplatin can be a risk factor for coronary heart disease. Cardiotoxicity remains a major problem because of a high correlation between the degree of heart injury and the dose of cisplatin used. 7 The mechanisms underlying the antitumour effects of cisplatin are relatively well understood; however, the cellular and molecular mechanisms involved in the toxic side-effects of cisplatin in the heart remain unknown. As one of the most energy demanding tissues in the body, the heart is almost completely dependent upon oxidative phosphorylation to supply the large amount of ATP required for contraction and relaxa- tion. 11 The mitochondria are important for these metabolic processes. These vital organelles generate over 90% of the cellular ATP via oxi- dative phosphorylation, using energy derived from oxidation in the respiratory chain. 12 This process is driven by the consumption of molecular oxygen. Thus, because of their critical role in cell survival, mitochondria serve as targets for cellular toxins and chemotherapeu- tic agents. 13 Previous studies indicated that the mitochondria are also likely to be a major target for cisplatin in cancer cells. 14 Cisplatin binding results in a significant decrease in the mitochondrial function of melanoma cells 15 and changes in mitochondrial function have been implicated in cancer cell resistance to chemotherapeutic agents. 16 Determining whether the mitochondria are the primary tar- gets of cisplatin chemotherapy is important for an understanding of the mechanism underlying the cardiotoxic action of cisplatin. How- ever, the effect of cisplatin on myocardial mitochondrial function remains unclear and warrants further investigation. The endoplasmic reticulum (ER) stress response (also known as the unfolded protein response) is known to be closely associated with mitochondrial func- tion and contributes to cardiac contractile dysfunction, 17 yet there is little if any evidence that ER stress mediates the toxic effects of Correspondence: Dr Heng Ma, Division of Pharmaceutical Science, School of Pharmacy, Department 3375, University of Wyoming, 1000 E University Ave, Laramie, WY 82071, USA. Email: hma2@uwyo.edu Received 23 September 2009; revision 25 October 2009; accepted 26 October 2009. Ó 2010 The Authors Journal compilation Ó 2010 Blackwell Publishing Asia Pty Ltd Clinical and Experimental Pharmacology and Physiology (2010) 37, 460–465 doi: 10.1111/j.1440-1681.2009.05323.x