Cisplatinum enhancement of myocardial Mg2+ transport

Anticancer drug-induced cardiac rhythm disorders: Current knowledge and basic underlying mechanisms

Significant advances in cancer treatment have resulted in decreased cancer related mortality for many malignancies with some cancer types now considered chronic diseases. Despite these improvements, there is increasing recognition that many cancer patients or cancer survivors can develop cardiovascular diseases, either due to the cancer itself or as a result of anticancer therapy. Much attention has focused on heart failure; however, other cardiotoxicities, notably cardiac rhythm disorders, can occur without underlying cardiomyopathy. Supraventricular tachycardias occur in cancer patients treated with cytotoxic chemotherapy (anthracyclines, gemcitabine, cisplatin and alkylating-agents) or kinase-inhibitors (KIs) such as ibrutinib. Ventricular arrhythmias, with a subset of them being torsades-de-pointes (TdP) favored by QTc prolongation have been reported: this may be the result of direct hERG-channel inhibition or a more recently-described mechanism of phosphoinositide-3-kinase inhibition. The major anticancer drugs responsible for QTc prolongation in this context are KIs, arsenic trioxide, anthracyclines, histone deacetylase inhibitors, and selective estrogen receptor modulators. Anticancer drug-induced cardiac rhythm disorders remain an underappreciated complication even by experienced clinicians. Moreover, the causal relationship of a particular anticancer drug with cardiac arrhythmia occurrence remains challenging due in part to patient comorbidities and complex treatment regimens. For example, any cancer patient may also be diagnosed with common diseases such as hypertension, diabetes or heart failure which increase an individual's arrhythmia susceptibility. Further, anticancer drugs are generally usually used in combination, increasing the challenge around establishing causation. Thus, arrhythmias appear to be an underappreciated adverse effect of anticancer agents and the incidence, significance and underlying mechanisms are now being investigated.

Cisplatin modulates voltage gated channel currents of dorsal root ganglion neurons of rats

The anticancer drug cis-diammindichloroplatin (CDDP, cisplatin) causes severe side effects like peripheral sensitive neuropathy. The toxicity of CDDP has been linked to changes in intracellular calcium homeostasis ([Ca2+]i). Voltage activated calcium channel currents (ICa(V)) are important for the regulation of [Ca2+]i; therefore, this study was designed to examine the effect of CDDP on ICa(V) in comparison to voltage activated potassium (IK(V)) and sodium (INa(V)) channel currents using the whole cell patch clamp method on dorsal root ganglion neurons of rats. In small neurons (<or=Ø20 microm) CDDP reduced peak and sustained ICa(V) concentration dependently (1-100 microM). The IC50 was 23.9+/-4.5 microM (+/-S.D.) for the peak current with a Hill-coefficient of 0.6+/-0.1 and 38.8+/-6.1 microM for the sustained current (Hill-coefficient: 0.7+/-0.1). IK(V) were reduced by 20.9+/-4.8% (10 microM) and INa(V) were only reduced by 9.2%+/-7.2% (10 microM). ICa(V) of large neurons (>or=Ø25 microm) were less sensitive to CDDP. The peak ICa(V) was reduced by 14.1+/-2.3% and IK(V) by 12.8+/-3.4% (100 microM). The sensitivity of INa(V) in large neurons to CDDP was not different compared to small neurons. We conclude that the reduction of ICa(V) in small cells may be responsible for the neurotoxic side effects CDDP causes in sensory neurons.

Protective effect of labedipinedilol-A, a novel dihydropyridine-type calcium channel blocker, on myocardial apoptosis in ischemia-reperfusion injury

The effects of labedipinedilol-A, a novel dihydropyridine-type calcium channel blocker with alpha-/beta-adrenoceptor blocking activities, on myocardial infarct size, apoptosis and necrosis in the rat after myocardial ischemia/reperfusion (45 min/120 min) were investigated. Ten minutes prior to left coronary artery occlusion, rats were treated with vehicle or labedipinedilol-A (0.25 or 0.5 mg/kg, i.v.). In the vehicle group, myocardial ischemia-reperfusion induced creatine kinase (CK) release and caused cardiomyocyte apoptosis, as evidenced by DNA ladder formation and terminal dUTP deoxynucleotidyltransferase nick end-labeling (TUNEL) staining. Treatment with labedipinedilol-A (0.25 or 0.5 mg/kg) reduced infarct size significantly compared to vehicle group (18.75+/-0.65% and 8.27+/-0.29% vs. 41.72+/-0.73%, P<0.01). Labedipinedilol-A also reduced the CK, CK-MB, lactate dehydrogenase (LDH) and troponin T levels in blood. In addition, labedipinedilol-A (0.5 mg/kg) significantly decreased TUNEL positive cells from 19.21+/-0.52% to 9.73+/-0.81% (P<0.01), which is consistent with absence of DNA ladders in the labedipinedilol-A group. Moreover, labedipinedilol-A pretreatment also decreased calcium content in ischemic-reperfused myocardial tissue. In conclusion, these results demonstrate that labedipindielol-A, through reduction of calcium overload and apoptosis, exerts anti-infarct effect during myocardial ischemia-reperfusion and would be useful clinically in the prevention of acute myocardial infarction.

Anti-apoptotic effect of benidipine, a long-lasting vasodilating calcium antagonist, in ischaemic/reperfused myocardial cells

1. Ischaemia/reperfusion causes intracellular calcium overloading in cardiac cells. Administration of calcium antagonists reduces myocardial infarct size. Recent in vitro studies have demonstrated that calcium plays a critical role in the signal transduction pathway leading to apoptosis. However, whether or not calcium antagonists may reduce myocardial apoptosis induced by ischaemia-reperfusion, and thus decrease myocardial infarction, has not been directly investigated. 2. The present study investigated the effects of benidipine, an L-type calcium channel blocker, on myocardial infarct size, apoptosis, necrosis and cardiac functional recovery in rabbits subjected to myocardial ischaemia/reperfusion (MI/R, 45 min/240 min). Ten minutes prior to coronary occlusion, rabbits were treated with vehicle or benidipine (10 microg x kg(-1) or 3 microg x kg(-1), i.v.). 3. In the vehicle-treated group, MI/R caused cardiomyocyte apoptosis as evidenced by DNA ladder formation and TUNEL positive nuclear staining (12.2+/-1.1%). Treatment with 10 microg x kg(-1) benidipine lowered blood pressure, decreased myocardial apoptosis (6.2+/-0.8%, P<0.01 vs vehicle) and necrosis, reduced infarct size (20+/-2.3% vs 49+/-2.6%, P<0.01), and improved cardiac functional recovery after reperfusion. Administering benidipine at 3 microg x kg(-1), a dose at which no haemodynamic effect was observed, also exerted significant anti-apoptosis effects, which were not significantly different from those observed with higher dose benidipine treatment. However, treatment with this low dose benidipine failed to reduce myocardial necrosis. 4. These results demonstrate that benidipine, a calcium antagonist, exerts significant anti-apoptosis effects, which are independent of haemodynamic changes. Administration of benidipine at a higher dose produced favourable haemodynamic effects and provided additional protection against myocardial necrotic injury and further improved cardiac functional recovery.