Myocardial energy balance and metabolism as causes of myocardial ischemia.

The current approach to myocardial ischemia has been influenced by the misconception of a close link between ischemia and coronary atherosclerotic obstructions. Recent guidelines have, however, acknowledged the multifactorial nature of this condition, with an identifiable cause present in less than half of angina patients, and a large fraction with angina of unknown origin. Because of this background, focusing on cardiac energy metabolim offers new opportunities to manage myocardial ischemia even when its cause is unknown.

Chronic testosterone deficiency increases late inward sodium current and promotes triggered activity in ventricular myocytes from aging male mice.

Clinical studies suggest low testosterone levels are associated with cardiac arrhythmias, especially in later life. We investigated whether chronic exposure to low circulating testosterone promoted maladaptive electrical remodeling in ventricular myocytes from aging male mice and determined the role of late inward sodium current (INa,L) in this remodeling. C57BL/6 mice had a gonadectomy (GDX) or sham surgery (1 mo) and were aged to 22-28 mo. Ventricular myocytes were isolated; transmembrane voltage and currents were recorded (37°C). Action potential duration at 70 and 90% repolarization (APD70 and APD90) was prolonged in GDX compared with sham myocytes (APD90, 96.9 ± 3.2 vs. 55.4 ± 2.0 ms; P < 0.001). INa,L was also larger in GDX than sham (-2.4 ± 0.4 vs. -1.2 ± 0.2 pA/pF; P = 0.002). When cells were exposed to the INa,L antagonist ranolazine (10 µM), INa,L declined in GDX cells (-1.9 ± 0.5 vs. -0.4 ± 0.2 pA/pF; P < 0.001) and APD90 was reduced (96.3 ± 14.8 vs. 49.2 ± 9.4 ms; P = 0.001). GDX cells had more triggered activity (early/delayed afterdepolarizations, EADs/DADs) and spontaneous activity than sham. EADs were inhibited by ranolazine in GDX cells. The selective NaV1.8 blocker A-803467 (30 nM) also reduced INa,L, decreased APD and abolished triggered activity in GDX cells. Scn5a (NaV1.5) and Scn10a (NaV1.8) mRNA was increased in GDX ventricles, but only NaV1.8 protein abundance was increased in GDX compared with sham. In vivo studies showed QT prolongation and more arrhythmias in GDX mice. Thus, triggered activity in ventricular myocytes from aging male mice with long-term testosterone deficiency arises from APD prolongation mediated by larger NaV1.8- and NaV1.5-associated currents, which may explain the increase in arrhythmias.NEW & NOTEWORTHY Older men with low testosterone levels are at increased risk of developing cardiac arrhythmias. We found aged mice chronically exposed to low testosterone had more arrhythmias and ventricular myocytes had prolonged repolarization, abnormal electrical activity, larger late sodium currents, and increased expression of NaV1.8 sodium channels. Drugs that inhibit late sodium current or NaV1.8 channels abolished abnormal electrical activity and shortened repolarization. This suggests the late sodium current may be a novel target to treat arrhythmias in older testosterone-deficient men.

The antianginal ranolazine fails to improve glycaemia in obese liver-specific pyruvate dehydrogenase deficient male mice.

AIMS: Recent studies have demonstrated that stimulating pyruvate dehydrogenase (PDH, gene Pdha1), the rate-limiting enzyme of glucose oxidation, can reverse obesity-induced non-alcoholic fatty liver disease (NAFLD), which can be achieved via treatment with the antianginal ranolazine. Accordingly, our aim was to determine whether ranolazine's ability to mitigate obesity-induced NAFLD and hyperglycaemia requires increases in hepatic PDH activity. METHODS: We generated liver-specific PDH-deficient (Pdha1Liver-/- ) mice, which were provided a high-fat diet for 12 weeks to induce obesity. Pdha1Liver-/- mice and their albumin-Cre (AlbCre ) littermates were randomized to treatment with either vehicle control or ranolazine (50 mg/kg) once daily via oral gavage during the final 5 weeks, following which we assessed glucose and pyruvate tolerance. RESULTS: Pdha1Liver-/- mice exhibited no overt phenotypic differences (e.g. adiposity, glucose tolerance) when compared to their AlbCre littermates. Of interest, ranolazine treatment improved glucose tolerance and mildly reduced hepatic triacylglycerol content in obese AlbCre mice but not in obese Pdha1Liver-/- mice. The latter was independent of changes in hepatic mRNA expression of genes involved in regulating lipogenesis. CONCLUSIONS: Liver-specific PDH deficiency is insufficient to promote an NAFLD phenotype. Nonetheless, hepatic PDH activity partially contributes to how the antianginal ranolazine improves glucose tolerance and alleviates hepatic steatosis in obesity.

Ranolazine rescues the heart failure phenotype of PLN-deficient human pluripotent stem cell-derived cardiomyocytes.

Phospholamban (PLN) is a key regulator that controls the function of the sarcoplasmic reticulum (SR) and is required for the regulation of cardiac contractile function. Although PLN-deficient mice demonstrated improved cardiac function, PLN loss in humans can result in dilated cardiomyopathy (DCM) or heart failure (HF). The CRISPR-Cas9 technology was used to create a PLN knockout human induced pluripotent stem cell (hiPSC) line in this study. PLN deletion hiPSCs-CMs had enhanced contractility at day 30, but proceeded to a cardiac failure phenotype at day 60, with decreased contractility, mitochondrial damage, increased ROS production, cellular energy metabolism imbalance, and poor Ca2+ handling. Furthermore, adding ranolazine to PLN knockout hiPSCs-CMs at day 60 can partially restore Ca2+ handling disorders and cellular energy metabolism, alleviating the PLN knockout phenotype of HF, implying that the disorder of intracellular Ca2+ transport and the imbalance of cellular energy metabolism are the primary mechanisms for PLN deficiency pathogenesis.

Ranolazine alleviates contrast-associated acute kidney injury through modulation of calcium independent oxidative stress and apoptosis.

This study investigates the role of ranolazine in contrast-associated acute kidney injury (CA-AKI) and potential mechanisms. For in vivo studies, mouse models of CA-AKI and control mice were treated with ranolazine or vehicle. Blood urea nitrogen (BUN) and serum creatinine were detected by spectrophotometry. Anti-T-cell immunoglobulin and mucin domain 1 (TIM 1) and anti-lipocalin 2 antibody (LCN2) were detected by immunofluorescence. Hemodynamic parameters were detected via invasive blood pressure measurement and renal artery color doppler ultrasound, capillary density was measured by CD31 immunofluorescence, vascular permeability assay was performed by Evans blue dye. The expressions of oxidative stress and apoptotic markers were measured and analyzed by immunofluorescence and western blotting. For in vitro studies, intracellular calcium concentration of HUVECs was measured with Fluo 3-AM under confocal microscopy. Results show that compared with control mice, serum BUN, creatinine, TIM 1 and LCN2 levels were elevated in CA-AKI mice, but this effect was alleviated by ranolazine-pretreatment. Safe doses of ranolazine (less than 64 mg/kg) had no significant effect on overall blood pressure, but substantially improved renal perfusion, reduced contrast-induced microcirculation disturbance, improved renal capillary density and attenuated renal vascular permeability in ranolazine-pretreated CA-AKI mice. Mechanistically, ranolazine markedly down-regulated oxidative stress and apoptosis markers compared to CA-AKI mice. Intracellularly, ranolazine attenuated calcium overload in HUVECs. These results indicate that ranolazine alleviates CA-AKI through modulation of calcium independent oxidative stress and apoptosis.

Ranolazine Improves Glycemic Variability and Endothelial Function in Patients with Diabetes and Chronic Coronary Syndromes: Results from an Experimental Study.

BACKGROUND: Ranolazine is a second-line drug for the management of chronic coronary syndromes (CCS). Glucose-lowering and endothelial effects have also been reported with this agent. However, whether ranolazine may improve short-term glycemic variability (GV), strictly related to the prognosis of patients with type 2 diabetes (T2D), is unknown. Thus, we aimed to explore the effects of adding ranolazine to standard anti-ischemic and glucose-lowering therapy on long- and short-term GV as well as on endothelial function and oxidative stress in patients with T2D and CCS. METHODS: Patients starting ranolazine (n = 16) were evaluated for short-term GV, haemoglobin 1Ac (Hb1Ac) levels, endothelial-dependent flow-mediated vasodilation (FMD), and oxidative stress levels at enrolment and after 3-month follow-up. The same measurements were collected from 16 patients with CCS and T2D that did not receive ranolazine, matched for age, gender, and body mass index. RESULTS: A significant decline in Hb1Ac levels was reported after 3-month ranolazine treatment (mean change -0.60%; 2-way ANOVA p = 0.025). Moreover, among patients receiving ranolazine, short-term GV indexes were significantly improved over time compared with baseline (p = 0.001 for time in range; 2-way ANOVA p = 0.010). Conversely, no significant changes were reported in patients without ranolazine. Finally, greater FMD and lower oxidative stress levels were observed in patients on ranolazine at 3 months. CONCLUSIONS: Ranolazine added to standard anti-ischemic and glucose-lowering therapy demonstrated benefit in improving the glycemic status of patients with T2D and CCS. How this improvement contributes to the overall myocardial benefit of ranolazine requires further studies.

Ranolazine may exert its beneficial effects by increasing myocardial adenosine levels.

We hypothesized that ranolazine-induced adenosine release is responsible for its beneficial effects in ischemic heart disease. Sixteen open-chest anesthetized dogs with noncritical coronary stenosis were studied at rest, during dobutamine stress, and during dobutamine stress with ranolazine. Six additional dogs without stenosis were studied only at rest. Regional myocardial function and perfusion were assessed. Coronary venous blood was drawn. Murine endothelial cells and cardiomyocytes were incubated with ranolazine and adenosine metabolic enzyme inhibitors, and adenosine levels were measured. Cardiomyocytes were also exposed to dobutamine and dobutamine with ranolazine. Modeling was employed to determine whether ranolazine can bind to an enzyme that alters adenosine stores. Ranolazine was associated with increased adenosine levels in the absence (21.7 ± 3.0 vs. 9.4 ± 2.1 ng/mL, P < 0.05) and presence of ischemia (43.1 ± 13.2 vs. 23.4 ± 5.3 ng/mL, P < 0.05). Left ventricular end-systolic wall stress decreased (49.85 ± 4.68 vs. 57.42 ± 3.73 dyn/cm2, P < 0.05) and endocardial-to-epicardial myocardial blood flow ratio tended to normalize (0.89 ± 0.08 vs. 0.76 ± 0.10, P = nonsignificant). Adenosine levels increased in cardiac endothelial cells and cardiomyocytes when incubated with ranolazine that was reversed when cytosolic-5'-nucleotidase (cN-II) was inhibited. Point mutation of cN-II aborted an increase in its specific activity by ranolazine. Similarly, adenosine levels did not increase when cardiomyocytes were incubated with dobutamine. Modeling demonstrated plausible binding of ranolazine to cN-II with a docking energy of -11.7 kcal/mol. We conclude that the anti-adrenergic and cardioprotective effects of ranolazine-induced increase in tissue adenosine levels, likely mediated by increasing cN-II activity, may contribute to its beneficial effects in ischemic heart disease.NEW & NOTEWORTHY Ranolazine is a drug used for treatment of angina pectoris in patients with ischemic heart disease. We discovered a novel mechanism by which this drug may exhibit its beneficial effects. It increases coronary venous levels of adenosine both at rest and during dobutamine-induced myocardial ischemia. Ranolazine also increases adenosine levels in endothelial cells and cardiomyocytes in vitro, by principally increasing activity of the enzyme cytosolic-5'-nucleotidase. Adenosine has well-known myocardial protective and anti-adrenergic properties that may explain, in part, ranolazine's beneficial effect in ischemic heart disease.

New Anti-Anginal Drugs: Ranolazine.

Chronic angina represents a condition that impairs quality of life and is associated with decreased life expectancy in the industrialized countries. Current therapies that reduce angina frequency include old drugs such as nitrates, ß -blockers and calcium antagonists. Several new investigational drugs are being tested for the treatment of chronic angina. This review will focus on ranolazine, a drug approved by the US Food and Drug Administration (FDA) in 2006 for patients with chronic angina who continue to be symptomatic despite optimized therapies. The main molecular mechanism underlying ranolazine-mediated beneficial effects has been identified as inhibition of the late Na+ current during the action potential, which potentially improves oxygen consumption, diastolic dysfunction and coronary blood flow. The aim of this review is to update the evidence for ranolazine treatment in chronic angina and discuss its therapeutic perspectives based on the most recent clinical and experimental studies.