Glutamate protects against Ca2+ paradox‐induced injury and inhibits calpain activity in isolated rat hearts

This study determined the effects of glutamate on the Ca²⁺ paradoxical heart, which is a model for Ca²⁺ overload‐induced injury during myocardial ischaemia and reperfusion, and evaluated its effect on a known mediator of injury, calpain. An isolated rat heart was retrogradely perfused in a Langendorff apparatus. Ca²⁺ paradox was elicited via perfusion with a Ca²⁺‐free Krebs‐Henseleit (KH) solution for 3 minutes followed by Ca²⁺‐containing normal KH solution for 30 minutes. The Ca²⁺ paradoxical heart exhibited almost no viable tissue on triphenyltetrazolium chloride staining and markedly increased LDH release, caspase‐3 activity, cytosolic cytochrome c content, and apoptotic index. These hearts also displayed significantly increased LVEDP and a disappearance of LVDP. Glutamate (5 and 20 mmol/L) significantly alleviated Ca²⁺ paradox‐induced injury. In contrast, 20 mmol/L mannitol had no effect on Ca²⁺ paradox. Ca²⁺ paradox significantly increased the extent of the translocation of μ‐calpain to the sarcolemmal membrane and the proteolysis of α‐fodrin, which suggests calpain activation. Glutamate also blocked these effects. A non‐selective inhibitor of glutamate transporters, dl ‐TBOA (10 μmol/L), had no effect on control hearts, but it reversed glutamate‐induced cardioprotection and reduction in calpain activity. Glutamate treatment significantly increased intracellular glutamate content in the Ca²⁺ paradoxical heart, which was also blocked by dl ‐TBOA. We conclude that glutamate protects the heart against Ca²⁺ overload‐induced injury via glutamate transporters, and the inhibition of calpain activity is involved in this process.     

Luteoloside attenuates anoxia/reoxygenation‐induced cardiomyocytes injury via mitochondrial pathway mediated by 14‐3‐3η protein

Ischemia/reperfusion (I/R) injury is the major cause of acute cardiovascular disease worldwide. 14‐3‐3η protein has been demonstrated to protect myocardium against I/R injury. Luteoloside (Lut), a flavonoid found in many Chinese herbs, exerts myocardial protection effects. However, the mechanism remains unclear. We hypothesize that the cardioprotective role of Lut is exerted by regulating the 14‐3‐3η signal pathway. To investigate our hypothesis, an in vitro I/R model was generated in H9C2 cardiomyocytes by anoxia/reoxygenation (A/R) treatment. The effects of Lut on cardiomyocytes with A/R injury were assessed by determining the cell viability, lactate dehydrogenase levels, intracellular reactive oxygen species levels, mitochondrial permeability transition pores (mPTP) openness, caspase‐3 activity, and apoptosis rate. The effects on protein expression were tested using western blot analysis. Lut attenuated A/R‐induced injury to cardiomyocytes by increasing the expression of 14‐3‐3η protein and cell viability; decreasing levels of lactate dehydrogenase, reactive oxygen species, mPTP openness, caspase‐3 activity, and low apoptosis rate were observed. However, the cardioprotective effects of Lut were blocked by AD14‐3‐3ηRNAi, an adenovirus knocking down the intracellular 14‐3‐3η expression. In conclusion, to our knowledge, this is the first study to demonstrate that Lut protected cardiomyocytes from A/R‐induced injury via the regulation of 14‐3‐3η signaling pathway.     

Diazoxide acts more as a PKC-epsilon activator, and indirectly activates the mitochondrial K(ATP) channel conferring cardioprotection against hypoxic injury

BACKGROUND AND PURPOSE: Diazoxide, a well-known opener of the mitochondrial ATP-sensitive potassium (mitoK(ATP)) channel, has been demonstrated to exert cardioprotective effect against ischemic injury through the mitoK(ATP) channel and protein kinase C (PKC). We aimed to clarify the role of PKC isoforms and the relationship between the PKC isoforms and the mitoK(ATP) channel in diazoxide-induced cardioprotection. EXPERIMENTAL APPROACH: In H9c2 cells and neonatal rat cardiomyocytes, PKC-epsilon activation was examined by Western blotting and kinase assay. Flavoprotein fluorescence, mitochondrial Ca(2+) and mitochondrial membrane potential were measured by confocal microscopy. Cell death was determined by TUNEL assay. KEY RESULTS: Diazoxide (100 microM) induced translocation of PKC-epsilon from the cytosolic to the mitochondrial fraction. Specific blockade of PKC-epsilon by either epsilonV1-2 or dominant negative mutant PKC-epsilon (PKC-epsilon KR) abolished the anti-apoptotic effect of diazoxide. Diazoxide-induced flavoprotein oxidation was inhibited by either epsilonV1-2 or PKC-epsilon KR transfection. Treatment with 5-hydroxydecanoate (5-HD) did not affect translocation and activation of PKC-epsilon induced by diazoxide. Transfection with wild type PKC-epsilon mimicked the flavoprotein-oxidizing effect of diazoxide, and this effect was completely blocked by epsilonV1-2 or 5-HD. Diazoxide prevented the increase in mitochondrial Ca(2+), mitochondrial depolarization and cytochrome c release induced by hypoxia and all these effects of diazoxide were blocked by epsilonV1-2 or 5-HD. CONCLUSIONS AND IMPLICATIONS: Diazoxide induced isoform-specific translocation of PKC-epsilon as an upstream signaling molecule for the mitoK(ATP) channel, rendering cardiomyocytes resistant to hypoxic injury through inhibition of the mitochondrial death pathway.     

Early cardiotoxicity of the CHOP regimen in aggressive non-Hodgkin's lymphoma.

BACKGROUND: To determine the incidence of early cardiotoxicity induced by the CHOP regimen in patients with aggressive non-Hodgkin's lymphoma (NHL) and to identify associated risk factors. PATIENTS AND METHODS: A retrospective analysis included 135 consecutive patients who had been treated with the CHOP (cyclophosphamide, doxorubicin, vincristin, prednisone) regimen as first-line therapy between 1994 and 2000. The cardiac evaluation was based on a determination of the resting left ventricular ejection function (LVEF) by gated blood-pool imaging. Cardiotoxicity was defined as a significant decrease in LVEF or clinical evidence of congestive heart failure (CHF). RESULTS: Twenty-seven (20%) patients developed a cardiac event within 1 year of treatment. Among these, 14 patients had clinical signs of CHF. Three patients died suddenly from presumed cardiac causes. In multivariate analysis, a cumulative dose of doxorubicin >200 mg/m(2) [odds ratio (OR) = 4.2, P = 0.005)] and age over 50 years (OR = 2.9, P = 0.03) appeared to be significant risk factors. CONCLUSION: Early clinical and subclinical cardiotoxicity was frequent in patients receiving the CHOP regimen. The threshold of the cumulative dose of doxorubicin appeared to be low: at doses >200 mg/m(2), 27% of patients had cardiac events. Elderly patients appeared to be at higher risk. The development of cardioprotective strategies or alternative treatments are mandatory for aggressive NHL patients.     

Prospects for Creation of Cardioprotective and Antiarrhythmic Drugs Based on Opioid Receptor Agonists

It has now been demonstrated that the μ, δ₁, δ₂, and κ₁ opioid receptor (OR) agonists represent the most promising group of opioids for the creation of drugs enhancing cardiac tolerance to the detrimental effects of ischemia/reperfusion (I/R). Opioids are able to prevent necrosis and apoptosis of cardiomyocytes during I/R and improve cardiac contractility in the reperfusion period. The OR agonists exert an infarct‐reducing effect with prophylactic administration and prevent reperfusion‐induced cardiomyocyte death when ischemic injury of heart has already occurred; that is, opioids can mimic preconditioning and postconditioning phenomena. Furthermore, opioids are also effective in preventing ischemia‐induced arrhythmias.     

New Aspects for the Treatment of Cardiac Diseases Based on the Diversity of Functional Controls on Cardiac Muscles: Mitochondrial Ion Channels and Cardioprotection

Mitochondrial ATP-sensitive K⁺ (mitoK_ATP) and Ca²⁺-activated K⁺ (mitoK_Ca) channels exist in cardiac myocytes, and they play key roles in cardioprotection. We have recently reported that K⁺ influx through mitoK_ATP or mitoK_Ca channels occurs independently of each other and confers cardioprotection in a similar manner. Activation of mitoK_ATP channel is augmented by protein kinase C (PKC), whereas mitoK_Ca channel is activated by protein kinase A (PKA). However, phosphatidylinositol 3-kinase (PI3-K) is linked to neither mitoK_ATP nor mitoK_Ca channels. We have demonstrated that bioactive substances modulate the opening of mitoK_ATP channels via a PKC-dependent pathway or opening of mitoK_Ca channels via a PKA-dependent pathway and thereby protecting the heart from ischemia/reperfusion injury. Several endogenous substances such as adenosine and bradykinin can reduce infarct size by activation of mitoK_ATP channels in a PKC-dependent manner. Adrenomedullin, a potent vasodilator peptide, potentiates the opening of mitoK_Ca channels by PKA activation. Treatment with adrenomedullin prior to ischemia results in the reduction of infarct size via a PKA-mediated activation of mitoK_Ca channels. Thus, some endogenous substances confer cardioprotection via PKA- or PKC-mediated activation of mitoK_ATP or mitoK_Ca channels.     

Cardioprotective activity of alcoholic extract of Tinospora cordifolia （Willd.） Miers in calcium chloride-induced cardiac arrhythmia in rats

The present study investigated the antiarrhythmic activity of alcoholic extract of Tinospora cordifolia (T.cordifolia) in CaCl 2 induced arrhythmia.CaCl 2 (25 mg/kg) was administered by intravenous infusion (iv) to produce arrhythmia in rats.The animals were then treated with T.cordifolia extract (150,250,and 450 mg/kg) and verapamil (5 mg/kg,iv).Lead II electrocardiogram was monitored.Plasma calcium,sodium and potassium levels were measured.In CaCl 2 induced arrhythmia,heart rate was decreased by 41.10%,T....     

Sevoflurane-induced cardioprotection depends on PKC-alpha activation via production of reactive oxygen species

BACKGROUND: We previously demonstrated the involvement of the Ca2+-independent protein kinase C-delta (PKC-delta) isoform in sevoflurane-induced cardioprotection against ischaemia and reperfusion (I/R) injury. Since sevoflurane is known to modulate myocardial Ca2+-handling directly, in this study we investigated the role of the Ca2+-dependent PKC-alpha isoform in sevoflurane-induced cardioprotective signalling in relation to reactive oxygen species (ROS), adenosine triphosphate-sensitive mitochondrial K+ (mitoK+(ATP)) channels, and PKC-delta. METHODS: Preconditioned (15 min 3.8 vol% sevoflurane) isolated rat right ventricular trabeculae were subjected to I/R, consisting of 40 min superfusion with hypoxic, glucose-free buffer, followed by normoxic glucose-containing buffer for 60 min. After reperfusion, contractile recovery was expressed as percentage of force development before I/R. The role of PKC-alpha, ROS, mitoK+(ATP) channels, and PKC-delta was established using the following pharmacological inhibitors: Go6976 (GO; 50 nM), n-(2-mercaptopropionyl)-glycine (MPG; 300 microM), 5-hydroxydecanoic acid sodium (5HD; 100 microM), and rottlerin (ROT; 1 microM). RESULTS: Preconditioning of trabeculae with sevoflurane improved contractile recovery after I/R [65 (3)% (I/R + SEVO) vs 47 (3)% (I/R); n = 8; P < 0.05]. This cardioprotective effect was attenuated in trabeculae treated with GO [42 (4)% (I/R + SEVO + GO); P > 0.05 vs (I/R)]. In sevoflurane-treated trabeculae, PKC-alpha translocated towards mitochondria, as shown by immunofluorescent co-localization analysis. GO and MPG, but not 5HD or ROT, abolished this translocation. CONCLUSIONS: Sevoflurane improves post-ischaemic contractile recovery via activation of PKC-alpha. ROS production, but not opening of mitoK+(ATP) channels, precedes PKC-alpha translocation towards mitochondria. This study shows the involvement of Ca2+-dependent PKC-alpha in addition to the well-established role of Ca2+-independent PKC isoforms in sevoflurane-induced cardioprotection.     

Cardiotoxicity in children with cancer treated with anthracyclines: A position statement on dexrazoxane

Cardiovascular disease is the leading cause of non-malignant morbidity and mortality in childhood cancer survivors (CCSs). Anthracyclines are included in many treatment regimens for paediatric cancer, but unfortunately, these compounds are cardiotoxic. One in 10 CCSs who has received an anthracycline will develop a symptomatic cardiac event over time. Given the crucial need to mitigate anthracycline-related cardiotoxicity (ARC), the authors critically examined published data to identify effective cardioprotective strategies. Based on their expert analysis of contemporary literature data, it was concluded that consideration should be given for routine use of dexrazoxane in children with cancer who are at risk of ARC.