Calcium channel blockade limits cardiac remodeling and improves cardiac function in myocardial infarction-induced heart failure in rats

Development of the cardioprotective drugs class based on pathophysiology of myocardial infarction: A comprehensive review

The cardiovascular system is mainly responsible for the transport of substances necessary to cellular metabolism. However, for the good performance of this function, there is need for adequate control of blood pressure levels of tissue perfusion and systemic arterial. Acute myocardial infarction is one of the complications of the cardiovascular system, that most affects the population around the world. This condition can be defined as a disease generated by an imbalance of oxygen concentrations used in cardiovascular metabolism, this change usually occurs because coronary occlusion, which prevents myocardial blood flow. The diagnosis is based on the set of clinical and laboratory investigations, which are in the release of cardiac enzyme biomarkers, cardiovascular and hemodynamic changes and cardiac accommodations. The treatment consists in the use of concomitant cardiovascular drugs, such as: antihypertensive, antiplatelet and hypolipidemic. Despite improvements in clinical and pharmacological management, acute myocardial infarction remains the leading cause of death worldwide. This finding encourages the scientific research of new drugs for the treatment of myocardial infarction or supporting therapies aimed at reducing the levels of deaths and comorbities generated by cardiovascular diseases.

Acylated ghrelin protection inhibits apoptosis in the remote myocardium post-myocardial infarction by inhibiting calcineurin and activating ARC

This study investigated if acylated ghrelin (AG) could inhibit myocardial infarction (MI)-induced apoptosis in the left ventricles (LV) of male rats and tested if this protection involves modulating ARC anti-apoptotic protein. Rats (n = 12/group) were assigned as a sham-operated, a sham + AG (100 µg/kg, 2x/d, S.C.), MI, and MI + AG. With no antioxidant activity or expression of FAS, AG inhibited caspase-3, 8, and 9 and decreased cytosolic/mitochondrial levels of cytochrome-c, Bax, Bad, and Bad-BCL-2 complex in the LVs of the sham-operated and MI-treated rats. Concomitantly, AG preserved the mitochondria structure, decreased mtPTP, and enhanced state-3 respiration in the LVs of both treated groups. These effects were associated with increased mitochondrial levels of ARC and a reduction in the activity of calcineurin. Overall, AG suppresses MI-induced ventricular apoptosis by inhibition of calcineurin, activation of ARC, and preserving mitochondria integrity.

Fibroblasts under pressure: cardiac fibroblast responses to hypertension and antihypertensive therapies

Approximately 50% of Americans have hypertension, which significantly increases the risk of heart failure. In response to increased peripheral resistance in hypertension, intensified mechanical stretch in the myocardium induces cardiomyocyte hypertrophy and fibroblast activation to withstand increased pressure overload. This changes the structure and function of the heart, leading to pathological cardiac remodeling and eventual progression to heart failure. In the presence of hypertensive stimuli, cardiac fibroblasts activate and differentiate to myofibroblast phenotype capable of enhanced extracellular matrix secretion in coordination with other cell types, mainly cardiomyocytes. Both systemic and local renin-angiotensin-aldosterone system activation lead to increased angiotensin II stimulation of fibroblasts. Angiotensin II directly activates fibrotic signaling such as transforming growth factor β/SMAD and mitogen-activated protein kinase (MAPK) signaling to produce extracellular matrix comprised of collagens and matricellular proteins. With the advent of single-cell RNA sequencing techniques, heterogeneity in fibroblast populations has been identified in the left ventricle in models of hypertension and pressure overload. The various clusters of fibroblasts reveal a range of phenotypes and activation states. Select antihypertensive therapies have been shown to be effective in limiting fibrosis, with some having direct actions on cardiac fibroblasts. The present review focuses on the fibroblast-specific changes that occur in response to hypertension and pressure overload, the knowledge gained from single-cell analyses, and the effect of antihypertensive therapies. Understanding the dynamics of hypertensive fibroblast populations and their similarities and differences by sex is crucial for the advent of new targets and personalized medicine.

Activated fibroblasts in cardiac and cancer fibrosis: An overview of analogies and new potential therapeutic options

Heart disease and cancer are two major causes of morbidity and mortality in the industrialized countries, and their increasingly recognized connections are shifting the focus from single disease studies to an interdisciplinary approach. Fibroblast-mediated intercellular crosstalk is critically involved in the evolution of both pathologies. In healthy myocardium and in non-cancerous conditions, resident fibroblasts are the main cell source for synthesis of the extracellular matrix (ECM) and important sentinels of tissue integrity. In the setting of myocardial disease or cancer, quiescent fibroblasts activate, respectively, into myofibroblasts (myoFbs) and cancer-associated fibroblasts (CAFs), characterized by increased production of contractile proteins, and by a highly proliferative and secretory phenotype. Although the initial activation of myoFbs/CAFs is an adaptive process to repair the damaged tissue, massive deposition of ECM proteins leads to maladaptive cardiac or cancer fibrosis, a recognized marker of adverse outcome. A better understanding of the key mechanisms orchestrating fibroblast hyperactivity may help developing innovative therapeutic options to restrain myocardial or tumor stiffness and improve patient prognosis. Albeit still unappreciated, the dynamic transition of myocardial and tumor fibroblasts into myoFbs and CAFs shares several common triggers and signaling pathways relevant to TGF-β dependent cascade, metabolic reprogramming, mechanotransduction, secretory properties, and epigenetic regulation, which might lay the foundation for future antifibrotic intervention. Therefore, the aim of this review is to highlight emerging analogies in the molecular signature underlying myoFbs and CAFs activation with the purpose of identifying novel prognostic/diagnostic biomarkers, and to elucidate the potential of drug repositioning strategies to mitigate cardiac/cancer fibrosis.

Targeting Myocardial Fibrosis—A Magic Pill in Cardiovascular Medicine?

Fibrosis, characterized by an excessive accumulation of extracellular matrix, has long been seen as an adaptive process that contributes to tissue healing and regeneration. More recently, however, cardiac fibrosis has been shown to be a central element in many cardiovascular diseases (CVDs), contributing to the alteration of cardiac electrical and mechanical functions in a wide range of clinical settings. This paper aims to provide a comprehensive review of cardiac fibrosis, with a focus on the main pathophysiological pathways involved in its onset and progression, its role in various cardiovascular conditions, and on the potential of currently available and emerging therapeutic strategies to counteract the development and/or progression of fibrosis in CVDs. We also emphasize a number of questions that remain to be answered, and we identify hotspots for future research.

Calcium inhibitor inhibits high glucose‑induced hypertrophy of H9C2 cells

The aim of the present study was to explore whether the hypertrophy of H9C2 cardiomyocytes was induced by high glucose, to investigate whether the calcium channel inhibitor (Norvasc) could inhibit this process and to clarify the possible signaling pathways. The morphology of H9C2 cells was observed under an optical microscope, and the cell surface area was measured by Image Pro Plus 6.1 software. Furthermore, fluorescence spectrophotometry was used to detect intracellular calcium concentration ([Ca²⁺]i). ELISA was performed to detect calcineurin (CaN) activity; reverse transcription-quantitative PCR and western blotting were performed to detect the mRNA and protein expression levels of CaN Aβ subunit (CnAβ), nuclear factor of activated T cells 3 (NFAT3) and β type myosin heavy chain (β-MHC). Cell size was increased with the increase in glucose concentration of culture medium at 48 and 72 h, respectively, and decreased with the addition of Norvasc compared with those without Norvasc (P<0.05). There was no significant difference in cell size with the addition of Norvasc compared with cells cultured with 5 mM glucose (P>0.05). The average [Ca²⁺]i activity of single cells in the 48- and 72-h culture groups treated with 50 mM glucose was significantly higher than cells treated with 5 mM glucose (P<0.05); and the fluorescent value of average [Ca²⁺]i activity of single cells was lower, following the addition of Norvasc than that without Norvasc (P<0.05). CaN activity in the 48- and 72-h culture group treated with 50 mM glucose was markedly higher than that treated with 5 mM glucose, and the activity of CaN notably decreased with the addition of Norvasc compared with those without Norvasc. The mRNA and protein expression levels of CnAβ, NFAT3 and β-MHC in the 48- and 72-h culture groups treated with 50 mM glucose were all significantly higher than those treated with 5 mM glucose (P<0.05). The mRNA and protein expression of CnAβ, NFAT3 and β-MHC cultured with 50 mM glucose were significantly decreased following the addition of Norvasc (P<0.05). Thus, the calcium channel inhibitor Norvasc may inhibit high glucose-induced hypertrophy of H9C2 cardiomyocytes by inhibiting the Ca²⁺-CaN-NFAT3 signaling pathway.

Deficit of resolution receptor magnifies inflammatory leukocyte directed cardiorenal and endothelial dysfunction with signs of cardiomyopathy of obesity

Chronic unresolved inflammation is the primary determinant of cardiovascular disease. Precise mechanisms that define the genesis of unresolved inflammation in heart failure with preserved ejection fraction (HFpEF) are of interest due to the obesity epidemic. To examine the obesity phenotype and its direct/indirect consequences, multiple approaches were employed using the lipoxin receptor (abbreviated as ALX) dysfunction mouse model. Indirect calorimetry analyses revealed that the deletion of ALX dysregulated energy metabolism driving toward age-related obesity. Heart function data suggest that obesity-prone ALX deficient mice had impaired myocardium strain. Comprehensive measurement of chemokines, extracellular matrix, and arrhythmogenic arrays confirmed the dysregulation of multiple ion channels gene expression with amplified inflammatory chemokines and cytokines response at the age of 4 months compared with WT counterparts. Quantitative analyses of leukocytes demonstrated an increase of proinflammatory Ly6C^hi CCR2⁺ macrophages in the spleen and heart at a steady-state resulting in an inflamed splenocardiac axis. Signs of subtle inflammation were marked with cardiorenal, endothelial defects with decreased CD31 and eNOS and an increased iNOS and COX2 expression. Thus, ALX receptor deficiency serves as an experimental model that defines multiple cellular and molecular mechanisms in HFpEF that could be a target for the development of HFpEF therapy in cardiovascular medicine.

Comparison of effects of L/N-type and L-type calcium channel blockers on post-infarct cardiac remodelling in spontaneously hypertensive rats

Hypertension and coronary events are becoming more prevalent in aging societies, and myocardial infarction usually occurs in calcium channel blocker (CCB)-treated hypertensive patients. We herein compared the effects of cilnidipine, an L/N-type CCB and amlodipine, an L-type CCB, on post-infarct left ventricular (LV) remodelling in spontaneously hypertensive rats (SHRs). Male SHRs were subjected to 30 minutes of left coronary artery occlusion followed by reperfusion (MI group). The administration of cilnidipine (10 mg/kg/d; MI + Cil group) or amlodipine (10 mg/kg/d; MI + Aml group) was initiated one week before surgery and continued for five weeks. Both CCBs decreased blood pressure. Four weeks after surgery, cilnidipine, but not amlodipine, attenuated LV dilatation, fractional shortening impairments, end-diastolic pressure elevations, and tau elongation. In the non-infarct region, myocyte hypertrophy and brain natriuretic peptide (BNP) mRNA levels were similarly attenuated by both CCBs. On the other hand, interstitial fibrosis, the mRNA expression of collagen type III and transforming growth factor (TGF) β and immunohistological TGF β protein expression in the non-infarct region were reduced more in the MI + Cil group than in the MI + Aml group. Additionally, elevated angiotensin-converting enzyme activity and interstitial noradrenaline concentrations in the non-infarct region were reduced by cilnidipine. These results suggest that cilnidipine reduced cardiac noradrenaline concentrations and inhibited the renin-angiotensin system, which attenuated post-infarct remodelling more than amlodipine in hypertensive rats.

Cardioprotective effects induced by hydroalcoholic extract of leaves of Alpinia zerumbet on myocardial infarction in rats

ETHNOPHARMACOLOGY RELEVANCE

The leaves of Alpinia zerumbet is used in folk medicine in Brazil to treat hypertension. However, the cardioprotective effect of this plant has not been studied yet.

AIM OF THIS STUDY

To evaluate the cardioprotective effects of the hydroalcoholic extract of the leaves of Alpinia zerumbet (AZE) against isoproterenol (ISO)-induced myocardial infarction in rats.

MATERIAL AND METHODS

Rats were pretreated orally with AZE (300 mg/kg) for 30 days prior to ISO-induced myocardial infarction. The rats were sacrificed and hearts were collected and homogenized for biochemical analysis. At the end of the experiment, cardiac marker enzyme levels, histological and morphometric parameters, and hemodynamic measurements were assessed. Phytochemical compounds were verified by gas chromatography-mass spectrometry (GC-MS).

RESULTS

Rats administered with ISO showed a significant increase in cardiac marker enzymes, i.e., in creatine kinase-NAC (CK-NAC) and CK-MB. Triphenyltetrazolium chloride (TTC) staining exhibited an increase in infarct areas. In the animals treated with ISO induced a significant increase in heart rate. Pretreatment with AZE significantly inhibited these effects of ISO. Moreover, biochemical findings were supported by histopathological observations. The GC-MS analyses of AZE identified volatile oils, kavalactones, and phytosterols.

CONCLUSIONS

Haemodynamic, biochemical alteration and histopathological results suggest a cardioprotective protective effect of oral administration of AZE in isoproterenol induced cardiotoxicity.

Adverse Metabolic Effects of Diltiazem Treatment During Diabetic Cardiomyopathy

Diabetes is a global epidemic disease, which leads to multiorgan dysfunction, including heart disease. Diabetes results from the limited absorption of glucose into insulin-sensitive tissues. The heart is one of the main organs to utilize glucose as an energy substrate. Glucose uptake into striated muscle is regulated by a family of membrane proteins called glucose transporters (GLUTs). Although calcium channel blockers, including diltiazem, are widely prescribed drugs for cardiovascular diseases, including in patients with diabetes, their pharmacological effects on glucose metabolism are somewhat controversial. We hypothesized that diltiazem treatment will exhibit detrimental effects on whole body glucose homeostasis and glucose transport in the striated muscle of patients with diabetes. Healthy and streptozotocin-treated rats were randomly assigned to receive diltiazem treatment or a placebo for 8 weeks. Blood glucose was significantly increased in the untreated diabetic groups, which worsened after diltiazem treatment. Diabetes decreased protein content of both GLUT4 (the predominate insulin-sensitive glucose transporter) and AS160 (Akt Substrate at 160 kDa, the downstream protein in the signaling cascade that regulates GLUT4 trafficking) in striated muscle of diabetic rats, with a more pronounced alteration after diltiazem treatment. We additionally reported that diabetic rodents displayed marked systolic dysfunction, which was not rescued by diltiazem treatment. In conclusion, diltiazem treatment worsened the effects of diabetes-induced hyperglycemia and diabetes-induced alterations in the regulation of glucose transport in striated muscle.

Hypoxia-induced interaction of filamin with Drp1 causes mitochondrial hyperfission-associated myocardial senescence

Defective mitochondrial dynamics through aberrant interactions between mitochondria and actin cytoskeleton is increasingly recognized as a key determinant of cardiac fragility after myocardial infarction (MI). Dynamin-related protein 1 (Drp1), a mitochondrial fission-accelerating factor, is activated locally at the fission site through interactions with actin. Here, we report that the actin-binding protein filamin A acted as a guanine nucleotide exchange factor for Drp1 and mediated mitochondrial fission-associated myocardial senescence in mice after MI. In peri-infarct regions characterized by mitochondrial hyperfission and associated with myocardial senescence, filamin A colocalized with Drp1 around mitochondria. Hypoxic stress induced the interaction of filamin A with the GTPase domain of Drp1 and increased Drp1 activity in an actin-binding-dependent manner in rat cardiomyocytes. Expression of the A1545T filamin mutant, which potentiates actin aggregation, promoted mitochondrial hyperfission under normoxia. Furthermore, pharmacological perturbation of the Drp1-filamin A interaction by cilnidipine suppressed mitochondrial hyperfission-associated myocardial senescence and heart failure after MI. Together, these data demonstrate that Drp1 association with filamin and the actin cytoskeleton contributes to cardiac fragility after MI and suggests a potential repurposing of cilnidipine, as well as provides a starting point for innovative Drp1 inhibitor development.

Identification of the difference in the pathogenesis in heart failure arising from different etiologies using a microarray dataset

OBJECTIVES

Clinically, patients with chronic heart failure arising from different etiologies receive the same treatment. However, the prognoses of these patients differ. The purpose of this study was to elucidate whether the pathogenesis of heart failure arising from different etiologies differs.

METHODS

Heart failure-related dataset GSE1145 was obtained from the Gene Expression Omnibus database. Differentially expressed genes were identified using R. A protein-protein interaction network of the differentially expressed genes was constructed using Search Tool for the Retrieval of Interacting Genes. The modules in each network were analyzed by Molecular Complex Detection of Cytoscape. The Database for Annotation, Visualization and Integrated Discovery was used to obtain the functions of the modules.

RESULTS

Samples contained in GSE1145 were myocardial tissues from patients with dilated cardiomyopathy, familial cardiomyopathy, hypertrophic cardiomyopathy, ischemic cardiomyopathy, and post-partum cardiomyopathy. The differentially expressed genes, modules, and functions of the modules associated with different etiologies varied. Abnormal formation of extracellular matrix was overlapping among five etiologies. The change in cytoskeleton organization was specifically detected in dilated cardiomyopathy. The activation of the Wnt receptor signaling pathway was limited to hypertrophic cardiomyopathy. The change in nucleosome and chromatin assembly was associated with only familial cardiomyopathy. Germ cell migration and disrupted cellular calcium ion homeostasis were solely detected in ischemic cardiomyopathy. The change in the metabolic process of glucose and triglyceride was detected in only post-partum cardiomyopathy.

CONCLUSION

These results indicate that the pathogenesis of heart failure arising from different etiologies varies, which may provide molecular evidence supporting etiology-based treatment for heart failure patients.

Cissampelos pareira Linn. ameliorates thyroxin-induced cardiac hypertrophy in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Cissampelos pareira extract has been traditionally used in ayruveda as cardiotonic, diuretics and in heart complains but its pharmacological evaluation in thyroxin-induced cardiac hypertrophy has not yet been explored.

AIM OF THE STUDY

The aim of this study was to assess the cardioprotective effect of C. pareira root extract in experimentally induced hyperthyroidism in rats.

MATERIALS AND METHODS

Male Wistar rats were treated with (i) thyroxin (0.1 mg/kg/day, i.p.) for 30 days, (ii) C. pareira extract (200 mg/kg/day, p.o.) alone for 60 days, (iii) C. pareira extract (100 and 200 mg/kg/day, p.o., respectively) for 30 days then with thyroxin for another 30 days, (iv) thyroxin for 30 days then C. pareira extract (100 and 200 mg/kg/day, p.o., respectively) for another 30 days. At the end of experiment, serum calcineurin, nitric oxide, lactate dehydrogenase, and thiobarbituric acid reactive substance as well as serum and/or myocardial antioxidant enzymes activity were estimated.

RESULTS

Hyperthyroid induced cardiotoxicity was characterized by a significant (P<0.001) increase in heart weight/body weight ratio, serum calcineurin, nitric oxide, lactate dehydrogenase and thiobarbituric acid reactive substance levels as well as a significant decrease in serum reduced glutathione, myocardial glutathione peroxidase, glutathione reductase and glutathione-S-transferase levels, which were significantly (P<0.05 and P<0.01) reverted by C. pareira extract treatment. Reversal of histological changes on treatment with C. pareira extract was also supported the biochemical parameters. These results were quite comparable with amlodipine, the standard drug taken in this study.

CONCLUSIONS

Treatment with C. pareira extract ameliorates thyroxin-induced oxidative stress and cardiac hypertrophy, probably through amelioration of calcineurin activity and augmentation of antioxidant enzyme activities.

Persistent phenotypic shift in cardiac fibroblasts: impact of transient renin angiotensin system inhibition

Fibrotic cardiac remodeling ultimately leads to heart failure - a debilitating and costly condition. Select antihypertensive agents have been effective in reducing or slowing the development of cardiac fibrosis. Moreover, some experimental studies have shown that the reduction in fibrosis induced by these agents persists long after stopping treatment. What has not been as well investigated is whether this transient treatment results in a protection against future fibrotic cardiac remodeling. In the present review, previously published studies are re-examined to assess whether the relative percent increase in collagen deposition over an off-treatment period is attenuated, relative to control, following transient antihypertensive treatment in young or adult rats. Present findings suggest that transient inhibition of the renin angiotensin system (RAS) not only produces a sustained reduction in cardiac fibrosis, but also results in a degree of protection against future collagen deposition. In addition, prior transient RAS inhibition appears to alter the cardiac fibroblast phenotype such that these cells show a muted response to myocardial injury - namely reduced proliferation, chemokine release, and collagen deposition. This review puts forth several potential mechanisms underlying this long-term cardiac protection that is afforded by transient RAS inhibition. Specifically, fibroblast phenotypic change, cardiac fibroblast apoptosis, sustained suppression of the RAS, persistent reduction in left ventricular hypertrophy, and persistent reduction in arterial pressure are each discussed. Identifying the mechanisms ultimately responsible for this change in cardiac fibroblast response to injury, hypertension, and aging may reveal novel targets for therapy.

Voltage-gated calcium channel blockers deregulate macroautophagy in cardiomyocytes

Voltage-gated calcium channel blockers are widely used for the management of cardiovascular diseases, however little is known about their effects on cardiac cells in vitro. We challenged neonatal ventricular cardiomyocytes (CMs) with therapeutic L-type and T-type Ca(2+) channel blockers (nifedipine and mibefradil, respectively), and measured their effects on cell stress and survival, using fluorescent microscopy, Q-PCR and Western blot. Both nifedipine and mibefradil induced a low-level and partially transient up-regulation of three key mediators of the Unfolded Protein Response (UPR), indicative of endoplasmic (ER) reticulum stress. Furthermore, nifedipine triggered the activation of macroautophagy, as evidenced by increased lipidation of microtubule-associated protein 1 light chain 3 (LC3), decreased levels of polyubiquitin-binding protein p62/SQSTM1 and ubiquitinated protein aggregates, that was followed by cell death. In contrast, mibefradil inhibited CMs constitutive macroautophagy and did not promote cell death. The siRNA-mediated gene silencing approach confirmed the pharmacological findings for T-type channels. We conclude that L-type and T-type Ca(2+) channel blockers induce ER stress, which is divergently transduced into macroautophagy induction and inhibition, respectively, with relevance for cell viability. Our work identifies VGCCs as novel regulators of autophagy in the heart muscle and provides new insights into the effects of VGCC blockers on CMs homeostasis, that may underlie both noxious and cardioprotective effects.

CaV3.2 T-type calcium channels in peripheral sensory neurons are important for mibefradil-induced reversal of hyperalgesia and allodynia in rats with painful diabetic neuropathy

We recently showed that streptozotocin (STZ) injections in rats lead to the development of painful peripheral diabetic neuropathy (PDN) accompanied by enhancement of Ca_V3.2 T-type calcium currents (T-currents) and hyperexcitability in dorsal root ganglion (DRG) neurons. Here we used the classical peripherally acting T-channel blocker mibefradil to examine the role of Ca_V3.2 T-channels as pharmacological targets for treatment of painful PDN. When administered intraperitoneally (i.p.), at clinically relevant doses, mibefradil effectively alleviated heat, cold and mechanical hypersensitivities in STZ-treated diabetic rats in a dose-dependent manner. We also found that Ca_V3.2 antisense (AS)-treated diabetic rats exhibit a significant decrease in painful PDN compared with mismatch antisense (MIS)-treated diabetic rats. Co-treatment with mibefradil (9 mg/kg i.p.) resulted in reversal of heat, cold and mechanical hypersensitivity in MIS-treated but not in AS-treated diabetic rats, suggesting that mibefradil and Ca_V3.2 AS share the same cellular target. Using patch-clamp recordings from acutely dissociated DRG neurons, we demonstrated that mibefradil similarly blocked T-currents in diabetic and healthy rats in a voltage-dependent manner by stabilizing inactive states of T-channels. We conclude that antihyperalgesic and antiallodynic effects of mibefradil in PDN are at least partly mediated by inhibition of Ca_V3.2 channels in peripheral nociceptors. Hence, peripherally acting voltage-dependent T-channel blockers could be very useful in the treatment of painful symptoms of PDN.

Comparing effects of lacidipine, ramipril, and valsartan against experimentally induced myocardial infarcted rats

In this study, the effects of lacidipine (LAC), ramipril (RAM), and valsartan (VAL) on biochemical and histopathologic changes in heart tissue were studied in rats with isoproterenol-induced (ISO-induced) myocardial infarction (MI). LAC, RAM, and VAL had been administered via oral gavage at 3, 3, and 30 mg/kg doses, respectively, once per day during a 30-day time period. On days 29 and 30, the drug treatment group and the control group (with the exception of the intact control group, in which no medications were given, and ISO was not administered) were administered 180 mg/kg ISO subcutaneously over an interval of 24 h. After this period, the hearts of the rats were removed and processed for biochemical and histopathologic studies. The antioxidant parameters superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) were estimated. A diagnosis of MI was confirmed with antioxidant parameters and histopathologic findings. In MI control groups, histopathologic indicators were found to be statistically higher than those in drug groups; an increase in histopathologic indicators of MI correlates with significant decreases in SOD and CAT levels, and an increase in MDA level. Histopathologic grades of MI indicators were significantly higher in MI group that did not receive any cardioprotective medications in comparison with MI groups that received LAC, RAM, and VAL. Each of the three medications favorably modulated most of the biochemical and histopathologic parameters observed. No significant difference existed with regard to any of the estimated parameters in the rat groups that received medications without MI induction. In conclusion, results indicate that LAC, RAM, and VAL significantly reduced myocardial injury and emphasize the cardioprotective nature of these agents.

LASSBio-294, A compound with inotropic and lusitropic activity, decreases cardiac remodeling and improves Ca²(+) influx into sarcoplasmic reticulum after myocardial infarction

BACKGROUND

Myocardial infarction (MI) is commonly associated with cardiac hypertrophy, reduced Ca²(+) uptake into the sarcoplasmic reticulum (SR) and impaired myocardial relaxation. Treatment to prevent MI-associated complications is currently lacking. The purpose of the present study was to investigate the remodeling and function of hearts subjected to experimental MI and to evaluate the response to treatment with a new thienylhydrazone: 3,4-methylenedioxybenzoyl-2-thienylhydrazone (LASSBio-294), which has demonstrated positive inotropic properties.

METHODS

LASSBio-294 (2 mg/kg) or vehicle (dimethyl sulfoxide) was administered daily by intraperitoneal injection for 4 weeks in sham-operated rats and rats with MI. Cardiac remodeling and hemodynamic parameters were monitored through histological and intraventricular pressure analyses. Intracellular Ca²(+) regulation (uptake and release) and the sensitivity of contractile proteins to Ca²(+) were evaluated by determining the contractile response of saponin-skinned cardiac cells from infarcted hearts.

RESULTS

Cardiac hypertrophy occurred at 4 weeks post-MI and was partially reverted by treatment with LASSBio-294. LASSBio-294 treatment also reduced the nuclear density, collagen volume fraction, and left ventricular end-diastolic pressure (LV EDP) induced by MI. MI led to reduced Ca²(+) uptake from the SR, but did not modify the Ca²(+) release or the Ca²(+)-force relationship. LASSBio-294 restored SR function and enhanced the sensitivity of contractile proteins to Ca²(+).

CONCLUSION

LASSBio-294 is a promising candidate for improving intracellular Ca²(+) regulation and preventing MI-induced cardiac dysfunction, which could potentially prevent heart failure (HF).

3-(R)-[3-(2-methoxyphenylthio-2-(S)-methylpropyl]amino-3,4-dihydro-2H-1,5-benzoxathiepine bromhydrate (F 15845) prevents ischemia-induced heart remodeling by reduction of the intracellular Na+ overload

The present study investigates whether 3-(R)-[3-(2-methoxyphenylthio-2-(S)-methylpropyl]amino-3,4-dihydro-2H-1,5-benzoxathiepine bromhydrate (F 15845), a new, persistent sodium current blocker, can reduce the ischemic Na(+) accumulation and exert short- and long-term cardioprotection after myocardial infarction. First, F 15845 concentration-dependently reduced veratrine-induced diastolic contracture (IC(50) = 0.14 microM) in isolated atria. Second, F 15845 from 1 microM preserved viability in 54.2 +/- 12.5% of isolated cardiomyocytes exposed to lysophosphatidylcholine. Third, the effect of F 15845 on intracellular Na(+) of isolated hearts from control and diabetic db/db mice was monitored using (23)Na-nuclear magnetic resonance spectroscopy. F 15845 (0.3 microM) significantly counteracted [Na(+)](i) increase during no-flow ischemia in control mouse hearts. In diabetic db/db mouse hearts, the reduction in [Na(+)](i) was delayed relative to control. However, it was more marked and maintained upon reperfusion. The cardioprotective properties after myocardial infarction associated with short- (24-h) and long-term (14-day) reperfusion were measured in anesthetized rats. After 24-h reperfusion, F 15845 (5 mg/kg) significantly reduced infarct size (32.4 +/- 1.7% with vehicle and 24.2 +/- 3.4% with F 15845; P < 0.05) and decrease of troponin I levels (524 +/- 93 microg/l with vehicle versus 271 +/- 63 microg/l with F 15845; P < 0.05). It is important that F 15845 limits the long-term expansion of infarct size (35.2 +/- 2.6%, n = 19 versus 46.7 +/- 1.6%, n = 27 in the vehicle group; P < 0.001). Overall, F 15845 attenuates [Na(+)](i) and prevents (or reverses) contractile and biochemical dysfunction in ischemic and remodeling heart. F 15845 constitutes a new generation of cardioprotective agent.

Effects of SM-20550 against myocardial infarction-induced arrhythmias, late infarct expansion, and left ventricular dysfunction

The aim of the study was to evaluate the cardioprotective and antiarrhythmic effects of intravenous Na+/H+ blockers (cariporide and SM-20550) in a rat model of ischemia and a long period reperfusion (14 days). This model allowed study of the role of Na+/H+ exchanger against late myocardial infarct expansion and left ventricular dysfunction. Each compound was administered 5 min before ischemia. Cariporide (from 0.16 mg/kg) and SM-20550 (from 0.04 mg/kg) significantly and dose-dependently reduced the number of ventricular premature beats during ischemia. The duration of ventricular tachycardia was importantly shortened in the presence of cariporide (0.63 mg/kg) and SM-20550 (0.16 mg/kg). Furthermore, cariporide (0.63 mg/kg) and SM-20550 (from 0.04 mg/kg) significantly reduced the infarct expansion: 43 +/- 2% in the cariporide group and 42 +/- 2% at 0.16 mg/kg SM-20550 versus 48 +/- 1% in the vehicle group. Cariporide and SM-20550 significantly prevented the left ventricular free wall thinning associated with the thickness ratio, suggesting a significant reduction of the ventricular dilation. Cariporide and SM-20550 significantly improved the negative dP/dtmax, suggesting a partial restoration of the cardiac relaxation. Collectively, Na+/H+ blockers administered before ischemia reduced arrhythmias and also prevented the remodeling process of the heart during postinfarction.

Amlodipine inhibits granulation tissue cell apoptosis through reducing calcineurin activity to attenuate postinfarction cardiac remodeling

Although amlodipine, a long-acting L-type calcium channel blocker, reportedly prevents left ventricular remodeling and dysfunction after myocardial infarction, the mechanism responsible is not yet well understood. Myocardial infarction was induced in mice by ligating the left coronary artery. Treatment of mice with amlodipine (10 mg·kg−1·day−1), beginning on the third day postinfarction, significantly improved survival and attenuated left ventricular dilatation and dysfunction 4 wk postinfarction compared with treatment with saline or hydralazine. Although infarct sizes did not differ among the groups, the infarcted wall thickness was greater and the infarct segment length was smaller in the amlodipine-treated group, and cellular components, including vessels and myofibroblasts, were abundant within the infarcted area. Ten days postinfarction (the subacute stage), the proliferation of granulation tissue cells in the infarcted area was similar among the groups, but the incidence of apoptosis was significantly lower in the amlodipine-treated group, where Bad, a proapoptotic Bcl-2 family protein, was significantly phosphorylated (inactivated). Calcineurin, which dephosphorylates (activates) Bad, was upregulated in infarcted hearts, but its levels were significantly reduced by amlodipine treatment. In vitro, Fas stimulation augmented calcineurin activity and induced apoptosis among infarct tissue-derived myofibroblasts; both of those effects were strongly inhibited by amlodipine, two other calcium channel blockers (verapamil or nifedipine), and two calcineurin inhibitors (cyclosporin A or FK-506). Amlodipine inhibits Fas-mediated granulation tissue cell apoptosis in infarcted hearts, possibly by attenuating the activities of calcineurin and Bad. These findings may provide new insight into the mechanism by which calcium channel blockers attenuate postinfarction cardiac remodeling and dysfunction.

The MRL mouse repairs both cryogenic and ischemic myocardial infarcts with scar

OBJECTIVE

The MRL mouse strain shows extraordinary wound healing capacities. Some years ago, Leferovich et al. (Proc Natl Acad Sci U S A 2001;98:9830-35) have reported the absence of scar formation after cryogenically-induced right ventricular myocardial infarcts in adult MRL mice. An independent group (Oh et al., Cardiovasc Pathol 2004;13:203-6) found that MRL mice repair left ventricular ischemic infarcts after coronary artery ligation with regular scar formation. Given the divergent outcomes in infarct healing in MRL mice reported by those two studies, we have investigated whether MRL mice heal myocardial infarcts without scar both in the cryoinjury and in the coronary ligation model.

METHODS AND RESULTS

Four different protocols of cryogenically induced right and left ventricular injury, as well as permanent ligation of the left anterior descending coronary artery, were tested in adult MRL and control C57Bl/6 mice. At 60 days after experimental infarction, MRL mice showed pronounced scarring of the affected right and left ventricular areas, with no significant differences in infarct size and thickness between MRL and C57Bl/6 mice using any of the five experimental protocols. Analysis of cell proliferation by 5-bromo-2'-deoxyuridine (BrdU) incorporation into the DNA did not show any difference between the two strains of mice after infarction. Histological analysis of infarct areas using picrosirius red staining did not show differences in extent of collagen and distribution between the two mouse strains.

CONCLUSIONS

MRL mice heal myocardial infarcts with scar formation in response to ischemic as well as to cryogenic injuries.

Different Effects of Calcium Channel Blockers on Matrix Metalloproteinase-2 Expression in Cultured Rat Cardiac Fibroblasts

The cardiac effects of calcium channel blockers (CCBs) related to cardiac remodeling are inconsistent. Matrix metalloproteinases (MMPs) contribute to tissue remodeling. Cardiac fibroblasts play an important role in the regulation of collagen degradation by MMPs. Using gelatin zymography, Western blotting, Griess reagent, and a calcium kit-fluo 3, we investigated the effects of nifedipine, verapamil, diltiazem, and amlodipine on MMP-2 expression and further elucidate the mechanisms in cultured rat cardiac fibroblasts. Nifedipine increased and amlodipine decreased the expression of MMP-2; however, neither verapamil nor diltiazem altered MMP-2 expression. Nifedipine also increased nitrite production, and this increase was blunted by a nitric oxide (NO) synthases inhibitor (L-NAME). Nifedipine-induced MMP-2 expression was also blunted by L-NAME. An NO donor (sodium nitroprusside) induced MMP-2 expression. Data indicated that nifedipine might increase MMP-2 expression through a possible NO-dependent pathway. Amlodipine had no influence on nitrite production. The amlodipine-induced decrease of MMP-2 expression was abolished by two protein tyrosine kinase inhibitors, genistein and herbimycin A, indicating that amlodipine might decrease MMP-2 expression through a possible protein tyrosine kinase pathway. None of the four CCBs could alter the fluoscence intensity of fluo 3, indicating that the effects of CCBs on MMP-2 expression were independent of the variation in intracellular C2+ concentration. Our findings revealed that different CCBs exerted different effects on MMP-2 expression in cardiac fibroblasts.

Management of calcium channel antagonist overdose

Calcium channel antagonists are used primarily for the treatment of hypertension and tachyarrhythmias. Overdose of calcium channel antagonists can be lethal. Calcium channel antagonists act at the L-type calcium channels primarily in cardiac and vascular smooth muscle preventing calcium influx into cells with resultant decreases in vascular tone and cardiac inotropy and chronotropy. The L-type calcium channel is a complex structure and is thus affected by a large number of structurally diverse antagonists. In the setting of overdose, patients may experience vasodilatation and bradycardia leading to a shock state. Patients may also be hyperglycaemic and acidotic due to the blockade of L-type calcium channels in the pancreatic islet cells that affect insulin secretion. Aggressive therapy is warranted in the setting of toxicity. Gut decontamination with charcoal, or whole bowel irrigation or multiple-dose charcoal in the setting of extended-release products is indicated. Specific antidotes include calcium salts, glucagon and insulin. Calcium salts may be given in bolus doses or may be employed as a continuous infusion. Care should be exercised to avoid the administration of calcium in the setting of concomitant digoxin toxicity. Insulin administration has been used effectively to increase cardiac inotropy and survival. The likely mechanism involves a shift to carbohydrate metabolism in the setting of decreased availability of carbohydrates due to decreased insulin secretion secondary to blockade of calcium channels in pancreatic islet cells. Glucose should be administered as well to maintain euglycaemia. Supportive care including the use of phosphodiesterase inhibitors, adrenergic agents, cardiac pacing, balloon pump or extracorporeal bypass is frequently indicated if antidotal therapy is not effective. Careful evaluation of asymptomatic patients, including and electrocardiogram and a period of observation, is indicated. Patients ingesting a nonsustained-release product should be observed in a monitored setting for 12 hours, while those who ingest a sustained-release preparation should be observed for no less than 24 hours. Charcoal should be given to the asymptomatic patient with a history of calcium channel antagonist overdose.

Bradykinin B1 and B2 receptors differentially regulate cardiac Na+-H+ exchanger, Na+-Ca2+ exchanger and Na+-HCO3- symporter

Bradykinin B(1) and B(2) receptors are up-regulated in the infarcted myocardium, and both receptors are involved in the regulation of intracellular pH and Ca(2+). The present study investigated the role of bradykinin B(1) and B(2) receptors in the regulation of Na(+)-H(+) exchanger (NHE-1), Na(+)-Ca(2+) exchanger (NCE-1) and Na(+)-HCO(3)(-) symporter (NBC-1) in the infarcted myocardium. NHE-1, NCE-1 and NBC-1 mRNA expression was determined by Northern blot analysis and the protein levels by Western blot analysis. Measurements were performed 1, 7 and 14 days after induction of myocardial infarction. Localization of NHE-1, NCE-1 and NBC-1 within the myocardium was studied using confocal microscopy. Cardiac morphology was measured in picrosiris-red-stained hearts. Rats were treated with placebo, the bradykinin B(2) receptor antagonist icatibant (0.5 mg/kg/day) or the bradykinin B(1) receptor antagonist des-Arg(9)-[Leu(8)]bradykinin (1 mg/kg/day). Treatment was started 1 week prior to surgery and continued until 1, 7 and 14 days post infarction. NHE-1, NCE-1 and NBC-1 mRNA expression and protein levels were increased 1 day and reached maximum values on day 7 post infarction. NHE-1 was localized in the plasma membrane, NCE-1 in the membrane of the sarcoplasmatic reticulum and NBC-1 near the Z-line. Icatibant reduced NHE-1 and inhibited NCE-1 mRNA- and protein up-regulation, while des-Arg(9)-[Leu(8)]bradykinin had no effect on NHE-1 and NCE-1 expression and translation. Transcriptional and translational up-regulation of NBC-1 was unaffected by the bradykinin B(1) and B(2) receptor antagonists. Icatibant, but not des-Arg(9)-[Leu(8)]bradykinin, limited infarct size and reduced left ventricular dilation, septal thickening and interstitial fibrosis post infarction. Bradykinin B(2) receptors are involved in transcriptional and translational regulation of NHE-1 and NCE-1 in the ischemic myocardium. Chronic B(2) receptor blockade might exert an anti-ischemic effect via limitation of NHE-1-mediated acidosis and NCE-1-mediated Ca(2+)-overload.

Synergistic effect of Nicorandil and Amlodipine on tissue defense system during experimental myocardial infarction in rats

The synergistic protective effect of Nicorandil (K(ATP) channel opener) and Amlodipine (calcium channel blocker) on heart tissue antioxidant defense system and lipid profile were examined on isoproterenol induced myocardial infarction in rats. The rats given isoproterenol (150 mg kg(-1) daily, i.p.) for 2 days showed significant changes in antioxidant defense system and lipid profile levels. Pretreatment with Nicorandil (2.5 mg kg(-1) daily, p.o.) and Amlodipine (5.0 mg kg(-1) daily, p.o.) for 3 days significantly prevented these alterations and restored the enzyme activities to near normal. These findings indicate the synergistic protective effect of Nicorandil and Amlodipine on tissue defense system and lipid metabolism during isoproterenol induced cardiac damage.

Calcium channel blockade limits transcriptional, translational and functional up-regulation of the cardiac calpain system after myocardial infarction

Abnormal Ca(2+) inward current through cardiac Ca(2+) channels during ischemia has been shown to be an initial signal for activation of myocardial Ca(2+)-dependent enzymes. This study investigated the contribution of cardiac L- and T-type Ca(2+) channels in the calpain-mediated myocardial damage following myocardial infarction. Myocardial infarction was induced by permanent ligation of the left coronary artery. Infarcted rats were orally treated with placebo, amlodipine (L-channel blockade; 4 mg/kg/day) or mibefradil (L-/T-channel blockade; 10 mg/kg/day) beginning 7 days before induction of myocardial infarction. Gene expression, protein levels and enzyme activity of calpains I and II were measured 1, 3, 7 and 14 days postcoronary occlusion in the noninfarcted and infarcted myocardium. Infarct size, left ventricular dilation and interstitial collagen volume fraction were determined in picrosirius red-stained hearts. Myocardial infarction induced an up-regulation of calpain I mRNA, protein and activity in the noninfarcted myocardium (maximum 14 days postinfarction), whereas mRNA, protein and activity of calpain II were maximally increased in the infarcted myocardium 3 days postinfarction. Fourteen days postinfarction, infarct size was 49%, the left ventricle was dilated and interstitial collagen volume fraction was increased. Amlodipine-inhibited mRNA, protein and activity up-regulation of calpain I decreased interstitial collagen volume fraction and infarct size. Mibefradil-attenuated mRNA, protein and activity up-regulation of calpain II at all four time points measured and of calpain I at 7 and 14 days postinfarction reduced infarct size and prevented left ventricular dilation. Infarction-induced cardiac hypertrophy was accompanied by an up-regulation of calpain I, whereas calpain II was up-regulated in the infarcted myocardium. Cardiac L- and T-type Ca(2+) channel blockade differentially reduced postinfarction remodeling associated with selective inhibition of cardiac calpains I and II, respectively.

Verapamil reduces coronary endothelium damage and cardiomyocyte necrosis but not apoptosis after ischemia and reperfusion: ex-vivo study in rat hearts

We tested the hypothesis of beneficial effects of the calcium-blocker verapamil in a model of ischemia-reperfusion, and investigated its effects against coronary microcirculation and cardiomyocyte apoptosis. Isolated working rat hearts were subjected to 15 min global ischemia and 22-180 min reperfusion in the presence or absence of verapamil (0.25 &mgr;M). We evaluated creatinephosphokinase (CK) in coronary effluent, heart weight changes, microvascular permeability (extravasation of fluoresceine-labeled albumin), ultrastructural alterations, and cardiomyocyte apoptosis (by 1.5% agarose gel electrophoresis and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labelling technique). In this model, 0.25 &mgr;M verapamil significantly reduced myocardial damage, CK release and vascular hyperpermeability, concomitant with a reduction in endothelial and cardiomyocyte lesions; on the contrary, 0.25 &mgr;M verapamil was unable to reduce cardiomyocyte apoptosis. In conclusion, in the absence of perfusing granulocytes, the acute administration of a pharmacologically relevant verapamil concentration reduces ischemia-reperfusion injury and prevents coronary endothelial cell and cardiomyocyte necrotic cell death but it is unable to reduce apoptotic cell death in isolated working rat hearts.

Vascular remodeling during healing after myocardial infarction in the dog model: effects of reperfusion, amlodipine and enalapril

OBJECTIVES

We sought to determine whether reperfusion and the calcium channel blocker amlodipine or the angiotensin-converting enzyme inhibitor enalapril, during healing over six weeks after myocardial infarction (MI), limit structural vascular remodeling in the noninfarct zone (NIZ).

BACKGROUND

The effect of reperfusion and amlodipine or enalapril on structural vascular remodeling during healing of MI has not been determined.

METHODS

We randomly assigned 54 dogs to reperfused or nonreperfused MI, followed by twice-daily doses of oral placebo, amlodipine (5 mg) or enalapril (5 mg) for six weeks and three days off treatment, or to three matching sham groups. We measured in vivo hemodynamic data and left ventricular (LV) function and remodeling (by echocardiography) over the six weeks, as well as ex vivo structural vascular, ventricular and collagen remodeling in the hearts after six weeks.

RESULTS

Compared with placebo and sham groups, both amlodipine and enalapril with or without reperfusion produced LV unloading and limited structural LV remodeling and dysfunction over six weeks in vivo, and also decreased the NIZ resistance vessel media/lumen area ratio at six weeks ex vivo. In addition, amlodipine, but not enalapril, preserved infarct scar collagen and increased the border zone collagen volume fraction and perivascular fibrosis, as well as NIZ resistance vessel media thickness. Enalapril, but not amlodipine, decreased transforming growth factor-beta in the border zone and NIZ.

CONCLUSIONS

The results indicate that therapy with amlodipine and enalapril during healing after reperfused MI limits structural vascular remodeling in the NIZ, probably by different mechanisms.

Synergistic effect of nicorandil and amlodipine on mitochondrial function during isoproterenol-induced myocardial infarction in rats

The synergistic effects of nicorandil (KATP-channel opener) and amlodipine (calcium-channel blocker) on heart mitochondrial enzymes and the mitochondrial antioxidant defence system was examined on isoproterenol-induced myocardial infarction in rats. The rats given isoproterenol (150 mg kg(-1) daily, i.p.) for two days showed significant changes in marker enzymes, mitochondrial enzymes and the mitochondrial defence system. Pre-co-treatment with nicorandil (2.5 mg kg(-1) daily, p.o.) and amlodipine (5.0 mg kg(-1) daily, p.o.) for 3 days significantly prevented these alterations and restored enzyme activity to near normal. These findings demonstrate the protective and synergistic effect of nicorandil and amlodipine in combination against isoproterenol-induced cardiac damage.