Role of Vasoactive Hormone-Induced Signal Transduction in Cardiac Hypertrophy and Heart Failure.

Heart failure is the common concluding pathway for a majority of cardiovascular diseases and is associated with cardiac dysfunction. Since heart failure is invariably preceded by adaptive or maladaptive cardiac hypertrophy, several biochemical mechanisms have been proposed to explain the development of cardiac hypertrophy and progression to heart failure. One of these includes the activation of different neuroendocrine systems for elevating the circulating levels of different vasoactive hormones such as catecholamines, angiotensin II, vasopressin, serotonin and endothelins. All these hormones are released in the circulation and stimulate different signal transduction systems by acting on their respective receptors on the cell membrane to promote protein synthesis in cardiomyocytes and induce cardiac hypertrophy. The elevated levels of these vasoactive hormones induce hemodynamic overload, increase ventricular wall tension, increase protein synthesis and the occurrence of cardiac remodeling. In addition, there occurs an increase in proinflammatory cytokines and collagen synthesis for the induction of myocardial fibrosis and the transition of adaptive to maladaptive hypertrophy. The prolonged exposure of the hypertrophied heart to these vasoactive hormones has been reported to result in the oxidation of catecholamines and serotonin via monoamine oxidase as well as the activation of NADPH oxidase via angiotensin II and endothelins to promote oxidative stress. The development of oxidative stress produces subcellular defects, Ca2+-handling abnormalities, mitochondrial Ca2+-overload and cardiac dysfunction by activating different proteases and depressing cardiac gene expression, in addition to destabilizing the extracellular matrix upon activating some metalloproteinases. These observations support the view that elevated levels of various vasoactive hormones, by producing hemodynamic overload and activating their respective receptor-mediated signal transduction mechanisms, induce cardiac hypertrophy. Furthermore, the occurrence of oxidative stress due to the prolonged exposure of the hypertrophied heart to these hormones plays a critical role in the progression of heart failure.

Nerolidol attenuates isoproterenol-induced acute myocardial infarction in rats.

Cardiovascular diseases have high morbidity and mortality rates, and their treatment is not effective in reducing the damage caused by myocardial infarction (MI). This study aimed to investigate whether nerolidol (NRD), a sesquiterpene alcohol, could attenuate MI in an isoproterenol-treated rat model. MI was induced by the administration of two doses of isoproterenol (ISO, 100 mg/kg, i.p.) with an interval of 24 h between doses.The animals were divided into four groups: control (CTR) (vehicle - NaCl 0.9% + Tween 80 0.2%), MI (ISO + vehicle), MI + NRD (50 mg/kg) and MI + NRD (100 mg/kg). An electrocardiogram was performed, and contractile parameters, cardiac enzymes, infarction size, and antioxidant parameters in the heart were measured to evaluate the effects of NRD. The ISO group showed a significant rise in ST segment, QTc, and heart rate associated with a reduction in left ventricular developed pressure (LVDP), + dP/dt, and -dP/dt. In addition, there were increases in levels of creatine kinase (CK), creatine kinase-myocardial band (CK-MB), lactate dehydrogenase (LDH), and thiobarbituric acid (TBARS); reductions in superoxide dismutase (SOD) and catalase (CAT) activities; and an increase in the infarction size. Interestingly, NRD significantly attenuated almost all the parameters of ISO-induced MI mentioned above. Our results suggest that nerolidol attenuates MI caused by ISO by a marked reduction in myocardial infarct size and suppression of oxidative stress. CK total, creatine kinase total; CK-MB, creatine kinase myocardial band; LDH, lactate dehydrogenase; SOD, superoxide dismutase; CAT, catalase. CTR (vehicle group), MI (100 mg/kg of isoproterenol), ISO + NRD 50 (50 mg/kg of nerolidol), and ISO + NRD 100 (100 mg/kg of nerolidol).

Redox-Active Drug, MnTE-2-PyP5+, Prevents and Treats Cardiac Arrhythmias Preserving Heart Contractile Function.

BACKGROUND: Cardiomyopathies remain among the leading causes of death worldwide, despite all efforts and important advances in the development of cardiovascular therapeutics, demonstrating the need for new solutions. Herein, we describe the effects of the redox-active therapeutic Mn(III) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin, AEOL10113, BMX-010 (MnTE-2-PyP5+), on rat heart as an entry to new strategies to circumvent cardiomyopathies. METHODS: Wistar rats weighing 250-300 g were used in both in vitro and in vivo experiments, to analyze intracellular Ca2+ dynamics, L-type Ca2+ currents, Ca2+ spark frequency, intracellular reactive oxygen species (ROS) levels, and cardiomyocyte and cardiac contractility, in control and MnTE-2-PyP5+-treated cells, hearts, or animals. Cells and hearts were treated with 20 µM MnTE-2-PyP5+ and animals with 1 mg/kg, i.p. daily. Additionally, we performed electrocardiographic and echocardiographic analysis. RESULTS: Using isolated rat cardiomyocytes, we observed that MnTE-2-PyP5+ reduced intracellular Ca2+ transient amplitude, without altering cell contractility. Whereas MnTE-2-PyP5+ did not alter basal ROS levels, it was efficient in modulating cardiomyocyte redox state under stress conditions; MnTE-2-PyP5+ reduced Ca2+ spark frequency and increased sarcoplasmic reticulum (SR) Ca2+ load. Accordingly, analysis of isolated perfused rat hearts showed that MnTE-2-PyP5+ preserves cardiac function, increases SR Ca2+ load, and reduces arrhythmia index, indicating an antiarrhythmic effect. In vivo experiments showed that MnTE-2-PyP5+ treatment increased Ca2+ transient, preserved cardiac ejection fraction, and reduced arrhythmia index and duration. MnTE-2-PyP5+ was effective both to prevent and to treat cardiac arrhythmias. CONCLUSION: MnTE-2-PyP5+ prevents and treats cardiac arrhythmias in rats. In contrast to most antiarrhythmic drugs, MnTE-2-PyP5+ preserves cardiac contractile function, arising, thus, as a prospective therapeutic for improvement of cardiac arrhythmia treatment.

p-Cymene attenuates cancer pain via inhibitory pathways and modulation of calcium currents.

BACKGROUND: Oncological pain is one of the most prevalent and difficult-to-treat symptoms in patients with cancer. p-Cymene (PC) is a monoterpene found in more than 100 different plant species, endowed with various pharmacological properties-particularly antinociceptive. HYPOTHESIS/PURPOSE: PC has antinociceptive effect in a model of oncologic pain due to the activation of the descending inhibitory pathway of pain. STUDY DESIGN: A pre-clinical, longitudinal, blind and randomized study. METHODS: Male Swiss mice were induced with S180 cells in the right hind paw, then treated daily with PC (12.5, 25 and 50 mg/kg, s.c.) and screened for mechanical hyperalgesia, spontaneous nociception, nociception induced by non-noxious palpation, tumor growth, changes in the neuromuscular function and existence of bone degradation in the tumor area. The effect of PC on Ca2+ currents (electrophysiological records), histological and neurochemical changes (immunofluorescence for Fos) were also evaluated. RESULTS: PC reduced (p < 0.05) the mechanical hyperalgesia, the spontaneous (p < 0.001) and non-noxious palpation (p < 0.001) nociceptions, not changing the tumor development, neuromuscular function or histopathological aspects of the paw affected. PC reduced Fos expression in the spinal cord (p < 0.001) and increased this expression in the PAG (p < 0.05) and in the NRM (p < 0.01). PC decreased the density of calcium channel currents (p < 0.05). CONCLUSION: These results suggest the antinociceptive effect of PC on oncologic pain, probably acting in both ascending and descending pain pathways, and modulating the calcium channel currents in order to exert its effects.

Negative inotropism of terpenes on guinea pig left atrium: structure-activity relationships.

The aim of this work was to evaluate the pharmacological effect of seven structurally related terpenes on the contractility of cardiac muscle. The effect of terpenes was studied on isolated electrically driven guinea pig left atrium. From concentration-response curves for inotropic effect were determined the EC50 and relative potency of such terpenes. Our results revealed that all terpenes, except phytol, showed ability to reduce the contractile response of guinea pig left atrium. Further, relative potency was directly related to the number of isoprene units and to the lipophilicity of the compounds. For example, sesquiterpenes farnesol and nerolidol showed higher relative potency when compared with the monoterpenes citronellol, geraniol and nerol. We can conclude that most of the evaluated terpenes showed a promising negative inotropism on the atrial muscle. Future studies are necessary to investigate their action mechanism.

Cardioprotective Action of Ginkgo biloba Extract against Sustained ß-Adrenergic Stimulation Occurs via Activation of M2/NO Pathway.

Ginkgo biloba is the most popular phytotherapic agent used worldwide for treatment of several human disorders. However, the mechanisms involved in the protective actions of Ginkgo biloba on cardiovascular diseases remain poorly elucidated. Taking into account recent studies showing beneficial actions of cholinergic signaling in the heart and the cholinergic hypothesis of Ginkgo biloba-mediated neuroprotection, we aimed to investigate whether Ginkgo biloba extract (GBE) promotes cardioprotection via activation of cholinergic signaling in a model of isoproterenol-induced cardiac hypertrophy. Here, we show that GBE treatment (100 mg/kg/day for 8 days, v.o.) reestablished the autonomic imbalance and baroreflex dysfunction caused by chronic ß-adrenergic receptor stimulation (ß-AR, 4.5 mg/kg/day for 8 days, i.p.). Moreover, GBE prevented the upregulation of muscarinic receptors (M2) and downregulation of ß1-AR in isoproterenol treated-hearts. Additionally, we demonstrated that GBE prevents the impaired endothelial nitric oxide synthase activity in the heart. GBE also prevented the pathological cardiac remodeling, electrocardiographic changes and impaired left ventricular contractility that are typical of cardiac hypertrophy. To further investigate the mechanisms involved in GBE cardioprotection in vivo, we performed in vitro studies. By using neonatal cardiomyocyte culture we demonstrated that the antihypertrophic action of GBE was fully abolished by muscarinic receptor antagonist or NOS inhibition. Altogether, our data support the notion that antihypertrophic effect of GBE occurs via activation of M2/NO pathway uncovering a new mechanism involved in the cardioprotective action of Ginkgo biloba.

Aqueous leaf extract of Averrhoa carambola L. (Oxalidaceae) reduces both the inotropic effect of BAY K 8644 on the guinea pig atrium and the calcium current on GH3cells / Extrato aquoso das folhas de Averrhoa carambola L. (Oxalidaceae) reduz tanto o efeito inotrópico do BAY K 8644 em átrio de cobaia, quanto a corrente de cálcio em células GH3

It was previously showed that aqueous leaf extract (AqEx) of Averrhoa carambola depresses the guinea pig atrial inotropism. Therefore, experiments were carried out on guineapig left atrium and on pituitary GH3 cells in order to evaluate the effect of AqEx on the cellular calcium infl ux. The atrium was mounted in an organ chamber (5 mL, Tyrode, 27 ± 0.1 °C, 95% O2, 5 % CO2), stretched to 10 mN, and paced at 2 Hz (0.5 ms, 400 V) and GH3 cells were submitted to a whole cell voltage clamp confi guration. In the atrium, the AqEx (1500 μg/mL) shifted to the right the concentration-effect curve of the positive inotropic effect produced by (±) BAY K 8644, an L-type calcium channel agonist. The AqEx increased EC50 (concentration required to promote 50% of the maximum effect) of the inotropic effect of BAY K 8644 from 7.8 ± 0.38 to 115.1 ± 0.44 nM (N = 3; p < 0.05). In GH3 cells assayed with 500 μg/mL of AqEx, the L-type calcium inward current declined 30 % (from 282 to 190 pA). Nevertheless, the extract did not change the voltage correspondent to the peak current. These data suggest that, at least in part, the negative inotropic effect of AqEx on the guinea pig atrium is due to a reduction of the L-type calcium current.

Em estudo prévio mostrou-se que o extrato aquoso das folhas de Averrhoacarambola (ExAq) reduziu o inotropismo atrial da cobaia. Por isso, este trabalho avaliou se o ExAq interfere com o infl uxo de cálcio através da membrana celular. A investigação foi conduzidaem átrio esquerdo de cobaia, montado em cuba (5 mL, Tyrode, 27 ± 0,1 °C, 95 % O2, 5 % CO2), estirado para uma tensão de repouso de 10 mN e submetido a uma estimulação de 2 Hz (0,5 ms, 400 V). O efeito do ExAq sobre a entrada de cálcio nas células foi avaliado em átrio de cobaia e em células GH3, estas submetidas a ‘patch clamp’ na confi guração ‘whole cell’. No átrio, o ExAq (1500 μg /mL) deslocou para direita a curva concentração-efeito do (±) BAY K 8644 (agonista dos canais de cálcio tipo-L), aumentando a CE50 (concentração capaz de produzir 50 % do efeito máximo) de 7,8 ± 0,38 para 115,1 ± 0,44 nM (N = 3, p < 0,05). Em células GH3, este extrato (500 μg /mL) reduziu de 282 para 190 pA (30 %) a corrente de cálcio, sem contudo alterar a voltagem de pico da curva desta corrente. Estes resultados mostram que, pelo menos em parte, o efeito inotrópico negativo do ExAq em átrio de cobaia se deve a uma diminuição do infl uxo de cálcio pelos canais tipo-L.