In vivo tebuconazole administration impairs heart electrical function and facilitates the occurrence of dobutamine-induced arrhythmias: involvement of reactive oxygen species.

Tebuconazole (TEB), a widely used pesticide in agriculture to combat fungal infections, is commonly detected in global food, potable water, groundwater, and human urine samples. Despite its known in vivo toxicity, its impact on heart function remains unclear. In a 28-day study on male Wistar rats (approximately 100 g), administering 10 mg/kg/day TEB or a vehicle (control) revealed no effect on body weight gain or heart weight, but an increase in the infarct area in TEB-treated animals. Notably, TEB induced time-dependent changes in in vivo electrocardiograms, particularly prolonging the QT interval after 28 days of administration. Isolated left ventricular cardiomyocytes exposed to TEB exhibited lengthened action potentials and reduced transient outward potassium current. TEB also increased reactive oxygen species (ROS) production in these cardiomyocytes, a phenomenon reversed by N-acetylcysteine (NAC). Furthermore, TEB-treated animals, when subjected to an in vivo dobutamine (Dob) and caffeine (Caf) challenge, displayed heightened susceptibility to severe arrhythmias, a phenotype prevented by NAC. In conclusion, TEB at the no observed adverse effect level (NOAEL) dose adversely affects heart electrical function, increases arrhythmic susceptibility, partially through ROS overproduction, and this phenotype is reversible by scavenging ROS with NAC.

d-Limonene complexed with cyclodextrin attenuates cardiac arrhythmias in an experimental model of doxorubicin-induced cardiotoxicity: Possible involvement of calcium/calmodulin-dependent protein kinase type II.

BACKGROUND: Arrhythmias are one manifestation of the cardiotoxicity that results from doxorubicin (Doxo) administration. Although cardiotoxicity is an anticipated outcome in anticancer therapies, there is still a lack of treatment options available for its effective management. This study sought to evaluate the possible cardioprotective effect of complex d-limonene (DL) plus hydroxypropyl-ß-cyclodextrin (HßDL) during treatment with Doxo, focusing on the arrhythmic feature. METHODS: Cardiotoxicity was induced in Swiss mice with Doxo 20 mg/kg, with 10 mg/kg of HßDL being administered 30 min before the Doxo. Plasma CK-MB and LDH levels were analyzed. Cellular excitability and susceptibility to cardiac and cardiomyocyte arrhythmias were evaluated using in vivo (pharmacological cardiac stress) and in vitro (burst pacing) ECG protocols. Ca2+ dynamics were also investigated. The expression of CaMKII and its activation by phosphorylation and oxidation were evaluated by western blot, and molecular docking was used to analyze the possible interaction between DL and CaMKII. RESULTS: Electrocardiograms showed that administration of 10 mg/kg of HßDL prevented Doxo-induced widening of the QRS complex and QT interval. HßDL also prevented cardiomyocyte electrophysiological changes that trigger cellular arrhythmias, such as increases in action potential duration and variability; decreased the occurrence of delayed afterdepolarizations (DADs) and triggered activities (TAs), and reduced the incidence of arrhythmia in vivo. Ca2+ waves and CaMKII overactivation caused by phosphorylation and oxidation were also decreased. In the in silico study, DL showed potential inhibitory interaction with CaMKII. CONCLUSION: Our results show that 10 mg/kg of ßDL protects the heart against Doxo-induced cardiotoxicity arrhythmias, and that this is probably due to its inhibitory effect on CaMKII hyperactivation.

The effects of flavonoids in experimental sepsis: A systematic review and meta-analysis.

Sepsis is a host's dysregulated immune response to an infection associated with systemic inflammation and excessive oxidative stress, which can cause multiple organ failure and death. The literature suggests that flavonoids, a broad class of secondary plant metabolites, have numerous biological activities which can be valuable in the treatment of sepsis. This study aimed to review the effects of flavonoids on experimental sepsis, focusing mainly on survival rate, and also summarizing information on its mechanisms of action. We searched in the main databases up to November 2022 using relevant keywords, and data were extracted and analyzed qualitatively and quantitatively. Thirty-two articles met the study criteria for review and 29 for meta-analysis. Overall, 30 different flavonoids were used in the studies. The flavonoids were able to strongly inhibit inflammatory response by reducing the levels of important pro-inflammatory mediators, for example, tumor necrosis factor-alpha and interleukin-1ß, oxidative stress, and showed antibacterial and anti-apoptotic actions. The meta-analysis found an increase of 50% in survival rate of the animals treated with flavonoids. They appear to act as multi-target drugs and may be an excellent therapeutic alternative to reduce a number of the complications caused by sepsis, and consequently, to improve survival rate.

Estudo Morfofuncional do Átrio Esquerdo Isolado de um Modelo Experimental de Hipertensão Pulmonar em Ratos / Isolated Left Atrium Morphofunctional Study of an Experimental Pulmonary Hypertension Model in Rats

Resumo Fundamento A alta incidência de arritmias atriais na hipertensão pulmonar (HP) pode estar associada a um prognóstico ruim, e o átrio esquerdo (AE) pode desempenhar um papel neste quadro. Um achado importante nos estudos de HP é que a remodelação do AE é subestimada. Objetivo Este estudo investigou a morfologia e a função mecânica do AE, bem como a suscetibilidade ao desenvolvimento de arritmias em um modelo de HP induzida por monocrotalina (HP-MCT). Métodos Ratos Wistar com 4 semanas de idade receberam 50 mg/kg de MCT. Foram realizadas análises eletrocardiográficas e histológicas para avaliar o estabelecimento do modelo de HP-MCT. O tecido foi montado em banho de órgão isolado para caracterizar a função mecânica do AE. Resultados Em comparação com o grupo controle, o modelo de HP-MCT apresentou hipertrofia do AE e alterações da atividade elétrica cardíaca, conforme evidenciadas pelo aumento da duração da onda P, PR e intervalo QT. Não foi observada alteração no inotropismo do AE isolado de ratos com HP-MCT; no entanto, o tempo para atingir a contração máxima foi atrasado. Finalmente, não observamos diferença na suscetibilidade à arritmia no AE dos ratos com HP-MCT após o protocolo de estimulação intermitente. Conclusão A remodelação morfofuncional do AE não levou ao aumento da suscetibilidade à arritmia ex vivo após a aplicação do protocolo de estimulação intermitente.

Abstract Background The high incidence of atrial arrhythmias in pulmonary hypertension (PH) might be associated with poor prognosis, and the left atrium (LA) may play a role in this. An important finding in PH studies is that LA remodeling is underestimated. Objective This study investigated LA morphology and mechanical function, as well as the susceptibility to develop arrhythmias in a monocrotaline-induced PH (MCT-PH) model. Methods Wistar rats aged 4 weeks received 50 mg/kg of MCT. Electrocardiography and histology analysis were performed to evaluate the establishment of the MCT-PH model. The tissue was mounted in an isolated organ bath to characterize the LA mechanical function Results Compared with the control group (CTRL), the MCT-PH model presented LA hypertrophy and changes in cardiac electrical activity, as evidenced by increased P wave duration, PR and QT interval in MCT-PH rats. In LA isolated from MCT-PH rats, no alteration in inotropism was observed; however, the time to peak contraction was delayed in the experimental MCT-PH group. Finally, there was no difference in arrhythmia susceptibility of LA from MCT-PH animals after the burst pacing protocol. Conclusion The morphofunctional remodeling of the LA did not lead to increased susceptibility to ex vivo arrhythmia after application of the burst pacing protocol.

A (-)-Carvona Modula a Sinalização de Cálcio Intracelular com Ação Antiarrítmica em Corações de Ratos / (-)-Carvone Modulates Intracellular Calcium Signaling with Antiarrhythmic Action in Rat Hearts

Resumo Fundamento: A (-)-carvona é um monoterpeno encontrado em óleos essenciais com atividade antioxidante e anti-inflamátoria. Objetivos: O objetivo deste estudo foi analisar a propriedade antiarrítmica da (-)-carvona no coração de rato e seus efeitos sobre a sinalização de Ca+2 intracelular. Métodos: Os efeitos da (-)-carvona foram avaliados sobre a contratilidade atrial (0,01 - 4 mM) e ventricular (0,5 mM), e no eletrocardiograma (0,5mM). A fração de encurtamento, a corrente de cálcio do tipo L (ICa,L) e a sinalização de Ca+2 foram medidas no cardiomiócito isolado (0,5 mM). O efeito antiarrítmico foi avaliado no modelo de arritmia induzida por sobrecarga de cálcio (0,5 mM) (n = 5). Um p < 0,05 foi adotado como nível de significância estatística. Resultados: No átrio, a (-)-carvona causou inotropismo negativo de maneira concentração-dependente (EC50 0,44 ± 0,11 mM) e diminuiu o inotropismo positivo induzido pelo CaCl2 (0,1 - 8,0 mM) e BAY K8644 (5 - 500 nM), um agonista de canal de cálcio do tipo L. Em coração isolado, a (-)-carvona (0,5mM) reduziu a contratilidade ventricular em 73% e a frequência cardíaca (em 46%), aumentou o Pri (30,7%, tempo desde o início da onda P até a onda R) e o QTc (9,2%, uma medida de despolarização e repolarização dos ventrículos), sem mudar a duração do complexo QRS. A (-)-carvona diminuiu a fração de encurtamento (61%), a (ICa,L) (79%) e o transiente intracelular de Ca+2 (38%). Além disso, a (-)-carvona apresentou ação antiarrítmica, identificada pela redução do escore de arritmia (85%) e ocorrência de fibrilação ventricular. Conclusão: A (-)-carvona reduz a entrada de Ca+2 através de canais de Ca+2 do tipo L e, assim, diminui a contratilidade cardíaca e o Ca+2 intracelular e apresenta promissora atividade antiarrítmica no coração de ratos.

Abstract Background: (-)-Carvone is a monoterpene found in essential oils with antioxidant and anti-inflammatory activity. Objective: The aim of this paper was to analyze the antiarrhythmic property of (-)-carvone in the rat heart and its effects on the intracellular Ca2+ signaling. Methods: The effects of (-)-carvone were evaluated on the ventricular (0.5 mM) and atrial contractility (0.01 - 4 mM) and on electrocardiogram (0.5 mM). Fractional shortening, L-type calcium current (ICa,L) and Ca2+ signaling were measured in the isolated cardiomyocyte (0.5 mM). Antiarrhythmic effect was evaluated in arrhythmia model induced by calcium overload (0.5 mM) (n = 5). P < 0.05 was used as the significance level. Results: In the atrium, (-)-carvone evoked negative inotropism that was concentration-dependent (EC50 0.44 ± 0.11 mM) and decreased the positive inotropism evoked by CaCl2 (0.1 to 8.0 mM) or BAY K8644 (5 to 500 nM), an agonist of L-type Ca2+ channel. In isolated heart, (-)-carvone (0.5 mM) promoted reduction of ventricular contractility (73%) and heart rate (46%), increased PRi (30.7%, time from the onset of the P wave until the R wave) and QTc (9.2%, a measure of the depolarization and repolarization of the ventricles) without changing the QRS complex duration. (-)-Carvone decreased the fractional shortening (61%), ICa,L (79%) and Ca2+ intracellular transient (38%). Furthermore, (-)-carvone showed antiarrhythmic action, verified by decrease of the arrhythmia score (85%) and occurrence of ventricular fibrillation. Conclusion: (-)-Carvone decreases Ca2+ entry through L-type Ca2+ channels, reducing the cardiac contractility and intracellular Ca2+, and, therefore, presenting promising antiarrhythmic activity in the rat hearts.

Efeito Cardiodepressor do Acetato de Eugenil em Coração de Roedor / Cardiodepressive Effect of Eugenyl Acetate in Rodent Heart

Resumo No presente trabalho investigou-se o efeito inotrópico do acetato de eugenil (AE), bem como sua ação sobre a corrente de Ca2+ do tipo L (ICa,L). Os experimentos de contratilidade foram realizados em átrio esquerdo isolado de cobaia exposto às concentrações crescentes da droga (1 a 5.000μM). O AE reduziu a força de contração atrial (IC50=558±24,06μM) de modo dependente de concentração. O efeito do AE sobre a ICa,L também foi avaliado em cardiomiócitos ventriculares isolados de camundongos, utilizando-se a técnica de "patch-clamp". O AE apresentou um efeito inibitório (IC50=1.337±221μM) sobre os canais de Ca2+ sensíveis à voltagem (CaV1.2). Em conclusão, o AE apesenta efeito cardiodepressor que se deve, pelo menos em parte, à diminuição da entrada de Ca2+ nos cardiomiócitos.

NOTCH1 is critical for fibroblast-mediated induction of cardiomyocyte specialization into ventricular conduction system-like cells in vitro.

Cardiac fibroblasts are present throughout the myocardium and are enriched in the microenvironment surrounding the ventricular conduction system (VCS). Several forms of arrhythmias are linked to VCS abnormalities, but it is still unclear whether VCS malformations are cardiomyocyte autonomous or could be linked to crosstalk between different cell types. We reasoned that fibroblasts influence cardiomyocyte specialization in VCS cells. We developed 2D and 3D culture models of neonatal rat cardiac cells to assess the influence of cardiac fibroblasts on cardiomyocytes. Cardiomyocytes adjacent to cardiac fibroblasts showed a two-fold increase in expression of VCS markers (NAV1.5 and CONTACTIN 2) and calcium transient duration, displaying a Purkinje-like profile. Fibroblast-conditioned media (fCM) was sufficient to activate VCS-related genes (Irx3, Scn5a, Connexin 40) and to induce action potential prolongation, a hallmark of Purkinge phenotype. fCM-mediated response seemed to be spatially-dependent as cardiomyocyte organoids treated with fCM had increased expression of connexin 40 and NAV1.5 primarily on its outer surface. Finally, NOTCH1 activation in both cardiomyocytes and fibroblasts was required for connexin 40 up-regulation (a proxy of VCS phenotype). Altogether, we provide evidence that cardiac fibroblasts influence cardiomyocyte specialization into VCS-like cells via NOTCH1 signaling in vitro.

Ações Transmurais Inotrópicas e Antiarrítmicas da Ranolazina em um Modelo Celular da Síndrome do QT Longo Tipo 3 / Inotropic and Antiarrhythmic Transmural Actions of Ranolazine in a Cellular Model of Type 3 Long QT Syndrome

Resumo A Ranolazina (RANO), conhecida na clínica como Ranexa, é um fármaco que previne a arritmia cardíaca através da inibição da corrente de sódio tardia (INaT). Um gradiente de voltagem transmural do canal Nav1.5 encontra-se na parede ventricular esquerda do coração. Assim, investigamos os efeitos da RANO em cardiomiócitos saudáveis e em modelo celular da Síndrome do QT longo tipo 3 (SQTL tipo 3). Usamos células isoladas do endocárdio (ENDO) e do epicárdio (EPI) e um software de medição com detecção de bordas por vídeo e microscopia de fluorescência para monitorar os transientes de cálcio. A RANO (0,1, 1, 10 e 30 uM, a 25OC) em uma série de frequências de estimulação teve impacto pouco significativo sobre ambos os tipos de células, mas a RANO (30uM) a 35OC minimizou o encurtamento dos sarcômeros em ~21% para células do endocárdio. Em seguida, para simular a SQTL tipo 3, as células do ENDO e EPI foram expostas à toxina ATX-II da anêmona do mar, que aumenta a INaT. As arritmias celulares induzidas por ATX-II foram suprimidas com o uso da RANO (30 µM) a 35OC. Com base nesses resultados, podemos concluir que a RANO tem um impacto pouco significativo sobre o encurtamento dos sarcômeros de células saudáveis do ENDO e EPI. Além disso, ela suprime as arritmias induzidas por INaT para níveis semelhantes nas células do ENDO e EPI.

Abstract Ranolazine (RANO) prevents cardiac arrhythmia by blocking the late sodium current (INaL). A transmural gradient of Nav1.5 is found in the left ventricular wall of the heart. Thus, we investigated the effects of RANO in healthy cardiomyocytes and in a cellular model of type 3 long QT syndrome (LQT3). We used isolated endocardium (ENDO) and epicardium (EPI) cells and a video edge detection system and fluorescence microscopy to monitor calcium transients. RANO (0.1, 1, 10 and 30 uM, at 25oC) at a range of pacing frequencies showed a minor impact on both cell types, but RANO at 30uM and 35oC for ENDO cells attenuated sarcomere shortening by~21%. Next, to mimic LQT3, we exposed ENDO and EPI cells to anemone toxin II (ATX-II), which augments INaL. Cellular arrhythmias induced by ATX-II were abrogated by RANO (30 µM) at 35oC. Based on our results we can conclude that RANO has a minor impact on sarcomere shortening of healthy ENDO and EPI cells and it abrogates arrhythmias induced by INaLto a similar level in ENDO and EPI cells.

Reactive oxygen species and nitric oxide imbalances lead to in vivo and in vitro arrhythmogenic phenotype in acute phase of experimental Chagas disease.

Chagas Disease (CD) is one of the leading causes of heart failure and sudden death in Latin America. Treatments with antioxidants have provided promising alternatives to ameliorate CD. However, the specific roles of major reactive oxygen species (ROS) sources, including NADPH-oxidase 2 (NOX2), mitochondrial-derived ROS and nitric oxide (NO) in the progression or resolution of CD are yet to be elucidated. We used C57BL/6 (WT) and a gp91PHOX knockout mice (PHOX-/-), lacking functional NOX2, to investigate the effects of ablation of NOX2-derived ROS production on the outcome of acute chagasic cardiomyopathy. Infected PHOX-/- cardiomyocytes displayed an overall pro-arrhythmic phenotype, notably with higher arrhythmia incidence on ECG that was followed by higher number of early afterdepolarizations (EAD) and 2.5-fold increase in action potential (AP) duration alternans, compared to AP from infected WT mice. Furthermore, infected PHOX-/- cardiomyocytes display increased diastolic [Ca2+], aberrant Ca2+ transient and reduced Ca2+ transient amplitude. Cardiomyocyte contraction is reduced in infected WT and PHOX-/- mice, to a similar extent. Nevertheless, only infected PHOX-/- isolated cardiomyocytes displayed significant increase in non-triggered extra contractions (appearing in ~75% of cells). Electro-mechanical remodeling of infected PHOX-/-cardiomyocytes is associated with increase in NO and mitochondria-derived ROS production. Notably, EADs, AP duration alternans and in vivo arrhythmias were reverted by pre-incubation with nitric oxide synthase inhibitor L-NAME. Overall our data show for the first time that lack of NOX2-derived ROS promoted a pro-arrhythmic phenotype in the heart, in which the crosstalk between ROS and NO could play an important role in regulating cardiomyocyte electro-mechanical function during acute CD. Future studies designed to evaluate the potential role of NOX2-derived ROS in the chronic phase of CD could open new and more specific therapeutic strategies to treat CD and prevent deaths due to heart complications.

Absence of suppressor of cytokine signaling 2 turns cardiomyocytes unresponsive to LIF-dependent increases in Ca2+ levels.

Little is known regarding the role of suppressor of cytokine signaling (SOCS) in the control of cytokine signaling in cardiomyocytes. We investigated the consequences of SOCS2 ablation for leukemia inhibitory factor (LIF)-induced enhancement of intracellular Ca2+ ([Ca2+]i) transient by performing experiments with cardiomyocytes from SOCS2-knockout (ko) mice. Similar levels of SOCS3 transcripts were seen in cardiomyocytes from wild-type and SOCS2-ko mice, while SOCS1 mRNA was reduced in SOCS2-ko. Immunoprecipitation experiments showed increased SOCS3 association with gp130 receptor in SOCS2-ko myocytes. Measurements of Ca2+ in wild-type myocytes exposed to LIF showed a significant increase in the magnitude of the Ca2+ transient. This change was absent in LIF-treated SOCS2-ko cells. LIF activation of ERK and STAT3 was observed in both wild-type and SOCS2-ko cells, indicating that in SOCS2-ko, LIF receptors were functional, despite the lack of effect in the Ca2+ transient. In wild-type cells, LIF-induced increase in [Ca2+]i and phospholamban Thr17 [PLN(Thr17)] phosphorylation was inhibited by KN-93, indicating a role for CaMKII in LIF-induced Ca2+ raise. LIF-induced phosphorylation of PLN(Thr17) was abrogated in SOCS2-ko myocytes. In wild-type cardiomyocytes, LIF treatment increased L-type Ca2+ current (ICa,L), a key activator of CaMKII in response to LIF. Conversely, SOCS2-ko myocytes failed to activate ICa,L in response to LIF, providing a rationale for the lack of LIF effect on Ca2+ transient. Our data show that absence of SOCS2 turns cardiomyocytes unresponsive to LIF-induced [Ca2+] raise, indicating that endogenous levels of SOCS2 are crucial for full activation of LIF signaling in the heart.

Molecular mechanisms of cardiac electromechanical remodeling during Chagas disease: Role of TNF and TGF-ß.

Chagas disease is caused by the trypanosomatid Trypanosoma cruzi, which chronically causes heart problems in up to 30% of infected patients. Chagas disease was initially restricted to Latin America. However, due to migratory events, this disease may become a serious worldwide health problem. During Chagas disease, many patients die of cardiac arrhythmia despite the apparent benefits of anti-arrhythmic therapy (e.g., amiodarone). Here, we assimilate the cardiac form of Chagas disease to an inflammatory cardiac disease. Evidence from the literature, mostly provided using experimental models, supports this view and argues in favor of new strategies for treating cardiac arrhythmias in Chagas disease by modulating cytokine production and/or action. But the complex nature of myocardial inflammation underlies the need to better understand the molecular mechanisms of the inflammatory response during Chagas disease. Here, particular attention has been paid to tumor necrosis factor alpha (TNF) and transforming growth factor beta (TGF-ß) although other cytokines may be involved in the chagasic cardiomyopathy.

Functional cross-talk between aldosterone and angiotensin-(1-7) in ventricular myocytes.

High serum levels of aldosterone have been linked to the development of cardiac disease. In contrast, angiotensin (Ang)-(1-7) was extensively shown to possess cardioprotective effects, including the attenuation of cardiac dysfunction induced by excessive mineralocorticoid activation in vivo, suggesting possible interactions between these 2 molecules. Here, we investigated whether there is cross-talk between aldosterone and Ang-(1-7) and its functional consequences for calcium (Ca(2+)) signaling in ventricular myocytes. Short-term effects of aldosterone on Ca(2+) transient were assessed in Fluo-4/AM-loaded myocytes. Confocal images showed that Ang-(1-7) had no effect on Ca(2+) transient parameters, whereas aldosterone increased the magnitude of the Ca(2+) transient. Quite unexpectedly, addition of Ang-(1-7) to aldosterone-treated myocytes further enhanced the amplitude of the Ca(2+) transient suggesting a synergistic effect of these molecules. Aldosterone action on Ca(2+) transient amplitude was mediated by protein kinase A, and was related to an increase in Ca(2+) current (I(Ca)) density. Both changes were not altered by Ang-(1-7). When cardiomyocytes were exposed to aldosterone, increased Ca(2+) spark rate was measured. Ang-(1-7) prevented this change. In addition, a NO synthase inhibitor restored the effect of aldosterone on Ca(2+) spark rate in Ang-(1-7)-treated myocytes and attenuated the synergistic effect of these 2 molecules on Ca(2+) transient. These results indicate that NO plays an important role in this cross-talk. Our results bring new perspectives in the understanding of how 2 prominent molecules with supposedly antagonist cardiac actions cross-talk to synergistically amplify Ca(2+) signals in cardiomyocytes.

Role of SOCS2 in modulating heart damage and function in a murine model of acute Chagas disease.

Infection with Trypanosoma cruzi induces inflammation, which limits parasite proliferation but may result in chagasic heart disease. Suppressor of cytokine signaling 2 (SOCS2) is a regulator of immune responses and may therefore participate in the pathogenesis of T. cruzi infection. SOCS2 is expressed during T. cruzi infection, and its expression is partially reduced in infected 5-lipoxygenase-deficient [knockout (KO)] mice. In SOCS2 KO mice, there was a reduction in both parasitemia and the expression of interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), IL-6, IL-10, SOCS1, and SOCS3 in the spleen. Expression of IFN-γ, TNF-α, SOCS1, and SOCS3 was also reduced in the hearts of infected SOCS2 KO mice. There was an increase in the generation and expansion of T regulatory (Treg) cells and a decrease in the number of memory cells in T. cruzi-infected SOCS2 KO mice. Levels of lipoxinA(4) (LXA(4)) increased in these mice. Echocardiography studies demonstrated an impairment of cardiac function in T. cruzi-infected SOCS2 KO mice. There were also changes in calcium handling and in action potential waveforms, and reduced outward potassium currents in isolated cardiac myocytes. Our data suggest that reductions of inflammation and parasitemia in infected SOCS2-deficient mice may be secondary to the increases in Treg cells and LXA(4) levels. This occurs at the cost of greater infection-associated heart dysfunction, highlighting the relevance of balanced inflammatory and immune responses in preventing severe T. cruzi-induced disease.

Morphine peripheral analgesia depends on activation of the PI3Kgamma/AKT/nNOS/NO/KATP signaling pathway.

Morphine is one of the most prescribed and effective drugs used for the treatment of acute and chronic pain conditions. In addition to its central effects, morphine can also produce peripheral analgesia. However, the mechanisms underlying this peripheral action of morphine have not yet been fully elucidated. Here, we show that the peripheral antinociceptive effect of morphine is lost in neuronal nitric-oxide synthase null mice and that morphine induces the production of nitric oxide in primary nociceptive neurons. The activation of the nitric-oxide pathway by morphine was dependent on an initial stimulation of PI3Kgamma/AKT protein kinase B (AKT) and culminated in increased activation of K(ATP) channels. In the latter, this intracellular signaling pathway might cause a hyperpolarization of nociceptive neurons, and it is fundamental for the direct blockade of inflammatory pain by morphine. This understanding offers new targets for analgesic drug development.

(S)-reticuline induces vasorelaxation through the blockade of L-type Ca(2+) channels.

In Brazil, various species of the genus Ocotea are used in folk medicine for treating several diseases. The chemical characterization of this plant showed the presence of alkaloids belonging to the benzyltetrahydroisoquinoline family, the major component of which is (S)-reticuline. The present study investigated whether (S)-reticuline exerts an inhibitory effect on smooth muscle L-type Ca(2+) channels. Tension measurements and patch clamp techniques were utilized to study the effects of (S)-reticuline. Whole-cell Ca(2+) currents were measured using the A7r5 smooth muscle cell line. (S)-reticuline antagonized CaCl(2)- and KCl-induced contractions and elicited vasorelaxation. It also reduced the voltage-activated peak amplitude of I (Ca,L) in a concentration-dependent manner. (S)-reticuline did not change the characteristics of current density vs. voltage relationship. (S)-reticuline shifted leftwards the steady-state inactivation curve of I (Ca,L). The application of dibutyryl cyclic adenosine monophosphate to the cell decreased the amplitude of Ca(2+) currents. In cells pretreated with forskolin, an adenylate cyclase activator, the addition of (S)-reticuline caused further inhibition of the Ca(2+) currents suggesting an additive effect. The results obtained show that (S)-reticuline elicits vasorelaxation probably due to the blockade of the L-type voltage-dependent Ca(2+) current in rat aorta. The reported effect may contribute to the potential cardioprotective efficacy of (S)-reticuline.