Virginia Perez

Role of the parasympathetic nervous system in cardioprotection by remote hindlimb ischaemic preconditioning

•  What is the central question of this study? Ischaemia–reperfusion of peripheral tissues protects the heart from subsequent myocardial ischaemia–reperfusion‐induced injury and cardiac dysfunction, a phenomenon referred to as ‘remote ischaemic preconditioning’ (rIPC). This study addressed whether activation of sensory afferent nerves in the ischaemic hindlimb and vagal efferent nerves innervating the heart mediate rIPC. •  What is the main finding and its importance? Spinal cord section, bilateral vagotomy or blockade of muscarinic cholinergic receptors in vivo abolished rIPC and cardioprotection measured in vitro. Electrical stimulation of the vagus nerve induced cardioprotection, thus mimicking rIPC. The finding that sensory and parasympathetic neural mechanisms mediate rIPC confirms and extends previous results, with implications for translational studies in patients with coronary artery disease.

Metformin therapy and prognosis of patients with heart failure and new-onset diabetes mellitus. A propensity-matched study in the community

OBJECTIVE To assess the effect of the commencement of metformin therapy (CMet) on the prognosis of patients with newly diagnosed heart failure (HF) and new-onset diabetes mellitus (DM) treated with a contemporary medical regimen. METHODS Prospective study of 1519 HF patients with DM during 9 years. Mean age was 71.7+/-7.8 years, 817 (53.8%) were women, and 780 (51.3%) had preserved systolic function. During a median follow-up of 56.9+/-18.2 months, 1045 patients (68.8%) died, 1344 (88.5%) were hospitalized for worsening HF, 593 (39.0%) did not CMet, and 391 of the patients CMet (42.2%) had a mean HbA1c=<7.0%. No case of lactic acidosis due to metformin was observed. We propensity-score matched 592 patients who CMet with another 592 patients non-CMet. RESULTS CMet was associated with a decreased mortality (HR [CI 95%]: .85 [.82-.88]), mainly due to a reduced cardiovascular mortality (HR: .78 [.74-.82]), and with a lower hospitalization rate (HR: .81 [.79-.84]). Nevertheless, CMet was not associated with an improved prognosis of HF patients with a mean HbA1c=<7.0%. These relationships of CMet with prognosis were maintained, independently of the gender, the type of HF (systolic or, non-systolic), the comorbidities, and the medication used (P<.01). CONCLUSION Metformin therapy is associated with a reduced mortality of heart failure patients with new-onset diabetes mellitus, mainly due to a decreased cardiovascular mortality, and with a lower hospitalization rate. Nevertheless, CMet was not associated with an improved prognosis of HF patients with a mean HbA1c=<7.0%.

Impact of new-onset diabetes mellitus and glycemic control on the prognosis of heart failure patients: A propensity-matched study in the community ☆

OBJECTIVES To assess the incidence of type 2 diabetes mellitus (DM) in patients with heart failure (HF), and to evaluate the effect of new-onset DM and glycemic control on the prognosis of HF patients treated with a contemporary medical regimen. METHODS Prospective study of 5314 HF patients and previously unknown DM during 9 years. Their mean age was 71.8 ± 7.9 years, 53.0% were women, and 50.2% had non-systolic HF. During a median follow-up of 56.9 ± 18.2 months, 68.9% of the patients died, 88.6% were hospitalized for HF, and 1519 (27.3%) developed new-onset DM. We propensity-matched those 1519 HF patients with DM, with 1519 HF patients non-diagnosed with DM. RESULTS The age- and sex-adjusted incidence (per 100 HF patients/years) of DM in HF patients was 3.20, higher in women and in patients with non-systolic HF (p<0.01). Patients with HF and DM and those with a mean HbA1c>7.0% presented an increased mortality (HR of death [CI 95%]: 2.44 [1.68-3.19] and, HR: 2.56 [1.77-3.35], respectively), mainly due to an increased cardiovascular mortality (HR ≥ 2.40 [1.46-3.34]) (P<0.001). The rate of hospitalization, of 30-day readmissions, and the number of visits were higher among HF patients with DM or with HbA1c>7.0% (p<0.001). These relationships of DM and its poor metabolic control with prognosis were maintained, independently of the gender, the type of HF (systolic or, non-systolic), the comorbidities, and the medication used (P<0.01). CONCLUSION New-onset diabetes mellitus and its poor metabolic control (HbA1c>7.0%) are associated with a increased mortality and morbidity of patients with heart failure.

Preischemic efferent vagal stimulation increases the size of myocardial infarction in rabbits. Role of the sympathetic nervous system

rabbits. Role of the sympathetic nervous system Bruno Buchholz , Martin Donato , Virginia Perez , Flavio C. Ivalde , Christian Hocht , Emiliano Buitrago , Manuel Rodriguez , Ricardo J. Gelpi a,⁎,2 a Institute of Cardiovascular Physiopathology and Department of Pathology, School of Medicine, University of Buenos Aires, Argentina b Department of Pharmacology, School of Pharmacy and Biochemistry, University of Buenos Aires, Argentina

High cholesterol diet effects on ischemia–reperfusion injury of the heart

Ischemic heart disease is the leading cause of morbi-mortality in developed countries. Both ischemia-reperfusion injury and mechanisms of cardioprotection have been studied for more than 50 years. It is known that the physiopathological mechanism of myocardial ischemia involves several factors that are closely related to its development, of which hypercholesterolemia is one of the main ones. Therefore, the objective of this review was to elucidate the effects of a high-cholesterol diet on normal ventricular function and ischemia-reperfusion injury associated phenomenon such as post-ischemic ventricular dysfunction (stunned myocardium). Although there exist many studies considering several aspects of this physiopathological entity, the majority were carried out on normal animals. Thus, experiments carried out on hypercholesterolemic models are controversial, in particular those evaluating different mechanisms of cardioprotection such as ischemic preconditioning and postconditioning, and cardioprotection granted by drugs such as statins, which apart from exerting a lipid-lowering effect, exert pleiotropic effects providing cardioprotection against ischemia-reperfusion injury. These controversial results concerning the mechanisms of cardioprotection vary according to quality, composition, and time of administration of the high-cholesterol diet, as well as the species used in each experiment. Thus, to compare the results it is necessary to take all of these variables into account, since they can change the obtained results.

Myocardial triggers involved in remote ischemic preconditioning activation

New Findings What is the central question of this study? Ischemia/reperfusion of peripheral tissues protects the heart from subsequent myocardial ischemia/reperfusion injury, a phenomenon referred to as remote ischemic preconditioning (rIPC). This study evaluated the possible myocardial triggers of rIPC. What is the main finding and its importance? rIPC reduces infarct size through a vagal pathway and a mechanism involving Akt and eNOS phosphorylation, opening of mitochondrial K+ATP channels and increasing of mitochondrial H2O2 production. All these phenomena occur prior to the myocardial ischemia, therefore they could act as “triggers” of rIPC. Aims: It has been proposed that remote ischemic preconditioning (rIPC) activates a parasympathetic neural pathway. However, the myocardial rIPC intracellular mechanism remains unclear. Here we characterized some of the intracellular signals participating as rIPC triggers. Methods and Results: Isolated rat hearts were subjected to 30 minutes of global ischemia and 120 minutes of reperfusion (Non-rIPC). In a second group, before the isolation of the heart, a rIPC protocol (3 cycles of hindlimb ischemia/reperfusion) was performed. The infarct size was measured with tetrazolium staining. Akt and eNOS expression/phosphorylation, and mitochondrial H2O2 production were evaluated at the end of rIPC protocol, before myocardial ischemia/reperfusion. rIPC significantly decreased the infarct size and induced Akt and eNOS phosphorylation. The protective effect on infarct size was abolished by cervical vagal section (CVS), L-NAME (NO synthesis inhibitor) and 5-HD (mK+ATP channels blocker). Mitochondrial production of H2O2 was increased by rIPC while it was abolished by CVS, L-NAME and 5-HD. Conclusions: rIPC activates a parasympathetic vagal pathway and a mechanism involving the Akt and eNOS phosphorylation, the opening of mK+ATP, and the release of H2O2 by the mitochondria. These entire phenomena occur prior to the myocardial ischemia, which could act as triggers of rIPC. This article is protected by copyright. All rights reservedWhat is the central question of this study? Ischaemia–reperfusion of peripheral tissues protects the heart from subsequent myocardial ischaemia–reperfusion injury, a phenomenon referred to as remote ischaemic preconditioning (rIPC). This study evaluated the possible myocardial triggers of rIPC. What is the main finding and its importance? Remote ischaemic preconditioning reduces infarct size through a vagal pathway and a mechanism involving phosphorylation of Akt and endothelial nitric oxide synthase, opening of mitochondrial ATP‐dependent K+ channels and an increase in mitochondrial H2O2 production. All these phenomena occur before the myocardial ischaemia; hence, they could act as ‘triggers’ of rIPC.

Myocardial triggers involved in activation of remote ischaemic preconditioning.

New Findings What is the central question of this study? Ischemia/reperfusion of peripheral tissues protects the heart from subsequent myocardial ischemia/reperfusion injury, a phenomenon referred to as remote ischemic preconditioning (rIPC). This study evaluated the possible myocardial triggers of rIPC. What is the main finding and its importance? rIPC reduces infarct size through a vagal pathway and a mechanism involving Akt and eNOS phosphorylation, opening of mitochondrial K+ATP channels and increasing of mitochondrial H2O2 production. All these phenomena occur prior to the myocardial ischemia, therefore they could act as “triggers” of rIPC. Aims: It has been proposed that remote ischemic preconditioning (rIPC) activates a parasympathetic neural pathway. However, the myocardial rIPC intracellular mechanism remains unclear. Here we characterized some of the intracellular signals participating as rIPC triggers. Methods and Results: Isolated rat hearts were subjected to 30 minutes of global ischemia and 120 minutes of reperfusion (Non-rIPC). In a second group, before the isolation of the heart, a rIPC protocol (3 cycles of hindlimb ischemia/reperfusion) was performed. The infarct size was measured with tetrazolium staining. Akt and eNOS expression/phosphorylation, and mitochondrial H2O2 production were evaluated at the end of rIPC protocol, before myocardial ischemia/reperfusion. rIPC significantly decreased the infarct size and induced Akt and eNOS phosphorylation. The protective effect on infarct size was abolished by cervical vagal section (CVS), L-NAME (NO synthesis inhibitor) and 5-HD (mK+ATP channels blocker). Mitochondrial production of H2O2 was increased by rIPC while it was abolished by CVS, L-NAME and 5-HD. Conclusions: rIPC activates a parasympathetic vagal pathway and a mechanism involving the Akt and eNOS phosphorylation, the opening of mK+ATP, and the release of H2O2 by the mitochondria. These entire phenomena occur prior to the myocardial ischemia, which could act as triggers of rIPC. This article is protected by copyright. All rights reservedWhat is the central question of this study? Ischaemia–reperfusion of peripheral tissues protects the heart from subsequent myocardial ischaemia–reperfusion injury, a phenomenon referred to as remote ischaemic preconditioning (rIPC). This study evaluated the possible myocardial triggers of rIPC. What is the main finding and its importance? Remote ischaemic preconditioning reduces infarct size through a vagal pathway and a mechanism involving phosphorylation of Akt and endothelial nitric oxide synthase, opening of mitochondrial ATP‐dependent K+ channels and an increase in mitochondrial H2O2 production. All these phenomena occur before the myocardial ischaemia; hence, they could act as ‘triggers’ of rIPC.

DYSTROPHIN PROTEOLYSIS: A POTENTIAL TARGET FOR MMP-2 AND ITS PREVENTION BY ISCHEMIC PRECONDITIONING

Dystrophin is responsible for the mechanical stabilization of the sarcolemma, and it has been shown that it is one of the most sensitive proteins to ischemic injury. However, the enzyme responsible for this proteolysis is still unknown. Isolated rabbit hearts were subjected to 30 min of global ischemia with and without reperfusion (180 min) to determine whether dystrophin is cleaved by matrix metalloproteinase (MMP)-2 during acute ischemia and whether ischemic preconditioning (PC) prevents dystrophin breakdown through MMP-2 inhibition. The activity of MMP-2 was evaluated by zymography and using doxycycline as an inhibitor. Also, to stimulate MMP-2 activity without ischemia, SIN-1 was administered in the absence and presence of doxycycline. Finally, we considered the PC effect on MMP-2 activity and dystrophin expression. The dystrophin level decreased during ischemia, reaching 21% of control values (P < 0.05), but the spectrin level remained unchanged. MMP-2 activity increased 71% during ischemia compared with control values (P < 0.05). Doxycycline administration before ischemia prevented dystrophin breakdown. In normoxic hearts, SIN-1 increased thiobarbituric acid-reactive substances by 33% (P < 0.05) and MMP-2 activity by 36% (P < 0.05) and significantly reduced the dystrophin level to 23% of control values (P < 0.05). PC significantly prevented dystrophin breakdown by inhibiting MMP-2 activity, and the dystrophin level reached 89% of control values (P < 0.05). In conclusion, MMP-2 could be responsible for the proteolysis of dystrophin. Thus, dystrophin emerges as a possible novel substrate for MMP-2 in the context of ischemic injury. Furthermore, our results demonstrate that ischemic PC prevents dystrophin breakdown most likely by inhibiting MMP-2 activity.

Selective TNF-α targeting with infliximab attenuates impaired oxygen metabolism and contractile function induced by an acute exposure to air particulate matter

Inflammation plays a central role in the onset and progression of cardiovascular diseases associated with the exposure to air pollution particulate matter (PM). The aim of this work was to analyze the cardioprotective effect of selective TNF-α targeting with a blocking anti-TNF-α antibody (infliximab) in an in vivo mice model of acute exposure to residual oil fly ash (ROFA). Female Swiss mice received an intraperitoneal injection of infliximab (10 mg/kg body wt) or saline solution, and were intranasally instilled with a ROFA suspension (1 mg/kg body wt). Control animals were instilled with saline solution and handled in parallel. After 3 h, heart O2 consumption was assessed by high-resolution respirometry in left ventricle tissue cubes and isolated mitochondria, and ventricular contractile reserve and lusitropic reserve were evaluated according to the Langendorff technique. ROFA instillation induced a significant decrease in tissue O2 consumption and active mitochondrial respiration by 32 and 31%, respectively, compared with the control group. While ventricular contractile state and isovolumic relaxation were not altered in ROFA-exposed mice, impaired contractile reserve and lusitropic reserve were observed in this group. Infliximab pretreatment significantly attenuated the decrease in heart O2 consumption and prevented the decrease in ventricular contractile and lusitropic reserve in ROFA-exposed mice. Moreover, infliximab-pretreated ROFA-exposed mice showed conserved left ventricular developed pressure and cardiac O2 consumption in response to a β-adrenergic stimulus with isoproterenol. These results provides direct evidence linking systemic inflammation and altered cardiac function following an acute exposure to PM and contribute to the understanding of PM-associated cardiovascular morbidity and mortality.

Ischemic postconditioning reduces infarct size through the α1-adrenergic receptor pathway.

Abstract: The &agr;1-adrenergic receptors (&agr;1-ARs) are involved in preconditioning. Given that certain intracellular pathways seem to be shared by preconditioning and postconditioning, it is possible that postconditioning could also be mediated by &agr;1-ARs. The objective was to evaluate, by analyzing infarct size, if &agr;1-ARs activation could trigger postconditioning and also determine Akt and glycogen synthase kinase 3&bgr; (GSK-3&bgr;) phosphorylation. Langendorff-perfused rat hearts were subjected to 30 minutes of ischemia and 120 minutes of reperfusion (I/R; n = 8). After 30 minutes of global ischemia, we performed 6 cycles of reperfusion/ischemia of 10 seconds each, followed by 120 minutes of reperfusion [ischemic postconditioning group (postcon); n = 9]. In another postcon group, we administered prazosin during postcon protocol (postcon + prazosin; n = 7). Finally, we repeated the I/R group, but prazosin (prazosin; n = 7), phenylephrine (PE; n = 5) and clonidine (CL; n = 6) were administered during the first 2 minutes of reperfusion. Infarct size was measured using the triphenyltetrazolium chloride technique. Total and phosphorylated Akt and mitochondrial GSK-3&bgr; expression were measured by Western blot. Infarct size was 58.1 ± 5.1% in I/R. Postcon and PE reduced infarct size to 40.1 ± 2.9% and 35.3 ± 5.5%, respectively (P < 0.05 vs. I/R). Postcon + prazosin administration abolished the beneficial effect on infarct size (61.6 ± 4.5%; P < 0.05 vs. postcon). Cytosolic Akt phosphorylation and mitochondrial GSK-3&bgr; phosphorylation were higher in the postcon and PE groups compared with the I/R and postcon + prazosin groups. Prazosin or clonidine administration did not modify neither protein expression nor infarct size. Our data demonstrate that postconditioning decrease infarct size by activation of the &agr;1-AR pathway through Akt and GSK-3&bgr; phosphorylation.