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Background Reactive oxygen species, such as superoxide, are being increasingly recognized as key components of a vast array of signaling pathways. Angiotensin II is a well-recognized stimulus for superoxide production through NADPH oxidase activation and opening of the mitochondrial ATP-sensitive potassium channels (mK ATP ). A role for this mechanism has been proposed to explain several physiological effects of the peptide. The aim of this study was to evaluate the involvement of this mechanism in the inotropic response to 100 nmol/L angiotensin II. Methods Sarcomere shortening and intracellular pH (BCECF-epifluorescence technique) were evaluated in isolated cat ventricular myocytes placed in a perfusion chamber on the stage of an inverted microscope. Myocardial superoxide production was evaluated by the lucigenin quimioluminiscence method. Results Angiotensin II (100 nmol/L) increased~70% sarcomere shortening, effect that was only partially prevented by NADPH oxidase inhibition, mK ATP channel blockade or inhibition of the cardiac Na + /H + exchanger (NHE-1). Moreover, angiotensin II stimulates NHE-1 activity by a NADPH oxidase-dependent mechanism. Myocardial superoxide production was also increased by angiotensin II, and this action was completely prevented either by NADPH oxidase inhibition or mK ATP channel blockade. Conclusions The positive inotropic response to 100 nmol/L angiotensin II is due to both ROS/NHE-1 dependent and independent pathways, this being a point of divergence with the signaling previously described to be triggered by lower concentrations of angiotensin II (i.e.: 1 nmol/L). [ABSTRACT FROM AUTHOR]

Background Although the participation of the electrogenic sodium/bicarbonate cotransporter (NBCe1) in the recovery from an intracellular acid load is recognized, its role in ischemia–reperfusion is still unclear. Methods and results Our objective was to assess the role of NBCe1 in reperfusion injury. We use selective functional antibodies against extracellular loop 3 (a-L3) and loop 4 (a-L4) of NBCe1. a-L3 inhibits and a-L4 stimulates NBCe1 activity. Isolated rat hearts were submitted to 40 min of coronary occlusion and 1 h of reperfusion. a-L3, a-L4 or S0859 — selective Na + -HCO 3 - co-transport inhibitor — were administered during the initial 10 min of reperfusion. The infarct size (IS) was measured by triphenyltetrazolium chloride staining technique. Postischemic systolic and diastolic functions were also assessed. a-L3 and S0859 treatments decreased significantly ( P <.05) the IS (16±3% for a-L3 vs. 32±5% in hearts treated with control nonimmune serum and 19±3% for S0859 vs. 39±2% in untreated hearts). Myocardial function during reperfusion improved after a-L3 treatment, but it was not modified by S0859. The infusion of a-L4 did not modify neither the IS nor myocardial function. Conclusions The NBCe1 hyperactivity during reperfusion leads to Na + and Ca 2+ loading, conducing to Ca 2+ overload and myocardial damage. Consistently, we have shown herein that the selective NBCe1 blockade with a-L3 exerted cardioprotection. This beneficial action strongly suggests that NBCe1 could be a potential target for the treatment of coronary disease. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract The electrogenic sodium bicarbonate co-transporter isoform 1 (NBCe1) plays an important role in ischemia-reperfusion injury. The cardioprotective action of an antibody directed to the extracellular loop 3 (a-L3) of NBCe1 was previously demonstrated by us. However, the role of a-L3 on mitochondrial post-ischemic alterations has not yet been determined. In this study, we aimed to elucidate the effects of a-L3 on post-ischemic mitochondrial state and dynamics analysing the involved mechanisms. Isolated rat hearts were assigned to the following groups: 1) Non-ischemic control (NIC): 110 min of perfusion; 2) Ischemic control (IC): 30 min of global ischemia and 60 min of reperfusion (R); 3) a-L3: a-L3 was administered during the initial 10 min of R; 4) SB + a-L3: SB202190 (p38MAPK inhibitor) plus a-L3. Infarct size (IS) was measured by TTC staining. Developed pressure (LVDP), maximal velocities of rise and decay of LVP (+dP/dt max, −dP/dt max) and end-diastolic pressure (LVEDP) of the left ventricle were used to assess systolic and diastolic function. Mitochondrial Ca2+ response (CaR), Ca2+ retention capacity (CRC), membrane potential (ΔΨm) and MnSOD levels were measured. The expression of P-p38MAPK, calcineurin, P-HSP27, P-Drp1, Drp1, and OPA1 were determined. a-L3 decreased IS, improved post-ischemic recovery of myocardial function, increased P-p38MAPK, P-HSP27, P-Drp1, cytosolic Drp1, and OPA1 expression and decreased calcineurin. These effects were abolished by p38MAPK inhibition with SB. These data show that NBCe1 inhibition by a-L3 limits the cell death, improves myocardial post-ischemic contractility and mitochondrial state and dynamic through calcium decrease/calcineurin inhibition-mediated p38MAPK activation and p38MAPK/HSP27-dependent pathways. Thus, we demonstrated that a-L3 is a potential therapeutic strategy in post-ischemic alterations. [ABSTRACT FROM AUTHOR]

Ventricular hypertrophy is a risk factors for arrhythmias, ischemia and sudden death. It involves cellular modifications leading to a pathological remodeling and is associated with heart failure. The activation of the G protein-coupled estrogen receptor (GPER) mediates beneficial actions in the cardiovascular system. Our goal was to prevent and regress the hypertrophy by the activation of GPER in neonatal cardiac myocytes (NRCM) and SHR male rats. Aldosterone increased the neonatal cardiomyocytes cell surface area after 48 h of incubation. The aldo-induced hypertrophy was blocked by the mineralocorticoid receptor (MR) inhibitor Eplererone or the reduction of MR expression by siRNA. The activation of GPER by the agonist G-1 totally prevented the increase surface area by Ald. The transfection of neonatal rat cardiac myocytes with a siRNA against GPER or the incubation with GPER blockers G-15 and G-36 inhibited the protection of G-1. The significant increase of cell surface area after 48 h of incubation with Ald was totally regressed in 24 h by the presence of G-1, indicating that the activation of GPER not only prevent the hypertrophy but also regress the hypertrophy when it is already established. In the in vivo model, G-1 or Vehicle was constantly infused via the minipump to SHR. The reduction of the hypertrophy by G-1 was evident by the cross-sectional area, BNP and ANP markers and by echocardiography. In this studied we demonstrated that the activation of GPER prevented and regressed the hypertrophy induced by Ald in NRCM and regressed hypertrophy in SHR rats. [ABSTRACT FROM AUTHOR]