The effect of intracoronary sodium nitrite on the burden of ventricular arrhythmias following primary percutaneous coronary intervention for acute myocardial infarction

Dexmedetomidine exerts cardioprotective effect through miR-146a-3p targeting IRAK1 and TRAF6 via inhibition of the NF-κB pathway

BACKGROUND

Myocardial ischemia/reperfusion (I/R) injury is a common cause of mortality. Cardiac miR-146a is emerging as a potent regulator of myocardial function. Dexmedetomidine preconditioning provides cardioprotective effects, of which mechanisms related to miR-146a-3p are unclear.

METHODS

A myocardial I/R model in rats and a cellular anoxia/reoxygenation (A/R) model in H9C2 cells were established and preconditioned with dexmedetomidine or not. H9C2 cells were transfected with mimics, inhibitor, or negative controls of miR-146a-3p, and siRNAs of IRAK1 or TRAF6. Relative expressions of miR-146a-3p were determined by quantitative real-time polymerase chain reaction. The apoptosis rates and reactive oxygen species (ROS) levels in H9C2 cells were examined by flow cytometry. Protein expressions of IRAK1, TRAF6, cleaved Caspase-3, BAX, BCL-2, NF-κB p65, phosphorylated NF-κB p65 (p-NF-κB p65), IκBα, and phosphorylated IκBα (p-IκBα) in H9C2 cells were detected by Western blot.

RESULTS

Dexmedetomidine decreased myocardial infarction size and apoptosis rates of H9C2 cells. Dexmedetomidine upregulated expression of miR-146a-3p. Dexmedetomidine significantly decreased protein expressions of IRAK1, TRAF6, cleaved Caspase-3, BAX, and NF-κB p65, but increased expressions of BCL-2 in H9C2 cells. miR-146a-3p overexpression strengthened the anti-apoptotic effect induced by dexmedetomidine in H9C2 cells via decreasing protein levels of IRAK1, TRAF6, cleaved Caspase-3, BAX, NF-κB p65, p-NF-κB p65, and p-IκBα and increasing protein level of BCL-2. Downregulation of miR-146a-3p reversed the changes in these proteins in H9C2 cells. Expressions of NF-κB p65 and p-NF-κB p65 were further decreased following knockdown of IRAK1 or TRAF6. ROS emission was significantly increased after A/R, while significantly decreased following dexmedetomidine preconditioning in H9C2 cells transfected with siIRAK1 or siTRAF6.

CONCLUSION

miR-146a-3p targeting IRAK1 and TRAF6 through inhibition of NF-κB signaling pathway and ROS emission is involved in cardioprotection induced by dexmedetomidine pretreatment.

Effects of Oral Sodium Nitrite on Blood Pressure, Insulin Sensitivity, and Intima-Media Arterial Thickening in Adults With Hypertension and Metabolic Syndrome

The nitrate-nitrite-NO pathway regulates NO synthase-independent vasodilation and NO signaling. Ingestion of inorganic nitrite has vasodilatory and blood pressure-lowering effects. Preclinical studies in rodent models suggest there may be a benefit of nitrite in lowering serum triglyceride levels and improving the metabolic syndrome. In a phase 2 study, we evaluated the safety and efficacy of chronic oral nitrite therapy in patients with hypertension and the metabolic syndrome. Twenty adult subjects with stage 1 or 2 hypertension and the metabolic syndrome were enrolled in an open-label safety and efficacy study. The primary efficacy end point was blood pressure reduction; secondary end points included insulin-dependent glucose disposal and endothelial function measured by flow-mediated dilation of the brachial artery and intima-media diameter of the carotid artery. Chronic oral nitrite therapy (40 mg/3× daily) was well tolerated. Oral nitrite significantly lowered systolic, diastolic, and mean arterial pressures, but tolerance was observed after 10 to 12 weeks of therapy. There was significant improvement in the intima-media thickness of the carotid artery and trends toward improvements in flow-mediated dilation of the brachial artery and insulin sensitivity. Chronic oral nitrite therapy is safe in patients with hypertension and the metabolic syndrome. Despite an apparent lack of enzymatic tolerance to nitrite, we observed tolerance after 10 weeks of chronic therapy, which requires additional mechanistic studies and possible therapeutic dose titration in clinical trials. Nitrite may be a safe therapy to concominantly improve multiple features of the metabolic syndrome including hypertension, insulin resistance, and endothelial dysfunction. Registration- URL: https://www.clinicaltrials.gov; Unique identifier: NCT01681810.

ArrhythmoGenoPharmacoTherapy

This review is focusing on the understanding of various factors and components governing and controlling the occurrence of ventricular arrhythmias including (i) the role of various ion channel-related changes in the action potential (AP), (ii) electrocardiograms (ECGs), (iii) some important arrhythmogenic mediators of reperfusion, and pharmacological approaches to their attenuation. The transmembrane potential in myocardial cells is depending on the cellular concentrations of several ions including sodium, calcium, and potassium on both sides of the cell membrane and active or inactive stages of ion channels. The movements of Na+, K+, and Ca2+ via cell membranes produce various currents that provoke AP, determining the cardiac cycle and heart function. A specific channel has its own type of gate, and it is opening and closing under specific transmembrane voltage, ionic, or metabolic conditions. APs of sinoatrial (SA) node, atrioventricular (AV) node, and Purkinje cells determine the pacemaker activity (depolarization phase 4) of the heart, leading to the surface manifestation, registration, and evaluation of ECG waves in both animal models and humans. AP and ECG changes are key factors in arrhythmogenesis, and the analysis of these changes serve for the clarification of the mechanisms of antiarrhythmic drugs. The classification of antiarrhythmic drugs may be based on their electrophysiological properties emphasizing the connection between basic electrophysiological activities and antiarrhythmic properties. The review also summarizes some important mechanisms of ventricular arrhythmias in the ischemic/reperfused myocardium and permits an assessment of antiarrhythmic potential of drugs used for pharmacotherapy under experimental and clinical conditions.

2-methoxy-isobutyl-isonitrile-conjugated gold nanoparticles improves redox and inflammatory profile in infarcted rats

The tissue response to acute myocardial infarction (AMI) is key to avoiding heart complications due to inflammation, mitochondrial dysfunction, and oxidative stress. Antioxidant and anti-inflammatory agents can minimize the effects of AMI. This study investigated the role of 2-methoxy-isobutyl-isonitrile (MIBI)-associated gold nanoparticles (AuNP) on reperfusion injury after ischemia and its effect on cardiac remodeling in an experimental AMI model. Three-month-old Wistar rats were subjected to a temporary blockade of the anterior descending artery for 30 min followed by reperfusion after 24 h and 7 days by intraventricularly administering 0.4, 1.3, and 3 mg/kg AuNP-MIBI. The cardiac toxicity and renal and hepatic function levels were determined, and the infarct and peri-infarct regions were surgically removed for histopathology, analysis of inflammation from oxidative stress, and echocardiography. MIBI-conjugated AuNP promoted changes in oxidative stress and inflammation depending on the concentrations used, suggesting promising applicability for therapeutic purposes.