Ablation of B1- and B2-kinin receptors causes cardiac dysfunction through redox-nitroso unbalance

Inclusion complex with β-cyclodextrin is a key determining factor for the cardioprotection induced by usnic acid

Ischemia-reperfusion (I/R) injury causes oxidative stress, leading to severe cardiac dysfunction. Thus, biologically active compounds with antioxidant properties may be viewed as a promising therapeutic strategy against oxidative-related cardiac disorders. Usnic acid (UA), a natural antioxidant, was complexed with β-cyclodextrin (βCD) to improve its bioavailability. Wistar male rats were orally treated with the free form of UA (50 mg/kg) or the inclusion complex UA/βCD (50 mg/kg) for seven consecutive days. Afterward, hearts were subjected to I/R injury, and the cardiac contractility, rhythmicity, infarct size, and antioxidant enzyme activities were evaluated. Here, we show that neither UA nor UA/βCD treatments developed signs of toxicity. After I/R injury, animals treated with UA/βCD showed improved post-ischemic cardiac functional recovery while the release of cell injury biomarkers decreased. Following reduced cardiac damage, a lower incidence of ventricular arrhythmias and smaller myocardial infarct size were associated with reduced lipid peroxidation, along with preserved activity of antioxidant enzymes compared to untreated rats. Surprisingly, uncomplexed UA did not protect hearts against IR injury. Altogether, our results indicate that the inclusion complex UA/βCD is a critical determining factor responsible for the cardioprotection action of UA, suggesting the involvement of an antioxidant-dependent mechanisms. Moreover, our findings support that UA/βCD is a structurally engineered compound with active cardioprotective properties.

NOX-dependent reactive oxygen species production underlies arrhythmias susceptibility in dexamethasone-treated rats

Dexamethasone is the most clinically used glucocorticoid with an established role in the treatment of a wide spectrum of inflammatory-related diseases. While the therapeutic actions are well known, dexamethasone treatment causes a number of cardiovascular side effects, which are complex, frequent and, in some cases, clinically unnoticeable. Here, we investigated whether a therapeutic regimen of dexamethasone affects cardiac arrhythmogenesis, focusing on the contribution of Nox-derived reactive oxygen species (ROS). Male Wistar rats were treated with dexamethasone (2 mg/kg, i.p.) for 7 days. Afterward, hemodynamic measurements, autonomic modulation, left ventricular function, cardiac fibrosis, reactive oxygen species (ROS) generation, Nox protein expression, superoxide dismutase (SOD) and catalase activities, and arrhythmias incidence were evaluated. Here, we show that dexamethasone increases blood pressure, associated with enhanced cardiac and vascular sympathetic modulation. Moreover, a marked increase in the cardiac ROS generation was observed, whereas the enhanced SOD activity did not prevent the higher levels of lipid peroxidation in the dexamethasone group. On the other hand, increased cardiac Nox 4 expression and hydrogen peroxide decomposition rate was observed in dexamethasone-treated rats, while Nox 2 remained unchanged. Interestingly, although preserved ventricular contractility and β-adrenergic responsiveness, we found that dexamethasone-treated rats displayed greater interstitial and perivascular fibrosis than control. Surprisingly, despite the absence of arrhythmias at basal condition, we demonstrated, by in vivo and ex vivo approaches, that dexamethasone-treated rats are more susceptible to develop harmful forms of ventricular arrhythmias when challenged with pharmacological drugs or burst pacing-induced arrhythmias. Notably, concomitant treatment with apocynin, an inhibitor of NADPH oxidase, prevented these ectopic ventricular events. Together, our results reveal that hearts become arrhythmogenic during dexamethasone treatment, uncovering the pivotal role of ROS-generating NADPH oxidases for arrhythmias vulnerability.