Acute antioxidant effect of glucocorticoids improve cardiac function following ischemia/reperfusion

ESCUDERO, DS; FANTINELLI JC; MARTINEZ VR; PEREZ, NG; DIAZ, RG

Mar del Plata

Congreso; REUNIÓN CONJUNTA SAIC SAI&FAIC SAFIS 2022; 2022

SOCIEDAD ARGENTINA DE INVESTIGACIÓN CLÍNICA (SAIC) - SOCIEDAD ARGENTINA DE INMUNOLOGÍA (SAI) - SOCIEDAD ARGENTINA DE FISIOLOGÍA (SAFIS)

Introduction: Glucocorticoids (GCs) are steroid hormones involved in several physiological processes including cardiovascular function. The endogen GC cortisol as well as the synthetic ones both exhibit the ability to bind and activate either the GC receptor (GR) or the mineralocorticoid receptor (MR), highly expressed in cardiac tissue. Experimental results have provided evidence that overstimulation of the cardiac MR promotes ventricular remodeling and proarrhythmogenic effects leading to myocardial dysfunction. Furthermore, reliable data suggest that such deleterious effects involve a novel non-genomic signaling pathway that ends with a hyperactivation of the cardiac sodium-hydrogen exchanger (NHE1). Despite the extensive characterization of MR signaling, little is known about the effects of GR activation in cardiac tissue. In this line, this study was aimed to evaluate whether acute GCs may protect the myocardium against ischemia/reperfusion injury (I/R).Methods: Experiments were carried out in 5-month-old Wistar rats. Acute myocardial infarction (I) was promoted in isolated Langendorff-perfused heart, by ligation of left anterior descending coronary artery followed by reperfusion (R). I/R protocol (40min I/60min R) was performed in absence (ischemic control “I”) or presence of Hydrocortisone (HC, 10nM) during the first five minutes of R. To confirm GR activation, a third group of hearts receiving HC was simultaneously treated with the GR inhibitor Mifepristone (M, 10μM). At the end of the I/R protocol, a set of each experimental group was assigned to infarct size estimation (Evans blue plus Triphenyltetrazolium chloride staining), and another set to oxidative stress determinations. The oxidative stress tests included evaluation of reactive oxygen species (ROS) and the reduced/oxidized glutathione ratio (GSH/GSSG) by fluorescence, and lipid peroxides as thiobarbituric acid-reactive substances (TBARS) by absorbance. In a separate series of experiments, isolated papillary muscles from non-ischemic hearts were used to evaluate the effect of GC on NHE1 activity. The muscles were loaded with the pH sensitive BCECF epifluorescence dye, and the recovery of pHi following an ammonium prepulse-induced transient acidosis was evaluated in the absence (TA) or presence of HC 1nM (HC1) or 10nM (HC10). A different group of papillary muscles were exposed to TA to evaluate Ser648-NHE1 phosphorylation by immunoprecipitation followed by western blot (WB).Results: HC treatment reduced infarct size as shown in Figure 1a, effect that was accompanied by a significant improvement in post-ischemic mechanical function evidenced by a better recovery in left ventricular developed pressure, LVDP at the end of reperfusion (Figure 1b), together with a significant reduction in left ventricular end diastolic pressure, LVEDP (in mmHg: from 55±4 I to 28±5 HC, p