Abstract 61: miR-28 Induces Oxidative Stress via Nrf2 in Right Ventricular Failure but not in Left Ventricular Failure

Abstract

MicroRNAs (miRs) are crucial regulators of cardiac remodeling in left ventricular hypertrophy and failure (LVH/LVF). However, there is minimal data on their role in right ventricular hypertrophy and failure (RVH/RVF), a risk for patients with congenital heart disease or pulmonary hypertension. Utilizing a murine model of RVH/RVF, we have described RV-specific overexpression of miR-28, not found in LVH/LVF. We used this model to evaluate miR-28 regulation of its downstream target Nrf2, a master regulator of antioxidant defenses, and a potential mechanism of the enhanced susceptibility of the RV to fail under pressure overload. Methods: miR-28 and Nrf2 gene and protein expression and ROS production and antioxidant defenses were assessed at 10d in RVH/RVF (pulmonary artery banding) and LVH/LVF (aortic banding). miR-28 was overexpressed in HEK293 cells and Nrf2 and ROS production assessed. Plasma miRs were also profiled. Results: Mice developed RVH by d4, at which time miR-28 was not increased vs. sham, and RVF by d10, when miR-28 was increased 2-fold. This was accompanied by decreases in Nrf2 gene (2-fold) and protein (0.4±0.2 vs. 0.8±0.1, p<0.05) expression, Nrf2-regulated SOD expression (2-fold), and SOD activity (80±15% vs. 90±18%, p<0.05). ROS production (4HNE) was increased (1.5±0.1 vs. 1.0±0.1, p<0.05). In contrast, at the same stage of LVH/LVF, miR-28 is not increased, Nrf2 expression is increased (0.45±0.2 vs. 0.1±0.02, p<0.05) and SOD is unchanged. Lentiviral miR-28 overexpression in HEK293 cells showed downregulation of Nrf2, SOD and heme oxygenase expression (1.6-2.1 fold) with a 35% increase in ROS production (p<0.05). Finally, plasma miR-28 decreased with the progression from RVH to RVF in mice, and this was confirmed in children undergoing pulmonary valve replacement for RV failure (patients vs controls, n=4/group). Conclusions: Our data show that RV-specific miR-28 enhances RVH/RVF through suppression of Nrf2 signaling and increased oxidative stress. Although we did not find Nrf2 downregulation at the same stage of LVH/LVF, others have shown this at 4-6 wks, suggesting this process may occur earlier in RVF vs. LVF. Finally, miR-28 plasma expression may be a biomarker for early RVF in patients.