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

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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.

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