Abstract 61: miR-28 Induces Oxidative Stress via Nrf2 in Right Ventricular Failure but not in Left Ventricular Failure
0
Citation
0
Reference
10
Related Paper
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.Keywords:
Pressure overload
Right ventricular hypertrophy
Pressure overload
Ventricular hypertrophy
Cite
Citations (0)
Protein posttranslational modifications (PTMs) by O-linked β-N-acetylglucosamine (O-GlcNAc) rise during pressure-overload hypertrophy (POH) to affect hypertrophic growth. The hexosamine biosynthesis pathway (HBP) branches from glycolysis to make the moiety for O-GlcNAcylation. It is speculated that greater glucose utilization during POH augments HBP flux to increase O-GlcNAc levels; however, recent results suggest glucose availability does not primarily regulate cardiac O-GlcNAc levels. We hypothesize that induction of key enzymes augment protein O-GlcNAc levels primarily during active myocardial hypertrophic growth and remodeling with early pressure overload. We further speculate that downregulation of protein O-GlcNAcylation inhibits ongoing hypertrophic growth during prolonged pressure overload with established hypertrophy. We used transverse aortic constriction (TAC) to create POH in C57/Bl6 mice. Experimental groups were sham, 1-week TAC (1wTAC) for early hypertrophy, or 6-week TAC (6wTAC) for established hypertrophy. We used western blots to determine O-GlcNAc regulation. To assess the effect of increased protein O-GlcNAcylation with established hypertrophy, mice received thiamet-g (TG) starting 4 weeks after TAC. Protein O-GlcNAc levels were significantly elevated in 1wTAC versus Sham with a fall in 6wTAC. OGA, which removes O-GlcNAc from proteins, fell in 1wTAC versus sham. GFAT is the rate-limiting HBP enzyme and the isoform GFAT1 substantially rose in 1wTAC. With established hypertrophy, TG increased protein O-GlcNAc levels but did not affect cardiac mass. In summary, protein O-GlcNAc levels vary during POH with elevations occurring during active hypertrophic growth early after TAC. O-GlcNAc levels appear to be regulated by changes in key enzyme levels. Increasing O-GlcNAc levels during established hypertrophy did not restart hypertrophic growth.
Cite
Citations (16)
The accumulation of collagen within the myocardium is termed fibrosis. In left ventricular pressure overload a reactive interstitial fibrosis, having distinctive biochemical and structural features, is seen. This reactive fibrosis occurs in the absence of myocyte necrosis, is progressive in nature, and initially is an adaptive response that preserves the force generating capacity, or active (systolic) stiffness, of the hypertrophied myocardium. Later in hypertrophy a reparative (or replacement) fibrosis occurs in response to cell loss, the pathogenesis of which is not clear. Nevertheless, independently of cell loss, interstitial fibrosis can have a detrimental influence on the diastolic and systolic stiffness of the myocardium and can result in pathologic hypertrophy with heart failure. In established hypertrophy with disproportionate collagen matrix remodeling (ie, interstitial heart disease), it would be desirable to retard the continued formation of collagen and, if necessary, degrade collagen fibers that are responsible for impeding the stretching and shortening of muscle fibers. Prevention of interstitial fibrosis in pressure overload hypertrophy with pharmacologic agents with both antihypertensive and antifibrotic properties must also be considered. Future research should address these issues with a view toward developing corrective and preventative forms of therapy. Such advances will require a better understanding of cardiac fibroblast growth, collagen synthesis and the regulation of collagen gene expression in the heart. Am J Hypertens 1989;2:931-940.
Pressure overload
Myocardial fibrosis
Interstitial cell
Cite
Citations (116)
Pressure overload
Concentric hypertrophy
Ventricular remodeling
Cite
Citations (38)
Pressure overload
Phenylephrine
Constriction
Atrial natriuretic peptide
Brain natriuretic peptide
Pathogenesis
Cite
Citations (53)
Pressure overload
Constriction
Cite
Citations (1)
Pressure overload
Ventricular hypertrophy
Myocardial fibrosis
Hydroxyproline
Cite
Citations (3)
Right ventricular (RV) failure induced by sustained pressure overload is a major contributor to morbidity and mortality in several cardiopulmonary disorders. Reliable and reproducible animal models of RV failure are therefore warranted in order to investigate disease mechanisms and effects of potential therapeutic strategies. Banding of the pulmonary trunk is a common method to induce isolated RV hypertrophy but in general, previously described models have not succeeded in creating a stable model of RV hypertrophy and failure. We present a rat model of pressure overload induced RV hypertrophy caused by pulmonary trunk banding (PTB) that enables different phenotypes of RV hypertrophy with and without RV failure. We use a modified ligating clip applier to compress a titanium clip around the pulmonary trunk to a pre-set inner diameter. We use different clip diameters to induce different stages of disease progression from mild RV hypertrophy to decompensated RV failure. RV hypertrophy develops consistently in rats subjected to the PTB procedure and depending on the diameter of the applied banding clip, we can accurately reproduce different disease severities ranging from compensated hypertrophy to severe decompensated RV failure with extra-cardiac manifestations. The presented PTB model is a valid and robust model of pressure overload induced RV hypertrophy and failure that has several advantages to other banding models including high reproducibility and the possibility of inducing severe and decompensated RV failure.
Pressure overload
Right ventricular hypertrophy
Volume overload
Cite
Citations (20)
Pressure overload
Concentric hypertrophy
Volume overload
Cite
Citations (114)