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Bioluminescence Imaging of NADPH Oxidase Activity in Different Animal Models
Published on: October 22, 2012
Cardiac-targeted NADPH oxidase 4 in the adaptive cardiac remodelling of the murine heart
Adam Nabeebaccus1, Anne Hafstad2, Tom Eykyn1
1Cardiovascular Division, King's College London, London, UK.
Background:
The mechanisms that determine whether the heart adapts to overload stress, or fails, are poorly understood. NADPH oxidase (NOX) proteins produce reactive oxygen species (ROS) involved in redox signalling, and our recent studies have found that an increase in Nox4 during pressure overload protects the heart against failure. We aimed to identify novel Nox4-driven cardioprotective mechanisms that promote adaptive cardiac remodelling.
Methods:
We first undertook a proteomic comparison of heart tissue from cardiac-targeted Nox4-overexpressing mice and controls. The Nox4 cardiac metabolome was then investigated by (1)H nuclear magnetic resonance (NMR) spectroscopy. Effects on cardiac metabolism were assessed by ex-vivo working heart perfusions and isolated mitochondrial respiration studies. Ex-vivo cardiac energetics were assessed by (31)P NMR. Alterations to cardiac fatty acid oxidation were explored in primary cardiomyocytes (extracellular flux analysis).
Findings:
Cardiac-targeted Nox4 overexpression profoundly remodelled the cardiac proteome in an isoform-specific manner, both in the unstressed and stressed heart. Glycolysis and fatty acid oxidation were identified as the most enriched pathways that were altered by Nox4. Metabolomic analysis showed a 2·2 times increase in acetylcarnitine concentrations (p=0·002). Ex-vivo heart perfusions demonstrated a profound increase in palmitate oxidation relative to wild-type hearts (3·6 times increase, p=0·01), with opposite findings observed in primary cardiomyocytes with a knockdown of Nox4. A preference for fatty acid oxidation in Nox4 hearts correlated with a better energetic state (phosphocreatine:ATP ratio) when subjected to increasing doses of isoprenaline stress under baseline and pressure-overload.
Interpretation:
In this study we identified a novel role for Nox4 in the regulation of cardiac fatty acid oxidation. Cardiomyocyte-targeted Nox4 hearts preferentially oxidised fatty acids for energy provision, improving myocardial energetics under stress. Enhancing fatty acid oxidation might have an adaptive role in the setting of pressure-overload hypertrophy. These data provide novel insights into ROS-dependent metabolic programming.
Funding:
UK Medical Research Council, British Heart Foundation.
Insights
NADPH oxidase 4 (Nox4) enhances cardiac fatty acid oxidation, improving heart energetics under stress. This suggests Nox4 plays a protective role in pressure-overload hypertrophy by promoting adaptive metabolic programming.
Area of Science:
- Cardiovascular Biology
- Metabolic Regulation
- Oxidative Stress Signaling
Background:
- Mechanisms of heart adaptation versus failure under stress are unclear.
- NADPH oxidase (NOX) proteins produce reactive oxygen species (ROS) involved in signaling.
- Increased Nox4 expression protects the heart against pressure overload-induced failure.
Purpose of the Study:
- Identify novel Nox4-driven cardioprotective mechanisms.
- Investigate Nox4's role in adaptive cardiac remodeling.
- Elucidate Nox4's impact on cardiac metabolism.
Main Methods:
- Proteomic analysis of cardiac tissue from Nox4-overexpressing mice.
- Metabolomic profiling using NMR spectroscopy.
- Assessment of cardiac metabolism via ex-vivo heart perfusion, mitochondrial respiration, and cardiomyocyte studies.
Main Results:
- Nox4 overexpression significantly altered cardiac proteome and metabolic pathways, including glycolysis and fatty acid oxidation.
- Increased acetylcarnitine levels and enhanced palmitate oxidation were observed in Nox4-overexpressing hearts.
- Nox4-dependent fatty acid oxidation improved cardiac energetic status under stress.
Conclusions:
- Nox4 plays a novel role in regulating cardiac fatty acid oxidation.
- Preferential fatty acid utilization in Nox4-expressing hearts enhances myocardial energetics.
- Boosting fatty acid oxidation may be adaptive in pressure-overload hypertrophy, offering insights into ROS-dependent metabolic programming.
