Abstract 17946: The Role Of Nox4 In Mediating Oxidation of HDAC4 In Response to Hypertrophic Stimulation
Reduction and oxidation are critically involved in the pathogenesis of cardiac hypertrophy. Oxidation of cysteine residues in histone deacetylase 4 (HDAC4) induces nuclear export, thereby mediating cardiac hypertrophy through activation of nuclear factor of activated T cells (NFAT). The cellular source of reactive oxygen species responsible for oxidation of HDAC4 remains unknown. We hypothesized that Nox4, a major NADPH oxidase isoform localizing at intracellular membranes, plays an essential role in mediating cardiac hypertrophy by oxidating cysteine residues in HDAC4. Nox4 exists on the mitochondrial and nuclear membranes in cardiomyocytes (CM). Phenylephrine (PE,100μM) induced upregulation of Nox4 (1.5 fold vs. control, p<0.05) within 5 min, which was accompanied by increases in O2- production (2 fold, p<0.01) from the nuclear membrane, as evaluated by lucigenin assays, and rapid (< 5min) nuclear export of HDAC4. Knockdown of Nox4, but not Nox2, attenuated O2- production in the nucleus and prevented PE-induced oxidation and nuclear export of HDAC4. A subpressor dose of PE (20 mg/kg/day) or saline alone was continuously infused into wild type (WT) and cardiac specific Nox4 knockout (cNox4-/-) mice via osmotic mini-pumps. After 14 days, aortic pressure was similar in WT and cNox4-/- mice. Left ventricular (LV) weight/ tibial length (5.7±0.1 vs. 6.4±0.1 mg/mm, p<0.05) and CM cross sectional area (223±13 vs. 258±12 μm2, p<0.05) were significantly smaller in cNox4-/- than in WT mice. Nuclear O2- production in the heart was significantly lower in cNox4-/- than in WT mice (4116±314 vs. 7057±1710 RLU, p<0.05), and was accompanied by a decrease in oxidation of HDAC4. In a microarray analysis, downstream targets of NFAT, including Myh7 and Rcan1, were downregulated in cNox4-/- compared to in WT mice. Iodoacetamide labeling assays indicated that PE-induced increases in HDAC4 cysteine oxidation were significantly attenuated in cNox4-/- mice. cNox4-/- mice also showed less HDAC4 oxidation and cardiac hypertrophy than WT mice 2 weeks after transverse aortic constriction. In conclusion, Nox4 plays an essential role in mediating cysteine oxidation and nuclear export of HDAC4, thereby mediating cardiac hypertrophy in response to PE and pressure overload.
- © 2012 by American Heart Association, Inc.