Oxidant stress from nitric oxide synthase–3 uncoupling stimulates cardiac pathologic remodeling from chronic pressure load
Eiki Takimoto, Hunter C. Champion, Manxiang Li, Shuxun Ren, E. Rene Rodriguez, Barbara Tavazzi, Giuseppe Lazzarino, Nazareno Paolocci, Kathleen L. Gabrielson, Yibin Wang, David A. Kass
Eiki Takimoto, Hunter C. Champion, Manxiang Li, Shuxun Ren, E. Rene Rodriguez, Barbara Tavazzi, Giuseppe Lazzarino, Nazareno Paolocci, Kathleen L. Gabrielson, Yibin Wang, David A. Kass
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Article Cardiology

Oxidant stress from nitric oxide synthase–3 uncoupling stimulates cardiac pathologic remodeling from chronic pressure load

Abstract

Cardiac pressure load stimulates hypertrophy, often leading to chamber dilation and dysfunction. ROS contribute to this process. Here we show that uncoupling of nitric oxide synthase–3 (NOS3) plays a major role in pressure load–induced myocardial ROS and consequent chamber remodeling/hypertrophy. Chronic transverse aortic constriction (TAC; for 3 and 9 weeks) in control mice induced marked cardiac hypertrophy, dilation, and dysfunction. Mice lacking NOS3 displayed modest and concentric hypertrophy to TAC with preserved function. NOS3–/– TAC hearts developed less fibrosis, myocyte hypertrophy, and fetal gene re-expression (B-natriuretic peptide and α–skeletal actin). ROS, nitrotyrosine, and gelatinase (MMP-2 and MMP-9) zymogen activity markedly increased in control TAC, but not in NOS3–/– TAC, hearts. TAC induced NOS3 uncoupling in the heart, reflected by reduced NOS3 dimer and tetrahydrobiopterin (BH4), increased NOS3-dependent generation of ROS, and lowered Ca2+-dependent NOS activity. Cotreatment with BH4 prevented NOS3 uncoupling and inhibited ROS, resulting in concentric nondilated hypertrophy. Mice given the antioxidant tetrahydroneopterin as a control did not display changes in TAC response. Thus, pressure overload triggers NOS3 uncoupling as a prominent source of myocardial ROS that contribute to dilatory remodeling and cardiac dysfunction. Reversal of this process by BH4 suggests a potential treatment to ameliorate the pathophysiology of chronic pressure-induced hypertrophy.

Authors

Eiki Takimoto, Hunter C. Champion, Manxiang Li, Shuxun Ren, E. Rene Rodriguez, Barbara Tavazzi, Giuseppe Lazzarino, Nazareno Paolocci, Kathleen L. Gabrielson, Yibin Wang, David A. Kass

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GSH/GSSH levels, MMPs, and Akt activation. (A) HPLC determination of GSH...
GSH/GSSH levels, MMPs, and Akt activation. (A) HPLC determination of GSH/GSSH, xanthine, and NADPH. GSH/GSSH markedly declined with TAC in WT hearts but not NOS3–/– hearts. Xanthine increased in both, but somewhat more in WT, whereas NADPH declined similarly in both genotypes. *P < 0.05 versus sham hearts of the same genotype. (B) Gelatin zymography of myocardium in controls and following 3 weeks of TAC, and quantification results. Positive control (Con) bands for activated MMP-2 and MMP-9 are shown. Basal gel lysis was minimal but markedly increased in WT TAC hearts. This was not observed in NOS3–/– hearts either at base line or with TAC. *P < 0.05 versus other groups. (C) Response of total Akt (t-Akt) and p-Akt to TAC in both genotypes and quantification results as a ratio of p-Akt to total Akt (n = 3 per group). TAC induced a marked increase in levels of p-Akt and total Akt in WT hearts. In contrast, there was no change in NOS3–/– hearts. **P < 0.01 versus WT sham at 3 weeks.