Phenylephrine-induced cardiomyocyte injury is triggered by superoxide generation through uncoupled endothelial nitric-oxide synthase and ameliorated by 3-[2-[4-(3-chloro-2-methylphenyl)-1-piperazinyl]ethyl]-5,6-dimethoxyindazole (DY-9836), a novel calmodulin antagonist.
ABSTRACT The pathophysiological relevance of endothelial nitric-oxide synthase (eNOS)-induced superoxide production in cardiomyocyte injury after prolonged phenylephrine (PE) exposure remains unclear. The aims of this study were to define the mechanism of O2(*) production by uncoupled eNOS and evaluate the therapeutic potential of a novel calmodulin antagonist 3-[2-[4-(3-chloro-2-methylphenyl)-1-piperazinyl]ethyl]-5,6-dimethoxyindazole (DY-9836) to rescue hypertrophied cardiomyocytes from PE-induced injury. In cultured rat cardiomyocytes, prolonged exposure for 96 h to PE led to translocation from membrane to cytosol of eNOS and breakdown of caveolin-3 and dystrophin. When NO and O2(*) production were monitored in PE-treated cells by 4-amino-5-methylamino-2',7'-difluorofluorescein and dihydroethidium, respectively, Ca(2+)-induced NO production elevated by 5.7-fold (p < 0.01) after 48-h PE treatment, and the basal NO concentration markedly elevated (16-fold; p < 0.01) after 96-h PE treatment. On the other hand, the O2(*) generation at 96 h was closely associated with an increased uncoupled eNOS level. Coincubation with DY-9836 (3 microM) during the last 48 h inhibited the aberrant O2(*) generation nearly completely and NO production by 72% (p < 0.01) after 96 h of PE treatment and inhibited the breakdown of caveolin-3/dystrophin in cardiomyocytes. PE-induced apoptosis assessed by TdT-mediated dUTP nick-end labeling staining was also attenuated by DY-9836 treatment. These results suggest that O2(*) generation by uncoupled eNOS probably triggers PE-induced cardiomyocyte injury. Inhibition of abnormal O2(*) and NO generation by DY-9836 treatment represents an attractive therapeutic strategy for PE/hypertrophy-induced cardiomyocyte injury.
- [Show abstract] [Hide abstract]
ABSTRACT: The paper presents a constitutive framework for solids with dissipative micro-structures based on compact variational statements. It develops incremental minimization and saddle point principles for a class of gradient-type dissipative materials which incorporate micro-structural fields (micro-displacements, order parameters, or generalized internal variables), whose gradients enter the energy storage and dissipation functions. In contrast to classical local continuum approaches to inelastic solids based on locally evolving internal variables, these global micro-structural fields are governed by additional balance equations including micro-structural boundary conditions. They describe changes of the substructure of the material which evolve relatively to the material as a whole. Typical examples are theories of phase field evolution, gradient damage, or strain gradient plasticity. Such models incorporate non-local effects based on length scales, which reflect properties of the material micro-structure. We outline a unified framework for the broad class of first-order gradient-type standard dissipative solids. Particular emphasis is put on alternative multi-field representations, where both the microstructural variable itself as well as its dual driving force are present. These three-field settings are suitable for models with threshold- or yield-functions formulated in the space of the driving forces. It is shown that the coupled macro- and micro-balances follow in a natural way as the Euler equations of minimization and saddle point principles, which are based on properly defined incremental potentials. These multi-field potential functionals are outlined in both a continuous rate formulation and a time–space-discrete incremental setting. The inherent symmetry of the proposed multi-field formulations is an attractive feature with regard to their numerical implementation. The unified character of the framework is demonstrated by a spectrum of model problems, which covers phase field models and formulations of gradient damage and plasticity.Journal of the Mechanics and Physics of Solids 01/2011; 59(4):898-923. · 4.29 Impact Factor
- European Journal of Integrative Medicine 01/2009; 1(4):244-244. · 0.56 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Reactive oxygen species (ROS) produced by different NADPH oxidases (NOX) play a role in cardiomyocyte hypertrophy induced by different stimuli, such as angiotensin II and pressure overload. However, the role of the specific NOX isoforms in Phenylephrine (PE)-induced cardiomyocyte hypertrophy is unknown. Therefore we aimed to determine the involvement of the Nox isoforms NOX1, NOX2 and NOX4 in PE-induced cardiomyocyte hypertrophy. Hereto rat neonatal cardiomyoblasts (H9c2 cells) were incubated with 100μM PE to induce hypertrophy after 24 and 48hours as determined via cell and nuclear size measurements using digital imaging microscopy, electron microscopy and an automated cell counter. Digital-imaging microscopy further revealed that in contrast to NOX1 and NOX4, NOX2 expression increased significantly up to 4hours after PE stimulation, coinciding and co-localizing with ROS production in the cytoplasm as well as the nucleus. Furthermore, inhibition of NOX-mediated ROS production with apocynin, diphenylene iodonium (DPI) or NOX2 docking sequence (Nox2ds)-tat peptide during these first 4hours of PE stimulation significantly inhibited PE-induced hypertrophy of H9c2 cells, both after 24 and 48hours of PE stimulation. These data show that early NOX2-mediated ROS production is crucial in PE-induced hypertrophy of H9c2 cells.Cellular Signalling 04/2014; · 4.47 Impact Factor