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Abstract
Elevated levels of homocysteine (Hcy) known as hyperhomocysteinemia (HHcy) are associated with arrhythmogenesis and sudden cardiac death (SCD). Hcy decreases constitutive neuronal and endothelial nitric oxide (NO), and cardiac diastolic relaxation. Hcy increases the iNOS/NO, peroxynitrite, mitochondrial NADPH oxidase, and suppresses superoxide dismutase (SOD) and redoxins. Hcy activates matrix metalloproteinase (MMP), disrupts connexin-43 and increases collagen/elastin ratio. The disruption of connexin-43 and accumulation of collagen (fibrosis) disrupt the normal pattern of cardiac conduction and attenuate NO transport from endothelium to myocyte (E-M) causing E-M uncoupling, leading to a pro-arrhythmic environment. The goal of this review is to elaborate the mechanism of Hcy-mediated iNOS/NO in E-M uncoupling and SCD. It is known that Hcy creates arrhythmogenic substrates (i.e. increase in collagen/elastin ratio and disruption in connexin-43) and exacerbates heart failure during chronic volume overload. Also, Hcy behaves as an agonist to N-methyl-D-aspartate (NMDA, an excitatory neurotransmitter) receptor-1, and blockade of NMDA-R1 reduces the increase in heart rate-evoked by NMDA-analog and reduces SCD. This review suggest that Hcy increases iNOS/NO, superoxide, metalloproteinase activity, and disrupts connexin-43, exacerbates endothelial-myocyte uncoupling and cardiac failure secondary to inducing NMDA-R1.
| Abbreviations | ||
| ADAM | = | a disintegrin and metalloproteinase |
| ADMA | = | asymmetric dimethyl arginine |
| AV | = | aorta-venacava shunt |
| L-arg | = | L-arginine |
| BH4 | = | tetrahydrobiopterin |
| BM | = | basement membrane |
| CBS | = | cystathionine beta synthatase |
| CHF | = | chronic heart failure |
| DDAH | = | dimethyl arginine hydrolase |
| DZA | = | 3-deazaadenosine |
| ECM | = | extracellular matrix |
| EDRF | = | endothelial-derived relaxing factor |
| EDHF | = | endothelial-derived hyperpolarizing factor |
| EE | = | endocardial endothelial |
| EET | = | epoxy-eicosatrienoic acid |
| E-M | = | endothelial-myocyte |
| eNOS | = | endothelial nitric oxide synthase |
| Hcy | = | homocysteine |
| HETE | = | 20-hydroxyeicosatetraenoic acid |
| HHcy | = | hyperhomocysteinemia |
| LV | = | left ventricle |
| MK | = | MK-801 |
| MMP | = | matrix metalloproteinase |
| MT-MMP | = | membrane type-MMP |
| MTHFR | = | methylene tetrahydrofolate reductase |
| MVEC | = | microvascular endothelial cells |
| NADPH | = | nicotinamide adenosine diphosphate |
| NE | = | norepinephrine |
| NMDA-R1 | = | N-methyl-D-aspartate receptor-1 |
| nNOS | = | neural nitric oxide synthase |
| PVC | = | premature ventricle contraction |
| Redox | = | reduction-oxidation |
| RNS | = | reactive nitrogen species |
| ROS | = | reactive oxygen species |
| SAHH | = | S-adenosyl-homocysteine hydrolase |
| SAM | = | S-adenosyl-methionine |
| SOD | = | superoxide dismutase |
| TIMP | = | tissue inhibitor of metalloproteinase |
| t-PA | = | tissue plasminogen activator |
| VF | = | ventricular fibrillation |
| VT | = | ventricular tachycardia |
| Q-RT-PCR | = | quantitative real time polymerase chain reaction |
| WT | = | wild type |
| Abbreviations | ||
| ADAM | = | a disintegrin and metalloproteinase |
| ADMA | = | asymmetric dimethyl arginine |
| AV | = | aorta-venacava shunt |
| L-arg | = | L-arginine |
| BH4 | = | tetrahydrobiopterin |
| BM | = | basement membrane |
| CBS | = | cystathionine beta synthatase |
| CHF | = | chronic heart failure |
| DDAH | = | dimethyl arginine hydrolase |
| DZA | = | 3-deazaadenosine |
| ECM | = | extracellular matrix |
| EDRF | = | endothelial-derived relaxing factor |
| EDHF | = | endothelial-derived hyperpolarizing factor |
| EE | = | endocardial endothelial |
| EET | = | epoxy-eicosatrienoic acid |
| E-M | = | endothelial-myocyte |
| eNOS | = | endothelial nitric oxide synthase |
| Hcy | = | homocysteine |
| HETE | = | 20-hydroxyeicosatetraenoic acid |
| HHcy | = | hyperhomocysteinemia |
| LV | = | left ventricle |
| MK | = | MK-801 |
| MMP | = | matrix metalloproteinase |
| MT-MMP | = | membrane type-MMP |
| MTHFR | = | methylene tetrahydrofolate reductase |
| MVEC | = | microvascular endothelial cells |
| NADPH | = | nicotinamide adenosine diphosphate |
| NE | = | norepinephrine |
| NMDA-R1 | = | N-methyl-D-aspartate receptor-1 |
| nNOS | = | neural nitric oxide synthase |
| PVC | = | premature ventricle contraction |
| Redox | = | reduction-oxidation |
| RNS | = | reactive nitrogen species |
| ROS | = | reactive oxygen species |
| SAHH | = | S-adenosyl-homocysteine hydrolase |
| SAM | = | S-adenosyl-methionine |
| SOD | = | superoxide dismutase |
| TIMP | = | tissue inhibitor of metalloproteinase |
| t-PA | = | tissue plasminogen activator |
| VF | = | ventricular fibrillation |
| VT | = | ventricular tachycardia |
| Q-RT-PCR | = | quantitative real time polymerase chain reaction |
| WT | = | wild type |
Notes
*This work was supported in part by NIH grant HL-71010, and HL-74185.