title: Arrhythmia and neuronal/endothelial myocyte uncoupling in hyperhomocysteinemia.
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.
authors.affiliation: Department of Physiology and Biophysics, University of Louisville School of Medicine, Louisville, Kentucky 40202, USA.
authors.forename: Dorothea
authors.initials: D
authors.lastname: Rosenberger
authors.forename: Karni S
authors.initials: KS
authors.lastname: Moshal
authors.forename: Ganesh K
authors.initials: GK
authors.lastname: Kartha
authors.forename: Neetu
authors.initials: N
authors.lastname: Tyagi
authors.forename: Utpal
authors.initials: U
authors.lastname: Sen
authors.forename: David
authors.initials: D
authors.lastname: Lominadze
authors.forename: Claudio
authors.initials: C
authors.lastname: Maldonado
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Roberts
authors.forename: Suresh C
authors.initials: SC
authors.lastname: Tyagi
mesh_terms: D001145:Arrhythmias, Cardiac / Q000209:etiology / Q000503:physiopathology*; D003094:Collagen / Q000378:metabolism; D016757:Death, Sudden, Cardiac / Q000209:etiology; D004730:Endothelium, Vascular / Q000378:metabolism* / Q000473:pathology; D005355:Fibrosis / Q000378:metabolism / Q000473:pathology; D006329:Heart Conduction System; D006339:Heart Rate; D006710:Homocysteine / Q000097:blood; D006801:Humans; D020138:Hyperhomocysteinemia / Q000150:complications / Q000503:physiopathology*; D020782:Matrix Metalloproteinases / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000502:physiology*; D009569:Nitric Oxide / Q000172:deficiency; D052248:Nitric Oxide Synthase Type I; D052250:Nitric Oxide Synthase Type III
chemical_list: D006710:Homocysteine; D009569:Nitric Oxide; D003094:Collagen; D052248:Nitric Oxide Synthase Type I; D052250:Nitric Oxide Synthase Type III; D020782:Matrix Metalloproteinases