Gap junctional remodeling by hypoxia in cultured neonatal rat ventricular myocytes

Article (PDF Available)inCardiovascular Research 66(1):64-73 · May 2005with24 Reads
DOI: 10.1016/j.cardiores.2005.01.014 · Source: PubMed
Altered gap junctional coupling of ventricular myocytes plays an important role in arrhythmogenesis in ischemic heart disease. Since hypoxia is a major component of ischemia, we tested the hypothesis that hypoxia causes gap junctional remodeling accompanied by conduction disturbances. Cultured neonatal rat ventricular myocytes were exposed to hypoxia (1% O(2)) for 15 min to 5 h, connexin43 (Cx43) expression was analyzed, and conduction velocity was measured using the Micro-Electrode Array data acquisition system. After 15 min of hypoxia, conduction velocity was unaffected, while total Cx43, including the phosphorylated and nonphosphorylated isoforms, was increased. After 5 h of hypoxia, total Cx43 protein was decreased by 50%, while the nonphosphorylated Cx43 isoform was unchanged. Confocal analyses yielded a 55% decrease in the gap junctional Cx43 fluorescence signal, a 55% decrease in gap junction number, and a 26% decrease in size. The changes in Cx43 were not accompanied by changes in mRNA levels. The reduction in Cx43 protein levels was associated with a approximately 20% decrease in conduction velocity compared to normoxic cultures. Short-term hypoxia (5 h) decreases Cx43 protein and conduction velocity, thereby contributing to the generation of an arrhythmogenic substrate.


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Available from: Zaid Abassi, Jan 04, 2016
    • "In comparison, SCMs were selected for α-MHC expression using puromycin resistance and therefore, the resulting cell pool was free of any non-cardiac cells. Interestingly, pure SCM strands presented significantly lower CVs compared to pure PCMs, corroborating the results of other research groups (Satin et al., 2004; Zeevi-Levin et al., 2005; Mureli et al., 2013). In mixed cultures, we found that increasing the amount of PCMs resulted in an increase in CV. "
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    • "During short periods of hypoxia (up to 15 min) Cx43 content remains unchanged (Zeevi-Levin et al., 2005; Matsumura et al., 2006). With prolonged hypoxia (several hours), downregulation of Cx43 at gap junctions occurs (Danon et al., 2010), Cx43 is internalized (Sato et al., 2009 ) and subsequently the total cellular Cx43 content decreases (Zeevi-Levin et al., 2005). Metabolic inhibition activates c-Src kinase, an effect inhibited by 17ß-estradiol (Chung et al., 2009 ). "
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    • "suggest the existence of underlying functional alterations that are not expressed morphologically, a circumstance that has been reported elsewhere (Friedman et al., 1973). Ischemia produces a reorganization of the gap junctions and, as a consequence, modifies the conduction velocity in the cardiomyocytes: the gap junctions close and the connexin-43 proteins are dephosphorylated and transferred from the intercalated discs to the cytoplasm and other membrane domains, that is, there is a redistribution (García Dorado et al., 2004; Oosthoek et al., 1993; Shimada et al., 2004; Suarez and Bravo, 2006; Zeevi-Levin et al., 2005). In the Purkinje fibers, and under normal conditions, these junctions are distributed throughout the entire fiber cell membrane, except in that adjoined to the connective tissue. "
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    Article · Feb 2015
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