Abstract 15111: Connexin43 Participates in the Cardioprotective Effects of High-Density Lipoprotein
High-density lipoprotein (HDL) has been reported to have cardioprotective properties independent from its cholesterol transport activity. Phosphorylation of connexin 43 (Cx43), the predominant gap junction protein in ventricular myocardium, at Serine-368 is cardioprotective during preconditioning. Therefore, we hypothesized that Cx43 gap junction channels may be implicated in the cardioprotective properties of HDL. Neonatal rat cardiomyocytes were isolated and treated with different doses of HDL for 5min up to 24hrs. Cx43 expression and phosphorylation was evaluated by Western blotting and immunofluorescence. We found that HDL promoted phosphorylation of Cx43 in a dose- and time-dependent manner with the highest efficiency at 400μg/ml and 5min. Cx43 expression was not affected at this time. Involvement of various kinases was then studied by pre-treating cardiomyocytes with specific inhibitors. We observed that HDL-induced Cx43 phosphorylation was inhibited by the pre-treatment with the PKC inhibitor chelerythrin (5 μM), but not influenced by pre-treatment with inhibitors against p38-MAPK, JNK, ERK or PI3K/Akt. Using phosphorylation site-specific antibodies, we showed that HDL-dependent phosphorylation involved Ser368 in the C-terminus of Cx43. Finally, the effect of HDL on intercellular communication was evaluated by microinjection of the fluorescent dye Lucifer Yellow on clusters of neonatal cardiomyocytes. HDL decreased dye coupling (control=12±2 cells, HDL=5±1 cells, n=17–19, p<0.01), and this effect was reversed by pre-incubating cardiomyocytes with the PKC inhibitor (14±2 cells, n=11, p<0.01). In conclusion, short-term treatment with HDL induces phosphorylation of Cx43 at Ser368, which in turn, decreases intercellular communication between neonatal cardiomyocytes, thereby possibly preventing the spread of damaging factors. These results link Cx43 for the first time to the cardioprotective effects of HDL. A better understanding of molecular pathways involved in cardioprotection may lead to the identification of new molecules for the treatment of heart disease.
- © 2010 by American Heart Association, Inc.