Abstract 335: Carbon Nanoparticles Cause Loss of Gap Junctional Intercellular Communication and Nuclear Translocation of ß-Catenin in Endothelial Cells
Introduction: Environmental factors like industrial or consumer derived pollution are known to increase the risk for cardiovascular diseases. Previous studies demonstrated that senescent endothelial cells contribute to the onset of atherosclerosis. We have recently shown that non-toxic and non-inflammatory concentrations of carbon nanoparticles (CNP), a major component of industrial pollution, induce senescence in human primary endothelial cells (EC). However, the underlying molecular mechanisms leading to senescent EC are far from understood. Gap junctional intercellular communication (GJIC), which depends on Connexin 43 (Cx43) and β-catenin, is important for endothelial function and seems to be dysregulated during aging. Phosphorylation of Cx43 on serine 368 reduces the trafficking of Cx43 to the plasma membrane and assembly of Cx43 into gap junctional structures.
Objective: The aim of this study was to investigate whether CNP affect GJIC and β-catenin in EC.
Material and Methods: EC were treated with CNP at a measured size of 10 - 34 nm and GJIC was measured by dye transfer assay. The localization of Cx43 and β-catenin was assessed by immunofluorescence and phosphorylation and protein levels of Cx43 were by immunoblots.
Results: Two weeks incubation with CNP concentrations, which we are exposed to everyday, elevated the number of senescent EC. This was determined by increased staining for senescence-associated beta-galactosidase and the cell cycle inhibitor p21 - two established markers of senescence. The same concentrations of CNP resulted in an enhanced phosphorylation of Cx43 on serine 368. Moreover, CNP induced internalization of Cx43 and led to nuclear translocation of the Cx43 interacting protein β-catenin. This resulted in reduced GJIC, which was shown by decreased dye transfer. Thus, CNP-induced senescence is accompanied by loss of cell-cell communication.
Conclusion: These data indicate for the first time that Cx43 and β-catenin, which are essential for endothelial functionality, are affected by CNP and that loss of GJIC is involved in CNP-induced senescence. Overexpression studies will investigate whether a causal link exists between CNP-induced senescence and loss of GJIC in primary EC.
Author Disclosures: N. Ale-Agha: None. K. Unfried: None. J. Altschmied: None. J. Haendeler: None.
- © 2014 by American Heart Association, Inc.