Adenovirus vector E4 gene regulates connexin 40 and 43 expression in endothelial cells via PKA and PI3K signal pathways

Connexins (Cxs) provide a means for intercellular communication and play important roles in the pathophysiology of vascular cardiac diseases. Infection of endothelial cells (ECs) with first-generation E1/E3deleted E4(+) adenovirus (AdE4(+)) selectively modulates the survival and angiogenic potential of ECs by as of yet unrecognized mechanisms. We show here that AdE4(+) vectors potentiate Cx expression in ECs in vitro and in mouse heart tissue. Infection of ECs with AdE4(+), but not AdE4(-), resulted in a time- and dose-dependent induction of junctional Cx40 expression and suppression of Cx43 protein and mRNA expression. Treatment of ECs with PKA inhibitor H89 or PI3K inhibitor LY294002 prevented the AdE4(+)- mediated regulation of Cx40 and Cx43 that was associated with diminished AdE4(+)- mediated survival of ECs. Moreover, both PKA activity and cAMP-response element (CRE)-binding activity were enhanced by treatment of ECs with AdE4(+). However, there is no causal evidence of a cross-talk between the 2 modulatory pathways, PKA and PI3K. Remarkably, Cx40 immunostaining was markedly increased and Cx43 was decreased in the heart tissue of mice treated with intra-tracheal AdE4(+). Taken together, these results suggest that AdE4(+) may play an important role in the regulation of Cx expression in ECs, and that these effects are mediated by both the PKA/CREB and PI3K signaling pathways.