The Bioactive Phenolic Agents Diaryl Ether CVB2-61 and Diarylheptanoid CVB4-57 as Connexin Hemichannel Blockers

Inflammation mediators enhance the activity of connexin (Cx) hemichannels especially in the epithelial and endothelial tissues. As potential release route for injury signals like (oligo)nucleotides, Cx hemichannels may contribute to long lasting inflammation. Specific inhibition of Cx hemichannels may therefore be a mode of prevention and treatment of long lasting, chronic sterile inflammation. The activity of Cx hemichannels was analysed in N2A and HeLa cells transfected with human Cx26 and Cx46 as well as in Calu-3 cells using the dye uptake as functional assay. Moreover, possible impact of the bioactive phenolic agents CVB2-61 and CVB4-57 on the barrier function of epithelial cells was analysed using Calu-3 cells. Both agents inhibited the dye uptake in N2A cells expressing Cx26 (> 5 µM) and Cx46 (> 20 µM). In Calu-3 cells, CVB2-61 and CVB4-57 reversible inhibited the dye uptake at concentrations as low as 5 µM, without affecting the gap junction communication and barrier function, even at concentrations of 20 µM. While CVB2-61 or CVB4-57 maintained a reduced dye uptake in Calu-3 cells, an enhancement of the dye uptake in response to stimulation of adenosine signaling was still observed after removal of the agents. The report shows that CVB2-61 and CVB4-57 reversible block Cx hemichannels. Deciphering the interaction mechanisms with Cx hemichannels could allow further development of phenolic compounds to target Cx hemichannels for a better and safer use in treatment of pathologies that involve Cx hemichannels.