Evaluation of Cx43 gap junction inhibitors using Quantitative Structure-Activity Relationship model

Gap junctions (GJs) made of connexin-43 (Cx43) are important for the conduction of electrical impulses in the heart. Modulation of Cx43 activity may be useful in the treatment of cardiac arrhythmias and other dysfunctions. Search of novel GJ modulating agents using molecular docking approach allows to predict the binding affinities that often significantly differ from experimentally estimated their potencies. The objective of this study was to demonstrate that Quantitative Structure-Activity Relationship (QSAR) model could be used for more precise identification of potent Cx43 GJ inhibitors. Using the QSAR model and molecular docking, we evaluated the known Cx43 GJ inhibitors, suggested a new one, and tested it experimentally. Our QSAR model predicted the concentrations required to produce 50% of the maximal effect (IC50) for each of these compounds and estimated the correlation between predicted and experimental IC50ies (pIC50 and eIC50). This led to suggestion of monocyclic monoterpene d-limonene as putative Cx43 inhibitor with pIC50 = 1.07. In turn, dual whole-cell patch-clamp measurements provided eIC50=1.41. The pIC50ies of d-limonene and other Cx43 GJ inhibitors examined by our QSAR model well correlated with their eIC50ies (R = 0.88) in contrast to pIC50s obtained from molecular docking (R = 0.42). However, the molecular docking suggested that inhibitor potency may depend on their docking sites on Cx43.