Connexin mimetic peptides reversibly inhibit Ca²⁺ signaling through gap junctions in airway cells

The effect of peptides with sequences derived from connexins, the constituent proteins of gap junctions, on mechanically stimulated intercellular Ca²⁺ signaling in tracheal airway epithelial cells was studied. Three peptides with sequences corresponding to connexin extracellular loop regions reversibly restricted propagation of Ca²⁺ waves to neighboring cells. Recovery of communication began within 10 min of removal of the peptides, with inhibition totally reversed by 20-40 min. The peptides were shown to be more effective in inhibiting Ca²⁺ waves than glycyrrhetinic acid or oleamide. Inhibition of intercellular Ca²⁺ waves by connexin mimetic peptides did not affect the Ca²⁺ response to extracellular ATP. Although the intracellular Ca²⁺ response of tracheal epithelial cells to ATP was greatly reduced by either pretreatment with high doses of ATP or application of apyrase, mechanically stimulated intercellular Ca²⁺ signaling was not affected by these agents. We conclude that connexin mimetic peptides are effective and reversible inhibitors of gap junctional communication of physiologically significant molecules that underlie Ca²⁺ wave propagation in tracheal epithelial cells and propose a potential mechanism for the mode of action of mimetic peptides.