Carbenoxolone and 18β-glycyrrhetinic acid inhibit inositol 1,4,5-trisphosphate-mediated endothelial cell calcium signalling and depolarise mitochondria.

BACKGROUND AND PURPOSE

Coordinated endothelial control of cardiovascular function is proposed to occur by endothelial cell communication via gap junctions and connexins. To study intercellular communication, the pharmacological agents carbenoxolone (CBX) and 18β-glycyrrhetinic acid (18βGA) are used widely as connexin inhibitors and gap junction blockers.

EXPERIMENTAL APPROACH

We investigated the effects of CBX and 18βGA on intercellular Ca waves, evoked by inositol 1,4,5-trisphosphate (IP ) in the endothelium of intact mesenteric resistance arteries.

KEY RESULTS

Acetycholine-evoked IP -mediated Ca release and propagated waves were inhibited by CBX (100 μM) and 18βGA (40 μM). Unexpectedly, the Ca signals were inhibited uniformly in all cells, suggesting that CBX and 18βGA reduced Ca release. Localised photolysis of caged IP (cIP ) was used to provide precise spatiotemporal control of site of cell activation. Local cIP photolysis generated reproducible Ca increases and Ca waves that propagated across cells distant to the photolysis site. CBX and 18βGA each blocked Ca waves in a time-dependent manner by inhibiting the initiating IP -evoked Ca release event rather than block of gap junctions. This effect was reversed on drug washout and was unaffected by small or intermediate K -channel blockers. Furthermore, CBX and 18βGA each rapidly and reversibly collapsed the mitochondrial membrane potential.

CONCLUSION AND IMPLICATIONS

CBX and 18βGA inhibit IP -mediated Ca release and depolarise the mitochondrial membrane potential. These results suggest that CBX and 18βGA may block cell-cell communication by acting at sites that are unrelated to gap junctions.

© 2020 The Authors. British Journal of Pharmacology published by John Wiley & Sons Ltd on behalf of British Pharmacological Society.