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. We investigated the effects of CBX and 18βGA on intercellular Ca2+ waves, evoked by inositol 1,4,5-trisphosphate (IP3 ) in the endothelium of intact mesenteric resistance arteries. Acetycholine-evoked IP3 -mediated Ca2+ release and propagated waves were inhibited by CBX (100 μM) and 18βGA (40 μM). Unexpectedly, the Ca2+ signals were inhibited uniformly in all cells, suggesting that CBX and 18βGA reduced Ca2+ release. Localised photolysis of caged IP3 (cIP3 ) was used to provide precise spatiotemporal control of site of cell activation. Local cIP3 photolysis generated reproducible Ca2+ increases and Ca2+ waves that propagated across cells distant to the photolysis site. CBX and 18βGA each blocked Ca2+ waves in a time-dependent manner by inhibiting the initiating IP3 -evoked Ca2+ 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. CBX and 18βGA inhibit IP3 -mediated Ca2+ 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.
Charlotte Buckley, Xun Zhang, Calum Wilson, John G McCarron. Carbenoxolone and 18β-glycyrrhetinic acid inhibit inositol 1,4,5-trisphosphate-mediated endothelial cell calcium signalling and depolarise mitochondria. British journal of pharmacology. 2021 Feb;178(4):896-912
PMID: 33269468
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