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Carbenoxolone and 18β-Glycyrrhetinic Acid Inhibit IP3-Mediated Endothelial Cell Calcium Signalling and Depolarise Mitochondria
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  • Charlotte Buckley,
  • Xun Zhang,
  • Calum Wilson,
  • John McCarron
Charlotte Buckley
University of Strathclyde
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Xun Zhang
University of Strathclyde
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Calum Wilson
University of Strathclyde
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John McCarron
University of Strathclyde
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Peer review status:IN REVISION

29 Jun 2020Submitted to British Journal of Pharmacology
01 Jul 2020Assigned to Editor
01 Jul 2020Submission Checks Completed
03 Jul 2020Reviewer(s) Assigned
18 Jul 2020Review(s) Completed, Editorial Evaluation Pending
21 Jul 2020Editorial Decision: Revise Minor

Abstract

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 IP3-evoked intercellular Ca2+ waves in the endothelium of intact mesenteric resistance arteries. Key Results Acetylcholine (ACh)-evoked IP3-mediated Ca2+ release and propagated waves were inhibited by CBX (100µM) and 18βGA (40µM). 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. Conclusion and Implications CBX and 18βGA inhibit IP3-mediated Ca2+ release and depolarise the mitochondrial membrane potential. These results suggest that CBX and 18βGA block cell-cell communication by acting at sites that are unrelated to gap junctions.