Mitochondria control IP3-evoked Ca2+ release triggered by voltage-dependent Ca2+ entry in intact resistance arteries

The contractility of vascular smooth muscle cells (VSMCs) is a major contributor of vascular tone and blood pressure. In VSMCs, intracellular Ca 2+ level determines the contractile activity that generates the force to contract arteries. A major source of Ca 2+ is via influx through voltage dependent Ca 2+ channels (VDCCs). While mitochondria are now recognised as key regulators of intracellular Ca 2+ homeostasis in several cell types, their role in modulating Ca 2+ signalling mediated by VDCC in VSMCs is unresolved. Given the potential physiological significance, and unclarified interaction between mitochondria and VDCCs in VSMCs, we hypothesize that mitochondria directly regulate Ca 2+ signalling mediated by VDCCs. The interplay between mitochondria and VDCCs was investigated by imaging and analysing intracellular Ca 2+ signals in smooth muscle cells in intact arteries from rat mesentery. Depolarization of the plasma membrane potential, by high potassium (20 mM) physiological saline solution, triggered Ca 2+ influx through VDCCs and a sustained increase in intracellular Ca 2+ on which repetitive Ca 2+ oscillations occurred. All Ca 2+ signals were abolished by removal of external Ca 2+ and by dihydropyridine inhibitors of VDCCs. Significantly, the repetitive Ca 2+ oscillations, but not the sustained Ca 2+ signals, were blocked by the IP 3 receptor inhibitor 2-APB and SERCA inhibitor cyclopiazonic acid. Neither the repetitive Ca 2+ oscillations or the sustained Ca 2+ signals were altered by the ryanodine receptor inhibitors ryanodine and dantrolene. These results suggest that Ca 2+ influx via VDCC triggers Ca 2+ -induced Ca 2+ release at IP 3 receptors in intact mesenteric arteries. Depolarization of the mitochondrial membrane potential (ψm), with the uncoupler CCCP or complex I inhibitor rotenone, but not ATP deprivation with the ATP synthesis blocker oligomycin, inhibited VDCC evoked IP 3 mediated Ca 2+ oscillations but not the sustained Ca 2+ signals. Furthermore, in intact arteries, depolarization of ψm directly suppressed inositol triphosphate receptors (IP 3 Rs) mediated Ca 2+ release from the internal Ca 2+ store evoked by photolysis of caged IP 3 . These results suggest that mitochondria regulate Ca 2+ release via IP 3 R triggered by Ca 2+ entry via VDCC. In return, Ca 2+ entry via VDCCs did not alter ψm, but upregulated ROS production. Together, these results suggest that mitochondria regulate Ca 2+ -induced Ca 2+ release at IP 3 receptors triggered by Ca 2+ influx via VDCCs but do not directly regulate VDCC activity. British Heart Foundation (RG/F/20/110007; PG/20/9/34859). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.