title: Endothelial mitochondria regulate the intracellular Ca2+ response to fluid shear stress.
abstract: Shear stress is known to stimulate an intracellular free calcium concentration ([Ca(2+)]i) response in vascular endothelial cells (ECs). [Ca(2+)]i is a key second messenger for signaling that leads to vasodilation and EC survival. Although it is accepted that the shear-induced [Ca(2+)]i response is, in part, due to Ca(2+) release from the endoplasmic reticulum (ER), the role of mitochondria (second largest Ca(2+) store) is unknown. We hypothesized that the mitochondria play a role in regulating [Ca(2+)]i in sheared ECs. Cultured ECs, loaded with a Ca(2+)-sensitive fluorophore, were exposed to physiological levels of shear stress. Shear stress elicited [Ca(2+)]i transients in a percentage of cells with a fraction of them displaying oscillations. Peak magnitudes, percentage of oscillating ECs, and oscillation frequencies depended on the shear level. [Ca(2+)]i transients/oscillations were present when experiments were conducted in Ca(2+)-free solution (plus lanthanum) but absent when ECs were treated with a phospholipase C inhibitor, suggesting that the ER inositol 1,4,5-trisphosphate receptor is responsible for the [Ca(2+)]i response. Either a mitochondrial uncoupler or an electron transport chain inhibitor, but not a mitochondrial ATP synthase inhibitor, prevented the occurrence of transients and especially inhibited the oscillations. Knockdown of the mitochondrial Ca(2+) uniporter also inhibited the shear-induced [Ca(2+)]i transients/oscillations compared with controls. Hence, EC mitochondria, through Ca(2+) uptake/release, regulate the temporal profile of shear-induced ER Ca(2+) release. [Ca(2+)]i oscillation frequencies detected were within the range for activation of mechanoresponsive kinases and transcription factors, suggesting that dysfunctional EC mitochondria may contribute to cardiovascular disease by deregulating the shear-induced [Ca(2+)]i response.
authors.affiliation: Departments of Biomedical Engineering and Internal Medicine, Division of Cardiovascular Medicine, and Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio;
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Scheitlin
authors.affiliation: Departments of Biomedical Engineering and Internal Medicine, Division of Cardiovascular Medicine, and Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio;
authors.forename: Justin A
authors.initials: JA
authors.lastname: Julian
authors.affiliation: Department of Medical Genetics and Molecular Biochemistry and Center for Translational Medicine, Temple University, Philadelphia, Pennsylvania; and.
authors.forename: Santhanam
authors.initials: S
authors.lastname: Shanmughapriya
authors.affiliation: Department of Medical Genetics and Molecular Biochemistry and Center for Translational Medicine, Temple University, Philadelphia, Pennsylvania; and.
authors.forename: Muniswamy
authors.initials: M
authors.lastname: Madesh
authors.affiliation: Department of Biomedical Engineering, Florida International University, Miami, Florida.
authors.forename: Nikolaos M
authors.initials: NM
authors.lastname: Tsoukias
authors.affiliation: Departments of Biomedical Engineering and Internal Medicine, Division of Cardiovascular Medicine, and Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio; rita.alevriadou@osumc.edu alevriadou.1@osu.edu.
authors.forename: B Rita
authors.initials: BR
authors.lastname: Alevriadou
mesh_terms: D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000378:metabolism*; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D015290:Second Messenger Systems / Q000502:physiology; D013314:Stress, Mechanical
chemical_list: D053496:Inositol 1,4,5-Trisphosphate Receptors; D002118:Calcium
keywords: calcium oscillations; endothelial cell; fluid shear stress; intracellular calcium; mitochondria