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Role of Mitochondrial Injury During Oxidative Injury to Hepatocytes: Evidence of a Mitochondrial Permeability Transition by Laser Scanning Confocal Microscopy
Published in John J. Lemasters, Constance Oliver, Cell Biology of Trauma, 2020
Anna-Liisa Nieminen, Roberto Imberti, Alice K. Saylor, Samuel A. Tesfai, Brian Herman, John J. Lemasters
We also investigated the ability of fructose to protect against hepatocellular injury by Br-A23187. Br-A23187 and its parent compound, A23187, are calcium ionophores whose cytotoxicity is sometimes used as a model of Ca2+-dependent cell killing.10 Br-A23187 caused time-dependent killing of isolated hepatocytes, and virtually all cells were nonviable after 2 h of exposure (Figure 4). Fructose alone only slightly improved cell survival, but fructose in combination with oligomycin virtually eliminated cell killing. Cell killing by CCCP showed the same pattern of oligomycin and fructose-dependent protection (Figure 4). These observations indicated that mitochondrial uncoupling and accelerated ATP hydrolysis were causing lethal cell injury from Br-A23187, rather than increases of intracellular Ca2+ per se. This is consistent with observations in isolated mitochondria, where A23187 is well known to be an uncoupler.11
Regulation of the Arachidonic Acid Cascade and PAF Metabolism in Reproductive Tissues
Published in Murray D. Mitchell, Eicosanoids in Reproduction, 2020
John M. Johnston, Noriei Maki, Marlane J. Angle, Dennis R. Hoffman
The effects of PAF, as well as that of the Ca2+ ionophore, A23187, on the release of PGE2 by amnion tissue were also examined.96 Tissue discs were prepared from amnion obtained from women at term and not in labor. Following an equilibration period, the discs were incubated for an additional 30 min in pseudo-amniotic fluid containing either PAF, A23187, or no addition. We found that exposure of amnion tissue to PAF resulted in a threefold increase in the release of PGE2 into the incubation media. Increased release of PGE2 was also observed in amnion tissue exposed to A23187 plus Ca2+. A similar increase in PGE2 production, as induced by PAF, has been found when human amnion cells were grown in culture.180
Prostaglandin Regulation of Macrophage Function
Published in Gloria H. Heppner, Amy M. Fulton, Macrophages and Cancer, 2019
Bruce S. Zwilling, Louis B. Justement
Treatment of macrophages with calcium ionophore A23187 has been shown to cause an increase in intracellular cAMP.70-73 The increase required extracellular calcium and was inhibited by the addition of indomethacin. The increase in cAMP occurred within 1 min following the addition of ionophore and was not due to inactivation of phosphodiesterases. Additional studies73 found that the increase in cAMP following treatment with A23187 could be blocked by the addition of calcium channel blockers, calmodulin blockers, and inhibitors of phospholipase A2 or cyclooxygenase. Furthermore, A23187-induced prostaglandin production was markedly reduced when cells were preincubated with 8-bromo-cAMP, dibutyryl cAMP, or cholera toxin. The addition of arachidonic acid alleviated the inhibition. These observations suggest the existence of a self-limiting regulatory mechanism in which A23187-treated macrophages respond to an influx of Ca2+ into the cell: the Ca2+ stimulates turnover of arachidonic acid which is converted to prostaglandin which in turn activates adenylate cyclase. cAMP then modulates subsequent prostaglandin production in a feedback mechanism by affecting steps prior to formation of arachidonic acid.
A retrospective analysis of artificial oocyte activation in patients with low or no fertilisation in intracytoplasmic sperm injection cycles
Published in Journal of Obstetrics and Gynaecology, 2022
Kevin K. W. Lam, Jacki Y. Y. Wong, Tak-Ming Cheung, Raymond H. W. Li, Ernest H. Y. Ng, William S. B. Yeung
Calcium ionophores are lipid soluble molecules. They transport calcium ions across the cell membrane which in turn induce a single transient rise in intracellular calcium level. When used for AOA, the concentration of A23187 varies from 5–10 µM (Montag et al. 2012; Lv et al. 2020). Although the concentration of the ready-to-use A23187 reagent is not disclosed by the manufacturer, it has been shown to induce a single rise in intracellular calcium to a peak within two minutes (Nikiforaki et al. 2016). The safety and efficacy of the ready-to-use A23187 has been proven in previous studies (Ebner et al. 2012; Caglar et al. 2015; Ebner et al. 2015). Exposure of A23187 in conjunction with calcium chloride injection together with spermatozoon has also been reported (Vanden Meerschaut et al. 2012). Our data indicated that the performance of two protocols were comparable. The observation is understandable as the injection of calcium chloride and the subsequent A23187 exposure might increase the intracellular calcium concentration to a level higher than that using A23187 alone, both protocols could not generate calcium oscillations (Nikiforaki et al. 2016). To the best of our knowledge, there is no commercially available mouse embryo-tested calcium chloride for AOA. The calcium chloride solution was mainly prepared from research grade chemicals (Vanden Meerschaut et al. 2012; Nikiforaki et al. 2016), the safety of which is in doubt. Based on the current data, AOA should be performed without the concomitant injection of calcium chloride.
Ca2+ mediates extracellular vesicle biogenesis through alternate pathways in malignancy
Published in Journal of Extracellular Vesicles, 2020
Jack Taylor, Iman Azimi, Gregory Monteith, Mary Bebawy
At rest, non-malignant hCMEC-D3 cells are low vesiculators and increase in intracellular Ca2+ result in the induction of plasma membrane EV production. Consistent with our previous work, high-resolution AFM images show hCMEC-D3 cells have a smooth topography with very few vesicle-derived pits observable in their resting state (Figure 1(a)). Following cellular activation with the Ca2+ ionophore, A23187, plasma membrane vesicle biogenesis is efficiently “turned on” in non-malignant cells. A23187 has been shown previously to elevate [Ca2+]i and induce plasma membrane EV formation in a number of cell types [58] and these results are consistent with this. Non-malignant cells stimulated with A23187 displayed a dramatically altered surface morphology consistent with cells undergoing active membrane vesiculation.
Assisted oocyte activation with calcium ionophore 44 hours after intracytoplasmic sperm injection resulting in successful pregnancy
Published in Gynecological Endocrinology, 2020
Haitao Xi, Yanghua Fu, Chang Liu, Xiaosheng Lu, Liucai Sui, Yulu Chen, Junzhao Zhao
During in vitro fertilization, both sperm and ovum need to undergo the process of capacitation. Sperm capacitation could be operated by using A23187 calcium solution or heparin. Calcium ionophore A23187 is a kind of mobile ionophore, which could transport bivalent cation such as calcium ion or magnesium ion into the cells and take two hydrogen ions outside the cells simultaneously. When A23187 is added to the culture medium containing calcium ion, the calcium ion could enter into the cytoplasm quickly. Thus, A23187 is widely used in cell biological research to increase the concentration of free calcium in the cytoplasm.