Endoplasmic reticulum Ca2+ depletion unmasks a caffeine-induced Ca2+ influx in human aortic endothelial cells

Stefano Corda, Harold A. Spurgeon, Edward G. Lakatta, Maurizio C. Capogrossi, Roy C. Ziegelstein

Research output: Contribution to journalArticlepeer-review

Abstract

Intracellular Ca2+ pools contribute to changes in cytosolic [Ca2+] ([Ca2+]i), which play an important role in endothelial cell signaling. Recently, endothelial ryanodine-sensitive Ca2+ stores were shown to regulate agonist-sensitive intracellular Ca2+ pools. Since caffeine binds the ryanodine Ca2+ release channel on the endoplasmic reticulum in a variety of cell types, we examined the effect of caffeine on [Ca2+]i in human aortic endothelial cell monolaycrs loaded with the fluorescent probe indo 1. Under baseline conditions, 10 mmol/L caffeine induced a small increase in [Ca2+]i from 86±10 to 115±17 nmol/L (mean±SEM); this effect was similar to that of 5 μmol/L ryanodine and was unaffected by buffer Ca2+ removal. After depletion of an intracellular Ca2+ store by the irreversible endoplasmic reticulum Ca2+-ATPase inhibitor thapsigargin (1 μmol/L), ryanodine did not affect [Ca2+]i. In contrast, caffeine induced a large rapid increase in [Ca2+]i (176±19 to 338±35 nmol/L, P2+ was present. A similar increase in [Ca2+]i was induced by caffeine after depletion of ryanodine- and histamine-sensitive Ca2+ stores or after pretreatment with the endoplasmic reticulum Ca2+-ATPase inhibitor cyclopiazonic acid (10 μmol/L). Thus, under baseline conditions the effect of caffeine on [Ca2+]i is similar to that of ryanodine and appears to be due to the release of an intracellular store. However, after depletion of an endoplasmic reticulum Ca2+ store, caffeine, but not ryanodine, stimulates Ca2+ influx, resulting in a large increase in [Ca2+]i. The data suggest that caffeine-induced Ca2+ influx is controlled by the status of Ca2+ loading of intracellular Ca2+ stores in human aortic endothelial cells.

Original languageEnglish
Pages (from-to)927-935
Number of pages9
JournalCirculation Research
Volume77
Issue number5
Publication statusPublished - Nov 1995

Keywords

  • Caffeine
  • Cell calcium
  • Endothelium
  • Indo 1
  • Thapsigargin

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

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