Close Functional Coupling Between Ca(2+) Release-Activated Ca(2+) Channels and Reactive Oxygen Species Production in Murine Macrophages

Aim. To investigate the role of Ca(2+) release-activated Ca(2+) (CRAC) channels in the ROS production in macrophages. Methods. The intracellular [Ca(2+)](i) was analyzed by confocal laser microscopy. The production of ROS was assayed by flow cytometry. Results. Both LPS and thapsigargin induced an increase in intracellular [Ca(2+)](i), either in the presence or absence of extracellular Ca(2+) in murine macrophages. The Ca(2+) signal was sustained in the presence of external Ca(2+) and only initiated a mild and transient rise in the absence of external Ca(2+). CRAC channel inhibitor 2-APB completely suppressed the Ca(2+) entry signal evoked by thapsigargin, and suppressed approximately 93% of the Ca(2+) entry signal evoked by LPS. The increase in intracellular [Ca(2+)](i) was associated with increased ROS production, which was completely abolished in the absence of extracellular Ca(2+) or in the presence of CRAC channel inhibitors 2-APB and Gd(3+). The mitochondrial uncoupler carbonyl cyanide p-trifluoromethoxy-phenylhydrazone and the inhibitor of the electron transport chain, antimycin, evoked a marked increase in ROS production and completely inhibited thapsigargin and LPS-evoked responses. Conclusions. These findings indicate that the LPS-induced intracellular [Ca(2+)](i) increase depends on the Ca(2+) entry through CRAC channels, and close functional coupling between CRAC and ROS production in murine macrophages.