Bastadin 12 and ryanodine reveal similarities between thapsigarginand tetrabromobisphenola-induced intracellular ca2+ release in cultured cerebellar granule cells

Tetrabromobisphenol a (tbbpa) is a commonly used brominated flame retardant with recognized neuro- and cytotoxic properties that are presumably mediated by intracellular ca2+ release. other studies have demonstrated that ryanodine is able to inhibit ca2+ efflux from skeletal sarcoplasmic reticulum (sr) membranes in response to the known ca2+ releaser thapsigargin,provided that the macrocyclic brominated tyrosine derivative bastadin 5 is also present. similar effects supporting the role of ryanodine receptors in thapsigargin-evoked ca2+ release have been observed in primary cultures of rat cerebellar granule cells (cgcs). here,we used cgcs and the fluorescent intracellular ca2+ probe fluo-3 to test the following hypotheses: (1) tbbpa shares ca2+ releasing properties with thapsigargin,and (2) synthetic bastadin 12 can replace bastadin 5 as a pharmacological tool to identify these similarities. the results demonstrated that either 200 nm thapsigargin or 30 μm bastadin 12 alone induced an increase in the intracellular ca2+ level in cgcs,whereas 2.5 and 10 μm bastadin 12 had no effect on the basal ca2+ concentration. the thapsigargin-induced ca2+ release was partially reduced by co-administration of either 2.5 μm bastadin 12 or 200 μm ryanodine,and the release of ca2+ was nearly completely attenuated by these compounds when they were given together. tbbpa (5,10 and 25 μm) administration caused a concentration-dependent increase in cgc ca2+ levels. administration of 2.5 μm bastadin 12 with 200 μm ryanodine blocked the increase in intracellular ca2+ evoked by 10 μm tbbpa,although these compounds were ineffective when applied separately. these results indicate that bastadin 12 may replace bastadin 5 when testing the ability of ryanodine to inhibit ca2+ release from the intracellular stores of cultured neurons,and our findings support the hypothesis that tbbpa and thapsigargin induce intracellular ca2+ release through a common mechanism. © 2014,polish physiological society. all rights reserved.