Effects of inhibitors of the lipo-oxygenase family of enzymes on the store-operated calcium current I(CRAC) in rat basophilic leukaemia cells.

Journal article

In non-excitable cells, the major Ca2+ entry pathway is the store-operated pathway in which emptying of intracellular Ca2+ stores activates Ca2+ channels in the plasma membrane. In many cell types, store-operated influx gives rise to a Ca2+-selective current called I(CRAC) (Ca2+ release-activated Ca2+ current). Using both the whole-cell patch clamp technique to measure I(CRAC) directly and fluorescent Ca2+ imaging, we have examined the role of the lipo-oxygenase pathway in the activation of store-operated Ca2+ entry in the RBL-1 rat basophilic leukaemia cell-line. Pretreatment with a variety of structurally distinct lipo-oxygenase inhibitors all reduced the extent of I(CRAC), whereas inhibition of the cyclo-oxygenase enzymes was without effect. The inhibition was still seen in the presence of the broad protein kinase blocker staurosporine, or when Na+ was used as the charge carrier through CRAC channels. The lipo-oxygenase blockers released Ca2+ from intracellular stores but this was not associated with subsequent Ca2+ entry. Lipo-oxygenase blockers also reduced both the amount of Ca2+ that could subsequently be released by the combination of thapsigargin and ionomycin in Ca2+-free solution and the Ca2+ influx component that occurred when external Ca2+ was re-admitted. The inhibitors were much less effective if applied after I(CRAC) had been activated. This inhibition of I(CRAC) could not be rescued by dialysis with 5(S)-hydroxyperoxyeicosa-6E,8Z,11Z,14Z,tetraenoic acid (5-HPETE), the first product of the 5-lipo-oxygenase pathway. Our findings indicate that exposure to pharmacological tools that inhibit the lipo-oxygenase enzymes all decrease the extent of activation of the current. Our results raise the possibility that a lipo-oxygenase might be involved in the activation of I(CRAC). Alternative explanations are also discussed.

Authors: Glitsch, M; Bakowski, D; Parekh, AB

• Publication status: Published
• Journal: Journal of physiology
• Volume: 539
• Issue: Pt 1
• Pages: 93-106
• Publication date: 2002-02-01
• DOI: 10.1113/jphysiol.2001.012826
• EISSN: 1469-7793
• ISSN: 0022-3751
• Language: English
• Keywords: Permeability; Basophils; Caffeic Acids; Lipoxygenase Inhibitors; Thapsigargin; Rats; Animals; Osmolar Concentration; Patch-Clamp Techniques; Calcium; Adenosine Triphosphate; Enzyme Inhibitors; Nordihydroguaiaretic Acid; Leukotrienes; Staurosporine; Tumor Cells, Cultured; Electric Conductivity; Intracellular Membranes; Sodium