title: Polyenoic very-long-chain fatty acids mobilize intracellular calcium from a thapsigargin-insensitive pool in human neutrophils. The relationship between Ca2+ mobilization and superoxide production induced by long- and very-long-chain fatty acids.
abstract: Fatty acids with more than 22 carbon atoms (very-long-chain fatty acids; VLCFAs) are normal cellular components that have been implicated in the pathophysiology of a number of peroxisomal disorders. To date, however, essentially nothing is known regarding their biological activities. Ca2+ mobilization is an important intracellular signalling system for a variety of agonists and cell types. Given that several polyunsaturated long-chain fatty acids mobilize intracellular Ca2+ and that we have postulated that the VLCFAs may be involved in signal transduction, we examined whether the tetraenoic VLCFA induced Ca2+ mobilization in human neutrophils. We report that fatty acid-induced intracellular Ca2+ mobilization declined for fatty acid species of more than 20 carbon atoms, but increased again as the carbon chain length approached 30. This Ca2+ mobilization occurred independently of inositol 1,4,5-triphosphate production and protein kinase C translocation and involved both the release of Ca2+ from the intracellular stores and changes to the influx or efflux of the ion. We further observed that triacontatetraenoic acid [30:4(n-6)] mobilized Ca2+ from a thapsigargin-insensitive intracellular pool distinct from the thapsigargin-sensitive pools affected by arachidonic acid [20:4(n - 6)] or N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP). 20:4 (n - 6) induced strong superoxide production (chemiluminescence) which was inhibited by thapsigargin pretreatment. In contrast, fatty acid-induced superoxide production progressively declined as the carbon chain length increased beyond 20-22 carbon atoms. Further studies suggested that the thapsigargin-insensitive Ca2+ mobilization elicited by 30:4 (n - 6) was not related to oxyradical formation, while the thapsigargin-sensitive Ca2+ mobilization induced by 20:4 (n - 6) may be involved in the initiation but not necessarily the maintenance of superoxide production. In conclusion, this is the first report to demonstrate a biological activity for the VLCFA and indicates that 30:4 (n - 6) influences second messenger systems in intact cells that differ from those affected by long-chain fatty acids such as 20:4 (n - 6).
mesh_terms: D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005227:Fatty Acids / Q000494:pharmacology*; D016257:Fura-2 / Q000031:analogs & derivatives / Q000378:metabolism; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008163:Luminescent Measurements; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D010047:Ovalbumin / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism; D015290:Second Messenger Systems; D012710:Serum Albumin, Bovine / Q000494:pharmacology; D013329:Structure-Activity Relationship; D013481:Superoxides / Q000378:metabolism*; D013729:Terpenes / Q000494:pharmacology*; D019284:Thapsigargin
chemical_list: D004791:Enzyme Inhibitors; D005227:Fatty Acids; D013729:Terpenes; C049925:fura-2-am; D013481:Superoxides; D012710:Serum Albumin, Bovine; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; D010047:Ovalbumin; D011493:Protein Kinase C; D000252:Calcium-Transporting ATPases; D002118:Calcium; D016257:Fura-2