Potentiation of calcium levels by extracellular arachidonic acid in nucleiisolated from macrophages stimulated with receptor-recognized forms of alpha(2)-macroglobulin

Ligation of macrophage alpha(2)-macroglobulin signalling receptors (alpha(2 )MSR) with activated alpha(2)-macroglobulin (alpha(2)M*) increases intracel lular Ca2+, and cytosolic phospholipase A(2) (cPLA(2)) and phospholipase D activities. In view of the relationship between cellular Ca2+ and mitogenes is, we examined the effect of the product of cPLA(2) activity, arachidonic acid (AA), on nuclear Ca2+ levels in macrophages stimulated with alpha(2)M* , platelet derived growth factor, and bradykinin. AA addition increased Ca2 + levels in Fura-2/AM loaded nuclei from both buffer-treated and agonist-st imulated cells, but the increase in stimulated macrophages was 2-4-fold hig her. Preincubation of Fura-2/AM loaded nuclei with EGTA or BAPTA/AM abolish ed AA-induced increase in nuclear Ca2+ levels. Preincubation of nuclei with indomethacin did not affect AA-induced increase in nuclear Ca2+ in agonist -stimulated nuclei. It is concluded that in macrophages stimulated with var ious agonists, AA, derived from cPLA(2)-dependent hydrolysis of phospholipi ds, plays a significant role in regulating nuclear Ca2+ levels and thus nuc lear functions. (C) 2000 Elsevier Science Inc. All rights reserved.