Inhibition of U937 eicosanoid and DNA synthesis by 5,8,11,14-eicosatetraynoic acid, an inhibitor of arachidonic acid metabolism and its partial reversal by leukotriene C4.

When replicating U937 cells were incubated with up to 80 microM concentrations of the in vitro inhibitor of eicosanoid biosynthesis, 5,8,11,14-eicosatetraynoic acid (ETYA), DNA synthesis measured by labeling with [3H]thymidine was inhibited in a concentration-dependent manner. No reduction in cellular viability occurred, as judged by exclusion of trypan blue, unaltered release of 51Cr-labeled proteins, and the reversibility of inhibition after incubation for 72 h with ETYA. Neither indomethacin nor acetylsalicylic acid, inhibitors of cyclooxygenase, altered DNA synthesis in control or ETYA-inhibited cells, excluding participation of the products of this enzyme in the inhibition of DNA synthesis. Incubation of inhibited cells with extracts prepared from log-phase media partially reversed the inhibition of DNA synthesis. Addition of leukotriene B4 or D4 at 10(-7) to 10(-8) M did not reverse ETYA-induced inhibition of DNA synthesis, nor did the addition of a series of long chain fatty acids, including arachidonic acid. However, leukotriene C4 at 10(-7) M partially reversed the inhibition of DNA synthesis. Extracts of media from log-phase cells were shown by high-pressure liquid chromatography to contain leukotriene C4, and synthesis of this compound was inhibited by ETYA, as judged by measurement of UV absorbance and radioactivity. Additional inhibitors of eicosanoid metabolism including nordihydroguaiaretic acid and esculetin also suppressed DNA synthesis in U937, K562, and prostate PC3 cells, without altered cellular viability; the effect is not limited to lymphohematopoietic cells or to a single inhibitor of arachidonic acid metabolism. Suppression of U937 DNA and eicosanoid synthesis by ETYA and the partial reversal of DNA synthesis by leukotriene C4 suggest that in these cells eicosanoids may modulate DNA synthesis. Other possible consequences of incubating cells with ETYA including creation of arachidonic acid-deficient membranes, and even incorporation of the agent into membrane phospholipids, may also contribute to the reversible inhibition of DNA synthesis.