Abstract
We compared the effect of leukotriene B4 (LTB4), one of 5-lipoxygenase (5-LO) products of arachidonic acid, with that of leukotriene B5 (LTB5), one of 5-LO products of eicosapentaenoic acid, on interleukin 1 (IL-1) production and calcium mobilizing activity in human blood monocytes. LTB4 was significantly more active than LTB5 in the enhancement of IL-1 production and calcium mobilization in human monocytes. IL-1 production in monccytes was reported to be dependent on cytosolic free calcium. These results, therefore, may indicate that the different activity between LTB4 and LTB5 in the enhancement of IL-1 production could be partly ascribed to the different potency in inducing calcium mobilization between LTB4 and LTB5 in human blood monocytes. Although effective concentrations of LTB on IL-1 production with LPS co-stimulation was shifted to the left as compared to those without LPS, effective concentrations of LTB in inducing calcium mobilization was nearly in the same range regardless of the presence or absence of LPS. Further, LPS itself could not induce a detectable calcium mobilization in fura-2-loaded monocytes. Therefore, LPS may enhance IL-1 production in human monocytes through a mechanism different from that of LTB.
