Effects of lipoxins A and B on functional responses of human granulocytes

The effects of synthetic lipoxin A and B (LXA and LXB) as well as several of their isomers were assessed as inducers of functional responses of human granulocytes. LXA stimulated migration at 1 nM and exhibited a variable effect as inducer of chemiluminescence at concentrations greater than or equal to 1 microM. Both migration and chemiluminescence evoked by LXA proved to be highly stereospecific, since e.g. 6S-LXA was less active than LXA. Neither synthetic LXA nor several of its stereoisomers provoked degranulation, aggregation, membrane potential changes or intracellular calcium fluxes. In addition, LXB and its isomers did not stimulate aggregation, degranulation or chemiluminescence. Pretreatment of granulocytes with LXA did not modify subsequent challenges with leukotriene B4. Together, these results indicate that granulocyte responses to LXA are highly stereospecific and are mediated by other mechanisms than those evoked by leukotriene B4.