Effect of sulphasalazine and sulphapyridine on neutrophil superoxide production: role of cytosolic free calcium.

As the neutrophil granulocyte plays an important part in rheumatoid inflammation the effect of sulphasalazine on neutrophil function was studied. The results show that sulphasalazine, and its metabolite sulphapyridine, inhibit neutrophil superoxide production elicited by the receptor mediated stimulus N-formyl-methionyl-leucyl-phenyl-alanine (fMLP) and by the calcium ionophore A23187. This effect seems to be dependent on inhibition of intracellular Ca++ increase as both substances reduce this increase upon cell activation with fMLP and A23187. Sulphasalazine and sulphapyridine do not inhibit superoxide production after stimulation with the ester phorbol myristate acetate, a stimulus response coupling which is independent of intracellular Ca++ increase. The reported inhibition of superoxide generation may explain, at least partly, the antirheumatic property of sulphasalazine.