Conversion of leukotriene A4 by neutrophils and platelets from patients with atopic dermatitis.

The generation of arachidonic acid-derived inflammatory mediators from unstimulated and stimulated neutrophils (PMN) and platelets in the presence of exogenous LTA4 has been studied in patients with atopic dermatitis (AD) as well as in healthy volunteers. PMN were stimulated with the interleukins IL-3, IL-8, C5a, and the Ca-ionophore A23187. In addition, NaF and thrombin were used to stimulate platelets. The release of leukotriene (LT)B4, 20-COOH- and 20-OH-LTB4, cysteinyl-leukotrienes and 12-HETE was measured. The proinflammatory mediator release from PMN and platelets of patients with AD was significantly higher as compared to the control group. The spontaneous conversion of LTA4 by PMN and platelets was markedly enhanced in patients with AD. Different results with receptor-specific and non-specific stimuli (Ca-ionophore A23187) in the presence of exogenous LTA4 were obtained. The results indicate a higher state of activation for enzymes involved in leukotriene formation. Furthermore, the production of 12-HETE by platelets from patients with AD was enhanced in unstimulated and stimulated cells. Our data emphasize that neutrophils and platelets may play an important role in the pathogenesis of AD by an increased responsiveness to receptor-specific stimuli and cell-cell interaction via LTA4.