Leukotriene A4 hydrolase in peripheral leukocytes of patients with atopic dermatitis.

We examined the enzymatic activity of leukotriene (LT) A4 hydrolase, which catalyzes the conversion of LTA4 to LTB4, in peripheral leukocytes of patients with atopic dermatitis. The patients were divided into three categories (severe, moderate and mild) on the basis of clinical severity. The LTA4 hydrolase activities in the supernatant fraction of peripheral blood polymorphonuclear leukocytes (PMN) were significantly higher in preparations of cells from severe atopic dermatitis patients (123.94 +/- 16.61 pmol/10(6) cells per min) than in those from moderate (49.03 +/- 9.43 pmol/ 10(6) cells per min; P < 0.01) and mild (28.75 +/- 11.42 pmol/10(6) cells per min; P < 0.01) atopic dermatitis patients and normal controls (15.14 +/- 1.74 pmol/10(6) cells per min; P < 0.01). LTA4 hydrolase activities were also higher in peripheral blood mononuclear cells (PBMC) from severe atopic dermatitis patients (27.81 +/- 8.28 pmol/10(6) cells per min) than in those from moderate (11.31 +/- 2.11 pmol/10(6) cells per min; P < 0.05) and mild (6.16 +/- 2.62 pmol/10(6) cells per min; P < 0.05) atopic dermatitis patients and normal controls (11.17 +/- 0.83 pmol/10(6) cells per min; P < 0.05). LTA4 hydrolase activities in PMN were reduced after improvement of the disease in eight patients with severe or moderate atopic dermatitis. These results suggest that LTA4 hydrolase, which synthesizes LTB4, plays a significant role in the pathogenesis and development of atopic dermatitis.