Leukotriene A sub(4) hydrolase in human bronchoalveolar lavage fluid

We examined cell-free human bronchoalveolar lavage fluid (BALF) for enzymes of the 5-lipoxygenase pathway. BALF was obtained from six patients who were active smokers and six nonsmokers. Enzymatic activity in cell-free BALF was assessed by specific assays for leukotriene (LT) A sub(4) hydrolase, 5-lipoxygenase, and LTC sub(4) synthase using HPLC. Only LTA sub(4) hydrolase enzymatic activity was found. This activity ranged from 101 to 667 when expressed as picomoles of LTB sub(4) produced per milliliter BALF. Enzymatic activity in smokers vs nonsmokers was 484 plus or minus 120 vs 129 plus or minus 32 pmol LTB sub(4)/ml BALF. There were no leukotrienes found in BALF before assay. Immunoblot analysis revealed an immunoreactive band at a relative molecular mass of 69,000 D in all samples, consistent with LTA sub(4) hydrolase, but no evidence of 5-lipoxygenase. BALF had greater LTA sub(4) hydrolase activity per milligram of protein than neutrophil cytosol, epithelial cell cytosol, plasma, or serum. The synthesis of LTB sub(4) was significantly increased when neutrophils were stimulated in BALF. These data indicate the selective presence of LTA sub(4) hydrolase in BALF which is significantly increased in smokers. This enzyme in BALF may contribute to the inflammatory response in tobacco-related lung disease. (DBO)