Person:

Drazen, Jeffrey

In 1979 and 1980, the chemical structures of the material previously known as slow-reacting substance of anaphylaxis were elucidated as 5(S)- hydroxy- 6(R)-glutathionyl- 7,9-trans-11,14- cis - eico- satetraenoic acid1 and its cysteinyl-glycyl and cysteinyl congener (also known as leukotrienes C4, D4, and E4, respectively). These molecules were so named because the parent molecule was originally isolated from leukocytes, and its carbon backbone contained three double bonds in series, which constitutes a triene. This structural information provided the key to the oxidative pathway of lipid metabolism known as the 5-lipoxygenase pathway.

Compared with normal individuals, subjects with asthma have elevated levels of expired nitric oxide (NO). These levels are hypothesized to reflect the degree of airway inflammation. Expired NO levels rise during the late phase of allergen challenge and decrease in asthmatics after steroid treatment. Isocapnic cold air hyperventilation (ISH) is believed to cause airway narrowing through noninflammatory mechanisms. We measured mixed expired NO in 10 individuals with atopic asthma who underwent both ISH challenge and allergen challenge, and compared these measurements with the change in expired NO that occurred after serial spirometry alone. We found that ambient NO levels affected mixed expired NO. Controlling for inspired NO, we found that repeated spirometry alone produced a significant fall in mixed expired NO (p < 0.01) that was maximal after 30 min (36.6 ± 8.5% fall). After allergen and ISH challenges, expired NO was elevated relative to levels after repeated spirometry (p < 0.01 and p = 0.065, respectively). In addition, we found that prechallenge expired NO levels were significantly correlated with the magnitude of the late fall in FEV1 following allergen challenge (r = 0.80, p < 0.01). These data demonstrate that repeated spirometry results in reduced mixed expired NO and suggest that both ISH and allergen-induced bronchoconstriction share pathobiologic mechanisms that produce increases in mixed expired NO.

Five lipoxygenase (5-LO) is the first committed enzyme in the metabolic pathway leading to the synthesis of the leukotrienes. We examined genomic DNA isolated from 25 normal subjects and 31 patients with asthma (6 of whom had aspirin-sensitive asthma) for mutations in the known transcription factor binding regions and the protein encoding region of the 5-LO gene. A family of mutations in the G + C-rich transcription factor binding region was identified consisting of the deletion of one, deletion of two, or addition of one zinc finger (Sp1/Egr-1) binding sites in the region 176 to 147 bp upstream from the ATG translation start site where there are normally 5 Sp1 binding motifs in tandem. Reporter gene activity directed by any of the mutant forms of the transcription factor binding region was significantly (P < 0.05) less effective than the activity driven by the wild type transcription factor binding region. Electrophoretic mobility shift assays (EMSAs) demonstrated the capacity of wild type and mutant transcription factor binding regions to bind nuclear extracts from human umbilical vein endothelial cells (HUVECs). These data are consistent with a family of mutations in the 5-LO gene that can modify reporter gene transcription possibly through differences in Sp1 and Egr-1 transactivation.