Arachidonic acid metabolism has been explored in preparations of purified human lung mast cells prelabeled with arachidonic acid (AA). Cells were of 83 to > 96% purity, and each experiment was performed with four to six different preparations of mast cells. After overnight culture of the purified cells in the presence of 3H-AA, followed by extensive washing in buffer, mast cell uptake of labeled AA was 61.4 ± 14.8 pmol/106 cells with 21 ± 2.4% of the label in phospholipids, 73 ± 2.1% in neutral lipids, and 3.6 ± 0.8% as free AA. Analysis of the distribution of radioactivity in phospholipid classes revealed 51.4 ± 5.5% of the label in phosphatidylcholine, 14.5 ± 1.6% in phosphatidylinositol, 12.0 ± 3.0% in phosphatidylethanolamine, and 9.1 ± 2.4% in sphingomyelin, with the rest in other phospholipid classes. Challenge of these cells with an optimal concentration of anti-Ige led to the release of 20 ± 4.0% of cellular histamine and to a reduction in labeled phosphatidylcholine and phosphatidylinositol to 75.5 ± 8.8% and 84.2 ± 4.5% of the control levels, respectively, (p < 0.05); anti-IgE challenge produced no statistically significant change in the quantities of other labeled phospholipids. Activation of human lung mast cells with anti-IgE led to the release of 3.4 ± 1.3% of the cellular 3H as AA and AA metabolites (1.5 ± 0.6% as unmetabolized AA) in conjunction with 16 ± 4.3% of the cellular histamine. Although activation of human lung mast cells with ionophore A23187 caused 70 ± 1.1% histamine release, a similar quantity of AA and AA metabolites was released (a total of 4.0 ± 0.8% with 2.3 ± 1.5% as unmetabolized AA). Analysis of the released metabolites by liquid scintillation spectrometry after high performance liquid chromatography separation showed that approximately equal amounts of metabolites were produced after mast cell activation with anti-IgE and ionophore A23187. In this series of experiments approximately equal amounts of cyclooxygenase and lipoxygenase products were generated. The distribution of metabolites (as a percentage of total metabolites) after activation with anti-IgE and A23187 were as follows: prostaglandin D2, 56 ± 6.4%, 51 ± 12% (anti-IgE and A23187, respectively); leukotriene C, 21 ± 5.2%, 17 ± 4.1%; leukotriene B isomers 16 ± 3.1%, 12 ± 0.5%; an unknown product 5.8 ± 1.5%, 7.1 ± 2.8%; and 5HETE 2.3 ± 2.1%, 13 ± 8.1%. We conclude that activation of purified preparations of human lung mast cells with anti-IgE leads to phospholipid turnover (phosphatidylcholine and phosphatidylinositol), and to the release of AA metabolites from both the cyclooxygenase (prostaglandin D2) and lipoxygenase (leukotriene C, leukotriene B isomers, and 5HETE) pathways. Although challenge with anti-IgE and ionophore A23187 resulted in histamine release that was markedly different, the two stimuli led to the release of similar quantities and types of AA metabolites. The procedures described here should be useful in exploring biochemical and pharmacologic aspects of AA metabolism in purified human lung mast cells.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of Immunology|
|State||Published - 1984|
ASJC Scopus subject areas
- Immunology and Allergy