AJP - Lung Cellular and Molecular Physiology, Vol 262, Issue 1 78-L85, Copyright © 1992 by American Physiological Society

ARTICLES

Lipopolysaccharide stimulates de novo synthesis of PGH synthase in human alveolar macrophages

R. J. Pueringer and G. W. Hunninghake
Department of Internal Medicine, University of Iowa College of Medicine, Iowa City.

Lipopolysaccharide (LPS)-stimulated human alveolar macrophages (HAMs) produce large amounts of prostaglandin (PG) E2 for up to 72 h. The mechanism of this enhanced and prolonged metabolism of arachidonic acid to PGE2 is unknown. To determine whether LPS-stimulated HAM PGE2 production is due in part to an increase in the new synthesis of the first committed enzyme, PGH synthase, we measured PGE2 formation, PGH synthase activity, and newly synthesized PGH synthase at 2, 6, and 24 h after LPS-stimulation. PGE2, measured by radioimmunoassay, was not increased at 2 h but was increased at 6 and 24 h after stimulating HAMs with LPS. Unstimulated HAMs did not produce PGE2. Likewise, the activity of PGH synthase extracted from HAMs was not increased at 2 h but was increased at 6 and 24 h after LPS stimulation. Cycloheximide and actinomycin D markedly inhibited PGE2 production in LPS-stimulated HAMs. Newly synthesized PGH synthase measured by immunoprecipitating 35S-labeled PGH synthase was not detected at 2 h but was detected at 6 and 24 h after stimulation. The parallel increases in PGE2 production, PGH synthase activity, and newly synthesized PGH synthase coupled with the dependence of PGE2 on the ability of the alveolar macrophage to synthesize protein suggest that LPS-stimulated HAM PGE2 production is in part regulated by the de novo synthesis of PGH synthase.

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