Activin A and Retinoic Acid Synergize in Cyclooxygenase‐1 and Thromboxane Synthase Induction During Differentiation of J774.1 Macrophages

Abstract

The murine macrophage cell line J774.1 was used to study the development of prostanoid biosynthesis under the influence of activin A and retinoic acid. Treatment of cells with 3 nM activin A for 48 h increased the biosynthesis of the prostaglandins E,, D,, FZa and thromboxane A, more than fourfold due to an induction of cyclooxygenase-1 while cyclooxygenase-2 was unaffected. Transforming growth factor-/I acted in a similar way. Retinoic acid, when present alone, was without effect on the total cyclooxygenase products and only slightly changed the pattern of prostanoids. However, when coincubated with activin A, retinoic acid specifically induced the synthesis of thromboxane-A-synthase-specific mRNA and induced an increase in enzyme activity with a synergistic effect on cyclooxygenase-1 protein and mRNA. JunB, but not c-jun, mRNA expression was found under these conditions in addition to a transient c-fos mRNA increase. The combination of activin A and retinoid acid may be regarded as a differentiation model to study the development of cell-specific prostanoid patterns in macrophages and possibly other differentiating cells.Keywords. Activin A ; retinoic acid ; cyclooxygenases ; prostaglandins ; differentiation.Prostanoids, consisting of the various prostaglandins, thromboxane and prostacyclin, regulate diverse cellular functions under physiological and pathophysiological conditions [ 13. They act in an autocrine or paracrine way and are derived from the same precursor, prostaglandin (PG) endoperoxide, which is made available from arachidonic acid by the enzyme cyclooxygenase. This enzyme, at the branchpoint of prostanoid synthesis, is known to exist in two isoforms, cyclooxygenase-1 and cyclooxygenase-2. Cyclooxygenase-1 is encoded by a housekeeping gene and generally thought to be ubiquitously expressed at a basal level for the various physiological roles of prostanoids in cells and tissues ([2-61, for review see [7]), whereas the expression of cyclooxygenase-2, the product of an immediate early gene, is regulated by inflammatory signals, such as cytokines, growth factors or lipopolysaccharides ([8-121, for review see 113 3 ) . While after arachidonate release the concentrations of the generated prostanoids seem to be regulated by the activity of cyclooxygenase, the prostanoid pattern is determined by the presence and activity of the subsequent isomerases, leading to PGE2, PGD2, PGF,,, prostacyclin and thromboxane. It has been widely accepted that each cell type, and even each differentiation stage, possesses a characteristic composition of such enzymes, resulting in a specific pattern of prostanoids. At present, attention is mainly focused on the expression of cyclooxygenase and, due to a lack of molecular tools, less attention is being paid to the regulation of the secondary enzymes leading to the cellspecific prostanoid patterns.

Acute regulation of activin A and its binding protein, follistatin, in serum and tissues following lipopolysaccharide treatment of adult male mice

“…This effect of blocking activin A by follistatin was consistent with studies that have shown that activin A stimulates production of these cytokines, and other proinflammatory genes, in human, rat, and mouse mononuclear phagocytes in vitro (22,23,42). These data indicate a crucial role for activin A, and, consequently, for endogenous follistatin, in controlling the severity of acute inflammation and its subsequent actions.…”

Effect of cyclic AMP and prostaglandin E2 on the induction of nitric oxide- and prostanoid-forming pathways in cultured rat mesangial cells

“…We suggest that the rapid but transient expression of Jun B mRNA contributes to the induced expression of COX-2. We recently reported on the participation of JunB mRNA expression in COX induction in a macrophage cell line [33]. Like the Jun-Fos heterodimers which mainly form the AP-1 factor JunB homodimers also possess trans-activity [34] and are thought to serve as tissue-specific activators of target genes regulated by AP-1.…”

The oral administration of retinoic acid enhances nociceptive withdrawal reflexes in rats with soft-tissue inflammation

“…Some studies, for example, have shown a clear relationship between retinoic acid and the generation of nitric oxide (NO) [9,12,28], prostaglandins [4,11] and the expression of cyclooxigenase 1 (COX-1) [23] and COX-2 [14,17]. All these mediators are involved in the generation or maintenance of sensitization and pain due to inflammation and are the targets for many painkillers studied in our lab among many others [7,10,26].…”