Transient expression of prostaglandin endoperoxide synthase-2 during mouse macrophage activation

Abstract

We investigated regulation of macrophage prostaglandin production during activation by interferon gamma (IFN-gamma) and lipopolysaccharide (LPS). An in vitro model was established using the mouse macrophage-like cell line RAW 264.7. Cells were cultivated in the presence of IFN-gamma and LPS for up to 48 h and changes in the secretion of nitric oxide (NO.) and tumor necrosis factor alpha (TNF-alpha) were observed as activation markers. Under these conditions a prompt and strong increase in PGE2 production was found in the first 8 h followed by nearly constant generation of PGE2 during the next 40 h. In contrast, the activity of prostaglandin endoperoxide synthase (PGHS), measured as PGE2 production of microsomal protein fractions, was also increased, but reached a clear maximum at 24 h. Recently a second form of PGHS was cloned (PGHS-2) and specific antibodies and mRNA probes for both isoforms are available. PGHS-2 enzyme was expressed maximally after 24 h of activation whereas PGHS-1 was not influenced. In the presence of IFN-gamma and LPS, PGHS-2 mRNA expression reached a maximum at 8 h but PGHS-1 mRNA was not induced during the whole time period. These data indicate that changes in PG synthesis following macrophage activation are due to regulation of PGHS-2 expression.

Regulation of Cyclooxygenase-2 by Interferon γ and Transforming Growth Factor α in Normal Human Epidermal Keratinocytes and Squamous Carcinoma Cells

“…DISCUSSION IFN-␥ has been reported to regulate the expression of COX-2 in several cell systems. In human bronchial epithelial cells and macrophages (42,62), IFN-␥ induces COX-2, while it has no effect in osteoblast and smooth muscle cells (41) and inhibits COX-2 expression in microglial cells (63). In this study, we demonstrate that in NHEK IFN-␥, treatment causes a dramatic induction in the expression of COX-2, while COX-1 expression is inhibited.…”

Cyclooxygenase-2 Expression in Macrophages: Modulation by Protein Kinase C-α

“…In addition to inducing the expression of several genes, incubation of macrophages with IFN-␥ enhances their responsiveness to LPS (10,24). To determine whether PKC-␣ plays a role in the regulation of IFN-␥-induced responses, we have measured the induction of COX-2 mRNA accumulation and protein synthesis in control RAW 264.7 cells and in the DN PKC-␣-overexpressing clones B1 and C2 in response to 100 U/ml IFN-␥ alone or in combination with 100 ng/ml LPS.…”

“…In human and murine macrophages, COX-2 expression is induced by LPS, IL-1, and phorbol esters (6 -9). Studies with the murine macrophage cell line RAW 264.7 indicated that accumulation of COX-2 mRNA can be induced by a combination of IFN-␥ and LPS but not by IFN-␥ alone (10). In addition to soluble mediators, pathogens such as the intracellular parasite Leishmania donovani can increase synthesis of PGE 2 , possibly by inducing alterations in the COX pathway (11,12).…”

Redundancy in the Signaling Pathways and Promoter Elements Regulating Cyclooxygenase-2 Gene Expression in Endotoxin-treated Macrophage/Monocytic Cells

“…COX-1 is expressed constitutively in most tissues and may be responsible for housekeeping functions (4). In contrast, COX-2 is not detectable in most normal tissues or resting immune cells, but its expression can be induced by endotoxin, cytokines, growth factors, and carcinogens (5)(6)(7).…”

“…Macrophage activation is accompanied by a significant increase in COX-2 expression, whereas levels of COX-1 remain unchanged (7,8). In vivo macrophage COX-2 immunoreactivity is a characteristic finding in the synovium of patients with osteoarthritis as well as in other forms of inflammation, whereas COX-1 expression typically remains unchanged (9,10).…”