Submitted on January 6, 2005
Revised on January 28, 2005
Accepted on January 28, 2005
RAW264.7 cells lack prostaglandin-dependent autoregulation of tumor necrosis factor-
secretion
Carol A. Rouzer, Aaron T. Jacobs, Chetan S. Nirodi, Phillip J. Kingsley, Jason D. Morrow, and Lawrence J. Marnett
Biochemistry, Vanderbilt University Medical Center, Nashville, TN 37232-0146
Corresponding Author: c.rouzer{at}vanderbilt.edu
Studies of the response of RAW264.7 cells (RAW) to lipopolysaccharide (LPS) were carried out to determine why these cells do not demonstrate the prostaglandin (PG)-dependent autocrine regulation of TNF-
secretion observed in primary resident peritoneal macrophages (RPM). The major cyclooxygenase (COX) product of LPS-stimulated RAW was PGD2 with lesser amounts of PGE2. LPS-treated RAW produced PGs more slowly and reached their maximal PG synthetic rate later than do LPS-treated RPM, due to lower constitutive COX-1 expression and a slower rate of COX-2 induction. Cytosolic phospholipase A2 and levels of free arachidonic acid were similar in RAW and RPM. In contrast to RPM, LPS-treated RAW produced high quantities of TNF-, which were not altered in the presence of COX inhibitors. This failure of endogenous PGs to suppress TNF- secretion was explained by the absence of the DP1 receptor, and the low levels of PGE2 produced during the first two hours of the LPS response. These studies demonstrate that autocrine regulation of TNF- secretion in response to LPS is greatly facilitated by a COX-1 mediated rapid accumulation of PGs, as well by a correspondence between the PGs produced and the receptors expressed by the cells.
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