RAW264.7 cells lack prostaglandin-dependent autoregulation of tumor necrosis factor-alpha secretion.
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 tumor necrosis factor-alpha (TNF-alpha) secretion observed in primary resident peritoneal macrophages (RPMs). 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 did LPS-treated RPMs, as a result of 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 RPMs. In contrast to RPMs, LPS-treated RAW produced high quantities of TNF-alpha, which were not altered in the presence of COX inhibitors. This failure of endogenous PGs to suppress TNF-alpha secretion was explained by the absence of the prostaglandin D2 receptor and the low levels of PGE2 produced during the first 2 h of the LPS response. These studies demonstrate that autocrine regulation of TNF-alpha 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.
Rouzer
Carol A
CA
Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA. c.rouzer@vanderbilt.edu
Jacobs
Aaron T
AT
Nirodi
Chetan S
CS
Kingsley
Philip J
PJ
Morrow
Jason D
JD
Marnett
Lawrence J
LJ
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D011453:Prostaglandins / Q000096:biosynthesis / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D017931:DNA Primers; D008070:Lipopolysaccharides; D011453:Prostaglandins; D014409:Tumor Necrosis Factor-alpha