CD44-mediated cyclooxygenase-2 expression and thromboxane A2 production in RAW 264.7 macrophages.
OBJECTIVE
CD44 is the major cell surface receptor for hyaluronan (HA) on macrophages. Stimulation of macrophages via the HA-CD44 pathway leads to the enhanced expression of inflammatory gene products, including cytokines, chemokines, and adhesion molecules. We have examined whether activation of CD44 by crosslinking is capable of activating the cyclooxygenase (COX) and prostaglandin (PG)/thromboxane (TX) pathway in cultured macrophages.


METHODS
CD44 was crosslinked on RAW 264.7 mouse macrophages using specific rat anti-mouse CD44 monoclonal antibodies and anti-rat IgG. Total RNA was extracted and subjected to RT-PCR analysis for genes of the PG/TX synthetic pathway. Supernatants were analyzed for PGE2 and TXB2 using specific ELISAs.


RESULTS
Transcripts for COX-1, COX-2, TX synthase (TXS), and PGE2 synthase (PGES) were all constitutively expressed in the mouse macrophage cell line RAW 264.7. Crosslinking of CD44 markedly enhanced COX-2 and weakly increased TXS mRNA, whereas COX-1 and PGES mRNA did not change significantly in these cells. Crosslinking of CD44 selectively increased the production of TXB2 but not PGE2.


CONCLUSIONS
These findings suggest that the activation of the CD44 pathway plays a unique role in PG synthesis. Activation of this pathway results in enhanced TXA2 but not PGE2 production. This leads to an imbalance of the TXA2/PGE2 profile which favors a proinflammatory and vasoconstrictory response.
Sun
L K
LK
Department of Medicine, Kantonsspital, St Gallen, Switzerland.
Wahl
P
P
Bilic
G
G
Wüthrich
R P
RP
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D003432:Cross-Linking Reagents; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D005434:Flow Cytometry; D018960:Hyaluronan Receptors / Q000502:physiology*; D007527:Isoenzymes / Q000096:biosynthesis*; D008264:Macrophages / Q000378:metabolism* / Q000502:physiology; D008565:Membrane Proteins; D051379:Mice; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis*; D012313:RNA / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013928:Thromboxane A2 / Q000096:biosynthesis*; D013930:Thromboxane-A Synthase / Q000096:biosynthesis
D003432:Cross-Linking Reagents; D018960:Hyaluronan Receptors; D007527:Isoenzymes; D008565:Membrane Proteins; D013928:Thromboxane A2; D012313:RNA; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; C496512:Ptgs1 protein, mouse; D013930:Thromboxane-A Synthase