Licofelone suppresses prostaglandin E2 formation by interference with the inducible microsomal prostaglandin E2 synthase-1.
The anti-inflammatory drug licofelone [=ML3000; 2-[6-(4-chlorophenyl)-2,2-dimethyl-7-phenyl-2,3-dihydro-1H-pyrrolizin-5-yl] acetic acid], currently undergoing phase III trials for osteoarthritis, inhibits the prostaglandin (PG) and leukotriene biosynthetic pathway. Licofelone was reported to suppress the formation of PGE(2) in various cell-based test systems, but the underlying molecular mechanisms are not entirely clear. Here, we examined the direct interference of licofelone with enzymes participating in PGE(2) biosynthesis, that is, cyclooxygenase (COX)-1 and COX-2 as well as microsomal PGE(2) synthase (mPGES)-1. Licofelone concentration-dependently inhibited isolated COX-1 (IC(50) = 0.8 microM), whereas isolated COX-2 was less affected (IC(50) > 30 microM). However, licofelone efficiently blocked the conversion of PGH(2) to PGE(2) mediated by mPGES-1 (IC(50) = 6 microM) derived from microsomes of interleukin-1beta-treated A549 cells, being about equipotent to 3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2,2-dimethylpropanoic acid (MK-886), a well recognized mPGES-1 inhibitor. In intact interleukin-1beta-treated A549 cells, licofelone potently (IC(50) < 1 microM) blocked formation of PGE(2) in response to calcimycin (A23187) plus exogenous arachidonic acid, but the concomitant generation of 6-keto PGF(1alpha), used as a biomarker for COX-2 activity, was not inhibited. We conclude that licofelone suppresses inflammatory PGE(2) formation preferentially by inhibiting mPGES-1 at concentrations that do not affect COX-2, implying an attractive and thus far unique molecular pharmacological dynamics as inhibitor of COX-1, the 5-lipoxygenase pathway, and of mPGES-1.
Pharmaceutical Institute, University of Tuebingen, Auf der Morgenstelle 8, D-72076 Tuebingen, Germany.
Andreas
A
Koeberle
Ulf
U
Siemoneit
Ulrike
U
Bühring
Hinnak
H
Northoff
Stefan
S
Laufer
Wolfgang
W
Albrecht
Oliver
O
Werz
D000328:Adult; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D015232:Dinoprostone / Q000037:antagonists & inhibitors* / Q000096:biosynthesis*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D019746:Intramolecular Oxidoreductases / Q000037:antagonists & inhibitors* / Q000096:biosynthesis*; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism*; D000071876:Prostaglandin-E Synthases; D011758:Pyrroles / Q000494:pharmacology*; D012756:Sheep
D011758:Pyrroles; D019746:Intramolecular Oxidoreductases; C000605862:PTGES protein, human; D000071876:Prostaglandin-E Synthases; D015232:Dinoprostone; C088092:licofelone