System A neutral amino acid transporter regulation by interleukin-1beta in human osteoarthritic synovial cells: evidence for involvement of prostaglandin E(2) as a second messenger.
We studied the long-terms effects of interleukin-1beta (IL-1beta; 3 to 6 h) on alpha-(methylamino) isobutyric acid (MeAIB), a nonmetabolizable amino acid transported by system A. We found that IL-1beta induced a large decrease in MeAIB uptake by human osteoarthritic synovial cells and a concomitant increase in prostaglandin E(2) (PGE(2)) synthesis. Therefore, we investigated whether PGE(2) acts as a mediator for the long-term action of IL-1beta. We found that exogenous PGE(2) inhibited MeAIB uptake, and that AH6809, a PGE(2) receptor antagonist, inhibited IL-1beta-mediated MeAIB uptake. To identify the enzymes involved in the IL-1beta-mediated synthesis of PGE(2) that inhibits MeAIB uptake, we studied the expression of secreted (s) and cytosolic (c) phospholipase A(2) (PLA(2)). Because both were expressed, we selected a broad spectrum of inhibitors to determine which of the two PLA(2)s was involved. We used AACOCF3, a cPLA(2) inhibitor, and dithiothreitol (DTT) and bromophenacyl bromide (BPB), which are sPLA(2) inhibitors. Our results suggest that the PLA(2) involved in the IL-1beta-mediated synthesis of PGE(2) was sPLA(2). We also showed the expression of cyclooxygenase (COX)-2 and its partial involvement using a potent selective COX-2 inhibitor, L-745337. These findings provide insight into the mechanisms underlying the IL-1beta-mediated regulation of transport system A. The Il-1beta-induced inhibition of MeAIB uptake in human osteoarthritic synovial cells thus seems to be essentially mediated by PGE(2) production via the activation of sPLA(2) and the partial activation of COX-2.
Le Maire
V
V
Laboratoire de Biochimie A, AP-HP, Hôpital Cochin, Paris, France.
Solito
E
E
Russo-Marie
F
F
Hernvann
A
A
Le Marechal
H
H
Ekindjian
O G
OG
Aussel
C
C
D026905:Amino Acid Transport Systems; D001095:Arachidonic Acids / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D051546:Cyclooxygenase 2; D003600:Cytosol / Q000201:enzymology; D015232:Dinoprostone / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D007189:Indans / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008565:Membrane Proteins; D010003:Osteoarthritis / Q000473:pathology / Q000503:physiopathology*; D010741:Phospholipases A / Q000235:genetics / Q000378:metabolism; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics; D015290:Second Messenger Systems / Q000187:drug effects / Q000502:physiology*; D013583:Synovial Membrane / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology*; D014966:Xanthenes / Q000494:pharmacology; D044004:Xanthones; D015091:beta-Alanine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics
D026905:Amino Acid Transport Systems; D001095:Arachidonic Acids; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D007189:Indans; D007375:Interleukin-1; D007527:Isoenzymes; C093700:L 745337; D008565:Membrane Proteins; D014966:Xanthenes; D044004:Xanthones; C081565:arachidonyltrifluoromethane; D015091:beta-Alanine; C012924:2,2-dimethyl-beta-alanine; C053876:6-isopropoxy-9-oxoxanthene-2-carboxylic acid; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D010741:Phospholipases A; D015232:Dinoprostone