Vascular amine oxidases are needed for leukocyte extravasation into inflamed joints in vivo.
OBJECTIVE
Leukocyte traffic from the blood to the joints is crucial in the pathogenesis of arthritis. A bifunctional endothelial cell-surface glycoprotein, AOC3 (amine oxidase, copper-containing 3; also known as vascular adhesion protein 1), has both adhesive and enzymatic properties. We undertook this study to determine the contribution of AOC3 and its oxidase activity to leukocyte trafficking into inflamed joints in vivo.


METHODS
We used gene-modified animals, molecular modeling, an AOC3 enzyme inhibitor, oxidase assays, and arthritis models (adjuvant-induced arthritis [AIA] in rats and anti-type II collagen antibody-induced arthritis in mice) to dissect the importance of AOC3 in vivo.


RESULTS
The AOC3 inhibitor fitted well with a covalent binding mode into the active site of the AOC3 crystal structure. It selectively blocked the oxidase activity of AOC3 in enzyme assays. Intraperitoneal and oral administration of the AOC3 inhibitor significantly ameliorated rat AIA. In anti-type II collagen antibody-induced arthritis in mice, the AOC3 inhibitor also improved the outcome of the joint inflammation. The acute semicarbazide-sensitive amine oxidase blockade by the inhibitor had even more pronounced effects than genetic deletion of AOC3. Enzymatic analyses showed that the inhibitor also blocked 2 other structurally very closely related AOCs, but not any of more than 100 other enzymes tested.


CONCLUSIONS
These are the first data to demonstrate that the enzymatic activity of the atypical endothelial adhesion molecule AOC3, and possibly that of other closely related ecto-oxidases, is crucial for leukocyte exit from the vessels in inflamed joints in vivo.
Marttila-Ichihara
Fumiko
F
University of Turku, and National Public Health Institute, Turku, Finland.
Smith
David J
DJ
Stolen
Craig
C
Yegutkin
Gennady G
GG
Elima
Kati
K
Mercier
Nathalie
N
Kiviranta
Riku
R
Pihlavisto
Marjo
M
Alaranta
Sakari
S
Pentikäinen
Ulla
U
Pentikäinen
Olli
O
Fülöp
Ferenc
F
Jalkanen
Sirpa
S
Salmi
Marko
M
D006631:Amine Oxidase (Copper-Containing) / Q000097:blood* / Q000737:chemistry / Q000235:genetics; D000818:Animals; D001169:Arthritis, Experimental / Q000201:enzymology / Q000503:physiopathology*; D015815:Cell Adhesion Molecules / Q000097:blood* / Q000737:chemistry / Q000235:genetics; D003001:Cloning, Molecular; D030562:Databases, Protein; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007249:Inflammation / Q000201:enzymology; D007596:Joints / Q000201:enzymology / Q000503:physiopathology*; D007962:Leukocytes / Q000201:enzymology*; D008297:Male; D051379:Mice; D008958:Models, Molecular; D011487:Protein Conformation; D051381:Rats; D011917:Rats, Inbred Lew
D015815:Cell Adhesion Molecules; D004791:Enzyme Inhibitors; D006631:Amine Oxidase (Copper-Containing); C510433:vascular adhesion protein-1, rat