Soluble interleukin-1 receptor accessory protein ameliorates collagen-induced arthritis by a different mode of action from that of interleukin-1 receptor antagonist.
OBJECTIVE
To discern the mode of interleukin-1 (IL-1) inhibition of soluble IL-1 receptor accessory protein (sIL-1RAcP) by comparison with IL-1 receptor antagonist (IL-1Ra) in arthritis.


METHODS
Adenoviral vectors encoding either sIL-1RAcP or IL-1Ra were administered systemically before onset of collagen-induced arthritis in DBA/1 mice. Anti-bovine type II collagen IgG and IL-6 were quantified in serum. Proliferative response of splenic T cells was determined in the presence of sIL-1RAcP or IL-1Ra. The effect on IL-1 inhibition of recombinant sIL-1RAcP and IL-1Ra was further examined in vitro, using NF-kappaB luciferase reporter cell lines. Quantitative polymerase chain reaction was used to determine the relative messenger RNA expression of the IL-1 receptors.


RESULTS
Adenoviral overexpression of both sIL-1RAcP and IL-1Ra resulted in amelioration of the collagen-induced arthritis. Both IL-1 antagonists reduced the circulating levels of antigen-specific IgG2a antibodies, but only IL-1Ra was able to inhibit lymphocyte proliferation. By using purified lymphocyte populations derived from NF-kappaB reporter mice, we showed that sIL-1RAcP inhibits IL-1-induced NF-kappaB activity in B cells but not T cells, whereas IL-1Ra inhibited IL-1 on both cell types. A study in a panel of NF-kappaB luciferase reporter cells showed that the sIL-1RAcP inhibits IL-1 signaling on cells expressing either low levels of membrane IL-1RAcP or high levels of IL-1RII.


CONCLUSIONS
We show that the sIL-1RAcP ameliorated experimental arthritis without affecting T cell immunity, in contrast to IL-1Ra. Our results provide data in support of receptor competition by sIL-1RAcP as an explanation for the different mode of IL-1 antagonism in comparison with IL-1Ra.
Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands.
R L
RL
Smeets
L A B
LA
Joosten
O J
OJ
Arntz
M B
MB
Bennink
N
N
Takahashi
H
H
Carlsen
M U
MU
Martin
W B
WB
van den Berg
F A J
FA
van de Loo
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D001169:Arthritis, Experimental / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D002417:Cattle; D049109:Cell Proliferation; D004195:Disease Models, Animal; D015870:Gene Expression; D015316:Genetic Therapy; D007375:Interleukin-1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D053577:Interleukin-1 Receptor Accessory Protein; D008297:Male; D051379:Mice; D008811:Mice, Inbred DBA; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D017472:Receptors, Interleukin-1 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D013154:Spleen / Q000276:immunology / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism
C507767:Il1rap protein, mouse; D007375:Interleukin-1; D053577:Interleukin-1 Receptor Accessory Protein; D016328:NF-kappa B; D011506:Proteins; D012333:RNA, Messenger; D017472:Receptors, Interleukin-1