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Interleukin 1beta mediated calciotropic activity in serum of children with juvenile rheumatoid arthritis
S J Schurman1, W H Bergstrom, A W Root
1Department of Pediatrics, University of South Florida College of Medicine, Tampa, USA.
Objective:
To detect the presence and source of calciotropic activity in the serum of children with juvenile rheumatoid arthritis (JRA).
Methods:
Metabolic evaluation of an adolescent with polyarticular JRA and hypercalcemia/hypercalciuria included testing with a bone disc bioassay. The bioassay detects calciotropic activity (increased bone resorption or reduced bone formation) in serum. Interleukin 1 receptor antagonist (IL-1RA) was added to patient sera to test the role of IL-1beta. The results in this index case prompted additional study in 9 children with JRA. Correlation of calciotropic activity with disease activity score, erythrocyte sedimentation rate (ESR), and urinary calcium excretion was by Spearman rank correlation.
Results:
Calciotropic activity was found in 2 consecutive samples from the index patient. This activity was eliminated by addition of IL-1RA (p < 0.001 compared to serum alone). Testing of the other 9 children showed calciotropic activity at least once in 7/9 and 10/15 samples studied. Addition of IL-1RA completely (6/8) or partially (2/8) neutralized calciotropic activity (p < 0.001 compared to serum alone) in the specimens available for testing. Calciotropic activity did not significantly correlate with disease activity score, ESR, or urine calcium.
Conclusion:
Our data indicate the presence of IL-1beta mediated calciotropic activity in the sera of children with JRA, and suggest a role for IL-1beta in JRA associated osteopenia.