Serum tartrate-resistant acid phosphatase isoforms in rheumatoid arthritis.
OBJECTIVE
Our objective was to evaluate the significance and source of serum tartrate-resistant acid phosphatase (TRACP) in patients with rheumatoid arthritis (RA).


METHODS
Thirty-five RA, 32 osteoarthritis (OA) and 16 control subjects were studied. Serum TRACP-5b activity and total TRACP protein were determined by immunoassay. TRACP isoforms were analyzed by non-denaturing polyacrylamide gel electrophoresis (PAGE). Serum bone alkaline phosphatase (BAP), cross-linked N-terminal telopeptides (NTx), and C-terminal telopeptides (ICTP) of type I collagen were estimated as markers of bone turnover. C-reactive protein (CRP) was measured as a marker of chronic inflammation. Macrophages and dendritic cells (DC) were developed from peripheral blood monocytes. Cell lysates and culture supernatants were analyzed for TRACP isoforms by immunoassay and PAGE.


RESULTS
In RA, mean TRACP-5b activity was normal, but median total TRACP protein was increased twofold (p<0.001). In OA, TRACP-5b activity and protein were normal. In RA, TRACP-5b activity correlated weakly with ICTP (r=0.56) while TRACP protein levels correlated weakly with NTx (r=0.43). Additionally, TRACP protein, but not TRACP-5b activity correlated significantly with CRP (r=0.42). Macrophage and DC lysates contained TRACP-5b, while tissue culture supernatants contained TRACP-5a.


CONCLUSIONS
Increased total TRACP protein in RA sera was probably due to TRACP-5a and not derived from osteoclasts. Rather, it could be a secreted product of inflammatory macrophages and DC.
Janckila
Anthony J
AJ
Special Hematology Laboratory, US Department of Veterans Affairs Medical Center, 800 Zorn Ave., Louisville, KY 40206, USA. anthony.janckila@med.va.gov
Neustadt
David H
DH
Nakasato
Yuri R
YR
Halleen
Jussi M
JM
Hentunen
Teuvo
T
Yam
Lung T
LT
D000135:Acid Phosphatase / Q000097:blood*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000201:enzymology*; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000032:analysis; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000201:enzymology; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007118:Immunoassay; D007249:Inflammation / Q000097:blood / Q000201:enzymology; D007527:Isoenzymes / Q000097:blood*; D008264:Macrophages / Q000201:enzymology; D008875:Middle Aged; D010003:Osteoarthritis / Q000097:blood / Q000201:enzymology; D012680:Sensitivity and Specificity; D000071681:Tartrate-Resistant Acid Phosphatase
D015415:Biomarkers; D007527:Isoenzymes; D002097:C-Reactive Protein; C000605510:ACP5 protein, human; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase