Connective tissue activation. XXXVI. The origin, variety, distribution, and biologic fate of connective tissue activating peptide-III isoforms: characteristics in patients with rheumatic, renal, and arterial disease.
OBJECTIVE
To determine the origin, distribution, and biologic fate of platelet-derived connective tissue activating peptide-III (CTAP-III), to define the relative amounts of the antigen forms (CTAP-III, beta-thromboglobulin [beta-TG], neutrophil activating peptide-2 [NAP-2]) in plasma of normal persons and those with rheumatic or end-stage renal disease, and to define the isoforms of CTAP-III in platelets, plasma, transudates, and tissue deposits.


METHODS
CTAP-III in plasma was measured by enzyme-linked immunosorbent assay, and growth promoting activity of CTAP-III isoforms was tested in synovial and peritoneal cell cultures by measuring increased synthesis of 14C-glycosaminoglycan (14C-GAG) and 3H-DNA. Isolated CTAP-III was characterized by Western blotting, microsequencing, and mass spectrometry.


RESULTS
CTAP-III was the primary isoform of this antigen family in normal platelets and platelet-rich plasma; beta-TG and NAP-2 accounted for < 1% of CTAP-III isoforms. Previously undescribed isoforms, i.e., CTAP-III des 1, des 1-2, des 1-3, and a phosphate adduct of CTAP-III, were observed in varying amounts. Elevated plasma levels of CTAP-III antigen were found in a substantial fraction of rheumatic disease patients: 24% of those with rheumatoid arthritis, 36% of those with systemic sclerosis, and 15% of those with systemic lupus erythematosus. All 10 patients with end-stage kidney disease had marked elevations of plasma CTAP-III levels, which stimulated DNA and GAG synthesis by peritoneal cells in culture. Only large isoforms (such as CTAP-III) were detected in venous plasma of normal subjects, rheumatic disease patients, and patients receiving long-term dialysis. Normal human spleen and kidney contained substantial (micrograms/gm) amounts of CTAP-III and traces of an isoform with the electrophoretic mobility of CTAP-III des 1-15/NAP-2. Liver, lung, and urine contained lesser (ng/gm) amounts of CTAP-III.


CONCLUSIONS
These data show that, among the 10 known isoforms, intact CTAP-III itself was the major circulating isoform (> 90%), and beta-TG was the most rare (0-1%). Deposition of CTAP-III in tissues, such as synovium, spleen, and kidney, is associated with partial processing to NAP-2-like isoforms and the potential to induce neutrophil and fibroblast activation in patients with rheumatic or end-stage renal disease.
Castor
C W
CW
Rackham Arthritis Research Unit, University of Michigan Medical School, Ann Arbor.
Andrews
P C
PC
Swartz
R D
RD
Ellis
S G
SG
Hossler
P A
PA
Clark
M R
MR
Matteson
E L
EL
Sachter
E F
EF
D000328:Adult; D000368:Aged; D001779:Blood Coagulation Factors / Q000032:analysis*; D001792:Blood Platelets / Q000737:chemistry*; D003327:Coronary Disease / Q000097:blood*; D003922:Diabetes Mellitus, Type 1 / Q000097:blood; D005260:Female; D006801:Humans; D007668:Kidney / Q000737:chemistry; D008297:Male; D008875:Middle Aged; D010455:Peptides; D051437:Renal Insufficiency / Q000097:blood* / Q000652:urine; D012216:Rheumatic Diseases / Q000097:blood*
D001779:Blood Coagulation Factors; D010455:Peptides; C009862:connective tissue-activating peptide; C018329:low affinity platelet factor 4