CONNECTIVE-TISSUE ACTIVATION .36. 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-t hromboglobulin [beta-TG], neutrophil activating peptide-2 [NAP-2]) in plasma of normal persons and those with rheumatic or end-stage renal d isease, and to define the isoforms of CTAP-III in platelets, plasma, t ransudates, and tissue deposits. Methods. CTAP-III in plasma was measu red by enzyme-linked immunosorbent assay, and growth promoting activit y of CTAP-III isoforms was tested in synovial and peritoneal cell cult ures by measuring increased synthesis of C-14-glycosaminoglycan (C-14- GAG) and H-3-DNA. Isolated CTAP-III was characterized by Western blott ing, microsequencing, and mass spectrometry. Results. CTAP-III was the primary isoform of this antigen family in normal platelets and platel et-rich plasma; beta-TG and NAP-2 accounted for < 1% of CTAP-III isofo rms. Previously undescribed isoforms, i.e., CTAP-III des 1, des 1-2, d es 1-3, and a phosphate adduct of CTAP-III, were observed in varying a mounts. Elevated plasma levels of CTAP-III antigen were found in a sub stantial fraction of rheumatic disease patients: 24% of those with rhe umatoid arthritis, 36% of those with systemic sclerosis, and 15% of th ose 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 no rmal subjects, rheumatic disease patients, and patients receiving long -term dialysis. Normal human spleen and kidney contained substantial ( mug/gm) amounts of CTAP-III and traces of an isoform with the electrop horetic mobility of CTAP-III des 1-15/NAP-2. Liver, lung, and urine co ntained lesser (ng/gm) amounts of CTAP-III. Conclusion. These data sho w that, among the 10 known isoforms, intact CTAP-III itself was the ma jor circulating isoform (>90%), and beta-TG was the most rare (0-1%). Deposition of CTAP-III in tissues, such as synovium, spleen, and kidne y, is associated with partial processing to NAP-2-like isoforms and th e potential to induce neutrophil and fibroblast activation in patients with rheumatic or end-stage renal disease.