To study the enzyme content and the "releasability" of lysosomal enzymes (lysozyme and beta-glucuronidase) in neutrophils purified from peripheral blood of patients with rheumatoid arthritis (RA) or normal subjects.
Neutrophils were obtained from 13 patients (10 women and 3 men) with rheumatoid arthritis and from 11 healthy subjects (8 women and 3 men). We measured: (1) lysosomal enzyme (lysozyme and beta-glucuronidase) content; (2) spontaneous enzyme release; (3) lysosomal enzyme release after cell challenge with different segretagogues (FMLP, C5a, aggregated IgG, zymosan and Ca2+ ionophore A23187).
The lysosomal enzyme content was not statistically different in control subjects and in patients with RA (7.4 +/- 1.9 vs 6.3 +/- 0.8 micrograms/10(6) neutrophils for lysozyme; 102.9 +/- 16.4 vs 78.9 +/- 11.2 micrograms/10(6) neutrophils for beta-glucuronidase in control and RA subjects, respectively, p = NS). Unstimulated release of lysozyme was significantly lower in RA patients (3.8 +/- 1.1%) when compared to control subjects (9.5 +/- 2.1%) (p < 0.05). In contrast, spontaneous release of beta-glucuronidase did not differ in the two groups (5.5 +/- 0.9% and 3.8 +/- 1.1% in control and RA subjects, respectively). Enzyme release induced by FMLP (3 x 10(-9)-3 x 10(-7) M), C5a (10(-8)-10(-7) M), aggregated IgG (0.1-0.6 mg/ml), or Ca2+ ionophore A23187 (0.1-1 microgram/ml) did not differ statistically in the two groups of subjects. Neutrophil stimulation by serum-treated zymosan, at the concentration of 0.3 mg/ml, induced a release of lysozyme that was significantly higher in patients with RA when compared to control subjects (p < 0.05), whereas zymosan-activated beta-glucuronidase secretion was similar in the two donor populations.
This study suggests that the contribution of leukocytes to the inflammatory processes typical of RA does not depend on an altered "releasability" of preformed mediators from peripheral blood neutrophils.