Objective: 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.
Methods: 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).
Results: 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.
Conclusions: 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.