Pharmacodynamics of recombinant human DNase I in serum

• Published in: Clinical and experimental immunology Vol. 113; no. 2; pp. 289 - 296
• Main Authors: PRINCE, W. S, BAKER, D. L, DODGE, A. H, AHMED, A. E, CHESTNUT, R. W, SINICROPI, D. V
• Format: Journal Article
• Language: English
• Published: Oxford BSL Blackwell Science Ltd 01.08.1998; Blackwell; Oxford University Press; Blackwell Publishing Ltd
• Subjects: Antigen-Antibody Complex - metabolism; Autoantibodies - blood; Biological and medical sciences; Blood - metabolism; Bones, joints and connective tissue. Antiinflammatory agents; chromatin; Chromatin - metabolism; Deoxyribonuclease I - antagonists & inhibitors; Deoxyribonuclease I - metabolism; DNA; DNA - metabolism; DNA, Viral - metabolism; DNase I; enzyme assays; Enzyme Inhibitors - blood; Humans; immune complexes; Lupus Erythematosus, Systemic - blood; Medical sciences; Original; Pharmacology. Drug treatments; Recombinant Proteins - metabolism; systemic lupus erythematosus; Human; Immunopathology; Connective tissue disease; Skin disease; Enzyme; Autoimmune disease; Esterases; In vitro; Biological activity; Deoxyribonuclease I; Systemic disease; Hydrolases; Lupus erythematosus; Serum; Disseminated; Recombinant protein; ELISA assay; Immune complex
• ISSN: 0009-9104; 1365-2249
• DOI: 10.1046/j.1365-2249.1998.00647.x

Recombinant human deoxyribonuclease I (rhDNase) may be an effective therapeutic for the treatment of systemic lupus erythematosus (SLE). The pharmacodynamics of rhDNase in serum was investigated using two activity assays: one based on hydrolysis of a radiolabelled phage DNA and the other based on hydrolysis of human chromatin. The concentration of endogenous immunoreactive DNase in sera from 16 normal subjects was 3.2 ± 1.4 ng/ml (mean ± s.d.); however, low levels or no nuclease activity were detected in the same sera, suggesting the presence of DNase inhibitors. We assessed the ability of rhDNase to degrade DNA in undiluted serum, since the observed inhibition of endogenous DNase was reversed upon dilution. Addition of rhDNase to undiluted serum at a concentration of 50–100 ng/ml was necessary for degradation of radiolabelled phage DNA. The activity of rhDNase added to serum from normal subjects and SLE patients was similar. rhDNase degraded human chromatin and chromatin/anti‐DNA immune complexes in serum with similar potency (EC50 ≈ 100–200 ng/ml). A 500‐fold variation in the chromatin/anti‐DNA stoichiometry did not significantly affect the digestion of these immune complexes by rhDNase in buffer. These results indicate that a minimum rhDNase concentration of 50–100 ng/ml in serum was required to achieve detectable catalytic activity and that the presence of antibodies to DNA did not inhibit the degradation of DNA/anti‐DNA immune complexes.