Lysosomal enzyme activities: New potential markers for Sjögren’s syndrome

Objective: To evaluate the changes in lysosomal enzyme activities in leukocytes of patients with Sjögren’s syndrome. Methods: Leukocytes were obtained from 38 patients with Sjögren’s syndrome and 36 healthy subjects. The activities of the following glycosidases were measured: α-glucosidase (AGU), β-galactosidase (BGA), α-mannosidase (AMAN), β-glucuronidase (GCU), β-hexosaminidase (HEX), and the following proteases: cathepsin B (CATH B), dipeptidyl peptidase I (DPP I), cathepsin H (CATH H), dipeptidyl peptidase II (DPP II), tripeptidyl peptidase I (TPP I), and cathepsin D (CATH D) activity. Results: Activity of the glycosidases β-galactosidase, α-mannosidase, β-glucuronidase and β-hexosaminidase, as well as of the peptidases cathepsin B, cathepsin D, dipeptidyl peptidase I, and tripeptidyl peptidase I, was elevated during the first 5 years of SS, and it increased further between 5 and 10 years after diagnosis. Conclusions: The elevated activities of the lysosomal enzymes in Sjögren’s syndrome patients may play a role in tissue damage by accelerated breakdown of glycoproteins in lysosomes.