Urinary Proteins Induce Lysosomal Membrane Permeabilization and Lysosomal Dysfunction in Renal Tubular Epithelial Cells in Seronegative Rheumatoid Artritis

Introduction: To determine the effects of non-treated seronegative rheumatoid arthritis (RA) on proximal renal tubule, sensitivity of Alanine aminopeptidase (AAP), γ-glutamyltransferase (γ--GT), β2 microglobulin in urine β2M), as well as relation with rheumatoid factor (RF) and C-Reactive protein (CRP), DAS 28 disease activity index.

Methods: RF was determined by agglutination test (Latex RF test, while kinetic methods were used for determination of Alanine aminopeptidase (AAP) and γ-glutamyltransferase (γ-GT), as well as MEIA (Microparticle Enzyme Immunoassay) to determine β2 microglobulin in urine. Samples (serum and urine) of 70 participants were examined (35 RA not treated, 35 health control group).

Results: In 35 RF negative RA, AAP enzymuria was present in 12 (34.28%) patients, γ-GT was present in 7 patients (20%), while β2 microglobulin was present in 3 patients (8.57%). In the healthy control group, 4 patients showed AAP positivity (11.42%), 2 patients γ-GT positivity (5.71%) and 1 patient showed presens of 2 microglobulin in urine (2.85). RF was not present in any patient (0%).

Conclusion: AAP has a higher sensitivity of γ-GT and β2 microglobulin in the detection of asymptomatic renal lesions in non trated seronegative RA.

Keywords: Alanine aminopeptidase, (AAP); γ-glutamyl transferase (γ--GT), β2 microglobulin (β2M); Rheumatoid arthritis (RA), Rheumatoid factor (RF).