Protease inhibitors in rheumatoid synovial fluid: a quantitative analysis

Area of Science:

• Biochemistry
• Immunology
• Rheumatology

Background:

• Rheumatoid arthritis (RA) involves joint inflammation and degradation.
• Endogenous protease inhibitors regulate granulocyte proteases, crucial in inflammatory processes.
• Understanding inhibitor levels in RA synovial fluid is key to disease mechanisms.

Purpose of the Study:

• To quantify main endogenous protease inhibitors in RA synovial fluid and serum.
• To investigate the influence of the synovial membrane on inhibitor concentrations.
• To differentiate between intra-articular production and altered protein flux.

Main Methods:

• Collected paired synovial fluid and serum/plasma samples from RA patients and controls.
• Measured concentrations of anti-leukoprotease, alpha 1-antitrypsin, alpha 1-antichymotrypsin, and alpha 2-macroglobulin.
• Utilized regression analysis with non-inhibitory proteins (orosomucoid, albumin, ceruloplasmin) to assess synovial membrane influence.

Main Results:

• RA synovial fluid had significantly higher levels of alpha 1-antichymotrypsin and alpha 2-macroglobulin.
• Anti-leukoprotease and alpha 1-antitrypsin showed evidence of consumption within the rheumatoid joint.
• Elevated alpha 1-antichymotrypsin and alpha 2-macroglobulin likely reflect altered trans-synovial protein flux.

Conclusions:

• Synovial fluid inhibitor levels in RA are influenced by both local joint processes and systemic factors.
• Altered protein transport across the synovial membrane plays a significant role in elevated inhibitor concentrations.
• Specific inhibitors like anti-leukoprotease and alpha 1-antitrypsin may be consumed during RA pathogenesis.