Sialoglycans modulate Siglec-5-TLR4 interactions in osteoarthritis

Area of Science:

• Immunology
• Biochemistry
• Rheumatology

Background:

• Osteoarthritis (OA) involves chronic inflammation, cartilage degradation, and joint pain.
• Sialic acid-binding immunoglobulin-like lectin-5/14 (Siglec-5/14) was identified in OA synovial fluid.
• The interaction between Siglec-5 and the proinflammatory receptor Toll-like receptor 4 (TLR4) was investigated.

Purpose of the Study:

• To investigate the interaction between Siglec-5 and TLR4 in monocytes from OA patients.
• To explore the role of sialylation patterns in OA inflammation.
• To identify potential therapeutic targets for mitigating OA inflammation.

Main Methods:

• Monocytes were stimulated with OA synovial fluid (OA SF), M-CSF, LPS, and sialidase.
• Interleukin-6 (IL-6) production was measured.
• Cellular phenotypes were assessed.
• Siglec-5 and TLR4 colocalization was analyzed.

Main Results:

• An inverse correlation between Siglec-5 and TLR4 suggests Siglec-5 suppresses inflammation.
• OA SF-induced IL-6 production mirrored LPS- or sialidase-treated cells, indicating sialylation's role.
• Siglec-5 and TLR4 demonstrated a time- and sialoglycan-dependent direct interaction.

Conclusions:

• A Siglec-5-TLR4 axis modulated by sialylation was identified in OA.
• This axis represents a potential therapeutic strategy for reducing inflammation and preserving joint integrity in OA.