Stripping cell-free DNA from its immune complex is essential for inflammation control using DNase I

Area of Science:

• Immunology
• Biochemistry
• Nanotechnology

Background:

• Accumulated cell-free DNA (cfDNA) is a key factor in autoimmune diseases.
• Circulating deoxyribonuclease (DNase) is suppressed, and cfDNA forms immune complexes (ICs) with peptides like LL37, hindering DNase activity and promoting inflammation.
• These ICs (LL37-DNA) deactivate DNase I by forming ternary complexes, impairing its function in inflammatory environments.

Purpose of the Study:

• To investigate the mechanism of DNase inhibition by LL37-DNA immune complexes.
• To develop a strategy for restoring cfDNA degradation in autoimmune conditions.
• To evaluate the therapeutic potential of combining heparin with a sustained-release DNase formulation in a rheumatoid arthritis model.

Main Methods:

• Investigated the interaction between LL37-DNA complexes and DNase I in vitro.
• Tested the efficacy of heparin in disrupting ICs and restoring cfDNA degradation.
• Engineered DNase nanoparticles (DNase@TANP) for sustained enzyme release.
• Administered sequential heparin and DNase@TANP treatment in a collagen-induced arthritis mouse model.

Main Results:

• LL37-DNA complexes sterically hinder DNase I access and induce its deactivation via ternary complex formation.
• Heparin disrupted LL37-DNA ICs, facilitating cfDNA degradation and inhibiting TLR9 activation in vitro.
• Sequential administration of heparin and DNase@TANP synergistically degraded cfDNA, suppressed TLR-mediated inflammation, and ameliorated joint inflammation in the RA model.

Conclusions:

• LL37-DNA immune complexes significantly impair DNase I activity in inflammatory settings.
• Heparin combined with sustained-release DNase nanoparticles offers a promising strategy for cfDNA clearance.
• This approach effectively targets cfDNA-driven inflammation and shows therapeutic potential for autoimmune disorders like rheumatoid arthritis.