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

Excessive accumulation of cell-free DNA (cfDNA) has been identified as a primary pathogenic factor in autoimmune diseases. The circulating deoxyribonuclease (DNase) maintaining cfDNA homeostasis is suppressed, and thus exogenous DNase has been applied to degrade cfDNA for inflammation control. However, in pathological states, cfDNA and cationic endogenous peptide (e.g., LL37) form immune complexes (ICs), which not only weaken DNase efficacy but also facilitate immune cell internalization to induce an inflammatory response. With LL37-DNA as a model IC, here we found that the LL37 occupancy not only sterically hinders cfDNA's access to the catalytic sites but also induces deactivation of DNase via formation of ternary complexes (LL37-DNA-DNase I). This transition critically impairs the activity of DNase I within LL37-rich inflammatory microenvironments. Thus, we postulated that heparin, a clinically approved anionic glycosaminoglycan, could destruct the ICs and liberate cfDNAs, restoring their susceptibility to degradation. Indeed, we found that a combination of heparin and DNase I facilitates the DNA degradation and inhibits the ICs-mediated TLR9 activation in vitro. However, the therapeutic outcome observed in rheumatoid arthritis (RA) model was still suboptimal, attributed to the short plasma half-life of DNase. To validate this, we engineered a DNase nanoparticle (DNase@TANP) capable of sustained release of the enzyme. Consequently, the sequential administration of heparin and DNase@TANP (with a 30-min interval) to RA model demonstrated a synergistic cfDNA degradation efficiency, effectively suppressing Toll-like receptor (TLR) mediated inflammatory pathways and ameliorating joint inflammation. This strategy, leveraging clinically approved agents for cfDNA clearance, establishes a promising therapeutic paradigm for cfDNA-associated autoimmune disorders.