Background/Purpose:

Aptamers are short single stranded DNA or RNA oligonucleotides that are specifically selected to bind and neutralize a wide range of biomedically relevant proteins.  Aptamers are being used in the clinic for the treatment of macular degeneration while eight others are in clinical trials. Aptamers are particularly useful in targeting cell surface and extracellular proteins. We have previously demonstrated that the nuclear chromatin binding protein DEK is actively secreted by human macrophages, serves as a chemoattractant for neutrophils, can be taken up by adjacent cells in a bioactive form, and is abundant in the inflamed synovia of patients with juvenile arthritis (JA).  We now demonstrate that targeting DEK with specific anti-DEK aptamers can prevent joint inflammation induced by zymosan.

Methods:

DEK-targeting aptamers were selected from a pool of random-sequence oligonucleotides by SELEX (Systematic Evolution of Ligands by Exponential Enrichment). Two single-stranded DNAs, 40 and 42 nucleotides long with high affinity to DEK were identified. 129/B6 wild type (WT) and DEK null (KO) mice were injected with zymosan through the suprapatellar ligament into the joint cavity to induce inflammatory arthritis. To neutralize DEK, WT mice were additionally injected with either control or DEK-targeting aptamers. Neutrophils were isolated from the blood of healthy human volunteers, synovial fluid of JA patients, or mouse bone marrow.  Neutrophil extracellular traps (NETs) were detected in vivo and in vitro by immunofluorescence with elastase, LL-37, myeloperoxidase (MPO) and DEK antibodies. DEK-targeting aptamers were used to neutralize DEK during in vitro induction of NETs. 

Results:

DEK KO mice display significantly less joint inflammation than wild-type mice in a zymosan-induced arthritis model (ZIA). Targeting DEK in the joints with specific aptamers significantly reduced joint inflammation induced by zymosan. Indeed, we found a significant reduction in NET formation in joints treated with DEK-targeting aptamers compared to joints treated with control aptamers. Moreover, activation of DEK KO neutrophils demonstrated appreciably reduced NET formation compared to WT neutrophils. Interestingly, NET formation could be rescued in DEK KO neutrophils with the addition of exogenous recombinant DEK. NETs released by synovial neutrophils from JA patients stained prominently for DEK.  Similar to the mouse studies, NET release from human neutrophils was drastically abrogated by treatment with DEK-targeting aptamers.

Conclusion:

These results show that the nuclear DNA-binding protein DEK is a major factor in the development of joint inflammation. Specifically, DEK is implicated in the formation of NETs, in addition to its already established role as a leukocyte chemoattractant. These results strongly support the pro-inflammatory function of extracellular DEK, a protein that is crucial to both intracellular and extracellular chromatin structure.  Targeting DEK with the newly developed anti-DEK aptamers is a promising therapeutic strategy for the treatment of local and systemic inflammatory conditions such as arthritis.

« Back to 2015 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/dek-targeting-dna-aptamers-as-novel-therapeutics-for-inflammatory-arthritis/