Cell-free DNA-induced alteration of autophagy response and TLR9-signaling: Their relation to amelioration of DSS-colitis

- I.v. colitic-DNA had stronger influence on TLR9-autophagy response than normal-DNA.
- This effect is dependent on the origin of cell-free DNA (i.e. inflammatory or not).
- The characteristics of the local immunobiologic milieu also matters.

BackgroundThe influence of cell-free DNA (fDNA) administration on the TLR9-autophagy regulatory crosstalk within inflammatory circumstances remains unclear.AimsTo examine the immunobiologic effects of iv. fDNA injection on the TLR9-mediated autophagy response in murine DSS-colitis.MethodsDifferent types of modified fDNAs were administered to DSS-colitic mice. Disease and histological activities, spleen index were measured. Changes of the TLR9-associated and autophagy-related gene expression profiles of lamina proprial cells and splenocytes were assayed by quantitative real-time PCR, and validated by immunohistochemistries. Ultrastructural changes of the colon were examined by transmission electron microscopy (TEM).ResultsA single intravenous injection of colitic fDNA (C-DNA) exhibited beneficial clinical and histological effects on DSS-colitis, compared to normal (N-DNA). C-DNA administration displayed a more prominent impact on the outcome of the TLR9-autophagy response than N-DNA. C-DNA resulted in a decreased spleen index in DSS-colitic mice. C-DNA treatment of normal mice resulted in a downregulation of Beclin1 and ATG16L1 mRNA and protein expression in the colon. These as well as LC3B were downregulated in the spleen. In contrast, the Beclin1, ATG16L1 and LC3B gene and protein expressions were upregulated in both the colon and the spleen by C-DNA injection. Moreover, C-DNA administration to DSS-colitic mice resulted in a remarkable increase of epithelial autophagic vacuoles representing an intensified macroautophagy.ConclusionsThe effect of intravenously administered fDNA on the TLR9-mediated autophagy response is expressly dependent on the origin of fDNA (i.e. inflammatory or not) and on the characteristics of the local immunobiologic milieu (i.e. inflammatory or not, as well).