However, as shown in Fig. 5B, the intensity and position of the bands of ODN1668 at incubation time 0 were not affected by the see more change in the ratio of DNase I-treated ODN1720 to ODN1668. These results

suggest that the DNase I-treated DNA does not bind to ODN1668. Therefore, other mechanism than the nucleotide binding to ODN would be involved in the DNase I-treated DNA-mediated increase. Therefore, other mechanisms than these should be involved in the increased cytokine production by DNase I-treated DNA. In recent reports, the conformational changes of both TLR9 and CpG DNA were shown to be an important process for the activation of the TLR9 pathway. CpG DNA allosterically changes the TLR9 protein to

the dimer accessible to CpG motif and MyD88, which results in the activation of NF-κB and cytokine release 30. In addition, TLR9 recognition requires an intramolecular or intermolecular double-stranded DNA region at the position of the CpG motif and single-stranded DNA region at the 5′ end 31, 32. Conformational changes in TLR9 would not be involved in the DNase I-treated ODN1720, because the TNF-α production induced by A-type or B-type CpG ODN, other TLR9 ligands, was not increased by DNase I-treated DNA. These ligand-dependent effects of DNase I-treated ODN1720 could be explained by assuming that DNase I-treated ODN1720 has some direct effects on ODN1668 and pCMV-Luc, both of which are the only two PO DNA used in the present study. One possible LY294002 cell line mechanism

is that DNase I-treated DNA alters the conformations of PO-CpG ODN into forms with a high ability to interact with TLR9 protein. This hypothesis is also compatible with the results of an absence of significant effects of DNase I-treated ODN on the non-CpG lipoplex-induced TNF-α production (Fig. 2A), which was mediated by receptors other than TLR9 18, 19. Glutathione peroxidase Further studies are needed to identify the mechanism for the increase in the cytokine release by DNase I-treated DNA. It is reported that DNase I-deficient mice and humans have anti-DNA antibody with high frequency and are prone to SLE 33, 34. Moreover, the DNase I activity was lower in SLE patients than in the control group 35. In the sera of DNase I-deficient individuals, an increasing amount of undegraded self-DNA containing CpG motifs can be an exacerbating factor of CpG-dependent immune response. For the purpose of treatment for lupus nephritis, in which the deposition of self-DNA/anti-DNA antibody complex in glomeruli is thought to be crucial for the disease pathogenesis, recombinant human DNase I was intravenously administered into the patients. Although serum hydrolytic activity of recombinant human DNase I was achieved after administration, there were no significant changes in serum inflammatory cytokines, including TNF-α and IL-6 36.