Synthetic oligodeoxynucleotides containing suppressive TTAGGG motifs inhibit AIM2 inflammasome activation

Synthetic oligodeoxynucleotides (ODNs) comprised of the immunosuppressive motif TTAGGG block TLR9 signaling, prevent STAT1 and STAT4 phosphorylation and attenuate a variety of inflammatory responses in vivo. In this study, we demonstrate that such suppressive ODN abrogate activation of cytosolic nucleic acid-sensing pathways. Pretreatment of dendritic cells and macrophages with the suppressive ODN-A151 abrogated type I IFN, TNF-alpha, and ISG induction in response to cytosolic dsDNA. In addition, A151 abrogated caspase-1-dependent IL-1beta and IL-18 maturation in dendritic cells stimulated with dsDNA and murine CMV. Inhibition was dependent on A151\u27s phosphorothioate backbone, whereas substitution of the guanosine residues for adenosine negatively affected potency. A151 mediates these effects by binding to AIM2 in a manner that is competitive with immune-stimulatory DNA and as a consequence prevents AIM2 inflammasome complex formation. Collectively, these findings reveal a new route by which suppressive ODNs modulate the immune system and unveil novel applications for suppressive ODNs in the treatment of infectious and autoimmune diseases

Inflammasome-derived cytokine IL18 suppresses amyloid-induced seizures in Alzheimer-prone mice

Alzheimer\u27s disease (AD) is characterized by the progressive destruction and dysfunction of central neurons. AD patients commonly have unprovoked seizures compared with age-matched controls. Amyloid peptide-related inflammation is thought to be an important aspect of AD pathogenesis. We previously reported that NLRP3 inflammasome KO mice, when bred into APPswe/PS1DeltaE9 (APP/PS1) mice, are completely protected from amyloid-induced AD-like disease, presumably because they cannot produce mature IL1beta or IL18. To test the role of IL18, we bred IL18KO mice with APP/PS1 mice. Surprisingly, IL18KO/APP/PS1 mice developed a lethal seizure disorder that was completely reversed by the anticonvulsant levetiracetam. IL18-deficient AD mice showed a lower threshold in chemically induced seizures and a selective increase in gene expression related to increased neuronal activity. IL18-deficient AD mice exhibited increased excitatory synaptic proteins, spine density, and basal excitatory synaptic transmission that contributed to seizure activity. This study identifies a role for IL18 in suppressing aberrant neuronal transmission in AD

RNA and beta-hemolysin of Group B streptococcus induce IL-1beta by activating NLRP3 inflammasomes in mouse macrophages

The inflammatory cytokine IL-1beta is critical for host responses against many human pathogens. Here, we define Group B streptococcus (GBS)-mediated activation of the Nod-like Receptor-P3 (NLRP3) inflammasome in macrophages. NLRP3 activation requires GBS expression of the cytolytic toxin, beta-hemolysin, lysosomal acidification, and leakage. These processes allow the interaction of GBS RNA with cytosolic NLRP3. The present study supports a model in which GBS RNA, along with lysosomal components including cathepsins, leaks out of lysosomes and interacts with NLRP3 to induce IL-1beta production