The Mucosal Adjuvant Cyclic di-AMP Exerts Immune Stimulatory Effects on Dendritic Cells and Macrophages

Škrnjug, Ivana; Rueckert, Christine; Libanova, Rimma; Lienenklaus, Stefan; Guzmán, Carlos A.

doi:10.1371/journal.pone.0095728

Cited by 29 publications

(24 citation statements)

References 45 publications

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“…Cyclic di-AMP released from intracellular pathogens is sensed by STING within the host cytosol and induces a type I IFN response (26)(27)(28)(29)(30)(31)(32)(33)(34). A previous report described IFN-␤ production following c-di-AMP treatment in vivo and in human and murine dendritic cells in vitro (46); how- ever, effects of extracellular c-di-AMP on macrophages have not yet been reported. To assess the impact of extracellular c-di-AMP on macrophage activation, murine primary BMDMs were treated with purified c-di-AMP (0.01 to 10 M) for 3 or 6 h, whereupon RNA was isolated and analyzed for cytokine expression.…”

Section: Resultsmentioning

confidence: 99%

Cyclic di-AMP Released from Staphylococcus aureus Biofilm Induces a Macrophage Type I Interferon Response

et al. 2016

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Staphylococcus aureus is a leading cause of community-and nosocomial-acquired infections, with a propensity for biofilm formation. S. aureus biofilms actively skew the host immune response toward an anti-inflammatory state; however, the biofilm effector molecules and the mechanism(s) of action responsible for this phenomenon remain to be fully defined. The essential bacterial second messenger cyclic diadenylate monophosphate (c-di-AMP) is an emerging pathogen-associated molecular pattern during intracellular bacterial infections, as c-di-AMP secretion into the infected host cytosol induces a robust type I interferon (IFN) response. Type I IFNs have the potential to exacerbate infectious outcomes by promoting anti-inflammatory effects; however, the type I IFN response to S. aureus biofilms is unknown. Additionally, while several intracellular proteins function as c-di-AMP receptors in S. aureus, it has yet to be determined if any extracellular role for c-di-AMP exists and its release during biofilm formation has not yet been demonstrated. This study examined the possibility that c-di-AMP released during S. aureus biofilm growth polarizes macrophages toward an anti-inflammatory phenotype via type I interferon signaling. DacA, the enzyme responsible for c-di-AMP synthesis in S. aureus, was highly expressed during biofilm growth, and 30 to 50% of total c-di-AMP produced from S. aureus biofilm was released extracellularly due to autolytic activity. S. aureus biofilm c-di-AMP release induced macrophage type I IFN expression via a STING-dependent pathway and promoted S. aureus intracellular survival in macrophages. These findings identify c-di-AMP as another mechanism for how S. aureus biofilms promote macrophage anti-inflammatory activity, which likely contributes to biofilm persistence. Staphylococcus aureus is a leading cause of prosthetic joint infections (1, 2), whereupon adherence to the implant surface facilitates biofilm formation. These infections are particularly challenging to treat and typically require a two-stage surgical process for insertion of a new device (1). Moreover, biofilms actively skew the host immune response toward an anti-inflammatory state, thereby contributing to the chronic nature of biofilm-mediated infections (3-5). This is evident by macrophage polarization toward an alternatively activated phenotype and the recruitment of myeloid-derived suppressor cells (MDSCs) (3,(6)(7)(8). While this immune deviation appears to be driven by S. aureus biofilm products, the effectors and their mechanism(s) of action remain to be fully identified.To further understand mechanisms of immune modification by S. aureus biofilms, we investigated the role of the essential bacterial second messenger cyclic diadenylate monophosphate (c-di-AMP), since it has been identified as an emerging pathogen-associated molecular pattern (PAMP) that influences immune responsiveness (9, 10). While c-di-AMP has been found to regulate many important functions in bacteria, including cell wall stress and peptidoglycan homeostas...

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Section: Resultsmentioning

confidence: 99%

Cyclic di-AMP Released from Staphylococcus aureus Biofilm Induces a Macrophage Type I Interferon Response

et al. 2016

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“…The intracellular niche and immunostimulatory activity of Lm have prompted the development of live, attenuated Lm vaccine vectors that retain the ability to enter the cytoplasm (Bruhn et al, 2007). Similarly, the use of cdNs as adjuvants or in immunotherapeutic formulations has shown significant promise in the therapeutic protection against infectious and malignant disease (Skrnjug et al, 2014). Vaccine and immunotherapeutic formulations that contain c-di-AMP and/or 3′3′-cGAMP may elicit RECON-mediated responses that may shape the outcome and interpretation of these pre-clinical studies.…”

Section: Discussionmentioning

confidence: 99%

Sensing of Bacterial Cyclic Dinucleotides by the Oxidoreductase RECON Promotes NF-κB Activation and Shapes a Proinflammatory Antibacterial State

et al. 2017

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SUMMARY Bacterial and host cyclic dinucleotides (cdNs) mediate cytosolic immune responses through the STING signaling pathway, though evidence suggests alternative pathways exist. We used cdN-conjugated beads to biochemically isolate host receptors for bacterial cdNs, and identified the oxidoreductase RECON. High-affinity cdN binding inhibited RECON enzyme activity by simultaneously blocking the substrate and co-substrate sites, as revealed by structural analyses. During bacterial infection of macrophages, RECON antagonized STING activation by acting as a molecular sink for cdNs. Bacterial infection of hepatocytes, which do not express STING, revealed that RECON negatively regulates NF-κB activation. Loss of RECON activity, via genetic ablation or inhibition by cdNs, resulted in increased NF-κB activation and reduced bacterial survival, suggesting that cdN inhibition of RECON promotes a proinflammatory, antibacterial state that is distinct from the anti-viral state associated with STING activation. Thus, RECON functions as a cytosolic pattern recognition receptor specific for bacterial cdNs, shaping inflammatory gene activation via its effects on STING and NF-κB.

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“…CDNs released from bacterial biofilm can also activate host immune responses . Previous studies showed that CDNs could be used as novel vaccine adjuvants or immunostimulatory molecules for host defense . Intranasal administration with c‐di‐GMP enhances bacteria clearance and protects mice from Klebsiella pneumoniae infection through stimulation of dendritic cell‐meditated responses .…”

Section: Introductionmentioning

confidence: 99%

Cyclic Dinucleotides Inhibit Osteoclast Differentiation Through STING-Mediated Interferon-β Signaling

Kwon

Park

Kim

et al. 2019

Journal of Bone and Mineral Research

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Cyclic dinucleotides (CDNs), such as cyclic diadenylate monophosphate and cyclic diguanylate monophosphate, are commensal bacteria‐derived second messengers in the gut that modulate bacterial survival, colonization, and biofilm formation. Recently, CDNs have been discovered to have an immunomodulatory activity by inducing the expression of type I interferon (IFN) through STING signaling pathway in macrophages. Because CDNs are possibly absorbed and delivered into the bone marrow, where bone‐resorbing osteoclasts are derived from monocyte/macrophage lineages, CDNs could affect bone metabolism by regulating osteoclast differentiation. In this study, we investigated the effect of CDNs on the differentiation and function of osteoclasts and osteoblasts. When bone marrow‐derived macrophages (BMMs) were differentiated into osteoclasts with macrophage colony‐stimulating factor (M‐CSF) and receptor activator of NF‐κB ligand (RANKL) in the presence of CDNs, the differentiation was inhibited by CDNs in a dose‐dependent manner. In contrast, CDNs did not influence the differentiation of committed osteoclasts or osteoblast precursors. STING signaling pathway appeared to be critical for CDNs‐mediated inhibition of osteoclast differentiation since CDNs induced the phosphorylation of TBK1 and IRF3, a representative feature of STING activation, and osteoclast differentiation was restored in STING knockdown BMMs with siRNA. Moreover, CDNs increased the mRNA expression of STING‐meditated IFN‐β, which is a negative regulator of osteoclastogenesis. In addition, CDNs also induced the phosphorylation of STAT1, which mediates IFN‐α/β receptor (IFNAR) signal transduction. The inhibitory effects of CDNs on osteoclast differentiation were not observed in the presence of antibody blocking IFNAR or in macrophages derived from IFNAR1‐/‐ mice. Experiments using a mouse calvarial implantation model showed that RANKL‐induced bone resorption was inhibited by CDNs. Taken together, these results suggest that CDNs inhibit osteoclast differentiation and bone resorption through induction of IFN‐β via the STING signaling pathway. © 2019 American Society for Bone and Mineral Research.

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The Mucosal Adjuvant Cyclic di-AMP Exerts Immune Stimulatory Effects on Dendritic Cells and Macrophages

Cited by 29 publications

References 45 publications

Cyclic di-AMP Released from Staphylococcus aureus Biofilm Induces a Macrophage Type I Interferon Response

Cyclic di-AMP Released from Staphylococcus aureus Biofilm Induces a Macrophage Type I Interferon Response

Sensing of Bacterial Cyclic Dinucleotides by the Oxidoreductase RECON Promotes NF-κB Activation and Shapes a Proinflammatory Antibacterial State

Cyclic Dinucleotides Inhibit Osteoclast Differentiation Through STING-Mediated Interferon-β Signaling

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