Biology subjects

Kubatzky, K. F.

Publications and source records attributed to Kubatzky, K. F..

3 recordsLinked to original sources

bioRxiv2026

cGAS-STING induced IFN-β acts as a dual regulator of osteoclastogenesis via direct and osteoblast-mediated mechanisms

Osteolytic bone diseases are driven by excessive osteoclast formation and bone resorption. While cGAS-STING signaling is known to regulate bone homeostasis via macrophage-intrinsic mechanisms, its role in osteoblast-mediated control of osteoclastogenesis remains poorly defined. Here, we show that cGAS-STING activation of macrophages suppresses their osteoclastogenic potential while promoting immune activation. In osteoblasts, cGAS-STING triggers IRF3-mediated IFN-{beta} production and, notably, shifts the OPG-RANKL axis toward increased osteoprotegerin. In transwell co-culture, pre-activated osteoblasts reduce osteoclast differentiation of strain-matched macrophages. Mechanistically, osteoblast-derived IFN-{beta} is sufficient to inhibit osteoclastogenesis in a paracrine manner. Furthermore, autocrine IFN-{beta} signaling appears to modulate the OPG-RANKL axis, although additional regulatory factors may contribute. Together, these findings identify cGAS-STING-IFN-{beta} signaling as a dual regulator of osteoclastogenesis, acting directly on macrophages and indirectly via osteoblast-derived anti-osteoclastogenic mediators. This highlights osteoblasts as cGAS-STING-responsive bystander cells within the bone microenvironment that can be targeted as an alternative strategy to limit pathological bone resorption. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=127 SRC="FIGDIR/small/724040v1_ufig1.gif" ALT="Figure 1"> View larger version (70K): org.highwire.dtl.DTLVardef@1984f3corg.highwire.dtl.DTLVardef@7a15fdorg.highwire.dtl.DTLVardef@139c99aorg.highwire.dtl.DTLVardef@e2cb39_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2026

Mechanistic Insights into Impaired cGAS Activation in Staphylococcus aureus Biofilm Environments Reveal That STING Activation via 2'3'-cGAMP Restores Macrophage Immune Responses

Biofilm formation is a major cause of chronic implant-related bone infections and is associated with impaired immune responses. In a previous study, we identified the cGAS-STING pathway as a potential therapeutic target, as its activation--observed in response to planktonic Staphylococcus aureus (SA)--was absent in the corresponding biofilm setting. The present study aimed to identify potential mechanisms underlying the lack of cGAS activation in the biofilm environment. As biofilm-derived nucleases might degrade cGAS ligands, we assessed presence and activity of micrococcal nuclease in conditioned media from planktonic and biofilm-grown SA and evaluated the impact of extracellular DNases on cGAS pathway activation in macrophages. In addition, we examined altered cGAS expression, the requirement for continuous biofilm exposure and potential downstream inhibition resulting from degradation of the cGAS product. Biofilm formation was associated with dynamic nuclease expression, and exposure to the biofilm environment led to reduced cGAS levels in macrophages, accompanied by a lack of interferon response. Exogenous cGAS activation by G3-YSD failed to restore signaling, independent of nuclease activity or continuous biofilm exposure. In contrast, supplementation with the cGAS product and STING ligand 2'3'-cGAMP fully restored interferon responses and enhanced macrophage activation, indicating that increased degradation of the second messenger in the biofilm environment is not responsible for impaired pathway activation. Similar effects observed with Staphylococcus epidermidis and primary macrophages suggest a broader mechanism that is not SA- or cell line-specific. In conclusion, our data provide novel mechanistic insight into biofilm-mediated impairment of cGAS-STING signaling, revealing a previously unrecognized mechanism of immune evasion in staphylococcal biofilms. These findings extend our previous work and support the therapeutic potential of targeting STING as promising strategy to restore immune responses in chronic implant-related bone infections. HighlightsO_LIBiofilm-derived factors impair cGAS-STING pathway activation and suppress interferon responses in macrophages. C_LIO_LIImpaired signaling is not primarily explained by extracellular micrococcal nuclease-mediated degradation of potential cGAS ligands. C_LIO_LIBiofilm exposure reduces cGAS expression levels and inhibits exogenous cGAS activation independently of continuous presence. C_LIO_LIExogenous 2'3'-cGAMP fully restores interferon responses, indicating that impaired signaling is not due to degradation of the cGAS product. C_LIO_LIDirect activation of STING broadly enhances macrophage activation and by this could amplify overall immune responses. C_LIO_LIBypassing cGAS via direct STING targeting represents a potential therapeutic strategy to overcome immune evasion in chronic implant-related bone infections. C_LI

immunology↗

bioRxiv2023

Staphylococcus aureus planktonic but not biofilm environment induces an IFN-β macrophage immune response via the STING/IRF3 pathway

Chronic implant-related bone infections are a severe complication in orthopedic surgery. Biofilm formation on the implant surface impairs an effective immune response leading to bacterial persistence. In a previous study, we found that Staphylococcus aureus (SA) induced IRF3 activation and Ifnb gene expression only in its planktonic form but not in the biofilm. The aim of this study was to clarify the role of the stimulator of interferon genes (STING) in this process. We treated murine RAW 264.7 macrophages with conditioned media (CM) generated from planktonic or biofilm cultured SA in combination with agonists or inhibitors of the cGAS/STING pathway. We further evaluated bacterial gene expression of planktonic and biofilm SA to find potential mediators. STING inhibition resulted in a loss of IRF3 activation and Ifnb induction in SA planktonic CM, whereas STING activation induced an IRF3 dependent IFN-{beta} response in SA biofilm CM. Expression levels of genes associated with virulence decreased with biofilm formation while those associated with cyclic dinucleotide (CDN) synthesis did not correlate with Ifnb induction. We further observed that cGAS contributed to the Ifnb induction by SA planktonic CM although cGAS activation was not sufficient to induce Ifnb gene expression in SA biofilm CM. Our data indicate that the different degrees of virulence associated with planktonic and biofilm SA environments result in an altered induction of an IRF3 mediated IFN-{beta} response via the STING pathway. This finding suggests that the STING/IRF3/IFN-{beta} axis is a potential candidate for further investigation as immunotherapeutic target in implant-related bone infections.

immunology↗