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Phagocytic clearance of apoptotic cells by the macrophages (efferocytosis) is impaired in sepsis, but its mechanism is poorly understood. Extracellular cold-inducible RNA-binding protein (eCIRP) is a novel damage-associated molecular pattern that fuels inflammation. We identify that eCIRP-induced neutrophil extracellular traps (NETs) impair efferocytosis through a novel mechanism. Coculture of macrophages and apoptotic thymocytes in the presence of recombinant murine CIRP (rmCIRP)–induced NETs significantly inhibited efferocytosis. Efferocytosis was significantly inhibited in the presence of rmCIRP-treated wild-type (WT), but not PAD4-/- neutrophils. Efferocytosis in the peritoneal cavity of rmCIRP-injected PAD4-/-mice was higher than WT mice. Milk fat globule–EGF–factor VIII (MFG-E8), an opsonin, increased macrophage efferocytosis, whereas the inhibition of efferocytosis by NETs was not rescued upon addition of MFG-E8, indicating disruption of MFG-E8’s receptor(s) αvβ3 or αvβ5 integrin by the NETs. We identified neutrophil elastase in the NETs significantly inhibited efferocytosis by cleaving macrophage surface integrins αvβ3 and αvβ5. Using a preclinical model of sepsis, we found that CIRP-/- mice exhibited significantly increased rate of efferocytosis in the peritoneal cavity compared with WT mice. We discovered a novel role of eCIRP-induced NETs to inhibit efferocytosis by the neutrophil elastase–dependent decrease of αvβ3/αvβ5 integrins in macrophages. Targeting eCIRP ameliorates sepsis by enhancing efferocytosis. [ABSTRACT FROM AUTHOR]

The DNA repair enzyme 8-oxoguanine DNA glycosylase 1 (OGG1), which excises 8-oxo-7,8-dihydroguanine lesions induced in DNA by reactive oxygen species, has been linked to the pathogenesis of lung diseases associated with bacterial infections. A recently developed small molecule, SU0268, has demonstrated selective inhibition of OGG1 activity; however, its role in attenuating inflammatory responses has not been tested. In this study, we report that SU0268 has a favorable effect on bacterial infection both in mouse alveolar macrophages (MH-S cells) and in C57BL/6 wild-type mice by suppressing inflammatory responses, particularly promoting type I IFN responses. SU0268 inhibited proinflammatory responses during Pseudomonas aeruginosa (PA14) infection, which is mediated by the KRAS-ERK1-NF-κB signaling pathway. Furthermore, SU0268 induces the release of type I IFN by the mitochondrial DNA-cGAS-STING-IRF3-IFN-β axis, which decreases bacterial loads and halts disease progression. Collectively, our results demonstrate that the small-molecule inhibitor of OGG1 (SU0268) can attenuate excessive inflammation and improve mouse survival rates during PA14 infection. This strong anti-inflammatory feature may render the inhibitor as an alternative treatment for controlling severe inflammatory responses to bacterial infection. [ABSTRACT FROM AUTHOR]

Oxygen is supplied as a supportive treatment for patients suffering from acute respiratory distress syndrome. Unfortunately, high oxygen concentration increases reactive oxygen species generation, which causes DNA damage and ultimately cell death in the lung. Although 8-oxoguanine-DNA glycosylase (OGG-1) is involved in repairing hyperoxia-mediated DNA damage, the underlying molecular mechanism remains elusive. In this study, we report that ogg-1-deficient mice exhibited a significant increase of proinflammatory cytokines (TNF-α, IL-6, and IFN-γ) in the lung after being exposed to 95% oxygen. In addition, we found that ogg-1 deficiency downregulated (macro)autophagy when exposed to hyperoxia both in vitro and in vivo, which was evident by decreased conversion of LC3-I to LC3-II, reduced LC3 punctate staining, and lower Atg7 expression compared with controls. Using a chromatin immunoprecipitation assay, we found that OGG-1 associated with the promoter of Atg7, suggesting a role for OGG1 in regulation of Atg7 activity. Knocking down OGG-1 decreased the luciferase reporter activity of Atg7. Further, inflammatory cytokine levels in murine lung epithelial cell line cells were downregulated following autophagy induction by starvation and rapamycin treatment, and upregulated when autophagy was blocked using 3-methyladenine and chloroquine. atg7 knockout mice and Atg7 small interfering RNA-treated cells exhibited elevated levels of phospho-NF-κB and intensified inflammatory cytokines, suggesting that Atg7 impacts inflammatory responses to hyperoxia. These findings demonstrate that OGG-1 negatively regulates inflammatory cytokine release by coordinating molecular interaction with the autophagic pathway in hyperoxia-induced lung injury. [ABSTRACT FROM AUTHOR]