Active Release of eCIRP via Gasdermin D Channels to Induce Inflammation in Sepsis.

Extracellular cold-inducible RNA binding protein (eCIRP) is an inflammatory mediator that causes inflammation and tissue injury in sepsis. Gasdermin D (GSDMD) is a protein that, when cleaved, forms pores in the cell membrane, releasing intracellular contents into the extracellular milieu to exacerbate inflammation. We hypothesize that eCIRP is released actively from viable macrophages via GSDMD pores. We found that LPS induced eCIRP secretion from macrophages into the extracellular space. LPS significantly increased the expression of caspase-11 and cleavage of the GSDMD, as evidenced by increased N-terminal GSDMD expression in RAW 264.7 cells and mouse primary peritoneal macrophages. GSDMD inhibitor disulfiram decreased eCIRP release in vitro. Treatment with glycine to prevent pyroptosis-induced cell lysis did not significantly decrease eCIRP release from LPS-treated macrophages, indicating that eCIRP was actively released and was independent of pyroptosis. Downregulation of GSDMD gene expression by siRNA transfection suppressed eCIRP release in vitro after LPS stimulation. Moreover, GSDMD-/- peritoneal macrophages and mice had decreased levels of eCIRP in the culture supernatants and in blood treated with LPS in vitro and in vivo, respectively. GSDMD inhibitor disulfiram inhibited serum levels of eCIRP in endotoxemia and cecal ligation and puncture-induced sepsis. We conclude that eCIRP release from living macrophages is mediated through GSDMD pores, suggesting that targeting GSDMD could be a novel and potential therapeutic approach to inhibit eCIRP-mediated inflammation in sepsis.

The protective effect of H151, a novel STING inhibitor, in renal ischemia-reperfusion-induced acute kidney injury.

Renal ischemia-reperfusion (RIR)-induced acute kidney injury (AKI) is a common renal functional disorder with high morbidity and mortality. Stimulator of interferon (IFN) genes (STING) is the cytosolic DNA-activated signaling pathway that mediates inflammation and injury. Our recent study showed that extracellular cold-inducible RNA-binding protein (eCIRP), a newly identified damage-associated molecular pattern, activates STING and exacerbates hemorrhagic shock. H151 is a small molecule that selectively binds to STING and inhibits STING-mediated activity. We hypothesized that H151 attenuates eCIRP-induced STING activation in vitro and inhibits RIR-induced AKI in vivo. In vitro, renal tubular epithelial cells incubated with eCIRP showed increased levels of IFN-ß, STING pathway downstream cytokine, IL-6, tumor necrosis factor-α, and neutrophil gelatinase-associated lipocalin, whereas coincubation with eCIRP and H151 diminished those increases in a dose-dependent manner. In vivo, 24 h after bilateral renal ischemia-reperfusion, glomerular filtration rate was decreased in RIR-vehicle-treated mice, whereas glomerular filtration rate was unchanged in RIR-H151-treated mice. In contrast to sham, serum blood urea nitrogen, creatinine, and neutrophil gelatinase-associated lipocalin were increased in RIR-vehicle, but in RIR-H151, these levels were significantly decreased from RIR-vehicle. In contrast to sham, kidney IFN-ß mRNA, histological injury score, and TUNEL staining were also increased in RIR-vehicle, but in RIR-H151, these levels were significantly decreased from RIR-vehicle. Importantly, in contrast to sham, in a 10-day survival study, survival decreased to 25% in RIR-vehicle, but RIR-H151 had a survival of 63%. In conclusion, H151 inhibits eCIRP-induced STING activation in renal tubular epithelial cells. Therefore, STING inhibition by H151 can be a promising therapeutic intervention for RIR-induced AKI.NEW & NOTEWORTHY Renal ischemia-reperfusion (RIR)-induced acute kidney injury (AKI) is a common renal functional disorder with a high morbidity and mortality rate. Stimulator of interferon genes (STING) is the cytosolic DNA-activated signaling pathway responsible for mediating inflammation and injury. Extracellular cold-inducible RNA-binding protein (eCIRP) activates STING and exacerbates hemorrhagic shock. H151, a novel STING inhibitor, attenuated eCIRP-induced STING activation in vitro and inhibited RIR-induced AKI. H151 shows promise as a therapeutic intervention for RIR-induced AKI.

Release mechanisms of major DAMPs.

Damage-associated molecular patterns (DAMPs) are endogenous molecules which foment inflammation and are associated with disorders in sepsis and cancer. Thus, therapeutically targeting DAMPs has potential to provide novel and effective treatments. When establishing anti-DAMP strategies, it is important not only to focus on the DAMPs as inflammatory mediators but also to take into account the underlying mechanisms of their release from cells and tissues. DAMPs can be released passively by membrane rupture due to necrosis/necroptosis, although the mechanisms of release appear to differ between the DAMPs. Other types of cell death, such as apoptosis, pyroptosis, ferroptosis and NETosis, can also contribute to DAMP release. In addition, some DAMPs can be exported actively from live cells by exocytosis of secretory lysosomes or exosomes, ectosomes, and activation of cell membrane channel pores. Here we review the shared and DAMP-specific mechanisms reported in the literature for high mobility group box 1, ATP, extracellular cold-inducible RNA-binding protein, histones, heat shock proteins, extracellular RNAs and cell-free DNA.

Extracellular CIRP and TREM-1 axis promotes ICAM-1-Rho-mediated NETosis in sepsis.

Extracellular cold-inducible RNA-binding protein (eCIRP) is a damage-associated molecular pattern (DAMP). Intercellular adhesion molecule-1 (ICAM-1) expressing neutrophils produce excessive amounts of neutrophil extracellular traps (NETs). We reveal that eCIRP generates ICAM-1+ neutrophils through triggering receptor expressed on myeloid cells-1 (TREM-1) and the ICAM-1+ neutrophils involve Rho GTPase to promote NETosis. Treatment of BMDN with rmCIRP increased the frequency of ICAM-1+ BMDN, while rmCIRP-treated TREM-1-/- BMDN or pretreatment of BMDN with TREM-1 inhibitor LP17 significantly decreased the frequency of ICAM-1+ neutrophils. The frequencies of ICAM-1+ neutrophils in blood and lungs were markedly decreased in rmCIRP-injected mice or septic mice treated with LP17. Coculture of ICAM-1-/- neutrophils or wild-type (WT) neutrophils with WT macrophages in the presence of a peptidylarginine deiminase 4 (PAD4) inhibitor reduced TNF-α and IL-6 compared to WT neutrophils treated with rmCIRP. Treatment of ICAM-1-/- neutrophils with rmCIRP resulted in reduced quantities of NETs compared to WT rmCIRP-treated neutrophils. Treatment of BMDN with rmCIRP-induced Rho activation, while blockade of ICAM-1 significantly decreased Rho activation. Inhibition of Rho significantly decreased rmCIRP-induced NET formation in BMDN. TREM-1 plays a critical role in the eCIRP-mediated increase of ICAM-1 expression in neutrophils, leading to the increased NET formation via Rho activation to exaggerate inflammation.

A Machine Learning Prediction Model of Respiratory Failure Within 48 Hours of Patient Admission for COVID-19: Model Development and Validation.

BACKGROUND: Predicting early respiratory failure due to COVID-19 can help triage patients to higher levels of care, allocate scarce resources, and reduce morbidity and mortality by appropriately monitoring and treating the patients at greatest risk for deterioration. Given the complexity of COVID-19, machine learning approaches may support clinical decision making for patients with this disease. OBJECTIVE: Our objective is to derive a machine learning model that predicts respiratory failure within 48 hours of admission based on data from the emergency department. METHODS: Data were collected from patients with COVID-19 who were admitted to Northwell Health acute care hospitals and were discharged, died, or spent a minimum of 48 hours in the hospital between March 1 and May 11, 2020. Of 11,525 patients, 933 (8.1%) were placed on invasive mechanical ventilation within 48 hours of admission. Variables used by the models included clinical and laboratory data commonly collected in the emergency department. We trained and validated three predictive models (two based on XGBoost and one that used logistic regression) using cross-hospital validation. We compared model performance among all three models as well as an established early warning score (Modified Early Warning Score) using receiver operating characteristic curves, precision-recall curves, and other metrics. RESULTS: The XGBoost model had the highest mean accuracy (0.919; area under the curve=0.77), outperforming the other two models as well as the Modified Early Warning Score. Important predictor variables included the type of oxygen delivery used in the emergency department, patient age, Emergency Severity Index level, respiratory rate, serum lactate, and demographic characteristics. CONCLUSIONS: The XGBoost model had high predictive accuracy, outperforming other early warning scores. The clinical plausibility and predictive ability of XGBoost suggest that the model could be used to predict 48-hour respiratory failure in admitted patients with COVID-19.

Extracellular cold-inducible RNA-binding protein regulates neutrophil extracellular trap formation and tissue damage in acute pancreatitis.

Neutrophil extracellular traps (NETs) play a key role in the development of acute pancreatitis (AP). In the present study, we studied the role of extracellular cold-inducible RNA-binding protein (eCIRP), a novel damage-associated-molecular-pattern molecule, in severe AP. C57BL/6 mice underwent retrograde infusion of taurocholate into the pancreatic duct. C23, an eCIRP inhibitor, was given 1 h prior to induction of AP. Pancreatic, lung, and blood samples were collected and levels of citrullinated histone 3, DNA-histone complexes, eCIRP, myeloperoxidase (MPO), amylase, cytokines, matrix metalloproteinase-9 (MMP-9), and CXC chemokines were quantified after 24 h. NETs were detected by electron microscopy in the pancreas and bone marrow-derived neutrophils. Amylase secretion was analyzed in isolated acinar cells. Plasma was obtained from healthy individuals and patients with mild and moderate severe or severe AP. Taurocholate infusion induced NET formation, inflammation, and tissue injury in the pancreas. Pretreatment with C23 decreased taurocholate-induced pancreatic and plasma levels of eCIRP and tissue damage in the pancreas. Blocking eCIRP reduced levels of citrullinated histone 3 and NET formation in the pancreas as well as DNA-histone complexes in the plasma. In addition, administration of C23 attenuated MPO levels in the pancreas and lung of mice exposed to taurocholate. Inhibition of eCIRP reduced pancreatic levels of CXC chemokines and plasma levels of IL-6, HMGB-1, and MMP-9 in mice with severe AP. Moreover, eCIRP was found to be bound to NETs. Coincubation with C23 reduced NET-induced amylase secretion in isolated acinar cells. Patients with severe AP had elevated plasma levels of eCIRP compared with controls. Our novel findings suggest that eCIRP is a potent regulator of NET formation in the inflamed pancreas. Moreover, these results show that targeting eCIRP with C23 inhibits inflammation and tissue damage in AP. Thus, eCIRP could serve as an effective target to attenuate pancreatic damage in patients with AP.

Deoxyribonuclease Reduces Tissue Injury and Improves Survival After Hemorrhagic Shock.

BACKGROUND: Hemorrhagic shock (HS) caused by rapid loss of a large amount of blood is the leading cause of early death after severe injury. When cells are damaged during HS, many intracellular components including DNA are released into the circulation and function as endogenous damage-associated molecular patterns (DAMPs) that can trigger excessive inflammatory response and subsequently multiple organ dysfunction. We hypothesized that the administration of deoxyribonuclease I (DNase I) could reduce cell-free DNA and attenuate tissue damage in HS. METHODS: Eight-week-old male C57BL/6 mice underwent HS by controlled bleeding from the femoral artery for 90 min, followed by resuscitation with Ringer's lactate solution (vehicle) or DNase I (10 mg/kg BW). RESULTS: At 20 h after HS, serum levels of cell-free DNA were increased by 7.6-fold in the vehicle-treated HS mice compared with sham, while DNase I reduced its levels by 47% compared with the vehicle group. Serum levels of tissue injury markers (lactate dehydrogenase, aspartate aminotransferase, and alanine aminotransferase) and proinflammatory cytokine interleukin 6 were significantly reduced in the DNase I-treated mice. In the lungs, messenger RNA levels of proinflammatory cytokines (interleukin 6 and interleukin 1 ß), chemoattractant macrophage inflammatory protein - 2, and myeloperoxidase activity were significantly decreased in HS mice after DNase I. Finally, DNase I significantly improved the 10-day survival rate in HS mice. CONCLUSIONS: Administration of DNase I attenuates tissue damage and systemic and lung inflammation, leading to improvement of survival in HS mice. Thus, DNase I may potentially serve as an adjunct therapy for managing patients with HS.

Recombinant human milk fat globule-EGF factor VIII (rhMFG-E8) as a therapy for sepsis after acute exposure to alcohol.

BACKGROUND: Alcohol intake predisposes to infections and sepsis. Alcohol and sepsis inhibit the expression of milk fat globule epidermal growth factor-factor VIII (MFG-E8), a glycoprotein essential for optimal efferocytosis, resulting in the release of proinflammatory molecules and increased sepsis severity. We previously reported that recombinant mouse (rm) MFG-E8 attenuates sepsis-induced organ injury in rats with acute alcohol intoxication. In order to develop a therapy that can be safely used in humans, we have produced recombinant human (rh) MFG-E8 and evaluated its efficacy to ameliorate sepsis after acute exposure to alcohol. METHODS: We induced acute alcohol intoxication with a bolus injection of alcohol (1.75 g/kg BW) followed by an intravenous infusion of 300 mg/kg/h alcohol for 10 h. Sepsis was then induced by cecal ligation and puncture (CLP). At -10, 0, and 10 h relative to CLP, rats received MFG-E8 or vehicle (albumin) intravenously. Animals were euthanized at 20 h after CLP for blood and tissue collection. Additional groups of animals were used for a survival study. RESULTS: Compared to vehicle, rhMFG-E8 treatment ameliorated blood levels of proinflammatory cytokines (% improvement: TNF-α 49.8%, IL-6 34.7%) and endotoxin (61.7%), as well as of transaminases (AST 36.2%, ALT 40.1%) and lactate (18.4%). Rats treated with rhMFG-E8 also had a significant histological attenuation of the acute lung injury, as well as a reduction in the number of apoptotic cells in the thymus (43.4%) and cleaved caspase 3 (38.7%) in the spleen. In addition, rhMFG-E8 improved the 10-day sepsis survival rate from 45 to 80% CONCLUSION: rhMFG-E8 significantly ameliorated sepsis in rats with acute alcohol exposure, demonstrating rhMFG-E8's potential to be developed as an effective therapy for sepsis in alcohol abusers.

Extracellular cold inducible RNA-binding protein mediates binge alcohol-induced brain hypoactivity and impaired cognition in mice.

BACKGROUND: Alcohol abuse affects the brain regions responsible for memory, coordination and emotional processing. Binge alcohol drinking has shown reductions in brain activity, but the molecular targets have not been completely elucidated. We hypothesized that brain cells respond to excessive alcohol by releasing a novel inflammatory mediator, called cold inducible RNA-binding protein (CIRP), which is critical for the decreased brain metabolic activity and impaired cognition. METHODS: Male wild type (WT) mice and mice deficient in CIRP (CIRP-/-) were studied before and after exposure to binge alcohol level by assessment of relative brain glucose metabolism with fluorodeoxyglucose (18FDG) and positron emission tomography (PET). Mice were also examined for object-place memory (OPM) and open field (OF) tasks. RESULTS: Statistical Parametric Analysis (SPM) of 18FDG-PET uptake revealed marked decreases in relative glucose metabolism in distinct brain regions of WT mice after binge alcohol. Regional analysis (post hoc) revealed that while activity in the temporal (secondary visual) and limbic (entorhinal/perirhinal) cortices was decreased in WT mice, relative glucose metabolic activity was less suppressed in the CIRP-/- mice. Group and condition interaction analysis revealed differing responses in relative glucose metabolism (decrease in WT mice but increase in CIRP-/- mice) after alcohol in brain regions including the hippocampus and the cortical amygdala where the percent changes in metabolic activity correlated with changes in object discrimination performance. Behaviorally, alcohol-treated WT mice were impaired in exploring a repositioned object in the OPM task, and were more anxious in the OF task, whereas CIRP-/- mice were not impaired in these tasks. CONCLUSION: CIRP released from brain cells could be responsible for regional brain metabolic hypoactivity leading to cognitive impairment under binge alcohol conditions.

Huntingtin-interacting protein 1 (HIP1) regulates arthritis severity and synovial fibroblast invasiveness by altering PDGFR and Rac1 signalling.

OBJECTIVES: While new treatments for rheumatoid arthritis (RA) have markedly improved disease control by targeting immune/inflammatory pathways, current treatments rarely induce remission, underscoring the need for therapies that target other aspects of the disease. Little is known about the regulation of disease severity and joint damage, which are major predictors of disease outcome, and might be better or complementary targets for therapy. In this study, we aimed to discover and characterise a new arthritis severity gene. METHODS: An unbiased and phenotype-driven strategy including studies of unique congenic rat strains was used to identify new arthritis severity and joint damage genes. Fibroblast-like synoviocytes (FLS) from rats and patients with RA expressing or not Huntingtin-interacting protein 1 (HIP1) were studied for invasiveness, morphology and cell signalling. HIP1 knockout mice were used in in vivo confirmatory studies. Paired t-test was used. RESULTS: DNA sequencing and subcongenic strains studied in pristane-induced arthritis identified a new amino acid changing functional variant in HIP1. HIP1 was required for the increased invasiveness of FLS from arthritic rats and from patients with RA. Knocking down HIP1 expression reduced receptor tyrosine kinase-mediated responses in RA FLS, including RAC1 activation, affecting actin cytoskeleton and cell morphology and interfering with the formation of lamellipodia, consistent with reduced invasiveness. HIP1 knockout mice were protected in KRN serum-induced arthritis and developed milder disease. CONCLUSION: HIP1 is a new arthritis severity gene and a potential novel prognostic biomarker and target for therapy in RA.

Short-term low-magnesium diet reduces autoimmune arthritis severity and synovial tissue gene expression.

Magnesium has been suggested to have anti-inflammatory properties in short-term, mostly in vitro studies. To examine the effect of dietary magnesium modifications in arthritis severity and joint damage DA rats were placed on one of three diet regimens before the induction of autoimmune pristane-induced arthritis (PIA): a 4 wk low-magnesium diet, normal diet, and a magnesium-supplemented diet. The diets were switched to a normal diet 14 days after the induction of PIA (typical time of disease onset). Arthritis severity was scored for 38 days, and joints were examined by histology and quantitative PCR for proinflammatory genes. Rats on the low-magnesium diet were significantly and reproducibly protected and had 70% lower median arthritis severity score, with preservation of normal joint histology without erosive changes. Rats on the normal or magnesium-supplemented diets were not protected and developed equally severe and erosive disease. While the dietary modifications were at disease onset (day 14 postinduction), the protective effect of the short-term low-magnesium diet persisted, suggesting a lasting effect on a critical pathogenic pathway. Rats on the low-magnesium diet had significant reduction in synovial tissue expression of IL-6, RORA, and RORC, which are genes required for the development of Th17 T cells. This study revealed a novel role for dietary magnesium in the regulation of autoimmune arthritis and opens new possibilities for the treatment of autoimmune diseases such as rheumatoid arthritis and psoriatic arthritis with short courses of dietary or drug-induced modulations of magnesium levels.

Recombinant human MFG-E8 ameliorates colon damage in DSS- and TNBS-induced colitis in mice.

Inflammatory bowel disease (IBD) is characterized by chronic inflammation of the digestive system and typically requires lifelong medical care. Recombinant human MFG-E8 (rhMFG-E8) is a 364-amino acid protein, which promotes apoptotic cell clearance and reduces inflammation. This study investigates the therapeutic effect of rhMFG-E8 on two well-established mouse models of IBD. Acute mucosal injury leading to colitis was caused by exposing C57BL/6 mice to 4% dextran sodium sulfate (DSS) in the drinking water over 7 days, and BALB/c mice to a single intrarectal dose of 2.75 mg of 2,4,6-trinitrobenzene sulfonic acid (TNBS). Upon clinical onset of colitis (day 2 in the DSS model and day 1 in the TNBS model), mice were treated with daily subcutaneous injections of rhMFG-E8 (60 or 120 µg/kg/day) or vehicle (saline) for 6 days. Treatment with rhMFG-E8 significantly attenuated colitis in both models in a dose-dependent way. Treatment of DSS-induced colitis with rhMFG-E8 (120 µg/kg/day) decreased weight loss by 59%, the colitis severity score by 71%, and colon shrinkage by 49% when compared with vehicle. Similarly, treatment of TNBS-induced colitis with rhMFG-E8 (120 µg/kg/day) decreased weight loss by 97%, the colitis severity score by 82%, and colon shrinkage by 62% when compared with vehicle. In both models, the colons of animals receiving rhMFG-E8 showed marked reduction in neutrophil infiltration, cytokine and chemokine expression, and apoptotic cell counts. In conclusion, rhMFG-E8 ameliorates DSS- and TNBS-induced colitis, suggesting that it has the potential to become a novel therapeutic agent for IBD.

DAMPs and radiation injury.

The heightened risk of ionizing radiation exposure, stemming from radiation accidents and potential acts of terrorism, has spurred growing interests in devising effective countermeasures against radiation injury. High-dose ionizing radiation exposure triggers acute radiation syndrome (ARS), manifesting as hematopoietic, gastrointestinal, and neurovascular ARS. Hematopoietic ARS typically presents with neutropenia and thrombocytopenia, while gastrointestinal ARS results in intestinal mucosal injury, often culminating in lethal sepsis and gastrointestinal bleeding. This deleterious impact can be attributed to radiation-induced DNA damage and oxidative stress, leading to various forms of cell death, such as apoptosis, necrosis and ferroptosis. Damage-associated molecular patterns (DAMPs) are intrinsic molecules released by cells undergoing injury or in the process of dying, either through passive or active pathways. These molecules then interact with pattern recognition receptors, triggering inflammatory responses. Such a cascade of events ultimately results in further tissue and organ damage, contributing to the elevated mortality rate. Notably, infection and sepsis often develop in ARS cases, further increasing the release of DAMPs. Given that lethal sepsis stands as a major contributor to the mortality in ARS, DAMPs hold the potential to function as mediators, exacerbating radiation-induced organ injury and consequently worsening overall survival. This review describes the intricate mechanisms underlying radiation-induced release of DAMPs. Furthermore, it discusses the detrimental effects of DAMPs on the immune system and explores potential DAMP-targeting therapeutic strategies to alleviate radiation-induced injury.

TAG-FREE GLYCOSYLATED RHMFG-E8 AS A THERAPY FOR ACUTE KIDNEY INJURY.

ABSTRACT: Background: Acute kidney injury (AKI) can result from renal ischemia and reperfusion (I/R) and often occurs during surgical procedures in cardiac, liver, kidney transplantation, and trauma-hemorrhage. Milk fat globule epidermal growth factor-factor VIII (MFG-E8) functions as a bridging molecule to promote the removal of dying cells by professional phagocytes. Because MFG-E8 promotes clearance of apoptotic cells, we have explored its therapeutic potential in various organ injury conditions. To develop human MFG-E8 as a potential therapy, we have generated a human cell-expressed, and thus glycosylated, tag-free recombinant human (rh) MFG-E8 and tested its safety and biological activity in vitro . We hypothesize that the tag-free glycosylated rhMFG-E8 is protective in I/R-induced AKI and it can be developed as an effective therapy for AKI. Methods: To assess the pharmacokinetic properties of the tag-free rhMFG-E8, Sprague-Dawley rats were either untreated or treated with a bolus dose of the tag-free rhMFG-E8, blood collected at various time points and the recovery of human MFG-E8 in the blood were measured by ELISA. Adult male C57BL6 mice underwent bilateral renal ischemia for 30 min, and immediately upon reperfusion, mice were treated intraperitoneally with either normal saline (vehicle) or 20 µg/kg human cell expressed, glycosylated tag-free rhMFG-E8. At either 24 h or 48 h after I/R, blood and kidneys were harvested for further analysis. In separate cohorts of mice after I/R and treatment, mice were observed for 10 days, and survival recorded. Results: AKI rats treated with the tag-free rhMFG-E8 had similar half-life as those in the treated control rats. At 48 h after I/R-induced AKI, renal function markers, blood urea nitrogen, and creatinine were increased and treatment with the tag-free rhMFG-E8 significantly decreased these markers. At both 24 h and 48 h after AKI, inflammatory cytokines, TNF-α, IL-6, and IL-1ß were increased and treatment decreased these levels. The kidney mRNA expressions of these cytokines were also increased at 24 h after AKI and treatment significantly decreased those mRNA expressions. Histologically, at 48 h after AKI, tubular damage, and the number of TUNEL staining cells were increased and treatment markedly decreased these measurements. Administration of tag-free rhMFG-E8 at the time of reperfusion improved survival in a 10-day survival study. Conclusion: Our new human cell-expressed tag-free rhMFG-E8 is protective in I/R-induced AKI and it may have the potential to be further developed as a safe and effective therapy for AKI.

Radiation-induced eCIRP impairs macrophage bacterial phagocytosis.

Macrophages are essential immune cells for host defense against bacterial pathogens after radiation injury. However, the role of macrophage phagocytosis in infection following radiation injury remains poorly examined. Extracellular cold-inducible RNA-binding protein (eCIRP) is a damage-associated molecular pattern that dysregulates host immune system responses such as phagocytosis. We hypothesized that radiation-induced eCIRP release impairs macrophage phagocytosis of bacteria. Adult healthy mice were exposed to 6.5-Gy total body irradiation (TBI). Primary peritoneal macrophages isolated from adult healthy mice were exposed to 6.5-Gy radiation. eCIRP-neutralizing monoclonal antibody (mAb) was added to the cell culture prior to irradiation. Bacterial phagocytosis by peritoneal macrophages was assessed using pHrodo Green-labeled E. coli 7 days after irradiation ex vivo and in vitro. Bacterial phagocytosis was also assessed after treatment with recombinant murine CIRP (rmCIRP). Rac1 and ARP2 protein expression in cell lysates and eCIRP levels in the peritoneal lavage were assessed by Western blotting. Bacterial phagocytosis by peritoneal macrophages was significantly decreased after irradiation compared to controls ex vivo and in vitro. Rac1 and ARP2 expression in the peritoneal macrophages were downregulated after TBI. TBI significantly increased eCIRP levels in the peritoneal cavity. rmCIRP significantly decreased bacterial phagocytosis in a dose-dependent manner. eCIRP mAb restored bacterial phagocytosis by peritoneal macrophages after irradiation. Ionizing radiation exposure impairs bacterial phagocytosis by macrophages after irradiation. Neutralization of eCIRP restores the phagocytic ability of macrophages after irradiation. Our findings elucidate a novel mechanism of immune dysfunction and provide a potential new therapeutic approach for limiting infection after radiation injury.

Analyses of synovial tissues from arthritic and protected congenic rat strains reveal a new core set of genes associated with disease severity.

Little is known about the genes regulating disease severity and joint damage in rheumatoid arthritis (RA). In the present study we analyzed the gene expression characteristics of synovial tissues from four different strains congenic for non-MHC loci that develop mild and nonerosive arthritis compared with severe and erosive DA rats. DA.F344(Cia3d), DA.F344(Cia5a), DA.ACI(Cia10), and DA.ACI(Cia25) rats developed mild arthritis compared with DA. We found 685 genes with significantly different expression between congenics and DA, independent of the specific congenic interval, suggesting that these genes represent a new nongenetic core group of mediators of arthritis severity. This core group includes genes not previously implicated or with unclear role in arthritis severity, such as Tnn, Clec4m, and Spond1 among others, increased in DA. The core genes also included Scd1, Selenbp1, and Slc7a10, increased in congenics. Genes implicated in nuclear receptor activity, xenobiotic and lipid metabolism were also increased in the congenics, correlating with protection. Several disease mediators were among the core genes reduced in congenics, including IL-6, IL-17, and Ccl2. Analyses of upstream regulators (genes, pathways, or chemicals) suggested reduced activation of Stat3 and TLR-related genes and chemicals in congenics. Additionally, cigarette smoking was among the upstream regulators activated in DA, while p53 was an upstream regulator activated in congenics. We observed congenic-specific differential expression and detection in each individual strain. In conclusion, this new nongenetically regulated core genes of disease severity or protection in arthritis should provide new insight into critical pathways and potential new environmental risk factor for arthritis.

Arthritis severity locus Cia4 is an early regulator of IL-6, IL-1ß, and NF-κB activators' expression in pristane-induced arthritis.

Cia4 is a locus on rat chromosome 7 that regulates disease severity and joint damage in models of rheumatoid arthritis, including pristane-induced arthritis (PIA). To identify molecular processes regulated by Cia4, synovial tissues from MHC-identical DA (severe erosive) and DA.F344(Cia4) congenics (mild nonerosive) rats were collected at preclinical and recent onset stages following the induction of PIA and analyzed for gene expression levels. Il6 levels were significantly higher in DA compared with congenics on day 10 (135-fold) after PIA induction (preclinical stage) and remained increased on days 14 (47.7-fold) and 18 (29.41-fold). Il6 increased before Il1b suggesting that Il6 could be driving Il1b expression and early synovial inflammation; 187 genes had significantly different expression levels and included inflammatory mediators increased in DA such Slpi (10.94-fold), Ccl7 (5.17-fold), and Litaf (2.09-fold). Syk or NF-κB activating and interacting genes, including Cd74 Ccl21, were increased in DA; 59 genes implicated in cancer-related phenotypes were increased in DA. Genes involved in cell metabolism, transport across membranes, and tissue protection such as Dgat1, Dhcr7, and Slc1a1 were increased in DA.F344(Cia4) congenics; 21 genes differentially expressed or expressed in only one of the strains were located within the Cia4 interval and could be the gene accounting for the arthritis effect. In conclusion, the Cia4 interval contains at least one new arthritis gene that regulates early Il6, Il1b expression, and other inflammatory mediators. This gene regulates the expression of cancer genes that could mediate the development of synovial hyperplasia and invasion, and cartilage and bone destruction.

The multiple chemokine-binding bovine herpesvirus 1 glycoprotein G (BHV1gG) inhibits polymorphonuclear cell but not monocyte migration into inflammatory sites.

Chemokines facilitate the recruitment of inflammatory cells into tissues, contributing to target organ injury in a wide range of inflammatory and autoimmune diseases. Targeting either single chemokines or chemokine receptors alters the progression of disease in animal models of rheumatoid arthritis and lupus with varying degrees of efficacy but clinical trials in humans have been less successful. Given the redundancy of chemokine-chemokine receptor interactions, targeting of more than one chemokine may be required to inhibit active inflammatory disease. To test the effects of multiple-chemokine blockade in inflammation, we generated an adenovirus expressing bovine herpesvirus 1 glycoprotein G (BHV1gG), a viral chemokine antagonist that binds to a wide spectrum of murine and human chemokines, fused to the Fc portion of murine IgG2a. Administration of the adenovirus significantly inhibited thioglycollate-induced migration of polymorphonuclear leukocytes into the peritoneal cavity of BALB/c mice and reduced both clinical severity and articular damage in K/BxN serum transfer-induced arthritis. However, treatment with BHV1gG-Ig fusion protein did not prevent monocyte infiltration into the peritoneum in the thioglycollate model and did not prevent renal monocyte infiltration or nephritis in lupus-prone NZB/W mice. These observations suggest that the simultaneous inhibition of multiple chemokines by BHV1gG has the potential to interfere with acute inflammatory responses mediated by polymorphonuclear leukocytes, but is less effective in chronic inflammatory disease mediated by macrophages.

Identification of two new arthritis severity loci that regulate levels of autoantibodies, interleukin-1ß, and joint damage in pristane- and collagen-induced arthritis.

OBJECTIVE: Cia3 is a locus on rat chromosome 4 that regulates severity and joint damage in collagen- and pristane-induced arthritis (CIA and PIA). This study was undertaken to refine the Cia3 gene-containing interval toward gene identification and obtain insights into its mode of action. METHODS: Five DA.F344(Cia3) subcongenic rat strains were generated and studied using the PIA and CIA models. Levels of antibodies against type II collagen (both allo- and autoantibodies) were measured. Joints and synovial tissue were collected 32 days after the induction of PIA (chronic stage) for histologic and quantitative polymerase chain reaction analysis of interleukin-1ß (IL-1ß) and matrix metalloproteinase (MMP) levels. RESULTS: Three subcongenic strains sharing the centromeric Cia3d interval were protected and 2 subcongenic strains sharing the telomeric Cia3g interval, which did not overlap with Cia3d, were also protected, developing significantly less severe CIA and PIA. Normal joint architecture was preserved in DA.F344(Cia3) and DA.F344(Cia3d) congenic rats with PIA, while DA rats had pronounced synovial hyperplasia, angiogenesis, inflammatory infiltration, and bone or cartilage erosions. The DA.F344(Cia3d) and DA.F344(Cia3g) strains had significantly lower synovial levels of IL-1ß (5-fold and nearly 2-fold, respectively [the latter not reaching statistical significance]), MMP-1 (expressed predominantly in DA rats), MMP-3 (79-fold and 8-fold, respectively), and MMP-14 (21-fold and 1.4-fold, respectively) and reduced levels of pathogenic autoantibodies against type II collagen, compared with DA rats. CONCLUSION: We have identified 2 new arthritis severity and articular damage loci within Cia3. These loci regulate pathogenic processes in 2 different models of rheumatoid arthritis, and the identification of these genes has the potential to generate new targets for therapies aimed at reducing disease severity and articular damage, and may additionally have prognostic value.

Human cell-expressed tag-free rhMFG-E8 as an effective radiation mitigator.

Human milk fat globule epidermal growth factor-factor VIII (MFG-E8) functions as a bridging molecule to promote the removal of dying cells by professional phagocytes. E. coli-expressed histidine-tagged recombinant human MFG-E8 (rhMFG-E8) is protective in various disease conditions. However, due to improper recombinant protein glycosylation, misfolding and the possibility of antigenicity, E. coli-expressed histidine-tagged rhMFG-E8 is unsuitable for human therapy. Therefore, we hypothesize that human cell-expressed, tag-free rhMFG-E8 will have suitable structural and functional properties to be developed as a safe and effective novel biologic to treat inflammatory diseases including radiation injury. We produced a new tag-free rhMFG-E8 protein by cloning the human MFG-E8 full-length coding sequence without any fusion tag into a mammalian vector and expressed it in HEK293-derived cells. The construct includes the leader sequence of cystatin S to maximize secretion of rhMFG-E8 into the culture medium. After purification and confirmation of the protein identity, we first evaluated its biological activity in vitro. We then determined its efficacy in vivo utilizing an experimental rodent model of radiation injury, i.e., partial body irradiation (PBI). HEK293 cell supernatant containing tag-free rhMFG-E8 protein was concentrated, purified, and rhMFG-E8 was verified by SDS-PAGE with the standard human MFG-E8 loaded as control and, mass spectrometry followed by analysis using MASCOT for peptide mass fingerprint. The biological activity of human cell-expressed tag-free rhMFG-E8 was superior to that of E. coli-expressed His-tagged rhMFG-E8. Toxicity, stability, and pharmacokinetic studies indicate that tag-free rhMFG-E8 is safe, highly stable after lyophilization and long-term storage, and with a terminal elimination half-life in circulation of at least 1.45 h. In the 15 Gy PBI model, a dose-dependent improvement of the 30-day survival rate was observed after tag-free rhMFG-E8 treatment with a 30-day survival of 89%, which was significantly higher than the 25% survival in the vehicle group. The dose modification factor (DMF) of tag-free rhMFG-E8 calculated using probit analysis was 1.058. Tag-free rhMFG-E8 also attenuated gastrointestinal damage after PBI suggesting it as a potential therapeutic candidate for a medical countermeasure for radiation injury. Our new human cell-expressed tag-free rhMFG-E8 has proper structural and functional properties to be further developed as a safe and effective therapy to treat victims of severe acute radiation injury.