GSDMD-mediated NETosis promotes the development of acute respiratory distress syndrome.

Gasdermin D (GSDMD) is a classical molecule involved in pyroptosis. It has been reported to be cleaved into N-terminal fragments to form pores in the neutrophil membrane and promote the release of neutrophil extracellular traps (NETs). However, it remains unclear if GSDMD is involved in neutrophil regulation and NET release during ARDS. The role of neutrophil GSDMD in the development of ARDS was investigated in a murine model of ARDS induced by lipopolysaccharide (LPS) using the neutrophil specific GSDMD-deficient mice. The neutrophil GSDMD cleavage and its relationship with NETosis were also explored in ARDS patients. The cleavage of GSDMD in neutrophils from ARDS patients and mice was upregulated. Inhibition of GSDMD by genetic knockout or inhibitors resulted in reduced production of NET both in vivo and in vitro, and attenuation of LPS-induced lung injury. Moreover, in vitro experiments showed that the inhibition of GSDMD attenuated endothelial injury co-cultured with neutrophils from ARDS patients, while extrinsic NETs reversed the protective effect of GSDMD inhibition. Collectively, our data suggest that the neutrophil GSDMD cleavage is crucial in NET release during ARDS. The NET release maintained by cleaved GSDMD in neutrophils may be a key event in the development of ARDS.

Corrigendum: PD-L1 maintains neutrophil extracellular traps release by inhibiting neutrophil autophagy in endotoxin-induced lung injury.

[This corrects the article DOI: 10.3389/fimmu.2022.949217.].

PD-L1 maintains neutrophil extracellular traps release by inhibiting neutrophil autophagy in endotoxin-induced lung injury.

Programmed death ligand 1 (PD-L1) is not only an important molecule in mediating tumor immune escape, but also regulates inflammation development. Here we showed that PD-L1 was upregulated on neutrophils in lipopolysaccharide (LPS)-induced acute respiratory distress syndrome (ARDS). Neutrophil specific knockout of PD-L1 reduced lung injury in ARDS model induced by intratracheal LPS injection. The level of NET release was reduced and autophagy is elevated by PD-L1 knockout in ARDS neutrophils both in vivo and in vitro. Inhibition of autophagy could reverse the inhibitory effect of PD-L1 knockout on NET release. PD-L1 interacted with p85 subunit of PI3K at the endoplasmic reticulum (ER) in neutrophils from ARDS patients, activating the PI3K/Akt/mTOR pathway. An extrinsic neutralizing antibody against PD-L1 showed a protective effect against ARDS. Together, PD-L1 maintains the release of NETs by regulating autophagy through the PI3K/Akt/mTOR pathway in ARDS. Anti-PD-L1 therapy may be a promising measure in treating ARDS.

Efficacy and safety of tocilizumab in COVID-19 patients.

In this retrospective study we assessed the efficacy and safety of tocilizumab in patients with critical or severe coronavirus disease 2019 (COVID-19). We enrolled 181 patients admitted to Huoshenshan Hospital (Wuhan, China) with confirmed COVID-19 between January 2020 and February 2020. Ninety-two patients were treated with tocilizumab, and 89 patients were treated conventionally. We analyzed the clinical manifestations, changes in CT scan images, and laboratory tests before and after tocilizumab treatment, and compared these results with the conventionally treated group. A significant reduction in the level of C-reactive protein was observed 1 week after tocilizumab administration. In some cases this meant the end of the IL-6-related cytokine storm. In addition, tocilizumab relieved fever, cough, and shortness of breath with no reported adverse drug reactions. These findings suggest tocilizumab improves clinical outcomes and is effective for treatment of patients with critical or severe COVID-19. However, future clinical trials are needed to better understand the impact of tocilizumab interference with IL-6 and provide a therapeutic strategy for treatment of COVID-19.

FcRγ deficiency improves survival in experimental sepsis by down-regulating TLR4 signaling pathway.

Fc receptor common γ signaling chain (FcRγ), a common subunit shared by Fc receptors (FcγRI, III, IV, FcαRI, and FcεRI), is an important immune regulator both in innate and adaptive immunity. Previous studies have shown that FcRγ was a potential target of inflammatory diseases, whereas the role of FcRγ in sepsis has been poorly understood. In this study, we found that deficiency of FcRγ resulted in increased survival in lipopolysaccharide (LPS)/D-galactosamine and E. coli-induced sepsis in mice. This protective effect was characterized by decreased TNF-α, IL-6, and IL-10. Further experiments in bone marrow-derived macrophages (BMDMs) in vitro also showed that FcRγ deficiency resulted in decreased production of TNF-α, IL-6, and IL-10 upon LPS stimulation. The mechanism study showed that FcRγ was physiologically associated with toll-like receptor 4 (TLR4), and tyrosine phosphorylation of FcRγ mediated TLR4 signaling pathway, followed by increased ERK phosphorylation upon LPS stimulation. Our results suggest that FcRγ might be a potential therapeutic target of sepsis.

Up-regulation of programmed cell death 1 ligand 1 on neutrophils may be involved in sepsis-induced immunosuppression: an animal study and a prospective case-control study.

BACKGROUND: Recent studies have shown that neutrophils may display an antigen-presenting function and inhibit lymphocyte proliferation by expressing programmed cell death 1 ligand 1 (PD-L1). The current study was performed to investigate the effect of neutrophils and their pathophysiological significance during sepsis. METHODS: Neutrophil PD-L1 expression was determined in both septic mice (n = 6) and patients (n = 41). Neutrophils from septic mice were subtyped into PD-L1 and PD-L1 populations to determine their phenotypes and functions. Septic neutrophils were cocultured with lymphocytes to observe the effect of septic neutrophils on lymphocyte apoptosis. RESULTS: The PD-L1 level on neutrophils from septic mice was significantly up-regulated (21.41 ± 4.76%). This level increased with the progression of sepsis and the migration of neutrophils from the bone marrow to the blood and peritoneal cavity. The percentages of CD11a, CD62L, and C-C chemokine receptor type 2 were lower, whereas the percentages of CD16 and CD64 were higher on PD-L1 neutrophils than on PD-L1 neutrophils. The migratory capacity of PD-L1 neutrophils was compromised. Septic neutrophils induced lymphocyte apoptosis via a contact mechanism, and this process could be reversed by anti-PD-L1 antibody. PD-L1 was also up-regulated on neutrophils from patients with severe sepsis (14.6% [3.75%, 42.1%]). The levels were negatively correlated with the monocyte human leukocyte antigen-DR level and positively correlated with the severity of septic patients. Neutrophil PD-L1 was a predictor for the prognosis of severe sepsis, with an area of 0.74 under the receiver operating curve. CONCLUSIONS: PD-L1 is up-regulated on neutrophils during sepsis, which may be related to sepsis-induced immunosuppression.

Plasma HSPA12B is a potential predictor for poor outcome in severe sepsis.

INTRODUCTION: Endothelium-derived molecules may be predictive to organ injury. Heat shock protein (HSP) A12B is mainly located in endothelial cells, which can be detected in the plasma of septic patients. Whether it is correlated with prognosis of sepsis remains unclear. METHODS: Extracellular HSPA12B (eHSPA12B) was determined in plasma of septic mice at 6 h, 12 h, 24 h and 48 h after cecal ligation and puncture (CLP). It was also detected in plasma of patients with severe sepsis, sepsis, systemic inflammatory response syndrome and healthy volunteers. The predictive value for prognosis of severe sepsis was assessed by receiver operating curve (ROC) and Cox regression analyses. RESULTS: eHSPA12B was elevated in plasma of CLP mice at 6 h and peaked at 24 h after surgery. A total of 118 subjects were included in the clinical section, including 66 patients with severe sepsis, 21 patients with sepsis, 16 patients with SIRS and 15 volunteers. Plasma eHSPA12B was significantly higher in patients with severe sepsis than in patients with sepsis, SIRS and volunteers. The level of eHSPA12B was also higher in non-survivals than survivals with severe sepsis. The area under the curve (AUC) of eHSPA12B in predicting death among patients with severe sepsis was 0.782 (0.654-0.909) in ROC analysis, much higher than that of IL-6 and IL-10. Cox regression analysis showed that cardiovascular diseases, IL-6 and eHSPA12B were risk factors for mortality in patients with severe sepsis. Survival curve demonstrated a strikingly significant difference between 28-day survival rates of patients with an eHSPA12B lower or not lower than 1.466 ng/ml. CONCLUSIONS: Plasma eHSPA12B is elevated in both septic mice and patients. It may be a good predictor for poor outcome in patients with severe sepsis.

Blockade of ICAM-1 improves the outcome of polymicrobial sepsis via modulating neutrophil migration and reversing immunosuppression.

Intercellular adhesion molecule-1 (ICAM-1) is a key adhesion molecule mediating neutrophil migration and infiltration during sepsis. But its role in the outcome of sepsis remains contradictory. The current study was performed to investigate the role of anti-ICAM-1 antibody in the outcome of polymicrobial sepsis and sepsis-induced immune disturbance. Effect of anti-ICAM-1 antibody on outcome of sepsis induced by cecal ligation and puncture (CLP) was evaluated by the survival analysis, bacterial clearance, and lung injury. Its influence on neutrophil migration and infiltration, as well as lymphocyte status, in thymus and spleen was also investigated. The results demonstrated that ICAM-1 mRNA was upregulated in lung, thymus, and spleen of CLP mice. Anti-ICAM-1 antibody improved survival and bacterial clearance in CLP mice and attenuated lung injury. Migration of neutrophils to peritoneal cavity was enhanced while their infiltration into lung, thymus, and spleen was hampered by ICAM-1 blockade. Anti-ICAM-1 antibody also prevented sepsis-induced apoptosis in thymus and spleen. Positive costimulatory molecules including CD28, CD80, and CD86 were upregulated, while negative costimulatory molecules including PD-1 and PD-L1 were downregulated following anti-ICAM-1 antibody administration. In conclusion, ICAM-1 blockade may improve outcome of sepsis. The rationale may include the modulated neutrophil migration and the reversed immunosuppression.

Association between inflammatory genetic polymorphism and acute lung injury after cardiac surgery with cardiopulmonary bypass.

BACKGROUND: Recently, single nucleotide polymorphisms were proposed as potentially new predictors for perioperative risks, such as myocardial infarction and organ dysfunction. The objectives of this study were to investigate whether IL-6 -572C/G, IL-10 -1082A/G, and TNF-alpha -308G/A were associated with acute lung injury after cardiac surgery with cardiopulmonary bypass. MATERIAL/METHODS: One hundred patients with acute lung injury at 24 hours after cardiac surgery with cardiopulmonary bypass and 112 patients without acute lung injury as controls were included. Genotyping assay was performed with real-time fluorescence-based allele-specific PCR. Serum levels of IL-6, IL-10, and TNF-alpha were also determined by ELISA. Associations between these polymorphisms and acute lung injury, as well as serum cytokine levels, were analyzed. All patients were genotyped for IL-6 -572C/G, IL-10 -1082A/G, and TNF-alpha -308G/A. Circulating level of these cytokines were also determined. RESULTS: Acute lung injury after cardiac surgery with cardiopulmonary bypass was associated with IL-6 -572C/G polymorphism, but not IL-10 -1082A/G or TNF-alpha -308G/A. This functional polymorphism was further confirmed by multivariate analyses. The ratio of circulating concentrations of IL-10/IL-6 was associated with IL-6 genotypes and incidence of acute lung injury as well. CONCLUSIONS: The IL-6 -572 polymorphism was associated with acute lung injury after cardiac surgery with cardiopulmonary bypass. Proinflammatory and anti-inflammatory imbalance might be the clinical significance of IL-6 polymorphism (ClinicalTrials.gov number, NCT00826072).

Serum miR-146a and miR-223 as potential new biomarkers for sepsis.

OBJECTIVE: Current biomarkers cannot completely distinguish sepsis from systemic inflammatory response syndrome (SIRS) caused by other non-infectious diseases. Circulating microRNAs (miRNAs) are promising biomarkers for several diseases, but their correlation with sepsis is not totally clarified. METHODS: Seven miRNAs related to inflammation or infection were included in the present study. Serum miRNA expression was investigated in 50 patients diagnosed with sepsis, 30 patients with SIRS and 20 healthy controls to evaluate the diagnostic and prognostic value. Expression levels of serum miRNAs were determined by quantitative PCR using the Qiagen miScript system. Serum CRP and IL-6 levels were determined by enzyme linked immunosorbent assay. RESULTS: Serum miR-146a and miR-223 were significantly reduced in septic patients compared with SIRS patients and healthy controls. The areas under the receiver operating characteristic curve of miR-146a, miR-223 and IL-6 were 0.858, 0.804 and 0.785, respectively. CONCLUSION: Serum miR-146a and miR-223 might serve as new biomarkers for sepsis with high specificity and sensitivity. (ClinicalTrials.gov number, NCT00862290.).