The link between neutrophils, neutrophil extracellular traps, and NLRP3 inflammasomes: The dual effect of CD177 and its therapeutic potential in acute respiratory distress syndrome/acute lung injury.

Neutrophils are important inflammatory effector cells that protect against foreign invasion but also cause self-harm. Numerous neutrophils infiltrate the lungs in acute respiratory distress syndrome/acute lung injury (ARDS/ALI) patients. However, the exact impact of neutrophil infiltration on ARDS's onset and progression remains unclear. To investigate this, we analyzed two ARDS-related datasets from the Gene Expression Omnibus public database and discovered an association between CD177, a neutrophil-specific surface protein, and ARDS progression. We used quantitative flow cytometry to assess CD177+ neutrophils in the peripheral blood of clinical ARDS patients versus healthy controls, finding a significant increase in CD177+ neutrophils percentage among total neutrophils in ARDS patients. This finding was further confirmed in ALI mouse models. Subsequent animal experiments showed that anti-CD177 effectively reduces pulmonary edema, neutrophil infiltration, and inflammatory cytokine release, along with a decrease in reactive oxygen species (ROS) and myeloperoxidase (MPO) levels. We also established an in vitro co-culture system to mimic neutrophil and lung epithelial cell interactions. In the anti-CD177 group, we observed decreased expression of NLRP3, caspase 1, PAD4, MPO, and ROS, along with a reduction in certain inflammatory cytokines. These results indicate a crucial role for the CD177 gene in ARDS's development and progression. Inhibiting CD177 may help mitigate excessive activation of NLRP3 inflammasomes, ROS, and neutrophil extracellular traps (NETs), thus alleviating ARDS.

HMGB1 promotes HLF-1 proliferation and ECM production through activating HIF1-α-regulated aerobic glycolysis.

Aerobic glycolysis is a crucial event in fibroblast differentiation, and extracellular matrix (ECM) production in the progression of pulmonary fibrosis (PF). Abnormal high mobility group protein B1 (HMGB1) activation is involved in the pathogenesis of PF. However, whether aerobic glycolysis contributes to HMGB1-induced fibroblast proliferation and ECM production in PF has not yet been determined. In this study, we investigated the effects of HMGB1 on human embryonic lung fibroblast (HLF-1) proliferation, ECM production, and aerobic glycolysis. The lactate dehydrogenase inhibitor oxamic acid (OA), and PFKFB3 inhibitor 3PO were used to block certain crucial steps of aerobic glycolysis. As a result, we observed an increase of HMGB1 in bronchoalveolar lavage fluid (BALF) in bleomycin (BLM)-treated rats as compared to non-treated rats (control group). A concentration-dependent increase of HLF-1 proliferation and expression of α-SMA and α-collagen I were observed in the HMGB1 group, as well as increases of LDHA activation, glucose uptake levels, glycolytic rate, lactate level, and ATP production. OA and 3PO, or suppression of HIF1-α, blocked the effects of HMGB1. In summary, HMGB1 promotes fibroblast proliferation and ECM production though upregulating expression of HIF1-α to induce an increase of aerobic glycolysis.

Blockage of glycolysis by targeting PFKFB3 alleviates sepsis-related acute lung injury via suppressing inflammation and apoptosis of alveolar epithelial cells.

Sepsis-related acute lung injury (ALI) is characterized by excessive lung inflammation and apoptosis of alveolar epithelial cells resulting in acute hypoxemic respiratory failure. Recent studies indicated that anaerobic glycolysis play an important role in sepsis. However, whether inhibition of aerobic glycolysis exhibits beneficial effect on sepsis-induced ALI is not known. In vivo, a cecal ligation and puncture (CLP)-induced ALI mouse model was set up and mice treated with glycolytic inhibitor 3PO after CLP. The mice treated with the 3PO ameliorated the survival rate, histopathological changes, lung inflammation, lactate increased and lung apoptosis of mice with CLP-induced sepsis. In vitro, the exposure of human alveolar epithelial A549 cells to lipopolysaccharide (LPS) resulted in cell apoptosis, inflammatory cytokine production, enhanced glycolytic flux and reactive oxygen species (ROS) increased. While these changes were attenuated by 3PO treatment. Sequentially, treatment of A549 cells with lactate caused cell apoptosis and enhancement of ROS. Pretreatment with N-acetylcysteine (NAC) significantly lowered LPS and lactate-induced the generation of ROS and cell apoptosis in A549 cells. Therefore, these results indicate that anaerobic glycolysis may be an important contributor in cell apoptosis of sepsis-related ALI. Moreover, LPS specifically induces apoptotic insults to A549 cell through lactate-mediated enhancement of ROS.