Elk1 enhances inflammatory cell infiltration and exacerbates acute lung injury/acute respiratory distress syndrome by suppressing Fcgr2b transcription.

OBJECTIVE: Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are associated with significant mortality rates. The role of Fcgr2b in the pathogenesis of ALI/ARDS is not fully elucidated. This study aimed to investigate the functions of Fcgr2b in ALI/ARDS and explore its underlying mechanisms. METHODS: Methods: In this study, rat models of ARDS and pulmonary microvascular endothelial cell (PMVEC) injury models were established through the administration of lipopolysaccharide (LPS). The expression levels of Fcgr2b and Elk1 were quantified in both LPS-induced ARDS rats and PMVECs. Subsequent gain- and loss-of-function experiments were conducted, followed by comprehensive assessments of lung tissue for pathomorphological changes, edema, glycogen storage, fibrosis, and infiltration of inflammatory cells. Additionally, bronchoalveolar lavage fluid was analyzed for T-helper 17 (Th17) cell infiltration, inflammatory response, and microvascular permeability to evaluate lung injury severity in ARDS models. Furthermore, the activity, cytotoxicity, apoptosis, and angiogenic potential of PMVECs were assessed to gauge cell injury. The interaction between Elk1 and Fcgr2b was also examined to confirm their regulatory relationship. RESULTS: In the context of LPS-induced ARDS and PMVEC injury, Fcgr2b expression was markedly reduced, whereas Elk1 expression was elevated. Overexpression of Fcgr2b led to a decrease in Th17 cell infiltration and mitigated lung tissue damage in ARDS models, in addition to reducing LPS-induced injury in PMVECs. Elk1 was found to suppress Fcgr2b transcription through the recruitment of histone 3 lysine 9 trimethylation (H3K9me3). Knockdown of Elk1 diminished Th17 cell infiltration and lung tissue damage in ARDS models, and alleviated LPS-induced injury in PMVECs, effects that were reversed upon Fcgr2b upregulation. CONCLUSION: Elk1 negatively regulates Fcgr2b transcription, thereby augmenting the inflammatory response and exacerbating lung injury in LPS-induced ALI/ARDS.

[Modulation of endothelial progenitor cells by tumor necrosis factor-α in multiple organ dysfunction syndrome in swine].

OBJECTIVE: To study the modulation in number and function of endothelial progenitor cell (EPC) in multiple organ dysfunction syndrome (MODS) after trauma in swine, and to investigate its pathogenesis. METHODS: Forty pigs were divided into sham group and MODS group (each, n=20). The model of MODS of "two-hit" injury, namely hemorrhagic shock and endotoxemia, was reproduced. The peripheral blood was collected before hemorrhage (T1) and endotoxin injection (T2), and 1 hour (T3), 24 hours (T4), 48 hours (T5) after endotoxin injection. Phosphorylation of p38 mitogen-activated protein kinase (p-p38MAPK ) in mononuclear cell was determined by Western Blot, the content of tumor necrosis factor-α (TNF-α) was determined with enzyme linked immunosorbent assay (ELISA), and the number of EPC was determined with flow cytometry. RESULTS: Model of MODS was successfully reproduced in 17 pigs. In model group, the expression of p-p38MAPK (A value) peaked at T3 (4.83±0.52), and gradually declined at T4 and T5 (4.36±0.43, 1.93±0.33), and the expression of p-p38MAPK at T3-T5 was significantly higher than that at T1 (1.00±0.22, all P<0.01). The plasma concentration of TNF-α (ng/L) at T3 in MODS group was obviously elevated compared with that of sham group (532.43±52.17 vs. 129.03±20.45, t=31.163, P<0.001), and it peaked at T3, it then gradually lowered, and it was significantly higher at T4 and T5 than that in sham group (T4: 398.93±35.75 vs. 131.12±29.53, t=26.562, P<0.001; T5: 287.48±27.26 vs. 126.44±26.96, t=17.861, P<0.001). The number of EPC (×10(7)/L) was apparently increased in MODS group at T3 compared with sham group (4.832±0.624 vs. 3.545±0.363, t=9.542, P<0.001), and it peaked at T3, then gradually decreased, and the number of EPC at T4 and T5 was significantly lower than that in sham group (T4: 2.628±0.627 vs. 3.442±0.325, t=5.043, P<0.001; T5: 2.203±0.711 vs. 3.471±0.323, t=2.972, P<0.001). CONCLUSIONS: Phosphorylation of p38MAPK could increase the plasma concentration of TNF-αand decrease the quantity of EPC in MODS,which may be one of the mechanisms of MODS.