Objective To explore the changes in the expression of CX3CR1 in natural killer (NK) cells from peripheral blood mononuclear cells (PBMC) in sepsis patients and its association with gut microbiota. Methods A total of 24 sepsis patients were selected from January 2020 to January 2021 at Zhongshan Hospital, Fudan University, and 10 healthy volunteers were recruited in January 2021 as healthy controls. Fecal samples and peripheral blood were collected from sepsis patients on the first and fourth days of hospitalization. Sequencing of the V3-4 region of the 16S rDNA gene of gut microbiota was performed using the Illumina MiSeq platform. The peripheral blood samples were isolated by positively selected magnetic beads, and the CD3^－CD56^＋NK cells were identified by flow cytometry. The mRNA expression of CX3CR1 was detected by qPCR, and the changes in CX3CR1 expression and its correlation with gut microbiota were analyzed. Results Compared with healthy control group, the Shannon diversity index of the gut microbiota and the proportion of Firmicutes in sepsis patients decreased; compared with admission day, the Shannon diversity of the gut microbiota in sepsis patients on the fourth day of hospitalization significantly decreased, the proportion of Proteobacteria on phylum level and the relative abundance of Enterococcus and Klebsiella on genus level significantly increased. The CX3CR1 expression of PBMC-NK cells in sepsis patients on the fourth day was significantly lower than that on the admission day (P＜0.001). Compared with surviving patients, CX3CR1 expression in non-surviving patients significantly decreased on the fourth day (P＜0.05). Spearman correlation analysis showed that CX3CR1 expression of PBMC-NK cells was positively correlated with the quantity of gut microbiota and the Shannon diversity index (P＜0.01). Conclusions The expression of CX3CR1 in PBMC-NK cells in sepsis patients decreases with disease progression, and is related to prognosis. Furthermore, its expression is found to be closely related to the gut microbiota.

ObjectiveTo investigate the effect and potential mechanism of caffeic acid （CA） on severe acute pancreatitis （SAP） induced by caerulein combined with lipopolysaccharide （LPS）， and to provide a basis for the research on novel drugs for the treatment of SAP. MethodsC57BL/6J mice， aged 6 weeks， were divided into control group， model group， CA group， and octreotide acetate （OA） group， with 6 mice in each group. The mice in the control group were given injection of normal saline， and those in the other groups were given intraperitoneal injection of caerulein combined with LPS to establish a mouse model of SAP. At 1 hour after the first injection of caerulein， the mice in the CA group and the OA group were given intraperitoneal injection of CA or subcutaneous injection of OA at an interval of 8 hours. The general status of the mice was observed after 24 hours of modeling， and serum， pancreas， lung， and colon samples were collected. HE staining was used to observe the histopathological changes of the pancreas and lungs， and the serum levels of α-amylase， lipase， tumor necrosis factor-α （TNF-α）， interleukin-6 （IL-6）， alanine aminotransferase， aspartate aminotransferase， and creatinine were measured. RT-PCR was used to measure the expression of proinflammatory factors in the pancreas and lungs； myeloperoxidase （MPO） immunohistochemistry was used to observe the degree of neutrophil infiltration； Western blot was used to measure the activation of nuclear factor-kappa B （NF-κB） and the level of citrullinated histone H3 （CitH3）， a marker for the formation of neutrophil extracellular traps （NETs）， in the pancreas and lungs， as well as the expression level of ZO-1 in colon tissue. A one-way analysis of variance was used for comparison of continuous data between multiple groups， and the Dunnett’s t-test was used for further comparison between two groups. ResultsCompared with the control group， the model group had severe injury in the pancreas and lungs and significant increases in the activity of serum α- amylase and lipase and the levels of the proinflammatory cytokines IL-6， interleukin-1β （IL-1β）， and TNF-α in serum and lung tissue （all P<0.05）， as well as significant increases in NF-κB activation， neutrophil infiltration， and the formation of NETs in the pancreas and lungs （all P<0.05）. Compared with the model group， the CA group had alleviated pathological injury of the pancreas and lungs and significant reductions in the activity of serum α-amylase and the levels of the proinflammatory cytokines IL-6， IL-1β， and TNF-α in serum and lung tissue （all P<0.05）， as well as significant reductions in NF-κB activation， neutrophil infiltration， and the formation of NETs in the pancreas and lungs （all P<0.05）. ConclusionCA can alleviate SAP induced by caerulein combined with LPS in mice， possibly by inhibiting neutrophil recruitment and the formation of NETs.