Screening of potential core genes in the peripheral blood of adult patients with sepsis based on immunoregulation and signal transduction functions
Authors: Tian Ye , Li Shaolan , Lu Qiangyong , Zhang Chuan , Hu Lin , Ling Jiamei , Chen Muhu , Hu Yingchun 
Published: September 2022

Objective
Based on the functions of immunoregulation and signal transduction, septic peripheral blood sequencing and bioinformatics technology were used to screen potential core targets.
Methods
According to the SEPSIS 3.0 standard, patients with sepsis (n = 23) admitted to the ICU of the Affiliated Hospital of Southwest Medical University from January 2019 to December 2020 were enrolled, and normal volunteers were included in the control group (n = 10). Their peripheral blood underwent RNA-seq processing within 24 hours after admission to the hospital. Data quality control and differential gene screening were performed based on R language (P < 0.01; log2FC ≥ 2). Gene function enrichment analysis was conducted on differentially expressed genes. Then, genes related to immunoregulation interactions were selected for protein interaction analysis using STRING to screen out potential core targets, and the data in the public dataset GSE65682 were used to explore the prognostic relevance of potential core genes. Public datasets were collected, and a meta-analysis was used to verify the expression trends of core genes in the sepsis group. Then, 5 PBMC samples (NC = 2; SIRS = 1; SEPSIS = 2) were collected, and their core genes underwent cell line localization analysis using 10X single-cell sequencing.
Results
Compared with the normal group, there were a total of 1128 differentially expressed genes in the peripheral blood cells of the sepsis group, of which 721 were upregulated and 407 downregulated. These differentially expressed genes were mainly enriched in leukocyte-mediated cytotoxicity, cell killing regulation, adaptive immune response regulation, lymphocyte-mediated immune regulation, and negative regulation of adaptive immune response. In this study, PPI interaction network analysis was performed on immunoregulation-related genes to screen several genes, such as CD160, KLRG1, S1PR5, and RGS16, in the core area, which are related to adaptive immune regulation, signal transduction, and intracellular components. The above four genes in the core area were found to be related to the prognosis of patients with sepsis, of which RGS16 was negatively correlated with the survival rate, and CD160, KLRG1, and S1PR5 were positively correlated. However, several public datasets showed that CD160, KLRG1, and S1PR5 were all downregulated in the peripheral blood of patients with sepsis, while RGS16 was upregulated in the sepsis group. Single-cell sequencing analysis showed that they were mainly expressed in NK-T cells.
Conclusion
Compared with the normal group, CD160, KLRG1, and S1PR5 were downregulated in the sepsis group and positively correlated with survival, whereas RGS16 was upregulated in the sepsis group and negatively correlated with survival. These four genes were mainly located in human peripheral blood NK-T-cells and might be targets for potential immunoregulation research.