Integrated multiomics and Mendelian randomization identify CHIT1 as a novel sepsis biomarker and therapeutic target

Sepsis is characterized by severe organ failure due to an impaired response to infection. The underlying pathophysiology of sepsis is characterized by concurrent unbalanced hyperinflammatory and immunoparalysis. This study aimed to identify new key biomarkers that could predict outcomes in sepsis patients and explore theirunderlying molecular mechanisms. Bulk transcriptome data (GSE65682, GSE28750, GSE57065, GSE95233) and scRNA-seq data (GSE167363) of sepsis were obtained from the GEO database. Data for MR analysis were sourced from the eQTLGen Consortium and IEU OpenGWAS project. Prognostic biomarkers and potential drug targets for sepsis were identified through univariate Cox regression and MR analysis. The expression of these biomarkers was further validated using scRNA-seq data to investigate the underlying molecular mechanisms. Significantly higher expression of CHIT1 was found at sepsis non-survivor and associated with 28-day mortality of sepsis. scRNA-seq data of septic samples found that CHIT1 mainly expressed in neutrophils, which was also higher in sepsis non-survivors. The CHIT1 + neutrophils expressed higher inflammation related genes of S100A8, S100A9, S100A11, S100A12, IL1R2, IFNGR2, TLR2 and CXCL8 and reduced expression of HLA related genes of HLA-DMA, HLA-DPA1, HLA-DPB1, HLA-DRA, HLA-DRB1 and HLA-DRB5. Moreover, cell-chat analysis also showed that CHIT1 + neutrophils could interact with other immune cell types, including NK cells, erythroid cells, monocytes/macrophages, and DC by the way of ICAM1-(ITGAM + ITGB2) pathway. We identified CHIT1 as new biomarker and potential drug target for sepsis, which may intensify hyperinflammation and immune suppression of neutrophils. Developing immunotherapeutic strategies aimed at targeting CHIT1 would help to enhance sepsis outcomes.