Leukocyte transcriptional signatures dependent on LPS dosage in human endotoxemia

Abstract

The host immune response is characterized by a complex interplay of signal‐specific cellular transcriptional responses. The magnitude of the immune response is dependent on the strength of the external stimulus. Knowledge on leukocyte transcriptional responses altered in response to different stimulus dosages in man is lacking. Here, we sought to identify leukocyte transcriptional signatures dependent on LPS dose in humans. Healthy human volunteers were administered 1 ng/kg (n = 7), 2 ng/kg (n = 6), or 4 ng/kg (n = 7) LPS intravenously. Blood was collected before (pre‐LPS) and 4 h after LPS administration. Total RNA was analyzed by microarrays and generalized linear models. Pathway analysis was performed by using Ingenuity pathway analysis. Leukocyte transcriptomes altered per LPS dosage were predominantly shared, with 47% common signatures relative to pre‐LPS. A univariate linear model identified a set of 3736 genes that exhibited a dependency on differing LPS dosages. Neutrophil, monocyte, and lymphocyte counts explained 38.9% of the variance in the LPS dose‐dependent gene set. A multivariate linear model including leukocyte composition delineated a set of 295 genes with a dependency on LPS dose. Evaluation of the 295 gene signature in patients with sepsis due to abdominal infections showed significant correlations. Promoter regions of the LPS dose gene set were enriched for YY1, EGR1, ELK1, GABPA, KLF4, and REL transcription factor binding sites. Intravenous injection of 1, 2, or 4 ng/kg LPS was accompanied by both shared and distinct leukocyte transcriptional alterations. These data may assist in assessing the severity of the insult in patients with abdominal sepsis.

Sex-specific differences in peripheral blood leukocyte transcriptional response to LPS are enriched for HLA region and X chromosome genes

“…This was largely driven by lower gene expression levels in the vehicle-treated cells and larger responses to LPS treatment in males, resulting in similar gene expression levels between males and females in LPS-treated cells. This is consistent with previous studies reporting stronger cytokine responses to LPS in males compared to females 46,54,55 . For example, a study of sex differences in cytokine secretion in response to LPS reported significantly greater TNF, IL-1, IL-8, and IFN γ production in males compared to females (n = 72 and 82, respectively, both adjusted and unadjusted for cell counts and independent of age effects 56 ).…”

“…A direct comparison of these findings to similar studies is not possible owing to differences in study design. For example, previous studies of LPS exposure in humans were not population-based [43][44][45][46] , did not look at sex-specific differences in response 44,46 , and/or did not include the X chromosome 44 . One additional study assessed sex-specific differences in gene expression in the presence of immune stimulators but did not include LPS and focused on only a panel of immune-response genes 17 , and one study included X-linked genes in sex-specific eQTL studies but did not examine stimulated cells 18 .…”

A Novel Single Cell RNA-seq Analysis of Non-Myeloid Circulating Cells in Late Sepsis

“…We also observed that the majority of the downregulated differentially expressed genes in non-myeloid cells of late sepsis encode for glycolytic, ribosomal and mitochondrial proteins. Previous studies report similar alterations in leukocyte transcriptomic profiles in early inflammation (72,73). However, the perseverance of this transcriptome has not been well delineated in late sepsis.…”

Combined Transcriptome and Proteome Leukocyte’s Profiling Reveals Up-Regulated Module of Genes/Proteins Related to Low Density Neutrophils and Impaired Transcription and Translation Processes in Clinical Sepsis

“…First, the transcripts were collapsed to unique genes by calculating the mean expression of transcripts from the same gene locus using tidyverse and dplyr packages. The annotation file used to map the probes to genes was previously published in Khan, Perlee ( 18 ). Comparisons were performed using limma with Benjamini-Hochberg (BH) adjusted p-value < 0.05 and Log 2 Fold-Change (FC) < −0.26 or > 0.26 significance thresholds.…”