Effects of Lipopolysaccharide Exposure on Gene Expression and Immune Pathways in CD14+ Monocytes

Lipopolysaccharide (LPS) is a major component of the outer membrane of Gram-negative bacteria and can trigger a strong inflammatory response in immune cells. This study investigated how LPS exposure changes gene expression in human CD14+ monocytes and which biological processes and signaling pathways are associated with those changes. RNA-seq data from the GSE87290 dataset were analyzed in RStudio using DESeq2. Gene counts were filtered, normalized, and compared between Pre-LPS and Post-LPS samples. Principal component analysis, sample-to-sample distance heatmaps, and a heatmap of the 30 most variable genes were used to examine overall expression patterns. Differentially expressed genes were identified using an adjusted p-value below 0.05 and an absolute log2 fold change greater than 1. Gene Ontology Biological Process and KEGG pathway enrichment analyses were then performed on upregulated and downregulated genes. The results showed that LPS exposure was the largest source of variation between samples and caused substantially more gene upregulation than downregulation. Strongly upregulated genes included IL1A, IL1B, CCL4, MMP9, and GPR84. Upregulated genes were enriched in immune-related biological processes such as leukocyte-mediated immunity, chemotaxis, and leukocyte migration. KEGG analysis also identified several inflammatory pathways, including cytokine-cytokine receptor interaction, chemokine signaling, TNF signaling, NF-κB signaling, IL-17 signaling, and NOD-like receptor signaling. Overall, these results show that LPS exposure causes broad and coordinated changes in immune-related gene expression and activates multiple inflammatory signaling pathways in CD14+ monocytes.