Gene Networks and Pathways Involved in LPS-Induced Proliferative Response of Bovine Endometrial Epithelial Cells

Abstract

Lipopolysaccharide (LPS) is a component of the outer membrane of Gram-negative bacteria involved in the pathogenic processes leading to mastitis and metritis in animals such as dairy cattle. LPS causes cell proliferation associated with endometrium inflammation. Former in vitro studies have demonstrated that LPS induces an intense stimulation of the proliferation of a pure population of bovine endometrial epithelial cells. In a follow-up transcriptomic study based on RNA-sequencing data obtained after 24 h exposure of primary bovine endometrial epithelial cells to 0, 2, and 8 μg/mL LPS, 752 and 727 differentially expressed genes (DEGs) were detected between the controls and LPS-treated samples that encode proteins known to be associated with either proliferation or apoptosis, respectively. The present bioinformatic analysis was performed to decipher the gene networks involved to obtain a deeper understanding of the mechanisms underlying the proliferative and apoptosis processes. Our findings have revealed 116 putative transcription factors (TFs) and the most significant number of interactions between these TFs and DEGs belong to NFKβ1, TP53, STAT1, and HIF1A. Moreover, our results provide novel insights into the early signaling and metabolic pathways in bovine endometrial epithelial cells associated with the innate immune response and cell proliferation to Escherichia coli-LPS infection. The results further indicated that LPS challenge elicited a strong transcriptomic response, leading to potent activation of pro-inflammatory pathways that are associated with a marked endometrial cancer, Toll-like receptor, NFKβ, AKT, apoptosis, and MAPK signaling pathways. This effect may provide a mechanistic explanation for the relationship between LPS and cell proliferation.

Keywords: RNASeq; bovine endometrium epithelial cells; cell proliferation; lipopolysaccharide.

Figure 1

Comparison between different groups following LPS challenge including Control 0 h, Control 24 h, LPS-2 µg/mL 24 h, and LPS-8 µg/mL 24 h. Dots in red show DEGs (adjusted p value < 0.05 from Benjamini-Hochberg correction). Significant means positive log2 fold changes correspond to increased expression, whereas negative values correspond to decreased expression.

Figure 2

Classes of 116 putative expressed TFs in bovine endometrial epithelial cells.

Figure 3

Endometrial cancer pathway obtained from detected DEGs following LPS challenge. Red asterisks () show DEGs in our RNASeq reads. The red font in the figure shows tumor suppressor genes.

Figure 4

Biological pathways related to cell proliferation based on our results. Red denotes upregulated genes and green denotes downregulated genes. MDM2 and Bax (purple circles) were listed in published studies but were not among our detected DEGs. An arrow pointing (blue lines) signifies activation (e.g., binding, phosphorylation); orange lines signify direct protein interactions.