Label-free quantitative proteomics analysis of bovine mammary glands induced with Escherichia coli

To establish a model of Escherichia coli-induced bovine mammary gland inflammation and investigate alterations in protein expression in bovine mammary glands under different health conditions.

6 Chinese Holstein cows were selected and randomly assigned to 2 groups. Bovine mammary glands were induced with either 105 CFU/mL E coli (n = 3) or 1 X PBS (n = 3), and label-free quantitative proteomics was applied to explore the effect of E coli on the expression of proteins in bovine mammary glands. Then, these data were combined with transcriptome sequencing data for integrative analysis.

A total of 944 differentially expressed proteins (DEPs) were identified; 588 proteins were upregulated and 356 were downregulated in mastitis tissues compared to healthy tissues. Gene Ontology functional annotations unveiled that the identified DEPs were predominantly enriched in processes, such as the single-organism metabolic process, extracellular region, and catalytic activity. According to Kyoto Encyclopedia of Genes and Genomes enrichment analysis, DEPs were prominently enriched in pathways related to type I diabetes mellitus, graft-versus-host disease, and peroxisome signaling pathways. InterPro analysis identified that the most significantly enriched functional structural domains were the epidermal growth factor-like calcium-binding domains, C-type lectin folds, and C-type lectins. By combining transcriptomic with proteomics data, 7 (cytochrome P450 family 51 subfamily A member 1, ethanolamine kinase 1, carbonic anhydrase 2, complement factor H, indoleamine 2,3-dioxygenase 1, CD5, and IL-33) hub genes (proteins) closely associated with mastitis development were identified.

These findings offer a theoretical basis for understanding the molecular regulatory mechanisms underlying bovine mastitis.

Our study presents a promising approach to understanding the mechanism of E coli infection, with a particular focus on the induction of bovine mastitis.