Comparative Proteome Analysis of Serum Uncovers Differential Expression of Proteins in Donkeys (Equus Asinus) With Endometritis Caused by Escherichia Coli.

Endometritis is a common disease in donkeys that causes economic losses to donkey farms and the common cause is bacterial infection. Uterine flush fluid proteomics has been used to study protein biomarkers associated with endometritis in mares. As a convenient diagnostic tool, serum proteomics has not been studied yet in equine species with endometritis. This study is aiming to evaluate the serum proteomics in jennies with and without endometritis and identify potential proteins as biomarker for endometritis diagnosis. Nine donkeys recruited into this study were diagnosed of bacterial (Escherichia coli) endometritis and nine healthy jennies were selected as control. Blood samples of each donkey was collected, and serum was separated from each sample. Peptides samples extracted from the serum were analyzed using nano-ultrahigh-performance liquid chromatography-tandem mass spectrometry in data-independent acquisition mode. Protein identification and quantification were performed followed by differential and functional analysis. Of 579 proteins identified in all jennies, 12 proteins were exclusively identified in jennies with endometritis (group E) including myeloperoxidase and Ras-related protein Rab-1B, which might be associated with bacterial infection. There were 11 differentially expressed proteins detected between the two groups of jennies with 4 downregulated proteins and 7 upregulated proteins in jennies with endometritis. Some upregulated proteins along with the GO and KEGG annotation indicated inflammatory response against uterine infection. Characteristic serum proteins identified in jennies with endometritis were associated with inflammation or bacterial infection. These proteins might be potential biomarkers for endometritis diagnosis in jennies.