Abstract
BackgroundProteomics and bioinformatics may help us better understand the biological adaptations occurring during bovine mastitis. This systems approach also could help identify biomarkers for monitoring clinical and subclinical mastitis. The aim of the present study was to use isobaric tags for relative and absolute quantification (iTRAQ) to screen potential proteins associated with mastitis at late infectious stage.ResultsHealthy and mastitic cows’ mammary gland tissues were analyzed using iTRAQ combined with two-dimensional liquid chromatography-tandem mass spectrometry (2D-LC-MS/MS). Bioinformatics analyses of differentially expressed proteins were performed by means of Gene Ontology, metabolic pathways, transcriptional regulation networks using Blast2GO software, the Dynamic Impact Approach and Ingenuity Pathway Analysis. At a false discovery rate of 5%, a total of 768 proteins were identified from 6,499 peptides, which were matched with 15,879 spectra. Compared with healthy mammary gland tissue, 36 proteins were significantly up-regulated (>1.5-fold) while 19 were significantly down-regulated (<0.67-fold) in response to mastitis due to natural infections with Staphylococci aureus. Up-regulation of collagen, type I, alpha 1 (COL1A1) and inter-alpha (Globulin) inhibitor H4 (ITIH4) in the mastitis-infected tissue was confirmed by Western blotting and Immunohistochemistry.ConclusionThis paper is the first to show the protein expression in the late response to a mastitic pathogen, thus, revealing mechanisms associated with host tissue damage. The bioinformatics analyses highlighted the effects of mastitis on proteins such as collagen, fibrinogen, fibronectin, casein alpha and heparan sulfate proteoglycan 2. Our findings provide additional clues for further studies of candidate genes for mastitis susceptibility. The up-regulated expression of COL1A1 and ITIH4 in the mastitic mammary gland may be associated with tissue damage and repair during late stages of infection.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-839) contains supplementary material, which is available to authorized users.
Highlights
Proteomics and bioinformatics may help us better understand the biological adaptations occurring during bovine mastitis
In this study, we performed a comprehensive evaluation of proteomic profile in the mammary glands of cows infected naturally by S. aureus, providing new data on the in vivo events occurring in the lactating mammary epithelium during persistent infection
Proteomics analysis highlighted the effects of proteins like collagen, fibrinogen, fibronectin, casein alpha and heparan sulfate proteoglycan 2 among others in mammary gland tissues infected naturally by S. aureus
Summary
Proteomics and bioinformatics may help us better understand the biological adaptations occurring during bovine mastitis. This systems approach could help identify biomarkers for monitoring clinical and subclinical mastitis. Mastitis involves a complex set of interactions between an invading pathogen and immune systems of the host. Proteomics and the associated bioinformatics are considered as complimentary tools for the study the dynamic interactions between the immune system and pathogens [4]. Most proteomic studies on mastitis conducted to date have been performed using two-dimensional electrophoresis (2-DE) and liquid chromatography (LC) coupled with tandem mass spectrometry (MS) methods [5,6,7,8] and using milk, serum or somatic cells. Differential expression analysis of the whey from both mastitic and non-mastitic milk revealed a series of proteins including acute phase proteins (APP), lactotransferrin and immunoglobulins that present a marked alternation during infection [6,7]
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