Serum concentration and mRNA expression in milk somatic cells of toll-like receptor 2, toll-like receptor 4, and cytokines in dairy cows following intramammary inoculation with Escherichia coli

• Published in: Journal of dairy science Vol. 94; no. 12; pp. 5903 - 5912
• Main Authors: Ma, J.L., Zhu, Y.H., Zhang, L., Zhuge, Z.Y., Liu, P.Q., Yan, X.D., Gao, H.S., Wang, J.F.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.12.2011; Elsevier
• Subjects: acute phase proteins; amyloid; Animal productions; Animals; Biological and medical sciences; blood serum; bovine mastitis; Cattle; cytokine; Cytokines - analysis; Cytokines - blood; dairy cows; enzyme-linked immunosorbent assay; Enzyme-Linked Immunosorbent Assay - veterinary; Escherichia coli; Escherichia coli Infections - immunology; Escherichia coli Infections - metabolism; Escherichia coli Infections - veterinary; Female; Food industries; Fundamental and applied biological sciences. Psychology; gene expression; genes; Holstein; immune response; interleukin-1beta; interleukin-6; Interleukin-6 - analysis; Interleukin-6 - blood; interleukin-8; leukocytes; mastitis; Mastitis, Bovine - blood; Mastitis, Bovine - immunology; Mastitis, Bovine - microbiology; messenger RNA; milk; Milk - chemistry; Milk - cytology; Milk and cheese industries. Ice creams; quantitative polymerase chain reaction; Real-Time Polymerase Chain Reaction - veterinary; receptors; RNA, Messenger - analysis; Serum Amyloid A Protein - analysis; somatic cells; temperature; Terrestrial animal productions; toll-like receptor; Toll-Like Receptor 2 - analysis; Toll-Like Receptor 2 - blood; Toll-Like Receptor 4 - analysis; Toll-Like Receptor 4 - blood; tumor necrosis factor-alpha; Tumor Necrosis Factor-alpha - analysis; Tumor Necrosis Factor-alpha - blood; Vertebrates; cytokine; toll-like receptor; bovine mastitis; Escherichia coli; Mastitis; Farming animal; Dairy cattle; Cytokine; Dairy product; Somatic cell; Concentration; Vertebrata; Inoculation; Mammalia; Dairy industry; Bacteria; Serum; Artiodactyla; Ungulata; Enterobacteriaceae; Milk
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2011-4167

The objective of the current study was to investigate the toll-like receptors (TLR), including the soluble forms sTLR2 and sTLR4, involved in innate immune responses of dairy cows to experimentally induced Escherichia coli mastitis. Six clinically healthy Holstein dairy cows received an intramammary inoculation of E. coli O111:K58 between 63 and 83 d postpartum. Concentrations of sTLR2 and sTLR4, the proinflammatory cytokines IL-6 and tumor necrosis factor-α (TNF-α), and acute phase proteins serum amyloid A (SAA) and haptoglobin (Hp) in blood were measured by ELISA. Furthermore, 10mL of milk was collected from challenged quarters immediately before inoculation and at 6, 12, 24, 48, and 72h after inoculation, and mRNA expression of selected genes, including TLR2, TLR4, IL-1β, IL-6, TNF-α, and IL-8, was quantified by real-time PCR. Escherichia coli intramammary infection elicited a decrease in the circulating levels of leukocytes. Rectal temperature was elevated at 6h postinoculation (PI). Similarly, the serum concentrations of TNF-α, IL-6, and SAA increased at 6h PI. However, serum concentrations of sTLR2, sTLR4, and Hp did not differ after challenge. The mRNA expression of TLR2, IL-1β, and IL-8 in milk somatic cells increased at 12h PI, whereas a decreased IL-6 mRNA expression was detected from 6 to 48h PI. In conclusion, we found that TLR2 mRNA expression increased in milk somatic cells collected from infected quarters of cows challenged with E. coli, whereas the concentrations of sTLR2 and sTLR4 remained unchanged after challenge. Thus, sTLR2 and sTLR4 may protect the host by sequestrating pathogen-associated molecular patterns during E. coli mastitis.