Neutrophils as one of the major haptoglobin sources in mastitis affected milk

Abstract

The antioxidant haptoglobin (Hp) is an acute-phase protein responsive to infectious and inflammatory diseases. Hp and somatic cell counts (SCC) are sharply elevated in bovine milk following intramammary administration of endotoxin or bacteria. However, the sources of milk Hp responsible for such increases are not fully understood. The purpose of this study was to define the source of milk Hp from dairy cows with naturally occurring mastitis. Quarter milk samples selected from 50 dairy cows were separated into four groups according to SCC as group A: < 100 (n = 19); B: 100–200 (n = 10); C: 201–500 (n = 10); and D: > 500 × 103 (n = 11) cells/mL. Our results reveal that milk Hp concentrations were correlated with SCC (r = 0.742; P < 0.01), and concentrations in group D were ~10-fold higher than in group A. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis indicates that the milk somatic cells from group D were not only capable of synthesizing Hp but could also markedly increase Hp mRNA expression. Western blot, immunocytochemistry, double confocal immunofluorescence, and Hp releasing experiments demonstrate that neutrophils were associated with the biosynthesis and release of Hp in milk. It further shows that Hp was significantly elevated in the epithelium of mammary gland tissue with mastitis and was also expressed in the cultured mammary epithelial cells. We propose that neutrophils and epithelial cells may play an essential role in elevating milk Hp in addition to previous suggestions that Hp may be derived from mammary tissues and circulation.

Haptoglobin is an Exercise-Responsive Acute-Phase Protein

“…These neutrophils are then attributed for the release of Hp into the plasma shown in our study. A similar study was conducted by us in cows with mastitis, large accumulation of neutrophils in mammary glands resulted in a marked Hp increase in milk (Lai et al, 2009). We suggest that neutrophils are responsible for the elevated Hp levels in plasma following the exercise.…”

Production and Release of Antimicrobial and Immune Defense Proteins by Mammary Epithelial Cells following Streptococcus uberis Infection of Sheep

“…Lactotransferrin is an iron-binding protein mainly synthesized by MECs and, to a lesser extent, by neutrophils (47), having antibacterial, immune-modulating, antiinflammatory, and antioxidant activity (48,49). Haptoglobin is found to be increased in plasma and in milk in clinical mastitis and in chronic subclinical mastitis, together with amyloid protein A (24), and several studies indicated that one of the main sources of these two proteins in milk might be MECs (50)(51)(52). S100A9 and S100A8 are mainly expressed in the cytoplasm of neutrophils and monocytes but also in activated endothelial and epithelial cells (53)(54)(55)(56)(57)(58)(59).…”

Discovery and Validation of Immunological Biomarkers in Milk for Health Monitoring of Dairy Cows - Results from a Multiomics Approach

“…However, in MC the mRNA expression was still elevated during disease in our experiments. In this case the mammary epithelial cells might be an additional source of HP mRNA [49]. In mammary tissue HP mRNA expression was also found to be increased during mastitis [50].…”