5-Lipoxygenase, cyclooxygenase-2 and tumor necrosis factor alpha gene expression in somatic milk cells

The goal of this work was to investigate whether different fractions of somatic cells in cow milk do produce prostaglandins, leukotrienes and the cytokine tumor necrosis factor alpha (TNFα) mRNA expressions of TNFα and of key enzymes of prostaglandin and leukotriene biosynthesis, cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LO), respectively, were quantitatively determined. Eleven clinically healthy Brown Swiss cows were either defined as control (C) group (n=5; all quarters < 150000 cells/ml) or as group with partially elevated quarter somatic cell counts (SCC; n=6) with at least 1 quarter > 150 000 cells/ml (H) and 1 quarter < 150000 cells/ml (L). Total quarter milk from 1 quarter of control animals and from 2 quarters of cows with partially elevated SCC (1 of H and 1 of L) was collected. Cells were fractionized into macrophages and lymphocytes (MAC+LYM) and polymorphonuclear leukocytes (PMN) using a density gradient. RNA was isolated, reversely transcribed and quantitative PCR was carried out. mRNA expression was similar for 5-LO, COX-2 and TNFα: no differences between C and L quarters were detected. However, expression was markedly elevated in H quarters. mRNA expression of all parameters tested was higher in MAC+LYM than in the PMN fraction. In conclusion, this investigation underlines that somatic milk cells are able to synthesize 5-LO, COX-2 and TNFα.