Chemerin Regulates Epithelial Barrier Function of Mammary Glands in Dairy Cows

SIMPLE SUMMARY: This study evaluated the production and the function of chemerin, known as a chemoattractant and an antimicrobial protein, with regard to mammary epithelial defense in cows. The result demonstrated that mammary epithelial cells express chemerin protein. Chemerin treatment promoted the proliferation of bovine mammary epithelial cells and protected epithelial cells from oxidative stress. Meanwhile, mammary chemerin production was elevated by mastitis, which was possibly attributed to inflammatory cytokines. Therefore, the present study demonstrates the supportive ability of chemerin for mammary epithelial tissue and its regulation by inflammatory stimuli, suggesting its role in mammary epithelial defense against pathogen infection in cows. ABSTRACT: Epithelial barrier function in the mammary gland acts as a forefront of the defense mechanism against mastitis, which is widespread and a major disorder in dairy production. Chemerin is a chemoattractant protein with potent antimicrobial ability, but its role in the mammary gland remains unelucidated. The aim of this study was to determine the function of chemerin in mammary epithelial tissue of dairy cows in lactation or dry-off periods. Mammary epithelial cells produced chemerin protein, and secreted chemerin was detected in milk samples. Chemerin treatment promoted the proliferation of cultured bovine mammary epithelial cells and protected the integrity of the epithelial cell layer from hydrogen peroxide (H(2)O(2))-induced damage. Meanwhile, chemerin levels were higher in mammary tissue with mastitis. Tumor necrosis factor alpha (TNF-α) strongly upregulated the expression of the chemerin-coding gene (RARRES2) in mammary epithelial cells. Therefore, chemerin was suggested to support mammary epithelial cell growth and epithelial barrier function and to be regulated by inflammatory stimuli. Our results may indicate chemerin as a novel therapeutic target for diseases in the bovine mammary gland.