Short communication: opposing effects of lactoferrin on the proliferation of fibroblasts and epithelial cells from bovine mammary gland.

Lactoferrin is present in several physiologic fluids, including milk and colostrum. Recently, evidence has accumulated that lactoferrin acts as a regulator of cell proliferation. Lactoferrin mRNA and protein levels in bovine mammary glands are known to markedly increase after cessation of milking. To clarify the role of bovine lactoferrin (bLF) in mammary involution and remodeling during dry periods, we investigated whether bLF affects the proliferation of cultured cells derived from bovine mammary gland and examined the mechanism underlying the proliferative response to bLF. Addition of bLF to the culture medium increased the proliferation of bovine mammary stromal fibroblasts (bMSF), but decreased that of bovine mammary epithelial cells (bMEC). Proliferation was significantly increased in the bMSF treated with bLF (100µg/mL or greater) as compared with unstimulated cells. The maximal proliferative effect of bLF on bMSF occurred at 1,000µg/mL, such that the proliferation of the bLF-stimulated bMSF was approximately 2.5 times that of unstimulated cells. The bLF increased the production of proliferating cell nuclear antigen and rapid phosphorylation of the p44/p42 mitogen-activated protein kinase in bMSF, but not in bMEC. The bLF-induced proliferation and production of proliferating cell nuclear antigen in bMSF was suppressed by U0126, a specific inhibitor of mitogen-activated protein kinase. Furthermore, treatment with bLF for 24h decreased the mRNA levels of the 3 isoforms of transforming growth factor ß in bMSF (16-66%) but upregulated those in bMEC (122-157%). These opposite effects of bLF on the proliferation of epithelial and fibroblast cells and their expression of transforming growth factor ß may play a crucial role in bovine mammary involution and remodeling.

Cloning, expression analysis, and regulatory mechanisms of bovine chemerin and chemerin receptor.

Recently, we reported that chemerin, a new adipokine, is highly expressed in the adipose tissue, up-regulated during adipocyte differentiation, and regulates adipogenesis via its own receptor in mice. The objectives of this study were to clone chemerin and its receptor from the adipose tissues of Japanese Black cattle and to investigate the expression of these genes in 16 different tissues. We compared the gene expression of chemerin and its receptor between adipocytes and stromal-vascular (S-V) cells (non-adipocytes) prepared from subcutaneous adipose tissue. In addition, we investigated the mRNA expression levels of chemerin and its receptor in bovine differentiated adipocytes. The DNA sequences of bovine chemerin and its receptor were determined, and they were found to be highly homologous to those of humans, mice, and pigs. The amino acid sequences predicted for the full-length cDNA of bovine chemerin and its receptor were also similar to those of humans, mice, and pigs, suggesting that these genes have similar functions. Bovine chemerin mRNA was highly expressed in the adipose and liver tissues, and the transcripts of chemerin receptor were widely expressed in several tissues including adipose, muscle, liver, and brain tissues. The expression of bovine chemerin mRNA was higher in adipocytes than in S-V cells prepared from adipose tissue. The transcripts of chemerin and its receptor were up-regulated during adipocyte differentiation. Treatment with tumor necrosis factor (TNF)-alpha (10 ng/mL) in bovine differentiated adipocytes increased the mRNA expression of chemerin and its receptor. These results indicate that chemerin, a new adipokine highly expressed in the adipocytes of bovine adipose tissue, is the TNF-alpha-up-regulated gene with a role in adipogenesis.