Selenomethionine increases proliferation and reduces apoptosis in bovine mammary epithelial cells under oxidative stress.

The decline in mammary epithelial cell number as lactation progresses may be due, in part, to oxidative stress. Selenium is an integral component of several antioxidant enzymes. The present study was conducted to examine the effect of oxidative stress and selenomethionine (SeMet) on morphology, viability, apoptosis, and proliferation of bovine mammary epithelial cells (BMEC) in primary culture. Cells were isolated from mammary glands of lactating dairy cows and grown for 3 d in a low-serum gel system containing lactogenic hormones and 0 or 100 µM H2O2 with 0, 10, 20, or 50 nM SeMet. Hydrogen peroxide stress increased intracellular H2O2 to 3 times control concentrations and induced a loss of cuboidal morphology, cell-cell contact, and viability of BMEC by 25%. Apoptotic cell number more than doubled during oxidative stress, but proliferating cell number was not affected. Supplementation with SeMet increased glutathione peroxidase activity 2-fold and restored intracellular H2O2 to control levels with a concomitant return of morphology and viability to normal. Apoptotic BMEC number was decreased 76% below control levels by SeMet and proliferating cell number was increased 4.2-fold. These findings suggest that SeMet modulated apoptosis and proliferation independently of a selenoprotein-mediated reduction of H2O2. In conclusion, SeMet supplementation protects BMEC from H2O2-induced apoptosis and increased proliferation and cell viability under conditions of oxidative stress.

Selenomethionine stimulates expression of glutathione peroxidase 1 and 3 and growth of bovine mammary epithelial cells in primary culture.

This study examined the localization of cellular glutathione peroxidase (GPx1) and extracellular glutathione peroxidase (GPx3) in lactating mammary tissue and in primary cultures of bovine mammary epithelial cells (BMEC). The effect of selenium as selenomethionine (SeMet) on the growth and viability of BMEC and GPx protein expression and activity were also studied. Single mammary epithelial cells were recovered by serial collagenase/hyaluronidase digestion from lactating bovine mammary tissue and cultured in a low-serum collagen gel system enriched with lactogenic hormones and 0, 10, 20, or 50 nM SeMet. Positive immunostaining with anti-cytokeratin and bovine anti-casein confirmed the epithelial nature and differentiated state of BMEC. Addition of SeMet to media facilitated rapid confluence of BMEC and formation of dome structures. Immunohistochemical and immunocytochemical staining revealed that both GPx1 and GPx3 are synthesized by BMEC and localized in the cytoplasm and nucleus. Up to 50 nM SeMet linearly increased BMEC number and viability over 5 d of culture. Bovine mammary epithelial cells cultured in SeMet-supplemented medium also exhibited markedly elevated GPx activity and linear increases in abundance of GPx1 and GPx3 proteins. It is apparent that SeMet degradation to release Se for synthesis of selenoproteins is carried out by BMEC. Results indicate that bovine mammary epithelial cells express GPx1 and GPx3 in vivo and in vitro; SeMet enhances expression of these selenoproteins in vitro and the growth and viability of BMEC.

A preliminary study on the usefulness of huIL-8 in cervical relaxation of the ewe for artificial insemination and for embryo transfer.

The efficacy of using human interleukin 8 (huIL-8) as an agent for inducing cervical relaxation in estrous and diestrous sheep was assessed in a small pilot study. Multiparous, estrus-synchronized ewes were treated for either 2 or 5 consecutive days with vaginal suppositories with or without 5 micrograms cytokine. Cervical penetration with an insemination instrument was then assessed in vivo. After euthanasia, physical, histological and enzymological properties of the cervix were examined. Treatment of diestrous sheep with huIL-8 did not result in recruitment of neutrophils into the cervix. Treatment of estrous sheep with huIL-8 usually led to neutrophil recruitment to the cervix and to either full or partial penetration of the cervix. However, some animals receiving placebo treatment had neutrophil infiltration of both the vagina and cervix and, in one of these, partial penetration of the cervix was also achieved. Thus, treatment with IL-8 as the sole agent in the vaginal suppository was not sufficient to relax the cervix of the nonpregnant ewe in this study.