Effect of cortisol on mammary epithelial cell Bax and Bcl-2 gene expression at lactation peak of goats

• Published in: Journal of animal science Vol. 94; p. 410
• Main Author: Bomfim, G F
• Format: Journal Article
• Language: English
• Published: Champaign Oxford University Press 01-10-2016
• Subjects: Adrenocorticotropic hormone; Animal lactation; Apoptosis; BAX gene; Bcl-2 protein; Biopsy; Caprinae; Cell culture; Epithelial cells; Gene expression; Goats; Hormones; Lactation; Mammary gland; Mitochondria; Polymerase chain reaction; Pretreatment; Statistical analysis; Stress response; Variance analysis
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/jam2016-0852

Cortisol is one of the main hormones that characterize stress, and chronically elevated cortisol can induce apoptosis, as well as expression of Bax (pro-apoptotic), which, in high levels, signals to cellular mitochondria causing cell apoptosis. In contrast, Bcl-2 (anti-apoptotic) acts as a "protector" of cells. Thus, the aim of this study was to analyze the effects of different levels of cortisol on Bax and Bcl-2 expression in mammary epithelial cells. Twenty-four Saanen goats were distributed in two groups: ACTH administration (cortisol group) or placebo (control group), during the lactation peak, i.e., 60 d of lactation. Four goats from each group were submitted to a biopsy of mammary gland after 1 h of treatment administration. Epithelial cells were isolated and four different concentrations of cortisol were added to this culture: 0.0 (control), 10, 100, or 1000 ng/mL. After 5 d, mRNA was extracted and Bax and Bcl-2 gene expression was measured by RT-PCR. Statistical analysis was performed using ANOVA, and significance was declared at P ≤ 0.05. In the cortisol group, there was no effect of pre-treatment on expression of Bax and Bcl-2 in cell culture. However, in the placebo group, there was a significant difference (P < 0.05) in Bax expression, such that at higher levels of cortisol in the culture, Bax expression was lower (2.28 ± 0.58 and 2.01 ± 0.4, respectively, for 100 and 1000 ng/mL), compared to the control (4.38 ± 1.1, 0.0 ng/mL). For Bcl-2 there was no significant difference (P > 0.05). In summary, high levels of cortisol in mammary epithelial cells can interfere with Bax gene expression.