Moderate High Temperature Condition Induces the Lactation Capacity of Mammary Epithelial Cells Through Control of STAT3 and STAT5 Signaling

Abstract

In lactating mammary glands, alveolar mammary epithelial cells (MECs) synthesize and secrete milk components. MECs also form less permeable tight junctions (TJs) to prevent the leakage of milk components. During lactation, MECs are exposed to temperature changes by metabolic heat production and air ambient temperature. In this study, we investigated whether temperature changes influence milk production ability and TJ barriers in MECs by using two lactating culture models. The results showed that 39 °C treatment activated milk production and enhanced the formation of less-permeable TJs. In contrast, 41 °C treatment caused adverse effects on the TJ barrier and cell viability, although the milk production ability of MECs was temporarily up-regulated. MECs cultured at 37 °C showed relatively low milk production ability and high proliferation activity. Furthermore, we investigated three kinds of transcription factors relating to lactogenesis, signal transducer and activator of transcription 5 (STAT5), STAT3 and glucocorticoid receptor (GR). STAT5 signaling was activated at 39 and 41 °C by an increase in total STAT5. However, long-term treatment led to a decrease in total STAT5. STAT3 signaling was inactivated by high temperature treatment through a decrease in total STAT3 and inhibited phosphorylation of STAT3. GR signaling was continuously activated regardless of temperature. These results indicate that a moderate high temperature condition at 39 °C induces a high lactation capacity of MECs through control of STAT5 and STAT3 signaling. In contrast, long-term exposure at 41 °C leads to a decline in milk production capacity by inactivation of STAT5 and a decrease in the total number of MECs.

Menthol from Mentha piperita Suppresses the Milk Production of Lactating Mammary Epithelial Cells In Vivo and In Vitro

“…A lactating MEC culture model was prepared as previously reported. [ 27 ] Intracellular and secreted β‐caseins were detected in the MEC layer and the culture medium, respectively, by western blotting ( Figure 2 A). MECs treated with 0.033% PMO showed significant decreases in both intracellular and secreted β‐caseins (Figure 2A,B).…”

“…A culture model of lactating MECs was prepared as previously reported. [ 27 ] Briefly, MECs were isolated from the mammary glands of virgin mice by collagenase treatment and the low spin centrifugation in 50% fetal bovine serum (Thermo Fisher Scientific). MECs were cultured in RPMI‐1640 supplemented with 10% fetal bovine serum (GIBCO‐BRL, Grand Island, NY), 10 μg mL −1 insulin (Sigma‐Aldrich), 10 ng mL −1 epidermal growth factor (BD Biosciences, San Diego, CA), 100 U/mL penicillin (GIBCO‐BRL, Grand Island, NY), and 100 μg mL −1 streptomycin (GIBCO) at 37 °C on a cell culture insert in a 24‐well plate (0.4‐μm pore size; Falcon, Thermo Fisher Scientific).…”

TRPV4 Increases the Expression of Tight Junction Protein-Encoding Genes via XBP1 in Mammary Epithelial Cells

“…Mild heat stress (39 • C-40 • C) can positively regulate cell proliferation and differentiation [6]. Indeed, a previous study has shown that heat-shock at 39 • C has activated milk production and enhanced the formation of less-permeable TJs [7,8]. However, detailed molecular mechanisms of the mammary epithelial cell response to mild heat shock have not yet been elucidated.…”

Mild heat stress induces transcription of the β‐casein gene via unfolded protein response‐activated XBP1 signaling in undifferentiated mammary epithelial cells

“…Recent studies have reported that the expression of milk protein β‐casein is increased by mild heat treatment at 39°C in mammary epithelial cells (Kobayashi et al, ), although the detailed mechanism is unknown. Our previous studies suggested that UPR factors, XBP1 and ATF4, regulate the differentiation of mammary epithelial cells by controlling the expression of lactogenic hormones (Tsuchiya et al, ; Yonekura et al, ).…”

“…Secretory epithelial cells, including sweat glands and salivary glands, have been found to exhibit temperature-dependent changes (DiPasquale, Buono, & Kolkhorst, 2003;Elishoov, Wolff, Kravel, Shiperman, & Gorsky, 2008). In mammary epithelial cells, the expression of β-casein, a representative milk protein, increases under mild heat stress (39°C) (Kobayashi, Tsugami, Matsunaga, Suzuki, & Nishimura, 2018). These findings suggest that the physiological functions of mammary epithelial cells may change with temperature.…”