Stress-Induced Suppression of Milk Protein Is Involved in a Noradrenergic Mechanism in the Mammary Gland

Acute and chronic sleep restriction differentially modify maternal behavior and milk macronutrient composition in the postpartum rat

BACKGROUNDS

Sleep restriction is considered a stressful condition itself, causing a wide variety of physiological alterations, from cognitive and hormonal to immunological status. In addition, it is established that stress in mother rats can modify milk ejection, milk composition, and maternal care of the pups. Also, sleep disturbances during the early stages of motherhood are a common feature of all studied species. In this context, while the impacts of sleep disruption in non-lactating animals were extensively investigated, its repercussions during the initial phases of motherhood have been poorly explored. Therefore, we wonder if maternal behavior, milk ejection and its macronutrient composition would be disrupted when mother rats are subjected to an additional acute or chronic sleep restriction to the already existing sleep disturbances.

METHODS

Lactating rats were implanted with unilateral electrodes for polysomnographic recordings and for deep brain electrical stimulation into mesopontine waking-promoting area (for sleep deprivation). During the early postpartum period (postpartum day 5-9), mother rats were randomly assigned into one of three groups: chronic sleep restriction group (CSR; 6 h of sleep deprivation/day for five consecutive days), acute sleep restriction group (ASR; 6 h of sleep deprivation only for one day), or undisturbed group (control group). Active maternal behaviors (retrievals of the pups into the nest, mouthing, lickings [corporal and anogenital] and sniffing the pups) and passive maternal behaviors (kyphotic and supine nursing postures) were evaluated during a 30 min period without sleep restriction immediately after the sleep restriction or control period. The litter weight gain was assessed every day, and on the last experimental session mothers were milked for posterior macronutrients analysis (protein, carbohydrates and fat).

RESULTS

When compared to control group, CSR decreased the amount of milk ejected in the middle days of the sleep restriction period, while ASR did not affect this parameter. Moreover, ASR reduced milk protein content compared to control and CSR groups. Finally, compared to the control group, CSR reduced active maternal behaviors towards the end of the treatment days.

CONCLUSIONS

We demonstrated that not only acute but also chronic sleep restriction impacts on the postpartum period, each one affecting different aspects of maternal behavior and lactation. Our results suggest the existence of a homeostatic recovery mechanism in breastfeeding during CSR, possibly ensuring the survival of the litter, while the decline in active maternal behaviors appears to be cumulative.

β2-Adrenoceptor Activation Favor Acquisition of Tumorigenic Properties in Non-Tumorigenic MCF-10A Breast Epithelial Cells

Noradrenaline and adrenaline, and their cognate receptors, are currently accepted to participate in cancer progression. They may also participate in cancer initiation, although their role in this phase is much less explored. The aim of this work was to study the influence of adrenergic stimulation in several processes related to breast cancer carcinogenesis, using several adrenergic agonists in the MCF-10A non-tumorigenic breast cells. Activation of the β-adrenoceptors promoted an epithelial phenotype in MCF-10A cells, revealed by an increased expression of the epithelial marker E-cadherin and a decrease in the mesenchymal markers, N-cadherin and vimentin. MCF-10A cell motility and migration were also impaired after the β-adrenoceptors activation. Concomitant with this effect, β-adrenoceptors decrease cell protrusions (lamellipodia and filopodia) while increasing cell adhesion. Activation of the β-adrenoceptors also decreases MCF-10A cell proliferation. When the MCF-10A cells were cultured under low attachment conditions, activation the of β- (likely β2) or of α2-adrenoceptors had protective effects against cell death, suggesting a pro-survival role of these adrenoceptors. Overall, our results showed that, in breast cells, adrenoceptor activation (mainly through β-adrenoceptors) may be a risk factor in breast cancer by inducing some cancer hallmarks, providing a mechanistic explanation for the increase in breast cancer incidences that may be associated with conditions that cause massive adrenergic stimulation, such as stress.

Human Milk Exosomes Induce ZO-1 Expression via Inhibition of REDD1 Expression in Human Intestinal Epithelial Cells

Human milk exosomes (HMEs) enhance intestinal barrier function and contribute to an improvement in inflammation and mucosal injury, such as necrotizing enteritis (NEC), in infants. Here, we aimed to elucidate the intracellular factors involved in HME-induced expression of zonula occludens-1 (ZO-1), a tight junction protein, in Caco-2 human intestinal epithelial cells. HME treatment for 72 h significantly increased transepithelial electrical resistance in these cells. The mean ZO-1 protein levels in cells treated with HME for 72 h were significantly higher than those in the control cells. The mRNA and protein levels of regulated in development and DNA damage response 1 (REDD1) in HME-treated cells were significantly lower than those in the control cells. Although HME treatment did not increase the mechanistic target of rapamycin (mTOR) level in Caco-2 cells, it significantly increased the phosphorylated mTOR (p-mTOR) level and p-mTOR/mTOR ratio. The ZO-1 protein levels in cells treated with an inducer of REDD1, cobalt chloride (CoCl₂) alone were significantly lower than those in the control cells. However, ZO-1 protein levels in cells co-treated with HME and CoCl₂ were significantly higher than those in cells treated with CoCl₂ alone. Additionally, REDD1 protein levels in cells treated with CoCl₂ alone were significantly higher than those in the control cells. However, REDD1 protein levels in cells co-treated with HME and CoCl₂ were significantly lower than those in cells treated with CoCl₂ alone. This HME-mediated effect may contribute to the development of barrier function in the infant intestine and protect infants from diseases.

Suppression of milk-derived miR-148a caused by stress plays a role in the decrease in intestinal ZO-1 expression in infants

BACKGROUND & AIMS

Milk-derived miR-148a-3p (miR-148a), which is abundant in breast milk, has been shown to be associated with the development of infants' intestines. Although it is well known that stress during lactation changes milk constituents in terms of lipid and protein, no studies have examined the influence of stress on miR-148a expression in breast milk. The objective of this study is to investigate the relationship between stress and miR-148a expression in milk, and to evaluate whether the changes in milk-derived miR-148a expression-caused by the mother's exposure to stress-influence intestinal ZO-1 expression in infants.

METHODS

The participants of this study were healthy Japanese women who were nursing. Psychological stress evaluation of the subjects was conducted using a short form of the Profile of Mood State Second Edition-Adult (POMS-2). Additionally, miR-148a expressions in restraint stressed nursing mice were investigated using quantitative real-time PCR. The levels of a tight junction protein zonula occludens-1 (ZO-1) and DNA methyltransferase 1 (DNMT1), which is a direct target of miR-148a, in ileum in neonatal mice breastfed by stressed nursing mice were investigated using Western blot. Furthermore, to investigate the influence of miR-148a on ZO-1 expression within the intestine, the levels of ZO-1 and DNMT1 in human intestinal epithelial Caco-2 cells with lentivirus-mediated miR-148a overexpression were evaluated.

RESULTS

A significantly negative correlation was observed between relative miR-148a expression in breast milk and the total mood disturbance T-score. Each T-score on negative mood subscales of anger-hostility, confusion-bewilderment, depression-dejection, fatigue-inertia, and tension-anxiety was significantly negatively correlated with relative miR-148a expression in breast milk: a positive mood subscale vigor-activity T-score was significantly positively correlated with relative miR-148a expression in breast milk. A positive mood friendliness T-score, estimated separately from other scores, was significantly positively correlated with relative miR-148a expression in breast milk. Additionally, the relative expression of miR-148a in the milk obtained from stressed mice was significantly lower than that of control mice. The relative level of ZO-1 in ileum of neonatal mice nursed by stressed mice was significantly lower than that of neonatal mice nursed by control mice. Additionally, the relative level of DNMT1 in ileum of neonatal mice nursed by stressed mice was significantly higher than that of neonatal mice nursed by control mice. Furthermore, the relative level of ZO-1 in miR-148a-overexpressed Caco-2 cells was significantly higher than that in control cells. The relative level of DNMT1 in miR-148a-overexpressed Caco-2 cells was significantly lower than that in control cells.

CONCLUSIONS

Mothers' exposure to stress during lactation may cause miR-148a expression in breast milk. Additionally, stressed-induced suppression of miR-148a expression in breast milk may cause a decrease in intestinal ZO-1 level via the increase in DNMT1 in infants' intestines. These observations are beneficial information for breastfeeding mothers and their families and perinatal medical professionals. Our findings encourage monitoring maternal psychological stress during lactation to promote breastfeeding and adequate infant nutrition.

Milking It for All It's Worth: The Effects of Environmental Enrichment on Maternal Nurturance, Lactation Quality, and Offspring Social Behavior

Breastfeeding confers robust benefits to offspring development in terms of growth, immunity, and neurophysiology. Similarly, improving environmental complexity, i.e., environmental enrichment (EE), contributes developmental advantages to both humans and laboratory animal models. However, the impact of environmental context on maternal care and milk quality has not been thoroughly evaluated, nor are the biological underpinnings of EE on offspring development understood. Here, Sprague Dawley rats were housed and bred in either EE or standard-housed (SD) conditions. EE dams gave birth to a larger number of pups, and litters were standardized and cross-fostered across groups on postnatal day (P)1. Maternal milk samples were then collected on P1 (transitional milk phase) and P10 (mature milk phase) for analysis. While EE dams spent less time nursing, postnatal enrichment exposure was associated with heavier offspring bodyweights. Milk from EE mothers had increased triglyceride levels, a greater microbiome diversity, and a significantly higher abundance of bacterial families related to bodyweight and energy metabolism. These differences reflected comparable transcriptomic changes at the genome-wide level. In addition to changes in lactational quality, we observed elevated levels of cannabinoid receptor 1 in the hypothalamus of EE dams, and sex-dependent and time-dependent effects of EE on offspring social behavior. Together, these results underscore the multidimensional impact of the combined neonatal and maternal environments on offspring development and maternal health. Moreover, they highlight potential deficiencies in the use of "gold standard" laboratory housing in the attempt to design translationally relevant animal models in biomedical research.

Contribution of adrenergic mechanisms for the stress-induced breast cancer carcinogenesis

Breast cancer is the most common and deadliest type of cancer in women. Stress exposure has been associated with carcinogenesis and the stress released neurotransmitters, noradrenaline and adrenaline, and their cognate receptors, can participate in the carcinogenesis process, either by regulating tumor microenvironment or by promoting systemic changes. This work intends to provide an overview of the research done in this area and try to unravel the role of adrenergic ligands in the context of breast carcinogenesis. In the initiation phase, adrenergic signaling may favor neoplastic transformation of breast epithelial cells whereas, during cancer progression, may favor the metastatic potential of breast cancer cells. Additionally, adrenergic signaling can alter the function and activity of other cells present in the tumor microenvironment towards a protumor phenotype, namely macrophages, fibroblasts, and by altering adipocyte's function. Adrenergic signaling also promotes angiogenesis and lymphangiogenesis and, systemically, may induce the formation of preneoplastic niches, cancer-associated cachexia and alterations in the immune system which contribute for the loss of quality of life of breast cancer patients and their capacity to fight cancer. Most studies points to a major contribution of β₂ -adrenoceptor activated pathways on these effects. The current knowledge of the mechanistic pathways activated by β₂ -adrenoceptors in physiology and pathophysiology, the availability of selective drugs approved for clinical use and a deeper knowledge of the basic cellular and molecular pathways by which adrenergic stimulation may influence cancer initiation and progression, opens the possibility to use new therapeutic alternatives to improve efficacy of breast cancer treatments.

Expression profiles of hsa-miR-148a-3p and hsa-miR-125b-5p in human breast milk and infant formulae

Background

Milk-derived microRNAs (miRNAs), including hsa-miR-148a-3p (miR-148a) and hsa-miR-125b-5p (miR-125b), have been shown to be beneficial to the gastrointestinal function in infants. Here, we investigated their expression during lactation in humans and determined whether the infant formulae available in Japan contain these miRNAs.

Methods

Healthy Japanese women (n = 16) who gave birth vaginally or by cesarean section at the Teine Keijinkai Hospital between 1 September 2020, and 31 April 2021 were included in this study. Breast milk was collected by nurses on days 4 or 5 after delivery (hereinafter, transition milk) and on day 30 of postpartum (hereinafter, mature milk). The levels of miR-148a and miR-125b in breastmilk and six commercially available infant formulae were compared and evaluated using quantitative reverse transcription-polymerase chain reaction.

Results

In all participants, the miR-148a level in mature breastmilk was significantly lower than that in the transition milk. The changes in miR-125b expression during lactation showed similar trends to the changes in miR-148a expression. The miR-148a and miR-125b levels in all analyzed infant formulae were lower than 1/500th and 1/100th of those in mature breastmilk, respectively.

Conclusions

The levels of both miR-148a and miR-125b in human breast milk decreased on day 30 postpartum compared with those in the transition milk. Additionally, the expression of these miRNAs in infant formulae available in Japan was very low. Further studies with larger populations are required to understand precisely the lactational changes in the expression of miR148a and miR-125b in breast milk.

Norepinephrine transporter expressed on mammary epithelial cells incorporates norepinephrine in milk into the cells

Mammary epithelial cells synthesize and secrete norepinephrine (NE) into breast milk to regulate β-casein expression through the adrenergic β₂ receptor. We investigated the expression, localization, and roles of NE transporter (NET) in the mammary epithelium during lactation. mRNA and protein levels of NET were determined in primary normal human mammary epithelial cells (pHMECs) and non-malignant human mammary epithelial MCF-12A cells. In nursing CD1 mice, NET localized to the apical membranes of the mammary epithelium. The intracellular NE content of pHMECs incubated with NE increased. Although the β-casein concentration in milk was slightly higher at day 10 than at day 2 of lactation, the NE concentration and lactation-related proteins were only slightly changed on days 2-10. Restraint stress increased the NE concentration in milk from nursing mice and NET protein levels were significantly higher than in non-stressed nursing mice. NET is expressed on the apical membrane of mammary epithelial cells and incorporates NE in milk into cells, potentially regulating the NE concentration in milk.

β-Adrenoceptor Activation in Breast MCF-10A Cells Induces a Pattern of Catecholamine Production Similar to that of Tumorigenic MCF-7 Cells

Adrenaline, which participates in the neuroendocrine response that occurs during stress and perimenopause, may be tumorigenic. This exploratory study aimed at investigating whether non-tumorigenic and tumorigenic human breast epithelial cell lines are able to synthesize adrenaline. The study was carried out in non-tumorigenic (MCF-10A) and tumorigenic (MCF-7) human breast cell lines. Expression of enzymes involved in adrenaline synthesis was characterized by RT-qPCR, immunocytochemistry and western blot. Catecholamines and analogue compounds were quantified by HPLC-ECD. Functional assessment of the impact of drugs on cells’ tumorigenic potential was assessed by determination of cell viability and clonogenic ability. Both MCF-10A and MCF-7 cells produce catecholamines, but the capacity to produce adrenaline is lower in MCF-10A cells. β-adrenoceptor activation increases the capacity of MCF-10A cells to produce adrenaline and favor both cell viability and colony formation. It is concluded that exposure of human breast epithelial cells to β-adrenoceptor agonists increases cell proliferation and the capacity to produce adrenaline, creating an autocrine potential to spread these adrenergic effects in a feed-forward loop. It is conceivable that these effects are related to tumorigenesis, bringing a new perspective to understand the claimed anticancer effects of propranolol and the increase in breast cancer incidence caused by stress or during perimenopause.