Progesterone and luteinizing hormone secretion following stress-induced interruption of constant estrus in aged rats

Allostatic Load and Preterm Birth

Preterm birth is a universal health problem that is one of the largest unmet medical needs contributing to the global burden of disease. Adding to its complexity is that there are no means to predict who is at risk when pregnancy begins or when women will actually deliver. Until these problems are addressed, there will be no interventions to reduce the risk because those who should be treated will not be known. Considerable evidence now exists that chronic life, generational or accumulated stress is a risk factor for preterm delivery in animal models and in women. This wear and tear on the body and mind is called allostatic load. This review explores the evidence that chronic stress contributes to preterm birth and other adverse pregnancy outcomes in animal and human studies. It explores how allostatic load can be used to, firstly, model stress and preterm birth in animal models and, secondly, how it can be used to develop a predictive model to assess relative risk among women in early pregnancy. Once care providers know who is in the highest risk group, interventions can be developed and applied to mitigate their risk.

Ancestral exposure to stress epigenetically programs preterm birth risk and adverse maternal and newborn outcomes

BACKGROUND

Chronic stress is considered to be one of many causes of human preterm birth (PTB), but no direct evidence has yet been provided. Here we show in rats that stress across generations has downstream effects on endocrine, metabolic and behavioural manifestations of PTB possibly via microRNA (miRNA) regulation.

METHODS

Pregnant dams of the parental generation were exposed to stress from gestational days 12 to 18. Their pregnant daughters (F1) and grand-daughters (F2) either were stressed or remained as non-stressed controls. Gestational length, maternal gestational weight gain, blood glucose and plasma corticosterone levels, litter size and offspring weight gain from postnatal days 1 to 30 were recorded in each generation, including F3. Maternal behaviours were analysed for the first hour after completed parturition, and offspring sensorimotor development was recorded on postnatal day (P) 7. F0 through F2 maternal brain frontal cortex, uterus and placenta miRNA and gene expression patterns were used to identify stress-induced epigenetic regulatory pathways of maternal behaviour and pregnancy maintenance.

RESULTS

Progressively up to the F2 generation, stress gradually reduced gestational length, maternal weight gain and behavioural activity, and increased blood glucose levels. Reduced offspring growth and delayed behavioural development in the stress cohort was recognizable as early as P7, with the greatest effect in the F3 offspring of transgenerationally stressed mothers. Furthermore, stress altered miRNA expression patterns in the brain and uterus of F2 mothers, including the miR-200 family, which regulates pathways related to brain plasticity and parturition, respectively. Main miR-200 family target genes in the uterus, Stat5b, Zeb1 and Zeb2, were downregulated by multigenerational stress in the F1 generation. Zeb2 was also reduced in the stressed F2 generation, suggesting a causal mechanism for disturbed pregnancy maintenance. Additionally, stress increased placental miR-181a, a marker of human PTB.

CONCLUSIONS

The findings indicate that a family history of stress may program central and peripheral pathways regulating gestational length and maternal and newborn health outcomes in the maternal lineage. This new paradigm may model the origin of many human PTB causes.

Gender-dependent effect on nociceptive response induced by chronic variable stress

It has previously been reported that exposure to repeated restraint stress induces hyperalgesia in male rats, an effect that was not observed in females. The aim of the present study was to investigate the effects of chronic variable stress over 40days on nociception threshold indexed by tail-flick latency in male and female adult rats. The results showed different behavior in chronically stressed animals when compared to the control group: male rats showed a decrease in tail-flick latency while females presented an increase in this parameter. For female rats this effect was independent of the phase of the estrous cycle. Several sources of data indicate that behavioral and physiological responses to stress are sexually dimorphic, including in nociception, and the estrous cycle appears to be a factor that influences opioid analgesia in female. These effects are modulated by the strain and conditions of nociception assay. Additional studies concerning the mechanisms involved in the hyperalgesic response in males and the differences on nociceptive response in females chronically exposed to stress are needed.

The progesterone derivative dydrogesterone abrogates murine stress-triggered abortion by inducing a Th2 biased local immune response

Stress is known to induce abortions in mice and humans, putatively via increased levels of abortogenic Th1 cytokines and a decrease of progesterone. Adequate levels of progesterone exert an antiabortive response through binding to the progesterone-receptor, which induces the release of progesterone-induced blocking factor (PIBF) from lymphocytes. PIBF is highly pregnancy-protective by induction of a Th2 biased immune activity. The aim of this study was to investigate the effect of the progesterone derivative dydrogesterone (6-dehydro-retroprogesterone) in stress-triggered murine abortion. DBA/2J-mated CBA/J female mice were randomized in different groups: two groups were treated with different dydrogesterone dosages in a single injection before exposure to sound stress on Day 5 of pregnancy, one group was exposed to stress without dydrogesterone treatment, the fourth group received no stress and no dydrogesterone. On gestation Day 13, a highly elevated abortion rate was detected in stressed mice compared to control mice. Stressed animals presented lower levels of progesterone and PIBF in plasma and a reduced staining intensity of progesterone receptor at the feto-maternal interface. Injection of dydrogesterone abrogated the effect of stress on the abortion rate. Further, dydrogesterone increased levels of plasma PIBF in stressed mice, but did not affect progesterone levels. Interestingly, dydrogesterone dramatically increased the percentage of IL-4 positive decidual immune cells in stressed mice. Our data suggest that dydrogesterone abrogates stress-triggered abortion by inducing a Th2 biased local immune response.

Basal concentrations of various steroids in the nonobese diabetic (NOD) mouse and effect of immobilization stress

The progression of type I diabetes in the NOD mouse is modulated by, among other things, stressful events and steroids. We measured in 2-month-old prediabetic NOD mice various circulating steroids (progesterone, corticosterone, dehydroepiandrosterone, delta4-androstenedione, testosterone, estrone and estradiol) under basal and stressful conditions (1.5h immobilization). Basal progesterone concentrations were low but measurable in randomized cycling NOD females and under the detection limit in NOD males. Immobilization increased progesterone concentrations in both sexes. Serum corticosterone concentrations also increased after immobilization but with the sexual dimorphism normally observed in rodents. Dehydroepiandrosterone concentrations were similar in both sexes and remained unaffected by stress. Testosterone and delta4-androstenedione were drastically reduced after immobilization in NOD males. Serum estrone and estradiol were not found to be statistically different in NOD females and males, but slightly higher to that described in the literature, and immobilization increased estrone concentrations in NOD males. In conclusion, while nonspecific to the NOD mouse, the modulation of circulating corticosteroids, estrogens and androgens induced by environmental factors may be part of the mechanism(s) by which these factors modulate the progression of type I diabetes. The hormonal changes may act in a complex manner at different levels: the immune system, the islet of Langerhans and the other structures involved in glucose homeostasis.

The effects of acute and repeated restraint stress on the nociceptive response in rats

The effects of acute and repeated restraint stress on nociception, as measured by the tail-flick latency, were studied in adult male and female rats. After the exposure to a single restraint session, both male and female rats presented an increased latency in the tail-flick test. On the other hand, chronically stressed females presented a performance similar to the control group, whereas chronically stressed male rats responded to restraint with a decrease in the tail-flick latency. This response could be determined by the chronic treatment itself or by the restraint done just before the measurement. Thus, the effect of chronic stress upon basal tail-flick latency was evaluated. In male rats, this latency was significantly decreased in the stressed animals compared with the control group. In female rats, no difference between those groups was observed. Therefore, the results suggest that: (a) acute restraint stress induces an analgesic response in both male and female rats, and (b) there is a gender-specific nociceptive response induced by repeated restraint stress with a hyperalgesic effect in response to stress only in males.

Effects of acute metabolic stress on plasma progesterone and testosterone in male subjects: relationship to pituitary-adrenocortical axis activation

Stress effects on progesterone and testosterone as well as the relationship of these effects to the hypothalamic-pituitary-adrenal (HPA) axis activation have been extensively investigated in laboratory animals. There is less information about the impact of stress on sex steroids in humans. The purpose of the present study was to examine the influence of acute arterial levels of progesterone, testosterone, adrenocorticotropic hormone (ACTH), cortisol, gonadotropins and sex hormone binding globulin (SHBG) in healthy male subjects. The stressor used was glucoprivation induced by pharmacological doses of 2-deoxy-D-glucose (2DG) (40mg/kg). This stress resulted in increases in progesterone, decreases in testosterone and no significant change in gonadotropins or SHBG. ACTH and cortisol were robustly elevated and these elevations related significantly to changes in progesterone but not testosterone. The implications of these data for the understanding of the role of sex steroids in the stress response is discussed.

Chronic stress increases estrogen and other steroids in inseminated rats

Physical restraint, like many other stressors, can block early pregnancy, but the underlying physiological mechanisms have not been established. Exogenous estrogens in minute doses will also block early pregnancy. In the present study, female rats were exposed to 5 h of restraint daily for the first 5 days after insemination. A subset of animals was sacrificed after 1, 2, 3, 4, and 5 days of restraint, and blood was collected for radioimmunoassay. Blood was also collected from unstressed control animals on each of the first 5 days after insemination. Plasma concentrations of estradiol, as well as those of corticosterone and progesterone, were increased in the stressed animals as compared to the controls. The finding of significantly enhanced maternal estrogen suggests the possibility that estrogens mediate psychogenic pregnancy blocks.

Psychogenic pregnancy disruptions in mammals

Evidence scattered over the literatures of zoology, psychology, agricultural science, and medicine indicates that diverse stressors will interfere with pregnancy in its early stages. It is probable that the most sensitive period is around the point of intrauterine implantation of fertilized ova. Although there is some indication that conventional "stress" hormones of the pituitary-adrenal axis can inhibit implantation, this evidence is too weak and inconsistent to suggest that these hormones are primary mediators of early pregnancy disruptions. Increasingly, evidence indicates that the balance of ovarian steroids is most important for pregnancy maintenance. It is well known that minute amounts of exogenous estrogens can completely disrupt pregnancy, and some new evidence suggests that endogenous estrogens may be released from the adrenals and/or ovaries during psychological stress.

The effects of metabolic stress on plasma progesterone in healthy volunteers and schizophrenic patients

A number of preclinical studies suggest that progesterone may play an important role in the stress response, however, the effects of stress on progesterone in humans has not been established. Also, several lines of evidence indicate that schizophrenia may be associated with abnormal neurobiological responses to stress, but the effects of stress on progesterone in schizophrenia has not been investigated. The purpose of the present study was to examine the effects of stress on plasma progesterone and cortisol in healthy subjects and to determine if schizophrenic patients have altered stress-induced plasma progesterone levels compared to normal controls. Stress was induced through administration of 2-deoxyglucose (2DG), a glucose analog that impairs glucose metabolism resulting in a clinical state comparable to hypoglycemia. There were significant increases in plasma progesterone and cortisol levels following 2DG-induced glucoprivic stress in healthy controls. There was no relationship between stress related progesterone and cortisol elevations. Schizophrenic patients, in comparison to controls, had significantly greater 2DG-induced elevations in progesterone levels but no differences in stress-related cortisol levels. There was evidence that basal progesterone and cortisol levels were elevated in the schizophrenic patients. The implications of these data are discussed.

Reversal of stress-induced pregnancy blocks in mice by progesterone and metyrapone

It is established that diverse psychological stressors administered in the first trimester of pregnancy can cause the pregnancy to fail. The physiological mediators of this phenomenon are unknown. In Experiment 1, two strains of female mice were inseminated and randomly assigned to either first trimester physical restraint, restraint plus progesterone, or control conditions. Restrained females produced fewer pregnancies than did controls, and a reversal of this block through the daily administration of 500 micrograms progesterone was seen in HS but not C57 mice. Experiment 2 demonstrated that exposure to a predator will also block pregnancy in the first trimester in C57 mice, and that this can also be counteracted with progesterone administration. Experiment 3 showed that metyrapone, a drug which blocks the conversion of progesterone to corticosterone, also partially reverses a restraint-induced pregnancy block. These results suggest that lowered progesterone levels may be involved in pregnancy blocks induced by psychological stress.