Hernán E. Lara

Stress and the Reproductive Axis

There exists a reciprocal relationship between the hypothalamic‐pituitary‐adrenal (HPA) and the hypothalamic‐pituitary‐gonadal (HPG) axes, wherein the activation of one affects the function of the other and vice versa. For example, both testosterone and oestrogen modulate the response of the HPA axis, whereas activation of the stress axis, especially activation that is repeating or chronic, has an inhibitory effect upon oestrogen and testosterone secretion. Alterations in maternal care can produce significant effects on both HPG and HPA physiology, as well as behaviour in the offspring at adulthood. For example, changes in reproductive behaviour induced by altered maternal care may alter the expression of sex hormone receptors such as oestrogen receptor (ER)α that govern sexual behaviour, and may be particularly important in determining the sexual strategies utilised by females. Stress in adulthood continues to mediate HPG activity in females through activation of a sympathetic neural pathway originating in the hypothalamus and releasing norepinephrine into the ovary, which produces a noncyclic anovulatory ovary that develops cysts. In the opposite direction, sex differences and sex steroid hormones regulate the HPA axis. For example, although serotonin (5‐HT) has a stimulatory effect on the HPA axis in humans and rodents that is mediated by the 5‐HT1A receptor, only male rodents respond to 5‐HT1A antagonism to show increased corticosterone responses to stress. Furthermore, oestrogen appears to decrease 5‐HT1A receptor function at presynaptic sites, yet increases 5‐HT1A receptor expression at postsynaptic sites. These mechanisms could explain the heightened stress HPA axis responses in females compared to males. Studies on female rhesus macaques show that chronic stress in socially subordinate female monkeys produces a distinct behavioural phenotype that is largely unaffected by oestrogen, a hyporesponsive HPA axis that is hypersensitive to the modulating effects of oestrogen, and changes in 5‐HT1A receptor binding in the hippocampus and hypothalamus of social subordinate female monkeys that are restored or inverted by oestrogen replacement. This review summarises all of these studies, emphasising the profound effect that the interaction of the reproductive and stress axes may have on human reproductive health and emotional wellbeing.

Beta2-adrenergic receptor regulates cardiac fibroblast autophagy and collagen degradation

Autophagy is a physiological degradative process key to cell survival during nutrient deprivation, cell differentiation and development. It plays a major role in the turnover of damaged macromolecules and organelles, and it has been involved in the pathogenesis of different cardiovascular diseases. Activation of the adrenergic system is commonly associated with cardiac fibrosis and remodeling, and cardiac fibroblasts are key players in these processes. Whether adrenergic stimulation modulates cardiac fibroblast autophagy remains unexplored. In the present study, we aimed at this question and evaluated the effects of b(2)-adrenergic stimulation upon autophagy. Cultured adult rat cardiac fibroblasts were treated with agonists or antagonists of beta-adrenergic receptors (b-AR), and autophagy was assessed by electron microscopy, GFP-LC3 subcellular distribution, and immunowesternblot of endogenous LC3. The predominant expression of b(2)-ARs was determined and characterized by radioligand binding assays using [(3)H]dihydroalprenolol. Both, isoproterenol and norepinephrine (non-selective b-AR agonists), as well as salbutamol (selective b(2)-AR agonist) increased autophagic flux, and these effects were blocked by propanolol (b-AR antagonist), ICI-118,551 (selective b(2)-AR antagonist), 3-methyladenine but not by atenolol (selective b(1)-AR antagonist). The increase in autophagy was correlated with an enhanced degradation of collagen, and this effect was abrogated by the inhibition of autophagic flux. Overall, our data suggest that b(2)-adrenergic stimulation triggers autophagy in cardiac fibroblasts, and that this response could contribute to reduce the deleterious effects of high adrenergic stimulation upon cardiac fibrosis.

Role of stress and sympathetic innervation in the development of polycystic ovary syndrome

This article presents a review of the role of the sympathetic activity in ovarian pathologies affecting reproductive function. We provide a succinct outline of the findings of our group in this area. The participation of stress as an etiological factor for ovarian pathologies throughout animal models and data in patients with polycystic ovary syndrome give strong support for participation of sympathetic nerves in the ovary function both in normal and pathological status.

Placental steroidogenesis in pregnant women with polycystic ovary syndrome

OBJECTIVE To evaluate the placental activity of steroid sulfatase (STS), 3β-hydroxysteroid dehydrogenase type 1 (3β-HSD-1) and P450 aromatase (P450arom) in polycystic ovarian syndrome (PCOS) compared to normal pregnant women. DESIGN Twenty pregnant women with PCOS and 30 control pregnant women who delivered at term were studied. Samples of placental tissue and cord blood were obtained after delivery. A maternal blood sample was obtained during the 34th week of gestation. In placental tissue, the activities of STS, 3β-HSD-1 and P450arom were evaluated. In the blood samples, progesterone, DHEAS, DHEA, androstenedione, testosterone, estrone, estradiol and total estriol were determined. RESULT In placental tissue from women with PCOS, higher 3β-HSD-1 and lower P450 aromatase activities were observed compared to control women. Moreover, women with PCOS showed higher androstenedione and testosterone concentrations compared to normal pregnant women (p=0.016 and p=0.025, respectively). In cord blood, female newborns of women with PCOS exhibited lower androstenedione and higher estriol concentrations compared to daughters of control women (p=0.038; p=0.031, respectively). CONCLUSION These data suggest that placental tissue from women with PCOS shows changes in the activities of two important enzymes for steroid synthesis, higher 3β-HSD-1 and lower P450, which could increase androgen production during pregnancy.

Neonatal Exposure to Estradiol Valerate Programs Ovarian Sympathetic Innervation and Follicular Development in the Adult Rat

Abstract A single injection of estradiol valerate (EV) to 14-day-old rats (when the ovarian follicle population has been already established) disrupts cyclicity, increases the activity of key enzymes of androgen biosynthesis, and develops polycystic ovary by a causally related increase in ovarian noradrenaline (NA). The current study examined an early window of ovarian development to look for a specific stage of development at which estradiol can induce such changes in sympathetic activity and follicular development. A single dose of EV applied to rats before the first 12 h of life rapidly increases (after 24 h) the ovarian expression of nerve growth factor (Ngfb) and p75 low-affinity neurotrophic receptor (Ngfr) mRNAs. When adults, rats presented early vaginal opening, disrupted cyclicity, appearance of follicular cyst, absence of corpus luteum, and infertility. Total follicles decreased, mainly due to a reduced number of primordial follicles, suggesting that estradiol acts in the first stages of folliculogenesis, when primordial follicles are organizing. These changes paralleled a 6-fold increase in NA concentration. No changes in NA content were found in the celiac ganglia, suggesting a local, non-centrally mediated effect of estradiol. Surgical section of the superior ovarian nerve (the main source of sympathetic nerves to the ovary) to rats neonatally treated with EV decreased intraovarian NA, delayed vaginal opening, and blocked the development of follicular cyst and that of preovulatory follicles. Therefore, we can conclude that early exposure to estradiol permanently modifies ovarian sympathetic activity and causes profound changes in follicular development, leading to the polycystic ovary condition.

Chronic Intermittent Cold Stress Activates Ovarian Sympathetic Nerves and Modifies Ovarian Follicular Development in the Rat

Abstract We studied the effects of a chronic intermittent cold stress regime on sympathetic nerve activation and ovarian physiology. This paradigm (4°C for 3 h/day, Monday–Friday, for 3 or 4 wk) does not affect basal plasma levels of corticosterone. After 3 wk of stress, we detected a decrease in noradrenaline (NA) in the ovary, but after 4 wk, this ovarian neurotransmitter concentration increased over that of unstressed control rats. To analyze whether this effect on NA is preceded by an activation of the neurotrophic factor system responsible for growth and survival of sympathetic neurons, we measured both nerve growth factor (NGF) (by enzyme immunoassay) and the intraovarian levels of its low affinity receptor mRNA (by reverse transcription-polymerase chain reaction). The activation of sympathetic nerves was followed by an increase in NGF concentration without affecting the ovarian levels of either NGF or the mRNA of its receptor. Interestingly, follicular development changed during the stress procedure; after 3 or 4 wk of stress, we found a decrease in preantral healthy follicles without a compensatory increase in atresia. Concomitantly with the increase in NA and NGF in the ovary, we observed that a new population of follicles with hypertrophied thecal cell layers appeared after 4 wk of stress. These results suggest that chronic stress, through an intraovarian neurotrophin-mediated sympathetic activation, produces changes in follicular development that could lead to an impairment of reproductive function.

Stress promotes development of ovarian cysts in rats : The possible role of sympathetic nerve activation ()

AbstractActivation of the sympathetic innervation precedes the induction of polycystic ovaries in rats given estradiol valerate (EV). The mechanism of induction by EV may thus involve both direct and neurogenic components. We tested this hypothesis using a combined cold and restraint stress to induce an increase in sympathetic tone, including that of the ovarian sympathetic nerves. Three weeks after the start of stress we found:1.An increase in the content of norepinephrine (NE) in the celiac ganglion.2.An increase in the release of NE from the ovary.3.An unchanged NE uptake by the ovary.4.An unchanged content of NE in the ovary. The ovarian content of neuropeptide Y (NPY) (colocalized with NE) was significantly decreased. These results suggest that NE synthesis and its secretion are increased during this period and correlate with the increase in secretion of androgens and estradiol, the development of precystic follicles, and a decrease in the ovulatory rate. After 11 wk, NE release had returned to control values, whereas the ovarian NE content had risen significantly, suggesting a maintained high rate of NE synthesis. In the ovary, NPY contents, steroid secretion, morphology, and ovulation had returned to the control state. These results suggest the participation of an extraovarian factor that might act locally to control the release of NE from the ovary, and further support the hypothesis that increased sympathetic activity plays a role in the development and maintenance of ovarian cysts.

Locus Coeruleus Mediates Cold Stress-Induced Polycystic Ovary in Rats

Previous reports about the rat ovary have shown that cold stress promotes ovarian morphological alterations related to a polycystic ovary (PCO) condition through activation of the ovarian sympathetic nerves. Because the noradrenergic nucleus locus coeruleus (LC) is activated by cold stress and synaptically connected to the preganglionic cell bodies of the ovarian sympathetic pathway, this study aimed to evaluate the LCs role in cold stress-induced PCO in rats. Ovarian morphology and endocrine and sympathetic functions were evaluated after 8 wk of chronic intermittent cold stress (4 C, 3 h/d) in rats with or without LC lesion. The effect of acute and chronic cold stress upon the LC neuron activity was confirmed by Fos protein expression in tyrosine hydroxylase-immunoreactive neurons. Cold stress induced the formation of follicular cysts, type III follicles, and follicles with hyperthecosis alongside increased plasma estradiol and testosterone levels, irregular estrous cyclicity, and reduced ovulation. Considering estradiol release in vitro, cold stress potentiated the ovarian response to human chorionic gonadotropin. Ovarian norepinephrine (NE) was not altered after 8 wk of stress. However, LC lesion reduced NE activity in the ovary of cold-stressed rats, but not in controls, and prevented all the cold stress effects evaluated. Cold stress increased the number of Fos/tyrosine hydroxylase-immunoreactive neurons in the LC, but this effect was more pronounced for acute stress as compared with chronic stress. These results show that cold stress promotes PCO in rats, which apparently depends on ovarian NE activity that, under this condition, is regulated by the noradrenergic nucleus LC.

Hormonal Programming Across the Lifespan

Hormones influence countless biological processes across an animals lifespan. Many hormone-mediated events occur within developmental sensitive periods, during which hormones have the potential to cause permanent tissue-specific alterations in anatomy and physiology. There are numerous selective critical periods in development with different targets being affected during different periods. This review outlines the proceedings of the Hormonal Programming in Development session at the US-South American Workshop in Neuroendocrinology in August 2011. Here we discuss how gonadal steroid hormones impact various biological processes within the brain and gonads during early development and describe the changes that take place in the aging female ovary. At the cellular level, hormonal targets in the brain include neurons, glia, or vasculature. On a genomic/epigenomic level, transcription factor signaling and epigenetic changes alter the expression of critical hormone receptor genes across development and following ischemic brain insult. In addition, organizational hormone exposure alters epigenetic processes in specific brain nuclei and may be an important mediator of sexual differentiation of the neonatal brain. Brain targets of hormonal programming, such as the paraventricular nucleus of the hypothalamus, may be critical in influencing the development of peripheral targets, such as the ovary. Exposure to excess hormones can cause abnormalities in the ovary during development leading to polycystic ovarian syndrome (PCOS). Exposure to excess androgens during fetal development also has a profound effect on the development of the male reproductive system. In addition, increased activity of the sympathetic nerve and stress during early life have been linked to PCOS symptomology in adulthood. Finally, we describe how age-related decreases in fertility are linked to high levels of nerve growth factor (NGF), which enhances sympathetic nerve activity and alters ovarian function.

Long‐Term Impact of Early Life Events on Physiology and Behaviour

This review discusses the effects of stress and nutrition throughout development and summarises studies investigating how exposure to stress or alterations in nutrition during the pre‐conception, prenatal and early postnatal periods can affect the long‐term health of an individual. In general, the data presented here suggest that that anything signalling potential adverse conditions later in life, such as high levels of stress or low levels of food availability, will lead to alterations in the offspring, possibly of an epigenetic nature, preparing the offspring for these conditions later in life. However, when similar environmental conditions are not met in adulthood, these alterations may have maladaptive consequences, resulting in obesity and heightened stress sensitivity. The data also suggest that the mechanism underlying these adult phenotypes might be dependent on the type and the timing of exposure.