Species and tissue-independent rapid regulation of aromatase activity by phosphorylations.

in Acta Neurologica Belgica (2009)

Aromatase activity (AA) is rapidly inhibited in male quail brains, following expression of sexual behavior, activation of glutamatergic receptors or exposure to phosphorylating conditions. Questions ... [more ▼]

Aromatase activity (AA) is rapidly inhibited in male quail brains, following expression of sexual behavior, activation of glutamatergic receptors or exposure to phosphorylating conditions. Questions remain as to whether direct aromatase phosphorylation is the common key regulatory mechanism and whether these inhibitions are specific to quail hypothalamus. We now showed that AA is rapidly downregulated in quail ovary homogenates incubated in phosphorylating conditions, similarly to what is observed in hypothalamic homogenates. To understand the processes underlying this control, we expressed human aromatase in the human cell line HEK293 and 1) researched whether human aromatase can also be rapidly modulated by phosphorylations and 2) investigated more precisely the processes involved in this rapid control of activity. AA in HEK293 was rapidly inhibited following depolarization of intact cells with 100 mM KCl or in cell lysates exposed to phosphorylating conditions. Thus inhibition of AA in phosphorylating conditions is not unique to the quail hypothalamus neural environment but seems to be a general process. We are now defining the contribution of single residues of the aromatase protein to this enzymatic control. [less ▲]

Behavioral effects of brain-derived estrogens in birds.

in Annals of the New York Academy of Sciences (2009), 1163

In birds as in other vertebrates, estrogens produced in the brain by aromatization of testosterone have widespread effects on behavior. Research conducted with male Japanese quail demonstrates that ... [more ▼]

In birds as in other vertebrates, estrogens produced in the brain by aromatization of testosterone have widespread effects on behavior. Research conducted with male Japanese quail demonstrates that effects of brain estrogens on all aspects of sexual behavior, including appetitive and consummatory components as well as learned aspects, can be divided into two main classes based on their time course. First, estrogens via binding to estrogen receptors regulate the transcription of a variety of genes involved primarily in neurotransmission. These neurochemical effects ultimately result in the activation of male copulatory behavior after a latency of a few days. Correlatively, testosterone and its aromatized metabolites increase the transcription of the aromatase mRNA, resulting in an increased concentration and activity of the enzyme that actually precedes behavioral activation. Second, recent studies with quail demonstrate that brain aromatase activity can also be modulated within minutes by phosphorylation processes regulated by changes in intracellular calcium concentration, such as those associated with glutamatergic neurotransmission. The rapid upregulations or downregulations of brain estrogen concentration (presumably resulting from these changes in aromatase activity) affect, by nongenomic mechanisms with relatively short latencies (frequency increases or decreases respectively within 10-15 min), the expression of male sexual behavior in quail and also in rodents. Brain estrogens thus affect behavior on different time scales by genomic and nongenomic mechanisms similar to those of a hormone or a neurotransmitter. [less ▲]

Interplay among catecholamine systems: dopamine binds to alpha2-adrenergic receptors in birds and mammals.

in Journal of Comparative Neurology (The) (2008), 511(5), 610-27

Dopaminergic and adrenergic receptors are G-protein-coupled receptors considered to be different based on their pharmacology and signaling pathways. Some receptor subtypes that are members of one family ... [more ▼]

Dopaminergic and adrenergic receptors are G-protein-coupled receptors considered to be different based on their pharmacology and signaling pathways. Some receptor subtypes that are members of one family are actually closer in phylogenetic terms to some subtypes belonging to the other family, suggesting that the pharmacological specificity among these receptors from different families is not perfect. Indeed, evidence is accumulating that one amine can cross-talk with receptors belonging to the other system. However, most of these observations were collected in vitro using artificial cell models transfected with cloned receptors, so that the occurrence of this phenomenon in vivo as well as its distribution in the central nervous system is not known. In this study the pharmacological basis of possible in vivo interactions between dopamine and alpha(2)-adrenergic receptors was investigated in quail, zebra finches, and rats. Binding competitions showed that dopamine displaces the binding of the selective alpha(2)-adrenergic ligand, [(3)H]RX821002, in the brain of the three species with an affinity approximately 10-28-fold lower than that of norepinephrine. Dopamine also displaces with an affinity 3-fold lower than norepinephrine the binding of [(3)H]RX821002 to human alpha(h2A)-adrenergic receptors expressed in Sf9 cells. The anatomical distribution of this interaction was assessed in brain slices of quail and rat based on autoradiographic methods. Both norepinephrine and dopamine significantly displace [(3)H]RX821002 binding in all brain nuclei considered. Together, these data provide evidence for an interaction between the dopaminergic and noradrenergic systems in the vertebrate brain, albeit with species variations. [less ▲]

Individual variation and the endocrine regulation of behaviour and physiology in birds: a cellular/molecular perspective.

in Philosophical Transactions : Biological Sciences (2008), 363(1497), 1699-710

Investigations of the cellular and molecular mechanisms of physiology and behaviour have generally avoided attempts to explain individual differences. The goal has rather been to discover general ... [more ▼]

Investigations of the cellular and molecular mechanisms of physiology and behaviour have generally avoided attempts to explain individual differences. The goal has rather been to discover general processes. However, understanding the causes of individual variation in many phenomena of interest to avian eco-physiologists will require a consideration of such mechanisms. For example, in birds, changes in plasma concentrations of steroid hormones are important in the activation of social behaviours related to reproduction and aggression. Attempts to explain individual variation in these behaviours as a function of variation in plasma hormone concentrations have generally failed. Cellular variables related to the effectiveness of steroid hormone have been useful in some cases. Steroid hormone target sensitivity can be affected by variables such as metabolizing enzyme activity, hormone receptor expression as well as receptor cofactor expression. At present, no general theory has emerged that might provide a clear guidance when trying to explain individual variability in birds or in any other group of vertebrates. One strategy is to learn from studies of large units of intraspecific variation such as population or sex differences to provide ideas about variables that might be important in explaining individual variation. This approach along with the use of newly developed molecular genetic tools represents a promising avenue for avian eco-physiologists to pursue. [less ▲]

Site-specific effects of anosmia and cloacal gland anesthesia on Fos expression induced in male quail brain by sexual behavior.

in Behavioural Brain Research (2008), 194(1), 52-65

In rats, expression of the immediate early gene, c-fos observed in the brain following male copulatory behavior relates mostly to the detection of olfactory information originating from the female and to ... [more ▼]

In rats, expression of the immediate early gene, c-fos observed in the brain following male copulatory behavior relates mostly to the detection of olfactory information originating from the female and to somatosensory feedback from the penis. However, quail, like most birds, are generally considered to have a relatively poorly developed sense of smell. Furthermore, quail have no intromittent organ (e.g., penis). It is therefore intriguing that expression of male copulatory behavior induces in quail and rats a similar pattern of c-fos expression in the medial preoptic area (mPOA), bed nucleus of the stria terminalis (BSTM) and parts of the amygdala. We analyzed here by immunocytochemistry Fos expression in the mPOA/BSTM/amygdala of male quail that had been allowed to copulate with a female during standardized tests. Before these tests, some of the males had either their nostrils plugged, or their cloacal area anesthetized, or both. A control group was not exposed to females. These manipulations did not affect frequencies of male sexual behavior and all birds exposed to a female copulated normally. In the mPOA, the increased Fos expression induced by copulation was not affected by the cloacal gland anesthesia but was markedly reduced in subjects deprived of olfactory input. Both manipulations affected copulation-induced Fos expression in the BSTM. No change in Fos expression was observed in the amygdala. Thus immediate early gene expression in the mPOA and BSTM of quail is modulated at least in part by olfactory cues and/or somatosensory stimuli originating from the cloacal gland. Future work should specify the nature of these stimuli and their function in the expression of avian male sexual behavior. [less ▲]

Down-regulation of the coactivator SRC-1 reveals different thresholds for testosterone-dependent regulation of male sexual behavior and brain aromatase

Poster (2006)

Targeting steroid receptor coactivator-1 expression with locked nucleic acids antisense reveals different thresholds for the hormonal regulation of male sexual behavior in relation to aromatase activity and protein expression.

in Behavioural Brain Research (2006), 172(2), 333-43

Steroid receptors such as the androgen and estrogen receptors require the presence of several proteins, known as coactivators, to enhance the transcription of target genes. The first goal of the present ... [more ▼]

Steroid receptors such as the androgen and estrogen receptors require the presence of several proteins, known as coactivators, to enhance the transcription of target genes. The first goal of the present study was to define the role of SRC-1 on the steroid-dependent expression of the aromatase protein and its activity in male Japanese quail. The second goal was to analyze the rapid plasticity of the POM following antisense treatment interruption. We confirm here that the inhibition of SRC-1 expression by daily intracerebroventricular injections of locked nucleic acid antisense oligonucleotides in the third ventricle at the level of the preoptic area-hypothalamus (HPOA) significantly reduces testosterone-dependent male sexual behavior. In the first experiment, aromatase protein expression in HPOA was inhibited in SRC-1-depleted males but the enzymatic activity remained at the level measured in controls. We observed in the second experiment a recovery of the behavioral response to testosterone treatment after interruption of the antisense injection. However, several morphological characteristics of the POM were not different between the control group, the antisense-treated birds and antisense-treated birds in which treatment had been discontinued 3 days earlier. Antisense was also less effective in knocking-down SRC-1 in the present experiments as compared to our previous study. An analysis of this variation in the degree of knock-down of SRC-1 expression suggests dissociation among different aspects of steroid action on brain and behavior presumably resulting from the differential sensitivity of behavioral and neurochemical responses to the activation by testosterone and/or its estrogenic metabolites. [less ▲]

Brain expression of the steroid receptor coactivator SRC-1 changes during the day.

Poster (2005)

Rapid plasticity of the medial preoptic nucleus in male Japanese quail following testosterone treatment

Conference (2005)

Modulation of steroid-dependent male sexual behavior and neural gene expression: A role for steroid receptor co-activators

in Trabajos del Instituto Cajal (2005), 80

One of the best-characterized actions of steroids is the regulation of brain areas involved in endocrine function and in the activation of reproductive behaviors in male and female vertebrates. Progress ... [more ▼]

One of the best-characterized actions of steroids is the regulation of brain areas involved in endocrine function and in the activation of reproductive behaviors in male and female vertebrates. Progress in the understanding of the mechanisms that control the expression of the eukaryotic genome by nuclear receptors has brought forward the importance of steroid receptor coactivators in mediating efficient gene transcription. However, little is know about the specific physiological requirements of these coactivators in vivo. In Japanese quail, testosterone treatment of castrated males restores the full copulatory behavior and increases the volume of the sexually dimorphic medial preoptic nucleus (POM) to the level observed in intact males [1]. Testosterone also affects a number of sexually dimorphic neurochemical characteristics such as the vasotocineric innervation of the septum and meadial preoptic nucleus [2]. The quail therefore provides an excellent model to study steroid-dependent sexual behavior and the associated neuroplasticity and should provide insights into the modulation of steroid action by steroid receptor coactivators. The present studies were focused on the steroid receptor co-activator-1 (SRC-1), which was already shown to be involved in the process of sexual differentiation of brain and behavior in rats [3]. We first amplified by RT-PCR from quail brains a 3,411bp fragment highly homologous with the chicken (94.5%) and mammalian (70%) SRC-1 and designed digoxigenin-labeled oligonucleotides for in situ hybridization. A broad distribution of SRC-1 transcripts was observed throughout the male quail brain. A particularly dense coactivator expression was observed in limbic (e.g. POM, nucleus striae terminalis) and mesencephalic (e.g. substantia grisea centralis) nuclei associated with the control of male sexual behavior [4]. Because male and female quail exhibit a very pronounced sexual dimorphism in the steroid-dependent mechanisms that activate male-typical copulatory behavior, we investigated the potential role of SRC-1 in the sexually differentiated responses to steroids by quantifiying the SRC-1 mRNA by real time quantitative polymerase chain reaction (qPCR) and the corresponding protein by western blot (WB). Contrary to previous results, which had identified a higher SRC-1 mRNA expression in the POM of males compared to females [4], we found in two separate experiments that sexually mature females had higher concentrations of SRC-1 in the preoptic area-hypothalamus (HPOA) compared to males. Additional studies should be carried out to identify the origins of this discrepancy but seasonality and time of the day when brains were collected are potentially involved. We also quantified the SRC-1 mRNA and protein in the preoptic area-hypothalamus (HPOA) of castrated males treated or not with testosterone. SRC-1 mRNA was increased by testosterone in two independent experiments but not in a third one. This difference is likely due to the differential manipulations of the birds during these experiments. Birds had been repeatedly handled to test their sexual behavior in the first experiment and we showed that stress tends to decrease the coactivator expression in the male HPOA. This interpretation is strengthened by recent work in rats indicating that stress regulates SRC-1 expression in hypothalamus and hippocampus [5]. More surprisingly, we found a significant correlation between the expression of SRC-1 and the time of the day when birds were killed in the optic lobes, hippocampus and hindbrain. The expression of SRC-1 in the optic lobes increased throughout the day, independently of sex, testosterone treatment or stress. In the hippocampus and hindbrain, the coactivator concentration varied in opposite directions during the morning and afternoon and reached respectively its lowest or highest concentration around the middle of the day, here again independently of sex, stress and hormonal treatment. Together, these data support the idea that SRC-1 is not constitutively expressed but regulated by steroids, stress and possibly other unidentified factors. Differential controls also appear to take place in specific brain nuclei and these differential controls should be further analyzed by immunohistochemistry and in situ hybridization. A second part of our work was dedicated to the study of the physiological significance of SRC-1 whith the use of daily intra-cerebroventricular injections of modified antisense (AS) oligonucleotides (Locked nucleic acid LNA) to disrupt SRC-1 expression in the POM. AS injections significantly reduced the expression of male copulatory behavior in response to exogenous testosterone compared to control animals (Ctrl group) that received the vehicle alone or scrambled (SC) oligonucleotides. Moreover, sexual behavior was restored and even enhanced within 48 hours after interruption of AS injection (ASSC group). Western blot analysis confirmed the decrease of SRC-1 expression in AS animals and demonstrated an over-expression of the coactivator in ASSC animals. The effects of SRC-1 knock down on behavior was related to a reduced POM volume defined by Nissl-staining and aromatase immunohistochemistry. The aromatase index, indicative of the relative amount of aromatase in the POM as well as the vasotocinergic innervation of this nucleus were higher in the Ctrl group. Taken together, these findings indicate that SRC-1 functions as a critical regulatory molecule in the brain to modulate steroid-dependent gene transcription and behavior. The study of the modulation of nuclear receptors activity by different co-regulatory proteins is still in its infancy. Abnormal co-activator expression or function is currently being linked to some endocrine/neurological disorders in humans and it is thus critical to understand how co-activator expression and function are controlled in the developing as well as in the adult brain. [less ▲]