Identifying the stress transcriptome in the adrenal medulla following acute and repeated immobilization

Genome and transcriptome of Ips nitidus provide insights into high-altitude hypoxia adaptation and symbiosis

Ips nitidus is a well-known conifer pest that has contributed significantly to spruce forest disturbance in the Qinghai-Tibet Plateau and seriously threatens the ecological balance of these areas. We report a chromosome-level genome of I. nitidus determined by PacBio and Hi-C technology. Phylogenetic inference showed that it diverged from the common ancestor of I. typographus ∼2.27 mya. Gene family expansion in I. nitidus was characterized by DNA damage repair and energy metabolism, which may facilitate adaptation to high-altitude hypoxia. Interestingly, differential gene expression analysis revealed upregulated genes associated with high-altitude hypoxia adaptation and downregulated genes associated with detoxification after feeding and tunneling in fungal symbiont Ophiostoma bicolor-colonized substrates. Our findings provide evidence of the potential adaptability of I. nitidus to conifer host, high-altitude hypoxia and insight into how fungal symbiont assist in this process. This study enhances our understanding of insect adaptation, symbiosis, and pest management.

Transcriptome Profile of the Rat Adrenal Gland: Parenchymal and Interstitial Cells

The homeostasis of the adrenal gland plays a decisive role in its proper functioning, both in non-stressful conditions and under the influence of various types of stress. This consists of interactions between all types of cells that make up the organ, including parenchymal and interstitial cells. The amount of available information on this subject in the rat adrenal glands under non-stressful conditions is insufficient; the aim of the research was to determine the expression of marker genes for rat adrenal cells depending on their location. The material for the study consisted of adrenal glands taken from intact adult male rats that were separated into appropriate zones. Transcriptome analysis by means of Affymetrix^® Rat Gene 2.1 ST Array was used in the study, followed by real-time PCR validation. Expression analysis of interstitial cell marker genes revealed both the amount of expression of these genes and the zone in which they were expressed. The expression of marker genes for fibroblasts was particularly high in the cells of the ZG zone, while the highest expression of specific macrophage genes was observed in the adrenal medulla. The results of this study, especially with regard to interstitial cells, provide a so far undescribed model of marker gene expression of various cells, both in the cortex and medulla of the sexually mature rat adrenal gland. The interdependence between parenchymal and interstitial cells creates a specific microenvironment that is highly heterogeneous within the gland with respect to some of the interstitial cells. This phenomenon most likely depends on the interaction with the differentiated parenchymal cells of the cortex, as well as the medulla of the gland.

Neuropeptides and small-molecule amine transmitters: cooperative signaling in the nervous system

Neuropeptides are expressed in cell-specific patterns throughout mammalian brain. Neuropeptide gene expression has been useful for clustering neurons by phenotype, based on single-cell transcriptomics, and for defining specific functional circuits throughout the brain. How neuropeptides function as first messengers in inter-neuronal communication, in cooperation with classical small-molecule amine transmitters (SMATs) is a current topic of systems neurobiology. Questions include how neuropeptides and SMATs cooperate in neurotransmission at the molecular, cellular and circuit levels; whether neuropeptides and SMATs always co-exist in neurons; where neuropeptides and SMATs are stored in the neuron, released from the neuron and acting, and at which receptors, after release; and how neuropeptides affect 'classical' transmitter function, both directly upon co-release, and indirectly, via long-term regulation of gene transcription and neuronal plasticity. Here, we review an extensive body of data about the distribution of neuropeptides and their receptors, their actions after neuronal release, and their function based on pharmacological and genetic loss- and gain-of-function experiments, that addresses these questions, fundamental to understanding brain function, and development of neuropeptide-based, and potentially combinatorial peptide/SMAT-based, neurotherapeutics.

A Rat Model of Human Behavior Provides Evidence of Natural Selection Against Underexpression of Aggressiveness-Related Genes in Humans

Aggressiveness is a hereditary behavioral pattern that forms a social hierarchy and affects the individual social rank and accordingly quality and duration of life. Thus, genome-wide studies of human aggressiveness are important. Nonetheless, the aggressiveness-related genome-wide studies have been conducted on animals rather than humans. Recently, in our genome-wide study, we uncovered natural selection against underexpression of human aggressiveness-related genes and proved it using F1 hybrid mice. Simultaneously, this natural selection equally supports two opposing traits in humans (dominance and subordination) as if self-domestication could have happened with its disruptive natural selection. Because there is still not enough scientific evidence that this could happen, here, we verified this natural selection pattern using quantitative PCR and two outbred rat lines (70 generations of artificial selection for aggressiveness or tameness, hereinafter: domestication). We chose seven genes—Cacna2d3, Gad2, Gria2, Mapk1, Nos1, Pomc, and Syn1—over- or underexpression of which corresponds to aggressive or domesticated behavior (in humans or mice) that has the same direction as natural selection. Comparing aggressive male rats with domesticated ones, we found that these genes are overexpressed statistically significantly in the hypothalamus (as a universal behavior regulator), not in the periaqueductal gray, where there was no aggressiveness-related expression of the genes in males. Database STRING showed statistically significant associations of the human genes homologous to these rat genes with long-term depression, circadian entrainment, Alzheimer’s disease, and the central nervous system disorders during chronic IL-6 overexpression. This finding more likely supports positive perspectives of further studies on self-domestication syndromes.

Inflammatory Signaling in Hypertension: Regulation of Adrenal Catecholamine Biosynthesis

The immune system is increasingly recognized for its role in the genesis and progression of hypertension. The adrenal gland is a major site that coordinates the stress response via the hypothalamic-pituitary-adrenal axis and the sympathetic-adrenal system. Catecholamines released from the adrenal medulla function in the neuro-hormonal regulation of blood pressure and have a well-established link to hypertension. The immune system has an active role in the progression of hypertension and cytokines are powerful modulators of adrenal cell function. Adrenal medullary cells integrate neural, hormonal, and immune signals. Changes in adrenal cytokines during the progression of hypertension may promote blood pressure elevation by influencing catecholamine biosynthesis. This review highlights the potential interactions of cytokine signaling networks with those of catecholamine biosynthesis within the adrenal, and discusses the role of cytokines in the coordination of blood pressure regulation and the stress response.

Chicken domestication changes expression of stress-related genes in brain, pituitary and adrenals

Domesticated species have an attenuated behavioral and physiological stress response compared to their wild counterparts, but the genetic mechanisms underlying this change are not fully understood. We investigated gene expression of a panel of stress response-related genes in five tissues known for their involvement in the stress response: hippocampus, hypothalamus, pituitary, adrenal glands and liver of domesticated White Leghorn chickens and compared it with the wild ancestor of all domesticated breeds, the Red Junglefowl. Gene expression was measured both at baseline and after 45 min of restraint stress. Most of the changes in gene expression related to stress were similar to mammals, with an upregulation of genes such as FKBP5, C-FOS and EGR1 in hippocampus and hypothalamus and StAR, MC2R and TH in adrenal glands. We also found a decrease in the expression of CRHR1 in the pituitary of chickens after stress, which could be involved in negative feedback regulation of the stress response. Furthermore, we observed a downregulation of EGR1 and C-FOS in the pituitary following stress, which could be a potential link between stress and its effects on reproduction and growth in chickens. We also found changes in the expression of important genes between breeds such as GR in the hypothalamus, POMC and PC1 in the pituitary and CYP11A1 and HSD3B2 in the adrenal glands. These results suggest that the domesticated White Leghorn may have a higher capacity for negative feedback of the HPA axis, a lower capacity for synthesis of ACTH in the pituitary and a reduced synthesis rate of corticosterone in the adrenal glands compared to Red Junglefowl. All of these findings could explain the attenuated stress response in the domesticated birds.

The Role of Early Growth Response 1 (EGR1) in Brain Plasticity and Neuropsychiatric Disorders

It is now clearly established that complex interactions between genes and environment are involved in multiple aspects of neuropsychiatric disorders, from determining an individual's vulnerability to onset, to influencing its response to therapeutic intervention. In this perspective, it appears crucial to better understand how the organism reacts to environmental stimuli and provide a coordinated and adapted response. In the central nervous system, neuronal plasticity and neurotransmission are among the major processes integrating such complex interactions between genes and environmental stimuli. In particular, immediate early genes (IEGs) are critical components of these interactions as they provide the molecular framework for a rapid and dynamic response to neuronal activity while opening the possibility for a lasting and sustained adaptation through regulation of the expression of a wide range of genes. As a result, IEGs have been tightly associated with neuronal activity as well as a variety of higher order processes within the central nervous system such as learning, memory and sensitivity to reward. The immediate early gene and transcription factor early growth response 1 (EGR1) has thus been revealed as a major mediator and regulator of synaptic plasticity and neuronal activity in both physiological and pathological conditions. In this review article, we will focus on the role of EGR1 in the central nervous system. First, we will summarize the different factors influencing its activity. Then, we will analyze the amount of data, including genome-wide, that has emerged in the recent years describing the wide variety of genes, pathways and biological functions regulated directly or indirectly by EGR1. We will thus be able to gain better insights into the mechanisms underlying EGR1's functions in physiological neuronal activity. Finally, we will discuss and illustrate the role of EGR1 in pathological states with a particular interest in cognitive functions and neuropsychiatric disorders.

Adrenal cortical and chromaffin stem cells: Is there a common progeny related to stress adaptation?

The adrenal gland is a highly plastic organ with the capacity to adapt the body homeostasis to different physiological needs. The existence of stem-like cells in the adrenal cortex has been revealed in many studies. Recently, we identified and characterized in mice a pool of glia-like multipotent Nestin-expressing progenitor cells, which contributes to the plasticity of the adrenal medulla. In addition, we found that these Nestin progenitors are actively involved in the stress response by giving rise to chromaffin cells. Interestingly, we also observed a Nestin-GFP-positive cell population located under the adrenal capsule and scattered through the cortex. In this article, we discuss the possibility of a common progenitor giving rise to subpopulations of cells both in the adrenal cortex and medulla, the isolation and characterization of this progenitor as well as its clinical potential in transplantation therapies and in pathophysiology.

Analyses of differentially expressed genes after exposure to acute stress, acute ethanol, or a combination of both in mice

Alcohol abuse is a complex disorder, which is confounded by other factors, including stress. In the present study, we examined gene expression in the hippocampus of BXD recombinant inbred mice after exposure to ethanol (NOE), stress (RSS), and the combination of both (RSE). Mice were given an intraperitoneal (i.p.) injection of 1.8 g/kg ethanol or saline, and subsets of both groups were exposed to acute restraint stress for 15 min or controls. Gene expression in the hippocampus was examined using microarray analysis. Genes that were significantly (p < 0.05, q < 0.1) differentially expressed were further evaluated. Bioinformatic analyses were predominantly performed using tools available at GeneNetwork.org, and included gene ontology, presence of cis-regulation or polymorphisms, phenotype correlations, and principal component analyses. Comparisons of differential gene expression between groups showed little overlap. Gene Ontology demonstrated distinct biological processes in each group with the combined exposure (RSE) being unique from either the ethanol (NOE) or stress (RSS) group, suggesting that the interaction between these variables is mediated through diverse molecular pathways. This supports the hypothesis that exposure to stress alters ethanol-induced gene expression changes and that exposure to alcohol alters stress-induced gene expression changes. Behavior was profiled in all groups following treatment, and many of the differentially expressed genes are correlated with behavioral variation within experimental groups. Interestingly, in each group several genes were correlated with the same phenotype, suggesting that these genes are the potential origins of significant genetic networks. The distinct sets of differentially expressed genes within each group provide the basis for identifying molecular networks that may aid in understanding the complex interactions between stress and ethanol, and potentially provide relevant therapeutic targets. Using Ptp4a1, a candidate gene underlying the quantitative trait locus for several of these phenotypes, and network analyses, we show that a large group of differentially expressed genes in the NOE group are highly interrelated, some of which have previously been linked to alcohol addiction or alcohol-related phenotypes.

Molecular determinants of the adrenal gland functioning related to stress-sensitive hypertension in ISIAH rats

Background

The adrenals are known as an important link in pathogenesis of arterial hypertensive disease. The study was directed to the adrenal transcriptome analysis in ISIAH rats with stress-sensitive arterial hypertension and predominant involvement in pathogenesis of the hypothalamic-pituitary-adrenal and sympathoadrenal systems.

Results

The RNA-Seq approach was used to perform the comparative adrenal transcriptome profiling in hypertensive ISIAH and normotensive WAG rats. Multiple differentially expressed genes (DEGs) related to different biological processes and metabolic pathways were detected.

The discussion of the results helped to prioritize the several DEGs as the promising candidates for further studies of the genetic background underlying the stress-sensitive hypertension development in the ISIAH rats. Two of these were transcription factor genes (Nr4a3 and Ppard), which may be related to the predominant activation of the sympathetic-adrenal medullary axis in ISIAH rats. The other genes are known as associated with hypertension and were defined in the current study as DEGs making the most significant contribution to the inter-strain differences. Four of them (Avpr1a, Hsd11b2, Agt, Ephx2) may provoke the hypertension development, and Mpo may contribute to insulin resistance and inflammation in the ISIAH rats.

Conclusions

The study strongly highlighted the complex nature of the pathogenesis of stress-sensitive hypertension. The data obtained may be useful for identifying the common molecular determinants in different animal models of arterial hypertension, which may be potentially used as therapeutic targets for pharmacological intervention.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3354-2) contains supplementary material, which is available to authorized users.

Short-term pre- and post-operative stress prolongs incision-induced pain hypersensitivity without changing basal pain perception

BACKGROUND

Chronic stress has been reported to increase basal pain sensitivity and/or exacerbate existing persistent pain. However, most surgical patients have normal physiological and psychological health status such as normal pain perception before surgery although they do experience short-term stress during pre- and post-operative periods. Whether or not this short-term stress affects persistent postsurgical pain is unclear.

RESULTS

In this study, we showed that pre- or post-surgical exposure to immobilization 6 h daily for three consecutive days did not change basal responses to mechanical, thermal, or cold stimuli or peak levels of incision-induced hypersensitivity to these stimuli; however, immobilization did prolong the duration of incision-induced hypersensitivity in both male and female rats. These phenomena were also observed in post-surgical exposure to forced swimming 25 min daily for 3 consecutive days. Short-term stress induced by immobilization was demonstrated by an elevation in the level of serum corticosterone, an increase in swim immobility, and a decrease in sucrose consumption. Blocking this short-term stress via intrathecal administration of a selective glucocorticoid receptor antagonist, RU38486, or bilateral adrenalectomy significantly attenuated the prolongation of incision-induced hypersensitivity to mechanical, thermal, and cold stimuli.

CONCLUSION

Our results indicate that short-term stress during the pre- or post-operative period delays postoperative pain recovery although it does not affect basal pain perception. Prevention of short-term stress may facilitate patients' recovery from postoperative pain.

Regulation of nonclassical renin-angiotensin system receptor gene expression in the adrenal medulla by acute and repeated immobilization stress

The involvement of the nonclassical renin-angiotensin system (RAS) in the adrenomedullary response to stress is unclear. Therefore, we examined basal and immobilization stress (IMO)-triggered changes in gene expression of the classical and nonclassical RAS receptors in the rat adrenal medulla, specifically the angiotensin II type 2 (AT2) and type 4 (AT4) receptors, (pro)renin receptor [(P)RR], and Mas receptor (MasR). All RAS receptors were identified, with AT2 receptor mRNA levels being the most abundant, followed by the (P)RR, AT1A receptor, AT4 receptor, and MasR. Following a single IMO, AT2 and AT4 receptor mRNA levels decreased by 90 and 50%, respectively. Their mRNA levels were also transiently decreased by repeated IMO. MasR mRNA levels displayed a 75% transient decrease as well. Conversely, (P)RR mRNA levels were increased by 50% following single or repeated IMO. Because of its abundance, the function of the (P)RR was explored in PC-12 cells. Prorenin activation of the (P)RR increased phosphorylation of extracellular signal-regulated kinase 1/2 and tyrosine hydroxylase at Ser31, likely increasing its enzymatic activity and catecholamine biosynthesis. Together, the broad and dynamic changes in gene expression of the nonclassical RAS receptors implicate their role in the intricate response of the adrenomedullary catecholaminergic system to stress.

A systems approach identifies co-signaling molecules of early growth response 1 transcription factor in immobilization stress

Background

Adaptation to stress is critical for survival. The adrenal medulla, the major source of epinephrine, plays an important role in the development of the hyperadenergic state and increased risk for stress associated disorders, such as hypertension and myocardial infarction. The transcription factor Egr1 plays a central role in acute and repeated stress, however the complexity of the response suggests that other transcription factor pathways might be playing equally important roles during acute and repeated stress. Therefore, we sought to discover such factors by applying a systems approach.

Results

Using microarrays and network analysis we show here for the first time that the transcription factor signal transducer and activator of transcription 3 (Stat3) gene is activated in acute stress whereas the prolactin releasing hormone (Prlh11) and chromogranin B (Chgb) genes are induced in repeated immobilization stress and that along with Egr1 may be critical mediators of the stress response.

Conclusions

Our results suggest possible involvement of Stat3 and Prlh1/Chgb up-regulation in the transition from short to repeated stress activation.

Bradykinin B2 receptor in the adrenal medulla of male rats and mice: glucocorticoid-dependent increase with immobilization stress

Bradykinin, acting via the bradykinin B2 receptor (B2R), is a potent stimulator of adrenomedullary catecholamine biosynthesis and release and likely plays an important role in the adrenomedullary stress response. However, the effects of stress on the expression of this receptor in the adrenal medulla are currently unclear. Here, we examined the changes in adrenomedullary B2R gene expression in male rats in response to single (1 time) and repeated (6 times) exposure to 2 hours immobilization stress (IMO). Immediately after 1 or 6 times IMO, B2R mRNA levels were increased by 9-fold and 7-fold, respectively, and returned to unstressed control levels 3 hours later. This large, but transient, increase in mRNA elicited a doubling of protein levels 3 hours after the stress exposure. Next, the role of the hypothalamic-pituitary-adrenocortical axis in the stress-induced upregulation of B2R gene expression was examined. Treatment with endogenous (corticosterone) and synthetic (dexamethasone) glucocorticoids dose-dependently increased B2R mRNA levels in adrenomedullary-derived PC12 cells. Furthermore, cortisol supplementation at levels mimicking stress exposure elevated B2R mRNA levels in the adrenal medulla of hypophysectomized rats. In response to 1 exposure to IMO, the stress-triggered rise in plasma corticosterone and adrenomedullary B2R mRNA levels was attenuated in CRH-knockout mice and absent in pharmacologically adrenalectomized rats, indicating a requirement for glucocorticoids in the upregulation of B2R gene expression with stress. Overall, the increase in B2R gene expression in response to the stress-triggered rise in glucocorticoids likely enhances catecholamine biosynthesis and release and may serve as an adaptive response of the adrenomedullary catecholaminergic system to stress.

Transcriptome analysis of artificial hybrid pufferfish Jiyan-1 and its parental species: implications for pufferfish heterosis

Jiyan-1 puffer, the F1 hybrid of Takifugu rubripes and Takifugu flavidus, displays obvious heterosis in the growth performance, flavor and stress tolerance. In the present study, comparative analysis for the transcriptomes of T. rubripes, T. flavidus and Jiyan-1 was performed aiming to reveal the possible mechanisms of heterosis in pufferfish. Whole transcriptomes were sequenced using the SOLiD4 platform, and a total of 44,305 transcripts corresponding to 18,164 genes were identified collectively. A total of 14,148 transcripts were differentially expressed. By comparing the gene expression patterns of the three samples, the coexistence of overdominance, dominance, underdominance and additivity was observed in the gene action modes of Jiyan-1. There were 2,237 transcripts in the intersection of the differentially expressed transcripts from Jiyan-1 versus T. rubripes and Jiyan-1 versus T. flavidus, among which 213 transcripts were also in the T. rubripes versus T. flavidus. The potential functions of the remaining 2,024 transcripts were mainly associated with metabolic process, nucleotide binding and catalytic activity. The enrichment results indicated metabolism was the most activated biological function in the heterosis. In addition, 35 KEGG pathways were retrieved as affiliated with more than three differentially expressed transcripts and 8,579 potentially novel transcript isoforms were identified for Jiyan-1. The present study revealed the coexistence of multiple gene actions in the hybrid puffer, indicated the importance of metabolism, ion binding function and kinase activity, as well as provided a list of candidate genes and pathways for heterosis. It could be helpful for the better understanding of the determination and regulation mechanisms of heterosis.

Stress-triggered changes in peripheral catecholaminergic systems

The sympathetic nervous system not only regulates cardiovascular and metabolic responses to stress but also is altered by stress. The sympathoneural and sympathoadrenomedullary systems are modified by different metabolic pathways and have different responses to short- and to long-term stressors. Stress also induces nonneuronal catecholamine enzymes, primarily through corticosteroids. Catecholamine synthetic enzymes are induced by different pathways in response to short- and long-term acting stressors, like cold exposure or immobilization, and differently in the sympathetic ganglia and the adrenal medulla. However, a long-term exposure to one stressor can increase the response to a second, different stressor. Tyrosine hydroxylase gene transcription increases after only 5min of immobilization through phosphorylation of CREB, but this response is short lived. However, repeated stress gives a longer-lived response utilizing transcription factors such as Egr-1 and Fra-2. Glucocorticoids and ACTH also induce sympathoneural enzymes leading to distinct patterns of short-term and long-lived activation of the sympathetic nervous system. Nonneuronal phenylethanolamine N-methyltransferase (PNMT) develops early in the heart and then diminishes. However, intrinsic cardiac adrenergic cells remain and nonneuronal PNMT is present in many cells of the adult organism and increases in response to glucocorticoids. Both stress-induced and administered glucocorticoids induce fetal PNMT and hypertension. Human stressors such as caring for an ill spouse or sleep apnea cause a persistent increase in blood norepinephrine, increased blood pressure, and downregulated catecholamine receptors. Hypertension is associated with a loss of slow-wave sleep, when sympathetic nerve activity is lowest. These findings indicate that stress-induced alteration of the sympathetic nervous system occurs in man as in experimental animals.

Role of leaky neuronal ryanodine receptors in stress-induced cognitive dysfunction

The type 2 ryanodine receptor/calcium release channel (RyR2), required for excitation-contraction coupling in the heart, is abundant in the brain. Chronic stress induces catecholamine biosynthesis and release, stimulating β-adrenergic receptors and activating cAMP signaling pathways in neurons. In a murine chronic restraint stress model, neuronal RyR2 were phosphorylated by protein kinase A (PKA), oxidized, and nitrosylated, resulting in depletion of the stabilizing subunit calstabin2 (FKBP12.6) from the channel complex and intracellular calcium leak. Stress-induced cognitive dysfunction, including deficits in learning and memory, and reduced long-term potentiation (LTP) at the hippocampal CA3-CA1 connection were rescued by oral administration of S107, a compound developed in our laboratory that stabilizes RyR2-calstabin2 interaction, or by genetic ablation of the RyR2 PKA phosphorylation site at serine 2808. Thus, neuronal RyR2 remodeling contributes to stress-induced cognitive dysfunction. Leaky RyR2 could be a therapeutic target for treatment of stress-induced cognitive dysfunction.

Regulation of angiotensin II type 2 receptor gene expression in the adrenal medulla by acute and repeated immobilization stress

While the renin-angiotensin system is important for adrenomedullary responses to stress, the involvement of specific angiotensin II (Ang II) receptor subtypes is unclear. We examined gene expression changes of angiotensin II type 1A (AT(1A)) and type 2 (AT(2)) receptors in rat adrenal medulla in response to immobilization stress (IMO). AT(2) receptor mRNA levels decreased immediately after a single 2-h IMO. Repeated IMO also decreased AT(2) receptor mRNA levels, but the decline was more transient. AT(1A) receptor mRNA levels were unaltered with either single or repeated IMO, although binding was increased following repeated IMO. These effects of stress on Ang II receptor expression may alter catecholamine biosynthesis, as tyrosine hydroxylase and dopamine β-hydroxylase mRNA levels in PC12 cells are decreased with Ang II treatment in the presence of ZD7155 (AT(1) receptor antagonist) or with CGP42112 (AT(2) receptor agonist) treatment. Involvement of stress-triggered activation of the hypothalamic-pituitary-adrenocortical or sympathoadrenal axis in AT(2) receptor downregulation was examined. Cultured cells treated with the synthetic glucocorticoid dexamethasone displayed a transcriptionally mediated decrease in AT(2) receptor mRNA levels. However, glucocorticoids are not required for the immediate stress-triggered decrease in AT(2) receptor gene expression, as demonstrated in corticotropin-releasing hormone knockout (Crh KO) mice and hypophysectomized rats, although they can regulate basal gene expression. cAMP and pituitary adenylate cyclase-activating polypeptide also reduced AT(2) receptor gene expression and may mediate this response. Overall, the effects of stress on adrenomedullary AT(1A) and AT(2) receptor expression may contribute to allostatic changes, such as regulation of catecholamine biosynthesis.

Isolation, characterization, and differentiation of progenitor cells from human adult adrenal medulla

Chromaffin cells, sympathetic neurons of the dorsal ganglia, and the intermediate small intensely fluorescent cells derive from a common neural crest progenitor cell. Contrary to the closely related sympathetic nervous system, within the adult adrenal medulla a subpopulation of undifferentiated progenitor cells persists, and recently, we established a method to isolate and differentiate these progenitor cells from adult bovine adrenals. However, no studies have elucidated the existence of adrenal progenitor cells within the human adrenal medulla. Here we describe the isolation, characterization, and differentiation of chromaffin progenitor cells obtained from adult human adrenals. Human chromaffin progenitor cells were cultured in low-attachment conditions for 10-12 days as free-floating spheres in the presence of fibroblast growth factor-2 (FGF-2) and epidermal growth factor. These primary human chromosphere cultures were characterized by the expression of several progenitor markers, including nestin, CD133, Notch1, nerve growth factor receptor, Snai2, Sox9, Sox10, Phox2b, and Ascl1 on the molecular level and of Sox9 on the immunohistochemical level. In opposition, phenylethanolamine N-methyltransferase (PNMT), a marker for differentiated chromaffin cells, significantly decreased after 12 days in culture. Moreover, when plated on poly-l-lysine/laminin-coated slides in the presence of FGF-2, human chromaffin progenitor cells were able to differentiate into two distinct neuron-like cell types, tyrosine hydroxylase (TH)(+)/β-3-tubulin(+) cells and TH(-)/β-3-tubulin(+) cells, and into chromaffin cells (TH(+)/PNMT(+)). This study demonstrates the presence of progenitor cells in the human adrenal medulla and reveals their potential use in regenerative medicine, especially in the treatment of neuroendocrine and neurodegenerative diseases.

Role of TrkB expression in rat adrenal gland during acute immobilization stress

Expression of tyrosine receptor kinase B (TrkB), a receptor for brain-derived neurotrophic factor (BDNF), is markedly elevated in the adrenal medulla during immobilization stress. Catecholamine release was confirmed in vitro by stimulating chromaffin cells with recombinant BDNF. We investigated the role of TrkB and the localization of BDNF in the adrenal gland during immobilization stress for 60 min. Blood catecholamine levels increased after stimulation with TrkB expressed in the adrenal medulla during 60-min stress; however, blood catecholamine levels did not increase in adrenalectomized rats. Furthermore, expression of BDNF mRNA and protein was detected in the adrenal medulla during 60-min stress. Similarly, in rats undergoing sympathetic nerve block with propranolol, BDNF mRNA and protein were detected in the adrenal medulla during 60-min stress. These results suggest that signal transduction of TrkB in the adrenal medulla evokes catecholamine release. In addition, catecholamine release was evoked by both the hypothalamic–pituitary–adrenal axis and autocrine signaling by BDNF in the adrenal gland. BDNF–TrkB interaction may play a role in a positive feedback loop in the adrenal medulla during immobilization stress.

Stress triggered changes in expression of genes for neurosecretory granules in adrenal medulla

With acute stress, the release of adrenomedullary catecholamines is important for handling the emergency situation. However, when chronic or repeated, stress alters the allostatic load and leads to a hyperadrenergic state, resulting in the development or worsening of a wide range of diseases. To help elucidate the mechanism, we examined the effects of single and repeated immobilization stress on gene expression of components of neurosecretory vesicles in the adrenal medulla. Male Sprague-Dawley rats were exposed to immobilization stress once for 2 h (1× IMO) or daily for six consecutive days (6× IMO). Compared to unstressed controls, 1× IMO elevated gene expression of vesicular monoamine transporter 2 (VMAT2). In response to 6× IMO, not only was VMAT2 mRNA still elevated, but chromogranin A (CgA) and chromogranin B (CgB) mRNAs were also increased two to three-fold above basal levels. To investigate the possible role of the hypothalamic-pituitary-adrenal axis in the induction of VMAT2, PC12 cells were treated with the synthetic glucocorticoid dexamethasone, which was found to elevate VMAT2 mRNA expression. The findings suggest that following repeated stress, elevations of various components of neurosecretory vesicles in the adrenal can facilitate more efficient utilization of the well-characterized heightened catecholamine levels.

Urocortin-dependent effects on adrenal morphology, growth, and expression of steroidogenic enzymes in vivo

Urocortin (UCN) 1, 2, and 3 are members of the corticotropin-releasing factor (CRF) family that display varying affinities to the CRF receptor 1 (CRFR1 (CRHR1)) and 2 (CRFR2 (CRHR2)). UCNs represent important modulators of stress responses and are involved in the control of anxiety and related disorders. In addition to the CNS, UCNs and CRFRs are highly expressed in several tissues including the adrenal gland, indicating the presence of UCN-dependent regulatory mechanisms in these peripheral organ systems. Using knockout (KO) mouse models lacking single or multiple Ucn genes, we examined the potential role of the three different Ucns on morphology and function of the adrenal gland. Adrenal morphology was investigated, organ size, cell size, and number were quantified, and growth kinetics were studied by proliferative cell nuclear antigen staining and Ccnd1 expression analysis. Furthermore, mRNA expression of enzymes involved in steroidogenesis and catecholamine synthesis was quantified by real-time PCR. Following this approach, Ucn2, Ucn1/Ucn2 dKO and Ucn1/Ucn2/Ucn3 tKO animals showed a significant cellular hypotrophy of the adrenal cortex and an increase in Ccnd1 expression, whereas in all other genotypes, no changes were observable in comparison to age-matched controls. For steroidogenesis, Ucn2/Ucn3 dKO animals displayed the most pronounced changes, with significant increases in all investigated enzymes, providing indirect evidence for increased stress behavior. Taken together, these data suggest that mainly Ucn2 and Ucn3 could be involved in adrenal stress response regulation while Ucn2 additionally appears to play a role in morphology and growth of the adrenal gland.

PACAP: a master regulator of neuroendocrine stress circuits and the cellular stress response

The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) is released from stress-transducing neurons. It exerts postsynaptic effects required to complete the hypothalamo-pituitary-adrenocortical (HPA) and hypothalamo-sympatho-adrenal (HSA) circuits activated by psychogenic and metabolic stressors. Upon activation of these circuits, PACAP-responsive (in cell culture models) and PACAP-dependent (in vivo) transcriptomic responses in the adrenal gland, hypothalamus, and pituitary have been identified. Gene products produced in response circuits during stress include additional neuropeptides, neurotransmitter biosynthetic enzymes, and neuroprotective factors. Major portions of HPA and HSA stress responses are abolished in PACAP-deficient mice. This deficit occurs at the level of both the hypothalamus (HPA axis) and the adrenal medulla (HSA axis). PACAP-dependent transcriptional stress responses are conveyed through noncanonical cyclic AMP- and calcium-initiated signaling pathways within the HSA circuit. PACAP transcriptional regulation of the HPA axis, in the hypothalamus, is likely to be mediated via canonical cyclic AMP signaling through protein kinase A.

Proteomic analysis yields an unexpected trans-acting point in control of the human sympathochromaffin phenotype

BACKGROUND

The secretory protein chromogranin A (CHGA) plays a necessary role in formation of catecholamine storage vesicles and gives rise to a catecholamine release-inhibitory fragment. Because genetic variation in the proximal human CHGA promoter predicts autonomic function and blood pressure, we explored how a common genetic variant alters transcription of the gene.

METHODS AND RESULTS

Bioinformatic analysis suggested that the common G-462A promoter variant (rs9658634) may disrupt as many as 3 transcriptional control motifs: LEF1, COUP-TF, and PPARγ-RXRα. During electrophoretic mobility shifts, chromaffin cell nuclear proteins bound specifically to the A (though not G) allele of CHGA promoter G-462A. On oligonucleotide affinity chromatography followed by electrospray ionization followed by 2-dimensional (tandem) mass spectrometry analysis of A allele eluates, the transcription factor LEF1 (lymphoid enhancer-binding factor-1) was identified. Interaction of LEF1 with the A allele at G-462A was confirmed by supershift. On cotransfection, LEF1 discriminated between the allelic variants, especially in chromaffin cells. Allele specificity of trans-activation by LEF1 was transferable to an isolated G-462A element fused to a heterologous (SV40) promoter. Because β-catenin (CTNNB1) can heterodimerize with LEF1, we tested the effect of cotransfection of this factor and again found A allele-specific perturbation of CHGA transcription.

CONCLUSIONS

Common genetic variation within the human CHGA promoter alters the interaction of specific factors in trans with the promoter, with LEF1 identified by proteomic analysis and confirmed by supershift. Coexpression experiments show functional effects of LEF1 and CTNNB1 on CHGA promoter. The findings document a novel role for components of the immune and WNT pathways in control of human sympathochromaffin phenotypes.

Cardiac and vascular gene profiles in an animal model of takotsubo cardiomyopathy

We investigated cardiac and vascular gene profiles in response to immobilization stress (IMO) in rats, an animal model of emotional stress-induced takotsubo cardiomyopathy using microarray analysis, followed by re-confirmation with real-time reverse transcription-polymerase chain reaction. Expression levels of the identified genes were further estimated by pretreatment with an α1-adrenoceptor blocker and/or a β1-adrenoceptor blocker. In response to IMO, expression of 46 genes was significantly altered in the heart and that of 49 genes was significantly altered in the aorta. Pathway analysis with DAVID Bioinformatics Resources indicated that regulation of transcription and response to endogenous stimulation were the top two scoring pathways. Altered expression of cardiac genes was blunted by pretreatment with a β1-adrenoceptor blocker or α1 + β1-adrenoceptor blockers. In contrast, that of aortic genes was blunted by pretreatment with an α1-adrenoceptor blocker or α1 + β1-adrenoceptor blockers. Activation of α1-adrenoceptor in the blood vessels or activation of β1-adrenoceptors in the heart were mainly responsible for emotional stress-induced alteration of cardiac and vascular gene profiles.

Chromaffin progenitor cells from the adrenal medulla

Chromaffin cells of the adrenal medulla are neural crest-derived cells of the sympathoadrenal lineage. Different lines of evidence suggest the existence of a subpopulation of proliferation-competent progenitor cells even in the adult state. The identification of sympathoadrenal progenitors in the adrenal would greatly enhance the understanding of adrenal physiology and their potential role in adrenal pathogenesis. Isolation and differentiation of these progenitor cells in culture would provide a tool to understand their development in vitro. Furthermore, due to the close relation to sympathetic neurons, these cells might provide an expandable source of cells for cell therapy in the treatment of neurodegenerative diseases. We therefore aim to establish protocols for the efficient isolation, enrichment and differentiation of chromaffin progenitor cells to dopaminergic neurons in culture.

Catecholaminergic systems in stress: structural and molecular genetic approaches

Stressful stimuli evoke complex endocrine, autonomic, and behavioral responses that are extremely variable and specific depending on the type and nature of the stressors. We first provide a short overview of physiology, biochemistry, and molecular genetics of sympatho-adrenomedullary, sympatho-neural, and brain catecholaminergic systems. Important processes of catecholamine biosynthesis, storage, release, secretion, uptake, reuptake, degradation, and transporters in acutely or chronically stressed organisms are described. We emphasize the structural variability of catecholamine systems and the molecular genetics of enzymes involved in biosynthesis and degradation of catecholamines and transporters. Characterization of enzyme gene promoters, transcriptional and posttranscriptional mechanisms, transcription factors, gene expression and protein translation, as well as different phases of stress-activated transcription and quantitative determination of mRNA levels in stressed organisms are discussed. Data from catecholamine enzyme gene knockout mice are shown. Interaction of catecholaminergic systems with other neurotransmitter and hormonal systems are discussed. We describe the effects of homotypic and heterotypic stressors, adaptation and maladaptation of the organism, and the specificity of stressors (physical, emotional, metabolic, etc.) on activation of catecholaminergic systems at all levels from plasma catecholamines to gene expression of catecholamine enzymes. We also discuss cross-adaptation and the effect of novel heterotypic stressors on organisms adapted to long-term monotypic stressors. The extra-adrenal nonneuronal adrenergic system is described. Stress-related central neuronal regulatory circuits and central organization of responses to various stressors are presented with selected examples of regulatory molecular mechanisms. Data summarized here indicate that catecholaminergic systems are activated in different ways following exposure to distinct stressful stimuli.