CRH: The link between hormonal-, metabolic- and behavioral responses to stress

Stress integration by an ascending adrenergic-melanocortin circuit

Stress is thought to be an important contributing factor for eating disorders; however, neural substrates underlying the complex relationship between stress and appetite are not fully understood. Using in vivo recordings from awake behaving mice, we show that various acute stressors activate catecholaminergic nucleus tractus solitarius (NTSTH) projections in the paraventricular hypothalamus (PVH). Remarkably, the resulting adrenergic tone inhibits MC4R-expressing neurons (PVHMC4R), which are known for their role in feeding suppression. We found that PVHMC4R silencing encodes negative valence in sated mice and is required for avoidance induced by visceral malaise. Collectively, these findings establish PVHMC4R neurons as an effector of stress-activated brainstem adrenergic input in addition to the well-established hypothalamic-pituitary-adrenal axis. Convergent modulation of stress and feeding by PVHMC4R neurons implicates NTSTH → PVHMC4R input in stress-associated appetite disorders.

Chronic kidney disease may evoke anxiety by altering CRH expression in the amygdala and tryptophan metabolism in rats

Chronic kidney disease (CKD) is associated with anxiety; however, its exact mechanism is not well understood. Therefore, the aim of the present study was to assess the effect of moderate CKD on anxiety in rats. 5/6 nephrectomy was performed in male Wistar rats. 7 weeks after, anxiety-like behavior was assessed by elevated plus maze (EPM), open field (OF), and marble burying (MB) tests. At weeks 8 and 9, urinalysis was performed, and blood and amygdala samples were collected, respectively. In the amygdala, the gene expression of Avp and the gene and protein expression of Crh, Crhr1, and Crhr2 were analyzed. Furthermore, the plasma concentration of corticosterone, uremic toxins, and tryptophan metabolites was measured by UHPLC-MS/MS. Laboratory tests confirmed the development of CKD. In the CKD group, the closed arm time increased; the central time and the total number of entries decreased in the EPM. There was a reduction in rearing, central distance and time in the OF, and fewer interactions with marbles were detected during MB. CKD evoked an upregulation of gene expression of Crh, Crhr1, and Crhr2, but not Avp, in the amygdala. However, there was no alteration in protein expression. In the CKD group, plasma concentrations of p-cresyl-sulfate, indoxyl-sulfate, kynurenine, kynurenic acid, 3-hydroxykynurenine, anthranilic acid, xanthurenic acid, 5-hydroxyindoleacetic acid, picolinic acid, and quinolinic acid increased. However, the levels of tryptophan, tryptamine, 5-hydroxytryptophan, serotonin, and tyrosine decreased. In conclusion, moderate CKD evoked anxiety-like behavior that might be mediated by the accumulation of uremic toxins and metabolites of the kynurenine pathway, but the contribution of the amygdalar CRH system to the development of anxiety seems to be negligible at this stage.

Sub-region expression of brain-derived neurotrophic factor in the dorsal hippocampus and amygdala is Affected by mild traumatic brain injury and stress in male rats

The US population suffers 1.5 million head injuries annually, of which mild traumatic brain injuries (mTBI) comprise 75%. Many individuals subsequently experience long-lasting negative symptoms, including anxiety. Previous rat-based work in our laboratory has shown that mTBI changes neuronal counts in the hippocampus and amygdala, regions associated with anxiety. Specifically, mTBI increased neuronal death in the dorsal CA1 sub-region of the hippocampus, but attenuated it in the medial (MeA) and the basolateral nuclei of the amygdala nine days following injury, which was associated with greater anxiety. We have also shown that glucocorticoid receptor (GR) antagonism prior to concomitant stress and mTBI extinguishes anxiety-like behaviors. Using immunohistochemistry, this study examines the expression of brain-derived neurotrophic factor (BDNF) following social defeat and mTBI, and whether this is affected by prior glucocorticoid receptor antagonism as a potential mechanism behind these anxiety and neuronal differences. Here, stress and mTBI upregulate BDNF in the MeA, and both GR and mineralocorticoid receptor antagonism downregulate BDNF in the dorsal hippocampal CA1 and dentate gyrus, as well as the central nucleus of the amygdala. These findings suggest BDNF plays a role in the mechanism underlying neuronal changes following mTBI in amygdalar and hippocampal subregions, and may participate in stress elicited changes to neural plasticity in these regions. Taken together, these results suggest an essential role for BDNF in the development of anxiety behaviors following concurrent stress and mTBI.

Stress-related cellular pathophysiology as a crosstalk risk factor for neurocognitive and psychiatric disorders

In this narrative review, we examine biological processes linking psychological stress and cognition, with a focus on how psychological stress can activate multiple neurobiological mechanisms that drive cognitive decline and behavioral change. First, we describe the general neurobiology of the stress response to define neurocognitive stress reactivity. Second, we review aspects of epigenetic regulation, synaptic transmission, sex hormones, photoperiodic plasticity, and psychoneuroimmunological processes that can contribute to cognitive decline and neuropsychiatric conditions. Third, we explain mechanistic processes linking the stress response and neuropathology. Fourth, we discuss molecular nuances such as an interplay between kinases and proteins, as well as differential role of sex hormones, that can increase vulnerability to cognitive and emotional dysregulation following stress. Finally, we explicate several testable hypotheses for stress, neurocognitive, and neuropsychiatric research. Together, this work highlights how stress processes alter neurophysiology on multiple levels to increase individuals' risk for neurocognitive and psychiatric disorders, and points toward novel therapeutic targets for mitigating these effects. The resulting models can thus advance dementia and mental health research, and translational neuroscience, with an eye toward clinical application in cognitive and behavioral neurology, and psychiatry.

Effects of sub-chronic CRH administration into the hypothalamic paraventricular and central amygdala nuclei in male rats with a focus on food intake biomarkers

CRH neurons are found in the paraventricular nucleus(PVN) and central amygdala(CeA) nuclei. This study investigated the effects of sub-chronic CRH administration into the PVN and CeA nuclei on food intake biomarkers in rats divided into five groups: control, two shams, and two CRH-PVN and CRH-CeA groups(receiving CRH in nuclei for seven days). The CRH-PVN group had significantly higher cumulative food intake and food intake trends than the CRH-CeA group. The CRH-CeA and CRH-PVN groups exhibited significant increases in food intake during hours 1 and 2, respectively. Moreover, to be time-dependent, food intake is modulated by different brain nuclei. The CRH signaling pathway appeared to be activated later in the PVN than CeA. Both groups exhibited significantly higher leptin levels, the CRH-PVN group exhibited higher ghrelin levels and lower glucose levels. Repetitive administration of CRH into the PVN and CeA significantly reduced body weight differences. CRH administration into the PVN affected both leptin and ghrelin levels, but ghrelin had a greater impact on glucose variations and cumulative food intake than leptin. Finally, CRH administration into the PVN and CeA likely activated the HPA axis, and the CeA had a greater impact on the stress circuit than on food intake behavior.

Knockout of TSC2 in Nav1.8+ neurons predisposes to the onset of normal weight obesity

OBJECTIVE

Obesity and nutrient oversupply increase mammalian target of rapamycin (mTOR) signaling in multiple cell types and organs, contributing to the onset of insulin resistance and complications of metabolic disease. However, it remains unclear when and where mTOR activation mediates these effects, limiting options for therapeutic intervention. The objective of this study was to isolate the role of constitutive mTOR activation in Nav1.8-expressing peripheral neurons in the onset of diet-induced obesity, bone loss, and metabolic disease.

METHODS

In humans, loss of function mutations in tuberous sclerosis complex 2 (TSC2) lead to maximal constitutive activation of mTOR. To mirror this in mice, we bred Nav1.8-Cre with TSC2fl/fl animals to conditionally delete TSC2 in Nav1.8-expressing neurons. Male and female mice were studied from 4- to 34-weeks of age and a subset of animals were fed a high-fat diet (HFD) for 24-weeks. Assays of metabolism, body composition, bone morphology, and behavior were performed.

RESULTS

By lineage tracing, Nav1.8-Cre targeted peripheral sensory neurons, a subpopulation of postganglionic sympathetics, and several regions of the brain. Conditional knockout of TSC2 in Nav1.8-expressing neurons (Nav1.8-TSC2KO) selectively upregulated neuronal mTORC1 signaling. Male, but not female, Nav1.8-TSC2KO mice had a 4-10% decrease in body size at baseline. When challenged with HFD, both male and female Nav1.8-TSC2KO mice resisted diet-induced gains in body mass. However, this did not protect against HFD-induced metabolic dysfunction and bone loss. In addition, despite not gaining weight, Nav1.8-TSC2KO mice fed HFD still developed high body fat, a unique phenotype previously referred to as 'normal weight obesity'. Nav1.8-TSC2KO mice also had signs of chronic itch, mild increases in anxiety-like behavior, and sex-specific alterations in HFD-induced fat distribution that led to enhanced visceral obesity in males and preferential deposition of subcutaneous fat in females.

CONCLUSIONS

Knockout of TSC2 in Nav1.8+ neurons increases itch- and anxiety-like behaviors and substantially modifies fat storage and metabolic responses to HFD. Though this prevents HFD-induced weight gain, it masks depot-specific fat expansion and persistent detrimental effects on metabolic health and peripheral organs such as bone, mimicking the 'normal weight obesity' phenotype that is of growing concern. This supports a mechanism by which increased neuronal mTOR signaling can predispose to altered adipose tissue distribution, adipose tissue expansion, impaired peripheral metabolism, and detrimental changes to skeletal health with HFD - despite resistance to weight gain.

Gene expression in the female tree swallow brain is associated with inter- and intra-population variation in glucocorticoid levels

Studies of the evolutionary causes and consequences of variation in circulating glucocorticoids (GCs) have begun to reveal how they are shaped by selection. Yet the extent to which variation in circulating hormones reflects variation in other important regulators of the hypothalamic-pituitary-adrenal (HPA) axis, and whether these relationships vary among populations inhabiting different environments, remain poorly studied. Here, we compare gene expression in the brain of female tree swallows (Tachycineta bicolor) from populations that breed in environments that differ in their unpredictability. We find evidence of inter-population variation in the expression of glucocorticoid and mineralocorticoid receptors in the hypothalamus, with the highest gene expression in a population from an extreme environment, and lower expression in a population from a more consistent environment as well as in birds breeding at an environmentally variable high-altitude site that are part of a population that inhabits a mixture of high and low altitude habitats. Within some populations, variation in circulating GCs predicted differences in gene expression, particularly in the hypothalamus. However, some patterns were present in all populations, whereas others were not. These results are consistent with the idea that some combination of local adaptation and phenotypic plasticity may modify components of the HPA axis affecting stress resilience. Our results also underscore that a comprehensive understanding of the function and evolution of the stress response cannot be gained from measuring circulating hormones alone, and that future studies that apply a more explicitly evolutionary approach to important regulatory traits are likely to provide significant insights.

Knockdown of endoplasmic reticulum chaperone BiP leads to the death of parvocellular AVP/CRH neurons in mice

Arginine vasopressin (AVP) is expressed in both magnocellular (magnAVP) and parvocellular AVP (parvAVP) neurons of the paraventricular nucleus, and AVP colocalizes with corticotropin-releasing hormone (CRH) only in the parvocellular neurons. The immunoglobulin heavy chain binding protein (BiP) is a major endoplasmic reticulum (ER) chaperone which regulates the unfolded protein response under ER stress. We previously demonstrated that knockdown of BiP in magnAVP neurons exacerbated ER stress, which resulted in the autophagy-associated cell death of magnAVP neurons. Using the same approach, in the present study we examined the role of BiP in mouse parvAVP/CRH neurons. Our data demonstrate that BiP is expressed in mouse parvAVP/CRH neurons under nonstress conditions and is upregulated in proportion to the increase in CRH expression after adrenalectomy. For BiP knockdown in parvAVP/CRH neurons, we utilized a viral approach in combination with shRNA interference. Knockdown of BiP expression induced ER stress in parvAVP/CRH neurons, as reflected by the expression of C/EBP homologous protein. Furthermore, BiP knockdown led to the loss of parvAVP/CRH neurons after 4 weeks. In summary, our results demonstrate that BiP plays a pivotal role in parvAVP/CRH neurons, which function as neuroendocrine cells producing a large number of secretory proteins.

Some Aspects of Pituitary-Adrenal and Autonomic Nervous Systems Functioning in Patients with Chronic Consciousness Disorders

Patients with chronic disorders of consciousness (CDoC) have various variants of the pathological organization of functions including sympathetic hyperactivity and hormonal changes.

The objective: to determine the severity of paroxysmal sympathetic hyperactivity (PSH), the function of the pituitary-adrenal system in patients with CDoC.

Subjects and Methods. 54 patients with CDoC were enrolled in the study. Patients were randomized in the groups depending on assessment on the Coma Recovery Scale-Revised scale and CRS-R index calculation. PSH severity was assessed 7 times a day for two days. During the first week from the moment of admission, blood sampling was performed 7 times a day to study the levels of ACTH and cortisol.

Results. PSH syndrome was detected in all groups, there were no significant dependencies of its severity on the time of day. There were no significant differences in the levels of ACTH and cortisol during the day.

Conclusions: PSH syndrome is observed in most patients with CDoC. In patients with CDoC, the daily rhythm of ACTH and cortisol secretion are disrupted.

Perioperative Changes in Serum Concentration of Glial Fibrillar Acid Protein and Delayed Cognitive Recovery: an Experimental Observational Study

A number of studies have found an association between the increased concentration of glial fibrillar acid protein (GFAP) in blood serum in patients with various types of brain damage (ischemic stroke, traumatic brain injury, neurodegenerative and neuro-oncological diseases), as well as with a rapid decline in cognitive functions in elderly people with initially normal cognitive abilities.

The objective: to identify the relationship between delayed cognitive recovery and changes in serum GFAP concentration in the perioperative period in patients operated for various oncological diseases.

Subjects and Methods. The study included 30 patients who underwent surgical treatment for prostate cancer, colorectal cancer and pancreatic cancer under combined general anesthesia.

The inclusion criteria were the expected duration of the operation over 300 minutes and the age over 60 years. GFAP was determined in plasma by enzyme immunoassay before anesthesia, the next day after surgery and on the 4th–5th day. Neuropsychological testing was performed before surgery and on the 4th–5th postoperative day. Delayed cognitive recovery was defined as a decrease in the composite z-score of more than one standard deviation (SD) compared to the preoperative assessment.

Correlation analysis was performed between changes in the composite z-score (in absolute values) and the difference in GFAP concentration between the outcome and the first postoperative day, the outcome and the 4th–5th postoperative day and the first and 4th–5th postoperative days.

Results. In five cases (16.6%), a decrease in the composite z-score > 1 SD was revealed indicating a delayed cognitive recovery. In the remaining 25 (83.4%) patients, changes in the composite z-score were less than one standard deviation. The median concentration of GFAP in patients with delayed cognitive recovery was 0.13 [0.1; 0.14] before surgery, 0.12 [0.09; 0.14] the day after surgery and 0.16 [0.05; 0.19] on the 4th–5th day after surgery. In patients without cognitive impairment, the concentration of GFAP was 0.15 [0.125; 0.184] before surgery, 0.15 [0.121; 0.163] 24 hours after surgery and 0.13 [0.079; 0.151] on the 4th–5th day after surgery. The correlation values between changes in the composite z-score and the difference in GFAP concentrations were: between the outcome and the first postoperative day – rs = 0.107, p = 0.37, outcome and the 4th–5th postoperative day – rs = 0.134, p = 0.37, the first and 4th‒5th postoperative days – rs = 0.21, p = 0.37.

Discussion. There was no statistically significant difference in GFAP levels between patients with delayed cognitive recovery and patients without cognitive impairment. There was also no correlation between the difference in GFAP concentrations in plasma before surgery and 24 hours after, before surgery and on the 4th–5th day of the postoperative period and the composite z-score.

Conclusions. The use of GFAP to predict cognitive decline associated with surgical treatment of colorectal cancer, prostate cancer and pancreatic cancer under general anesthesia is not yet possible.

Invisible wounds: Suturing the gap between the neurobiology, conventional and emerging therapies for posttraumatic stress disorder

A sharp increase in the prevalence of neuropsychiatric disorders, including major depression, anxiety, substance use disorders and posttraumatic stress disorder (PTSD) has occurred due to the traumatic nature of the persisting COVID-19 global pandemic. PTSD is estimated to occur in up to 25% of individuals following exposure to acute or chronic trauma, and the pandemic has inflicted both forms of trauma on much of the population through both direct physiological attack as well as an inherent upheaval to our sense of safety. However, despite significant advances in our ability to define and apprehend the effects of traumatic events, the neurobiology and neuroanatomical circuitry of PTSD, one of the most severe consequences of traumatic exposure, remains poorly understood. Furthermore, the current psychotherapies or pharmacological options for treatment have limited efficacy, durability, and low adherence rates. Consequently, there is a great need to better understand the neurobiology and neuroanatomy of PTSD and develop novel therapies that extend beyond the current limited treatments. This review summarizes the neurobiological and neuroanatomical underpinnings of PTSD and discusses the conventional and emerging psychotherapies, pharmacological and combined psychopharmacological therapies, including the use of psychedelic-assisted psychotherapies and neuromodulatory interventions, for the improved treatment of PTSD and the potential for their wider applications in other neuropsychiatric disorders resulting from traumatic exposure.

The hypothalamic paraventricular nucleus as a central hub for the estrogenic modulation of neuroendocrine function and behavior

Estradiol and hypothalamic paraventricular nucleus (PVN) help coordinate reproduction with body physiology, growth and metabolism. PVN integrates hormonal and neural signals originating in the periphery, generating an output mediated both by its long-distance neuronal projections, and by a variety of neurohormones produced by its magnocellular and parvocellular neurosecretory cells. Here we review the cyto-and chemo-architecture, the connectivity and function of PVN and the sex-specific regulation exerted by estradiol on PVN neurons and on the expression of neurotransmitters, neuromodulators, neuropeptides and neurohormones in PVN. Classical and non-classical estrogen receptors (ERs) are expressed in neuronal afferents to PVN and in specific PVN interneurons, projecting neurons, neurosecretory neurons and glial cells that are involved in the input-output integration and coordination of neurohormonal signals. Indeed, PVN ERs are known to modulate body homeostatic processes such as autonomic functions, stress response, reproduction, and metabolic control. Finally, the functional implications of the estrogenic modulation of the PVN for body homeostasis are discussed.

The Pituitary-Adrenal Response to Paradoxical Sleep Deprivation Is Similar to a Psychological Stressor, Whereas the Hypothalamic Response Is Unique

Stressors of different natures induce activation of the hypothalamic-pituitary-adrenal (HPA) axis at different magnitudes. Moreover, the HPA axis response to repeated exposure is usually distinct from that elicited by a single session. Paradoxical sleep deprivation (PSD) augments ACTH and corticosterone (CORT) levels, but the nature of this stimulus is not yet defined. The purpose of the present study was to qualitatively compare the stress response of animals submitted to PSD to that of rats exposed once or four times to cold, as a physiological stress, movement restraint (RST) as a mixed stressor and predator odour (PRED) as the psychological stressor, whilst animals were submitted for 1 or 4 days to PSD and respective control groups. None of the stressors altered corticotropin releasing factor immunoreactivity in the paraventricular nucleus of the hypothalamus (PVN), median eminence (ME) or central amygdala, compared to control groups, whereas vasopressin immunoreactivity in PSD animals was decreased in the PVN and increased in the ME, indicating augmented activity of this system. ACTH levels were higher after repeated stress or prolonged PSD than after single- or 1 day-exposure and control groups, whereas the CORT response was habituated by repeated stress, but not by 4-days PSD. This dissociation resulted in changes in the CORT : ACTH ratio, with repeated cold and RST decreasing the ratio compared to single exposure, but no change was seen in PRED and PSD groups. Comparing the magnitude and pattern of pituitary-adrenal response to the different stressors, PSD-induced responses were closer to that shown by PRED-exposed rats. In contrast, the hypothalamic response of PSD-exposed rats was unique, inasmuch as this was the only stressor which increased the activity of the vasopressin system. In conclusion, we propose that the pituitary-adrenal response to PSD is similar to that induced by a psychological stressor.

The role of the corticotropin-releasing hormone and its receptors in the regulation of stress response

Stress is an essential part of everyday life. The neuropeptide corticotropin-releasing hormone (CRH, also called CRF and corticoliberin) plays a key role in the integration of neuroendocrine, autonomic and behavioral responses to stress. The activation of the hypothalamic-pituitary-adrenal axis (HPA axis) by neurons of the paraventricular hypothalamic nucleus (PVN), the primary site of synthesis CRH, triggers stress reactions. In addition to the hypothalamus, CRH is widespread in extrahypothalamic brain structures, where it functions as a neuromodulator for coordination and interaction between the humoral and behavioral aspects of a stress response. The axons of neurons expressing CRH are directed to various structures of the brain, where the neuropeptide interacts with specific receptors (CRHR1, CRHR2) and can affect various mediator systems that work together to transmit signals to different brain regions to cause many reactions to stress. Moreover, the effect of stress on brain functions varies from behavioral adaptation to increased survival and increased risk of developing mental disorders. Disturbances of the CRH system regulation are directly related to such disorders: mental pathologies (depression, anxiety, addictions), deviations of neuroendocrinological functions, inflammation, as well as the onset and development of neurodegenerative diseases such as Alzheimer’s disease. In addition, the role of CRH as a regulator of the neurons structure in the areas of the developing and mature brain has been established. To date, studies have been conducted in which CRHR1 is a target for antidepressants, which are, in fact, antagonists of this receptor. In this regard, the study of the participation of the CRH system and its receptors in negative effects on hormone-dependent systems, as well as the possibility of preventing them, is a promising task of modern physiological genetics. In this review, attention will be paid to the role of CRH in the regulation of response to stress, as well as to the involvement of extrahypothalamic CRH in pathophysiology and the correction of mental disorders.

Polymorphisms of COMT and CREB1 are associated with treatment-resistant depression in a Chinese Han population

Genetic factors play a crucial role for the pathophysiology of treatment-resistant depression (TRD). It has been established that Catechol-O-methyltransferase (COMT) and cyclic amp-response element-binding protein (CREB) are associated with antidepressant response. The aim of this study was to explore the association between single nucleotide polymorphisms (SNPs) in COMT and CREB1 genes and TRD in a Chinese population. We recruited 181 patients with major depressive disorder (MDD) and 80 healthy controls, including 81 TRD patients. Depressive symptoms were assessed with the Hamilton Depression Rating Scale-17 (HDRS). Genotyping was performed using mass spectrometry. Genetic analyses were conducted by PLINK Software. The distribution of COMT SNP rs4818 allele and genotypes were significantly different between TRD and controls. Statistical differences in allele frequencies were observed between TRD and non-TRD groups, including rs11904814 and rs6740584 in CREB1 gene, rs4680 and rs4818 in COMT gene. There were differences in the distribution of HDRS total scores among different phenotypes of CREB1 rs11904814, CREB1 rs6740584, COMT rs4680 and rs4818. Gene-gene interaction effect of COMT-CREB1 (rs4680 × rs6740584) revealed significant epistasis in TRD. There findings indicate that COMT and CREB1 polymorphisms influence the risk of TRD and affect the severity of depressive symptoms of MDD.

Stress and central autonomic network

The central autonomic network (CAN) plays a critical role in the stress response, which is triggered by challenges on the homeostasis (physiological stressors) or unpleasant social or environmental situations. This review focuses on the role of areas of the CAN including the insular and anterior cingulate cortices, extended amygdala, hypothalamus, periaqueductal gray and locus coeruleus in the stress response. These areas are interconnected and affect sympathetic or parasympathetic output via their influence on premotor or preganglionic autonomic neurons in the lower brainstem and spinal cord. The insula integrates multiple inputs to create a sense of the physiological state of the body, whereas the anterior cingulate initiates predictive visceromotor commands. The amygdala and bed nucleus of the stria terminalis provide automatic emotional tagging and trigger automatic survival responses to threat via their outputs to the hypothalamus, periaqueductal gray, and lower brainstem. Several regions of the hypothalamus, including the paraventricular nucleus, dorsomedial nucleus and lateral hypothalamic area participate in different patterns of stress response according to the type of stimulus and projections to premotor and preganglionic autonomic neurons. The periaqueductal gray initiates different patterns of autonomic, pain modulatory, and motor responses, including the "fight or flight" or "playing dead" responses. The locus coeruleus promotes emotional learning in the amygdala associated with states of anxiety. Neurons of the C1 area of the rostral ventrolateral medulla elicit sympathoexcitatory responses to internal stressors such as hypoxia and inflammation. The ventromedial medulla, including the nucleus raphe pallidus, initiates sympathoexcitatory responses to social and other external stressors.

ComparativeStudyofCRHMicroinjections Into PVN and CeA Nuclei on Food Intake, Ghrelin, Leptin, and Glucose Levels in Acute Stressed Rats

Introduction:

Corticotropin-Releasing Hormone (CRH) is involved in stress and energy homeostasis. On the other hand, CRH receptors also exist within the paraventricular nucleus (PVN) and Central Amygdala (CeA) nuclei. The present study compared the effect of CRH microinjections into PVN and CeA on three consecutive hours and cumulative food intake, internal regulatory factors of food intake, such as serum leptin and ghrelin, as well as blood glucose levels in rats under different acute psychological (Social Stress [SS] and Isolation Stress [IS] group) stresses.

Methods:

Sixty-six male Wistar rats were randomly allocated to 11 groups: Control, Sham, CRH-PVN, CRH-CeA, SS, IS, SS-CRH-PVN, SS-CRH-CeA, IS-CRH-PVN, and IS-CRH-CeA groups. The CRH (2 µg/kg in 0.5 µL saline) was injected into PVN and CeA nuclei in rats under everyday, acute social stress and isolation stress conditions.

Results:

Acute isolation and social stresses did not affect cumulative food intake. Whereas isolation stress led to changes in both leptin and glucose levels, social stress reduced only glucose levels. Cumulative food intake significantly decreased under acute CRH injection into the CeA and particularly into the PVN. Blood glucose significantly reduced in all the groups receiving CRH into their CeA.

Conclusion:

The PVN played a more important role compared to CeA on food intake. These nuclei probably employ different mechanisms for their effects on food intake. Besides, it seems that exogenously CRH injection into the PVN probably had a more anorectic effect than naturally activated CRH by stresses. Acute isolation stress had a greater impact than social stress on leptin level and cumulative food intake. Thus, elevated food intake related to leptin compared to ghrelin and glucose levels in the CRH-PVN group under acute social stress.

Stress hormones mediate developmental plasticity in vertebrates with complex life cycles

The environment experienced by developing organisms can shape the timing and character of developmental processes, generating different phenotypes from the same genotype, each with different probabilities of survival and performance as adults. Chordates have two basic modes of development, indirect and direct. Species with indirect development, which includes most fishes and amphibians, have a complex life cycle with a free-swimming larva that is typically a growth stage, followed by a metamorphosis into the adult form. Species with direct development, which is an evolutionarily derived developmental mode, develop directly from embryo to the juvenile without an intervening larval stage. Among the best studied species with complex life cycles are the amphibians, especially the anurans (frogs and toads). Amphibian tadpoles are exposed to diverse biotic and abiotic factors in their developmental habitat. They have extensive capacity for developmental plasticity, which can lead to the expression of different, adaptive morphologies as tadpoles (polyphenism), variation in the timing of and size at metamorphosis, and carry-over effects on the phenotype of the juvenile/adult. The neuroendocrine stress axis plays a pivotal role in mediating environmental effects on amphibian development. Before initiating metamorphosis, if tadpoles are exposed to predators they upregulate production of the stress hormone corticosterone (CORT), which acts directly on the tail to cause it to grow, thereby increasing escape performance. When tadpoles reach a minimum body size to initiate metamorphosis they can vary the timing of transformation in relation to growth opportunity or mortality risk in the larval habitat. They do this by modulating the production of thyroid hormone (TH), the primary inducer of metamorphosis, and CORT, which synergizes with TH to promote tissue transformation. Hypophysiotropic neurons that release the stress neurohormone corticotropin-releasing factor (CRF) are activated in response to environmental stress (e.g., pond drying, food restriction, etc.), and CRF accelerates metamorphosis by directly inducing secretion of pituitary thyrotropin and corticotropin, thereby increasing secretion of TH and CORT. Although activation of the neuroendocrine stress axis promotes immediate survival in a deteriorating larval habitat, costs may be incurred such as reduced tadpole growth and size at metamorphosis. Small size at transformation can impair performance of the adult, reducing probability of survival in the terrestrial habitat, or fecundity. Furthermore, elevations in CORT in the tadpole caused by environmental stressors cause long term, stable changes in neuroendocrine function, behavior and physiology of the adult, which can affect fitness. Comparative studies show that the roles of stress hormones in developmental plasticity are conserved across vertebrate taxa including humans.

Characterization and evaluation of the tissue distribution of CRH, apelin, and GnRH2 reveal responses to feeding states in Schizothorax davidi

Schizothorax davidi is a rare fish in Southwest China and is considered a promising species for aquaculture. Compared with other teleosts, little is known about the endocrine regulation of feeding in this species. In this study, we identified the CRH, apelin, and GnRH2 genes in S. davidi and assessed the effects of different energy statuses on CRH, apelin, and GnRH2 expression. Our results showed that the full-length cDNA sequences of CRH, apelin, and GnRH2 of S. davidi were 995, 905, and 669 bp long, respectively. Furthermore, CRH was mainly expressed in the hypothalamus, telencephalon, and myelencephalon; apelin was highly expressed in the spleen and heart; and GnRH2 mRNA was widely distributed in all examined tissues, with the highest level in the hypothalamus. Notably, the levels of CRH and GnRH2 increased in the hypothalamus at 1 h and 3 h post-feeding, while hypothalamic apelin levels decreased. Conversely, CRH and GnRH2 expression in the hypothalamus significantly decreased after fasting for 7 days and returned to the control levels after re-feeding for 3 or 5 days. In contrast, fasting increased apelin levels in the hypothalamus. Overall, this study suggests that CRH, apelin, and GnRH2 play critical roles in appetite regulation in S. davidi. These results provide an essential groundwork to elucidate the appetite regulatory systems in S. davidi as well as in other teleosts.

Pathophysiological implications of neuroinflammation mediated HPA axis dysregulation in the prognosis of cancer and depression

Cancer patients are more likely to develop depressive symptoms and show a poor prognosis compared to the normal healthy individuals. Cancer occurrence and the anticancer treatments result in the pro-inflammatory cytokines-mediated inflammation, which dysregulates the HPA-axis activity that may result in depression-like behaviour. Conversely, depression causes the activation of the HPA-axis that results in the downstream release of endogenous glucocorticoids which may result in depressive signs and symptoms in some cancer patients. Depression may also result in non-adherence to treatment and increased mortality in cancer patients. In this review, we have focused on the role of neuroimmune axis and hyperactive HPA-axis in case of both cancer and depression. Therefore, therapeutics targeting the HPA-axis dysregulation could be effective in ameliorating symptoms of depression in cancer patients.

Advances in Treatment of Post-Traumatic Stress Disorder with Chinese Medicine

"Timely, near, and expectation" is the main principle of battlefield rescue for military combat stress reaction (CSR). Post-traumatic stress disorder (PTSD) is the most common form of CSR and a long-term persistent mental disorder that is caused by unusual threatening or catastrophic psychological trauma. Chinese medicine (CM) has abundant resources, is simple, easy to master, with few side effects. This article summarizes the cellular and animal experimental mechanisms of CM treatment on PTSD, suggesting that traditional Chinese herbs and acupuncture can protect brain functional areas, and adjust hypothalamus-pituitary-adrenal axis. Traditional Chinese herbs and acupuncture have shown good anti-stress efficacy and fewer side effects in clinical application, which may improve the CSR in the battlefield.

PAI-1 protein is a key molecular effector in the transition from normal to PTSD-like fear memory

Moderate stress increases memory and facilitates adaptation. In contrast, intense stress can induce pathological memories as observed in post-traumatic stress disorders (PTSD). A shift in the balance between the expression of tPA and PAI-1 proteins is responsible for this transition. In conditions of moderate stress, glucocorticoid hormones increase the expression of the tPA protein in the hippocampal brain region which by triggering the Erk1/2^MAPK signaling cascade strengthens memory. When stress is particularly intense, very high levels of glucocorticoid hormones then increase the production of PAI-1 protein, which by blocking the activity of tPA induces PTSD-like memories. PAI-1 levels after trauma could be a predictive biomarker of the subsequent appearance of PTSD and pharmacological inhibition of PAI-1 activity a new therapeutic approach to this debilitating condition.

Drug Addiction: Hyperkatifeia/Negative Reinforcement as a Framework for Medications Development

Compulsive drug seeking that is associated with addiction is hypothesized to follow a heuristic framework that involves three stages (binge/intoxication, withdrawal/negative affect, and preoccupation/anticipation) and three domains of dysfunction (incentive salience/pathologic habits, negative emotional states, and executive function, respectively) via changes in the basal ganglia, extended amygdala/habenula, and frontal cortex, respectively. This review focuses on neurochemical/neurocircuitry dysregulations that contribute to hyperkatifeia, defined as a greater intensity of negative emotional/motivational signs and symptoms during withdrawal from drugs of abuse in the withdrawal/negative affect stage of the addiction cycle. Hyperkatifeia provides an additional source of motivation for compulsive drug seeking via negative reinforcement. Negative reinforcement reflects an increase in the probability of a response to remove an aversive stimulus or drug seeking to remove hyperkatifeia that is augmented by genetic/epigenetic vulnerability, environmental trauma, and psychiatric comorbidity. Neurobiological targets for hyperkatifeia in addiction involve neurocircuitry of the extended amygdala and its connections via within-system neuroadaptations in dopamine, enkephalin/endorphin opioid peptide, and γ-aminobutyric acid/glutamate systems and between-system neuroadaptations in prostress corticotropin-releasing factor, norepinephrine, glucocorticoid, dynorphin, hypocretin, and neuroimmune systems and antistress neuropeptide Y, nociceptin, endocannabinoid, and oxytocin systems. Such neurochemical/neurocircuitry dysregulations are hypothesized to mediate a negative hedonic set point that gradually gains allostatic load and shifts from a homeostatic hedonic state to an allostatic hedonic state. Based on preclinical studies and translational studies to date, medications and behavioral therapies that reset brain stress, antistress, and emotional pain systems and return them to homeostasis would be promising new targets for medication development. SIGNIFICANCE STATEMENT: The focus of this review is on neurochemical/neurocircuitry dysregulations that contribute to hyperkatifeia, defined as a greater intensity of negative emotional/motivational signs and symptoms during withdrawal from drugs of abuse in the withdrawal/negative affect stage of the drug addiction cycle and a driving force for negative reinforcement in addiction. Medications and behavioral therapies that reverse hyperkatifeia by resetting brain stress, antistress, and emotional pain systems and returning them to homeostasis would be promising new targets for medication development.

Activation of stress response axis as a key process in environment-induced sex plasticity in fish

The determination of sex is an important hallmark in the life cycle of organisms, in which the fate of gonads and then the individual sex are defined. In gonochoristic teleost fish, this process is characterized by a high plasticity, considering that in spite of genotypic sex many environmental factors can cause shifts from one to another molecular pathway, resulting in organisms with mismatching genotypic and phenotypic sexes. Interestingly, in most instances, both female-to-male or male-to-female sex-reversed individuals develop functional gonads with normal gametogenesis and respective progenies with full viability. The study of these mechanisms is being spread to other non-model species or to those inhabiting more extreme environmental conditions. Although water temperature is an important mechanism involved in sex determination, there are other environmental stressors affected by the climate change which are also implicated in stress response-induced masculinization in fish. In this regard, the brain has emerged as the transducer of the environment input that can influence the gonadal fate. Furthermore, the evaluation of other environmental stressors or their synergic effect on sex determination at conditions that simulate the natural environments is growing gradually. Within such scope, the concerns related to climate change impacts rely on the fact that many of biotic and abiotic parameters reported to affect sex ratios are expected to increase concomitantly as a result of increased greenhouse gas emissions and, particularly worrying, many of them are related to male bias in the populations, such as high temperature, hypoxia, and acidity. These environmental changes can also generate epigenetic changes in sex-related genes affecting their expression, with implications on sex differentiation not only of exposed individuals but also in following generations. The co-analysis of multi-stressors with potential inter- and transgenerational effects is essential to allow researchers to perform long-term predictions on climate change impacts in wild populations and for establishing highly accurate monitoring tools and suitable mitigation strategies.

Gut-Amygdala Interactions in Autism Spectrum Disorders: Developmental Roles via regulating Mitochondria, Exosomes, Immunity and microRNAs

BACKGROUND

Autism Spectrum Disorders (ASD) have long been conceived as developmental disorder. A growing body of data highlights a role for alterations in the gut in the pathoetiology and/or pathophysiology of ASD. Recent work shows alterations in the gut microbiome to have a significant impact on amygdala development in infancy, suggesting that the alterations in the gut microbiome may act to modulate not only amygdala development but how the amygdala modulates the development of the frontal cortex and other brain regions.

METHODS

This article reviews wide bodies of data pertaining to the developmental roles of the maternal and foetal gut and immune systems in the regulation of offspring brain development.

RESULTS

A number of processes seem to be important in mediating how genetic, epigenetic and environmental factors interact in early development to regulate such gut-mediated changes in the amygdala, wider brain functioning and inter-area connectivity, including via regulation of microRNA (miR)-451, 14-3-3 proteins, cytochrome P450 (CYP)1B1 and the melatonergic pathways. As well as a decrease in the activity of monoamine oxidase, heightened levels of in miR-451 and CYP1B1, coupled to decreased 14-3-3 act to inhibit the synthesis of N-acetylserotonin and melatonin, contributing to the hyperserotonemia that is often evident in ASD, with consequences for mitochondria functioning and the content of released exosomes. These same factors are likely to play a role in regulating placental changes that underpin the association of ASD with preeclampsia and other perinatal risk factors, including exposure to heavy metals and air pollutants. Such alterations in placental and gut processes act to change the amygdala-driven biological underpinnings of affect-cognitive and affect-sensory interactions in the brain.

CONCLUSION

Such a perspective readily incorporates previously disparate bodies of data in ASD, including the role of the mu-opioid receptor, dopamine signaling and dopamine receptors, as well as the changes occurring to oxytocin and taurine levels. This has a number of treatment implications, the most readily applicable being the utilization of sodium butyrate and melatonin.

Sex-Dependent Mechanisms of Glucocorticoid Regulation of the Mouse Hypothalamic Corticotropin-Releasing Hormone Gene

To limit excessive glucocorticoid secretion following hypothalamic-pituitary-adrenal (HPA) axis stimulation, circulating glucocorticoids inhibit corticotropin-releasing hormone (CRH) expression in paraventricular nucleus (PVN) neurons. As HPA function differs between sexes and depends on circulating estradiol (E2) levels in females, we investigated sex/estrous stage-dependent glucocorticoid regulation of PVN Crh. Using NanoString nCounter technology, we first demonstrated that adrenalectomized (ADX'd) diestrous female (low E2), but not male or proestrous female (high E2), mice exhibited a robust decrease in PVN CRH mRNA following 2-day treatment with the glucocorticoid receptor (GR) agonist RU28362. Immunohistochemical analysis of PVN CRH neurons in Crh-IRES-Cre;Ai14 mice, where TdTomato fluorescence permanently tags CRH-expressing neurons, showed similarly abundant co-expression of GR-immunoreactivity in males, diestrous females, and proestrous females. However, we identified sex/estrous stage-related glucocorticoid regulation or expression of GR transcriptional coregulators. Out of 17 coregulator genes examined using nCounter multiplex analysis, mRNAs that were decreased by RU28362 in ADX'd mice in a sex/estrous stage-dependent fashion included: GR (males = diestrous females > proestrous females), signal transducer and activator of transcription 3 (STAT3) (males < diestrous = proestrous), and HDAC1 (males < diestrous > proestrous). Steroid receptor coactivator 3 (SRC-3), nuclear corepressor 1 (NCoR1), heterogeneous nuclear ribonucleoprotein U (hnrnpu), CREB binding protein (CBP) and CREB-regulated transcription coactivator 2 (CRTC2) mRNAs were lower in ADX'd diestrous and proestrous females versus males. Additionally, most PVN CRH neurons co-expressed methylated CpG binding protein 2 (MeCP2)-immunoreactivity in diestrous female and male Crh-IRES-Cre;Ai14 mice. Our findings collectively suggest that GR's sex-dependent regulation of PVN Crh may depend upon differences in the GR transcriptional machinery and an underlying influence of E2 levels in females.

Converging Relationships of Obesity and Hyperuricemia with Special Reference to Metabolic Disorders and Plausible Therapeutic Implications

BACKGROUND

Obesity and hyperuricemia mutually influence metabolic syndrome. This study discusses the metabolic relationships between obesity and hyperuricemia in terms of pathophysiology, complications, and treatments.

METHODS

We searched for preclinical or clinical studies on the pathophysiology, complications, and therapy of obesity and hyperuricemia on the PubMed database.

RESULTS

In this systemic review, we summarized our searching results on topics of pathophysiology, complications and therapeutic strategy. In pathophysiology, we firstly introduce genetic variations for obesity, hyperuricemia and their relationships by genetic studies. Secondly, we talk about the epigenetic influences on obesity and hyperuricemia. Thirdly, we describe the central metabolic regulation and the role of hyperuricemia. Then, we refer to the character of adipose tissue inflammation and oxidative stress in the obesity and hyperuricemia. In the last part of this topic, we reviewed the critical links of gut microbiota in the obesity and hyperuricemia. In the following part, we review the pathophysiology of major complications in obesity and hyperuricemia including insulin resistance and type 2 diabetes mellitus, chronic kidney disease, cardiovascular diseases, and cancers. Finally, we recapitulate the therapeutic strategies especially the novel pharmaceutic interventions for obesity and hyperuricemia, which concurrently show the mutual metabolic influences between two diseases.

CONCLUSION

The data reviewed here delineate the metabolic relationships between obesity and hyperuricemia, and provide a comprehensive overview of the therapeutic targets for the management of metabolic syndromes.

Metabolic Association between Leptin and the Corticotropin Releasing Hormone

Objective

In healthy individuals, leptin is produced from adipose tissue and is secreted into the circulation to communicate energy balance status to the brain and control fat metabolism. Corticotropin-Releasing Hormone (CRH) is synthesized in the hypothalamus and regulates stress responses. Among the many adipokines and hormones that control fat metabolism, leptin and CRH both curb appetite and inhibit food intake. Despite numerous reports on leptin and CRH properties and function, little has been actually shown about their association in the adipose tissue environment.

Methods

In this article, we summarized the salient information on leptin and CRH in relation to metabolism. We also investigated the direct effect of recombinant CRH on leptin secretion by primary cultures of human adipocytes isolated from subcutaneous abdominal adipose tissue of 7 healthy children and adolescents, and measured CRH and leptin levels in plasma collected from peripheral blood of 24 healthy children and adolescents to assess whether a correlation exists between CRH and leptin levels in the periphery.

Results and Conclusion

The available data indicate that CRH exerts a role in the regulation of leptin in human adipocytes. We show that CRH downregulates leptin production by mature adipocytes and that a strong negative correlation exists between CRH and leptin levels in the periphery, and suggest the possible mechanisms of CRH control of leptin. Delineation of CRH control of leptin production by adipocytes may explain unknown pathogenic mechanisms linking stress and metabolism.

Thermal Manipulation During Embryogenesis Impacts H3K4me3 and H3K27me3 Histone Marks in Chicken Hypothalamus

Changes in gene activity through epigenetic alterations induced by early environmental challenges during embryogenesis are known to impact the phenotype, health, and disease risk of animals. Learning how environmental cues translate into persisting epigenetic memory may open new doors to improve robustness and resilience of developing animals. It has previously been shown that the heat tolerance of male broiler chickens was improved by cyclically elevating egg incubation temperature. The embryonic thermal manipulation enhanced gene expression response in muscle (P. major) when animals were heat challenged at slaughter age, 35 days post-hatch. However, the molecular mechanisms underlying this phenomenon remain unknown. Here, we investigated the genome-wide distribution, in hypothalamus and muscle tissues, of two histone post-translational modifications, H3K4me3 and H3K27me3, known to contribute to environmental memory in eukaryotes. We found 785 H3K4me3 and 148 H3K27me3 differential peaks in the hypothalamus, encompassing genes involved in neurodevelopmental, metabolic, and gene regulation functions. Interestingly, few differences were identified in the muscle tissue for which differential gene expression was previously described. These results demonstrate that the response to embryonic thermal manipulation (TM) in chicken is mediated, at least in part, by epigenetic changes in the hypothalamus that may contribute to the later-life thermal acclimation.

Identification of a neurocircuit underlying regulation of feeding by stress-related emotional responses

Feeding is known to be profoundly affected by stress-related emotional states and eating disorders are comorbid with psychiatric symptoms and altered emotional responses. The neural basis underlying feeding regulation by stress-related emotional changes is poorly understood. Here, we identify a novel projection from the paraventricular hypothalamus (PVH) to the ventral lateral septum (LSv) that shows a scalable regulation on feeding and behavioral changes related to emotion. Weak photostimulation of glutamatergic PVH→LSv terminals elicits stress-related self-grooming and strong photostimulation causes fear-related escape jumping associated with respective weak and strong inhibition on feeding. In contrast, inhibition of glutamatergic inputs to LSv increases feeding with signs of reduced anxiety. LSv-projecting neurons are concentrated in rostral PVH. LSv and LSv-projecting PVH neurons are activated by stressors in vivo, whereas feeding bouts were associated with reduced activity of these neurons. Thus, PVH→LSv neurotransmission underlies dynamic feeding by orchestrating emotional states, providing a novel neural circuit substrate underlying comorbidity between eating abnormalities and psychiatric disorders.

Prenatal maternal vaginal inflammation increases anxiety and alters HPA axis signalling in adult male mice

BACKGROUND

Maternal infection during pregnancy is known to adversely affect foetal development, but previous studies have rarely investigated the impact of gynaecological diseases during pregnancy on offspring during adulthood. Vaginitis is one of the most prevalent gynaecological diseases during pregnancy.

METHODS

The effect of maternal vaginal inflammation on offspring was simulated by inducing maternal vaginal infection. We performed a transvaginal injection of lipopolysaccharide (LPS) in pregnant mice to induce vaginitis and investigated their offspring by means of behavioural tests and molecular and cellular measurements.

RESULTS

Behavioural tests revealed that the offspring of mothers transvaginally injected with LPS exhibited sex-dependent differences. Male offspring showed increased anxiety-related behaviours, including reduced time exploring the open arm in the elevated plus maze test and light chamber in the light-dark box test. Serum levels of corticosterone were increased in LPS male offspring, indicating activation of the hypothalamic-pituitary-adrenal (HPA) axis. Corticotropin-releasing hormone (CRH) protein expression and c-Fos positive cells were increased in the hypothalamic paraventricular nucleus (PVN) in LPS male offspring, which presented with an increased number of microglia.

CONCLUSION

This study suggests that prenatal vaginal infection increases anxiety-like behaviour in male offspring, possibly via activation of the HPA axis.

Twenty-Seven Tamoxifen-Inducible iCre-Driver Mouse Strains for Eye and Brain, Including Seventeen Carrying a New Inducible-First Constitutive-Ready Allele

To understand gene function, the cre/loxP conditional system is the most powerful available for temporal and spatial control of expression in mouse. However, the research community requires more cre recombinase expressing transgenic mouse strains (cre-drivers) that restrict expression to specific cell types. To address these problems, a high-throughput method for large-scale production that produces high-quality results is necessary. Further, endogenous promoters need to be chosen that drive cell type specific expression, or we need to further focus the expression by manipulating the promoter. Here we test the suitability of using knock-ins at the docking site 5′ of Hprt for rapid development of numerous cre-driver strains focused on expression in adulthood, using an improved cre tamoxifen inducible allele (icre/ERT2), and testing a novel inducible-first, constitutive-ready allele (icre/f3/ERT2/f3). In addition, we test two types of promoters either to capture an endogenous expression pattern (MaxiPromoters), or to restrict expression further using minimal promoter element(s) designed for expression in restricted cell types (MiniPromoters). We provide new cre-driver mouse strains with applicability for brain and eye research. In addition, we demonstrate the feasibility and applicability of using the locus 5′ of Hprt for the rapid generation of substantial numbers of cre-driver strains. We also provide a new inducible-first constitutive-ready allele to further speed cre-driver generation. Finally, all these strains are available to the research community through The Jackson Laboratory.

Neural Mechanisms Involved in the Noxious Physical Stress-Induced Inhibition of Ovarian Estradiol Secretion

Stress is known to change the secretion of ovarian steroid hormones via the hypothalamic-pituitary-ovarian (HPO) axis. Noxious physical stress can cause reflex responses in visceral function via autonomic nerves. This article reviews our recent animal studies on neural mechanisms involved in ovarian estradiol secretion induced by noxious physical stress stimulation. In anesthetized rats, noxious physical stress (pinching the hindpaw or electrical stimulation of the tibial nerve) decreased ovarian estradiol secretion. These noxious stress-induced ovarian hormonal responses were observed after decerebration but were abolished after spinal transection. Electrical stimulation of the ovarian sympathetic nerves (superior ovarian nerves: SON) decreased ovarian estradiol secretion. The reduced secretion of ovarian estradiol induced by hindpaw pinching was abolished by bilateral severance of the SON. Efferent activity of the SON was increased following hindpaw pinching. Thus, the inhibition of ovarian estradiol secretion during noxious physical stress was mainly integrated in the brainstem, and this inhibitory response was due to reflex activation of sympathetic nerves to the ovary. In rats, the sympathetic inhibitory regulation of ovarian estradiol secretion was pronounced when the HPO axis was inhibited by chronic estradiol treatment. Considering the female life cycle, extensive physical stress may inhibit ovarian function, especially before puberty and during old ages when the HPO axis is inactive. Anat Rec, 302:904-911, 2019. © 2019 Wiley Periodicals, Inc.

Promoter haplotypes of the corticotropin-releasing hormone encoding gene modulate the physiological stress response in vitro and in vivo

The corticotropin-releasing hormone (CRH) is a neuropeptide mediating stress responses. CRH exerts effects via the hypothalamus pituitary adrenal axis as well as immediate effects on the sympathetic-adrenal-medullary system. Genetic variants of the CRH promoter were previously found to be associated with altered CRH promoter activity and physiological reactions. Functional characterization of three CRH promoter haplotypes have been performed in vitro using a reporter gene assay under different stimulation conditions. Furthermore, 232 healthy subjects were genotyped and the influence of CRH haplotypes on basal parameters such as post-awakening cortisol and blood pressure as well as on stress reactivity measured after socially evaluated cold pressor test (SeCPT) was investigated. In vitro, CRH haplotype 2 showed the highest promoter activity under baseline conditions and after forskolin stimulation compared with other haplotypes. Forskolin treatment resulted in a two fold increase of haplotype 2 promoter activity compared with the baseline condition. Cell line-dependent promoter activation was found after hydrocortisone treatment. In vivo, CRH haplotype 2 carriers showed significant higher baseline blood pressure (p = .002) and blood pressure after SeCPT (p < .001), but did not differ in cortisol levels. This study provides converging evidence for the importance of CRH promoter variants on physiological stress response parameters.

The central nervous system acts as a transducer of stress-induced masculinization through corticotropin-releasing hormone B

Exposure to environmental stressors, like high temperature (HT), during early development of fish induces sex reversal of genotypic females. Nevertheless, the involvement of the brain in this process is not well clarified. In the present work, we investigated the mRNA levels of corticotropin-releasing hormone b (crhb) and its receptors (crhr1 and crhr2), and found out that they were up-regulated at HT during the critical period of gonadal sex determination in medaka. In order to clarify their roles in sex reversal, biallelic mutants for crhr1 and crhr2 were produced by CRISPR/Cas9 technology. Remarkably, biallelic mutant of both loci (crhr1 and crhr2) did not undergo female-to-male sex reversal upon HT exposition. Inhibition of this process in double crhrs mutants could be successfully rescued through the administration of the downstream effector of the hypothalamic-pituitary interrenal axis, the cortisol. Taken together, these results revealed for the first time the participation of the CNS acting as a transducer of masculinization induced by thermal stress.

Effect of Electroacupuncture on the Activity of Corticotrophin-Releasing Hormone Neurons in the Hypothalamus and Amygdala in Rats Exposed to Restraint Water-Immersion Stress

Objective

To investigate the effects of electroacupuncture (EA) treatment on gastric mucosal lesions and the activity of corticotrophin-releasing hormone (CRH) neurons in the paraventricular nucleus (PVN) of the hypothalamus and the central nucleus of the amygdala (CNA) in a rat model of restraint water-immersion stress (RWIS).

Methods

24 male Wistar rats were randomly divided into three groups: normal, RWIS, and RWIS+EA (n=8 per group). Rats in the RWIS group and RWIS+EA group received RWIS for 3 hours. For rats in the RWIS+EA group, EA was applied at ST36 in the bilateral hind legs for 30 min before RWIS. Rats in the normal group did not receive stressors or EA treatment. The gastric mucosal lesions of each rat were evaluated by the erosion index (EI) according to the methods of Guth. The activity of CRH neurons in the PVN and CNA was measured by a dual immunohistochemical test for Fos and CRH in the brain sections.

Results

RWIS induced serious gastric mucosal lesions. The mean gastric EI was significantly decreased in the RWIS+EA group versus the RWIS group (P=0.005). Stress induced significant activation of CRH neurons in the PVN and CNA compared with the normal group (P<0.001 for both). The mean number of Fos+CRH immunoreactive neurons in the PVN and CNA were both decreased inRWIS+EA versusRWIS groups (P<0.001 and P=0.001).

Conclusions

EA at ST36 can ameliorate RWIS-induced gastric mucosal lesions and suppress the Fos expression of CRH neurons in the PVN and CNA, suggesting a potentially therapeutic role for EA in stress-related gastric disorders.

Health, pre-disease and critical transition to disease in the psycho-immune-neuroendocrine network: Are there distinct states in the progression from health to major depressive disorder?

The psycho-immune-neuroendocrine (PINE) network is a regulatory network of interrelated physiological pathways that have been implicated in major depressive disorder (MDD). A model of disease progression for MDD is presented where the stable, healthy state of the PINE network (PINE physiome) undergoes progressive pathophysiological changes to an unstable but reversible pre-disease state (PINE pre-diseasome) with chronic stress. The PINE network may then undergo critical transition to a stable, possibly irreversible disease state of MDD (PINE pathome). Critical transition to disease is heralded by early warning signs which are detectible by biomarkers specific to the PINE network and may be used as a screening test for MDD. Critical transition to MDD may be different for each individual, as it is reliant on diathesis, which comprises genetic predisposition, intrauterine and developmental factors. Finally, we propose the PINE pre-disease state may form a "universal pre-disease state" for several non-communicable diseases (NCDs), and critical transition of the PINE network may lead to one of several frequently associated disease states (influenced by diathesis), supporting the existence of a common Chronic Illness Risk Network (CIRN). This may provide insight into both the puzzle of multifinality and the growing clinical challenge of multimorbidity.

Neuropeptide and steroid hormone mediators of neuroendocrine regulation

To maintain the health and well-being of all mammals, numerous aspects of physiology are controlled by neuroendocrine mechanisms. These mechanisms ultimately enable communication between neurones and glands throughout the body and are centrally mediated by neuropeptides and/or steroid hormones. A recent session at the International Workshop in Neuroendocrinology highlighted the essential roles of some of these neuropeptide and steroid hormone mediators in the neuroendocrine regulation of stress-, reproduction- and behaviour-related processes. Accordingly, the present review highlights topics presented in this session, including the role of the neuropeptides corticotrophin-releasing factor and gonadotrophin-releasing hormone in stress and reproductive physiology, respectively. Additionally, it details an important role for gonadal sex steroids in the development of behavioural sex preference.

Glucocorticoid withdrawal affects stress-induced changes of urocortin 2 gene expression in rat adrenal medulla and brain

Corticotropin-releasing factor is well known activator of the hypothalamic-pituitary-adrenocortical axis, that represents crucial system participating on stress response of the organism. Urocortins are members of the corticotropin-releasing factor family of peptides with proposed effects on neuroendocrine and behavioral stress response mechanisms. Urocortin 2, one of three known urocortins, is present in central and peripheral stress response system and its expression can be augmented by glucocorticoids. In the present study we have examined how glucocorticoid withdrawal affects urocortin 2 gene expression after acute immobilization in the adrenal medulla and selected brain areas in rats. We used pharmacological adrenalectomy to block synthesis of corticosterone. Our results show that the immobilization-induced rise in urocortin 2 mRNA levels in rat adrenal medulla was not inhibited by glucocorticoid withdrawal. On the other hand, observed changes in the brain indicate that the effect of stress and pharmacological adrenalectomy on urocortin 2 gene expression is site-specific. While in the paraventricular nucleus and locus coeruleus the immobilization induced rise of urocortin 2 was not inhibited by pharmacological adrenalectomy in the arcuate nucleus and central amygdala it was. Moreover, we have seen a significant depletion of urocortin 2 plasma levels after immobilization. The immobilization induced rise of urocortin 2 gene expression in rat adrenal medulla and brain areas regulating stress response pathways and preservation of its induction after adrenalectomy suggests a role of urocortin 2 in the neuroendocrine stress response of an organism. This article is protected by copyright. All rights reserved.

c-Fos mapping of brain regions activated by multi-modal and electric foot shock stress

Real-world stressors are complex and multimodal, involving physical, psychological, and social dimensions. However, the brain networks that mediate stress responses to these stimuli need to be further studied. We used c-Fos mapping in mice to characterize brain circuits activated by exposure to a single episode of multimodal stress (MMS), and compared these to circuits activated by electric foot shocks (EFS). We focused on characterizing c-Fos activity in stress-relevant brain regions including the paraventricular nucleus (PVN) of the hypothalamus and the bed nucleus of the stria terminalis (BNST). We also assessed stress-induced activation of CRH-positive neurons in each of these structures. MMS and EFS activated an overlapping network of brain regions with a similar time course. c-Fos expression within the PVN and the BNST peaked 30–60 min after exposure to both MMS and EFS, and returned to baseline levels within 24 h. Quantification of c-Fos expression within BNST subregions revealed that while c-Fos expression peaked in all subregions 30–60 min after MMS and EFS exposure, the neuronal density of c-Fos expression was significantly higher in the dorsomedial and ventral BNST relative to the dorsolateral BNST. Our preliminary assessment indicated that a great majority of MMS or EFS-activated neurons in the PVN were CRH-positive (>87%); in contrast, about 6–35% of activated neurons in the BNST were CRH-positive. Our findings indicate that both MMS and EFS are effective at activating stress-relevant brain areas and support the use of MMS as an effective approach for studying multidimensional stress in animal models. The results also reveal that the PVN and BNST are part of a common neural circuit substrate involved in neural processing related to stress.

miR-212 mediates counter-regulation on CRH expression and HPA axis activity in male mice

The mechanisms of hypothalamic-pituitary-adrenal (HPA) axis regulation have been studied persistently but still are not elucidated. Considering the emerging roles of microRNA in stress response, we conducted a microRNA microarray in mice hypothalamus to identify the potential role of microRNAs in regulating the HPA axis. In total, 41 microRNAs changed during heat stress in which we found that miR-212 contains a binding sequence with corticotropin-releasing hormone (Crh) 3'UTR according to a sequence analysis. We observed that miR-212 expression in the hypothalamus was escalated by repeated heat and restraint stress. By overexpression or inhibition of miR-212 and the dual-luciferase reporter assay, we proved that miR-212 could bind with Crh 3'UTR to regulate its expression in mice hypothalamus primary cells and in the hippocampus neuron cell line HT-22. In addition, we injected miR-212 agomir or antagomir in mice hypothalamus to overexpress or inhibit miR-212, which leads to alterations of CRH expression and HPA axis activity in vivo Furthermore, miR-212 and CRH were both transcribed by the cAMP response element-binding protein (CREB). Overexpression and inhibition of miR-212 affect CREB-dependent CRH expression. Taken together, our results suggest an inhibitory role of miR-212 on the HPA axis, which acts in a counter-regulatory manner.

Altered brain and gut responses to corticotropin-releasing hormone (CRH) in patients with irritable bowel syndrome

Stress is a known trigger of irritable bowel syndrome (IBS) and exacerbates its gastrointestinal symptoms. However, underlying the physiological mechanism remains unknown. Here, we investigated hypothalamic–pituitary–adrenal (HPA) axis, colonic motility, and autonomic responses to corticotropin-releasing hormone (CRH) administration as well as brain activity alterations in IBS. The study included 28 IBS patients and 34 age and sex-matched healthy control subjects. IBS patients demonstrated greater adrenocorticotropic hormone (ACTH) responses to CRH than control subjects. Male IBS patients had greater increases in colonic motility than male HCs after CRH. Female IBS patients showed altered sympathovagal balance and lower basal parasympathetic tone relative to female control subjects. Brain responses to rectal distention were measured in the same subjects using functional magnetic resonance imaging, and their associations with individual ACTH responses to CRH were tested. A negative association between ACTH response to CRH and activity in the pregenual anterior cingulate cortex (pACC) during rectal distention was identified in controls but not in IBS patients. Impaired top-down inhibitory input from the pregenual ACC to the HPA axis may lead to altered neuroendocrine and gastrointestinal responses to CRH. Centrally acting treatments may dampen the stress induced physical symptoms in IBS.

Neuroendocrine disruption without direct endocrine mode of action: Polychloro-biphenyls (PCBs) and bisphenol A (BPA) as case studies

Endocrine disruption is commonly thought to be restricted to a direct endocrine mode of action i.e. the perturbation of the activation of a given type of hormonal receptor by its natural ligand. Consistent with the WHO definition of an endocrine disrupter, a key issue is the "altered function(s) of the endocrine system". Such altered functions can result from different chemical interactions, beyond agonistic or antagonistic effect at a given receptor. Based on neuroendocrine disruption by polychlorinated biphenyls and bisphenol A, this paper proposes different mechanistic paradigms that can result in adverse health effects. They are a consequence of altered endocrine function(s) secondary to chemical interaction with different steps in the physiological regulatory processes, thus accounting for a possibly indirect endocrine mode of action.

Endocrinology and the brain: corticotropin-releasing hormone signaling

Corticotropin-releasing hormone (CRH) is a key player of basal and stress-activated responses in the hypothalamic-pituitary-adrenal axis (HPA) and in extrahypothalamic circuits, where it functions as a neuromodulator to orchestrate humoral and behavioral adaptive responses to stress. This review describes molecular components and cellular mechanisms involved in CRH signaling downstream of its G protein-coupled receptors (GPCRs) CRHR1 and CRHR2 and summarizes recent findings that challenge the classical view of GPCR signaling and impact on our understanding of CRHRs function. Special emphasis is placed on recent studies of CRH signaling that revealed new mechanistic aspects of cAMP generation and ERK1/2 activation in physiologically relevant contexts of the neurohormone action. In addition, we present an overview of the pathophysiological role of the CRH system, which highlights the need for a precise definition of CRHRs signaling at molecular level to identify novel targets for pharmacological intervention in neuroendocrine tissues and specific brain areas involved in CRH-related disorders.

Epigenetic programming of the neuroendocrine stress response by adult life stress

The hypothalamic-pituitary-adrenal (HPA) axis is critically involved in the neuroendocrine regulation of stress adaptation, and the restoration of homeostasis following stress exposure. Dysregulation of this axis is associated with stress-related pathologies like major depressive disorder, post-traumatic stress disorder, panic disorder and chronic anxiety. It has long been understood that stress during early life can have a significant lasting influence on the development of the neuroendocrine system and its neural regulators, partially by modifying epigenetic regulation of gene expression, with implications for health and well-being in later life. Evidence is accumulating that epigenetic plasticity also extends to adulthood, proposing it as a mechanism by which psychological trauma later in life can long-lastingly affect HPA axis function, brain plasticity, neuronal function and behavioural adaptation to neuropsychological stress. Further corroborating this claim is the phenomenon that these epigenetic changes correlate with the behavioural consequences of trauma exposure. Thereby, epigenetic modifications provide a putative molecular mechanism by which the behavioural phenotype and transcriptional/translational potential of genes involved in HPA axis regulation can change drastically in response to environmental challenges, and appear an important target for treatment of stress-related disorders. However, improved insight is required to increase their therapeutic (drug) potential. Here, we provide an overview of the growing body of literature describing the epigenetic modulation of the (primarily neuroendocrine) stress response as a consequence of adult life stress and interpret the implications for, and the challenges involved in applying this knowledge to, the identification and treatment of stress-related psychiatric disorders.

Mechanism of physical stress-induced inhibition of ovarian estradiol secretion in anesthetized rats

This study examined the site of main integration center in the physical stress-induced inhibition of ovarian estradiol secretion because of ovarian sympathetic nerve (superior ovarian nerve: SON) activation in anesthetized rats. In central nervous system-intact rats, electrical stimulation of the tibial afferent nerve at 10V increased the efferent activity of the SON by 39±13% and reduced the ovarian secretion of estradiol by 34±7%. These responses were observed in decerebrate rats but were abolished in spinal rats. Thus, the main integration center for this ovarian hormonal response is located in the brain stem.