Relationship of varying patterns of cytokine production to the anorexic and neuroendocrine effects of repeated Staphylococcal enterotoxin A exposure

Staphylococcal enterotoxin A (SEA) is a superantigen that stimulates T cells and induces the production of multiple cytokines. Previous studies have shown that SEA augments gustatory neophobia and activates the hypothalamic-pituitary-adrenal (HPA) axis. This study aimed to determine if the cytokine response, behavioral effects, and HPA axis activation persisted after repeated SEA treatment. Male C57BL/6J mice were given 1-4 intraperitoneal injections of 5 microg SEA, after which food intake, corticosterone, or peripheral cytokines were measured. In a series of experiments, it was found that secondary exposure to SEA two or three days after priming increased corticosterone, but attenuated splenic TNFalpha, while augmenting IL-1beta, IL-2, and IFNgamma. The anorexic response was intact after secondary exposure, but absent after a third injection, which was still able to elevate corticosterone. It is unlikely that IL-1 mediated the persistent effects on corticosterone, since this was increased in groups lacking corticosterone elevations. Similarly, TNFalpha was only modestly elevated under repeated SEA conditions that elevated plasma corticosterone. This attenuation appeared to be inversely related to the levels of IL-10, the production of which incrementally rose with each successive injection. In conclusion, repeated exposure to SEA activates the HPA axis and alters behavior. However, there may be dissociation between the behavioral and endocrine effects of SEA with increased SEA exposure. Furthermore, it is possible that while TNFalpha was previously shown to be important in response to acute SEA-induced HPA axis activation, further exposure to SEA elicits other cytokines that may exert neuromodulatory effects through sensitization and/or synergistic mechanisms.     

Influence of age on behavioral, immune and endocrine responses to the T-cell superantigen staphylococcal enterotoxin A

Aged subjects are more vulnerable to administration of the endotoxin lipopolysaccharide, but research on age-associated sensitivity to other immune stimulants has been limited. The current study examined the effects of administering the superantigen, staphylococcal enterotoxin A (SEA), to young (4-month-old) and aged (20-month-old) male C57BL/6J mice on consumption of a novel liquid, cytokine production, corticosterone levels, and expression of central mRNA levels of cytokines and corticotropin-releasing hormone. SEA produced exaggerated hypophagia in aged mice, as they showed decreased consumption that persisted for 24 h. SEA increased hypothalamic mRNA levels of interleukin-1β in the aged, but not the young, mice 2 h after administration. No differences in cytokine expression were observed 24 h after SEA. Both age groups showed increased plasma corticosterone levels 2 h after SEA administration. However, 24 h after SEA exposure the aged, but not the young, mice showed an augmented corticosterone response to the consumption test. Collectively, these data show that aging may exacerbate the behavioral and neuroinflammatory response to superantigen exposure. Further, the present study suggests that immune activation may result in delayed alterations in stress-induced corticosterone production in aged subjects.     

Role of opioid receptor like-1 receptor in modulation of endocrine,immunological, and behavioral responses to the T-cell superantigen staphylococcal enterotoxin A

Opioid receptor like-1 receptor (ORL₁) is selective for orphaninFQ/nociceptin (OFQ/N), a peptide linked to stress. Since immunologic stimuli exert stressor-like effects, the neuroendocrine and behavioral effects of the T-cell superantigen staphylococcal enterotoxin A (SEA) were tested in ORL₁^?/? and ORL₁^+/+ wildtype 129S6 mice. Within 2 h of SEA challenge both genotypes showed elevated corticosterone, but only wildtypes were elevated after 4 h, and had altered hypothalamic CRH mRNA. Although amygdaloid CRH and TNFα mRNA was increased by SEA, this did not vary with genotype. Interestingly, gustatory neophobia due to SEA challenge was augmented in ORL₁^?/? mice, although object neophobia tested 4 days later was abrogated. These results suggest differential requirements for ORL₁ in the mediation of neuroimmune effects exerted at different times after an immune challenge.     

On the role of corticotropin-releasing hormone receptors in anxiety and depression

On the basis of extensive basic and clinical studies, corticotropin-releasing hormone (CRH) and its related family members are considered to play a pivotal role in stress-related disorders, such as anxiety and depression. CRH is regarded as the principal mediator in the brain of the stress response, as it mediates neuroendocrine, autonomic, and behavioral responses to stressful challenges. Recently, this neuropeptide family has expanded due to the discovery of two new members, urocortin II (also termed stresscopin-related peptide) and urocortin III (also termed stresscopin), which are selective agonists for the CRH receptor type 2. They show a discrete neuroanatomical localization and are involved in stress-coping responses, such as anxiolysis. Here, on the basis of recent developments, we suggest that CRH, the urocortins, and their receptors form a complex system in the brain, which is recruited during both the acute and the recovery phases of the stress response.     

The effects of corticotropin-releasing hormone on peptidergic neurons in the rat forebrain

Our previous study showed that intracerebroventricular (ICV) administration of corticotropin-releasing hormone (CRH) produced a significant increase in locomotor activity at a dose of 1 microgram and slow stereotypy with prominent grooming at a dose of 10 micrograms. In addition, the ICV administration of CRH caused a significant increase in dopamine (DA) and norepinephrine turnover (NE) in various forebrain regions. The present study was designed to investigate the effects of the ICV administration of CRH on cholecystokinin (CCK), neuropeptide Y (NPY), somatostatin (SOM) and gamma-amino butyric acid (GABA) in the rat forebrain. The ICV administration of 1 and 10 micrograms CRH caused a marked reduction in CCK-like immunoreactivity (CCK-LI), NPY-LI and SOM-LI in the medial frontal cortex (MFC) and anterior cingulate cortex (Ant.CC), whereas it induced an increment of NPY-LI in the nucleus accumbens (NAc) and striatum. Increased SOM-LI and decreased NPY-LI were observed in the hippocampus following the ICV administration of CRH at both doses. The ICV administration of CRH caused a significant decrease in the BAGA content in the MFC, ant.CC, NAc and striatum. Taken together with our previous findings, these results indicate that the ICV administration of CRH induced classical neurotransmitter and neuropeptide abnormalities in the central nervous system which resulted increased emotionality, especially anxiety, in rats.     

The role of corticotropin-releasing factor--norepinephrine systems in mediating the effects of early experience on the development of behavioral and endocrine responses to stress.

Naturally occurring variations in maternal care in early postnatal life are associated with the development of individual differences in behavioral and hypothalamic-pituitary-adrenal responses to stress in the rat. These effects appear to be mediated by the influence of maternal licking and grooming on the development of central corticotropin-releasing factor (CRF) systems, which regulate the expression of behavioral, endocrine, and autonomic responses to stress through activation of forebrain noradrenergic systems. These findings provide a neurobiologic basis for the observed relationship between early life events and health in adulthood. In more recent studies, we explored the behavioral transmission of individual differences in stress reactivity, and thus, vulnerability to stress-induced illness, across generations.     

Organization of the corticotropin-releasing hormone and corticotropin-releasing hormone-binding protein systems in the central nervous system of the sea lamprey Petromyzon marinus

The expression of the corticotropin-releasing hormone (PmCRH) and the CRH-binding protein (PmCRHBP) mRNAs was studied by in situ hybridization in the brain of prolarvae, larvae, and adults of the sea lamprey Petromyzon marinus. We also generated an antibody against the PmCRH mature peptide to study the distribution of PmCRH-immunoreactive cells and fibers. PmCRH immunohistochemistry was combined with antityrosine hydroxylase immunohistochemistry, PmCRHBP in situ hybridization, or neurobiotin transport from the spinal cord. The most numerous PmCRH-expressing cells were observed in the magnocellular preoptic nucleus-paraventricular nucleus and in the superior and medial rhombencephalic reticular formation. PmCRH expression was more extended in adults than in larvae, and some cell populations were mainly (olfactory bulb) or only (striatum, ventral hypothalamus, prethalamus) observed in adults. The preopto-paraventricular fibers form conspicuous tracts coursing toward the neurohypophysis, but many immunoreactive fibers were also observed coursing in many other brain regions. Brain descending fibers in the spinal cord mainly come from cells located in the isthmus and in the medial rhombencephalic reticular nucleus. The distribution of PmCRHBP-expressing neurons was different from that of PmCRH cells, with cells mainly present in the septum, striatum, preoptic region, tuberal hypothalamus, pretectum, pineal complex, isthmus, reticular formation, and spinal cord. Again, expression in adults was more extended than in larvae. PmCRH- and PmCRHBP-expressing cells are different, excluding colocalization of these substances in the same neuron. Present findings reveal a complex CRH/CRHBP system in the brain of the oldest extant vertebrate group, the agnathans, which shows similarities but important divergences with that of mammals.     

Corticosterone effects on corticotropin-releasing hormone mRNA in the central nucleus of the amygdala and the parvocellular region of the paraventricular nucleus of the hypothalamus

Using in situ hybridization histochemistry, we report differential expression of corticotropin-releasing hormone (CRH) mRNA in the central nucleus of the amygdala (CEA) and the parvocellular region of the paraventricular nucleus of the hypothalamus (PVN) following systemic treatment with corticosterone (CORT) in adrenally-intact rats. Both injection of low (1 mg/kg/day) and high (5 mg/day) CORT reduced CRH mRNA expression in the PVN in a dose-dependent manner, although it returned to normal at the low dose by 14 days. By contrast, the high dose of CORT increased CRH mRNA transiently in the CEA at 4 days, although the low dose of CORT decreased it at 14 days. In a second experiment, we implanted a slowly-releasing CORT pellet for 2 weeks (200 mg, 60 day release) subcutaneously. This treatment produced an elevation of CRH mRNA in the CEA both at 1 and 2 weeks, whereas CRH mRNA in the PVN was decreased to a large extent as seen in the high CORT group of the first experiment. These results suggest that glucocorticoids can facilitate CRH mRNA expression in the CEA, a site implicated in anxiety and fear, while restraining the hypothalamic-pituitary-adrenal axis as indicated by the reduction in CRH mRNA in the PVN.     

Overproduction of corticotropin-releasing hormone blocks germinal center formation: role of corticosterone and impaired follicular dendritic cell networks

Corticotropin-releasing hormone (CRH) is a central mediator in the response to stress, coordinating behavioral, autonomic and neuroendocrine activation. CRH overproduction is implicated in several affective disorders, including major depression, panic-anxiety disorder and anorexia--diseases also associated with altered immune function. We investigated the link between CRH overdrive and immune function using CRH transgenic mice. Following immunization, CRH transgenic mice fail to form germinal centers; chronic glucocorticoid administration recapitulates this effect in wild-type mice. Regulation of germinal centers by glucocorticoids appears to be mediated, in part, through effects on follicular dendritic cells (FDC), providing a novel mechanism by which CRH dysregulation may significantly impair humoral immune responses.     

A direct androgenic involvement in the expression of human corticotropin-releasing hormone

We investigated the possibility of a direct action of androgens on the expression of the human corticotropin-releasing hormone (CRH), which plays a central role in the hypothalamic-pituitary-adrenal (HPA)-axis. Colocalization of CRH and nuclear/cytoplasmic androgen receptor (AR) was found in neurons of the paraventricular nucleus (PVN) in the human hypothalamus. A potential androgen-responsive element (ARE) in the human CRH promoter was subsequently analyzed with bandshifts and cotransfections in neuroblastoma cells. In the presence of testosterone, recombinant human AR bound specifically to the CRH-ARE. Expression of AR in combination with testosterone repressed CRH promoter activity through the ARE. We conclude that androgens may directly affect CRH neurons in the human PVN via AR binding to the CRH-ARE, which may have consequences for sex-specific pathogenesis of mood disorders.     

The role of corticotropin-releasing factor-like peptides in cannabis, nicotine, and alcohol dependence

The corticotropin-releasing factor (CRF)-like peptides, which include the mammalian peptides CRF, urocortin 1, urocortin 2, and urocortin 3, play an important role in orchestrating behavioral and physiological responses that may increase an organism's chance of survival when confronted with internal or external stressors. There is, however, evidence that a chronic overactivity of brain CRF systems under basal conditions may play a role in the etiology and maintenance of psychiatric disorders such as depression and anxiety disorders. In addition, there is evidence of a role for CRF-like peptides in acute and protracted drug abstinence syndromes and relapse to drug-taking behavior. This review focuses on the role of CRF-like peptides in the negative affective state associated with acute and protracted withdrawal from three widely abused drugs, cannabis, nicotine, and alcohol. In addition, we discuss the high comorbidity between stress-associated psychiatric disorders and drug dependence. A better understanding of the brain stress systems that may underlie psychiatric disorders, acute and protracted drug withdrawal, and relapse to drug-taking behavior may help in the development of new and improved pharmacotherapies for these widespread psychiatric disorders.     

The role of central dopaminergic systems in the behavioral effects of H-Phe-Ile-Tyr-His-Ser-Tyr-Lys-OH

In the present study the role of the central dopaminergic systems in the behavioral action of H-Phe-Ile-Tyr-His-Ser-Tyr-Lys-OH was investigated. The heptapeptide inhibited the extinction of active avoidance behavior if the treatment was performed intracerebroventricularly (icv) in a dose of 1 microgram, but was ineffective in a dose of 0.1 micrograms. If the peptide was injected into the nucleus accumbens septi (NAS) in a dose of 1 microgram, 0.1 micrograms or 0.01 micrograms it inhibited the extinction, but in the latter dose its effect was only a short one. H-Phe-Ile-Tyr-His-Ser-Tyr-Lys-OH in a dose of 1 microgram, 10 micrograms or 20 micrograms (icv) did not influence the turning activity of unilateral substantia nigra (USN)-lesioned animals. These results suggest that the NAS plays an important role in the behavioral action of H-Phe-Ile-Tyr-His-Ser-Tyr-Lys-OH and the heptapeptide has no direct dopamine receptor stimulatory or dopamine-releasing effect in the striatum.     

Cerebrospinal fluid levels of somatostatin, corticotropin-releasing hormone and corticotropin in alcoholism

Reduced brain and cerebrospinal fluid (CSF) levels of somatostatin, corticotropin-releasing hormone (CRH) and corticotropin (ACTH) have been reported among neuropsychiatric patients with cognitive dysfunction. Alcoholism is a disorder in which associated neuropsychiatric disorders occur. Therefore, we compared CSF levels of somatostatin, CRH and ACTH in alcoholics (n = 100) and normal controls (n = 30). There were no significant differences between the groups in concentrations of the 3 peptides. Moreover, there were no significant correlations between concentrations of the peptides in CSF and computed tomographic measures of the size of brain ventricles. There were, however, significant correlations between CSF concentrations of CRH and ACTH and between CSF concentrations of CRH and somatostatin in both the alcoholic and control groups.     

The role of corticotropin-releasing factor in the pathogenesis of major depression

It is well established that corticotropin-releasing factor (CRF), a peptide comprised of 41 amino acids, is the major physiological regulator of the pituitary-adrenal axis by virtue of its role as the hypothalamic hypophysiotropic hormone that modulates the secretion of adrenocorticotropin (ACTH) from the anterior pituitary gland. In addition to its neuroendocrine role, CRF appears to function as a neurotransmitter or neuromodulator in extrahypothalamic brain areas. The peptide and its receptors are distributed throughout the central nervous system (CNS), and CRF is released by depolarizing concentrations of potassium in a calcium-dependent manner. After direct CNS administration, CRF produces a number of behavioral and physiological effects that are reminiscent of both an organism's response to stress and to the symptoms of patients with major depression. These include: diminished food consumption, decreased sexual behavior, disturbed sleep, alterations in locomotor activity and sympathetic nervous system activation. Alterations in regional brain CRF concentration in rats were observed after acute and chronic stress, i.e. decreased hypothalamic and increased locus coeruleus CRF concentrations. To test the hypothesis that CRF is hypersecreted in patients with major depression, the concentration of CRF in cerebrospinal fluid (CSF) in drug-free depressed patients and age- and sex-matched controles was measured in two studies. The depressed patients exhibited a clear group-related increase in CSF CRF concentrations. To further test this hypothesis that CRF is chronically hypersecreted in depressed patients, the number and affinity of CRF receptors in frontal cortex was measured in a group of suicides and age-matched controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

The role of corticotropin-releasing factor and urocortin in the modulation of ingestive behavior

Participation of the hypothalamo-pituitary-adrenocortical axis, and its primary brain trigger, corticotropin-releasing factor (CRF) in the control of ingestive behavior can be inferred from data suggesting that CRF and its homologue urocortin act in brain to limit appetite following administration in rodents. Moreover, levels of endogenous CRF, CRF(1)and CRF(2)receptors and CRF-binding protein, which sequesters CRF and urocortin, are altered by changes in nutritional status brought about by food restriction/repletion. Mediation of the anorexic effects of CRF and urocortin appear not to privilege CRF(1)receptors, unlike the anxiogenic effects of CRF which are primarily a consequence of CRF(1)receptor activation. Such fear-like consequences of CRF system activation constitute a non-specific mechanism whereby the emergence of behaviors incompatible with food intake may appear to suppress appetite without affecting hunger per se. However, enhanced appetite following administration of CRF receptor antagonists and the involvement of CRF systems in sexual appetite and drug-seeking behavior all suggest a role for CRF in ingestive behavior. In particular, available evidence suggests that physiologically relevant suppression of appetite may accompany CRF system activation occurring as a consequence of stressor exposure induced by nutrient imbalance, for example, or under conditions of excessive intake or consumption of unfamiliar foodstuffs.     

The effects of intracerebroventricularly injected corticotropin-releasing factor (CRF) on the central nervous system: behavioural and biochemical studies

Intracerebroventricularly (ICV) administered corticotropin-releasing factor (CRF) produces behavioural activation in rats. The present study was designed to investigate the effects of ICV administered CRF on not only locomotor activity, but also the turnover rates of dopamine (DA) and norepinephrine (NE) in various discrete brain regions in rats. ICV administration of 1 microgram CRF produced a significant increase in locomotor activity, while ICV administration of 10 micrograms CRF caused slow stereotypy with prominent grooming. The 3,4-dihydroxyphenylacetic acid/DA ratio, e.g. DA utilization, was increased in the frontal cortex (FC), striatum, hippocampus (HIPP) and amygdala. DA utilization in the FC increased in a dose dependent manner, suggesting that the hyperactivity of the mesocortical DA system is relevant to the grooming response. The 3-methoxy-4-hydroxy-phenylglycol/NE ratio was increased in the FC and HIPP, indicating the involvement of the dorsal NE pathway in ICV CRF-induced behavioural changes in rats. These findings are discussed in connection with the hypothesis that CRF produces behavioural changes consistent with increasing emotionality, especially anxiety, and may serve as a neuroendocrine modulator of stress-enhanced behaviour.     

Nociceptin/orphanin FQ-induced delay in gastric emptying: role of central corticotropin-releasing factor and glucocorticoid receptors

Abstract  When injected intracerebroventricularly (i.c.v.) in rats, nociceptin/orphanin FQ (N/OFQ) delays gastric emptying and increases plasma corticosterone levels. Our aim in this study was to investigate changes in gastric emptying of a phenol red meal, and the plasma corticosterone response to N/OFQ in adrenalectomized (ADX) rats, in ADX rats injected with corticosterone at 1, 24 and 72 h before the gastric emptying assay, and in intact rats i.c.v. pretreated with a glucocorticoid antagonist (RU486) and with a corticotropin-releasing factor receptor antagonist ( α -helical CRF_9–41). In adrenal intact rats, i.c.v. injection of N/OFQ (2.5 nmol rat⁻¹) significantly delayed gastric emptying (by 70%) and increased plasma corticosterone concentrations. Conversely, in ADX rats, N/OFQ left gastric emptying unchanged. In ADX rats, corticosterone injected at 1, 24 and 72 h before the gastric emptying assay almost restored the N/OFQ-induced delay in gastric emptying. Finally, pretreatment with RU486- and α -helical CRF_9–41 abolished the N/OFQ-induced inhibition of gastric emptying. These findings suggest that central N/OFQ inhibits gastric emptying through an integrated orphaninergic system–CRF interaction in which corticosterone plays a permissive role.     

Differential impact of predator or immobilization stressors on central corticotropin-releasing hormone and bombesin-like peptides in Fast and Slow seizing rat

Lines of rats selectively bred for amygdala excitability, as reflected by kindling rates in response to electrical stimulation, also exhibit differences in tests of anxiety. Inasmuch as corticotropin-releasing hormone (CRH) and bombesin (BN) have been associated with anxiety, regional levels and release of these peptides, as well as plasma adrenocorticotropic hormone (ACTH) and corticosterone, were assessed in 'Slow' and 'Fast' seizing rats following predator exposure (ferret) or immobilization. Ferret exposure elicited a greater increase of plasma ACTH and corticosterone concentrations in the Slow than in the Fast rats. In contrast, immobilization provoked a greater rise of plasma ACTH levels in the Fast rats, paralleling the vigorous struggling observed in this line. In Slow rats, stressor exposure elicited increased levels of ir-BN at the anterior hypothalamus, and increased ir-CRH at the median eminence/arcuate nucleus (Me/Arc), paraventricular hypothalamic nucleus (PVN) and pituitary (Pit), whereas decreased levels of ir-BN were found at the nucleus tractus solitarius (NTS). Fast rats likewise showed decreased ir-BN at the NTS, but unlike the Slow rats, ir-CRH was reduced in the Me/Arc, PVN and Pit in response to both stressors. In vivo microdialysis experiments revealed that in response to ferret exposure, the Slow rats showed a greater CRH release at the central nucleus of the amygdala (CeA) as compared to Fast rats. However, immobilization elicited a more pronounced release of CRH in Fast than in Slow rats. Taken together, the results demonstrate that these two lines of rats show differential endocrinological and neurochemical response patterns to these stressors.     

Recombinant human growth hormone in abstinent androgenic-anabolic steroid use: psychological, endocrine and trophic factor effects

This study examined whether six days recombinant human growth hormone (rhGH) affected psychological profile in an abstinent androgenic-anabolic steroid (AAS) abusing group, compared with an abstinent AAS control group. Male subjects (n = 48) were assigned in a random fashion into one of two groups: (1): (n=24) control group (C); (2): (n=24) rhGH group (GH). A hospital anxiety scale (HADS) questionnaire was completed by all subjects. Physiological responses investigated included anthropometry. Biochemical markers examined included; serum glucose, sodium, urea, lipid profile, high sensitivity C-reactive protein (hsCRP), homocysteine (HCY), tetra-iodothyronine (T4), thyroid stimulating (TSH), luteinising (LH) and follicle stimulating (FSH) hormones, testosterone (T), prolactin (PRL), cortisol and insulin like growth factor-1 (IGF-I). HADS questionnaire significantly decreased in both anxiety (A) and depression (D) symptoms within GH (P<0.017) and compared with C (P<0.05). Body mass index (BMI) and fat-free mass index (FFMI) significantly increased (both P<0.017) while body fat significantly decreased within GH (P<0.017). IGF-I significantly increased within GH (P<0.017) and significantly increased compared with C (P<0.05). Serum sodium significantly increased (P<0.017) and serum HCY, hsCRP, TSH and T4, significantly decreased within GH (all P<0.017). PRL significantly increased and T4 significantly decreased compared with C (both P<0.05). The findings of this study suggest that short term use of rhGH has beneficial effects on mental state in individuals who were previous abusers of AAS and appeared to have a beneficial effect on cardiovascular risk markers associated with adverse mental health.