The roles of prolactin, growth hormone, insulin-like growth factor-I, and thyroid hormones in lymphocyte development and function: insights from genetic models of hormone and hormone receptor deficiency

Female offspring gestated in hypothyroxinemia and infected with human Metapneumovirus (hMPV) suffer a more severe infection and have a higher number of activated CD8+ T lymphocytes

Maternal thyroid hormones (THs) are essential for the appropriate development of the fetus and especially for the brain. Recently, some studies have shown that THs deficiency can also alter the immune system development of the progeny and their ability to mount an appropriate response against infectious agents. In this study, we evaluated whether adult mice gestated under hypothyroxinemia (Hpx) showed an altered immune response against infection with human metapneumovirus (hMPV). We observed that female mice gestated under Hpx showed higher clinical scores after seven days of hMPV infection. Besides, males gestated under Hpx have higher lung viral loads at day seven post-infection. Furthermore, the female offspring gestated in Hpx have already reduced the viral load at day seven and accordingly showed an increased proportion of activated (CD71⁺ and FasL⁺) CD8⁺ T cells in the lungs, which correlated with a trend for a higher histopathological clinical score. These results support that T₄ deficiency during gestation might condition the offspring differently in males and females, enhancing their ability to respond to hMPV.

Alteration of Endocrine Hormones and Antibody Responses in Different Spectrum of Tuberculosis Disease

Effective control of Mycobacterium tuberculosis (Mtb) infection is mediated by multifaceted factors that involve both the endocrine and immune system. Profiling hormones and antibodies in different stages of TB provides insight in the pathogenesis of the disease. In this study, we profiled endocrine hormones (dehydroepiandrosterone (DHEA), cortisol, testosterone, estradiol, growth hormone and leptins) and Mtb strain H37RV lipoarabinomannan (LAM)-specific antibody levels in plasma samples, collected from pulmonary TB (PTB) patients, TB lymphadenitis (TBLN) patients and latently infected (QFT-positive) or uninfected (QFT-negative) apparently healthy individuals using ELISA. Plasma levels of leptin and DHEA were significantly low in PTB and TBLN patients compared to healthy controls (P<0.0001 and P=0.02, respectively), whereas these levels significantly increased following anti-TB treatment (P=0.002 and P=0.0001, respectively) among TB patients. The levels of estradiol and testosterone significantly improved following anti-TB treatment (P=0.03 and P=0.0003, respectively), whereas cortisol and growth hormones declined significantly (P <0.05). Similarly, LAM-specific IgG, IgM and IgA were significantly higher in PTB patients compared to other groups, whereas levels of IgG1 subtype were significantly higher among LTBI groups compared to both TB patients and QFT-negative individuals (P<0.0001). Overall, we observed significantly variable levels of endocrine hormones as well as immunoglobulins across the spectrum of TB illness and such profiling has a significant contribution in selection of effective biomarkers that have roles in TB treatment monitoring or diagnostics. Although this study did not show a functional association between hormones and antibodies, alterations in the levels of these biomarkers suggest the key roles these markers play in TB pathogenesis.

Resilience in Long-Term Viral Infection: Genetic Determinants and Interactions

Virus-induced neurological sequelae resulting from infection by Theiler's murine encephalomyelitis virus (TMEV) are used for studying human conditions ranging from epileptic seizures to demyelinating disease. Mouse strains are typically considered susceptible or resistant to TMEV infection based on viral persistence and extreme phenotypes, such as demyelination. We have identified a broader spectrum of phenotypic outcomes by infecting strains of the genetically diverse Collaborative Cross (CC) mouse resource. We evaluated the chronic-infection gene expression profiles of hippocampi and thoracic spinal cords for 19 CC strains in relation to phenotypic severity and TMEV persistence. Strains were clustered based on similar phenotypic profiles and TMEV levels at 90 days post-infection, and we categorized distinct TMEV response profiles. The three most common profiles included "resistant" and "susceptible," as before, as well as a "resilient" TMEV response group which experienced both TMEV persistence and mild neurological phenotypes even at 90 days post-infection. Each profile had a distinct gene expression signature, allowing the identification of pathways and networks specific to each TMEV response group. CC founder haplotypes for genes involved in these pathways/networks revealed candidate response-specific alleles. These alleles demonstrated pleiotropy and epigenetic (miRNA) regulation in long-term TMEV infection, with particular relevance for resilient mouse strains.

Heat stress response in slick vs normal-haired Criollo Limonero heifers in a tropical environment

To assess the effect of hair type on the heat stress response, 20 Criollo Limonero heifers with slick (n = 11) or normal hair (n = 9) were studied. Under a high temperature-humidity index (THI) environment, heat stress response was assessed through physiological variables that included respiration rate (RR), heart rate (HR), ruminal frequency (RMF), rectal temperature (RT), saliva pH (SPH), and lymphocyte count (LC) in the morning (5:00 AM, 27.4 °C, 64% relative humidity, THI = 77) and afternoon (1:00 PM, 34.5 °C, 70% relative humidity, THI = 88). A case-control study using a split plot design was used. Data were analyzed using ANOVA (PROC MIXED SAS 2010) and a statistical model comprising the fixed effects of hair length, sampling hour, interaction of hair length by sampling hour, and the random effect of animal nested within hair type on physiological variables associated with heat stress response. Sampling hour influenced (P < 0.0001) RR, RT, and (P < 0.003) SPH. Hair length influenced RR (P < 0.01) and RT (P < 0.04) and tended to influence LC (P < 0.07). The interaction of sampling hour by hair influenced RR (P < 0.04), RT (P < 0.0002), and both SPH and LC (P < 0.05). During afternoon hours, slick-haired heifers had lower values for RR (81 ± 4.2 vs 102 ± 4.7 bpm; P < 0.01), RT (39.5 ± 0.1 vs 40.3 ± 0.1 C°; P < 0.002), and LC (60 ± 3.2 vs 72.3 ± 3.6; P < 0.09) than normal-haired heifers. In normal-haired heifers, SPH increased during afternoon compared to morning-hours (8.66 ± 0.1 vs 9.11 ± 0.1; P < 0.04). It was concluded that slick-coated heifers exhibited an enhanced capability to cope with heat stress compared to normal-haired heifers likely due to an enhanced capacity for heat dissipation.

The role of prolactin in central nervous system inflammation

Prolactin has been shown to favor both the activation and suppression of the microglia and astrocytes, as well as the release of inflammatory and anti-inflammatory cytokines. Prolactin has also been associated with neuronal damage in diseases such as multiple sclerosis, epilepsy, and in experimental models of these diseases. However, studies show that prolactin has neuroprotective effects in conditions of neuronal damage and inflammation and may be used as neuroprotector factor. In this review, we first discuss general information about prolactin, then we summarize recent findings of prolactin function in inflammatory and anti-inflammatory processes and factors involved in the possible dual role of prolactin are described. Finally, we review the function of prolactin specifically in the central nervous system and how it promotes a neuroprotective effect, or that of neuronal damage, particularly in experimental autoimmune encephalomyelitis and during excitotoxicity. The overall studies indicated that prolactin may be a promising molecule for the treatment of some neurological diseases.

The combination of nutraceuticals and functional feeds as additives modulates gut microbiota and blood markers associated with immune response and health in weanling piglets

This study aimed to evaluate the effects of a combination of feed additives with complementary functional properties on the intestinal microbiota, homocysteine, and vitamins E and B status as well as systemic immune response of weanling piglets. At weaning, 32 litters were assigned to one of the following dietary treatments (DT): 1) conventional diet (CTRL); 2) CTRL diet supplemented with antibiotics (ATB); 3) a cocktail of feed additives containing cranberry extract, encapsulated carvacrol, yeast-derived products, and extra vitamins A, D, E, and B complex (CKTL); or 4) CKTL diet with bovine colostrum in replacement of plasma proteins (CKTL + COL). Within each litter, the piglets with lowest and highest birth weights (LBW and HBW, respectively) and two piglets of medium birth weight (MBW) were identified. The MBW piglets were euthanized at 42 d of age in order to characterize the ileal and colonic microbiota. Blood samples were also collected at weaning and at 42 d of age from LBW and HBW piglets to measure insulin-like growth factor-1 (IGF-1), cysteine, homocysteine, and vitamins E, B₆, and B₁₂, and to characterize the leukocyte populations. At 42 d of age, cytokine production by stimulated peripheral blood mononuclear cells was also measured. In a second experiment, piglets were reared under commercial conditions to evaluate the effects of the DT on the growth performance. At the indicator species analysis, the highest indicator value (IV) for Succinivibrio dextrinosolvens was found in the CKTL group, whereas the highest IV for Lactobacillus reuteri and Faecalibacterium prausnitzii was evidenced in the CKTL + COL group (P < 0.05). Compared with the other DT, CTRL piglets had higher concentrations of homocysteine, whereas the CKTL and CKTL + COL supplementations increased the concentrations of vitamins E and B₁₂ (P < 0.05). DT had no effect on IGF-1 concentration and on blood leukocytes populations; however, compared with HBW piglets, LBW animals had lower values of IGF-1, whereas the percentages of γδ T lymphocytes and T helper were decreased and increased, respectively (P < 0.05). CKTL + COL also improved the growth performance of piglets reared under commercial conditions (P < 0.05). This study highlights the impact of birth weight on piglet systemic immune defenses and the potential of weaning diet supplemented with feed additives and bovine colostrum to modulate the homocysteine metabolism and the intestinal microbiota.

Adaptive Resetting of Tuberoinfundibular Dopamine (TIDA) Network Activity during Lactation in Mice

Giving birth triggers a wide repertoire of physiological and behavioral changes in the mother to enable her to feed and care for her offspring. These changes require coordination and are often orchestrated from the CNS, through as of yet poorly understood mechanisms. A neuronal population with a central role in puerperal changes is the tuberoinfundibular dopamine (TIDA) neurons that control release of the pituitary hormone, prolactin, which triggers key maternal adaptations, including lactation and maternal care. Here, we used Ca²⁺ imaging on mice from both sexes and whole-cell recordings on female mouse TIDA neurons in vitro to examine whether they adapt their cellular and network activity according to reproductive state. In the high-prolactin state of lactation, TIDA neurons shift to faster membrane potential oscillations, a reconfiguration that reverses upon weaning. During the estrous cycle, however, which includes a brief, but pronounced, prolactin peak, oscillation frequency remains stable. An increase in the hyperpolarization-activated mixed cation current, I_h, possibly through unmasking as dopamine release drops during nursing, may partially explain the reconfiguration of TIDA rhythms. These findings identify a reversible plasticity in hypothalamic network activity that can serve to adapt the dam for motherhood.SIGNIFICANCE STATEMENT Motherhood requires profound behavioral and physiological adaptations to enable caring for offspring, but the underlying CNS changes are poorly understood. Here, we show that, during lactation, neuroendocrine dopamine neurons, the "TIDA" cells that control prolactin secretion, reorganize their trademark oscillations to discharge in faster frequencies. Unlike previous studies, which typically have focused on structural and transcriptional changes during pregnancy and lactation, we demonstrate a functional switch in activity and one that, distinct from previously described puerperal modifications, reverses fully on weaning. We further provide evidence that a specific conductance (I_h) contributes to the altered network rhythm. These findings identify a new facet of maternal brain plasticity at the level of membrane properties and consequent ensemble activity.

Immunological Drivers in Graves' Disease: NK Cells as a Master Switcher

Graves' disease (GD) is a common autoimmune cause of hyperthyroidism, which is eventually related to the generation of IgG antibodies stimulating the thyrotropin receptor. Clinical manifestations of the disease reflect hyperstimulation of the gland, causing thyrocyte hyperplasia (goiter) and excessive thyroid hormone synthesis (hyperthyroidism). The above clinical manifestations are preceded by still partially unraveled pathogenic actions governed by the induction of aberrant phenotype/functions of immune cells. In this review article we investigated the potential contribution of natural killer (NK) cells, based on literature analysis, to discuss the bidirectional interplay with thyroid hormones (TH) in GD progression. We analyzed cellular and molecular NK-cell associated mechanisms potentially impacting on GD, in a view of identification of the main NK-cell subset with highest immunoregulatory role.

Exercise and Vitamin D Supplementation Modify Spleen Morphology in Lean, but not, in Monosodium-Glutamate-Obese Rats

We evaluated the effect of exercise and vitamin D supplementation on histological aspects of the spleens of lean and obese rats. Male Wistar rats received neonatal administration of monosodium glutamate (MSG; 4g/Kg), while Control (CON) rats received an equimolar solution. At 30 days of age, CON and MSG rats were subdivided into Exercised (E) or Sedentary (S) groups and Vitamin D (VD; 12µg/Kg) supplemented or non-supplemented (NS) groups. At the 86th day of life, rats were euthanized, and their body weights and adiposity were evaluated. Spleens were submitted to histomorphometric analysis of the white pulp (WP), germinal center (GC) and lymphatic nodule (LN). Data are presented as mean ± SEM (p<0.05). MSG treatment promoted a reduction in spleen weight, increased LN thickness and WP area, but reduced GC occupation, compared to spleens of CON-lean rats (p<0.05). Exercise and VD did not provoke changes in the spleens of MSG-obese rats. In CON-lean rats, E and VD induced augmentation of LN thickness. VD supplementation increased the WP area, while E reduced GC area occupation in spleens of CON-lean rats (p<0.05). In conclusion, exercise and VD supplementation increased LN thickness and WP area, but had the opposite effect on the GC in spleens of CON-lean rats. However, neither exercise nor VD supplementation prevented the development of morphological abnormalities in the spleens of MSG-obese rats.

Natural Killer Cells and Thyroid Diseases

Abnormal production of thyroid hormone is one of the common endocrine disorders, and thyroid hormone production declines with age. The aging process also negatively affects the immune system. An interaction between endocrine system and the immune system has been proposed to be bidirectional. Emerging evidence suggests an interaction between a lymphocyte population, called natural killer (NK) cells and thyroid gland function. Here, we review the relationship between NK cells and thyroid function and disease.

Glucocorticoid receptor involvement in goose (Anas cygnoides) pituitary somatotroph differentiation induced by glucocorticoids during embryonic development

1. In this study, geese (Anas cygnoides) embryonic pituitary cells were cultured in vitro to determine if glucocorticoids could induce growth hormone (GH) expression and to investigate the molecular mechanisms involved in this process. 2. On embryonic day 15 (e15) and e20 the pituitary cells were treated with corticosterone (CORT), membrane impermeable bovine serum albumin-conjugate corticosterone (CORT-BSA), dexamethasone (DEX), and a glucocorticoid receptor (GR) antagonist (RU486) to detect responsiveness of somatotrophs to glucocorticoids. 3. Treatment with CORT, CORT-BSA, and DEX for as little as 6 h increased the percentage of GH-positive cells (P < 0.01) and increased GH mRNA expression (P < 0.01) in e15 goose pituitary cells compared to the control. CORT significantly increased the level of GH protein secreted from cultured e15 goose embryonic pituitary cells, and CORT-BSA increased GH secretion from e20 goose embryonic pituitary cells. 4. A significant increase was observed in the glucocorticoid receptor in GR transcription levels (P < 0.01) with CORT, CORT-BSA, and DEX treatment. Furthermore, the CORT-stimulated GH mRNA expression was completely negated by pre-treatment with RU486. 5. These findings demonstrate that glucocorticoids can stimulate somatotroph differentiation in vitro, as characterised by enhanced GH protein secretion andmRNA expression in cultured geese embryonic pituitary cells. The membrane GR was involved in pituitary somatotroph differentiation induced by glucocorticoids during the embryonic development of geese.

Exploring immunomodulation by endocrine changes in Lady Windermere syndrome

Lung disease due to nontuberculous mycobacteria (NTM) occurs with disproportionate frequency in postmenopausal women with a unique phenotype and without clinically apparent predisposing factors. Dubbed 'Lady Windermere syndrome', the phenotype includes low body mass index (BMI), tall stature and higher than normal prevalence of scoliosis, pectus excavatum and mitral valve prolapse. Although the pathomechanism for susceptibility to NTM lung disease in these patients remains uncertain, it is likely to be multi-factorial. A role for the immunomodulatory consequences of oestrogen deficiency and altered adipokine production has been postulated. Altered levels of adipokines and dehydroepiandrosterone have been demonstrated in patients with NTM lung disease. Case reports of NTM lung disease in patients with hypopituitarism support the possibility that altered endocrine function influences disease susceptibility. This paper catalogues the evidence for immunomodulatory consequences of predicted endocrine changes in Lady Windermere syndrome, with emphasis on the immune response to NTM. Collectively, the data warrant further exploration of an endocrine link to disease susceptibility in Lady Windermere syndrome.

The relation of serum prolactin levels and Toxoplasma infection in humans

BACKGROUND

Toxoplasma gondii is an intracellular protozoan parasite distributed worldwide. Although the infection is benign in immunocompetent individuals, it is life threatening and complicated in immunocompromised patients and fetuses of pregnant women who received their first exposure to T. gondii during the pregnancy. Prolactin (PRL) is a hormone that is secreted by the pituitary gland, and it is confirmed that it plays a role in the immune system. The present study was carried out to assess the possible relation between serum PRL levels and Toxoplasma infection frequency in human.

METHODS

In this cross-sectional study, 343 serum samples (240 from women and 103 from men) were collected from individuals who were referred for PRL checking in laboratories of Karaj, Iran. Blood samples were collected, and sera were separated and analyzed for the detection of anti-Toxoplasma IgG antibody by ELISA method. The levels of PRL were measured by Roche Elecsys 2010 analyzer, electrochemiluminescence technology.

RESULTS

Of 343 sera, 110 samples (32%) consisting of samples from 42 men and 68 women had anti-T. gondii IgG antibody. The prevalence of T. gondii infection in women with high PRL levels was lower than that in the comparison group with normal levels of PRL and the relationship between these two parameters was statistically significant (P=0.016). In women with hyperprolactinemia, by increasing of PRL levels, the prevalence of T. gondii infection was reduced.

CONCLUSION

The results of the current study confirmed the previous studies based on immunoregulatory role of PRL and indicated that high levels of PRL could be related to Toxoplasma seronegativity in women.

Growth Hormone (GH) Deficient Mice With GHRH Gene Ablation Are Severely Deficient in Vaccine and Immune Responses Against Streptococcus pneumoniae

The precise impact of the somatotrope axis upon the immune system is still highly debated. We have previously shown that mice with generalized ablation of growth hormone (GH) releasing hormone (GHRH) gene (Ghrh^−/−) have normal thymus and T-cell development, but present a marked spleen atrophy and B-cell lymphopenia. Therefore, in this paper we have investigated vaccinal and anti-infectious responses of Ghrh^−/− mice against S. pneumoniae, a pathogen carrying T-independent antigens. Ghrh^−/− mice were unable to trigger production of specific IgM after vaccination with either native pneumococcal polysaccharides (PPS, PPV23) or protein-PPS conjugate (PCV13). GH supplementation of Ghrh^−/− mice restored IgM response to PPV23 vaccine but not to PCV13 suggesting that GH could exert a specific impact on the spleen marginal zone that is strongly implicated in T-independent response against pneumococcal polysaccharides. As expected, after administration of low dose of S. pneumoniae, wild type (WT) completely cleared bacteria after 24 h. In marked contrast, Ghrh^−/− mice exhibited a dramatic susceptibility to S. pneumoniae infection with a time-dependent increase in lung bacterial load and a lethal bacteraemia already after 24 h. Lungs of infected Ghrh^−/− mice were massively infiltrated by inflammatory macrophages and neutrophils, while lung B cells were markedly decreased. The inflammatory transcripts signature was significantly elevated in Ghrh^−/− mice. In this animal model, the somatotrope GHRH/GH/IGF1 axis plays a vital and unsuspected role in vaccine and immunological defense against S. pneumoniae.

Adipocyte DIO2 Expression Increases in Human Obesity but Is Not Related to Systemic Insulin Sensitivity

Deiodinase type II (D2), encoded by DIO2, catalyzes the conversion of T4 to bioactive T3. T3 not only stimulates adaptive thermogenesis but also affects adipose tissue (AT) lipid accumulation, mitochondrial function, inflammation, and potentially systemic metabolism. Although better defined in brown AT, the precise role of DIO2 expression in white AT remains largely unknown, with data derived only from whole fat. Therefore, the purpose of this study was to determine whether subcutaneous (SAT) and visceral (VAT) adipocyte-specific gene expression of DIO2 differs between obese and lean patients and whether these differences relate to alterations in mitochondrial function, fatty acid flux, inflammatory cytokines/adipokines, and ultimately insulin sensitivity. Accordingly, adipocytes of 73 obese and 21 lean subjects were isolated and subjected to gene expression analyses. Our results demonstrate that obese compared to lean human individuals have increased adipocyte-specific DIO2 expression in both SAT and VAT. Although higher DIO2 was strongly related to reduced fatty acid synthesis/oxidation and mitochondrial function, we found no relationship to proinflammatory cytokines or insulin resistance and no difference based on diabetic status. Our results suggest that adipocyte-derived DIO2 may play a role in weight maintenance but is likely not a major contributor to obesity-related insulin resistance.

Role of Hormonal Circuitry Upon T Cell Development in Chagas Disease: Possible Implications on T Cell Dysfunctions

T cell response plays an essential role in the host resistance to infection by the protozoan parasite Trypanosoma cruzi, the causative agent of Chagas disease. This infection is often associated with multiple manifestations of T cell dysfunction, both during the acute and the chronic phases of disease. Additionally, the normal development of T cells is affected. As seen in animal models of Chagas disease, there is a strong thymic atrophy due to massive death of CD4⁺CD8⁺ double-positive cells by apoptosis and an abnormal escape of immature and potentially autoreactive thymocytes from the organ. Furthermore, an increase in the release of corticosterone triggered by T. cruzi-driven systemic inflammation is strongly associated with the alterations seen in the thymus of infected animals. Moreover, changes in the levels of other hormones, including growth hormone, prolactin, and testosterone are also able to contribute to the disruption of thymic homeostasis secondary to T. cruzi infection. In this review, we discuss the role of hormonal circuits involved in the normal T cell development and trafficking, as well as their role on the thymic alterations likely related to the peripheral T cell disturbances largely reported in both chagasic patients and animal models of Chagas disease.

Neuroimmune Interactions: From the Brain to the Immune System and Vice Versa

Because of the compartmentalization of disciplines that shaped the academic landscape of biology and biomedical sciences in the past, physiological systems have long been studied in isolation from each other. This has particularly been the case for the immune system. As a consequence of its ties with pathology and microbiology, immunology as a discipline has largely grown independently of physiology. Accordingly, it has taken a long time for immunologists to accept the concept that the immune system is not self-regulated but functions in close association with the nervous system. These associations are present at different levels of organization. At the local level, there is clear evidence for the production and use of immune factors by the central nervous system and for the production and use of neuroendocrine mediators by the immune system. Short-range interactions between immune cells and peripheral nerve endings innervating immune organs allow the immune system to recruit local neuronal elements for fine tuning of the immune response. Reciprocally, immune cells and mediators play a regulatory role in the nervous system and participate in the elimination and plasticity of synapses during development as well as in synaptic plasticity at adulthood. At the whole organism level, long-range interactions between immune cells and the central nervous system allow the immune system to engage the rest of the body in the fight against infection from pathogenic microorganisms and permit the nervous system to regulate immune functioning. Alterations in communication pathways between the immune system and the nervous system can account for many pathological conditions that were initially attributed to strict organ dysfunction. This applies in particular to psychiatric disorders and several immune-mediated diseases. This review will show how our understanding of this balance between long-range and short-range interactions between the immune system and the central nervous system has evolved over time, since the first demonstrations of immune influences on brain functions. The necessary complementarity of these two modes of communication will then be discussed. Finally, a few examples will illustrate how dysfunction in these communication pathways results in what was formerly considered in psychiatry and immunology to be strict organ pathologies.

The Severe Deficiency of the Somatotrope GH-Releasing Hormone/Growth Hormone/Insulin-Like Growth Factor 1 Axis of Ghrh-/- Mice Is Associated With an Important Splenic Atrophy and Relative B Lymphopenia

A debate is still open about the precise control exerted by the somatotrope GH-releasing hormone (GHRH)/growth hormone (GH)/insulin-like growth factor 1 axis on the immune system. The objective of this study was to directly address this question through the use of Ghrh^-/- mice that exhibit a severe deficiency of their somatotrope axis. After control backcross studies and normalization for the reduced global weight of transgenic mice, no difference in weight and cellularity of the thymus was observed in Ghrh^-/- mice when compared with C57BL/6 wild-type (WT) control mice. Similarly, no significant change was observed in frequency and number of thymic T cell subsets. In the periphery, Ghrh^-/- mice exhibited an increase in T cell proportion associated with a higher frequency of sjTREC and naïve T cells. However, all Ghrh^-/- mice displayed an absolute and relative splenic atrophy, in parallel with a decrease in B cell percentage. GH supplementation of transgenic mice for 6 weeks induced a significant increase in their global as well as absolute and relative splenic weight. Interestingly, the classical thymus involution following dexamethasone administration was shown to recover in WT mice more quickly than in mutant mice. Altogether, these data show that the severe somatotrope deficiency of Ghrh^-/- mice essentially impacts the spleen and B compartment of the adaptive immune system, while it only marginally affects thymic function and T cell development.

Prolactin: Friend or Foe in Central Nervous System Autoimmune Inflammation?

The higher prevalence of multiple sclerosis (MS) in females, along with the modulation of disease activity observed during pregnancy and the post-partum period, has suggested a hormonal influence in MS. Even if prolactin (PRL) does not belong to the sex hormones family, its crucial role in female reproduction and lactation has prompted great efforts to understand if PRL could represent a gender factor in the pathogenesis of MS and experimental autoimmune encephalomyelitis (EAE), the animal model for this disease. Extensive literature has documented a remarkable immune-stimulating potential for this hormone, indicating PRL as a disease-promoting factor in MS and EAE. However, recent work has pointed out that PRL is endowed with important neuroprotective and remyelinating properties and has encouraged a reinterpretation of the involvement of this hormone in MS. In this review we summarize both the protective functions that PRL exerts in central nervous system tissue as well as the inflammatory activity of this hormone in the context of autoimmune responses against myelin. Last, we draw future lines of research that might help to better clarify the impact of PRL on MS pathology.

Infectious diseases and immunological responses in adult subjects with lifetime untreated, congenital GH deficiency

Growth hormone is important for the development and function of the immune system, but there is controversy on whether growth hormone deficiency is associated to immune disorders. A model of isolated growth hormone deficiency may clarify if the lack of growth hormone is associated with increased susceptibility to infections, or with an altered responsiveness of the immune system. We have studied the frequency of infectious diseases and the immune function in adults with congenital, untreated isolated growth hormone deficiency. In a cross-sectional study, 35 adults with isolated growth hormone deficiency due to a homozygous mutation in the growth hormone releasing hormone receptor gene and 31 controls were submitted to a clinical questionnaire, physical examination serology for tripanosomiasis, leishmaniasis, HIV, tetanus, hepatitis B and C, and serum total immunoglobulin G, M, E and A measurement. The immune response was evaluated in a subset of these subjects by skin tests and response to vaccination for hepatitis B, tetanus, and bacillus Calmette-Guérin. There was no difference between the groups in history of infectious diseases and baseline serology. Isolated growth hormone deficiency subjects had lower total IgG, but within normal range. There was no difference in the response to any of the vaccinations or in the positivity to protein Purified Derived, streptokinase or candidin. Adult untreated isolated growth hormone deficiency does not cause an increased frequency of infectious diseases, and does not alter serologic tests, but is associated with lower total IgG levels, without detectable clinical impact.

The role of the prolactin/vasoinhibin axis in rheumatoid arthritis: an integrative overview

Rheumatoid arthritis (RA) is a chronic, autoimmune, inflammatory disease destroying articular cartilage and bone. The female preponderance and the influence of reproductive states in RA have long linked this disease to sexually dimorphic, reproductive hormones such as prolactin (PRL). PRL has immune-enhancing properties and increases in the circulation of some patients with RA. However, PRL also suppresses the immune system, stimulates the formation and survival of joint tissues, acquires antiangiogenic properties upon its cleavage to vasoinhibins, and protects against joint destruction and inflammation in the adjuvant-induced model of RA. This review addresses risk factors for RA linked to PRL, the effects of PRL and vasoinhibins on joint tissues, blood vessels, and immune cells, and the clinical and experimental data associating PRL with RA. This information provides important insights into the pathophysiology of RA and highlights protective actions of the PRL/vasoinhibin axis that could lead to therapeutic benefits.

Effects of Graded Dietary L-arginine Supply on Organ Growth in Four Genetically Diverse Layer Lines during Rearing Period

Little information has been available about the influence of genetic background and dietary L-arginine (Arg) supply on organ growth of chickens. Therefore, the present study examined the effects of a graded ad libitum Arg supply providing 70, 100 and 200% of recommended Arg concentration on organ growth of female chickens from hatch to 18 weeks of age. The chickens derived from four layer lines of different phylogeny (white vs. brown) and laying performance (high vs. low). Based on residual feed and absolute body and organ weights recorded in six-week-intervals, feed consumption, changes of relative organ weights and allometric organ growth were compared between experimental groups. Surplus Arg caused higher feed intake than insufficient Arg (p<0.01) that induced growth depression in turn (p <0.05). During the entire trial chicken's heart, gizzard and liver decreased relatively to their body growth (p<0.001) and showed strong positive correlations among each other. On the contrary, proportions of pancreas and lymphoid organs increased until week 12 (p<0.001) and correlated positively among each other. Due to their opposite growth behaviour (p<0.001), internal organs were assigned to two separate groups. Furthermore, insufficient Arg induced larger proportions of bursa, gizzard and liver compared with a higher Arg supply (p<0.05). In contrast to less Arg containing diets, surplus Arg decreased relative spleen weights (p<0.01). The overall allometric evaluation of data indicated a precocious development of heart, liver, gizzard, pancreas and bursa independent of chicken's genetic and nutritional background. However, insufficient Arg retarded the maturation of spleen and thymus compared with an adequate Arg supply. In conclusion, the present results emphasised the essential function of Arg in layer performance, and indicated different sensitivities of internal organs rather to chicken's dietary Arg supply than to their genetic background.

Medial Septal NMDA Glutamate Receptors are Involved in Modulation of Blood Natural Killer Cell Activity in Rats

The purpose of the present study was to determine the specific role of the medial septal (MS) NMDA glutamate receptors on peripheral blood natural killer cell cytotoxicity (NKCC) and their (large granular lymphocyte, LGL) number, as well as the plasma concentration of tumor necrosis factor α (TNF-α) and corticosterone in male Wistar rats exposed to elevated plus maze (EPM) stress or non-stress conditions. The NMDA groups were injected with NMDA glutamate receptor agonist (N-methyl-D-aspartate; 0.25 μg/rat), the D-AP7 group was injected with DL-2-amino-7-phosphoheptanoate (0.1 μg/rat), an antagonist of NMDA glutamate receptors, and the control Sal group with saline (0.5 μl/rat) via previously implanted cannulae into the MS. There was an increase in the NKCC, NK/LGL number and plasma TNF-α concentration after the NMDA injections, being much stronger within the rats under non-stress conditions rather than the rats exposed to EPM stress. These parameters were decreased in the D-AP7 rats, suggesting receptor/ion channel specificity. Moreover, a lower plasma corticosterone concentration within the NMDA rather than the Sal and D-AP7 groups was found. The obtained results suggest that activation of the NMDA glutamate receptors in the MS, accompanied by changes in the corticosterone and cytokine responses, may be involved in modulation of the blood natural anti-tumor response, under EPM stress and non-stress conditions.

Hormones and immunity in cancer: are thyroid hormones endocrine players in the microglia/glioma cross-talk?

Accumulating evidence indicates that the endocrine and immune systems engage in complex cross-talks in which a prominent role is played by thyroid hormones (THs). The increase of resident vs. monocyte recruited macrophages was shown to be an important effector of the TH 3,3′,5′-Triiodo-L-thyronine (T3)-induced protection against inflammation and a key role of T3 in inhibiting the differentiation of peripheral monocytes into macrophages was observed. Herein, we report on the role of T3 as a modulator of microglia, the specialized macrophages of the central nervous system (CNS). Mounting evidence supports a role of microglia and macrophages in the growth and invasion of malignant glioma. In this respect, we unveil the putative involvement of T3 in the microglia/glioma cell communication. Since THs are known to cross the blood-brain barrier, we suggest that T3 not only exerts a direct modulation of brain cancer cell itself but also indirectly promotes glioma growth through a modulation of microglia. Our observations expand available information on the role of TH system in glioma and its microenvironment and highlight the endocrine modulation of microglia as an important target for future therapeutic development of glioma treatments.

Neuroendocrine control of photoperiodic changes in immune function

Seasonal variation in immune function putatively maximizes survival and reproductive success. Day length (photoperiod) is the most potent signal for time of year. Animals typically organize breeding, growth, and behavior to adapt to spatial and temporal niches. Outside the tropics individuals monitor photoperiod to support adaptations favoring survival and reproductive success. Changes in day length allow anticipation of seasonal changes in temperature and food availability that are critical for reproductive success. Immune function is typically bolstered during winter, whereas reproduction and growth are favored during summer. We provide an overview of how photoperiod influences neuronal function and melatonin secretion, how melatonin acts directly and indirectly to govern seasonal changes in immune function, and the manner by which other neuroendocrine effectors such as glucocorticoids, prolactin, thyroid, and sex steroid hormones modulate seasonal variations in immune function. Potential future research avenues include commensal gut microbiota and light pollution influences on photoperiodic responses.

Photoperiodic time measurement and seasonal immunological plasticity

Seasonal variations in immunity are common in nature, and changes in day length are sufficient to trigger enhancement and suppression of immune function in many vertebrates. Drawing primarily on data from Siberian hamsters, this review describes formal and physiological aspects of the neuroendocrine regulation of seasonal changes in mammalian immunity. Photoperiod regulates immunity in a trait-specific manner, and seasonal changes in gonadal hormone secretion and thyroid hormone signaling all participate in seasonal immunomodulation. Photoperiod-driven changes in the hamster reproductive and immune systems are associated with changes in iodothyronine deiodinase-mediated thyroid hormone signaling, but photoperiod exerts opposite effects on select aspects of the epigenetic regulation of reproductive neuroendocrine and lymphoid tissues. Photoperiodic changes in immunocompetence may explain a proportion of the annual variance in disease incidence and severity in nature, and provide a useful framework to help understand brain-immune interactions.

Minireview: prolactin regulation of adult stem cells

Adult stem/progenitor cells are found in many tissues, where their primary role is to maintain homeostasis. Recent studies have evaluated the regulation of adult stem/progenitor cells by prolactin in various target tissues or cell types, including the mammary gland, the prostate, the brain, the bone marrow, the hair follicle, and colon cancer cells. Depending on the tissue, prolactin can either maintain stem cell quiescence or, in contrast, promote stem/progenitor cell expansion and push their progeny towards differentiation. In many instances, whether these effects are direct or involve paracrine regulators remains debated. This minireview aims to overview the current knowledge in the field.

Neuroendocrine regulation of maternal behavior

The expression of maternal behavior in mammals is regulated by the developmental and experiential events over a female's lifetime. In this review the relationships between the endocrine and neural systems that play key roles in these developmental and experiential processes that affect both the establishment and maintenance of maternal care are presented. The involvement of the hormones estrogen, progesterone, and lactogens are discussed in the context of ligand, receptor, and gene activity in rodents and to a lesser extent in higher mammals. The roles of neuroendocrine factors, including oxytocin, vasopressin, classical neurotransmitters, and other neural gene products that regulate aspects of maternal care are set forth, and the interactions of hormones with central nervous system mediators of maternal behavior are discussed. The impact of prior developmental factors, including epigenetic events, and maternal experience on subsequent maternal care are assessed over the course of the female's lifespan. It is proposed that common neuroendocrine mechanisms underlie the regulation of maternal care in mammals.

Neuro-endocrine networks controlling immune system in health and disease

The nervous and immune systems have long been considered as compartments that perform separate and different functions. However, recent clinical, epidemiological, and experimental data have suggested that the pathogenesis of several immune-mediated disorders, such as multiple sclerosis (MS), might involve factors, hormones, and neural mediators that link the immune and nervous system. These molecules are members of the same superfamily, which allow the mutual and bi-directional neural-immune interaction. More recently, the discovery of leptin, one of the most abundant adipocyte-derived hormones that control food intake and metabolism, has suggested that nutritional/metabolic status, acting at central level, can control immune self-tolerance, since it promotes experimental autoimmune encephalomyelitis, an animal model of MS. Here, we summarize the most recent advances and the key players linking the central nervous system, immune tolerance, and the metabolic status. Understanding this coordinated interaction may pave the way for novel therapeutic approaches to increase host defense and suppress immune-mediated disorders.

Cell-autonomous iodothyronine deiodinase expression mediates seasonal plasticity in immune function

Annual rhythms in morbidity and mortality are well-documented, and host defense mechanisms undergo marked seasonal phenotypic change. Siberian hamsters (Phodopus sungorus) exhibit striking immunological plasticity following adaptation to short winter day lengths (SD), including increases in blood leukocytes and in the magnitude of T cell-mediated immune responses. Thyroid hormone (TH) signaling is rate-limited by tissue-level expression of iodothyronine deiodinase types II and III (dio2, dio3), and dio2/dio3 expression in the central nervous system gate TH-dependent transduction of photoperiod information into the neuroendocrine system. THs are also potent immunomodulators, but their role in seasonal immunobiology remains unexamined. Here we report that photoperiod-driven changes in triiodothyronine (T3) signaling mediate seasonal changes in multiple aspects of immune function. Transfer from long days (LD) to SD inhibited leukocyte dio3 expression, which increased cellular T4→T3 catabolism. T3 was preferentially localized in the lymphocyte cytoplasm, consistent with a non-nuclear role of T3 in lymphoid cell differentiation and maturation. Exposure to SD upregulated leukocyte DNA methyltransferase expression and markedly increased DNA methylation in the dio3 proximal promoter region. Lastly, to bypass low endogenous T3 biosynthesis in LD lymphocytes, LD hamsters were treated with T3, which enhanced T cell-dependent delayed-type hypersensitivity inflammatory responses and blood leukocyte concentrations in a dose-dependent manner, mimicking effects of SD on these immunophenotypes. T3 signaling represents a novel mechanism by which environmental day length cues impact the immune system: changes in day length alter lymphoid cell T3-signaling via epigenetic transcriptional control of dio3 expression.

Effect of cabergoline on insulin sensitivity, inflammation, and carotid intima media thickness in patients with prolactinoma

The aim of this study was to evaluate the effect of Cabergoline on insulin sensitivity, inflammatory markers, and carotid intima media thickness in prolactinoma patients. Twenty-one female, newly diagnosed patients with prolactinoma were included in the study. None of the patients were treated previously. Cabergoline was given as treatment, starting with 0.5 mg/day and tapered necessarily. Blood samples were taken for prolactin, highly sensitive C-reactive protein, homocysteine, total cholesterol, low density lipoprotein (LDL) cholesterol, fasting glucose, insulin, and HOMA (homeostasis model assessment of insulin resistance) score was calculated, prior to and 6 months after starting treatment. The body mass index (BMI) was measured and carotid intima media thickness (CIMT) was evaluated for each patient prior to and 6 months after the treatment. The prolactin levels and LDL decreased significantly after cabergoline treatment. Insulin sensitivity improved independently from the decrease in prolactin levels and BMI. The significant decrease in homocysteine and hs-CRP was not related with the decrease in prolactin levels. The significant decrease in CIMT was independent from the decrease in prolactin levels, HOMA score, and BMI. Our data suggest that cabergoline treatment causes an improvement in insulin sensitivity and inflammatory markers and causes a decrease in CIMT independent from the decrease in prolactin, LDL cholesterol, and BMI. We conclude that short term cabergoline treatment can improve endothelial function independently from the changes in metabolic disturbances and inflammatory markers.

Prolactin promotes cartilage survival and attenuates inflammation in inflammatory arthritis

Chondrocytes are the only cells in cartilage, and their death by apoptosis contributes to cartilage loss in inflammatory joint diseases, such as rheumatoid arthritis (RA). A putative therapeutic intervention for RA is the inhibition of apoptosis-mediated cartilage degradation. The hormone prolactin (PRL) frequently increases in the circulation of patients with RA, but the role of hyperprolactinemia in disease activity is unclear. Here, we demonstrate that PRL inhibits the apoptosis of cultured chondrocytes in response to a mixture of proinflammatory cytokines (TNF-α, IL-1β, and IFN-γ) by preventing the induction of p53 and decreasing the BAX/BCL-2 ratio through a NO-independent, JAK2/STAT3-dependent pathway. Local treatment with PRL or increasing PRL circulating levels also prevented chondrocyte apoptosis evoked by injecting cytokines into the knee joints of rats, whereas the proapoptotic effect of cytokines was enhanced in PRL receptor-null (Prlr(-/-)) mice. Moreover, eliciting hyperprolactinemia in rats before or after inducing the adjuvant model of inflammatory arthritis reduced chondrocyte apoptosis, proinflammatory cytokine expression, pannus formation, bone erosion, joint swelling, and pain. These results reveal the protective effect of PRL against inflammation-induced chondrocyte apoptosis and the therapeutic potential of hyperprolactinemia to reduce permanent joint damage and inflammation in RA.

Endometrial signaling pathways during ovarian stimulation for assisted reproduction technology

OBJECTIVE

To determine the effects of different hormonal levels on endometrial biochemical development during ovulation induction for assisted reproduction technology (ART) cycles.

DESIGN

Prospective controlled study.

SETTING

University center.

PATIENT(S)

Nine women during a natural cycle (control) and 9 oocyte donors (treated) during an ART cycle.

INTERVENTION(S)

At the time consistent with day 3 embryo transfer (LH+5 in control, hCG+5 in treated), transvaginal ultrasound, endometrial biopsy, and blood sampling were performed. Real-time reverse-transcription polymerase chain reaction was used to measure mRNA levels for insulin receptor (InsR), type I IGF receptor (IGFRI), prolactin receptor (PRL-R), androgen receptor (AR), TSH receptor (TSHR), nuclear receptors for T3 and T4 (TRα1, TRα2, and TRβ1), iodothyronine deiodinase (DIO2), and 1,25-dihydroxyvitamin D3 receptor (VDR) in the endometrial tissue.

MAIN OUTCOME MEASURE(S)

Biochemical endometrial development.

RESULT(S)

IGFRI mRNA levels were 69% lower in treated patients than in control subjects, 0.12 ± 0.005 pg/μg RNA versus 0.39 ± 0.01 pg/μg RNA. TSHR mRNA was 57% lower, 2.6 ± 0.1 fg/μg RNA versus 6.0 ± 0.2 fg/μg RNA. TRα1 and TRα2 mRNA did not change, but TRβ1 mRNA levels were 63% higher. DIO2 mRNA was 63% lower, 1.2 ± 0.07 pg/μg RNA versus 3.2 ± 0.2 pg/μg RNA. InsR mRNA levels, despite being 68% lower in treated patients, did not reach significance, and PRL-R, AR, and VDR did not significantly change.

CONCLUSION(S)

Exposure of the endometrium to ovarian stimulation appears to influence insulin and thyroid hormone signaling pathways in the decidua at day 3 embryo transfer, whereas prolactin, androgen, and vitamin D pathways are uninfluenced. These findings echo the known delayed endometrial maturation during ovarian stimulation.

Causes, consequences, and reversal of immune system aging

The effects of aging on the immune system are manifest at multiple levels that include reduced production of B and T cells in bone marrow and thymus and diminished function of mature lymphocytes in secondary lymphoid tissues. As a result, elderly individuals do not respond to immune challenge as robustly as the young. An important goal of aging research is to define the cellular changes that occur in the immune system and the molecular events that underlie them. Considerable progress has been made in this regard, and this information has provided the rationale for clinical trials to rejuvenate the aging immune system.

Microcirculation and atherothrombotic parameters in prolactinoma patients: a pilot study

Atherothrombosis is a multifactorial process, governed by an interaction between the vessel wall, hemodynamic factors and systemic atherothrombotic risk factors. Recent in vitro, human ex vivo and animal studies have implicated the hormone prolactin as an atherothrombotic mediator. To address this issue, we evaluated the anatomy and function of various microvascular beds as well as plasma atherothrombosis markers in patients with elevated prolactin levels. In this pilot study, involving 10 prolactinoma patients and 10 control subjects, sidestream dark field (SDF) imaging revealed a marked perturbation of the sublingual microcirculation in prolactinoma patients compared to control subjects, as attested to by significant changes in microvascular flow index (2.74 ± 0.12 vs. 2.91 ± 0.05, respectively; P = 0.0006), in heterogeneity index (0.28 [IQR 0.18-0.31] vs. 0.09 [IQR 0.08-0.17], respectively; P = 0.002) and lower proportion of perfused vessels (90 ± 4.0% vs. 95 ± 3.0%, respectively; P = 0.016). In the retina, fluorescein angiography (FAG) confirmed these data, since prolactinoma patients more often have dilatated perifoveal capillaries. In plasma, prolactinoma patients displayed several pro-atherogenic disturbances, including a higher endogenous thrombin potential and prothrombin levels as well as decreased HDL-cholesterol levels. Prolactinoma patients are characterized by microvascular dysfunction as well as plasma markers indicating a pro-atherothrombotic state. Further studies are required to assess if prolactin is causally involved in atherothrombotic disease.

Genetic regulation of thymocyte progenitor aging

The number of T cell progenitors is significantly reduced in the involuted thymus, and the growth and developmental potential of the few cells that are present is severely attenuated. This review provides an overview of how aging affects T cell precursors before and following entry into the thymus and discusses the age-related genetic changes that may occur in them. Finally, interventions that rejuvenate thymopoiesis in the elderly by targeting T cell progenitors are discussed.

Prolactin regulation of the prostate gland: a female player in a male game

Prolactin is best known for its actions on the mammary gland. However, circulating prolactin is also detected in males and its receptor (PRLR) is expressed in the prostate, suggesting that the prostate is a target of prolactin. Germline knockout of prolactin or its receptor has failed to reveal a key role for prolactin signaling in mouse prostate physiology. However, several studies involving rodent models and human prostate cell lines and specimens have supported the contribution of the canonical PRLR-Jak2-Stat5a/b pathway to prostate cancer tumorigenesis and progression. Increased expression of prolactin in the prostate itself (rather than changes in circulating prolactin levels) and crosstalk with androgen receptor (AR) signaling are potential mechanisms for increased Stat5a/b signaling in prostate cancer. In the mouse prostate, prolactin overexpression results in disorganized expansion of the basal/stem cell compartment, which has been proposed to house putative prostate tumor-initiating cells. These findings provide new insight into the molecular and cellular targets by which locally produced prolactin could contribute to prostate cancer initiation and progression. A number of pharmacological inhibitors targeting various levels of the PRLR-Jak2-Stat5a/b pathway have been developed and are entering clinical trials for advanced prostate cancer.

Prolactin receptor is a negative prognostic factor in patients with squamous cell carcinoma of the head and neck

Background:

The influence of human prolactin (hPRL) on the development of breast and other types of cancer is well established. Little information, however, exists on the effects of hPRL on squamous cell carcinomas of the head and neck (SCCHNs).

Methods:

In this study, we evaluated prolactin receptor (PRLR) expression in SCCHN cell lines and assessed by immunohistochemistry the expression in 89 patients with SCCHNs. The PRLR expression was correlated with clinicopathological characteristics as well as clinical outcome. The effect of hPRL treatment on tumour cell growth was evaluated in vitro.

Results:

Immunoreactivity for PRLR was observed in 85 out of 89 (95%) tumours. Multivariate COX regression analysis confirmed high levels of PRLR expression (>25% of tumour cells) to be an independent prognostic factor with respect to overall survival (HR=3.70, 95% CI: 1.14–12.01; P=0.029) and disease-free survival (P=0.017). Growth of PRLR-positive cancer cells increased in response to hPRL treatment.

Conclusion:

Our data indicate that hPRL is an important growth factor for SCCHN. Because of PRLR expression in a vast majority of tumour specimens and its negative impact on overall survival, the receptor represents a novel prognosticator and a promising drug target for patients with SCCHNs.

Research resource: Comparative nuclear receptor atlas: basal and activated peritoneal B-1 and B-2 cells

Naïve murine B cells are typically divided into three subsets based on functional and phenotypic characteristics: innate-like B-1 and marginal zone B cells vs. adaptive B-2 cells, also known as follicular or conventional B cells. B-1 cells, the innate-immune-like component of the B cell lineage are the primary source of natural antibodies and have been shown to modulate autoimmune diseases, human B-cell leukemias, and inflammatory disorders such as atherosclerosis. On the other hand, B-2 cells are the principal mediators of the adaptive humoral immune response and represent an important pharmacological target for various conditions including rheumatoid arthritis, lupus erythematosus, and lymphomas. Using the resources of the Nuclear Receptor Signaling Atlas program, we used quantitative real-time PCR to assess the complement of the 49 murine nuclear receptor superfamily expressed in quiescent and toll-like receptor (TLR)-stimulated peritoneal B-1 and B-2 cells. We report the expression of 24 nuclear receptors in basal B-1 cells and 25 nuclear receptors in basal B-2 cells, with, in some cases, dramatic changes in response to TLR 4 or TLR 2/1 stimulation. Comparative nuclear receptor profiling between B-1 and peritoneal B-2 cells reveals a highly concordant expression pattern, albeit at quantitatively dissimilar levels. We also found that splenic B cells express 23 nuclear receptors. This catalog of nuclear receptor expression in B-1 and B-2 cells provides data to be used to better understand the specific roles of nuclear receptors in B cell function, chronic inflammation, and autoimmune disease.

Effects of prolactin on TSC2-null Eker rat cells and in pulmonary lymphangioleiomyomatosis

RATIONALE

Lymphangioleiomyomatosis, a cystic lung disease of women, is characterized by proliferation of smooth muscle-like lymphangioleiomyomatosis cells, which possess mutations in the tuberous sclerosis complex genes, TSC1/TSC2. Growth factors involved in lymphangioleiomyomatosis cell proliferation are unknown. Prolactin, an important reproductive hormone in women, is known to promote cell proliferation and survival in other tissues.

OBJECTIVES

To determine the role of prolactin in signaling and proliferation in lymphangioleiomyomatosis.

METHODS

Prolactin levels in the sera of patients with lymphangioleiomyomatosis were correlated with clinical status. Components of prolactin signal transduction pathways were assessed in lymphangioleiomyomatosis lesions from human lung explants by real-time reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. Prolactin effects on proliferation and signaling were quantified in tuberin-deficient and tuberin-expressing rat cells in vitro.

MEASUREMENTS AND MAIN RESULTS

Higher prolactin levels in the sera of patients with lymphangioleiomyomatosis were associated with a faster rate of decline in FEV(1) and an increased history of pneumothorax (P < 0.01). Higher levels of prolactin and prolactin receptor mRNA and immunoreactivity were found in lymphangioleiomyomatosis lesions when compared with vascular smooth muscle cells in the same region of tissue. This was accompanied by evidence of activation of signal transducer and activator of transcription-1 (STAT1), STAT3, p44/42, and p38 mitogen-activated protein kinase. Tsc2(-/-) Eker rat embryonic fibroblasts expressed more prolactin receptor than did Tsc2(+/+) cells, and responded to prolactin with increased proliferation and activation of the same signaling pathways seen in vivo.

CONCLUSIONS

Prolactin may be an important growth factor in the pathogenesis of lymphangioleiomyomatosis.

Rejuvenation of the aging thymus: growth hormone-mediated and ghrelin-mediated signaling pathways

One of the major fundamental causes for the aging of the immune system is the structural and functional involution of the thymus, and the associated decline in de novo naïve T-lymphocyte output. This loss of naïve T-cell production weakens the ability of the adaptive immune system to respond to new antigenic stimuli and eventually leads to a peripheral T-cell bias to the memory phenotype. While the precise mechanisms responsible for age-associated thymic involution remain unknown, a variety of theories have been forwarded including the loss of expression of various growth factors and hormones that influence the lymphoid compartment and promote thymic function. Extensive studies examining two hormones, namely growth hormone (GH) and ghrelin (GRL), have demonstrated their contributions to thymus biology. In the current review, we discuss the literature supporting a role for these hormones in thymic physiology and age-associated thymic involution and their potential use in the restoration of thymic function in aged and immunocompromised individuals.

Insulin-like growth factor I messenger RNA and protein are expressed in the human lymph node and distinctly confined to subtypes of macrophages, antigen-presenting cells, lymphocytes and endothelial cells

Insulin-like growth factor I (IGF-I) is a potent hormone that stimulates growth and differentiation and inhibits apoptosis in numerous tissues. Preliminary evidence suggests that IGF-I exerts differentiating, mitogenic and restoring activities in the immune system but the sites of synthesis of local IGF-I are unknown. Identification of these sites would allow the functional role of local IGF-I to be clarified. The presence of IGF-I in non-immune cells suggests that it acts as a trophic factor, while its occurrence in subtypes of lymphocytes or antigen-presenting cells indicates paracrine/autocrine direct regulatory involvement of IGF-I in the human immune response. The present study investigated the location of IGF-I messenger RNA and protein on archival human lymph node samples by in situ hybridization, immunohistochemistry and double immunofluorescence staining using an IGF-I probe and antisera specific for human IGF-I and CD3 (T lymphocytes), CD20 (B lymphocytes), CD68 (macrophages), CD21 (follicular dendritic cells), S100 (interdigitating dendritic cells) and podoplanin (fibroblastic reticular cells). Numerous cells within the B- and T-cell compartments expressed the IGF-I gene, and the majority of these cells were identified as macrophages. Solitary follicular dendritic cells exhibited IGF-I. A few T lymphocytes, and no B lymphocytes, contained IGF-I immunoreactive material. Furthermore, IGF-I immunoreactive cells outside the follicles that did not react with CD3, CD20, S100 or podoplanin markers were identified as high-endothelial venule (HEV) cells. From this we conclude that the main task of IGF-I in human non-tumoral lymph node may be autocrine and paracrine regulation of the differentiation, stimulation and survival of lymphocytes, antigen-presenting cells and macrophages and the differentiation and maintenance of HEV cells.

Nuclear factor (NF)-kappaB-dependent thyroid hormone receptor beta1 expression controls dendritic cell function via Akt signaling

Despite considerable progress in our understanding of the interplay between immune and endocrine systems, the role of thyroid hormones and their receptors in the control of adaptive immunity is still uncertain. Here, we investigated the role of thyroid hormone receptor (TR) beta(1) signaling in modulating dendritic cell (DC) physiology and the intracellular mechanisms underlying these immunoregulatory effects. Exposure of DCs to triiodothyronine (T(3)) resulted in a rapid and sustained increase in Akt phosphorylation independently of phosphatidylinositol 3-kinase activation, which was essential for supporting T(3)-induced DC maturation and interleukin (IL)-12 production. This effect was dependent on intact TR beta(1) signaling as small interfering RNA-mediated silencing of TR beta(1) expression prevented T(3)-induced DC maturation and IL-12 secretion as well as Akt activation and I kappaB-epsilon degradation. In turn, T(3) up-regulated TR beta(1) expression through mechanisms involving NF-kappaB, suggesting an autocrine regulatory loop to control hormone-dependent TR beta(1) signaling. These findings were confirmed by chromatin immunoprecipitation analysis, which disclosed a new functional NF-kappaB consensus site in the promoter region of the TRB1 gene. Thus, a T(3)-induced NF-kappaB-dependent mechanism controls TR beta(1) expression, which in turn signals DCs to promote maturation and function via an Akt-dependent but PI3K-independent pathway. These results underscore a novel unrecognized target that regulates DC maturation and function with critical implications in immunopathology at the cross-roads of the immune-endocrine circuits.

Infection, immunity and the neuroendocrine response

The Central Nervous (CNS) and Immune Systems (IS) are the two major adaptive systems which respond rapidly to numerous challenges that are able to compromise health. The defensive response strictly linking innate to acquired immunity, works continuously to limit pathogen invasion and damage. The efficiency of the innate response is crucial for survival and for an optimum priming of acquired immunity. During infection, the immune response is modulated by an integrated neuro-immune network which potentiates innate immunity, controls potential harmful effects and also addresses metabolic and nutritional modifications supporting immune function. In the last decade much knowledge has been gained on the molecular signals that orchestrate this integrated adaptive response, with focus on the systemic mediators which have a crucial role in driving and controlling an efficient protective response. These mediators are also able to signal alterations and control pathway dysfunctions which may be involved in the persistence and/or overexpression of inflammation that may lead to tissue damage and to a negative metabolic impact, causing retarded growth. This review aims to describe some important signalling pathways which drive bidirectional communication between the Immune and Nervous Systems during infection. Particular emphasis is placed on pro-inflammatory cytokines, immunomodulator hormones such as Glucocorticoids (GCs), Growth hormone (GH), Insulin-like Growth Factor-1 (IGF-1), and Leptin, as well as nutritional factors such as Zinc (Zn). Finally, the review includes up-to-date information on this neuroimmune cross-talk in domestic animals. Data in domestic animal species are still limited, but there are several exciting areas of research, like the potential interaction pathways between mediators (i.e. cytokine-HPA regulation, IL-6-GCS-Zn, cytokines-GH/IGF-1, IL-6-GH-Leptin and thymus activity) that are or could be promising topics of future research in veterinary medicine.

Role of neuropeptides, hormones, and growth factors in regulating thymopoiesis in middle to old age

The deterioration in adaptive immunity and T-lymphocyte output and the narrowing of the T cell receptor repertoire with age are largely attributable to thymic involution. The loss of thymic function with age may be due to diminished numbers of early thymic progenitors and epithelial cells, and the loss of critical tropic factors within the thymic microenvironment. Here we review some of the recent literature demonstrating a role for neuropeptides, hormones, and growth factors that can influence thymopoiesis associated with stress and aging.

Impact of growth hormone (GH) deficiency and GH replacement upon thymus function in adult patients

BACKGROUND

Despite age-related adipose involution, T cell generation in the thymus (thymopoiesis) is maintained beyond puberty in adults. In rodents, growth hormone (GH), insulin-like growth factor-1 (IGF-1), and GH secretagogues reverse age-related changes in thymus cytoarchitecture and increase thymopoiesis. GH administration also enhances thymic mass and function in HIV-infected patients. Until now, thymic function has not been investigated in adult GH deficiency (AGHD). The objective of this clinical study was to evaluate thymic function in AGHD, as well as the repercussion upon thymopoiesis of GH treatment for restoration of GH/IGF-1 physiological levels.

METHODOLOGY/PRINCIPAL FINDINGS

Twenty-two patients with documented AGHD were enrolled in this study. The following parameters were measured: plasma IGF-1 concentrations, signal-joint T-cell receptor excision circle (sjTREC) frequency, and sj/beta TREC ratio. Analyses were performed at three time points: firstly on GH treatment at maintenance dose, secondly one month after GH withdrawal, and thirdly one month after GH resumption. After 1-month interruption of GH treatment, both plasma IGF-1 concentrations and sjTREC frequency were decreased (p<0.001). Decreases in IGF-1 and sjTREC levels were correlated (r = 0.61, p<0.01). There was also a decrease in intrathymic T cell proliferation as indicated by the reduced sj/beta TREC ratio (p<0.01). One month after reintroduction of GH treatment, IGF-1 concentration and sjTREC frequency regained a level equivalent to the one before GH withdrawal. The sj/beta TREC ratio also increased with GH resumption, but did not return to the level measured before GH withdrawal.

CONCLUSIONS

In patients with AGHD under GH treatment, GH withdrawal decreases thymic T cell output, as well as intrathymic T cell proliferation. These parameters of thymus function are completely or partially restored one month after GH resumption. These data indicate that the functional integrity of the somatotrope GH/IGF-1 axis is important for the maintenance of a normal thymus function in human adults.

TRIAL REGISTRATION

ClinicalTrials.gov NTC00601419.

Failure of antibody response to polysaccharide antigen in treated panhypopituitary adults

Although pituitary hormones are known to affect immune function, treated hypopituitarism is not a recognized cause of immune deficiency in humans. We set out to assess integrity of baseline and stimulated immune function in severely hypopituitary adults. Twenty-one panhypopituitary adults (group 1), on stable pituitary replacement including growth hormone, and 12 healthy volunteers (group 2) were studied. Lymphocyte subsets, pneumococcal antibody levels pre- and 1 month after polysaccharide vaccination, T cell numbers and in-vitro interferon (IFN)-gamma response were studied. There were no significant differences in T cell numbers or IFN-gamma secretion. B cell numbers were lower in group 1, especially those with low prolactin levels. Independent of this finding, nine of 21 patients in this group had low antibody response to polysaccharide antigen. This was most striking in those with low insulin-like growth factor 1 levels and appeared to be independent of the use of anti-convulsants or corticosteroid replacement. Significant humoral immune deficiency is seen in panhypopituitarism and may contribute to morbidity.

Free triiodothyronine plasma concentrations are positively associated with insulin secretion in euthyroid individuals

BACKGROUND

Thyroid hormones (TH) may influence glucose metabolism. Hyperthyroid subjects have higher insulin secretion rates when compared with euthyroid individuals.

OBJECTIVE

To evaluate the association between TH concentrations and insulin secretion in euthyroid, healthy Pima Indian adults (n=55, 29+/-7 years, females/males 36/19) with normal glucose tolerance (NGT) admitted to a Clinical Research Unit.

METHODS

TSH, free thyroxine (FT4), 3,5,3'-L-tri-iodothyronine (FT3), and fasting plasma insulin (FPI) concentrations were measured in fasting plasma samples, percentage of body fat (%BF) by dual energy x-ray absorptiometry (DXA), acute insulin response (AIR), and incremental area under the curve (AUC) of insulin in response to a 25 g intravenous glucose tolerance test (IVGTT) and 75 g oral glucose tolerance test (OGTT) respectively and insulin action (M) during an euglycemic clamp.

RESULTS

FT3 concentrations were associated with FPI, AIR, and insulin AUC both before (r=0.33, P=0.01; r=0.29, P=0.03; and r=0.35, P=0.008 respectively) and after adjustment for age, sex, %BF, glucose (fasting concentrations or glucose AUC), and M (beta=0.09, P=0.01; beta=0.16, P=0.03; and beta=0.24, P=0.0007 respectively). No associations were found for TSH or FT4.

CONCLUSION

FT3 was associated with several measurements of insulin secretion in euthyroid individuals with NGT. T3 concentrations may play a role in the regulation of insulin secretion.