From hormones to immunity: the physiology of immunology

Effect of Spray-Dried Plasma Form and Duration of Feeding on Broiler Performance During Natural Necrotic Enteritis Exposure

The effect of duration of feeding (continuous or discontinued after d 14) and form (granular vs. powder) of spray-dried plasma (SDP) on performance and mortality of broilers using used litter was evaluated with 240 Ross × Ross 308 male broilers (6 broilers per pen, 8 pens per treatment). Dietary treatments were control (no SDP) or SDP as powder or granular included in the pellet and fed continuously (d 0 to 35) or discontinued after d 14. During the experiment, broilers developed necrotic enteritis, and tissue cultures were positive for Escherichia coli and Salmonella, resulting in 50% mortality on control broilers. Addition of SDP to the feed improved (P < 0.05) average daily gain, feed intake, and feed efficiency for each period of the study (d 0 to 14, 15 to 28, 29 to 35, and 0 to 35). Continuous feeding of SDP improved (P < 0.05) average daily gain, feed intake, and feed efficiency from d 15 to 35 compared with broilers fed SDP to d 14. Liveability was improved (P < 0.05) in broilers consuming SDP either for 14 d or continuously throughout the experiment compared with control broilers. Spray-dried granular plasma was more effective than spray-dried powder plasma from d 0 to 14. The results of this experiment confirmed that SDP improved broiler growth rate, feed intake, feed efficiency, and minimized enteric challenge associated with necrotic enteritis with maximal protection afforded by continuous feeding. The response to SDP was independent of age of the broiler.

Autologous minced muscle grafts improve endogenous fracture healing and muscle strength after musculoskeletal trauma

The deleterious impact of concomitant muscle injury on fracture healing and limb function is commonly considered part of the natural sequela of orthopedic trauma. Recent reports suggest that heightened inflammation in the surrounding traumatized musculature is a primary determinant of fracture healing. Relatedly, there are emerging potential therapeutic approaches for severe muscle trauma (e.g., volumetric muscle loss [VML] injury), such as autologous minced muscle grafts (1 mm3 pieces of muscle; GRAFT), that can partially prevent chronic functional deficits and appear to have an immunomodulatory effect within VML injured muscle. The primary goal of this study was to determine if repair of VML injury with GRAFT rescues impaired fracture healing and improves the strength of the traumatized muscle in a male Lewis rat model of tibia open fracture. The most salient findings of the study were: (1) tibialis anterior (TA) muscle repair with GRAFT improved endogenous healing of fractured tibia and improved the functional outcome of muscle regeneration; (2) GRAFT repair attenuated the monocyte/macrophage (CD45+CDllb+) and T lymphocyte (CD3+) response to VML injury; (3) TA muscle protein concentrations of MCP1, IL-10, and IGF-1 were augmented in a proregenerative manner by GRAFT repair; (4) VML injury concomitant with osteotomy induced a heightened systemic presence of alarmins (e.g., soluble RAGE) and leukocytes (e.g., monocytes), and depressed IGF-1 concentration, which GRAFT repair ameliorated. Collectively, these data indicate that repair of VML injury with a regenerative therapy can modulate the inflammatory and regenerative phenotype of the treated muscle and in association improve musculoskeletal healing.

The psychoneuroimmunological effects of music: a systematic review and a new model

There has been a growing interest over the past decade into the health benefits of music, in particular examining its psychological and neurological effects. Yet this is the first attempt to systematically review publications on the psychoneuroimmunology of music. Of the selected sixty-three studies published over the past 22 years, a range of effects of music on neurotransmitters, hormones, cytokines, lymphocytes, vital signs and immunoglobulins as well as psychological assessments are cataloged. Research so far points to the pivotal role of stress pathways in linking music to an immune response. However, several challenges to this research are noted: (1) there is very little discussion on the possible mechanisms by which music is achieving its neurological and immunological impact; (2) the studies tend to examine biomarkers in isolation, without taking into consideration the interaction of the biomarkers in question with other physiological or metabolic activities of the body, leading to an unclear understanding of the impact that music may be having; (3) terms are not being defined clearly enough, such as distinctions not being made between different kinds of stress and 'music' being used to encompass a broad spectrum of activities without determining which aspects of musical engagement are responsible for alterations in biomarkers. In light of this, a new model is presented which provides a framework for developing a taxonomy of musical and stress-related variables in research design, and tracing the broad pathways that are involved in its influence on the body.

Pathogenesis and treatment of HIV infection: the cellular, the immune system and the neuroendocrine systems perspective

Infections with HIV represent a great challenge for the development of strategies for an effective cure. The spectrum of diseases associated with HIV ranges from opportunistic infections and cancers to systemic physiological disorders like encephalopathy and neurocognitive impairment. A major progress in controlling HIV infection has been achieved by highly active antiretroviral therapy (HAART). However, HAART does neither eliminate the virus reservoirs in form of latently infected cells nor does it completely reconstitute immune reactivity and physiological status. Furthermore, the failure of the STEP vaccine trial and the only marginal efficacies of the RV144 trial together suggest that the causal relationships between the complex sets of viral and immunological processes that contribute to protection or disease pathogenesis are still poorly understood. Here, we provide an up-to-date overview of HIV-host interactions at the cellular, the immune system and the neuroendocrine systems level. Only by integrating this multi-level knowledge one will be able to handle the systems complexity and develop new methodologies of analysis and prediction for a functional restoration of the immune system and the health of the infected host.

Insulin-like growth factor 1 and 2 (IGF1, IGF2) expression in human microglia: differential regulation by inflammatory mediators

BACKGROUND

Recent studies in experimental animals show that insulin-like growth factor 1 (IGF1) plays a trophic role during development and tissue injury and that microglia are important sources of IGF1. However, little information is available regarding the expression, regulation, and function of IGF1 and related proteins in human brain cells. In the current study, we examined the expression of IGF1 and IGF2 in human microglia in vivo and in vitro.

METHODS

Expression of IGF1 and IGF2 was examined by immunohistochemistry in post-mortem human brain sections derived from HIV+ and HIV- brains. In primary cultures of human fetal microglia, IGF1 and IGF2 mRNA and protein expression was examined by Q-PCR, ELISA, and Western blot analysis. Additionally, the role of IGF1 and IGF2 in neuroprotection was examined in primary human neuronal glial cultures.

RESULTS

Immunohistochemistry of human brain tissues showed that nonparenchymal cells (vessels and meninges), as well as parenchymal microglia and macrophages were positive for IGF1, in both HIV encephalitis and control brains, while IGF2 was undetectable. Cultured microglia expressed IGF1 mRNA and produced pg/ml levels of IGF1 protein; this was significantly suppressed by proinflammatory mediators, such as lipopolysaccharide (LPS), poly(I:C), and IFNγ. The Th2 cytokines IL-4 and IL-13 had no significant effect, but the cAMP analog (dibutyryl cAMP) significantly increased IGF1 production. In contrast, microglial IGF2 mRNA and protein (determined by Western blot) were upregulated by LPS. IGF1 receptor (IGF1R) immunoreactivity was predominantly expressed by neurons, and both IGF1 and IGF2 significantly protected neurons from cytokine (IL-1/IFNγ) induced death.

CONCLUSIONS

Our study in human brain tissues and cells indicates that microglia are important sources of neurotrophic growth factors IGF1 and IGF2, and that microglial activation phenotypes can influence the growth factor expression. Importantly, our results suggest that chronic neuroinflammation and upregulation of proinflammatory cytokines could lead to neurodegeneration by suppressing the production of microglia-derived neuronal growth factors, such as IGF1.

Parenteral administration of vitamins A, D and E on the oxidative metabolism and function of polymorphonuclear leukocytes in swine

The weaning period of piglets is characterized by physiological alterations, such as decreased weight gain, increased reactive oxygen species (ROS) and increased serum cortisol levels with possible effects on the immune response. The effect of parenteral administration of vitamins A, D and E on production performance, oxidative metabolism, and the function of polymorphonuclear leukocytes (PMNLs) was assessed in piglets during the weaning period. The sample was comprised of 20 male piglets that were given an injectable ADE vitamin combination (135,000 IU vitamin A, 40,000 IU vitamin D and 40mg vitamin E/ animal) at 20 and 40 days of age. Weight gain, concentration of reduced glutathione (GSH), malondialdehyde (MDA), superoxide dismutase (SOD) and the microbicidal and phagocytic activity of PMNLs were assessed. No difference was observed in the average piglet weight during the study; however, a greater percentage of weight gain was observed after weaning in the treated group. The concentrations of GSH and SOD did not differ between groups, although lipid peroxidation was greater in the control group at 60 days of age. The investigated variables of oxidative metabolism were correlated as follows: -0.41 for GSH and MDA, -0.54 for GSH and SOD and 0.34 for MDA and SOD. The intensity of intracellular ROS production, the percentage of ROS-producing PMNLs and the intensity of phagocytosis by PMNLs did not differ between treatment groups. Administration of the injectable ADE combination improved the percentage of weight gain between 20 and 40 days of age, decreased oxidative stress at 60 days of age and did not influence the function of PMNLs in piglets.

Inflammation and mortality in a frail mouse model

Mice homozygous for targeted deletion of the interleukin 10 gene (Il-10) have been partially characterized as a model for human frailty. These mice have increased serum interleukin (IL)-6 in midlife, skeletal muscle weakness, and an altered skeletal muscle gene expression profile compared to age and sex-matched C57BL/6 (B6) control mice. In order to further characterize for use as a frailty model, we evaluated the evolution of inflammatory pathway activation, endocrine change, and mortality in these mice. Serum was collected in groups of age- and sex-matched B6.129P2-Il10(tm1Cgn)/J (IL-10(tm/tm)) mice and B6 control mice at age 12, 24, 48, 72, and 90 weeks. Cytokines including IL-6, interleukin 1 beta (IL-1β), tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), chemokine (C-X-C motif) ligand 1 (KC), IL-12, and IL-10 were measured using electro-chemiluminescent multiplex immunoassay and insulin-like growth factor 1 (IGF-1) was measured using solid-phase enzyme-linked immunosorbent assay. A separate longitudinal cohort was monitored from age 35 weeks to approximately 100 weeks. Survival was evaluated by Kaplan-Meier survival estimates and detailed necropsy information was gathered in a subset of mice that died or were sacrificed. In IL-10(tm/tm) mice compared to B6 controls, serum IL-6, IL-1β, TNF-α, IFN-γ, KC levels were significantly elevated across the age groups, serum mean IGF-1 levels were higher in the 48-week-old groups, and overall mortality rate was significantly higher. The quadratic relationship between IGF-1 and age was significantly different between the two strains of mice. Serum IL-6 was positively associated with IGF-1 but the effect was significantly larger in IL-10(tm/tm) mice. These findings provide additional rationale for the use of the IL-10(tm/tm) mouse as a model for frailty and for low-grade inflammatory pathway activation.

Gene expression patterns of insulin-like growth factor 1, 2 (IGF-1, IGF-2) and insulin-like growth factor binding protein 3 (IGFBP-3) in human placenta from preterm deliveries: influence of additional factors

OBJECTIVE

To compare patterns of human placental gene expression of IGF from pregnancies that ended with preterm delivery vs. full term pregnancies as controls.

STUDY DESIGN

Real-time PCR was used to assess gene expression of IGF in human placental samples from 104 preterm and 140 full term pregnancies.

RESULTS

In the preterm delivery group, the proportion of smokers was significantly higher than in the control group. A history of preterm delivery was more common in the preterm delivery group compared to the control group. In the preterm delivery group, placental samples showed an underexpression of the IGF-1 gene compared to controls. In cases of male fetal gender an overexpression of both the IGF-2 and the IGFBP-3 genes was observed.

CONCLUSION

Among environmental factors influencing preterm delivery, smoking was the most significant in our study. In the majority of cases, preterm delivery was induced by intrauterine infection leading to a decreased activity of the IGF system. This mechanism may also play a role in the development of neurological sequelae and in decreased tolerance to fetal distress. The overexpression of the IGF-2 gene observed in the placenta with male fetal gender can be explained by its physiological role in the development of the male phenotype.

Voluntary wheel running reverses age-induced changes in hippocampal gene expression

Normal aging alters expression of numerous genes within the brain. Some of these transcription changes likely contribute to age-associated cognitive decline, reduced neural plasticity, and the higher incidence of neuropathology. Identifying factors that modulate brain aging is crucial for improving quality of life. One promising intervention to counteract negative effects of aging is aerobic exercise. Aged subjects that exercise show enhanced cognitive performance and increased hippocampal neurogenesis and synaptic plasticity. Currently, the mechanisms behind the anti-aging effects of exercise are not understood. The present study conducted a microarray on whole hippocampal samples from adult (3.5-month-old) and aged (18-month-old) male BALB/c mice that were individually housed with or without running wheels for 8 weeks. Results showed that aging altered genes related to chromatin remodeling, cell growth, immune activity, and synapse organization compared to adult mice. Exercise was found to modulate many of the genes altered by aging, but in the opposite direction. For example, wheel running increased expression of genes related to cell growth and attenuated expression of genes involved in immune function and chromatin remodeling. Collectively, findings show that even late-onset exercise may attenuate age-related changes in gene expression and identifies possible pathways through which exercise may exert its beneficial effects.

Tumor necrosis factor inhibits glucocorticoid receptor function in mice: a strong signal toward lethal shock

As glucocorticoid resistance (GCR) and the concomitant burden pose a worldwide problem, there is an urgent need for a more effective glucocorticoid therapy, for which insights into the molecular mechanisms of GCR are essential. In this study, we addressed the hypothesis that TNFα, a strong pro-inflammatory mediator in numerous inflammatory diseases, compromises the protective function of the glucocorticoid receptor (GR) against TNFα-induced lethal inflammation. Indeed, protection of mice by dexamethasone against TNFα lethality was completely abolished when it was administered after TNFα stimulation, indicating compromised GR function upon TNFα challenge. TNFα-induced GCR was further demonstrated by impaired GR-dependent gene expression in the liver. Furthermore, TNFα down-regulates the levels of both GR mRNA and protein. However, this down-regulation seems to occur independently of GC production, as TNFα also resulted in down-regulation of GR levels in adrenalectomized mice. These findings suggest that the decreased amount of GR determines the GR response and outcome of TNFα-induced shock, as supported by our studies with GR heterozygous mice. We propose that by inducing GCR, TNFα inhibits a major brake on inflammation and thereby amplifies the pro-inflammatory response. Our findings might prove helpful in understanding GCR in inflammatory diseases in which TNFα is intimately involved.

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.

Aged human thymus hassall's corpuscles are immunoreactive for IGF-I and IGF-I receptor

Although Hassall's corpuscles have been proposed to act in both maturation of developing thymocytes and removal of apoptotic cells, their function remains an enigma. The involvement of insulin-like growth factor I (IGF-I) in the local autocrine and paracrine control of T-cell development in human thymus is still unclear. In this study, we investigated the structure and distribution of IGF-I and IGF-I receptor (IGF-IR)-immunopositive Hassall's corpuscles in aged human thymus using bright-field immunohistochemistry and immunoelectron microscopy. We report new immunocytochemical data for the presence of IGF-I/IGF-IR double-immunopositive Hassall's corpuscles in structurally preserved regions of age-involuted thymus and discuss the involvement of these unique thymic components in the local regulation of T-cell development and thymus plasticity during aging by IGF-I/IGF-IR-mediated cell signaling pathway.

AKT/eNOS signaling module functions as a potential feedback loop in the growth hormone signaling pathway

Background

While evidence suggested that the activity states of Protein kinase B (AKT/PKB) and endothelial nitric oxide synthase (eNOS) play an important role in the progression of the Growth Hormone (GH) signal cascade, the implication of the activation of AKT/PKB and eNOS in terms of their function in the signaling pathway was not clear.

Results

Using a specific AKT/PKB inhibitor and a functional proteomic approach, we were able to detect the activities of multiple signal transduction pathway elements, the downstream targets of the AKT/PKB pathway and the modification of those responses by treatment with GH. Inhibiting the AKT/PKB activity reduced or eliminated the activation (phosphorylation) of eNOS. We demonstrated that the progression of the GH signal cascade is influenced by the activity status of AKT and eNOS, wherein the suppression of AKT activity appears to augment the activity of extracellular signal-regulated kinases 1 and 2 (Erk1/2) and to antagonize the deactivation (phosphorylation) of cyclin-dependent kinase 2 (CDC2/Cdk1) induced by GH. Phosphorylation of GSK3a/b (glycogen synthase kinase 3), the downstream target of AKT/PKB, was inhibited by the AKT/PKB inhibitor. GH did not increase phosphorylation of ribosomal S6 kinase 1 (RSK1) in normal cells but increases phosphorylation of RSK1 in cells pre-treated with the AKT and eNOS inhibitors.

Conclusion

The MAP kinase and CDC2 kinase-dependent intracellular mechanisms are involved in or are the targets of the GH's action processes, and these activities are probably directly or indirectly modulated by AKT/PKB pathways. We propose that the AKT/PKB-eNOS module likely functions as a negative feedback mediator of GH actions.

Thymic epithelial cells of human patients affected by myasthenia gravis overexpress IGF-I immunoreactivity

Accumulating evidence shows that several kinds of thymic cells express insulin-like growth factor-I (IGF-I), which is known to play an important role in T cell ontogeny under both physiological and pathological conditions. Still, little is known about the mechanisms of IGF-I involvement in the pathological transformation of the thymocyte microenvironment. The present study focuses on a comparative analysis of the IGF-I immunoreactivity of thymic epithelial cells (EC) from human patients with hyperplasia-associated myasthenia gravis (MG) versus physiological thymic tissue from healthy controls using immunohistochemistry and immunoelectron microscopy. We show that myasthenic EC overexpress IGF-I in comparison to EC from control subjects. The IGF-I immunoreactivity in the medullary and cortical EC from MG patients was stronger than in the normal gland. The increased expression of IGF-I and more frequent distribution of IGF-I and IGF-I-receptor (IGF-IR) immunopositive EC correlated with modulation in the immunoreactivity of double (IGF-I/IGF-IR) positive EC. Our data provide new immunocytochemial evidence for alterations of IGF-I and IGF-IR immunoreactivity in EC from pathological thymi. The persisting expression of IGF-I and IGF-IR most likely indicates that the myasthenic thymus is still capable of governing IGF-I signaling pathways, which are involved in the local regulation of T cell development and plasticity.

Prototypical anti-inflammatory cytokine IL-10 prevents loss of IGF-I-induced myogenin protein expression caused by IL-1beta

Prolonged and excessive inflammation is implicated in resistance to the biological actions of IGF-I and contributes to the pathophysiology of neurodegenerative, metabolic, and muscle-wasting disorders. IL-10 is a critical anti-inflammatory cytokine that restrains inflammatory responses in macrophages and T cells by inhibiting cytokine and chemokine synthesis and reducing expression of their receptors. Here we demonstrate that IL-10 plays a protective role in nonhematopoietic cells by suppressing the ability of exogenous IL-1beta to inhibit IGF-I-induced myogenin and myosin heavy chain expression in myoblasts. This action of IL-10 is not caused by impairment of IL-1beta-induced synthesis of IL-6 or the ability of IL-1beta to activate two members of the MAPK family, ERK1/2 and p38. Instead, this newly defined protective role of IL-10 occurs by specific reversal of IL-1beta activation of the JNK kinase pathway. IL-10 blocks IL-1beta-induced phosphorylation of JNK, but not ERK1/2 or p38, indicating that only the JNK component of the IL-1beta-induced MAPK signaling pathway is targeted by IL-10. This conclusion is supported by the finding that a specific JNK inhibitor acts similarly to IL-10 to restore IGF-I-induced myogenin expression, which is suppressed by IL-1beta. Collectively, these data demonstrate that IL-10 acts in a novel, nonclassical, protective manner in nonhematopoietic cells to inhibit the IL-1beta receptor-induced JNK kinase pathway, resulting in prevention of IGF-I resistance.

Neuroendocrine hormones such as growth hormone and prolactin are integral members of the immunological cytokine network

Neuroendocrine hormones such as growth hormone (GH) and prolactin (PRL) have been demonstrated to accelerate the recovery of the immune response after chemotherapy and bone marrow transplantation and to enhance the restoration of immunity in individuals infected with HIV and in normal individuals with compromised immune systems associated with aging. As the mechanism of action of these hormones has been elucidated, it has become clear that they are integral members of the immunological cytokine/chemokine network and share regulatory mechanisms with a wide variety of cytokines and chemokines. The members of this cytokine network induce and can be regulated by members of the suppressor of cytokine signaling (SOCS) family of intracellular proteins. In order to take advantage of the potential beneficial effects of hormones such as GH or PRL, it is essential to take into consideration the overall cytokine network and the regulatory effects of SOCS proteins.

Regulation of IGF-I function by proinflammatory cytokines: at the interface of immunology and endocrinology

During the past decade, the immune and endocrine systems have been discovered to interact in controlling physiologic processes as diverse as cell growth and differentiation, metabolism, and even human and animal behavior. The interaction between these two major physiological systems is a bi-directional process. While it has been well documented that hormones, including prolactin (PRL), growth hormone (GH), insulin-like growth factor-I (IGF-I), and thyroid-stimulating hormone (TSH), regulate a variety of immune events, a great deal of data have accumulated supporting the notion that cytokines from the innate immune system also affect the neuroendocrine system. Communication between these two systems coordinates processes that are necessary to maintain homeostasis. Proinflammatory cytokines often act as negative regulatory signals that temper the action of hormones and growth factors. This system of 'checks and balances' is an active, ongoing process, even in healthy individuals. Dysregulation of this process has been implicated as a potential pathogenic factor in the development of co-morbid conditions associated with several chronic inflammatory diseases, including type 2 diabetes, cardiovascular disease, cerebrovascular disease, inflammatory bowel disease, rheumatoid arthritis, major depression, and even normal aging. Over the past decade, research in our laboratory has focused on the ability of the major proinflammatory cytokines, tumor necrosis factor (TNF)alpha and interleukin (IL)-1beta, to induce a state of IGF resistance. This review will highlight these and other new findings by explaining how proinflammatory cytokines induce resistance to the major growth factor, insulin-like growth factor-I (IGF-I). We also highlight that IGF-I can induce resistance or reduce sensitivity to brain TNFalpha and discuss how TNFalpha, IL-1beta, and IGF-I interact to regulate several aspects of behavior and cognition.

Differential Effects of Sex and Genetics on Behavior and Stress Response of Turkeys

Three lines of turkeys were tested for response in T-maze and open-field tests during the first 8 d after hatch, and behavior was observed after catching, moving, and transport. They were also compared for corticosterone (CORT) levels and heterophil:lymphocyte ratios (H:L) at 15 wk of age in response to an Escherichia coli challenge followed by transport stress. Large commercial-(COMM) line birds were faster and more active in the T-maze at d 2 than egg-line birds. Male COMM-line birds were faster than male egg-line birds when tested in an open field at d 8. Egg-line birds had more sleeping behavior after moving to a new floor pen as compared with both an intermediate-sized line (F line) and the COMM line. Transport stress increased CORT levels in all 3 lines, and the increase was greater in males compared with females. The egg line had higher basal CORT levels (P = 0.03) and higher levels after transport (P < 0.0001). The H:L ratios were affected by both transport stress and line but not by sex. The H:L ratio was lower in the egg line as compared with both the F line and the COMM line (P < 0.0001), with the COMM line having the greatest increase in response to transport. These data, combined with those from previous studies of these lines, suggest that differences in activity of fast-growing turkeys may be used to select birds that are less susceptible to inflammatory bacterial disease and that the H:L ratio may be more useful than serum CORT in evaluating the deleterious effects of stress.

Inflammation at birth and the insulin-like growth factor system in very preterm infants

BACKGROUND

Foetal inflammation is associated with an increased risk of brain damage in preterm infants whereas IGF-I is essential for cerebral development and exhibits anti-apoptotic properties.

AIM

To assess levels of IGF-I and IGF binding proteins at very preterm birth and to evaluate their relationship with foetal pro-inflammation and cerebral damage.

METHODS

Levels of IGF-I, IGF binding protein 3 (IGFBP-3), high- (hp) and low-phosphorylated (lp) IGFBP-1 in cord blood and neonatal blood at 72 h after delivery were analysed in relation to levels of cytokines and cerebral damage as detected by ultrasound in 74 inborn infants [mean gestational age (GA) 27.1 weeks]. Evaluation was performed separately according to birth weight for GA.

RESULTS

In cord blood of infants appropriate for gestational age (AGA) higher levels of IL-6 and IL-8 were associated with lower IGF-I (r =-0.38, p = 0.008 and r =-0.36, p = 0.014). Higher levels of IL-6, IL-8 and TNF-alpha were associated with both higher levels of lpIGFBP-1 (r = 0.54, p < 0.001, r = 0.50, p < 0.001 and r = 0.13, p = 0.012, respectively) and hpIGFBP-1 (r = 0.55, p < 0.001, r = 0.45, p = 0.002 and r = 0.32, p = 0.026, respectively). Infants with intraventricular haemorrhage grade III (n = 5) had higher levels of lp/hpIGFBP-1 in cord blood (p = 0.001 and 0.002, respectively).

CONCLUSION

Pro-inflammation at birth is associated with changes in the IGF-system. This may be of importance for development of brain damage in preterm infants.

Protein hormones and immunity

A number of observations and discoveries over the past 20 years support the concept of important physiological interactions between the endocrine and immune systems. The best known pathway for transmission of information from the immune system to the neuroendocrine system is humoral in the form of cytokines, although neural transmission via the afferent vagus is well documented also. In the other direction, efferent signals from the nervous system to the immune system are conveyed by both the neuroendocrine and autonomic nervous systems. Communication is possible because the nervous and immune systems share a common biochemical language involving shared ligands and receptors, including neurotransmitters, neuropeptides, growth factors, neuroendocrine hormones and cytokines. This means that the brain functions as an immune-regulating organ participating in immune responses. A great deal of evidence has accumulated and confirmed that hormones secreted by the neuroendocrine system play an important role in communication and regulation of the cells of the immune system. Among protein hormones, this has been most clearly documented for prolactin (PRL), growth hormone (GH), and insulin-like growth factor-1 (IGF-I), but significant influences on immunity by thyroid-stimulating hormone (TSH) have also been demonstrated. Here we review evidence obtained during the past 20 years to clearly demonstrate that neuroendocrine protein hormones influence immunity and that immune processes affect the neuroendocrine system. New findings highlight a previously undiscovered route of communication between the immune and endocrine systems that is now known to occur at the cellular level. This communication system is activated when inflammatory processes induced by proinflammatory cytokines antagonize the function of a variety of hormones, which then causes endocrine resistance in both the periphery and brain. Homeostasis during inflammation is achieved by a balance between cytokines and endocrine hormones.

Temporal response of liver signal transduction elements during in vivo endotoxin challenge in cattle: effects of growth hormone treatment

We quantified the changes in abundance of inducible nitric oxide synthase (iNOS) and associated tissue signal transduction pathway elements (STPEs) in the bovine liver in response to lipopolysaccharide (LPS) challenge and further assessed the impact on the LPS-driven variable responses as affected by daily treatment with recombinant growth hormone (GH) prior to LPS challenge. Twenty-four cross-bred beef steers were divided into GH-treated (recombinant bovine GH, Monsanto Inc., St. Louis, MO; 0.1mg/kg BW, i.m., daily for 12 days) and non-GH-treatment (control) groups (n=12/group). Liver biopsy samples were obtained from all animals at 0, 3, 6, and 24h after LPS challenge (E. coli 055:B5, 2.5 microg/kg BW, i.v. bolus) for Western blot analyses of iNOS and STPEs. In response to LPS, tissue levels of iNOS increased significantly (P<0.001) in the first 3h and persisted at levels greater than those at time 0 until 24h. GH further augmented levels of iNOS at 0, 3, and 6h resulting in an overall significant increase in the iNOS protein level (P<0.01). AKT/protein kinase B (AKT/PKB) phosphorylation levels at time 0 were not different between GH-treated and control animals; LPS increased the phosphorylation of AKT/PKB with GH treatment stimulating a four-fold further increase of AKT/PKB phosphorylation. Effects similar to those on AKT/PKB were also observed on signal transducer and activator of transcription 5b (STAT5b). The family of mitogen-activated protein kinase (MAPK) showed different pattern of response. ERK1/2 phosphorylation increased 3h after LPS challenge but only in GH-treated group (P<0.01). Compared to 0 h, SAPK/JUN phosphorylation increased in both experimental groups 3, 6h (P<0.01), and 24h (P<0.05) after LPS. However, at 3h the increase was greater (P<0.01) in GH-treated than in control animals. No effect of LPS challenge or GH treatment on p38(MAPK) was observed. These results suggest that GH treatment has a significant impact on the differential activation of STPEs in the clinical response to LPS.

Endocrinology: the active partner in PNI research

For the past two decades, research appearing in the pages of Brain, Behavior, and Immunity (BBI), as well as other journals, has significantly deepened our understanding of the complexities of endocrine regulation of immunity in states of health and disease. This mini-review discusses contributions that endocrinology has made to the field of psycho-neuroimmunology (PNI), as well as discoveries that PNI researchers have made of the pervasive interactions between the endocrine and immune systems. We highlight the endocrine-immune interface, emphasizing similarities between the immune and endocrine systems as well as hormone/cytokine interactions. Differing endocrine-immune responses to acute and chronic psychosocial stress have been clarified during this time frame with the use of novel stress and endocrine sampling paradigms. Furthermore, investigations examining the role of cytokine involvement in acquired glucocorticoid resistance in illnesses like depression have expanded our understanding of the complexity of the endocrine-immune response to psychosocial stress. We have selected literature, with a focus on human studies, to illustrate these principals. We conclude with a discussion of the clinical relevance of endocrine-immune investigations and thoughts about the next decade of endocrine research in PNI.

Cytokine-effects on glucocorticoid receptor function: relevance to glucocorticoid resistance and the pathophysiology and treatment of major depression

Glucocorticoids play an essential role in the response to environmental stressors, serving initially to mobilize bodily responses to challenge and ultimately serving to restrain neuroendocrine and immune reactions. A number of diseases including autoimmune, infectious and inflammatory disorders as well as certain neuropsychiatric disorders such as major depression have been associated with decreased responsiveness to glucocorticoids (glucocorticoid resistance), which is believed to be related in part to impaired functioning of the glucocorticoid receptor (GR). Glucocorticoid resistance, in turn, may contribute to excessive inflammation as well as hyperactivity of corticotropin releasing hormone and sympathetic nervous system pathways, which are known to contribute to a variety of diseases as well as behavioral alterations. Recent data indicate that glucocorticoid resistance may be a result of impaired GR function secondary to chronic exposure to inflammatory cytokines as may occur during chronic medical illness or chronic stress. Indeed, inflammatory cytokines and their signaling pathways including mitogen-activated protein kinases, nuclear factor-kappaB, signal transducers and activators of transcription, and cyclooxygenase have been found to inhibit GR function. Mechanisms include disruption of GR translocation and/or GR-DNA binding through protein-protein interactions of inflammatory mediators with the GR itself or relevant steroid receptor cofactors as well as alterations in GR phosphorylation status. Interestingly, cAMP signal transduction pathways can enhance GR function and inhibit cytokine signaling. Certain antidepressants have similar effects. Thus, further understanding the effects of cytokines on GR signaling and the mechanisms involved may reveal novel therapeutic targets for reversal of glucocorticoid resistance and restoration of glucocorticoid-mediated inhibition of relevant bodily/immune responses during stress and immune challenge.

Effects of cyadox and olaquindox on intestinal mucosal immunity and on fecal shedding of Escherichia coli in piglets

A 2 x 3 factorial arrangement of treatments was used to determine the effects of olaquindox and cyadox on the intestinal mucosal immune response and on fecal shedding of Escherichia coli in Landrace x Large White barrows that had been orally given 10(10) cfu of E. coli (O139:K88). Factors included 1) E. coli inoculation or no inoculation, and 2) no antimicrobial, 100 mg of olaquindox/kg, and 100 mg of cyadox/kg in the basal diet, respectively. The effects of cyadox and olaquindox were assessed in terms of fecal shedding of E. coli, the number of intraepithelial lymphocytes (IEL), immunoglobulin A-positive cells (APC) in the intestinal lamina propria, and ADG. There was no difference in the fecal shedding of total E. coli or the inoculated E. coli between olaquindox-supplemented pigs and cyadox-supplemented pigs during the experiment. However, fecal shedding of the inoculated E. coli in olaquindox- or cyadox-supplemented pigs was less (P < 0.05) than that in nonsupplemented pigs. Escherichia coli inoculation increased IEL and APC in the jejunum and ileum, but olaquindox or cyadox decreased IEL and APC (P < 0.05). Jejunal APC in cyadox-supplemented pigs was less (P < 0.05) than that in olaquindox-supplemented pigs. Escherichia coli inoculation reduced (P < 0.05) ADG, whereas the supplementations improved ADG (P < 0.01) during the experiment. Average daily gain in cyadox-supplemented pigs was greater (P < 0.05) than that in olaquindox-supplemented pigs. The data indicated that olaquindox and cyadox reduced the number of intestinal E. coli and suppressed E. coli-induced immune activation, which might be responsible for the enhanced growth that was observed.

Olaquindox and cyadox stimulate growth and decrease intestinal mucosal immunity of piglets orally inoculated with Escherichia coli

One hundred and fifty piglets were randomly allotted to one of six treatments to determine the effects of olaquindox and cyadox on growth and intestinal immune response including the number of intraepithelial lymphocytes and immunoglobulin A secreting cells (ASCs) during the three-week period. A 2 x 3 factorial arrangement of treatments was employed with the following factors: (1) Escherichia coli (O(139):K(88), 10(10) CFU) inoculation or control and (2) no antimicrobials, 100 mg/kg olaquindox and 100 mg/kg cyadox in the basal diet respectively. The antimicrobial supplementations improved (p < 0.01) average daily gain and feed conversion ratio (FCR) during the experiment. Average daily gain and FCR in the cyadox-supplemented pigs were higher (p < 0.05) than those in the olaquindox-supplemented pigs. Intraepithelial lymphocytes and ASCs decreased (p < 0.05) when the diets were supplemented. Jejunal ASCs in the cyadox-supplemented pigs were lower (p < 0.05) than those in the olaquindox-supplemented pigs. Olaquindox and cyadox suppressed E. coli-induced intestinal immune activation, which may be involved in the observed growth promotion.

Monitoring insulin-like growth factors in HIV infection and AIDS

There is a close association between the growth hormone (GH)-insulin-like growth factor I (IGF-I) axis, infection and immunity. Infection with the human immunodeficiency virus (HIV) is often associated with a decrease of the concentrations of IGF-I, IGF-II, IGF-binding protein 3 (IGFBP-3) and an increase of IGFBP-1 and -2. Many investigators have studied the relationship between the GH-IGF-I system and some of the most common characteristics of disease progression, such as decreased CD4 cell counts, weight loss and fat redistribution. Although conditions for restoration of thymic function and lymphopoiesis with GH or IGF-I are still not well defined, many studies led to the development of clinical trials on the therapeutic use of GH, IGF-I and GHRH for the treatment of weight loss or fat redistribution, two problems which persist despite the introduction of highly active antiretroviral therapy. Monitoring IGF-I concentrations during treatment with GH and GHRH is likely to become an essential component of their therapeutic use. IGF-I levels are the first indicator of treatment efficacy and can be used to monitor compliance. High levels of IGF-I are a warning sign for the increased risk of potential adverse effects, such as acromegalic-like symptoms or malignancy. This could lead to a reduction of the therapeutic dose or the temporary interruption of treatment until IGF levels reach a safe range. IGF-I levels are also likely to increase with other hormones used in HIV patients, such as erythropoietin for the treatment of anemia or anabolic androgens in HIV-infected women.

Proinflammatory cytokine impairment of insulin-like growth factor I-induced protein synthesis in skeletal muscle myoblasts requires ceramide

GH and IGF-I control over 80% of postnatal growth. We recently established that TNFalpha impairs the ability of IGF-I to increase protein synthesis and promote expression of myogenin in myoblasts. Here we extend these results by showing that ceramide, a second messenger in both TNFalpha and IL-1beta receptor signaling pathways, is a key downstream sphingosine-based lipid that leads to IGF-I resistance. A cell-permeable ceramide analog, C2-ceramide, inhibits IGF-I-induced protein synthesis by 65% and blocks the ability of IGF-I to increase expression of two key myogenic factors, myogenin and MyoD. Identical results were obtained with both TNFalpha and IL-1beta (1 ng/ml). Consistent with these data, neutral sphingomyelinase (N-SMase), an enzyme that catalyzes formation of ceramide from sphingomyelin, blocks IGF-I-induced protein synthesis and expression of both myogenin and MyoD. The possibility that cytokine-induced ceramide production is required for disruption of IGF-I biologic activity was confirmed by treating C2C12 myoblasts with inhibitors of all three ceramide-generating pathways. A N-SMase inhibitor, glutathione, as well as an acidic sphingomyelinase (A-SMase) inhibitor, D609, reverse the cytokine inhibition of IGF-I-induced protein synthesis by 80% and 45%, respectively. Likewise, an inhibitor of de novo ceramide synthesis, FB1, causes a 50% inhibition. Similarly, all three inhibitors significantly impair the ability of both TNFalpha and IL-1beta to suppress IGF-I-driven expression of myogenin. These experiments establish that ceramide, derived both from sphingomyelin and de novo synthesis, is a key intermediate by which proinflammatory cytokines impair the ability of IGF-I to promote protein synthesis and expression of critical muscle-specific transcription factors.

IL-1beta impairs insulin-like growth factor i-induced differentiation and downstream activation signals of the insulin-like growth factor i receptor in myoblasts

Proinflammatory cytokines are elevated in disorders characterized by muscle wasting and weakness, such as inflammatory myopathies and AIDS wasting. We recently demonstrated that TNF-alpha impairs the ability of insulin-like growth factor (IGF)-I to promote protein synthesis in muscle precursor cells. In this study we extend these findings by showing that low concentrations of IL-1beta impair IGF-I-dependent differentiation of myoblasts, as assessed by expression of the muscle specific protein, myosin heavy chain. In the absence of exogenous IGF-I, IL-1beta (1 ng/ml) did not impair muscle cell development. However, in the presence of IGF-I, 100-fold lower concentrations of IL-1beta (0.01 ng/ml) significantly suppressed myoblast differentiation, protein synthesis, and myogenin expression. Increasing IL-1beta to 1 ng/ml completely blocked the anabolic actions of IGF-I in murine C(2)C(12) myoblasts. Similarly, IL-1beta inhibited IGF-I-stimulated protein synthesis in primary porcine myoblasts. IL-1beta impaired the actions of IGF-I at a point distal to the IGF receptor, and this was not due to IL-1beta-induced cell death. Instead, IL-1beta inhibited the ability of IGF-I to phosphorylate tyrosine residues on both of its downstream docking proteins, insulin receptor substrate 1 and insulin receptor substrate 2. These data establish that physiological concentrations of IL-1beta block the ability of IGF-I to promote protein synthesis, leading to reduced expression of the myogenic transcription factor, myogenin, and the subsequent development of more mature differentiated cells that express myosin heavy chain. Collectively, the results are consistent with the notion that very low concentrations of IL-1beta significantly impair myogenesis, but they are unable to do so in the absence of the growth factor IGF-I.