The central role of SOCS-3 in integrating the neuro-immunoendocrine interface

Seasonal food intake and energy balance: Neuronal and non-neuronal control mechanisms

Animals inhabiting temperate and high latitudes undergo drastic seasonal changes in energy storage, facilitated by changes in food intake and body mass. Those seasonal changes in the animal's biology are not mere consequences of environmental energy availability but are anticipatory responses to the energetic requirements of the upcoming season and are actively timed by tracking the annual progression in photoperiod. In this review, we discuss how photoperiod is used to control energy balance seasonally and how this is distinct from energy homeostasis. Most notably, we suggest that photoperiodic control of food intake and body mass does not originate from the arcuate nucleus, as for homeostatic appetite control, but is rather to be found in hypothalamic tanycytes. Tanycytes are specialized ependymal cells lining the third ventricle, which can sense metabolites from the cerebrospinal fluid (e.g. glucose) and can control access of circulating signals to the brain. They are also essential in conveying time-of-year information by integrating photoperiod and altering hypothalamic thyroid metabolism, a feature that is conserved in seasonal vertebrates and connects to seasonal breeding and metabolism. We also discuss how homeostatic feedback signals are handled during times of rapid energetic transitions. Studies on leptin in seasonal mammals suggest a seasonal shift in central sensitivity and blood-brain transport, which might be facilitated by tanycytes. This article is part of the Special Issue on "Food intake and feeding states".

Clinical Biology of the Pituitary Adenoma

All endocrine glands are susceptible to neoplastic growth, yet the health consequences of these neoplasms differ between endocrine tissues. Pituitary neoplasms are highly prevalent and overwhelmingly benign, exhibiting a spectrum of diverse behaviors and impact on health. To understand the clinical biology of these common yet often innocuous neoplasms, we review pituitary physiology and adenoma epidemiology, pathophysiology, behavior, and clinical consequences. The anterior pituitary develops in response to a range of complex brain signals integrating with intrinsic ectodermal cell transcriptional events that together determine gland growth, cell type differentiation, and hormonal production, in turn maintaining optimal endocrine health. Pituitary adenomas occur in 10% of the population; however, the overwhelming majority remain harmless during life. Triggered by somatic or germline mutations, disease-causing adenomas manifest pathogenic mechanisms that disrupt intrapituitary signaling to promote benign cell proliferation associated with chromosomal instability. Cellular senescence acts as a mechanistic buffer protecting against malignant transformation, an extremely rare event. It is estimated that fewer than one-thousandth of all pituitary adenomas cause clinically significant disease. Adenomas variably and adversely affect morbidity and mortality depending on cell type, hormone secretory activity, and growth behavior. For most clinically apparent adenomas, multimodal therapy controlling hormone secretion and adenoma growth lead to improved quality of life and normalized mortality. The clinical biology of pituitary adenomas, and particularly their benign nature, stands in marked contrast to other tumors of the endocrine system, such as thyroid and neuroendocrine tumors.

Obesity and neuroinflammatory phenotype in mice lacking endothelial megalin

BACKGROUND

The multiligand receptor megalin controls the brain uptake of a number of ligands, including insulin and leptin. Despite the role of megalin in the transport of these metabolically relevant hormones, the role of megalin at the blood-brain-barrier (BBB) has not yet been explored in the context of metabolic regulation.

METHODS

Here we investigate the role of brain endothelial megalin in energy metabolism and leptin signaling using an endothelial cell-specific megalin deficient (EMD) mouse model.

RESULTS

We found megalin is important to protect mice from developing obesity and metabolic syndrome when mice are fed a normal chow diet. EMD mice developed neuroinflammation, by triggering several pro-inflammatory cytokines, displayed reduced neurogenesis and mitochondrial deregulation.

CONCLUSIONS

These results implicate brain endothelial megalin expression in obesity-related metabolic changes through the leptin signaling pathway proposing a potential link between obesity and neurodegeneration.

Naringenin Suppresses Neuroinflammatory Responses Through Inducing Suppressor of Cytokine Signaling 3 Expression

Accumulating evidence suggests that neuroinflammation is closely associated with the pathogenesis of neurodegenerative disorders such as Parkinson's disease and Alzheimer's disease. The hallmark of neuroinflammation is considered to be microglial activation in the central nervous system (CNS). Activated microglia release pro-inflammatory cytokines which cause neuroinflammation and progressive neuronal cell death. Therefore, inhibition of microglial activation is considered an important strategy in the development of neuroprotective strategy. Naringenin, a flavonoid found in citrus fruits and tomatoes, has been reported to have anti-oxidant, anti-cancer, and anti-inflammatory properties. However, the mechanism of its beneficial anti-inflammatory effects in the CNS is poorly understood. In this study, we demonstrated that naringenin inhibites the release of nitric oxide (NO), the expression of inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2), as well as pro-inflammatory cytokines in microglial cells. Treatment of naringenin also induced suppressors of cytokine signaling (SOCS)-3 expression in microglia. The SOCS-3 expression and anti-inflammatory effects of naringenin were found to be regulated by adenosine monophosphate-activated protein kinase α (AMPKα) and protein kinase C δ (PKCδ). Besides, naringenin exerted protective property against neurotoxicity caused by LPS-induced microglial activation. Our findings suggest that naringenin-inhibited iNOS and COX-2 expression is mediated by SOCS-3 activation through AMPKα and PKCδ signaling pathways. In a mouse model, naringenin also showed significant protective effects on microglial activation and improved motor coordination function as well. Therefore, naringenin that involves in anti-neuroinflammatory responses and neuroprotection might be a potential agent for treatment of inflammation-associated disorders.

Impaired hypothalamic insulin signaling in CUMS rats: restored by icariin and fluoxetine through inhibiting CRF system

Epidemiological evidence demonstrates the neuroendocrine link between stress, depression and diabetes. This study observed glucose intolerance of rats exposed to chronic unpredictable mild stress (CUMS) in oral glucose tolerance test (OGTT). CUMS procedure significantly up-regulated corticotropin-releasing factor (CRF)-related peptide urocortin 2 expression and elevated cAMP production, resulting in over-expression of suppressor of cytokine signaling 3 (SOCS3) in hypothalamic arcuate nucleus (ARC) of rats. Furthermore, SOCS3 activation blocked insulin signaling pathway through the suppression of insulin receptor substrate 2 (IRS2) phosphotyrosine and phosphatidylinositol-3-kinase (PI3-K) activation in hypothalamic ARC of CUMS rats after high-level of insulin stimulation. These data indicated that CUMS procedure induced the hyperactivity of CRF system, and subsequently produced conditional loss of insulin signaling in hypothalamic ARC of rats. More importantly, icariin and fluoxetine with the ability to restrain CRF system hyperactivity improved insulin signaling in hypothalamic ARC of CUMS rats, which were consistent with the enhancement of glucose tolerance in OGTT, showing anti-diabetic efficacy. Although effective in OGTT, anti-diabetic drug pioglitazone failed to restore hypothalamic ARC CRF system hyperactivity, paralleling with its inability to ameliorate the loss of insulin signaling and depression-like behavior in CUMS rats. These observations support the hypothesis that signal cross-talk between hypothalamic CRF system and insulin may be impaired in depression with glucose intolerance and suggest that icarrin and fluoxetine aiming at CRF system may have great potential in the prevention and treatment of depression with comorbid diabetes.

Influence of pregnancy on the adipocytokine and peroxisome proliferator-activated receptor pathways in peripheral blood mononuclear cells from healthy donors and rheumatoid arthritis patients

OBJECTIVE

To identify candidate genes that are regulated by human pregnancy and have the potential to modulate rheumatoid arthritis (RA) disease activity.

METHODS

Peripheral blood mononuclear cells (PBMCs) from healthy pregnant volunteers were analyzed using Affymetrix GeneChips at 4 time points (during the first, second, and third trimesters and 6 weeks postpartum). Based on the GeneChip data, target genes were further analyzed via real-time quantitative polymerase chain reaction (qPCR) using PBMCs from healthy controls and RA patients. In order to determine the cellular source of the candidate gene messenger RNA (mRNA), monocytes and lymphocytes from healthy controls and RA patients were positively selected using magnetic beads, and their mRNA was analyzed by qPCR.

RESULTS

One-way analysis of variance identified 1,286 mRNAs that were differentially expressed with regard to the 4 time points. The changes became more pronounced as pregnancy progressed, and they were reversed postpartum. A subsequent pathway analysis suggested a regulatory role of pregnancy on the adipocytokine pathway as well as on the peroxisome proliferator-activated receptor (PPAR) signaling pathway. Of 19 preselected candidate genes, AKT3, SOCS3, FADS2, STAT1, and CD36 proved to be differentially regulated by pregnancy. In samples from RA patients, the differences were concordant with those in healthy controls but more pronounced. Both T lymphocytes and monocytes contributed to the regulated expression of these genes.

CONCLUSION

Our findings indicate that normal human pregnancy leads to changes in the expression of several molecular pathways in PBMCs, which are reversed postpartum. Changes in RA patients, although concordant, exceed the levels observed in healthy controls. Genes of the adipocytokine and PPAR signaling pathways qualify as candidates for the modulation of RA disease activity during pregnancy.

SOCS3 modulates interleukin-6R signaling preference in dermal fibroblasts

AIMS

This study aims to investigate the mechanisms in the apparent preference for mitogen-activated protein kinase /ERK signaling through interleukin (IL)-6R in dermal fibroblasts.

METHODS

Dermal fibroblasts isolated from IL-6KO mice were pretreated with specific ERK or STAT3 chemical inhibitors or SOCS3 specific siRNA and treated with rmIL-6. Phosphorylation was monitored via enzyme-linked immunosorbent assay or immunohistology. SOCS3 interaction with p120Ras-Gap was examined by co-immunoprecipitation and Western blot. Expression of MMP2 mRNA was assessed via real-time quantitative polymerase chain reaction.

RESULTS

A dose response phosphorylation of ERK1/2 occurred while no STAT3 activation (p-Tyr705) was induced after IL-6 treatment, despite an increase in Ser727 phosphorylation. Inhibition of STAT3 in fibroblasts potentiated IL-6R induced ERK phosphorylation and vice versa. Phosphorylated SOCS3 and p120 RasGAP co-immunoprecipitated in response to IL-6 treatment. SOCS3 siRNA knockdown allowed STAT3 phosphorylation after rmIL-6 treatment. Chemical inhibition of IL-6R signaling altered the IL-6 modulated mRNA expression of MMP-2.

CONCLUSIONS

SOCS3 interaction with p120 Ras-Gap plays a role in determining the preference for IL-6R signaling through ERK in dermal fibroblasts. This study provides insight into the pleiotropic nature of IL-6 and the selective signaling mechanism elicited by the IL-6R system in dermal fibroblasts. It may further indicate a method for manipulation of IL-6R function.

Dental pulp neuropathophysiology

Mechanisms of pulpal pathophysiology are complex and the low compliance environment in which the dental pulp is allocated, further enhances the complexity of this process. Although it is known that it involves the interaction of the immune cells, pulpal cells, cytokines, chemokines and multiple neuropeptides but still there are many gaps in our current knowledge. The understanding of the biochemical and molecular pathways involved in the pulpal inflammation is important so that it can be used clinically to keep the dental pulp vital and healthy. It may thus provide an opportunity to develop potentially new treatment modalities for the inflamed dental pulp in future.

Targeted activation of astrocytes: a potential neuroprotective strategy

Astrocytes are involved in many key physiological processes in the brain, including glutamatergic transmission, energy metabolism, and blood flow control. They become reactive in response to pathological situations, a response that involves well-described morphological alterations and less characterized functional changes. The functional consequences of astrocyte reactivity seem to depend on the molecular pathway involved and may result in the enhancement of several neuroprotective and neurotrophic functions. We propose that a selective and controlled activation of astrocytes may switch these highly pleiotropic cells into therapeutic agents to promote neuron survival and recovery. This may represent a potent therapeutic strategy for many brain diseases in which neurons would benefit from an increased support from activated astrocytes.

Neuroinflammatory response to lipopolysaccharide is exacerbated in mice genetically deficient in cyclooxygenase-2

Background

Cyclooxygenases (COX) -1 and -2 are key mediators of the inflammatory response in the central nervous system. Since COX-2 is inducible by inflammatory stimuli, it has been traditionally considered as the most appropriate target for anti-inflammatory drugs. However, the specific roles of COX-1 and COX-2 in modulating a neuroinflammatory response are unclear. Recently, we demonstrated that COX-1 deficient mice show decreased neuroinflammatory response and neuronal damage in response to lipopolysaccharide (LPS).

Methods

In this study, we investigated the role of COX-2 in the neuroinflammatory response to intracerebroventricular-injected LPS (5 μg), a model of direct activation of innate immunity, using COX-2 deficient (COX-2^-/-) and wild type (COX-2^+/+) mice, as well as COX-2^+/+ mice pretreated for 6 weeks with celecoxib, a COX-2 selective inhibitor.

Results

Twenty-four hours after LPS injection, COX-2^-/- mice showed increased neuronal damage, glial cell activation, mRNA and protein expression of markers of inflammation and oxidative stress, such as cytokines, chemokines, iNOS and NADPH oxidase. Brain protein levels of IL-1β, NADPH oxidase subunit p67^phox, and phosphorylated-signal transducer and activator of transcription 3 (STAT3) were higher in COX-2^-/- and in celecoxib-treated mice, compared to COX-2^+/+ mice. The increased neuroinflammatory response in COX-2^-/- mice was likely mediated by the upregulation of STAT3 and suppressor of cytokine signaling 3 (SOCS3).

Conclusion

These results show that inhibiting COX-2 activity can exacerbate the inflammatory response to LPS, possibly by increasing glial cells activation and upregulating the STAT3 and SOCS3 pathways in the brain.

Transcriptional activation of the suppressor of cytokine signaling-3 (SOCS-3) gene via STAT3 is increased in F9 REX1 (ZFP-42) knockout teratocarcinoma stem cells relative to wild-type cells

Rex1 (Zfp42), first identified as a gene that is transcriptionally repressed by retinoic acid (RA), encodes a zinc finger transcription factor expressed at high levels in F9 teratocarcinoma stem cells, embryonic stem cells, and other stem cells. Loss of both alleles of Rex1 by homologous recombination alters the RA-induced differentiation of F9 cells, a model of pluripotent embryonic stem cells. We identified Suppressor of Cytokine Signaling-3 (SOCS-3) as a gene that exhibits greatly increased transcriptional activation in RA, cAMP, and theophylline (RACT)-treated F9 Rex1(-/-) cells (approximately 25-fold) as compared to wild-type (WT) cells ( approximately 2.5-fold). By promoter deletion, mutation, and transient transfection analyses, we have shown that this transcriptional increase is mediated by the STAT3 DNA-binding elements located between -99 to -60 in the SOCS-3 promoter. Overexpression of STAT3 dominant-negative mutants greatly diminishes this SOCS-3 transcriptional increase in F9 Rex1(-/-) cells. This increase in SOCS-3 transcription is associated with a four- to fivefold higher level of tyrosine-phosphorylated STAT3 in the RACT-treated F9 Rex1(-/-) cells as compared to WT. Dominant-negative Src tyrosine kinase, Jak2, and protein kinase A partially reduce the transcriptional activation of the SOCS 3 gene in RACT-treated F9 Rex1 null cells. In contrast, parathyroid hormone peptide enhances the effect of RA in F9 Rex1(-/-) cells, but not in F9 WT. Thus, Rex1, which is highly expressed in stem cells, inhibits signaling via the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway, thereby modulating the differentiation of F9 cells.

JAK-STAT pathway in carcinogenesis: Is it relevant to cholangiocarcinoma progression

The features of JAK-STAT signaling in liver cells are discussed in the current review. The role of this signaling cascade in carcinogenesis is accentuated. The possible involvement of this pathway and alteration of its elements are compared for normal cholangiocytes, cholangiocarcinoma predisposition and development. Prolactin and interleukin-6 are described in detail as the best studied examples. In addition, the non-classical nuclear translocation of cytokine receptors is discussed in terms of its possible implication to cholangiocarcinoma development.

Hepatitis-C patients have reduced growth hormone (GH) secretion which improves during long-term therapy with pegylated interferon-alpha

OBJECTIVES

In vitro and in vivo data indicate multiple, but contradictory effects of interferon on pituitary hormone secretion. We therefore investigated prospectively basal and stimulated pituitary hormone secretion in 21 patients with chronic hepatitis C virus (HCV) infection before and during antiviral therapy.

METHODS

Twenty-one patients received pegylated interferon-alpha plus either ribavirin or levovirin. Baseline and stimulated growth hormone (GH), cortisol, luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin (PRL), and thyroid-stimulating hormone (TSH) responses were measured using standard pituitary function tests, before therapy in all and during therapy in 17 out of the 21 patients.

RESULTS

Before therapy 17 patients (81%) had severe GH insufficiency and 9 of these had low insulin-like growth factor-1 (IGF-1) concentrations. Basal and stimulated GH concentrations increased significantly during therapy, reducing the number of patients with severe GH insufficiency to four, but IGF-1 remained low. Basal PRL and TSH concentrations were normal before and during therapy, while thyroid-releasing hormone (TRH)-stimulated concentrations increased significantly during therapy. The adrenocorticotropic hormone (ACTH)/cortisol axis, basal and stimulated gonadotropin, and testosterone concentrations were normal throughout. Neither the HCV RNA level nor transaminases correlated with hormone concentrations before or during therapy.

CONCLUSIONS

GH insufficiency is common in patients with chronic HCV infection. While GH secretion improves during antiviral therapy, IGF-1 remains low, indicating persistent GH resistance of hepatocytes. Whether improvement in GH secretion during treatment is due to a direct drug effect or related to the suppression of viral load could not be differentiated, as most patients demonstrated a positive virologic response.

Concentrations of the acute phase reactants high-sensitive C-reactive protein and YKL-40 and of interleukin-6 before and after treatment in patients with acromegaly and growth hormone deficiency

BACKGROUND

Acromegaly is accompanied by increased cardiovascular mortality and a cluster of proatherogenic risk factors. In the general population, ischaemic heart disease (IHD) is associated with elevated levels of inflammatory markers. The acute phase reactant (APR) C-reactive protein (CRP) has been reported to be reduced in acromegaly and increase after treatment, suggesting that excess of GH/IGF-I could have anti-inflammatory effects. This is in accordance with results obtained in patients with growth hormone deficiency (GHD), where increased levels of CRP have been reported.

OBJECTIVE

To investigate the hypothesis that the GH/IGF-I system is a suppressive regulator of inflammatory processes.

SUBJECTS AND METHODS

Twenty-one acromegalic patients and 19 GH-deficient patients were studied. The two APRs CRP and YKL-40 and the proinflammatory cytokine interleukin-6 (IL-6) were measured before and after treatment and in healthy matched controls.

RESULTS

In acromegalic patients, serum concentrations of high-sensitive CRP (hsCRP) and YKL-40 were reduced compared to controls (P < 0.001) and increased (P < 0.001) after treatment, together with IL-6 (P = 0.021), to levels comparable with controls. Pretreatment serum YKL-40 and IL-6 showed a significant inverse correlation with IGF-I and GH. In GH-deficient patients, hsCRP and YKL-40 were elevated compared to controls (P = 0.001 and P = 0.048). During treatment, levels of both APRs showed a trend towards a decrease (P = 0.087 and P = 0.060), and after treatment, levels of YKL-40 no longer differed from that of controls. Serum IL-6 was not different from controls and did not change during GH treatment.

CONCLUSION

The results point to the possibility of a relationship between GH disturbances and inflammatory processes.

Regulation of Suppressor of Cytokine Signaling 3 (SOC3) by Growth Hormone in Pro-B Cells

Suppressor of cytokine signaling 3 (SOCS3) is expressed by lymphoid cells and can modulate the sensitivity of these cells to cytokine stimulation through inhibition of Janus kinase (JAK)/signal transducers and activators of transcription (STAT) signaling pathways. This study employed a mouse pro-B cell line expressing the human GH receptor (BaF/3-GHR), to elucidate the signal transduction pathways used by GH to elicit SOCS3 expression. GH treatment of these cells caused a rapid, dose-dependent increase in SOCS3 mRNA expression, which was independent of de novo protein synthesis. As expected, GH treatment increased JAK-dependent STAT5 tyrosine phosphorylation, which bound to the proximal STAT response element (pSRE) on the SOCS3 promoter. This process appeared to involve STAT5b, rather than STAT5a. In addition, GH activation of the SOCS3 promoter required a nearby activator protein (AP) 1/cAMP response element (CRE), which bound cAMP response element binding protein, c-Fos, and c-Jun. Moreover, inhibitors of p38 MAPK and c-Jun N-terminal kinase prevented GH-stimulation of SOCS3 mRNA expression in these cells, suggesting a role for these kinases in SOCS3 transcription. Importantly, GH stimulation increased binding of FOXO3a to the SOCS3 promoter at a site overlapping the AP1/CRE response element, and overexpression of FOXO3a in these cells augmented SOCS3 promoter activation. In addition, we show a direct interaction between FOXO3a and STAT5 in these cells, which may provide a link between STAT5 and the AP1 transcription factors on the SOCS3 promoter. We conclude that regulation of SOCS3 expression by GH in a pro-B cell involves not only the pSRE, but also a transcriptionally active complex involving cAMP response element binding protein/c-Fos/c-Jun and FOXO3a. This study has implications for cytokine regulation of SOCS gene expression in lymphoid cells.

SOCS1 silencing enhances antitumor activity of type I IFNs by regulating apoptosis in neuroendocrine tumor cells

IFN-alpha is commonly used for biotherapy of neuroendocrine carcinomas. However, its antitumor efficacy is often limited due to IFN resistance. In this study, we evaluate the role of suppressor of cytokine signaling protein 1 (SOCS1) in modulating the effects of type I IFNs (IFN-alpha and IFN-beta) in human neuroendocrine BON1 and CM tumor cells. In both cell lines, type I IFNs activated signal transducers and activators of transcription (STAT) and significantly decreased cell viability. However, the effects of IFN-beta were significantly more pronounced than those of IFN-alpha and involved the induction of the intrinsic apoptotic pathway as shown by cleavage of caspase-8, Bid, and caspase-9. Stable overexpression of SOCS1 completely abolished the apoptotic effects of both type I IFNs. In contrast, small interfering RNA (siRNA)-mediated silencing of SOCS1 resulted in strongly enhanced type I IFN signaling as shown by increased and prolonged STAT phosphorylation and stronger induction of apoptosis. Silencing of SOCS1 was associated with down-regulation of basal Bcl-2 and Bcl-xL and up-regulation of basal Bak and Bax, suggesting that reduced SOCS1 expression might lower the threshold of susceptibility to type I IFN-mediated apoptosis by decreasing the ratio of antiapoptotic to proapoptotic molecules. In summary, our results indicate an important role of SOCS1 in IFN resistance of neuroendocrine tumor cells, mediated through negative regulation of type I IFN-induced Jak/STAT signaling. Knocking down SOCS1 by siRNA is a promising new approach to enhance the therapeutic potency of type I IFNs in neuroendocrine tumors.

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.

Janus kinase 3 inhibition with CP-690,550 prevents allograft vasculopathy

Janus kinase 3 (JAK3) mediates signal transduction from cytokine receptors using the common gamma chain. The rationally designed inhibitor of JAK3, CP-690,550, prevents acute allograft rejection in rodents and in nonhuman primates. Here we investigated the ability of CP-690,550, to prevent allograft vasculopathy in a rodent model of aorta transplantation. Aortas from AxC Irish (RT1(a)) or Lewis (RT1(l)) rats were heterotopically transplanted into the infra-renal aorta of Lewis recipients and harvested at 28 or 56 days. Treated recipients received CP-690,550 by osmotic pumps (mean drug exposure of 110 +/- 38 ng/ml). Significant intimal hyperplasia was demonstrated in untreated allografts when compared with isografts at 28 days (2.08 +/- 0.85% vs. 0.43 +/- 0.2% luminal obliteration, respectively, P = 0.001) and 56 days (5.3 +/- 2.4% vs. 0.38 +/- 0.3%, P = 0.002). Treatment caused a 51% reduction in intimal hyperplasia at day 56. CP-690,550-treated animals also had a significant reduction of donor-specific IgG production and of the gene expression for suppressor of cytokine signaling-3 and with unchanged levels of expression of RANTES, IP-10 and transforming growth factor-beta1. These results are the first to show that JAK3 blockade by CP-690,550 effectively prevents allograft vasculopathy in this rat model of aorta transplantation.

Acute myeloid leukemia-associated Mkl1 (Mrtf-a) is a key regulator of mammary gland function

Transcription of immediate-early genes--as well as multiple genes affecting muscle function, cytoskeletal integrity, apoptosis control, and wound healing/angiogenesis--is regulated by serum response factor (Srf). Extracellular signals regulate Srf in part via a pathway involving megakaryoblastic leukemia 1 (Mkl1, also known as myocardin-related transcription factor A [Mrtf-a]), which coactivates Srf-responsive genes downstream of Rho GTPases. Here we investigate Mkl1 function using gene targeting and show the protein to be essential for the physiologic preparation of the mammary gland during pregnancy and the maintenance of lactation. Lack of Mkl1 causes premature involution and impairs expression of Srf-dependent genes in the mammary myoepithelial cells, which control milk ejection following oxytocin-induced contraction. Despite the importance of Srf in multiple transcriptional pathways and widespread Mkl1 expression, the spectrum of abnormalities associated with Mkl1 absence appears surprisingly restricted.

Tumor necrosis factor-alpha activates signal transduction in hypothalamus and modulates the expression of pro-inflammatory proteins and orexigenic/anorexigenic neurotransmitters

Tumor necrosis factor-alpha (TNF-alpha) is known to participate in the wastage syndrome that accompanies cancer and severe infectious diseases. More recently, a role for TNF-alpha in the pathogenesis of type 2 diabetes mellitus and obesity has been shown. Much of the regulatory action exerted by TNF-alpha upon the control of energy stores depends on its action on the hypothalamus. In this study, we show that TNF-alpha activates canonical pro-inflammatory signal transduction pathways in the hypothalamus of rats. These signaling events lead to the transcriptional activation of an early responsive gene and to the induction of expression of cytokines and a cytokine responsive protein such as interleukin-1beta, interleukin-6, interleukin-10 and suppressor of cytokine signalling-3, respectively. In addition, TNF-alpha induces the expression of neurotransmitters involved in the control of feeding and thermogenesis. Thus, TNF-alpha may act directly in the hypothalamus inducing a pro-inflammatory response and the modulation of expression of neurotransmitters involved in energy homeostasis.

Novel interferon-lambdas induce antiproliferative effects in neuroendocrine tumor cells

Interferon-alpha (IFN-alpha) is used for biotherapy of neuroendocrine carcinomas. The interferon-lambdas (IL-28A/B and IL-29) are a novel group of interferons. In this study, we investigated the effects of the IFN-lambdas IL-28A and IL-29 on human neuroendocrine BON1 tumor cells. Similar to IFN-alpha, incubation of BON1 cells with IL-28A (10 ng/ml) and IL-29 (10 ng/ml) induced phosphorylation of STAT1, STAT2, and STAT3, significantly decreased cell numbers in a proliferation assay, and induced apoptosis as demonstrated by poly(ADP-ribose) polymerase (PARP)-cleavage, caspase-3-cleavage, and DNA-fragmentation. Stable overexpression of suppressor of cytokine signaling proteins (SOCS1 and SOCS3) completely abolished the aforementioned effects indicating that SOCS proteins act as negative regulators of IFN-lambda signaling in BON1 cells. In conclusion, the novel IFN-lambdas IL-28A and IL-29 potently induce STAT signaling and antiproliferative effects in neuroendocrine BON1 tumor cells. Thus, IFN-lambdas may hint a promising new approach in the antiproliferative therapy of neuroendocrine tumors.

Predictive factors of virological non-response to interferon-ribavirin combination therapy for patients infected with hepatitis C virus of genotype 1b and high viral load

Patients with high viral load (> or =1.0 x 10(5) IU/ml) of hepatitis C virus (HCV) genotype 1b do not achieve high sustained virological response rates to interferon (IFN)/ribavirin combination therapy. Previous studies suggested that pretreatment amino acid (aa) substitution patterns in the HCV core region could affect virological non-response especially in patients who could not achieve HCV-RNA negativity during treatment. The present study evaluated 167 consecutive Japanese adults with high HCV genotype 1b viral load who received combination therapy for > or =24 weeks. A case-control study matched for age, sex, genotype, and viral load was conducted to investigate the predictive factors for virological non-response, especially absolute virological non-response (patients who could not achieve >2 log decline of HCV RNA from baseline during the initial 24 weeks of therapy). Virological non-response was identified in 26.3% of patients, and 45.5% of these were absolute virological non-responders. Multivariate analysis identified ribavirin dose <11.0 mg/kg, moderate-to-severe hepatocyte steatosis, and substitutions of aa 70 and/or 91 in the core region as significant independent factors associated with virological non-response. The majority of absolute virological non-responders had such substitutions in the core region (95.0%), as well as substitution of glutamine at aa 70 and/or methionine at aa 91 (90.0%). In the present work, such substitutions significantly affected the viral kinetics in virological non-responders. The results suggest that viral, host, and treatment-related factors determine the response to IFN/ribavirin combination therapy in patients with high HCV genotype 1b viral load, and that amino acid substitution patterns in the core region is potentially useful pretreatment predictor of virological non-response.

Hypothalamus–pituitary–adrenal axis during Trypanosoma cruzi acute infection in mice

Functional interactions between neuroendocrine and immune systems are mediated by similar ligands and receptors, which establish a bi-directional communication that is relevant for homeostasis. We investigated herein the hypothalamus-pituitary-adrenal (HPA) axis in mice acutely infected by Trypanosoma cruzi, the causative agent of Chagas' disease. Parasites were seen in the adrenal gland, whereas T. cruzi specific PCR gene amplification product was found in both adrenal and pituitary glands of infected mice. Histological and immunohistochemical analyses of pituitary and adrenal glands of infected animals revealed several alterations including vascular stasis, upregulation of the extracellular matrix proteins fibronectin and laminin, as well as T cell and macrophage infiltration. Functionally, we detected a decrease in CRH and an increase in corticosterone contents, in hypothalamus and serum respectively. In contrast, we did not find significant changes in the amounts of ACTH in sera of infected animals, whereas the serum levels of the glucocorticoid-stimulating cytokine, IL-6 (interleukin-6), were increased as compared to controls. When we analyzed the effects of T. cruzi in ACTH-producing AtT-20 cell line, infected cultures presented lower levels of ACTH and pro-opiomelanocortin production when compared to controls. In these cells we observed a strong phosphorylation of STAT-3, together with an increased synthesis of IL-6, suppressor of cytokine signaling 3 (SOCS-3) and inhibitor of activated STAT-3 (PIAS-3), which could explain the partial blockage of ACTH production. In conclusion, our data reveal that the HPA axis is altered during acute T. cruzi infection, suggesting direct and indirect influences of the parasite in the endocrine homeostasis.

Abundant hypermethylation of SOCS-1 in clinically silent pituitary adenomas

Janus kinase (JAK)/signal transducers and activators of transcription (STAT) cascade are required for cytokines, growth factors, G-proteins and hormones (growth hormone and prolactin). Gatekeepers in this pathway are the suppressor of cytokine signalling (SOCS) family of proteins. Their expression level is epigenetically regulated by DNA methylation. We have investigated the CpG island methylation status of SOCS-1 in a cohort of pituitary adenomas (PA; n=57), craniopharyngiomas (CP; n=30) and normal pituitary tissue (NP; n=11) using methylation sensitive single-strand conformation polymorphism analysis (MS-SSCP) and direct sequencing. SOCS-1 hypermethylation was identified in 51% (29/57) of surgical specimens obtained from PA patients. 83% of these tumours were clinically silent. In contrast, no methylation of SOCS-1 was observed in CPs or NPs. Quantitative real-time PCR and western blot analysis confirmed reduced SOCS-1 expression in the majority of pituitary adenomas. The data is compatible with epigenetic silencing of the SOCS-1 gene and constitutive activation of the JAK-STAT pathway in PA. This appears to contribute particularly to those tumours characterized by a hormone-inactive status.

Comparative proteomics analysis of human pituitary adenomas: current status and future perspectives

This article will review the published research on the elucidation of the mechanisms of pituitary adenoma formation. Mass spectrometry (MS) plays a key role in those studies. Comparative proteomics has been used with the long-term goal to locate, detect, and characterize the differentially expressed proteins (DEPs) in human pituitary adenomas; to identify tumor-related and -specific biomarkers; and to clarify the basic molecular mechanisms of pituitary adenoma formation. The methodology used for comparative proteomics, the current status of human pituitary proteomics studies, and future perspectives are reviewed. The methodologies that are used in comparative proteomics studies of human pituitary adenomas are readily exportable to other different areas of cancer research.

IL-28A and IL-29 mediate antiproliferative and antiviral signals in intestinal epithelial cells and murine CMV infection increases colonic IL-28A expression

Human cytomegalovirus virus (CMV) is a major cause of morbidity and mortality in immunocompromised individuals. Recently, a novel group of cytokines [interleukin (IL)-28A/B and IL-29, also termed interferon (IFN)-lambdas] has been described. Here, we demonstrate that intestinal epithelial cell (IEC) lines as well as murine and human colonic tissue express the IFN-lambda receptor subunits IL-28R and IL-10R2. IL-28A and IL-29 binding to their receptor complex activates ERK-1/2 and stress-activated protein kinase/c-Jun NH2-terminal kinase MAPKs and Akt, resulting in increased IL-8 protein expression. IFN-lambdas also induce phosphorylation of signal transducer and activator of transcription 1 and significantly increase mRNA expression of suppressor of cytokine signaling 3 and the antiviral proteins myxovirus resistance A and 2',5'-oligoadenylate synthetase. These signals result in an up to 83% reduction of cells positive for human CMV immediate-early protein after human CMV infection. In mice, IL-28A mRNA expression is upregulated after infection with murine CMV in vivo. Both IL-28A and IL-29 significantly decrease cell proliferation but have no effect on Fas-induced apoptosis. In conclusion, IECs express functional receptors for IFN-lambdas, which mediate antiviral and antiproliferative signals in IECs, suggesting a potential for therapeutic use in certain viral infections and as (antiproliferative) anticancer therapy.

Association of amino acid substitution pattern in core protein of hepatitis C virus genotype 1b high viral load and non-virological response to interferon-ribavirin combination therapy

OBJECTIVE

Patients with high titer (>/=100 kIU/ml) of hepatitis C virus (HCV) genotype 1b do not achieve highly sustained virological response rates to combination therapy with interferon plus ribavirin. Non-virological responders (NVRs, namely ultimate resistant cases) who do not achieve HCV-RNA negativity during treatment are also encountered. We investigated the pretreatment virological features of NVRs.

METHODS

We evaluated 50 consecutive Japanese adults with high titer of HCV genotype 1b who received combination therapy for 48 weeks. We investigated the pretreatment substitution patterns in amino acids 1-191 of the core region and amino acids 2209-2248 of NS5A, and early viral kinetics.

RESULTS

Overall, a non-virological response was noted in 12 (24%) patients. Multivariate analysis identified serum albumin <3.9 g/dl, substitutions of amino acid 70 in the core region, and substitutions of amino acid 91 as independent and significant factors associated with a non-virological response. Especially, substitutions of arginine (R) by glutamine (Q) at amino acid 70, and/or leucine (L) by methionine (M) at amino acid 91 were significantly more common in NVRs. The falls in HCV-RNA levels during treatment in patients with specific substitutions in the core region were significantly less than in those without such substitutions.

CONCLUSIONS

Our results suggest that serum albumin and amino acid substitution patterns in the core region in patients with high titers of HCV genotype 1b may have an effect on combination therapy in NVRs. Further large-scale studies are required to examine the role of amino acid substitutions specific to a non-virological response to combination therapy.

SOCS-1 inhibits expression of the antiviral proteins 2',5'-OAS and MxA induced by the novel interferon-lambdas IL-28A and IL-29

Recently, we have shown that SOCS-1/3 overexpression in hepatic cells abrogates signaling of type I interferons (IFN) which may contribute to the frequently observed IFN resistance of hepatitis C virus (HCV). IFN-lambdas (IL-28A/B and IL-29), a novel group of IFNs, also efficiently inhibit HCV replication in vitro with potentially less hematopoietic side effects than IFN-alpha because of limited receptor expression in hematopoietic cells. To further evaluate the potential of IFN-lambdas in chronic viral hepatitis, we examined the influence of SOCS protein expression on IFN-lambda signaling. First, we show that hepatic cell lines express the IFN-lambda receptor complex consisting of IFN-lambdaR1 (IL-28R1) and IL-10R2. Whereas in mock-transfected HepG2 cells, IL-28A and IL-29 induced STAT1 and STAT3 phosphorylation, overexpression of SOCS-1 completely abrogated IL-28A and IL-29-induced STAT1/3 phosphorylation. Similarly, IL-28A and IL-29 induced mRNA expression of the antiviral proteins 2',5'-OAS and MxA was abolished by overexpression of SOCS-1. In conclusion, we assume that despite antiviral properties of IFN-lambdas, their efficacy as antiviral agents may have similar limitations as IFN-alpha due to inhibition by SOCS proteins.

Diencephalic syndrome: a cause of failure to thrive and a model of partial growth hormone resistance

Diencephalic syndrome is a rare but potentially lethal cause of failure to thrive in infants and young children. The diencephalic syndrome includes clinical characteristics of severe emaciation, normal linear growth, and normal or precocious intellectual development in association with central nervous system tumors. Our group initially described a series of 9 patients with diencephalic syndrome and found a reduced prevalence of emesis, hyperalertness, or hyperactivity compared with previous reports. Also, the tumors were found to be larger, occur at a younger age, and behave more aggressively than similarly located tumors without diencephalic syndrome. We have been able to extend our follow-up of the original patients, as well as describe 2 additional cases. Because the mechanism of the growth and endocrinologic findings in diencephalic syndrome has not been explained, we report on these patients in light of current research on hypothalamic factors that affect growth and weight. This study emphasizes diencephalic syndrome as a model for additional study of growth hormone resistance and metabolic regulation of adiposity.

Novel neurotrophin-1/B cell-stimulating factor-3 (NNT-1/BSF-3)/cardiotrophin-like cytokine (CLC)--a novel gp130 cytokine with pleiotropic functions

Novel neurotrophin-1/B-cell stimulating factor-3 (NNT-1/BSF-3) is a new member of the gp130 cytokine family. NNT-1/BSF-3 is a second ligand to the tripartite CNTFR complex and activates Jak-STAT, MAPK and PI3/Akt signaling pathways in various cell systems. So far, the known functions of NNT-1/BSF-3 encompass neurotrophic and B cell stimulatory effects, as well as neuroimmunoendocrine modulation of corticotroph function. Gene expression of NNT-1/BSF-3 is stimulated by PKA- and PKC-dependent pathways. Cellular secretion of NNT-1/BSF-3 requires heteromeric complex formation with other factors, e.g. cytokine-like factor-1 (CLF-1) or soluble ciliary neurotrophic factor receptor (sCNTFR). This article reviews the current knowledge on NNT-1/BSF-3 expression, secretion, receptor interaction, signal transduction and physiologic effects of this novel gp130 cytokine. Remark: After preparation of this manuscript, another novel gp130 cytokine named neuropoietin (NP) has been reported and shown to be a ligand of the CNTFR complex.

Role of the intracellular receptor domain of gp130 (exon 17) in human inflammatory bowel disease

AIM

To study the role of the intracellular receptor domain of gp130 in human inflammatory bowel disease (IBD).

METHODS

We amplified and sequenced the complete exon 17 of the human gp130 gene in 146 patients with IBD. According to clinical and histopathological signs, the 146 patients with IBD were classified as having Crohn's disease (n = 73) or ulcerative colitis (n = 63), or as indeterminate status (n = 10).

RESULTS

No mutations in exon 17 of the gp130 gene could be detected in any of the 146 patients with IBD examined.

CONCLUSION

There is no evidence that mutations in exon 17 of the gp130 gene are involved in the pathogenesis of human IBD.

The suppressor of cytokine signaling (SOCS)-7 interacts with the actin cytoskeleton through vinexin

To understand the function of the suppressor of cytokine signaling (SOCS)-7, we have looked for proteins interacting with SOCS-7 in a stringent yeast two-hybrid screen of a human leukocyte cDNA-library. We identified the cytoskeletal molecule vinexin as a partner interacting with SOCS-7. Tests with deletion mutants of SOCS-7 demonstrated that a central region of the molecule containing several proline-rich regions, N-terminal to the SH2 domain, was responsible for the binding to vinexin. It is thus likely that one of the SH3 domains of vinexin interacts with a poly-proline region of SOCS-7. The interaction with vinexin was confirmed biochemically as vinexin-alpha was co-precipitated with SOCS-7. Confocal laser-scanning microscopy in HEK293T, MCF-7, and 3T3-L1 cells showed that part of the transfected SOCS-7-green fluorescent protein (GFP) molecules merged with vinexin and with actin. Taken together, our data indicate that SOCS-7 interacts with vinexin and the actin cytoskeleton.

SOCS-1 and SOCS-3 inhibit IFN-alpha-induced expression of the antiviral proteins 2,5-OAS and MxA

Although the use of IFN-alpha in combination with ribavirin has improved the treatment efficacy of chronic hepatitis C virus (HCV) infection, 20-50% of patients still fail to eradicate the virus depending on the HCV genotype. Recently, overexpression of HCV core protein has been shown to inhibit IFN signaling and induce SOCS-3 expression. Aim of this study was to examine the putative role of SOCS proteins in IFN resistance. By Western blot analysis, a 4-fold induction of STAT-1/3 phosphorylation by IFN-alpha was observed in mock-transfected HepG2 clones. In contrast, IFN-induced STAT-1/3 phosphorylation was considerably downregulated by SOCS-1/3 overexpression. In mock-transfected cells, IFN-alpha induced 2',5'-OAS and myxovirus resistance A (MxA) promoter activity 40- to 80-fold and 10- to 35-fold, respectively, and this effect was abrogated in SOCS-1/3 overexpressing cells. As detected by Northern blot technique, IFN-alpha potently induced 2',5'-OAS and MxA mRNA expression in the control clones. Overexpression of SOCS-1 completely abolished both 2',5'-OAS and MxA mRNA expression, whereas SOCS-3 mainly inhibited 2',5'-OAS mRNA expression. Our results demonstrate that SOCS-1 and SOCS-3 proteins inhibit IFN-alpha-induced activation of the Jak-STAT pathway and expression of the antiviral proteins 2',5'-OAS and MxA. These data suggest a potential role of SOCS proteins in IFN resistance during antiviral treatment.

Role of NK and NKT cells in the immunopathogenesis of HCV-induced hepatitis

Natural killer (NK) cells constitute the first line of host defense against invading pathogens. They usually become activated in an early phase of a viral infection. Liver is particularly enriched in NK cells, which are activated by hepatotropic viruses such as hepatitis C virus (HCV). The activated NK cells play an essential role in recruiting virus-specific T cells and in inducing antiviral immunity in liver. They also eliminate virus-infected hepatocytes directly by cytolytic mechanisms and indirectly by secreting cytokines, which induce an antiviral state in host cells. Therefore, optimally activated NK cells are important in limiting viral replication in this organ. This notion is supported by the observations that interferon treatment is effective in HCV-infected persons in whom it increases NK cell activity. Not surprisingly, HCV has evolved multiple strategies to counter host's NK cell response. Compromised NK cell functions have been reported in chronic HCV-infected individuals. It is ironic that activated NK cells may also contribute toward liver injury. Further studies are needed to understand the role of these cells in host defense and in liver pathology in HCV infections. Recent advances in understanding NK cell biology have opened new avenues for boosting innate and adaptive antiviral immune responses in HCV-infected individuals.

Hypothalamic gene expression is altered in underweight but obese juvenile male Sprague-Dawley rats fed a high-energy diet

The incidence of obesity, with its associated health risks, is on the increase throughout the western world affecting all age groups, including children. The typical western diet is high in fat and sugar and low in complex carbohydrates. This study looks at the effects of feeding an equivalent high-energy (HE) diet to growing rats. Juvenile male Sprague-Dawley rats that were fed an HE (18.9 kJ/g) diet starting approximately 10 d after weaning gained less weight than littermates fed a nonpurified (14 kJ/g) diet. Despite an initial hyperphagia following the change in diet, HE rats also consumed less energy. Although they exhibited reduced weight gain, HE rats were relatively obese; fat pad weights were elevated for all 4 dissected depots. HE-fed rats exhibited symptoms of developing metabolic syndrome with elevated plasma concentrations of glucose, triglycerides, nonesterified fatty acids, insulin, and leptin. In addition, leptin receptor gene expression in the hypothalamic arcuate nucleus (ARC) and ventromedial nucleus of HE rats was reduced. Consistent with the elevated serum leptin and other peripheral signals in HE rats, hypothalamic gene expression for the orexigenic neuropeptides, neuropeptide Y (ARC and dorsomedial nucleus), and agouti-related peptide (AgRP), was reduced. This reduction in orexigenic signaling and decline in energy intake is consistent with an apparent attempt to counter the further development of an obese state in rats consuming an energy-dense diet. The juvenile Sprague-Dawley rat has potential in the development of a model of childhood diet-induced obesity.

Human growth hormone induces SOCS3 and CIS mRNA increase in the hypothalamic neurons of hypophysectomized rats

The activation of the growth hormone (GH) receptor is followed by activation of the JAK2-STAT system in peripheral tissues, which in turn induces the expression of suppressors of cytokine signaling (SOCS) and/or cytokine-inducible SH2 protein (CIS) to achieve the attenuation of the signaling. To examine whether GH involves the SOCS/CIS system as intracellular negative regulators in the hypothalamus, we observed the effects of human GH on the gene expression of SOCS/CIS in the rat hypothalamus. The mRNAs of CIS, SOCS2, and SOCS3 in the hypothalamus of hypophysectomized male rats were examined by Northern analysis following the intravenous administration of recombinant human GH (hGH), 50 microg/100 g BW. The SOCS3 and CIS mRNAs were increased transiently with maximum expression at 1 h after hGH administration. The intravenous hGH did not induce SOCS2 mRNA expression in the hypothalamus. In situ hybridization demonstrated the increase of SOCS3 and CIS mRNAs in the arcuate nucleus after hGH administration, and the increase of SOCS3 mRNA in the periventricular nucleus. The hGH applied to primary cultured hypothalamic neurons at 500 ng/ml induced transient increase of SOCS3 and CIS mRNAs, but not SOCS2 mRNA. The results show that hGH acts directly on the neurons in the hypothalamus, and increases SOCS3 and CIS mRNAs, suggesting that these negative regulators may be involved in the mechanism that turns off the hGH action in the hypothalamic neurons.

Photoperiodic regulation of leptin sensitivity in the Siberian hamster, Phodopus sungorus, is reflected in arcuate nucleus SOCS-3 (suppressor of cytokine signaling) gene expression

We present the first evidence that suppressor of cytokine signaling-3 (SOCS3), a protein inhibiting Janus kinase/signal transducer and activator of transcription (STAT) signaling distal of the leptin receptor, conveys seasonal changes in leptin sensitivity in the Siberian hamster. Food deprivation (48 h) reduced SOCS3 gene expression in hamsters acclimated to either long (LD) or short (SD) photoperiods, suggesting that leptin signals acute starvation regardless of photoperiod. However, SOCS3 mRNA levels were substantially lower in the hypothalamic arcuate nucleus of hamsters acclimated to SD than in those raised in LD. In juveniles raised in LD, a rapid increase in SOCS3 mRNA was observed within 4 d of weaning, which was completely prevented by transfer to SD on the day of weaning. The early increase in SOCS3 gene expression in juvenile hamsters in LD clearly preceded the establishment of different body weight trajectories in LD and SD. In adult LD hamsters, SOCS3 mRNA was maintained at an elevated level despite the chronic food restriction imposed to lower body weight and serum leptin to or even below SD levels. A single injection of leptin in SD hamsters elevated SOCS3 mRNA to LD levels, whereas leptin treatment had no effect on SOCS3 gene expression in LD hamsters. Our results suggest that the development of leptin resistance in LD-acclimated hamsters involves SOCS3-mediated suppression of leptin signaling in the arcuate nucleus. Increased SOCS3 expression in LD hamsters is independent of body fat and serum leptin levels, suggesting that the photoperiod is able to trigger the biannual reversible switch in leptin sensitivity.

Cell-specific pituitary gene expression profiles after treatment with leukemia inhibitory factor reveal novel modulators for proopiomelanocortin expression

Leukemia inhibitory factor (LIF) mediates the hypothalamo-pituitary-adrenal stress response. Transgenic mice overexpressing LIF in the developing pituitary have altered pituitary differentiation with expansion of corticotropes, maintenance of Rathke's cleft cysts, and suppression of all other pituitary cell types. Affymetrix GeneChips were used to identify modulators of LIF effects in corticotrope (AtT-20) and somatolactotrope (GH(3)) cells. In addition to genes known to respond to LIF in corticotrope cells [e.g. suppressor of cytokine signaling-3 (SOCS-3), signal transducer and activator of transcription-3, SH2 domain-containing tyrosine phosphatase-1, and proopiomelanocortin (POMC)], corticotrope-specific changes were also observed for genes involved in glycolysis and gluconeogenesis, transcription factors, signaling molecules, and expressed sequence tags. Two transcription factors identified, CCAAT/enhancer-binding protein beta (C/EBPbeta) and glial cell-derived neurotrophic factor (GDNF)-inducible factor (GIF), dose-dependently induced expression of the rat POMC promoter when overexpressed in AtT-20 cells. LIF further induced POMC transcription with C/EBPbeta, but not with GIF. C/EBPbeta also induced expression of the SOCS-3 promoter that was further enhanced by cotreatment with LIF. However, GIF did not affect SOCS-3 expression. These results indicate that C/EBPbeta and GIF are downstream effectors of LIF corticotrope action. LIF also stimulates the expression of inhibitors of its actions, such as SOCS-3 and SH2 domain-containing tyrosine phosphatase-1. alpha(2)-HS-glycoprotein (AHSG)/fetuin, a secreted protein that antagonizes bone TGFbeta/bone morphogenic protein signaling, was induced by LIF in a signal transducer and activator of transcription-3-dependent fashion. Pretreatment with AHSG/fetuin blocked LIF-induced expression of the POMC promoter independently of SOCS-3. Thus, using GeneChips, C/EBPbeta and GIF have been identified as novel mediators and AHSG/fetuin as an inhibitor of LIF action in corticotropes.

Comparative study of gp130 cytokine effects on corticotroph AtT-20 cells--redundancy or specificity of neuroimmunoendocrine modulators?

OBJECTIVE

This comparative in vitro study examined the effects of all known gp130 cytokines on murine corticotroph AtT-20 cell function.

METHODS

Cytokines were tested at equimolar concentrations from 0.078 to 10 nM. Tyrosine phosphorylation of the signal transducer and activator of transcription (STAT)3 and STAT1, the STAT-dependent suppressor of cytokine signaling (SOCS)-3 promoter activity, SOCS-3 gene expression, STAT-dependent POMC promoter activity and adrenocorticotropic hormone (ACTH) secretion were determined.

RESULTS

Leukemia inhibitory factor (LIF), human oncostatin M (OSM) and cardiotrophin (CT)-1 (LIFR/gp130 ligands), as well as ciliary neurotrophic factor (CNTF) and novel neurotrophin-1/B-cell stimulating factor-3 (CNTFR alpha/LIFR/gp130 ligands) are potent stimuli of corticotroph cells in vitro. In comparison, interleukin (IL)-6 (IL-6R/gp130 ligand) and IL-11 (IL-11R/gp130 ligand) exhibited only modest direct effects on corticotrophs, while murine OSM (OSMR/gp130 ligand) showed no effect.

CONCLUSION

(i) CNTFR complex ligands are potent stimuli of corticotroph function, comparable to LIFR complex ligands; (ii) IL-6 and IL-11 are relatively weak direct stimuli of corticotroph function; (iii) differential effects of human and murine OSM suggest that LIFR/gp130 (OSMR type I) but not OSMR/gp130 (OSMR type II) are involved in corticotroph signaling. (iv) CT-1 has the hitherto unknown ability to stimulate corticotroph function, and (v) despite redundant immuno-neuroendocrine effects of different gp130 cytokines, corticotroph cells are preferably activated through the LIFR and CNTFR complexes.

NEUROPEPTIDES AND NEUROGENIC MECHANISMS IN ORAL AND PERIODONTAL INFLAMMATION

It is generally accepted that the nervous system contributes to the pathophysiology of peripheral inflammation, and a neurogenic component has been implicated in many inflammatory diseases, including periodontitis. Neurogenic inflammation should be regarded as a protective mechanism, which forms the first line of defense and protects tissue integrity. However, severe or prolonged noxious stimulation may result in the inflammatory response mediating injury rather than facilitating repair. This review focuses on the accumulating evidence suggesting that neuropeptides have a pivotal role in the complex cascade of chemical activity associated with periodontal inflammation. An overview of neuropeptide synthesis and release introduces the role of neuropeptides and their interactions with other inflammatory factors, which ultimately lead to neurogenic inflammation. The biological effects of the neuropeptides substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP), and neuropeptide Y (NPY) are summarized, and evidence for their involvement in the localized inflammatory lesions which characterize periodontitis is presented. In this context, the role of CGRP in bone metabolism is described in more detail. Recent research highlighting the role of the nervous system in suppressing pain and inflammation is also discussed.

Pituitary corticotroph ontogeny and regulation in transgenic zebrafish

We characterized zebrafish proopiomelanocortin (POMC) gene promoter, and sequence analysis revealed that the promoter contains regulatory elements conserved among vertebrate species. To monitor the ontogeny of the pituitary POMC lineage in living vertebrates, we generated transgenic zebrafish expressing green fluorescent protein (GFP) driven by the POMC promoter. Zebrafish POMC-GFP is first expressed asymmetrically as two bilateral groups of cells most anterior to the neural ridge midline at 18-20 h post fertilization (hpf). POMC-GFP-positive cells then fuse into a single-cell mass within the pituitary anlage after 24 hpf and subsequently organize as distinct anterior and posterior domains between 48 and 64 hpf. Immunohistochemical studies with ACTH and alphaMSH antisera showed that POMC-GFP was mainly targeted to both anterior and posterior pituitary corticotrophs, whereas posterior pituitary region melanotrophs did not express GFP. To determine in vivo zebrafish corticotroph responses, dexamethasone (10(-5) m) was added to live embryos, which selectively suppressed POMC-GFP expression in the anterior group of corticotrophs, suggesting a distinct domain that is responsive to glucocorticoid feedback. Transgenic zebrafish with specific POMC-GFP expression in pituitary corticotrophs offers a powerful genetic system for in vivo study of vertebrate corticotroph lineage development.

Novel neurotrophin-1/B cell-stimulating factor-3 (cardiotrophin-like cytokine) stimulates corticotroph function via a signal transducer and activator of transcription-dependent mechanism negatively regulated by suppressor of cytokine signaling-3

Novel neurotrophin-1/B cell-stimulating factor-3 (NNT-1/BSF-3) is a recently cloned gp130 cytokine, acting through the tripartite ciliary neurotrophic factor receptor (CNTFR) alpha/leukemia inhibitory factor receptor (LIFR)/gp130 receptor complex. The aim of the current study was to investigate the role of NNT-1/BSF-3 in corticotroph cell function and further characterize NNT-1/BSF-3 signaling pathways. Using RT-PCR, expression of ciliary neurotrophic factor receptor alpha, leukemia inhibitory factor receptor, and gp130 could be demonstrated in mRNA derived from murine corticotroph AtT-20 cells and murine pituitary tissue. Incubation of AtT-20 cells with 10 ng/ml recombinant human NNT-1/BSF-3 rapidly induced tyrosine-phosphorylation of signal transducer and activator of transcription (STAT)3 and STAT1 at 5 and 10 min. Proopiomelanocortin promoter activity and suppressor of cytokine signaling (SOCS)-3 promoter activity were significantly stimulated by NNT-1/BSF-3 4.0 +/- 0.3- and 5.9 +/- 0.2-fold, respectively. In comparison with untreated control, NNT-1/BSF-3 significantly stimulated ACTH secretion at 24 and 48 h 1.7 +/- 0.2-fold and 1.5 +/- 0.1-fold above baseline. In comparison with mock-transfected cells, stable overexpression of SOCS-3 in AtT-20 cells abolished NNT-1/BSF-3-induced STAT1 and STAT3 phosphorylation and almost completely inhibited STAT-dependent proopiomelanocortin promoter and SOCS-3 promoter activities. In addition, NNT-1/BSF-3-induced ACTH secretion at 48 h was significantly attenuated by SOCS-3 overexpression. In summary, we have shown that NNT-1/BSF-3 is a modulator of corticotroph cell function, which is negatively regulated by SOCS-3. Our data indicate that the activation of the Jak-STAT cascade is essential for corticotroph NNT-1/BSF-3 signaling. Further studies will have to investigate the possible in vivo role of NNT-1/BSF-3 as a neuroimmunoendocrine modulator of hypothalamus-pituitary-adrenal axis stress response.

Endotoxin stimulates leptin in the human and nonhuman primate

Leptin, which plays a key role in regulating energy homeostasis, may also modulate the inflammatory response. An inflammatory challenge with endotoxin has been shown to stimulate leptin release in the rodent. This finding has not been reproduced in humans or in nonhuman primates, although leptin levels have been reported to increase in septic patients. We have therefore examined the effects of endotoxin injection on plasma leptin levels in nine ovariectomized monkeys and four postmenopausal women. In an initial study in five monkeys, mean leptin levels did not increase during the first 5 h after endotoxin treatment, but did increase significantly from 6.4 +/- 2.1 ng/ml at baseline to 12.3 +/- 4.4 ng/ml at 24 h (P = 0.043). In a second study, a significant increase in leptin over time was noted after endotoxin treatment (P < 0.001); leptin release during the 16- to 24-h period after endotoxin injection was 48% higher than during the control period (P = 0.043). A similar stimulatory effect of endotoxin on leptin was observed when monkeys received estradiol replacement. In a third study, repeated injections of endotoxin over a 3-d period stimulated IL-6, ACTH, cortisol, and leptin release (P < 0.001). Leptin increased during the first day of treatment in all animals, but only monkeys with baseline plasma leptin levels greater than 10 ng/ml exhibited a sustained increase in leptin throughout the 3-d period. There was a significant correlation (r = 0.81; P = 0.008) between the mean baseline leptin level and the percent increase in leptin over baseline on the last day of treatment. In the human subjects, plasma leptin concentrations did not change significantly during the 7-h period after endotoxin injection. However, leptin increased in all four women from a mean baseline of 8.34 +/- 3.1 to 13.1 +/- 4.3 ng/ml 24 h after endotoxin (P = 0.038). In summary, endotoxin stimulates the release of leptin into peripheral blood in the human and nonhuman primate, but the time course is different from that reported in the rodent. These results are consistent with previous reports of increased blood leptin levels in patients with sepsis. The significance of these findings and the potential role of leptin in modulating the response to inflammation in the human require further study.

The suppressor of cytokine signaling-1 (SOCS1) is a novel therapeutic target for enterovirus-induced cardiac injury

Enteroviral infections of the heart are among the most commonly identified causes of acute myocarditis in children and adults and have been implicated in dilated cardiomyopathy. Although there is considerable information regarding the cellular immune response in myocarditis, little is known about innate signaling mechanisms within the infected cardiac myocyte that contribute to the host defense against viral infection. Here we show the essential role of Janus kinase (JAK) signaling in cardiac myocyte antiviral defense and a negative role of an intrinsic JAK inhibitor, the suppressor of cytokine signaling (SOCS), in the early disease process. Cardiac myocyte-specific transgenic expression of SOCS1 inhibited enterovirus-induced signaling of JAK and the signal transducers and activators of transcription (STAT), with accompanying increases in viral replication, cardiomyopathy, and mortality in coxsackievirus-infected mice. Furthermore, the inhibition of SOCS in the cardiac myocyte through adeno-associated virus-mediated (AAV-mediated) expression of a dominant-negative SOCS1 increased the myocyte resistance to the acute cardiac injury caused by enteroviral infection. These results indicate that strategies directed at inhibition of SOCS in the heart and perhaps other organs can augment the host-cell antiviral system, thus preventing viral-mediated end-organ damage during the early stages of infection.