Sostdc1: A soluble BMP and Wnt antagonist that is induced by the interaction between myeloma cells and osteoblast lineage cells

Multiple myeloma (MM) is characterised by destructive lytic bone disease, caused by induction of bone resorption and impaired bone formation. Our understanding of the molecular mechanisms responsible for osteoblast suppression, are limited. Using the 5T2MM murine model of MM we have previously shown that suppression of the activity of a known inhibitor of bone formation Dikkopf-1 (Dkk1) prevents the development of lytic bone disease. Here we have demonstrated that another potential inhibitor of bone formation, sclerostin domain containing 1 (Sostdc1) is expressed at low levels in MM and osteoblast lineage cells when these cells are grown separately in cell culture but its expression is significantly induced in both cell types when these cells are in contact. The distribution of Sostdc1 staining in bones infiltrated with 5TGM1 myeloma cells in vivo suggested its presence in both myeloma and osteoblast lineage populations when in close proximity. We have also shown that recombinant Sostdc1 inhibits both bone morphogenic proteins (BMP2 and 7) and Wnt signalling in primary osteoblasts and suppresses differentiation of these cells. Together, these findings suggest that Sostdc1 expression in 5TGM1-infiltrated bones as a result of the interaction between myeloma and osteoblast lineage populations, could result in suppression of osteoblast differentiation.

Inhibition of DNA Methylation With Zebularine Alters Lipopolysaccharide-Induced Sickness Behavior and Neuroinflammation in Mice

Activity of DNA methyltransferases (DNMTs), the enzymes that catalyze DNA methylation, is dynamically regulated in the brain. DNMT inhibitors alter DNA methylation globally in the brain and at individual neural plasticity-associated genes, but how DNMT inhibitors centrally influence lipopolysaccharide (LPS)-induced neuroinflammation is not known. We investigated whether the DMNT inhibitor, zebularine, would alter sickness behavior, DNA methylation of the Il-1β promoter and expression of inflammatory genes in hippocampus and microglia. Contrary to our hypothesis that zebularine may exaggerate LPS-induced sickness response and neuroinflammation, adult mice treated with an intracerebroventricular (ICV) injection of zebularine prior to LPS had surprisingly faster recovery of burrowing behavior compared to mice treated with LPS. Further, genes of inflammatory markers, epigenetic regulators, and the microglial sensory apparatus (i.e., the sensome) were differentially expressed by zebularine alone or in combination with LPS. Bisulfite pyrosequencing revealed that ICV zebularine led to decreased DNA methylation of two CpG sites near the Il-1β proximal promoter alone or in combination with LPS. Zebularine treated mice still exhibited decreased DNA methylation 48 h after treatment when LPS-induced sickness behavior as well as hippocampal and microglial gene expression were similar to control mice. Taken together, these data suggest that decreased DNA methylation, specifically of the Il-1β promoter region, with a DNMT inhibitor in the brain disrupts molecular mechanisms of neuroinflammation.

Butyrate and Dietary Soluble Fiber Improve Neuroinflammation Associated With Aging in Mice

Aging results in chronic systemic inflammation that can alter neuroinflammation of the brain. Specifically, microglia shift to a pro-inflammatory phenotype predisposing them to hyperactivation upon stimulation by peripheral immune signals. It is proposed that certain nutrients can delay brain aging by preventing or reversing microglial hyperactivation. Butyrate, a short-chain fatty acid (SCFA) produced primarily by bacterial fermentation of fiber in the colon, has been extensively studied pharmacologically as a histone deacetylase inhibitor and serves as an attractive therapeutic candidate, as butyrate has also been shown to be anti-inflammatory and improve memory in animal models. In this study, we demonstrate that butyrate can attenuate pro-inflammatory cytokine expression in microglia in aged mice. It is still not fully understood, however, if an increase in butyrate-producing bacteria in the gut as a consequence of a diet high in soluble fiber could affect microglial activation during aging. Adult and aged mice were fed either a 1% cellulose (low fiber) or 5% inulin (high fiber) diet for 4 weeks. Findings indicate that mice fed inulin had an altered gut microbiome and increased butyrate, acetate, and total SCFA production. In addition, histological scoring of the distal colon demonstrated that aged animals on the low fiber diet had increased inflammatory infiltrate that was significantly reduced in animals consuming the high fiber diet. Furthermore, gene expression of inflammatory markers, epigenetic regulators, and the microglial sensory apparatus (i.e., the sensome) were altered by both diet and age, with aged animals exhibiting a more anti-inflammatory microglial profile on the high fiber diet. Taken together, high fiber supplementation in aging is a non-invasive strategy to increase butyrate levels, and these data suggest that an increase in butyrate through added soluble fiber such as inulin could counterbalance the age-related microbiota dysbiosis, potentially leading to neurological benefits.

Glia- and tissue-specific changes in the Kynurenine Pathway after treatment of mice with lipopolysaccharide and dexamethasone

Behavioral symptoms associated with mood disorders have been intimately linked with immunological and psychological stress. Induction of immune and stress pathways is accompanied by increased tryptophan entry into the Kynurenine (Kyn) Pathway as governed by the rate-limiting enzymes indoleamine/tryptophan 2,3-dioxygenases (DO's: Ido1, Ido2, Tdo2). Indeed, elevated DO expression is associated with inflammation- and stress-related depression symptoms. Here we examined central (brain, astrocyte and microglia) and peripheral (lung, liver and spleen) DO expression in mice treated intraperitoneally with lipopolysaccharide (LPS) and dexamethasone (DEX) to model the response of the Kyn Pathway to inflammation and glucocorticoids. LPS-induced expression of cytokines in peripheral tissues was attenuated by DEX, confirming inflammatory and anti-inflammatory responses, respectively. Increased Kyn levels following LPS and DEX administration verified Kyn Pathway activation. Expression of multiple mRNA isoforms for each DO, which we have shown to be differentially utilized and regulated, were quantified including reference/full-length (FL) and variant (v) transcripts. LPS increased Ido1-FL in brain (∼1000-fold), a response paralleled by increased expression in both astrocytes and microglia. Central Ido1-FL was not changed by DEX; however, LPS-induced Ido1-FL was decreased by DEX in peripheral tissues. In contrast, DEX increased Ido1-v1 expression by astrocytes and microglia, but not peripheral tissues. In comparison, brain Ido2 was minimally induced by LPS or DEX. Uniquely, Ido2-v6 was LPS- and DEX-inducible in astrocytes, suggesting a unique role for astrocytes in response to inflammation and glucocorticoids. Only DEX increased central Tdo2 expression; however, peripheral Tdo2 was upregulated by either LPS or DEX. In summary, specific DO isoforms are increased by LPS and DEX, but LPS-dependent Ido1 and Ido2 induction are attenuated by DEX only in the periphery indicating that elevated DO expression and Kyn production within the brain can occur independent of the periphery. These findings demonstrate a plausible interaction between immune activation and glucocorticoids associated with depression.

Desipramine decreases expression of human and murine indoleamine-2,3-dioxygenases

Abundant evidence connects depression symptomology with immune system activation, stress and subsequently elevated levels of kynurenine. Anti-depressants, such as the tricyclic norepinephrine/serotonin reuptake inhibitor desipramine (Desip), were developed under the premise that increasing extracellular neurotransmitter level was the sole mechanism by which they alleviate depressive symptomologies. However, evidence suggests that anti-depressants have additional actions that contribute to their therapeutic potential. The Kynurenine Pathway produces tryptophan metabolites that modulate neurotransmitter activity. This recognition identified another putative pathway for anti-depressant targeting. Considering a recognized role of the Kynurenine Pathway in depression, we investigated the potential for Desip to alter expression of rate-limiting enzymes of this pathway: indoleamine-2,3-dioxygenases (Ido1 and Ido2). Mice were administered lipopolysaccharide (LPS) or synthetic glucocorticoid dexamethasone (Dex) with Desip to determine if Desip alters indoleamine-dioxygenase (DO) expression in vivo following a modeled immune and stress response. This work was followed by treating murine and human peripheral blood mononuclear cells (PBMCs) with interferon-gamma (IFNγ) and Desip. In vivo: Desip blocked LPS-induced Ido1 expression in hippocampi, astrocytes, microglia and PBMCs and Ido2 expression by PBMCs. Ex vivo: Desip decreased IFNγ-induced Ido1 and Ido2 expression in murine PBMCs. This effect was directly translatable to the human system as Desip decreased IDO1 and IDO2 expression by human PBMCs. These data demonstrate for the first time that an anti-depressant alters expression of Ido1 and Ido2, identifying a possible new mechanism behind anti-depressant activity. Furthermore, we propose the assessment of PBMCs for anti-depressant responsiveness using IDO expression as a biomarker.

Maternal viral infection during pregnancy elicits anti-social behavior in neonatal piglet offspring independent of postnatal microglial cell activation

Maternal infection during pregnancy increases risk for neurodevelopmental disorders and reduced stress resilience in offspring, but the mechanisms are not fully understood. We hypothesized that piglets born from gilts infected with a respiratory virus during late gestation would exhibit aberrant microglia activity, cognitive deficits and reduced sociability. Pregnant gilts were inoculated with porcine reproductive and respiratory syndrome virus (PRRSV; 5×10⁵ TCID₅₀ of live PRRSV) or saline at gestational day 76. Gilts infected with PRRSV exhibited fever (p<0.01) and reduced appetite (p<0.001) for 2weekspost-inoculation and were PRRSV-positive at parturition. Piglets born from infected and control gilts were weaned at postnatal day (PD) 1 and assigned to two groups. Group 1 was challenged with lipopolysaccharide (LPS, 5μg/kg body weight i.p.) or saline on PD 14 and tissues were collected. Group 2 was tested in a T-maze task to assess spatial learning and in a 3-chamber arena with unfamiliar conspecifics to assess social behavior from PD 14-27. Microglia (CD11b⁺ CD45^low) isolated from Group 2 piglets at PD 28 were challenged ex vivo with LPS; a subset of cells was analyzed for MHCII expression. Maternal infection did not affect offspring circulating TNFα, IL-10, or cortisol levels basally or 4h post-LPS challenge. While performance in the T-maze task was not affected by maternal infection, both sociability and preference for social novelty were decreased in piglets from infected gilts. There was no effect of maternal infection on microglial MHCII expression or LPS-induced cytokine production. Taken together, these results suggest the reduced social behavior elicited by maternal infection is not due to aberrant microglia activity postnatally.

Immunomodulatory Factors Galectin-9 and Interferon-Gamma Synergize to Induce Expression of Rate-Limiting Enzymes of the Kynurenine Pathway in the Mouse Hippocampus

Elevated levels of circulating pro-inflammatory cytokines are associated with symptomology of several psychiatric disorders, notably major depressive disorder. Symptomology has been linked to inflammation/cytokine-dependent induction of the Kynurenine Pathway. Galectins, like pro-inflammatory cytokines, play a role in neuroinflammation and the pathogenesis of several neurological disorders but without a clearly defined mechanism of action. Their involvement in the Kynurenine Pathway has not been investigated. Thus, we searched for a link between galectins and the Kynurenine Pathway using in vivo and ex vivo models. Mice were administered LPS and pI:C to determine if galectins (Gal's) were upregulated in the brain following in vivo inflammatory challenges. We then used organotypic hippocampal slice cultures (OHSCs) to determine if Gal's, alone or with inflammatory mediators [interferon-gamma (IFNγ), tumor necrosis factor-alpha (TNFα), interleukin-1beta (IL-1β), polyinosine-polycytidylic acid (pI:C), and dexamethasone (Dex; synthetic glucocorticoid)], would increase expression of indoleamine/tryptophan-2,3-dioxygenases (DO's: Ido1, Ido2, and Tdo2; Kynurenine Pathway rate-limiting enzymes). In vivo, hippocampal expression of cytokines (IL-1β, TNFα, and IFNγ), Gal-3, and Gal-9 along with Ido1 and Ido2 were increased by LPS and pI:C (bacterial and viral mimetics). Of the cytokines induced in vivo, only IFNγ increased expression of two Ido1 transcripts (Ido1-FL and Ido1-v1) by OHSCs. Although ineffective alone, Gal-9 accentuated IFNγ-induced expression of only Ido1-FL. Similarly, IFNγ induced expression of several Ido2 transcripts (Ido2-v1, Ido2-v3, Ido2-v4, Ido2-v5, and Ido2-v6). Gal-9 accentuated IFNγ-induced expression of only Ido2-v1. Surprisingly, Gal-9 alone, slightly but significantly, induced expression of Tdo2 (Tdo2-v1 and Tdo2-v2, but not Tdo2-FL). These effects were specific to Gal-9 as Gal-1 and Gal-3 did not alter DO expression. These results are the first to show that brain Gal-9 is increased during LPS- and pI:C-induced neuroinflammation. Increased expression of Gal-9 may be critical for neuroinflammation-dependent induction of DO expression, either acting alone (Tdo2-v1 and Tdo2-v2) or to enhance IFNγ activity (Ido1-FL and Ido2-v1). Although these novel actions of Gal-9 are described for hippocampus, they have the potential to operate as DO-dependent immunomodulatory processes outside the brain. With the expanding implications of Kynurenine Pathway activation across multiple immune and psychiatric disorders, this synergy provides a new target for therapeutic development.

Aging and peripheral lipopolysaccharide can modulate epigenetic regulators and decrease IL-1β promoter DNA methylation in microglia

In aged mice, peripheral stimulation of the innate immune system with lipopolysaccharide (LPS) causes exaggerated neuroinflammation and prolonged sickness behavior due in part to microglial dysfunction. Epigenetic changes to DNA may play a role in microglial dysfunction; therefore, we sought to determine whether aged microglia displayed DNA hypomethylation of the interleukin-1 beta (IL-1β) promoter and altered expression of epigenetic regulators. We further examined whether the demethylating agent 5-azacytidine induced IL-1β expression in BV2 and primary microglia similar to microglia from aged mice. Novel findings indicated that aged mice had decreased methylation of the IL-1β gene promoter in primary microglia basally or following systemic LPS that is associated with increased IL-1β mRNA, intracellular IL-1β production, as well as prolonged sickness behavior. Last, 5-azacytidine increased IL-1β gene expression and decreased DNA methylation of BV2 and primary microglial cells similar to microglia from aged mice. Taken together, these data indicate that DNA methylation promotes heightened microglial activation in the aged brain.

Differential Transcriptome Networks between IDO1-Knockout and Wild-Type Mice in Brain Microglia and Macrophages

Microglia in the brain and macrophages in peripheral organs are cell types responsible for immune response to challenges. Indoleamine 2,3-dioxygenase 1 (IDO1) is an immunomodulatory enzyme of the tryptophan pathway that is expressed in the brain. The higher activity of IDO1 in response to immune challenge has been implicated in behavioral disorders. The impact of IDO1 depletion on the microglia transcriptome has not been studied. An investigation of the transcript networks in the brain microglia from IDO1-knockout (IDO1-KO) mice was undertaken, relative to peripheral macrophages and to wild-type (WT) mice under unchallenged conditions. Over 105 transcript isoforms were differentially expressed between WT and IDO1-KO within cell type. Within microglia, Saa3 and Irg1 were over-expressed in IDO1-KO relative to WT. Within macrophages, Csf3 and Sele were over-expressed in IDO1-KO relative to WT. Among the genes differentially expressed between strains, enriched biological processes included ion homeostasis and ensheathment of neurons within microglia, and cytokine and chemokine expression within macrophages. Over 11,110 transcript isoforms were differentially expressed between microglia and macrophages and of these, over 10,800 transcripts overlapped between strains. Enriched biological processes among the genes over- and under-expressed in microglia relative to macrophages included cell adhesion and apoptosis, respectively. Detected only in microglia or macrophages were 421 and 43 transcript isoforms, respectively. Alternative splicing between cell types based on differential transcript isoform abundance was detected in 210 genes including Phf11d, H2afy, and Abr. Across strains, networks depicted a predominance of genes under-expressed in microglia relative to macrophages that may be a precursor for the different response of both cell types to challenges. The detected transcriptome differences enhance the understanding of the role of IDO1 in the microglia transcriptome under unchallenged conditions.

Microglia Transcriptome Changes in a Model of Depressive Behavior after Immune Challenge

Depression symptoms following immune response to a challenge have been reported after the recovery from sickness. A RNA-Seq study of the dysregulation of the microglia transcriptome in a model of inflammation-associated depressive behavior was undertaken. The transcriptome of microglia from mice at day 7 after Bacille Calmette Guérin (BCG) challenge was compared to that from unchallenged Control mice and to the transcriptome from peripheral macrophages from the same mice. Among the 562 and 3,851 genes differentially expressed between BCG-challenged and Control mice in microglia and macrophages respectively, 353 genes overlapped between these cells types. Among the most differentially expressed genes in the microglia, serum amyloid A3 (Saa3) and cell adhesion molecule 3 (Cadm3) were over-expressed and coiled-coil domain containing 162 (Ccdc162) and titin-cap (Tcap) were under-expressed in BCG-challenged relative to Control. Many of the differentially expressed genes between BCG-challenged and Control mice were associated with neurological disorders encompassing depression symptoms. Across cell types, S100 calcium binding protein A9 (S100A9), interleukin 1 beta (Il1b) and kynurenine 3-monooxygenase (Kmo) were differentially expressed between challenged and control mice. Immune response, chemotaxis, and chemokine activity were among the functional categories enriched by the differentially expressed genes. Functional categories enriched among the 9,117 genes differentially expressed between cell types included leukocyte regulation and activation, chemokine and cytokine activities, MAP kinase activity, and apoptosis. More than 200 genes exhibited alternative splicing events between cell types including WNK lysine deficient protein kinase 1 (Wnk1) and microtubule-actin crosslinking factor 1(Macf1). Network visualization revealed the capability of microglia to exhibit transcriptome dysregulation in response to immune challenge still after resolution of sickness symptoms, albeit lower than that observed in macrophages. The persistent transcriptome dysregulation in the microglia shared patterns with neurological disorders indicating that the associated persistent depressive symptoms share a common transcriptome basis.

Osteolytica: An automated image analysis software package that rapidly measures cancer-induced osteolytic lesions in in vivo models with greater reproducibility compared to other commonly used methods

Methods currently used to analyse osteolytic lesions caused by malignancies such as multiple myeloma and metastatic breast cancer vary from basic 2-D X-ray analysis to 2-D images of micro-CT datasets analysed with non-specialised image software such as ImageJ. However, these methods have significant limitations. They do not capture 3-D data, they are time-consuming and they often suffer from inter-user variability. We therefore sought to develop a rapid and reproducible method to analyse 3-D osteolytic lesions in mice with cancer-induced bone disease. To this end, we have developed Osteolytica, an image analysis software method featuring an easy to use, step-by-step interface to measure lytic bone lesions. Osteolytica utilises novel graphics card acceleration (parallel computing) and 3-D rendering to provide rapid reconstruction and analysis of osteolytic lesions. To evaluate the use of Osteolytica we analysed tibial micro-CT datasets from murine models of cancer-induced bone disease and compared the results to those obtained using a standard ImageJ analysis method. Firstly, to assess inter-user variability we deployed four independent researchers to analyse tibial datasets from the U266-NSG murine model of myeloma. Using ImageJ, inter-user variability between the bones was substantial (±19.6%), in contrast to using Osteolytica, which demonstrated minimal variability (±0.5%). Secondly, tibial datasets from U266-bearing NSG mice or BALB/c mice injected with the metastatic breast cancer cell line 4T1 were compared to tibial datasets from aged and sex-matched non-tumour control mice. Analyses by both Osteolytica and ImageJ showed significant increases in bone lesion area in tumour-bearing mice compared to control mice. These results confirm that Osteolytica performs as well as the current 2-D ImageJ osteolytic lesion analysis method. However, Osteolytica is advantageous in that it analyses over the entirety of the bone volume (as opposed to selected 2-D images), it is a more rapid method and it has less user variability.

A review of current murine models of multiple myeloma used to assess the efficacy of therapeutic agents on tumour growth and bone disease

Pre-clinical in vivo models of multiple myeloma are essential tools for investigating the pathophysiology of multiple myeloma and for testing new therapeutic agents and strategies prior to their potential use in clinical trials. Over the last five decades, several different types of murine models of multiple myeloma have been developed ranging from immunocompetent syngeneic models, e.g. the 5 T series of myeloma cells, to immunocompromised models including the SCID xenograft models, which use human myeloma cell lines or patient-derived cells. Other models include hybrid models featuring the implantation of SCID mice with bone chips (SCID-hu or SCID-rab) or 3-D bone scaffolds (SCID-synth-hu), and mice that have been genetically engineered to develop myeloma. Bearing in mind the differences in these models, it is not surprising that they reflect to varying degrees different aspects of myeloma. Here we review the past and present murine models of myeloma, with particular emphasis on their advantages and limitations, characteristics, and their use in testing therapeutic agents to treat myeloma tumour burden and bone disease.

Analytical workflow profiling gene expression in murine macrophages

Comprehensive and simultaneous analysis of all genes in a biological sample is a capability of RNA-Seq technology. Analysis of the entire transcriptome benefits from summarization of genes at the functional level. As a cellular response of interest not previously explored with RNA-Seq, peritoneal macrophages from mice under two conditions (control and immunologically challenged) were analyzed for gene expression differences. Quantification of individual transcripts modeled RNA-Seq read distribution and uncertainty (using a Beta Negative Binomial distribution), then tested for differential transcript expression (False Discovery Rate-adjusted p-value < 0.05). Enrichment of functional categories utilized the list of differentially expressed genes. A total of 2079 differentially expressed transcripts representing 1884 genes were detected. Enrichment of 92 categories from Gene Ontology Biological Processes and Molecular Functions, and KEGG pathways were grouped into 6 clusters. Clusters included defense and inflammatory response (Enrichment Score = 11.24) and ribosomal activity (Enrichment Score = 17.89). Our work provides a context to the fine detail of individual gene expression differences in murine peritoneal macrophages during immunological challenge with high throughput RNA-Seq.

Advancing the understanding of behaviors associated with Bacille Calmette Guérin infection using multivariate analysis

Behavioral indicators in the murine Bacille Calmette Guérin (BCG) model of inflammation have been studied individually; however, the variability of the behaviors across BCG levels and the mouse-to-mouse variation within BCG-treatment group are only partially understood. The objectives of this study were: (1) to gain a comprehensive understanding of sickness and depression-like behaviors in a BCG model of inflammation using multivariate approaches, and (2) to explore behavioral differences between BCG-treatment groups and among mice within group. Adult mice were challenged with either 0mg (saline), 5mg or 10mg of BCG (BCG-treatment groups: BCG0, BCG5, or BCG10, respectively) at Day 0 of the experiment. Sickness indicators included body weight changes between Day 0 and Day 2 and between Day 2 and Day 5, and horizontal locomotor activity and vertical activity (rearing) measured at Day 6. Depression-like indicators included duration of immobility in the forced swim test and in the tail suspension test at Day 6 and sucrose consumption in the sucrose preference test at Day 7. The simultaneous consideration of complementary sickness and depression-like indicators enabled a more precise characterization of behavioral changes associated with BCG-treatment and of mouse-to-mouse variation, relative to the analysis of indicators individually. Univariate and multivariate analyses confirmed differences between BCG-treatment groups in weight change early on the trial. Significant differences between BCG-treatment groups in depression-like behaviors were still measurable after Day 5. The potential for multivariate models to account for the correlation between behavioral indicators and to augment the analytical precision relative to univariate models was demonstrated both for sickness and for depression-like indicators. Unsupervised learning approaches revealed the complementary information provided by the sickness and depression-like indicators considered. Supervised learning approaches using cross-validation confirmed subtle differences between BCG-treatment groups and among mice within group identified by the consideration of sickness and depression-like indicators. These findings support the recommendation for multivariate and multidimensional analyses of sickness and depression-like indicators to augment the systemic understanding of the behavioral changes associated with infection.

The saturated fatty acid, palmitic acid, induces anxiety-like behavior in mice

OBJECTIVES

Excess fat in the diet can impact neuropsychiatric functions by negatively affecting cognition, mood and anxiety. We sought to show that the free fatty acid (FFA), palmitic acid, can cause adverse biobehaviors in mice that last beyond an acute elevation in plasma FFAs.

METHODS

Mice were administered palmitic acid or vehicle as a single intraperitoneal (IP) injection. Biobehaviors were profiled 2 and 24 h after palmitic acid treatment. Quantification of dopamine (DA), norepinephrine (NE), serotonin (5-HT) and their major metabolites was performed in cortex, hippocampus and amygdala. FFA concentration was determined in plasma. Relative fold change in mRNA expression of unfolded protein response (UPR)-associated genes was determined in brain regions.

RESULTS

In a dose-dependent fashion, palmitic acid rapidly reduced mouse locomotor activity by a mechanism that did not rely on TLR4, MyD88, IL-1, IL-6 or TNFα but was dependent on fatty acid chain length. Twenty-four hours after palmitic acid administration mice exhibited anxiety-like behavior without impairment in locomotion, food intake, depressive-like behavior or spatial memory. Additionally, the serotonin metabolite 5-HIAA was increased by 33% in the amygdala 24h after palmitic acid treatment.

CONCLUSIONS

Palmitic acid induces anxiety-like behavior in mice while increasing amygdala-based serotonin metabolism. These effects occur at a time point when plasma FFA levels are no longer elevated.

Methylphenidate prevents high-fat diet (HFD)-induced learning/memory impairment in juvenile mice

The prevalence of childhood obesity has risen dramatically and coincident with this upsurge is a growth in adverse childhood psychological conditions including impulsivity, depression, anxiety and attention deficit/hyperactive disorder (ADHD). Due to confounds that exist when determining causality of childhood behavioral perturbations, controversy remains as to whether overnutrition and/or childhood obesity is important. Therefore, we examined juvenile mice to determine if biobehaviors were impacted by a short-term feeding (1-3wks) of a high-fat diet (HFD). After 1wk of a HFD feeding, mouse burrowing and spontaneous wheel running were increased while mouse exploration of the open quadrants of a zero maze, perfect alternations in a Y-maze and recognition of a novel object were impaired. Examination of mouse cortex, hippocampus and hypothalamus for dopamine and its metabolites demonstrated increased homovanillic acid (HVA) concentrations in the hippocampus and cortex that were associated with decreased cortical BDNF gene expression. In contrast, pro-inflammatory cytokine gene transcripts and serum IL-1α, IL-1β, TNF-α and IL-6 were unaffected by the short-term HFD feeding. Administration to mice of the psychostimulant methylphenidate prevented HFD-dependent impairment of learning/memory. HFD learning/memory impairment was not inhibited by the anti-depressants desipramine or reboxetine nor was it blocked in IDO or IL-1R1 knockout mice. In sum, a HFD rapidly impacts dopamine metabolism in the brain appearing to trigger anxiety-like behaviors and learning/memory impairments prior to the onset of weight gain and/or pre-diabetes. Thus, overnutrition due to fats may be central to childhood psychological perturbations such as anxiety and ADHD.

Intracerebroventricular administration of lipopolysaccharide induces indoleamine-2,3-dioxygenase-dependent depression-like behaviors

BACKGROUND

Activation of the tryptophan degrading enzyme indoleamine-2,3-dioxygenase 1 (IDO1) is associated with the development of behavioral signs of depression. Systemic immune challenge induces IDO1 in both the periphery and the brain, leading to increased circulating and brain concentrations of kynurenines. However, whether IDO1 activity within the brain is necessary for the manifestation of depression-like behavior of mice following a central immune challenge remains to be elucidated.

METHODS

We investigated the role of brain IDO1 in mediating depression-like behavior of mice in response to intracerebroventricular injection of saline or lipopolysaccharide (LPS, 10 ng).

RESULTS

LPS increased the duration of immobility in the tail suspension test and decreased preference for a sucrose solution. These effects were associated with an activation of central but not peripheral IDO1, as LPS increased brain kynurenine but had no effect on plasma concentrations of kynurenine. Interestingly, genetic deletion or pharmacological inhibition of IDO1, using 1-methyl-tryptophan, abrogated the reduction in sucrose preference induced by intracerebroventricular LPS. 1-Methyl-tryptophan also blocked the LPS-induced increase in duration of immobility during the tail suspension test.

CONCLUSIONS

These data indicate that activation of brain IDO1 is sufficient to induce depression-like behaviors of mice in response to central LPS.

Interleukin-1 beta converting enzyme is necessary for development of depression-like behavior following intracerebroventricular administration of lipopolysaccharide to mice

Background

Interleukin-1 beta converting enzyme (ICE, caspase 1) is a cysteine protease that processes immature pro-IL-1β into active mature IL-1β. IL-1β is a pro-inflammatory cytokine that mediates many of the physiological and behavioral responses to inflammation. Genetic deletion of ICE has previously been shown to prevent some negative physiologic responses to lipopolysaccharide (LPS)-induced inflammation.

Methods

Here we used a preclinical murine model to test the hypothesis that ICE is necessary for development of depression-like behaviors following intracerebroventricular (ICV) treatment with LPS. Adult male ICE knockout (ICE KO) and congenic wild-type C57BL/6 J (WT) mice were administered LPS either ICV at 100 ng/mouse or intraperitoneally (IP) at 830 μg/kg body weight or an equal volume of saline as controls. Mice were monitored up to 48 h after treatment for both sickness and depression-like behaviors.

Results

LPS given ICV induced a loss of body weight in both WT and ICE KO mice. This sickness response was similar between WT and ICE KO mice. As expected, LPS administered ICV increased immobility in the forced swim test (FST) and decreased sucrose preference in WT mice but no change in either of these two depression-like behaviors was observed in ICE KO mice. Expression of TNF-α and CD11b in brain was lower in ICE-KO mice at 24 h following ICV administration of LPS compared to WT mice. In contrast, when LPS was given systemically, sickness response, depression-like behaviors, and expression of these genes were similar between the two strains of mice.

Conclusions

These findings indicate that ICE plays a specific role in depression-like behavior induced by a central inflammatory stimuli even though it is not required when LPS is administered systemically.

Intracerebroventricular administration of HIV-1 Tat induces brain cytokine and indoleamine 2,3-dioxygenase expression: a possible mechanism for AIDS comorbid depression

Human immunodeficiency virus (HIV) remains a major public health concern despite a large education effort during the past 25 years. A persistent problem with HIV infection is the high comorbity rate of clinical depression. We previously established that increasing proinflammatory cytokines within the brain of mice induces sickness that can culminate in depressive-like behavior. Here we investigated the role of the HIV transactivator of transcription (Tat) protein in activation of brain cytokine signaling and subsequent induction of depressive-like behavior in a murine model. Adult Balb/c mice were administered a single intracerebroventricular (ICV) injection of Tat (40 ng). Social investigation of a novel juvenile was measured at 2, 4, 8 and 24 h post-treatment. Mice treated with Tat did not display signs of sickness, as measured by either decreased social investigation or loss of body weight. At 24 h post-injection, mice were subjected to the forced swim test (FST). ICV administration of Tat to Balb/c mice increased immobility in the FST at 24 h post injection. A different strain of mice, C57BL/6J, responded similarly in the FST. Furthermore, adult C57BL/6J mice injected with Tat and tested in a two-bottle 1% sucrose preference test displayed reduced preference for sucrose during the 24 h post-injection period. Subsequently, brain tissues from Tat-treated and control C57BL/6J mice were collected at 4 and 24 h post injection. CNS tissue from Tat-treated mice had increased expression of IL-1β, TNF-α, IL-6, and IDO mRNAs at 4 h post injection. These data demonstrate that a single exposure to Tat in the brain is sufficient to induce brain cytokine signaling that culminates in depressive-like behavior. The results reveal a potential role for Tat in the development of comorbid depression in HIV-infected individuals.

Rate of fall in blood glucose and recurrent hypoglycemia affect glucose dynamics and noradrenergic activation in the ventromedial hypothalamus

Noradrenergic activity in the ventromedial hypothalamus (VMH) is increased and activates a sympathoadrenal response during hypoglycemia. How the rate at which hypoglycemia develops affects local glucose concentrations and norepinephrine (NE) release was evaluated by placing microdialysis probes into the VMH of male Sprague-Dawley rats receiving insulin (20 mU·kg(-1)·min(-1)) and variable glucose infusions. During a first episode of hypoglycemia, interstitial glucose concentrations in the VMH generally declined at the same rate as plasma glucose; however, the faster hypoglycemia developed, the greater the magnitude of the initial NE release in the VMH (r(2) = 0.72, P < 0.001). Following recurrent episodes of hypoglycemia, VMH glucose decreased at a slower rate than plasma glucose, and the initial NE release was attenuated at the same rates of blood glucose decline. The plasma glucose threshold for the initial NE release in VMH was similar for all groups (∼3.23 mM); however, the VMH glucose threshold was stimulated and was lower when blood glucose declined more slowly (0.86 ± 0.06 vs. 1.06 ± 0.04 mmol/l, P < 0.01). The timing of the initial increase in NE release in VMH corresponded with an increase in plasma epinephrine during the first episode of hypoglycemia but not following recurrent hypoglycemia. Although a decrease in VMH glucose concentration is required for noradrenergic activation in VMH, there does not appear to be a set glucose threshold within the VMH for activation of this response.

HIV-1 Tat activates indoleamine 2,3 dioxygenase in murine organotypic hippocampal slice cultures in a p38 mitogen-activated protein kinase-dependent manner

Background

We have established that activation of the tryptophan degrading enzyme indoleamine 2,3 dioxygenase (IDO) mediates the switch from cytokine-induced sickness behavior to depressive-like behavior. Because human immunodeficiency virus type 1 (HIV-1) Tat protein causes depressive-like behavior in mice, we investigated its ability to activate IDO in organotypic hippocampal slice cultures (OHSCs) derived from neonatal C57BL/6 mice.

Methods

Depressive-like behavior in C57BL/6J mice was assessed by the forced swim test. Expression of cytokines and IDO mRNA in OHSCs was measured by real-time RT-PCR and cytokine protein was measured by enzyme-linked immunosorbent assays (ELISAs). p38 MAPK phosphorylation was analyzed by western blot.

Results

Intracerebroventricular (i.c.v.) administration of Tat (40 ng) induced depressive-like behavior in the absence of sickness. Addition of Tat (40 ng/slice) to the medium of OHSCs induced IDO steady-state mRNA that peaked at 6 h. This effect was potentiated by pretreatment with IFNγ. Tat also induced the synthesis and release of TNFα and IL-6 protein in the supernatant of the slices and increased expression of the inducible isoform of nitric oxide synthase (iNOS) and the serotonin transporter (SERT). Tat had no effect on endogenous synthesis of IFNγ. To explore the mechanisms of Tat-induced IDO expression, slices were pretreated with the p38 mitogen-activated protein kinase (MAPK) inhibitor SB 202190 for 30 min before Tat treatment. SB 202190 significantly decreased IDO expression induced by Tat, and this effect was accompanied by a reduction of Tat-induced expression of TNFα, IL-6, iNOS and SERT.

Conclusion

These data establish that Tat induces IDO expression via an IFNγ-independent mechanism that depends upon activation of p38 MAPK. Targeting IDO itself or the p38 MAPK signaling pathway could provide a novel therapy for comorbid depressive disorders in HIV-1-infected patients.

Inflammation-associated depression: from serotonin to kynurenine

In the field of depression, inflammation-associated depression stands up as an exception since its causal factors are obvious and it is easy to mimic in an animal model. In addition, quasi-experimental studies can be carried out in patients who are treated chronically with recombinant cytokines for a medical condition since these patients can be studied longitudinally before, during and after stimulation of the immune system. These clinical studies have revealed that depression is a late phenomenon that develops over a background of early appearing sickness. Incorporation of this feature in animal models of inflammation-associated depression has allowed the demonstration that alterations of brain serotoninergic neurotransmission do not play a major role in the pathogenesis. This is in contrast to the activation of the tryptophan degrading enzyme indoleamine 2,3-dioxygenase that generates potentially neurotoxic kynurenine metabolites such as 3-hydroxy kynurenine and quinolinic acid. Although the relative importance of peripherally versus centrally produced kynurenine and the cellular source of production of this compound remain to be determined, these findings provide new targets for the treatment of inflammation-associated depression that could be extended to other psychiatric conditions mediated by activation of neuroimmune mechanisms.

Targeting RANK/RANKL in the treatment of solid tumours and myeloma

Cancers which damage the human skeleton include multiple myeloma, where the primary tumour colonises bone directly, or breast and prostate cancer, where malignant cells travel from the primary tumour to form clonal outgrowths within the bone. Owing to the interaction of tumour cells with those normally found in the bone microenvironment, such as osteoclasts and osteoblasts, these cancers affect the closely linked processes of bone formation and resorption. As a result, these twin processes contribute to the clinical manifestations of cancer metastasis, including bone pain and pathological fractures. A critical component of physiologically normal bone remodelling, the RANK/RANKL/OPG pathway, has been implicated in the formation of osteolytic, and possibly osteoblastic, lesions, which characterise the bone disease associated with these malignancies. In these cancers that affect the skeleton in this way the abnormally regulated RANK/RANKL system appears to be the final effector pathway. As a result, there has been much research focused upon targeting these molecules using OPG constructs, peptidomimetics, soluble receptor constructs and antibodies to RANKL, in pre-clinical studies. The success of these studies has paved the way for a clinical programme, the success of which is likely to lead to a new therapeutic approach to treating cancers that develop in the skeleton.

CSF concentrations of brain tryptophan and kynurenines during immune stimulation with IFN-alpha: relationship to CNS immune responses and depression

Cytokine-induced activation of indoleamine 2,3-dioxygenase (IDO) catabolizes L-tryptophan (TRP) into L-kynurenine (KYN), which is metabolized to quinolinic acid (QUIN) and kynurenic acid (KA). QUIN and KA are neuroactive and may contribute to the behavioral changes experienced by some patients during exposure to inflammatory stimuli such as interferon (IFN)-alpha. A relationship between depressive symptoms and peripheral blood TRP, KYN and KA during treatment with IFN-alpha has been described. However, whether peripheral blood changes in these IDO catabolites are manifest in the brain and whether they are related to central nervous system cytokine responses and/or behavior is unknown. Accordingly, TRP, KYN, QUIN and KA were measured in cerebrospinal fluid (CSF) and blood along with CSF concentrations of relevant cytokines, chemokines and soluble cytokine receptors in 27 patients with hepatitis C after approximately 12 weeks of either treatment with IFN-alpha (n=16) or no treatment (n=11). Depressive symptoms were assessed using the Montgomery-Asberg Depression Rating Scale. IFN-alpha significantly increased peripheral blood KYN, which was accompanied by marked increases in CSF KYN. Increased CSF KYN was in turn associated with significant increases in CSF QUIN and KA. Despite significant decreases in peripheral blood TRP, IFN-alpha had no effect on CSF TRP concentrations. Increases in CSF KYN and QUIN were correlated with increased CSF IFN-alpha, soluble tumor necrosis factor-alpha receptor 2 and monocyte chemoattractant protein-1 as well as increased depressive symptoms. In conclusion, peripheral administration of IFN-alpha activated IDO in concert with central cytokine responses, resulting in increased brain KYN and QUIN, which correlated with depressive symptoms.

Differences between bisphosphonates in binding affinities for hydroxyapatite

Bisphosphonates (BPs) inhibit bone resorption and are widely used for the treatment of bone diseases, including osteoporosis. BPs are also being studied for their effects on hydroxyapatite (HAP)-containing biomaterials. There is a growing appreciation that there are hitherto unexpected differences among BPs in their mineral binding affinities that affect their pharmacological and biological properties. To study these differences, we have developed a method based on fast performance liquid chromatography using columns of HAP to which BPs and other phosphate-containing compounds can adsorb and be eluted by using phosphate buffer gradients at pH 6.8. The individual compounds emerge as discrete and reproducible peaks for a range of compounds with different affinities. For example, the peak retention times (min; mean +/- SEM) were 22.0 +/- 0.3 for zoledronate, 16.16 +/- 0.44 for risedronate, and 9.0 +/- 0.28 for its phosphonocarboxylate analog, NE10790. These results suggest that there are substantial differences among BPs in their binding to HAP. These differences may be exploited in the development of biomaterials and may also partly explain the extent of their relative skeletal retention and persistence of biological effects observed in both animal and clinical studies.

LPS-induced indoleamine 2,3-dioxygenase is regulated in an interferon-gamma-independent manner by a JNK signaling pathway in primary murine microglia

Inflammation-induced activation of the tryptophan catabolizing enzyme indoleamine 2,3-dioxygenase (IDO) causes depressive-like behavior in mice following acute activation of the innate immune system by lipopolysaccharide (LPS). Here we investigated the mechanism of IDO expression induced by LPS in primary cultures of microglia derived from neonatal C57BL/6J mice. LPS (10 ng/ml) induced IDO transcripts that peaked at 8h and enzymatic activity at 24h, resulting in an increase in extracellular kynurenine, the catabolic product of IDO-induced tryptophan catabolism. This IDO induction by LPS was accompanied by synthesis and secretion of the proinflammatory cytokines TNFalpha and IL-6, but without detectable IFNgamma expression. To explore the mechanism of LPS-induced IDO expression, microglia were pretreated with the c-Jun-N-terminal kinase (JNK) inhibitor SP600125 for 30 min before LPS treatment. We found that SP600125 blocked JNK phosphorylation and significantly decreased IDO expression induced by LPS, which was accompanied by a reduction of LPS-induced expression of TNFalpha and IL-6. Collectively, these data extend to microglia the property that LPS induces IDO expression via an IFNgamma-independent mechanism that depends upon activation of JNK. Inhibition of the JNK pathway may provide a new therapy for inflammatory depression.

Induction of IDO by bacille Calmette-Guérin is responsible for development of murine depressive-like behavior

Chronic inflammation activates the tryptophan-degrading enzyme IDO, which is well known to impair T cell proliferation. We have previously established that bacille Calmette-Guérin (BCG), an attenuated form of Mycobacterium bovis, is associated with persistent activation of IDO in the brain and chronic depressive-like behavior, but a causative role has not been established. In these experiments we used both pharmacologic and genetic approaches to test the hypothesis that IDO activation is responsible for the development of chronic depression that follows BCG infection. BCG induced TNF-alpha, IFN-gamma, and IDO mRNA steady-state transcripts in the brain as well as the enzyme 3-hydroxyanthranilic acid oxygenase (3-HAO) that lies downstream of IDO and generates the neuroactive metabolite, quinolinic acid. Behaviors characteristic of depression were apparent 1 wk after BCG infection. Pretreatment with the competitive IDO inhibitor 1-methyltryptophan fully blocked BCG-induced depressive-like behaviors. Importantly, IDO-deficient mice were completely resistant to BCG-induced depressive-like behavior but responded normally to BCG induction of proinflammatory cytokines. These results are the first to prove that the BCG-induced persistent activation of IDO is accompanied by the induction of 3-hydroxyanthranilic acid oxygenase and that IDO is required as an initial step for the subsequent development of chronic depressive-like behavior.

Interferon-gamma and tumor necrosis factor-alpha mediate the upregulation of indoleamine 2,3-dioxygenase and the induction of depressive-like behavior in mice in response to bacillus Calmette-Guerin

Although the tryptophan-degrading enzyme, indoleamine 2,3-dioxygenase (IDO), is a pivotal mediator of inflammation-induced depression, its mechanism of regulation has not yet been investigated in this context. Here, we demonstrate an essential role for interferon (IFN)gamma and tumor necrosis factor (TNF)alpha in the induction of IDO and depressive-like behaviors in response to chronic immune activation. Wild-type (WT) control mice and IFNgammaR(-/-) mice were inoculated with an attenuated form of Mycobacterium bovis, bacille Calmette-Guérin (BCG). Infection with BCG induced an acute episode of sickness that was similar in WT and IFNgammaR(-/-) mice. Increased immobility during the forced swim and tail suspension tests occurred in WT mice 7 d after BCG inoculation but was entirely absent in IFNgammaR(-/-) mice. In WT mice, these indices of depressive-like behavior were associated with chronic upregulation of IFNgamma, interleukin(IL)-1beta, TNFalpha, and IDO. Proinflammatory cytokine expression was elevated in BCG-infected IFNgammaR(-/-) mice as well, but upregulation of lung and brain IDO mRNA was completely abolished. This was accompanied by an attenuation of BCG-induced TNFalpha mRNA and the lack of an increase in plasma kynurenine/tryptophan ratio in the BCG-inoculated IFNgammaR(-/-) mice compared with WT controls. Pretreatment of mice with the TNFalpha antagonist, etanercept, partially blunted BCG-induced IDO activation and depressive-like behavior. In accordance with these in vivo data, IFNgamma and TNFalpha synergized to induce IDO in primary microglia. Together, these data demonstrate that IFNgamma, with TNFalpha, is necessary for induction of IDO and depressive-like behavior in mice after BCG infection.

Orexin-induced feeding requires NMDA receptor activation in the perifornical region of the lateral hypothalamus

Food intake is stimulated following administration of orexin-A into the perifornical region of the lateral hypothalamus (LH/PFA). Orexin neurons originating in the LH/PFA interact with a number of hypothalamic systems known to influence food intake, including glutamatergic neurons. Glutamatergic systems in the LH/PFA were demonstrated to initiate feeding through N-methyl-d-aspartic acid (NMDA) receptors. Male Sprague-Dawley rats fitted with brain guide cannulas to the LH/PFA were used in two experiments. In the first experiment, a combination microdialysis/microinjection probe was used to deliver artificial cerebrospinal fluid (aCSF) or 500 pmol of orexin-A into the LH/PFA. Orexin-A increased interstitial glutamate to 143 ± 12% of baseline ( P < 0.05), which remained elevated over the 120-min collection period. In the second experiment, the NMDA receptor antagonist d-2-amino-5-phosphonopentanoic acid (d-AP5; 10 nmol) was administered before orexin-A. The orexin-induced increase in food intake (from 1.1 ± 0.4 to 3.2 ± 0.5 g, P < 0.05) during the first hour was absent in rats receiving d-AP5 + orexin-A (1.2 ± 0.5 g). There was no effect of d-AP5 alone on food intake. These data support glutamatergic systems in the LH/PFA mediating the feeding response to orexin-A through NMDA receptors.

Hypoglycemia-induced noradrenergic activation in the VMH is a result of decreased ambient glucose

During insulin-induced hypoglycemia, there is an increase in extracellular norepinephrine (NE) in the ventromedial hypothalamus (VMH). This brain area is known to play an important role in integrated hormonal and behavioral responses to systemic hypoglycemia. Selective glucoprivation restricted to the VMH is both necessary and sufficient to initiate secretion of counterregulatory hormones. The present study was designed to investigate whether increased release of NE in the VMH depends on detection of glucoprivation localized in this area. In awake, chronically catheterized male Sprague-Dawley rats, extracellular NE in the VMH was monitored using 1-mm microdialysis probes perfused with Krebs Ringer buffer (KRB) or KRB + 100 mM d-glucose (d-Glc). During insulin-induced hypoglycemia (glycemic nadir approximately 2.4 mM) extracellular NE was increased to >160% of baseline (P < 0.01) only in the KRB + insulin group. There was no increase in NE from baseline when glucose was added to the perfusate to maintain euglycemia at the periprobe environment. The sympathoadrenal response to hypoglycemia, present in the KRB + insulin group, was attenuated in the d-Glc + insulin group. The present results confirm that noradrenergic activation in the VMH during systemic hypoglycemia depends on detection of glucoprivation locally in this area. These data provide additional support for the importance of increased noradrenergic activity in the VMH in the counterregulatory hormonal responses to hypoglycemia.

Transmission of two Australian strains of murine cytomegalovirus (MCMV) in enclosure populations of house mice (Mus domesticus)

To control plagues of free-living mice (Mus domesticus) in Australia, a recombinant murine cytomegalovirus (MCMV) expressing fertility proteins is being developed as an immunocontraceptive agent. Real-time quantitative PCR was used to monitor the transmission of two genetically variable field strains of MCMV through mouse populations after 25% of founding mice were infected with the N1 strain, followed by the G4 strain 6 weeks later. Pathogen-free wild-derived mice were released into outdoor enclosures located in northwestern Victoria (Australia). Of those mice not originally inoculated with virus, N1 DNA was detected in more than 80% of founder mice and a third of their offspring and similarly, G4 DNA was detected in 13% of founder mice and in 3% of their offspring. Thus, prior immunity to N1 did not prevent transmission of G4. This result is promising for successful transmission of an immunocontraceptive vaccine through Australian mouse populations where MCMV infection is endemic.

Species-specificity of a murine immunocontraceptive utilising murine cytomegalovirus as a gene delivery vector

Cytomegaloviruses are species-specific DNA viruses. Recombinant murine cytomegaloviruse (MCMV) expressing the mouse egg-coat protein zona pellucida 3 (mZP3) has been shown to sterilise female mice by breaking self-tolerance and inducing an immune response against the host ZP3. This virus has the potential to be used for mouse population control, however the effect of this recombinant immunocontraceptive virus in non-host species must be determined. Recombinant MCMV-mZP3, based on both laboratory and wild strains of virus, induced long-lived antibody responses against structural viral proteins and mZP3 when inoculated into laboratory rats, although no viral DNA or replicating virus was identified. The anti-mZP3 antibodies were specific for mouse ZP3, did not cross-react with rat ZP3, and had no effect on the fertility of the rats.

Adhesion and Growth of Bone Marrow Stromal Cells on Modified Alginate Hydrogels

Alginate is a biodegradable, immunocompatible biopolymer that is capable of immobilizing viable cells and bioactive factors. Few investigations have analyzed the efficacy of alginate gels as substrata for cell attachment and proliferation. Here we have compared the adhesion and subsequent growth of human and rat bone marrow stromal fibroblastic cells on unmodified alginate hydrogel surfaces. It was found that, in contrast to rat cells, human cells did not readily attach or proliferate on unmodified alginates. In attempts to enhance these features, or collagen type I was incorporated into the gels, with no significant improvements in prolonged human cell adherence. However, alginate gels containing both collagen type I and beta-tricalcium phosphate were found to enhance human cell adherence and proliferation. Furthermore, interactions between the collagen and beta-tricalcium phosphate prevented loss of the protein from the hydrogels. These results indicate that alginate gels containing collagen have potential uses as vehicles for delivery of adherent cells to a tissue site. In addition, gels containing beta-tricalcium phosphate, with or without collagen type I incorporation, have potential to support cell growth and differentiation in vitro before implantation. This study emphasizes the limitations of the uses of cells derived from experimental animals in certain model studies relating to human tissue engineering.

Pathogens of house mice on arid Boullanger Island and subantarctic Macquarie Island, Australia

Studies on island populations of house mice (Mus domesticus) and their viruses reveal insights into viral persistence in isolated communities. We surveyed the ectoparasites, endoparasites, and antiviral antibodies for 11 murine viruses and two bacteria of house mice inhabiting two islands off Australia. House mice on Boullanger Island were seropositive to two viruses, murine cytomegalovirus and epizootic diarrhea of infant mice. On subantarctic Macquarie Island, house mice were seropositive for five viruses: murine cytomegalovirus, lymphocytic choriomeningitis virus, mouse parvovirus, epizootic diarrhea of infant mice, and Theiler's murine encephalomyelitis virus. The diversity of antiviral antibodies was lower among populations of house mice on islands than those inhabiting mainland Australia. The decreased diversity of viruses in island populations of house mice may be a function of which agent the founder mice transfer to the island and related to the low densities which the host population may periodically reach over time.

Isolates of cytomegalovirus (CMV) from the black rat Rattus rattus form a distinct group of rat CMV

Two different betaherpesviruses, the English and Maastricht species of rat cytomegalovirus (CMV), have previously been isolated from Rattus norvegicus. CMVs were isolated from both the brown rat, R. norvegicus, and the black rat, R. rattus, within Australia. The viruses isolated from R. norvegicus appeared to be genetically related to the English species of rat CMV by PCR, RFLP, and sequencing, but the viruses isolated from R. rattus were distinct from both prototype virus species, although more closely genetically related to the Maastricht virus. This is the first genetic characterization of cytomegaloviruses from R. rattus, and the first isolation of CMVs from Australian rats.

Dissociation of hypothalamic noradrenergic activity and sympathoadrenal responses to recurrent hypoglycemia

This study evaluated whether attenuation of sympathoadrenal responses to recurrent hypoglycemia is mediated by diminished noradrenergic activity in the hypothalamus. Male Sprague-Dawley rats received either once daily insulin (1.0 units/kg) injections or an equal administration of saline for 3 days. Both groups received an administration of insulin on the fourth day, during which blood glucose and plasma catecholamines were determined, and extracellular norepinephrine (NE) in the ventromedial hypothalamus (VMH) or paraventricular hypothalamic nucleus (PVN) was monitored with microdialysis. The peak response of plasma epinephrine to insulin-induced hypoglycemia (nadir approximately 3.2 mmol/l) was significantly reduced during the fourth hypoglycemic episode (774 +/- 134 pg/ml) compared with the first episode (2,561 +/- 410 pg/ml, P < 0.001). Baseline levels of extracellular NE were elevated approximately 25% (P = 0.07) in the VMH and approximately 46% (P = 0.03) in the PVN after multiple hypoglycemic episodes. There was no difference in noradrenergic activity during the first or fourth hypoglycemic episode in either brain area. The reduced sympathoadrenal output after recurrent hypoglycemia is likely postsynaptic from hypothalamic NE release or is mediated via a collateral pathway.

Ecological basis for fertility control in the house mouse (Mus domesticus) using immunocontraceptive vaccines

Laboratory studies confirm the potential for fertility control in the house mouse Mus domesticus using mouse cytomegalovirus (MCMV) as a vector for an immunocontraceptive vaccine. This article presents an overview of key results from research in Australia on enclosed and field populations of mice and the associated epidemiology of MCMV. The virus is geographically widespread in Australia. It also persists in low population densities of mice, although if population densities are low for at least a year, transmission of the virus is sporadic until a population threshold of approximately 40 mice ha(-1) is reached. The serological prevalence of MCMV was high early in the breeding season of four field populations. Enclosure studies confirm that MCMV has minimal impact on the survival and breeding performance of mice and that it can be transmitted to most adults within 10-12 weeks. Other enclosure studies indicate that about two-thirds of females would need to be sterilized to provide effective control of the rate of growth of mouse populations. If this level is not maintained for 20-25 weeks after the commencement of breeding, the mouse population can compensate through increased recruitment per breeding female. The findings from this series of descriptive and manipulative population studies of mice support the contention that MCMV would be a good carrier for an immunocontraceptive vaccine required to sustain female sterility levels at or above 65%.

Androgen responsiveness of the pituitary gonadotrope cell line LbetaT2

Androgens have a profound effect on the hypothalamic-pituitary axis by reducing the synthesis and release of the pituitary gonadotropin LH. The effect on LH is partly a consequence of a direct, steroid-dependent action on pituitary function. Although androgen action has been well studied in vivo, in vitro cell models of androgen action on pituitary gonadotropes have been scarce. Recently, an LH-expressing cell line, LbetaT2, was generated by tumorigenesis targeted to the LH-producing cells of the mouse pituitary. The purpose of these studies was to determine the presence of androgen receptor (AR) and establish its function in this cell line. RT-PCR analysis indicated that the LbetaT2 cell line expresses AR mRNA. Transient transfection assays, using the mouse mammary tumor virus (MMTV) promoter, showed that a functional AR is also present. Testosterone (TEST), dihydrotestosterone (DHT), 7alpha-methyl-19-nortestosterone (MENT), and fluoxymesterone (FLUOXY) increased reporter gene activity in the rank order of potencies MENT>DHT> TEST>FLUOXY. Additionally, activation of MMTV promoter activity by DHT in LbetaT2 cells was diminished by the AR antagonists casodex and 2-hydroxy-flutamide, indicating that the effects of DHT are mediated through AR. In summary, these studies showed that the LbetaT2 cell line is a useful model for the evaluation and molecular characterization of androgen action in pituitary gonadotropes.

Development of components of the extracellular matrix, basal lamina and sarcomere in chick quadriceps and pectoralis muscles

1. The purpose of this study was to investigate differences in the development of components of the cell/matrix linkage in two functionally different muscle types: the pectoralis muscle, a major locomotory muscle in birds but not particularly functional in chickens, and the quadriceps muscle, a smaller and more functionally active muscle in the chicken. 2. The development of the extracellular matrix, basal lamina and sarcomere in the pectoralis and quadriceps muscles in chick embryos was examined biochemically to determine differences in the rate of development between these two muscles. Samples of these muscle types were dissected out from chick embryos from embryonic day 10 until 8 weeks post hatch. 3. Using SDS-PAGE electrophoresis and western blotting with antibodies against sarcomeric actin, laminin and collagens I, III and IV, it was apparent that muscle development begins earlier in the quadriceps muscle than in the pectoralis, and that late in the developmental process (d 18) both muscle types were well differentiated. The final concentration of collagens in the mature muscle remained higher in the quadriceps than in the pectoralis muscle. 4. The onset of development of the extracellular matrix, basal lamina and sarcomere was earlier in the quadriceps than the pectoralis, which could have functional implications for these muscles as a whole.

Activation of translation in pituitary gonadotrope cells by gonadotropin-releasing hormone

The neuropeptide GnRH is a central regulator of mammalian reproductive function produced by a dispersed population of hypothalamic neurosecretory neurons. The principal action of GnRH is to regulate release of the gonadotropins, LH and FSH, by the gonadotrope cells of the anterior pituitary. Using a cultured cell model of mouse pituitary gonadotrope cells, alphaT3-1 cells, we present evidence that GnRH stimulation of alphaT3-1 cells results in an increase in cap-dependent mRNA translation. GnRH receptor activation results in increased protein synthesis through a regulator of mRNA translation initiation, eukaryotic translation initiation factor 4E-binding protein, known as 4EBP or PHAS (protein, heat, and acid stable). Although the GnRH receptor is a member of the rhodopsin-like family of G protein-linked receptors, we show that activation of translation proceeds through a signaling pathway previously described for receptor tyrosine kinases. Stimulation of translation by GnRH is protein kinase C and Ras dependent and sensitive to rapamycin. Furthermore, GnRH may also regulate the cell cycle in alphaT3-1 cells. The activation of a signaling pathway that regulates both protein synthesis and cell cycle suggests that GnRH may have a significant role in the maintenance of the pituitary gonadotrope population in addition to directing the release of gonadotropins.

Differentiation of myoblasts in serum-free media: effects of modified media are cell line-specific

Myoblast cell lines are grown and differentiated readily in cell culture. Two cell lines typically used for investigating the growth and differentiation of muscle are the mouse cell line C2C12 and the rat cell line L6. The differentiation of these cells in vitro requires a switch from a serum-rich medium to a less rich medium after the cells have reached confluence. Since the components present in serum are not well characterized, the use of a better defined medium for these studies was investigated. C2C12 and L6 myoblasts were differentiated in both serum-containing and serum-free media. The differentiation state of these cultures was then tested both microscopically and biochemically. Cultures were checked for myotube formation, the activity of creatine phosphokinase and the presence of sarcomeric actin. In C2C12 cells, the extent of differentiation was greater in the serum-free than in the serum-containing system. In both media types, the C2C12 cells produced sarcomeric actin, showing the presence of sarcomere structure in the myotubes. In L6 cells, however, myotubes were readily formed in medium containing 2% horse serum, but not in the serum-free system. In addition, the ability of C2C12 cells to differentiate on substrates coated with extracellular matrix proteins was shown to be media-dependent. The presence of extracellular matrix proteins did not enable L6 cells to form myotubes when cultured in serum-free media. Primary cultures of chick myoblasts were able to differentiate in both media tested, with Dulbecco's modified Eagle medium containing horse serum being a more efficient medium for cell fusion. This study shows a divergence in muscle cell line responses in three cell lines, two of which are typically used as 'model systems' for understanding muscle growth and development.

Neuron-specific expression of the rat gonadotropin-releasing hormone gene is conferred by interactions of a defined promoter element with the enhancer in GT1-7 cells

Neuroendocrine control of the reproductive cascade is mediated by GnRH, which in mammals is produced by a subset of neurons scattered throughout the hypothalamus and forebrain. Utilizing a cultured cell model of GnRH neurons (GT1-7 cells), two regulatory regions in the rat GnRH 5' flanking DNA were identified as essential for cell-type specificity: a 300-bp enhancer and a 173-bp conserved proximal promoter. Using transient transfections to compare expression in GT1-7 cells to a non-GnRH-expressing cell type (NIH 3T3), we show that the GnRH enhancer and the proximal promoter each play roles in conferring this specificity. Deletion of footprint 2 (FP2; -26 to -76) from the promoter when coupled to the GnRH enhancer diminishes reporter activity in GT1-7 cells more strongly than in NIH 3T3 cells. Furthermore, deletion of FP2 from the promoter when coupled to the heterologous Rous sarcoma virus 5'-long terminal repeat promoter abolishes the difference in reporter activity between GT1-7 and NIH 3T3 cells, suggesting that FP2 of the GnRH promoter is necessary for cell-specific expression. In addition, FP2 alone is sufficient to confer cell-specific expression and can interact with the GnRH enhancer to augment reporter gene expression specifically in GT1-7 cells. Finally, a 31-bp sequence from within FP2 (-63 to -33) synergistically activates transcription when coupled with the GnRH enhancer in GT1-7 cells but not in NIH 3T3 cells. Thus, this 31-bp region contains elements necessary for interaction between the GnRH enhancer and promoter. We show that two of five protein complexes that bind to the -63 to -33 region are GT1-7 cell specific, and both of them appear to be homeodomain proteins. The identification of a cell-specific element in the GnRH proximal promoter significantly advances our understanding of the transcriptional basis for neuron-specific GnRH gene expression.

Oriented endocytic recycling of alpha5beta1 in motile neutrophils

During cell migration, integrin attachments to the substratum provide the means to generate the traction and force necessary to achieve locomotion. Once the cell has moved over these attachments, however, it is equally important that integrins detach from the substratum. The fate of integrins after detachment may include release from the cell, lateral diffusion across the cell surface, or endocytosis and redelivery to the cell surface. Polymorphonuclear neutrophils (PMNs) become stuck on the extracellular matrix proteins fibronectin and vitronectin when their intracellular free calcium concentration ([Ca(++)]i) is buffered. Taking advantage of this feature of PMN migration, we investigated the fate of integrins to differentiate among various models of migration. We demonstrate that alpha5beta1, one of the fibronectin-binding integrins, is responsible for immobilization of [Ca(++)](i)-buffered PMNs on fibronectin. We find that alpha5 and beta1 are in endocytic vesicles in PMNs and that alpha5 colocalizes with a marker for an endocytic recycling compartment. When [Ca(++)](i) is buffered, alpha5 and beta1 become concentrated in clusters in the rear of the adherent cells, suggesting that [Ca(++)](i) transients are required for alpha5beta1 detachment from the substratum. Inhibition of alpha5beta1 detachment by buffering [Ca(++)](i) results in the depletion of alpha5 from both endocytic vesicles and the recycling compartment, providing compelling evidence that integrins are normally recycled by way of endocytosis and intracellular trafficking during cell migration. This model is further refined by our demonstration that the endocytic recycling compartment reorients to retain its localization just behind the leading lamella as PMNs migrate, indicating that membrane recycling during neutrophil migration has directionality. (Blood. 2000;95:2471-2480)

Epinephrine upregulates calpain activity in cultured C2C12 muscle cells

C2C12 cells were grown to confluence at 37 degrees C under a continuous 5% CO(2) stream and myotube formation was stimulated. The cultures were then incubated with or without 2 microg/mL epinephrine for 18 h prior to harvesting and calpain extraction. Epinephrine treatment resulted in a three-fold increase in extractable mu-calpain activity (P < 0.05), a three-fold increase in extractable m-calpain activity (P < 0.05), a 36% increase in calpastatin activity (P < 0.001), and a 16% decrease (P < 0.05) in the total protein content in the C2C12 cell homogenate. These results suggest that calpains may play a role in protein metabolism and that the hormone epinephrine may be directly involved in the regulation of their cellular expression.

Functional brain mapping using positron emission tomography scanning in preoperative neurosurgical planning for pediatric brain tumors

OBJECT

The purpose of this report is to demonstrate the value of functional brain mapping using the positron emission tomography (PET) method for preoperative neurosurgical planning in children with brain tumors. Brain maps were used to characterize the relationship between potentially resectable tumors and functionally eloquent brain areas.

METHODS

Five children, ranging in age from 3 to 13 years, with hemispheric brain tumors adjacent to eloquent cortex were studied. Magnetic resonance (MR) imaging was used to identify the brain tumors; PET imaging after injection of [18F] fluorodeoxyglucose (FDG), [11C]L-methionine (CMET), or a combination of the two was performed to grade the tumors; and a [15O] H2O uptake study was used to characterize the anatomical relationships of the tumors to functional cortex. The cortical activation maps were obtained during control periods and during behavioral tasks and were used to document motor, visual, and speech and language organizational areas. Wada tests were performed in two patients. Language and speech activation was concordant with the results of Wada testing.

CONCLUSIONS

Functional brain mapping using PET scans and coregistered MR images provided the neurosurgeon with precise definitions of structural and functional cortical areas; this altered surgical management in some cases and/or was used to predict outcome. The combination of PET imaging with FDG and/or CMET and measurements of [15O] water uptake was useful in characterizing and grading tumors and instrumental in achieving effective neurosurgical planning. Postoperative results in the five cases suggest that preoperative functional brain mapping has the potential to improve outcome by defining a surgical plan to maximize resection and minimize the risk of neurological sequelae.

Positron emission tomography using [18F] fluorodeoxyglucose and [11C] l-methionine to metabolically characterize dysembryoplastic neuroepithelial tumors

Dysembryoplastic neuroepithelial tumors are unique and benign congenital tumors occurring frequently in children and adolescents. Differentiation from other low-grade tumors is important for management. Five patients with confirmed dysembryoplastic neuroepithelial tumors were studied with positron emission tomography using glucose and protein metabolic uptake in an attempt to categorize these tumors metabolically. Functional brain mapping also was obtained to aid in operative management. Results of the study conclude that dysembryoplastic neuroepithelial tumors, although having similar neuroimgaing characteristics to other low-grade tumors, are distinguished by a unique metabolic profile. They are inactive tumors with no significant glucose or protein metabolic activity. The combination of preoperative positron emission tomographic metabolic studies with functional brain mapping allowed for prediction of tumor type, defined eloquent areas of cortical function, and improved approach and resection of the tumors with minimal risk of neurologic impairment.